Geology of Fort Polk Region, Louisiana

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Geology of the Fort Polk Region, Sabine, Natchitoches, and Vernon Parishes, Louisiana

by Richard P. McCulloh and Paul V. Heinrich

Louisiana Geological Survey Louisiana State University

208 Howe-Russell Geoscience Complex Baton Rouge, Louisiana 70803-4101

with a chapter on Natural Occurrence Of Bogs, Seeps, and Springs by Bradford C. Hanson

\)«l.F>-LRESO& ~ '90 & ~ {)jrewitt

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Louisiana Geological Survey

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US Army Corps of Engineers

Fort Worth District

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15 November 1999 Final Report 12/2/96-11/15/99 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Geology of the Fort Polk Region, Sabine, Natchitoches,

and Vernon Parishes, Louisiana DACA63-95-D-0051

6. AUTHOR(S} Delivery Order No. 0008

Richard P. McCulloh and Paul V. Heinrich

with a chapter by Bradford C. Hanson

7. PERFORMING ORGANIZATION NAME(S} AND ADDRESS(ES} 8. PERFORMING ORGANIZATION REPORT NUMBER

Prewitt and Associates and Louisiana Geological Survey 7701 N. Lamar, Suite 104 Louisiana State University Austin, Texas 78752-1012 208 Howe-Russell Geoscience Complex

Baton Rouge, Louisiana 70803-4101 9. SPONSORING I MONITORING AGENCY NAME(S} AND ADDRESS(ES) 10. SPONSORING I MONITORING

U.S. Army Corps of Engineers AGENCY REPORT NUMBER

Fort Worth District

819 Taylor St., Box 17300

Fort Worth, Texas 76102-0300

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION I AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The Fort Polk region is underlain by Cenozoic terrigenous sediment comprising mostly the Oligocene Catahoula Formation, six formation-rank subunits of the Fleming (Miocene), and Holocene alluvium. Pliocene and Quaternary surface-stratigraphic units incise older units. These surface Cenozoic strata show gentle, homoclinal dip toward the Gulf of Mexico basin and record deposition transitional between continental and shallow-marine, but are dominantly progradational and increasingly terrestrial upsection. The Miocene units comprise alternating coarser-grained, tluvial-dominated lithofacies and fmer-grained, more marine-influenced lithofacies.

Gentle dips, semiconsolidated sediment, thick soils, and vegetation generally do not permit direct recognition of surface structure. Drainage lineaments, though suggestive of joint control of drainage, show no clear relation to strikes of measured systematic joints .

. The primary nonfuel mineral commodity of economic significance, aside from ground water, is gravel. Gravel occurs primarily in the upper Willis, assigned here to the upper Pliocene. Younger Quaternary units have varying but lesser potential for gravel.

Flooding is the sole geologic hazard. Flood-hazard potential was compiled from Federal Emergency Management Agency data and modified based on flood-plain topography. Landslide potential, inferred from steepest slopes and clayey substrates, is insufficient to constitute a hazard.

14. SUBJECT TERMS 15. NUMBER OF PAGES

Fort Polk, Surface Geology, Geologic Mapping, Stratigraphy, Sedimentology, Oligocene, Catahoula, x + 119 + appendices Miocene, Fleming, Pliocene, Quaternary Geology, Pleistocene, Willis, Lissie, Structural Geology, 16. PRICE CODE

Economic Geology, Geologic Hazards, Bogs, Seeps, Springs, GIS

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT

T Tn{'las~fiecl T Tnc1::lssifiecl T Tncll'lc;:c;:itip.n T Tnc1::lssifiecl NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89J USAPPC V1.00

Geology of the Fort Polk Region, Sabine, Natchitoches, and Vernon Parishes, Louisiana

Final Report

Prepared for Fort Polk

by Richard P. McCulloh and Paul V. Heinrich


with a chapter on Natural Occurrence Of Bogs, Seeps, and Springs by Bradford C. Hanson


for Prewitt and Associates, Inc.

under contract to U.S. Army Corps of Engineers, Fort Worth District

Contract No. DACA63-95-D-0051 Delivery Order No. 0008

Submitted by Elton R. Prewitt

Co-Principal Investigator Prewitt and Associates, Inc.

and Richard P. McCulloh and Paul V. Heinrich

Co-Principal Investigators

15 November 1999

CONTENTS

ABSTRACT Richard P. McCulloh and Paul V. Heinrich ....................... VI

ACKNOWLEDGMENTS .............................................. vii

INTRODUCTION Richard P. McCulloh and Paul V. Heinrich .................. 1 Location .......................................................... 1 Purpose ........................................................... 1 Methodology ....................................................... 1 Previous Work ..................................................... 4 Problems of Observation and Interpretation ............................... 7

REGIONAL SETTING Paul V. Heinrich .................................. 13 Physiography ..................................................... 13 Climatology ...................................................... 16 Flora and Fauna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 16

GEOLOGIC SETTING Richard P. McCulloh and Paul V. Heinrich ............. 18

STRATIGRAPHY Richard P. McCulloh and Paul V. Heinrich ................. 22 Tertiary System .................................................... 22

Eocene Series .................................................. 22 Claiborne Group ............................................. 22

Cockfield Formation ....................................... 22 Jackson Group (Undifferentiated) ................................ 24

Oligocene Series ................................................ 25 Vicksburg Group (Undifferentiated) .............................. 25

Catahoula Formation ....................................... 25 Miocene Series ................................................. 27

Fleming Group .............................................. 27 Lena Formation ........................................... 28 Carnahan Bayou Formation ................................. 30 Dough Hills Formation ..................................... 35 Williamson Creek Formation ................................ 36 Castor Creek Formation .................................... 37 Blounts Creek Formation ................................... 39

Piiocene Series Paul V Heinrich and Richard P. McCulloh .............. 43 Upland Allogroup ............................................ 43

Willis Formation .......................................... 46 Lithology ............................................. 47

Sandy Facies ....................................... 47 Gravelly Facies ..................................... 55 "Bleached" Sediments ............................... 57

1

Stratigraphy ........................................... 57 Allomembers ....................................... 59 Basal Contact ...................................... 59

Age ................................................. 60 Quaternary System Paul V Heinrich and Richard P. McCulloh .............. 70

Pleistocene Series ............................................... 70 Intermediate Allogroup ........................................ 70

Lissie Formation .......................................... 71 Prairie Allogroup (Undifferentiated) ............................. 71

Holocene Series ................................................ 72 Unnamed Alluvium (Undifferentiated) ......................... 72 Big Brushy Formation ..................................... 74

STRUCTURE Richard P. McCulloh and Paul V Heinrich .................... , 80 Structural Setting .................................................. 80 Faults ............................................................ 81 Joints ............................................................ 82

GEOMORPHOLOGY Paul V Heinrich and Richard P. McCulloh .............. 84 Geomorphic Setting ................................................ 84

Coast-Parallel Terraces ........................................... 84 Stepped Topography ............................................. 84 Ridge and Ravine Topography ..................................... 85

Structural Control Richard P. McCulloh and Paul V Heinrich ............... 85

NATURAL OCCURRENCE OF BOGS, SEEPS, AND SPRINGS Bradford C. Hanson ................................................... 87

South Group ...................................................... 88 North Group ...................................................... 97 Summary ........................................................ 100

ECONOMIC GEOLOGY (NONFUELS) Paul V Heinrich and Richard P. McCulloh 101

GEOLOGIC HAZARDS Paul V Heinrich and Richard P. McCulloh ........... 102 Flooding .......................................... ",.,',....... 1 02 Landslides ....................................................... 102

SUMMARY Richard P. McCulloh and Paul V. Heinrich ..................... 103

RECOMMENDATIONS Richard P. McCulloh and Paul V Heinrich ........... 104

BIBLIOGRAPHY .................................................... 105

11

APPENDICES A: Munsell Colors Detennined for Catahoula and Fleming Sediments ....... A-I B: Subsurface Geologic Sections ..................................... B-1

ILLUSTRATIONS

Figures 1. Location map and 7.5-minute quadrangle index ........................ . . .. 2 2. Location map showing major roads and highways .......................... 3 3. Supplementary location scheme used in text .............................. 5 4. Index of previous mapping incorporated to varying degrees in this investigation .. 8 5. Schematic diagram of relations among surficial deposits in the study area ...... 10 6. The problem presented by deeply cased oil and gas wells to correlation from the

subsurface to the surface ............................................. 11 7. Major drainages in Fort Polk region .................................... 15 8. Regional geologic and tectonic framework of the study area ................. 19 9. Dip section through the northern Gulf Coast along 94° west longitude ......... 20 10. Dip section along the Calcasieu River valley showing hypothesized allofonnational

interrelations among Plio-Pleistocene and Quaternary units ................. 21 11. Generalized paleogeographic aspects of nearshore Miocene (Fleming) facies ... 29 12. Photograph of channeloid lens of sand and sandstone cutting silt and siltstone,

Carnahan Bayou Formation of the Fleming Group, in quarry in Dowden Creek quadrangle [WC] ................................................... 33

13. Combined outcrop sketch and measured section of sediment of the Upland Allogroup cutting out two units of the Carnahan Bayou Fonnation of the Fleming Group, along roadcut, Peason quadrangle [SC] ...................................... 34

14. Unconfonnable relationship of Willis Fonnation and underlying Blounts Creek Fonnation ofthe Fleming Group, along U.S. Highway 171 in Kansas City Railway cut south of Pickering, New Llano quadrangle [SE] (redrafted from Welch 1942) 41

15. Measured section of Blounts Creek sediments exposed along south side of Holly Springs Road east of its T-intersection with Dugout Road, in Birds Creek quadrangle [C] .............................................................. 42

16. View to the west-northwest of "yellow loam" on grayish sandy clay of the Blounts Creek Fonnation of the Fleming Group, the uppennost portion of which shows

Puml''''h mott1A'" riA"" +he "'ortl ... .,ont adgo o.f' n ~o"l'n~ +n¥~ot : ... +1-.0 l\1DDC n-en D~-dn y.l...I.l...l'.I..1. .I."-'~, l..J.vu..1 L.l .1J..l.lI VVv.::t \.I v ~ a 111 v 1 1:5 l.a.le,\..I 11.1 Ll.1\..- 1V .1..1.'- cu a., VIi ~

Creek quadrangle [NW] ............................................. 44 17. Close-up view, looking approximately to the east, of purplish mottling ........ 45 18. Cross section along crest of Kisatchie Wold and across Calcasieu River Valley .. 49 19. Index map of locations of cross sections relative to the main post of Fort Polk .. 51 20. Dip sections across Main Fort and Peason Ridge areas of Fort Polk ........... 52 21. Combined outcrop sketch and measured section of Upland Allogroup strata in steep

gully, northwestern MPRC area, Birds Creek quadrangle [NW] .............. 54 22. Dip section along crest of Sabine-Red River drainage divide, and index map .. , 58 23. Cross section along interfluve on which Fort Polk and North Fort Polk lie ...... 61

111

24. Cross section along crest ofinterfluve separating Birds Creek and Little Sixmile Creek-Sixmile Creek drainages ....................................... 63

25. Cross section along crest of interfluve forming drainage divide between watersheds of Big Brushy and Ten Mile creeks ...................................... 65

26. Suggested correlation of stratigraphic units in southwest Louisiana with sea-level and coastal onlap cycles ................................................. 69

27. Stratigraphic profile of unnamed alluvium exposed by Mill Creek Road trench along Whiskey Chitto Creek in Zion Hills area ................................ 73

28. Depositional history of Big Brushy formation at 16VN794 Fort Polk .......... 76 29. Schematic diagram of processes associated with Big Brushy formation ........ 77 30. Joint-rose map of the study area, with stream net for comparison with

strike-frequency maxima of joints ..................................... 83 31. Spatial characteristics of bog polygons situated atop the Evangeline and Chicot

Aquifer Systems for the South Group area ............................... 89 32. Spatial characteristics of bog polygons situated atop the Miocene Aquifer System for

the North Group area ............................................... 90 33. Hydrologic and geologic relationships of bogs, Fort Polk quadrangle .......... 91 34. Hydrologic and geologic relationships of bogs, Birds Creek quadrangle ........ 92 35. Hydrologic and geologic relationships of bogs, Fullerton Lake quadrangle ..... 93 36. Hydrologic and geologic relationships of bogs, Kisatchie and northern Kurthwood

quadrangles ....................................................... 94

Tables 1. Stratigraphic classification of units mapped for this investigation ............. 23 2. Gravel sample, Willis Formation ...................................... 56 3. Radiometric dates from Eagle Hill II site (16SA50) ....................... 79 4. Hydrologic classification of stratigraphic units ........................... 98

Plates [CD-ROM] 1. Geology: Peason Quadrangle .................................... in pocket 2. Geology: Kisatchie Quadrangle ......................................... " 3. Geology: Dowden Creek Quadrangle .................................... " 4. Geology: Kurthwood Quadrangle ....................................... " 5. Geology: Slagle Quadrangle ........................................... " 6. Geology: Fort Polk Quadrangle ......................................... " 7. Geology: Simpson South Quadrangle .................................... " 8. Geology: Birds Creek Quadrangle ....................................... " C'GI L r..', " ':I. eo ogy: acamp ~uaQrangle ......................................... . 10. Geology: Fullerton Lake Quadrangle .................................... " 11. Economic Geology: Peason Quadrangle .................................." 12. Economic Geology: Kisatchie Quadrangle ................................ " 13. Economic Geology: Dowden Creek Quadrangle ............................ " 14. Economic Geology: Kurthwood Quadrangle ............................... " 15. Economic Geology: Fort Polk Quadrangle ................................ " 16. Economic Geology: Birds Creek Quadrangle .............................. "

IV

17. Economic Geology: Fullerton Lake Quadrangle ............................ " 18. Geologic Hazards: Peason Quadrangle .................................. :" 19. Geologic Hazards: Kisatchie Quadrangle ................................. " 20. Geologic Hazards: Dowden Creek Quadrangle ............................. " 21. Geologic Hazards: Kurthwood Quadrangle ................................ " 22. Geologic Hazards: Slagle Quadrangle .................................... " 23. Geologic Hazards: Fort Polk Quadrangle ................................. " 24. Geologic Hazards: Simpson South Quadrangle ............................. " 25. Geologic Hazards: Birds Creek Quadrangle ............................... " 26. Geologic Hazards: Lacamp Quadrangle .................................. " 27. Geologic Hazards: Fullerton Lake Quadrangle ............................. "

Diskette Differential GPS Location Readings of Point Data, Geology Theme ........ in pocket

v

ABSTRACT

Richard P. McCulloh and Paul V Heinrich

The Fort Polk region is underlain by Cenozoic terrigenous sediment comprising mostly the Oligocene Catahoula Formation, six formation-rank subunits of the Fleming (Miocene), and Holocene alluvium. Pliocene and Quaternary surface-stratigraphic units incise older units. These surface Cenozoic strata show gentle, homoclinal dip toward the Gulf of Mexico basin and record deposition transitional between continental and shallow-marine, but are dominantly progradational and increasingly terrestrial upsection. The Miocene units comprise alternating coarser-grained, fluvial-dominated lithofacies and finer-grained, more marine-influenced lithofacies.

Gentle dips, semiconsolidated sediment, thick soils, and vegetation generally do not permit direct recognition of surface structure. Drainage lineaments, though suggestive of joint control of drainage, show no clear relation to strikes of measured systematic joints.

The primary nonfuel mineral commodity of economic significance, aside from ground water, is gravel. Gravel occurs primarily in the upper Willis, assigned here to the upper Pliocene. Younger Quaternary units have varying but lesser potential for gravel.

Flooding is the sole geologic hazard. Flood-hazard potential was compiled from Federal Emergency Management Agency data and modified based on flood-plain topography. Landslide potential, inferred from steepest slopes and clayey substrates, is insufficient to constitute a hazard.

VI

ACKNOWLEDGMENTS

Many people gave to us assistance that was integral in the conduct of this project, and without which it could not have been completed. We are indebted especially to certain staff working on the base. The most frequent and essential help with operational matters was given by Jim Grafton, Bob Hays, and Gina Lay of the Environmental Learning Center at Fort Polk, and by Barry Oswald and the other Range Control staff who provided general scheduling of our access to land on the military reservation. Grafton and Hays also identified the different vertebrate-fossil sites and sub sites for Salley Marcantel, Wildlife Biologist and GPS technician at Fort Polk, who made differential GPS readings of the locations for inclusion in the file of GPS readings of point data on the accompanying diskette. Dr. Charles H. Stagg, Chief, Environmental and Natural Resources Management Division of the Directorate of Public Works at Fort Polk, was uniformly supportive of our efforts, and Mr. McCann provided crucial help in our scheduling of access to military land during training rotations. Millie Tew and Tamie Morgan (consultant) provided helpful GIS-related consultation early in the project.

Dr. A. Frank Servello, of the U.S. Army Corps of Engineers (US ACE) Fort Worth office, served as project technical manager for the greater part of the period of performance during which field work was conducted and, in addition to the specific assistance required for a number of needed contract modifications, contributed an avid interest in the work. Stephen Austin of the USACE Fort Worth office, following Servello's departure and our completion of most of the field work, served as project technical manager for the remainder of the period of performance.

David Hinds, masters student at Louisiana State University, provided fruitful consultation on the results of his own geological investigations of a portion of the present study area over a two-pIus-year period, and his pre-Prairie contacts are incorporated with minimal revision in the maps accompanying the present work. Dr. Judith Schiebout, who served on Hinds's thesis committee and has directed the investigations into the Miocene vertebrate fossil localities in the Castor Creek Formation of the Fleming Group, contributed helpful discussion and support on many occasions. John Anderson, who directs the Cartographic Information Center administered by the Louisiana State University Department of Geography and Anthropology, provided invaluable access to and assistance with assorted maps and images in that archive.

Several U.S. Geological Survey (USGS) personnel provided information and assistance in the form of consultation, file data, and copies of USGS reports. The following hydrologists assisted us with information about USGS subsurface data and helpful discussion regarding ongoing USGS work at Fort Polk: Mark Gremillion, of the office at Fort Polk, and John Lovelace, Larry Prakken, Rob Fendick, and Roland Tollett, of the Water Resources Division district office in Baton Rouge. In the Baton Rouge office, Wendy Lovelace assisted us with access to subsurface data in the USGS files, Larry Prakken provided data including digitized well logs and cross sections compiled by him for the Fort Polk region, and Darlene Smothers provided us with copies of open-file and water-resources investigations reports.

vii

M. Earl Stewart, wildlife biologist with the U.S. Department of Agriculture, provided access to aerial photos and maps in the files of the National Forest Service, Vernon Ranger District, Kisatchie National Forest. The following employees of timber companies active in the study area helped provide critical access to large tracts of nonmilitary land: Robert H. Crosby, of Crosby Land and Resources, Mandeville, Louisiana; Darwin Foster, of Temple Inland Inc., Diboll, Texas; Mike Hudson, of the Temple Inland Inc. office in De Ridder, Louisiana, who gave a positive account of our work to Darwin Foster and helped us obtain permission for access; Rick Leeper, forester with the Temple Inland Inc. De Ridder office, who provided keys for access to gated properties; and Bob Nolan, of the Boise Cascade office in Provencal, Louisiana, who gave us permission and keys to access gated properties.

Latimore Smith, ecologist with the Louisiana Natural Heritage Program, Louisiana Department of Wildlife and Fisheries, has for years been a source of fruitful discussion regarding the relationship of geology to natural habitats, specifically plant communities. For this project he provided helpful orientation for the work on hillside seepage bogs. Phil Hyatt of the Kisatchie National Forest in Pineville, Louisiana was an invaluable source of information on hillside bogs, and provided the data utilized in this report.

Reed Bourgeois, Computer Analyst with the Louisiana State University Basin Research Institute (BRI), provided the crucial use of BRI's large-format scanner and scanned the work sheets of all the plates. His services were also instrumental to the subsurface component of the work: he compiled for us from the BRI database a comprehensive listing of oil and gas wells drilled in the study area, and constructed and produced the subsurface geologic cross sections and base map (Appendix B).

For producing the illustrations-including the accompanying suites of maps-in-house at the Louisiana Geological Survey (LGS), we are indebted to the staff of the LGS Cartographic Section under the direction of John Snead, Cartographic Manager. Lisa Pond, Research Associate, produced most of the illustrations for this report. Production and assistance with the production of a number of the illustrations was provided by Robert Paulsell, Research Associate; Edward Koch, Research Associate; Edwin B. "Bud" Millet, Cartographic Supervisor; and David W. Griffin, Research Associate. R. Hampton Peele, Research Associate, designed, and supervised the development of, the Geographic Information System. The following persons contributed to the GIS data compilation: David W. Griffin, Research Associate; Meenakshi Gnanaguruparan, Graduate Assistant; Mohiuddin Shaik, Graduate Assistant; Louis Temento, Graduate Assistant; Barbara Olinde, Student Worker; Sait Ahmet Binselam, Graduate Assistant; Jesus G. Franco, Research Associate; Asheka Rahman, Graduate Assistant; Tiffani Cravens, Student Worker; Andrew Beall, Graduate Assistant; Xiaojue Pan, Graduate Assistant; and Steven J. Rainey, Graduate Assistant.

Margo Olinde, LGS editor, provided helpful consultation regarding the formatting and editing of the draft in all stages of its preparation. Louisiana State University geology undergraduate student Tiffani Cravens, with support from the Mentored Field Experience Program of the Association of American State Geologists, assisted with field work and with GIS-related tasks in the final phase of the project.

V1l1

Finally, acknowledgment is made to two geologists who have had a positive shaping influence on this work through their previous investigations and their helpful conversations about them over a period of some fifteen years: H. V. Andersen (Professor Emeritus, Louisiana State University Department of Geology & Geophysics), who mapped the geology of Sabine and Natchitoches parishes; and James E. Rogers (U.S. Geological Survey retired, now a consulting ground-water hydrologist), who has investigated the surface and shallow-subsurface geology in Vernon Parish and many other parts of the state. Each has spent decades working in his respective areas. The basic framework of pre-Plio-Pleistocene geology available in our study area in the years since the mapping of Rapides and Vernon parishes by Fisk and Welch, and prior to the work of Hinds-and within which we were fortunate to be able to conduct our investigation-was laid principally by these two geologists. Where our own observations (exposures and/or access) and the information available to us have proved inadequate or inconclusive, we have generally deferred to a previous map interpretation made by one of them. It is our hope to have done so no more than was necessary and appropriate. We are also indebted to Rogers for fruitful consultation and for his comprehensive technical review of the draft version of this document; nevertheless, we are wholly responsible for all aspects of this final report and its accompanying plates.

IX

INTRODUCTION


LOCATION

The study area, herein termed the Fort Polk region, comprises the ten 7.S-minute quadrangles encompassing the Fort Polk Military Reservation and the Peason Ridge Military Installation, in portions of Sabine, Natchitoches, and Vernon parishes, Louisiana (figures 1,2).

PURPOSE

The objectives of this investigation were basically threefold. The first was to provide the u.S. Army at Fort Polk with basic geologic data essential to the environmental applications of its ongoing environmental programs. Next was to continue and enlarge upon the work of Hinds (1997a, b; 1998a, b, c; 1999) toward providing a more detailed stratigraphic and geologic context and framework for the Miocene vertebrate fossil localities recently discovered at Fort Polk and investigated by Schiebout (1994, 1997; Schiebout et al. 1996). Finally, the work continues and refines the Louisiana Geological Survey's recent geologic mapping activities encompassing the Fort Polk region (Louisiana Geological Survey 1993; Snead et al. 1998), and its efforts toward placing the region in a statewide geologic context.

METHODOLOGY

Access to military land in the study area was coordinated primarily through the Fort Polk Range Control office, and access to nonmilitary properties was obtained principally through coordination with timber companies and hunting clubs. Field work was conducted in excursions of several-day to two-week duration. The widespread presence of surficial deposits covering the stratigraphic units mapped for this investigation, and of thick vegetation, are such that exposures are in general scarce. Artificial exposures occur with greatest frequency along roads and trails, and natural exposures along the beds, cutbanks, and valley walls of streams and rivers. The overwhelming majority of exposures examined for this investigation comprised those of a small and inconspicuous nature in the ditches along roads, although the better exposures included roadcuts and natural bluffs, some sizable. An attempt was made to cover all roads accessible with a standard four-wheel drive vehicle, and to selectively gain access to intervening areas on foot where exposures appeared likely.

Notes were recorded on copies of the topographic base maps for each of the ten 7.S-minute quadrangles in the study area, and in field books. Field observations were used to discriminate areas of consistent gross lithology and internal features to delineate the different map-unit polygons, the boundaries of which were fitted to the topography as

1

N

Figure 1. Location map and index to 7.S-minute quadrangles covered by the study area.

w

Figure 2. Location map showing major roads and highways traversing the study area.

much as possible. The interpreted polygons were then selectively checked against aerial photography, including principally that used as a base for soils mapping by the Natural Resources Conservation Service (NRCS) [formerly Soil Conservation Service (SCS)], and against soils mapping and data included in NRCS/SCS parish soil surveys for Sabine, Natchitoches, and Vernon parishes.

Pliocene units, and Pleistocene units associated with terrace surfaces, were found to be divisible into three main groups: Upland, Intermediate, and Prairie. As indicated by Snead and others (1998), their characteristics are suitable for informal classification as allogroups (units characterized by bounding unconformities), and this was the approach used in this investigation.

The alluvium underlies the bottomlands of streams and their upland tributaries. Because these are incised into the older and higher strata of the surrounding uplands, alluvium could be mapped as a network of low-relief flood-plain and bottomland landforms discernible from the topographic information on the base maps of the 10 quadrangles composing the study area. This is the most systematic method of mapping alluvium, and the one that provides the greatest consistency of interpretation within and among the constituent quadrangles. No differentiation of constituent geomorphic/depositional facies was possible in the largest river system in the Fort Polk region, the Calcasieu River flood plain and the bottomlands of its larger tributaries; therefore, all the stream alluvium rendered on geologic maps accompanying this report is undifferentiated.

In this report, priority is given to metric units of measure, which are followed by equivalents given in English (U.S. Customary) units. Exceptions are made for direct references to elevation values from the topographic base maps, which give elevations in feet, and with measurements derived from subsurface information, for which usage in the US. dictates measurements in feet. In these instances, measurements are given first in feet and are followed by equivalents given in meters, except on the subsurface geologic sections of Appendix B, the scales of which are given in feet only. When referring to locations in the text, we have used the U.S. public land survey grid system (section-township-range designations); we have done so because this grid is rendered on the US. Geological Survey topographic quadrangle sheets used as base maps for this investigation, whereas the Universal Transverse Mercator (UTM) grid is indicated only by ticks along the edges of the base maps. The scheme diagramed in figure 3 is used in parts of the text as a supplementary loeational aid; thus, "Peason quadrangle [NET' refers to the northeastern ninth of the named quadrangle. In some parts of the narrative where we refer to color in general terms rather than using Munsell designations, we have appended the suffix -ish to color names (e.g., "grayish") to emphasize the general nature of the designation.

PREVIOUS WORK

The basic framework of pre-Plio-Pleistocene geology in the study area is the work of Welch (1942) as emended by Rogers (1980) and Hinds (1998a, b, c; 1999) for the Miocene, and that of Andersen (1960, 1993) for the Eocene and Oligocene. The primary

4

NW NC NE

we C EC

SW SC SE

o 1 2 Miles I I I

o 1 2 Ki!ometers I I I

Figure 3. Supplementary location scheme used in this report, utilizing 2.5-minute ticks on individual 7.5-minute quadrangles of which the study area is composed.

5

foundation for the present study was originally laid by Fisk (1940) and by his student Welch (1942). Fisk (1940) introduced the sixfold subdivision used for the surface and near-surface Miocene Fleming as part of his investigation of the geology of Rapides and Avoyelles parishes to the east, and Welch (1942) applied this framework in his investigation of the geology of Vernon Parish. Welch did his field work principally in the late 1930s, at a time when much of Vernon Parish was clear-cut by timber interests, but he had essentially no topographic control with which to guide the rendering of his observations and interpretations.

Watson and Kirksey (1963) conducted photogeologic mapping of a large area in west-central Louisiana and adjacent Texas- for Sinclair Oil & Gas Company, and supplemented it with extensive field checking. The study area encompassed portions of two Texas counties and four Louisiana parishes, and included all of Vernon Parish. Their investigation was done at an impressive level of detail, although it appears that at least some of their photogeologic map units were defined differently from the stratigraphically defined units mapped for this investigation.

Rogers and Calandro (1965) revised the mapping of Vernon Parish geology from that of Welch (1942) based primarily on shallow-subsurface data from water wells. Rogers (1980) continued this revision based on both water well data and field checking, and his rendering of Vernon Parish geology was the one used for the 1984 compilation of the 1 :500,OOO-scale Geologic Map of Louisiana. This investigation follows very closely his mapping of the Lena Formation of the Fleming Group. Though the Lena is relatively well exposed, it has a narrow outcrop belt and can be distinguished from adjacent units more by its somewhat higher proportions of finer-grained textures than by any suite of lithologies that could be considered diagnostic; thus, we were unable to improve on his mapping of it.

Andersen (1960,1993) mapped the geology of Sabine and Natchitoches parishes, the southernmost portions of which overlap the study area of this investigation. Andersen did not subdivide the Fleming, and lumped it with the Catahoula as "Miocene (Undifferentiated)." This investigation follows very closely his mapping of the older Paleogene Tertiary units (Cockfield, Jackson, Vicksburg) in the northern- and northwesternmost reaches of the study area because of extremely sparse exposures there.

Schiebout (1994, 1997; Schiebout et al. 1996) has elaborated a new and growing biostratigraphic framework for the Miocene of Fort Polk and the surrounding region following the recent discovery of vertebrate fossils in the Castor Creek Formation of the Fleming Group on Fort Polk. Her investigations of these fossils and the need to place them in a more detailed geologic framework provided the main impetus for the work of Hinds (1997a, b; 1998a, b, c; 1999), and led to U.S. Geological Survey support for his work under its Geologic Mapping Education Program (EDMAP). Because of overlap of the periods of performance of Hinds's and our projects, we were privileged to engage with him in an ongoing dialogue, and to participate jointly in the accumulation of new observations and evolution of concepts regarding their interpretation. For Hinds and the present authors, our situation was essentially the reverse of that obtaining during the work of Welch (1942): we had good, detailed, and comprehensive topographic control, available as the 7.5-minute quadrangles used as base maps, but a general scarcity of exposures. Early in the conduct of this investigation the mapping of Hinds (1998b, c)

6

was still in progress; in ongoing consultations with him and with Fort Polk it was agreed to incorporate his Miocene unit contacts in our mapping for the portion of our study area overlapped by his study area, and to focus our efforts primarily on other parts of the Fort Polk region. We have done so with minimal revision, although our mapping makes substantial revisions to his Plio-Pleistocene contacts in places.

Prior to the recent work of Hinds (1998a, b, c; 1999) the only refinements of Welch's (1942) original Plio-Pleistocene framework of the area that were both publicly available and based on substantial field work were Andersen (1960) and Bianchi (1982). Rogers (1982, 1993, personal communication) had suggested for many years the potential for the occurrence of surface Pliocene strata in the area based on lithological characteristics and elevation of the older and higher Citronelle-type remnants, and had led the present authors and Hinds to some of the better candidate examples on different occasions beginning in 1993. Snead and others (1998) utilized both the mapping of Hinds (1998b, c) and preliminary results from this investigation, principally those relating to the postulated presence of surface Pliocene strata, in their preparation of a Quaternary Geologic Map of Louisiana as part of a cooperative agreement with the U.S. Geological Survey under its State Geologic Mapping Program (STATEMAP).

The distributions of the areas in which we relied to a substantial degree on the mapping of Tertiary units by previous investigators as mentioned above is shown in figure 4.

PROBLEMS OF OBSERVATION AND INTERPRETATION

Problems encountered in the conduct of the work derive primarily from the scarcity of exposures. In addition to being generally scarce and largely inconspicuous, exposures in the study area also tend to have an ephemeral character except where they are frequently renewed by stream erosion or road-related maintenance. (This was illustrated to the authors when they took David Hinds to see some joints measured less than two months earlier in a road ditch in the Lacamp quadrangle [NW], only to find the exposure now covered with deadwood and redeposited sediment.) Additionally, repetitious textures occur in sediment of all ages in the study area; virtually all strata consist of sediment of the same basic types, comprising sand, silt, and clay in varying proportions, reflecting the repetitive recycling of terrigenous material through time and blurring possible lithologic distinctions. The closest thing to a diagnostic lithology is the calcareous-nodule-bearing clay of the finer-grained Fleming subunits, though such clay may also occur with lesser frequency in certain of the coarser-grained subunits. The members of the Fleming defined by Fisk (1940) constitute gross lithofacies, and though they may approximate lithostratigraphic units locally, they are identified primarily on the basis of gross lithology and position in the stratigraphic sequence.

The generally unfossiliferous nature of the Catahoula Formation and younger strata of the surface and shallow subsurface is such that fossils are largely unavailable to help with the problems of identification and classification. The only potential guide fossils are represented by Potamides matsoni and its associated fauna, reported by others from the Castor Creek Formation ofthe Fleming Group (Fisk 1940, in Rapides Parish;

7

Peason Kisatchie

Dowden Creek Kurthwood

Andersen (1960, 1993)

_ Rogers (1980)

lLI Hinds (1998 b,c)

Simpson South Lacamp

Birds Creek Fullerton Lake

Figure 4. Index of previous mapping incorporated to varying degrees in the mapping done for this investigation.

8

and Welch 1942, from a hand-auger borehole in Vernon Parish), but not observed by Jones and others (1995), Hinds (1998a, 1999), or by us in the course of recent investigations.

The sediment composing the stratigraphic units in the study area is generally poorly consolidated, and is heavily weathered in places. Lithified rock, primarily sandstone, occurs with noteworthy frequency only in the Catahoula and Carnahan Bayou Formations. All the map units of the landscape except for Holocene alluvium are routinely mantled by veneers of surficial units (figure 5); these comprise mostly red and yellow loams less than 2 m thick, but also include brownish red to reddish brown sandy colluvium and pedisediment up to 1 m thick in places, as well as lightish sandy material less than 1 m thick, and postulated to have an eolian origin at least in part, on ridge crests. The latter constitutes the informal Big Brushy formation previously described by Bianchi (1984), in which A and E soil horizons tend to be developed where it is present.

Generally, the Plio-Pleistocene is heavily oxidized and the Miocene shows more of a gleyed aspect, but exceptions occur both ways: cross-bedded Miocene sands of relatively coarser texture (principally of the Carnahan Bayou and Williamson Creek formations of the Fleming Group) are oxidized heavily in places and resemble the Plio-Pleistocene, while the Willis in places is bleached-looking and colored in grayish hues similar to those more characteristic of the Miocene. The Catahoula can also be heavily oxidized and resemble the Plio-Pleistocene locally.

The irregular configuration, with potentially substantial relief, of the base of the older and geomorphic ally higher of the Pliocene and Pleistocene units (those classified herein as subunits of the Willis and Lissie), together with the low structural dip of the underlying Tertiary units, can also present problems of interpretation. For some areas there are indications that narrow tracts of Miocene may be exposed along the escarpments delineating and separating the overlying Plio-Pleistocene units, but it was not practicable to ground-truth them all. Such narrow tracts of Miocene sediment probably occur mostly in areas where subunits of the Willis and Lissie are the main map units. For example, a few such occurrences of the Blounts Creek Formation of the Fleming Group were observed in the Fullerton Lake quadrangle [N"E], and may in that area be more numerous than depicted.

We consulted subsurface information, primarily electric logs of water wells and oil and gas wells, in an attempt to provide an independent constraint on the mapping of the surface units. Typically (though not uniformly), the depth distribution of subsurface information in the northern Gulf Coast contains a sizable gap owing to the deep casing of oil and gas wells from the surface and the failure of most water and other types of wells to bridge this gap (figure 6). Nevertheless, we speculated that enough well logs could be found and examined in enough critical places to constitute effective third-dimensional control. Review of available subsurface information for the study area initially indicated it to be of limited help in this regard because of its incompleteness (too-deep surface casing or too-shallow total depth) relative to our purposes. Our aims became modified to focus on complementing the subsurface work already presented by Rogers and Calandro (1965) and Hinds (1998a, 1999), and on determining the precise stratigraphic position within the Castor Creek interval of the conglomerate beds containing the vertebrate fossil accumulations described by Schiebout (1994, 1997; Schiebout et al. 1996).

9

...... o

E horizon/"Big Brushy" IHolocene Colluvium

" i .;:~~~\~1-:~'fr:'!Z\:.'i:;.,;;' _""""~,,, ~~ .. ' .. :t;.;;: ....... ':: .. ':' : Upland Allogroup·.·. : . : " "---.:,, ' '" "':::: ~*'" .: ::,' . '. ". ....... .. '. .... . . . "~'''~'~'~~''~'''':;: ~.:.'... :.: ........... :." .' .. ' .'. ' .. ; ..... :' .. '

"~,,,,~,, "", ?:"""~"~~ .':-:":' .:...... .' '.' " '., ..' "~~~"~'::~~2:-,\~~ ~~~~"'~'::"--~2:-,~.:.::::::> Holocene and : ;.:.:::: ,:.; :.:.:- ....... :.: .. :,::. ,:.: :.:.:-: ...... :.; <: .::. ,:.: ... :.:..- ....... :;. " :::?' ~~"~" ~~' ,,~, :::?'?: ~"'~" ~;~' ,,' .... . .;:....... . .. :'.;. :., ::.::: :':;':.:': :.;. .'::::.:'.: :'. ;':.:: '.;' . .:::: .... : :':":.:: '.;' :.:. ~,?:,,,~,,,~,,,,~:\:,,~"~""~~"'~".\:\:",,,.,:. ':'.:. Pleistocene . : ....... :,,':'" .: ... :: ........ : ... : .. :.: ..... :-: ....... : ... :.::.: .... :...: ...... : .. : "~,~",,,:\:""'" "~'''''''':\:'\''~' : ':/'(:>", .;'. :::: :'" :' ••. '. "':.' :.'. :' .•. '. "':.' :.'. :' ••. '. '.' .... :." ~~'\~~~~~~~,~~~~~~~ ~~~~~~::-,~~~~~.::::. :;:'. '!/"·';F. alluvial fill . :::·r·:·'::: :.::-,,: ::'. ':.; :.:-:. '.": :.:-.. : ::'. ':.: :: .... '.": .: .... : ::'. ':.: ...... :<:.: ... :' ~~\~~\~~~~:;~~~~\~~\~~~~\1'~~~\~~'\~.: .. :: .. :(:>""0 ":': :'. , .. : .;.:::»' .. ::>::,::'. ::::':':.:':':'.::>::":'. ::::':'::':':"::::'::'::'. ::::;':.:';:".::::'::,::'.: ",~~ ,,~, ,,~,~~:;, "'~~ ,~, ,~,~::::,~, :\:,~~ ,,~, ,,::;: ..•.. tp. ~ ::.. . ... : :: .. '. ..... .:. :." .. ..... . ... :." .. ..... .:. :." ., ..... . ...

~~~~~~~t)~tt~~~~~~~\~~\\~~\~j~.;~<:'f;;.~:·: {;\//'//::::; ... :/.>.:: .. :./>~~:::~ .. ~.:::;:'.:. .. :: ... :::}.::;::.:;::.:.:.; .. ::~.:.~:;: ... > .. ::;: .. :.~./:.~\:::;> . .;:. .. <": .. :;'::' ~\\'2:~,~~ ,,~~ ,~---':,MlOcene Fiemmg ::::\\~~,~~:\:~~~~~ .: :: .. ;.... . '.:::.::: ::.;-:' .. :.:: .. , :.::::.::: .;.;.MlOcene Flemmg :. '.::.:: ::".;-:' :.::.:. '.: .

,,::,::,,' ",~~,,~,~ ::::~''''~''' '" ,,~,,';' '.':' .:.':'" ................. : .... ;.. ...: .... ;.. : ....... '. ?'~'::£~\~~,~~:\:~'\ n~~d!/mu~st4?ne ~~h~~~~~~1:~~~~~ ':'. ::,:.:.. ..: ;.: .. :.:.: .... : .... :: .... :: .. ;.>:>.: .. :: .... :> .. sand/s~dstone >: .... : .... :: .... :::. :<::':: . . '" ?:" ''''~''''?:.:\:' ,,~'\ ~,,\ ~"'~" .,~' ,~' ~,~ ~"'~' ,,~ ~~'~'". . . :.' '. . .:.' .: ..... :.' ' .... : ......... : .. ' .... : .' .: ..... :., ' .. '.:.' .:. ". :., ' .. '.:.' .: ..... : ~~~ ?:'::~''''~''?:.~' ,,~, ~,::,,~,,~'\' ~:\:' ,,~, ~'\~"'~"?:.~' ,,~, ~,~ ... : '.:" .. :: :'.: .'.,,'.: .. : .... ::: .. : '.',": .. : .... ::: .. : '.',": '.:" .. :: :.: '.':': .. : .... ::: .. '.':': :"",,,~,~~,,, :\:"'''' "::::''::'''''':\:'''''' "~'''''':\:''''':\:' ", ?:," ..... :.: .......... :.: ... :. :.: ......... : .. : .. :' .. :: .......... :.: ... : .. :: ....... : .. : .. : ... : .. :: ....... :: .... : ... :. ~ ,,~, ~,"~~, "'~~ :...~, ,,~,~~, ' "'~~ "~',,~ ,::::~,~ ~,~, "~'''~ ,~~ .... :. : .. , . ' .. '.: ........ :. : .. ' . ' .. '.: ...... '.:. : .. , . ' .. '.: ...... :.: . .:.- .... '.: : .... :.: ...... : .... :." ~~ ,,:::::~ ,,~~'::~:;-:::: ~,,~~ ,,~, ,,~,~:::::\\'2:~,~~ "~,, ,,~~\:::::::~'Z~,\::~ ,,~\,~?:~~~ .. ;.': :: ....... '.:::; ....... : :: ....... .: ;:; .' .... : :: ....... .:;:; .' .... : :: ........ :;:; .' . '. ::. :: ...... ::;:. 2..,~~ ,,~, ,,~,'::~\\'Z~,~~ ,,::::' ,~,'::::::.,~~,,~~ ,,~',~ ~'::~,~:\:'~~ ~'~:...~ ~':::::::"~ . ;'::: .: ..... : :'.::' :.:'., ;'::: :':'.: ".< .. :., ;'::: :'.'.: ".<.:'., ;'::: :':'.« .. :., ;'::: : ':'.: ".

,-::::-,~~ ~~~~~~~~0~~'~~::::~~~~,::::.\::~0~~'~~:\:~~~~ ,~'::h~~'\::';:, ~,~~~ ~~~~" .; ........... : ... ::,' :.:;.;' .;.:.: ..... :'.:. ::: .... :-.-: .;.:.,' ..... :'.:. ::,' :':;':' .. : .. ,' ..... :'.:. ::,' :':;':' ... :.,' ..... :'.:. ''',~''',',,~,:::::~, :"'",,,, "",,~~, ~",'\", ,,,,,,,,,,~,,,,,,, ",',""".: .............. : . .; ................ : .. ; ................ : .. ; .................. : . .; ............. . ~\'(~,~~~~\~~~'::~~\~~,~~:\::::::~~~:;~~~~~,~'::~~~~~~~~~h~~~~~~\~~~~h,,~ ":":':':~' :':'.:'" :.:.::::-;, ... :: ...... :: ... : ... :.:.0::-.",.' ... :.: ...... :.: .... : .:.: . ....:.: ;:': .. :.:/:.: .. :.; :.: ..... : ;.'''::, "," ~"" '" ...... , ""'"~''' '" "" ="""~" ,~,,,~, "''',,,'S,,,,:\:'''~' :\'~~'" ' .. ' . .' ......... '.:-. .' :.' ..... '.:-.::' ......... :-. :' ....... ": ,:::::~~, ",~~ ,,~, ,,~0.~:::::' ' ~,,~~ ,,\::',,~ ,,::~,~ :\:'~' '" "~'\::~''''~''' '" "~~,,,,,,~.,, . ..... .... ...... ' ................ '. ; ..... ' .. ....... '. ; ........... . ","0~'~ ,,0.0 ,~, ,~,0 0.~" ",~~ ,~, ,~"~0':" 0.':\:~ ,~, '~'0~,,' -0.'~~ ,,~, ,,~ ,~~,,~ , .. :.' .. ' ..... " '.' ..... : .... '. " .. " '.' ..... : .... '. " .. " '.' ...... : .... '. " .. " '.' ... . '_"''0-0.,,,> ,"Y>" " ',"',,:-.:' '.' .":\".",.,, ~,-' '" "" ,:;:", " ~",' .......... : .. : ..... : ......... : ..... : ...... :: '.:'.' .: ...... '.

Figure 5. Schematic diagram (no scale) of relations among surficial deposits in the study area, and the problems presented by such deposits to the mapping of the underlying surface-stratigraphic units recognized in this investigation. Only one type of surface deposit-the black surface soils-serves as an actual guide to the underlying parent material, the finer-grained formations of the Miocene Fleming Group (Welch 1942; Rogers and Calandro 1965); all the other surficial deposits can be underlain by any of the mapped surface-stratigraphic units.

........ ......

I~

/

SCHEMATIC DEPTH DISTRIBUTION OF SUBSURFACE INFORMATION FROM

GULF COAST WELL LOGS

NO

r WELLS. I T- , _ WATER MINERAL-EXPLORATION

WELLS, ETC~ -J

DATA

s

OIL AND GAS

-WELLS

Figure 6. The problem presented by deeply cased oil and gas wells to the correlation of subsurface stratigraphic units to the surface (reprinted from McCulloh 1993).

In addition to the above problems of interpretive lithostratigraphy, the stratigraphic classification of many of the units mapped for this investigation is beset by long-standing problems and controversies relating to their age, because no unequivocal age-diagnostic faunas are known from their updip portions. The older units of the strata herein given the general designation of "Plio-Pleistocene" [Citronelle-equivalent =

Upland Complex of Hinds 1998a, 1999], and comprising subunits of the Willis and Lissie as used herein, have been classified exclusively as either Pliocene or Pleistocene by various workers in the past. Hinds (1998a, 1999) reviewed the context of Fisk's (1938) probable predisposition toward a Pleistocene classification of these units in Louisiana, which over the last several decades could have created an apparent dearth of surface Pliocene strata as an artifact of the classification prevailing here. Some of these units are herein given a Pliocene classification, as inferred from aspects of their distribution in three dimensions, and in accordance with the ideas of Rogers (1982, 1993, personal communication) and Hinds (1998a, 1999). The Catahoula Formation has a tradition of being classified as Miocene among surface mappers (e.g., Andersen 1960 and 1993), whereas its accepted subsurface equivalents (Frio and Anahuac) have long been classified as Oligocene. The validity of the correlation of these surface and subsurface units, and the accuracy of the relative-age dating of the subsurface Frio and Anahuac as Oligocene by foraminiferal micropaleontology, are both upheld despite decades of these two different usages. We therefore follow the interpretation of Galloway (1977) and Galloway and others (1982), as was done by Hinds (1998a, 1999) and tentatively by Snead and McCulloh (1984), and accordingly classify the Catahoula as Oligocene.

An added operational complication was presented by the age of the editions of the base maps used for the field work, which date from the early 1950s, early 1970s, and late 1970s. Many of the roads on them have been reconfigured to a substantial degree since their release: many are now gone, many of those remaining are now significantly changed, and a number of new ones have been added. In some instances it became necessary to spot-check locations with a Global Positioning System (GPS) receiver to trace the routes of present-day roads on the field/work maps.

12

REGIONAL SETTING

Paul V Heinrich

PHYSIOGRAPHY

The study region lies in the West Gulf Coastal section of the Coastal Plain Province of Thornbury (1965). It consists of coast-parallel Quaternary terraces along its seaward edge and deeply dissected Tertiary uplands characterized by a series of coast-parallel cuestas and lowlands inland of the terraces. The cuestas are commonly called "wolds" and the lowlands are less commonly called "vales." The cuestas have steep inland-facing escarpments and slope gulfward. Erosionally resistant gulfward-dipping strata create these cuestas. This belted topography is less well developed in the West Gulf Coastal section than it is in the Coastal Plain Province east of the Mississippi River (Murray 1961; Thornbury 1965).

Within the West Gulf Coastal section, the Fort Polk region lies at the boundary between the coast-parallel terraces and the belted uplands between the Sabine and Calcasieu River valleys. The southernmost cuesta, called the "Kisatchie Wold," dominates this region almost completely. Within the Fort Polk region, the Kisatchie Wold consists of two distinct cuestas. Only a very small part of the coast-parallel terraces lies within the study region. Local alluvial valleys of local streams and rivers that drain the Fort Polk region are an additional and significant part of its physiography.

The southern of two cuestas of the Kisatchie Wold encompasses all of the Main Post and most of the Birds Creek, Fort Polk, Fullerton Lake, Lacamp, Slagle, and Simpson South quadrangles. The southern edge of this cuesta is a well-defined escarpment 30 to 50 ft (9 to 15 m) high. This escarpment separates the highly dissected cuesta from the flatter, less dissected coast-parallel terrace surface to the south. Except in the Fullerton quadrangle, this escarpment lies south and out of the study region. The northern boundary of this cuesta is a coast- and strike-parallel lowland occupied by the alluvial valleys of Bayou Castor, Cypress Creek, and an east-west segment of the Calcasieu River.

The southern cuesta rises in elevation from about 270 to 290 ft (82 to 88 m) along its southern edge to an elevation of 400 to 440 ft (122 to 134 m) along its crest. Northward of this crest, it drops rapidly into the lowland formed by the valleys of Bayou Castor, Cypress Creek, and Calcasieu River. The southern cuesta is deeply dissected by a series of northwest-southeast trending drainages. Topographic profiles along the crests of ridges between the major drainages show that the southern cuesta rises as a series of topographic steps instead of as a gradual slope. The southern cuesta is composed of gulfward-dipping strata of the Blounts Creek and Castor Creek formations of the Fleming Group capped by the Willis Formation of the Upland Allogroup.

The northern cuesta encompasses all of the Peason ridge area (Peason Ridge Military Installation) and most of the Dowden Creek, Kisatchie, Kurthwood, and Peason Ridge quadrangles. The southern boundary of the northern cuesta is the previously noted

13

strike-parallel lowland. The northern boundary of northern cuesta is another strike-parallel lowland composed of the alluvial valleys of Bayou Toro, Mill Creek, Goodson Creek, and Middle Creek. The northern cuesta rises gently and irregularly from an elevation of about 350 ft (107 m) along its southeastern edge to just over 450 ft (137 m) within the Peason ridge area. The highest summit in the region, Eagle Hill, which has an elevation of 463 ft (141 m), lies within the Peason ridge area. North of Eagle Hill, the northern cuesta drops down to about 400 ft (122 m) where it forms an inland-facing escarpment. The Fleming and Catahoula Formations underlie the northern cuesta.

Coast-parallel terraces, which comprise the southern fifth of the West Gulf Coastal section, were mapped only within southern and eastern parts of the Fullerton Lake quadrangle. This study recognizes two terrace surfaces, which represent separate members of the Lissie Allogroup. The higher and older terrace surface forms a narrow belt, about 0.8 to 1.3 miles (1.3 to 2.1 km) wide, that lies between the Kisatchie Wold and the lower terrace. It is dissected, but unlike the Kisatchie Wold, it still retains large remnants of its original terrace surface and has far less relief. The lower and younger terrace surface is the northern edge of an extensive, gulfward-dipping terrace that extends southward from the study region into Calcasieu Parish. Except where it is offset by fault-line scarps, this terrace surface dips gulfward at 4 ft/mi (0.8 mlkm).

The local stream and river valleys are dominant features of the regional physiography. They deeply dissect the belted topography of the Tertiary uplands and the Pleistocene coast-parallel terraces. Within the Tertiary Upland, coalesced valleys form the lowlands separating the cuestas. The drainages associated with these valleys belong to one of three major drainage basins present within the Fort Polk region.

Tributaries of the Sabine River drain the western edges of both the southern and northern cuestas (figure 7). Bayou Zourie, Cypress Creek, Dowden Creek, and other tributaries of Anacoco Bayou drain the northwestern corner of the Fort Polk quadrangle, the western edge of both the Slagle and Kurthwood quadrangles, all but the northeast corner of the Dowden Creek quadrangle, and southwestern part of the Peason quadrangle. The valley of Cypress Creek, forms part of the lowlands that separate the southern and northen cuestas. The northwestern part of the Peas on quadrangle is drained by Goodson Creek, a tributary of Bayou Toro. The valley of Goodson Creek, like the valley of Cypress Creek, forms part of a prominent coast-parallel lowland valley lying at the base of a cuesta's inland-facing escarpment.

The remainder of the Fort Polk region is drained by tributaries, Kisatchie Bayou and Middle Creek, of the Red PJver (figure 7). Kisatchie Bayou drains most of the Kisatchie quadrangle, the northern edge of the Kurthwood quadrangle, the northeast corner of the Dowden Creek quadrangle, and the eastern half of the Peason quadrangle. Middle Creek drains a small accurate slice of the northern edge of the Peason and Kisatchie quadrangles. The valley of Middle Creek forms a coast-parallel lowland that forms the northern boundary of the Kisatchie Wold.

The Kisatchie 15-minute quadrangle provides unmistakable evidence that Kisatchie Bayou was once a major tributary of the Calcasieu River (Andersen 1993). The evidence includes a large wind gap separating Devil's Creek and Bayou L'Ivrogne, both of which are noticably underfit for the valleys that they currently occupy. As noted by Andersen (1993), the northwest-southeast trending segment of Kisatchie Bayou exhibits a

14

93'22'30~

3'"30"00'+

3'"22"30"+

3'"'5"00'+ 93"22'30"

KEY -----

I I ;------

I I I I I I I I I

Miltary Reservation Parish Drainage

Features (::7 Lake

Iii Town ~ Swamp

Major Summit

, __ - Crest of drainage divide or cuesta

Prehistoric direction of flow

ARC = ancient Red River Calcasieu River drainage divide

MRC=modern Red River -Calcasieu River drainage divide

ASC = ancient Sabine River -Calcasieu River drainage divide

;--<

3'"00'00"+~ 93'15'00"

,.,- ....

J I -, , ,

1 I I

, , I ,

( /

93"OOW"

+

u~" ~~&/ DEVIL SWAMP

I I

eaa::: .. _ ......... =------: ___ 1

o 1 2 3 kilomete~

Figure 7. Major drainages and drainage divides in the Fort Polk region (derived from local 15-minute quadrangle maps).

15

+

barbed drainage pattern. The barbed drainage pattern implies that this segment of Kisatchie Bayou once flowed southeastward into Bayou L'Ivrogne across the wind gap and down Devil's Creek to Comrade Creek. It is obvious that Kisatchie Bayou once flowed southward into the Calcasieu River until pirated by a tributary ofthe Red River.

CLIMATOLOGY

The Fort Polk region has a humid SUbtropical climate. Moist, subtropical air masses from the Gulf of Mexico dominate the region's climate particularly in the summer. Because it lies 50 to 11 0 miles (80 to approximately 180 km) inland from the Gulf of Mexico, drier continental air masses from the west and north significantly influence the Fort Polk region. As a result, its climate is drier than experienced along the Gulf Coast to the south (Louisiana Office of State Climatology n.d.).

During the summer, temperatures are typically very warm. Daytime maximum temperatures average 90°F (32°C) or above from June into early September. Days with maximum temperatures above lOO°F (38°C) are not rare and often occur in runs of two to three days in a row. Because of the high humidity, heat indices or apparent temperatures above 110°F (43°C) are frequent during these heat spells. As in the winter, summer maximum and minimum temperatures usually show a range of 20°F (11°C) (Louisiana Office of State Climatology n.d.).

Winter temperatures are typically mild. The average monthly minimum temperatures for the winter months are all above freezing. However, common cold spells with rare periods of sub-freezing weather occur with polar outbreaks. The duration of extremely cold weather is typically short. In rare winters, they might last from several days to as long as a few weeks. January is typically the coldest month (Louisiana Office of State Climatology n.d.).

Precipitation occurs throughout the year with recordable rainfall occurring on about 100 days during a typical year. According to monthly average precipitation values, rainfall is well distributed throughout the year with summer and fall months being the driest part of the year. Typical weather patterns consist of frontal rain in fall, winter, and spring including possible, but rare, snow and sleet in the winter. Frontal storms can produce damaging ice storms in the winter and other hazardous weather throughout the year. Thunderstorms also produce precipitation throughout the year, but most commonly during the summer. Frontal thunderstorms and squalls, which occur most frequently during the spring and fall, may cause locally heavy rainfall, regional flooding, high winds, dangerous lightening, hail, and tornadoes. On average, about 50 inches (127 cm) of rain falls per year with as much 80 inches (203 em) and as little as 30 inches (76 cm) in any year (Louisiana Office of State Climatology n.d.).

FLORA AND FAUNA

The Fort Polk region lies within the West Gulf Coast Plain Longleaf Pine Forest region. The upland forests of this region are characterized by longleaf pine forest with major stands of slash pine and oaks. In its virgin state, the longleaf pine forest consisted

16

of almost pure, open, parklike stands of longleaf pine with a scattering of shortleaf and loblolly pine and a highly diverse understory of bluestem grasses. The exceptionally rich understory of the longleaf pine forest was dominated by grasses, composites, legumes, and a wide assortment of other forbs. Associated with the upland longleaf pine forests were the hillside bogs, wooded seeps, sandy woodlands, and the very rare calcareous prairie natural communities. The longleaf pine forest has been replaced by slash pine and loblolly pine throughout much of the Fort Polk region as a result of logging and reforestation. The virgin forests of the area were completely logged between the 1890s and 1930s. Starting in the 1950s, large parts of the longleaf pine forests have been converted to pine plantations devoted to the agricultural production of pulp wood and other paper products (Environmental and Natural Resource Management Division 1990; Martin and Smith 1991; Cantley et aI1993).

The mixed hardwood-loblolly pine forest and shortleaf pine/oak-hickory forest natural communities characterize the hillslopes and terraces located between the upland longleaf pine forests and the bottomlands of the Fort polk region. The mixed hardwood-loblolly pine forest consists of a variable mixture of hardwoods, i.e. various oaks and hickories, and a significant percentage of loblolly pine. Within the mixed hardwood-loblolly pine forest, dogwood, redbud, persimmon, black cherry, and other woody shrubs form a midstory canopy. The shortleaf pine/oak-hickory forest is an open-canopied, moderately dense forest composed of shortleaf pine and various hardwoods. This type of forest is associated with the xeric to dry-mesic upper and middle slopes and hilltops found within the study region. This natural community has thick middle and understory components composed of small trees and vines. The herbaceous ground cover is sparse to moderate in extent. The wooded seeps natural community also occurs on the hillslopes within the Fort Polk region (Martin and Smith 1991; Cantley et al 1993).

The riparian forest natural community occupies the narrow flood plain of permanent small to intermediate streams within the Fort Polk region. This natural community contains a wide variety of hardwood species, including three species of maple; two species of hickory; persimmon; three species of ash; black walnut; sycamore; seven species of oak; and four species of elm. Where a closed canopy is present, the understory is open and parklike and contains relatively few shrubs and regenerating trees. Where the canopy is open, the riparian forest often contains a fairly dense midstory and understory composed of a wide variety of shrubs, trees, and vines (Martin and Smith 1991; Cantley et al1993).

A diverse natural fauna inhabits the local natural communities. This fauna includes 40 species of mammals, seven species of lizards, 23 species of snakes, 10 species of turtles, nine species of salamanders, 13 species of frogs and toads, and 223 species of birds. The mammals that can be found in the Fort Polk region include white-tailed deer, nine-banded armadillo, opossum, spotted skunk, striped skunk, woodland mole, cottontail and swamp rabbits, and gray and fox squirrels. The important predator mammals found within these forests are red fox, gray fox, mink, bobcat, raccoon, long-tailed weasel, and the endangered and regionally expatriated red wolf (Martin and Smith 1991; Tomas 1978).

17

GEOLOGIC SETTING


The study area lies downdip of the Sabine uplift, north Louisiana salt basin, and Angelina-Caldwell flexure to the north; the Toledo Bend flexure and Gulf Coast salt and growth-fault basin lie to the south (figures 8, 9). The Angelina-Caldwell flexure is marked at the surface by a zone of faults mapped in Louisiana by Andersen (1960, 1993). Tertiary strata range in age from Eocene to some high and discontinuous remnants of oxidized, sandy strata herein assigned a Pliocene age. The Tertiary section consists of varying proportions of sand, silt, and mud, with sand constituting the greater volume, and reflects deposition ranging from fluvial to shallow-marine, with overall increasingly terrestrial character upsection. Quaternary units comprise strata underlying Pleistocene terraces, and Holocene alluvium; various surficial deposits of Quaternary age form thin veneers on other map units, and with a single exception were not mapped for this investigation. Pliocene units, and Pleistocene units associated with terrace surfaces, are divisible into three main groups, here classified as allogroups (units characterized by bounding unconformities): Upland, Intermediate, and Prairie (figure 10). The study area lies in the area of transition between fluvial terraces to the north and coast-parallel terraces to the south. The stream net over much of the study area shows rectangular drainage that is suggestive of potential structural control.

18

---No LOUISIANA

SALT BASIN

Figure 80 Regional geologic and tectonic framework of study area (redrawn and adapted from numerous sources)o

19

tv o

Projection of Study Area ...------..

~ ARKANSAS I LOUISIANA LOUISIANA I TEXAS

a 50 MILES

II) 50 KILOMETERS VERTICAL EXAGGERATION: 20.8

GULF OF MEXICO

I Sl!ALEVa

• ~_. 1_ I II/ I WJlII

lOA FT

Figure 9. Dip section through the northern Gulf Coast along 94° west longitude. The study area of this report lies 60 kIn (37 mi) east of this line of section, and spans units ranging at the surface from the uppermost or farthest-downdip portion of the outcrop belt of the Claiborne Group to the iovver or updip portion of the outcrop belt of strata of Plio-Pleistocene age. (Geopressure on this diagram refers to "hard" geopressure, equivalent to 13 pounds-per-gallon equivalent drilling-mud weight or the approximate base of the transition zone). Redrawn and adapted, with permission, from American Association of Petroleum Geologists (1990; copyright 1990 by the American Association of Petroleum Geologists).

tv .......

L ••• vill.tDOK ...... I Alexandria tOOK I -+-·vmo Platt. tOOK

Simpson Birds I South Creek I 107B 1070 I

Fullerton Lake lOSe

lPitkin 135A

Grant 13SC

Mittie 143A

i

III Miocene Fleming Formation

III Upland Allogroup

Inrermediate A1logroup

LJ Prairie Allogroup

~ Deweyville Allogroup

Holocene Undifferentiated

VIll.PI.tt.tOOK ...... I C;:~Y I +- Lak. Chari •• tOOK

LeBlanc 143C

I I

I

Indian Village 170A

Topsy 171B

~ .. S) ~" c,+-e

~e Moss Bluff 171C

,,~'O .... "e'b

v~"" If-e

,,~ Westlake

II 177B

! I

Louisiana

500

401l

300

Moss ~200 Lake 1770

100

ii.;;::j'IjM~;~o o kilometers 10

Vertical Exaggeration ~ 417 miles 10

Figure 10. Dip section from the highest uplands of the study area along the Calcasieu River valley to the edge of the south Louisiana coastal marsh, showing geomorphic and hypothesized alloformational interrelations among Plio-Pleistocene and Quaternary units incised into the Miocene Fleming Group.

STRATIGRAPHY


The composite stratigraphic column for the Fort Polk region, with the classification of units used herein, is given in Table 1. The Paleogene units of the Tertiary, represented in the study area by Eocene and Oligocene strata, follow the classification employed by Andersen (1960, 1993); the exception is that the Catahoula Formation is here assigned to the Oligocene, following the interpretation of Galloway (1977, his figure 2) and Galloway and others (1982, their figure 3), as mentioned in the introduction. The older Neogene units, represented by Miocene strata, follow the classification devised by Fisk (1940) in Rapides Parish and employed by Welch (1942) in Vernon Parish, with the exception noted above of adopting usage (suggested by Rogers 1999) reflecting the group rank of the Fleming and formation rank of its constituent subunits. The classification of Pliocene and Pleistocene strata elaborates further the work of Snead and others (1998) in largely following and deriving from usage established in adjacent portions of eastern Texas for the pre-Prairie units; this schema was found to be the most natural and readily applicable, considering the number and three-dimensional distribution of inferred Pliocene and Pleistocene units found in the study area. While no independent control is available on the age of inferred surface Pliocene strata, the distribution of the two constituent units recognized (lower and upper Willis) in relation to that of the younger Pleistocene units makes this a plausible inference, as outlined in the Pliocene Series section below.

A total of 95 electric logs of selected oil & gas and water wells in and surrounding the study area was examined. The logs were correlated and used to construct a series of geologic sections, presented in Appendix B, which show the subsurface distribution of stratigraphic units mapped at the surface.

TERTIARY SYSTEM

EOCENE SF,RJ:ES

Claiborne GrouD ..

COCKFIELD FORMATION

The Cockfield Formation crops out in a small portion of the study area at its northwesternrnost edge, and within this area is very poorly exposed. The authors were able to examine only two limited exposures of this unit, comprising very fine sand of generally grayish to grayish brown coloration. For these reasons we have followed Andersen's (1960, 1993) mapping ofthe Cockfield, as well as of the superjacent Jackson and Vicksburg groups, very closely. Andersen notes that above its basal sand unit the Cockfield comprises "interbedded clays, silts, and muds" (1960, p. 92), and is

22

Stratigraphic Column of Fort Polk Region Time - StratigraiJhic Units Rock - Stratigraphic Units

E III Q) Q)

Stage Formation Member .... .;: Group III Q) >. In In

Holocene alluvium + Biq Brushy undifferentiated "-

~ <>:>

C1i :E e (undifferentiated alluvium) 11:1 c &:~ c: C1i <: ... u

~ ~~ ~ C1i 0 ..... +-' Calabrian VI 11:1 '(jj

~g. Upper :::I Ci c::: ]e Lissie E'" ~ 0

<>= :E< Lower

C1i Piacenzian ~ ~ ~ c

C1i <. raVellitll Allomember U "- Tower Road .Q ,,:>

Zanclean co

Willis Duaout Road Allomember "'~ c::: - '" g-g Kisatchie Allomember « Fort Polk Allomember

~ Messinian

~ ~ ~ j Tortonian ::;)

C1i Blounts Creek undifferentiated c 2 C1i C1i 0 Serravallian 0'1 Q)

c_ Z C1i "0 C Castor Creek undifferentiated u "0 'E 0

~ ~ Langhian C1i

u::: Williamson Creek u nd ifferenti ated

"- Burdigalian Dough Hills undifferentiated C1i ~ Carnahan Bayou undifferentiated

c:: 0 -I

11:1 Aquitanian Lena undifferentiated 'E ~ ....

C1i

~g Chattian Catahoula undifferentiated C1i u 0

.Q1 0'1 (5 .... ....

C1i :J ~ .0

Rupelian VI undifferentiated IV .3 ti c :> 2 0 Q)

m c Q.. L- 0

Q. VI

Priabonian ..:.: undifferentiated g u Q) ~ c Q) u 0 Q) UJ

Q) C .... "0 0 "0 Bartonian :9 Cockfield undifferentiated ~ <1:l

0

Table 1. Stratigraphic classification of units mapped for this investigation.

23

"predominantly composed of very fine sand and silt" (1993, p. 87), with scattered occurrences of petrified wood, leaf fossils, lignite, and glauconite (Andersen 1960). These characteristics suggest that the Cockfield represents deltaic deposition on a shallow shelf. Its thickness penetrated by a well in Sec. 54, T. 7 N., R. 6 W. (15.2 km or 9.5 mi northeast of the study area) is listed by Andersen (1993) as 630 ft (192 m). Among the electric logs examined for this investigation the Cockfield shows a thickness range of 740 to 1,090 ft (226 to 332 m), and shows individual sand intervals as thick as 150 ft (46 m).

Jackson Group (Undifferentiated)

According to Andersen (1960), the Jackson Group comprises primarily clay with varying admixtures of sand, glauconite, and volcaniclastic material, is fossiliferous in its lower portions (Moodys Branch and Yazoo formations and Danville Landing beds), and has a total thickness of 600 ft (180 m) near the Sabine-Vernon Parish line. Like the Cockfield, the Jackson outcrop is limited to a small area in the northwestern portion of the study area. Though it is not particularly well exposed, we were able to observe it at more localities than we were the Cockfield; still, our observations were insufficient to improve on the mapping of Andersen (1960, 1993), and as a result we follow his mapping of the unit very closely, and thus also his definition of it. Andersen (1993) mentions the overall scarcity of Jackson Group exposures in Natchitoches Parish; although apparently it is not much better exposed in Sabine Parish, Andersen (1960) found exposures adequate to describe its constituent formations there, and was also able to use this subdivision later in his description of the unit in Natchitoches Parish. In Sabine Parish, Andersen (1960) mentions several specific outcrops, all but one of which are west of the present study area; in Natchitoches Parish, he specifically mentions three outcrops, plus somewhat fragmentary data from two wells, all of which are north of the study area (Andersen 1993).

We were able to examine exposures of the Jackson at approximately 15 localities, most of which lie in the Peason quadrangle [NC]; all the following references are to localities from this area. At these sites the Jackson Group is represented principally by grayish silty and sandy clay and clayey very fine sand, with reddish mottles. Where observed in NW/SE Sec. 19, T. 6 N., R. 9 W., the Jackson is a silty clay, light brownish gray 2.5Y 6/2 and gray 5Y 5/1, with red 7.5R 4/6 mottles. Petrified wood fragments were observed in float at two localities, in SE/SW Sec. 13 and SE Sec. 17, T. 6 N., R. 9 W. At another locality in SEINE Sec. 19, T. 6 N., R. 9 W., we were able to observe cobble- and boulder-sized carbonate nodules up to 20 em x 30 em in the Jackson, indicating this to be an exposure of the Moodys Branch Formation. These nodules are approximately light greenish gray lOY 8/1 [not their exact color, but the closest to a match with a Munsell color], and occur in grayish green, clayey very fine to fine sand. The overall fine-grained character of the Jackson and the reported presence of glauconite are suggestive of deposition on a shallow, muddy shelf.

24

OLIGOCENE SERIES

Vicksburg Group (Undifferentiated)

Andersen (1960, 1993) provided the stratigraphic framework for the Vicksburg Group in the study area; he described two members of formation rank in Sabine Parish, the Sandel and Nash Creek formations, plus a third in Natchitoches Parish, the overlying Rosefield Formation. The lowermost formation, the Sandel, comprises sand with interbedded conglomerate containing cobbles and slabs of carbonaceous bentonitic clay like that of the overlying Nash Creek. Based on the investigation of Rukas and Gooch (1939), Andersen (1993) portrayed the Rosefield as comprising lentils of marly clay that form a marine tongue extending into Natchitoches Parish from the east, and which pinches out westward approximately 13 km (8 mi) east of the present study area; it follows that the Vicksburg in the Fort Polk region consists of the same two formations that Andersen (1960) described in Sabine Parish. Because of sparse exposures and the narrowness of the Vicksburg outcrop belt, Andersen (1960, 1993) did not differentiate its constituent formations on his maps; as with the Cockfield Formation and Jackson Group, our maps follow closely his rendering of the Vicksburg. On electric logs the Jackson and Vicksburg Groups appear as a combined interval of fine-grained sediment, which among the logs examined for this investigation ranges from 640 to 1,040 ft (195 to 317 m).

We were able to observe Vicksburg sediment at approximately 15 localities. Sandier sediment is typically a grayish, clayey very fine sand, with red mottles in places. Muddier sediment is typically a dark gray to dark reddish brown to chocolate brown, thinly laminated silty clay. Where examined at one locality in SE Sec. 19,T. 6 N., R. 8 W. (Kisatchie quadrangle [NWD, the laminae separate readily, giving the sediment a flaky aspect in hand specimen. Munsell colors determined for finer-grained sediment of the Vicksburg range from light brownish gray 10YR 6/2 for silty clay in NWINE Sec. 26, T. 6 N., R. 8 W. (Kisatchie quadrangle [NED to light brown 7.5YR 6/3 and reddish brown 5YR 5/3 for clay in SWINW Sec. 32, T. 6 N., R. 9 W. (Peason quadrangle [NC]). Petrified wood was found in float at three localities (two in Peason quadrangle [NE], and one in Kisatchie quadrangle [NED, comprising two exposures of grayish, clayey very fine sand (NW Sec. 27, T. 6 N., R. 9 W., SW Sec. 14, T. 6 N., R. 8 W.) and one exposure of dark reddish brown mud (SE Sec. 22-NE Sec. 27, T. 6 N., R. 9 W.).

CATAHOULA FOR1VIATION

Rogers and Calandro (1965) gave a thickness range of200 to 500 ft (61 to 152 m) for the Catahoula near the outcrop in Vernon Parish and 600 to 1,000 ft (183 to 305 m) in the subsurface near the southern parish line. Hinds (1998a, 1999, Plates 3, 4) shows Catahoula intercepts indicating a thickness of approximately 475 ft (145 m) for well V-505 in T. 2 N., R. 9 W. On electric logs examined for this investigation, the Catahoula ranges from 225 to 865 ft (69 to 264 m), with individual sandy intervals ranging up to 180 ft (55 m).

25

The Catahoula in the study area is relatively well exposed and could be examined at numerous localities. The formation comprises sediments that are texturally quite heterogeneous, and which tend to be poorly sorted. The lithologies that occur with the greatest frequency where we observed it are in the range of silt/siltstone to very fine quartzose sand/sandstone, with or without admixtures of clay. Even where coarser grains of medium sand to granule sizes are present, the overall or predominant grain size of sand/sandstone at a majority of localities tends to average very fine to fine sand. Coarser grains may comprise quartz, chert, and/or mud clasts; darker grains, observed in some places, appear in hand specimen to predominantly consist of chert. Colors tend mostly toward lighter hues with substantial amounts of gray, with red mottles showing in silty and sandy clay and clayey sand in places. Silt and siltstone, with or without admixtures of clay, show a tendency toward a greenish cast. Sand may be loose, semiconsolidated, well consolidated, or orthoquartzitic; better consolidated examples, which include occurrences with opaline cement in places, tend toward more nearly whitish hues. Catahoula sediments weather locally in places (as in Peason quadrangle [SW], where the parent material consists primarily of silty clay, clayey silt/siltstone, and clayey very fine to fine sand) to produce a thick (up to 2 m) gray/tan loamy surface unit.

Internal features most commonly observed are cross bedding in sand/sandstone, thin beds in very fine sand/sandstone, and laminations in silt/siltstone, although apparently massive examples of these textural types are also common. Other features include the lightish mud rip-up clasts mentioned above, and petrified wood, wood impressions, and root casts. Ophiomorpha nodosa burrows, with characteristic "com-cob" texture on the outer surface of outer whitish mud "skins," were observed in salmon-red-weathering cross-bedded sand at one locality in Peason quadrangle [NE].

Local diagenetic effects observed, aside from silicification and opalization, comprise iron-oxide concentration, ranging from orangish weathering stains through brownish orange liesegang-type bands to ironstone concretions up to 2 em across. Silicified, orthoquartzitic rock is mined from the Catahoula by Apeck Construction Company at the Ellzey quarry in SE/SE Sec. 15 and SW/SW Sec. 14, T. 5 N., R. 10 W., Peason quadrangle [SW], in southeastern Sabine Parish.

Munsell colors were noted for Catahoula sediments at numerous localities. These and colors of Fleming sediments are listed in Appendix 1 by portions of quadrangles, approximateiy from southwest to northeast along the outcrop belt.

The characteristics of the Catahoula observed in the study area accord for the most part with its traditional interpretation as reflective of continental, fluvial~dominated

deposition. The Ophiomorpha nodosa burrows are the single exception; Ophiomorpha is generally considered a reliable indicator of deposition in a shallow marine, nearshore setting, but according to Frey and Howard (1970) "has been found ... in brackish to fresh water deposits" and "do[es] not have unequivocal significance" (p. 155). The large proportion of silt observed in Catahoula textures is, in any case, consistent with deposition near the transition to a coastal flood-basin setting with onset of influence by deltaic deposition. In his investigation of the geology of Rapides and A voyelles parishes, Fisk (1940, his plate 6) interpreted the transition from continental to brackish-water facies in the Catahoula to lie in the shallow subsurface approximately at the position of the parish boundary separating southern Natchitoches and northwestern Rapides parishes.

26

MIOCENE SERIES

Fleming Group

The members of the Fleming defined by Fisk (1940) in Rapides Parish and mapped by Welch (1942) in Vernon Parish comprise alternating coarser-grained, fluvial-dominated lithofacies and finer-grained, more marine-influenced lithofacies. Fisk (1940) interpreted the coarser-grained members as fluvial and the finer-grained members as estuarine. Hinds (1998a, 1999) elaborated both on Fisk's (1940) surface- and near-surface characterization of depositional settings and on Rainwater's (1964) deeper-subsurface depositional framework for the Louisiana Miocene, and attempted to integrate these and his observations with the genetic stratigraphic framework developed by Galloway (1989a, b) and Galloway and others (1991) for the northern Gulf Coast. Hinds made the refinement of interpreting Fleming members as representing upper and lower delta-plain deposition, and the latter, corresponding to the finer-grained members, as potentially the updip expression of subsurface marine shale tongues and associated flooding surfaces corresponding to periods of maximum transgression during the Miocene. He correlated the Dough Hills with the Marginulina ascensionensis tongue of the subsurface, the Castor Creek with the Amphistegina fauna tongue, and the Blounts Creek with the Textularia stapperi and Bigenerinajloridana tongues (Hinds 1998a, 1999, his figures 31 and 34). The hypothesized downdip marine shale of the Lena Member on his figure 34 corresponds in position to the major Siphonina davisi tongue (Rainwater 1964). According to Ye and others (1995), the nature of depositional sequence cycles in the Miocene of the northern Gulf Coast indicates that glacioeustatic control of cyclicity was operative, and the Siphonina davisi, Marginulina ascensionensis, and Amphistegina fauna tongues correspond to the three major transgressions in the northern Gulf Coast Miocene.

The gross textures observed for the sandier Fleming subunits in the study area suggest that the Fleming interval reflects increasing regression followed by marine encroachment: the Carnahan Bayou is texturally similar to the Catahoula, encompassing a wide range of textures but with mean grain size in the silt to fine sand range; the Williamson Creek has the largest proportion of coarse textures, which comprise mostly very coarse sand and granules; and the Blounts Creek comprises mostly fine and very fine sand, siit, and mud. This sequence accords with Hinds's (l998a) account of the environments of deposition (cf. his figure 28), in which the Lena and Dough Hills members show "a lesser degree of brackish-water influence than that seen in the Castor Creek Member" (p. 63), the Williamson Creek is "the terrestrially influenced end member of the Fleming Formation depositional model," and "[t]he basal section of the Castor Creek Member forms the brackish-water-influenced end member of the Fleming depositional model" (p. 68). It is also consistent with the observation by Ye and others (1995) that parasequence-set cycles in the upper Miocene sequence cycles of southwestern Louisiana comprise mostly intervals of highstand (HST) and transgressive (TST) systems tracts.

27

The vertebrate fossils discovered recently at Fort Polk occur in one of these overall finer-grained subunits, the Castor Creek, but within a notably coarser-grained subinterval consisting of conglomerate and sandstone, The conglomerate consists of carbonate nodules reworked from the subjacent mudstone, which is typical of the Castor Creek elsewhere in Vernon Parish, and the conglomerate-and-sandstone subinterval lies on this mudstone with an erosive base (Hinds 1998a, 1999, his figure 11). Jones and others (1995) showed that at least this portion of the Castor Creek sequence can be interpreted as fluviatile; however, this subinterval constitutes a relatively small portion of the total Castor Creek interval, and as suggested by Hinds (1998a, 1999) is unrepresentative of the interval as a whole. Another of the finer-grained subunits, the Dough Hills, shows an increased frequency of coarse material affecting its entire interval near its eastern extent in the study area, which Hinds (1998a, 1999) inferred corresponds to a persistent fluvial axis in that position.

Although the Fleming is traditionally classified as a formation, in Louisiana and in the study area in particular, the unit is more appropriately described as of group rank and consisting of formation-rank subunits. In this report we have, therefore, followed the suggestion of Rogers (1999) and designated the Fleming as a group and its constituent subdivisions as formations. Because the Fleming subdivisions constitute lithofacies recognizable principally by gross lithology and position in the sequence, these units should only be mappable within a transitional paleogeographic belt centered around the position of the Miocene coastal plain. An examination of selected subsurface well logs in southern Vernon and northern Beauregard parishes, and in areas along strike as far east as West Feliciana Parish across the Mississippi River flood plain, showed the downdip position at which correlation of Fleming subunits becomes notably more difficult and complicated owing to a thickened sequence with log character indicative of fine-scale irregular variation. This position should mark the farthest downdip extent of continental fluvial facies into the coastal flood-basin setting in the Fleming, and is rendered on figure 11 (sawtooth line) as a transition between fluvial and mixed fluvial-deltaic facies. In his investigation in Rapides and Avoyelles parishes, Fisk (1940, his plate 6) placed this facies boundary in the shallow subsurface nearly as far south as the parish line separating southwestern Rapides and northwestern Allen parishes, in the same position as that depicted in figure 11 from an analysis of selected well logs.

LENA FORMATION

Rogers and Calandro (1965) listed the range of Lena thicknesses in Vernon Parish as 185 to 300 ft (56 to 91 m), and electric logs and sections figured on their Plate 2 suggest 200 feet (approximately 60 m) as a representative thickness. Hinds (1998a, 1999, Plates 3, 4) showed Lena intercepts in water wells indicating a thickness range of approximately 175 to 300+ ft (53 to 91 + m) in the Fort Polk area. Among the electric logs examined for this investigation the Lena shows a thickness range of 90 to 320 ft (27 to 98 m); the thinner values are from wells drilled near the outcrop in southern Sabine and Natchitoches parishes.

The Lena Formation shows constituent lithologies essentially like those observed in the underlying Catahoula, the difference being primarily in the increased proportion of

28

Fluvial

t

r-~---r--~------------r-----c-I I '\' ! l ' I J I I , \ ," I ). " ,-'-- ( I , I '"' (.... ,'11- 1'1 I \ r-.... -LJ. r . II .\ L" 'J--'--\ Monroe Shrel(eport, - " I I -., ... ·1 .... ~ I' ..... -, I -- ; \--, ----,

Generalized Miocene

Outcrop Belt

\ J. \ ' ~ " I---r-,-~ ,J I 'r--I -1 !;---.; . '\

Mixe}Fluvial-Oeltaic

Farthest Oowndip Extent

Overall Change from Continental to Coastal Flood-Basin Setting

of Fluvial Miocene (afte __ r_.l.IIIIIIIIII.!~~~h

Galloway et al. 1991, -:t:~;:=~;!:~:~E;~~~'~~:!!~~ Fig. 25) .-c,......:....

Farthest Updip Position of Miocene Shelf Edge (after Woodbury et al. 1973, Fig. 3;Winker 1982, Fig. 8) 11M WI I

o 10 20 30 40 50 Miles

Figure 11. Generalized paleogeographic aspects of nearshore Miocene (Fleming) facies in Louisiana. The sawtooth line shown as separating fluvial and mixed fluvial-deltaic regimes represents the farthest downdip extent of continental fluvial facies into the coastal flood-basin setting, and is rendered based on changes in thickness and electric-log character recognizable on selected logs of oil and gas wells.

29

the finer-grained textures. Among the surface exposures of the Lena we were able to examine are 16 occurrences of clay, with and without admixed sand and silt; 20 occurrences of silt/siltstone, mostly without substantial admixed clay; and 26 occurrences of sand/sandstone, with and without admixed clay. In some areas, such as in parts of the Peason quadrangle [EC] and the Kisatchie quadrangle [C], the Lena weathers to produce a brownish gray to lightish surface sand. Though it is relatively well exposed, the lack of a clear lithologic distinction, together with the relative thinness of the interval and the consequent narrowness of its outcrop belt, are such that delineating the Lena from field observations becomes a largely statistical exercise. This is also underscored by the lack of a distinct soils signature (Guillory 1997; Martin et al. 1990) and of known characteristic plant communities specific to the Lena (Smith 1994, personal communication). For the above reasons our mapping largely follows that of Rogers (1980). The lithologic similarity of the underlying upper portion of the Catahoula Formation with the overlying Carnahan Bayou Formation was noted by Andersen (1960, p. 110), and in eastern Texas the Lena and Carnahan Bayou are in fact classified as the uppermost portion of the Catahoula (American Association of Petroleum Geologists 1988).

Lena sediments show overall coloration similar to that of equivalent Catahoula lithologies, tending toward grayish, greenish, and brownish hues among finer-grained textures and toward more nearly whitish hues in sandstones lacking substantial admixed clay. Sand and sandstone also may rarely weather to reddish hues and resemble Plio-Pleistocene strata. Grayish silt and siltstone tend to have a greenish cast, but commonly weather to nearly whitish hues. Grayish and greenish gray silty clay, clayey silt, sandy clay, and clayey sand show red and/or yellow mottles where observed in a few places. Sand and sandstone average very fine to fine, but show the same overall poor sorting as noted for Catahoula sediments, and in places contain coarse sand and granules. Few structures were observed in sand/sandstone except for rare laminations. Notable differences from the Catahoula include discernibly plastic clay observed at two localities, and calcareous clay (with calcareous nodules) also from two localities. Munsell colors noted for Lena sediments are listed in Appendix 1 by portions of quadrangles, approximately from southwest to northeast along the outcrop belt.

CAru~AHAN BAYOU FORMATION

The Carnahan Bayou Formation of the Fleming Group has the widest outcrop belt, and is perhaps the best exposed, of any of the map units in the study area, and could be observed at hundreds of exposures. Rogers and Calandro (1965) indicated a thickness range of approximately 500 to 1,100 ft (i 52 to 335 m) for the Carnahan Bayou in Vemon Parish, making it and the Blounts Creek the thickest Fleming subunits. Hinds (1998a, 1999) estimated the thickness range of the Carnahan Bayou in the Fort Polk area as 500 to 550 ft (152 to 168 m); his Plates 3 and 4 show subsurface intercepts in water wells indicating a thickness range of approximately 475 to 550 ft (145 to 168 my. Well logs examined for this investigation indicate a thickness range of 545 to 1,260 ft (166 to 384 m) for the Carnahan Bayou in the study area and vicinity, with individual sandy intervals as thick as 140 ft (43 my.

30

Generally, the Carnahan Bayou shows the same textural variability and poor sorting as the Catahoula, comprising varying admixtures of sand/sandstone, with granules in places; silt/siltstone; and clay/mud. But it is coarser overall, with some occurrences of medium to coarse and coarse to very coarse sand with granules, in addition to the clayey very fine to fine sand with some coarse and very coarse sand and granules reminiscent of some Catahoula exposures. Granules and pebbles include both quartz and rock fragments. The granules comprise predominantly quartz, but include black and dark chert grains in places; some lightish mud rock fragments also occur in the granule size range. Pebbles and cobbles consist mostly of rock fragments, predominantly lightish clay/mud rip-up clasts with varying degrees of rounding, but in some places dominated by black chert. Associated finer-grained versions of sediment with discernible dark grains consist of "salt-and-pepper" quartzose very fine to fine sandstone. Another aspect of Carnahan Bayou sand and sandstone distinctive from that of the Catahoula is the common occurrence of whitish flecks. In hand specimen the larger examples of these resemble clay, though we cannot say at present whether they consist of more finely comminuted representatives of the lightish clay/mud rock fragments, or if they result from weathering alteration of precursor mineral grains to clay.

The Carnahan Bayou shows the same colors typical of the Catahoula: lightish gray, green, and brown, with red and yellow mottles in places. In Peason quadrangle [SC, SE], for example, it shows a fairly monotonous repetition of silty clay, clayey silt, greenish-grayish (whitish-weathering) siltstone, and grayish clayey sand and sandy clay, with some whitish-weathering very fine to fine sandstone. It also contains, however, more sediment with reddish and yellowish hues, giving it a more varicolored aspect overall. The latter comprise additional reddish to reddish brown and yellowish to yellowish brown hues, plus some roseate hues in a few places. In Dowden Creek quadrangle [SW, sq, for example, two lithologies occur singly and in alternation. One comprises lightish, grayish clayey silt to very fine sand with red mottles. The other is cross-bedded reddish sand, very fine to fine overall, with coarser grains up to and including 3- to 4-mm granules in some places; these include relatively large examples of the whitish flecklike grains on cross beds, and these grains are numerous enough to become welded into irregular cross laminae in places. The greater weathering indicated by the greater abundance of reds and yellows in the Carnahan Bayou may partly reflect the coarser grain size, but it also appears to mark the preservation of higher portions of the weathering sequence in the outcrop belts of the Carnahan Bayou and the other sandy Miocene lmits downdip. Grayish mottles occur in reddish and yellowish sand just as red and yellow mottles may occur in grayish sediment, and include grayish clay lining partings, cracks, fractures, and root traces. Munsell colors were noted for Carnahan Bayou sediments at numerous localities, and are listed in Appendix 1 by portions of quadrangles, approximately from southwest to northeast along the outcrop belt.

Internal features observed in Carnahan Bayou sand and sandstone comprise primarily cross bedding, including climbing ripples and medium-scale trough cross bedding, with cross beds delineated by cross laminae of clay in places. Laminations were more commonly observed in silt and clayey very fine to fine sand and sandstone, and contorted bedding was observed in very fine sandstone at a single locality. Red, yellow, and brown fine to coarse sand may commonly contain whitish clay/mud interbeds and

31

rip-up clasts. Purplish clay/mud beds were seen in red cross-bedded sand in a few places and purplish clay/mud rip-up clasts were also observed in Dowden Creek [WC], in SE Sec. 24, T. 4 N., R. 10 W. This was the single exception to the generalization that such clasts are diagnostic of Plio-Pleistocene strata [discussed below]; it occurs below 450 feet (137 m) elevation, and observations indicate Carnahan Bayou sediments above that nearby (1000 to 1200 ft, or approximately 305 to 365 m, to the east). Root molds and casts, including mud- and silt-filled and ironstone-filled representatives, were observed in sediment at a number of exposures, and wood impressions were observed at one locality.

Megascopic features of Carnahan Bayou sediments could be clearly observed in quarry exposures in Dowden Creek quadrangle [WC], in SE Sec. 25, T. 4 N., R. 10 W. (figure 12). These consist of channeloid lenses of medium-scale cross-bedded, pale yellow 5Y 7/3 very fine to fine sand and sandstone, cutting out olive 5Y 5/3 silt and siltstone. The sand and sandstone have individual beds containing grains up to very coarse and granule sizes (the larger grains consisting of clay/mud, and with quartz grains up to about coarse size). These megascopic features and the smaller-scale internal features noted above accord with the interpretation of fluvial deposition originally given by Fisk (1940) and more recently elaborated by Hinds (1998a, 1999). As with the Catahoula, the notably high proportion of silt among the observed textures in Carnahan Bayou sediments is at least suggestive of proximity to the coast and to the transition into deltaic facies.

A common feature of silt and coarser sediment of the Carnahan Bayou is silicification, indicating a higher mobility of silica relative to sediment with equivalent textures observed in the Catahoula. This is shown by the formation of sandstone ledges, and also by blebs of selective silica cementation, occurrence of silcrete layers and veins, and siliceous root traces/nodules in sand and sandstone. Localized cementation by common opal was observed in the Peason quadrangle [SC], in NW Sec. 21, T. 5 N., R. 9 W. Localized silicification along joints in whitish very fine sandstone and siltstone was observed at one locality in the Kisatchie quadrangle [SW], in NE/SW Sec. 29, T. 5 N., R. 8 W. The joints are nonvegetated, but occur as part of a single predominant set that includes preferentially vegetated joints that form microlineaments. The joint set strikes between approximately 75° and 85°, but good-quality examples at this locality were not considered numerous enough to take multiple strike readings. The widespread occurrence of the above silicification features may reflect the greater weathering inferred from the more varied coloration observed in the Carnahan Bayou.

A combination outcrop sketch and measured section of Carnahan Bayou sediments was made at a locality where they are cut out by sediments of the Upland Allogroup, in the northwestern portion of the Peason Ridge military installation, in Peason quadrangle [SC] (figure 13). The contact here shows the "purplish" alteration of Miocene clayey sediment (here red 7.5R 4/6) seen at many localities and considered herein characteristic of the unconformity between it and overlying Plio-Pleistocene strata. Mud of the same color composes rip-up clasts in the base of the overlying Willis sediments, and also fills burrows in the upper portion of the Carnahan Bayou strata.

32

w w

Figure 12. Photograph of channel Old lens of pale yellow 5Y 7/3 sand and sandstone cutting out olive 5Y 5/3 silt and siltstone; Carnahan Bayou FormatIOn of Fleming Group, in quarry at SE comer Sec. 25, T. 4 N., R. 10 W., Dowden Creek quadrangle [WC]. The sand size is very fine to fine overall, wIth beds contaimng grams up to very coarse and granule SIzes; of the latter, quartz grams range up to approxImately coarse SIze, whereas larger grains conSIst of claylmud clasts. (Hammer length IS 33 cm = 13 m.).

4

'1-:""" . t' .' .' . . - -'

. '.'

~. ~ .

. -' 3

.:}

2

1

~I· Yellow loam lDtlt!J Brownish yellow 10YR 6/6

~ Sand, overall very fine to fine, some sparse medium to very coarse grains ciili Yellowish red SYR 5/6-8, with abundant white 10YR 8/1 to very pale brown 10YR 8/2 burrow mottles Red 7.SR 4/6 mud rip-up clasts near base

Clayey very fine to fine sand p ---© Light gray 2.SY 7/2 with red lOR 4/8 mottles - ---.:::: In places beneath contact with overiying sand at north end of cut, mud shows alteration

to red 7.SR 4/6 in interior cores of peds, with light gray 2.SY 7/2 remaining along ped surfaces Apparent dip 4°

Cross-bedded sand ~ Overall very fine to medium, with some grains ranging from coarse sand to granules ~ Reddish yellow SYR 6/6, with very pale brown 10YR 8/4 burrows and root molds

Red 7.5 4/6 mud burrow casts up to 0.5 m below upper contact

Figure 13. Combined outcrop sketch and measured section (no horizontal scale) along roadcut, SEINW Sec. 30, T. 5 N., R. 9 W., Peason quadrangle [sq. Mottled sediment of the Upland Allogroup is mantled by "yellow loam" and cuts out two units of the Carnahan Bayou Formation of the Fleming Group.

34

DOUGH HILLS FORMATION

Rogers and Calandro (1965) gave approximately 400 to 500 ft (122 to 152 m) as the representative thickness of the Dough Hills in Vernon Parish. Hinds (1998a, 1999) estimated its thickness range as 400 to 450 ft (122 to 137 m), and subsurface intercepts in water wells figured in his Plates 3 and 4 show it ranging from approximately 400 up to 540 ft (122 to 165 m) thick. On well logs examined for this investigation the Dough Hills ranges from 310 to 760 ft (95 to 232 m) thick. An exception was noted in the log of well V-234 drilled by the U.S. Geological Survey, which shows an anomalously thin Dough Hills interval of 110ft (34 m) accompanied by similarly anomalous thickening of the overlying Williamson Creek; this well was drilled in Sec. 1, T. 2 S., R. 11 W., far to the southwest of the study area. The Dough Hills consistently shows a noteworthy development of sand up to 90 ft (27 m) thick near the middle of its interval on logs of wells drilled in the study area and vicinity.

In the study area the Dough Hills Formation of the Fleming Group crops out in the southeastern Kurthwood quadrangle and northwestern Slagle quadrangle. Within this area it is relatively well exposed and comprises varying proportions of clay, sand and sandstone, and silt and siltstone. Clay is fairly uniformly of grayish coloration, is silty and sandy in many places, and includes calcareous clay-containing characteristic calcareous nodules--observed at several exposures. Sand and sandstone are poorly sorted, range in grain size from very fine to very coarse but average very fine to fine, and are clayey in many places and contain sparse granules at a number of localities. They are predominantly grayish, with a greenish cast in some places (mostly for the very fine size fraction), and sand shows reddish and yellowish mottles in places. Sand is colored reddish where coarser-grained (overall fine to medium or coarser) at a number of localities, and reddish sand was observed with yellow mottles at one locality; sand is colored any combination of grayish, reddish, and yellowish where coarser-grained at a few localities. Silt and siltstone are colored grayish with a tendency toward a greenish cast; both reddish and grayish silt were observed at one locality in association with reddish very fine to very coarse sand with granules. The only Munsell colors determined for Dough Hills sediments were for specimens from the Slagle quadrangle [NW], in Sec. 24, T. 3 N., R. 9 W. Clayey very fine to fine sand there is light gray IOYR 712, with red lOR 4/6-4/8 mottles.

The following internal features were observed in sediments of the Dough Hills at only a fe\v localities: llli'11inations in sand and sandstone; lightish clay/mud rip-up clasts (generally pebbles, but including some granules); and siliceous nodules in grayish clay and grayish-greenish laminated sand.

The eastern edge of the southern Kurthwood quadrangle [EC, SE], east of the Calcasieu River, contains a relatively higher proportion of grayish clay and sand, and red-weathering sand containing granules, in the Dough Hills outcrop belt. Hinds (1998a, 1999) suggested that the larger average grain sizes along with the decrease in frequency of calcareous clay in this area could reflect a coarse-grained subfacies of the Dough Hills corresponding to a fluvial axis. Such a subfacies might correspond to the surface outcrop of the sand up to 90 ft (27 m) thick seen near the near the middle of the Dough Hills interval on well logs.

35

As mentioned above the clay of the Dough Hills includes calcareous clay, which contains calcareous nodules in places. It appears that an anomalous localized concentration of fine-grained calcareous rock is being quarried from the Dough Hills in the Leesville quadrangle [NC] west of the southern portion of the study area. We were unable to gain access to the site of the quarry, but it appears to be located in an area 1 km (0.6 mi) east-southeast of the northeastern arm of Vernon Lake and 0.3 to 0.4 km (0.5 to 0.6 mi) east of Hwy. 171, along the boundary between the western halves of Secs. 20 and 29, T. 3 N., R. 9 W. An informant indicated that the material, locally known as "soapstone," is mined by Apeck Construction for Boise Cascade on Boise property, and that it holds up well as a durable road metal and is used principally to repair "bad spots" in roads. Our inference that the material quarried is calcareous rock is based on specimens examined in a roadcut on the east side of Hwy. 171 directly north of the road leading to the site. In hand specimen it is essentially white, with possibly a slightly greenish cast, and has a chalky appearance overall. Examination in thin section shows it to consist of aphanocrystalline calcium carbonate. Ezat Heydari (1998, personal communication) indicated that it is a lime mud of a sort that could possibly be of either marine or lacustrine origin.

WILLIAMSON CREEK FORMATION

Rogers and Calandro (1965) indicated a thickness range of 400 to 900 ft (122 to 274 m) for the Williamson Creek in Vernon Parish. Hinds (1998a, 1999) estimated its thickness range as 400 to 600 ft (122 to 183 m) in the Fort Polk area, and his Plates 3 and 4 show subsurface intercepts in water wells indicating thicknesses ranging from approximately 350 to 500 ft (107 to 152 m) for the formation. Well logs examined for this investigation show the Williamson Creek ranging from 340 to 810ft (104 to 247m) thick; an exception, as noted above, is the U.S. Geological Survey's well V-234 in Sec. 1, T. 2 S., R. 11 W., far to the southwest of the study area, in which the Williamson Creek thickens to 1,075 ft (328 m) in conjunction with thinning of the underlying Dough Hills F ormation. Individual sandy intervals in the Williamson Creek seen on well logs range up to 135 ft (41 m) thick.

Most of the Williamson Creek outcrop belt within the study area is in the Slagle quadrangle, essentially all of which was mapped by Hinds (1998a, c; 1999); we observed it almost exclusively in exposures in the northern Simpson South and Lacamp quadrangles, where the outcrop belt flanks the Calcasicu River flood plain on both sides. The Williamson Creek shows the same poor sorting characteristic of other portions of the Fleming sequence, and its finer-grained sediment, consisting of grayish clayey silt to very fine sand with some reddish mottles in places, resembles that common in other parts of the Fleming. But the overall grain size appears coarser than in other Fleming subunits, with sands containing much more of the coarser size fractions and a larger proportion of granules in places.

Sand is the most common lithology observed in the Williamson Creek; it ranges in grain size from very fine to very coarse, averages very fine to medium overall, and in the coarser-grained examples contains less admixed clay overall than in other parts of the Fleming. Granules are extremely abundant locally, and consist almost exclusively of

36

quartz. The best example of such coarser-grained, granule-rich sediment we observed in the Williamson Creek is a large roadcut exposure south-southeast of Simpson, in the Lacamp quadrangle [NW]; it consists of reddish quartzose coarse to very coarse sand with abundant granules and some small pebbles, and in part (principally along specific cross bed sets) comprises sandy granule conglomerate. Rare small pebbles observed elsewhere in the Williamson Creek, as at this locality, consist primarily of quartz and comprise the largest size fraction in quartzose granuliferous sediment; lightish clay/mud rip-up clasts were seen at a single locality. Colors comprise primarily grayish hues in finer-grained sediment and reddish hues in coarser-grained sediment, apparently reflecting greater weathering of the coarser portions; the coarser sediment also includes some with yellowish/brownish and roseate hues in places. Rare beds of indurated sandstone weather to whitish hues as in the Catahoula and Carnahan Bayou, and the more reddish examples of the coarser-grained sands show notable colluviation in many places. Silt observed in the Williamson Creek is generally clayey and grayish, with some reddish and yellowish-brownish mottles in places; clay is generally grayish and silty, and is rarely mottled. [No Munsell color determinations were made for Williamson Creek sediment. It appears that localities we tentatively identified as lying in its outcrop belt at the time of the field work may later have become classified as Dough Hills. Obtaining representative Munsell colors for this unit will be one of the minor goals of the work to be completed in the ensuing months.]

Internal features observed in Williamson Creek sediment include medium-scale trough cross beds in coarser, granule-rich sand and sandy granule conglomerate such as that in the Lacamp quadrangle [NW] mentioned above, and a pervasive occurrence of scattered whitish grains in some of the reddish sands. The latter appear to possibly represent coarser-grained analogues of the whitish flecklike grains observed in some reddish sands of the Carnahan Bayou Formation. Laminations were observed in silt and fine to very fine sand at a few localities. At a few places in the Simpson South quadrangle [EC], yellowish-brownish mottles in clayey sand show a gradation to a more generalized stain, with associated ironstone nodule formation observed at one locality. Calcareous beds up to a few cm thick were observed in grayish silt and fine to very fine sand near the contact with overlying Plio-Pleistocene sediment at one locality in the Lacamp quadrangle [NE], in SW Sec. 17, T. 3 N., R. 5 W.

CASTOR CREEK FORMATION

Rogers and Calandro (1965) indicated approximately 300+ ft (91+ m) as representative of the thickness of the Castor Creek in Vernon Parish. Hinds (1998a, 1999) estimated 450 to 500 ft (137 to 152 m) as the thickness range of the Castor Creek in the Fort Polk area, and his Plates 3 and 4 show subsurface intercepts in water wells indicating thicknesses of approximately 270 to 550 ft (82 to 168 m). Among the well logs examined for this investigation, the Castor Creek ranges from 250 to 500 ft (76 to 152 m) thick, and can contain individual sandy intervals of up to 45 ft (14 m) thick.

For this investigation the Castor Creek Formation of the Fleming Group was observed mostly in the area south of the Calcasieu River flood plain in the Simpson South and Lacamp quadrangles; the remainder of its outcrop belt within the study area

37

courses through the Fort Polk and Slagle quadrangles and was mapped by Hinds (1998a, b; 1999), whose Fleming contacts are incorporated in our maps. Where observed in surface exposures the Castor Creek consists primarily of clay that is silty to very fine sandy and of grayish color, and which shows reddish mottles in places. Calcareous clay, with irregular calcareous nodules up to several cm long, was observed at numerous localities in the Castor Creek, and except for the contained calcareous nodules it is otherwise similar in appearance to clay of the overlying Blounts Creek Formation. The next most common lithology is very fine to fine sand, also generally grayish and showing reddish mottles in places; it is generally clayey, but is silty in a few places. Petrified wood was found in float at two localities in the Castor Creek where clayey sand was exposed, in SW Sec. 6 and NW Sec. 7, T. 2 N., R. 5 W., Lacamp quadrangle [C]. Rare silt, where it occurs, is grayish and clayey. Sand weathers locally to colors ranging from yellowish brown to brownish red, and the Castor Creek in some areas weathers to produce surficial mantles of red and yellow loam, the red loam attaining substantial thickness (up to 2 m) in places. Munsell color determinations for Castor Creek sediment are listed in Appendix 1; a differential GPS location reading on the "Shamrock" vertebrate fossil site is given on the attached diskette.

In the southeastern portion of the Simpson South quadrangle, in Slagle areas 8, 9, and 10, the unconformable contact between grayish and greenish gray silty clay of the Castor Creek and reddish sandy sediment of the overlying Upland Allogroup, Willis Formation, is exposed and shows the characteristic alteration seen between the Miocene and Plio-Pleistocene elsewhere in the study area. Along the east valley wall of tributary of Brushy Creek in Slagle area 10, in NE Sec. 19, T. 2 N., R. 6 W., Simpson South quadrangle [SE], grayish silty clay of the Castor Creek directly beneath the contact shows purplish alteration of rectangular peds delineated by the gray separating them, and cross-bedded sand of the overlying Willis contains purple clay/mud clasts near its base.

Vertebrate fossil finds at Fort Polk of the last several years (Schiebout 1994, 1997; Schiebout et al. 1996) all lie within the drainage basin of Bayou Zourie in the Fort Polk quadrangle. Jones and others (1995) showed that at least this portion of the Castor Creek sequence exposed in this area can be interpreted as showing more of a fluvial influence than previously thought, and inferred episodes of repetitive paleosol formation on a flood plain surface from detailed descriptions and analyses of several 50-foot (15-m) cores. Hinds (1998a, 1999) pointed out, and we concur, that this portion of the interval, characterized as it is by concentration of reworked calcareous nodules into conglomerate beds, is probably not representative of the Castor Creek interval overall; rather, it appears to reflect incision of the more characteristic sequence such as would occur in conjunction with a drop in base level. Hinds (1998a, 1999) suggested that such a drop in relative sea level could have accompanied increased progradation associated with the eastward shifting of depocenters documented across the northern Gulf of Mexico (Williamson 1959; Woodbury et al. 1973; Galloway et al. 1991), which accompanied renewed uplift of the southern Rocky Mountains beginning in the early Miocene (Winker 1982), and which reached southwestern Louisiana in the early Miocene and southeastern Louisiana in the late Miocene.

Unfortunately, the drilling of the above cores did not permit determination of the position of the conglomerate beds relative to the top and base of the Castor Creek. An

38

electric log on file at the U.S. Geological Survey Water Resources Division district office in Baton Rouge, of its 340-ft (104-m) well V-642 drilled in 1993 at the Fort Polk landfill ("Discovery" vertebrate-fossil site), shows the top of the Williamson Creek Formation of the Fleming Group encountered at a depth of 330 ft (100 m). Hinds (1998a, 1999, Plate 4) showed the thickness of the Castor Creek near the outcrop in this area as scarcely greater than 300 ft (91 m), indicating that the vertebrate-fossil-bearing conglomerates exposed at the surface there lie very near the top of the Castor Creek. Subsurface geologic section D-D' (Appendix B) was constructed specifically to correlate the Castor Creek interval in well V-642 into the subsurface downdip in order to determine the stratigraphic position of the Discovery landfill site relative to the top of the formation; the section shows that the site essentially represents the outcropping of the uppermost portion of the unit.

Schiebout (1997) and her collaborators applied a variety of techniques, e.g., paleomagnetism, palynology, and stable isotopes, in order to determine the age of their cores. For this investigation we inquired into possible additional techniques that might be used to date the cores. The main promise appeared to be held by uranium-lead dating techniques (e.g., Rasbury et al. 1997), which we expected might be applicable to the dating of pedogenic carbonate nodules recovered in the cores. The carbonate nodules, however, were revealed to be far too young for dating by such techniques (Rasbury 1997).

The North American land mammal age of the Fort Polk vertebrate fauna is estimated as early late Barstovian (Schiebout 1994, 1997; Schiebout et al. 1996), corresponding to a late Middle Miocene age (Hinds 1998a, 1999). Table 1 follows Salvador and Mufieton (1989) and the American Association of Petroleum Geologists (1988) in using European stage/age names, and suggests an equivalent age of middle to late Serravallian for this portion of the Castor Creek interval. This is in agreement with the time scale incorporating land mammal ages compiled by Woodburne and Swisher (1995, their figure 5).

BLOUNTS CREEK FORMATION

The Blounts Creek Formation of the Fleming Group is the youngest unit underlying and truncated by Plio-Pleistocene strata in the study area. Only one of the wells for which we examined logs, U.S. Geological Survey well V-437 in NWINE Sec. 36, T. 1 S., R. 6 W., appears to have penetrated the entire Blounts Creek interval; in this well the formation is 780 ft (238 m) thick, with individual sandy intervals ranging up to 150 ft (46 m) thick. Rogers and Calandro (1965) estimated a thickness of up to approximately 1,100 ft (335 m) for the Blounts Creek in Vernon Parish, based on the greatest thickness of the interval between the Plio-Pleistocene and the Castor Creek Formation in the southeastern portion of the parish. Although this thickness is comparable to that of the Carnahan Bayou, the Blounts Creek surface outcrop belt is notably less extensive than that of the Carnahan Bayou owing to this greater amount of Plio-Pleistocene cover, which reflects the extension of the Blounts Creek southward beneath the zone of transition between fluvial and coast-parallel Plio-Pleistocene strata. In the present study area the outcrop belt courses through the Fort Polk, Birds Creek, and

39

Fullerton Lake quadrangles, and slightly overlaps the southern Simpson South and Lacamp quadrangles. Hinds (1998a, b; 1999) mapped most of the Fort Polk quadrangle and a small portion of the Simpson South quadrangle; our observations of the Blounts Creek were made principally in the Birds Creek and Fullerton Lake quadrangles.

The Blounts Creek can be described as a relatively nondescript series of grayish clayey and silty very fine to fine sands, silty and very fine to fine sandy clays, and clayey silts. It is the finest-grained of the sandy Fleming subunits, essentially because it generally lacks grains coarser than its mean grain size. The coarsest texture we noted in the Blounts Creek was medium sand. Whereas sands of the Carnahan Bayou and Williamson Creek also have a very fine to fine or fine to medium mean grain size in many places, they typically contain additional coarser grains in varying proportions; thus, although sands of the Blounts Creek are not well sorted, they are relatively better sorted than those of the Carnahan Bayou and Williamson Creek, with a finer overall texture. Although rare reddish mottles were observed in Blounts Creek sediments, such mottling, along with weathering to reddish hues overall, is less common than for sediments of the Carnahan Bayou and the Williamson Creek formations, which could be a function of this overall finer grain size. Surface sands colored in yellowish, orangish, and roseate hues, including some containing granules in places, were seen in the Blounts Creek outcrop belt in places, but all such localities are near contacts with reddish sandy sediments of the overlying Willis Formation, and are inferred to likely represent surface wash deriving from that unit.

As suggested above, our observations of Blounts Creek sediment within the study area revealed few distinctive features of the unit; aside from the measured section locality figured below, the only sedimentary structures we noted were rare laminations and cross beds. An exposure of the Blounts Creek examined southwest of the railroad crossing at Pickering, west of the southwestern portion of the study area in the New Llano quadrangle ESE], constitutes the best example of structures seen in the unit; this locality was figured by Welch (1942, pp. 60-61, his figures 10 and II-the latter redrafted herein as figure 14). Abundant and well preserved fine-scale stratification and low-angle cross stratification are traceable across much of the exposure, and the clayey to very fine sandy sediment exposed there also contains whitish fossil wood.

Diagenetic features observed in the Blounts Creek comprise only rare ironstone concretions and incipient and spotty silica cementation. The sands are rarely indurated, and in many places where they are this appears to be a surface case-hardening phenomenon rather than cementation affecting an entire bed or beds.

A section was measured at the best exposure of sediments of the Blounts Creek Formation we were able to find within the study area (figure 15), where they are exposed in roadside gullies along the south side of Holly Springs Road just east of its T -intersection with Dugout Road, in the northeastern Big Creek area, Birds Creek quadrangle [C], in WC/NW Sec. 13, T. 1 N., R. 7 W. Much of the section is characterized by fine-scale low-angle cross lamination, somewhat similar to the structures exposed at the Pickering locality mentioned above. One noteworthy feature at this locality is an intraformational conglomerate bed formed from pebbles of reworked ironstone, suggestive of penecontemporaneous iron-oxide cementation interrupted by an

40

NORTH

FEET

300 SELLERS STORE

SOUTH

WILLIS FORM - - _ ATION

- UNCONFORMITY __ 250 - -

BLOUNTS CREEK MEMBER OF FLEMING

200

ONE MILE

Explanation 1. Light gray silty clay. 2. Sandstone lentil and ironstone at base of weathered material. 3. Weathered silty clay and residual terrace sand, 2 feet. 4. Sandy siltstone lintil, thickness 0-6 feet, well exposed in railroad cut. 5. Small remnant of Willis Formation; O-to feet red massive sand exposed above

highway, cross bedded. Contact with underlying Blounts Creek member irregular; chert gravel and clay balls at contact.

6. Sandy siltstone 0-6 feet thick underlain by unconsolidated silty clay and overlain by about 6-10 feet of orange red and purple mottled, weathered, argillaceous silt; distinct contact with Willis Formation and suggestion of pre-Willis soil horizon.

7. Massive sand, thicker down hill, is result of soil creep and occurs extensively on outcrops of both terrace formations and on sandy Miocene strata.

8. Massive red sand, gravel at base. 9. Gray weathered silty clay.

Figure 14. Unconformable relationship of Willis Formation and underlying Blounts Creek Formation of the Fleming Group along U.S. Highway 171 in Kansas City Southern Railway cut 2.4 km (1.5 mi) south of Pickering (Sec. 3, T. 1 S., R. 9 W., New Llano quadrangle [SED. Redrawn and adapted, with permission, from figure 11 of Welch (1942:61; copyright 1942 by the Louisiana Geological Survey).

41

Silty clay with surface 'popcorn weathering' Light gray 2.5Y 7/2 with yellowish brown lOYR 5/8 mottles ~ ~----~ .. ~~.~.4.~.~.~.4-- 7

~il~~~~;:72~~;e i/2fine sand "-:. -:- .;. (:--;: ... ~ .':\:. :,;,:

.' ...... .

• Clayey silt with pebbles comprising reworked ironstone nodules

Matrix: light gray 2.SY 7/2 to

Silty day with surface 'popcorn weathering' Light gray 2.5Y 7/2

Light gray 2.5Y 7/2

Brown 7.5YR 5/4, light gray 2.5Y 7/2 [gley?]

Light gray 2.5Y 7/2 with red 2.5YR 4/6 mottles

--

--

--

--

--

-

pale yellow 2.SY 7/3 with brown .(5 7.SYR S/6 mottles --? O·

Pebbles: dark reddish brown SYR 3/4Q~D<;::;(;::;LO·Q.O·0 0.0 Q 9: t7o.:o: .. c::~ to dark red 2.SYR 3/6

.... E ., -g

~ '" .t: '0 o '"

Light gray 2.5Y 7/2 with yellowish brown lOYR 5/8 mottles

Yellowish brown lOYR 5/8 to brownish yellow lOYR 6/8 interlaminations

Light gray 2.5Y 7/2 with yellowish brown lOYR 5/8 mottles

Subhorizontally oriented gleyed blebs, contains lightish flecks I Yellow 2.5Y 7/6

light gray 2.5Y 7/2, in three zones Brownish yellow 1 OYR 6/6 contains lightish flecks

Light brown 7.5YR 6/3, pinkish white 7.5YR 8/2 = noncase·hardened sand, alternates with the other colors ('salmon' - 'orange')

Yellowish brown lOYR 5/8 to olive yellow 2.5Y 6/6 ~ ~ ~

Clayey silt interbed L -:- :.... "j Light gray lOYR 7/2 with red lOR 4/6-8 mottles J. _--~

.~

Yellowish brown 10YR 5/8

• Ironstone gravel bed in south gully is more sandy and thicker, color ranges toward light brownish gray 2.5Y 6/2 with mottles strong brown 7.5YR 5/8, yellowish red 5YR 4/6; ironstone gravel bed in north gully is less sandy and thinner. Reworked ironstone pebbles also occur in surficial slope-wash mantle, primarily below this bed.

~ 6

r-- 5

3

Figure 15. Measured section of sediments of the Blounts Creek Formation of the Fleming Group, exposed in roadside gullies along the south side of Holly Springs Road just east of its T-intersection with Dugout Road, in WC/NW Sec. 13, T. 1 N., R. 7 W., Birds Creek quadrangle [C].

42

episode of local base-level lowering during Blounts Creek deposition. A differential GPS reading of this location is included on the attached diskette.

In places near its unconformable contact with overlying Plio-Pleistocene strata, the Blounts Creek shows the purplish alteration characteristic of the Miocene-Plio-Pleistocene contact observed where it involves other formations of the Fleming Group. Welch (1942, his figure 11) depicted the contact with this alteration at the railroad-cut exposure of the Blounts Creek at Pickering (figure 14). A large exposure of an area near the Blounts Creek-Plio-Pleistocene contact was examined in the northwestern Multi-Purpose Range Complex (MPRC) area, in SCINW Sec. 4, T. 1 N., R. 7 W., Birds Creek quadrangle [NW]; figures 16 and 17 show the characteristic purplish mottles in the uppermost portion of gray sandy clay of the Blounts Creek, overlain at this locality by a 'surficial mantle of yellow loam. In SW Sec. 1, T. 1 S., R. 9 W., Fort Polk quadrangle [SW], reddish Plio-Pleistocene sand overlies gray clayey very fine to fine sand of the Blounts Creek Formation, which shows an identical zone of purplish mottled peds near its top; the Plio-Pleistocene sand incorporates purplish mud rip-up clasts near its base. Also in SW Sec. 1, T. 1 S., R. 9 W., 0.3 to 0.5 km (0.2 to 0.3 mi) northwest of the above locality, weathered sand of the Blounts Creek Formation exposed in a large roadcut is cut by a number of graveliferous slope-wash gully fills; these probably represent surficial wash of Holocene age reworked from sediments of the Upland Allogroup nearby.

PLIOCENE SERIES

(Paul V. Heinrich and Richard P. McCulloh)

Upland Allogroup

Although its outcrop is highly dissected and discontinuous, the Upland Allogroup, which is equivalent to the "High Terraces" of earlier usage, is one of the more widespread and recognizable stratigraphic units within the Coastal Plain Province. The deposits of the Upland Allogroup occur as remnants of a once regionally extensive blanket of coarse-grained sediments, which are recognizable along the Coastal Plain Province from Virginia to Texas. The deposits of the Upland Allogroup commonly occur as erosional remnants capping isolated hilltops and comprising the ridge crests of interfluves (Autin et al. 1991).

The sediments that comprise the Upland Allogroup differ from the underlying Miocene strata and the deposits of the Intermediate Allogroup, which onlap unconformably onto it. First, the sediments of the Upland Allogroup are generally coarser than the Miocene strata underlying it and the younger sediments of the Intermediate Allogroup that onlap onto it. Generally, but not always, the coarser nature of the Upland Allogroup is manifest in the presence of an abundance of gravel throughout its thickness (Matson 1916; Doering 1935, 1956; Forney 1950; Autin et al. 1991). Second, in contrast to younger and older strata, sediments within the Upland Allogroup are characteristically very highly weathered. As a result they exhibit deep reddish,

43

.j:::..

.j:::..

Figure 16. View to the west-northwest of "yellow loam" on grayish sandy clay of the Blounts Creek Formation of the Fleming Group, the uppermost portion of which shows purplish mottles; the large exposure is near the northwest edge of a moving target near the 4-91E, 34-40N UTM grid in the MPRC area, in SC/NW Sec. 4, T. 1 N., R. 7 W., Birds Creek quadrangle [NW]. (Hammer, right, foreground, has overall length of33 cm = 13 in.; pick end of hammer spans 17 cm = 6.7 in.).

~ VI

Figure 17. Close-up view, looking approximately to the east, of the purplish mottling in figure 16. (Overall hammer length is 33 em = 13 in.; piek end of hammer spans 17 em = 6.7 in.).

brownish, and purplish colors of ferric iron oxides not seen in the strata lying stratigraphically above and below it (Doering 1956; Aronow 1982; Autin et al. 1991). Third, the Upland Allogroup erodes into resistant hills, which creates well defined cuestas and sharp ridges that contrast with the relatively dissected, but flat terrace surfaces associated with sediments composing the Intermediate Allogroup. Finally, the soils, principally ultisols and some alfisols, developed in the sediments of the Upland Allogroup are typically far more mature than those developed in either the Fleming Group or the Intermediate Allogroup (Forney 1950; Autin et al. 1991; Dubar et al. 1991).

WILLIS FORMATION

Traditionally, the deposits of the Upland Allo group , which has also been designated as either the "High Terrace" or "Upland Complex," have been correlated with the Williana formation of Fisk (1938, 1940). For example, Bernard (1950) classified strata equivalent to the Upland Allogroup in southeast Texas as belonging to the Williana Formation of Fisk (1938, 1940). Similarly, both Welch (1942) and Hinds (1998a, 1999) argued that the Willis and Williana Formations are equivalent stratigraphic units and, thus, classified the strata within the Fort Polk region as belonging to the Williana Formation.

However, a carefully constructed regional cross section, figures 18 and 19, confirms an observation by Doering (1956) that along strike, the deposits mapped by Fisk (1938, 1940) as the Williana Formation in Rapides Parish lie below the level of the deposits of the Upland Allogroup in the Fort Polk region. The deposits of the Upland Allogroup occur as much as 200 ft (60 m) above the top of Fisk's (1940) Williana Formation just across the Calcasieu River in Rapides Parish. The base of the lowermost deposits of the Upland Allogroup in the Fort Polk region lies barely level with the top of the Williana Formation and about 50 ft (15 m) above its base. Winker (1991) further illustrates differences in the stratigraphic position of the Upland Allogroup in the Fort Polk region and the Williana Formation across the Calcasieu River. He maps the Upland Allogroup in the Fort Polk region as part of his pre-Lissie surface(s) and the Williana Formation of Fisk (1940) as being part of his Lissie surface. The significant difference in stratigraphic position and lithology between the Upland Allogroup in the Fort Polk region and the Williana Formation in Rapides Parish demonstrate that they are different units of formation rank within the Upland Allogroup.

With regard to lithology and stratigraphic position, the deposits of the Upland Allogroup are identical to the Willis Formation of Doering (1935) (Forney 1950; Bernard and LeBlanc 1965; Aronow 1982). Thus, they are correlated with and designated as the Willis Formation in this investigation. Contrary to previous studies, this correlation implies that the Willis Formation and Williana Formation are two different stratigraphic units. Furthermore, because the deposits of the Williana Formation lie more deeply entrenched into the Miocene strata of the Gulf Coastal province with its surface even lower than the youngest of the Willis Formation, the Williana Formation is clearly younger than the Willis Formation.

46

Lithology As first noted by Bianchi (1982), the Willis Formation, which he referred to as the

"Citronelle Formation," consists of two recognizable sedimentary facies, a sandy facies and a gravelly facies (figure 20). The sandy facies, which Bianchi (1982) called the "fine sandy facies" of his "high coastwise group," constitute the basal and middle parts of the Willis Formation. The gravelly facies, which Bianchi (1982) called the "graveliferous facies" of his "low coastwise group," constitutes the youngest part of the Willis Formation in the Fort Polk region.

Sandy Facies-The sandy facies of the Willis Formation consists of mostly very fine to medium sand and muddy sand. These sediments contain common clasts of purplish clay and silty clay, with minor amounts of coarse sand, gravel, clay, and silt. Commonly, the sandy facies is largely massive, having been homogenized by plant roots and weathering. Generally, these sediments exhibit sedimentary structures, which include planar cross bedding, trough cross bedding, ripple lamination, climbing ripple lamination, and scour-and-fill structures. The most commonly observed sedimentary structure in this investigation was medium-scale trough cross bedding. Fine-grained sediments, which vary from clay to silt, occur as isolated, commonly discontinuous, beds and lenses. No evidence for any overall upward fining or coarsening trends within the sandy facies was observed.

A prominent character of the sandy facies is the presence of fine-grained rip-up clasts. In varying abundance, almost every outcrop observed in this investigation contains rounded purplish clasts consisting of clay to silty clay. These clasts typically range in diameter from 2 to 5 cm (0.8 to 2 inches). The largest of these rip-up clasts are in the cobble size range; the largest rip-up clast we observed was about 8 cm (3 inches) in diameter, whereas Hinds (1997b) reported rip-up clasts as large as 25 cm (10 inches). The rip-up clasts are frequently abundant enough to form thin beds of rip-up-clast conglomerate. Also, they are typically found concentrated along cross-beds and at the base of scours. Whitish clay/mud clasts of sand size commonly occur on and delineate cross beds.

In places the sediments are gravelly, and can include discrete gravel stringers on cross beds. In a few places, they contain a significant content of granules. Typically, the gravel consists of subrounded to sub angular quartz clasts 1 to 2 em (0.4 to 0.8 inches) in diameter. The gravel occurs either scattered thoughout the sand or concentrated in very thin to thin beds and at the base of scours.

The sandy facies exhibits bright and variable colors. Although predominantly various shades red, the sandy facies can vary from red, weak red, to strong brown and yellow. Commonly some combination of these colors can be seen in one outcrop as illustrated by Figure 16 of Hinds (1998a, 1999), a measured section located in SWINW Sec. 24, T. 2 N., R. 7 W., about 1.2 miles (2k m) northeast of Artillery Lake in the Simpson South quadrangle [SC]. In a measured section in the northwestern MPRC area (figure 21), similar variation in the color within one outcrop is illustrated. The sandy facies in this measured section exhibits pale red purple 5RP 6/2, pale yellow 2.5Y 8/4 with yellow 2.5Y 7/8 mottles, reddish brown 2.5YR 4/4 to red 2.5YR 4/6, yellowish red 5YR 5/6, strong brown 7.5YR 5/8, and olive yellow 2.SYR 6/8 coloration.

47

Legend for Figures 18, 23, 24, and 25 Stratigraphic Units

Quaternary System

Holocene Series

Hua Unnamed Alluvium

I: : : I Hbb Big Brushy Formation

Pleistocene Series

• Pp Prairie Allogroup undifferentiated

• Intermediate Allogroup

III Pilu Lissie Formation, upper

~ Pill Lissie Formation, lower

~ Upland Allogroup, undifferentiated

Tertiary System

Pliocene Series

Puw Upland Allogroup, Willis Formation

Puwg Willis Formation, Gravel Hill Allomember

Puwt Willis Formation, Tower Road Allomember

Puwd Willis Formation, Dugout Road Allomember

Puwk Willis Formation, Kisatchie Allomember

Puwf Willis Formation, Fort Polk Allomember

Miocene Series

D Mfb Blounts Creek Member

D Mfcc Castor Creek Member

48

500

(j) 400

If .£ c 300 o

~ ill 200

Lacamp Section

West

Puwf

.c

~ :; 0

~ (fJ

~ OJ '" 0 OJ If) ~ ro 0-W E

ii5

intersection with Birds Creek Section

I Puwf

Mfcc

£; :J o (fJ(\\

5;:: ~~ E

ii5

Intersection with Fullerton Section

Puwf I

Mfcc

Puwt

92 52' 30"

===-_ ...... e:==::::ioo ........... "==::::i5 Miles

o 300 600 900 1200 1500 1800 2100 2400 Feel

i=:::::i.._"=:::i. ..... i::=::i.. ..... 6 Kilometers

Mfcc

"Bentley Formation" of Fisk (1940)

\

East

"Williana Formation" of Fisk (1940)

I \

93 07' 30" 93 00' 00" 94 45' 00" 100~--~~~~--------------------____________ ~~~~ ______________ ~ ________________________________________ ~~ __ ~=: ____ ~~~ ____________ jL

Figure 18. Cross section along crest of Kisatchie Wold and across Calcasieu River Valley. Horizontal scale = 1:125,000. Vertical exaggeration = 52X.

49

500

400

300

200

100

••••••••••••••••••••••••••••••••••••••••••••

VI

93"15'00" 93"07'30" 93"00'00" 92"52'30" 92"45'00" 92"37'30" 31 "15'00"ISla r1"15'00"

N

+ II I .1".,('1111111. •• _"'T'I~L·16"1r.1I

Elmer

31 "07'30"1_ I Ii' I ~ lC l'rt_~1}1._A. ~?:;:::_1 __ I.~ I Melder III 131 "07'30" .. ..... ! ... '. r1_~-':".~ i_

II Melder

31 "00'00'" f 1 Lq I '31 "00'00" 93"00'00" ., 92"52'30" 92"45'00" 92"37'30" 93"15'00"

LEGEND

Q Main Post area of Fort Polk

--......., Cross section line

.. Small-size town

• Medium-size town

Figure 19. Index map showing locations of cross sections relative to the main post of Fort Polk, Louisiana.

3474500 m N. 474500 m E.

3445500 m N. 994250 m E.

Northwest

Zone 1

fine sandy facies 'high' coastwise group Citronelle formation ~

Castor Creek member Fleming formation (Welsh 1942)

Zone I Eagle Hill

. .. , ...... · . · . · .

Zone II

460- 146.3

3436000 m N., 499750 m E.

\rt"'~~,

Zone III Zone IV

3430000 m N., 502900 m E.

fine sandy facies 'high' coastwise group Citronelle formation ___ 0:-

460-

440-134.1

graveliferous facies "low· coastwise group Citronelle formation

fine sandy facies / "'ow· coastwise group Citronelle formation

Lena member (Welsh 1942, Pane 1966) Undifferentiated Miocene (Anderson 1960)

\v ~Alluvium2

Lena andlor Carnahan Bayou member Fleming formation (Welsh 1942)

420-

400-122

360-

360-109.6

340-

320- 97.6

300-

260_ 65.4

Blounts Creek member Fleming formation (Welsh 1942)

400m scale: horizontal L....--.J

131211

site - •

vertical 1 Oft J 3m

Figure 20. Dip sections across Main Fort and Peason Ridge areas of the Fort Polk Military reservation. Redrawn from Bianchi (1982:74).

52

Southeast

•••• ~ - Colluvium I Alluvium . ... Aliuvium2B

Aliuvium2A

Elevation above mean sea level

feet meters

490 -

470 - 143.3

450 -

430 - 131

410-

390 - 116.9

370 -

350 - 106.7

330-

310 - 94.5

290 -

270 - 62.3

250-

230 - 70.1

210-

190 - 57.9

170-

150 - 45.7

130-

[This page left intentionally blank]

53

Massive Sand

Yellowish red SYR S/6

{Strong b~n 7.5YO 5/B

Olive Yellow 2.SYR 6/8

o

.. ~¥ o/";. .

.. ::>;'0/ oJ-- . • <:l •

Sand, fine to medium, with scattered pebbles and faintly discernible cross beds Reddish brown 2.5YR 4/4 to red 2.SYR 4/6

Conglomerate and gravelly sand with dark reddish gray SYR 4/2 clay pebbles Matrix grades updip along bed from red lOR 4/6·8 in gravelly sand to light gray lOYR 7/2 to brownish yellow lOYR 6/8 in clay-pebble conglomerate

Sand, very fine to medh.inl, iippled and flat-laminated, pale red purple 5RP 6/2 Grades downward to pale yellow 2.SY 8/4 with yellow 2.SY 7/8 mottles (colors cut irregularly across bedding)

5

4

3

1

Figure 21. Combined outcrop sketch and measured section (no horizontal scale) of Upland Allogroup strata in steep gully, SWINE Sec. 5, T. 1 N., R. 7 W., northwestern MPRC area, Birds Creek quadrangle [NW].

54

The only fossils observed in the sandy facies of the Willis Formation consist of rare petrified wood. Petrified wood was found at two locations in the Fort Polk region, in both cases at the base of this facies. Petrified wood was found in roadcuts just north of Engineer Lake along Artillery Road in the Birds Creek quadrangle [NC], in SWINE Sec. 27, T. 2 N., R. 7 W. A piece of petrified wood was also found in an outlier of the Willis Formation exposed in a roadcut in the Dowden Creek quadrangle [NC], in SWISE Sec. 6, T. 4 N., R. 9 W. Within southeast Texas, Bernard (1950) noted that petrified wood was common in the graveliferous sands of the Willis Formation, with large logs and stumps being more common in its sands. The petrified wood that was observed in the Fort Polk region was judged to be native to the Willis Formation. The large logs and stumps that Bernard (1950) observed in the sands of the Willis Formation are also likely to be native to it.

Gravelly Facies-The gravelly facies consists primarily of commonly muddy, medium to coarse sands, gravelly sands, sandy gravel, and gravel. Like the sandy facies, the gravelly facies is frequently homogenized by plant roots or weathering. Generally, the gravels and sandy gravels exhibit well-developed medium to thick sets of trough cross bedding. The sand beds show tabular and trough cross bedding of varying scales, and ripple lamination. Purplish rip-up clasts identical to those found in the sandy facies also occur within this facies. No evidence for any overall upward fining or coarsening trends within the gravelly facies was observed during fieldwork.

The gravel consists of granule- to pebble-sized chert gravel, with the largest size fraction observed ranging from 4 to 5 cm (1.5 to 2 inches). Lenzer (1982) studied the composition of the gravel from a gravel pit along Lookout Road between Birds Creek and Sixmile Creek. As illustrated by Table 2, he found that the gravel consists mainly of "dense" brown and brownish gray chert with minor amounts of other types of cherts, sedimentary quartzite, and metamorphic quartzite. Quartz, which is abundant in the sandy facies, is noticeably absent among the rock types identified by Lenzer (1982).

The only fossils found in the gravelly facies are those contained within scattered individual clasts of the chert gravel, consisting of molds of rare brachiopods, crinoid stems, and corals, and are thus not native to the Willis Formation, but rather reflect the age and depositional environments of the Paleozoic carbonate rocks from which the chert was derived. Although they fail to provide any information concerning the age and paleoenvironments during the deposition of the Willis Formation, they should provide some evidence concerning the source of the chert gravels found in the gravelly facies.

The general lack of fossils found or observed within both the facies of the Willis Formation implies that conditions during the deposition of the Willis were generally not conducive to the preservation of fossils. The coarse-grained character of the Willis would have allowed for the oxidation of organic matter and leaching of bones and shells. In addition, intensive weathering of these sediments during and after deposition would have precluded the preservation of fossils; the petrified wood is preserved because silicification occurs relatively soon after burial.

The gravelly facies typically exhibits various shades of red as exemplified by red 2.5YR 5/8 gravelly sand in the Fort Polk quadrangle [SW], in NE Sec. 12, T. 1 S., R. 9 W. This is also illustrated by a measured section shown as Figure 22 of Hinds (1998a,

55

Table 2. Gravel Sample, Willis Formation (Lenzer 1992).

Two to Four cm Greater Than Four cm Longest Dimension Largest Dimension

Rock Type Number % of Total sample Number % of Total sample

sand concretion, 1 0.6 iron-oxide cement

brown chert, dense 96 53.0 26 13.6

porous brown and 8 4.4 1 0.6 tan chert

silicified sandstone 3 1.7 3 1.7

dense red and 4 2.2 4 2.2 brown chert

white and gray 1 0.6 banded chert

Porous red chert 4 2.2 1 0.6 with brown cortex

sedimentary quartzite 2 1.1 1 0.6

Jasper 3 1.7

chalcedonic chert 13 7.2 5 2.8

gray chert with tan to 2 1.1 1 0.6 black cortex

dense metamorphic 2 1.1 quartzite

Subtotal 138 76.3 43 24.1

Total Sample = 181

56

1999) in NE/SW Sec. 5, T. 1 S., R. 7 W., in the Bird Creek quadrangle [SW]. In an abandoned gravel pit, the gravelly facies is dark reddish brown 5YR 3/4, red lOR 4/6, yellowish red 5YR 4/6, and brownish yellow 10YR 6/6. It also contains purplish rip-up clasts, characteristic of the Upland Allogroup in general, colored 5RP 4/6 (Hinds 1998a, 1999).

The reddish, brownish, or purplish ferric iron oxides that pervasively stain, even cement, the sediments of both the sandy and gravelly facies show that the entire Willis Formation has been highly weathered to very deep depths. The deeply weathered nature of the Willis Formation reflects a number of influences. These include: (1) the high initial permeability of the coarse parent materials; (2) the thickness of the drained soil column above the water table; (3) the comparatively great age of the strata within the Upland Allogroup; and (4) contemporaneous weathering of these strata during their accumulation as a result of warm Pliocene paleoclimates (Aronow 1982).

"Bleached" Sediments-Both the sandy and gravelly facies contain outcrops of bleached-looking, grayish sediments, not unlike those of the Catahoula and Fleming in coloration, with red mottling in places. These bleached sediments are typically homogenous mixtures of sand, mud, and in places gravel. Abundant root molds and haloes are commonly associated with these sediments. For example, grayish, bleached sediments were observed overlying typical reddish cross-bedded sand [but with the contact between the two covered] in a roadcut exposure on the north side of Lookout Road, in the Birds Creek quadrangle [SW], in NEINW Sec. 4, T. 1 S., R. 7 W. Similar sediments occur within the Willis formation on the north side of Artillery Road in Slagle area 7, in the Birds Creek quadrangle [NC], in SEINE Sec. 27, T. 2 N., R. 7 W. At the former locality, the grayish sediment ranges from light gray 10YR 711-2 to very pa1e brown 10YR 8/2 to white 10YR 811, with mottles ranging from dark yellowish brown 1 OYR 4/4-6 to yellowish brown lOYR 5/6-8 and yellow 10YR 7/6-8. Within the gravelly facies, red and gray variants were observed in a single bed in the Willis Formation where the section was measured in the northwestern MPRC area (figure 21). This bed grades updip from gravelly sand with a red lOR 4/6-8 matrix to clay-pebble conglomerate with a light gray 10YR 7/2 to brownish yellow 10YR 6/8 matrix. In the Birds Creek quadrangle [SC], in NW Sec. 27, T. 1 N., R. 7 W., these sediments range in color from light gray 10YR 7/2 to very pale brown 10YR 812, with mottles ranging from yellowish brown 10YR 5/6-8 to brownish yellow 10YR 6/6-8 and weak red lOR 4/4 to red lOR 4/6-8.

Stratigraphy Two major interpretations have been proposed for the stratigraphy of the Willis

Formation within the Fort Polk region. First, Welch (1942) and Doering (1956) inferred that the Willis Formation consists of a single stratigraphic unit with a gulfurard-tilted, but highly dissected terrace that dips below the deposits of the Lissie Formation. The Lissie Formation was interpreted as conformably onlapping the deposits of the Willis Formation in the Fort Polk region and extending northward through its outcrop within the Mississippi Valley. Bianchi (1982) showed the Willis Formation as forming a single pediment cut into the Miocene and forming a relatively flat terrace surface (figures 20 and 22). According to his interpretation both the Willis Formation and its terrace, instead

57

Vl 00

North

Eagle Hill

r·o ," \ ,

121.9 --- Peason Rtidge Structural Surface

106.7

91.5

76.2 ---

60.9

45.7

30.5

15.2

0.0·--

Caster Creek Structural Surface

--- Williana Structural Surface

Miocene clays predominanft

~?

I

: ~ ? I

o o

000

-. 0 00

I~ 0 Uplifted 1 Pediment 11 -

o

o

300 00'+

950 38'

-76.2m -

f

;~~ -76.2m -

~0.9m-

Bentley Erosional Surface

__ 30.5m - -r lI9per S\fI.lC\Ura.\ Sl.Irt3C

e _ -r? _30.5m -

Prairie Structural Surface

\ \.~o~~~~~I.It\ace ~~1_1.6m

_ \5.2 11'

__ 1.6 11'

T/R Sequence (Otvos, 1981)

Map of a portion of the Sabine River - Red River Interfluviatile Area

South

? I I

:~ 1:~ 1 :~ ?

...

Figure 22. Dip section along crest of Sabine-Red River drainage divide and index map by Mr. Thomas H. Bianchi. Redrawn from figures 2 and 4 of Bianchi (1984:65, 67).

of dipping beneath the deposits of the Lissie Formation, are instead truncated and completely cut out by it. Bianchi (1982) recognized additional steps in the topography of the southern cuesta. He interpreted these as erosional surfaces cut across the Fleming (figure 22). For southeast Texas, Bernard (1950) made an interpretation that combines aspects of both models in that he interpreted the Willis Formation as a single gulfward-dipping unit truncated by the Lissie Formation.

The production of the 7.5-minute geologic quadrangles and construction of both cross sections resulted in an interpretation that is a modification of the interpretation of Bianchi (1982). The topographic profiles confirmed the existence of the stepped topography discussed by Bianchi (1982). However, integration of data from the geologic mapping revealed that the base of the Willis Formation generally parallels the concordant summits of each of the steps (figures 19,23-25). The steps are interpreted to represent a series of relatively flat coast-parallel terraces underlain by fluvial deposits of the Willis formation. Each terrace is lower than the next terrace to the north, and its associated fluvial deposits are correspondingly downcut into the Miocene relative to the fluvial deposits to the north. These terraces and associated fluvial deposits are inferred to be separated by erosional contacts (figures 23-25); as such they are interpreted as allostratigraphic units.

Allomembers-As a result of the mapping, five informal allostratigraphic units are recognized and mapped: the Fort Polk allomember, Kisatchie allomember, Dugout Road allomember, Tower Road allomember, and Gravel Hill allomember (figures 23-25). The Fort Polk and Kisatchie allomembers consist of the sandy facies. The Dugout Road, Tower Road, and Gravel Hill allomembers consist of the gravelly facies.

Because the southern cuesta is deeply dissected by local drainages, the sediments of these allomembers are preserved only along the crests of the major interfluves between drainages. Also, the deep dissection of the Willis Formation has reduced the surfaces of its allomembers to a series of concordant summits. In the case the of the Fort Polk allomember, all evidence of its surface has been obliterated. Even its fluvial deposits have been reduced to erosional remnants capping the east-west crest of the southern cuesta and isolated summits along the interfluves extending southward from it (figures 18,23).

Within the northern cuesta of the Kisatchie Wold, the Willis Formation occurs as widely scattered, discontinuous outliers of limited extent. Typically, these outliers are associated with only the highest summits, commonly with maximum elevations exceeding 400 ft (122 m). The highest known outliers lie at elevations above 470 ft (143 m) in the Dowden Creek quadrangle [NC, EC, NE]. The outliers consist of sands, which may closely resemble the sands of underlying Oligocene and Miocene strata where these have been oxidized. The presence of the purplish clay/mud rip-up clasts, therefore, is a very useful indicator helping to distinguish them. In this investigation we ultimately came to regard such occurrence as diagnostic of the Upland Allogroup with essentially no observed contradictions.

Basal Contact-As mentioned above, the Fleming at its unconformable contact with the overlying Willis Formation exhibits in many places purplish alteration of rectangular

59

blocky peds of its finer-grained sediment extending about 1 m directly beneath the contact. Commonly, the sediments of the overlying Willis Formation incorporate purplish clay/mud rip-up clasts. The purplish alteration of the Miocene and incorporation of purplish rip-up clasts into the overlying Willis Formation was observed at numerous localities. Welch (1942, his figure 11) depicted these relations at this contact at the railroad-cut exposure ofthe Blounts Creek at Pickering (figure 14). The largest such exposure with such alteration of the Fleming found in this investigation lies just northwest of a moving target at approximately the 4-91 E, 34-40N UTM grid in the MPRC area, in the Birds Creek quadrangle [NW], SCINW Sec. 4, T. 1 N., R. 7 W. Over a large area at this locality "yellow loam" has been stripped away from gray sandy clay of the Blounts Creek Formation, which is riddled with purple mottling of peds in its upper portion (figures 16, 17). Virtually identical mottling of the Miocene directly beneath the contact, with incorporation of purplish mud rip-up clasts into the overlying reddish cross-bedded sand of the Willis Formation, characterizes grayish clayey very fine to fine sand of the Blounts Creek Formation in the Fort Polk quadrangle [SW], in SW Sec. 1, T. 1 S., R. 9 W. An exposure of similar alteration in grayish silty clay of the Castor Creek Formation was observed in the Simpson South quadrangle [SE], in NE Sec. 19, T. 2 N., R. 6 W., on the east valley wall of a tributary of Brushy Creek. The combined outcrop sketch and measured section of Willis Formation sediments cutting out those of the Carnahan Bayou Formation (figure 13) in the Peas on quadrangle [SC], SEINW Sec. 30, T. 5 N., R. 9 W., depicts both the purplish alteration of finer-grained sediment below the contact and the purplish clasts above it, as well as some burrow casts of purplish mud in reddish Carnahan Bayou sand. The Willis Formation sediments at this locality are also mottled heavily in contrast to the Carnahan Bayou, which aids in distinguishing the two.

Not all ofthe observed contacts between the Willis Formation and Fleming Group exhibit this alteration below the contact. For example, a "clean" contact on unaltered Miocene sediments was observed on the north side of Lookout Road west of Birds Creek, in the Birds Creek quadrangle [SC], in NE/SW Sec. 35, T. 1 N., R. 7 W. At this exposure sandy conglomerate and gravelly sand with substantial admixed clay, of the grayish color variant of the Upland Allogroup, overlie grayish silt and very fine sand of the Blounts Creek Formation.

Age Unfortunately, the lack of fossils in the Willis Formation makes the direct dating

of it impossible at this time. Instead, approximate limits on its age must be inferred from what is known about the age of the stratigraphic units that unconformably onlap it and which it unconformably overlies. In this connection it can be observed that the degree of development of both unconformities is such that they must represent major eustatic and/or tectonic events in the prehistory of the Gulf of Mexico significant enough to have been recognized and dated.

The age of the Lissie Formation, which unconformably onlaps the Willis Formation, provides an approximate minimum age for it. In Texas, the Lissie Formation contains Pleistocene vertebrate remains that include Bison latifrons (Harlan), Mammuthus columbi (Falconer), Mammuthus imperator (Leidy), Equus excelsus Leidy, Equus francisi Hay, Equus complicatus Leidy, and Equus semiplicatus Cope (Forney 1950).

60

Fort Polk Section

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61

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63

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65

500

400

300

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100

Dubar and others (1991) noted that Kukla and Opdyke (1972) reported sediments with reverse magnetic polarity from the "Lissie," "Bentley," and "2nd terrace," which Dubar and others (1991) suggested are equivalent to the Lissie Formation. This indicates that the deposits of the Lissie Formation and their associated terraces are older than 0.75 million years.

As discussed previously, the Willis Formation is older than the Williana F ormation found east of the Calcasieu River and west of the Mississippi River. Woodward and Gueno (1941) interpreted the presence of very large boulders of chert, quartzite, sandstone, and petrified wood within the Williana as being the result of downstream transport by ice-rafting. In addition, Fisk (1939) found pebbles of igneous rock and Baraboo Quartizite in gravels of the Williana Formation. Although, as hypothesized by Autin and others (1991), these gravels might belong to pockets of glacial outwash included in the Williana Formation along the sides of the Mississippi River Valley, the above pebbles imply that the gravels are in part of glacial-outwash origin. Being older than the Lissie Formation, the Williana Formation would, in part, have formed during Early Pleistocene or Late Pliocene glaciations. This would imply that the Willis Formation is no younger than the Early Pleistocene or Late Pliocene.

The lower limit of the age of the Willis Formation is constrained by vertebrate faunas described from both the Goliad Formation in Texas and the Fleming in Louisiana. The vertebrate fauna from the Castor Creek Formation of the Fleming Group is estimated to be between 12.5 and 14.5 million years old (Schiebout 1994, 1997). The Willis Formation is significantly younger than this given the thickness of the Blounts Creek Formation lying between it and the vertebrate-bearing beds in the underlying Castor Creek Formation. In Texas the Willis Formation overlies the Goliad Formation, which contains the Lapara Creek Fauna, which Prothero and Manning (1987) estimated to be 10 to 11 million years old. Taken together these faunas suggest that the Willis Formation is significantly younger than 10 million years old.

Vertebrate fossils correspondingly provide a maximum age for the stratigraphic equivalents of the Willis Formation, the Citronelle and Miccosukee Formations, east of the Mississippi Alluvial Valley. In the case of the Ashville local fauna of north Florida, Huddlestun (1988) argued that these late Barstovian vertebrate fossils came from strata underlying the Miccosukee Formation. Thus, the Miccosukee Formation postdates a middle Miocene (late Barstovian) age of about 11 to 16 million years (Woodbume and Swisher 1995). In southwest Alabama, the Mauvilla local fauna occurs in paralic-alluvial deposits of the "Miocene coarse clastics" of Raymond (1985), which underlie the Citronelle Formation. The Mauvilla local fauna consists of late Miocene (eady Hemphillian) vertebrates that date these sediments to about 7.0 to 9.0 million years ago (Hulbert and Whitmore 1997, Woodbume and Swisher 1995). Thus, the Citronelle and Miccosukee Formations are younger than middle to late Miocene.

Within southeast Texas, Morton and others (1988) correlated the base of the Willis Formation with the Bigenerina "A" (Bigenerina floridana) benthic foraminifer datum. Taking the arbitrary drop in datum in account, the correlation by Morton and others (1988) implies that the Willis Formation correlates with the middle and upper portions of the Bigenerina shale. The age of the benthic foraminifer datums and correlation with the transgressive Bigenerina shale implies that the Willis Formation

67

correlates with major sea level highstands that occurred during the Early Pliocene (Paleo-Data, Inc. 1993) (figure 26). '

This interpretation is consistent with the finding of Kukla and Opdyke (1972) of normally magnetized sediments within the Willis Formation. They interpreted the normal magnetism of its sediments to represent the Gauss polarity epoch, Chron C2An, 2.6 to 3.5 million years ago. However, normal magnetism is also consistent with Chron C3n, 4.1 to 5.2 million years ago, which includes many of the Early Pliocene sea level highstands. Without additional data, it is impossible to determine which of these normal polarity intervals these samples represent. .

Finally, Otvos (1997) reported the presence of trace amounts Sciadopytis (Japanese umbrella pine) pollen from peats exposed in pits dug into the Citronelle Formation at Vancleave, Alabama, and Mossy Head, Florida. As Otvos (1997, 1998) argued, this precludes a Pleistocene age for the Citronelle Formation because the Japanese umbrella pine became extinct in North America prior to the end of the Pliocene. This is illustrated by the presence of Sciadopytis pollen in the Pliocene-age Yorktown Formation of North Carolina and Virginia and the lower Beavertown Formation of Delaware and New Jersey and its absence in the overlying Late Pliocene and Pleistocene strata (Groot 1991; Cronin et al. 1993).

The period of geologic time covering the Pliocene and late Miocene epochs, 3.0 to 6.0 million years ago, is hypothesized to be the most likely time during which the Willis Formation in the Fort Polk region accumulated. The unconformity at the base of the Willis Formation correlates best to a major drop in sea level about 10.5 million years ago (figure 26). During this lowstand of sea level, deposition within the Fort Polk area would have shifted southward ending the accumulation of the Blounts Creek Formation of the Fleming Group (Wornardt and Vail 1991; Paleo-Data, Inc. 1993). Between 5.8 and 10.5 million years ago, sea level would have been low enough that even during the highstands the edge of coastal plain deposition would have remained well south of the Fort Polk region (figure 26). During this time, erosion of the Fleming would have occurred in response to sea level drop and ongoing uplift. Between 5.8 and 3.0 million years ago, a series of highstands pushed sea level up to where the inner edge of coastal plain deposition might have transgressed during the highstands back into the Fort Polk region and resulted in the deposition of fluvial sediments (Wornardt and Vail 1991; Paleo-Data, Inc. 1993). If so, the Willis Formation could represent this period of high sea levels, while individual allomembers represent individual highstands (figure 26).

Dtvos (1997, 1998) presented evidence of sea level highstands higher than modem during the deposition of the Citronelle Formation. It consists of 0.5- to 7.0-m-thick units composed of muddy sands and muddy, pebbly, fine-to-coarse sands deposited in inshore and nearshore environments. These strata are characterized by either Ophimorpha burrows produced by ghost shrimp; the tubes of polychaete worms; the internal molds of veneroid and other shallow marine bivalves; or some combination of them. Otvos (1997) reported such marine beds near both the base and top of the Citronelle Formation.

In the case of the Citronelle and Miccosukee Formations, Huddlestun (1988) and Otvos (1998) have correlated them with Upper Pliocene, not Lower Pliocene, sea level highstands. They consider the Miccosukee Formation and the correlative Citronelle

68

Geologic Time

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Figure 26. Suggested correlation of stratigraphic units in southwest Louisiana with sea-level and coastal onlap cycles of Paleo-Data, Inc. (1993). Modified from Paleo-Data, Inc. (1993).

69

Formation in adjacent Florida to be of late Pliocene (Piacenzian) age. Otvos's (1998) determination is based upon research that shows the Citronelle Formation to overlie the fossiliferous Upper Pliocene Jackson Bluff Formation in the Florida panhandle and on Huddlestun's (1988) correlation of the Miccosukee Formation with the microfossil-dated Cypresshead Formation of eastern Georgia.

Given the uncertainties in correlations and facies changes between Florida and south-central Louisiana, a Late Pleistocene age for the Citronelle Formation in Georgia and Florida fails to preclude an Early Pliocene age for the Willis Formation in south-central Louisiana. However, it does imply that the younger allomembers of the Willis Formation likely are of Late Pliocene age (Figure 26). If Late Pliocene age deposits exist within the Willis formation, the younger, graveliferous Tower Road and Gravel Hill allomembers, which closely resemble the Citronelle Formation in lithology, would be the most likely candidates for such deposits. In this case, the major unconformity between the Willis Formation and the onlapping Lissie Formation would represent a major lowstand of sea level that occurred about 1.8 million years ago (Figure 26).

QUATERNARY SYSTEM

(Paul V Heinrich and Richard P. McCulloh)

PLEISTOCENE SERIES

Intermediate Allogroup

Within western Louisiana, the Intermediate Allogroup consists of fluvial deposits of the Calcasieu and Sabine Rivers, their tributaries, and various coastal plain streams. This allogroup includes strata and their associated terraces that have been previously classified as Bentley, Lissie, DeRidder, and Montgomery. The Intermediate Allogroup is topographically higher than the terrace surfaces of the Prairie Allogroup and topographically lower than the dissected uplands underlain by strata of both the Upland Allogroup and Fleming Group. Although generally dissected, terrace surfaces associated with the Intermediate Allogroup are recognizable as flat-topped ridge crests. Slightly south of the Fort Polk region in west-central Louisiana, the Intermediate Allogroup consists of 100 to 300 ft (30 to 90 m) of red, brown, and buff interbedded sand, silt, and clay (Autin et al. 1991; Dubar et al. 1991; Snead et al. 1998).

The Intermediate Allogroup is differentiated from the Prairie Allogroup on the basis of lithology, soils, slope, and degree of dissection of the terraces associated with it. The terraces associated with the Intermediate Allogroup are more dissected and have steeper gulfward dips than the terraces associated with the Prairie Allogroup. Also, the terraces of the Intermediate Allogroup lack the relict channels, meander-belt ridges, coastal ridges, and other constructional topography normally associated with the terraces of the Prairie Allogroup. In general, the sediments of the Intermediate Allogroup are

70

much sandier and have more mature soils, mostly alfisols, than characterize the Prairie Allogroup (Autin et al. 1991; Dubar et al. 1991).

LISSIE FORMATION

The Lissie Formation consists of the deposits of the Calcasieu and Sabine Rivers, their tributaries, and various coastal streams. The terrace associated with the Lissie Formation consists of an extensive rarnplike surface that extends from the edge of the Tertiary Uplands southward into Calcasieu Parish. This terrace surface dips to the south at 4 ftlmi (0.8 mlkm) except where it is offset by fault-line scarps. The formation extends eastward along the entire Texas coastal plain, where it was named, into Mexico as illustrated by Bernard and LeBlanc (1965) and Winker (1991).

Only within the "Cooter's Bogs" area in the Fullerton Lake quadrangle [SE, EC] were small outcrops of the Lissie Formation observed. In this region, the Lissie Formation is associated with two coast-parallel terraces. A higher and older terrace forms a narrow belt along the edge of the Tertiary Uplands. The younger terrace is the northern edge of the extensive, gulfward-dipping surface that extends southward from the study region into Calcasieu Parish. Welch (1942) mapped both of these terraces as the Bentley Terrace as he did most of the Lissie Formation within the Fort Polk region.

In the "Cooter's Bogs" area, small exposures of the Lissie Formation consist of grayish clayey silt and very fine sand with yellowish brown mottles. In hand specimen, these sediments superficially resemble sediment of the Fleming. They contrast sharply with the sediments of the Willis Formation, which are pervasively stained, even cemented, with reddish, brownish, and purplish ferric iron oxides. In places, yellow loam mantles these sediments.

As previously discussed, the Lissie Formation is likely Early Pleistocene in age. In Texas, the Lissie Formation contains Pleistocene vertebrate fossils. Kukla and Opdyke (1972) report sediments with reverse magnetic polarity from the "Lissie," "Bentley," and "2nd terrace," which Dubar and others (1991) suggest are equivalent to the Lissie F ormation. These paleomagnetic data indicate that the deposits of the Lissie Formation are older than 0.79 million years.

Prairie Allogroup (Undifferentiated)

The Prairie Allogroup consists of fluvial, deltaic, estuarine, and beach deposits of late to middle Pleistocene age. It lies topographically below the Intermediate Allogroup and topographically above the Deweyville Allogroup. The terrace surfaces associated with it exhibit little dissection and commonly show relict constructional topography (Autin et al. 1991; Dubar et al. 1991).

Within the Fort Polk region, the Prairie Allogroup consists of fluvial sediments that form discontinuous terraces found within the valleys of local drainages. Hinds (1998a, 1999) noted that the deposits of the Prairie Allogroup are recognized as relatively flat areas lying slightly above the level of the Holocene flood plain. It can be inferred from the types of soils associated with the terraces of the Prairie Allogroup that it consists

71

largely of silts, silty sands, and sands within the Fort Polk region, as described by Guillory (1997) and Martin and others (1990).

Although its internal structure is poorly known, existing research shows that the Prairie Allogroup consists of multiple valley-fill complexes and coastal plain sediments deposited by glacial-interglacial cycles over the last 700,000 years. Aronow and others (1991), Blum and Price (1994, 1998), and Winker (1979) have documented the presence of multistory sand bodies and major paleosols within the Beaumont Formation of southeast Texas. In addition, Blum and Price (1994, 1998) and Van Siden (1985, 1991) mapped multiple highstand fluvial-deltaic plains composing the Prairie Allogroup, Beaumont Formation, in the Houston area. Using thermoluminescence dating, Blum and Price (1998) defined valley fills that accumulated during oxygen isotope stages 5,7, and 9. Finally, seismic data interpreted by Thomas (1991) illustrate the presence of deposits of older oxygen isotope stages above the R6 regional reflector. As summarized by Blum and Price (1994, 1998), sufficient evidence exists to conclude that the Prairie Allogroup consists of a complex assemblage of fluvial and deltaic deposits representing multiple glacial-interglacial sea-level cycles over the last 700,000 years. Within southwest Louisiana, it appears that only deposits and landforms of the last interglacial highstand of sea level compose the surface of the Prairie Allogroup (Snead et al. 1998).

HOLOCENE SERIES

Within the Fort polk region, the only major stratigraphic units containing sediments of Holocene age are the unnamed alluvium and the informal Big Brushy formation. The unnamed alluvium, which underlies the modem flood plain, consists of sediments of both Holocene and late Pleistocene age. The Big Brushy formation, the widespread mantle of sand that forms the sandy epipedons of many of the soil series within Fort Polk, consists almost entirely of Holocene pedisediments.

UNNAMED ALLUVIUM (UNDIFFERENTIATED)

The unnamed alluvium is an informal name for the alluvial sediments that underlie the flood plains of the streams and rivers within the Fort Polk area. Although a stratigraphic unit of formation rank, it is left unnamed until such time as it is formally described. The unnamed alluvium fills valleys cut into older sediments ranging from the Miocene Fleming Group to the middle to late Pleistocene Prairie Complex.

In backhoe trenches excavated along the Whisky Chitto Creek, Cantley and others (1997) found the unnamed alluvium to consist of light brownish gray 10YR 6/2 to light yellowish brown 10YR 6/4 silty sand and sand with layers of brown 10YR 5/4 to yellowish brown 10YR 5/6 muddy sand and sandy mud (figure 27). In each of their backhoe trenches, which were 2 to 3 m (6 to 10 ft) deep, the thickness of the unnamed alluvium exceeded the trench depth. Although individual beds and buried soils can be resolved, they were internally massive and lacking in discernible sedimentary structures. The layers of muddy sand and sandy mud are the Band Bt horizons of paleosols (Cantley

72

---~ Q) ...... Q)

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73

et al. 1997). The clay is not detrital in origin, but rather was concentrated in these layers by illuviation.

In excavations at 16VN791 on the flood plain of Birds Creek within the MPRC area, Johnson (1990a, 1990b) observed that the unnamed alluvium at that site consisted of brown 10YR 4/3 to dark yellowish brown 10YR 4/6 silty sand and dark brown 7.5YR 4/6 to strong brown 7.5YR 4/6 muddy sand overlying brownish yellow 10YR 6/6 clayey sand and light gray 2.5Y 7/2 sandy clay. Johnson (1990b) interprets the muddy sands to be Bt horizons and the clayey sand to be a truncated Bt horizon of an older paleosoL The unnamed alluvium at 16VN791 is massive.

Judging from the limited available information, the unnamed alluvium consists of both Holocene and late Pleistocene alluvium. Based upon several dates obtained by the Oxidizable Carbon Ratio (OCR) dating method, i.e., figure 27, Cantley and others (1997) concluded that the unnamed alluvium within the Whisky Chitto drainage consists of alluvial deposits of Holocene to Late Pleistocene in age. They argue that the upper 1 to 1.5 m (3 to 5 ft) of the alluvium is of Holocene age and that the sediments and paleosols lying below a discontinuity at these depths dates back well into the late Pleistocene. Johnson (1990b) also argues that the alluvium at 16VN791, which lies on a tributary of Whisky Chitto Creek, consists of 0.8 m (2.6 ft) of Holocene alluvium as old as 5200 BP overlying a truncated paleosol developed in late Pleistocene alluvium. Similarly, Bianchi (1982) shows the unnamed alluvium as consisting of alluvium of Holocene age, "Alluvium 2B," overlying that of Pleistocene age, "Alluvium 2a" (figure 20).

The limited observations by Bianchi (1982), Cantley and others (1997), and Johnson (1990b) indicate that the unnamed alluvium consists of a relatively thin accumulation of Holocene alluvium over late Pleistocene alluvium. If these observations are substantiated by additional study and are applicable to other streams, they suggest that the flood plains of the streams within the Fort Polk region are far more stable than previously thought (Cantley et al. 1997). They would suggest that over the last few tens of thousands of years the streams within the Fort Polk region have been gradually aggrading by the periodic accumulation of sediments on their flood plains. However, given the relatively few places where the unnamed alluvium has been investigated in detail, additional study is needed to substantiate these observations.

BIG BRUSHY FORMATION

The Big Brushy formation consists of the mantle of sand that forms the sandy epipedon of soils developed <;m the Tertiary uplands in south-central Louisiana. The Big Brushy formation has also been recognized within the Post Oak Savannah of east-central Texas (Collins 1995; Fields and Heinrich 1987; Thoms 1993) and the Piney Woods of East Texas (Perttula et al. 1986).

The Big Brushy formation was informally named by Bianchi (1984) for the Big Brushy Site, 16VN24, a stratified, multicomponent site on the east bank of Big Brushy Creek in the Fullerton Lake quadrangle [SE]. At the Big Brushy Site, the Big Brushy formation was found to consist of 1.2 m (3.9 ft) of yellow silty, fine to very fine grained sand exhibiting no discernible depositional stratigraphy, and to contain four stratified archaeological clusters representing San Patrice, Middle Archaic, Late Archaic, and

74

Ceramic components (Guderjohn and Morehead 1980). Unfortunately, the Big Brushy Site has been destroyed by road construction; the geomorphological studies conducted at the site were never published; and its geomorphological data remains missing. However, at sites 16VN1505 and 16VN126 northwest of 16VN24 along Big Brushy Creek and described by Meyer and others (1996), deposits representative of the character and stratigraphy of the Big Brushy formation can be found (Morehead 1999).

Detailed geoarchaeological studies provide detailed descriptions of the typical characteristics of the Big Brushy formation in the Fort Polk region. At 16VN794, the A and E horizons consist of silty sand and the Bt horizon consists of muddy sand. As is often typical of the Big Brushy formation, it can be a complex mixture of sediment transported by multiple processes. At 16VN794, Foss and others (1993) argued that its sands were transported by both eolian and slopewash processes (figure 28). Color variations, gross lithology, and visible stratigraphy primarily reflect pedogenic processes that are continually modifying this unit. Additional descriptions of the character of the Big Brushy formation within the Fort Polk region can be found in Gunn and Kerr (1984), Servello and Bianchi (1982), and other reports concerning the results of archaeological excavations in the Fort Polk region.

Detailed research concerning the Big Brushy formation in Louisiana and Texas demonstrates that it consists of a sandy mantle produced and modified by a variety of processes (figure 29). Downslope transport of the sediment can be the result of either gullying, sheetwash, wind, graviturbation, or some combination of these processes. As a result, the thickest accumulations of the Big Brushy formation tend to be at the bases of slopes or at breaks in the slope on hillslopes. In some cases, it is possible that wind can transport sand upslope from exposed sand bars in adjacent streams such that it can even accumulate on the summits of adjacent hills. Although upslope transport of sand might have been important at some sites, the vast bulk of the Big Brushy formation represents sediment, primarily sand, transported downslope from a hill summit or ridge crest (Fields and Heimich 1987; Thomas 1993).

Because the vast bulk of the sandy sediment comprising the Big Brushy formation has been transported downslope, its source at a given locality must be the summits and upper slopes of either a ridge or hill. The most plausible explanation is that the sand is released from the summit by pedogenesis and erosion as proposed by Thoms and Clive (1993). The process is initiated when either colluvial or eolian processes erode sand off the crest and upper slopes of either a ridge or hill (figure 29). Once the sandy A and E horizons have been removed by erosion, eluviation acts to remove clay from and otherwise alter the B horizon. Eventually, illuviation will translocate clay and other materials downward into the underlying C horizon transforming it into a B horizon and the former B horizon into A and E horizons. Eventually, when the landscape is disturbed, the loose sand of this new sandy epipedon will be eroded and moved downward onto the slopes and ultimately into the fluvial systems within the valleys. This cycle of erosion and pedogenesis serves as a source of sand for the Big Brushy formation and the sandy epipedon of which it is a part.

As sediment of the Big Brushy is actively being transported downslope and, at times, possibly upslope, the formation is continually subjected to churning by pedogenic processes (figure 29). Because it lies within the A and E horizons of the modem soil, it is

75

-....l 0\

...,: "." .... . ........... .:,.· .. c .... . .... ~ .:...._ :...'".-0:....

I. Deep Weathering, Pleistocene.

-- . .. . .... - - - -' -' -:, : .C :

--':'-.:.:..-:... '. " , ..

...... ,-

II. Erosion Cycles, Early-Late Pleistocene.

A. Eolian Sands B. Mixed Zones C. Strongly Developed Reddish Paleosol D. Weathered Eolian Sands

III. Erosion-Deposition Cycles; Eolian Sands Early to Mid-Holocene .

• 0 ••• _0 _ ..

.......... ~.

IV. Continued Erosion-Deposition Cycles Mid-Holocene to Present.

Figure 28. Depositional history of the Big Brushy formation at 16VN794 Fort Polk, Vernon Parish, Louisiana. (Redrawn and adapted from figure 33, Foss et al. 1993: 129.)

-....J -....J

E

'*l!!tO

~cn ~m 1 ._ E t:::c cn'-> 2

o 1 2 3 I I I I horizontal scale

in meters

~~ Willis and/or Fleming

o pebbles ~ C colluvial transport

A artifacts ~ IE eolian transport

t:II::::U::::J intact features ~ IEf eluviation of fines

@) bioturbation A+E A and E horizons

~kBt~~ 2Bt horizons ~ ~

Figure 29. Schematic diagram of processes associated with Big Brushy formation. Drawn with data from Thoms (1993) and Foss et al. (1993).

subject to continuing pedogenic processes, including pedoturbation, as it slowly accumulates. What results is an environment in which churning of the sediment is contemporaneous with its slow accumulation. Thoms (1993) argued that this results in a situation in which archaeological features and stratigraphy are initially preserved, but are eventually with time dismembered and mixed. He also argued that colluvial processes and pedoturbation can act to reconstitute an archaeological stratigraphy from displaced artifacts. Thoms (1993), Thoms and Clive (1993), and Fields and Heinrich (1987) demonstrated that the processes that create and alter the Big Brushy formation have drastic effects on the integrity of the archaeological record that it contains. Furthermore, these processes place severe constraints on the paleoenvironmental interpretation of pollen and phytoliths recovered from the formation.

The age of the Big Brushy formation is well constrained. Cultural materials and radiocarbon and thermoluminescence dates recovered from the formation show that it can range in age from Late Holocene to Late Pleistocene. The bulk of it ranges in age from middle to late Holocene, although early Holocene deposits have been found at a few sites, e.g., the Big Brushy Site. The oldest known in situ artifacts and dates have been found at the Eagle Hill II site and at other sites in the northern part of the Peason Ridge area (Gunn et al. n.d.; Servello and Bianchi 1982; Gunn and Kerr 1984). Gunn and others (n.d.) list thermoluminescence dates as old as 10,000 to 13,000 BP for artifacts from the Eagle Hill II site (Table 3).

For this investigation, only the portions of the Big Brushy where it greatly exceeds its normal thickness are mapped. These constitute a single polygon straddling the Fullerton Lake quadrangle [NW] and Lacamp quadrangle [SW]. Topographic relief within this polygon exceeds 100 ft (30 m). Its thickness as depicted in figure 25 is on the order of 6 to 9 m (20 to 30 ft). Our informal field term for the area was "the sand hills," which gives a good idea as to its character; Sand Hill Road approaches this general area from the east-southeast, and makes a T-intersection with Hwy. 489 approximately 3.2 km (2 mi) east of the northern tip of the mapped polygon. Elsewhere in the Fort Polk region, the thickness of Big Brushy deposits is generally less than 0.8 m, and the formation is treated as a surface veneer on the underlying "bedrock" units depicted on the geologic quadrangle maps (cf. figure 5).

78

Table 3. Radiometric Dates From Eagle Hill II Site (16SA50). From Gunn et al. (n.d.).

Soil Horizon Thermoluminescence* Radiocarbon (uncalibrated) Cultural (Depth) Sample BP Date Sample Date BP C-14 Affiliation

Upper part of Big Brushy formation

A2 1172 1290±105 Uga-3703 1015±80 (35 cm)

Bl 1707 1250±120 Uga-3704 1130±70 (52 cm)

Lower part of Big Brushy formation with truncated paleosol

IIB2ltx (68 cm)

IIB22tx (85 cm)

IIB23 (l00 cm)

2146 1974 1995B 1995A

2605A 2605B

2716

7500±1252 7110±575 8090±410 801O±525

12,800±2100 10,250±550

10,200±500

Coles Creek

Coles Creek

Archaic Archaic Archaic Archaic

Paleoindian

* Thermoluminescence dating was done at the University of Missouri at Columbia.

79

STRUCTURE


STRUCTURAL SETTING

The regional structural context of the study area is dominated by the Sabine uplift and Angelina-Caldwell flexure updip and to the north (figure 8). The Sabine and Monroe uplifts in north Louisiana appear to have existed as positive features since at least Late Triassic time (Anderson 1979), when they formed along with other positive elements that separated the "complex systems of rhombic grabens or rift basins . . . formed on thinned continental crust" (Foote et al. 1992, p. 1) during the early phase of separation of the North American plate from the South American and African plates (Salvador 1987).

The Angelina-Caldwell flexure constitutes a hinge zone that marks an increase in the dip and/or thickness of strata downdip. It formed on the southeast flank of the Sabine uplift in conjunction with the overall regression and progressive outbuilding of the continental shelf during the Cenozoic, and marks a boundary between epeirogenic uplift updip and basinal subsidence and deposition downdip, corresponding to the inner limit of gulfward monoclinal dip toward Neogene depocenters (Dixon 1965). The flexure could correspond to a boundary between continental crust and thinner transitional crust (Worrall and Snelson 1989; Walper et al. 1979). In the Sabine and Vernon Parish areas it influenced the deposition of the Wilcox Group, which thickens notably across the flexure (Glawe 1989, his figure 3). Andersen (1960) places its inception sometime during the deposition of the lower Paleocene Porters Creek Formation (upper Midway Group), based on isopach maps of the Upper Cretaceous and Paleocene series that show changes in thickness patterns across the feature beginning in the Porters Creek interval (his plate 10).

The trace of the flexure as drawn by different authors varies considerably. In work undertaken in the context of petroleum exploration, investigators have shown a tendency to depict it far to the south of where it is shown in figure 8 (in some cases nearly or virtually coincident with the Lower Cretaceous shelf edge or Toledo Bend flexure), and to join it with the Wiggins anticline in southern Mississippi and southeastern Louisiana (e.g., Walper et al. 1979; Worrall and Snelson 1989). The usage of this report follows that of Andersen (1960; 1993, his figure 56), Dixon (1965, his plates 13 and 14), Baumgardner (1987, his figures 1 and 13), and Glawe (1989, his figure 1). This is coincident with the feature originally named by Veatch (1906), and also roughly coincides with the gulfward limit of Paleogene outcrops in Louisiana as rendered by Dixon (1965, his figure 2).

According to Andersen (1960), in Sabine Parish the Angelina-Caldwell flexure is a zone downdip of which the regional homoclinal gulfward dip changes from approximately 45 ftlmi (8.5 mlkm, or approximately 0.5°) to approximately 250 ftlmi (47.3 mlkm, or approximately 2.7°) or greater. In Natchitoches Parish the change in dip manifested in the Porters Creek and in selected Cretaceous units across the flexure

80

amounts to an increase from 1 °_1.5° to 2.6°-2.8° (Andersen 1993, his table 10). The regional structural dip in the Fort Polk region is on the order of 1°; stick sections constructed from well log data by Rogers and Calandro (1965, their plate 2) indicate a maximum dip slightly less than 1°, and those of Hinds (1998a, 1999, his plate 4) indicate a maximum dip ranging from approximately 1 ° to slightly greater than 1 0.

In addition to the influence of the above regional structures, Hinds (1998a, 1999) noted a concordance of the strikes of formations of the Fleming Group (and, more strikingly, of the orientations of interfluves) in his study area with those in the Austin Chalk (Upper Cretaceous) in the deep subsurface as mapped by Zimmerman (1996). He interpreted such concordance as suggesting the possibility of deep-seated structural influence via harmonic folding.

The gentle dips and semiconsolidated nature of most of the Cenozoic sediment, together with thick soils and vegetation, are such as to generally preclude direct recognition of local surface structure in the study area.

FAULTS

The surface expression of the Angelina-Caldwell flexure comprises a zone of surface faults with a complex, intersecting and anastomosing pattern mapped by Andersen (1960, 1993). In some areas downdip of the main zone of these faults Andersen (1960) mapped scattered, smaller faults. These are reproduced on the accompanying geologic maps in the northwestemmost portions of Peason and Kisatchie quadrangles, in the areas where we have relied on Andersen's mapping of the Cockfield Formation, Jackson Group, and Vicksburg Group (figure 4). A suggestion of a small fault was seen in a single roadcut exposure in this portion of our study area, in NW/SE Sec. 28, T. 6 N., R. 9 W., Peason quadrangle [NC], within 0.4 km (0.25 mi) of faults to the northeast and southwest mapped by Andersen (1960); aside from this single locality, no evidence of faults was noted in the field. Rogers and Calandro (1965) also noted the difficulty of fault recognition from available data at the surface and in the shallow subsurface in the outcrop belts of the Catahoula and Fleming formations in Vemon Parish.

Subsurface geologic section B-B' (Appendix B) indicates a possible discontinuity suggestive of a fault between the Ramrod #2 Pickering and USGS well V-425. Such a fault would at the surface create a fault contact between the Dough Hills and Williamson Creek formations of the Fleming Group. Hinds's (1998c) mapped contact between the Dough Hills and Williamson Creek in this area (in the Slagle quadrangle [NED is occupied by the alluvium of two small tributaries on either side of the Ca1casieu River, which give the appearance of drainage lineaments oriented N 65° E and N 50° E (Plate 5). In the two wells on section B-B' immediately downdip of the possible discontinuity (downdip of the Ramrod #2 Pickering), the Catahoula thins over a subtle positive structure, whereas in the three wells farther downdip it has the same thickness as in wells updip of the structure. In a fault interpretation such a structure would represent an associated rollover-type structure. The association of the structure with this localized thinning of the Catahoula suggests that if a fault is present it was active during deposition

81

of the Catahoula Formation and affected its thickness distribution. Section B-B' indicates that such a fault would have a displacement of approximately 300 ft (91 m) in units younger than the Catahoula at and near the surface, and a displacement of nearly 400 ft (122 m) in units older than the Catahoula down to the top of the Wilcox Group.

JOINTS

Strikes of systematic joints (fractures without associated displacement) could be measured at a number of localities. The joints are vertical or nearly so, and at rare localities where joint faces are exposed to view no subsidiary features could be observed on them. Systematic joints generally consist of two main sets intersecting at a high angle, and commonly oriented orthogonally or nearly so, at a given locality. The above characteristics collectively suggest that the joints are extension joints. An exposure of the Blounts Creek Formation of the Fleming Group in the northwestem Big Creek area, EC Sec. 21, T. 1 N., R. 7 W., Birds Creek quadrangle [WC], is the most heavily jointed locality found within the study area; a total of 190 measurements was made there in semiconsolidated sands and moderately indurated sandstones. In places at this locality, both N-S and E-W sets were observed in association with diagonal sets in the same rock on a scale of tens of centimeters.

The particular joint sets expressed can differ greatly at nearby localities, e.g., showing predominantly N-S and E-W strikes at one locality and NW-SE and NE-SW strikes nearby. Joint roses for the localities where joint strikes were measured for this investigation are plotted in figure 30; also included are joint roses reproduced from two of Hinds's (1998a) localities not duplicated by our measurements. From these limited data no regional continuity of joint-strike trends appears visually traceable across the study area.

82

31'05'_

':3()'W-

93'45' 93'40'

I I 93'35' 93'30

I I

* = from Hinds 199Ba (two localities)

93'25'

I

Strike Frequencies of Joints Fort Polk Region and Vicinity

9no' 93'15' 93'15'

I I I 9:r05' I

93'00

I

I (' \

''C'7------j---'T~~)S .... -.-.. ----~,~~.~ '=-.~~~ ~ L.

N=45 \q

1012 3 4J.4~ -

,,~. ;

1 o 123456Ki1oroot!!B

N

t Figure 30. Joint-rose map of the study area, with stream net for comparison with strike-frequency maxima of joints. Strike frequencies are prepared with 10° classes, and those at all localities except the two incorporated from Hinds (1998a) are prepared with a 30° moving average. There appears to be no simple, clear relationship between stream-course orientations and the strike-frequency maxima ofjoints.

83

GEOMORPHOLOGY

Paul V Heinrich and Richard P. McCulloh

GEOMORPHIC SETTING

Within the Fort Polk region, three geomorphic terrains were recognized on the basis of geomorphology. They consist of the coast-parallel terraces, the stepped topography of the southern cuesta, and the ridge and ravine topography of the northern cuesta.

COAST-PARALLEL TERRACES

As previouly noted, the southern and eastern edge of the Fullerton Lake quadrangle is characterized by gulfward-tilted, dissected terraces associated with the Lissie Formation. Along its contact with the uplands of the southern cuesta, a higher and older terrace forms a narrow strip about 1.3 to 2.1 km (0.8 to 1.3 mile) wide. Within the Fullerton Lake quadrangle the surface of this terrace varies in elevation from 245 to 255 ft (75 to 78 m) above sea level. It is deeply dissected by local drainages and truncated by a lower coast-parallel terrace. Lying below it is a younger and regionally extensive terrace that forms the top of the Lissie Formation. It is the northernmost edge of a large ramplike terrace that extends southward into CaIcasieu Parish at about 4 ft per mile (0.8 m per km). The surface of this terrace lies at an elevation of about 225 ft (69 m) above sea level. It is less dissected than the higher terrace. Still, the younger terrace has been modified by erosion to the point that relict constructional landforms have been completely obliterated. Both it and the higher coast-parallel terrace are former coastal plains that were formed during the Pleistocene.

STEPPED TOPOGRAPHY

The second terrain, which forms the southern cuesta, is characterized by a gulfward-sloping cuesta dissected by southeastward drainages. Topographic profiles show that the crests of the interfluves between the drainages show a stepped profile. The correspondance between these steps and the base of the Willis formation indicate that the steps are the remnants of a series of terraces that have been reduced by erosion to a series of concordant summits. In places, the sediments of the Willis Formation have been completely stripped even from the ridge crests. The direction of the drainages was likely controlled by the regional slope of the cuesta and the former terrace surfaces that once composed its surface.

Within the second terrain, the crest of the southern cuesta consists of the relatively unconsolidated sands of the Willis Formation, which rises above lowlands underlian by comparatively consolidated clayey strata of the Castor Creek Formation. Although part of this apparently contradictory situation, involving unconsolidated sandy deposits

84

fonning a ridge crest towering above lowlands underlain by more consolidated fine-grained deposits, might be the result of structure, lithology also plays an important role. The sands show more resistance to erosion than the clays because they have a higher infiltration capacity. Rain falling onto the thick sands of the Willis Fonnation infiltrates readily and flows through rather than on top of the unit (Markewich et al. 1991). Because of the low penneability of its clayey soils, rain falling on hills underlain by the Castor Creek Fonnation quickly reaches its infiltration capacity. Water rapidly collects on the surface or runs downslope as sheetflow. As a result, a much heavier rain is needed to produce the sheetflow that would erode the surface of a ridge or hill underlain by the Willis F onnation than one underlain by the Castor Creek F onnation. Thus, when disturbed, the landscape underlain by the Castor Creek Fonnation is much more prone to erosion. In addition, where it overlies the clayey Castor Creek Fonnation, the Willis Fonnation is subceptible to erosion by spring sapping (Hinds 1998a, 1999).

RIDGE AND RAVINE TOPOGRAPHY

Finally, the terrain that characterizes the northern cuesta of the Kisatchie Wold within the Fort Polk region consists predominantly of terrain called "ridge and ravine topography." Ridge and ravine topography consists of rolling terrain characterized by a monotonous network of branching valleys and low, rounded intervening ridges and hills. This type of topography is an erosionally graded landscape that forms through erosion within humid climates (Hack 1960).

Within this terrain, the strata have been so deeply eroded that all constructional topography except for the terraces and flood plains within stream valleys has been totally destroyed. Differences in relief are related to the relative resistance of strata to erosion and distance from the major trunk drainages. The drainage network within this terrain generally will have adjusted its courses as it has cut downward to exploit any zones of weakness along structural features (Hack 1960). In addition, sapping along joints and faults will exert a strong control on the direction of tributary entrenchment (Hayward et al. 1990).

STRUCTURAL CONTROL

(Richard P. McCulloh and Paul V. Heinrich)

Drainage lineaments are recognizable across the study area, and suggest at least a measure of structural control of drainage. No faults could definitely be inferred coincident with such lineaments. However, the systematic joints measured provide a basis for comparison. Hinds (1998a, 1999), following up the suggestion of McCulloh (1995) that many drainage courses in Louisiana reflect probable control of their orientations by joints, compared measured joint strikes with stream-course orientations in his study area. He concluded that a correlation likely existed between the two, but his joint-strike data, comprising a total of four localities, ultimately did not permit more than a qualitative appraisal of the suspected strength of such a correlation.

85

The joint roses shown in figure 30 are plotted on a base with a generalized stream net for comparison. No clear relationship appears discernible between the strikes of measured joints and the orientations of drainage courses, including those that appear obviously to constitute lineaments on larger-scale maps. (Many of the latter stream courses do not appear on figure 30 owing to the generalization for the reduced scale.) The observed variability of expression of joint sets mentioned above, possibly in conjunction with the small sample size available for this investigation, may account for this. If structural control of drainage courses in the study area is real, the phenomenon is evidently more complex than initially hypothesized. Establishment of such a relationship, provided it exists, will likely require more comprehensive data than those available to this investigation-including both greater quantity and a finer level of detail-as well as a statistical treatment of the data such as that given by Scheidegger (1980).

The flood plains of Comrade Creek and the Calcasieu River bear special mention in appearing to show what may potentially constitute strikingly different examples of drainage lineaments. These are notably straight yet broad reaches of fairly uniform width, which in addition to having the same east-west orientation appear rather neatly aligned in the north-south direction. The wide flood plains of both are criss-crossed by numerous channels in an anastomosing pattern. They do not fit the definition of strike valleys because neither is coincident with or parallel to the contacts of the Fleming subunits traversed, instead intersecting them at a low oblique angle. It is herein speculated that these east-west-trending reaches follow zones of increased fracture density of east-west-striking joints, zones essentially similar to the "fracture traces" of Lattman (1958). The anastomosing channels may reflect response to a combination of effects, including an oversupply of coarse sediment sourced by headward drainage of the outcrop belts of the Carnahan Bayou (Comrade Creek) and Dough Hills and Williamson Creek formations (Calcasieu River).

86

NATURAL OCCURRENCE OF BOGS, SEEPS, AND SPRINGS

Bradford C. Hanson

Springs are generally the result of a groundwater table intersecting surface topography where flow onto the surface is through a natural orifice. Such features are often located on mid- and lower slopes of hillsides or in stream channels. They may be seasonal'or perennial in nature, the latter dependent upon the lateral extent of the recharge area or watershed, hydraulic characteristics of the permeable zone, groundwater reserves, and hydraulic gradient. Some springs may be the result of fault(s) cutting a confined aquifer at depth with resultant groundwater flow upward along the fault plane to a point on the fault trace where it flows onto the surface. There are a number of scenarios for which springs may result, but they generally depend upon stratigraphic and structural relationships between surface and subsurface strata.

Seeps occur generally where the groundwater table closely approximates surface topography, but does not intersect it. The distinction between what constitutes a seep or a spring is the existence of a visible orifice and rate of flow for the latter, though the distinction between the two in the literature seems to blur and be left to the reader as intuitive. There does not appear to be broad agreement on what constitutes a threshold value for rate of flow, but a seep is generally referred to as a small area where water percolates slowly to the land surface (Bates and Jackson 1980), but neither an orifice nor the rate of flow is readily visible through observation. A spring is a place where groundwater is observed to flow naturally onto the land surface through a natural orifice.

Bogs generally occur where there is sufficient water trapped in a topographic depression in the land surface. Such depressions may be fed by precipitation, surface runoff, or subsurface water. If a bog is the result of either precipitation or surface runoff, the base of the bog will be composed of a low permeability material, such as a fine-grained silt or clay, in order to trap the water and prevent its infiltration into the subsoil. The silt or clay unit at the base of the bog is often a remnant of a prior erosional surface (Smith 1996). Mapping such erosional surfaces in order to gain insight into the lateral extent of the bog's watershed boundaries can be challenging because present day topography may not reflect the general slope and drainage pattern of the older erosional surface (Smith 1996). Bogs formed in this manner may be perennial or seasonal in nature with longevity dependent upon volume, rate, and timing of inflow, duration of the inflow event, and retention of water in the bog.

Bogs associated with seeps and springs occur under different hydrologic conditions. Bogs that develop where long term outflow is reliable and somewhat consistent should develop more stable biological communities. Bogs developed where outflow is intermittent, or where cultural activities have had negative impacts on water quality, may undergo more stress and plant species may vary. Size of the bog site should also be an important factor when discussing plant species supported. Intuitively, as the physical size of the bog increases, so should the number of plant species. Research appears to have justified intuition because MacRoberts and MacRoberts (1988) reportedly

87

have found more than 100 plant species associated with larger bogs. In later work (MacRoberts and MacRoberts 1992, 1993), the size of bogs appears to be related to the number of species present. However, formulating a comprehensive assessment of the validity of this intuitive relationship was beyond the scope of this investigation.

A comprehensive work on bogs is contained in a management document entitled Conservation Assessment for Hillside Seepage Bogs of the Kisatchie National Forest (Hyatt 1998). Hyatt reports the hillside seeps, locally referred to as hillside bogs or pitcher-plant bogs, are unique localized wetlands. He also reports that the hydrology of the bogs is complex. Inflow into the bog may either be the result of a groundwater table intersecting surface topography where flow is through a natural orifice, as in the case of a spring, or the result of a groundwater table that lies just beneath the surface at a topographic depression that results in a soggy area fed by water seepage.

The bog data utilized in this report were obtained from the Conservation Assessment Document referenced above. These data are not for public release, but are available to cooperators who have a verified need for the data and were made available to LGS for the purpose of this report. Bog data exist for five out of the ten quadrangles defining the study area (figure 1): Fort Polk, Birds Creek, and Fullerton Lake to the south, and Kisatchie and Kurthwood quadrangles to the north. These data were acquired through various means including field work and aerial photography by Phil Hyatt and other staff working with the Kisatchie National Forest. Out of a data base of about 250 points, a single point was acquired using GPS technology, but the accuracy of this point is in question (Hyatt 1999). A subsequent discussion with the author of the data set revealed that GPS point data was not a requirement and that a lack of time on his part precluded its acquisition. Our contract calls for existing available records to be used; DGPS-generated UTM reference points do not exist.

The data were provided to LGS by Kisatchie National Forest personnel on a CD-ROM, which allowed LGS to produce polygons representing the location and configuration of various bogs and to merge these with existing map products. Regional trend analyses were accomplished by combining these data with Aquifer Recharge Atlas maps (Boniol 1988) to determine whether regional trends could be extracted from hydrologic data on file with LGS. Figures 31 and 32 were created by merging the bog data polygons with the Alexandria quadrangle (1 :250,000 scale), one of the recharge maps referenced above. The same polygon data were also merged with the geologic maps created for this report to produce figures 33, 34, 35, and 36, but were correlated according to the hydrologic units present (Table 4).

The remainder of the discussion deals with observations and apparent trends and is subdivided into a South Group, covered by figures 31, 33, 34, and 35, and a North Group which is illustrated in figures 32 and 36.

SOUTH GROUP

A number of observations were noted for the area represented by the southern quadrangles of Fort Polk, Birds Creek, and Fullerton Lake when merged with the Aquifer

88

00 \0

'~ I .1 ' ]J1 'r f(~ 1-' ~ , .4b ..

Figure 31. Regional trend analysis illustrating the spatial characteristics of the bog polygons situated atop the Evangeline and Chicot Aquifer Systems for the South Group area. The area encompassed by the South Group covers the Fort Polk (figure 33), Birds Creek (figure 34), and Fullerton Lake (figure 35) topographic quadrangles. This figure merges appropriate bog data polygons with the Alexandria quadrangle from the Aquifer Recharge Atlas (Boniol 1988).

1..0 o

Figure 32. Regional trend analysis illustrating the spatial characteristics of the bog polygons situated atop the Miocene Aquifer-System for the North Group area. The area encompassed by the North Group covers the Kisatchie and north portion ofthe Kurthwood (figure 36) topographic quadrangles. This figure merges appropriate bog data polygons with the Alexandria quadrangle from the Aquifer Recharge Atlas (Boniol 1988).

Figure 33. Hydrologic and geologic relationships of bogs for the area encompassed by Fort Polk topographic quadrangle.

91

( . Figure 34. Hydrologic and geologic relationships of bogs for the area encompassed by Birds Creek topographic quadrangle.

92

Figure 35. Hydrologic and geologic relationships of bogs for the area encompassed by Fullerton Lake topographic quadrangle.

93

Figure 36. Hydrologic and geologic relationships of bogs for the area encompassed by the Kisatchie and north portion ofthe Kurthwood topographic quadrangles.

94

Recharge data (figure 31). The spatial characteristics of the bog polygons situated atop the Evangeline aquifer appear to lie closer to the Evangeline-Chicot contact than polygons occurring on the Chi cot aquifer side of the same contact. A possible explanation lies in the methodology for compiling the regional aquifer map. The contact in question has been grossly oversimplified in order to accommodate the scale (1 :250,000) of the base map. It is shown in figure 31 as a distinct and regular line implying a definite, linear contact between the two aquifer systems. In reality, however, this may not be the case. Upon examination of figures 33-35, the contact between the Evangeline (Pliocene to late Miocene age) and Chicot/Terraces (Pleistocene age) aquifers is highly irregular. Its location as depicted on figure 31 may be erroneous; thus this observation may be invalid.

Second, while the bog polygons appear scattered, the scatter appears to be restricted to an arcuate, northeast trending band that parallels the contact between the Evangeline and Chicot/Terraces aquifers (figure 31). This observation may be the result of two integrated factors: first, the oversimplification of the Evangeline-Chicot aquifer contact discussed earlier may alter the apparent arcuate linear nature of the trend. If the irregular nature of the contact were more apparent, the apparent arcuate trend may be less obvious. And second, the northern boundary of bogs comprising this regional trend may be influenced by the data collection methodology. The data provided to LGS applies only to Kisatchie National Forest (KNF) property which includes only the southern portion of the Fort Polk Military Reservation. Bog sites were not mapped beyond the (KNF) boundary. Close examination of figures 33-35 appear to indicate a truncation of bog polygons upon reaching the KNF boundary especially in the Birds Creek and Fullerton Lake quadrangles (figures 34, 35). This data acquisition limitation was confirmed by Phil Hyatt (1999). Thus what appears to be a narrow, arcuate, northeast trending band is more a function of the data collection methodology and its limitations than due to a hydrologic or geologic characteristic.

Third, a clear majority of bog sites appears to be clustered on, and along the flanks of, the uplands between major stream valleys and not situated on the major flood plains as might be expected (figure 31). This may be, in part, due to the oversimplification of the regional base map. However, Hyatt (1998) reports that the bog sites are situated along hillsides. And this observation appears to be substantiated when examining the detailed maps in figures 33-35. Thus such an observation may be expected.

Finally, bogs also occur in an area characterized by high recharge potential (figure 31, stippled pattern). This also would be expected because one of the criteria for bog development is an adequate, long term source of fresh water. Development on, or in close proximity to, permeable geologic materials is a prerequisite for sustained plant growth and longevity. Aquifer recharge potential for each soil association within the geologic recharge areas is based on such soil characteristics as parent material; subsoil texture, permeability, and drainage; surface slope; and surface runoff. These characteristics affect the movement of water through surficial materials and into the subsurface, through the soil horizons, and into the underlying geohydrologic systems. It is important to realize that the aquifer recharge characterizations are based on soil characteristics down to a depth of approximately 6 ft below the surface.

95

Merging the bog data with the geologic maps created for this report reveals a greater level of detail regarding the relationship of specific bog sites to the geology. The quadrangles covered are Fort Polk, Birds Creek, and Fullerton Lake (figures 33, 34, 35 respectively). Excluding the previous observations discussed earlier, bog sites appear to be restricted to the Blounts Creek Member of the Fleming Group and to the younger aged Willis (Pliocene) and Lissie (Pleistocene) formations.

The Blounts Creek Member of the Fleming Formation is the youngest unit underlying and truncated by Plio-Pleistocene strata in the study area. The authors of this report refer to the Blounts Creek as a nondescript series of clayey and silty fine-grained materials and as the finest-grained of the various sandy Fleming subunits. They also report that it has a much finer grain size overall when compared to the other formations within the Fleming. This may account for the apparent preference of bog sites for Blounts Creek sediments, at least in the Fort Polk quadrangle. But this observation tends not to hold when examining the Birds Creek and especially the Fullerton Lake quadrangles (figures 34 and 35, respectively). Bogs tend to be evenly distributed between both Blounts Creek and Willis formations on the Birds Creek quadrangle (figure 34), but tend to also occur on the Lissie Formation in the Fullerton Lake quadrangle (figure 35).

There are a number of possible explanations. First, the restrictive nature of the data collection methodology (restriction to KNF land) may be skewing the real nature of the relationship by creating an apparent one. What appears to be an affinity for Blounts Creek, Willis, and Lissie geologic units may be an artifact of sampling bias.

Close examination of figures 33, 34 and 35 shows that the bogs are located on a wide range of geologic and hydrologic units. The Evangeline Aquifer System consists of Blounts Creek and Willis geologic formations while the ChicotiTerraces Aquifer System consists of various permeable units within the Lissie Formation and undifferentiated alluvium (Table 4). Utilizing this approach, bogs appear to be scattered throughout the two dominant aquifer systems for the region. Thus it is difficult to suggest that bogs are somehow restricted only to certain aquifers.

Why bogs tend to show an affinity for certain locations is probably related more to localized lithologic and textural considerations rather than to specific geologic or hydrologic units. For bogs to develop, there must be a depression in which to hold water, a source of water, and the plant life. Assuming the latter will develop if the other two criteria are met, then an adequate source of water and a vessel or "bowl" in which to put it, are primary inputs. The "bowl" in this analogy would be a depression on an existing surface, such as where the ground surface truncates the Blounts Creek. Such a depression may result from either differential erosion of surficial material or perhaps be due to a pre-existing undulating surface created by an ancient erosional event. Whatever the case, the depression must retain water in sufficient quantities to sustain the flora.

A second needed input is a reliable, long-term source of fresh water flowing into the bog site. This means that a source for the water would, by necessity, be located up the hydrologic gradient from the bog. The geologic nature of this source would necessitate that it be a permeable material, perhaps a sand or gravel in order to accommodate the rapid infiltration of precipitation and the transmittal of the groundwater down the hydrologic gradient.

96

This investigator suspects that bog development requires finer-grained material at the base in which to trap the water with coarser grained material located up gradient supplying a reliable influx of fresh water. The geologic unit supplying these ingredients is not relevant to the equation, only that the ingredients be present. Blounts Creek is a nondescript series of clayey and silty fine-grained materials and it has a much finer grain size overall when compared to the other formations within the Fleming. The Willis and Lissie formations are more sandy and contain gravel throughout, but they also exhibit a wide range of lithologies and textures. Where the proper mix of fine and coarse grained materials co-exist, conditions may be present for the development of a bog. It is important to note, however, that while specific textural and lithologic characteristics may create favorable locations for bog development, this in itself does not guarantee that bogs will develop or that flora will be established. The answers to these issues were beyond the scope of this investigation.

This hypothesis was tested by examining the descriptive field map notes recorded by McCulloh and Heinrich as part of their geologic mapping task for this report. Field map notes were examined for the Fort Polk, Birds Creek, and Fullerton Lake quadrangles in those areas where bog sites had been identified. Unfortunately, very few outcrop sites occur in close proximity to bogs and none correspond with specific bog locales. This is not surprising, however, because comprehensive field examination of bog sites was beyond the scope of the investigation. In the few instances where geologic outcrops were noted and could be correlated to nearby bogs, the field description tended to support the hypothesis. But the lack of sufficient data precludes any definitive conclusions at this time.

NORTH GROUP

Bogs that occur in the northern region of the study area (figure 32) present a different set of problems. The north cluster comprises bogs located in the northern quadrant of the Kisatchie quadrangle (figure 36), which display more scatter and are situated atop surficial material characterized by moderate recharge potential. Moderate recharge potential implies moderately to well drained soils having medium textures and moderate rates of water transmission. They include soil associations possessing a variety of both high and low recharge characteristics. The south cluster, comprising bogs located in the southeast quadrant of the Kisatchie and northeast quadrant of the Kurthwood quadrangles (figure 36), displays a different spatial relationship. These bogs tend to possess less scatter and to be concentrated in a rather restricted area. They are situated on surficial material characterized by low recharge potential. Low recharge potential generally refers to poorly drained silts and clays with slow to very slow infiltration, low permeability rates, and high runoff potential. They include shallow soils over nearly impervious materials and include soils with a claypan or a thick clay layer at or near the surface.

While the spatial characteristics of both clusters of bogs differ, both lie upon geologic materials characterized as Miocene aquifers (Boniol 1988). The Miocene aquifers of central Louisiana include most of the Fleming Group beginning with the

97

Stratigraphic Column of fort Polk Region Time - Stratigraphic Units Rock - Stratigraphic Units Hydrologic Units

E ~

~ .~ Stage Group formation Member Aquifer System ., :Ji' VI

Holocene Alluvium + Bic Brushv undifferentiated Alluvial 0. . ~

C QJ :!: e (undifferentiated alluvium) '" c ~~ C QJ '< ... U

~ ~~ ~ QJ 0 Chicot(T erraces ...., ..... Calabrian

'" '" :::I 'iii 2;0. Upper Ci E ~ e Lissie §g'I

~~ Lower

QJ Piacenzian ~ ~ ~ C

QJ 0. u

,Q 'O~

Zanclean g e Willis I E g-ff Kisatchie Allomember

< FprtPolk Allomember

! Messinian

~ ~ ~ Evangeline

Tortonian =>

QJ Blounts Creek undifferentiated c

~ 2:!..s! 0 Serravallian 0\ QJ

Z QJ"C C Castor Creek undifferentiated U"C 'E 0 ~ ~ Langhian

QJ

u:: Williamson Creek undifferentiated

L. Burdigalian Dough Hills undifferentiated QJ

3 Carnahan Bayou undifferentiated Miocene 0 t: ...J

'" Aquitanian Lena undifferentiated t ~ L.

QJ

2:!§ Chattian Catahoula undifferentiated QJ u

,~ ~ <5 L. QJ ::J

Vicksburg 3 ..0 Rupelian '" undifferentiated

QJ 0 -'>!. (confining unit) ...J u c :> ~ 0 QJ

;;; C L. c.. 0 Jackson ~

VI

Priabonian -'>!. undifferentiated (confining unit) u QJ=> ..!!!. c QJ U 0 QJ UJ

QJ C

=0 0 "C Bartonian ..0 Cockfield undifferentiated Cockfield ~

'n; 0

Table 4. Hydrologic classification of stratigraphic units.

98

Castor Creek confining units at the top of the section extending downward to and including the Catahoula (Table 4). Close examination of Table 4 reveals that the Miocene aquifer system includes Upper Oligocene age sediments. This apparent inconsistency is due to past uncertainty regarding the geologic age of the Catahoula aquifer. The Aquifer Recharge Map (Boniol 1988) considers it to be Lower Miocene in age while the authors of this report map it as Oligocene. Its specific age is unimportant to this discussion; it is considered as part of the Miocene Aquifer System for this report.

An explanation that will adequately account for the two clusters may be difficult to identify. Clearly, virtually all of the Kisatchie quadrangle falls within KNF except for a narrow band along the western edge. Thus the argument discussed earlier, bog data being an artifact of the collection methodology, is not valid in this case. However, the southern extent of bog sites on the Kurthwood quadrangle does appear to be a function of the KNF boundary.

But this explanation does not account for the wide spatial variability of bog density between the north and south clusters. This observation suggests different controlling mechanism(s). These mechanisms may be reflected in the recharge potential of the surficial materials upon which the bogs are located. But figure 32 does not differentiate between individual formations comprising the Miocene Aquifer System.

So another approach was tried by merging regional bog data with the detailed geology mapped for this region. Figure 36 illustrates refinements not observed on the regional map (figure 32). For example, in the north cluster more scattered bog polygons are situated atop Catahoula (Oc) material. Those of the south cluster, on the other hand, are situated on Carnahan Bayou (Mfcb). Utilizing this approach, bogs appear to be scattered throughout the two dominant aquifers for the region, the Carnahan Bayou and Catahoula aquifers. Thus it is difficult to suggest that bogs are somehow restricted only to certain aquifers.

The stratigraphic units comprising the Miocene Aquifer System that occur in this region were described earlier in this report as comprising alternating coarser-grained, fluvial-dominated lithofacies and finer-grained, more marine-influenced lithofacies. In terms of gross textures, the Carnahan Bayou (Mfcb) is similar to Catahoula (Oc) with both encompassing a wide range of sediments that are texturally heterogeneous, poorly sorted, and comprise various admixtures of sand, silt, and clay. From examination of the data sets from a variety of approaches, it appears that the critical geologiclhydrologic factor is that of textural and lithologic relationships. At the present time and based upon the data available, it appears that bogs have an affinity for locations that exhibit fine to very fine grained material juxtaposed beneath coarser grained material, a similar conclusion reached for the South Group of bog sites.

This hypothesis was again tested by examining the descriptive field map notes recorded by McCulloh and Heinrich as part of their geologic mapping task for this report. Field map notes were examined for the Kisatchie and Kurthwood quadrangles in those

areas where bog sites had been identified. Again, very few outcrop sites occur in close proximity to bogs and none correspond with specific bog locales. In the few instances where geologic outcrops were noted and could be correlated to nearby bogs, the field description tended to generally support the hypothesis. But the lack of sufficient data precludes any definitive conclusions.

99

SUMMARY

This investigator has examined the hydrologic relationships between the bog sites and the aquifers, but viable explanations that can withstand scrutiny are not available at this time. A number of possibilities have been examined and discussed [above], but none offers a basis for a reliable predictive model. What is evident is that bogs appear to cluster on a variety of geologic formations of var-ying ages representing a number of aquifer systems. A controlling factor may be lithology rather than specific geologic formations or aquifers. Suggesting a predictive model however, is tenuous at best because of the limitations of this study. Examination of field notes on various working copies of field maps of individual quadrangles suggests a link may exist between localized lithological variations and bog sites. But these notes were not collected with this purpose in mind and therefore are neither complete nor contain adequate descriptions at specific bog locales. While a relationship may exist, the precise nature of this relationship is difficult to postulate without further field study.

100

ECONOMIC GEOLOGY (NONFUELS)


Nonrenewable commodities of potential economic significance in the Fort Polk region comprise gravel, sand, crushed stone, and opal. Actual and potential economic occurrences of these materials are rendered on the Economic Geology plates, totaling seven of the ten quadrangles making up the study area. Ground water is also a commodity of economic significance in the region, but its economic aspects were not evaluated in this investigation.

Gravel in economic concentrations is confined to the gravelly facies of the Pliocene Willis Formation. Gravel lenses are also known to occur in the Carnahan Bayou Formation of the Miocene Fleming Group, but none of these has proved economic. Sand has local but variable economic potential within the coarser-grained Fleming subunits and in Quaternary strata. The only sand excavations observed in the conduct of this investigation are the ones noted in the Carnahan Bayou Formation in Dowden Creek quadrangle [WC], in SE Sec. 25, T. 4 N., R. 10 W. (figure 12). The greatest potential for crushed stone resources is in the Catahoula Formation outcrop belt, and consists of sedimentary quartzite. It is mined from the Catahoula by Apeck Construction Company at the Ellzey quarry in SE/SE Sec. 15 and SW/SW Sec. 14, T. 5 N., R. 10 W., Peason quadrangle [SW], in southeastern Sabine Parish. Similar rock also occurs in the outcrop belt of the Carnahan Bayou Formation, but its occurrence is more variable and localized. Another excavation for crushed stone composed of what we infer to be aphanocrystalline carbonate rock is the "soapstone" quarry noted in the Dough Hills Formation and located outside the study area to the west. This rock is reportedly used by Apeck Construction Company as road metal.

Common opal was observed in small quantities as a cement in sandstones of the Catahoula Formation and the Carnahan Bayou Formation. Only one occurrence of common opal in greater quantity, in the Carnahan Bayou in NW Sec. 21, T. 5 N., R. 9 W., Peason quadrangle [SC], was observed and considered worth noting. The opal at this site occurs as lenticular beds up to approximately 3 cm thick that have replaced or displaced the sandstone host rock. Mr. John Guy of Anacoco, Louisiana has collected a nodule of common opal 25 cm (10 inches) in diameter from the Carnahan Bayou in the Eagle Hill area in the Peason quadrangle [SE]. Precious opal, known from occurrences as cement in sandstone of the Carnahan Bayou Formation west of the Fort Polk region, was not observed in the study area.

101

GEOLOGIC HAZARDS


FLOODING

Flooding is inferred to constitute the sole geologic hazard in the study area. Flood-hazard potential is rendered on the attached plates from a compilation of publicly available data distributed by the Federal Emergency Management Agency (FEMA), and modified based on flood-plain topography interpreted from the topographic base information. The areas delineated are those interpreted to lie within the 100-year flood plain.

LANDSLIDES

Landslide potential was also evaluated, but was found to be not predictably of sufficient magnitude to constitute a significant hazard. The comprehensive account of the categories and contexts of landslide failure developed by Hernandez (1990) in north Louisiana served as a guide in this evaluation because, although landslide occurrence in southwestern Louisiana was surveyed by Smith (1987), he focused exclusively on man-made embankments. Of the situations susceptible to landslide failure outlined by Hernandez (1990), those involving a combination of slope steepness and clay content of the substrate are most applicable to the present study area. Accordingly, we evaluated landslide-hazard potential based on a conjunction of steep slopes and clay/mud substrates. Regional overviews of landslide-hazard susceptibility (Radburch-Hall et al. 1982; Walker and Coleman 1987), while indicating none for the study area, show the areas with known hazard susceptibility in Louisiana as coincident with the Mississippi river flood plain and delta plain. In light of the above considerations, the authors felt that the steepest slopes in the study area would be those associated with flood plains of the rivers and streams, and that any areas of significant landslide-hazard potential that might occur could be defined based on a coincidence of valley walls and channel cutbanks with clay substrates.

The channel cutbanks within flood plains are the steepest slopes found in the study area. These erode both clayey and sandy subfacies ofthe alluvium which, however, was not differentiated in this investigation. Thus, while the authors felt that occurrences of a conjunction of river and stream cutbanks and clay/mud substrates would be spotty, in any case it was not feasible to predict them. After cutbanks, the steepest slopes are those along the valley walls delineating the flood plains and bottomlands of streams and rivers. These slopes are essentially all less than 10°, and the steeper of them tend to occur where flood plains course across the outcrop belts of the sandier lithostratigraphic and lithofacies units of Tertiary age. The potential for formation of slopes greater than 10° in the 1Jluddier units was therefore evaluated as insufficient to constitute a substantial landslide hazard.

102

SUMMARY


The surface of the Fort Polk region is underlain entirely by Cenozoic strata, composed of terrigenous sediment ranging in age from Eocene to Holocene, and comprising varying admixtures of sand, silt, clay, and some gravel. The sediment is virtually all poorly sorted, and was deposited in environments transitional between fluvial and shallow-marine, but collectively these strata show a dominantly progradational character and become increasingly terrestrial upsection. The greater part of the surface is underlain by relatively coarser-grained sediment of the Catahoula and Fleming, the Upland Allogroup, and Holocene alluvium. These Cenozoic strata show gentle, homoclinal dip toward the Gulf of Mexico basin; regional structural dip is low, averaging 10 or less. Surface structure is likely to be subtle except for faults, but in any case is generally not directly recognizable solely from surface observations. Nonfuel mineral commodities of potential economic significance comprise gravel, and ground water. The only recurrent geologic hazard that can be projected systematically within the region is flooding.

Three main objectives of this investigation were listed at the beginning of this report: providing the U.S. Army with basic geologic data essential to the conduct of environmental applications and programs at Fort Polk; extending the work of Hinds (1997a, b; 1998a, b, c; 1999) and the stratigraphic and geologic context of the Fort Polk Miocene vertebrate fossil localities (Schiebout 1994, 1997; Schiebout et al. 1996); and supporting the Louisiana Geological Survey's geologic mapping efforts in the Fort Polk region and vicinity (Louisiana Geological Survey 1993; Snead et al. 1998). It is the authors' belief that these objectives have been met-the first objective principally by the accompanying maps (Plates 1-27); the second by the report and Plates 1-10; and the third principally by Plates 1-10.

103

RECOMMENDATIONS


1. Creation of a centralized, comprehensive archive of shallow-subsurface information from oil & gas wells, water wells, heat-pump wells, and soil borings that have been drilled in the Fort Polk region, to serve as an integrated database and three-dimensional framework for future surface and shallow-subsurface geological investigations.

2. Regional investigation of subsurface units utilizing electric-log data in an area encompassing the Fort Polk region, including mapping of gross e-Iog facies and inferred depositional environments for selected units. Depositional-systems characterizations of the subsurface Wilcox, Catahoula-Frio, and Fleming have been done comprehensively in the Texas coastal plain eastward to the Sabine River, whereas no analogous work is publicly available for onshore southwestern Louisiana. Such a subsurface framework would provide a much-needed larger context into which the surface observations of this investigation could be integrated.

3. Sampling of relatively fine-grained and less-oxidized portions of the Catahoula and Willis formations for age-diagnostic palynomorphs, to address the long-standing age controversies surrounding the Catahoula and Citronelle-equivalent units at the surface in the northern Gulf Coast.

4. Reconnaissance of the outcrop belts of the finer-grained formations of the Fleming Group for additional development of conglomerate beds with potential for the occurrence of vertebrate fossils. The known occurrences of fossiliferous conglomerate and sandstone in the upper Castor Creek along tributaries of Bayou Zourie are irregular, discontinuous, and of limited areal extent. Undiscovered occurrences of similar beds with spotty distribution must be considered a possibility elsewhere in the Castor Creek, as well as in the Lena and Dough Hills.

5. Preparation at 1 :24,000 scale from the Fort Polk GIS database of a suite of 7.S-minute topographic quadrangles in the Fort Polk region, with a comprehensive and accurate rendering of current, active roads. At the time of this investigation, the published base maps covering the study area dated from the early 1950s, early 1970s, and late 1970s, and since their pUblication the roads in many parts of the study area have changed drastically. To the best of our knowledge, only one of these quadrangles has been re-issued recently, since the time of our field work. A set of 1 :24,000-scale topographic maps in 7.5-minute quadrangle format with roads accurately rendered would greatly expedite future archaeological and geological field work.

104

BIBLIOGRAPHY

American Association of Petroleum Geologists 1988. Correlation of stratigraphic units in North America-Gulf Coast region correlation chart. Tulsa, Oklahoma: American Association of Petroleum Geologists. One oversized sheet.

American Association of Petroleum Geologists 1990. Gulf coast regional cross section. Tulsa, Oklahoma: American Association of Petroleum Geologists. Three oversized sheets.

Andersen, H. V. 1960. Geology of Sabine Parish. Geological bulletin no. 34. Baton Rouge: Department of Conservation, Louisiana Geological Survey. 164 pp. plus plates (includes one 1 :62,500-scale geologic map).

Andersen, H. V. 1993. Geology of Natchitoches Parish. Geological bulletin no. 44. Baton Rouge: Louisiana Geological Survey. 227 pp. plus plates (includes one 1 :62,500-scale geologic map).

Anderson, E. G. 1979. Basic Mesozoic study in Louisiana, the northern coastal region and the Gulf basin province. Folio Series no. 3. Baton Rouge: Louisiana Geological Survey. 58 pp.

Armentrout, J. M., and 1. F. Clements 1990. Biostratigraphic calibration of depositional cycles: a case study in High Island-Galveston East Breaks Area, offshore Texas. In Armentrout, J. M., and B. F. Perkins, eds., Sequence Stratigraphy as an Exploration Tool: Concepts and Practice in the Gulf Coast. Houston, Texas: Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists. Pp.21-51.

Aronow, S. 1982. Surface geology. In Neitsch, C. L., Soil Survey of Jasper and Newton Counties, Texas. Washington, D.C.: U.S. Department of Agriculture, Soil Conservation Service. Pp. 102-107.

Aronow, S., R. W. Neck, and W. L. McClure 1991. The Carolina Street local fauna: a Late Pleistocene freshwater molluscan/vertebrate fauna from Houston, Harris Co., Texas. Transactions of the Gulf Coast Association of Geological Societies 41: 17-28.

Autin, W. 1., S. F. Bums, B. J. Miller, R. T. Saucier, and J. I. Snead 1991. Quaternary geology of the Lower Mississippi Valley. Chapter 18 in Morrison, R. B., ed., Quaternary nonglacial geology: Conterminous U. S. The Geology of North America, v. K-2. Boulder, Colorado: Geological Society of America. Pp.547-582.

Bates, R. L., and 1. A. Jackson 1980. Glossary of geology. Falls Church, Virginia: American Geological Institute. Second edition. 749 pp.

105

Baumgardner, R. W., Jr. 1987. Landsat-based lineament analysis, East Texas Basin and Sabine Uplift area. Report of investigations no. 167. Austin: The University of Texas at Austin, Bureau of Economic Geology. 26 pp.

Bernard, H. A. 1950. Quaternary Geology of Southeast Texas. Ph.D. dissertation. Baton Rouge: Louisiana State University. 165 pp. plus plates.

Bernard, H. A., and R. 1. LeBlanc 1965. Resume of the Quaternary geology of the northwestern Gulf of Mexico province. In Wright, H. E., Jr., and D. G. Frey, eds., The Quaternary of the United States. Princeton, New Jersey: Princeton University Press. Pp. 137-224.

Bianchi, T. H. 1982. Geomorphic setting in the Fort Polk region: an abstract. Section 3 in Servello, A. F., ed., U.S.L. Fort Polk Archaeological Survey and Cultural Resources Management Program. Unpublished report prepared for U.S. Army Corps of Engineers, Fort Worth District, Fort Worth, Texas, under contract no. DACA63-76-C-0253. Fort Worth, Texas: U.S. Army Corps of Engineers. Pp. 71-76.

Bianchi, T. H. 1984. The surficial stratigraphy of State Highway 16 within the Amite River valley. Appendix 5 in Servello, A. F., ed., The Cultural Resources along Louisiana Highway 16 Between Watson and Amite: The Intensive Survey. Unpublished report prepared by Kisatchie Regional Environmental Management Group, Inc., Anacoco Louisiana, for Louisiana Department of Transportation and Development under state project no. 700-13-38. Baton Rouge, Louisiana: Louisiana Department of Transportation and Development. Pp.416-469.

Blum, M. D., and D. M. Price 1994. Glacio-eustatic and climate controls on Quaternary alluvial plain deposition, Texas Coastal Plain. Transactions of the Gulf Coast Association of Geological Societies 44:87-92.

Blum, M. D., and D. M. Price 1998. Quaternary alluvial plain construction in response to glacio-eustatic and climatic controls, Texas Gulf coastal plain. In Shanley, K. W., and P. J. McCabe, eds., Relative Role of Eustasy, Climate, and Tectonism in Continental Rocks. SEPM Special Publication no. 59. Tulsa, Oklahoma: Society for Sedimentary Geology. Pp.31-48.

Boniol, D. P. (compiler) 1988. Aquifer recharge potential of the Alexandria Quadrangle. Aquifer recharge atlas, map #8. Baton Rouge: Louisiana Geological Survey. Scale 1:250,000.

Cantley, C., L. Raymer, L. Raymer, and J. Joseph. 1993. Environmental and Cultural Background. Chapter 2 in Cantley, C. E., Principle Investigator, Data Recovery at Site 16VN794: Investigations into Site Formational Processes and the Cultural Sequence of West Central Louisiana. Technical Report no. 119. Unpublished report

106

prepared for National Park Service by New South Associates, Stone Mountain, Georgia under contract no. CX 5000-0-0014. Atlanta, Georgia: National Park Service. Pp.3-48.

Cantley, C. E., L. Danielsson-Murphy, T. Murphy, U. McEvoy, L. Raymer, J. Cable, R. Yallop, C. Rhodes, M. B. Reed, and L. A. Abbott 1997. Fort Polk, Louisiana: A Phase 1 Archaeological Survey of 14,622 Acres in Vernon Parish. Unpublished report prepared for National Park Service by New South Associates, Stone Mountain, Georgia under contract no. 1443CX500095057. Atlanta, Georgia: National Park Service. 175 pp.

Collins,M. B. 1995. Forty years of archaeology in central Texas. Bulletin of the Texas Archaeological Society 66:361-400.

Cronin, T. M., D. A. Willard, H. J. Dowsett, S. E. Ishman, T. R. Holtz, Jr., and 1. C. Liddicoat 1993. The Yorktown Formation of Virginia: implications for late Pliocene climate and sea level history. Abstract. Geological Society of America Abstracts with Programs 25(6):334.

Dixon, L. H. 1965. Cenozoic cyclic depositon in the subsurface of central Louisiana. Geological bulletin no. 42. Baton Rouge: Department of Conservation, Louisiana Geological Survey. 124 pp. plus plates.

Doering, J. 1935. Post-Fleming surface formations of southeast Texas and south Louisiana. Bulletin of the American Association of Petroleum Geologists 19(5):651-688.

Doering, J. 1956. Review of Quaternary surface formations of Gulf Coast region. Bulletin of the American Association of Petroleum Geologists 40(8): 1816-1862.

Dubar, J. R., T. E. Ewing, E. L. Lundelius, Jr., E. G. Otvos, and C. D. Winker 1991. Quaternary geology of the Gulf of Mexico Coastal Plain. Chapter 19 in Morrison, R. B., ed., Quaternary nonglacial geology: Conterminous U. S. The Geology of North America, v. K-2. Boulder, Colorado: Geological Society of America. Pp.583-61O.

Fields, R. C., and P. V. Heimich 1987. Geoarcheology of the Alley Road Site. Chapter 7 in Fields, R. C., ed., Excavations at the Alley Road Site (41LNI49B) and the Harris Hole Site (41LN30), Jewett Mine Project, Leon County, Texas. Prewitt and Associates Report of Investigations no. 61. Unpublished report prepared by Prewitt and Associates, Austin, Texas for Northwestern Resources, Inc. Huntsville, Texas: Northwestern Resources, Inc. Pp. 63-48.

Fisk, H. N. 1938. Geology of Grant and La Salle parishes. Geological bulletin no. 10. Baton Rouge: Department of Conservation, Louisiana Geological Survey. 246 pp. plus plates (includes two 1 :62,500-scale geologic maps).

107

Fisk, H. N. 1939. Igneous and metamorphic rock from Pleistocene gravels of central Louisiana. Journal of Sedimentary Petrology 9(1 ):20-27.

Fisk, H. N. 1940. Geology of Avoyelles and Rapides parishes. Geological bulletin no. 18. Baton Rouge: Department of Conservation, Louisiana Geological Survey. 240 pp. plus plates (includes two 1 :62,500-scale geologic maps).

Foote, R. Q., L. M. Massingill, R. H. Wells, G. L. DoHon, and M. M. Ball 1992. Geologic framework for petroleum assessment of the Western Gulf basin, Province 112. Open-file report 89-4S0B. Denver: U.S. Geological Survey. 32 pp.

Forney, L. B. 1950. The Willis Formation of the Texas Gulf Coast. M.S. thesis. Houston, Texas: University of Houston. 39 pp.

Foss, 1., C. Cantley, R. Lewis, and C. Stiles 1993. Pedological investigations. Chapter IV in Cantley, C. E., ed., Data Recovery at Site 16VN794: Investigations into Site F ormation Processes and the Cultural Sequence of West Central Louisiana. Unpublished report prepared for National Park Service by New South Associates, Stone Mountain, Georgia under contract no. CX5000-0-0014. Atlanta, Georgia: National Park Service. Pp. 95-130.

Frey, R. W., and 1. D. Howard 1970. Comparison of Upper Cretaceous ichnofaunas from siliceous sandstones and chalk, Western Interior Region, U.S.A. In Crimes, T. P., and 1. C. Harper, eds., Trace Fossils. Liverpool Geological Society, Geological Journal Special Issue No.3. Liverpool, England: Seel House Press. Pp. 141-166.

Galloway, W. E. 1977. Catahoula Formation of the Texas coastal plain: depositional systems, composition, structural development, ground-water flow history, and uranium distribution. Report of investigations no. 87. Austin: The University of Texas at Austin, Bureau of Economic Geology. 59 pp.

Galloway, W. E. 1989a. Genetic stratigraphic sequences in basin analysis I: architecture and genesis of flooding-surface bounded depositional units. Bulletin of the American Association of Petroleum Geologists 73(2):125-142.

Galloway, W. E. 1989b. Genetic stratigraphic sequences in basin analysis II: application to northwest Gulf of Mexico Cenozoic basin. Bulletin of the American Association of Petroleum Geologists 73(2):143-154.

Galloway, W. E., D. K. Hobday, and K. Magara 1982. Frio Formation of the Texas Gulf coastal plain: depositional systems, structural framework, and hydrocarbon distribution. Bulletin of the American Association of Petroleum Geologists 66(6):649-688.

108

Galloway, W. E., D. G. Bebout, W. L. Fisher, J. B. Dunlap, Jr., R. Cabrera-Castro, J. W. Lugo-Rivera, and T. M. Scott 1991. Cenozoic. Chapter 11 in Salvador, A., ed., The Gulf of Mexico Basin. The Geology of North America, v. J. Boulder, Colorado: The Geological Society of America. Pp. 245-324.

Glawe, L. N. 1989. Stratigraphic relationships between Odontogryphaea thirsae beds and the Big Shale of the Wilcox (Paleocene-Eocene) in Louisiana. Transactions of the Gulf Coast Association of Geological Societies 39:375-383.

Goins, C. R., and J. M. Caldwell 1995. Historical atlas of Louisiana. Norman, Oklahoma: University of Oklahoma Press. [Maps and texts for 99 headings.]

Groot, J. J. 1991. Palynological evidence for Late Miocene, Pliocene, Early Pleistocene climate changes in the middle U.S. Atlantic coastal plain. Quaternary Science Reviews 10(2/3):147-162.

GUderjohn, T. H., and J. R. Morehead 1980. Big Brushy: a stratified multiple component site at Fort Polk, Louisiana. Louisiana Archaeology 7:1-29.

Guillory, C. M. 1997. Soil Survey of Sabine Parish. Washington, D.C.: U.S. Department of Agriculture, Natural Resources Conservation Service. 194 pp.

Gunn, J., and A. C. Kerr 1984. Occupation and settlement in the uplands of west-central Louisiana. Center for Archaeological Research special publication no. 17. San Antonio, Texas: Center for Archaeological Research, University of Texas at San Antonio. 183 pp.

Gunn, J., D. O. Brown, E. C. Gibson, and A. Kerr n.d. A dated colluvial-cultural sequence for west-central Louisiana, occupation floor archaeology and settlement patterns. San Antonio, Texas: Center for Archaeological Research, University of Texas at San Antonio. Unpublished manuscript.

Hack, J. T. 1960. Interpretation of erosional topography in humid climates. American Journal of Science 258-A:80-97.

Hayward, O. T., P. Allen, and D. Amsbury 1990. The Lampasas cut plain-evidence for the cyclic evolution of a regional landscape, central Texas. GSA Field Trip #19, November 2-3, 1990. Boulder, Colorado: Geological Society of America. 126 pp.

Hernandez, M. W. 1990. Distribution, Development, and Risk Mapping of Landslides in Northeastern Louisiana. M.S. thesis. Ruston, Louisiana: Louisiana Tech University. 433 pp. plus seven oversized plates.

109

Heydari, E. 1998. Personal communication. Assistant Professor of Research: Louisiana State University, Louisiana Geological Survey, Basin Research Institute, Baton Rouge, Louisiana.

Hinds, D. J. 1997a. A report to accompany the geologic map, Fort Polk area, western Louisiana, scale 1 :24,000. Unpublished report. Baton Rouge: Louisiana State University. 49 pp. plus plates (includes one 1 :24,000-scale geologic map).

Hinds, D. J. 1997b. A report to accompany the geologic map, Slagle area, western Louisiana, scale 1 :24,000. Unpublished report. Baton Rouge: Louisiana State University. 61 pp. plus plates (includes one 1 :24,000-scale geologic map).

Hinds, D. J. 1998a. Neogene Stratigraphy and Depositional Environments of the Fort Polk and Slagle Area, Western Louisiana. M.S. thesis. Baton Rouge: Louisiana State University. 100 pp. plus plates (includes two geologic maps at an approximate scale of 1 :53,333).

Hinds, D. J. 1998b. Geologic map of the Fort Polk area, Vernon Parish, Louisiana. Geologic quadrangle map no. GQ-1. Baton Rouge: Louisiana Geological Survey. Produced in cooperation with U.S. Geological Survey, EDMAP program, under assistance award no. 1434-HQ-96-AG-01535. Scale 1 :24,000.

Hinds, D. J. 1998c. Geologic map of the Slagle area, Vernon Parish, Louisiana. Geologic quadrangle map no. GQ-2. Baton Rouge: Louisiana Geological Survey. Produced in cooperation with U.S. Geological Survey, EDMAP program, under assistance award no. 1434-HQ-97-AG-01753. Scale 1:24,000.

Hinds, D. J. 1999. Neogene stratigraphy and depositional environments of the Fort Polk and Slagle areas of western Louisiana. Report of investigations 99-01. Baton Rouge: Louisiana Geological Survey. 60 pp. plus appendix.

Huddlestun, P. F. 1988, A revision of the lithostratigraphic units of the coastal plain of Georgia: the Miocene through Holocene. Bulletin no. 104. Atlanta: Georgia Geological Survey. 162 pp.

Hulbert, R. C., Jr., and F. C. Whitmore, Jr. 1997. Late Miocene mammals from the Mauvilla local fauna, Alabama. Abstract. Geological Society of America Abstracts with Programs 29(2):25.

Hyatt, P. E. 1998. Conservation assessment for hillside seepage bogs of the Kisatchie National Forest. Pineville, Louisiana: Kisatchie National Forest. 107 pp.

Hyatt, P. E. 1999. Personal communication. Biologist: Kisatchie National Forest, Pineville, Louisiana.

110

Johnson, W. C. 1990a. Geomorphic Setting. In Campbell, L. 1., 1. R. Moorehead, and A. F. Servello, Data Recovery at 16VN791, a Multi-Component Prehistoric Site in the Birds Creek Drainage. New World Research Report of Investigations no. 188. Unpublished report prepared by New World Research, Fort Walton Beach, Florida for National Park Service under contract no. CX5000-9-0009. Atlanta, Georgia: National Park Service. Pp.32-35.

Johnson, W. C. 1990b. Stratigraphy. In Campbell, L. 1., 1. R. Moorehead, and A. F. Servello, Data Recovery at 16VN791, a Multi-Component Prehistoric Site in the Birds Creek Drainage. New World Research Report of Investigations no. 188. Unpublished report prepared by New World Research, Fort Walton Beach, Florida for National Park Service under contract no. CX5000-9-0009. Atlanta, Georgia: NationaL Park Service. Pp.35-41.

Jones, M. H., J. A. Schiebout, and J. T. Kirkova 1995. Cores from the Miocene Castor Creek Member of the Fleming Formation, Fort Polk Louisiana: relationship to the outcropping Miocene terrestrial vertebrate fossil-bearing beds. Transactions of the Gulf Coast Association of Geological Societies 45:293-301.

Killeen, M., D. EIfert, K. Long, M. Surman, R. Bourgeois, and B. Harder 1997. Louisiana desktop well reference. Baton Rouge: Petroleum Technology Transfer Council, Louisiana State University. One compact disc.

Kukla, G. J., and N. D. Opdyke 1972. American glacial stages in paleomagnetic time scale. Geological Society of America Abstracts with Programs 4:569-570.

Lattman, L. H. 1958. Technique of mapping geologic fracture traces and lineaments on aerial photographs. Photogrammetric Engineering 24:568-576.

Lenzer, J. 1982. Geomorphology of the Fort Polk Military Reservation. Appendix 4 in Thomas, P. M., S. Shellyey, L. 1. Campbell, M. T. ~wanson, C. S. Weed, and 1. P. Lenzer, Cultural Resources Investigations at the Fort Polk Military Reservation, Vernon, Sabine, and Natchitoches Parishes, Louisiana. New World Research Technical Report no. 69. Unpublished report prepared by New World Research, Fort Walton Beach, Florida for National Park Service under contract no. C-54052(80). Atlanta, Georgia: National Park Service. Pp. 4-1 to 4-49.

Louisiana Geological Survey (compiler) 1993. Alexandria 1 :250,000 geologic quadrangle. Unpublished map plus explanation and notes. Prepared in cooperation with U.S. Geological Survey, COGEOMAP program, under cooperative agreement no. 14-08-0001-A0878. Scale 1 :250,000.

Louisiana Office of State Climatology n.d. Climate of West Central Louisiana. Baton Rouge, Louisiana: Louisiana Office of State Climatology, Louisiana State University. 3 pp.

111

MacRoberts, B. R, and M. H. MacRoberts 1988. Floristic composition of twowest Louisiana pitcher plant bogs. Phytologia 65:184-190.

MacRoberts, B. R, and M. H. MacRoberts 1992. Floristics of four small bogs in western Louisiana with observations on species/area relationships. Phytologia 73:49-56.

MacRoberts, B. R, and M. H. MacRoberts 1993. Floristics of a bog in Vernon Parish, Louisiana with comments on noteworthy bog plants of western Louisiana. Phytologia 75:247-258.

Maher, J. C., W. F. Guyton, W. J. Drescher, and P. H. Jones 1943. Ground-water conditions at Camp Polk and North Camp Polk, Louisiana. Open-file report. Baton Rouge, Louisiana: U.S. Geological Survey. 29 pp. plus tables and plates.

Markewich, H. W., M. 1. Pavich, and G. R Buell 1991. Contrasting soils and landscapes of the Piedmont and coastal plain, eastern United States. Geomorphology 3(3-4):417-447.

Martin, D. L., and L. M. Smith 1991. A Survey and Description of the Natural Plant Communities of the Kisatchie National Forest Winn and Kisatchie Districts. Unpublished report on file with the Louisiana Department of Wildlife and Fisheries, Baton Rouge, Louisiana. 282 pp.

Martin, P. G., C. L. Butler, E. Scott, 1. E. Lyles, M. Mariano, J. Ragus, P. Mason, and L. Schoelerman 1990. Soil Survey of Natchitoches Parish. Washington, D.C.: U.S. Department of Agriculture, Soil Conservation Service. 192 pp.

Matson, G. C. 1916. Pliocene Citronelle Formation of the Gulf Coastal Plain. U.S. Geological Survey Professional Paper 98. Washington, D.C.: U.S. Government Printing Office. Pp. 167-192.

McCulloh, R P. 1993. Surface geologic mapping in Louisiana-its beginnings, rise, and recent decline. In Autin, W., and 1. Snead, eds., Quaternary Geology and Geoarchaeology of the Lower Red River Valley. Friends of the Pleistocene, South Central Cell, 11th Annual Field Conference. Pp. 153-157.

McCulloh, R P. 1995. Fisk's NE- and NW-striking "faults" and the potential for joint control of stream courses in Louisiana. Transactions of the Gulf Coast Association of Geological Societies 45:415-422.

McWreath, H. C., III, and C. W. Smoot 1989. Geohydrology and development of ground water at Fort Polk, Louisiana. Water-Resources Investigations Report

112

88-4088. Baton Rouge: U.S. Geological Survey, Louisiana District. 53 pp. plus plate.

Meyer, J., J. R. Morehead, J. H. Mathews, P. M. Thomas, Jr., and L. J. Campbell 1996. Fort Polk -18: the results of a eighteenth program of site testing at ten sites, Fort Polk Military Reservation, Vernon Parish, Louisiana. Unpublished report prepared for Headquarters, Joint Readiness Training Center, Fort Polk, Louisiana by New South Associates, Stone Mountain, Georgia under contract no. CX5000-1-0027, Delivery Order 1443PX500094741. Fort Polk, Louisiana: Joint Readiness Training Center. 241 pp.

Morehead, J. R. 1999. Personal communication on February 2. Staff Archaeologist: Prentice Thomas & Associates Cultural Resources Managment, Inc., Fort Walton Beach, Florida.

Morton, R. A., L. A. Jirik, and W. E. Galloway 1988. Middle-upper depositional sequences of the Texas Coastal Plain and continental shelf: framework and hydrocarbon plays. Report of investigations no. 174. University of Texas Bureau of Economic Geology. 40 pp. plus plates.

Miocene geologic Austin:

Munsell Color 1994. Munsell soil color charts. New Windsor, New York: GretagMacbeth. Revised edition.

Murray, G. E. 1961. Geology of the Atlantic and Gulf coastal province of North America. New York: Harper and Brothers. 692 pp.

Muse, B., and M. Cooley Soil Survey of Vernon Parish. Washington, D.C.: U.S. Department of Agriculture, Natural Resources Conservation Service (in press).

Otvos, E. G. 1997. Northeastern Gulf coastal plain revisited: Neogene and Quaternary units and events-old and new concepts. Guidebook, Louisiana to northwest Florida field trip, October 18-19, 1997. New Orleans: New Orleans Geological Society. 143 pp.

Otvos, E. G. 1998. Citronelle Formation, northeast Gulf coastal plain-stratigraphic and age Issues. Abstract. American Association of Petroleum Geologists Bulletin 82(9):1789.

Paleo-Data, Inc. 1993. Gulf of Mexico chronostratigraphic correlation chart. New Orleans: Schlumberger and Geco-Prakla. 1 sheet.

Perttula, T. K., B. D. Skiles, M. B. Collins, M. C. Trachte, and F. Valdez 1986. "This everlasting sand bed": cultural resources investigations at the Texas Big Sandy Project, Wood and Upshur Counties. Prewitt and Associates report of investigations

113

no. 52. Austin, Texas: Prewitt and Associates Consulting Archaeologists, Inc. 234 pp.

Prothero, D. R., and E. M. Manning 1987. Miocene rhinoceroses from the Texas Gulf Coastal Plain. Journal of Paleontology 61(2):388-423.

Radburch-Hall, D. H., R. B. Colton, W. E. Davies, 1. Lucchirta, B. A. Skipp, and D. J. Varnes 1982. Landslide Overview Map of the Conterminous United States. u.s. Geological Survey Professional Paper 1183. Washington, D.C.: U.S. Government Printing Office. 25 pp.

Rainwater, E. H. 1964. Regional stratigraphy of the Gulf Coast Miocene. Transactions of the Gulf Coast Association of Geological Societies 14:81-124.

Rasbury, E. T. 1997. Personal communication. Research Associate: State University of New York, Department of Geosciences, Stony Brook, New York.

Rasbury, E. T., G. N. Hanson, W. J. Meyers, and A. H. Saller 1997. Dating of the time of sedimentation using U-Pb ages for paleosol calcite. Geochimica et Cosmochimica Acta 61(7)1525-1529.

Raymond, D. E. 1985. Depositional sequences in the Pensacola Clay (Miocene) of Alabama. Bulletin no. 114. Tuscaloosa: Alabama Geological Survey. 87 pp.

Rogers, J. E. 1980. Unpublished data, Alexandria quadrangle. Alexandria, Louisiana: U.S. Geological Survey. Scale 1 :250,000.

Rogers, J. E. 1982. Personal communication. Hydrologist: U.S. Geological Survey, Alexandria, Louisiana.

Rogers, J. E. 1993. Personal communication. Consulting ground-water hydrologist: Alexandria, Louisiana.

Rogers, J. E. 1999. Personal communication. Consulting ground-water hydrologist: Alexandria, Louisiana.

Rogers, J. E., and A. J. Calandro Water resources bulletin no. Louisiana Geological Survey. geologic map).

1965. Water resources of Vernon Parish, Louisiana. 6. Baton Rouge: Department of Conservation, 104 pp. plus plates (includes one 1: 126, 720-scale

Rukas, J. M., and D. D. Gooch 1939. Exposures of Vicksburg Oligocene fauna in western Louisiana. Bulletin of the American Association of Petroleum Geologists 23:246-253.

114

Salvador, A. 1987. Late Triassic-Jurassic paleogeography and origin of Gulf of Mexico basin. Bulletin of the American Association of Petroleum Geologists 71 :419-451.

Salvador, A., and 1. M. Q. Mufieton (compilers) 1989. Stratigraphic correlation chart, Gulf of Mexico basin. Plate 5 in Salvador, A., ed., The Gulf of Mexico Basin. The Geology of North America, v. 1. Boulder, Colorado: The Geological Society of America.

Saucier, R. T., and 1. 1. Snead (compilers) 1989. Quaternary geology of the Lower Mississippi Valley. Plate 6 in Morrison, R. B., ed., Quaternary nonglacial geology: Conterminous U. S. The Geology of North America, v. K-2. Boulder, Colorado: The Geological Society of America. Scale 1 :1,100,000.

Scheidegger, A. E. 1980. Alpine joints and valleys in light of the neotectonic stress field. Rock Mechanics, Suppl. 9:109-124.

Schiebout, J. A. 1994. Fossil vertebrates from the Castor Creek Member, Fleming Formation, western Louisiana. Transactions of the Gulf Coast Association of Geological Societies 44:675-680.

Schiebout, 1. A. 1997. Paleofaunal survey, collecting, processing, and documentation at two locations on Fort Polk, Louisiana. Unpublished report prepared for U.S. Army Corps of Engineers, Fort Worth District, under contract no. DACW63-90-D-0008, delivery order no. 13. Fort Worth, Texas: U.S. Army Corps of Engineers. 92 pp.

Schiebout, J. A. 1999. Personal communication. Associate Curator: Louisiana State University, Museum of Natural Science, Baton Rouge, Louisiana; and Adjunct Associate Professor: Louisiana State University, Department of Geology & Geophysics, Baton Rouge, Louisiana.

Schiebout, 1. A., M. H. Jones, 1. H. Wrenn, and P. R. Aharon 1996. Age of the Fort Polk, Louisiana, Miocene terrestrial vertebrate sites. Transactions of the Gulf Coast Association of Geological Societies 46:373-378.

Servello, A. F., and T. H. Bianchi 1982. Geomorphology and cultural stratigraphy of the Eagle Hill area of Peason Ridge. Appendix V in Servello, A. F., ed., Fort Polk Archaeological Survey and Cultural Resources Management Program. Unpublished report prepared by the Fort Polk Archaeological Survey, University of Southwestern Louisiana, Lafayette, Louisiana for the U.S. Army Corps of Engineers, Fort Worth District, Fort Worth, Texas under contract number DACA63-76-C-02353. Fort Worth, Texas: U.S. Army Corps of Engineers. Pp.377-566.

Smith, 1. M. 1994. Personal communication. Ecologist: Louisiana Department of Wildlife and Fisheries, Louisiana Natural Heritage Program, Baton Rouge, Louisiana.

115

Smith, L. M., 1996. The rare and sensitive natural wetland plant communities of interior Louisiana. Baton Rouge: Louisiana Natural Heritage Program, Louisiana Department of Wildlife and Fisheries. 38 pp.

Smith, S. M. 1987. Properties of embankment slope instability in southwestern Louisiana. M.S. thesis. Ruston, Louisiana: Louisiana Tech University. 226 pp.

Snead, J. 1., and R. P. McCulloh (compilers) 1984. Geologic map of Louisiana. Baton Rouge: Louisiana Geological Survey. Scale 1 :500,000.

Snead, J. 1., P. V. Heinrich, R. P. McCulloh, and W. 1. Autin (compilers) 1998. Quaternary geologic map of Louisiana. Unpublished map plus 12-pp. expanded explanation and notes. Prepared in cooperation with U.S. Geological Survey, STATEMAP program, under cooperative agreement no. 1434-HQ-97-AG-01812. Scale 1 :500,000.

Spradlin, S. D. 1980. Miocene Fluvial Systems: Southeast Texas. M.S. thesis. Austin: The University of Texas. 139 pp. plus plates.

Thomas, M. A. 1991. The Impact of Long-term and Short-term Sea Level Changes on the Evolution of the Wisconsinan-Holocene Trinity/Sabine Incised Valley System, Texas Continental Shelf. Ph.D. dissertation. Baton Rouge: Louisiana State University. 351 pp.

Thoms, A. V. 1993. Buried in the sandy mantle: site formation in the Post Oak Savannah. Chapter 5 in Thoms, A. V., ed., The Brazos Valley Slopes Archaeological Project: Cultural Resources Assessments for the Texas A&M University Animal Science Teaching and Research Complex, Brazos County, Texas. Texas A&M Archaeological Research Laboratory reports of investigations no. 14. College Station, Texas: Texas A&M Archaeological Research Laboratory. Pp.51-60.

Thoms, A. V., and B. W. Olive 1993. The ASTRC landscape and natural site formation processes: sandy mantle sediments and reconstituted cultural stratigraphy. Chapter 6 in Thoms, A. V., ed., The Brazos Valley Slopes Archaeological Project: Cultural Resources Assessments for the Texas A&M University Animal Science Teaching and Research Complex, Brazos County, Texas. Texas A&M Archaeological Research Laboratory reports of investigations no. 14. College Station, Texas: Texas A&M Archaeological Research Laboratory. Pp.61-80.

Thoms, A. V., B. W. Olive, and P. A. Clabaugh 1994. Disarticulation of the Valley Branch site: landscape evolution and natural site formation processes. Chapter 9 in Thoms, A. V. ed., The Valley Branch Site Archaeological Project: Excavations at an Archaic Site (41MU55) in the Cross Timbers Uplands, North-Central Texas. Texas A&M Archaeological Research Laboratory reports of investigations no. 15.

116

Unpublished report prepared for the Texas State Department of Highways and Public Transportation, Austin, Texas under agreement number IAA (93-94) 02. College Station, Texas: Texas A&M Archaeological Research Laboratory. Pp. 167-186.

Thornbury, W. D. 1965. Regional Geomorphology of the United States. New York: John Wiley and Sons, Inc. 609 pp.

Tomas, R. N. 1978. Mission Change, Fort Polk Military Reservation, Fort Polk, Louisiana: Final Environmental Impact Statement. Unpublished report prepared by 5th Infantry Division (Mechanized), Fort Polk, Louisiana for U. S. Department of the Army, Headquarters Forces Command. Washington, D.C.: Department ofthe Army. 536 pp.

Turcan, A. N., Jr., J. B. Wesselman, and C. Kilburn 1966. Interstate correlation of aquifers, southwestern Louisiana and southeastern Texas. In Geological Survey Research 1966, Chapter D. U.S. Geological Survey Professional Paper 550-D. Washington, D.C.: U.S. Government Printing Office. Pp. D231-D236.

U.S. Geological Survey 1994. Stratigraphic nomenclature databases for the United States, its possessions, and territories. A computerized lexicon of geologic- or stratigraphic-unit names (GNULEX). Digital Data Series DDS-6, Release 2. Reston, Virginia: U.S. Geological Survey. One compact disc.

Van Siclen, D. C. 1985. Pleistocene meander-belt ridge patterns in the vicinity of Houston, Texas. Transactions of the Gulf Coast Association of Geological Societies 35:525-532.

Van Siclen, D. C. 1991. Surficial geology of the Houston area: an offlapping series of Pleistocene (& Pliocene?) highest-sealevel fluviodeltaic sequences. Transactions of the Gulf Coast Association of Geological Societies 41 :651-666.

Veatch, A. C. 1906. Geology and underground water resources of northern Louisiana with notes on adjoining districts. Bulletin 4 in Report of 1905. Baton Rouge: Geological Survey of Louisiana. Pp. 249-457.

Walker, H. J., and J. M. Coleman 1987. Atlantic and Gulf Coastal Province. Chapter 3 in Graf, W. L., ed., Geomorphic systems of North America. Centennial Special Volume 2. Boulder, Colorado: Geological Society of America. Pp.51-110.

Walper, J. L., F. H. Henk, Jr., E. J. Loudon, and S. N. Raschilla 1979. Sedimentation on a trailing plate margin: the northern Gulf of Mexico. Transactions of the Gulf Coast Association of Geological Societies 29: 188-201.

117

Watson, S. and D. Kirksey 1963. Miocene photo and surface geology of west central Louisiana. Unpublished report. Lafayette, Louisiana: Sinclair Oil & Gas Company. 40 pp. plus plates (includes one 1:126,nO-scale photogeologic map).

Welch, R. N. 1942. Geology of Vernon Parish. Geological bulletin no. 22. Baton Rouge: Department of Conservation, Louisiana Geological Survey. 90 pp. plus plates (includes one 1 :62,500-scale geologic map).

Williamson, J. D. M. 1959. Gulf Coast Cenozoic history. Transactions of the Gulf Coast Association of Geological Societies 9: 15-29.

Winker, C. D. 1979. Late Pleistocene Fluvial-Deltaic Deposition on the Texas Coastal Plain and Shelf. M.A. thesis. Austin, Texas: University of Texas at Austin. 187 pp.

Winker, C. D. 1982. Cenozoic shelf margins, northwestern Gulf of Mexico. Transactions of the Gulf Coast Association of Geological Societies 32:427-448.

Winker, C. D. (compiler) 1991. Quaternary geology, northwestern Gulf Coast. Plate 8 in Morrison, R. R, ed., Quaternary nonglacial geology: Contenninous U. S. The Geology of North America, v. K-2. Boulder, Colorado: The Geological Society of America. Scale 1 :2,000,000.

Woodburne, M. 0., and C. C. Swisher, III 1995. Land mammal high-resolution geochronology, intercontinental overland dispersals, sea level, climate, and vicariance. In Berggren, W. A., D. V. Kent, and M. P. Aubry, eds., Geochronology, Time Scales and Global Stratigraphic Correlation: Unified Temporal Framework for an Historical Geology. Special publication no. 54. Tulsa, Oklahoma: Society of Economic Paleontologists and Mineralogists (Society for Sedimentary Geology). Pp. 335-364.

Woodbury, H. 0., I. R Murray, Jr., P. J. Pickford, and W. H. Akers 1973. Pliocene and Pleistocene depocenters, outer continental shelf, Louisiana and Texas. American Association of Petroleum Geologists Bulletin 57:2428-2439.

Woodward, T. P., and A. J. Gueno 1941. The sand and gravel deposits of Louisiana. Geological bulletin no. 19. Baton Rouge: Department of Conservation, Louisiana Geological Survey. 429 pp.

Wornardt, W. W., and P. R.Vail 1991. Revision of the Plio-Pleistocene cycles and their application to sequence stratigarphy and shelf and slope sediments in the Gulf of Mexico. Transactions of the Gulf Coast Association of Geological Societies 41:719-744.

Worrall, D. M., and S. Snelson 1989. Evolution of the northern Gulf of Mexico, with emphasis on Cenozoic growth faulting and the role of salt. Chapter 7 in Bally, A. W.,

118

and A. R. Palmer, eds., The Geology of North America-An Overview. The Geology of North America, v. A. Boulder, Colorado: The Geological Society of America. Pp.97-138.

Ye, Q., W. E. Galloway, and R. K. Mathews 1995. High-frequency glacioeustatic cyclicity of the Miocene in central Texas and western Louisiana and its applications in hydrocarbon exploration. Transactions of the Gulf Coast Association of Geological Societies 45:587-594.

Zimme1111an, R. 1996. Overview of probable facture genesis in the central Louisiana Austin Chalk horizontal drilling trend. The Basin Research Institute Bulletin 6: 3-15.

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APPENDIX A

Munsell Colors Determined for Catahoula and Fleming Sediments

Munsell colors were noted for Catahoula and Fleming sediments at numerous localities. These are listed below by portions of quadrangles, approximately from southwest to northeast along the outcrop belt.

Catahoula Formation In Peason quadrangle [SW], in SE Sec. 13, T. 5 N., R. 10 W., silty clay shows

colors of brown 10 YR 5/3 to pale brown 10YR 6/3 and light olive gray 5Y 6/2 - pale olive 5Y 6/4 to light gray 5Y 7/2 - pale yellow 5Y 7/4, and clayey silt/siltstone from the same area shows color ranging from light gray 5Y 7/2 to pale yellow 5Y 8/2.

In Peason quadrangle [NE], in WC Sec. 26, T. 6 N., R. 9 W., Catahoula cross-bedded sand, very fine to fine overall but containing some very coarse grains and granules, shows color of light red lOR 7/6; it has interbeds of grayish clayey very fine sand with red mottles in places, and weathers to a "salmon" outer surface color.

In Kisatchie quadrangle [NW], in SW Sec. 30, T. 6 N., R. 8 W., sandy clay is pale brown 10YR 6/3.

In Kisatchie quadrangle [C, NW], in SW/SE Sec. 32, T. 6 N., R. 8 W., silt exposed along a creek is light gray 5Y 7/2.

In Kisatchie quadrangle [NC]: in SE Sec. 28, T. 6 N., R. 8 W., silty clay ranges from grayish brown 10YR 5/2 to pale yellow 5Y 7/3, and siltstone/very fine sandstone in the same area is pale yellow 2.5Y 8/3. In SE Sec. 27, T. 6 N., R. 8 W., very fine sandstone rock ranges from very pale brown 10YR 8/2 to grayish brown 10YR 5/2. In SWINW Sec. 28, T. 6 N., R. 8 W., very fine to very coarse Catahoula sandstone with opal/silica cement and white and black grains visible in hand specimen shows overall color ranging from very pale brown 10YR 8/2 to approximately white 10YR 8/1.

Fleming Group

Lena Formation In Peason quadrangle [SW], in NWINW Sec. 35, T. 5 N., R. 10 W., silty clay

shows colors of grayish brown 10 YR 5/2 - light brownish gray 10YR 6/2 to light gray 5Y 7/2 - pale yellow 5Y 8/2.

In Peason quadrangle [SC], in SWINE and SEINW Sec. 17, T. 5 N., R. 9 W., silty clay with plastic consistence is colored grayish brown 10 YR 5/2 to light brownish gray 10 YR 6/2. Clay at some localities in this area has color verging on dark reddish gray 5YR 4/2 to reddish gray 5YR 5/2.

In Kisatchie quadrangle [C]: in NWINW Sec. 10, T. 5 N., R. 8 W., silty clay is colored light gray 10YR 7/2, and in SW/SW Sec. 3, T. 5 N., R. 8 W., light gray 10YR 7/2 silty clay shows red 7.5R 4/6 mottles. In SE Sec. 4 and NE Sec. 9, T. 5 N., R. 8 W., calcareous clay observed in the Lena is light olive gray 5Y 6/2.

A-I

Carnahan Bayou Formation In Dowden Creek quadrangle [SW]: in SY2 Sec. 36, T. 4 N., R. 10 W., silty clay is

light gray SY 7/2, with dark red 10R 3/6, and yellowish brown 10YR S/8 mottles. Clayey very fine sand in SW corner Sec. 36, T. 4 N., R. 10 W. on the east side of Hwy. 171 is light brownish gray 2.SY 6/2, and silty clay is grayish brown 10YR S/2. On the west side ofHwy. 171 in NE Sec. 3S, T. 4 N., R. 10 W., very fine to fine sandstone is white SY 8/1, clayey silt and silty clay are pale yellow SY 7/3, and siltstone/silt is pale olive SY 6/3 to pale yellow SY 7/3. In SE Sec. 26, T. 4 N., R. 10 W., very fine to fine sandstone rock ranges from approximately white 10YR 811 to very pale brown 10YR 8/2. In NE Sec. 3S, T. 4 N., R. 10 W., very fine to fine sandy clay is approximately reddish gray SYR S/2, with yellowish red SYR 4/6-5/8 mottles.

In Dowden Creek quadrangle [WC]: on the west side of Hwy. 171 in NW Sec. 26, T. 4 N., R. 10 W. clayey very fine sand comprises colors in the light gray 2.SY-SY 7/2 range. In SE Sec. 2S, T. 4 N., R. 10 W., Carnahan Bayou sediments exposed in a quarry comprise medium-scale cross-bedded very fine to fine sand/sandstone, with beds containing grains up to very coarse and granule sizes (the larger grains consisting of clay/mud, and with quartz grains up to about coarse size), cutting out silt and siltstone. The sand is pale yellow SY 7/3, and it and sandstone occur as channeloid lenses; the underlying silt here and farther down the road to the south-southwest is olive SY S/3. In SEINE Sec. 23, T. 4 N., R. 10 W., the darker portions of lightish very fine to fine sand average pale yellow 2.SY 7/3 to 2.SY 7/4. In NW/SW Sec. 12, T. 4 N., R. 10 W., fine to medium sand containing some coarse grains and whitish flecks averages approximately strong brown 7.SYR S/6, and clay is light brownish gray 10YR 6/2. In SE/SW Sec. 1, T. 4 N., R. 10 W., silty clay is approximately dark grayish brown 10YR 4/2.

In Dowden Creek quadrangle [SC]: in SY2 Sec. 6, T. 3 N., R. 9 W., silty clay is light brownish gray 10YR 6/2 and light yellowish brown 2.SY 6/3. In NE Sec. 6, T. 3 N., R. 9 W., clayey very fine sand is light brownish gray 10YR 6/2, with incipiently silicified portions colored pale yellow 2.SY 7/3. In SW Sec. 32, T. 4 N., R. 9 W., incipiently silicified and faintly jointed very fine sandstone is pale yellow SY 7/3.

In Dowden Creek quadrangle [C], in WCINW Sec. 20, T. 4 N., R. 9 W., siltstone and very fine sandstone are light gray 2.SY-SY 7/2, and very fine to medium clayey sand is pinkish gray 7.SYR 6/2 - pink 7.SYR 7/3 to light brownish gray 10 YR 6/2 - very pale brown 10 YR 7/3, with red lOR S/6 mottles.

In Dowden Creek [NC]: in SEINW Sec. 32, T. 5 N., R. 9 W., plastic clay is approximately pale yellow 5Y 8/2. In SC Sec. 31, T. 5 N., R. 9 W., silty clay is light olive gray SY 6/2, and varying between approximately dark reddish gray 5YR 4/2 and olive gray SY 4/2; orthoquartzitic sandstone is light yellowish brown 10YR 6/4 weathering to light gray 10YR 7/2, and

In Peason quadrangle [SW], in SW Sec. 30, T. S N., R. 9 W., siltstone is between pale olive SY 6/4 and olive SY 5/6. In SW-WC Sec. 30, T. S N., R. 9 W., clay is light olive gray SY 6/2, silty clay is light gray SY 7/2 and gray 5Y 611, siltstone is light olive gray SY 6/2, and clayey very fine to fine sand is very pale brown 10 YR 8/2 to pale yellow 5Y 8/2.

A-2

In Peas on quadrangle [SC], in NW Sec. 21, T. S N., R. 9 W., silty clay is light olive gray SY 6/2.

In Kurthwood quadrangle [NW], in SE/SW Sec. 1, T. 4 N., R. 9 W., "whitish" very fine to fine sandstone with some coarse and very coarse sand and granules shows an average color between gray SY 6/1 and light gray 10YR 7/2; other sandstone in the same general area is light gray 10YR 7/2.

In Kurthwood quadrangle [C], near SE comer Sec. 21, T. 4 N., R. 8 W., sandy clay is approximately light brownish gray 10YR 6/2 to light olive gray SY 612 with red lOR 4/6 mottles.

In Kurthwood quadrangle [NC], in Sec. 33, T. S N., R. 8 W., the color of "green-gray" sandy clay is near pinkish gray 5YR 612 and possibly verges on light olive gray SY 6/2.

In Kisatchie quadrangle [SW]: silty clay in NE/SW Sec. 30, T. S N., R. 8 W. is dark gray 5Y 411 and SYR 411; clayey sand in C/NW Sec. 30 is approximately dark gray SYR 411. In SW/SW Sec. 29, T. 5 N., R. 8 W., sandy clay is olive gray SY S/2.

In Kisatchie quadrangle [SC], in EC/SW Sec. 16, T. 5 N., R. 8 W., sandy clay is light gray 10YR 7/2 verging on SY 712.

In Kisatchie quadrangle [C], in NWINE Sec. IS, T. S N., R. 8 W., very fine sand is pale olive SY 6/3.

Dough Hills Formation In Leesville quadrangle [NE], in NW Sec. 24, T. 3 N., R. 9 W., silt and very fine

sand is light gray to very pale brown 10YR 711-3, with red 2.SYR 4/6 and brownish yellow 10YR 6/6-8 mottles.

In Slagle quadrangle [NW], in NW/SWINE Sec. 24, T. 3 N., R. 9 W., clayey very fine to fine sand is light gray 10YR 712, with red lOR 4/6-8 mottles.

In Slagle quadrangle [NW], in SWINE Sec. 24, T. 3 N., R. 9 W., clayey very fine to fine sand is light gray 10YR 712, with red 2.SYR 4/6--8 and yellowish brown 10YR S/8 mottles.

In Slagle quadrangle [NC], in SE/SW Sec. IS, T. 3 N., R. 8 W., clayey medium to very coarse sand is red 2.SYR 4/6-8.

In Slagle quadrangle [NC], in SW/SE Sec. IS, T. 3 N., R. 8 W., siltstone to very fine sandstone is white 10YR 8/1, with red lOR 4/6 and brownish yellow 10YR 6/6 mottles.

Williamson Creek Formation In Simpson South quadrangle [NW], in NW/SE Sec. 16, T. 3 N., R. 7 W., very

fine to fine sand with medium to coarse grains, granules, and whitish flecks is light red lOR 7/6, with yellow 10YR 7/6 and red 2.SYR S/6 mottles.

In Simpson South quadrangle [NW], in the south half ofNE Sec. 16, T. 3 N., R. 7 W., very fine to fine clayey sand is light gray 10YR 712, with yellowish brown 10YR 5/6 and dark red 2.SYR 3/6 mottles.

In Simpson South quadrangle [NE], in SWINE Sec. 13, T. 3 N., R. 7 W., very fine to very coarse granuliferous sand is light gray 10YR 712, with red 2.SYR 4/6-8 mottles.

A-3

In Simpson South quadrangle [NE], in SE Sec. 8, T. 3 N., R. 6 W., clayey silt and very fine sand is pinkish gray 5YR 6/2 and 7.5YR 7/2.

In Simpson South quadrangle [NE], on the south line of SW Sec. 7, T. 3 N., R. 6 W., very fine to fine sand with quartz granules and small pebbles is brownish yellow 10YR6/6-8.

In Lacamp quadrangle [NW], in SW/SW Sec. 9, T. 3 N., R. 6 W., very fine to fine clayey sand is light gray 10YR 7/2, with reddish brown 2.5YR 4/4 and brownish yellow 10YR 6/6-8 mottles.

In Lacamp quadrangle [NW], in SE/SW Sec. 9, T. 3 N., R. 6 W.: granuliferous very fine to very coarse sandstone and sand is very pale brown 10YR 8/2, with red 2.5YR 4/8 and strong brown 7.5YR 5/6-8 mottles; and very fine clayey sandstone is white lOYR 8/1, with brownish yellow to yellow 10YR 6-7/6 and red 2.5YR 4/6 and 2.5YR 5/8 mottles.

In Lacamp quadrangle [NW], in SW Sec. 10, T. 3 N., R. 6 W., very fine to fine sandstone with whitish flecks is light gray 10YR 7/2.

Castor Creek Formation In Fort Polk quadrangle [NW], in NE Sec. 36, T. 2 N., R. 9 W., clayey silt is light

gray 10YR 7/2 to very pale brown 10YR 8/2, with red lOR 4/6-4/8 mottles. In SE Sec. 36, T. 2 N., R. 9 W., generally south of the above location, clayey sand and silt in a roadcut exposure on the west side ofHwy. 467 is light gray 2.5Y-5Y 7/2 to pale yellow 2.5Y -5Y 8/2.

At the "Shamrock" vertebrate fossil site in the Fort Polk quadrangle [NC], in SW Sec. 28, T. 2 N., R. 8 W., silty clay of the Castor Creek is light gray 5Y 7/2, with whitish calcareous nodules (these appear lighter than any color chips of the Munsell guide, even white N 8, and may be closest to white 5Y 8/1).

In the Simpson South quadrangle [C], in SW Sec. 3, T. 2 N., R. 7 W., clayey very fine sand is light gray 2.5Y 7/2 with weak red lOR 4/4 mottles.

Blounts Creek Formation In Fort Polk quadrangle [SW], in NE Sec. 1, T. 1 S., R. 9 W., clayey very fine to

fine sand is light gray 10YR-2.5Y 7/2, and the same lithology nearby to the southwest is approximately very pale brown 10YR 8/2. In SE Sec. 1, T. 1 S., R. 9 W., clayey very fine to fine sand is light gray 10YR 7/2, with brownish yellow 10YR 6/8 and red 5R-IOR 5/6 to light red 5R-I0R 6/6 mottles.

In Birds Creek quadrangle [WC], in SE Sec. 16, T. 1 N., R. 7 W., clayey silt and very fine sand is light gray 10YR 711 to white 10YR 8/1, with red lOR 4/6 and dusky red lOR 3/2 to 3/3 mottles. In SE Sec. 21, T. 1 N., R. 7 W., clayey very fine sand (at the heavily jointed locality discussed above under Structure) is light gray lOYR-5Y 7/2, with dark yellowish brown 10YR 4/6 to yellowish brown 10YR 5/6-8 mottles.

A-4

APPENDIXB

Subsurface Geologic Sections

Subsurface work done for this investigation utilized a database consIstmg of copies of electric logs of oil & gas wells and water wells available through the Louisiana State University Basin Research Institute and the U.S. Geological Survey Water Resources Division district office in Baton Rouge. From this database we constructed subsurface geologic sections after the manner of Rogers and Calandro (1965) and Hinds (1998a, 1999). A comprehensive regional study of the electric-log character of subsurface units, involving mapping of gross e-log facies and inferred depositional environments for the stratigraphic units mapped at the surface, was beyond the scope of this investigation. Such a framework would have considerable value, as outlined above under Recommendations.

Subsurface data available to us in and near the study area and examined for this investigation totaled 95 electric logs of oil & gas and water wells. Copies of the logs were correlated with one another, and the intercepts then used to construct the following sections ("stick" sections). Based on the areal distribution of available data, five lines of section were chosen. These were constructed primarily to check and verify the concordance of subsurface information with the surface mapping and to show the subsurface configuration of stratigraphic units mapped at the surface. Placement of the sections was designed as much as possible to complement, but avoid duplicating, the geologic subsurface sections previously made by Rogers and Calandro (1965) and Hinds (1998a, 1999). Intercepts are projected in places beneath the total depths of shallower wells, as well as across the upper intervals masked by surface casing, for the sake of continuity. The sections were produced using the facilities of the Louisiana State University Basin Research Institute.

Section B-B' suggests possible offset by a fault between two of its wells; evidence for this is discussed under Structure in the section entitled Faults. One section, D-D', was constructed specifically to correlate the Castor Creek Formation of the Fleming Group to its outcrop at the Discovery vertebrate-fossil site, in order to ascertain the position within the Castor Creek interval of the fossiliferous conglomerate and sandstone beds cropping out at the surface there. The section shows that the fossiliferous beds lie within the uppermost portion of the Castor Creek, if not at the top of the unit.

B-1

-93.40 -93.30 -93.20 -93.10 -93.00 -92.90

o o o o o

31.50 o 0 6N/-gW 0 6N/6W 0 cetil5W 0

31.50

o o o NATCHI aCHE E' o

w o 31.40 5N/6~ 31.40

o

4N/7W 31.30 31.30

3NI W

31.20 31.20

2N/10W

o 31.10 ~1---1f-.i...-t-----I----I--11 31.10

o

o 1N/10W 1N/9W 1NI W

o o

o o

31.00 VER ON 0 31.00

1S/10W 1S/9W C1S/8W 1~/7W

30.90

-93.40 -93.30 -93.20

@eOIOI.

~ C'Q)

.; ~/IJI .; ~ ~ o - : .> LG ~

FORT POLK AREA

Louisiana Geological Survey Basin Research Institute (LSU)

Rick McCulloh I I 8/26/99

Reed Bourgeois I Scale 1 :265000 I -1934-

-93.10

Scale 1 :265000 . 2, .... =-=~o~. =~2. __ 4'===:J6~. _~8c:, =~10. '1 _ • • Imles

2. O. 2. 4. 6. 8. 10. M • • I kilometers

-92.90

--

30.90

Rogers and Calandro 1965

Hinds 1998a Hinds 1999

. Study Area

STRUCTURAL CROSS-SECTION: ACTUAL

A Datum = Sea Level Domain = Depth AI Vertical Exaggeration = 11.67X

NA-338 NA-318 GL GL 140. 170.

500. 0 0

CROW DOMESTIC HUNTER HALBOUTY

MAGNOLIA WILHITE ETAL. SOCONY MOBIL & CHANCE BURTON #B-1 UNION #1 UNION #A-3 BENTLEY #4 BENTLEY #2 PARDEE #1 BURTON #1 BURTON #2 FEE V-450 V-437

DF DF KB KB RKB KB DF DF GL GL 229. 204. 245. 284. 201. 390. 261. 235. 225. 165.

0 0 0 0 0 0 0 0 0 0 500.

PLIO-PLEISTOCENE O. BLOUNTS CREEK O.

-500.

-1000.

-1500.

-500.

CASTOR CREEK

WILLIAMSON CREEK

DOUGH HILLS

-1000.

-1500.

-2000.

-2500.

-2000.

-2500. CARNAHAN BAYOU

-3000. -3000.

-3500. -3500.

-4000. -4000.

-4500. -4500.

-5000. -5000.

-5500. -5500.

-6000. -6000.

-6500. -6500.

-7000. -7000.

-7500. -7500.

-8000. -8000.

-8500. -8500.

-9000. -9000.

-9500. -9500.

~ •••••••••••••••••••••••••••••••••••••••••••

B STRUCTURAL CROSS-SECTION: ACTUAL

Datum = Sea Level Domain = Depth Vertical Exaggeration = 11.67X 8'

BURTON LENT ETAL. OWEN RAMROD GAMBLE GAMBLE HALBOUTY & #1 HODGES #1 MARTIN #1 PICKERING #2 PICKERING V-425 #1 CROSBY #1 PICKERING V-400 CHANCE #1 BURTON

OF OF KB OF GL KB KB GL OF 334 431 374 334 305 295 350. 390 261

~. 00. 0 0 0 0 0 0 0 0 0 500.

1- ~ ~~~~SCREErc-- 1 ~ IiVJLLJAA1S~!rOR CREEK o. O.

-500.

-1000.

-1500.

-2000.

-2500.

-3000.

-3500.

-4000.

-4500.

-5000.

-5500.

-6000.

- -6500.

- -7000.

-7500.

-8000.

~RI\/£R WILC~ SPARIA

CQOK

~H CREEK I -500.

CAR~HILLS NAHAN ~ II -1000.

,,"",YOU ---:::___ I -1500.

CAIAH ~ULA ~ ~ III -2000.

\/ICKS8U~ II -2500.

G~JA CKSOtv --------III -3000.

COC~ I -3500.

~tv ---I -4000.

IAltv -4500.

-5000.

-5500.

-6000.=~

-6500.=~

-7000.--

-7500.

-8000.

• • • • C • • MARATHON #1 JOHNSON

• KB

• 240 500. 0

• • O.

• -500.

• -1000. • • -1500.

• -2000.

• -2500. • • -3000.

• -3500. • • -4000.

• -4500.

• -5000. • • -5500.

• -6000.

• -6500. • • -7000.

• -7500. • • -8000.

• -8500.

• -9000. • • -9500.

• -10000.

• -10500. • • -11000.

• -11500.

• • •

STRUCTURAL CROSS-SECTION: ACTUAL Datum = Sea Level Domain = Depth

Vertical Exaggeration = 11 .67X

PRUET #1 EDWARDS

KB V-451

GL

V-437

GL

200 165

C"

175 o o 0 500.

PLIO-PLEISTOCENE

BLOUNTS CREEK

CASTOR CREEK

WILLIAMSON CREEK

DOUGH HILLS

CARNAHAN BAYOU

LENA.

CATAHOULA

VICKSBURG - JACKSON

COCKFIELD

-----1-----1 COOK MOUNTAIN

SPARTA

CANE RIVER

WILCOX

o.

-500.

-1000.

-1500.

-2000.

-2500.

-3000.

-3500.

-4000.

-4500.

-5000.

-5500.

-6000.

-6500.

-7000.

-7500.

-8000.

-8500.

-9000.

-9500.

-10000.

-10500.

-11000.

-11500.

---• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • !'

STRUCTURAL CROSS-SECTION: ACTUAL Datum = Sea Level Domain = Depth

Vertical Exaggeration = 11.67X

500.

o V-642 V-101 V-497 V-670 V-492 GL GL GL GL GL

348 3q7 325 340 286 o 0 0 0 0

0' 500.

LOUNTS CREEK

O. O.

-500. -500.

-1000. -1000.

-1500. -1500.

E

500.

V-407 V-432 V-462 V-443 GL RT V-444

V-431 GL 315 381 GL GL 372 \ / 330 GL

'\. / 330 360......... '\. ./ .......... 0 000 OO/"

o.

-500.

-1000.

STRUCTURAL CROSS.,SECTION: ACTUAL Datum = Sea Level Domain = Depth

Vertical Exaggeration = 11.67X

MAGNOLIA #1 LONGLEAF

OF 379 o

HODGES & UNION #1 MARTIN

OF

412 o

LENT ETAL. #1 MARTIN OF 431 o

CARNAHAN BAYOU

WILHITE ETAL. #1 UNION OF 204

Ell

o 500.

o.

-500.

-1500.

VICKSBURG-· _ --=J~A ___ CK_S_O_N ___ -l ------~--~-L=--

-1000.

-1500. COCKFiELD

-2000. -2000.

-2500. -2500.

-3000. -3000.

-3500. -3500.

-4000. -4000.

-4500. -4500.

-5000. -5000.

-5500. -5500.

-6000. -6000.

-6500. -6500.

-7000. -7000.

-7500. -7500.

-8000. -8000.

-8500. -8500.

-9000. -9000.

-9500. -9500.

-10000. -10000.

-10500. -10500.

-11000. -11000.

-11500. -11500.

-12000. -12000.

I )

Revised Cross‐Sections for Fort Polk region, South Central Louisiana (Version 2010b)

by Paul V. Heinrich

Louisiana Geological Survey Louisiana State University

Baton Rouge, Louisiana 70803 September 29, 2010

Small-size townCross section line

Main Post area of Fort Polk

Medium-size town

LEGEND

N

Fo

rt Polk Sec

tion

BCS Fu

lle

rton Se

ctio

n

LS Lacamp Section (LS)

Birds Creek Section (BCS)

Fullerton Br anch Section

31˚15'00''

31˚07'30''

31˚00'00''

31˚15'00''

31˚07'30''

92˚37'30''92˚45'00''92˚52'30''93˚15'00'' 93˚07'30'' 93˚00'00''

92˚37'30''92˚45'00''92˚52'30''93˚15'00'' 93˚07'30'' 93˚00'00''31˚00'00''

Fullerton Section

Lacamp Section

Fullerton LakeNorth

Fort Polk

Birds Creek

Fort Polk

Fort Polk

Slagle Simpson South Lacamp Sieper

AfemanMelder

Melder

Elmer

ElmerHinestonLeanderLacamp

Hicks

Slagle

LEGEND

TOWN/CITY

Fullert on

Sec

tion

Birds Creek Section

Fullerton Branch Section

Fullerton

Lacamp Section

Lacamp Section Lacamp Section

31° 00'

31° 07'30"

Lacamp

CROSS SECTION LINES

FORT POLK BOUNDARY

93° 07'30"93° 15' 92° 37'30"92° 45'92°52'30"93° 00'31° 15'

93° 15' 93° 07'30" 92° 37'30"92° 45'92° 52'30"93° 00'31° 00'

31° 07'30"

31° 15'

Birds

Creek

Sectio

n

Fort Polk

Fort Pol

k Se

ction

Fort PolkNorth

Fort Polk

Melder

ElmerHinestonLeander

HicksLacamp

Slagle

Afeman

Sieper

Melder

Elmer

Fullerton LakeBirds Creek

Fort Polk

Slagle Simpson South

RELATIVE TO THE MAIN POST OF FORT POLK, LOUISIANAFigure INDEX MAP SHOWING LOCATION OF CROSS SECTIONS

Quaternary System

Holocene Series

Hua Unnamed alluvium

Hbb Big Brushy formation

Pleistocene Series

Pp Prairie Allogroup undifferentiated

Intermediate allogroup

Pil Lissie Alloformation

Pib Bentley alloformation

Tertiary System

Pliocene Series

Puw Upland allogroup, Willis Formation

Puwg Willis Formation, Gravel Hill allomember

Puwt Willis Formation, Tower Road allomember

Puwd Willis Formation, Dugout Road allomember

Puwk Willis Formation, Kisatchie allomember

Puwf Willis Formation, Fort Polk allomember

Miocene Series

Mf Fleming Group

Mfb Blounts Creek Formation

Mfcc Castor Creek Formation

Legend for Revised Fort Polk Cross-SectionsStratigraphic Units

Slag

le7

1/2

Fort

Polk

7 1/

2

Fort

Polk

7 1/

2N

ew L

lano

7 1/

2Fo

rt Po

lk7

1/2

New

Lla

no7

1/2

Ros

epin

e7

1/2

New

Lla

no7

1/2

Laca

mp

7 1/

2

Sim

pson

Sou

th7

1/2

Sim

pson

Sou

th

7 1/

2

Slag

le 7

1/2

Lacamp Section

East-west cross-section along the crest of the Kisatchie Wold and across the Calcasieu River Valley. Vertical Exaggeration = 52X

Cross-section through Fort Polk, Louisiana along crest of interfluve. Vertical Exaggeration = 52X

Mfw

PuwfPuwfPuwf

Mfcc PilMfb

Mfcc

MfccPuwd

PuwfPuwk

Pil

Puwd Puwt

Puwd Puwg?

Pil

Pil

Pib

Fort PolkNorth Fort Polk

East

Elev

atio

n in

Fee

t

100

400

500

300

200

100

300

200

100

400

500

300

200

Fort Polk Section

SouthwestNortheast

intersection withBirdsCreek Section

93˚ 00' 00"

Puwf

intersection withFullerton Section

Mfcc

Elev

atio

n in

Fee

t

Pil

Puwf

West

Puwf

Mfcc

PuwgPuwt

92˚ 52' 30"93˚ 07' 30"

Mfcc94˚ 45' 00"

Pib

“Bentley Formation”of Fisk (1940) “Williana Formation”

of Fisk (1940)

Hua Hua

CypressBayou

CalcasieuRiver

Pp

Puwf

100

400

500

300

200

300

200

Miles54321

Kilometers6543210

0

Elev

atio

n in

Fee

tEl

evat

ion

in F

eet

500

400

300

200

100

500

400

300

200

100

NorthSouth

intersection withLacamp Section

Birds Creek Section

Sugr

ue7

1/2

Bird

sC

reek

7 1/

2

Bird

sC

reek

7 1/

2

Laca

mp

7 1/

2

Cross-section along crest of interfluve seperating Birds Creek and Little Sixmile Creek–Sixmile Creek drainage. Vertical exaggeration = 52x.

PuwPuwf PuwkPuwf Puwk profile

off-sectionPuwd

Mfb

MfbMfcc

Mfb

PuwtPuwg Pil

0

0 1 2 3 4 5 6 Kilometers

1 2 3 4 5 Miles

500

400

300

200

100

SouthFullerton Branch Section

North

Puwk Puwk Puwd

Puwg

400

300

200

100Feet

abo

ve se

a le

vel

400

300

200

100

South

Pitk

in7

1/2

Full.

7 1/

2

Mfb

500

400

300

200

100

PuwkPuwf

HbbPuwfNorth

Fullerton Section

Puwg?PpPilu?

Hua

PuwdPuwk

PuwgPil

Sim

pson

Sout

h7

1/2

Fulle

rton

7 1/

2Mfcc Mfcc

intersection withLacamp Section Mfb

Mfb

Cross-secton along crest of interfluve that forms drainage divide between the watersheds of Big Brushy Creek and Ten Mile Creek and cross-section along crest of side interfluve. Vertical exaggeration = 52x.

Stee

pG

ully

7 1/

2

Pitk

in7

1/2

Pitk

in7

1/2

Full.

7 1/

2

Mfb

Pil

Pil

Pil

SoutheastNorthwest

Figure 20. Dip sections across the Main Fort and Peason Ridge areas of the Fort Polk Military Reservation by Mr. Thomas H. Branchi. Redrawn from Branchi 1982:74.

3m10ft1312 ft

vertical

site -

scale: horizontal400m

Zone II Zone III Zone IV

3465000 n N.472500 m E.

3430000 m N.502900 m E.

3438000 m N.499750 m E.

3445500 m N.994250 m E.

3474500 m N.474500 m E.

Alluvium 2

Eagle Hill

Castor Creek memberFleming formation (Welch 1942)

fine sandy facies"high" coastwise groupCitronelle formation

Zone 1

Zone I

Colluvium 2

146.3

134.1

122

109.8

97.6

85.4

480

460

440

420

400

380

360

340

320

300

280

meters

143.3

131

118.9

106.7

94.5

82.3

70.1

57.9

45.7

Blounts Creek memberFleming formation (Welch 1942)

Lena member (Welch 1942, Paine 1968)Undifferentiated Miocene (Andersen 1960)

Lena and/or Carnahan Bayou memberFleming formation (Welch 1942)

fine sandy facies"high" coastwise groupCitronelle formation

Alluvium 2

Alluvium 2

graveliferous facies"low" coastwise groupCitronelle formation

fine sandy facies"low" coastwise groupCitronelle formation

Alluvium 2A

Alluvium 2B

Colluvium / Alluvium

feet

Elevation abovemean sea level

490

470

450

430

410

390

370

350

330

310

290

270

250

230

210

190

170

150

130

76.2 m

60.9 m60.9 m

30.5 m

15.2 m

15.2 m

7.6 m

7.6 m

30.5 m

76.2 m

PrairieStructuralSurface

95° 38'

T/R Sequence(Otvos, 1981)

Lower Structural SurfaceUpper Structural Surface

BentleyErosionalSurface

Map of a portion of the Sabine River - Red River Interfluviatile Area

Figure 22. Dip section along crest of Sabine River - Red River drainage divide and index map by Mr. Thomas H. Bianchi. Redrawn from figures 2 and 4, Bianchi, 1982:65, 67.

?

30° 11'

95° 38'30° 00'

Sabin

e Rive

r

South

North

Peason Ridge Structural Surface

Eagle Hill

Castor Creek Structural Surface

Williana Structural Surface

Mioceneclayspredominant

0.0

15.2

30.5

45.7

60.9

76.2

91.5

106.7

121.9

UpliftedPediment

?

?

?

?

Pediment Base

Documents

Geology of Fort Polk Region, Louisiana