Louisiana State UniversityLSU Digital Commons

LSU Historical Dissertations and Theses Graduate School

1975

The Geology of the Limon Area of Costa Rica.Gilbert Dunlap TaylorLouisiana State University and Agricultural & Mechanical College

Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses

This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion inLSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contactgradetd@lsu.edu.

Recommended CitationTaylor, Gilbert Dunlap, "The Geology of the Limon Area of Costa Rica." (1975). LSU Historical Dissertations and Theses. 2812.https://digitalcommons.lsu.edu/gradschool_disstheses/2812

INFORMATION TO USERS

This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted.

The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction.

1.The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity.

2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You will find a good image of the page in the adjacent frame.

3. When a map, drawing or chart, etc., was part of the material being photographed the photographer followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections with a small overlap. If necessary, sectioning is continued again — beginning below the first row and continuing on until complete.

4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation. Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced.

5. PLEASE NOTE: Some pages may have indistinct print. Filmed as received.

Xerox University Microfilms300 North Zeeb RoadAnn Arbor, Michigan 48106

75-22,228TAYUDR, Gilbert Dunlap, 1944- THE GEOLOGY OF THE LIMON AREA OF COSTA RICA.The Louisiana State University and Agriculturaland Mechanical College, Ph.D., 1975Geology

Xerox University Microfilms , Ann Arbor, M ich igan 48106

THE GEOLOGY OF THE LIMON AREA OF COSTA RICA

A Thesis

Submitted to the Graduate Faculty of the Louisiana State University and

Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of

Doctor of Philosophy

in

The Department of Geology

byGilbert Dunlap Taylor

B.A., Thiel College, 1966 M.S., University of Illinois, 1971

May, 1975

DEDICATION

The author would like to dedicate this dissertation to the

memory of Mr. Thomas J. Brazelton, formerly a Professor of Biology

and Geology at Thiel College. It was Tom Brazelton who first

interested the author in geology and who gave a good basic

background in geology to the author.

Although his basic background was in microbiology, Tom Brazelton

showed a grasp of geological principles equal to many professional

geologists. More important, he had the ability to impart this knowledge

to his students. Although he never lived to see his dream materialize,

Mr. Brazelton consistently worked toward developing a full-fledged

Department of Geology at Thiel. His dedication to geology, his

students, and his friends was nearly total and has served well as a

standard for the author throughout his academic and professional

career.

ii

ACKNOWLEDGEMENTS

The writer wishes to thank his parents for their encouragement

and help. There is no doubt that the writer's present educational

level could not have been attained without their support.

The help of Dr. W.A. van den Bold of the L.S.U. Department of

Geology is gratefully acknowledged. As supervisor of this research,

he suggested the problem, assisted during the initial reconnaissance

portion of the mapping, field checked the final results, gave

invaluable assistance on both regional and local relationships, assisted

during the paleontological analysis and critically read the manuscript.

Drs. Bob Perkins, Donald Lowe, Harold Anderson, Donald Kupfer and

Clyde Moore also criticized the manuscript and gave advice on some of

the local relationships encountered.

This research was supported by Grant F70-16 from the Organization

for Tropical Studies (OTS). The assistance of that organization is

gratefully acknowledged. Logistical problems in Central America were

reduced considerably as a result of the assistance of Mr. Jorge

Campabadal, the Resident Director in Costa Rica for OTS.

Many other persons aided in the field mapping and interpretation

phases of this research. These persons are too numerous to mention

individually. All the author can do is thank the residents of Limon,

fellow students at L.S.U. and fellow employees at Mobil Oil who helped

during the course of this work.

Finally, the author would like to acknowledge the assistance of

his wife, Betty. Her moral support, proofreading and typing ability

made the final stages of writing this report much easier.

iii

TABLE OF CONTENTS

Dedication ii

Ac knowledgement s iii

Table of Contents iv

List of Tables vi

List of Figures vii

List of Plates viii

Abstract ix

Introduction 1

Climatology and Geography h

Field Mapping Techniques 6

Summary of Central American Geology 9

Previous Work 11

Stratigraphy 12

Uscari Shale lU

Rio Banano Formation 21

Sandstone facies 22

Conglomerate facies 2h

Reef facies 25

Moin Clay Member 26'’Pueblo Nuevo Sands” 28

Relationship between Facies in the Rio Banano Formation 30

Ruretka Conglomerate 1+0

TABLE OF CONTENTS (continued)

Paleontological Data kk

Faunas Found k6

Biostratigraphy k9

Depositional Environments 53

Environmental Interpretations 55

Mollusk Faunas 59

Radiocarbon Dating 6l

Structure 63

Geologic History 66

Bibliography 81

Appendix 86

Petrographic Summaries 87

Photographic Plates 97

Geologic Map - Limon, Costa Rica Back Cover

Geographical Location Map - Limon, Costa Rica Back Cover

Sample Location Map - Limon, Costa Rica Back Cover

Faunal Distribution Charts (U) Back Cover

Vita 116

v

LIST OF TABLES

Table 1 - Summary of Grain Size Analyses from the Contact 17 between the Uscari and Rio Banano Formations

Table 2 - Petrographic Summary, Uscari Shale dj

Table 3 - Petrographic Summari, Rio Banano Formation, 88sandstone facies

Table - Petrographic Summary, Rio Banano Formation, 90conglomerate facies

Table 5 - Petrographic Summary, Rio Banano Formation, 92Moin Clay Member

Table 6 - Petrographic Summary, "Pueblo Nuevo Sands" 93

Table J - Petrographic Summary, Suretka Conglomerate 95

vi

LIST OF FIGURES

Figure 1

Figure 2

Figure 3

Figure U

Figure 5

Figure 6

Figure 7

- Index Map of Costa Rica Showing Area of Study 3

- Geologic Map - Limon, Costa Rica 13

- Geographic Location Map - Limon, Costa Rica 15

- Relationship between the sandstone and reef 31 facies of the Rio Banano Formation

- Relationship between the sandstone and reef 31 facies of the Rio Banano Formation

- Diagrammatic representation of the "thick 73 pile" hypothesis for the origin of the stratigraphic sequences found near Limon

- Diagrammatic representation of the "thin pile" hypothesis for the origin of the stratigraphic sequences fould near Limon 73

vii

LIST OF PLATES

Plate 1 - Planktonic Foraminifera from the Limon Area 98Plate 2 - Planktonic Foraminifera from the Limon Area 100

Plate 3 - Benthonic Foraminifera from the Limon Area 102

Plate U - Benthonic Foraminifera from the Limon Area 10U

Plate 5 - Benthonic Foraminifera from the Limon Area 106

Plate 6 - Mollusca and Benthonic Foraminifera from 108the Limon Area

Plate 7 - Photographs of Limon Area Outcrops: Suretka 110Conglomerate and Uscari Shale

Plate 8 - Photographs of Limon area Outcrops: Rio 112Banano Formation, sandstone and reef facies

Plate 9 - Photographs of Limon Area Outcrops: Rio liltBanano sandstone facies and ’’Pueblo Nuevo Sands"

viii

ABSTRACT

Field mapping of the Limon, Costa Rica area and laboratory analy­

sis of sediment samples taken from the area have revealed a different

geologic history from previous interpretations. Earlier workers

postulated considerable post-depositional deformation, but field

relationships found indicate that relatively little deformation has

occurred in the series of interfingering, predominantly shallow marine

clastic and carbonate (reef) sediment bodies mapped.

The oldest stratigraphic unit in the area, the Uscari Shale, with

a late Miocene to early Pliocene age, was deposited in an outer neritic

environment (300-500 m). This deep marine environment shallowed

abruptly, but apparently conformably, through the lowermost portions

of the Rio Banano Formation (new formation name) to approximately 50 m

depth, and the middle section of the formation shows a less abrupt

shallowing to 10 m. This shallowing appears to be related to the

formation of the Victoria Dome, centered to the southwest of the map

area. The middle and upper portions of the Rio Banano Formation

contain lithologies which differ from the sandstone that comprises

most of the unit. The middle portion of the formation contains a

cyclic pebble conglomerate, and the upper part includes numerous

coral reefs, which consist principally of Montastrea forms with some

Diploria, Porites , and Acropora present. The reefs vary in thickness

from 2 to over 15 meters with those reefs closer to the modern shorelinebeing thicker. Both the reef and conglomerate lithologies appear to

interfinger with marine sandstones. All three are considered to be

in facies with one another and are referred to as the sandstone,

conglomerate, and reef facies of the Rio Banano Formation.ix

Overlying and appearing to smother some of the reefs of the Rio

Banano reef facies is a well-sorted, in part brackish, coarse sand,

referred to informally as the "Pueblo Nuevo Sands." These sands form

low, often badly-leached outcrops in which no paleontologic or

stratigraphic trends can be established. The "Pueblo Nuevo Sands"

may have been formed by several agencies reworking sediments of the

Rio Banano sandstone facies, although tidal currents appear to be the

most likely agent.

Unconformably overlying the reefs and sandstones of the upper

Rio Banano Formation is a sequence of deep marine (+_100 m) siltstones

and claystones. Since these resemble the sandstone facies of the Rio

Banano Formation closely and appear to have the same source, they are

referred to as the Moin Clay Member of the Rio Banano Formation.

Planktonic foraminiferal faunas from the Moin Member show it to be of

upper Pleistocene age. The deep marine siltstones and claystones of

the Moin Clay Member are conformably overlain by shallow marine coral

reefs which are, in part, still living. The Moin Clay Member is

interpreted as being the result of deposition during an interglacial

period when sea levels were at a higher position than normal.

The youngest stratigraphic unit in the area is the Suretka

Conglomerate, a series of fluviatile sand, cobble, and boulder bodies.

The outcrop band of the Suretka includes sediments presently being

deposited by the Rio Chirripo.

Structural deformation in the mapped area is limited, with the major

structural feature being the Victoria Dome. Faults radiating from this

dome have determined the position of major streams and evidently affected

past sediment distribution in the area. The only fault block containing

coral reefs is also structurally the highest block in the area.

Adjacent fault-bounded basins appear to have acted as sediment traps,

causing the horst block to enter a sediment-starved depositional regime.

Some minor folding in the uppermost Rio Banano has also occurred, but

field evidence was not sufficient to indicate its origin.

INTRODUCTION

The southern half of Central America, including the countries

of Panama, Costa Rica, El Salvador, and Nicaragua is a very young

area primarily of volcanic origin. The map of Roberts and Irving

(1957) demonstrates the importance of volcanic rocks and the scar­city of sedimentary outcrops in the region. One of the largest

areas of sedimentary rocks in southern Central America extends

in a band 30 to 60 kilometers wide on the Caribbean coast from 50

km north of Puerto Limon south to Boca del Toro, Panama. This

sedimentary area, termed the Limon Basin by Dengo (1962), presents a smooth coast to the sea except for two comparatively large pro­

montories, one at Limon near the northern end of the basin and a

second at Puerto Viejo, approximately 90 km south of Limon. The

size and economic importance of Limon as Costa Rica's only east­

ern port has led to the construction of a good road net creating

relatively easy access to the adjacent outlying areas. This

ease of communication makes the northern promontory a suitable

area for a detailed stratigraphic study.

Previous petroleum exploration carried out by the Union Oil

Company of California in the Limon area mapped the general geology

of a 600 square km area inland from the Limon peninsula. Detailed

stratigraphic analyses, however, were impractical in reconnaissance.

This study showed the Victoria Dome to be the dominant structural

feature in the area. The many lithologic contacts on the Limon

promontory were interpreted as structural contacts and a consider­

able amount of post-depositional deformation was invoked in the

CARIBBEAN SEA

COSTARICA

Limon

r~».

Index Map of Costa Rica

Showing Area of Study

Union Oil geologist's interpretation of the geologic history of

the area.

These interpretations were at variance with data from samples

collected by W.A. van den Bold. The author has attempted to re­

concile these differences by undertaking a detailed stratigra­

phic study of sedimentation in the northern portion of the Limon

Basin. The present project covers an area of about 100 km^ in­

cluding the Limon promontory and the more easily accessible areas

to the west and south of Limon.

Climatology and Geography

Limon is situated on the Caribbean coast of Costa Rica within

ten degrees of the Equator and experiences a high rainfall of be­

tween 2000 and 5000 mm per year. This high rainfall and low mean

annual evaporation of 800 to 1000 mm per year creates a large surface runoff as well as a high water table. The average temper­

ature of the region varies little with the season with a summer

mean temperature of 75 to 85 degrees F. and a winter mean of 70 to

80 degrees F. Weather patterns of the area are under the year-

round influence of the moisture-laden northeast trade winds from

the Caribbean. This climate supports a lush tropical rain forest

although much of the growth around Limon is secondary. The origi­

nal tree cover was removed to make room for agriculture, usually

banana and cocoa plantations. Following the abandonment of these

plantations, natural growth of herbaceous plants turned much of

this formerly cultivated area into a tangle of undergrowth. The

climate is also responsible for the extensive development of lat-

erite soils. Deep and rapid weathering has destroyed most of the

rock outcrops and the only geologically usable outcrops are in the

valleys of streams with a velocity sufficient to erode rapidly.

The Limon area is a part of the low Caribbean coastal plain.

The inland portions of the map area reach elevations as high as

100 m but most of the area is less than 50 m above sea level.

Communications are well developed by Central American stand­

ards with several gravel roads providing all-weather access to out­

lying areas (See Figure 2). One of these roads connects Limon to

La Bomba and has a parallel road from Pueblo Nuevo to near La Bomba.

The other major road goes from Limon to San Jose and provides access

to the western portion of the coast of the Limon peninsula as well

as inland areas to the west of Limon. The Northern Railroad,

which has its main line across the base of the promontory, pro­

vides access to the inland areas between Limon and Moin.

Field Mapping Techniques

Most of the field mapping for this project was carried out

during June, July and August of 1970. Subsequent laboratory

analyses and discussions with various people indicated the presence

of certain problem areas. These were re-examined in more detail

in February of 1971 and January of 1972. In addition, during this

last trip, the type section for the Gatun Formation in the Panama

Canal Zone was examined.

The paucity of outcrops and difficulty of communications makes

geologic mapping in any tropical country difficult, Costa Rica not

excepted. The climate causes very deep and rapid weathering; fresh

outcrops can be destroyed in a matter of a few months. Location of

outcrops from air photos, although attempted, was thwarted by the

dense brush which covers most of the area. Usable outcrops can be

found only in the stream beds, where erosion and mass wasting

periodically form fresh outcrops, or in man-made exposures in road and

railroad cuts.

Although man-made exposures are quite important in some portions

of the area mapped, the poor economic condition of this area of

Costa Rica has prevented development of an extensive road network.

Roads are of very limited extent and only one railroad line pene­

trates the area. The condition of all roads, except those within

one km of Limon, is such that a four-wheel drive is the only re­

liable means of transportation. For this purpose, a Toyota Land

Cruiser was rented in San Jose. Even these roads are often washed

out or made impassible by periodic floods. At the time of my

first arrival in the area, the Limon-San Jose road had been washed

out in the Rio Reventazon area, forcing me to transport the field

vehicle hy rail. High water also prevented the author from cross­

ing the Rio Banano except by foot during the entire first mapping

period (which was three months long). This severely limited the

extent to which the south bank of that river could be mapped.

As a result of the problems in locating and using man-made

outcrops, much of the area was mapped from natural exposures found

by wading streams. Some areas were still inaccessible even by this

method. The area to the east of Nueva Castle and La Bomba, for ex­

ample, was blocked by quicksand in the river bed. In those areas

the geology was inferred from nearby data. A different pattern is

used to indicate this on the geologic map.

The base map for this study was the 1:50,000 topographic map

of the Limon area published by the Geographical Institute of Costa

Rica. Additional detail concerning the stream courses found was

obtained through the use of a modified pace-and-compass method.

Major changes in direction were measured with a Brunton compass;

distances were determined by the use of a 50 m. rope knotted at

measured intervals. This method of mapping the streams was made

necessary by the heavy brush, which forms a canopy over all but the

largest streams, obscuring them from the aerial camera. Sample

location, strike and dip information, and outcrop sketches were

noted on these maps. Whenever possible, the accuracy of these

stream maps was checked by reference to prominent landmarks, aerial

photographs, and the topographic base map.

Local variations in outcrop character obviously creates

considerable variation in the quality of the data which can be ob-

tained from these outcrops. In many cases, outcrop character was

such that only the stratigraphic unit present could be determined

with the outcrops being weathered and leached to an extent that

precluded taking a meaningful sample or measuring attitude.

In spite of all these problems outlined above, the extensive

stream system present permitted sufficient access and data to allow

a fairly detailed geologic map of the 100 square kilometer area to

be drawn.

9

Summary of Central American Geology

Most authors divide Central America into two orogens. The

northern orogen, comprising Mexico, Guatemala, Honduras, and north­

ern Nicaragua, is considerably older, having a Paleozoic and Pre-

eambrian basement. The southern orogen, comprising southern Nicara­

gua, Costa Rica, and western Panama, is much younger with a Cre­

taceous and possibly Jurassic basement.

There have been numerous attempts to explain the origin of

Central America and the Caribbean region. These range from Lloyd's

(1963) suggestion of a series of island archipelagos building up the Central American isthmus to Malfaid and Dinkleman's discussion

(19T2) of the origin of the Caribbean Plate based on the "New Global

Tectonics” of Molnar and Sykes(l966). Although the author is not

in complete accord with their sequence of events with time, the model

by Dinkleman (1972) seems to agree best with the known geological

and geophysical features of the region.

Tertiary volcanism on the Pacific coast and in the Cordillera

de Talamanca in the interior, along with interior uplifts, provided

spurce areas for sediments subsequently deposited in the Limon

Basin. These sediments have been studied by a number of authors.

The basic stratigraphy of the Panama Canal Zone has been described

by Woodring (1957). Recent refinement of the stratigraphy in this

area by Blacut and Kleinpell (1968) and Bold (1971) has clarified the stratigraphic position of the La Boca Formation. According to

these authors, the La Boca was deposited during the middle early

Miocene (zones N.6 and N.7 of Blow, 1967) in a relatively deep

marine environment. Unconformably overlying the lower Miocene is

10

the Gatun Formation, deposited in a shallow marine environment

during the upper Miocene (Bold, 1971).

The sediments in the southern portion of the Limon Basin in

the Rio Sixaola area of southern Costa Rica were described by

Redfield (1923). He reported a deep marine unit, the Uscari

Shale, which he considered to be of early Miocene age, to be un-

conformably overlain by a shallow marine sequence which he re­

ferred to the Gatun Formation. Samples from the type area of the

Uscari Shale collected by W.A. van den Bold show a planktonic

foraminiferal assemblage of late early to early middle Miocene age

(zones N.8-R.10 of Blow, 19&7)

A third area with a similar stratigraphic sequence has been

described by Bold (1967) and Rivier (1971) in the Rio Reventazon

area of north-central Costa Rica. Both authors show a relatively

deep marine, lower to middle Miocene Uscari Shale unconformably

overlain by shallow marine Gatun. Rivier's data (1971) show same

unusual associations of planktonic foraminifera, and there is seme

evidence to suggest that some of his specific identifications may

be incorrect, especially in the Globorotalia archaeomenardii-G.

praemenardii-G. menardii group. Bold (1967) ascribes an early middle Miocene age to the upper Uscari (zones N.9 and N.10 of Blow,

1967).

Different stratigraphic relationships from those described above

are shown in the Limon area. There, an upper Miocene (N.l8) deep

water sequence grades gradually upward into a shallow marine sequence

with no evidence of an intervening unconformity. The evidence for

this will be discussed below.

Previous Work

Previous geological work in the Limon area has been limited.

Gabb (l88l) was the first to publish descriptions of fossils, hut

he also described some stratigraphy, naming the Moin Formation.

Olsson (1922), also a mollusk specialist, did a considerable amount

of stratigraphic work, introducing the Uscari Shale as a formal

name and extending the Gatun Formation into Costa Rica. Woodring

(1957) also worked in the Limon area, describing some stratigraphic

relationships and refining some of Olsson's (1922) correlations.

Mapping by the Union Oil Company of California was carried out

from 1953 to 1962, but the results, except for a brief examination

of the geologic map, were not available to the author. Union Oil

also drilled two test wells around Limon, but the samples were not

available for examination.

STRATIGRAPHY

Stratigraphic nomenclature in Costa Rica is quite confused,

as can be learned from a perusal of Hoffstetter (i960). Many of

the early workers either described type localities so vaguely that

they cannot be found today or the outcrops are now badly weathered.

In addition to this problem, some formations were given more than

one name. This was often due to lack of knowledge of the early

literature by later workers, which in turn was caused by the pub­

lishing of early efforts in little-known publications or journals

of limited distribution which quickly became unavailable (Gabb,

l88l, for example). Another problem in nomenclature crops up with

spelling differences from author to author. This has caused apparent

stratigraphic differences between areas where no true difference

exists. Thus, the Moin Formation of Gabb (l88l) has also been

termed the Moen (Gabb, 1885), Limon(Moen) (Hill, 1898), Limon (Dali and Hill, 1898), and Port Limon (Rathburn, 1918). See also

the uncertainty of the stratigraphic position of the Sheroli

(Xirores) Formation of Redfield (1923), referred to in the discus­

sion of the Rio Banano Formation. These problems must be resolved

before the actual stratigraphic work can be satisfactorily pre­

sented.

Incorporated in the appendix of this report is a considerable

body of sedimentological data. This information has been included

with this report so that future workers will have these data should

they wish to do a sedimentological analysis. Since a detailed

sedimentological analysis was beyond the scope of the original

research proposal, these data have not been used extensively in the

12

GEOLOGIC MAPLIMON, COSTA RICA1 0 1 2 i 1— atn— 1

14preparation of this report.

Rocks in the Limon area have been divided into three main formations: the Uscari Shale of upper Miocene age; the Rio Banano

Formation (described and named here) of upper Miocene through

Pleistocene age; and the Suretka Conglomerate of probable Pleistocene

age. The term "Rio Banano Formation" is used here to replace the

name "Gatun Formation" of Olsson (1922).

Uscari Shale

The oldest stratigraphic unit in the map area is the Uscari

Shale. There is some discussion as to who formally named the unit

with many authors citing Vaughan (1924) as the original reference.

The Lexique Stratigraphique states, however, that the name "Uscari"

was originally an informal name used by field geologists and later

formalized by Olsson (1922). Berry (1921) used the term but only

in an informal sense.

Type area

The name for the Uscari Shale is derived from Quebrada Uscari

(Uscari Creek) which provides the exposures for the type locality

in the Rio Amoura (Amoura River) area of southeastern Costa Rica.

Uscari outcrops in this area were originally described by Olsson

(1922) as consisting of "soft, dark-colored shales which, because

of their slight resistance to denudation, frequently forms (sic)

wide valleys and interior basins."

In contrast to Olsson's description, the Limon Uscari Formation

outcrops form some of the most rugged topography in the map area.

In view of its soft lithology, this topographic expression probably

reflects a relatively recent uplift.

, r?- a»ir n M m l m i u m m **< /

The Limon Uscari Formation would be best described as a silty

clay-shale. It is rather poorly indurated in outcrop and is easily

broken with the fingers. Its color is a greenish gray (5GY6/1 in

the Munsell System of color classification) in fresh outcrop,

weathering to a yellowish gray (5Y8/I) with dusky yellow (5Y6/U) spots. Weathered outcrops are quite platy in contrast to the

relatively non-fissle exposures of fresh Uscari. The only

sedimentary structures visible in outcrop or hand specimens are

fine, parallel laminations which thin section analysis shows is due

to the parallel alignment of platy clay particles and mica flakes.

These laminae are deformed around larger grains in the rock (silt­

sized quartz fragments and planktonic foraminifera). Planktonic

foraminifera characterize this formation, with the prolific

fauna sometimes being visible to the naked eye. Thin section

analysis shows this rock to be fine-grained and comprised princi­

pally of clay minerals, most notably mixed-layer montmorillonite

(determined by X-ray diffraction).

Contacts

The lower contact of the Uscari Formation lies outside the

map area and was not observed during the present study. The upper

contact, according to Olsson (1922), is formed by an unconformity

between the Uscari Formation and the overlying "Gatun" Formation

(here renamed the Rio Banano Formation) with a basal conglomerate

developed in the "Gatun". No evidence for this unconformity was

found in the Limon area.

A detailed study was made of an exposure approximately 2l*0m

17

long on the northwestern side of the Rio Banano across the area

containing the contact between the Uscari and Rio Banano Formations.

Shale of Uscari lithology was found at the southwestern end of this

area and sandstone similar to that found in the type locality of the

Rio Banano sandstone facies at the northeastern end. No structural

unconformity was found and the bedding planes observed were essentially

parallel throughout the exposure. There was no evidence of a

conglomerate layer. Grain size analyses of samples taken every

thirty meters across this area show am irregular change in grain

size with a net increase upward in the section toward the Rio Banano

Formation (to the northeast). The grain size data (estimated from

thin section) are summarized in Table 1 below. Also included is

grain size analysis of a sample taken well into an area of Rio

Banano sandstone facies lithology (sample llU7).Table 1 - Summary of Grain Size Analyses from the Contact Area

between the Uscari and Rio Banano Formations

Sample Distance Average Total Range of GriLocation from Uscari Grain SizesNumber (Loc. 1150) Size Minimum Maximum

(m) (u) (u) (u)

1150 0 10 clay *2001151 60 U0 clay 1001152 90 60 clay 2501153 120 ho clay 150115^ 150 60 clay 2501155 180 30 clay 15011U8 2U0 120 clay 1*00IIJ47 1100 250 clay 700

%aximum grain size excludes fossil grains since the other samples involved were non-fossiliferous

This analysis serves to show that, although samples of Uscari

and Rio Banano sandstone facies lithology are present at opposite ends

18of the sampled section, there is no real trend within samples taken

between the end members. This relationship suggests that the Uscari-

Rio Banano Formational contact in the Limon area, instead of being

an abrupt, unconformable contact, is rather a conformable, generally

gradational contact with intertonguing layers of clay, silt and sand.

The contact was mapped between samples 1155 and llU8 on the basis of the abrupt increase in grain size noted (See Table l) at this point

(both in the grain size analyses and in the field).

Although most of the samples taken in the contact area were not

fossiliferous, faunal comparisons of samples llU8 and 1150 show a definite shallowing of the depositional environment of the younger

sample. The evidence for this environmental change will be discussed

in the section on Paleontology.

It may be that the conglomerate layer found near Nueva Castle

(approximately 1+ km northeast of the Uscari-Rio Banano Formation

contact as mapped in this study along the Rio Banano) is the "Gatun"

basal conglomerate referred to be Olsson (1922). The present author

did not consider the base of this conglomerate to mark the upper

contact of the Uscari Formation because of a total lack of change in

either lithology or environment of deposition from one side of the

conglomerate to the other.

Source and Environment of Deposition

The volcanic nature of the most probable source area for the

Uscari sediments is emphasized by the montmorillonitic clay which

comprises such a large percentage of this sediment. The absence

19

of all tut the most stable minerals suggests either long transport

distances, a warm climate or, most probably the case here, both. The

fine-grained nature of the sediment is indicative of deposition in

a quiet area. Paleontological evidence, to be discussed in detail

below, indicates that deposition of the Uscari Shale took place in

1+00 to 600 m of water in an outer neritic or upper continental slope environment.

Age

Paleontological evidence also shows the Limon Uscari to be

of a different age than that determined for the type section of the

formation in southeastern Costa Rica by both Olsson (1922) and the

present author. The Limon Uscari Formation contains a planktonic

foraminiferal assemblage characteristic of late Miocene time (zone

N.l8 of Blow, 196?) while the type Uscari samples show an early middle Miocene age (zones N.8-N.10).

This might suggest that the Uscari from the type area and the

Limon Uscari are not actually related and that the Limon Uscari

should be renamed. This has not been done, however, since the

sampling program carried out in the Limon Uscari was not sufficient

to permit conclusions as to the regional relationships involved.

The present study was oriented toward the younger outcrops of the

Limon peninsula, so only the Uscari outcrops in the vicinity of

the contact with the Rio Banano Formation were sampled. It is

entirely possible that the older portions of the Limon Uscari are

the same age as the type Uscari and that the upper portions of the

Uscari have been removed from the type area. These regional

20

reconstructions must await a more detailed sampling program in the

Limon Uscari outcrops.

21

Rio Banano Formation

Introduction

Most of the mapped area shows outcrops of sandstone and

coralline limestone described by Olsson (1922) as the Gatun Formation.

He states that the Costa Rican Gatun Formation "is equivalent in

part to the Gatun Formation of the Canal Zone....In Costa Rica, the

Gatun is very much thicker and represented a longer depositional

period." He further states that "the Gatun of the Canal Zone seems

to represent only the lower part of the formation as developed in

Costa Rica." On the basis of the molluscan faunas present, Olsson

assigned a middle to late Miocene age to the Canal Zone Gatun

Formation and the Costa Rican Gatun. No foraminiferal age or

environmental data are available on the Panamanian Gatun since samples

taken by the author from the type area for the Canal Zone Gatun were

non-fossiliferous.

Terry (1956) shows the Panamanian Gatun to be of middle Miocene

age with unconformities forming both contacts. The overlying Chagres

Formation, consisting of the Chagres Sandstone and Toro Limestone

Members, is shown to be early Pliocene in age.

Planktonic foraminiferal faunas from samples of the "Gatun"

of the Limon area taken for this study show that these sediments are

of late Miocene (N.l8) to Recent age with the bulk of the strati- graphic unit being of Pliocene and Pleistocene age.

Since there is an age disparity between the oldest "Gatun" in

the Limon area and the youngest Panamanian Gatun, the term Gatun should

not be used in the Limon area since that would imply a lateral

22

continuity, postulated by Olsson (1922) that apparently does not

exist. To avoid the implication that there is stratigraphic

continuity between the Limon area and the Panama Canal Zone, the

term Rio Banano Formation is proposed for the Limon "Gatun" of

Olsson (1922).

Redfield (1923) described a unit he referred to as the Sheroli

(also Xirores) Formation which he equated with the littoral facies

of the Gatun of Olsson (1922). His description of the Sheroli as a

"massive to distinctly-bedded, dark gray to dark-bluish argillite...

which are (sic), for the most part, clayey and fine-grained" suggests

that this may be part of the Uscari Formation rather than Olsson's

Gatun (1922). The clayey lithology of Redfield's Sheroli (1923) is

quite different from the sandstone lithology emphasized by Olsson

(1922) for the Gatun. The position of the type area for the Sheroli

Formation within one minute of latitude and 17 minutes of longitude

also partially supports the lithologic indications that the Sheroli

may actually be an Uscari equivalent.

General Description and Type Locality

The Rio Banano Formation is a series of intertonguing shallow

marine clastic and coral reef facies. The formation can be divided

lithologically into four facies: a sandstone facies, a conglomerate

, facies, a coral reef facies, and a clay facies.

Lithologic (Field) Descriptions

Sandstone Facies

The sandstone facies forms the greatest part of the Rio Banano

23

Formation and is typical of its lithology. The facies consists of a

greenish, poorly indurated sandstone which is best exposed in bluffs

along the cut bank of the Rio Banano at and above La Bomba. The

exposure on the north bank of the Rio Banano, TOO m east south east

of the railroad bridge at La Bomba is here designated as the type

locality for the Rio Banano Formation. This location has the

advantage of being on the cut bank of the river, which will constantly

provide fresh exposures. This type area is found on the Rio Banano

1:50,000 topographic map, edition 1-IGCR (sheet 35^5-1) at 9°55'N,

83°0U»W.

The sandstone facies of the Rio Banano Formation would be best

described as a muddy, fine-grained sandstone. Most outcrops are

poorly indurated although there is some local cementation by calcite.

Fresh outcrops of this facies show a medium greenish gray (505/1)

color which weathers to a medium grayish orange (10YR6/U). Although

rarely preserved in hand specimens, sedimentary structures are commonly

well-developed, especially in the younger portions of the facies.

None of the outcrops examined showed any fine sedimentary structures,

although larger-scale structures, especially in coarser sediments,

were common. Smaller sedimentary structures, such as laminae, appear

to have been destroyed by bioturbation. This bioturbation is further

evidenced by well-developed lebensspuren, found in some areas, which

closely resemble the "digitating feeding tubes" of Warme (1971, p.38). The coarser sand layers show moderate-angle (20-30 degrees) cross­

bedding on scales ranging from 3-5 cm. to as much as 20 cm. One

coarse sand layer in the banks of Q. Chocolate shows well-developed

moderate-angle (25°) cross beds interrupted by symmetrical ripple

2h

marks. Other outcrops in the Q. Chocolate area (in the upper part

of the Rio Banano Formation) shov what could be referred to as

festoon cross beds on a scale of about one meter and parallel to the

front of a small reef. Features which probably represent primary

inclined bedding were observed in a backreef position where sediments

of the Rio Banano sandstone facies appeared to have been draped

over a carbonate reef rubble sequence.

Conglomerate Facies

The conglomerate facies of the Rio Banano Formation occurs

within the sandstone facies of the formation in the Nueva Castle area.

This facies is best exposed in outcrops 500 m northwest of Nueva

Castle (Rio Banano topographic map) at 9°56'N, 83°0Vw where they

form a series of resistant, low outcrops in the stream beds. .

This facies is poorly indurated, although the coarser portions

are more resistant to erosion, forming ridges in the stream beds.

Its color is nearly the same as that of the Rio Banano sandstone facies-

a medium greenish gray (5G5/1) in fresh outcrop, weathering to a

medium grayish orange (10YR6/1). The entire facies shows repetitive

graded bedding with a basal pebble conglomerate developed in a

medium to coarse sand matrix. This repetition is not apparent in hand

specimens since the repetition is on a scale varying from one to as

much as twenty meters. The basal conglomerate contains pebbles up

to cm in diameter in a matrix with an estimated mean grain size of

0.50 mm (medium sand). This matrix gradually fines upward to a

sandstone with an estimated mean grain size of 0.25 mm immediately beneath the base of the next conglomerate layer. Each pebble bed

25

shows some scour at its base as well as small scale (2-5 cm) cross­bedding in the finer sands above the conglomerates. Overall,

sorting is poor with the conglomerates appearing the beat sorted.

Reef Facies

The reef facies of the Rio Banano Formation is best developed

in the upper part of the formation, although coral occurs sporadi­

cally throughout the Rio Banano sequence. The best exposures of

the reef facies, as well as the reef facies-sandstone facies contacts,

are in a 1500 meter-long series of outcrops in Q. Chocolate 2200 m

southeast of the railroad station at Sandoval (see the Rio Banano

topographic map referred to above).

The reef facies is best developed in the upper portion of the

Rio Banano Formation. Corals in the older portions of the formation

are commonly solitary species with the lowest appearance of reef-

forming species being in the upper third of the formation. These

initial reefs are relatively thin (2-3 m thick) but the thickness of individual reefs progressively increases toward the top of the

formation with the youngest exposed reef having a cave system

approximately 15 m in height developed in it, indicating a reef thickness of at least that magnitude.

All of these reefs are composed of hermatypic corals identified

in the field by the author as belonging to the modern genera

Montastrea, Acropora, Porites and Diploria with most of the forms

being Montastrea species. In many places, these reefs have been

extensively recrystallized by ground water. In most cases, however,

26

there is still sufficient evidence to demonstrate a coralline origin

for these reefs.

Moin Clay Member

The unit referred to above lithologically as the clay facies of

the Rio Banano Formation will be referred to formally here as the

Moin Clay Member of the Rio Banano Formation. This unit forms a flat

plateau immediately to the west of Limon. These sediments outcrop

over the entire six kilometer length to the plateau and are exposed

in low shoreline outcrops near Portete and Piuta.

Gabb (l88l) described rich mollusk faunas from outcrops of clay between Moin and Limon which he called the Moin (also Moen) clay beds.

In his manuscript of I87U (published in 1895), he employed the Moin Formation as a formal name for the first time without, however,

precisely indicating a type locality. Hill (1898) refers to what are these same beds as the Pliocene Limon Formation (Limon [Moen] beds).

Woodring (1928, p. 27) calls the mollusk faunas from this sediment body the only large Pliocene fauna described from the

Caribbean. This may be taken as an indication of its very young age

since Woodring assigns a Miocene age to such strata as the Bowden Beds

of Jamaica which, according to all planktonic foraminifera workers,

belong in the Pliocene.

The clay and sand unit referred to by Gabb (l88l) between Limon and Moin is recognized here as the Moin Clay Member of the Rio Banano

Formation. The Moin Formation of Gabb (l88l) is reduced to member status within the Rio Ranano Formation because of its lithologic and

mineralogic similarities to the Rio Banano sandstone facies. X-ray

27

diffraction analysis shows the clay mineralogy of the two sediment

bodies to be nearly identical; both are also nearly the same color

in both fresh and weathered outcrops. Grain size analysis of the

Moin Clay Member shows a coarsening to the southeast with the coarser

samples being very similar to finer-grained samples from the Rio

Banano sandstone facies. These two sediment bodies appear to be

closely related, suggesting that the Moin Clay Member is a deep water

representative of the sandstone facies of the Rio Banano Formation.

The Moin Clay Member, however, is a distinct sediment body that is

easily recognizable in the field.

As was mentioned above, Gabb (l88l) did not specify a type locality for his Moin Formation, specifying only that these sediments

were to be found between Limon and Moin. A type locality for the

Moin Clay Member of the Rio Banano Formation is here designated as

the series of outcrops to be found in the bed of an unnamed stream

800 m east of Portete at 10°01'N, 83°03'30"W. This stream exposes

approximately 2.5 km of this member and shows the grain size gradation noted below (see samples 1001-1018).

The Moin Clay Member of the Rio Banano Formation is a more

highly variable body of sediment which, in general, shows a finer

grain size and different depositional environment than the sandstone

facies. Lithologic changes, distributed over at least five meters

in the underlying sandstone facies, take place in one or two meters

in the Moin Member.

This member is soft and easily eroded. Its color in fresh

outcrop is a greenish gray (5GY6/1), showing a chroma and hue

28

difference of only one division from fresh Rio Banano sandstone

facies. Its weathered color, a moderate brown (5YR1+A) is also quite

close to that found in weathered exposures in the older portions of

the Rio Banano Formation. No sedimentary structures were observed,

possibly having been destroyed by burrowing organisms. The Moin

Member contains occasional local horizons with good mollusk faunas and

an overall strong microfauna.

Grain size in this facies seems to show an irregular, but

consistent increase to the southeast. This relationship was first

noted in the field and later confirmed by thin section and sieve

analysis of samples taken through the middle of the outcrop area of

this member. Those samples farthest to the northwest (nearest to the

present shoreline) are nearly pure clay while samples taken further

inland toward the southeast are coarser. This grain size trend is

probably indicative of a southerly or southeasterly source for this

sediment body with the finer-grained portions being the farthest from

shore at the time of its deposition.

"Pueblo Nuevo Sands"

A series of well-sorted sandstone bodies was also discovered

behind and capping the thicker reefs of the Rio Banano reef facies.

This series of sand bodies could possibly be considered to be a

member or a facies of the Rio Banano Formation. It is almost certain,

however, that the well-sorted sands are derived from older Rio

Banano sandstone facies outcrops and should, therefore, be named

separately. These sand bodies are of very limited extent and many of

the present outcrops are being destroyed for road and building material.

29

To avoid burdening the stratigraphic literature with yet another name

usable at only one locality, it was decided not to give a formal name

to these sediments. As these sands are best exposed near Pueblo

Nuevo, they will be referred to hereafter as the "Pueblo Nuevo Sands"

with the understanding that this is not meant to be a formal

stratigraphic name.

In outcrop, these sands are quite friable and easily crumbled.

These "Pueblo Nuevo Sands” were not observed in fresh outcrop; weathered

outcrops show a moderate yellowish brown color (10YR5/^). The

outcrop character of these sands generally prevented the observation

of sedimentary structures since these non-resistant sands generally

form low, often badly-weathered outcrops. Two exposures, however,

did show moderate angle (about 25°) cross-bedding up to five cm in

height.

In the field, this sand has the appearance of being quite coarse

and porous. Sieve analysis supported this idea, with most of the

sediment falling into the sand category (see Appendix). Thin section

analysis added the extra information that porosity is quite high.

This high porosity evidently leads to high permeability since fossil

remains are rapidly leached by ground water. Outcrops of these sands

which were fossiliferous in 1968 (van den Bold, personal communication), were totally barren when sampled in 1970 by the author. Fresher

outcrops commonly show leaching of the fossil fauna consisting of

mollusks, foraminifera and/or ostracods. Extensive ground water

circulation is also probably the source of the hematite cement noted

in the thin section analysis of the "Pueblo Nuevo Sands." No hematite

30

cement or fossil leaching were noted in the more poorly sorted and

less permeable Rio Banano sandstone facies.

Relationships between Facies in the Rio Banano Fonnation

The sandstone and conglomerate facies of the Rio Banano Formation

seem to be conformable with one another. Although poor outcrop

quality prevented a detailed examination of the contact, the Rio

Banano sandstone facies appears to grade, albeit rapidly, into the

coarser conglomerate facies. In a similar manner, the conglomerate

facies appears to grade upward into typical Rio Banano sandstone

facies lithology. No other facies of the Rio Banano Formation is

in contact with the conglomerate facies.

The sandstone and reef facies of the Rio Banano Formation

interfinger laterally and succeed one another vertically. This

relationship is best shown in exposures in the Q. Chocolate valley,

two of which are shown in Figs. b and 5- The reef rubble shown in

Fig. b can be traced laterally into a thin reef. Fig. 5 is a drawing

of an outcrop approximately one kilometer north of the exposure shown

in Fig. b and shows an interstratified sequence of coral reef, reef

rubble, and greenish sand of the Rio Banano sandstone facies. In all

cases, the base of the reef material is relatively flat but the upper

surface is irregular with reef pinnacles extending into the overlying

sand. The lowermost sand layer in this figure contains a thin

horizon of coral fragments, most of which are identifiable as Porites,

with a few pieces possibly referrible to Acropora cervicornis.

2n1057

OJr0

RIO v:l B A N A N O SAN D- FA CIES

1--------------T1 2Sea le: M e t e r s

p e b b l e l a V •

F i g u r e 4

1023

#1054

RIO B A NA N O SAN D FAC I IS

■i .!lO-i,.l'x..L‘gCOlRAL^EF Ffe

^ \ ° 5 3 '

%• W *micoral/.traqmin't lQ 5 i;# .^

W&SSSSBSA

A

32-1-

0-*I---1--- 1---- 1-- I0 1 2 3 4

S c a l e : M e t e r s F i g u r e 5

32

Several samples taken from the exposure shown in Fig. 5

contained chunks of lignitic wood fragments. Attempts to date these

fragments in the LSU Radiocarbon Laboratory were unsuccessful as the

samples showed a radioactivity level which did not differ significantly

from the background count. All that can be said about the age of

these samples and the sediments from which they came is that they

are at least 3 X 10^ years old and probably much older.

The relationship between the sandstone and reef facies of the

Rio Banano Formation is also well demonstrated in a series of

outcrops found immediately behind the Standard Fruit Company box

factory between Pueblo Nuevo and Limon, 2.5 km WSW of Limon. Here,

bulldozing has uncovered a thick reef underlain by a broad expanse

of Rio Banano sandstone with an excellent fauna of marine mollusks.

Stream exposures beneath this reef show a number of smaller reefs

less than one meter thick scattered throughout the Rio Banano

sandstone. These reefs are accompanied by an increase in the numbers

of solitary corals in the sandstone. As the main (largest) reef is

approached from below, the size and number of these solitary corals

increases as does the amount of non-coralline calcareous material,

possibly indicating a physical or chemical environment which became

increasingly more favorable for the formation of calcareous shells

or colonies.

The Moin Clay Member of the Rio Banano Formation lies with an

angular relationship on the coral reef trends and sandstone

intercalations of the upper Rio Banano Formation. Paleontologic

evidence, to be discussed in detail below, indicates that a hiatus,

33

if present at all, is negligible. The sediments of the Moin Clay

Member are thin enough to permit the reef trends of the upper Rio

Banano,to be visible as ridges on air photographs. Field evidence

suggests that the Moin Member was draped over these reefs, with the

primary depositional inclination appearing to reflect folds in the

Moin Member. This will be discussed in more detail in the Structure

section.

The upper contact of the Moin Member is conformable with overlying

Recent (in part, living) coral. Although the contact between the

two lithologies is abrupt, there is an increase in the number of

solitary coral species immediately below the contact, suggesting a

gradual change to an environment more favorable to coral growth.

The contacts of the "Pueblo Nuevo Sands" with the underlying

Rio Banano Formation facies are somewhat problematical as, in

most outcrops, the contact is not visible. In the few outcrops

which do show a contact, weathering has often destroyed many details.

In some cases, however, reef pinnacles, which do not appear to be

the result of leaching (karst topography on the reef) but rather a

localized growth increase, can be seen protruding into the overlying

"Pueblo Nuevo Sands." Growth lines in those parts of the reef are

dome-shaped rather than roughly horizontal, giving the pinnacle the

appearance of having been buried. There is no evidence of any

transition between the coral reef facies and the "Pueblo Nuevo Sands."

Where no reef is present (for example, to the south of the reef

at the box factory outcrop referred to above), "Pueblo Nuevo Sand"

lies directly on the (marine) Rio Banano sandstone, again with no

evidence, either paleontologic or sedimentologic, of any transition.

The lower contact, where it is visible, is rough and uneven and

probable is unconformable. No sediments were observed to overlie

the "Pueblo Nuevo Sands."

The relationship between the "Pueblo Nuevo Sands" and the Moin

Member of the Rio Banano Formation is unknown in spite of the fact

that both appear to unconformably overlie the reefs of the Rio

Banano reef facies. Paleontologic evidence shows a wide difference

in depositional environment; quite shallow for the "Pueblo Nuevo

Sands" and rather deep for the Moin Member (see Paleontology section

for more details). The Moin Member is younger than the bulk of the

"Pueblo Nuevo Sands" so it is possible that the Moin Member overlies

"Pueblo Nuevo" deposits. No evidence was seen for this in the field,

however.

Environmental Interpretations

As might be expected from the wide variations in lithology

within the Rio Banano Formation, these sediments were deposited

under varying conditions. The source of these sediments appears

to remain as the volcanic highlands to the west of the map area.

Direct evidence for this comes from the volcanic pebbles found in

the conglomerate facies as well as the calcic feldspars and

pyroxenes found in both the conglomerate and sandstone facies

(see data in Appendix). The high montmorillonite percentages

found in all three clastic units of the Rio Banano Formation are

also indicative of a volcanic source. Folk (1968) states that montmorillonite is typically formed "in a Mg-rich environment,

most of it by alteration of volcanic ash....Marine diagenesis has

little effect on volcanic montmorillonite, except to change ad­

sorbed cations."

Sedimentary outcrops are also present in the source area as

evidenced by the sandstone pebbles found in the conglomerate facies.

The illite component of the clay fraction,found in all three

clastic units is also somewhat indicative of reworked sedimentary

rocks. Folk (1968) states that "much illite is derived from older illitic. shales..." Some of the original illite may have been de­

graded (stripped of its K* ions) during weathering and became mont­

morillonite when it entered sea water and regained much of its

original KT*" content. The textural inversion noted in the conglom­

erate facies with quartz grains being better rounded than the less

stable feldspar grains suggests sedimentary outcrops in the source

area shedding second or third generation quartz grains into the

36

Limon Basin.

Considerable information is available concerning the deposi­

tional environment of these sediments. Paleontological data from

the Bio Banano sandstone facies, to be covered in detail below,

indicate that that facies was deposited, for the most part, in a

shallow marine environment. The wide range in lithology that was

noted in the field and borne out by the grain size analysis (see

Appendix) indicates that conditions were quite variable over the

depositional basin. Locally strong currents created the festoon

cross beds and ripple marks noted in this facies. The limited

extent of these sedimentary structures indicates that the currents

were not persistent for any significant period of time. Further

indications of a shallow environment for the sandstone facies comes

from the extensive bioturbation noted in the sediment. Although

this process is by no means limited to shallow water sediments, it

is more common in sediments deposited in that environment (Visher,

1972; Warme, 1971).The pebbles of the conglomerate facies of the Rio Banano

Formation are indicative, most probably, of either hard shoreline

outcrops being reworked by cyclic storm action or of normal stream

deposition. Other hypotheses are possible, however, such as cyclic

tidal channel deposits or a migrating sand-gravel bar. The repeti­

tive nature of this facies with a basal conglomerate and scour

followed by upward fining would most favor the stream hypothesis.

This would be a normal sedimentary process with the conglomerate

layer being the result of flooding. It is also possible that these

pebble layers resulted from cyclic storm erosion of lithified

beach deposits. This interpretation would require two different

lithologies (basalt and sandstone) outcroppings near one another,

an occurrence which is not at all unreasonable. The larger

drainage area of a stream would, however, make it easier for these

disparite lithologies to be found in the same sediment body. A

third possible interpretation for these graded beds is that they

are the result of higher stream gradients due to volcanic uplift

and/or tectonic uplift in the source areas. Although possible,

this latter explanation is tenuous at best due to the short dura­

tion of this sedimentary episode as well as its repetitive nature,

which would involve repeated volcanic and/or uplift surges over a

fairly short period of time.

The reef facies of the Rio Banano Formation is indicative

of shallow water since the hermatypic coral species found in these

reefs must live within the photic zone. Although this may be over

100 m deep in clear tropical waters, a lower limit is placed on the depositional environment of this facies. Its association in

lateral continuity with the shallow water clastic sediments of the

Rio Banano sandstone facies further supports a shallow marine

environment of deposition for the reef facies of the same formation.

The Moin Clay Member of the Rio Banano Formation was deposited

in a middle- to outer neretic environment, according to paleontological

evidence. The small grain size (mudstone) found in this facies

indicates a quiet environment of deposition. The total lack of any

sedimentary structures is most probably the result of intensive

38

burrowing.

The discontinuous nature of the "Pueblo Nuevo Sands" makes

interpretation of their origin difficult since no paleontologic or

lithologic trends can be established. Fossil evidence suggests

at least some mixing of fresh and salt waters since both normal

marine and brackish faunas are found in these sands. The probable

unconformable nature of these sediments to normal marine sediments

(both carbonate and clastic) could be explained in two ways. The

unconformity could be erosional in nature with some hiatus involved.

The presence of essentially undisturbed reef pinnacles projecting

into the "Pueblo Nuevo Sands", however, suggests a more rapid

environmental change. Any erosion would be expected to attack these

relatively thin (3-6 cm), high pinnacles first and form a smoother

surface than the contorted one noted above.

The preservation of these pinnacles suggests that the reef was

buried quickly before erosion could begin to reduce these topographic

highs. The high degree of sorting shown by this sand is indicative

of currents in the area with some degree of persistence to move the

fine fraction of these sediments away. The presence of brackish

faunas suggests fresh water influx, possibly due to periodic

climatic changes causing heavier than normal rainfall, changing a

normal marine environment temporarily into a brackish one.

Further indications as to the origin of the "Pueblo Nuevo

Sand" comes from their distribution. They are found associated with

the thicker, more extensive reef trends. The smaller reefs are

39

capped lay sediments of the Rio Banano sandstone facies while the

thicker reefs are most commonly covered with the better-sorted

"Pueblo Nuevo Sands." This relationship suggests that the "Pueblo

Nuevo Sands" are actually derived secondarily by reworking of

sediments of the Rio Banano sandstone facies. This reworking could

be done by tidal currents flowing through and around the reefs in

a manner similar to that observed by the author in the Florida Keys.

These tidal currents would be the strongest around the offshore

reefs and weakest further inshore, where the reefs are also

smaller. Periodic floods could distribute a blanket of sediment

over the entire area which these tidal currents could sort, removing

the finer fraction into deeper water outside of the reefs. This

hypothesis for the origin of the "Pueblo Nuevo Sands" could

theoretically be tested by determining whether there is a gradual

gradation from well-sorted "Pueblo Nuevo Sand" to poorly-sorted

Rio Banano sandstone facies sediments. The nature of "Pueblo Nuevo

Sand" outcrops is such, however, that this cannot be done.

Uo

Sureties Conglomerate

The Suretka Conglomerate was first described by Berry (1921)

from outcrops near the village of Suretka (now abandoned) in the Rio

Sixaola area of southeastern Costa Rica. In the Limon area, the

conglomerate is exposed over a broad area west of Limon in road-

cuts and stream exposures. Although no direct relationship

exists between the type locality and the Limon outcrops, no age or

lithologic difference can be shown between the two occurrences.

Neither can any age equivalence be demonstrated. Since no signi­

ficant differences can be shown between the type occurrences and

the Limon Conglomerates, the term Suretka Conglomerate has been

retained in the Limon area to avoid burdening the stratigraphic

literature with yet another local formation, even though the Limon

occurrences may not be related in any way to the Rio Sixaola sed­

iments. Since no upper contact was observed, no estimate can be

made for the thickness of this formation in the Limon area. A

minimum thickness of ten meters is indicated by outcrops of that

height, however.

This conglomerate contains a wide variety of grain sizes

ranging from clay particles to boulders up to a meter in diameter.

These widely-separated grain sizes do not occur together, how­

ever, as the formation is internally divided into many distinct

sediment bodies (not mappable at the scale of this report), each

of which is well-sorted.

The Suretka is characterized by an abundance of moderate-

angle (25°) cross-bedding and trough cross-stratification. Small

cross beds are best developed in an isolated outcrop of sand and

hi

gravel near Sandoval where cross beds up to five cm high are found.

Cross-bedding is also developed in the more extensive exposures

along the Limon-San Jose road but on a much larger scale (on the

order of meters rather than centimeters). The most common sed­

imentary structure in Suretka outcrops is trough cross-stratifica­

tion. This is especially well-developed in the Rio Toro area

where symmetrical and asymmetrical bodies of cobble-sized parti­

cles cut across sand bodies, and boulder beds interrupt cobble and

sand layers.

Contacts

The Suretka-Rio Banano contact was mapped on the basis of the

upstream limit of Suretka-lithology cobbles and boulders in the

stream gravels. This contact is often also marked by the reappear­

ance of Rio Banano sandstone facies outcrops. The presence of a

boulder or cobble conglomerate on top of the Rio Banano makes it

difficult to determine if any angular relationship exists between

the two since dips were patently impossible to determine in the

Suretka due to the nature of the formation. The relationship be­

tween the Rio Banano and Suretka Formations seems to be an angular

unconformity with some scour indicated at the base of the Suretka.

No overlying sediments were observed.

Source

The high percentage of basaltic rock fragments found in the

Suretka as well as its clay mineralogy (chlorite and montmorillonite)

demonstrates a basic igneous source for this sediment, obviously the

volcanic belt a few tens of kilometers to the west. No sedimentary

rock fragments were noted in the Suretka.

Depositional Environment

The sedimentary structures found in the Suretka Conglomerate

are indicative of deposition in a fluviatile environment when

compared with data in Visher (1972). The width of the outcrop band

(sone 15 km of nearly continuous exposure) suggests that a major stream was responsible for Suretka deposition. The more southeast­

ern exposures (in the Rio Toro area) are much more significantly

weathered than outcrops further west. This shows evidence for a

net northwestern migration of the stream in addition to its con­

siderable short-term lateral migrations, evidenced by the rapid

lateral changes in sediment characteristics.

A part of the Suretka outcrop area includes the flood plain

of the Rio Chirripo, a river approximately 1*0 km north-north-west

of Limon. Although it is presently depositing cobble and pebble­

sized particles, the presence of large boulders on its banks shows

that its flow regime has been considerably different in the not

too distant past. Air photos show that this stream meanders

greatly and is commonly braided. This stream is most probably

similar to the type of stream responsible for the deposition of

the entire Suretka Conglomerate, even to its highly variable flow

regime.

Because no fossils were found in the Suretka and attempts to

obtain radiocarbon dates on wood fragments taken from these sedi­

ments showed only negative results, the age of this formation can­

not be positively determined. Because it is the youngest strati-

graphic unit in an area of known Pleistocene deposits and includes

recent deposits, it most probably is of late Pleistocene to Recent

43age

PALEONOTOLOGICAL DATA

Field Collecting of Samples

During the course of the field work for this project, an

extensive sediment sampling program was undertaken. The location of

each sample was determined hy the author on the basis of outcrop

freshness (leached or weathered outcrops were avoided whenever

possible), proximity to other sample locations, and lithologic

uniqueness (monotonous lithologies were sampled less frequently than

areas with rapidly changing lithology). In the case of long, more

or less continuous outcrops, samples were taken at measured intervals,

at lithologic changes, or both. A completely statistical sampling

program with sample locations determined by random selection on a

grid or at specific measured intervals was deemed logistically

impractical due to the irregular distribution of small outcrops

throughout the area. A purely statistical sampling program, if

carried out in an area with this kind of outcrop pattern, would

result in many samples not showing bedrock but rather soil or Recent

stream deposits. Shipping costs prohibited any but outcrop samples.

Logistics problems also led to the non-random sampling program

with the most accessible areas being along roads and streams, where

most of the outcrops are also located.

Processing

The samples taken were processed for micropaleontological

examination by Varsol preparation and standard washing techniques,

kb

using a Curtain power washer with a 200-mesh sieve. To prevent

contamination from sample to sample, this sieve was immersed in green dye after each sample and green-stained fossils were discarded.Isolation of Specimens

Collections of macrofossils were made in the field in horizons

containing good faunas. These specimens were removed individually from the outcrop and high graded in the field to select the best

representative sample possible while maintaining a reasonable

collection size. These specimens were wrapped individually in soft paper for shipment.

Microfossil collections were made utilizing standard micropaleontological picking techniques. The greater majority of the samples were examined until 300 individual ostracods and/or

foraminifers were found, or until the sample was determined to be

barren or nearly so. According to Dennison and Hays (1967), the examination of 300 individuals permits the detection of any species

which comprises at least 2% of the population. Samples with high

percentages of planktonic foraminifera, which have a greater potential of being biostratigraphically significant, were examined until 1000 individuals had been counted. According to Dennison and Hay (1967),

this permits the detection of forms which comprise as little as 0.5% of the population. These percentages are given for a significance

level ( , ) of 0.01 (1% probability of missing a species present in

k6

greater than 0.5% or 2% of the population. Since no statistical

analysis of these faunas has been attempted, the application of the more detailed technique to a few samples will introduce no bias.

The increased probability of detecting species present in low frequencies greatly increases the reliability and precision of

biostratigraphic determinations.Specimens were selected for the faunal plates (see Appendix) on

the basis of the best specimen of that species observed. Foraminifera were photographed on a Joelco JSM-2 Scanning Electron Microscope

following the evaporation of a gold thin film coating over the

specimens. Macrofossils were whitened with magnesium oxide and

photographed with a 35 mm camera. These plates are not all-inclusive

of the Limon faunas since many of the species (both macro- and microfossils) did not have specimens which were well enough preserved

for inclusion. The plates are, however, representative of the faunas

since no common or significant form was excluded.

Faunas Found

Uscari ShaleThe Uscari Shale samples contained some of the most prolific

faunas encountered. Following is a list of the more common species

found in the Uscari Shale.

hi

Globlgerlnoides trllobus Slgmolopsls schltimbergeriGloborotalla cultrata menardll Uvigerina hispido-costataGloborotalla cultrata cultrata Globlgerinoides obliquusGyroldina altiformls Textulariella barrettiNodosaria sp. Lagena sp.Sphaeroidinellopsis subdehiscens s.s.Spirolocullna soldanll Pullenla bulloldes Marglnullnopsls marginulinoidesGloblgerinoides ruber "Cibidices floridanusEggerella bradyi Orbulina unlversaPyrgo sp. Nodosaria pyrulaNodosaria lamnulifera Nodosaria albattossiRio Banano Formation

Faunas recovered from the Rio Banano Formation are quite varied,

as might be expected from its variable lithology. The basal portionof the sandstone facies contains a fauna with some elements of the

Uscari list above. This basal Rio Banano sandstone facies faunaincludes:

Quinqueloculina sp, Uvigerina perigrinaGloblgerinoides trllobus Orbulina universaLenticulina calcar Sphaeroidlnellopsis subdehiscensPyrgo sp. Globoquadrina altispira"Cibicides" floridanus Nodosaria subsolutaHanzawaia strattoni Textularia panamanensisFrondicularia sp. Orbulina bilobataGloborotalla cultrata cultrata Pulleniatlna obliqueloculataGloborotalla cultrata menardii pr~l mails

The stratigraphically younger portions of the Rio Banano sandstone facies contain different faunal elements. Samples from the upper portion of the Rio Banano sandstone facies commonly include the following foraminiferal species:Cribroelphidium poeyanum Bolivina striatulaAmphistegina lessoni Archaias compressusCribroelphidium gunteri Glob igerinoldes trllobusReusella atlantica Globigerinoides ruberFloralis atlantica Hanzawaia strattoniAmmonia beccarii Orbulina universa

1*8

Faunal List - Upper Rio Banano sandstone facies (continued)

Siphonina pulchra Planulina foveolataPoroeponides repandus

Samples taken from the conglomerate facies of the Rio BananoFormation were, for the most part, barren. One sample which didhave a fauna present contained the following species:

Neoeponides regularia Cribroelphidium gunteriGloborotalla cultrata menardil Nodobaculariella sp.Textularia conica Rosallna florldanaAssorted miliollds Globigerinoides trllobusPyrgo sp. Poroeponides repandusTextularia panamenensls

No attempt was made to separate foraminiferal faunas from the

reef facies of the Rio Banano Formation. Faunas were derived,rather,

from the closely-associated sandstone facies samples.

The Moin Member of the Rio Banano Formation also contained aprolific and varied foraminiferal fauna. This fauna commonly includedthe following species:

Globorotalla truncatullnoides Sphaeroidinella dehiscensGloborotalla cultrata menardii Slgmoliaopsis scbl uwhergeriMarginulinopsis marginulinoides Uvigerina perigrinaOrbulina universa Globlgerinoides trllobusBolivina subaeneriensis Globlgerinoides ruberAssorted miliolids Pulleniatina obliqueloculata ss.Planulina foveolata Globoquadrina dutertreiTritaxla mexicana Siphonina pulchraNodosaria sp. Siphonina bradyana

Samples from the "Pueblo Nuevo Sands" generally show a ratherdepauperate and limited fauna with the following forms comprisingmost of the population:Cribroelphidium poeyanum Amphistegina lesson!Assorted Miliolids Hanzawaia strattoniAmmonia beccarii Cribroelphidium gunteri

Suretka Conglomerate

None of the samples taken, from Suretka Conglomerate outcrops showed any fossil material at all.

Biostratigraphy

Age determinations for this study were done exclusively with

planktonic foraminifera to avoid the correlation of facies rather than time intervals, a problem which commonly crops up when

attempts are made to use benthonic organisms for establishment of ages.

Specific determinations for this study were made from Blow

(1969), Postuma (1966) and Berggren (1973). Stratigraphic ranges for these species follow Blow (1969). Data from Lamb and Beard

(1972) were not used in the biostratigraphic analysis because the

author feels that significant discrepancies exist between their

work and what has been published on the Calabrian faunal succession in the Italian type section, which is the basis for determining the

basal Pleistocene. These discrepancies result in significantly younger age determinations when compared to data from other workers. Distribution charts for all samples are included in the appendix as an aid to future evaluation of the Limon data.

Good planktonic foraminiferal assemblages were recovered only from the Uscari Shale, the lower Rio Banano sandstone facies and from the Moin Clay Member of the Rio Banano Formation.

Uscari ShaleThe Uscari Shale samples, while having a more abundant

50

planktonic fauna, did not contain the indicator species necessary for detailed zonation, permitting refinement only to an N.14 to N.18 determination (middle Miocene to lower Pliocene). This age is based on the concurrent ranges of Globorotalia cultrata menardil and Sphaeroidinellopsis subdehiscens s.s.Rio Banano Formation

Basal sandstone faciesThe most accurate biostratigraphic determinations (based on the

presence of more short-ranging species) were made from the basal Rio Banano sandstone facies. Sample 1146, for example, shows a

good N.18 fauna (upper Miocene to lower Pliocene age). This age determination was madei on the basis of the concurrent ranges of Sphaeroidinellopsis subdehiscens. s.s. and Globlgerinoides

conglobatus s.s. This age determination is supported by data from

sample 1148, taken approximately 75 m stratlgraphically above

sample 1146. Sample 1148 shows a mid N.17 to upper N.18 age (lower

upper Miocene to lowermost Pliocene). This age determination is

based on the concurrent ranges of Pulleniatina obllquelata and Sphaeroidinellopsis subdehiscens s,s.

Upper sandstone faciesAlthough most of the samples from the upper portion of the

Rio Banano sandstone facies contained a biostratlgraphically non­diagnostic fauna, samples 1070 and 1233 from the Empalme Moin area

are datable. The presence of Pulleniatina Qbliqueloculata prlmalis

51

in sample 1233 would place its age between mid N.17 and lower

N.20 (late Miocene to upper middle Pliocene). Sample 1070 contains IP. obliqueloculata praecursor, whose stratigraphic range is N.19 to middle N.21 (upper lower Pliocene to uppermost Pliocene), The apparent position of these two samples nearly on strike with one another suggests that the sediments in the Empalme Moin area may be middle Pliocene (N.19 to middle N.20) in age. It cannot, however,

be absolutely demonstrated that these two samples came from the same

stratigraphic unit, so this age refinement is speculative. These two samples do, however, demonstrate at least a Pliocene age for

sediments in the Empalme Moin area.Moin Clay Member

Samples from the Moin Clay Member of the Rio Banano Formation

from the plateau west of Limon show an excellent planktonic

foraminiferal fauna. These samples all contain Globorotalla truncatullnoides, a form which is restricted to the Pleistocene (Bolli, 1966; Blow, 1969; Berggren, 1973). The presence of

Sphaeroidinella dehiscens excavata permits further refinement since Blow (1969) restricts that subspecies to his N.23 zone (Globigerina

calida/Sphaeroidinella dehiscens excavata assemblage zone) which is late Pleistocene to recent in age. Other planktonic forms present

which are not, however, of biostratigraphic importance are:

Globlgerinoides trllobus, G, elongatus, £. sacculifer, £. ruber, Globoquadrina dutertrei, Globorotalla cultrata s.s., G. cultrata

52

menardii, Orbulina universa, Spaaeroidinella dehiscens and

miscellaneous Globigerina sp. This Pleistocene determination from

the Limon area is supported by data from Akers (1973) on planktonic

foraminifera from the Limon area.

Strong differences of opinion exist between mollusk specialists

and planktonic foraminiferal workers on the age of these sediments.

Olsson (1922) reports an early Miocene age for the Type Uscari

although this author has determined a younger late early to early

middle Miocene age (zones N.8-N.10) on samples from the type area of

that formation. Nothing as young as Pleistocene has been reported

by mollusk workers, yet the author has found a rather large area of

Pleistocene outcrop (determined as Pliocene by Gabb (l88l), a determination with which Woodring (1928) concurs). These

differences may be due to the nature of the organism used for

dating. Planktonic foraminifera, while showing a certain amount of

provincialism in that they are not found in abundance in shallow

water and are temperature controlled, nevertheless show variations

only over several tens of degrees of latitude. Mollusks, on the

other hand, are strongly facies controlled, and a good possibility

exists that facies, rather than time intervals, are being correlated.

The most commonly-used method of dating by mollusk workers, that

of determining the percentage of extant species in a fossil fauna,

compounds the correlation problem. Although it is the author's firm

belief that the planktonic foraminifera are a more biostratigraphically

reliable group of organisms, this discrepancy between mollusk and

53

planktonic foraminiferal dates will have to be resolved in the

future.

Depositional Environments

Previous Work

Paleoecologic analyses and paleontologic determinations were

done principally by comparison with data presented by Phleger and

Parker (1951), Albens (1966), Cebuski (1967)5 Bandy (195**,1956) and Smith (196I*). Most of these references cover faunas slightly

deeper than the majority of the faunas found in this study, making

Bandy (195*0 the most useful reference, both for specific

determinations and paleoecologic analyses, due to its considerable

information on very shallow water faunas.

Bandy (195*0 divided the inner and middle neritic environments

into four zones. Not all of the species that he utilized were

present in the Limon shallow water samples, possibly due to the

warmer Caribbean waters in contrast to Bandy's sampling area in the

Gulf of Mexico, 20-30 degrees further north.

Very shallow water (l-ll m) is characterized, in the Limon area,

by a fauna comprised of Archaias compressus, Florilis atlanticus,

Cribroelphidium gunteri, Ammonia beccarii and sometimes Cribroelphidium

poeyanum with low planktonic percentages (0-20 percent).Deeper water (11-25 m) is characterized by Rosalina floridana,

Hanzawaia strattoni, Planulina foveolata, Asterigerina carinata, and

rarely, Quinqueloculina horrida. This fauna is accompanied by more

planktonic foraminifera, commonly comprising 15 to 35 percent of the

5

foraminiferal fauna.

The zone between 25 and 60 meters is characterized by Planulina foveolata and Bigenerina irregularis with the disappearance of

Rosalina floridana from the fauna. Uvigerina perigrlna also makes

its first appearance here. Planktonic percentages climb higher to 30-50 percent of the foraminiferal fauna.

Bandy's fauna 4 (Bandy, 1954), representing water depths from

60 to 90 meters is represented in the Limon area by Planulina

foveolata, Uvigerina perigrina, Eggerella bradyi and Hanzawaia concentrica. Planktonic percentages are even higher here, averaging between 50 and 70 percent of the foraminiferal fauna.

The shallow (littoral) habitat is strongly dominated by Ammonia beccarli and Cribroelphidium poeyanum. This environment is

also often marked by the presence of a rich ostracod fauna,

especially the genus Perissocytheridea and possibly Reussicythere

(van den Bold, personal communication). A relationship shown in

Bandy (1954) between salinity and generic distribution can probably be extended into the Caribbean. This shows a salinity range of

5-36°/00 for Ammonia, 10-36°/oo for Cribroelphidium, 20-36°/oo for Miliolids and 27-36°/00 for other species.

In many cases, the overlap of the indicator species listed

above were used to informally subdivide these depth zones. For

example, the occurrence of Rosalina floridana and Bigenerina irregularis together would suggest a depth toward the bottom of the

Rosalina-Planulina and the top of the Planullna-Bigenerina depth zones or about 30-40 meters.

55

The sample by sample results of the paleontological analysis

are incorporated in distribution charts in the back pocket of this

report.

In general, the paleoecologic analyses made were internally

consistent with no sample or group of samples contradicting the

overall pattern to be presented below.

Environmental Determinations

The samples analyzed show four main faunas indicative of the

following environments: outer neritic (300-600 m), middle neritic(+100 m), inner neritic (1-70 m),and a shallow brackish environment (1-10 m). These depth suggestions result from a comparison of

the faunas from Limon and the depth-salinity information from the

literature cited above. Although some paleontologists might draw

somewhat different conclusions as to absolute water depth, the

relative depth determinations would generally be the same regardless

of the analyst.

Uscari Shale

The deepest environment was found in samples from the Uscari

Shale on the north bank of the Rio Banano, especially sample 1150.

This outer neritic environment is characterized by a high percentage

(60-80$) of planktonic foraminifera with the benthonic fauna strongly dominated by Uvigerina perigrina and U. hispido-costata.

Also present in the fauna were Pullenia bulloides, Nodosaria pyrula,

N_. lamnulifera and "Cibicides11 floridanus. This fauna suggests

deposition in 200 to ^00 meters of water with sample 1150 possibly

being as deep as 500 meters.

Rio Banano sandstone facies

Immediately across the Uscari-Rio Banano contact in the Rio Banano sandstone facies, sample 1148 shows an abrupt shallowing to an outer to middle neritic environment (100-150 m). The horizontal distance between this sample and those taken in the Uscari is 180 m

with the Uscari-Rio Banano contact between the two groups of samples. This horizontal distance translates to approximately 90 m of

stratigraphic separation. Unfortunately, the close-spaced samples taken across the contact area were barren, precluding a more

precise location for this environmental change.

Samples 1146 and 1147, taken in the lower portion of the Rio

Banano sandstone facies approximately 300 m stratlgraphically above the near-basal sample 1148, show deposition in even shallower water with a 20-50 m depth range. This overall shallowing trend continues

to sample locations 1145 and 1144a, another 250 m stratlgraphically above sample 1147, which show deposition in only 10-20 m of water. This last shallow water fauna is found through the remainder of the samples taken to the east toward La Bomba with an occasional sample showing an even shallower 1-10 m depth (see samples 1132 and 1163, for example).

The south side of the Rio Banano shows a similar relationship between faunas with the exception that the deepest marine environment was not found. It is believed that this lack of the deeper environment is due to sampling problems rather than an actual

57

environmental difference from one "bank of the river to the other.

The Uscari-Rio Banano contact on the south side of the river has

been shifted south and west by faulting into a remote area with

few outcrops in the Uscari Shale. Sample 1183, taken in the

immediate vicinity of the contact in the Rio Banano sandstone facies,

shows a fauna characteristic of deposition in approximately 100 m of water. A shallowing sequence found in samples taken

stratlgraphically above this sample is almost identical to that

found on the northern bank of the river. This parallelism suggests

to the author that both sides of the fault (which trends up the

modern river channel) had the same tectonic and sedimentologic

history and that the deeper marine facies are actually present on the

southern side of the fault but were not sampled due to the remoteness

and paucity of the outcrops.

Samples taken from the upper portions of the Rio Banano

sandstone facies in the Q. Chocolate-Q. Bartolo area vary in depth

from very shallow (less than five meters) to around 20 m. (samples

[1019-1063]) , at the deepest. Although there is no strong evidence

from the foraminifer and ostracod populations, there may be some brack­

ish influxes in the Q. Chocolate area (two samples, 1060 and 1063 do

contain a brackish fauna). These possible brackish layers are

marked by a restricted macrofauna with Crassostrea, a form which has

been restricted to a brackish environment in recent sediments by the

oyster drill. Several instances of Crassostrea shells filled with

58

sediment containing a marine foraminiferal fauna indicate the

possibility of considerable reworking and distribution of sediment

and fossils. This implies periodic strong currents crossing a

brackish environment, moving some of the macrofauna offshore and

leaving it as a lag deposit in a normal marine environment.

Rio Banano conglomerate facies

The samples taken from the Rio Banano conglomerate facies in

the Nuevo Castle area show a fauna characteristic of deposition in

shallow marine conditions (1-10 m).Moin Clay Member of the Rio Banano Formation

A fauna indicative of middle to outer neritic environments

was found in the samples from the Moin Clay Member outcrops found

west of Limon. This fauna is characterized by a high percentage of

planktonic foraminifera (60-80 percent) and a benthonic fauna with Planulina foveolata, Uvigerina perigrina, Bolivina subaeneriensis

and Siphonina pulchra. Also present, although in lower frequency,

-s Tritaxia mexicana and miscellaneous Nodosaria species. This

fauna is characteristic of deposition in a middle to outer neritic

environment (60-100 m). The samples furtherest north (see sample

lOOlf) have a fauna which, according to data in Phleger and Parker

(1957)> most likely lived in 90 to 100 meters of water. Sample

1018, taken near the middle of the plateau, does not contain as high a percentage of the deeper forms such as Uvigerina perigrina and

shows the appearance of shallower forms such as Siphonina pulchra

and Virgulina sp. The suggested depth of deposition for this sample

59

is 60-90 meters."Pueblo Nuevo Sands"

Samples from the "Pueblo Nuevo Sands" show a mixture of

environments. Some samples show a normal shallow marine fauna

consisting of Cribroelphidium poeyanum, Amphistegina lessoni,

assorted Miliolids, Textularia conica and Globigerinoides trilobus

with around 5% planktonic foraminifera. The ostracods from these

samples also show a very shallow environment under normal or near­

normal salinities (van den Bold, personal communication). Other

samples show a distinctly brackish fauna of Ammonia beccarii,

Cribroelphidium poeyanum and £. gunteri along with brackish ostracods

(Perissocytheridea sp. and possibly Reussicythere sp. -van den Bold,

personal communication). Since these beds are defined on the basis

of a particular lithology (a well-sorted sand), it is evident from the

paleontological data that these sediments were deposited in different

or possibly periodically changing shallow water environments.

Mollusk Faunas

Numerous horizons in the Rio Banano sandstone facies, Moin Clay

Member , and "Pueblo Nuevo Sands" yielded mollusk faunas. These

collections were turned over to Dr. E.H. Vokes of the Tulane

University Department of Geology who kindly identified the specimens.

Representative species from this study and previous collections by

Dr. Vokes are figured in Plate 12.

On the basis of fairly restricted, possibly non-representative

sampling, there appears to be some form of faunal restriction shown by

60

the mollusk faunas : the Moin Clay Member of the Rio Banano Formationcontains a deeper water fauna including Sconsla striata, Drillia macilenta and Conus mayel. According to Dr, Vokes (personal communication) , this latter species has been reported only from

deep water sediments between 92 and 240 fathoms (184 to 480 m) .

Sconsia striata is also a deep water form. This deep water mollusk

fauna gives independent support to the foraminiferal paleoecologic

determinations.

The remaining mollusk faunas do not show the restrictions found

in the Moin Clay Member. Outcrops of "Pueblo Nuevo Sand" often show Murex olssoni, Fusinus miocosmus and Dermomurex aspella. Rio

Banano sandstone facies collections commonly include Velnta virescens, Chicoreus sp. (commonly jC. moinensis) and Conus recognitus.

Plate 12 does not contain all of the mollusk species in the

Limon area but is representative of the faunas found. Many of the

specimens were not preserved well enough for inclusion in the plates.

Others were well-preserved in the outcrop but had been leached to the point where they could not be removed from the matrix without breaking the specimen.

61

Radiocarbon Dating

The presence of wood fragments in several samples from the Rio

Banano sandstone facies and the Suretka Conglomerate led the author

to attempt to date these samples by radiocarbon methods. Nine

samples of both wood and shell were processed by the author in the

LSU Radiocarbon Laboratory in the Nuclear Science Department, but

the material was radiometrically dead.

This laboratory utilizes the benzine process for radiocarbon

dating. In this process, the carbon is liberated from the sample as

carbon dioxide by acidification, in the case of carbonate material,

or by burning in pure oxygen, in the case of wood fragments. This

carbon dioxide is then run onto pure lithium metal heated to 700°C

to produce lithium carbide. The addition of water to the lithium

carbide produces acetelyne gas which then passes onto a vanadium

catalyst, converting the acetelyne to benzine. To this known

volume of benzine is added a measured amount of a liquid which

flouresces upon alpha particle bombardment. This mixture is then

placed in a Beckman Liquid Scintillation Counter for at least ten

100 minute counting periods in alternation with National Bureau of

Standards oxalic acid and petroleum coke standards. Age calculations

are made on the basis of a ratio of the net counts per minute per

gram for the sample to that of the oxalic acid contemporary standard.

Nine samples were processed in the laboratory: samples 1052,

1053,1056,1060,1093,1010,1025,101+7, and 1239. None of the samples

gave a usable date with none having a mean disintegration count that

62

was significantly above that of the background standard (petroleum

coke NBS standard). Although the lack of success with this method

prevents any positive conclusions, the negative evidence that

even the stratigraphically youngest sample processed (sample 1010) was at least 30,000 years old is useful data.

STRUCTUREFolds

The major structural feature in the Limon region is the Victoria

Dome, which was defined by mapping l»y Union Oil. This dome is centered at Petroleo, to the southeast of the study area. The

northeast-dipping strata of the Limon area art on the northeast flank

of this doubly-plunging anticline. In the map area, the dome can be

demonstrated by the change in strike from east along the Rio Blanco, to WNW along the Rio Banano, to north in Q. Maria Luisa and then back to NW further to the southeast of Q. Maria Luisa. The dips also

generally flatten to the northeast, away from the dome center.

The northeast flank of the dome is also roughly outlined by a persistent topographic ridge which occurs in the Rio Banano

Formation, hereafter referred to as the Rio Banano ridge, between

the Rio Banano and the Rio Blanco. It changes in strike from east-

west along the Rio Blanco to NNW-SSE along the Rio Banano. This

ridge, which was observed only on topographic maps, is believed to be the result of a resistant layer or layers similar to those

described above as the conglomerate facies of the Rio Banano Formation near Nueva Castle. This Rio Banano ridge is indicated on the

geologic map (see pocket in back) by oversized attitude symbols with

no order of magnitude indicated for the dip. As can be seen from the map, this ridge appears to be offset across the Rio Banano.

The strata generally dip away from the center of the dome,

63

although some exceptions are found. The Q. Chocolate exposures show two broad, gentle folds which cause the reef section to repeat in

outcrop. Total dip changes across these folds are in the order of magnitude of 20-25 degrees.

Another set of broad folds is found in the Empalme Moin area. These are shown by dip information obtained primarily from the

Moin Clay member. Total dip changes across these features are also in the 20 to 25 degree range.Faults

Three faults were recognized on the basis of stratigraphic

offsets and field relations. None of the faults mapped showed any

evidence of an escarpment or of fault gouge.All of the faults (or fault zones) mapped are on the site of

streams. The largest of these is a combination flexure and fault zone which is presently the site of the Rio Banano. It shows a

horizontal offset of the Uscari-Rio Banano contact of approximately

one kilometer with the northern block being upthrown relative to the southern. Using an average dip of 30° over the area, this

would imply a vertical displacement of 200 to 250 m. The offset of

the Rio Banano ridge mentioned above is in the same direction and of the same magnitude as the offset of the Uscari-Rio Banano contact. Further evidence for this fault zone was found on the river bank

in the Uscari Shale 100 m south of the Rio Banano contact where a small fault has downfaulted a wedge of Rio Banano sandstone facies

into the Uscari.

65

Two other faults were mapped, one trending down the Rio Blanco

and the other down the Rio Madre. Both were mapped on the basis of

stratigraphic offsets of the Uscari-Rio Banano contact.

There is a suggestion on the topographic maps that the Rio

Banano ridge may be offset along a line which skirts the southern

flank of the Limon promontory. This may indicate the presence of a

northeast-southwest trending, down-to-the-southeast fault which

is buried in the alluvium closer to Limon. Due to the remoteness

of the area of this possible fault, it was not possible to

examine the area of the Rio Banano ridge for further evidence of

this fault. This apparent topographic offset is the only evidence

for this fault and there is no apparent offset of the topographic

expression of the Uscari-Rio Banano contact.

All of these faults are regarded as hinge faults with

displacements decreasing to zero at the center of the dome.

Relative motion analysis of these faults shows all of them to

be down-to-the-southeast faults, except for the one which trends down

the valley of the Rio Madre, which is a down-to-the-west fault.

A more complex structural interpretation of this area,

invoking a considerable amount of post-depositional deformation is

also possible. The reef trends could be interpreted as being

repeated by eastward-plunging folds. This interpretation would

necessitate a major compressional period, which is not reflected in

the regional geology of southern Central America (Dengo, 1962).

The more complex interpretation would also need a reef approximately

five kilometers square, a rather unlikely occurrence.

GEOLOGIC HISTORY

According to Hoffstetter (1962), sedimentation in eastern Costa Rica during the Paleogene and early Neogene was primarily

deep marine, reflecting a relatively stable, slowly subsiding basin.

During the early Pliocene, this tectonic stability was ended by a

period of regional uplift and volcanism.

The uppermost Miocene-lower Pliocene in the Limon area reflects

this regional tectonic change. Paleoecologic information shows

a rapid shallowing from the deep marine Uscari Shale (300-500 m)

to the quite shallow (+20 m) Rio Banano sandstone facies. Sediments

also became noticeably coarser as is evidenced in the grain size

difference between the Uscari Shale and Rio Banano sandstone facies.

Much of this shallowing in the Limon area is probably due to

the formation of the Victoria Dome. The cause of its formation

is not known but is undoubtedly related to the regional tectonic

change. During this period of time, the entire southern Central

American orogen was affected by uplift and volcanism, some intrusions

and uplift. The Limon area, being more remote from the center of

tectonic activity, was not lifted above sea level as were the

Talamanca land masses to the west as all samples taken for this

study indicate that marine or near-marine conditions existed during

most of the geologic history of the area. Although considerable

shallowing is noted in the Limon area, there is no evidence to

demonstrate any unconformity within the Miocene-Pliocene succession.

The uplift of the Talamanca source area would be expected to change

the sedimentary regime of the Limon area from slow (shale) to rapid

66

67

(sandstone). This change in regime has been noted above as the change

from the Uscari Shale to the basal Rio Banano sandstone facies.

During the deposition of the greater part of the Rio Banano

sandstone facies, tectonic conditions evidently stabilized as indicated

by the nearly constant depositional environment. Normal marine

sedimentary processes gradually deposited the mass of sandstone and

siltstone referred to here as the Rio Banano sandstone facies.

Although no direct evidence can be shown to indicate the

origin of the rapid vertical and horizontal changes in lithology

noted in both the field descriptions and laboratory analyses of the

sandstone facies, combined with the tectonic stability noted above,

several hypotheses will be put foreward. It should be noted that

these suggestions are speculative and not supported by any specific

evidence. They are being presented to indicate what the author's

thoughts are concerning the problem.

Source area changes could condietvably explain these rapid

lithologic changes to some extent although uplift or increased

volcanism would be more likely to produce greater, more consistent

lithologic changes rather than the minor, rapid changes noted in

the sandstone facies. Changes in stream regime could cause these

rapid, local changes, however. Episodes of strong stream flow

would naturally bring coarser material into the area while slower

flow would deposit finer silt and clay. This hypothesis is strengthened

by the presence in several outcrops of coarse sand layers with

ripple marks on top overlain by a silty clay (see p. 23). The ripple

marks give evidence of a current much stronger than could have been

68

present during the deposition of the silty clay.

These continuous and rapid changes in stream regime are a

common occurrence in the area with nearly daily changes being

observed in present streams.

This regime change hypothesis also can explain the Rio Banano

conglomerate facies by exceptionally large floods bringing unusually

large particles into the map area. This type of flood is by no means

unusual since one of the extant rivers, the Rio Blanco, is able to

transport boulders up to five meters in diameter at peak flow. It

would also be possible to regard the Rio Banano conglomerate facies

as a cyclic storm deposit except that there are no known coarse-grained

sediment bodies in the area to be reworked. It is possible that storm

action was responsible for distributing this conglomerate along the

shore after deposition near a stream mouth. In general, the simplest

explanation for both the conglomerate facies and the variable lithology

in the sandstone facies is periodic changes in the flow regime of the

streams supplying sediment to the area.

It ic difficult to determine what tectonic style affected the

area following the cessation of uplift. As was noted above, the

paleoenvironmental analyses show the environment to be relatively

stable after the initial uplift surge. Whether this represents

deposition in a slowly subsiding basin with sedimentation equaling

subsidence or a gradual accretion to the northeast, with the deeper

facies not being exposed, is not known. The regional picture of

uplift and volcanism would, however, suggest that a sudden change

to a negative tectonic style would be rather unlikely. Assuming

69

tectonic stability (rather than slow subsidence), normal sedimentation

would move the shoreline to the northeast, forming a relatively

thin, but laterally extensive, body of shallow marine sediments. If

a slowly subsiding basin existed, a thick sedimentary package

would be formed.

A United Nations exploratory water well drilled near La Bomba

was reported (personal communication from the driller) to have

encountered 200-300 feet of sand underlain by "mud." This could

indicate a relatively thin Rio Banano section immediately underlain

by older, finer (Uscari?) sediment. The author did not see any

cuttings and was not able to obtain samples from any of the U.N.

wells in the area or the Union of California well drilled near

Limon to test this hypothesis. Although by no means, conclusive,

the information volunteered by the U.N. driller suggests a relatively

thin, but widespread package of Rio Banano sediments. No firm

conclusions can be drawn from this type of hearsay evidence, however.

At some time during the shallow water depositional phase of

the geologic history of the Limon area, local tectonics became

important as differential uplift across the fault zones became

significant. This differential uplift cannot be demonstrated from

paleontologic evidence since no outcrops are found in the younger

portions of the section to the north and south of the fault block

containing Limon, but are buried under recent alluvium. The

Limon block is unique in that it remained high while the surrounding

blocks dropped down relative to the Limon block. This relative

motion has been demonstrated previously in the Structure section

70

across the Rio Banano and Rio Madere fault zones. Stratigraphic

offsets show these to be down-to-the-southeast and down-to-the-west

faults respectively.

The formation of local fault basins on either side of the Limon

block would effectively trap any clastic sediment (except for

suspension and chemical load) moving toward the map area, changing

the sediment budget of the Limon area to a sediment-starved

situation. This sediment budget change is evidenced by the start

of coral growth. Since coral cannot tolerate rapid sedimentation

or turbid conditions, the initiation of coral growth on the Limon

block reflects this change in sediment budget or at least a drastic

reduction in sedimentation.

Coral growth on the Limon block appears to follow a pattern.

Those reefs encountered the farthest from the modern shoreline are

quite thin, do not have a great lateral extent, and are interbedded

with the Rio Banano sandstone facies. As the modern shoreline is

approached, these reefs become thicker and of greater lateral extent.

This is obviously due to more favorable conditions for coral growth,

with conditions becoming increasingly more favorable with time or

with environment.

In the former explanation, coral growth would begin at the

environmental limits for corals. Growth would be slow and the reefs

easily destroyed by sediment influx or salinity changes. As conditions

became more favorable for these shelf-edge reefs, they would become

more lush, thicker, extend further laterally, and become more difficult

to destroy. This change in conditions would be the result of lower

71

sedimentation with time.

This explanation is summarized graphically in Figure 6. This

figure is not meant to accurately reflect the geology of the Limon

area, hut is strictly diagrammatic. It shows the "thick pile"

hypothesis advanced above with a thick sequence of sediments

comprising the upper Tertiary section in Limon. As conditions

became more sediment-starved toward the upper portions of the column,

the reefs became thicker and more luxuriant.

An alternative hypothesis is summarized in Figure 7- Again,

this figure is strictly diagrammatic and is not meant to reflect

accurately exact geologic conditions in the Limon area. This second

hypothesis assumes that all or most of the reefs are contemporaneous.

This hypothesis further would favor the "thin pile" hypothesis

with a thin shallow marine section overlying older deep marine

sequences. According to this hypothesis, reefs formed closer to

shore would tend to be less luxuriant and more vulnerable to fresh

water and sediment influxes. As the position of the reef moved

further into an open marine environment, many conditions

(sedimentation, salinity, aid food supply, to name a few) would

improve, allowing the reef to expand in all directions. Thus, the

outer reef would be the largest, both in thickness and lateral

extent.

Although both alternatives can account for the coral

distribution that has been noted in the Limon area, the first

explanation (see Figure 6) requires a more complex set of conditions.

The change in sediment budget must continue to become increasingly

72

sediment-starved, since the "younger" reefs are thicker. At the same

time, sediment influxes (of decreasing importance with time) must

enter the area periodically since clastic sediments are associated

with all of the reefs. This association is closer with the "older"

reefs situated further inland (toward the "bottom of the section).

This explanation, although plausable, is more complex than

assuming all the reefs to be more or less contemporaneous. In the

second case, the reefs nearest the shore would be periodically

smothered by rapid sedimentation brought about by flooding of the

local streams. Following the re-establishment of a sediment-

starved budget, these reefs would start over, creating an inter­

stratified reef-sediment sequence such as that noted in the Q.

Chocolate area sketched in Figure 5. At the same time, reefs

growing further offshore would be less affected by these sediment

and fresh water influxes and in a more stable environment as to

salinity and food supply. Those reefs would be able to grow to a

greater thickness in this more favorable environment.

This sort of reef distribution on a shallow shelf with an

outer (fringing) reef and a series of patch reefs behind it is by

no means unique. It has been observed by the author in the Florida

Keys and has been reported by Newell (196*0 from the Bahamas.

Since no well data were available to test these hypotheses,

no choice can be made between these two interpretations. The

simplicity of the contemporaneous theory makes it more attractive,

but both are possible.

Either hypothesis for the origin of the reefs can account for

the well-sorted, reef-capping sands referred to above as the "Pueblo

73

LIVING REEFMOIN MEMBER, RIO BANANO FORMATION

o - O

. o ‘ :0SURETKA CONGLOMERATE

PUEBLO NUEVO SANDS" RIO BANANO FORMATION

RIO BANANO REEF FACIES

RIO BANANO SANDSTONE FACIES

RIO BANANO CONGLOMERATE FACIES'O '* O '* o».o*. o *.0 &*&.

USCARI SHALE

Figure 6. - Diagrammatic representation of the "thick pile" hypothesis for the origin of the stratigraphic sequences found near Lir.on. Top of diagram is northeast (near Limon), bottom issouthwest.

vly*v-

mm

w

' ! ! !

i M mHi ! m

LIVING REEF

RIO BANANO MOIN MEMBER

PUEBLO NUEVO SANDS”, RIO BANANO FORMATION

RIO BANANO REEF FACIES

RIO BANANO SANDSTONE FACIES

RIO BANANO CONGLOMERATE FACIES

USCARI SHALE

Figure 7 — Diagrammatic representation of the "thin pile hypothesis for the origin of the stratigraphic sequence found near Limon. Top of diagram is northeast (near Limon), bottom is southwest.

75

Nuevo Sands." These sands are associated only with the reef

deposits, usually lying behind or capping the reefs. The thicker,

more extensive exposures of the "Pueblo Nuevo Sands" are associated

with the larger reefs. As was noted in the Stratigraphy section,

this unit is characterized by its well-sorted nature and sand­

sized particles. Any hypothesis as to its origin must account

for both its sorted character and its apparent close relation with

the reef deposits.

The local nature of this unit makes interpretation difficult

since no petrographic or paleontologic trends can be demonstrated.

The fauna present in these sands is mixed, with some of the faunas

being brackish and others open marine. The situation suggests

that periodic influxes of fresh water could be reducing local

salinities to brackish levels. The local floods or periodic

climate changes suggested by the burying of the thinner reefs

could also provide sediment for the "Pueblo Nuevo Sands," Re­

working of these sediments, which would most probably have an

initial grain size distribution similar to that found in the Rio

Banano sandstone facies (although sometimes containing a brackish

fauna), could result in a well-sorted sediment. This reworking

could be the result of tidal, or wave-generated currents stirring

these sediments and sorting out the fine fraction. A certain

amount of sorting would probably occur during the initial depo­

sition, but the degree of sorting shown by the "Pueblo Nuevo"

would require some sort of secondary reworking. This reworking

would not significantly affect the fauna because it is of a

grain size similar to or larger than the sands.

76

A mechanism observed by the author in the Florida Keys could

easily account for this reworking. Tidal surge channels are to

be found in and around these Florida reefs with tidal currents being

sufficient to sort the debris coming off the reefs. Since the

south Florida area is in a sediment-starved condition with no

nearby source of clastic sediments, this material is all reef rubble.

With periodic clastic influxes such as have been shown to occur

in the Limon area, there is no reason why this surge channel

material could not be primarily clastic in nature.

The series of shallow-water events which has been outlined above

was abruptly terminated by a wedge of upper Pleistocene middle to

outer neritic sediment. This is deposited unconformably on the

shallow marine sediments of the Rio Banano reef and sandstone facies

and is immediately overlain by Recent (living in part) coral reef.

This rather abrupt change in environment could be due to two main

possibilities, eustatic sea level change or tectonics. The rapid

return to an environment similar to that which existed before the

initial change argues strongly against a tectonic cause for this

change. Eustatic sea level changes in the 50 to 100 m range have

been suggested from Pleistocene sediments (Erickson and Wollin, 1968;

Erickson, et_.al., 1963) in other areas. An abrupt rise in sea

level would kill the reefs and limit the effectiveness of the sediment

traps of the adjacent fault basins, causing a fine-grained, deep-

water clastic sediment body to be deposited over the entire area.

As has been documented in the Stratigraphy section, this is a good

77

brief description of the Moin Clay Member of the Rio Banano Formation.

Following the close of the interglacial period which caused the

sea level rise responsible for these changed conditions, sea level

would drop to normal levels, returning the Limon area to conditions

similar to those that existed before the sea level rise. Reef

limestone which immediately overlies these deeper-water sediments

gives evidence for this return to a shallow marine, sediment-Btarved

condition. A portion of this capping reef is still living although

some of it has been killed by exposure above sea level.

The exposure of this reef gives evidence for an uplift, possibly

epeiric, in the uppermost Pleistocene or Recent. The magnitude of

this uplift cannot be quantified but is undoubtedly small (no more

than 15 m) since the reef could not have been formed at a great depth and is now exposed only a few meters above sea level at its

highest point.

The planktonic foraminiferal dating of the Moin Clay Member of

the Rio Banano Formation cannot be refined any further than upper

Pleistocene. It is tempting to try to correlate this sediment package

with the Sangamon interglacial period, which was the warmest of the

interglacial periods (Erickson and Wollin, 1968; Erickson, et.al., 196M although the longer Yarmouth interglacial could have allowed

more complete melting of the glaciers and thus a higher sea level.

Since both of these interglacial periods are beyond the capabilities

of radiocarbon dating, neither of these suggestions can be proven.

Future research may provide the biostratigraphic detail needed for

78

more refined upper Neogene zonation, but that detail does not yet

exist.

The presence of down-thrown fault blocks on either side of the

Limon peninsula following the uplift mentioned above has allowed the

basins formed to continue as sediment traps, maintaining the high

Limon block in a sediment-starved condition, except where local

streams are eroding older clastic sediments.

The epeiric uplift deduced above from the exposure of the coral

overlying the Moin Clay Member was also probably the cause of the

extension into the area of the fluviatile sediments of the Suretka

Conglomerate. Previously, paleoecologic evidence had indicated that

deposition in the map area was almost entirely marine with the

paleoshoreline being further west. The epeiric uplift moved the

shoreline to its present position, forcing the streams in the area

to lengthen and form fluviatile deposits in the Rio Madre area, as

well, possibly, as other areas along the coast. The large size of

the particles present and the sedimentary structures outlined above

in the Stratigraphy section suggest that the depositing agent for

the Suretka Conglomerate was a braided stream. The lateral continuity

between weathered Suretka and the modern flood plain of the Rio Chirripo,

which air photos show to be braided, indicates that both may have

been formed by the same stream which gradually migrated to the northwest.

This epeiric uplift may also account for the series of folds

occurring in the Empalme Moin-Moin area in the Rio Banano Moin Clay

Member. Slight differences in the local magnitude of this uplift

79

could have formed these broad folds. They could also have been

formed through gravity sliding of the still-soft sediments following

this uplift. A third explanation can be found in field indications

which suggest that these folds may be due to differential compaction

between the competent Rio Banano reef facies and the incompetent

Moin Clay Member of the Rio Banano Formation which overlies these

reefs. The greater majority of the dip measurements taken in this

part of the map area were taken in the Moin Clay Member sediments,

giving some credence to the differential compaction explanation.

The closely-detailed structural field mapping needed to resolve this

question was not done at the time that the initial mapping was done

since this problem was not recognized at that time. Since the data

needed to resolve the problem are not available, all that can be

said concerning the origin of these folds is that any or all of the

three processes outlined could be responsible for these features.

The series of stratigraphic sequences outlined above in the

Summary of Central American Geology between Panama, southern Costa

Rica, northern Costa Rica, and the Limon area may be more closely

related than is immediately apparent. Examination of the distance

to the nearest uplift area shows that the Limon area would be

situated the farthest from its uplift axis, the Cordillera de

Talamanca (100 km). The others are closer (50-60 km) to inland

uplift areas. Comparison of the length of the hiatus represented

by the unconformity in that area with the distance to the uplift axis

suggests that an offlap relationship may exist between these four

areas.

80

This offlap relationship could be generated by an uplift causing

regional shallowing, deforming the areas closer to the axis of

uplift to a greater extent than more remote areas. Those areas

closest to the axis of uplift would be exposed to erosion, producing

an angular unconformity between pre-uplift rocks and later-deposited

shallow marine sediments. This unconformity would gradually be

reduced in importance away from the axis of uplift, finally becoming

an inconspicuous bedding plane disconformity farther offshore. The

age of the sediments immediately beneath this unconformity would

become younger as the distance from the uplift axis increased

since the amount of section removed through erosion would be less.

The apparent transgressive nature of the Uscari-Gatun

unconformity would fit closely with this model. The greatest time

gap (the middle Miocene) occurs in Panama, where the outcrop area

is also the closest to the area of uplift. The gap across the

unconformity becomes of lesser importance in the Rio Sixaola and Rio

Reventazon areas where the Talamancan source areas are further away.

The Limon area, comprised of outcrops located in an even more remote

position from any uplift axis, has no apparent unconformity between

the deep and shallow marine deposits of the Uscari and Rio Banano

Formations.

These broad regional relationships may be complicated in

detail by slightly different times of uplift in the widespread areas

tinder consideration, but the model does explain many of the stratigraphic

differences observed.

BIBLIOGRAPHY

Akers, W.H., 1972; Planktonic Foraminifera and Biostratigraphy of some Neogene Formations, Northern Florida and Atlantic Coastal Plain; Tulane Studies in Geology and Paleontology, v. 9, no. 1-1, lUo p.

Albers, C.C., 1966; Foraminiferal Ecological Zones of the Gulf Coast; Proceedings, GCAGS, pp. 3^5-3U8.

Bandy, O.L., 1951; Distribution of some Shallow-water Foraminifera in the Gulf of Mexico; USGS Prof. Paper 25l-f, pp. 125-112.

Bandy, O.L., 1956; Ecology of Foraminifera in Northeastern Gulf of Mexico; USGS Prof. Paper 27l-g, pp. 179-199*

Bandy, O.L. and R.E. Arnal, 1957; Distribution of Recent Foraminifera off the West Coast of Central America; Bull. AAPG, v. ll, pp. 2037-2053.

Barker, R.W., i960; Taxonomic Notes on the Species Figured by H.B.Bradley in his Report on the Foraminifera Dredged by the H.M.S. Challanger During the Years 1873-1876; SEPM Special Publication 9>238 p.

Beard, J.H., 1969; Pleistocene Paleotemperature Record Based on Planktonic Foraminifers, Gulf of Mexico; Trans. GCAGS, pp.535-553.

Berggren, W.A., 1973; Recent Advances in Cenozoic PlanktonicForaminiferal Biostratigraphy, Biochronology, and Biogeography: Atlantic Ocean; Woods Hole Ocean. Inst. Contribution 3161, 125 p.

Berry, E.W., 1921; Tertiary Fossil Plants from Costa Rica; Proc. U.S. National Museum, v. 59? PP* I69-I85.

Blacut, G. and R.N. Kleinpell, 1969; Stratigraphic Sequence ofBenthonic Foraminifera from the La Boca Formation, Panama; Cushman Fdn. Foram. Res., v. 20, pt. 1, pp. 1-22.

Blow, W.H., 1967 (1969); Late Middle Eocene to Recent Planktonic Foraminiferal Biostratigraphy; Proc. First Int. Conf. on Planktonic Microfissils, v. 1, pp. 199- +21.

Bolli, H.M., 1959; Zonation of Cretaceous to Pliocene Marine Sediments Based on Planktonic Foraminifera; Bol. Informativo de Venezuela, pp. 17-33.

Bold, W.A., 1967; Miocene Ostracods from Costa Rica; Micropaleontology, v. 13, no. 1, pp. 75-86.

81

82

Bold, W.A., 1971; La Posicion Estratigrafica de la Formacion La Boca, Panama; III Reunion de Geologos de America Central, Actividades Generales y Resumenes, p. 31.

Bold, W.A., 1973a; Ostracoda of the La Boca Formation, Panama Canal Zone; Micropaleontology, v. 18, no. *+, pp. 1+10-1+1+2.

Bold, W.A. , 1973"b; La Posicion Estratigrafica de la Formacion La Boca, Panama; Publ. Geol. ICAITI, Ho. IV, pp. 167-170.

Cebuski, C.E., 1967; Foraminiferal Populations and Faunas in Barrier Reef and Lagoon, British Honduras; In AAPG Memoir 11, pp. 311- 327.

Dengo, G., 1962; Tectonic-Igneous Sequence in Costa Rica; GSA Buddington Volume, pp. 133-161.

Erickson, D.B. and G. Wollin, 1968; Pleistocene Climates andChronology in Deep-sea Sediments; Science, v. 162, no. 3859, pp. 1227-123*+.

Erickson, D.B. , et.al. , 196*+; The Pleistocene Epoch in Deep-sea Sediments; Science, v. l*+6, no. 361+5, PP- 723-732.

Folk, R.M., 1968; Petrology of Sedimentary Rocks; Austin, 170 p.

Gabb, W.M., l88l; Descriptions of New Species of Fossils from thePliocene Clay Beds between Limon and Moin, Costa Rica, together with notes on Previously-known Species from There and Elsewhere in the Caribbean Area; Jour. Acad. Nat. Sci. Phildelphia (2 Ser.), v. 8, pp. 3*+9-380.

Gabb, W.M., 1895; Informe Sobre la Exploracion de Talamanca Verificado Durante loe Anos 1873-187*+; Am. Inst. Fis. Mac. Costa Rica, v. 5 (1892), pp. 67-90.

Hill, R.T., 1898; The Geological History of the Isthmus of Panama and Portions of Costa Rica; Bull. Mus. Comp. Zool. Harvard Coll., v. 28, pt. 236, 21+8, 27*+.

Hitchcock, C.B. and F. Debenham, 1968; Reader’s Digest Great World Atlas; Pleasantville, N.Y., 232 p.

Hoffstetter, R. (ed.), 1962; Lexique Stratigraphique International Amerique Latine, Fash. II - America Centrale; Centre Nacional de la Recherche Scientifique, 38*+ p.

Lamb, J. and J.H. Beard, 1972; Late Neogene Planktonic Foraminifera in the Caribbean, Gulf of Mexico and Italian Stratotypes; Univ.Kansas Paleont. Inst., Article 57 (Protozoa 8), 67p.

ft83

Lehmann, E.P., 1957; Statistical Studies of Texas Gulf Coast RecentForaminiferal Facies; Micropaleontology, v. 3, no. U, pp. 325-356.

Lloyd, J.J, 1963: Tectonic History of South-Central American Orogen;In Backbone of the Americas, AAPG Memoir 2, pp. 88-100.

Lowman, S.W., 19^9; Sedimentary Facies in the Gulf Coast; Bull. AAPG, v. 33, no. 12, pp. 1939-1997.

Malfait, B.T. and M.G. Dinkleman, 1972; Cireum-Caribbean Tectonic and Igneous Activity and the Evolution of the Caribbean Plate;Bull. GSA, v. 83, pp. 251-272.

Molnar, J. and L.R. Sykes, 1967; Seismology and the New Global Tectonics; JGR, v. 73, no. l8, pp. 5855-5899.

Moore, W.E., 1957; Ecology of Recent Foraminifera in the Northern Florida Keys; Bull. AAPG, v. Ul, no. k, pp. 727-7^1.

Natland, M.L., 1933; The Temperature and Depth Distribution of Some Recent and Fossil Foraminifera in the Southern California Region; Bull. Scripps Inst. Oceanorgaphy, Technical Series, v. 3, no. 10, pp. 225-230.

Olsson, A.A., 1922; The Miocene of Northern Costa Rica; Bull. American Paleontology, v. 9, no. 39, pp. 1-309-

Parker, F.P., et_. al_., 1951; Ecology of Foraminifera from San Antonio Bay and Environs, Southwest Texas; Cushman Fdn. Foram. Research Special Publication 2, 7 -p.

Phleger, F.B. , 191*8; Studies of Foraminifera Ecology in the Northwestern Gulf of Mexico; The Micropaleontologist, v. 2, no. 2, pp. 2U-31.

Phleger, F.B., 195**; Ecology of Foraminifera and AssociatedMicro-organisms from Mississippi Sound and Environs; Bull. AAPG, v. 38, no. U, pp. 585-6U7.

Phleger, F.B., 1955; Ecology of Foraminifera in Southeastern Mississippi Delta Area; Bull. AAPG, v. 39, PP* 712-752.

Phleger, F.B., 1956; Significance of Living Foraminiferal Populations Along the Central Texas Coast; Cont. Cush. Found. Foram. Res.,v. v i i, pt. U, pp. 106-151.

Phleger, F.B. and F.L. Parker, 1951; Ecology of Foraminifera, Northwest Gulf of Mexico; GSA Memoir 1*6, 15** p.

8U

Postuma, J.A., 1966; Manual of Planktonic Foraminifera; BataafseInternationale Petroleum Maatschapping N.V. - The Hague, 83 p.

Rathburn, M.J., 1918; Decapods, Crustaceans from the Panama Region;U.S. Wat. Museum Bull. 103, pp. 123-18U.

Redfield, A.H., 1923; Petroleum Possibilities in Costa Rica; Econ. Geology, v. 18, no. 3, pp. 35^-381.

Reynolds, J. and H.V. Hover, 1970; The Nature of Interlayering in Mixed-layer Illite-Montmorillonites; Clay and Clay Minerals, v. 18, pp. 25-36.

Rivier, F., 1971; Contribucion Estratigrafica sobre la Geologia de la Cuenca de Limon, Zona de Turrialba, Costa Rica; III Reunion de Geologos de America Central, Act. Generales y Resumenes, p. U0.

Rivier, F. 1973; Contribucion Estratigrafica sobre la Geologia de la Cuenca de Limon, Zona de Turrialba, Costa Rica; Publ. Geol.ICAITI, No. IV, pp. 1U9-159.

Roberts, R. and E. Irving, 1957; Mineral Deposits of Central America; USGS Bulletin 103^, Washington, D.C., 323 p.

Selli, R. 1967; The Pliocene-Pleistocene Boundary in Italian Marine Sections and its Relationship to Continental Stratigraphies; Progress in Oceanography, v. U, pp. 67-86.

Smith, P.B., I96U; Ecology of Benthonic Species; USGS Prof. Paper U29-b, 63 p.

Taylor, G.D., 1971; Preliminary Report on the Stratigraphy ofLimon, Costa Rica; III Reunion de Geologos de America Central,Act. Generales y Resumenes, pp. 27,28.

Taylor, G.D., 1973; Preliminary Report on the Stratigraphy ofLimon, Costa Rica; Publ. Geol. ICAITI, no. IV, pp. I6I-I65.

Terry, R.A., 1956; A Geological Reconnaissance of Panama; Occas.Papers Calif. Acad. Sci., no. XXIII, k3 p.

Todd, R. and P. Bronniman, 1957; Recent Foraminifera and Thecamoebina from the Eastern Gulf of Paria; Cushman Found. Foram. Res.Special Pub. 16, pp. 8U-98.

Vaughan, T.W., 192 ; West Indian, Central American and European Miocene and Pliocene Molluscs; Bull. GSA, v. 355 PP• 867-886.

Vi ner, G.S., 1972; Physical Characteristics of Fluvial Deposits;In Recognition of Anvient Sedimentary Environments, SEPM Special Pub. 16, pp. '1-97 .

85

Warme, J.E., et.al., 1971; Trace Fossils-A Guide to Selected Localities in Pennsylvanian, Permian, Cretaceous and Tertiary Rocks of Texas and Related Papers; LSU School of Geoscience Misc. Publ. 71-1, lU8 p.

Woodring, W.P., 1957; Geology and Paleontology of the Canal Zone and Adjoining Parts of Panama; USGS Prof. Paper 306-a, pp. 1-1^5.

APPENDIX

87

Table 2 - Petrographic Summary, Uscari Shale

A) Texture1)End Member Percentages

Terrigenous materials - 88%Allochemical materials - 12%Orthochemical materials - 0%

Main rock group - impure allochemical rock (after Folk, 1968)2)Grain Size (estimated from thin section)

Mean - lOuExtreme range - clay size to 200u

(Note: This excludes fossils, which may reachlOOOu)

16-84% - clay size to 90u3) Cementing

No cementing materials were observed, The rock is held together by mutual attraction of parallel grains of clays and mica.

B) Mineral Composition1)Terrigenous component

Quartz - very fine sand and silt-sized particles(0.125-0.0078 mm) with irregular distribution; grains angular to subangular and roughly equant; extinction straight to slightly undulose (unstrained); comprises an estimated 5% of the rock

Feldspar - only orthoclase observed as very fine sand to silt-sized particles (0.125-0.0078 mm) with irregular distribution; comprises an estimates 1% of the rock

Clay minerals - comprises most of the rock (approx. 80%) with individual grains not identifyable in thin section. X-ray diffraction shows the presence of chlorite and mixed-layer montmorillonlte (65% montmorillonite)

2)Allochemical componentGlauconite - identified in some grains (less than 2%)

in thin section by its green color in both plane polarized light and under crossed nicols as well as its granular appearance; grains in the silt range and ovoid in shape

Calcite - present as foraminiferal tests comprising up to 10% of the rock (by volume estimation in thin section), distribution random, mean size around 750u (range 500-1000u)

3)Orthochemical component - none

88

Table 3 - Petrographlc Summary, Rio Banano Formation, sandstone faciesA) Texture

1) End Member Percentages (formation range)Terrigenous materials - 60-90%Allochemical materials -5-35%Orthochemical materials - 0-5%

Main rock group - fine sandy clay to muddy sand2) Grain size (ranges)

MeanFormation - 0.30-0.90 mm Type section - 0.125-0.09 mm

Extreme range - clay size to 1 mm 16-84% Range

Formation - 0.05mm - clay Type section - 0.15am-clay

Sorting (based on Inclusive Graphic Standard Deviation) Formation - very well sorted (IGS®=*0.2990) to

moderately well sorted (IGSD=O.9O50)Type section - well sorted to very well sorted

Gravel fraction - no gravel sized particles were found Sand fraction (formation range)

Percent - 98.6-62.9 Mean - 0.9mm Range - 0.5*»0.625mm

Mud fractionPercent - 1.4-37.1Silt vs. clay - 2-30% claySilt median not determined

3)Textural maturityImmature (clay percentage greater than 5%)

4)CementingSome samples show poor cementing by secondary calcite.

Most, however, have no cement with the rock being held together by a clay matrix. Those samples with secondary calcite also commonly have a low clay percentage.

B. Mineral Composition1)Terrigenous component

Quartz - grains range in size throughout the siltand sand size range with irregular distribution; grains usually subangular and roughly equant; extinction straight to slightly undulose (unstrained); comprises up to 95% of the rock.

Feldspar - both orthoclase and plagioclase observed (ratio - about 1:4 with more plagioclase) as sand-sized particles; distribution irregular; plagioclase commonly kaolinized; comprises up to 10% of the rock.

Table 3 (Continued)

Micas - very minor accessory mineral, comprises less than 1% of the rock; the few grains observed were probably biotite (high birefringence)

- Clay minerals - comprises up to 30% of the rock with individual grains unidentifyable in thin section. X-ray diffraction shows these clays to be comprised of mixed-layer montmorillonite (58-59% montmorillonite), illite and either kaolinite or chlorite or possibly both of these last two clay minerals.

2)Allochemical componentGlauconite - identified in thin section and x-ray

diffractograms from some samples. Present in low percentages (less than 5%).

Calcite - present as foraminiferal tests, ostracod valves, mollusc shells and mollusc shell fragments; distribution generally random; comprises up to 25% of the rock

3)Orthochemical componentsCalcite-present as rare cement in some samples.

Most samples show no cement although it is locally important, forming hard nodules. It is most probably derived from ground water solution of calcareous fossils.

Pyrite - present in a very few thin sections invery low percentages (much less than 1%). It is probably an alteration product of glauconite since it is found only in samples which do contain glauconite.

90

Table U - Petrographic Summary, Rio Banano Formation, conglomerate facies

A) Texture1) End member percentages

Terrigenous materials - 99%Allochemical materials - 1%Orthochemical materials - none observed

Main rock group - gravelly sand2. Grain sizes

Mean - 0.6mmExtreme range - 40mm to clay size 16-84% range - 1-0.25mm Sorting - poor (IGSD=1.063)Gravel fraction

Percent - 0-5%Mean - approximately 5mm Range - 2-40mm

Sand fractionPercent - 90-94%Mean - 0.5-0.25mm Range - 0.625-2mm

Mud fractionPercent - less than 2%Mean - not measured directly but probably in the

silt category (0.0625-0.0039mm)Range - 0.625mm - clay

3) Textural maturitySubmature - clays less than 5% but grain size

(16-84% statistic) is greater than one phi unit.4) Cementing - nearly nonexistant with the clay fraction

providing the only bonding notedB) Mineral composition

1)Terrigenous componentQuartz - grains range in size from a medium pebble

(up to 16mm in diameter) to fine silt; distribution irregular; crains compact and angular to subangular; extinction straight to slightly undulose; comprises up to 97% of the rock

Feldspar - grains range in size from 0.5mm to fine silt; distribution shows a concentration of feldspars in the coarser layers; both plagioclase and orthoclase present (x-ray diffraction shows the former to be calcic) in approximately a 1:3 ratio; grains equant and regular; comprises from 0 to 8% of the rock

Micas - very rare flakes of biotite (?) present

Table If (Continued)Clay minerals - comprised of mixed-layer

montmorillonite (60% montmorillonite), chlorite, kaolinite and ittlie; comprises no more than 2% of the rock; comcentrated in the finer portions of the facies

Rock fragments - comprises a large part of the coarse portion of the facies (up to 50%); consists of basaltic pebbles with some sandstone pebbles (similar in lithology to the Rio Banano sandstone facies) present

2) Allochemical componentCalcite - present as rare foraminiferal tests;

concentrated in the finer portions of the facies; comprises considerably less than 1% of the rock .

3) Orthochemical component - none noted

92

Table 5 - Petrographlc Summary, Rio Banano Formation, Moin Clay Member

A) Texture1) End member percentages (unit range)

Terrigenous materials- 80-90%Allochemical materials - 1-20%Orthochemical materials - none noted

Main rock group - claystone or mudstone2) Grain size (sample 1017 only)

Mean - 0.3mmExtreme range - clay size to 0.7mm16-84% range - 0.4-0.12mmSorting - moderately sorted (IGSD=-.662)

Grain Size estimated for the unit in thin section Mean - 0.0078mm (70)Extreme range - clay size to 0.12nm 16-84% range - clay size to 0.312mm (50)Sorting - poor Sand fraction

Percent - 1-20%Mean - not determined Range - l-010625mm

Mud fractionPercent - 80-90%Silt vs. clay - 30-90X clay Silt median not determined

3)Textural maturity-immature (clay percentage greater than 5%)

4) Cementing - no secondary cement was observed; theclay matrix provides the only bonding

B) Mineral compositionQuartz - grains range in size throughout the sand and

silt range with irregular distribution, grains subangular and equant, extinction straight to slightly undulose, comprises up to 51 of the rock

Feldspar - very rare grains of anorthite (composition from x-ray diffraction) showing severe kaolinization

Clay minerals - dominated by mixed-layer montmorillonite (58% montmorillonite) and kaolinite with some chlorite and illite present; comprises an estimated 30-90% of the rock

Calcite - present as foraminiferal tests, ostracod valves mollusc shells and mollusc fragments; distribution shows local layering; comprises from 1-20% of the rock; fossils show little or no dissolution by ground water

No orthochemical minerals were noted

93

Table 6 -Petrographic Summary, "Pueblo Nuevo Sands"

A) Texture1)End member percentages

Terrigenous materials - 90-99%Allochemical materials - 0.9%Orthochemical materials - 1% and less

Main rock group - sandstone2) Grain sizes

Mean - 0.18mmExtreme range - clay size to 0.5mm16-84% range - 0.25 -0.125mmSorting - very well sorted (IGSD = 0.463)Gravel fraction - none Sand fraction

Percent - 94-99%Mean 0.18mm (estimated)Range - 0.5-0.125mm

Mud fractionPercent - 3-6%Silt vs. clay - 25% clay Silt median not determined

3) Textural maturity - MatureClay percentage low, 16-84% range small (less than

10); grains subrounded to rounded4) Cementing - secondary hematite only bonding agent,

present In all samples in small quantities (up to 1% of the rock)

B) Mineral composition1) Terrigenous component

Quartz - ranges in size throughout the sand and silt range, comprises the bulk of the sand fraction; distribution random, grains rounded subrounded, roughly equant; extinction straight to slightly undulose, comprises 90-95% of the rock

Feldspar - only orthoclase observed as fine and very fine sand grains; distribution random; grains subangular; most show strong kaolinization; comprises less than 1% of the rock

Clay minerals - comprise no more than 2-3% of the rock; X-ray diffraction shows the presence of mixed layer montmorillonite (53% montmorillonite), Chlorite, kaolinite and possibly illite

2) Allochemical componentCalcite - present as foraminiferal tests and ostracod

valves with some molluscan shells and shell fragments; comprises up to 9% of the rock but is absent in many samples

9k

Table 6 (Continued)

3) Ortho chemical componentHematite - present as a coating on sand grains;

only cement present; comprises up to 1% of the rock

Kaolinite - results from the kaolinization of orthoclase and is impossible to seperate from primary kaolinite (if present), comprises less than 1% of the rock

95

Table 7 - Petrographic Summary, Suretka Conglomerate

A) Texture1)End mamber percentages

Terrigenous materials - 99-100%Allochemical materials - none Orthochemical materials - 0% to less than 1%

2) Grain size - meaningless due to the wide ranges ingrain sizes along with very rapid vertical and horizontal changes

3) Textural maturity - SubmatureClay percentage less than 5% but the 16-84% range is probably greater then one phi

4) Cementing - some samples show hematite coatings whichmay act as cement. Thin sections of some finer- grained samples show no secondary overgrowths or diagenetic interpenetrations.

B) Mineral composition1) Terrigenous component

Quartz - present in low percentages as angular grains showing straight of slightly undulose extinction; distribution confined to finer-grained (sand­sized) sediment bodies

Feldspar - orthoclase present in fine-grained (sand­sized) bodies as rare, angular grains. Plagioclase (determined by x-ray diffraction to be anorthite) common (in finer-grained bodies) as angular grains.

Rock fragments - comprises the bulk of this formation, especially the coarser-grained bodies. Most of these fragments are basaltic in nature (with plagioclase, pyroxene, amphibole and olivine graine identified in thin section) with two general types being noted; one is aphanitic and the other contains plagioclase phenocrysts up to 300u long.

Pyroxene - Comprises up to 15% of the finer, sand­sized sediment bodies as angular, elongate grains. These grains have a tendancy to be concentrated in layers with individual grains showing somewhat of a parallel orientation.

Olivine - present as rare, angular but equant grains, usually associated with concentrations of pyroxene grains in the finer portions of the formation

Clay minerals - x-ray diffraction shows the presenceof mixed-layer montmorillonite (62% montmorillonite) lllite, kaolinite and chlorite from a 62u filtrate sample from a fine-grained bed.

Table f (Continued)

2) Allochemical component - none noted3) Orthochemical component - very minor amounts of

hematite present as grain coatings in a few samples. Its distribution seems to be limited to the sand-sized sediment bodies in the formation.

PHOTOGRAPHIC PLATES

Plate 1 - Planktonic Foraminifera from the Limon Area

1,2,6 - Hastigerina aequilateralis 100X (sample 1211)

3,7,30 - Sphaeroidinella dehiscens 100X (sample 1018)

^,5,9 - Glohorotalia acostaensis pseudopima 200X (sample 1211)

8,lU,15 - Pulleniatina obliqueloculata 100X (sample 1018)10,11,12 - Globigerina bulloides 200X (sample 1018)13 - Orbulina bilobata 100X (sample 1211)

16,22,27 - Globigerinoides trilobus 100X (sample 100M

17,18 - Globigerina dutertrei 100X (sample 100U)

19,20121 - Globigerinoides sacculifer 100X (sample 1102)

25,29 - Globigerinoides conglobatus 100X (sample 1018)

26 - Sphaeroidinella dehiscens excavata 100X (sample 1018)

100

Plate 2 - Planktonic Foraminifera from the Limon Area

1 - Orbulina universa 200X (sample 1004)

2,3,7 - Globorotalia truncatulinoides (sinistral) 200X (sample 1018)

4,8,10 - Globorotalia acostaensis humerosa 200X (sample 1211)

5.6 - Globigerinoides ruber 200X (sample 1004)

9.12.13.1.6 - Sphaeroidinelopsis subdehiscens 200X (samples 1147,1148)

11,14,15 - Globoauadrina altisnira 200X (sample 1189)

.IrV.'Vk'/r

u m m

Plate 3 - Benthonic Foraminifera from the Limon Area

I,2,3 - "Cibicides" floridanus 100X (sample 11^7)

U,0 - Triloculina linneana 100X (sample 1156)5,10 - Nonion affine 200X (sample 100U)

6,7 ~ Uvigerina cf. hispida 200X (sample 1211)

8 - Plectofrondicularia floridana 100X (sample 100U)II,15 - Ammonia teccarii 200X (sample 1060)

12,16 - Lenticulina americanus 100X (sample 1190)

13,111 ,17 - Discorbis floridanus 200X (sample 1082)

18,19,20 - Siphonina pulchra 200X (sample IOOH)

103

r * *'• hifk

Plate U - Benthonic Foraminifera from the Limon Area

1 - Lagena splrata 100X (sample 1211)

2,8 - Spiroloculina soldanii 100X (sample 11*4*4)

3, *4 - Tritaxia mexicana 50X (sample 100*4)5 - Reusella atlantica 100X (sample 1019)

6,7 - Amphistegina lessoni 100X (sample 1066)

9 - Bolivina subaenariensis var. mexicana 100X (sample 1075)10 - Nodosaria albatrossi 50X (sample 11**7)

11,12 - Floralis atlanticus 20OX (sample 1019)

13,114,15 - Bigenerina irregularis 100X (sample 1158)

16,17 - Cribroelphidium gunteri 100X (sample 1029)

l8,19 - Kanzawaia concent.ricus 100X (sample 116*4)

21 - Virgulina pontoni 100X (sample 1177)22,25 - Marginulinopsis margulinoides 50X (sample 100*4)

23,214,28 - Poroeponides repandus 100X (sample 1066)

26,27 - Planulina foveolata 100X (sample 100*0

29,3*4 - Uvigerina perigrina 100X (sample 11*47)

30 - Archais compressus 100X (sample 1178)

31 - Peneroplis proteus 100X (sample ll6l)32 - Textularia panamanensis? 200X (sample 1156)

33 - Textularia conica 200X (sample 1066)

35>36,37 - Nonionella basiloba 200X (sample 1211)

Plate 5 - Benthonic Foraminifera from the Limon Area

I - Lagena tenuis 200X (sample 1039)

2,3,!* - Gyrodina multilocula 200X (sample 1211)

5 - Uvigerina flinti 200X (sample 100l*)

6,9,13 - "Cihicides" floridanus 100X (sample 111*7)

7,8,12 - Quinqueloculina sp. 200X (sample 100l*)

10,lU - Textularia mayori 100X (sample 1069)

II - Bifarina decorata 200X (sample 1019)

15,16 - Nodotaculariella atlantica 100X (sample 1082)

17,PI - Cribroelphidium poeyanum 200X (sample 1056)

18,19,20 - Pyrgo sp. 200X (sample 100l*)

m m

•V'.' jpas 'Mv. 'hmA• • a :

108

Plate 6 - Mollusca and Benthonic Foraminifera from the Limon Area

Mollusca

1,16 - Chicoreus consuela 2X (sample 1075)

2,15 - Demomurex aspella 2X (Glades Unit, Belle Glade, Florida)

3,U - Voluta virescens 2X (sample 1066)

5,11 - Voluta virescens 2X (sample 1086)

6,8 - Chicoreus moinensis (holotype) 2X (sample 1086)

7,13 - Conus mayei 2X (sample 1075)

9,lU - Demomurex aspella 2X (Empalme Moin Area)10,17 - Conus recognltus 2X (sample 1086)

.12 - Mitra swainsone var. limonensis 2X (sample 1010)

18 - Murex olssoni (holotype) 2X (sample 1010)19.21 - Sconsia striata 2X (sample 1010)

21.22 - Voluta alfaroi 2X (sample 1030)

23,25 - Drillia macilenta 2X (sample 1010)

2h,26 - Fusinus miocosmus 2X (Empalme Moin Area)

27 - Voluta virescens 2X (sample 1086) (photographed in ultraviolet light to show color banding)

Foraminifera

28,29 - Spirillina decorata 90X (sample 1177)

30 - Textularia conica 90X (sample 1066)

31 - Kodosaria subsoluta 1+5X (sample lll+8)32 - Textularia conica 90X (sample 1066)

ppPP||fii

‘jmrtfc

110

Plate 7 - Photographs of Limon Area Outcrops: Suretka Conglomerate and Uscari Shale

Top - Typical outcrop of the Suretka Conglomerate showing the rapid vertical changes in lithology found in that formation. Photograph taken of an outcrop near Sandoval.

Bottom - Weathered outcrop of Uscari Shale demonstrating the fissility which developes upon weathering. This outcrop is located on the north bank of the Rio Banano at sample location 1150.

112

Plate 8 - Photographs of Limon Area Outcrops: Rio Banano Formation, sandstone and reef facies

Top - Coral pinnacle of the Rio Banano reef facies penetrating overlying clastic rocks. These overlying sediments are too badly weathered to determine their lithology but they are closely related laterally with sediments of the Rio Banano sandstone facies. Photograph taken in the Q. Chocolate valley.

Bottom - Fresh exposure of Rio Banano sandstone facies showing reef derbis intermixed with the sandstone. This reef detritus evidently came from a large reef approximately ItO m from this outcrop. This roadcut occurrs at the top of the hill north and east from the Q. Chocolate valley.

l ilt

Plate 9 - Photographs of Limon Area Outcrops: Rio Banano sandstone facies and "Pueblo Nuevo Sands"

Top - This view shows the contact between the Rio Banano sandstone facies (highly fossiliferous [mollusk fragments] at this location) and the "Pueblo Nuevo Sands" with the "Pueblo Nuevo Sands" being on top. This outcrop is formed by a railroad cut between Limon'and Empalme Moin.

Bottom - Photograph from the Q. Chocolate area showing coarse, ripple-marked sandstone overlain by a fine silty clay. Outcrop occurrs in the Rio Banano sandstone facies.

C

116

VITA

Gilbert Dunlap Taylor was born on September 21, 19 l* in Sharon,

Pa., the son of Mr. and Mrs. Gilbert Taylor, Sr. He received his

secondary education in the Sharon Public School System, graduating from

Sharon High School in 1962. He then went to Thiel College and received

a Bachelor of Arts degree in zoology in 196*6. He went to the University

of Illinois for graduate study in geology and as a teaching assistant

in introductory geology courses. After two years there, he left Illinois

to attend Louisiana State University for further graduate training in

geology. He completed his Master of Science degree at the University of

Illinois in 1971 with a thesis entitled The Conodonts of the Mans field

and Brazil Formations (Morrowan) of the Illinois Basin. While a student

at L.S.U., he served as a teaching assistant in both introductory and

advanced geology and paleontology courses.

In 1972, he left L.S.U. to accept a position as a Research Geologist

at the Mobil Field Research Laboratory in Dallas, Texas. After 9

months, he was transferred to the Mobil Exploration Services Center as

a Senior Paleontologist, a position which he still holds.

In February of 1975» he married the former Mary Elizabeth Anglim

of Dallas, Texas.

EXAMINATION AND THESIS REPORT

Candidate: Gilbert Dunlap Taylor, Jr.

Major Field: G eo lo g y

T it le of Thesis: The Geology of the Limon Area of Costa Rica.

Approved:

Major Professor and Chairman

Dean of the Graduate School

EXAMINING COMMITTEE:

/ / 'f A —

Date of Examination:

March 6, 1975

FAUNAL DISTRIBUTION CHARTMOIN MEMBER - RIO BANANO FORMATION1 1 1 1 1 1 1 1 1 1 1 1 1o o o o o o o o o o o o o0 0 0 0 0 0 0 0 0 1 1 1 71 2 3 9 5 6 7 8 9 2 6 8 5

9.13.15.17. 20.25. 10.X * 7. 21.I:3.58.

19. 5. 6119.n.12.23.29.18.16. 2.26.30.31.27.28. 29. 39. 36. 38.91.92. 52. 81. 97.110.196.197.198. 217.

TAXONORBULINA u n i v e r s a UVIGERINA PERIGRINAg l o b i g e r i n o i d e s TRILOBUS c y t h e r e l l a s p .KRITHE DOLICHODEIRA CYTHEROPTERON REN2I SPHAEROIDINELLA DEHISCENS 6L0B0R0TALIA TRUNCATULlNOIOES PLANULINA FOVEOLATA PARAKRITHE SP.NOQOSARIA SP.TRITAXlA MEXICANA MARGINULOPSIS MARGlNULlNOIOES p a r a k r i t h e l l a SP.KRITHE SP •BOLIVINa SUBAENARIENSIS VAR. MEXICANAMILIOLIOSMELONIS AFFINISSPHAEROrOINELLA OEHISCENS EXCAVATA SIGMOLINA SCHLUMBERGERI BOSOUETINA 7 SP.COSTA AFF. ROBINSONI ARGILLOECIA SP.PULLENIATINA OBLIOUELOCULATA GLOBOROt ALIA MENARDII LOXOCONCHA DORSOTUBERCULATA LANKESTRINA SP.s i p h o n i n a . p u l c h r a GLOBOGUaDRINA o u t e r t r e i PULLENIATINA FlNALlSs i p h o n i n a b r a d y a n a FLORALIS ATLANTICUSr e u s s e l l a a t l a n t i c a POROEPOn IDES r e p a n d u s b a i r d i a s p .RAOIMELLA EX GR. CONFRAGOSA PARACYT h ERIDEA s p . a m p h i s t e g i n a l e s s o n i GLOBIGERINA SP.PYRGO SP.ELPHIDIIJM ADVENUM ANCHISTROCHILES SP.CATIVELLA SP.CYTHEROPTERON RENZI

* *

*****

* - . * . *

***

*. * *

- - * * * *- * 1 * * ** *.m *'* » * * - * - * * - *m * e * *- - _ * ** *. *

. . . ♦- ■ T * « * * ♦

• * '«■ ♦- ** ■ • „ **

* * ** *

*«*

i w & M m ' m w ' * *3 A NO "PUEBLO NUEVO SANDS"TftVivj

S 2 * C P l M M 0 E f P H T ^ r U f * P o r Y f l N U M 3 3 . C r M . M M F i P l l l ' M U ' O ' f i T T P l 3 9 . F L U 9 A L 1 * a T u a n T J C U Sj f i . n n ^ p i n i i r n F s p f p a * n u s5 i . S r M H j - . i l M A P-JLTMMA5 6 . » e ' » s < 5 f : u a An a ^ t t c a5 7 . « p c h a m « r o * P r te s s u .s l 7 . f i Y T p r r » r i U A S O .S i . ^ A l P M f A S P .U I . p C H S S T C y T p f i f ‘♦ f c . M U S I A N A S P .? ? . P A » A r r T u r F T O F . \ %c-.^ S . s r s f U L F o r M r s S M .5 N . T E X T » I l A« r A *A Y OP T

? 0 < * . O r t I < l N l N f l S E M H U L A T A i * 9 , P A 0 T v r m A r * O R , r r : i r P A O n . ; AS O .uO < O C ‘) l a p t o t s c o l a99. NJ?M »1 -Tf A H P A P V fH A S N . L U X O C ' J N r H A F I S C M E H t .■ t f e . L O r fn c O ’ j r j . A OOP > O T l i n F ' » C l J L A T As s . c l i ' A C O r u E A s p . v » • « A i t f . w i t >’'A a n c y l yS U . M A H Q l h t U L i N A P L H N i I L A T A t.r,AJ»«A"nrYTME»TnEA*» PLTCaTa '

3 5 , ' " i l F o - U m A m .1 K C O P A T A * 5 3 . r t T H C !u i , ' A p - i A f - r ‘♦ t t . H A S S L E H T T E S C U S P l D A T i J S ‘» 7 .o C C I ' l .T 0 P Y T * iF 0 F T % SP.**.*/Mi«LT Na I -111 v L K S /»

S 9 , P F ' i T H S - l r Y T I ' E P TOF A S P .H U .M tL L U C Is V U P tt S P ,

1 1 6 . i . 0 * n r T i r< i f . S P .57.HAML<'Cl'TrttPfMt/» S«. l 4 p . l ' T » : T Y r . i r T 7 H P f » P T - ; < M .

A f i . C T T H f - ^ O P T t P d i J S P .S P . O A O . V O t Y M F l 1.1 S P .

! > H . C ' J S f A ( C T T 1 C - I S T AT A ' , 7 . r Y r - i r - i j -j a s p .

' A H . S E S t C r f w P H U S A -SM*70 .Pft 7 ACYTufPr.'H. «n.S h . C Y r : * f ;»F| J .OI ) £ a L E O N F h S l *A U . ' ^ A S t i F . M T L V ‘t i l 1 « T " Sitf •€&( t V E l i A a F F . S E m I T M A N S L U C E N S, i . . p J U L ' ^ r r T ' - . r i / r r ' F . ' . s o .7 3 » . f : A M u i : U A M J W I S71 • ,1 P' .p s ' C y T H F M F T S p a m i t c A I Q . L r t ' N P i t S f o I N A S M .77. MS lCYTon-TT* SP.7 A . C A t - ‘ ' 1 T F c S P .7H.rfT"i */)•>#, -;j.7 5 . J U A ' I K A C t T H E k K s p ,7 f l . 1.0 / »'• r r r -j a { ' i u 7 3 , r r i “ i F . < r i i n j i r n s p ,7 ( 4 , i M ' i ' V j T ' F Y P H T s 7 P .ii,ai P’-mstfmpa Lt'ssoiir UP. i.\«r»inrhf Pti.*o.,r!A

7 . * l L » » ' l t | L I ' ! « F l ’ V F o i . r . r «I S . -.L V * i S F i - i r f . r . i E S T M T I V < l l *' » 3 . - * A ^ 7 A ^ A r A s r « A r r » » * » i

i r r » i - T.»r D . c | sS S . I - A » A i :Y T k M : f I t A TSCHO MMT t 49, -t tr A iP r i J •; s»«.S A . l . A f t F w A T f | | U f S7P.‘F iI r/f r»i.‘f.M U F7/, tFM'YF STcH 5 , 0 , \ ' * n I TF v A ' O M L M i J Sf t ^ . i O ' - i f i m . r . •» TA ' .7 .< ; ) r i s l - :

1 1 9 , rA H O i IE * ; l e s 'j h I i ' o s u s7 3 . f O J . ' T ' 1 a t f , , ?H A . I* A * M t T u f P I " F A V A o H F i'H U l M U . ' f ' L r v r I ' sT'< T AT. , i A l 3 « ; i t f l f t K > M » - A M t * s t U M ! N A i s . r - • r a r e c A M j v a m . t l I t h a■*7• S L ’ ! ' ( !< »* *> f - a S P .

1 T-. r .lit.. S'.riff SP.•j . h -j l ! V I <lrt S i i H A f . N f t P l E ' i S l S V A N , H f Y l C A M A

7 9 . r Y T . i r ' i r j i I l i r / i 5 P .I i .3. *5 I * T A I- I-FC . M U S I H !)Cf,1 ) 3 , n F T C Y T i ^ t - r s p .l U b . M U H ! ANA t o IS A

7 f t . A S T F f ( T 0 r r > I if . r r * u „ A T A ♦ A . P L A T i . L L - v

1 AM . ■ Im T A .* • 1 -1Tn l l l . M A s S L f . H r U * . A F F A N G o - ' F G aI n 7 , f . Y T M r P H 7 ' ‘. I l i r T A r - 7 l ' « N , s C L f M ( . C * ( l L *9II n.PY i Sr .1 l i . H A S S L E k T O ' * S M .I I 1 , . ,' T 5 1 o f " T |l f Y P . l | S vriJT I-»•), /AO t, f LI A su.I S 3 . • r L l . ' M J l ' . ' U A A - . o y v r - 1 T M Ai i s , L O < “ c o ' ' i r H A p i s t j I u s o l a T aI I o » p :< i - Y r T i r r T - i r i r m .1 I M . P / . A f f Y T w f »■(. «rt . | ‘ )14 -|S0 >r 1 ?0 •>' IMA m Klai T ’ I: A tat A IP l.^ U H T A N A H O S M L M A

A M f i - r » s iI ' l O . r Y T - p i i n - f , / , f p * jn - « - < is i ) i f 1 IM .»* )l. 1 Jf r 7| I I A1 ? h » C H ( S M . j F i KH ? .11 ' I ' * C 1 - 4 .H I A r i > L U *

S . f t T 01 1 ' s 1 74 4 . . , L I s H- l ' lF -JJ > 5 . ' j c f i r M '.A I M r o n t /»•» J s 1 9 3 , T t * f ML AM I A ^F.AK» . ' - S I S 1 3(j. TF kTi it. A -1 A C7 I10A I 51 . < M m , ) L ' ) r t l L l i ' , A S O f l A 1T T\ i M . O P I / O P I . r r i A « - r - M F O M f l V A1 5 3 , ' l J T o u i j lL ' iF u L I - I A , l 'H « fMA

1 A . P i l L l . F - T f T T • 1A o f t T U I T L OC ’ IL A T A I 5 P . 0 A M I O J ' t ' - A G ' - « M i f S ( M A ' l Y l 9. "LO K-tO | Al I A I 5 7 . H « S M n F " l A A « F u t f L A T F M A t r s 1 3 S . "■ l l . i . f * t r T T ' - i ; 0 ' : l T l ' i r t . 7 C ' ! L A T r t o n T M f t L T s 1 3 A . - J l l . ’ p F L * C : I L I • :A s*M.I ' . M . P S F I ' l ' T f ( AT f »A • ' . / • i l i r . F H l

<»7. i»L J u i ' . « l A i ' h I ' I h i i i l E M T M E I 1 -ip.roi ii *7/. so.I M . ■•KL " > \ •; »*FF I r f s

r » . 5 . i c r ' - i r n r Y i i - r - j r t c v m i s t „1 4 l » • (£ '< « A •-1 T l s S M ,1 MM.OYT it I-,, U - 7 • S loorTTf'Ji «TU 4 1 r - ' f v f - « i > s p .1 - i r j , • • . ' O ' lO r t r , . , / \n I I L L A > M .1 ‘j l . - ( A M i v AT ( « | . iCF - TH I F Ar ,» n onj-ff.

9 0 . a ' i i r o F *•:•». t ***'»•»* »a* t ^1 e M . ' * £ »>*i;0 O| I s p p . i m - cI S 3 , ' » T S C ' H H T , V L>' jp 1 0 A l j I I S 1 9 A . - J U L I ' ; r 5f * iA ; P .i ' i 7 . r n r » [ * H i , a f « c o ' i f * r s t o c o c t a t a1 S H . - H I I U J " M T L ' I P a T A I S M , l A C M ' I C Y P M l H A S M ,

A . T P l T A V l r ' - r / J C A . A I n U . ’F ' P ' | A ^ ( T * - ' f S -H . A- I I AM J S i M P . C A T T . / r u ». < ; p ,

1,-iLUPU-OJTAL r A TMiiNCAT'ILlr'OtneS 1 W .OLOl'ljnif| TA C tASSAFOMMls fHTlOA T A p . C Y » V / i > . r S SM 1 S 3 . S I M < .7L-Nr . i l I IA A i r | L l 7 0 d i s s . s L O H io F M iN o r n E s s a c c o l i f f r1 A7 ■ U'.M Tl u r.v ■1 o A . f * t r - < £ L » - A 7 I ' i I S O S A1 M t . i I ' - I F A i l l f T f ; ' r M c-i I ;T > I ATM S

? S . C Y l o t < U n l f H . t u H F ^ ^ I 1 f>9 . *'? T 7* l-f *' f. S I M l . I S

.3, - m o , I “ Jl OP?; i s « AMO 1*1 IL I HO T OF S ? 1 , i 1Ai* A k '• T 7 * -'F S ! ' .

I T O . G L U l I U E P l H n r o F S C 0 N O L 0 B A T U S 1 71 • S - I L 1 .T s r * t A T 7 1 7 ? . I C- *1 ’■ OC vTHF o f I s c t - ,W i . - ' A M f C Y P - ' l S S - ' . lAB.MHAOLEYA SP.1 7 M , . » I S . h > •-.•f ' C Y M t i c < - * ,1 7 S , 'fA C ,»'1< YP*' ! s S P . i 7 A » p A T A C Y r w n < r *a s o ,1 7 7 , T E X T ' J L A * I A P r t N A M A t i F f . j s l S1 7A. urTTorf.vTHrnr is ao .I 7 9 , *.<M I i l • I -1A S P .1 < 3 . 1 F H T l r > l | 1 1 A CA| r t . r ,P iJ 2 ,T H lL < J C U l 1I4A L ! n N E ! a *I«p . M . ^ ' l J - j n A r -i T TFS c p ,

C Y T-4f '<£4 | A P , j L 1 r 4%7 n s , '1'J‘< I A' A SP ,1 M 3 , H A ^ C L / N r t .SM.9 1 7 , T F < T U S P .

1 2 . S I N I O l I a A S C H L N * M F H f . r R l ? t W l , A I** T I . Fl r i V t P A P I

- ^ _ a t t ^ .A u K lL A CLUK llJA N A ?

: i i u u i i u i a u m i u u i u i a i i i i U i U i U i a i U i i H i U* - - - - • - • • - • •

* • • • • ' * • * • • • . m • • • a a a a a a a a • - a * a _ 9 a . 9 a a a a 9 9 . a a* <• - • . _ - - - - • • * * • •»• A * * ‘ • ** • 4 a * a • • a a a a • * a a a a a a a • a 4 9* — • m » — « • a m <* m m >. • • • • - a ■ 9 a a a a a.a a ™ a a a a a a a a a a a a a a* - - - m • “ • - _ “ * - - “ • * • * • • • a a « a a a a a • a a - * a a a a a a a a a a a• • * m • m m m m m • a m m m m * 9 a . m * ' 0- m a a * 9 a a a a a m a a a 9 a a a a a a a a a a a a a• 4 . * . m m * • * m » * • » - m - - * « a a a a a a a 9 * • • « * • a a.a a• - • “ " “ ” “ * " • • * • • • • * « • • * • - • • • * *

• * - ‘ - - • • - - - - - - - • •" * • • * a * *

* - - . _ _. _ . __ _ _ „ . _ . a _ a a a * a a * a * a a - . a a a a a • * a• • • m m • • • m m m • m m w ■ • -* ' • • a .m • 9 a a • a a a a a a a a a a a a a a 9 a 9 9 a a a 9• * 4 • * _ • A * m * m w m m v * • • • • • a a * * a a - a - *»a a a a • a a a *• • m * - * • • •# “ « • m • m m • « m • * a a a a a • a a* * • • «• • • * • • — • • • 9 m 0 m a a a « a a

* " -• • - * ” • “ ~ ” a a a - “ “

- •

- - - *

♦ - • • • *

M M H A

*fp'livievt»|3

VNVD

IX3*

Slb'-iHl s>,

Xc

hr a -if*.j ? s m .|<AYOn tH(&?Tf;0!jrpAr;o<;A L a P T ' I T ^ C O L A PADTAHa F IS C H E H Ih n « S ‘1 T » in f V C N tA TA I S P .N C Y UI m l a h m l a t aE P T n C rt? PLTC ATA * fifX O P A T ABrtf'TIcuspinaTus t i r i s s p .IvtlHSn

r r t n f A s :> .SM .

fcp *BtHLrt s o .rr»P T*; s » \ u u s p .LA S P .E1ST AT A

■ i E a t C O N F ; i t s l « i l - I I I ' - I T H CF F .S *> IT M A N S L U C E N S rT P E a s p . b v i s .f e r |S PA»H:1SA

SM

« « * • I . . - ’V

“ • ■ • . - • • m‘ :* + '‘ • • • “ • • • • * • ; • • " * " • • ■- - - - - - - ............ * * * . * • . • • • • . . • * • *

m • ■ . . • • • • • m m • 9 • • •• . . - • . - . . • • • #' * . - • - * . •- tt * - - • ............ • « . • • A <• A “ ■ “ * - * - . * - - . - - - ■ - -- - - - - - - - - - - - - - - - - - - - - - - - - ~ - * - • - - - - - - - - * - * *

4 • • A . • * • * . * • •' • • • • . • . - . z • z z z z z «■ “ » * * “ ■- - m - « - ■ • • • m - . . . - - - - * . - . . _ - " ” “ • - " - - • - - • *- • • „ • • • * - • * * * - • • • • . . . . * . *• “ * * " • ..... - * . - - . - .... “ “

•

*“ ” * -

I E s p .

l i r n s p ,U fs i p . h L t s s n r i r

J t r P K .n » ifT A ■tWKOl.A Tft IO F S TH Tl V < ll ‘ iH A T T H M t B PC' I*-* I S P t f t TSCHOPMf | S P .r/, iErvE stcJ H IL A T llS§ ,A T A '. .~ . .M r 'S l- :lU M ti'O S U SI ?® E A VAwMEXMDi . f IITAT..LAfM IfrM fty At A ? t 7 VAi< . T.P TPA■ SM .I SP .PAF.tvflP I K‘ iS IS V AM .b n . : n .I h i i s i il o s a |S J * .

■<T n1 A F F A M G u^fS A BCI/.r?

IS v r i j T

A A 'ifvp .- lT M A►•j s t o o m s o l a T a h r - :n ,1* j ' . ) ' n s ( » 11 | p . l i - r t a Ta I t IL A I AI < i r i- ; fI f jn ~ r*s u it■ A| l » l * C 1M.TM1A T»H.U *

i f *F s K i ( M F «J - T - i r r . l l l /!•> I S ‘ H £a KJ.*'S]SS i n r :a Ba s * . l i a i |T I * f 11 t r i . - m n v il T > 4 A H 'H U in A I n i l . T J S in .lC ILATA■ lITS IMAOYI■ .f t* |,i* T f | n r .U l!C A T F .M A t.rs1 n ^ T v i r L i c ' i l a T a I f IA SM*I 'm ' l i i i i i r . r . i j

<k i t n f c ' W T* *E I

. 'is| * » C T s i» . r , 1ST,.| p .

S l ' * f » F T T r U i « T U n * 1 S SM,( > ' L L r. s p .|).>iCp .TmIPp p n I ~-ft • • A J< M) M KTP A ■p.irrpc lO P M A H IIS |P «

|i Sata'I S P .BC A; ,A1I..Si JLAPTS

f T M U N C A T N L l f ' l I O E S J rS A S S A F lP M T S °< V |lA

A IT IL I 'S d v J>ES S A C C 'iU lF f f l

».lSOSAT M P I I ;T U A T l l S HFn2IS i . n

'A ^ G t ' i J t i ' i o i n F s

h E S Cf >M R LO BA TU S T A T 'f TS s o .

- * - - •

♦ * * *

m • • •

I SP.ht>IAMAflf NS ISfts sn.

ElHElAMaI cp i.fciti n» • . - - *

A H A ? cnsATft srrusa n r s s p , LORTOAN'IS Fui.TOATA BES iiPlI '4*IU

P Al T I S P T M A

i m i m M m m m i i m m u n H m m u m i m m m mI 2 S H ? 6 7 ! 9 2 6 8 9 15 U M ? 16 T 0 5 i 7 » M H H 1 2 66 9 0 J 56 r S 0 2 1 8 0 1 2 l J H 07#PLANULlNA rgVEOLATA 9#N000SARfA SP.tt:im8tiii£iUsmow>4.0R8ULINA UNIVERSA S.MARSINUlOPSIS marginulinoides21 .PARAKRlTHE. SP.I.GLOROROtALIA TRUNCATULlNOIOESU : ™ osiES!Mii50.PARAKRITHELLA SP. 10.SPHAEROIOINELLA OEHISCENSlL&8£i8E«i5-12.SXGM0LINA SCHLUHBERGERI -.80UIWINA SUBAtNARIENSirS VAR. MEXICANAt!t«ilSh2illDI&itL.A OCHKCiNS EXCAVATAIJliroiTA FF? ROaiNSONId - j m m mitluOxJfebNHOORSOTUBERCULATA31.SIPHONINA PULCHRA SO.LAimCftfftlNA SP#29.siphonina bradyana27.6L0800UADRINA DUTERTREISilElfttfgtfWHfSlSW ANUN33.CRIBR0ELPHI0IUH GUNTERI 3M.PLORALIS ATLANTICUS • Sa.POROEPONlULS REPANOUS S6.REUSSCLI.A ATLANTICA 4b.PUR.IANA SP.41#8AIRDIA SP#•A SiiSiTCOM RESSUS52.PARACYTHEHI0EA SP.SS.XESTOLErERIS SP.aOM.O ON NA SERRiLATASg:ESS5SBhbaAE£Ag?6Si8SKAGOSAK:fcSJ8SaiS8esFBSHERIm.KANGARXNA ANCYLA AO.tfARGlNULlNA PLAWULATA JJ.GA GAMJCYTHEHI0EA7 PL1CATA

« • * •

- -----

- - - * *

**.***-

*****•-

SsIcyWIJrUrA SMAOECOBATATQEYlHtREIS SP# “—.INI

- - * ** - *- • * .

- - - - *

4tt#BASSLiRlTtS CUSPIQATUS S9#PERISS0CYTHERX0EA SP# aO.PELUUCISTOPA SP.106.LOXOCONCHA SP# 66.CYTHLK0PTER0N SP. S7#HAPLOCYTHERIOCA SP. 1S2#PTCRYG0CYTHERE IS SP.129.C0STA RFCTICOSTATA...70.PAKACYTHEROMA SP.62.CATIVELLA APF.SEMITRANSLUCENS 5fa.CTTHERELLOiaLA LEUNENSIS GO.PUNltpCYTHCRIOCA SP#69#bASSLtRlTtS MINUTOS72.CATIVELUA NAVIS 71#JUGOSOCyTHEREXS PANNOSA T?#JUCOCYThCRC1S SP.7G.CAUDITES SP#79.CYTHERURA SP.

73.CYTHERtLLOIOEA SP# 7*t#PROPONfOCYPRIS SP. dl.AHPHlSTEblNA LESSONI.lia.OUAORACtTHEHC PRODUCTA33#HAN2AwATA SIHATTONI139.CAU0ITES NJPEENSIS34.LAGENA TENUIS . ~**#PAAACVTuER1D£A TSCMOPP1142.NE0CAU0ITES SP, 90#HEMICYTHCRUHA CRANEKEYtNSIS ab#CA'JQiTES ANGULATOS it.LOJiOCONrNA NATAGOROCNSlS119#CA0qTt£s LEGUMMOSUS93.COOUIM0A SP.?SM.PAKACYThERIDEA VAMOEWBOLOI 1.SOLIVINA ftiftlAZULA*95.AMMONIA BECCAHII VAR.TUMIDA

• - - *

„ SP#. PUST'JLOSA 102.HEMICYTHERE SP.109URIANkAMiiEu ^akgomesai m m t u n & i108.SCLEK0CH1UUS 110.PYRG0 SP# KEIJI2d#RA0IMELLA SP# ss.pellucxstoma magniventrali:Wf?^?^iI§^SUL,'TA1B#PARACYThEH0MA JOHNSONI 20.PURIANA RUGIPUNCTATAit:m sa kiosk•9#CYTHEHURA AFF JOHNSONI 4#P0L1TA POLITA IMBR1ATULUMJ«bTgEn£rxna Irregularis•TEXTULARIA SEAKENSIS -ih WStaSi£, ‘il£DAN„134.SPIR0PLFCTAMHINA FLORIDANA 133#aUlNU0EL0CUL|NA HORRIOA8:S!ft!»&B£Ii M “0CUL“T''PRIMALIS iifcSStilSIS6lKiliNA t2°?SERI1. occult qcyihlre'is" angusta 41.HERMANITES SP#SygrtETXCULATUM48#CATIVELLA SP#47.ANCHiStrOCHILES SP#.......49.N0D0BACULARULLA SP.Sl.HANZANATA CQNCENTRICAjo.hosalIna flokiqanaM«KMClOALlAM)alKai.. ■.H:HSH8811B.',tf!:,',ANUS JbSUiiUBS 4f£ofimEST.OCOSTArA1S9#MACR0CYPKINA SP.160#NE0CP0N|0LS RtGULARlSckSssafohmis ronoam-K&murULrncs-ahtGEyBuifclrMSikUtii,ii§:y|?SaYSITlf«I£fgL,STHlATUSCOJOLOBMUS 5186.318141*.

m u m t ! n ; m f U t i l ! n iIf ? H it f it If ? f f f! H i i H * * *i** * * ** * * * * * * *»* * *n !? ? ?\ H u ««u11‘IXXXXIIXIXIXttttXXXIXIttXItXTtlltflTIlItXXIXXIIIIIIIIIIIXtXIIIXXII

6UNTERIICUSS*.«CU9SCLt* ATLANTIC*3?;*6i!§IliisTCOM&RESSOS92.PARACYTHEHI0EA SP. SS*XCSTOLEN£RIS SP.S9.TCXTULARIA MAYOR!204*ORI0NXNA 8ERRULATAMimsm/ir?1*159.KANGAKINA ANCYLA 40.MAM6INUL.INA PLANULATA Sl.SANGAMQCYTHERIOEA? PLICATA »»• *51? AMINA* OCCORATA H7.0CCULl0erlHk.REIS SP. fS.CYTHCRUAA StfAINI -3t:untt»l%svsei saU.PELLUClsrOPA SP. 106.LUX0C0NCHA SP.66.CYTHLKOPIERON SP, 57.HAPL0CYTHCR10EA SP.1S2.PTERT60CTTHEREIS SP.129.C0STA RECTICOSTATA67.CYTHERURA SP,AA.ACHICTThCRURA sp.7Q.PARACY THEROMA SP." ----- ‘ ‘FF.SE*ITRANSLUCENS . ... . fttofllK*1*6*».bASSLLRtTtS MIUUTUS — ----Lfl NAVIS

- • • -

* » m m -* - - • • •

• - - *

• • - •

I a nit u ■ iv.uaHERURA SP, iCVTMCfUMA _..acy theroma _62.CATIVELLA AFF.S6*».bASSLLRtTtS MIfU 72.CATIWELCA NAVIS 7I.UUGOSOCrTHEReiS PAHNQ&A Tf.JIMOCVTHCRCIS SP. 7S.CAUDITES SP.79.CYTHERURA SP.MSgfei&SSi75.CYTHEKELL0IUEA SP. 74.PR0P0NTGCYPRXS SP.<)3.han2aaaia sihattoni I39.CAU0ITES NIPEEMSIS.l*CkiI£c5ii£aiDi* tscmop.il?o;HiSlCr?iERUK«PJ(IANEKE»tNS:SiilLSiSiiMEH MAWsORDENSIS119.CAUUITLS ULSUMMOSUS 9S.coeuiKBa SP.?99.pakacyth£ridea uanoeNbuldi...91.B0LIVIIU StfU.tUL.9S.AMAUNIA BECCAHII VAR.TUMIDAxRMffiliH Ip: .mfelWiFtfPWfcWcos. •102.HEHXCVTRERE SP.loSl?URINlV4HiiKuTAOS.SCLEHOChILUS

• - - * -

• - * - -

tfcMUMMKMSi______TOMA MAGNIVENTRA2.UUOCQNCHA PUSTDORSOLATA .PMLYCTOCYTHCRE SP. LB.PARACYThENOmA OOHNSON1 jo.purianA NUGXPUNCTATAU.PURXAAA POSTULATA.pujuana matthEmsiU9.CYTHEHURA AFF JOHNSON! •POLITA POLITAjtiEeSsiEtitltiieli Ji28SlATULUMJ' "bxsenerina Ikregularis •tektularia seakensis -X3M.SPIR0PLECTAMMINA FLORIOANA“■ uecoculina HORRIOA''•'-AGMOIOES BRADY I .NA- ACOUILATCRAlXSISS.QUINttUCCOCl __

PRIMALISDROOGEKI irs.occultocytherYis a OCCULTOcYT__.41. HERMAN ITES SP.i2itiii!Sa56SS!s?y 1E.T iCUL AT UH48.CATIVELLA SP.-47.ANCHISTR0CH1LES SP. .149.N000BACULARILLLA SP. lSl.HANZAWAlA CONCENTRIC*i M S » Fi$;i0ANUS m m aaas Mo62¥iEsiocosTATA199.MACRUCYPRINA SP.160.NEOEPONIOES REGULARISii4#808ffl«8Llp CRASSAFOrtMIS R0NiJA

RU60SA16B.UEOCAUOITES TRIPlISTRIATUS 169.0RIONINA SIM1LIS. HfcEkBUSESttUKI GUQBATUS i?S:gSSiik?J8ilp5p. HUilUHifciUttiV.175.HACR0CTPR1S SP.ij!i«?f«h Ecs!iIsi Ns,silltGLBORfALI& CULTRATA 182.GL0B1GER1N0I0ES ORLIQUUS iSO.SPHAEROlQINELLOPIS SUBOEHXSCCNS 184.LENTICULINA SP. *165.LENTICUtINA CALCARiS$: Sp §gSx ^ r oRioANA

1*1

tifiMSf:191.FRaN01< ... — CULARIA SP.HCIB&tHK IiArlex -TROOINa multilo194.6YR00INA ttULTlLOCULA 197.UV1GERINA HlSPlpO-COSTATA}?l:I5SsErrELSP.BA,",ETT‘*oi*hShr?ho5£lla SP.202.TR1LOCULINA L1NNEXANA-203.AMMOBACULITCS SP. . 20A.CYYHCntlLA POLITA205.PURIAUA SP.207.TCXfULARIA SP.206.AUKILA CONRAD!209.AURXLA FLORIOANA? 210.5P1RILLINA OECDRATA 211.BAIR02A L0N6ISET0SAiii:M£fc8SHS«M0IDES SP-214.GL0B0BUL|MlNA AFFINIS 216.SPHACR00INA RULLOIOES215.bULIM2NA SPICATA

USCAR^ SHALE*AND*LOWER^R10 BANANO SANDSTONE FACIES1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1* ( M M 5 5 6 f i 7 8 8 0 8 85 6 7 B 9 0 3 a s 9 0 1 2 3 « »

TAXON, ORBULINft UNIVERSA.g l o r T g e r i n o i d e s t r i l o b u s .TEXTUl Ar IA p a n a m a n e n s i s .MILIOLId S ,PYRf,0 So..CRIBROEl PHIDIUM g u n t e r i.a m p h i s t f g i n a l e s s o n i ,NOOOBACllLARIELLA SP. iROSALINA FLORIDANA .POROEPOn IOES REPANDUS ,PUR I a n a s p ..c y t h e r e l l a s p ..BASSLERtTEs s p ..h e m i c y t h e r e s p .. CATIVELLA SP..l o x o c o n c h a s p .ppARACYTwEPIDEA Sp.•g l o b o r o t a l i a m e n a r d i i .MARGINUl OPSTS MARGlNULlNOIOESiNODOSARIA SP. „__________ _ „pSPHAEROTDIWELLOPSIS SUBDEHISCENS ,GLOBOROTALIA c u l t r a t a ^ pGLOBIGEr INOIOES CONGLOBATUS pGLOBIGEr INA s p . pHASTIGEr INA AEQUILATERALIS pFLORALIs aTl a n t i c u s .SLOBIGEr INOIDES o b l i o u u s pBRADLEYA SP..t e x t u l a r i a s e a k e n s i s .l e n t i c u l i n a SP. pGLOBIGEr INOIOES s a c c u l i f e r .••CIBICIo ES" f l o r i o a n u spPLECTOFr ONDICULARIA FLORIOANA .LENTICUl INA CALCAR pTRITAXIa MEXICANA .UVIGERIn A p e r i g r i n apQUTNOUELOCULINA SP..B0LIVINA SUBAENARIENSIS.t e x t u l a r i a c o n i c a pPARAKRITHE s p . pBOLIVINa s p ..FRONOICULARIA SP. pGLOBOQUADRINA a l t i s p i r a

s t r a t t

* * * * * ♦ * ' * * * * * * ■* “ "* " • "• * * * * V ' • «► . «•

* - * * —

“ T

VAR. MEXICANA

- * - -ONI.HANZAMAlA .HAZELINA s p ..CYTHEROPTERON SP..PULLENIATINA 0BLJQUELOCULATA PRlMALlS

.BOLIVINA SIMPLEX .GYROOINA MULTILOCULA .UVIGERIm A HISPIOO-COSTATA .s i g m o l i n a SCHLUMBERGERI

.p u l l e n i a b u l l o i d e s.SPIROLOCULINA SOLOANII .EGGERELLA BRADYI.l a g e n a t e n u i s .e c h i n o c y t h e r e i s s p ..TEXTULAr IELLA b a r r Et t i .m u n s e y e l l a s p ..COSTA SP..h e n r y h o w e l l a s p ..PURIANA AFF.PUSTULOSA .CYTHERELLA POLITA pAMMOBACULITES s p ..ARCHAIAS COMPRESSUS .REUSSICYTHERE pPENEROPlIS PROTEUS ------- * - REGUlpNEOEPONIOES JLARISpQUINQUELOCULINA HORRIDA.b i g e n e r i n a Ir r e g u l a r i s .t e x t u l a r i a s p .,l a g e n a «?p .pGLOBIGEr INOIOES RUBER .p l a n u l i n a f o v e o l a t a .o r b u l i n a b i l o b a t a,SIPHONINA BRAOYANAi H C S S H K

FACIES

l i i i i l l i i i i i i i i i l i i i i l ! i i ii 4 i i i i i l i i i4 4 4 4 4 5 5 6 6 7 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 0 0 0 0 0 0 0 1 1 1 5 6 7 8 9 0 3 8 9 9 0 1 2 3 4 6 7 8 9 0 1 2 3 5 6 7 9 0 1 2 5 6 7 8 0 1 2

4 4 4 ♦ * * ♦ • ♦ * ♦ 4t ♦ • • ♦ ♦ * * ♦ ♦ ♦ ♦ * * 4 ♦ 4 4 4 * 4 .

4 4 4 ♦ ♦ ♦ ♦ ♦ * ♦ * * * * * ♦ ♦ * * ♦ * ♦ 3H # * * * 4 ♦ 4 . 4 4 4 ..4 . 0» ♦ - - • * * * - - - - - - * . *! 04 • * - . . 44 ♦ 4 4 . 4 - 44 4 44 ♦ 44 m 44 ♦ ♦ ♦ ... * " ** •» m ♦ ♦ ' 44 " ..

' 44 ♦ 44 44 . — 4 * • ' • . . 44 4 m * -» * «4 4 ♦ 44 44 — * • mm • • * 44 • — — . * « — • . 44 - m 4* • ** * ♦ * - m • m * # • * * * . ♦ 44 • . *

4 - - • — - * ♦ • f- tm «a — * * * • - m 04 * — *

4 4* • • . - • . . ♦, * * , 44„ 44 m 4» m • 44 m >*vy<#44 4 • - — ' - - * ♦ * * ‘ • «4 « * ♦ • • * • 04 *

4 m ■* m — " • • * • - 44 • ♦ *

* * * * *

* - -* 4„ «* - -* - -* - - ** 4* ♦ . ♦ «

* ** —4 ** - 4 - - -' *" * 4 .

* * - . - 4 4 * * * * * * * * * - * *

- * • * *

* * * * * * 4 - 4 4 4 4 4 4- ~ 4 . - - - - - - - 4 - - - - 4 - '• V « - ' . - - . ' • . « m m m rn . * . .- „ * - 4 * - - - - - - * - 4 * 4 *- . . — * * 4 . - 4 — - - - — - * *

ICANA

V’ “ * - * - ■* ■ 4 4c *4c

*4c4c4c***4c*

# * «.-• » * • ' * ' * '4 * * 4c *'4 * 4c 4c - -— — . — — * . — — — 4 — — — 4 — — — 4 — *- - - 4 * * * - - - * - - - * - - - - * 4

- ~ 4c - 4c 4c * - - 4c * 4 * * ' - * * -- - * - -

4c . * ;4f4 • 4 - 4c -4« 4c. . ' « . ■

4c “ 4 - * *4c “

* ” m m* •4c - 4c 4c 4c -

4c • ♦ - « *- 4c - - - 4cm 4 « 4i • *4c * * - . *4 * . . . 4- - - 44. - 4 •- 4 4-4 .

’ 4 ■ ** — 4. — _ 4 — —. 4 4 4 4 “4» *• mi m • •. 4 4 '4 4 " -. . . . 4 -

m m m m ' m . 4 4 . . . » — . 4 4 4 '4 4 4 4» — » — . — — — — — — . . * 4 . 4 4 — * 4. 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 . 4 4 . . . . . . . . . . . . . 4 . 4 . 4 4 4. . * 4 . 4 * 4 . 4 4 • 4 # •' 4 4. . . . . . . . . . *

MALIS

- 4 - 4 - -. . . . . .4

- - 4 - * - - 4 - 4 - 4- • 4 - 4 4

. * . 4 . 4- . 4 - 4

- - 4

- — , 7_ * . .4. *-" - 4

4 - 4 - ' 4

- .4 - - - 4 4 *. . . . . . - 4 4 4. . . 4 4 4 4 . 4

;>t.J.'pmW'ii'ifc-'u •4 4 4 44 4

44 * - - - - 4 4 - - - - - 4

..4....... 4

■wpaiwii&.'t'' 1 nw ’*■. W2*4 4 — - — — “ 4

4 . - 4 4 4 - - - 4 — — — — — ■ 4

4 _♦ • 44 •

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 14 4 4 4 4 5 5 6 6 7 8 8 8 8 8 85 6 7 fl 9 0 3 0 9 9 0 1 2 3 4 6

U

TAXON4.0RBULINa UNIVERSA * * * *15.GL0r IGEp IN0IDES TRILOb US * * * *177.t e x t u l a r i a PANAMANENSIS .* - - *6.MILI0LIDS * * - *110.PYRRO So. * * - *33.CRIBROEl PHIDIUM GUNTERl * - - -51.AMPHlSTrGINA LESSONI * - - -149.N000BACHLARIELLA SP. * * - *i s o .r o s a l i n a f l o r i d a n a * * - -38.P0R0EP0NI0ES REPANDUS * - - -46.PURIANA SP. * - - -17.CYTHERELLA SP. .. . . * * - -113.RASSLERTTES SP. * - - -102.HEMTCYTHERE SP. * - - -14B.CATIVELLA SP. * - - *106.LOXOCONCHA SP. * *52.PARACYTWERIDEA Sp. *2.g l o b o r o t a l i a MENARDII * - * - * *3•MARGINUl OPSIS MARGINUl INOIDES * * - - * *9.N0D0SARIA SP. „ ' * - * • *180.SPHAEROTDINELLOPSIS SUBDEHISCENS * * * * * *181.GLOBOROTALIA CULTRATA * - * . * *170.GLOBIGERINOIDES COWGLOBATUS 97.GL0RIGERINA SP. * * * «, * * - - *137.HASTIGERINA AEQUILATERAl IS * - - - - = _ -34.FL0RALIS ATLANTlCUS * -182.SL0BIGERIN0IDES OBLIOUUS * -•BRADLEYA SP. . * *•TEXTULARIA s e a k e n s i s *LENTICULINA s p . . *

g l o b i g e r i n o i d e s s a c c u l i f e r *"CIBICIo ES h f l o r i o a n u s *PLECTOFr ONDICULARIA FLORIOANA *LENTICULINA c a l c a r *TRITAXIA MEXICANA *UVIGERIn A PERIGRINA *q u t n q u e l o c u l i n a s p . * -BOLIVINA SUBAENARIENSIS VAR. MEXICANA * -TEXTULARIA c o n i c a *PARAKRITHE SP. *BOLIVINA SP. *FRONDICULARIA SP. *GLOBOQUAOFINA ALTISPIRA *h a n z a w a i a s t r a t t o n i *HAZELINA SP. *CYTHEROPTERON SP. * - -PULLENIATINA OBLIQUELOCULATA PRlMALlS *BOLIVINA SIMPLEX *GYRODINA MULTILOCULA *UVIGERINA HISPIDO-COSTATA *SIGMOLIn A s c h l u m b e r g e r i *p u l l e n i a b u l l o i d e s *SPIROLOCULINA SOLDANII *EGGERELLA b r a o y i *l a g e n a t e n u i s *ECHINOCYTHEREIS s p . *TEXTOLAr IELLA BARRETTI *m u n s e y e l l a s p . *COSTA SP.HENRYHOwELLA SP. p u r i a n a a f f .p u s t u l o s aCYTHERELLA POLITA AMM09ACULITES s p .ARCHAIAS COMPRESSUS REUSSICYTHERE PENEROPl IS PROTEUS NEOEPONIOES REg OLARIS

* * * * - * * * * ** ** «*

* * * _ , . _ ** * * * * * *- - - « * . *• <» • ft ♦ * *- * - * - * - - - - * -• - - * * * - - - - - * - - - * - * >- - - _ * * - - - * * * * • » - * * .

«» ■> ft• «• — • *a. . • *

- - ** - -

* * *

184. 165* 186. 187.185. 8.13. 136. . 5.130. 21.190.191.192.83.193. 66 .135.189.194.197. 12.195.131.196.84. 172.198.199.200. 201. 103. 206. 203.37.45.154.160*133.125.207.i i 2 :7.158.29.31.36.219.95.151.216.215.

" " *, " “ ”

* * - * . - * * •

- _ * - * * - -- „ - . * * * •* - * * *

- . * . - - - *♦ j * * " * — " *“ * « * * * •

; ? - * -_ * * * * -

■* ■* * * * ’ -

**

** * * *. *

*

*QUINQUEl OCULINA h o r r i d a BIGENERINa Ir r e g u l a r i s t e x t u l a r i a s p .LAGENA «5P.g l o b i g e r i n o i d e s r u b e rPLANULINA FOVEOLATAo r b u l i n a b i l o b a t a s i p h o n i n a b r a d y a n aSIPHONIlr e u s s e l lGLOBOBUl IMINA AFFINISa m m o n i a b e c c a r i i v a r .t u m i d a h a n z a w a i a c o n c e n t r i c a s p h a e r o d i n a b u l l o i d e s b u l i m i n a s p i c a t a

**

PULCHRA ATLANTICA

* - - * * *

CO

\ *i: Ji • ;

• 1 M ** | *k 1 UH * * l f l «; i' s ’ I

1 1 l*ll i-i

I 4 i i |§ji J-. i• * *

i *ltjirr*

i *i*f if£ t*

!** i i * * i f ii• * « i i i ii *; i * i ? si• * i t . * i ii *' i * i J i• * * • ■*1 ; 'I t i t i

1 i ; i1 j i i i *

M 1 «t i £

* i ! *! i*

: ** ft ft ftft* * *

ill*:• •

i ..i •

• i •• *

* * i * i *i * : •

************* • • 111 • 11*111**1ftft

********* • i i i * i 1 ft 1 ft 1 111111II I 1 II 1 ft * 'M-PMj

******** 11 * 1* I • i i i*i ft* * 1* ft 11111I t 1 1 ftft* ft*

i • i i 1 * 11 * 1« 3 1 i i i • i 1 ft 1 11 11111119 1 1 I I ft*

i i i i 1 1 1III 1 1 « * 1 1 * 1 * * •* ft 11111II 1 1 ft I 1 * ft OU)H

• ■ i i 1 1 11 1 1 * 8 <* i i i * i ft ft* * tf 111111 1 1 1 1 1 1 ft *

i i i i i 11 i 1 1 1111 1 1 ML; 1 I I I I 1 111 1 ft1111******** 1 - ©O'**

i i i i i 11 i 1 1 11 1 11 1 9‘ 1*111 1 111 1 ft 911ft * 1 ft 1***1

i n i l *• i 1 1 11 II 1 1 « 1 (* 1 1II 1 1 « 1 II ' • ft 1ft ft *# * ft ft 1 ft 1 ( vO-J**

i i i i i • * 1 1 11 * 1* i e * * * *1 I ft 1 ft I 1» r 111 * • * * OIH

i MIH i i 1 1 11 *1 * i <i 1*1 HI I I I ! 1 1• ♦ 11111 •» * l-» OEM

i I I I I i * 1 * 11 * 1** I • I I I I • ft 1 1ft 1it 11 i i i ** UBM

i I I I I i i 1 1 ' • 1 * 1* 1 * *11*1 • ft 1 1ft 1• 111 111** OtO)M

i 1; 1 1 1 i i 1 1 1* I 1i i i .* 11*1*111 ft 1• * * i * 11 * * ■pobm

i I I I I i i 1 1 1III i i I 1 * * *1 I I I I ft ft•* ft* 1*1 * 1

* II II * i 1 1 11 1 1i i i 1 1 1*1 1 III * ft 11 * * t • i * i i CBM

•** 1 1 i i 1 1 11 1 1* i • • 11*1 ft 1 1 1* i i i i 111 *• 03 091*

1*1 1• i i * 1 1 11 • 1* i i *11*1 I I I I ft i i i «11« * * ' «£03M

i * i i i i 1 1 11 * 1* i i ft ft * • 11 1 1 ft 1 i i i* i i .**« ; o>«i*

i* i i i * 1 1 1III * i I *11*1 1 ft 1 1ft i i i * 111**

i i i i i i 1 1 11 * 1* i i *11*1 I I I I ft **»* i * i ** FO DJ-*

• * i » i i 1 1 11 * 1* I * 1 1 1*1 I ft 1 1ft ' ■ 1111** WvAl*

■ i i i »1 1 11 * 1* i * ft 1 * * 11**1 ft 1111•**

, i i i * i 1 1 11 1 1* i i ft ft 1 1 1ft ft 1 ft ft * i i i i *» 99Vfl|l

i i i 1*19 11 * 1* i i 1 ft* 1 1ft ft 1 1ft * * 11**

\» i i * 11 1 * I ft 1• i i ft ** ft 1ft 1 1 ft ft ** i •• «vol|

!i i i • • I 1 1 II • i i ■ i i »• °o|

!••• 11 • 1 • 1• i e i i * ** HO*

1 i 1 11 1 * ** •• 1 • I* *• MO*

* 1 * I'l I * 1 * * * 1*111 1 1 ft 11 i • • * i * mo*

*11 11 • • •ft I * • ft 1* 1 * ft 1 1• i i ** : 09 OM

* 1 1 • 1 1 * 1 »* • ft 1 I ft * ft* 1 i *** ■MON

• II 11 • • *1 * * • 11 ft* 1ft 11 •* 030Ml

i * * * • I 1 * * 1 * • * I 1 ft 1I • »11

’ •* • • • *• * • • I I I ft *** MHW

* * *■# ft ft ft** *• Ml-* Ml

LEGENDRECENT

LIVING REEF 'RIO BANANO RIDGE’

RECENT

UPPER ' MIOCENE

LEGEND

LIVING REEF

QUATERNARY ALLUVIUM

SURETKA CONGLOMERATE

RIO BANANO FORMATION

MOIN MEMBER

REEF FACIES

SANDSTONE FACIES

’ ’PUEBLO NUEVO” SANDS

UNDIFFERENTIATED RIO BANANO

USCARI SHALE

’RIO BANANO RIDGE"

— FAULT

>» ....... RAILROAD

ROAD

> = ( BRIDGE

* SPRING

~ V ~ FOLD AXES

)

KIL

OM

ET

ER

S

2

Legend

Read _______Railroad ................ ..

Stream

Cora! Roof

SlnkHala ~

B.-ldga

SCALE

Oam

Mein'

Sente Ro* a

Empalni*\Moln

Geographical Location Map

Llmon, Costa Rica

Liverpool

Legend

Caral Roof

SCALE

Portataor

impalmo

Geographical Location Map

Limon, Costa Rica

1234,1235

1237

1223

1247

1249125112521249

1201120212071241- 119511921195|•1242 U06 1105 1J°*.243 1194.

Sandoval

V/ I1215 121*

1061-1020 , 10J9J 1038.10)9

1044-1045, 1046"] 1013“1047.1J6®>Tff34-4 1049> 105010401041

1056— 1.058 * 104111042

1174 1171.74 /

x K T'!!•1172

1173

.1164#1162 1125

1126

MARCAR/BE

10751076

1099 1007*7“ 11121124 T-^ 1101-loeo uo91

Empilme Ik , Moin

1068*1069 1097.

1067' 1177

.1035}1036-1037V1023**1051-1055 * 1024 •*1025, 1026 •1027

Sample Location Map

LIM O N, COSTA RICA

1 2L— I I

MILES0 1 2 31 1 , 1

KILOMETERS

*1180-1191,

1045. 10461. X"1045.gorW*1 I 1033“

1047 i^Si1049'1 0 5 0 *

10401043

P if| low/1032rio2i vj'-101*1023 1020

'1051 — 1055 "1024'1025, 1026 '10271056— 1050

\

1171

1151— 1155 H 4 8 1147

1236 1150

sI

11611 1 5 9 112811601132M.114411571156

1 1 2 7

11651166

1 1 6 9116B

1179

1161

'•1162

C0

TI

(y