Evolution of some depositional models in late Carboniferous rocks of the Appalachian coal fields

International Journal of Coal Geology, 12 (1989) 259-292 259 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Evolut ion of some deposi t ional models in Late Carboni ferous rocks of the Appalachian coal f ields

J.C. FERM and G.A. WEISENFLUH

Department of Geological Sciences, University of Kentucky, Lexington, KY 40506-0059, U.S.A.

(Received March 1, 1988; revised and accepted August 1, 1988)

ABSTRACT

Ferm, J.C. and Weisenfluh, G.A., 1989. Evolution of some depositional models in Late Carboni- ferous rocks of the Appalachian coal fields. In: P.C. Lyons and B. Alpern (Editors), Peat and Coal: Origin, Facies, and Depositional Models. Int. J. Coal Geol., 12: 259-292.

Models for Carboniferous coal-bearing strata developed early in this century and consisted of vertical columns that described commonly occurring sequences of coal beds and associated rocks. These were followed by other models that expressed patterns of both vertical and lateral variation but, in those, as well as earlier models, depositional interpretation did not extend much beyond a basic marine-nonmarine dichotomy. Subsequently, depositional processes were linked to lithic components and showed that the areal distribution of these components formed a lateral, geo- morphically controlled continuum ranging from alluvial plains seaward to barrier islands. Evalu- ation of this model within a tectonic setting of rapid and differential subsidence produced by growth faulting in the southern part of the Appalachian coal fields has shown that, while depositional processes are substantially the same as those suggested by the model, the form and spatial distribution of resulting lithic components are profoundly affected by movements on contempor- aneously active subsurface structures. This leads to the conclusion that previous models are a product of depositional processes strongly controlled by their tectonic setting and that further attempts at model generation will require careful assessment of the relationships of lithic distribution to subsurface structures and amounts of data necessary to recognize them.

INTRODUCTION

The history of development of depositional models for coal-bearing Carbon- iferous rocks in the Appalachian Basin is short, spanning about 60 years. The 'coal measures' as a rock unit were recognized and mapped in the 19th century, but documentation of individual coal beds did not begin until the early 1900's. The major effort at that time, which marked intensive mining development in the bituminous coal fields, was naming, correlating, and mapping individual coal seams as well as some of the strata between them. Unfortunately, systems

0166-5162/89/$03.50 © 1989 Elsevier Science Publishers B.V.

260

of coal-bed nomenclature developed with a strong local flavor and the number of synonyms ibr correlative beds multiplied. This, combined with uncertainty about correlations, led to a tangle of stratigraphic names that, at least in some cases, has yet to be resolved. Given the effort required in resolving these problems plus the view of some authorities of the time that variation within the coal measures was basically unsystematic {e.g., Ashley, 1931 ), it is small won- der that little was accomplished toward interpreting modes of sedimem deposition.

But beginnings were made and it is the objective of this paper to trace the development and growth of some concepts of depositional environments for parts of the Appalachian coal fields and to indicate directions for future study. The starting point will be the essentially descriptive models of vertical sequences that were developed in the Illinois Basin. It will be shown that these were ancestors for a later model for the Allegheny Formation in the northern

Fig. 1. Distribution of Carboniferous rocks in eastern United States showing the major coal-bearing basins. Cross sections A-B and X- Y are on Figures 7 and 8, respectively. Modified from the Geologic Map of the U.S., King ( 1961 ) and King and Beikman { 1974 ).

261

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Fig. 2. Stratigraphic names of rock units used in this paper. (W) =West Virginia nomenclature; (K) = eastern Kentucky nomenclature. Outcrop areas of major units shown on Figure 1.

Appalachian Plateau which, although descriptive, stressed the relationship of rock units to specific depositional environments. This model will be applied to rocks of the Pocahontas and Warrior Basins, two very thick wedges of Carbon- iferous rocks in the southern Appalachian region. The results of these tests will demonstrate the effects of movements of deep-seated structures on depositional processes described for the Allegheny and will suggest a scale of observation required to detect these effects.

Figure 1 shows the outcrop of the major rock units in the Appalachian and Illinois Basins and Figure 2 shows the stratigraphic names of some of the rock units or coal beds within the Pocahontas Basin.

THE CYCLOTHEM AND OTHER MORPHOLOGICAL MODELS

Early models that led to recognition of depositional environments in the United States were devoted primarily to the establishment of the vertical se- quential arrangement of rock units. (See Merriam, 1964; Duff et al., 1967; Heckel, 1984 for excellent summaries.) The first was that of Udden (1912) who recognized a commonly recurring sequence in the coal-bearing strata in northwestern Illinois (Fig. 3A). Examination of Udden's 'cycle' shows that it consists of what is now commonly recognized as a 'coarsening-upward sequence' which resulted from progradation of sediment into a body of open water whose volume far exceeded that of sediment-bearing streams entering it. Fine- grained, further transported sediments make up the lower part of the sequence

262

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Erosional base

Fig. 3. Column models for coal-bearing rocks in western Illinois. A = Udden (1912); B = Weller (1930). Symbols on A are the same as on B. Modified from Krumbein and Sloss ( 1963, p. 536).

and provide a platform over which coarser sediment prograded. Marine fossils were found only in the fine-grained rocks in the lower part of the sequence indicating its basically regressive character. Moreover, because coal beds and underclays form the top and bottom of the sequence and the intervening rocks were probably subaqueously deposited, the total thickness of the sequence provided a rough, postcompactional depth estimate of the water body being filled. Not all of this was evident to Udden, but both he and, in Ohio, Stout (1931) clearly make the point that the process involved subsidence followed by or concurrent with sediment in-filling.

The next major attempt at characterizing depositional sequences was that of Weller (1930) and Wanless and Weller (1932). This model (Fig. 3B), also developed in western Illinois, was much more detailed than Udden's model and especially stressed the erosional surface at the base of the sandstones. These sandstones with erosional bases had been noted previously, especially in coal mines where they cut into and removed the coal, and Weller believed that they represented unconformities of regional extent. Although both Udden's 'cycle'

263

and Weller's 'cyclothem' were described from the same area, Weller's idea received greater acceptance and was later applied in the Appalachian Basin, (e.g., Cross and Arkle, 1952; Sturgeon et al., 1958; Beerbower, 1961; Gray, 1961; Branson, 1962).

Although the regional extent of the erosional surfaces proposed by Weller have been very difficult to prove, the main contribution of the cyclothem to depositional interpretations is that it described and, in a general way, interpreted correctly what is now the well-established 'fining-upward' point-bar model for channel deposits of meandering streams. Although features such as lateral accretion beds and levee deposits were not noted, major descriptive ele-

A KANSAS ILLINOIS WEST VIRGINIA

B

Limest one'~r

Fig. 4. Models for lateral variation in coal-bearing rocks. A. Regional model by Wanless (1950). B. Model for the Allegheny Formation in the northern Appalachian Basin by Ferm and Williams (1963). Outcrop area of the Allegheny Formation is shown on Figure 1.

264

ments were presented and, as will be shown, became incorporated into later models.

These early models were essentially single columns with strong emphasis placed on vertical sequences of rock types but with only general reference to lateral variation. Two subsequent models treat this subject. The first was that of Wanless ( 1950 ) who attempted to develop a pattern of lateral variat;.on for Weller's cyclothem from the Western Interior Basin, through Illinois, to the Appalachian Plateau (Fig. 4A). The Appalachian portion was based on his studies in eastern Kentucky and southern West Virginia (Wanless, 1939, 1946 ). The principal feature of this model is a steady reduction of marine strata in an eastward (landward) direction and an increase in the number of coal beds arising either by splitting of a major coal bed or by generation entirely de novo

below the split bed. Perhaps the most important aspect of this model is the thickness variation

arising from differential subsidence. The Illinois portion reflects less sediment accumulation than does the Appalachian portion, and hence, if sedimentation and subsidence were about in balance, it can be inferred that subsidence in the Appalachian Basin was greater than in Illinois. However, the lesser marine influence and fewer carbonate rocks in the Appalachian Basin also suggest that clastic sediment accumulation was probably greater than that in Illinois. The importance of the influence of subsidence on patterns of sediment distribution will become evident in following portions of this paper.

A second model describing lateral variation was suggested by Ferm and Wil- liams (1963) on the basis of their studies of the 100-m-thick Allegheny For- mation in western Pennsylvania (Figs. 1, 2). The most obvious feature of this model (Fig. 4B ) is the reconciliation of the coarsening-up and fining-up detrital sequences of the Udden and Weller models. These sequences occur side by side, and in a general way, the coarsening-upward portion was believed to represent 'seaward' deposition and the fining-upward 'landward'. These interpretations about deposition were also reflected in the 'chemically' derived sediment at the top and bottom of the model. Coal was found on the landward side, marine limestone on the seaward side, with beds of nodular, sideritic ironstone between them. The model, as drawn, showed neither transgression nor regres- sion; marine limestone, ironstone and coal occur directly above one another. In transgressive sequences, coal would be expected to be more widespread on the bottom and limestone and ironstone similarly developed on the top with a coarsening-upward sequence dominating the intervening detrital sequence. In a regressive sequence, the reverse arrangement would occur. Finally, given that one of these models would be overlain and underlain by others, a series of' 'regressive' models superimposed one upon the other would yield the common occurrence of marine limestone overlying the coal seams as in the Udden and Weller models.

The greatest contrast between this model and that of Wanless was the treat-

265

ment of the landward and seaward extremes of the rock bodies (Fig. 4). Wan- less showed increasing thickness in both directions, whereas Ferm and Wil- liams (1963) visualized 'no sediment' points with soil (underclay) at the landward end and marine water at the seaward extreme. As will be shown, this proved to be a reflection of the tectonic setting of the groups of rocks from which each model was derived.

THE ALLEGHENY MODEL

The models described above included important elements for deducing depositional environments but, for the most part, inferences at that time did not go much beyond 'peat swamp', 'marine mud', and 'channel sandstone'. In the 1960s, data concerning recent deposits of the modern Mississippi delta became available, (e.g., Fisk, 1960; Scruton, 1960; Coleman and Gagliano, 1964; Allen, 1965; Shirley, 1966; Coleman et al., 1969; Morgan, 1970; Saxena et al., 1972). Combining these data with a concurrent study of the Allegheny Formation led to a model that followed morphological lines, but placed stronger emphasis on interpretations of how the rock bodies were formed (Fig. 5). Hence, the coarsening-upward sequence in this model (C, Fig. 5 ) does not differ substantially from that of the Udden model, but, in this case, it is interpreted as a deposit of an interdistributary bay or small delta front similar to those on the lower delta plain of the Mississippi River. Similarly, Weller's fining-upward channel model can be seen at H on Figure 5, but lateral accretion in the point-bar deposits are clearly indicated as are levee deposits on the upper flanks of the channel sandstones.

A major difference between this model and that on Figure 4B, is the quart- zose, barrier-island deposit at A on Figure 5. These quartz arenites occurred only at the northern limit of the Allegheny outcrop and, although the amount of information about them was limited, it could be shown that limestones and

I LOWER OELT i PLAIN I BARRIER SANDSTONE INTERDISTRIBUTARY MOUTH BAR SAND

BAY - DELTA FRONT

UPPER DELTA PLAIN J ALLUVIAL PLAIN

I SHALLOW LAKES I FLUVIALCHANNEL I SOIL AND PONDS

~ H 15M

Fig. 5. The Allegheny model. Dots = lithic arenites; dots with " Q " - quartz arenites; triangles point toward diminishing grain size in siltstone and shale; brick=limestone; black=coal; wiggly lines = seat rock; X = sideritic ironstone; M = marine or brackish water fossils. A through H are locations on the model to which reference is made in the text. Earlier versions are in Ferm (1974) and Ferm (1975).

266

thin coals intertongue with them, and, in some cases, flint clays are found on their upper surfaces (Williams and Ferm, 1964; Ferm and Cavaroc, 1969). De- posits seaward of the barrier have been lost to erosion, but it was inferred that they would be open-water marine limestones or clays.

Another new feature of the Allegheny model was recognition of 'mouth-bar' sandstones at E (Fig. 5 ). The mineral composition of these sandstones did not differ substantially from the fluvial lithic arenites (Ferm, 1962; Flores, 1966; Pedersen, 1970; Saxena, 1971 } and, like them, were cross bedded on the scale of about 30 cm. The 'mouth-bar' sandstones differ from their fluvial counter- parts, however, in their general lack of lateral-accretion surfaces found in point- bar deposits. Also, unlike fluvial sandstones that distinctly truncate and re- move subjacent deposits, 'mouth-bar' sandstones show only minor scours on the order of a meter and intertongue laterally into surrounding fine-grained sediments.

Relationships of the mouth-bar sandstones with laterally equivalent, fine- grained rocks differ, depending on the kinds of rocks with which they intertongue. On the 'seaward' side (D, Fig. 5 ), tongues of the mouth-bar sandstone extend into the 'bay' shales at any vertical position in the sequence. Where they overlie the basal coal, the top and basal contacts are sharp, and there is no substantial change in grain size vertically through the sandstone body. In many cases these sandstones are burrowed, particularly at the top where they are often capped by a thin, nodular ironstone layer. Sandstone tongues extending into the 'bay' shales higher in the sequence are almost invariably gra- dational at the base and have a sharp upper contact. Like the lower sandstone, burrows and ironstone caps are common and, in some examples, limestones are also present.

Intertonguing of the mouth-bar sandstones with 'landward', fine-grained deposits is equally complex (G, Fig. 5). Sandstone tongues are found at any position in the sequence but are bounded at top and bottom by underclays and coal beds. The sandstones may form the coarse component of a thin, shale- dominated, coarsening- or fining-upward sequence or may occupy the entire interval from the top of one coal bed to the underclay of the next overlying coal.

The principal interpretive features to be noted in these intertonguing relationships arise from the kinds of surfaces upon which the sandstones were introduced. Where the water was shallow, or the setting was subaerial, such as where sandstone overlies coal (D and F, Fig. 5), the mode of deposition is probably similar to that of splay sands of the Mississippi Delta in which rapidly prograding, sheet-like bodies are constructed in overbank areas. In contrast, the sandstone bodies projecting from the upper part of the main body at D are probably analogous to sands deposited in the last stage of filling of interdistributary bays on the lower delta plain of the Mississippi. That the filling in Allegheny deposits was, in some cases, incomplete is shown by sandstones that

267

are burrowed and capped by ironstone or limestone. Here, the water never became sufficiently shallow for plants to take root and peat accumulation to begin. Instead, marine to freshwater faunas occupied the abandoned platform and, in some cases, the sediment supply was sufficiently low that carbonates could be precipitated.

Because this model was generated from the entire Allegheny outcrop, general facies maps could be produced and some estimate of dimensions of parts of the model could be made (Fig. 6). The 'upper delta' to 'alluvial' side of the model (G and H, Fig. 5), occurred essentially along the southern and eastern side of the outcrop (Fig. 6B), whereas the western and northern side was primarily composed of 'lower delta plain' deposits (C to E, Fig. 5, Fig. 6A ). These latter deposits were found to consist of overlapping, individual coarsening-

A

S W ~ ~ c . . . , . . . ~ : . ~ , t , , ~ NE

14°m 200 km

B

120m 8 km

Fig. 6. Models depicting differing rates of lateral variation among rock types in the Allegheny Formation. A. Western and northern outcrop. B. Southern and eastern outcrop. Outcrop areas shown on Figure 1. Symbols as on Figure 5. Note especially the change in scale on A and B. Also note offsetting in sediment bodies by delta 'switching' in A as in Gould (1970) and differential compaction and avulsion in B; similar process but different scales. A modified from Ferm (1970); B from Ferm and Cavaroc (1968) and Howell and Ferm (1980).

268

upward wedges about 20 m thick and 200 km wide whereas, in the south and east, 'alluvial to upper-delta' sandstones were about the same thickness but less laterally extensive, about 10 m thick and 20 km wide. Smaller 'lake' and splay deposits in this southeastern area, such as those at G (Fig. 5), were on the order of 4-5 km wide and 5-10 m thick.

These data supplied two significant pieces of information. The first was that the alluvial and delta plain of the Allegheny Formation was not a product of a single channel like many modern rivers, but rather consisted of a series of multiple and probably shifting channels that merged into relatively wide lower delta plains to the north and west. The second was the differing levels of control necessary to locate and generally characterize these components in these two geographically separated areas. Recognition of individual sandstone bodies along the southern outcrop would require data points with spacing of about 3 km, whereas the large lower delta plain wedges on the northwestern outcrops could be generally characterized by data points roughly 20 km apart. Less extensive features such as individual coat beds on Figure 6B would require much closer control. This point of matching data spacing to the rate of lateral variation became especially significant in the analysis of the Pocahontas and War- rior Basin deposits.

MODEL TESTING IN THE POCAHONTAS AND WARRIOR BASINS

In order to test the general applicability of the Allegheny model as a predic- tive device for lateral variation in coal-bearing strata, a number of experiments were conducted in two large Appalachian subbasins, the Pocahontas and the Warrior. The Pocahontas Basin is composed of Pottsville as well as Lower Carboniferous rocks which attain a maximum thickness of 1700 m in southern West Virginia and thin northward to roughly 30 m where they underlie the Allegheny Formation in northeastern Ohio and western Pennsylvania (Fig. t ). The Warrior Basin is located in northern Alabama and western Mississippi and its thinned northern margin is now connected to the Pocahontas Basin by a series of small outliers in southeastern Tennessee. Like the Pocahontas Basin, the coal-bearing rocks of the Warrior are assigned to the Pottsville, and this unit plus the Lower Carboniferous thicken southward to at least 2000 m as recorded in deep oil and gas wells drilled through Cretaceous strata of the Gulf Coastal Plain.

Regional testing

A cross section through the Pocahontas Basin from southern West Virginia to western Pennsylvania is shown on Figure 7. The section, which uses upper- most Pottsville and lower Allegheny strata as an approximate datum, is based on records of coal, gas and oil tests spaced about 5-10 km apart. This section

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demonstrates the rapid southward thickening of the coal-bearing strata and indicates that the thickening arises from addition of progressively older coal- bearing units. The underlying sandstones, the red, green and gray mudstones, and the Lower Carboniferous Greenbriar Limestone also thicken southward. Consistent recognition of this limestone by drillers and spacing of the data are sufficient to demonstrate a series of downward displacements of this unit that increase in magnitude toward the south. The coal beds above the Lower Car- boniferous are not shown to be displaced, but subsequent work in West Vir- ginia by Keiser et al. (1981) shows that some of the lower beds are displaced and that the displacement decreases and finally disappears upward in the section. This pattern of displacement concomitant with thickening of the section is characteristic of 'growth faulting' which occurs concurrent with sedimentation, allowing greater thicknesses of sediment to accumulate on the downthrown sides of the faults.

Within the coal-bearing part of the section (Fig. 7), several of the components of the Allegheny model (Fig. 5) can be recognized. Coal-test records show that the portions of the section that include the major coal beds also contain thinner seams separated by thin coarsening-upward sequences and thick lithic arenites, rock types indicative of an 'upper delta' to 'alluvial plain' setting (Ferm, 1974; E through H, Fig. 5). It was not possible to distinguish between fluvial and mouth-bar sandstones with the data on Figure 7, but it was assumed that both types are represented.

Separating the coal-bearing components are thick mudstone units labeled 'lower deltaic and offshore facies' on Figure 7. These sequences, when exam- ined in detail, showed a coarsening-upward pattern and some contained marine fossils. These could be recognized as belonging to the shaley portion of the 'lower delta plain' of the Allegheny model (C on Fig. 5). These thick, mudstone-dominated sequences appear to grade northward into a quartz-rich sandstone facies which underlies the barrier facies of the Allegheny Formation in western Pennsylvania (Cavaroc, 1969; Ferm and Cavaroc, 1969). Like those of the Allegheny, the underlying Pottsville quartz arenites are interpreted as barrier sands that owe their greater quartz content to reworking of lithic sands that were transported northward across the delta plain onto the shoreline. There are no 'open-marine' deposits seaward of the quartz arenites in the Allegheny (Fig. 5), but in the Pottsville (Fig. 7), mudstones and limestones with abundant marine fauna appear to represent seaward equivalents. However, because these marine shales and limestones have been assigned a Mississippian age, whereas the coal measures were regarded as Pennsylvanian, a controversy developed concerning the interpretation of the depositional setting of the quartz arenites and their relationship to the underlying shales and limestones. This controversy endures (e.g., Ettensohn and Chesnut, 1985; Rice, 1985; Etten- sohn, 1986; Rice et al., 1987).

The section across the Warrior Basin shows lithic components and distri-

274

bution patterns similar to those of the Pocahontas (Fig. 8). Groups of coal beds interbedded with thin, coarsening-upward sequences and lithic arenites characteristic of the 'upper delta plain' facies are separated by thick, marine fossil-bearing, coarsening-upward sequences similar to the Allegheny 'lower delta plain'. These grade northward into quartz arenites that are interpreted as barrier shoreline deposits (Hobday, 1969; Horne et al., 1976).

One of the primary differences between the Pocahontas and Warrior Basin sections is the thickness of the mudstone-dominated, coarsening-upward sequences separating the coal-bearing strata. In the Pocahontas, these appear to be on the order of only 20-50 m whereas in the Warrior they are 50-100 m. This strong separation of coal-bearing strata has given rise in the Warrior to a practice of designating 'coal groups' or, more recently, 'coal zones' (Lyons et al., 1985) that contain a number of individually named seams. Another major difference between the Warrior and Pocahontas is the character of the marine rocks below the quartz arenites. In the northern part of the Warrior Basin, they consist of limestones overlain by red, green and gray mudstones as are found in many areas of the Pocahontas Basin. Southward in the Warrior Basin, however, these rocks grade into thick, dark shales overlain by sandstones with a few thin coal beds (Lower Carboniferous, Floyd and Parkwood Formations; Thomas, 1974). Finally, the Warrior section differs from that of the Pocahon- tas in that the deep-seated growth faults that displace the Lower Carboniferous Limestone can be traced upward to the surface where they are represented by small ( < 10 m displacement) normal faults in the coal-bearing rocks (Weisen- fluh and Ferm, 1984).

Although the amount and quality of these data are relatively modest, they do suggest some similarities as well as significant differences between the AI- legheny model and the regional sedimentary pattern in the Pocahontas and Warrior Basins. The greatest similarity appears to be found at the seaward extremity of the coal-bearing groups of strata in the Pocahontas and Warrior Basins where one or perhaps two coal beds overlain and underlain by thick, mudstone-dominated, coarsening-upward sequences pass northward (seaward ) into quartz arenites. This appears to reproduce most clearly the arrangement of the 'lower delta' and barrier portion of the Allegheny model (A through D, Fig. 5). The greatest difference arises in the southward (landward) direction. In the Allegheny model, the 'lower delta plain' facies (C, D and E, Fig. 5 ) passes southeastward (landward) into a thinner sequence consisting of multiple beds of coal, thin coarsening-upward sequences and thick lithic arenites of the 'upper delta and alluvial plain' (E through H, Fig. 5). In both the Po- cahontas and Warrior Basins, however, the shale-dominated 'lower delta' facies persist and thicken southward (and presumably landward) and lie between 'coal zones' that have the general appearance of the Allegheny 'upper delta' to 'alluvial plain' facies. In addition, these 'upper delta' to 'alluvial' deposits, instead of thinning landward as they do in the Allegheny model, become

275

progressively thicker and acquire additional coal seams in a fashion similar to that shown by Wanless (1950). (Compare A and B on Fig. 4). These differences appear to be the result of greater subsidence in the southern parts of both the Pocahontas and the Warrior Basins and, as shown by displacement of the Lower Carboniferous Limestone, the primary mechanism of subsidence appears to be deep-seated growth faulting.

Finally, it should be noted that 'lower delta plain' is not an appropriate term for the coarsening-upward, shaley sequences separating the coal zones. Rather, they appear to be delta front and prodelta deposits upon which coal-bearing 'upper delta' to 'alluvial plain' deposits are formed. Similarly these delta plain, coal-bearing deposits cannot be attributed specifically to an 'upper delta' or 'alluvial' facies without closer examination. This is provided in the following sections that describe in more detail the pattern of facies variation in a differentially subsiding tectonic setting.

Differential subsidence and facies variation

In the regional analyses above, the greatest degree of discrimination of rock facies within the coal-bearing part of the section was simply between quartz arenites and shale-dominated vs. coal and sandstone-dominated components. In order to test more precisely the effects of greater southern subsidence on facies components of the Allegheny model, a subregional test was undertaken that consisted of facies analysis of three sections of the same stratigraphic interval from the northern (least subsiding) to the southern (most subsiding) portions of the Pocahontas Basin in eastern Kentucky. These sections, com- posited from new highway cuts and closely spaced coal-test borings, represent areas with a maximum dimension of about 10 km and include a stratigraphic interval extending from the Hazard No. 9 downward to the Hazard No. 4 coal beds (Fig. 2 ). The upper part of this interval, from the Hazard No. 9 downward to the Magoffin beds (Fig. 9 ), consists of abundant coal beds, thin coarsening- upward sequences and thick sandstones, which could be regarded as an 'upper delta' or 'alluvial plain' facies (E through H, Fig. 5 ). Beneath this interval is the Magoffin Shale, a marine fossil-bearing, shale-dominated, coarsening-upward sequence that is one of the most widespread 'marker' beds in the eastern Kentucky coal fields. Below the Magoffin and including the Hazard No. 4 seam is another group of rocks that consists of abundant coal beds, thin coarsening- upward sequences and sandstones that could be assigned to the 'upper delta' to 'alluvial plain' facies of the Allegheny model. Hence, the test interval includes two coal-bearing 'upper delta' to 'alluvial plain' units separated by a relatively thick, coarsening-upward 'lower delta plain' sequence similar to those shown on Figures 7 and 8.

The initial observation of greater subsidence in the south is confirmed. The total thickness of the interval is increased about three times with similar increases in the upper and lower coal-bearing components as well as in the coar-

276

N

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Fig. 9. Composite sections of the interval between the Hazard No. 4 and No. 9 seams at three locations shown on inset map. Symbols as on Figure 5. LDP=lower delta plain; UDP=upper delta plain. Distances below columns indicate size of area represented by composite. Data for location I from Horne (1979b); 2 from Weisenfluh and Horne (1980); 3 from coal-test borings. Correlations by Welch (1958); Outerbridge (1964,1966, 1968); Puffett (1964); Rice {1964, 1966, 1967); Seiders (1964); Mixon (1965); Prostka (1965); Prostka and Seiders (1968); Csejtey (1970, 1971 ); Danilchik ( 1977a, 1977b); Ping (1977); Connor and Flores (1978); Danilchik and Waldrop {1978); Hinrichs {1978); Hinrichs and Ping (1978); Sanchez et al. (1978) and Ward (1978).

sen ing-upward Magoff in in te rva l be tween them. Dif ferences arise, however , when the upper and lower coal -bear ing sequences are ex am in ed in detail . In the nor th , the coal-bearing in terval above the Magoff in is domina ted by s t rongly downcut t ing , fluvial sands tones wi th p r o m i n e n t la teral accre t ion beds. W h e r e sands tones have no t cut into one ano ther , r o o t - p e n e t r a t e d s i l t s tones and clay- s tones and coal beds be tween the sands tones are typical of the 'al luvial p la in ' facies. B e n e a t h these rocks and ex tend ing down to the Magoff in beds are sev-

277

eral thin coarsening-upward sequences, underclays and coals that could be associated with the 'upper delta plain' facies of the Allegheny model (G, Fig. 5).

Southward, in the central section (2, Fig. 9), this same interval, which consists of numerous coal beds and thick sandstones between the No. 9 seam and the Magoffin, also includes locally thick, coarsening-upward sequences con- taining marine fossils above the Hazard No. 8 and No. 9 seams. Above the No. 9 seam, sandstone intertongues with these marine rocks in a fashion similar to that of the thick coarsening-upward sequence and the mouth-bar sandstone of the Allegheny model (D, Fig. 5). In the southernmost section, this same interval appears to contain proportionally fewer thick sandstones and includes a number of coarsening-upward sequences. Although some of these sequences are thin, others are as thick as the Magoffin interval in the northern and central sections, and some contain marine fossil-bearing shales and limestones.

The coal-dominated sequence beneath the Magoffin shows a similar change. Although the interval is dominated by coals, underclays, and sandstones, it also contains thin coarsening-upward sequences in the north. Southward, one of these increases in thickness and contains abundant marine fossils.

The primary conclusion drawn from these data is that differential subsidence, noted in the regional analysis, is a major factor controlling lithic components of the Allegheny model. This is particularly evident in comparing the shale-dominated, coarsening-upward sequences, the thickness of which is of prime importance in differentiating fine-grained 'lower' and 'upper delta plain' deposits in the Allegheny model (C and G, Fig. 5 ). In a differentially subsiding area such as that shown on Figure 9, greater subsidence in the south evidently exceeded the sediment supply at many times, which generated a relatively large number of thick, lake or bay deposits, some inhabited by a marine fauna. The areal extent of these marine deposits is not precisely known, but at least one, now represented by the Magoffin beds, eventually covered a large portion of the eastern Kentucky coal field. Subsidence to which this event is linked was, however, much greater in the south than in the north.

Sandstone bodies record differential subsidence in a different way. The total thickness of sandstone in the south is greater than in the north, but except where an overlying sandstone has channeled into an underlying one, the thicknesses of individual bodies in north and south are not substantially different, with a maximum of about 20 m in both areas. The principal difference appears to lie in the character of the sandstone bodies. At location I (Fig. 9 ), the prom- inent basal scour and lateral accretion bedding are indicative of a fluvial setting, whereas further south, where some lateral accretion and scour do occur, lateral intertonguing of the sandstones with fine-grained, marine fossil-bearing, coarsening-upward sequences suggests mouth-bar sands that have prograded into an open-water marine to brackish setting. These observations lead to the conclusion that, except on the largest scale, the criteria for recognizing 'land-sea' positions of sedimentary environments in the Allegheny model are

278

not applicable in the rapidly subsiding Pocahontas Basin and presumably not in the Warrior. Individual lithic components such as fluvial channel and mouth- bar sandstones can be recognized and the processes that generated them are probably similar to those of the Allegheny model, but their geographic position is more strongly influenced by differential subsidence than by regional land- sea relationships.

The remaining question is the degree to which the down-to-the-south growth faults, noted in the regional analysis, can be related to variation in both thickness and character of the lithic components observed in the differentially subsiding eastern Kentucky area. The data in the latter analysis are not totally suited for this purpose as the sizes of the areas portrayed in the three columns on Figure 9 are less than 10 km across, whereas the spacing of the faults in the regional analysis appear to be on the order of 5-15 km. Hence, at best, they could encompass only one fault and only part of the adjoining fault blocks. The size of the areas in the following data sets are sufficiently large to allow examination of at least two faults spaced about 10 km apart and their effects on patterns of sediment distribution.

Growth faulting and sediment distribution

The first data set is that generated by Horne (1979b) who described rocks in large exposures along a 15-km stretch of a newly constructed highway and other nearby exposures in the vicinity of locality 1 on Figure 9. These results, summarized on Figure 10, show that a fluvial channel was diverted from a northwestward to westsouthwestward course along the downthrown side of a west-southwest-trending normal fault. The diversion here is believed to be a paleotopographic response to contemporaneous structural movement in which a small topographic scarp formed by the upthrown side of the fault was sufficient to generate a low area into which the channel was diverted. Such features have also been described by Fielding and Johnson (1987) and Bristow (1988) in northern England. The present surface expression of faulting at this im- mediate location is minor, but 2 km to the southwest along the same structural trend, a normal fault with a displacement of 30 m has been mapped from surface exposures (Ward, 1978). In the deep subsurface, this structure lies toward the northern edge of the Rome Trough as described by Sutton (1974) and Black {1986).

A second set of data used to test the effect of 'growth' faulting on the distribution of environmental components consisted of core-hole records spaced about 500-1000 m apart and of underground coal-mine data with 20-m spacing from the Pratt seam in a 22 × 26 km area in northern Alabama. Details of this study are given elsewhere (Weisenfluh, 1982; Weisenfluh and Ferm, 1984 ), and the results are shown in a paleoenvironmental reconstruction on Figure 11. The faults in this area, which at present show displacement of about 6 m at the

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surface, extend downward into the Lower Carboniferous Limestone, which has been displaced about 50 m (Fig. 8).

The rocks associated with the Pratt seam in the Pratt coal zone are coal beds of varying thickness (0.5-2 m), both mudstone- and sandstone-dominated coarsening-upward sequences 3-8 m thick, and erosive-based, fining-upward sandstones 10-15 m thick. The significance of these components is their spatial distribution relative to the faults. The thick (about 2 m) coal bodies are found in linear areas about 8 km wide on the upthrown sides of the fault blocks (Fig. 11). Toward the downthrown side, the seam thins and splits, and the intervals between the thin splits are occupied by coarsening-upward sequences.

The thick, fining-upward sandstones associated with the Pratt occur in two areas. The first is in narrow channels perpendicular to the trend of thick coal areas on the upthrown edge of the fault block. These bodies crosscut the area of thick coal, extend fanwise down the block, lose their basal scour and intertongue with the coarsening-upward sequences in a fashion similar to the mouth- bar sandstones on Figure 5. The second area where thick sandstones occur is the downthrown edge of the blocks where they form narrow (1-km-wide) bodies that extend for distances of 5-10 km parallel to the fault trace in a manner

280

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Fig. 11. Reconstruction of the depositional setting of the Pratt seam, northern Alabama. U-=up and D = down indicate relative movement on faults. Location of study area on Figure 8. From data by Weisenfluh (1982).

similar to that in Figure 10. In this narrow zone, sandstones are stacked one upon the other through an interval of about 30 m. Elsewhere on the block, sandstones are offset as they are on figure 6B.

The arrangement of components in this case is similar to that described by Horne in Kentucky (Fig. 10), except that here sandstone comprises a relatively small part of the total interval. More importantly, these data strongly suggest that the areal distribution of sandstones, thin fine-grained sequences, and thick coals is controlled by a paleotopographic setting arising from contemporaneous growth faults, the traces of which are 15-20 km apart and extend horizontally for at least 30 km. Similar effects of structures on the distribution of coal beds have been noted in other regions (Broadhurst and Simpson, 1983; Fielding, 1984; Broadhurst and French, 1986; Courel, 1988; Guion and Fielding, 1988).

The final data set, directed toward establishing the relationship of lithic components and growth faults, is a 30 × 40 km area with about 500 coal test and 21 oil and gas well records located about 10 km northeast of location 2 on Figure 9 (Figs. 12 and 13A). The stratigraphic interval shown in these data is substantially the same as that on Figure 9 and includes two coal,bearing in-

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tervals; a lower one which contains the Hazard No. 4 seam and an upper one that includes the Hazard No. 5, No. 6, No. 7 and No. 8 seams. These two coal- bearing intervals are separated by the shale-dominated, coarsening-upward Magoffin marine sequence. A cross section of the area illustrating the charac- teristics of the Hazard No. 8 to Hazard No. 4 interval is shown on the upper half of Figure 12. The general features of the Lower Carboniferous Limestone and lower strata in the deeper subsurface are shown on the lower half of the figure. The most obvious feature of the more deeply buried rocks is the down- to-the-south displacement of the limestone and lower strata in a fashion similar to that on Figures 7 and 8. The oil-test data used in this section are not sufficiently precise to define movement higher in the section, but the coal-test data on the upper half of Figure 12 suggest that these structures experienced movement at the time of deposition and influenced both the thickness and character of the coal-bearing strata.

The coal-bearing interval between the Hazard No. 5 to No. 8 seams increases in thickness southward, but most of this occurs between the No. 5 and No. 6 seams where a thick sandstone is found mainly south of the central subsurface fault. Also in the No. 5 to No. 8 interval, the Hazard No. 7 and No. 8 seams, which are the thickest in the area, appear to have their greatest thickness on upthrown sides of blocks defined by the southern and central faults (Figs. 12 and 13C). Elsewhere, both seams are thinner, and in the case of the No. 7 and the northwestern part of the No. 8 seam, thinning is accompanied by splitting as is the case in the Pratt of northern Alabama.

In the lower coal-bearing interval, which includes the Hazard No. 4 seam, a sandstone at the top of the interval (S on Fig. 12) appears to thicken rapidly on the southern (downthrown) sides of the central and southern subsurface faults, and the No. 4 seam itself appears to be displaced in the proximity of the central fault. In addition, a thick, marine fossil-bearing, coarsening-upward sequence (T on Fig. 12) found within this coal-bearing interval becomes especially thick in the general area of the southern fault. Finally, the Magoffin coarsening-upward sequence between the two coal-bearing intervals thickens southward, but is replaced by sandstone at what appears to be the downthrown sides of both the central and northern faults.

These data demonstrate that distribution patterns of thick coal beds and sandstones observed in Horne's study (1979a) and in the Pratt are repeated

Fig. 13. Maps of area of detailed study located about 10 km northeast of location 2 on Figure 9. A. Location of drill holes, surface fault traces and sections P-P ' and Q-Q' on Figure 12. B. Areas of thick sandstone overlying the Hazard No. 8 seam {labelled V on Fig. 12 ) indicated by reduced thickness of shale lying between the sandstone and the No. 8 seam. Also, areas of thick sandstone above Hazard No. 4 seam (labelled R on Fig. 12). C. Areas of thick coal in the Hazard No. 7 and No. 8 seams. Faults on B and C are derived from cross section on Figure 12 and distribution of sandstone and coal bodies.

284

here. In addition, the data show that thick portions of the No. 7 and No. 8 seams overlie each other on the upthrown sides of the subsurface growth faults and that sandstone in the upper parts of the Hazard No. 4 coal-bearing interval and in the upper part of the Magoffin coarsening-upward interval also thickens on the downthrown sides of these faults. This suggests that the effects of structure on the sedimentary setting continued at least through the time of deposition extending from the Hazard No. 4 through the Hazard No. 8.

If the faults that govern deposition of the Hazard No. 4 through No. 8 interval are essentially linear, as are those in the Pratt, it may be expected that mapping the lithologic trends described above should yield a similar linear pattern. Preliminary maps (Fig. 13B and C) show that this is not the case. Figure 13B shows the areal distribution of thicker portions of two sandstone bodies, one above the Hazard No. 8 seam and the other about 20 m above the Hazard No. 4 seam (labelled V and R, respectively on the upper half of Fig. 12). This map also shows the inferred locations of subsurface faults based on the position of the faults indicated by deep oil wells and the distribution pattern of the sandstone bodies. Areas where the sandstone body above the Haz- ard No. 4 seam is thick are relatively narrow, but have a distinctly reticulate pattern with strong east-west-oriented components on the inferred downthrown sides of the southern and central faults (upper half of Fig. 12). These east-west trends, particularly the southernmost, appear to be offset where they intersect northwest-trending sandstone bodies. In addition, a 'fan-shaped' body of sandstone in the central and north-central part of the area opens in a northward direction in a fashion similar to that shown by sandstone bodies that spread out toward the downthrown sides of fault blocks in the Pratt study (Fig. 11 ). A second, larger, fan-shaped body lies just to the east, but it generally broadens in an eastward direction. If the orientation of such bodies indicates the downthrown side of a block, then another northwest-oriented fault may lie just east of the study area.

The area of thick sandstone above the Hazard No. 8 seam is also indicated on Figure 13B by reduced thicknesses of the shale lying between the base of the sandstone and the coal seam. This shale is replaced by the overlying sandstone where the latter is particularly thick. As in the case of the R sandstone above the Hazard No. 4, the effect of the southern fault is clearly shown as is the northwest offset. The main body of sandstone seems to occupy this northwest trend to the area of the central fault where it is diverted west-southwest in a manner similar to that noted by Home on Figure 10. Although this sandstone body is much more widespread than is the R sandstone above the No. 4 seam, both bodies appear to be stacked one upon the other as would be expected if their distribution were controlled by subsurface faulting that, continuing through time, yielded minor topographic relief on successive surfaces of deposition.

Figure 13C shows the distribution of areas of thick coal in the Hazard No. 7

285

and No. 8 seams. Although the area of thick coal in the No. 7 are much smaller than those in the No. 8, these bodies, like the sandstones described above, are stacked one above the other and lie in the upthrown sides of the fault blocks. Northwestwardly, the offset of the southern fault observed in the sandstones in Figure 13B is also indicated by the coal data for the southern fault, but is not obvious elsewhere.

Some additional data for the thick bodies of No. 7 and No. 8 seams in the southwestern corner of the map is not shown but suggests that the major east- west-oriented blocks are not only offset but also that they may have been differentially tilted. In this southwestern corner, the No. 7 seam is slightly over 3 m thick and is separated from the overlying No. 8 seam of almost equal thickness by as little as 2 m of mudstone and underclay. Eastward and northward from this area both coal beds diverge and thin toward the area where the thick sandstone above the No. 8 seam trends first northwest and then southwest as though encircling the thick coal bodies (Fig. 13B, C). If the areas of thick sandstone and coal are controlled by paleotopography produced by subsurface fault blocks, it can be inferred that the highest point on this block was in the southwest and that it sloped to the east, northeast and north.

These maps on Figure 13B, C are still preliminary, but they do suggest that the down-to-the-south growth fault pattern shown on Figures 7, 8 and 12 may be more complex than formerly believed, and that the subsurface structure that influenced the deposition of the coal measures may consist of roughly east- west-oriented blocks 8-10 km by 10-15 km in which down-to-the-south movements are modified by northwest displacements. Such a reticulate pattern in the deep subsurface of eastern Kentucky is shown by Black (1986).

Pocahontas- Warrior summary

The data described above all show that the southward thickening of the rock sequence on Figures 7 through 9, appears to arise from growth faults spaced about 10 km apart and that these faults appear to be the primary mechanism for differential subsidence. Figure 12 shows thickening of 65 m across two {or three) faults over a distance of 35 km which yields an average rate of thickening of about 2 m/kin. On a more regional scale, the rate of thickening between the northern and southern sections on Figure 9 is about 3 m/kin. Hence, the regional thickening rate, although slightly greater, is on the same order of magnitude as the local rate that is known to be fault controlled. This suggests that regional differential subsidence could be entirely attributed to growth faulting. The areal distribution of thickening between sections on Figure 9, however, suggests that these increases are probably not uniform but rather are more concentrated in the south than in the north.

These thickness data indicating structural control of sedimentary volumes are also reinforced by the distribution of lithic components, particularly the

286

sandstones and coal beds. In both the Prat t and eastern Kentucky data on Figures 11 and 13C, the thickest coals were formed on the upthrown sides of fault blocks, which at the time of deposition, would have been elevated above major detrital influx. The sandstones, except where they were deposited in eroded notches on the upthrown sides of the blocks, are concentrated on the downthrown sides of the blocks where they would naturally be deposited by aqueous transport. Finally, these data show that because of the very rapid rate of variation of these lithic components within blocks, data spacing required to discover trends would be on the order of 0.5 km.

CONCLUSIONS

This history of the development of concepts of paleodepositional environments in some of the coal-bearing rocks of the eastern United States strongly suggests that the models of lithic variation that have evolved are very much 'creatures' of their tectonic setting. The setting of Udden's and Weller's models in western Illinois is nothing if not cratonic, and widespread, coarsening-upward sequences of uniform thickness can be seen to be a product of this setting. In such regions, where subsidence is modest and sediment supply is sufficient to produce rapid progradation, fluvial sandstones can be expected to supplant their predecessor mouth-bar deposits and the fluvial channel aspect will dominate.

Allegheny deposits in parts of the northern Appalachian Plateau, with some notable exceptions (Hook and Ferm, 1988), reflect a tectonic setting not totally dissimilar to that of the Illinois Basin. As a whole, the Allegheny is relatively uniform in thickness and, on its northern and western outcrop, displays a series of thick coarsening-upward sequences and channel deposits not unlike those described by Udden (1912) and Weller (1930). Along its eastern and southern outcrops, however, a thinner total section characterized by fluvial sandstones, thin coarsening-upward sequences, thick but poorly developed underclays, and thin coals suggests an approach to a landward setting in which much sediment was bypassed. This setting, located just south of the present Allegheny outcrop, is the same area found by Horne (1979a; Fig. 10) and Mer- rill (1988) to be structurally positive at times roughly contemporaneous with Allegheny deposition. Hence, the tidy land-sea environmental model described for the Allegheny could also be a product of structural control.

Testing the Allegheny model in the thick sedimentary wedges of the Potts- ville rocks of the Pocahontas and Warrior Basins has shown that differential subsidence produced by growth faulting drastically rearranges the spatial distribution of sedimentary environments and their lithic products. The processes by which these rock units are generated are probably similar to those inferred for the Allegheny model, but their thickness and distribution are structurally controlled. This information, combined with estimates of the

287

amount of data necessary to define structural effects, yields a tool that can lead to a more complete but more sophisticated understanding of the rock record.

There is a certain irony in all of this. Structures, which in the past (and even in the present) have generally been regarded as independent features that serve only to produce outcrop and subcrop areal distribution patterns of sedimentary rocks, must now be viewed as possibly integrated and interrelated components of sedimentary development. Similarly, structural geologists may find support for structural inferences from the sedimentary record, for example Dean et al. (1988). There may be important advantages in this. Where deep subsurface data are lacking or of indifferent quality and near-surface data are abundant (for example, areas of intensive coal exploration and mining), the near-surface data may be used as a clue to more deep-seated structures. Likewise, where near surface data are incomplete, high-quality subsurface data may provide clues for near-surface investigations.

The results of the studies described here raise at least as many questions about distribution patterns of sedimentary rocks as it provides answers. For example, to what degree do the same sedimentary patterns and linked structures prevail in other fine- to medium-grained clastic, shallow-water deposits, such as the Catskill and associated strata lying beneath the Carboniferous in the Appalachian region or the Jurassic and Cretaceous clastic sequences of the Rocky Mountains? What are the effects of contemporaneous structures on the distribution of the carbonates and mixed clastics and carbonates of the Lower Carboniferous in Figures 7 and 8? Also on Figures 7 and 8, how did structures affect the orthoquartzite barrier islands and their relationships to the overlying coal measures? There is no lack of problems.

Finally, in broader terms, what does this summary indicate about the status of studies of paleodepositional environments in the context of an expected general sequence of scientific investigations? Many lines of scientific inquiry proceed through an initial stage involving description and categorization with a strong qualitative emphasis. This passes into the next stage in which interrelationships are established quantitatively and supported by an empirical understanding of the processes that govern the interrelationships. This leads to a goal in which prediction and precise understanding of interrelationships are expressed in a quantitative form. In the case of paleodepositional environments of coal-bearing rocks, it would appear that we may be nearly 'half-way'. The purely descriptive phase seems to be nearing its end, and there is some rudimentary idea about interrelationships between rock bodies and the processes that bring them about. But with some notable exceptions (e.g., Duff and Walton, 1964; Preston and Henderson, 1964; Read and Dean, 1982) the quantitative aspects have lagged, and hence, predictions remain vague and the degree of certainty about them imprecise. Obviously, most of it, as our computer friends are inclined to express it, is still 'out there' somewhere.

288

ACKNOWLEDGEMENTS

J.S. Ester le , R.W. Hook , E.S. Belt , R .T . Ryder , and P.C. Lyons careful ly reviewed the m a n u s c r i p t a n d c o n t r i b u t e d i m p o r t a n t sugges t ions for its im- p r o v e m e n t and T i m Moore ass i s ted in p r e p a r i n g Figure 1. F.R. E t t e n s o h n sup- pl ied re fe rences conce rn ing the M i s s i s s i p p i a n - P e n n s y l v a n i a n b o u n d a r y con- t roversy . Some of the da t a have been con t r i bu t ed by Cyprus Coal C o m p a n y and by B H P - U t a h In t e rna t i ona l . We especia l ly w a n t to t h a n k J .R. S t aub who c o n t r i b u t e d m u c h to our p r e s e n t ideas of s t ruc tu ra l con t ro l of depos i t iona l e n v i r o n m e n t s .

REFERENCES

Allen, J.R.L., 1965. Late Quaternary Niger delta and adjoining areas; sedimentary environments and lithofacies. Bull., Am. Assoc. Pet. Geol., 49: 547-600.

Ashley, G.H., 1931. Pennsylvanian cycles in Pennsylvania. Ill. Geol. Surv., Bull., 60: 241-246. Beerbower, J.R., 1961. Origin of cyclothems of the Dunkard Group (Upper Pennsylvanian-Lower

Permian) in Pennsylvania, West Virginia and Ohio. Geol. Soc. Am. Bull., 72: 1029-1050. Black, D.F.B., 1986. Basement faulting in Kentucky. In: M.J. Aldrich and A.W. Laughlin (Edi-

tors), Proceedings of the 6th Inter. Conference on Basement Tectonics, Santa Fe, NM, Sept. 1985, pp. 125-139.

Branson, C.C., 1962. Pennsylvanian system of central Appalachians. In: C.C. Branson (Editor), Pennsylvanian System in the United States. Am. Assoc. Pet. Geol., Tulsa, OK, pp. 97-116.

Bristow, C.S., 1988. Controls on the sedimentation of the Rough Rocks Group (Namurian) from the Pennine basin of Northern England. In: B.M. Besley and G. Kelling (Editors), Sedimen- tation in a Synorogenic Basin Complex, the Upper Carboniferous of Northwest Europe. Chap- man and Hall, New York, NY, pp. 114-131.

Broadhurst, F.M. and Simpson, I.M., 1983. Syntectonic sedimentation, rifts and fault reactivation in the coal measures of Britain. J. Geol., 91: 330-337.

Broadhurst, F.M. and French, A.A., 1986. Time represented by coal seams in the coal measures of England. Int. J. Coal Geol., 6: 43-54.

Cavaroc, V.V., Jr., 1969. Geology of some lower delta plain sediments in western Pennsylvania. Ph.D. Dissertation, LA. State Univ., Baton Rouge, LA, 200 pp. (unpubl.)

Cleaves, A.W., 1983. Carboniferous terrigenous clastic facies, hydrocarbon producing zones and sandstone provenance, northern shelf of Black Warrior Basin. Trans., Gulf Coast Assoc. Geol. Soc., 33: 41-53.

Coleman, J.M. and Gagliano, S.M., 1964. Cyclic sedimentation in the Mississippi River deltaic plain. Trans., Gulf Coast Assoc. Petrol. Geol., 14: 67-80.

Coleman, J.M., Gagliano, S,M. and Morgan, J.P., 1969. Mississippi River subdeltas: natural models of deltaic sedimentation. LY. State Univ., Coastal Studies Inst. Bull., 3: 23-27.

Connor, C.W. and Flores, R.M., 1978. Geologic map of the Louisa quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1462.

Courel, L., 1988. Intramontane Stephanian and Permian coal basins of the French Massif Central; new sedimentologic data. In: B.M. Besly and G. KeUing (Editors), Sedimentation in a Syno- rogenic Basin Complex - the Upper Carboniferous of Northwest Europe. Blackie, London, pp. 153-177.

Cross, A.T. and Arkle, T., 1952. The stratigraphy, sedimentation and nomenclature of the upper

289

Pennsylvanian lower Permian (Dunkard) strata of the Appalachian area. Congr. Avan. ]~tudes. Stratigr. G~ol. Carbonif~re., C.R., 3, Heerlen, 1951, 1: 101-111.

Csejtey, B., Jr., 1970. Geologic map of the Nolansburg quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 868.

Csejtey, B., Jr., 1971. Geologic map of the Bledsoe quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 889.

Danilchik, W., 1977a. Geologic map of the Handshoe quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1372.

Danilchik, W., 1977b. Geologic map of the Tiptop quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1410.

Danilchik, W. and Waldrop, H.A., 1978. Geologic map of the Vest quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1441.

Dean, S.L., Kulander, B.R., and Skinner, J.M., 1988. Structural chronology of the Alleghanian orogeny in southeastern W.Va. Geol. Soc. Am. Bull., 100: 299-310.

Duff, P.McL.D. and Walton, E.K., 1964. Trend surface analysis of sedimentary features of the Modiolaris Zone, East Pennine coal field. In: L.M.J.U. Van Straaten (Editor), Developments in Sedimentology, 1. Elsevier, Amsterdam, pp. 114-122.

Duff, P.McL.D., Hallam, A. and Walton, E.K., 1967. Cyclic Sedimentation, Developments in Se- dimentology 10. Elsevier, Amsterdam, 280 pp.

Ettensohn, F.R., 1986. The Mississippian-Pennsylvanian transition along 1-64, northeastern Kentucky. Geol. Soc. Am., Cent. Field Guide - Southeastern Section, pp. 37-41.

Ettensohn, F.R. and Chesnut, D.R., 1985. Depositional environments and stratigraphy of the Pennington formation (upper Visean-Namurian A), east-central and eastern Kentucky, U.S.A. Dixibme Congr. Int. Stratigr. G~ol. Carbonifere, Madrid, C.R., 3: 269-283.

Ferm, J.C., 1962. Petrology of some Pennsylvanian sedimentary rocks. J. Sediment. Petrol., 32: 104-123.

Ferm, J.C., 1970. Allegheny deltaic deposits. In: J.P. Morgan (Editor), Deltaic Sedimentation - Ancient and Modern. Soc. Econ. Paleontol. Mineral., Spec. Publ., 15: 246-255.

Ferm, J.C., 1974. Carboniferous paleogeography and continental drift. Septi~me Congr. Int. Stra- tigr. G~ol. Carbonifbre, Krefeld 1971, C.R., 3: 9-25.

Ferm, J.C., 1975. Pennsylvanian cyclothems of the Appalachian plateau. In: E.D. McKee, E.J. C rosby et al. (Editors), Paleotectonic Investigations of the Pennsylvanian System in the U.S., Part If. U.S. Geol. Surv., Prof. Pap., 853: 57-64.

Ferm, J.C. and Cavaroc, V.V., Jr., 1968. A non-marine sedimentary model for the Allegheny rocks of West Virginia. In: G.dV. Klein (Editor), Late Paleozoic and Mesozoic Continental Sedi- mentation. Geol. Soc. Am., Spec. Pap., 106: 1-20.

Ferm, J.C. and Cavaroc, V.V., Jr., 1969. A field guide to Allegheny deltaic deposits in the upper Ohio Valley. Ohio Geol. Soc. and Pittsburgh Geol. Soc. Fieldtrip, 21 pp.

Ferm, J.C. and Williams, E.G., 1963. Model for cyclic sedimentation in the Appalachian Penn- sylvanian. Bull., Am. Assoc. Pet. Geol., 47: 356-357.

Fielding, C.R., 1984. A coal depositional model for the Durham Coal Measures of NE England. J. Geol. Soc. London, 141: 919-931.

Fielding, C.R. and Johnson, G.A.L., 1987. Sedimentary structures associated with extensional fault movement from the Westphalian of NE England. In: M.P. Coward, J.F. Dewey and P.L. Hancock (Editors), Continental Extensional Tectonics. Geol. Soc. London, Spec. Publ., 28: 511-516.

Fisk, H.N., 1960. Recent Mississippi River sedimentation and peat accumulation. Congr. Av. l~tudes Stratigr. Gdol. Carbonif'ere, 1958, Heerlen, C.R., pp. 187-199.

Flores, R.M., 1966. Middle Allegheny paleogeography in eastern Ohio. Ph.D. dissertation, La. State Univ., Baton Rouge, LA, 136 pp. (unpubl.).

290

Gould, H.R., 1970. The Mississippian delta complex. In: J.P. Morgan (Editor), Deltaic Sedimen. tation - Modern and Ancient. Soc. Econ. Paleontol. Mineral., Spec. Pap., 15: 3-30.

Gray, H.H., 1961. Determinants of cyclic sedimentation in Pottsville rocks near Dundee, Ohio. Ohio J. Sci., 61: 353-366.

Guion, P.D. and Fielding, C.R., 1988. Westphalian A and B sedimentation in the Pennine Basin, UK. In: B.M. Besly and G. Kelling (Editors), Sedimentation in a Synorogenic Basin Complex - the Upper Carboniferous of Northwest Europe. Blackie, London, pp. 153-177.

Heckel, P.H., 1984. Changing concepts of mid-continent Pennsylvania cyclothems, North Amer- ica. In: E.S. Belt and R.W. Macqueen (Editors), Part 3: Sedimentology and Geochemistry. Neuvi~me Congres. Int. Stratigr. Gdol. Carbonif~re, (Urbana, IL, May 17-26, 1979), Compte Rnd, pp. 535-553.

Hinrichs, E.N., 1978. Geologic map of the Noble quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1476.

Hinrichs, E.N. and Ping, R.G., 1978. Geologic Map of the Wayland quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1451.

Hobday, D.K., 1969. Upper Carboniferous shoreline systems in northern Alabama. Ph.D. dissertation, La. State Univ., Baton Rouge, LA, 75 pp. (unpubl.).

Hook, R.W. and Ferm, J.C., 1988. Paleoenvironmental controls on vertebrate-bearing abandoned channels in the Upper Carboniferous. Palaeogeogr., Palaeoclimatol., Palaeoecol., 63: 159-181.

Horne, J.C., 1979a. Sedimentary responses to contemporaneous tectonism. In: J.C. Ferm and J.C. Home (Editors), Carboniferous Depositional Environments in the Appalachian Region. Car- olina Coal Group, Univ. SC, Columbia, SC, pp. 259-265.

Home, J.C., 1979b. Geologic cross section along U.S. Highway 23 between Louisa and Paintsville, Lawrence and Johnson Counties, Ky. Geol. Cross Section GSC-2, Carolina Coal Group, Univ. SC, Columbia, SC (unpubl.).

Horne, J.C., Ferm, J.C. Saxena, R.S. and Hobday, D.K., 1976. A field guide to Carboniferous littoral deposits in the Warrior Basin. New Orleans Geol. Soc., New Orleans, LA, 80 pp.

Howell, D.J. and Ferm, J.C., 1980. Exploration model for Pennsylvanian upper delta plain coals, southwest West Virginia. Bull., Am. Assoc. Pet. Geol., 64: 938-941.

Keiser, A.F., Reppert, R.S., Blacke, B.M., Jr. and Trinkle, E.J., 1981. Low-sulfur coals of southern West Virginia: a depositional model. Trans. Soc. Min. Eng., 272: 1812-1820.

King, P.B., 1961. The subsurface Ouachita structural belt east of the Ouachita Mountain. In: P.T. Flawn, A. Goldstein, P.B. King and C.E. Weaver (Editors), The Ouachita System. Texas Bur. Econ. Geol., Publ. 6120, pp. 83-98.

King, P.B. and Beikman, H.M., 1974. Geological map of the United States. U.S. Geol. Surv. Krumbein, W.C. and Sloss, L.L., 1963. Stratigraphy and Sedimentation, 2nd Edition, Freeman

and Co., San Francisco, CA, 497 pp. Lyons, P.C., Meissner, C.R., Jr., Barwood, H.L. and Adinolfi, F.E., 1985. North American and

European megafloral correlations within the upper part of the Pottsville Formation of the Warrior Coal Field, Alabama, U.S.A. In: J.L. Escobedo et al. (Editors), Dixi~me Congr. Int. Stratigr. G~ol. Carbonifere, Madrid, Sept. 1983, C.R., 2: 203-245.

Merriam, D.F. (Editor), 1964. Symposium on Cyclic Sedimentation. Kans. State Geol. Surv., Bull. 169,636 pp.

Merrill, G.K., 1988. Marine transgression and syndepositional tectonics; Ames member (Glenslaw formation, Conemaugh group, Upper Carboniferous) near Huntington, W.Va. Southeast. Geol., 28: 153-166.

Mixon, R.B., 1965. Geologic map of the Krypton quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 389.

Morgan, J.P. (Editor), 1970. Deltaic Sedimentation - Ancient and Modern. Soc. Econ. Paleontol. Mineral., Spec. Publ., 15, Tulsa, OK, 312 pp.

Outerbridge, W.F., 1964. Geologic map of the Offutt quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 586.

291

Outerbridge, W.F., 1966. Geologic map of the Paintsville quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 495.

Outerbridge, W.F., 1968. Geologic map of the David quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 720.

Pedersen, D.E,, 1970. Petrology of some Allegheny Pennsylvanian rocks near Ashland, KY. Ph.D. dissertation, La. State Univ., Baton Rouge, LA, 118 pp. (unpubl.).

Ping, R.G., 1977. Geologic map of the Cutshin quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1424.

Preston, F.W. and Henderson, J.H., 1964. Fourier series characterization of cyclic sediments for stratigraphic correlation. In: D.F. Merriam (Editor), Symposium on Cyclic Sedimentation. Kans. Geol. Surv., Bull., 169: 415-425.

Prostka, H.J., 1965. Geologic map of the Hyden East quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 423.

Prostka, H.J. and Seiders, V.M., 1968. Geologic map of the Leatherwood quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 723.

Puffett, W.P. 1964. Geologic map of the Hazard South quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 343.

Read, W.A. and Dean, J.M., 1982. Quantitative relationships between numbers of fluvial cycles, bulk lithological composition and net subsidence in a Scottish nonmarine basin. Sedimentol- ogy, 29: 181-200.

Rice: C.L., 1964. Geologic map of the Lancer quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 347.

Rice, C.L., 1966. Geologic map of the Martin quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 563.

Rice, C.L., 1967. Geologic map of the Prestonsburg quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 461.

Rice, C.L., 1985. Terrestrial vs. marine depositional models - a new assessment of subsurface lower Pennsylvanian rocks of southwest Virginia. Geology, 13: 786-789.

Rice, C.L., Currens, J.C., Henderson, J.A. and Nolde, J.E., 1987. The Betsie shale member, a datum for exploration and stratigraphic analysis of the lower part of the Pennsylvanian in the central Appalachian basin. U.S. Geol. Surv., Bull. 1834, 17 pp.

Sanchez, J.D., Alvord, D.C. and Hayes, P.T., 1978. Geologic map of the Richardson Quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 1460.

Saxena, R.S., 1971. Petrology of some Allegheny Pennsylvanian rocks in eastern Ohio and western Pennsylvania. Ph.D. dissertation, La. State Univ., Baton Rouge, LA, 169 pp. (unpubl.).

Saxena, R.S., Ferm, J.C. and Coleman, J.M., 1972. Deltas - ancient and recent. New Orleans Geol. Soc., New Orleans, LA, 169 pp.

Scruton, P.C., 1960. Delta building and the deltaic sequence. In: F.P. Shepard et al. (Editors), Recent Sediments, Northwest Gulf of Mexico. Am. Assoc. Pet. Geol., Tulsa, OK, pp. 82-102.

Seiders, V.M., 1964. Geologic map of the Hazard North quadrangle, Ky. U.S. Geol. Surv., Geol. Quad. Map GQ 344.

Shirley, M.L. (Editor), 1966. Deltas in their Geologic Framework. Houston Geol. Soc., Houston, TX, 251 pp.

Stout, Wilbur, 1931. Pennsylvanian cycles in Ohio. Ill. Geol. Surv., Bull., 60: 195-216. Sturgeon, M.T. and Associates, 1958. The geology and mineral resources of Athens County. Ohio

Div. Geol. Surv., Bull. 57,600 pp. Sutton, E.M., 1974. Deep exploration in eastern Kentucky by the SCLAW group during the early

seventies. In: M.I. Luther (Editor), Proceedings of the Technical Sessions KY Oil and Gas Assoc. 38th Annu. Meeting, June, 1974. Ky. Geol. Surv., Ser. XI, Spec. Publ., 3: 31-44.

Thomas, W.A., 1974. Converging clastic wedges in the Mississippian of Alabama. In: G. Briggs (Editor), Carboniferous of the Southeastern U.S. Geol. Soc. Am., Spec. Pap., 148: 187-208.

292

Udden, J.A., 1912. Geology and mineral resources of the Peoria quadrangle, Illinois. U.S. Geol. Surv., Bull. 506, 103 pp.

Wanless, H.R., 1939. Pennsylvanian correlations in the Eastern Interior and southern Appala- chian coal fields. Geol. Soc. Am., Spec. Pap. 17, 130 pp.

Wanless, H.R., 1946. Pennsylvanian geology of the southern Appalachian coal field. Geol. Soc. Am., Mem. 13,162 pp.

Wanlcss, H.R., 1950. Late Paleozoic cycles of sedimentation in the U.S. Int. Geol. Cong., 18th, Great Britain, 1948, 4: 17-28.

Wanless, H.R. and Weller, J.M., 1932. Correlation and extent of Pennsylvanian cyclothems. Geol. Soc. Am. Bull., 43: 1003-1016.

Ward, D.E., 1978. Geological map of the Adams quadrangle, Lawrence County, Kentucky. U.S. Geol. Surv., Geol. Quad. Map GQ 1489.

Weisenfluh, G.A., 1982. Controls on deposition of the Pratt seam, Black Warrior Basin, Alabama. Ph.D. dissertation, Univ. of S. Carolina, Columbia, S.C., 75 pp. (unpubl.).

Weisenfluh, G.A. and Ferm, J.C., 1984. Geologic controls on deposition of the Pratt seam, Black Warrior basin, Alabama, U.S.A. Int. Assoc. Sedimentol., Spec. Publ., 7: 317-330.

Weisenfluh, G.A. and Horne, J.C., 1980. Geologic cross section along Ky. Rt. 15 between Krypton and Hazard, Perry County, Ky. Dep. Geol., Univ. Ky., Lexington, KY, (unpubl.).

Welch, S.W., 1958. Geology and coal resources of the Tiptop Quadrangle, Ky. U.S. Geol. Surv., Bull., 1042-P: 585-612.

Welch, S.W., 1978. Deposition of the Carter-Sanders zone of the Black Warrior Basin, Mississippi and Alabama. In: Mississippian Rocks of the Black Warrior Basin. Guideb. 17th Fieldtrip Miss. Geol. Soc., pp. 25-33.

Weller, M.J., 1930. Cyclic sedimentation of the Pennsylvanian period and its significance. J. Geol., 38: 97-135.

Williams, E.G. and Ferm, J.C., 1964. Sedimentary facies in the lower Allegheny rocks of western Pennsylvania. J. Sediment. Petrol., 34: 610-614.

Documents

Evolution of some depositional models in late Carboniferous rocks of the Appalachian coal fields