Allegheny Formation Research Articles

Paleoshoreline patterns in the transgressive-regressive sequences of Pennsylvanian rocks in the northern Appalachian Basin, U.S.A.

Sheets of sponge spicule flint of Pennsylvanian age (Bashkirian, Moscovian, Kasimovian) that are present in the northern Appalachian Basin of Ohio and adjacent parts of Kentucky, Pennsylvania and West Virginia, are important indicators of paleoshorelines. This flint typically occurs with or occupies the position normally held by shallow-water limestone and contains a normal marine fauna. The flint was deposited above coal or underclay, representing the detritus-starved marine portion of a transgressive-regressive sequence and marking the eastern limit of transgression across a westward-spreading alluvial plain. Flint occurs at several stratigraphic positions in the upper Pottsville-lower Conemaugh interval. The most important are: Boggs, Upper Mercer and Kanawha flints of the upper Pottsville Group; Kilgore-Flint Ridge, Zaleski and Vanport flints of the lower Allegheny Group; and Brush Creek flint of the lower Conemaugh Group. Lithofacies maps of these beds were constructed to show the distribution of the flint. Limestone-hosted flint occurs in long discontinuous chains of sheetlike bodies, whereas shale-hosted flint occurs in single sheets with restricted geographic distribution. Chains of limestone-hosted flint attain maximum dimensions of a few meters in thickness, a few kilometers in width and several hundreds of kilometers in length. The Upper Mercer, Vanport and Brush Creek flints are particularly extensive, forming arcuate shoreline patterns that parallel the fronts of large delta systems. Beds of clay ironstone and/or coal above flint indicate that the lagoonal environment in which flint was deposited was followed closely by a change to stagnant waters. Cementation of flint with silica likely occurred under the lower pH conditions existing at that time and when depths of burial were shallow.

Lacustrine carbonate deposition in Middle Pennsylvanian cyclothems ? the Upper Freeport Formation, Appalachian Basin, USA

The Upper Freeport Formation (Upper Allegheny Group, Middle Pennsylvanian) is one of the earliest non-marine cyclothems in the Appalachian Basin and contains carbonates, siliciclastics, and coal. A detailed facies analyses of 25 cores from the Upper Freeport Limestone in western Pennsylvania (Armstrong and Indiana Counties) identified four facies associations containing thirteen separate facies: rudstone-limestone (Association A), rudstone-laminated limestone (Association B), laminated limestone (Association C), and coal — siliciclastics (Association D). We interpreted them, respectively, as shallow, high energy lacustrine margin (A); littoral to sublittoral lacustrine (B); offshore lake (C); and vegetated swamp and marsh (D). The depositional environment is envisaged as an anastomosed channel system surrounded by extensive wetlands containing adjacent densely vegetated swamp and marsh areas and freshwater, carbonate-producing lakes.

Coal-Bed Methane Resources and Subsurface Definition of the Middle Pennsylvanian Allegheny Formation in Northern West Virginia

Traditional correlation methods have not proven effective in the subsurface definition of the Allegheny Formation. Sandstones are discontinuous, of channel fill origin, and have log signatures that are not uniquely traceable on a regional basis. Erosion and/or non-deposition associated with fluvial-deltaic channels were responsible for observed coal-bed discontinuities and resulted in preservation of incomplete depositional sequences. Lowermost Allegheny Formation and underlying Pottsville Group sandstones often coalesce and/or split. The regional unconformity between Mississippian and Pennsylvanian systems effectively prohibits correlation of sandstones above the middle Mississippian Greenbrier Limestone due to gross variations in sediment thickness and lithology. In the overlying Conemaugh Group, core descriptions are helpful in locating marine zones and red beds, which may then be located on geophysical logs and used in correlations. The combined use of data from coal exploration core holes, gamma-ray and density logs, oil and gas well drillers' logs, and interval thicknesses derived from outcrop studies has allowed tentative subsurface definition of the Allegheny Formation. The number and thicknesses of Allegheny coal beds, associated sandstones, and reported gas shows have been mapped for use in future coal-bed methane development. The West Virginia Geological and Economic Survey developed this integrated approach to correlation while studying themore » coal-bed methane potential of the Allegheny Formation in northern West Virginia under contract to the Texas Bureau of Economic Geology and funded by the Gas Research Institute.« less

Clastic diversion by fold salients and blind thrust ridges in coal-swamp development

Abrupt shifts from single widespread coal swamps to coarse siliciclastic alluvial channel deposits occur in at least five coal beds and zones within the Pennsylvania Allegheny Formation. One of these, the Upper Freeport coal zone, was deposited over and area at least 200 {times} 200 km with a spacing of alluvial channels one-half to possibly one-fifth that of the immediately overlying coarse clastics. All these shifts occured next to the rising Appalachian orogen, far from the eustatic effects of a marine shoreline. Recent models relating coal-swamp formation to isostatic warping of orogenic forelands by tectonic loads surely apply to this environment, but they seem to need an additional, more delicate mechanism to produce such abrupt but widespread switches in grain size and drainage spacing. The authors propose that irregularities in the advancing front folds and blind thrusts caused temporary geomorphic diversions into the recessed areas and allowed a widespread coal swamp to form in the sedimentary shadow of the salients, a shadowing process that is occurring today in the central Zagros Mountains of Iraq and Iran.

Preliminary Feasibility Study of the Coal-Bed Methane Resource in Pennsylvania

Coal-bed methane gas content data were obtained from exploratory drill holes, premining degasification drill holes, and methane recovery test projects from the Main Bituminous and Northern Anthracite fields of Pennsylvania. Exploratory coal cores tested ranged from the Pennsylvanian-Permian Dunkard Group to the Pennsylvanian Allegheny Group. Total gas contents were determined for each coal sample by using the UD Bureau of Mines direct method of testing. Graphical analyses of depth and thickness vs. total gas content revealed a direct correlation between depth and gas content. However, further study is needed to determine if significant gas contents are a functions of thickness. Gas values were approximately 1,000 Btu/scf, comparable to that of natural gas. Extremely low heating values, however, accompanied shallow, above-drainage coal beds (less than 500 ft) proximal to mining operations. Geologic factors that determine the feasibility of coal-bed methane development are (1) coal rank, (2) depth of overburden, (3) coal-bed thickness, (4) favorable structure and fracture permeability, (5) permeability of adjacent strata (6) water content, and (7) pressure/stress relationships. The developer must also evaluate economic, political, and legal issues when planning a project in the Northern Appalachian coal basin. Most of the available coal information in Pennsylvania is base onmore » the minable coals. A more definitive estimate of the basin's deepest coal resources and gas contents are critical to the development of coal-bed methane as a resource.« less

Facies in the Lower Kittanning coal bed, Appalachian Basin (U.S.A.)

Facies changes in the form of maceral and palynomorphic composition and textures are observed in thin sections and polished sections, both vertically and horizontally in the Lower Kittanning coal bed (Allegheny Formation, Middle Pennsylvanian, Westphalian D) over a large area in western Pennsylvania, U.S.A. The lower half of the coal bed is characterized by abundant well-defined telocollinate and thin-walled lycopod spores which are interbedded with thin layers of mixtures of clearly outlined inertodetrinite and vitrodetrinite. The uppermost layer, in places where the coal is thought to be influenced by marine conditions, is characterized by a densosporerich desmocollinite with abundant inertinite cluster (quasigelifusinite). The transitional layers between the lower half and the uppermost layer are dominated by fine-grained vitrinite with disseminated spores of distinctive shape and size ( Punctatisporites sp. and Schopfites sp.). In many places, a clay- or mineral-rich parting with abundant alginite, fragmented megaspores, and clay-filled microspores are also observed in the transitional layers. Any layer composed of unique plant assemblage (a plant community representing a specific environment in time and space) is termed a phytostrome. The unique association of macerals is termed a lithotype. Five genetic lithotypes are recognized: kittosite, herbosite, klastosite, arborosite, and allosite, representing (1) brackish, (2) transitional, (3) limnic, (4) freshwater arboreous, and (5) reworked peat, respectively. The accumulation of the last phase of the Lower Kittanning coal appears to have been influenced by a transgressive sea.

Paleoecology of an upper Middle Pennsylvanian coal swamp from Western Pennsylvania, U.S.A.

The first sufficient quantitative analysis of vegetation preserved in coal balls from the Allegheny Formation, late Middle Pennsylvanian age, was made in the present study by measuring 13,203 cm 2 from middle peels of over 300 coal balls or pieces of coal balls. The distinctive features of this flora are the dominance of lycopods, the absence of cordaitean plants, and the extremely low shoot/root ratio (0.74 for total plant remains, 0.24 for lycopods). It is suggested that the climate at the Derringer Corners coal swamps was a drier tropical climate, compared to that of some earlier coal-forming environment of the Appalachian Basin, and to those of coal swamps in the Illinois Basin during the Middle Pennsylvanian. The discrepancy between the abundance of lycopods (as an indicator of a wet environment or habitat) and the low shoot/root ratio (inferring relatively dry conditions) in the coal-forming peat swamps at the Derringer Corners indicates that the actual set of factors causing massive reduction of arborescent lycopods at, or near, the boundary between Middle and Late Pennsylvanian would be much more complex than simply a “drier climate”. Some local factors, such as edaphic, perhaps geomorphic conditions, and local events, might play an important role in creating a favorable environment for the growth of lycopod trees.

A Quantitative Assessment of the Natural Abatement of Acid Mine Drainage by Interaction with Allegheny Group Lithologies

A Quantitative Assessment of the Natural Abatement of Acid Mine Drainage by Interaction with Allegheny Group Lithologies

Depositional Model for Freshwater Limestones of Upper Allegheny Group (Pennsylvanian System) of Western Pennsylvania: ABSTRACT

A depositional model is proposed for the freshwater limestones of the upper Allegheny Group of western Pennsylvania, specifically the Upper Freeport limestone. The model is based on a facies sequence analysis of core logs through the limestone-bearing interval, on isopachs of limestone and sandstone of the same coal-to-coal interval, and on microfacies analysis of the limestone itself.

Depositional Environment and Early Diagenetic Controls on Mineralogy of Kittanning Formation, Allegheny Group, Eastern Ohio: ABSTRACT

Depositional Environment and Early Diagenetic Controls on Mineralogy of Kittanning Formation, Allegheny Group, Eastern Ohio: ABSTRACT

The Diamond Coal Mine of Linton, Ohio, and its Pennsylvanian-age vertebrates

ABSTRACT The village of Linton in Jefferson County, Ohio, was the site of the Ohio Diamond Coal Mine, a drift mine exploiting the Upper Freeport coal of the Allegheny Group, Middle Pennsylvanian (equivalent to late Westphalian D, Upper Carboniferous). Beginning in 1856, extensive collecting from the cannel underlying the coal has yielded a diverse assemblage of nearly 40 vertebrate genera making Linton the most prolific Upper Carboniferous vertebrate locality in the world. Examination of over 6000 Linton specimens indicates that fish remains are approximately ten times more abundant than tetrapods, with coelacanths, haplolepid palaeoniscoids, and xenacanth sharks predominating. The most common tetrapods are small aquatic amphibians, including urocordylid and keraterpetontid nectrideans, trimerorhachoid and colosteoid temnospondyls, aistopods, and lysorophid microsaurs. Other amphibian and reptilian genera are exceedingly rare and show more terrestrial adaptations, suggesting that they were biological tran...

Arsenic Concentration Variability and Inorganic Affinity for Selected Coal Beds of Central Appalachian Basin: ABSTRACT

The mean arsenic concentration on a whole-coal basis, for 613 complete channel samples representing 34 coal beds from the central Appalachian basin, is 14.0 ppm (standard deviation, s.d. = 14.9). An F-test for variance equality and the appropriate t-test on the means can separate stratigraphic units into three categories: (1) Kanawha Formation, which has a mean of 5.04 ppm; (2) New River, Pocahontas, and Monongahela Formations, which have means of 10.1, 10.9, and 12.4 ppm, respectively; and (3) Allegheny Formation, which has a mean of 18.1 ppm. Data from 40 complete channel samples of the Upper Freeport coal bed (Allegheny Formation) were used for statistical evaluations (F- and t-tests as applied in the stratigraphic comparison) of the regional (western Pennsylvania) versus local (within mine) arsenic variation. The arsenic concentration and variation in whole-coal samples are greater on a regional scale (mean = 40.8 ppm, s.d. = 30.6, n = 21) than on a local scale (mean = 23.8 ppm, s.d. = 18.7, n = 19). Nine channel samples of the Upper Freeport coal bed were subjected to a 21-part size-gravity washability study. A mean of 86 wt. % of the coal floated at a specific gravity of 1.6. The mean arsenic concentration (6.05 ppm) in this float recovery is 55% less than the mean arsenic concentration in the unprocessed samples (14.3 ppm). The mean arsenic concentration in the remaining 14 wt. % of the coal was 123 ppm. The float-sink analysis verified an inorganic affinity of arsenic and indicated that arsenic is associated with pyritic sulfur in the Upper Freeport coal bed. Three samples with a mean arsenic concentration of 4.20 ppm had a mean of 36.4% reduction of pyritic sulfur, while 6 samples with a mean arsenic concentration of 19.3 ppm had a mean of 63.8% reduction of pyritic sulfur. C ncentrations of arsenic in complete channel samples above some threshold, approximately 10 ppm for these samples, appears to be associated with removable pyrite. End_of_Article - Last_Page 1436------------

Coal Occurrence in Progradational Deltaic Sequence, Raleigh County, West Virginia: ABSTRACT

Surface outcrops and data from 75 core holes were used to study the Pennsylvanian Kanawha Formation in a 100 mi2 area of western Raleigh County, West Virginia. The interval consists of approximately 1,400 ft of prograding alluvial-deltaic deposits and includes 22 coal seams. The interval developed across drowned orthoquartzite coastal sandstones (Nutall) that mark the approximate top of the New River Formation. Its lower portion (Douglas to Eagle coals) is a generally coarsening-upward, prodelta/distal-deltaic succession of units dominated by dark shale and containing brackish-marine intercalations that extend across most of the area. Coals are widespread but commonly thin (about 1 ft), and the rate of lateral change is low. The top of this lower section is capped by outer deltaic sandstones (Eagle coals). The upper portion of the Kanawha Formation is dominated by outer deltaic strata (to Hernshaw coal) grading upward to inner (Stockton coal) deltaic sandstones. Brackish-marine intercalations associated with autocyclic shifting of detrital lobes are restricted in areal extent. The outer deltaic coal beds are thick (up to about 6 ft) and laterally uniform; succeeding inner deltaic coals are thinner (less than 3-4 ft) and are variable laterally. Deltaic deposits grade upward into lower alluvial plain strata of the Allegheny Formation near the ridge crests. Associated coals locally may be thick (up to 6 ft), but abrupt changes in thickness and shale partings are typical. End_of_Article - Last_Page 1439------------

Correlations of Coal Beds near Allegheny-Conemaugh Contact in Tri-State Area of Ohio, Kentucky, and West Virginia: ABSTRACT

The top of the Upper Freeport coal bed marks the contact between the Allegheny Formation (Middle Pennsylvanian) and the Conemaugh Formation (Upper Pennsylvanian) at their type area in western Pennsylvania. The position of the Upper Freeport is uncertain in the tri-state area of Ohio, Kentucky, and West Virginia because of lack of continuity and apparent miscorrelations of coal beds. Our stratigraphic analysis of coal-bed correlations with respect to our identification of the Brush Creek Limestone Member, the lowest marine member of the Conemaugh Formation, indicates probable miscorrelations of coal beds by previous workers in this area. In Lawrence County, Ohio, Condit identified the Mahoning coal bed as 46 ft below the Brush Creek Limestone and 24 ft above the Upper Free ort coal bed. Northward along the Ohio River in southeastern Ohio, the Brush Creek Limestone-Mahoning interval is about 30 ft. Wanless correlated the Princess 9 coal bed of Kentucky with the Upper Freeport of Ohio and Pennsylvania. Huddle et al indicated that in eastern Kentucky the Princess 9 is in the Conemaugh Formation, about 45 ft below the Cambridge Limestone Member (correlated with the Brush Creek Limestone Member) and about 35 ft above the Upper Freeport. Thus, the Mahoning coal bed of Ohio appears to correlate with three units in eastern Kentucky--the Princess 9 of Huddle et al, the uppermost Princess 9 of Connor and Flores, and the Brush Creek coal bed of Sharps--and with the Brush Creek coal bed in parts of the adjoining areas of West Virginia. This stratigraphic analysis indi ates that the true Brush Creek Limestone-Upper Freeport interval is about 70-110 ft in the tri-state area, which is consistent with the same stratigraphic interval to the north. End_of_Article - Last_Page 1440------------

Paleoenvironmental Control of Accumulation and Quality of Upper Freeport Coal Bed (Allegheny Formation, Middle Pennsylvanian), Castleman Coalfield, Maryland: ABSTRACT

The upper Freeport is generally a thick, widespread coal bed in the north-central Appalachian basin. It is a principal bed mined in the Castleman coalfield, Garrett County, Maryland, as delineated on a new geologic map of the coalfield. In the northern part of the coalfield, the upper Freeport is 21-48 in. (53-122 cm) thick and thickens toward the northwest, where the ash and sulfur contents are generally 7-10 wt. % and less than 1.5 wt. %, respectively. This coal bed thins southward and eastward and is absent from a large area in the central part of the coalfield, where its position is occupied by a carbonaceous claystone or flint clay. Toward the south and east, the upper Freeport coal bed generally contains 12-15 wt. % ash and 1.5-6.2 wt. % sulfur. Lithofacies analysis of the floor rocks and their lateral equivalents indicates deposition of the upper Freeport coal bed in floodplain swamps. Limestone and limy claystone floor rocks in the northwest represent distal floodplain lake deposits. Where the coal is unminable or absent to the south, proximal overbank floodplain shale, siltstone, and silty claystone grade laterally into channel sandstone. The gradation of thin coal into carbonaceous claystone to the south indicates increased oxidation and shoaling in a well-drained swamp. There, the coal has the highest ash and sulfur contents, which probably reflect the influx of detritus and iron-rich clays. Thus, the upper Freeport is thickest and has the lowest ash and sulfur contents where the paleoenvironment was a poorly drained, di tal floodplain swamp. End_of_Article - Last_Page 1924------------

Fluoride in the Ground Water of Northeastern Ohio

ABSTRACTFluoride contents range from <0.05 to 5.9 milligrams per liter (mg/1) based upon 255 water samples collected from wells in nine counties of northeastern Ohio. Only 16 samples had fluoride contents exceeding 1 mg/1, and all are from the southern trio of counties. Furthermore, all samples high in fluoride are from wells close to or penetrating the contact between the Allegheny and Pottsville Formations.Data from a line of 34 wells for which logs were obtained indicate that high fluoride water occurs in either the lower part of the Allegheny Formation, or more probably, in the upper part of the Pottsville Formation.Ground waters high in fluoride are related to the bedrock geology. Fluoride data, particularly in the area of potentially high values, are important to health professionals in the prescription of fluoride supplements for children. Such prescriptions should be made only after the water has been tested.

Provenance Study of Upper Freeport (Pennsylvanian: Allegheny Group) and Mahoning (Pennsylvanian: Conemaugh Group) Sandstones in Eastern Ohio: ABSTRACT

Deposition of the complex sedimentary facies in the Allegheny basin exhibits a change in the dominant source of sediment influx from north to southeast through Pennsylvanian time. Lobate deltas entered eastern Ohio from both the rising Appalachian Mountains to the east and southeast and from the Canadian shield to the north. Confusion exists regarding the limits of the respective deltas. The present study is an attempt to define the limits of these sedimentary domains for a small portion of the basin in space and time. Samples of the upper Freeport (Upper Desmoinesian) and Mahoning (Lower Missourian) sandstones were collected along their western outcrop through eastern Ohio from Summit to Gallia Counties along a north-south transect. Thin sections were point-counted and a alyses of the data made to determine whether the individual samples had their source in the high-grade metamorphic and igneous crystalline basement of the Canadian shield, or among the sedimentary and low-grade metamorphic rocks of the Appalachians. Determination of the source of the samples allows delineation of the boundary between respective delta lobes. End_of_Article - Last_Page 1166------------

Application of vitrinite reflectance anisotropy in the evaluation of coal metamorphism

Measurement of the maximum plus either the minimum or mean vitrinite reflectance provides a method for quantification of anisotropy of the reflectance. Previous research has suggested that anisotropy of vitrinite reflectance may be a direct indicator of static pressure (depth of burial) at which coal metamorphism occurred. The combination of thermal information (from vitrinite reflectance) and pressure information should, therefore, provide a means of evaluating the metamorphic history of a single coal seam or a series of coals in a sedimentary basin (given the independent placement of coal-rank parameters on a pressure-temperature grid). Occurrence of coals in strata with diagnostic metamorphic minerals is rare. Therefore, evaluation of coal metamorphic conditions can seldom proceed parallel to mineralogical evaluation of rock metamorphic conditions. Rather, the coal petrologist has generally relied upon time-temperature nomograms to estimate metamorphic temperature from coal rank. In this study, the level of organic metamorphism (LOM)-time-temperature scale of Hood and others (1975) was considered the most versatile nomogram for evaluation of metamorphic conditions. Coals from throughout the Appalachians were studied, but this study concentrates on coals from the Allegheny plateau in western Pennsylvania. Vitrinite maximum reflectance (in oil at 546 nm) and reflectance anisotropy ((R maximum − R mean )/R maximum = anisotropy) were measured on Pennsylvania coals. In order to estimate rank gradients and subsequently paleogeothermal gradients, however, it was necessary to rely upon previously published volatile matter data from the Lower Kittanning, Upper Freeport, and Pittsburgh seams. From equivalent metamorphic temperatures from the LOM-time-temperature scale and from vertical separation of the seams, paleogeothermal gradients were calculated for Somerset County, adjacent to the Allegheny front, (about 40°C/km) and for Westmoreland County to the west (about 33°C/km). Past depths of burial for both localities were calculated to have been 3.5 to 4 km for the Allegheny Group coals. Calculated gradients are each in areas on the plateau where vitrinite reflectance is nearly constant within each area. Two similar areas, for which geothermal gradient could not be calculated directly due to insufficient vertical exposure of coals, lie immediately to the north. The crustal blocks appear to be divided by the southwest-to-northeast Chestnut Ridge anticline, which marks a major tectonic division on the plateau, and by the southeast-to-northwest “Gwinn-type” lineament, which marks a northward reduction in amplitude of the plateau folds. Coal rank is 1.6% R (low volatile bituminous) in the Somerset County block (associated with the 40 °C/km gradient), 1.3% R (medium volatile) in the block northeast of the lineament (centered in Clearfield County), 0.9% R (high volatile A) in the Westmoreland County block (associated with the 33 °C/km gradient) west of Chestnut Ridge, and 0.8% R (high volatile A) in the block northeast of the lineament (Clarion County). The rank decrease west across Chestnut Ridge occurs in a zone about 50 km wide. Width of the zone of northeastward rank that decreases across the lineament is not as well defined but is probably of the same magnitude. As burial depths of the blocks appear to have been similar, the primary cause for rank variation was variation in geothermal gradients between blocks. Anisotropy did not change significantly across the region, suggesting that it can be correlated with past depth of burial.

BEDDING GEOMETRY IN A PENNSYLVANIAN CHANNEL SANDSTONE

Cross-bedded sandstone in the Pennsylvanian Kittanning Formation of the Allegheny Group exposed in a strip mine near Philipsburg, Pennsylvania, consists of large, inclined, sigmoid sedimentation units that overlap each other uniformly toward the west. Such features as the arrangement of sedimentation units and their internal bedding geometry suggest that the sandstone originated by deposition on the inside of a meander curve of a westwardly migrating stream channel.

Genetic Types of Some Sandstones in the Allegheny Formation of Ohio: ABSTRACT

Sandstones between the Middle Kittanning and Lower Freeport coal beds in the Allegheny Formation of southeastern Ohio are divisible into three genetic categories based on gross external morphology of the sand body, proportion of major mineral components, grain size, and homogeneity of cross-bed orientation. The following types are continuously arrayed in eastwest trending bands along a northeast-southwest outcrop: 1) Thin, lenticular, discontinuous sand bodies with quartz content about 58 per cent. Among all other constituents, feldspar averages 15 per cent, muscovite 25 per cent, chlorite-biotite 60 per cent. Sands are predominantly fine to medium grained and cross-bedding is randomly oriented. 2) Thick, less widespread, partly continuous, elongate sand bodies in which quartz averages 54 per cent. Among all other constituents, feldspar, averages 25 per cent, muscovite 30 per cent, chlorite-biotite 45 per cent. Sand is medium grained and cross-bedding is weakly oriented. 3) Thick, widespread apron or sheet sands in which quartz averages 62 per cent. Among all other constituents, feldspar averages 35 per cent, muscovite 30 per cent, chlorite-biotite 35 per cent. Sands are predominantly medium to coarse grained and cross-bedding is oriented in a northwest-southeast direction. Type 1, found in the southern part of the area, is believed to represent a meandering, relatively nearshore portion of a fluvial system. In contrast, Type 3, found in the northern part of the area, probably represents sand distribution beyond the area of well-developed channels, perhaps near distributary mouths. Type 2, found between areas of Types 1 and 3, presumably reflects an intermediate situation. End_of_Article - Last_Page 340------------