Sediment composition variation in the two southernmost major Carboniferous basins of the eastern United States, the Black Warrior and the Pocahontas, permits location of their source terranes and reconstruction of the Carboniferous crust. These basins were involved in the tectonics which led to the rifting of Pangaea; thus, understanding of basin tectonics should limit the range of geophysical models for the rifting event. Examination of the immature sandstones of the Black Warrior basin indicates denudation of an uplifted greenschist terrane laced with extrusive and intrusive volcanics. Location of this southern Alabama source terrane, probably an extension of the Ouachita trend, was determined from compositional variation within the barrier island facies. Compositional variation within the Pocahontas basin suggests erosion of a granodioritic batholithic complex overlain by sediments, volcanics, and low-grade metamorphics, and underlain by migmatites. The source area for sediments in the Black Warrior terrane apparently subsided or was buried before erosion had penetrated the greenschist cover, whereas erosion reduced the Pocahontas source terrane to the sub-batholithic terrane now exposed in the Piedmont. The “premature death” of the southern terrane has been linked to formation of the early Gulf of Mexico.

A prominent unconformity, present across shallow shelf areas of the Euramerican paleoequatorial basins, is used to demark the boundary between the Mississippian and Pennsylvanian subsystems. This unconformity, the mid-Carboniferous eustatic event, is generally attributed to a major glacio-eustatic sea-level fall. Although a Mississippian-Pennsylvanian unconformity is recognized throughout most of the Appalachian region, the record of the mid-Carboniferous eustatic event in the structurally deepest part of the basin has been controversial. Based on early reports that suggested the most complete Pennsylvanian section was present in southern West Virginia, various conceptual depositional models postulated continuous sedimentation between the youngest Mississippian Bluestone Formation and the oldest Pennsylvanian Pocahontas Formation. In contrast, tabular-erosion models envisioned axial drainage systems that evolved in response to changing basin dynamics. These models predicted a Mississippian-Pennsylvanian unconformity. All these models suffered from a lack of biostratigraphic control. The presence of a sub-Pocahontas paleovalley, herein named the Lashmeet paleovalley, has been confirmed in southern West Virginia. The Lashmeet paleovalley was incised over 35 m into Bluestone strata and filled by lithic sands derived from the Appalachian orogen to the northeast and east. The polygenetic Green Valley paleosol complex marks the Bluestone-Pocahontas contact on associated interfluves. Together, these features indicate a substantial period of subaerial exposure and argue strongly in favor of a Mississippian-Pennsylvanian unconformity. Paleontologic data from the Bluestone Formation, including marine invertebrates and conodonts from the marine Bramwell Member and paleofloral data, support a late, but not latest, Arnsbergian age assignment. Marine fossils are not known from the Pocahontas Formation, but macrofloral and palynomorph taxa support a Langsettian age for most of the Pocahontas. The biostratigraphic, sedimentologic, and paleogeographic data support the presence of an early Pennsylvanian (middle to late Namurian) disconformity in the Appalachian Basin that corresponds to the mid-Carboniferous eustatic event.

Abstract The Central Appalachian Basin occupies an estimated 22,850 sq mi over parts of Maryland, West Virginia, Virginia, Kentucky, and Tennessee. The Mississippian and Pennsylvanian strata that underlie the basin contain numerous coalbeds that have generated significant amounts of methane. Data for analyzing and estimating this resource were obtained from desorption data published by Diamond and Levine (1981); gas data from the USGS/R-9 well in Clay County, Kentucky; data from the horizontal borehole project at Island Creek Coal Company’s Virginia Pocahontas No. 5 mine; and the Clinchfield Coal Company’s Jawbone coalbed methane drainage project. Mine methane emission studies published by MSHA have been investigated, and these data have indicated that the coalbeds—especially the Pocahontas No. 3 and No. 4 coals—emit substantial quantities of methane. The Beckley mine in Raleigh County, Virginia, was monitored in 1974 to measure methane emission rates during mining. The methane potential of this area has been estimated from the published gas content information, related projects, mine emission data, and methane-related incidents. It has been estimated that the basin contains a potential in-place methane resource ranging from a low of 10 to a high of 48 trillion cubic feet. A coalbed methane primary target area for the Central Appalachian Basin has been defined over an area of southwest Virginia, eastern Kentucky, and southeast West Virginia. This area contains the highest measured coalbed gas content values, and other available project data suggest this area contains exceedingly high amounts of methane.

Clastic sediments in the Pocahontas Formation of the east-central Appalachian basin in Virginia and West Virginia were deposited in a series of stacked delta lobes along the southeastern shoreline of a Carboniferous Appalachian seaway. These sediments prograded northwestward and were depositionally continuous with precursor Mississippian coal-bearing strata presently located primarily to the southeast in the faulted and folded belt of the Appalachians. During periodic stillstands in Early Pennsylvanian time, coastal currents and waves reworked and segregated sand along the delta front, forming a system of curvilinear barrier-bars. Behind these protective barriers, vegetation flourished in swamps on the abandoned delta lobes. An analysis of the relationship of coal occurrences to the geometries of sandstone units indicates that the origin of thick, low-sulfur coal in the Pocahontas Formation can be attributed to the initial and continuing accumulation of peat on the periodically inactive delta lobes. Conversely thin, impure, and discontinuous peat (coal) accumulated in the shale-dominated interlobe areas. An increase in the sulfur content of the coal to the northwest may have resulted from the proximity of marine conditions to the distal ends of the delta lobes. The genetic relation of coal distribution and sulfur content to the delta system provides a basis for designing exploration programs in coal-bearing strata of the Appalachian basin, particularly for predicting both the quantity and the quality of the coal.

Abstract The establishment of a standard reference section for the Pennsylvanian System in the Appalachian basin was necessitated by inconsistencies and variations in the application and correlation of the loosely defined Lower, Middle, and Upper Pennsylvanian Series. To provide rock-representative definitions for these units, the Pennsylvanian System stratotype study was undertaken in consultation with interested geologists and paleontologists from State geological surveys, U.S. Geological Survey, academia, and industry. An essential criterion for the designation of the stratotype section was the selection of the most complete and continuous sequence of Pennsylvanian strata that are also conformable with underlying and overlying systems. This requirement was only met in West Virginia where Pennsylvanian rocksextend from the Mississippian strata of the Pocahontas coal field to the Permian strata of the Dunkard basin, a location that follows the recommendation of the Pennsylvanian Subcommittee of the National Research Committee on Stratigraphy that the best standard section for Pennsylvanian rocks in the Appalachian basin would be in West Virginia (Moore and others, 1944, p. 665). The Pennsylvanian System is defined by a composite stratotype consisting of 14 outcrop sections extending from the base to the top of the system over a distance of 100 mi (160 km). Fieldguide site 14 includes a description of strata in the Lower Pennsylvanian Series at three successive sites; A, A-B, and B-C in south-central West Virginia (Fig. 1). Field guide site 13 includes descriptions of strata in the Middle and Upper Pennsylvanian Series. Corroborative investigations include (1) geologic mapping of areas between

The rocks of the Pennsylvanian and Permian Systems of the central Appalachians are a series of shales and fine- to coarse-grained sandstones, locally conglomeratic, arranged in repetitious sequences with thinner coals, clays, lacustrine and marine limestones, chert, and ironstone. Isopachous and facies maps of arbitrarily selected thick units suggest two bodies of rocks, each with distinct orientations and distributions of swamp (organic) and lacustrine-marine (chemical) environments with respect to alluvial (deltaic) deposits. The earlier body, including the Pocahontas, New River, Kanawha, and Charleston, is a wedge of fine- to coarse-grained clastic rocks derived principally from older rocks of the Appalachians to the southeast. The sediments were deposited in a northeast-southwest–trending rapidly subsiding basin in western Virginia, southern West Virginia, and southeastern Kentucky. The coal-bearing facies thins rapidly to the northwest into massive marine (early) and deltaic (later) sandstones. The later body of rocks is divided into two groups distributed in a northerly deepening restricted basin of deposition. The lower group includes the Pottsville, Allegheny, and lower Conemaugh to the top of the Saltsburg Sandstone. Coarse- to fine-grained clastic sediments encroached on swamp, lacustrine, and marine environments in northeastern Kentucky, northern West Virginia, Maryland, Ohio, and Pennsylvania. The upper group includes the upper Conemaugh, Monongahela, and Dunkard, in ascending order. Fine (red)- to medium-grained clastic sediments of southwestern West Virginia and adjacent areas of Ohio and Kentucky encroached on swamp and lacustrine environments of northern West Virginia and contiguous areas of Maryland, Ohio, and Pennsylvania.

Abstract The type area of the Pennsylvanian System is the central part of the Appalachian Mountains, and specifically, the state of Pennsylvania. The Pennsylvanian rocks of the area are divided into the Pottsville supergroup, the Allegheny group, the Conemaugh group, the Monongahela group; and are overlain by the Dunkard group. The thick, primarily sandy, sequence of the Appalachian basin grades westward into cyclical units. Marine units are but a minor part of the system. Several biofacies are well developed—those with plant compressions, a large number of fresh-water zones, a few vertebrate communities, and thin, marine invertebrate-bearing limestones and shales. Structural deformation of the region developed through much of the Paleozoic Era, and the culminating westward thrusting and folding in the miogeosynclinal sediments is attributable to the Allegheny orogeny of post-Pennsylvanian (and perhaps pre-Permian) time. Pennsylvanian rocks of the area contain many minable coal beds, of which the anthracites, the Pittsburgh seam, and the Pocahontas coals are the more valuable; and the Kittanning and Freeport coals are of major importance. Petroleum and natural gas of local importance are produced in a restricted area within the central Appalachians.