An overview of factors affecting coal quality and use in the United States With a contribution on coal quality and public health Cover: Chunk of Texas subbituminous coal in the field. Pen for scale. Note the very thin, light-colored laminations that indicate bedding. Top-left enlargement is an example of a scanning photomicrograph showing minerals in coal. The bright-white, oval-shaped fragment is a pyrite framboid; the bright-white triangular fragment is zircon; each fragment is about 10 microns wide. The light-colored, equant blebs are quartz grains. They are set in a light-gray matrix consisting of coal macerals and a variety of clay minerals. Topright enlargement is an example of a transmitted-light photomicrograph showing various coal macerals (organic components) such as vitrinite (dark reddish orange); liptinite (yellow and light orange); and fusinite, inertinite, and minerals (black). View is about 200 micrometers wide.
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
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