Late Devonian and Carboniferous strata in the Central Appalachian Basin, USA Donald R. CHESNUT*, Brandon C. NUTTALL, David C. HARRIS and Stephen F. GREB Kentucky Geological Survey, 228 MMRB, Lexington, KY 40506, USA; chesnut@uky.edu A new cross section, designed to be a primary reference section for the identification of deep coal beds, extends for about 230 km across southeastern Kentucky, a part of the Central Appalachian Basin in the eastern United States. The section was constructed using digital geophysical logs from 40 oil and gas drillings. Geophysical data used here consist of gamma ray, caliper, and formation density logs, a suite very useful for coal-bearing rocks. Although the coal-bearing strata are Westphalian in age, the section extends down through the Late Devonian strata for correlation and structural purposes. The maximum depth of the sections (to Middle Devonian) was as much as 1,500 m. The section illustrates the transition between basinal organic-rich shales (Late Devonian to earliest Tournaisian) through subaqueous, deltaic siliciclastics (Tournaisian), basin fill with mixed siliciclastics and carbonates (Early Viséan), then through carbonate platform (mid-Late Viséan) and finally through the alternating marine to terrestrial cyclothems (Serpukhovian through Westphalian). All strata were deposited in a cratonic, foreland-basin setting. The Ohio/Chattanooga Shales (Late Devonian) are organic-rich shales and siltstones deposited in basinal settings. The depth of water is controversial, but the high organic content indicates a low- oxygen, probably stratified, water column. Several gray shales, siltstones and sandstones (Late Devonian), thickening to the east, indicate influx of siliciclastics from the east (e.g., Three-Lick Beds, Bedford Shale, and Berea Sandstone). The lower organic content could be due to changes in oxygen levels, changes in sedimentation rate, or changes in patterns of organic-matter production. Overlying the Late Devonian strata are shales, siltstones and sandstones of the Borden/Grainger Formations (Tournaisian). These shallowing-upward basin fills were deposited as prodelta and turbidite sediments derived from the east and northeast (from early Appalachian highlands). A glauconitic bed marks the Borden Delta Front and represents either a deepening of water. Mixed siliciclastics and carbonates of the Fort Payne Formation (Early Viséan) filled in the rest of the basin, west of the Borden Delta Front. The sediments of the Borden/Grainger and Fort Payne Formations provided a widespread platform for later carbonate deposition. Following topographic basin fill, widespread carbonates (Warsaw-Salem, St. Louis, Ste. Genevieve, Slade, and Newman Limestones) of mid-Mississippian age (Viséan) were deposited in environments ranging from open marine, to shoal, to supratidal. The overlying mixed siliciclastics and carbonates of the Pennington Group (Serpukhovian) mark a new introduction of clastics from highlands to the east. Sediments from the Pennington were deposited in a wide variety of environments ranging from open marine to clastic tidal flats and channels and even to terrestrial settings (indicated by thin coals and paleosols). Several sequences of marine to terrestrial settings may be caused by changes in sea level. A regional erosional unconformity separates the Pennington from the overlying Breathitt Group (Westphalian). The Breathitt is composed of shales, siltstones, sandstones, quartzarenites, rooted paleosols and coals. Regular alternation of coals and siliciclastics (cyclothems) are thought to result from glacio-eustatic changes in sea level. Most of the clastics were derived from highlands to the east. Quartzarenite belts were probably trunk fluvial systems derived from the northeast flowing to the southwest, trapped in the foreland basin during lowstand. The cross section shows many stratigraphically distinct coal beds throughout the Breathitt Group. Most of the coal that has been mined in this region occurs between the valley bottoms and the mountain tops (uppermost part of cross section). This cross section demonstrates that a significant number of coal beds exists in the deeper parts of the basin. Expanded versions of this digital cross section can be used as a reference for the stratigraphic identification of deeper coals. This section is the first reference section to be developed for this purpose in eastern Kentucky.