Abstract For the biostratigraphy of mixed continental-marine and purely continental sections in the palaeotropical belt of Euramerica, 9 insect and 8 conchostracan zones are newly defined or improved. These zones encompass the time interval from the Early Pennsylvanian (middle Bashkirian) up into the early Permian (early Asselian) of the Euramercian biotic province. They are linked as much as possible to the marine Standard Global Chronostrigraphic Scale by common occurrences of insects and/or conchostracans with conodonts in mixed marine-continental sections as well as by the thus far available and reliable radioisotopic ages of associated volcanic rocks. This insect and conchostracan zonation is an alternative tool to the well-established macro-plant biostratigraphy of the Pennsylvanian. In contrast to the latter, only single specimens of insects or conchostracans, even if more rare than plant remains, allow biostratigraphic dating with a similar high temporal resolution.

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.

The stratigraphy of the Kanawha Formation in West Virginia has been confused by regional miscorrelations of many units. To resolve these inconsistencies, this report has: (1) revised and defined three widely distributed marine units as the Betsie, Dingess, and Winifrede Shale Members of the Kanawha Formation (Middle Pennsylvanian); (2) extended the name “Fire Clay” into West Virginia from Kentucky for a coal bed regionally identified by its flint clay (tonstein) parting and miscorrelated in different areas of West Virginia as the older Hernshaw coal bed or the younger Chilton coal bed; and (3) reestablished the stratigraphic positions of several key coal beds that have been regionally miscorrelated from their type areas. A stratigraphic section parallel to depositional strike, from the Kanawha River Valley in central West Virginia to the Tug Fork of the Big Sandy River in southwestern West Virginia, shows the correlation and continuity of marine members and coal beds of the middle part of the Kanawha Formation.