Walchian conifers from the Mid-Late Pennsylvanian Conemaugh Group in the Appalachian Basin: Stratigraphic and depositional context, and paleoclimatic significance

Late Pennsylvanian, upland (or dryland) conifer communities were comprised of Walchia, Cordaites, and Sigillaria which produced a forest with seed ferns as an understory. The Cedar Run assemblage was probably transported into the valley from adjacent, well-drained coastal plain uplands formed during valley incision, and deposited within the early transgressive systems tract. It is also possible that Walchia expanded into the valleys when drainage became ephemeral during more arid climatic phases. The revised correlations of Appalachian Basin Walchia horizons indicate their appearance closely followed, rather than predated the abrupt climate change and extinctions at the Desmoinesian-Missourian boundary.