Sequence stratigraphy of fluvially-dominated strata of the Mid-Late Pennsylvanian Conemaugh Formation, Central Appalachian Basin

Mature, polygenetic, high-chroma calcic vertisols and calcisols are the regionally developed interfluvial sequence boundaries (IFSBs) of seven fourth-order sequences (major cyclothems) between the Upper Freeport and Harlem coal horizons. Initial paleosol development occurred under well-drained conditions and strongly seasonal, semiarid-arid climate approaching and during glacial maxima at a time of minimal accommodation space on the interfluves. Subsequent rising water table associated with rising base level occurred as interglacial sea level rose and the climate became less seasonal and more humid. This initially led to deposition of thin, carbonaceous mud and peat followed by lacustrine and palustrine limestones. The presence of spirorbid microconchids indicates that the lakes were at least intermittently connected to the sea, which reached to within 50-80 km of all outcrops in the study during five transgressions. The tops of these limestones represent maximum flooding surfaces. They are overlain by coarsening-upward lake-fill sequences formed during high accommodation on the interfluves during the HST. A nonmarine sequence stratigraphic model and a polygenetic paleosol model are proposed for the Conemaugh in central West Virginia. This study underscores the importance of recognizing regionally developed IFSB paleosols and microconchid limestones in correlation and sequence stratigraphic analysis.