Patterns of deposition during the Early Pennsylvanian (Morrowan) in the Illinois Basin

Abstract

The early Pennsylvanian (Morrowan) transgressions in the Illinois Basin can be documented by mapping the depositional limits of the subdivisions of the Mansfield Formation. Initial Morrowan subsidence and/or sea level rises resulted in northeastward onlap in three separate centers of deposition that are associated with paleovalley systems on the sub-Pennsylvanian landscape. In the central and southern parts of the basin most of the sub-Pennsylvanian topography was buried by late Morrowan time. In middle Pennsylvanian (Atokan) time onlap deposition had extended beyond the present outcrop belt of Pennsylvanian rocks in the Illinois Basin.