Modifications of Pennsylvanian Stratigraphy in Indiana

This study critically reviews selected Pennsylvanian stratigraphy units in Indiana and, based on the available data, makes changes to improve the Pennsylvanian stratigraphic scheme for the Illinois Basin. The overall purpose of the stratigraphic changes is to facilitate the correlation of the rock units within Indiana and the entire Illinois Basin by making unit ranges and nomenclature more compatible with those formally used in Illinois and western Kentucky. We collected numerous rock samples from outcrops, coal mines, and boreholes, and generated new biostratigraphic (palynological and conodont) data on coals, limestones, and shales to address important stratigraphic questions. The main changes for the Pennsylvanian stratigraphy in Indiana include: a) abandoning the use of the names “Brazil Formation” and “Staunton Formation” as formal stratigraphic units and introducing the name “Tradewater Formation”; b) abandoning the name “Mansfield Formation” and introducing the name “Caseyville Formation”; c) formalizing two coal seams in the former Staunton Formation as the Wise Ridge Coal Bed and Montgomery Coal Bed of the Tradewater Formation; and d) formalizing four distinctive black, fissile shale units as the Veale Shale Member of the Tradewater Formation, the Logan Quarry Shale Member of the Tradewater Formation, the Turner Mine Shale Member of the Dugger Formation, and the Anna Shale Member of the Dugger Formation.