Application of palynology and petrography in the correlation of the Pennsylvanian Brazil and Staunton Formation coals in the eastern part of the Illinois Basin

The coals of the Brazil and the lower part of the Staunton Formations (Atokan and early Desmoinesian, Pennsylvanian) in Indiana (Illinois Basin) are typically thin and discontinuous. As a result, both researchers and the industry have experienced problems with coal bed identification and correlation. The discrepancies in coal nomenclature and frequent miscorrelations affect coal exploration, mine planning, and communication between mines and customers. Our previous study, based on exploration boreholes, mine-scale observations, and coal quality and petrographic data from Daviess, Greene, and Clay Counties, Indiana, suggested that the coal mapped as the Upper Block Coal Member of Clay County might be the same seam as the Lower Block Coal Member of Daviess County. This study is an extension of the previous research conducted farther south to Pike, Warrick, and Spencer Counties, Indiana. In the southern part of Indiana, correlation of these late Atokan and early Desmoinesian coal beds is even more difficult because of the absence of well-defined marker horizons and limited mining and subsurface well data. Although palynological and coal petrography data generally correspond, these data alone cannot resolve the correlation of the coal beds in this southern region with the coals of Clay or Greene Counties, and they must be supplemented with the analysis of associated limestones. The ability to accurately identify the Perth Limestone Member, which occurs close to the Buffaloville Coal Member of the Brazil Formation, and the Holland Limestone Member, which occurs higher up in the Staunton Formation, will help to distinguish between Brazil and Staunton Formation coals.