Due to different environmental conditions and paleogeographic settings of ancient times, some past sedimentary environments have no good modern analogues. For instance, previous interpretations of environmental conditions of black shale deposition centered on applying modern analogs of coastal upwelling or "Black-Sea type" silled basin topographies. However, a superestuarine circulation model has been proposed recently to explain the abundant and widespread Paleozoic black shale deposits of Midcontinent North America. It is the purpose of this research project to use an interdisciplinary approach to investigate paleoceanographic conditions during the deposition of Pennsylvanian cyclothems of Midcontinent North America and to test the "superestuarine circulation hypothesis." This work is a comprehensive data-model synthesis study and geochemical proxies (strontium and oxygen isotopes of biogenic apatite; bulk major- and trace-element abundance data, TOC-TIC-S concentrations, and petrographic data) will be compared to biofacies distribution patterns and to results of numerical ocean circulation models.