GEOCHEMICAL CONSTRAINTS ON THE HYDROGRAPHY OF DEVONIAN-MISSISSIPPIAN SHALE BASINS IN SOUTH-CENTRAL AND EASTERN NORTH AMERICA

Chemostratigraphic evidence from organic-rich mudstones of the south-central and eastern North America elucidates the restricted nature and hydrography of the depositional environments in various basins preceding and during the late Paleozoic Alleghany-Ouachita Orogeny. Using an environmental proxy developed from the sediment geochemistry of modern anoxic silled basins, the stratigraphic concentrations of total organic carbon (TOC) and molybdenum (Mo) in the Devonian-Mississippian organic-rich strata can be used to assess the deep-water residence time in each basin. For example, the Mo-TOC relationship preserved within the Barnett Formation of the Fort Worth Basin reveal a high degree of subpycnoclinal water mass restriction and an extended timescale of deep-water renewal of at least 8000 years and potentially as long as 20,000 years. Deep-water residence times for organic-rich shales of the Illinois and Appalachian Basins were much shorter. Molybdenum-TOC results, along with additional TOC-S-Fe data from the New Albany, Ohio, Marcellus, and Barnett Shales will be presented and evaluated.