Biostratigraphy, paleogeography, and paleoenvironments of the Upper Cretaceous (Campanian) northern Mississippi Embayment

Most paleogeographic and paleoenvironmental reconstructions of the northern Mississippi Embayment during the Late Campanian (Late Cretaceous) illustrate a generalized gulf between central Mississippi and Arkansas stretching northward into southern Illinois. The most detailed reconstruction shows a large river flowing from the Appalachians to the northeastern edge of the gulf with a river delta covering most of the northern embayment and stretching from southern Illinois to west-central Alabama. Lack of age constraints, incorrect stratigraphic correlations, paucity of detailed geologic maps and subsurface data, and misunderstanding of the basin geometry have led to inaccurate or vague paleogeographic interpretations of the Upper Cretaceous northern Mississippi Embayment. This project correlates the marine and nonmarine biostratigraphy, identifies the upper Campanian lithofacies, interprets the paleoenvironment of each lithofacies, and maps these interpretations to create a paleogeographic model of the northern Mississippi Embayment during the Late Campanian. Biostratigraphic indicators used in this project include foraminifera, calcareous nannoplankton, palynomorphs, ammonites, and other mollusks. Uppermost Campanian units correlated in this project include the uppermost Demopolis Chalk and lowermost Ripley Formation in Alabama and Mississippi; a basal volcaniclastic deposit of the subsurface Demopolis Chalk in Mississippi; the Coon Creek Formation lower facies in Tennessee; the Coffee Sand in northern Tennessee, Kentucky, Illinois, and Missouri; the smectite clays (proposed name of Glenallen Clay) in Missouri; the lower Nacatoch Sand and upper Saratoga Chalk in Arkansas; and the Saratoga and Demopolis Chalks undifferentiated calcareous clay in the central embayment subsurface. Paleoenvironments identified in the study area include molluscan-rich clastic shelf; barrier bar complex; carbonate shelf; estuaries and tidal flats; depression marshes and lakes; and volcanoes with clastic and carbonate rims. (Published By University of Alabama Libraries