Late Mississippian Sandstones of Illinois

Sandstones, one of the distinctive lithologies of the late Mississippian sediments of the Illinois Basin, constitute approximately one-fourth of the section. The sandstones consist chiefly of well sorted and moderately well rounded, mineralogically stable detrital grains and their chief sedimentary structures are cross-bedding and ripple marks. The sandstones occur as sheets and as four types of elongate sand bodies: pods, ribbons, dendroids, and belts. Detailed local maps showing the thickness of sand of the Degonia, Waltersburg, and Cypress Formations and regional maps for the Degonia, Palestine, Waltersburg, and Hardinsburg Formations display the recurring types of sand bodies and emphasize the essential similarity of all the late Mississippian sandstones. This similarity is a basis for better understanding and improved prediction of sandstone trends. Data gained from the study of the sandstones integrates well with other known features relative to paleogeography of late Mississippian time