100 MILLION YEAR OLD PALEODRAINAGE SYSTEMS IN WESTERN GEORGIA-EASTERN ALABAMA

The location of paleovalleys in the vicinity of the modern Lower Chattahoochee River Valley (LCRV) of western Georgia (GA) and eastern Alabama (AL) indicates the presence of Late Cretaceous (ca. 100 Ma) drainage systems that may represent forerunners to the modern Chattahoochee and Tallapoosa rivers. The Coastal Plain unconformity (CPu), which separates overlying sediment of the Tuscaloosa Formation from underlying metamorphic-igneous crystalline rocks (Dadeville Complex, Opelika Complex, Pine Mountain belt, and Uchee belt) or a residual paleosol formed atop these crystalline rocks, was mapped in order to analyze paleotopography on this Late Cretaceous surface. Elevation data on the CPu and rocks above and below this contact was analyzed via a kriging interpolation technique in ArcGIS. In addition, Tuscaloosa Formation and crystalline basement outcrops were utilized to interpolate the theoretical location of the CPu in areas where the contact was not visible, and subsequently used to create a hand contoured paleotopographic map for comparison to the kriging technique. Additionally, heavy mineral assemblages from fluvial deposits of the Tuscaloosa Formation were characterized in order to assess both spatial and temporal changes in the headwaters of these paleodrainage systems. Identifying the source terranes of the headwaters should provide valuable insight into landscape evolution in this part of AL and GA during the Late Cretaceous. Previous work suggests a possible paleo-divide in the vicinity of the modern divide separating the Chattahoochee River and Tallapoosa River watersheds, suggesting these drainage systems may have persisted in some basic form for ~100 million years.