ABSTRACT

In southwest Georgia, relatively little detailed mapping has been conducted in the Midway and Wilcox Group equivalents. Part of the problem has been the poor accessibility of many outcrops, apparent rapid facies changes, and minimal subsurface data. During 1975-1978, new surface and subsurface data were collected through detailed quadrangle mapping, government and commercial well-drilling activities, and data acquired from Corps of Engineers projects.

These new data provide the basis for a reevaluation of early Tertiary lithostratigraphic relationships present in an area consisting of four counties in southwest Georgia and one in Alabama. The research area was chosen to include: a) areas which have previously presented correlation problems due to apparent rapid facies changes; b) regional mining districts; and c) the classical outcrops present along the Chattahoochee River. The local early Tertiary (Paleocene) stratigraphic units included in the research were the Clayton, Nanafalia, and Tuscahoma Formations.

The primary conclusions and resulting lithostratigraphic interpretation of southwest Georgia's Tertiary geologic history are: a) the research area provides an excellent opportunity to analyze the pre-Tuscahoma erosional degradation surface and the subsequent transgressional onlap of the Tuscahoma formation over the truncated Nanafalia, Clayton, and Providence Formations (Late Cretaceous); b) a basal Tuscahoma deltaic sequence is present which includes an interval of quartz pebble conglomerates and kyanite-bearing sands, petrified wood, and silicified clasts of chalk; and c) the interpretation of lithologic associations which correlates the economic zones in the Springvale, Andersonville, and Eufaula mining districts with the Tuscahoma Formation which may provide an exploration aid for analysis of other regional bauxite and kaolin deposits.