In southwest Georgia, relatively little detailed mapping has previously been conducted in the Midway and Wilcox Group equivalents even though there has been mining activity and numerous outcrops are available. Part of the problem has been the poor accessibility of many outcrops, apparent abrupt facies changes, and minimal subsurface data. During 1975-78, new surface and subsurface data were collected through detailed quadrangle mapping, government and commercial well-drilling activities, and data acquired from U.S. Corps of Engineers projects.

These new data provide the basis for a reevaluation of early Tertiary lithostratigraphic relations in four counties in southwest Georgia and one county in Alabama. The research area was chosen to include (1) areas which have previously presented correlation problems owing to apparent abrupt facies changes, (2) regional mining districts, and (3) the classic outcrops 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: (1) the selected research area provides an excellent opportunity to analyze the pre-Tuscahoma erosional degradation surface and the subsequent transgressive onlap of the Tuscahoma over the truncated Nanafalia, Clayton, and Providence (Late Cretaceous); (2) the presence of a basal Tuscahoma deltaic sequence which includes an interval of quartz pebble conglomerates and kyanite-bearing sands, petrified wood, and silicified clasts of chalk; and (3) the interpretation of lithologic associations which correlates the economic zones in the Springvale, Andersonville, and Eufaula mining districts with the Tuscahoma which may provide an exploration aid for analysis of oth r regional bauxite and kaolin deposits.

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