Abstract: Upper Mesozoic and Paleogene Geology and Unconformities, Coastal Plain of Georgia

Howard Ross Cramer, Daniel Douglas Arden, Jr.

Probable Late Jurassic and certainly Comanchean clastic sedimentation, caused by overlap from the southwest, followed the filling of Triassic grabens with clastic terrestrial sediments and diabase. Post-Comanchean deformation was followed by Gulfian overlap from both the gulf and Atlantic sides. Midwayan deposition was preceded by regional uplift, and followed by arching of the Gulfian and older rocks in the southern part of the coastal plain. Extensive erosion followed the arching, removing most of the Midwayan and thinning much of the Gulfian. Sabinian rocks--carbonate on the south and clastic on the north--with growth faulting, resulted from overlap, with the thickest parts in the southeast, and contain evaporite.

Overlap continued during the Claibornian; evaporitic carbonate material was deposited toward the south, and clastic rocks were deposited toward the north. The thickest parts of the Claiborne, toward the southeast, are inland from the thickest parts of the underlying Sabinian. The up-arched Cretaceous rocks are downwarped, thus forming the Suwannee saddle. Jackson and Oligocene rocks are shelf carbonates with some evaporite, and represent the maximum time of overlap. Post-Oligocene uplift and faulting initiated the Neogene. The "basement"-Comanchean, Comanchean-Gulfian, Gulfian-Sabinian, and Oligocene-Miocene unconformities are particularly widespread and should be recognizable in the offshore Atlantic rocks.

AAPG Search and Discovery Article #90965©1978 GCAGS and GC Section SEPM, New Orleans, Louisiana