Evidence for Cenozoic tectonism in the southwest Georgia Piedmont

Abstract

Paleocene nonmarine sediment in the Georgia Piedmont has been isolated from correlative Coastal Plain deposits by high-angle reverse faults and subsequent erosion. The reverse faults also offset surficial deposits of probable Pliocene age. The sediments, preserved north of Pine Mountain, in the vicinity of Warm Spring9s, Georgia, consist of (1) a lower sedimentary sequence, herein called the “Republic Mine beds,” composed mainly of massive, locally bauxitic, kaolinitic clay and well-bedded, coarse to fine quartz sand; and (2) an upper sequence, herein called “surficial deposits,” composed predominantly of clayey quartz sand and quartzite gravel. The compositional and textural dissimilarities between the two sequences indicate differences in provenance, depositional environment, and tectonic setting. The orientation of the faults and the sense of fault movement near Warm Springs indicate that this area of the western Georgia Piedmont is unlike that of the tectonic regimes previously documented in the Atlantic and Gulf Coastal Plains. The orientation of some structures and the amount and rate of fault deformation are more similar to features in the Gulf Coastal tectonic province, whereas the involvement of basement rocks in fault zones and the compressional style of deformation are comparable to tectonic features described elsewhere in the eastern United States, especially in Coastal Plain sediments along the Fall Line of the Atlantic Coastal Plain.