David C. Prowell

Evidence for Cenozoic tectonism in the southwest Georgia Piedmont

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.

Effect of faults on fluid flow and chloride contamination in a carbonate aquifer system

Abstract A unified, multidiscipline hypothesis is proposed to explain the anomalous pattern by which chloride has been found in water of the Upper Floridan aquifer in Brunswick, Glynn County, Georgia. Analyses of geophysical, hydraulic, water chemistry, and aquifer test data using the equivalent porous medium (EPM) approach are used to support the hypothesis and to improve further the understanding of the fracture-flow system in this area. Using the data presented herein we show that: (1) four major northeast-southwest trending faults, capable of affecting the flow system of the Upper Floridan aquifer, can be inferred from structural analysis of geophysical data and from regional fault patterns; (2) the proposed faults account for the anomalous northeastward elongation of the potentiometric surface of the Upper Floridan aquifer; (3) the faults breach the nearly impermeable units that confine the Upper Floridan aquifer from below, allowing substantial quantities of water to leak vertically upward; as a result, aquifer transmissivity need not be excessively large (as previously reported) to sustain the heavy, long-term pumpage at Brunswick without developing a steep cone of depression in the potentiometric surface; (4) increased fracturing at the intersection of the faults enhances the development of conduits that allow the upward migration of high-chloride water in response to pumping from the Upper Floridan aquifer; and (5) the anomalous movement of the chloride plume is almost entirely controlled by the faults.

Belair fault zone; evidence of Tertiary fault displacement in eastern Georgia

The Belair fault zone is a series of northeast-trending oblique-slip reverse faults that cut the inner margin of the Coastal Plain near Augusta, Georgia, in juxtaposition with Coastal Plain sediments and crystalline rocks. The fault zone is composed of at least eight en echelon faults and has been mapped for more than 24 km (15 mi). Geologic mapping and drilling indicate that the fault zone has had as much as 30 m (100 ft) of apparent vertical offset since the deposition of the Late Cretaceous to middle Tertiary Coastal Plain sedimentary rocks, and ∼ 23 km (14 mi) of apparent left-lateral offset since the metamorphism of the Paleozoic crystalline rocks. The configuration of the inner margin of the Coastal Plain northeast of Augusta suggests that the Belair fault zone is much longer than presently mapped and that Coastal Plain rocks were possibly involved in the transcurrent displacement.

The Stratigraphic and structural significance of Paleocene pollen from warm springs, Georgia

Abstract Twenty pollen species recovered from auger samples of an isolated pod of sediment within the Piedmont Province of Meriwether County, Georgia, indicate a late Paleocene (early Sabinian) age for the deposit. The age assignment is based on the concurrent ranges of the species as they occur in the Gulf and Atlantic Coastal Plains. No dinoflagellate cysts or acritarchs were observed in the samples examined, and their absence supports stratigraphic and sedimentologic evidence for a nonmarine origin of the sediments. The sediments have been protected from erosion by faulting along the southern margin of the basin containing them. The structural relationships and the Paleocene age for the deposit provide evidence of Cenozoic tectonic activity within the Piedmont Province of Georgia. Regional stratigraphic and sedimentologic evidence suggests that the deposit was probably a northward extension of the bauxite districts of Andersonville, Georgia, and Eufaula, Alabama. Illustrations of the twenty biostratigr...

The Belair fault: A Cenozoic reactivation structure in the eastern Piedmont

The Belair fault zone near Augusta, Georgia, oriented approximately N25°E, is a fundamentally important structural feature of the southeastern Piedmont and adjacent Coastal Plain. Geologic studies by Prowell and O9Connor in 1978 indicated that during the Late Cretaceous and Eocene, the Belair fault zone was an oblique-slip reverse fault that resulted in vertical separations of the Barnwell (Eocene) and Middendorf (Upper Cretaceous) Formations of 10 m and 30 m, respectively. By means of an extensive drilling program, Prowell and O9Connor (1978) determined that the horizontal separation of the late Paleozoic Augusta fault by the Belair fault was ∼23 km. They furthermore suggested that because of an apparent offset of the margin of the Atlantic Coastal Plain in the region, much of this displacement may have occurred in post-Cretaceous time. During the past few years, we have been engaged in field studies along the projected course of the Belair fault zone in the Kiokee and Carolina slate belts of South Carolina. These studies indicate that the Belair fault zone does not significantly displace rock units laterally in the footwall of the Augusta thrust. It now appears that the Belair fault zone is a tear fault in the upper plate of the Augusta thrust and, therefore, most of the lateral displacement along the Belair fault zone probably occurred during the late Paleozoic Hercynian (or Alleghanian) deformation which has recently been documented in the Kiokee belt of South Carolina by Snoke and others (1980b). During the Late Cretaceous and Cenozoic, the Belair fault zone was reactivated as an oblique-slip reverse fault, resulting in the displacement of the Middendorf and Barnwell Formations of the Atlantic Coastal Plain.