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.