DEVELOPMENT OF MESOZOIC AND CENOZOIC FRACTURE-SETS IN EASTERN GEORGIA

Analysis of brittle deformation structures (joints and faults) found in quarries in postkinematic plutons emplaced during the Alleghanian orogeny in eastern Georgia show a similar sequence of Triassic and Jurassic structures to those found in similar granites along the Fall Line across western SC. Two quarries near Appling, GA as well as the nearby Heggies Rock exposures and the Cedar Rock quarry near Camak, GA. Here, age relationships show that the oldest Triassic fracture-set trends E-W followed by 2 sets that trend more ESE-WNW, perhaps associated with early failed rifting along the margin of the Gulf of Mexico. The next 3 younger Triassic sets trend NNE-SSW, N-S, and NE-SW, more typical of trends of Triassic basins associated with the Atlantic rifted margin. The older N-S Jurassic set pre-dates the NW-SE set commonly associated with widespread emplacement of diabase dikes. Analysis of fracture-sets from the Avant mine in Coastal Plain sediments near Sandersville, GA shows multiple fracture-sets of Eocene and Miocene that are similar to those across western SC.