Appalachian Thrust Belt Between Trenton, Georgia, and Tuscaloosa, Alabama: ABSTRACT

Of the 260 km of late Paleozoic westward transport inferred for the Blue Ridge thrust mass, 70 to 100 km affect the Valley and Ridge thrust belt. Transport is End_Page 775------------------------------ powered by subductive closing of the Ural-Proto-Atlantic ocean system, but distinct styles and kinematic sequences are imposed through gravity spreading by synorogenic topography, and by 1.5 to 4.5 km of foreland subsidence succeeding 2.5 to 6 km of cratonic shelf subsidence. Traditional exploration prospects are surface folds and frontal thrusts within a Silurian to Mississippian clastic wedge thinning southward from 6.5 to 0.5 km. Future prospects are in lower Paleozoic carbonate rocks involved in subthrust structures and, perhaps, in rift fill below the regional decollement. Risk is related to porosity distribution and to surface-water invasion. Overthrust styles include: detached folds and bed-parallel decollements; sled-runner thrusts, folded-fault structures, and polyphase thrus s; and fold-discordant thrust sheets. Some styles predominate regionally: folded-fault structures in the north and the south, imbricate stacks in the middle, and fold-discordant thrusts in the south. There is no hard evidence of eastward migration of thrusting. Kinematic sequences suggest that a frontal subbelt of detached folds or decollement always was located west of a subbelt of thrust imbrication. Basement subsidence, thrust pileup, erosion, and foredeep sedimentation caused the subbelts to shift position and width, thereby generating kinematic sequences essential for the definition of prospects. End_of_Article - Last_Page 776------------