ABSTRACT

Several aulacogens, the failed-arm troughs radiating from RRR triple junctions, mark the southern margin of the early Paleozoic North American continent. The Delaware aulocogen in West Texas and the Wichita aulacogen in southern Oklahoma, now consist of paired basins and uplifts trending at high angles from the rifted continental margin. The Reelfoot aulacogen lies beneath the Mississippi embayment, and the Mount Rogers trends from southwestern Virginia across North Carolina then beneath the Piedmont into South Carolina. Although the rifting of the continent and opening of the proto-Atlantic (Iapetus) Ocean was a late Precambrian or early Paleozoic event, still older Precambrian trends may have influenced the location of these features. The final stages of their geotectonic evolution was influenced by the late Paleozoic continental collisions that formed Pangaea, and their presence controlled the shape of the resulting Ouachita-Marathon orogenic belt and may have influenced the subsequent rifting and breakup of that supercontinent during the Mesozoic.

The Delaware aulacogen, adjacent the Diablo-Coahuila platform, a Precambrian orogenic trend, produced the early Paleozoic Tobosa basin before the continental collision that formed the Delaware Basin and the Central Basin Range. It determined the location of the Rio Grande embayment, a Mesozoic aulacogen formed during the breakup of Pangaea. The Wichita aulacogen, also probably influenced by an ancient Precambrian basement trend, gave rise to the early Paleozoic southern Oklahoma basin, again long before late Paleozoic plate collision initiated the transcurrent stage that produced the Anadarko Basin and the Wichita-Arbuckle uplift. Troughs of thick early Paleozoic sedimentation also mark positions of the Reelfoot and Mount Rogers aulacogens, but these now lie beneath the younger deposits of the Mississippi embayment and the allochthonous Piedmont respectively. All of these aulacogens influenced deposition on the retreating North American plate margins, and as a result of subsequent plate convergence, influenced the structure and geometry of later Paleozoic orogenic belts and the location of associated foreland basins.