Abstract: Paleozoic Tectonics of Southern Margin of North America

Jack L. Walper

Several aulacogens, the failed-arm troughs radiating from RRR triple junctions, marked the southern margin of the early Paleozoic North American continent. Two, the Delaware aulacogen in West Texas and the Wichita in southern Oklahoma, now consist of paired basins and uplift trending at high angles from the rifted continental margin. The Reelfoot aulacogen lies beneath the Mississippi Embayment, and the Mount Rogers trends from southwest 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 an early Paleozoic event, still older Precambrian basement 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 also may have influenced the subsequent rifting and breakup of that supercontinent during the Mesozoic.

The Delaware aulacogen, adjacent to 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 "geosyncline," again long before late Paleozoic continental collision initiated the transcurrent stage that produced the Anadarko basin and the Wichita-Arbuckle uplift. Troughs of thick early Paleozoic sedimentary rocks also mark positions of the Reelfoot and Mount Rogers aulacogens, but these now lie benea h the younger deposits of the Mississippi embayment and the allochthonous Peidmont respectively. All of these aulacogens influenced deposition on the retreating North American plate margins, and then, as a result of subsequent plate convergence, influenced the geometry of later Paleozoic orogenic belts and the location of associated foreland basins.

AAPG Search and Discovery Article #90967©1977 GCAGS and GC Section SEPM 27th Annual Meeting, Austin, Texas