ABSTRACT

The origin of the Gulf Coast basin and many of the structures in the basin are logically explained by using a modified version of plate tectonic principles. Evidence that the major North American plate is broken into smaller segments or "miniplates" is found in the Appalachian Mountains and the Appalachian basin. In this area, compressional forces from the southeast during much of Paleozoic time have been recognized by many geologists. Compression was replaced by tension after the Allegheny orogeny.

The Gulf basin miniplate lies between a large right lateral megashear which extends from under the eastern Gulf of Mexico to the east end of the Ouachita Mountains, and a left lateral megashear of similar proportions which parallels the Mexican coastline and extends to the Marathon uplift. The Llano uplift acted as a buttress against northwestward movement of the Gulf basin plate.

The plate is believed to have moved more than 400 miles to the northwest during a Precambrian-Paleozoic compression cycle. When compression ceased, at or near the end of the Paleozoic Era, the Mesozoic Gulf Coast basin was formed over the slowly tilting plate. Rebound, associated with the cessation of compression, caused tension faults to form along old zones of crustal weakness. The graben and other fault trends in and adjacent to the interior salt basins are believed to overlie these crustal faults as are some of the similar structural features of the coastal basin.