ABSTRACT: Evolution of Pre-Jurassic Basement Beneath Northern Gulf of Mexico Coastal Plain

Dewit C. Van Siclen

Data from the northern Gulf Coast region reveal a late Paleozoic wrench fault system along which North America (NA) moved southeast (present directions) alongside the northeastern edge of future South America (SA), to where collision with that continent converted a broad continental embankment off the Southern Oklahoma aulacogen into the Ouachita thrust belt. At the same time, Africa farther east, to which protruding SA was firmly joined (within the less-mobile megacontinent of Pangea), was continuing to advance the Appalachian thrusts on the opposite side of these faults. This relationship left no space between the American continents for the conventional remnant ocean or microcontinents.

By Late Triassic time, however, extension south of the Ouachita Mountains was forming the series of Interior rift (or salt dome) basins, at both ends of which new wrench faults transferred the extension southward to the DeSoto Canyon and South Texas rift (or salt dome) basins. Genetically, the Ouachita thrusts are part of the subduction zone along the front of a former SA forearc basin, which continued to receive marine sediments into middle Permian. The Wiggins arch southeast of it is a sliver of that continent, left with NA when the Interior basin rifting "jumped" from that forearc basin southward across bordering "outer basement highs" to begin opening the deep Gulf of Mexico (GOM) basin.

The Late Triassic crustal extension resulted from right-lateral translation of NA around the bulge of northwestern Africa. About 200 mi (320 km) of this placed Cape Hatteras against Africa's Cap Blanc, in the configuration from which the magnetic data indicate spreading began in the Central North Atlantic Ocean. The reality of this translation is confirmed by widespread rifting at the same time in western North Africa and between all three northern Atlantic continents; this drew the tip of the Tethys sea southward to Cape Hatteras and led to deposition of voluminous Late Triassic "red beds" and evaporites along it.

AAPG Search and Discovery Article #90999©1990 GCAGS and Gulf Coast Section SEPM Meeting, Lafayette, Louisiana, October 17-19, 1990