Effects of Inherited of Pre-Jurassic Tectonics on the U.S. Gulf Coast

Abstract

ABSTRACT The Triassic separation of North America from South America resulted in an irregular fragmented arc which now extends from Central America to South Florida. Stranded blocks of continental crust control the location of major basins over the attenuated crust between the stranded blocks, permitting early thick evaporite precipitation and thicker than normal sediment deposition. Post-rifting tectonic patterns retain an inherited fabric reflecting the Triassic rifting. Triassic horsts, grabens, and half-grabens localized and delineated later microbasins, herein defined as a limited area of deposition, the boundaries of which reflect, or can be presumed to reflect, buried basement-related faulting. Mapping of trend offsets indicate that NW-SE linear patterns exist and imply the presence of small-scale strike-slip transform faults within these basins that control the lateral position and size of individual microbasins. Mapping of these microbasins is essential to the understanding of exploration play concepts within a geologic province. It is inferred that many Gulf Coast growth-fault basins are at depth related to basement block-faulting and thus fit this definition of microbasins. Irregular thicknesses of Louann salt have resulted from salt precipitation on a block-faulted basement. The uneven thickness of salt within individual grabens and half-grabens has controlled the spatial distribution and size of the resultant salt domes, pillows, and withdrawal areas. This salt movement is one link between the original basement block faults and the resultant growth fault basins.