--> Abstract: Basement Geometry of the US Gulf Coast Basin, by J. A. Lopez; #90987 (1993).

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LOPEZ, JOHN A., Amoco Production Company, New Orleans, LA

ABSTRACT: Basement Geometry of the US Gulf Coast Basin

Poor seismic imaging of sub-salt basement requires reliance on more traditional methods of inferring basement geometries within US Gulf coast basin; e.g. subsidence history, potential fields, tectonic evolution, and distribution of syn-tectonic units. However we can now interpret the basement geometry in light of geometries better understood from other margins or rifts.

Basin asymmetry is defined by the varying widths of extended margins across the Gulf of Mexico from the northern US margin to the southern Mexican margin. On the broader US margin non-uniform extension is indicated by basement arches and differentially subsided, intervening basins. These regional characteristics suggests regional basement detachments were active during the rift phase of the margins. In a simple-shear detachment model, the wider US margin would likely be the lower plate, but any model is undoubtedly complicated by tectonic heredity.

The most southerly basement arch on the US margin stretches for 250 miles along the present coastline of Texas and Louisiana. This unnamed arch is the northern limit of the most southerly and largest of all salt basins in the greater Gulf of Mexico basin and was probably the position of a "central" rift structure. The unnamed salt basin which underlies the present shelf and slope was thicker toward the northerly basement arch and thinner toward the presumed oceanic central Gulf. The great thickness of salt originally within this basin is the probable source for most or all of the present diapiric and allochthonous salt widespread on the present shelf and slope of the northern side of the Gulf of Mexico basin. Widespread allochthonous salt complicates interpretation of the underlying b sement geometry as can becommonly done in typical diapiric basins.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.