BIPOLAR SIMPLE-SHEAR RIFTING RESPONSIBLE FOR DISTRIBUTION OF MEGA-SALT BASINS IN GULF OF MEXICO?
Published:December 01, 1993
JOEL S. WATKINS, GRANT MacRAE, GREGORY R. SIMMONS, 1993. "BIPOLAR SIMPLE-SHEAR RIFTING RESPONSIBLE FOR DISTRIBUTION OF MEGA-SALT BASINS IN GULF OF MEXICO?", Salt, Sediment and Hydrocarbons, Adam’s Mark Hotel
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Major salt basins in the Gulf of Mexico region are distributed in a diagonally symmetric manner with greatest abundances of salt located in the northeastern (Texas-Louisiana shelf and slope basin) and southwestern (Campeche basin) quadrants. Basement elevation and hydrocarbon distribution are also diagonally symmetric. Highest basement elevations occur in the southeastern (Yucatan) and northwestern (Llano-San Marcos Arch) quadrants. Hydrocarbon distribution mimics salt distribution.
We believe that these diagonal symmetries are a consequence of the nature of the rifting process. We envisage a simple-shear rift sequence in which the Gulf basin is fractured and fragmented by a series of northwest-southeast trending transfer faults. The transfer faults divide the lithosphere into segments characterized by different rates of extension, amounts of extension, and most importantly, directions of detachment dip.
The principal transfer fault is the Brazos transfer fault (BTF). It parallels the eastern margin of the Llano Uplift-San Marcos Arch in the northern Gulf and may follow the Ticul fault in western Yucatan. The basal detachment surface in the segment northeast of the BTF dips southeast, whereas the detachment southwest of the BTF dips northwest. The Llano-San Marcos and Yucatan areas belong to paleo upper (or breakoff) plates, whereas major salt basins overlie subsided lower (or breakaway) plates.