--> Early Mesozoic Rift-Stage Graben Formation, DeSoto Canyon Salt Basin: Implications for the Early Evolution of the Gulf of Mexico, by G. MacRae and J. S. Watkins; #90986 (1994).

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Abstract: Early Mesozoic Rift-Stage Graben Formation, DeSoto Canyon Salt Basin: Implications for the Early Evolution of the Gulf of Mexico

Grant MacRae, Joel S. Watkins

Seismic reflection data integrated with computed isostatic relations based on a lithospheric buoyancy, Airy-type model, provide the basis for quantification of the crustal structure and recognition of a Late Triassic-Early Jurassic graben complex beneath the DeSoto Canyon Salt basin (DSCSB) on the northwest Florida shelf, and evidence for NW-SE rift-stage extension during the early evolution of the Gulf region.

The distinct geometry and seismic-stratigraphic character of widespread dipping intrabasement or sub-salt seismic events define an asymmetric graben system characterized by two major subbasins. Onlapping relationships of strata within the rift-fill may be the seismic expression of a suprarift lacustrine sequence representing the transition from terrigenous clastic-dominated rift-stage sedimentation to shallow water terrestrial or restricted marine deposition of evaporites and salt during drifting.

The DSCSB occurs within an oblique-shear extensional terrane, the Northeast Gulf corridor, bounded by the NW-SE trending Florida-Bahamas transfer fault and Pearl River transfer fault. Mapped fault trends and the asymmetric basinward widening of the graben complex reflect fault trajectories predicted by theoretical models for extensional terranes experiencing left-lateral slip and a component of fault block rotation. A pole of rotation in the southwestern North Atlantic or southeastern United States could accommodate the required component of counterclockwise rotation. The proposed oblique-shear extensional mechanism offers a favorable explanation for the alternating high-low structural pairs which characterize the Northeast Gulf corridor. NW-SE rift-stage extension accommodated by tra sfer faults probably followed pre-existing structural weaknesses.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994