MARTON, GYORGY, and RICHARD BUFFLER, Institute for Geophysics, Univ. of Texas at Austin, Austin, TX

ABSTRACT: Evolution of a Mesozoic Seaway, Southwestern Gulf of Mexico

Evolution of a Mesozoic seaway between the Gulf of Mexico and the "proto-Caribbean" in the southeastern Gulf of Mexico area is closely related to the early Mesozoic breakup of Pangea and to the subsequent opening of the Gulf of Mexico/proto Caribbean system. Rifting and subsidence in the seaway area was controlled by the following factors: (A) transform motion which accommodated the southeastward motion of Yucatan during Jurassic time and introduced a NW-trending grain in the area, (B) upper plate character of the southern Gulf, which explains the prolonged uplift of the western part of the seaway during Jurassic time, and the lack of major northwestward faultingthroughout the area and, (C) local extension between the Florida Straits and Yucatan blocks, which resulted in a complex NW rending rift system in the central part of the seaway. This trend is orthogonal to the expected opening direction of the Gulf of Mexico and proto Caribbean basins.

Sedimentation in the central part of the seaway during Middle to early Upper Jurassic time possibly reflects a continental rift setting, while the areas to the east (Florida block) and to the west (Yucatan block) remained uplifted. The central part of the seaway subsided below sea level sometime in Upper Jurassic time, and is characterized by shallow water carbonate sedimentation, similar to that observed in Cuba and around the Gulf of Mexico. Latest Jurassic to Early Cretaceous sedimentation reflects a thermally subsiding area, characterized by the establishment of the Early Cretaceous platforms on the Yucatan and Florida blocks and corresponding deep-sea sedimentation in the central part of the seaway.

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