Seafloor Through Mantle Dynamics Apparently Guide Geologic Evolution of the Gulf of Mexico and Similar Thickly Sedimented Continental Margins

Allen Lowrie and Linda H. Jenkins
RFI Explorationists, Picayune, MS

In describing geologic processes and mechanisms and the structural strength along the northern Gulf of Mexico, dynamics of the sediments, lithosphere, and mantle need to be included and interrelated. The Pratt gravity model (1840s) of “floating” blocks of differing densities provides dynamics. A cross section from Little Rock, Arkansas, to the Yucatan incorporates differing basement densities with changes in transitional crust from granite to basalt. Seafloor and/or back-arc spreading were restricted to the Gulf.

We further incorporate the published notion that the entire continental margin from fall-line/hinge-line fault to abyssal plain is intermittently migrating basinward. The sedimentary wedge and basement are characterized by extensional and lateral migration along normal faults. The migration is driven via “instantaneous” energy releases (earthquakes, silent/slow earthquakes, meteor impacts) and long-term sources.

Seismic tomography shows increased thermal activity in the mantle beneath the Gulf from the Kulla Plate subduction under Mexico. This heat may have weakened the Gulf’s lithosphere, which responds also to increased loading from rapid deposition. Additional complexity can be provided by transcrustal stresses from regional plate tectonics from Mesozoic subduction under North America, Mexico, Cuba, and the Caribbean and from shearing along the Cayman Trough and subsequent seafloor spreading.

A structurally weakened and stressed basement may explain possible anomalous depths to sediment layers in the Gulf. These anomalies are described within a single stress field. The Indus and Bengal continental margins have comparable sediment wedge thickness.

What similarities/dissimilarities do these thick margins exhibit?

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas