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Abstract: An Interpretation of the Crustal Framework and
Continent-Oceanic Boundary in U.S. OCS of the
Gulf of Mexico, Based on Gravity and Refraction
1Chevron Energy Technology Company
3Hunter 3-D, Inc.
Geophysical evidence suggests the existence of oceanic crust in the deep-water Gulf of Mexico. However, there is no consensus on the location of the continent-ocean boundary in this important geologic province. A number of distinct kinematic models have been published for the crustal framework and early tectonic history of the Gulf of Mexico. All these models have been constrained by similar seismic refraction data, tectonic subsidence analyses, global plate motions, and/or potential fields data, but draw different conclusions on the areal extent of true oceanic crust. In support of our sub-regional petroleum systems models for the United States Outer Continental Shelf (OCS), we analyzed regional gravity and refraction data and constructed a number of 2D and 3D deep crustal models. Our models suggest that most of the U.S. OCS is underlain by attenuated continental crust and that the extent of true oceanic crust in the Gulf of Mexico may be significantly less than indicated in many other published models.
Only a limited area of crust has geophysical properties consistent with true oceanic crust observed elsewhere on the globe. However, the enigmatic nature of the crustal velocity and thickness data from refraction studies, as well as the gravity data, may also be consistent with an interpretation of an absence of oceanic crust in the Gulf of Mexico. High crustal densities and velocities in the Gulf of Mexico may be indicative of exhumed mantle, thin underplated lower crust, serpentinization and/or magmatic extrusives, but not true “drift phase” crust. Perhaps no new crust was ever accreted at a mid-ocean ridge in the Gulf of Mexico.
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