Laramide Orogenic Influence on Late Mesozoic-Cenozoic Subsidence History, Western Deep Gulf of Mexico Basin

Jianhua Feng, Richard T. Buffler, Michelle A. Kominz

The Gulf of Mexico basin is considered an example of a Mesozoic passive margin basin. The deep part of the basin underlain by oceanic crust has generally been regarded as a tectonically stable part of the basin since its formation by seafloor spreading during the Late Jurassic-earliest Cretaceous. An isostatic and flexural backstripping analysis, however, shows that the present depths of the oceanic crust under the western deep Gulf are much greater (>=2.5km) than predicted subsidence due to thermal cooling and sediment loading. This anomaly evidently is reflecting a later tectonic event or events, the exact time and duration of which cannot be determined exactly because of uncertainties in paleo-water depths. If a water depth approximately equivalent to today's water epth is assumed since the mid-Cretaceous, a rapid tectonic subsidence event is predicted approximately between 66-40 Ma. The most logical explanation for an event of this scale and magnitude is tectonic loading along the western deep Gulf due to Laramide folding and thrusting, a regional compressive event that affected all of nearby eastern Mexico from Late Cretaceous through middle Eocene. The deposition in the deep western Gulf of a thick section of Late Cretaceous-Paleogene sediments further suggests that the western Gulf possibly had been transformed into a large foreland basin at this time.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995