Abstract: Structure and Early Geologic History of the Deep Central Gulf of Mexico Basin

By

Richard T. Buffler

Multichannel seismic reflection data combined with refraction data from the deep central Gulf of Mexico show details of the deep structure and early (pre-middle Cretaceous) geologic history. A strong reflector extending from the base of the Campeche Escarpment northward up to 50 km beneath the deep Gulf is a major unconformity that truncates older (Triassic?) sedimentary layers and is overlain by Jurassic salt. This reflector possibly represents the top of an attenuated continental crust. The salt layer onlaps and pinches out against the unconformity along the base of the entire northwestern Campeche Escarpment. Deformed salt and sedimentary rocks are overlain by relatively horizontal sedimentary rocks (Upper Jurassic?-Lower Cretaceous?), indicating an early (Jurassic) period of salt deformation (probably the result of gravity sliding associated with early subsidence of the Gulf basin).

Seaward of the zone of salt tectonics the thick sedimentary section of the deep Gulf basin is underlain by an irregular reflector or acoustic basement. The seismic character plus refraction velocity data suggest that this reflector represents the top of oceanic crust, possibly formed during an early phase of rifting and seafloor spreading.

Overlying acoustic basement and onlapping and filling in above the deformed salt is a thick (Upper Jurassic?-Lower Cretaceous?) sedimentary sequence characterized by strong reflections. The upper part of this sequence probably represents the starved deep- equivalent of the Lower Cretaceous carbonate banks that rimmed the early Gulf basin. The top of this sequence is a major regional unconformity. This unconformity represents a major change in sedimentation across the deep Gulf and probably corresponds to the Middle Cretaceous drowning of the outer margin of the Lower Cretaceous carbonate banks. These events are tentatively correlated with a major Middle Cretaceous (Middle Cenomanian?) global sea level change.

End_of_Record - Last_Page 3---------------

Copyright © 2005 by Houston Geological Society. All rights reserved.