Geologic History of Deep Gulf of Mexico Based on Regional Multifold Seismic Lines: ABSTRACT

Abstract

End_Page 554------------------------------Four annotated regional multifold seismic lines across the deep Gulf of Mexico illustrate details of many of the major geologic features. The thick sedimentary section (up to 9 to 10 km) underlying the deep gulf is subdivided into six major sequences or units whose boundaries are major unconformities along the southern margin of the basin, tentatively dated as middle Cenomanian, early Tertiary, middle Oligocene, late Miocene, and the Pliocene-Pleistocene boundary. These units provide a framework for analyzing and discussing the stratigraphy, structure, and geologic history of the deep gulf. A northeast-southwest line 1,000 mi (1,600 km) long from the Florida Escarpment to the Mexican Shelf shows the following major geologic features: (1) the Mexican Ridges foldbelt as a decollement an possible large gravity slides; (2) details of salt deformation in the Campeche-Sigsbee salt dome province; (3) a smooth subsalt basement reflector that possibly represents a major unconformity on top of an attenuated continental crust; (4) an irregular acoustic basement beneath the central Gulf of Mexico that possibly represents some type of oceanic crust; (5) a cross section of the thick Pleistocene Mississippi fan; and (6) a thick Jurassic to Lower Cretaceous sedimentary section thickening beneath the northern Florida Escarpment. Some of the geologic features seen along three north-south seismic depth sections include: (1) unusual salt or shale wedges beneath the upper Mississippi fan; (2) evidence for Jurassic sedimentation and early salt deformation in a basin just northwest of the ampeche Escarpment; and (3) details of the basement structure and the overlying Jurassic to Lower Cretaceous sedimentary sequences in the deep gulf between the northeastern Campeche Escarpment and the Florida Escarpment. End_of_Article - Last_Page 555------------