SUBSIDENCE AND TEMPERATURE HISTORIES FOR JURASSIC SEDIMENTS IN THE NORTHERN GULF COAST: A THERMAL-MECHANICAL MODEL

Abstract

Abstract The northern coast of the Gulf of Mexico contains major depositional basins in East Texas, North Louisiana, and Central Mississippi. Basin subsidence can be interpreted as resulting from the extension of continental crust by rifting related to the opening of the Gulf of Mexico during Late Triassic to Early Jurassic times. For example, subsidence of the North Louisiana Salt Basin, determined from well data, is consistent with crustal extension by a factor of 1.5 to 2. A seismic survey across the Central Mississippi Salt Basin also indicates crustal extension by about a factor of 1.6. The thermal-mechanical model presented here describes the subsidence and temperature histories of a continental margin, assuming that the lithosphere is stretched and thinned during rifting. The effects of thermal blanketing by overlying sediments are included. The observed position of strata and current thermal regime are used as model constraints. Subsidence and temperature histories for Jurassicage sediments predicted from this model are compared with observational data. The results of this comparison indicate that geothermal gradients were higher in the past and that thermal conditions in Jurassic-age sediments were favorable for hydrocarbon generation.