Abstract: Thermal and Time-Temperature Index (TTI) Patterns During Geologic Evolution of North and Central Gulf of Mexico

Allen Lowrie, Rhett Hamiter, Michael A. Fogarty, Thomas Orsi, Ian Lerche

Regional thermal and Time-Temperature Index (TTI) contours were prepared for 12 dip paleo-tectonic reconstructions extending from central Arkansas to the central Gulf Basin. The first 9 reconstructions are based on back-stripping of Series-long sequences above the Louann Salt with the salt not restored. Additional reconstructions through Lower Jurassic set a geologic scenario prior to continental rifting.

The reconstructions with salt not restored reveal a paleo-Sigsbee salt wedge, undergirding the Upper Jurassic to Pleistocene continental slope, has been a "permanent" ocean-side feature of the prograding margin, a salt-sediment geometry not in existent salt tectonic theories. Such a permanent and laterally migrating "salt nose" provides an obstacle against which descending gravity-driven sediments can interact, creating reservoir-grade deposits against protruding salts features. The nose migration has left a lubricating layer of salt welds and other features. This salt-surrounded unit, beneath and down-dip, may be termed a "salt-floored sub-basin" containing mostly "shallow" sediments of coastal plain, shelf, and slope genesis and growing through time.

By Lower Cretaceous (131-96 mybp) times, the salt-floored basin updip from the then Sigsbee salt wedge was deep enough, approximately 5-7 km, that hydrocarbon maturation had begun. In the Upper Cretaceous (96-66 mybp), hydrocarbon maturation extended to sediments along flanks of the recently extinct mid-ocean ridge. From then to the present, ever more of the sedimentary volume has been subject to maturation.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas