Implications of Early Gulf of Mexico Tectonic History for Distribution of Upper Jurassic to Mid Cretaceous Source Rocks in Deep Water Exploration Areas of US and Mexico

Abstract

The central GoM Basin formed by Callovian rifting, followed by oceanic spreading during anticlockwise rotation of Yucatan Block between Oxfordian (160Ma) and Valanginian (140Ma). The rotation pole was in Straits of Florida, resulting in a wiper-blade motion with greatest sweep along a transform paralleling the coast offshore Tampico-Misantla Basin. Oceanic crust progressively separated the 160-140Ma stratigraphy, creating bands of ocean crust lacking Oxfordian, Kimmeridgian, Tithonian and, near the ridge, even Berriasian deposition: present day, these stages appear progressively absent towards the spreading center. After a basin-wide 140Ma (Valanginian) unconformity on the rimming shelves at the end of spreading, thermal subsidence resumed and water deepened further, in the basin. However the North Cuban Arch, separating the GoM and Paleo-Caribbean basins across the Florida Straits, remained a bathymetric sill to deep ocean circulation post-140Ma as before. The impact of this tectonic/bathymetric evolution on the presence and Ultimate Expellable Potential (UEP) of source rocks in the basin center is profound. Using a scheme of basin-wide correlated OM depositional Acmes (recently developed by TIPS, where the Acme age is expressed in Ma), candidate source rocks in the Gulf of Mexico are: Acme A157 (late Oxfordian); A154 (Kimmeridgian); A148 (Tithonian); A144 (Berriasian/Portlandian). All four Acmes have zones of non-deposition due to oceanic spreading, with older Acmes absent over a greater area. Some workers have proposed the main deep water basin source rock in the US to be centered on Tithonian; however, new work (so far limited to eastern deep water Mississippi Canyon, Atwater Valley and Desoto Canyon) indicates that A157 (i.e. the oldest, most susceptible to non-deposition) is the most effective source rock. Risk on Acme 157-144 non-deposition can be mitigated if source rocks younger than 140Ma, with significant UEP, were deposited in the deep basin. Based on recent re-appraisal of data in DSDP Leg 77, Cuba and rafted sediment blocks in US waters, significant UEP does exist in five younger Early to mid-Cretaceous Acmes: A138 (Valanginian); A120 (early Aptian); A110 (early Albian); A101 (late Albian); A98 (early Cenomanian). A138 may result from restricted circulation, reinforced during the 140Ma uplift of rimming shelves, while A120, A110 and A101 can be correlated with oceanic anoxic events OAE1a, b and d.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017