The Structural and Stratigraphic Evolution of the Perdido Foldbelt, Alaminos Canyon, Northwestern Deep Gulf of Mexico

Bruce D. Trudgill, Weimer Paul, Mark G. Rowan, Joseph C. Fiduk, Peter E. Gale, Bryant E. Korn, Ronald L. Phair, William T. Gafford James B. Dischinger, Joseph J. Garbee

The Perdido Foldbelt, lying in the NW part of the Gulf of Mexico basin, is defined by a series of large-scale fold structures that extend SW into Mexican waters and NE beneath the well-defined Sigsbee Salt Escarpment. Within the Alaminos Canyon area, the foldbelt consists of a series of NE-SW trending, sub-parallel, concentric, box folds cut on one or both of their flanks by high-angle reverse faults. The folds are slightly asymmetric and verge both landward and basinward, a geometry typical of compressional foldbelts formed above a weak detachment layer. The folds uplift the regional Mid-Cretaceous Sequence Boundary (MCSB) by up to 3 km, with a decrease in height and amplitude of the folds basinward.

Detailed structural mapping and cross section restoration have produced a model for the structural evolution of the Perdido Foldbelt that is consistent with seismic stratigraphic analysis of the data. The main phase of compressional deformation in the Perdido Foldbelt occurred during the Oligo-Miocene by gravity sliding on a detachment at the top of the Jurassic Louann salt sequence. Middle to Upper Miocene strata onlap the folded sequences, with further Pliocene to present-day uplift possibly a result of either active diapirism of the salt-filled cores of the highest-relief structures, or contractional reactivation of the folds and/or faults. Topographic relief over the highest folds has in turn influenced the evolution of the advancing allochthonous Sigsbee salt nappe.

With more than 7000m of strata involved in the foldbelt structures, the presence of both reservoir and source horizons within the section is predicted. On the basis of correlations with deep Gulf of Mexico sequences, folded strata include Upper Jurassic through Oligocene age rocks. Anticipated reservoir horizons include Lower Cretaceous forereef debris deposits, Upper Cretaceous Chalk, and Lower Tertiary turbidite sandstones. With an advantageous thermal history, migration of hydrocarbons into the structures and adequate sealing horizons, the Perdido Foldbelt contains the potential for the discovery of giant hydrocarbon accumulations in water depths that are accessible by modern drilling technology.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995