MARGIN GEOMETRY AND ENHANCED GRAVITY DRIVEN DEFORMATION ACROSS THE DEEP-WATER MEXICAN PERDIDO FOLD AND THRUST BELT

Outboard of the Sierra Madre Oriental (SMO) fold and thrust belt lies the deep-water Perdido fold and thrust belt, a prolific hydrocarbon provenance extensively explored in the United States and Northern Mexico deep water. The Mexican Perdido comprises the bulk of entire fold belt, but has remained relatively unexplored, largely due to lack of access, but also because of subsalt imaging challenges. The fold belt formed as part of a large-scale Cenozoic gravity driven linked system, established after the cessation of sea floor spreading, with extension along the Gulf Coast translated into downdip compression in the deep-water. Compression occurred from the late Cretaceous to present day, with the main phase occurring between the Lower-Middle Eocene and the Oligocene, forming four complex salt cored linear SW-NE fold belts, each with distinct deformation styles. The style of deformation is directly related to underlying salt thickness, which directly relates to the pre-salt crustal architecture. Post Oligocene extension translated most of the stress via the upper shale detachment in the outboard, but inboard the salt detachment was still the dominant slip surface resulting in out of sequence thrusting affecting the entire stratigraphic package. In the Northern GoM, up-dip extension was translated across a wide, shallow dipping (~2º) passive margin resulting in a classical deep-water fold belt. In contrast, across most of the Mexican margin, extension was translated along a steep (~8º) and southward tapering transform margin influenced by the advancing SMO thrust fronts. Laramide shortening along the salt detachment cannot be ruled out, however the model proposed suggests that the unique tectonic arrangement, created a steep margin with a large gravity potential, where a significant amount of extension was translated directly into the down dip fold and thrust belt. This deviates from other GoM deep-water fold belts where a significant portion of up-dip extension is absorbed by intervening salt structures. This increased shortening is manifested through a variety of complex detachment fold styles, imbricate thrusts, recumbent limbs, and emergent thrust-allochthons, features which strongly influence seismic image quality as well as the risk and uncertainty associated with frontier exploration.