Stratigraphy and Structural Timing of the Perdido Foldbelt, an Emerging Toe-of-Slope Play in the Northwestern Deep-Water Gulf of Mexico

C. D. Winker
Shell Exploration and Production

In 2000-2001 the Baha-2 (AC557-1) dry hole penetrated for the first time the entire lower Tertiary section and part of the Cretaceous section of the northwestern Gulf of Mexico abyssal plain. This well also validated the basic play elements for the Perdido Foldbelt, subsequently confirmed by the Trident (AC903) and Great White (AC857) discoveries. 

The main objective sections are equivalent in age to the onshore Wilcox Group (Paleocene to early Eocene) and Frio Formation (middle Oligocene). These units contain turbidite sandstones with channel and lobe geometries deposited in large basin-floor fans. Sandstone compositions are similar to contemporaneous deltaic sandstones in south Texas. The Wilcox and Frio units are separated by the distal, downlapping, northern flank of a large submarine fan derived from the Tampico-Poza Rica region of Mexico; this unit is equivalent to the Claiborne, Jackson, and Vicksburg. The Wilcox unit overlies Midway-equivalent Paleocene shale, which in turn overlies Cenomanian to Maastrichtian deep-marine carbonates, sandstone, and shale, including Upper Cenomanian source rocks. The former “Mid-Cretaceous Sequence Boundary” (MCSB) is actually the top of Cretaceous. Upper Jurassic to Lower Cretaceous carbonates, presumed to include Tithonian source rocks, were not penetrated.

The main episode of gravity-driven, salt-detachment folding occurred in late Oligocene to early Miocene time. This folding episode was preceded by an early phase of slow structural growth during the early Cenozoic. The folding episode was followed by a late Cenozoic phase of salt inflation and structural reorganization in the proximal foldbelt.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004