James Timothy (Tim) Ford¹, H. Scott Sumner¹, John H. Shinol², Michael J. DiMarco¹

(1) Spirit Energy Deepwater Exploration, Unocal Corporation, Sugar Land, TX
(2) Unocal Corporation, Sugar Land, TX

ABSTRACT: Salt Feeder Systems and the Perdido Foldbelt: Impact on Deposystems in Southwestern Garden Banks and Keathley Canyon Areas, Gulf of Mexico

The southwestern portion of the Garden Banks protraction area represents a region within the deep water Gulf of Mexico with a complex structural history. Recognition of structural features is obscured by allochthonous salt (primarily canopy) which locally degrades sub-salt seismic image. Detailed mapping (3D) of the supra-salt section suggests that the Perdido foldbelt, which extends from the Alaminos Canyon protraction area, northeastward beneath the Sigsbee Salt Canopy, continues into and terminates in the southwest Garden Banks area. This termination is roughly coincident with the NW-SE-trending Brazos transform fault which is a regional basement offset zone which locally impacts salt deformation/distribution and likely controls the lateral, northeastward extent of Perdido deformation. The Perdido compressional event initiated in Late Eocene to Early Oligocene time, forming a seafloor high in the southwest Garden Banks area which has persisted since inception. Regional mapping (2D) demonstrates that a salt feeder system, located approximately 15 miles east of the Perdido foldbelt termination, has been emergent since Paleogene time. These two concurrent structural complexes have directed the down-slope flow of ancestral shelf/upper-slope sediments from the north to the lower slope and abyssal plain areas to the south, in the Keathley Canyon protraction area. This interaction between deformation and sedimentation resulted in the formation of a depositional fairway, operative throughout much of Paleogene and Neogene time, which has evolved to become the modern day Keathley Canyon feature.

Mapping of emergent salt feeder systems and localized structural highs such as described above has implications for understanding sediment distribution patterns in sub-canopy areas throughout the deep water Gulf of Mexico. Depositional focusing between emergent structures can be inferred and, subsequently, conventional turbidite fan models may be applied in support of reservoir prediction.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado