Kinematic Evolution of the Perdido Fold Belt

Rion H. Camerlo¹ and Randy Marrett^2
1 ChevronTexaco, Houston, TX
² The University of Texas at Austin, Austin, TX

The Perdido fold belt, located in the northwestern deepwater Gulf of Mexico, is comprised of northeast-southwest trending folds. The highest structural elevation within the foldbelt occurs along the edge of the Sigsbee salt nappe. Many of the folds are asymmetric, hinterland vergent detachment folds that are bounded by kink bands. These kink bands are often broader on the fold forelimb than on the backlimb. The oldest and youngest stratigraphic units showing evidence of fold growth occur in the fold belt hinterland.

We interpret the raised elevation of the fold belt nearest the Sigsbee salt nappe to result from salt intrusion beneath the hinterland. Salt intrusion produced basinward tilting of the fold train and inclination of the stratigraphic layering to the principal shortening axis, thereby producing asymmetric folds. Salt intrusion also resulted in a transition of shortening mechanisms and the formation of disharmonic detachment folds, with open to tight fold cores, without requiring a deepening of the detachment level. Basin-filling sedimentation buried the lower lying foreland and may have pinned the salient sections of the fold belt. The thinner stratigraphic interval overlying thick salt in the hinterland was more easily deformed, thus allowing for continued fold growth.

Intrusion of ductile material beneath an actively deforming contractional belt may be an important mechanism for fold development in other fold belts such as deepwater Nigeria, the Sierra Madre Oriental, and the Mexican Ridges fold belt. This kinematic evolution has important implications for timing of trap formation and hydrocarbon charge.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005