Camerlo, Rion H.1, Stacy A. Smith1
(1) ChevronTexaco, New Orleans, LA
ABSTRACT: Deformation Associated with Emplacement of Allochthonous Salt in the Perdido Fold Belt, Gulf of Mexico
One of the striking aspects of the plan view geometry of the folds of the Perdido fold
belt is the association of large domal structures within the trend that is largely
dominated by cylindrical folds. Folds located proximal to the edge of the allochthonous
salt nappe have most recently undergone large-scale folding and extensional faulting. This
late-stage deformation appears coeval to salt nappe emplacement. The recent folding and
faulting as well as the domal geometries are interpreted as superposed features resulting
from shortening and flexural isostacy associated with salt nappe emplacement.
Emplacement of the salt nappe is associated with shallow thrusting in front of the advancing salt. Fold geometries are less cylindrical after this refolding event and show fold interference geometries. The significant bathymetry and corresponding large density contrasts of the Sigsbee escarpment with the surrounding water is interpreted to result in flexural isostacy compensated in the very weak ductile decollement layer underlying the fold belt. Structural inversion occurs wherein previous growth strata within synclines are inverted into anticlines and anticlines are unfolded. Contractional kink bands developed in the earlier stage of folding are reactivated in extension. Fold relationships can be observed where extensional fault relationships are observed in contractional kink planes in the outer-arc of the superposed fold.
This late stage re-structuring has had significant impact on fetch areas and structural geometries of the Perdido folds and folding related to flexural isostacy has impacted the location of extensional faulting within the fold belt and compartmentalization of the traps.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.