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Structural Timing and Evolution of the Perdido Fold Belt: Deepwater Western Gulf of Mexico, Usa

Waller, Troy D.1; Spang, John H.2; Kilsdonk, Bill 1
1 Hess Corporation, Houston, TX.
2 Geology and Geophysics, Texas A&M University, College Station, TX.

The Perdido fold belt is the compressed toe of a detached gravity driven, complex linked system in the deepwater, western Gulf of Mexico. The folds studied are those outboard of the allochthonous salt canopy in the southeast quarter of the Alaminos Canyon protraction area. The base of the autochthonous Jurassic Louann salt serves as the detachment horizon for this NE-SW trending fold belt. We have developed new geometric models for detachment folds, which have a deformable lower layer (salt) and extend the interpretation of excess-area vs. depth plots to them. The weak lower layer can both accommodate massive thickness changes and flow laterally allowing anticlines to move absolutely up and synclines absolutely down displacing the weak (autochthonous) layer until it thins to zero, which is referred to as a weld. Initially, anticlines grow rapidly in response to compression coupled with addition of material from beneath subsiding synclines. The resulting plots of excess-area vs. depth to detachment identify (1) the amount of material either added (to the core of the anticlines) or lost (from under the synclines), (2) the onset of folding and deformation, (3) the termination of folding, and
4 a period of cessation of folding at about early Eocene time during which undeformed “growth sediments” were deposited. The geometric models also reveal “quick look” techniques for interpreting seismic using patterns of dip changes that reflect the calculated changes from the excess-area plots. The results of the seismic interpretations, analysis of the geometric models and interpretation of excess-area plots show that the oldest and largest amplitude folds (most northwestern) were formed as early as the early Paleocene and they appear to continue to grow to near present day. With time the fold belt propagates to the southeast, and the deformation becomes increasingly younger with a majority of the folds originating in late Oligocene/earliest Miocene, having lower amplitude due to a limited salt budget (i.e. salt thins in this direction). The evolution of the fold belt is identified by the evaluation of the onset of growth sedimentation in both plotted excess-area curves and interpreted seismic data. This study indicates that the more westward folds originated first, and as a general rule, development of the fold belt progressed basinward/eastward.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009