Rowan, Mark G.¹, Kerry F. Inman², J. Carl Fiduk³ 
(1) Rowan Consulting, Inc, Boulder, CO
(2) Independent Consultant, Houston, TX
(3) CGG Americas, Inc, Houston, TX

ABSTRACT: Physical and Temporal Linkage between Proximal Loading and Extension and Distal Deposition and Contraction in the Northwestern Gulf of Mexico Basin

Despite many years of study, explorationists and researchers are still debating a number of issues regarding the linkage between updip extension and downdip contraction in south Texas and the adjacent shelf, slope, and ultra-deepwater provinces. Multiple detachment levels on both salt and shale accommodate extension along the Wilcox, Vicksburg, Frio, and Miocene trends and shortening in the Port Isabel and Perdido foldbelts. We examine this complex margin using new seismic and well data and tie the various structural elements together both spatially and temporally. 
Our interpretation has several key elements. First, the Wilcox event involved extensional rafting on thin salt, not diapir collapse and local salt extrusion, with matching contraction largely accommodated by more distal salt extrusion into the Frio/Miocene canopy. Second, the Frio/Miocene and Port Isabel are detached on allochthonous salt welds, not shale, with Oligocene contraction accommodated within the canopy and at the seafloor. Third, Miocene extension was first linked by the allochthonous salt level to the Port Isabel foldbelt and further canopy extrusion, but was then transferred to the Louann level and the Perdido foldbelt along the Corsair trend due to thickening and strengthening of the weld overburden. 
The proposed evolution has implications for distal sedimentation during the Paleogene. The late Paleocene to early Eocene was characterized by unconfined Wilcox deposition in primary basins between scattered diapirs rooted in the Louann salt. In contrast, the development of regional allochthonous canopies by the Oligocene resulted in more confined and ponded Frio deposition on the slope.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.