Louis M. Liro1,
Mary S. Kadri1,
Mark J. Lahr1,
Michael B. Jackson1
(1) Veritas Exploration Services, Houston, TX
Abstract: Allochthonous salt distribution, Walker Ridge lease area, deepwater Gulf of Mexico
A 3D seismic grid covering 144 OCS lease blocks along the southern portion of the Walker Ridge lease area was examined to categorize and map the distribution of allochthonous salt in the shallow subsurface. Several classes of 3D seismic data, including grids of prestack depth migration lines, were utilized to effectively describe the geometry of the salt masses. Data visualization of the entire seismic grid allowed for compilation of a regional understanding of the origin and development of the allochthonous salt.
Although in-place Jurassic salt is observed in the vicinity of the Sigsbee Escarpment, no source stocks connecting this mother salt layer to the allochthonous salt masses were observed. Based on ties to abyssal plain stratigraphy, the deepest salt roots were observed at the level of Miocene strata, implying that significant remobilization and lateral extrusion of salt began no later than that time. Numerous significant salt source regions have been identified in the study area.
Based on the geometry of the base of extensive lateral salt masses in the area, subsequent emplacement and lateral extrusion occurred in a series of low-angle and high-angle ramps, likely related to episodes of updip clastic loading. Deformation of the upper surface of the salt masses is determined by the development of sedimentary mini-basins, compressional thrust regions, and salt deflation surfaces.
Allochthonous salt masses are observed as individual canopies, amalgamated canopies, extensive tongues, and shallow salt massifs. Emplacement of these salt masses generally follows a first-order regional ramp surface, with deeper salt bases in the northern and central portions of the study area, moving successively up-section to form the modern escarpment. Depth-slicing of the volume allows reconstruction of the development and origin of individual salt features.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana