From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, May 04, 2007
Salt Diapir-Induced Slide Blocks
Devon Energy, Houston
The initiation and movement of slide blocks normally result from gravitational slumps originated either on the outer-shelf regions or in localized steep dip areas that were affected by tectonic mechanisms. These processes, in the majority of cases, are sufficient to explain the presence of stratigraphically out-of-place clastic features that are commonly identified in many sedimentary basins around the world. The example addressed in this work is partly an exception to this concept. The presence of large, thick, and highly stratified allochthonous features in the current study area requires an alternative model to explain the mechanism that delivered them to the younger Oligo/Miocene sedimentary unit. Interpretation of high-quality 3D seismic data revealed that the largest slide-blocks, which are not compatible in thickness with their equivalent collapsed outer-shelf sedimentary unit, are present in areas that were heavily affected by salt tectonics, dominantly collapsed salt diapirs. The amplitude extraction of the paleo-seafloor, on which these features slid, demonstrated clear groove-mark tracks that allow the identification of their source areas. Seismic and well-data interpretation indicate that the slide blocks were part of the underlying lower Tertiary (Eocene/Paleocene) sedimentary unit that was locally broken, and then pieces of it were lifted to the seafloor by salt diapirs in a pumplike process. Once on the seafloor, the blocks slid a relatively short distance toward the east and west, in relation to associated salt domes.