2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 5
Presentation Time: 2:45 PM

Paleocene to Eocene Deepwater Slope Canyons, Western Gulf of Mexico: Further Insights for Provenance of Deep Offshore Wilcox Plays

MCDONNELL, Angela, The University of Texas at Austin, Bureau of Economic Geology, University Station, Box X, Austin, TX 78713, GALLOWAY, William E., Institute for Geophysics, The University of Texas at Austin, 10100 Burnet Rd, ROC-196, Austin, TX 78758-4445 and LOUCKS, Robert G., Bureau of Economic Geology, The University of Texas at Austin, Box X, University Station, Austin, TX 78713, angela.mcdonnell@beg.utexas.edu

Although the lower Tertiary Wilcox Group forms a significant deepwater exploration target, connections to equivalent-aged onshore fluvial, deltaic, and shallow-marine reservoirs are poorly documented. We examined the lower Tertiary stratigraphy of the Texas state waters, ~60 mi downdip of the Wilcox-aged paleoshelf edge, yet 200 mi updip of the deepwater discoveries. Analysis of a large, three-dimensional, seismic volume (3,300 mi2/8,500 km2) reveals stacked submarine canyons of inferred late Paleocene to early Eocene age (Wilcox Group), clustered off Matagorda Bay. Canyons are typically 2–2.5 mi (3–4 km) wide and 600–1600 ft (200–500 m) deep. In all, the main incisional axes run downslope, whilst some of the canyons bifurcate. Two canyon geometries are observed. The first is a strongly incisional system, filled with low-amplitude, discontinuous reflections, that displays a relatively straight downslope trend, and the second is less incisional, being represented by discontinuous, high-amplitude reflections that display a meandering downslope trend. This study confirms the presence of extensive submarine-slope canyons beneath the inner Texas shelf. Furthermore, they are located directly downdip of Paleocene to lower Eocene canyon systems that incised the lower Tertiary paleoshelf. This system is interpreted to represent a middle- to lower-slope sediment transport pathway, potentially linking some of the shelfal canyons updip to the successfully drilled lower Tertiary plays (e.g., Great White, Cascade, Chinook) in the deepwater Gulf of Mexico Basin.