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Regional Controls on the Formation of DeSoto Canyon, Gulf of Mexico

Richard Denne and Robert Blanchard
[email protected]

DeSoto Canyon is a deep, subsea canyon in the Northeast Gulf of Mexico. Its presence is easily identifiable on seismic data as well as ocean bottom images. The canyon cuts into the modern continental shelf south of Pensacola, Florida. Northwest of the canyon is a clastic depositional system dominated by the Mississippi River Delta, while southeast of the canyon is a wide, carbonate-dominated shelf. The history of the canyon can be reconstructed to the Cretaceous / Paleogene (K/Pg) boundary, when seismic and regional well data indicate the canyon was first formed. Over the last 65 million years, the canyon has changed position through time, but it has never migrated away from its controlling factor: a large, basement controlled rift graben, which formed in the Early Jurassic. The preexisting accommodation, created by the rift, was filled by early, anticlinal growth structures initiated by rafting Norphlet Fm. sandstones and Smackover Fm. carbonates down dip on top of the Louann Salt décollement. Lower Cretaceous rocks are characterized by isopachous seismic reflectors, suggesting the basin's earlier accommodation did not significantly affect deposition. The earliest erosion is visible on seismic as a 'wedge' of truncated reflectors, biostratigraphically tied to the K/Pg boundary, that cut as deep as the Lower Cretaceous. We hypothesize that the link to the K/Pg boundary is significant. Impact-induced instability, magnified by the preexisting basement structure, may have produced mass wasting large enough to initiate canyon formation.

AAPG Search and Discovery Article #90167©2013 GCAGS and GCSSEPM 63rd Annual Convention, New Orleans, Louisiana, October 6-8, 2013