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SASSEN, ROGER, JAMES M. BROOKS, IAN R. MacDONALD, MAHLON C. KENNICUTT II, and NORMAN L. GUINASSO, JR., Geochemical and Environmental Research Group, Texas A&M University, College Station, TX

ABSTRACT: Association of Oil Seeps and Chemosynthetic Communities with Oil Discoveries, Upper Continental Slope, Gulf of Mexico

A belt of sea-floor oil seeps and chemosynthetic communities has been mapped across the upper continental slope, offshore Louisiana, at depths ranging from 200 to 1000 m. Visibly oil-stained sediments and thelmogenic gas hydrates have been recovered using piston cores and research submarines. Biomarker fingerprinting of seep oils suggests an origin from deeply buried Cretaceous or Jurassic source rocks characterized by marine kerogen. The abundance of seeps provides a unique opportunity to define their relationship to oil discoveries including Auger, Cooper, Jolliet, Marquette, Vancouver, Popeye, and Mars. Seeps are preferentially distributed over shallow salt ridges that rim intrasalt basin cooking pots, over salt diapirs, and along shallow fault traces near discoveries. Diagnostic s ep-related features on the sea floor include gas hydrate mounds and outcrops, pockmarks and craters, mud volcanoes, and carbonate buildups. Many of the 50 chemosynthetic communities including tube worms, mussels, or clams thus far documented in the Gulf occur near discoveries. Recent imagery from orbital platforms, including the space shuttle, shows that natural oil slicks are common on the sea surface in this area. Additional mapping of seep distributions should contribute to better defining of the limits of the deep Gulf play fairway.

AAPG Search and Discovery Article #90989©1993 GCAGS and Gulf Coast SEPM 43rd Annual Meeting, Shreveport, Louisiana, October 20-22, 1993.