HYDROCARBON SEEP REGIMES IN THE GULF OF MEXICO

Thirty years of research in the northern Gulf of Mexico have assembled an unequaled overview of the geological and biological effects of natural hydrocarbon seepage in a marine basin. Recent findings from the Gulf expand this model, documenting structural and taxonomic affinities that span the entire basin. Communities of tube worms (c.f. Lamellibrachia) and seep mussels (Bathymodiolus heckeri) were discovered among jointed carbonates and associated rubble at the base of the Florida Escarpment (3270m water depth) in 1984 (1). In 1990, the similar species were found in a very similar setting, but on the opposite side of the basin at 2800m in Alaminos Canyon (2). Discovery of asphalt volcanism and associated chemosynthetic communities in the Campeche Knolls (3000m) document a new seep process (3), but appears to have taxonomic affinity with the Florida Escarpment and Alaminos Canyon sites. Interestingly, the Campeche Knoll findings were partially anticipated by a 1971 photograph from the Sigsbee Knolls in the Gulf of Mexico abyss (4). In contrast, the seeps of the Green Canyon in the northern at slope depths (500-2000m) appear to comprise a distinct zoogeographic province, a broad depth range, and distinct geologic styles. Despite the long history of research, many gaps and unexplored regions remain. Satellite remote sensing of the Gulf of Mexico hydrocarbon system is an effective tool for filling in these gaps and testing the Gulf of Mexico seep model in analogous areas in the Caribbean Sea and West Africa offshore.

Literature Cited 1. C. K. Paull et al., Science 226, 965 (1984). 2. J. M. Brooks et al., EOS 71, 1772 (1990). 3. I. R. MacDonald et al., Science 304, 999 (2004). 4. W. E. Pequegnat, L. M. Jeffrey, Contributions in Marine Science 22, 63 (1978).