THE SEEP CARBONATE ARCHIVE: ADVANCES AND APPLICATIONS

While seafloor hot springs and gas and petroleum seeps of the world’s oceans had been known or expected for a long time, chemosynthesis based communities flourishing around submarine hydrothermal vents and hydrocarbon seeps were found only in relatively recent times (Lonsdale, 1977; Paull et al., 1984). Their dynamic food webs are driven largely by microbial oxidation of hydrogen sulfide or methane and sulfate reduction localized around vent-seep fluid exudates, to produce chemical gradients toxic to most marine life and yet essential to affiliated, endemic invertebrates bearing microbial symbionts. These and subsequent discoveries point to the existence of a vast, virtually unexplored microbial biosphere (hot/cold, seafloor/subsurface); have opened up consideration of microbial worlds on other planets and icy moons; and expanded views on the distribution and tolerances of life on Earth, including conditions at the time of its origin. In the geological record, seafloor hydrocarbon seep deposits with unusual metazoan associations were hypothesized by at least the late 1800’s, although most early studies were unable to assign the correct paleoenvironmental interpretation to such texturally and faunally strange, stratigraphically isolated carbonates. Arthur et al. (1982) pioneered the use of stable isotope geochemistry to fingerprint hydrocarbon seep carbonates in the geological record, first applied to characterizing hundreds of Cretaceous marine conical mounds (Tepee Buttes) scattered along the Laramide uplift belt from Montana to New Mexico. Since then, the number of known modern and fossil hydrocarbon seeps has grown rapidly, such that seep-carbonates – absent from geological textbooks in the 1980’s – are now known to be common in both active and passive tectonic settings around the world’s continental margins (Campbell, 2006; Hovland & Judd, 2007; Suess, 2010). This talk explores advances and applications of the seep-carbonate archive, e.g., identification of (paleo)biogeochemical cycles; drivers of global distributions in time and space; and combined with geophysics, its use in estimating fluid expulsion rates and volumes within basinal histories.