Massive asphalt deposits, oil seepage, and gas venting support abundantchemosynthetic communities at the Campeche Knolls, southern Gulf of Mexico

作者：Heiko Sahling, Christian Borowski, Elva Escobar‐Briones, Adriana Gaytán-Caballero, Chieh‐Wei Hsu, Markus Loher, Ian R. MacDonald, Yann Marcon, Thomas Pape, Miriam Römer, Maxim Rubin‐Blum, Florence Schubotz, Daniel Smrzka, Gunter Wegener, Gerhard Bohrmann · 发表于：Biogeosciences · 年份：2016 · DOI：10.5194/bg-13-4491-2016 · 被引用次数：51 · 研究领域：Methane Hydrates and Related Phenomena、Hydrocarbon exploration and reservoir analysis、Oil Spill Detection and Mitigation

Abstract. Hydrocarbon seepage is a widespread process at the continental margins of the Gulf of Mexico. We used a multidisciplinary approach, including multibeam mapping and visual seafloor observations with different underwater vehicles to study the extent and character of complex hydrocarbon seepage in the Bay of Campeche, southern Gulf of Mexico. Our observations showed that seafloor asphalt deposits previously only known from the Chapopote Knoll also occur at numerous other knolls and ridges in water depths from 1230 to 3150 m. In particular the deeper sites (Chapopopte and Mictlan knolls) were characterized by asphalt deposits accompanied by extrusion of liquid oil in form of whips or sheets, and in some places (Tsanyao Yang, Mictlan, and Chapopote knolls) by gas emission and the presence of gas hydrates in addition. Molecular and stable carbon isotopic compositions of gaseous hydrocarbons suggest their primarily thermogenic origin. Relatively fresh asphalt structures were settled by chemosynthetic communities including bacterial mats and vestimentiferan tube worms, whereas older flows appeared largely inert and devoid of corals and anemones at the deep sites. The gas hydrates at Tsanyao Yang and Mictlan Knolls were covered by a 5-to-10 cm-thick reaction zone composed of authigenic carbonates, detritus, and microbial mats, and were densely colonized by 1–2 m-long tube worms, bivalves, snails, and shrimps. This study increased knowledge on the occurrences and dimensions o...