Massive asphalt deposits, oil seepage, and gas venting support abundant chemosynthetic communities at the Campeche Knolls, southern Gulf of Mexico
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...
| Main Authors: | , , , , , , , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-08-01
|
| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/4491/2016/bg-13-4491-2016.pdf |
| Summary: | 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 of asphalt fields and associated gas hydrates at
the Campeche Knolls. The extent of all discovered seepage structure areas
indicates that emission of complex hydrocarbons is a widespread, thus
important feature of the southern Gulf of Mexico. |
|---|---|
| ISSN: | 1726-4170 1726-4189 |