carbonate structures several meters in height. Other locations of extensive authigenic carbonate formation are
found offshore Costa Rica, South China Sea, New
Zealand, and in the Gulf of Cadiz (reviewed by Suess,
2010).
Although not as common as the carbonate occurrences,
barite (BaSO 4 ) deposits have been observed along structurally controlled sites of cold-fluid seepage in several
continental margins. Barite pillars along the San Clemente
fault can reach 10 m in height, and similar deposits have
been reported on the Sea of Okhotsk. Less massive but
distinct barite occurrences have also been reported in the
Alaska margin, Monterey Canyon, Peru margin, and the
Gulf of Mexico (Torres et al., 2003). The formation of
these deposits is intimately linked with the sulfate concentrations, which in the highly reduced environments that
characterize cold seeps is depleted at shallow depths
within the sediments. At low sulfate, any barite in the sediment will dissolve, leading to high levels of dissolved
barium in the upwardly migrating fluids. Upon
discharging at the seafloor, barium quickly reacts with seawater sulfate and precipitates in the newly formed barite
deposits.
Paleoseeps
The occurrence of carbonates in the geologic record
enriched in the light
12 C isotope has been commonly
attributed to authigenic formation at paleo-methane seeps,
which indicate significant methane release from the Proterozoic to the present (Campbell, 2006). The cold seep barite deposits likely constitute the modern analogues to
Paleozoic stratiform barite deposits, now being mined in
Nevada, Arkansas, Mexico, and South China. These barite
deposits represent large-scale submarine methane venting,
which could have affected the Paleozoic carbon cycle and
perhaps modified ancient climate (Torres et al., 2003).
Summary
Along the ocean margins, sediments experience chemical,
microbial, and physical transformations that result in the
generation and expulsion of reduced gases and water at
the seafloor, in what is known as cold seepage.
Methane is generated by microbial or thermochemical
processes in the organic-rich marine sediments. Hydrogen
sulfide is a by-product of microbial oxidation of methane
under anaerobic conditions. Water is produced at greater
depths by dehydration reactions of smectite and to a lesser
extent opal. Accumulation of the excess water and gas creates overpressures that can fracture the overlying geological formations and drive fluid flow. Sediment compaction,
generation of hydraulic heads, and tectonic compression
also act as driving forces for fluids that eventually discharge at the seafloor.
Whereas the majority of life in the deep ocean floor rely
upon low levels of sinking organic matter, the chemosynthetic microbial communities at cold seeps take advantage
of high fluxes of bioreactive reductants to support unique,
oasis-type cold seep biomes in which the density of organisms is several orders of magnitude greater than in the surrounding regions. Authigenic carbonate and barite
deposits, which can reach extremely large accumulations,
characterize areas of cold seepage and constitute a geologic record of methane discharge at paleo-seep sites.
Bibliography
Barnes, R. O., and Goldberg, E. D., 1976. Methane production and
consumption in anoxic marine sediments. Geology, 4, 297–300.
Boetius, A., and Suess, E., 2004. Hydrate Ridge: a natural laboratory for the study of microbial life fueled by methane from
near-surface gas hydrates. Chemical Geology, 205, 291–310.
Bohrmann, G., Greinert, J., Suess, E., and Torres, M., 1998.
Authigenic carbonates from the Cascadia subduction zone and
their relation to gas hydrate stability. Geology, 26, 647–650.
Campbell, K. A., 2006. Hydrocarbon seep and hydrothermal
vent paleoenvironments: past developments and future
research directions. Palaeogeography, Palaeoclimatology,
Palaeoecology, 232, 362–407.
Colten-Bradley, V. A., 1987. Role of pressure in smectite dehydration–effects on geopressure and smectite-to-illite transformation. AAPG Bulletin, 71, 1414–1427.
Faure, K., Greinert, J., Schneider von Deimling, J., McGinnis, D. F.,
Kipfer, R., and Linke, P., 2010. Methane seepage along the
Hikurangi Margin of New Zealand: geochemical and physical
data from the water column, sea surface and atmosphere. Marine
Geology, 272, 170–188.
Heeschen, K. U., Collier, R. W., de Angelis, M. A., Suess, E.,
Rehder, G., Linke, P., and Klinkhammer, G. P., 2005. Methane
sources, distributions, and fluxes from cold vent sites at Hydrate
Ridge, Cascadia Margin. Global Biogeochemical Cycles, 19.
GB2016. doi:10.1029/2004GB002266.
Kulm, L. D., Suess, E., Moore, J. C., Carson, B., Lewis, B. T.,
Ritger, S. D., Kadko, D. C., Thornburg, T. M., Embley, R. W.,
Rugh, W. D., Massoth, G. J., Langseth, M. G., Cochrane,
G. R., and Scamman, R. L., 1986. Oregon subduction zone:
venting, fauna, and carbonates. Science, 231, 561–566.
Legg, M. R., Luyendyk, B. P., Mammerickx, J., Moustier, C., and
Tyce, R. C., 1989. Sea Beam survey of an active strike-slip fault:
the San Clemente fault in the California Continental Borderland.
Journal of Geophysical Research, Solid Earth, 94(B2),
1727–1744.
Levin, L. A., 2005. Ecology of cold seep sediments: interactions of
fauna with flow, chemistry, and microbes. Oceanography and
Marine Biology an Annual Review, 43, 1–46.
MacDonald, I. R., Buthman, D. B., Sager, W. W., Peccini, M. B.,
and Guinasso, N. L., 2000. Pulsed oil discharge from a mud volcano. Geology, 28, 907–910.
MacDonald, I. R., Bohrmann, G., Escobar, E., Abegg, F., Blanchon,
P., Blinova, V., and De Farago, M., 2004. Asphalt volcanism and
chemosynthetic life in the Campeche Knolls, Gulf of Mexico.
Science, 304, 999–1002.
Paull, C. K., Chanton, J. P., Neumann, A. C., Coston, J. A., Martens,
C. S., and Showers, W., 1992. Indicators of methane-derived carbonates and chemosynthetic organic carbon deposits: examples
from the Florida Escarpment. Palaios, 7, 361–375.
Reeburgh, W. S., 1976. Methane consumption in Cariaco Trench
waters and sediments. Earth and Planetary Science Letters, 28,
337–344.
Reeburgh, W. S., 2007. Oceanic methane biogeochemistry. Chemical Reviews, 107, 486–513.
Römer, M. 2011., Gas bubble emissions at continental
margins: detection, mapping, and quantification. University of
COLD SEEPS
121
found offshore Costa Rica, South China Sea, New
Zealand, and in the Gulf of Cadiz (reviewed by Suess,
2010).
Although not as common as the carbonate occurrences,
barite (BaSO 4 ) deposits have been observed along structurally controlled sites of cold-fluid seepage in several
continental margins. Barite pillars along the San Clemente
fault can reach 10 m in height, and similar deposits have
been reported on the Sea of Okhotsk. Less massive but
distinct barite occurrences have also been reported in the
Alaska margin, Monterey Canyon, Peru margin, and the
Gulf of Mexico (Torres et al., 2003). The formation of
these deposits is intimately linked with the sulfate concentrations, which in the highly reduced environments that
characterize cold seeps is depleted at shallow depths
within the sediments. At low sulfate, any barite in the sediment will dissolve, leading to high levels of dissolved
barium in the upwardly migrating fluids. Upon
discharging at the seafloor, barium quickly reacts with seawater sulfate and precipitates in the newly formed barite
deposits.
Paleoseeps
The occurrence of carbonates in the geologic record
enriched in the light
12 C isotope has been commonly
attributed to authigenic formation at paleo-methane seeps,
which indicate significant methane release from the Proterozoic to the present (Campbell, 2006). The cold seep barite deposits likely constitute the modern analogues to
Paleozoic stratiform barite deposits, now being mined in
Nevada, Arkansas, Mexico, and South China. These barite
deposits represent large-scale submarine methane venting,
which could have affected the Paleozoic carbon cycle and
perhaps modified ancient climate (Torres et al., 2003).
Summary
Along the ocean margins, sediments experience chemical,
microbial, and physical transformations that result in the
generation and expulsion of reduced gases and water at
the seafloor, in what is known as cold seepage.
Methane is generated by microbial or thermochemical
processes in the organic-rich marine sediments. Hydrogen
sulfide is a by-product of microbial oxidation of methane
under anaerobic conditions. Water is produced at greater
depths by dehydration reactions of smectite and to a lesser
extent opal. Accumulation of the excess water and gas creates overpressures that can fracture the overlying geological formations and drive fluid flow. Sediment compaction,
generation of hydraulic heads, and tectonic compression
also act as driving forces for fluids that eventually discharge at the seafloor.
Whereas the majority of life in the deep ocean floor rely
upon low levels of sinking organic matter, the chemosynthetic microbial communities at cold seeps take advantage
of high fluxes of bioreactive reductants to support unique,
oasis-type cold seep biomes in which the density of organisms is several orders of magnitude greater than in the surrounding regions. Authigenic carbonate and barite
deposits, which can reach extremely large accumulations,
characterize areas of cold seepage and constitute a geologic record of methane discharge at paleo-seep sites.
Bibliography
Barnes, R. O., and Goldberg, E. D., 1976. Methane production and
consumption in anoxic marine sediments. Geology, 4, 297–300.
Boetius, A., and Suess, E., 2004. Hydrate Ridge: a natural laboratory for the study of microbial life fueled by methane from
near-surface gas hydrates. Chemical Geology, 205, 291–310.
Bohrmann, G., Greinert, J., Suess, E., and Torres, M., 1998.
Authigenic carbonates from the Cascadia subduction zone and
their relation to gas hydrate stability. Geology, 26, 647–650.
Campbell, K. A., 2006. Hydrocarbon seep and hydrothermal
vent paleoenvironments: past developments and future
research directions. Palaeogeography, Palaeoclimatology,
Palaeoecology, 232, 362–407.
Colten-Bradley, V. A., 1987. Role of pressure in smectite dehydration–effects on geopressure and smectite-to-illite transformation. AAPG Bulletin, 71, 1414–1427.
Faure, K., Greinert, J., Schneider von Deimling, J., McGinnis, D. F.,
Kipfer, R., and Linke, P., 2010. Methane seepage along the
Hikurangi Margin of New Zealand: geochemical and physical
data from the water column, sea surface and atmosphere. Marine
Geology, 272, 170–188.
Heeschen, K. U., Collier, R. W., de Angelis, M. A., Suess, E.,
Rehder, G., Linke, P., and Klinkhammer, G. P., 2005. Methane
sources, distributions, and fluxes from cold vent sites at Hydrate
Ridge, Cascadia Margin. Global Biogeochemical Cycles, 19.
GB2016. doi:10.1029/2004GB002266.
Kulm, L. D., Suess, E., Moore, J. C., Carson, B., Lewis, B. T.,
Ritger, S. D., Kadko, D. C., Thornburg, T. M., Embley, R. W.,
Rugh, W. D., Massoth, G. J., Langseth, M. G., Cochrane,
G. R., and Scamman, R. L., 1986. Oregon subduction zone:
venting, fauna, and carbonates. Science, 231, 561–566.
Legg, M. R., Luyendyk, B. P., Mammerickx, J., Moustier, C., and
Tyce, R. C., 1989. Sea Beam survey of an active strike-slip fault:
the San Clemente fault in the California Continental Borderland.
Journal of Geophysical Research, Solid Earth, 94(B2),
1727–1744.
Levin, L. A., 2005. Ecology of cold seep sediments: interactions of
fauna with flow, chemistry, and microbes. Oceanography and
Marine Biology an Annual Review, 43, 1–46.
MacDonald, I. R., Buthman, D. B., Sager, W. W., Peccini, M. B.,
and Guinasso, N. L., 2000. Pulsed oil discharge from a mud volcano. Geology, 28, 907–910.
MacDonald, I. R., Bohrmann, G., Escobar, E., Abegg, F., Blanchon,
P., Blinova, V., and De Farago, M., 2004. Asphalt volcanism and
chemosynthetic life in the Campeche Knolls, Gulf of Mexico.
Science, 304, 999–1002.
Paull, C. K., Chanton, J. P., Neumann, A. C., Coston, J. A., Martens,
C. S., and Showers, W., 1992. Indicators of methane-derived carbonates and chemosynthetic organic carbon deposits: examples
from the Florida Escarpment. Palaios, 7, 361–375.
Reeburgh, W. S., 1976. Methane consumption in Cariaco Trench
waters and sediments. Earth and Planetary Science Letters, 28,
337–344.
Reeburgh, W. S., 2007. Oceanic methane biogeochemistry. Chemical Reviews, 107, 486–513.
Römer, M. 2011., Gas bubble emissions at continental
margins: detection, mapping, and quantification. University of
COLD SEEPS
121