Rouchy, J. M., Suc, J. P., Ferrandini, J., and Ferrandini, M., 2006.
The Messinian salinity crisis revisited. Editorial. Sedimentary
Geology, 188–189, 1–8.
Ryan, W. B. F., 2009. Decoding the Mediterranean salinity crisis.
Sedimentology, 56, 95–136.
Ryan, W. B. F., Hsü, K. J., et al., 1973. Initial Reports of the Deep
Sea Drilling Project. Washington, DC: U.S. Government Printing Office, Vol. 13, Parts 1 and 2, p. 1447.
Schreiber, B. C., and El Tabakht, M., 2000. Deposition and early
alteration of evaporates. Sedimentology, 47, 215–238.
Schreiber, B. C., Friedman, G. M., Decima. A., and Schreiber, E.,
1976. Depositional environments of Upper Miocene
(Messinian) evaporite deposits of the Sicilian Basin. Sedimentology, 23, 729–760.*
Scruton, P. C., 1953. Deposition of evaporates. American Association of Petroleum Geologists, 37, 2498–2512.
Shearman, D. J., 1966. Origin of marine evaporites by diagenesis.
Institute of Mining and Metallurgy Transactions, Section B, 75,
208–215.
Stoffers, P., and Ross, D. A., 1974. Sediment history of the Red Sea.
In Whitmarsh, R. B., Weser, O. E., Ross, D. A., et al. (eds.), Initial Reports of the Deep Sea Drilling Project. Washington, DC:
U.S. Government Printing Office, Vol. 23, pp. 849–865.
Usiglio, J., 1849. Analyse de L’eau de la Mediterranee sur les cotes
de France. Annalen der Chemie, 27(92–107), 172–191.
Warren, J. K., 2006. Evaporites: Sediments, Resources and Hydrocarbons. Berlin: Springer.
Warren, J. K., 2010. Evaporites through time: tectonic, climatic, and
eustatic controls on marine and nonmarine deposits. EarthScience Reviews, 98, 217–268.
Cross-references
Anoxic Oceans
Astronomical Frequencies in Paleoclimates
Events
Laminated Sediments
Marine Mineral Resources
Ocean Drilling
Organic Matter
Paleoceanography
Source Rocks, Reservoirs
MARINE GAS HYDRATES
Gerhard Bohrmann
1 and Marta E. Torres
2
1
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
2
College of Earth, Ocean, and Atmospheric Sciences,
Oregon State University, Corvallis, OR, USA
Synonyms
Clathrates; Gas hydrates; Methane hydrates
Definition
Gas hydrates are non-stoichiometric solid compounds in
which low-molecular-weight gases are trapped (guests)
within water cavities (hosts). The presence of gas hydrates
is controlled by temperature, pressure, and the availability
of appropriate gases and water.
Historic background
Gas hydrates were first described in the nineteenth century
by Sir Humphry Davy, with his pioneering synthesis of
chlorine hydrate. This type of compounds sparked industrial interest in the 1930s, when it became apparent that
methane hydrates formed spontaneously within natural
gas pipelines in permafrost regions. Research spearheaded
by the oil and gas industry at that time created the foundation for our current understanding of the behavior of these
compounds (Sloan and Koh, 2008). By the 1970s, Russian
scientists had postulated that under certain temperature
and pressure conditions, methane hydrates could form in
natural systems and indeed observed these natural
deposits in the Siberian permafrost. This discovery was
soon followed by reports of methane hydrate presence in
Canada’s MacKenzie Delta and the Caspian and Black
Seas. The next important advance in the study of these
deposits came with the realization that sediments hosting
gas hydrate could be imaged by seismic data (Stoll et al.,
1971), thus providing a prospecting tool that fueled
exploratory efforts along continental margins worldwide.
Gas hydrates were first cored by the Deep Sea Drilling
Project (DSDP) in 1970 on the Blake Ridge
(US continental margin), and the first deep-sea gas hydrate
specimens were observed in sediments recovered from the
Middle America Trench during DSDP Legs 66 and 67 in
1979. Since then, scientific ocean drilling has provided
critical data toward the fundamental understanding of the
nature, composition, and distribution of naturally occurring gas hydrates (Sloan and Koh, 2008). Large-scale
new projects spearheaded by national-industry consortia
are targeting gas hydrate deposits in search for new energy
resources. Such projects are under way in the Indian
Ocean, the South China Sea, the eastern sea off Korea,
and both the eastern and western margins of Japan
(Collett et al., 2009). In addition to scientific drilling
efforts, near-surface gas hydrate deposits have been recovered from continental margins worldwide (Kvenvolden,
1988). These near-surface deposits are usually associated
with locations of active cold seepage, where rapid transport of methane allows for massive deposits to form near
the seafloor (Suess et al., 1999; Torres et al., 2011).
Gas hydrate stability in marine sediments
The stability of gas hydrate is fundamentally controlled by
thermodynamic equilibria (Sloan and Koh, 2008). The
pressure/temperature conditions required for pure methane hydrate stability are illustrated in Figure 1. The phase
boundary is determined by the gas composition and by the
ionic strength of the water (Figure 1a). The presence of
CO 2 , H 2 S, ethane, and/or propane shifts the stability curve
to the right, in effect increasing the gas hydrate stability.
The presence of dissolved ions in the pore fluids, on the
other hand, decreases the gas hydrate stability, so that an
increase in salinity of the fluids from which the gas
hydrate is forming shifts the phase boundary to the left
(Figure 1a).
MARINE GAS HYDRATES
433
The Messinian salinity crisis revisited. Editorial. Sedimentary
Geology, 188–189, 1–8.
Ryan, W. B. F., 2009. Decoding the Mediterranean salinity crisis.
Sedimentology, 56, 95–136.
Ryan, W. B. F., Hsü, K. J., et al., 1973. Initial Reports of the Deep
Sea Drilling Project. Washington, DC: U.S. Government Printing Office, Vol. 13, Parts 1 and 2, p. 1447.
Schreiber, B. C., and El Tabakht, M., 2000. Deposition and early
alteration of evaporates. Sedimentology, 47, 215–238.
Schreiber, B. C., Friedman, G. M., Decima. A., and Schreiber, E.,
1976. Depositional environments of Upper Miocene
(Messinian) evaporite deposits of the Sicilian Basin. Sedimentology, 23, 729–760.*
Scruton, P. C., 1953. Deposition of evaporates. American Association of Petroleum Geologists, 37, 2498–2512.
Shearman, D. J., 1966. Origin of marine evaporites by diagenesis.
Institute of Mining and Metallurgy Transactions, Section B, 75,
208–215.
Stoffers, P., and Ross, D. A., 1974. Sediment history of the Red Sea.
In Whitmarsh, R. B., Weser, O. E., Ross, D. A., et al. (eds.), Initial Reports of the Deep Sea Drilling Project. Washington, DC:
U.S. Government Printing Office, Vol. 23, pp. 849–865.
Usiglio, J., 1849. Analyse de L’eau de la Mediterranee sur les cotes
de France. Annalen der Chemie, 27(92–107), 172–191.
Warren, J. K., 2006. Evaporites: Sediments, Resources and Hydrocarbons. Berlin: Springer.
Warren, J. K., 2010. Evaporites through time: tectonic, climatic, and
eustatic controls on marine and nonmarine deposits. EarthScience Reviews, 98, 217–268.
Cross-references
Anoxic Oceans
Astronomical Frequencies in Paleoclimates
Events
Laminated Sediments
Marine Mineral Resources
Ocean Drilling
Organic Matter
Paleoceanography
Source Rocks, Reservoirs
MARINE GAS HYDRATES
Gerhard Bohrmann
1 and Marta E. Torres
2
1
MARUM-Center for Marine Environmental Sciences,
University of Bremen, Bremen, Germany
2
College of Earth, Ocean, and Atmospheric Sciences,
Oregon State University, Corvallis, OR, USA
Synonyms
Clathrates; Gas hydrates; Methane hydrates
Definition
Gas hydrates are non-stoichiometric solid compounds in
which low-molecular-weight gases are trapped (guests)
within water cavities (hosts). The presence of gas hydrates
is controlled by temperature, pressure, and the availability
of appropriate gases and water.
Historic background
Gas hydrates were first described in the nineteenth century
by Sir Humphry Davy, with his pioneering synthesis of
chlorine hydrate. This type of compounds sparked industrial interest in the 1930s, when it became apparent that
methane hydrates formed spontaneously within natural
gas pipelines in permafrost regions. Research spearheaded
by the oil and gas industry at that time created the foundation for our current understanding of the behavior of these
compounds (Sloan and Koh, 2008). By the 1970s, Russian
scientists had postulated that under certain temperature
and pressure conditions, methane hydrates could form in
natural systems and indeed observed these natural
deposits in the Siberian permafrost. This discovery was
soon followed by reports of methane hydrate presence in
Canada’s MacKenzie Delta and the Caspian and Black
Seas. The next important advance in the study of these
deposits came with the realization that sediments hosting
gas hydrate could be imaged by seismic data (Stoll et al.,
1971), thus providing a prospecting tool that fueled
exploratory efforts along continental margins worldwide.
Gas hydrates were first cored by the Deep Sea Drilling
Project (DSDP) in 1970 on the Blake Ridge
(US continental margin), and the first deep-sea gas hydrate
specimens were observed in sediments recovered from the
Middle America Trench during DSDP Legs 66 and 67 in
1979. Since then, scientific ocean drilling has provided
critical data toward the fundamental understanding of the
nature, composition, and distribution of naturally occurring gas hydrates (Sloan and Koh, 2008). Large-scale
new projects spearheaded by national-industry consortia
are targeting gas hydrate deposits in search for new energy
resources. Such projects are under way in the Indian
Ocean, the South China Sea, the eastern sea off Korea,
and both the eastern and western margins of Japan
(Collett et al., 2009). In addition to scientific drilling
efforts, near-surface gas hydrate deposits have been recovered from continental margins worldwide (Kvenvolden,
1988). These near-surface deposits are usually associated
with locations of active cold seepage, where rapid transport of methane allows for massive deposits to form near
the seafloor (Suess et al., 1999; Torres et al., 2011).
Gas hydrate stability in marine sediments
The stability of gas hydrate is fundamentally controlled by
thermodynamic equilibria (Sloan and Koh, 2008). The
pressure/temperature conditions required for pure methane hydrate stability are illustrated in Figure 1. The phase
boundary is determined by the gas composition and by the
ionic strength of the water (Figure 1a). The presence of
CO 2 , H 2 S, ethane, and/or propane shifts the stability curve
to the right, in effect increasing the gas hydrate stability.
The presence of dissolved ions in the pore fluids, on the
other hand, decreases the gas hydrate stability, so that an
increase in salinity of the fluids from which the gas
hydrate is forming shifts the phase boundary to the left
(Figure 1a).
MARINE GAS HYDRATES
433