Data Description

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Teichert, BMA et al. (2005): (Table 1) Stable isotope data of chemoherm carbonates at Hydrate Ridge on the Cascadia continental margin. doi:10.1594/PANGAEA.770414,
Supplement to: Teichert, Barbara MA; Bohrmann, Gerhard; Suess, Erwin (2005): Chemoherms on Hydrate Ridge - Unique microbially mediated carbonate build-ups growing into the water column. Palaeogeography, Palaeoclimatology, Palaeoecology, 227(1-3), 67-85, doi:10.1016/j.palaeo.2005.04.029
Two active chemoherm build-ups growing freely up into the oceanic water column, the Pinnacle and the South East-Knoll Chemoherms, have been discovered at Hydrate Ridge on the Cascadia continental margin. These microbially-mediated carbonate formations rise above the seafloor by several tens of meters and display a pinnacle-shaped morphology with steep flanks. The recovered rocks are pure carbonates dominated by aragonite. Based on fabric and mineralogic composition different varieties of authigenic aragonite can be distinguished. Detailed visual and petrographic investigations unambiguously reveal the involvement of microbes during the formation of the carbonates. The fabric of the cryptocrystalline and fibrous aragonite can be described as thrombolitic. Fossilized microbial filaments in the microcrystalline aragonite indicate the intimate relationship between microbes and carbonates. The strongly 13C-depleted carbon isotope values of the samples (as low as -48.1 per mill PDB) are characteristic of methane as the major carbon source for the carbonate formation. The methane-rich fluids from which the carbonates are precipitated originate most probably from a gas reservoir below the bottom-simulating reflector (BSR) and rise through fault systems. The d18O values of the aragonitic chemoherm carbonates are substantially higher (as high as 5.0 per mill PDB) than the expected equilibrium value for an aragonite forming from ambient seawater (3.5 per mill PDB). As a first approximation this indicates formation from glacial ocean water but other factors are considered as well. A conceptual model is presented for the precipitation of these chemoherm carbonates based on in situ observations and the detailed petrographic investigation of the carbonates. This model explains the function of the consortium of archaea and sulfate-reducing bacteria that grows on the carbonates performing anaerobic oxidation of methane (AOM) and enabling the precipitation of the chemoherms above the seafloor surrounded by oxic seawater. Beggiatoa mats growing on the surface of the chemoherms oxidize the sulfide provided by sulfate-dependent anaerobic oxidation of methane within an oxic environment. The contact between Beggiatoa and the underlying microbial consortium represents the interface between the overlying oxic water column and an anoxic micro-environment where carbonate formation takes place.
Median Latitude: 44.541027 * Median Longitude: -125.125463 * South-bound Latitude: 44.448233 * West-bound Longitude: -125.153000 * North-bound Latitude: 44.568500 * East-bound Longitude: -125.030317
Date/Time Start: 2000-07-28T08:33:00 * Date/Time End: 2000-07-28T11:07:00
Minimum Elevation: -812.0 m * Maximum Elevation: -616.0 m
3422-11-1 * * Latitude: 44.568500 * Longitude: -125.152700 * Elevation: -774.0 m * Campaign: AT3-35B * * Basis: Atlantis (1997) * * Device: Submersible Alvin (ALVIN) *
3424-4-A * * Latitude: 44.568330 * Longitude: -125.152830 * Elevation: -812.0 m * Campaign: AT3-35B * * Basis: Atlantis (1997) * * Device: Manipulator arm (ROV_MA) *
3424-4-C * * Latitude: 44.568500 * Longitude: -125.152700 * Elevation: -812.0 m * Campaign: AT3-35B * * Basis: Atlantis (1997) * * Device: Manipulator arm (ROV_MA) *
#NameShort NameUnitPrincipal InvestigatorMethodComment
1Event label *Event
2Latitude of event *Latitude
3Longitude of event *Longitude
4Elevation of event *Elevationm
5Sample code/label *LabelTeichert, Barbara MA *
6Location type *Loc typeTeichert, Barbara MA *
7delta 13C, carbonate *d13C carbper mil PDBTeichert, Barbara MA *
8delta 13C, standard deviation *d13C std dev±Teichert, Barbara MA *
9delta 18O, carbonate *d18O carbper mil PDBTeichert, Barbara MA *
10delta 18O, standard deviation *d18O std dev±Teichert, Barbara MA *
264 data points

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