Methan-induzierte Karbonate entlang des Cascadia Kontinentalrandes: Archive des episodischen Methanausstroms
Final Report Abstract
Since the discovery of methane seepage settings in the mid-1980s, significant progress has been achieved in understanding the processes and controlling factors of these environments. They have been identified as highly dynamic systems, both, in space and time, ranging in extent from a restricted local occurrence to a wider regional distribution over tens of kilometers. The successful dating of authigenic carbonates has greatly advanced our understanding of the controlling mechanisms of methane flux. In addition, they provide information about the biogeochemical processes responsible for carbonate precipitation, the source depth of the emanating fluids, diagenetic processes within the sediments, and finally fluid flow rates. This project has advanced our understanding of methane seep locations with respect to mechanisms that trigger methane outflow on the seafloor namely climatic or tectonic changes. The results from Teichert et al. (2014) as well as Kocherla et al. (2015) have shown that the influence of glacial/interglacial sea level changes on methane systems is a globally important controlling process in several methane seep systems. For the first time, it was possible to trace distinct horizons of authigenic carbonates along the continental margin of India (Krishna-Godavari Basin) over a distance of about 130 km. The results show that also local tectonic activity can be an important controlling process that can possibly be used as part of an earthquake warning system if the composition of the outflowing fluids change already prior to an earthquake event. This will be part of further investigations in future projects. This project has also advanced our understanding of the mineralogical composition of methane seep carbonates. Carbonate mineralogies like aragonite, high Mg-calcite and Carich dolomite are a typical paragenesis occurring at methane seeps. This has been shown at two different locations at the Cascadia continental margin as well as the Indian continental margin. This points towards a successive Ca-depletion in pore waters of shallow sediments due to rapid carbonate formation. The extensive carbonate formation at such locations might play an underestimated role in the global carbon cycle.
Publications
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(2014) Composition and origin of authigenic carbonates in the Krishna- Godavari and Mahanadi Basins, eastern continental margin of India. Marine and Petroleum Geology 58, 438-460
Teichert, B.M.A., Johnson, J., Solomon, E.A., Giosan, L., Rose, K., Kocherla, M., Connolly, E.C., Torres, M.E.
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(2015) Formation of methane-related authigenic carbonates in a highly dynamic biogeochemical system in the Krishna-Godavari Basin, Bay of Bengal. Marine and Petroleum Geology 64, 324-333
Kocherla, M., Teichert, B.M.A., Pillai, S., Satyanarayanan, M., Ramamurthy, P.B., Patil, D.J., Rao, A.N.
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Sulfate-dependent anaerobic oxidation of methane at a highly dynamic bubbling site in the Eastern Sea of Marmara (Çinarcik Basin). Deep-Sea Research Part II
Teichert, B.M.A., Chevalier, N., Gussone, N., Bayon, G., Ponzevera, E., Ruffine, L., Strauss, H.
