Publication Date:
2011-05-10
Description:
Quantifying in-situ gas hydrates at active seep sites in the eastern Black Sea using pressure coring technique Biogeosciences Discussions, 8, 4529-4558, 2011 Author(s): K. Heeschen, M. Haeckel, I. Klaucke, M. K. Ivanov, and G. Bohrmann In the eastern Black Sea, we determined methane (CH 4 ) concentrations, gas hydrate volumes and their vertical distribution from combined gas and chloride (Cl − ) measurements within pressurized sediment cores. The total gas volume collected from the cores corresponds to concentrations of 1.2–1.4 mol of methane per kg porewater at in-situ pressure, which is equivalent to a gas hydrate saturation of 15–18% of pore volume and amongst the highest values detected in shallow seep sediments. At the central seep site, a high-resolution Cl − profile resolves the upper gas hydrate stability boundary and a continuous layer of hydrates in a sediment column of 120 cm thickness. Including this information, a more precise gas hydrate saturation of 22–24% pore volume can be calculated. This is higher in comparison to a saturation calculated from the Cl − profile alone, resulting in 14.4%. The likely explanation is an active gas hydrate formation from CH 4 gas ebullition. The hydrocarbons at Batumi Seep are of shallow biogenic origin (CH 4 〉 99.6%), at Pechori Mound they originate from deeper thermocatalytic processes as indicated by the lower ratios of C 1 to C 2 –C 3 and the presence of C 5 .
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
