New insights into geology and geochemistry of the Kerch seep area in the Black Sea

Zander, Timo, Haeckel, Matthias, Klaucke, Ingo, Bialas, Jörg, Klaeschen, Dirk, Papenberg, Cord, Pape, Thomas, Berndt, Christian and Bohrmann, Gerhard (2019) New insights into geology and geochemistry of the Kerch seep area in the Black Sea Marine and Petroleum Geology (Article number 104162). DOI 10.1016/j.marpetgeo.2019.104162.

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Supplementary data:

Abstract

Highlights

• Combining porewater geochemistry, geochemical modeling and subsurface geophysical data in order to understand the fluid flow system of Kerch seep area.
• This seep area is not in steady state.
• Methane transport is in the form of gas bubbles not porewater advection.
• High surface temperatures are the result of hydrate formation and not an indication for elevated geothermal gradients.
• Modeling says this seep is young (<500 years old).

Abstract

High-resolution 3D seismic data in combination with deep-towed sidescan sonar data and porewater analysis give insights into the seafloor expression and the plumbing system of the actively gas emitting Kerch seep area, which is located in the northeastern Black Sea in around 900 m water depth, i.e. well within the gas hydrate stability zone (GHSZ). Our analysis shows that the Kerch seep consists of three closely spaced but individual seeps above a paleo-channel-levee system of the Don Kuban deep-sea fan. We show that mounded seep morphology results from sediment up-doming due to gas overpressure. Each of the seeps hosts its own gas pocket underneath the domes which are fed with methane of predominantly microbial origin along narrow pipes through the GHSZ. Methane transport occurs dominantly in the form of gas bubbles decoupled from fluid advection. Elevated sediment temperatures of up to 0.3 °C above background values are most likely the result of gas hydrate formation within the uppermost 10 m of the sediment column. Compared to other seeps occurring within the GHSZ in the Black Sea overall only scarce gas indications are present in geoacoustic and geophysical data. Transport-reaction modeling suggests that the Kerch seep is a young seep far from steady state and probably not more than 500 years old.

Document Type: Article
Keywords: Black Sea, Gas hydrates, Cold seep, Seismic imaging, Fluid flow, Porewater geochemistry, POS427, M84/2
Research affiliation: MARUM
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
DOI etc.: 10.1016/j.marpetgeo.2019.104162
ISSN: 0264-8172
Projects: DOKU-GAS, SUGAR
Expeditions/Models:
Date Deposited: 12 Dec 2019 10:37
Last Modified: 12 Dec 2019 13:05
URI: http://eprints.uni-kiel.de/id/eprint/48422

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