Investigating a gas hydrate system in apparent disequilibrium in the Danube Fan, Black Sea.

Hillman, Jess I. T., Burwicz, Ewa B. , Zander, Timo, Bialas, Jörg , Klaucke, Ingo , Feldman, Howard, Drexler, Tina and Awwiller, David (2018) Investigating a gas hydrate system in apparent disequilibrium in the Danube Fan, Black Sea. Earth and Planetary Science Letters, 502 . pp. 1-11. DOI 10.1016/j.epsl.2018.08.051.

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Abstract

Highlights

• BSR position does not match BGHS as predicted based on regional TP conditions.
• Use steady state and transient models to determine extent of hydrate stability.
• Investigate the influence of topographic focusing on hydrate stability.
• Variable thermal properties of sediment impact hydrate stability.

The Danube Fan in the western Black Sea shows many features indicating the presence of gas and gas hydrates, including a bottom simulating reflection (BSR), high-amplitude anomalies beneath the BSR and the presence of gas flares at the seafloor. The BSR depth derived from 3D P-cable seismic data of an older slope canyon of the fan (the S2 canyon) suggests that the BSR is not in equilibrium with the present-day topography. The Danube Fan was abandoned ∼7.5 ka, and the S2 canyon was likely incised ∼20 ka, suggesting that the gas hydrate system has had at least 7.5 ka years to equilibrate to the present-day conditions.

Here we examine the extent and position of the hydrate stability zone through constructing both steady and transient state models of a 2D profile across the S2 canyon. This was done using inputs from mapping of the 3D P-cable seismic data and geochemical analysis of core samples. Using these models, we investigate the effects of different factors including variable thermal properties of heterogeneous sediments in the vicinity of the canyon and, topographic focusing on the geothermal gradient on the extent of the hydrate stability zone. Our results indicate that both factors have a significant effect and that the hydrate system may actually be in, or approaching equilibrium.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/603418
Keywords: gas hydrate, modelling, Danube Fan, Black Sea, BSR
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.epsl.2018.08.051
ISSN: 0012-821X
Projects: MIDAS, SUGAR
Expeditions/Models/Experiments:
Date Deposited: 10 Sep 2018 10:12
Last Modified: 01 Feb 2019 15:07
URI: http://oceanrep.geomar.de/id/eprint/44183

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