The Character and Formation of Elongated Depressions on the Upper Bulgarian Slope.

Xu, Cuiling, Greinert, Jens, Haeckel, Matthias, Bialas, Jörg, Dimitrov, L. and Zhao, Guangtao (In Press / Accepted) The Character and Formation of Elongated Depressions on the Upper Bulgarian Slope. Journal of Ocean University of China, 17 (1).

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Abstract

Seafloor elongated depressions are indicators of gas seepage or slope instability. Here we report a sequence of slope-parallel elongated depressions that link to headwalls of sediment slides on upper slope. The depressions of about 250 m in width and several kilometers in length are areas of focused gas discharge indicated by bubble-release into the water column and methane enriched pore waters. Sparker seismic profiles running perpendicular and parallel to the coast, show gas migration pathways and trapped gas underneath these depressions with bright spots and seismic blanking. The data indicate that upward gas migration is the initial reason for fracturing sedimentary layers. In the top sediment where two young stages of landslides can be detected, the slope-parallel sediment weakening lengthens and deepens the surficial fractures, creating the elongated depressions in the seafloor supported by sediment erosion due to slope-parallel water currents.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/228344
Additional Information: This is publication 27 of the DeepSea Monitoring group at GEOMAR.
Keywords: methane seepage, elongated depression, pockmark, landslide, Black Sea; SPUX cruise, RV Akademik, AK211
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems > DeepSea Monitoring
Refereed: Yes
Open Access Journal?: No
ISSN: 1672-5182
Projects: Eurofleets
Contribution Number:
ProjectNumber
DSM27
Date Deposited: 04 Sep 2017 08:39
Last Modified: 05 Sep 2017 12:57
URI: http://oceanrep.geomar.de/id/eprint/39236

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