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

作　　者：XU Cuiling GREINERT Jens HAECKEL Matthias BIALAS Jorg DIMITROV Lyubomir ZHAO Guangtao 

机构地区：[1]College of Marine Geo-Sciences, Ocean University of China, Qingdao 266100, China [2]GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel 24148, Germany [3]Institute of Oceanology Bulgarian Academy of Science, Varna 9000, Bulgaria

出　　处：《Journal of Ocean University of China》2018年第3期555-562,共8页中国海洋大学学报（英文版）

基　　金：funded by the European project EUROFLEETS (Seventh Framework Programme, No. 228344)

摘　　要：Seafloor elongated depressions are indicators of gas seepage or slope instability. Here we report a sequence of slopeparallel 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 slopeparallel 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.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 en-riched 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 sup-ported by sediment erosion due to slope-parallel water currents.

关 键 词：methane seepage elongated depression POCKMARK LANDSLIDE Black Sea 

分 类 号：P736.12[天文地球—海洋地质]