BURSTER: BOTTOM CURRENTS IN A STAGNANT ENVIRONMENT

The glacigenic Kveithola Trough is an abrupt and narrow (100 km-long and 13 kmwide) sedimentary system located in the NW Barents Sea (Rebesco et al., 2011; Ruther et al., 2012; Bjarnadóttir et al., 2013). Along with the larger Storfjorden glacial system, it hosted, during the last glaciation, ice streams draining ice from the southern Svalbard in the north and Bear Island in the south (Andreassen et al., 2008; Pedrosa et al., 2011). During the CORIBAR Cruise on board RV Maria S. Merian (16.07. - 15.08.2013; Tromsø - Tromsø) a wealth of geophysical data including PARASOUND sub-bottom profiles and multibeam, and sediment samples retrieved by gravity-, multi-, boxcorer, and the seafloor drill rig MeBo (Hanebuth et al., 2013) were collected on the Kveithola Drift, a complex morphological and depositional feature confined in the innermost part of the glacially-erode Kveithola Trough. The internal seismic reflections of the drift show a drastic thinning and termination towards the north. Here a distinct moat can be identified, which implies the strong influence of dense bottom currents, inferred to flow (or at least to have flown in the past) towards the outer shelf. The highly dynamic environment depicted from the morphological and structural characteristics of the sediment drift is in contrast with the sediment facies and preserved biota observed in surface sediments. The retrieved sediments have a strong smell of H2S and are mostly black, organic matter-rich, with abundant black worm tubes (Pogonophora worms), and occasionally with living reddish polychaetes (possibly ampharetid polychaetes). The recent and living benthic foraminiferal assemblage observed in the sediments is characterized by the presence of typically oxygen-depleted environmental taxa. Any bottom current-related sedimentary structure was observed on surface sediments. The Kveithola Drift that formed under persistent dense bottom currents appears today as a “stagnant environment” strongly affected by low-oxygen conditions with likely ongoing seep activity. The presence of an apparently stagnant, possibly chemosynthetic, environment in the sediment drift area of the inner Kveithola Through was an unexpected discovery. We therefore think it is of primary importance to better define the bio-geochemical and oceanographic characteristics of the inner area of the Kveithola Trough in order to better define this “anomalous” sedimentary system and to understand the local and global impact of this type of environment in terms of carbon cycle and the transfer of chemosynthetic-derived products to the deeper environments as consequence of regional oceanographic patterns. The BURSTER project aims to investigate the geodynamic and hydrographic conditions, and the active gas seepage present in the pockmark-field piercing the sediment drift located in the inner part of the Kveithola Trough. The type of investigation is strongly multidisciplinary including physical and biological oceanography, water, sediment and gas geochemistry, micropaleontology, microbiology geophysics, and sedimentology. The investigations will be carried out within three working days with the aim of outlining the principal oceanographic, biological and geological aspects of the area on which building up further investigations.