Stagnant, oxygen reduced environment in the inner Kveithola Trough (Barents Sea): Preliminary report from the CORIBAR cruise (R/V Maria S. Merian, July-August 2013).

The Kveithola Through is a small, confined, sedimentary system that hosted a fast flowing ice stream during the last glacial maximum (Rüther et al., 2012; Bjarnadóttir et al., 2013). The inner area of the through contains a morphologically-complex sediment drift formed by two depocentres separated by the innermost Grounding Zone Wedge testifying the episodic retreat of the Kveithola ice stream after LGM (Rebesco et al., 2011). Bathymetry and seismic reflectors suggest a dynamic environment accompanied the build-up of the sediment drift with persistent currents scoop-out the northern moat (Hanebuth et al., 2013). Such a type of environment is in discordance with the present bottom environmental characteristics. Surface sediments in the Kveithola drift area are fine grained, soft and soupy with a “jellylike” consistency. The sea-bottom surface is usually cracked and slightly hummocky with cm-large, open holes similar to burrows, and small, mounded feature with a shallow depression on the top filled by black, organic matter rich sediments (Fig. 1). Indurated/cemented worm burrows were also observed. The sediments have a strong smell of H2S and they are mostly black, organic matter rich, with abundant worm tubes and occasionally reddish polychaetes living into the soft sediment surface (Fig. 1). The lack of any sediment structures indicating bottom currents and the presence of a benthic foraminiferal fauna typical of oxygen-depleted environments, suggest that the inner Kveithola through is presently a stagnant environment and the above described sedimentary structures are re-interpreted and associated to surface fluid escape.