Sedimentary processes on the continental slope off Kvitøya and Albertini troughs north of Nordaustlandet, Svalbard – The importance of structural-geological setting in trough-mouth fan development

Abstract

New marine-geophysical data were analyzed to investigate the sedimentary processes operating on the continental slope north of Nordaustlandet, Svalbard. Kvitøya Trough terminates in a trough-mouth fan (TMF) on the slope, whereas Albertini Trough incises the shelf edge and a TMF is notably absent. Instead, the continental slope beyond Albertini Trough is dominated by thick, acoustically stratified units likely formed by down-slope and along-slope sedimentological processes combined. The morphological and sedimentological differences between Albertini and Kvitøya troughs may partly be due to the larger dimensions of Kvitøya Trough and its associated glacial catchment area relative to Albertini, suggesting that the transport of a larger volume of glacigenic sediments potentially was a contributing factor in building Kvitøya TMF. By contrast, the downfaulted bedrock below outer Albertini Trough provided larger accommodation space for glacigenic sediments which accumulated in an outer-shelf basin, highlighting the importance of the structural-geological setting in TMF development. Debris-flow deposits and/or channel-levee deposits on the lower continental slope and rise off Kvitøya Trough indicate bypassing of glacigenic sediments from the shelf to the deep ocean, a process that is likely a result of locally steep slope gradients (<9°). The volume of the Kvitøya TMF is smaller than TMFs along the western Svalbard margin, which may be linked to the more erosion-resistant bedrock of the northern margin and/or the comparatively small drainage basin of Kvitøya Trough compared to drainage basins of ice streams that drained westwards from Barents Sea. In addition, the Kvitøya TMF is incised by gullies indicating that they formed after Last Glacial Maximum (LGM) while larger tributary canyons flanking the Kvitøya TMF likely have developed during a longer time span. High seafloor backscatter values in the tributary canyons and gullies are interpreted as coarse-grained deposits that lead down-slope to debris-flow deposits, suggesting an origin for the tributary canyons and gullies through incision by gravity flows of sediment-laden meltwater during and/or after deglaciation.