Characterization of a glacial paleo-outburst flood using high-resolution 3-D seismic data: Bjornelva River Valley, SW Barents Sea

Proglacial braided river systems discharge large volumes of meltwater from ice sheets and transport coarse-grained sediments from the glaciated areas to the oceans. Here, we test the hypothesis if high-energy hydrological events can leave distinctive signatures in the sedimentary record of braided river systems. We characterize the morphology and infer a mode of formation of a 25 km long and 1-3 km wide Early Pleistocene incised valley recently imaged in 3-D seismic data in the Hoop area, SW Barents Sea. The fluvial system, named Bjornelva River Valley, carved 20 m deep channels into Lower Cretaceous bedrock at a glacial paleo-surface and deposited 28 channel bars along a paleo-slope gradient of similar to 0.64 m km(-1). The landform morphologies and position relative to the paleo-surface support that Bjornelva River Valley was formed in the proglacial domain of the Barents Sea Ice Sheet. Based on valley width and valley depth, we suggest that Bjornelva River Valley represents a braided river system fed by violent outburst floods from a glacial lake, with estimated outburst discharges of similar to 160 000 m 3 s(-1). The morphological configuration of Bjornelva River Valley can inform geohazard assessments in areas at risk of outburst flooding today and is an analogue for landscapes evolving in areas currently covered by the Greenland and Antarctic ice sheets.

Automated summary

The study describes the morphology and formation of the Bjornelva River Valley in the SW Barents Sea, suggesting it may represent a braided river system fed by outburst floods from a glacial lake. The valley's configuration could be useful for geohazard assessments in areas at risk of outburst flooding today and as an analogue for landscapes evolving in regions currently covered by ice sheets.