LATE WEICHSELIAN SUBMARINE DEBRIS FLOW DEPOSITS ON THE BEAR-ISLAND-TROUGH-MOUTH-FAN

Sedimentary processes on the Bear Island Trough Mouth Fan during the last glacial were studied using high resolution reflection seismics and gravity cores. The fan succession is dominated by large debris flow deposits of up to 24 km in width and 50 m thick. Debris lobes can be followed over 100 km downslope and the largest cover an area of 1880 km(2). The large debris flows were generated when the Barents Sea Ice Sheet reached the shelf break. Glacigenic sediments transported to the grounding-line were temporarily stored on the upper slope. Due to the high sedimentation rate, the sediments were unstable and earthquakes, oversteepening and/or build up of excess pore pressure triggered sediment release generating large debris hows. Sediments were also eroded and incorporated during the downslope how. Debris flows were the most important sediment distributing process due to the relatively high shear strength, low flow mobility of the glacigenic diamicton, and the low fan gradient. The Weichselian evolution of the fan was characterized by a relatively low sedimentation rate during the Early and Mid Weichselian. The Barents Sea Ice Sheet might have reached the shelf break twice during the Late Weichselian. On average one large debris flow, comprising 18 km(3) of sediments, was released between every 35 to 75 years during the last glacial maximum.