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

Sedimentary processes on the Bear Island Trough Mouth Fan during the l ast glacial were studied using high resolution reflection seismics and gravity cores. The fan succession is dominated by large debris flow d eposits of up to 24 km in width and 50 m thick. Debris lobes can be fo llowed 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 She et reached the shelf break. Glacigenic sediments transported to the gr ounding-line were temporarily stored on the upper slope. Due to the hi gh sedimentation rate, the sediments were unstable and earthquakes, ov ersteepening and/or build up of excess pore pressure triggered sedimen t release generating large debris hows. Sediments were also eroded and incorporated during the downslope how. Debris flows were the most imp ortant sediment distributing process due to the relatively high shear strength, low flow mobility of the glacigenic diamicton, and the low f an gradient. The Weichselian evolution of the fan was characterized by a relatively low sedimentation rate during the Early and Mid Weichsel ian. The Barents Sea Ice Sheet might have reached the shelf break twic e during the Late Weichselian. On average one large debris flow, compr ising 18 km(3) of sediments, was released between every 35 to 75 years during the last glacial maximum.