THE ORIGIN OF MASSIVE DIAMICTON FACIES BY ICEBERG RAFTING AND SCOURING, SCORESBY-SUND, EAST GREENLAND

Almost 90% of 39 m of core material recovered from Scoresby Sund and t he adjacent East Greenland shelf is massive diamicton, interpreted to be formed predominantly by the release of iceberg rafted debris and re working by iceberg scouring. There is also likely to be a contribution from suspension settling of fines derived from glaciofluvial sources. Model calculations suggest that the C-14 derived Holocene sedimentati on rate of 0.1-0-3 m 1000 yr-1 in Scoresby Sund can be accounted for m ainly by iceberg rafting of debris. A further 4% of core material is o f gravel or coarse sand lenses, interpreted to reflect iceberg dumping of debris. Intensive iceberg scouring, which reworks sea floor sedime nts, is observed on acoustic records from over 30 000 km2 of the Score sby Sund fiord system and the adjacent East Greenland shelf (69-72-deg rees-N and 75-degrees-N). The rate of iceberg production from Greenlan d Ice Sheet outlet glaciers, and iceberg drift tracks on the shelf, su ggests that iceberg rafting and scouring may be important over a signi ficant proportion of the 500 000 km2 area above the shelf break. The r elatively extensive modem occurrence of massive diamicton, formed by i ceberg rafting and scouring, together with suspension settling of fine s, suggests that it may also be a significant facies in the glacier-in fluenced geological record. The recognition in the geological record o f the massive diamicton facies described above may also indicate the f ormer presence of fast flowing ice sheet outlet glaciers.