SPATIAL AND TEMPORAL PATTERNS OF ICEBERG RAFTING (IRD) ALONG THE EASTGREENLAND MARGIN, CA-68-DEGREES-N, OVER THE LAST 14-CAL-KA

Twelve 1-2 m, 10-cm-diameter gravity cores collected in 1988 and 1991, from the continental shelf and fjords of East Greenland near Kangerlu ssuaq Fjord/Trough (ca. 68 degrees N, 32 degrees W), have distinct cha nges in lithofacies and in the quantity of iceberg rafted (IRD) sedime nts. These changes are readily observed in X-radiographs of the split cores. We quantify the IRD contribution through grain-size analyses an d counting the number of clasts >2 mm from the X-radiographs. Chronolo gical control is provided by acclerated mass spectroscopy C-14 dates o n foraminifera. During deglaciation, after 14 cal.ka there was one int erval of IRD accumulation ca. 12-13 cal.ka, followed by a brief return to IRD conditions centred at 9 cal.ka. Thereafter, a prominent featur e of most cores on the shelf is an increase in IRD accumulation that s tarted ca. 5-6 cal.ka, and which has increased toward the present. Ind icators of iceberg rafting, such as the net sand flux and numbers of c lasts >2 mm ka(-1), follow a power law distribution when graphed again st distance from the present East Greenland coast, a measure of the po sition of the glacier margins. The form of the relationship indicates that there is a dramatic decrease in the supply of sediment from the f jords to the shelf. These relationships are used to estimate changes i n the location of the ice margin during the late Quaternary based on a site on the East Greenland slope, Denmark Strait, and to discuss fact ors that can negate such a simple transfer function. (C) 1997 by John Wiley & Sons Ltd.