SEDIMENT FLUX FROM A FJORD DURING GLACIAL PERIODS, ISFJORDEN, SPITSBERGEN

Sediment has accumulated in Isfjorden, a deep fjord in Spitsbergen, at a rate of similar to 1.7 km(3)/k.y. during the past 13 k.y. Between 2 00 ka and 13 ka the fjord was free of ice for similar to 120 ky. Assum ing a similar sediment delivery rate during this ice-free time, simila r to 200 km(3) of sediment would have accumulated in the fjord. An alt ernative calculation based on erosion rates suggests that 400 km(3) co uld have been delivered to Isfjorden during this 120 k.y. Seismic stud ies have identified a similar to 330 km(3) package of sediment on the continental shelf and slope west of Isfjorden. This sediment is believ ed to have accumulated between 200 ka and 13 ka. Herein we argue that this is sediment that was originally deposited in the fjord, and that it was transferred to the shelf by glaciers in the similar to 70 ka du ring which the fjord was occupied by ice. Calculations using a steady- state numerical model suggest that the sediment could have been moved in a deforming layer of subglacial till and in subglacial melt streams at rates of 7.6 x 10(6) m(3) a(-1) and 0.3 x 10(6) m(3) a(-1) respect ively, resulting in a total flux of similar to 7.9 x 10(6) m(3) a(-1). It is unlikely that much sediment was moved in a basal layer of dirty ice, as intense basal melting would have inhibited sediment entrainme nt. Of the time that glaciers occupied the fjord, similar to 60% would have been required to evacuate the accumulated sediment. During the r emaining time, the ice could have been deepening the fjord.