SEDIMENT THICKNESSES AND HOLOCENE GLACIAL MARINE SEDIMENTATION-RATES IN 3 EAST GREENLAND FJORDS (CA 68-DEGREES-N)

We compared measured and estimated sediment budgets in heavily glaciated fjords in East Greenland. Mass balance calculations and regional glacio-climatic conditions suggest that the sediment flux to the seafloor in Kangerdlugssuaq and Nansen fjords should be dominated by iceberg rafting and not by the rain-out of suspended particulates in meltwater, as the glacier calving flux is estimated at 15 and 2 km3/yr, compared to meltwater volumes of 4.4 and 1.7 km3/yr, respectively. Gravity cores in the three fjords indicate that the uppermost 1-2.5 m of sediment consists of diamictons or fine-grained laminated muds. AMS radiocarbon dates on calcareous foramininfera or shells (16 total) indicate sedimentation rates of 110 to 340 cm/ka within the fjords over the last 1 ka, and 10-20 cm/ka during the Holecene on the inner and middle shelf. Annual sediment discharge is around 0.67 x 10(6) tonnes/yr within the Kangerdlugssuaq Fjord and Trough system, which translates into an average basin-wide rate of denudation of 0.01 mm/yr (0.01 m/ka). Air gun and deep-towed (Huntec) seismic profiling was carried out in Kangerdlugssuaq and Nansen fjords, East Greenland, and showed that sediment fills average 500 and 350 m respectively; they consist primarily of acoustically stratified sediments. If the sediment fills are entirely Holocene in age then the required average sediment accumulation rates of 35-50 m/ka are an order of magnitude larger than the C-14 controlled rates of the last 1-2 ka. This raises the possibility that fjord sediments may be by-passed and not always recycled during glacial advances; this will affect sedimentation rates on adjacent shelves and deep-sea areas during successive glaciations.