Contrasting glacimarine sedimentary environments of two arctic fiords on Disko, West Greenland

Abstract

Two fiords, Kangerluk and Akulliit, on the island of Disko, central West Greenland have very different sedimentary regimes caused by differences in the characteristics of their drainage basins and in the exposure of their waters to the open sea of Baffin Bay. Their insular location also results in much lower input of water and sediment than in nearby fiords on the mainland of Greenland that are affected by glaciers from the Greenland Ice Cap. Akulliit has a small drainage basin and low input of water and sediment; it is directly exposed to the higher energy wave environment of Baffin Bay. As a consequence, the mean thickness of Holocene glacimarine sediment assessed in acoustic records is less than 6 m in the inner and middle reaches of the fiord (mean Holocene accumulation, 0.4 mm/a) and about 11 m (1 mm/a) near the mouth. Dated core sediment indicates that rates are less than 0.5 mm/a in the outer fiord in the last 2 ka. The larger, more glacier-covered drainage basin of Kangerluk contributes much larger loads of sediment to a fiord environment protected from the open sea. As a result, Holocene glacimarine sediment is more than 80 m thick in the inner fiord (mean Holocene accumulation up to 5 mm/a), decreasing to 10–40 m (about 1 mm/a) in the middle reaches. Accumulation rates in Kangerluk are within the range of arctic fiords, including those of Baffin Island, but those in Akulliit are near the lower limit. The decrease in thickness distally in Kangerluk is typical of arctic fiords, but the opposite trend in Akulliit is probably due to erosion and re-distribution of sediment in the higher energy environment there.