Sedimentary processes and paleoenvironments in Moskusoksefjord and Nordfjord, North-East Greenland.

Abstract

Multi-proxy analyses of five sediment cores (including lithostratigraphy, physical properties and XRF-scanning) and analyses of swath bathymetry and high resolution seismic data were integrated in order to reconstruct the Holocene glacial history and paleoenvironment of Moskusoksefjord and inner parts of Nordfjord, North-East Greenland. In Moskusoksefjord, the large-scale bathymetry is divided into an inner-, middle- and outer basins, separated by relatively large deltas prograding into the fjord from both sides. Several slide scars and sediment lobes are also found, in addition to numerous channels. No glacial landforms have been observed in the study area apart from two transverse ridges in the outer basin of Moskusoksefjord which may represent buried glacial moraines. The seismostratigraphy revealed two main units with a stratified acoustic signature as well as MTDs of various dimensions. From their distribution, mass-transport activity in Moskusoksefjord and Nordfjord probably occurred episodically throughout the entire Holocene. Suspension settling, as well as mass-transport deposits and ice-rafting from icebergs and sea-ice are the main sedimentary processes of both fjords. The two main sources of sediment were theWaltershausen Gletscher and the river coming from Badlandal at the fjord head of Moskusoksefjord. The estimated average sedimentation rates are 58 cm/ka for the last ~8 ka and 85-446 cm/ka for the last 1 ka. Ice-rafting was of higher relative importance with increasing influence away from the glacier margin. However, rafting of material from icebergs and sea ice has proven to be of less importance in the two studied fjords than in other East-Greenland fjords (cf. Smith and Andrews, 2000). After retreating onto land during the warm Holocene Climate Optimum, Waltershausen Gletscher probably advanced into tidewater after a climate cooling ~6500 cal. yr. BP. An increase in the glacial activity continued through the Neoglaciation, with shorefast sea-ice suppressing iceberg rafting and an increase in the amount of laminations characterizing the time period. No clear glacial advance and little IRD are observed related to the Little Ice Age. In addition to the late cooling signal in the sediment cores, it is interpreted to indicate a late onset and a restricted advance of the Little Ice Age ice front in Moskusoksefjord and Nordfjord.