Glacial history of Northeast Greenland: cosmogenic nuclide constraints on chronology and ice dynamics

University dissertation from Department of Geology, Quaternary Sciences

Abstract: The aim of this thesis was to use cosmogenic exposure dating to investigating whether highly weathered landscapes in the Northeast Greenland fjord zone have developed during prolonged ice free conditions or have been preserved beneath cold-based ice. Previous work along the Northeast Greenland coast has presented two conflicting hypotheses for the extent of the Greenland Ice Sheet during the last glacial maximum (LGM). Land-based investigations have suggested that low gradient outlet glaciers were restricted to fjord troughs and terminated at the inner continental shelf. In contrast, marine studies have recently indicated that the margin of the Greenland Ice Sheet reached the outer shelf during the LGM. Results from cosmogenic 10Be and 26Al exposure dating show that during the LGM, local cold-based ice-caps covered and preserved weathered interfjord plateaus in the Northeast Greenland fjord zone, whereas fjord troughs were filled up with dynamic ice draining the Greenland Ice Sheet. The dynamic ice reached at least 250 m a.s.l. at the mouth of Scoresby Sund at the southernmost end and probably ~600 m a.s.l. at the northernmost end of the fjord zone, indicating that there was a N-S gradient in glacial style presumably reflecting regional differences in topography of the coastal areas. The results presented in this thesis reveals a dynamic picture for the northeastern sector of the Greenland Ice Sheet suggesting that LGM ice margins were substantially more advanced than indicated by earlier reconstructions from the terrestrial record.

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