Sedimentation history along the East Greenland margin

Abstract

Geophysical and geological investigations in the Arctic region are very important for a betterunderstanding of the present day global climate. Changes in global climate is one of the highlyspeculative aspect in the Northern Hemipsphere, especially the onset of glaciation. Advancesand retreats of grounded ice sheets during glacial-interglacial times play an important role interms of the deposition of large sediment deposits. Depositional pattern on the continentalslope and rise reflect interactions between the effects of ice sheet fluctuations, mass transportprocesses and bottom currents. The main focus of this thesis is the sedimentation historyalong the East Greenland margin in late Cenozoic times. Different seismic reflection surveysgathered between 1997 and 2003, represent the sedimentary structure along this margin fromthe shelf up into the deep sea area. A for the first time an applied seismostratigraphy onthe Northeast Greenland margin made it possible to differenciate between glacial (youngerthan middle Miocene) and pre-glacial (older than middle Miocene) sediment units. Glacialadvances and retreats appear not synchronous along the continental margin. Therefore, eithernorth of 70 degrees N the extension of the shelf by glacial erosion seems to be more intensive likeon the Southeast Greenland margin or the onset of glaciation started earlier in the norththan in the south. The results of the modelling of different sediment maps enables a lotof varibiabilities in the sediment supply along the continental margin. The greatest totalsediment amount is observed in the prolongation of glacial drainage outlets like the ScoresbySund. Other influences on the sediment thickness along this margin are caused by tectonicelements, the opening history of the basins and the existing current activity. The glacialsediment thickness map, however, enables the highest amount of glacial sediments in thenorthern Molloy Basin (around 1500 m), probably caused by mass transport from the ArcticOcean. Analyses of the deep sea sediment structure provide an insight into a well-laminatedsedimentary succession within the Molloy Basin, which has been interpreted as currentcontrolledaccumulation. An outflow of Arctic Ocean bottom water and an inflow of NorthAtlantic deep-water could be identified. Especially, the levee structure west of the channelpoints to an intensification of current activity since around 5 Ma, also supported by turbiditychannel activity in the deep Greenland Basin.This study demonstrates the interaction between sediment accumulation, climatic changesand changes in ocean circulation. The results provide a basis for a proposal of future OceanDrilling Programms and further geological studies on this margin.