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Seismic reflection data of the Eirik Drift: A first step to decipher the Neogene development of the Western Boundary Undercurrent (WBUC)

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Citation:
Mueller-Michaelis, A. and Uenzelmann-Neben, G. (2012): Seismic reflection data of the Eirik Drift: A first step to decipher the Neogene development of the Western Boundary Undercurrent (WBUC) , 72. Jahrestagung der Deutschen Geophysikalischen Gesellschaft, Universität Hamburg, 6 March 2012 - 8 March 2012 .
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Abstract:

The Eirik Drift off the southern tip of Greenland contains sedimentary records since the Miocene. This archive of depositional processes has been shaped by the Western Boundary Undercurrent (WBUC), the Greenland ice sheet, and the material input from the Labrador Sea through the Davis Strait. High resolution seismic reflection data collected during RV Maria S. Merian cruise MSM 12/2 were incorporated with geologic information from ODP and IODP sites to deduce information on the development of the WBUC as well as the dimensions and expansion/retreat of the Greenland ice sheet and a much clearer understanding of the evolution of the climate southwest of Greenland. After correlating synthetic seismograms based on density and P-wave velocity data from ODP Leg 105 Site 646 and IODP Expedition 303 Sites 1305, 1306, and 1307 with the processed seismic reflection data we identified four seismic units and the reflectors R1 (onset of ice rafting), R2 (higher carbonate content, increased deep circulation), and R3/R4 (brief hiatus and/or increased sedimentation rate) as defined by Arthur et al. (1989). Tracking of both reflectors and units leads to information about the redistribution of the WBUC in the vicinity of the Eirik Drift during the Neogene. By means of the four seismic units four phases for the build-up of the Eirik Drift can be distinguished: Phase 1 (>7.5 Ma): highest sedimentation underneath the eastern flank of the presently main crest of the drift Phase 2 (7.5-4.5 Ma): the high sedimentation shifted ~200 km to the west Phase 3 (4.5-2.5 Ma): onset of drift building; build-up of two almost separated lenticular shaped sediment bodies above the Phase 1 and Phase 2 sedimentation centers Phase 4 (<2.5 Ma): in the north similar to Phase 3 with build-up of two almost separated lenticular shaped sediment bodies. In the south, higher sedimentation only occurs above the Phase 2 drift body and just a thin band of almost constant thickness is found over the present main crest and its flanks. These changes in deposition of sediments are addressed to changes in direction and strength of the WBUC.

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