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Agulhas Plateau and Transkei Basin, southwest Indic: Key targets for learning about the evolution of oceanic currents

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Citation:
Uenzelmann-Neben, G. , Schlüter, P. and IODP, p. (2006): Agulhas Plateau and Transkei Basin, southwest Indic: Key targets for learning about the evolution of oceanic currents , 4th Inkaba yeAfrica Scientific Workshop, 1-3 Jun, Potsdam, Germany. .
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Abstract:

The region south of South Africa is a key area in the global conveyor belt since here warm surface currents and cold deep water masses meet, and heat and energy are transferred to sustain the global thermo-haline circulation. Furthermore, this gateway is characterised by a number of tectonic structures the Agulhas Passage, the Aguhas Plateau and the Transkei Basin - , which restrict and channelise the paths of the oceanic currents. To understand the development of those tectonic structures is hence of major importance in order to learn about the evolution of the currents systems, which have shaped the global climate.The proposed SAFARI IODP drilling campaign targets this location for theretrieval of long multiple APC cores. They will enable to track thevariability of Southern Ocean deep water back through time acrosskey-periods of past climate changes and its possible role in mode shifts ofthe global THC at these times: the mid-Pliocene onset of northernhemisphere glaciation and the mid-Pleistocene transition from the 41-kyr tothe 100-kyr world.We further propose to drill two locations on the central and southern Agulhas Plateau to depict the origin of the plateau. The evolution and structure of the Agulhas Plateau is still under heavy debate. It has been decribed as a continental remnant from the Falkland Plateau, but the crustal structure and seismic velocities deduced from seismic reflection and refraction investigations put the Agulhas Plateau into the worldwide suite of Large Igneous Provinces. According to those data it was formed after the break-up of Gondwana under the influence of the Bouvet Hotspot. The proposed drill sites target lavaflows as a result of excessive volcanism and will lead to an understanding of the formation and the age of the plateau.The proposed site in the Transkei Basin offers the unique opportunity to study the influence of Antarctic Bottomwater and North Atlantic deep water, which here have shaped a major sediment drift the Agulhas Drift - at least since Pliocene times. We observe a migration of the drift from south to north as well as an older sediment drift with a different orientation below the Agulhas Drift. The proposed site will advance our knowledge on the evolution and the paths of the water masses in this part of this critical gateway.

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