Pleistocene to Holocene Glaciomarine Environments in the Prydz Bay Region and its Implications for East Antarctic Ice Sheet Dynamics and Antarctic Bottom Water Production


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gerhard.kuhn [ at ] awi.de

Abstract

The Lambert Graben-Amery Ice Shelf system is one of the world's largest outlet glaciers, draining about 20% of the East Antarctic Ice Sheet. It is an important feature for the global water budget and for the production of dense Antarctic Bottom Water, which contributes to the global Thermohaline Circulation. On the basis of environmental proxy data, inferred from sedimentological, mineralogical, and geochemical studies, the response of the glacial drainage system to climate changes in the past is investigated. Sediment cores from a depth transect down the continental slope off MacRobertson Land cover the time-span of the last one million years, revealed from palaeomagnetic data. At least three lithofacies units can be distinguished and related to different conditions of the depositional environment: (1) a massive sediment facies with a high content of sand and gravel, and a heavy-mineral assemblage dominated by hornblende, points to strong input of ice- rafted material, advantaged by open-water conditions and prolonged iceberg calving in Prydz Bay; (2) a lithofacies characterized by sand- and silt stringers in combination with conspicuous presence of sediment clasts, indicating sediment reworking and bulldozing over the shelf edge, and sediment dispersal to the deep by turbidity currents during times of increased ice-sheet mobility; (3) a clayey-silty laminite facies that captivates through a low amount of ice-rafted debris, suggesting stable glacial conditions and the activity of contourite currents. The longterm trend reveals the dominance of the massive sediment facies between 1000 and 650 ka and since 100 ka, while the interval in between is mostly characterized by the laminite facies. Apparently, downcore changes in lithofacies are hard to correlate with shortterm glacial-interglacial climate stages. Sediment cores from the Prydz Bay shelf and the MacRobertson shelf document the Holocene environmental history. Grain-size data of a sediment core recovered from MacRobertson shelf marks the onset of deglaciation at around 11.0 ka BP with enhanced bottom water circulation. The end of deglaciation appeared at around 8.8 ka BP and is associated with a drop in the supply of ice-rafted debris and increasing biogenic opal concentrations which then remain fairly constant through the Holocene with a short interruption 4.4 ka ago.



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Conference (Poster)
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Not peer-reviewed
Publication Status
Published
Event Details
AGU Fall Meeting 2008, San Francisco. - 19. December 2008..
Eprint ID
19912
Cite as
Borchers, A. , Frederichs, T. , Grobe, H. , Kuhn, G. and Diekmann, B. (2008): Pleistocene to Holocene Glaciomarine Environments in the Prydz Bay Region and its Implications for East Antarctic Ice Sheet Dynamics and Antarctic Bottom Water Production , AGU Fall Meeting 2008, San Francisco. - 19. December 2008. .


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