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Sedimentary and geochemical cycles in the Maxwell Bay cores

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Citation:
Kuhn, G. , Wittenber, N. , Monien, P. and Hass, H. C. (2010): Sedimentary and geochemical cycles in the Maxwell Bay cores , International IMCOAST Workshop, Cordoba, Argentina, August 8-12 .
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Abstract:

In Maxwell Bay, King George Island, 100 m thick Holocene sediments have been deposited. These allow high-resolution environmental studies in the South Shetland Island area covering the recent warm climate period. Using sediment cores taken during Polarstern cruise ANT-XXIII/4 (2006), we were able to detect the impact of climate phases like the Little Ice Age on local sedimentation processes.In sediment core PS69/335-2 a cyclic pattern was found in the magnetic susceptibility (MS) parameter. High magnetic susceptibility correlates to low content in total organic carbon (TOC) and total sulfur (TS). This pattern was found in the other sediment cores as well and we suppose that lower values in MS can be related to higher biogenic productivity (TOC and TS values) or less input of terrigenous sediment. Partly destruction of the magnetic susceptibility signal by a reduction of ferric to ferrous iron is another alternative that has to be account for. The negative correlation between MS and TS possibly indicates this early diagenetic alteration. But the good correlation between XRF Fe counts and the MS does not support a destruction of high MS Fe-minerals. MS correlates to the dry bulk density (DBD) of the sediment and negatively to the biogenic opal as well as to the water content, all of this indicates a dilution of the MS signal by higher organic input.Spectral analyses of some sediment parameters of core PS69/335-2 resulted in cyclic frequencies of approximately 200 years. Similar frequencies were found in sediments from Collins Harbor and Bransfield Basin, which have been discussed as indicators for changing sea ice coverage. We are investigating additional parameters in our cores to detect comparable environmental changes.

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