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Deep Drilling at Laguna Potrok Aike, Argentina: Recovery of a Paleoclimate Record for the Last Glacial from the Southern Hemisphere

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Zolitschka, B. , Anselmetti, F. S. , Ariztegui, D. , Corbella, H. , Francus, P. , Gebhardt, C. , Hahn, A. , Kliem, P. , Lücke, A. , Ohlendorf, C. and Schäbitz, F. (2009): Deep Drilling at Laguna Potrok Aike, Argentina: Recovery of a Paleoclimate Record for the Last Glacial from the Southern Hemisphere , Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract PP14A-10. .
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Abstract:

Laguna Potrok Aike, located in the South-Patagonian province of Santa Cruz (52°58S, 70°23W), was formed 770 ka ago by a volcanic (maar) eruption. Within the framework of the ICDP-funded project PASADO two sites were drilled from September to November 2008 using the GLAD800 drilling platform. A total of 513 m of lacustrine sediments were recovered from the central deep basin by an international team. The sediments hold a unique record of paleoclimatic and paleoecological variability from a region sensitive to variations in southern hemispheric wind and pressure systems and thus significant for the understanding of the global climate system. Moreover, Laguna Potrok Aike is close to many active volcanoes allowing a better understanding of the history of volcanism in the Pali Aike Volcanic Field and in the nearby Andean mountain chain. These challenging scientific themes need to be tackled in a global context as both are of increasing socio-economic relevance. On-site core logging based on magnetic susceptibility data documents an excellent correlation between the quadruplicate holes drilled at Site 1 and between the triplicate holes recovered from Site 2. Also, correlation between both sites located 700 m apart from each other is feasible. After splitting the cores in the lab, a reference profile was established down to a composite depth of 107 m for the replicate cores from Site 2. Sediments consist of laminated and sand-layered lacustrine silts with an increasing number of turbidites and homogenites with depth. Below 80 m composite depth two mass movement deposits (10 m and 5 m in thickness) are recorded. These deposits show tilted and distorted layers as well as nodules of fine grained sediments and randomly distributed gravel. Such features indicate an increased slump activity probably related to lake level fluctuations or seismicity. Also with depth coarse gravel layers are present and point to changes in hydrological conditions in the catchment area. Intercalated throughout the record are 24 macroscopic volcanic ash layers that document the regional volcanic history and open the possibility to establish an independent time control through tephrochronology. These isochrones potentially act as links to marine sediment records from the South Atlantic and to Antarctic ice cores. Preliminary interpretation of all available data and extrapolation of sedimentation rates determined for the upper 16 ka indicate that the record may go back in time to oxygen isotope stage 5a and covers approximately the last 80 ka.

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