by Bernd Zolitschka, Flavio Anselmetti, Daniel Raul Ariztegui, Raymond S. Bradley, Laurie L. Brown, Pierre Francus, Andreas Lücke, Christian Ohlendorf, Frank Schäbitz, Stefan Wastegård

We propose to recover long sediment cores from Laguna Potrok Aike, a 770 ka old maar lake in the dry steppe of southern Patagonia (Province of Santa Cruz, Argentina). Seismic surveys demonstrate that ~400 m of pelagic sediments were deposited in the lake centre underlain by a yet unknown thickness of volcaniclastic breccias. Based on this seismic data, three primary and three alternative drilling sites were selected: (1) from the deepest part to obtain a continuous and high-resolution record of climatic and environmental changes and to unveil the phreatomagmatic history including more precise age constrains for the maar-diatreme formation from the volcaniclastic sediments below, (2) from a subaquatic lake level terrace at 35 m water depth to constrain the range of lake level variations and (3) from an angle hole passing through lacustrine sediments and the crater wall into the molassetype basement rocks to study the impact of explosive volcanism, post-eruptive structural evolution and early processes of sedimentation in a relatively young maar-diatreme structure. Within the framework of an international and interdisciplinary scientific approach the recovered sediments will be used to test hypotheses related to this two broad themes: • High-resolution quantitative climate and environmental reconstructions from orbital and suborbital (multimillennial) down to decadal timescales supported by multiple dating (e.g. 14C, OSL, Ar/Ar) and stratigraphic correlation (e.g. pollen, tephra, paleomagnetics) with emphasis on marine – ice core – terrestrial linkages and incorporation of results from GCM climate simulations; • Detailed analyses of volcanic rocks and sediments provide insights into processes related to phreatomagmatic explosions and early sedimention in a mid-Pleistocene maar lake. Never before the entire lacustrine sediment record has been recoverd and underlying volcaniclastic sediments have been drilled and investigated in a young maar-diatreme structure. An international team of scientists has been attracted to cooperate in the framework of PASADO to develop a comprehensive environmental, climatic and volcanological data set. Proposed science management and drilling operation plans have the objective to achieve all necessary technical and scientific needs to make PASADO internationally successful.

• Scientific deep drilling: The main goal of PASADO is to recover long, undisturbed and continuous lacustrine and volcaniclastic sediments from Laguna Potrok Aike as the basis for the following scientific objectives. Quantitative climate and environmental reconstructions: On orbital to decadal timescales a variety of multidisciplinary analytical methods will be applied to reach these scientific goals:
• Multiple dating to provide a sound timeframe for all analyses using 14C, OSL, Ar/Ar, tephrochronology, paleomagnetics High-resolution quantitative reconstruction of temperature, precipitation and hydrological variations based on chironomids, pollen, stable isotopes, inorganic carbon and biomarkers;
• Quantitative reconstruction of terrestrial vegetation and fire history applying pollen and charcoal;
• Development of high-resolution dust storm and volcanic tephra records based on mineralogical and geochemical fingerprints;
• Reconstruction of a paleosecular variation record of the Earth’s magnetic field;
• Establishing marine – ice core – terrestrial linkages focusing on magnitude and abruptness of glacial/interglacial transitions and periodicities during glacials and interglacials;
• Evaluation of proxy-based hypotheses with GCM climate simulations to establish mechanistic links between climate variability and forcing factors. Questions relate to (1) latitudinal shifts in the position of Southern Hemispheric westerlies,
• (2) recurrence patterns of synoptic-scale phenomena like polar outbreaks,
• (3) the role of ice sheets, oceanic and atmospheric circulation on climate change. Understanding the phreatomagmatic history: Analysis of volcanic rocks and accidental clasts will provide a unique dataset to better understand the geometry and structure of maar-diatrems in soft-rock environments. This includes:
• Processes related to phreatomagmatic maar explosions;
• Investigation of early sedimention in a maar lake;
• Post-sedimentation and compaction history in Quaternary maar sediments.

Argentina, Atmospheric Dust, Climate Modeling, GLAD800, ICDP-2007/01, Lake Drilling, Maar Formation, Maar Lake, PASADO, Patagonia, Potrok Aike, Quantitative Climate Reconstruction, Southern Hemispheric Westerlies, Volcanology

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