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10Be Surface Exposure Dating in the Central Andes

Description: Das Projekt "10Be Surface Exposure Dating in the Central Andes" wird vom Umweltbundesamt gefördert und von Universität Bern, Geographisches Institut durchgeführt. Surface exposure dating has become an important tool for glacial and climate reconstructions in recent years. Especially in arid mountain areas, where organic material for radiocarbon dating is scarce, it is now possible to establish precise glacial chronologies from moraine deposits. In previous and ongoing SNF-projects, we have mapped moraines in many parts of the Central Andes. Only recently we started to apply surface exposure dating using in-situ 10Be in the Cordillera Real and Cochabamba, Bolivia (ca.15 S), and in the Andes of Central Chile/Argentina (30-40 S). We expect to get important insights into past changes of the tropical and the ek-tropical atmospheric circulation, i.e. the westerlies in the south and the South American Summer Monsoon in the north. First results from northern Chile (ca.30 S) show that glaciers advanced ca.30 ka BP and again between ca.14 and 12 ka BP. Moisture advection during the temperature minimum of the global LGM (last glacial maximum: 18-20 ka BP) seems to have been insufficient to allow considerable glacial extents. Preliminary exposure ages indicate that glaciers in the Cordillera Real and Cochabamba did not only advance during the LGM, triggered by temperature reductions, but also during the Late Glacial and the Early Holocene - likely due to increased precipitation during the 'Tauca' and 'Coipasa' wet phases (18-14 and 13-11 ka BP). Although our preliminary results are promising and show the high potential of surface exposure dating for Late Quaternary glacier and climate reconstruction, three aspects are evident that currently limit the paleoclimatic interpretations: I.) our preliminary chronologies in Bolivia are based on too few exposure ages II.) there is a gap of glacial chronologies in NW-Argentina and South Bolivia III.) up to now there is a complete absence of calibration sites in the Central Andes In order to further assess the role of temperature and the tropical and ek-tropical moisture sources, respectively, on the glaciation history in the Central Andes, we intend to apply surface exposure dating in six selected research areas in NW-Argentina (4) and Bolivia (2). In combination with the glacier-climate model, which has previously been developed in our working group, the exposure age chronologies will allow the quantitative reconstruction of temperature and precipitation conditions for the dated glacial stages. An important focus of the proposed project is to carry out calibration studies. This implies the necessity to independently date glacial deposits using for example radiocarbon dating of lake sediments. This is the only way to minimize the systematic uncertainties of the exposure ages and thus to confirm the paleoclimatic interpretations.

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SupportProgram

Origin: /Bund/UBA/UFORDAT

Tags: Hirsch ? Naturwerkstoff ? Monsun ? Gletschersee ? Kalibrierung ? Seensediment ? Skigebiet ? Wind ? Anden ? Argentinien ? Chile ? Datierung ? Gletscher ? Kartographie ? Regenwasser ? Sommer ? Temperatur ? Karte ? Exposition ? Klimamodell ? Standortwahl ? Studie ? Tropengebiet ? Sediment ? Trockengebiet ? Lebensalter ? Atmosphärische Zirkulation ? Globale Aspekte ? Advektion ? Arbeit ? Forschung ? in situ ? Klima ? Niederschlag ? Feuchtigkeit ? Gebirge ? Erlass [Recht] ? WICHTIG ? EINGESCHRAENKT ? ERFORDERNIS ? BEISPIEL ? ERGEBNIS ? Werkzeug ? ASPEKT ? FORTSCHRITTLICH ? GROESST ? GRUPPE ? HOLOZAEN ? MISCHUNG ? Muskelarbeit ? NEU ? NOERDLICH ? OBERFLAECHE ? PRAEZIPITATION ? PROJEKT ? BEWERTEN ? CHRONOLOGIE ? QUARTAER ERDZEITALTER ? SUEDLICH ? AUSGEWAEHLT ? ANDEN ? TEIL ? UMGESTALTUNG ? VERHAELTNIS ? VERRINGERUNG ? Vermehrung ?

License: cc-by-nc-nd/4.0

Language: Deutsch

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Time ranges: 2006-11-01 - 2009-10-31

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