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10Be Surface Exposure Dating in the Central Andes

English title 10Be Surface Exposure Dating in the Central Andes
Applicant Veit Heinz
Number 113461
Funding scheme Project funding (Div. I-III)
Research institution Geographisches Institut Universität Bern
Institution of higher education University of Berne - BE
Main discipline Pedology
Start/End 01.11.2006 - 31.10.2009
Approved amount 266'973.00
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Keywords (11)

paleoclimate; quaternary; glaciation; glacial chronology; moraines; surface exposure dating; cosmogenic nuclides; 10Be; Central Andes; NW-Argentina; Bolivia

Lay Summary (English)

Lead
Lay summary
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 (~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 (~30°S) show that glaciers advanced ~30 ka BP and again between ~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 exposureages
II.)there is a gap of glacial chronologies in NW-Argentina and SouthBolivia
III.)up to now there is a complete absence of calibration sites in theCentral 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.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
109207 Glacier Reconstruction along a N-S Andean Transect (Chile, 30-40°S) using 10Be Surface Exposure Dating 01.10.2005 Project funding (Div. I-III)

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