References

CPD

Climate of the Past Discussions

CPD

1814-9359

Copernicus GmbH

Göttingen, Germany

10.5194/cpd-3-839-2007

LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from <sup>10</sup>Be surface exposure dating

Zech

¹ Kull

Ch.

² Kubik

P. W.

³ Veit

Geographical Institute, University of Bern, Switzerland

OcCC, Scwarztorstr. 9, 3007 Bern, Switzerland

Paul Scherrer Institute c/o Institute of Particle Physics, ETH Zurich, Switzerland

27 06 2007

3 3 839 869

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Surface exposure dating (SED) is an innovative tool being already widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22–25 ka and thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been substantially overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions further west and south.

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