LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating R. Zech1, Ch. Kull2, P. W. Kubik3, and H. Veit1 1Geographical Institute, University of Bern, Switzerland 2OcCC, Schwarztorstr. 9, 3007 Bern, Switzerland 3Paul Scherrer Institute c/o Institute of Particle Physics, ETH Zurich, Switzerland
Abstract. Surface exposure dating (SED) is an innovative tool already being 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 was 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
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
farther west and south.
Citation: Zech, R., Kull, Ch., Kubik, P. W., and Veit, H.: LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from 10Be surface exposure dating, Clim. Past, 3, 623-635, doi:10.5194/cp-3-623-2007, 2007.