Timing of the late Quaternary glaciation in the Andes from ∼15 to 40° S

Abstract The Central Andes play a pivotal role for glacier and climate reconstruction along the American Pole–Equator–Pole transect. Nevertheless, knowledge about late Quaternary palaeoenvironmental changes in this region is extremely limited. With the advent and application of surface exposure dating during the last few years, the establishment of more detailed glacial chronologies could provide important insights into forcings and mechanisms of glaciation and climate change. This paper reviews previously published exposure ages and compares them with independent age control on glacial chronologies and with information about the palaeohydrological conditions. Although available data are still very limited and there are remaining systematic uncertainties related to surface exposure dating, the following simplified palaeoglacial/palaeoclimate model is presented to serve as a testable hypothesis for future studies. (i) Glaciers in the humid tropical Andes were mainly temperature sensitive and therefore advanced during temperature minima. Advances are dated to 20–25 ka, ∼15 ka and 11–13 ka, i.e. synchronous to the global Last Glacial Maximum (LGM), the Heinrich event 1 and the Younger Dryas/Antarctic Cold Reversal. (ii) Further south and west, precipitation decreases and glaciers therefore become more precipitation sensitive. Maximum or at least prominent glacial advances as far south as 30° S are dated into the Lateglacial, i.e. synchronous with lake transgression phases (Tauca: 14–18 ka, and Coipasa: 11–13 ka). (iii) Between ∼30 and 40° S, glaciers reached their maximum extent much earlier during the pre‐LGM (∼35–40 ka). This is attributed to a northward shift and/or intensification of the westerlies, whereas conditions during the global LGM were too dry to allow for significant glacial advances. (iv) South of 40°, glaciers become temperature sensitive again and reached their maximum accordingly synchronous to the global LGM. Copyright © 2008 John Wiley & Sons, Ltd.