Climate of the Past www.clim-past.net 1814-9324 1814-9332 5 2 2009 10.5194/cp-5-157-2009 http://www.clim-past.net/5/157/2009/ http://www.clim-past.net/5/157/2009/cp-5-157-2009.html http://www.clim-past.net/5/157/2009/cp-5-157-2009.pdf 157 169 2009-04-23 Three exceptionally strong East-Asian summer monsoon events during glacial times in the past 470 kyr D.-D. Rousseau denis.rousseau@lmd.ens.fr N. Wu Y. Pei F. Li Ecole Normale Supérieure de Paris, Laboratoire de Météorologie Dynamique (UMR INSU/CNRS 8539), and CERES-ERTI, 24 rue Lhomond, 75231 Paris cedex 5, France Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Chinese loess sequences are interpreted as a reliable record of the past variation of the East Asian monsoon regime through the alternation of loess and paleosols units, dominated by the winter and summer monsoon, respectively. Different proxies have been used to describe this system, mostly geophysical, geochemical or sedimentological. Terrestrial mollusks are also a reliable proxy of past environmental conditions and are often preserved in large numbers in loess deposits. The analysis of the mollusk remains in the Luochuan sequence, comprising L5 loess to S0 soil, i.e. the last 500 ka, shows that for almost all identified species, the abundance is higher at the base of the interval (L5 to L4) than in the younger deposits. Using the present ecological requirements of the identified mollusk species in the Luochuan sequence allows the definition of two main mollusk groups varying during the last 500 kyr. The cold-aridiphilous individuals indicate the so-called Asian winter monsoon regime and predominantly occur during glacials, when dust is deposited. The thermal-humidiphilous mollusks are prevalent during interglacial or interstadial conditions of the Asian summer monsoon, when soil formation takes place. In the sequence, three events with exceptionally high abundance of the Asian summer monsoon indicators are recorded during the L5, L4 and L2 glacial intervals, i.e., at about 470, 360 and 170 kyr, respectively. 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