ELSEVIER Earth and Planetary Science Letters 168 (1999) 219–232 Asian summer monsoon instability during the past 60,000 years: magnetic susceptibility and pedogenic evidence from the western Chinese Loess Plateau Xiao-Min Fang a,b,c,L , Yugo Ono b , Hitoshi Fukusawa c , Pan Bao-Tian a , Ji-Jun Li a , Guan Dong-Hong a , Keiichi Oi b , Sumiko Tsukamoto c , Masayuki Torii d , Toshiaki Mishima e a Department of Geography, Lanzhou University, Lanzhou, Gansu 730000, China b Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060, Japan c Department of Geography, Tokyo Metropolitan University, Hachioji 192-03, Japan d Faculty of Informatics, Okayama University of Science, Okayama 700-0005, Japan e Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan Received 28 January 1999; revised version received 20 February 1999; accepted 20 February 1999 Abstract The 28 m high-resolution Shajinping loess section in Lanzhou on the western Chinese Loess Plateau records a 60 ka, millennial summer monsoon variation. The record shows that Asian summer monsoons have rapid episodic pulse enhancements spanning only ca. 1–2 ka in high-frequency domain and having sub-Milankovitch cycles of progressive weakening in low frequency domain in the last glaciation. Soil formation seems to occur with a surprisingly fast response to these summer monsoon enhancements, resulting in weakly or moderately developed paleosol sequences. Both the pattern and timing of the summer monsoon enhancements show that they can be correlated to most major warm (Dansgaard–Oeschger) episodes and long-term cooling (Bond) cycles of the North Atlantic climatic records, indicating a possible teleconnection between tropic oceanic air masses and the North Atlantic climatic system. But differences exist for the transition of MIS 2=3 and the Holocene, where extraordinarily heavy dust-input events and fairly variable climatic fluctuations occur for the former and latter, respectively. A westerlies-swing model is proposed to interpret this link.  1999 Elsevier Science B.V. All rights reserved. Keywords: monsoons; paleoclimatology; climate effects; magnetic susceptibility; loess; Paleosols; Loess Plateau 1. Introduction Asian monsoons are a very important part of the global climatic system and consist mainly of summer and winter monsoons [1]. Summer’s warm, moist air masses over the tropical Pacific (East Asian mon- L Corresponding author. C86-931-891-3362; E-mail: fangxm@lzu.edu.cn soon) and Indian (Indian monsoon) oceans bring heat and rain to East Asia [1] and develop soils. Cold masses of Siberian High air in winter generate dust storms and long-distance dust transport [2]. Contin- uous Chinese paleosol–loess sequences recorded the past 2.5 Ma of the Asian monsoon system variations [2,3]. The high correlation between Chinese loess– paleosol climatic and marine oxygen isotope (MIS) records further shows that summer monsoon varia- 0012-821X/99/$ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII:S0012-821X(99)00053-9