LOESS MAGNETIC SUSCEPTIBILITY IN CENTRAL ASIA AND ITS PALEOCLIMATIC SIGNIFICANCE Yougui Song 1) Zhengtao Shi 2) Hongmei Dong 3) Junsheng Nie 4) Libo Qian 1) Hong Chang 1) Xiaoke Qiang 1) 1) State Key Laboratory of Loess and Quaternary Geology, Institute of Earth and Environment, Chinese Academy of Sciences, Xi’an 710075, China. Email: syg@ieecas.cn 2) School of Tourism and Geography, Yunnan Normal University, Kunming 650092, China 3) School of Management, Xi’an Science and Technology University & School of Tourism and Environment, Shaanxi Normal University, Xi’an 710061, China 4) Graduate School of Oceanography, University of Rhode Island, RI 02882, USA ABSTRACT For standard loess sections in the Chinese Loess Plateau (CLP), paleosols always have higher magnetic susceptibility (MS) than adjacent loesses. But this characteristic is not always suitable to MS records in loess-paleosol sequences from Central Asia. Here we report MS results of two loess sections in Yili basin, Central Asia. The MS variation of one loess section with an elevation of 1432m is identical with that of loess-paleosol sequences in the CLP, but the other one at 875m have opposite trend. Based on field investigation, pedogenesis characteristics observations, carbonate, lithological and grain-size correlations, the authors suggest that the differences of regional paeloprecipitation related to altitudes during last interglacial period between the two sections are responsible for their differences of MS. Carbonate deposits also have influence on decrease MS. The susceptibility enhancement of pedogenesis model for loess-paleosol sequences in the CLP can not interpret completely the MS variations of loess sections from Central Asia area. It should be careful to reconstruct paleoclimatic change using susceptibility as a proxy in Central Asia area. Index Terms Loess-paleosol, magnetic susceptibility, paleoprecipitation, paleoclimatic significance, Central Asia 1. INTRODUCTION For standard loess sections in the Chinese Loess Plateau (CLP), paleosols always have higher magnetic susceptibility (MS) than their adjacent loess layers. Based on detail MS analysis of a loess borecore, Heller and Liu [1] conclude that MS variation is closely to paleoclimatic change. Further investigation [2,3,4] indicated that the curve of MS in Luochuan loess is well correlated with that of marine oxygen isotope (MIS). Hereafter, loess MS has been extensively used as a proxy of East Asian summer monsoons intensity [5]. Previous studies also show that loess MS can reflect the climatic change both in orbital [6] timescale and millennial timescale [7,8], and it is also applied to estimate quantitatively paleoprecipitation [9,10]. However, the paleoclimatic significance and enhancement mechanism of MS in Central Asia is still unclear by now. Here we report MS results of two loess sections at Talede and Nalati in Yili Basin, Central Asia and discuss their paleoclimatic significance. Yili Nalati Talede Ti a n Sha n Ti a n S h an Yili Yi Li Basin Figure 1. The locations of selected sections (Satellite map from http://maps.google.com) 2. PHYSIOGRAPHIC SETTING Loess deposits are widespread within the piedmont and intramontane depressions of Central Asia. They cover piedmont plains, river terraces, ridge slopes and watersheds. Loess is a significant component in the piedmonts of Tian Shan, eastern Fergana depression, the Afgan-Tajik depression, piedmonts of Kopetdag, Badchyz and Karabil Hills north of Parapamiz, in the Kashmir valley [11]. Yili II - 1227 978-1-4244-2808-3/08/$25.00 ©2008 IEEE IGARSS 2008 2008 IEEE International Geoscience & Remote Sensing Symposium July 6-11, 2008 | Boston, Massachusetts, U.S.A