Onset of Xiashu loess deposition in southern China by 0.9 Ma and its implications for regional aridification  

作　　者：Xusheng LI Zhiyong HAN Huayu LU Yingyong CHEN Yang LI Xiaokang YUAN Yuwen ZHOU Mengyao JIANG Cunjuan LV 

机构地区：[1]School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210023, China [2]CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China [3]College of Environment and Planning, Henan University, Kaifeng 475001

出　　处：《Science China Earth Sciences》2018年第3期256-269,共14页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41571188,41671191,41690111&40971004)

摘　　要：The Xiashu loess is a typical Quaternary eolian deposit in southem China and represents an important terrestrial paleoclimate archive in this low-latitude monsoon region. However, the chronological framework of Xiashu loess deposition has yet to be established. Determining the timing of the onset of Xiashu loess deposition will allow researchers to better understand late Quaternary aridification across the Asian continent, the evolution of the East Asian monsoon and regional environmental changes in subtropical regions. Therefore, in this study, a systematic chronological study of the Xiashu loess is conducted to answer this question. For the first time, magnetostratigraphic classification reveals that the Matuyama/Bnmhes （M/B） reversal is present in the Xiashu loess at two sites in Jiangsu Province, the Qingshan profile at Yizheng and the Dagang core in Zhenjiang. Based on the results of magnetostratigraphy and optically stimulated luminescence （OSL） dating, the age of the lower boundary of the Xiashu loess is estimated to be approximately 0.9 Ma. Consequently, this Xiashu loess deposit is the oldest reported to date and is comparable in age to the red soil deposit in Xuancheng, Anhui Province. The onset of Xiashu loess deposition by 0.9 Ma represents the further expansion of arid range in Asia in the late Quaternary in response to significant aridification and winter monsoon strengthening in this subtropical region. We suggest that these climate changes were primarily driven by global cooling and an increase in high-latitude ice volume in the Northern Hemisphere and that the initiation of Xiashu loess accumulation was a regional response of southern China to the 0.9 Ma global cooling event.The Xiashu loess is a typical Quaternary eolian deposit in southern China and represents an important terrestrial paleoclimate archive in this low-latitude monsoon region. However, the chronological framework of Xiashu loess deposition has yet to be established. Determining the timing of the onset of Xiashu loess deposition will allow researchers to better understand late Quaternary aridification across the Asian continent, the evolution of the East Asian monsoon and regional environmental changes in subtropical regions. Therefore, in this study, a systematic chronological study of the Xiashu loess is conducted to answer this question. For the first time, magnetostratigraphic classification reveals that the Matuyama/Brunhes(M/B) reversal is present in the Xiashu loess at two sites in Jiangsu Province, the Qingshan profile at Yizheng and the Dagang core in Zhenjiang.Based on the results of magnetostratigraphy and optically stimulated luminescence(OSL) dating, the age of the lower boundary of the Xiashu loess is estimated to be approximately 0.9 Ma. Consequently, this Xiashu loess deposit is the oldest reported to date and is comparable in age to the red soil deposit in Xuancheng, Anhui Province. The onset of Xiashu loess deposition by 0.9 Ma represents the further expansion of arid range in Asia in the late Quaternary in response to significant aridification and winter monsoon strengthening in this subtropical region. We suggest that these climate changes were primarily driven by global cooling and an increase in high-latitude ice volume in the Northern Hemisphere and that the initiation of Xiashu loess accumulation was a regional response of southern China to the 0.9 Ma global cooling event.

关 键 词：Xiashu loess CHRONOLOGY Magnetic stratigraphy ARIDIFICATION East Asian monsoon 

分 类 号：P463[天文地球—大气科学及气象学] P512.2