OSL Chronology of Loess Deposits in East China and its Implications for East Asian Monsoon History

Lai, Z.P.¹

¹Luminescence Dating Group, Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, XiNing 810008, China

Controversy exists regarding the chronology of loess in the Nanjing area in Jiangsu Province and the Jiujiang area in Jiangxi Province, East China. The chronology is of special interest, because the age of the initial accumulation for loess in these areas indicates that dust accumulation has been extended from the Loess Plateau in North China to East China at that time. This implies a threshold in the evolution of the East Asian monsoon, with the strengthened winter monsoon transporting aeolian dust further to the south. In this study nine luminescence samples were collected from the Jiujiang area and four samples from the Nanjing area. Quartz grains of 38-63 μm were isolated and the single-aliquot regenerative- dose (SAR) protocol was employed for De determination. For all samples from the Nanjing area, during the SAR measurement cycles the test-dose sensitivity was dose dependent and dropped significantly when the regeneration dose reached >300 Gy, while it increased linearly when the regeneration dose value ranged from 25 to 300 Gy. The reason for this is not yet known. The OSL chronology and its implications for paleoenvironmental change are discussed. Quartz OSL dating results for samples from the Nanjing area suggested that the first loess layer was accumulated during the Last Glaciation. The loess layers below should be much older, indicating that loess deposition started much earlier than the early Last Glaciation. The OSL ages for loess samples from the Jiujiang area indicated that loess accumulation took place since the early Last Glaciation. This is in agreement with the previous view that dust transported by the winter monsoon reached the Jiujiang area in the early Last Glaciation.

Corresponding author: Lai, Z.P. | zplai@isl.ac.cn