青海南山风成沉积光释光年代学研究

The Optically Stimulated Luminescence Study of Aeolian Deposits in Qinghai South Mountain

青海湖地区的黄土是独立于湖相沉积的重要古气候记录。对青海南山夏拉水库和橡皮山黄土剖面进行了沉积学、地貌学和光释光年代学的研究,重建了全新世以来青海湖地区的环境变化。结果表明,1）青海南山地区至少在10.4 ka之前由河流沉积转换为风成堆积,指示气候转型期;2）10.4~5.0 ka间以黄土堆积为主,偶尔夹杂风成砂,指示气候整体比较温暖适宜,有个别的降温事件;3）3.4~1.0 ka古土壤发育为主,指示气温—降水组合较好,气候最适宜;4）0.6 ka以来发育现代土壤。研究数据基本与青藏高原东北缘的古气候/环境变化记录相一致,但在时间上存在一定的相位差,可能与海拔较高,区域对气候反应滞后有关。

Due to its extremely sensitive to global climate change,the Qinghai Lake area is one of the most hottest research spots attracting global paleoenvironmental researchers. Qinghai South Mountain,situated in the northeast of Qinghai Province,is the boundary of Qinghai Lake Basin and Chaka Lake Basin. The loess can provide valuable archives for reconstructing Holocene paleo-environmental change. In the present work,the XL and XPS loess sections,located at the south and north of Qinghai South Mountain are examined by using sedimentology,geomorphology and geochronological methods. The chronostratigraphy is established by using nine optically stimulated luminescence（ OSL） ages. The environment evolution records since the Holocene in the region of Qinghai Lake were rebuilt. We concluded that：（ 1） the aeolian sediment of Qinghai South Mountain changed from river deposits into aeolian accumulation at least 10. 4 ka,indicating large climate transition;（ 2） During 10. 4 ka ~ 5 ka,the loess dominated,occasional interbedded eolian sand thin layers,（ 3） During 3. 4 ~ 1. 0 ka,the pedogenesis was relatively strong,inferred a good combination of temperature-precipitation;（ 4） since 1. 0 ka,the modern soil developed.These paleoenvironmental information of the Qinghai lake basin was generally in accordance to the Qinghai-Tibet plateau / environmental changes during the Holocene.