昆仑山垭口地区第四纪冰川遗迹及冰期演化

Quaternary glaciation remains and glaciation sequences around the Kunlun Pass

基于成因-环境原则和多指标综合原则,依据昆仑山垭口地区的冰川地貌特征、冰碛物特征和孢粉信息,重建了该地区古环境演化历史。其中,冰碛物中的石英砂扫描电镜结果揭示了冰川、流水、风等地质营力对冰碛物的影响,孢粉分析结果在一定程度上可以恢复当时的植被类型。根据垭口冰碛ESR年龄280 ka B.P.和冰碛剖面特征,将其时代暂定为300～260 ka B.P.;根据纳赤台地区的冰川地貌和沉积物特征,确定纳赤台后沟沉积为冰水扇沉积,纳赤台冰期为600～400 ka B.P.;根据玉虚峰U形谷两道侧碛垄的ESR和OSL年龄将其时代暂定为末次冰期早-中期。结合前人的研究成果,将昆仑山垭口地区的冰期序列厘定为望昆冰期(700～500 ka B.P.)、纳赤台冰期(600～400 ka B.P.)、垭口冰期(300～260 ka B.P.)、玉虚峰冰期(115～44 ka B.P.)、本头山冰期(20～13 ka B.P.)。

The Kunlun Pass is one of the great glaciated areas in the East Kunlun Mountains, where there is a sequence of glacial moraines. The Kunlun Pass is located in the Tibetan Plateau, between the Qangtang Plateau and the Qaidam Basin. In this paper, based on the principles of cause-environmental and multi-index comprehensive, combined with the glacial geomorphology, characteristics of moraine, sporopollen information, the paleoenvironment in the study area is reconstructed. Among them, scanning electron microscopy(SEM) analysis of quartz in the moraine provides the origin of moraine and the influences of flowing water, wind and other geologic forces. Sporopollen analysis has restored the vegetation types at that time. According to the characteristics of glacial geomorphology and sedimentation in Nachitai, it is revealed that the deposition in Nachitaihougou is an outwash fan, and the age of Nachitai Glaciation is 400-600 ka B.P. According to ESR and OSL ages of the two lateral moraine bars on the Yuxu Peak glacial valley, it is believed that their age is in the early-middle stage of the Last Glaciation. Combined with the previous research results, the glaciation sequence in the Kunlun Pass can be determined as Wangkun Glaciation(700-500 ka B.P.), Nachitai Glaciation(600-400 ka B.P.), Yakou Glaciation(300-260 ka B.P.), Yuxu Peak Glaciation(115-44 ka B. P.) and Bentou Mountain Glaciation(20-13 ka B.P.).