摘要
通常认为青藏高原东南部第四纪曾发育过一个冰帽——稻城冰帽,然而关于这个冰帽发育的年代和变化的过程,还缺乏足够的年代数据的支撑。本文选自稻城第四纪古冰帽南缘雄古附近的冰碛垄、冰碛台地、羊背石和冰川漂砾进行了宇生核素^(10)Be和^(26)Al暴露年代测定。结果显示,稻城古冰帽南缘至少发生过5次冰川前进事件,每次冰川前进到达最大规模的时间分别为19.0±0.7～19.8±0.7kaB.P.,25.8±0.6～27.4±0.7kaB.P.,52.5±0.9～59.6±1.1kaB.P.,162.2±2.7～287.4±9.9kaB.P.和大于480.2±2.2kaB.P.。根据年龄数据以及空间位置关系的分析,稻城古冰帽很可能形成于约800～600kaB.P.之间,此后冰川的规模呈现出随着时间不断缩小的趋势,可能与该区气候的变干有关。MIS 3的冰川规模比MIS 2大,可能与MIS 3时期气候比MIS 2相对湿润有关。
It is generally considered that an ice cape called Daocheng ice cape （29°02＇～30°08＇N,99°48＇ ～100°30＇E） must have been developed on the south eastern Qinghai-Xizang Plateau during the Quaternary epoch. However,the chronology research about its formation and activities is far from enough. In this paper, six samples were collected from near Xionggu township （29°09＇N, 100 °11＇E） of Daoeheng County and dated. It is discussed that Quaternary activities of the Daocheng ice cape on its south margin,based on the exposure dating of moraines,Roche moutonne＇e and erratic boulders by using in situ eosmogenic isotopes Be-10 and A1-26. It is found that the Daoeheng ice cape was probably developed in the period between 800 ～ 600kaB. P. and shrank afterward. Four advances of the ice cape at its south margin occurred at 287.4 ～ 162.7kaB. P., 59.6 ～ 52.5kaB. P., 27.4 ～ 25.8kaB. P. and 19.8 ～ 19.0kaB. P. ,respectively. The shrinking of the ice cape since at least 0.6MaB. P. is a probable result of the drying of climate in this region. That the Daoeheng ice cape at the MIS 2 is smaller,not bigger than that at the MIS 3 ,may be due to the fact that climate at the MIS 2 is drier than that at the MIS 3.
出处
《第四纪研究》
CAS
CSCD
北大核心
2012年第3期394-402,共9页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:40572097)
江苏省优势学科项目共同资助
