末次冰期以来格尔木河填充-切割及驱动机制初探  

LATE QUATERNARY DEPOSITION AND INCISION SEQUENCES OF THE GOLMUD RIVER AND THEIR ENVIRONMENTAL IMPLICATION

作　　者：陈艺鑫[1] 李英奎 张跃[1] 张梅[1] 张敬春[1] 易朝路[3] 刘耕年[1] 

机构地区：[1]北京大学城市与环境学院,北京100871 [2]Department of Geography, University of Tennessee [3]中国科学院青藏高原研究所高原环境变化和表生过程重点实验室,北京100085

出　　处：《第四纪研究》2011年第2期347-359,共13页Quaternary Sciences

基　　金：国家自然科学基金面上项目(批准号:40571014和40971002);国家重点基础研究发展规划项kt(973项目)(批准号:2005CB422001)资助

摘　　要：格尔木河水系是位于青藏高原东北部的一个较大的内陆水系,它发源于东昆仑山主脊,由南向北流经于昆仑山间,最终流入柴达木盆地中的达布逊盐湖。格尔木河水系河谷地貌和沉积,尤其是晚第四纪以来发育的阶地系列是本区构造运动和气候变化信息的良好载体,对研究青藏高原的环境演化具有重要意义。通过对格尔木河水系小干沟、纳赤台和三岔河等典型河段的阶地序列进行野外观测和采样,应用光释光(OSL)和^(14)C等方法对阶地进行年代学研究。根据河流阶地的形成时代,结合气候、构造和地貌演化特征,将格尔木河水系末次冰期以来地貌演化过程划分为82～16ka的三岔河填充期和16ka至今的格尔木河切割期两个阶段。晚更新世中后期构造相对稳定,奠定了三岔河组堆积的基础,而同时冰川作用加强,降水增多也促进了堆积作用,其中38～36ka期间堆积速率最大,反映了MIS 3阶段强烈的剥蚀作用。格尔木河切割期主要由构造抬升驱动,期间又存在4次阶段性下切,时代分别为16～13ka,13～11ka,11～5ka和5ka至今,形成4级阶地。切割速率先逐渐增大,进入全新世后迅速降低,反映了区域构造抬升先增强后减弱的变化过程。Golmud River is a large interior river that originates from the Kunlun Mountains and drains into the Qaidam Basin on Northern Tibetan Plateau. Golmud River valley has experienced intensively tectonic movements and drastic climate changes since the Last Glacial, which deeply influenced the geomorphologic evolution of the river. In addition,well-developed fluvial terraces and sediments are preserved in the river valley. Therefore, Golmud River is an ideal place to examine the climate changes and tectonic movements on the Northern Tibetan Plateau, as well as their roles in influencing fluvial landform evolution. This research is mainly through field investigation and sediments analysis. The chronology of the terrace sequences is established using optically stimulated luminescence（OSL）and radiocarbon dating methods. Detailed work was carried out in Sanchahe （35 °52. 567＇ - 35 °52. 992＇N ,94°21. 590＇ - 94°21.990＇E; 3728 - 3793m a. s. l.）, Nachitai（35°52.951＇ - 35°54.229＇N,94°32.904＇ - 94°37.291＇E; 3510 - 3584m a. s. l. ） , and Xiaogangou （36°08. 173＇N, 94°48. 645＇E; 3198m a. s. l. ） sections, and 24 OSL samples and 2 radiocarbon samples were collected. Four terraces were identified in the Golmud River valley,T4 expands continuously and raises 26 -62m above the riverbed. It is a filled terrace consisting of Sanchahe Formation. The Sanchahe Formation, typical braided river sediments, started to deposit no later than 82ka, and ended in 16ka when the river began to cut clown and formed T4. T3 ,T2 and T1 are all strath terraces with 0.5 - 5.0m-thick layers of fluvial sediments covering the Sanchahe Formation. These terraces are not continuously distributed, but could be found at Nachitai and Sanchahe sections. The OSL ages of these three terraces are 13ka, 11 ka and 5ka correspondingly. Based on these results, two landform evolution stages since Last Glacial are identified： Sanchahe deposition stage（82 - 16ka）and Golumd incision stage（ since 16ka）. During the deposi

关 键 词：青藏高原 格尔木河水系 河流阶地 气候变化 构造运动 填充-切割 

分 类 号：P941.74[天文地球—自然地理学]