摘要
对黑河中游酒东盆地大洼井（DWJ）和新开九队（XKJD）两个钻孔以及现代黑河干流和支流进行重矿物采集与分析。分析结果发现：DWJ钻孔下部（140～69.7 m）沉积物重矿物特征同摆浪河与马营河的相似性较高;DWJ钻孔上部（69.7～0 m）和XKJD钻孔（65.6～0 m）的沉积物重矿物特征与现代黑河干流、梨园河和山丹河两个支流比较吻合。重矿物组合特征的变化指示了沉积物的源区发生明显变化。DWJ钻孔上部与下部的岩性和沉积相均发生明显变化,重矿物组合特征所反映的源区变化指示了黑河中游水系发生重要调整。对比钻孔岩芯和走廊区第四系岩相剖面特征,推测此次黑河中游沉积环境与水系格局发生变化的时间大致为早-中更新世之交。
The northern Qilian Mountains have been experiencing intense tectonic uplift and denudation since the late Cenozoic, which resulted in an exceptionally thick sediment building up in the Hexi Corridor. The mineral characteristics of these deposits preserved substantial information about the mountain uplift and drainage evolution. Heavy minerals are the stable components in the sedimentary cycle; its characteristics and assemblages are useful tools to acquire the sediment provenance information, by inference, drainage pattern evolution. With the purpose of deciphering the drainage evolution history in Jiudong Basin, we collected heavy mineral samples from two cores（DWJ and XKJD） and modern fluvial samples in Jiudong Basin.We find that： 1） The heavy mineral characteristics in the lower part of DWJ Core（140-69.7 m） are similar to those in the two tributaries, Bailang River and Maying River; 2） The heavy mineral characteristics in the upper part of DWJ Core（69.7-0 m） and the XKJD Core（65.6-0 m） are similar to those in the trunk Heihe River as well as two tributaries, Liyuan River and Shandan River. The concentration of heavy mineral grains in sand-sized terrigenous sediments may fluctuate considerably because of several factors, mainly the sedimentary processes and post-depositional dissolution. To eliminate the effects of these fators on heavy mineral assemblages as much as possible,we analyize the samples with same grain size（63-125 um）, which means they represent similiar hydrodynamic condition. The presence of abundant less resistant minerals（e.g. amphiboles, epidotes） in cores indicates that chemical weathering is negligible and most unstable grains are preserved. Given the significant changes of both lithology and sedimentary facies around 70 m in DWJ Core, the change of heavy assemblages in cores could be attributed to the drainage reorganization of midstream of Heihe River. By comparing sedimentary features from DWJ Core with previous studies in the Hexi Corridor, we speculated that this drainage evolution and subsequent sedimentary environment change occurred between early and middle Pleistocene. This drainage reorganization of Heihe River in the Hexi Corridor happened during the Kunlun-Huanghe Movement, which allow us to attribute there organization to the tectonic movement surrounding this areas. As a whole, the paleodrainage evolution of the Jiudong Basin since the Pleistocene may be summarized as follows： during the Middle Pleistocene, Jiudong Basin were mainly sourced from Maying River and Bailang River, while the Heihe River flowed to the Minle Basin. At the end of the middle Pleistocene, the tectonic uplift of the Qilian Mountain caused a progressive reorganization of the drainage pattern of the Jiudong Basin. The provenance of the upper part of DWJ Core（69.7-0 m） and the XKJD Core（65.6-0 m） samples from trunk Heihe River indicates the northwestward shifting of Heihe River to its present-day position in the Jiudong Basin.
作者
张建
胡小飞
耿豪鹏
陈殿宝
潘保田
Zhang Jian Hu Xiaofei Geng Haopeng Chen Dianbao Pan Baotian(Key Laboratory of Western China s Environmental Systems~Ministry of Education, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, Gansu, Chin)
出处
《地理科学》
CSCD
北大核心
2016年第10期1595-1604,共10页
Scientia Geographica Sinica
基金
国家自然科学基金重大研究计划-重点支持项目(91125008)
国家自然科学基金面上项目(41571003)
国家自然科学基金项目(41201004)资助
国家重点基础研究发展计划(2011CB403301)
兰州大学西部环境教育部重点实验室开发基金
兰州大学中央高校基本科研业务费专项资金(lzujbky-2015-bt01)~~
关键词
黑河中游
水系演化
重矿物组合
早-中更新世
祁连山北缘
midstream of the Heihe River
drainage evolution
heavy mineral assemblages
early and middle Pleistocene
the northern Qilian Mountains
