金塔南山河流砾石特征指示的青藏高原东北缘地貌演化  

THE FLUVIAL GRAVELS FEATURES OF JINTA＇NANSHAN MOUNTAINS AND ITS IMPLICATION ON THE LANDFORM EVOLUTION IN THE NE TIBETAN PLATEAU

作　　者：温振玲 胡小飞[1] 潘保田[1] 张建[1] 曹喜林[1] 

机构地区：[1]兰州大学资源环境学院,西部环境教育部重点实验室,兰州730000

出　　处：《第四纪研究》2016年第4期907-916,共10页Quaternary Sciences

基　　金：国家自然科学基金项目（批准号：41471009和41571003）和中央高校基本科研业务专项基金项目（批准号：lzujbky-2015-126）共同资助 致谢感谢审稿老师建设性的修改意见.

摘　　要：青藏高原的隆升扩展不但塑造了高原及其周边的地貌，影响了气候的变化，而且极大地改造了其周缘的水系格局。其中，河流沉积物最直接地记录了河流演化与水系演变的过程。本研究主要利用河流砾石层的沉积特征分析金塔南山地区水系演化对高原东北缘扩展过程的响应。金塔南山顶面普遍沉积一套磨圆度较好、分选较好的河流砾石层，其砾石岩性主要组分为岩屑砂岩、石英砂岩和硅质岩，在局部地区也存在较多的砾岩和灰岩。祁连山北部主要的7条河流出山口主河道的砾石组分统计结果显示砾石岩性主要组分存在较大差异;河流之间的砾石岩性差异很好的解释了金塔南山顶面砾石岩性组分自东向西的变化。根据对比金塔南山顶面砾石组分和祁连山北部主要的7条河流主河道砾石组分中不同抗风化能力岩性的含量与分布，我们认为金塔南山顶面砾石主要来源于祁连山。对金塔南山顶面砾石ab面的测量发现：东段砾石倾向单一，指示古流向为北；而中西段倾向复杂。总体来说，砾石倾向指示的古水流方向是北向。结合砾石岩性组分与分布以及古流向，认为在金塔南山顶面沉积砾石层时，此处的河流处于摆荡状态且河流之间可能有汇合现象，造成局地砾石ab面指示的古流向与整体流向不一致；而后随着中更新世以来金塔南山的抬升，黑河和北大河下切分别形成正义峡和鸳鸯峡，形成两个相对独立和稳定的水系。The extension and uplift of the Tibetan Plateau has not only shaped the landforms of the plateau and surrounding areas, induced climate changes, but also greatly changed the drainage pattern around the plateau edges. River sediments are the most direct evidences in recording river evolutions. In this study, we focus on the drainage evolution of Jinta＇nanshan Mountains, northeastern margin of the plateau. The main methods we used are lithology components and fabric statistics of fluvial gravels from an old gravel layer and modern rivers. In the field we found that a layer of rounded and well sorted fluvial gravels was preserved on the top surface of the Jinta＇nanshan Mountains. The gravels are composed by different kinds of rocks, which are far more complicated than the local lithology. Results of gravel lithology statistics show that main components are litharenite, quartz sandstone and chert, which are not derived from local areas. In order to find their sources, we also counted lithology components of fluvial gravels in 7 major river of the northern Qilian Mountains. The results indicate the differences between the main components of the rivers are large. But the differences well coincide with the differences of the lithology components for gravels lying on the Jinta＇nanshan Mountains. Correlations of the content and the spatial distribution for gravel lithology components on the surface of the Jinta＇nanshan Mountains with that in the 7 rivers indicate that some parts of the gravels were derived from these rivers. Additionally, the gravel layer fabric showed that the ancient flows were northward in eastern part of the Jinta＇nanshan Mountains, while the flows in western part are relatively complex. Based on the gravel lithology and fabric analysis, we speculate that Jinta＇nanshan Mountains gravels were mainly derived from the rivers draining the Qilian Mountains. Combining the upper analysis, we can conclude that when the gravels were depositing on the surface of the Jinta＇nanshan Mountain, rivers

关 键 词：砾石特征 金塔南山 地貌演化 水系变迁 高原扩展 

分 类 号：P512.2[天文地球—地质学] P931.2