祁连山构造地貌特征:青藏高原东北缘晚新生代构造变形和地貌演化过程的启示  

TECTONIC GEOMORPHOLOGY OF THE QILIAN SHAN:INSIGHTS INTO THE LATE CENOZOIC LANDSCAPE EVOLUTION AND DEFORMATION IN THE NORTH EASTERN TIBETAN PLATEAU

作　　者：张会平[1] 张培震[1] 郑德文[1] 郑文俊[1] 陈正位[1] 王伟涛[1] 

机构地区：[1]中国地震局地质研究所地震动力学国家重点实验室,北京100029

出　　处：《第四纪研究》2012年第5期907-920,共14页Quaternary Sciences

基　　金：中国地震局地质研究所中央公益性科研院所基本科研业务专项项目(批准号:IGCEA1115);国家自然科学基金项目(批准号:41030317;41272196)共同资助

摘　　要：祁连山地区作为青藏高原向北东方向扩展生长的前缘地区之一,对构造地貌发育特征及其控制因素研究是理解青藏高原东北缘晚新生代构造变形过程的重要内容之一。通过地形坡度、起伏度以及河流纵剖面分析,研究揭示出祁连山高坡度、高陡度的造山带边缘山系及高海拔、低起伏山间盆地发育地貌特征。结合区域隆升、侵蚀速率研究表明,祁连山山脉边缘部分山系发育接近平衡状态,而河流裂点的广泛发育进一步表明整个祁连山山脉地区的地貌特征,特别是河流地貌发育仍然处于瞬时(transient)状态。通过对比祁连山山脉10个不同背景下的流域盆地,发现无论是内流水系,还是外流水系,流域上游地区均发育有低起伏、低坡度的山间盆地,这一特征表明控制祁连山内部发育平坦地形的因素并非取决于是内流还是外流水系,而可能主要受控于河流水系搬运能力的强弱。除此之外,通过对比祁连山地区盆地形态研究表明,西北侧的狭长、平行盆地主要受控于阿尔金断裂走滑应变在祁连山地区的缩短吸收,而东南侧的菱形盆地则受控于海原、东昆仑左旋走滑断裂带及其次级鄂拉山、日月山右旋走滑断裂所夹持的块体。以现有流域盆地宽度与面积之间的关系为基础,我们初步推测了祁连山造山带西北侧的构造缩短量大致为61km,对应整个祁连山的缩短率大致为17%,与祁连山南侧区域结果相当。当然,考虑到祁连山东南侧大通河流域区的缩短量与周边研究的差异,我们不能排除祁连山造山带早期的构造缝合线或先存断裂对部分流域的线性排列也起到了一定的控制作用。Late Cenozoic upward and outward growth of the Tibetan Plateau was resulted from post-collision convergence between the Indian and Eurasian plates, despite of its progressive northward growth, either steadily or in an oblique stepwise style. North eastern Tibet offers both a missing link in our understanding of Tibet＇s overall growth and it has long been regarded as an ideal field laboratory for studies of both how and why high, regionally extensive plateaux grow and how such terrains affect regional climate. Tectonically, it lies in the transition between two contrasting styles of topography and associated deformation. South of ca. 35° N as far east as ca. 100° E,the plateau＇s surface is relatively gentle, and obvious manifestations of major thrust faulting and horizontal shortening of the upper crust are sparse. Here, eastward lateral, or ＂channel,＂ flow of a weak lower crust into previously thinner crust that lay east of Tibet offers a testable hypothesis for how this part of the Tibetan Plateau has developed. Northwest of this area, more rugged topography of the Qilian Shan, with numerous fault-bounded ranges and intermontane basins, resembles that of the Tibetan Plateau,Tien Shan and other,older intracontinental belts like the Rocky Mountains of Laramide time in the western USA. Late Cenozoic uplift and landscape evolution of the Qilian Shan in north eastern Tibetan Plateau was continuously fed by the upward and outward growth of the Tibetan Plateau since the collision. Timing and style of uplift of the Qilian Shan to its present elevation,and its bearing of the slip of the Ahyn Tagh fault have been the focus of considerable research aimed at understanding the strain portioning during continental plate collision and the influence of topographic growth on global/regional atmospheric circulation and climatic conditions in Asia. Geomorphometric indices, like slope, local relief and longitudinal profiles, reveal high-refief steep marginal ranges,and sub-summit low-relief intermontane basins in the Q

关 键 词：祁连山 构造地貌 青藏高原 构造变形 地貌演化 

分 类 号：P534.63[天文地球—第四纪地质学]