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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。
As one of the frontier areas where the Qilian Mountains expand to the northeast, the study on tectonic and geomorphological development and its controlling factors is one of the important contents in understanding the tectonic deformation process of the Late Cenozoic in the northeast margin of the Qinghai-Tibet Plateau. Based on the analysis of terrain slope, undulation and river profile, the study reveals that the Qilian Mountains have high gradient and high steepness orogenic belt margins and high-altitude and low-elevation basin features. The study on the regional uplift and erosion shows that the mountain ranges of the Qilian Mountains are close to equilibrium and that the extensive development of the river fissures further indicates that the landscape features of the Qilian Mountains, especially the river topography, are still in a transient state. By comparing the basin basins in 10 different backgrounds in the Qilian Mountains, it is found that there are both low-lying and low-slope mountain basins in the upper and lower reaches of the basin in both the inland water system and the outflow water system. Is not dependent on whether it is in or out of the water system and may be mainly controlled by the strength of the river system’s handling capacity. In addition, the comparison of the basin morphology in the Qilian Mountains shows that the narrow and parallel basins on the northwest side are mainly controlled by the shortening absorption of the strike-slip strain of the Altyn Tagh fault in the Qilian Mountains, whereas the southeast-shaped rhombic basins are controlled by the Haiyuan, Lost strike-slip faulting belt of the East Kunlun Mountains and its block sandwiched by the second-level Ela Mountain and the Riyadongshan dextral strike-slip fault. Based on the relationship between basin width and area in the existing basins, we initially speculated that the structural shortening on the northwestern Qilian orogenic belt is about 61km, and the shortening rate corresponding to the entire Qilian Mountains is about 17%, equivalent to the results in the southern Qilian Mountains . Of course, taking into account the difference between the shortening of the Dartong area on the southeast side of the Qilian Mountains and the surrounding areas, we can not rule out that the early structural seams or preexisting faults in the Qilian orogenic belt also played a certain role in controlling the linear arrangement of some drainage basins.