【作者】 王义祥；

【导师】 潘保田；

【作者基本信息】 兰州大学 ， 自然地理， 2007， 博士

【摘要】 造山带的隆升过程、机理和影响一直是地学研究的热点。长期以来，地质学、地貌学、大气科学和生物学等众多学科，分别从各自不同的角度探寻青藏高原和祁连山隆升的证据，以推算高原隆升的幅度，探讨隆升的机理，形成、演化历史以及对环境的影响等。但迄今为止，对祁连山地区分布于不同高度的夷平面，是由统一夷平面解体而成，还是不同期次构造运动的产物?夷平面的解体和山体的隆升是构造运动所主导，还是受气候变化、均衡抬升所支配?祁连地区典型的山—盆耦合地貌形式是如何形成的等问题，并未取得一致的认识。而构造隆升和侵蚀的关系是解决上述问题的关键，但直接对地貌隆升进行定量研究是比较困难的。古地貌面的隆升，提供了一个很好的起点与终点，通过对古地貌面的恢复，可以计算出古地貌面解体后的侵蚀量，从而为深入探讨隆升与侵蚀的定量关系创造了条件。在古地貌面的恢复研究中，确定古地貌面的层级关系是至关重要的，鉴于断层对划分古地貌面层级的重要影响，我们运用参数法和高差阴影图像法等技术手段，成功提取了祁连山地区断层的分布和性质，并对断层与地貌面的空间关系进行了叠加分析，结果显示，仅有约23.1％的断层线横切分布不同高度的古地貌面，相关沉积也具有多期次、多旋回的特点，这就说明，祁连山地区分布于不同高度的地貌面，不是由统一的夷平面因构造错断形成的，而是不同期次、不同构造旋回的产物。对古地貌面的自动识别与提取，也是客观准确地进行古地貌面恢复的关键，研究表明，随着研究区域的扩大，地貌结构复杂程度的提高，简单的基于图像处理技术的分类方法难以完成复杂地貌类型的划分工作。引入坡位指数和基于空间尺度的分类方法，较好地解决复杂地貌单元的划分和古地貌面的识别问题。对古地貌面的统计显示：山顶面解体前西高东低，北高南低，坡度为8°左右；而主夷平面解体前由西南向东北倾斜，坡度为4°左右。基于地貌分类和古地貌面识别的插值计算，是古地貌面恢复中的最后一个环节。计算显示，剥蚀面解体以来已经抬升约600m，因地貌均衡作用造成地表的抬升量为124m，占总抬升量的21％；主夷平面解体以来已经抬升约1550m，因地貌均衡作用造成地表的抬升量约为376m，占总抬升量的24.3％；山顶面解体以来已经抬升约2150m，因地貌均衡作用造成地表的抬升量约为428m，占总抬升量的19.9％。因侵蚀而引起的均衡抬升量均未超过总隆升量的30％。而人工地震所测地壳厚度显示，地壳厚度与地表高程有良好的对应关系说明，祁连山的整体隆升，主要是地壳缩短加厚引起的均衡抬升所致，而山峰高度与地壳厚度的不相称，可能主要是地表侵蚀引起的减荷隆升所造就。根据断层走向所计算出的区域主应力的方向为N32°E，与印度板块自西南向东北挤压的方向基本一致，主夷平面拱曲变形的特征也说明，印度板块与欧亚板块碰撞后，继续向北东方向推进，是导致祁连山地区的地壳的缩短加厚和地表隆起升的直接原因。而在推进中，遇到先成横向断层的阻挡，并在这些断裂上形成强烈的挤压—逆冲运动，将原来的侧向水平走滑运动转化为逆冲垂直运动，是形成山—盆耦合地貌形式的必要条件。更多还原

【Abstract】 The uplift process, mechanism and effects of orogen have been a hotspot ingeo-science for a long time. And the relationship between tectonic uplift and erosionis the key to resolve these problems. In the past, there were many studies, whichexplored evidences for the uplift of Tibetan Plateau and Qilian Mountains, in geology,geomorphology, atmospheric science and biology. However, there was still not aconsistent opinion about some problems, such as, whether there was a uniformpeneplanation in Qilian Mountains or not? The main cause of peneplanationdeformation and uplift is tectonic movement or climate change and erosion isostaticeffect? How did the typical coupled mountain with basin geomorphological form beshaped? In the research of the relationship between tectonic uplift and erosion, it wasvery difficult to quantify the amount of uplift directly. However, the uplift of steppedgeomorphic surfaces provided the beginning and ending position of paleo-relief. Byrebuilding paleo-relief, we can calculate the amount of erosion after steppedgeomorphic surfaces deformation and it is also benefit advanced studies for exploringquantitative relationships between uplift and erosion.In rebuilding paleo-relief, it is very important to make sure the stage ofpeneplanation. Whereas the fault have very important influence on partition ofdifferent grade peneplanation, we used some methods such as horizontal curvature,vertical curvature and shaded-relief images, to extract the distribution and propertiesof faults in Qilian Mountains successfully. Then we made overlay analysis on spatialrelationships between faults and different grade peneplanation surfaces. The resultsshowed that there was only 20 percent faluts which cut across different gradepeneplanation surfaces at different altitude and related sediments had multi-periodsand multi-cycled properties. It indicated that those geomorphic surfaces distributing atdifferent altitude in Qilian Mountains were not a uniform planation which wasdisturbed by tectonic movements, but a result of different tectonic movement cycles.The auto-identification and extraction of stepped geomorphic surfaces was alsothe key to rebuild paleo-relief exactly. Studies also indicated that, with scale-up ofstudy area and increase of complexity in geomorphical structure, simple classification methods based on image process were not enough to complete classification ofcomplex geomorphical forms. With introducing slope position index and space-scale,we could resolve this problem well. After statistics, the results suggest that from westto east, from north to south, the elevation of Summit Surface decreased, and itsslope was about 8°. However, the elevation of Main surface decreased fromnorthwest to southeast and its slope was about 4°. Based on these quantitativecharacters, we can rebuild paleo-relief easily.The interpolated calculation based on the result of auto-classification is the laststep in rebuilding paleo-relief. The calculation indicated that surface has been raised600m after the erosion surface broke. The amount of uplift caused by isostatic effectwas 124m which occupied 21% of total amount of uplift. To Main Surface andSummit Surface, the total amounts of uplift were 1550m and 2150m respectively afterthe two surfaces broke, the amounts of uplift caused by isostatic effect were 376m and428m, which occupied 24.3% and 19.9% of total amounts of uplift. Since the crustdepth measured by using artificial earthquakes showed that crust depth correspondedwith elevation of surface, the main reason of the tectonic uplift in Qilian Mountainswas isostatic uplift caused by curst shortening and thickening rather than surfaceerosion.According to the fault strike, we calculated the direction of regional main stressis N32°E, consisting with the direction of compression from southwest to northeastof Indian plate. The character of the arched deformation of Main Surface also showedthat Indian plate continued pushing northwestwards after it collided with Eurasianplate. And it directly caused the surface uplift and the crust shortening and thickeningin Qilian Mountains. It was necessary for the formation of coupled mountain-basingeomorphological form that the discontinuous push blocked by pre-formed transversefaults forming strong compress-strike motion and changed lateral slip motion tovertical strike motion.更多还原