天山南麓库车褶皱带晚第四纪地壳缩短及变形机制

发布时间：2018-06-06 10:26

本文选题：南天山 + 库车盆地　；参考：《中国地震局地质研究所》2016年博士论文

【摘要】：由于受到印度—欧亚板块碰撞远程作用的影响,天山自早-中中新世开始重新活动并快速隆升。现代GPS数据显示横跨天山~80°E以西的地壳缩短速率为10-13mm/a,至东部降低为2-5mm/a。天山西部的地壳缩短速率是印度—欧亚板块汇聚速率45mm/a的四分之一。由于经历了强烈的构造变形,天山成为了探索陆—陆碰撞造山机制和演化历史的天然实验室。仪器和历史记录的综合地震资料显示天山地区的活动变形主要集中在其南北两侧山麓地带。然而,地质时间尺度的天山山前地壳缩短速率由于欠佳的年代学约束而存在很多争议。同时,虽然由GPS所计算的现代缩短速率十分准确,但因为两方面原因而不能简单地用来理解造山过程。一方面,GPS速率仅代表十分狭窄时间窗内的缩短速率,因而必然会受到主要毗邻断层之上幕式滑动事件相伴的弹性应变释放的显著影响;另一方面,造山过程本质上是非弹性的,但由GPS导出的应变既包含非弹性部分又包含弹性部分。因此,我们仍需要计算一个准确的、长期的,并且独立于大地变形速率的汇聚缩短速率。天山南缘的山麓地带是典型的前陆褶皱逆冲带,也是塔里木盆地的最北缘,在新近纪和第四纪持续沉降,同时也记录了这一时期天山和塔里木盆地之间的相互作用。本文的研究区位于南天山山前的库车盆地。堆积于库车盆地内部的巨厚新生代沉积物已遭受了强烈变形从而形成了一个复杂逆断裂褶皱带,也就是我们称之为的库车逆断裂褶皱带。在广泛观察的基础上,我们通常认为库车逆冲推覆前缘是通过薄皮式逆断裂褶皱带向盆地方向迁移的。我们在野外实际观察中发现库车盆地内亚肯背斜带、秋里塔格背斜带和喀桑托开背斜带在晚第四纪均是活动的。随着库车盆地内部石油勘探的不断深入,其深部构造信息不断被揭露,尤其是其深部的隐伏断层。库车逆断裂褶皱带下部存在一个低角度的主滑脱逆冲断层,其上存在大量复合及对冲断层。这些断层有些是活动的,并且吸纳了天山—塔里木盆地边缘现今的地壳缩短;另外一些则是不活动断层。目前仅仅凭借地震反射剖面,我们很难判断这些断层的活动性。通过利用二维简单断层位错模型拟合晚第四纪地表变形速率来确定深部断层活动性及滑脱面上的滑动速率分布。其中,晚第四纪地表变形数据基于构造地貌制图和宇宙成因核素10Be测年。本文所取得的结论总结如下:(1)在库车逆断裂褶皱带中,地表变形通过对已变形的地貌面进行绝对定年来定量化。在地表没有风化侵蚀的前提假设下,我们得到所有被测地貌面的最小暴露年龄。所有年龄结果分布在3个区间内,分别为:125.4~140ka、43.9~79.9ka和18.9~26.2ka。我们将其与晚第四纪温度曲线进行对比,发现并不是所有的年龄结果都有幕式气候波动相对应。同时,我们不能忽略区域构造作用的影响,它在地貌面保留上起到了非常关键的作用。(2)通过一步一步不断推进的模拟显示,在一阶近似中,在前陆沉积楔中的变形总体上来说是因为主滑脱层上向上不断减小滑动速率产生的,并且促进了老断层的重新活动。亚肯背斜仅是由低角度滑脱断层的终端效应产生的,它的变形幅度与断层前沿的滑动速率呈正比。滑脱面向下伸展段几乎并不对亚肯背斜地表变形产生任何影响。与之毗邻的秋里塔格背斜是由位于主滑脱面上的断坡和向上减小的滑动速率共同作用产生的。在深入天山内部的滑脱面北端的断坪—断坡—断坪构造造成了喀桑托开背斜带内的构造隆升和轻微掀斜。模拟曲线还显示更北地区的靠近天山山前和天山内部几乎没有地壳隆升。但是这个观点仍需要更多的地质证据加以约束。(3)不断推进的反演模拟同时给出了晚第四纪横跨天山的地壳缩短速率。通过与秋里塔格背斜T2和T1,3地貌面变形拟合所计算的缩短速率分别为11.54~12.96mm/a和10.92~12.11mm/a。但是值得注意的是,因为基于地表零侵蚀假设所计算的地貌面年龄为最小暴露年龄,计算所得的均为最大地壳缩短速率。(4)研究区内大部分晚第四纪地表变形均是由深部隐伏滑脱断层产生的。但是,之前的研究成果报道在秋里塔格背斜带和喀桑托开背斜带南北翼发育大量断续、短迹线的活动断层断错了晚第四纪地貌面。我们认为这些地表断层都是主滑脱断层的次级断层。
[Abstract]:Due to the impact of the long-range impact of the India Eurasian plate collision, the Tianshan mountains began to reactivate and quickly uplifted from the early Middle Miocene to the middle Miocene. Modern GPS data showed that the crustal shortening rate across the west of the Tianshan ~80 E was 10-13mm/a, and the crustal shortening rate in the eastern part of the eastern 2-5mm/a. Tianshan Mountains was the convergence rate of the India Eurasian plate 45mm/. 1/4 of a. Due to the strong tectonic deformation, Tianshan has become a natural laboratory for exploring the land land collision orogenic mechanism and evolution history. The comprehensive seismic data of instrument and historical records show that the activity deformation of Tianshan area is mainly concentrated in the piedmont of the north and south sides. The rate of shell shortening has a lot of controversy due to the poor chronological constraints. While the modern shortening rate calculated by GPS is very accurate, it can not be simply used to understand the orogenic process for two reasons. On the one hand, the GPS rate represents only the shortening rate within a very narrow time window, so it is bound to be mainly adjacent to it. On the other hand, the orogenic process is essentially inelastic, but the strain derived by GPS includes both the inelastic and the elastic. Therefore, we still need to calculate an accurate, long-term, and independent convergence speed of the deformation rate. The piedmont area of the southern margin of the Tianshan Mountain is a typical foreland fold thrust belt and the northern margin of the Tarim Basin. It continues to settle in the Neogene and quaternary periods, and also records the interaction between the Tianshan and Tarim basins in this period. The study area is located in the Kuche basin in front of the South Tianshan Mountain. The huge Cenozoic sediments have been strongly deformed and formed a complex reverse fault fold belt, which is called the Kuche reverse fault fold belt. On the basis of extensive observation, we usually think that the front edge of the Kuche thrust nappe is migrated to the basin by a thin skin type reverse fault fold belt. It is found that the inner subken anticline belt in the Kuche basin, the kurintag anticline and the kharsanto open anticline are all active in the late Quaternary. With the deepening of the oil exploration in the Kuche basin, the deep tectonic information is constantly exposed, especially the hidden faults in the deep part of the basin. There is a low angle in the lower part of the Kuche reverse fault fold belt. There are a large number of complex and hedging faults on the main slip faults. Some of these faults are active and absorb today's crustal shortening at the edge of the Tianshan Tarim Basin; others are inactive faults. At present, only by the seismic reflection profile, we are very difficult to judge the activity of these faults. By using two-dimensional simple. The fault dislocation model fitted the late Quaternary surface deformation rate to determine the activity of deep faults and the sliding velocity distribution on the slippage surface. The late Quaternary surface deformation data were based on the tectonic geomorphology mapping and the cosmic genetic nuclide 10Be dating. The conclusions of this paper are summarized as follows: (1) the surface deformation in the Kuche reverse fault fold belt The deformed geomorphic surface is quantified by absolute dating. Under the assumption that the surface has no weathering erosion, we get the minimum exposure age for all the geomorphic surfaces. The results of all ages are distributed in 3 intervals: 125.4~140ka, 43.9~79.9ka and 18.9~ 26.2ka., which we do with the late Quaternary temperature curve. At the same time, we can not ignore the effect of episodic climate fluctuations. At the same time, we can not ignore the effect of regional tectonics, and it plays a very important role in the reservation of geomorphology. (2) through the step by step the simulation shows that in the first order near, the deformation in the foreland sedimentary wedge is generally speaking. Because the sliding rate of the main sliding layer is continuously reduced and the old fault is reactivated. The anacid anticline is produced only by the terminal effect of the low angle slip fault, and its deformation amplitude is proportional to the sliding rate of the fault front. The contiguous Chu tge anticline, which is adjacent to it, is produced by the joint action of the broken slope on the main slipping surface and the sliding speed decreasing upward. The tectonic uplift and slight tilting in the kashanto open anticline belt in the north end of the slipping surface inside the Tianshan Mountains resulted in the tectonic uplift and slight tilting in the kashanto open anticline zone. The simulation curve also shows the north. There is almost no crustal uplift in the area near the Tianshan Mountains and the Tianshan Mountains. But this view still needs more geological evidence to be constrained. (3) the continuous advances in the inversion simulation also give the crustal shortening rate of the late Quaternary across the Tianshan Mountains. The shortening rate calculated by fitting the T2 and T1,3 geomorphic surface deformation to the Kurtag anticline It is 11.54~12.96mm/a and 10.92~12.11mm/a., but it is worth noting that the maximum crustal shortening rate calculated by the calculated geomorphic age based on the surface zero erosion assumption is the maximum crustal shortening. (4) most of the late Quaternary surface deformation in the study area is produced by deep concealed slip faults. The previous research results reported that the north and South wings of the anticlinal anticline belt and the kaisao anticlinal belt were widely developed, and the active faults of the short traces had broken the late Quaternary geomorphic surface.
【学位授予单位】：中国地震局地质研究所
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P542

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