天山北麓四棵树河山前晚第四纪河流地貌研究

发布时间：2018-04-28 20:29

本文选题：河流阶地 + 阶地位相　；参考：《华东师范大学》2017年硕士论文

【摘要】：河流地貌对构造运动和气候变化的响应一直是河流地貌学和构造地貌学研究的核心内容之一。作为最基本的河流地貌类型之一的河流阶地,自然而然也成为了这方面研究的重要对象。通过对河流阶地的研究,不单可以重建河流地貌的演化历史,而且还可以获取区域气候变化与构造运动的信息。而河流阶地形成年代则是相关研究的基础。近些年来宇宙成因核素测年等新测年技术的发展和不断完善,为河流阶地研究奠定了基础,极大地促进了河流地貌学与构造地貌学的研究与发展。作为亚洲内陆规模巨大的年轻山系,天山历来都是构造地貌学研究的一个重点区域。由于受到欧亚板块与印度板块挤压碰撞的远程响应,天山新生代构造重新复活以及山脉的再次隆升。这一地质过程导致在天山北麓发育形成了与天山山体走向近于平行的三排逆断裂-背斜带。一系列南北流向的河流横切这些背斜带,发育形成了特征典型的河流地貌单元,并受背斜生长的影响而呈现向上拱曲变形的特征。前人基于详细的河流阶地位相测量与阶地年代研究,分析了第Ⅱ、Ⅲ排逆断裂-背斜带在晚第四纪时期的构造活动特征(构造活动时间、幅度与速率),但目前对于第Ⅰ排逆断裂-背斜带(即山麓背斜带)在晚第四纪构造活动性的认识仍不明确。另外,对于河流下切、阶地形成机制问题的认识仍有争议,天山是探讨这一问题的理想区域。论文选择天山北麓四棵树河山前为研究区域(四棵树河深切了山麓背斜带西端的托斯台背斜),以河流地貌为研究对象,基于详细的野外考察、卫星影像分析、阶地年代测定等方面的工作,划分了四棵树河山前河流地貌序列,进一步根据河流阶地位相特征,分析了托斯台背斜在晚第四纪的构造活动性,探讨了四棵树河河流下切以及阶地发育机制。论文取得的主要认识如下:(1)天山北麓四棵树河山前主要发育5级河流阶地,由老到新依次命名为T1、T2、T3、T4、T5。基于宇宙成因核素暴露测年法(CN),确定T1阶地的废弃年龄为77.27±6.92ka。通过光释光测年,T2、T3阶地的废弃时间分别估计为15.925±3.04ka、14.98±1.62ka。(2)基于冲积扇扇面特征、形态和分布,将四棵树河山前冲积扇划分为三期,由老到新依次命名为F1、F2、F3,其中F1冲积扇由于严重的后期侵蚀,仅零星分布与出山口,F2、F3冲积扇则广泛分布在山前。基于对地貌关系的考察,冲积扇F1、F2、F3分别对应于阶地T1、T2、T5。(3)基于野外实测和数字高程模型(DEM)的分析,得到了四棵树河山前T2、T3、T4阶地的纵剖面。结果显示,三级阶地的纵剖面呈现向下游收敛的特征,即阶地坡度呈现逐渐减小的趋势。尽管阶地纵剖面位于托斯台背斜之上,但这些阶地的纵剖面并没有呈现向上拱曲变形的特征。野外地貌考察也没有发现包括T1在内的阶地面上存在构造变形行迹。据此认为托斯台背斜在晚第四纪期间构造上不活动,或者活动性不显著。四棵树河山前的构造活动已向盆地方向迁移,并导致最前缘的西湖隆起的发育形成。(4)根据阶地拔河高度与阶地年代,得到四棵树河自T3阶地形成以来(即约15ka以来)的下切速率约为6mmyr-1,在T1与T2阶地之间的河流下切速率约为1.14mmyr-1(即～77-16ka期间)。综合来看,四棵树河山前晚更新世-全新世的河流下切速率明显高于之前的河流下切速率。(5)基于阶地年代与天山地区晚第四纪古气候记录的对比,认为四棵树河晚第四纪沉积和下切过程可能主要受气候控制,河流堆积作用主要发生在冰期,而河流下切主要发生在冰期-间冰期的气候过渡阶段,此时气候相对温暖、湿润,河水流量增大、河流侵蚀能力增强。
[Abstract]:The response of river geomorphology to tectonic movement and climate change has been one of the core contents of river geomorphology and tectonic geomorphology. As one of the most basic River landforms, river terrace naturally becomes an important object in this field. By studying the river order, the river landforms can not be rebuilt only. The evolution history and the information of regional climate change and tectonic movement can also be obtained. The formation age of river terrace is the basis of related research. In recent years, the development and continuous improvement of new dating techniques, such as cosmic genetic nuclide year, have laid the foundation for river terrace research and greatly promoted River geomorphology and tectonic geomorphology. The Tianshan Mountains have always been a key area for the study of tectonic geomorphology. Because of the long-range response to the collision between the Eurasian plate and the India plate, the Cenozoic structure of the Tianshan Mountain is resurrected and the mountain rises again. This geological process led to the development of the northern foot of the Tianshan Mountain. A series of three rows of anticline anticline belts formed near the Tianshan Mountains were formed. A series of North-South streams cross these anticlinal belts and developed a typical river geomorphic unit, which is characterized by the upward arch deformation of the anticline growth. The characteristics of tectonic activity (tectonic activity time, amplitude and rate) of the second and third row anticline anticline zone during the late Quaternary period are analyzed, but the understanding of the tectonic activity of the first row of the anticline anticline anticline zone (that is, the Piedmont anticline zone) in the late Quaternary is still unclear. In addition, the understanding of the problem of the formation mechanism of the river cutting and terrace formation It is still controversial, Tianshan is an ideal area to discuss this problem. The paper chooses four tree river mountains in the northern foot of the Tianshan Mountain as the research area (four tree rivers deep the tothis anticline in the western end of the foothill anticline zone), and takes the river geomorphology as the research object, based on the detailed field investigation, satellite image analysis, and terrace dating. The river geomorphic sequence of four trees before the tree and the river, further according to the characteristics of the position of the river order, analyses the tectonic activity of the tusthe anticline in the late Quaternary, discusses the mechanism of the lower cutting and terrace development of the four tree river rivers. The main understanding of the paper is as follows: (1) the main 5 level river terraces in front of the four tree rivers in the north foot of the Tianshan Mountain are from the old. T1, T2, T3, T4, T5., based on the Cosmogenetic nuclide exposure dating (CN), determine that the abandoned age of the T1 terrace is 77.27 + 6.92ka. through the light release year, T2 and T3 terrace is estimated to be 15.925 + 3.04ka, 14.98 + 1.62ka. (2) is based on the fan sector characteristics, morphology and distribution of the alluvial fan, and the alluvial fan of the four tree river mountains It is divided into three stages, from old to new, named F1, F2, F3, and the F1 alluvial fan is widely distributed in the front of the mountain because of severe late erosion, only sporadic distribution and Yamano, F2, F3 alluvial fan are widely distributed in the mountain. Based on the investigation of geomorphic relations, alluvial fans F1, F2, F3 are respectively corresponding to the terrace T1, T2, T5. (3) based on field measurement and digital elevation model analysis. The longitudinal section of T2, T3, T4 terrace in front of four tree rivers and mountains shows that the longitudinal section of the three terrace appears to be convergent to the downstream, that is, the gradient of terrace gradually decreases. Although the vertical section of terrace is above the totha anticline, the longitudinal section of these terrace does not have the characteristics of upwards arch deformation. Field geomorphological investigation It is also found that there is no structural deformation on the terrace, including the T1, and it is considered that the tussl anticline is inactive during the late Quaternary period, or its activity is not significant. The tectonic movement before the four tree river mountains has migrated to the basin direction and resulted in the development of the West Lake uplift at the most leading edge. (4) the height of the tug of tug in the terrace and the terrace In the terrace age, the cutting rate of the four tree river since the formation of the T3 terrace (since about 15ka) is about 6mmyr-1, and the river cutting rate between the T1 and the T2 terrace is about 1.14mmyr-1 (i.e., the period to 77-16ka). In a comprehensive view, the rate of the lower cutting rate of the four tree river mountains in the late Pleistocene to Holocene is obviously higher than that of the previous river cutting rate. (5) Based on the comparison of the terrace age and the paleoclimate records of the late Quaternary period in the Tianshan area, it is believed that the sedimentary and cutting processes of the late Quaternary period of the four tree river may be mainly controlled by climate, and the accumulation of rivers mainly occurs in the glacial period, while the river cut down mainly occurs in the climate transition stage of the glacial interglacial period, and the climate is relatively warm, moist and river flow. As the amount increases, the river erosion capacity is enhanced.

【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P931.1;P534.63

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