【作者】 程理；

【导师】 陈国星； 苏刚； 高战武；

【作者基本信息】 中国地震局地震预测研究所 ， 构造地质学， 2010， 硕士

【摘要】 怒江断裂带南段(六库以南)沿怒江河谷发育一系列新生代构造盆地,呈串珠状分布,其中道街盆地是一个面积最大、第四纪地层最为发育的断陷盆地,是研究怒江断裂带第四纪构造活动理想的场所。它是滇西地区在总体隆升背景下发生差异性断块运动而形成的地堑式断陷盆地。怒江断裂带东支控制了该盆地的地貌格局,盆地主要沉积物为洪积层,位于怒江西侧,物源来自高黎贡山。怒江断裂带作为青藏高原东部边缘的一条大型陆内走滑断裂带,其形成、演化与青藏高原的隆升有着密不可分的联系。本文以道街盆地为研究对象,以盆地第四纪地层和控盆断裂为主线,着重研究盆地的构造活动特征,以此反映怒江断裂带南段第四纪以来的构造活动性。这有助于了解整个怒江断裂带的构造活动特征,并对揭示青藏高原在向南东方向挤出过程中的机制和运动方式,探讨怒江流域中下游地区地震危险性和水电工程的抗震设防等方面,都具有重要意义。研究取得的主要进展和认识如下:1、通过钻探、寻找地层剖面、测量盆地横剖面等工作建立了道街盆地第四纪充填序列及年代序列。而对充填序列的分析得出盆地形成以来可能存在四个构造活跃期,并从构造地貌和断层活动方面进行论证。其中前三个构造活跃期是怒江断裂带的活动引起的,第四个构造活跃期是盆地内部的断层活动。2、结合释光测年和地层资料,通过孢粉分析显示出盆地形成后自中更新世晚期以来气候环境变化具有不稳定的特点,即温湿、干凉交替波动变化。3、利用差分GPS测量了道街盆地西部8条冲沟的纵剖面。从冲沟纵剖面与控盆断裂的位置关系发现冲沟急流段及麓原面的形成与控盆断裂有关,并通过三者的关系推测盆地边缘应该存在一条隐伏断层。4、利用差分GPS测得怒江道街盆地段21处阶地特征数据,并取阶地OSL样品进行测年,经计算得出该地区自晚更新世以来的平均抬升速率为1.17mm/a。5、综合地层、构造地貌和断层活动的资料认为怒江断裂带南段在早-中更新世有过活动,而晚第四纪以来没有明显的活动迹象。沿断裂带发育的盆地内存在少量次级断层,并在晚更新世以来仍有活动,且规模较小。6、第四纪以来滇西地区发生大面积掀斜抬升,并伴随块体的差异升降运动,构造应力场以北东向挤压、南西向拉张为主要特征。在这种构造背景下怒江断裂以张剪性活动为主,经过三次断陷活动控制了道街盆地的发育。更多还原

【Abstract】 A series of tectonic basins in Cenozoic were developed in the south of Nujiang fault zone (the south of Liu Ku), distributed with beads in line. As the biggest and the most developed faulted basin in quaternary strata, Daojie basin is the most perfect area for researching on tectonic activity in Quaternary of Nujiang fault zone. It is a graben faulted basin developed when blocks in the western Yunnan undergone otherness movement under the background of overall oblique uplift. East branch of Nujiang fault control the physiognomy of the basin, and its main sediments are diluvium, which are derived from Gaoligong Mountain and located in the west of Nujiang River.Nujiang fault is a large inner continental strike-slip fault in eastern Tibetan margin. It is closely related to uplift of the Tibetan plateau. Based on study object of the Daojie basin, clue of strata in Quaternary and basin-controlled faults, the thesis research on tectonic activity of the basin, which reflect tectonic activity of Nujiang fault since Quaternary. It helps to understand the tectonic activity characteristic of Nujiang fault, which is important for revealing mechanism of the eastern extrusion of Tibetan plateau and discussing anti-seismic of hydropower engineering in Nujiang River area. The main achievements and new understandings are described as follows:1. Through drilling, finding strata profile, measuring transverse section of the basin, the filling sequence in Quaternary and time sequence are established. Analysis of the filling sequence indicates there may be four tectonic activity periods after formation of the basin, which are proved in fault activity and tectonic geomorphology. The first three tectonic activity periods are caused by Nujiang fault, and the fourth is the fault activity in Daojie basin.2. Combined with OSL/TL dating and strata data, analysis of pollen show climate change was not stable since late middle Pleistocene, namely, the characteristic of alternating warm wet and cool dry fluctuation change. 3. Using Post-operation difference GPS, it surveyed 8 vertical sections of gully in the west of Daojie basin. It is found that the formation of gully rapids and pediments were related to basin-controlled fault from the relations between vertical sections of gully and pediments. Besides, it is inferred that there should be a fault in the edge of Daojie basin through the relationship of vertical section, pediment and basin-controlled fault.4. Using Post-operation difference GPS, it measured several data of Nujiang River terraces, and taken many OSL samples to data. Through calculating, it show that the average rate of uplift in western Yunnan is 1.17mm/a since late Pleistocene.5. Analysis of the data about strata, tectonic geomorphology and fault activity indicate that newest activity of the south of Nujiang fault is early-middle Pleistocene, namely, there is no obvious signs of activity since late Quaternary. Some sub-faults in basins which developed along Nujiang fault are still active since late Pleistocene, and are still smaller.6. Western Yunnan undergone overall oblique uplift since the Quaternary, following different lift of blocks. Modern tectonic stress field in western Yunnan is characteristic of NE-direction compression and SW-direction extension. Under this tectonic background, Nujiang fault is characteristic of tensile-shear activity, and control the development of Daojie basin through 3 tectonic activity periods.更多还原