| This paper focused on the deep and shallow tectonic deformation in the Upper Yangtze region, analyzed structural features of Micang-Hannan terrane, Longmenshan orogenic belt, Dabashan nappe, as well as Er-Yu-Xiang and Xuefeng dome based on Digital Elevation Model, gravity and aeromagnetic, characteristics of water system and geomorphology. According to study results above, following conclusions are obtained.The water system is mainly characterized as dendritic or latticed within the Upper Yangtze region. Water system was controlled by tectonic activities, especially deep faults. The characters of water system in different tectonic belts are different. Sichuan basin, northern of Ankang fault, and north of Micangshan mainly developed dendritic river, whereas Dabashan, Longmenshan, east of Sichuan basin, and Er-Yu-Xiang area mainly formed latticed river system. It was noticed that river system shown as sharp turns, from NW to NE or reverse, especially in Longmenshan and Dabashan area, indicating that there were multi-stress in different directions existed during Cenozoic.The study area has experienced multi-phase tectonic activities, and the characteristics of geomorphology were diversified and significant different. Overall the terrain of the study area is characterized as wedge ramp with higher NW and lower SE. Elevation is quite different in the different regions. The Longmanshan and Dabashan, Micangshan slop is steep, gully landform in multiple napping, but valley and mountains are arranged in parallel dabsahan area. The middle of Sichuan basin is a flat area of low elevation. Basic landform pattern of the study area is controlled by the deep fault.The deep structure features is reflected by the Bugur gravity anomaly. It is primarily characterized by alternation of uplift and depression with morphology of EW structure in the northern region, and NE structure in the Sichuan basin and east area. This tectonic pattern is a result of combined effects of variety factors controlled by Qinling orogenic belt, Tibet plateau and Pacific Plates.The top of the upper mantle presents a step shape with higher eastern and northeastern, flat central and lower western. It can be divided into several regions of western and eastern Wulingshan and northern Qinling mantles slopes, and middle mantle flat. It is consistent with the tectonic zoning. By calculating the cross-section, it was found that the gravity anomaly was caused by mantle depth difference in the study area.Anomalies nature is relatively large difference in different regions, and it reflect the distribution of magmatic rocks and the crystalline basement metamorphic, by aeromagnetic data processing. The basement of the study area was consisting of more than one block. Combining the condition of rock magnetism, magnetic basement can be divided into four types. A number of buried faults were inferred that were north-west and nearly east-west trending, which were oblique crossing with near surface faults. It showed that directions of tectonic activity in the formation process of the basement and post-sedimentary history were significant differences in Yangtze region.The tectonic deformation of upper sediments changed from the thick-skinned structure into the thin-skinned structure, from west to east. Tectonic deformation of the northern regions is characterized by a thick-skinned tectonic and nappe structure with long distance. The relationship between the deep and shallow structure is complexity in Yangtze area, indicated by superimposed, inheritance and transformation in vertical direction, whereas sudden and gradual change relationship in lateral direction. This diversification of relation was the results of collision between the Yangtze plate and adjacent blocks of Qinling orogenic and the Songpan continental segment. |
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