| The Basin and Range tectonic zone of Jin-Ji-Meng area is located in the joint zone between Shanxi graben system and Yanshan fold system, where intense activities triggered the differential movement among fault blocks, and formed the characteristic landforms of uplift mountains and faulted basins alternated with inclined column——Basin and Range structure. Statistics shows that in the region, earthquake happened frequently and these earthquakes are closely related to tectonic activities. Researching the tectonic geomorphology features is helpful to understand the tectonic activities in the area and can provide important basis for the earthquake research and prediction. Yangyuan-Zhuolu area, located in the northeast part of the Basin and Range tectonic zone of Jin-Ji-Meng area, is affected by the regional stress field of the Basin and Range tectonic zone of Jin-Ji-Meng area. Therefore, it can be considered that this area is a miniature of the Basin and Range tectonic zone of Jin-Ji-Meng area. The focused research of Yangyuan-Zhuolu area has certain significance for understanding the evolution of tectonic geomorphology of the Basin and Range tectonic zone of Jin-Ji-Meng. The differential movement among fault blocks of Yangyuan-Zhuolu area had a huge impact on the formation and evolution of the Sanggan River, and multi-stage terraces developed on both sides of the river. The river terraces documented the tectonic activities of its basin, so it is helpful to understand the geomorphic evolution of the Sanggan River, characteristics of neotectonic activities and the relationship between the river evolution and neotectonic activities to research the rive terraces of Yangyuan-Zhuolu area.On the basis of that the relevant data were compiled and analyzed,the author carried out field investigation of geological features of the Basin and Range tectonic zone of Jin-Ji-Meng area for main faults and rivers in the area. Combined previous research results and data analysis of investigation, uplift mountains, faulted basins, river terraces and active faults in the Basin and Range tectonic zone of Jin-Ji-Meng area were studied so as to understand the characteristics of the tectonic geomorphology in the region.On this basis, with the area of Yangyuan-Zhuolu as a key study area, the author studied and analyzed the morphological evolution of Sanggan River and neotectonic characteristics of this area. Through RS image interpretation, high-resolution DEM data analysis,and systematical exploration of the terraces of the Yangyuan-Zhuolu segment of the Sanggan River, the author conclude that the region has experienced strong differential uplift movement, and tectonic activities play an important role in the landscape and the evolution of river in the region:(1) The cross section shape of the Wangjiawan Canyon is sets valley of young "V" type valley sitting on the"U" type wide valley. There develops at least 6 levels of the river terraces in the valley. T1-T3 terraces develop in the "V" type valley and T4-T6 terraces develop in the "U" type wide valley. The terraces in the "U" type wide valley mostly are accumulation terraces with terrace face that is up to hundreds of meters to one thousand meters, while the terraces in the "V" type valley mostly are high base terraces or erosion terraces, showing Sanggan River has experienced two characteristic development stages, the early period of slow incision and late period of strong downward cutting, during its development.(2) There 4 levels terraces develop within the basin section, and 6 levels terraces develop in canyon segment, reflecting the canyon section with respect to the basin section of both sides had a strong block uplift activities, and showing the strong activities of the basin edge faults. In the Wangjiawan Canyon, the T4-T6 terraces have a significant deformation of the arch curve, while the T1-T3 terraces have no obvious abnormalities. Considering the distribution of the Pliocene red clay in this area and tectonic activities, the author thinks that Wangjiawan region strongly arched.(3) The uplift of the Wangjiawan region has an enormous impact on the flow of the Sanggan River. Results show that: the composition of T4-T6 terraces is different at the eastern part and the western part of Wangjiawan Canyon, but all show that the near-source accumulation characteristics. The gravel alignment of T4 terrace in Putaowan also shows that the river flowed to ancient Yangyuan Lake once. Therefore we infer that: in the early, the rivers in the area flowed to west and east with the middle of the canyon as a watershed. The features of T1-T3 terraces indicate that in the development period of T1-T3 terraces the Wangjiawan Canyon has been opened. Therefore, the age of T3 and T4 terraces direct the time when the valley went through, that is in the early and middle of Middle Pleistocene to early Late Pleistocene.(4) The result of the Wangjiawan Canyon's going through is the headward erosion of the Sanggan River. In the late Middle Pleistocene, the sudden demise of the ancient Zhuolu Lake enhanced the erosion of the eastern river, and ultimately opened the central watershed, and captured the western river, causing that ancient Yangyuan Lake leaked into dry and the Sanggan River went through.Overall, since the late Tertiary, there are two intense activities periods in Yangyuan-Zhuolu region. The first is in the Pliocene-Early Pleistocene, the other one in the late Middle Pleistocene-early Late Pleistocene. The intense activities in the Pliocene-Early Pleistocene made that basins faulted and mountains uplifted, and the pattern of that basins alternate with mountaisn formed, and two rivers (one flows to east, the one flows to west) formed in Yangyuan-Zhuolu segment. The intense activities in the late Middle Pleistocene-early Late Pleistocene made that the erosion base of the Zhuolu area substantially reduced, leading to the head-ward erosion capacity enhancement of the eastern river, and the ancient lake of Yangyuan eventually leaked into dry and disappeared, Sanggan River ran through, the modern topographic feature gradually formed.
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