I found an article here, which belongs to Qiantang River Administration Bureau of Zhejiang Province. Analyze the geological structure of Qiantang River and talk about the understanding of Jiangshan-Shaoxing fault;
Geological Structure Since Proterozoic, Qiantang River Basin has experienced three stages of crustal evolution: geosyncline, platform and continental margin activity, and six tectonic movements: Shen Gong, Jinning, Caledonian, Variscan-Indosinian, Yanshan and Himalayan. Under the action of these tectonic movements, a series of deep faults, NE syncline and syncline fold belts have been produced (Figure 2- 1). Jiangshan-Shaoxing deep fault is divided into two structural units: the northwest is a part of Yangtze paraplatform and the southeast is a part of South China fold belt. Their development history is different, and their structures and strata also show obvious differences, thus affecting the development of inland landscape and water system in the basin.
The Yangtze paraplatform is divided into two secondary structural units: Jiangnan platform uplift and western Zhejiang and southern Anhui platform fold belt. Tailong in the south of the Yangtze River is mainly distributed in Anhui Province in the northwest corner of the basin and consists of pre-Sinian metamorphic rocks. In Mesozoic, NE-trending and EW-trending faults collapsed, forming Tunxi basin, accompanied by intermediate-acid volcanic eruption and clastic deposition. The intrusive rocks are divided into several stages: Jinning intrusive granitoids, Caledonian ultrabasic rocks and Yanshanian intrusive rocks dominated by intermediate acidity. The platform fold belt in western Zhejiang and southern Anhui is located in the northwest of Jiangshan-Shaoxing deep fault and the east of Jiangnan platform uplift. It is mainly composed of Sinian-Triassic sedimentary rocks with a total thickness of over 20,000 meters. Indosinian movement caused strong fold deformation of Paleozoic and Mesozoic Lower Triassic strata, accompanied by fracture deformation, forming the basic outline of geological structure in this area. During this period, the tight folds formed by the movement were slightly parallel to the belt, with the axial direction of 50 northeast, the axial surface inclined to the northwest and the northwest wing steep, forming several large anticlinorium and syncline respectively. The development of basins is often at the core of folds or controlled by deep and large fault zones, and they are arranged in long strips. A series of coal-bearing detritus from late Triassic to early and middle Jurassic in western Zhejiang were deposited in these basins. Subsequently, a series of volcanic eruption-sedimentary basins or eruption zones were formed one after another.
The South China Fold Belt in East Zhejiang is located in the southeast of Jiangshan-Shaoxing deep fault, which is the development area of Cao 'e River, Dongyang River, Wuyi River, Wuxi River and Jiangshan Port. Metamorphic rocks of Mesoproterozoic in Chencai Chen constitute the basement of this belt, and the composition line mainly extends along the northeast direction of 50 ~ 60. Basement caprock is a continental volcanic rock series erupted by Mesozoic Yanshan movement volcano. Yanshan movement is characterized by basement faults with strongly different uplifts and expansions of blocks, accompanied by central volcanic eruption and multi-stage extensive intrusion of intermediate-acid magma, forming smaller depressed or faulted basins, annular volcanic tectonic basins and late graben or semi-graben tectonic basins.
Generally speaking, the basement of each structural unit in the basin is old and hard, the neotectonic movement is weak and the active faults are not obvious. The earthquake intensity is less than six degrees, and the earthquake magnitude is rarely greater than five, which belongs to the basic stable area.
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