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Physical geography of Danxia in Chishui

Since Paleogene, Chishui City has formed a series of east-west and north-south small structural systems, mainly including Dabaitang syncline, Moziyan anticline, Tuchengbi anticline, Wanglongchang anticline and Guandu anticline. Guandu anticline is a nearly north-south anticline, which is the main anticline structure of Danxia in Chishui, and its northeast is Yanzi Rock syncline. The upper sandstone of Penglai Town Formation can be seen in the axis of anticline, and Cretaceous sandstone can be seen in the wing, with the dip angle of 4 ~ 6 in the east wing and 7 ~ 9 in the west wing. Yanzi Rock syncline is located at the northeast edge of Chishui City, and it is northwest-east. In addition, the elephant trunk syncline is also the main syncline structure in this area, showing an east-west trend. The dip angle of the strata is 3 ~ 10, and the exposed strata in the axial direction are purplish red thick-layer massive fine-grained calcareous timely sandstone of Jiaguan Formation.

Influenced by the strong rigidity of Sichuan Basin, Danxia in Chishui has weak internal stratigraphic folds and small stratigraphic dip, but the steep yoke shear joints create favorable conditions for the formation of the tall and straight Ya Dan in Chibi. At the same time, the cross bedding, cracks and ripples in the rock strata are well developed, which highlights the sedimentological characteristics of river and lake facies. The Danxia fault structure in Chishui is mainly distributed in the west of Chishui River, which mostly extends in the east-west direction and the northeast-southeast direction. A group of east-west and north-south faults intersect in the area of gold and hongqi, forming a grid structure, which obviously controls the trend of river valley water system.