The geological processes that formed the Danxia landform

Danxia landform is defined as a terrestrial red bed landform with steep cliffs. It was first named by Feng Jinglan and others during their inspection of Danxia Mountain in Renhua County, Guangdong Province in 1928. Today I will introduce to you the geological processes that formed the Danxia landform. I hope it will be helpful to you! The geological processes that formed the Danxia landform

1. The material basis for the formation of the Danxia landform

In It can be found in many Danxia landforms, and its material carrier is red layer. The red bed is relatively complex. Different sedimentary basins, different sedimentary environments, and different lithofacies have greatly different lithologies. However, the red bed is basically composed of terrestrial debris, and its lithology is breccia, conglomerate, sandy conglomerate, sandstone, mudstone, chemical sedimentary rock, and bioclastic rock. But it is mainly conglomerate, sandy conglomerate and sandstone. The clastic composition of rocks is generally closely related to the source of the clastic material. The areas around the red basin are mostly material sources. The composition of gravel is particularly noticeable.

The red color in the red layer is mainly caused by the high content of high-priced iron in the rock. The paleogeographic environment in which the red layer formed is one of the external conditions that determine the color of sediments. During geological time, redbed deposition occurred in paleotropical and subtropical basins, deposited in arid and semiarid oxidizing environments. The sorting of materials in the red layer during transportation and deposition affects the composition. There are color differences between them. The red layer cemented with iron has a bright red hue. If the red formation is made of calcium or silica as the main cement, the color will be lighter.

2. Faults and joints control the development of Danxia landforms.

The structures inside the basin control the pattern and shape of the Danxia landform mountains. Take Danxia Mountain as an example: Large faults control the arrangement direction of the Danxia Mountain body, and the intersection of secondary faults and large joints is where the development characteristics of the Danxia landform are more significant. Chuanyan Nineteenth Peak in Xinchang, Zhejiang is located at the intersection of a north-northeast fault and a northwest-trending secondary fault. The extension direction of the large fault is basically the same as the arrangement direction of the Nineteen Peaks. The arrangement direction of Danxia Mountain is north-northeast, which is basically consistent with the direction of large faults. The arrangement direction of peak clusters and stone pillars is basically consistent with the extension direction of east-west faults and large joints. Large north-northeast-trending compression-torsional joints and east-west tensile joints cut the strata, forming rhombus-shaped and polygonal network blocks. Through water erosion, chemical decomposition, and gravity collapse, Danxia landform types such as Danya, square mountains, stone pillars, and valleys have developed.

The occurrence of Danxia landform formations is relatively slow. The top of the Danxia landform is related to the lithology and weathered matter of the overlying strata. The top is composed of some iron cement and harder lithology that resists weathering. Steep slopes controlled by vertical joints are mainly caused by the collapse of large areas of rock blocks along the vertical joint planes to form spectacular cliffs. Collapse materials accumulate at the foot of the cliff, and the steep slope at the foot of the cliff is affected by the collapsed rock blocks. The accumulation of larger rock blocks creates a steep slope, and vice versa.

3. The function of flowing water

The function of flowing water plays an important role in the evolution of Danxia landform. Water erosion can be divided into physical erosion (undercutting and side erosion), chemical dissolution, etc. The erosion of running water hollows out the material at the foot of the slope and accelerates the process of gravity collapse. Running water dissolves soluble components in the red layer, promoting hydrodynamic erosion and weathering.

4 Weathering

Weathering carries out transformation activities on the rocks exposed in the red layer, and various weathering effects are very clear. The differences in weathering resistance due to differences in lithology lead to differences in the microscopic landscapes on the cliffs of the Danxia landform. Sandstone and conglomerate appear as positive landforms, manifesting as raised rock ridges; mudstone and siltstone appear as Negative landforms appear as bedding grooves or caves. Flaking and gravity collapse are common in Danxia landforms, which are related to periodic temperature changes. It is estimated that one layer will peel off in 5-10 years.

5 Gravity effects

Gravity effects often occur on free valley slopes formed by flowing water and lateral erosion. However, when lateral erosion by flowing water hollows out the foot of the slope, the suspended rock mass may Under the action of gravity, collapse occurs along structural weak surfaces (joint surfaces, primary structural surfaces). The suspended rock mass may produce unloading joints, and the overlying rock mass will lose balance and accelerate collapse along the vertical structural plane. Gravity is one of the important factors in the development process of Danxia landforms. The development of Danxia landform slopes is closely related to gravity. The collapsed rocks on the steep cliff slope accumulated at the foot of the slope, forming a gentle slope. Characteristics of Danxia landform

The sedimentary layers of alternating thickness and fineness can be seen on the cliff. The coarse-grained rock layer is called "conglomerate", and the fine and uniform rock layer is called "sandstone". The most prominent feature of the Danxia landform is the extensive development of red cliffs, forming square mountains with flat tops, steep bodies and gentle slopes, stone walls, stone peaks, stone pillars and other strange and dangerous landforms. Different rocks are formed A landscape with high ornamental value, it is a veritable "Red Rock Park". The origin of the definition of Danxia landform

In 1938, structural geologist Chen Guoda called the landform developed on the red rock layer "Danxia landform" and used this landform as a symbol to judge the Danxia formation. .

In 1977, geomorphologist Zeng Zhaoxuan used "Danxia landform" in geomorphological terms for the first time.

In 1982, Li Jianxian (Huang Jin), a geographer known as the "Danxia Madman", published "A Basic Method for the Development of Danxia Landform Slopes", which was the first Chinese discussion of Danxia. First paper on geomorphology. This period was the initial stage of large-scale development of China's tourism industry. As an important tourism resource, Danxia landform has attracted more and more attention from all walks of life.