Red beds (or redbeds) are sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain thin beds of conglomerate, marl, limestone, or some combination of these sedimentary rocks.
The ferric oxides, which are responsible for the red color of red beds, typically occur as a coating on the grains of sediments comprising red beds. Classic examples of red beds are the Permian and Triassic strata of the western United States and the Devonian Old Red Sandstone facies of Europe.
Primary red beds may be formed by the erosion and redeposition of red soils or older red beds, but a fundamental problem with this hypothesis is the relative scarcity of red-colored source sediments of suitable age close to an area of red-bed sediments in Cheshire, England. Primary red beds may also form by in situ (early diagenetic) reddening of the sediment by the dehydration of brown or drab colored ferric hydroxides. These ferric hydroxides commonly include goethite (FeO-OH) and so-called "amorphous ferric hydroxide" or limonite. Much of this material may be the mineral ferrihydrite (Fe2O3 H2O).
Secondary red beds are characterized by irregular color zonation, often related to sub-unconformity weathering profiles. The color boundaries may cross-cut lithological contacts and show more intense reddening adjacent to unconformities. Secondary reddening phases might be superimposed on earlier formed primary red beds in the Carboniferous of the southern North Sea.[9] Post-diagenetic alteration may take place through reactions such as pyrite oxidation: 3O2 + 4FeS2→ Fe2O3 (hematite) + 8S E = −789 kJ/mol
and siderite oxidation: O2 + 4FeCO3 → 2Fe2O3 (hematite) + 4CO2 E = −346 kJ/mol
Secondary red beds formed in this way are an excellent example of telodiagenesis. They are linked to the uplift, erosion and surface weathering of previously deposited sediments and require conditions similar to primary and diagenetic red beds for their formation.
If you want to witness this landform with your own eyes, traveling to China will be a good choice.
As a typical rock mass, red beds are widely distributed throughout South China. In a typical tropical and subtropical continental environment, red beds are the product of multiple sedimentary cycles, which have resulted in complicated rock mass structures that play an important role in rock mass stability.
Danxia is the name for a unique type of landform and a natural landscape. Literally in Chinese, Danxia means “reddish rays” or “rosy cloud” during a sunrise or sunset. In Chinese geoscience circles, the term “Danxia” was initially designated by geologists in the 1920s to classify a specific stratigraphic sequence of red beds that forms hoodoo peaks in the mountainous terrain of Mt. Danxiashan in southern China. Danxia landform refers to an erosional landscape developed on red beds, characterized by scarp slopes.
Being one of the most important tourism attractions in China, Danxia landform plays a significant role in the development of local economy. Besides tourism development, this resource is also beneficial for society and the environment. With the ever increasing tourists, the value of Danxia landform as a scenic resource has become more and more apparent.
