Formation setting and karst development characteristics of red beds in Wuhan, Hubei Province, China

The red beds in Wuhan are mainly Cretaceous–Paleogene Donghu Group (K-E dn ) strata, and the main lithologies are purplish red semi-cemented and weakly cemented mudstone, sandstone, and conglomerate. The formation setting of the red beds in Wuhan is analyzed from the regional tectonic movement and sedimentary environment. In addition, the karst development characteristics of red beds in Wuhan are studied on the basis of a large number of karst borehole data. The results show that the karst development of red beds in Wuhan is mainly controlled by the tectonic position and stratigraphic lithology. The soluble rock in the red beds of Wuhan is a calcareous cemented conglomerate, and the gravel component of conglomerate is mainly limestone. The karst phenomena in the red beds are mainly karst caves and karst fissures, while the surface karst phenomena, such as karst ditch and karst trough, are not prominent. The karstification is mainly weakly developed, and the degree of karstification positively correlates with that of the underlying karstification belt. When the lithology of the underlying formation of the red beds is carbonatite, the red bed karst is developed; by contrast, when the lithology of the underlying formation is insoluble clasolite, the red bed karst is not developed. The filling mode of the karst cave in the red beds may also be from top to bottom. The filling material mainly comes from the disintegration of the red beds themselves, and part of them comes from the overlying Quaternary strata.