Research On Formation Mechanism And Geo-scientific Effects Of Danxia Landform In Southeast China

Danxia landform is a specific petrographic geomorphology, named from Danxiashan, in Guangdong Province, in China. Danxia geology and geomorphology have been studied for about 80 years in China. Over the past years most studies focusd on the research of Danxia landscape resources and tourism market development, but few attached to the geological formation mechanism, morphology development process, or its geoscientific values.Based on the extensive investigation and analysis, Danxia landform in southeast China is selected as the research object, the latest theory in modern geomorphology is applied. Through the field survey and literature study, connecting contrast analysis of different region, combining the single factor analysis and correlation analysis, sampling rockmine outdoor and characterizing rock indoor, the Southeastern Danxia landform and geo-scientific effects were comprehensively researched.The first systemic research on Southeast China danxia landform development factors including tectonic background, sedimentary environment, lithology, tectonic movement, the exogenic action mechanism and the evolution process has been finished. The geo-scientific effects of danxia landform have been groundbreakinglly analyzed. The landscape characteristics and its world heritage value of Danxia landform in Langshan have been made known. Main conclusions as following:The red bed basins were formed in hot and dry climates environment in the Mesozoic. Yanshan movement in eastern prompted to massive magmatic activity in fault red bed basins, then calcium alkaline volcanic rocks and bi-model volcanic series were formed. The phenomenon gives a explain of a kind of special red bed basin development mode. But there were lack of magmatic activity in inland red bed basin. Red diluvial clastic rocks are composed of the main material base of danxia landform.From the study of the various units of the geological structure, the Southeast China region has mostly a series of sparse NNE and near NS faults, leading to the arrangement of hill blocks oriented NNE or nearly NS. On the other hand, most parts of the basins in the Southeast China area also developed some near EW, NE, and NWW faults. These large tectonic lineaments controlled the general arrangement of hill blocks, and the small structures controlled the trend, density and plane pattern of hill blocks.Danxia landforms were in a differential and intermittent uplift zone during the Neotectonics Movement. Where the region was uplifted in an early stage followed by a long-term stable state this allowed for successive and gradual evolution of Danxia landsapes from infancy to old stage. However, intermittent uplift causes the development of multi-layered Danxia landscapes.Fluvial erosion and rain flushing action is the dominant exogenic action sculpturing danxia landform, the lithology differences between soft rocks and hard rocks lead to different role of erosion, then create unique landscape on Danxia cliff. Gravitational collapse plays a role of the accelerator in shaping the danxia landform acting on another round of water erosion and weathering. The figure of Southeast danxia landforms will be divided into five types such as fluvial erosion type, rain flushing type, vestigital type after collapse, talus ruoble type and dissolution type. Southeast danxia landforms include landscapes at different stages in their geomorphic evolution, with different landform types and different combinations of landscape features. All stages in landscape evolution are present from youth through maturity to old age.Collectively, Southeast Danxia landforms display geological diversity, landform diversity, biological diversity, ecology uniqueness and landscape rareness. Because of the unique geological structural background and natural geographic location, Danxia landform displays the earth's history since the late Mesozoic, showing geological and landform process of the continental crust, and is a model site for the study of the evolution of earth's continental fault basins and on-going geological process. It also is an ideal place to study the global climate change over long geological periods. Evidence of important geological events are included such as aeolian accumulations, dinosaur life and extinction, basin uplift, continental volcanism and crustal deformation -all occurring in a region of hot-arid climate. The evolution of Danxia landform reflects global changes and major events in the earth's land surface system since the late Mesozoic-Cenozoic, which may be significant for research on current global changes. Southeast danxia landform displays the development of landscapes and landforms with a distinct morphology, shape, colour and appearance. And gives the presence of various typical and outstanding, rare and endangered biological species and habitats. All these give collectively expression to geo-scientific vaule, natural beauty and aesthetic importance, Ecological values and harmonious coexistence between humanity and nature.Chinese cretaceous red beds was land facies, but the most foreign's was not only land facies, but also a few of littoral facies. The Chinese Cretaceous red beds was fashioned to Danxia landform to after the conversion from the dry heat climate to the hot and damp, however, when overseas red beds landform developed, it lacked this condition of climate transformation. Mainland China Mesozoic, because of the doubly extrusions between the Indian Plate and the Pacific Ocean Plate, the crust lifted intensely, especially the uplift of Qinghai-Tibet Plain, was an important milestone for the Chinese modern atmospheric circulation and the modern topography distribution. In such a specific geological period, the Chinese Danxia landform was formed to be one kind of special vicissitude symbolic rock landform of ecological environment. But the overseas same time red beds landform did not have this kind of symbol.In Langshan Mountain the thickness of Langshan red beds changes from 200 to 2320m. There are multitudinal kinds of rocks charactered with good anti-airstake ability and obvious karst phenomenon. Due to high content of SiO₂ and Al₂O₃ and low content of CaO, K₂O and Na₂O, Langshan has experienced intermittent crustal uplift. The landscape of Langshan features dome-shaped landforms, with dense peak clusters and peak forests. There are linear valleys, large-scale natural bridges, and unusual karst-like features. The landscape here also has a rare degree of natural beauty. It is representative of a landscape in the mature stage of development, and is also an excellent example of a classic Danxia landscape.