Characteristics and genetic mechanism of the stone forest in Sinan County, Guizhou Province

The Sinan stone forest is located between the Wuling mountain and the Daloushan mountain range in the northern edge of the transition slope between Guizhou plateau and Xiangxi hills. The Liangshan group, Qixia group and Maokou group of the upper Paleozoic Permian are the major strata in the scenic. There are no strata of the Devonian and the Carboniferous of the lower Palaeozoic. The Sinan scenic is being constructed into the Changba stone forest scenic area of the Wujiang karst national geopark now. By means of comparative study on the morphologic characteristics of different stone forests and survey on region geologic environments and scenic resources, the geologic conditions for the formation and development of the Sinan stone forest are analyzed. The results show that，(1)The Sinan stone forest is depression-slope stone forest with various morphs involving sword-shaped, castle-shaped, tower-shaped and cylindrical as well as needle-shaped, and the single stone peak is high up to 20 to 30 m, furthermore the pictographic landscapes are multitudinous, not only very graceful, the formation and evolution also provide a typical case for the research of stone forest and science education. And the ecology is kept very well, the stone forest, trees and farmhouses mix together, having a very high aesthetic value and the value of tourism development；(2)Geologically speaking, the Sinan stone forest are mainly developed in the pure and thick dark-colored micrite of the Permian system and lies on the southeast-northwest tectonic stress zone where cracks and joints networks are good for the formation and preservation of the high stone; geomorphologically, the Sinan stone forests are developed on the slope between the karst cuesta and the uvala, the hydrodynamic conditions at different parts of the landform caused the differences in morphology and distribution of the stone forest; climatically, from the Neogene, the Sinan is mainly the tropical, subtropical humid, the cold and dry climate only briefly interludes in the course, the warm, humid and rainy weather have provided plentiful external agents for the formation of the stone forest; hydrogeologically, the Sinan stone forest is developed in carbonate interbeded with clastic rock strata, the erosion by exogenous water from clastic rocks and the jacking of the underlying clastic rocks provide good water conditions for the formation of the large area of stone forests; in addition, the favorable vegetation also provide large quantities of CO2 and organic acids for the dissolution；(3)Its formation process can be reduced to five stages: the diagenetic stage(P-T2), the lifting denudation stage(T3-J3), the tectonic deformation stage(K1-Q1), the soil erosion stage(Q1-Q3) and the surface shaped stage(Q3-Q4). According to the erosion data it is calculated that the Sinan stone forest is formed around 30.04-45.06kaBP, that is in the middle and late period of the late Pleistocene.