Sedimentary Characteristics and Paleoenvironment Evolution of Paleoplanation in Xiangxi Hunan

The Xiangxi fault and fold structures in Hunan Province are well-developed, which have undergone multiple tectonic movements, large-scale fault block uplift, and large-scale erosion and leveling, forming two levels of planation planes, which is very conducive to the study of planation plane evolution. On the basis of extensive field investigations on several karst red weathering crust profiles in the western Hunan region, the author selected two typical profiles in Xiangxi Prefecture to conduct a comprehensive study on the particle size, magnetic susceptibility, and spore pollen of ancient weathering crust. From the perspectives of geomorphology, epigeochemistry, soil science, and spore pollen, this study explores the relationship between the formation age of karst weathering crust in the western Hunan region and the evolution of the planation plane. The research results indicate that the development period of the planation plane in the study area should be from the Middle Pleistocene to the Middle Miocene, and after entering the Paleogene, it is generally in a relatively stable state for a long time; The sedimentary environment of the Jiaba section is slightly dry or cool and moist compared to the Luota section, with more developed planation. Although there were significant climate fluctuations during the sedimentation period, the overall sedimentary environment of the two sections was moist, and the accompanying dry fluctuations were relatively small.