Geochemistry characteristics of Paleogene-Neogene sedimentary rocks in the Lingwu area of Yinchuan Basin, Ningxia and its enlightenment for paleoenvironmental evolution

Elemental geochemistry of sedimentary rocks is an effective method to study the ancient sedimentary environment, which is especially suitable for areas with restricted outcrops.Yinchuan Basin has wide Quaternary coverage with great sedimentary thickness.The Paleogene-Neogene is only distributed in some areas around the basin, with discontinuous outcrops and relatively weak research on the sedimentary environment.Through systematic sampling and analysis of the major, trace and rare earth elements of the Paleogene-Neogene clastic rocks in the Lingwu area of the Yinchuan Basin, the characteristics of sediment sources, sedimentary environment and paleoclimate changes were discussed.The results show that the Paleogene-Neogene source in the Lingwu area of the Yinchuan Basin is dominated by felsic volcanic rocks; the sedimentary environment of the Paleogene-Neogene period was generally an oxidizing environment with high salinity, and the climate was mainly dry and hot; compared with the Qingshuiying Formation, the Zhang'enpu Formation had relatively increasing oxygen content, relatively low salinity, relatively changeable water bodies, and the lake basin gradually transitioned from a closed system to an open system.The research results provide basic geological data for the establishment of an unified lake basin system in Yinchuan Basin and Ningnan Basin from Oligocene to Late Miocene.