关键词: 红色砂岩, 成土作用, 地球化学, 古气候, 信江盆地, 塘边组, 晚白垩世

Abstract: Paleosol is a significant carrier for studying paleoclimate. Presently, the research on pedogenesis principally focuses on the migratory behavior of elements and the evolutionary process of pedogenesis, with limited reports on the manifestations of pedogenesis. The Upper Cretaceous Tangbian Formation in Xinjiang basin is dominantly composed of red sandstone with large cross-beddings, which is a typical representative of Cretaceous greenhouse climate terrestrial deposits in South China. Based on detailed field investigation, petrological and geochemical methods were employed to study the pedogenesis of red sandstone during the Cretaceous Tangbian Formation and explore paleoclimate characteristics of the Xinjiang basin during the Upper Cretaceous. The red sandstone of Tangbian Formation in the study area is primarily medium-grained arkose. The sediments have universally experienced pedogenesis, the key identification features of red sandstone include clay films on the edge of the detrital grains, micritic-sparry carbonate cement and gleization. The CIA (Chemical Index of Alteration) ranges from 50.20 to 83.30 (58.08 on average), indicating that the red sandstone is at a low level of chemical weathering. The analysis of microelement and the recognition of pedogenesis collectively indicate that the sandstone in the study area was formed in a hot and dry paleoclimate. This may be attributed to the high coastal mountain system that emerged during the Upper Cretaceous period in Eastern China, hindering the flow of moist water vapor from the Paleo-Pacific Ocean into the inland areas of Southeast China and forming a sedimentary paleogeographic environment dominated by aridity and torridity.

Key words: red sandstone, pedogenesis, geochemistry, ancient climate；Xinjiang basin, Tangbian Formation, Upper Cretaceous