Identification, characterization, and paleoclimatic implication of Early Cretaceous (Aptian-Albian) paleosol succession in Zhangye Danxia National Geopark, northwestern China

Paleosols are useful evidence of paleoclimates and paleoenvironments independent of fossils. Zhangye Danxia National Geopark of Gansu Province (northwestern China) has been protected for its stunning varicolored badlands of Early Cretaceous (Aptian-Albian) claystones. However, the paleoclimates and paleoenvironments forming such unique succession are currently not well understood. The widespread pedogenic features, for example root traces and soil horizons, indicate different paleosols, which provides clues of associated paleoclimates and paleoenvironments. In the present study, combining field work and soil micromorphology, we recognized, classified, and interpreted 155 sequential paleosol profiles of 14 different pedotypes (soil types) in the 755-m-thick section. These pedotypes have modern analogues in South Asia, indicating hotter and more humid paleoclimate than at present in Zhangye. Systematic analysis of soil units based on comparison to their modern analogues allows reconstruction of paleoenvironments in eleven humidity stages. Variation in waterlogging of the paleosols based on the ratio of Hm / Gt agreed well with regional and global paleoclimatic records, confirming its utility in paleoclimate reconstruction during Aptian and Albian. The identification and characterization of the paleosol succession provides a significant base for detailed paleoclimatic reconstruction during this period.