Weathering characteristics of quaternary red clay in Xuancheng, Anhui Province and its paleoclimatic significance

The widely distributed Quaternary laterite in Xuancheng, Anhui Province, has good continuous depositional characteristics, and is a key information carrier for the study of palaeoclimate evolution and palaeoenvironmental changes in the southern region of China. The newly discovered DCRC in Xuancheng is 10.7 m thick, with remarkable development of red and yellow bands, and can be divided into 15 layers from bottom to top. Combining electron spin resonance (ESR) dating and elemental geochemical data, we investigated the weathering characteristics of the DCRC laterite profile and their palaeoclimatic significance. The results show that: 1) With depth, the Al2O3 content, Fe2O3 content, and CIA value decrease, whereas the SiO2 content, BA value, Na/K ratio, and Mg/Ca ratio increase. Based on these trends, the profile is divided into three intervals: Interval I (10.7-6.8 m), Interval II (6.8-3.0 m), and Interval III (3.0-0.3 m). 2) Chronologically, Interval I [(844—603) ka B. P.] underwent strong weathering, Interval II [(603—468) ka B. P.] experienced the most intense weathering, and Interval III [ (468—356) ka B. P.] shows a gradual weakening of weathering intensity. 3) Climate element analysis indicates that precipitation played a more dominant role than temperature in controlling the weathering intensity of the DCRC profile. Consequently, regional precipitation is reconstructed in three stages: a wet period in (844—603) ka B. P., a peak humid and warm period in (603—468) ka B. P., and a transition to a drier climate in (468—356) ka B. P.. 4) The weathering indices correlate negatively with global palaeoclimate records (e.g., continental ice cores, deep-sea cores, and terrestrial loess). Specifically, the relative wet periods in the DCRC profile broadly correspond to global glacial periods and loess accumulation, whereas the dry periods synchronize with global interglacials and palaeosol development. This study investigates the weathering characteristics of the DCRC in Xuancheng and the regional paleoclimate information it contains, providing foundational data for paleoclimate research in southern China. While preliminary findings suggest a potential negative correlation between paleoclimate changes in the study area and global paleoclimate records, further research is needed to elucidate the specific causes and underlying mechanisms of this relationship.