Objective The aim was to analyze the profile changes and relationships between Rb/Sr ratios and other physical and chemical indicators in the Quaternary red earth in Southern China, and to discuss the suitability of Rb/Sr ratios as an environmental indicator for the Quaternary red earth in Southern China.

Method Taking the red soil profile in Langxi, Anhui as the research object, the soil element contents and grain size compositions were measured by X-ray fluorescence spectroscopy (XRF) and laser particle size analyzer. The variation characteristics of the Rb/Sr ratios in the profile were compared and analyzed with the geochemical parameters and grain size distribution characteristics.

Result The effects of intense weathering and leaching have been resulted in a considerable depletion of both Rb and Sr in the Langxi profile, with Sr content being extremely low, whose behavior are significantly mediated by the adsorptive properties of clay minerals present in the soil. The Rb/Sr ratios did not accurately reflect the real migration of elements, which affected the accurate evaluation of weathering intensity. The Rb/Sr ratios in the heavily weathered red earth of the Langxi profile contradicted the weathering and leaching conditions reflected by various indicators. The Rb/Sr ratios as an indicator of the climatic environment of lateritic sedimentation had certain limitations, but it remained valid under moderate weathering conditions and initial weathering conditions.

Conclusion When using Rb/Sr ratios to reconstruct paleo-environment, the interference of weathering and grain size should be considered, and other environmental proxies such as magnetic susceptibility, grain size and element index should be combined to indicate the situation of the study area in practical application.