Synchronous Formation and Consistent Provenance Across Different Particle Sizes in Loess Deposits on the Chinese Loess Plateau

Abstract Loess deposits on the Chinese Loess Plateau (CLP) serve as key terrestrial archives of late‐Cenozoic paleoclimate. However, the formation timing and origin of different‐size fractions remain unclear. This study applies the ( 234 U/ 238 U) activity ratio to seven silt‐size fractions (2–63 μm) from the CLP loess to estimate the pre‐deposition transport time and infer loess provenance. All fractions show a consistent decrease in ( 234 U/ 238 U) with depositional time, aligning well with uranium‐comminution‐age‐model predictions. Results yield a relatively uniform transport time of ∼222 ± 25 kyr across all sizes, suggesting near‐synchronous production of loess materials through mountainous processes. This timescale closely matches the transport duration of silts from the Alxa arid lands (AALs), suggesting that AALs likely served as the primary transit hub for silt‐sized materials where they get mixed and collectively delivered to the CLP. These findings shed new light on loess transport dynamics and provide crucial constraints for interpreting CLP‐based paleoclimate records.