A Novel Soil Chronometer: Uranium Comminution Ages Measure Soil Production Rates in a Deep Granitic Weathering Profile

Abstract Soil production, through bedrock weathering, regulates landscape evolution, biogeochemical cycles, and societal sustainability, yet quantifying soil production rates (SPRs) remains difficult due to limited tools. Here, we present a new framework for measuring SPRs based on uranium comminution ages and validate this approach at a deep granitic weathering profile in subtropical South China. Measured ( 234 U/ 238 U) activity ratios increase with depth in soil and remain stable in saprolite. Using a 1D mass‐transport model, we resolve a SPR of 2.4 ± 0.4 m/Ma, which is consistent with independent estimates by U‐series and 10 Be dating. Set by inherent α‐recoil processes, uranium comminution ages do not rely on environmental conditions (e.g., lithology and soil thickness) that present challenges to conventional tools such as 10 Be. We expect our approach to contribute a tool that could expand measurements of SPRs—a key parameter of Earth surface systems—to broader landscapes where SPR measurements have been limited.