Anomalous ²¹⁰Pb activity and implications for chronological reconstruction of a remote lake on the southeastern Tibetan Plateau

Lead-210 (²¹⁰Pb) dating is widely used to establish high-resolution chronology of lake sediments, providing robust age controls for the past 100-150 years. However, anomalously low ²¹⁰Pb activities that deviate from the expected exponential decline with depth can compromise the chronological data. Here we report on anomalously low ²¹⁰Pb activities in sediments from Lake Cuomujiri on the southeastern Tibetan Plateau. We established a ²¹⁰Pb chronology based on three correction methods: raw data, averaged data, and screened data. The chronological reliability of each method was assessed by comparison with an independent ¹³⁷Cs age model, regional hydroclimate records, and meteorological data. Our results indicate that the constant initial concentration (CIC)-derived ²¹⁰Pb chronology, with the anomalously low ²¹⁰Pb activity data screened, provides the most reliable age model. The anomalous ²¹⁰Pb activities were likely caused by a rapid sedimentation event in the early 1990s related to dam construction and enhanced precipitation, as supported by multiple proxy data obtained from the lake sediments. This study highlights the effectiveness of removing anomalously low ²¹⁰Pb activity data in refining ²¹⁰Pb-based chronology, and provides a methodological framework for the high-sedimentation lacustrine environments.