A record of late Holocene precipitation on the Central Tibetan Plateau inferred from varved lake sediments

Lake sediments on the Tibetan Plateau are important natural archives for studying past climate and environment changes. A precise sediment core chronology is a fundamental prerequisite for reconstructing past climate and environment changes. However, radiocarbon dates on bulk carbon in lake sediment cores are subject to old carbon reservoir effects, which can cause problems when trying to establish depth-age relations for sediment cores, especially those from the Tibetan Plateau (TP). Here we present a varve chronology that spans the last similar to 2000 years, from Jiang Co, on the central TP. Clastic-biogenic varves in Jiang Co sediments are comprised of two laminae, a coarse-grain and a fine-grain layer, observed by petrographic microscope and Electron Probe Micro Analyzer. The varve chronology is supported by Pb-210 and Cs-137 dating and was used to estimate the radiocarbon reservoir ages for the past similar to 2000 years. The thickness percentage of the coarse-grain layer within a single varve was used as a proxy for summer precipitation amount, as coarse grains are transported mainly by runoff. During the past 2000 years, the precipitation record inferred from Jiang Co sediments shows centennial-scale fluctuations that are consistent with other records from the region. The varve chronology from Jiang Co provided a valuable opportunity to estimate the old carbon reservoir effect in Jiang Co and reconstruct past precipitation on the Tibetan Plateau.

Automated summary

Lake sediments on the Tibetan Plateau serve as important natural archives for studying past climate and environmental changes. A varve chronology from Jiang Co spanning the last 2000 years reveals centennial-scale fluctuations in precipitation, providing valuable insights into past climate and environment changes in the region. The study demonstrates the utility of analyzing varve thickness as a proxy for summer precipitation amount in the area.