Middle to Late Holocene lake level variations recorded by shoreline tufa of Longmu Co Lake, northwestern Tibet Plateau

Tufa deposits have significant potential for reconstructing past lake-level fluctuations. Here, we conducted U-Th dating of tufa deposits exposed along the shoreline of Longmu Co Lake in the northwestern Tibetan Plateau to reconstruct its water level history during the middle-late Holocene. Our data demonstrate that Longmu Co Lake reached its highest level (61 m above the present level) at around 7.4 ka in response to the strengthened Indian Summer Monsoon and increased glacial meltwater; its lake level subsequently decreased due to solar insolation-induced decline in summer monsoon and glacial meltwater. Moreover, we find that the lake level experienced an abrupt decline at ~2.2 ka with a maximum amplitude of 13 m, probably owing to the rapid cooling of the local climate. The δ¹⁸O and δ¹³C of Longmu Co tufa also show a covariance trend, which supports the regional climate change reflected by the lake level fluctuation of Longmu Co. Additionally, we observed an inverse correlation between initial δ²³⁴U content in tufa and lake level variation, suggesting that initial calcium δ²³⁴U can serve as a proxy for reconstructing environmental changes. Our study therefore implies that lake tufa as a reliable archive for accurately reconstructing lake level changes.