Lake level variations of Qinghai Lake in northeastern Qinghai-Tibetan Plateau since 3.7 ka based on OSL dating

Qinghai Lake is the largest internally drained lake in China and its unique location makes it sensitive to climate changes. Late glacial climate changes associated with variation in Qinghai Lake levels have been intensively investigated for the past 40 years, with particular attention paid to lake level fluctuation histories between the last interglacial and the Holocene. However, the details of lake level fluctuations during the Holocene are still unclear. Using both optically stimulated luminescence (OSL) dating of quartz (for 22 samples) and infra-red stimulated luminescence (IRSL) of feldspars (only for sample HYW1 whose IRSL age is 37 ± 15 years), a total of 23 samples are dated from paleoshoreline deposits, fluvial sediments and aeolian sands (a total of 13 sections) near the modern lake shore, with ages from 37 ± 15 to 3710 ± 350 years. These ages are used to reconstruct the lake level fluctuation history spanning the last 3700 years. The results indicate that: (1) the youngest IRSL age of 37 ± 15 years is in agreement with the independent age of 39–29 years, suggesting that luminescence dating is able to date decadal samples for sediments from the study area; (2) the lake experienced several oscillations imposed on an overall regressive trend during the past 3700 years; (3) the dated paleoshoreline deposits are generally related to warm and wet periods, suggesting that those shoreline deposits formed during cold and dry periods, if any, may have been modified by later transgressions; (4) lake level fluctuations during the period of 3700–240 years ago are generally consistent with the climate conditions identified in other proxies, with the highest lake level occurring about 1770 years ago; and (5) after 240 years ago the lake level dropped more rapidly, which is inconsistent with the proxy records (showing a warmer and wetter phase).