OSL Dating of Paleo-Shorelines at Dagze Co, Central Tibetan Plateau

Abstract

Well-preserved paleo-shoreline systems suggest lake shrinkage occurred in a vast region of the Tibetan Plateau, indicating dramatic paleo-environmental changes that linked closely to variations in Asian monsoon precipitation, glacial meltwater, and evaporation. The elevation and chronology of these shoreline features can be used to reconstruct lake level fluctuation history and regional paleo-climate. Here, we report optically stimulated luminescence (OSL) dating of 14 sediment samples from three of seven paleo-shorelines at south of Dagze Co, central Tibetan Plateau, using coarse-grained quartz and K-feldspar. Two fine grain silt samples were also measured. The results suggest the following: 1) The highest paleo-shoreline for Dagze Co has an elevation around 4,525 m (+55 m above modern lake). Its age is estimated to be 9.1 ± 0.5 to 9.6 ± 0.6 ka, suggesting a relative humid condition in the early Holocene. 2) After that, the lake level dropped ∼20 m and remained relatively stable (+35 m) from ∼8 to 5 ka, implying a dry condition with reduced runoff. Lake level further declined for ∼40 m since about 5 ka. 3) The general trend of shrinkage for Dagze Co broadly matches studies from adjacent lakes, suggesting a common pattern of lake’s evolution on the south/central plateau in the late Quaternary. The long-term decreasing trend of Asian monsoon precipitation should be the main reason.