ALBERT

Description: Massive carbonate banks representing ancient lacustrine deposits are exposed in the catchment of the lake Tangra Yumco (southern-central Tibetan Plateau) and nearby lake Xuru Co. Nine sediment samples were taken below and above these lacustrine deposits to determine periods of changing lake level using optically stimulated luminescence (OSL) applying a multiple aliquot regeneration (MAR) protocol. According to facies and stratigraphy samples below the carbonate banks indicate a rising and samples from above a falling lake level. The results indicate that the rising lake level of Tangra Yumco passed the sampling location at 10.5 ka and 2.1 ka while a falling lake level passed the sampling location at 0.9 ka. The rising lake level of Xuru Co passed the sampling location 7.9 ka and 1.7 ka and a falling lake level passed the sampling location at 0.5 ka showing a similar trend. Combining these results with recalculated cosmogenic nuclide ages and previously published feldspar luminescence data allow the establishment of an improved Holocene lake level reconstruction for Tangra Yumco, which is unique for the southern-central Tibetan Plateau. Within the last 10.5 ka the lake level of Tangra Yumco crested a lake level highstand of 181-183 m above the recent lake level at 8.5 ka and has generally fallen since, with a minor lake level rise at 2.1 ka. Lake level variations at Tangra Yumco occur simultaneously with other lakes on the Tibetan Plateau indicating that variations were controlled by monsoonal dynamics with a moist early Holocene and a successive reduction of available moisture thereafter. The precipitation directly reaching the lake via runoff that was required for the lake level rise between 10.5-8.5 ka is 9 mm a-1 (compared to a modern value of 35 mm a-1), providing valuable insights in the magnitude of monsoonal variations on the southern central Tibetan Plateau.