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10Be-26Al cosmogenic surface exposure, optically stimulated luminescence, and radiocarbon dates from the site of Xidatan 2 (∼4300 m above sea level [asl] in the Kunlun Pass, northern Tibetan Plateau) suggest the site was intermittently and briefly occupied approximately 9200-6400 yr B.P. This age is substantially younger than expected given the late Upper Paleolithic character of the lithic assemblage, which is dominated by microlithic and unique discoidal prepared core technologies. Comparisons between Xidatan 2 and known surface lithic assemblages in the Kekexili and Chang Tang regions of the central high Plateau show not only that the latter are technologically similar to Xidatan 2, but also that they are demonstrably connected to Xidatan 2 through utilization of the same stone raw materials, which includes a chemically distinctive obsidian. Contrary to most accounts of Tibetan Plateau colonization, our results suggest that the earliest substantial occupations on the interior Tibetan Plateau above 4000 m asl may date to the Pleistocene/Holocene transition. [ABSTRACT FROM AUTHOR]

Abstract: Qinghai Lake, located on the northeastern Qinghai–Tibet Plateau (Qing-Zang Gaoyuan), is China''s largest extant closed-basin lake. Its position relative to major Asian climate systems makes it sensitive to global climate change. The lake has been the subject of numerous paleoenvironmental investigations including dating of shoreline features around the lake basin. Here we report new age estimates of shoreline features, geomorphic exposures and archaeological sites that contribute to the development of a lake-level history for Qinghai Lake and a landscape model of the Qinghai Lake Basin. Lake highstands above 3230m (∼36m above the modern lake level) appear to date to late MIS 5, ∼70–110ka. The lake has had much more modest highstands since then: no evidence of MIS 3 lake stands higher than modern were found, and early Holocene highstands are no more than ∼12m above modern. If the age of highstands greater than 3230m is confirmed through future work, then the Qinghai Lake Basin hydrologic balance prior to ∼70ka was dramatically different than after that time, including during the Holocene. A simple hydrologic balance model provides insights into the combination of precipitation, evaporation, and runoff generation needed to sustain the lake at 3260m, the highest shoreline observed. A range of factors may explain the difference, primarily the relative strength of the East Asian monsoon. The basin was apparently subject to extensive alluviation during MIS 3, interrupted by widespread erosion and development of cryogenic features before and during the last glacial maximum (LGM). Loess that presently drapes much of the lower basin landscape began to be deposited after the LGM, ∼16–18ka. The landscape model outlined here has implications for archaeological visibility of early human occupation of the Qinghai–Tibet Plateau. [Copyright &y& Elsevier]