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Geomorphology; OSL dating; Paleoclimate; Tibetan Plateau
Abstract:
Palaeoclimate reconstruction on the northern Tibetan Plateau resulted in a large spectrum of different and partly divergent interpretations for the climate evolution during the late glacial and the Holocene. In some cases this is caused by incomplete understanding of the geomorphological processes influencing the different proxies used. To overcome these limitations and to enhance the understanding of the complex process interactions in a sensitive and highly dynamical environment a detailed analysis of different members of the sedimentary system at Lake Heihai on the northern Tibetan Plateau was conducted. Lake level variations during the late Pleistocene were influenced by sediment supply to an alluvial fan. This sediment surplus resulted in the temporary blocking of the outflow of Lake Heihai. High sediment supply presumably occurred during or shortly after large glaciations in the Kunlun Shan. The spatial distribution of aeolian sediments revealed a strong relationship to possible source areas. This resulted in a spatially heterogeneous distribution of the aeolian sediments. Furthermore, topographic effects have an important influence on the preservation of the sediments. Aeolian sediments deposited in sheltered positions might not be comparable with other archives with a similar grain size. Nevertheless, deposition of loess during the mid-Holocene indicates a shift to wetter climate conditions on the northern Tibetan Plateau. This might be caused by the intrusion of the East Asian Summer monsoon into the area. During the late Holocene, the Asian summer monsoon retreated and aeolian sediments were reactivated.
