Neotectonic subsidence along the Cenozoic Kunlun fault (Tibetan Plateau)

Data refer to grain size and LOI data against calibrated age

Quantifying geomorphological response to climate change by unmixing of lake sediments from Lake Donggi Cona, north-eastern Tibetan Plateau, China

The catchment of Lake Donggi Cona, situated at north-eastern Tibetan Plateau, is a region influenced by monsoonal air masses of different origin and character, highly variable in space and time. Reconstruction of Quaternary monsoon dynamics focuses mainly on high-resolution archives (e.g. glacier ice and speleothem records) with detailed proxy information on temperature and precipitation regimes in the past. However, also sedimentological and geomorphological processes respond to and register monsoon dynamics, mainly amount and spatio-temporal variation of precipitation. In lake catchments, climatic signals affect the whole process system within the geomorphological inventory on different scales. Sediment traps store these signals and the landscapes response to them, though buffering and topological dependencies of archives have to be considered. Within temporal or final sediment storage basins, sediment properties represent a mixture of terrestrial and lacustrine processes during and after deposition (e.g. aeolian, fluvial transport, and water current directions). Each process as well as different sediment sources (e.g. sub-catchments with a certain geochemical and mineralogical fingerprint) can be regarded as an end-member.We present an approach of unmixing lake sediment properties, i.e. grain size distributions, geochemical and mineralogical compositions, to reveal end-members of geomorphological processes and sediment source. In a first step, modern surface samples from the bottom of Lake Donggi Cona are used to test a flexible iterative end-member modelling algorithm (EMMA) with different types of data transformation, eigenspace analysis and goodness-of-fit tests. Empirical end-members are derived and compared to natural end-members, i.e. terrestrial surface samples from locations dominated by a single geomorphological process regime or sediment source. Using Bayesian approaches, conditional probabilities can be given for the variation within and between sediment properties. This determines the significance of a single value against randomness and accounts for interferences and/or buffering of external signals in the sediments. As a second step, end-members derived from modern analogues as probability density functions can be applied to fossil lake sediments of high resolution reaching back to the Last Glacial Maximum. Thus, a spatio-temporal quantification of geomorphic processes and regions is facilitated probabilistically and allows a coupling with climate records

Landscape and climate on the northern Tibetan Plateau during the late Quaternary

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. (C) 2017 Elsevier B.V. All rights reserved