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19Lake high-stand sediments are found in three onshore terraces at Lake Donggi Cona, north-eastern 20Tibetan Plateau, and reveal characteristics of hydrological changes on lake shorelines triggered by 21 climate change, geomorphological processes, and neo-tectonic movements. The terraces consist of 22 fluvial, alluvial to littoral-lacustrine facies. End-member modeling of grain size distributions allowed 23 quantification of sediment transport processes and relative lake levels during times of deposition. 24Radiocarbon dating revealed higher than modern lake levels during the early and mid-Holocene. Lake 25 levels follow the trend of Asian monsoon dynamics, and are modified by local non-climatic drivers. 26Site-specific impacts explain fluctuations during the initial lake level rise ~11 cal ka BP. Maximum lake 27 extension reached ~9.2 cal ka BP, at ~16.5 m above present lake level (a.p.l.l.). Littoral and lacustrine 28 sediment deposition paused during a phase of fluvial activity and post-depositional cryoturbations at 29 ~8.5 cal ka BP, when the lake level fell to ~8 m a.p.l.l. After a second maximum at ~7.5 cal ka BP, lake 30 level declined slightly at ~6.8 cal ka BP, probably due to a non-climatic pulse that caused lake 31 opening. The level remained high until a transition towards drier conditions of ~4.7 cal ka BP. Though 32 discontinuous, high-stand sediments provide a unique, high-resolution archive.

Abstract. Grain-size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy, this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain-size end-member modelling analysis. Between three and five robust grain-size end-member subpopulations were distinguished at different sites from similarly-likely end-member model runs. Their main modes were grouped and linked to common sediment transport and depositional processes that can be associated with contemporary Tibetan climate (precipitation patterns and lake ice phenology, gridded wind and shear stress data from the High Asia Reanalysis) and local catchment configurations. The coarse sands and clays with grain-size modes > 250 µm and < 2 µm were probably transported by fluvial processes. Aeolian sands (∼ 200 µm) and coarse local dust (∼ 60 µm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ∼ 25 µm may derive from near-by sources that keep in longer term suspension. The continuous background dust is differentiated into two robust end members (modes: 5-10 and 2-5 µm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upperlevel westerly and episodic northerly wind transport. According to this study grain-size end members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19 ± 5 %), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14 % and 51 ± 11 %). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history.

Sediment distribution is investigated applying grain size analysis to 279 surface samples from the transitional zone between high mountains (Qilian Shan) and their arid forelands (Hexi Corridor) in north-western China. Six main sediment types were classified. Medium scale (10 3 m) geomorphological setting is carefully considered as it may play an important role concerning sediment supply and availability. A tripartite distribution of sedimentological landscape units along the mountain to foreland transition is evident. Aeolian sediments (e.g. loess and dune sands) are widespread. They are used to identify aeolian transport pathways. The mU/fS-ratio (5-11 μm/48-70 μm) among primary loess opposes the two grain size fractions being most sensitive to varying accumulation conditions. The first fraction is attributed to long-distance transport in high suspension clouds whereas the latter represents local transport in saltation mode. The ratio shows strong correlation with elevation (R 2 = 0.77). Thus, it indicates a relatively higher far-traveled dust supply in mountainous areas (>3000 m above sea level [a.s.l.]) compared to the foreland. The contribution of westerlies to high mountain loess deposits is considered likely. Hereby, the influence of the geomorphological setting on grain size composition of aeolian sediments becomes apparent: the contribution from distant dust sources is ubiquitous in the study area. However, the far-distance contribution may be reduced by the availability of fine sand provided in low topography settings. Plain foreland areas support fine sand deflation from supplying river beds, allowing the formation of sandy loess in foreland areas and intramontane basins. In contrast, high mountain topography inhibits strong sand deflation into loess deposits. Eastern parts of the Hexi Corridor show higher aeolian sand occurrence. In contrast, the western parts are dominated by gravel gobi surfaces. This is attributed to higher sand supply in eastern parts provided by the Badain Jaran Desert and fluvial storages as sand sources.

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