In this paper,we applied End-Member unmixing method developed by previous workers to try to separate different processes determining grain size distribution in the Huaitoutala section in the northeastern Qaidam Basin,northeastern Tibet.The section spans from:37°13'48.5"N,96°43'02.0"E to 37°14'37.0"N,96°44'11.4"E.The total thickness of the section is ca.4500m.This section has been dated with paleomagnetic dating and the age model of the middle portion (ca.1100m in thickness) of the section dominated by lacustrine sediments was further refined based on higher-resolution sampling,resulting in a solid age model constraint for the portion deposited between 10Ma and 6Ma.We reveal that the grain size data can be decomposed into 4 End-Members.End-Member 1 consists of a sand-sized main component and a silt-sized minor component.The grain size pattern is similar to fluvial sand reported before.So we attribute this End-Member to fluvial component.End-Member 2 and 3 consist of a silt-sized main component and two minor components,similar to typical lake deposits reported before.We attribute these two End-Members to lacustrine deposits with End-Member 2 indicating wetter climate than End-Member 3.It is hard to find a modern analog for End-Member 4 which exhibits a bimodal main peak distribution and some minor components.Loess is reported to exhibit similar bimodal main peak distribution pattern but the grain size is significant smaller than the End-Member 4 here.We attribute End-Member 4 to dalta depositing processes which are affected by both fluvial processes and lacustrine processes.This explains why this End-Member shows similar pattern both to End-Member 1 and End-Member 2 or 3.The relative content of these End-Members all show significant fluctuations,similar to evaporate mineral content variations reported from the other sites in the Qaidam Basin.However,separating 4 End-Members from the bulk grain size data allows a better understanding of different depositional processes through time.The mean grain size of the studied section decreased during ca.8.3~7.0Ma,indicating higher lake level and larger lake area in the Qaidam Basin.To further test this hypothesis,we compiled paleoenvironmental proxy records from both Eastern and Southern Asia areas.These data consistently showed that climate was wetter in Asian continent during ca.8.3 ~ 7.0Ma,likely associated with Asian monsoon precipitation intensification.We attribute monsoon intensification to Tibetan uplift because substantive evidence existed about northeastward growth of the Tibetan Plateau around 8Ma.Considering global sea surface temperature variations,we attribute the Qaidam drying after 7Ma to atmospheric CO_2 forcing.Orbital timescale studies reveal that Qaidam climate experienced larger amplitude fluctuations during ca.8.3 ~7.0Ma,confirming the opinion that the Tibetan uplift can increase climate system's sensitivity to insolation forcing.