Evolution of the Asian monsoon recorded by Holocene aeolian sediments in the northeastern Tibetan Plateau

Abstract

Aeolian sediments in the northeastern Tibetan Plateau may contain information about changes of the atmospheric circulation changes in the region, and can be used to investigate the varying characteristics of the East Asian monsoons and the evolution of the regional environment. In this study, parameterized grain size end-member analysis is used to analyze the grain size of climate change-sensitive aeolian profiles in Zeku. Then, the environmental significance indicated by each end-members and the environmental evolution in the northeastern Tibetan Plateau since the Holocene were explored by combining magnetic susceptibility, elements and other indexes. On this basis, the factors affecting aeolian sediments under the Asian monsoon are analyzed. The following conclusions were drawn: (1) The grain size components of the sediments in the ZK profile were divided into three end-members: EM1 is related to weathering and pedogenesis, and can indirectly indicate the dry and humid changes of the regional environment; Both EM2 and EM3 are near-source dust accumulations that relatively indicate the strength of regional aeolian activities. (2) The environmental evolution can be divided into the following three phases: 9.4–4.3 ka BP was a geological period with strong summer winds, a warm and humid climate, and weaker aeolian activities. 4.3–1.5 ka BP entered the westerlies control period, the climate developed to cool and dry, aeolian activities were more frequent, and there were secondary climate fluctuations in 4–2.0 ka BP and 1.7–1.5 ka BP. From 1.5 ka BP to present, the climate has become further cold and dry, and aeolian activities have intensified. (3) At the suborbital scale, the succession of sedimentary phase in the Northeastern Tibetan Plateau is controlled by a combination of monsoon strength and sources changes.