Abstract
Abstract. The extensive loess deposits of the Eurasian mid-latitudes provide important terrestrial archives of Quaternary climatic change. As yet, however, loess records in Central Asia are poorly understood. Here we investigate the grain size and magnetic characteristics of loess from the Nilka (NLK) section in the Ili Basin of eastern Central Asia. Weak pedogenesis suggested by frequency-dependent magnetic susceptibility (χfd%) and magnetic susceptibility (MS) peaks in primary loess suggest that MS is more strongly influenced by allogenetic magnetic minerals than pedogenesis, and may therefore be used to indicate wind strength. This is supported by the close correlation between variations in MS and proportions of the sand-sized fraction. To further explore the temporal variability in dust transport patterns, we identified three grain size end-members (EM1, mode size 47.5 µm; EM2, 33.6 µm; EM3, 18.9 µm) which represent distinct aerodynamic environments. EM1 and EM2 are inferred to represent grain size fractions transported from proximal sources in short-term, near-surface suspension during dust outbreaks. EM3 appears to represent a continuous background dust fraction under non-dust storm conditions. Of the three end-members, EM1 is most likely the most sensitive recorder of wind strength. We compare our EM1 proportions with mean grain size from the Jingyuan section in the Chinese loess plateau, and assess these in the context of modern and Holocene climate data. Our research suggests that the Siberian High pressure system is the dominant influence on wind dynamics, resulting in loess deposition in the eastern Ili Basin. Six millennial-scale cooling (Heinrich) events can be identified in the NLK loess records. Our grain size data support the hypothesis that the Siberian High acts as teleconnection between the climatic systems of the North Atlantic and East Asia in the high northern latitudes, but not for the mid-latitude westerlies.
Highlights
Central Eurasia experiences extremely continental climatic conditions, in large part due to its position far from the oceans
We investigated the applicability of this approach to the Ili Basin loess at NLK by unmixing grain size distributions with Bayesian model for end-member modeling analysis (BEMMA) (Yu et al, 2016) and generating a mixing model consisting of three end-members (Fig. S2)
Our data from NLK in the eastern Ili Basin provide a paleoenvironmental record over the last ca. 70 kyr
Summary
Central Eurasia experiences extremely continental climatic conditions, in large part due to its position far from the oceans. Arid Central Asia (ACA), the mid-latitude region spanning the Caspian Sea across to the eastern Tian Shan mountains, is a sensitive recorder of past climate change due to its location in the transitional region between the Asian monsoons (Cheng et al, 2012; Dettman et al, 2001), mid-latitude westerlies (Vandenberghe et al, 2006), and the North Asian polar front (Machalett et al, 2008). The relative importance and intensity of these major climate subsystems has varied across the latitudinal and longitudinal range of Central Asia through time. Identification of the predominant climate regimes in this region, using geological archives, is a crucial precondition for tracing paleoclimatic evolution. Li et al.: Eolian dust dispersal patterns since the last glacial period
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
