Radiometric dating of late Quaternary loess in the northern piedmont of South Tianshan Mountains: Implications for reliable dating

Abstract

Reliable chronologies are prerequisites when interpreting proxy records in terrestrial archives of Quaternary climate and environmental change. Optically stimulated luminescence (OSL) dating and accelerator mass spectrometry radiocarbon dating (AMS 14C) are commonly used to date late Quaternary loess deposits in the Chinese Loess Plateau, but the range and reliability of the two methods in Central Asia are still debated. In this study, we investigate both fine‐grained quartz OSL and AMS 14C dating of a late Quaternary loess section located at the northern piedmont of the South Tianshan Mountains in Central Asia and discuss the reliability of the two radiometric dating methods. The results show that the OSL and AMS 14C ages are generally consistent with the stratigraphic sequence when the ages are younger than 25 cal ka BP, which means that both can be used to establish a reliable chronology in the Ili Basin. But beyond this age, the OSL dating method seems to be a more reliable approach. The results also supported previous dates based on medium‐grained quartz OSL dating of the Ili loess in the southern piedmont of the North Tianshan Mountains. Radiocarbon ages older than 25 cal ka BP should be treated with caution, and attention must be paid to the influence of pedoturbation on OSL signals in the Central Asian loess. Multiple dating approaches for mutual authentication and exploring new dating materials are suggested in further loess chronological research. These findings will be helpful in establishing a reliable timescale and in reconstructing high‐resolution environmental change in Central Asia.

Eolian dust dispersal patterns since the last glacial period in eastern Central Asia: insights from a loess-paleosol sequence in the Ili Basin

“…A similar case also occurs in the L1 loess layers at other sites in the Ili Valley, such as the Talede (TLD), Zeketai (ZKT), and Axike (AXK) sections ( Fig. 1) (Jia et al, 2012(Jia et al, , 2010Song et al, 2010).…”

“…The basin is surrounded to the south and north by the Tian Shan mountain range, widens to the west and drains into the endorheic basin of Lake Balkhash (Fig. 1), and provides a conducive situation for loess accumulation (Feng et al, 2011;Jia et al, 2012;Li et al, 2016a;Song et al, 2017Song et al, , 2010. In this paper we present new data on the physical properties of a 20.5 m thick loess deposit at NLK in the eastern Ili Basin.…”

“…Magnetic susceptibility (MS) in loess is predominantly determined by the concentration of iron-bearing magnetic minerals within the sediment (Liu et al, , 1994Song et al, 2010). Generally, this varies between primary loess and soil horizons.…”

“…Therefore, EM1 and EM2 correspond to coarse silt and EM3 to fine silt. duce during pedogenesis (Song et al, 2010), such minerals are more likely to be detrital in nature and are derived from the original protolith.…”

The relationship between environmental factors and magnetic susceptibility in the Ili loess, Tianshan Mountains, Central Asia

“…Located in the east of Arid Central Asia (ACA), the Ili Valley (42°14′–44°50′N, 80°09′–84°56′E) in the Xinjiang Province is one of the important loess deposits areas in China and loess in this valley (hereafter referred as “Ili loess”) ranges in thickness from a few meters to 200 m (Song et al, ). Recent years have witnessed much research on the Ili loess, with the focuses of the chronology (E et al, ; Kang et al, ; Qin & Zhou, ; Song, Lai, Li, Chen, & Wang, ; Song, Luo, et al, ; Song, Li, Zhao, Chen, & Zeng, ; Yang et al, ), distribution (Y. Li, Song, Yan, Chen, & An, ; Song et al, ), magnetic susceptibility (MS; Jia, Xia, Wang, Wei, & Liu, ; Y. Liu, Shi, Deng, Su, & Zhang, ; Shi, Dong, & Fang, ; Song, Nie et al, ; Song et al, ; Song, Shi et al, ), geochemistry (X. Chen et al, ; Honda, Yabuki, Suzuki, Ye, & Tatsumi, ; W. Zhang et al, ), and mineral composition (Y. Li, Song, Zeng, et al, ; Song, Zeng, et al, ; Ye, ; Zeng & Song, , ), and many important conclusions have been reached. For example, pertaining to the origin of the aeolian material and the pedogenetic processes it underwent.…”