Dating of a late Quaternary loess section from the northern slope of the Tianshan Mountains (Xinjiang, China) and its paleoenvironmental significance

Abstract

Late Quaternary loess deposits from the Tianshan Mountains are potentially valuable archives for the study of environmental change. However, the reported chronologies of the loess deposits in this area are still controversial. Previous studies have shown that there remain discrepancies between the optically stimulated luminescence (OSL) ages and accelerator mass spectrometry (AMS) 14C ages of the loess deposits from the Yili Valley. To establish a robust chronological sequence of the Shichengzi section (SCZ17) from the northern slope of the Tianshan Mountains in Xinjiang, we adopted both AMS14C and quartz OSL dating methods and the dates-based chronology was further refined by correlating sedimentary proxies (loss-on-ignition and grain size) with the proxy information from other sequences. Comparison of the AMS 14C and quartz OSL ages suggests that the AMS 14C ages of bulk organic matter are generally younger than the quartz OSL ages, with the maximum age discrepancy reaching up to ~10 ka. Regional correlation of the Holocene lithology of the SCZ17 section with other Holocene lithologies from the Tianshan Mountains reveals that the Holocene paleosol formation occurred in the late Holocene. The analyzed proxy data (e.g., grain size, carbonate content) indicate a cold and dry climate from 21.6 to ~10 ka, and a persistent wetting trend during the past ~10 ka. This study provided interesting and new evidence of late Quaternary environmental changes in arid central Asia.