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Hebei loess section in the Anyemaqen Mountains, northeast Tibetan Plateau: a high-resolution luminescence chronology

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Abstract

The extensive aeolian deposits of the Tibetan Plateau (TP) represent important environmental archives, recordinginformation about the past interplay between the Asian monsoon and Westerlies and the link between dustaccumulation and Quaternary glaciations. In the northeast TP, mantles of sandy loess form a distinct belt lyingbetween 3500 and 4500 m a.s.l. on the east-facing slopes of the Anyemaqen Mountains. However, there is littlechronological information about the loess deposits in this region. This study provides a detailed chronology for loessformation in the region using luminescence dating. A total of 29 samples were collected from an 8-m-thickhomogeneous loess section at Hebei (HB) in order to date sand-sized (63–90 lm) quartz and K-feldspar fractionsusing optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL and pIRIR) signals,respectively. The resulting quartz and feldspar ages are in good agreement over the last 40 ka; beyond this (i.e. De>120 Gy),the quartz age is underestimated, and the pIRIR170feldspar ages are consideredmore reliable. The HB loesssection records continuous environmental information from c. 50 to c. 30 ka, i.e. throughout Marine Isotope Stage(MIS) 3. Mass accumulation rates (MARs) varied considerably over this period with increased dust accumulationaroundc. 38 ka and afterc. 32 ka; in between, andat the beginning of MIS 3 (50–40 ka), the dust accumulation ratewas~50% lower. Finally, the HB section also records a MIS 2 hiatus of c. 17 ka duration, probably resulting from deflation.This study implies that loess deposition on the TP is predominantly an interglacial/interstadial phenomenon and theTP may be deflating at the same time as the Chinese Loess Plateau is accumulating, at least during MIS 2.