First investigation of the luminescence dating of loess in the eastern Tibetan Plateau using K-feldspar MAR MET-pIRIR protocol

Abstract

The multi-aliquot regenerative dose (MAR) multi-elevated-temperature post-infrared infrared stimulated luminescence (MET-pIRIR) dating protocol exhibits great potential for extending the luminescence dating limit. However, further investigations are needed. Loess deposits on the Tibetan Plateau (TP) significantly differ from those on the Chinese Loess Plateau in terms of both formation age and dust source, making them ideal for studying the past climatic and environmental changes on the TP. However, detailed chronological studies are lacking. This study investigates the applicability of the MAR MET-pIRIR protocol to the Danba (DB) loess-paleosol sequence in the eastern TP, aiming to establish a chronological framework for this typical loess sequence. For TP loess samples with equivalent doses (D_e) below ∼950 Gy, multi-aliquot MET-pIRIR₂₅₀ and single-aliquot pIR₂₀₀IR₂₉₀ dating methods yield consistent results. However, for samples with D_e exceeding ∼950 Gy, the SAR-pIR₂₀₀IR₂₉₀ method underestimates ages, while the MAR MET-pIRIR₂₅₀ procedure remains reliable up to ∼1100 Gy. Using MAR MET-pIRIR protocol with the global standard growth curve method, we have established a new absolute chronological framework for the DB loess-paleosol sequence, indicating that loess deposition in the TP began at least ∼230 ka ago. The magnetic susceptibility records of this loess sequence reveal a pattern of alternating moist interglacial and dry glacial periods. During the last interglacial period, precipitation levels were significantly elevated and exhibited considerable variation in the eastern TP.