This electronic supplement describes the test procedure of optically stimulated luminescence (OSL) samples and a figure showing natural OSL decay curve, growth curves, and equivalent dose (De) distributions.
Coarse-grained (90–125 μm) and fine-grained (4–11 μm) quartz fractions were prepared through routine methods for luminescence sample preparation (Aitken, 1998), followed by 30% hydrogen peroxide (H2O2) and 10% hydrochloric acid (HCl) treatment to remove organic materials and carbonates, respectively. The coarse-grained fraction was selected by wet sieving, 40% hydrofluoric acid (HF) etching (for 40 min) and magnetic separation. The fine-grained fraction was separated using Stokes’ law and 30% H2SiF6 etching. The purity of prepared quartz was checked by the ratio of infrared-stimulated luminescence (IRSL) to blue light stimulated luminescence (BLSL) (<5%).
All irradiation, heating, and luminescence measurements were conducted by a Risø TL/OSL-DA-20 reader at Zhejiang Zhongke Institute of Luminescence Testing Technology, equipped with a 90Sr/90Y beta source (~0.12 Gy/s), blue LEDs (470 ± 20 nm, ~80 mW/cm2), and two Hoya U340 filters (290–370 nm). Small aliquots of coarse-grained quartz were measured using a Synthetic Aperture Radar (SAR) dating protocol (Murray and Wintle, 2000; Table 2 in the main article) after mounting within 9.7 mm diameter steel discs using silicon oil. Large aliquots of fine-grained quartz were measured using simplified multiple aliquot regenerative dose (SMAR) (Table 2 in the main article). Laboratory dose (120 Gy) recovery tests were performed on the sample YCW-OSL-3, using preheat temperatures from 200°C to 280°C in increments of 20°C. The average measured dose for all aliquots was 120.6 Gy. A dose recovery ratio plateau is observed from 220°C to 260°C (Fig. S1). Therefore, preheat was at 220°C for 10 s for natural and regenerative doses, and cut-heat was at 180°C for test doses. A recycling ratio of 0.9–1.1 and recuperation of <5% were used as criteria for the SAR protocol.
Figure S1. Natural OSL decay curve, growth curves, and De distributions for samples (a,b) YCW-OSL-1 and (c,d) YCW-OSL-2.
Aitken, M. J. (1998). An Introduction to Optical Dating: The Dating of Quaternary Sediments by the Use of Photon-Stimulated Luminescence, Oxford University Press, Oxford, United Kingdom.
Murray, A. S., and A. G. Wintle (2000). Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol, Radiat. Meas. 32, no. 1, 57–73.
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