OSL dating of fine-grained quartz from Holocene Yangtze delta sediments

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• 作者：Saiko Sugisaki^a ; ^{ssugisaki@eps.s.u-tokyo.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Jan-Pieter Buylaert^b ; ^c ; Andrew Murray^b ; Ryuji Tada^a ; Hongbo Zheng^d ; Wang Ke^e ; Keita Saito^a ; Luo Chao^f ; Shiyi Li^f ; Tomohisa Irino^g
• 关键词：OSL ; Yangtze delta ; Holocene ; Fine-grains ; Quartz ; Polymineral ; IR50 ; pIRIR160 ; Quaternary
• 刊名：Quaternary Geochronology
• 出版年：2015
• 出版时间：October 2015
• 年：2015
• 卷：30
• 期：part_PB
• 页码：226-232
• 全文大小：1604 K

文摘

Holocene flood events in the Yangtze River are associated with variations in East Asian Summer Monsoon (EASM) precipitation, and so Yangtze delta sediments may preserve information about the frequency and magnitude of EASM precipitation. These flood/drought cycles of the EASM directly affect the living standards of East Asian population. However, despite its importance, little chronological control is available for the Yangtze Delta sediments; because biogenic carbonate only occurs sporadically, it has proved the difficulty to discuss sedimentation mechanisms and rates in any detail.

In 2013 two sediment cores (YD13-G3 and H1) were taken from the Yangtze subaqueous delta to investigate precipitation history. In this study, we investigate the potential of quartz OSL dating of the fine silt fraction (fine-grained quartz; 4–11 μm) from these cores to estimate the depositional age of the sediments. We test whether: (1) Yangtze subaqueous delta sediments contain quartz with suitable characteristics for dating, and (2) quartz grains are well-bleached during/before the transportation process, by examining a modern analogue of suspended particulate matter, and by cross-checking with the doses derived from infrared stimulated luminescence (IRSL) signals (both IR₅₀ and pIRIR₁₆₀) from feldspar in polymineral fine grains. We find that both the quartz and feldspar luminescence characteristics are satisfactory (quartz dose recovery ratio 1.067 ± 0.004; n = 250, pIRIR₁₆₀ dose recovery ratio 1.01 ± 0.02; n = 151). Modern suspended particulate matter has measured quartz equivalent doses between 0.1 and 0.2 Gy, suggesting that this material was sufficiently bleached during/before transportation to allow dating of Holocene sediments (mean dose rates of ∼3 Gy ka⁻¹). OSL ages of 44 samples from the 2 cores show apparently rapid accumulation at ∼6 ka between 9.65 and 5.50 m in core H1 and ∼2 ka throughout core G3 and between 5.0 and 0.0 m in core H1. The pIRIR₁₆₀ signals suggest less light exposure of the core top sediments and of those from the transition layer between ∼6 ka to ∼2 ka, although there is no evidence for incomplete bleaching of quartz. The question remains as to whether significant deposition took place only at these two times, or whether the record has been disturbed by erosion/reworking.