11:00 〜 13:00
[HQR05-P03] Testing fine-grained quartz and feldspar luminescence dating on a deep marine sediment core from the Sea of Japan: upper age limit and dust source fingerprinting
キーワード：光ルミネッセンス年代測定、日本海
Quaternary hemi-pelagic sediments in the Japan Sea record millennial and orbital scale changes in the East Asian Monsoon as alternating dark and light layers. Two holes were cored to explore the development and evolution of monsoonal patterns and their relationship to past changes in the Japan Sea. A tuned age model was constructed using tephro-stratigraphy, magneto-stratigraphy and the sediment GRA profile tuned to the δ18O profiles of LR04 (Lisiecki and Raymo, 2005, Tada et al., 2018).
We have used OSL dating of fine-grained detrital quartz (of aeolian origin) to provide high-resolution numerical age models for the late Quaternary in the cores from holes U1424C and U1425C.Comparison with the quartz OSL ages and the tuned age model indicates that the older quartz ages (>130 ka) should be considered minimum estimates.
Here we test the potential of a post-IR IRSL signal from polymineral fine-grains to date these cores beyond MIS5e. As modern analogue samples, we measured the sea floor sediments taken from the top ~5cm of short multiple cores. Post-IR IR230 apparent equivalent doses from these samples are high, ~30 Gy, suggesting that the pIRIR230 signal may not have been fully reset at deposition. Down the long cores equivalent doses increase with depth, up to ~1000 Gy. However, the pIRIR230 ages also appear to underestimate from ~150 ka onwards, with field saturation reached at ~300-400 ka (800-1000 Gy). From our results, it appears that pIRIR230 dating does not allow us to date significantly beyond the quartz OSL age limit.
Furthermore, we also test the potential of the use of quartz OSL sensitivity (as measured by the natural test dose, Tx) as an indicator for dust source changes with time. This sensitivity correlates with the quartz ESR signature from the same material. Interestingly, the Tx of U1424C and U1425C shows the inverse variation from MIS 6 to 5b, then conformable variation from MIS 4 to 1. These indicators may allow us to distinguish between predominantly Taklimakan Desert, Loess Plateau area and Siberia–Northeast China area dust sources (Nagashima et al., 2007).
We have used OSL dating of fine-grained detrital quartz (of aeolian origin) to provide high-resolution numerical age models for the late Quaternary in the cores from holes U1424C and U1425C.Comparison with the quartz OSL ages and the tuned age model indicates that the older quartz ages (>130 ka) should be considered minimum estimates.
Here we test the potential of a post-IR IRSL signal from polymineral fine-grains to date these cores beyond MIS5e. As modern analogue samples, we measured the sea floor sediments taken from the top ~5cm of short multiple cores. Post-IR IR230 apparent equivalent doses from these samples are high, ~30 Gy, suggesting that the pIRIR230 signal may not have been fully reset at deposition. Down the long cores equivalent doses increase with depth, up to ~1000 Gy. However, the pIRIR230 ages also appear to underestimate from ~150 ka onwards, with field saturation reached at ~300-400 ka (800-1000 Gy). From our results, it appears that pIRIR230 dating does not allow us to date significantly beyond the quartz OSL age limit.
Furthermore, we also test the potential of the use of quartz OSL sensitivity (as measured by the natural test dose, Tx) as an indicator for dust source changes with time. This sensitivity correlates with the quartz ESR signature from the same material. Interestingly, the Tx of U1424C and U1425C shows the inverse variation from MIS 6 to 5b, then conformable variation from MIS 4 to 1. These indicators may allow us to distinguish between predominantly Taklimakan Desert, Loess Plateau area and Siberia–Northeast China area dust sources (Nagashima et al., 2007).