5:15 PM - 7:15 PM
[SCG44-P06] Applicability of feldspar OSL dating: A case study of dated MIS 5c marine terrace in the Suzu, Noto Peninsula
Keywords:feldspar, luminescence, OSL, pIRIR
Optically stimulated luminescence (OSL) dating of feldspar is one of the most promising methods for determining the emergence ages of Middle–Late Pleistocene marine terraces on account of the following reasons: (1) feldspar is ubiquitous in Quaternary sediments; (2) the applicable dating range extends from several thousand to several hundred thousand years; and (3) the OSL signal is reset during sediment transport and exposure to sunlight, and is therefore capable of constraining burial (depositional) ages. Previous studies have demonstrated the application of feldspar OSL dating to Japanese marine terraces by cross-checking with the known tephrochronological framework [1-4]. However, there are still few examples, and thus the accumulation of the case studies is required to improve the reliability.
In Suzu area, Noto Peninsula, the MIS 5c and 5e marine terraces were correlated by Sambe Kisuki tephra [5] and U series ages of corals [6], respectively. In addition, the higher marine terraces are continuous distributed above the MIS 5e terraces [7-8]. For MIS 5c terrace, ca. 100 ka of feldspar OSL age were reported [9]. In this study, we apply feldspar OSL dating to dated marine terraces to validate the accuracy of the OSL dating method.
In this presentation, we will present the results of feldspar OSL dating of MIS 5c marine terrace sediments. The samples were collected from an outcrop, whose sediments were divided into, from the bottom to the top, the bedrock, the sand with gravels, the sandy silt, the loess and the soil layers. The sand with gravels and the sandy silt layers are considered to be marine deposits. The three and one samples were collected at the sand with gravels and sandy silt layers, respectively. Post-infrared infrared stimulated luminescence (pIRIR) signals of K-feldspar from the samples were measured at 50 °C and 225 °C. The pIRIR ages calculated using the central age model [10], which assumes that the equivalent doses are log-normally distributed, are 135 ± 9 ka, 129 ± 8 ka, 125 ± 9 ka and 108 ± 7 ka from the bottom. On the other hand, we also applied the minimum and the maximum age models [10-11] to the sandy silt sample because it has a bimodal distribution. The ages are calculated to be 95 ± 11 ka and 118 ± 13 ka for the young and old peaks, respectively. From these results, the sand with gravels and the sandy silt layers were estimated to be MIS 5e sediment, and mixed sediment of MIS 5c and 5e, respectively, in agreement with the tephrochronology of the previous studies [5, 7-8]. We concluded that OSL dating can be useful for constraining the ages of Late Pleistocene marine terraces; however, although marine sediment is prone to be totally bleached during transport sediment and exposure sunlight, in the case of measurement of the samples collected from near the boundary of the layers, the sample may be a mixture of sediments of different ages due to the disturbance, and thus evaluation of the equivalent dose distribution is required. The applicability of feldspar OSL dating to marine terraces will be tested on MIS 5e and older marine terraces in Suzu.
This study was funded by the Ministry of Economy, Trade and Industry, Japan as part of its R&D supporting programs entitled “Establishment of Technology for Comprehensive Evaluation of the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (Fiscal Years 2023-2024)” (Grant number: JPJ007597).
References: [1] Thiel et al. (2015). Quaternary Geochronology, 29, 16-29. [2] Ito et al. (2017). Geochronometria, 44, 352-365. [3] Hayashizaki (2022). CRIEPI Report, NR21005. [4] Okazaki et al. (2022). Quaternary Science Reviews, 285, 107507. [5] Toyokura et al. (1991). The Quaternary Research, 30, 79-90. [6] Omura (1980). Trans. Proc. Palaeont. Soc. Japan, N. S., 117, 247-253. [7] Ota and Hirakawa (1979). Geographical Review of Japan, 52, 169-189. [8] Koike and Machida (2001). University of Tokyo Press. [9] Ito and Tamura (2017). JpGU2017, STT60-P02. [10] Galbraith et al. (1999). Archaeometry, 41, 339-364. [11] Olley et al. (2006). Quaternary Science Reviews, 25, 2469-2474.
In Suzu area, Noto Peninsula, the MIS 5c and 5e marine terraces were correlated by Sambe Kisuki tephra [5] and U series ages of corals [6], respectively. In addition, the higher marine terraces are continuous distributed above the MIS 5e terraces [7-8]. For MIS 5c terrace, ca. 100 ka of feldspar OSL age were reported [9]. In this study, we apply feldspar OSL dating to dated marine terraces to validate the accuracy of the OSL dating method.
In this presentation, we will present the results of feldspar OSL dating of MIS 5c marine terrace sediments. The samples were collected from an outcrop, whose sediments were divided into, from the bottom to the top, the bedrock, the sand with gravels, the sandy silt, the loess and the soil layers. The sand with gravels and the sandy silt layers are considered to be marine deposits. The three and one samples were collected at the sand with gravels and sandy silt layers, respectively. Post-infrared infrared stimulated luminescence (pIRIR) signals of K-feldspar from the samples were measured at 50 °C and 225 °C. The pIRIR ages calculated using the central age model [10], which assumes that the equivalent doses are log-normally distributed, are 135 ± 9 ka, 129 ± 8 ka, 125 ± 9 ka and 108 ± 7 ka from the bottom. On the other hand, we also applied the minimum and the maximum age models [10-11] to the sandy silt sample because it has a bimodal distribution. The ages are calculated to be 95 ± 11 ka and 118 ± 13 ka for the young and old peaks, respectively. From these results, the sand with gravels and the sandy silt layers were estimated to be MIS 5e sediment, and mixed sediment of MIS 5c and 5e, respectively, in agreement with the tephrochronology of the previous studies [5, 7-8]. We concluded that OSL dating can be useful for constraining the ages of Late Pleistocene marine terraces; however, although marine sediment is prone to be totally bleached during transport sediment and exposure sunlight, in the case of measurement of the samples collected from near the boundary of the layers, the sample may be a mixture of sediments of different ages due to the disturbance, and thus evaluation of the equivalent dose distribution is required. The applicability of feldspar OSL dating to marine terraces will be tested on MIS 5e and older marine terraces in Suzu.
This study was funded by the Ministry of Economy, Trade and Industry, Japan as part of its R&D supporting programs entitled “Establishment of Technology for Comprehensive Evaluation of the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (Fiscal Years 2023-2024)” (Grant number: JPJ007597).
References: [1] Thiel et al. (2015). Quaternary Geochronology, 29, 16-29. [2] Ito et al. (2017). Geochronometria, 44, 352-365. [3] Hayashizaki (2022). CRIEPI Report, NR21005. [4] Okazaki et al. (2022). Quaternary Science Reviews, 285, 107507. [5] Toyokura et al. (1991). The Quaternary Research, 30, 79-90. [6] Omura (1980). Trans. Proc. Palaeont. Soc. Japan, N. S., 117, 247-253. [7] Ota and Hirakawa (1979). Geographical Review of Japan, 52, 169-189. [8] Koike and Machida (2001). University of Tokyo Press. [9] Ito and Tamura (2017). JpGU2017, STT60-P02. [10] Galbraith et al. (1999). Archaeometry, 41, 339-364. [11] Olley et al. (2006). Quaternary Science Reviews, 25, 2469-2474.