5:15 PM - 7:15 PM
[MIS06-P09] Correlation of Miocene tephra layers between the ODP and IODP sites in the Japan Sea using XRF core scanner: A ReCoRD project
Keywords:IODP Exp. 346, ODP Leg 127, The Repository Core Re-Discovery Program (ReCoRD), tephra, age model, The Japan Sea
The Japan Sea ReCoRD project, “The Japan Sea paleoceanography and paleoclimatology during the Miocene (ReC23-03)” aims to understand the short time scale oceanic environmental changes in the warmer-than-today world, which is important for addressing the consequence of future global warming. In this project, the Miocene Japan Sea sediments obtained from Sites 794, 795, and 797 (drilled by ODP Leg 127 in 1989) and Sites U1425 and U1430 (drilled by IODP Exp. 346 in 2013) are analyzed in higher resolution than previous studies to reveal high resolution oceanographic and climatic changes. For example, we focus on rapid warming event (Tortonian Thermal Maximum, ~10.8Ma) reported in the South China Sea, which lasted less than 200kyr (Holbourn et al., 2021). Although high sedimentation rate of the Japan Sea sediments could preserve such a short time scale event well, this event have not been detected by previous studies because of sparse sampling intervals. We also focus on centennial to millennial scale oceanographic changes recorded in laminated sediments, which have not been investigated in detail.
Although the age models for sediment cores used by the Japan Sea ReCoRD project is already constructed by previous studies (Tada, 1994; Kurokawa et al., 2019), they only used biostratigraphic datums, and the number of datums and the accuracy of the age models are not sufficient during the Miocene interval to find exact stratigraphic intervals corresponding to the target ages in the Japan Sea ReCoRD project, such as the Tortonian Thermal Maximum. Moreover, even though laminated intervals were found at some of the sites in close timings, resolution of existing age models are not sufficient to test the synchroneity of these laminated intervals.
Therefore, we utilized wide-spread tephra for inter-site correlation of the Miocene intervals of the Japan Sea sediments obtained from five sites used in the Japan Sea ReCoRD project. The vertical profiles of chemical composition of these cores were measured by XRF core scanner (ITRAX) with 1cm resolution, tephra layers were identified based on their chemical characteristics, which were also used to correlate tephras between the studied sites.
We will conduct U-Pb dating of Zircon from some of correlated tephra layers, and revise existing low-resolution age models. Since biostratigraphic studies were also conducted in the Japan Sea ReCoRD project, the results of our study will contribute to revise the ages for biostratigraphic datums which could be used to interpret past short time scale oceanographic and climatic changes.
Although the age models for sediment cores used by the Japan Sea ReCoRD project is already constructed by previous studies (Tada, 1994; Kurokawa et al., 2019), they only used biostratigraphic datums, and the number of datums and the accuracy of the age models are not sufficient during the Miocene interval to find exact stratigraphic intervals corresponding to the target ages in the Japan Sea ReCoRD project, such as the Tortonian Thermal Maximum. Moreover, even though laminated intervals were found at some of the sites in close timings, resolution of existing age models are not sufficient to test the synchroneity of these laminated intervals.
Therefore, we utilized wide-spread tephra for inter-site correlation of the Miocene intervals of the Japan Sea sediments obtained from five sites used in the Japan Sea ReCoRD project. The vertical profiles of chemical composition of these cores were measured by XRF core scanner (ITRAX) with 1cm resolution, tephra layers were identified based on their chemical characteristics, which were also used to correlate tephras between the studied sites.
We will conduct U-Pb dating of Zircon from some of correlated tephra layers, and revise existing low-resolution age models. Since biostratigraphic studies were also conducted in the Japan Sea ReCoRD project, the results of our study will contribute to revise the ages for biostratigraphic datums which could be used to interpret past short time scale oceanographic and climatic changes.