5:15 PM - 6:45 PM
[SCG41-P06] A marine terrace probably created during much older period than estimated from its morphostratigraphical position: A case in the Noto Peninsula
Keywords:uplift, marine terrace, Early Pleistocene, cryptotephra, pollen, Noto Peninsula
Elucidating formation ages of marine terraces located higher than those correlated with Marine Isotope Stage (MIS) 5e, so-called higher marine terraces, is a key to understand the uplift rate over a period longer than ~100,000 years. To acquire knowledge about chronological limitation of higher marine terraces, we conducted a case study in the northern side of Nanao Bay, Noto Peninsula, where higher marine terraces are well-preserved in Japan.
Our study site is a marine erosional terrace, named the H1 surface (Ota and Hirakawa, 1979), which develops at the 5th step from the first step of the marine terrace (the M1 surface) correlated with MIS 5e; the H1 surface is correlated with MIS 13 estimated from its morphostratigraphical position (Koike and Machida, 2001). Aeolian deposit consisting of the terrace-forming material contained some beta-quartz grains. Major chemical element compositions of glass inclusions in beta-quartz grains detected in the upper part of the deposit almost matched those of Hakkoda 1st-stage pyroclastic flow deposits (Hkd1; 760 ka; Suzuki et al., 2005). Additionally, pollen of the genus Metasequoia, which is considered to have become extinct before MIS 19 (~790 ka) (Hongo, 2009), was detected in both the marine and aeolian deposits. These results suggest that the H1 surface was created during an interglacial period before MIS 19, possibly MIS 21.
Correlation of the H1 surface with MIS 21 raises the question of when and how each marine terrace surface was formed, because each of the five marine terraces from the H1 to M1 surfaces cannot simply correspond to the eight interglacial peaks from MIS 21 to MIS 5e; we suppose that the consideration of Malatesta et al. (2022) regarding the formation and preservation of individual marine terraces is a clue to solve this question. In any case, more chronological data constraining the formation ages of each marine terrace surface are needed to solve the question.
Acknowledgments: This study was funded by the Ministry of Economy, Trade and Industry, Japan as part of its R&D supporting programs (Grant number: JPJ007597), Establishment of Advanced Technology for Evaluating the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (Fiscal Years 2020-2021).
We thank Ogata, M., Nakanishi, T., Goto, A., and staff of Chuo Kaihatsu Co. for help in the field.
References: Hongo (2009) Journal of the Geological Society of Japan, 115, 64-79. Malatesta et al. (2022) Geology, 50, 101-105. Koike and Machida (2001). Atlas of Quaternary Marine Terraces in the Japanese Islands. Tokyo: University of Tokyo Press. Ota and Hirakawa (1979) Geographical review of Japan, 52, 169-189. Suzuki et al. (2005) The Island Arc, 14, 666-678.
Our study site is a marine erosional terrace, named the H1 surface (Ota and Hirakawa, 1979), which develops at the 5th step from the first step of the marine terrace (the M1 surface) correlated with MIS 5e; the H1 surface is correlated with MIS 13 estimated from its morphostratigraphical position (Koike and Machida, 2001). Aeolian deposit consisting of the terrace-forming material contained some beta-quartz grains. Major chemical element compositions of glass inclusions in beta-quartz grains detected in the upper part of the deposit almost matched those of Hakkoda 1st-stage pyroclastic flow deposits (Hkd1; 760 ka; Suzuki et al., 2005). Additionally, pollen of the genus Metasequoia, which is considered to have become extinct before MIS 19 (~790 ka) (Hongo, 2009), was detected in both the marine and aeolian deposits. These results suggest that the H1 surface was created during an interglacial period before MIS 19, possibly MIS 21.
Correlation of the H1 surface with MIS 21 raises the question of when and how each marine terrace surface was formed, because each of the five marine terraces from the H1 to M1 surfaces cannot simply correspond to the eight interglacial peaks from MIS 21 to MIS 5e; we suppose that the consideration of Malatesta et al. (2022) regarding the formation and preservation of individual marine terraces is a clue to solve this question. In any case, more chronological data constraining the formation ages of each marine terrace surface are needed to solve the question.
Acknowledgments: This study was funded by the Ministry of Economy, Trade and Industry, Japan as part of its R&D supporting programs (Grant number: JPJ007597), Establishment of Advanced Technology for Evaluating the Long-term Geosphere Stability on Geological Disposal Project of Radioactive Waste (Fiscal Years 2020-2021).
We thank Ogata, M., Nakanishi, T., Goto, A., and staff of Chuo Kaihatsu Co. for help in the field.
References: Hongo (2009) Journal of the Geological Society of Japan, 115, 64-79. Malatesta et al. (2022) Geology, 50, 101-105. Koike and Machida (2001). Atlas of Quaternary Marine Terraces in the Japanese Islands. Tokyo: University of Tokyo Press. Ota and Hirakawa (1979) Geographical review of Japan, 52, 169-189. Suzuki et al. (2005) The Island Arc, 14, 666-678.