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Ogata, Manabu; Komatsu, Tetsuya; Nakanishi, Toshimichi*
Earth, Planets and Space (Internet), 76, p.123_1 - 123_11, 2024/09
Times Cited Count：0 Percentile：0.00(Geosciences, Multidisciplinary)Marine terraces developed along the southeastern coast of Kii Peninsula, southwestern Japan, face a seismogenic region along the Nankai Trough. We determined the emergence age of one of these marine terraces by using feldspar OSL dating of the marine terrace sediments. The target marine terrace has previously been correlated with MIS 5e on the basis of morphostratigraphy. Samples for pIRIR dating were obtained from foreshore deposits of the marine terrace. pIRIR signals were measured at 150 
C (pIRIR
) and 225 C (pIRIR
). These results show that the surface of the marine terrace corresponds to MIS 5e rather than MIS 5c or 7, which is consistent with the chronological framework based on the morphological features of the terraces in this study area.
Kitamura, Akihisa*; Okazaki, Sota*; Kondo, Mitsuru*; Watanabe, Takahiro; Nakanishi, Toshimichi*; Hori, Rie*; Ikeda, Masayuki*; Ichimura, Koji*; Nakagawa, Yuki*; Mori, Hideki*
Shizuoka Daigaku Chikyu Kagaku Kenkyu Hokoku, (49), p.73 - 86, 2022/07
On July 3 2021, a debris flow caused by a landslide from a landfill occurred along the Aizome River in the Izusan area of Atami City, Shizuoka. In this study, debris flow deposits and soil samples were characterized in terms of their sedimentology and geochemically analyzed.
Nakanishi, Toshimichi*; Komatsu, Tetsuya; Ogata, Manabu; Kawamura, Makoto; Yasue, Kenichi*
Gekkan Chikyu "Kiso deta Kara Kangaeru Dai Yonkigaku No Shintenkai-I" Gogai No.71, p.148 - 155, 2022/02
The formation process of terrace topography was investigated by observing and analyzing boring core samples collected in the middle reaches of the Kumano River. It was assumed that the older terrace topography was distributed higher than the current riverbed surface. However, since tributary debris flow deposits may be thickly distributed beneath the old gyre river valley, care must be taken when using the surface of the ground as an index of uplift and erosion.
Ogata, Manabu; Komatsu, Tetsuya; Nakanishi, Toshimichi
Dai Yonki Kenkyu, 60(2), p.27 - 41, 2021/06
no abstracts in English
Nakanishi, Toshimichi*; Okuno, Mitsuru*; Yamasaki, Keiji*; Hong, W.*; Fujita, Natsuko; Nakamura, Toshio*; Horikawa, Yoshiyuki*; Sato, Eiichi*; Kimura, Haruo*; Tsutsumi, Hiroyuki*
Nagoya Daigaku Nendai Sokutei Kenkyu, 5, p.38 - 43, 2021/03
no abstracts in English
Nanayama, Futoshi*; Yamaguchi, Tatsuhiko*; Nakanishi, Toshimichi; Tsuji, Tomohiro*; Ikeda, Michiharu*; Kondo, Yasuo*; Miwa, Michiko*; Sugiyama, Shinji*; Kimura, Kazunari*
no journal, ,
The characteristics of the post-LGM incised valley fills and the depositional sequence were examined the SKM core collected in the Sukumo coastal lowland, where is expected to huge seismic subsidence due to the Nankai Trough great earthquakes. Our sedimentological, radiocarbon dating and paleoenvironmental results are as bellows. Sediments of the SKM core clearly show a succession influenced by post-glacial sea level change. The Matsuda River incised valley was formed in LGM and filled by fluvial sand and gravels in late Pleistocene. After the postglacial transgression, sea level reached -30 m (a.s.l.) at 9.8 ka and the incised valley changed to an estuary environment. The sea level continued to rise and it became an inner bay mud bottom environment, and reaching a maximum water depth was at 7.5 ka. The 7.3 ka Kikai caldera eruption in southern Kyushu caused heavy K-Ah ash fall in southwestern Shikoku, and then large-scale lahars frequently occurred immediately after the ash fall because of the vicinity of volcanic source. After ash fall, the K-Ah secondary sediments rapidly deposited on the inner bay environment and caused forced regression. After 7.0 ka, the growth of the delta became active ahead of the other regions, which may be due to the large K-Ah ash fall. At 5 ka, the sea level reached + 2.5 m (a.s.l.) estimated by the Sukumo midden and this altitude is recognized as the Holocene marine limit in this area. The information on relative sea level change during the past 10000 years has revealed that the Sukumo Bay area has not subsided due to seismic crustal deformation.
Yamaguchi, Tatsuhiko*; Tsuji, Tomohiro*; Nanayama, Futoshi*; Nakanishi, Toshimichi; Ikeda, Michiharu*; Kondo, Yasuo*; Miwa, Michiko*; Hamada, Yohei*
no journal, ,
Shikoku Island is situated 150 km northwest of the Nankai trough that has developed in response to the convergence of the subducting Philippine Sea Plate and overriding Eurasian Plate. This tectonism causes deformation of the island, megathrust earthquakes, and tsunamis. Shikoku Island experiences coseismic and interseismic deformation. The middle Holocene tectonics of the island are still poorly understood. Relative sea-level (RSL) changes indicated by coastal sediments potentially record seismic uplift and subsidence. To infer RSL changes between 8 and 4 cal. kyr BP, we studied Holocene ostracode assemblages from the SKM drill core in Sukumo, southwest Shikoku Island (Tsuji et al., 2018, JpGU, MIS11-P19), and from six cores in the northern part of the island (Yasuhara et al., 2005, Palaeo3; Yasuhara and Seto, 2006, Paleontol. Res. 10). To estimate paleo-water depth and RSL, we employed the ostracode assemblages and modern analog technique. The SKM core is composed of conglomerate, ash, and mud chiefly. Its geological age was examined, using the 
C dating method (Nakanishi et al., 2019, Radiocarbon). The differences in RSL were identified across the island, possibly due to convergence of the Philippine Sea Plate.
Shigeno, Kiyoyuki*; Nakanishi, Toshimichi; Hong, W.*; Nanayama, Futoshi*
no journal, ,
To estimate the sedimentary process of chronological samples in tsunami deposits, the radiocarbon ages of 10 pairs of marine shells and terrestrial plants were measured from one core obtained of lagoon lake sediments from the Lake Harutori in Kushiro City, eastern Hokkaido. This core of 12.6 meters length was obtained in the central part of the frozen lake in winter, which locates on a tectonic active region in the southwestern Kuril arc associated by the oblique subduction of the Pacific Plate under the Okhotsk. The radiocarbon ages from the tsunami deposits were more than 1000-4000 years older than the depositional curve constructed by previous radiocarbon ages and tephrochronology. It clearly suggests that these materials were reworked from older sediments by catastrophic tsunamis.
Noguchi, Marie*; Miyamoto, Tatsuki*; Sugai, Toshihiko*; Nakanishi, Toshimichi*; Komatsu, Tetsuya; Suginaka, Yusuke*; Endo, Kunihiko*
no journal, ,
Discussions on the history of crustal development based on sedimentary facies analysis using the boring cores GC-NG-1, GC-OY-1, and GC-OY-2 in the central Kanto Plain, from the Sarushima Plateau to the Takaragi Plateau, are underway. In the study, paleoenvironmental restoration based on diatom analysis was performed. These core samples are likely to preserve sea-level changes and landing processes since MIS9. From the results of the diatom community analysis, the paleoenvironment in each core was found to change according to the boring site, such as inner bay, brackish water to freshwater, freshwater, lakes, river environment, and land environment. We also attempted to objectively present changes in community composition by cluster analysis of diatom analysis results.
Ogata, Manabu; Tsukahara, Yuzuko; Kawamura, Makoto; Kanno, Mizuho; Nishiyama, Nariaki*; Sueoka, Shigeru; Komatsu, Tetsuya; Nakanishi, Toshimichi*; Yasue, Kenichi*
no journal, ,
Optically stimulated luminescence (OSL) dating method on feldspar is useful to date sediments on geomorphological time scale. In this presentation, we present the case studies for marine terraces in the Noto Peninsula and abandoned river valleys along the Oi River, for which the emergence ages were estimated by using feldspar OSL dating. This study was carried out as a part of the establishment of advanced technology for estimation of uplift rates using emergence ages of emergent landforms project.
Ogata, Manabu; Komatsu, Tetsuya; Nakanishi, Toshimichi*
no journal, ,
Marine terraces are formed by regional uplift and sea level change, being useful for estimating uplift rates on geomorphological time scale (10
-10
years). However, the emergent ages, and then the uplift rates, are difficult to determine when the sediments include few organic materials and tephra. Optically stimulated luminescence (OSL) dating method on feldspar is useful to date sediments on 10-10-year timescales. Thus, this method has been applied to date marine terrace deposits in the last several years. In this presentation, we will present the case study for MIS 5e marine terraces in the Kii Peninsula, for which the depositional ages were estimated by using feldspar OSL dating.
Kagami, Saya; Niwa, Masakazu; Umeda, Koji*; Danhara, Toru*; Fujita, Natsuko; Nakanishi, Toshimichi*; Kamataki, Takanobu*; Kurosawa, Hideki*
no journal, ,
The Kikai-Akahoya (K-Ah) volcanic ash from the 7.3 Ka Kikai caldera eruption is one of the representative tephra of the Quaternary. We newly found the event deposit associated with the tsunami of the K-Ah eruption in the core (MMS1) from the Miyazaki Plain. Here, we present the results of tephra analysis and C dating of samples in the MMS1 core. The sediments between 10.4 m and 12.0 m in depth contained volcanic glasses and pumices that developed planar lamination with sand, indicating that tephra was deposited secondarily as submerged sediments. A previous study founded the similar sediments in a river near the boring site and interpreted to be deposit of tsunami during the 7.3 Ka Kikai caldera eruption. The results of C ages and identification by chemical composition and refractive index of volcanic glass are consistent with the assumption that the sediments between 10.4 m and 12.0 m in depth were tsunami sediments related to the K-Ah eruption. Chemical composition of volcanic glass in the K-Ah tephra is bimodal: 
65wt.% (Type L) and 75wt.% (Type H) of SiO
concentration. Previous studies suggested that Type H erupted in the early K-Ky eruption, and then the magma mixed with Type L erupted in the late K-Ky eruption. The samples contained the K-Ah volcanic ash in this study consist of mainly Type H and slightly Type L. Type H from 11.810.2 m depth was subdivided into two clusters and that from 12.3 m depth contained only one cluster of higher SiO concentration. The feature of the volcanic glasses may indicate the change in magma composition during the eruption.
Tsukahara, Yuzuko; Saito, Toshihito*; Nakanishi, Toshimichi*; Nishiyama, Nariaki; Fujita, Natsuko; Kawamura, Makoto; Umeda, Koji*
no journal, ,
Paleo-sea levels estimated from the elevation and age of emerged shoreline features and fossil calcareous assemblages are one of the useful tools for reconstructing the tectonic features of the Holocene. In this study, we reconstruct the paleo-sea levels around the eastern part of Izu Peninsula using fossil calcareous assemblages to verify case studies in areas with active volcanism and seismic activity. In addition, we will infer the characteristics of crustal deformation through comparison with previous studies. Shishikura et al. (2023) surveyed emerged shoreline features and fossil calcareous assemblages around the coast in the vicinity of Ito, the northeastern part of the Izu Peninsula, to clarify the emerged process. They concluded that the cause of the emergence is associated with a volcanotectonic uplift due to subsurface magma movement. In order to verify the representativeness of this crustal feature, we conducted a field survey of the Jogasaki Coast, 89 km south of the area studied by Shishikura et al. (2023). We found four fossil calcareous assemblages at three sites on the Jogasaki Coast, and dated them to 13561470 CE using the C. Fossil assemblages with similar ages have been reported by Shishikura et al. (2023), but the elevation in this study is about 1 m higher. This difference may suggest a spatial variation in tectonic features in this area.
Nakanishi, Toshimichi; Komatsu, Tetsuya; Ogata, Manabu; Hosoya, Takashi*; Kaga, Takumi*
no journal, ,
no abstracts in English
Nakanishi, Toshimichi; Nanayama, Futoshi*; Hori, Kazuaki*; Niwa, Yuichi*; Komatsubara, Junko*; Kitamura, Akihisa*; Hong, W.*
no journal, ,
To identify chronological and spatial changes in the radiocarbon (C) marine reservoir effects, the C ages of eight pairs of marine shells and terrestrial plants were measured from the same horizons of one core of Holocene sediments around Japan. To determine the direct chronological changes of the marine reservoir effect between the Kuroshio and Oyashio Currents, radiocarbon ages were measured from the same stratigraphic horizons within Holocene sediment cores alomg the Pasific coast of Japan (eastern Hokkaido; Nanayama et al., 2003, Nanayama, 2020, Sanriku Coast; Niwa et al., 2017, 2019, Arakawa Lowland; Komatsubara et al., 2009, 2010, Shimizu Plain; Kitamura and Kobayashi, 2014; Nobi Plain) and Taiwan.
Nakanishi, Toshimichi; Nanayama, Futoshi*; Katsuki, Kota*; Yamada, Keitaro*
no journal, ,
The Holocene sediments of Lake Harutori in Kushiro City, eastern Hokkaido, are mainly composed of annually laminated sediments, organic mud layers with plant fragments, sand layers with shell and plant fragments and tephra layers. Fluctuations of the marine reservoir effect of radiocarbon and the information on the paleo-tsunami caused by the huge interplate earthquakes were identified by the high-resolution sedimentological analysis.
Miyamoto, Tatsuki*; Sugai, Toshihiko*; Komatsu, Tetsuya; Nakanishi, Toshimichi*; Niwa, Yuichi*; Hiura, Yuki
no journal, ,
no abstracts in English
Miyamoto, Tatsuki*; Sugai, Toshihiko*; Niwa, Yuichi*; Nakanishi, Toshimichi*; Komatsu, Tetsuya; Hiura, Yuki
no journal, ,
no abstracts in English
Tsukahara, Yuzuko; Ogata, Manabu; Kawamura, Makoto; Kanno, Mizuho*; Nishiyama, Nariaki; Sueoka, Shigeru; Nakanishi, Toshimichi*; Komatsu, Tetsuya
no journal, ,
One hundred thousand-year-scale uplift rate of the Japanese mountains is estimated mainly based on the Terrace to Terrace method (TT method; Yoshiyama and Yanagida, 1995). To apply the TT method, it is necessary to identify the pair of the sedimentary terraces of the last glacial period and the one before last glacial period. However, there are many mountains where such terrace pairs are not recognized. Therefore, as an alternative method to the TT method, we suggest the method based on landforms and deposits of incised meandering rivers (for example, Yasue et al., 2014; Ogata et al., 2021). In this presentation, we will report the results of a survey conducted in the middle of the Oi River as part of such research.
Ogata, Manabu; Tsukahara, Yuzuko; Nishiyama, Nariaki; Komatsu, Tetsuya; Uchida, Mao; Kawamura, Makoto; Ishihara, Takanori; Nakanishi, Toshimichi*
no journal, ,
Terrace to terrace (TT) method is mainly used for estimating uplift rate on mountain areas of Japan on 10-year time scale. However, this method cannot be applied to the area with poor distribution of fluvial terraces. In such area, the method based on the emergence ages of the fluvial landform, e.g., an abandoned river valley around a cutoff spur, and the relative elevation between old and present reiver bed is expected instead of TT method. This method calculates the river-incision rate by dividing the relative elevation by the emergence age. The river-incision rate is equal to the uplift rate if the river is at equilibrium (graded stream). We are investigating the fluvial landform in the Oi River basin for verifying this method. In this presentation, we will present the incision and uplift rate estimated by feldspar OSL dating results.
