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Sueoka, Shigeru; Kohn, B. P.*; Tagami, Takahiro*
no journal, ,
no abstracts in English
Miyakawa, Kazuya; Imai, Hisashi*; Hirai, Satoru*; Ono, Hirokazu; Nakata, Kotaro*; Hasegawa, Takuma*
no journal, ,
no abstracts in English
Murakami, Hiroaki; Ishii, Eiichi
no journal, ,
no abstracts in English
Sakuma, Keisuke; Ishii, Eiichi; Murakami, Hiroaki; Honda, Norihisa
no journal, ,
no abstracts in English
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.
Sato, Naomi; Hayano, Akira; Kashihara, Koji*; Teshima, Minoru*; Negi, Tateyuki*
no journal, ,
The objective of this study was to assess the effect of borehole siting on collocated cokriging (COK) for estimating the three-dimensional distribution of chloride ion concentration (Cl
) and stable isotope (
O, D) compositions of groundwater in the Horonobe area, which are indicators of paleo-saline water. When compared to the full model consisting of ten borehole surveys, COK with a partial dataset consisting of 1-3 borehole surveys covering the entire range of resistivity from the electromagnetic survey in the study area performed better than other datasets. The results suggested that a borehole survey at a site with the representative geochemical feature in the region could yield adequate coefficients in the COK and, as a result, produce reasonable estimates with a cost-effective procedure. This survey was funded by the Ministry of Environment, Trade and Industry.
Nakajima, Toru; Fukuda, Shoma; Niki, Sota*; Sueoka, Shigeru; Kawakami, Tetsuo*; Danhara, Toru*; Tagami, Takahiro*
no journal, ,
We conducted monazite fission-track (MFT) etching experiments for Quaternary monazite dating. Quite low-temperature annealing of the MFT system (45-25 degree: Jones et al., 2021) has been proposed, and application as an ultra-low-temperature thermochronometer is expected. The practical application of MFT dating gives us access to a geological event at ultra-low temperatures, such as shallow crustal denudation and faulting. Jones et al. (2019) examined the etching conditions and suggested that the etching rate can vary between grains depending mainly on the accumulated radiation damage. Since the monazites used in previous studies were pre-Mesozoic (Weise et al., 2009; Jones et al., 2021), younger monazites with less radiation damage would be expected to have higher etching resistance. In this study, we attempted to etch FT using the Quaternary monazites, which are expected to have less radiation damage, to investigate appropriate etching conditions and discuss a relation between etching rate and radiation damage. Monazites from the Toya Ignimbrite (ca. 0.1 Ma: Niki et al., 2022) and the Kurobegawa Granite (ca. 0.8 Ma: Ito et al., 2013) were used in this study. Euhedral monazite-(Ce) crystals have weak magnetism and can be separated by the conventional magnetic separation method. The Cretaceous monazite from the Kibe Granite (ca. 98 Ma: Skrzypek et al., 2016) was also etched for comparison.
Niwa, Masakazu
no journal, ,
For the safety assessment of geological disposal of high-level radioactive waste, it is essential to evaluate the influence of natural phenomena such as volcanic/hydrothermal activity, fault movement, uplift/erosion, and climate/sea level change. The evaluation is generally based on the records of these natural phenomena from the past to the present. Thus, chronological studies play a very important role in the evaluation. In this presentation, recent research outcomes and future's prospects by JAEA on geochronology and thermochronology are showcased.
Zwingmann, H.*; Niwa, Masakazu; Todd, A.*
no journal, ,
Active inland faults are widespread in Japan and investigations are important for earthquake forecasting and seismic hazard assessments. We describe authigenic illite fault gouge age dating results from a unique outcrop of the active Atera Fault, central Japan. This study investigates the timing of fault formation by K-Ar dating of authigenic illite separated from 3 fresh, non-weathered samples from the outcrop. Prior to age dating, extensive mineral characterization was carried out comprising petrography (TS, SEM, TEM) and XRD clay analyses. An undeformed host rock yields an age of 55 Ma (Paleogene-Eocene) and the Atera fault gouges clay ages range from 40 to 60 Ma (Paleogene-Eocene to Paleocene) and will be discussed within the geochronological and thermochronological background of the study area.
Nagata, Mitsuhiro
no journal, ,
The U-Pb zircon dating have been determined by the constraints of formation (or depositional) age of various rocks and provenance analysis of clastic rocks. However, there are some problems that are difficult to discuss only with U-Pb zircon dates. I think that some of these problems can be solved by measuring Hf isotopes of zircon. In this presentation, I will introduce some of the usefulness of the measured Hf isotopes of zircon.
Yomogida, Takumi; Yamada, Shinya*; Ichinohe, Yuto*; Sato, Toshiki*; Hayakawa, Ryota*; Okada, Shinji*; Toyama, Yuichi*; Hashimoto, Tadashi; Noda, Hirofumi*; Isobe, Tadaaki*; et al.
no journal, ,
The reduction of uranium on biotite was studied to obtain insight into the immobilization of uranium in the environment. The chemical species of uranium in biotite were studied using a superconducting transition edge sensor and an X-ray emission spectrometer to remove interference from rubidium in biotite. As a result, the speciation of uranium in biotite collected from former uranium deposits was possible. The XANES spectra of the biotite indicated that the uranium in the biotite was partially reduced.
Yamaguchi, Akiko; Okumura, Masahiko; Takahashi, Yoshio*
no journal, ,
no abstracts in English
Fukuda, Shoma; Sueoka, Shigeru; Kagami, Saya; Kajita, Yuya*; Tagami, Takahiro*
no journal, ,
To understand geoscientific phenomena (e.g., magmatism, seismicity, and, orogenesis) that occur actively along plate subduction zones at the Earth's surface, a quantitative approach plays a key role in uplift/subsidence and denudation on various timescales to reveal the mechanism of strain release and accumulation. In this study, we focus on the Northeast Japan Arc (NEJA) as an island arc with a typical topographic alighnment, and attempt to estimate the mountain formation process of the Ou Backbone Range (hereinafter, OBR) which locates in the center axis of the NEJA as a volcanic arc, based on thermochronology. It is expected to lead to the proposal of a vertical deformation model for volcanic arcs distributed in the plate subduction zone. We have applied low-temperatures (
300 degree Celsius) thermochronometric approaches, mainly the apatite fission track and apatite (U-Th)/He (AFT and AHe, respectively) methods, to estimate the uplift of each island arc components (i.e., fore-arc, volcanic arc, back-arc) in the Northeast Japan Arc (NEJA). In this presentation, regarding the spatial distribution of ca. 20 AHe ages (39.1-1.5 Ma) and ca. 10 AFT ages (29.8-4.4 Ma) obtained so far in the southern part of the OBR, which already provided the doming uplift of the OBR, we attempted to obtain new AFT age data in order to expand the data for the blank areas where no ages were reported in order to develop a detailed uplift model. As a result, about 10 new AFT ages were obtained in the southern part of the OBR, ranging from a few tens to a few Ma. These results are consistent with the previously reported AFT ages, and suggest that the ages of a few Ma reflect uplift and denudation associated with strong compressive stress in the east-west direction after 3 to 2 Ma.
Nishimura, Hiroki*; Kozuka, Mariko*; Fukuda, Akari*; Ishimura, Toyoho*; Amano, Yuki; Beppu, Hikari*; Miyakawa, Kazuya; Suzuki, Yohei*
no journal, ,
no abstracts in English
Battulga, B.; Nakayama, Masataka; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
A growing attention has been addressed on microbial attachment and biofilm formation on plastic debris especially on microplastics (MPs; sizes: 5 mm) in the aquatic environment. The current study is focused on bacterial and fungal community composition, diversity, and structure in MP-associated biofilms to emphasize potential alteration of elemental cycling by the presence of MPs in the coastal aquatic environment. We collected MP, surface water, bottom sediment, and coastal sand samples from two contrasting coastal areas of Japan on a seasonal basis. Surface morphology and attached microorganisms on MPs were visually inspected by scanning electron microscopy (SEM). A high-throughput sequencing using Illumina MiSeq was performed in the collected samples to investigate the microbial community composition and diversity among different samples.
Munkhbat, D.*; Battulga, B.; Oyuntsetseg, B.*; Kawahigashi, Masayuki*
no journal, ,
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.
Shimada, Koji; Takeuchi, Ryuji; Omatsu, Keita*; Terusawa, Shuji*; Uehara, Yasuhiro*
no journal, ,
We retrieved 2 boring cores of basement rocks of granite from the Monju (prototype FBR at the Tsuruga city, the shore on the Sea of Japan) site. Excavation lengths are 100m and 200m. Objectives of the drilling are presence check of weak zones that could became as slip plane for slope failure, and large crush zones. Because of the presence of these zones can be problems for large-building constructions, we were asked for prompt confirmations. We tried, therefore, to measure the weight of each 1m core of granite during geological classification of the rock grades. The average wet density and data range of each rock classes as follows, classes B: wet density 2.53 (g/cm, same as below); range 0.10, CH: 2.51; 0.11, CM: 2.48; 0.42, CL: 2.42; 0.11. The decreased density (less than 2.42 g/cm) continuous zone of 5m (44-49m in depth of 100m hole) is corresponds to brecciated deterioration. This low-density zone is, however, shorter than the example of the Nojima active fault which possesses a few decameter scale zone, and discontinuous to the next 200m hole (distance between the two holes is about 30m). Therefore, the data identified do not show any large-scale weaknesses that would pose an immediate problem for the construction of heavy structures.
Abe, Takeyasu; Iida, Yoshihisa; Sasamoto, Hiroshi; Ishii, Eiichi
no journal, ,
In order to validate safety&performance assessment methodology of radioactive waste disposal, JAEA has been studying geochemical data of boring cores and groundwater in Horonobe. In this study, cation-exchange reactions of meteoric water infiltration zone of Neogene marine sediments in Horonobe were simulated by geochemical model. Calculation results of static cation-exchange in a batch system suggested that NaO/AlO
decrease and CaO/AlO increase should be observed in the infiltration zone. Expected geochemical features cannot be fully confirmed in measured geochemical data, and this result implies that other geochemical effects by additional chemical reactions and/or coupled reactive transport should be considered.
Kawasaki, Kazuo*; Hisashi, Kanta*; Yasue, Kenichi*; Niwa, Masakazu; Yokoyama, Tatsunori
no journal, ,
The Kurehayama Hills is located within the Toyama sedimentary basin that consists of late Pliocene to late Pleistocene clastic sediments. In the hills, the middle-late Pleistocene Kurehayama gravel formation unconformably overlay the Chokeiji sand formation. In this study, paleomagnetic analyses were carried out on 3 boring cores from the Kurehayama Hills to estimate deposition ages of the sand layers in the Kurehayama gravel formation. Most characteristic remanent magnetization (ChRM) directions obtained from three cores show positive inclination. However, negative inclination is found at all cores between ~26 m and ~29 m in depth with 10-30 cm thickness. Based on the ~0.6 Ma Kamitakara tephra found at the uppermost part of the Kurehayama gravel formation, the observed positive and negative inclination are likely one of four subschrons in the Matuyama Chron. The above layer of the studied sand layer consists of gravels and therefore detailed magnetostratigraphy is not clear. However, the observed magnetostratigraphic information could help to constrain the deposition ages of the Kurehayama gravel formation.