Late-Holocene salinity changes in Lake Ogawara, Pacific coast of northeast Japan, related to sea-level fall inferred from sedimentary geochemical signatures

Nara, Fumiko*; Watanabe, Takahiro; Matsunaka, Tetsuya*; Yamasaki, Shinichi*; Tsuchiya, Noriyoshi*; Seto, Koji*; Yamada, Kazuyoshi*; Yasuda, Yoshinori*

Palaeogeography, Palaeoclimatology, Palaeoecology, 592, p.110907_1 - 110907_11, 2022/04

https://doi.org/10.1016/j.palaeo.2022.110907

Radiocarbon dating, tephrochronology, and geochemical signatures such as bromine (Br), iodine (I), total sulfur (TS), total organic carbon (TOC), and total nitrogen (TN) in a continuous sediment core (OG12-2) were applied to estimate past salinity change on the Lake Ogawara, Pacific coast of northeast Japan. Since the Lake Ogawara was the inner bay of the Pacific Ocean and became the brackish lake in the late Holocene, clarifying the past salinity change on the lake Ogawara could give us important insight into the past sea level changes of the Pacific Ocean. The core OG12-2 has two tephra layers, the Towada eruption and the Changbaishan eruption (B-Tm: AD 946). The age model for the core OG12-2 was established using the radiocarbon measurements of the plant residues in the core, also was constrained by the B-Tm tephra. Depletions of marine-derived elements (Br, I, and TS), from 88.4 to 64.2 mg/kg, 20.0 to 14.1 mg/kg, and 3.1 to 1.1 mass %, respectively, were observed in the layers with 2200-2000 cal BP. These results indicate paleosalinity changes from saline (inner bay) to brackish conditions within Lake Ogawara caused by sea level fluctuations during the late Holocene.

Characteristics in trace elements compositions of tephras (B-Tm and To-a) for identification tools

Nara, Fumiko*; Yokoyama, Tatsunori; Yamasaki, Shinichi*; Minami, Masayo*; Asahara, Yoshihiro*; Watanabe, Takahiro; Yamada, Kazuyoshi*; Tsuchiya, Noriyoshi*; Yasuda, Yoshinori*

Geochemical Journal, 55(3), p.117 - 133, 2021/00

https://doi.org/10.2343/geochemj.2.0619

The absolute date of the Millennium Eruption (ME) of Changbaishan Volcano is widely recognized as AD 946. The Baegdosan-Tomakomai (B-Tm) tephra dispersed during the ME is a robust-age key bed. In order to identify the tephra, refractive index and major-element compositions of volcanic glass shards are conventionally used. However, trace-element analysis has been rarely carried out, especially for rare-earth elements (REEs) and for tephra layer bulk sediments. Here we present the datasets of major- and trace-element compositions datasets for the glass shards and bulk sediments of the B-Tm and Towada caldera eruptions (To-a) tephra deposits from the Lake Ogawara sediment core, Tohoku region, northern Japan. The depth profiles of the major and trace elements show the significant peaks for the KO and some trace elements (Zn, Rb, Zr, Nb, Sn, Y, La, Ce, Nd, Th, and U) at the B-Tm tephra layer in the Lake Ogawara sediment core, but no peaks of these elements at the To-a tephra layer. High concentrations of the trace elements in the B-Tm tephra layer were observed in individual glass shards as well as in the bulk sediment. These concentrations are highlighted by the elemental abundance pattern normalized by the crustal abundance. The elemental pattern in individual glass shards from other Japanese tephras showed significant differences from those of the B-Tm tephra, especially in REEs compositions. The trace-element compositions of the glass shards and bulk sediment show strong advantages for distinguishing the B-Tm tephra from other Japanese tephras.

New precise measurements of muonium hyperfine structure at J-PARC MUSE

Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.

EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01

https://doi.org/10.1051/epjconf/201919800003

The Anisotropy of the superfluid density in noncentrosymmetric CePtSi

Bonalde, I.*; Brmer-Escamilla, W.*; Haga, Yoshinori; Bauer, E.*; Yasuda, Takashi*; Onuki, Yoshichika

Physica C, 460-462(1), p.659 - 660, 2007/09

https://doi.org/10.1016/j.physc.2007.03.029

High pressure study on the heavy fermion superconductor CePtSi by AC calorimetry

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

Physica B; Condensed Matter, 378-380, p.381 - 382, 2006/05

https://doi.org/10.1016/j.physb.2006.01.472

We have determined the pressure-temperature phase diagram of heavy-fermion superconductor CePtSi by the ac heat capacity measurement. The Nel temperature = 2.2 K decreases with increasing pressure and becomes zero at the critical pressure 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa. The phase diagram of CePtSi is thus very unique and has never been reported before for other heavy fermion superconductors.

Evidence for novel pairing state in noncentrosymmetric superconductor CePtSi; Si-NMR Knight shift study

Yogi, Mamoru*; Mukuda, Hidekazu*; Kitaoka, Yoshio*; Hashimoto, Shin*; Yasuda, Takashi*; Settai, Rikio*; Matsuda, Tatsuma; Haga, Yoshinori; Onuki, Yoshichika; Rogl, P.*; et al.

Journal of the Physical Society of Japan, 75(1), p.013709_1 - 013709_4, 2006/01

https://doi.org/10.1143/JPSJ.75.013709

We report the measurements of the Si Knight shift K on the noncentrosymmetric heavy-fermion compound CePtSi in which antiferromagnetism (AFM) with =2.2 K coexists with superconductivity (SC) with =0.75 K. Its spin part K, which is deduced to be K0.11 and 0.16 at respective magnetic fields H=2.0061 and 0.8671 T,. does not decrease across the superconducting transition temperature Tc for the field along the c-axis. The temperature dependence of nuclear spin-lattice relaxation of Pt below Tc has been accounted for by a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. From this result, it is shown that the Knight-shift data are consistent with the occurrence of the two-component order parameter for CePtSi.

Two critical pressure in heavy fermion superconductor CePtSi

Tateiwa, Naoyuki; Haga, Yoshinori; Matsuda, Tatsuma; Ikeda, Shugo; Yasuda, Takashi*; Takeuchi, Tetsuya*; Settai, Rikio*; Onuki, Yoshichika

no journal, , 

Last year, Bauer et al. reported the co-existence of the superconductivity ( = 0.75 K) and antiferromagnetism (= 2.2 K) in CePtSi which has no inversion center in the crystal structure. We have investigated the pressure dependence of the antiferromagnetic and superconducting transition temperatures by ac heat capacity measurement. The Neel temperature decreases with increasing pressure and becomes zero at the critical pressure 0.6 GPa. On the other hand, the superconducting phase exists in a wider pressure region from ambient pressure to about 1.5 GPa, which is far above . The pressure phase diagram of CePtSi is thus very unique and has never been reported before for other heavy fermion superconductors.

Trace element distributions of Lake Ogawara sediment core: Implication for the past sea level change at the late Holocene

Nara, Fumiko*; Yamasaki, Shinichi*; Watanabe, Takahiro; Tsuchiya, Noriyoshi*; Yamada, Kazuyoshi*; Yasuda, Yoshinori*

no journal, , 

Lake Ogawara is located northernmost Honshu island Japan, Tohoku region alongside Pacific Ocean. In this study, the trace elements (Br and U) in the Lake Ogawara sediment core were analyzed using XRF to reconstruct the past sea level and salinity changes during the late Holocene. The depth profiles of the trace elements (Br and U) showed the gradual decrease from 160 cm depth to the top of the core (corresponding to ca. 2,200 cal BP). These results showed that the sea level was decreased at around 2,200 cal BP.