研究者詳細 - 南　雅代

論文 - 南　雅代

分割表示 375 件中 61 - 80 件目／全件表示 >>

Sr-87/Sr-86 age determination by rapidly formed spherical carbonate concretions (9, 1003, 2019) 査読有り

Yoshida Hidekazu, Asahara Yoshihiro, Yamamoto Koshi, Katsuta Nagayoshi, Minami Masayo, Metcalfe Richard

SCIENTIFIC REPORTS 9 巻 ( 1 ) 頁： 7184 2019年5月

高崎の烏川に産する巨石「聖石」の起源査読有り

佐藤興平・南雅代・武者巌・柴田賢

群馬県立自然史博物館研究報告 23 巻頁： 49 - 56 2019年3月

火山泥流に含まれる木片の14C不一致年代：前橋泥流と塚原泥流の例

南雅代, 中村俊夫

群馬県立自然史博物館研究報告 23 巻頁： 57 - 64 2019年3月

Landscape and early farming at Neolithic sites in Slemani, Iraqi Kurdistan: A case study of Jarmo and Qalat Said Ahmadan. 査読有り国際共著

Tsuneki, A., Rasheed, K., Watanabe, N., Anma, R., Tatsumi, Y., Minami, M.

Paleorient 45 巻 ( 2 ) 頁： 33-52 2019年

西アジアの古環境復元に向けてーイラン北西部のザグロス山脈に分布する石灰質化学沈殿岩の現地調査報告

南雅代

新学術領域研究(研究領域提案型)「都市文明の本質：古代西アジアにおける都市の発生と変容の学際研究」研究成果報告2018年度 - 巻頁： 143 - 148 2019年

Fe-oxide concretions formed by interacting carbonate and acidic waters on Earth and Mars

Yoshida H., Hasegawa H., Katsuta N., Maruyama I., Sirono S., Minami M., Asahara Y., Nishimoto S., Yamaguchi Y., Ichinnorov N., Metcalfe R.

SCIENCE ADVANCES 4 巻 ( 12 ) 2018年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Science Advances

Spherical Fe-oxide concretions on Earth, especially in Utah, USA, have been investigated as an analog of hematite spherules found in Meridiani Planum on Mars to support interpretations of water-rock interactions in early Mars. Although several formation mechanisms have been proposed for the Fe-oxide concretions on Earth, it is still unclear whether these mechanisms are viable because a precise formation process and precursor of the concretions are missing. This paper presents evidence that Fe-oxide concretions in Utah and newly found Fe-oxide concretions in Mongolia had spherical calcite concretions as precursors. Different formation stages of calcite and Fe-oxide concretions observed, both in Utah and Mongolia, indicate that calcite concretions initially formed within eolian sandstone strata and were dissolved by infiltrating Fe-rich acidic waters to form spherical FeO(OH) crusts due to pH buffering. The similarity between these Fe-oxide concretions on Earth and the hematite spherule occurrences in Meridiani Planum, combined with evidence of acid sulfate water influences on Mars, suggest that the hematite spherules also formed from dissolution of preexisting carbonate spherules possibly formed under a dense carbon dioxide early martian atmosphere.

DOI： 10.1126/sciadv.aau0872

Web of Science

Scopus

Sr-87/Sr-86 compositional linkage between geological and biological materials: A case study from the Toyota granite region of Japan

Minami M., Suzuki K.

CHEMICAL GEOLOGY 484 巻頁： 224 - 232 2018年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemical Geology

The strontium isotope value (87Sr/86Sr) is often used to identify the origins of agricultural products and the movements of ancient people. Maps delineating the distribution of 87Sr/86Sr values can therefore be of great use. Previous 87Sr/86Sr distribution maps of stream sediments covering small areas of Japan largely reflect the 87Sr/86Sr values of underlying bedrock. It remains unclear, however, whether the 87Sr/86Sr values of stream sediments may also reflect the 87Sr/86Sr values of the nearby vegetation and fauna. We sought to resolve this question by investigating the relationship between 87Sr/86Sr values in biological samples and in geological samples from the sites from which the biological samples grew. The geological samples consisted of soil samples from 2 paddy fields and 13 bed sediment samples (grain size <180 μm) from streams surrounding the paddy fields. All were collected from regions underlain by Inagawa granite bedrock, i.e., granite geology, around Toyota, Aichi Prefecture, Japan. The biological samples consisted of 4 rice plants and 1 wild boar bone, all collected in or near the same paddy fields. In the geological samples, the 87Sr/86Sr values of water-extracted Sr (water-soluble Sr) and ammonium-acetate-extracted Sr (exchangeable Sr) fractions in paddy soils were almost the same as each other (0.7098–0.7100) and slightly lower than the 87Sr/86Sr values of bulk Sr fractions (0.7099–0.7106). The 87Sr/86Sr values of biological samples (0.7098–0.7100) were also similar to those of the water-soluble Sr and exchangeable Sr fractions in paddy soils, though they varied among the parts of plants analyzed. This indicates that exchangeable Sr is absorbed by plants from soils through nutrients and water, and ingested by herbivorous animals from soils through plants and water. The 87Sr/86Sr values of bulk Sr in paddy soils ranged somewhat widely, while those from stream sediments collected around paddy fields were less variable (0.7099–0.7100). The difference in 87Sr/86Sr values between the paddy soils and stream sediments, samples similarly derived from Inagawa granite bedrock, may be related to the variable degree of weathering, and ultimately to the mineral composition, of the samples. This difference, however, was smaller than the range of 87Sr/86Sr values observed in the watershed geology. We therefore propose that in a silicate-dominated geology of the type typical of Japan, an 87Sr/86Sr spatial distribution map (using both exchangeable Sr and bulk Sr fractions in stream sediments) can provide useful guidance for identifying the geographic origins of food or for serving other related purposes.

DOI： 10.1016/j.chemgeo.2018.03.013

Web of Science

Scopus

Pseudo-fixed dead time circuit for designing and implementation of JEOL-type X-ray counting systems

Kato Takenori, Suzuki Kazuhiro, Jeen Mi-Jung, Minami Masayo

CHEMICAL GEOLOGY 484 巻頁： 16 - 21 2018年5月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemical Geology

Quantitative electron probe microanalysis (EPMA) of trace elements using wavelength dispersive spectrometers (WDS) requires high probe current and/or accelerating voltage and long X-ray sampling times to measure weak X-ray signals from target materials. The X-ray count rate of a standard material is extremely high when measured under the same conditions. Consequently, the accuracy of the dead time correction becomes a significant issue for quantification. Accurate dead time correction requires an exact knowledge of the X-ray counting system, including the behavior of the proportional counter and electronic circuits. Each spectrometer has a specific dead time that depends on factors such as electronic circuit design, counter bias, and X-ray energies. The dead time also changes with aging degradation. A pseudo-fixed dead time correction circuit with non-extendable approximation is described that prevents systematic errors in quantitative EPMA caused by inappropriate dead time corrections. The circuit, which is added to the output of the single channel analyzer, includes one extendable and two non-extendable dead time generators with dead times of 0.68 μs, 1.08 μs, and 1.92 μs, respectively. The behavior of the whole system can be treated as non-extendable for most applications, with a dead time of approximately 2.01 μs. The pseudo-fixed dead time circuit suppresses systematic error of the dead time correction to 0.6% or less when the original dead time is between 0.8–2.0 μs and the true X-ray count rate is < 200 kcps. This makes it possible to perform accurate dead time corrections without periodic measurement of the dead time throughout the life of the proportional counter by implementing a high-precision crystal oscillator in the system.

DOI： 10.1016/j.chemgeo.2017.12.030

Web of Science

Scopus

Generalized conditions of spherical carbonate concretion formation around decaying organic matter in early diagenesis 査読有り

Yoshida Hidekazu, Yamamoto Koshi, Minami Masayo, Katsuta Nagayoshi, Sin-ichi Sirono, Metcalfe Richard

SCIENTIFIC REPORTS 8 巻 ( 1 ) 頁： 6308 2018年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

Isolated spherical carbonate concretions observed in marine sediments are fascinating natural objet trouve because of their rounded shapes and distinct sharp boundaries. They occur in varied matrices and often contain well preserved fossils. The formation process of such concretions has been explained by diffusion and rapid syn-depositional reactions with organic solutes and other pore water constituents. However, the rates, conditions and formation process of syngenetic spherical concretions are still not fully clear. Based on the examination of different kinds of spherical concretions from several locations in Japan, a diffusion based growth diagram was applied to define the generalized growth conditions of spherical concretions formed around decaying organic matter. All analytical data imply that the spherical concretions formed very rapidly, at least three to four orders of magnitude faster than previously estimated timescales. The values indicate that spherical concretions are preferentially grown within clay- to silt-grade marine sediments deposited in relatively deep (a few tens of metres) environments dominated by diffusive solute transport, very early in diagenesis.

DOI： 10.1038/s41598-018-24205-5

Web of Science

Scopus

PubMed

Bomb-C-14 Peak in the North Pacific Recorded in Long-Lived Bivalve Shells (Mercenaria stimpsoni) 査読有り

Kubota Kaoru, Shirai Kotaro, Murakami-Sugihara Naoko, Seike Koji, Minami Masayo, Nakamura Toshio, Tanabe Kazushige

JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 123 巻 ( 4 ) 頁： 2867 - 2881 2018年4月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Geophysical Research: Oceans

The excess radiocarbon produced by nuclear bomb testing in the atmosphere in the 1950s–1960s (bomb-14C) is used as a tracer in the surface ocean, extending our understanding of geophysics and biogeochemical cycles. However, there is no bomb-14C record for the high-latitude western North Pacific Ocean because of the paucity of long-lived marine calcifying organisms equivalent to reef-building corals. The shells of Stimpson's hard clam, Mercenaria stimpsoni, potentially provide such a record because the clam's lifespan is very long (>100 years). We analyzed 14C in six live-caught M. stimpsoni shells from the western North Pacific (39.4°N, 142°E) and report, for the first time, the bomb-14C record with robust calendar ages based on annual growth increments. The value was constant in 1934–1952 (Δ14C = −66‰), with a sudden increase in 1959, a peak in 1974 (107‰), which was 60‰ lower than that of the Kuroshio Current, a gradual decline after 1974, and a current value of 16–18‰, which is ∼10‰ higher than the atmospheric value. The bomb-14C values are between the Kuroshio Current (the northwestern subtropical gyre) and Oyashio Current (the Western Subarctic Gyre) values, suggesting that the Tsugaru Current, downstream from the Kuroshio Current, mixes with the Oyashio Current after passing through Tsugaru Strait.

DOI： 10.1002/2017JC013678

Web of Science

Scopus

関東山地北西縁下仁田地域に産する珪長質火成岩体のU-Pbジルコン年代査読有り

佐藤興平・竹内誠・鈴木和博・南雅代・柴田賢

群馬県立自然史博物館研究報告 22 巻頁： 79 - 94 2018年3月

木片の14C年代測定による前橋泥流堆積時期の再検討（予察）査読有り

南雅代, 中村俊夫

群馬県立自然史博物館研究報告 22 巻頁： 95 - 101 2018年

初期続成過程における巨大球状炭酸塩コンクリーション形成

村宮悠介, 吉田英一, 山本鋼志, 南雅代

地質学雑誌 123 巻 ( 11 ) 頁： 939 - 952 2017年11月

記述言語：日本語出版者・発行元：一般社団法人日本地質学会

球状炭酸塩コンクリーションは，世界各地の様々な地質時代の海成層から普遍的に産するが，その形成過程はいまだ完全には理解されていない．本研究では，愛知県知多半島の先端部に分布する中新統師崎層群下部豊浜累層中にみられる長径約1.5mの巨大ドロマイト質コンクリーションについて，その形成過程を明らかにすることを目的に，堆積学的および地球化学的な種々の観察・分析を行った．その結果，埋没深度数百mに達するまでのごく初期続成過程においてメートルサイズの巨大なコンクリーションが形成することが示された．その形成時間は数十年と見積もられ，これまで考えられていた巨大炭酸塩コンクリーションの形成速度よりもはるかに速いものである．

DOI： 10.5575/geosoc.2017.0039

CiNii Research

J-GLOBAL

Comparing the Sr-87/Sr-86 of the bulk and exchangeable fractions in stream sediments: Implications for Sr-87/Sr-86 mapping in provenance studies 査読有り

Jomori Yuka, Minami Masayo, Sakurai-Goto Akiko, Ohta Atsuyuki

APPLIED GEOCHEMISTRY 86 巻頁： 70 - 83 2017年11月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Geochemistry

We are preparing a nationwide distribution map of strontium isotope ratio (87Sr/86Sr) in Japan, using stream sediment to obtain basic 87Sr/86Sr data for the provenance analysis of food production and archaeological substances. To clarify the effect of particle size on 87Sr/86Sr in stream sediments, we analyzed stream sediment from the Shigenobu River system in Matsuyama, Ehime Prefecture, Japan, where a variety of silicate-dominated lithologies, that is, several bedrocks of andesitic, granitic, and siliciclastic sedimentary rocks, are distributed. This paper reports elemental concentrations and 87Sr/86Sr in stream sediments for six particle-size fractions (1000–500, 500–300, 300–180, 180–125, 125–75, and <75 μm). The results from stream sediments were compared with results from bedrock units and stream water over the catchment. The elemental concentrations in stream sediment tended to increase with decreasing particle size in all lithologies; however, Sr concentrations varied less than other elements across particle sizes. For most of the samples, 87Sr/86Sr varied by less than 0.001 among the six particle-size fractions, which was less than the variation among the different lithologies. Therefore, 87Sr/86Sr in the <180 μm particle-size fraction, which is normally used in Japanese nationwide geochemical mapping, should be a reliable proxy for bedrock 87Sr/86Sr. The 87Sr/86Sr values in water samples from the Shigenobu River system were lower and less variable than 87Sr/86Sr in the stream sediments, and they did not faithfully correspond to the watershed geology. The inconsistency may reflect selective dissolution of Sr from plagioclase. Interestingly, 87Sr/86Sr values of the exchangeable fraction of stream sediment in the <180 μm fraction were strongly correlated with 87Sr/86Sr of stream water samples. Because 87Sr/86Sr in plant and animal bodies reflects that of their water sources, the exchangeable fraction of stream sediment may be a useful proxy for geochemical provenance in Japan instead of stream water.

DOI： 10.1016/j.apgeochem.2017.09.004

Web of Science

Scopus

Grain-size variations in Sr-87/Sr-86 and elemental concentrations of stream sediments in a granitic area: Fundamental study on Sr-87/Sr-86 spatial distribution mapping

Minami Masayo, Jomori Yuka, Suzuki Kazuhiro, Ohta Atsuyuki

GEOCHEMICAL JOURNAL 51 巻 ( 6 ) 頁： 469 - 484 2017年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本地球化学会

The strontium isotope ratio (87Sr/86Sr) is often used to identify the origin of agricultural products and the movement of ancient people, and a nationwide 87Sr/86Sr distribution map would greatly assist such studies. The Geological Survey of Japan (GSJ), AIST has already created nationwide element distribution maps using the <180 μm fraction of stream sediments, but this grain size fraction may not necessarily be suitable for mapping the 87Sr/86Sr isotopic ratio. Therefore, this study investigated the effect of grain size on elemental concentrations and 87Sr/86Sr ratios in stream sediments and compared their values with those of the source rocks. The stream sediments studied were collected from the granitic drainage basin of the Yahagi and Yada rivers in Aichi Prefecture, central Japan. The elemental concentrations and 87Sr/86Sr ratios of five fractions in the size range 1000-75 μm from the stream sediments of the Yahagi River tributaries varied with the grain size, and the variations corresponded to the heterogeneity of the mineral compositions in each fraction. The difference in the elemental concentrations and 87Sr/86Sr ratios among the sampling points was smallest in the 300-75 μm fractions, which showed 87Sr/86Sr and 87Rb/86Sr values that were closest to those of the source rocks. The coarser (>300 μm) and the fine (<75 μm) fractions of the stream sediments showed systematically higher 87Rb/86Sr and lower 87Sr/86Sr ratios than the Rb-Sr mineral isochron for the source rock, and the result suggests that 1) these fractions are enriched in K- and Rb-rich minerals such as K-feldspar, biotite, and hornblende; and 2) Sr is lost relative to Rb because of weathering processes. Furthermore, temporal variations in 87Sr/86Sr of the <180 μm stream sediments collected at a fixed sampling site in the Yada River were 0.001, which is smaller than the variations associated with grain size seen in the 87Sr/86Sr values in the granitic study area. Consequently, we concluded that, in granite areas, the <180 μm fraction of the stream sediments can be used for 87Sr/86Sr mapping, implying that a nationwide 87Sr/86Sr map can be made using sediment samples with a grain size of less than 180 μm.

DOI： 10.2343/geochemj.2.0478

Web of Science

Scopus

CiNii Research

A distinctive chemical composition of the tektites from Thailand and Vietnam, and its geochemical significance 査読有り

Lee, S-G., Tanaka, T., Asahara, Y., Minami, M.

Jour. Petrol. Soc. Korea 26 巻頁： 281-295 2017年

宮古島南東海岸のマイバーバマ東部に打ち上げられたハマサンゴ岩塊の14C年代とその意義

小元久仁夫, 南雅代

季刊地理学 69 巻 ( 3 ) 頁： 119 - 127 2017年

記述言語：日本語出版者・発行元：東北地理学会

Maibah beach is located between Higashihenna promontory and Miyato-zaki （promontory）, southeast of Miyako Island. Along the sandy beach, beachrock develops intertidal zone. A large boulder lying on the eastern part of the beach has been recognized as a fossil Tridacna gigas. We collected two samples from the boulder in order to determine the age of its outer layer, and noticed that the cross section was different from Tridacna gigas. The samples indicated obviously a characteristic of coralline structure. Then identification and radiocarbon dating of the samples were performed.The results show that coral is Porites sp. and probably in situ, and that it was transported from lagoon and beached on the shore, judged from the field observation. The calibrated ages were 1626 cal AD and 1679 cal AD, respectively. It is considered that Porites had transported and beached on the shore by huge tsunamis or high waves of typhoon. Unfortunately there was no huge typhoon record, and then we tried to correlate calibrated age of Porites with historical tsunami and earthquake records. According to historical record, Miyako Islands were attacked by strong earthquake of AD 1667 which probably caused tsunami. An average calibrated age of Porites （1653±23 cal AD） coincides with AD 1667 earthquake tsunami with a margin of statistical error. However, age of removed soft outer layers of Porites strongly suggests that it was transported from its original habitat to the present location not only by AD 1667 earthquake tsunami but also by AD 1771 Meiwa Tsunami.

DOI： 10.5190/tga.69.3_119

CiNii Research

炭化物の高確度14C年代測定のための試料調製法の検討

南雅代, 中村俊夫

第19回AMSシンポジウム・2016年度「樹木年輪」研究会報告集 1 巻頁： 82 - 85 2017年

A distinctive chemical composition of the tektites from Thailand and Vietnam, and its geochemical significance. 査読有り国際共著

南雅代

Jour. Petrol. Soc. Korea 26 巻頁： 281 - 295 2017年

CHANGES OF CHEMICAL STRUCTURE AND COMPOSITION OF CHARCOAL BY RADIOCARBON PRETREATMENTS: DECONTAMINATION BY ABA AND ABOx TREATMENTS 査読有り

Tomiyama Shinji, Minami Masayo, Nakamura Toshio, Mimura Koichi, Kagi Hiroyuki

RADIOCARBON 58 巻 ( 3 ) 頁： 565 - 581 2016年9月

記述言語：日本語出版者・発行元：Radiocarbon

Charcoal is widely used for radiocarbon dating in archaeological and paleoenvironmental studies. Reliable14C dating requires appropriate chemical treatment to remove postdeposition contamination from the charcoal samples. This study assesses two pretreatments: acid-base-acid (ABA) and acid-base-oxidation with stepped combustion (ABOx-SC). In addition to14C, the effects of the treatments on the chemical structure and composition of charcoal were studied using Fourier transform infrared spectroscopy (FTIR) and C/H/O elemental analysis. Samples of pine wood charred in the laboratory at 270, 300, 400, 500, and 600°C, and environmental samples of charred pine wood from pyroclastic flow deposits in southern Kyushu, Japan, were tested. The laboratory-charred samples showed that NaOH treatment removed highly hydrophilic organic components derived from endogenous and exogenous organic materials in the samples and that oxidation treatment caused the oxidative degradation of molecules in samples starting from its edges. The ABA-treated environmental charcoal yielded younger14C dates than the ABOx-treated samples, probably owing to the effects of remaining organic contaminants bound to the edges of the aromatic molecular structures produced by the original pyrolysis. Meanwhile, it was found that ABA-SC treatment can reduce contaminants as effectively as ABOx-SC treatment. This implies that the stepped combustion (SC), not the chemical oxidation, is the key to reduce contaminant residue left after ABA and ABOx treatments. The results in this study indicate that the investigation of the structural and compositional changes of charcoal during its pretreatment is useful for assessment of the reliability of the14C ages.

DOI： 10.1017/RDC.2016.29

Web of Science

Scopus

　前のページ - 次のページ　

<南 雅代>

論文 - 南 雅代

<南　雅代>

論文 - 南　雅代