著者

窪田 薫

出版者

日本古生物学会

雑誌

化石 (ISSN:00229202)

巻号頁・発行日

vol.111, pp.5-16, 2022-03-31 (Released:2022-04-15)

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Unlike the tropical to subtropical areas where reef-building corals are distributed, high latitude paleoenvironmental records with high temporal resolution over the past centuries are scarce. Long-living bivalve shells can be a good candidate for paleoenvironmental recorders. In such a situation, it has recently been revealed that modern cold-water bivalve Mercenaria stimpsoni (Stimpson's hard clam) living in shallow seafloors of North Japan have a lifespan of over 100 years. In this review, details of sclerochronological analysis and analytical procedures oxygen stable isotope and radiocarbon measurements of M. stimpsoni shells collected from shallow seafloors of Funakoshi Bay and Otsuchi Bay are described. Then, ecological (e.g., shell growth patterns) and paleoenvironmental (e.g., oceanic currents, tsunamis) findings that were obtained through these analyses are described.

著者

窪田 薫

出版者

日本地球惑星科学連合

雑誌

日本地球惑星科学連合2018年大会

巻号頁・発行日

2018-03-14

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北日本の浅海底から見つかった二枚貝の一種ビノスガイ(Mercenaria stimpsoni)は100歳を超す寿命を持ち、日本産の二枚貝としては最長寿であることが最近明らかになった。本発表では、 岩手県大槌・船越湾から得られたビノスガイの殻の成長パターンについて概観するとともに、年輪解析と放射性炭素分析を通じて明らかになった、過去の海水の放射性炭素変動と、2011年3月の大津波に伴う船越湾のビノスガイの大量死について発表する。年輪幅の変動は個体間で同期しており、厳密な暦年代を構築することを可能にしている(年輪年代学)。複数個体のビノスガイの殻の放射性炭素分析結果をもとに、北西太平洋高緯度域としては初となる、1950~1960年代に盛んに行われた大気圏核実験に伴う14C濃度の急増を含む、海水の放射性炭素変動曲線(Bomb-14C曲線)を復元した。復元されたBomb-14C曲線の形状から、三陸沿岸の浅海域においては、津軽暖流(対馬海流を起源とする)の影響が強く見られることがわかった。さらに、得られたBomb-14C曲線を船越湾の海底から得られた死殻の高精度の年代決定ツールとして用いることで、2011年3月の大津波に伴う海底環境への擾乱がビノスガイの大量死を招いていたことが明らかになった。さらに、過去の大津波(1933年の昭和三陸地震および1896年の明治三陸地震)が同じくビノスガイの大量死を招いていた可能性についても示す。

著者

窪田 薫

出版者

一般社団法人日本地球化学会

雑誌

地球化学 (ISSN:03864073)

巻号頁・発行日

vol.54, no.2, pp.61-78, 2020-06-25 (Released:2020-06-25)

参考文献数

122

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Biogenic calcium carbonate (coral skeleton, foraminifera shell, bivalve shell, otolith, etc.) is one of the best archives of the past changes of aquatic environment that includes ocean, river, and lake. I have dedicated myself to the development and application of the environmental proxies such as trace element, stable isotope, and radiogenic isotope in calcium carbonate of marine organisms to study paleoclimate, paleoceanography, marine carbon cycle, and calcification processes of them. In this manuscript, I focus on boron isotope proxy of skeleton of marine calcifiers, coral and foraminifera, that are often used in paleoclimatology. Boron isotopes can record pH of the seawater, from which atmospheric carbon dioxide concentration can be estimated, thus it has been recognized as a holy grail in marine carbon cycle study. First, I review the mechanism of boron isotope as seawater pH proxy, history in technical development in the isotope measurement, issues with regard to fractionation factor between boric acid and borate ion in seawater, reconsideration of the boron incorporation mechanism into calcium carbonate skeleton, and recent findings. Then I overview my recent marine carbon cycle studies using boron isotope proxy in different timescales, since the Industrial Revolution (since 1750 C.E.) and since the last glacial period (since ~20,000 years ago).The boron isotopic composition was determined in high precision and accuracy by using thermal ionization mass spectrometry and multi-collector inductively-coupled plasma mass spectrometry in Japan Agency for Marine–Earth Science and Technology.

著者

窪田 薫 白井 厚太朗 杉原 奈央子 清家 弘治 棚部 一成 南 雅代 中村 俊夫 Kubota Kaoru Shirai Kotaro Sugihara-Murakami Naoko Seike Koji Tanabe Kazushige Minami Masayo Nakamura Toshio

出版者

名古屋大学宇宙地球環境研究所

雑誌

名古屋大学年代測定研究

巻号頁・発行日

vol.2, pp.1-6, 2018-03-31

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Mercenaria stimpsoni (Stimpson's hard clam), found in shallow sandy seafloor of northeast Japan, has been proved to have longevity of more than 100 years, which is the longest record in Japan. The present study established nuclear bomb testing induced bomb-14C records from M. stimpsoni shells, for the first time in high latitude western North Pacific, in which chronology is robustly constrained from a synchronized annual growth width pattern among individuals. The record revealed a strong influence of Tsugaru Warm Current on shallow water of northeast Japan. Furthermore, age-determination of dead shells collected from the seafloor of the study region by utilizing the established bomb-14C records suggests that past tsunamis are one of the most important reasons of death of M. stimpsoni.東北日本(岩手県大槌)から見つかった二枚貝の一種ビノスガイ(Mercenaria stimpsoni)は100歳を超す寿命を持ち,日本産の二枚貝としては最長寿であることが最近明らかになった.本研究では,ビノスガイの殻を用いて,複数個体間で同期した年間成長パターンをもとに厳密な年代モデルを構築し,東北地域としては初となる核実験起源の放射性炭素曲線を復元した.その結果,三陸沖の浅海域においては,津軽暖流(対馬海流を起源とする)の影響が強く見られることがわかった.さらに,得られた放射性炭素曲線を大槌の海底から得られた死殻の死亡年代の推定に用いることで,過去の津波イベントがビノスガイの死を招く重要な要因になっている可能性が示された.

著者

窪田 薫

出版者

理学系研究科地球惑星科学専攻

巻号頁・発行日

2015-03-24

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学位の種別: 課程博士

著者

窪田 薫

出版者

東海大学

雑誌

東海大学紀要. 文学部 (ISSN:05636760)

巻号頁・発行日

vol.12, pp.47-60, 1969

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Princess Nukata (630〜715 or more), one of the greatest poetesses in Japan, was a priestess in the Court. Her first poem (Manyo, No. 7) remaining in the Manyo-shu (万葉集) is a tanka (a Japanese ode with 31 syllables) reciting yrically her dear recollection of the cottage life in her adolescence when the ritual of the priestesses-in-Court was held at Udi (宇治) in 644 A. D. They thatched the hut with spiritual miscanthus which they had cut for themselves upon the beautiful autumn field. There in the mysterious cottage, she probably, as a hostess-of-god, accepted Prince Ohoshiama(大海人) as a guest-god, conceiving Princess Toiti (十市). Her second poem (M., No. 9) was made in 659 when the amily of the Queen Saimei (斉明) visited the spa of Ki (紀) located at the sea-side with scenic beauty. This tanka has been very famous for its enigmatical letters giving hitherto no satisfactory solution. According to my decipherment, the uzzling poetry reads as follows : Thou shalt keep serene, oh, the Calm Sea! Th' My Crown Prince might stand under the oly Oak To perform the Archery Rite divining New Year. When the capital was removed to Afumi (近江) on the Lake Biwa (琵琶湖) in 667, the King Tenti (天智) ordered her to make odes (M., No. 17,18,19) for the chorus to pacify the master-spirit of Mt. Miwa (三輪山), standing by the old capital. We find with interest, in those odes of hers, flattery to the awful master of the mountain and high-handed attitude to the less dire spirit of the hanging clouds. With respect to her lineage of much doubtfulness, the diagram shown on the next page is my speculative proposal to be repared for the settlement.