BPT27-01

会場:104

時間:5 月 24 日 09:00-09:15

ガスキエス氷期の続成痕跡とそのエディアカラ紀層序に対する意義
Diagenetic signatures of the Gaskies glaciation and their implication to the Ediacaran
stratigraphy
狩野 彰宏 1∗ ; 古山 精史朗 2
KANO, Akihiro1∗ ; FURUYAMA, Seishiro2
1
1

九州大学, 2 産業総合研究所
Kyushu University, 2 AIST

地球史を通じて頻繁に生じた無機炭素同位体のエクスカーションは，生物進化と絶滅イベントと同調する一方で，大規模環境変動にも対応する. 多細胞動物が大きく進化したエディアカラ紀 (635 ? 542 Ma) においても，いくつかのエクス
カーションが記録されている．南中国に分布するエディアカラ系堆積岩である揚子プラットフォームは変成度が低く，解像度の高い無機炭素同位体比プロファイルが多く報告されている (e.g. Sawaki et al., 2010)．その多くは汎世界的であると認定できるが，Doushantuo 層中部に確認された負のエクスカーションは南部中国に特有のものであり，ガスキエス氷期に対比される (Tahata et al., 2013)．本研究では，湖南省北西部 Yangjiaping セクションで確認された約 15 ‰で細かな変動を持つ負のエクスカーション (Kunimitsu et al., 2011) について，セメントなどの続成成分を詳細に検討した．特異なエクスカーションが確認されたのは，Yangjiaping セクションの Doushantuo 層 Unit 3 中部?上部である．ここでは，方解石セ
メントの無機炭素同位体が˜25 ‰，酸素同位体が˜2 ‰ほど全岩の値より低いことが分った．これを説明するための最も有力なプロセスは，天水続成環境での有機物酸化である．方解石セメントを生成するためには，やや嫌気的な環境で起こる硫酸還元とのカップリングが想定され，共産するパイライトはそれを支持している．Yangjiaping セクションは化石産出で有名な貴州省 Wengan とともに南中国プラットフォーム内でも最も浅い位置にあり，海水準低下により堆積場は陸上に露出したと思われる．この負のエクスカーションのいくつかの特徴は模式値の Doushantuo 層中部や Wengan の古土壌層下位のエクスカーションとも共通する．すなわち陸上露出はエディアカラ紀中頃（580 Ma）に起きたガスキエス氷期にともなうものと考えられる．Doushantuo 層 Unit 3 にはリン酸に富む堆積物があり，氷期に伴う湧昇水強化を暗示する。ガスキエス氷期は栄養塩と酸素を海洋に効率的に循環させ，その後の動物進化を促したと考えられる．

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BPT27-02

会場:104

時間:5 月 24 日 09:15-09:30「カンブリア紀の農耕革命」はいつ始まったのか？
When did the ”Cambrian agronomic revolution” start?
矢田 圭吾 1∗ ; 大路 樹生 2 ; ドーンボス スティーブ 3 ; 長谷川 精 2 ; ゴンチグドルジュ セルスマ 4 ;望月 貴史 5 ; 高柳 栄子 4 ; 井龍 康文 6
YADA, Keigo1∗ ; OJI, Tatsuo2 ; DORNBOS, Stephen3 ; HASEGAWA, Hitoshi2 ; GONCHIGDORJ, Sersmaa4 ;MOCHIZUKI, Takafumi5 ; TAKAYANAGI, Hideko4 ; IRYU, Yasufumi6
1

名古屋大学大学院環境学研究科, 2 名古屋大学博物館, 3 ウィスコンシン大学, 4 モンゴル科学技術大学, 5 岩手県立博物館,
東北大学大学院理学研究科
1
Graduate School of Environmental Studies, Nagoya University, 2 Nagoya University Museum, Nagoya University, 3 Universityof Wisconsin-Madison, 4 Mongolian University of Science and Technology, 5 Iwate Prefectural Museum, 6 Department of Earth
Science, Tohoku University
6

カンブリア紀に多様な底生生物が出現し、海底の堆積物は撹拌され始め、エディアカラ紀に広く海底を覆っていた微生物マットが衰退した。この現象は「カンブリア紀の農耕革命」 (Seilacher and Pfluger, 1994) と呼ばれ、エディアカラ紀からカンブリア紀に入る際に起きた、底質、底生動物活動の大きな変化と捉えられている。従来の研究ではエディアカ
ラ紀に農耕革命が始まっていた明確な証拠は見出されていない。しかし我々はモンゴル西部のエディアカラ系から、海底下に深く潜入した動物活動の証拠を得ることができ、当時活発な底生動物活動が明瞭に始まっていたことが明らかになったので、ここに報告する。
モンゴル西部の Govi Altay 地域には原生代後期〜カンブリア紀の地層が広く分布する。その中で Bayan Gol 渓谷南部に発達するエディアカラ系上部の層状石灰岩中の 11 の層準から垂直かつ大型の穿孔痕Arenicolites isp. を多数確認することができた。Arenicolites isp. は最深で約 4 cm 垂直方向に潜入している。同地域において 2 m 間隔で資料サンプルを採集し、炭素同位体比の測定を行い、他地域との対比を行った。
Arenicolites isp. が含まれる層準は Tsagaan Oloom Formation 上部にあり、カンブリア紀の基底を示す生痕化石
Treptichnus pedum が初産出する層準よりも 190 ‐ 140 m 下位に位置する。炭素同位体比測定の結果から、Arenicolites
isp. が含まれる層準は Pc/C 境界付近に対比される BACE event より 120 ‐ 70m 下位に位置すると判断される。したがってArenicolites isp. を産する層準はエディアカラ系上部と考えられる。これらの結果から、「カンブリア紀の農耕革命」が地域によってはエディアカラ紀にすでに始まっていたということが考えられる。モンゴル西部で他地域より早く「カンブリア紀の農耕革命」が始まったのはおそらく地理的な理由、すなわち当時モンゴルが低緯度に位置していたことと関係していたと推察される。

キーワード: エディアカラ紀, カンブリア紀, 生痕化石, カンブリア爆発, カンブリア紀の農耕革命
Keywords: Ediacaran, Cambrian, ichnofossil, Cambrian explosion, Cambrian agronomic revolution

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BPT27-03

会場:104

時間:5 月 24 日 09:30-09:45

GSSP セクションに記録された後期デボン紀大量絶滅時の土壌浸食事件
Soil erosion event during the Late Devonian mass extinction recorded at the GSSP section
三浦 真実 1∗ ; 海保 邦夫 1 ; カジエ ジャンジョルジュ 2
MIURA, Mami1∗ ; KAIHO, Kunio1 ; CASIER, Jean-georges2
1
1

東北大学, 2 ベルギー王立自然史博物館
Tohoku University, 2 Royal Belgian Institute of Natural Sciences

The Late Devonian mass extinction occurred in a stepwise manner and culminated close to the Frasnian-Famennian (F-F)
boundary (372 million years ago). Organic-molecular indices from marine sedimentary rocks at the GSSP section at Coumiac,France, indicate that the sequence of soil erosion and euxinia occurred close to this boundary. The increased concentrationsof organic molecules indicating combustion and soil erosion measured in the Coumiac section suggest that terrigenous organic
matter flowed into the ocean at this time, leading to reduction of the ocean that caused marine extinctions. Since this soil erosion
event simultaneously occurred at the Sinsin section in Belgium (Kaiho et al., 2013), expansion of the reducing environment of
the ocean due to soil inflow is thought to have occurred in a wide area. The study of sedimentary organic molecules presents
several lines of evidence to link reduction of the ocean due to soil erosion to the Late Devonian mass extinction.
Kaiho, K., Yatsu, S., Oba, M., Gorjan, P., Casier, J.-G., Ikeda, M., 2013. A forest fire and soil erosion event during the Late
Devonianmass extinction. Palaeogeogr. Palaeoclimatol. Palaeoecol. 392, 272-280.
キーワード: 大量絶滅, デボン紀, 土壌浸食
Keywords: mass extinction, Devonian, Soil erosion

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BPT27-04

会場:104

時間:5 月 24 日 09:45-10:00

形態空間分布パターンと種‐個体数関係に基づく絶滅・回復イベントの様式の評価
方法
Assessment of mode of extinction and recovery based on changes in morphospace andspecies-abundance relationship
生形 貴男 1∗UBUKATA, Takao1∗
1
1

京都大学
Kyoto University

Morphological disparity has been attracting attention as a clue for understanding mode of mass extinction because selective
extinctions readily reduce the disparity than do random extinctions. In recent years, changes in morphospace occupation are
also used to assess selectivity of extinction and subsequent recovery. However, hitherto approaches to this subject have been
based on among-species variation and have omitted abundance of each species. Recent developments of database systems suchas the Paleobiology Database allow us to utilize data of collection-based occurrences as a proxy of abundance of each species.
Here I would propose a method to determine which model of extinction and recovery best explains the observed data on speciesabundance relationship as well as on the patterns of morphospace occupation. In the present method, the mode of mass extinction
and subsequent recovery is categorized into three models: 1) random extinction and random recovery, 2) selective extinction andrandom recovery and 3) selective extinction and selective recovery. The method is based on a statistical model selection inwhich each model is rated in terms of congruence with observed data according to an information criterion. Likelihood functions
are computed for various model conditions through simulations of extinction and origination. Prior to the simulations, themorphological values and the number of fossil occurrences are provided for each species through measurements and tabulationof database information. In the simulation of mass extinction, a given percentage of actual occurrences are stochastically removed
from the morphospace. In the case of selective extinction, fitness is defined as a function of a morphological variable to determine
the probability of removal for each occurrence with a value of the variable. The recovery process is simulated by adding new
hypothetical occurrences to the morphospace such that the total number of species is same as the actual data. An addition of new
occurrence originates a new species or just increases abundance of a preexisting species randomly chosen. In the former case,morphological values of the new species are stochastically determined so that the new species is located in the neighborhoodof the ancestral species in the morphospace. In the selective recovery model, the fitness function defined above also determines
where a new occurrence is likely to be introduced in the morphospace. Maximum-likelihood estimation of model parameters
requires vast number of simulations with various conditions for each model. In order to select the best model among the three
scenarios, the present method refers to the Akaike Information Criterion and its modified version for a small sample sizes.
キーワード: 形態空間, 異質性, 大量絶滅と回復, 統計的モデル選択
Keywords: morphospace, disparity, mass extinction and recovery, statistical model selection

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BPT27-05

会場:104

時間:5 月 24 日 10:00-10:15

ペルム紀中期末の生相・環境変化：中緯度での応答
Changes in biofacies and environments at the end-Gudalupian: response in mid-latitude
磯崎 行雄 1∗ ; 林 隆太郎 1 ; 可児 智美 2
ISOZAKI, Yukio1∗ ; HAYASHI, Ryutaro1 ; KANI, Tomomi2
1
1

東京大学大学院, 2 熊本大学
University of Tokyo, 2 Kumamoto University

The Guadalupian-Lopingian boudnary (Permian) recorded the most significant environmental change in the Paleozoic on all
aspects; i.e. major global cooling, biodiversity decline, ocean chemistry, and even geomagnetism. Previous studies focused
mostly on the fossiliferous limetones deposited in low-latitude domains both in peri-Pangean shelves and mid-oceanic atoll
complexes. In order to check the relevant environmental changes in mid-latitude, the Iwaizaki Limestone in the South Kitakami
Blet, NE Japan, was analyzed in litho-, bio-, and isotope stratigraphy. In particular, the top part of the limestone, ca. 50 m-thickinterval, recorded the collapse of a patch reef complex. Except the Capitanian fusulines from the basal part of this interval, mostof the interval lacks index fossil. The present Sr isotope analysis newly identified the uniquely low Sr-ratio, as low as 0.7068,
throughout the interval, confirming the Capitanian age. The collapse of reef occurred during the Capitanian in accordance with
the Kamura cooling event, but probably much earlier than the low-latitude domains.
キーワード: ペルム紀, キャピタン世, 寒冷化, Sr 同位体比, 南部北上, 陸棚石灰岩
Keywords: Permian, Capitanian, cooling, Sr isotope ratio, South Kitakami, shelf limestone

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BPT27-06

会場:104

時間:5 月 24 日 10:15-10:30

ペルム紀中期末における陸棚礁の崩壊：北上山地岩井崎石灰岩の Sr 同位体層序
The collapse of a Capitanian (Middle Permian) reef: Sr-isotope profile at Iwaizaki, NEJapan
可児 智美 1∗ ; 磯崎 行雄 2 ; 林 隆太郎 2
KANI, Tomomi1∗ ; ISOZAKI, Yukio2 ; HAYASHI, Ryutaro2
1
1

熊本大学, 2 東京大学
Kumamoto University, 2 The University of Tokyo

The Iwaizaki Limestone in the South Kitakami Belt, NE Japan, represents shallow-marine shelf carbonates deposited along
the Guadalupian (Middle Permian) South China margin. The main part of the limestone is composed of massive fossiliferous
limestone (ca. 100 m) of reef complex, while the upper part (ca. 35 m thick) consists of interbedded limestone and mudstone.
This facies transition corresponds to the onset of reef collapse, and the disappearance of tropical fauna. The main part and thelowermost upper part yielded Capitanian (Upper Guadalupian) fusulines but the rest of the upper limestone is barren of index
fossils. As the overlying black mudstone yields Late Permian (Lopingian) ammonoids, the extinction-related G-L boundary
exists somewhere within the uppermost limestone or in much higher mudstones. In order to constrain the age of the fossil-free
uppermost limestone, we analyzed 87 Sr/86 Sr stratigraphy of the Iwaizaki Limestone, and correlated with the global secular trend.
The present results confirmed that the topmost Iwaizaki limestone, as well as the main part, has the same low 87 Sr/86 Sr ratioof 0.7068-0.7069. The extremely low 87 Sr/86 Sr ratio (<0.7069; the lowest values of the Phanerozoic) continued to the topmost
bedded limestone in the section. The coeval limestones in the world, including those at Akasaka and Kamura in Japan, recorded
a unique interval of extremely low 87 Sr/86 Sr ratio (0.7068-0.7070) as called the “Capitanian minimum” . Therefore, the topmost
Iwaizaki Limestone no doubt belongs to Capitanian, suggesting that the collapse of reef started clearly before the G-L boundary,probably by the onset of the putative Capitanian cooling.
Keywords: Permian, Sr isotope, shelf, South Kitakami belt, reef

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BPT27-07

会場:104

時間:5 月 24 日 10:30-10:45

硫黄・炭素同位体組成で推定するペルム紀中‐後期境界における海洋環境変遷
Sulfur and carbon isotope study for understanding environmental changes across the Middle/Late Permian boundary
丸岡 照幸 1∗ ; 磯崎 行雄 2
MARUOKA, Teruyuki1∗ ; ISOZAKI, Yukio2
1
1

筑波大学・生命環境系, 2 東京大学大学院・総合文化研究科
University of Tsukuba, 2 University of Tokyo

ペルム紀末の大量絶滅は顕生代最大規模であったとされているが、この絶滅イベントは単一の事象ではなく、ペルム
紀中期-後期 (Guadalupian-Lopingian; G-L) 境界、狭義のペルム紀-トリアス紀（Permian-Triassic; P-T）境界の二つのイベントからなることが指摘されている [1, 2]。生物相が回復するよりも前に次のイベントが起こったことで、絶滅の規模が拡大したと考えられている [3]。これまで狭義の P-T 境界に関わる研究は精力的に進められてきているが、G-L 境界に関わる研究例は少なく、何が起きたのかについては不明な点が多い。しかし、ペルム紀末の大量絶滅を本質的に理解する
ためには、G-L 境界に関する研究は不可欠であり、本研究でもこの境界について取り扱う。硫黄・炭素同位体比に関する議論を組み合わせて G-L 境界における海洋環境の変遷を議論する。
宮崎県高千穂町の上村地域に分布する古海山起源のペルム系中部上部統石灰岩を対象とした。海洋硫酸の硫黄同位体比の復元に使われる炭酸塩構造置換態硫酸 (carbonate-associated sulfate; CAS) は文献 [4] にある方法に従って回収した。
酸処理後の残渣を回収し、その硫黄・炭素同位体比分析も行った。残渣の硫黄・炭素同位体はそれぞれ硫化物・有機物の同位体を表す。炭酸塩鉱物の同位体に関しては、すでに Isozaki et al. [5] に報告があり、本研究でもその値を議論に用いる。
G-L 境界を挟む上位下位両方で、δ 34 SCAS と δ 13 Ccarbonate の逆相関を見出した。通常の海洋では、堆積物への有機物供給量の増加に伴い硫化物埋没量が増加する。前者は δ 13 Ccarbonate 、後者は δ 34 SCAS として記録されるので、これらの指標は正相関を示すことが多い。硫酸還元が堆積物内で起こっている酸化的な海洋では、バクテリアの利用可能な有機物のほとんどは堆積物に供給される前に（沈降中に）酸化されている。したがって、有機物供給量が増加すると（濃度が低いがわずかに残る）バクテリア利用可能有機物量が増加する。このために硫酸還元量は有機物供給量と相関する。
一方で、硫化水素が海水に存在するような貧酸素状態の海洋では、バクテリアによる硫酸還元によって沈降中の有機物が酸化分解される。このために硫化物生成量が増えると有機物埋没量は減少し、δ 34 SCAS -δ 13 Ccarbonate の逆相関を示すことになる。この逆相関の存在は、G-L 境界前後の海洋ですでに貧酸素環境が生じていたことを示している。
G-L 境界では δ 34 SCAS -δ 13 Ccarbonate 逆相関の傾きが変化している。これは海洋に供給される C/S 比が変化したことを示し、火山活動様式の変化を示している。境界後には CO2 により富んだ火山活動へと変化したことを示している。

[1] Jin, Y.G., Zhang, J. and Shang, Q.H. (1994) Can. Soc. Petr. Geol. Mem., 17, 813-822. [2] Stanley, S.M. and Yang, X.
(1994) Science, 266, 1340-1344. [3] Isozaki, Y. (2009) J. Asian Earth Sci. 36, 459-480. [4] Kampschulte, A., Bruckschen, P.,
Strauss, H. (2001) Chem. Geol. 175, 165-189. [5] Isozaki, Y., Kawahata, H. and Ota, A. (2007) Global Planet. Change 55,
21-38.

キーワード: ペルム紀中‐後期境界, 大量絶滅, 海洋無酸素, 炭酸塩置換体硫酸, パンサラッサ
Keywords: Guadalupian-Lopingian boundary, mass extinction, oceanic anoxia, carbonate-associated sulfate, Panthalassan paleoatoll carbonates

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BPT27-08

会場:104

時間:5 月 24 日 11:00-11:15

ペルム紀中期末における超海洋パンサラッサの窒素循環変動
Perturbations of the nitrogen cycle in mid-Panthalassa in the Late Guadalupian (Middle
Permian)斎藤 誠史 1∗ ; 西澤 学 1 ; 上野 雄一郎 2 ; 小福田 大輔 3 ; 磯崎 行雄 3 ; 高井 研 1
SAITOH, Masafumi1∗ ; NISHIZAWA, Manabu1 ; UENO, Yuichiro2 ; KOFUKUDA, Daisuke3 ; ISOZAKI, Yukio3 ;TAKAI, Ken1
1
1

海洋研究開発機構, 2 東京工業大学, 3 東京大学
JAMSTEC, 2 Tokyo Tech., 3 Univ. Tokyo

To examine the changes in the oceanic N cycle and their possible relationships to the extinction at the end-Guadalupian (Middle Permian), we analyzed the N isotopic compositions (d15 N) of the upper Guadalupian paleo-atoll limestone, accumulated on
the top of a mid-oceanic seamount in the superocean Panthalassa, at Akasaka in central Japan. The d15 N values of the limestone
are substantially high (ca. +20 permil on average) throughout the analyzed interval. These values are the highest in the previously reported d15 N records throughout the entire Phanerozoic. The substantially high d15 N values suggest enhanced oceanic
denitrification/anammox in the Capitanian (Late Guadalupian). Moreover, the present results revealed remarkably large d15 N
fluctuations in the analyzed limestone at Akasaka. We interpret that periodic expansion and reduction of the oxygen minimum
zone (OMZ) in mid-Panthalassa caused the observed d15 N fluctuations in the Capitanian. The suggested OMZ expansions may
have been attributed to the high productivity ’Kamura event’ in the surface oceans enhancing a biological pump. Chemostratigraphic correlations imply that the enhanced denitrification in the expanded OMZ may have been a global phenomenon in the
Capitanian. Widespread developments of the anoxic deep-waters prior to the extinction may have stressed the shallow-marine
biota by upwelling at the end-Guadalupian.

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BPT27-09

会場:104

時間:5 月 24 日 11:15-11:30

超海洋中央部起源の G-L 境界石灰岩に挟在されるクロムに富む層について
A unique Cr-enriched bed across the Guadalupian-Lopingian boundary (Permian) in midPanthalassan paleo-atoll carbonates
石川 晃 1∗ ; 磯崎 行雄 1 ; 小福田 大輔 1 ; 小豆川 勝見 1
ISHIKAWA, Akira1∗ ; ISOZAKI, Yukio1 ; KOFUKUDA, Daisuke1 ; SHOZUGAWA, Katsumi1
1
1

東京大学大学院総合文化研究科
The University of Tokyo, Komaba

We examined in detail the chemical composition of a thin clayey bed (˜1 cm) recognized at the Guadalupian-Lopingian boundary (G-LB) in the mid-oceanic paleo-atoll limestone in Japan (Kamura and Akasaka sections), to clarify whether or not the clayey
bed is the product of a large-scale explosive volcanism that led to the end-Guadalupian mass extinction (Isozaki and Ota, 2001;
Isozaki, 2007). Results of X-ray mapping and ICP-MS analyses revealed that the clay materials both in Kamura and Akasaka
are roughly identical in compositions and are characterized by high-chromium contents (ca. 3000 ppm in anhydrous basis).
This contradicts the previous notion that the bed represents rhyo-dacitic tuff brought by explosive eruption of acidic magma.
Despite this, the widespread occurrence of Cr-enrichment at the G-LB horizon is inferred from the fact that the G-LB mudstones
in continental shelf limestone in South China (Wangpo Bed at Chaotian and Shangsi sections) have geochemical affinity to the
Cr-rich clayey bed at Kamura and Akasaka sections deposited in western Panthalassa. From these data, together with the normal
platinum-group element signatures throughout the G-LB samples, we invoke a global fall-out of Cr-rich air-borne ash originatedfrom mafic or ultramafic magma, most likely related to the mantle plume-derived large igneous provinces (LIPs). This might bepossible at the initial phase of intrusion/eruption of basaltic to picritic magma that formed the Emeishan LIP in South China (˜260
Ma) or other continental LIPs emplaced during the breakup of the supercontinent Pangea, if such high-temperature magmas wereeffectively carbonated and hydrated through the reaction with the thick sedimentary piles of limestones and shales.
キーワード: 地球化学, ICP-MS, 粘土層, ペルム紀中ー後期, 大量絶滅, 峨眉山洪水玄武岩
Keywords: geochemistry, ICP-MS, clayey bed, Guadalupian-Lopingian boundary, mass extinction, Emeishan flood basalts

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BPT27-10

会場:104

時間:5 月 24 日 11:30-11:45

岐阜県郡上八幡地域でのペルム紀三畳紀境界の有機炭素同位体比変化
Organic carbon isotope changes at P-T boundary in Gujohachiman, Japan
田畑 美幸 1∗ ; 戎崎 俊一 2 ; 磯崎 行雄 3 ; 西澤 学 4 ; 藤崎 渉 1
TAHATA, Miyuki1∗ ; EBISUZAKI, Toshikazu2 ; ISOZAKI, Yukio3 ; NISHIZAWA, Manabu4 ; FUJISAKI, Wataru1
11

東京工業大学, 2 理化学研究所, 3 東京大学, 4 海洋研究開発機構
Tokyo Institute of Technology, 2 RIKEN, 3 University of Tokyo, 4 Japan Agency for Marine-Earth Science and Technology

There was large extinction from Guadalupian- Lopingian boundary (GLB) to Permian- Triassic boundary (PTB), ca. 260- ca.
251Ma (Sepkoski, 1984; Knoll et al., 1996; Isozaki, 1997; Stanley and Yang, 1994; Kaiho et al., 2005). The extinction will
have correlation with Oceanic environment (e.g. oxic level in ocean, climatic change). Black shale layer is observed in chert ofaccretionary complex in Japan and Canada. The layers indicate anoxic in entire Ocean (Oceanic Anoxic Events) (Isozaki, 1997).
However, the correlation between extinction and environmental changes is not known. Therefore, we need to study life cyclechanges and influence to oceanic environment in extinction by changes of carbon isotope ratio.
The stable isotope ratios d13Ccarb and d13Corg are believed to reflect the change in the global status of photosynthesis, sincebiological organisms preferentially use light carbon during photosynthesis. When the biological mass with light-carbon content
becomes large, the inorganic carbon (mantle CO2) in the atmosphere and ocean become heavier. In other words, carbon isotopechanges in carbonate and organic carbon will reflect carbon cycle changes by extinctions (Rothman et al., 2003; Tahata et al.,2014).
There were many previous studies of carbonate carbon isotope ratio from GLB to PDB. The carbon isotope records show
over +6 permil before GLB, calling to Kamura event. The d13Ccarb after Kamura event decrease to ca. 0 permil around GLB.
Moreover, the d13Ccarb decreases from ca. +3 permil to ca. -2 permil at PTB and shows large excursions from PTB to middle
Triassic (Isozaki et al., 2007a,b; Korte et al., 2005a,b; Payne et al., 2008). As the carbonate carbon isotope records, there areno continuous carbon isotope records of organic carbon from GLB to PTB, because the carbonate-rich rocks have low organic
contents and difficult to analyze organic carbon isotope ratio.
Accretionary complex in Gujohachiman, Gifu-ken, Japan constitute of alternation of chert and shale. The sediments show
continuous depositions in deep sea from GLB to PTB. We analyze organic carbon isotope ratio from continuous shale layers in
Gujohachiman, because the shale layers between shert layers have organic-rich.
The results of organic carbon ratio show coupling to carbonate carbon isotope changes, except for GLB. Organic carbon
isotope records in GLB decouple carbonate carbon isotope ratio. The carbon isotope change indicate to reflect to carbon cyclechanges by extinction.

キーワード: P-T 境界, 有機炭素同位体比, 炭素循環, 郡上八幡

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BPT27-11

会場:104

時間:5 月 24 日 11:45-12:00

ペルム紀末大量絶滅時の表層水還元化と大量土壌流入
Abrupt surface-water reduction accompanied with massive soil inflow during the endPermian mass extinction
海保 邦夫 1∗ ; 伊藤 幸佑 1 ; 齊藤 諒介 1 ; 宮地 崇至 1 ; 大庭 雅寛 1 ; 高橋 聡 2 ; ビスワス ラマン 1
KAIHO, Kunio1∗ ; ITO, Kosuke1 ; SAITO, Ryosuke1 ; MIYAJI, Takashi1 ; OBA, Masahiro1 ;TAKAHASHI, Satoshi2 ; BISWAS, Raman111東北大学, 2 東京大学
Tohoku University, 2 University of Tokyo

The largest mass extinction of biota in Earth history occurred at the end of the Permian Period, which led to a turnover ofbiosphere from Paleozoic Fauna to Modern Fauna. Siberian volcanism is the most possible cause, however, the direct causal
mechanism for the mass extinction is unclear. We report that the worst redox condition in the shallow sea appeared during themass extinction on the way to a gradual reduction of deep sea. An abrupt decrease in oxygen in the shallow sea is thought to bea direct cause of the marine mass extinction. A significant decrease in atmospheric oxygen should also have occurred during themass extinction to explain the shallow surface water reduction and land mass extinction.
A soil erosion event occurring at the end-Permian mass extinction has already been reported. However, those records are
restricted in a few near-shore sequences. We demonstrate that a organic-molecule soil-erosion proxies have peaks during theend-Permian mass extinction throughout the inner continental shelf to the upper continental slope in Paleotethys and a sea mountin the central Panthalassic ocean, and in contrast to this, no peaks at isolated platform area in Paleotethys and deep Panthalassic
ocean. Furthermore, we found high DBF/Phe ratio values throughout the inner continental shelf to the upper slope and a sea
mount, and low values at isolated platform, its slope, and in central deep ocean during the mass extinction. This phenomenon is
supported by other organic molecule proxies sourced from land. The distribution of soil erosion proxies in the end-Permian sea
clarifies that massive soil erosion event surly occurred during the end-Permian mass extinction.
In summary, abrupt surface-water reduction accompanied with massive soil inflow occurred during the end-Permian mass
extinction.

キーワード: 海洋還元, 土壌, ペルム紀, 三畳紀, 大量絶滅
Keywords: oceanic reduction, soil, Permian, Triassic, mass extinction

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BPT27-12

会場:104

時間:5 月 24 日 12:00-12:15

Os 同位体から探る超海洋パンサラッサにおけるトアルシアン海洋無酸素事変時の火成活動の影響Osmium isotope composition in the deep pelagic Panthalassa ocean during the Toarcian
Oceanic Anoxic Event
藤崎 渉 1∗ ; 上田 修裕 1 ; 須田 好 1 ; 佐藤 友彦 2 ; 澤木 佑介 1 ; 横山 哲也 1
FUJISAKI, Wataru1∗ ; UEDA, Hisahiro1 ; SUDA, Konomi1 ; SATO, Tomohiko2 ; SAWAKI, Yusuke1 ;YOKOYAMA, Tetsuya1
1

東工大地球惑星科学, 2 東工大地球生命研究所
Department of Earth and Planetary Science, Tokyo Institute of Technology, 2 Earth-Life Science Institute, Tokyo Institute ofTechnology
1

The Toarcian Oceanic Anoxic Event (T-OAE) represents one of the most significant paleo-environmental perturbations in
the Phanerozoic, which resulted in marked disruption to both the climate system and marine ecosystem. The causes for thiswidespread deposition of organic carbon-rich sediments under the reducing condition are still controversial. Several mechanisms
have been proposed to explain the occurrence of T-OAE including; abrupt seawater warming, an increase in continental weathering rates, enhanced rates of biotic turnover, atmospheric pCO2 changes, and ocean acidification. In particular, volcanic activities
in the large igneous Karoo-Ferrar province have been considered as the most fundamental trigger for the Toarcian perturbations.
Radiogenic Os isotope compositions of sedimentary rocks are useful for estimating the influx from both ancient basaltic magmatism and continental weathering. However, the relationship between biotic crisis, anoxic event, and the volcanic activity in the
deep pelagic environment is still ambiguous because of the lack of detailed Os isotope records during T-OAE. In this study, wereconstructed a detailed lithological column in the Inuyama area where the Pliensbachian to Toarcian deep-sea cherts well cropout along the Kiso river. For Os isotope analysis, we collected 12 chert samples from a section where two black bedded chert
intervals T-OAE1 and T-OAE2 were observed.
The rock powder was spiked with 190Os and 185Re prior to digestion. The sample was digested by CrO3-H2SO4 in a sealed
Carius tube at 240 oC for more than 48 hours. Subsequently, Os was separated by solvent extraction using CCl4 and backextracted from CCl4 into HBr, followed by the final purification using the micro-distillation method. The Os isotope ratios were
determined by N-TIMS at Tokyo Tech. Re-bearing solution after the CCl4 extraction was stored in a Teflon vessel, and Cr6+ inthe solution was completely reduced to Cr3+ by the addition of ethanol in order to avoid the disturbance of the elution profile ofthe following chromatography due to the coexistence of Cr6+. After this process, Re was purified by chemical separation using
an anion exchange resin, and the isotopic composition was determined using a quadrupole-type ICP-MS at Tokyo Tech. The Os
and Re concentrations were determined by the isotope dilution method.
The Re and Os abundances in 12 chert samples across T-OAE varied from 2.1 to 128.6 ng/g, and from 32.8 to 2284.3 pg/g,
respectively. The 187Os/188Os ratio in the samples before T-OAE1 decreased from 0.44 to 0.27, resulting in the minimum valueof 0.24 at the onset of T-OAE1. However, the 187Os/188Os ratio increased abruptly to be 0.77 towards the end of T-OAE1, anddecrease down to 0.30 at the interval between T-OAE1 and T-OAE2. During T-OAE2, the 187Os/188Os ratio gradually increased
up to 0.56. Take into account organic carbon isotope record in the same section by Grocke et al. (2011), we envisage the following
scenario for the cause of Os and C isotopic variation during T-OAE observed in the chert samples: The Karoo-Ferrar volcanic
activity induced an anoxic condition, which resulted in negative 187Os/188Os before T-OAEs. The Karoo-Ferrar volcanism
released significant amount of CO2, which triggered the global warming and continental erosion during T-OAE1. Subsequentgradual increase of Os isotope ratios most likely reflects its aftermath. These indicate that the Karro-Ferrar volcanism played an
important role for induing anoxic condition and global worming during Toarcian in the deep pelagic Panthalassa ocean.
Keywords: Toarcian Oceanic Anoxic Event, deep pelagic Panthalassa ocean, osmium isotope, Karoo-Ferrar volcanism

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BPT27-13

会場:104

時間:5 月 24 日 12:15-12:30

霊長類の誕生場に関する新モデルの提案
Birth place and migration history of primates: Proposal of new model
丸山 茂徳 1∗MARUYAMA, Shigenori1∗
1
1

東京工業大学地球生命研究所
Earth-Life Science Institute, Tokyo Institute of Technology

The origin and evolution of ancestor of human being, so-called Primates, has not been well known yet, although several
conflicting models were proposed so far. Here, a new model is proposed to satisfy (1) genomic phylogeny, (2) fossil evidence,and (3) paleogeographic constraints based on not only ocean-floor age constraints but also surface geology.
Birth place of Primates must have been a rift in the Gondwana ca. 100Ma, which was 25 m.y. earlier than 75Ma that wasestimated by most genome biologists. The existence of new world monkey (Platyrrhini) in South America can be explained
assuming the birth place of ancestor of new world monkey was between Antarctica and South America at 100Ma, migrated toSouth America and land bridge was disconnected at 34Ma between Antarctica and S. America. On the other hands, lemur andaye-aye in Madagascar could be migrated from northward-moving Indian continent around 65Ma to intercross with ancestral
primates originated in Madagascar that was migrated southward from Northeastern margin of African continent. Land bridge
between those two islands was generated as the result of rising plume at 65Ma between these two islands. Also, primates in
the Indonesian region could have been transported by fragmented continents disconnected from Antarctica-Australia (origin of
Borneo). Primates on the Indian continent arrived at Central South Asia at 50Ma, and highly diversified ecosystem was generated
by crown evolution which is the most bio-diverse region since then.

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BPT27-P01

会場:コンベンションホール

時間:5 月 24 日 18:15-19:30

日立カンブリア系赤沢層の変成凝灰岩から見いだされた海綿動物状組織
Spongy parenchyma found in meta-tuff of Hitachi Cambrian Akazawa Formation
田切 美智雄 1∗ ; 塙 勝利 2 ; 及川 晃 2
TAGIRI, Michio1∗ ; HANAWA, Katsutoshi2 ; OIKAWA, Akira211

日立市郷土博物館, 2 ジオネット日立
Hitachi City Museum, 2 Geonet Hitachi

阿武隈山地南端の日立変成地域にはカンブリア系が広く分布する（Tagiri et al., 2011）．カンブリア系赤沢層は島弧火山岩を原岩とする変成岩からなる地層で，砂泥質岩や石灰岩を原岩とする変成岩はほとんどない．変成作用は地域の南東部ほど弱く，火山岩組織がよく残っている．火山砕屑岩起源の変成岩もみられ，一部には凝灰岩組織が観察できる．しかし，これまで化石の報告は無い．今回，赤沢層の変成凝灰岩中に海綿動物状組織が多数発見されたので，これらを報告し，化石の可能性を示す．
海綿動物状組織がみられる変成凝灰岩試料は，宮田川河口の河床礫や，鮎川上流の赤沢層露出域の沢の転石として発見された．変成度は緑色片岩相程度で，細粒で片理は局所的にあり，層理が認められる．変成鉱物は緑泥石―角閃石―緑簾石―アルバイト―石英で，白雲母と黒雲母が少量含まれる．
これらの変成凝灰岩には，直径 2 mm 前後の球状のものが集合した海綿動物状組織が観察される．球状体の直径は5˜0.5 mm である．球状体集合部は断面で層理面に平行に転倒した楕円状ないし眼球状の形で．層理面上では楕円形である．球状体集合部の大きさは層理面に垂直な断面で 0.5˜4 cm 程度，層理面に平行な面で 1˜10 cm 程度である．基質部は暗色で，球状体集合部内で球状体とその基質部の割合では，基質部の方が多い．１つの集合部では球状体の大きさはそろっていることが多い．また，球状体は集合部の縁に多い傾向がある．
球状体は珪質物質から構成されている．球状体には２˜３層の球果層構造が観察されるものと，球体の一方が基質部につながっていて，球状層が開いているものとがある．この場合に，球体の形を保ったまま球状層が開いたものと，球体の形が崩れて開口部が大きくなり，球状体中心部が基質につながっているものとがある．また，球状体内部が数個の小室に細分されているものもある．球状体には長楕円形のものや柔軟に変形した形のものも多い．球状体が球状体集合部の縁部内面に配列しているものや，いくつかの球状体が接したり合体したりするもの，球状体が直線状に配列するもの
や，白色部が糸状になったものまである．球状体の外殻部は白色度が高く，微小石英結晶で構成されている．球状体の中心部は灰色で，微細な結晶質物質の集合である．球状体には，緑簾石と石英で置換されているものもある．石英結晶のみで構成される球状体もあり，この場合は球状体内の層構造はみえない．灰色の球状体が集合している部分では，球状体は石英質ではなく，少し軟らかい．その基質部は珪化されて硬く，スポンジ状の組織がみえる．これと同じスポンジ組織が別の変成凝灰岩試料の表面で認められる．この試料では風化によってスポンジ組織が表れている．
球状体内部や球状体集合部の周囲には針状のものがある．針の幅は 1 mm 以下，長さ 4 mm 以下で，針の中心は灰色，縁部は球状体と同じ白色である．
数 mm サイズの珪質球状体としてよく知られているものに魚卵状珪石がある．魚卵状珪石の球状体は３次元的に球状で，球体の一部が開放されることはない．凝灰岩中の球状体として火山豆石が知られている．この大きさは 5 mm より大きいのが普通で，1 mm 程度の微細な豆石は知られていない．流紋岩溶岩中の球果構造もよく知られているが，この構造は樹枝状結晶の放射状成長によって形成されるもので，凝灰岩中には同様な球果は知られていない．クリストバル石などが球状に集合して生じる球状組織もあるが，この場合は球体組織全体が石英多結晶の球体に再結晶するので，本報告のもののうち，石英結晶のみで構成される球状体に相当する．
報告したものは海綿動物の珪化した化石と考えると観察された組織の多くが説明可能である．海綿動物の珪酸とコラーゲンで作られたスポンジ組織や細胞が化石化すると同時に，海綿動物にある無数の小孔や大孔が珪酸分や火山灰物質で充填されて生じた組織とみることができる．もしこの考えが正しいなら，これらの岩石にはカンブリア紀の他の動物化石が含まれている可能性がある．
文献
Tagiri, M., Dunkley, D.J., Adachi, T., Hiroi, Y. and Fanning, C.M., 2011, SHRIMP dating of magmatism in the Hitachi
metamorphic terrane, Abukuma belt, Japan: evidence for a Cambrian volcanic arc. Island Arc, 20, 259-279.

キーワード: 日立カンブリア系, 変成凝灰岩, 海綿動物状組織, 球状体
Keywords: Hitachi Cambrian, meta-tuff, spongy parenchyma, sphere

1/1

BPT27-P02

会場:コンベンションホール

時間:5 月 24 日 18:15-19:30

北欧エストニアにおけるオルドビス紀中後期動物多様化と環境変動
Middle-Late Ordovician biodiversification and relevant environmental changes in Estonia
島塚 桃子 1∗ ; 磯崎 行雄 2 ; 可児 智美 3 ; 石川 晃 4
SHIMATSUKA, Momoko1∗ ; ISOZAKI, Yukio2 ; KANI, Tomomi3 ; ISHIKAWA, Akira41

東京大学大学院理学系研究科地球惑星科学専攻, 2 東京大学大学院総合文化研究科広域科学専攻広域システム科学系, 3
熊本大学大学院自然科学研究科（理学）, 4 東京大学大学院総合文化研究科
1
Department of Earth and Planetary Science - Graduate School of Science, The University of Tokyo, 2 Department of Earth
Science and Astronomy, Multi-disciplinary Sciences - General Systems Studies, Gr, 3 Department of Earth and Environmental
Sciences, Kumamoto University, 4 Department of Earth Science and Astronomy, The University of Tokyo

Following up the ’Cambrian explosion’ , marine biodiversity increased dramatically during the Ordovician, as known as the’Great Ordovician Biodiversification Event’ (GOBE). Estonia in central Batoscandia provides excellently continuous Ordovician
sedimentary package for detailed analysis. We are analyzing the drilled core samples of the Middle-Upper Ordovician strata (ca.
150 m-thick) collected from Velise in central Estonia, in order to clarify litho-, bio-, and isotope stratigraphy of C and Sr, and toreveal the cause and processes of the GOBE. We will report on our preliminary results.
Keywords: Ordovician, Baltscandia, GOBE, stratigraphy, drilled core

1/1

BPT27-P03

会場:コンベンションホール

時間:5 月 24 日 18:15-19:30

白亜紀ー古第三紀境界における衝突燃焼煙雲の有機地球化学的証拠: 恐竜絶滅の原
因か？
Organic geochemical evidences for smoke clouds induced by an asteroid impact at theCretaceous-Paleogene boundary
海保 邦夫 1∗ ; 藤林 恵 1 ; 齊藤 諒介 1
KAIHO, Kunio1∗ ; FUJIBAYASHI, Megumu1 ; SAITO, Ryosuke1
1
1

東北大学
Tohoku University

An asteroid impacted the continental shelf of Mexico 66 Myr ago. Although the resulting ejecta containing asteroidal andterrestrial materials in the stratosphere caused acid rain, darkness, and a mass extinction, the mechanisms of the extinction
remain under debate. We demonstrate that the impact caused the ejection of combusted fossil oil into the stratosphere, forming
a smoke plume that remained for several years. The absorption of solar radiation by the smoke led to the devastation of plants,
causing the extinction of the dinosaurs and some marine invertebrates at the end of the Cretaceous. Combusted organic molecules
containing coronene are concentrated in the microspherule-dominated coarse deposits and the superjacent fine layer containing
iridium derived from the asteroid in Haiti. The coronene percentage in the completely combusted organic molecules and δ 13 C
values in the ejected layers show similar values in the coarse deposits and the iridium layer in the proximal site and also in
the iridium layer in a distal site (Spain) for the impact crater, implying that the combusted organic molecules remained in thestratosphere globally for several years. The carbon preference index values of n -alkanes in the coarse ejected layers indicate thatthe n -alkanes were primarily sourced from oil. The stable carbon isotope ratio values of short-chain n-alkanes in Haiti show
devastation of marine life occurred within a year after the impact. The δ 13 C profile of long-chain n -alkane implies devastationof land vegetation by darkness. Therefore, we suggest that these smoke clouds contributed to the mass extinction.
キーワード: コロネン, 白亜紀, 古第三紀, 燃焼煙雲, 安定炭素同位体比
Keywords: coronene, Cretaceous, Paleogene, smoke clouds, stable carbon isotope ratio

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BPT27-P04

会場:コンベンションホール

時間:5 月 24 日 18:15-19:30

先カンブリア紀?カンブリア紀境界付近の、全球的な酸化とは対照的な還元的な三峡の海洋環境
Euxinic conditions at Three Gorges area as opposed to global oxidation event, around
PC/C boundary
澤木 佑介 1∗SAWAKI, Yusuke1∗
1
1

東京工業大学Tokyo Tech

It is widely accepted that the Neoproterozoic was a transitional period to modern Earth in terms of oceanic redox condition.
Some geological evidences, including carbon and sulfur molybdenum isotopic data, support this idea, and fossils of large multicellular animal have been discovered from Neoproterozoic strata throughout the world. In contrast, some of the fossils werediscovered from anoxic sediments and iron speciation analyses indicate existences of ferruginous and euxinic conditions in somepoints.
Three Gorges area, South China, is one of the best places to decipher surface environmental changes during the Ediacaran andCambrian due to the successive deposition on Yangtze platform. Our group conducted on-land drilling at the Three Goregs tocollect fresh and continuous rock samples. The age range of the core samples is from the beginning of the Ediacaran to the endof the early Cambrian. I measured molybdenum concentration of the core samples by XRF analysis using glass bead. The resultshows that molybdenum concentrations of organic carbon-rich black shale layers deposited at ca. 560 Ma and 525 Ma are up to
800 ppm. Same horizons contain high levels of rhenium, approaching 3 ppm, and TOC, more than 10 %. Abundant pyrites arealso included in the black shale, and all of these evidences suggest that euxinic conditions occurred at Three Gorges during these
periods.
In modern Black Sea, surface layer is oxic but bottom layer is euxinic because of down-welling of organic matter. As referringto this concept, euxinic conditions of Three Gorges area might imply both onset of effective burial of organic material and oxic
surface layer around PC/C boundary.
Keywords: Three Gorges, molybdenum, euxinic

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