BPT27-01

Room:104

Time:May 24 09:00-09:15

Diagenetic signatures of the Gaskies glaciation and their implication to the Ediacaran
stratigraphy
KANO, Akihiro1∗ ; FURUYAMA, Seishiro2
1

Kyushu University, 2 AISTThe isotopic excursion of inorganic carbon that repeatedly happened in Earth history were linked to biological evolutions andextinctions as well to the significant environmental changes. During the Ediacaran period when multicellular animals dramatically evolved, several distinct isotopic excursions recorded from the stratigraphic sections. The Ediacaran platform in South
China exposes well-preserved sedimentary rocks, and high-resolution carbonate carbon isotopic data have been extensively studied (e.g., Sawaki et al., 2010). Although most of the excursions were global, a negative excursion in the middle Doushantuo
Formation is unique in South China and presumably correlated with the Gaskiers glaciation (Tahata et al., 2013). These data
could have reflected characteristic oceanic structure and influenced by oceanic oxidation in Ediacaran, those causes have been
not fully understood. This study investigated a negative excursion observed in the Yangjiaping section in NE Hunan, which
records large fluctuation in inorganic carbon isotope (e.g. Kunimitsu et al., 2011). The unique excursion was developed in middle to upper parts of Doushantuo Formation Unit 3. Here, we found that the calcite cement exhibit lower isotopic values thanbulk component, by 25 permil for carbon and by 2 permil for oxygen. A reasonable process for these observations was most
likely decomposition of organic matter in a meteoric diagenetic environment. Co-occurrence of pyrite implies that the process
would be coupled with sulfate reduction in an anoxic condition. Yangjiaping section was located in the shallowest part of theplatform together with the famous Wengan section in Guizhou province, and was easily exposed subaerially during the sea-levelfall. Some characteristics of this negative excursion were commonly seen in the middle Doushantuo in the type section, andan excursion below the paleokarst in Wengan. Thus, the subaerial exposure was associated with the Gaskiers glaciation in the
middle Ediacaran period (580 Ma). Thick phosphoric sediments in the Doushantuo Unit 3 imply intensified upwelling during
the glaciation. The Gaskiers glaciation enhances ocean circulation that distributes nutrients and oxygen in the water column andinduced the animal evolution in late Ediacaran.
Kunimitsu et al., 2011. Precambrian Research, 191, 194-208.
Sawaki et al., 2010. Gondwana Research 14, 134-147.
Tahata et al., 2013. Gondwana Research 23, 333-353.

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BPT27-02

Room:104

Time:May 24 09:15-09:30

When did the ”Cambrian agronomic revolution” start?
YADA, Keigo1∗ ; OJI, Tatsuo2 ; DORNBOS, Stephen3 ; HASEGAWA, Hitoshi2 ; GONCHIGDORJ, Sersmaa4 ;MOCHIZUKI, Takafumi5 ; TAKAYANAGI, Hideko4 ; IRYU, Yasufumi6
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
A variety of benthic animals have appeared in the Cambrian, marine bottom sediments have started to be subjected to bioturbation, and microbial mats, which had widely covered the sea floor in the Proterozoic, have generally declined except for special
environment. This phenomenon is known as ”the Cambrian agronomic revolution” (Seilacher and Pfluger, 1994), and this is
one of the major evolutionary changes caused by the evolution of benthic anmimals. Previous studies showed that this kind of
substrate change has started only after the early Cambrian. However, we have discovered a new evidence that indicate existenceof deep burrows made by benthic animals from the Ediacaran of western Mongolia.
Upper Proterozoic to Cambrian deposits are widely distributed in the Govi Altay area in western Mongolia. In the Bayan
Gol valley, we found large-sized Arenicolites isp. with vertical burrows from as many as 11 horizons in the Ediacaran bedded
limestones. These burrows reaches 4 cm in maximum in vertical orientation. We collected rock samples in 2 m interval, for the
carbon isotope stratigraphy.
The horizons with Arenicolites isp. are in the bedded limestone of the upper Tsagaan Oloom Formation. They are locatedat 190-140 m lower than the base of the Cambrian determined by the first occurrence of the ichnofossil Treptichnus pedum inthis section, and at 120-70 m lower than the horizon of the ”BACE event”, which is characterized by a clear negative excursion
and is correlated approximately to the horizon of the Pc/C boundary. It is clarified that the ichnofossil Arenicolites isp. withvertical structure certainly occurs from the Ediacaran as opposed to the previous interpretation. This shows that ”The Cambrianagronomic revolution” had already begun in Ediacaran in western Mongolia. This early start of this revolution can be attributed
to the geographic position of Mongolia in late Ediacaran-early Cambrian, because Mongolia was located near the equator underwarm environment during this interval.

Keywords: Ediacaran, Cambrian, ichnofossil, Cambrian explosion, Cambrian agronomic revolution

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BPT27-03

Room:104

Time:May 24 09:30-09:45

Soil erosion event during the Late Devonian mass extinction recorded at the GSSP section
MIURA, Mami1∗ ; KAIHO, Kunio1 ; CASIER, Jean-georges2
1

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.
Keywords: mass extinction, Devonian, Soil erosion

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BPT27-04

Room:104

Time:May 24 09:45-10:00

Assessment of mode of extinction and recovery based on changes in morphospace andspecies-abundance relationship
UBUKATA, Takao1∗
1

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.
Keywords: morphospace, disparity, mass extinction and recovery, statistical model selection

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BPT27-05

Room:104

Time:May 24 10:00-10:15

Changes in biofacies and environments at the end-Gudalupian: response in mid-latitude
ISOZAKI, Yukio1∗ ; HAYASHI, Ryutaro1 ; KANI, Tomomi2
1

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.
Keywords: Permian, Capitanian, cooling, Sr isotope ratio, South Kitakami, shelf limestone

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BPT27-06

Room:104

Time:May 24 10:15-10:30

The collapse of a Capitanian (Middle Permian) reef: Sr-isotope profile at Iwaizaki, NE
Japan
KANI, Tomomi1∗ ; ISOZAKI, Yukio2 ; HAYASHI, Ryutaro2
1

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

Room:104

Time:May 24 10:30-10:45

Sulfur and carbon isotope study for understanding environmental changes across the Middle/Late Permian boundary
MARUOKA, Teruyuki1∗ ; ISOZAKI, Yukio2
1

University of Tsukuba, 2 University of Tokyo

The mass extinction at the end of the Paleozoic Era has been recognized as the most severe extinction event in the historyof life. Such severe diversity loss could be attributed to the combined consequences of two successive mass extinctions, which
occurred at the Guadalupian-Lopingian (G-L) (Middle-Late Permian) boundary (260 Ma) and the Permian-Triassic (P-T) boundary (250 Ma). Drastic environmental change during this time likely started immediately before the G-L boundary and reached amaximum around the P-T boundary. In order to understand paleoenvironmental change in oceans across the G-L boundary, we
analyzed secular changes in sulfur and carbon isotope ratios of Middle-Upper Permian carbonates of an accreted mid-oceanic
paleoatoll complex at Kamura in central Kyushu, Japan.
Negative correlations were observed between δ 34 SCAS and δ 13 Ccarbonate values for Guadalupian and Lopingian carbonates,
respectively. These correlations imply that the bottom water anoxia expanded to the open oceans before and after the G-Lboundary. In such environments, organic matter was oxidized by sulfate-reducing bacteria in the water column, which produced
negative δ 34 SCAS -δ 13 Ccarbonate correlations.
The slopes of the negative correlations varied at the G-L boundary. This implies that the supply processes of carbon andsulfur into the oceans changed at the boundary. This finding suggests that the magmatic chemistry changed at the boundary from
sulfur-rich type to CO2 -rich type.

Keywords: Guadalupian-Lopingian boundary, mass extinction, oceanic anoxia, carbonate-associated sulfate, Panthalassan paleoatoll carbonates

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BPT27-08

Room:104

Time:May 24 11:00-11:15

Perturbations of the nitrogen cycle in mid-Panthalassa in the Late Guadalupian (Middle
Permian)
SAITOH, Masafumi1∗ ; NISHIZAWA, Manabu1 ; UENO, Yuichiro2 ; KOFUKUDA, Daisuke3 ; ISOZAKI, Yukio3 ;TAKAI, Ken1
1

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

Room:104

Time:May 24 11:15-11:30

A unique Cr-enriched bed across the Guadalupian-Lopingian boundary (Permian) in midPanthalassan paleo-atoll carbonates
ISHIKAWA, Akira1∗ ; ISOZAKI, Yukio1 ; KOFUKUDA, Daisuke1 ; SHOZUGAWA, Katsumi1
1

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.
Keywords: geochemistry, ICP-MS, clayey bed, Guadalupian-Lopingian boundary, mass extinction, Emeishan flood basalts

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BPT27-10

Room:104

Time:May 24 11:30-11:45

Organic carbon isotope changes at P-T boundary in Gujohachiman, JapanTAHATA, Miyuki1∗ ; EBISUZAKI, Toshikazu2 ; ISOZAKI, Yukio3 ; NISHIZAWA, Manabu4 ; FUJISAKI, Wataru1
1

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.

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BPT27-11

Room:104

Time:May 24 11:45-12:00

Abrupt surface-water reduction accompanied with massive soil inflow during the endPermian mass extinction
KAIHO, Kunio1∗ ; ITO, Kosuke1 ; SAITO, Ryosuke1 ; MIYAJI, Takashi1 ; OBA, Masahiro1 ;TAKAHASHI, Satoshi2 ; BISWAS, Raman1
1

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.

Keywords: oceanic reduction, soil, Permian, Triassic, mass extinction

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BPT27-12

Room:104

Time:May 24 12:00-12:15

Osmium isotope composition in the deep pelagic Panthalassa ocean during the Toarcian
Oceanic Anoxic Event
FUJISAKI, Wataru1∗ ; UEDA, Hisahiro1 ; SUDA, Konomi1 ; SATO, Tomohiko2 ; SAWAKI, Yusuke1 ;YOKOYAMA, Tetsuya1
1

Department of Earth and Planetary Science, Tokyo Institute of Technology, 2 Earth-Life Science Institute, Tokyo Institute ofTechnology
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

Room:104

Time:May 24 12:15-12:30

Birth place and migration history of primates: Proposal of new model
MARUYAMA, Shigenori1∗
1

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

Room:Convention Hall

Time:May 24 18:15-19:30

Spongy parenchyma found in meta-tuff of Hitachi Cambrian Akazawa Formation
TAGIRI, Michio1∗ ; HANAWA, Katsutoshi2 ; OIKAWA, Akira2
1

Hitachi City Museum, 2 Geonet Hitachi

Hitachi Cambrian meta-tuffs containing spongy parenchyma occur as gravels in the Miyata River and the Ayukawa River.
Spongy parenchyma consists of siliceous sphere with several layers and dark matrix. This texture is not like to siliceous oolite,
pisolite, and spherulite, but to silicified sponge.
Keywords: Hitachi Cambrian, meta-tuff, spongy parenchyma, sphere

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BPT27-P02

Room:Convention Hall

Time:May 24 18:15-19:30

Middle-Late Ordovician biodiversification and relevant environmental changes in Estonia
SHIMATSUKA, Momoko1∗ ; ISOZAKI, Yukio2 ; KANI, Tomomi3 ; ISHIKAWA, Akira41

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

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BPT27-P03

Room:Convention Hall

Time:May 24 18:15-19:30

Organic geochemical evidences for smoke clouds induced by an asteroid impact at theCretaceous-Paleogene boundary
KAIHO, Kunio1∗ ; FUJIBAYASHI, Megumu1 ; SAITO, Ryosuke1
1

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.
Keywords: coronene, Cretaceous, Paleogene, smoke clouds, stable carbon isotope ratio

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BPT27-P04

Room:Convention Hall

Time:May 24 18:15-19:30

Euxinic conditions at Three Gorges area as opposed to global oxidation event, around
PC/C boundary
SAWAKI, Yusuke1∗
1

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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