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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.gloplacha.2021.103650

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Scandinavian University Press / Universitetsforlaget AS  

DOI： 10.1111/let.12432

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/let.12432

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Geological Society of America  

Both the duration and severity of deep-water anoxic conditions across the Permian-Triassic mass extinction (PTME) are controversial. Panthalassa Ocean circulation models yield varying results, ranging from a well-ventilated deep ocean to rapidly developing northern-latitude, but not southern-latitude, anoxia in response to Siberian Traps–driven global warming. To address this uncertainty, we examined a southern-paleolatitude pelagic record. Trace metal and pyrite framboid data suggest bottom-water euxinic conditions developed in the southern Panthalassa Ocean at the PTME, coincident with enhanced volcanic activity indicated by Hg geochemistry. While a global ocean euxinic event at the PTME placed extraordinary stress on marine life, southern surface waters appear to have recovered more quickly as radiolarian populations returned several million years before they did in northern Panthalassa.

DOI： 10.1130/g48928.1

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.palaeo.2020.110143

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Language：English   Publishing type：Research paper (scientific journal)  

Lower Triassic sedimentary rocks deposited in pelagic regions of Panthalassa show anomalously clay-rich and silica-poor lithologies compared with the deep marine chert-dominated successions that characterise older and younger strata. The end-Permian mass extinction, which impacted radiolarians, has been proposed as an explanation for this so-called “chert gap” through its inferred impact on biogenic silica production. To test this hypothesis, we evaluated linear sedimentation rates (LSRs) for an upper Olenekian (upper Lower Triassic) siliceous claystone succession in Tsukumi, Oita Prefecture, Southwest Japan. Correlation of conodont biohorizons allows extrapolation of absolute ages obtained by previous studies in South China onto our studied sections. Results show that LSR is higher in the Lower Triassic claystone than in typical Mesozoic radiolarian bedded chert. This implies that increased burial flux of clastic material, not decreased biogenic silica burial flux, drove deposition of clay-rich sediments in pelagic Panthalassa during the late Olenekian.

DOI： 10.1016/j.gloplacha.2020.103330

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.gloplacha.2020.103195

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.palaeo.2019.03.034

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

© 2018 Elsevier B.V. This study determined chemical species of iron (Fe) and molybdenum (Mo) in a pelagic deep-sea Permian–Triassic boundary section, that records redox variations across the severe mass extinction event. We applied X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) at the Fe K-edge and X-ray absorption near-edge structure (XANES) at the Mo K-edge to silicic sedimentary rock samples for analysis of the studied section. According to the EXAFS and XRD analyses, pyrite was the dominant Fe-bearing mineral in most samples, whereas ferric minerals such as hematite were absent throughout the Permian–Triassic transition. This result supports those of previous studies of other deep-sea Japanese Permian-Triassic boundary (PTB) sections. The Fe in pyrite mineral quantified by EXAFS spectra displayed synchronous variation with sulphide-sulphur (S sulphide ) but with total organic carbon content, which revealed the Fe-limited conditions for pyrite formation in the pelagic Panthalassa region. The XANES analysis indicated the presence of tetrahedral and octahedral configurations of Mo bonded to oxygen (O) and sulphur (S), which were referred to as MoO 42− , MoO 3 (as a possible alternative reference material of Mo in organic ligands), MoO 2 and MoS 2 . The MoS 2 species dominated in the end-Permian horizons, coinciding with high abundances of total Mo, which suggests a sulphidic depositional environment. The MoS 2 and MoO 3 species were the main contributors to these high Mo abundances in the end-Permian strata. The presence of the molybdenite (MoS 2 ) species in the studied section indicates that the samples were subjected to alteration under high temperatures, with sufficiently sulphidic and limited reactive Fe availability conditions for MoS 2 formation during late diagenesis. The Fe in pyrite decreased across the mass extinction boundary, which coincided with the highest total Mo amount with the MoS 2 and MoO 3 species. These trends reflected a decrease in reactive Fe in the sediments and contemporaneous seawaters under sulphidic conditions. The low reactive Fe condition could be due to massive pyrite formation under prolonged sulphidic water conditions in the pelagic and ambient continental margin regions in the end-Permian.

DOI： 10.1016/j.palaeo.2018.12.014

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Language：English   Publisher：国立研究開発法人 産業技術総合研究所 地質調査総合センター  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

Ecosystem recovery from the end-Permian mass extinction took around 5 million years of the Early Triassic. In the pelagic deep-sea of the superocean Panthalassa, deposition of bedded chert ceased during this period, and instead, siliceous claystone lithofacies with minor chert beds was deposited. The reappearance of bedded chert around the Early-Middle Triassic (Olenekian-Anisian) boundary (OAB) was assumed to be related to recovery of radiolarian production in the pelagic realm. This study reports a new pelagic deep-sea section covering the transition from siliceous claystone lithofacies to bedded chert from Ogama in Tochigi Prefecture, Japan. Based on conodont and radiolarian biostratigraphy and carbon isotope stratigraphy, the Ogama section was dated as uppermost Olenekian to middle Anisian. The OAB was recognised by the occurrence of the conodont Chiosella timorensis, while the radiolarian-based OAB adopted by previous studies on bedded chert in Japan was revealed to be within the middle Anisian. In the Ogama section, the transition from siliceous claystone lithofacies to bedded chert is in the middle Anisian. The OAB is characterised by black organic-rich siliceous claystone, which implies oceanic oxygen depletion. Importantly, the linear sedimentation rate of the siliceous claystone lithofacies was found to be higher than that of Middle Triassic and Jurassic bedded chert. This shows that increased accumulation of clastic material was an important factor that caused the deposition of siliceous claystone in the pelagic Panthalassa at the OAB. Hence, the deposition of black siliceous claystone at the OAB may have occurred under different conditions from that at the end-Permian mass extinction, which is thought to be a result of diminished biogenic silica production.

DOI： 10.1016/j.palaeo.2017.11.060

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Biphytanes, which are derived from glycerol dialkyl glycerol tetraether (GDGT) lipids, are biomarkers for the presence of Archaea in geological samples. They (especially cyclic structures) are rarely reported from sediments or oils that are older than the Triassic period, where their first record may be traced back to the Late Archean. There have been only two studies that have reported diagenetic products of cyclic biphytanes using two dimensional gas chromatography. In this study, we used full scan and multiple reaction monitoring (MRM) mass spectrometry (MS) to tentatively assign a series of diagenetic products of cyclic biphytanes within uppermost Permian and Lower Triassic sedimentary rocks. We observed three distinct groups derived from mono-, bi-, or tricyclic biphytanes, echoing previous studies. Each group could be further divided into three discrete series according to structure and composition. Using MRM also revealed that numerous sedimentary rocks contained such diagenetic products, but at trace concentration below the limit of detection of full scan MS. This indicates that the presence of Archaea-containing GDGT lipids has been underestimated within paleoenvironments. Episodic occurrences of biphytanes in the Permian-Triassic transition also provide additional evidence for the distribution of Archaea in the geological past. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.orggeochem.2017.04.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The Early Triassic, following the end-Permian mass extinction, was an interval of severe low diversity. Increasing amounts of evidence demonstrate that variable environmental stresses were widespread and intense after the end-Permian mass extinction. Here we report biomarkers from lowest Triassic to lower Middle Triassic strata in South China (Qingyan and Chaohu sections), including biomarkers for environmental stress (2-methyl hopane index) and eukaryotic algae (steranes and C-21 n-alkylbenzene ratio). Using the 2-methyl hopane index, we detected the persistence of environmental stress during most of the Early Triassic. Using steranes and the C21 n-alkylbenzene ratio, we found a gradual increase in the biomass of eukaryotic algae during the Early to early Middle Triassic. A decrease in environmental stress in the Qingyan section (Leidapo Member) during the early Middle Triassic was synchronous with the "explosion" of the Qingyan Biota, which is characterized by a high abundance and diversity of invertebrate marine animals. Because the environmental stresses revealed by the 2-methyl hopane index encompass various factors (e.g., pH and temperature), we cannot identify the exact stresses at that time; however, our results reflect the amelioration of harsh environments for life during the interval of complete biotic recovery. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2016.03.006

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.2015.0034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

The largest mass extinction of biota in the Earth's history occurred during the Permian–Triassic transition and included two extinctions, one each at the latest Permian (first phase) and earliest Triassic (second phase). High seawater temperature in the surface water accompanied by euxinic deep-intermediate water, intrusion of the euxinic water to the surface water, a decrease in pH, and hypercapnia have been proposed as direct causes of the marine crisis. For the first-phase extinction, we here add a causal mechanism beginning from massive soil and rock erosion and leading to algal blooms, release of toxic components, asphyxiation, and oxygen-depleted nearshore bottom water that created environmental stress for nearshore marine animals. For the second-phase extinction, we show that a soil and rock erosion/algal bloom event did not occur, but culmination of anoxia–euxinia in intermediate waters did occur, spanning the second-phase extinction. We investigated sedimentary organic molecules, and the results indicated a peak of a massive soil erosion proxy followed by peaks of marine productivity proxy. Anoxic proxies of surface sediments and water occurred in the shallow nearshore sea at the eastern and western margins of the Paleotethys at the first-phase extinction horizon, but not at the second-phase extinction horizon. Our reconstruction of ocean redox structure at low latitudes indicates that a gradual increase in temperature spanning the two extinctions could have induced a gradual change from a well-mixed oxic to a stratified euxinic ocean beginning immediately prior to the first-phase extinction, followed by culmination of anoxia in nearshore surface waters and of anoxia and euxinia in the shallow-intermediate waters at the second-phase extinction over a period of approximately one million years or more. Enhanced global warming, ocean acidification, and hypercapnia could have caused the second-phase extinction approximately 60 kyr after the first-phase extinction. The causes of the first-phase extinction were not only those environmental stresses but also environmental stresses caused by the soil and rock erosion/algal bloom event.

DOI： 10.1016/j.heliyon.2016.e00137

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

This study focuses on an upper Lower Triassic (Spathian) to lowermost Middle Triassic (Anisian) section representing the central Panthalassic deep sea. Analysed organic carbon isotope ratio (delta C-13(org)) records from the section demonstrate that lower values in the Spathian increase by up to 6 parts per thousand at the Spathian-Anisian transition. This trend accords with the carbonate carbon isotope (delta C-13(carb)) record from shallow-water carbonate sections. Most horizons during late Spathian-early Anisian show features of redox conditions of not fully oxic but dysoxic conditions, inferred from low Mn, U, V. Mo and euhedral pyrite-dominated occurrences. Conversely, in the end-Spathian black-coloured beds and underlying siliceous claystone beds, relatively higher concentrations of redox-sensitive elements such as U, V. Mo and abundant pyrite framboids are detected. As enrichment factors of redox-sensitive elements are not much higher than the typical anoxic-sulphidic trend and large pyrite framboids are found, these trends suggest suboxic rather than strong anoxic conditions. These oxygen-poor conditions coincide with carbon isotope minimum values at the late Spathian. At the same time, reducing seawater conditions have been also reported in from continental sections. These coincidences imply global environmental perturbations that may have been related to the delayed recovery of life after the end-Permian mass extinction. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2015.04.018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Manganese (Mn) carbonate nodules, which differ from seafloor Mn nodules mainly composed of MnO2, are occasionally embedded in the form of a lens shape in the Jurassic accretionary complexes, such as the Mino Belt in Japan. The interpretation of the formation process of Mn carbonate is still controversial, particularly concerning whether the Mn carbonate was formed primarily or secondarily. In this study, a fresh Mn carbonate nodule incorporated into the red siliceous mudstone was collected for geochemical and sedimentological analysis. The optical observation of thin sections indicates that the Mn carbonate nodules are composed of abraded grains of rhodochrosite spherule with radiolarians and are sedimentary embedded in siliceous mudstone. Microfossil radiolarians from the Mn carbonate nodules and the host red siliceous mudstone are dated as the Bajocian, but the radiolarians in the nodules are somewhat older than those in the host red siliceous mudstone.
Geochemical analysis using the X-ray absorption near-edge structure on Ce indicates the dominance of trivalent Ce at present, despite the observation of a positive Ce anomaly in the PAAS-normalized REE pattern of Mn carbonate. The REE adsorption experiment on synthesized MnCO3 does not show any distinctive positive Ce anomaly, and a thermodynamic calculation suggests the possible coexistence of rhodochrosite and spontaneous oxidation of Ce. A leaching experiment that can selectively decompose the carbonate phase demonstrated no Ce anomaly in the carbonate phase of the Mn carbonate and a poor contribution to the bulk REE concentration. The carbon isotope data of Mn carbonate nodule implied the dominance of inorganic marine carbonate origin with small contribution of organic decomposition. The most plausible account of all of the observational and geochemical results is that the rhodochrosite grains were primarily formed on the depositional site and subsequently transferred to a different site, where siliceous mudstone was deposited. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jseaes.2014.08.032

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The greatest mass extinction on Earth occurred 252 million years ago during the latest Permian. Complete biotic recovery, characterized by a return to pre-extinction diversity levels, took an extraordinarily long time (ca. 5 x 10(6) yr), probably because harsh conditions developed repeatedly during the Early Triassic. Here, we show the recurrence of euxinic conditions during the Early Triassic and the development of especially severe such conditions during the late Early Triassic, just prior to full biotic recovery from the mass extinction. Dibenzothiophenes and carotenoids accumulated in upper Lower Triassic sediments from South China, located on the western margin of the Paleotethys Ocean. Among these, chlorobactane, a biomarker for green-pigmented green sulfur bacteria, and okenane, a biomarker for purple sulfur photosynthetic bacteria, were identified in upper Early Triassic samples. Both compounds were detected in limestone (micrite) and we therefore infer that planktonic green and purple sulfur bacteria were the sources of these carotenoids, and that their presence indicates photic zone euxinia at the time of deposition. Concentrations of redox sensitive elements (M, V, and U), relative to that of Al, and the U/Th ratio, progressively increased during the late Early Triassic. The euxinic conditions represented by the carotenoids and the elements were likely caused by a combination of locally shallow restricted conditions and global environmental oscillations, such as those related to global warming, during the late Early Triassic. The presence of these biomarkers, together with the increase in the abundance of redox sensitive elements relative to Al and the U/Th, suggests that euxinic conditions could be one of the causes for the delayed recovery of marine communities in the Paleotethys Ocean after the latest Permian mass extinction event. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.orggeochem.2014.05.007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Asia Pacific  

The ornament on a small external cast in pink chert shows considerable similarity with that of various Middle Palaeozoic and Triassic fish genera. It comes from the Permian-Triassic Oruatemanu Formation of Arrow Rocks, Whangaroa area, eastern Northland. Conodont faunas from a few metres above and below the sample allow correlation with the Neospathodus pakistanensis zone of the Early Triassic, which is assigned to the late Dienerian (late Induan), with adjacent conodont zone faunas in their correct stratigraphic association. The cast is assumed to be that of a small fragment of fin spine, most likely from the junction area of the crown and root on the right-hand side of a dorsal fin spine, possibly anterior, of a marine ctenacanthoid shark, a basal shark order not previously recorded from New Zealand.

DOI： 10.1080/00288306.2014.889722

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To improve international stratigraphic correlation of the Lower Guadalupian-Lower Lopingian (Permian), we examined the stratigraphies of conodonts and organic carbon isotopes from pelagic chert sequences in the Gujo-hachiman section, Gifu, southwest Japan. Age-diagnostic conodonts, such as Jinogondolella nankingensis and Jinogondolella shannoni were found in the study section. The conodont stratigraphy in the Gujo-hachiman section was correlated with those in South China and West Texas, USA, to date the study section. From these correlations, it was found that the study section was from the upper Roadian (Lower Guadalupian) through Wuchiapingian (Lower Lopingian). Kerogen delta C-13 values were relatively high, around -29.0% in the upper Roadian-Wordian (Middle Guadalupian), decreasing over time to 29.4%. A negative-positive swing in delta C-13 values of around 1%o magnitude was recognized in the middle Capitanian (Upper Guadalupian). A similar negative-positive swing was also found in the Guadalupian-Lopingian (G-L) transitional zone in the Gujo-hachiman section, and is comparable to the isotopic change around the G-L boundary in the Penglaitan section, South China. Subsequently, delta C-13 values decreased to values below 30.0%0 above the G-L transitional zone, i.e., at the lower Wuchiapingian. Overall, delta C-13 values decreased from the lower Capitanian to the lower Wuchiapingian by over 1.4%0. A gradual increase in the delta C-13 values followed this long-term negative trend. These delta C-13 trends in the Gujo-hachiman section are comparable with time-equivalent delta C-13 records in different sections, suggesting that they record first-order variations in atmospheric delta C-13. The high delta C-13 values during the upper RoadianWordian interval could reflect high primary productivity in the surface water of the pelagic Panthalassa Ocean, and imply global cooling. In contrast, the negative delta C-13 shift during the Capitanian-Wuchiapingian interval implies global warming. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2014.02.033

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The Carnian pluvial event (CPE) is considered as the drastic environmental change that occurred in the western Tethys during the Carnian (late Triassic). Although some studies have suggested that the CPE was a global event, no studies have referred to pelagic environment related to the CPE. To reveal the pelagic environment during the Carnian, X-ray absorption fine structure (XAFS) analysis was used to determine the iron (Fe) species in chest samples collected from the Ladinian-Carnian strata in the Tamba-Mino-Ashio Belt, Japan. The X-ray absorption near-edge structure (XANES) analysis shows that all the red chests contain hematite with a combination of clay minerals, such as illite, chlorite, and smectite. The existence of these minerals is identified using extended XAFS (EXAFS). The XANES analysis of the green and the white cherts does not show any hematite signatures, while the EXAFS analysis indicated increasing amounts of chlorite.
The stratigraphic change in the Fe-bearing compositions observed in this study can be divided into three stages: (i) a stage where a relatively stable mineral composition (chlorite + illite + hematite) is observed in cherts deposited during the early Carnian (Julian), (ii) the abrupt change in mineral composition (lack of chlorite and appearance of smectite) observed in the middle area in the studied section and corresponding to the middle part of Carnian (late Julian-early Tuvalian), and (iii) the recovery of the previous stable mineral composition during the late Carnian (Tuvalian). These variations in the mineralogical composition of pelagic chests can be interpreted to mean that the continental climate conditions changed during the Carnian, and different clay fractions were delivered to the pelagic region. These data, combined with the results of previous studies performed around the continental realm, can be interpreted as follows: (i) there was a relatively stable dry climate before the CPE, (ii) there were increasing amounts of precipitation owing to the CPE, and (iii) the climate returned to dry conditions similar to those prior to the CPE. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2013.10.014

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Land-plant productivity was greatly reduced after the end-Permian mass extinction, causing a pronounced "coal gap" worldwide during the Early Triassic. Newly obtained organic geochemistry data from the Chaohu area, south China, indicated an abrupt and profound terrestrial vegetation change over the middle part of the Early Triassic Smithian-Spathian (S-S) interval. Herbaceous lycopsids and/or bryophytes dominated terrestrial vegetation from Griesbachian to Smithian times. The terrestrial ecosystem underwent an abrupt change, and woody conifers became dominant over the S-S interval. Several important biomarkers, namely retene, simonellite, and dehydroabietane (with multiple sources: conifer, lycopsid, and/or herbaceous bryophyte), were relatively abundant during Griesbachian, Dienerian, and Smithian times. The relatively low C/N ratio values during the Griesbachian-Smithian interval indicate that these biomarkers were likely sourced from herbaceous lycopsids and/or bryophytes. The extremely abundant conifer-sourced pimanthrene, combined with relatively high C/N ratio values, suggested the recovery of woody conifers after the S-S boundary. The new data revealed that the switch from herbaceous vegetation to woody coniferous vegetation marked a terrestrial plant recovery, which occurred globally within 3 million years after the end-Permian crisis rather than at a later date estimated in previous studies. In Chaohu, the S-S terrestrial event was marked by a reappearance of woody vegetation, while the S-S marine event was marked by an increase in ichnodiversity, trace complexity, burrow size, infaunal tiering level, and bioturbation level, and a possible intense upwelling event indicated by the extended tricyclic terpane ratios (ETR). Coeval vegetation changes with comparable patterns have also been documented in Europe and Pakistan based on palynologic studies. The S-S boundaries in Asia and Europe are associated with a positive delta C-13 excursion, the rebound of woody vegetation, a turnover of ammonoid faunas, and possible global climate cooling. This is the first study to document the S-S event using biomarkers and C/N ratios. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gloplacha.2012.07.008

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Publishing type：Research paper (scientific journal)  

Mesozoic accretionary complexes in Japan and New Zealand contain Panthalassic low latitude and southern mid-latitude deep-water sedimentary rock respectively. These sedimentary rocks record environmental changes in the pelagic Panthalassic Ocean during the transition associated with the severe Permian-Triassic mass extinction. This study presents sulfur isotope records of sulfide from continuous deep-sea Permian-Triassic boundary sections located in northeast Japan (the Akkamori section-2, the most continuous section among other previously reported deep-sea sections) and North Island of New Zealand (the Waiheke-1 section, providing the first sulfur isotopic record from a southern hemisphere deep-sea section). Both sections show sharp ~15‰ drops of the sulfur isotope ratio coupled with a negative shift of organic carbon isotope ratio. Similar decreases in sulfur isotope ratio of carbonate-associated sulfates by ~10‰ accompanied with a negative shift of inorganic carbon isotope ratio at the end-Permian mass extinction horizon have been reported in some shallow water Paleotethyan sections. These sulfur isotope changes suggest that a massive release of 32S-enriched sulfur from the H2S-rich water to the oxic surface-waters coincided with the end-Permian mass extinction. © 2012 Elsevier B.V.

DOI： 10.1016/j.gloplacha.2012.12.006

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Changes in redox conditions during the Changhsingian to Griesbachian spanning the end-Permian mass extinction were recently reported based on analyses of organic molecules. We provide more precise organic-molecular data, that detail redox conditions spanning the end-Permian mass extinction at different palaeowater depths in the neritic Palaeotethys (estimated water depths: 10, 40, 100, and 200 m; Bulla, Huangzhishan, Meishan, and Chaohu sections, respectively) during this period. Here we propose that a change from occasional euxinia to anoxia in the shallow Palaeotethys occurred at the time of the mass extinction intercalated with oxic pulses. The second extinction at 0.7 myr after the main extinction was also caused by anoxia. New and published sulfur-isotope ratios (S-34/S-32) measured in carbonate-associated sulfate from the neritic Palaeotethys and in sulfide from pelagic central Panthalassa sediments show high values during the Changhsingian, consistent with the development of euxinia. The mass extinction coincided with a global fall in delta S-34 values, as well as a shift in delta C-13 values, indicating a global oxidation of H2S. This organic and isotopic geochemistry implies that accumulation of hydrogen sulfide in intermediate and deep waters followed by oxidation of hydrogen sulfide led to dissolved oxygen consumption, surface-water anoxia, and acidification, resulting in the end-Permian mass extinction in the seas. (c) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gloplacha.2012.05.024

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This study examines a Triassic deep-sea sequence consisting of rhythmically bedded radiolarian cherts and shales and its ifcmplications for early Induan radiolarian fossils. The sequence, obtained from the Waipapa terrane, Waiheke Island, New Zealand, is composed of six lithologic Units (A-F) and, based on conodont biostratigraphy, spans at least the interval from the lowest Induan to the Anisian. Unit A (the basal unit) consists of black chert and shale beds containing fine pyrite minerals
this corresponds to the oceanic anoxic event described at Arrow Rocks further north in New Zealand. The δ13Corg values of Unit A show a pronounced negative shift between the pale-green chert and black shale/chert, which may represent the negative excursion across the Permian-Triassic boundary that has been documented worldwide. The black cherts, which give minimum C-isotopic ratios (around -30‰), are early Induan, and contain a rich radiolarian fauna characterized by Entactinosphaera? crassispinosa Sashida and Tonishi, E.? spoerlii Takemura and Aono, Bistarkum martiali Feng, Entactinia cf. itsukaichiensis Sashida and Tonishi, Ellipsocopicyntra? sp., and rare Nassellaria. A new Induan nassellarian species, Tripedocorbis? blackae n. sp., from the black chert bed, is described herein. Its presence indicates that Triassic-type Nassellaria had already appeared in the early Induan in the pelagic realms of southern hemisphere Panthalassa. © 2011 Elsevier Ltd and Nanjing Institute of Geology and Palaeontology, CAS.

DOI： 10.1016/j.palwor.2011.02.001

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Guadalupian-Lopingian sedimentary rocks are widely distributed in accretionary complexes in Japan, but the Guadalupian-Lopingian boundary (G-LB) is not well documented from these pelagic sediments. To identify the G-LB and to better correlate an extinction event that occurred around the Guadalupian-Lopingian boundary, we examined the conodont biostratigraphy from a Permian pelagic chert sequence in the Gujo-hachiman section, Gifu, southwest Japan. Age-diagnostic conodonts, including Clarkina postbitteri postbitteri, were found in this section. The biostratigraphic occurrences of these age-diagnostic conodonts can pinpoint the "G-L transitional zone" in the Gujo-hachiman section by comparison with well-studied sections from south China, including the GSSP section. The transitional zone was recognized by the first occurrence horizons of both Clarkina postbitteri hongshuiensis and C. p. postbitteri. The G-LB has been placed at or above the first occurrence horizon of the radiolarians Albaillella yamakitai or Albaillella cavitata in previous studies from China and Japan. We detected the first occurrence horizon of A. yamakitai below the base of the "G-L transitional zone," in the Upper Capitanian. The conodont biostratigraphy is consistent with the radiolarian biostratigraphy in this section, which can be correlated to relevant sections in China. © 2010 Elsevier B.V.

DOI： 10.1016/j.marmicro.2010.10.002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The end-Permian mass extinction is associated with a global perturbation in the carbon isotopic composition of carbonates and organic matter, but such changes are not well documented from pelagic deep-sea sediments. One of the most continuous pelagic deep-sea Permian/Triassic boundary (PTB) sections, the Am-2 section, is exposed in the accretionary complexes of Japan. New data for organic carbon isotope ratios (delta(13)C(org)) were obtained from 36 samples from section Am-2. The delta(13)C(org) excursion curve exhibits a negative shift of 2.0 parts per thousand in the low-latitude, pelagic Panthalassic Ocean at the end of the Permian, which coincides with a radiolarian extinction. The delta(13)C(org) values of pelagic, deep-sea Panthalassic sections and those of shallow-water sections from Panthalassic seamounts exhibit a smooth, negative shift that lacks temporary increases like those reported from Paleotethyan PTB sections. Absence of temporary delta(13)C(org) increases at the PTB in Panthalassa may reflect less algal and bacterial blooming in pelagic Panthalassa compared to the shallow-water Paleotethys. (C) 2010 Published by Elsevier B.V.

DOI： 10.1016/j.palaeo.2010.04.025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CHINA UNIV GEOSCIENCES  

Web of Science

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Fossil data show that the recovery of life after the end-Permian mass extinction occurred in the Anisian (early Middle Triassic). The process by which oceanic environments recovered from anoxia after the end-Permian event is uncertain. To determine the timing of known recovery stages, the nature of oceanic redox conditions and the health of cyanobacterial plankton populations, this study analyses conodonts and organic molecules from siliceous claystones and cherts from accretionary complexes in Japan that span the upper Lower Triassic to the lowermost Middle Triassic. Conodonts indicate that the study section ranges from upper Olenekian to Anisian, and includes the Olenekian/Anisian boundary. An increase in polycyclic aromatic hydrocarbons (probably derived from algae dominated organic matter) and a decrease in methylhopane index (2 alpha-methylhopane/hopane, a measure of cyanobacterial activity) are present in end-Olenekian black chert. Pristane/phytane ratios (a measure of redox conditions) in all stratigraphic units are lower than 1, indicating the prevalence of deep-sea anoxia during the late Olenekian to Anisian. High concentrations of dibenzothiophene (an index of anoxic depositional environments), high sulphur/carbon ratios, and high organic carbon contents are present in two upper Olenekian intervals and at the end of the upper Olenekian, suggesting development of anoxic deep water. One of the anoxic events in the end of the upper Olenekian coincided with decreased radiolarian diversity. This implies that anoxic deep water in the Panthalassic Ocean reached intermediate water depths at the end of the Early Triassic, killing marine organisms including radiolaria. This event may be related to the delay in the recovery of life and environments after the end-Permian mass extinction. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2009.01.010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The greatest mass extinction occurred at the end of the Permian. Most records of the mass extinction are not from pelagic sediments, but from shallow-marine and terrestrial sediments. Although several pelagic sections that span the end-Permian mass extinction have been found, these sections contain few index fossils and are often discontinuous because of small faults. We found the index fossils Albaillella cf. triangularis (Radiolaria) in siliceous claystone beds, Hindeodus parvus (Conodont) in the overlying black claystone beds, and Neospathodus cf cristagalli and Ns. waageni (Conodont) in the subsequent siliceous claystone beds in Akkamori section-2 in northern Japan. These fossils suggest that this section ranges from the late Permian to the Early Triassic, including the early Induan and Olenekian stages. Furthermore, the lithological changes in the section, i.e., starting from bedded chert through siliceous claystone and black claystone to siliceous claystone, are concordant with those of well-known Permian-Triassic pelagic sequences in Japan. There is no gap between each lithofacie of the Akkamori section-2. Critical lithological continuity between Upper Permian siliceous claystone beds and uppermost Permian to lowermost Triassic black claystone beds of the Akkamori section-2 was recognized by observing hand-polished specimens and thin sections. Such paleontological and sedimentological evidence implies that the Akkamori section-2 is a continuous pelagic section that records the end-Permian mass extinction event. The carbonaceous black claystone beds have high total organic carbon (TOC) concentrations (1.06-3.31 wt.%), suggesting oceanic anoxia at least deep and probably stable primary productivity. A decrease in radiolarian abundance from 26-563 to 0.27-20 specimens/cm(2) coincided with an increase in TOC content from 0.01-0.16 to 1.06-3.31 wt.% at the boundary of the siliceous claystone and the overlying black claystone beds near the top of the Permian, implying that radiolarian extinction occurred at the end of the Permian coinciding with oceanic anoxia. Although TOC contents decreased in the early Olenekian (Smithian), radiolarian abundance did not increase at that time, indicating that radiolarian recovery was delayed by > 1.5 m.y. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2008.08.016

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Language：English   Publishing type：Research paper (scientific journal)  

We have detected a family of benzohopanes cyclised at C-20 and two families of diaromatic 8(14)-secohopanoids, in carbonates from the Late Permian Meishan (China) and Bulla (Italy) sections. Furthermore, we have identified a C 33 8(14)-secohopanoid possessing a fluorene moiety. The relative distribution of 8(14)-secohopanoids with a fluorene moiety was similar to that of benzohopanes cyclised at C-20, suggesting that the secohopanoids might be diagenetic products of benzohopanes, or that the benzohopanes and secohopanoids share the same precursor. Furthermore, the series of benzohopanes cyclised at C-16 was not detected from the carbonates of the two sections, which might suggest that the benzohopanes cyclised at C-16 are thermodynamically less stable than those with the aromatic ring attached at C-20. Copyright © 2009 by The Geochemical Society of Japan.

DOI： 10.2343/geochemj.1.0004

Scopus

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.114.s121

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.113.274

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Language：Japanese   Publisher：The Geological Society of Japan  

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2016.0_103

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2015.0_334

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Language：Japanese   Publisher：東京大学大学院理学系研究科・理学部  

核融合エネルギー実現への道のり／ニュージーランドに眠る太古の地質記録を求めて

CiNii Books

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2014.0_075

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Publisher：The Geological Society of Japan  

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2014.0_070

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Publisher：The Geological Society of Japan  

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2013.0_574

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2013.0_358

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Publisher：The Geological Society of Japan  

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Publisher：The Geological Society of Japan  

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Publisher：The Geological Society of Japan  

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2013.0_622

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2013.0_361

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2013.0_272

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J-GLOBAL

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2011.0.54.0

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2010.0.116.0

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J-GLOBAL

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2009.0.93.0

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2008.0.92.0

CiNii Books

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2008.0.67.0

CiNii Books

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2008.0.92.0

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2008.0.67.0

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Language：Japanese   Publisher：The Geological Society of Japan  

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Language：Japanese   Publisher：The Geological Society of Japan  

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