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

DOI： 10.1016/j.gloplacha.2021.103650

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Hematite is a commonly occurring magnetic mineral in nature that has numerous scientific and technological applications. A characteristic property of hematite is a low-temperature spin-flop transition called the Morin transition. Above the transition temperature, hematite is a canted antiferromagnet that can carry a remanent magnetization. Below this transition, spin canting disappears and hematite becomes a true antiferromagnet although a small defect moment is usually preserved. We observe Morin transition behavior in natural samples that has not been reported before for hematite. During repeated thermal cycling of a remanent magnetization acquired at room temperature, the remanence intensity at the end of the cycle oscillates between a high remanence state at the end of odd-numbered cycles and a low remanence state (LRS) at the end of even-numbered cycles. Alternation of the high and LRSs during repeated thermal cycling points to hysteretic behavior of the spin-flop process, likely due to sublattice magnetization alignment switches along different easy magnetization axes in samples with preferred crystallographic orientations of hematite particles. We report these observations to seek to expand explanations of the magnetism of hematite.

DOI： 10.1029/2021GC010094

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

The phylogenetic affiliation of Oroscenidae, a family of Radiolaria possessing large siliceous skeletons, was thoroughly revised in this study. Plankton sampling was conducted over seven years in seven sea areas of the Northern Hemisphere. Molecular analyses on the obtained specimens revealed that living oroscenids are phylogenetically different from hitherto-known radiolarian orders. The detailed examinations by Microfocus X-ray Computed Tomography and Scanning Electron Microscopy clarified that oroscenids and the related family (Thalassothamnidae) have unique skeletal characteristics different from other radiolarian orders. Judging from their phylogenetic distinctiveness and the difference in the morphology and ecology, Oroscenidae and Thalassothamnidae should be classified in a single order distinct from other radiolarian orders, and consequently, a new order, Orodaria, is established. (C) 2021 Elsevier GmbH. All rights reserved.

DOI： 10.1016/j.protis.2021.125808

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

Experimental culture studies of living radiolarians experience many difficulties because radiolarians are too sensitive to be maintained alive in artificial conditions. We here developed an improved experimental protocol in order to detect newly-formed parts of the polycystine radiolarian skeletons after they were labeled with fluorescent markers. Living samples were collected from surface seawater of the Kuroshio Current offshore from Kashiwajima Island, Kochi Prefecture on the island of Shikoku, Japan. The taxonomic composition of the Kashiwajima radiolarian samples varied markedly across the seasons and sampling sites. Spumellaria were usually abundant in samples collected near Kashiwajima, and had high diversity in shell morphology. Here, we performed experimental studies on living spumellarian radiolarians to clarify their siliceous skeletogenesis. Our culture-based research on spumellarians provided the following results.(A) The pattern of silica deposition on the skeleton of Spongaster tetras tetras varies depending on the growth stage. Three ontogenetic stages were identified: (1) young, (2) progressively-growing and (3) fully-grown. Furthermore, novel varied types of skeletal growth modes were determined as follows: (i) rapid growth on the outermost shell with enlargement of shell size and (ii) internal deposition on skeletal components without change in shell size. From measurements of the growth rate of cultured radiolarians, it is assumed that S. tetras tetras cell has at least a monthlong life cycle.(B) Spherical spumellarians have their own shell-forming strategy that permits additional silicogenesis while maintaining the taxonomically-specific shape of their shell; the meshwork of their shell surface consists of polygonal-shaped pore-frames formed by heterogeneous patterns of added silica.Our direct observation with fluorescence markers detected a skeletogenesis process of Haliommilla capillacea possessing a fragile spherical shell. We thus confirm the bridge-growth hypothesis for morphogenesis of the polygonal frame as proposed in previous studies. Spongosphaera streptacantha, having extremely long spines, exhibited a special growth pattern of spine elongation in a centrifugal direction, without a change in width. This was achieved by a particular temporal pattern of silicification characterized by an alternating pattern of patchy addition of new silica on the entire part of each blade from the base to the tip. Moreover, a thin layer of new silica was added by a flowing deposition along the edge of the spine. Based on these culture-based studies using living radiolarians, we conclude that Spumellaria control and maintain a particular shell shape by regulating where silicification takes place on the skeleton, particularly depending on the growth stage.

DOI： 10.1016/j.revmic.2021.100504

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

© 2020 Author(s). In its gender equality status, Japan lags behind the European Union (EU) and other Organisation for Economic Co-operation and Development (OECD) countries. Only 16.7 % of academic staff in national universities are women. Although there has been a slow improvement during the last 45 years, the percentage of female staff remains particularly low in the STEM (science, technology, engineering, and mathematics) fields. In 2018, female stuff accounted for only 12.3 % in agriculture, 8.7 % in science, and 6.2 % in engineering. The number of female graduate students and the number of female members of the Japanese geoscience societies have been steadily increasing since the 1998 campaign that increased the total number of graduate school places. However, low representation of females in academic job positions, as well as among the recipients of academic awards, suggests that a strong unconscious bias against women still exists in Japan. Continuing public attention to these issues is essential for the improvement of the situation.

DOI： 10.5194/adgeo-53-195-2020

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Language：English  

File： 71_04_08.pdf

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File： 20200605_1.pdf

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

One of the most profound environmental changes in the Mesozoic occurred during the Pliensbachian-Toarcian (Pl/To) time interval, including massive black shale deposition across Pl/To boundary and early Toarcian Oceanic Anoxic Event (T-OAE). These events are associated with negative carbon isotope excursions (CIEs), but their temporal link with C-12-rich carbon injection, possibly related with Karoo-Ferrar volcanisms and carbon cycle feedbacks, such as terrestrial methanogenesis and methane hydrate dissociation, is still debated. Here we present a new chemostratigraphy of the carbon isotopic ratio of organic matter (delta C-13(org)) from Pl/To deep-sea successions, in conjunction with bio-astrochronology. The deep-sea successions are located at the Katsuyama and Sakahogi outcrops in the Inuyama area, Japan, and contain two black bedded chert intervals named T-BBCs 1 and 2, which have astrochronologic ages of 183.25-183.01 +/- 0.2 Ma and 183.55-182.80 +/- 0.2 Ma. Negative CIEs of similar to 2 parts per thousand and similar to 5 parts per thousand are recognized across the base of T-BBCs 1 and 2, respectively, which are correlated with Pl/To boundary and classical T-OAE in shallow marine sections based on biostratigraphy. Astrochronologic ages of the onset of T-BBCs 1 and 2 are within the errors of the oldest high-precision U-Pb ages of Karoo and Ferrar LIPs, respectively. These temporal relations suggest a link between the C-12-rich carbon injection associated with Karoo and Ferrar volcanism, and CIEs associated with widespread black shale deposition across the Pl/To and T-OAE, respectively. Obliquity cycles in classic T-OAE CIE could have linked with terrestrial methanogenesis and methane hydrate dissociation in high-latitudes areas, whereas 405-kyr pacing of termination of T-CIE and T-BBCs deposition would be related with decreased chemical weathering and nutrient supply under weaker monsoon intensity, and possibly suppressed methane cycle across the termination of Pl/To and T-OAE periods.

DOI： 10.1016/j.gloplacha.2018.08.012

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

A phaeodarian morphotype, characterized by the feet surrounded with forked pedal spines with anchor-like structures, was collected in the subtropical North Pacific. Considering the morphological and phylogenetic uniqueness, this morphotype is described as Gazelletta kashiwaensis sp. nov. The distribution of this new species is possibly affected by the Kuroshio Current. The feeding behavior of living phaeodarians was first filmed: the present new species floated in the water column stretching "protoplasmic webs" and collected diatoms by repeating the expansion and retraction of "pseudopodium-like tentacles".

DOI： 10.1111/jeu.12516

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Cross-sections were prepared by ultramicrotome (UM) and focused ion beam (FIB) system in order to examine the skeletal structure of ecologically and geologically important shell-bearing protists: phaeodarians and radiolarians. The elemental composition of the skeleton was clarified by the energy dispersive X-ray spectroscopy, suggesting that the skeletons of both groups are mainly made of amorphous silica (SiO2 center dot nH(2)O) with other minor elements (Na, Mg, Al, Cl, K, Ca and Fe) and that these two groups have similar elemental composition, compared with other siliceous organisms (diatoms and sponges). However, the structural difference among the two groups was confirmed: phaeodarian skeletons are porous, unlike radiolarians with solid skeletons. It was also revealed that the phaeodarian skeleton contains concentric layered structure with spaces, presumably related to the ontogenetic skeleton formation. The distinction in the skeletal ultrafine structure (porous/solid and non-dense/dense) would reflect the ecological difference among the two groups and could be an effective criterion to determine whether microfossils belong to Radiolaria or Phaeodaria. The UM and FIB combined method presented in this study could be a useful approach to examine the chemical and structural characteristics of unculturable and/or rare microorganisms.

DOI： 10.1016/j.jsb.2018.06.008

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InterRed XV in Niigata 2017 Niigata University (JAPAN) Oct/22-Oct/27, 2017

CiNii Books

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Understanding the contribution of biogenic magnetic particles into sedimentary assemblages is a current challenge in palaeomagnetism. It has been demonstrated recently that magnetic particles produced through biologically controlled mineralization processes, such as magnetosomes from magnetotactic bacteria, contribute to the recording of natural remanent magnetization in marine and lacustrian sediments. Contributions from other, biologically induced, mineralization types, which are known from multiple laboratory experiments to include magnetic minerals, remain largely unknown. Here, we report magnetic properties of iron minerals formed by a community of iron- and manganese-reducing bacteria isolated from a natural groundwater deposit during a 2 yr long incubation experiment. The main iron phases of the biomineralized mass are lepidocrocite, goethite and magnetite, each of which has environmental significance. Unlike the majority of the previous studies that reported superparamagnetic grain size, and thus no remanence carrying capacity of biologically induced magnetite, hysteresis and first-order reversal curves measurements in our study have not detected significant superparamagnetic contribution. The biomineralized mass, instead, contains a mixture of single-domain to pseudo-single-domain and multidomain magnetite particles that are capable of carrying a stable chemical remanent magnetization. Isothermal remanent magnetization acquisition parameters and first-order reversal curves signatures of the biomineralized samples deviate from previously proposed criteria for the distinction of extracellular (biologically induced) magnetic particles in mixtures. Given its potential significance as a carrier of natural remanent magnetization, environmental requirements, distribution in nature and the efficiency in the geomagnetic field recording by biologically induced mineralization need comprehensive investigation.

DOI： 10.1093/gji/ggw221

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

The end-Triassic extinction event marks one of the "big five" mass extinction events of the Phanerozoic. The ultimate cause of the extinction is considered to be volcanic activity at the Central Atlantic magmatic province (CAMP), yet the underlying nature of global environmental changes that accompanied the biotic turnover remains elusive. Here we present chemical and mineralogical studies across the end-Triassic extinction level of the deep-sea chert sequence (Inuyama, Japan). Depleted hematite content normalized by terrigenous material predated the end-Triassic extinction level with significant rock color change from brick red to purple, which is consistent with the rock magnetic records of hematite reported. This suggests the loss of authigenic hematite possibly due to the acidification of bottom-water and the underlying sediment pore-water. This timing is consistent with the initial eruption of CAMP volcanism, suggesting a catastrophic release of greenhouse gases as a cause of deep-ocean acidification. Across the end-Triassic extinction interval, MgO/Al2O3, Fe2O3/Al2O3, and Al2O3/SiO2 increased with change in color from purple to dusty red. This trend became close to those of weathered CAMP basalts in arid area, implying that it became the considerable source of aeolian dust in cherts after the end-Triassic extinction event. These temporal relations support the synchrony among the initial eruption of CAMP, deep-ocean acidification, and the end-Triassic extinction. Similar rock color changes of cherts might have potential information for the volcanisms and deep-ocean acidification in other geologic events. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2015.09.046

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

Two new species and one new subspecies of genus Capnuchosphaera, (. Capnuchosphaera tumida nov. sp., C.waihekeensis nov. sp. and C.texensis australis nov. ssp.) are described herein from phosphatic nodules included in mudstone and sandstone beds of the Waipapa Terrane, Waiheke Island, New Zealand. The phosphatic nodules yielded a rich Late Triassic (Carnian-Norian) radiolarian fauna, with a high abundance of spumellarian taxa including numerous species of the genera Capnuchosphaera, Vinassaspongus, Kahlerosphaera, Sarla and Dumitricasphaera. Waiheke Island Capnuchosphaera are characterized by a large cortical shell and a distinctively low ratio of spine length to cortical shell diameter. These features differ significantly from those of Capnuchosphaera in the Tethyan Realm and are considered to be the result of adaptation to an Austral-New Zealand peripheral ocean of Gondwanaland in the Mesozoic Southern Hemisphere.

DOI： 10.1016/j.revmic.2015.02.001

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

DOI： 10.1016/j.revmic.2015.03.001

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Language：Japanese  

J-GLOBAL

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Language：Japanese   Publishing type：Research paper (conference, symposium, etc.)  

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

We present a comprehensive data set of organic and inorganic geochemistry from a lower Cretaceous pelagic bedded chert succession of the Shimanto accretionary belt in the Yokonami Peninsula (Kochi, Japan). Based on stable isotopic composition of total organic carbon (δ&lt
sup&gt
13&lt
/sup&gt
C&lt
inf&gt
org&lt
/inf&gt
), in conjunction with radiolarian biostratigraphic data, we propose that a 1.3-m-thick interval within the examined section is correlative with Tethyan Selli Level (Apennines, Italy), a sedimentary expression of oceanic anoxic event (OAE) 1a. Specifi cally, the δ&lt
sup&gt
13&lt
/sup&gt
C&lt
inf&gt
org&lt
/inf&gt
record illustrates a discernible negative shift and subsequent positive excursions upsection, a pattern that resembles the typical δ&lt
sup&gt
13&lt
/sup&gt
C&lt
inf&gt
org&lt
/inf&gt
pattern across OAE 1a reported from various sites such as the Mediterranean Tethys and Pacifi c seamount fl anks. Our δ&lt
sup&gt
13&lt
/sup&gt
C&lt
inf&gt
org&lt
/inf&gt
record from the deep Pacifi c basin supports the idea that the δ13C variation across OAE 1a was induced by a signifi cant perturbation of global carbon cycle. The slight increase in total organic carbon contents of sediment deposited during OAE 1a suggests slight or no expansion of oxygendefi cient water mass in the overlying water column. Rare earth elements and lead isotopic compositions indicate relatively higher contributions of volcanic or hydrothermally altered components before and after OAE 1a. The volcanic or hydrothermal source may be associated with emplacement of the Ontong Java Plateau during the early Aptian, or tectonically induced hydrothermal alteration associated with the formation of the accretionary complex.

DOI： 10.1130/2015.2511(16)

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOLOGICAL SOC PUBL HOUSE  

The secretion process of the siliceous skeleton in polycystine radiolarians has drawn a great deal of interest during the last century; however, little is known about the actual physiological process of silica deposition. Recently, the PDMPO (2-(4-pyridyl)-5-[(4-(2-dimethylaminoethylaminocarbamoyl) methoxy)-phenyl] oxazole) method for staining silica deposition sites in polycystines was developed. In the present study we examined over 30 polycystine cells with PDMPO and found that both the skeletons and pseudopodia of three species (Lithelius sp., Rhizosphaera trigonacantha and Arachnosphaera hexasphaera) were stained and emitted green fluorescent light. Staining of the skeleton was probably the result of skeletal thickening growth, whereas staining of the pseudopodia may indicate that siliceous matter is assimilated within pseudopodia. We refer to this hypothesis as the 'pseudopodial silica absorption hypothesis' (PSA hypothesis). If this hypothesis is correct, PSA is an intermittent process, and the absorbed silica within pseudopodia is quickly transferred to the cytokalymma where it is deposited on the skeleton. To date, the PSA process has been observed in only the three species cited above; therefore we are unable to evaluate whether the PSA process is unique to these species or a common process that occurs in all polycystines; further investigation is necessary.

DOI： 10.1144/jmpaleo2013-028

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

One of the most profound environmental changes in the Mesozoic took place during Pliensbachian-Toarcian (Early Jurassic), including oceanic anoxia (Toarcian Oceanic Anoxic Event; T-OAE). The T-OAE is thought to have been caused by increased atmospheric CO2 triggered by Karoo-Ferrar volcanism. This idea, however, remains debated, primarily due to uncertainties in their age constraints of the relevant sedimentary sequences. To examine their temporal relationships, herein, we provide the astronomical time scale of the Lower Jurassic deep-sea bedded chert sequences from the pelagic Panthalassa superocean, which are exposed in the Inuyama area, central Japan. A 405-kyr tuned astrochronology, anchored to the end-Triassic extinction as 201.4 +/- 0.2 Ma (Ikeda and Tada, 2013), allows us to constrain the ages of two black bedded cherts (T-OAE1 and T-OAE2). The ages of these T-OAEs overlap U-Pb ages of Karoo volcanic rocks. T-OAE in the European region is also synchronous with the Karoo-Ferrar volcanism, based on radiolarian and ammonite biostratigraphic correlation. These temporal relationships support the potential impact of Karoo-Ferrar volcanism on T-OAEs on a global scale. On the other hand, the onset of T-OAEs occur at the maxima of similar to 40 kyr, similar to 100 kyr, and 405 kyr cycles of chert thickness variation. The termination of T-OAEs and the recovery to oxic conditions in pelagic ocean coincide with the minima of similar to 40 kyr, similar to 100 kyr, and 405 kyr cycles of chert thickness. Moreover, the termination of final black chert and grey chert deposition coincide with the minima of similar to 1800 kyr cycles of chert thickness. These temporal relationships imply that orbital-scale productivity cycles were important in controlling the onset and termination of T-OAEs through the carbon cycle dynamics, which have been already amplified by Karoo-Ferrar volcanism. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2014.05.026

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

Understanding the primary relationships between basaltic rocks and fossiliferous sedimentary rocks provides direct information on the timing and geologic setting of past oceanic igneous activity. Though the basalts associate with cherts in the Northern Chichibu Belt have been petrographically identified as OIA/OIT or MORB, such primary relationships of them are not well understood.This paper provides the primary intrusive relation of basaltic rocks contact with chert and calcareous siliceous shale of Sugyo area in the Northern Chichibu Belt on Shikoku Island. The sediments are included within the basalt as xenoliths and in the contact zone with the basalt they have been recrystallized and contain metamorphic minerals possibly produced by contact metamorphism due to the basalt intrusion. These indicate that the basalts are sills or dykes that have intruded the sediments. The cherts are radiolarian chert which alternate with the calcareous siliceous shale and include minerals of oceanic volcanic origins. Asselian radiolarian fossils are yielded from a subangular chert xenolith that was intruded by the basalt possibly before the chert had undergone complete diagenesis. The petrography of the sills indicates they are alkali basalts. X-ray fluorescence analyses indicate that the basaltic rocks include subalkaline basalts and oceanic island tholeiite or oceanic island alkaline basalts.We have concluded that the basaltic dykes and sills were products of Asselian or younger intra-plate volcanism at an oceanic area covered by a pile of pelagic siliceous sediments. These Asselian cherts are earlier than the Sakmarian, Wordian and Capitanian limestones that overlie intra-plate basalts of Ohnogahara part of the Northern Chichibu Belt. The basalt sills may therefore represent the early stages of intra-plate igneous activity in the paleo-Pacific Ocean. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jseaes.2013.09.016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

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  

Recent studies on the global distribution of Pliensbachian and Toarcian polycystine radiolarians allowed us to examine faunal turnovers and the biogeography through this critical time interval around a major ecologic and biotic crisis. The analysis is based on the distribution of 167 species belonging to 69 genera. Significant variations in the ratio between the number of originating and extinct species have been recognized. During the early Early Pliensbachian FADs greatly exceeded LADs and the maximum diversity was reached in the late Early Pliensbachian. The trend then reversed with the number of LADs exceeding FADs throughout the Late Pliensbachian and Early Toarcian (extinction interval). Recovery started in the Middle and Late Toarcian, when the number of FADs again surpassed the number of LADs.
Three differing evolutionary patterns are observed amongst radiolarian genera through the studied time interval. The largest group diversified rapidly in the Early Pliensbachian and experienced higher extinction rates in the Late Pliensbachian and Early Toarcian; a second group exhibited no major changes; and a third group of mainly spongy spumellarians was successful during the extinction interval. The overall trend of radiolarian diversity is in a fairly good agreement with that of other marine faunas (ammonites and also benthos), but shows an inverse correlation with diversity trends of phytoplankton.
Correlation with concomitant environmental changes indicates that radiolarian radiation/extinction rates were not consistently linked with temperature fluctuations or sea-level changes. It is also evident that the diversity decrease started well before the Early Toarcian negative delta C-13 peak and the Oceanic Anoxic Event (OAE). The extinction interval corresponds well to the duration of a short-term anomaly in the strontium-isotope record, including the rapid decrease of Sr-87/Sr-86 values in the Late Pliensbachian as well as the rapid increase in the Early Toarcian. This coincidence supports the hypothesis that the predominance of extinctions over originations was caused by a series of climate and environmental changes related to intensified magmatic activity.
Some distinct biogeographic differences have been observed. Generic differences are most strongly displayed by the presence or absence of a particular genus or by changes in abundance while species differences range from greater variability to having completely different species in separate palaeolatitudinal realms. Two groups of genera are distinguished: those that are common to abundant in the Tethys (low latitudes) and rare to absent in mid to high latitudes, and those common to abundant in mid to high latitudes and rare to absent in the Tethys. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2013.06.028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOLOGICAL SOC AMER, INC  

The end-Triassic mass extinction event is regarded as one of the five largest extinction events of the Phanerozoic. The emerging consensus points to volcanic activity at the Central Atlantic Magmatic Province (CAMP) as the ultimate cause of the extinction, yet the underlying mechanisms and the nature of global environmental changes that accompanied the biotic turnover remain elusive. We present a rock magnetic study of the extinction interval found within a continuous chert sequence that provides an uninterrupted record of pelagic sedimentation in the Panthalassa Ocean. The variations in the relative abundances and characteristics of authigenic magnetic phases indicate that the Triassic-Jurassic transition progressed in two stages. The initial stage, characterized by a disappearance of the previously ubiquitous magnetofossils, started a few tens of thousands of years to 100 k.y. prior to the formal Triassic-Jurassic boundary as identified by the diagnostic radiolarian species. The second stage, defined by significant changes in optical and magnetic properties of hematite pigment, lasted a few tens of thousands of years. The stepwise change in magnetic properties is suggestive of the protracted environmental deterioration, likely prompted by the early episodes of the CAMP volcanism, which was followed by a sudden ocean acidification event, perhaps triggered by a catastrophic release of gas hydrates.

DOI： 10.1130/G34343.1

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

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 similar to 15 parts per thousand 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 similar to 10 parts per thousand 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 S-32-enriched sulfur from the H2S-rich water to the oxic surface-waters coincided with the end-Permian mass extinction. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gloplacha.2012.12.006

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

We present initial isotopic ratios of lead for Early Cretaceous (Barremian-Aptian) sections from Shatsky Rise (Pacific) and Gorgo a Cerbara (Italy). Our Pb isotopic data track an interval representing Oceanic Anoxic Event (OAE)-1a, which is characterized by quasi-global deposition of organic carbon-rich black shale. Pb isotopic compositions of sediments from Shatsky Rise decrease at the end of Barremian time, from radiogenic continental values to unradiogenic values, and subsequently remained less radiogenic until the end of early Aptian time. We explain the isotopic shift by a significant increase in supply rate of unradiogenic Pb, most likely due to massive volcanism. In contrast, the Pb isotopic compositions from the Italian section, which was situated at the western end of Tethys, are mostly identical to those of upper continental crust, showing no significant change in supply rate of unradiogenic Pb. The discrepancy between two sites is attributed to quiescent deep-submarine eruptions of Pacific large igneous provinces (LIPs) such as the Ontong Java Plateau (OJP), which severely limited dispersion of Pb-carrying particles out of the Pacific Ocean. Published Os isotopic data from the Italian section indicate two episodes of massive eruptions of OJP or contemporaneous Manihiki and Hikurangi plateaus starting from earliest Aptian time, slightly later than that indicated by the sedimentary Pb isotopic record from Shatsky Rise. Differences in isotopic variations between Pb and Os likely reflect differences in their chemical behaviors in the oceans, i.e., Pb isotopic compositions would have varied in response to local or regional changes in sediment provenances, whereas large-scale changes in Os inputs are required to explain variations in seawater Os isotopic compositions. Our Pb isotopic data, together with the published Os isotopic record, provide new evidence for the eruptive history of OJP together with contemporaneous Pacific plateaus and its environmental consequences, starting from end-Barremian time and extending through early Aptian time. (c) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2011.04.021

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Bedded chert is the only sediment type representative of the Paleozoic to early Mesozoic pelagic marine environment. Because of their association with ophiolites and island arc rocks, presence of datable microfossils and paleohorizontal reference provided by well-developed bedding surfaces, bedded chert sequences are often targeted for paleomagnetic tectonic studies. However, processes of magnetization acquisition in biosiliceous sediments, and consequently, the significance of their magnetic record, are not well understood. Our rock magnetic study of a Triassic-Jurassic radiolarian chert sequence, the Mino Terrane, Central Japan, shows that the ferrimagnetic assemblage of the gray chert units is of detrital origin, while the red chert's assemblage is dominated by authigenic phases - pigmentary hematite and biogenic magnetite - which contribute to the natural remanent magnetization. The presence of magnetofossils places red oxic chert in the category of prospective environmental archives. Magnetite-producing magnetotactic bacteria were apparently able to tolerate elevated concentrations of dissolved silica as well as a steep redox gradient in sedimentary pore-waters during the deposition of red chert layers. A strong uniaxial anisotropy due to chain-alignment of the biogenic magnetite grains likely contributes to the acquisition of anomalously stable partial thermoviscous magnetization by chert even at low metamorphic temperatures. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2011.02.047

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：COPERNICUS GESELLSCHAFT MBH  

Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales) and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associated with a pronounced (ca. 7 parts per thousand) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the lower Toarcian is thought to represent an oceanic anoxic event (the T-OAE). If the T-OAE was indeed a global event, an isotopic expression of this event should be found beyond the epi- and pericontinental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (delta C-13(org)) of lower Toarcian organic matter-rich cherts from Japan, deposited in the open Panthalassa Ocean, was analysed. The results show the presence of a major (>6 parts per thousand) negative excursion in delta C-13(org) that, based on radiolarian biostratigraphy, is a correlative of the lower Toarcian negative CIE known from Pangaean epi- and pericontinental strata. A smaller negative excursion in delta C-13(org) (ca. 2 parts per thousand) is recognized lower in the studied succession. This excursion may, within the current biostratigraphic resolution, represent the excursion recorded in European epi-continental successions close to the Pliensbachian/Toarcian boundary. These results from the open ocean realm suggest, in conjunction with other previously published datasets, that these Early Jurassic carbon cycle perturbations affected the active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric).

DOI： 10.5194/se-2-245-2011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOLOGICAL SOC AMER, INC  

The Triassic-Jurassic (T-J) boundary ca. 200 Ma represents one of the major mass extinction events of the Phanerozoic; however, the cause of this event remains controversial because of a paucity of geological evidence. In this study we present an isotopic record of osmium extracted from a bedded chert succession across the T-J boundary in the Kurusu section of Japan, deposited within a Paleo-Pacific (Panthalassa) deep basin. The data show a gradual decrease in seawater Os-187/Os-188 values during the Rhaetian, followed by a sharp increase in the latest Rhaetian, and a subsequent stable phase across the T-J boundary. The decreasing trend of Os-187/Os-188 values during the Rhaetian indicates a gradual increase in the relative supply rate of unradiogenic Os from the mantle associated with emplacement of the Central Atlantic Magmatic Province. The subsequent shift toward radiogenic values reflects an increased supply of radiogenic Os due to enhanced continental weathering. This interval marks more negative isotopic values of organic carbon, the onset of radiolarian faunal turnover, and conodont extinctions, indicating that the rapid increase in continental weathering rate was closely linked to the perturbation of the carbon cycle and the T-J biotic crisis.

DOI： 10.1130/G31223.1

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

Skeletogenesis in polycystine radiolarians was detected, using a fluorescent compound called PDMPO (2-(4-pyridyl)-5-[(4-(2-dimethylaminoethylaminocarbamoyl)methoxy)-phenyl] oxazole). This compound binds under acidic conditions with silica in the silica deposition vesicle (SDV) of radiolarians, and only newly added silica emits a green fluorescence under ultraviolet light. We used cells fixed with formaldehyde of two species of spherical Spumellaria (Hexacontium philosophica and Rhizosphaera trigonacantha) and three species of cyrtid Nassellaria (Anthocyrtidium angulare, Clathrocyclas (?) cassiopeiae, and Lophophaena hispida), in which green fluorescence occurred in the entire skeleton outside the endoplasm. In contrast, the conical nassellarian species Eucyrtidium hexagonatum emitted green fluorescence only on the cephalo-thorax-abdominal part of the skeleton, and on part of the inner ring at the segmental suture, and the margins of pores, suggesting partial biological silicification. Two flat spumellarian species (Dictyocoryne profunda and Rhopalastrum elegans) showed bright green fluorescence over the full skeleton in some cells, but other cells did not fluoresce at all, even though young cells in good condition were tested, suggesting that intermittent growth occurs in these species, as known from a controlled incubation experiment. We did not observe development of new skeletons, but "skeletal thickening growth" (STG), defined as silica deposition over the surface of an existing skeleton, occurred to varying degrees in the polycystines, and may result in the formation of lamellar structures, as observed in sectioned skeletons of polycystines. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.marmicro.2010.08.005

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Jurassic radiolarians from 220 samples in Queen Charlotte Islands, B.C., Williston Lake, B.C., east-central Oregon, Baja California Sur, southern Spain, Austria, Slovenia, Turkey, Oman, Japan and Argentina were studied in order to construct global zonation for the Pliensbachian, Toarcian and Aalenian stages. Well-preserved faunas from continuous stratigraphic sections in Queen Charlotte Islands provide the most detailed record for this time interval, and all collections are tied to North American ammonite zones or assemblages. Collections from nearly all other areas lack independent dating except for early Toarcian carbon-isotope dating in Slovenia and late Aalenian ammonites in Spain.A database of 197 widely distributed updated taxonomic species was used to construct a Unitary Association (UA) zonation for the interval. A global sequence of 41 UAs was obtained for the top of the Sinemurian to the base of the Bajocian. The first and the last UAs represent the Late Sinemurian and the Early Bajocian respectively. The remaining 39 UAs were merged into nine zones (four Early Pliensbachian, one Late Pliensbachian, one Early Toarcian, one Middle-Late Toarcian, and two Aalenian) according to prominent radiolarian faunal breaks and ammonite data. The new zones are the Canutus tip pen - Katroma clara Zone (latest Sinemurian/earliest Pliensbachian); Zartus mostleri - Pseudoristola megaglobosa, Hsuum mulleri - Trillus elkhornensis and Gigi fustis - Lantus sixi zones (Early Pliensbachian); Eucyrtidiellum nagaiae - Praeparvicingula tlellensis Zone (Late Pliensbachian); Napora relica - Eucyrtidiellum disparile Zone (Early Toarcian); Elodium pessagnoi - Hexasaturnalis hexagonus Zone (Middle and Late Toarcian); Higumastra transversa - Napora nipponica Zone (early Aalenian); and Mirifusus proavus - Transhsuum hisuikyoense Zone (late Aalenian). These zones can be correlated worldwide and link previously established UA zonations for the Hettangian-Sinemurian and the Middle to Upper Jurassic. The new zonation allows high-resolution dating in the studied interval and provides a solid basis for analyzing faunal turnovers and the paleobiogeography of Jurassic radiolarians. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2010.08.024

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MICRO PRESS  

We have examined the stable carbon isotope stratigraphy, bio- and litho-stratigraphy of the Upper Triassic (Otapirian) - Lower Jurassic (Aratauran) boundary strata from the Awakino gorge and Kawhia coast sections, Murihiku Terrane, North Island, New Zealand. Successive occurrences of species of the bivalve genus Otapiria, O. dissimilis, O. marshalli and O. aff. marshalli, and also of age diagnostic ammonites indicate that the Hettangian strata in both sections are very thin compared with the Rhaetian sequences. Lamination structures are well developed at the Tr-Jr (Rhaetian-Hettangian) boundary transition interval. The delta C-13 values of organic matter from siltstone and carbonate nodules in the sedimentary rocks range from -28.5 to -25.5 parts per thousand and there is no correlation between delta C-13(org) and C/N ratios. The excursion patterns of delta C-13(org) from both sections are similar, showing a negative spike at the uppermost Rhaetian and a positive spike immediately below the Tr-Jr boundary. A long-lived positive shift is also recognized in the Awakino gorge section, which coincides in pattern with those reported in Tr-Jr boundary successions from the Queen Charlotte Islands, British Columbia, Canada. These results suggest that although magnitude and absolute values are slightly different, the integrated pattern of stable carbon isotope signatures over the Tr-Jr boundary could be a valuable tool for correlation, at least between sedimentary rocks from similar depositional settings in the Panthalassa.

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Language：Japanese   Publisher：The Geological Society of Japan  

Early Jurassic radiolarian faunae were extracted from mudstone samples collected at three localities (Se1, Ik1, and Jo2) in an accretionary complex within the Ashio Terrane in the Kambara Mountains, Niigata Prefecture, Japan. The faunae of both Se1 and Ik1 are dominated by <i>Canoptum</i> species, in association with two characteristic species belonging to <i>Gorgansium</i> (<i>G</i>. sp. A and <i>G</i>. sp. B) for Se1, and species belonging to <i>Parahsuum</i>, <i>Lantus</i>, and <i>Helvetocapsa</i> for Ik1. The fauna in Jo2 consists mainly of the species of <i>Parvicingula</i>, <i>Zhamoidellum</i>, and gen. et sp. indet. B.<br>Based on a comparison of these radiolarians with those from North America, Europe, and Southwest Japan, the ages of the faunae from Se1, Ik1, and Jo2 are Hettangian, Late Pliensbachian, and Middle to Late Toarcian/Aalenian?, respectively.<br>This is the first report of radiolarian fossils from terrigenous clastic rocks (mudstone) in the Kambara Mountains; thus, this result contributes to reconstructions of oceanic plate stratigraphy in the region and to correlating the area with other accretionary complexes in the Ashio Terrane.

DOI： 10.5575/geosoc.116.441

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A new genus (Triassiphaeodina gen. nov.) and two new species (Medusetta japonica sp. nov. and Triassiphaeodina niyodoensis sp. nov.) of Late Triassic (Rhaetian) phaeodarian Radiolaria are described from a phosphatic nodule found in melange rocks of the Northern Chichibu Belt, Shikoku, Japan. The Rhaetian age of the nodule and of the phaeodarian new taxa is based on co-occurring Polycystina Radiolaria, including Bipedis acrostylus Bragin, Livarella densiporata Kozur and Mostler, Fontinella primitiva Carter, and Ferresium sp. A of Carter (1993). This finding shows that phaeodarian Radiolaria were already represented in Late Triassic oceans, with morphologies similar to those known in the Late Cretaceous and Cenozoic, from which they have previously been reported. The new taxa described herein represent the oldest known phaeodarian fossils.

DOI： 10.2517/1342-8144-13.1.053

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

Phytoremediation, a plant-based and cost-effective technology for the cleanup of contaminated soil and water, is receiving increasing attention. In this study, the aquatic macrophyte Eleocharis acicularis was examined for its ability to take up multiple heavy metals and its potential application for phytoremediation at an abandoned mining area in Hokkaido, Japan. Elemental concentrations were measured in samples of F. acicularis, water, and soil collected from areas of mine tailing and drainage. The results reveal that Pb, Fe, Cr, Cu, Ni, and Mn accumulation in the plants increased over the course of the experiment, exceeding their initial concentrations by factors of 930, 430, 60, 25, 10, and 6, respectively. The highest concentrations of Fe, Pb, Zn, Ni, Cr, Cu, and Ni within the plants were 59500, 1120, 964, 388, 265, 235, and 47.4 mg/kg dry wt., respectively, for plants growing in mine drainage after 11 months of the experiment. These results indicate that E. acicularis is a hyperaccumulator of Pb. We also found high Si concentrations in E. acicularis (2.08%). It is likely that heavy metals exist in opal-A within cells of the plant. The bioconcentration factors (BCF; ratio of metal concentration in the plant shoots to that in the soil) obtained for Cr, Cu, Zn, Ni, Mn, and Pb were 3.27, 1.65, 1.29, 1.26, 1.11, and 0.82, respectively. The existence of heavy metals as sulphides is thought to have restricted the metal-uptake efficiency of E. acicularis at the mine site. The results of this study indicate that E. acicularis shows great potential in the phytoremediation of mine tailing and drainage rich in heavy metals.

DOI： 10.1002/clen.200900009

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Language：English   Publisher：PALAEONTOLOGICAL SOC JAPAN  

Light microscopic studies, using both video imaging and normal camera, were made on living nassellarian radiolarians Eucyrtidium hexagonatum Haeckel, Pterocotys zancleus (Muller) and Dictyocodon prometheus Haeckel from the East China Sea off Okinawa Island, Japan. Continuous and careful observations revealed pseudopodial activity related mostly to feeding behavior. The results are presented in detail with the definition of 11 descriptive terms for nassellarian pseudopodia. Among them, terminal projections (TP) extending as straight projections from the aperture of the shell body and forming a conical structure (terminal cone: TC) and axial projections (XP) prolonged outward from the center of the aperture and proximally surrounded by TP are used for feeding. Although there are some minor differences, feeding activities of the three species can be subdivided into the following three cyclic phases; Phase I characterized by gradual extension of TP and XP from the aperture, Phase 2 marked by an abrupt withdrawal of TP and XP toward the aperture to engulf captured prey, and Phase 3 during which entangled TP used for capturing prey are completely retracted into the aperture. These lines of evidence suggest that the shell aperture plays the same role of a feeding apparatus as does a mouth. Interestingly, XP of E. hexagonatum sometimes shows abnormal branching, fusion and separation, which is different from the spumellarian axotlagellum.

DOI： 10.2517/1342-8144-12.3.209

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Well-preserved Lower Jurassic (Hettangian-Sinemurian) radiolarian fossils were obtained from black chert and shale of the Wakai complex in the Ikuno, area, Tamba Terrane, Southwest Japan. These faunas are dominated by the genera Natoba, Canoptum, Ovumella, and Droltus. We define a Natoba-rich Assemblage as one containing &gt;10% Natoba in the nassellarian assemblage. This assemblage is also characterized by relatively high abundance of Canoptum and Ovumella (combined abundance &gt;15% nassellarian assemblage) and a low nassellarian/spumellarian ratio (&lt;0.2). Based on data from Lower Jurassic radiolarian faunas from Japan, the Natoba-rich Assemblage is very similar to the Canoptum Assemblage. These two assemblages both contain common Natoba and occur exclusively in fine-grained silicielastic rocks and black cherts. Considering the global distribution of Natoba, the Natoba-rich Assemblage appears to be restricted to oceanic regions peripheral to the western Panthalassa and Tethys.

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MICRO PRESS  

Well-preserved Lower Jurassic (Hettangian-Sinemurian) radiolarian fossils were obtained from black chert and shale of the Wakai complex in the Ikuno area, Tamba Terrane, Southwest Japan. These faunas are dominated by the genera Natoba, Canoptum, Ovumella, and Droltus. We define a Natoba-rich Assemblage as one containing >10% Natoba in the nassellarian assemblage. This assemblage is also characterized by relatively high abundance of Canoptum and Ovumella (combined abundance >15% nassellarian assemblage) and a low nassellarian/spumellarian ratio (<0.2). Based on data from Lower Jurassic radiolarian faunas from Japan, the Natoba-rich Assemblage is very similar to the Canoptum Assemblage. These two assemblages both contain common Natoba and occur exclusively in fine-grained siliciclastic rocks and black cherts. Considering the global distribution of Natoba, the Natoba-rich Assemblage appears to be restricted to oceanic regions peripheral to the western Panthalassa and Tethys.

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The ionic migration of antimony in various weathered and country rocks during chemical weathering was studied The Ichinokawa abandoned mine of Shikoku Island, Japan is famous for the production of stibnite. The antimony deposits are mainly in Sambagawa metamorphic rocks and the brecciated rocks (Ichinokawa breccia) formed through a hydro-fracturing process associated with hydrothermal fluid related to Tertiary igneous activity around the area. Antimony content in stream water around the mine was extremely high (over 200 □g/L), which indicates that antimony dissolves into the water from the country rocks by chemical weathering. We examined the antimony contents in variously weathered and altered country rocks in the streambed, to understand the transfer of the element into the stream water. Consequently, antimony content in brown-colored, strongly weathered and altered part of the rocks was higher than that in the unweathered (or weakly weathered) part. The antimony content in the strongly weathered part was several tens to hundreds ppm, although the content in unweathered part was significantly low, sometimes under the detection of XRF. This may indicate that the antimony in the stream water is adsorbed selectively in the strongly weathered and altered part of the streambed rock. The strongly weathered and altered rocks contain many iron hydroxides, which may trap antimony ion from the water. A similar phenomenon was observed in the other area. This suggests that a high distribution of antimony ion into the strongly weathered and altered rocks including iron hydroxides against the water is ubiquitous.

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

Micropalaeontological and geochemical analyses were performed on samples from a continuous sequence of bedded chert from the Kurusu (KU) section, Inuyama area, southwest Japan. The sequence contains the Triassic-Jurassic (T-J) boundary and is representative of deep-sea sediments from Panthalassa. The succession records a rapid, stepwise extinction pattern of radiolarian faunas, and the disappearance of conodonts at the T-J boundary. Comparison of micropalaeontological results and geochemical data reveals anomalously high abundances of platinum group elements (PGEs) in the latest Rhaetian, at the beginning of the radiolarian extinction at the T-J boundary. The PGE anomaly suggests that the radiolarian ooze of Panthalassa was contaminated by siderophile-rich materials during the late Rhaetian. The rare earth element (REE) pattern shows no distinct change across the T-J boundary, except for one significant positive Ce anomaly immediately below the PGE anomaly. These geochemical signatures imply the anomalous input of PGE-rich materials, but no obvious anoxic event in deep-sea sediments during latest Triassic time. The PGE anomaly at the end of the Triassic may be linked to the first phase of marine plankton extinction, but would not have been directly connected with the main radiolarian extinction at the T-J boundary. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2006.06.038

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Authorship：Corresponding author   Language：English   Publisher：CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS  

Precise comparison of the change in radiolarian faunas 3.5 m above a U-Pb zircon dated 199.6 +/- 0.3 Ma tuff and approximately coincident with a negative delta C-13 anomaly in the Queen Charlotte Islands, B.C. (Canada) with Inuyama (Japan) sequences indicates that major global changes occurred across the Triassic-Jurassic (T-J) boundary. Nearly 20 genera and over 130 Rhaetian species disappeared at the end of the Triassic. The index genera Betraccium and Risella disappear and the final appearance of Globolaxtorum tozeri, Livarella valida, and Pseudohagiastrum giganteum sp. nov. are also diagnostic for the end of the Triassic. The low-diversity Hettangian survival fauna immediately above the boundary is composed mainly of small, primitive spumellarians with spongy or irregularly latticed meshwork and rod-like spines, and new genera Charlottea, Udalia, and Parahsuum s.l. first appear in the lowest Hettangian in both localities. Irrespective of different sedimentation rates and sedimentary environments, such as shelf to upper slope (Queen Charlotte Islands) and deep sea below carbonate compensation depth (CCD; Inuyama), radiolarians show a similar turnover pattern at the T-J boundary.

DOI： 10.1139/E05-020

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Authorship：Lead author   Language：English   Publisher：The Geological Society of Japan  

A lingulid brachiopod <i>Lingularia</i> sp. is described from Middle Triassic (Anisian) bedded chert in the Northern Chichibu Terrane, Shikoku, Japan. The fossil occurrence is unusual because of its association within deep-sea sediments. Lingulids are well known from Early and Middle Triassic successions and their apparent abundance may relate to the recovery following the Permian/Triassic (P/T) extinction event. This find in Japan tends to support the view that lingulids favoured dysoxic conditions and became widespread in vacant niches of the ocean after the P/T boundary anoxic event as &ldquo;opportunistic taxa&rdquo;.

DOI： 10.5575/geosoc.110.758

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

Triassic Radiolaria are documented from phosphatic nodules obtained from the Karoro Formation and Potiki Siltstone from Kaka Point Structural Belt, Otago, New Zealand. There are abundant Glomeropyle and Spumellaria, and rare Nassellaria and Entactinaria. By comparison with radiolarian faunas from Japan, Thailand, European Tethys, and other Triassic strata in New Zealand, the Karoro Formation is correlated with upper Lower Triassic (Olenekian), older than the Potiki Siltstone. We believe that the fauna is strongly affected by non-Tethyan radiolarians based on the abundance of Glomeropyle, rare occurrence of Tethyan taxa, and the presence of many undescribed forms. Three new species are described herein: Glomeropyle bispinosa, G. campbelli, and Poulpus (?) caveaformis.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SIR PUBLISHING  

Triassic radiolarians are reported from two horizons in Waipapa Terrane at Arrow Rocks, Whangaroa area, Northland. This relatively undisturbed succession represents an ocean-floor sequence, consisting (in ascending order) of basalt with limestone layers, bedded chert, black shale, and red, maroon and green siliceous mudstone. The age of the lower part of the section is Middle-Late Permian. The radiolarian assemblages reported here indicate Early or Middle Triassic and Middle Triassic (Anisian) ages for maroon siliceous mudstones in the upper part of the section. Between strata of known Permian and Triassic age there is a thin potential Permian/Triassic boundary interval consisting of alternating black shale and grey chert. Radiolarian paleogeography indicates that the Arrow Rocks sequence experienced long distance plate tectonic displacement from a position of relatively low latitude in the Middle Permian and to a high latitude in mid-Triassic time.

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Authorship：Lead author   Language：Japanese   Publisher：日本地質学会  

We discuss the progress and future problems of geochemical studies on bedded chert sequences from accretionary complexes in Japan. Bedded cherts contain geochemical information about oceans and surfaces of upper continental crust in the past because they are a physical mixture of continental detritus (also rarely volcanic rocks), biogenic opal and hydrogenous materials such as Fe-Mn oxides.To reveal the sedimentary environments of bedded cherts, the REE patterns and abundance ratios of some elements have commonly been used. However, the REE patterns of marine sediments are complicated in origin, especially for the Ce anomalies. Indicators for oxic and anoxic environments are introduced, such as the Fe^<2+> and Fe^<3+> contents, V/Al, U/Al, Mn/Al (Ti) ratios, S abundance and also S isotopic ratios. V/Al_2O_3,U/Al_2O_3 and S are extremely high and show different trends in anoxic environments than they do in ordinary sea floor environments. On the contrary, MnO/TiO_2 ratios are extremely low in anoxic environments and much higher in oxic sediments after anoxic ones.Geochemical information about the surfaces of past continents is also seen in bedded cherts from Rb/K ratio and Eu anomaly, but it is difficult to evaluate other suitable elements for the examination of past continents.

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.104.V

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Green rock including chert xenoliths has been found in an outcrop of the Pippu area, central Hokkaido, Japan. It is petrologically divided into two types: massive hornblende basalt and picritic basaltic hyaloclastite. The former structurally overlies the latter. The hornblende basalt includes a large amount of chert xenoliths and was subjected to the high-P/T Kamuikotan metamorphism. Radiolarian fossils indicating late Callovian have been obtained from xenoliths of red chert in the hornblende basalt. The picritic basaltic hyaloclastite displays mineral assemblages corresponding to the prehnite-pumpellyite facies. The hornblende basalt is alkalic and rich in TiO2 and P2O5, being similar to oceanic island baslat, whereas picritic basalt is tholeiitic, but very poorer in TiO2 and P2O5 than oceanic ridge basalt. These data suggest that the hornblende basalt belongs to the Kamuikotan complex, whereas the picritic basaltic hyaloclastite is correlative with with Sorachi Group. The Kamuikotan green rocks is inferred to have been generated as intra-plate volcanism after late Calluvian.

DOI： 10.5575/geosoc.103.953

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.103.953

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Lower Jurassic Radiolaria are documented from Aratauran strata of the Murihiku Supergroup at the northern end of Sandy Bay, south of Nugget Point, Otago, New Zealand. The fossils were extracted from small carbonate nodules in fine grey sandstone in the middle part of the Aratauran sequence. The following genera were identified: Eptingium(?), Gigi, Hsuum, Orbiculiforma, Pantanellium, Paronaella(?), Poulpus(?), Saitoum, Spongostaurus(?), and Thetis. Comparison with radiolarian faunas of Europe, southwest Japan, and North America suggests that the study fauna is of Pliensbachian age, probably Early Pliensbachian, indicating the possibility that the Aratauran local stage, previously equated approximately with Hettangian-Sinemurian internationally, extends into the Early Pliensbachian.

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Language：Japanese   Publisher：海洋出版  

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

A drastic faunal turnover of radiolarians in the early Toarcian, termed the Toarcian Radiolarian Event (TRE), recognized in bedded chert sequences of southwestern Japan, is marked by the first co-appearance of the genus Praeparvicingula and Mesosaturnalis hexagonus and by high diversity among multicyrtids. The event resulted in the replacement of latest Triassic through earliest Jurassic taxa by Late Jurassic to Early Cretaceous taxa. At TRE levels in bedded cherts in southwestern Japan, the size of radiolarians decreased drastically, reworked conodont fossils appeared, and anoxic sediments (black cherts with FeS2 nodules) were deposited. The lithologic and faunal changes suggest that global marine environmental changes, including the occurrence of anoxia, caused the TRE.

DOI： 10.1016/S0377-8398(96)00024-2

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.103.167

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Language：Japanese   Publisher：Ehime University  

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

Well-preserved radiolarians from the Newcastle Group in southwest Kawhia, New Zealand, constitute the first record of Lower Jurassic radiolarians from in situ deposits in high latitudes of the Southern Hemisphere on the margin of Gondwana. The radiolarians were extracted from carbonate nodules from five horizons in the Rewarewa Formation and the lower part of the Arawhero Formation, in the Murihiku Terrane. The radiolarian-bearing sequence, which lies within the upper part of the type section of the local Aratauran Stage, is roughly datable as Hettangian-Sinemurian from rare ammonite occurrences. The radiolarian assemblages consist, on average, of 80-90% spumellarians and 10-20% nassellarians. Spumellarians include species of the following genera: Archaeotriastrum, Cnicella, Emiluvia (?) Homeoparonaella, Orbiculiforma, Pantanellium, Paronaella (?), Pseudocrucella, Pseudoheliodiscus, Spongostaurus and Spongotrochus. Nassellarians are composed of species of Bagotum, Bipedis, Droltus, Jacus (?) Perispyridium (?) Raoultius, Riedelius, Saitoum and Thetis. From data of Lower Jurassic radiolarian faunas of Europe, North America and Japan, the New Zealand fauna shows stronger affinity with those of the European Tethys such as Turkey (e.g. De Wever 1982) and the Northern Alps (Kozur &amp
Mostler 1990) than with faunas from other areas of the circum-Pacific. This connection between the European Tethyan and New Zealand faunas is not well explained by presently accepted continental reconstructions (Smith et al. 1994) for the Early Jurassic.

DOI： 10.1111/j.1440-1738.1996.tb00017.x

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Language：Japanese   Publisher：愛媛大学  

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Language：Japanese   Publisher：Ehime University  

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Language：English   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.100.575

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.1994.0_245_2

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Authorship：Corresponding author   Language：English   Publisher：The Geological Society of Japan  

The Mikabu greenrocks extend more than 800 km in length in the outer zone of Southwest Japan. They are composed mainly of volcanic sedimentary rocks, basalts, dolerite, gabbro, and ultrabasic rocks, and are associated with minor limestone and chert. Recently, the Mikabu greenrocks have been interpreted to be accreted oceanic plateaus or seamounts. Red radiolarian chert xenoliths have been found in the Mikabu dolerite, Okuki area, western Shikoku. The paper discusses the geological significance of the fossil evidence constraining the formative age of the Mikabu greenrocks. -from Authors

DOI： 10.5575/geosoc.99.831

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Abstract The abundance of magnetic microspherules in a Triassic‐Jurassic continuous sequence of alternating chert and shale beds in the Mino accretionary complex, central Japan, was measured systematically. Depending on time, the magnetic microspherules extracted from shale beds change in abundance considerably from the minimum 0.9ppm/cm3 at latest Triassic (ca 208Ma) and the maximum 75ppm/cm3 at late Early Jurassic (ca 187Ma)
however, the abundance is always higher approximately 10–100 (average 70) times than those from adjacent chert bed at any stratigraphic horizon. Such systematic difference reveals the origin of radiolarian bedded chert as cyclic‐rapid accumulation of biogenic SiO2 under extremely slow accumulative environments of shale with probable aeolian dust in origin. The accumulation data for individual shale and chert beds were obtained based on the microspherule abundance and radiolarian biostratigraphy, i.e., ca 0.018g/cm2Ka for lower Jurassic shale beds and ca 1.9g/cm2Ka for adjacent chert beds. Duration time to make a chert‐shale couplet corresponds to a dominantly 15–20Ka interval (average 23 Ka) in Upper Triassic bedded cherts with a low paleolatitude, whereas a 40–45 Ka interval (average 42 Ka) in Lower Jurassic ones which may been formed in higher latitude than Triassics before the final accretion to the Asian continental margin. Depending on paleolatitude, the cyclicity of 23 and 42 Ka may correspond to Milankovitch cycles which have been well documented in deep‐sea sediments. Copyright © 1993, Wiley Blackwell. All rights reserved

DOI： 10.1111/j.1440-1738.1993.tb00084.x

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Detailed structural and biostratigraphical analysis of the Jurassic Inuyama Sequence, a coherent chert-clastic complex in the Mino-Tamba Belt, central Japan, clarifies the evolution of accretionary processes at shallow structural levels. The Inuyama Sequence is characterized by a series of stacked thrust sheets. Each sheet consists of an Early Triassic to Middle Jurassic oceanic plate stratigraphy composed of four lithologic units which are, in ascending order: siliceous claystone
ribbon chert
siliceous mudstone
and clastic rocks. The structural features of the Inuyama Sequence demonstrate a four-stage progressive deformation. (1) A décollement was initiated within the siliceous mudstone when this sequence was just seaward of the deformation front. Clastic dikes and sills formed at the horizon just above the décollement at this time. (2) The stratigraphic section above the décollement was imbricated by in-sequence thrusting in the frontal part of the wedge. This initial stage of thrusting and imbrication was followed by (3) the formation of duplex structures with fault-related folds within the lower stratigraphic section as the décollement stepped down-section to the lowest siliceous claystone interval. Finally, (4) these thrust packages were overprinted by secondary prism thickening in the form of out-of-sequence thrust faulting. © 1993.

DOI： 10.1016/0191-8141(93)90092-O

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One of the keys to understanding the origin of Archaean greenstone belts lies in the geological relationships between mafic and ultramafic greenstones, felsic to intermediate volcanic rocks and terrigenous sediments. Traditional models for greenstone belt evolution have been based on in-situ stratigraphic relationships. Most of these models, for example an oceanic island-arc developed on oceanic basement, back-arc basins, and the recently popular plume model, predict concordant stratigraphic relationships among the various greenstone belt lithologies. However, rather than being depositional in nature, several authors have indicated that many of the relationships between the different lithologies in greenstone belts are in fact tectonic, suggesting an allochthonous origin for most greenstone sequences. All of these latter models make analogies to Phanerozoic tectonic processes involving accretion of oceanic materials with volcanism related to both plate subduction and rifting. In this paper, we have evaluated the geological relationships between volcanic rocks and sediments in three regions in the Superior province, where the accretion of oceanic material can be documented, and direct comparisons are made to geological processes in Phanerozoic accretionary complexes. In the Malartic area in the southeastern Abitibi Subprovince, 3 to 4 km thick slices of komatiite and tholeiite, with intercalated terrigenous sediment, are tectonically imbricated and are overlain by calc-alkaline volcanics which postdate tectonic stacking. In both the Larder Lake region of the southwestern Abitibi belt and in the Beardmore-Geraldton belt, at the south-eastern limit of the Wabigoon belt, slices of iron-rich tholeiite and chemical sediments of an oceanic origin are tectonically imbricated with terrigenous sediment. The Malartic-Val d'Or area is considered to be an example of accretion of an Archaean oceanic plateau, while the Larder Lake and the Beardmore-Geraldton regions are potentially typical of accretion of normal oceanic crust in an arc-environment. Phanerozoic accretion of oceanic crust is accompanied by a step-back in subduction, and in this paper we suggest that oceanic crust accretion may have been the principal mechanism by which the locus of subduction migrated towards the south of the Superior province. Asthenospheric upwelling associated with the isolated sinking plate may have been responsible for widespread late-magmatism. This scenario requires that magmas be erupted through previously accreted volcanic, plutonic and sedimentary material. Furthermore, later ridge subduction will result in transpressional tectonics and eruption of mafic sequences over mature and immature volcano-plutonic sequences. The combined result of the plate tectonic scenario envisaged would result in the well-described "cyclic stratigraphy" of many granite greenstone sequences. © 1993.

DOI： 10.1016/0024-4937(93)90044-D

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Vertical distribution of microfossils such as radiolarians and conodonts across the Triassic/Jurassic (T/J) boundary were clarified through the biostratigraphic study of two continuous sequences of bedded cherts in the Inuyama area, central Japan. Three types of taxons were recognized around the T/J boundary, (1) Upper Triassic type such as Squinabolella, (2) Upper Triassic-Lower Jurassic type such as Canoptum, and (3) transition type (possibly earliest Jurassic tye) such as Parahsuum and Bipedis. The radiolarian fossils changed gradually, not drastically, from Triassic type into Jurassic ones during the interval (c7 m.y.) from the extinction of conodonts to the first appearance of a species of Bagotum. -Author

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Authorship：Lead author   Language：English   Publisher：The Palaeontological Society of Japan (PSJ)  

Four Lower Jurassic radiolarian assemblage-zones and four subzones are established on the basis of radiolarian biostratigraphic data from the Inuyama and three other areas of SW Japan. These zones are as follows in ascending order : the Parahsuum simplum (divided into Subzone I to IV), Mesosaturnalis hexagonus (newly proposed), Parahsuum (?) grande and Hsuum hisuikyoense Assemblage-zones. These zones range in age from latest Triassic/earliest Jurassic (Rhaetian/Hettangian?) to early Middle Jurassic (Bajocian). This age assignment is based on comparison with Early to Middle Jurassic radiolarian biostratigraphy established in North America and Turkey.

DOI： 10.14825/prpsj1951.1990.159_562

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Other Link： https://jlc.jst.go.jp/DN/JALC/10014400819?from=CiNii

Language：English   Publisher：Osaka City University  

This paper focuses on the late early Jurassic radiolarian assemblage of bedded cherts and siliceous mudstones in the Mt. Norikuradake area, central Japan. Nine multi-segmented nassellarians of the assemblage including two new species, are described herein. They belong to the genera Hsuum, Parahsuum and Parvicingula and are characterised by forms possessing features of both Parahsuum and Hsuum, with also a form of Parvicingula having small tests. The assemblage containing these taxa, recognisable in various localities in Southwest Japan and North America, is regarded as a fauna of the transitional period from early Jurassic to middle Jurassic forms. This assumption is based on a consideration of the morphology of its component species. On the basis of its biostratigraphic position and faunal content, the assemblage is probably to be dated to a certain time in the late Early to early Middle Jurassic, at least including Toarcian time. -Authors

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Language：English   Publisher：Osaka City University  

Parahsuum is a characteristic genus of Jurassic Radiolaria. In this paper, four species of Parahsuum, Parahsuum simplum Yao and three new species, are described from chert sequences of the Inuyama area, central Japan. From the stratigraphic horizons of their first occurrences and their morphologic features, the phylogenic relationships among P. simplum and two of the three new species are considered.-Authors

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Four radiolarian species, including two new species, of the family Syringocapsidae Foreman are described from the lowest Jurassic bedded cherts of the Inuyama area, central Japan. These species belonging to the genera Katroma, Syringocapsa and Gigi are representatives of the Parahsuum simplum Assemblage, one of the important early Jurassic radiolarian assemblages established in Southwest Japan. On the basis of morphology and biostratigraphic distribution, both genera Gigi and Katroma are regarded as descendants of the genus Syringocapsa. The species of Katroma in the Lower Jurassic are biostratigraphic marker taxa because of their short range and world-wide occurrences. Therefore, the upper part of the Parahsuum simplum Assemblage-zone with species of Katroma is probably assignable to upper Sinemurian to upper Pliensbachian.

DOI： 10.14825/prpsj1951.1988.151_543

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2021.0_049

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DOI： 10.14863/geosocabst.2017.0_238

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DOI： 10.14863/geosocabst.2017.0_515

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<b> [Program canceled for typhoon]</b> Program canceled for typhoon. However, This abstract is quotable and viewable on PDF.

DOI： 10.14863/geosocabst.2017.0_337

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2017.0_236

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Language：Japanese   Publisher：Japan Science Support Foundation  

DOI： 10.5363/tits.22.1_70

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DOI： 10.14863/geosocabst.2016.0_276

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2014.0_085

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DOI： 10.14863/geosocabst.2014.0_075

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DOI： 10.14863/geosocabst.2013.0_591

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DOI： 10.14863/geosocabst.2013.0_361

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DOI： 10.14863/geosocabst.2013.0_574

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DOI： 10.14863/geosocabst.2013.0_272

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DOI： 10.14863/geosocabst.2012.0_124

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DOI： 10.14863/geosocabst.2012.0_378

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Language：Japanese   Publisher：National Institute of Advanced Industrial Science and Technology, Geological Survey of Japan  

&nbsp;&nbsp;&nbsp;&nbsp;Late Triassic radiolarian fossils were extracted from siliceous mudstone in an accretionary complex of the Ashio Terrane in the Kamo district (Quadrangle series 1:50,000 of the Geological Survey of Japan), Niigata Prefecture, Japan. The siliceous mudstone occurs as a block within a muddy matrix. The siliceous mudstone also belongs to the upper unit of the Senmi Complex, which is distributed widely in the Kanbara Mountains within the Kamo district. The fauna in the siliceous mudstone consists mainly of species of the genera <i>Canoptum</i>, <i>Betraccium</i>, <i>Cantalum</i> and <i>Fontinella</i>, including <i>Canoptum</i> sp. cf. <i>C. rhaeticum</i>, <i>Fontinella</i> sp. cf. <i>F. clara</i>, <i>Fontinella</i> sp. cf. <i>F. primitiva etc</i>. Based on radiolarian biostratigraphy of these taxa previously documented elsewhere, the radiolarian fauna studied was dated to the Late Triassic (Rhaetian). This is a first report of Triassic radiolarian fossils from clastic rocks of the Ashio Terrane in the Kanbara Mountains; thus, this find contributes to reconstructions of oceanic plate stratigraphy of the Ashio Terrane in this region.

DOI： 10.9795/bullgsj.62.191

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2011.0.52.0

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DOI： 10.14863/geosocabst.2011.0.54.0

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

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DOI： 10.14863/geosocabst.2010.0.116.0

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Language：Japanese   Publisher：愛媛大学理学部紀要委員会  

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Other Link： https://opac1.lib.ehime-u.ac.jp/iyokan/TD00003999

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

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DOI： 10.14863/geosocabst.2009.0.92.0

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DOI： 10.14863/geosocabst.2009.0.210.0

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DOI： 10.14863/geosocabst.2009.0.378.0

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白亜紀の中期（BarremianからTuronian）は、顕生代で最も温暖な時代Greenhouse age である。この時代を特徴づける地質イベントとして、「海洋無酸素イベントOceanic Anoxic Event (OAE)」が挙げられる。OAEは、テチス海や大西洋、太平洋など世界中の海洋底に有機炭素に富む黒色頁岩が堆積するイベントであり、白亜紀の中頃に繰り返し発生した。その中でも、前期AptianとCenomanian-Turonian 境界におきたOAE-１aとOAE-2は、汎世界的に有機質黒色頁岩が堆積することから、最大級のOAEと考えられている。このOAEは寒冷化した新生代では認められない。OAEの出現メカニズムについては古くから盛んに議論されてきたが、発生機構、維持機構についてわかっていない。私たちはさまざまな同位体記録を用いてOAEと大規模火山活動との関連について検討してきた。本講演では、火山活動がグローバルな環境変動のトリガーになっていることを明らかにする試みについて詳細に紹介する。

DOI： 10.14862/geochemproc.56.0.304.0

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DOI： 10.14863/geosocabst.2009.0.93.0

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DOI： 10.14863/geosocabst.2008.0.70.0

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DOI： 10.14863/geosocabst.2008.0.293.0

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Language：Japanese   Publisher：一般社団法人日本地球化学会  

白亜紀のAptianからTuronianにかけて、海洋底に有機質泥が堆積する海洋無酸素イベントOceanic Anoxic Event (OAE)が繰り返し発生した。その中でも、前期AptianにおきたOAE-１aは汎世界的に有機質泥が堆積する最大級のOAEである。このOAE-1aの年代（約120 Ma）は地球最大の洪水玄武岩であるオントンジャワ海台の形成時期（123～119Ma）に近く、このため両者の関連が注目されてきた。オントンジャワ海台の火山活動とOAE-1aの関連を調べることで、大規模な火成活動と地球表層環境変動とのリンクを理解することができる。しかし、両者の時間的関連や因果関係について未解明の問題が多く、前者については年代学的・層序学的精査が、また後者については数値モデル実験などを用いた検討が必要である。本研究では、Aptian前期にテチス海や太平洋で堆積した遠洋性堆積物の炭素、鉛、オスミウム同位体比を測定し、OAE-1aの層準の周辺でオントンジャワ海台の形成に関連した大規模火山活動の痕跡が認められるかどうかを検討し、両者の同時性を層序学的に評価した。用いた試料はテチス海西部の遠洋性堆積物（イタリア中部ウンブリア州）、太平洋中央部の浅海遠洋性堆積物（シャツキー海台のODP198-1207Bコア）および深海遠洋性堆積物（高知県横波半島の四万十帯チャート；庵谷ほか、印刷中）の３サイトの遠洋性堆積物を使用した。これら３サイトにおいて、微化石および炭素同位体比変曲線からOAE-1aの層準を正確に見出した。横波半島の四万十帯チャートは、OAE-1aのインターバルを含む数少ない太平洋の深海底堆積物である（庵谷ほか、印刷中）。イタリアセクションのOs同位体比はOAE-1aの開始時およびその数１０万年前の２回、明瞭なシフトが認められ、同位体比の低いOsの供給が増加したことが明らかになっている(Tejada et al., submitted）。特にOAE-1aの開始時に起きたOs同位体比のシフトは極めて大きく、数１０万年間続くことから、オントンジャワ海台の形成に関連したマントルからの物質供給でのみ説明可能である。今回、低いOs同位体比が横波チャートにも認められることが明らかになった。先に述べたOｓ同位体比の変動は地球規模のものと結論付けられる。一方、海洋での滞留時間の短いPbはOsと異なり、サイト間で同位体比が異なる。イタリアのセクションでは当時のユーラシア大陸地殻に近いPb同位体比を示し、同位体比の大きな変動は認められない。これに対し、横波チャートのPb同位体比はオントンジャワ海台玄武岩の同位体比にほぼ一致し、オントンジャワからの物質供給が活発であったことを示している。シャツキー海台の堆積物のPb同位体比はイタリアセクションと横波チャートの中間的な値を示す。また、シャツキー海台の堆積物には、OAEが開まる時期にオントンジャワ海台からの物質供給が増加したことを示唆するPb同位体比の変化が認められた。このように、Pb同位体組成には当時の古地理（オントンジャワ海台からの距離、深海/浅海）に対応した違いが認められた。本発表では上記の新知見に加えて、３サイトのPb同位体比と古地理分布からオントンジャワ海台からの物質供給プロセスなどを検討する。

DOI： 10.14862/geochemproc.55.0.398.0

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2008.0.70.0

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2008.0.293.0

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2007.0.129.0

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2006.0_172_2

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2006.0_173_1

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2006.0_49_2

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2006.0_172_1

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2005.0_42_1

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Language：Japanese   Publisher：Japan Association of Mineralogical Sciences  

本研究では，愛媛県西条市，市之川中流域に分布する市之川礫岩を対象として，環境岩石学的検討を行い，熱水変質作用および地表付近の環境における主要・微量元素の移動・再濃集プロセスについて考察した．市之川礫岩の礫はすべて熱水変質作用を受けていることから，礫岩形成後に熱水変質作用を被り，熱水沈殿物としてドロマイトを主とする基質が沈殿したと考えられる．その際，As，Sb，Sなどが添加，SiO&lt;SUB&gt;2&lt;/SUB&gt;，Fe&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;，MgOなどが溶脱した．黄鉄鉱が多く形成されていることからAs，SbおよびSは黄鉄鉱として岩石中に固定されたと考えられる．その後，表層風化の過程で，黄鉄鉱が分解・溶脱し，S，Fe&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;，AsおよびSbが岩石中から溶脱したと考えられるが，風化部でFe&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt;，AsおよびSbが増加している．これらの元素は風化部で褐鉄鉱中に含有されていると推定される．また，黄鉄鉱の分解とともにドロマイトが溶脱し，CaOおよびMgOが減少したと考えられる．

DOI： 10.14824/jampeg.2005.0.26.0

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2005.0_208_2

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2005.0_320_2

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Language：Japanese   Publisher：Ehime University  

Phytoremediation is the use of plants for the in situ cleanup of contaminated soils, sediments, and ground water. Pot-scale experiment evaluated phytoremediation by Pteris vittata L. (Chinese brake fern) for mudstone containing arsenic (12.3 mg/kg-DW) of the Hakobuchi Group in the Yubari City, central Hokkaido, Japan. In this experiment, fronds of Pteris vittata L. were taken after 18 weeks growth in soil. The following properties became clear after examining the experimental results. (1) The brake fern can growth in the soil made from mudstone containing arsenic. (2) The highest arsenic concentrations in the frond of Pteris vittata L. growing in the soil are about 3000 mg/kg-DW. (3) The fern removed arsenic about 10 % from mudstone. The results suggested that the brake fern has a great poten tial to be used for phytoremediating soils with low concentration of arsenic.

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Other Link： https://opac1.lib.ehime-u.ac.jp/iyokan/TD00002878

Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2005.0_42_2

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Language：Japanese   Publisher：Ehime University  

In this paper, formation process of Ichinokawa breccia and antimony-arsenic mineralization in the breccia in the Ichinokawa area of Saijyo City, Ehime Prefecture, Japan, has been studied on the basis of geological, petrological and geochemical data. We have focussed on "hydraulic fracturing" process for the genesis of the Ichinokawa conglomerate. Ichinokawa conglomerate can be divided mainly into Ichinokawa breccia and Myojin Group. Carbonate-rich breccia and sandstone filling fractures are also found in the Sanbagawa schists adjacent to the Ichinokawa breccia. High-angle breccia zones, the Ichinokawa breccia, cut across the Sanbagawa schistocity. The Ichinokawa breccia consist principally of breccias which have been partly altered and veined by quartz, carbonate minerals and pyrite, and matrix of carbonate-rich sandstone. Schist clasts (up to 10 m across) in the breccia are angular but not variably rotated. Breccias are both clast- and matrix-supported and show evidence for single fracturing and healing by hydrothermally precipitated minerals such as carbonate minerals, pyrite, stibnite, pyrite and quartz. Two Sb and As-rich zones in the Ichinokawa breccia along the Ichinokawa River are about 10-30 m wide adjacent to the Sanbagawa schists. As and Sb values of carbonate matrix in the breccia are extremely high. These observations suggest that the the Ichinokawa breccia formed through a hydrofracturing process associated with hydrothermal fluid infiltrated into Sanbagawa metamorphic as precursor of the antimony ore forming. Hydrothernal fluid seems to have caused mineralization of carbonate minerals and sulfide minerals. Afterwards, the Myojin Group was accumulated above on the Ichinokawa breccia.

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Other Link： https://opac1.lib.ehime-u.ac.jp/iyokan/TD00002884

Language：Japanese   Publisher：Ehime University  

The weathering process of Mannen altered andesite in Tobe Town, Ehime Prefecture, Japan, has been investigated based on geology, petrography and geochemistry. The Mannen andesite intrudes into the Sanbagawa metamorphic rocks and the Middle Miocene Kuma group. The andesite dyke have undergone extensive hydrothermal alteration and mineralization, and has domains of a high concentration of As, S and Sb. Index alteration minerals are pyrite, arsenopyrite, marcasite, stibnite, quartz, carbonate, chlorite, titanite and illite. The weathering types in the near surface of the Mannen andesite is divided into five based on the degree of progress of weathering. That results show that domains of sulphide minerals-rich altered andesite are extremely weathered. CaO, Fe_2O_3, MgO, Pb, Cu, Sb, S and As are depleted in weathered parts of the Mannen andesite based on isocon analysis. Especially, Fe_2O_3, S and As are extremely depleted in weathered parts of sulphide minerals-rich altered andesites. It shows that sulphide minerals in the andesite are decomposed by interaction of surface water and microbial activity, and these elements are leaching away to surrounding environments.

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Other Link： https://opac1.lib.ehime-u.ac.jp/iyokan/TD00002881

Language：Japanese   Publisher：Ehime University  

Mode of occurrences of sulfide minerals and As concentrations of samples from a HORIzontal boring core of Mannen altered andesite in the Tobe Town, Ehime Prefecture, Japan, has been investigated based on petrography, mineralogy and geochemistry. The Mannen altered andesite intrudes into the vicinity of boundary between the Sanbagawa metamorphic rocks and the Middle Miocene Kuma group. The andesite body has undergone extensive hydrothermal alteration, and has domains of a high concentration of As, S and Sb. Index alteration minerals are pyrite, arsenopyrite, marcasite, stibnite, quartz, opal, carbonate minerals, chlorite, illite and kaolinite. In the Mannen arrear textures of sulphide minerals can be divided into the following six types; sparse, sand spot pool and vein, and black-ink-drawing types. The black-ink-drawing type is characterized by the abundance in marcasite and arsenopyrite. The high concentration domains in arsenic are in general agreement with that characterzed by sulphide minerals of the black-ink-drawing type. Sb, S and As are extremely added and Na_2O, MgO, CaO and FeO are depleted in the Mannen andesites during the hydrothermal alteration on the basis of isocon analyses.

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Other Link： https://opac1.lib.ehime-u.ac.jp/iyokan/TD00002880

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2004.abst.0_291_1

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DOI： 10.14863/geosocabst.2004.abst.0_279_2

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DOI： 10.14863/geosocabst.2004.abst.0_290_1

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DOI： 10.14863/geosocabst.2004.abst.0_197_2

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DOI： 10.14863/geosocabst.2004.abst.0_233_2

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DOI： 10.14863/geosocabst.2003.0_218_1

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DOI： 10.14863/geosocabst.2003.0_274_1

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DOI： 10.14863/geosocabst.2003.0_10_2

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Language：English   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.109.XXIII

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DOI： 10.14863/geosocabst.2002.0_241_2

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DOI： 10.14863/geosocabst.2002.0_242_1

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DOI： 10.14863/geosocabst.2002.0_240_2

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DOI： 10.14863/geosocabst.2002.0_241_1

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DOI： 10.14863/geosocabst.2002.0_223_2

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DOI： 10.14863/geosocabst.2001.0_212_1

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DOI： 10.14863/geosocabst.2001.0_214_1

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DOI： 10.14863/geosocabst.2001.0_214_2

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DOI： 10.14863/geosocabst.2001.0_213_1

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DOI： 10.14863/geosocabst.2001.0_213_2

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Language：Japanese   Publisher：日本地質学会  

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DOI： 10.14863/geosocabst.1999.0_191_1

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DOI： 10.14863/geosocabst.1999.0_157_2

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DOI： 10.14863/geosocabst.1999.0_190_2

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.1998.0_451

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DOI： 10.14863/geosocabst.1998.0_093

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DOI： 10.14863/geosocabst.1997.0_158_1

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DOI： 10.14863/geosocabst.1997.0_158_2

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DOI： 10.14863/geosocabst.1997.0_159_1

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DOI： 10.5575/geosoc.103.953

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.1995.0_47

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DOI： 10.14863/geosocabst.1995.0_134_1

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DOI： 10.14863/geosocabst.1994.0_103_2

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.1993.0_76

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DOI： 10.14863/geosocabst.1993.0_241

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DOI： 10.14863/geosocabst.1991.0_318

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DOI： 10.14863/geosocabst.1990.0_152

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DOI： 10.14863/geosocabst.1990.0_153

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyod.44.1.0_83_1

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.1989.0_346

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DOI： 10.14863/geosocabst.1988.0_475

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DOI： 10.14863/geosocabst.1987.0_242

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Language：Japanese   Publisher：日本地質学会  

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DOI： 10.14863/geosocabst.1986.0_212

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DOI： 10.14863/geosocabst.1986.0_219

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Language：Japanese   Publisher：一般社団法人 日本地質学会  

DOI： 10.14863/geosocabst.1985.0_189

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