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

The Renge Belt is a rare subduction-related metamorphic belt that contains blocks of eclogites, meta-gabbros, schists and other rocks in a serpentinite me acute accent lange that formed in the early-to-middle Paleozoic of proto-Japan. We report here a detailed geochemical and Sr--Nd isotope study of two major groups of rocks within the Omi serpentine me acute accent lange: 1. medium-grade metamorphosed blocks of meta-gabbros, and 2. high-pressure low-temperature eclogites and mafic schists. Bulk rock geochemistry of the meta-gabbros reveals that they have prominent Nb, Ta and Ti negative anomalies, suggesting an arc origin. In contrast, the eclogites, and mafic schists have trace element spider diagrams and REE patterns that resemble modern oceanic crust. The Sr--Nd isotopic compositions also show concomitant variations with a highly depleted source for the meta-gabbros (epsilon Nd values of +1.3 - +9.6 and Sriratios of 0.70301-0.70460) compared with a MORB/OIB-like source of the eclogites and mafic schists (epsilon Nd values of -1.94 - +4.83), although the latter have Sr isotopes variably affected by seawater interaction (Sr(i)ratios of 0.70518-0.71050). Altogether, the geochemical features suggest that the meta-gabbros were part of a magmatic arc, which developed in the Cambrian and was tectonically eroded and subducted together with oceanic crust and sediments in the Devonian-Carboniferous. The ages of detrital zircons in the pelitic schist (3200-600 Ma) suggests that the South China Craton and northeastern fringes of Gondwana were potential source regions and that the sedimentation occurred most likely in a trench. The abundant Early Paleozoic (peak around ca. 470 Ma) detrital zircons were derived from an active subduction-related arc. The protoliths of metagabbros are lower crustal equivalents of an infant arc, which was subducted via subduction erosion in the Devonian-Carboniferous and reached a HP metamorphic depth in the Tournasian. Our results suggest that the formation of proto-Japan was related to the initiation of intra-oceanic arc as early as Cambrian. Following tectonic erosion, the remnant mafic rocks were amalgamated with trench-fill sediments during incorporation in an accretionary complex. Subduction erosion was active where sediment supply was low and where the arc was immature. Subduction of oceanic crust was continuing to at least the middle Carboniferous, when the eclogites and blueschists were formed and later exhumed along with the meta-gabbros in serpentinite diapirs in the mid-late Paleozoic.

DOI： 10.1016/j.lithos.2021.106260

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The Permian volcano-sedimentary strata of the Hida Gaien belt of SW Japan are characterized by Lower Permian felsic tuffs and tuffaceous clastic rocks, Middle Permian andesites and sandstones rich in volcanic detritus, and upper Middle to Upper Permian feldspathic sandstones and mudstones. A combination of petrographic and geochemical analyses together with zircon U-Pb dating for the sandstones reveals a provenance change from an immature undissected arc with active felsic and intermediate volcanism during the Early-Middle Permian to a mature arc with basement uplift during the Late Permian. The Upper Permian sandstone yields syn-depositional zircons with 500-400 Ma zircons. This age distribution suggests that sediment was derived from the Permian arc and early Paleozoic basement. Similar characteristics to Permian strata in the Hida Gaien belt are recognized in the eastern Central Asian Orogenic Belt in terms of detrital zircon ages and the change in dominant lithology from volcanic to clastic rocks. In particular, Permian strata of the Jilin area (NE China) are lithostratigraphically similar to those of the Hida Gaien belt and have similar detrital zircon U-Pb ages. As such, Permian strata in both areas would have been deposited proximal to each other in the same tectonic setting along a single subduction zone in the western Paleo-Pacific Ocean.

DOI： 10.1016/j.jseaes.2021.104888

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press (CUP)  

<title>Abstract</title>
Detrital zircon U–Pb ages for sediments in and around the Palaeo-Tethyan convergence zone in northern Thailand provide constraints for tectonic interpretations of the Indochina Block, the Sibumasu Block, the Inthanon Zone accretionary complex and the Nan Back-arc Basin during the Triassic. In sedimentary rocks of the Indochina Block, almost all of the Palaeozoic and Triassic zircons were sourced from the collision zone between the Indochina and South China blocks, and an active continental margin in the western Indochina Block. Sediments of the Sibumasu Block were supplied by erosion of Archaean basement and from the Grenville and the Pan African orogenies, but show no record of Permian to Triassic igneous activity. Accretionary complex sediments have provenances of both the Sukhothai Arc and the Indochina and South China blocks, with detrital zircons of various ages being supplied from crustal uplift and erosion related to the Indosinian I orogeny. Sedimentary rocks of the Nan Back-arc Basin are widely distributed not only in the Nan–Uttaradit but also in northern Sukhothai areas. The origin of the Pha Som Metamorphic Complex and associated formations can be traced to basin-filling sediments in the Nan Back-arc Basin. These detrital zircon U–Pb ages have also allowed identification of the changing tectonic setting in the Palaeo-Tethys convergence zone from the ‘erosion of Proterozoic continental basement’ to ‘Palaeozoic active continental margin in the western Indochina Block’ and ‘Palaeozoic, Permian to Triassic collision zone between the South China and Indochina blocks’ through to ‘Triassic active Sukhothai Arc’.

DOI： 10.1017/s0016756820001028

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PALAEONTOLOGICAL SOC JAPAN  

The three-dimensional morphology of the flat-shaped spumellarian radiolarian Dictyocoryne was analysed using a microfocus X-ray CT with a special focus on whether it was capable of a planktonic lifestyle. Two types of 3D models, the shell model, which represents a realistic 3D shell, and the wrapped model, which mimics the whole body outline without pseudopodia, were reconstructed in order to estimate volume, surface area, and centres of gravity for the shell model and buoyancy for the wrapped model. The calculated values showed that the volume of shell with respect to the total volume was negatively allometric, regardless of the differences between threshold settings. Stepwise secretions of the patagium layer may result in a comparatively lightweight shell, thereby decreasing the total density during growth but not below the density of seawater. Estimated positions for the centres of gravity and buoyancy were too close to maintain an autonomous posture while floating. Instead, the ratio between surface area and volume was greater than that in an ideal sphere. Such a broad surface area could obtain the viscous resistance necessary for sinking retardation. Spumellarian radiolarians, including Dictyocoryne, have photosynthetic symbionts located primarily in the ectoplasmic layer, which is a habitable space that can be maximised within the larger surface area. Given that radiolarians float when extending their pseudopodia, it can be hypothesised that pseudopodia may play a role in the adjustment of life posture in a hydraulically unstable shell, which can be integrated into sinking retardation, enhancement of photosynthetic activity and manoeuvrability of life posture within a unique flat-shaped morphogenesis.

DOI： 10.2517/2019PR020

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Language：English   Publisher：PALAEONTOLOGICAL SOC JAPAN  

DOI： 10.2517/2020PR002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PALAEONTOLOGICAL SOC JAPAN  

It has been suggested that the pseudopodia of radiolarians play a role in controlling buoyancy for floating behaviour. To understand the function of pseudopodia in terms of planktonic capability, we performed culture experiments on the flat-shaped radiolarian Dictyocoryne. A glass cell, a stereomicroscope and an X-Y-Z stage were used to observe the behaviour of Dictyocoryne from a lateral view. Under static conditions, Dictyocoryne grounded on the bottom of the glass cell extended pseudopodia from both sides of the flat disc surface. Subsequently, these individuals rose slightly by a length equal to that of the extended pseudopodia but remained attached to the bottom. These results suggest that Dictyocoryne lacks the ability to surface by obtaining buoyancy through the emergence of pseudopodia. Under conditions of convection flow, Dictyocoryne moved in the downstream direction only when pseudopodia were completely extended. When the convection flow moved upward, the individuals moved with the flow to just under the surface. In addition, convection flow changed the direction of a long, thick pseudopodium, called the axoflagellum, to be parallel with the flow. Consequently, the axoflagellum was always oriented towards the downstream side, being the disc face in the axollagellum side on the upturn. Given that the flat-shaped spumellarians has c symbiotic algae inside their cells, their unique planktonic capability leads to the stable efficiency of the algal photosynthesis.

DOI： 10.2517/2018PR023

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Language：English   Publisher：PALAEONTOLOGICAL SOC JAPAN  

DOI： 10.2517/2019PR014

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

Silurian and Devonian chitinozoans and scolecodonts are recorded from strata of the Hida-Gaien Terrane, central Honshu. Silurian chitinozoans include Eisenackitina, Bursachitina, and the species Angochitina elongata. The latter provides a precise biostratigraphical tie between the Japanese succession and the Type Ludlow Series of the Welsh Borderland, UK, and indicates a Ludlow age (Gorstian or early Ludfordian) for the upper member of the Yoshiki Formation in the Ichinotani Valley. Chitinozoans from other Yoshiki Formation localities contain other specimens of Lagenochitinidae. Scolecodonts are more common than chitinozoans in the palynological residues, but are mostly represented by fragments or minor apparatus elements with a low biostratigraphical value. However, material from the Yoshiki and Fukuji Formations includes several species of Mochtyella as well as representatives of Oenonites, Kettnerites, Lunoprionella, Vistulella? and possibly other placognath taxa. Scolecodonts are also present in the Silurian Middle Member of the Gionyama Formation, Kyushu, including a well-preserved jaw of Pistoprion, and fragments of putative Kettnerites and Oenonites. These finds of scolecodonts suggest close similarity in assemblages between Paleozoic polychaete faunas of Japanese terranes and those of Baltica-Laurentia.

DOI： 10.1111/iar.12294

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

DOI： 10.5575/geosoc.2018.0071

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

The Sa Kaeo Back-arc Basin in Southeastern Thailand developed behind the Sukhothai Arc along the western margin of the Indochina Block during the Permian to Triassic in response to the subduction of the Paleo-Tethys oceanic plate. To clarify its tectonic evolution of spreading, basin-infilling, and closure, we have investigated the provenance of its clastic sediments, the U-Pb ages of detrital zircons, the geochemistry of its basaltic rocks, and the structures in melange. The rocks in the Sa Kaeo Back-arc Basin include two contrasting lithological units: the Thung Kabin Melange, composed mainly of basaltic rocks, chert, limestone, and sandstone, along with melange; and the Pong Nam Ron Formation, a thick succession of elastic sediments. Our observations suggest that the clastic sediments of the Pong Nam Ron Formation were deposited widely over the oceanic rocks (basaltic rocks, chert, and limestone) of the Thung Kabin Melange. Geochemical analyses indicate that sandstones in both units (the Thung Kabin Melange and the Pong Nam Ron Formation) are characterized by a provenance of mostly basaltic rocks. The U-Pb ages of detrital zircons from both units present similar age distributions: the youngest single-grain zircon (YSG) is early Late Triassic in age, the youngest cluster of zircons (YC1 sigma) is latest Permian to earliest Triassic in age, and there is a range of other Paleozoic and Proterozoic zircons. Based on these geochemical analyses and the U-Pb dating, the sandstones of both units had the same provenance. In addition, the basaltic rocks of the Thung Kabin Melange are originated from back-arc basin basalts. These new observations have allowed us to reconstruct the tectonic evolution of the basin. In the Early Permian, spreading took place in the basin accompanied by basaltic magmatism. Subsequently, corresponding to an inactive period of the Sukhothai Arc into the Middle Triassic, the Sa Kaeo Back-arc Basin subsided, and a deep-sea environment prevailed with the formation of Permian cherts, Permian limestones, and Middle Triassic cherts. During the Triassic, the basin was filled by elastic sediments and eventually closed. The elastic sediments were sourced directly from the back-arc basin basalts, as well as from the felsic volcanic rocks of the active Sukhothai Arc (which yield Permian to Triassic zircons), and from the continental materials of the Indochina Block (Paleozoic and Proterozoic zircons). After the closure of the Sa Kaeo Back-arc Basin, the discussed area was affected by the termination fault fan related to the Mae Ping Fault Zone. (C) 2018 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.gr.2018.06.007

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Sinking experiments using living nassellarian radiolarians with a conical shell form were performed to examine the spatial behaviour of nassellarians and a related feeding model. A small water tank and surface-reflecting mirror were used to observe the vertical movement of each specimen, and the sinking posture and speed were analysed. The experimental results showed that the sinking posture of nassellarians was stable with a cephalis-down orientation, and the sinking speed was considerably slower than that of Dictyocoryne spp. as a control experiment. The stable posture was maintained by a streamlining shell form and the relationship between the centres of gravity and buoyancy. Moreover, a lift force in moving fluids would likely change the posture of the organism to the cephalis facing upstream, as in a weathercock effect. As a result, nassellarians were able to capture organic matter around the rear side of the aperture where prey-capturing pseudopodia are extended. Because the pseudopodia may be attributed to the lifelong performance of the surface of cell membranes, the drastic change in flow intensity around the pseudopodia leads to an easier collapse of the prey-capturing apparatus. A slower sinking speed as the size increases is a beneficial feature for avoiding the feeding risk, resulting in effective predation as a form of homeostatic spatial behaviour.

DOI： 10.1016/j.marmicro.2018.02.002

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We have studied the petrography, geochemistry, and detrital zircon U-Pb ages of sandstones from shallow marine forearc sediments, accretionary complexes (ACs), and metamorphosed accretionary complexes (Meta-ACs) within the Kurosegawa belt of Southwest Japan. Those rocks formed in a forearc region of a Permian island arc associated with subduction of the Panthalassa oceanic crust along the eastern margin of the South China block (Yangtze block). The provenance of the shallow-marine sediments was dominated by basaltic to andesitic volcanic rocks and minor granitic rocks during the late Middle to Late Permian. The ACs were derived from felsic to andesitic volcanic rocks during the Late Permian. The provenance of Meta-ACs was dominated by andesitic volcanic rocks in the Middle Permian. The provenance, source rock compositions, and zircon age distribution for the forearc sediments, ACs and Meta-ACs have allowed us to reconstruct the geological history of the Permian arc system of the Kurosegawa belt. During the Middle Permian, the ACs were accreted along the eastern margin of the South China block. The Middle Permian arc was an immature oceanic island arc consisting of andesitic volcanic rocks. During the Late Permian, the ACs formed in a mature arc, producing voluminous felsic to andesitic volcanic rocks. A forearc basin developed during the late Middle to Late Permian. Subsequently, the Middle Permian ACs and part of the Late Permian AC underwent low-grade metamorphism in the Late to Early Jurassic, presenting the Meta-ACs.

DOI： 10.1016/j.jseaes.2017.10.025

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

Detrital zircon multi-chronology combined with provenance and low-grade metamorphism analyses enables the reinterpretation of the tectonic evolution of the Cretaceous Shimanto accretionary complex in Southwest Japan. Detrital zircon U-Pb ages and provenance analysis defines the depositional age of trench-fill turbidites associated with igneous activity in provenance. Periods of low igneous activity are recorded by youngest single grain zircon U-Pb ages (YSG) that approximate or are older than the depositional ages obtained from radiolarian fossil-bearing mudstone. Periods of intensive igneous activity recorded by youngest cluster U-Pb ages (YC1 sigma) that correspond to the younger limits of radiolarian ages. The YC1 sigma U-Pb ages obtained from sandstones within melange units provide more accurate younger depositional ages than radiolarian ages derived from mudstone. Determining true depositional ages requires a combination of fossil data, detrital zircon ages, and provenance information. Fission-track ages using zircons estimated YC1 sigma U-Pb ages are useful for assessing depositional and annealing ages for the low-grade metamorphosed accretionary complex. These new dating presented here indicates the following tectonic history of the accretionary wedge. Evolution of the Shimanto accretionary complex from the Albian to the Turonian was caused by the subduction of the Izanagi plate, a process that supplied sediments via the erosion of Permian and Triassic to Early Jurassic granitic rocks and the eruption of minor amounts of Early Cretaceous intermediate volcanic rocks. The complex subsequently underwent intensive igneous activity from the Coniacian to the early Paleocene as a result of the subduction of a hot and young oceanic slab, such as the Kula-Pacific plate. Finally, the major out-of-sequence thrusts of the Fukase Fault and the Aki Tectonic Line formed after the middle Eocene, and this reactivation of the Shimanto accretionary complex as a result of the subduction of the Pacific plate.

DOI： 10.1111/iar.12218

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Provenance analysis and U-Pb dating of detrital zircons in Permian-Triassic forearc sediments from the Sulchothai Arc in northern Thailand clarify the evolution of a missing arc system associated with Paleo-Tethys subduction. The turbidite-dominant formations within the forearc sediments include the Permian Ngao Group (Kiu Lom, Pha Huat, and Huai Thak formations), the Early to earliest Late Triassic Lampang Group (Phra That and Hong Hoi formations), and the Late Triassic Song Group (Pha Daeng and Wang Chin formations). The sandstones are quartzose in the Pha Huat, Huai Thak, and Wang Chin formations, and lithic wacke in the Kiu Lom, Phra That, Hong Hoi and Pha Daeng formations. The quartzose sandstones contain abundant quartz, felsic volcanic and plutonic fragments, whereas the lithic sandstones contain mainly basaltic to felsic volcanic fragments. The youngest single-grain (YSG) zircon U-Pb age generally approximates the depositional age in the study area, but in the case of the limestone-dominant Pha Huat Formation the YSG age is clearly older. On the other hand, the youngest cluster U-Pb age (YC1 sigma) represents the peak of igneous activity in the source area. Geological evidence, geochemical signatures, and the YC1 sigma ages of the sandstones have allowed us to reconstruct the Sukhothai arc evolution. The initial Sukhothai Arc (Late Carboniferous Early Permian) developed as a continental island arc. Subsequently, there was general magmatic quiescence with minor I-type granitic activity during the Middle to early Late Permian. In the latest Permian to early Late Triassic, the Sukhothai Arc developed in tandem with Early to Middle Triassic I-type granitic activity, Middle to Late Triassic volcanism, evolution of an accretionary complex, and an abundant supply of sediments from the volcanic rocks to the trench through a forearc basin. Subsequently, the Sukhothai Arc became quiescent as the Paleo-Tethys closed after the Late Triassic. In addition, parts of sediments of supposed Devonian Carboniferous age within the Sukhothai Arc were revised as the Triassic Lampang Group, and the Early Cretaceous Khorat Group.

DOI： 10.1016/j.jseaes.2017.04.021

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

A detailed radiolarian biostratigraphy of pelagic sediments overlying basaltic extrusive lavas of the Oman Ophiolite is reported for the type locality of the suhaylah Formation near the Wadi Jizzi river, northern Oman Mountains. the extrusive lavas in the studied section are classified as V1 lava produced by mid-ocean-ridge magmatism. the sedimentary succession in the type section (ca. 18 m thick) is subdivided into three units (in stratigraphic order): metalliferous sediments (Unit 1), red mudstone intercalated with radiolarian chert (Unit 2), and micritic limestone (Unit 3).the recovery of well-preserved radiolarians from all units led to the recognition of three distinctive assemblages: Assemblage A, obtained from metalliferous sediments and chert intercalations within red mudstone, could be correlated with the middle-late Cenomanian fauna; Assemblage B, recovered from red mudstone and chert, is assigned to the early Turonian, based on correlation with radiolarian occurrences across the Cenomanian-Turonian boundary; Assemblage C, recognized in micritic limestone, is broadly identified as Turonian-Coniacian.the age of the suhaylah Formation has previously been interpreted as early Cenomanian to Coniacian-Santonian; however, the revised age could be from late Cenomanian to Turonian-Coniacian. the estimated possible maximum age of metalliferous sediments (96.5-93.9 Ma) is in good agreement with high-precision U-Pb zircon dates of ophiolite crust attributed to ridge magmatism. the depositional age of the pelagic sediments clearly indicates that the ridge magmatism had ended by ca. 95.5 Ma.

DOI： 10.4454/ofioliti.v42i2.446

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

We considered the geometrical properties of skeletons of the genus Pantanellium, a type of Mesozoic radiolarian. We constructed four 3D models of fossil specimens of Pantanellium, using X-ray Micro-CT and layered manufacturing technology. Focusing on cortical shells, we approximated the skeletal structures with convex polyhedrons and investigated their geometrical properties. We summarized these properties using planar graphs. The geometrical properties differ for fossils that are believed to belong to the same species. The results of numerical simulations based on a mathematical model for spherical radiolarians were partially consistent with the skeletal structures of the specimens. We conclude that the skeletal structure of the genus Pantanellium is not fixed and is not completely optimized from the viewpoint of symmetry.

DOI： 10.1016/j.revmic.2015.01.002

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2015.0_470

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DOI： 10.5047/forma.2014.004

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

The dating of radiolarian biostratigraphic zones from the Silurian to Devonian is only partially understood. Dating the zircons in radiolarian-bearing tuffaceous rocks has enabled us to ascribe practical ages to the radiolarian zones. To extend knowledge in this area, radiometric dating of magmatic zircons within the radiolarian-bearing Hitoegane Formation, Japan, was undertaken. The Hitoegane Formation is mainly composed of alternating beds of tuffaceous sandstones, tuffaceous mudstones and felsic tuff. The felsic tuff and tuffaceous mudstone yield well-preserved radiolarian fossils. Zircon grains showing a U-Pb laser ablation-inductively coupled plasma-mass spectrometry age of 426.6 +/- 3.7 Ma were collected from four horizons of the Hitoegane Formation, which is the boundary between the Pseudospongoprunum tauversi to Futobari solidus-Zadrappolus tenuis radiolarian assemblage zones. This fact strongly suggests that the boundary of these assemblage zones is around the Ludlowian to Pridolian. The last occurrence of F.solidus is considered to be Pragian based on the reinterpretation of a U-Pb sensitive high mass-resolution ion microprobe (SHRIMP) zircon age of 408.9 +/- 7.6 Ma for a felsic tuff of the Kurosegawa belt, Southwest Japan. Thus the F.solidus-Z.tenuis assemblage can be assigned to the Ludlowian or Pridolian to Pragian. The present data also contribute to establishing overall stratigraphy of the Paleozoic rocks of the Fukuji-Hitoegane area. According to the Ordovician to Carboniferous stratigraphy in this area, Ordovician to Silurian volcanism was gradually reduced to change the sedimentary environment into a tropical lagoon in the early Devonian. And the quiet Carboniferous environment was subsequently interrupted, throwing it once more into the volcanic conditions in the Middle Permian.

DOI： 10.1111/iar.12044

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We have investigated the petrography, geochemistry, and detrital zircon U-Pb LA-ICPMS dating of sandstone from the Gorkhi Formation of the Khangai-Khentei belt in the Ulaanbaatar area, central Mongolia. These data are used to constrain the provenance and source rock composition of the accretionary complex, which is linked to subduction of the Paleo-Asian Ocean within the Central Asian Orogenic Belt during the Middle Devonian to Early Carboniferous. Field and microscopic observations of the modal composition of sandstone and constituent mineral chemistry indicate that the sandstone of the Gorkhi Formation is feldspathic arenite, enriched in saussuritized plagioclase. Geochemical data show that most of the sandstone and shale were derived from a continental margin to continental island arc setting, with plutonic rocks being the source rocks. Detrital zircon Pb-206/U-238 ages of two sandstones yields age peaks of 322 +/- 3 and 346 +/- 3 Ma. The zircon Pb-206/U-238 age of a quartz-pumpellyite vein that cuts sandstone has a weighted mean age of 339 +/- 3 Ma. Based on these zircon ages, we infer that the depositional age of sandstone within the Gorkhi Formation ranges from 320 to 340 Ma (i.e., Early Carboniferous). The provenance and depositional age of the Gorkhi Formation suggest that the evolution of the accretionary complex was influenced by the intrusion and erosion of plutonic rocks during the Early Carboniferous. We also suggest that spatial and temporal changes in the provenance of the accretionary complex in the Khangai-Khentei belt, which developed aound the southern continental margin of the Siberian Craton in relation to island arc activity, were influenced by northward subduction of the Paleo-Asian Ocean plate. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jseaes.2013.07.019

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We describe the mode of occurrence and geochemical characteristics of basalts, in the KhangaiKhentei belt in Mongolia, overlain by Middle Paleozoic radiolarian chert in an extensive accretionary complex. These basalts are greatly enriched in K, Ti, Fe, P, Rb, Ba, Th, and Nb in comparison to the composition of the mid-ocean ridge basalts, indicative of within-plate alkaline type. Ti/YvsNb/Y and MnO/TiO2/P2O5 ratios of the basalts also suggest within-plate affinities. Considering the geochemical characteristics as well as the conformable relationship with the overlying radiolarian chert, the alkaline basalts were clearly not continental but formed a pelagic oceanic island. The mode of occurrence and geochemistry of the basalts show that the alkaline basaltic volcanic activity had taken place to form an oceanic island in the Paleozoic pelagic region sufficiently far from continents to allow radiolarian ooze accumulation.

DOI： 10.1111/iar.12028

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

We characterize the tectono-stratigraphic architecture and low-grade metamorphism of the accretionary complex preserved in the Kurosegawa belt of the Kitagawa district in eastern Shikoku, Southwest Japan, in order to understand its internal structure, tectono-metamorphic evolution, and assessments of displacement of continental fragments within the complex. We report the first ever documented occurrence of an Early Jurassic radiolarian assemblage within the accretionary complex of the Kurosegawa belt that has been previously classified as the Late Permian accretionary complex, thus providing a revised age interpretation for these rocks. The accretionary complex is subdivided into four distinct tectono-stratigraphic units: Late Permian melange and phyllite units, and Early Jurassic melange and sandstone units. The stratigraphy of these four units is structurally repeated due to an E-W striking, steeply dipping regional fault. We characterized low-grade metamorphism of the accretionary complex via illite crystallinity and Raman spectroscopy of carbonaceous material. The estimated pattern of low-grade metamorphism showed pronounced variability within the complex and revealed no discernible spatial trends. The primary thermal structure in these rocks was overprinted by later tectonic events. Based on geological and thermal structure, we conclude that continental fragments within the Kurosegawa belt were structurally translated into both the Late Permian and Early Jurassic accretionary complexes, which comprise a highly deformed zone affected by strike-slip tectonics during the Early Cretaceous. Different models have been proposed to explain the initial structural evolution of the Kurosegawa belt ( i.e., micro-continent collision and klippe tectonic models). Even if we presuppose either model, the available geological evidence requires a new interpretation, whereby primary geological structures are overprinted and reconfigured by later tectonic events. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tecto.2013.02.006

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

DOI： 10.1111/j.1440-1738.2012.00820.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Society for Science on Form  

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

The provenance, source rock compositions, and sediment supply system for a convergence zone of the Paleo-Tethys were reconstructed based on the petrography and geochemistry of clastic rocks of the Inthanon Zone, northern Thailand. The clastic rocks are classified into two types based on field and microscopic observations, the modal composition of sandstone, and mineral compositions: (I) lithic sandstone and shale within melange in a Permo-Triassic accretionary complex; and (2) Carboniferous quartzose sandstone and mudstone within the Sibumasu Block. Geochemical data indicate that the clastic rocks of the melange were derived from continental island arc and continental margin settings, which correspond to felsic volcanic rocks within the Sukhothai Zone and quartz-rich fragments within the Indochina Block, respectively. The results of a mixing model indicate the source rocks were approximately 35% volcanic rocks of the Sukhothai Zone and 65% craton sandstone and upper continental crust of the Indochina Block. In contrast, Carboniferous quartzose sedimentary rocks within the Sibumasu Block originated from a continental margin, without a contribution from volcanic rocks. In terms of Paleo-Tethys subduction, a continental island arc in the Sukhothai Zone evolved in tandem with Late Permian-Triassic forearc basins and volcanic activity during the Middle-early Late Triassic. The accretionary complex formed contemporaneously with the evolution of continental island arc during the Permo-Triassic, supplied with sediment from the Sukhothai Zone and the Indochina Block. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jseaes.2012.06.012

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Nylon models of earliest Cretaceous Pantanellium were produced from a real fossil specimen by applying X-ray micro-CT and layered manufacturing technology. These models enable us to elucidate the exact number of polygonal pore frames and their configuration on the cortical shell, which is difficult to recognize from scanning electron microscope or light microscope images. The specimen has a total number of 27 polygonal (12 pentagonal and 15 hexagonal) pore frames. The pore frame number and the configuration are important criteria in the taxonomy of the Family Pantanelliidae. Planar graphs showing the distribution of polygonal pore frames on the cortical shell are depicted. They are expected to be a standard method for presenting and examining geometrical characters of pantanellid cortical shells. The new technology of X-ray micro-CT can shed light on detailed morphological examinations of not only radiolarians but also any other microfossils. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.marmicro.2012.02.005

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

A dropstone-bearing, Middle Permian to Early Triassic peri-glacial sedimentary unit was first discovered from the KhangaiKhentei Belt in Mongolia, Central Asian Orogenic Belt. The unit, Urmegtei Formation, is assumed to cover the early Carboniferous KhangaiKhentei accretionary complex, and is an upward-fining sequence, consisting of conglomerates, sandstones, and varved sandstone and mudstone beds with granite dropstones in ascending order. The formation was cut by a felsic dike, and was deformed and metamorphosed together with the felsic dike. An undeformed porphyritic granite batholith finally cut all the deformed and metamorphosed rocks. LA-ICP-MS, UPb zircon dating has revealed the following 206Pb/238U weighted mean igneous ages: (i) a granite dropstone in the Urmegtei Formation is 273 +/- 5?Ma (Kungurian of Early Permian); (ii) the deformed felsic dike is 247 +/- 4?Ma (Olenekian of Early Triassic); and (iii) the undeformed granite batholith is 218 +/- 9?Ma (Carnian of Late Triassic). From these data, the age of sedimentation of the Urmegtei Formation is constrained between the Kungurian and the Olenekian (273-247?Ma), and the age of deformation and metamorphism is constrained between the Olenekian and the Carnian (247-218?Ma). In Permian and Triassic times, the global climate was in a warming trend from the Serpukhovian (early Late Carboniferous) to the Kungurian long and severe cool mode (328-271?Ma) to the Roadian to Bajocian (Middle Jurassic) warm mode (271168 Ma), with an interruption with the Capitanian Kamura cooling event (266-260 Ma). The dropstone-bearing strata of the Urmegtei Formation, together with the glacier-related deposits in the Verkhoyansk, Kolyma, and Omolon areas of northeastern Siberia (said to be of Middle to Late Permian age), must be products of the Capitanian cooling event. Although further study is needed, the dropstone-bearing strata we found can be explained in two ways: (i) the Urmegtei Formation is an autochthonous formation indicating a short-term expansion of land glacier to the central part of Siberia in Capitanian age; or (ii) the Urmegtei Formation was deposited in or around a limited ice-covered continent in northeast Siberia in the Capitanian and was displaced to the present position by the Carnian.

DOI： 10.1111/j.1751-3928.2012.00204.x

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

Cretaceous radiolarians were recovered from three mudstone samples within the Shimanto accretionary complex in the Kitagawa district, Tokushima Prefecture, Southwest Japan. Two of them, red mudstone and gray mudstone, in the Osodani Unit yield radiolarian faunas indicating the ages of late Albian to Cenomanian and late Cenomanian, respectively. Black mudstone within the Taniyama Unit includes a representative radiolarian fauna presenting a Turonian age. Based on the age determination by our present data together with the radiolarian evidences reported from surrounding area, the accretionary age of the Osodani Unit is constrained to be Turonian to early Coniacian, and those of the Taniyama Unit is reinterpreted as the age of Turonian to Santonian. New findings of radiolarian fossils in the Kitagawa district help establish the age constraint for the Cretaceous Shimanto accretionary complex in eastern Shikoku.

DOI： 10.9795/bullgsj.63.301

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Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2012.0_519

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DOI： 10.14863/geosocabst.2012.0_122

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This study presents the first direct age determination for the Kirinai Formation in the Kitakami Mountains, Northeast Japan, and a new model that correlates the Kirinai Formation with Upper Permian accretionary complexes of the Ultra-Tamba belt, Southwest Japan. The correlation is based on similarities in lithology, age, and structural relationships. The Kitakami Mountains are geotectonically divided into several belts, with subduction-related complexes occurring in the North Kitakami and Nedamo belts, whereas Ordovician ophiolites and stratigraphically overlying Paleozoic-Mesozoic sedimentary sequences are respectively exposed in the so-called " Hayachine tectonic belt" and South Kitakami belt. The Kirinai Formation, previously thought to belong to the North Kitakami belt, is tectonically underlain by the Jurassic Kamaishi and Tassobeguchi formations of the North Kitakami belt, and is overlain by the Lower Carboniferous Nedamo Complex of the Nedamo belt. The Kirinai Formation is lithostratigraphically subdivided into three members: a lower member dominated by black phyllitic mudstone with minor amount of bedded siliceous mudstone, a middle member consisting mainly of greenish gray massive sandstone and phyllitic mudstone, and an upper member composed of phyllitic mudstone locally intercalated with felsic tuff. The radiolarian fauna obtained from the lower member includes age-diagnostic species such as Follicucullus sp. cf. F. dilatatus Rudenko and Albaillella sp. cf. A. protolevis Kuwahara, corresponding to the interval from the Neoalbaillella ornithoformis Assemblage Zone to the lower part of the Neoalbaillella optima Assemblage Zone of Kuwahara et al. (1998). These findings indicate a Changhsingian (Upper Permian) assignment for the lower member of the Kirinai Formation. This newly obtained age and the obtained correlations provide the key to understanding the original relationships among the various subduction-related complexes in Japan. © 2010 Elsevier Ltd and Nanjing Institute of Geology and Palaeontology, CAS.

DOI： 10.1016/j.palwor.2010.12.003

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

The opening of the Paleo-Tethys are reconstructed, including the depositional setting and redox conditions, based on an analysis of radiolarian fossils and the geochemistry of a Devonian siliceous succession in the Chiang Dao area of northern Thailand. The succession is subdivided into the following five rock types (in ascending stratigraphic order): black shale (Lower Devonian), siliceous shale (Middle Devonian), tuffaceous chert and tuff (Middle/Upper Devonian), and chert (Upper Devonian). The succession was deposited in continental margin and pelagic environments between the Sibumasu Block and the Indochina-North China blocks. The concentrations of terrestrial-derived elements (Al2O3, TiO2, Rb, and Zr) suggest that the succession (except for the chert) was supplied with terrigenous material and volcanic ash from the adjacent continent, deposited within a SiO2-rich environment. Geochemical indicators of redox conditions (total organic carbon and the Th/U ratio) reveal a gradual change from anoxic to oxic oceanic conditions between the black shale and chert. Taking into account the interpreted depositional setting and redox conditions, the initial Paleo-Tethys developed as a small, closed anoxic-suboxic oceanic basin during the Early to Middle Devonian, located close to the continental margin. Black shale and siliceous shale were deposited in the basin at this time. Opening of the Paleo-Tethys started around the Middle and Upper Devonian boundary, marked by voluminous volcanic activity. The tuffaceous chert was deposited under oxic conditions, suggesting that ash and pumice within the chert were derived from a continental source. After the Late Devonian, the Paleo-Tethys developed as a deep, broad ocean in which pelagic chert was deposited. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.palaeo.2010.08.029

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

We reconstructed the tectono-metamorphic evolution of the low-grade metamorphosed Cretaceous Shimanto accretionary complex in the Kanto Mountains, Central Japan, based on radiolarian fossils, metamorphic temperatures derived from illite crystallinity analysis, and timing of metamorphism based on illite K-Ar dating. The accretionary age of the Kobotoke Group is Turonian to Maastrichtian (66-94 Ma), based on radiolarian fossils. Illite crystallinity data indicate metamorphic temperatures of approximately 300 degrees C. The illite K-Ar ages constrain the timing of metamorphism to the Middle Eocene around 40 Ma. Combining our results and previous study, we defined two types of low-grade metamorphism within Cretaceous Shimanto accretionary complex of the Kanto Mountains. The early metamorphism, in excess of 300 degrees C, was related to the uplift of the Sambagawa metamorphic rocks, in turn associated with the subduction of the Kula-Pacific ridge during the Late Cretaceous (65-75 Ma). This metamorphism is recorded in the Otaki Group within the northernmost part of the complex in the Kanto Mountains. Subsequent to the subduction of the Kula-Pacific ridge, a later period of metamorphism, recorded in the Kobotoke Group, is characterized by the thermal effects of the subduction of the young, hot Pacific Plate during the Middle Eocene. The effect of the early metamorphism occurred synchronously 500 km along the trench from Southwest to Central Japan. The later metamorphism occurred at 50 Ma in Kyushu and Shikoku of Southwest Japan, and at 40 Ma in the Kanto Mountains of Central Japan. This difference in the timing of metamorphism between Southwest and Central Japan is explained by the northward migration of the young, hot Pacific Plate. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tecto.2009.11.017

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We present the first record of a living solitary spherical polycystine radiolarian, Haliommilla capillaceum (Haeckel), with a chain of extracellular cells. The extracellular cells divided seven times over about 4 h from the 8-cell to the 1024-cell stage and then swam away. At the 1024-cell stage the cells were very small, isospores (ca. 12 mu m in length). After final cytokinesis, the cells remained essentially immobile, with only occasional movement. After this immobile stage, they abruptly swam out in a burst into seawater. The cell division patterns and cell shape are similar to the sporogenesis of the host-specific parasitic dinoflagellate Duboscquella sp. infecting a tintinnid. Precise identification, however, needs molecular analysis, transmitted scanning images and proliferation test. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.marmicro.2009.04.007

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Recent mapping projects undertaken in Central Mongolia have revealed the widespread occurrence of radiolarian chert within a Paleozoic accretionary complex. We present the results of the first detailed tectonostratigraphic and radiolarian biostratigraphic investigations of the Gorkhi Formation in the Khangai-Khentei belt of the Central Asian Orogenic Belt.The Gorkhi Formation consists of sandstone shale, alternating sandstone and shale of turbidite affinity and chert with small amounts of siliceous shale, basalt, limestone, and clast-bearing mudstone. Radiolarian chert that is completely devoid of terrigenous clastic material is commonly associated with underlying basalt (sedimentary contact) and with conformably overlying siliceous shale and turbidite deposits. The tectonic stacking of basalt-chert and chert-turbidite successions is the most remarkable structural feature of the formation.The recovery of moderately well-preserved radiolarians and conodonts from red chert led to the recognition Of four radiolarian assemblages that have a combined age range from the latest Silurian (Pridolian) to the Late Devonian (Frasnian). No age control exists for the siliceous shale, shale, and sandstone, although they are considered to be latest Devonian or slightly younger on the basis of stratigraphic relationships with underlying chert.The Gorkhi Formation has previously been interpreted as a thick sedimentary basin deposit overlying an unexposed Archean-Neoproterozoic basement; however. the stratigraphy within individual tectonic slices clearly corresponds to that of an ocean plate stratigraphy of an accretionary complex generated by the trenchward movement of an oceanic plate. From the lowermost to uppermost units, the stratigraphy comprises ocean floor basalt, pelagic deep-water radiolarian chert, hemipelagic siliceous shale, and terrigenous turbidite deposits. The biostratigraphic data obtained in the present study provide corroborating evidence for the existence of an extensive deep-water ocean that enabled the continuous sedimentation of pelagic chert over a period of nearly 50 million years. These data, together with structural data characterized by tectonic repetition of the stratigraphy, indicate that these rocks formed as an accretionary wedge along an active continental margin, possibly that of the Angara Craton. The mid-oceanic chert was probably deposited in the Northern Hemisphere portion of the Pateo-Pacific Ocean that faced the Angara Craton and the North China-Tarim blocks. Thus, We propose that subduction-accretion processes along the Paleo-Pacific rim played an important role in the accretionary growth of the active continental margin of the Angara Craton, directly influencing the evolution of the Central Asian Orogenic Belt. (C) 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jseaes.2008.04.010

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2-(4-pyridyl)-5-[(4-(2-dimethylaminoethylaminocarbamoyl)methoxy)-phenyl] oxazole (PDMPO) is a fluorescent compound that accumulates in acidic cell compartments. PDMPO is accumulated with silica under acidic conditions, and the newly developed silica skeletons show green fluorescent light. This study is the first to use PDMPO in polycystine radiolarians, which are unicellular planktonic protists. We tested Acanthodesmia sp., Rhizosphaera trigonacantha, and Spirocyrtis scalaris for emission of green fluorescence. Entire skeletons of Acanthodesmia sp. and Sr. scalaris emitted green fluorescent light, whereas only the outermost shell and radial spines of Rz. trigonacantha showed fluorescence. Two additional species, Spongaster tetras tetras and Rhopalastrum elegans did not show fluorescence. Green fluorescence of the entire skeleton is more like the "skeletal thickening growth" defined by silica deposition throughout the surface of the existing skeleton. The brightness of the fluorescence varied with each cell. This difference in fluorescence may reflect the rate of growth in these cells. Green fluorescence in PDMPO-treated polycystines suggests the presence of similar metabolic systems with controlled pH. The results of this study shed light not only on the feasibility of using PDMPO in diatoms and siliceous sponges, but also in polycystines. Further application of PDMPO could refine polycystine skeletogenic hypotheses and offer new insight on the physiological functions of silica assimilation. © The Plankton Society of Japan.

DOI： 10.3800/pbr.4.89

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Institute of Aeronautics and Astronautics Inc.  

Morphology development of marine plankton, which has a five hundred million evolutional history, is really diversifying fitted to environmental changes. We focus on not only biological functions but also mechanical functions due to the environmental factor of temperature, chemical substance, boundary condition, etc., however the current classification pays attention to only morphological appearance. In addition, we try to design space systems inspired by these plankton, because plankton in water is released from gravity due to buoyancy effect similar to a structure in space. The boundary condition of floating plankton is free-free also like that of floating space structures. In this paper, we introduce hierarchical modular structures, which are composed of many hierarchically connected unit modules. This modular approach is effective for the large-sized space structure since a small size unit module is convenient for the ground test and production. Despite that size and environment are quite different, marine plankton and space structures are similar from the point of modular structures. We try to design hierarchical modular structures based on geometrical symmetry inspired by marine plankton in this paper. It is our final purpose of the research to establish applicable methodology of multiple scale design from plankton to space structure using mathematical morphology and structural mechanics, from the viewpoint of structural morphology under gravity-free and free-free boundary condition. © 2009 by the American Institute of Aeronautics and Astronautics, Inc.

DOI： 10.2514/6.2009-2142

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

The stratigraphy and radiolarian age of the Mizuyagadani Formation in the Fukuji area of the Hida-gaien terrane, central Japan, represent those of Lower Permian clastic-rock sequences of the Paleozoic non-accretionary-wedge terranes of Southwest Japan that formed in island arc-forearc/back-arc basin settings. The Mizuyagadani Formation consists of calcareous clastic rocks, felsic tuff, tuffaceous sandstone, tuffaceous mudstone, sandstone, mudstone, conglomerate, and lenticular limestone. Two distinctive radiolarian faunas that are newly reported from the Lower Member correspond to the zonal faunas of the Pseudoalbaillella u-forma morphotype I assemblage zone to the Pseudoalbaillella lomentaria range zone (Asselian to Sakmarian) and the Albaillella sinuata range zone (Kungurian). In spite of a previous interpretation that the Mizuyagadani Formation is of late Middle Permian age, it consists of Asselian to Kungurian tuffaceous clastic strata in its lower part and is conformably overlain by the Middle Permian Sorayama Formation. An inter-terrane correlation of the Mizuyagadani Formation with Lower Permian tuffaceous clastic strata in the Kurosegawa terrane and the Nagato tectonic zone of Southwest Japan indicates the presence of an extensive Early Permian magmatic arc(s) that involved almost all of the Paleozoic non-accretionary-wedge terranes in Japan. These new biostratigraphic data provide the key to understanding the original relationships among highly disrupted Paleozoic terranes in Japan and northeast Asia.

DOI： 10.1111/j.1440-1738.2008.00632.x

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Language：Japanese   Publisher：The Geological Society of Japan  

An Oligocene radiolarian fauna was recovered from silty mudstone within the Hyuga Group of the Shimanto accretionary complex in the Murasho district, central Kyushu, Southwest Japan. The fauna includes Artophormis gracilis, Lophocyrtis aspera group, Theocyrtis aff. setanios, and Theocorys bianulus. The radiolaria-dated Oligocene unit occupies the structurally lowest position in the imbricate stacks of the Hyuga Group. Previous workers reported middle Eocene to probably early Oligocene microfossils from structurally upper units, and thus these together imply the presence of the younging polarity toward a structurally lower unit.

DOI： 10.5575/geosoc.114.92

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Other Link： http://hdl.handle.net/10191/26523

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

Two distinctive uppermost Silurian to Lower Devonian radiolarian assemblages, the Pseudospongoprunum tauversi Assemblage and the Futobari solidus-Zadrappolus tenuis Assemblage, occur in new localities of felsic tuffaceous strata in the Hitoegane area of the Hida-gaien terrane of central Japan. The first is characterized by the presence of P. tauversi and diverse inaniguttids, which can be correlated with the well-constrained Pridolian radiolarian zonal fauna defined in west Texas. The second occurs stratigraphically above beds containing the P. tauversi Assemblage and in strata correlative to beds from which a probably Lower Devonian flora has been recovered. These occurrences indicate that the F. solidus-Zadrappolus tenuis Assemblage ranges from uppermost Silurian to Lower Devonian. Based on the stratigraphic context for the underlying Pridolian P. tauversi Assemblage, the probably Lower Devonian flora, and the reinterpretation of the previously dated zircon U/Pb age, the F. solidus-Z. tenuis Assemblage is the first confirmed radiolarian assemblage from the lowermost Devonian. Previous workers have suggested that entactimid radiolarians became increasingly dominant in the latest Silurian to Early Devonian, but the present study shows that inaniguttids such as Futobari and Zadrappolus were dominant in the early to probably middle Early Devonian. A new inaniguttid species is described: Zodrappolus (?) nudus n. sp.

DOI： 10.2113/gsmicropal.53.3.221

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2006.0_110_1

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DOI： 10.14863/geosocabst.2006.0_110_2

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DOI： 10.14863/geosocabst.2006.0_111_1

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Early Carboniferous radiolarians were newly discovered from siltstone of the Nedamo Complex in the Hayachine Terrane, Northeast Japan. This siltstone and other clastic rocks along with greenstone and chert are the components of an accretionary complex. Radiolarian fauna contains Palaeoscenidium cladophorum Deflandre that ranges in age from Early or Middle Devonian to Early Carboniferous. Since the Fe-Mn chert intercalated in a MORB-type basalt of the Nedamo Complex was assigned an age of Late Devonian (Hamano et al., 2002), the accretionary age of the Hayachine Terrane is no older than Late Devonian, most probable Early Carboniferous. This is the first report of an Early Carboniferous accretionary complex recognized by biostratigraphic data in Japan.

DOI： 10.5575/geosoc.111.249

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Other Link： http://hdl.handle.net/10191/26525

Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2005.0_133_2

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Language：Japanese   Publisher：The Geological Society of Japan  

Silurian and Devonian radiolarian biostratigraphy was studied for tuffaceous clastic rocks developed in the Fukuji - Hitoegane and Kuzuryu Lake - Upper Ise River areas of the Hida Gaien belt, central Japan. The objective of the study was to improve chronostratigraphic calibration of these intervals and to discuss local correlation among the Middle Paleozoic strata in Japan. Radiolarian zones characterized by eight distinctive assemblages have been ・defined in the seven measured sections, as follows: Haplotaeniatum tegimentum - Syntagen-tactinia excelsa (middle to upper Llandovery), Fusalfanus osobudaniensis - Secuicollacta itoigawai (lower Ludlow). Zadrappolus spinosus - Praespongocoelia parva (lower or middle Ludlow), Stylosphaera (?) magnaspina (upper Ludlow), Pseudospongoprunum (?) tauversi (lower to middle Pridoli), Futobari solidus - Zadrappolus tenuis (lower or middle Pridoli to Lower Devonian), Palaeoscenidium ishigai - Deflantrica furutanii (Lochkovian or Pragian to lower Emsian), and Pactarentinia intermedia - Pactarentinia igoi (lower Emsian) Assemblage Zones. Age control is based on the stratigraphic relationship between the zones, other fossils, and correlation with other radiolarian zones established in the southern Urals, west Texas, and the Kurosegawa belt, Southwest Japan. Biostratigraphic correlations clearly show that Ludlow to Emsian tuffaceous clastic rocks of deep-water origin in the Hida Gaien belt are exceedingly similar to those in the Kurosegawa and South Kitakami belts in depositional age. It provides a constraining link between these terranes during the early evolutionary stage of their geologic history.

DOI： 10.5575/geosoc.110.620

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Other Link： http://hdl.handle.net/10191/26546

Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2004.abst.0_50_1

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Middle Paleozoic tuffaceous clastic and carbonate rocks are well developed in the Kuzuryu Lake-Upper Ise River area of the Hida-gaien Terrane in central Japan and are lithologically subdivided into the Kagero, Shibasudani, and Kamianama formations. The Kagero Formation consists mainly of tuffaceous sandstone and tuffaceous shale, which sometimes alternate, and differs from the other Paleozoic formations by having well-stratified tuffaceous rocks and an overall abundance of calcareous grains. The Shibasudani Formation is subdivided into three parts. The lower and upper parts consist mainly of sandstone and shale, with alternating sandstone and shale containing siliceous shale intercalations. The middle part of this formation is characterized by limestone blocks that are inferred to be exotic inclusions. The Kamianama Formation, which is correlative with the Lower Devonian Fukuji Formation, consists of limestone, felsic tuff, and sandstone. Radiolarians clearly indicate that the Kagero and Shibasudani formations are early Early Silurian and Late Silurian to Early Devonian in age, respectively. Terrane-wide correlations clearly show that the Middle Paleozoic strata of the Kuzuryu Lake-Upper Ise River area strongly resemble those of the Fukuji-Hitoegane area in age, lithology, and assemblage of lithologic units, and just as strongly differ from strata in the Hongo-Arakigawa and Naradani areas. Both Lower Devonian shallow-marine carbonates and deep-water tuffaceous elastics are present in the study area. Their occurrence together implies the presence of a diverse sedimentary system in a differentiated Middle Paleozoic basin.

DOI： 10.5575/geosoc.109.425

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Other Link： http://hdl.handle.net/10191/26548

Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.14863/geosocabst.2002.0_54_2

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DOI： 10.14863/geosocabst.2001.0_112_1

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DOI： 10.14863/geosocabst.1999.0_164_2

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DOI： 10.14863/geosocabst.1999.0_44_2

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DOI： 10.5575/geosoc.104.845

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Other Link： http://hdl.handle.net/10191/26506

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Other Link： http://hdl.handle.net/10191/24759

Language：Japanese   Publisher：The Geological Society of Japan  

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Language：Japanese   Publisher：The Geological Society of Japan  

DOI： 10.5575/geosoc.113.11.XVII_XVIII

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Language：English   Publishing type：Book review, literature introduction, etc.  

The Khabarovsk Complex, a Jurassic accretionary complex distributed in and around the Khabarovsk city area, Far East Russia, comprises mélange and schist facies. From the review of previous studies including Russian papers, the lithology and age of the constituent rocks of the mélange facies can be summarized as follows: Upper Paleozoic basic volcanic rocks, mainly pillow lava, and altered gabbro, Upper Carboniferous to Upper Permian fusulinoidean-bearing limestone associated with tuff, Lower and Middle Jurassic siliceous mudstone, Upper Jurassic tuffaceous mudstone, uppermost Jurassic carbonate concretions embedded in mudstone, and age-unknown sandstone. Newly found sequences of limestone-chert and of basalt-chert in the mélange facies crop out along the Amur River in the Khabarovsk city area. A chert sample of the limestone-chert sequence contains Albaillella aff. asymmetrica and Pseudoalbaillella aff. lomentaria, and a chert sample of the basalt-chert sequence includes Follicucullus monacanthus, Follicucullus porrectus, and Pseudoalbaillella cf. yanaharaensis. The radiolarian assemblages from the limestone-chert and basalt-chert sequences have a maximum age of middle Early Permian and late Middle Permian, respectively, overlapping the time of deposition of the fusulinoidean-bearing limestone. The co-occurrence of chert and limestone indicates that the fusulinoidean-bearing limestone was formed on a basaltic topographic high in a pelagic ocean whereas the radiolarians accumulated in a deeper part. Limestone debris occasionally flowed into the depositional site of the radiolarian chert. Although the Khabarovsk Complex was simply considered as a northern extension of the Mino-Tamba Belt of the Inner Zone of southwest Japan, we propose a new correlation based on the lithologic associations. The mélange facies of the Khabarovsk Complex is correlative with one of the Kasugano, Funabuseyama, Nabi, and Yabuhara Formations in the Mino-Tamba Belt, whereas the schist facies is correlative with the Hikami Formation of the Ultra-Tamba Belt. Copyright © 2005, The Paleontological Society.

DOI： 10.1666/0022-3360(2005)079[0687:PRFFCI]2.0.CO;2

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Language：Japanese   Publisher：実業公報社  

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Language：Japanese   Publisher：University of Tsukuba  

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Other Link： http://hdl.handle.net/2241/99831