bluuebunny/crossref_metadata_2025 huggingface dataset:
Rb‐Sr dating for the Jiaodong gneiss of the Su‐Lu ultra‐high pressure province, eastern China
Authors: Ishizaka K. , Hirajma T. , Zheng X.
Published: April 2006

Abstract Gneiss samples were collected from the Shandong Peninsula, eastern China, in order to carry out Rb‐Sr dating using whole rock powder and biotite mineral separates. Middle Proterozoic whole rock age (1808 ± 71 Ma) and Middle to Late Proterozoic biotite ages (1312 and 729 Ma) were obtained for country gneisses in the northwestern part of the peninsula. Late Proterozoic whole rock age (707 ± 61 Ma) and Mesozoic biotite ages (172 and 222 Ma) were obtained for orthogneisses in the southeastern part of the peninsula. These new age data, as well as recent petrological results and published radiometric data, support the subdivision of the Shandong Peninsula into two geological districts: (i) a northwestern area of Proterozoic age represented by a low‐ and middle‐pressure metamorphic sequence belonging to the Sino‐Korean craton; and (ii) a southeastern area of Late Proterozoic and Mesozoic age accompanied by ultra‐high pressure eclogite.
Palaeozoic and early Mesozoic fish faunas of the Japanese Islands
Authors: GOTO MASATOSHI
Published: April 2006

Abstract In recent years, many fish teeth and scales have been found from the Palaeozoic and Mesozoic age strata of the Japanese Islands. This study is a compilation of the Japanese fish record from the Palaeozoic and early Mesozoic age deposits. Based on the published and unpublished data, the fossil fishes from the Palaeozoic and Early Mesozoic of Japan can be classified into 27 genera and 33 species, that is, one species of Devonian placoderms, 19 species of Permian to Jurassic elasmobranchs, three species of Permian cochliodonts, seven species of Carboniferous to Permian petalodonts, and three species of Triassic to Jurassic osteichthyans.
Late Mesozoic and Cenozoic fish faunas of Japan
Authors: Yabumoto Yoshitaka , Uyeno Teruya
Published: April 2006

Abstract A review of the chondrichthyan and osteichthyan fish fossils found in Japan is provided in the form of a series of tabular compilations covering the Late Mesozoic and Cenozoic Era. On the basis of this compilation, considerable changes are recognized in the fish faunas over a period of time. At the end of the Cretaceous Period a number of cartilaginous fishes disappeared. From the Oligocene to the Miocene, modern sharks including the family Carcharhinidae increased, whereas the Hexanchidae and Lamnidae declined. Most Miocene teleostean fishes differ from the Recent congeners at the species level.
Phylogenetic systematics of chelonioid sea turtles
Authors: Hirayama Ren
Published: April 2006

Abstract Chelonioid sea turtles (Order Testudinata; Superfamily Chelonioidea) first appear in the early Cretaceous (Aptian‐Albian). Their long fossil record is excellent compared to most marine tetrapods. Nonetheless, there has been no inclusive attempt to provide an analysis of cladistic relationships among this group. In this paper, the following chelonioid classification is proposed, based on 76 characters among 20 fossil and six living well‐ represented genera:

Family Cheloniidae (Coniacian to Recent); Toxochelys, Ctenochelys, Osteopygis, Erquelinnesia, Allopleuron, Argillochelys, Puppigerus, Eochelone, Syllomus, Natator, Eretmochelys, Chelonia, Caretta, Lepidochelys

Family Protostegidae (Aptian to Maastrichtian?); ‘Santana new protostegid’,Rhinochelys, Notochelone, Desmatochelys, Chelosphargis, Protostega, Archelon

Family Dermochelyidae (Santonian? to Recent); Corsochelys, ‘HMG new dermo‐chelyid’, Eosphargis, Psephophorus, Dermochelys.
Miocene fossil pinnipeds of the genera Prototaria and Neotherium (Carnivora; Otariidae; Imagotariinae) in the North Pacific Ocean: Evolution, relationships and distribution
Authors: Kohno Naoki , Barnes Lawrence G. , Hirota Kiyoharu
Published: April 2006

Abstract Fossil otariid pinnipeds of the extinct genera Prototaria Takeyama and Ozawa, 1984, and Neotherium Kellogg, 1931, known from Middle Miocene deposits bordering the North Pacific Ocean, are small, primitive pinnipeds in the subfamily Imagotariinae. They have a small supraorbital process of the frontal or have lost it entirely, a three‐rooted first molar, small paroccipital process, and ear morphology indicating that they belong in the subfamily Imagotariinae. Their unique derived characters include extreme intertemporal constriction and highly modified cheek teeth, the premolars having become molarized by the addition of protocones and lingual cingula. Prototaria Takeyama and Ozawa, 1984, the most primitive known imagotariine genus, contains two species, P. primigena Takeyama and Ozawa, 1984, and P. planicephala Kohno, 1994, both of early Middle Miocene age from Japan. Prototaria has a few derived characters, including a large antorbital process, narrow intertemporal region, and large orbit, but its primitive characters apparently were inherited from enaliarctine ancestors. The long enigmatic Neotherium mirum Kellogg, 1931, of Middle Miocene age from California, USA, is related to Prototaria, but differs by having an elongate skull, very slender zygomatic arch, ventrally exposed median lacerate foramen, and smaller but more molarized premolars. A more primitive new genus and species, Proneotherium repenningi Barnes, related to N. mirum, is from the early Middle Miocene Astoria Formation, coastal Oregon, USA. It shares some derived characters with Prototaria, and shares many other important derived characters with N. mirum. Imagotariines probably arose from some species of Early Miocene enaliarctines, became diverse in Middle and Late Miocene time, and are only known from the North Pacific realm. Although they might include the ancestors of true walruses of the subfamily Odobeninae, no known imagotariines appear to have been adapted for mollusk feeding as are the highly evolved modern walruses. Instead, imagotariines appear to have retained a primitive piscivorous diet, as did the fur seals and sea lions of the subfamily Otariinae.
A primitive odobenine walrus of Early Pliocene age from Japan
Authors: Horikawa Hideo
Published: April 2006

Abstract The well preserved cranium of Protodobenus japonicus, a new genus and species of odobenine walrus, is from the lower part of the Tamugigawa Formation at Ooshima‐mura, Higashi Kubiki‐gun, Niigata Prefecture, central Japan. The lower part of the formation that yielded P. japonicus is Early Pliocene, dating approximately from 5.0 to 4.9 Ma. The skull of P. japonicus is generally shaped like that of the modern walrus, Odobenus rosmarus (Linnaeus, 1758), but is much more primitive, especially in the dentition.

Protodobenus japonicus is derived from the Imagotariinae. It is similar to such primitive fossil walruses as Prorosmarus alleni from the Western Atlantic and Aivukus cedrosensis from Baja California, and has some similarities as well as significant differences from them. Protodobenus japonicus could have evolved directly into Odobenus in the North Pacific Ocean, and could have dispersed directly to the Arctic Ocean. This is contrary to the scenario proposed by Repenning and Tedford, in which primitive odobenids, like Aivukus cedrosensis, migrated to the Atlantic Ocean through the Central American Seaway and returned to the North Pacific Ocean as O rosmarus via the Arctic about 0.6 Ma.

Regarding the first lower premolar of the living walrus, Fay concluded after studying fetal O. rosmarus that the first premolar (P1) of the mandible is absent, and that the lower tooth row consists of: C1 P2, P3, P4. Protodobenus japonicus has in its mandible I 1‐2 C1 P2, P3, P4, and this is the primitive pinniped formula. Pinnipeds typically lose the molars, not the anterior premolars, and the present author believes that the correct tooth formula for O rosmarus is C1 P1, P2, P3. Its skull, palate, and mandible suggest that P. japonicus had morphology pre‐adapted to an early stage of benthic suction feeding, but it probably was unable to rely on that method of feeding. The discovery of P. japonicus demonstrates that the odobenine lineage (true walruses) goes back in time at least 5 Ma. Other more aberrant odobenine walruses, such as Aivukus and Prorosmarus, and pseudo‐walruses of the subfamily Dusignathinae, are more distantly removed from the lineage leading to living walruses than has previously been suspected.
General aspects of the evolutionary history of whales and dolphins
Authors: Fordyce R. Ewan , Barnes Lawrence G. , Miyazah Nobuyuki
Published: April 2006

Abstract The Cetacea are the most diverse and highly aquatically adapted group of mammals. Their fossil record extends back at least to the Middle Eocene (ca 50 Ma), and they will possibly be found earlier, judging by the relatively highly evolved nature of the earliest known whales. The most likely terrestrial ancestors of whales are the mesonychids, primitive hoofed mammals with omnivorous diets. Recently discovered archaeocetes with large, mesonychid‐like heads and dentitions and functional hind limbs reconfirm earlier ideas about the mesonychid origin of cetaceans and the amphibious nature of the earliest transitional forms. Fossil cetaceans are relatively abundant and diverse thoughout the world, and are now known from every continent, including Antarctica. Odontocetes evolved echolocation to locate food. Mysticetes developed bulk feeding adaptations. Both undoubtedly evolved from archaeocetes, and the monophyly of Cetacea is the most parsimonious present hypothesis. Chromosomal and molecular evidence has taken an increasingly important role in determining cetacean relationships, but fossils and classical comparative morphological studies remain a necessary and pivotal source of information about cetacean phylogeny.
A new species of Middle Miocene sperm whale of the genus Scaldicetus (Cetacea; Physeteridae) from Shiga‐mura, Japan
Authors: Hirota Kiyoharu , Barnes Lawrence G.
Published: April 2006

Abstract A nearly complete skeleton of a fossil sperm whale from the Middle Miocene age Bessho Formation at Shiga‐mura, Nagano Prefecture, the most complete fossil physeterid skeleton found in Japan, is here named Scaldicetus shigensis, new species. Its abruptly tapered rostrum, deep supracranial basin, and high occipital crest are typical of physeterids. Large teeth with crenulate enamel on conical crowns, present in both the palate and mandible, are consistent with the genus Scaldicetus du Bus, 1867, a genus originally based on fossils discovered in the Antwerp Basin, Belgium. Scaldicetus shigensis is relatively primitive, having a relatively long, slender rostrum, large zygomatic arches, large tympanic bullae, prominent occipital condyles, low tooth count and a sloping occipital shield that is deeply emarginated laterally by large temporal fossae. The probable mandibular tooth count is 12, only one more than the primitive eutherian mammalian dentition. Despite its abundant primitive characters, Scaldicetus shigensis has very asymmetrical external nares, comparable to the living sperm whale, Physeter catodon, and is in this way more derived than most of the contemporaneous fossil physeterids. At a time when other sperm whales were more highly evolved, Scaldicetus shigensis retained a primitive occipital shield, large tympanic bullae, and low tooth count, as in primitive Oligocene odontocetes such as Agorophiidae. It was a relict form in Middle Miocene time, and provides an indication of a primitive stage of sperm whale evolution heretofore undocumented. Fossils from elsewhere previously referred to as Scaldicetus, largely on the basis of tooth characters, range in age from Early Miocene to Plio‐Pleistocene time. Cranial material that would clarify relationships is lacking for most of these, and this time range seems too long for a cetacean genus. Because of this simplistic approach to identifications, Scaldicetus is probably a grade taxon, not a natural biological grouping. However, the tooth morphology of Scaldicetus shigensis is correct for the genus Scaldicetus, so we provisionally assign it to this genus. Redefinition of the genus Scaldicetus and revision of the Physeteridae are beyond the scope of the present study.
Summary of taxa and morphological adaptations of the Desmostylia
Authors: Inuzuka Norihisa , Domning Daryl P. , Ray Clayton E.
Published: April 2006

AbstractDesmostylians from the Pacific coasts of Japan and North America are compared and taxonomy and adaptations in the mammalian order Desmostylia discussed. The taxonomy is based mainly on teeth and skulls. Feeding adaptations and habitat are discussed using teeth and restored skeletons, respectively. In the extinct order two families, six genera and 10 species can now be recognized. Each genus is distinguished by a set of tooth characters. The three species of the genusPaleoparadoxiahave different body sizes. Two species of the genusDesmostyluscan be distinguished on morphological differences in the cranium. As a result it is clear that both species,D. hesperus, which had long been recognized only in North America, andD. japonicus, which has hitherto been recognized only in Japan, inhabited both coasts of the Pacific. All genera of the Order Desmostylia share a common and distinctive body form, interpreted by Inuzuka as having a laterally placed limb posture. Based on this body form, the optimum habitat is thought to have been an intertidal sandy beach. The dental morphology is variable, and derived species show an adaptation for wear by an abrasive diet. In conclusion, we theorize that the Order Desmostylia was adapted for a coastal habitat from its inception, with each genus adapting to a different sort of herbivorous diet.
Rifting and basin inversion in the eastern margin of the Japan Sea
Authors: Okamura Yukinobu , Watanabe Mahito , Morijiri Rie , Satoh Mikio
Published: April 2006

Abstract Extensional basin formation and subsequent basin inversion in the southern area of the eastern margin of the Japan Sea were studied on the basis of the interpretation of seismic profiles (total length approximately 15 000 km) and the fossil analyses of 77 sea‐bottom samples. Rift (Early to Early Middle Miocene), post‐rift (Middle to Late Miocene), pre‐inversion (Late Miocene to Pliocene) and inversion stages (Pliocene to Quaternary) were differentiated by the extension and contraction of the crust. Many small‐scale rifts were formed in the Sado Ridge and the Mogami Trough during the rift stage, simultaneous with back‐are spreading of the Japan Sea. Most of the rifts were east‐ or southeast‐facing, rotational half‐grabens bounded by west‐dipping normal faults at their eastern boundaries. The syn‐rift sequence can be divided into lower and upper units by an erosional surface. The sequences are presumed to be composed mainly of fining‐upward sediments. The trend of most rifts is north‐northeast with the remainder being of east‐northeast‐bias. The north‐northeast trending rifts are distributed widely in the Sado Ridge and Mogami Trough and do not show an en échelon arrangement, suggesting that they were formed mainly by pure extension nearly perpendicular to the arc. The east‐northeast trending rifts are presumed to have been developed by a north‐northwest extension in the late rift stage, which may have accompanied a right‐lateral movement in the eastern margin of the Japan Sea. During the post‐rift stage, the rifts and adjacent horsts subsided and became covered by the post‐rift sequence, characterized by parallel and continuous reflections. This suggested no significant tectonic movements in this period. In the pre‐inversion stage many of the rifts subsided again, presumably because of down‐warping due to weak compressional stress. The normal faults reactivated as reverse faults during the inversion stage due to an increase in compressional stress. Many of the rifts have been uplifted and transformed into east‐vergent asymmetric anticlines. The basin inversion is greatest in the Sado Ridges and in the Dewa Bank Chain, while it is least developed in the Mogami Trough and in the western slope of the Sado Ridge, in which some normal faults have not been reactivated. The increase and decrease of the inversion corresponds to the peak and trough of undulation at an interval of about 50 km trending parallel to the arc.
Ultrahigh‐pressure metamorphism and tectonics
Authors: Liou J. G. , Banno S. , Ernst W. G.
Published: April 2006

Abstract Recognition of several ultrahigh‐pressure (UHP) metamorphic terranes in continental collision belts has revolutionized the concept of geodynamic processes. In order to facilitate better communication and focus among active investigators, the Task Group III‐6 of the International Lithosphere Program‘Ultrahigh‐Pressure Metamorphism and Geodynamics in Collision‐type Orogenic Belts’held the first two day workshop at Stanford University in December, 1994. Petrotectonic settings, mineral paragenesis, geochronoldgy, and geochemical characteristics of UHP rocks from several recognized and suspected UHP terranes were addressed. This special issue presents 11 papers from the more than 50 contributions from the 88 participants representing 15 countries. Many challenging petrotectonic and petrochemical problems remain to be investigated. These include detailed P‐T time paths for both the UHP unit and adjacent units, the role of fluids at mantle depths, deep seismic profiles and mechanisms and rate of exhumation of the UHP unit.
Petrology and retrograde P‐T path for eclogites of the Maksyutov Complex, Southern Ural Mountains, Russia
Authors: Beane R. J. , Liou J. G. , Coleman R. G. , Leech M. L.
Published: April 2006

Abstract The Maksyutov Complex, situated in the southern Ural Mountains of Russia, is the first location where quartz aggregates within garnets exhibiting radial fractures were identified as coesite pseudomorphs (Chesnokov & Popov 1965). The complex consists of two tectonic units: a structurally lower eclogite‐bearing schist unit and an overlying meta‐ophiolite unit. Both units show evidence for multiple stages of metamorphism and deformation. The high‐pressure metamorphism of the eclogite‐bearing schist unit, discussed in this report, is suspected to be related to a collision between the Russian platform and a fragment of the Siberian continent during the early Cambrian. At least three stages of metamorphism (M1‐3) and two stages of deformation (S1 and S2) were observed in thin sections: M1) garnet (Alm55‐60, Prp22‐28, Grs16‐20) + omphacite (Jd46‐56) + phengite (Si ≅ 3.5) + rutile; M2) garnet + glaucophane ± lawsonite + white mica; and M3) epidote + chlorite ± albite ± actinolite + white mica. Observed mineral parageneses define a retrograde P‐T path for the eclogite. Mineral assemblages within the most representative eclogite from the lower unit of the Maksyutov Complex indicate minimum peak pressures of 15 kbar at temperatures of approximately 600°C. If the presence of coesite pseudomorph is confirmed, the peak ultrahigh‐pressure metamorphism may be as high as 27 kbar at 615°C.
Mineral parageneses and metamorphic P‐T paths of ultrahigh‐pressure eclogites from Kyrghyzstan Tien‐Shan
Authors: Tagiri M. , Yano T. , Bakirov A. , Nakajima T. , Uchiumi S.
Published: April 2006

Abstract Eclogites occur in three districts of the northern and southern parts of Tien‐Shan. Three eclogites collected from the Aktyuz, Makbal and Atbashy districts were analyzed; the P‐T paths of three eclogites were estimated by analyzing compositional growth zoning and retrograde reaction of garnet and omphacite. Aktyuz and Makbal eclogites have not preserved the prograde path. An Aktyuz eclogite that underwent a quartz eclogite facies metamorphism (about T = 600°C, P = 12 kbar) has recorded three stages of retrograde metamorphism. Four stages of retrograde metamorphism were recognized in a Makbal eclogite; the garnet‐omphacite geothermometer gave about T = 560°C at 20 kbar as the highest metamorphic condition. Garnet from a garnetchloritoid‐talc schist of the Makbal district includes quartz pseudomorphs after coesite; some units evidently underwent a low‐temperature part of coesite eclogite fades metamorphism. Prograde and retrograde paths were recognized in an Atbashy eclogite; five stages of metamorphic reaction were observed in the Atbashy sample. The prograde path from stage I to stage III has been recorded in garnet and omphacite in which quartz pseudomorphs after coesite are included. The peak metamorphism of stage III took place at about 660°C at 25 kbar. The stages IV and V are retrograde. UHP eclogite facies metamorphism took place twice in Kyrghyzstan. The Aktyuz and Atbashy eclogites gave Rb‐Sr mineral‐isochron ages of about 750 Ma and 270 Ma, respectively. The K‐Ar age of paragonite from the Makbal eclogite is about 480 Ma.
Ultrahigh‐pressure metamorphism and decompressional P‐T paths of eclogites and country rocks from Weihai, eastern China
Authors: Zhang R. Y. , Liou J. G. , Ernst W. G.
Published: April 2006

Abstract Altered quartz‐rich and nearly quartz‐free eclogitic rocks and completely retrograde quartz‐rich garnet amphibolites occur as blocks or lenses in gneisses at Weihai, northeastern tip of the Sulu ultrahigh‐P belt. Eclogitic rocks with assemblage garnet ± clinopyroxene ± coesite + rutile have experienced three‐stage metamorphic events including ultrahigh‐pressure eclogite, granulite and amphibolite facies. Granulite metamorphic event is characterized by formation of the hypersthene + salite + plagioclase ± hornblende corona between garnet and quartz + clinopyroxene. P‐T conditions for the three‐stage recrystallization sequence are 840 ± 50°C, >28 kbar, about 760±50°C, 9 kbar, and ~650°C, <8 kbar respectively. Most country rock gneisses contain dominant amphibolite‐facies assemblages; some garnet‐bearing clinopyroxene gneisses recrystallized under granulite‐facies conditions at about 740±50°C and 8.5 kbar; similar to granulite‐facies retrograde metamorphism of the enclosed eclogitic blocks. Minor cale‐silicate lenses within gneisses containing an assemblage grossular + salite + titanite + quartz with secondary zoisite and plagioclase may have formed within a large pressure range of 14‐35 kbar. Eclogitic boudins and quartzo‐feldspathic country rocks may have experienced coeval in situ UHP and subsequent retrograde metamorphism. The established nearly isothermal decompression P‐T path suggests that this area may represent the interior portion of a relatively large subducted sialic block. The recognized UHP terrane may extend eastward across the Yellow Sea to the Korean Peninsula.
Petrology of the Hujialin garnet clinopyroxenite in the Su‐Lu ultrahigh‐pressure province, eastern China
Authors: Hiramatsu N. , Hirajima T.
Published: April 2006

Abstract Garnet clinopyroxenite containing porphyroclastic clinopyroxene with garnet lamellae from the Su‐Lu ultrahigh‐pressure (UHP) province, eastern China, records a three‐stage evolutionary history. Stage A: precursor aluminous clinopyroxene associated with Mg‐rich spinel was stable. Stage B: Mg‐rich spinel and aluminous clinopyroxene recrystallized to form porphyroblasts of garnet and diopside with garnet lamellae, respectively. Thereafter, these porphyroblasts were granulated and recrystallized to form equigranular neoblasts in the matrix, being driven by subsolidus deformation. Stage C: the assemblage developed retrograde hornblende, epidote, spinel, chlorite, calcite, and dolomite. The estimated composition of the precursor aluminous clinopyroxene indicates that equilibrium conditions of the stage A were 900‐1000°C, and 1.0‐1.5 GPa. The neoblast garnet‐clinopyroxene pairs, not conjectural, give 740 ± 50°C and higher than 2.5 GPa for the climax conditions of stage B. This implies that the Hujialin garnet clinopyroxenite was transported from a low dP/dT setting to a high dP/dT setting, probably related to subduction during stage B. The Hujialin garnet clinopyroxenite as well as adjacent UHP eclogite which records 700°C and 3.0 GPa as the maximum physical conditions, experienced amphibolite facies retrogression, suggesting that they shared a common P‐T history during exhumation.
Ultrahigh‐pressure garnet lherzolite from Chijiadian, Rongcheng County, in the Su‐Lu region of eastern China
Authors: Hiramatsu N. , Banno S. , Hirajima T. , Cong B.
Published: April 2006

Abstract Petrological studies of a serpentinized garnet lherzolite body in Rongcheng of the Su‐Lu region of eastern China revealed unusually high pressure. Spinel lherzolite probably in a subducting slab was transformed to garnet lherzolite at mantle depth. During exhumation, they were subsequently subjected to the granulite and then amphibolite overprinting and a phase of serpentinization. The peak P–T conditions of the garnet lherzolite estimated after detailed analysis of the metamorphic texture are 4–5 GPa and 820°C or 5–6 GPa and 780°C, depending on the chosen geothermobarometers. The lower dP/dT of the garnet lherzolite can be interpreted as the results of subduction of an old (say 100 Ma older than the time of collision) and cold, slab underneath the margin of the Sino–Korean craton.
Eclogites of southern Henan and northern Hubei Provinces, central China
Authors: Cui W. , Wang X.
Published: April 2006

Abstract According to field occurrence and P‐T condition, eclogites of southern Henan and northern Hubei Provinces can be divided into two types: medium temperature (MT) and low temperature (LT) eclogites. MT eclogite occurs as layers or lenticular bodies within migmatized gneiss of the Dabie Group. This study is the first to report an occurrence of the assemblages coesite and kyanite + talc in this area. Garnet exhibits a distinct prograde compositional zoning and has mineral inclusions with rotational textures indicating syntectonic growth. Five evolutionary stages are outlined. (1) Pre‐eclogite stage, determined by the inclusions of barroisite + zoisite + quartz in the cores of zoned garnets. (2) Eclogite stage, characterized by garnet + omphacite + kyanite ± talc + coesite + rutile, represents the peak metamorphism. The peak conditions are estimated to be T = 600‐700°C, P >27 kb. (3) Glaucophane stage, without an appearance of plagioclase, is assigned to a transitional stage. Blades of glaucophane form rims around garnet grains as a result of the reaction talc + jadeite = glaucophane. This marks the beginning of retrograde metamorphism. (4) Symplectite stage, where eclogitic minerals break down, and Amp + Pl symplectite develops around garnet or omphacite; (5) Later retrograde stage is represented by epidote‐amphibolite assemblages. Low temperature eclogite appears as blocks in the Qijiaoshan Formation (part of the Susong Group). Four stages can be identified: (1) Pre‐eclogite stage, amphibole + epidote + sphene inclusions occur in garnet core; (2) Eclogite stage, consists of garnet + omphacite + rutile + quartz + phengite + glaucophane + zoisite. The peak conditions are T = 490‐560°C, P <15 kb; (3) Symplectitic stage, is characterized by the breakdown of eclogitic minerals; (4) Greenschist facies stage, is recorded by a greenschist facies assemblage. The difference between the two types of eclogites suggests contrasting processes. A model is proposed whereby partial melting of continental crust and the emplacement of tonalite occurs during the exhumation of ultrahigh‐pressure eclogite terrain.
Occurrences of hydrous and carbonate phases in ultrahigh‐pressure rocks from east‐central China: Implications for the role of volatiles deep in cold subduction zones
Authors: Liou J. G. , Zhang R. Y. , Ernst W. G.
Published: April 2006

Abstract Minor epidote‐zoisite, phengite, glaucophane, nyböite, talc, magnesite, and dolomite occur as matrix phases or as mineral inclusions in some ultrahigh‐pressure (UHP) rocks from the Dabie‐Sulu terrane. Some of these phases contain inclusions of coesite or coesite pseudomorphs and appear to have been in equilibrium with coesite at the time of formation. Their occurrences in the UHP rocks together with experimentally determined and calculated phase relations indicate that they are stable at mantle depths in relatively low‐temperature environments. Because of the apparently dry nature of subducted continental protoliths of the Yangtze craton, small amounts of volatile components at depths exceeding 50 km along a cold subduction zone may have been stored mainly by these hydrous and carbonate phases. These minerals, in addition to some dense hydrous magnesian silicates, act as important carriers for H2O and CO2 recycled at mantle depths. Available petrological and geochemical data support limited or no fluid flow in this region. At very high pressures and low temperatures, the subducted sialic crust evidently served as a desiccating agent. Partial melting of the subducting slab, therefore, may not have occurred, and near absence of volatile expulsion from the subducting slab to the overlying mantle wedge + continental crust may have inhibited large‐scale partial melting, accounting for the lack of a typical contemporaneous calc‐alkaline magmatic arc.
Morphological characteristics of the earthquake surface ruptures on Awaji Island, associated with the 1995 Southern Hyogo Prefecture Earthquake
Authors: Ian Aiming , Uda Shinichi
Published: April 2006

Abstract
The earthquake surface ruptures on the northern side of Awaji Island accompanying the 1995 Southern Hyogo Prefecture Earthquake in Japan consist of three earthquake surface rupture zones called the Nojima, Matsuho, and Kusumoto Earthquake Surface Rupture Zones. The Nojima Earthquake Surface Rupture Zone is ‐ 18 km long and was formed from Awaji‐cho at the northern end of Awaji Island to Ichinomiya‐cho. It occurred along the pre‐existing Nojima geological fault in the northern segment and as a new fault in the southern segment. The northern segment of the Nojima Earthquake Surface Rupture Zone is composed of some subparallel shear faults showing a right‐step en echelon form and many extensional cracks showing a left‐step en echelon form. The southern segment consists of some discontinuous surface ruptures which are concentrated in a narrow zone a few tens of meters in width. This surface rupture zone shows a general trend striking north 30°‐60° east, and dipping 75°‐85° east. The deformational topographies and striations on the fault plane generated during the co‐seismic displacement show that the Nojima Earthquake Surface Rupture Zone is a right‐lateral strike‐slip fault with some reverse component. Displacements measured at many of the outcrops are generally 100‐200 em horizontally and 50‐100 em vertically in the northern segment and a few em to 20 em both horizontally and vertically in the southern segment. The largest displacements are 180 em horizontally, 130 em vertically, and 215 em in netslip measured at the Hirabayashi fault scarp. The Matsuho Earthquake Surface Rupture Zone striking north 40°‐60° west was also found along the coastline trending northwest‐southeast in Awaji‐cho for ∼1 km at the northern end of Awaji Island. The Kusumoto Earthquake Surface Rupture Zone occurred along the pre‐existing Kusumoto geological fault for ∼ 1.5 km near the northeastern coastline, generally striking north 35°‐60° east, dipping 60°‐70° west. From the morphological and geomorphological characteristics, the Nojima Earthquake Surface Rupture Zone can be divided into four segments which form a right‐step en echelon formation. The geological and geomorphological evidence and the aftershock epicenter distributions show clearly that the distributions and geometry of these four segments are controlled by the pre‐existing geological structures.
Impact of tectonic erosion by subduction processes on intensity of arc volcanism
Authors: Lallemand Serge E.
Published: April 2006

Abstract
According to new estimates, more than 2 km3 of terrestrial material is transported every year with the subducting lithospheric plates to depths greater than 20‐30 km. A comparable amount of subducted material is partly restored to the nearby margins through underplating, diapirism or forearc volcanism; partly rejuvenated through arc and back‐arc magmatism; and the rest is recycled into the deep mantle. This study emphasizes the connection between the consumption of some arcs and the intensity of arc volcanism. In many cases (Japan, Peru, Izu‐Bonin, Guatemala), interruption in tectonic erosion of the margin is followed by a hiatus of arc volcanism. The delay between the presumed cause (i.e. absence of subducted arc‐type crust) and the response (i.e. lack of explosive volcanism) corresponds to the time required for the subducting slab to reach the melting depth (i.e. 2‐4 million years). Alternately, intense tectonic erosion of the margin is followed by paroxysms of arc volcanism. Crustal contamination of volcanic rocks may be caused directly by magma sources which may contain arc material derived from the subcrustal erosion of the margin.
Seismic stratigraphy and structural characteristics of back‐arc rifts on the Izu‐Ogasawara Arc
Authors: Murakami Fumitoshi
Published: April 2006

Abstract
Seven back‐arc rifts are recognized in the Izu‐Ogasawara Arc, namely, the Hachijo, the Aogashima, the Myojin, the Sumisu, the Torishima, the Sofu and the Nishinoshima Rifts from north to south. The acoustic stratigraphy is divided into three units (Units A, B and C) based on the seismic reflection profiles crossing the rifts. The structure of the rifts systematically changes from a half‐graben type to a full graben type in the back‐arc rifts from the Hachijo Rift to the Torishima Rift. The Hachijo and the Aogashima Rifts have a structure of half‐graben, and the Myojin Rift has both structural characteristics of a half‐graben and a full graben. The Sumisu and the Torishima Rifts are an asymmetric full graben. The Sofu and the Nishinoshima Rifts have different structural characteristics from the remaining rifts, from the Hachijo Rift to the Torishima Rift. The boundary faults in the back‐arc rifts from the Hachijo to the Torishima Rifts cut to Unit B. Unit B correlates with volcaniclastic sediments during pre‐rift volcanism between 4 and 2 Ma. The pre‐rift volcanism was probably widespread on the northern Izu‐Ogasawara Arc as is the present arc volcanism. These factors suggest that the beginning of rifting is dated at some time after 2 Ma. The developing process of the rift consists of three stages; (i) a sag stage in the crust at the location of the large offset boundary fault; (ii) a stage of half‐graben formation; (iii) a stage of full graben formation. The offset of the boundary faults becomes larger from the Hachijo Rift to the Torishima Rift and the east‐west width of the rifts also widens to the south. This is presumably because the Hachijo Rift is an earlier rifting stage than the Sumisu and the Torishima Rifts. The more primitive structure in the rifting stage from the Torishima Rift to the Hachijo Rift is probably caused by the propagation of rifting from south to north. The structural difference between the rifts in the northern part and the Sofu and the Nishinoshima Rifts seems to be due to structural differences in the crust between the northern and the southern parts from the tectonic gap.
Thermal structure and uplift of the Cretaceous Shimanto Belt, Kii Peninsula, Southwest Japan: An illite crystallinity and Mite bo, lattice spacing study
Authors: Awan M. Aslam , Imura Katsumi
Published: April 2006

Abstract
Illite crystallinity (IC) and illite b, lattice spacing were measured across the Cretaceous Shimanto Belt, Kii Peninsula, Southwest Japan. For the IC survey, 103 samples of argillaceous rocks were analyzed from the central area and the western area of the belt. Values of IC (Kubler Index) vary between 0.28 and 0.71 Δ°2θ and indicate diagenetic and anchizone metamorphism respectively. The IC distribution reveals two contrasting patterns of thermal maturity. The Hanazono Formation, exposed in the northern area of the belt, generally dips north, but IC values increase systematically from 0.28 Δ°2θ in the north to 0.54 Δ°2θ in the south and indicate an inverted thermal structure. Values in other formations vary widely in the southern area of the belt ranging between 0.45 and 0.71 Δ°2θ, but the values do not show any systematic change from north to south and on average remain almost constant. Illite bo, lattice spacing values for 56 samples vary between 9.006 and 9.041 Å corresponding to intermediate pressure conditions of the metamorphic facies. These values, combined with paleotemperatures estimated from IC, indicate paleogeothermal gradients of 22 and 31°C/km for the northern and southern areas of the belt, respectively. The inverted thermal structure of the Hanazono Formation, together with a lower paleogeothermal gradient, possibly is a result of the subduction of a relatively cold oceanic plate during the Late Cretaceous. The higher geothermal gradient could be a product of late thermal overprinting caused by the later subduction of a comparatively younger and hotter oceanic plate during the Eocene.
Late Paleozoic radiolarians from the Bentong‐Raub suture zone, Peninsular Malaysia
Authors: Spiller Frances C. P.
Published: April 2006

Abstract
Radiolarians extracted from marine siliceous sediments from the Bentong‐Raub suture zone, Peninsular Malaysia have indicated a range of ages for olistostromal blocks of bedded chert, siliceous argillite and tuffaceous argillite, and chert clasts and lenses within the mélange from the suture zone. Late Devonian (Faniennian), Early Carboniferous (Tournaisian and Viséan) and Early Permian (Wolfcampian and Leonardian) ages are represented by seven radiolarian zones from ten localities along the suture zone. In stratigraphic order these include Holoeciscus 2–3 Assemblage Zones, Albaillella paradoxa Zone, Albaillella dejendrei Zone, Albaillella cartalla Zone, Pseudoalbaillella lomentaria Zone, Albaillella sinuata Zone and Pseudoalbaillella longtanensis Zone. Fifteen genera are represented by 35 species. The range of ages from Late Devonian to Early Permian suggests that an ocean existed between the Sibumasu and East Malaya terranes from at least Late Devonian to late Early Permian time and that closure of the ocean between the two terranes could not have occurred until after late Early Permian time. The range of ages and rock types from different depositional environments, indicate that the Bentong‐Raub suture zone includes a disrupted accretionary complex.
Preliminary report on Lower Jurassic radiolaria of Gondwana origin from the Kawhia coast, New Zealand
Authors: Hori R. S. , Aita Y. , Grant‐Mackie J. A.
Published: April 2006

Abstract
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, Crucella, Emiluvia (?) Homeoparo‐riaella, Orbictilifomaa, Pantanellium, Paronaella (?), Pseudocrucella, PseIIdoheliodiscus, Spon‐gostaurus and Spongotrochus. Nassellarians are composed of species of Ragotum, Bipedis, Droltus, Jams (?) 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 & 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.
Age of radiolarian‐chert blocks from the Senonian Ophiolitic Mélange (Ankara, Turkey)
Authors: Bragin Nikita yu. , Tekin U. Kagan
Published: April 2006

Abstract
The Senonian Ophiolitic Mélange of the Ankara Mélange Supergroup includes numerous blocks of radiolarian cherts. These blocks contain various radiolarian assemblages from the Albian to the Turonian (Pseudodictyomitra pseudomacrocephala, Thanarla tieneta), the Lower Cretaceous (Thanarla conica, Alievium helenae, Pseudodictyomitra carpatica), the Kimmeridgian‐Tithonian (Ristola altissima, Sethocapsa cetia, Podocapsa umphitreptera) and the lower Jurassic (Parahsuum simplum). Upper Norian radiolarians were obtained from two of these blocks. The assemblage is represented by Betraccium deweveri Pessagno and Blome, Ferresium triquetrum Carter, Pylostephanidium ankaraense n. sp. (Genus Pylostephanidizi was formerly unknown in the upper Triassic) and other taxa. Thus, upper Norian fauna of Turkey exhibits close similarity to the radiolarian assemblages of western North America, Eastern Russia, Japan and the Philippines. This provides further evidence for the correlation of Mediterranean and Pacific Triassic sequences. These data allow for the conclusion that the sedimentation of radiolarian cherts was common in this part of Tethys during the Late Triassic and the Jurassic.
Tectonic reorganizations and radiolarian assemblages of the northwest Pacific continental framing of Russia
Authors: Vishnevskaya Valentina
Published: April 2006

Abstract
Main stages of radiolarian taxonomic evolution in the Pacific rim of Russia are discussed. The diversity and distribution of radiolarian assemblages displayed in the studied sections and their geological and tectonic setting have implications regarding paleoecological and paleo‐oceanographic conditions as well as paleotectonic reconstructions. Radiolarian events show the close relationship with the tectonic rearrangements in the Pacific and in North America. The attempt to analyze paleo‐oceanological aspects and major factors affecting radiolarian events is presented.
New data on the geology and age of the Koreyskaya River area (south Sikhote‐Alin)
Authors: Kemkin Igor V.
Published: April 2006

Abstract
The geological structure of the Koreyskaya River area exhibits a complex combination of turbidite—olistostrome deposits making up a matrix and synsedimentary tectonic enclosures represented by allochthons of formations different in age and genesis. Three tectono‐stratigraphic units can be distinguished, that have been combined into a single section by accretion. New data on radiolarians have been used to date the tectonic enclosures and matrix. Abundant Mesozoic radiolarians (from Triassic to Late Jurassic) and also Late Permian radiolarians were found in cherty and siliceous mudstone olistoliths and cherty allochthons.
Off‐scraped Permian‐Jurassic bedded chert thrust on Jurassic‐early Cretaceous accretionary prism: Radiolarian evidence from le Island, central Ryukyu Island Arc
Authors: Shen Gaoping , Ujilé Hiroshi , Sashida Katsuo
Published: April 2006

Abstract
The pre‐Neogene basement of the central Ryukyu Island Arc shows zonal structures analogous to those of the outer belt of southwest Japan. The innermost terrane (Iheya Zone) consists of isoclinally folded beds dipping northwestward; the anticlinal cores are composed mainly of Permian chert, whereas the synclinal parts are represented by Jurassic to Cretaceous sandstone‐rich alternating siliceous shale and chert, bearing appropriate radiolarian fossils. At the east‐central area of Ie Island, the basement rocks are exposed as a 172 m high peak, Tattyu. The flank area of Tattyu is composed of latest Jurassic to Berriasian siliceous shale and chert as part of an accretionary prism, while most of Tattyu is composed of a continuous and very compact sequence of Norian through Kimmeridgian (?) bedded chert which is rather gently inclined. Beyond an unexposed part below the Norian chert, Guadalupian chert is recognized. It is inferred that this pelagic chert (Tattyu sequence) was off‐scraped and thrust on to the accretionary prism which developed on its flank area in an accretion process after the Early Cretaceous.
Geochemical characteristics of pelagic chert sequences across the Permian‐Triassic boundary in southwest Japan
Authors: Ishiga Hroaki , Ishida Kotaro , Dozen Kaori , Musashino Makoto
Published: April 2006

Abstract
Geochemical characteristics, mainly of major and trace elements and REE (rare earth elements) of bedded chert and shale/mudstone sequences, across the Permian/Triassic boundary in southwest Japan are examined. The boundary is characterized by the disappearance of bedded cherts, and the interval between the Upper Permian cherts and Lower Triassic (probably Smithian) cherts comprises siliceous shales and organic black mudstones. Bedded cherts are characterized by a gradual depletion of chemical elements from Middle to Upper Permian. However, overlying siliceous shales exhibit a clear enrichment in some elements, especially alkaline metals (such as K, Rb and Cs) and Ti, Th, Y, P2O5, and REE in comparison with elements of the PAAS (post Archean Australian shales). This indicates that average components of the upper continental crust were transported in the boundary interval, possibly caused by volcanic activity. Ce‐negative shifting in NASC (North American Shales Composite)‐normalized REE patterns is characteristic of this interval, and could be related to the deposition of siliceous rocks in Ce‐depleted seawater. This was probably caused by an invasion of water mass with a Ce‐negative anomaly into the previously existing water mass of the Paleo‐Tethys. Weak negative Eu‐anomalies in this interval are suggestive of plagioclase fractionation caused by acid volcanisms and the LREE/HREE ratios in the interval show a slightly light‐REE enrichment. Organic black mudstones are characteristically intercalated in the interval. These rocks are usually regarded as a product of oceanic deterioration, but in pelagic conditions, organic materials were formed by high primary production that resulted from the active upwelling of ocean floor water currents with rich nutrients. This may have been caused by the inferred mixing of water masses of the Paleo‐Tethys and of the Panthalassa in Early Triassic time which was regarded as an event synchronous with an increase in volcanic activity on highly matured island arcs and/or continents.
Mesozoic radiolarians and radiolarian‐bearing sequences in the circum‐Pacific regions: A report of the symposium‐‘Radiolarians and Orogenic Belts’
Authors: Matsuoka Atsushi , Aita Yoshiaki , Munasri  , Wakita Koji , Shen Gaoping , Ujilé Hiroshi , Sashida Katsuo , Vishnevskaya Valentina S. , Bragin Nkita Y. , Cordey Fabrice
Published: April 2006

Abstract
This paper contains extended abstracts of the seven papers presented at the symposium ‘Radiolarians and Orogenic Belts’ held at the seventh meeting of the International Association of Radiolarian Paleontologists (INTERRAD). Important results of the symposium include the following: (1) Upper Paleozoic and Mesozoic cherts are widely distributed within accretionary complexes in the circum‐Pacific orogenic belt. Radiolarian dating reveals that long durations of chert sedimentation in a pelagic environment are recorded on both sides of Pacific‐rim accretionary complexes (e.g. New Zealand, Japan, Russian Far East, Canadian Cordillera). (2) Triassic radiolarian faunas from New Zealand and the Omolon Massif, northeast Siberia are similar in composition and are characterized by the absence of typical Tethyan elements. This suggests that radiolarian faunal provincialism may have been established as early as the Triassic. High‐latitude radiolarian taxa exhibit a bi‐polar distribution pattern. (3) The Lower Triassic interval in chert dominant pelagic sequences is mechanically weaker than other levels and acted as a décollement in accretionary events. This lithologic. contrast in physical property is considered to reflect radiolarian evolution, such as the end‐Permian mass extinction.