Linear structures perpendicular to an outcrop surface are easily discovered, but those parallel to the surface are not, giving rise to a biased orientation distribution of the structures. Here, we ...propose a bias correction method: Statistical inversion was conducted to unbias the distribution of the axes of mesoscale slump folds in the Cretaceous Izumi Group, Japan using the orientation distribution of outcrop surfaces. The observed axes showed a cluster in the SE quadrant. Their unbiased distribution had a girdle pattern with a maximum concentration orientation in the same quadrant, but the unbiased one had a lower peak density than the observed one, and was more girdle-like than the observed one. The maximum concentration axis of the unbiased distribution was roughly perpendicular to the paleocurrents observed in the same area. Therefore, the popular view that the axes of slump folds are perpendicular to paleoslope applies to the folds in the area in a statistical sense. The hypothesis about the vergences of slump folds and paleoslope hold only about a half of the observed slump folds.
► Linear structures perpendicular to an outcrop surface are easily discovered. ► But, those subparallel to the surface are not. ► Observation of the orientation distribution of the structures is affected by this bias. ► A statistical inverse method is proposed to unbias the orientation distribution.
Izumi Kyoka (1872-1939) wrote some 300 stories, plays, and essays. In the first book-length study in English of Kyoka, Charles Shiro Inouye argues that his writings were a refinement of a vision that ...came into focus around 1900. This narrative archetype formed the aesthetic and ethical bases of his work. Kyoka does not fit the conventional story of Japanese literary modernization. Unlike most of his contemporaries, he did not jettison the Japanese literary tradition in favor of modernist imports from the West. The highly visual mode of figuration that was Kyoka's compromise with the demands of literary modernism allows us to see the continuation of Edo culture in the Japanese modern and expand our understanding of literary reform in the early twentieth century.
The Izumi Group in southwestern Japan is considered to represent deposits in a forearc basin along an active volcanic arc during the late Late Cretaceous. The group consists mainly of felsic volcanic ...and plutonic detritus, and overlies a Lower to Upper Cretaceous plutono‐metamorphic complex (the Ryoke complex). In order to reconstruct the depositional environments and constrain the age of deposition, sedimentary facies and U–Pb dating of zircon grains in tuff were studied for a drilled core obtained from the basal part of the Izumi Group. On the basis of the lithofacies associations, the core was subdivided into six units from base to top, as follows: mudstone‐dominated unit nonconformably deposited on the Ryoke granodiorite; tuffaceous mudstone‐dominated unit; tuff unit; tuffaceous sandstone–mudstone unit; sandstone–mudstone unit; and sandstone‐dominated unit. This succession suggests that the depositional system changed from non‐volcanic muddy slope or basin floor, to volcaniclastic sandy submarine fan. Based on a review of published radiometric age data of the surrounding region of the Ryoke complex and the Sanyo Belt which was an active volcanic front during deposition of the Izumi Group, the U–Pb age (82.7 ±0.5 Ma) of zircon grains in the tuff unit corresponds to those of felsic volcanic and pyroclastic rocks in the Sanyo Belt.
後期白亜紀における活動的島弧の前縁に堆積した和泉層群は, 珪長質な火山岩や深成岩の砕屑物を主体とし, 前期〜後期白亜紀の深成変成コンプレックス(領家コンプレックス)を不整合に覆う. この和泉層群の堆積環境の復元と堆積年代の制約を目的として, 和泉層群基底部を貫くボーリングコア試料の堆積相解析と挟在する凝灰岩に含まれるジルコン粒子のU−Pb年代を測定した. コア観察による岩相組合 せに基づき, コア試料は下位より, 1) 花崗閃緑岩との不整合直上の泥岩優勢相, 2) 凝灰質泥岩相, 3) 凝灰岩相, 4) 凝灰質砂岩泥岩相, 5) 砂岩泥岩相, 6) 砂岩優勢相の6つのユニットからなる. このことは, 非火山砕屑性泥質堆積物を主体とする前弧斜面が火山砕屑性砂質堆積物を主体とする海底扇状地へと遷 移したことを示している. 周辺地域に分布する火成岩類の既存放射年代と比較すると, U−Pb年代の測定値(82.7 ±0.5 Ma)は当時の活動的な火山フロントであった山陽帯の珪長質火山岩や火山砕屑岩の放射年代と一致する.
A schematic model of suggested depositional environment at the coring site. The basement rock was nonconformably covered by mass‐transport deposits on an inner forearc slope or basin floor. Increase of sediment supply from penecontemporaneous volcanic activity in the arc led to progradation of the submarine fan in the forearc basin.
Taxonomy and stratigraphic distribution of the Upper Cretaceous marine reptiles from Japan are reviewed. Remains of the Chelonioidea (sea turtles), Mosasauridae, and Plesiosauria are known in various ...parts of Japan, including the holotypes of the dermochelyid Mesodermochelys undulatus, mosasaurine Mosasaurus hobetsuensis and M. prismaticus, tylosaurine Taniwhasaurus mikasaensis, and elasmosaurid Futabasaurus suzukii. Less diagnostic materials of other groups such as protostegiids, plioplatecarpines, polycotylids, pliosauroids, were also collected. Mesodermochelys dominates the chelonioid fauna, and in comparison with European and North American faunas, suggests a rather restricted geographical distribution of chelonioid species during the Late Cretaceous. The mosasaurid records support the world-wide trend of increasingly mosasaurine-dominated post-Santonian assemblages, and demonstrate suprageneric-level compositional changes in the northwestern Pacific through time. Elasmosaurid fossils are known from all stages of the Upper Cretaceous in Japan and indicate their continuous presence in the northwestern Pacific. Polycotylid remains are fewer in number and limited to the lower Upper Cretaceous. Pliosauroid specimens are even rarer but raise the upper limit of the stratigraphic range of the group in Northern Pacific to the Turonian.
Many structures that were once interpreted as fossils of plants, sea-grasses, or seaweeds are now treated as ichnofossils produced by ancient marine benthic animals. However, the origin of ...Archaeozostera has still debated owing to a lack of clear and persuasive evidence. At last, we found special specimens that Archaeozostera is not a fossil of the Zosteracean sea-grass but a trace fossil produced by infaunal benthic animal from the late Cretaceous submarine fan deposits in Japan. Detailed field observations of occurrence, morphological analysis, and X-ray diffraction analysis revealed that previous discussions of Archaeozostera were based not only on incomplete specimens but also on biased outcrop observations. On the basis of morphological analysis of new specimens, we demonstrate the first complete overall morphology of Archaeozostera and clear evidence that Archaeozostera is a trace fossil produced by a sedentary endobenthic detritus feeder, which systematically excreted fecal matter deep in sediments. A representative specimen of Archaeozostera, which has recently found from Eocene deep-sea sediments in Spanish Pyrenees, strongly suggests that it is no longer an endemic trace fossil of the Upper Cretaceous of Japan.
•Clear and persuasive evidence that Archaeozostera is a trace fossil was found at last.•Ontogeny of the producing animal is successively recorded in Archaeozostera.•Archaeozostera was produced by an endobenthic detritus feeder adopting sedentary lifestyle in a same burrow.•Complete overall morphology of Archaeozostera was first demonstrated in this paper.•A rhizome of Archaeozostera is a horizontal tunnel of trace fossil Ophiomorpha rudis.
BackgroundThe Hooded Crane (Grus monacha) is listed as a vulnerable species by IUCN. Knowledge about the migration of the Hooded Crane is still limited. Here we reported the spatio-temporal migration ...patterns of Hooded Cranes wintering in Izumi, Japan, as well as important stopover areas for their conservation.MethodsFour adult and five subadult cranes, all wintering in Izumi, Japan, were fitted with satellite transmitters (GPS–GSM system) at their stopover sites in northeastern China in 2014 and 2015. We analyzed the time and duration of adults and subadults in spring and autumn migration, as well as the time and duration they stayed in breeding and wintering ground. In addition, we analyzed the land use of the cranes in stopover areas.ResultsAdult cranes took much longer time to migrate both north in spring (mean = 44.3 days) and south in fall (mean = 54.0 days) compared with subadult cranes (15.3 and 5.2 days, respectively). However, the subadults had longer wintering (mean = 149.8 days) and nomadic (breeding season for adults) seasons (mean = 196.8 days) compared with adults (133.8 and 122.3 days, respectively). Three important stopover areas have been identified: the region around Muraviovka Park in Russia, the Songnen Plain in China, and the west coast of South Korea, where cranes spent most of their migration time (62.2 and 85.7% in spring and autumn, respectively). During migration, nomadic period and winter, Hooded Cranes usually stay in croplands for resting and feeding. In non-wintering season, less than 6% of stopover sites were located within protected areas.ConclusionOverall, our results contribute to understanding the annual spatio-temporal migration patterns of Hooded Cranes in the eastern flyway, and planning conservation measures for this species.
The legend that Daikichi Taki affected construction of 1890 of the Ryouunkaku as a taskmaster has been written down in the biography of Rentaro Taki repeatedly until late years, it inspects this ...point, and it is following many points to become clear. The opinion that Daikchii Taki affected construction of 1890 of the Ryouunkaku is listed in a biography of Rentaro Taki widely, but the clear grounds are not shown. There is the opinion that Daikichi Taki performed the taskmaster on the occasion of a building in 1890 of the Ryouunkaku, but it has been skeptical about before from the relations with the career of the Daikichi Taki by the building-related study. It was the investigation and repair after the Tokyo-Meiji Earthquake of 1886 that Daikichi Taki affected the Ryouunkaku. What Daikichi Taki showed as repair plan of the Ryouunkaku after the Meiji-Tokyo earthquake posted hoop iron in the window neighborhood and the trumeau and fastened it with an iron bolt and posted with metal fittings at the opposite angle of the octagon plane more. Kojiro Izumi of the original contractor of the Ryouunkaku and Daikichi Taki had the interchange since at least 1886. I can think that Izumi asked Daikichi Taki for the investigation of the Ryouunkaku which suffered from the Meiji-Tokyo earthquake of 1894 from these relations.
Two exceptionally large cephalopod jaws collected from the Upper Cretaceous marine deposits of the Hidaka area, Hokkaido (Yezo Group), and Awaji Island, Southwest Japan (Izumi Group), respectively, ...are described. Further, their taxonomic relationships and functional morphologic aspect for feeding are discussed. Based on a comparison to counterparts of modern and extinct cephalopods, they were identified as the lower jaws of ammonoids. Owing to the development of a thick calcareous tip in the large outer chitinous lamella, the lower jaw from the Yezo Group is classified as a rhychaptychus-type known from the Cretaceous Lytoceratina and Phylloceratina. The lower jaw from the Izumi Group lacks a sharply pointed calcareous tip and is characterized by a posteriorly elongated outer chitinous lamella, whose outer surface is sculptured by a median furrow in the anterior portion. These features categorize it as an intermediate-type lower jaw shared by the Cretaceous Desmoceratoidea. As determined from the co-occurring ammonoids and the relationship between the dimensions of in situ lower jaws and conchs for ammonoids previously described, the two lower jaws from the Yezo and Izumi groups were, respectively, thought to belong to large gaudryceratid and pachydiscid specimens, both of which have shell diameters greater than 40 cm. The overall shape and structure of the two lower jaws suggest a scavenging-predatory feeding habit for the gaudryceratid and a passive microphagous habit for the pachydiscid.
We have investigated K-feldspar recrystallisation in granitoid mylonites within a ductile shear zone from the Ryoke metamorphic belt, SW Japan. Fine-grained K-feldspar (20μm on average) occurs in the ...matrix and in pull-apart areas within fractured K-feldspar porphyroclasts. These fine grains are elongated and oriented parallel to the main foliation in the matrix, and their grain surfaces, observed with the scanning electron microscope, are not smooth, but rough due to the development of very fine (<1μm) round grains of K-feldspar on the surface of each grain. In pull-apart areas, the crystallographic orientation of fine-grained K-feldspar, as measured by electron backscatter diffraction (EBSD), is strongly controlled by that of the host porphyroclast, and shows rotations with shear components parallel to fractures. In the matrix, the crystallographic orientation of fine-grained K-feldspar is not consistent with intracrystalline plasticity, but rather with a growth rate that is slightly controlled by nearby porphyroclasts. All this, together with the growth features on grains, suggests that solution–precipitation of K-feldspar from K-rich aqueous fluid occurred during progressive deformation. Infrared (IR) mapping was performed to evaluate the distribution of water in pull-apart areas and the matrix. Water is heterogeneously distributed within K-feldspar porphyroclasts, which contain 150–2200ppm H2O. In contrast, the water content is low (150–300ppm H2O) and homogeneously distributed in fine-grained K-feldspar in the matrix and pull-apart areas, even though included in these analyses are grain boundaries that can generally contain abundant aqueous fluid. The results of EBSD analysis and IR mapping indicate that water is released during solution–precipitation of K-feldspar under mid-crustal conditions. The solution–precipitation process under a water-rich environment in the middle crust results in the formation of fine grains, possibly deforming dominantly by grain-size-sensitive creep, and with the release of aqueous fluid involved in the process.
► We focus on fine-grained K-feldspar in granitoid mylonites. ► Growth features of grains indicate a solution–precipitation process. ► Host-controlled crystallographic orientation may be related to grain growth. ► Water contents of fine-grained K-feldspar are low and homogeneous (250ppm H2O). ► Aqueous fluid may be released during the solution–precipitation process.
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