DOCSLIB.ORG

Accreted Oceanic Materials in Japan

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Accreted Oceanic Materials in Japan ~eefo~u~~~s~c~,181 (1990) 179-205 179 Elsevier Science Publishers B.V., Amsterdam Accreted oceanic materials in Japan Y. Isozaki I, S. Maruyama 2 and F. Furuoka 3 ’ Department of Geology and Mineralogical Sciences, Faculty of Science, Yamaguchi University, Yamaguchi 753 (Japan) 2 Departmen! of Earth Sciences and Astronomy, College of Arts and Sciences, University of Tokyo at Komaba, Tokyo 153 (Japan) ’ Department of Earth Sciences, Faculty of Education, Toyama University, Toyama 930 (Japan) (Received June 61989; revision accepted September 4,1989) ABSTRACT Isozaki, Y., Maruyama, S. and Furuoka, IF., 1990. Accreted oceanic materials in Japan. In: M. Kono and B.C. Burchfiel (Editors), Tectonics of Eastern Asia and Western Pacific Continental Margin. Tectonophysics, 181: 179-205. The Phanerozoic &cum-Pacific erogenic belts contain numerous ocean-derived materials accreted through plate converg- ing processes. Japanese Islands, in particular, display various kinds of oceanic materials of different origins including fragments of seamounts, oceanic reef limestone, MORB-like rocks and oceanic mantle, and pelagic sediments. The compila- tion of these rocks in many subduction complexes of Late Permian to the present, led to following conclusions. Accretion processes work effectively only for materials primarily composing the upper portion of subducting oceanic crust, i.e. Layer 1 and Layer 2. Many fragments of seamount with alkali basalt (600), hot-spot seamount (26), oceanic reef limestone (291), MORB-like basalt (200), and numerous cherts (more than 1000) are recognized as ancient oceanic materials accreted to the Japanese Islands. However, gabbros and mantle materials of Layer 3 and lower parts of the oceanic lithosphere, scarcely occur in subduction-accretion complexes except for a few examples of back-arc basin or fore-arc origin. Accretion occurs episodically. In Southwest Japan, oceanic materials were accreted intermittently in (a) end-Permian, (b) Middle-Late Jurassic, (c) Late Cretaceous times, (d) at ea. 50 Ma, and (e) in Miocene times, while in Northeast Japan and Hokkaido this ocwrred in (b) Middle-Late Jurassic, (cf Late Cretaceous, and (f) Early Cretaceous times. In wntrast to the general belief on accretion of younger oceanic plates, the majority of Japanese subduction-accretion complexes were formed during the subduction of plates, up to 160 Ma old. The accretionary events in end-Permian and Middle-Late Jurassic times coincide with northward collision of ancient island arcs, oceanic rises or seamount chains (of hot-spot origin) with the Asian continent. Accretion relevant to subduction of older plates may be controlled by the collision-subduction process of these topographic reliefs on an oceanic plate. In addition, the chronological coincidence with the continent collision-amalgamation between the Sino-Korean and Siberian platforms and between the Sino-Korean and Yangtze blocks, also implies collision-induced voluminous supply of elastics from back-arc regions and its contribution to the formation of huge accretionary complexes. Accreted fragments of ancient seamounts are much smaller than the average size of modem seamounts. This impties that most parts of a colliding seamount are not accreted but subducted together with the underlying oceanic crust to much deeper levels. With respect to the metamorphic grades for Japanese subduction complexes, oceanic materials have less than 1 vol.% in the zeolite facies, 15-20% in the prehnite-pumpellyite metagraywacke facies, and ca. 30% in the greenschist/glaucophane schist facies and albite-epidote amphibolite facies. This relationship indicates that the major process for landward accretion of oceanic materials is not off-scraping or sedimentary mixing at the trench, but underplating (subcretion) at much deeper levels of a subduction zone. Introduction been interpreted as products of tectono-sedimen- tary processes active at ancient subduction zones. Since the pioneering studies by Dietz (1964) Studying these complexes is important for under- Hamilton (1969) and Dewey and Bird (1970) un- standing accretionary processes once active at an- der the breaking-through paradigm of plate cient convergent margins, and complements stud- tectonics (cf. Miyashiro et al., 1982), accretionary ies of modern systems (e.g. Dickinson, 1971; complexes in Cord~~er~-tee erogenic belts have Maxwell, 1974). The recognition of oceanic 0040-1951/90/$03.50 0 1990 - Elsevier Science Publishers B.V. 180 Y. 1SOZAKl ET AL materials in ancient erogenic belts, in particular, is critical as these materials provide the only affor- dable source of information on extinct oceanic plates that have interacted with the continents to form orogens. Such understanding was once culminated in the simple analogy between on-land ophiolites and modern oceanic crust-upper man- tle materials (cf. Coleman, 1971). Furthermore, under the influence of the “allochthonous terrane” concept since late 1970s (e.g. Coney et al., 1980), strong emphasis has been given on landward ter- rane-accretion by collision of topographic reliefs on the ocean floor, such as seamounts, oceanic rises, plateaus and aseismic ridges (e.g. Nur and Ben-Avraham, 1982). However, such over-sim- plified ideas are now faced with criticism (e.g. SengBr, 1988). The Japanese Islands, a segment of circum- Pacific erogenic chain, record a history of accre- Fig. 1. Distribution of modem topographic reliefs such as tion that has been active since the Late Paleozoic seamounts, plateaus, rises and ridges on the western Pacific and still continues at present. Adjacent to the seafloor near the Japanese Islands. Oceanic features: solid Japanese Islands on the western Pacific seafloor black = se~ount, blank = hot-spot seamount, striped = rise are abundant topographic reliefs including and ridge. Broken tines show predicted outer limit of the disappearing part of the ocean floor in the coming 10, 20, and seamounts of hot-spot origin such as the Hawai- 30 Ma. See Table 1 with the predicted numbers and categories ian-Emperor seamount chain, oceanic rises such of toppographic reliefs, which are now on the westernmost as the Shatsky and Hess Rise and other minor Pacific seafloor but will collide against the Japanese Islands in seamounts and/or aseismic ridges. These topo- 10, 20 and 30 Ma after the present. graphic features will eventually travel to the Japan-Izu-Ogasaw~a Trench in the near future. Given the current convergence rate of the Pacific accretion from topographic highs, episodic rhythm plate along the Japan Trench (10.4 cm y-l; Ad- in accretion, and the intimate relations between dicott and Richards, 1981), it is estimated that accretion depth and volume of oceanic rocks. In more than 300 topographic highs will approach addition, we will criticize some previous ideas and collide against the active arc-trench system of conveming subduction-accretion processes, in- Japan in the next 30 Ma (Fig. 1, Table 1). Ex- cluding the relationship between age of subduct- trapolating this back into time, this estimate im- ing plate and its ability in forming an accretionary plies that several thousands of oceanic features complex (Uyeda and Kanamori, 1979). may have been consumed since the Late Paleozoic to form the Japanese Islands. Geologic overview of pre-Miocene Japan In this paper, we compile all accreted oceanic materials exposed in late Paleozoic to Tertiary The pre-Miocene geology of Japan consists of subduction-accretion (S-A) complexes through- an amalgamation of ancient S-A complexes, re- out the Japanese Islands. Through the examina- mnant arc complexes, and ~cr~ontinent~ frag- tion of late Paleozoic to Tertiary subduction- ments. These complexes and landmass fragments accretion processes accompanied by numerous are distributed in belts that are separated from collision-subduction of oceanic reliefs, some es- one another by low-angle thrusts and/or vertical sential tectonic constraints that controlled build- strike-slip faults with unknown, but probably large, ing S-A complexes are clarified, such as selective amounts of displacement (Fig. 2A). ACCRETED OCEANIC MATERIALS IN JAPAN 181 Southwest Japan, west of the Itoigawa- lel to the general trend of Southwest Japan and Shizuoka Tectonic Line (Fig. 2B), is underlain the Nankai Trough (Fig. 2A). From the inner mainly by several late Paleozoic to Tertiary S-A continent side to the outer ocean side, these com- complexes which are oriented parallel to subparal- plexes include: the Late Permian complex of the 3 P -ii m Granittc intrusives tf Miocene and yo”“gW Sedl~tS 0 Pre-Miocene BCCretIon-COIIiwll complexes % % % ltoi@ewa-Shizuoka Tectrmlc Line x ..& .x % % ‘- Eurasia Plate Pacific Plate PhlllpplnoSea Plate (arc) 3WJkm UC comprx I , - A Fig. 2. Geologic overview of Japan. A. Tectonic framework of the Japanese Islands, showing distribution of su~uction-a~retion complexes and collided microcontinental blocks. Ak = Akiyoshi belt; Sn = Sangun belt; Mr = Maizuru belt; Ry = Ryoke belt; $6 = Sanbagawa belt; Ch = Chichibu belt; Kr = Kurosegawa belt; Sh = Shimanto belt, Ng = Nagasaki belt; Jo = Joetsu belt; As = Ashio belt; Ab = Abukuma belt; Eu = Eastern Abukuma belt; SK = Southern Kitakami belt; Kt-Iw = Kitakami-Iwaizumi belt; Kk = Kamuikotan belt; Hd-Tk = Hidaka-Tokoro belt; Nm = Nemuro belt; MTL = Median Tectonic Line; TTL = Tanakura Tectonic Line; ATL = Abashiri Tectonic Line, m = triple junction. B. Distribution of Miocene and younger cover sediments and grtitic intrusives. Note the extensive areas in Northeast Japan where subduction-accretion complexes are concealed by thick sedimentary cover. 182 Y. ISOZAKI ET AL TABLE 1 Kitakami massif towards the eastern part of Number of oceanic topographic reliefs on western Pacific Northeast Japan, a belted arrangement of units seafloor which will collide and/or subduct along the Japan similar to that in Southwest Japan occurs. How- and Mariana trenches in the coming 10, 20 and 30 Ma ever, the belts have an oblique trend to the ad- Arc Ma Rise Seamount Seamount jacent Japan Trench (Fig. 2A) suggesting tectonic AP of hot-spot erosion or t~ncation at the Japan Trench during origin the opening of the Japan Sea at about 15 Ma B.P.
Load more

Recommended publications
  • Manuscript Preparation for the English Journal of the Japan Society of Erosion Control Engineering
    APPLICATIONS BY NARA PREFECTURE FOR UTILIZ- ING LESSONS LEARNED FROM THE GREAT FLOODS ON KII PENINSULA Masaichi NAGATA1,*, Kotaro SAKANO1, Yoshihiro UEDA1and Hiroyuki YASUI1 1 Deep-Seated Landslide Control Office, Infrastructure Management Department, Nara Prefecture （30 Noboriojicho, Nara-shi, Nara 6308501, Japan） *Corresponding author. E-mail: [email protected] In 2011, Typhoon Talas brought record-breaking heavy rain and the Great Floods on Kii Peninsula, and caused ex- tensive sediment-related disasters such as deep-seated landslides, especially in the south of Nara Prefecture with 24 casualties and where 184 homes were damaged. In April 2012, in light of this disaster, Nara Prefecture formed the Deep-Seated Landslide Control Office and the “Deep-Seated Landslide Study Group (‘Study Group’)” to identify the mechanism of deep-seated landslides and to establish countermeasures, in addition to the “Investigative Panel on Mon- itoring, Warning, and Evacuation Systems for Large-Scale Sediment Disasters (‘Panel’)” to establish an evacuation system that withstands large-scale sediment disasters. This report describes the outcomes of our efforts and counter- measures against disasters. Key words: large-scale sediment disasters, monitoring, warning, evacuation 1. OUTLINE OF THE GREAT FLOODS ON KII PENINSULA Nara Pref. 1.1 Outline of Typhoon Talas and the Character- istics of the rainfall in 2011 The large-scale, powerful, and slow-moving Typhoon Talas was formed in the vicinity of the Kamikitayama Mariana Islands at 9:00 on August 25, 2011, moved Kazeya northward, cut across the landmass of Japan by passing over the Shikoku and Chugoku areas, and exited onto the Japan Sea on September 4.
    [Show full text]
  • Reservoir Sedimen Tation Part 2
    IAHR is sponsored by: 8 1 0 2 / 4 R E B M U N RESERVOIR SEDIMEN TATION PART 2 INNOVATIVE STRATEGIES FOR MANAGING RESERVOIR SEDIMENTATION IN JAPAN SEE PAGE 100 Hosted by SILTING OF RECHARGE DAMS IN OMAN SEE PAGE 115 RESERVOIR SEDIMENTATION: CHALLENGES AND MANAGEMENT STRATEGIES EDITORIAL BY KAMAL EL KADI ABDERREZZAK & ANGELOS N. FINDIKAKIS The last issue of Hydrolink focused on reservoir Each technique has its advantages and short - sedimentation with articles on the problems experi - comings in terms of cost, applicability and environ - enced in different parts of the world and the mental impacts, as described by Kondolf and mitigation measures taken in response. Because Schmitt in the previous issue of Hydrolink. A perfectly of the large interest among IAHR members and the sustainable strategy for every situation does not exist, broader water resources management community, but efforts can be optimized for the particular condi - the current issue includes more articles on the tions of each reservoir. In the current issue, examples subject where researchers and other technical of operations and strategies are given from Japan by experts from different countries share their views Sumi and Kantoush and from Taiwan by Wang and on how to deal with this problem. This is the Kuo, showing that current and new facilities need to second of three issues of Hydrolink focusing on the be designed, re-operated, and/or retrofitted to limit challenges related to reservoir sedimentation and Angelos N. Findikakis Kamal El kadi Abderrezzak the loss of reservoir capacity due to sedimentation. aiming at disseminating knowledge and lessons Hydrolink Editor Guest Editor Both articles provide lessons to help guide planning learned on successful sediment management and design of new dams, and establish design strategies.
    [Show full text]
  • Title Development of 2D-3D Numerical Coupling Model For
    Development of 2D-3D Numerical Coupling Model for Title Inundation Flow Analysis and Its Application to Urban Area( Dissertation_全文 ) Author(s) LEE, Dongkeun Citation 京都大学 Issue Date 2011-03-23 URL https://doi.org/10.14989/doctor.k16056 Right Type Thesis or Dissertation Textversion author Kyoto University Development of 2D-3D Numerical Coupling Model for Inundation Flow Analysis and Its Application to Urban Area By LEE Dongkeun 2010 Abstract Inundation disasters due to heavy rainfall are common throughout the world, which contain inundation due to insufficient drainage capacity of sewerage, overflow from a river channel and inundation due to levee failure. Inundation disasters are frequently reported to have brought about extensive property damage and loss of life. Therefore, understanding of mechanism and behavior of inundation flow and research of countermeasures are very important in order to manage inundation disasters and prevent hazards in a river basin. To reduce inundation disasters, it is common to couple structural and non-structural countermeasures and consider various scenarios involving conditions of river and floodplain and variations of flood discharge. Most of the inundation studies have been related to insufficient drainage capacity of sewerage or levee failure. But, study of inundation flow considering overflow from a river channel is also very important to establish countermeasures against inundation disasters. Hydraulic structures in a river such as pier and girder cause water level rise during flood period. In fact, flood disasters are occurring in all parts of the country. To evaluate effective non-structural preventive countermeasures against inundation disasters, it is necessary to estimate precisely the inundation flow considering overflow from a river channel and complicated flow in a river.
    [Show full text]
  • From Kyushu, Japan
    J. Jpn. Bot. 87: 385–391 (2012) A New Species of Padus (Rosaceae–Prunoideae) from Kyushu, Japan a, b Hideaki OHBA * and Masami SAITO aUniversity Museum, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033 JAPAN; bMiyazaki Prefectural Museum of Nature and History, 2-4-4, Jingu, Miyazaki, 880-0053 JAPAN *Corresponding author: [email protected] (Accepted on August 27, 2012) A new species of the genus Padus (Rosaceae–Prunoideae), P. nakatakei H. Ohba & Mas. Saito, from the Morotsuka area, Miyazaki Prefecture, Kyushu, Japan, is described. It is similar to P. obtusata (Koehne) T. T. Yu & T. C. Ku and P. ssiori (F. Schmidt) C. K. Schneid. Padus obtusata from China and Taiwan differs from P. nakatakei in having racemes with two leaves and leaves with crenulate margins. Padus ssiori differs in the leaves with a cordate base and glabrous pedicels 7–8 mm long. Key words: Flora of Japan, new species, new taxon, Padus nakatakei, taxonomy. Since the 1970s the flora of Miyazaki racemosa Gilib., P. brunnescens T. T. Yu & T. C. Prefecture, Kyushu, Japan, has been Ku, P. brachypoda (Batalin) C. K. Schneid., P. enthusiastically surveyed by members of velutina (Batalin) C. K. Schneid., P. integrifolia Miyazaki-Shokubutsu-Kenkyûkai [Society for T. T. Yu & T. C. Ku and P. cornuta (Wall. ex the Flora of Miyazaki] represented by Tadashi Royle) Carrière. Padus nakatakei is undoubtedly Minamitani. This paper describes a new species closest to both P. ssiori and P. obtusata. Padus of Padus (Rosaceae–Prunoideae) discovered ssiori occurs in Ussuri, Sakhalin, the Kuriles, by Hidenori Nakatake in the Morotsuka area in Japan (Hokkaido to northern and central the northwestern part of Miyazaki Prefecture.
    [Show full text]
  • New Names Introduced by H. A. Pilsbry in the Mollusca and Crustacea, by William J
    jbyH.l in the 1 ILML 'r-i- William J. Clench Ruth D. Turner we^ f >^ ,iV i* * ACADKMY OF NATURAL SCIENCES OF PHILADELPHLV'-' NAMES INTRODUCED BY PILSBRY m mLT) Oi -0 Dr^ 5: D m NEW NAMES INTRODUCED BY H. A. PILSBRY IN THE MOLLUSCA AND CRUSTACEA by William J. C^lencli and Ivutli _L). liirner Curator ana Research Associate in Aialacology, respectively, Aiiiseum ol Comparative Zoology at Harvara College ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA — Special Publication No. 4 1962 SPECIAL PUBLICATIONS OF THE ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA No. I.—The Mineralogy of Pennsylvania, by Samuel Gordon. No. 2.—Crystallographic Tables for the Determination of Minerals, by V. GoLDSCHMiDT and Samuel Gordon, (Out of print.) No. 3.—Gabb's California Cretaceous and Tertiary Lamellibranchs, by Ralph B. Stewart. No. 4.—New Names Introduced by H. A. Pilsbry in the Mollusca and Crustacea, by William J. Clench and Ruth D. Turner. Publications Committee: H. Radclyffe Roberts, Chairman C. Willard Hart, Jr., Editor Ruth Patrick James A. G. Rehn James Bond James Bohlke Printed in the United States of America WICKERSHAM PRINTING COMPANY We are most grateful to several people who have done much to make this present work possible: to Drs. R. T. Abbott and H. B. Baker of the Academy for checking several names and for many helpful suggestions; to Miss Constance Carter of the library staff of the Museum of Comparative Zoology for her interest and aid in locating obscure publications; to Drs. J. C. Bequaert and Merrill Champion of the Museum of Comparative Zoology for editorial aid; and to Anne Harbison of the Academy of Natural Sciences for making possible the publication of Pilsbry's names.
    [Show full text]
  • River Metabolism Along a Latitudinal Gradient Across Japan and in A
    www.nature.com/scientificreports OPEN River Metabolism along a Latitudinal Gradient across Japan and in a global scale Received: 10 September 2018 Anandeeta Gurung1, Tomoya Iwata2, Daisuke Nakano3 & Jotaro Urabe1 Accepted: 8 March 2019 Since temperature is a key factor afecting photosynthetic and respiration rates, the rates of gross Published: xx xx xxxx primary production (GPP) and ecosystem respiration (ER) are expected to be lower for rivers at higher latitudes, while the net ecosystem production (NEP) rate likely decrease in rivers at lower latitude due to higher sensitivity of ER to temperature compared with GPP. To examine these possibilities, we estimated the ecosystem metabolism of 30 rivers located from 43.03°N to 32.38°N in Japan during summer using a Bayesian model with hourly changes in dissolved oxygen concentrations. In addition, we examined latitudinal trends of GPP, ER and NEP in a global scale by compiling and analyzing river metabolic data estimated in previous studies. Our analysis showed that both GPP and ER tended to increase with latitude, although these rates were positively related to water temperature in Japanese rivers. Global dataset of GPP and ER also showed increasing trend towards higher latitude. In addition, contrary to our initial expectations, NEP decreased with latitude and most rivers were net heterotrophic at both regional (Japanese rivers) and global scales. These results imply that the latitudinal temperature efect on river metabolism is masked by other factors not examined in this study, such as land use in the watershed, which play pivotal roles in explaining the latitudinal variation of river metabolism.
    [Show full text]
  • Division of Forest and Biomaterials Science
    2.2 DIVISION OF FOREST AND BIOMATERIALS SCIENCE 1. Outline of the Division Forests play a very important role in the environment of the earth and provide wood resources that are continuously renewable in contrast with fossil resources such as petroleum and coal. Research and educational activities of this division cover not only preservation, cultivation, and continuous production of forest resources, but also utilization of forest products for our life and culture with the aim of coexistence of forest and human beings This division consists of 20 laboratories, including 2 laboratories of Field Science Education and Research Center and 5 laboratories of Research Institute for Sustainable Humanosphere (renamed Wood Research Institute reconstructed in April, 2005), and their activities are international and interdisciplinary 2. Number of students There are 83 students (41 freshmen and 52 2nd year students) in the Master’s program and 60 students in the doctor’s program of this division 3. Divisions and laboratories offering lectures Division of Forest and Biomaterials Science: Laboratories of Forest Resources and Society, Forest Environment Planning, Tropical Forest Resources and Environments, Forest Utilization, Forest Biology, Landscape Architecture, Erosion Control, Biomaterials Design, Wood Processing, Biofibrous Materials, Tree Cell Biology, Composite Materials Chemistry, and Chemistry of Biomaterials Field Science Education and Research Center: Laboratories of Forest Information, and Silviculture Research Institute for Sustainable Humanosphere: Laboratories of Active Bio-based Materials, Sustainable Materials, Structural Function, Innovative Humano-habitability, Biomass Morphologenesis and Information 4. Event in 2007 The orientation course for freshmen on April ６ at the Graduate School of Agriculture in Kitashirakawa Campus offered a curriculum-guidance.
    [Show full text]
  • 24 September 1999 Regarding the Results of the Urgent Simultaneous Nationwide Survey of Dioxins (Conducted in 1998)
    24 September 1999 Regarding the Results of the Urgent Simultaneous Nationwide Survey of Dioxins (Conducted in 1998) Attached File Survey results Information source: Environment Agency press release Regarding the Results of the Urgent Simultaneous Nationwide Dioxin Survey (Conducted in 1998) In order to determine the status of dioxin (Note 1) pollution throughout Japan, in 1998, in a cooperative effort by the Health Division of the Environment Agency, air quality control stations, and water quality control stations, the Environment Agency carried out the Urgent Simultaneous Nationwide Dioxin Survey to determine the current status of pollution of environmental media, including air, water, soil and bottom sediment, etc., by using uniform methods nationwide. The text of this attachment summarizes the results based on the evaluation of the Comprehensive Dioxin Monitoring Survey Committee (Chair: Masayuki Ikeda, Professor Emeritus, Kyoto University). 1. At approximately 400 sites throughout Japan (the number varied according to the medium studied), including the vicinity of generation sources, large cities, medium/small cities, and background, the concentration of dioxins (co-planar PCBs were measured at some sites) was measured in air (measured 4 times, in summer, autumn, winter, and spring), soot/dust (measured twice, in summer and winter), public waters (measured once, in summer, except around generation sources, where it was measured twice, in summer and winter), groundwater (measured once, in summer), bottom sediment of public waters (measured once, in summer), soil (measured once, in summer), and aquatic organisms (measured once, in autumn). The results are summarized in the table below. (The figures on the top line for each medium are the data for PCDDs and PCDFs, and the figures on the bottom line are for dioxins).
    [Show full text]
  • A Checklist of the Parasites of Ayu (Plecoglossus Altivelis Altivelis) (Salmoniformes: Plecoglossidae) in Japan (1912-2007)
    J. Grad. Sch. Biosp. Sci. Hiroshima Univ. (2007), 46：59～89 REVIEW A Checklist of the Parasites of Ayu (Plecoglossus altivelis altivelis) (Salmoniformes: Plecoglossidae) in Japan (1912-2007) 1） 1） 2） Kazuya Nagasawa , Tetsuya Umino and Mark J. Grygier 1）Graduate School of Biosphere Science, Hiroshima University 1-4-4 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8528, Japan 2）Lake Biwa Museum, 1091 Oroshimo, Kusatsu, Shiga 525-001, Japan Abstract The ayu or sweetfish Plecoglossus altivelis altivelis is distributed in many rivers and some lakes in Japan and also occurs in rivers of the Korean Peninsula and along the east coast of China and northern Vietnam. In Japan, this species is one of the most important freshwater fishes for commercial fisheries, aquaculture, and recreational fishing. In the present paper, information on the protistan and metazoan parasites of ayu in Japan is compiled based on the literature published for 96 years between 1912 and 2007, and the parasites, including 29 named species and those not identified to species level, are listed by higher taxon as follows: Ciliophora (no named species), Microspora (1), Myxozoa (1), Trematoda (13), Monogenea (3), Cestoda (1), Nematoda (1), Acantho- cephala (3), Copepoda (4), and Branchiura (2). For each taxon of parasite, the following information is given: its currently recognized scientific name, any original combination, synonym(s), or other previous identification used for the parasite occurring in ayu; habitat (freshwater, brackish, or marine); site(s) of infection within or on the host; known geographical distribution in Japanese waters; and the published source of each locality record. There has been no record of parasites from a subspecies of ayu, the ryukyu-ayu Plecoglossus altivelis ryukyuensis.
    [Show full text]
  • Method of Estimation for Flood Discharges Caused by Overflow Erosion of Landslide Dams and Its Application in As a Countermeasure
    METHOD OF ESTIMATION FOR FLOOD DISCHARGES CAUSED BY OVERFLOW EROSION OF LANDSLIDE DAMS AND ITS APPLICATION IN AS A COUNTERMEASURE Toshio Mori1*, Tetsuo Sakaguchi1, Youji Sawa1 Takahisa Mizuyama2, Yoshifumi Satofuka3 Kiichiro Ogawa4, Nobuhiro Usuki4, Kousuke Yoshino4 ABSTRACT When a landslide dam forms, it is essential at an early stage to estimate the flood discharge generated by overflow erosion, which is known to be the most common pattern for a dam to burst, as well as to promptly discuss emergency measures for reducing the flood discharge and to put a warning and evacuation system in place for residents in the downstream areas. This report describes the result of the application of the “two-layer model” suggested by Ta- kahama et al. (Takahama et al., 2000) to the overflow and burst phenomena of the Tangjia- shan landslide dams formed due to the Wenchuan Earthquake in May 2008. Moreover, it de- scribes model sensitivity analysis of the flood discharge volume reducing effect of excavating landslide dams crown and makes model study on effective means of reducing the value of flood discharges caused by overflow erosion of landslide dams. Key Words: Landslide dam, Outburst, Flood discharge, Two-layer model, Risk-analysis INTRODUCTION The impact of the bursting of landslide dams on flood discharge is a very important factor from the standpoint of preventing secondary disasters. However, not many studies or reports have been made on specific flood data, although a large number of cases of such bursts have been reported. For this reason, only modest progress has been made in research in this field up to now.
    [Show full text]