New record of occurrence ofSergia lncens (Hansen) (crustacea,sergestidae) off Tung-kang,Taiwan, with special reference to phylogeny and distribution of the species     

Makoto Omori  Yoshiyuki Ukishima  Fumio Muranaka 《Journal of Oceanography》1988,44(6):261-267

The commercially important sergestid shrimp,Sergia lucens (Hansen), has long been considered an endemic species of Japan because it had been found only in Suruga Bay and neighbouring waters. Recently, however, a considerable amount of a similar shrimp was caught by trawl nets off Tung-kang, southwestern Taiwan. This shrimp is distributed at depths of 100–300 m on the continental slope, around a deep submarine canyon adjacent to the mouth of the Kao-ping River. A morphological comparison with specimens from Suruga Bay reveals that the shrimp is identical toS. lucens. However, a slight difference in the patterns of water-soluble proteins was observed in a thin layer isoelectrophoretic examination. A difference was also observed in the spawning season of the two populations, indicating sexual and geographic isolation. Considering the distribution and phylogeny of the family Sergestidae, based on a possible evolutionary development from a benthic neritic organism to a pelagic oceanic one along the generaSicyonella-Sergestes-Sergia, it is assumed thatS. lucens entered a lower epipelagic habitat in the coastal waters from the warm oceanic mesopelagic habitat of the original stock. A hypothesis is proposed that speciation ofS. lucens from the original stock occurred when it was trapped in a semi-enclosed inlet (the paleo-East China Sea Gulf) that existed at the present Okinawa Trough during the late Pliocene to early Pleistocene. The inlet was deep, but had a neritic environment due to drainage from ancient large river systems, including the paleo-Yangtze River. The species expanded its distribution to the neighbouring waters during the warm interglacial period. However, a rapid rise in sea level after 14,000 years significantly changed the environmental conditions in the distributional area and the species could not expand into a neritic environment, which was too shallow for survival. Accordingly,S. lucens populations remained only in Suruga Bay and Tung-kang waters, where the environment has remained stable for the last 17,000 years or more. The two areas have the following common characteristics:

1. A large amount of fresh water is discharged into the deep submarine canyon adjacent to the river mouth.
2. The northeastern part is surrounded by land so that a direct inflow of boreal water into the environment is blocked.
3. Warm Kuroshio extension water intrudes and mixes with water from the rivers, and for Suruga Bay there is a current system that keeps distribution of the eggs and larvae restricted to the local habitats.

Taiwan annually exported some tens of metric tons of the driedS. lucens to Japan for the last few years, but the standing stock of Tung-kang waters is probably not as large as that in Suruga Bay.  相似文献   

Formation and shortening deformation of a back-arc rift basin revealed by deep seismic profiling, central Japan   总被引：1，自引：0，他引：1  

Hiroshi Sato  Takaya Iwasaki  Shinji Kawasaki  Yasutaka Ikeda  Nobuhisa Matsuta  Tetsuya Takeda  Naoshi Hirata  Taku Kawanaka   《Tectonophysics》2004,388(1-4):47

The northern Fossa Magna (NFM) basin is a Miocene rift system produced in the final stages of the opening of the Sea of Japan. It divides the major structure of Japan into two regions, with north-trending geological structures to the NE of the basin and EW trending structures to the west of the basin. The Itoigawa-Shizuoka Tectonic Line (ISTL) bounds the western part of the northern Fossa Magna and forms an active fault system that displays one of the largest slip rates (4–9 mm/year) in the Japanese islands. Deep seismic reflection and refraction/wide-angle reflection profiling were undertaken in 2002 across the northern part of ISTL in order to delineate structures in the crust, and the deep geometry of the active fault systems. The seismic images are interpreted based on the pattern of reflectors, the surface geology and velocities derived from refraction analysis. The 68-km-long seismic section suggests that the Miocene NFM basin was formed by an east dipping normal fault with a shallow flat segment to 6 km depth and a deeper ramp penetrating to 15 km depth. This low-angle normal fault originated as a comparatively shallow brittle/ductile detachment in a high thermal regime present in the Miocene. The NFM basin was filled by a thick (>6 km) accumulation of sediments. Shortening since the late Neogene is accommodated along NS to NE–SE trending thrust faults that previously accommodated extension and produce fault-related folds on their hanging wall. Based on our balanced geologic cross-section, the total amount of Miocene extension is ca. 42 km and the total amount of late Neogene to Quaternary shortening is ca. 23 km.  相似文献   

Experimental and theoretical study of stability of dense hydrous magnesium silicates in the deep upper mantle     

Tetsuya Komabayashi  Soichi Omori  Shigenori Maruyama 《Physics of the Earth and Planetary Interiors》2005,153(4):191-209

Fluid-undersaturated experiments were conducted to determine the phase relations in the simplified peridotite system MgO-SiO₂-H₂O (MSH) at 11.0-14.5 GPa and 800-1400 °C. Stability relations of dense hydrous magnesium silicates (DHMSs) under fluid-undersaturated conditions were experimentally examined. From the fluid-absent experimental results, we retrieved thermodynamic data for clinohumite, phase A, phase E, and hydrous wadsleyite, consistent with the published data set for dry mantle minerals. With this new data set, we have calculated phase equilibria in the MSH system including dehydration reactions. The dehydration reactions calculated with lower water activities of 0.68-0.60 match the fluid-present experiments of this study above 11.0 GPa and 1000 °C, indicating that considerable amounts of silicate component were dissolved into the fluid phase. The calculated phase equilibria illustrate the stability of the post-antigorite phase A-bearing assemblages. In the cold subducting slab peridotite, phase A + enstatite assemblage survives into the transition zone, whereas phase A + forsterite + enstatite assemblage forms hydrous wadsleyite at a much shallower depth of about 360-km. The slab is subducted with no dehydration reactions occurring when entering the transition zone. The phase equilibria also show the high temperature stability of phase E. Phase E is stable up to 1200 °C at 13.5 GPa, a plausible condition in the mantle of relatively low temperature, i.e., beneath subduction zones. Phase E is a possible water reservoir in the mantle as well as wadsleyite and ringwoodite.  相似文献   

Managing and bridging communities in temporary housing: case of the Great East Japan Earthquake and Tsunami in Kesennuma City,Japan     

Yasutaka Ueda  Rajib Shaw 《Natural Hazards》2016,80(1):567-587

  相似文献   

Nd and Sr isotopic variations in acidic rocks formed under a peculiar tectonic environment in Miocene Southwest Japan     

Yasutaka Terakado  Hiroshi Shimizu  Akimasa Masuda 《Contributions to Mineralogy and Petrology》1988,99(1):1-10

Initial Nd and Sr isotopic ratios were obtained for middle Miocene igneous rocks as well as for related rocks from the Outer Zone of Southwest Japan to investigate the petrogenesis of acidic magmas and their relation to a peculiar tectonic environment bearing on the back-arc spreading of the Japan Sea. On the _Nd- _Sr diagram, data points for the acidic rocks fall in the – _Nd, + _Sr quadrant occupying different positions from those for sedimentary and old crustal rocks, and seem to define several subparallel lines which extend towards the lower-righthand sedimentary field. The S-type acidic rocks occupy an intermediate position between I-type rocks and sedimentary ones, a fact suggesting mixing of an igneous component and a sedimentary one. The linear mixing trend observed on the _Nd- _Sr diagram can be attained in the restricted case that the igneous component has similar Sr/Nd concentration ratios to that of the sedimentary one, which implies an intermediate to acidic composition for the igneous component. Inconsistency between the elemental and isotopic variations observed may be reconciled by considering that mixing, probably in the relatively deep part of the crust, might have occured prior to chemical differentiation processes. The episodic igneous activity and the high heat energy required to melt such materials involving sedimentary rocks may be explained by a model in which a hot mantle region probably corresponding to the rising part of the mantle convection supplied the heating energy to the Outer Zone of Southwest Japan when passing beneath Southwest Japan in the course of movement of the hot rising part from the Shikoku basin areas to the Japan Sea area.  相似文献   

Garnet metagabbro-ultramafic complexes in the Pekulney Range, northeast Russia     

Akira  Ishiwatari  Galina V.  Ledneva  Boris A.  Bazylev  Yasutaka  Hayasaka  Suren A.  Palandzhyan  Odin L.  Morozov  Kazuto  Koizumi  Vasily D.  Stcherbakov  Sergey D.  Sokolov 《Island Arc》2007,16(1):1-3

  相似文献   

Petrogenesis of impure dolomitic marble from the Dabie Mountains, central China   总被引：2，自引：0，他引：2  

S. Omori  J. G. Liou  R. Y. Zhang  & Y. Ogasawara 《Island Arc》1998,7(1-2):98-114

Petrogeneses of impure dolomitic marble and enclosed eclogite from the Xinyan area, Dabie ultrahigh-pressure (UHP) metamorphic terrane, central China were investigated with a special focus on fluid characteristics. Identified carbonate-bearing UHP assemblages are Dol + Coe ± Arg (or Mgs) ± Ap, Dol + Omp ± Coe ± Ap ± Arg (or Mgs), Phen + Omp + Coe + Dol ± Arg and Dol + Coe + Phen + Rt ± Omp ± Arg ± Ap. Retrograde assemblages are characterized by symplectitic replacement of Tr–Ab and Di–Ab after omphacite, and Phl–Pl symplectite after phengite. The P–T conditions of UHP metamorphism were estimated to be P > 2.7 GPa and T > 670 °C by the occurrence of coesite inclusions in garnet in enclosed eclogite and garnet–clinopyroxene geothermometer. The P–T conditions of initial amphibolitization were estimated to be 620 < T < 670 °C and 1.1 < P < 1.3 GPa by calcite–dolomite solvus thermometer and mineral parageneses. Phase relations in P–T– X CO ₂ space in the systems NaAl–CMSCH and KCMASCH were calculated in order to constrain fluid compositions. Compositions and parageneses of UHP-stage minerals suggest the presence of fluid in UHP and exhumation stages. Occurrence of retrograde low-variance assemblages indicates that fluid composition during amphibolitization was buffered. A metastable persistence of magnesite and very restricted occurrence of calcite, magnesite and dolomite suggest a low fluid content in the post-amphibolitization stage.  相似文献   

Hydraulic properties of and pressure-head dynamics in thick pyroclastic-fall deposits in Atsuma,Northern Japan: implications for the role of water in shallow landslides induced by the 2018 Hokkaido Eastern Iburi Earthquake     

Aoki  Toshiya  Katsura  Shin&#;ya  Koi  Takashi  Tanaka  Yasutaka  Yamada  Takashi 《Landslides》2022,19(8):1813-1824

Landslides - The 2018 Hokkaido Eastern Iburi Earthquake triggered numerous shallow landslides on slopes covered with thick pyroclastic-fall deposits. The landslides occurred more frequently on...  相似文献   

Effect of ocean acidification on coastal phytoplankton composition and accompanying organic nitrogen production     

Takeo Hama  Shoko Kawashima  Koichi Shimotori  Yuhi Satoh  Yuko Omori  Shigeki Wada  Taiki Adachi  Shun Hasegawa  Takashi Midorikawa  Masao Ishii  Shu Saito  Daisuke Sasano  Hiroko Endo  Tsuyoshi Nakayama  Isao Inouye 《Journal of Oceanography》2012,68(1):183-194

The effect of ocean acidification, caused by the increase in pCO₂ in seawater, on phytoplankton population and on related organic nitrogen production was experimentally examined by use of a natural coastal microbial population. pCO₂ and pH were controlled by aeration with air in which pCO₂ was at the current level (control), for which ambient air was used, and with air in which pCO₂ was ??800?? and ??1200?? ppm, in 500-L culture vessels. The experiment was continued for 15?days after addition of the inorganic nutrients such as nitrate, phosphate, and silicate. During most of the experimental period, a minor increase in phytoplankton biomass was noted, probably because of low irradiance, an increase in phytoplankton biomass was observed at the end of the experiment. Flow cytometric and microscopic observations revealed that this increase was because of Chrysochromulina sp. (Haptophyceae). The growth of Chrysochromulina sp. was most obvious in the control vessel, and tended to be obscured by increasing pCO₂ (decrease in pH), indicating the possibility that ocean acidification inhibits the growth of specific phytoplankton groups, for example Chrysochromulina sp. Production of particulate organic nitrogen (PON), determined by the ¹⁵N tracer method, also diminished under acidified conditions compared with that at the current level.  相似文献   

Anomalous change in atmospheric radon concentration sourced from broad crustal deformation: A case study of the 1995 Kobe earthquake     

Yumi Yasuoka  Yusuke Kawada  Yasutaka Omori  Hiroyuki Nagahama  Tetsuo Ishikawa  Shinji Tokonami  Masahiro Hosoda  Tetsuo Hashimoto  Masaki Shinogi 《Applied Geochemistry》2012

Before the Kobe earthquake, an anomalous increase in atmospheric Rn concentration was observed. By separating the measured concentration of atmospheric Rn into three components according to the distance from the monitoring station, the variation of Rn exhalation rate can be estimated for the respective area using the daily minimum and maximum concentrations. The mean rate of Rn exhalation gradually increased in an area of 20 km around the monitoring station, becoming five times higher than normal in the period between October 1994 and the date of the earthquake. This area had a large co-seismic displacement of up to 30 cm, which roughly corresponds to the crustal strain of 10⁻⁶-order, and it is considered the main source for the atmospheric Rn prior to the Kobe earthquake. Analyses revealed that the pre-seismic change in the atmospheric Rn concentration exhibited an anomalous pattern which would yield information on the spatial distribution of the mechanical response of the ground.  相似文献