Nature of accretion related to Paleo-Tethys subduction recorded in northern Thailand: Constraints from mélange kinematics and illite crystallinity     

Hidetoshi Hara  Koji Wakita  Katsumi Ueno  Yoshihito Kamata  Ken-ichiro Hisada  Punya Charusiri  Thasinee Charoentitirat  Pol Chaodumrong 《Gondwana Research》2009,16(2):310

We reconstructed the accretion process related to Paleo-Tethys subduction recorded in northern Thailand, based on mélange and thrust structures, and metamorphic temperatures derived from illite crystallinity data. Mélange formation was characterized by hydrofracturing and cataclastic deformation, with mud injection under semi-lithified conditions followed by shear deformation and pressure solution. Illite crystallinity data suggest metamorphic temperatures below 250 °C during mélange formation. The combined structural and metamorphic data indicate that during mélange formation, the accretionary complex related to Paleo-Tethys subduction developed at shallow levels within an accretionary prism. Asymmetric shear fabrics in mélange indicate top-to-south shear. After correction for rotation associated with collision between the Indian and Eurasian continents, the trend of the Paleo-Tethys subduction zone is estimated to have been N80 °E. We conclude that the Paleo-Tethys was subducted northward beneath the Indochina Block from the Permian to Triassic.  相似文献   

Paleosol profiles in the Shiohama Formation of the Lower Cretaceous Kanmon Group,Southwest Japan and implications for sediment supply frequency     

Yu Horiuchi  Ken-ichiro Hisada  Yong Il Lee 《Cretaceous Research》2009,30(5):1313-1324

This paper describes the pedogenic features of paleosols in the upper Lower Cretaceous Shiohama Formation, the lowest unit of the Shimonoseki Subgroup, in Yoshimi, Yamaguchi Prefecture, southwest Japan. The paleosol profiles in the Shiohama Formation are compound and complex, characterized by the presence of abundant calcrete horizons. An analysis of these profiles reveals that the floodplain upon which the Shiohama Formation was deposited was part of an unstable aggradation system characterized by the intermittent influx of sediments and occasional erosion. Furthermore, the mean annual range of precipitation was less than about 30 mm, suggesting only minor seasonal change between wet and dry conditions during deposition of the Shiohama Formation. The microstructures of the observed calcretes include dense microfabric, floating detrital grains, micronodules, circum-granular cracks, and complex cracks. These features formed by chemical precipitation under dry conditions, with little bioactivity. The calcrete horizons are classified into seven types (I–VII) based on their modes of occurrence. Two processes of carbonate accumulation can be identified based on the size and abundance of nodules: VI–V–III–(II)–I and VI–(V)–IV–II–I. These processes represent the development of calcrete horizons from the early to late stages of calcretization. Type I represents the most highly developed stage of calcretization. Calcretes within the Lower Member sequence of the Shiohama Formation show repetitions of type I and types II and III. Thus, it is interpreted that the frequency of sediment supply to the floodplain changed repeatedly over time.  相似文献   

Provenance diversification within an arc‐trench system induced by batholith development: the Cretaceous Japan case     

Kazumasa Aoki  Yukio Isozaki  Daisuke Kofukuda  Tomohiko Sato  Atsushi Yamamoto  Kenshi Maki  Shuhei Sakata  Takafumi Hirata 《地学学报》2014,26(2):139-149

By comparing detrital zircon U–Pb age spectra of coeval fore‐arc and back‐/intra‐arc basin sandstones, we identified the overall distributary pattern of terrigenous clastic material within the Cretaceous arc system of SW Japan. Abundant Proterozoic (c. 1500–2500 Ma) detrital grains from the interior of East Asia are present in the Cretaceous intra‐arc basin. However, after a barrier mountain range formed during batholith emplacement, Proterozoic clastics were rarely transported into the fore‐arc domain. Episodic batholith formation in Pacific‐type orogens likely played a major role in controlling terrigenous supply routes between coeval back‐arc and fore‐arc domains. The Cretaceous orogen in Japan thus provides a good template for analysing the tectono‐sedimentary development of other arc‐related basins.  相似文献   

Monitoring volcanoes using seismic noise correlations     

Florent Brenguier  Daniel Clarke  Yosuke Aoki  Nikolai M. Shapiro  Michel Campillo  Valérie Ferrazzini 《Comptes Rendus Geoscience》2011,343(8-9):633-638

In this article, we summarize some recent results of measurements of temporal changes of active volcanoes using seismic noise cross-correlations. We first present a novel approach to estimate volcano interior temporal seismic velocity changes. The proposed method allows to measure very small velocity changes (≈ 0.1%) with a time resolution as small as one day. The application of that method to Piton de la Fournaise Volcano (La Réunion Island) shows velocity decreases preceding eruptions. Moreover, velocity changes from noise cross-correlations over 10 years allow to detect transient velocity changes that could be due to long-lasting intrusions of magma without eruptive activity or to pressure buildup associated to the replenishing of the magma reservoir. We also present preliminary results of noise cross-correlation waveform perturbation associated with the occurrence of dike injection and volcanic eruption. We show that such an analysis leads us to locate the areas of dike injection and eruptive fissures at Piton de la Fournaise Volcano. These recent results suggest that monitoring volcanoes using seismic noise correlations should improve our ability to forecast eruptions, their intensity and thus potential environmental impact.  相似文献   

Gaetice depressus (Crustacea,Varunidae): Species profile and its role in organic carbon and nitrogen flow     

Wahyudi  A’an. J.  Wada  Shigeki  Aoki  Masakazu  Hama  Takeo 《Ocean Science Journal》2015,50(2):389-401

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A GIS-based study toward forecast of suburban forest change     

Yasuhiro Suzuki  Keiji Kimura  Tatsuto Aoki 《GeoJournal》2000,52(3):203-212

At a time when the concept of ‘human and environmental symbiosis’ has taken on much significance, protection of suburban forests (i.e. forests adjacent to or near developed areas) is a topic that has drawn much attention. Suburban forests have, since ancient times, been places where people have gathered firewood and cultured trees. As a result, the vegetation of suburban forests is only partially natural and continues to change as the forms of human activity in and around them changes. Accurate forecasts of how suburban forests will change are, therefore, an important element in the debate over how to protect them. In this study, a suburban forest was analyzed with laser radar sensing, multi-spectrum scanning, digital photogrammetry analysis, aerial photograph interpretation, and a field survey. Data gathered using these techniques were compiled on a GIS to forecast future changes in the forest. Aerial photographs taken over the past 50 years were analyzed to illuminate changes in the forest over that period. Specifically, comparisons of precise Digital Elevation Models (DEMs) measured by using digital photogrammetry workstations made it possible to estimate growth in forest height. The possible future conversion of such results to estimates of amounts of carbon dioxide consolidated by forests should be very significant for discussions of global environmental problems. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Formation of density inhomogeneity in laser produced plasmas for?a?test bed of magnetic field amplification in supernova remnants     

Y. Kuramitsu  Y. Sakawa  T. Morita  S. Dono  H. Aoki  H. Tanji  C. D. Gregory  J. N. Waugh  B. Loupias  M. Koenig  N. Woolsey  T. Ide  T. Sano  H. Takabe 《Astrophysics and Space Science》2011,336(1):269-272

Density inhomogeneities for a test bed of magnetic field amplification in supernova remnants (SNRs) were created in laser produced plasmas. The density inhomogeneity is considered to be essential to the large magnetic field amplification to account for the very fast cosmic ray acceleration. In order to model the density variations about an order of magnitude in an interstellar medium, we performed three types of experiments using a high-power laser system: (1) irradiating a plastic (CH) plane with a single focal spot beams, (2) the same target with spatial separation of laser focal spots, and (3) irradiating a striped target of thin and thick CH plane. By irradiating a CH plane target with a single focal spot laser beams, a plasma plume was produced with the large density range. On the other hand, when the several laser beams with displacements of the focal spots, bumpy structures of electron density were produced. Making thin stripes on a CH plane target, density and velocity inhomogeneities were produced by irradiating the striped target with the laser beams. In the all methods the density variations were very large, which can be used for a model experiment of the magnetic field amplification.  相似文献   

Bidirectional loading hybrid tests of square cross‐sections of steel bridge piers     

Ji Dang  Tetsuhiko Aoki 《地震工程与结构动力学》2013,42(8):1111-1130

Steel rectangular section columns with stiffened plates are commonly used for elevated highway bridges in the urban areas of Japan. The seismic design of bridge piers is usually performed by dynamic analysis in the horizontal direction using various independent directional seismic acceleration data. However, this simple treatment does not reflect the effect of bilateral loading as a structural response to inelastic interaction. In this study, unidirectional and bidirectional loading hybrid tests were conducted to examine the seismic response and performance of square cross‐sections of steel bridge piers subjected to bidirectional seismic accelerations. Comparison of the results of unidirectional and bidirectional loading tests revealed that the maximum load is the same as the average of unidirectional loading in the NS and EW directions; however, the maximum response displacement and residual displacement increase in proportion with hard to soft ground types. Moreover, a modified seismic design is proposed considering these bidirectional loading effects. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Unsteady flows in Io’s atmosphere caused by condensation and sublimation during and after eclipse: Numerical study based on a model Boltzmann equation     

Shingo Kosuge  Kazuo Aoki  Takeshi Inoue  David B. Goldstein  Philip L. Varghese 《Icarus》2012,221(2):658-669

The behavior of Io’s atmosphere during and after eclipse is investigated on the basis of kinetic theory. The atmosphere is mainly composed of sulfur dioxide (SO₂) gas, which condenses to or sublimates from the frost of SO₂ on the surface depending on the variation of surface temperature (～90–114 K). The atmosphere may also contain a noncondensable gas, such as sulfur monoxide (SO) or oxygen (O₂), as a minor component. In the present study, an accurate numerical analysis for a model Boltzmann equation by a finite-difference method is performed for a one-dimensional atmosphere, and the detailed structure of unsteady gas flows caused by the phase transition of SO₂ is clarified. For instance, the following scenario is obtained. The condensation of SO₂ on the surface, starting when eclipse begins, gives rise to a downward flow of the atmosphere. The falling atmosphere then bounces upward when colliding with the lower atmosphere but soon falls again. This process of falling and bounce back of the atmosphere repeats during the eclipse, resulting in a temporal oscillation of the macroscopic quantities, such as the velocity and temperature, at a fixed altitude. For a pure SO₂ atmosphere, the amplitude of the oscillation is large because of a fast downward flow, but the oscillation decays rapidly. In contrast, for a mixture, the downward flow is slow because the noncondensable gas adjacent to the surface hinders the condensation of SO₂. The oscillation in this case is weak but lasts much longer than in the case of pure SO₂. The present paper is complementary to the work by Moore et al. (Moore, C.H., Goldstein, D.B., Varghese, P.L., Trafton, L.M., Stewart, B. [2009]. Icarus 201, 585–597) using the direct simulation Monte Carlo (DSMC) method.  相似文献   

泰国北部Inthanon带混杂岩碎屑锆石U-Pb年龄及碎屑岩岩石学和地球化学研究：对古特提斯消减和汇聚的启示     

Hidetoshi HARA  Miyuki KUNII  Ken-ichiro HISADA  Katsumi UENO  Yoshihito KAMATA  Punya CHARUSIRI  Thasinee CHAROENTITIRAT 《地球学报》2012,33(S1):15-15

The accretionary complex related to the Pa-leo-Tethys subduction was developed along western margin of the Indochina Block in northern Thailand. The provenance, source rock compositions, and sedi-ment supply system of the accretionary complex were reconstructed based on the petrography and geochem-istry of clastic rocks, U-Pb dating of detrital zircons.  相似文献