Dinoflagellate Cysts in Surface Sediments from Southern Coast of Korea     

Hyeon Ho Shin  Yang Ho Yoon  Young-Ok Kim  Kazumi Matsuoka 《Estuaries and Coasts》2011,34(4):712-725

To investigate the distributions of dinoflagellate cysts in relation to environmental conditions from southern coast of Korea, surface sediment samples collected from 11 stations in Gamak Bay, Yeoja Bay and the offshore area of Yeoja Bay were analyzed. Dinoflagellate cyst assemblages observed in the study area included many species commonly reported from other temperate regions. Among them, Polykrikos cysts were dominant, together with Brigantedinium spp. and Spiniferites spp. Based on cluster analysis, dinoflagellate cyst assemblages were divided into two main groups; group I, located in Yeoja Bay and group II, located in Gamak Bay and the offshore area of Yeoja Bay. Principal component analysis identified differences in salinity levels as the main environmental factors affecting the distributional characteristics of dinoflagellate cyst assemblages in the study area. Gamak Bay is a typical eutrophied area as result of extensive human activities around the bay, and heterotrophic cysts, including Polykrikos cysts, are remarkably abundant and likely to be a useful indicator for eutrophication in Gamak Bay.  相似文献   

Kinematics of an alpine retrogressive rockslide in the Japanese Alps     

Ryoko Nishii  Norikazu Matsuoka 《地球表面变化过程与地形》2012,37(15):1641-1650

The Aresawa rockslide in the Japanese Alps experienced a partial collapse (5–10 × 10⁵ m³) in 2004, followed by an accelerated downward movement of the head area rather than stabilization. This paper discusses the kinematics of a retrogressive rockslide area and factors promoting slope instability subsequent to the 2004 collapse, on the basis of geodetic surveys and meteorological observations from 2006 to 2010. The unstable area covers at least 2·3 × 10⁴ m² and consists of five active blocks. The main blocks are separated from the stable rock slope by pre‐existing ‘sackung features’ that follow the strike of the bedding plane. Shear zones below these sackung features have developed into slip planes potentially causing the next collapse. In particular, the propagation of a slip plane causing movement at 70 cm yr^?1 in the head area is promoted by bidirectional movement. It consists of slow ‘dip‐slip’ movement in snow‐accumulating periods and rapid ‘side‐slip’ movement in snow‐melting and snow‐free periods, both of which occur on the same slip plane. This bidirectional movement appears to result from the combination of a loss of lateral support by the 2004 event and the immature state of the slip plane. The primary trigger of the acceleration in the unstable area is the stress release by the 2004 collapse. In addition, the presence of a potential slip plane below the sackung features also promotes slope instability, suggesting that sackung features behind a rockslide area may predefine the new head scarp of a forthcoming collapse. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Microbial community respiration and structure of dead zone sediments of Omura Bay, Japan   总被引：1，自引：0，他引：1  

Minoru Wada  Shotaro Suzuki  Tadashi Nara  Yu Umezawa  Motohiro Shimanaga  Kazumi Matsuoka  Hideaki Nakata 《Journal of Oceanography》2012,68(6):857-867

Monitoring sediment microbial community metabolism and structure is instrumental to understanding biogeochemical processes in and ecological impacts on bottom environments. The aim of this study was to determine potential community respiration and to reveal community dynamics of the microorganisms in the dead zone sediments of Omura Bay, Japan. The bay is highly enclosed and develops severe hypoxia in the central regions every summer. We collected sediment core samples from the center of the bay during hypoxia, estimated sediment oxygen consumption by using an adapted in vivo electron transport system activity (in vivo ETSA) assay, enumerated abundance of bacteria, and analyzed bacterial community structure by automated ribosomal intergenic spacer analysis. Higher ETSA and bacterial diversity were found in upper sediments (within 3?cm depth) from the center than the fringe of the bay. Sediment bacterial community structure of the bay center was distinct from that of the fringe. From these results, upper sediment in the dead zone of Omura Bay was characterized by (1) greater community respiration and (2) greater diversity of bacterial components compared with the non-hypoxic sediment of the bay fringe. These characteristics have important implications for understanding the interaction between microbial communities and the development of hypoxia in Omura Bay.  相似文献   

Laboratory frost sorting by needle ice: a pilot experiment on the effects of stone size and extent of surface stone cover          下载免费PDF全文

Chizuru Yamagishi  Norikazu Matsuoka 《地球表面变化过程与地形》2015,40(4):502-511

Sorted patterned ground is ubiquitous where gravelly fine soil experiences freeze–thaw cycles, but experimental studies have rarely been successful in reproducing such patterns. This article reports an attempt to reproduce miniature sorted patterns by repeating needle‐ice formation, which simulates frost sorting in regions dominated by diurnal freeze–thaw cycles. Six full‐scale laboratory models were tested. They consisted of near‐saturated volcanic fine soil topped by small stones of uniform size; the models explored a range of stone size (~6, ~12, ~17 and ~22 mm) and surface abundance (20, 40 and 60% cover). The stones were placed in a grid on the surface. These models were subjected to 20–30 temperature excursions between 10 °C and ?5 °C in 12 hours. The evolution of surface patterns were visually traced by photogrammetry. A data logging system continuously monitored vertical soil displacements, soil temperatures and moistures at different depths. All experimental runs displayed needle‐ice formation (2–3 cm in height) and resulting displacement of stones. The soil domains tended to heave faster and higher than the stones, leading to outward movement of the former and concentration of the stones. In plan view, smaller stones showed relatively fast and long‐lasting movements, while larger stones stabilized after the first five cycles. The 20% stone cover produced stone islands, whereas the 40% cover resulted in sorted labyrinths (a circle‐island complex) that may represent incipient sorted circles. The average diameter or spacing of these forms are 12–13 cm, being comparable to those in the field. The experiments imply that needle‐ice activity promotes rapid formation of sorted patterns, although the formation of well‐defined sorted circles may require hundreds of diurnal frost heave cycles. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Ultraviolet Fe ii emission in z∼ 2 quasars     

H. Sameshima  J. Maza  Y. Matsuoka  S. Oyabu  K. Kawara  Y. Yoshii  N. Asami  N. Ienaka  Y. Tsuzuki 《Monthly notices of the Royal Astronomical Society》2009,395(2):1087-1091

We present spectra of six luminous quasars at   z ∼ 2  , covering rest wavelengths 1600−3200 Å. The fluxes of the UV Fe  ii emission lines and Mg  ii λ2798 doublet, the line widths of Mg  ii and the 3000 Å luminosity were obtained from the spectra. These quantities were compared with those of low-redshift quasars at   z = 0.06–0.55  studied by Tsuzuki et al. In a plot of the Fe  ii (UV)/Mg  ii flux ratio as a function of the central black hole mass, Fe  ii (UV)/Mg  ii in our   z ∼ 2  quasars is systematically greater than in the low-redshift quasars. We confirmed that luminosity is not responsible for this excess. It is unclear whether this excess is caused by rich Fe abundance at   z ∼ 2  over low-redshift or by non-abundance effects such as high gas density, strong radiation field and high microturbulent velocity.  相似文献   

Improving the quality of the “ventilation chamber” technique for surveying the radon exhalation rate continuously     

Yanliang Tan  Hiromi Kudo-Yokota  Chanis Pornnumpa  Paitoon Wanabongse 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(8):2101-2106

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Early diagenesis of fatty acids in lacustrine sediments—III. Changes in fatty acid composition in the sediments from a brackish water lake     

Hiromi Matsuda 《Geochimica et cosmochimica acta》1978,42(7):1027-1034

A 3-m sediment core taken from Lake Suigetsu, in which a shift from fresh to brackish water occurred about three hundred years ago, has been examined for variation with depth of organic carbon and fatty acids. From the difference in total amounts of sulphur between sediments under fresh and brackish water environments, the surface sediments above approximately 35 cm depth were deduced to be accumulated under a brackish water environment. The total contents of organic carbon and fatty acids, and percentage composition of fatty acids gave discontinuous profiles above and below the 35–40 cm sediment layer. At a depth of 12.5 cm, the distribution in chain length of the fatty acids changed from a unimodal (the predominance of C₁₂-C₁₈ over C₂₀-C₃₄) to a bimodal pattern, which was mirrored by the composition diversity index (CDI).Although the fatty acids in the surface sediments (0–40 cm) from Lake Suigetsu seemed to suffer milder degradation through microbial activity than those in a core (0–150 cm) from Lake Suwa, a freshwater eutrophic lake, both lacustrine sediments showed similar trends in the alteration of fatty acid composition with depth.  相似文献   

Origin of organic matter in the early solar system—VII. The organic polymer in carbonaceous chondrites     

Ryoichi Hayatsu  Sumiko Matsuoka  Robert G. Scott  Martin H. Studier  Edward Anders 《Geochimica et cosmochimica acta》1977,41(9):1325-1339

The insoluble polymer from the Murchison C2 chondrite was studied by a variety of degradation techniques: pyrolysis, depolymerization by Na₄P₂O₇ or CF₃COOH, and oxidation by HNO₃, Na₂Cr₂O₇, or O₂/UV light. Products were identified by IR spectroscopy, gas chromatography, and mass spectrometry (time-of-flight and high-resolution). In some cases, parallel measurements were made on a synthetic polymer produced by the Fischer-Tropsch reaction, a meteoritic polymer from the Allende C3V chondrite, and samples of coal or related materials.Our studies confirm the prevailing view that the meteoritic polymer has a bridged aromatic structure with functional groups such as COOH, OH, and CO, but provides much new detail. Oxidation with HNO₃ shows that the meteoritic and synthetic polymers have a similar degree of condensation, greater than that of high-volatile bituminous coal. Gentler oxidation with Cr₂O^2?₇ or O₂/UV led to the identification of 15 aromatic ring systems as the corresponding carboxylic acids: benzene, biphenyl, naphthalene and phenanthrene and their methyl derivatives, fluoranthene (or pyrene), chrysene, fluorenone, benzophenone, anthraquinone; and the heterocyclics dibenzofuran, benzothiophene, dibenzothiophene, pyridine, quinoline (or isoquinoline), and carbazole. Of 11 aliphatic acids identified, three dicarboxylic acids presumably came from hydroaromatic portions of the polymer, whereas eight monocarboxylic acids probably are derived from bridging groups or ring substituents.Depolymerization with CF₃COOH yielded some of the same ring systems, as well as alkanes (C₁–C₈) and alkenes (C₂–C₈), alkyl (C₁–C₅) benzenes and naphthalenes, and methyl- or dimethyl-indene, -indane, -phenol, -pyrrole, and -pyridine. All these compounds were detected below 200°C, and hence probably were indigenous constituents rather than pyrolysis products.Though the match between the synthetic and meteoritic polymer is only fair, several properties of the latter suggest that it, too, was produced by surface catalysis: the predominance of n-alkyl fragments, its occurrence as a surface coating on specific kinds of mineral grains, and the $\text{C}{}^{13}\text{C}{}^{12}$ fractionation between polymer and coexisting carbonates.  相似文献   

Accretion and postaccretion tectonics of the Calamian Islands, North Palawan block, Philippines     

Lawrence R.  Zamoras  Atsushi  Matsuoka 《Island Arc》2004,13(4):506-519

Abstract   Upper Paleozoic to Mesozoic sedimentary sequences of chert (Liminangcong Formation), clastics (Guinlo Formation) and a number of limestone units (Coron Formation, Minilog Formation and Malajon Limestone) constitute the accretionary complex of the North Palawan block, Philippines. Based on chert-to-clastic transitions from different stratigraphic sequences around the Calamian Islands, three accretionary belts are delineated: the Northern Busuanga Belt (NBB), the Middle Busuanga Belt (MBB) and the Southern Busuanga Belt (SBB). The accretion events of these belts along the East Asian accretionary complex, indicated by their sedimentary transitions, began with the Middle Jurassic NBB accretion, followed by the Late Jurassic MBB accretion and the Early Cretaceous SBB accretion. Several limestone blocks that formed over the seamounts became juxtaposed with chert–clastic sequences during accretion. During the Late Cretaceous, accretion-subduction along the East Asian margin subsided bringing tectonic stability to the region. The seafloor spreading during the mid-Oligocene disconnected the entire North Palawan block from the Asian mainland and then migrated southward. The collision between the North Palawan block and the Philippine Island Arc system in the middle Miocene generated a megafold structure in the Calamian Islands as a result of the clockwise turn of the accretionary belts in the eastern Calamian from originally northeast–southwest to northwest–southeast.  相似文献   

Comment on 'Evaluating the statistical validity beyond chance of 'VAN' earthquake precursors' by Francesco Mulargia and Paolo Gasperini     

Hiromi Takayama 《Geophysical Journal International》1993,115(3):1197-1198

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