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1.
Kenneth Neil Mertens Manuel Bringué Nicolas Van Nieuwenhove Yoshihito Takano Vera Pospelova Andre Rochon Anne De Vernal Taoufik Radi Barrie Dale R. Timothy Patterson Kaarina Weckström Elinor Andrén Stephen Louwye Kazumi Matsuoka 《第四纪科学杂志》2012,27(7):734-744
Process length variation of cysts of the dinoflagellate Protoceratium reticulatum (Claparède et Lachmann) Bütschli in surface sediments from the North Pacific was investigated. The average process length showed a significant inverse relation to annual seawater density: σt annual = ?0.8674 × average process length + 1029.3 (R2 = 0.84), with a standard error of 0.78 kg m?3. A sediment trap study from Effingham Inlet in British Columbia revealed the same relationship between average process length and local seawater density variations. In the Baltic–Skagerrak region, the average process length variation was related significantly to annual seawater density: σt annual = 3.5457 × average process length ? 993.28 (R2 = 0.86), with a standard error of 3.09 kg m?3. These calibrations cannot be reconciled, which accentuates the regional character of the calibrations. This can be related to variations in molecular data (small subunit, long subunit and internal transcribed spacer sequences), which show the presence of several genotypes and the occurrence of pseudo‐cryptic speciation within this species. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
2.
Volcanism related to subduction of the Philippine Sea (PHS) plate began in Central Kyushu at 5 Ma, after a pause of igneous activity lasting about 10 m.y. It formed a large volcano-tectonic depression, the Hohi volcanic zone (HVZ), and has continued to the present at a decreasing eruption rate. The products are largely andesite and dacite, which became enriched in K with time. The proportion of tholeiitic to calc alkalic rocks also increases with time. Calc-alkalic high-Mg basaltic andesites (YbBs) were erupted in the early stage of the HVZ activity (5–3 Ma), and high-alumina basalts (KjBs) were erupted in the later stage (2–0 Ma). In contrast to the basalts in the HVZ, Northwest Kyushu basalts (NWKBs) have been erupted on the backarc side of the HVZ since 11 Ma, and hence are not related to the PHS plate subduction. They are mainly high-alkali tholeiitic to alkali basalt that shows no notable chemical change with time. NWKB, YbB, and KjB have MORB-normalized incompatible-element spectra that differ from each other, as is well expressed in both Nb and Sr anomalies. The patterns of KjB and NWKB are typical of those for island-arc basalt (IAB) and ocean-island basalt (OIB), respectively. YbB shows a pattern intermediate between the two. We suggest that the magma source beneath the HVZ changed in composition from an OIB-type mantle to an IAB-type mantle as the subduction of PHS plate advanced. However, the magma source remained fertile under Northwest Kyushu. In order to explain the temporal change of source mantle beneath the HVZ, we propose a model for progressive contamination of the mantle wedge, in which three processes (contamination by a slab-derived component, subtraction of magma from the mantle, and mixing of the mantle residue and slab-derived component) are repeated as subduction continues. As long as the progressive contamination of mantle wedge proceeds, its trace-element composition converges at a steady-state value for a short period. This value does not depend on the initial composition of the mantle wedge but instead on the composition of the slab-derived component. The trace-element composition of the magma produced in such a mantle wedge approaches that of the slab-derived component with time, but the major-element composition is determined by the phase relations of mantle peridotite. The slab-derived component may be basaltic liquid that is partially melted from rutile-bearing eclogite. 相似文献
3.
To understand the oxidation state and process of oxidation of lava domes, we carried out magnetic petrological analyses of lava samples obtained from domes and block-and-ash-flow deposits associated with the 1991–1995 eruption of Unzen volcano, Japan. As a result, we recognize three different types of magnetic petrology, each related to deuteric high-temperature oxidation during initial cooling. Type A oxides are characterized by homogenous titanomagnetite and titanohematite, indicating a low oxidation state and high titanomagnetite concentrations. Type B oxides are weakly exsolved and contain titanohematite laths and rutile lenses, indicating a higher oxidation state. Type C oxides, which represent the highest oxidation state, are completely exsolved and composed of Ti-poor titanomagnetite, titanohematite, rutile, and pseudobrookite, indicating high hematite concentrations. Some grains in Types A and B show indications of reduction, which was related to interaction with volcanic gases subsequent to high-temperature oxidation. In terms of geological occurrence, the oxidation processes probably differed for endogenous and exogenous domes. Endogenous dome lavas are oxidized concentrically and are classified into the three types according to their location within the dome: samples from the surface are strongly oxidized and classified as Type C, while the inner part is unoxidized and classified as Type A. Exogenous dome lavas are unoxidized and assigned to Type A. Some samples show signs of reduction, which may have occurred around fumaroles. We propose that location within the dome and the process of dome growth are the factors that control oxidation. 相似文献
4.
Morita T Ohtsuka Y Fujimoto K Minamisako Y Iida R Nakamura M Kayama T 《Marine pollution bulletin》2010,60(12):2311-2322
The anthropogenic radionuclides, 137Cs, 90Sr, 108mAg, 239+240Pu, were measured in two Chionoecetes species, red queen crab (Chionoecetes japonicus) and snow crab (Chionoecetes opilio) collected around Japan during 1996–2007. There was no increase in the concentrations of these radionuclides and no large variation of the atom ratio of 240Pu/239Pu during this research period. These results indicated that the source of the radionuclides was not the radioactive wastes dumped by the former USSR and Russia and originated from past nuclear weapon tests. The higher atom ratio in the crab species than that from global fallout would be contributed by the Pacific Proving Grounds close-in fallout. The variability of the concentration of radionuclides in the crab species would result from the variability of the composition and quantity in the diet. However, the decrease in the concentration of radionuclides with sampling depth would depend on the concentration in the seawater and diet. 相似文献
5.
Hidetoshi HARA Koji WAKITA Jun-ichiro KURODA Toshiyuki KURIHARA Katsumi UENO Yoshihito KAMATA Ken-ichiro HISADA Punya CHARUSIRI Thasinee CHAROENTITIRAT Pol CHAODUMRONG 《地球学报》2009,30(Z1):12-12
The Paleo-Tethys formed a large ocean basin that existed between Laurasia and Gondwana during Late Paleozoic to Early Mesozoic times. It opened in the Early Devonian by the rifting of Gondwanaland and closed at around latest Triassic time by the collision of the Cimmerian continent to Laurasia (Metcalfe, 1999). We reconstructed opening and closing process of the Paleo-Tethys in Northern Thailand. 相似文献
6.
Yoshihito KAMATA Hidetoshi HARA Katsumi UENO Apsorn SARDSUD Thasinee CHAROENTITIRAT Punya CHARUSIRI Ken-ichiro HISADA 《地球学报》2012,33(S1):36-37
The Inthanon Zone of Northern Thailand, origi-nally proposed by Barr and Macdonald (1991), is characterized by the occurrence of Paleo-Tethyan pe-lagic sediments including Carboniferous–Permian seamount-type carbonate associated with oceanic ba-saltic rocks and Middle Devonian–Middle Triassic radiolarian chert (Ueno, 1999; Ueno and Hisada, 2001; Ueno and Charoentitirat, 2011). These pelagic rocks have been mainly studied from the viewpoint of bio-stratigraphy to clarify the duration of their deposition. These studies concluded the Paleo-Tethys to be a vast ocean basin once existed between the Indochina and Sibumasu continental blocks during Devo-nian–Triassic times. 相似文献
7.
A rich foraminiferal assemblage, consisting of abundant Aulotortus sinuosus and A. tumidus in association with Lamelliconus multispirus, Endoteba ex gr. controversa, E. ex gr. badouxi, Endotebanella kocaeliensis, Endotriada tyrrhenica, Endotriadella wirzi, Malayspirina fontainei, Ammobaculites rhaeticus, Diplotremina astrofimbriata, Agathammina austroalpina, and others, was found in the Doi Long Formation of the Triassic Lampang Group, Northern Thailand. These foraminifers suggest that the formation is referable to the Carnian (early Late Triassic), which is consistent with the age estimated by ammonoids. In microfacies, peloidal grainstone, bioclastic grainstone, sponge-microbial boundstone, and oolitic grainstone were recognized in the Doi Long Formation. Based on microfacies, three depositional facies, the lagoon facies, reef facies, and shoal facies, are recognized in this formation. These lines of evidence are suggestive that the Doi Long Formation was deposited in a reef or bank setting rather than a ramp setting. 相似文献
8.
N. Hayashida M. Nagano D. Nishikawa H. Ohoka N. Sakaki M. Sasaki M. Takeda M. Teshima R. Torii T. Yamamoto S. Yoshida K. Honda N. Kawasumi I. Tsushima N. Inoue E. Kusano K. Shinozaki N. Souma K. Kadota F. Kakimoto K. Kamata S. Kawaguchi Y. Kawasaki H. Kitamura Y. Matsubara K. Murakami Y. Uchihori H. Yoshii 《Astroparticle Physics》1999,10(4):125-311
Anisotropy in the arrival directions of cosmic rays with energies above 1017 eV is studied using data from the Akeno 20 km2 array and the Akeno Giant Air Shower Array (AGASA), using a total of about 114 000 showers observed over 11 years. In the first harmonic analysis, we have found a strong anisotropy of 4% around 1018 eV, corresponding to a chance probability of 0.2% after taking the number of independent trials into account. with two-dimensional analysis in right ascension and declination, this anisotropy is interpreted as an excess of showers near the directions of the Galactic Center and the Cygnus region. 相似文献
9.
Sosuke Otani Yasunori Kozuki Ryoichi Yamanaka Hiromitsu Sasaoka Tetsu Ishiyama Yoshihito Okitsu Hajime Sakai Yoji Fujiki 《Estuarine, Coastal and Shelf Science》2010,86(3):434-440
The objective of this study is to elucidate the burrow structure and to clarify the role of burrows in material cycle in the tidal flat. In our work, we focused on the dominant species in muddy tidal flat, crab Macrophthalmus japonicus.Burrow structure of Macrophthalmus japonicus was investigated on a Katsuura river tidal flat in Tokushima prefecture, Japan, using in situ resin casting. Sampling was conducted in August 2006, and a total of 48 burrow casts were obtained. Burrows consisted mainly of J-shaped structures (98%) while the rest belonged to U-shaped structures (2%). The maximum measured burrow volume was 120 cm3 and wall surface area was 224 cm2, while maximum burrow length and depth were 23.2 cm and 16.5 cm, respectively. Burrow volume and surface area were strongly correlated with carapace width of M. japonicus. Investigation of the individual number of M. japonicus in 13 quadrats (50 × 50 × 20 cm) was conducted using 2 mm sieve. The number of M. japonicus was 15–31 ind./m2. Using cohort analysis we estimated that surface area of burrows was 0.07–0.15 m2/m2.CO2 emission rate was measured at the surface sediment during the period from June to December 2008. Results varied from 13.8 ± 2.2 to 49.4 ± 3.2 mg CO2/m2/h, and organic carbon decomposition was 3.8 ± 0.6–13.5 ± 0.9 mg C/m2/h. This leads the increase of organic carbon decomposition by 1.1 times, because of the expansion of the tidal flat surface area by burrowing activity. Organic carbon decomposition in burrow walls therefore contributed to organic matter decomposition in the tidal flat. These results indicated that in situ activities of Macrophthalmus japonicus significantly influence the material cycle and it is important to consider the existence of burrow in order to understand the fluxes of materials and to evaluate the purification function of the tidal flat. 相似文献
10.
Flow direction patterns have been determined by imbrication measurements of pumice and lithic fragments of the Handa pyroclastic
flow deposit, in order to estimate the source vent location and to analyze the flow behavior. The pyroclastic flow deposit
studied is dacitic in composition, 2 km2 in volume, and >32,300 Y.B.P. in age. Flow directions from 52 outcrops indicate a source vent located within the area of
recent lava domes of Kuju Volcano. The distribution of the pyroclastic flow deposit and the flow direction patterns determined
by imbrication suggest that the pyroclastic flow accurately followed the topographic relief at the time of eruption. The presence
of imbrication indicates the change of flow-regime from turbulent condition to laminar condition according to the distance
from the source vent. Imbrication is visible within the lower-half reaches of the pyroclastic flow distribution, where the
pyroclastic flow had developed the laminar flow characteristics of a dense gravity current. 相似文献