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Crude petroleum was emulsified or degraded by marine microorganisms and physically altered by an artificial weathering process. Only the water-soluble fraction from emulsified crude petroleum inhibited glutamate uptake by marine microorganisms from South Carolina and Georgia coastal waters. Chloroform extraction recovered almost equal amounts of total hydrocarbon from each water-soluble fraction. Chromatographic data indicated that the composition of microbially emulsified petroleum was similar to that of microbially degraded petroleum. Emulsification of crude petroleum was only observed in summer water samples and did not consistently occur at a given location. Results of this study indicate that the process by which crude petroleum is altered will influence its toxicity to microbial heterotrophic activity. 相似文献
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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
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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
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New data on the structure and composition of the rock complexes making up the Otrozhnaya sheet of the Ust-Belaya Terrane are discussed. This sheet is currently regarded as a complete section of the Early Devonian oceanic crust. The U-Pb age of zircon (547 ± 17 Ma) from plagiogranite porphyry that cuts through the ultramafic-gabbroic complex indicates that the country rocks are much older. Basalts of volcanic complex are similar to MORB-type rocks. The contact between volcanic and volcano-sedimentary complexes is tectonic. No volcanic-cherty association of rocks typical of ophiolites has been established at the base of the sedimentary sequence. The U-Pb age of detrital zircons from the base of this section is 571 Ma. As follows from the composition of terrigenous rocks and the suprasubduction origin of andesitic lavas and tuffs, the rocks of the lower part of volcano-sedimentary complex were deposited at the marginal part of the basin near convergent boundary. The remains of conodont elements make it possible to estimate the age of the upper part of the volcano-sedimentary complex as Late Devonian. The composition of terrigenous rocks shows that the provenance has abruptly changed. Sporadic rock fragments evidence the erosion of ophiolitic sections. Silurian rocks became the main source of clastic material. This is corroborated by redeposited microfauna species and U-Pb age of detrital zircons (～432 Ma). The geochemistry of dacite pebbles from conglomerate indicates that this volcanic rock was formed in a suprasuduction setting. The Ordovician-Silurian island arc could have been a source. 相似文献
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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
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Vertical and cross-wind profiles of mean currents were measured systematically in vertical cross-sections of two wind-wave
tanks with aspect ratios of order one to study the secondary flow in the tanks. A pair of Langmuir cells turned out to be
driven by a close combination of the pressure gradient along the tank and the side-wall effects. That is, part of the adverse
pressure gradient produced a parabolic cross-wind profile with the smallest downwind current at the centerline and the largest
current along the two sidewalls. As a result, upwelling occurred in the center zone where the return flow was strongest, probably
because of the entrainment action of the wind-driven current. In order to compensate for this upwelling, downwelling occurred
along the two side-walls from the flow continuity. The resulting vertical circulation formed a pair of Langmuir circulations
across the span and served to maintain the parabolic profile formed by the pressure gradient. A positive feedback mechanism
is thus found between the primary and secondary circulations through upwelling of the return flow in the center zone. Vertical
shears of the span-averaged downwind current measured in two tanks were found to be systematically different from each other.
This difference seems to depend on the magnitude of the advective Reynolds stresses in the two tanks. 相似文献
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Active roles of both sea surface temperature (SST) and its frontal characteristics to the atmosphere in the mid-latitudes have been investigated around the western boundary current regions, and most studies have focused on winter season. The present study investigated the influence of the variation of the summertime Oyashio extension SST front (SSTF) in modulating low-level cloud properties (i.e., low-level cloud cover [LCC], cloud optical thickness [COT], and shortwave cloud radiative effect [SWCRE]) on inter-annual timescales, based on available satellite and Argo float datasets during 2003–2016. First, we examined the mechanism of summertime SSTF variability itself. The strength of the SSTF (SSSTF), defined as the maximum horizontal gradient of SST, has clear inter-annual variations. Frontogenesis equation analysis and regression analysis for subsurface temperature indicated that the inter-annual variations of the summertime SSSTF in the western North Pacific are closely related to the variations of not surface heat flux, but western boundary currents, particularly the Oyashio Extensions. The response of low-level cloud to intensified SSSTF is that negative SWCRE with positive COT anomaly in the northern flank of the SSTF can be induced by cold SST anomalies. The spatial scale of the low-level cloud response was larger than the SST frontal scale, and the spatial distribution of the response was mainly constrained by the pathways of Kuroshio and Oyashio Extensions. Multi-linear regression analysis revealed that the local SST anomaly played largest role in modulating the SWCRE and COT anomalies among the cloud controlling factors (e.g., estimated inversion strength, air-temperature advection) accounting for more than 50% of the variation. This study provides an observational evidence of the active role of local SST anomalies in summertime associated with the western boundary currents to the oceanic low-level cloud.
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