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1.
Sedimentary core samples were collected from Mikawa Bay and analyzed for organic C, N and P, carbohydrate and protein including amino acids. Sedimentation rates for each of the core samples were found to lie in the range of 0.21–0.24 g cm–2yr–1 by the210Pb method. Degradation rate constants of organic C, N and P, carbohydrate and protein including amino acids had ranges of 3.8–5.5, 4.7–5.9, 6.3–7.4, 5.7–6.8 and 3.9–6.8×10–2yr–1, respectively. The rate of degradation of organic matter in the sediment was also calculated and is discussed in relation to the flux of particulate organic matter to the surface of the sediment. 相似文献
2.
Katsuhiko Matsunaga 《Journal of Oceanography》1976,32(1):48-50
Variation of mercury concentration in the oceans during the last several decades has been investigated by determining the mercury concentration in rock fishes caught recently andca. 20 years ago. From this result, it is concluded that there has been no variation of mercury concentration in the oceans during the last several decades. 相似文献
3.
The relationship between Cd and PO4 in the Kuroshio and Oyashio regions and the Okhotsk Sea was examined. The resultant equations are as follows: Cd (ng l–1)=37.0 PO4 (M)+2.6; Cd(ng l–1)=32.1 PO4 (M)+1.2 and Cd (ng l–1)=34.1 PO4 (M)+7.9, respectively. These results are in good agreement with previously reported studies, and indicate that during removal from surface waters to deeper waters by biological assimilation and regeneration in deeper waters Cd and PO4 maintain the same ratio in the open ocean. The relationship between Cd and PO4 in coastal waters, however, differed from that in the open ocean. 相似文献
4.
Sediment trap experiments were carried out 39 times during the years from 1977 to 1981 in Funka Bay, Hokkaido, Japan. The observed total particulate flux varies seasonally, that is, the particulate fluxes in winter and spring are larger than those in summer. The fluxes in all seasons increased with depth. Major components of settling particles are aluminosilicate in winter, biogenic silicate in spring and organic matter and terrestrial material in summer, respectively. The fluxes of each chemical component observed with sediment traps are normalized to that of Al by assuming that the actual flux of Al is equal to the accumulation rate onto the sediment surface. Vertical changes of the normalized flux of each chemical component indicate the following: Fe was not regenerated from the settling particles in the water column. Mn was regenerated from the settling particles in the lower layer exclusively between 80 m depth and the sediment surface. Cd was actively regenerated in the upper layer above 80 m depth. Phosphate was regenerated in the upper layer, while biogenic silicate was in the lower layer. The silicate regeneration, therefore, occurs after phosphate regeneration. The material decomposing in the water column below 40 m has an atomic ratio of P ∶ Si ∶ C = 1 ∶ 52 ∶ 128. 相似文献
5.
We have reinvestigated the mid-Cretaceous plume pulse in relation to paleo-oceanic plateaus from accretionary prisms in the circum-Pacific region, and we have correlated the Pacific superplume activity with catastrophic environmental changes since the Neoproterozoic. The Paleo-oceanic plateaus are dated at 75–150 Ma; they were generated in the Pacific superplume region and are preserved in accretionary prisms. The volcanic edifice composed of both modern and paleo-oceanic plateaus is up to 10.7 × 106 km2 in area and 19.1 × 107 km3 in volume. The degassing rate of CO2 (0.82 − 1.1 × 1018 mol/m.y.) suggests a significant impact on Cretaceous global warming. The synchronous occurrence of paleo-oceanic plateaus in accretionary complexes indicates that Pacific superplume pulse activities roughly coincided at the Permo-Triassic boundary and the Vendian–Cambrian boundary interval. The CO2 expelled by the Pacific superplume probably contributed to environmental catastrophes. The initiation of the Pacific superplume contributed to the snowball Earth event near the Vendian–Cambrian boundary; this was one of the most dramatic events in Earth's history. The scale of the Pacific superplume activity roughly corresponds to the scale of drastic environmental change. 相似文献
6.
Deep structure of the northeastern Japan arc and its implications for crustal deformation and shallow seismic activity 总被引:7,自引:1,他引:7
Seismic tomography studies in the northeastern Japan arc have revealed the existence of an inclined sheet-like seismic low-velocity and high-attenuation zone in the mantle wedge at depths shallower than about 150 km. This sheet-like low-velocity, high-attenuation zone is oriented sub-parallel to the subducted slab, and is considered to correspond to the upwelling flow portion of the subduction-induced convection. The low-velocity, high-attenuation zone reaches the Moho immediately beneath the volcanic front (or the Ou Backbone Range) running through the middle of the arc nearly parallel to the trench axis, which suggests that the volcanic front is formed by this hot upwelling flow. Aqueous fluids supplied by the subducted slab are probably transported upward through this upwelling flow to reach shallow levels beneath the Backbone Range where they are expelled from solidified magma and migrate further upward. The existence of aqueous fluids may weaken the surrounding crustal rocks, resulting in local contractive deformation and uplift along the Backbone Range under the compressional stress field of the volcanic arc. A strain-rate distribution map generated from GPS data reveals a notable concentration of east–west contraction along the Backbone Range, consistent with this interpretation. Shallow inland earthquakes are also concentrated in the upper crust of this locally large contraction deformation zone. Based on these observations, a simple model is proposed to explain the deformation pattern of the crust and the characteristic shallow seismic activity beneath the northeastern Japan arc. 相似文献
7.
Ken-ichi Uzaki Nobuhiro Matsunaga Yasuhiro Nishii Yoshito Ikehata 《Ocean Engineering》2010,37(2-3):155-163
Long-period oscillations of moored ships whose periods are about 1 or 2 min cause many troubles in many ports and harbours. It is necessary to investigate these phenomena and verify their causes and countermeasures in each case because they are strongly dependent on the environment of each port and harbour. From this point of view, long-period oscillations of moored ships in the Port of Shibushi in Japan were investigated by means of wave observations, the image processing of moored ship motions using the video camera and motion-capture software and numerical simulations. From observation results, the relationship between offshore long-period waves and long-period oscillations of moored ships was recognized and surge and heave amplitudes were quantified by using wave data in order to forecast moored ship motions. Furthermore, from observation and numerical results, it was revealed that long-period waves with the peak period of 120 s from the offshore typhoon kept or exaggerated the local harbour oscillation of 60–70 s and it caused long-period oscillations of moored ships. Numerical results in case of reducing the reflection coefficient of the target berth implied that it ceased the local harbour oscillation and it would give an effective countermeasure to reduce long-period oscillations of moored ships in the Port of Shibushi. 相似文献
8.
Double-planed deep seismic zone and anomalous structure in the upper mantle beneath northeastern Honshu (Japan) 总被引:1,自引:0,他引:1
Seismicity located by using the most recent data obtained from the high-gain seismograph network of Tohoku University shows that the deep seismic zone beneath northeastern Honshu, Japan, is composed of two thin planes which are parallel to each other and are 30–40 km apart. Focal mechanisms derived from the earthquakes in the upper plane are reverse-faulting, or, some of them, down-dip compression. As a contrast, those in the lower plane are down-dip extension. The location of the upper boundary of the descending lithospheric slab, inferred from the arrival-time difference between ScS and ScSp waves and from the travel-time anomaly of intermediate-depth earthquakes observed at the small-scale seismic array, coincides exactly with the upper plane of the double-planed deep seismic zone. Anelasticity (1/Q) structure of the upper mantle consists of three distinct zones: a high-Q (Qs− 1500) inclined lithospheric slab, an intennediate-Q (Qs−350) land-side mantle between the Pacific coast and the volcanic front, and a low-Q (Qs − 100) land-side mantle between the volcanic front and the coast of the Japan Sea.The evidence obtained here provides valuable information as to the definition of the type of mechanism producing the plate motion beneath island arcs. 相似文献
9.
10.
Early Miocene sediments of the Morozaki Group in central Japan contain deep-sea fossils that have been dated using biostratigraphic and radiometric data. In this study, we utilize magnetostratigraphy to provide a more precise age for mudstones from just below the layer containing the fossils. Rock magnetic experiments suggest that both magnetic iron sulfide and Ti-poor titanomagnetite carry the remanent magnetization of the mudstones. Two different stratigraphic sites have normal polarity directions with a northeastern declination, which can be correlated with Chronozone C5Dn. Given their magnetostratigraphic position near the C5Dn/C5Dr chronozone boundary (17.466 Ma) and a high sedimentation rate, the estimated age for both the sites and the deep-sea fossils is ~17.4 Ma. The northeasterly-directed site-mean directions suggest clockwise tectonic rotation, most likely due to the Early Miocene clockwise rotation of Southwest Japan associated with the back-arc opening of the Japan Sea. The deep-sea fossils, dated at ~17.4 Ma, represent organisms deposited within a submarine structural depression formed by crustal extension during the back-arc opening stage. 相似文献