Architecture of growth basins in a tidally influenced,prodelta to delta-front setting: The Triassic succession of Kvalpynten,East Svalbard     

Aleksandra Smyrak-Sikora  Per Terje Osmundsen  Alvar Braathen  Kei Ogata  Ingrid Anell  Mark J. Mulrooney  Valentin Zuchuat 《Basin Research》2020,32(5):949-978

World-class examples of fault-controlled growth basins with associated syn-kinematic sedimentary fill are developed in Upper Triassic prodelta to delta-front deposits exposed at Kvalpynten, SW Edgeøya in East Svalbard. They are interpreted to have interacted with north-westerly progradation of a regional delta system. The syn-kinematic successions consist of 4 to 5 coarsening-upward units spanning from offshore mudstones to subtidal heterolithic bars and compound tidal dunes, which were blanketed by regional, post-kinematic sandstone sheets deposited as laterally continuous, subaqueous tidal dune fields. The rate of growth faulting is reflected in the distribution of accommodation, which governs sedimentary architecture and stacking patterns within the coarsening-upward units. Fully compartmentalized basins (12, 200–800 m wide and c. 150 m high grabens and half grabens) are characterized by syn-kinematic sedimentary infill. These grabens and half-grabens are separated by 60–150 m high horsts composed of pro-delta to distal delta-front mudstones. Grabens host tabular tidal dunes (sandwaves), whereas half-grabens bound by listric faults (mainly south-dipping) consist of wedge-shaped, rotated strata with erosive boundaries proximal to the uplifted fault block crests. Heterolithic tidal bars (sand ridges) occur in narrow half-grabens, showing migration oblique to the faults, up the dipslope. Structureless sandstone wedges and localized subaqueous slumps that formed in response to collapse of the block crests were only documented in half-grabens. Late-kinematic deposition during the final stages of faulting occurred in partly compartmentalized basins, filled with variably thick sets of continuous sandstone belts (compound tidal dunes).  相似文献   

Modeling low salinity waters along the coast around Japan using a high-resolution river discharge dataset     

L. Shogo Urakawa  Masao Kurogi  Kei Yoshimura  Hiroyasu Hasumi 《Journal of Oceanography》2015,71(6):715-739

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Contamination status of POPs and BFRs and relationship with parasitic infection in finless porpoises (Neophocaena phocaenoides) from Seto Inland Sea and Omura Bay, Japan     

Isobe T  Oshihoi T  Hamada H  Nakayama K  Yamada TK  Tajima Y  Amano M  Tanabe S 《Marine pollution bulletin》2011,63(5-12):564-571

Contamination status of brominated flame retardants (BFRs) and persistent organic pollutants (POPs) in blubber of finless porpoises (Neophocaena phocaenoides) stranded along the coasts of Seto Inland Sea and Omura Bay in Japan were investigated. Levels of PCBs, DDTs and CHLs were significantly higher than those of HCHs, HCB, PBDEs and HBCDs. Concentrations of PBDEs and HBCDs, as well as organochlorine compounds in males increased with body length (p<0.05). Among 14 PBDE congeners analyzed, BDE-47 was the predominant, which is similar to those generally reported in biota. PBDEs, HBCDs and PCBs showed no obvious temporal trend in concentrations during the study period, suggesting continuous environmental release of these chemicals. On the other hand, levels of DDT, CHLs and HCHs have decreased. Concentrations of PCBs in liver trematode infected individuals were significantly higher than those in not infected individuals, implying there could be a relationship between contaminant levels and parasitic infection.  相似文献   

Effect of heavy oil on the development of the nervous system of floating and sinking teleost eggs     

Irie K  Kawaguchi M  Mizuno K  Song JY  Nakayama K  Kitamura S  Murakami Y 《Marine pollution bulletin》2011,63(5-12):297-302

Heavy oil (HO) on the sea surface penetrates into fish eggs and prevents the normal morphogenesis. To identify the toxicological effects of HO in the context of the egg types, we performed exposure experiments using floating eggs and sinking eggs. In the course of development, HO-exposed embryos of floating eggs showed abnormal morphology, whereas early larva of the sinking eggs had almost normal morphology. However, the developing peripheral nervous system of sinking eggs showed abnormal projections. These findings suggest that HO exposed fishes have problems in the developing neurons, although they have no morphological malformations. Through these observations, we conclude that HO is strongly toxic to floating eggs in the morphogenesis, and also affect the neuron development in both floating and sinking eggs.  相似文献   

Water Ingress Assessment for Rock Tunnels: A Tool for Risk Planning   总被引：2，自引：0，他引：2  

Wing Kei Kong 《Rock Mechanics and Rock Engineering》2011,44(6):755-765

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Effects of large-scale wind on the Kuroshio path south of Japan in a 60-year historical OGCM simulation     

Hiroyuki Tsujino  Shiro Nishikawa  Kei Sakamoto  Norihisa Usui  Hideyuki Nakano  Goro Yamanaka 《Climate Dynamics》2013,41(9-10):2287-2318

The effects of large-scale wind forcing on the bimodality of the Kuroshio path south of Japan, the large meander (LM) and non-large meander (NLM), were studied by using a historical simulation (1948–2007) with a high-resolution Ocean general circulation models (OGCM). The Kuroshio in this simulation spent much time in the NLM state, and reproduced several aspects of its long-term path variability for the first time in historical OGCM simulation, presumably because the eddy kinetic energy was kept at a moderate level. By using the simulated fields, the relationships between wind forcing (or Kuroshio transport) and path variation proposed by past studies were tested, and specific roles of eddies in those variations were investigated. The long-term variation of the simulated net Kuroshio transport south of Japan was largely explained by the linear baroclinic Rossby wave adjustment to wind forcing. In the simulated LM events, a triggering meander originated from the interaction of a wind-induced positive sea surface height (SSH) anomaly with the upstream Kuroshio and was enlarged by cyclonic eddies from the recirculation gyre. The cyclonic eddy of the trigger meander was followed by a sizable anticyclonic eddy on the upstream side. Subsequently, a weak (strong) Kuroshio favored the LM (NLM). The LM tended to be maintained when the Kuroshio transport off southern Japan was small, and increasing Kuroshio transport promoted decay of an existing LM. The supply of disturbances from upstream, which is related to the wind-induced SSH variability at low latitudes, contributed to the maintenance of an existing LM.  相似文献   

Statistical analysis of seismicity in a wide region around the 1998 Mw 8.1 Balleny Islands earthquake in the Antarctic Plate     

Tetsuto Himeno  Masaki Kanao  Yosihiko Ogata 《Polar Science》2011,5(4):421-431

A large earthquake (Mw 8.1) that occurred off the North Coast of the Antarctic continent near the Balleny Islands on 25 March 1998 was the largest intra-plate earthquake ever recorded in the Antarctic Plate. The earthquake hypocenter catalog for this area shows a marked change in seismicity following the main shock in a large area around the Balleny aftershock region. However, the earthquake catalog includes many aftershocks and is affected by a variable detection rate. To overcome these limitations, we applied statistical models and methods, including Gutenberg–Richter’s magnitude frequency distribution, the Epidemic-Type Aftershock Sequences (ETAS) model, and the space–time ETAS model, thereby enabling calculation of the change in detection rate. The results show a change in the spatial pattern of background seismicity over a large region after the 1998 event.  相似文献   

Textural and Chemical Evolution of Unidirectional Solidification Textures in Highly Differentiated Granitic Rocks at Kharaatyagaan,Central Mongolia   总被引：1，自引：0，他引：1  

Jamsran Erdenebayar  Takeyuki Ogata  Akira Imai  Jargalan Sereenen 《Resource Geology》2014,64(4):283-300

Unidirectional solidification texture (UST) in an aplite body is recognized in the Neoproterozoic highly differentiated granitic rocks at Kharaatyagaan, central Mongolia. On the basis of crystal morphology, two main types of UST were identified in the aplite body: (i) thin crenulate UST layers; and (ii) thick intergrowth UST layers. Bulk geochemistry indicates that the Kharaatyagaan UST‐bearing aplite and aplite dike are alkaline, and are enriched in light rare‐earth elements. Scanning electron microscopy and cathadoluminescence imaging of UST quartz from Kharaatyagaan show four types of quartz: euhedral quartz phenocrysts with well‐developed concentric growth zoning (Qa1) in the aplite; euhedral quartz with weak growth zoning in the aplite (Qa2); UST quartz exhibiting distinct growth zones (Qu1); and UST quartz showing mosaic texture (Qu2). Crystallization temperatures determined by the Ti‐in‐quartz geothermometer of Qa1 and Qu1 quartz range between around 500°C and 780°C and Qa2 and Qu2 range between about 490° and 630°C. The cathodoluminescence textures of quartz are predominantly caused by variations in the trace elements contents of quartz. The Qa1 and Qu1 quartz crystals are characterized by high Ti and Al concentrations in the quartz lattice, and are observed in the bottom of the Kharaatyagaan hill, which formed in the early, less evolved magmatic stage. The Qa2 and Qu2 UST quartz characterized by low Ti and variable Al concentrations are found at the top. The UST layers crystallized along the upper part of the magma chamber in the presence of fluid phases exsolved from felsic magma.  相似文献   

Gold Mineralization in Banded Iron Formation in the Amalia Greenstone Belt,South Africa: A Mineralogical and Sulfur Isotope Study     

Kofi Adomako‐Ansah  Toshio Mizuta  Napoleon Q. Hammond  Daizo Ishiyama  Takeyuki Ogata  Hitoshi Chiba 《Resource Geology》2013,63(2):119-140

The Blue Dot gold deposit, located in the Archean Amalia greenstone belt of South Africa, is hosted in an oxide (± carbonate) facies banded iron formation (BIF). It consists of three stratabound orebodies; Goudplaats, Abelskop, and Bothmasrust. The orebodies are flanked by quartz‐chlorite‐ferroan dolomite‐albite schist in the hanging wall and mafic (volcanic) schists in the footwall. Alteration minerals associated with the main hydrothermal stage in the BIF are dominated by quartz, ankerite‐dolomite series, siderite, chlorite, muscovite, sericite, hematite, pyrite, and minor amounts of chalcopyrite and arsenopyrite. This study investigates the characteristics of gold mineralization in the Amalia BIF based on ore textures, mineral‐chemical data and sulfur isotope analysis. Gold mineralization of the Blue Dot deposit is associated with quartz‐carbonate veins that crosscut the BIF layering. In contrast to previous works, petrographic evidence suggests that the gold mineralization is not solely attributed to replacement reactions between ore fluid and the magnetite or hematite in the host BIF because coarse hydrothermal pyrite grains do not show mutual replacement textures of the oxide minerals. Rather, the parallel‐bedded and generally chert‐hosted pyrites are in sharp contact with re‐crystallized euhedral to subhedral magnetite ± hematite grains, and the nature of their coexistence suggests that pyrite (and gold) precipitation was contemporaneous with magnetite–hematite re‐crystallization. The Fe/(Fe+Mg) ratio of the dolomite–ankerite series and chlorite decreased from veins through mineralized BIF and non‐mineralized BIF, in contrast to most Archean BIF‐hosted gold deposits. This is interpreted to be due to the effect of a high sulfur activity and increase in fO₂ in a H₂S‐dominant fluid during progressive fluid‐rock interaction. High sulfur activity of the hydrothermal fluid fixed pyrite in the BIF by consuming Fe²⁺ released into the chert layers and leaving the co‐precipitating carbonates and chlorites with less available ferrous iron content. Alternatively, the occurrence of hematite in the alteration assemblage of the host BIF caused a structural limitation in the assignment of Fe³⁺ in chlorite which favored the incorporation of magnesium (rather than ferric iron) in chlorite under increasing fO₂ conditions, and is consistent with deposits hosted in hematite‐bearing rocks. The combined effects of reduction in sulfur contents due to sulfide precipitation and increasing fO₂ during progressive fluid‐rock interactions are likely to be the principal factors to have caused gold deposition. Arsenopyrite–pyrite geothermometry indicated a temperature range of 300–350°C for the associated gold mineralization. The estimated δ³⁴S_ΣS (= +1.8 to +2.5‰) and low base metal contents of the sulfide ore mineralogy are consistent with sulfides that have been sourced from magma or derived by the dissolution of magmatic sulfides from volcanic rocks during fluid migration.  相似文献   

The dependence of surface tidal stress on the internal structure of Europa: The possibility of cracking of the icy shell     

Yuji Harada  Kei Kurita 《Planetary and Space Science》2006,54(2):170-180

This study shows dependence of the surface diurnal tidal stress on the internal structure of Europa. Its purpose is to investigate possibility of cracking of the icy shell. The stress is evaluated under the plausible model of the internal structure constrained by the gravity field data. The possible effective stress at the sub-Jovian point decreases with thickening of the shell, while it does not depend on the core radius and the thickness of the H₂O layer. The range of this value is from 0.095 to 0.161 MPa, which does not exceed the tensile strength of ice. The stress required for the surface cracking would be mainly due to longer period deformations, especially non-synchronous rotation. And/or the actual strength of the ice at the surface would be smaller because of the preexisting cracks than that at a laboratory of the same temperature.  相似文献