Zircon U–Pb ages from tuff beds of the upper Mesozoic Tetori Group in the Shokawa district,Gifu Prefecture,central Japan†     

Nao Kusuhashi  Ai Matsumoto  Masaki Murakami  Takahiro Tagami  Takafumi Hirata  Tsuyoshi Iizuka  Takeshi Handa  Hiroshige Matsuoka 《Island Arc》2006,15(3):378-390

Abstract The upper Mesozoic Tetori Group contains numerous fossils of plants and marine and non‐marine animals. The group has the potential to provide key information to improve our understanding of the Middle Jurassic to Early Cretaceous biota of East Asia. However, the depositional age of the Tetori Group remains uncertain, and without good age constraints, accurate correlation with other areas is very difficult. As a first step in obtaining reliable ages for the formations within the Tetori Group, we used laser ablation‐inductively coupled plasma–mass spectrometry to measure the U–Pb ages of zircons collected from tuff beds in the Shokawa district, Takayama City, Gifu Prefecture, central Japan. The youngest reliable U–Pb ages from the tuff beds of the Ushimaru, Mitarai and Okurodani Formations are 130.2 ± 1.7, 129.8 ± 1.0 and 117.5 ± 0.7 Ma, respectively (errors represent 2 SE). These results indicate that the entire Tetori Group in the Shokawa district, which was previously believed to be correlated to the Upper Jurassic to Lower Cretaceous, is in fact correlated to the Lower Cretaceous. The maximum ages of the Ushimaru, Mitarai and Okurodani Formations are late Hauterivian to Barremian, late Hauterivian to Barremian and Barremian to Aptian, respectively.  相似文献   

Transition of eruptive style in an arc–arc collision zone: K–Ar dating of Quaternary monogenetic and polygenetic volcanoes in the Higashi-Izu region, Izu peninsula, Japan     

Noriko Hasebe  Ayako Fukutani  Masafumi Sudo  Takahiro Tagami 《Bulletin of Volcanology》2001,63(6):377-386

K-Ar ages were measured on Quaternary polygenetic and monogenetic volcanoes in the Higashi-Izu region, Izu peninsula, central Japan, using the unspiked sensitivity method with mass-fractionation correction procedure to investigate when eruptive style changed, whether a hiatus existed between the two types of eruptive activity, and the effect of tectonics on the change in eruptive style. The K-Ar ages range from 0.3-0.08 Ma for monogenetic volcanoes and from 1.8-0.2 Ma for polygenetic volcanoes; thus, no volcanic hiatus was found between the two types of eruptive styles. The transition from polygenetic to monogenetic volcanism occurred during a time of overlap between 0.3 and 0.2 Ma, after collision of the Izu block (the future Izu peninsula) with central Japan, estimated as 1.0-0.8 Ma by previous researchers. Based on the review of several tectonic models of the area, the measured age of transition in eruptive style is interpreted to correspond to the change in the stress field of the Higashi-Izu region.  相似文献   

Experiments on the Element Distribution between the Granodiorite JG-1a and 2M NaCl Hydrothermal Solution at Temperatures of 300 to 800°C and a Pressure of 1 kb     

Etsuo Uchida    Takuro Haitani    Takayuki Suetsugu    Takahiro Kashima  Ken Tsutsui 《Resource Geology》2003,53(2):155-161

Abstract. The distribution of Na, K, Ca, Mg, Mn and Fe between the granodiorite JG-la, one of the geochemical standard rocks, and 2M NaCl aqueous solution was experimentally determined at temperatures of 300 to 800C and a pressure of 1 kb using standard cold seal-type pressure vessels. The solid run products melted partially at 800C. Only K shows a significantly different behavior from the experiments using the basalt JB-la (Uchida and Tsutsui, 2000) due to the presence of ortho-clase in the JG-la. The transition elements tend to be preferably partitioned into the aqueous chloride solutions with increasing temperature. At 800C and 1 kb, the Fe concentration of the aqueous chloride solutions reached up to 5,000 ppm, and the Mn concentration up to 350 ppm. The distribution coefficient, K_{D, i} = C_{i, sol}/C_i, rock, is in the order of Na>K>Mn>Ca> Fe>Mg at 300C, but changed in the order of Mn>N>K>Fe>Ca>Mg at 800C. The distribution coefficients of the divalent cations for the JG-la are higher than those for the JB-1a. The distribution coefficient of the transition elements, Fe and Mn, increases significantly with increasing temperature. The thermodynamic analysis for aqueous speciation revealed that this is attributable to the formation of the tri-chloro complexes of the transition elements at higher temperatures.  相似文献   

Interannual-decadal variability of wintertime mixed layer depths in the North Pacific detected by an ensemble of ocean syntheses     

Toyoda  Takahiro  Fujii  Yosuke  Kuragano  Tsurane  Kosugi  Naohiro  Sasano  Daisuke  Kamachi  Masafumi  Ishikawa  Yoichi  Masuda  Shuhei  Sato  Kanako  Awaji  Toshiyuki  Hernandez  Fabrice  Ferry  Nicolas  Guinehut  Stéphanie  Martin  Matthew  Andrew Peterson  K.  Good  Simon A.  Valdivieso  Maria  Haines  Keith  Storto  Andrea  Masina  Simona  Köhl  Armin  Yin  Yonghong  Shi  Li  Alves  Oscar  Smith  Gregory  Chang  You-Soon  Vernieres  Guillaume  Wang  Xiaochun  Forget  Gael  Heimbach  Patrick  Wang  Ou  Fukumori  Ichiro  Lee  Tong  Zuo  Hao  Balmaseda  Magdalena 《Climate Dynamics》2017,49(3):891-907

Climate Dynamics - The interannual-decadal variability of the wintertime mixed layer depths (MLDs) over the North Pacific is investigated from an empirical orthogonal function (EOF) analysis of an...  相似文献   

Synchrotron X-ray analysis of norbergite, Mg_2.98Fe_0.01Ti_0.02Si_0.99O₄(OH_0.31F_1.69) structure at high pressure up to 8.2?GPa     

Takahiro Kuribayashi  Masahiko Tanaka  Yasuhiro Kudoh 《Physics and Chemistry of Minerals》2008,35(10):559-568

The natural norbergite, Mg_2.98Fe_0.01Ti_0.02Si_0.99O₄(OH_0.31F_1.69) is examined by synchrotron X-ray diffraction analysis at pressures up to 8.2 GPa. The measured linear compressibilities of the crystallographic axes are β _a  = 2.18(4) × 10⁻³, β _b  = 2.93(7) × 10⁻³, and β _c  = 2.77(7) × 10⁻³ (GPa⁻¹), respectively and the calculated isothermal bulk modulus of the norbergite is K _T = 113(2) GPa based on the Birch–Murnaghan equation of state assuming a pressure derivative of K′ = 4. The crystal structures of norbergite are refined at room temperature and pressures of 4.7, 6.3, and 8.2 GPa, yielding R values for the structure refinements of 4.6, 5.3, and 5.3%, respectively. The bulk moduli of the polyhedral sites are 293(15) GPa for the tetrahedron, 106(5) GPa for the M2 octahedron, 113(2) GPa for the M3 octahedron, and 113(3) GPa for the total void space. The bulk modulus exhibits a good linear correlation with the filling factor for polyhedral sites in structures of the humite minerals and forsterite, reflecting the Si⁴⁺ + 4O²⁻ ⇔ □ + 4(OH, F)⁻ substitution in the humite minerals. Moreover, two simply linear trends were observed in the relationship between bulk modulus and packing index for natural minerals and dense hydrous magnesium silicate minerals. This relationship would reflect that the differences in compression mechanism were involved with hydrogen bonding in these minerals. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

东亚东倾地形格局的形成与季风系统演化历史寻踪——综合大洋钻探计划683号航次建议书简介   总被引：2，自引：1，他引：1  

郑洪波  汪品先  刘志飞  杨守业  王家林  李前裕  周祖翼  贾军涛  李上卿  贾健宜  John Chappell  Yoshiki Saito  Takahiro Inoue 《地球科学进展》2008,23(11):1150-1160

围绕IODP 683号建议书,介绍东亚东倾地形格局与季风系统演化历史的相关研究。新生代全球宏观环境格局发生了一系列重大变化,表现为岩石圈活动强烈,板块漂移导致海陆格局和地貌格局的变化,并引发洋流和大气环流的改组,最终导致全球气候的重大变化。新生代岩石圈运动和气候变化表现最为典型的地区是亚洲,其中最具标志性和全球意义的地质事件是喜马拉雅山和青藏高原的隆升及亚洲季风系统的形成与演化。青藏高原隆升最直接的结果是亚洲地区现代地貌格局的形成,大江大河的发育,并在很大程度上影响了亚洲季风系统的形成与演化。综合大洋钻探计划683号航次建议书,计划在长江中下游盆地和东海陆架盆地实施钻探,以获得长江历史演化和东亚季风演化的地质记录,并为研究青藏高原的演化提供新的证据。  相似文献   

The 1989 submarine eruption off eastern Izu Peninsula,Japan: ejecta and eruption mechanisms     

Takahiro Yamamoto  Tatsunori Soya  Shigeru Suto  Kozo Uto  Akira Takada  Keiichi Sakaguchi  Koji Ono 《Bulletin of Volcanology》1991,53(4):301-308

The submarine eruption of a new small knoll, which was named Teishi knoll, off eastern Izu Peninsula behind the Izu-Mariana arc occurred in the evening of 13 July 1989. This is the first historic eruption of the Higashi-Izu monogenetic volcano group. The eruption of 13 July followed an earthquake swarm near Ito city starting on 30 June. There were subsequent volcanic tremors on 11 and 12 July, and the formation of the Teishi knoll on the 100 m deep insular shelf 4 km northeast of Ito city. There were five submarine explosions, which were characterized by intermittent domelike bulges of water and black tephra-jets, which occurred within 10 min on 13 July. Ejecta of the eruption was small in volume and composed of highly crystalline basalt scoria, highly vesiculated pumice, and lithic material. Petrographical features suggest that the pumice was produced by vesiculation of reheated wet felsic tuff of an older formation. The Teishi knoll, before the eruption, was a circular dome, 450 m across and 25 m high, with steep sides and a flat summit. Considerations of submarine topographic change indicate the knoll was raised by sill-like intrusion of 10⁶ m³ of magma beneath a 30 m thick sediment blanket. This shallow intrusion is assumed to have started on 11 July when volcanic tremors were observed for the first time, but there was no indications of violent interaction between wet host sediments and intruding magma. The submarine eruption of 13 July appears to have been Friggered by a major lowering of the magma-column. The basalt scoria, having crystal-contents of more than 60%, is assumed to be derived from the cooled plastic margin of the shallow intrusive body. However, glassy scoria, which would indicate the interaction between hot fluidal magma and external water, was not observed. A scenario for the 1989 submarine eruption is as follows. When rapid subsidence of the hot interior of the intrusive magma occurred, reduced pressure caused the implosion of cooled plastic magma, adjacent pressurized, hot host material, and wet sediment. The mixing of these materials triggered the vigorous vapor explosions.  相似文献   

Temporal and spatial variability of chlorophyll concentrations in the Bering Sea using empirical orthogonal function (EOF) analysis of remote sensing data   总被引：2，自引：0，他引：2  

Takahiro Iida  Sei-Ichi Saitoh 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2657

Seasonal and interannual variability of surface chlorophyll concentration in the Bering Sea was examined using Empirical Orthogonal Function (EOF) analysis of data obtained by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) from 1998 to 2002. The analysis of normalized monthly fields (removing temporal and spatial monthly means) shows that different temporal and spatial patterns are evident in the eastern and western Bering Sea during the spring bloom period. The first EOF mode explains 30% of the variability and shows how the eastern shelf break region and the western Bering Sea are out of phase during the spring bloom. The second EOF mode (17.6%) indicates a pattern involving the eastern shelf break region and the Kamchatka Basin. This strong east–west signal is linked by both surface winds and light. EOF modes of wind-speed anomalies, derived from Special Sensor Microwave Imager (SSM/I), and photosynthetically active radiance (PAR) from SeaWiFS, show a similar dipole feature where the east–west pattern is related to the position and strength of the Aleutian Low pressure system. In years when the Aleutian Low shifts from west to east, weaker wind stress facilitates the development of stratification resulting in a strong spring bloom in the western Bering Sea. The variability of spring chlorophyll has a strong connection with variability in atmospheric forcing in the Bering Sea.  相似文献   

Upper limit of heaving pressure derived by pore-water pressure measurements of partially frozen soil     

Tsutomu Takashi  Takahiro Ohrai  Hideo Yamamoto  Jun Okamoto 《Engineering Geology》1981,18(1-4):245-257

Experiments were conducted to estimate heaving pressures of saturated soil partially frozen in a closed system. Temperatures at both ends of a specimen were kept constant, i.e., positive at the top and negative at the bottom. When the overburden pressure P was maintained at a constant value, the pore-water pressure P_w, which showed a certain value before freezing, decreased gradually as freezing progressed, finally attaining a specific value, whereafter the specimen ceased taking water into it. The pressure difference between P and P_w, at this stage was defined as the upper limit of heaving pressure σ_u, which evidently depended on the temperature θ_c of the cooling end, in accordance with the relation: σ_u = −11.4 θ_c (kg/cm²)

It corresponds to the modified Clausius-Clapeyron's formula, which gives the freezingpoint depression of an ice—water system, where the pressure acting on the ice differs from that on the water. This is the same as the value obtained by Radd and Oertle (1973). It is considered, however, that, when θ_c lowers, the value of θ_u reaches finally a constant value smaller than the one obtained by the above equation. Denoted by σ_{u max}, it was defined as a maximum heaving pressure. The value of σ_{u max} depended on soil type.  相似文献   

Redox processes and occurrence of arsenic in a volcanic aquifer system of Kumamoto Area,Japan     

Shahadat Hossain  Takahiro Hosono  Kiyoshi Ide  Midori Matsunaga  Jun Shimada 《Environmental Earth Sciences》2016,75(9):740

  相似文献