Radiolaria‐dated Lower Permian clastic‐rock sequence in the Fukuji area of the Hida‐gaien terrane,central Japan,and its inter‐terrane correlation across Southwest Japan     

Toshiyuki Kurihara  Masao Kametaka 《Island Arc》2008,17(4):531-545

The stratigraphy and radiolarian age of the Mizuyagadani Formation in the Fukuji area of the Hida‐gaien terrane, central Japan, represent those of Lower Permian clastic‐rock sequences of the Paleozoic non‐accretionary‐wedge terranes of Southwest Japan that formed in island arc–forearc/back‐arc basin settings. The Mizuyagadani Formation consists of calcareous clastic rocks, felsic tuff, tuffaceous sandstone, tuffaceous mudstone, sandstone, mudstone, conglomerate, and lenticular limestone. Two distinctive radiolarian faunas that are newly reported from the Lower Member correspond to the zonal faunas of the Pseudoalbaillella u‐forma morphotype I assemblage zone to the Pseudoalbaillella lomentaria range zone (Asselian to Sakmarian) and the Albaillella sinuata range zone (Kungurian). In spite of a previous interpretation that the Mizuyagadani Formation is of late Middle Permian age, it consists of Asselian to Kungurian tuffaceous clastic strata in its lower part and is conformably overlain by the Middle Permian Sorayama Formation. An inter‐terrane correlation of the Mizuyagadani Formation with Lower Permian tuffaceous clastic strata in the Kurosegawa terrane and the Nagato tectonic zone of Southwest Japan indicates the presence of an extensive Early Permian magmatic arc(s) that involved almost all of the Paleozoic non‐accretionary‐wedge terranes in Japan. These new biostratigraphic data provide the key to understanding the original relationships among highly disrupted Paleozoic terranes in Japan and northeast Asia.  相似文献   

Middle Permian radiolarians from Anmenkou, Chaohu, Northeastern Yangtze platform, China     

Masao  Kametaka  Hiromi  Nagai  Sizhao  Zhu  Masamichi  Takebe 《Island Arc》2009,18(1):108-125

The biostratigraphy of the Middle Permian Gufeng Formation in the northeastern Yangtze platform is examined based on radiolarians. This study is concentrated on the Anmenkou section in the Chaohu area of Anhui Province, China. The Gufeng Formation is divided into the Phosphate Nodule-bearing Mudstone Member (PNMM) and the Siliceous Rock Member (SRM) in ascending order. The former primarily consists of mudstone including abundant phosphate nodules, and the latter consists mainly of alternating beds of chert, siliceous mudstone and mudstone, with intercalations of porous chert. Ammonoids in the mudstone of the lower PNMM are Wordian. Chert, siliceous mudstone and mudstone of the SRM include abundant radiolarians with sponge spicule assemblages suggestive of the Wordian–Capitanian. Albaillellaria are predominant in the lower SRM, while Entactinaria and Spumellaria are predominant in the middle and upper SRM. These radiolarians correspond to three radiolarian assemblage zones: Pseudoalbaillella longtanensis – Pseudoalbaillella fusiformis , Follicucullus monacanthus , and Follicucullus scholasticus – Ruzhencevispongus uralicus . The assemblage of radiolarians and sponge spicule fauna suggests a depositional depth of 150–500 m. The radiolarian fauna of the Gufeng Formation is considered to be representative of the relatively shallow, tropical radiolarian fauna of the Middle Permian eastern Paleotethys.  相似文献   

Magnetic anomaly lineations from Late Jurassic to Early Cretaceous in the west-central Pacific Ocean   总被引：1，自引：0，他引：1  

Masao Nakanishi  Kensaku Tamaki  Kazuo Kobayashi 《Geophysical Journal International》1992,109(3):701-719

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Phase transition in Ca-poor clinopyroxenes     

Norimasa Shimobayashi  Masao Kitamura 《Physics and Chemistry of Minerals》1991,18(3):153-160

High(C2/c)-low(P2₁/c) phase transition in clinoenstatite and pigeonite was successfully observed in situ at high temperatures for the first time under a transmission electron microscope. The phase transition was revealed to possess the characteristics of a first-order transition, due to the coexistence of both phases separated by the sharp interfaces and the nucleation-growth process. The diffusionless and time-independent reaction suggests that the transition occurs athermal-martensitically. Furthermore, the small or even negative thermal hysteresis and the interface motion suggest that the transition is not a typical type but a thermoelastic type of the martensitic transformation. This type of the transformation, studied extensively in metallurgy in relation to shape memory effect, is first recognized in rock-forming minerals.  相似文献   

Response of a phytoplankton community to nutrient addition under different CO2 and pH conditions     

Takeo Hama  Tomoki Inoue  Risa Suzuki  Hiroto Kashiwazaki  Shigeki Wada  Daisuke Sasano  Naohiro Kosugi  Masao Ishii 《Journal of Oceanography》2016,72(2):207-223

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Observation of the Soya Warm Current using HF ocean radar     

Naoto Ebuchi  Yasushi Fukamachi  Kay I. Ohshima  Kunio Shirasawa  Masao Ishikawa  Toru Takatsuka  Takaharu Daibo  Masaaki Wakatsuchi 《Journal of Oceanography》2006,62(1):47-61

Three High Frequency (HF) ocean radar stations were installed around the Soya/La Perouse Strait in the Sea of Okhotsk in order to monitor the Soya Warm Current (SWC). The frequency of the HF radar is 13.9 MHz, and the range and azimuth resolutions are 3 km and 5 deg., respectively. The radar covers a range of approximately 70 km from the coast. The surface current velocity observed by the HF radars was compared with data from drifting buoys and shipboard Acoustic Doppler Current Profilers (ADCPs). The current velocity derived from the HF radars shows good agreement with that observed using the drifting buoys. The root-mean-square (rms) differences were found to be less than 20 cm s⁻¹ for the zonal and meridional components in the buoy comparison. The observed current velocity was also found to exhibit reasonable agreement with the shipboard ADCP data. It was shown that the HF radars clearly capture seasonal and short-term variations of the SWC. The velocity of the Soya Warm Current reaches its maximum, approximately 1 m s⁻¹, in summer and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 40 km. The surface transport by the SWC shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records at Wakkanai and Abashiri. Deceased.  相似文献   

On the distribution of isothermal layers in the vicinity of the shoal,Kokushô-sone     

Masao Fukasawa 《Journal of Oceanography》1983,39(1):15-21

Data from XBT observations in the vicinity of the shoal, Kokushô-sone (30°00′N, 128°30′E) which is located in the current zone of the Kuroshio in the East China Sea, are analysed to show the distribution of isothermal layers. Isothermal layers are found in abundance in and near a cold water region along the slope of the shoal where the existence of upwelling is suggested. It is found that there is a good spatial correlation between the distribution of isothermal layers and that of cold waters along the slope, and that the distribution of isothermal layers is a helpful indicator for elucidating the nature of oceanic structures in the vicinity of the shoal.  相似文献   

Testing of a towed CTD     

Yukio Fujinawa  Yoshinobu Tsuji  Isao Watabe  Ken Sasaki  Masao Nomoto  Toshiaki Hara  Yoshito Tsuji 《Journal of Oceanography》1980,36(5):253-258

The results of laboratory and field experiments on a CTD measuring unit attached to a controllable towed body is described. It was verified that the three-dimensional distribution of salinity and temperature could be observed with sufficient accuracy (to 0.03 in salinity and to 0.01°C in temperature if proper correction is adopted) while cruising at up to 4 knots. A double integrated A/D converter is used to compensate for effects of extraneous environmental changes.  相似文献   

Algal Growth Potential and the limiting nutrient in Mikawa Bay     

Masao Kondo  Tsutomu Sakai  Hajime Yamamoto  Yukio Arakawa 《Journal of Oceanography》1984,40(5):391-396

The Algal Growth Potential (AGP) of water samples collected off Gamagori in Mikawa Bay was measured from May 1978 through February 1979, and the limiting nutrient was determined using regression analysis and enrichment bioassays. The surface and bottom water samples had AGP that produced increments of chemical oxygen demand (COD) of 2.1 mg l^–1 and 3.1 mg l^–1, respectively, on average. These values ofCOD correspond to 46% and 97% of the average COD values of the raw water samples at the surface and bottom, respectively. Seasonal changes of AGP showed a close correlation with those of dissolved inorganic nitrogen (DIN) concentration. Enrichment bioassays showed that DIN was the most deficient nutrient. The DIN:phosphate-phosphorus (PO₄ ^3–-P) ratios and DIN: dissolved phosphorus (DP) ratios in the water samples were below the cellular N:P ratios of the natural algal populations. These results suggest that AGP was mainly limited by DIN concentration.  相似文献   

N2 fixation variability in the oligotrophic Sulu Sea, western equatorial Pacific region over the past 83 kyr     

Keiji Horikawa  Masao Minagawa  Yoshihisa Kato  Masafumi Murayama  Seiya Nagao 《Journal of Oceanography》2006,62(4):427-439

N₂ fixation is an important biological process that adds new nitrogen to oceans and plays a key role in modulating the oceanic nitrate inventory. However, it is not known how, when, and where N₂ fixation rates have varied in response to past climate changes. This study presents a new record of nitrogen isotopic composition (δ¹⁵N) over the last 83 kyr from a sediment core (KH02-4 SUP8) taken in the Sulu Sea in the western equatorial Pacific region; data allow the N₂ fixation variability in the sea to be reconstructed. Sediments, sinking, and suspended particulate organic matter (POM) all have lighter isotopic values compared to the δ¹⁵N values of substrate nitrate (av. 5.8‰) in North Pacific Intermediate Water. These lighter δ¹⁵N values are regarded as reflecting N₂ fixation in the Sulu Sea surface water. A δ¹⁵N mass balance model shows that N₂ fixation rates were significantly enhanced during 54–34 kyr in MIS-3 and MIS-2. It has been speculated that higher interglacial denitrification rates in the Arabian Sea and the eastern tropical Pacific would have markedly decreased the global oceanic N inventory and contributed to the increase in N₂ fixation in oligotrophic regions, but such a model was not revealed by our study. It is possible that changes in N₂ fixation rates in the Sulu Sea were regional response, and accumulation of phosphate in the surface waters due to enhanced monsoon-driven mixing is thought to have stimulated enhancements of N₂ fixation during MIS-3 and MIS-2.  相似文献