Ecologic and taxonomic diversification in the Mesozoic brackish-water bivalve faunas in Japan, with emphasis on infaunalization of heterodonts     

Yasuo Kondo  Takeshi Kozai  Naoki Kikuchi  Kazuhiro Sugawara 《Gondwana Research》2006,10(3-4):316-327

Mesozoic brackish-water bivalve faunas in Japan diversified in three steps: at the beginning of the Early Jurassic, Early and Late Cretaceous. The Hettangian Niranohama Fauna in northeastern Honshu represents the establishment of a heterodont-dominated brackish-water fauna that persisted until the early Late Cretaceous. No similar composition is known from the Triassic. The infauna consists mostly of non-siphonate and some short-siphonate heterodonts, while the epifauna is represented by diverse pteriomorphian families. In the Early Cretaceous Tetori Group in central Honshu, the long-siphonate heterodonts Tetoria (Corbiculidae) and the semi-infaunal soft-bottom oyster Crassostrea appeared. The evolutionary diversification of the latter, known as the most important element of modern brackish-water faunas, may thus originate at that time. In the early Late Cretaceous (Cenomanian) of the Goshoura and Mifune Groups in west Kyushu, several euryhaline deep-burrowing heterodont families, such as Veneridae and Tellinidae, further diversified in the brackish and marine environments. The Late Cretaceous is characterized by massive shell biolithic beds in which large Crassostrea species are common, a feature common for Cenozoic brackish-water faunas. The long-term changes in the composition of the brackish-water faunas in Japan represents thus an evolutionary record, irrespective of the severe physiological and environmental conditions imposed on the highly conservative nature of the fauna.  相似文献   

Temperature trends in Japan: 1900–1996     

S. Yue  M. Hashino 《Theoretical and Applied Climatology》2003,75(1-2):15-27

Summary ?Long-term trends in annual, seasonal, and monthly mean temperature (abbreviated as AMT, SMT, MMT, respectively) in Japan are investigated. The magnitude of a trend is measured by assuming it to be linear. The statistical significance of a site trend is assessed by the Mann-Kendall (MK) with consideration of serial correlation. The statistical field significance of trends in three major climatic regions: Hokkaido (I), areas adjacent to the Japan sea (II), and to the Pacific Ocean (III), is evaluated by the bootstrapping test which preserves cross-correlation among sites. From 1900 to 1996, AMT increased from 0.51 to 2.77 °C averaged across all 46 sites. At the regional scale, AMT increased by 1.38, 1.08, and 1.32 °C in regions I, II, and III, respectively. The trends at both sites and regions are statistically significant even at the significance level (α) of 0.005. SMT increased from 0.47 to 3.69 °C at all the 19 available sites with the highest increases in winter and spring. Except for a few series, the changes in SMT are statistically significant at α = 0.01. The upward trends in SMT are statistically significant even at α = 0.001 in both regions II and III. MMT at 19 sites increased within a wide range from 0.17 to 4.12 °C. The increases are largest in the winter and spring months, and most of the site increases are statistically significant at α = 0.05. The trends are statistically significant at α = 0.025 and 0.001 in regions II and III, respectively. The trends in both SMT and MMT in region III are larger than those in region II. Received January 28, 2002; revised November 11, 2002; accepted December 1, 2002 Published online May 19, 2003  相似文献   

Simultaneous identification of time and space variant dynamic soil properties during the 1995 Hyogoken-Nanbu earthquake   总被引：2，自引：0，他引：2  

A. Mikami  T. Sawada 《Soil Dynamics and Earthquake Engineering》2005,25(1):69-77

Time and space variant soil properties at a liquefied site were simultaneously identified in the time domain by using borehole array strong motion records. During soil liquefaction at a site, soils usually show a wide variety of non-linear behavior along the depth as well as non-stationary behavior. Strong ground motion records were obtained at Port Island borehole array observatory, Kobe, during the 1995 Hyogoken-Nanbu earthquake. In this study, the instrumented soil was modeled by the equivalent linear MDOF system, and an extended Kalman filter with local iteration was employed for the identification of the soils. The identification process was successfully conducted, and the stress–strain relationships of the soils at the liquefied site were obtained from different depths all at once.  相似文献   

Numerical simulation of 3D liquefaction disasters using an automatic time stepping method     

Xiwen Zhang  Xiaowei Tang  Ryosuke Uzuoka 《Natural Hazards》2015,77(2):1275-1287

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Dynamics of unsaturated poroelastic solids at finite strain     

Ryosuke Uzuoka  Ronaldo I. Borja 《国际地质力学数值与分析法杂志》2012,36(13):1535-1573

We derive the governing equations for the dynamic response of unsaturated poroelastic solids at finite strain. We obtain simplified governing equations from the complete coupled formulation by neglecting the material time derivative of the relative velocities and the advection terms of the pore fluids relative to the solid skeleton, leading to a so‐called u^s ? p^w ? p^a formulation. We impose the weak forms of the momentum and mass balance equations at the current configuration and implement the framework numerically using a mixed finite element formulation. We verify the proposed method through comparison with analytical solutions and experiments of quasi‐static processes. We use a neo‐Hookean hyperelastic constitutive model for the solid matrix and demonstrate, through numerical examples, the impact of large deformation on the dynamic response of unsaturated poroelastic solids under a variety of loading conditions. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Quaternary vertical offset and average slip rate of the Nojima Fault on Awaji Island, Japan   总被引：5，自引：0，他引：5  

Akihiro Murata  Keiji Takemura  Takao Miyata  Aiming Lin 《Island Arc》2001,10(3-4):360-367

Abstract Drilling was carried out to penetrate the Nojima Fault where the surface rupture occurred associated with the 1995 Hyogo-ken Nanbu earthquake. Two 500 m boreholes were successfully drilled through the fault zone at a depth of 389.4 m. The drilling data show that the relative uplift of the south-east side of the Nojima Fault (south-west segment) was approximately 230 m. The Nojima branch fault, which branches from the Nojima Fault, is inferred to extend to the Asano Fault. From the structural contour map of basal unconformity of the Kobe Group, the vertical component of displacement of the Nojima branch–Asano Fault is estimated to be 260–310 m. Because the vertical component of displacement on the Nojima Fault of the north-east segment is a total of those of the Nojima Fault of the south-west segment and of the Nojima branch–Asano Fault, it is estimated to total to 490–540 m. From this, the average vertical component of the slip rate on the Nojima Fault is estimated to be 0.4–0.45 m/10³ years for the past 1.2 million years.  相似文献   

Nutrients adsorption from seawater by new porous carrier made from zeolitized fly ash and slag     

Khelifi O  Kozuki Y  Murakami H  Kurata K  Nishioka M 《Marine pollution bulletin》2002,45(1-12):311-315

This study investigated the adsorption and precipitation of phosphate by blast furnace slag (BFS) separately.

In order to evaluate the adsorption capacity of BFS, BFS was treated before its use by acid. The authors aim to develop a new porous carrier to adsorb simultaneously ammonium and phosphate from seawater under eutrophic conditions. The current paper deals with a promising new approach to improve the utilization of some industrial solid wastes such as BFS and zeolite synthesized from fly ash [ZFA(Fe)] by their solidification to cylindrical porous carriers using a hydrothermal hot-pressing (HHP) method.

Attempts to produce porous carriers using an arranged HHP method with different porosities (24%, 40% and 52% (v/v)) were carried out. Physical properties of carriers such as porosity, compressive strength and height have been investigated. Laboratory studies showed strong evidence that the porous carrier was very selective towards phosphate and ammonium. The results demonstrated the role of porosity in enhancing phosphate and ammonium adsorption by the increase of the surface area per weight. The estimates of the parameters and the correlation coefficients according to the Freundlich equations revealed that adsorption was related to the porosity of carriers and phosphate and ammonium were adsorbed well on the carriers having large porosity.

The results suggested that developing carrier with high porosity was a promising way to enhance nutrients adsorption.  相似文献   

Shigar valley gemstones,their chemical composition and origin,Skardu, Gilgit-Baltistan,Pakistan     

Muhammad Hassan Agheem  Mohammad Tahir Shah  Tahseenullah Khan  Mamoru Murata  Muhammad Arif  Humaira Dars 《Arabian Journal of Geosciences》2014,7(9):3801-3814

A variety of gemstones is being mined in the Shigar valley, Skardu, Pakistan. These include beryl (goshenite and aquamarine), tourmaline (schorl), garnet (almandine–spessartine), apatite, topaz, fluorite, zoisite, clinozoisite, and axinite, mostly occurring in complex or zoned pegmatites and metamorphic rocks. These have been analyzed using electron probe micro-analyzer and X-ray diffractometer. The mineral chemistry of each gemstone is similar to its respective typical gemstone variety with homogenous chemical composition. Field and chemical characteristics suggest that beryl, tourmaline, garnet, apatite, topaz, and fluorite are occurring in zoned pegmatites which are largely formed by magmatic hydrothermal fluids in the cavities and vugs within the intermediate zone. However, zoisite, clinozoisite, and axinite may have a metamorphic and/or metasomatic origin.  相似文献   

Widespread distribution and molecular diversity of diatom frustule bound aliphatic long chain polyamines (LCPAs) in marine sediments     

《Organic Geochemistry》2012

The siliceous skeletal remains of diatoms are a primary component of sediments, covering vast areas of the sea floor. We used high performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC–ESI–MSⁿ) under high resolution time-of-flight MS (TOF-MS) conditions, as well as nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR), to investigate the distribution and molecular diversity of long chain polyamines (LCPAs) entrapped in sedimentary diatom biosilica in sediments from the Indian sector of the Southern Ocean, the Bering Sea and the Northeast Pacific. This revealed the existence of complex polyamine populations with both known and unknown structural features, including the presence of ketone and carboxylic acid groups in the LCPA backbone, functional groups that likely modulate the silica precipitating properties of LCPAs in the environment and which may constitute points of initial silica deposition (Wallace, A.F., De Yoreso, J.J., Dove, P.M., 2009. Kinetics of silica nucleation on carboxy- and amine-terminated surfaces: insights for biomineralization. Journal of the American Chemical Society 131, 5244–5250). Although various LCPA species overlapped between samples (putrescine-based LCPAs with various degrees of methylation and N-methyl propylamine repeat units were ubiquitous in all samples), clear regional differences were shown in composition and structural characteristics, likely reflecting the various diatom species contributing to the total LCPA pool for each sedimentary environment. We further show, using scanning electron microscopy and energy dispersive X-ray analysis (SEM–EDX) that LCPAs purified from diatom skeletal remains rapidly re-direct the formation of silica nanospheres in vitro, and become embedded in the precipitated silicified matrix, forming an LCPA–silica composite material. The results show that aliphatic polyamines produced by diatoms for morphogenesis of their cell walls are widespread in sediments where the fossil frustules are preserved. These newly assigned components constitute useful biological markers of diatom input to sediments.  相似文献   

Middle Jurassic radiolarian chert,Indarung, Padang District,and its implications for the tectonic evolution of western Sumatra,Indonesia     

《Journal of Asian Earth Sciences》2001,19(1-2):31-44

Radiolaria from chert in the Indarung Area belong to the Transhsuum hisuikyoense Zone, indicating an Aalenian, lower Middle Jurassic, age. Carbonate in the area has been dated as Upper Jurassic to Lower Cretaceous from the occurrence of Lovcenipora, and overlying tuff has given a radiometric K/Ar age of 105±3 (Albian, uppermost Lower Cretaceous). The chert and carbonate are probably in tectonic contact, with the chert faulted into the limestone during ENE-directed compression. This comprises one of the best dated occurrences of allochthonous material in Sumatra and confirms the accretion of oceanic material along the Sunda margin during Mid- to Late-Cretaceous times.  相似文献