A major sulphur isotope event at c. 510 Ma: a possible anoxia–extinction–volcanism connection during the Early–Middle Cambrian transition?     

M.L. Hough  G.A. Shields  L.Z. Evins  H. Strauss  R.A. Henderson  S. Mackenzie 《地学学报》2006,18(4):257-263

A new approach to constraining seawater δ³⁴S and sulphate concentration using francolite‐bound sulphate reveals an abrupt increase in δ³⁴S to +50‰ around the Early–Middle Cambrian boundary. Such high δ³⁴S values are best explained by increased rates of pyrite burial due to ocean anoxia coupled with an increased sensitivity of the ocean sulphate reservoir to perturbations due to low sulphate concentrations of 500–700 μgL^?1. We argue that the spread of anoxic waters at this time was partly the result of greenhouse warming related to the eruption of the Kalkarindji Large Igneous Province of northern Australia and that it triggered the collapse of early metazoan reef ecosystems during the latest Early Cambrian. Mass extinctions of the last 260 Myr have all coincided with enhanced volcanic activity, while several are also associated with positive shifts in seawater δ³⁴S. Extending this correlation back in time further implicates volcanically induced climate change as a major determining factor in biosphere evolution. Terra Nova, 18, 257–263, 2006  相似文献   

Na-rich carbonate inclusions in perovskite and calzirtite from the Guli intrusive Ca-carbonatite,polar Siberia     

L. N. Kogarko  D. A. Plant  C. M. B. Henderson  B. A. Kjarsgaard 《Contributions to Mineralogy and Petrology》1991,109(1):124-129

Carbonate phases, some rich in Na₂O and comparatively rich in SrO and BaO, occur as inclusions in perovskite and calzirtite (Ca₂Zr₅Ti₂O₁₆) in the carbonatite of the Guli complex, Siberia. This is the first record of alkali carbonates, akin to nyerereite [Na₂Ca(CO₃)₂], in plutonic igneous rocks. The inclusion populations suggest that the parental magma of the complex was Ca-rich but developed Na-rich differentiates during the latest stages. This points to the dominant calcic carbonatites of the complex not being derivatives of alkali-rich parental carbonatites. These alkali-rich carbonate inclusions (and rare inclusions of djerfisherite) have been preserved due to the resistance of perovskite and calzirtite to processes of leaching, hydrothermal alteration and weathering.  相似文献   

CS,C34S,and CH3OH observations of the molecular cloud associated with NGC 7538     

Osamu Kameya  Tatsuhiko Hasegawa  Naomi Hirano  Munezo Seki  Makoto Tosa  Yoshiaki Taniguchi  Keiya Takakubo 《Astrophysics and Space Science》1986,118(1-2):449-451

CS(J=1–0), C³⁴S(J=1–0), and CH₃OH(1₀–0₀A and E) emission lines in the core region of molecular cloud associated with NGC 7538 have been surveyed at angular resolution of 33. Distribution of CS column density shows two prominent peaks. Both blue and red wings in CS line are most prominent at 30 northwest of IRS 11.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.This work was carried out under the common use observation program at the Nobeyama Radio Observatory (NRO). NRO, a branch of the Tokyo Astronomical Observatory, University of Tokyo, is a cosmic radio observing facility open to outside users.  相似文献   

Can turbidity caused by Corophium volutator (Pallas) activity be used to assess sediment toxicity rapidly?     

Briggs AD  Greenwood N  Grant A 《Marine environmental research》2003,55(3):181-192

The standard toxicity test organism, Corophium volutator, exhibits a behavioural response to contaminated sediments that causes increased turbidity of overlying water. We quantify the effects of this response to an estuarine sediment spiked with copper and hydrocarbon contaminated sediments from an oil installation in the North Sea. Turbidity measured 24 h after the start of a toxicity test shows a strong relationship with contaminant concentrations and with mortality after 10 days. Turbidity measurements can therefore give a rapid indication of sediment toxicity, permitting a reduction in storage time of sediments to be used in dilution series and toxicity identification evaluation (TIE) tests, reducing the likelihood of contaminants degrading prior to testing.  相似文献   

Multi-AUV Control and Adaptive Sampling in Monterey Bay   总被引：3，自引：0，他引：3  

Edward Fiorelli Naomi Ehrich Leonard Pradeep Bhatta Derek A. Paley Ralf Bachmayer David M. Fratantoni 《Oceanic Engineering, IEEE Journal of》2006,31(4):935-948

Operations with multiple autonomous underwater vehicles (AUVs) have a variety of underwater applications. For example, a coordinated group of vehicles with environmental sensors can perform adaptive ocean sampling at the appropriate spatial and temporal scales. We describe a methodology for cooperative control of multiple vehicles based on virtual bodies and artificial potentials (VBAP). This methodology allows for adaptable formation control and can be used for missions such as gradient climbing and feature tracking in an uncertain environment. We discuss our implementation on a fleet of autonomous underwater gliders and present results from sea trials in Monterey Bay in August, 2003. These at-sea demonstrations were performed as part of the Autonomous Ocean Sampling Network (AOSN) II project  相似文献   

Cu 2p absorption spectroscopy as a probe for the site occupancy of (ZnxCu1−x)WO4 solid solution     

P. F. Schofield  C. M. B. Henderson  S. A. T. Redfern  G. van der Laan 《Physics and Chemistry of Minerals》1993,20(6):375-381

The solid solution sanmartinite (ZnWO₄)—cuproscheelite (CuWO₄) has been studied using Cu 2p X-ray absorption spectroscopy. While a single L₃ absorption peak is observed for CuWO₄, two distinct L₃ absorption peaks with a separation of ～0.8 eV are observed for the intermediate samples in the solid solution. The two peaks represent distinct Cu sites: one with all CuO₆ next nearest neighbours in the (Cu,Zn)O₆ chains, another having at least one ZnO₆ next nearest neighbour. Both sites show a linear increase in covalency as a function of increasing Cu-content. The relative intensities of the two absorption peaks is dependent upon the Cu-content and has been used to model the site occupancies. The results reveal that the local structural effects can be associated with a composition-dependent structural phase transition from P2/c (ZnWO₄) to P $\bar 1$ (CuWO₄). Deviations from a single-site model are explained in terms of the local environments, and evidence for site preferences and local clustering are explored.  相似文献   

The Wuchiapingian–Changhsingian boundary (Upper Permian) at Meishan of Changxing County, South China     

Wang Yue  Shen Shuzhong  Cao Changqun  Wang Wei  Charles Henderson  Jin Yugan   《Journal of Asian Earth Sciences》2006,26(6):575-583

Section D at Meishan, Changxing County in the Zhejiang Province, China, has been extensively studied in various aspects of the stratigraphy during the past 20 years. It was ratified by the International Union of Geological Sciences (IUGS) as the Global Standard Stratotype Section and Point (GSSP) for the Permian–Triassic boundary in 2000, and is also a potential stratotype for the Wuchiapingian–Changhsingian boundary. However, the contact relationship between the Longtan (Wuchiapingian) and Changxing (Chainghsingian) formations has been a controversial subject for years. Recent studies on Section C, about 300 m west of Section D, at Meishan confirm a complete depositional succession around the boundary and suggest that the proposed boundary level, the FAD of Clarkina wangi within the lineage from C. longicuspidata to C. wangi, is consistent with the first appearance of the index Changhsingian fusulinid Palaeofusulina sinensis and tapashanitid ammonoids.  相似文献   

2500年来艾比湖的环境演变信息   总被引：22，自引：9，他引：22  

阎顺  穆桂金  远藤邦彦  Nobuhiko Handa  Masao Uchida  Naomi Harada 《干旱区地理》2003,26(3):227-232

通过对艾比湖缘1，8m浅孔的沉积相和孢粉组合，结合14C测年资料分析。指出近2500年来艾比湖的沉积环境总体是比较稳定的，但由于气候波动引起艾比湖水位曾发生较明显的变化。约在公元前300～400年，是艾比湖面积缩小时期；约公元前300—公元300年，即东周末至西晋，是艾比湖水位较高时期；约公元300—1400年，即东晋至15世纪初，是艾比湖的高水位时期；约15世纪初至17世纪中是艾比湖的水位下降期，但水位比现代仍然高；约17世纪中至19世纪初的小冰期是艾比湖的水位上升期。研究还提供了历史时期湖泊的盐度变化和湖周发生大火的信息。  相似文献   

Makah and Inuit to resume whaling     

Shirley Henderson 《Marine pollution bulletin》1997,34(12):989

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A rain on snow climatology and temporal analysis for the eastern United States     

Lori J. Wachowicz  Thomas L. Mote  Gina R. Henderson 《自然地理学》2020,41(1):54-69

ABSTRACT

Rain-on-snow (ROS) has the potential to produce devastating floods by enhancing runoff from snowmelt. Although a common phenomenon across the eastern United States, little research has focused on ROS in this region. This study used a gridded observational snow dataset from 1960–2009 to establish a comprehensive seasonal climatology of ROS for this region. Additionally, different rain and snow thresholds were compared while considering temporal trends in ROS occurrence at four grid cells representing individual locations. Results show most ROS events occur in MAM (March-April-May). ROS events identified with rainfall >1 cm are more frequent near the east coast and events identified with >1 cm snow loss are more common in higher latitudes and/or elevations. Decreasing trends in DJF (December-January-February) ROS events were identified near the coastal areas, with increasing trends in the northern portion of the domain. Significant decreasing trends in MAM ROS are likewise present on a regional scale. Factors playing a role in snowpack depth and rainfall, such as movement of storm tracks in this region, should be considered with future work to discern mechanisms causing the changes in ROS frequency.  相似文献