Variability of Isotope and Major Ion Chemistry in the Allequash Basin, Wisconsin   总被引：1，自引：0，他引：1  

John F. Walker  Randall J. Hunt  Thomas D. Bullen  David P. Krabbenhoft  Carol Kendall 《Ground water》2003,41(7):883-894

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Characterization of the physical and hydraulic properties of the sediment in karst aquifers of the Springfield Plateau,Central Missouri,USA     

Eric W. Peterson  Carol M. Wicks 《Hydrogeology Journal》2003,11(3):357-367

Physical and hydraulic properties of sediment from two karst aquifers were measured to determine (1) the similarity of sediment between karst aquifer systems and (2) the importance of sediment in modeling flow through karst aquifers. The sediment from the two systems was similar in size and composition. Within both aquifers, the silt-sized sediment was composed primarily of quartz, with minor amounts of plagioclase and clays. Hydraulic conductivity of the sediment measured directly (falling-head test) ranged from 1.61×10⁻⁷ to 1.33×10⁻⁶ m s^–1 and estimated using the Campbell equation ranged from 8.30×10⁻⁸ to 8.98×10⁻⁷ m s^–1. These values of hydraulic conductivity fall within the span of hydraulic conductivities for carbonate rocks, indicating that the sediment and carbonate matrix could be represented as one mathematical unit in modeling flow through karst aquifers. Statistical agreement in the hydraulic conductivity values generated by the two methods indicates that the estimation technique could be used to calculate hydraulic conductivities; thus allowing karst scientist to collect bulk sediment samples instead of having to collect cores from within karst aquifers. Electronic Publication  相似文献   

Mid-Pleistocene lavas from the Seguam volcanic center,central Aleutian arc: closed-system fractional crystallization of a basalt to rhyodacite eruptive suite   总被引：7，自引：0，他引：7  

Bradley S. Singer  James D. Myers  Carol D. Frost 《Contributions to Mineralogy and Petrology》1992,110(1):87-112

In contrast to adjacent volcanic centers of the modern central Aleutian arc, Seguam Island developed on strongly extended arc crust. K-Ar dates indicate that mid-Pleistocene, late-Pleistocene, and Holocene eruptive phases constitute Seguam. This study focuses on the petrology of the mid-Pleistocene, 1.07–07 Ma, Turf Point Formation (TPF) which is dominated by an unusual suite of porphyritic basalt and basaltic andesite lavas with subordinate phenocryst-poor andesite to rhyodacite lavas. Increasing whole-rock FeO^*/MgO from basalt to dacite, the anhydrous Plag+Ol+Cpx±Opx±Mt phenocryst assemblage, groundmass pigeonite, and the reaction Ol+Liq=Opx preserved in the mafic lavas indicate a tholeiitic affinity. Thermometry and comparison to published phase equilibria suggests that most TPF basalts crystallized Plag+Ol+Cpx±Mt at 1160°C between about 3–5 kb (±1–2% H₂O), andesites crystallized Plag+Cpx+Opx±Mt at 1000°C between 3–4 kb with 3–5% H₂O, and dacites crystallized Plag +Cpx±Opx±Mt at 1000°C between 1–2 kb with 2–3% H₂O. All lavas crystallized at f _{o 2} close to the NNO buffer. Mineral compositions and textures indicate equilibrium crystallization of the evolved lavas; petrographic evidence of open-system mixing or assimilation is rare. MgO, CaO, Al₂O₃, Cr, Ni, and Sr abundances decrease and K₂O, Na₂O, Rb, Ba, Zr, and Pb increase with increasing SiO₂ (50–71%). LREE enrichment [(Ce/Yb)_n=1.7±0.2] characterizes most TPF lavas; total REE contents increase and Eu anomalies become more negative with increasing SiO₂. Relative to other Aleutian volcanic centers, TPF basalts and basaltic andesites have lower K₂O, Na₂O, TiO₂, Rb, Ba, Sr, Zr, Y, and LREE abundances. ⁸⁷Sr/⁸⁶Sr ratios (0.70361–0.70375) and ratios of ²⁰⁶Pb/²⁰⁴Pb (18.88–18.97), ²⁰⁷Pb/²⁰⁴Pb (15.58–15.62), ²⁰⁸Pb/²⁰⁴Pb (38.46–38.55) are the highest measured for any suite of lavas in the oceanic portion of the Aleutian arc. Conversely, Nd values (+5.8 to+6.7) are among the lowest from the Aleutians. Sr, Nd, and Pb ratios are virtually constant from basalt through rhyodacite, whereas detectable isotopic heterogenity is observed at most other Aleutian volcanic centers. Major and trace element, REE, and Sr, Nd, and Pb isotopic compositions are consistent with the basaltic andesitic, andesitic, dacitic, and rhyodacitic liquids evolving from TPF basaltic magma via closed-system fractional crystallization alone. Fractionation models suggest that removal of 80 wt% cumulate (61% Plag, 17% Cpx, 12% Opx, 7% Ol, and 3% Mt) can produce 20 wt% rhyodacitic residual liquid per unit mass of parental basaltic liquid. Petrologic and physical constraints favor segregation of small batches of basalt from a larger mid-crustal reservoir trapped below a low-density upper crustal lid. In these small magma batches, the degree of cooling, crystallization, and fractionation are functions of the initial mass of basaltic magma segregated, the thermal state of the upper crust, and the magnitude of extension. Tholeiitic magmas erupted at Seguam evolved by substantially different mechanisms than did calc-alkaline lavas erupted at the adjacent volcanic centers of Kanaga and Adak on unextended arc crust. These variable differentiation mechanisms and liquid lines of descent reflect contrasting thermal and mechanical conditions imposed by the different tectonic environments in which these centers grew. At Seguam, intra-arc extension promoted eruption of voluminous basalt and its differentiates, unmodified by interaction with lower crustal or upper mantle wallrocks.  相似文献   

Development and assessment of an analytical system for the accurate and continual measurement of total dissolved inorganic carbon     

Carol Robinson  P. J. leB. Williams 《Marine Chemistry》1991,34(3-4)

An automated coulometric titration system based on that described by Johnson, Sieburth, Williams and Brandstrom (1987, Mar. Chem., 21: 117–133) has been evolved for the accurate and continual measurement of total dissolved inorganic carbon (TCO₂). The instrument achieves an analytical precision (1 SD) of ±0.5–1.0 μmol kg⁻¹ (0.025–0.05%). The accuracy of the system has been examined by a limited comparison with other coulometric-based titrators and with a manometric-based system; agreement was to 1 μmol kg⁻¹. The capability for automatic continual analysis allows surface mapping of TCO₂; a sample rate of 10 analyses h⁻¹ gives a mapping resolution of 1–2 km. Provision for frequent standardization with a liquid substandard has been included in the development. The ability to achieve high-density analyses while maintaining interlaboratory consistency and standardization constitutes a vital contribution to surveys of ocean carbon chemistry (e.g. Joint Global Ocean Flux Study, World Ocean Circulation Experiment).  相似文献   

Adaptation of the polychaete Neanthes Arenaceodentata to copper     

Carol E. Pesch  Gerald L. Hoffman 《Marine environmental research》1982,6(4):307-317

Neanthes arenaceodentata were exposed to 292, 146, 92 and 56 μg litre⁻¹ Cu (measured) and control seawater after a 27-day pre-exposure to a sublethal concentration of Cu (10, 16 and 28 μg litre⁻¹ and control) to determine if the worms increased their tolerance to Cu after the pre-treatment. The worms pre-exposed to 28 μg litre⁻¹ Cu were significantly more resistant to Cu toxicity than control and 10 and 16 μg litre⁻¹ Cu pre-exposed worms. For example, the time to 50 % mortality at 92 μg litre⁻¹ Cu was 18 and 11 days for worms pre-exposed to 28 μg litre⁻¹ Cu and control conditions, respectively. The net rate of Cu uptake during the toxicity test was lower for worms pre-exposed to 28 μg litre⁻¹ Cu than for the control and 10 and 16 μg litre⁻¹ Cu pre-exposed worms. For example, the net rate of Cu uptake at 292 μg litre⁻¹ Cu by worms pre-exposed to 28 μg litre⁻¹ Cu and control conditions was 42 and 102 μg g⁻¹ day ⁻¹, respectively.  相似文献   

Micromorphological analysis of liquefaction features in alluvial and coastal environments of Christchurch,New Zealand     

Monica Giona Bucci  Carol M. Smith  Peter C. Almond  Pilar Villamor  Martitia P. Tuttle 《Sedimentology》2019,66(3):963-982

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Mineral matter and trace elements in coals of the Gunnedah Basin, New South Wales, Australia     

Colin R. Ward  D. A. Spears  Carol A. Booth  Ian Staton  Lila W. Gurba 《International Journal of Coal Geology》1999,40(4):2843

The concentrations of major and trace inorganic elements in a succession of Permian coals from the Gunnedah Basin, New South Wales, have been determined by X-ray fluorescence techniques applied to both whole-coal and high-temperature ash samples. The results have been evaluated in the light of quantitative data on the minerals in the same coals, determined from X-ray diffraction study of whole-coal samples using a Rietveld-based interpretation program ( ™), to determine relationships of the trace elements in the coals to the mineral species present. Comparison of the chemical composition of the coal ash interpreted from the quantitative mineralogical study to the actual ash composition determined by XRF analysis shows a high degree of consistency, confirming the validity of the XRD interpretations for the Gunnedah Basin materials. Quartz, illite and other minerals of detrital origin dominate the coals in the upper part of the sequence, whereas authigenic kaolinite is abundant in coals from the lower part of the Permian succession. These minerals are all reduced in abundance, however, and pyrite is a dominant constituent, in coals formed under marine influence at several stratigraphic levels. Calcite and dolomite occur as cleat and fracture infillings, mostly in seams near the top and bottom of the sequence. The potassium-bearing minerals in the detrital fraction are associated with significant concentrations of rubidium, and the authigenic kaolinite with relatively high proportions of titanium. Zirconium is also abundant, with associated P and Hf, in the Gunnedah Basin coal seams. Relationships exhibited by Ti, Zr, Nd and Y are consistent with derivation of the original sediment admixed with the seams from an acid volcanic source. Pyrite in the coals is associated with high concentrations of arsenic and minor proportions of thallium; no other element commonly associated with sulphides in coals, however, appears to occur in significant proportions with the pyrite in the sample suite. Small concentrations of Cl present in the coal are inversely related to the pyrite content, and appear to represent ion-exchange components associated with the organic matter. Strontium and barium are strongly associated with the cleat-filling carbonate minerals. Ge and Ga appear to be related to each other and to the coal's organic matter. Cr and V are also related to each other, as are Ce, La, Nd and Pr, but none of these show any relationship to the organic matter or a particular mineral component.  相似文献   

Integrating geochronologic and instrumental approaches across the Bengal Basin     

Elizabeth L. Chamberlain  Steven L. Goodbred  Richard Hale  Michael S. Steckler  Jakob Wallinga  Carol Wilson 《地球表面变化过程与地形》2020,45(1):56-74

Constraining time is of critical importance to evaluating the rates and relative contributions of processes driving landscape change in sedimentary basins. The geomorphic character of the field setting guides the application of geochronologic or instrumental tools to this problem, because the viability of methods can be highly influenced by geomorphic attributes. For example, sediment yield and the linked potential for organic preservation may govern the usefulness of radiocarbon dating. Similarly, the rate of sediment transport from source to sink may determine the maturity and/or light exposure of mineral grains arriving in the delta and thus the feasibility of luminescence dating. Here, we explore the viability and quirks of dating and instrumental methods that have been applied in the Bengal Basin, and review the records that they have yielded. This immense, dynamic, and spatially variable system hosts the world's most inhabited delta. Outlining a framework for successful chronologic applications is thus of value to managing water and sediment resources for humans, here and in other populated deltas worldwide. Our review covers radiocarbon dating, luminescence dating, archaeological records and historical maps, short-lived radioisotopes, horizon markers and rod surface elevation tables, geodetic observations, and surface instrumentation. Combined, these tools can be used to reconstruct the history of the Bengal Basin from Late Pleistocene to present day. The growing variety and scope of Bengal Basin geochronology and instrumentation opens doors for research integrating basin processes across spatial and temporal scales. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.  相似文献   

Ceres internal structure from geophysical constraints          下载免费PDF全文

Scott D. King  Julie C. Castillo‐Rogez  M. J. Toplis  Michael T. Bland  Carol A. Raymond  Christopher T. Russell 《Meteoritics & planetary science》2018,53(9):1999-2007

Thermal evolution modeling has yielded a variety of interior structures for Ceres, ranging from a modestly differentiated interior to more advanced evolution with a dry silicate core, a hydrated silicate mantle, and a volatile‐rich crust. Here we compute the mass and hydrostatic flattening from more than one hundred billion three‐layer density models for Ceres and describe the characteristics of the population of density structures that are consistent with the Dawn observations. We show that the mass and hydrostatic flattening constraints from Ceres indicate the presence of a high‐density core with greater than a 1σ probability, but provide little constraint on the density, allowing for core compositions that range from hydrous and/or anhydrous silicates to a mixture of metal and silicates. The crustal densities are consistent with surface observations of salts, water ice, carbonates, and ammoniated clays, which indicate hydrothermal alteration, partial fractionation, and the possible settling of heavy sulfide and metallic particles, which provide a potential process for increasing mass with depth.  相似文献   

Gap analysis on open data interconnectivity for disaster risk research     

Guoqing Li  Jing Zhao  Virginia Murray  Carol Song  Lianchong Zhang 《地球空间信息科学学报》2019,22(1):45-58

Open data strategies are being adopted in disaster-related data particularly because of the need to provide information on global targets and indicators for implementation of the Sendai Framework for Disaster Risk Reduction 2015–2030. In all phases of disaster risk management including forecasting, emergency response and post-disaster reconstruction, the need for interconnected multidisciplinary open data for collaborative reporting as well as study and analysis are apparent, in order to determine disaster impact data in timely and reportable manner. The extraordinary progress in computing and information technology in the past decade, such as broad local and wide-area network connectivity (e.g. Internet), high-performance computing, service and cloud computing, big data methods and mobile devices, provides the technical foundation for connecting open data to support disaster risk research. A new generation of disaster data infrastructure based on interconnected open data is evolving rapidly. There are two levels in the conceptual model of Linked Open Data for Global Disaster Risk Research (LODGD) Working Group of the Committee on Data for Science and Technology (CODATA), which is the Committee on Data of the International Council for Science (ICSU): data characterization and data connection. In data characterization, the knowledge about disaster taxonomy and data dependency on disaster events requires specific scientific study as it aims to understand and present the correlation between specific disaster events and scientific data through the integration of literature analysis and semantic knowledge discovery. Data connection concepts deal with technical methods to connect distributed data resources identified by data characterization of disaster type. In the science community, interconnected open data for disaster risk impact assessment are beginning to influence how disaster data are shared, and this will need to extend data coverage and provide better ways of utilizing data across domains where innovation and integration are now necessarily needed.  相似文献