CLIMATE CHANGE AND THE BATHURST CARIBOU HERD IN THE NORTHWEST TERRITORIES, CANADA     

JANET Brotton  GEOFFREY Wall 《Climatic change》1997,35(1):35-52

The Bathurst barren-ground caribou herd was chosen as the focus of a study of the possible effects of a changed climate on hunting of a caribou herd in the Northwest Territories. Four climate change scenarios representing conditions under a doubling of atmospheric carbon dioxide concentrations were used in the study. The locations of the Bathurst herd throughout the year were determined, and the 1951 to 1980 average monthly temperatures and total monthly precipitation amounts were ascertained at those locations. The four climate change scenarios were applied, with changes in average monthly temperatures and in total monthly precipitation amounts noted. Analyses indicate a possible increase in winter snowfall, and increased insect harassment of caribou in the summer, due to an increase in average monthly temperatures. The reduced accessibility and health of caribou in the Bathurst herd suggest a reduced hunting potential. Management options are briefly discussed.  相似文献   

Fe-Mn partitioning between garnet and ilmenite: experimental calibration and applications   总被引：2，自引：0，他引：2  

Mark I. Pownceby  Victor J. Wall  Hugh St. C. O'Neill 《Contributions to Mineralogy and Petrology》1987,97(1):116-126

A new mineralogic geothermometer based on the partitioning of Fe and Mn between garnet and ilmenite has been calibrated by reversal experiments in the P-T range 600–900° C, 2 and 5 kbars and for fO₂=QFM. The results constitute a sensitive geothermometer applicable over a broad range of composition and conditions. Garnetilmenite thermometry has advantages relative to existing geothermometers because of its accurate calibration, marked temperature sensitivity and the chemical and structural simplicity of the crystalline solutions involved. Application to natural assemblages reveals that the garnet-ilmenite geothermometer yields temperatures that agree well with other estimates. The reactivity of, and relatively rapid Fe-Mn diffusion in ilmenite may lead to retrograde resetting of high temperature partition values, but these factors may be useful for estimating rock cooling rates. Analysis of the experimental data indicates minor positive deviations from ideality for Fe-Mn garnets and ilmenites. Absolute magnitudes of interaction parameters (W _AB) derived from a regression analysis are subject to considerable uncertainty. The partition coefficient is, however, strongly dependent on the difference between solution parameters. These differences are well constrained with a magnitude of W _FeMn ^ilm –W _FeMn ^gar 300 cal mol^–1. The accuracy and applicability of garnet-ilmenite thermometry will improve with the availability of better thermodynamic data for garnet crystalline solutions.Abbreviations and symbols used in text R universal gas constant (cal/mol/°K) - T absolute temperature (°K or °C) - P pressure (kbars) - V ⁰ volume change of reaction (1) - H _{1, T} ⁰ standard state enthalpy change of reaction (1) at 1 bar and the T of interest, in cal/mole - S _T ⁰ entropy change of reaction (1) at T of interest, in cal/mole/°K - G _P,T ⁰ standard free energy change of reaction (1) at the T and P of interest, in cal/mole - distribution coefficient for Fe-Mn partitioning between garnet and ilmenite - K apparent equilibrium coefficient for reaction (1) - _i ^j activity of component i in phase j - W _A-B binary A-B interaction (Margules) parameter - gar garnet - ilm ilmenite - biot biotite - ol olivine - opx orthopyroxene  相似文献   

The heat-capacity of ilmenite and phase equilibria in the system Fe-T-O     

Lawrence M. Anovitz  Allan H. Treiman  Eric J. Essene  Bruce S. Hemingway  Edgar F. Westrum  Victor J. Wall  Ramón Burriel  Steven R. Bohlen 《Geochimica et cosmochimica acta》1985,49(10):2027-2040

Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO₃) from 5 to 1000 K. These measurements yield S₂₉₈⁰ = 108.9 J/(mol · K). Calculations from published experimental data on the reduction of ilmenite yield Δ₂₉₈⁰(I1) = ?1153.9 kJ/(mol · K). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of $\text{?O}{}_2$ are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookite_ss and hematite-ilmenite_ss. Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling.  相似文献   

The Use of Field Dependence of Magnetic Susceptibility for Monitoring Variations in Titanomagnetite Composition - A Case Study on Basanites from the Vogelsberg 1996 Drillhole,Germany   总被引：1，自引：1，他引：1  

de Wall  H.  Nano  L. 《Studia Geophysica et Geodaetica》2004,48(4):767-776

In high Ti basanites from the Vogelsberg 1996 drillhole distinct variations in the field dependence of AC magnetic susceptibility correlate with compositional variations of titanomagnetite, as determined by temperature dependence of magnetic susceptibility. Curie temperatures for the basanites are in the range of 240 to 525°C. The field dependence reaches up to 20% for measurements in 30 A/m and 300 A/m AC field amplitude. It is demonstrated that two-field magnetic susceptibility measurements can prevail information about compositional changes of titanomagnetite and therefore support the interpretation of magnetic susceptibility logs from drillcores of basaltic rock suites.  相似文献   

Crustal structure and ocean–continent transition at marginal ridge: the Côte d’Ivoire–Ghana marginal ridge     

F. Sage  B. Pontoise  J. Mascle  C. Basile  L. Arnould 《Geo-Marine Letters》1997,17(1):40-48

 Crustal structure of the Co^te d’Ivoire–Ghana marginal ridge and its transition with oceanic lithosphere are deduced from multichannel seismic reflection, wide-angle seismic, and gravity data. The CIGMR is cut into rotated blocks and displays a crustal structure quite similar to that of the nearby northern Ivorian extensional basin. These results strongly support that the CIGMR represents an uplifted fragment of continental crust. Transition with the oceanic crust appears sharp; continental crustal thinning occurs over less than 5 km. We did not find evidence for underplating and/or contamination as anticipated from such a sharp contact between continental and oceanic crust. Received: 12 March 1995/Revision received: 2 July 1996  相似文献   

Rapid urbanization in a transitional economy in China: The case of Hainan Island     

Kai Gu  Geoffrey Wall 《Singapore journal of tropical geography》2007,28(2):158-170

The outcomes and forms of urbanization and modernization in China following the reform and opening of the late 1970s have attracted extensive attention and competing interpretations in scholarly documentation. This paper focuses on Hainan Island, established in 1988 as the biggest special economic zone in China. Since then, considerable inflows of human as well as speculative capital have led to rapid real estate, in particular tourism-related, development. While urban expansion and improvements have been encouraged, the ongoing over-building, unregulated conversion of land use and degradation of the urban environment present serious social and economic problems. This paper summarizes the trajectory, causal factors and outcomes of this urban growth and consequent planning problems that make the island an atypical case in China's urbanization experience. We argue that the establishment of a practical framework combining socioeconomic planning, land use planning, and the management of both, is crucial to achieve sustainable growth for this transitional economy.  相似文献   

Calcite-bearing dolomite carbonatite dykes from Veseloe, North Transbaikalia, Russia and possible Cr-rich mantle xenoliths     

A. G. Doroshkevich  F. Wall  G. S. Ripp 《Mineralogy and Petrology》2007,90(1-2):19-49

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Variations of the Nutrients Loads to the Mainland U.K. Estuaries: Correlation with Catchment Areas, Urbanization and Coastal Eutrophication     

D. B. Nedwell  L. F. Dong  A. Sage  G. J. C. Underwood 《Estuarine, Coastal and Shelf Science》2002,54(6):951

The annual loads of nutrients (TO_xN equal to nitrate+nitrite; ammonium, phosphate, silicate) to all the estuaries on the mainland of the United Kingdom were estimated from data on water flow through gauging stations at the tidal limits of estuaries, and from concentration measurements under the Harmonised Monitoring Scheme of nutrient concentrations in water samples from these stations. The annual loads of nutrients showed distinct regional variations, with estuaries along the west coast of Wales and northern Scotland having much smaller loads than those along the east coast of England. The largest nitrogen loads were of TO_xN, and ammonium loads were usually small in comparison. The Severn, Mersey, Humber and Thames had the highest loads, although these were small in relation to the larger continental European estuaries. Loads of TO_xN per unit of catchment area were surprisingly constant (about 10⁵ moles N km⁻² y⁻¹). The nutrient loads showed that most U.K. catchments were influenced by human activity, the majority being in the ‘ moderately influenced ’ category. Nutrient loads were also normalized for the area of each estuary, as a measure of the relative influence of nutrients on the receiving estuaries. The ratios of N:P, N:Si and P:Si in the annual loads suggested that most estuaries were likely to be, if anything, P limited rather than N or Si limited. However, crude annual loads may conceal significant seasonal variations.The spring maximum chlorophylla concentrations in coastal waters adjacent to each estuary were significantly correlated with the log total annual loads of TO_xN, ammonium and phosphate (but not silicate) for each estuary, providing a direct link between a measure of the degree of biological response in coastal waters and the nutrient load through the estuaries. There were no significant correlations between spring maximum chlorophyll a concentrations and either catchment-normalized or estuary-normalized nutrient loads. There was significant correlation between catchment area-normalized loads of phosphate and an urbanization index for the catchments, but not with the catchment area-normalized loads of the other nutrients.  相似文献   

Interactive analysis of the spatial distribution of disease using a geographic information systems   总被引：1，自引：0，他引：1  

Patrick A. Wall  Owen J. Devine 《Journal of Geographical Systems》2000,2(3):243-256

Geographic information systems (GIS) provide a variety of tools for the manipulation and display of public health data. Few, however, enable users to interactively evaluate hypotheses on spatial trends in disease risk that may be suggested by maps of measures of disease impact. We addressed this limitation by developing a seamless interface between a commercial GIS and a suite of spatial analysis algorithms. Users of the system can utilize the GIS's capability to interactively select and manipulate geographically referenced data and, through a series of pull-down menus, apply a variety of exploratory analysis methods to this information. In the presented application, we illustrate this capability by including algorithms for the reduction of random noise in observed incidence rates, for the detection of unusual aggregations of disease events, and for the statistical evaluation of inferences drawn from spatial trends. We demonstrate this application by examining lung cancer mortality in the state of Ohio. Received: 22 September 1999 / Accepted: 8 March 2000  相似文献   

Ultramafic-derived arsenic in a fractured bedrock aquifer     

Peter C. Ryan  Jonathan KimAndrew J. Wall  Jonathan C. MoenLilly G. Corenthal  Daniel R. ChowColleen M. Sullivan  Kevin S. Bright 《Applied Geochemistry》2011,26(4):444-457

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