Tracking recorded fires using charcoal morphology from the sedimentary sequence of Prosser Lake, British Columbia (Canada)     

Mihaela D. Enache  Brian F. Cumming 《Quaternary Research》2006,65(2):282-292

Quantitative analyses of variations in morphological features of charcoal were undertaken in a ²¹⁰Pb-dated sediment core from Prosser Lake (British Columbia, Canada). Seven morphological types of charcoal were defined by particle shape, major-minor axis ratio, apparent porosity and progradation to unburned material. The distribution of morphotypes and total charcoal abundances were assessed as a proxy for fire events recorded between 1919 and 2000 and to subsequent mechanisms of transportation-sedimentation to lake sediments. Charcoal morphotypes showed distinct relationships to recorded area burned by fires. Fragile charcoal fragments with highly irregular porosity (termed Type M) displayed the strongest correlation to burned area (r² = 0.51; P = 0.0001) and did not produce any false-positive signal for fires recorded within a radius of 20 km around the lake. We infer that high porosity and low density Type M fragments are aerially transported and directly deposited on the lake, and that the fragility of Type M charcoal prevents significant quantities from being secondarily transported and incorporated into the sedimentary record. We propose that charcoal morphology is an important but underutilized technique that can yield important insights into fire type, proximity and transportation-sedimentation processes.  相似文献   

Spontaneous Structural Reform in Australian Local Government: the case of the Gilgandra Co-operative Model in New South Wales     

Brian Dollery  Warrick Moppett  Lin Crase 《The Australian geographer》2006,37(3):395-409

Dire financial constraints and the threats of forced structural reform have had the unforeseen effect of forcing municipal councils across Australia to reconsider their operational activities and organisational arrangements. With considerable ingenuity, numerous municipalities have proposed and sometimes adopted new structural formations that embody various forms of co-operative service provision. This remarkable development has unfortunately been largely ignored in the scholarly literature on Australian local government. In a modest effort aimed at remedying this neglect, the present paper seeks to outline the small, rural New South Wales Gilgandra Shire Council's (2004) ‘Co-operative/Local Government Service Company’ model, place it in the broader context of alternative models of local governance suitable for Australian conditions, and evaluate its characteristics.  相似文献   

Lake Sediment Core Records of Sulphur Accumulation and Sulphur Isotopic Composition in Central Ontario, Canada Lakes     

M. Catherine Eimers  Andrew M. Paterson  Peter J. Dillon  Sherry L. Schiff  Brian F. Cumming  Roland I. Hall 《Journal of Paleolimnology》2006,35(1):99-109

Stable isotopic compositions and concentrations of total sedimentary sulphur (S) were determined in cores from 6 lakes in the acid-sensitive Muskoka-Haliburton region of south-central Ontario. The isotopic composition of S in deep sediment (> ~ 20 cm) was approximately constant in all lakes, and indicated a pre-industrial δ ³⁴S value between +4.0 and +5.3‰, which is similar to current bulk deposition. Similarly, total S concentrations in deep sediment were relatively low (1.9–5 mg S g⁻¹ dwt) and approximately constant with depth within cores. All lakes exhibited up-core increases in total S and decreases in δ ³⁴S at a depth corresponding to the beginning of industrialization in the Great Lakes region ( ~ 1900), resulting in a generally reciprocal depth pattern between total S concentration and δ ³⁴S ratios. While initial shifts in total S and δ ³⁴S were likely due to enhanced SO₄ reduction of newly available anthropogenic SO₄, both the magnitude and pattern of up-core S enrichment and shifts in δ ³⁴S varied greatly among lakes, and did not match changes in S deposition post 1900. Differences between lakes in total S and δ ³⁴S were not related to any single hydrologic (e.g., residence time) or physical (e.g., catchment-area-to-lake area ratio) lake characteristic. This work indicates that sediment cores do not provide consistent records of changes in post-industrial S deposition in this region, likely due to redox-related mobility of S in upper sediment.  相似文献   

Crustal structure across the Grand Banks–Newfoundland Basin Continental Margin – II. Results from a seismic reflection profile     

K. W. Helen Lau  Keith E. Louden  Sharon Deemer  Jeremy Hall  John R. Hopper  Brian E. Tucholke  W. Steven Holbrook  Hans Christian Larsen † 《Geophysical Journal International》2006,167(1):157-170

New multichannel seismic reflection data were collected over a 565 km transect covering the non-volcanic rifted margin of the central eastern Grand Banks and the Newfoundland Basin in the northwestern Atlantic. Three major crustal zones are interpreted from west to east over the seaward 350 km of the profile: (1) continental crust; (2) transitional basement and (3) oceanic crust. Continental crust thins over a wide zone (∼160 km) by forming a large rift basin (Carson Basin) and seaward fault block, together with a series of smaller fault blocks eastwards beneath the Salar and Newfoundland basins. Analysis of selected previous reflection profiles (Lithoprobe 85-4, 85-2 and Conrad NB-1) indicates that prominent landward-dipping reflections observed under the continental slope are a regional phenomenon. They define the landward edge of a deep serpentinized mantle layer, which underlies both extended continental crust and transitional basement. The 80-km-wide transitional basement is defined landwards by a basement high that may consist of serpentinized peridotite and seawards by a pair of basement highs of unknown crustal origin. Flat and unreflective transitional basement most likely is exhumed, serpentinized mantle, although our results do not exclude the possibility of anomalously thinned oceanic crust. A Moho reflection below interpreted oceanic crust is first observed landwards of magnetic anomaly M4, 230 km from the shelf break. Extrapolation of ages from chron M0 to the edge of interpreted oceanic crust suggests that the onset of seafloor spreading was ∼138 Ma (Valanginian) in the south (southern Newfoundland Basin) to ∼125 Ma (Barremian–Aptian boundary) in the north (Flemish Cap), comparable to those proposed for the conjugate margins.  相似文献   

Seismicity, structure and rheology of the lithosphere in the Lake Baikal region   总被引：2，自引：2，他引：2  

Brian Emmerson  James Jackson  Dan McKenzie  Keith Priestley 《Geophysical Journal International》2006,167(3):1233-1272

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'Toheroa Wars': Cultural politics and everyday resistance on a northern New Zealand beach     

Brian Murton 《New Zealand geographer》2006,62(1):25-38

Abstract:  This paper examines how the cultural politics of resource management were played out on the North Kaipara beach between about 1900 and 1971 between Māori and the representative of the Crown, the Marine Department. Particular attention is devoted to how, after regulations were introduced to protect toheroa, the giant surf clam, Māori struggled to assert their rights through a range of transgressions. The paper argues that this illustrates how cultural politics works both from the top down (the Marine Department's implementation of policy) and the bottom up (Māori resistance). It concludes that through an examination of this particular 'culture war', the foreshore emerges as a contested domain where politics, culture and epistemology are inseparable.  相似文献   

Implications of the relationship between catchment vegetation type and the variability of annual runoff   总被引：1，自引：0，他引：1  

Murray C. Peel  Thomas A. McMahon  Brian L. Finlayson  Fred G. R. Watson 《水文研究》2002,16(15):2995-3002

The impact of changing catchment vegetation type on mean annual runoff has been known for some time, however, the impact on the variability of annual runoff has been established only recently. Differences in annual actual evapotranspiration between vegetation types and the potential effect of changing vegetation type on mean annual runoff and the variability of annual runoff are briefly reviewed. The magnitude of any change in the variability of annual runoff owing to a change in catchment vegetation type is related to the pre‐ and post‐change vegetation types and the seasonality of precipitation, assuming that the variability of annual precipitation remains constant throughout. Significant implications of the relationship between vegetation type and the variability of annual runoff are presented and discussed for water resource management, stream ecology and fluvial geomorphology. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Processes in microbial transport in the natural subsurface     

Timothy R. Ginn  Brian D. Wood  Kirk E. Nelson  Timothy D. Scheibe  Ellyn M. Murphy  T.Prabhakar Clement   《Advances in water resources》2002,25(8-12)

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Weather as a Chronic Hazard for Road Transportation in Canadian Cities   总被引：2，自引：1，他引：2  

Jean Andrey  Brian Mills  Mike Leahy  Jeff Suggett 《Natural Hazards》2003,28(2-3):319-343

Inclement weather creates a chronic hazard for Canadian travellers. Past studies indicate that road collision rates increase during precipitation, although the magnitude of theincrease varies from study to study, partly as a result of variations in weather and driving conditions,but also because of differences in methods. The goal of the current study is to improve ourunderstanding of the links between weather and travel risk in mid-sized Canadian cities by using astandardized method for analyzing data from six cities with different climates: Halifax-Dartmouth,Ottawa, Québec, Hamilton, Waterloo Region, and Regina. The study has four interrelated objectives: (1) Toconduct a sensitivity analysis to determine the extent to which risk estimates vary depending onthe criteria used to define precipitation events and `normal' conditions; (2) To compare therelative risk of collision and injury during precipitation relative to `normal' conditions; (3) Todetermine the extent to which weather-related risks vary fordifferent Canadian cities; and (4) To explore any differences in collision characteristics between events and controls, especially as theyvary from city to city. Results are based on a matched-pair analysis, using six-hour time blocks over afour-year period, 1995 to 1998. Results indicate only modest sensitivity to the criteria used to define precipitation events and `normal' conditions. On average, precipitation is associated with a 75 percentincrease in traffic collisions and a 45 percent increase in related injuries, as compared to `normal'seasonal conditions, but risk levels vary depending on the characteristics of the weather event.Both sensitivity to specific weather conditions and weather-related accident profiles vary from city tocity in ways that are not easily explained.  相似文献   

Iron and Sulfur Chemistry in a Stratified Lake: Evidence for Iron-Rich Sulfide Complexes   总被引：5，自引：1，他引：5  

George W. Luther III  Brian Glazer  Shufen Ma  Robert Trouwborst  Bradley R. Shultz  Gregory Druschel  Charoenwan Kraiya 《Aquatic Geochemistry》2003,9(2):87-110

A four month study of a man-made lake used for hydroelectric power generation in northeastern Pennsylvania USA was conducted to investigate seasonal anoxia and the effects of sulfide species being transported downstream of the power generation equipment. Water column analyses show that the system is iron-rich compared to sulfide. Total Fe(II) concentrations in the hypolimnion are typically at least twice the total sulfide levels. In situ voltammetric analyses show that free Fe(II) as [Fe(H₂O)₆]²⁺ or free H₂S as H₂S/HS^- are either not present or at trace levels and that iron-rich sulfide complexes are present. From the in situ data and total Fe(II) and H₂S measurements, we infer that these iron-rich sulfide complexes may have stoichiometries such as Fe₂SH³⁺ (or polymeric forms of this and other stoichiometries). These iron-rich sulfide complexes appear related to dissolution of the iron-rich FeS mineral, mackinawite, because IAP calculations on data from discrete bottle samples obtained from bottom waters are similar to the pK_sp of mackinawite. Soluble iron-sulfide species are stable in the absence of O₂ (both in lake waters and the pipeline) and transported several miles during power generation. However, iron-sulfide complexes can react with O₂ to oxidize sulfide and can also dissociate releasing volatile H₂S when the waters containing them are exposed to the atmosphere downstream of the powerplant. Sediment analyses show that the lake is rich in oxidized iron solids (both crystalline and amorphous). Fe concentrations in FeS solids are low (<5 μmole/gr_{dry wt}) and the pyrite concentration ranges from about equal to the solid FeS to 30 times the solid FeS concentration. The degree of pyritization is below 0.12 indicating that pyrite formation is limited by free sulfide, which can react with the iron-rich sulfide complexes.  相似文献