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41.
42.
Interpretation of the recent high-resolution survey, CANADOU 2000, in the Bay of Douarnenez (Finistère, France) allowed us to restore the morphology of the substratum and the sedimentary filling of the bay. The Brioverian and Palaeozoic substratum reveals a well-defined network of incised valleys as results of successive emergence stages of the Bay during the Quaternary. Valleys join in a westward-widened mean valley, called Ys Valley. The present-day sedimentary fill of the bay of Douarnenez appears mainly controlled by the Holocene rise and the consecutive highstand. It comprises fluvial and estuarine deposits filling up incised valleys and marine sedimentation extending out of the incised valleys. To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003).To cite this article: G. Jouet et al., C. R. Geoscience 335 (2003).  相似文献   
43.
In central Tunisia, a synsedimentary tectonic episode has been pointed out through the tectonic movements affecting the Late Palaeocene–Early Eocene successions. This tectonic episode has controlled, to a large extent, the palaeogeographic setting of the area during that period and confirmed the important effect induced by the Pyrenean shortening phase on the edge of the African plate, which obviously has witnessed a common history with the southern part of the European plate. To cite this article: A. El Ghali et al., C. R. Geoscience 335 (2003).  相似文献   
44.
In eastern North Island New Zealand, oblique subduction of the Pacific Plate beneath the Australian Plate is associated with strain partitioning. Dextral along-strike component of displacement occurred first at Early Miocene major faults within the eastern fore-arc domain. These faults were active from Early Miocene to Pliocene times. Since Pliocene times, most of the movement occurs at western faults such as the Wellington Fault. The latter joins the back-arc domain to the north. The jump of wrench faulting is related to the oblique opening of the back-arc domain. Both phenomena are impeded southwards by the Hikurangi oceanic plateau entering the subduction zone. To cite this article: J. Delteil et al., C. R. Geoscience 335 (2003).  相似文献   
45.
This study presents the evolution of agreements between the governments of Canadaand Québec on flood damage reduction. In Québec, the implementation of a regulation about building in floodplains came about in 1983–1984. Today, this regulation takes the form of a policy called ``Policy of shores, littoral and floodplain protection'. Municipalities must adopt rules that concur with the principles of this policy.The Chaudiére River basin was selected for analysis of urban developmentduring the period following the application of building rules in flood-risk areas.Despite the ban on building in the strong current zone (0–20 year return periodflood zone), many buildings, essentially residential, have been erected in thiszone. These new constructions generally account for a low percentage of thetotal property value in the 0–100 year flooding area, but are legal since theyare connected to a water and sewage network that existed prior to the officialfloodplain regulation.Flood damage along the Chaudiére River will tend to increase for two reasons.Firstly, while respecting the policy mentioned above, sites are still available infloodplains for future development. Secondly, no structural flood protection workshave been erected in view of the fact they are only marginally profitable from anbenefit-cost point of view.  相似文献   
46.
Weather as a Chronic Hazard for Road Transportation in Canadian Cities   总被引:2,自引:1,他引:2  
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   
47.
We present new data and interpretations on the Neogene tectonics of the Shan scarp area (central Myanmar) and its relationship with the India–Indochina oblique convergence. We describe ductile and brittle fabrics associated with the major features in this area, the Mogok Metamorphic Belt (MMB), the Shan scarp and the Sagaing fault. From these data we identify a succession of two tectonic regimes. First, a dominant NNW–SSE-trending extension, marked by ductile stretching that characterizes the MMB, and associated N70E brittle normal faults. Later, from Middle or Upper Miocene to the Present, these structures were cross-cut by brittle right-lateral faults, among which the most important are the N20W transpressive Shan scarp fault zone and the N–S Sagaing fault. To explain this transition from a dominant transtensive to a transpressive stress regime, that occurred during Miocene, we place our data within a larger geodynamic context. We suggest that, like the intraplate deformation in the Indian Ocean, the end of spreading in the South China sea, the opening of the Andaman basin or the end of subduction within the Indo-Burma range, the change in the tectonic regime in central Myanmar could be in response to a major Miocene regional plate kinematic reorganization.  相似文献   
48.
Given the present commitment of the developed countries according to the Kyoto Protocol, most published scenarios demonstrate that global greenhouse gases concentrations would not be stabilized at any level. In order to stabilize these concentrations, a deeper global involvement is needed. Taking Israel as an example of a `recently-developed' country, we assess the role that such countries could play by assuming voluntary commitments in strengthening global involvement. This case as a model may encourage a global scheme for curbing carbon emissions, in which the more developed countries assume a stronger role and the less developed countries participate according to the principle of common but differentiated responsibility. The scheme builds on the inverse relation that exists between the per capita gross domestic product and the rate of increase of emissions due to economic growth. According to this theoretical scheme, the voluntary commitments assumed by the `recently-developed' countries encourage the more developed countries to deepen their involvement by assuming more stringent reductions of emissions at home and transferring technological and financial means to the less developed countries. The proposed scheme would enable non-Annex I countries, both `recently-developed' countries and less developed countries, to participate much earlier in the net mitigation of greenhouse gases.  相似文献   
49.
The Archean Shawmere anorthosite lies within the granulite facies portion of the Kapuskasing Structural Zone (KSZ), Ontario, and is crosscut by numerous linear alteration veins containing calcite + quartz ± dolomite ± zoisite ± clinozoisite ± margarite ±paragonite ± chlorite. These veins roughly parallel the trend of the Ivanhoe Lake Cataclastic Zone. Equilibria involving clinozoisite + margarite + quartz ± calcite ± plagioclase show that the vein minerals were stable at T < 600 °C, XCO2 < 0.4 at P ≈ 6 kbar. The stabilities of margarite and paragonite in equilibrium with quartz are also consistent with T < 600 °C and XCO2 < 0.4 at 6 kbar. Additional assemblages consisting of calcite + clinochlore + quartz + talc + margarite indicate T < 500 °C with XCO2 > 0.9. Thus, vein formation, while clearly retrograde, spanned a range of temperatures, and fluid compositions evolved from H2O-rich to CO2-rich. The calcite in the retrograde veins has δ18O values that range from 8.4 to 11.2‰ (average = +9.7 ± 0.9‰) and δ13C values that range from −3.9 to −1.6‰ (average = −3.1 ± 0.6‰). These values indicate that the fluids from which calcite precipitated underwent extensive exchange with the anorthosite and other crustal lithologies. The fluids may have been initially derived either from devolatilization of metamorphic rocks or crystallization of igneous rocks in the adjacent Abitibi subprovince. Vein quartz contains CO2-rich fluid inclusions (final melting T = −57.0 to −58.7 °C) that range in size from 5 to 17 μm. Measured homogenization temperatures (T h) range from −44.0 to 14.5 °C, however for most inclusions (46 of S1), T h = −44.0 to −21.1 °C (ρCO2 ≈ 1.13 to 1.05 g/cm3). At 400 to 600 °C, these densities correspond to pressures of 3.5 to 7 kbar, which is the best estimate of pressures of vein formation. It has been argued that some high density CO2-rich fluid inclusions found in the KSZ were formed during peak metamorphism and thus document the presence of a CO2-rich fluid during peak granulite facies metamorphism (Rudnick et al. 1984). The association of high density CO2-rich fluid inclusions with clearly retrograde veins documents the formation of similar composition and density inclusions after the peak of metamorphism. Thus, the coincidence of entrapment pressures calculated from fluid inclusion density measurements with peak metamorphic pressures alone should not be considered strong evidence for peak metamorphic inclusion entrapment. All fluid inclusion results are consistent with an initially semi-isobaric retrograde PT path. Received: 2 April 1996 / Accepted: 15 November 1996  相似文献   
50.
Re-Os Isotopic Measurements at the Femtomole Level in Natural Samples   总被引:17,自引:0,他引:17  
Here we describe a new chemical separation method for Os and an improved mass spectrometric procedure for Re and Os. This technique is based on the selective extraction of OsO4 from aqueous solution in liquid bromine. Among other advantages, this procedure avoids the cumbersome distillation procedure for Os and uses only commercial "off the shelf" PFA teflon labware. Blank levels for 0.5 g sample sizes are: 0.06 pg and 0.5 pg for Os and Re respectively. Samples containing as little as 1 pg g−1 Os can be analysed reliably with this method. Adaptation to other dissolution methods is also discussed.  相似文献   
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