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41.
42.
Generalised observations of wave characteristics on near‐horizontal shore platforms: Synthesis of six case studies from the North Island,New Zealand 下载免费PDF全文
Most field studies of wave processes on shore platforms in front of eroding cliffs focus on a single site, revealing aspects of wave dynamics at that location. Here, we analyse data from six platforms around northeastern New Zealand and describe the fundamental control of shore platform width, gradient and elevation on wave processes, including greater attenuation of short‐period waves at lower tidal stages and increases in longer period wave energy towards the cliff toe. These data suggest that empirical formulae developed from coral‐reef environments provide better predictions of wave height on platforms than formulae currently used in shore platform models. 相似文献
43.
Posterior probabilities of occurrence for Zn-Pb Mississippi Valley Type (MVT) mineralization were calculated based on evidence
maps derived from regional geology, Landsat-TM, RADARSAT-1, a digital elevation model and aeromagnetic data sets in the Borden
Basin of northern Baffin Island, Canada. The vector representation of geological contacts and fault traces were refined according
to their characteristics identified in Landsat-TM, RADARSAT-1, DEM, slope, aspect, and shaded relief data layers. Within the
study area, there is an association between the occurrence of MVT mineralization and proximity to the contact of platformal
carbonates and shale units of the adjacent geological formation. A spatial association also tends to exist between mineralization
and proximity to E-W and NW-SE trending faults. The relationships of known MVT occurrences with the geological features were
investigated by spatial statistical techniques to generate evidence maps. Supervised classification and filtering were applied
to Landsat-TM data to divide the Society Cliffs Formation into major stratigraphic subunits. Because iron oxides have been
observed at some of the MVT occurrences within the Borden Basin, Landsat-TM data band ratio (3/1) was calculated to highlight
the potential presence of iron-oxides as another evidence map. Processed Landsat-TM data and other derived geological evidence
maps provided useful indicators for identifying areas of potential MVT mineralization.
Weights of evidence and logistic regression were used independently to integrate and generate posterior probability maps showing
areas of potential mineralization based on all derived evidence maps. Results indicate that in spite of the lack of important
data sets such as stream or lake sediment geochemistry, Landsat-TM data and regional geological data can be useful for MVT
mineral-potential mapping. 相似文献
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In this article, we use parcel-based land-use data to analyze 50 years of residential development in the Toronto region. We test two hypotheses: (1) Toronto’s form does not conform to conventional definitions of suburban sprawl and (2) Toronto’s suburban development shows high levels of continuity over time with relatively high densities and mixed housing types. Contrary to recent research suggesting a convergence of urban forms among North American metropolitan regions, Ontario’s robust planning system has created a distinctive, highly consistent pattern of residential development that has, for half a century, achieved many of the core goals of smart growth including relatively compact, contiguous, and concurrent development. This form continues to be automobile dependent, however, and is not producing many of the benefits ascribed to smart growth. Rather than continuing to adopt United States-inspired smart growth policies, a more ambitious set of initiatives will be required to address current regional challenges. 相似文献
47.
Lithology and Mineral Resources - 相似文献
48.
Zhufeng Fang Zhangshuan Hou Guang Lin Dave Engel Yilin Fang Paul Eslinger 《Environmental Earth Sciences》2014,71(7):3025-3037
This study examined the impacts of reservoir properties on carbon dioxide (CO2) migration after subsurface injection and evaluated the possibility of characterizing reservoir properties using CO2 monitoring data such as spatial–temporal distributions of gas pressure, which can be reasonably monitored in practice. The injection reservoir was assumed to be located 1,400–1,500 m below the ground surface such that CO2 remained in the supercritical state. The reservoir was assumed to contain layers with alternating conductive and resistive properties, which is analogous to actual geological formations such as the Mount Simon Sandstone unit. The CO2 injection simulation used a cylindrical grid setting in which the injection well was situated at the center of the domain, which extended out 8,000 m from the injection well. The CO2 migration was simulated using the latest version of the simulator, subsurface transport over multiple phases (the water–salt–CO2–energy module), developed by Pacific Northwest National Laboratory. A nonlinear parameter estimation and optimization modeling software package, Parameter ESTimation (PEST), is adopted for automated reservoir parameter estimation. The effects of data quality, data worth, and data redundancy were explored regarding the detectability of reservoir parameters using gas pressure monitoring data, by comparing PEST inversion results using data with different levels of noises, various numbers of monitoring wells and locations, and different data collection spacing and temporal sampling intervals. This study yielded insight into the use of CO2 monitoring data for reservoir characterization and how to design the monitoring system to optimize data worth and reduce data redundancy. The feasibility of using CO2 saturation data for improving reservoir characterization was also discussed. 相似文献
49.
The Colville basin drains the North Slope of Alaska and is one of several large Arctic river systems located within permafrost. The timing and style of fluvial processes in the earth's permafrost regions differ from those occurring in midlatitude settings. Moreover, in comparison to temperate-zone systems, rivers located entirely within permafrost perform most of their work during relatively short periods of time. This paper examines river ice hydrology and the resulting geomorphic processes that occur within the Colville delta, Alaska. Fluvial processes and landform development within the Colville delta occur after the flood-pulse is initiated by the breakup of river ice. During this 4-month period, the geomorphic processes are largely influenced by the movement of ice. The flood-pulse and accompanying river ice influences erosional and depositional processes and results in unique styles of sediment transport, deposition, and riverbank erosion. 相似文献
50.
The composition and metallogeny of igneous rocks and relevant weathering crusts of Jurassic–Cretaceous provenances of the Russian Platform are considered. It is shown that the association of metals that accumulated in the process of weathering and erosion of ancient substratum includes P, Fe, Ti, V, and Cr. This process is reflected in the formation of nodular phosphorites, Ti and Zr placers, and iron ore deposits in the Jurassic–Cretaceous seas of the platform. 相似文献