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41.
Sedimentary and tectonic development of a high-arctic, thrust-moraine complex: Comfortlessbreen, Svalbard 总被引:1,自引:1,他引:1
DAVID HUDDART MICHAEL J. HAMBREY 《Boreas: An International Journal of Quaternary Research》1996,25(4):227-243
The glaciotectonic processes that have shaped the morphology and structural geology of the Comfortlessbreen thrust-moraine complex are shown to be largely proglacial in origin, with the development of low-angle thrusts, nappe-like structures and folds. The propagation of the deformation has extended into the glacier foreland. A style of deformation called the 'englacial deformation zone' explains the incorporation of subglacial debris into the ice by thrusting and subsequent deposition of thrust sheets is inherited from the ice structures. A model for thrust-moraine development and its possible chronology at Comfortlessbreen emphasizes the role played by glaciomarine sediment in facilitating deformation and also the role of thrusting, rathcr than pushing, in moraine formation. The importance of sediment type in controlling the overall development of the moraine is emphasized and a comparison to illustrate this control is made with neighbouring Uvrsbreen. 相似文献
42.
Origin and significance of mud-filled incised valleys (Upper Cretaceous) in southern Alberta, Canada
DAVID A. EBERTH 《Sedimentology》1996,43(3):459-477
Seven mud-filled incised valleys (MFIVs) in the paralic facies of the Dinosaur Park and Horseshoe Canyon formations (Upper Cretaceous) of southern Alberta were studied to better understand their morphology, geometry and depositional histories in an estuarine context. Two preservational geometries occur: simple, U-shaped forms; and internally complex forms. Both types of MFIV record deposition in the central zone of low energy (turbidity) in an estuarine setting. Simple, U-shaped MFIVs have sharp basal erosional surfaces and consist of mudstone-dominated heterolithic fills of channel-wide, concave-up laminae. Associated fossil assemblages are marine to brackish. Each simple MFIV records a cut-and-fill history associated with a cycle of relative sea-level drop and rise. Low-energy depositional settings, loss of channel form during infilling, and associated shoreface deposits, as well as the absence of clear tidal indicators suggest a coastal plain estuarine setting, along a wave-dominated, barred coastline. Complex MFIVs are rarer, and consist of imbricated, wedge-shaped sets of inclined-to-horizontal heterolithic strata. Tidal deposits and/or nonmarine-to-marine macrofossils occur locally. Complex MFIVs were infilled in meandering reaches of the central zone of low energy in tide-dominated estuaries. Their rarity compared to simple MFIVs and their freshwater palaeontological content suggest that they were contiguous landward with extensive fluvial channels. A complex MFIV near Onefour comprises three in-channel depositional cycles. Each cycle consists of an erosional surface overlain by lateral accretion bedding and a conformable transition to vertically aggraded strata. Each cycle reflects a cut-and-fill event under the control of changes in relative sea-level that culminated in overbank flooding. All MFIVs formed in low-gradient settings (≤0.03%) where estuarine zones were stretched out over many tens of kilometres. Tide-dominated estuaries apparently exhibited simple, straight-to-meandering upstream transitions and extensive landward penetration (≥200 km) of tidal backwater effects. Few modern estuaries serve as adequate modern analogues to these ancient, tide-dominated estuaries. Radiometric data indicate that MFIV cut-and-fill cycles were 100 000-400 000 years in maximum duration and thus, equivalent to 4th order sea-level cycles. However, negative evidence tentatively suggests that these cycles took place over time intervals 1-2 orders of magnitude smaller (5th order or higher sea-level cycles). 相似文献
43.
利用偏最小二乘法回归的多变量校正方式,建立了应用近红外反射光谱学方法无损快速测定各种地质样品中有机质的模型.设计了多重散射光校正、标准正常变量转换及导数光谱,扣除额外基线和重叠信号的影响,分离出与有机质含量有关的光谱信息.大多数地质样品的有机质近红外反射光谱估算结果与化学法符合. 相似文献
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45.
NEKVASIL H.; DONDOLINI A.; HORN J.; FILIBERTO J.; LONG H.; LINDSLEY D. H. 《Journal of Petrology》2004,45(4):693-721
Experimental simulation of incremental crystal fractionationof a hy-normative hawaiite indicates that the spectrum of compositionsfrom mildly alkalic hawaiite to sodic rhyolite found in silica-saturatedalkalic suites of the ocean islands and continental hotspotsand rifts can be produced by fractionation at 9·3 kbarwith bulk water contents > 相似文献
46.
基于XML的WebGIS体系结构 总被引:5,自引:1,他引:5
针对WebGIS中存在的地理空间数据语义共享问题,在分析XML和GML特点的基础上,论述了基于XML构架WebGIS系统的方案和应用方式,并详析了实现构架的相关技术。 相似文献
47.
基于分层的面状地图符号设计 总被引:3,自引:1,他引:3
根据面状符号的结构特征和实现机制 ,提出了基于分层的面状地图符号设计方法 ,把面状符号分为若干层 ,每层采用一种填充方式 ,并在基于VC 的Cartosymbol软件中实现。结果表明 ,该方法既便于地理现象的表达 ,又便于计算机实现。 相似文献
48.
This paper identifies contrasting environmental discourses on bushfire from the public debate that followed the Victorian fires of 2002–03. Submissions to the inquiry into the 2002–03 Victorian bushfires provide a particularly rich source of documentation. It is argued that environmental events such as bushfire only become political issues, or problems, when they are constituted as such through environmental discourse. Through the analysis, three contrasting discourses on bushfire are identified—here labelled the ‘conservationist’, ‘ruralist’ and ‘wise use’ discourses. In examining how different ‘constructions’ of bushfire have led to conflict, each discourse is shown to consist of a range of actors who draw on shared storylines. Having established a better understanding of the different attitudes, beliefs, interests and values that underpin debates about bushfire, the paper concludes with a brief discussion of the prospects for compromise among the discourses and the potential for improved land and fire management outcomes. 相似文献
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50.
This paper examines the transport of calcareous sand in unidirectional flow and its prediction through existing sediment transport models. A flume experiment of four sand samples collected on Oahu, Hawaii, provides 29 sets of sediment transport data in the bed-form and suspended transport stages. The measured transport data are compared with direct predictions from four energy-based transport models developed for siliceous particles. Corrections for the grain-size, fall velocity, and critical velocity of calcareous sand based on recent research are applied to the models and the results are compared with the direct calculations and measured data. The comparison illustrates the important role particle shape plays in the transport of calcareous sand. All four sediment transport models give consistent predictions and good agreement with the majority of the measured data. Two of the models respond positively to the corrections in both the bed-form and suspended transport stages indicating that such an approach may provide an interim solution for the transport of calcareous sand. 相似文献