Geomorphic effects of rural-to-urban land use conversion on three streams in the Central Redbed Plains of Oklahoma   总被引：2，自引：1，他引：2  

Ranbir S. Kang  Richard A. Marston   《Geomorphology》2006,79(3-4):488

This research evaluates the impact of rural-to-urban land use conversion on channel morphology and riparian vegetation for three streams in the Central Redbed Plains geomorphic province (central Great Plains ecoregion) of Oklahoma. The Deep Fork Creek watershed is largely urbanized; the Skeleton Creek watershed is largely rural; and the Stillwater Creek watershed is experiencing a rapid transition from rural to urban land cover. Each channel was divided into reaches based on tributary junctions, sinuosity, and slope. Field surveys were conducted at transects in a total of 90 reaches, including measurements of channel units, channel cross-section at bankfull stage, and riparian vegetation. Historical aerial photographs were available for only Stillwater Creek watershed, which were used to document land cover in this watershed, especially changes in the extent of urban areas (impervious cover).The three streams have very low gradients (< 0.001), width-to-depth ratios < 10, and cohesive channel banks, but have incised into red Permian shales and sandstone. The riparian vegetation is dominated by cottonwoods, ash, and elm trees that provide a dense root mat on stream banks where the riparian vegetation is intact. Channels increased in width and depth in the downstream direction as is normally expected, but the substrate materials and channel units remained unchanged. Statistical analyses demonstrated that urbanization did not explain spatial patterns of changes in any variables. These three channels in the central Redbed Plains are responding as flumes during peak flows, funneling runoff and the wash-load sediment downstream in major runoff events without any effect on channel dimensions. Therefore, local geological conditions (similar bedrock, cohesive substrates and similar riparian vegetation) are mitigating the effects of urbanization.  相似文献   

Surface pollen and its relationship to vegetation on the southern slope of the eastern Qilian Mountains     

LU Xinmiao  CHEN Hui  XU Qinghai 《地理学报》2006,16(2):215-222

The objective of this study is to investigate pollen-vegetation relationship in the Qilian Mountains. The eastern Qilian Mountains are located in the transitional zone of the Tibetan Plateau, the Loess Plateau and the arid region of Northwest China, which is one of the key areas of global environmental change. A total of 13 surface pollen samples from main vegetation have been collected. Pollen percentages were calculated in all samples. In order to reveal the relationship between pollen composition and the vegetation types from which the soil samples have been collected, Detrended Correspondence Analysis (DCA) ordination method was employed on the pollen data. The results show that dominating vegetation types can be recognized by their pollen spectra: Picea crassifolia forest, alpine shrub and alpine meadow as well. Altitude and temperature determine the distribution of the surface pollen and the vegetation. The good agreement between modern vegetation and surface samples across this area provides a measure of the reliability of using pollen data to reconstruct paleoenvironment and paleovegetation patterns in this or other similar regions. However the loss of Betula pollen in forest needs further investigation. Pollen oxidation is the most important factor contributing to the damage of modern pollen in the study area. Pollen concentrations decrease with the increase of pH values of soils, and decrease sharply when the pH exceeds 7.6.  相似文献   

Lake-Level Fluctuations and Small-Scale Vegetation Patterns During the Late Glacial in The Netherlands     

Johanna A. A. Bos  Sjoerd J. P. Bohncke  C. Roel Janssen 《Journal of Paleolimnology》2006,35(2):211-238

Late glacial changes in the vegetation were studied in and around a former lake on the southeastern side of a coversand ridge near Milheeze (southern Netherlands). Analyses of microfossils and macroremains and AMS ¹⁴C dating were performed on four sediment cores along a transect from sand ridge to the lake centre. Small-scale vegetation patterns and lake-level fluctuations were reconstructed in detail based on the information provided by the transect. For the first time in The Netherlands, cores along a transect within one lake were used to reconstruct the amplitude of late glacial lake-level fluctuations. Near Milheeze, a small and shallow lake was formed during the Bølling. The large increase in the water level during the Bølling and early Allerød, and the transition to more eutrophic conditions at the start of the Allerød, were probably related to the disappearance of permafrost. During the Allerød, open birch and pine woodlands developed in the area. In the lake, organic deposits accumulated, and the lake size and depth fluctuated. At the start of the Younger Dryas, higher lake water levels were recorded and woodlands became more open as a result of both a drop in the temperature and an increase in the effective precipitation. During the late Younger Dryas the lake water level dropped as the climate became drier and temperatures slightly increased. Accumulation of organic deposits in the lake ceased at the end of the Younger Dryas, which was caused by a drop in the water level in combination with the hydroseral succession process within the lake itself. The climatic signal reflected in the late glacial flora and lake-level fluctuations agree well with other published data from The Netherlands.  相似文献   

邢台矿区山字型构造的发现及其地质意义   总被引：1，自引：0，他引：1  

张纪勋  范志平 《中国煤田地质》2006,18(4):18-21

邢台山字型构造位于河北省邯邢煤田内，其前弧向ES突出，脊柱呈ES-WN走向。分别分析了山字型构造脊柱及其东、西翼反射弧构造形迹特征，对研究区找矿具有重要意义。  相似文献   

Site Investigation for the Effects of Vegetation on Ground Stability     

John R. Greenwood  Joanne E. Norris  Jo Wint 《Geotechnical and Geological Engineering》2006,24(3):467-481

The procedure for geotechnical site investigation is well established but little attention is currently given to investigating the potential of vegetation to assist with ground stability. This paper describes how routine investigation procedures may be adapted to consider the effects of the vegetation. It is recommended that the major part of the vegetation investigation is carried out, at relatively low cost, during the preliminary (desk) study phase of the investigation when there is maximum flexibility to take account of findings in the proposed design and construction. The techniques available for investigation of the effects of vegetation are reviewed and references provided for further consideration. As for general geotechnical investigation work, it is important that a balance of effort is maintained in the vegetation investigation between (a) site characterisation (defining and identifying the existing and proposed vegetation to suit the site and ground conditions), (b) testing (in-situ and laboratory testing of the vegetation and root systems to provide design parameters) and (c) modelling (to analyse the vegetation effects).  相似文献   

藏南地区金和锑矿床(点)类型及其时空分布特征   总被引：37，自引：5，他引：37       下载免费PDF全文

聂凤军  胡朋  江思宏  李振清  刘妍  周永章 《地质学报》2005,79(3):373-385

本文首次对藏南地区金和锑矿床(点)地质特征、成因类型和空间分布特点进行了总结，对金和锑成矿作用与中新生代构造一岩浆活动的关系进行了论证，对区域地壳演化过程中金和锑成矿动力学机制进行了讨论。该区的金和锑矿床(点)可按容矿围岩划分为：①变质岩为主要容矿围岩矿床(点)，包括金和金一锑矿床(点)；②沉积岩为主要容矿围岩矿床(点)，包括金、锑、金一锑和锑多金属矿床(点)；③火山岩为主要容矿围岩矿床(点)，以金一银矿床为代表。根据金和锑矿床(点)空间分布特点和地质特点，将本区划分为4个矿化集中区：拉昂错一马攸木一帕羊金矿化集中区(A)，然勒金和锑矿化集中区(B)，洛扎一措美锑矿化集中区(C)和邛多江金一锑矿化集中区(D)。各矿化集中区内大多数金和锑矿床(点)与燕山晚期～喜马拉雅早期富碱火成岩具密切时空分布关系，它们是古板块对接碰撞期和碰撞期后大规模构造一岩浆活动的产物。近东西向挤压性和南北向张性断裂交汇部位以及富碱火成岩发育区是寻找金和锑矿床(点)的有利场所。  相似文献   

陕西金矿床类型及其找矿方向     

齐文  侯满堂 《陕西地质》2005,23(1):1-10

通过对陕西金矿资源的分析、总结,将陕西金矿成因类型划分为7类14亚类;与金矿有关的成矿系列划分为3个矿床成矿系列组合,7个成矿系列类型,10个成矿系列和4个亚系列;金矿床空间分布严格受隐伏基底和出露基底,隐伏岩体、重磁吻合构造,构造和成矿时代的控制;与金成矿有关的Ⅲ级成矿区(带)有4条,有关的Ⅳ级成矿区(带)有10条,有关的Ⅴ级主要金成矿区(带)有16条;提出了金矿新的找矿方向,为今后本区金矿地质找矿的新突破提供信息.  相似文献   

土壤天然热释光法在相山火山岩型铀矿床中的应用   总被引：1，自引：0，他引：1  

许军才  黄临平  刘庆成  董业才  魏海  龙期华 《物探与化探》2005,29(3):224-226

介绍了天然热释光法在火山岩铀矿床上的应用效果,表明矿体上方热释光异常较大,无矿区域异常较小,矿体的分布范围与高值异常范围一致,还发现在一些构造薄弱带,裂隙、断层处出现大的异常,试验证明土壤天然热释光测量可以为评价火山岩铀资源提供线索。  相似文献   

黑山金矿地质特征及找矿标志   总被引：1，自引：0，他引：1  

王军年  邵慧君  何晓刚 《新疆地质》2005,23(4):355-358

黑山金矿位于精河县托托河中游，地表圈定6条金矿体．矿体赋存于花岗斑岩体内接触带的破碎蚀变带中．矿床类型为断控脉状造山型，局部石英脉含Au较高．总结了金矿找矿标志。  相似文献   

HD-4002型综合测井仪     

陆士立  袁明  焦仓文  马艳芳  谢海宁  赵志明  李继红  于延斌 《铀矿地质》2005,21(3):183-192

HD 4002型综合测井仪是核工业北京地质研究院于1998年开始研制的, 其目标是为铀矿地质系统提供适合砂岩型铀矿勘查的轻便型数字测井仪, 满足测井生产的需要。该仪器于2001 年3月通过部级鉴定, 2002至2003年投入海拉尔盆地铀矿勘查测井试生产。本文介绍了仪器的用途、功能及特点、性能指标, 简要说明了各部分的工作原理。  相似文献