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1.
泌阳凹陷南部陡坡带核二段物源及古水流研究   总被引:2,自引:0,他引:2  
用重矿物法、碎屑岩类法和地层厚度等微观和宏观方法分析了泌阳凹陷南部地层的物源和古水流。核二段时期泌阳凹陷主要受西北部社旗凸起、南部桐柏山,东北部伏牛山地形影响,其物源也形成了大致与地势相一致的趋势,即4个主物源区:西北部杜楼物源区,南部平氏物源区、杨桥物源区以及东北部孙岗物源区;2个次物源区:下二门物源和梨树洼物源。  相似文献   

2.
Living organisms are known to create structures in ancient rocks that are indigenous but not primary and that have been mistaken for fossils. Examination of burrows recently reported as fossils from 10(9)-year-old sedimentary rocks indicates that they are not the same age as the rocks but were probably made by termites working down after water. The burrows are partially filled with material from a modern lateritic surface from which they descend into steeply dipping, decomposed silt-stones of the Zambian Copperbelt. In fact, no authentic record of Metazoa that are demonstrably coeval with rocks older than 680 million years is known.  相似文献   

3.
The Mars Express Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) hyperspectral image data covering eastern Terra Meridiani indicate the ubiquitous presence of molecular water in etched terrain materials that disconformably overlie heavily cratered terrains and underlie the hematite-bearing plains explored by the Opportunity rover. Identification of crystalline water in kieserite (MgSO4.H2O) is linked to materials exposed in a valley and plateau to the north of hematite-bearing plains. The mineralogical similarities between the etched terrain deposits examined with OMEGA data and the layered rocks examined by Opportunity imply that the ancient aqueous environments inferred from analyses of the rover data extend over regional scales.  相似文献   

4.
The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.  相似文献   

5.
海洋环境噪声的分类及其对海洋动物的影响   总被引:2,自引:0,他引:2  
海洋环境条件特殊,地形复杂,海洋声学的研究进展相对缓慢。本文中对海洋环境噪声按频率范围进行了分类,包括极低频噪声、超低频及甚低频噪声和高频噪声,并探讨了海洋环境噪声对水产养殖动物及野生海洋动物(尤其是海洋哺乳动物)的影响,展望了海洋声学研究的前景。  相似文献   

6.
利用中低分辨率DEM提取坡耕地坡度信息的误差分析   总被引:2,自引:2,他引:0  
利用数字高程模型(DEM)实现坡耕地数据的自动提取和侵蚀状况调查,并与实地勘察及相关研究结果进行对比。结果表明,三峡库区平行岭谷地貌、出露的侏罗纪紫色泥(页)岩和砂岩互层结构及人为活动是小尺度坡耕地地形的关键控制因素。  相似文献   

7.
赵雯瑾  王思麒  李彬  罗言云 《安徽农业科学》2012,40(8):4758-4759,4797
在分析城镇密集区山地公园绿地的特点及问题的基础上,阐述了植被恢复的意义。以内江市塔山公园为例,调查了该公园的生态环境概况和植被情况,结果表明:内江市塔山公园地形陡峭,生态环境脆弱,坡地植被较少,岩石裸露率高,群落结构简单。针对调查结果,提出主要采用自然恢复、人工恢复两种方法进行植被恢复。其中,着重从坡度划分的角度,探索了如何利用植物筛选、群落配置技术对山地公园不同坡度类型的绿地进行植被恢复。  相似文献   

8.
Indications of shock metamorphism produced by pressures up to the megabar region have been observed in the fine material and the breccias, but very rarely in the coarser fragments of crystalline rocks. These indications are deformation structures in plagioclase and pyroxene, diaplectic plagioclase glasses, and glasses formed by shock-induced melting of lunar rocks. Two sources of shock waves have been distinguished: primary impact of meteorites and secondary impact of crater ejecta. There are two major chemical types of shock-induced melts. The differences in chemistry may be related to impact sites in mare and highland areas.  相似文献   

9.
Branching valley networks throughout the heavily cratered terrain of Mars exhibit no compelling evidence for formation by rainfall-fed erosion. The networks are diffuse and inefficient, with irregular tributary junction angles and large, undissected intervalley areas. Rather, the deeply entrenched canyons, with blunt amphitheater terminations, cliff-bench wall topography, lack of evidence of interior erosion by flow, and clear structural control, suggest headward extension by basal sapping. The size-frequency distributions of impact craters in these valleys and in the heavily cratered terrain that surrounds them are statistically indistinguishable, suggesting that valley formation has not occurred on Mars for billions of years.  相似文献   

10.
基于DEM的数字地形分析   总被引:29,自引:0,他引:29  
该文在对数字高程模型(DEM)数据来源及结构、数字地形分析及其应用、基于DEM的地形分析中的不确定性和误差分析的基础上,以日本东北地区岩手县早池峰山为研究对象,美国MicroImage公司开发的TNTmips地理信息系统为工具,日本国土地理院发行的“数字地图25000”为基础数据,研究基于DEM的数字地形特征提取与分析方法,以及DEM精度对地形特征的影响. 研究结果表明:①以DEM为基础可提取多种地形特征,如坡度、坡向、坡面形态、流域边界、水流路径等,这些特征在地理信息系统的支持下均可用图形和属性数据来表示;②DEM水平精度对基于DEM提取的数字地形特征影响表现为:低精度的DEM将导致研究区平均坡度变小、坡度标准差变大;同时,DEM精度对不同坡度区域表现为不同的影响,其结果按坡度大致可划分为3种不同类型,即0°~10°、10°~35°以及大于35°; DEM精度对坡向的影响除平坡外变化较小,其中平坡面积随DEM精度的降低而增大;低精度的DEM将导致水文地形信息受损,这将严重影响流域水文模型参数的确立及水文过程模拟分析的精度.   相似文献   

11.
A first-order analog to martian fretted terrain has been recognized on enhanced, ERTS-1 (Earth Resources Technology Satellite) imagery of Alaskan Arctic thermokarst terrain. The Alaskan analog displays flat-floored valleys and intervalley uplands characteristic of fretted terrain. The thermokarst terrain has formed in a manner similar to one of the processes postulated for the development of the martian fretted terrain.  相似文献   

12.
The preferential distribution of soddy podburs on loose sandy sediments of different genesis, as well as the possibility of their formation on loess-like carbonate rocks and, in rare cases, on the eluvium of metamorphic biotite–chlorite shales, has been revealed. The differences in the microstructure, composition, and properties of soils are due to the impact of different soil-forming rocks. The results of study will contribute to the classification of regional soils and the optimization of forest and agricultural land use.  相似文献   

13.
利用中低分辨率DEM提取坡耕地坡度信息的误差分析(英文)   总被引:1,自引:0,他引:1  
利用数字高程模型(DEM)实现坡耕地数据的自动提取和侵蚀状况调查,并与实地勘察及相关研究结果进行对比,分析利用中低分辨率DEM提取坡耕地坡度信息误差的来源及其对水土流失调查结果的影响。结果表明:利用忠县1∶50000地形图生成分辨率为25m的DEM,基于该分辨率DEM自动提取的坡耕地信息在评价其水土流失现状时与实地勘察和相关研究结果存在一定差异,其主要原因为:①该地区地貌特殊,平行岭谷地貌和出露的侏罗纪紫色泥(页)岩与砂岩互层结构共同作用形成的地形较为复杂,造成该区土地利用多以小地块为主的镶嵌结构,而分辨率较低的DEM对地形起伏的描述误差较大;②人为修建的梯田(水田)、坎田以及垄沟整地措施对坡耕地微观地形改变的影响较大。因此,在坡耕地水土流失现状评价中,单从中低分辨率DEM获取坡度信息来判断水土流失程度,将会产生较大误差。DEM分辨率越高,对与坡度有关的地貌和水文参数的描述越精确,提取的坡度信息越准确。中低分辨率坡度可以通过变换,使其接近较高分辨率坡度对地形起伏的反映能力。此外,还应加强实地勘察力度,并与计算机自动提取技术相结合,才是正确评价坡耕地水土流失的方法。  相似文献   

14.
The Holleford Crater, a circular depression in southern Ontario, is filled with Paleozoic sediments and underlain by brecciated Precambrian igneous and metamorphic rocks. The presence of coesite in two core samples of this breccia has been established by petrographic and x-ray diflraction methods. Shattered quartz in the coesite-bearing samples exhibits planar fractures. The shocked quartz is the result of great shock pressures and the association of coesite with the shocked quartz strongly suggests that Holleford Crater originated from a hypervelocity impact.  相似文献   

15.
2008年以来,我国北方大部分地区发生严重干旱,监测精度的高低直接影响着防旱、抗旱工作的开展。由于目前我国还没有一套完善的干旱监测方法,使得干旱监测的精度问题一直存在。针对全国复杂地形,对其不同气候区的干旱情况应用不同的监测方法进行可行性分析,提出了一些新的理论和方法,一定程度上提高了监测精度,形成了一个较为完备的干旱监测体系。  相似文献   

16.
金山  刘开宇  李腊平  张庆红 《安徽农业科学》2010,38(27):15103-15107
利用中尺度数值预报模式MM5,对贵州省2005年6月25~26日一次由中尺度对流系统(MCS)引起的暴雨过程进行数值模拟,并在MM5很好地模拟了此次MCS过程及伴随的云物理过程基础上,通过分别降低云贵高原的地势及削平云贵高原中东部以东地区模拟试验,研究了云贵高原西部阶梯型地形对贵州地区暴雨的影响。结果表明,云贵高原的第2阶梯地形仅对该地形下游地区对流云系的发展有影响,对上游地区降水影响不大,而云贵高原对高原西侧迎风坡降水有显著影响,对高原中东部地区暴雨的分布、强度和对流云系的持续时间有重要影响。  相似文献   

17.
Chao EC 《Science (New York, N.Y.)》1967,156(3772):192-202
Shock effects in quartz, plagioclase, biotite, amphibole, and some accessory minerals have been observed in rocks subjected to various degrees of meta morphism by meteoritic impact. The shock features described are unique; they are never observed in rocks from normal geologic environments. Such features are described: 1) Multiple sets of closely spaced planar microstructures occur in quartz, plagioclase, and other rock-forming minerals. Those characteristic of shock consist of alternating platelets, with a range of reduced mean index of re fraction and birefringence; they con sist of platelets that have been partially or completely transformed to an amor phous phase. 2) Quartz and plagioclase are selec tively and completely transformed to silica glass and plagioclase glass in the solid state, whereas the associated mafic minerals remained crystalline. There is no reaction between adjacent minerals. 3) High-pressure polymorphs occur, such as coesite or stishovite. Coesite oc Curs exclusively within silica glass; it has not been observed as a reaction or breakdown product. 4) Nickel-iron spherules occur in the fused glass or impactites. 5) The occurrence of droplets of ilmenite, rutile, pseudobrookite, and baddaleyite in impactites indicates a temperature of formation exceeding 150 degrees C. 6) Dense glass occurs, similar in composition to bulk rock, in which iron oxide, such as fine particles of mag netite, is completely dissolved. All these features are characteristic of a process involving the rapid rise and fall of extremiiely high pressures and temperatures. Minerals and mineral as semblages experiencing such high strain rates and sudden changes of pressures and temperatures react and change in dependently to the bulk chemical com position, under nonequilibrium condi tions. Many aspects of shock features re quire careful study. Kink bands in biotite and deformation lamellae in quartz occur in tectonically deformed rocks. These features should be studied with great care in order to determine whether reduction in mean index of refraction and total birefringence along the planar structures have resulted from vitrification or phase transition; their presence is additional evidence in favor of a shock mechanism. Vitreous phases or glasses formed by shock also have many unique prop erties; they have not been studied by such methods as thermoluminescence, electron spin resonance, low-angle x ray diffraction, or infrared spectroscopy. Shock-fused glass of high density needs to be studied in detail in carefully con trolled laboratory conditions. Experimental shock-wave studies of the equation-of-state of single minerals and mineral assemblages, under care fully controlled conditions, must pre cede estimates of peak pressures and peak and residual temperatures of shocked natural mineral assemblages. Detailed petrographic and mineralogic studies, however, have provided useful and definitive criteria for characteriza tion of impact events. Such data should be of paramount importance in the study of samples brought back from Moon.  相似文献   

18.
山区高分辨率遥感影像地形辐射校正方法研究   总被引:1,自引:0,他引:1       下载免费PDF全文
高空间分辨率的卫星影像和航摄影像越来越广泛地应用于山区农、林业资源调查和山区生态环境监测等领域.但是由于山区地形起伏和侧视成像等原因,使得影像存在一定的阴影,从而严重影响这些高分辨率影像的应用.针对这一问题,本文借鉴在遥感影像条带噪声去除中非常有效的矩匹配方法基本原理,提出了基于矩匹配的山区高分辨率遥感影像辐射校正方法,同时对被验证TM影像地形辐射校正最佳的C校正方法作了相应的改进.并以北京市西部山区的1 m分辨率的航空影像为例,分别用矩匹配方法和C校正改进方法进行了地形辐射校正,并对处理结果进行了对比分析.结果表明,对于地形复杂的山区,图像较大的高分辨率影像,矩匹配方法优于C校正改进方法.  相似文献   

19.
Impact has been an important rock-forming process on the moon. Electron- and ion-probe analyses of major and minor elements show that most glasses and chondrule-like particles formed by shock melting of various proportions of mainly pyroxene, plagioclase, and ilmenite. This is the first direct evidence that chondrule-like molten droplets can form in impact events. Welding and shock lithification resulted in rocks texturally similar to chondrites but composition rules out the moon as source for chondrites. Impact craters on a nickel-iron sample evidence the importance of secondary impacts by accelerated lunar matter.  相似文献   

20.
The preliminary characterization of the rocks and soils returned from the Apollo 16 site has substantiated the inference that the lunar terra are commonly underlain by plagioclase-rich or anorthositic rocks. No evidence has been found for volcanic rocks underlying the regolith in the Apollo 16 region. In their place, we have found anorthositic rocks that are thoroughly modified by crushing and partial melting. The textural and chemical variations in these rocks provide some evidence for the existence of anorthositic complexes that have differentiated on a scale of tens to hundreds of meters. The occurrence of deep-seated or plutonic rocks in place of volcanic or pyroclastic materials at this site suggests that the inference from physiographic evidence that the latter materials are widespread in terra regions may be incorrect. Several additional, more specific conclusions derived from this preliminary examination are: 1) The combination of data from the Descartes region with data from the orbital x-ray fluorescence experiment indicates that some backside, highland regions are underlain by materials that consist of more than 80 percent plagioclase. 2) The soil or upper regolith between North Ray and South Ray has not been completely homogenized since the time of formation of these craters. 3) The chemistry of the soil indicates that rocks rich in potassium, uranium, and thorium, similar to those that prevail at the Fra Mauro site, are relatively abundant (10 to 20 percent) in the Descartes region. 4) The K/U ratio of the lunar crust is similar to that of the KREEP basalts. 5) The carbon content of the premare lunar crust is even lower than that of the mare volcanic rocks.  相似文献   

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