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通过对广州夏茅村岩溶塌陷进行地质勘察,系统探讨了当地的地质环境条件、岩溶塌陷的灾害特征、岩溶发育条件和岩溶塌陷的形成原因。结果表明,区内第四系覆盖土层厚度大且分布不均,土洞大量发育,隐伏可溶岩的富水性好,溶洞发育;同时,覆盖层内的松散岩类孔隙水与下伏灰岩裂隙溶洞水之间的水力联系密切,含水砂层内地下水位的改变会直接引起下伏灰岩裂隙溶洞水的水位波动,构成岩溶塌陷的水动力因素;钻孔桩施工时钻孔揭穿覆盖层内土洞顶部的黏性土层盖板,造成盖板上部的细砂及淤泥流入土洞,是岩溶塌陷的直接触发因素。在此基础上,提出建立岩溶分布区的地下水动态长期监测网,对岩溶塌陷地段进行灌浆处理,是根治夏茅村岩溶塌陷的主要有效途径。 相似文献
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云南西南部地区由于地质构造等方面的原因，喀斯特洞穴不象滇东地区那样分布广泛和发育强烈，在以往对云南喀斯特与洞穴的研究与开发中并未引起人们足够的重视，有关喀斯特与洞穴学的探测和研究工作在滇西地区进行得不多，可以说还是一块“处女地”。１９９３年至１９９４年间，笔者等人在滇西保山市、施甸县和景谷县等地的洞穴进行了实地综合调查。调查结果表明，滇西南地区的洞穴由于所处的地理位置和特殊的自然环境，有着丰富的喀 相似文献
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Zhongfa Zhou Shaoyun Zhang Kangning Xiong Bo Li Zhonghui Tian Quan Chen Lihui Yan Shizhen Xiao 《地理学报(英文版)》2017,27(8):1011-1024
This research examines the distribution features of 4960 caves across Guizhou Province, while probing the relationship between the caves’ spatial patterns and geographic elements. This study is based on hydrogeological and topographic maps of Guizhou. ArcGIS software was used to process the adjacent index, spatial analysis, and coupling analysis of the caves altitude and longitude, as well as the rock properties, lithology, drainage and tectonic division of almost 5000 caves. Based on a point pattern analysis of Guizhou caves, the adjacent index is 0.53, and the coefficient of variation verified by Tyson polygon reached 72.469%. This figure reflects the clustered distribution pattern of the caves. Across the entire province, caves are divided into four concentrated areas and one weakly affected area. The four concentrated areas are Zunyi-Tongren, Bijie, Qianxinan-Liupanshui, and Guiyang- Anshun-Qinan. The one weakly affected zone is Qiandongnan. The most concentrated among them is the Guiyang-Anshun-Qiannan area, which covers 24.67% of the total province area, and accounts for 36.63% of the total province’s caves. Cave distribution in Guizhou is characterized as dense in the western part and sparse in the eastern part. Under this study background, the natural elements of formation, including lithology, structure, climate, hydrology, and altitude, and their effects on the distribution, number, and spatial pattern of cave development is analyzed. 相似文献
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THE INFLUENCE OF SEA-LEVEL CHANGE AND GEOLOGIC STRUCTURE ON CAVE DEVELOPMENT IN WEST-CENTRAL FLORIDA
The formation of caves in a portion of Citrus County, Florida is controlled structurally by northwest-southeast-trending joints that formed in the Suwannee Limestone during the uplift of Ocala Arch in the Miocene Epoch. The caves developed in a zone where saline water from the Gulf of Mexico and fresh water from the Ocala Uplift mixed. Further uplift elevated the caves above the mixing zone. Following subsequent lowering of regional baselevel, erosion caused sections of cave passages to collapse and/or be filled with sediment. The caves are fossil segments of a formerly larger, interconnected cave system. 相似文献
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The Guadalupe Mountains in New Mexico and Texas are home to more than 300 caves. Caves have been formed within the Upper Permian Capitan carbonate platform and are oriented along two structural trends, one of which is parallel to the platform margin and the other of which is roughly perpendicular to it. Our recent studies of the Capitan Platform have identified syndepositional faults associated with growth monoclines and synclines in Slaughter Canyon, New Mexico, and these are also parallel to the platform margin. In this study, we demonstrate that syndepositional faults and folds are also present in Rattlesnake and Walnut Canyons, as much as 19 km along strike, and that they have exerted control on karstification of the Guadalupe Mountains from the Upper Permian until present.Three distinctive episodes of karst formation have been recognised in outcrops on the basis of karst-filling deposits and crosscutting relationships. The syndepositional “Phase 1 karst” was formed along syndepositional faults and fractures and is filled by platform-derived sediments. The burial “Phase 2 karst” is filled by post-Permian siliciclastics and is limited to the youngest syndepositional faults and fractures that penetrate the platform in the proximity of its terminal margin. Connectivity of these youngest faults and fractures to the platform top and the overlying stratigraphy is inferred to have controlled the distribution of the Phase 2 karst. The “Phase 3 karst” includes the present cave systems, which were mainly formed by sulphuric acid produced by mixing of fossil and fresh underground waters in conjunction with the uplift of the Guadalupe Mountains in the Late Tertiary, and have since been modified by vadose karst processes. The Phase 3 karst caves are not solely developed along syndepositional faults and fractures as the earlier karst palaeocaverns are, but also follow another, uplift-related, structural trend.Syndepositional folds, faults, and fractures in the Capitan Platform have influenced the shaping of the modern surface geomorphology of the Guadalupe Mountains by controlling drainage and, hence, erosion. Trellis drainage parallel to the platform margin is developed where syndepositional folds, faults, and fractures occur. The morphology of the trellis drainage varies systematically across the range in response to the character of the deformation structures and karst features along which the drainage channels have developed. 相似文献
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The Otranto–Leuca coastal tract is marked by the presence of numerous sea caves placed close to present sea level. They are located generally at the back of a shore platform covered by a sequence of breccia deposits, marine sediments and speleothems. At Grotta di Masseria dell'Orte, marine cemented sands rest on a narrow shore platform at about 6.2 m above mean sea level and are covered by speleothems older than 185 ka. At Grotta del Diavolo, which is mostly filled by breccia deposits, three beach levels have been detected at about 3.0, 3.5 and 5.9 m above msl. They are either covered by or overlie speleothems that yield an U/Th age of 340, 78 ka and between 170.3 and 146.5, respectively. Geomorphological evidence and radiometric ages indicate that the area after a period of uplift has been tectonically stable since the last part of the Middle Pleistocene so that marine landforms close to the present shoreline underwent a polycyclic evolution. The sedimentary fills of sea caves formed during Middle-Late Pleistocene glacial stages, when arid or semiarid conditions promoted the removal of regolith and the development of thick breccia deposits. During Marine Isotope Stages (MIS) 9.3, 5.5 and 5.1, cave sediments were partially eroded whereas beach layers and related speleothems developed. These are, in fact, the only marine isotope stages marked by a sea level position which in this Mediterranean region was either close to, or slightly higher than, the present one. 相似文献
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丹霞山顺层洞穴风化特征的试验研究 总被引：1，自引：1，他引：0
以丹霞盆地丹霞组2段顺层洞穴为研究对象,探讨不同岩性红层抗风化能力的差异,重点关注软岩夹层的风化特征及其对顺层洞穴发育的影响。在野外考察的基础上,选择3个典型顺层洞穴为案例,采集了洞穴剖面不同岩性红层的岩样及夹层水样品,进行一系列的岩矿理化测试和水样分析实验。结果表明：洞穴剖面岩性的不均一性及软岩夹层的风化凹进是形成丹霞山顺层洞穴的主要原因。顺层洞穴发育的软岩夹层一般是粉砂质泥岩,粘土矿物含量高,以泥质胶结为主,吸水性较强,开型空隙率较大,抗压强度小,易于风化破碎;上下岩层主要是砂岩和砂砾岩,以钙质和铁质胶结为主,吸水性较弱,开型孔隙率较小,抗压强度较大,风化速度较慢。在洞穴岩层风化过程中,粘土矿物的胀缩、钙质胶结物的溶解, 及铁质胶结物的水化作用等是导致岩体结构破坏的重要因素,但促使不同岩性红层风化的主导因素有所差别。粉砂质泥岩的风化以粘土矿物的胀缩作用为主,砂岩和砂砾岩的风化则以钙质胶结物的溶解作用为主。此外,酸性雨水渗入岩体后与各种矿物进行的一系列离子交换作用也促进了顺层洞穴岩层的风化。 相似文献
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R. A. L. Osborne 《The Australian geographer》1993,24(1):62-74
Bungonia Caves are the result of three distinct phases of speleogenesis. The first, Late Cretaceous phase is characterised by the development of horizontal passages close to the plateau surface. Caves developed in the lower limestone during this phase probably drained southward to risings in Becks Gully. The second, Palaeocene phase resulted in the development of dolines and large dynamic phreatic conduits. Caves extended to depths approximating the level of the Efflux and drainage from caves in the lower limestone was captured by the caves in the middle limestone, rising above the level of the Efflux. The second phase ended when the caves were filled with laminated clays, blocking underground drainage, and the surface was buried by quartz‐rich fluvial sediments prior to the Eocene. The third, and continuing phase, which began in the Late Tertiary, is characterised by the development of vadose shafts and by the removal of sediment deposited following the second phase. 相似文献
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敦煌莫高窟窟前林带防护效应的风洞实验 总被引：4，自引：3，他引：1
洞窟环境包括窟内的温度、湿度、光照、气流等环境因素的适宜程度,对保护洞窟内的壁画和彩塑是十分重要的。洞窟环境不仅因洞窟所处的位置、大小、型制、有无窟门及窟门形式等而异,而且与窟外整个大环境密切相关。不同风况对洞窟内的气流交换起着重要的作用,也是造成石窟壁画彩塑风沙尘粒沉积、崖面风蚀的主要原因。通过风洞模拟实验,从窟前流场、洞窟环流、崖角形状及其受力等几个方面研究了窟前林带的防护效应和崖角防风蚀机理。结果表明：从控制洞窟水汽因素来讲,窟前以通风结构林带最佳,疏透结构林带次之,紧密结构林带欠佳。控制窟前林带灌溉强度,建立多次、少量的窟前林带灌溉制度,同时,在偏东风条件下尽量减少对窟前林带的灌溉,是控制林带生长和底层洞窟侧渗的重要一环。考虑到促进洞窟自然通风的需求,采用一定疏透度的窟门和采取必要的强迫通风,能够较大改善洞窟的自然通风和环境适宜状况。 相似文献
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Çetin Koca 《International journal of geographical information science》2014,28(9):1821-1847
Terrain rendering is a crucial part of many real-time applications. The easiest way to process and visualize terrain data in real time is to constrain the terrain model in several ways. This decreases the amount of data to be processed and the amount of processing power needed, but at the cost of expressivity and the ability to create complex terrains. The most popular terrain representation is a regular 2D grid, where the vertices are displaced in a third dimension by a displacement map, called a heightmap. This is the simplest way to represent terrain, and although it allows fast processing, it cannot model terrains with volumetric features. Volumetric approaches sample the 3D space by subdividing it into a 3D grid and represent the terrain as occupied voxels. They can represent volumetric features but they require computationally intensive algorithms for rendering, and their memory requirements are high. We propose a novel representation that combines the voxel and heightmap approaches, and is expressive enough to allow creating terrains with caves, overhangs, cliffs, and arches, and efficient enough to allow terrain editing, deformations, and rendering in real time. 相似文献
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Morphological features and processes in the central Algarve rocky coast (South Portugal) 总被引：1，自引：0，他引：1
Morphological features along the Algarve rocky coast, South Portugal, are identified and described, with an emphasis on shore platforms and notches. The contributions of processes, such as wave attack, chemical weathering and bioerosion, to sculpting the shore platforms are discussed. The preferential localization of shore platforms on sites exposed to waves, and the lack of significant chemical weathering, point to wave erosion as the first-order factor in platform formation, whilst bioerosion/bioprotection, lithology and geological structure determine platform morphological variations. In addition, platforms above the present intertidal zone appear to have a polygenetic evolution, being inherited from former sea-level highstands and currently undergoing chemical weathering. The occurrence of notch features is independent of the degree of exposure to waves, but they mostly occur where the substratum is sand. Hydrostatic pressure appears to be an important factor in the formation of marine caves in the more sheltered sites. 相似文献
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Brujas Cave, in the Southern Andean Range, is a well-known endokarstic site in Argentina. However, the origin and evolution of this cave system are poorly known. Based on morphological cave features as well as characteristics of cave deposits, we propose a meteogene drawdown cave genesis, including a change from phreatic to vadose conditions related to the high rate of fluvial downcutting in the area. During the vadose period, various cave-related deposits, including authogenic calcite and gypsum speleothems, allogenic volcanic ash and external tufas were deposited. Gypsum crusts are the oldest cave deposits identified (90.2–64.3 ky BP). Their origin, deduced from isotopic characteristics (∂34S=9.6‰), is related to the oxidation of pyrite contained in the Jurassic limestone bedrock as well as the dissolution of overlying Jurassic–Triassic evaporite formations. Gypsum crust deposition is associated with evaporation of water flowing and seeping into the cave during arid environmental conditions. Calcite deposits precipitated from flowing water under equilibrium conditions represent the main speleothem growth period (67.6–34 ky BP in age). Their stable isotope values (∂13C=−3‰ to −5‰ and ∂18O=−9‰ to −11‰) may indicate slightly humid and warm conditions related to the regional Minchin lacustrine phase and global oxygen isotope stage 3. Following this stage, a seismic event is evidenced by accumulations of broken stalactites. Seepage calcite speleothems covering cave walls were deposited under disequilibrium conditions by evaporation, probably during Holocene time. Finally, another more recent gypsum deposition period represented by gypsum balls has been differentiated. Micromorphological as well as isotopic (∂34S=5.6‰) data indicate that these gypsum forms are related to cyclic processes (solution–deposition) from water seeping into the cave under arid conditions. In addition, intense volcanic activity in the area during Holocene time is deduced from allogenic volcanic ash and lapilli located mainly at the entrance cave. At present, limited hydrological activity is observed in the cave and small tufa deposits at karstic discharge points are evidenced. We conclude that the geomorphological evolution of Brujas Cave was controlled by climatic changes (wet and dry stages) under semiarid environmental conditions in a very active tectonic and volcanic setting during Late Quaternary time. 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(4):183-209
The Pikhågan caves at Svartisen, North Norway, are described and then analysed using passage morphology and scallop morphometry. The caves consist of a multilevel network of essentially horizontal phreatic tubes with a total length of 2,000 + m. Vadose elements account for only about 4% of the total passage lengths, while paragenetic roof alterations arc more common (?10%). Palcocurrcnt direction and flow rates as deduced from scallops suggest a uniform network flow southwards through the system, which also fits well with hydraulic laws for tube networks. This model requires a hydraulic conductivity between entrances formed by glacial truncation. Evidence of a subsequent sediment fill and paragenetic incision of roof half-tubes is demonstrated. These phases were followed by a lowering of the local watertable from above 610 m to about 575 m, when a phase of high discharge occurred. If this shift of watertable was caused by bedrock erosion, it probably took place more than 220 ka ago. Subsequently the watertable was lowered further to its present level (<560 m). Two alternative origins are suggested: first, a possible pre-glacial genesis of the phreatic network in a paleic valley system, second, a possible sub-glacial genesis. The paragenetic phase is regarded as the most likely to have occurred subglacially, while the coarse sediment infilling and the high discharge regime arc associated with deglaciations. The previously proposed proglacial genesis of this phreatic cave system is rejected because of the present topography and because of the slow paleocurrent regime inferred from scallop measurements. 相似文献
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Silviu Constantin Theofilos Toulkeridis Oana Teodora Moldovan Marcos Villacís Aaron Addison 《自然地理学》2019,40(1):28-51
Current knowledge of caves and karst regions of Ecuador is scarce and broadly limited to discrete areas such as that of the Galápagos volcanokarst. In continental Ecuador, carbonate karst mostly outcrops in the Amazonian basin and accounts for 5–10% of the surface of the country. However, owing to the difficulties of access within the Amazonian rainforest, most surface and subterranean karst is yet to be revealed. In this review, we present an updated map of the solutional karst of Ecuador based on the most recent geological surveys and our own research. We describe the principal karst regions of Ecuador from the Amazonian basin (Napo and Santiago) as well as the Galápagos pseudokarst. We show that Ecuador karst research may be of considerable importance for both basic and applied research owing to its geographical position and intrinsic vulnerabilities. We discuss the main challenges of karst-related research in Ecuador, such as paleoclimatic studies, subterranean biodiversity, and archeology. We discuss the main vulnerabilities and hazards related to karst uses in Ecuador, considering the paramount importance of tourism for the country. 相似文献
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《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3-4):185-192
The distribution of active and abandoned caves in the Morecambe Bay karst is indicative of at least two phases of subsurface drainage development, separated by an episode of valley incision, landscape dissection and surface lowering. It is suggested that the phase of erosion was associated with glaciation by ice from the adjoining Cumbrian massif, and that the earlier phase of drainage development was of at least last interglacial age. This view is supported by the evidence of the age and mode of deposition of the sedimentary infill in the caves, and by estimates of cave palacocatchment area. The caves of the earlier phase of drainage development were formed in valleys that were already deeply incised. It would therefore appear that the last glaciation only succeeded in slightly modifying an existing topography, a view at odds with conventional ideas of landscape development in Cumbria as a whole. 相似文献