共查询到20条相似文献，搜索用时 812 毫秒
1.
The paper presents an attempt to determine the characteristics of karst aquifers using information on groundwater level (GWL) in natural holes and boreholes with different data quantity and time resolution of GWL measurements. In this paper the particulars of karst aquifers were analysed for four examples from the Dinaric karst. In all four study areas, aquifers are formed in bare, deep and well‐developed Dinaric karst consisting of Cretaceous limestones. The first example represents a wide area of Imotsko polje in the karst. The aquifer was analysed on the basis of infrequent water level monitoring in natural karst water features (jamas, lakes, wells) and discharges of springs and rivers. The karst aquifer in this example is complex, non‐homogenous and variable in space and time, which is frequent in the Dinaric karst. Regardless of the aforementioned it was possible to determine its elementary characteristics. The second example represents 10 wells used for the water supply for the city of Pula. The GWL and salinity were measured once a week in the period between 1981 and 1996. Even though these measurements were relatively infrequent in space and time, they served as bases for assessment of average and maximum aquifer conditions as well as boundaries of saltwater intrusion. In the third example only a portion of aquifer of the karst spring Blaz, which is in the contact with the Adriatic Seas, has been analyzed. It is a spring with an intrusion of salt water. For purposes of study of saltwater intrusion, 26 piezometers were drilled in its vicinity in which GWL, salinity and temperature were measured once a day during 168 days, a period comprising one complete cycle of seawater intrusion and retreat. These measurements proved the existence of dispersed discharge from the aquifer into the sea and its non‐homogeneity in space. In the fourth example GWL was measured continuously in 10 deep (up to 300 m) piezometers in the hinterland of the Ombla Spring catchment. The measurement period lasted 2 years (January 1988 to December 1989). The analyses are made with hourly data. The results made it possible to determine numerous characteristics of the karst aquifer and a significant non‐homogeneity of groundwater distribution in karst aquifers, depending more on the underground karst phenomena than the surface karst forms. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
2.
萍-乐坳陷带为江西省最主要的隐伏岩溶发育区带之一,岩溶地层发育,地表水、地下水循环交替强烈,地质构造复杂,为岩溶的发育、岩溶地下水的富集提供了良好的条件。查明岩溶发育规律及岩溶水的富集特征,可为地下水资源合理开发与地质环境保护提供科学依据。 相似文献
3.
Zi-Ling Lü Zheng Zhuang Zhu-Wu Fu Jia-Fu Hu Zhong-He Song Guo-Ying Chen Chang-Qiang An Li-Hua Chen 《地震科学（英文版）》1994,7(1):105-115
The average swelling height of Qinghai-Xizang Plateau (Tibet) is about 4.1 km. The area is about 2 300 000 km2. It is the highest and the largest plateau in the world. Mount Qomolangma, the highest peak in the world, is located in the southern fringe of the plateau, and its height is still increasing. What is the driving force for the rising of the Qinghai-Xizang plateau? How high will the plateau still rise from now on? These questions are much concerned by people. In this paper the distribution of the pressure at different depths in the region of Qinghai-Xizang Plateau are derived according to the three-dimensional structures of the S-wave velocity in the crust and upper mantle. The crust and upper mantle structures of the Qinghai-Xizang Plateau is deliberated on the basis of the distribution with a comprehensive analysis on the rock types, earthquakes and the relative crust movements. Then the two questions raised above are discussed. 相似文献
4.
Geochemical behavior of chemical elements is studied in a dolomitite weathering profile in upland of karst terrain in northern
Guizhou. Two stages can be recognized during the process ofin situ weathering of dolomitite: the stage of sedentary accumulation of leaching residue of dolomitite and the stage of chemical
weathering evolution of sedentary soil. Ni, Cr, Mo, W and Ti are the least mobile elements with reference to Al. The geochemical
behavior of REE is similar to that observed in weathering of other types of rocks. Fractionation of REE is noticed during
weathering, and the two layers of REE enrichments are thought to result from downward movement of the weathering front in
response to changes in the environment. It is considered that the chemistry of the upper part of the profile, which was more
intensively weathered, is representative of the mobile components of the upper curst at the time the dolomitite was formed,
while the less weathered lower profile is chemically representative of the immobile constitution. Like glacial till and loess,
the “insoluble” materials in carbonate rocks originating from chemical sedimentation may also provide valuable information
about the average chemical composition of the upper continental crust. 相似文献
5.
Many landforms on Earth are profoundly influenced by biota. In particular, biota play a significant role in creating karst biogeomorphology, through biogenic CO2 accelerating calcite weathering. In this study, we explore the ecohydrologic feedback mechanisms that have created isolated depressional wetlands on exposed limestone bedrock in South Florida – Big Cypress National Preserve –as a case study for karst biogeomorphic processes giving rise to regularly patterned landscapes. Specifically, we are interested in: (1) whether cypress depressions on the landscape have reached (or will reach) equilibrium size; (2) if so, what feedback mechanisms stabilize the size of depressions; and (3) what distal interactions among depressions give rise to the even distribution of depressions in the landscape. We hypothesize three feedback mechanisms controlling the evolution of depressions and build a numerical model to evaluate the relative importance of each mechanism. We show that a soil cover feedback (i.e. a smaller fraction of CO2 reaches the bedrock surface for weathering as soil cover thickens) is the major feedback stabilizing depressions, followed by a biomass feedback (i.e. inhibited biomass growth with deepening standing water and extended inundation period as depressions expand in volume). Strong local positive feedback between the volume of depressions and rate of volume expansion and distal negative feedback between depressions competing for water likely lead to the regular patterning at the landscape scale. The individual depressions, however, are not yet in steady state but would be in ~0.2–0.4 million years. This represents the first study to demonstrate the decoupling of landscape-scale self-organization and the self-organization of its constituent agents. © 2018 John Wiley & Sons, Ltd. 相似文献
6.
Responses of water yield and dissolved inorganic carbon export to forest recovery in the Houzhai karst basin,southwest China 
下载免费PDF全文
下载免费PDF全文 Karst terrain (carbonate rocks) covers a vast land of 0.446 million km2 in southwest China. Water yield and carbonate rocks weathering in this region have been receiving increased attention due to a large‐scale forest recovery. Using both hydrological measurements and forest inventories from 1986 to 2007 in the Houzhai karst basin (HKB), we analyzed the responses of water yield and dissolved inorganic carbon (DIC) export to forest recovery in southwest China. With implementation of both the Natural Forest Conservation Program (NFCP) and the Conversion of Farmland to Forests Program (CFFP), the fraction of forest area in HKB was increased from near zero to 18.9% during the study period, but the ratio of total water yield (surface and underground) to precipitation varied very little over the annual period, neither in wet season nor in dry season. By contrast, the concentration of DIC in water, especially in the surface water had a pronounced increase during the study period, with an increase of 0.53 and 0.25 g C m?3 yr?1 for surface water and underground water, respectively. As a result, total annual DIC export at mean annual rainfall significantly increased from the low to high forest area stage. This increase was largely driven by surface water during the wet season, presumably being related to biological activity. It was concluded that forest recovery in HKB had no significant effect on water yield, but resulted in more carbon dioxide (CO2) dissolved in karst water accompanying with carbon uptake by forests. Our results suggested that implementations of both NFCP and CFFP had no shifted water yield regimes in southwest China; instead, they might have alleviated global climate change by increasing carbon uptake through combined biological processes and carbonate rocks weathering. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
7.
Research on the 3—D Seismic Structures in Qinghai—Xizang Plateau 总被引：1，自引：0，他引：1
Based on the recording data from the analogue and broadband digital seismic stations in and around Qinghai-Xizang (Tibet)Platean,the three dimensiomal 3-D) seismic velocity stroctures in Qinghai-Xizang Plateau were obtained by using the regional body wave tomography and surface wave tomography.The results from these two tomography methods have similar characteristics for P-and S-wave velocity structures in crust and upper mantle.They show that there are remarkahle low velocity zones in the upper crust of L hasa block in the southern Qinghai-Xizang Plateau and the lower crust and upper mantle of Qiangtang block in the northern Qinghai-Xizang Plateau.These phenomena may be related to the different steps of collision process in southern and northern Qinghai-Xizang Plateau. 相似文献
8.
地壳缩短导致青藏隆升造山是普遍的认识.然而,在青藏东部,越来越多的观测数据和研究支持了中下地壳流与隆升造山的关系.目前,地壳缩短造山机制和中下地壳流造山机制仍然处于争论之中.本文建立了二维黏弹塑性有限元模型,模拟了龙门山断层带的多个地震循环的应变与变形,探讨了无与有中下地壳流情况下,地壳地表的位移、速度与变形的分布和演化;以及有中下地壳流情况下,不同流动范围、速度与黏度对模型结果的影响;并结合地形变观测数据的约束,推测了青藏东缘中下地壳流的流动状态.模拟结果显示,通过对比有和无中下地壳流的模拟结果,发现青藏东部震间的地表垂向速度在变形样式及数值上存在较大差异,即存在地壳流的地表垂向抬升速率显著大于无地壳流;震间在龙门山断层西侧附近产生的垂向凸状隆起随中下地壳流的速度、黏度及通道长度的变化而变化.此外,本文研究结果对青藏其他地区可能存在的地壳流的研究也具有一定的参考意义. 相似文献
9.
The St. Paul karst (Palawan, Philippines) is a tropical coastal karst, consisting of towers, cones, huge depressions and large caves. This area hosts the Puerto Princesa Subterranean River (PPSR, 24 km long), whose main entrance is a large spring along the coast and which is one of the largest cave complexes in eastern Asia. A geomorphological study performed by several field surveys and a morphometric analysis of the digital terrain model (DTM) and 3D cave models, allowed formulation of a first evolutionary framework of the karst system. The DTM was extracted from maps and aerial photographs in order to find different generations of ‘relict’ landforms, through the morphometric analysis of topographic surface and karst landforms. Several features suggest a long and multi‐stage evolution of the karst, whose age ranges from Pliocene to present. The southern and northern sectors of the area differ in their altimetric distribution of caves. In the southern sector, some large caves lie between 300 and 400 m asl and were part of an ancient system that developed at the base level of a past river network. In the northern sector, some mainly vadose caves occur, with a phreatic level at 120–130 m asl. An important phase of base‐level cave development is well documented in the inactive passages of PPSR at 50–80 m asl. Morphological features, such as horizontal solution passages and terraced deposits, suggest a phase of stillstand of the base level, which is recorded in the topography as low‐relief surfaces at 40–50 m asl. The age of this phase is probably Early Pleistocene, on the basis of assumed uplift rates. The more recent caves are still active, being located at the current sea level, but they show more than one cycle of flooding and dewatering (with calcite deposition). In the PPSR, several morphologic features, such as two main water level notches at +12·4 and +7·7 m asl and terraced alluvial deposits, suggest that the lower and active level passed through more than two high‐stands of sea level and so it could have formed throughout most of the Middle‐Late Pleistocene. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
Catchment‐scale conceptual modelling of water and solute transport in the dual flow system of the karst critical zone 下载免费PDF全文
下载免费PDF全文 Hydrological and hydrochemical processes in the critical zone of karst environments are controlled by the fracture‐conduit network. Modelling hydrological and hydrochemical dynamics in such heterogeneous hydrogeological settings remains a research challenge. In this study, water and solute transport in the dual flow system of the karst critical zone were investigated in a 73.5‐km2 catchment in southwest China. We developed a dual reservoir conceptual run‐off model combined with an autoregressive and moving average model with algorithms to assess dissolution rates in the “fast flow” and “slow flow” systems. This model was applied to 3 catchments with typical karst critical zone architectures, to show how flow exchange between fracture and conduit networks changes in relation to catchment storage dynamics. The flux of bidirectional water and solute exchange between the fissure and conduit system increases from the headwaters to the outfall due to the large area of the developed conduits and low hydraulic gradient in the lower catchment. Rainfall amounts have a significant influence on partitioning the relative proportions of flow and solutes derived from different sources reaching the underground outlet. The effect of rainfall on catchment function is modulated by the structure of the karst critical zone (e.g., epikarst and sinkholes). Thin epikarst and well‐developed sinkholes in the headwaters divert more surface water (younger water) into the underground channel network, leading to a higher fraction of rainfall recharge into the fast flow system and total outflow. Also, the contribution of carbonate weathering to mass export is also higher in the headwaters due to the infiltration of younger water with low solute concentrations through sinkholes. 相似文献
11.
ABSTRACTAny human intervention or action in karst terrains can unexpectedly, suddenly, strongly and, generally, dangerously change a local and/or a regional hydrological regime. A characteristic example of the Dinaric karst is given in this paper. The operation of two reservoirs in Livanjsko Polje at an altitude of about 702 m above sea level (m a.s.l.) and hydro-electric development of the Cetina River system started in 1973. This year marked a drastic and instantaneous change in the regional hydrological regime. A significant drop in the minimum, mean and maximum annual discharges of two neighbouring karst springs, Rumin Mali and Rumin Veliki, was caused by this anthropogenic construction. The exits of the two analysed karst springs, Rumin Mali and Veliki, are located at altitudes of about 326.8 m a.s.l. and 307.6 m a.s.l. respectively. The areal distance between them is 640 m. Their hydrological regimes have been altered in different ways. The drop in discharges is stronger for the Rumin Veliki than for the Rumin Mali. The analysis shows that the system development influenced the redistribution of the regional karst aquifer and, in this manner, contributed to the reduction of both karst springs’ recharge areas.
Editor D. Koutsoyiannis Associate editor E. Rozos 相似文献
12.
13.
Formation of extensive phreatic caves in eogenetic karst aquifers is widely believed to require mixing of fresh and saltwater. Extensive phreatic caves also occur, however, in eogenetic karst aquifers where fresh and saltwater do not mix, for example in the upper Floridan aquifer. These caves are thought to have formed in their modern settings by dissolution from sinking streams or by convergence of groundwater flow paths on springs. Alternatively, these caves have been hypothesized to have formed at lower water tables during sea level low‐stands. These hypotheses have not previously been tested against one another. Analyzing morphological data and water chemistry from caves in the Suwannee River Basin in north‐central Florida and water chemistry from wells in the central Florida carbonate platform indicates that phreatic caves within the Suwannee River Basin most likely formed at lower water tables during lower sea levels. Consideration of the hydrological and geochemical constraints posed by the upper Floridan aquifer leads to the conclusion that cave formation was most likely driven by dissolution of vadose CO2 gas into the groundwater. Sea level rise and a wetter climate during the mid‐Holocene lifted the water table above the elevation of the caves and placed the caves tens of meters below the modern water table. When rising water tables reached the land surface, surface streams formed. Incision of surface streams breached the pre‐existing caves to form modern springs, which provide access to the phreatic caves. Phreatic caves in the Suwannee River Basin are thus relict and have no causal relationship with modern surficial drainage systems. Neither mixing dissolution nor sinking streams are necessary to form laterally extensive phreatic caves in eogenetic karst aquifers. Dissolution at water tables, potentially driven by vadose CO2 gas, offers an underappreciated mechanism to form cavernous porosity in eogenetic carbonate rocks. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
14.
Sea level is the base level for groundwater circulation in coastal aquifers. The evolution of karst surface landforms and subsurface drainage systems in these aquifers has been conditioned in geological time by tectonics and glacio‐eustatic sea‐level changes. Present morpho‐structural settings and the type/distribution of karst surface and subsurface forms have developed in different carbonate formations according to differences in lithology, climate and exposure time, all driving the intensity of morphologic and karst processes. The repeated and significant changes of groundwater level linked to ‘sea‐level changes’ have had the most important role in driving the continuous evolution of karstic drainage systems, and has resulted in most cases in a multiphase karst. This study aims at defining a general method for identifying, in karst coastal settings, the elevations of flat or low topographic gradient surfaces (using morphometric analysis of Digital Elevation Models (DEMs) and geographical information systems (GISs), and their comparison with elevations of distinctive karstic levels (passages, lateral solution cavities) observed in vertical shafts and horizontal caves. Of the elevations of flat or low topographic gradient surfaces only those agreeing, within ±10 m or ±20 m, with elevation ranges marked by the high frequency of distinctive karst levels were considered as representative of the more probable past sea‐level stands. The method is applied to a regional coastal carbonate formation in southern Italy, by using a 10 m DEM and information on 140 complex caves and 85 shafts. Of the 15 elevations indicated by DEM analysis [620, 600, 470, 450, 425, 385, 355, 315, 270, 250, 205, 180, 150, 110, and 70 m above sea level (a.s.l.)], 13 match clearly those highlighted by significant frequencies of distinctive karstic levels. These elevations are validated by comparison to the elevation of terraces and karst plains indicated in the literature. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
15.
综合分析了前人对青藏高原岩石层构造和动力学研究的成果,提出印度板块和欧亚板块会聚、大陆碰撞及大陆形变的基本特征为青藏高原地壳的加厚和地壳缩短,地壳物质的横向流动;青藏高原隆升过程呈现出阶段性、多样性和复杂性;组成青藏高原的各块体可能有不同的主导隆升机制．认识到在板块构造理论所揭示的全球构造格局中,青藏高原不仅仅是印度板块和欧亚板块会聚、碰撞以及大陆形变的结果,它也是青藏高原大陆岩石层和下伏地幔物质运动的相互耦合、相互作用的结果．从地幔动力学的角度出发讨论了青藏高原隆升的断离险升－挤压隆升－对流隆升三阶段模式（ＢＣＣＭ）,结合数值模拟的结果分析了与此模式相对应的该区域岩石层构造、运动的地幔深部物质运移和动力学背景． 相似文献
16.
Yvonne Battiau-Queney 《地球表面变化过程与地形》1984,9(3):229-252
The classical explanation of the development of the Welsh landscape by the effects of a pulsed ‘eustatic’ uplift during the Cenozoic times is challenged by new data on the geology and geomorphology of Wales and the adjacent regions. The post-Caledonian surface developed over most of Wales in the upper Westphalian plays a major role in landform development. Since its emergence before mid-Cretaceous times, the Welsh Massif has suffered a long subaerial evolution which favoured a powerful chemical weathering. In Anglesey and St. David's Land, residual hills were formed by a process of differential weathering, and downwearing in saprolites. The Millstone Grit quartzites have been deeply weathered and dolines or flat-bottomed basins have been developed. From Cretaceous to Miocene times, a morphotectonic equilibrium has existed between uplift and denudation, so that, in the major part of Wales, the original planation surface was constantly maintained by lowering on itself and in some places it is possible to prove that no more than a few dozen metres of rock thickness disappeared during that period. Several main escarpments were produced by the warping of the planation surface along sharp flexures, during Neogene times. The Cenozoic vertical movements were controlled by the Caledonian or pre-Caledonian tectonic pattern which has divided the continental crust into major structural units. Welsh tectonic development is related to the opening of the North Atlantic, associated stresses reactivating ancient lines of weakness in the heterogeneous lower crust or upper mantle. 相似文献
17.
Martyn Unsworth 《Surveys in Geophysics》2010,31(2):137-161
Continent–continent collisions are an important tectonic process and have played a fundamental role in the evolution of the
modern continents. A combination of geological and geophysical data has provided new constraints on the structure and temporal
evolution of these orogens. Magnetotelluric (MT) studies have been an important part of these studies since they can constrain
the fluid content and thermal structure which are key parameters for defining the rheology of the crust and upper mantle.
MT studies of the Himalaya have defined the geometry of active faults associated with continued plateau growth. Orogen scale
MT studies have shown that both the India–Asia collision (Tibetan Plateau and Himalaya) and the Arabia–Eurasia collision (Eastern
Anatolia) have developed a low resistivity mid-crustal layer with upper surface at 10–20 km that is likely due to a combination
of partial melt and associated aqueous fluids. The properties of this layer are consistent with a strength contrast that permits
crustal flow over geological timescales. The upper mantle from the Moho to at least 100 km beneath both Northern Tibet and
the Anatolian Plateau is characterized by low resistivity values (10–30 Ωm) indicating the presence of shallow asthenosphere.
Future integrated seismic and MT studies of collision zones are needed fully to explore the 3D structures associated with
deformation and further constrain geodynamic models. 相似文献
18.
Stefan H. Doerr Rob R. Davies Alexander Lewis Graham Pilkington John A. Webb Peter J. Ackroyd Owen Bodger 《地球表面变化过程与地形》2012,37(3):253-261
The Australian Nullarbor Plain, one of the world's largest limestone platforms (~200 000 km2), has few distinctive surface karst features for its size, but is known for its enigmatic ‘blowholes’, which can display strong barometric draughts. Thousands of these vertical tubes with decimetre–metre (dm–m) scale diameter puncture the largely featureless terrain. The cause and distribution of these has remained unclear, but they have been thought to originate from downward dissolution and/or salt weathering. To elucidate blowhole distribution and mode of formation we (i) correlated existing location data with Shuttle Radar Topography Mission (SRTM) data, which distinguishes the subtle undulations (< 10 m per km) of the landscape, (ii) surveyed blowhole morphology and (iii) determined their rock surface hardness. Over a sampled area of 4200 km2, the distribution of 615 known blowholes is not correlated with present topography. Blowholes are often connected to small or, in some cases extensive, but typically shallow cavities, which exhibit numerous ‘cupolas’ (dome‐shaped pockets) in their ceilings. Statistical arguments suggest that cavities with cupolas are common, but in only a few cases do these puncture the surface. Hardness measurements indicate that salt weathering is not their main cause. Our observations suggest that blowholes do not develop downwards, but occur where a cupola breaks through the surface. Lowering of the land surface is suggested to be the main cause for this breakthrough. Although cupolas may undergo some modification under the current climate, they, as well as the shallow caves they are formed in, are likely to be palaeokarst features formed under a shallower water table and wetter conditions in the past. The findings presented have implications for theories of dissolutional forms development in caves worldwide. The environmental history of the Nullarbor platform allows testing of such theories, because many other factors, which complicate karst evolution elsewhere, have not interfered with landform evolution here. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
19.
Limestone dissolution in tropical and subtropical humid southern China created residual hills with steep slopes, a landform that is referred to as tower karst. Two types of tower karst landform feature, fenglin or peak forest (isolated towers) and fengcong or peak cluster (linked‐base towers), were identified in Guilin. Previous studies proposed two hypotheses regarding their origin and evolution. One is the sequential evolution model from peak cluster to peak forest. The other is a parallel development model, which postulates that both peak cluster and peak forest have developed simultaneously. Through detailed field survey and analysis of slope forms on tower karst in Guilin, it was found that the mean slope angle of the towers is very high (62·4°) and ranges from 60° to 75°. There is no significant difference in mean slope angle and slope angle distribution between towers in the peak cluster basin and peak forest floodplain areas. Mean slope angle increases with intensified fluvial dissection. Three levels of caves in the towers of the peak forest in Guilin were identified in previous research. The isolated towers of the peak forest as well as scattered residuals of peak cluster are generally distributed in the centre of the Guilin syncline. Favourable circumstances of allogenic water concentration indicate that development of the peak forest resulted from the combined effects of subcutaneous and subterranean dissolution as well as subsequent collapse and recession by fluvial erosion after uplifting. By contrast, peak clusters generally occur on the limbs of the syncline or at the periphery of the Guilin basin with relatively higher elevations. The thick vadose zone and predominantly vertical flow suggests that peak clusters are mainly formed by the combination of intensive uplifting and the enhancement of original dolines. The evidence of slope survey and slope analysis suggests that both isolated towers and linked‐base towers developed simultaneously but by different mechanisms of formation and different combinations of development processes. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献