Underground Karst Research Articles

KARST TERRAIN OF THE YUCATAN PENINSULA AND ITS MOUNTAIN FRAME (MEXICO, GUATEMALA, BELIZE)

Multilayered karst systems of both above- and underground types were formed on the Yucatan Peninsula at the absolute heights from -150 m offshore to more than 2000 m in the surrounding mountains. Several floors of karst topography were identified: shelf (Mesoamerican Reef) with flooded caves and cenotes; coastal areas with shallow caves and cenotes and dense network of flooded tunnels; the transition zone – sloping plain with deeper cenotes, caves and rare tunnels; hilly northern central part with the rare deep cenotes and caves and polje; Peten plateau with fragments of dry valleys, polje, caves; hilly-low mountains framing with inselberg karst, caves and partially underground rivers; mountains with numerous waterfalls, systems of extremely deep caves, underground rivers, polje. Multi-floor structure of underground karst forms are mainly due to fluctuations of sea level: a periodic drainage of the territory and changes of erosion basis had led to incise of surface and underground watercourses. As a result karst process extended to the entire zone of active water exchange. The most rapid formation of cavities was in the areas of halocline fluctuations. Numerous fractured zones of different origins were a decisive in the rise, development and spatial features of karst systems.

Karst bare slope soil erosion and soil quality: a simulation case study

Abstract. The influence on soil erosion by different bedrock bareness ratios, different rainfall intensities, different underground pore fissure degrees and rainfall duration are researched through manual simulation of microrelief characteristics of karst bare slopes and underground karst crack construction in combination with artificial simulation of rainfall experiment. The results show that firstly, when the rainfall intensity is small (30 and 50 mm h−1), no bottom load loss is produced on the surface, and surface runoff, underground runoff and sediment production are increased with the increasing of rainfall intensity. Secondly, surface runoff and sediment production reduced with increased underground pore fissure degree, while underground runoff and sediment production increased. Thirdly, raindrops hit the surface, forming a crust with rainfall duration. The formation of crusts increases surface runoff erosion and reduces soil infiltration rate. This formation also increases surface-runoff-erosion-damaged crust and increased soil seepage rate. Raindrops continued to hit the surface, leading the formation of crust. Soil permeability showed volatility which was from reduction to increases, reduction, and so on. Surface and subsurface runoff were volatile with rainfall duration. Fourthly, when rock bareness ratio is 50 % and rainfall intensities are 30 and 50 mm h−1, runoff is not produced on the surface, and the slope runoff and sediment production present a fluctuating change with increased rock bareness ratio. Fifthly, the correlation degree between the slope runoff and sediment production and all factors are as follows: rainfall intensity-rainfall duration-underground pore fissure degree–bedrock bareness ratio.

Edwards Aquifer Region Stakeholder Frame Analysis

ABSTRACTThe 2011 drought was the worst single-year climatic occurrence in Texas's recorded history (Texas AgriLife Extension Service 2011). Texas must meet residential and economic development requirements of a population that will nearly double over the next fifty years and will require dramatic improvements in water conservation and reuse. Located in the south central region of Texas, the Edwards Aquifer is an underground karst formation with water flowing through it that has been at the center of controversy for more than sixty years. As the sole source water supply for nearly 2 million people in San Antonio, the controversy over the use of the Edwards Aquifer water centers on four major concerns: its limited physical structure, multiple users, potential contamination, and the potential loss of endangered species. This qualitative study uses interactional frame theory to demonstrate characterization and identity framing, and provides a definition of frame theory, its nature, and its development. This research employs the concept of framing to shape, organize, and focus on new agendas of today's stakeholders. The purpose of this study is twofold. The first purpose is to revisit a previous case study by Putnam and Peterson (2003), reevaluate the nature of the conflict since that time, and reexamine and possibly reframe, if necessary, any lingering unsolved arguments by the original stakeholder groups included in the 1980 through 1997 analysis. The second purpose is to discover the extent to which new conflict has arisen from today's stakeholder groups, as well as the intensity of that conflict compared to the 1980 through 1997 period of legal turbulence. The results of this study identify key stakeholder groups in the Edwards Aquifer region that, as a result of Senate Bill 3 in 2007, through a consensus-based approach, have successfully mitigated the intractable environmental conflict of the aquifer. The stakeholder process has implemented a habitat conservation plan to protect spring flows, downstream economic interests, and endangered species. However, lingering problems related to property rights issues and potential “takings” liability, as well as a voting rights lawsuit brought by the League of United Latin American Citizens and enjoined by the San Antonio Water System, threaten to unravel the process.

Geomorphological significance of the palaeodrainage network on a karst plateau: The Una–Korana plateau, Dinaric karst, Croatia

Karst plateaus often have a complex geological and geomorphological history. It is widely accepted that their development requires a long period of karst denudation. This study reconstructs the palaeodrainage network of a karst plateau, analyses its properties and establishes its geomorphological significance. The main purpose of this research was to deepen our understanding of a key stage in the evolution of karst plateaus — the transition from a fluvial land surface to one dominated by karst surface processes. The study was conducted on a large part of the Una–Korana plateau, the largest plateau in the Dinaric karst. The majority of the plateau is made of carbonate rocks of Triassic, Jurassic and Cretaceous age that set the conditions for the development of the karst. We have reconstructed the palaeodrainage network based on 1:25,000 topographic maps with 10m contours. The transition of the surface drainage network to the underground karst drainage network is still in progress, so, depending on the degree of karstification, the drainage network was divided into three categories: active, dry and relict. It was found that 90.5% of the pre-existing drainage network has undergone some degree of karstification. The active surface drainage network gradually shifted to a dry network, then to a relict network. The surface drainage network is gradually replaced by a dense network of dolines. Today, the flat and karstified inter-fluvial area is drained underground towards the main watercourses and these drain the entire region over the surface towards the Pannonian basin. This is the largest known karst palaeodrainage network in the Dinaric karst that has been reconstructed in this way.

Storage of Heterogeneous Data in the Karst Processes Monitoring System

The paper is devoted to organization the storage of heterogeneous data in the karst processes monitoring system. We discussed the basic requirements for the storage system and described its structure. The system includes a databases monitoring of surface karst, monitoring of underground karst processes, monitoring of hydrogeological processes, the photographic collection of surface karst forms and cartographic collection. We present the results of the practical implementation of the system on the example research data of area allocated for the construction of the nuclear power plant in Nizhny Novgorod on Monakovo.

The role of condensation in the evolution of dissolutional forms in gypsum caves: Study case in the karst of Sorbas (SE Spain)

The karst of Sorbas (SE Spain) is one of the most important gypsum areas worldwide. Its underground karst network comprises over 100km of cave passages. Rounded smooth forms, condensation cupola and pendant-like features appear on the ceiling of the shallower passages as a result of gypsum dissolution by condensation water. Meanwhile, gypsum speleothems formed by capillarity, evaporation and aerosol deposition such as coralloids, gypsum crusts and rims are frequently observed closer to the passage floors. The role of condensation–dissolution mechanisms in the evolution of geomorphological features observed in the upper cave levels has been studied by means of long-term micro-erosion meter (MEM) measurements, direct collection and analysis of condensation waters, and micrometeorological monitoring. Monitoring of erosion at different heights on gypsum walls of the Cueva del Agua reveals that the gypsum surface retreated up to 0.033mmyr−1 in MEM stations located in the higher parts of the cave walls. The surface retreat was negligible at the lowest sites, suggesting higher dissolution rates close to the cave ceiling, where warmer and moister air flows. Monitoring of microclimatic parameters and direct measurements of condensation water were performed in the Covadura Cave system in order to estimate seasonal patterns of condensation. Direct measurements of condensation water dripping from a metal plate placed in the central part of the El Bosque Gallery of Covadura Cave indicate that condensation takes place mainly between July and November in coincidence with rainless periods. The estimated gypsum surface lowering due to this condensation water is 0.0026mmyr−1. Microclimatic monitoring in the same area shows differences in air temperature and humidity of the lower parts of the galleries (colder and drier) with respect to the cave ceiling (warmer and wetter). This thermal sedimentation controls the intensity of the condensation–evaporation mechanisms at different heights in the cave.

GEOECOLOGICAL EVALUATION OF THE ORLOVAČA CAVE

<p>Speleological tourism in the world has a long tradition. Тhe environment of the karst underground has long attracted nature lovers, various researchers and tourists. Orlovača cave is one of the largest and most beautiful cave systems in Bosnia and Herzegovina and Republic of Srpska. Accordingly, in order to evaluate the tourist values of this locality, geoecological evaluation is applied by method of recreational potential and appraisal. The results should indicate the importance of cave tourism on the domestic and international markets, as well as preserving the environment in locality</p>

Erosion-creep-collapse mechanism of underground soil loss for the karst rocky desertification in Chenqi village, Puding county, Guizhou, China

Carbonate rocks distribute widely in China. The total area of the carbonate rocks is about 3,430,000 km(2), and the exposed area of the carbonate is approximately 13 % of China's territory. In 2003, soil loss in Yunnan, Guizhou, and Guangxi provinces reached 179,600 km(2), which is almost 40.1 % of the total area, causing rocky desertification. In this study, the erosion-creep-collapse mechanism of underground soil loss for the karst rocky desertification in Chenqi village, Puding county, Guizhou province is proposed. The mechanism occurs under the following geological environment: slope surface undulation, underlying bedrock surface fluctuation and thin and inhomogeneous soil overlying, overlying soil generation by bedrock weathering, underground karst development, and large groundwater depth and lying water table under the bottom of soils. The erosion-creep-collapse mechanism of underground soil loss in the karst slopes is explained as follows: power loss due to human cultivation activities that destroy the soil structure, hydraulic force formed by rainfall infiltration, wet-dry cycle generated by rainfall, erosion effect caused by rainfall penetration, creeping and flowing of plastic-stream soil, and collapse. The erosion-creep-collapse mechanism of underground soil loss has seven steps: disturbance of soils filled in underground karst cave by human activities, internal soil erosion and partial collapse caused by hydraulic power, internal free surface formation within the soil in the filled karst cave, internal soil creeping, soil pipe formation, soil pipe collapse, and ground surface collapse and filling. Soil loss develops slowly, and sudden transportation occurs by collapse. Soil loss can be explained by the proposed mechanism, and soil loss can be prevented by controlling soil collapse.

Climate Change and Water Scarcity Adaptation Strategies in the Area of Pacitan, Java Indonesia

The Karst area in Indonesia consists of a total area of 154.000 km2 of which 15% is protected. Pacitan is a part of The Thousand Mountains (Gunung Sewu in Javanese language) karst area and located in Southern Coastal of Java Island. Gunung Sewu karst area ranges over 85km from west in Yogyakarta Special Province, to the east in East Java Province. Water scarcity is one of the issues in Pacitan due to the porous texture of the karst underground; most of the precipitation trickles immediately down into extensive system of sinkholes and caves. Thus, no surface water rivers, brooks or springs can be found in the area, especially during dry season where water supply, such as little lakes, called telaga, are depleted. Three sub-districts of Pacitan that include in Gunung Sewu karst area, i. e. Donorojo, Punung, and Pringkuku, suffer water shortage, especially during dry season, where the local communities need to walk up to 5 kilometers in order to take water for their domestic use. However, State-owned Water Company (Perusahaan Daerah Air Minum/PDAM) that has developed since 1992 in Pacitan, contributes in water supply in these areas and it has covered 70% in three kecamatan (sub-districts) by building IPA and is currently developing to cover the rest of the area by utilizing big water sources. PDAM and The Ministry of Public Work support the water treatment installation (Instalasi Pengolahan Air/IPA), especially in these three sub-districts. Furthermore, adaptive capacity has been developed in the local community of karst area in Pacitan, e.g. planting cultivars resistant to drought (cassava, maize, soybean, and groundnut) or doing multi cropping between those cultivars, and planting rainwater harvesting and artificial aquifer.

Karst Sinkholes Stability Assessment in Cheria Area, NE Algeria

This research work deals with the problem of karst sinkhole collapse occurring in the last few years in Cheria area (NE Algeria). This newly revealed phenomenon is of a major constrain in land use planning and urbanization, it has become necessary to locate and assess the stability of these underground features before any planning operation. Several exploration methods for the localization of underground cavities have been considered. Geological survey, discontinuity analysis, resistivity survey [ground penetrating radar has not been used as most of the Mio-Plio-Quaternary filling deposit covering Eocene limestone contains clay layers which limits the applicability of the method (Roth et al. in Eng Geol 65:225–232, 2002)] and borehole drilling were undertaken in order to locate underground cavities and assess their depth, geometry, dimensions, etc. Laboratory testing and field work were also undertaken in order to determine both intact rock and rock mass properties. All the rock mechanics testing and measurement were undertaken according to the ISRM recommendations. It has been found that under imposed loading, the stability of the karst cavities depends on the geo-mechanical parameters (RMR, Rock Mass Rating; GSI, Geological Strength Index; E, Young modulus) of the host rock as well as the depth and dimensions of the gallery. It increases with RMR, GSI, E and depth and decreases as the cavity becomes wider. Furthermore, the calculation results show that a ratio (roof thickness to gallery width) of 0.3 and more indicate, a stable conditions. The results obtained in this work allow identifying and assessing the stability of underground karst cavities. The methodology followed in this paper can be taken as a road map in the establishment of a hazard map related to the studied phenomenon. This map will be a useful tool for the future urban extension planning in Cheria area.

Drought Causes and Solutions of Down-Faulted Basin Groups in Nandong Underground River Basin

For many years, drought is severe in the basins and the mountain area of Nandong underground river basin. The author analyzes the reasons of the drought from the hydrogeological characteristics of the basin, climate characteristics, groundwater pollution ,and study indicates that the drought causes is that shallow groundwater and surface water has been seriously polluted, and it is extremely difficult to look for underground karst water. Then the author analyse solutions to solve these problems: building underground dam in Moshigou to develop Nandong underground river; rising underground water level elevation up to 1253m,it can intercept about 306 million m3 underground water. In this way, the author predict that the water shortage problem can be solved fundamentally in these three basins.

Identification of glacial meltwater runoff in a karstic environment and its implication for present and future water availability

Abstract. Glaciers all over the world are expected to continue to retreat due to the global warming throughout the 21st century. Consequently, future seasonal water availability might become scarce once glacier areas have declined below a certain threshold affecting future water management strategies. Particular attention should be paid to glaciers located in a karstic environment, as parts of the meltwater can be drained by underlying karst systems, making it difficult to assess water availability. In this study tracer experiments, karst modeling and glacier melt modeling are combined in order to identify flow paths in a high alpine, glacierized, karstic environment (Glacier de la Plaine Morte, Switzerland) and to investigate current and predict future downstream water availability. Flow paths through the karst underground were determined with natural and fluorescent tracers. Subsequently, geologic information and the findings from tracer experiments were assembled in a karst model. Finally, glacier melt projections driven with a climate scenario were performed to discuss future water availability in the area surrounding the glacier. The results suggest that during late summer glacier meltwater is rapidly drained through well-developed channels at the glacier bottom to the north of the glacier, while during low flow season meltwater enters into the karst and is drained to the south. Climate change projections with the glacier melt model reveal that by the end of the century glacier melt will be significantly reduced in the summer, jeopardizing water availability in glacier-fed karst springs.

Prevention and Control of Surface Water Hazard in Coal Mine

On the basis of different damage forms of surface water in coal mines, various prevention and control countermeasures to water hazard in different landforms, such as mountainous area, plain area and hilly area, were proposed. In general, the objects to be governed include river banks, plashes, slopes, gullies and surface collapses due to underground mining or karst cave to avoid the hazard. The principle is cutting off the relationship or passage between surface water and underground mining. Furthermore, advices and techniques on water passage detection were put forward to carry out the following work.

Geochemical and isotopic characteristics of karstic springs in coastal mountains (Southern Croatia)

Seventeen gravity springs from the slopes of the Biokovo, Sutvid and Rilić Mountains at the Adriatic coast of Croatia were investigated. Five of them are included in the regional and three of them are included in the local water supply system. Other springs are used by local inhabitants and tourists for drinking. The aim of this study was to determine the underground karst connections, source and type of the groundwater defining different hydrochemical facies, the aquifer behavior and the impact of the rehabilitated landfill Donja Gora on karstic springs due to the detected anomalous concentrations of lead in sediments. Hydrochemical facies was determined using a Piper diagram. It was shown that groundwater belongs to the Ca–HCO3 type of water.Concentrations of 17 dissolved and total trace elements, organic compounds, organic carbon, nutrients and ions, phenols, PCBs and mineral oil microbiological properties, physical and chemical indicators were determined in groundwater samples. Their concentrations were extremely low, more than 3 orders of magnitude less than allowed by the Croatian regulations for the first category of groundwater and drinking water, so the quality of water is excellent. Origin of some elements is discussed and complex statistical analysis is performed, using log-probability plots and partitioning of distributions following the Sinclair graphical procedure. Majority of minor and trace element concentrations show unimodal distribution of the data. Only five elements (Al, Mn, Ni, Pb and Zn) show the combinations of 2 or 3 log-normal distributed populations, probably reflecting the presence of different sources and/or processes.For the first time, isotopic investigations were performed in any karst region of Croatia, measuring the concentration of dissolved radon in the groundwater. The measured values of radon concentrations for spring water ranged from 0.45BqL−1 to 16.53BqL−1. These results are much lower than the reference level of 100BqL−1 set by the European Commission for drinking water. The lowest radon concentration 0.44BqL−1 was measured at the surface water intake on the Cetina River.The mass fractions of 16 elements were determined in 3 representative spring sediments. Highest concentrations of some metals in total sediments (mgkg−1, d.w.) are: lead 2601, chromium 244, silver 1.11, manganese 1178, zinc 322, copper 507 and barium 461. Lead concentrations are assumed to be of natural origin.

Modeling a network of turloughs in lowland karst

[1] In lowland karst areas of Ireland topographic depressions which get intermittently flooded on an annual cycle via groundwater sources are termed turloughs. These are sites of high ecological interest as they have communities and substrate characteristic of wetlands. The flooding in many turlough basins is due to insufficient capacity of the underground karst system to take increased flows following excessive precipitation events, causing the conduit-type network to surcharge. Continuous water level measurements have been taken in five linked turloughs in the lowland karst area of south Galway over a 3 year period. These water level fluctuations, in conjunction with river inputs and precipitation, were then used to elucidate the hydrogeological controls forming the hydraulic system beneath the ground. A model of the karst network has been developed using a pipe network model with the turloughs represented as ponds. The contribution to the karst network from diffuse flow through the epikarst via the matrix and fracture flow has also been modeled using a combination of an infiltration module and network of permeable pipes. The final model was calibrated against two separate hydrological years and in general provided a good simulation for all of the turloughs water levels particularly for the year with one main filling event. The model also accurately picked up the tidal response observed in these turloughs at shallow depths. The model has been used to predict the groundwater discharge to the coast via the main spring which had not heretofore been possible to measure, being below the sea level.

Discussion on the article ‘Coastal and inland karst morphologies driven by sea level stands: a GIS based method for their evaluation' by Canora F, Fidelibus D and Spilotro G

ABSTRACTComments are presented on the article by Canora et al. (2012) dealing with karst morphologies driven by sea level stands in the Murge plateau of Apulia, southern Italy. Our comments start from cave levels, that are considered in the cited article as a proof of sea level stands. We argue that the presence of sub‐horizontal passages in cave systems is not a sufficient condition for correlating them with hypothetical past sea level stands. Such a correlation must be based upon identification of speleogenetic features within the karst systems, and/or geological field data. The problems encountered when using cave surveys for scientific research, and their low reliability (especially in the case of old surveys) are then treated, since they represent a crucial point in the paper object of this discussion. Eventually, we present some final consideration on cave levels and terraces, and on the specific case study, pointing out once again to the need in including geological field data to correctly find a correspondance between flat landforms and sea level fluctuations. Our main conclusion is that field data and information on speleogenesis of the underground karst landforms cannot be disregarded in a study that claims to deal with the influence of sea‐level changes on caves. Copyright © 2013 John Wiley & Sons, Ltd.

Cave development under the influence of Pleistocene glaciation in the Dinarides - an example from Štirovača Ice Cave (Velebit Mt., Croatia)

This paper analyses for the first time the influence of glaciation on underground karst landforms in the Croatian part of the Dinarides, as well as the interrelation between underground and surface relief developments under glacial conditions. The karst environment, as a good recorder of palaeo-environments, provides some new information on Quaternary glaciation in the Velebit Mountain in Croatia, and reveals, generally, the morphogenetic evolution of Stirovaca Ice Cave (in Croatian, Ledenica u Stirovaci) and of the surrounding area. During cold periods, glacial exaration produced a particularly significant quantity of sediments. Consequently, underground karst conduits situated below the snow line during the Pleistocene were filled with high-energy sedimentary structures, glacial and fluvioglacial sediments. This reduced or even stopped their conduit function, and led to difficulties in the drainage of meteoric water, to lake formation within morphological depressions and to a rise in the local water-table level. With the denudation of these deposits, conduit reactivation and a drop in the underground water level occurred. Stabilisation during milder climatic conditions led to aggradation of the cave and to the deposition of flowstones from 8230 ± 150 years BP.

Failure Mode of Karst Water under Inclined Coal Seam Mining in Hilly Area

Using special hydrogeology survey, groundwater level observation, water pressure test, pit infiltration test, imaging well log technique and Hertz wave CT in the mining subsidence area and its nearby, failure mode of karst water under inclined coal seam mining in hilly area is studied. Contrasted surface infiltration capacity of limestone in 1955 with in 2011, it verifies that aquicludes and aquifers above goaf and near ground are damaged, therefore karst water in different aquifers become a unified water-bearing body. In the mining subsidence area, karst water forms a cone of depression, and water-bearing body of underground karst water supplied by vertical seepage is the main type of surface water infiltration. Outside of mining subsidence area, the surface water and the karst water are supplied by each other, and overland flow is the main type of surface water.

Two new freshwater fish species of the genus Telestes (Actinopterygii, Cyprinidae) from karst poljes in Eastern Herzegovina and Dubrovnik littoral (Bosnia and Herzegovina and Croatia)

Two new species, Telestes dabar and Telestes miloradi, are described on the basis of morphological comparisons of isolated geographical populations of fishes identified earlier as Telestes metohiensis. A lectotype is designated for Telestes metohiensis, whose range is shown to include waters of Gatačko, Cerničko, and Nevesinjsko poljes in Eastern Herzegovina. Telestes dabar from Dabarsko Polje (Eastern Herzegovina) and Telestes miloradi from Konavosko Polje (south Croatia) share with Telestes metohiensis the following combination of characters that distinguish them from the rest of the genus Telestes: pharyngeal teeth in one row, usually 5–4; preoperculo-mandibular canal not communicating with the infraorbital canal; mouth subterminal, the tip of the mouth cleft on or below the level of the ventral margin of the eye; postcleithrum minute or absent; ventral portion of the trunk with a dark stripe on a pale background; and dorsal portion of trunk uniformly dark and bordered ventrally by a dark midlateral stripe. Telestes dabar and Telestes miloradi are distinguishable from Telestes metohiensis in usually having 8½ branched dorsal-fin rays (vs. usually 7½), 9 or 10 gill rakers (vs. 7–10, usually 8), and the dark stripe on the ventral portion of the trunk below the main pigmented area of the back narrow and usually not reaching posteriorly to the caudal peduncle (vs. dark stripe wide and extending posteriorly to the caudal peduncle). Telestes dabar is distinguished from Telestes miloradi by having scales on most of the body situated close to one another and overlapping in a region behind the pectoral girdle and usually on the caudal peduncle (vs. overlapping scales on most of the body); the lateral line usually incomplete and interrupted, with 24–69, usually 54–65, total scales (vs. lateral line usually complete, with 55–67 total scales); scales above and below the lateral line slightly smaller than lateral-line scales (vs. of about equal size); head width 43–52% HL (vs. 48–58% HL); and lower jaw length 10–12% SL or 36–41% HL (vs. 8–10% SL or 33–38% HL). Telestes miloradi, a very local endemic species,is known only by historical samples. Telestes dabar is an abundant fish in Dabarsko Polje, but its range is critically restricted during the dry season by a few permanent sources. Nothing is known about its occurrence in underground karst waters.

Le karst de Casteljaloux (Lot-et-Garonne). Rôle du processus de fantômisation dans la genèse des grottes épikarstiques et du fonctionnement hydrologique

The underground karst of Casteljaloux (Lot-et-Garonne, France) : role of ghost-rock processes on epikarstic cave evolution and hydrological functioning of the springs. The karst of Casteljaloux is located on the left bank of the Garonne river , 80 km southeast of Bordeaux (70-150 m a.s.l.). The epikarstic caves develop a few meters below the surface in Miocene lacustrine limestones of Lower and Upper Aquitanian. The southern part is covered by a quarternary eolian sandy formation (Sables des Landes) covering the Tertiary. The ghost-rock process in limestone was observed in sections of quarries, roads and in caves. In the quarry of Trouyre, there are false galleries showing an evolution with weathered rock, brown clay injection on top and into the altered rock, compaction of the sediments, inwash of quartz gravels (paleo-terrace of Garonne), and finally recent deposits (charcoal). In the subhorizontal cave of Saint-Julien, 3 m below the topographic surface, there is an alteration of the Aquitanian limestone and the marly limestone forming the ceiling, resulting in densely packed sodastraws. The petrographic analysis confirms thaqt porosity is due to alteration. The hydrochemical regime of springs is very specific. The concentration of calcium and bicarbonate increases with flow rate (concentrative effect), opposite to classical karst. This hydrochemical response indicates a very porous karst, directly related to the strong alteration of Aquitanian limestone and the sandy cover which enhances retarded recharge in water.