spatial distribution morphometry and activity of la puebla de alfinden sinkhole field in the ebro river valley ne spain applied aspects for hazard zonation a highly active collapse sinkhole field in the evaporitic mantled karst of the ebro river valley is studied ne spain the subsidence is controlled by a nw se trending joint system and accelerated by the discharge of waste water from a nearby industrial state the morphometry spatial distribution and temporal evolution of the sinkholes have been analysed the volume of the sinkholes yields a minimum estimate of average lowering of the surface by collapse subsidence of 46 cm the clustering of the sinkholes and the tendency to form elongated uvalas and linear belts in a nw se direction have a predictive utility and allow the establishment of criteria for a hazard zonation with the precipitation record supplied by a pluviograph and periodic cartographic and photographic surveys the influence of heavy rainfall events on the triggering of collapses has been studied

impact of halite dissolution subsidence on quaternary fluvial terrace development case study of the huerva river ebro basin ne spain abstract this paper analyses the control of evaporite dissolution subsidence on the evolution of the lower 30 km long reach of the huerva river up to its confluence with the ebro river in the study area the huerva river flows across different interfingered lithofacies of the subhorizontally lying ebro basin fill 1 shales and sandstones upstream of cadrete 2 evaporites dominated by gypsum between cadrete and cuarte 3 gypsum with glauberite and halite units in the subsurface downstream of cuarte the halite shows a marked downvalley increase in thickness twelve terrace levels and seven pediment levels correlative to some of the terraces have been mapped in the studied area upstream of cadrete the terrace deposits with a relatively constant thickness less than 4 m and overlying unsoluble bedrock remain undeformed between cadrete and cuarte the deposits of some terraces show local thickening 60 m thick terrace alluvium that fills a 5 km long trough generated by synsedimentary subsidence phenomena caused primarily by the interstratal dissolution of halite the older terraces t1 to t4 show slight thickening 18 m and locally truncate paleocollapse structures ascribed to the interstratal karstification of halite beds the intermediate terraces t5 to t7 correspond to degradation surfaces that grade downstream of cuarte into aggradation flights underlain by the abruptly thickened deposits that fill this 5 km long dissolution trough subsidence migrated episodically downstream during the generation of these terraces and the subsidence aggradation rate was probably large enough to induce a base level drop and knickpoint migration upstream generating strath terraces with convergent longitudinal profiles the sedimentological changes that show the thickened terrace deposits in the subsidence area high proportion of overbank fines 60 including palustrine facies gravel channels with lower width depth ratio multiple fining upward cycles decrease in the calibre of the channel gravels indicate a change in the channel pattern from braided to meandering due to the lowering of the valley slope in the reach affected by subsidence some of the anomalous features of the lower terraces t8 to t12 attributable to dissolution subsidence include 1 steepening of the t8 terrace profile 2 change of the t10 terrace from degradational to aggradational downstream cuarte and 3 thickening recorded beneath the t11 terrace surface

geometry and distribution of regional joint sets in a non homogeneous stress field case study in the ebro basin spain abstract three regional joint sets striking n s e w and wnw ese affect the tertiary rocks of the central ebro basin from analysis of their chronological relationships and spatial distribution it is concluded that they correspond to two different tectonic events the n s set oldest and the e w set younger are present in the southern and central sectors while the wnw ese joint set predominates in the northern one the n s joints propagated in response to joint normal and fluid loads under an intraplate stress field with shmax oriented near n s related to forces caused by the convergence of africa iberia and europe and rifting at the valencia trough during the sedimentary infilling of the basin these joints are only present in the southern part of the area the e w joint set in the southern central sector records the same fracturing event as the wnw ese set does in the northern one its orientation was modified by the presence of the older n s set in the south which perturbed the regional stress field the younger wnw ese and e w joint sets are interpreted as unloading joints these propagated as a consequence of flexural uplift and exhumation related to isostatic rebound at the pyrenees and the ebro foreland basin a numerical approach is used to explain the inhomogeneous distribution of the n s joint set in terms of their absence being controlled by the depth of the water table at the time of their formation

a sinkhole susceptibility zonation based on paleokarst analysis along a stretch of the madrid barcelona high speed railway built over gypsum and salt bearing evaporites ne spain abstract this paper presents a methodology for producing sinkhole susceptibility zonations along linear infrastructures based on the analysis of the subsidence and dissolution features exposed in the adjacent cuttings and the distribution of karstic depressions the proposed approach have been applied to a 24 km long stretch of the high speed madrid barcelona railway built on halite and glauberite bearing evaporites of the tertiary zaragoza gypsum formation more than 100 km of this railway line have been built over salt bearing tertiary evaporites and trains run at a cruising speed of 300 km h the susceptibility assessment has been restricted to the sections located in karstic depressions 2 98 km and trenches excavated in the ground 13 93 km a low susceptibility has been assigned to the sections built on thickened alluvium of the huerva fluvial system 0 5 km and those in which the evaporites exposed in the cuttings do not show evidence of dissolution or subsidence 3 52 km a total of 4 5 km have received an intermediate susceptibility the cuttings in these sections show sagging structures cavities above the railway roadbed irregular rockhead or shallow alluvium bedrock boundary a high susceptibility has been assigned to a total of 6 59 km these correspond to cavities and collapse structures that reach the railway roadbed 3 61 km and karstic depressions generated by interstratal karstification and subsidence 2 98 km the paleokarst and geomorphic evidence in these sections reveals that cavities either air or sediment filled do exist beneath the railway the distribution of the karst features and susceptibility zones seems to be controlled to a large extent by the lithostratigraphy of the bedrock wedging out of the evaporites to the se and increase in the proportion of halite and glauberite to the nw the proposed zonation could be used as the basis for the selection of the stretches where further investigations and the application of mitigation measures would have a better cost benefit ratio

a revised surface age for the north polar layered deposits of mars this work was funded by nasa grant nnx13ag72g m e l was supported by the national science foundation graduate research fellowship program grant dge 1143953 hirise images referenced are available on the instrument s public website https hirise lpl arizona edu the crater catalog used in this work is included with this paper as supporting information the authors thank s sutton for help with socet set software m m sori for useful discussion on viscous relaxation and m e banks for useful discussion on the impact population the authors additionally thank j a skinner p becerra d laikko m sori n barlow and an anonymous reviewer for helpful comments on the manuscript

hypothesis on the hydrogeological context of wetland areas and springs related to evaporitic karst aquifers malaga cordoba and jaen provinces southern spain the northern sector of the external zone of the betic cordillera s spain is formed by an olistostrome unit known as the chaotic subbetic complexes csc this megabreccia is basically made of clays and evaporite rocks gypsum and salt of upper triassic keuper age as well as other lithologies dolostones limestones marls and calcareous sandstones belonging to different ages jurassic cretaceous and tertiary despite of low permeability has been traditionally assumed for these materials water flow and storage through them is possible due to the aquitard behavior of clays and sandstones and the presence of conduits generated by dissolution karstification processes within the evaporite rocks the lithological complexity of the csc determines its hydrogeological heterogeneity with groundwater flows of different length and various scales from recharge areas to discharge zones thus wetlands and springs placed at lower altitudes are associated with large regional groundwater flows of greater residence time within the aquifer and they normally drain high salinity waters mostly connected with ascending flow this work provides an overview of the main geological and hydrogeological aspects related to groundwater flow within the csc on the basis of several case studies conceptual models are proposed for these cases since they are the base to carry out a genetic functional classification of wetlands potentially useful for their management

glauberite halite association of the zaragoza gypsum formation lower miocene ebro basin ne spain glauberite is the most common mineral in the ancient sodium sulphate deposits in the mediterranean region although its origin primary or diagenetic continues to be a matter of debate a number of glauberite deposits of oligocene miocene age in spain display facies characteristics of sedimentologic significance in particular those in which a glauberite halite association is predominant in this context a log study of four boreholes in the zaragoza gypsum formation lower miocene ebro basin ne spain was carried out two glauberite halite lithofacies associations a and b are distinguished association a is composed of bedded cloudy halite and minor amounts of massive and clastic glauberite association b is made up of laminated to thin bedded clear macrocrystalline massive clastic and contorted lithofacies of glauberite and small amounts of bedded cloudy halite transparent glauberite cemented by clear halite as well as normal graded and reverse graded glauberite textures are common this type of transparent glauberite is interpreted as a primary subaqueous precipitate gypsum thenardite or mirabilite are absent in the two associations the depositional environment is interpreted as a shallow perennial saline lake system in which chloride brines association a and sulphate chloride brines association b are developed the geochemical study of halite crystals bromine contents and fluid inclusion compositions demonstrates that conditions for co precipitation of halite and glauberite or for precipitation of na sulphates mirabilite thenardite were never fulfilled in the saline lake system

investigation of a large collapse sinkhole affecting a multi storey building by means of geophysics and the trenching technique zaragoza city ne spain an active sinkhole around 100 m long has been investigated in the city of zaragoza ne spain subsidence activity on this depression including the sudden occurrence of a collapse sinkhole 5 m across led to the abandonment of a factory in the 1990s at the present time a building with 100 flats and shallow pad foundations partially built on the sinkhole is affected by rapid differential settlement the development of the sinkhole results from the karstification of the halite and glauberite bearing bedrock and the sagging and collapse of the overlying bedrock and alluvium more than 30 m thick gpr and electrical resistivity profiles have provided information on the distribution and geometry of the subsidence structure the application of the trenching technique and geochronological methods ams and osl dating has allowed us to infer objective and practical data on the sinkhole including 1 limits of the subsidence structure 2 subsidence mechanisms 3 cumulative subsidence 408 cm 4 subsidence rates on specific failure planes 1 8 cm year 5 episodic displacement regime of some fault planes the available information indicates that the progressive deformation recorded in the building will continue and might be punctuated by events of more rapid displacement this work illustrates the practicality of the trenching technique for the study of sinkholes in mantled karst areas

sinkhole swarms along the dead sea coast reflection of disturbance of lake and adjacent groundwater systems more than a thousand sinkholes have developed along the western coast of the dead sea since the early 1980s more than 75 of them since 1997 all occurring within a narrow strip 60 km long and 1 km wide this highly dynamic sinkhole development has accelerated in recent years to a rate of 150 200 sinkholes per year the sinkholes cluster mostly over specific sites up to 1000 m long and 200 m wide which spread parallel to the general direction of the fault system associated with the dead sea transform research employing borehole and geophysical tools reveals that the sinkhole formation results from the dissolution of an 10 000 yr old salt layer buried at a depth of 20 70 m below the surface the salt dissolution by groundwater is evidenced by direct observations in test boreholes these observations include large cavities within the salt layer and groundwater within the confined subaquifer beneath the salt layer that is undersaturated with respect to halite moreover the groundwater brine within the salt layer exhibits geochemical evidence for actual salt dissolution na cl 0 5 0 6 compared to na cl 0 25 in the dead sea brine the groundwater heads below the salt layer have the potential for upward cross layer flow and the water is actually invading the salt layer apparently along cracks and active faults the abrupt appearance of the sinkholes and their accelerated expansion thereafter reflects a change in the groundwater regime around the shrinking lake and the extreme solubility of halite in water the eastward retreat of the shoreline and the declining sea level cause an eastward migration of the fresh saline water interface as a result the salt layer which originally was saturated with dead sea water over its entire spread is gradually being invaded by fresh groundwater at its western boundary which mixes and displaces the original dead sea brine accordingly the location of the western boundary of the salt layer which dates back to the shrinkage of the former lake lisan and its transition to the current dead sea constrains the sinkhole distribution to a narrow strip along the dead sea coast the entire phenomenon can be described as a hydrological chain reaction it starts by intensive extraction of fresh water upstream of the dead sea continues with the eastward retreat of the lake shoreline which in turn modifies the groundwater regime finally triggering the formation of sinkholes

subsidence rates and urban damages in alluvial dolines of the central ebro basin ne spain in the central ebro basin alluvial dolines develop on quaternary materials overlying neogene evaporites this process is very active analysing aerial photographs of different years important differences can be observed since the 1970s when the urbanisation of the area took place karst processes have damaged many buildings and infrastructures from the dates of construction and the repair of a number of buildings and pavements we calculate subsidence rates 12 120 mm year moreover we decided to monitor for around 4 years three dolines developed on urban areas to determine their subsidence behaviour a water level device with an error of 2 3 mm was utilised for this purpose the subsidence rates so obtained are 64 5 39 and 21 mm year which fit with the previous data from repaired zones

paleosubsidence and active subsidence due to evaporite dissolution in the zaragoza area huerva river valley ne spain processes spatial distribution and protection measures for transport routes abstract the lowest 17 km long reach of the huerva river valley down to its confluence with the ebro river in zaragoza city flows across salt bearing evaporites of the ebro tertiary basin ne spain upstream the horizontally lying miocene evaporites are interfingered with non soluble distal alluvial fan facies shales and sandstones the proportion of soluble facies in the huerva river valley increases in a downstream direction towards the basin depocenter on the basis of the type and magnitude of the paleosubsidence features the valley has been divided into four reaches along reach i undeformed terrace deposits less than 4 m thick rest on insoluble detrital bedrock in reaches ii and iii dissolution at the alluvium bedrock boundary has generated local thickening deformation and paleocollapse structures which only affect the alluvial mantle in reach iv terrace deposits thicken to over 60 m resulting from a large scale synsedimentary subsidence in this sector subsidence locally affects to both the alluvium and the underlying bedrock this indicates that dissolution acts at the rockhead beneath the alluvial cover alluvial karst and within the evaporitic substratum interstratal karst the development of an intraevaporitic karst in reach iv is attributed to gypsum and salt dissolution irregular terrace gravel bodies gravel pockets embedded in a fine grained matrix associated with paleocollapse structures have been interpreted as liquefaction fluidization structures resulting from ground acceleration and suction induced by catastrophic collapses subsidence is currently active in the region affecting areas with a thin alluvial cover in reaches iii and iv the low subsidence activity in most of zaragoza city is explained by the presence of thickened around 50 m and indurated alluvial deposits in the surrounding area numerous buildings in cadrete and santa fe villages have been severely damaged by subsidence natural and human induced subsidence favours the development of slope movements in the gypsum scarp overlooking cadrete village several transport routes including the imperial canal irrigation canal and the recently completed madrid barcelona high speed railway are affected by human induced sinkholes the paleocollapse structures exposed in the trenches of this railway and a ring road under construction point to hazardous locations underlain by cavities and collapse structures where special protection measures should be applied rigid structures are recommended beneath the high speed railway with sufficient strength to span the larger sinkholes with no deformation electronic monitoring devices linked to a warning system can detect subtle subsidence induced deformations in carriageways or railways this research demonstrates that the study of the paleokarst helps to understand the processes involved in the present day subsidence phenomena and their general spatial distribution

geochemistry of platinum group elements in marine oil shale from the changshe mountain area china implications for modes of occurrence and origins abstract the shengli river changshe mountain oil shale zone located in the north qiangtang depression northern tibet plateau represents a potentially largest marine oil shale resource in china eighteen samples including oil shale and micritic limestone were collected from the changshe mountain oil shale to determine the concentrations the modes of occurrence and origins of platinum group elements pges in marine oil shale the oil shale samples from the changshe mountain area exhibit low total pge contents ranging from 3 196 to 8 071 ng g with a weighted mean value of 5 383 ng g while the micritic limestone samples from the changshe mountain area exhibit a little lower ranging from 0 471 to 5 669 ng g pges in oil shale samples are characterized by high contents in pd 3 23 ng g pt 1 60 ng g and os 0 32 ng g as compared to rh 0 083 ng g ru 0 112 ng g and ir 0 043 ng g the individual pges of oil shale samples from the changshe mountain area exhibit various modes of occurrence ru and ir are mainly controlled by clay minerals and partly present as sulfide rh is mainly associated with sulfide and possibly present as clay minerals pt is associated with clay minerals and sulfide and pd is controlled by organic matter and pyrite while os is mainly present in organic matter three possible sources of pges were identified in oil shale seams in the changshe mountain area ru and ir are mainly terrigenous inputs rh and pt are derived from mixed sources seawater and terrigemnous supply while pd and os are mainly derived from seawater the terrestrial source of the oil shale seams in the changshe mountain oil shale was the suowa formation limestone and the nadi kangri felsic volcanic rocks

space time distribution of ancient and active alluvial karst subsidence examples from the central ebro basin spain space and time variations of alluvial karst subsidence in the central ebro basin are analysed in trenches paleodolines aerial photographs historical dolines and field surveys present day active dolines the measured subsidence rates as well as a comparison between densities of paleodolines computed in randomly selected scan lines and density of active dolines computed in maps suggest that present day subsidence in favourable areas is more intense than that of pleistocene times according to diachronic maps drawn from a different aerial photographs taken after 1946 and b field surveys on deformations in urbanized areas subsidence behaved as a nearly steady process while the whole area was used for agriculture in contrast rapid changes through periods of several tens of years have occurred in urbanized areas in which dolines expand their boundaries through small marginal collapses shifting sharply their sinking centres to neighbouring sites these rapid changes do not have an equivalent in observed paleodolines

spatial analysis of a karst depression population clues to genesis a detailed analysis of depression spatial distribution on the parts of the western highland rim and pennyroyal plain underlain by the st louis and ste genevieve limestones indicates the presence of a depression infrastructure the major geomorphic elements of the infrastructure include depression density no km 2 doline swallet order and interdoline spacing a multigenerational diffusion and competition process model best explained 1 the presence of two lognormally distibuted depression density subpopulations 2 discrete clustered depression sets containing second order swallet dolines surrounded by first order swallet depressions 3 geomorphic competition between adjacent second order swallet dolines for runoff and catchment area and 4 a positive correlation between interdoline rim spacings of the small swallet order and the sum of their respective major axial lengths

gypsum karstification in the middle miocene fatha formation mosul area northern iraq abstract karstified middle miocene sediments are widely exposed in northern iraq particularly in the area surrounding the city of mosul the unit is dominated by gypsum and exposed in thirteen anticlinal structures within the investigated area of about 1600 square kilometers synclines though containing the same sequence are not karstified due to a quaternary cover karst features were located from air photos over 4000 were recorded the smallest detectable being two meters in diameter the majority are sinkholes dolines developed in gypsum and manifested in the overlying collapsing limestone they are singular in lines or clusters shafts and karren are fewer in number and are usually developed in uncovered gypsum sinkholes are visibly located along fractures and at fracture intersections over gently inclined limestone beds overlying the gypsum two karst systems were identified an active and recent system characteristic of all the anticlinal structures and an older pleistocene fossil karst system characteristic of alan ishkaft albu saif and hammam structures the fossil karst system is preserved on remnant elevated old land surfaces and produces characteristic tight undulations in the limestone due to collapse inwards in sinkholes and elongated tunnels formed along a series of sinkholes the fracture study of anticlinal structures reveals that the mean fracture density per area ranges between 4 and 8 km km 2 and shows a unimodal character for most of the structures however the distribution of karst in relation to fractures is bimodal for at least half of the structures with mean values ranging from 4 5 to 11 km km 2 the fractures in the anticlines are thought to have formed due to folding but some are associated with major lineaments cross cutting the structures which is reflected in the bimodality and the crude unimodal fracture karst distribution karst features are related to the general fracture pattern but are more localized in densely fractured areas karst areas were also found to correlate with lower slope gradient and lower drainage density

the origin typology spatial distribution and detrimental effects of the sinkholes developed in the alluvial evaporite karst of the ebro river valley downstream of zaragoza city ne spain three types of sinkhole have been mapped in a 50 km2 stretch of the ebro river valley downstream of zaragoza large collapse sinkholes large shallow subsidence depressions and small cover collapse sinkholes the sinkholes relate to the karstification of evaporitic bedrock that wedges out abruptly downstream giving way to a shale substratum twenty three collapse sinkholes up to 50 m in diameter by 6 m deep and commonly hosting saline ponds have been identified in the floodplain they have been attributed to the upward stoping of dissolutional cavities formed within the evaporitic bedrock by rising groundwater flows twenty four large shallow subsidence depressions were mapped in the floodplain these may reach 850 m in length and were formed by structurally controlled interstratal karstification of soluble beds halite or glauberite and gypsum by rising groundwater flow and the progressive settlement of the overlying bedrock and overburden sediments a total of 447 small cover collapse or dropout sinkholes have been recognized in a perched alluvial level along the southern margin of the valley these sinkholes result from the upward propagation of voids through the alluvial mantle caused by the downward migration of detrital sediments into dissolutional voids the majority of these sinkholes commonly 1 5 2 m in diameter are induced by human activities over the karstic bedrock there is a significant increase in sinkhole density downstream this is interpreted as being a result of the evaporitic bedrock wedging out and the convergence of the groundwater flow lines in the karstic aquifer the collapse sinkholes in this area locally with a probability of occurrence higher than 140 sinkholes km2 year cause substantial damage to the linear infrastructures buildings and agriculture and they might eventually cause the loss of human lives copyright 2006 john wiley sons ltd

halite karst geohazards natural and man made in the united kingdom in the united kingdom permian and triassic halite rock salt deposits have been affected by natural and artificial dissolution producing karstic landforms and subsidence brine springs from the triassic salt have been exploited since roman times or possibly earlier indicating prolonged natural dissolution medieval salt extraction in england is indicated by the names of places ending in wich indicating brine spring exploitation at northwich middlewich nantwich and droitwich later victorian brine extraction in these areas accentuated salt karst development causing severe subsidence problems which remain a legacy the salt was also mined but the mines flooded and consequent brine extraction caused the workings to collapse resulting in catastrophic surface subsidence legislation was enacted to pay for the damage and a levy is still charged for salt extraction some salt mines are still collapsing and the re establishment of the post brine extraction hydrogeological regimes means that salt springs may again flow causing further dissolution and potential collapse

karst system developed in salt layers of the lisan peninsula dead sea jordan the lisan peninsula jordan is a massive salt layer accumulated in the inner part of the dead sea s precursory lakes this tongue shaped emergent land results in a salt diapir uplifted in the dead sea strike slip regional stress field and modified by the water level fluctuations of the last lake during the holocene these two elements associated with dissolution caused by rainfall and groundwater circulation resulted in an authentic karst system since the 1960s the dead sea lowering of 80 cm to 1 m per year caused costly damages to the industrial plant set up on the peninsula the lisan karst system is described in this article and the components of the present dynamic setting clarified

the gis approach to evaporite karst geohazards in great britain evaporite karst in great britain has formed in permian and triassic gypsum and in triassic salt active dissolution of these deposits can occur on a human rather than a geological timescale causing subsidence and building damage the british geological survey has taken two approaches towards understanding and advising on hazards caused by dissolution of these soluble rocks at a detailed level a national database and gis of karstic features is being populated information gathered includes dolines springs stream sinks caves and building damage at a national level the soluble rocks in great britain have been identified and digital map polygon information relating to them was extracted from the british 1 50 000 scale digital geological map these areas have been assessed and in places their margins extended to include some overlying rocks where subsidence features are known to penetrate upwards through the overlying sequence the national areas have then been assessed using detailed local information to assign a susceptibility rating from a extremely low to e high depending on the nature and regularity of the subsidence events that occur this national zonation of the soluble rocks can be used for planning construction and in the insurance businesses this has proved useful for assessing the potential stability of linear routes such as roads and pipelines or for other important structures such as bridges and buildings the information can also be used to delineate zones of karstic groundwater flow

doline probability map using logistic regression and gis technology in the central ebro basin spain in the surroundings of zaragoza karstification processes are especially intense in covered karst areas where fluvial terraces lie directly on tertiary evaporites since the beginning of quaternary these processes have lead to the development of collapse and subsidence dolines with a wide range of sizes which have significant economic impacts to reduce economic impact and increase safety a regional analysis of this phenomenon is needed for spatial management therefore a probability map of dolines was developed using logistic regression and geographic information system gis techniques this paper covers the selection of input data manipulation of data using the gis technology and the use of logistic regression to generate a doline probability map the primary variable in the doline development in this area is geomorphology represented by the location of endorheic areas and different terrace levels secondary variables are the presence of irrigation and the water table gradient

identification prediction and mitigation of sinkhole hazards in evaporite karst areas sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas this is because evaporites have a higher solubility and commonly a lower mechanical strength subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world but the causes are only well understood in a few areas to deal with these hazards a phased approach is needed for sinkhole identification investigation prediction and mitigation identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources detailed sinkhole maps can be constructed from sequential historical maps recent topographical maps and digital elevation models dems complemented with building damage surveying remote sensing and high resolution geodetic surveys on a more detailed level information from exposed paleosubsidence features paleokarst speleological explorations geophysical investigations trenching dating techniques and boreholes may help in investigating dissolution and subsidence features information on the hydrogeological pathways including caves springs and swallow holes are particularly important especially when corroborated by tracer tests these diverse data sources make a valuable database the karst inventory from this dataset sinkhole susceptibility zonations relative probability may be produced based on the spatial distribution of the features and good knowledge of the local geology sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation alignment and nearest neighbor analysis more objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes number of sinkholes km2 year such spatial and temporal predictions frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future are non corroborated hypotheses validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole prone areas corrective measures could be applied to reduce the dissolution activity and subsidence processes a more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence proof designs

probabilistic sinkhole modelling for hazard assessment a method for quantitatively assessing sinkhole susceptibility spatial probability and hazard spatio temporal probability has been developed and independently tested in a 50 km2 sector of the ebro valley evaporite karst three genetic types of sinkholes have been mapped in the floodplain and a terrace surface 947 small cover collapse sinkholes type 1 terrace large collapse sinkholes type 2 floodplain and large subsidence depressions type 3 floodplain the type 1 sinkhole inventory includes two temporal populations 447 sinkholes formed before 24 november 2005 and 500 between that date and 2 november 2006 sinkhole susceptibility models have been elaborated analysing the statistical relationships between the sinkholes of the 2005 inventory and a set of potential conditioning factors the independent evaluation validation of the susceptibility models by means of several strategies random sequentially excluded and temporal has allowed us to select the most significant variables for each sinkhole type and assess quantitatively the quality of models which are reasonable for the three sinkhole types validation has also provided information on the contribution of specific variables and the effect of changing their accuracy to the prediction capability of models susceptibility models for type 3 sinkholes have been validated satisfactorily with the 2006 sinkhole inventory temporal validation the best susceptibility model has been transformed into a hazard map considering the frequency of sinkholes that occurred in each susceptibility class between 2005 and 2006 as well as their average size the susceptibility and hazard models obtained could be used as an objective basis for the application of mitigation measures either of preventive or corrective nature copyright 2008 john wiley sons ltd

a genetic classification of sinkholes illustrated from evaporite paleokarst exposures in spain this contribution analyses the processes involved in the generation of sinkholes from the study of paleokarst features exposed in four spanish tertiary basins bedrock strata are subhorizontal evaporites and in three of the basins they include halite and glauberite in the subsurface our studies suggest that formation of dolines in these areas results from a wider range of subsidence processes than those included in the most recently published sinkhole classifications a new genetic classification of sinkholes applicable to both carbonate and evaporite karst areas is thus proposed with the exception of solution dolines it defines the main sinkhole types by use of two terms that refer to the material affected by downward gravitational movements cover bedrock or caprock and the main type of process involved collapse suffosion or sagging sinkholes that result from the combination of several subsidence processes and affect more than one type of material are described by combinations of the different terms with the dominant material or process followed by the secondary one e g bedrock sagging and collapse sinkhole the mechanism of collapse includes any brittle gravitational deformation of cover and bedrock material such as upward stoping of cavities by roof failure development of well defined failure planes and rock brecciation suffosion is the downward migration of cover deposits through dissolutional conduits accompanied with ductile settling sagging is the ductile flexure of sediments caused by differential corrosional lowering of the rockhead or interstratal karstification of the soluble bedrock the paleokarsts we analysed suggest that the sagging mechanism not included in previous genetic classifications plays an important role in the generation of sinkholes in evaporites moreover collapse processes are more significant in extent and rate in areas underlain by evaporites than in carbonate karst primarily due to the greater solubility of the evaporites and the lower mechanical strength and ductile rheology of gypsum and salt rocks

geological and environmental implications of the evaporite karst in spain in spain evaporite outcrops cover approximately 7 of the total area of the country most of the evaporitic formations are made up of ca sulfates gypsum anhydrite or ca sulfates and halite certain paleogene marine evaporites also contain k mg chlorides and some tertiary continental formations bear substantial amounts of na sulfates in the subsurface glauberite and thenardite mesozoic evaporitic formations commonly wedge out towards the ground surface passing into condensed sequences and dissolution collapse breccias some of these highly porous breccias constitute major regional aquifers in several areas interstratal karstification of the evaporites has given rise to gravitational deformations such as basin structures monoclines and collapse structures covering several square kilometers that record a cumulative subsidence in excess of 200 m teruel and calatayud grabens a widespread consequence of evaporite dissolution processes in spain is the hydrochemical degradation of surface waters some of the largest and most outstanding lake systems from an environmental perspective occur in karstic depressions developed in evaporitic formations fuente de piedra gallocanta bujaraloz and banolas lakes sinkhole activity is a major geohazard in several evaporite karst areas the sinkhole risk has a particularly high impact in sectors where tertiary evaporites are overlain by quaternary alluvial aquifers calatayud zaragoza and madrid areas some of the detrimental effects of subsidence include severe damage to historical monuments calatayud the demolition of a whole village puilatos or the derailment of a freight train zaragoza area the deepest gypsum caves are found in triassic diapiric structures el sumidor cave 210 m deep and the longest ones are developed in horizontally lying neogene sequences sorbas caves and estremera maze cave the cardona diapir hosts salt caves up to 4 300 m long whose genesis is related to flooding of mine galleries caused by the interception of a phreatic conduit the main anthropogenic impacts on the endokarstic systems are related to the disposal of wastewaters and the destruction of caves by quarrying the fluvial valleys that cross tertiary evaporitic outcrops commonly show peculiar geological characteristics related to dissolution induced synsedimentary subsidence phenomena 1 thickened alluvium filling dissolution basins up to several tens of kilometers long and more than 100 m deep the largest thickenings are found in areas where the bedrock contains halite and glauberite 2 superimposed alluvial units locally bounded by angular unconformities 3 abundant deformational structures and paleosinkholes related to the rockhead and or interstratal karstification of the substratum these fluvial valleys typically are flanked by a prominent gypsum escarpment rock falls favored by the dissolutional enlargement of joints derived from these scarps are the type of mass movement which has caused the highest number of casualties in spain

development and validation of sinkhole susceptibility models in mantled karst settings a case study from the ebro valley evaporite karst ne spain abstract a preliminary sinkhole susceptibility analysis has been carried out in a stretch 50 km 2 in area of the ebro valley alluvial evaporite karst ne spain a spatial database consisting of a sinkhole layer and 27 thematic layers related to causal factors was constructed and implemented in a gis three types of sinkholes were differentiated on the basis of their markedly different morphometry and geomorphic distribution large subsidence depressions 24 large collapse sinkholes 23 and small cover collapse sinkholes 447 the susceptibility models were produced analysing the statistical relationships between the mapped sinkholes and a set of conditioning factors using the favourability functions approach the statistical analyses indicate that the best models are obtained with 6 conditioning factors out of the 27 available ones and that different factors and processes are involved in the generation of each type of sinkhole the validation of two models by means of a random split strategy shows that reasonably good predictions on the spatial distribution of future dolines may be produced with this approach around 75 of the sinkholes of the validation sample occur on the 10 of the pixels with the highest susceptibility and about 45 of the area can be considered as safe

sedimentary record of pleistocene paleodoline evolution in the ebro basin ne spain abstract pleistocene fluvial deposits of the ebro river in ne spain are widely affected by faults fractures and tilting of beds based on the lithological geometrical and textural features of these deposits seven architectural elements have been differentiated gravel bars gb gravel filled channels ch sheets and channel fill sands sb are the most common elements and together with less frequent overbank fines ff characterize a gravel dominated braided fluvial system gravel lobes gl that draw progressive unconformities and are laterally related to u shaped or basin form mud deposits sediment gravity flow deposits sg and sands with slumps and convolute bedding sgs are not typical architectural elements of braided fluvial environments and they are interpreted in this work as related to syn sedimentary deformation our research proves that deformation is due to dissolution of the underlying tertiary evaporites with genesis of dolines the development of these karst structures involved both subsidence and sudden collapses that affected previous fluvial sediments small depressions dolines generated that were progressively filled by syn sedimentary deformed detrital deposits a model for the evolution of the doline fills is purposed that envisages several stages 1 gravitational processes caused remobilisation of previous fluvial gravels that were dragged to the created depression 2 flooding of the depression and development of a backswamp area that was progressively filled by fine sediments and gravel lobes as a consequence of the overflow of nearby channels 3 gravel lobes draw progressive unconformities revealing several subsidence episodes related to dissolution dragging and compaction 4 non deformed fluvial facies at the top of the series mark the end of the karstification influence osl optically stimulated luminiscence ages the first from the terraces of the ebro river demonstrate that karst has developed in this area at least since the late pleistocene and that the dolines have been filled in throughout several thousand years this large span time of doline evolution without anthropogenic influence should be considered for a better planning and management in hazardous areas

sinkholes in the salt bearing evaporite karst of the ebro river valley upstream of zaragoza city ne spain geomorphological mapping and analysis as a basis for risk management abstract a detailed sinkhole map has been produced in a stretch of the ebro valley 40 8 km2 including the western sector of zaragoza city ne spain during the last few decades around 70 of the original sinkhole area has been filled with anthropogenic sediments causing the disappearance of 137 ha of wetlands the interstratal karstification of salts halite and glauberite and a wnw ese trending joint set have played a major control in the development of sinkholes three morphometric types of sinkholes have been differentiated each attributed to a specific subsidence mechanism inferred from the paleosinkholes exposed in the surrounding of zaragoza city sagging of bedrock and cover collapse of bedrock and cover and collapse of cover material related to the downward migration of particles through dissolutional conduits each type of sinkhole is characterised by a distinctive behaviour in terms of controlling factors spatio temporal distribution and kinematics and consequently the proposed differentiation may have a practical utility the vast majority of the subsidence damage identified in the area occurs within the boundaries of pre existing sinkholes identifiable in old aerial photographs and topographical maps this fact demonstrates that the application of preventive planning strategies based on detailed geomorphological maps would have allowed avoidance of most of the large financial losses caused by subsidence in the area of the order of hundreds of thousands of euros per year

evaporite karst problems and studies in the usa evaporites including rock salt halite and gypsum or anhydrite are the most soluble among common rocks they dissolve readily to form the same types of karst features that commonly are found in limestones and dolomites evaporites are present in 32 of the 48 contiguous states in usa and they underlie about 40 of the land area typical evaporite karst features observed in outcrops include sinkholes caves disappearing streams and springs whereas other evidence of active evaporite karst includes surface collapse structures and saline springs or saline plumes that result from salt dissolution many evaporites also contain evidence of paleokarst such as dissolution breccias breccia pipes slumped beds and collapse structures all these natural karst phenomena can be sources of engineering or environmental problems dangerous sinkholes and caves can form rapidly in evaporite rocks or pre existing karst features can be reactivated and open up collapse under certain hydrologic conditions or when the land is put to new uses many karst features also propagate upward through overlying surficial deposits human activities also have caused development of evaporite karst primarily in salt deposits boreholes petroleum tests or solution mining operations or underground mines may enable unsaturated water to flow through or against salt deposits either intentionally or accidentally thus allowing development of small to large dissolution cavities if the dissolution cavity is large enough and shallow enough successive roof failures can cause land subsidence and or catastrophic collapse evaporite karst natural and human induced is far more prevalent than is commonly believed

alluvial dolines in the central ebro basin spain a spatial and developmental hazard analysis abstract alluvial dolines are abundant in quaternary terraces and pediments overlying neogene gypsum in the zaragoza area central ebro basin spatial analysis and experimental simulation show that sulphate content in the groundwater grain size of the detrital cover topography of the tertiary quaternary boundary annual variation of the water table and thickness of the detrital cover are the main factors controlling their development taking into account these variables a theoretical spatial hazard model has been elaborated expressed as a mathematical equation and a hazard map both experiments and field data show a high correspondance between two basic mechanisms of evacuation and subsidence dragging slow subsidence and collapse of cavities and two basic types of morphology and internal structure of dolines basin doline funnel structure and well doline vault structures respectively a genetic classification of dolines and some evolutionary patterns based on these criteria are developed historical changes observed in doline distribution as well as field surveys of urban damage and microtopographic profiles allow us to evaluate the present day activity of dolines local subsidence rates measured in urban areas range from 2 5 to 10 cm year although doline generation and reactivation in the whole area tend to be compensated by filling by human activity

river response to quaternary subsidence due to evaporite solution gallego river ebro basin spain abstract the stream terrace evolution of the gallego river during the quaternary was controlled by both climatic change and subsidence quaternary terrace deposits overlying tertiary clay and limestone are between 2 and 5 m thick whereas above evaporite formations the alluvial deposits may be as much as 110 m thick chronologically the first period of alluvial thickening involved the stream terraces t2 105 m above the present thalweg t3 95 m and t4 85 m which have been dated by paleomagnetic reversals as matuyama pre 780 000 the second subsidence period affected the deposits of the stream terrace t9 30 dated as brunhes post 780 000 in both thickening periods the subsidence was due to solution of the underlying evaporite formations halite and gypsum presumably during intervals of high water flow in the proposed model the valley subsidence was balanced by stream aggradation maintaining the river equilibrium profile the subsidence recorded in the alluvial deposits shows a complex spatial and temporal evolutionary pattern and total subsidence was assumed to be equal to the alluvial thickening for each subsidence period reaching up to 165 and 25 m respectively

detection of underground cavities by combining gravity magnetic and ground penetrating radar surveys a case study from the zaragoza area ne spain a geophysical survey routine is proposed to detect underground cavities and dolines it is based on the sequential application of magnetic low frequency ground penetrating radar gpr and microgravity techniques a case study near zaragoza ebro valley spain demonstrates the applicability of these methods the strong contrast of magnetic and electromagnetic properties and to a lesser scale of density between the doline filling and the surrounding stratified tertiary and quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods