synsedimentary collapse of portions of the lower blomidon formation late triassic fundy rift basin nova scotia a chaotic mudstone unit within the lower blomidon formation late triassic has been traced for 35 km in the mesozoic fundy rift basin of nova scotia this unit is characterized by highly disrupted bedding that is commonly cut by small 0 5 m domino style synsedimentary normal faults downward movement of material geopetal structures variable thickness and an irregular partially faulted contact with the overlying unit the chaotic unit is locally overlain by a fluvial sandstone which is overlain conformably by mudstone although the thickness of the sandstone is highly variable the overlying mudstone unit exhibits only gentle regional dip the sandstone unit exhibits numerous soft sediment deformation features including dewatering structures convoluted bedding kink bands and convergent fault fans the frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit these stratigraphic relations suggest buried interstratal karst the subsurface

mechanics of upward propagation of cover collapse sinkholes cover collapse sinkholes occur by failure of the walls of a soil void above cavernous bedrock i examine conditions for failure in compression by crack propagation and coalescence and for failure by sloughing in which pore water pressure produces a net tension perpendicular to the wall of the void compressive failure without relaxation of stress does not explain observed long term stability of thick soils nor failures in thin residual soils if stress relaxation occurs with compressive failure soil voids tend to stabilize and sinkholes are not predicted sloughing failure is not predicted for steady state pore pressure fields even for a perched water table at the surface over a drained void transient pore pressure conditions that could produce sloughing may result from 1 rapid drawdown causing soil consolidation and transient high pore pressure gradients 2 approach of a wetting front in unsaturated soil with high permeability behind the front 3 dissolution of air from bubbles in the soil and exsolution near the void producing a low permeability zone near the void

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

early stage sinkhole formation in the acque albule basin of central italy from geophysical and geochemical observations abstract sinkhole occurrence along the tyrrhenian margin of the central apennines is of great importance for applied research land management and civil protection this study reports on gps altimetry magnetic gravity geoelectric seismic and soil gas measurements of a rapidly developing sinkhole near the guidonia military airport the measurements revealed an elliptical 2 m depression elongated 220 m in the nne ssw direction with the minor axis of 110 m in the spring of 2013 two vertical cavities formed in the eastern and northeastern flanks of the depression whose depths and shapes are rapidly evolving with the formation of widespread fracturing along the same side the geophysical observations image the developing sinkhole to a depth of some 50 m the presence of the travertino lithotype around the depression down to at least 40 m and the lack of this lithotype below the lowered area the sinkhole s evolution appears to be structurally controlled by local and regional faulting these results are useful for designing further geophysical geotechnical and geochemical studies to monitor the sinkhole s evolution and to assess the hazard it presents in densely urbanized area

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

geomorphology and natural hazards in karst areas a review 1 introductionsince human beings started to colonise the world slowly migrat ing in multiple directions from the african rift and ultimatelyreaching the southernmost territories of the americas they haveinteracted with the natural environment using its resources and suf fering from its hazardous processes survival of mankind was possiblethanks to its ability to adapt to an ever changing environment and itscapability to learn and communicate the new ndings from the ear liest times geomorphic features and processes were an essential partof social survival crozier et al 2011 in karst terrains caves wereused as shelters as well as burial and sacred places playing an instru mental role in the day to day struggle for survival especially duringthe ice ages fig 1 spectacular karst landmarks such as big cave en trances blue karst springs deep collapse sinkholes cenotes or rockarches just to name a few have often become part of the naturaland supernatural heritage of our ancestors in prehistoric times the human impact on the karst environmentwas very limited like the probability of properties and people beingdamaged by karst processes e g subsidence ooding both impactsandhazardsinkarstterrainshaveincreaseddramaticallyover thelasttwo centuries along with the exponential increase in population andour capability to modify the natural environment largely related tothe economic and technological development of the societies an in creasing number of scientists consider that humans are nowadaysthe most effective geomorphic agent and a prime factor in landscapeevolution zalasiewicz et al 2010 price et al 2011 in fact the for mal de nition of the anthropocene as a new epoch of the geologicaltime scale characterised by a signi cant and global human impact onthe earth s ecosystems is being debated at the present time around25 of the earth s population lives on or nearby karst areas ford andwilliams 2007 and the increasing exploitation of karst resources such as water and building material is leading to severe environmen tal impacts and unsustainable situations drew and hotzl 1999 gunn 2004 unfortunately the number of karst areas affected bywater pollution landscape degradation and other impacts is growingveryrapidly additionally thedamagecausedbyhazardouskarstpro cesses especially subsidence sinkholes beck 2003 waltham et al 2005 gutierrez et al 2008a will most likely keep on increasing exposed human elements augment and anthropogenic changes inthe karst systems frequently result in hazard enhancement karstgeomorphologists and hydrologists can play a decisive role in pre venting natural disasters in karst areas particularly those inducedby human activities dams with leakage and sinkhole problems milanovic 2000 cooper and gutierrez 2011 mines and tunnelsaffected by ooding and subsidence li and zhou 1999 autin 2002 casagrandeet al 2005 luchaetal 2008 high speedrailwaysbuilt in sinkhole prone areas guerrero et al 2008 or developmentof sinkholes at huge rates induced by lake level yechieli et al 2006 or water table sprynskyy et al 2009 declines the importance of properly managing karst areas and mitigatingthe detrimental effects caused by human activities on these inherentlysensitive environments has been boosted by a series of conferencesand projects since the early 1990s ford 1993 williams 1993 pariseet al 2008 2009 raising public awareness on the need to protectour endangered natural resources especially in developed countries has promoted the production of karst speci c environmental impactassessments veni 1999 recently severalapproacheshavebeenpro posedtoassessthedegreeofhuman induceddisturbanceinkarstareas van beynen and townsend 2005 calo and parise 2006 de waele 2009 north et al 2009 although these studies are essential for apropermanagementofthekarstresources theymaybefutileifnotfol lowed by adequate administrative decisions and regulations 2 karst geomorphology2 1 karst processeskarst is characterised by the predominance of rock dissolution overmechanical erosion and is typical of present temperate cold andwarm and tropical environments ford and williams 2007 in karstterrains surface and subsurface geomorphology and hydrology arelargely governed by dissolution of carbonate and or evaporite rocks in the most classical common situation surface waters acidi ed byco

karst breakdown mechanisms from observations in the gypsum caves of the western ukraine implications for subsidence hazard assessment the term karst breakdown is employed in this paper to denote the totality of processes and phenomena of gravitational and or hydrodynamic destruction of the ceiling of a karst cavity and of the overlying sediments it refers not only to the existence of a surface subsidence collapse feature but first of all to the internal hidden in the subsurface structures that precede development of a surface form this study reports and discusses the results of direct mapping and examination of breakdown structures in the gypsum karst of the western ukraine at the level of their origin i e in caves the accessibility of numerous laterally extensive maze cave systems in the region provided an excellent opportunity for such an approach which made it possible to examine the relationship between breakdown structures and particular morphogenetic or geological features in caves and to reveal stages of breakdown development it is found that breakdown is initiated mainly at specific speleogenetically or geologically weakened localities which classify into a few distinct types the majority of breakdowns which are potent to propagate through the overburden relate with the outlet cupolas domepits that represent places where water had discharged out of a cave to the upper aquifer during the period of transverse artesian speleogenesis distribution of breakdown structures does not correlate particularly well with the size of the master passages several distinct mechanisms of breakdown development are revealed and most of them proceed in several stages they are guided by speleogenetic geological and hydrogeological factors the study confirms that a speleogenetic approach is indispensable to the understanding of breakdown pre requisites and mechanisms as well as for eventual subsidence hazard assessment direct observations in caves aimed both at speleogenetic investigation and breakdown characterization on regional or site specific levels should be employed wherever possible

paleocave carbonate reservoirs origins burial depth modifications spatial complexity and reservoir implications paleocave systems form an important class of carbonate reservoirs that are products of near surface karst processes and later burial compaction and diagenesis features and origins of fractures breccias and sediment fills associated with paleocave reservoirs have been studied in modern and ancient cave systems information about such cave systems is used in this paper to reconstruct the general evolution of paleocave reservoirs and their associated scale pore networks and spatial complexities spatial complexities in paleocave reservoirs result from near surface and burial processes near surface processes include dissolutional excavation clastic sedimentation chemical precipitation and localized fracturing brecciation and collapse of cave walls and ceilings burial processes begin as cave systems subside into the subsurface remaining cave passages commonly collapse and early formed breccia clasts are rebrecciated differential compaction of strata around and over collapsed passages produces fractures crackle breccias and mosaic breccias near surface and burial processes combine to produce typically complex reservoirs with several scales of heterogeneity hydrocarbon reservoirs of paleocave origin are commonly the product of coalesced collapsed paleocave systems the coalescing of passages in a cave system into larger connected porosity zones results from a combination of multiple cave forming episodes at composite unconformities and from the collapse of cave systems during burial where surrounding host strata are brecciated and fractured this combination of processes creates spatially complex reservoirs that can be hundreds to several thousands of meters across commonly forming large exploration targets final size pore network types and spatial complexities of coalesced collapsed paleocave systems are products of their evolution from near surface development through burial into the deeper subsurface the coalesced collapsed paleocave reservoir hypothesis explains the scale of reservoirs observed and the spatial complexities involved

assessing sinkhole activity in the ebro valley mantled evaporite karst using advanced dinsar abstract sinkholes in karst areas may cause subsidence damage in transportation infrastructures demolition of buildings and even the loss of human lives when they occur in a catastrophic way differential interferometry dinsar is a promising technology for detecting and characterizing sinkholes as well as for reducing the associated risk when combined with other sources of data such as a sinkhole inventory in this work the usefulness of insar techniques and data for sinkhole risk management has been analyzed through the comparison of three dinsar derived velocity maps with a comprehensive sinkhole inventory in the ebro valley ne spain the dinsar maps have contributed to improve the sinkhole inventory in different ways 1 detection of non inventoried sinkholes 2 revision of sinkhole areas previously classified as inactive as active and 3 refinement of underestimated sinkhole boundaries the obtained results suggest that dinsar products are suitable for analyzing active dissolution induced subsidence the application of these techniques may help in recognizing and better characterizing previously unknown karst subsidence problems and in preventing personal and property losses however the analysis reveals that the available dinsar maps combined overlook about 70 of the previously mapped active sinkholes mainly due to decorrelation

the role of the subcutaneous zone in karst hydrology abstract the subcutaneous zone is the upper weathered layer of rock beneath the soil but above the permanently saturated phreatic zone it is of particular hydrological importance in karst because of its high secondary permeability arising from the considerable chemical solution in this zone however corrosional enlargement of fissures diminishes with depth thus permeability decreases in the same direction with the result that percolation is inhibited except down widened master joints and faults storage of water consequently occurs in this zone particularly after storms the upper surface of this suspended saturated layer in the subcutaneous zone is defined by a perched water table which slopes towards points of rapid vertical percolation the potential induces lateral water movement converging on the most permeable areas such as beneath dolines leakage from the subcutaneous store sustains slow percolation in the vadose zone cross correlation of rainfall with percolation rates in caves in new mexico u s a and new zealand reveal response lags of 2 14 weeks with no apparent relationship to depth below the surface other percolation sites show no correlation with rainfall interpreted as being a consequence of considerable friction in tight fissure networks the recognition of storage and rapid as well as very slow percolation from the subcutaneous zone requires re interpretation of the components of hydrographs from karst springs and of some conceptual models of karst aquifers the importance of subcutaneous storage in sustaining baseflow discharge at some sites must be recognised as must the contribution of subcutaneous water to flood hydrographs methods of estimating the volumes of subcutaneous and phreatic components of karst spring flood hydrographs are presented the paper concludes with a discussion of the significance of subcutaneous hydrologic processes for an understanding of karst geomorphology the desirability of explaining karst landform evolution in terms of hydrologic processes is stressed

paleoflood records from sinkholes using an example from the ebro river floodplain northeastern spain 53 pags 10 figs the definitive version is available at https www cambridge org core journals quaternary research

simulation experiment on sinkhole formation caused by soils disintegration and the advance forecasting of sinkhole risk sinkholes are a common geological hazard around the world however it is difficult to carry out the associated indoor simulation experiments because of the complicated factors involved our previous research showed that sinkholes in the aerated zone caused by soil disintegration exhibit accurate critical conditions therefore the kind of sinkhole formation is simulated in the paper before the simulate experiment the critical value of the disintegration of clay samples is tested which helps to control the simulation conditions with a designed simulation apparatus soil disintegration was conducted 70 times from october 23 2017 to june 1 2018 and a sinkhole formed this experiment results indicate two developmental laws of sinkholes forming in the aerated zone one is the forming process which has three stages soil void formation soil void expansion and roof collapse second is that the two conditions water content is less than the critical value and contact between water and soil causing the sinkhole formation at the forming two conditions are clear and can easily be monitored by the associated factors in the field where sinkholes have occurred or are about to occur according to the principle another simulation experiment was carried out as a result an advanced prediction of a sinkhole is achieved in the aerated zone

hydrochemistry and solution rates in gypsum karst case study from the western ukraine the gypsum karst in the western ukraine spreads through a large territory covering more than 20 000 km2 and is represented by a range of stages evolutionary types from deep seated through subjacent to entrenched correspondingly hydrogeological settings of karst development circulation patterns and chemical characteristics of groundwaters differ substantially between the respective areas based on 1 800 analyses this paper summarises hydrochemistry of the gypsum hosting miocene aquifer the majority of sampling has been performed in conjunction with a study regime of gypsum solution rates by means of standard tablets in this study which included 53 tablet stations representing varying conditions of water rock interaction 644 weight loss measurements were made over the period 1984 1992 the highest rates are characteristic of entrenched karst although active dissolution is localised along well defined sinking streams with short underground courses rare vertical percolation paths and the water table lower but still quite substantial rates are characteristic of subjacent and deep seated confined karst however the overall dissolution removal is greater due to higher flow through the gypsum and the larger area of rock solvent contact the results are generalised in order to derive the approximate solution rates characterising major situations and to be suitable for modeling purposes

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

improving sinkhole hazard models incorporating magnitude frequency relationships and nearest neighbor analysis abstract this work presents a methodology for elaborating sinkhole hazard models that incorporate the magnitude and frequency relationships of the subsidence process the proposed approach has been tested in a sector of the ebro valley mantled evaporite karst where sinkholes largely induced by irrigation practices have a very high occurrence rate 50 sinkholes km 2 yr in this area covering 10 km 2 a total of 943 new cover collapse sinkholes were inventoried in 2005 and 2006 multiple susceptibility models have been generated analyzing the statistical relationships between the 2005 sinkholes and different sets of variables including the nearest sinkhole distance the quantitative evaluation of the prediction capability of these models using the 2006 sinkhole population has allowed the identification of the method and variables that produce the most reliable predictions the incorporation of the indirect variable nearest sinkhole distance has contributed significantly to increase the quality of the models despite simplifying the modeling process by using categorical rather than continuous variables the best susceptibility model generated with the total sinkhole population and the selected method and variables has been transformed into a hazard model that provides minimum estimates of the spatial temporal probability of each pixel to be affected by sinkholes of different diameter ranges this transformation has been carried out combining two equations derived from the more complete 2006 sinkhole population one of them expressing the expected spatial temporal probability of sinkhole occurrence and the other the empirical magnitude and frequency relationships generated for two different types of land surfaces which control the strength of the surface layer and the size of the sinkholes the presented method could be applied to predict the spatial temporal probability of events with different magnitudes related to other geomorphic processes e g landslides

sinkholes related to discontinuous pumping susceptibility mapping based on geophysical studies the case of crestatx majorca spain the crestatx aquifer is the main source of water supply to the bay of alcudia one of the largest resorts on the island of majorca spain this water has been used since the 1970s using several pumping wells which draw an annual volume of 1 5 hm3 the seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level up to 120 m and dynamic water levels of down to 87 m below sea level at the end of the 1990s several sinkholes and subsidence depressions started being detected in a highly karstified area twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70 000 m2 with diameters up to 23 m and depth more than 15 m the intense and continuous rainfall during recent years 2008 2010 has considerably accelerated the process increasing the dimensions of existing sinkholes and the appearance of new morphologies by means of electrical tomography techniques a ground study was carried out numerous cavities have been identified in the upper 30 m using a map of the surface morphologies and the geophysical profiles we can determine that the propagation and orientation of the sinkholes lie along three main directions n30 e n130 e and n60 e the first is the most relevant which is parallel to the main tectonic structures in the area the interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas which is an effective tool to assess risk in the area as there are roads and a housing development nearby the high but discontinuous exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions as it causes large variations of pressure and accelerates the dissolution process in the underlying rock

a survey of the engineering properties of some anhydrite and gypsum from the north and midlands of england abstract the permian and triassic systems in the north and midlands of england contain notable beds of anhydrite and gypsum these rocks contain small but varying amounts of muddy material which often has some influence on their geomechanical properties anhydrite is a strong to very strong rock in terms of both its unconfined compressive strength and point load index whereas gypsum is of medium strength according to its unconfined compressive strength because of the low porosity of these rocks porosity does not have a significant influence on their strength however the strength and hardness of these rocks are strongly correlated in terms of the slake durability test anhydrite has a very high durability and gypsum a high to very high durability with the stronger rocks yielding higher values of durability most anhydrite and gypsum exhibit plastic elastic plastic deformation subsequent plastic deformation occurring at an earlier stage during loading of gypsum than of anhydrite as far as deformability is concerned that of anhydrite is very low while that of gypsum varies from low to high both rock types experience hysteresis on cyclic loading that of gypsum being more notable than that of anhydrite and the amount of hysteresis undergone increases with successive cycles of loading and unloading anhydrite and gypsum both undergo creep when subjected to constant loading gypsum being the more prone to creep under constant load

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

subsidence and foundering of strata caused by the dissolution of permian gypsum in the ripon and bedale areas north yorkshire underground dissolution of thick gypsum beds in the edlington formation and roxby formation of the zechstein sequence in north yorkshire england has resulted in a 3 km wide and 100 km long belt of ground susceptible to foundering within this belt a large subsidence depression at snape mires near bedale was largely filled with lacustrine deposits in the later part of the late devensian and during the flandrian south of snape mires the nosterfield ripon bishop monkton area has suffered about 40 episodes of subsidence in the past 150 years and the presence of several hundred other subsidence hollows indicates considerable activity from the later part of the devensian onwards the linear and grid like arrangement of these subsidence hollows indicates collapse at intersections in a joint controlled cave system linear subsidence features at snape mires are also joint controlled the transition from anhydrite at depth to secondary gypsum near surface marks the down dip limit of the subsidence prone belt cavities are propagated upwards by roof collapse of caverns in the gypsum leading to the formation of breccia pipes choking of the pipes can reduce the surface expression of the underground collapse but the larger cavities are liable to produce pipes that reach the surface even at the eastern boundary of the 3 km wide belt described further subsidence in the ripon area is predicted and some suggestions for remedial measures are given

the formation of a giant collapse caprock sinkhole on the barda negra plateau basalts argentina magnetic mineralogical and morphostructural evidences the 1 5 km wide 40 m deep crater like structure in the 10 ma old barda negra basaltic plateau in central argentina was discovered in the early 2000s based on remote sensing surveys and on its morphological characteristics similar to those of the barringer crater in arizona the structure is described to be originated by an impact in this study we ran several field work campaigns and collected and analysed samples in order to find more evidences to endorse or reject this hypothesis we observe a circular depression not generally surrounded by raised rims in contrast to craters produced either by a meteorite impact or phreatomagmatic eruption maars mineralogical investigations of rocks and sediments do not show high pressure and temperature minerals such as coesite or stishovite or any remnants of an impactite or impact melt glass likewise no textural evidences for impact related fracturing or stress are observed a detailed geomorphological mapping indicates a successive crater development which invokes local stepwise subsidence magnetic mapping performed with the eu funded newton multisensor novel instrument shows a 2000 nt field anomaly associated to the edges of the crater and susceptibility measurements cast an important contrast between the basaltic rims and plateau and the crater interior therefore we propose a sink hole origin for the crater with a former collapse of the plateau basalts and a latter infill with sedimentary material this hypothesis is supported by the fact that the 40 to 85 m thick and 14 to 15 ma old carbonate bearing collon cura formation underneath the 100 to 150 m thick basaltic plateau lava sheet represents ideal rocks for dissolution and karst formation remote sensing data show other nearby sinkholes 20 km westward with extensions of 3 6 km and 100 m depth which are emplaced within a cogenetic neighboring basaltic plateau with a similar underlying lithology and the consistence of the magnetic model computed with this scheme and on measured rock remanence and susceptibilities of the structure and surroundings these giant collapse sinkholes up to 6 km in diameter within caprocks of very thick plateau basalts represent unique examples for planetary surface shaping processes which also occur on mars and comets in areas with ba salts or rigid caprocks

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

evaluating and comparing methods of sinkhole susceptibility mapping in the ebro valley evaporite karst ne spain abstract multiple sinkhole susceptibility models have been generated in three study areas of the ebro valley evaporite karst ne spain applying different methods nearest neighbour distance sinkhole density heuristic scoring system and probabilistic analysis for each sinkhole type separately cover collapse sinkholes cover and bedrock collapse sinkholes and cover and bedrock sagging sinkholes the quantitative and independent evaluation of the predictive capability of the models reveals that 1 the most reliable susceptibility models are those derived from the nearest neighbour distance and sinkhole density these models can be generated in a simple and rapid way from detailed geomorphological maps 2 the reliability of the nearest neighbour distance and density models is conditioned by the degree of clustering of the sinkholes consequently the karst areas in which sinkholes show a higher clustering are a priori more favourable for predicting new occurrences 3 the predictive capability of the best models obtained in this research is significantly higher 12 5 82 5 than that of the heuristic sinkhole susceptibility model incorporated into the general urban plan for the municipality of zaragoza although the probabilistic approach provides lower quality results than the methods based on sinkhole proximity and density it helps to identify the most significant factors and select the most effective mitigation strategies and may be applied to model susceptibility in different future scenarios

the episodic rise net growing rate and kinematics of radial faults of the salinas de oro diapir using paleoseismological techniques ne spain salt upwelling versus karstic subsidence abstract this paper explores the use of trenching and paleoseismological techniques to determine salt flow rates into a salt diapir for the first time in the literature the salinas de oro diapir located in the northern spanish pyrenees is an oval shaped triassic salt stock that extends vertically for 7 km down to the paleozoic basement salt dissolution subsidence and diapir growth are coeval active processes karstification is responsible for the development of large sinkholes a thick caprock and the monocline folding and ring faulting of the cretaceous and early tertiary limestone rim the evaporite karstic aquifer discharges high concentration water of up to 137 g l of total dissolved solids and a conductivity over 200 ms cm into the salado creek which drains the diapir top the salinity monitoring of this drainage provides a maximum karstic surface lowering rate of around 2 8 mm yr salt upwelling has caused the 150 m uplift of the annular limestone escarpment and the development of 3000 m long radial grabens with up to 90 m of vertical offset that disrupt drainages displace quaternary deposits and overprint concentric faults the 260 cm drag folding of lacustrine facies exposed in a 42 m long and 6 5 m deep trench due to the creep motion of the western radial fault of azanza graben yielded a minimum short term uplift slip rate of 1 75 mm yr for the last 1485 years and provides a minimum salt supply rate of over 5 mm yr considering karstification lowering this value that is several hundred times higher than average evidence the discontinuous growth of salinas de oro diapir

subsidence sinkhole development in light of mud infiltrate structures within interstratal karst of the coastal plain southeast united states mud infiltrate structures mis are a class of clastic sedimentary structures that have formed by high angle gravitational sedimentation in vadose cavernous limestones beneath the miocene hawthorn group observations of mis in caves beneath the pelham escarpment southwest georgia suggest three main types occurring either beneath within or contiguous to subvertical feeder pipes in the ceiling 1 rubbly conical masses 2 polished striated cylindrical masses and 3 mud flow drape and splash forms mis abundance suggests gravitative deposits are a major component to the total volume of cave mud the muds apparently do not include soil mantle materials rather their sources are poorly cemented clay rich layers within the overlying hawthorn group in cases where an individual mis volume is large in proportion to the clastic cover thickness but no surface depression is found the mis location hypothetically predicts a directly overlying site of potential cover collapse sinkhole development smaller volume and or shallower mis predict the location of potential cover subsidence sinkholes the mis forms suggest plastic and fluid behavior of the sediments occurs during displacements the capacity for subsurface voids to accept mobile sediments depends on several factors that influence sinkhole development 1 void size and interconnectedness 2 spacing and size of subvertical solution pipes which can act as mis feeders 3 depth beneath the sediment source of any main horizontal cave development 4 thickness of the cover sediments and 5 the presence and depth of any breakout domes the hawthorn is present over more than 50 percent of the area underlain by the floridan aquifer system and is the system s major upper confining unit mis forming processes are likely to be widely distributed within this stratigraphic setting promoting ground subsidence and subsurface porosity obliteration given the existence of feeder pipes mis also are expected to form within the phreatic zone

structure and evolution of collapse sinkholes combined interpretation from physico chemical modelling and geophysical field work abstract in karst rocks limestone anhydrite gypsum etc water flowing through fissures and bedding partings can enlarge voids either by physical or chemical dissolution within a geologically short period of time the increase in void space creates a large secondary porosity typical for soluble rocks which is responsible for preferential flow through the karst rock often through cave systems with passages reaching the meter scale and more this large scale voids in the sub surface can initiate collapse of the overburden either through wall or roof breakdown and the initial void created by dissolution can migrate upwards and finally cause a surface collapse and create a collapse sinkhole while the dissolution part of this evolution is in the order of 10 000 100 000 years the final mechanical collapse can occur on time scales of days we have studied a typical collapse sinkhole site in the southern harz mountains in germany with anhydrite partly converted to gypsum as soluble rock in the sub surface we discuss geophysical measurements gravity electrical resistivity tomography self potential magnetics from the location to identify the local collapse sinkhole signal and the possibility to separate the collapse sinkhole signal from the broader geological signal of the study site we model the initiation of sub surface voids with our numerical tool karstaquifer a 3d karst evolution model describing flow and dissolution in karst rocks we apply this numerical model to predict collapse sinkholes in a locality in the harz mountains

antecedent aeolian dune topographic control on carbonate and evaporite facies middle jurassic todilto member wanakah formation ghost ranch new mexico usa

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

accurate evaluation of ocean tide loading effects for gravity in nearshore region the fg5 measurements at sakurajima volcano in kagoshima bay japan we detected 5 10 microgal diurnal semidiurnal gravity signals of ocean tide origin by the fg5 absolute gravimeter at two stations in sakurajima volcano located 300 m and 2500 m away from the shore we computed the gravity originating both from the global ocean tides and from the local ones in kagoshima bay considering the fine scale sealand distribution around the stations the observed fg5 records and the theoretical ocean tides agreed well with each other in both amplitude and phase indicating that the oceanic loading effects can be predicted to an accuracy better than 2 microgal within several hundred meters of the shore in sakurajima the apparently puzzling errors that have so far arisen on nearshore lacoste measurements were resolved by the correction of the effects

plio quaternary extensional seismotectonics and drainage network development in the central sector of the iberian chain ne spain abstract westward propagation of postorogenic rifting in the central sector of the iberian chain generated the teruel and calatayud mio pliocene grabens and the jiloca daroca and munebrega plio quaternary half grabens partially superimposed on the western margins of the pre existing basins the progressive capture and transformation from endorheic aggradational to exorheic incisional drainage of the active grabens resulted in the development of a drainage network dominated by axial streams controlled by neotectonic activity and the distribution of basin fill lithofacies this paper reviews the geomorphic and stratigraphic evidence of plio quaternary extensional tectonics and provides new chronological data radiocarbon and osl dating on offset deposits and the associated paleoseismic record the daroca fault offsets mantled pediment deposits dated at 113 119 ka based on a radiocarbon age of the colluvial sequence 43 ka affected by the rubielos de la cerida fault a vertical slip rate of 0 05 0 07 mm yr has been estimated for this fault four paleoearthquakes subsequent to 72 ka have been inferred from the classic exposure of the concud fault indicating a recurrence interval of less than 18 ka a gravitational origin related to the dissolution of subjacent evaporites is attributed to two faults affecting an upper pleistocene terrace 15 ka in the alfambra valley close to the concud fault these structures have recently been interpreted as evidence of coseismic deformation on the concud fault although the faults have a low slip rate and a long seismic cycle their length

physical modeling of structures formed by salt withdrawal implications for deformation caused by salt dissolution by creating 15 physical models we investigated deformation above subsiding tabular salt salt walls and salt stocks dry quartz sand simulated a brittle sedimentary roof above viscous silicone representing salt the modeled diapiric walls had linear planforms and rectangular semicircular triangular or leaning cross sectional shapes the stock was cylindrical in models where the source layer or allochthonous salt sheet was initially tabular a gentle flat bottomed syncline bounded by monoclinal flexures formed above a linear zone where the silicone was locally removed above all subsiding diapirs the deformed roof was bounded by an inner zone of steep convex upward reverse faults and an outer zone of normal faults above subsiding diapiric walls extensional and contractional zones were balanced above the subsiding salt stock conical concentric fault zones comprised inner reverse faults and outer normal faults sediments were added both before prekinematic and during synkinematic salt withdrawal in entirely prekinematic roofs reverse fault zones and normal fault zones both widened with time reverse faults propagated upward from the corners of the withdrawing diapirs new reverse faults formed in the footwalls of reverse faults each nearer the center of the deepening roof trough conversely new normal faults formed successively outward from the sagging trough synkinematic deposition retarded faulting but the pattern of inner reverse and outer normal faults was repeated however reverse faults formed successively outward whereas normal faults formed inward new conceptual models suggest that salt dissolution forms similar structures to those physically modeled for salt withdrawal the appropriate physical models resemble natural dissolution structures above tabular salt extension alone above diapirs is not caused merely by salt withdrawal or dissolution but by regional extension or active diapirism

stratigraphy and structure of a late wisconsinan salt collapse in the saskatoon low south of saskatoon saskatchewan canada an update the saskatoon low is a collapse structure that formed as a result of dissolution of salt from the middle devonian prairie evaporite formation in this study the collapse has affected the upper cretaceous lea park judith river and bearpaw formations of the montana group the early and middle pleistocene mennon dundurn and warman formations of the sutherland group and the late pleistocene floral battleford and haultain formations of the saskatoon group locally the collapse is about 180 m which is about equal to the thickness of the salt the first phase of collapse took place after deposition of the ardkenneth member of the bearpaw formation and before glaciation or during a pre illinoian glaciation the second phase of collapse occurred during the battleford glaciation late wisconsinan prior to deposition of the battleford formation the saskatoon low was glacially eroded removing the sutherland group and the floral formation after the glacial erosion up to 110 m of soft till of the battle

karst controlled reservoir heterogeneity in ellenburger group carbonates of west texas petroleum production from restricted shelf carbonates of the lower ordovician ellenburger group is commonly considered to have been a result of a pervasive relatively homogeneous tectonic fracture system within the reservoir rock however regional facies and diagenetic paleokarst studies of ellenburger strata based on cores and wireline logs have demonstrated that significant reservoir compartmentalization was caused by karst modification in the upper part of the unit ellenburger group carbonates which attain a thickness of over 1 700 ft 520 m record sedimentation on a shallow water restricted shelf occupying most of west texas logging of over 10 000 ft 3 050 m of core from 63 wells has allowed recognition of six facies assemblages 1 lithic arenite 2 mixed siliciclastic carbonate packstone grainstone 3 ooid peloid grainstone 4 mottled mudstone 5 laminated mudstone and 6 gastropod intraclast packstone grainstone these facies assemblages record initial transgression and subsequent progradation and aggradation paleoslope was generally south and east from the texas arch toward the ouachita and marathon orogenic belts all facies assemblages with the local exception of the ooid peloid grainstone assemblage are characterized y very low intergranular and intercrystalline porosity porosity development in ellenburger group carbonates is directly related to a prolonged period of subaerial exposure that coincided with a middle ordovician eustatic lowstand prior to transgression of simpson group siliciclastics during this episode a widespread system of caves sinkholes joint controlled solution features and collapse breccias developed of particular importance to reservoir development was the formation of a regionally extensive cave system between 100 and 300 ft 30 and 90 m beneath the exposed ellenburger surface infill of this cave system by simpson group sand and clay segmented the upper ellenburger into three karst facies which are in descending order 1 cave roof dolomites fracture and mosaic breccias 2 laterally persistent cave fill facies siliciclastic matrix supported and carbonate matrix supported breccias and 3 lower collapse facies chaotic clast supported breccias of the cave floor pronounced vertical segregation of permeable zones defined by the three karst facies is evident in the emma andector martin block 13 and several other major ellenburger reservoirs lateral reservoir heterogeneities formed by localized laterally extensive collapse structures such as in the shafter lake reservoir also contribute to compartmentalization of producing zones within the upper ellenburger group secondary and tertiary recovery programs in these ellenburger reservoirs can be optimized by integrating concepts of lateral and vertical heterogeneity predicted by the karst model

assessment of sediment and erosion rates by using the caesium 137 technique in a chinese polygonal karst depression karst depressions comprise geomorphologically important sources and sinks for sediments and associated pollutants yet the sedimentology of many depressions is not well understood in the world in this paper the 137cs technique was employed to estimate recent sedimentation rates in a chinese polygonal karst depression the results indicate that the sediment deposition rates ranged from 0 91 to 1 97 mm year 1 from 1963 to 2007 and the average sediment deposition rate and specific deposit yield were estimated to be 1 47 mm year 1 and 20 t km 2 year 1 respectively these results are consistent with the local monitoring data of runoff fields which confirms the validity of the overall approach this shows that the soil loss rate is very low in some karst areas of southwest china above all the approach appears to offer valuable potential to study surface erosion by estimating sediment deposition rates of karst depressions rather than the assessment of complicated soil erosion in stony soils of carbonate rock slopes in addition the space distribution of surface soil and 137cs inventories are affected remarkably by the inhomogeneous dissolution of limestone under the soil it may be an important phenomenon which exists widely in karst areas and it is significantly different from other places

human induced hydrogeological changes and sinkholes in the coastal gypsum karst of lesina marina area foggia province italy abstract in 1930 a canal was excavated to connect the lesina lagoon with the adriatic sea modifying the track of the previous existing acquarotta canal the 1100 m long stretch of the canal situated next to the coast exposed unknown highly cavernous gypsum bedrock underlying a loose sandy cover during the last two decades a large number of cover collapse and cover suffosion sinkholes have formed along two bands situated next to the canal impinging the adjacent lesina marina residential area the area affected by subsidence has increased exponentially from 1999 to 2009 the tight spatial correlation between the sinkholes and the canal reveals that the subsidence phenomenon has been induced by the local hydrogeological changes caused by the canal in the coastal evaporite aquifer 1 local lowering of the average water table 2 deflection of the groundwater flow lines towards the canal and increase in flow velocity 3 amplification of the groundwater level oscillations largely controlled by the tidal regime 4 local reversals in the groundwater flow changing the canal temporarily from effluent to influent these changes in the hydrogeological functioning of the system have favoured both internal erosion and karstification processes hydrochemical evidence reveals that gypsum dissolution is a currently active process favoured by fresh water and sea water mixing and cation exchange processes most likely the partial replacement of a concrete lining in the canal by pervious gabions in 1993 provided more adequate conditions for the evacuation of the sediments filling the karst conduits accelerating internal erosion and sinkhole development

subsidence hazard avoidance based on geomorphological mapping in the ebro river valley mantled evaporite karst terrain ne spain in the valley of the ebro river to the southeast of the city of zaragoza ne spain the dissolution of evaporite sediments gypsum halite and na sulphates which underlie alluvial deposits gives rise to numerous sinkholes these sinkholes are a potential hazard to human safety particularly where they develop in a catastrophic way even slow developing sinkholes are problematic as they damage urban and agricultural infrastructure necessitating costly repairs and vigilant maintenance to assist in developing avoidance strategies for these hazards the factors controlling sinkhole occurrence have been assessed using geomorphological maps produced from aerial photographs for 1956 and 1981 important controls on sinkhole development are found to include underlying geological structure manifest in preferred orientations of sinkholes on the azimuths n130 150e and n30 40e and the presence of glauberite in the groundwater flow path which apparently promotes accelerated gypsum dissolution perhaps surprisingly alluvium thickness does not appear to significantly correlate with the density of sinkholes on the floodplain in this area the maps for 1956 and 1981 reveal that both human activity and natural processes can serve to obscure the true density of sinkhole development for instance a large number of sinkholes which were conspicuous in 1956 have since been back filled by farmers in the most fluvially active zone of the ebro valley the meander belt the relatively low density of sinkholes compared with adjoining zones suggests that subsidence is being masked by morpho sedimentary dynamic processes aggradation and erosion careful geomorphological mapping for different time periods yields a much more accurate impression of the frequency of sinkhole development than would be gained from surveying currently visible sinkholes in the area of interest

geomorphology of the tertiary gypsum formations in the ebro depression spain abstract this paper reviews the current knowledge of the mainly karstic geomorphological features developed in the evaporitic formations of the ebro depression northern spain special emphasis is given to the recently published and unpublished scientific advances the gypsum formations of tertiary age have an extensive outcrop area within the ebro depression here their morphogenesis is controlled mainly by processes of surface and subsurface dissolution acting on the gypsum outstanding landforms in the gypsum terrain include saline lakes developed in flat bottom dolines saladas other characteristic morphologies include karren and gypsum domes which occur on a decimetre scale where the gypsum is covered by quaternary alluvial deposits the karstification processes are especially intense and cause subsidence phenomena karstic subsidence affects stream terraces mantled pediments and infilled valleys which in the region are called vales dissolution induced synsedimentary subsidence has produced interesting geological features which include significant thickening and deformation of the alluvial deposits in contrast to the rapid removal of gypsum by dissolution the amount of gypsum removed by erosion is low water erosion studies carried out on gypsiferous slopes of the ebro depression indicate that the sediment yield ranges from 0 59 to 7 82 t ha year this low yield results from the high infiltration capacity of the soils subsidence caused by gypsum dissolution has important socio economic consequences in the ebro depression the active alluvial karstification of the gypsum causes numerous sinkholes that are harmful to linear structures roads railway lines irrigation channels buildings and agricultural land unforeseen catastrophic subsidence also puts human lives at risk the benefits of such terrains include thickened alluvial deposits which act as valuable water reservoirs and which form excellent sources of aggregates fluvial valleys in this gypsiferous terrain commonly show an asymmetrical geometry with prominent gypsum scarps at one side these gypsum scarps are affected by numerous landslides these slope movements are hazardous may dam rivers and cause flooding of the alluvial plains

hydraulic boundary conditions as a controlling factor in karst genesis a numerical modeling study on artesian conduit development in gypsum 1 a coupled continuum pipe flow model is employed to simulate the development of karst conduits in an artesian setting where aggressive water flows upward from an insoluble aquifer into a gypsum unit speleogenetic processes and controlling parameters are identified first for single conduit development it is demonstrated that transient flow from the conduit into the surrounding fissured system of the rock enhances solutional conduit enlargement moreover single conduit development is found to be highly sensitive to variations in initial diameter and hydraulic gradient simulating the solutional enlargement of pipe networks reveals that these two factors determine the resulting conduit pattern structural preferences are found to be essential for horizontal conduit development otherwise flow paths are solely enlarged in vertical direction following the hydraulic gradient hydraulic gradients that increase with time can limit the extension or completely inhibit the development of horizontal caves even if lateral conduit development was structurally preferred

multiphase breakdown sequence of collapse doline morphogenesis an example from quaternary aeolianites in western australia abstract the morphology of collapse dolines varies according to their maturity and effectiveness of the removal of collapsed material in addition the variable balance between various geomorphic processes due to local geologic hydrologic and climatic settings results in a diverse morphology of collapse dolines and dynamics of their morphogenesis a single generalised proposed sequence of collapse dolines morphogenesis has therefore limited value and more detailed study is needed in terrains which differ in terms of geology hydrology and or climate there is a particularly well exposed karst in stockyard gully national park in the southwestern coastal part of western australia formed in quaternary aeolianites consisting of a dense field of collapse dolines up to 100 m in diameter and on average 10 m deep extensive field work combined with available data of local rock stratigraphy and a comparison to collapse dolines worldwide revealed that the principal processes of collapse doline formation in stockyard gully national park are similar to processes responsible for collapse doline formation worldwide i e collapses above underground chambers and removal of the collapsed material however rock characteristics in the area influence their morphometry due to the mechanical weakness of aeolianite compared to well cemented limestones and a surface calcrete layer with stronger mechanical resistance than underlying aeolianite consequently we propose a new 4 stage multiphase breakdown sequence of collapse doline morphogenesis in aeolianites divided into cave dome calcrete caprock dome young collapse doline and mature collapse doline calcrete caprock dome is stabilised by the uppermost well cemented calcrete and represents a distinctive phase just before the final breakdown to form an actual collapse doline

gypsum scarps and asymmetric fluvial valleys in evaporitic terrains the role of river migration landslides karstification and lithology ebro river ne spain abstract most of the spanish fluvial systems excavated in tertiary evaporitic gypsum formations show asymmetric valleys characterized by a stepped sequence of fluvial terraces on one valley flank and kilometric long and 100 m high prominent river scarp on the opposite side of the valley scarp undermining by the continuous preferential lateral migration of the river channel toward the valley margin leads to vertical to overhanging unstable slopes affected by a large number of slope failures that become the main geological hazard for villages located at the toe of the scarps detailed mapping of the gypsum scarps along the ebro and huerva rivers gypsum scarps demonstrates that landslides and lateral spreading processes are predominant when claystones crop out at the base of the scarp while rockfalls and topples become the dominant movement in those reaches where the rock mass is mainly constituted by evaporites the dissolution of gypsum nodules seasonal swelling and shrinking and dispersion processes contribute to a decrease in the mechanical strength of claystones the existence of dissolution enlarged joints sinkholes and severely damaged buildings at the toe of the scarp from karstic subsidence demonstrates that the interstratal karstification of evaporites becomes a triggering factor in the instability of the rock mass the genesis of asymmetric valleys and river gypsum scarps in the study area seem to be caused by the random migration of the river channel in the absence of lateral tilting related to tectonics or dissolution induced subsidence once the scarp is developed its preservation depends on the physicochemical properties of the substratum the ratio between bedrock erosion and river incision rates and climatic conditions that favour runoff erosion versus dissolution

gypsum karstification induced subsidence effects on alluvial systems and derived geohazards calatayud graben iberian range spain abstract the karstification of the tertiary gypsum formations in the calatayud graben has given rise to synsedimentary and postsedimentary subsidence phenomena in both the neogene sediments of the endorheic graben fill and in the quaternary alluvial sediments deposited under exorheic conditions in the so called maluenda and perejiles areas covering 4 4 and 12 km 2 respectively the neogene sedimentary units stratigraphically above the gypsum have subsided due to the karstification of the underlying evaporites the maximum subsidence in both areas has reached at least 200 m the jalon jiloca perejiles alluvial system has been affected by karstic subsidence during its quaternary evolution ten stepped alluvial levels pediment terrace have been identified as a consequence of synsedimentary karstic subsidence the deposit of an alluvial level can be locally thickened changing in a short distance from less than 10 m to more than 100 m in thickness thus the deposit of an individual terrace can be locally superimposed on the deposits of older terraces the palaeokarst recorded in the sediments of the different alluvial levels shows how the karstic subsidence has controlled the dynamics of the sedimentary system the alluvial karstic subsidence is currently active in the flood plains affecting fluvial channels buildings communication ways irrigation ditches and the calatayud gypsum scarp

natural and human induced sinkholes in gypsum terrain and associated environmental problems in ne spain the central ebro basin comprises thick evaporite materials whose high solubility produces typically karstic landforms the sinkhole morphology developed in the overlying alluvium has been studied using gravimetry and ground penetrating radar gpr on stream terraces as well as analyzing the evolution of sinkhole morphologies observed in aerial photographs taken in 1928 1957 and 1985 the sinkhole morphologies give some idea of possible subsurface processes as well as an indication of the final mechanisms involve in sinkhole development on stream terraces and cover pediments the most commonly encountered dolines are bowl shaped in their morphology with both diffuse and scarped edges in contrast dolines developed in the gypsiferous silt infilled valleys have a funnel and well shaped morphology the diffuse edged bowl shaped dolines are developed through the progressive subsidence of the alluvial cover due to washing down of alluvial particles through small voids and cracks into deeper subsurface caves resulting in a decrease alluvial density future compaction of the alluvial cover will produce surface subsidences this type of dolines are associated with negative gravity anomalies in contrast the scarped edge dolines are formed by the sudden collapse of a cavity roof the cavities and cracks formed in the gypsum karst may migrate to the surface through the alluvial deposits by piping and they may subsequently collapse in this instance the cavities can be detected by both gravity and gpr anomalies where the voids are not deeper than 4 5 m from the surface these processes forming sinkholes can be enhanced by man induced changes in the groundwater hydrologic regime by both inflows due to irrigation ditch losses or pipe leakages and by outflows from pumping activities

interplay between tectonics climate and fluvial transport during the cenozoic evolution of the ebro basin ne iberia 1 three dimensional modeling that integrates fluvial sediment transport crustal scale tectonic deformation and lithospheric flexural subsidence is carried out to simulate the landscape and drainage evolution of the ebro sedimentary basin ne iberia the ebro basin underwent a long period of closed intramountain drainage as a result of tectonic topography generation at the pyrenees the iberian range and the catalan coastal range in the late oligocene the catalan coastal range underwent extension leading to the formation of the valencia trough nw mediterranean but the ebro basin remained closed for nearly 15 myr more before the ebro river cut through the remnants of the topographic barrier this drainage opening caused widespread basin incision that shaped spectacular outcrops of the syntectonic and posttectonic infill here we investigate the processes controlling these major drainage changes the modeling results constrained by a large data set on the tectonic and transport evolution of the area predict a closed phase characterized by a large lake in the central eastern ebro basin dry climatic conditions probably lowered the lake level and contributed together with rift flank uplift to prolong this endorheic basin stage the age and amount of reworked sediment after the opening are consistent with an onset of basin incision between 13 and 8 5 ma as a result of lake capture by escarpment erosion and lake level rise associated with sediment accumulation and wetter climatic conditions sea level changes in the mediterranean had no major impact in the large scale drainage evolution of the ebro basin index terms 1625 global change geomorphology and weathering 1824 1886 1815 hydrology erosion and sedimentation 3210 mathematical geophysics modeling 3344 meteorology and atmospheric dynamics paleoclimatology 8102 tectonophysics continental contractional orogenic belts keywords pyrenees drainage evolution lake sediment budget erosion flexure

giant solution subsidence structure in the western mediterranean related to deep substratum dissolution terra nova 24 181 188 2012 abstract sinkholes are frequently observed where soluble rocks are present in meteoritic recharge areas or when subsurface dissolution causes ground collapse seismic profiles on the inner shelf of the gulf of lions w mediterranean display a giant atypical sub circular structure up to 800 m thick and 2 km wide it is characterized by down warped internal seismic reflections forming a concave v shaped depression rooted in the substratum most likely carbonated this structure is interpreted as a poly phased solution subsidence collapse structure of plio quaternary age the last phase of deformation probably occurred during the last sea level low stand phase the mechanism proposed for the creation of this structure is collapse dissolution of the soluble substratum as a result of a combination of several possible factors including pre existing deep messinian palaeo karst with active groundwater flows during plio quaternary lowstands and deep rooted acidic fluids ascending through the substratum

assessment of doline geometry using geophysics on the quercy plateau karst south france in the protection of karstic aquifers the role played by dolines is of interest as these shallow structures can be preferential infiltration pathways for groundwater recharge in this study three depressions in south france orniac lot were identified and characterized using combined geophysical methods apparent conductivity mapping allows precise definition of dolines corresponding to topographic depressions it also reveals other dolines that are hidden by soil cover electrical resistivity and seismic refraction tomography provide detailed cross sections even though the dolines studied are close one to another they exhibit great variability in shape and content moreover time lapse data show that the most saturated regions are on the edges of the first doline such information helps to evaluate human impacts and forecast potential groundwater contamination

geomorphological and sedimentological features in quaternary fluvial systems affected by solution induced subsidence ebro basin ne spain abstract the quaternary evolution and the morpho sedimentary features of some of the most important rivers in spain ebro and tagus rivers among others have been controlled by subsidence due to alluvial karstification of the evaporitic bedrock the subsidence mechanism may range from catastrophic collapse to slow sagging of the alluvium by passive bending in the ebro basin the mechanisms and processes involved in karstic subsidence were studied through the analysis of present day closed depressions as well as through old subsidence depressions palaeocollapses and solution induced basins and associated deformations recorded in the quaternary alluvial sediments the gallego ebro river system is presented as a case study of channel adjustments and geomorphic and sedimentary evolution of fluvial systems in dissolution induced subsidence areas in this fluvial system evaporite dissolution during particular quaternary time intervals namely early and middle pleistocene have lead to the development of a solution induced basin approximately 30 km long by 8 km wide filled by quaternary deposits with a total thickness in excess of 190 m the main river response to balance the subsidence in the alluvial plain was aggradation in the central reach of the subsiding area and degradation both in the upstream reach and in the valley sides where alluvial fans and covered pediments may prograde over the fluvial sediments the main sinking areas are recognized in the sedimentary record by anomalous thickenings in the alluvial deposits and fine grained sediments deposited in backswamp and ponded areas

sinkholes subsidence and subrosion on the eastern shore of the dead sea as revealed by a close range photogrammetric survey abstract ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide the rapid development of such phenomena around the dead sea in the last four decades poses a major geological hazard to the local population agriculture and industry nonetheless many aspects of this hazard are still incompletely described and understood especially on the eastern dead sea shore in this work we present a first low altitude our analysis reveals a kilometer scale sinuous depression bound partly by flexure and partly by non tectonic faults the estimated minimum volume loss of this subsided zone is 1 83 106 m3 with an average subsidence rate of 0 21 m yr 1 over the last 25 years sinkholes in the surveyed area are localized mainly within this depression the sinkholes are commonly elliptically shaped mean eccentricity 1 31 and clustered nearest neighbor ratio 0 69 their morphologies and orientations depend on the type of sediment they form in in mud sinkholes have a low depth to diameter ratio 0 14 and a long axis azimuth of nne ne in alluvium sinkholes have a higher ratio 0 4 and are orientated nnw n from field work we identify actively evolving artesian springs and channelized sediment laden groundwater flows that appear locally in the main depression consequently subrosion i e subsurface mechanical erosion is identified as a key physical process in addition to dissolution behind the subsidence and sinkhole hazard furthermore satellite image analysis links the development of the sinuous depression and sinkhole formation at ghor al haditha to preferential groundwater flow paths along ancient and current wadi riverbeds