on the viscosity of natural hyper saline solutions and its importance the dead sea brines summary the relationship between the density temperature and viscosity of hypersaline solutions both natural and synthetic is explored an empirical equation of the density viscosity relationship as a function of temperature was developed for the dead sea brine and its dilutions the viscosity levels of the dead sea brine density of 1 24 103 kg m3 viscosity of 3 6 mpa s at 20 c and of the more extremely saline natural brine density of 1 37 103 kg m3 were found to be 3 and 10 times greater than that of fresh water respectively the combined effect of the above changes in viscosity and density on the hydraulic conductivity is reduction by a factor of 3 7 the chemical composition significantly affects the viscosity of brines with similar densities whereby solutions with a higher mg na ratio have higher viscosity this explains the extremely high viscosity of the dead sea and related mg rich brines in comparison with the much lower values of nacl and kcl brines with similar density possible impacts of the results include reduced settling velocity of grains in hypersaline viscous brines and changing hydraulic dynamics at the freshwater saltwater and the vicinity of sinkholes

geochemical reaction models quantify the composition of transition zones between brine occurrence and unaffected salt rock abstract brine occurrences belong to the most significant risks in salt mining as they can lead to mine flooding and land subsidence especially within highly soluble potash seams which contain some of the economically most interesting types of salt the interactions between brine and salt rock result in cavernous structures surrounded by moisture penetration zones with different mineralogical regions in order to facilitate an early detection of cavernous structures the brine and rock composition along these transition zones was modelled the results show that the potash salt composition or more precisely the ratio between kieserite and sylvite determines the dissolution behaviour and therefore which types of secondary minerals occur according to the volume balance cavitation is only possible close to the centre of a cavernous structure where the solid fluid ratio is low furthermore an open system with frequent brine exchange is required along the transition zone the solid fluid ratio can increase to several tens of kilograms before the water is fully consumed and the unaffected salt rock is reached a comparison with measured data from a natural brine occurrence validates the model results and confirms a correlation between the brine composition and the distance from the centre of a cavernous structure in conclusion the models are suitable to determine the location of the central part of a cavernous structure based on rock and brine samples from the vicinity however in order to simulate the temporal and spatial development of geogenic cavities a coupling of chemistry and hydraulics will be necessary

quantitative assessment of in situ salt karstification using shear wave velocity dead sea abstract the dead sea ds coastal areas have been dramatically affected by sinkhole formation since around 1990 such sinkholes along both israeli and jordanian shores are linked to karst cavities that form through slow salt dissolution a quantitative estimate of such in situ salt karstification would be an important indicator of sinkhole hazard one of the indications of salt karstification is its increased hydraulic conductivity caused by the development of dissolution cavities forming conducting channels within the salt layer we measured the hydraulic conductivity k versus shear wave velocity vs of ds salt in situ for estimating the actual salt karstification in areas of sinkhole development these parameters were measured with the magnetic resonance sounding mrs and multichannel analysis of surface waves masw methods respectively understanding of the field relationships was augmented by similar inter relations obtained in the laboratory on samples of ds salt in situ salt velocities vs vary from 750 m s to over 1650 m s while hydraulic conductivity k in the same zones varies between about 10 4 m s to slightly over 10 8 m s both field and laboratory k and vs values fit the exponential function ln k 0 0045 vs 5 416 with a determination coefficient r2 of 0 88 a classification based on vs and k was generated for salt conditions and the corresponding degrees of sinkhole hazard which was verified in the mineral beach sinkhole development area the mapping of sinkhole sites shows that they form within highly conductive zones with k 5 5 10 5 it is suggested that this methodology with some modification can be used for evaluating the conductive properties of karstified rock and associated sinkhole hazards

late ordovician glacial pavements revisited a reappraisal of the origin of striated surfaces late ordovician glacial pavements revisited

salt dissolution and sinkhole formation along the dead sea shore 1 the formation of sinkholes at the dead sea area reflects subsurface cavities formed by salt dissolution this dissolution is related to the recession of the dead sea the groundwater level and the fresh saline water interface along the shore decline at a similar rate to the rate of the dead sea recession and brines that used to occupy layers below this interface are flushed out by freshwater our finite element modeling shows that dissolution of this salt layer is a plausible mechanism to explain the rapid creation of subsurface holes that collapse and form sinkholes the positive feedback between the rate of flow the rate of chemical reaction and the change in permeability accelerates the dissolution processes and might result in reactive infiltration instability which is manifested in fingers of cavities into which fluid is channeled and salt is dissolved the spacing between the sinkholes and the rate of their creation is controlled by several factors including properties of lineaments faults incoming groundwater flux the salinity of the incoming groundwater the rate of dissolution the effective specific surface area the permeability of the salt and clay layers the permeability porosity relation the dispersivity and the thickness of the layers we show that the creation of sinkholes occurs only under specific conditions these conditions must cause an unstable dissolution front which then causes formation of cavities and eventually sinkholes the simulations which utilized the best estimated parameters of the studied area yield results that are similar to those exhibited in the field

high resolution insar constraints on flood related subsidence and evaporite dissolution along the dead sea shores interplay between hydrology and rheology abstract sinkhole generation and land subsidence are commonly attributed to dissolution of subsurface layers by under saturated groundwater and formation of cavities along the dead sea ds shorelines this process also involves seasonal flash floods that are drained into the subsurface by existing and newly formed sinkholes we quantify the contribution of flash floods to salt dissolution and land subsidence using high resolution interferometric synthetic aperture radar insar subsidence rates during a 3 year period 2012 2015 were calculated from 57 cosmo skymed x band interferograms bracketing major flood events and intra flood periods in 21 sinkhole sites the sites are located within channels and alluvial fans along the western shores of the dead sea israel the observed subsidence reaches maximum rates of 2 5 mm day accumulating in specific sites to 500 mm year in most of the sinkhole sites a gradual increase in the annual subsidence rate is observed during the 3 year study period three different modes of response to floods were observed 1 sites where floodwater is not directly channeled into sinkholes do not respond to floods 2 sites adjacent to active channels with sinkholes are unaffected by specific floods but their subsidence rates increase gradually from early winter to mid summer and decay gradually until the following winter and 3 sites in active channels with sinkholes are characterized by an abrupt increase in subsidence rates immediately after each flood by a factor of up to 20 and by a subsequent quasi exponential subsidence decay over periods of several months in these latter sites subsidence rates after each flood are temporally correlated with alternating groundwater levels in adjacent boreholes the rapid rise in groundwater head following floods increases the hydraulic gradient of the under saturated groundwater and hence also the groundwater discharge and the dissolution rate of the subsurface salt layer a subsequent quasi exponential water level drop results in similar deceleration in dissolution and subsidence rates with a similar characteristic decay time of about 150 days the observed subsidence decay pattern may also be explained by viscoelastic relaxation of the overburden in response to instantaneously formed dissolution cavities utilizing a kelvin viscoelastic model we show that the contribution of this process is most probably

the role of fluid pressure and diagenetic cements for porosity preservation in triassic fluvial reservoirs of the central graben north sea anomalously high porosities and permeabilities are commonly found in the fluvial channel sandstone facies of the triassic skagerrak formation in the central north sea at burial depths greater than 3200 m 10 499 ft from which hydrocarbons are currently being produced the aim of our study was to improve understanding of sandstone diagenesis in the skagerrak formation to help predict whether the facies with high porosity may be found at even greater depths the skagerrak sandstones comprise fine to medium grained arkosic to lithic arkosic arenites we have used scanning electron microscopy petrographic analysis pressure history modeling and core analysis to assess the timing of growth and origin of mineral cements with generation and the impact of high fluid pressure on reservoir quality our interpretation is that the anomalously high porosities in the skagerrak sandstones were maintained by a history of overpressure generation and maintenance from the late triassic onward in combination with early microquartz cementation and subsequent precipitation of robust chlorite grain coats increasing salinity of pore fluids during burial diagenesis led to pore filling halite cements in sustained phreatic conditions the halite pore filling cements removed most of the remaining porosity and limited the precipitation of other diagenetic phases fluid flow associated with the migration of hydrocarbons during the neogene is inferred to have dissolved the halite locally dissolution of halite cements in the channel sands has given rise to megapores and porosities of as much as 35 at current production depths

an experimental and numerical study of evaporite mineral dissolution and density driven flow in porous media abstract subsurface mineral dissolution problems exhibit complex behaviors which are difficult to model and validate numerically controlled physically validated experimental problems can be used to better understand mineral dissolution and subsequent numerical representation bridging the gap between numerical models and field observations the objective of this work was to collect the first controlled physical measurements in a porous aquifer overlying an evaporite mineral and to create a numerical model of the system the problem studied was modified from the classic hydrocoin level 1 case 5 problem three flow gradients in a porous aquifer were investigated in duplicate in a 2 d box problem the duplicate measurements had high variability shown by numerical modeling to be a result of initial conditions variable flux representing dissolution sharp gradients and variable dispersivity the physical measurements of parameters and fields were important for calibration success the numerical models including sensitivity analyses were capable of simulating flow patterns observed concentrations and peaks resulting from observed initial conditions the numerical models were a key tool in understanding factors influencing the flow and spread of salt within the system the models were limited by the ability to detail physical observations difficult in both the laboratory and for potential field applications the results provided insight in the hydrocoin level 1 case 5 numerical simulations with flow appearing to be swept forward however observed concentrations were lower than commonly modeled

measurement and analysis of dissolution patterns in rock fractures 1 nuclear magnetic resonance imaging nmri is applied to noninvasively measure flow and dissolution patterns in natural rough walled water saturated halite fractures three dimensional images of water density and flow velocity acquired with nmri allow quantification of the developing fracture morphology and flow patterns the flow patterns are correlated strongly to the local apertures and the large scale wall roughness the correlations of the dissolution patterns to the fracture morphology flow patterns and mineralogical composition of the rock matrix are a function of the overall dimensionless damkohler number at high damkohler numbers the dissolution patterns are dominated by the flow structure in addition at high damkohler numbers buoyancy stratified flow becomes important in such cases the dissolution patterns also depend on the orientation and elevation of the fracture walls resulting in preferential upward dissolution at low damkohler numbers the dissolution patterns depend mainly on the mineralogical composition of the rock matrix these findings suggest that coupled flow and dissolution processes are much more complex and unpredictable than commonly assumed even under simplified conditions

velocity resistivity versus porosity permeability inter relations in dead sea salt samples abstract this study is intended to investigate dead sea ds salt porosity permeability hydraulic conductivity inter relations as well as their relationship to geophysical parameters such as compression and shear wave velocities vp vs respectively and specific resistivity x in laboratory and field conditions to estimate representative properties affected by porosity changes during sinkhole development some 41 salt samples were subjected to porosity measurements and 25 samples were tested to reveal hydraulic conductivity the salt of the coastal dead sea area composed of halite is revealed in 10 200 10 800 year old layers the halite commonly appears as rock salt the 7 30 m thick salt unit is located below the groundwater table at depths of 20 50 m from the surface salt layers are very conductive hydraulically and water saturated with the ds brine is of very high salinity with total dissolved solids tds of 340 380 g l two types of salt have been studied crystalline transparent salt cts distributed along the entire ds s western shore and white massive salt wms found locally along the southern ds and along the dike salt porosity measured in samples varies in the range of 5 21 whereas hydraulic conductivity varies between 10 5 to 10 9 m s density is changed in the range of 1681 2116 kg m 3 in wet samples and between 1638 and 2106 kg m 3 in dry samples during the laboratory testing of ds salt samples we have measured the following geophysical parameters vp 3700 4460 m s vs 1900 2620 m s and x 2 100 m on the other hand our previous field studies based on s wave seismic refraction surface wave prospecting swp and transient electromagnetic tem methods have shown that in in situ salt velocities vp range between 2900 and 4240 m s vs varies between limits of 750 m s to more than 1650 m s and x is of 0 8 to 2 5 m these values are considerably less than the analogous parameters measured in the salt samples the same conclusion has been made from the comparison of salt sample properties and borehole logging both studied by ultrasonic method geophysical data testify that in situ porosity calculated using relationships obtained during this study exceeds those in the laboratory samples especially in zones of heightened voidness where it is 25 hydraulic conductivities in the same zones exceed a value of 10 6 m s and even 10 5 m s we expect that in larger salt volumes these parameters can yet increase

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

scale free distribution of dead sea sinkholes observations and modeling there are currently more than 5500 sinkholes along the dead sea in israel these were formed due to the dissolution of subsurface salt layers as a result of the replacement of hypersaline groundwater by fresh brackish groundwater this process has been associated with a sharp decline in the dead sea water level currently more than one meter per year resulting in a lower water table that has allowed the intrusion of fresher brackish water we studied the distribution of the sinkhole sizes and found that it is scale free with a power law exponent close to 2 we constructed a stochastic cellular automata model to understand the observed scale free behavior and the growth of the sinkhole area in time the model consists of a lower salt layer and an upper soil layer in which cavities that develop in the lower layer lead to collapses in the upper layer the model reproduces the observed power law distribution without involving the threshold behavior commonly associated with criticality

the origins of glacially related soft sediment deformation structures in upper ordovician glaciogenic rocks implication for ice sheet dynamics in the upper ordovician glaciogenic rocks of west gondwana many soft sediment deformation structures are attributed to glaciotectonic processes however little is known about the subglacial and ice marginal processes associated with this ice sheet a systematic description and interpretation of these soft sediment deformation structures is supplemented by a comparison with late quaternary and modern glacial settings to provide qualitative constraints on the character of ancient subglacial thermal regimes soft sediment striations were formed by discontinuous shear induced deformation beneath an ice sheet that oscillated between warm and cold based thermal regimes beneath warm based ice coupling across the ice bed interface was poor with sliding and loading occurring at this surface loading of soft waterlogged sediments allowed the development of fluted surfaces which are also associated with the formation of truncated folded zones during times of cold thermal regimes coupling across the ice bed interface was enhanced by freezing which caused changes in the position of the freezing front these discontinuous changes coupled with sustained subglacial shearing resulted in the development of stacked soft sediment striated surfaces in areas where the subglacial substrate had an irregular topography complex shear zones formed that comprised stacked duplex systems interlayered with highly strained units preserving pervasive folded lineations at the ice front large glaciotectonic deformation structures comparable with push moraines developed during sustained periods of re advance that created composite thrust and fold systems deformation was transmitted for up to 1 km from the ice front and reduced in intensity with distance other deformation structures include dome like folds that consist of central anticlines 30 to 70 m in width with tight rim synclines that formed by the load induced diapiric intrusion of muds an ice sheet surging mechanism is inferred for the development of composite thrust and fold systems and the coeval sediment diapirs these surges potentially caused the widespread reorganisation of a glacial load resulting in the pro to subglacial extrusion of soft sediments

self accelerated development of salt karst during flash floods along the dead sea coast israel we document and analyze the rapid development of a real time karst system within the subsurface salt layers of the ze elim fan dead sea israel by a multidisciplinary study that combines interferometric synthetic aperture radar and light detection and ranging measurements sinkhole mapping time lapse camera monitoring groundwater level measurements and chemical and isotopic analyses of surface runoff and groundwater the 1 m yr drop of dead sea water level and the subsequent change in the adjacent groundwater system since the 1960s resulted in flushing of the coastal aquifer by fresh groundwater subsurface salt dissolution gradual land subsidence and formation of sinkholes since 2010 this process accelerated dramatically as flash floods at the ze elim fan were drained by newly formed sinkholes during and immediately after these flood events the dissolution rates of the subsurface salt layer increased dramatically the overlying ground surface subsided a large number of sinkholes developed over short time periods hours to days and salt saturated water resurged downstream groundwater flow velocities increased by more than 2 orders of magnitudes compared to previously measured velocities along the dead sea the process is self accelerating as salt dissolution enhances subsidence and sinkhole formation which in turn increase the ponding areas of flood water and generate additional draining conduits to the subsurface the rapid terrain response is predominantly due to the highly soluble salt it is enhanced by the shallow depth of the salt layer the low competence of the newly exposed unconsolidated overburden and the moderate topographic gradients of the ze elim fan

in situ gas permeability measurements to delineate damage in rock salt in situ gas permeability measurements can be used to distinguish regions within rock salt formations which have experienced disturbance or damage high resolution hydrologic testing reveals rock salt well removed from an excavation i e undisturbed is a low permeability low porosity porous medium with a significant pore brine pressure in this region rock salt is effectively impermeable to gas due to threshold capillary pressures which preclude gas from displacing the resident brine in a region confined to a depth of less than about one effective radius of an excavation rock salt is typically permeable to gas the measured gas permeabilities are consistent with a partially saturated dilated zone developing adjacent to the excavation the extent and nature of the damaged region interpreted from gas permeability measurements is consistent with other measurements and analyses thus gas permeability measurements serve as effective means for detecting and delineating the damaged region

natural versus human control on subsurface salt dissolution and development of thousands of sinkholes along the dead sea coast one of the most hazardous results of the human induced dead sea ds shrinkage is the formation of more than 6000 sinkholes over the last 25 years the ds shrinkage caused eastward retreat of underground brine replaced by fresh groundwater which in turn dissolved a subsurface salt layer to generate cavities and collapse sinkholes the areal growth rate of sinkhole clusters is considered the most pertinent proxy for sinkholes development analysis of light detection and ranging lidar digital elevation models dems and interferometric synthetic aperture radar insar allows translation of the areal growth rate to a salt dissolution rate of the salt layer revealing two peaks in the history of the salt dissolution rate these peaks cannot be attributed to the decline of the ds level instead we show that they are related to long term variations of precipitation in the groundwater source region the judea mountains and the delayed response of the aquifer system between the mountains and the ds rift this response is documented by groundwater levels and salinity variations we thus conclude that while the ds level decline is the major trigger for sinkholes formation the rainfall variations more than 30 km to the west dominate their evolution rate the influence of increasing rainfall in the judea mountains reaches the ds at a typical time lag of four years and the resulting increase in the salt dissolution rate lags by a total time of 5 6 years

numerical simulation of rock salt dissolution in dynamic water the dissolution process of the rock salt is actually a complicated process in fluid dynamics and chemical kinetics therefore the mathematical model for the solute fluid flow during the cavern building may be established to research the change rule of the form of the cavern boundary based on the kinetic analysis of the convection diffusion process with integration of the basic theories of fluid mechanics and the principles of chemical kinetics in order to research the dissolution mechanism of the rock salt under the condition of dynamic water the method of numerical simulation has been employed to simulate and study the factors with effect on the fluid transport mechanism in solution mining cavern of the rock salt and its dissolution in dynamic water has been simulated and researched the result shows that the model established in this paper may well describe the dissolution process of rock salt under the condition of dynamic water providing basic analyzing means for the research on the rock salt dissolution in dynamic water

is river avulsion style controlled by floodplain morphodynamics river relocation or avulsion is a fundamental process that fills alluvial basins however it is difficult to predict avulsion patterns because the landscape conditions associated with different avulsion styles are currently unknown two end member avulsion styles have been documented in modern rivers progradational avulsions during which significant floodplain deposition occurs as a new channel is built and incisional avulsions during which floodplain erosion captures flow from a parent channel here we propose that avulsion style is related to the tendency for overbank flows to erode or deposit sediment i e floodplain morphodynamics we present a scaling comparison of floodplain erosion and deposition rates test it with morphodynamic modeling and show field data from ancient deposits that are consistent with modeling results these results demonstrate that floodplain morphodynamics may determine how rivers relocate and that assessing the relative influence of floodplain erosion and deposition may be useful for predicting sedimentation patterns in avulsive systems

dynamic dissolution of halite rock during flow of diluted saline solutions 1 the dynamic dissolution pattern of halite salt rocks taken from coreholes near the dead sea was studied in laboratory scale experiments when unsaturated solution with respect to halite flowed through salt cores dissolution developed along preferential flow pathways in a channel structure the channel structure was related to the salt s properties and internal heterogeneities flow velocity and impact of gravity preferential dissolution pathways developed in areas of minimum resistance to flow such as large pore networks and cracks nevertheless in many cases no structural heterogeneity was observed along the dissolution channels prior to the experiments the initial formation of channels took place above a critical flow velocity below this threshold dissolution developed as a slowly propagating front in these cases salt re precipitation resulted in clogging and cessation of flow through a few of the salt cores solution density was found to be important as evidenced by the fact that more channels developed upward than downward due to gravitational fractionation the development of dissolution channels could have very important implications for the overall permeability of the salt layer in general and the use of salt formations for industrial waste storage and the development of sinkholes along the dead sea shore in particular