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

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

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

chemical and magnetic tracing of coal slag pollutants in karstic river sediments the mre nica river near duga resa croatia serves as an ideal natural laboratory for studying downstream transport of material in river systems this study expands the so far brief knowledge about magnetic and chemical properties of sediments along the lower course of this river contaminated by discharge of coal slag and ash from a former textile factory directly released into the river for 110 years 1884 1994 magnetic susceptibility of the river sediments is very high close to the pollution source and shows a decreasing trend downstream still being above the level of unpolluted sediments just before the confluence with the korana river app 7 km away from the point source thermomagnetic curves reveal magnetite as the dominant magnetic mineral and low frequency dependent susceptibility indicates an anthropogenic origin most heavy metals and other elements in the sediments show a decreasing trend in the downstream direction similar to the magnetic concentration signal correlation analysis between magnetic susceptibility and concentrations of 29 elements shows strongest correlations with co r 0 70 fe r 0 92 sr r 0 86 al r 0 74 u r 0 78 and b r 0 96 cluster analysis distinguishes three clusters cluster 1 is under strong influence of contamination and contains four sampling sites cluster 2 has extreme values of cd cr mo and ni and contains seventeen sites cluster 3 reflects rather clean sites and contains nine sites according to existing sediment quality criteria ni and cr show the largest degree of contamination among six evaluated heavy metals strong variability in the data and frequent extremes are to a large degree caused by heterogeneity in the spatial distribution of the coal derived material to account for this situation and to resolve the variability in more detail statistical sampling of sediments in river cross sections and estimation of the sediment volume are needed being a target for further research

sinkhole swarms from initiation to stabilisation based on in situ high resolution 3 d observations abstract we study in this paper the evolution of sinkhole fields along the dead sea coastal plains from initiation to stabilisation the prevailing hypothesis attributes their formation to the dissolution of a buried halite layer by groundwater but fails to explain their evolution in some places and their stability in others based on thirteen years of high resolution laser scanning and field surveys we trace a complete evolutionary cycle of sinkholes and show that the prevailing theory explains only the first out of a four stage cycle we show that following the formation stage an acceleration phase begins when the sinkholes interact with the drainage system a deepening and spatial localisation phase ensues then some parts of the field cease to expand leading to a fourth stage of stabilisation we further show that during their embryonic stage sinkhole development is limited due to a lack of connectivity between the surface and subsurface hydrological processes but as this connectivity evolves the development rate increases up to three orders of magnitude moreover observations show a high correlation with hydrological seasonality the most active field demonstrated a development rate of 13 540 m 3 month during the wet season in contrast to a rate of 1010 m 3 month during the dry season these measurements and observations allow us to propose a new theoretical model for sinkhole swarm development from initiation to stabilisation with linkage to seasonality and hydrology

geomagnetic and mineral magnetic characterization of the anthropocene geomagnetic and mineral magnetic data provide geological indices that are both independent of human impact i e geomagnetic and respond to human induced environmental impact i e mineral magnetic we provide the first discussion of such magnetic events for help in defining the anthropocene within the holocene a potential geomagnetic marker for the anthropocene is the low dipole latitude at c 2700 cal a bp which is associated with distinct palaeosecular variation features in northerly mid to high latitude sites mineral magnetic records from lake and marine sediments identify major deforestation and soil delivery events from catchment systems in many parts of the world during the last 4000 years in europe clusters of these events occur around both 2600 cal a bp and ad 1100 the former coinciding with a low in geomagnetic field dipole latitude and peak intensity mineral magnetic records in peats and lake sediments can reflect particulate pollution from fossil fuel burning the expansion of major coal burning began c ad 1800 in western europe and eastern north america but around ad 1900 this expanded due to more widely distributed coal use and this event is the most clear mineral magnetic marker for the base of the anthropocene

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

a comprehensive approach to karst identification and groutability evaluation a case study of the dehou reservoir sw china abstract yunnan province in sw china has one of the most developed karst terrains in china and has been historically affected by sinkholes and other instability phenomena caused by unpredictable cavity formation and well developed underground hydraulic conduits during construction of a karst seepage control reservoir project grouting of a 4 6 km long anti seepage curtain in yunnan province some typical detection methods electromagnetic and water injection tests failed to map the complex geo structural karst zones clearly resulting in considerable grout loss and excessive leakage during the grouting phase of this project to deal with this limitation a comprehensive approach including a new drilling process monitoring system borehole electrical resistivity tomography borehole sonic logging and water injection tests is employed to identify the general characterization geometry and spatial distribution of karst zones along the anti seepage curtain additionally a deep belief network dbn model replaced the empirical relationships typically used to predict the grouting quantity for groutability evaluation in karstified areas the dbn algorithm is trained by data collected using this comprehensive approach rate of penetration rock permeability resistivity and p wave velocities and two previous grouting quantities as input data the lessons learned in this case study permit us to define an effective comprehensive approach for delineating the general characterization of karst zones between two boreholes and locations of potential conduits for grout flow through the borehole the proposed dbn model can predict the grouting quantity for karst regions and the accuracy of prediction is greatly affected by previous grouting quantity rather than the collected parameters

geophysical evidence of deep hydrocarbon flow in mottled zone areas dead sea transform zone the origin of unusual magnetic initially sedimentary rocks of the mottled zone mz in israel and jordan remained enigmatic for several decades until integrated characterization of the mz area was achieved by ground magnetic measurements and geologic observations along representative profiles in parallel with reprocessing and reinterpretation of available aeromagnetic and gravity data micromagnetic profiling was combined with gamma radioactivity measurements and representative samples were selected to determine rock physical properties results of field measurements reduction and transformation of geophysical fields anomaly inversion and forward modeling accompanied by geologic analysis suggest that two types of magnetic anomalies and local gravity minima in the mz areas are related to the same event i e deep hydrocarbon flow associated with fossil mud volcanism physicochemical interaction of deep hydrocarbon flow and surrounding sedimentary rocks caused widespread weak magnetization and correspo

association between magnetic susceptibilities and hydrocarbon deposits in the barinas apure basin venezuela we have measured the magnetic susceptibility of 5425 drill cuttings coming from 20 oil wells distributed in eight fields of the petroliferous barinas apure basin barinas venezuela seeking evidence of magnetic anomalies associated with the presence of hydrocarbon deposits the rock samples are located between the near earth s surface and the basement s top approximately 4000 m in the magnetic susceptibility profiles we observed high magnetic susceptibilities at the top of the sedimentary units corresponding to reservoir and source rocks of oil producing wells whereas in the case of nonproducing wells we observed low magnetic susceptibilities a basic statistical analysis of the magnetic susceptibility measurements shows a significant difference between the mean values across producing and nonproducing wells at the correspondent oilrelated formations with a ratio of 4 1 of producing to nonproducing wells in the producing wells we have found a relation between the magnitudes of the magnetic susceptibility and the age of the formation the larger the magnetic susceptibility the younger the geological stratum the age and depth of the formations where the cuts were obtained exclude the presence of cultural human origin contamination of the samples suggesting the evidence of authigenic origin of the magnetic minerals due to the reductive effect of hydrocarbons in rocks

gis based assessment of risk due to salt mining activities at tuzla bosnia and herzegovina ground subsidence triggered by salt mining from deposits located beneath the city of tuzla bosnia and herzegovina is one of the major dangers acting on a very densely urbanized area since 1950 when the salt deposit exploitation by means of boreholes began as demonstrated in this paper subsidence induced several hazard factors such as severe ground deformations the arising of deep and superficial fractures and a very fast water table rise connected with the brine extraction now affecting several districts the above mentioned factors have been quantified by the use of geomatic methodologies including field surveys and analysis of geographical data in order to estimate the historical sinking rates authors processed the large and never before processed amount of topographical data collected during two periods from 1956 to 1991 and from 1992 to 2003 with only poor data collected afterward traditional surveys were completely and definitively stopped the analysis reveals a cumulative subsidence as high as 12 m during the whole period causing damage to buildings and infrastructures within an area that includes a large portion of the historical town at present almost entirely destroyed modern sinking rates have been monitored with static gps whereas the presence of superficial fractures monitored with kinematic gps factors related to the presence of deep fractures and water table rise have been evaluated by curvature analysis techniques and piezometric data respectively finally hazard factors have been combined in a risk map using the gis geographical information system map algebra capabilities and a simple multicriteria decision analysis mda in order to do that a vulnerability map has been derived on the basis of information reported on a couple of recently sensed high resolution satellite imageries the final risk arisen from the combination of single hazard factors and vulnerability map highlights critical scenarios and unsuspected threatening that are under consideration by the local decision makers and urban planners in particular as highlighted in the final risk map the present day water table rise triggered by the decrease in brine pumping is seriously posing a threat to a portion of the city which is not the most involved in ground deformations

utilising seasonal variations in hydrogeochemistry and excitation emission fluorescence to develop a conceptual groundwater flow model with implications for subsidence hazards an example from co durham uk groundwaters were sampled from four research boreholes a private supply well and a natural karst resurgence in southern county durham england time series data sets of piezometric levels groundwater major ions and fluorescence of dissolved organic matter dom were interpreted in the light of new geological mapping to assess the movement of groundwater and its potential for the dissolution of gypsum three distinct groundwater facies were identified representing contact with gypsiferous strata dolomitic limestone and quaternary till piezometric data indicated time varying transverse flow across the gypsifeorus strata which was confirmed from gradational mixing of groundwater types and cation ratios fluorescence of dissolved dom identified variations in protein and fulvic like acid fluorescence the former was taken to represent surface derived short lived material spatial and temporal variations in protein fluorescence offered a means to trace groundwater movement along the regional groundwater gradient and indicated rapid lateral movement of groundwater it was concluded that gypsum dissolution is occurring beneath the town of darlington however the presence of a thick deposit of quaternary till effectively confines the small head differences of approximately 1 m across the gypsum strata beneath the town further to the south the lowering of the ground surface results in a greater upwards flow of water across the gypsum and is used to explain the presence of historic collapse sinkholes

mineral magnetic characterization of anthropogenic magnetic phases in the danube river sediments bulgarian part abstract magnetic methods have been widely used for delineation of environmental pollution of soils and sediments under certain conditions during the last decade a number of structure sensitive magnetic characteristics coercive force coercivity of remanence remanent magnetization were utilized for deduction of the grain size of the anthropogenic particulate matter which serves as a proxy for the evaluation of the distance from the pollution source possible health effects etc however up to now there is no detailed study on the influence of the morphology internal structure and phase composition of anthropogenic particles on the corresponding magnetic characteristics the aim of the present investigation is to obtain detailed microscopic magnetic and microchemical data on single grains from polluted river sediments and thus to check the validity of the classical grain size dependent trends of coercivity and remanence parameters obtained for natural and synthetic magnetites for the anthropogenic magnetic phases single anthropogenic particles from magnetic extracts have been separated from several sites along the bulgarian part of the danube river which show the strongest magnetic enhancement results from the combined magnetic thermomagnetic analysis and magnetic hysteresis microscopic optical and scanning electron microscopy sem and microchemical electron microprobe analysis empa study on single anthropogenic particles show that there is a general trend for significant underestimation of the physical size of the anthropogenic particles due to the following reasons 1 in most cases the spherules possess a complex internal structure in which the magnetic phase is presented as dendrites exsolved within a glassy non magnetic aluminosilicate matrix 2 the surface morphology is characterized by orange peel or dendritic structures or smaller strongly magnetic spherules are adhered to the surface magnetic mineralogy as deduced from single grain thermomagnetic k t analysis and further elucidated by microprobe data on the same particles shows that magnetite is the main ferromagnetic phase in isolated cases significant al substitution leads to a decrease of t c down to 500 c hysteresis parameters for all studied single grains of physical sizes varying from 39 m up to 1 5 mm fall mainly in the pseudo single domain psd range on the basis of the results from single grain magnetic measurements a new approach for semiquantitative estimation of the degree of anthropogenic pollution is proposed

glacial interglacial climatic variations at the schirmacher oasis east antarctica the first report from environmental magnetism article i nfo we discuss in this paper the first detailed environmental magnetic record of glacial interglacial climatic varia tions in the schirmacher oasis east antarctica we determined environmental magnetic properties and inter parametric ratios lf fd arm s irm arm sirm arm lf arm fd s irm lf s ratio and hirm for sediment samples of a core from the sandy lake accelerator mass spectrometer ams 14 c dates were obtained on the organic matter from bulk sediment samples the sediment core spans the past 42 5 cal ka b p the magnetic minerals are mainly detrital and catchment derived as there is no evidence for the presence of authigenic greigite bacterialmagnetite ordiageneticdissolution the lastglacialperiodischaracterizedbya high concentra tion of ferrimagnetic minerals such as titanomagnetite high values of lf sirm etc and coarse magnetic grain size low arm sirm and arm lf values and high s ratio values deglaciation in the schirmacher oasis began around 21 cal kab p as suggested by the low magnetic mineral concentration the holocene period ischaracter ized by relatively warm climatic events as seen in the low values of magnetic susceptibility which is primarily contributed by fine grained titanomagnetite resulting from pedogenesis high fd v alues several of the rela

environmental magnetism as a dating proxy for recent overbank sediments of peri industrial regions in the czech republic and uk abstract twenty five floodplain sediment profiles from seven rivers in eastern czech republic and three in north west england were collected to examine the hypothesis that magnetic enhancement in recent sediments is predominantly of anthropogenic origin and that magnetic parameters can be used as a dating proxy reflecting changes in intensity of industry sources over time natural sources of magnetic enhancement were excluded and anthropogenic enhancement was identified as exhibiting elevated values of lf arm sirm sirm and s ratios with low values of fd magnetic spherules typically formed through fossil fuel combustion processes were observed by scanning electron microscopy sem in these sediments to assess the potential of magnetic parameters as a chronometer the approach was compared with frequently used dating techniques concentrations of heavy metals and 137 cs the floodplain profiles were divided to three groups according to the characteristics of their trends with depth in magnetic parameters lf in particular and the suitability of magnetic properties as a dating proxy group 1 which included the majority of the profiles exhibited magnetic enhancement in the upper part of its profiles and a single maximum in lf this group exhibited a clear suitability for our proposed magnetic dating as the magnetic record reflected the industrial history of the region and was aligned with the chronologies of the other dating techniques profiles magnetically enhanced throughout their depth and lacking any clear trend comprised group 2 here a mineral magnetic approach to dating was limited as the magnetic signal was diluted by a high sedimentation rate or impacted by local anthropogenic factors all profiles from england were included in group 3 because their magnetic depth profiles were influenced by natural sources of magnetic particles or specific sedimentary conditions and a longer industrial history and thus needed an individual interpretation however they still reflected the regional deposition history of industrial sources of ferrimagnetic particles overall magnetic parameters proved to be an efficient dating proxy with potential for recently aggrading rivers

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

authigenic or detrital origin of pyrrhotite in sediments resolving a paleomagnetic conundrum monoclinic pyrrhotite fe7s8 is widely claimed to carry magnetizations acquired during early diagenesis in anoxic sedimentary environments in contrast geochemical literature indicates that pyrrhotite formation is extremely slow below 180 c which makes it a highly unlikely carrier of early diagenetic remanences in sediments this view is confirmed by the occurrence of late diagenetic fe7s8 in ancient sediments and the general lack of fe7s8 in modern sediments horng et al c s horng m torii k s shea s j kao inconsistent magnetic polarities between greigite and pyrrhotite magnetite bearing marine sediments from the tsailiao chi section southwestern taiwan earth planet sci lett 164 1998 467 481 documented the presence of fe7s8 that carries a magnetic signal indistinguishable from that of detrital magnetite in pleistocene marine sediments from taiwan we tested the possibility that the fe7s8 could have a detrital origin by conducting a source to sink study and found fe7s8 in metamorphic rocks of the taiwan central range and in material eroded from these rocks in the transportation pathway and in the depositional sink this confirms that the fe7s8 has a detrital origin rapid transportation from source to sink e g by typhoon associated flood events probably assists preservation of the fe7s8 which might otherwise oxidize during transportation the widespread occurrence of exhumed metamorphic rocks in orogenic belts around the world makes them a likely source of fe7s8 in marginal sedimentary basins detrital fe7s8 should therefore be more routinely considered to be responsible for paleomagnetic records when it is present in sediments with partial metamorphic provenance

magnetic particle characterization in the seine river system implications for the determination of natural versus anthropogenic input 1 this study presents an innovative application of well established environmental magnetic proxy parameters on fluvial sediments with the aim to trace geological and human induced processes in the complex seine river drainage system in northern france we seek to identify environmental fingerprints of mechanical and chemical weathering processes the regional distribution of the suspended material and changes in the balance of natural input versus anthropogenic pollution in order to reach these goals we applied a combination of rock magnetic and advanced scanning electron microscopic techniques on a large number of sediment trap samples generally we observe an increase in magnetic concentration coupled with a coarsening in magnetic grain size downstream of the seine river system furthermore the dominant magnetomineralogy changes from high coercivity minerals upstream in more rural areas to magnetite dominated assemblages downstream each river segment shows its specific trend line depending on regional initial input weathering conditions drainage area and potential pollution sources one major outcome of this study is the observed significant correlation between anthropogenic antimony rich iron oxide particles and the magnetic concentration this shows the potential of magnetic remanence measurements as proxy parameters for specific heavy metal pollution concentrations hence the environmental magnetic study presented herein serves to identify major trends as well as local particularities and leads to quantitative analyses of the contributions of individual tributaries in the seine river system

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

benson rc yuhr lb site characterization in karst and pseudokarst terraines practical strategies and technology for practicing engineers hydrogeologists and geologists

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

correlating biodegradation to magnetization in oil bearing sedimentary rocks abstract a relationship between hydrocarbons and their magnetic signatures has previously been alluded to but this is the first study to combine extensive geochemical and magnetic data of hydrocarbon associated samples we report a detailed study that identifies a connection between magnetic mineralogy and oil biodegradation within oil bearing sedimentary units from colombia canada indonesia and the uk geochemical data reveal that all the oil samples are derived from mature type ii kerogens deposited in oxygen poor environments biodegradation is evident to some extent in all samples and leads to a decrease in oil quality through the bacterially mediated conversion of aliphatic hydrocarbons to polar constituents the percentage of oil components and the biodegradation state of the samples were compared to the magnetic susceptibility and magnetic mineralogy a distinct decrease in magnetic susceptibility is correlated to decreasing oil quality and the amount of extractable organic matter present further magnetic characterization revealed that the high quality oils are dominated by pseudo single domain grains of magnetite and the lower quality oils by larger pseudo single domain to multidomain grains of magnetite and hematite hence with decreasing oil quality there is a progressive dominance of multidomain magnetite as well as the appearance of hematite it is concluded that biodegradation is a dual process firstly aliphatic hydrocarbons are removed thereby reducing oil quality and secondly magnetic signatures are both created and destroyed this complex relationship may explain why controversy has plagued previous attempts to resolve the connection between magnetics and hydrocarbon deposits these findings reinforce the importance of bacteria within petroleum systems as well as providing a platform for the use of magnetization as a possible exploration tool to identify subsurface reservoirs and a novel proxy of hydrocarbon migration

mapping hydrocarbon charge points in the wessex basin using seismic geochemistry and mineral magnetics abstract this study reports a multidisciplinary approach to determining hydrocarbon charge points and migration in the wessex basin southern england geochemical analysis of reservoir core material bridport sandstone and inferior oolite using gas chromatography mass spectrometry gc ms suggests that the oil in the wessex basin is from a single source and that small variations in environmentally sensitive biomarkers are likely due to small differences in maturity or depositional conditions during the formation of the oil over millions of years using seismic data basin modelling revealed two potential hydrocarbon migration pathways from the hanging wall of the purbeck fault into the sherwood sandstone reservoir at wytch farm one of these potential pathways is represented by cores termed creech and the other bushey farm to try to distinguish between the two potential pathways cores were studied using mineral magnetic techniques the magnetic signature was characterised using low temperature

origin of the salt valleys in the canyonlands section of the colorado plateau evaporite dissolution collapse versus tectonic subsidence abstract the salt valleys over the axis of the salt cored anticlines in the paradox fold and fault belt canyonlands utah and colorado are created by subsidence of the anticline crests traditionally the collapse of the anticlinal crests was attributed to dissolution of the salt walls diapirs forming the anticline cores recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions this paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation the development of contractional structures in salt dissolution experiments led the advocates of the tectonic interpretation to reject the dissolution induced subsidence explanation however these salt dissolution models do not reproduce the karstification of salt walls in a realistic way since their analog involves removal of salt from the base of the diapirs during the experiments additionally numerous field examples and laboratory models conducted by other authors indicate that brittle subsidence in karst settings is commonly controlled by subvertical gravity faults field evidence against the regional extension model includes 1 a thick cap rock at the top of the salt walls 2 the concentration of subsidence deformation structures along the crest of the anticlines salt walls 3 deformational structures not consistent with the proposed nne extension like crestal synforms and ne sw grabens 4 dissolution induced subsidence structures controlled by ring faulting revealing deep seated dissolution 5 large blocks foundered several hundred meters into the salt wall 6 evidence of recent and active dissolution subsidence and 7 the aseismic nature of the recently active collapse faults although underground salt dissolution seems to be the main cause for the generation of the salt valleys this phenomenon may have been favored by regional extension tectonics that enhance the circulation of groundwater and salt dissolution

geomorphology and geochronology of sackung features uphill facing scarps in the central spanish pyrenees abstract the paper analyses uphill facing scarps and associated troughs developed in the oversteepened slopes of two neighbouring glacial valleys in the central spanish pyrenees previous studies of sackung landforms in the pyrenees have argued for deglacial unloading as the genetic mechanism but this causal and temporal relationship has not been proved due to the lack of chronological data the antislope scarps in the two studied locations vallibierna and estos are developed in palaeozoic metasedimentary rocks parallel to the contour lines and the structural grain occur in the intermediate sector of the hillslope and are up to 0 5 km long and several meters high a trench was excavated in a sackung trough fill in each of the valleys in order to gain information about their chronology and genesis charcoal from the lowermost unit in vallibierna provided an age of 5 9 cal ka for the sackung and extrapolation of the three dates obtained in estos indicates that the trough formed ca 7 6 7 8 cal ka deglaciation of the studied sectors of the valleys occurred between 16 and 13 ka the time lag of 5 ka suggests that glacial erosion and the subsequent debutressing of the oversteepened valley walls created slopes predisposed to sackung development but did not initiate the movement seismic shaking is proposed as a probable triggering factor this hypothesis although supported by the sudden deformation event recorded by a failure plane exposed in vallibierna trench and by the seismic and neotectonic activity of the area cannot be proved due to the lack of chronological information about paleoearthquakes

natural and human induced dissolution and subsidence processes in the salt outcrop of the cardona diapir ne spain the cardona diapir in ne spain with a salt outcrop about 0 9 km2 in area has a well developed endokarstic system that used to discharge into the cardener river underground mining for potassium salt carried out from 1930 to 1990 caused significant changes in the topography and hydrology of the diapir the accumulation of two halite slag heaps totalling around 10 million tons locally dammed the surface drainage creating closed depressions and preferential zones of water recharge the waters that infiltrated in one of these depressions largely derived from uncontrolled sewage disposal led to the generation of a 335 m long human induced cave excavated in one of the slag heaps moreover the inflow of freshwater from the surrounding sandstone aquifer caused by the excavation of a ventilation gallery resulted in the generation of a 280 m long cave in march 1998 the interception of a phreatic conduit by a halite mine gallery 50 m deep caused dramatic changes in the hydrology and geomorphology of the diapir including a a sudden decline in the piezometric level of the karstic aquifer b the inflow of freshwater and debris from the cardener river into the endokarstic system and the mine galleries a tunnel had to be constructed to divert the river flow from the salt outcrop c massive dissolution of salt creating new cavities and enlarging the pre existing ones including both mine galleries or cave passages the 4 300 m long salt meanders cave was largely generated by the inrush of water from the cardener river into the mine galleries and d the generation of a large number of sinkholes in the vicinity of the cardener river an inventory of 178 sinkholes has allowed us to estimate minimum probability values of 4 7 and 8 sinkholes km2 year for time intervals previous and subsequent to the 1998 mine flood event respectively

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

magnetic fingerprint of the sediment load in a meander bend section of the seine river france abstract this study aims to evaluate the potential of magnetic methods to determine the composition of the sediment load in a cross section of an unmanaged meander in the upstream stretch of the seine river marnay sur seine suspended particulate matter spm was collected based on a regular sampling scheme along a cross section of the river at two different depth levels during a low water stage may 2014 and a high water stage february 2015 riverbed sediments rbs were collected during the low water stage and supplementary samples were taken from the outer and inner banks magnetic properties of the dry bulk spm and sieved rbs and bank sediments were analysed after characterizing the main magnetic carrier as magnetite hysteresis parameters were measured giving access to the grain size and the concentration of these magnetite particles the results combined with sedimentary grain size data were compared to the three dimensional velocity profile of the river flow in the rbs where the magnetic grain size is rather uniform the concentration of magnetite is inversely proportional to the mean grain size of the total sediment indicating that magnetite is strongly associated with the fine sedimentary fraction the same pattern is observed in the samples from the outer and inner banks during the low water stage the uniformly fine spm grain size distribution characterizes the wash load the magnetic fraction is also relatively fine within the pseudo single domain range with concentration similar to that of the fine rbs fraction during the high water stage spm samples correspond to mixtures of wash load and resuspended sediment from the bedload and riverbanks here the grain size distribution is heterogeneous across the section showing coarser particles compared to those in the low water stage and more varying magnetite concentrations while the magnetic grain size is like that of the low water stage the magnetite concentration in the high water spm can be modelled based on a mixing of the magnetite concentrations of the different grain size fractions thus quantifying the impact of resuspension in the cross section

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

magnetic studies and elemental analysis of river sediments a case study from the ponnaiyar river southeastern india the ponnaiyar river is one of the largest rivers of the tamil nadu state india flowing a distance of 430 km from its point of origin to the sea this work contributes with new data of magnetic and elemental composition of river sediments and improves the knowledge obtained by preliminary and previous studies of rivers from southeastern india magnetic susceptibility anhysteretic and isothermal remanent magnetization and chemical determinations major and trace metals were measured magnetic results reveal the predominance of magnetite like mineral with magnetic grain size variations along the river and in depth most of the uppermost samples have the major presence of trace metals and higher values of magnetic concentration magnetic and chemical variables were also analysed as potential pollution indicators using multivariate statistical techniques canonical correlation and fuzzy c means clustering analyses which confirmed the existence of relationships but not in a simple way between magnetic and chemical variables furthermore fuzzy analysis allows classifying the data in different well differentiated groups regarding the trace metal load concentration and feature dependent parameters the most polluted samples show high concentration of trace elements and magnetic carriers softer and coarser magnetic minerals on the contrary the unpolluted samples from the deepest sediments have the opposite characteristics

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

future trends in paleoseismology integrated study of the seismic landscape as a vital tool in seismic hazard analyses this paper forms the introduction to this special issue of tectonophysics devoted to selected scientific research presented during events sponsored by the inqua subcommission on paleoseismicity in the past few years in this note we summarize the contents of the contributed papers and use the issues they raise to review the state of the art in paleoseismology from a quaternary geology perspective in our opinion the evolution of paleoseismological studies in the past decade clearly demonstrates that in order to properly understand the seismic potential of a region and to assess the associated hazards broad based multidisciplinary studies are necessary to take full advantage from the geological evidence of past earthquakes a major challenge in future paleoseismic research is to build detailed empirical relations between various categories of coseismic effects in the natural environment and earthquake magnitude intensity these relations should be compiled in a way that is fully representative of the wide variety of natural environments on earth in terms of climatic settings quaternary tectonic evolution rheological parameters of the seismogenic crust and stress environment for instance available data indicate that between earthquake magnitude and surface faulting parameters different scaling laws exist and they are a function of the local geodynamic setting including style of faulting typical focal depths heat flow in this regard we discuss in some detail the concept of seismic landscape which provides the necessary background for developing paleoseismological research strategies the large amount of paleoseismological data collected in recent years shows that each earthquake source creates a signature on the geology and the geomorphology of an area that is unequivocally related with the order of magnitude of its earthquake potential this signature is defined as the seismic landscape of the area e g serva l vittori e ferreli l michetti a m 1997 geology and seismic hazard in grellet b mohammadioun b hays w eds proceedings of the second france united states workshop on earthquake hazard assessment in intraplate regions central and eastern united states and western europe october 16 1995 nice france 20 24 ouest editions nantes france michetti a m hancock p l 1997 paleoseismology understanding past earthquakes using quaternary geology

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

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

compositional morphological and hysteresis characterization of magnetic airborne particulate matter in rome italy 1 the magnetic properties of tree leaves may be used to delineate the abundance and dispersal of anthropogenic airborne particulate matter pm in urban environments in the city of rome italy circulating vehicles are the main source of magnetic pm already characterized as prevalently low coercivity magnetite like particles to further constrain the nature and origin of such magnetic particles we carried out coupled field emission scanning electron microscopy and a variety of rock magnetic analyses on pm specimens from quercus ilex leaves and from potential pm sources in circulating motor vehicles in rome fe rich particles are mostly 0 1 5 m in size with irregular shapes and moss like surface particles from disk brakes and diesel and gasoline exhaust pipes show distinct compositional and magnetic hysteresis signatures suggesting that the magnetic pm collected on tree leaves consists of a mixture of particle populations deriving mostly from the abrasion of disk brakes and to a lesser extent from fuel combustion residuals emitted by diesel and gasoline exhausts the contribution of fine superparamagnetic particles to the overall magnetic assemblage has been evaluated with specific rock magnetic analyses the combined magnetic and microtextural compositional analyses provide an effective and original tool to characterize urban pm air pollution

remagnetization and chemical alteration of sedimentary rocks remagnetization is a common phenomenon in rocks and developing a greater understanding of its mechanisms has several benefits acquisition of a secondary magnetization is usually tangible evidence of a diagenetic or thermal event which can be dated using palaeomagnetic techniques this is important because the timing of diagenetic and thermal events is commonly difficult to determine remagnetization can also obscure primary magnetizations and a better understanding of remagnetization could improve our ability to uncover primary magnetizations many chemical remagnetization mechanisms have been proposed including those associated with chemical alteration by a number of different fluids e g orogenic weathering mineralizing hydrocarbons and burial diagenetic processes e g clay diagenesis maturation of organic matter this book contains case studies and review articles that focus on remagnetization chemical remagnetization mechanisms and magnetic changes associated with chemical alteration by hydrocarbons

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

formation of magnetic minerals at hydrocarbon generation conditions in this paper we report the pyrolysis and formation of magnetic minerals in three source rock samples from the wessex basin in dorset southern england the experimental conditions in the laboratory recreated the catagenesis environment of oil source rocks magnetic analysis of both the heated and the unheated samples at room temperature and at very low temperatures 5 k coupled with transmission electron microscopy imaging and x ray analysis revealed the formation of nanometre sized 10 nm magnetic particles that varied across the rock samples analysed but more importantly across the pyrolysis temperature range magnetic measurements demonstrated the formation of these magnetic minerals peaked at 250 c for all rock samples and then decreased at 300 c before rising again at 320 c the newly formed magnetic minerals are suggested to be primarily pyrrhotite though magnetite and greigite are also thought to be present the sizes of the magnetic minerals formed suggest a propensity to migrate together with oil potentially explaining the magnetic anomalies observed above and within oil fields

the lowest place on earth is subsiding an insar interferometric synthetic aperture radar perspective since the early 1990s sinkholes and wide shallow subsidence features wssfs have become major problems along the dead sea shores in israel and jordan sinkholes are readily observed in the field but their locations and timing are unpredictable wssfs are often difficult to observe in the field however once identified they delineate zones of instability and increasing hazard in this study we identify characterize and measure rates of subsidence along the dead sea shores by the interferometric synthetic aperture radar insar technique we analyze 16 sar scenes acquired during the years 1992 to 1999 by the european remote sensing ers 1 and ers 2 satellites the interferograms span periods of between 2 and 71 months wssfs are observed in the lisan peninsula and along the dead sea shores in a variety of appearances including circular and elongate coastal depressions a few hundred meters to a few kilometers in length depressions in ancient alluvial fans and depressions along salt diapir margins phase differences measured in our interferograms correspond to subsidence rates generally in the range of 0 20 mm yr within the studied period with exceptional high rates that exceed 60 mm yr in two specific regions during the study period the level of the dead sea and of the associated ground water has dropped by 6 m this water level drop within an aquifer overlying fine grained marly layers would be expected to have caused aquifer system consolidation resulting in gradual subsidence comparison of our insar observations with calculations of the expected consolidation shows that in areas where marl layers are known to compose part of the upper 30 m of the profile estimated consolidation settlements are of the order of the measured subsidence our observations also show that in certain locations subsidence appears to be structurally controlled by faults seaward landslides and salt domes gradual subsidence is unlikely to be directly related to the sinkholes excluding the use of the wssfs features as predictable precursors to sinkhole formation

a statistical and graphical workflow for the analysis of magnetic susceptibility data from drill cuttings in a hydrocarbon exploration setting abstractwe have analyzed the magnetic susceptibility measurements for more than 5000 samples of drill cuttings from oil gas wells in the venezuelan oil fields to facilitate information extraction and improve data presentation including the determination of threshold values used in hydrocarbon exploration the values for each well typically ranged over several orders of magnitude we have developed a new scale called the magnetization contrast magnitude scale m based on a logarithmic transformation of to better represent the data collectively the m data appear to be influenced by more than one process source resulting in skewed bimodal distributions with a significant degree of overlap between the individual modes each mode or subpopulation of the m data could be modeled with a lognormal distribution we have determined that a method based on normal probability plots could be used to decompose the observed bimodal distributions into their individual components and to obtain initial estim

magnetic parameters trace elements and multivariate statistical studies of river sediments from southeastern india a case study from the vellar river this contribution constitutes a new study using magnetic parameters and trace element determinations of pollutants in river sediments from the tamil nadu state the vellar river covers a total length of about 200 km and flows into the bay of bengal sediment samples were collected at different sediment depths up to 90 cm from 12 sites to investigate their magnetic properties 27 samples and the contents of trace elements 21 out of 27 samples along the river as well as to perform magnetic studies for various grain size fractions 16 sub samples the magnetic results of magnetic susceptibility and remanent magnetizations suggest that the magnetic signal of these sediments is controlled by ferrimagnetic minerals magnetite like minerals and a minor contribution of antiferromagnetic carriers such as hematite minerals detailed studies of selected samples showed a higher magnetic concentration in finer grain sized fractions and a slightly different magnetic mineralogy magnetic concentration dependent parameters evidenced high values which together with the background values allowed us to identify magnetic enhancement at some sites the pearson correlation and multivariate statistical studies principal component analysis canonical correlation analysis supported the relationship between the magnetic and chemical variables in particular magnetic susceptibility anhysteretic and isothermal remanent magnetization are closely correlated to co cr cu fe v zn and the pollution load index in addition principal coordinate analysis and fuzzy c means cluster analysis allowed us to make a classification and to perform a magnetic chemical characterization of the data into four groups thereby identifying critical possibly polluted sites from the vellar river

magnetic signature of heavy metals pollution of sediments case study from the east lake in wuhan china detailed magnetic measurements and geochemical analyses were performed on 114 sediment samples collected from the east lake wuhan city china to establish a possible link between the enhanced concentration of anthropogenic magnetic particles and heavy metals with known sources relatively higher magnetic susceptibility values mass specific 150 10 8 m3 kg 1 were observed for samples near the pollution sources e g the wuhan iron and steel company wisc the qingshan thermal power plant qtpp the banks driveways of the lake and near the sightseeing route of yachts on the lake moreover is positively correlated to the concentration of pb correlation coefficient r 0 682 but negatively or weakly correlated with both zn and cu in contrast anhysteretic remanent magnetization arm is significantly correlated with these major heavy metals r 0 645 for zn arm 0 699 for pb arm and 0 841 for cu arm respectively which indicate that arm serves a better indicator for the pollution of heavy metals in this lake thermomagnetic analysis combined with magnetic hysteresis measurements revealed that magnetites in the pseudo single domain multidomain grain size regions are dominant scanning electron microscopy and energy dispersive x ray examinations of the magnetic extracts showed that these fe rich particles have different morphologies orange peel structure hollow structure with adhered smaller particles zr rich melted like irregular particles pear shaped spherules and spherules with slick surfaces these features are typical for particles produced by anthropogenic activities because of the genetic relationship between the environmental setting of the east lake and the nearby pollution sources this study suggests that in situ magnetic surveys are sensitive to evaluate the environmental pollution on the lake bottom

magnetic fingerprints of surface sediment in the bohai sea china abstract the understanding of the surrounding river impacts on the sediment supply to the bohai sea northern china is insufficient in this study magnetic measurements on surface sediment from the bohai sea and surrounding rivers were performed to interpret the distribution and origin of sediment in the bohai sea different magnetic properties in the analyzed material correspond to seven provenance areas the magnetic mineral content decreases gradually toward the central bohai sea from its marginal areas sediment in the central and northern parts contains higher concentrations of finer magnetic minerals than the southern bohai sea the western bohai sea western bohai and liaodong bays has high contents of magnetic minerals because its provenance areas contain abundant old metamorphic rocks with magnetite the yellow river with the most elevated sediment flux contributes with fine high corercivity magnetic minerals e g hematite to the southern bohai sea mainly in the northwestern laizhou bay some local rivers e g fuzhou river are also important contributors to the coastal waters due to the magnetic similarities sediment from the north yellow sea is magnetically similar to the yellow river detritus the results highlight the use of the rapid magnetic method in provenance tracing

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

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

road and bridge construction across gypsum karst in england gypsum karst problems in the permian and triassic sequences of england have caused difficult conditions for bridge and road construction in northern england the ripon bypass crosses permian strata affected by active gypsum karst and severe subsidence problems here the initial borehole site investigation for the road was supplemented by resistivity tomography studies the roadway was reinforced with two layers of tensile membrane material within the earth embankment this will prevent dangerous catastrophic collapse but will allow sagging to show where problems exist the river ure bridge was constructed across an area of subsidence pipes filled with alluvial deposits it was built with extra strength larger than normal foundations if one pier fails the bridge is designed for adjacent arches to span the gap without collapse the bridge piers are also fitted with electronic load monitoring to warn of failure in the midlands area of england road construction over triassic gypsum has required a phase of ground improvement on the derby southern bypass here the gypsum caps a hill where it was formerly mined it dips through a karstic dissolution zone into an area of complete dissolution and collapse the road and an associated flyover were built across these ground conditions a major grouting program before the earthworks began treated the cavities in the mine workings and the cavernous margin of the gypsum mass within the karstic dissolution zone gypsum blocks and cavities along the route were identified by conductivity and resistivity geophysical surveys excavated and backfilled in the areas of complete dissolution and collapse the road foundation was strengthened with vibrated stone columns and a reinforced concrete road deck was used

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

theory and application of the day plot mrs ms versus hcr hc 2 application to data for rocks sediments and soils 1 new theoretical curves relating the hysteresis parameters mrs ms and hcr hc for single domain sd superparamagnetic sp pseudo single domain psd and multidomain md grains and their mixtures are applied to published data for natural materials the day plot of mrs ms versus hcr hc has been used to crudely classify samples into box like sd psd and md or sometimes incorrectly md sp regions with arbitrary boundaries new type curves for md psd sd md and sd sp grains and mixtures permit more subtle and precise modeling the predicted md trend and its junction with the psd trend are observed in two data sets for magnetite spherules from carbonate rocks and for temperature varying hysteresis results spanning the verwey transition the latter data are the basis of a suggested new method for pinpointing the psd md threshold size selected data for pottery clays soils and paleosols generally follow sd md type curves and indicate intermediate size psd magnetite with narrow to broad size distributions a lake sediment section with known grain size progression tracks in the predicted sense along the sd md trend selected data for glaciomarine and pelagic sediments are also generally compatible with sd md trends examples of remagnetized carbonate rocks submarine basaltic glasses and glassy rims of pillow basalts all follow predicted sp sd or sp psd mixing curves with a large range in volume fraction of sp grains 0 75 but a narrow range of sp particle sizes 10 2 nm larger sp grains spanning the range to sd size 25 30 nm are absent for unknown reasons oceanic dolerites gabbros and serpentinized peridotites in some cases fall in a novel region of the day plot parallel to but below magnetite sd md mixing curves

formation mechanism of large sinkhole collapses in laibin guangxi china on june 3 2010 a series of karst sinkholes occurred at jili village surrounded by gui bei highway wu ping highway and nan liu high speed railway in laibin guangxi china the straight line distances from an large sinkhole pit 85 m in diameter and 38 m in depth to the above mainlines are 200 600 and 500 m respectively several investigation methods including geophysical technology borehole and well drilling groundwater elevation survey and hydrochemistry analysis of groundwater were used to study the formation mechanisms of these sinkholes based on the results the spatial distribution of the jili underground river was confirmed with a strike of sn along the middle carboniferous limestone bedrock and the quaternary deposits controlled the sinkhole formation in addition both historical sinkhole events and analysis of the groundwater air pressure monitoring data installed in the underlying karst conduit system indicate that sinkholes in this area are more likely induced by extreme weather conditions within typical karst geological settings extreme weather conditions in the study area before the sinkhole collapses consisted of a year long drought followed by continuous precipitation with a daily maximum precipitation of 442 mm between may 31 and june 1 2010 typical geological conditions include the jili underground river overlain by the quaternary overburden with thick clayey rubble especially in the recharge zone of the underground river a stabilized shallow water table was formed in response to the extreme rainstorm because of the presence of the thick clayey rubble when the underground conduit was flooded through the cave entrance on the surface air blasting may have caused the cave roof collapse followed by formation of soil cavities and surface collapses borehole monitoring results of the groundwater air pressure monitoring show that the potential karst sinkhole can pose threats to shanbei village the high speed railway and the wu ping highway local government needs to be aware of any early indicators of this geohazard so that devastating sinkholes can be prevented in the future the results also suggest that groundwater air pressure monitoring data collected both the quaternary deposits and the bedrock karst system provide useful indicators for potential sinkhole collapses in similar karst areas where sinkholes usually occur during rainy season or karst groundwater level is always under the rockhead

environmental magnetic responses of urbanization processes evidence from lake sediments in east lake wuhan china summary we present a study on the environmental magnetic response to urbanization processes from nine sediment cores from east lake in wuhan china the concentration of magnetic particles heavy metals and organic matter in the upper 2 18 cm of the sediment cores have been significantly elevated due to the input of coarse magnetite grains from industrial e g power generation and steelmaking and other anthropogenic activities e g vehicle emissions concentration related magnetic parameters such as magnetic susceptibility saturation isothermal remanent magnetization and anhysteretic remanent magnetization are significantly correlated with concentration of heavy metals and organic matter for example pearson s correlation coefficients are 0 921 for cu 0 660 for pb and 0 848 for loss on ignition respectively the magnetic properties of the lake sediments document the pollution history caused by human impact on the lake catchment during urbanization the environmental quality of the lake was fairly good before the 1960s magnetic heavy metal and organic matter contents of the sediments were low and relatively constant which indicates relatively stable natural inputs from the lake catchment pollution trends since the 1960s are reflected in downcore magnetic property variations of the lake sediment the concentration of magnetic particles in the lake sediments started to increase since 1957 when the wuhan iron and steel company and the qingshan thermal power plant which are located upwind of the lake were built and put into production lake pollution was further aggravated since the acceleration of industrialization and urbanization in east lake area in the 1980s which is verified by the elevated concentration of heavy metals and organic matter in the sediments the magnetic mineral concentration in the lake sediment increased continuously until it peaked in the 1990s and has remained a high level since then these results suggest that magnetic properties respond sensitively to environmental status and that the magnetic properties of sediments can provide an excellent record of the industrial and anthropogenic history in an urban lake catchment

sagging and collapse sinkholes over hypogenic hydrothermal karst in a carbonate terrain abstract we show that clusters of karst sinkholes can occur on carbonate hypogene karst terrains unlike common doline karst of dissolution origin the studied sinkholes form mainly by sagging and collapse thermal survey osl dating and morphologic analysis during quarrying and excavations are applied to study the sinkholes at the ayyalon karst israel the thermal survey shows the spatial pattern of rising warm water plumes whose temperature is 2 c warmer than the surrounding aquifer water these plumes dissolve the limestone creating large voids and maze caves mass wasting forms surface sinkholes mainly by sagging and collapse both types of deformation often occur within the same depression lack of hydrologic connection between the surface and underground voids constrain drainage and promote rapid accumulation of colluvium dust and pedogenic clays these have filled the sinkholes up to their rim before the late holocene osl dating constrains the rate of sediment accumulation within the sinkholes the average filling rate thickness divided by elapsed time is 47 mm ka 1 for the last 53 4 ka in sinkhole 1 while in sinkhole 2 nesher ramla karst depression the rate is 61 mm ka 1 from 200 to 78 ka and 173 mm ka 1 since 78 ka between 170 and 78 ka sinkhole 2 was intensively used by middle paleolithic hominins the studied sinkholes may be considered as a type locality for hypogene sinkhole terrain on carbonate rocks

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

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

geomorphic development of the canadian river valley texas panhandle an example of regional salt dissolution and subsidence development of the canadian river valley in the texas panhandle resulted mostly from regional subsidence following dissolution of permian bedded salts salts of the clear fork glorieta san andres and seven rivers formations have undergone dissolution along the margins of the palo duro dalhart and anadarko basins the canadian river valley follows a zone of subsidence for

planning for gypsum geohazards in lithuania and england the rapid underground dissolution of gypsum and the evolution of the gypsum karst in lithuania and england results in subsidence problems which can make construction difficult the natural dissolution yields sulphate rich groundwater of poor quality and the karst is susceptible to the rapid transmission of pollutants in the north of lithuania gypsum karst is developed in devonian gypsum here the towns of birai pasvalys and the surrounding countryside suffer subsidence and some buildings have been damaged the majority of the potable water in these areas is derived from groundwater extracted from sandstone sequences that underlie the gypsum in lithuania conservation measures have been introduced to control agriculture and prevent pollution of the gypsum karst these measures include environmentally friendly farming restrictions on land use and exclusion zones around subsidence hollows in england subsidence caused by the dissolution of permian gypsum has caused severe problems in the vicinity of the town of ripon numerous buildings have been damaged and new sites are difficult to develop here formal planning regulations have recently been introduced to help to protect against the worst effects of subsidence resulting from gypsum dissolution

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

magnetic and mineralogical studies to characterize oil reservoirs in venezuela high resolution aeromagnetic surveys over oil fields and magnetic susceptibility ms measurements in soils sediments and drill cuttings have been proposed as complementary or alternative means of exploration and assessment of hydrocarbon reservoirs some micromagnetic anomalies detected by these studies could be the likely result of the existence at shallow depths of authigenic magnetite and or fe sulphides it has been hypothesized that such magnetic minerals are the chemical byproducts of primary fe oxides exposed to a reducing environment induced by the underlying reservoir secondary magnetite could appear as spherical aggregates framboids of submicronic crystals identifiable by scanning electron microscopy sem the formation of these framboids seems linked either to inorganic chemical processes associated with the presence of hydrocarbons or to oil biodegradation in the last few years we have examined the causal relationship between framboids of magnetic minerals and hydrocarbons via rock magnetic and electron paramagnetic resonance epr analyses of drill cuttings the samples used have been taken at different depths within the first 1500 m of producing and nonproducing wells from two oil fields in southwestern venezuela we have complemented ms results with s ratio logs sem x ray energy dispersion edx irm acquisition curves and high temperature susceptibility measurements more recently we have also studied soil samples from an oil prospective area in western venezuela where rock magnetic and epr results were compared with ethane gas analyses and remote sensing data rock magnetic and epr studies have been performed in 14 oil wells from la victoria 3 and guafita 11 fields figure 1 since our research has focused at the near surface expression of hydrocarbon migration the samples analyzed drill cuttings were taken from different depth at intervals of about 15 m between 100 and 1500 m all samples belong to a single group of molasses from strata that lie far above the producing levels

magnetic characterization of oil sands at osmington mills and mupe bay wessex basin uk this study combines magnetic experimentation and geochemical analysis on oil sands from osmington mills and mupe bay wessex basin uk to investigate the possibility of a relationship between hydrocarbons and magnetic mineralogy removal of hydrocarbons by chemical extraction was conducted to allow comparison of 1 oil sands and 2 cleaned sands detailed magnetic analysis including low temperature and high temperature experimentation revealed that all but one sample was dominated by siderite identified by the neel transition at 37 38 k as well as containing large grains of multidomain magnetite verwey transition 110 k and hematite morin transition 250 k scanning electron microscopy and energy dispersive x ray analysis confirmed the presence of iron oxides in particular framboids 500 nm 45 mm in diameter probably magnetite hysteresis parameters showed distinct grouping of oil sands compared to their clean counterparts and a negative linear regression in log space was observed r 1 4 0 7 between the percentage of extractable organic matter and magnetic susceptibility these results suggest a relationship exists between magnetic minerals and the alteration of oil due to biodegradation which is not yet fully understood possible mechanisms are suggested to be due to anaerobic bacteria or the transportation of the oil as it migrates through the host rock aeromagnetic surveys have established a general connection between magnetic anomalies and hydrocarbon accumulations on a regional scale but with a large degree of ambiguity e g donovan et al 1979 reynolds et al 1991 gay 1992 leblanc morris 1999 several major remagnetizations worldwide e g mccabe et al 1984 1987 elmore leach 1990 suk et al 1993 garner cioppa 2006 are associated with hydrocarbon provinces and anomalous aeromagnetic signals this is thought to be due to chemical alteration of minerals as fluids such as hydrocarbons migrate through the host rock but no definitive mechanism has been determined recent research by several groups has tried to identify the magnetic minerals themselves for hydrocarbon identification e g liu et al 1998 aldana et al 1999 diaz et al 2000 aldana costanzoalvarez 2003 ivakhnenko potter 2004 costanzo alvarez et al 2006 liu et al 2006 rijal et al 2010 aldana et al 2011 guzman et al 2011 rijal et al 2011 for example costanzo alvarez et al 2000 and liu et al 2006 conducted rock magnetic measurements on producing and nonproducing wells and identified anomalous values of magnetic susceptibility x at certain depth intervals within both oil producing and non producing wells characterized by a low coercivity mineral probably magnetite aldana et al 1999 categorized these anomalies into two types 1 fe rich spherical aggregates of authigenic origin as seen by scanning electron microscopy sem analysis only found in producing wells costanzo alvarez et al 2000 aldana costanzo alvarez 2003 and most likely magnetite and 2 characterized by magnetite and hematite but no association with spherical aggregates present in both non producing and producing wells costanzo alvarez et al 2000 aldana costanzo alvarez 2003 liu et al 2006 also found variances between oil producing and non oil producing layers using basic hysteresis parameters saturation remanence magnetization mrs saturation magnetization ms coercivity bc and remanent coercivity bcr the results showed that within an oil bearing layer its x ms and mrs values were between 24 and 36 times higher than the corresponding layer obtained from a dry well with maghemite siderite and pyrite contributing to the enhanced magnetic signature another study by ivakhnenko potter 2004 investigated the magnetic susceptibility of crude oils refined oil fractions and formation waters from sites worldwide it was found that all the fluids were diamagnetic but had distinct differences in magnetic susceptibility for example the crude oils were more negative than formation waters from the same location the physical and chemical properties of the oils appeared to correlate with the magnetic susceptibility such as gravity metal concentration density and api american petroleum index from elmore r d muxworthy a r aldana m m mena m eds 2012 remagnetization and chemical alteration of sedimentary rocks geological society london special publications 371 http dx doi org 10 1144 sp371 6 the geological society of london 2012 publishing disclaimer www geolsoc org uk pub ethics geological society london special publications published online june 27 2012 as doi 10 1144 sp371 6

gypsum karst problems in constructing dams in the usa gypsum is a highly soluble rock and is dissolved readily to form caves sinkholes disappearing streams and other karst features that typically are also present in limestones and dolomites gypsum karst is widespread in the usa and has caused problems at several sites where dams were built or where dam construction was considered gypsum karst is present at least locally in most areas where gypsum crops out or is less than 30 60 m below the land surface these karst features can compromise on the ability of a dam to hold water in a reservoir and can even cause collapse of a dam gypsum karst in the abutments or foundation of a dam can allow water to pass through around or under a dam and solution channels can enlarge quickly once water starts flowing through such a karst system the common procedure for controlling gypsum karst beneath the dam is a deep cut off trench backfilled with impermeable material or a close spaced grout curtain that hopefully will fill all cavities in oklahoma the proposed upper mangum dam was abandoned before construction because of extensive gypsum karst in the abutments and impoundment area catastrophic failure of the quail creek dike in southwest utah in 1989 was due to flow of water through an undetected karstified gypsum unit beneath the earth fill embankment the dike was rebuilt at a cost of us 12 million with construction of a cut off trench 600 m long and 25 m deep other dams in the usa with severe gypsum karst leakage problems in recent years are horsetooth and carter lake dams in colorado and anchor dam in wyoming

dissolution of titanomagnetite and sulphidization in sediments from lake kinneret israel summary magnetic extracts obtained from sediment cores recovered from lake kinneret israel were subjected to comprehensive scanning electron microscope and in line energy dispersive x ray spectroscopy analyses a variety of ferrimagnetic iron oxides and iron sulphide particles were identified along with apparently non magnetic iron sulphides the majority of the iron oxides are titanomagnetites that have undergone pervasive dissolution and in many cases were only preserved as skeletal 3 d lattices of ilmenite lamellae often the spaces between the submicron ilmenite lamellae are empty also sponge like dissolution features are observed in some residual titanomagnetite grains another group of titanomagnetite grains is characterized by superficial shrinkage cracks which indicate low temperature maghemitization in some cases these cracks appear to be where dissolution started most titanomagnetites contain impurities of al mg si and mn on the order of 1 per cent chromium magnetites with minor ti mg and al content on the order of a few percent but without mn were also found chromium magnetites mostly occur as octahedra in a well preserved state which indicates that they are less prone to dissolution magnetite spherules of 40 60 m in size which were mostly hollow were only found in material collected from the outer zone of the core section that was in contact with the steel core barrel these spherules were not found in material collected from the centre of the core they are therefore interpreted as contaminants that were produced during fabrication of the steel core barrel iron sulphides are present as pyrite either as larger aggregates of cubic crystals each of up to 20 m in size or as 5 10 m framboidal aggregates consisting mostly about 0 3 m idiomorphic octahedra the cubic pyrite crystals have heterogeneous compositions pure pyrite should be non magnetic but even aggregates of up to 150 m in size were magnetically separated they probably therefore contain a magnetic core of greigite or overgrown titanomagnetite the latter possibility is supported by observations of residual titanomagnetites with individual pyrite crystals residing directly on their surfaces or filling space between ilmenite lamellae irregular aggregates of flaky submicron iron sulphides were also found which are interpreted to be greigite the greigite has a low degree of visible crystallization pyrite and or greigite grains were found inside the aggregates or in agglomerates with organic remnants together visual observations and elemental analyses provide clear evidence of pervasive dissolution of primary titanomagnetite and concurrent sulphidization of sediments from lake kinneret

causes of the catastrophic failure of an earth dam built on gypsiferous alluvium and dispersive clays altorricon huesca province ne spain this paper analyses the causes of the catastrophic failure of an earth dam that took place on 21 january 2001 during the first filling test in the ne of spain altorricon village huesca province the san juan reservoir with a capacity of 850 000 m3 was built in 1999 on gypsiferous mantled pediment deposits overlying tertiary dispersive clay sediments the basin of the reservoir was excavated in the alluvial cover and tertiary bedrock an earth dam was constructed on the pediment surface along the perimeter of the artificial basin the dam has a core of compacted clay material derived from the excavation which is indented 1 m in the tertiary shales of the bedrock cutting the highly pervious alluvial mantle field observations analysis of the basin and dam materials and eyewitnesses accounts have helped to infer the processes involved in the failure of the earth dam these processes include 1 subsidence and ravelling suffosion processes induced by the dissolution of the 4 m thick detrital cover with a gypsum content of around 40 2 piping processes affecting the embankments and core of the dam built with dispersive clays that have high exchangeable sodium percentage esp and show active pipes and 3 water circulation through biogenic burrows in the pediment deposits this case study demonstrates the frequently hidden limitations that evaporite sediments and dispersive clay materials pose to the construction of dams it also shows that highly permeable surficial deposits should be stripped before the construction of the dam structure

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

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