the major ion composition of carboniferous seawater abstract the major ion chemistry na mg 2 ca 2 k so 4 2 and cl of carboniferous seawater was determined from chemical analyses of fluid inclusions in marine halites using the cryo scanning electron microscopy cryo sem x ray energy dispersive spectrometry eds technique fluid inclusions in halite from the mississippian windsor and mabou groups shubenacadie basin nova scotia canada asbian and pendleian substages 335 5 330 ma and from the pennsylvanian paradox formation utah usa desmoinesian stage 309 305 ma contain na mg 2 k ca 2 cl brines with no measurable so 4 2 which shows that the carboniferous ocean was a cacl 2 sea relatively enriched in ca 2 and low in so 4 2 with equivalents ca 2 so 4 2 hco 3 34 s values from anhydrite in the mississippian shubenacadie basin 13 2 14 0 and the pennsylvanian paradox formation 11 2 12 6 support seawater sources br in halite from the shubenacadie basin 53 111 ppm and the paradox basin 68 147 ppm also indicate seawater parentages carboniferous seawater modeled from fluid inclusions contained 22 mmol ca 2 kg h 2 o mississippian and 24 mmol ca 2 kg h 2 o pennsylvanian estimated sulfate concentrations are 14 mmol so 4 2 kg h 2 o mississippian and 12 mmol so 4 2 kg h 2 o pennsylvanian calculated mg 2 ca 2 ratios are 2 5 mississippian and 2 3 pennsylvanian with an estimated range of 2 0 3 2 the fluid inclusion record of seawater chemistry shows a long period of cacl 2 seas in the paleozoic from the early cambrian through the carboniferous when seawater was enriched in ca 2 and relatively depleted in so 4 2 during this 200 myr interval ca 2 decreased and so 4 2 increased but did not cross the ca 2 so 4 2 chemical divide to become a mgso 4 sea when so 4 2 in seawater became greater than ca 2 until the latest pennsylvanian or earliest permian 309 295 ma seawater remained a mgso 4 sea during the permian and triassic for 100 myr fluid inclusions also record a long interval from the early cambrian to the middle devonian when seawater had low mg 2 ca 2 ratios 2 ca 2 ratio of seawater rose from 0 9 in the middle devonian to 2 5 in the middle late mississippian 2 3 in the middle pennsylvanian and 3 5 in the early permian the transition from calcite seas to aragonite seas established from the mineralogy of oolites and early marine cements occurred in the late mississippian fluid inclusions show that seawater mg 2 ca 2 ratios rose above 2 by the middle to late mississippian coinciding exactly with the shift to aragonite seas aragonite seas existed for 100 myr from the late mississippian until the late triassic early jurassic

displacement efficiency of faults and fractures abstract faults and fractures evolve kinematically as somigliana dislocations as a result displacement gradients are always present with displacements reducing to zero at fault fracture tips we present a graphical method for the comparison of displacement gradients from fractures of various magnitudes and types displacement efficiency of a fault fracture is defined as its ability to maximise displacement across its surface

evaporites and siliciclastics of the permian nippewalla group of kansas usa a case for non marine deposition in saline lakes and saline pans the mid permian nippewalla group of kansas consists of bedded evaporites red bed siliciclastics and grey siliciclastics deposited in a non marine environment lithologies and sedimentary features indicate lacustrine and aeolian deposition subaerial exposure and palaeosol formation grey siliciclastic mudstones characterized by planar and convolute laminations ostracods peloids and plant material represent a freshwater brackish perennial lake facies bedded anhydrites containing gypsum crystal pseudomorphs clastic anhydrite grains and grey mud drapes and partings suggest deposition in saline lakes bedded halites consist of chevron and cumulate crystals dissolution surfaces and pipes and mudcracked microcrystalline salt crusts which were deposited in saline pans dominated by flooding evaporative concentration and desiccation chaotic halite composed of red bed mudstone and siltstone with displacive halite crystals formed in saline mudflats red bed mudstone and siltstone with little or no displacive halite but with abundant cracking root and plant features suggest deposition in a dry mudflat red bed sandstone composed of well sorted well rounded quartz grains cemented with halite indicate aeolian and rare shallow water deposition most deposition took place in halite dominated ephemeral saline lakes surrounded by saline and dry mudflats sandflats and sand dunes evaporation desiccation flooding and wind played significant roles in this environment the nippewalla group siliciclastics and evaporites represent an evolution from a perennial lacustrine system to a non marine acidic saline pan system in the mid continent of north america the problem of distinguishing between ancient marine and non marine evaporites as well as recognizing those evaporites deposited in acid settings with detailed field core and petrographical study of both evaporite deposits and associated sedimentary rocks has successfully been addressed in addition interpretations of mid permian palaeoclimate data in the form of short term air temperature proxies within longer term wet dry trends have been made these data provide a new palaeogeographic and palaeoclimatic model for the mid permian of western pangaea

probabilistic modeling of faults below the limit of seismic resolution in pelican field north sea offshore united kingdom faults which can compartmentalize a reservoir and which are too small to be seen on seismic can be predicted using a self similar or fractal model of faulting at various scales a computerized method has been developed for statistical analysis of a fault pattern interpreted from three dimensional 3 d seismic in order to fractally derive the distributions of fault size frequency and spatial variations and to verify their invariance within the seismic resolution range this analysis can be used for quality control of seismic interpretation and as input for extrapolation toward smaller scales using probabilistic techniques the application of this program to pelican field united kingdom north sea validated the interpretation of the complex fault pattern of that field but suggested that only limited extrapolations could be confidently made probabilistic maps showing distribution of faults down to 3 m 10 ft of throw and not resolved by 3 d seismic were made these maps subsequently were used as a qualitative aid in full field reservoir simulations to model differently zones of potential dense faulting from zones of reduced faulting this was done because nearby field behavior had shown that faulting is a significant factor in reservoir behavior and ultimately field deliverability field development planning therefore could be optimized

louann salt geochemistry gulf of mexico sedimentary basin u s a a preliminary synthesis abstract samples of jurassic salt and anhydrite were obtained from throughout the gulf of mexico sedimentary basin salt samples have been analyzed for bromide content and 87 sr 86 sr of anhydrite inclusions and anhydrite for 87 sr 86 sr most samples of diapiric salt contain 87 sr 86 sr ratios are commonly radiogenic relative to the ratio in presumed coeval jurassic callovian seawater both these observations suggest that during deformation salt undergoes extensive rock water interaction losing bromide to the reacting brines and incorporating radiogenic sr similar behavior of anhydrite during deformation with respect to sr is also observed samples of deeply buried salt exhibit bromide concentrations consistent with the precipitation of marine halite but include several samples with extremely high values few 87 sr 86 sr ratios however seem to be characteristic of coeval callovian seawater samples with normal bromide content but radiogenic sr suggest primary deposition from or recrystallization in the presence of radiogenic fluids with marine like bromide content samples with extremely high bromide content and radiogenic sr values suggest recrystallization in fluids with elevated bromide content due to loss of bittern phases or extensive rock water interaction of bedded salt during deep burial the data suggest a dynamic system in which physical modification of evaporites during deformation and deep burial is accompanied by chemical modification

isotope geochemistry of fluid inclusions in permian halite with implications for the isotopic history of ocean water and the origin of saline formation waters abstract d and 18o values have been determined for fluid inclusions in 45 samples of permian halite the inclusions are enriched in 18o relative to the meteoric water line but are depleted in d relative to ocean water inclusions with the more positive values coincide with the isotopic composition expected for evaporating sea water which follows a hooked trajectory on a d 18o diagram inclusions with more negative values may represent more highly evaporated sea water but probably reflect synsedimentary or diagenetic mixing of meteoric water with evaporite brines the isotope systematics in these inclusions are sufficiently similar to those of a modern evaporite pan to indicate that permian sea water was isotopically similar to modern sea water connate evaporite brines can have negative values because of the probable hooked isotope trajectory of evaporating sea water and or synsedimentary mixing of evaporite brines with meteoric waters subsurface formation waters composed of mixtures of remnant primary evaporite brines and later meteoric waters may be more common than previous isotopic evidence has suggested

sr s and oso4 isotopes and the depositional environments of the upper miocene evaporites spain abstract upper miocene evaporites in the nijar basin southeastern spain contain thick massive and coarse crystalline selenites of the middle messinian yesares formation on the basis of their sedimentary fabrics and structures such as euhedral terminations of crystals well preserved algal filament inclusions and standing growth orientations these selenites are interpreted to be primary bottom growth deposits most of these selenites have sr concentrations of about 1000 ppm range from 700 to 1800 ppm 87sr 86sr values of yesares selenites vary between 0 70890 and 0 70896 n 18 which are all within the known range of messinian seawater suggesting a marine origin however quantitative modeling of 87sr 86sr vs sr ca of fluids demonstrates that a minor amount of admixed nonmarine fluid e g 20 might have contributed to the yesares marine brines 34s and 18oso4 values of yesares selenites range from 21 to 24 cdt and from 10 to 16 smow respectively these ranges are more variable and most values are heavier than those expected for normal miocene marine gypsum on the basis of quantitative modeling these heavy 34s and 18oso4 values have most likely resulted from reduction and oxidation reactions of sulfur species that occurred in brines rather than from contributions of nonmarine water or from reservoir crystallization effects the use of sr s and o isotopes provides a possible means of distinguishing whether an ancient evaporite was deposited by marine nonmarine or hybrid brines sr isotopes however are insensitive to minor nonmarine contributions on the basis of quantitative modeling and consequently marine sr isotopes for evaporites e g gypsum do not necessarily indicate pure marine depositional environments compared to sr isotopes 34s and 18oso4 of marine gypsum are even more insensitive to minor nonmarine contributions because of much higher so4 concentrations in seawater and seawater evaporated brines than in most freshwaters therefore sr o and s isotopes should be used with caution to interpret depositional environments and to determine parent fluids of ancient evaporites

modeling wind driven circulation and landfast ice edge processes during polynya events in northern baffin bay abstract a high resolution sea ice ocean numerical model of the north water polynya has been developed to study the wind driven circulation during polynya events an idealized three layer stratified ocean is used to initialize the model to characterize the baroclinic response to realistic wind and ice conditions the model general circulation pattern is mainly forced by an along channel sea level gradient between the arctic ocean and baffin bay which determines the magnitude of the southward baffin current and by an across channel sea level gradient in baffin bay which drives the northward west greenland current wgc these two currents are found to be anticorrelated to each other in the smith sound area during strong northerly wind events occurring quite frequently in the winter spring period in the polynya nutrient rich baffin bay waters transported by the wgc are forced toward the greenland shelf coinciding with upwelling events along the greenland coast whenever an ice bridge is present i e

origin of secondary potash deposits a case from miocene evaporites of nw central iran abstract in early miocene times an extensive carbonate shelf developed in central iran and during several cycles of sea level fluctuations evaporite bearing carbonate sequences of the qom formation were deposited however in the early middle miocene development of restricted marine conditions led to a facies change from shelf carbonates of the qom formation to the evaporite series of the m 1 member of the overlying lower red formation this member is a facies mosaic of lagoonal and salina evaporites mainly halite beds admixed with wadi siliciclastics the purpose of this study which focuses on two salt mines in the northwestern portion of central iran in the zanjan province was to reveal the origin sedimentary environment and diagenesis of these potash bearing evaporite sequences petrographic examination revealed the following mineral assemblage halite gypsum anhydrite and carnallite as primary precipitates and langbeinite and aphthitalite as secondary metamorphic potash salts in the iljaq mine distorted halite beds are dominated by burial and deformational textures and a great deal of secondary potash salts in the qarah aghaje mine however the bedded halite shows pristine primary textures and is devoid of the secondary potash salts high bromine content of most evaporite minerals suggests their marine origin and confirms the absence of the extensive meteoric alterations and subsequent bromine depletions potash salts are mainly secondary and resulted from diagenetic replacements of distorted halite beds during thermal and dynamic metamorphism in a burial setting

sulfate borate association glauberite probertite in the emet basin implications for evaporite sedimentology middle miocene turkey abstract probertite and glauberite are the main rock forming minerals in the lacustrine doganlar succession of the emet basin the present paper seeks to characterize and interpret the facies and depositional settings of this mineral association probertite is made up largely of microfibers arranged in microbundles and displays a variety of lithofacies many lithofacies show deformation and flowage structures which can be assigned to multistage growth of probertite under synsedimentary conditions glauberite displays laminated lithofacies formed by fine grained clear crystals and thin to thick bedded lithofacies composed of coarser crystals and variable proportions of siliciclastic matrix depositional pairs of probertite and glauberite occur at millimeter laminites centimeter alternations and meter cycles scales probertite and glauberite are primary products grown subaqueously in a relatively shallow saline lake either on the bottom probertite and glauberite or as cumulate crystals glauberite and interstitially below and close to the bottom the laminites are made up of microcycles composed of several types of laminae the microcycles are interpreted as predominantly pluriannual precipitates in the proposed lake model the brine body is not deep as indicated by frequent episodes of subaerial exposure recorded in the succession this study provides new insight into the genesis of glauberite and probertite the interpretation of nodular lithofacies the type of microfiber evaporites the evaporite units made up of sulfate borate alternations and the petrographic description of glauberite laminites and their paleoenvironmental interpretation

polyhalite microfabrics in an alpine evaporite melange hallstatt eastern alps in the hallstatt salt mine austria polyhalite rocks occur in 0 5 1 m thick and several metre long tectonic lenses within the protocataclasite to protomylonite matrix of the alpine haselgebirge fm thin section analysis of hallstatt polyhalites reveals various fabric types similar to metamorphic rocks of crust forming minerals e g quartz and feldspar polyhalite microfabrics from hallstatt include 1 polyhalite mylonites 2 metamorphic reaction fabrics 3 vein filling fibrous polyhalite and 4 cavity filling polyhalite the polyhalite mylonites contain a wide range of shear fabrics commonly known in mylonitic quartzo feldspathic shear zones within the ductile crust and developed from a more coarse grained precursor rock the mylonites are partly overprinted by recrystallised statically grown polyhalite grains metamorphic reaction fabrics of polyhalite fibres between blodite or astrakhanite na2mg so4 2 4h2o and anhydrite have also been found according to previous reports blodite may occur primarily as nodules or intergrown with loweite reaction fabrics may have formed by exsolution re crystallisation parallel growth or replacement this fabric type was only found in one sample in relation with the decomposition of blodite at ca 61 c in the presence of halite or slightly above testifying therefore a late stage prograde fabric significantly younger than the main polyhalite formation

origin and recharge model of the late cretaceous evaporites in the khorat plateau abstract evaporites commonly occur in the mesozoic cenozoic tethyan domain which characterized by extensive late cretaceous potash deposits in the lanping simao basin lsb in southwestern china and in the khorat plateau kp in thailand and laos the lsb and the kp are located in the eastern tethyan tectonic belt the origin of the late cretaceous evaporites in these basins is controversial possibilities include marine continental or hydrothermal origins in addition the recharge model for the major solutes into these evaporitic basins is inadequate whether it is from the kp to the lsb or from the qiangtang to the lsb to the kp in this study 34 gypsum anhydrite and halite samples from two sediment cores collected from the kp were analyzed to determine their stable b sr s isotopic compositions this is the first time that 11b values have been reported for the anhydrite in the study area the origin and evolutionary relationships of these evaporitic basins were investigated based on the geochemical data sedimentary features mineral sequences and stratigraphic ages of the evaporites in the lsb and kp the tectonic evolution and stratigraphic comparisons during the triassic cretaceous in the eastern tethyan domain were systematically reviewed and summarized in order to determine a preferred recharge model for the evaporites in the kp the following conclusions were reached 1 the reconstructed 11b values 38 20 to 51 23 of the parent solution which were based on those of the anhydrite 8 20 to 21 23 and the isotopic fractionation levels 30 2 to 32 7 87sr 86sr ratios 0 70743 0 70846 and 34s values 14 39 to 15 94 of the anhydrite and halite in the kp overlap with those of late cretaceous seawater suggesting a marine origin 2 the similar mineral sequences and b sr s isotopic signatures and the comparable sedimentary features and inherited ore forming ages indicate that evaporites in the lsb and kp have similar solute sources and evolutionary relationships 3 the tectonic evolution and stratigraphy demonstrate that during the late cretaceous paleoseawater from the shan boundary ocean the eastern segment of the meso tethys ocean most likely passed through the southwestern part tengchong baoshan block of sibumasu and preferably recharged marine solutes into the lsb and kp

strains developed in the hangingwalls of thrusts due to their slip propagation rate a dislocation model reply abstract fault planes propagate radially from a point source and this failure propagation process is very similar to the movement of a dislocation through a crystal lattice an elastic strain represented by an extra half plane is necessarily imparted to the lattice at an edge dislocation and this is equivalent to the ductile bead which accompanies the propagating tip of a thrust fault this ductile bead migrates with the fault tip and imparts a characteristic internal strain to the thrust sheet a two dimensional model is presented to illustrate the inter relationship between fault plane slip fault tip propagation and internal strain in multilayered sequences internal strain is usually represented by asymmetric folds verging in the thrust transport direction a simple technique the displacement distance plot utilizes the fact that displacement dies out towards the fault tip this plot can be used to quantify the relative stretch measured parallel to the fault movement which is dependent on the slip propagation rate and it may be used to define exactly the position of the fault tip on a cross section examples of fold thrust structures from devon england and pembrokeshire wales are used to illustrate the technique

precambrian paleosols in canada although at least 38 precambrian paleosols have been reported in canada few have received the attention afforded most other geological phenomena the most intensively studied of these are widely distributed early proterozoic paleosols associated with the sub huronian and matonabbee new name unconformities criteria that have been most useful in identifying precambrian paleosols in canada include macrostructures ascending protolith disruption saprolith and corestones micromorphology sepic texture and peds mineralogical changes dissolution transformation geochemical signatures ascending depletion of some elements characteristic weathering indices and distinctive colour contrast diagenetic mechanical and geochemical overprinting of the paleosols evident in many canadian examples includes paleosol compaction veins cutting pedogenic features and widespread alkali and alkaline earth element metasomatism metamorphism and deformation also tend to mask pedogenic features as attested by th

warming of the polar water layer in disko bay and potential impact on jakobshavn isbrae a number of recent studies have shown enhanced retreat of tidewater glaciers over much of southern and western greenland one of the fastest retreats has occurred at jakobshavn isbrae with the rapid retreat linked to the arrival of relatively warm and saline irminger water along the west coast of greenland similar links to changes in ocean water masses on the coastal shelf of greenlandwere also seen on the east coast this study presents hydrographic data from disko bay additionally revealing that there was also a significant warming of the cold polar water entering disko bay from the mid to late 1990s onward this layer which lies at a depth of 30 200m warmedby 18 28c the heat content of the polar water layer increased by a factor of 3 6 for the post 1997 period compared to the period prior to 1990 the heat content in the west greenland irminger water layer between the same periods increased only by a factor of 2 but contained more total heat the authors suggest that the changes in the polar water layer are related to circulation changes in baffin bay

variability in sulfur isotope records of phanerozoic seawater sulfate the s of seawater sulfate reflects processes operating at the nexus of sulfur carbon and oxygen cycles however knowledge of past seawater sulfate s values must be derived from proxy materials that are impacted differently by depositional and post depositional processes we produced new timeseries estimates for the s value of seawater sulfate by combining 6710 published data from three sedimentary archives marine barite evaporites and carbonate associated sulfate with updated age constraints on the deposits robust features in multiple records capture temporal trends in the s value of seawater and its interplay with other phanerozoic geochemical and stratigraphic trends however high frequency discordances indicate that each record is differentially prone to depositional biases and diagenetic overprints the amount of noise quantified from the variograms of each record increases with age for all s proxies indicating that post depositional processes obscure detailed knowledge of seawater sulfate s s value deeper in time

mineralogy diagenesis and hydrochemical evolution in a probertite glauberite halite saline lake miocene emet basin turkey abstract the emet basin is one of the neogene basins in western turkey containing significant amounts of borate minerals mainly colemanite the petrologic study of core samples from two exploratory wells in the doganlar sector under optic and electron microscopy reveals a complex mineral association in which probertite glauberite and halite constitute the major primary phases without mineral precursors precipitated in a saline lake placed in a volcano sedimentary context other sulfates anhydrite gypsum thenardite celestite and kalistrontite borates colemanite ulexite hydroboracite tunellite kaliborite and aristarainite and sulfides arsenopyrite realgar and orpiment are attributed to early diagenesis so far the doganlar deposit is the most important deposit of probertite known up to now chemical changes in the groundwater inflow led to the precipitation of ca bearing borates colemanite in the tuff flat environment surrounding the lake while na ca sulfates and borates glauberite and probertite precipitated in the center of the lake fluid inclusion compositions in halite indicate that the advanced brines correspond to the na k cl so 4 type during restricted stages of the saline lake the residual brines seeped through the tuff flat sediments leading to transformations of previous precipitates that resulted in the formation of k bearing minerals the abundance of coccoid like biogenic dolomite colloidal arsenopyrite and the isotopic composition of sulfates are indicative of bacterial sulfate reduction in contrast arsenic sulfides are attributed to acidophilic micro organisms in oxidizing conditions fluctuations of redox conditions in both free and interstitial brines control the biological influence in some diagenetic transformations

parent brine of the castile evaporites upper permian texas and new mexico abstract the upper permian lower ochoan castile formation is a major evaporite sequence 10 000 km3 of calcite anhydrite and halite in west texas and southeastern new mexico traditionally the castile brine has been considered to have been derived from seawater this tradition has recently been challenged by two versions of the closed basin drawdown model they call for deposition from a mixed brine in part marine and in large part nonmarine they propose drawdown of as much as 500 m to form a major sink for ground water issuing from the surrounding capitan reef complex a large fraction of the solute in the brine body is inferred to have been recycled from older permian evaporites on the surrounding shelf strontium isotope analyses show no evidence that meteoric ground water was contributed to the castile brine from a stratigraphic geographic and lithologic array of 65 samples of anhydrite gypsum and calcite 59 have an 87sr 86sr ratio of 0 706923 sw of 225 0 a ratio that is the same as that of strontium in early ochoan ocean water if considerable 15 influx of meteoric water had occurred enough continental strontium would have been introduced to have resulted in higher ratios low bromide values 20 40 ppm in castile halite which have been used to argue for meteoric influx and for recycled salt probably resulted from diagenesis during shallow burial by halite centimeter size bottom grown crystals of gypsum were altered to nodular anhydrite the rising water of dehydration caused the halite to recrystallize during the recrystallization some bromide was expelled despite the large volume of water that evaporated annually from its surface 52 km3 yr assuming an evaporation rate of 2 m yr the castile brine body never completely desiccated the surrounding shelf was flat hot and generally dry it probably could not have supplied a significant volume of meteoric spring water to the basin over tens of thousands of years more likely during the entire history of the evaporite sequence influx was dominantly marine marine ground water flowed through the capitan formation into the evaporite basin along its southern and possibly western margin probably with a rate of flow that was usually fast enough to prevent major drawdown of the brine surface

searching for travertines calcretes and speleothems in deep time processes appearances predictions and the impact of plants common models for modern calcite precipitation in and around caves soils springs and streams involve co 2 supplied by thick high p co 2 biogenic soils which were probably thin or non existent before vascular plants indeed plant influenced chemical weathering might have caused accelerated terrestrial carbonate production from the devonian onwards however terrestrial carbonates have also been documented from the archaean proterozoic cambrian ordovician and silurian mechanisms which could have caused non marine carbonates to precipitate without organic rich soils are described and some geological events likely to have influenced non marine carbonate precipitation up to the origin of vascular plants are highlighted as organisms have evolved so have the petrographic characteristics of non marine carbonates some examples of this are also given here

observations on the incorporation of trace elements in halite of oligocene salt beds bourg en bresse basin france abstract it is common practice to employ trace elements found in chloride salts as indicators of the conditions of deposition because some halite contains abundant fluid inclusions it is necessary to separate the salt from the inclusions before analysis this study presents the data derived from the use of a simple preparative technique which permits analysis of the trace elements in solid halite and provides a guide to test the success in elimination of the contaminants contained in the fluid inclusions the differentiation is accomplished simply by crushing the salt in alcohol followed by separate analysis of the fluid and solid components thus yielding accurate trace element concentrations in the solids crystal lattice dislocations and grain boundaries and the fluids br and k are present both in the solid and liquid phases of the halite but mg is exclusively in the fluid inclusions the elimination of the mg from the analysis of the solid phase may thus be employed as a monitor to indicate the degree of purification of the samples being analysed

columnar concretions in the visakhapatnam red sediments on the east coast of india abstract calcareous and siliceous columnar concretions occur in some of the visakhapatnam red sediments on the east coast of india the carbonate externally derived was rapidly precipitated in the intergranular space of the sediments by displacement of the fine material intense evaporation at the surface in the dry periods and the initial high permeability of the red sediments are considered to have produced the columnar forms the fine grained nature low mg calcite and the negative 13 c and 18 o ratios of the carbonate cement suggest an evaporative precipitation in a fresh water environment late diagenetic changes and compaction of the red sediments caused the modern development of the concretions to cease irregular basement topography largely controlled the localized distribution of the concretions in the red sediments siliceous concretions are confined to a narrow zone along the coast amorphous silica biogenous matter and silica microspheres constitute the cementing material of these concretions the microspheres indicate a precipitation of silica from saturated solutions in a protected environment the siliceous concretions are interpreted to have replaced the carbonate ones during the post pleistocene sea level rise in the visakhapatnam region

structure and mixing across an arctic atlantic front in northern baffin bay 1 a front forms in northern baffin bay 75 25 n between atlantic derived water carried by the west greenland current and arctic derived waters exiting southward through nares strait and jones sound via the baffin current subsurface waters e g below 100 m of the west greenland current are as much as 2 c warmer than those of the baffin current confluence of these waters leads to a frontal transition between 100 500 m wherein cross frontal gradients of potential temperature l 0 06 0 07 c km 1 and salinity s l 0 005 0 007 psu km 1 are largely density compensating l 0 001 km 1 subsequent thermohaline interleaving establishes conditions conducive to mixing via cabelling and double diffusion the front s location would allow it to play a contributing role in the formation of baffin current water structure and eventual export of freshwater to the north atlantic

criteria for the recognition of salt pan evaporites layered evaporites can accumulate in 1 ephemeral saline pans 2 shallow perennial lagoons or lakes and 3 deep perennial basins criteria for recognizing evaporites deposited in these settings have yet to be explicitly formulated the characteristics of the ephemeral saline pan setting have been determined by examining eight holocene halite dominated pans salt pans and their deposits marine and non marine from the u s mexico egypt and bolivia these salt pans are typified by alternating periods of flooding resulting in a temporary brackish lake evaporative concentration when the lake becomes saline and desiccation which produces a dry pan fed only by groundwater the resulting deposits consist of alternating layers millimetres to decimetres of halite and mud the layers of halite are characterized by 1 vertical and horizontal cavities rounded crystal edges and horizontal truncation surfaces due to dissolution during flooding 2 vertical chevrons and cornets grown syntaxially on the bottom during the saline lake stage 3 halite cements overgrowths and euhedral cavity linings and disruption of layering into metre scale polygons produced during the desiccation stage the muddy interbeds are characterized by displacive growth of halite during the desiccation stage immediately below the surface of the pan the halite layers are matured by repeated episodes of dissolution and diagenetic crystal growth this results in porous crusts with patches of chevron and cornet crystals truncated by dissolution clear diagenetic halite cement and internal sediment these layers of mature halite closely resemble the patchy cloudy and clear textures of ancient halite deposits holocene salt pans are known to cover thousands of square kilometres and cap halite deposits hundreds of metres thick so they are realistic models for ancient evaporites in scale e g permian salado formation of new mexico texas which preserves many primary salt pan features

water column structure and circulation under the north water during spring transition april july 1998 abstract the north water is a large recurring polynya in northern baffin bay over 400 hydrographic ctd profiles taken over a grid of stations between april and july 1998 were analysed to understand the water column structures underlying the polynya during spring transition in the north water imported and dissimilar water masses converge over a complex bathymetry northern assembly na waters are derived from inflows through nares strait and jones sound southern assembly sa waters are derived from a northern moving branch of the west greenland current wgc na and sa waters mix primarily over the north south smith sound canyon between 76 5 n and 77 n latitude to form a distinct relatively thick halocline layer termed north water assembly nwa characterised by density compensating thermohaline intrusions in the southern portion of the north water a sharp front between nwa waters and sa waters roughly aligns with the 500 m isobath flow patterns deduced from potential temperature vs salinity s diagrams and from minima in stability frequency n profiles indicate that this front results from the convergence of nwa waters and a branch of the wgc that is cyclonically re directed as it approaches smith sound canyon not all sa waters are immediately re directed south towards the front as a second branch follows the greenland coast toward smith sound while s signatures show some evidence of upwelling along the greenland coast e g outcropping of isopycnal surfaces no surfacing of warm atlantic derived water was observed during the sampling period 1998 suggesting that mechanical removal of ice by winds and currents is the primary mechanism by which the north water forms some sensible heat exchange associated with brine rejection and penetrative convection may occur but only during periods of active ice formation

proterozoic aeolian quartz arenites from the hornby bay group northwest territories canada implications for precambrian aeolian processes abstract the hornby bay group is a middle proterozoic 2 5 km thick succession of terrestrial siliciclastics overlain by marine siliciclastics and carbonates a sequence of conglomeratic and arenaceous rocks at the base of the group contains more than 500 m of mature hematitic quartz arenite interpreted to have been deposited by migrating aeolian bedforms bedforms and facies patterns of modern aeolian deposits provided a basis for recognizing two sequences of aeolian arenite both sequences interfinger with alluvial wadi fan conglomerates and arenites deposited by braided streams depositional processes facies patterns and paleotopographic position of the arenites are consistent with modern sand sea dynamics distal aeolian facies in both sequences are composed of trough crossbed megasets deposited by climbing sinuous crested transverse dunes megasets comprise a gradational assemblage of tabular to wedge planar cosets formed by deflation reactivation of dune lee slopes and migration of smaller superposed aeolian bedforms small dunes and wind ripples megasets in the proximal facies are thinner display composite internal stratification and have a tabular planar geometry which suggests that they were formed by smaller straight crested transverse dunes most stratification within the crossbeds is inferred to have formed by the downwind climbing of aeolian ripples across the lee slopes of dunes remarkably few precambrian aeolian deposits have been reported previously this seems anomalous because most precambrian fluvial sediments appear to have been deposited by low sinuosity braided streams the emergent parts of which are prime areas for aeolian deflation frequent floods and rapid lateral migration of precambrian humid climate fluvial systems probably restricted aeolianite deposition to arid paleoclimates thus the apparent anomaly may reflect non recognition and or non preservation of aeolianites and or variations in some aspect of sand sea formation and migration unique to the precambrian reconstruction of the hornby bay group aeolianites using recently developed criteria for their recognition suggests that the latter reason did not exert a strong influence

evaluation of cold water carbonates as a possible paleoclimatic indicator abstract the common belief currently shared by many geoscientists concerning the climatic interpretation of limestones is that a warm water environment is essential this concept is not necessarily true because the rate and extent of terrigenous sediment dilution rather than water temperature is the primary factor determining whether or not a limestone forms at nearshore or continental shelf depths because carbonate productivity is lowest in cold climates however caco3 abundance and the thickness of carbonate accumulations tend to be least at high latitudes in this regard present day continental shelves and beaches offer a poor model for comparing cold water and warm water carbonates because of the generally emergent continental tectonic framework recent eustatic sea level changes and the presence of ice caps at the modern poles typically the influence of climate on non reef continental shelf and beach environments cannot be clearly distinguished by the presence or absence of major taxonomic groups faunal diversity and equitability are more sensitive in this regard the absence of shelf depth inorganic carbonate precipitates micrite envelopes and peloids may also point to the cold water origin of a rock skeletal mineralogy and oxygen isotopes of certain unrecrystallized carbonates may be good paleoclimatic indicators however trace elements and physical textural attributes of the carbonate fraction are probably temperature insensitive previous studies of high latitude continental shelves have concentrated merely on the abundance of calcareous material and there is seemingly a disproportionate amount of information with respect to low latitude carbonate studies further research on cold water carbonates may open up new avenues for alternative paleoenvironmental and paleoclimatic interpretations

geochemistry of k rich alkaline lakes western sandhills nebraska usa abstract the alkali lakes region of the western sandhills nebraska has lakes that range in composition from freshwater to brine with tds exceeding 250 000 mg 1 an unusual geochemical feature of these lakes is the conservative behavior of k with concentrations exceeding 1 900 mmoles kg 86 000 mg 1 the lakes are dominantly na k co3 so4 cl and na k so4 co3 cl waters lakes occupy interdunal areas where there is little or no surface runoff groundwater primarily from locally derived precipitation is the principle source of water and solutes this origin for the source water contrasts with closed basin saline lake complexes where surface water from the adjacent areas flows directly into the lakes or recharges the groundwater system the principle geochemical process controlling lake chemistry is evaporative concentration other processes are operating but to a lesser extent these include mineral precipitation and dissolution and organically mediated sulfate reduction geochemical mass balance modeling indicates distinct differences in the amount of water that is required to be evaporated to produce the observed lake compositions these differences are related to the groundwater inflow to outflow ratio for individual lakes this emphasizes that although evaporation and related processes control the geochemical evolution the local hydrology of individual lakes regulates the extent to which these processes will proceed

marine like potash evaporite formation on a continental playa case study from chott el djerid southern tunisia abstract an exceptional flood in january 1990 led to the formation of a large ephemeral lake on the chott el djerid a salt playa in southern tunisia repeated observations made during 1990 show that the ephemeral lake underwent four evolutionary stages 1 initial flooding 2 evaporative concentration of lake waters 3 the movement of concentrated brine pools over the playa surface as a result of wind action and 4 total desiccation of the lake by september 1990 during all four stages the brine chemistry of the lake was monitored water inflow into the chott el djerid basin was found to have a consistent ca so 4 cl rich and hco 3 co 3 poor chemistry reflecting the recycling of homogeneous assemblages of cretaceous mio pliocene and quaternary evaporites within the catchment as the ephemeral lake shrank these waters produced an na mg k cl so 4 brine which was similar to modern sea water mineral saturation data show that during the desiccation of the lake saturation with respect to both gypsum and halite was achieved and that the most concentrated brines were ultimately saturated with respect to potash phases after the desiccation of the lake the main mineral phases found on the chott included gypsum and halite in addition ephemeral deposits of carnallite observed as carnallitite 3kmgcl 3 6h 2 0 nacl were found this assemblage is that which would be expected to form if the waters had undergone salt norm evaporation at 1 bar pressure at 25 c snorm in the evaporation model proposed by jones and bodine 1987 the nature of both the brine chemistry and evaporite mineralogy provides a new and rare example of marine like potash bearing evaporites being formed in a contemporary continental playa

chemical and boron isotope compositions of non marine brines from the qaidam basin qinghai china the general chemistry and boron isotope composition were investigated in fresh waters and hypersaline brines from the qaidam basin northern qinghai xizang tibet plateau china this basin is a large tectonically active system isolated from the ocean and composed of thick clastic and evaporite sediments the modern playas are subject to intense evaporation and are characterized by hypersaline brines as well as potash and borate evaporites the chemical composition of the dissolved solutes in the modern brines and waters reveals three main sources 1 inflow of hot springs enriched in sodium sulphate and boron evaporation of these waters leads to a high na cl ratio 1 a na cl so4 brine and an evaporite mineral assemblage of halite mirabilite borate lakes daqaidam and xiaoqaidam 2 inflow surface river waters which are modified by preferential dissolution of halite and potassium and magnesium salts characterized by a na mg cl solute type with low na cl 1 brcl licl and bcl ratios and 3 ca chloridic subsurface brines which are controlled by both salt dissolution and dolomitization processes evaporation and salt crystallization of mixtures of the latter two types leads to a marine like brine e g na mg cl type nacl ratio 1 and mineral assemblages similar to that predicted for progressive evaporation of seawater e g qarhan playa halite sylvite carnallite bischofite the 11 b values of the input waters to the qaidam basin range of 0 7 to 10 9 vs nbs 951 and brines from salt lakes 0 5 to 15 0 are similar to those of associated granitic rocks 11b 2 3 to 3 7 n 3 and hence indicate the non marine origin of these fluids the highest 11b values are associated with fluids with low bli ratios indicating selective removal of elemental boron and 10b by adsorption onto clay minerals the magnitude of 11b enrichment due to adsorption is 15 20 and thus non marine brines are well distinguished from marine derived brines 11b of 39 to 59 preserving the large isotopic difference 40 of their source waters it is proposed to use this distinctive isotopic signature for tracing the origin of ancient evaporite environments

the major ion composition of cenozoic seawater the past 36 million years from fluid inclusions in marine halite fluid inclusions from ten cenozoic eocene miocene marine halites are used to quantify the major ion composition mg2 ca2 k na so42 and cl of seawater over the past 36 my criteria used to determine a seawater origin of the halites include 1 stratigraphic sedimentologic and paleontologic observations 2 br in halite 3 34s of sulfate minerals 4 87sr 86sr of carbonates and sulfates and 5 fluid inclusion brine compositions and evaporation paths which must overlap from geographically separated basins of the same age to confirm a global seawater chemical signal changes in the major ion chemistry of cenozoic seawater record the end of a systematic long term 150 my shift from the ca2 rich mg2 and so42 poor seawater of the mesozoic cacl2 seas to the mgso4 seas with higher mg2 and so42 ca2 of the cenozoic the major ion composition of cenozoic seawater is calculated for the eocene oligocene 36 34 ma serravallian tortonian 13 5 11 8 ma and the messinian 6 5 ma assuming chlorinity 565 mmolal salinity and the k concentration 11 mmolal are constant and the same as in modern seawater fluid inclusions from cenozoic marine halites show that the concentrations of mg2 and so42 have increased in seawater over the past 36 my and the concentration of ca2 has decreased mg2 concentrations increased from 36 mmolal in eocene oligocene seawater 36 34 ma to 55 mmolal in modern seawater the mg2 ca2 ratio of seawater has risen from 2 3 at the end of the eocene to 3 4 and 4 0 respectively at 13 5 to 11 8 ma and 6 to 5 ma and to 5 in modern seawater eocene oligocene seawater 36 34 ma has estimated ranges of so42 14 23 mmolal and ca2 11 20 mmolal if the ca2 so42 product is assumed to be the same as in modern seawater 300 mmolal2 eocene oligocene seawater had ca2 16 mmolal and so42 19 mmolal the same estimates of ca2 and so42 for serravallian tortonian seawater 13 5 11 8 ma are so42 19 27 mmolal and ca2 8 16 mmolal and so42 24 mmolal and ca2 13 mmolal if the ca2 so42 product is equal to that in modern seawater messinian seawater has an estimated range of so42 21 29 mmolal and ca2 7 15 mmolal with so42 26 mmolal and ca2 12 mmolal assuming the ca2 so42 product is equal to that in modern seawater regardless of the estimation procedure so42 shows progressively increasing concentrations from 36 ma to the present values which are the highest of the cenozoic

depositional environments of marine dominated bedded halite permian san andres formation texas the interpretation of the depositional environments in which bedded halite is formed is a frontier of evaporite sedimentology facies studies supplemented by geochemical data define an evaporite shelf depositional environment for the halite of the san andres formation of the palo duro basin texas panhandle that is significantly different from modern and previously described ancient halite precipitating environments such as playas salinas sabkhas and barred basins a coastal palaeoenvironmental setting for the san andres halite is defined by its facies position between normal marine shelf carbonates and aeolian deposits the san andres brine pool extended over more than 10 000 km2 but was very shallow perennial brine pool conditions thick sequences of halite alternated with ephemeral brine pool conditions halite haloturbated mudstone halite mudstone interbeds and microkarst the depositional sequence in the perennial brine pool includes 1 flooding and minor dissolution of previously deposited halite 2 precipitation of a thin lamina of gypsum and 3 evaporation and precipitation of halite bottom growth forms of halite including chevrons and vertically elongated crystals are well preserved cumulates of foundered floating crystals and rafts were probably abundant but have been almost completely recrystallized mudstone interbeds in halite and microkarst features cut into bedded halite record the episodic interruption of brine pool deposition and the establishment of subaerial conditions vertically elongated karst pits originate at the palaeosurfaces cross cut primary brine pool fabrics and are filled with geopetal sediment and coarse halite cement mudstone interbeds and mixtures of mudstone and halite have been haloturbated by the alternating growth and dissolution of halite reflecting conditions of fluctuating salinity the geochemistry of halite from both ephemeral and perennial brine pool environments reflects the frequent influx of marine brine indicating that communication with the marine environments to the south was good considering that restriction was sufficient to precipitate halite

co2 h2s cos s8 alo oh bearing fluid inclusions in ruby from marble hosted deposits in luc yen area north vietnam abstract fluid inclusions have been studied in rubies from marble hosted deposits in the luc yen mining district north vietnam raman and infrared spectroscopy combined with microthermometry investigations on primary and secondary fluid inclusions provided evidence of co 2 h 2 s cos s 8 alo oh bearing fluids with native sulphur and diaspore daughter minerals without visible water diaspore appeared as a nonvisible film of 2 3 m coating the wall of the fluid inclusion cavity and native sulphur was generally nucleated during raman irradiation the presence of diaspore and cos in the fluid inclusions indicates that water was present in the paleofluid the mole fractions of h 2 o and co 2 are around 10 2 and the expected concentration of water in the fluid inclusions is in the 1 10 mol range crush leach identified sulphates and chlorides that are assigned to the presence of anhydrite and na ca cl salts found by sem in the ruby crystals the co 2 rich inclusions which do not coexist with an aqueous phase by immiscibility process demonstrate that ruby grew from this co 2 rich and water poor fluid at equilibrium with na ca cl salts thermal reduction of evaporitic sulphates based on an initial assemblage of anhydrite calcite and graphite originating from the metamorphism of organic matter is proposed to explain the original fluid chemistry of these marble hosted rubies the marbles acted as a closed system and the carbonic composition of the parent fluids in ruby indicates that aluminium can be transported in co 2 rich fluids at high p t

rise in seawater sulphate concentration associated with the paleoproterozoic positive carbon isotope excursion evidence from sulphate evaporites in the 2 2 2 1 gyr shallow marine lucknow formation south africa past oceanic sulphate concentration is important for under standing how the oceansredox state responded to atmospheric oxygen levels the absence of extensive marine sulphate evaporites before 1 2 gyr probably reflects low seawater sulphate and or higher carbonate concentrations sulphate evaporites formed locally during the 2 22 2 06 gyr lomagundi positive d 13 c excursion however the 2 2 2 1 gyr lucknow formation south africa provides the first direct evidence for seawater sulphate precipitation on a carbonate platform with open ocean access and limited terrestrial input these marginal marine deposits contain evidence for evaporite molds pseudomorphs after selenite gypsum and solid inclusions of ca sulphate in quartz carbon and sulphur isotope data match the global record and indicate a marine source of the evaporitic brines the apparent precipitation of gypsum before halite requires 2 5 mm l 1 sulphate concentration higher than cur rent estimates for the paleoproterozoic during the lomagundi event which postdates the 2 32 gyr initial rise in atmospheric oxygen seawater sulphate concentration rose from archean values of 200 lm l 1 but dropped subsequently because of higher pyrite burial rates and a lower oceanic redox state

paleoproterozoic stark formation athapuscow basin northwest canada record of cratonic scale salinity crisis abstract the paleoproterozoic stark formation a thick breccia unit formed during the transition from marine to non marine foreland basin fill in the athapuscow basin northwest territories canada four types of breccia occur in the stark formation 1 bedded breccias at the base of the unit overlying the basinal facies of the underlying pethei group are interpreted as debris flows 2 massive chaotic breccias occur in the lower part of the stark formation throughout the basin and these are interpreted to be evaporite collapse breccias 3 siltstone and mudstone breccia occurs in the upper part of the stark formation and is also interpreted as evaporite collapse breccia though much less evaporite was involved in its formation than the underlying chaotic breccia and 4 laminar accretionary breccia consisting of laminar carbonate clasts commonly with flat bottoms and convex up upper surface geometries these clasts occur in lenticular pods and are interpreted to form in caves following dissolution of evaporites or carbonates the widespread presence and abundance of evaporite pseudomorphs especially halite in all breccia types the stratigraphic restriction of the stark formation and irregular filling above this unit indicates that all but the bedded breccia formed by the dissolution and collapse of evaporites chaotic breccia directly above underlying pethei group shallow water and deep water carbonates indicates the evaporates formed across the platform and adjacent deep basin foundered megaclasts up to 1 5 km long and 40 m thick in basinal settings suggest cumulative evaporite thicknesses on the order of a few tens to a few hundreds of meters carbonate clasts in all the breccias contain abundant wave ripples planar laminations stromatolites and ooids these structures along with a paucity of subaerial exposure features indicates nearly all carbonate deposition in the stark was subaqueous thus by inference the evaporites in the stark formation were also partially subaqueous displacive halite pseudomorphs are common throughout all facies in the stark formation silicified and dolomite filled halite pseudomorphs are common along the contact between the evaporite collapse breccia and underlying carbonate platform pethei group and surrounding large clasts in basinal settings silicified hopper crystal casts within deep water rhythmites of the uppermost pethei group indicate precipitation of halite over deep waters gypsum pseudomorphs are exceedingly rare and anhydrite pseudomorphs were not observed the dominance of halite features in this basin and two penecontemporaneous basins kilihigok basin and wopmay orogen surrounding the slave craton suggests that relative to the present day seawater at 1 9 to 1 8 ga was oversaturated with respect to calcium carbonate had higher hco3 concentration and possibly was depleted in so42 the dearth of extensive thick bedded marine gypsum in the archean and early paleoproterozoic can be explained by low atmospheric oxygen content prior to 2 ga in conjunction with increased carbonate saturation before 1 6 ga

acid saline lake systems of the triassic mercia mudstone group county antrim northern ireland abstract the triassic mercia mudstone group of county antrim northern ireland is dominated by red beds and evaporites after only limited study both marine and continental environments have been proposed previously here we describe these rocks for the first time from core and petrographic observations to interpret depositional environments and conditions such as water depth salinity and aridity bedded halite bedded gypsum displacive halite and red siliciclastic mudstone lithologies comprise most 80 of the 591 6 m thick mercia mudstone group in the gaelectric carnduff 2 core bedded halite consists of chevron and cornet crystals indicating bottom growth from shallow surface brines bedded gypsum lithology is composed of halite replaced pseudomorphs after swallowtail bottom growth gypsum crystals both bedded halite and bedded gypsum contain dissolution features and are commonly overlain by mud drapes bedded halite and bedded gypsum lithologies are interpreted to have formed in shallow saline lakes influenced by flooding and evapoconcentration the displacive halite lithology is composed of sub cubic halite crystals randomly oriented in mudstone and represents deposition in a saline mudflat some mudstones contain ripple cross lamination dewatering structures mudcracks and rip up clasts suggesting shallow surface water and desiccation other mudstones are massive structureless and may have been deposited by wind both of these mudstone units were likely deposited in dry mudflats other red mudstones contain soil slickensides blocky peds and circumgranular cracks and are interpreted as paleosols our observations indicate that the triassic mercia mudstone group was formed by shallow perennial saline lakes and associated continental environments in an arid climate furthermore lack of carbonates lack of fossils and paucity of organic matter suggest acid saline lakes and groundwaters the triassic mercia mudstone group is similar to some other pangean red beds and evaporites therefore we hypothesize that the supercontinent was an arid barren landscape hosting acid saline lakes

the evolution of the lorraine evaporite basin implications for the chemical and isotope composition of the triassic ocean abstract during the upper triassic times about 75 m of halite with minor anhydrite was deposited in the lorraine basin samples of halite and sulfates were systematically collected from a borehole intersecting the sequence the chemical evolution of the original brine was investigated by x ray microanalysis of primary inclusions trapped in halite the original brines were of the na mg k ca cl type being consistent with the mineral association of halite and minor anhydrite their solute content can be reproduced by evaporation of present day ocean composition in an open basin however some modifications are required the inflow of a small excess of cacl 2 into the basin 1 2 to 1 9 of the total recharge is required to explain the low so 4 values analyzed in fluid inclusions the same inflow helps to explain more satisfactorily the low na and high cl contents the back reaction of the brine with previous ca sulfate that forms polyhalite could explain the low and variable k values analyzed the excess of ca with respect to present day seawater and the formation of so 4 poor evaporite sequences is the rule rather than the exception in the geological record we have not been able to assess the ultimate origin of the ca excess in the basin nevertheless the great variation of the so 4 content within short vertical distances centimeter scale suggests that these variations are due to processes taking place within the evaporite basin rather than to changes in the composition of the ocean at a global scale the isotopic composition of sulfur and oxygen was determined using samples of sulfates from the same borehole the 34 s values of 21 samples analyzed show a narrow variation 34 s 15 5 0 4 the 18 o values of eight samples analyzed show a wider range of variation 18 o 13 0 1 1 none of the processes which modify the values such as sulfate reduction or additional sulfate sources continental recycling of sulfates from the margins were clearly identified the values of 34 s sw 15 7 to 14 5 and 18 o sw 13 7 to 12 2 for the sulfate dissolved in the triassic ocean explain the values of the sulfates interbedded in the halite of the lorraine basin and most analyses reported in the literature

traces of evaporites in upper cretaceous lacustrine deposits of korea origin and paleoenvironmental implications abstract diverse types of halite and sulfate evaporite traces occur in the upper cretaceous lacustrine deposits of the jindong formation and the jangdong tuff in korea in which dinosaur tracks are common the halite traces usually occur as casts or moulds and they include traces of primary halite hoppers primary and intrasedimentary skeletal halite and intrasedimentary tiny halite the sulfate traces occur as intrasedimentary and displacive casts filled with sediments and sparry calcite and the casts occur as diverse modes from single crystal casts through nodular aggregates to massive aggregates some aggregates of the sulfate casts are aligned in crack pattern and selective occurrence of the laths in ripple troughs are observed soluble sulfate evaporite minerals such as gypsum glauberite or mirabilite are probable for the precursors of these traces these halite and sulfate traces are interpreted to have been formed in a saline lake and mudflats it is interpreted that meteoric water was responsible for the evaporite precipitation in the jindong lake and jangdong lake recycled brine produced by the repeated dissolution of evaporites might contribute to the evaporite precipitation in the paleo jindong lake and the paleo jangdong lake the development of saline lake deposits in the jindong formation and the jangdong tuff suggests that the southern part of the korean peninsula remained an inland continental area during the cretaceous resulting in semi arid paleoclimatic condition due to an orographic effect by the location of the korean peninsula on continental margin in mid latitude with topographic barriers during the cretaceous the occurrence of dinosaur tracks in the lake margin deposits of saline lake with frequent inflow of dilute meteoric water suggests that upper cretaceous dinosaurs inhabiting lakes on the korean peninsula might have drunken brackish water

new evidence for 250 ma age of halotolerant bacterium from a permian salt crystal the purported oldest living organism the spore forming bacterium virgibacillus sp perm ian strain 2 9 3 was recently cultured from a brine inclusion in halite of the 250 ma permian salado formation however the antiquity of virgibacillus sp 2 9 3 has been chal lenged it has been argued that the halite crystal and the fluid inclusion from which the bacterial spores were extracted may be younger than the permian salado salts here we report that brine inclusions from the same layer of salt that housed virgibacillus sp 2 9 3 are composed of evaporated late permian seawater that was trapped in halite cement crys tals precipitated syndepositionally from shallow groundwater brines at temperatures of 17 37 8c these results support the 250 ma age of the fluid inclusions and by inference the long term survivability of microorganisms such as virgibacillus sp 2 9 3

visible and near infrared 0 4 2 5 μm reflectance spectra of playa evaporite minerals visible and near infrared vnir 0 4 2 4 m reflectance spectra were recorded for 35 saline minerals that represent the wide range of mineral and brine chemical compositions found in playa evaporite settings the spectra show that many of the saline minerals exhibit diagnostic near infrared absorption bands chiefly attributable to vibrations of hydrogen bonded structural water molecules vnir reflectance spectra can be used to detect minor hydrate phases present in mixtures dominated by anhydrous halite or thenardite and therefore will be useful in combination with x ray diffraction data for characterizing natural saline mineral assemblages in addition vnir reflectance spectra are sensitive to differences in sample hydration state and should facilitate in situ studies of minerals that occur as fragile transitory dehydration products in natural salt crusts the use of spectral reflectance measurements in playa studies should aid in mapping evaporite mineral distributions and may provide insight into the geochemical and hydrological controls on playa mineral and brine development

assessing uncertainties in balanced cross sections abstract balanced structural cross sections are models that are fit to incomplete data the models are under constrained with respect to any particular two dimensional line length model but enough data generally exists to yield a well constrained area balance solution furthermore the area balance encompasses all possible line length solutions therefore where the primary objective of section balancing is the determination of horizontal shortening magnitude area balancing provides an analytical solution we use this analytical solution to develop a comprehensive robust analysis of the uncertainty in shortening estimates resulting from cross section balancing the analytical solution allows us to propagate errors formally on the input parameters stratigraphic thicknesses depth to decollement eroded hanging wall cutoffs through the equations and produce the resulting uncertainty on the magnitude of shortening balanced cross sections from the subandean belt of the central andes are used to demonstrate the relative importance of stratigraphy and eroded hanging wall cutoffs in the contribution to the overall error

chemical and stable isotopic compositions of proterozoic metamorphosed evaporites and associated tourmalines from the houxianyu borate deposit eastern liaoning china an integrated major element trace and rare earth element and stable isotope b si o and s study has been carried out on the houxianyu borate deposit eastern liaoning china the present day mineralogy of the deposit is closely similar to that of magnesian skarn deposits and the borates are underlain by granite however the geochemical and isotopic evidence does not favour a skarn type origin in particular the boron isotopic compositions of the borate minerals and associated tourmalines preclude their origin from fluids derived from the granite rather the data are compatible with the borate deposit being a metamorphosed evaporite the mineralogy and chemistry of the deposit are most compatible with a non marineorigin although the high 34s and 11b values suggest that there may have been some marine components to the evaporitic brines overall the premetamorphic origin of the houxianyu borate deposit is similar to that of the tertiary non marine evaporite borate deposits of western turkey there are also similarities with other proterozoic early rifting environments e g the upper proterozoic damaran orogen of south africa that have implications for the structural evolution and mineral potential of the region

precambrian non marine stromatolites in alluvial fan deposits the copper harbor conglomerate upper michigan laminated cryptalgal carbonates occur in the precambrian copper harbor conglomerate of northern michigan which was deposited in the keweenawan trough an aborted proto oceanic rift this unit is composed of three major facies deposited by braided streams on a large alluvial fan complex coarse clastics were deposited in braided channels predominantly as longitudinal bars whereas cross bedded sandstones were deposited by migrating dunes or linguoid bars fine grained overbank deposits accumulated in abandoned channels gypsum moulds and carbonate filled cracks suggest an arid climate during deposition stromatolites interstratified with these clastic facies occur as laterally linked drapes over cobbles as laterally linked contorted beds in mudstone as oncolites and as poorly developed mats in coarse sandstones stromatolites also are interbedded with oolitic beds and intraclastic conglomerates stromatolitic microstructure consists of alternating detrital and carbonate laminae and open space structures radialfibrous calcite fans are superimposed on the laminae the laminae are interpreted as algal in origin whereas the origin of the radial fibrous calcite is problematic the stromatolites are inferred to have grown in lakes which occupied abandoned channels on the fan surface standing water on a permeable alluvial fan in an arid climate requires a high water table maintained by high precipitation or local elevation of the water table possibly due to the close proximity of a lake occurrence of stromatolites in the upper part of the copper harbor conglomerate near the base of the lacustrine nonesuch shale suggests that these depositional sites may have been near the nonesuch lake

calcrete conglomerate case hardened conglomerate and cornstone a comparative account of pedogenic and non pedogenic carbonates from the continental siwalik group punjab india the occurrence of authigenic carbonates formed in three different environmental situations within the continental siwalik group has been used to compare the lithological and petrographic characters of the contrasted lithofacies the three lithofacies are 1 calcrete conglomerate 2 case hardened conglomerate 3 cornstone pedogenic nodular calcrete the calcrete conglomerate facies laterally intertongues with the channel conglomerates it consists of pisolites which are interpreted to have formed from carbonate rich spring waters emerging on to the gravelly substrate of dry abandoned channels the laminae characteristics of these pisolites are distinctly different from those of marine origin and also from comparable biogenic materials case hardened conglomerate occurs in the youngest part of the siwalik stratigraphic column in boulder conglomerates having limestone as the principal clast component this lithofacies has resulted from cementation of the conglomerate through continued dissolution and re precipitation of calcite by meteoric water downwards from the surface it displays a coarsely crystalline sparry calcite cement with no evidence for displacive growth or replacement by calcite cornstones nodular calcrete occur in several sedimentary cycles of the middle siwalik sub group these are immature and commonly associated with thinly bedded sandstones levee and red shales overbank this lithofacies is a result of concentration of carbonate through capillary action associated with pedogenic activity ooids developed in cornstone are essentially micritic in nature and usually composed of less than five indistinct laminae

sodium sulphate deposits of neogene age the kirmir formation beypazari basin turkey the evaporite member of the kirmir formation was deposited in shallow lacustrine environments during the upper miocene the most soluble minerals of this member can be currently observed in the cayirhan mine the evaporite member which is composed of secondary gypsum at outcrop can be subdivided into a bedded lower unit and a massive upper unit in the bedded lower unit most of the gypsum throughout the basin can be identified as having been transformed from glauberite in the glauberite layers of the cayirhan mine some glauberite textures clear glauberite suggest a primary subaqueous free precipitation on a depositional floor more common however are the glauberite textures indicating an interstitial growth within a clayey magnesitic matrix in the thenardite layers accompanying the glauberite in the cayirhan mine some disruption structures can be assigned to synsedimentary dissolution these structures together with the textures of the thenardite suggest that the original sodium sulphate was mirabilite thenardite being a secondary phase which formed during early to moderate burial diagenesis the massive upper unit in which evidence of sodium bearing minerals is absent is characterized by laminated to banded gypsum and nodular gypsum in the marginal areas of the evaporitic basin whereas thick clast supported gypsum breccias prevail in the northern deeper part of the basin the brecciation of these calcium sulphate layers occurred as a result of synsedimentary gravitative slumping under tectonic control although the sulphur isotopic values d 34 s of the sulphates of the kirmir formation suggest a marine derived brine supply the oxygen isotopic values d 18 o and the strontium ratios 87 sr 86 sr do not support such a supply the origin of the mother brines the glauberite genesis the depositional model of the sodium sulphates and the salinity evolution are discussed d 2002 elsevier science b v all rights reserved

a model to estimate the depositional brine depths of ancient halite rocks implications for ancient subaqueous evaporite depositional environments a model is derived which allows a more general approach to the interpretation of bromine profiles in halite rocks than is possible with the models of kuhn or holser allowing for an open system with influx and reflux reduces the depth of brine necessary to generate a given salt deposit even very small and regular bromine gradients which historically have been interpreted as the result of deposition from deep brine bodies can be generated in an open system from brine no more than a few tens of metres deep the bromine gradient produced from a given depth of brine is strongly dependent on the composition and amount of influx but less so on the composition of brine already in the basin a zechstein profile is analysed which in a closed basin would require brine 2665 m deep it can equally be modelled by influx of normal seawater which fully replenishes a basin no more than 140 m deep a somewhat irregular profile from the paradox basin instead of requiring a basin 100 400 m deep can be modelled as being produced by deposition from brines only 10 m deep reflux in both cases can only be a few per cent of influx at a maximum

using strontium isotopes to determine the age and origin of gypsum and anhydrite beds the variation of 87sr 86sr in seawater with time can be used to determine the age of calcium sulfate beds precipitated from brine derived from seawater the determination of a marine origin can be established by the consistency of strontium isotope results from samples at different stratigraphic levels in a single gypsum anhydrite bed collected at separated sites the scatter of strontium isotope results in the gypsum anhydrite samples examined here is interpreted to result from the contribution of meteoric strontium to the salina strontium isotope results from three evaporite settings the jurassic todilto formation from new mexico the permian blaine formation from blaine county oklahoma and the permian salado formation from new mexico are used to determine the age and origin of the parent brine for these gypsum anhydrite beds the calcium sulfate beds from each of these formations precipitated from salinas that originated with a marine flooding but show at different times and localities volume do

epitaxial salt reefs and mushrooms in the southern dead sea salt usually accumulates in shallow ephemeral brines as simple flat beds however in permanent brines deepening in solar evaporation ponds in the southern dead sea salt accumulation is complicated by the growth of isolated vegetable like salt structures

anisotropic behaviour of white macael marble used in the alhambra of granada spain the role of thermohydric expansion in stone durability abstract one of the most commonly used marbles in spain is white macael marble quarried in the macael area of almeria throughout spanish history white macael has been in great demand as an ornamental stone and was used to build pieces of great importance and artistic beauty such as the fountain of lions in the alhambra granada over the centuries such pieces have suffered from decay due to exposure to the elements as has happened in many other marbles all over the world the main purpose of this paper was to determine the durability of white macael marble when subjected to changes in thermal conditions it was observed that these changes in the presence of humidity were an important factor in marble decay they produce a progressive loss of cohesion along grain boundaries and an increase in porosity which are starting points for marble degradation and facilitate the development of other pathologies

sulfate minerals in evaporite deposits evaporite deposits preserve a wealth of information on earth s past surface conditions the deposits are sensitive indicators of depositional environment and climate recorded in a wide variety of mechanically and chemically produced sedimentary structures and fabrics unique to evaporite deposits is the record they carry of the hydrochemistry of surface waters including seawater sulfate minerals are important components in understanding the hydrochemistry of ancient surface waters sedimentological aspects of evaporite deposits were compiled by melvin 1991 in the compilation sedimentology specific to ca bearing sulfates was described by warren 1991 lowenstein and hardie 1985 handford 1991 and smoot and lowenstein 1991 discussed the sedimentology of evaporites in general these general principles can be applied specifically to the sulfate minerals in evaporite deposits sedimentological aspects of sulfate minerals in evaporite deposits are not discussed here for this information the reader is referred to the above references hardie et al 1985 and spencer and lowenstein 1988 discussed the petrography of evaporites and the interpretation of fabrics of evaporite minerals examples of petrographic aspects of sulfate minerals in evaporites are presented here along with references specific to the sulfate minerals for a more complete understanding of these aspects the reader is referred to the above references the major focus of this chapter is on the chemical aspects of the common sulfate minerals that occur in evaporite deposits the discussion begins with an explanation of the concept of chemical divides and the determination of evaporation paths and the evolution of brines in accordance with mineral solubility and the composition of dilute inflow waters determination of the precipitation pathways of the more soluble salts is more complex examples of sulfate mineral assemblages in evaporation systems calculated via thermochemical modelling are given for both marine and non marine systems the mineralogy of evaporite deposits is

boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites boron isotope ratios 11b 10b have been measured on 60 tourmaline separates from over 40 massive sulfide deposits and tourmalinites from a variety of geologic and tectonic settings the coverage of these localities is global 5 continents and includes the giant ore bodies at kidd creek and sullivan canada broken hill australia and ducktown usa overall the tourmalines display a wide range in 11b values from 22 8 to 18 3 possible controls over the boron isotopic composition of the tourmalines include 1 composition of the boron source 2 regional metamorphism 3 water rock ratios 4 seawater entrainment 5 temperature of formation and 6 secular variations in seawater 11b the most significant control appears to be the composition of the boron source particularly the nature of footwall lithologies variations in water rock ratios and seawater entrainment are of secondary importance the boron isotope values seem especially sensitive to the presence of evaporites marine and non marine and carbonates in source rocks to the massive sulfide deposits and tourmalinites

a depositional model for the terminal neoproterozoic early cambrian ara group evaporites in south oman six evaporite carbonate sequences are recognized in the terminal neoproterozoic early cambrian ara group in the subsurface of oman individual sequences consist of a lower evaporitic part that formed mainly during a lowstand systems tract overlying platform carbonates contain minor amounts of evaporites and represent transgressive and highstand systems tracts detailed sedimentological and geochemical investigation of the evaporites allowed reconstruction of the depositional environment source of brines and basin evolution at the beginning of the evaporative phase prograding succession a shallow water carbonate ramp gradually evolved into a series of shallow sulphate and halite salinas minor amounts of highly soluble salts locally record the last stage of basin desiccation this gradual increase in salinity contrasts sharply with the ensuing retrograding succession in which two corrosion surfaces separate shallow water halite from shallow water sulphate and shallow water sulphate from relatively deeper water carbonate respectively these surfaces record repeated flooding of the basin dissolution of evaporites and stepwise reduction in salinity final flooding led to submergence of the basin and the establishment of an open water carbonate ramp marine fossils in carbonates and bromine geochemistry of halite indicate a dominantly marine origin for the brines the ara group sequences represent a time of relatively stable arid climate in a tectonically active basin strong subsidence allowed accommodation of evaporites with a cumulative thickness of several kilometres while tectonic barriers simultaneously provided the required restricted conditions subsidence allowed evaporites to blanket basinal and platform areas the study suggests a deep basin shallow water model for the evaporites

stratigraphy and sedimentary petrology of an archean volcanic sedimentary succession at mt goldsworthy in the pilbara block western australia implications of evaporite nahcolite and barite deposition abstract a approximately 3 3 ga sedimentary succession at mt goldsworthy in the northeastern pilbara block australia contains beds composed of silicified pseudomorphs of nahcolite nahco3 or barite baso4 this sedimentary succession correlates with the corboy formation and consists of lower middle and upper sedimentary units which conformably overlie mafic to ultramafic volcanic and volcaniclastic rocks the lower and middle units are predominantly siliciclastic whereas the upper unit is characterized by ferruginous cherts and banded iron formations with minor proportions of intercalated mature sandstone the succession defines an overall upward fining and deepening trend the detrital materials were derived from older greenstone successions volcaniclastics and reworked precipitative beds silicified pseudomorphs of nahcolite crystals up to 40 cm in length occur in a 20 m thick bed in the upper portion of the lower unit the formation of this unit was initiated by deposition of immature terrigenous clastic sediments and followed by the precipitation of nahcolite from na hco3 brines in a closed or semi closed evaporitic basin bladed barite deposits occur mainly in the middle unit which was deposited in a sub aerial to shallow marine environment barite may have precipitated as a result of mixing of so42 rich seawater and ba2 rich hydrothermal fluids the mt goldsworthy sedimentary succession records an archean shallow to sub aerial sedimentary environment that probably developed in a continental margin setting

oil shales evaporites and ore deposits abstract the relationships between oil shales evaporites and sedimentary ore deposits can be classified in terms of stratigraphic and geochemical coherence oil shale and black shale deposition commonly follows continental red beds and is in turn followed by evaporite deposition this transgressive regressive sequence represents an orderly succession of depositional environments in space and time and results in stratigraphic coherence the amount of organic carbon of a sediment depends on productivity and preservation both of which are enhanced by saline environments work on great salt lake utah allows us to estimate that only 5 of toc originally deposited is preserved inorganic carbonate production is similar to toc production but preservation is much higher oil shales and black shales commonly are enriched in heavy metals through scavenging by biogenic particles and complexation by organic matter ore deposits are formed from such rocks through secondary enrichment processes establishing a geochemical coherence between oil shales and ore deposits the permian kupferschiefer of n europe is used as an example to define a kupferschiefer type kst deposit here oxygenated brines in contact with red beds become acidified through mineral precipitation and acquire metals by dissolving oxide coatings oxidation of the black shale leads to further acid production and metal acquisition and eventually to sulfide deposition along a reducing front in order to form ore bodies the stratigraphic coherence of the red bed black shale evaporite succession must be joined by the geochemical coherence of the ore body evaporite black shale association the cretaceous cu zn deposits of angola the zambian copperbelt as well as the creta oklahoma deposits are other kst examples in the zambian copperbelt evaporites are indicated by the carbonate lenticles thought to be pseudomorphs after gypsum anhydrite nodules mvt deposits are also deposited by acid brines but at more elevated temperatures and with carbonates as principal host rocks the pine point deposits are cited for their close association with evaporites alkaline metal rich brines are postulated for the hyc deposit of mcarthur river australia such brines are known from the green river formation and deposits formed from such brines constitute the grt class they can be recognized by the presence of magadi type cherts and zeolite analcime k spar tuffs the cu co ore bodies of outokumpu finland might also belong to this type a new classification of sedimentary ore deposits is proposed based on their geochemical environment kst and mvt are formed from acid ore fluids while grt and ct creede type are derived from basic ore fluids ph of the fluids is best evaluated not from the ores themselves but from their effect on the host rocks

great salinity anomalies in the north atlantic abstract we revisited the great salinity anomaly of the 1970s gsa 70s dickson et al 1988 and documented the newly identified great salinity anomaly of the 1980s hence termed gsa 80s both propagated around the north atlantic in a similar fashion the advective mechanism initially proposed to explain the observed sequence of low salinity low temperature events during the gsa 70s apparently holds also for the gsa 80s the latter was successively observed in the west greenland current 1982 the labrador current 1983 the flemish pass 1984 near the charlie gibbs fracture zone 1984 1985 in the rockall channel 1985 south of iceland 1985 1988 in the north sea 1986 1987 norwegian sea 1987 1988 barents sea 1988 1989 and iceland sea 1989 1990 the advection speed of the gsa 80s seems to be greater than the one of the gsa 70s the 1980s anomaly reached the barents sea 6 to 7 years after peaking in the west greenland current while the 1970s anomaly traveled the same route in 8 to 10 years these anomalies however seem to be of different origin the gsa 70s was apparently boosted remotely by a freshwater sea ice pulse from the arctic via fram strait consequently the gsa 70s was accompanied by a large sea ice extent anomaly in the greenland and iceland seas which propagated into the labrador sea in contrast the gsa 80s was likely formed locally in the labrador sea baffin bay mainly because of the extremely severe winters of the early 1980s but supplemented with a possible contribution of the arctic freshwater outflow via the canadian archipelago facilitated by strong northerly winds which would have enhanced stability and ice formation this anomaly was also associated with a positive sea ice extent anomaly in the labrador sea baffin bay which however had no upstream precursor in the greenland sea thus the gsas are not necessarily caused solely by an increased export of freshwater and sea ice from the arctic via fram strait these results are corroborated by the early 1990s data when a new fresh cold anomaly was formed in the labrador sea and accompanied by a large positive sea ice extent anomaly the harsh winters of the early 1990s were however confined to the labrador sea baffin bay area while the atmospheric and oceanic conditions in the greenland iceland and irminger seas were normal the labrador sea baffin bay area appears therefore to play a key role in formation of gsas as well as in propagation of the gsas formed upstream a likely contribution of the enhanced canadian archipelago freshwater outflow to the gsa formation also seems to be significant two major modes of the gsa origin are thus identified remote generated by an enhanced arctic ocean freshwater export via either fram strait or the canadian archipelago and local resulting from severe winters in the labrador sea baffin bay both modes should be taken into account to model decadal variability of the coupled ocean ice atmosphere system in the north atlantic arctic basin

concretions in glacial sediments at seglvatnet norway abstract concretions in pleistocene glacial sediments at seglvatnet norway include a wide variety of forms the simplest of which apparently reflects relatively uniform growth rates in different directions the preferred orientation of others may be associated with water movement through the sediments concretion shape generally is influenced by the grain size and bedding of the enveloping sediments some concretions may have formed during or soon after deposition of the sediments others are forming at present

saline groundwater in israel its bearing on the water crisis in the country abstract one of the major causes for the deterioration of water quality bearing heavily on the water crisis in israel is the ongoing contamination of its water resources by saline water bodies the present paper reviews the geochemical processes forming saline water lists and explains certain chemical and isotopic parameters which enable understanding these processes and describes the saline groundwater bodies and various salinization phenomena occurring in the country s various aquifers deterioration of groundwater in israel is caused by numerous natural processes such as encroachment of sea water migration of connate highly pressurized brines penetrating into fresh groundwater by subsurface dissolution of soluble salts originating in surrounding country rocks and by water rock interaction in addition to sea water two saline water bodies were identified as the main factors causing salinization of fresh groundwater a ca chloride brines encountered in the jordan dead sea rift valley in various parts of the negev and of the coastal plain and b na chloride saline water identified in the subsurface of the negev and in the southern part of the coastal plain intensive exploitation of groundwater in israel has disturbed the natural equilibrium which prevailed between fresh and saline water the newly established groundwater flow regimes have facilitated the migration of saline water bodies their participation in the active hydrological cycle and the progressive contamination of fresh groundwater these processes which were not anticipated by planners and water resources managers emphasize that large scale groundwater exploitation was undertaken without giving sufficient consideration to the occurrence and subsurface migration of saline water and brines

evaporites marine or non marine division of evaporites into those types that retain information about primary mineralogy textures and structures primary evaporites and those types so extensively altered that few or no primary features remain secondary evaporites only primary evaporites can give unequivocal data bout their marine or non marine origin to help evaluate such primary deposits they have been further divided using the following attributes 1 whether the depositional setting was marine or non marine 2 whether the source water was a seawater b meteoric c hydrothermal d diagenetic e volcanogenic or f mixed specific criteria for making distinctions are 1 kinds of fossils 2 sedimentology of the associated non saline facies 3 kinds of primary saline minerals 4 association of such saline minerals both in qualitative and quantitative terms 5 trace element isotope and fluid inclusion geochemistry of such saline minerals modified journal abstract

an overview of physical processes in the north water the presence of a polynya strongly affects biological processes by influencing underwater light levels water column stratification the upwelling of nutrients and the timing of production cycles an overview of the existing literature on the oceanography meteorology and sea ice conditions of the north water a large recurring polynya in northern baffin bay is presented the north water is influenced by a cold inflow of arctic ocean water from the north and in some areas a warmer inflow of atlantic water from the south earlier observations and modeling studies suggested that both wind and ocean advection of sea ice as well as heat input to the surface waters by either upwelling or mixing were responsible for the formation and maintenance of the polynya recent data indicate the north water to be primarily generated by the southward drift of ice by winds and currents as opposed to melting ice by sensible heat input over large areas localized sensible heat effects occur in fall winter and spring along the greenland side of the polynya

evaluating seawater chemistry from fluid inclusions in halite examples from modern marine and nonmarine environments fluid inclusions from marine halites have long been studied to determine the chemical composition of ancient seawater chemical analyses of the major ions in fluid inclusions in halites from the solar saltwork of great inagua island bahamas and from the supratidal sabkha baja california mexico show that modern marine halites faithfully record the chemical signature of seawater the major ions in great inagua and baja california fluid inclusions display distinctive linear trends when plotted against one another ie na k and so42 vs mg2 and cl which track the evaporation path of seawater as it evolved during the crystallization of halite these evaporation paths defined for the major ions by fluid inclusions in halite overlap findings of computer simulations of the evaporation of modern seawater by the harvie moller and weare hmw computer program the close match between the hmw seawater evaporation paths and the great inagua fluid inclusion data is not surprising considering the carefully controlled inflow evaporation and discharge of seawater at the great inagua saltwork the major ion chemistry of fluid inclusions from the baja california halites matches the hmw seawater evaporation paths in most respects but one baja fluid inclusion has lower concentrations of mg2 than evaporated seawater nonmarine inflows and syndepositional recycling of preexisting salts in the baja california supratidal setting were not large enough to override the chemical signature of evaporating seawater as the primary control on the baja fluid inclusion compositions fluid inclusions in halites from the nonmarine qaidam basin qinghai province western china have a distinctly different major ion chemical signature than does global seawater the fluid inclusion chemistries from the qaidam basin halites do not lie on the evaporation pathways defined by modern seawater and can clearly be differentiated from fluid inclusions containing evaporated seawater if fluid inclusions in halites from modern natural settings contain unmistakable samples of evaporated seawater then evaluation of the chemistry of ancient seawater by chemical analysis of fluid inclusions in ancient marine halites by means of the same approach should be valid

displacement efficiency of faults and fractures discussion abstract higgs and williams present a kinematic classification of one event faults it is our contention that the new terms which they propose are misleading and that the conclusions drawn cannot be reconciled with the findings of earthquake seismologists

hydrochemical evolution of regional groundwaters to playa brines in central australia abstract a large scale groundwater system in central australia discharges to a chain of playas recharge in calcrete and fractured rock aquifers gives rise to relatively low salinity hco 3 cl so 4 groundwaters which evolve through regional saline groundwaters to highly saline playa brines the hydrochemical evolution of the groundwaters follows the anionic sequence hco 3 cl so 4 cl bhco 3 so 4 cl so 4 hco 3 cl so 4 cl with increasing salinity there is a relative increase in na k mg cl and so 4 however there is a relative decrease in hco 3 ca and sio 2 owing to the precipitation of carbonate sulphate and silicate minerals and the resultant brines are depleted in these ions significant chemical variation in the composition of playa brines is a result of complex processes of solution evaporative concentration precipitation and mineralogical change including dolomitisation thermodynamic calculations based on the pitzer equations have enabled a general model to be developed for these evolutionary processes in saline groundwaters up to the stage of halite saturation at an early stage the regional groundwaters are saturated with respect to the carbonate minerals dolomite first then calcite with increasing salinity sulphate minerals begin to precipitate saturation with respect to gypsum is attained at a chlorinity of 19 and saturation with respect to anhydrite is attained at 122 the playa brines attain saturation with respect to halite at a chlorinity of 144 solute budgets based on a chloride concentration factor show that final playa brines are 178 times more concentrated than recharge groundwaters and confirm the virtually complete loss of hco 3 ca and sio 2 through precipitation there are subtle differences in the hydrochemistry of different central australian playa brines and also vis a vis playa brines described from other parts of the world most australian playas have brines of the cl na type with so 4 and mg also important the generally accepted hardie eugster model for brine evolution and mineral precipitation sequences has therefore been modified and extended three pathways are defined following calcite precipitation on the basis of the ratio of molar ca to alkalinity these pathways lead to saline waters with different compositions subsequent evolution of the brines depends on the ratios between molar so 4 mg ca and alkalinity

the association of sulphate evaporites stromatolitic carbonates and glacial sediments examples from the proterozoic of australia and the cainozoic of antarctica abstract carbonate sediments are often considered diagnostic of warm water environments and thus the occurrence of dolomite and limestone beds within and immediately overlying many late proterozoic glacial deposits tillites has long been a source of controversy stromatolites are also conventionally thought to be warm water indicators we describe two examples of stromatolitic dolomite occurring together with barite at the top of late proterozoic glacial sequences in the amadeus and ngalia basins of central australia problems of interpretation may be largely resolved after examination of published data on antarctic lakes antarctic lakes of high salinity occupy enclosed glacial basins in both the vestfold hills and the taylor and wright dry valleys lake bonney is the most comprehensively described example carbonate sediments sulphate evaporites and even stromatolites are common components of cold arid climate lakes the stromatolitic mats and their constructing cyanobacteria are similar to those described from warmer climates the tundra plains and lakes and coastal lagoons of northern canada and siberia are better geomorphic analogues for the proterozoic deposits and these too seem to contain analogous sediments but only brief descriptions are available we suggest that environments such as these provide modern analogues of the association of proterozoic glacial sediments with carbonates evaporites and stromatolites

paleoclimatology of nonacho basin early proterozoic northwest territories canada abstract numerous features of paleoclimatic significance are preserved in terrestrial strata of nonacho basin early proterozoic minimal chemical weathering is indicated by relic corestones grus and talus and the absence of chemical alteration zones at the basal unconformity humid conditions are indicated by 1 dominance of siliciclastic lacustrine deposits even in lakes that had restricted drainage 2 paucity of caliche in extensive alluvial fan deposits 3 near absence of debris flows in alluvial fan deposits 4 absence of large scale high angle cross stratification in eolian deposits and 5 penecontemporaneous variegated redbeds drab sandstones red mudstones minimal chemical weathering under humid conditions implies a cold climate this is supported by published paleomagnetic data humid conditions implies a cold climate this is supported by published paleomagnetic data which indicate that nonacho basin probably formed at paleolatitudes of 40 55 by talus deposits formed as a result of frost action and by penecontemporaneous stratiform sandstone breccias for which the early cementing agent probably was ice high elevations probably contributed to the low temperatures the nonacho group probably was deposited in a moist continental climate with cold winters characterized by repeated freeze thaw cycles local chemically precipitated lacustrine sediments and caliche indicate brief dry intervals

sedimentology of ancient saline pans an example from the permian opeche shale williston basin north dakota u s a abstract the mid permian opeche shale of north dakota consists of bedded evaporites and red bed siliciclastics detailed core and petrographic study has documented sedimentary and early diagenetic features in order to develop a depositional model and to refine paleoclimatic data and paleogeographic setting for the late paleozoic of the u s midcontinent lithologies and sedimentary features indicate lacustrine distal alluvial and minor eolian deposition subaerial exposure and soil formation bedded halites consisting of chevron and cumulate crystals dissolution surfaces and pipes and mudcracked microcrystalline salt crusts were deposited in a saline pan dominated by flooding evaporative concentration and desiccation bedded halites containing chevron and cumulate crystals but lacking any dissolution or desiccation features formed in perennial saline lakes chaotic halite composed of red mudstone and siltstone with displacive halite crystals represents saline mudflat deposits red mudstone and siltstone with little or no displacive halite but with abundant cracks and root features suggest deposition in a dry mudflat red bed sandstones and conglomerates composed of poorly sorted subrounded quartz grains cemented with halite indicate distal alluvial deposition with possible transport by ephemeral streams sheet floods and debris flows most deposition took place in halite dominated shallow perennial and ephemeral saline lakes surrounded by saline and dry mudflats evaporation desiccation flooding and wind played significant roles in this environment therefore the opeche evaporites and red beds are representative of an ancient saline pan system an inland playa setting is favored as a depositional model for the opeche shale the abundance of soil features and halite dominance as well as lack of nearshore carbonates and lack of restricted marine fossils suggest a closed basin nonmarine setting for the mid permian of the u s midcontinent

stable chlorine isotopes in phanerozoic evaporites abstract modern seawater has a uniform 37cl value 0 0 with an exception in the upper current of the bosphorus 0 4 marine halite ranging in age from cambrian to miocene has 37cl values of 0 0 0 9 with most of the data in the range 0 0 0 5 mean 37cl values differ measurably between basins with no evident relationship to basin size or to age smaller evaporite bodies have the largest 37cl ranges potash facies halite has mean 37cl values lower than those of halite facies salt in the east siberia and zechstein basins the bulk 37cl of bedded halite preserving sedimentary textures cannot be shifted measurably after deposition under plausible natural conditions during the phanerozoic a detectable change in the 37cl values of the oceans is unlikely as a result of cl fluxes to and from the mantle and evaporites in halite the values of 37cl that cannot be explained by fractionation occurring on crystallization are best explained by the addition of non marine cl with 37cl 0 0 to evaporite brine

comment on the papers by large salt accumulations as a consequence of hydrothermal processes associated with wilson cycles a review part 1 and 2 abstract the geological model of large hydrothermal salt accumulations linked to wilson cycles as reviewed by hovland and coworkers un adequately addressed 1 the lack of well exposed submarine volcanogenic hydrothermal feeder zone 2 the sequential precipitation of different hydrothermal evaporite minerals and 3 the absence of hydrothermal alteration mineralogy around the major evaporites these aforementioned points are the main classical features to be linked to the hydrothermal model of evaporites experimentally heating seawater during submarine volcanism firstly results in precipitation of anhydrite followed by halite other evaporite minerals serpentine brucite talc metallic sulfides oxides and related hydrothermal alterations in this regard mg ca cl mg ca so4 mg ca na cl and mg ca tds biplots show that hydrothermal brines of riftogenic and subduction zone settings plot in a separate field than the subduction related andean salars as well as seawater this indicates that the hydrothermal serpentinization of basaltic oceanic crust and mantle peridotites removes magnesium from seawater and incorporates the mg into serpentine brucite and other hydrous mg silicates rather than the hydrothermal brines finally our comment arose from a recent global classification of the most distinguished marine non marine and exhalative hydrothermal evaporites

halite cementation and carbonate diagenesis of intra salt reservoirs from the late neoproterozoic to early cambrian ara group south oman salt basin late neoproterozoic to early cambrian carbonates of the ara group form important intra salt stringer reservoirs in the south oman salt basin differential loading of thick continental clastics above the six carbonate to evaporite cycles of the ara group led to the formation of salt diapirs encasing a predominantly self charging hydrocarbon system within partly highly overpressured carbonate bodies stringers these carbonates underwent a complex diagenetic evolution with one stage of halite cementation in a shallow early and another in a deep late burial environment early and late halite cements are defined by their microstructural relationship with solid bitumen the early phase of halite cementation is post dated by solid reservoir bitumen this phase is most pervasive towards the top of carbonate stringers where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics bromine geochemistry revealed significantly higher bromine contents up to 280 p p m in the early halite compared with the late halite 173 p p m the distribution patterns and the high bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval later in burial history relatively small quantities of early halite were dissolved locally and re precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements late halite cement also seals fractures which show evidence for repeated reopening initially these fractures formed during a period of hydrothermal activity and were later reopened by a crack seal mechanism caused by high fluid overpressures porosity plugging by early halite cements affects the poroperm characteristics of the ara carbonates much more than the volumetrically less important late halite cement the formation mechanisms and distribution patterns of halite cementation processes in the south oman salt basin can be generalized to other petroliferous evaporite basins

structural evolution of continental and marine permian rock salt of the north german basin constraints from microfabrics geochemistry and u pb ages analyzing the dynamics of microstructural response on natural deformation in rock salt we present microfabric ebsd geochemical and u pb data obtained from permian salt formations of the kiel honigsee salt wall in northern germany the samples were recovered from deep drillings which penetrated through an overturned rock salt sequence of both rotliegend and zechstein deposits the bromide concentration in halite indicates a continental and marine origin for the rotliegend and zechstein deposits respectively despite intense deformation relics of early diagenetic fabrics are still preserved deformation of the impure rotliegend rock salt was accommodated by pressure solution and hydrofracturing as is indicated by the microfabrics and bromide concentration in halite fractures in siliciclastic domains were filled with fibrous halite and deformed by subgrain rotation recrystallization sgr fluid rich zechstein rock salt on the other hand was deformed by formation of subgrains and grain boundary migration gbm the distribution of mineral phases and fluids had a significant impact on the fabric evolution and on strain localization u pb dating of carbonate phases of the rotliegend sequence yielded permian depositional ages and jurassic to cretaceous deformation ages the latter related to diapiric ascent the combination of results traces a dynamic evolution of the rock fabric inside the diapir structure driven by locally active deformation processes that can be correlated with early stages of halite deposition and diagenesis and syntectonic fabric reorganization related to diapirism in an extensional setting

ocean acidification in the three oceans surrounding northern north america 1 the uptake of anthropogenic co2 drives ocean acidification with attendant effects on the saturation state of calcium carbonate and marine ecosystems here we examine ocean acidification within the context of large scale water mass exchange and local physical and biogeochemical processes along a section around northern north america waters in the north pacific are preconditioned by the global scale circulation to be low source waters and as they move northward across the bering and chukchi seas they are modified by biological activity these waters then enter the canada basin and canadian arctic archipelago where cooling river discharge sea ice formation and biological activities modify water mass characteristics further continuing eastward into baffin bay relatively low waters extend from the surface to depth due to remineralization changes in are large along this pathway and the response of local marine ecosystems will likewise be shaped by the biogeography of species occupying a given region

in situ evidence for an ancient aqueous environment at meridiani planum mars sedimentary rocks at eagle crater in meridiani planum are composed of fine grained siliciclastic materials derived from weathering of basaltic rocks sulfate minerals including magnesium sulfate and jarosite that constitute several tens of percent of the rock by weight and hematite cross stratification observed in rock outcrops indicates eolian and aqueous transport diagenetic features include hematite rich concretions and crystal mold vugs we interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history the environmental conditions that they record include episodic inundation by shallow surface water evaporation and desiccation the geologic record at meridiani planum suggests that conditions were suitable for biological activity for a period of time in martian history

bromine geochemistry of salar de uyuni and deeper salt crusts central altiplano bolivia abstract the salar of uyuni in the central bolivian altiplano is probably the largest salt pan in the world 10 000 km 2 a 121 m deep well drilled in the central salar disclosed a complex evaporitic sequence of 12 salt crusts separated by 11 mud layers in the lower half of the profile thick halite beds alternate with thin mud layers the mud layers thicken upwards and show clear lacustrine features the thickness of the salt beds decreases markedly from the base upward the bromine content of the halite ranges from 1 3 to 10 4 mg kg the halite does not originate from the evaporation of the dilute inflow waters of the altiplano which would lead to br content of tens of mg kg the presence of halite of very low br content 2 mg kg in a gypsum diapir strongly suggests that most of the halite deposited at uyuni originated from the leaching of ancient salt formations associated with the numerous gypsum diapirs of the altiplano the deep and thick halite beds were probably deposited in a playa lake as suggested by their very low and fairly constant br content 1 6 2 3 mg kg and by the abundance of detrital minerals thereafter perennial salt lakes of increasing duration flooded the central altiplano increasing amounts of dilute inflow waters of low cl br ratio and the exhaustion of diapiric halite lead to an increase of both the thickness of the lacustrine layers and of the bromine content of the salt crusts 5 10 mg kg deposited as the lakes dried up paleolake levels in the central altiplano rose as those in the northern altiplano the titicaca basin were simultaneously falling the progressive fluvial erosion of the threshold between the northern and the central altiplano lowered the levels of the northern lakes and allowed more dilute waters of low cl br ratio to flood the central altiplano therefore both the thickness of lacustrine sediments and the bromine content of the salt crust increased to the present the three upper crusts show a decrease in bromine content which may reflect a recent modification of the inflow regime to the last lakes the salt crust deposited by the last salt lake 10 000 years ago shows a bromine distribution that unexpectedly increases with depth as the lake dried the salt crust was probably initialy distributed over a wider area than the present flat crust covering the topographic surface up to the level of the lake where halite reached saturation the dissolution of the initial salt of low br content from the margins of the lake to the center is probably responsible for the observed br distribution in the surface salt as in a playa during the holocene a severe drought hit the altiplano and drastically lowered the intracrustal brine table within the salt crust leaving a thin layer of high concentrated residual brine at the bottom of the crust bromine rich halite replaced primary halite by a temperature activated mechanism in the lower crust further increasing the br gradient with depth

the origins of the mengye potash deposit in the lanping simao basin yunnan province western china abstract the lanping simao basin lsb is a mesozoic cenozoic continental margin rift basin in western china it formed during the opening and closing of the tethys ocean this basin is also known as a metal belt as it hosts several metal deposits besides the mengye potash deposit however the exact dates of the formation either in the paleocene or the cretaceous and thus the origins of the marine continental or mixed origins of the mengye deposits remain disputed based on the basin s evolution materials of marine origin and or remnant seawater should be present but instead the salt layers of the mengye potash deposit present typically continental lithological features this study examines and reviews evaporative minerals br cl and i cl molar ratios and isotopes of s b and sr i and i cl data for this area has not been previously reported the basin s evaporative minerals are dominated by halite and sylvite the amounts of anhydrite chlorocalcite langbeinite glaserite tachyhydrite and glauberite are small all of these form in both marine and continental environments the values of i and the i cl molar ratios of halite and sylvite are from 0 07 to 0 27 ppm and from 0 03 to 0 11 10 6 respectively dependent on organic substances br and molar br cl values are from 89 08 to 555 45 ppm and from 0 06 10 3 to 0 38 10 3 respectively all of the br cl molar ratios are lower than those of seawater and most of them are 34 s 11 b and 87 sr 86 sr values for evaporative minerals indicate a continental origin for the mengye potash deposit however materials of hydrothermal origin are widely distributed in the basin and may have played an active role for the formation of the potash deposit thus the mengye potash deposit could be of continental origin with a remnant seawater trace