source type and extent of inorganic contamination within the birmingham urban aquifer system uk a survey of the inorganic quality of the groundwater of the birmingham triassic sandstone aquifer was carried out by sampling seventy 80 150 m deep industrial abstraction boreholes 11 shallow monitoring piezometers two submerged tunnels and two flooded industrial basements and a set of trial pits borehole logging and historical data were also obtained given that the city of birmingham is as long established as most industrial conurbations in the world the degree of groundwater inorganic contamination as indicated by abstraction well samples is not excessive out of the 28 determinands measured only no 3 and ba2 consistently approach and exceed their european community maximum admissible concentrations standards for drinking water and the barium is being supplied by the aquifer rather than having an anthropogenic source however a few abstraction boreholes have highly contaminated groundwaters with for example milligram per litre levels of heavy metals in addition there is a correlation between land use and chemistry with the highest salinity sulphate chloride sodium boron and total heavy metal concentrations being associated with metal working sites high concentrations of heavy metals and nh 4 are unexpected in the near neutral ph triassic sandstone groundwaters given the high sorption capacity of the sandstone it is concluded that one reason for the occasionally high concentrations observed is the presence of very locialized high concentration recharge data from shallow piezometers confirm the considerable degree of heterogeneity in groundwater quality on a small scale the pollution is mainly from point sources sampling from piezometers tunnels and basements demonstrates that the groundwater concentrations at shallow depths are often much higher than the pumped water analyses suggest however nitrate groundwaters appear to vary much less with depth than other species reflecting a longer history of supply and a wider range of sources geophysical logging and sampling of well columns and other observations indicate that the intermittent pumping of abstraction wells results in the pumped water quality being biased towards the shallower high concentrations groundwaters rather than being a uniform mixture from all screened depths historical data show various trends and these can be related to local hydrogeology land use and abstraction history comparisons of organic and inorganic pollution show that distributions are very different reflecting differences in physical transport processes chemical interactions and histories of chemical usage

observations from the basin and range province western united states pertinent to the interpretation of regional detachment faults this paper summarizes the results of completed and ongoing research in three areas of the basin and range province of the western united states that casts doubt on the interpretation of specific regional detachment faults and the large extensional strains with which such faults are commonly associated given that these examples were influential in the development of ideas about low angle normal faults and particularly in making the case for frictional slip at dips of appreciably less than the 308 lock up angle for m 0 6 where m is the coefficient of friction we advocate a critical re examination of interpreted detachments elsewhere in the basin and range province and in other extensional and passive margin settings the sevier desert detachment of west central utah is reinterpreted as a palaeogene unconformity that has been traced to depth west of the northern sevier desert basin along an unrelated seismic reflection most probably a splay of the cretaceous age pavant thrust the absence of evidence in well cuttings and cores for either brittle deformation above or ductile deformation below is inconsistent with the existence of a fault with as much as 40 km of displacement the pavant thrust and the structurally higher canyon range thrust are erosionally truncated at the western margin of the southern sevier desert basin and are not offset by the detachment in the manner assumed by those inferring large extension across the basin the mormon peak detachment of se nevada is reinterpreted as a series of slide blocks on the basis of detachment characteristics and spatially variable kinematic indicators that are more closely aligned with the modern dip direction than the inferred regional extension direction a particularly distinctive feature of the detachment is a basal layer of up to several tens of centimetres of polymictic conglomerate that was demonstrably involved in the deformation with clastic dykes of the same material extending for several metres into overlying rocks in a manner remarkably similar to that observed at rapidly emplaced slide blocks the castle cliff detachment in the nearby beaver dam mountains of sw utah is similarly regarded as a surficial feature as originally interpreted and consistent with its conspicuous absence in seismic reflection profiles from the adjacent sedimentary basin the middle miocene eagle mountain formation of eastern california interpreted on the basis of facies evidence and distinctive clast provenance to have been moved tectonically more than 80 km ese from a location close to the jurassic age hunter mountain batholith of the cottonwood mountains is reinterpreted as having accumulated in a fluvial lacustrine rather than alluvial fan lacustrine setting with no bearing on either the amount or direction of tectonic transport the conglomeratic rocks upon which the provenance argument was based are pervasively channelized with erosional relief of less than 1 m to as much as 15 m fining upwards successions at the same scale and abundant trough cross stratification all characteristic features of fluvial sedimentation and not of alluvial fans the interpretation of the eagle mountain formation as having been deposited within a few kilometres of the hunter mountain batholith which depends strongly on assumptions about the dimensions of alluvial fans is therefore not required the result is important because the eagle mountain offset has been viewed as representing the strongest evidence for extreme extension in this part of california and for the existence of detachment faults of regional

temporal changes in fault strike to 90 and extension directions during multiple episodes of extension an example from eastern nevada in areas with prolonged extensional histories or multiple episodes of extension temporally distinct extensional fault systems including dip slip normal oblique slip and or strike slip faults may form these fault systems may be spatially distinct overlapped or completely superimposed and different fault systems may have different fault strikes and extension directions although fault strike is not a very sensitive indicator of principal stress directions changes through time in fault strike of as much as 90 exceed the uncertainty overprinted extensional fault systems of different ages with significantly different to 90 fault strikes and extension directions provide strong evidence of changes in the regional stress field with time tens of millions of years of extension occurred in the basin and range province of the united states and many temporally distinct fault sets formed through that time we document at least four extensional episodes and the fault kinematics of each where possible in the central hiko range eastern nevada the four cenozoic extensional events are prevolcanic synvolcanic postvolcanic miocene pliocene and postvolcanic pliocene quaternary the prevolcanic faults strike north south and are interpreted as footwall faults to the regional eocene oligocene snake stampede extensional system which caused approximately east west extension the synvolcanic faults are late oligocene miocene age and strike east west although they are rare and have minor offset they accommodated north south directed extension postvolcanic faults part of the timpahute lineament are approximately east west striking normal and northeast striking oblique slip faults they also accommodated approximately north south extension during miocene time the northeast striking left normal oblique slip fault set formed as new faults and records a change between north south and east west extension in miocene time later east west extension occurred along the pliocene to quaternary hiko fault zone these four overprinted extensional systems show two separate changes in normal fault strike of 90 from north south to east west and from east west back to north south consequently the extension direction similarly changed through time we suggest that causes for the changes in direction of upper crustal extension include a change from stresses created by 1 plate interactions which generated approximately east west extension to 2 mantle motions which generated approximately north south extension and 3 back again the extension related to mantle motions is associated with a band of volcanism that passed across the northern basin and range province moving generally from north to south during the protracted period of extension therefore a change from plate boundary or interaction derived stresses to mantle or volcanism related stresses and back again is possible

geospatial applications in delineating groundwater prospect zones in a hard rock terrain an integrated approach this study involved the application of geospatial techniques to delineate groundwater potential zones in a hard rock terrain of oban massif and environs this goal was achieved using satellite remote sensing imagery and geographic information system techniques the method mapped groundwater controlling factors such as geology geomorphology lineament density slope land use and land cover and drainage density the study covered a total area of 677 298 km2 landsat etm imagery shuttle radar transmission mission srtm topographic and geological maps and aster dem were used in the analysis software used for image processing digitizing and lineament density computation are arcgis10 1 envi 4 2 and pci geomatica respectively supervised classification method was applied in land use and land cover mapping analysis of satellite imagery shows that band 4 was the best for showing textural features for lineament extraction the method of multi criteria evaluation by assigning relative weights to each groundwater controlling factor was used to produce their corresponding thematic maps the thematic maps were produced by weighted linear combination each class individual weight was multiplied by the map scores and then adding the results overlay analysis of the thematic maps produced the groundwater potential map results show four groundwater prospect zones classified into very good 38 365 km2 moderately good 230 999 km2 fair 381 865 km2 and poor 26 068 km2 from this study it is evident that lineament mapping is not the overriding factor in groundwater occurrence other groundwater controlling factors are necessary for a more credible groundwater potential modeling lineament slope geology and geomorphology are the most influential groundwater controlling factors in the study comparison of the results of this study with the collected sample data shows reasonable accuracy these findings are useful for borehole siting and environmental management strategies for groundwater potential investigation in both nigeria and other parts of world

using a binary logistic regression method and gis for evaluating and mapping the groundwater spring potential in the sultan mountains aksehir turkey summary the purpose of this study is to produce a groundwater spring potential map of the sultan mountains in central turkey based on a logistic regression method within a geographic information system gis environment using field surveys the locations of the springs 440 springs were determined in the study area in this study 17 spring related factors were used in the analysis geology relative permeability land use land cover precipitation elevation slope aspect total curvature plan curvature profile curvature wetness index stream power index sediment transport capacity index distance to drainage distance to fault drainage density and fault density map the coefficients of the predictor variables were estimated using binary logistic regression analysis and were used to calculate the groundwater spring potential for the entire study area the accuracy of the final spring potential map was evaluated based on the observed springs the accuracy of the model was evaluated by calculating the relative operating characteristics the area value of the relative operating characteristic curve model was found to be 0 82 these results indicate that the model is a good estimator of the spring potential in the study area the spring potential map shows that the areas of very low low moderate and high groundwater spring potential classes are 105 586 km 2 28 99 74 271 km 2 19 906 101 203 km 2 27 14 and 90 05 km 2 24 671 respectively the interpretations of the potential map showed that stream power index relative permeability of lithologies geology elevation aspect wetness index plan curvature and drainage density play major roles in spring occurrence and distribution in the sultan mountains the logistic regression approach has not yet been used to delineate groundwater potential zones in this study the logistic regression method was used to locate potential zones for groundwater springs in the sultan mountains the evolved model was found to be in strong agreement with the available groundwater spring test data hence this method can be used routinely in groundwater exploration under favourable conditions

convergent tracer tests in multilayered aquifers the importance of vertical flow in the injection borehole 1 a mathematical model describing the steady state flows in a forced gradient tracer test between an injection and pumping borehole in a multilayered sandstone aquifer has been developed that includes the effect of vertically variable background heads a second model describing the recovery of tracer from a layer in which there are discharges due to vertical flow in the injection borehole is also presented application of the models to field tracer test data indicates that the observed recoveries which are not proportional to the abstraction rate in each layer are consistent with the hydraulic behavior of the aquifer when natural vertical head gradients are taken into account investigation with the models illustrates that the vertical distribution of tracer recovery depends strongly upon the background heads and that tracer tests conducted in the same aquifer but at different times may interrogate different aquifer layers it is also shown generally that for a given abstraction rate the vertical distribution of tracer recovery in small scale tracer tests is controlled largely by the transmissivity distribution but that as the spatial scale of the test increases the distribution of recovery becomes proportional to the discharges from the injection borehole because of vertical flows within it which may be natural or induced by pumping in the monitoring borehole uncertainties inherent in the design of forced gradient tracer tests in multilayered aquifers and the problems of applying the results of such tests to natural gradient contaminant migration are discussed

gis based groundwater spring potential mapping in the sultan mountains konya turkey using frequency ratio weights of evidence and logistic regression methods and their comparison summary in this study groundwater spring potential maps produced by three different methods frequency ratio weights of evidence and logistic regression were evaluated using validation data sets and compared to each other groundwater spring occurrence potential maps in the sultan mountains konya turkey were constructed using the relationship between groundwater spring locations and their causative factors groundwater spring locations were identified in the study area from a topographic map different thematic maps of the study area such as geology topography geomorphology hydrology and land use cover have been used to identify groundwater potential zones seventeen spring related parameter layers of the entire study area were used to generate groundwater spring potential maps these are geology lithology fault density distance to fault relative permeability of lithologies elevation slope aspect slope steepness curvature plan curvature profile curvature topographic wetness index stream power index sediment transport capacity index drainage density distance to drainage land use cover and precipitation the predictive capability of each model was determined by the area under the relative operating characteristic curve the areas under the curve for frequency ratio weights of evidence and logistic regression methods were calculated as 0 903 0 880 and 0 840 respectively these results indicate that frequency ratio and weights of evidence models are relatively good estimators whereas logistic regression is a relatively poor estimator of groundwater spring potential mapping in the study area the frequency ratio model is simple the process of input calculation and output can be readily understood the produced groundwater spring potential maps can serve planners and engineers in groundwater development plans and land use planning

recharge velocity and geochemical evolution for the permo triassic sherwood sandstone northern ireland the triassic sherwood sandstone group is a major european aquifer system it is also the principal groundwater source in northern ireland however key aspects of its regional hydrogeology such as age distribution and geochemical evolution remain largely unknown here the groundwater geochemistry and isotopic composition were investigated in order to evaluate groundwater recharge and flow processes in a complex regional hydrogeological setting the dominant geochemical processes such as dissolution of carbonate cements were determined from the major and trace element chemistry stable and radio isotope measurements were taken as residence time and flow path indicators and together with physical and geochemical groundwater modelling revealed groundwater ages of up to 9000 years the importance of infiltration from overland flow from springs deriving water from the adjacent cretaceous chalk aquifer and subsequently re infiltrating into the sherwood sandstone was confirmed in addition evidence was found of a slow recharge component through low conductivity mudstones that yielded significant groundwater resident times throughout the lagan valley these findings provide improved understanding of groundwater flow processes in northern ireland and serve as an example of methods that can be applied to water management elsewhere

characteristics of high resolution hydraulic head profiles and vertical gradients in fractured sedimentary rocks summary accurately identifying the position of vertical hydraulic conductivity k v contrasts is critical to the delineation of hydrogeologic units that serve as the basis for conceptual and numerical models of groundwater flow high resolution head profiles have identified the position and thickness of k v contrasts in clayey aquitards but this potential has not yet been thoroughly evaluated in sedimentary rocks this paper describes an experiment in which head profiles with the highest technically feasible resolution were obtained using westbay multilevel systems mls installed in 15 cored holes at three sedimentary rock research sites with contrasting geologic and flow system conditions mlss were installed to maximum depths between 90 and 260 m with 2 5 monitoring zones per 10 m head profiles were measured over multiyear periods the vertical component of hydraulic gradient i e vertical gradient was calculated for each pair of adjacent monitoring intervals in every mls and then categorized based on its repeatability to facilitate interpretation of k v contrasts and comparisons within boreholes between boreholes at the same site and between sites the head and vertical gradient profiles from all three sites display systematic i e simple geometric shapes defined by repeatable intervals of no to minimal vertical gradient indicating relatively high k v units bounded by shorter depth intervals with large up to 50 m m vertical gradients indicating relatively low k v units the systematic nature of the profiles suggests flow in regular and interconnected fracture networks rather than dominated by a few key fractures with irregular orientations the low k v units were typically thin with their positions and thicknesses not predicted by lithostratigraphy or detailed lithologic geophysical and horizontal hydraulic conductivity data hence the position and thickness of units with contrasting k v would not be evident if mlss with the conventional number of monitoring zones had been used furthermore the detailed profiles can be strongly diagnostic of hydrogeologic unit boundaries or layers and can be used to improve the quantitative assessment of flow system conditions that is foundational to understanding contaminant plume migration

regional analysis of tertiary volcanic calderas western u s using landsat thematic mapper imagery abstract the basin and range province of southern nevada is an excellent setting to study landsat imagery over volcanic rock assemblages the area is semiarid sparsely vegetated and contains relatively youtful 6 14 ma volcanic calderas with compositionally diverse volcanic rock assemblages investigation of rock spectra whole rock geochemistry desert varnish and landsat imagery indicates that the longer wavelength visible and near infrared thematic mapper tm bands 3 5 and 7 provide more effective lithologic discimination than the shorter wavelength bands due partly to deeper penetration of lower frequency energy and greater primary rock compositional response spectral contamination of vegetation degrades lithologic information in tm band 4 thus ratios color composites and intensity saturation hue images using tm bands 3 5 and 7 generally lead to superior lithologic contrast shorter wavelength tm bands 1 and 2 are affected more by surficial weathering products including desert varnish which may or may not provide an indirect link to lithologic identity these relationships lead to a rock varnish albedo difference that aids identification of desert varnish on leucocratic rocks using tm band 2 5 and 5 2 ratio images principles component color composites provide best overall lithologic contrast but not specific lithologic identification pc2 tends to contain lithologically dominant variance and combines favorably with other images influenced strongly by lithology late magmatic differentiates that are evolved with respect to alkalies and the incompatible elements exhibit steep spectral curves throughout the tm bands 5 7 interval leading generally to low 5 7 ratios and dark contrast on 5 7 ratio images guidelines for lithologic analysis of volcanic terrain using landsat tm imagery are outlined

detailed tectonics near the tip of the galapagos 95 5 w propagator how the lithosphere tears and a spreading axis develops a model for propagation of an active spreading axis into preexisting lithosphere has been developed based on intensive detailed studies using seamarc ii sea beam deep tow and alvin near the tip of the propagator growing westward at 52 km m y along the east west trending galapagos spreading axis near 95 5 w initial lithospheric rifting appears to be accommodated along reactivated roughly east west abyssal hill faults at the tectonic tip extension leads to downdropping of a keystone block which is pervasively cut by normal faults and fissures the initial volcanism initial volcanic tip occurs about 6 5 km behind the tectonic tip as basalt erupts through these fissures covering most of the keystone block the neovolcanic axial tip occurs another 4 5 km back at the western termination of a well defined axial pillow ridge along which volcanism is localized spreading along the propagator axis accelerates to the full rate 29 mm yr half rate at the full rate tip interpreted to be 10 km behind the neovolcanic axial tip or 21 km behind the tectonic tip a complex pattern of strain in the tip area results from the interaction of plate spreading transform shear stress crack propagation dynamic depression of the western end of the axial valley and the transform zone and variations in the strength thickness heterogeneity and anisotropy of the lithosphere southwesterly curvature of the neovolcanic axis near its tip is inferred to result primarily from the response of young thin weak relatively homogeneous lithosphere to counterclockwise rotation of the maximum tensional stress direction relative to the spreading direction due to the influence of shear stress from the transform zone similar stress interactions likely occur at the tectonic tip but are inferred to be accommodated in this older thick strong heterogeneous and anisotropic lithosphere by oblique slip along a set of left stepping reactivated preexisting east west abyssal hill structures although on a time scale of 106 years the overall process of propagation is mostly continuous rifting at the tectonic tip appears discontinuous at a scale of 1500 m or 30 000 years based on the east west spacing of grabens formed as rifting begins the scale of discontinuity of propagation of the neovolcanic axis is 3 5 km or 50 000 100 000 years based on the distribution of northeast trending features interpreted as beheaded western terminations of paleoneovolcanic axes the extension involved in rifting is 10 20 based on summing the horizontal normal separation of all normal faults and fissures integrated and averaged over the zone of rifting these values are approximately doubled if simple shear listric faulting is dominant rather than pure shear normal faulting

pollution related acidification in the urban aquifer birmingham uk abstract comparison of groundwater quality data ten years apart and sampling of shallow level water and soil gas co 2 indicates that the groundwaters below birmingham are becoming more acidic six potential causes are considered 1 rise of water level into the carbonate poor upper levels of the sandstone aquifer 2 oxidation of the quaternary deposits overlying the aquifer 3 inorganic acid spills 4 other acidic recharge 5 oxidation of inorganic pollutants 6 degradation of industrial organic pollutants chemical and hydrogeological data suggest that 3 5 and 6 are dominant in different parts of the city the rate of fall in ph of 0 6 units over ten years is worrying with regard to increased solubility of toxic metals

stratigraphic relations and source areas of ash flow sheets of the black mountain and stonewall mountain volcanic centers nevada recent work has resulted in major changes in the stratigraphic correlations and source area assignments of ash flow sheets of the late miocene black mountain and stonewall mountain volcanic centers southern nevada ash flow tuffs exposed around stonewall mountain have different trace element patterns and thermoremanent magnetization directions than do ash flow sheetsof the thirsty canyon tuff erupted from the black mountain center with which they were previously correlated hafnium concentrations are particularly useful in distinguishing the megascopically and petrographically similar tuffs ofthe two centers the ash flow sheet overlyingthe spearhead member in the stonewall mountainarea herein named the civet cat canyon member can be traced northward continuously from outflow facies south of stonewall mountain to near vent facies on the southern flank of stonewall mountain this in conjunction with distribution thickness and facies relations show that these units are the outflow sheets of the stonewall mountain volcanic center they are herein assigned to a new formation the stonewall flat tuff of late miocene age tuffs previously mapped near black mountain as the labyrinth canyon member herein abandoned are correlated on the basis of trace element paleomagnetic petrographic and radiometric age data with the type spearhead member at goldfield tuffs previously assigned to the spearhead member in the black mountain frea are reassigned to the pahute mesa member new of the thirsty canyon tuff the stonewall mountain volcanic center is thus slightly younger than the black mountain center and the period of time over which the black mountain center was active probably was appreciably shorter than was previously inferred recognition of the stone wall flat tuff as a separate stratigraphic and genetic entity enables us to explain a number of geological inconsistencies including the marked asymmetric distribution previously attributed to the thirsty canyon tuff moreover the inferred original volume of the thirsty canyon tuff is significantly reduced increasing the importance of lava relative to tuff in the eruptive history of the black mountain center

equilibrium mineral fluid calculations and their application to the solid solution between alunite and natroalunite in the el indio pascua belt of chile and argentina abstract the effects of temperature and bulk fluid k na on the alunite natroalunite solid solution have been determined at 200 bar and 100 300 c these are conditions typical of magmatic hydrothermal alteration and precious metal mineral deposition in high sulfidation environments which are characterized by the presence of alunite bearing alteration zones our model is based on published experimental parameters which indicate that both alunite and natroalunite are stable over this temperature range and that increased na substitution is favored at higher temperature our calculation results predict that at all temperatures fluids in equilibrium with natroalunite are significantly more na rich than those typical of modern volcanic hydrothermal environments the results also indicate that a large variation in fluid k na is required to precipitate both k and na rich alunite at high temperature assuming near equilibrium conditions at lower temperature much less variation in fluid composition can yield compositions near those of the end members controls on alunite natroalunite solid solution in natural systems were evaluated using electron microprobe data from high sulfidation gold deposits of the el indio pascua belt the results indicate that higher temperatures of deposition correlate with a greater range of na substitution in alunite elevated na content in alunite is also locally attributed to higher concentrations of na in the source fluid as a result of the leaching and alteration of andesitic host rocks dacitic to granitic host lithologies in other regions of the belt are correlative with more k rich alunite compositions the results from this study suggest that the use of alunite k na composition as a guide to mineral exploration should be treated with caution

the gold flat tuff nevada insights into the evolution of peralkaline silicic magmas the gold flat tuff is the youngest 9 15 ma ash flow sheet erupted from the black mountain volcanic centre southwest nevada usa this paper explores some aspects of the very complex nature of the tuff s magmatic plumbing system the main body of the deposit is a mixed magma product comprising pantelleritic and comenditic melts derived from independently evolving reservoirs and antecrysts and enclaves derived from a range of basic to intermediate sources metre scale cognate xenoliths point to the presence of alkali feldspar accumulation zones the pantellerite contains phenocrysts of fluorite and chevkinite ce the inferred intermediate magma component contains perrierite ce phenocrysts the pantellerite has unusually high contents of f 2 2 wt f cl 2 9 wt and zro 2 1 04 wt the high halogen contents may have influenced the evolution of the strongly peralkaline magma the crystallization conditions are poorly constrained but those for the pantelleritic magma may have been close to water saturation 4 wt melt water at temperatures 740 c and fo 2 around fmq

gravity and aeromagnetic constraints on the structure of the woods mountains volcanic center southeastern california the woods mountain volcanic center is a well exposed mildly alkaline volcanic center that formed during the miocene in southeastern california detailed geologic mapping and geochemical studies have distinguished three major volcanic phases precaldera caldera forming and postcaldera geologic mapping indicates that caldera formation occurred incrementally during eruptions of three large ignimbrites and continued into a period of voluminous intracaldera lava flow eruptions rhyolitic ignimbrites and lava flows within the caldera are associated with large amplitude circular gravity and magnetic minima that are among the most prominent gravity and magnetic anomalies in southeastern california analysis of a bouguer gravity anomaly map reduced to the pole magnetic intensity map and three dimensional gravity and magnetic models indicates that there is a single funnel to bowl shaped caldera approximately 4 km thick and approximately 10 km wide at the surface this model is consistent with other siliceous pyroclastic filled calderas on continental crust except that most siliceous volcanic centers associated with more than one eruption are characterized by more than one caldera

vertical groundwater flow in permo triassic sediments underlying two cities in the trent river basin uk the vertical component of groundwater flow that is responsible for advective penetration of contaminants in sandstone aquifers is poorly understood this lack of knowledge is of particular concern in urban areas where abstraction disrupts natural groundwater flow regimes and there exists an increased density of contaminant sources vertical hydraulic gradients that control vertical groundwater flow were investigated using bundled multilevel piezometers and a double packer assembly in dedicated boreholes constructed to depths of between 50 and 92 m below ground level in permo triassic sediments underlying two cities within the trent river basin of central england birmingham nottingham the hydrostratigraphy of the permotriassic sediments indicated by geophysical logging and hydraulic packer testing demonstrates considerable control over observed vertical hydraulic gradients and hence vertical groundwater flow the direction and magnitude of vertical hydraulic gradients recorded in multilevel piezometers and packers are broadly complementary and range within error from 0 1 to 2 0 7 groundwater is generally found to flow vertically toward transmissive zones within the hydrostratigraphical profile though urban abstraction from the sherwood sandstone aquifer also influences observed vertical hydraulic gradients bulk downward darcy velocities at two locations affected by abstraction are estimated to be in the order of several metres per year consistency in the distribution of hydraulic head with depth in permo triassic sediments is observed over a one year period and adds support the deduction of hydrostratigraphic control over vertical groundwater flow q 2003 elsevier b v all rights reserved

residence time indicators in groundwater the east midlands triassic sandstone aquifer the east midlands triassic sherwood sandstone aquifer which has been the subject of detailed radiometric age studies is used to investigate both inert and reactive constituents of groundwater as indicators of residence time detailed resampling of the aquifer in 1992 has provided a considerable body of new inorganic geochemistry data though without radiocarbon several inert indicators are defined including the isotopic ratios 18o 2h 36cl noble gas ratios as well as the halogen elements cl br f i and their element ratios these form a group of essentially unreactive tracers primarily reflecting changing rainfall inputs and palaeoclimatic conditions except at outcrop where human impacts are also seen clearly the concentrations of cl mainly from atmospheric sources remain below 25 mg l 1 cl over a distance of some 30 km from outcrop reactive indicators the result of time dependent water rock interactions include 13c mg ca sr ca na cl and show diagnostic trends along the flow lines however the concentrations of certain trace elements li rb cs mn and mo which are not limited by solubility constraints show linear trends along the present day flow gradient this water rock interaction is taking place in groundwaters with low total mineralisation and it can be demonstrated that reactions involving these elements and isotopes are occurring entirely within the aquifer since high salinity groundwaters are found below the sherwood sandstone there is good correlation between some of the elements and 14c activities in the 1977 data set and this has been used to derive a concentration age relationship for the 1992 set of data a chemical timescale for the aquifer is then established using a li and b a combination of five trace elements the age of the fresh groundwater is thus shown to be up to 100 ka bp indicating the likelihood of semi continuous recharge during the devensian glacial period preceding the glacial maximum when no recharge occurred 10 20 ka bp this approach may be of value in extending groundwater dating beyond the radiocarbon timescale as well as interpreting sites where no radiocarbon data are available the scatter from the mean age line indicates those groundwaters which are derived from either rapid or slower than average flow zones within the aquifer as well as age stratification this stratification is borne out by a depth profile of groundwater from a new borehole near to outcrop which is shown by a combination of chemical and isotopic tracers to contain holocene overlying late pleistocene water

imaging spectroscopy earth and planetary remote sensing with the usgs tetracorder and expert systems 1 imaging spectroscopy is a tool that can be used to spectrally identify and spatially map materials based on their specific chemical bonds spectroscopic analysis requires significantly more sophistication than has been employed in conventional broadband remote sensing analysis we describe a new system that is effective at material identification and mapping a set of algorithms within an expert system decision making framework that we call tetracorder the expertise in the system has been derived from scientific knowledge of spectral identification the expert system rules are implemented in a decision tree where multiple algorithms are applied to spectral analysis additional expert rules and algorithms can be applied based on initial results and more decisions are made until spectral analysis is complete because certain spectral features are indicative of specific chemical bonds in materials the system can accurately identify and map those materials in this paper we describe the framework of the decision making process used for spectral identification describe specific spectral feature analysis algorithms and give examples of what analyses and types of maps are possible with imaging spectroscopy data we also present the expert system rules that describe which diagnostic spectral features are used in the decision making process for a set of spectra of minerals and other common materials we demonstrate the applications of tetracorder to identify and map surface minerals to detect sources of acid rock drainage and to map vegetation species ice melting snow water and water pollution all with one set of expert system rules mineral mapping can aid in geologic mapping and fault detection and can provide a better understanding of weathering mineralization hydrothermal alteration and other geologic processes environmental site assessment such as mapping source areas of acid mine drainage has resulted in the acceleration of site cleanup saving millions of dollars and years in cleanup time imaging spectroscopy data and tetracorder analysis can be used to study both terrestrial and planetary science problems imaging spectroscopy can be used to probe planetary systems including their atmospheres oceans and land surfaces

migration of contaminants in groundwater at a landfill a case study 2 groundwater monitoring devices abstract six types of devices for groundwater monitoring were used on an experimental basis in the investigation of the plume of contamination in the unconfined sandy aquifer at the borden landfill these include standpipe piezometers water table standpipes an auger head sampler suction type and positive displacement type multilevel point samplers and bundle piezometers with the exception of the first two each of these devices provides a means of obtaining vertical sample profiles of groundwater from a single borehole the auger head sampler which is a device that is attached to the cutting head of conventional continuous flight hollow stem augers yields samples from relatively undisturbed aquifer zones as the augers are advanced downward in the borehole from one depth of sampling to another this method is a rapid means of aquiring water quality profiles for mapping the distribution of a contaminant plume the other three profiling devices can be used to establish permanent networks for groundwater quality monitoring a suction type multilevel sampler consists of twenty or more narrow polyethylene or polypropylene tubes contained in a pvc casing that is capped at the bottom each tube extends to a different depth and is attached to a small screened sampling point that extends through the casing to draw water from the aquifer when suction is applied a positive displacement multilevel sampler is similar except that each sampling point is connected to a positive displacement pumping device located inside the pvc casing adjacent to the screen use of the suction type multilevel sampler is limited to zones where the water table is less than the suction lift depth of 8 or 9 m the positive displacement sampler can be used even if the water table is at a much greater depth a bundle piezometer consists of 1 2 cm o d flexible polyethylene tubes each with a short screened section at the bottom fastened as a bundle around a semi rigid center piezometer constructed of thick walled 2 cm o d pvc pipe in shallow water table areas water is withdrawn from each of the tubes and from the pvc piezometer by suction in areas with a deep water table samples are obtained by bailing with a narrow tube with a check valve on the bottom or by displacement using a double or triple tube gas drive sampler the positive displacement multilevel sampler or use of the gas drive samplers in the bundle piezometers provide the best opportunities for collecting samples that can be filtered and have preservatives added without the water being influenced excessively by degassing or by oxygen invasion networks of these three types of devices for multilevel groundwater monitoring were installed in the borden aquifer by means of hollow stem augers the devices are particularly well suited for use in aquifers composed of cohesionless sand or gravel that have little or no clay and groundwater flow that is primarily horizontal when 8 cm diameter hollow stem augers are used as many as eight polyethylene tubes are included conveniently in each bundle piezometer if augers with a larger hollow stem are used more tubes can be assembled in each bundle

migrating transform zone and lithospheric transfer at the galapagos 95 5 w propagator at the 95 5 w propagator system along the cocos nazca plate boundary the spreading axis is offset left laterally about 35 km 1 m y this offset migrates westward 52 km m y relative to points along the nearly east west trending ridge axis transferring lithosphere from the cocos to the nazca plate as it does so the required 58 km m y of right lateral motion across this migrating transform is apparently not accommodated by a throughgoing north south transform fault but rather by an approximately 15 to 20 km wide zone of shear deformation dominated by eastward curving of east west structures to a northwest southeast trend this pattern of curvature the coinciding zone of high seismicity and the abundance of talus in the area suggest that shear is distributed over this entire zone the deformation is inferred to be taken up by a bookshelf mechanism whereby faults oriented at high angles to the shear couple have left lateral slip antithetic to the right lateral shear couple rotating individual blocks clockwise these are interpreted as reactivated abyssal hill bounding normal faults probably dipping 45 60 northeast southwest shortening due to the rotation appears to be accommodated by reverse slip on the faults and may account for the uplift of de steiguer ridge in the zone of transferred lithosphere these faults have apparently had a very complex history initially normal faults formed as abyssal hills were created at the spreading axis and subsequently they had left lateral strike slip motion in the transform zone and reverse motion uplifting de steiguer ridge strain analysis based on observed structural curvature suggests that shear is distributed nonuniformly and lithospheric transfer requires 0 4 m y

the magma mixing origin of mantled feldspars the key to mantled feldspar genesis is epitaxial nucleation of plagioclase on k feldspar or k feldspar on plagioclase once this nucleation takes place there is a relatively straightforward process of crystal growth yielding rapakivi and antirapikivi textures the most common mantling is plagioclase on k feldspar which occurs in both volcanic and plutonic environments in the volcanic environment the morphology of the plagioclase overgrowth typically is dendritic though in subvolcanic and shallow plutonic environments dendritic growth is followed by a more or less continuous non cellular shell of plagioclase in the plutonic environment early stages of plagioclase overgrowth also tend to be dendritic although with coarser grained characteristics dendritic morphology is thus a common denominator in rapakivi genesis since growth of dendritic plagioclase is clearly related to marked undercooling in silicate melt systems its occurrence in many volcanic rocks is to be expected equivalent quenching in the plutonic environment requires a cooling mechanism independent of conductive heat transfer to wallrock and also independent of effective cooling related to sudden loss of volatile phases that could only occur late in the crystallization of most magmas and therefore after much dendritic plagioclase had already formed internal quenching of portions of magma systems must occur if mafic magma is abruptly mixed with felsic magma such magma mixing yields a heterogeneous system at first one that is in a drastic state of disequilibrium and tending to force nucleation of one feldspar type on the surface of another resulting in epitaxial crystallization of dendritic plagioclase on k feldspar mantling of one feldspar type by another during magma mixing is paralleled by dendritic growth zones in coexisting plagioclase crystals

hydrochemical evidence of the depth of penetration of anthropogenic recharge in sandstone aquifers underlying two mature cities in the uk pollution of urban groundwater is routinely reported but the profile of contamination with depth in urban aquifers is rarely resolved this limits understanding of the depth of penetration of urban recharge and contaminants and use of urban groundwater penetration of anthropogenic solutes major ions trace metals in permo triassic sandstone aquifers underlying two mature conurbations in the uk was investigated through depth specific groundwater sampling of dedicated multilevel piezometers identification of solute origin and biogeochemical processes e g denitrification mineral dissolution was aided by use of stable isotope ratios 34 s 32 s 18 o 16 o 15 n 14 n 13 c 12 c and chemical speciation modelling phreeqc depth profiles of aquifer hydrochemistry reveal penetration of anthropogenic solutes to depths of between 30 and 47 m below ground in the unconfined sandstone and confirm the contributions of faecal and industrial effluents to urban recharge they also highlight the complexity of solute loading and difficulty resolving solute origin from the range of potential sources in urban groundwater faecally derived no3 is the most pervasive contaminant exceeding drinkingwater quality guidelines and is associated with elevated concentrations of b and so4 elevated concentrations of li b cr and co are observed at depth in groundwater contaminated by long term industrial land use metalworking observed penetration of anthropogenic solutes in the unconfined sandstone is consistent with post development recharge of urban groundwater residence times 230 a indicated by flow modelling and suggests tentatively that urban abstraction to depths of up to 50 m below ground in the unconfined permo triassic sandstone is required to scavenge contaminated groundwater

a dual isotope approach to the nitrogen hydrochemistry of an urban aquifer the potential for exploitation of urban aquifers is partly dependent on understanding the distribution and fate of urban n sources such as sewage and fertilisers that can limit the use of groundwater for public supplies to investigate the application of the dual isotope approach to understanding the n hydrochemistry of urban groundwater this paper presents 15n no3 and 18o no3 data collected from two multi level piezometers in the sherwood sandstone aquifer beneath nottingham in the english midlands uk at one multi level piezometer old basford depth sample measurements of 15n no3 in the range 9 2 to 11 4 and 18o no3 in the range 8 2 to 10 9 together with no3 nitrate concentrations from 31 7 to 66 7 mg l are evidence for nitrification of sewage derived inputs in contrast at the other multi level piezometer the meadows isotopically enriched samples 15n no3 in the range 24 3 to 42 2 and 18o no3 in the range 20 5 to 29 4 are evidence for denitrification although the compositional range of 15n no3 does not identify the n source without corroborating data for the meadows location a cross plot of 15n no3 versus 18o no3 gave an enrichment of the 15n isotope relative to the 18o isotope by a factor of 1 9 within the range of 1 3 2 1 reported for denitrification in other studies this study has shown that the dual isotope approach provides improved understanding of n sources and fate in the urban environment but further work is required to identify nitrification pathways to provide more confidence in the application and interpretation of 18o no3 measurements

urban groundwater baseflow influence upon inorganic river water quality the river tame headwaters catchment in the city of birmingham uk summary understanding the linkage between urban land groundwater baseflow and river contamination at the city scale is lacking this study evaluates the influence of inorganic major minor ions and metals groundwater contamination in the triassic sandstone quaternary deposits aquifer system underlying the city of birmingham uk upon the baseflow and water quality of the river tame baseflow water quality data have been collected from a riverbed piezometer network installed in the 7 4 km reach crossing the effluent unconfined sandstone aquifer and compared to river and aquifer water quality data overall the inorganic chemical quality of the baseflow was not as poor as potentially surmised from the urbanisation present baseflow impact upon river water quality was also low these conclusions were underpinned by evidences of limited river water quality changes along the reach some river concentrations being diluted by better quality baseflow only occasional breaching of water quality criteria limited impact upon river reach quality local to elevated baseflow dicharges natural attenuation occurrence within the riverbed and modest albeit somewhat uncertain baseflow mass fluxes baseflow fluxes to the reach were in the ranges 100 3500 t yr for major ions 1 50 t yr for minor ions and 1 500 kg yr for toxic metals with zinc and nickel most prominent the sporadic occurrence of elevated baseflow concentrations was ascribed to discrete groundwater plume discharges more detailed sub reach studies would be required to fully resolve discrete plume baseflow contributions and improve mass flux estimates not uncommonly the urban river studied was already contaminated and hence persistent baseflow fluxes may assume more importance if the river became cleaner through other control measures future research should hence consider the emergent significance of urban baseflows there are needs to conduct similar studies to investigate if city scale baseflow impacts are comparable elsewhere research the importance of spatially and temporally dynamic attenuation in the riverbed and develop improved baseflow mass flux estimation methods

paleomagnetic and cooling constraints on the duration of the pahute mesa trail ridge eruptive event and associated magmatic evolution black mountain volcanic center southwestern nevada two successive ash flow cooling units of the black mountain volcanic center the pahute mesa and trail ridge members of the late miocene thirsty canyon tuff possess nearly indistinguishable reverse polarity remanent magnetization directions of about 178 declination and 10 inclination these are interpreted to reflect thermoremanent magnetization either during a single geomagnetic field excursion or polarity transition or possibly from a field oriented near the limit of secular variation regardless of the type of geomagnetic field behavior the pahute mesa member was apparently overlain by the trail ridge member before appreciable shift of the anomalous geomagnetic field this strongly suggests that the time between eruption of the two ash flow sheets was very short perhaps less than 100 years a conclusion that is independently supported by the local absence of a complete cooling break between the two units the interval between eruption of the pahute mesa and trail ridge members was too brief for reestablishment of chemical stratification in the black mountain magma system nevertheless a small volume of highly evolved comendite magma developed and was erupted as lava within the black mountain caldera and as a component of the trail ridge member the short repose interval and rapid development of the comendite together with evidence for mixing of magmas of silicic to near mafic composition vogel et al this issue and the presence of air fall tuff at the base of the trail ridge lead us to conclude that eruption of the trail ridge member was probably triggered by injection of hot relatively unevolved magma into the black mountain magma body

stonewall mountain volcanic center southern nevada stratigraphic structural and facies relations of outflow sheets near vent tuffs and intracaldera units directly south and southeast of stonewall mountain nevada a depression and north facing caldera scarp were formed during and or after eruption of the spearhead member of the late miocene stonewall flat tuff abundant large lithic and juvenile blocks are present in the spearhead member within 0 5 km of this topographic margin but absent elsewhere in the ash flow sheet consistent with eruption from vents in the stonewall mountain area within about 100 000 years comendite tuff of the overlying civet cat canyon member of the stonewall flat tuff buried the depression and associated scarp the civet cat canyon member is traceable continuously to the north from an outflow sheet capping northwestern pahute mesa into near vent tuff on the southeastern flank of stonewall mountain proximal outflow sheet tuff locally exhibits strong rheomorphic disruption and is overlain without a cooling break by surge flow and fall deposits of trachytic composition much of stonewall mountain is composed of welded tuff and megabreccia interpreted as intracaldera tuff of the civet cat canyon member strongly suggesting that the vent area of the member was largely within stonewall mountain welded tuff of trachytic composition comprises an important part of the intracaldera civet cat canyon member which was intruded by dikes and plugs of trachyte and rhyolite juvenile inclusions of basalt dispersed in near vent facies trachyte tuff provide direct evidence for the high level involvement of basaltic magma in the evolution of the highly potassic stonewall mountain center complex discordant compaction foliations and the widespread presence of megabreccia within the intracaldera tuff suggest following foley 1978 cauldron subsidence by piecemeal collapse during eruption of the civet cat canyon member the elevation of intracaldera tuff and intrusions in stonewall mountain above the surrounding ashflow sheet suggests a significant amount of magmatic uplift perhaps involving the emplacement of plugs dikes and small stocks within the intracaldera tuff prism

a geophysical geological transect of the silent canyon caldera complex pahute mesa nevada revision of lithological logs for boreholes penetrating the volcanic center at pahute mesa nevada has led to a thorough review of the volcanic stratigraphy and geologic structure we have combined this review with a compilation of old and newly acquired gravity and seismic travel time data producing a unified interpretation along a northwest to southeast profile the analysis supports a new interpretation of the silent canyon caldera complex the caldera is found to be more asymmetric than previously suggested with the southeastern boundary formed by linear high angle normal faults and a more gently sloping northwestern boundary the total thickness of volcanic units within the caldera complex does not appear to exceed 5 km the shallow structure at pahute mesa could have a profound effect on the seismic response for regional and teleseismic signals from this nuclear test site the silent canyon caldera complex is actually a set of nested calderas first filled by thick 1 km postcaldera lavas and subsequently buried by outflow sheets of the timber mountain caldera to the south thick postcaldera lavas filled a half graben structure formed west of the west greeley fault dropping the tops of the youngest caldera forming units to depths in excess of 2 km therefore the western boundary of the caldera complex is poorly defined east of the west greeley fault two overlapping calderas are defined and stratigraphic data suggest the presence of even older calderas the youngest caldera the calc alkaline area 20 caldera is well defined from drill hole data the area 20 caldera overlaps the 13 6 ma peralkaline grouse canyon caldera which is less well defined but apparently collapsed in trap door style along the almendro fault for both these calderas collapse continued after the main caldera forming eruption concurrent with the accumulation of thick 1 km lavas within the peripheral collapse zones the geophysical interpretation indicates that the major structural boundary of the caldera complex corresponds to the nne trending scrugham peak and almendro faults which offset the pre tertiary contact more than 1 km but have less than 200 m offset in rocks of 11 ma age drill hole data show that offsets along these faults increase systematically within older up to 15 ma units which are commonly rotated eastward in a style similar to units at the surface abrupt changes in the subsurface thickness of the caldera forming units occur across the faults indicating that these linear features served as caldera boundaries

tectonics of the failing spreading system associated with the 95 5 w galapagos propagator the failing spreading system associated with the galapagos 95 5 w propagator system comprises a complex set of volcanic and structural provinces data from detailed surveys using gloria seamarc ii sea beam deep tow the submersible alvin magnetics and bottom cameras constrain the plate boundary geometry and evolution of this area although the failing spreading system may involve diffuse spreading the patterns of sedimentation volcanism and faulting suggest localization the failed spreading axis composed of a set of right stepping en echelon basins extends and ages southeastward from offset and overlapping doomed failing axes the failing axis is offset 13 km left laterally from the doomed axis although there may have been a preexisting offset in the doomed axis lack of structural evidence for this and lack of an offset of this magnitude in the brunhes matuyama magnetic reversal argue against this possibility a model whereby the offset is transient does not explain the pattern of failed spreading basins which leads directly away from the currently failing axis detailed structural and volcanic patterns suggest that this offset may be caused by a westward progression of northward jumps in the location of the failing axis like a secondary propagator probably in association with the migrating strain stress field of the migrating transform zone of the propagator system this is modelled as a migrating extensional relay zone merz similar to the relay zones observed at some fast slipping transform faults except that it propagates westward with the overall system bathymetric and magnetic evidence for tectonic elements associated with the merz supports this model although the expected extinct trace of the doomed axis is not obvious in the present incomplete data set unlike other models for the plate boundary geometry the merz model does not require serendipity for temporal and spatial juxtaposition of the primary propagator and the offset within the failing spreading system observation of a similar geometry in the lau basin supports this preferred model present data from the galapagos failing spreading system are inconclusive however and the merz model remains speculative if valid this model implies that in at least some cases paired propagators act together the merz is too short and deep to drive its own propagation according to standard cracking models

exploration tools for linked porphyry and epithermal deposits example from the mankayan intrusion centered cu au district luzon philippines the mankayan mineral district of northern luzon philippines hosts several significant ore deposits and prospects of various types within an area of similar to 25 km 2 including the far southeast porphyry cu au deposit the lepanto high sulfidation epithermal cu au deposit the victoria intermediate sulfidation epithermal au ag vein deposit the teresa epithermal au ag vein deposit the guinaoang porphyry cu au deposit and the buaki old palidan porphyry cu au prospects all having formed in a period of about 2 m y from similar to 3 ma the geologic units include 1 a basement composed of late cretaceous to middle miocene metavolcanic rocks volcaniclastic rocks 2 the miocene 12 to 13 ma tonalitic bagon intrusive complex 3 the pliocene similar to 2 2 to 1 8 ma imbanguila dacite porphyry and pyroclastic rocks and 4 postmineralization cover rocks including die similar to 1 2 to 1 0 ma bato dacite porphyry and pyroclastic rocks and the similar to 0 02 ma lapangan tuff extensive advanced argillic alteration crops out for similar to 7 kin along the inconformity between the basement rocks and the imbanguila dacite formation consists of quartz alunite pyrophyllite or diaspore with local zones of silicic alteration and a halo of dickite kaolinite the alteration and its subhorizontal geometry indicate that it is a lithocap or coalesced lithocaps the northwest striking portion is similar to 4 km long and hosts the lepanto enargite au ore deposit also controlled by the lepanto fault the lepanto epithermal deposit is related to the underlying far southeast porphyry the quartz alunite alteration halo of lepanto is contemporaneous with the similar to 1 4 ma potassic alteration of the porphyry there are also silicic advanced argillic alteration patches similar to 600 m above the far southeast orebody at the present surface these are interpreted to be perched alteration there is no systematic mineralogical or textural zoning in the lepanto lithocap that indicates direction to the intrusive source most surface samples of the lithocap contain less than 50 ppb au despite many being less than a few hundred meters from underground cu au ore this study found that several characteristics of the lepanto lithocap change systematically with distance from the causative intrusion the alunite absorption peak at similar to 1 480 nm in the short wavelength infrared swir spectrum shifts to higher wavelengths where the sample is closer to the intrusive center due to higher na and lower k content in the alunite published experimental studies indicate that high na na k is related to higher formation temperature high ca alunite including huangite also occurs at locations proximal to the intrusive center alunite mineral composition analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms indicates that the pb content decreases toward the intrusive center whereas sr la sr ph and la pb increase markedly whole rock compositions using only nonmineralized taken as cu similar to 350 m above the upper extent of the veins an airborne geophysics survey indicates that the far southeast orebody is associated with a wide zone of demagnetization due to extensive magnetite destructive phyllic alteration such low magnetic anomalies on the margin of a large lithocap elsewhere may deserve attention the directional indicators and mineralization signatures found in this study have the potential to indicate direction to the intrusive center during exploration of similar porphyry epithermal districts

significance of vertical flow through low conductivity zones in bromsgrove sandstone aquifer abstract when water passes vertically through low conductivity zones in aquifers significant vertical head gradients occur the importance of such gradients is identified in a study of the bromsgrove sandstone aquifer unit a mathematical model incorporating the low conductivity layers has been developed to explain the changed conditions from 1900 when there were extensive spring flows to the present day when deep boreholes intercept much of the groundwater flow the mathematical model also helps in understanding the changing pumped drawdowns and water table elevations

tracing sources of carbon in urban groundwater using δ13ctdic ratios total dissolved inorganic carbon tdic and its stable isotope ratio 13ctdic are used to trace the evolution of the carbon system of groundwater in three uk permo triassic sandstone aquifers samples were collected from multilevel piezometers open boreholes and sewer sampling points in the british midlands nottingham birmingham and doncaster to evaluate both local and regional variations in 13ctdic 13c samples of matrix and pore water have also been analysed in each aquifer to further constrain the interpretations combining 13ctdic ratios with measurements of tdic and ph clearly distinguishes the principal processes underlying the geochemical evolution of groundwater in triassic sandstone aquifers where processes can be both natural e g carbonate dissolution and anthropogenic sewer derived recharge the paper shows that 13ctdic resolves ambiguities that arise from the interpretation of tdic and ph measurements in isolation field measurements demonstrate that under natural conditions the carbonate system evolves similarly in each aquifer an open system evolution during recharge largely saturates the groundwater with carbonate depending upon its availability in the sandstone matrix the contribution of sewer exfiltration to urban recharge is readily distinguished by lower ph and higher tdic values without significant changes in 13ctdic

near infrared spectra of white mica in the belt supergroup and implications for metamorphism the wavelength of the white mica illite and muscovite al oh absorption band near 2200 nm in 1036 samples from the belt supergroup and associated metasedimentary rocks was determined with a portable visible and near infrared reflectance spectrometer the al oh wavelength decreases from 2225 nm in sub biotite zone samples to 2194 nm in sillimanite zone samples this decrease corresponds with an increase in total al content of white mica from 2 0 to 2 8 atoms per 11 o atoms these observations indicate that 1 the frequency of the al oh vibration is controlled by the aluminoceladonite exchange reaction iv si vi mg fe 2 iv al vi al and 2 the reaction proceeds toward more al rich composition with increasing metamorphic grade in these circumstances al oh wavelength provides an indirect monitor of compositional variation and metamorphic grade metamorphic grade in most of the study area is in the biotite zone or lower yet al oh wavelengths in low grade rocks define systematic patterns that correlate with depth of burial and later structural displacements in higher grade areas wavelengths generally decrease from the garnet isograd through the sillimanite zone however anomalies occur locally and it is not clear whether these result from differences in bulk composition and mineral assemblage or whether they point to actual metamorphic or structural discontinuities these findings indicate that reflectance spectroscopy can yield valuable information on metamorphic intensity in rocks containing white mica particularly in low grade sequences where conventional indicators of metamorphic grade are lacking furthermore this information can be obtained with field portable spectrometers and the potential exists to obtain comparable results from airborne and spaceborne imaging spectrometers

petrologic evolution of divergent peralkaline magmas from the silent canyon caldera complex southwestern nevada volcanic field the silent canyon volcanic center consists of a buried miocene peralkaline caldera complex and outlying peralkaline lava domes its location has been corroborated by geophysical data and more than 50 drill holes two widespread ash flow sheets the tub spring and overlying grouse canyon members of the miocene belted range tuff were erupted from the caldera complex and have volumes of 60 100 km3 and 200 km3 respectively eruption of the ash flows was preceded by widespread extrusion of precaldera comendite domes and was followed by extrusion of postcollapse peralkaline lavas and tuffs within and outside the caldera complex lava flows and tuffs were also deposited between the two major ash flow sheets rocks of the silent canyon center vary significantly in silica content and peralkalinity the most mafic rocks are precollapse and postcollapse trachytes 65 69 sio2 low silica comendites 69 73 sio2 were erupted as the mafic upper part of the chemically zoned grouse canyon member and as postcollapse lavas the lower part of the grouse canyon member and the underlying rhyolite of split ridge are moderately peralkaline comendite pi is molar ratio na k al is 1 17 1 26 these comendites have major element characteristics and trace element enrichments approaching those of pantellerites the tub spring member by contrast is a weakly peralkaline chemically unzoned silicic comendite 75 76 sio2 ash flow tuff weakly peralkaline silicic comendites pi 1 0 1 1 are the most abundant precaldera lavas postcollapse lavas range from trachyte to silicic comendite some have anomalous light rare earth element lree enrichments silent canyon rocks follow a common petrologic evolution from trachyte to low silica comendite above 73 sio2 compositions of the moderately peralkaline comendites diverge from those of the weakly peralkaline silicic comendites these contrasting differentiation paths are shown in the behavior of fe and other transition metals al na k the trace elements ba zr nb and probably f and cl weakly peralkaline silicic comendites show a lree heavy ree crossover in early erupted late erupted rocks moderately peralkaline comendites are enriched in all ree the development of divergent peralkaline magmas toward both pantelleritic and weakly peralkaline compositions is unusual in a single volcanic center

eruptive history of the rhyolitic kane springs wash volcanic center nevada the 19 13 km kane springs wash caldera formed 14 ma ago following eruption of the three youngest members of the kane wash tuff two older cooling units of the kane wash tuff are dated 15 7 0 2 ma and 14 7 0 2 ma and apparently erupted from source areas west of the exposed caldera volcanic eruptions from the kane springs wash center began about 14 ma ago with extrusion of trachyte lavas now preserved north of the caldera member v1 of the kane wash tuff overlies the trachytes and is zoned from rhyolite to trachyte in contrast overlying members v2 and v3 are slightly peralkaline rhyolites comendite eruption of these tuffs 14 1 0 2 ma ago initiated caldera collapse following collapse trachyte lavas indistinguishable in age from the ash flow tuffs erupted within the caldera forming a 5 m diameter cumulodome whose interior portions crystallized to syenite this magmatic resurgence formed an extrusive complex within the caldera rather than doming the cauldron block as in classic resurgent calderas metaluminous ferroedenite rhyolite lavas and associated ash flow tuffs then erupted in the moat surrounding the central trachyte syenite complex pyroclastic deposits from the domes were covered by trachyandesite and basalt lava flows about 13 4 ma ago biotiterhyolite domes dated 13 4 0 2 ma continued to erupt in the northeastern moat and appear to be the last silicic eruptions from the kane springs wash magma system a 13 4 ma metaluminous biotite rhyolite dome containing vapor phase topaz overlies the trachyandesite lavas and appears to be the youngest biotite rhyolite dome these intracaldera units filled the moat resulting in a caldera filled with its own eruptive products local basalt flows covered both intracaldera units and outflow sheets between 12 7 and 11 5 ma ago prior to basin and range faulting the dominant volume of the system was trachytic as trachyte lavas erupted both prior to and following caldera collapse and trachyte inclusions occur as scoriaceous bombs at the top of member v2 fractionation of this trachyte magma produced the slightly peralkaline rhyolitic magma that erupted as the kane wash tuff the shift from an anhydrous mineral assemblage in the tuffs to hydrous assemblages in the later intracaldera rhyolites shows that the system was cooling and was possibly more hydrous in its late stages petrographic characteristics of trachyandesite lavas erupted late in the history of the center suggest that they represent basaltic magmas contaminated with silicic material

paleomagnetism and rotation constraints for the middle miocene southwestern nevada volcanic field middle miocene rocks of the southwestern nevada volcanic field swnvf lie across the projection of the walker lane belt within the basin and range province and thus provide an interesting opportunity to test for late cenozoic vertical axis rotation paleomagnetic data from individual ash flow sheets document no significant relative vertical axis rotation among localities within central swnvf an area of relatively low stratal tilts and widely spaced faults a time averaged mean paleomagnetic direction d 351 4 i 52 7 95 4 5 calculated from data from numerous separate rock units suggests that the central swnvf underwent minimal counterclockwise vertical axis rotation r 7 1 6 6 with respect to the north american craton no clockwise vertical axis rotation is found to support projection of dextral faults of the walker lane beneath the central swnvf clockwise rotation of variable magnitude is common at numerous sites from southern and western margins of the field these clockwise rotations probably reflect dextral shear strain developed at the interface between the little extended central swnvf block and more strongly extended areas to the south and southwest of the field negligible rotation of 11 45 ma to 13 25 ma tuffs relative to the central swnvf was found at the southeast margin of the field where 90 clockwise rotation at the northwest termination of the las vegas valley shear zone had been postulated any clockwise rotation in this area must predate 13 25 ma and thus dextral shear within this part of the walker lane belt was not synchronous or connected across the southern margin of the field small counterclockwise vertical axis rotation relative to the craton as found for the central swnvf block might be a regional feature in the western great basin

hydrochemical evolution of the east midlands triassic sandstone aquifer england a detailed hydrogeochemical interpretation has been made of the red bed sherwood sandstone triassic aquifer of the east midlands of england on which a radiocarbon model has been used to establish a chronology of groundwaters along the flow line groundwater evolution is dominated by carbonate and sulphate mineral solution and precipitation and by redox reactions cation exchange reactions are negligible and the hydrogeochemistry has evolved in the absence of residual saline water three distinct zones are recognised 1 i recent groundwater mainly 100 y oxidising dominated by congruent dissolution of dolomite and by inputs from atmospheric and anthropogenic sources 2 ii groundwater age 103 104 y predominantly reducing dominated by incongruent dissolution of dolomite 3 iii groundwater age 104 y reducing conditions approach to isotopic and chemical equilibrium in the carbonate system dominance of gypsum dissolution the minor and trace element variation can be interpreted in relation to the principal geochemical reactions and recharge history na cl f and b are controlled by atmospheric inputs sr2 and mn2 trends can be explained by carbonate and sulphate mineral dissolution ba2 is derived from carbonates but controlled by barite equilibrium fe so42 no3 and u are strongly influenced by redox reactions the concentrations of transition metals and other elements remain very low only li and k are considered to represent additions by reaction of silicate minerals the extent of direct anthropogenic influence is probably limited to enhanced so4 no32 and possibly cu zn and pb in zone i

a comprehensive analysis of groundwater resources using gis and multicriteria tools caldas da cavaca central portugal environmental issues hard rock watersheds are essentially confined to fractured and weathered horizons but they are a source of valuable water resources at a regional level namely for domestic industrial and agricultural purposes and public supply they commonly exhibit complex geological bedrock and morphological features as well as distinctive gradients in rainfall and temperature hydromineral and geothermal resources have relevant economic value both for the bottled water thermal spas industry and for energy supply a comprehensive evaluation and integrated groundwater resources study has been carried out for the caldas da cavaca hydromineral system in central portugal using hydrogeomorphology and gis mapping techniques thematic maps were organised from a geodatabase comprising several layers namely lithology tectonic lineaments density slope drainage density rainfall net groundwater recharge and water quality normalised weights were assigned to all these categories according to their relative importance to groundwater potential based on their effectiveness factors hydrogeochemistry natural radioactivity and intrinsic vulnerability assessment god s drastic fm sintacs si indexes issues were also cross checked based on all the compiled information a hydrogeomorphological map was produced this multidisciplinary approach highlights the importance of hydrogeomorphological mapping as a tool to support hydrological conceptualisation contributing to groundwater decision making process in different stages like water resources management and territory planning and thus to environmental sustainability

quantification of groundwater recharge in the city of nottingham uk groundwater is an important and valuable resource for water supply to cities in order to make full and wise use of the asset value a clear understanding of the quantities and sources of urban groundwater recharge is needed the water supply and disposal network is often an important source of recharge to urban groundwater through leakage from water mains and sewers an approach to establishing the spatial and temporal amounts of the three urban recharge sources precipitation mains and sewers is developed and illustrated using the nottingham uk urban aquifer a calibrated groundwater flow model is supplemented by calibrated solute balances for three conservative species cl so4 and total n thus providing four lines of evidence to use in the recharge estimation nottingham is located on a triassic sandstone aquifer with average precipitation of 700 mm year using the models current urban recharge is estimated to be 211 mm year of which 138 mm year 40 is from mains leakage and 10 mm year 100 is from sewer leakage the wide confidence intervals result from the scarcity of historical field data and the long turnover time in this high volume aquifer and should be significantly lower for many other aquifer systems

the control of sedimentary facies by climate during phases of crustal extension examples from the triassic of onshore and offshore england and northern ireland crustal extension controls the tectonic accommodation space available for sediments in rift settings and may be defined by the structural and depositional geometry of sedimentary successions observed on seismic data and the rate of subsidence through time as represented by the accommodation of sediment the characteristic features of each are dependant on three variables the time taken for deposition the interplay between tectonics and eustasy and the lithology thus facies of the succession observed the sherwood sandstone group has been considered to represent a syn rift phase of fluvial deposition throughout europe with the overlying mercia mudstone group interpreted as the succeeding phase of deposition in an evaporitic seaway during post rift thermal subsidence more recently however there has been the recognition that it is the mercia mst gp which is seen to thicken markedly into faults imaged on seismic data rather than the sherwood sandstone group this work demonstrates the mercia mst gp to be a syn rift phase of deposition with the fine grained nature of the sedimentary record at this time controlled by the prevailing arid climate such conditions were not conducive to the large scale and rapid movement of sediments from the hinterlands raised by relative footwall uplift thus the sediments are fine grained the minor thickening of the sherwood sst gp into faults is interpreted to be a combination of minor extension in the early triassic superimposed on thermal subsidence inherited from the important regional phase of extension in the early permian analysis of the timing of fault growth indicates a larger proportion of fault controlled synsedimentary movement occurred during the mid to late triassic mercia mst gp rather than the early triassic sherwood sst gp

mapping advanced argillic alteration at cuprite nevada using imaging spectroscopy mineral maps based on airborne visible infrared imaging spectrometer aviris data were used to study late miocene advanced argillic alteration at cuprite nevada distributions of fe bearing minerals clays micas sulfates and carbonates were mapped using the tetracorder spectral shape matching system the al content of white micas increases toward altered areas and near intrusive rocks alunite composition varies from pure k to intimate mixtures of na k endmembers with subpixel occurrences of huangite the ca analogue of alunite intimately mixed na k alunite marks areas of relatively lower alteration temperature whereas co occurring na alunite and dickite may delineate relict hydrothermal conduits the presence of dickite halloysite and well ordered kaolinite but absence of disordered kaolinite is consistent with acidic conditions during hydrothermal alteration partial lichen cover on opal spectrally mimics chalcedony limiting its detection to lichen free areas pods of buddingtonite are remnants of initial quartz adularia smectite alteration thus spectral maps provide a synoptic view of the surface mineralogy and define a previously unrecognized early steam heated hydrothermal event faulting and episodes of hydrothermal alteration at cuprite were intimately linked to upper plate movements above the silver peak lone mountain detachment and growth collapse and resurgence of the nearby stonewall mountain volcanic complex between 8 and 5 ma isotopic dating indicates that hydrothermal activity started at least by 7 61 ma and ended by about 6 2 ma spectral and stable isotope data suggest that cuprite is a late miocene low sulfidation adularia sericite type hot spring deposit overprinted by late stage steam heated advanced argillic alteration formed along the margin of the stonewall mountain caldera