catalogue of palaeomagnetic directions and poles from fennoscandia archaean to tertiary abstract palaeomagnetic data from fennoscandia ranging from the archaean to the tertiary have been compiled into a catalogue the data are presented in table format listing precambrian data according to tectonomagmatic blocks and late precambrian phanerozoic data according to geological periods each pole is graded with the modified briden duff classification scheme the catalogue complete to the end of 1988 contains 350 entries from 31 tectonomagmatic blocks and or geological periods normal and reversed polarity data are listed separately to allow polarity asymmetries to be studied each entry also has an indexed abstract summarizing relevant information such as the age of the rock the age of the natural remanent magnetization and the basis for the assigned reliability grade all the data are stored in the palaeomagnetic data bank which will be updated annually with new data the catalogue is the basic source of data for the microcomputer based palaeomagnetic database for fennoscandia now being compiled

investigating karst aquifers using pseudo 3 d electrical resistivity tomography to identify major karst features abstract this work presents the electrical resistivity imaging of the hydrogeological experimental site hes karst aquifer of poitiers france from pseudo three dimensional 3 d electrical resistivity tomography ert i e a three dimensional model obtained from the joint inversion of resistivity data collected along parallel profiles the inverse resistivity model provided a fairly reliable definition of the main hydrogeological units the survey also allowed the recognition of possible shallow dissolution enlarged fractures that do not show any ground expression at present but have been revealed at depth by vertical flowmeter data and high resolution video footage from wells these features seem to connect with middle depth sub vertical features down to a depth of 25 m which are likely to correlate with soil mantled incipient sinkhole formation features that do not show any ground expression at present as well as karst conduits at greater depth the resistivity model allowed the recognition of the first two main karst intervals 35 40 m and 85 87 m deep associated with water productive layers as revealed by well logs the opportunity to cross validate geophysical results with extensive ground truth provided by the hes allowed an assessment of the error the pseudo 3 d ert model makes in estimating the depth of the karst intervals synthetic dataset modelling provided the detectability of the pseudo 3 d ert model in identifying karst intervals synthetic dataset modelling also allowed an estimation of the response of the experimental and inversion setup to a variable degree of heterogeneity of the aquifer using well log data as geological a priori information

composite model with fractional flow dimensions for well test analysis in fractured rocks abstract the represented analytical model is addressed to fracture zone aquifers in which well test responses can be commonly matched with models involving fractional flow dimensions the model assumes a composite structure representing the fractures opening into the pumping well and the fracture system comprising the actual aquifer the aim is to assess the hydraulic properties for the near well zone and the aquifer in terms of concrete parameters even if flow dimensions have fractional values dimensionless drawdown in pumping and observation wells was solved by applying laplace transforms the early time approximation for the pumping well can be used to assess the transmissivity t 1 if the flow dimension in the inner zone n 1 is greater than about 1 7 the long time solutions indicate that the inner zone induces a pseudo skin effect that can be estimated by comparing the pumping well and observation well data if k 1 is known the extent of the inner zone r can be estimated from the pseudo skin factor the responses tend to form log log straight lines with slopes of 1 n 2 by plotting drawdown vs t 1 n 2 on the double logarithmic scale the product of the hydraulic conductivity and the through flow area at the wellbore radius ka 2 and the hydraulic diffusivity d 2 of the aquifer can be estimated from the slope and the intercept the hydraulic conductivity of the aquifer k 2 is estimated by considering the through flow area as a projection of an n 2 dimensional sphere with a radius of r wb through three dimensional space by an amount r 3 n 2 the analyzed field example comprises a pumping test of a fracture zone aquifer in south central finland for the pumping well simultaneous matching of drawdown and derivative type curves with observed responses can be used to verify the results of the early time analysis and the proposed straight line procedure in addition type curve matching yields estimates of the hydraulic diffusivity ratio and a value of the dimensionless wellbore storage the analyzed observation wells are considered to be sufficiently far from the inner zone consequently type curves are produced based on the dimensionless drawdown solution that is identical to generalized radial flow model type curve matching of the observation well responses produces estimates for ka 2 k 2 and d 2 the obtained values are similar to previous studies that included models relying on integer flow dimensions however models relying on the fractional flow dimensions are capable to simulate the observed responses more accurately

multi level slug tests in highly permeable formations 1 modification of the springer gelhar sg model a multi level slug test model and a method for the evaluation of vertical profiles of hydraulic conductivity in highly permeable formations are developed a double packer system is employed to estimate local hydraulic conductivity depending on the formation and double packer system parameters the water level recovery in the tested well can exhibit a monotonic or oscillatory response to discern information on aquifer properties from artifacts introduced by the measurement system the theory of flow in an aquifer and a double packer system is developed the mathematical model incorporates features of the springer and gelhar 1991 model and reduces to the bouwer and rice 1976 model in a special case the model involves equations of momentum and mass conservation for the double packer system with quasi steady well aquifer interaction equations the method is uniformly applicable for both monotonic and oscillatory well responses and can produce profiles of hydraulic conductivity for the tested well the criterion is given to determine the type of well response for given slug test conditions

gravity anomalies and deep structure of eastern hudson bay abstract the cape smith and belcher foldbelts of lower proterozoic aphebian rocks form parts of the proposed circum superior suture which separates the superior and churchill structural provinces of the canadian shield recent marine gravity surveys in eastern hudson bay 1976 1979 show that the distinctive linear gravity pattern of paired positive and negative anomalies along the cape smith foldbelt of northern ungava extends southwards into hudson bay to the belcher islands interpretation of five gravity profiles across the cape smith and belcher foldbelts suggests that the churchill crust is thicker and denser than the superior the boundary between the two contrasting crustal blocks is interpreted as a collisional suture the rocks of the foldbelts which are progressively more volcanic northwards are the source of a residual positive anomaly associated with the cape smith foldbelt and a series of discontinuous positive residual anomalies in the bay to the north the thicknesses of the foldbelt rocks are estimated to be between 4 and 9 km with a local maximum of 13 km in the northernmost profile to the south in the belcher islands where geological estimates of formation thickness and measured rock densities provide more constraints on the interpretation of the residual anomalies the foldbelt rocks are generally 6 7 km thick with a local maximum thickness of about 9 km one possible interpretation of paleomagnetic results for belcher islands rocks in terms of a two plate model lends support to the collision hypothesis

integrated paleomagnetic and upb geochronologic studies of mafic intrusions in the southern canadian shield implications for the early proterozoic polar wander path abstract integrated paleomagnetic and u pb geochronologic studies are critical to establishing well dated apparent polar wander paths in the precambrian by collecting samples for both paleomagnetism and u pb geochronology at the same sampling sites and conducting rigorous paleomagnetic field tests to ensure that magnetizations are primary it is now possible to establish the age of paleomagnetic poles with uncertainties of no more than a few million years we have conducted such integrated studies on mafic intrusions of the southern superior province and adjacent portions of the southern province of the canadian shield these studies yield paleomagnetic tiepoints with high precision ages for use in polar wander path construction in the 2220 to 2110 ma period they indicate a direction of polar wander contrary to that of the most widely used paths for the superior province and for the canadian shield as a whole thus current interpretations of the movement of the superior province and the relative location and movement of the superior province and other structural elements of the canadian shield during this period are no longer valid

paleomagnetism of archean granites and matachewan dikes in the wawa subprovince ontario reevaluation of the archean apparent polar wander path paleomagnetic measurements have been completed on 400 specimens from dated archean granites and matachewan dikes in the michipicoten and gamitagama greenstone belts in the western wawa subprovince

hydraulic tests in highly permeable aquifers 1 a semianalytical solution is presented for a mathematical model describing the flow of groundwater in response to a slug or pumping test in a highly permeable confined aquifer this solution which is appropriate for wells of any degree of penetration and incorporates inertial mechanisms at both the test and observation wells can be used to gain new insights into hydraulic tests in highly permeable settings the oscillatory character of slug and pumping induced responses will vary considerably across a site even in an essentially homogeneous formation when wells of different radii depths and screen lengths are used thus variations in the oscillatory character of responses do not necessarily indicate variations in hydraulic conductivity k existing models for slug tests in partially penetrating wells in high k aquifers neglect the storage properties of the media that assumption however appears reasonable for a wide range of common conditions unlike in less permeable formations drawdown at an observation well in a high k aquifer will be affected by head losses in the pumping well those losses which affect the form of the pumping induced oscillations can be difficult to characterize thus analyses of observation well drawdown should utilize data from the period after the oscillations have dissipated whenever possible although inertial mechanisms can have a large impact on early time drawdown that impact decreases rapidly with duration of pumping and distance to the observation well conventional methods that do not consider inertial mechanisms should therefore be viable options for the analysis of drawdown data at moderate to large times

cross borehole slug test analysis in a fractured limestone aquifer summary this work proposes new semi analytical solutions for the interpretation of cross borehole slug tests in fractured media our model is an extension of a previous work by barker barker j a 1988 a generalized radial flow model for hydraulic tests in fractured rock water resources research 24 10 1796 1804 butler jr j j zhan x 2004 hydraulic tests in highly permeable aquifers water resources research 40 w12402 doi 10 1029 2003 wr002998 it includes inertial effects at both test and observation wells and a fractional flow dimension in the aquifer the model has five fitting parameters flow dimension n hydraulic conductivity k specific storage coefficient ss and effective lengths of test well le and of observation well leo the results of a sensitivity analysis show that the most sensitive parameter is the flow dimension n the model sensitivity to other parameters may be ranked as follows k le leo ss the sensitivity to aquifer storage remains one or two orders of magnitude lower than that to other parameters the model has been coupled to an automatic inversion algorithm for facilitating the interpretation of real field data this inversion algorithm is based on a gauss newton optimization procedure conditioned by re scaled sensitivities it has been used to interpret successfully cross borehole slug test data from the hydrogeological experimental site hes of poitiers france consisting of fractured and karstic limestones hes data provide flow dimension values ranging between 1 6 and 2 5 and hydraulic conductivity values ranging between 4 4 10 5 and 7 7 10 4 m s 1 these values are consistent with previous interpretations of single well slug tests the results of the sensitivity analysis are confirmed by calculations of relative errors on parameter estimates which show that accuracy on n and k is below 20 and that on ss is about one order of magnitude the k values interpreted from cross borehole slug tests are one order of magnitude higher than those previously interpreted from interference pumping tests these findings suggest that cross borehole slug tests focus on preferential flowpath networks made by fractures and karstic channels i e the head perturbation induced by a slug test propagates only through those flowpaths with the lowest hydraulic resistance as a result cross borehole slug tests are expected to identify the hydrodynamic properties of karstic channels and fracture flowpaths and may be considered as complementary to pumping tests which more likely provide bulk properties of the whole fracture karstic channel matrix system

a new method of data inversion for the identification of fractal characteristics and homogenization scale from hydraulic pumping tests in fractured aquifers hydraulic interference pumping tests are widely used for identifying mid to large scale aquifer hydraulic parameters fractured reservoirs often behave as fractal media for which classical interpretations may fail because of the decrease in permeability and fracture porosity or equivalently transmissivity and storage capacity with the pumping time and the extent over which the pumping stress has propagated a solution to hydraulic interference tests in fractal media is developed in dimensional variables which allows for a very rapid and unique fitting to data hydraulic parameters their scale exponents and the fractal dimension of the medium can be determined for each pressure draw down curve without any prior information or other calculation the method is applied to a large series of tests completed on the calcareous fractured aquifer of the experimental site in poitiers france even though data of pressure draw downs are various and show a fractal behavior permeability seems to rapidly homogenize for distances of 100 200 m on the other hand the fracture porosity shows a much progressive decrease with distance and homogenization is reached for scales beyond 300 500 m it is also shown that the classical cooper jacob interpretation of pressure draw downs may yield artifacts in the identification of permeability and fracture porosity orders of magnitude are comparable to that from fractal interpretation but their evolution with respect to time or distance scaling laws may strongly differ

geophysics of proposed proterozoic sutures in canada abstract sutures have been identified or proposed at several sites in the canadian shield although many authors have suggested that some form of primitive plate tectonic processes have played a major role in the formation of the archean crust of the superior structural province proterozoic sutures resembling phanerozoic examples have been proposed only within the younger churchill and grenville provinces and at or near the boundaries between the older superior and slave provinces and the younger provinces gravity magnetic seismic and paleomagnetic data related to three proposed sutures in the latter category have been interpreted and generally support the view that the shield comprises a mosaic of once separated but now joined cratonic blocks the sutures vary in complexity from wide zones containing distinctive rocks formed at ancient accreting and consuming plate margins to cryptic sutures marked only by abrupt changes in metamorphism and zones of cataclasis paired negative and positive gravity anomalies associated with these sutures have been interpreted in terms of juxtaposed crustal blocks of different density and thickness magnetic anomaly patterns change abruptly at structural province boundaries available seismic results support the concept of thickened crust in the younger province as derived from gravity modelling most authors prefer interpretation of proterozoic pole positions in terms of one plate models but in some cases the interpretation of paleomagnetic data is equivocal and two plate models have been proposed

paleomagnetism of rocks from burin peninsula newfoundland hypothesis of late paleozoic displacement of acadia criticized the posttectonic st lawrence granite 360 5 ma and associated subvertical dikes have two magnetizations n and h n points north with an intermediate upward inclination declination 005 inclination 50 alpha 95 10 paleopole 12 n 120 e we consider n to have been acquired close to the time of initial cooling the h magnetization points south with low inclination h is also the dominant magnetization in the nearby permo carboniferous spanish room formation h is considered to be an overprint acquired chemically during the kiaman reversed superchron late carboniferous and permian the n magnetization corresponds to a paleolatitude of 31 7 s very different from the near equatorial values expected from the commonly accepted late devonian and earliest carboniferous tournaisian reference paleofields for cratonic north america this is generally consistent with the hypothesis of a southerly displaced acadia proposed by kent and opdyke although the displacement is much greater 30 rather than 15 however we show that all inclinations observed from middle to upper devonian and tournaisian rocks from the craton are not significantly different either from the kiaman paleofield or from the h overprints observed from newfoundland some of these cratonic studies are not very detailed but it is noteworthy that the declination observed in the most comprehensive of them catskill red beds also agrees with the kiaman paleofield and with the h overprints from newfoundland declinations in some other cratonic studies show small departures of only a few degrees with one exception based on limited sampling and two from the colorado plateau which may have been rotated which could be caused by experimental inaccuracies moreover the directions obtained from cratonic studies are 97 reversed as they are in rocks with kiaman magnetizations we suggest therefore that the commonly accepted late devonian to earliest carboniferous reference paleofield for north america is either entirely kiaman in age or has been seriously affected by kiaman overprinting consequently the 30 of southerly displacement which the n magnetization of the st lawrence granite apears to indicate and the 15 invoked by kent and opdyke we consider to be illusory three late precambrian rock units 623 to 606 ma have scattered declinations but similar inclinations yielding paleolatitudes of about 35 the scattered declinations presumable were caused by local pre carboniferous relative rotations there is little or no evidence of kiaman overprinting in precambrian rocks indicating that overprinting is comparatively superficial and is probably related to late paleozoic groundwater circulation

prefolding and overprint magnetic signatures in precambrian 2 9 2 7 ga igneous rocks from the pilbara craton and hamersley basin nw australia a total of 446 oriented samples have been collected from an archaean intrusion and the fortescue group volcanics and intrusions in the pilbara and hamersley regions of northwestern australia the paleomagnetism and rock magnetism of these samples have been investigated using susceptibility and hysteresis properties and both alternating field af and thermal demagnetization the most consistent paleomagnetic results were achieved by first applying af demagnetization and then stepwise thermal demagnetization evidence of the effects of lightning are widespread which accounts for the efficacy of this particular demagnetization strategy application of the fold test has resulted in placing significant constraints on the acquisition ages of some of the magnetizations and their corresponding pole positions a prefolding pole position from the millindinna complex is latitude 11 9 s longitude 161 3 e dp 6 8 dm 8 4 and is correlated with a radiometric age of 2 86 0 02 ga folding in the millindinna complex occurred prior to the deposition of the fortescue group new geochronological data indicate that the extrusion of the flood basalts commenced about 2 8 ga this provides a minimum age for the magnetization of the millindinna complex deformation responsible for the formation of the mobile belt separating the pilbara and yilgarn blocks during the ophthalmian orogeny has affected the fortescue group and produced a moderate degree of folding in the southern part of the hamersley basin in the region of millindinna complex outcrop the fortescue group is generally flat lying prefolding pole positions from the fortescue group are for the mount roe basalt latitude 52 4 s longitude 178 0 e dp 6 4 dm 9 1 and for the mount jope volcanics latitude 40 5 s longitude 128 7 e dp 19 9 dm 20 8 the overprint magnetization in the mount jope volcanics yields a pole position latitude 35 0 s longitude 211 5 e dp 2 8 dm 5 5 and is interpreted as having been acquired during folding relating to the formation of the ophthalmian fold belt

collision induced rifting the grenville orogeny and the keweenawan rift of north america abstract we propose that the keweenawan rift formed as a result of convergence related to the synchronous grenville orogeny this proposal is based on 1 1 isotopic ages in the keweenawan rift and the grenville province are similar according to the best u pb and rb sr dates the grenville orogeny existed from 1150 to 1100 ma and keweenawan rifting occurred 1120 1100 ma 2 2 a similar modern orogenic belt and rift relationship in the middle east serves as an actualistic model the red sea gulf of aden rift system has formed as a continuous series of coalesced pull apart basins and is opening parallel to the orogenic front of the zagros and bitlis mountains rifting began in the early miocene while the collision began in the eocene suggesting that rifting is related to the collision 3 3 many other ancient rift collision pairs have a similar age relationship and geometrical configuration based on comparisons of these tectonic regimes we have derived a model whereby these rifts formed as a result of strike slip faults forming in either the foreland or the hinterland of orogenic zones

insights on pumping well interpretation from flow dimension analysis the learnings of a multi context field database abstract the flow dimension parameter n derived from the generalized radial flow model is a valuable tool to investigate the actual flow regimes that really occur during a pumping test rather than suppose them to be radial as postulated by the theis derived models a numerical approach has shown that when the flow dimension is not radial using the derivative analysis rather than the conventional theis and cooper jacob methods helps to estimate much more accurately the hydraulic conductivity of the aquifer although n has been analysed in numerous studies including field based studies there is a striking lack of knowledge about its occurrence in nature and how it may be related to the hydrogeological setting this study provides an overview of the occurrence of n in natural aquifers located in various geological contexts including crystalline rock carbonate rock and granular aquifers a comprehensive database is compiled from governmental and industrial sources based on 69 constant rate pumping tests by means of a sequential analysis approach we systematically performed a flow dimension analysis in which straight segments on drawdown log derivative time series are interpreted as successive specific and independent flow regimes to reduce the uncertainties inherent in the identification of n sequences we used the proprietary siren code to execute a dual simultaneous fit on both the drawdown and the drawdown log derivative signals using the stated database we investigate the frequency with which the radial and non radial flow regimes occur in fractured rock and granular aquifers and also provide outcomes that indicate the lack of applicability of theis derived models in representing nature the results also emphasize the complexity of hydraulic signatures observed in nature by pointing out n sequential signals and non integer n values that are frequently observed in the database

paleomagnetism of the middle proterozoic laramie anorthosite complex and sherman granite southern laramie range wyoming and colorado we present the results of a combined paleomagnetic and 40ar 39ar geochronologic investigation of the middle proterozoic laramie anorthosite complex and sherman granite in the southern laramie range of wyoming and colorado anorthosites and monzosyenites of the laramie anorthosite complex yield a well defined characteristic magnetization of northeast declination d and moderate negative inclination i although antipodal normal and reverse polarity magnetizations are present at three sites a grand mean direction from 29 of 35 sites in the complex is d 44 6 i 48 7 k 77 4 95 3 1 alternating field af and thermal demagnetization behavior and rock magnetic experiments indicate that magnetization is carried by low ti titanomagnetite of single or pseudo single domain character that occurs as elongate to rod shaped inclusions in plagioclase and potassium feldspar the sherman granite contains a dual polarity magnetization that is less well defined than that of the laramie anorthosite complex but similar in declination and inclination d 53 1 i 48 1 k 46 5 95 7 6 n 8 14 sites rock magnetic data indicate the primary carrier of remanence in sherman granite is magnetite the 40ar 39ar geochronologic data from sherman granite hornblende biotite and microcline indicate that subsolidus cooling was moderate to relatively rapid through the range of temperatures over which magnetization was blocked and that the age of remanence is about 1415 ma microcline data indicate that the laramie anorthosite complex and sherman granite have probably not been thermally remagnetized paleomagnetic poles from the laramie anorthosite complex and sherman granite are indistinguishable at the 95 confidence level and individual virtual geomagnetic poles vgps from both units are combined to provide a mean pole at 215 0 e 6 7 s k 46 9 a95 3 5 n 37 vgps the location of this pole is similar to paleomagnetic poles derived from 1480 ma to 1450 ma intrusions elsewhere in north america but it plots significantly north of those from middle proterozoic sedimentary strata of the belt supergroup and sibley group in addition to the characteristic magnetization samples from some sites in sherman granite contain a remanence of southeast declination and shallow negative inclination d 154 9 i 16 0 k 90 6 95 9 7 n 4 sites this secondary magnetization was probably acquired during late paleozoic time

multi level slug tests in highly permeable formations 2 hydraulic conductivity identification method verification and field applications abstract using the developed theory and modified springer gelhar sg model an identification method is proposed for estimating hydraulic conductivity from multi level slug tests the computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double packer system field verification of the method was performed at a specially designed fully penetrating well of 0 1 m diameter with a 10 m screen in a sand and gravel alluvial aquifer msea site shelton nebraska during well installation disturbed core samples were collected every 0 6 m using a split spoon sampler vertical profiles of hydraulic conductivity were produced on the basis of grain size analysis of the disturbed core samples these results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi level slug test responses using the modified sg model the identification method was applied to interpret the response from 474 slug tests in 156 locations at the msea site more than 60 of responses were oscillatory the method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure the proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data recommendations generalizing this experience to massive application of the proposed method are developed

a new paleomagnetic pole for the neoproterozoic uinta mountain supergroup central rocky mountain states usa abstract hematite cemented strata of the neoproterozoic age 800 750 ma uinta mountain group umg provide a new well defined mid neoproterozoic paleomagnetic pole for laurentia thermal demagnetization results and rock magnetic experiments reveal the presence of two discrete magnetizations in umg rocks both magnetizations are carried by hematite the dominant characteristic remanent magnetization chrm is an east directed or antipode shallow positive to negative inclination magnetization that is typically unblocked over a narrow range of high laboratory temperatures between 660 and 680 c the second magnetization exclusively of normal polarity is north to northeast directed and has a moderate to steep positive inclination and probably represents a recent or modern day viscous remanent magnetization the response of umg samples to thermal and chemical demagnetization comparison with previously obtained data from umg rocks in the area results from rock magnetic experiments and the inferred low latitude of laurentia during umg deposition in the neoproterozoic are all consistent with the interpretation that the west or east directed shallow magnetization is a near primary remanence the presence of dual polarities of the chrm with the west directed remanence inferred to be of normal polarity and the east directed of reverse polarity suggests that magnetization acquisition in the umg rocks took place over a sufficient amount of time to average secular variation of the geomagnetic field the mean paleomagnetic pole derived from the inferred primary magnetizations from umg strata 0 8 n 161 3 e 95 4 6 n 9 sampling localities consisting of 79 sites is fully consistent with recently reported results from rocks of mid neoproterozoic age for southwest laurentia which define a tight counterclockwise loop located in the south pacific in the apparent polar wander path for laurentia during the neoproterozoic

an isotopic appraisal of the late jurassic greenhouse phase in the russian platform abstract oxygen and carbon isotope ratios have been determined from late jurassic callovian volgian belemnites from three locations on the russian platform gorodischi khanskaya gora and marievka all samples were examined by means of trace element geochemistry and petrography in order screen for diagenetic alteration oxygen and carbon isotopes from well preserved belemnites range from 2 24 to 0 09 and 0 57 to 1 77 respectively oxygen isotopes if interpreted in terms of temperature reveal a rise of temperatures during the oxfordian early kimmeridgian and indicate a prolonged episode of warmth during the kimmeridgian volgian the isotope data only equivocally reflect a number of significant changes in boreal tethyan ammonite assemblages a positive carbon isotope excursion is observed within the volgian but not seen within composite carbon isotope stratigraphies of the western tethys hence the jurassic may have been characterised by regional 13 c excursions related to non simultaneous organic matter deposition resulting from localised ponding semi restricted ocean circulation and a lack of tidal mixing

palaeomagnetic study of dated pre cambrian rocks of the front range colorado wyoming summary the mean direction of remanent magnetization after partial a c demagnetization of pre cambrian rocks from the front range of colorado and wyoming gives a palaeomagnetic pole position at 8 n 29 e rock types sampled include andesite dykes diorite inclusions in granite and a highly oxidized red granite all with a radiogenic age of 1 41 g y this preliminary study suggests there are at least two and probably as many as four field reversals recorded in these rocks and that remanent directions from andesite dykes may be useful in determining tectonic rotation of the front range

hydrogeological characterization and modelling of weathered karst aquifers applicability to dewatering operations in limestone quarries limestone aquifers represent an important part of groundwater resources in the world they are usually considered as fractured karstic rock formations however a different type called weathered or ghost rock karst aquifer has recently been highlighted in this particular type of aquifer the karst is not expressed as open conduits but consists in zones made of a residual alterite resulting from the in situ partial dissolution of limestone these particular structures are crucial in some areas because they actually govern groundwater flow and transport in the aquifer they have however never been studied from a hydrogeological perspective in this study we present a methodology to characterize and model such aquifers results show that the ghost rock features are usually organized into networks and that their hydraulic properties are variable within each feature according to the limestone weathering intensity measurements in a specific aquifer in belgium are presented the modelling approach derived from the common equivalent porous medium approach enables to spatially distribute the variable hydraulic properties within the features from the hard fresh rock to the alterite in finite difference grids the method allows creating models including thousands of features and respecting correct connectivity relations the approach is considered at different scales with varying grid cells sizes results show that the induced error increases significantly when the size of the grid cells exceeds the width of the main features controlling flow the approach is applied on a case study consisting in dewatering operations in an exploited quarry located in a weathered karst aquifer presented results provide new insights regarding characterization and modelling of this kind of aquifers and highlight their importance in hydrological studies

polar wander and paleomagnetic reference pole controversies the purpose of this paper is to review the progress made over the past four years in studies of phanerozoic and precambrian polar wander with an emphasis on the contributions made by u s scientists we perceive a general theme embracing the notion that the accuracy of cratonic reference poles and therefore of apparent polar wander apw paths is not as good as was generally believed four years ago a renewed interest in research concerning cratonic reference poles is largely the result of paleomagnetic studies in orogenic belts namely the western cordillera and appalachians of north america the andes of south america and elsewhere which seek to document the existence or non existence of displacements of suspect terranes i e rotation and or translation with respect to their presently associated cratons some of the results of this research are reviewed in this volume by hillhouse and mcwilliams an important realization of which paleomagnetists have long been aware but which was demonstrated recently by a number of sobering examples for both the paleozoic and mesozoic apw paths for north america is that the reliability of concordance discordance parameters that define terrane displacement is dependent not only on the precision and accuracy of the individual paleomagnetic study but also on the precision and accuracy of the appropriate cratonic reference pole

paleomagnetism and u pb geochronology of the lac de gras diabase dyke swarm slave province canada implications for relative drift of slave and superior provinces in the paleoproterozoicgeological survey of canada contribution 20080350 lac de gras diabase dykes trend north to nne across the central slave province of the canadian shield u pb baddeleyite ages of 2023 2 and 2027 4 ma are interpreted as dyke emplacement ages th

palaeomagnetism of middle proterozoic basic intrusives in central sweden and the fennoscandian apparent polar wander path abstract palaeomagnetic results are presented from three sets of post svecokarelian intrusions in central sweden the first is a system of e w trending doleritic dykes including the large breven and hallefors dykes and with a probable emplacement age of c 1530 ma their original nrm is disturbed by later events but two magnetic directions group ew1 with decl 359 5 incl 6 2 95 8 2 n 35 and group ew 2 with decl 11 1 incl 51 3 95 10 1 n 14 have been isolated and give palaeopoles at 27 7 n 196 8 e and 61 7 n 176 1 e respectively the group ew1 direction is considered to represent the original emplacement nrm this is based on comparison with contemporary palaeomagnetic data from elsewhere in fennoscandia the second set comprises dolerites and quartzporphyries the tuna dykes age 1371 ma they present a stable magnetization with decl 14 8 incl 18 1 95 9 6 and a palaeopole at 21 1 n 180 4 e the third set studied are dolerites belonging to the dala and jamtland complexes of the central scandinavian dolerite group csdg age c 1250 1200 ma post jotnian they present well defined magnetic directions that give palaeopoles close to the equator around 155 e in agreement with other published palaeomagnetic csdg data however there are deviating results obtain from dolerites belonging to the dala complex of the csdg those deviating have a mean decl of 12 9 incl 1 4 95 18 1 n 5 which gives a palaeopole at 27 0 n 179 5 e situated within the area of the 1600 1500 ma poles results from three probably sweconorwegian c 1000 850 ma doleritic dykes are also presented the results obtained are compared with other contemporary palaeomagnetic poles from fennoscandia and a revised apparent polar wander path is presented and discussed

geochemistry of the mamainse point volcanics ontario and implications for the keweenawan paleomagnetic record the keweenawan 1100 ma mamainse point volcanics located along the eastern shore of lake superior in ontario formed in the midcontinent rift of north america they are a 5250 m thick sequence of over 350 predominantly basaltic lava flows the mamainse point section is the most continuous keweenawan volcanic sequence and spans nearly the entire igneous history of the rift the lower part of the section consists of high mgo picrites and basalts but the upper part of the section is composed of olivine tholeiites intercalated with numerous conglomerate layers major and trace element data reveal that the section consists of numerous stratigraphically constrained geochemically distinct groups of lava flows the comprehensive geochemical data on the entire sequence indicate that the section has no repetition due to faulting as has been suggested by other workers on the basis of paleomagnetic studies evidently the three paleomagnetic reversals previously found in the mamainse point section are real and

baked contact test demonstrates primary nature of dominant n1 magnetisation of nipissing intrusions in southern province canadian shield abstract nipissing diabase sills cone sheets and dykes define a major episode of igneous intrusion in the southern province of the canadian shield at about 2200 ma the dominant n1 remanence of these intrusions has been established in several palaeomagnetic studies and hence is a key tie point for the north american apparent polar wander path yet the age of this magnetisation remains very controversial positive baked contact tests reported for the n1 remanence have often been dismissed as inconclusive and the n1 palaeopole attributed to overprinting during the hudsonian orogeny 1900 1800 ma due to its position on a widely accepted polar wander path for north america previous baked contact studies utilise sediments of the huronian supergroup as host rock the remanence of these sediments is often difficult to interpret in this study a positive baked contact test is described for an n1 nipissing sill or cone sheet using stably magnetized mafic dykes of the matachewan swarm as host thus the n1 remanence is primary and no longer supports the time calibration of polar wander paths which assume that it is a 1900 1800 ma overprint

belemnite taphonomy upper jurassic western tethys part i biostratinomy abstract a detailed taphonomic analysis was performed on 188 belemnites and 56 thin sections from the pozo canada section external prebetic as well as 101 belemnites and 31 thin sections from the rio segura internal prebetic both from the upper oxfordian lower kimmeridgian this manuscript is focused on biostratinomic features and a second part is focused on fossildiagenetic aspects the belemnites correspond to hibolithes and less commonly belemnopsis biostratinomic features including size fragmentation corrasion microboring and encrustation were analysed in each specimen using petrographic conventional cathodoluminescence epifluorescence and scanning electron microscopy techniques fragmentation affects the phragmocone and the rostrum cavum and is usually transversal and rarely longitudinal through the apical line isolated fragments of epirostrum are common corrasion produces irregular surfaces microborings are very common represented by a fungal hyphae b fascichnus dactilus like and scolecia filosa like borings cyanobacteria c entobia sponges d large microborings with y shaped branching diameter 100 500 m subparallel to rostrum surface e large cylindrical to ellipsoidal borings related to cirripeds and f palaeconchocelis starmachii rhodophyte microbes and sessile foraminifera vinelloidea bullopora tolypammina thurammina placopsilina and subdelloidina are the main encrusters microbial films are composed of dense micrite or clotted peloidal microfabrics the biostratinomic features analysed in the belemnite rostra are clearly influenced by the lithofacies and shelf setting the intensity of corrasion microborings and encrustation by indicating time exposure help establish which lithofacies shows the highest sedimentation rate the belemnites from internal prebetic lithofacies that is the outer shelf deposits lumpy limestone and lumpy oncolitic limestone present high values of corrasion microboring and encrustation thereby indicating long time exposure in sharp contrast belemnites from the lithofacies of the external prebetic represent deposition in mid shelf environments spongiolithic limestone spongiolithic marl peloidal limestone and marl limestone rhythmite featuring higher clay content

smnd mineral isochron ages of late proterozoic dyke swarms in australia evidence for two distinctive events of mafic magmatism and crustal extension two distinctive events of widespread dyke intrusion have been identified in central southern australia crystallization ages of the dykes were determined using sm nd mineral isochrons obtained by splitting clinopyroxene and plagioclase into different magnetic and density fractions respectively the stuart dyke swarm in the southern arunta inlier and the kulgera dyke swarm in the eastern musgrave inlier define essentially identical crystallization ages of 1076 33 and 1090 32 ma respectively marking the first episode of post orogenic mafic magmatism in the region two samples from the gairdner dyke swarm in the stuart shelf yield sm nd mineral isochron ages of 867 47 and 802 35 ma respectively whilst two samples from the amata suite in the central musgrave inlier 790 40 and 797 49 ma these four ages represent the second episode of mafic magmatism in central southern australia these ages allow new constraints to be placed on the timing of large scale crustal extension and formation of intracratic depositional basins in the region initial nd values of 7 8 to 6 6 for the stuart dykes and 0 7 for the kulgera dykes suggest they were derived from different mantle sources with the stuart dykes being produced from strongly enriched sources in contrast positive and relatively uniform initial nd values of 2 5 to 4 1 for the younger amata suite and gairdner dykes indicate that they were derived from relatively depleted and homogeneous mantle sources the 1076 33 ma sm nd age of the stuart dyke swarm is significantly older than its rb sr mineral isochron age of 897 9 ma previously reported suggesting mobility of rb and or sr and partial resetting of rb sr isotopic systematics this study demonstrates that reliable and relatively precise sm nd ages can be obtained for precambrian dykes despite the limited number of mineral phases available in the dykes

predictive modelling of hydraulic head responses to dipole flow experiments in a fractured karstified limestone aquifer insights from a comparison of five modelling approaches to real field experiments summary five modelling approaches were tested against a well studied limestone aquifer constituting the hydrogeological experimental site hes of poitiers france the modelling exercise consisted of predicting the drawdown responses of a series of observation wells for two dipole pumping injection flow experiments involving two distinct well pairs at the hes the differences between model predictions appear to be mainly related to the hydraulic datasets used for model parameterisation and to a much lesser extent to the conceptual modelling approach equivalent porous medium vs discrete fracture networks the model dimensionality two dimensional vs three dimensional and or the parameterisation approach forward vs inverse despite the abundance and diversity of calibration parameterisation data all of the models failed to predict the drawdowns with a reasonable degree of accuracy only the order of magnitude of the drawdowns was correctly predicted by three of the five models whereas all models failed to predict the drawdown behaviour at both intermediate and late times the primary source of error is attributed to a lack of information in the single well pumping test data which did not capture the multi permeability structure of the aquifer as revealed a posteriori by the responses to dipole flow experiments this highlights the need to develop novel or improved approaches to characterise the hydraulic properties of limestone aquifers

skin effect in generalized radial flow model in fractured media summary a generalized radial flow model treating the flow dimension as an arbitrary number and taking into account the well skin effect is presented to describe the transient head distribution in a fractured medium under the robin condition during constant head tests the laplace domain solution for the head distribution is first developed via the laplace transforms and the corresponding time domain solution in terms of the hydraulic head is then obtained using the bromwich integral method in addition based on the head solution and darcy s law the solution for the wellbore flux is further developed to investigate the skin effect it is found that the skin effect on the wellbore flux is significant at early times under this circumstance it would not be appropriate to neglect the skin effect in the model in determining the hydraulic parameters from the analysis of field data our solutions will be useful for the predictions of the spatial and temporal head distribution and wellbore flux or in investigating the skin effect on the head distribution and wellbore flux for flow with various dimensions in fractured media

taphonomy of cephalopod assemblages from middle jurassic hardgrounds of pelagic swells south iberian palaeomargin western tethys abstract taphonomic analysis of cephalopod assemblages together with analyses of ichnologic and sedimentologic features are useful tools in the interpretation of the history of unconformities in jurassic pelagic swells the external subbetic presents a complex evolution during the middle bathonian middle oxfordian interval that includes hardgrounds and condensed levels rich in ammonoids bathonian and callovian hardgrounds separated by a condensed calcarenitic bed can be differentiated in the bathonian hardground ammonoids are preserved with unfilled phragmocone chambers as a consequence of initial fast burial neomorphic calcite in the ammonoids is related to early diagenesis indicating a stop in sedimentation the ichnological features testify to an early diagenesis and progressive cementation of the sea bottom which is corroborated by the record of neptunian dykes subsequently sediment by passing and erosion produced reorientation of the ammonoids and belemnite remains and exhumation of moulds during which faceting and reelaboration took place finally the sedimentation began resulting in the deposition of a condensed calcarenite bed with fe mn macro oncoids the callovian hardground developed at the top of the calcarenite bed where the cephalopods show signs of long exposure on the sea bottom such as colonization by chemosynthetic microbial communities and sessile foraminifera the study proves that the middle bathonian middle oxfordian represents a time interval of strongly reduced and highly discontinuous sedimentation interrupted by periods of non deposition and erosion

isotopic signals from callovian kimmeridgian middle upper jurassic belemnites and bulk organic carbon staffin bay isle of skye scotland abstract the stable isotope data presented here significantly extend and expand upon previous isotopic investigations of the middle to late jurassic interval the belemnite samples collected from the staffin bay and staffin shale formations from the isle of skye scotland yielded oxygen isotope values consistent with callovian kimmeridgian palaeotemperatures of 6 7 20 6 c the carbon isotope data comprise one of the first moderately high resolution investigations of the relationship between terrestrial 13 c org predominantly fossil wood debris and marine 13 c carb belemnites as derived from a geologically coeval record the staffin bay data reveal a broad early to mid oxfordian positive carbon isotope excursion the excursion maximum occurs in the cordatum zone british boreal ammonite zonation although high values persist into the tenuiserratum zone the correspondence between the marine and terrestrial records indicates a strong coupling of the ocean atmosphere system and suggests that the total exchangeable carbon reservoir would have been affected at this time the mid oxfordian negative carbon isotope excursions identified in published tethyan records and commonly attributed to methane release are not recorded in the staffin bay data which may suggest that the tethyan excursions do not represent fluctuations in the global carbon reservoir and that the fidelity of the methane hypothesis should be re evaluated supplementary material isotopic and geochemical data are available at http www geolsoc org uk sup18339

interference pumping tests in a fractured limestone poitiers france inversion of data by means of dual medium approaches hydraulic interference pumping tests remain a valuable method for obtaining information on underground flows at a scale compatible with the operation of a reservoir combining a dual medium model with the inversion of interference testing data in fractured rocks is very recent probably because the model is ruled by very contrasted sensitivities to its main parameters it is shown that an accurate and stable inversion requires a specific procedure based on re scaled sensitivities to parameters both homogeneous and fractal dual media have been inverted on two sets of data obtained from the fractured limestone of the experimental site in poitiers france the first data set can be homogenized with both homogeneous and fractal approaches yielding almost constant hydraulic parameters or only weak statistical variations beyond experienced distances of 200 m the second data set collected in a site perturbed by forced flows from the first campaign shows preferential flow paths with a piston like propagation of the pressure depletion only the fractal dual medium is able to partly homogenize the hydrodynamic behavior surprisingly the hydraulic conductivity is constant but the dimensioning constants of the capacity parameters continue to decrease with the size of the system thus the intrinsic decrease of parameters with the size of the system in the fractal approach is not sufficient to mimic the scale effects recorded by interference tests superimposition of piston like effects onto dual media shall be further investigated to better account for the influence of scarce flow paths with very high velocities

an application of hydraulic tomography to a deep coal mine combining traditional pumping tests with water inrush incidents abstract water inrush incidents threaten the safety of coal mining understanding of hydrogeologic parameter distributions is critical for preventing water related hazards in coal mines during the deep mining 1000 m under the north china plain water from water bearing strata discharges into coal seams through geologic conduits i e water inrush due to the fractured zone under the floor of working faces in this study a water inrush incident was exploited as an active stimulus a 3d groundwater flow model was built for the eighth member of the middle ordovician system in xingdong coal mine using this model and an inverse approach we first checked if the data from the incident and an independent pumping test carry non redundant information about the heterogeneity of the mine afterward we combined these datasets to conduct a large scale approximately 10 km hydraulic tomography ht analysis the estimated hydraulic conductivity distribution from the ht analysis is found consistent with the distribution of known geologic faults that is a cluster of faults is characterized as a high conductivity zone a high conductivity zone is identified at locations close to the water inrush location which is the high cement consumption zone during the grouting project finally results of this study promote exploiting the water inrush events as a ht survey for mapping geologic structures over a large area

analytical models of slug tests in the present paper attempts are made to develop solutions to various models of slug tests that may be applicable in analyzing the results of such tests where existing solutions are inadequate various geometries that may be encountered in heterogeneous systems such as fractured rocks are considered solutions are presented for linear flow radial flow with boundaries two layer and concentric composite models with different flow geometries between the inner and outer region solutions are obtained in laplace space and inverted back to real space numerically type curves are presented for each solution analyses of the type curves and derivative response curves reveal that many curves have unique shapes only for certain combination of the flow parameters and the distance other sets of type curves are similar in shape although log log plots and derivative plots may emphasize some features that may not be apparent in semilog plots these results show that slug tests suffer problems of nonuniqueness to a greater extent than other well tests

paleomagnetism of the north american precambrian a look at the data base more than half of the approximately 650 paleopoles reported from all precambrian cratons have been obtained from north america the observations have spurred a proliferation of apparent polar wander paths to support different hypotheses for the tectonic evolution of the continent many of the reasons for this development can be traced to the inadequacy of the data base with its average of only 1 6 poles 10 ma 1 as compared to 7 poles 10 1 ma for the last 300 ma even when it is assumed that a primary pole has been derived from each rock unit sampled the total number of primary poles excluding the 900 1200 ma interval yields an average of only 0 4 pole 10 ma 1 an inspection of the data base shows a non systematic sampling of a non continuous fragmented paleomagnetic record with gaps as large as tens and even hundreds of ma more importantly a search through the literature reveals that very few poles have an age known to better than 50 ma and for many poles the age bracket could be as large as a few hundreds of ma this is partly owing to the fact that radiometric and paleomagnetic sites rarely originate from the same localities it is shown that this limited data base with all its deficiencies and uncertainties cannot be used to support certain hypotheses or for the drawing of a meaningful apparent polar path for the whole of the precambrian it appears that because of the enormous time scale precambrian paleomagnetism should rather be directed towards the construction of segments of polar paths such as those in the 900 1200 ma interval comparison of well dated contemporaneous segments from different parts or structural provinces could be used most effectively to delineate relative movements if any and reconstruct the mosaic of the past continent for certain time intervals one of the recent developments of precambrian paleomagnetism has been to show that the apparent pole did not remain constrained to the equatorial region but made several excursions into high latitudes

on the use of multiple point statistics to improve groundwater flow modeling in karst aquifers a case study from the hydrogeological experimental site of poitiers france abstract limestone aquifers often exhibit complex groundwater flow behaviors resulting from depositional heterogeneities and post lithification fracturing and karstification in this study multiple point statistics mps was applied to reproduce karst features and to improve groundwater flow modeling for this purpose mps realizations were used in a numerical flow model to simulate the responses to pumping test experiments observed at the hydrogeological experimental site of poitiers france the main flow behaviors evident in the field data were simulated particularly i the early time inflection of the drawdown signal at certain observation wells and ii the convex behavior of the drawdown curves at intermediate times in addition it was shown that the spatial structure of the karst features at various scales is critical with regard to the propagation of the depletion wave induced by pumping indeed i the spatial shape of the cone of depression is significantly affected by the karst proportion in the vicinity of the pumping well and ii early time inflection of the drawdown signal occurs only at observation wells crossing locally well developed karst features

the quasi rigid premise in precambrian tectonics abstract the proposition that movements between multiple continental fragments driven by plate tectonics have taken place during the earlier eons of geological time can be simply tested a random distribution will be derived when the collective palaeomagnetic poles are rotated into any quasi rigid reconstruction this elementary test surmounts the most serious limitation of precambrian palaeomagnetic data namely that the ages of magnetisation are mostly poorly known in the event the late archaean and proterozoic poles 2850 590 ma produce a non random distribution with a single peak which is only compatible with a quasi rigid continental configuration occupying a preferential position on the globe this solution is not favoured because uncertainties in definition of the poles contribute to their scatter and bias the solution towards the random one hence confirmation of the quasi rigid premise is derived in a debased form but is not suppressed by the deficiencies of the database this palaeomagnetic constraint explains the distinctive isotopic geochemical and lithofacies signatures of the proterozoic eon and is independently supported by the trend and long temporal continuity of crustal lineaments it does not preclude the opening of ocean basins between the shields but it does predict that development of these basins was limited by the influence of controlling mantle systems this constrained the continental crust into a form which was essentially rigid on the gross scale resolvable by palaeomagnetism

palaeotemperatures indicated by upper jurassic kimmeridgian tithonian fossils from mallorca determined by oxygen isotope composition abstract the oxygen and carbon composition of calcite has been determined for belemnites ammonite aptychi and the matrix surrounding these fossils from the kimmeridgian tithonian of mallorca petrography cathodoluminescence and trace element analyses indicate that both ammonite aptychi and matrix has been diagenetically altered whereas the belemnites have been undergone minimal or no modification the belemnites give the heaviest oxygen isotope values of 0 04 to 0 99 pdb and lighter values of 0 71 to 3 98 pdb come from the ammonite aptychi and matrix the carbon isotopic compositions obtained from all the fossils are positive and are similar to those derived from modern marine shallow water skeletons palaeotemperatures calculated on the basis of the oxygen isotopic composition of the belemnites give a range of values from 13 6 to 16 c these results agree with late jurassic palaeotemperatures from similar palaeolatitudes

paleomagnetism and upb geochronology of volcanic rocks from michipicoten island lake superior canada precise calibration of the keweenawan polar wander track abstract paleomagnetic poles have been determined for normally magnetized samples of late proterozoic volcanic rocks from 23 sites on michipicoten island lake superior canada the results are in general accord with an earlier less precise study by one of the authors and indicate a small polar shift between rocks of the mamainse point formation 186 e 38 n and the michipicoten island formation 175 e 26 n a quartz feldspar porphyry intruding the lower mamainse point formation but unconformably overlain by the michipicoten island formation was sampled for u pb zircon dating the zircons define an age of emplacement of 1086 5 1 3 3 0 ma this age and the pole positions are consistent with and supplement ages previously determined for the keweenawan paleomagnetic polar wander curve these data define an apparent polar wander rate of 14 cm a 1 this age combined with previously published u pb ages indicates a time span of 22 ma for most keweenawan igneous activity in addition the time of the keweenawan paleomagnetic reversal is constrained to be between 1086 5 1 3 3 0 and 1097 6 3 6 ma the age of the upper part of the reversely magnetized osler group the zircon population contained an inherited component from a source 1403 50 ma old this suggests that the porphyry magma was at least partly derived by melting of an anorogenic pluton emplaced during the mid proterozoic

inversion of a set of well test interferences in a fractured limestone aquifer by using an automatic downscaling parameterization technique summary this work inverts interference hydraulic tests from a karstic aquifer modeled as a single continuum with heterogeneous hydraulic properties hydraulic conductivity k and specific storage capacity ss an automatic technique of parameterization is proposed to solve the inverse problem sought parameters are located at the nodes of a parameter grid made of triangular elements and independently superimposed onto the calculation grid of the flow problem the parameter grid can be refined within the process of inversion so that the solution is improved locally because increasing the number of parameters better depicts spatial heterogeneity applied to hydraulic tests carried out at the hydrogeological experimental site hes of poitiers france this adaptative multi scale triangulation amt method of parameterization reveals that hydraulic conductivity k and hydraulic diffusion k ss are structured in space as correlated stochastic continuums this structure is not imposed a priori but is found as the mere consequence of inverting drawdown data the sought stochastic continuums are discussed and compared to previous results obtained by processing the same data with various techniques even though interference data show evidences of local karstic features the hydraulic bulk behavior of the aquifer is that of a diffusive continuous medium this reinforces the idea that at mid to large scales flow in fractured rocks can also be handled with relevance by means of a continuous heterogeneous approach this result would extend to fractured aquifers with local draining in open conduits as is the case in this study

a double porosity slug test model for a sloping fracture zone field investigation indicates the dip angle of a fracture zone in a cenozoic folded sandstone formation is as large as 47 when the dip angle is large the flow field generated by slug test becomes radially asymmetrical with respect to test well taking into account the dip angle effects a new double porosity slug test model and its laplace domain solution are necessarily developed for both the oscillatory test response as for a highly permeable condition and non oscillatory test response as for a low permeable condition for the oscillatory response it is found that a larger dip angle causes larger amplitude while introduces little impact on period the dip angle effect on the test response oscillatory or non oscillatory is found to be more pronounced for a larger hydraulic conductivity of the fracture zone a smaller specific storativity of the matrix or a smaller and the application range of the current model is determined for the limiting dip angle that is the dip angle effect should be considered in data analysis when dip angle is larger than 30 a set of test responses from a slug test data in the fracture zone of a 47 dip angle is analyzed by using the current model it is found that neglecting the dip angle can result in a 63 4 overestimate of the hydraulic conductivity of the fracture zone a 95 5 underestimate of the specific storativity of the matrix and a 63 3 underestimate of

sensitivity analysis of slug tests part 2 observation wells abstract an earlier paper part 1 this issue dealt with the use of sensitivity analysis for the design of a slug test that would give reasonably accurate estimates of the aquifer parameters by an informed choice of the number and times of measurements an investigation of the radial dependence of the cooper et al analytical solution for a slug test in a confined aquifer shows that the use of one or more observation wells can vastly improve the parameter estimates particularly the estimate of the storage parameter generally the observation well must be fairly close about 10 m or less to the slugged well to be effective the storage coefficient must be small in order to see the effect of the slug at greater distances from the stressed well since the temporal and spatial dependence of the sensitivities for transmissivity and storage are considerably different the addition of one or more observation wells will substantially reduce the correlation between these two parameters which will result in much better estimates than are usually obtained in slug tests these ideas are illustrated using typical data representative of our research sites

the palaeomagnetism of middle proterozoic dyke swarms of the gardar province and mesozoic dykes in sw greenland summary the precambrian metamorphic basement in sw greenland was subjected to widespread emplacement of dolerite dykes between circa 1290 and 1160 ma during this period the regional stress field rotated in a counter clockwise sense a regional palaeomagnetic study of 59 of these dykes and contacts is reported whilst contact tests generally indicate primary magnetizations two and three component structures in some dykes record partial overprinting at later stages of the igneous cycle component directions are distributed from shallow negative westerly to steep nw positive over most of the outcrop the former magnetizations are found in the earlist e w trending dykes steepening and rotation of magnetization directions correlates with rotation of dyke trends towards later ne sw trends the exception occurs where dykes are deflected in a sigmoidal way through an older alkaline complex the quasi continuous nature of dyke emplacement records migration of the palaeofield direction between circa 1290 and 1160 ma and representative sequential pole positions are a1 215 3de 3 1dn 21 dykes dp dm 4 8 9 6d a2 220 4de 7 4dn 5 dykes dp dm 4 3 8 5d and a3 222 3de 33 5dn 30 dykes dp dm 4 5 7 0d palaeomagnetic poles from the gardar igneous province define the major part of a double apw loop anchored by dated poles from igneous complexes and executed between 1300 and 1140 ma this interval appears to have been dominated by one field polarity palaeomagnetic results are also reported for five dykes belonging to the mesozoic coast parallel swarm and palaeomagnetic results from these dykes in south and south west greenland are reassessed they define a dual polarity axis of intermediate inclination d i 336 51d 13 sites palaeomagnetic pole td1 at 168 3de 55 6dn dp dm 4 7 6 9d plus a steeper single polarity group mean direction d i 329 69d 14 sites palaeomagnetic pole td2 at 207 7de 68 6dn dp dm 6 6 7 8d the td1 pole corresponds to north american apparent polar wander at circa 165 ma compatible with the 168 138 ma age constraint whilst the td2 pole correlates with near static apw between 129 and 88 ma it appears to record an episode of dyke emplacement across south greenland during the cretaceous normal superchron shortly before commencement of sea floor spreading between greenland and labrador

stromatolites and earth sun moon dynamics inclination of stromatolite columns caused by nonvertical direction of averaged incident solar radiation provides a signal for deducing astronomical and geophysical data at time of stromatolite formation a sample of anabaria juvensis bitter springs formation central australia shows a sinusoidal growth pattern which interpreted as an annual signal obliquity of the ecliptic with daily production of laminae indicates 435 days per year a result consistent with other available estimates a sample of inzeria from the same formation also shows a sinusoidal pattern and a similar estimate for days per year both samples indicate growth rates of centimeters per year several laboratory measurement techniques offer systematic procedures for extracting data

modeling cross hole slug tests in an unconfined aquifer abstract a modified version of a published slug test model for unconfined aquifers is applied to cross hole slug test data collected in field tests conducted at the widen site in switzerland the model accounts for water table effects using the linearized kinematic condition the model also accounts for inertial effects in source and observation wells the primary objective of this work is to demonstrate applicability of this semi analytical model to multi well and multi level pneumatic slug tests the pneumatic perturbation was applied at discrete intervals in a source well and monitored at discrete vertical intervals in observation wells the source and observation well pairs were separated by distances of up to 4 m the analysis yielded vertical profiles of hydraulic conductivity specific storage and specific yield at observation well locations the hydraulic parameter estimates are compared to results from prior pumping and single well slug tests conducted at the site as well as to estimates from particle size analyses of sediment collected from boreholes during well installation the results are in general agreement with results from prior tests and are indicative of a sand and gravel aquifer sensitivity analysis show that model identification of specific yield is strongest at late time however the usefulness of late time data is limited due to the low signal to noise ratios

paleomagnetism u pb geochronology and geochemistry of marathon dykes superior province and comparison with the fort frances swarm we report the first detailed study of the paleomagnetism u pb geochronology and major element geochemistry of paleoproterozoic north trending marathon dykes north of lake superior the paleomagnetic and geochemical results demonstrate that marathon dykes can be divided into two subsets one of normal magnetic polarity the other of reverse polarity normal and reverse marathon paleomagnetic poles at 43 n 196 e dm 9 dp 7 number of dykes n 16 and 51 n 175 e dm 9 dp 6 n 12 respectively are statistically distinct and may indicate different ages of normal and reverse dyke emplacement a u pb baddeleyite age of ma has been obtained at a normally magnetized marathon paleomagnetic site the reversely magnetized marathon dykes are undated but have a paleopole rather close to that of the reversely magnetized ma fort frances dykes and major element geochemical signatures as portrayed on jensen plots that are identical to those of the fort frances swarm therefore reverse marathon an

effects of early sea floor processes on the taphonomy of temperate shelf skeletal carbonate deposits abstract cool water shelf carbonates differ from tropical carbonates in their sources modes and rates of deposition geochemistry and diagenesis inorganic precipitation marine cementation and sediment accumulation rates are absent or slow in cool waters so that temperate carbonates remain longer at or near the sea bed early sea floor processes occurring between biogenic calcification and ultimate deposition thus take on an important role and there is the potential for considerable taphonomic loss of skeletal information into the fossilised record of cool water carbonate deposits the physical breakdown processes of dissociation breakage and abrasion are mediated mainly by hydraulic regime and are always destructive impact damage reduces the size of grains removes structure and therefore information and ultimately may transform skeletal material into anonymous particles abrasion is highly selective amongst and within taxa their skeletal form and structure strongly influencing resistance to mechanical breakdown dissolution and precipitation are the end members of a two way chemical equilibrium operating in sea water in cool waters inorganic precipitation is rare there is conflicting opinion about the importance of diagenetic dissolution of carbonate skeletons on the temperate sea floor but test maceration and early loss of aragonite in particular are reported dissolution may relate to undersaturated acidic pore waters generated locally by a combination of microbial metabolisation of organic matter strong bioturbation and oxidation of solid phase sulphides immediately beneath the sea floor in otherwise very slowly accumulating skeletal deposits laboratory experiments demonstrate that surface to volume ratio and skeletal mineralogy are both important in determining skeletal resistance to dissolution biological processes on the sea floor include encrustation and bioerosion encrustation a constructive process may be periodic or seasonal and can be reversed it produces both information and material bioerosion in contrast is destructive and permanent in temperate areas bioerosion may destroy even very large shells during their long residence at the sea floor on the order of hundreds to thousands of years overall processes on the temperate sea floor may combine to destroy more carbonate than they produce and the preservation potential of temperate shelf carbonate into the rock record may be significantly affected where preservation does occur in such a destructive regime the effects of early sea floor processes will be key determinants of the deposit resulting in a taphofacies characteristic of temperate shelf carbonate sediments

strontium isotope stratigraphy and oxygen and carbon isotope variation during the middle jurassic early cretaceous of the falkland plateau south atlantic abstract 87sr 86sr data of belemnites are presented from a middle jurassic early cretaceous succession from the falkland plateau deep sea drilling project sites 511 and 330 that was deposited in a periodically anoxic semi enclosed shallow water basin diagenetically screened strontium isotope values of 0 706789 rise to 0 707044 before increasing sharply to 0 707428 in the uppermost part of the sampled succession comparison with published strontium calibration curves suggests that the oldest samples were callovian to oxfordian in age whilst the remainder of the jurassic part of the succession consisted of kimmeridgian and early tithonian age sediments the nannofossil dinoflagellate and molluscan assemblages provide comparable age determinations the strontium isotope analysis of the youngest belemnites points to a hauterivian barremian age whilst age interpretations based upon the fauna provide a wide age range from the barremian to early albian strontium isotope stratigraphy of this succession hence offers increased age resolution providing data regarding the timing of episodes of bottom water anoxia which have been recorded throughout the south atlantic basin well preserved belemnite specimens display an oxygen isotope range between 0 08 and 2 22 pdb peedee belemnite international standard and a carbon isotope range from 2 35 to 1 33 pdb 13c values become increasingly negative through the late jurassic early cretaceous and in concert with the 87sr 86sr data reveal a trend that could be accounted for by increasing levels of weathering and erosion the oxygen isotope data if interpreted in terms of palaeotemperature are consistent with warm palaeotemperatures in the kimmeridgian and slightly cooler temperatures for the tithonian and early cretaceous parts of the succession the proposed relative kimmeridgian warmth based upon strontium isotope age assignments is thus in good agreement with other published palaeotemperature records

the palaeomagnetism of major middle proterozoic igneous complexes south greenland and the gardar apparent polar wander track abstract the gardar province comprises a major rift related igneous suite emplaced in three pulses at ca 1300 1280 ma ca 1220 ma and 1160 1125 ma this study reports a palaeomagnetic study of the northeastern sector of the present outcrop and incorporates igneous units belonging to the first and last episodes early lavas from the basal part of the rift infill record a reversal of magnetisation and define a palaeomagnetic pole at 207 e 10 n 5 sites dp dm 7 14 this primary magnetisation record has been partially overprinted in the aureoles of large alkaline complexes the latter plutons include the north qoroq intrusion 1291 61 ma yielding a pole position at 203 e 13 n 65 samples from 12 sites dp dm 6 12 the motzfeldt intrusion 1291 31 ma yielding a pole position at 212 e 10 n 25 samples dp dm 6 12 and the narssarssuaq stock yielding a pole position at 207 e 9 n 23 samples dp dm 4 7 the younger south qoroq complex 1160 8 ma yields a pole position at 216 e 42 n 67 samples from 9 sites dp dm 11 16 positive contact tests indicate primary cooling related magnetisations these bodies are predominantly of single polarity equivalent to w directions of magnetisations although reversals are recorded the majority of a suite of ne sw trending dykes emplaced at ca 1154 1143 ma are magnetised in a similar direction d i sol3 51 pole position at 231 e 33 n 18 dykes dp dm 5 7 to the slightly older south qoroq complex together with earlier results from the gardar province these data define a motion of the region from shallow to equatorial and then back to intermediate palaeolatitudes between 1290 and 1140 ma pole positions trace out an apparent polar wander path comprising a small loop followed by a long track this track is the outward path of the great logan palaeomagnetic loop for which data from the keweenawan province of north america ca 1100 1050 ma define the return path the loop was executed between ca 1200 and 1050 ma following a near static interval between ca 1290 and 1200 ma this long static interval was also characterised by constant field polarity asymmetry of geomagnetic field reversals is recognised in early gardar events it is not apparent in younger gardar data although it recurs in keweenawan times

cross well slug interference tests an effective characterization method for resolving aquifer heterogeneity summary in this study the potential of cross well slug interference tests for high resolution aquifer characterization of hydraulic heterogeneity was assessed the cross well slug interference tests were performed at the research site stegemuhle located in the leine river valley near gottingen germany the geological composition of the subsurface consisting mainly of 3 5 m silt and clay overlying 2 5 m sand and gravel was determined by geophysical well logging and bore core data to account for lateral changes a refraction seismic survey was conducted based on these data an area characterized by an aquifer thickness of approximately 2 m and an average hydraulic conductivity of 5 0 10 4 m s determined by pumping tests most appropriate for cross well slug interference tests was chosen altogether 196 cross well slug interference tests were performed using a tomographic measurement array the cross well slug interference tests were evaluated using type curve analysis which provided detailed information concerning the vertical changes of hydraulic conductivity and specific storage to assess hydraulic strata connectivity a travel time based tomographic inversion approach was utilized the potential of the inversion approach to determine lateral changes could be successfully demonstrated by the reconstruction of the pinch out of a high diffusivity layer close to the bottom of the aquifer the results demonstrate that the combined evaluation of cross well slug interference tests based on type curve analysis and travel time inversion allows for the development of a detailed model about subsurface hydraulic heterogeneity