palaeomagnetism and magnetostiatigraphy of triassic strata in the sangre de cristo mountains and tucumcari basin new mexico usa summary we report palaeomagnetic data and a composite magnetic polarity sequence for middle and upper triassic rocks assigned to the anton chico member of the moenkopi formation and chinle group respectively exposed along the eastern flank of the sangre de cristo mountains and in the tucumcari basin of eastern and northeastern new mexico thermal demagnetization isolates a well defined dual polarity characteristic magnetization carried in most cases by haematite and interpreted as an early acquired chemical remanent magnetization crm characteristic magnetizations from 74 palaeomagnetic sites one site one bed are used to define a magnetic polarity sequence which we correlate with previously published triassic data obtained from both marine and non marine rocks preliminary correlation suggests that the resolution of magnetostratigraphic data derived from continental strata is not necessarily of lesser quality than that from marine rocks on the basis of the magnetostratigraphic data a profound unconformity is believed to separate lower middle norian and upper norian rhaetian strata of the chinle group palaeomagnetic poles derived from selected sites in steeply dipping 85 strata for the middle triassic anisian 240 ma 50 n 121 e n 8 late carman early norian 225 ma 53 n 104 e n 16 and late norian rhaetian 208 ma 59 n 77 e n 8 are in relatively good agreement with previously published data for the moenkopi formation and chinle group and related strata in southwest north america none the less comparison with palaeomagnetic poles obtained from gently dipping or flat lying triassic strata from this study anisian 46 n 112 e n 13 late carnian 54 n 87 e n 12 and previously published triassic poles in southwest north america suggest that a modest apparent rotation not greater than about 5 affects declinations from steeply dipping rocks the distribution of palaeomagnetic poles indicates 25 angular distance of apparent polar wander between about 240 and 208 ma

permeability and stress in crystalline rocks groundwater from crystalline rocks is a significant resource in many areas of the world it is also an important medium for contaminant transport from for example deep nuclear waste repositories stress distributions in fractured rocks are important in controlling groundwater flow in several ways i palaeostress fields are responsible for the evolution of fracture systems which transmit groundwater ii current in situ stress fields will influence the shape and aperture of fractures iii humans can influence the natural stress field in a rock mass to enhance fracture flows the significance of stresses for groundwater flow can be investigated by field techniques hydraulic fracturing laboratory techniques stress cells or by numerical modelling

clean periodicity in secular variations of dolomite abundance in deep marine sediments abstract secular variations in dolomite abundance in deep marine sediments dadms indicate changing bio geochemical and sedimentary environments of deposition increasing dolomite abundances of the past indicate that past is the key to the present in this case spectral analyses of best available dadms record for the past 140 million years m y using a powerful clean spectral algorithm for the first time reveal a clean and statistically significant at 95 cl periodicity of about 24 5 1 5 m y maximum entropy spectral analysis mesa of the dadms record further confirms the above finding these results reinforce the general belief that changes in the earth s processes occurred in a cyclic manner interestingly 24 5 1 5 m y periodicity in the dadms record also compares extremely well within error limit with the marine mass extinction cycle 26 m y and lends credence to the cyclicity of marine processes it may be inferred that quasi periodic terrestrial records of sealevel climate and environmental changes coupled with some modest bio geochemical variations may have stimulated quasi periodic variations of dolomitization

changing fluvial environments across the permian triassic boundary in the karoo basin south africa and possible causes of tetrapod extinctions abstract the karoo supergroup is a 12 km thick succession of sedimentary rocks that accumulated in a large intracratonic retroarc foreland basin in southwestern gondwana the strata record 100 million years of almost continuous sediment accumulation from the permo carboniferous 300 ma through to the early jurassic 190 ma under a range of climatic regimes and within several tectonically controlled sub basins alluvial sediments dominate the succession from the late permian onwards fossils of synapsid reptiles and early dinosaurs are sufficiently common to be used in a ten fold biostratigraphic subdivision of these strata the permian triassic boundary in the karoo succession is marked by a major extinction of the herbivorous dicynodonts which co incides with a rapid change in fluvial facies this study uses field observations of the sedimentary facies palaeosols and in situ fossils of well exposed p tr boundary sequences in the southern karoo basin to provide evidence of environmental changes that may have caused the tetrapod extinctions in the main karoo basin below the p tr boundary sequence the sediments comprise drab greenish grey mudrocks with a few thick 3 12 m multistoried laterally accreted fine grained sandstone bodies the mudrocks host hydromorphic palaeosols with palustrine carbonate horizons and mostly disarticulated skeletal remains of dicynodon assemblage zone fauna above a transition zone of approximately 20 m thickness these strata change into reddish brown mudrocks with numerous thin 0 5 5 m ribbon sandstone bodies and more continuous sheet sandstones calcic palaeosols with rhizocretions nodular horizons and pervasive calcareous encrustation of articulated skeletons of lystrosaurus and associated fauna of the lystrosaurus assemblage zone within a 20 m thick interval of the transitional strata fossils of dicynodon and lystrosaurus occur together the facies transition that co incides with the latest permian dicynodont extinction is interpreted as a change in fluvial style from meandering to low sinuosity channels with general drying of the floodplain habitats and redistribution of vegetation belts the horsetails in particular became significantly reduced in areal distribution the changes in fluvial style in the karoo basin at the end of the permian were triggered by a pulse of thrusting in the southerly source area dated at 247 ma 2 ma which brought about rapid progradation of a large sandy braided fan system the katberg sandstone fm into the central parts of the basin a concomitant basinward migration of depositional environments allowed the lystrosaurus communities that were adapted to dry floodplains to colonise the entire basin to the detriment of most of the wet floodplain dicynodon fauna that lived there

global volcanism biological mass extinctions and the galactic vertical motion of the solar system summary the recent findings of nearly matching long term cyclicity in biological mass extinctions geomagnetic reversals impact cratering and other terrestrial processes have evoked a major controversy we report here a compilation and analysis of major global magmatic episodes showing a significant enhancement of volcanic activity with a periodicity of 33 million years for the last 250 million years these magmatic episodes match extremely well the best available astronomical estimates of the periodic 31 5 myr galactic disc crossing events during vertical motions of the solar system these events also have a close linkage with the marine biological mass extinctions and other geological rhythms it is argued that the prolonged volcanic activity instead of impact cratering may have been the more immediate primary cause for profound climatic and other environmental deterioration sufficient to create biological crises on a global scale the volcanic periodicity scheme is well supported by the evidence of recent increases in volcanic activity however the alternative hypothesis of the death star nemesis can be rejected since it does not explain the recent increase in volcanism and impact cratering during the last 4 3 myr in view of its quieter apehelion position lying beyond the oort cloud of comets

stress induced permeability changes in indiana limestone abstract this paper examines the influence of triaxial stress states with confining stresses between 5 and 30 mpa including post failure on the alteration of intrinsic permeability of indiana limestone the permeating fluid used in the experiments was distilled de aired water experimental results are used to develop an empirical state space model of permeability evolution due to the action of maximum and minimum principal stresses imposed on the sample the developed empirical model is implemented in a computational code to examine the influence of stress induced permeability alterations on the flow into an unlined cylindrical cavity located in a rock mass subjected to geostatic stresses

in situ behaviour of a stiff layered clay subject to thermal loading observations and interpretation the paper presents an interpretation of an in situ heating test carried out on opalinus clay in the mont terri underground laboratory opalinus clay is a stiff strongly bedded mesozoic clay of marine origin when subjected to thermal loading saturated stiff clays exhibit a strong pore pressure response that significantly affects the hydraulic and mechanical behaviour of the material the observations gathered in the in situ test have provided an opportunity to examine the integrated thermo hydro mechanical thm response of this sedimentary clay coupled thm numerical analyses have been carried out to provide a structured framework for interpretation and to enhance understanding of thm clay behaviour numerical analyses have been based on a coupled theoretical formulation that incorporates a constitutive law especially developed for this type of material the law includes degradation of bonding by damage by performing three dimensional computations it has been possible to incorporate anisotropy of m

evidence from crater ages for periodic impacts on the earth recent evidence has indicated that the impact of a comet or asteroid may have been responsible for mass extinction at the ends of both the cretaceous1 and the eocene2 4 quantitative analysis by raup and sepkoski5 showed that mass extinctions occur with a 26 myr period similar to the period seen in qualitative pelagic records by fischer and arthur6 to account for the possibility of periodic comet showers davis et al 7 proposed that such showers could be triggered by an unseen solar companion star as it passes through perihelion on a moderately eccentric orbit to test a prediction implicit in this model we examined records of large impact craters on the earth we report here that most of the craters occur in a 28 4 myr cycle within measurement errors this period and its phase are the same as those found in the fossil mass extinctions the probability that such agreement is accidental is 1 in 103

ice sheet load cycling and fluid underpressures in the eastern michigan basin ontario canada strong fluid underpressures have been detected in paleozoic strata in the eastern michigan basin with hydraulic heads reaching 400 m below land surface 4 mpa underpressure and 200 m below sea level in strata where unusually low permeabilities 10 20 10 23 m2 were measured in situ multiple glaciations including three with as much as 3 km of ice cover at the site in the last 120 ka suggest a causal link with the underpressures we examined this possibility using a one dimensional groundwater flow model incorporating mechanical loading from both ice weight and lithospheric flexure because hydrologic and mechanical changes during glaciation are not well characterized and subsurface properties are imperfectly known the model was used inversely to estimate flexural loads and loosely constrained permeabilities by matching observed pressures acceptable matches were obtained for a surprisingly wide range of scenarios with permeabilities close to measured values and plausible flexural loads matches were not obtained when too many parameters were preselected or when permeabilities were constrained to be significantly larger than measured values in successful model runs groundwater expulsion under glacial mechanical loads caused the underpressuring and flexural loads were important if aquifer and sub glacial pressures were significantly elevated during glaciation simulated fluid pressures in the low permeability strata fluctuated by 30 40 mpa during glacial cycles but resulted in advective transport of only tens of meters or less although other mechanisms cannot be ruled out we conclude that glacial mechanical forcing of a water saturated system can explain the observed underpressures

a mesozoic time scale we present an integrated geomagnetic polarity and stratigraphic time scale for the triassic jurassic and cretaceous periods of the mesozoic era with age estimates and uncertainty limits for stage boundaries the time scale uses a suite of 324 radiomenc dates including high resolution 40 ar 39 ar age estimates this framework involves the observed ties between 1 radiometric dates biozones and stage boundaries and 2 between biozones and magnetic reversals on the seafloor and in sediments interpolation techniques include maximum likelihood estimation smoothing cubic spline fitting and magnetochronology

axial flow hydraulic pulse testing of an argillaceous limestone lindsay limestone is an argillaceous limestone encountered in southern ontario canada the lindsay formation is regarded as a suitable geologic medium for the construction of a deep geologic repository for storing low to intermediate level nuclear waste the lindsay limestone is a nodular argillaceous rock with very low permeability requiring the use of hydraulic pulse tests for the measurement of its permeability characteristics the paper describes the triaxial testing facility the theoretical basis for the test and the procedures used to analyze the experimental results for estimating the permeability of the lindsay limestone the results are compared with the data available in the literature

periodic components in the diversity of calcareous plankton and geological events over the past 230 myr abstract we performed statistical analysis on high resolution records of the diversity of calcareous plankton planktonic foraminifera and calcareous nannoplankton and on records of global sea level marine isotopes 18 o 13 c 87 sr 86 sr large igneous province lip eruptions and dated impact craters over the last 230 myr results of continuous wavelet analysis cwt fast fourier transform fft spectral analysis and cross spectral analysis indicate that the records of diversity of calcareous nannoplankton cn and planktonic foraminifera pf and all of the geologic time series tested show similar dominant 25 33 myr cycles based on the statistical results best fit stationary periodic models for pf and cn evolutionary records can be constructed with t time in myr cn diversity 9 5 sin 2 t 7 5 myr 29 myr 4 8 sin 2 t 4 myr 15 3 myr and pf diversity 7 6 sin 2 t 12 myr 26 myr 3 sin 2 t 9 2 myr these periodic models describe major patterns in the diversity history such as 1 a sawtooth shaped 29 myr cycle for calcareous nannoplankton diversity with gradual increases and abrupt decreases in diversity 2 plateau shaped 26 myr cycles in the planktonic foraminiferal record with abrupt diversity increases and decreases and 3 the presence of 15 3 and 9 2 myr periodic components that modify the shapes of the 26 to 29 myr cycles except for the synchronous decreases in diversity of pf and cn at 65 and 34 ma the diversity extrema for the two planktonic groups have been on average 2 to 3 myr out of phase in the 30 myr cycle band cn diversity increased with sea level rise and increased paleotemperatures whereas pf diversity was in general greater during times of lower sea levels diversity of pf and cn was reduced at times of major lip eruptions and large impacts that follow 15 or 30 myr periodicities these results suggest that the diversity of calcareous plankton since their appearance in the early mesozoic has been modulated by long term cyclical changes in global environmental conditions and by periodic large volcanic and impact events the pacemaker or pacemakers for these cycles may be astrophysical geophysical or some combination of the two

the role of episodic bombardment in geophysics it is shown that cometary or asteroidal impacts strongly perturb the boundary conditions at the core outer mantle and atmosphere of the earth impact episodes occur following the capture or orbital disturbance of these bodies as the solarsystem passes through the spiral arms of the galaxy there is thus a tendency for magnetic field reversals principal plate movements ice ages and mass extinctions to be correlated and to recur on time scales dictated by galactic processes it follows on the basis of a purely astronomical theory that it may be possible to synthesise the major phenomena of geophysics knowledge of the continuous state of the galaxy then becomes a prerequisite for the understanding of terrestrial history

heat induced moisture movement in a clay barrier i experimental modelling of borehole emplacement abstract the paper presents the results of a series laboratory experiments which were conducted to study the heat induced moisture movement in a bentonitic clay buffer region in the experimental investigations hygro thermal phenomena are induced by a cylindrical heater which is placed within the compacted buffer material located in a borehole centrally situated in a granite block the paper summarizes the experimental methodologies and presents results for the time dependent distribution of temperatures within the granite block and the residual moisture distribution within the buffer at the termination of the experiment

terminal cretaceous environmental events the geologic record of terminal cretaceous environmental events indicates that iridium and other associated elements were not deposited instantaneously but during a time interval spanning some 10 000 to 100 000 years the available geologic evidence favors a mantle rather than meteoritic origin for these elements these results are in accord with the scenario of a series of intense eruptive volcanic events occurring during a relatively short geologic time interval and not with the scenario of a single large asteroid impact event

shear strain analysis and periodicity within shear gradients of metagranite shear zones abstract the distribution of natural ductile strain is studied by mapping continuous shear strain gradients across shear zones with widths of the order of tens of centimetres the shear zones are derived from granites and the most ductile mineral quartz accommodates most of the rock deformation shear strain maps are based on quartz gram orientation and finite strain maps on the shape of quartz grams measured by image analysis shear strain distribution shows discrete hands parallel to the shear plane which reflect the strain localization strain profiles across the strain maps are compared to exponentially decreasing profiles the significant variations of shear strain after subtraction of the smoothed profile are checked by fourier analysis in terms of wavelengths with this information at hand we argue that shear strain distribution in shear gradients is periodic

creep behaviour of a buffer material for nuclear fuel waste vault in the canadian nuclear fuel waste disposal concept currently under study one of the prime candidate procedures is the borehole emplacement technique each fuel waste container will be placed in a

the permeability of an intact granite the permeability of intact barre granite is determined by conducting transient hydraulic pulse tests that induce radial flow in saturated granite cylinders containing a water filled co axial cavity saturated specimens of granite are also subjected to uniform heating on the outer cylindrical surface and the permeability of the granite is measured at the termination of a heating sequence the theoretical basis for the use of simplified analytical solutions for evaluating the decay of the pressure pulse is examined and the permeability of the granite in the pre heating and post heating states is inferred from the results of pulse tests the reported investigations document one of the limited numbers of large scale laboratory tests conducted to determine the permeability characteristics of intact granite the results of the permeability measurements indicate the absence of any appreciable influences of micro structural alterations in the fabric of the granite due to its heating in a saturated condition at an average temperature of 140 celsius

influence of pressurized water influx on the hygro thermal behaviour of an engineered clay barrier in a waste emplacement borehole this paper presents the results of a series of experiments conducted to examine the hygro thermal behaviour of a compacted internally heated engineered clay barrier consisting of a mixture of bentonitic clay and sand compacted in a laboratory scale model simulating a waste emplacement borehole located in a granitic rock the experiments considered the supply of water at a prescribed pressure at the outer cylindrical and plane boundaries of the compacted engineered clay barrier the experiments examined the manner in which the water supply conditions influenced the extent of the moisture uptake within the compacted clay barrier the experimental results presented in this paper include contours of the time dependent variation of temperature within the granite block the time dependent variations of temperature at the midsection level of the internally placed heater and along the axis of the experimental facility and the residual volumetric moisture content distribution determined at the termination of the experiments

rainfall infiltration induced groundwater table rise in an unsaturated porous medium increased rainfall associated with climate change is becoming a common occurrence and can lead to a variety of geoenvironmental hazards infiltration during rainfall and deformations of a soil mass are coupled and the water table can easily experience a rise during these events a study of the coupling process is important to increase our knowledge concerning the impact of a water level rise on the environment based on the theory of seepage and flow in porous media the theory of elasticity and the soil water characteristic curve a two dimensional hydro mechanical model for an unsaturated porous medium is developed and incorporated in the comsol multiphysics software the numerical procedure is capable of considering the influences of the soil water characteristic curve the effects of varying the boundary conditions on the coupled unsaturated infiltration and deformation equations are investigated the examples demonstrate that the coupling effects significantly influence the position of the groundwater levels the rate of change in the water table is closely related to the coupled infiltration and deformation in an unsaturated porous medium

a full scale in situ heating test for high level nuclear waste disposal observations analysis and interpretation the paper describes the performance observations and interpretation of a large scale in situ heating test that simulates a disposal concept for heat emitting high level nuclear waste in the experiment heaters are emplaced in the axis of a tunnel excavated in granite to simulate the heat production of radioactive waste the test is fully instrumented and attention is focused on the thermo hydro mechanical thm behaviour of the near field region constituted by the compacted bentonite barrier surrounding the heater and the immediately adjacent rock interpretation of the test is assisted by the performance of a coupled numerical analysis based on a formulation that incorporates the relevant thm phenomena initial and boundary conditions for the analysis as well as material parameters are determined from an extensive programme of field and laboratory experiments the paper presents and discusses the thermal hydraulic and mechanical observations in the bentonite barrier and in the host rock special attention is paid to the progress of hydration in the barrier to the effects of heating and vapour transport and to the development of swelling pressures in the barrier after five years of heating one of the heaters was switched off and the experiment was partially dismantled allowing the final state of the barrier to be observed directly the numerical analysis performed has proved able to represent the progress of the experiment very satisfactorily in addition predictions concerning the final state of the clay barrier are very close to the observations obtained during dismantling the performance and analysis of the in situ test have significantly enhanced the understanding of a complex thm problem and have proved the capability of the numerical formulation to provide adequate predictive capacity

study of ground collapse induced by large diameter horizontal directional drilling in a sand layer using numerical modeling with large diameter horizontal directional drilling hdd becoming the preferred method to construct oil and gas pipelines and utility pipelines beneath rivers the issue of potential ground collapse arises when drilling in loose geological layers such as sand ground collapse is a result of borehole collapse and may cause significant damage to the topography and nearby facilities the present investigation considered the potential causes of ground collapse induced by an actual 1 219 m diameter hdd river crossing project using the flac3d numerical modeling tool the analysis showed that the failure zone first developed at the crown of the borehole resulting in subsequent borehole collapse due to instability of the sand above and eventually leading to ground collapse sequential reaming cycles have been simulated and the results indicate very little effect in comparison with a single reaming cycle the risk of borehole collapse and consequent ground collapse increases with borehole diameter parametri

swelling phenomena and effective stress in compacted expansive clays the central aim of this paper is to discuss the applicability of the effective stress principle as defined by terzaghi total stress minus pore water pressure to predict the behaviour of expansive

the role of the secondary standard in stratigraphy the dsvelopment of a series of internationally acceptablc chronostratigraphical units initially grew up through agreed use today s requirement of endorsement by the international commission on stratigraphy has resulled in the official rejection of names which are perfectly valid and still essential in the parts of the world for which they were introduced recognition of this fact is urged by the acceptance of the secondary emerging geological systems in particular major lithological changes or unconformities often provided the ideal criterion for drawing a boundary at a particular place thus the base of the cambrian is well defined at most places in britain by a basal unconformity paradoxically in the type area of north wales the basal boundary may be conformable on the underlying recambrim cowie rushton stubblefield 1972 the base of the carboniferous was drawn where marine hmestandards as locall defined chronost the rxlssible future correlation with the rima standard litholorical base of the old red sandstone was eaualed with the the eeolorical time scale has been developed piecemeal over almost two centuries initial work was concerned with the naming of formations in enelish eeoloeical literature usuallv referred to as strata these were often adaptations of quarrymen s terms such as we find in william smith s contribution to townsend s 1813 table of strata which listed formations between the coal measures and the chalk this was developed from earlier manuscript versions the fist of which deal with the formations around bath dates from 1797 strata were then grouped togkther as a result of syntheses of earlier work into formations or into series thus smith s jurassic stratal tenns were grouped into an oolite formation buckland 1818 or an oolite series conybeae phillips 1822 these terms were compared with the jura limestone of humboldt 1795 and following brogniart s introduction of the term jurassic

clean spectral analysis of long term sea level changes a new clean spectral technique has been applied for the first time to analyse a record of long term sea level fluctuation during the last 200 million year myr the technique is based on a one dimensional complex deconvolution algorithm and removes the effects of the data sampling as well as the artifacts arising from the choice of data window the analysis reveals a dominant periodicity of 33 myr in the sea level variations this periodicity compares well with the known half period of the sun s oscillation perpendicular to the galactic plane interestingly a 33 myr periodicity can also be correlated with the reported mass extinction cycles and other geological periodicities the results suggest galactic forcing as a possible driving mechanism for quasi periodic terrestrial processes

mechanical behaviour of heavily compacted bentonite under high suction changes the paper reports the results of an experimental study carried out on a bentonite compacted to a dry density of up to 1 7 mg m3 a high value for this type of soil the soil fabric has been studied using a variety of techniques revealing a clear bimodal pore distribution that corresponds to two distinct structural levels a microstructural one and a macrostructural one the main testing programme has been performed using oedometers especially designed to apply a very large range of suctions by applying the axis translation technique using nitrogen as the gas fluid it has been possible to reach suctions up to 15 mpa the higher suction range has been achieved by applying a controlled atmosphere where the relative humidity has been fixed by a solution of sulphuric acid or salts in this way suctions up to 550 mpa could be reached the maximum vertical stress that could be applied in the apparatus was 10 mpa two types of test have been carried out a tests in which a combination of loading paths at constant suction and drying wetting paths at constant load were applied b swelling tests under constant volume conditions in order to determine the swelling pressure and the stress path followed during wetting the results of the experimental programme are examined taking into account the role of the soil fabric in controlling observed mechanical behaviour in addition the results of the laboratory tests are reproduced and interpreted using a generalised plasticity model that considers explicitly the interaction between macrostructure and microstructure in this way it is possible to achieve a more complete understanding of the mechanisms that underlie observed behaviour and in particular the interplay between the two structural levels

supernormal fluid pressures in sedimentary rocks of southern ontario western new york state fluid pressures up to 1 7 times greater than hydrostatic have been measured in argillaceous paleozoic rocks of low permeability in southern ontario and western new york state these supernormal formation fluid pressures were measured at depths of 50 310 m using submersible pressure transducers with straddle packers and multiple packer casings isolating the test intervals measurements were obtained over periods of 7 46 months following casing installations the pressure measurements from 11 monitoring wells are compiled and supporting hydrogeologic data for 5 selected wells are used as examples to illustrate the occurrence of supernormal fluid pressures in the ordovician silurian and devonian sedimentary sequence of southern ontario and western new york state possible explanations for the occurrence of supernormal fluid pressures in sedimentary rock are evaluated considering the available geologic and hydrogeologic information obtained from the monitoring wells based on this review it is hypothesized

linear pressurization method for determining hydraulic permeability and specific storage of a rock sample summary we studied the methodology and applicability of linear pressurization for determining simultaneously hydraulic permeability and specific storage of a rock sample we analytically solved the governing equation for 1 d pressure diffusion through a homogenous isotropic cylindrical rock specimen located between a downstream and an upstream reservoir considering linear pressurization of the upstream fluid as the boundary condition the solution consists of a transient and a steady state for which both differential pressure between the two reservoirs and injection rate at the upstream reservoir assume constant values since the steady state differential pressure is linearly proportional to the compressive storage of the downstream reservoir tests conducted with a systematic variation of the size of the downstream reservoir permit determining permeability and specific storage from the intercept and slope of the linear relationship alternatively simultaneous measurement of differential pressure and fluid injection rate at steady state conditions provides a basis for calculation of the hydraulic properties as previously presented for linear injection experiments were performed on fontainebleau sandstone samples to document the feasibility of the method the determined storage capacity value is used to calculate various poroelastic parameters such as bulk and pore space compressibility skempton and the effective pressure coefficient

major episodes of geologic change correlations time structure and possible causes abstract published data sets of major geologic events of the past 250myr extinction events sea level lows continental flood basalt eruptions mountain building events abrupt changes in sea floor spreading ocean anoxic and blackshale events and the largest evaporite deposits have been synthesized with estimated errors these events show evidence for a statistically significant periodic component with an underlying periodicity formally equal to 26 6 myr and a recent maximum close to the present time the cycle may not be strictly periodic but a periodicity of 30myr is robust to probable errors in dating of the geologic events the intervals of geologic change seem to involve jumps in sea floor spreading associated with episodic continental rifting volcanism enhanced orogeny global sea level changes and fluctuations in climate the period may represent a purely internal earth pulsation but evidence of planetesimal impacts at several extinction boundaries and a possible underlying cycle of 28 36 myr in crater ages suggests that highly energetic impacts may be affecting global tectonics a cyclic increase in the flux of planetesimals might result from the passage of the solar system through the central plane of the milky way galaxy an event with a periodicity and mean phasing similar to that detected in the geologic changes

long term experimental evidences of saturation of compacted bentonite under repository conditions abstract this paper summarises the information gathered in the last 15 years on the saturation of compacted bentonite obtained from different laboratory scale tests a large scale mock up test and a real scale in situ test that were performed to simulate the conditions of the bentonite barrier in a high level radioactive waste repository and to better understand the hydration heating processes in all the tests the bentonite used was the spanish febex bentonite the maximum temperature in the system was 100 c and the water used was of the granitic type with low salinity some of the tests were running for more than thirteen years the migration of water vapour in areas affected by the high temperature induced by the radioactive waste decay is very rapid its extent depending on the actual temperature and bentonite porosity the water vapour condensates in cooler areas and this causes water content increases in internal zones of the barrier where the liquid water coming from the host rock has not yet arrived the hydration kinetics is initially quicker when the temperature is high provided no vapour phase is formed nevertheless the major effect of the thermal gradient on saturation is a delaying of it in the inner parts of the barrier which can be very persistent and depends on the actual thermal gradient and consequently on the barrier thickness and boundary conditions during the transient period in which the barrier is saturating important changes in the water content and dry density of the bentonite are generated which induce bentonite density and water content gradients along its thickness these gradients could eventually disappear once the barrier is fully saturated depending on the irreversibility of the deformations the average density of the water in the saturated barrier will be higher than 1 g cm3 due to the predominance of high density interlayer water in the compacted bentonite and consequently more water than expected according to calculations made considering the density of free water would fit in the bentonite pores the rate of hydration of the barrier depends on the bentonite and surrounding media hydraulic properties that is water availability waste temperature and buffer thickness and geometry

early triassic terrestrial tetrapod fauna a review abstract the permian triassic mass extinction ptme ca 252 mya was one of the most severe biotic crises of the phanerozoic eliminating 90 of marine and terrestrial species this was followed by a long period of recovery in the early and middle triassic which revolutionised the structure of both marine and terrestrial ecosystems triggering the new ecosystem structure of the mesozoic and cenozoic entire new clades emerged after the mass extinction including decapods and marine reptiles in the oceans and new tetrapods on land in both marine and terrestrial ecosystems the recovery is interpreted as stepwise and slow from a combination of continuing environmental perturbations and complex multilevel interaction between species in the new environments as ecosystems reconstructed themselves here we present a review of early triassic terrestrial tetrapod faunas geological formations and outcrops around the world and provide a semi quantitative analysis of a data set of early triassic terrestrial tetrapods we identify a marked regionalisation of early triassic terrestrial tetrapods with faunas varying in both taxonomic composition and relative abundance according to palaeolatitudinal belt we reject the alleged uniformity of faunas around pangaea suggested in the literature as a result of the hot house climate in addition we can restrict the tetrapod gap of terrestrial life in the early triassic to palaeolatitudes between 15 n and about 31 s in contrast to the earlier suggestion of total absence of tetrapod taxa between 30 n and 40 s there was fairly strong provincialism following the ptme according to cluster analysis of a taxon presence matrix entirely consistent with early triassic palaeobiogeography unexpectedly the overall pattern for early triassic terrestrial tetrapod faunas largely reflects that of the late permian suggesting that the recovery faunas in the early triassic retained some kind of imprint of tetrapod distributions according to palaeogeography and palaeoclimate despite the near total extinction of life through the ptme

a new tracer density criterion for heterogeneous porous media tracer experiments provide information about aquifer material properties vital for accurate site characterization unfortunately density induced sinking can distort tracer movement leading to an inaccurate assessment of material properties yet existing criteria for selecting appropriate tracer concentrations are based on analysis of homogeneous media instead of media with heterogeneities typical of field sites this work introduces a hydraulic gradient correction for heterogeneous media and applies it to a criterion previously used to indicate density induced instabilities in homogeneous media the modified criterion was tested using a series of two dimensional heterogeneous intermediate scale tracer experiments and data from several detailed field tracer tests the intermediate scale experimental facility 10 0 3 1 2 3 0 06 m included both homogeneous and heterogeneous sln k 2 5 1 22 zones the field tracer tests were less heterogeneous 0 24 sln k 2 0 37 but measurements were sufficient to detect density induced sinking evaluation of the modified criterion using the experiments and field tests demonstrates that the new criterion appears to account for the change in density induced sinking due to heterogeneity the criterion demonstrates the importance of accounting for heterogeneity to predict density induced sinking and differences in the onset of density induced sinking in two and three dimensional systems

modelling the response of lechago earth and rockfill dam lechago dam teruel spain is a 40 m high zoned earth and rockfill dam sitting on soft continental deltaic deposits a relatively narrow central clay core is stabilised by wide rockfill shoulders the dam was well instrumented and continuous records of stress development pore water pressures and vertical displacements are available for the construction period compaction conditions were followed by means of laboratory and in situ control tests core clay material was investigated by means of tests performed on compacted specimens of tertiary clays rockfill samples were excavated in outcrops of highly fractured cambrian quartzitic shale a testing programme on compacted rockfill gravels was conducted under relative humidity control in a large diameter oedometer and triaxial cells a coupled finite element model has been developed to analyse the tests performed and dam behaviour during construction model predictions essentially based on laboratory tests are compared with measurements during constructi

the thermo hydro mechanical behavior of the argillaceous cobourg limestone the cobourg limestone is a low permeability argillaceous rock that forms a part of the paleozoic sedimentary sequence found in southern ontario canada the limestone has a heterogeneous fabric consisting of nodular regions of calcite and dolomite and argillaceous partings of a similar composition but with a low clay content which gives the appearance of nominal stratifications the thermo hydro mechanical thm behavior of the rock is of interest to the proposals for using sedimentary formations as candidate rocks for siting deep geological repositories for the storage of heat emitting nuclear fuel waste the paper presents the results of experiments where thm processes were initiated in an intact cylindrical sample of the cobourg limestone containing a central cylindrical fluid filled cavity biot s classical theory of poroelasticity extended to include thermal effects is used to examine the thm response of the fluid cavity due to boundary heating of the cylinder the rise and decay of thermally induced cavity fluid pressure is used to examine the applicability of the thm modeling the experiments were conducted on cylindrical samples of the cobourg limestone with their axes either along or normal to the nominal planes of the argillaceous partings

the febex benchmark test case definition and comparison of modelling approaches abstract the febex full scale engineered barriers experiment in crystalline host rock in situ test was installed at the grimsel test site underground laboratory switzerland and is a near to real scale simulation of the spanish reference concept of deep geological storage in crystalline host rock a modelling exercise aimed at predicting field behaviour was divided in three parts in part a predictions for both the total water inflow to the tunnel as well as the water pressure changes induced by the boring of the tunnel were required in part b predictions for local field variables such as temperature relative humidity stresses and displacements at selected points in the bentonite barrier and global variables such as the total input power to the heaters were required in part c predictions for temperature stresses water pressures and displacements in selected points of the host rock were required ten modelling teams from europe north america and japan were involved in the analysis of the test differences among approaches may be found in the constitutive models used in the simplifications made to the balance equations and in the geometric symmetries considered several aspects are addressed in the paper the basic thm physical phenomena which dominate the test response are discussed a comparison of different modelling results with actual measurements is presented and a discussion is given to explain the performance of the various predictions

thermohydromechanical modelling of the buffer container experiment abstract in order to investigate how heat affects the performance of a dense bentonite sand buffer material a full scale in situ experiment the buffer container experiment bce was conducted by atomic energy of canada limited aecl in the bce an electric heater simulating the heat output of a disposal container of used fuel was installed vertically in a 1 24 m diameter by 5 m deep borehole surrounded by bentonite sand buffer the borehole was drilled in the floor of a room excavated in canadian shield granite on the 240 level of aecl s underground research laboratory url the thermal hydraulic and mechanical responses were monitored in the bentonite sand buffer and in the surrounding rock power was provided to the heater for approximately 896 days in order to get a better understanding of the coupled thermohydromechanical t h m process in the bce numerical simulations were conducted using code bright to model the evolution of the temperature thermally induced pore water pressure and mechanical response in the bentonite sand buffer and the surrounding rock the thermal response in the experiment was successfully modelled the simulated water seepage from the rock to the borehole was compared with measured results for the bce the thermally induced moisture movement in the buffer was also reasonably well simulated the comparison of the simulated pore water pressure in the rock with the measurement indicates that the influence of temperatures on the hydraulic parameters of rock should be further studied the modelled vertical displacements in the rock are also compared with the measured data in the bce and the analysis of the rock displacement suggested that the in situ thermal expansion coefficient of the rock could be much higher than the coefficient determined in the laboratory

synchrony and causal relations between permian triassic boundary crises and siberian flood volcanism the permian triassic boundary records the most severe mass extinctions in earth9s history siberian flood volcanism the most profuse known such subaerial event produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less analysis of 40 ar 39 ar data from two tuffs in southern china yielded a date of 250 0 0 2 million years ago for the permian triassic boundary which is comparable to the inception of main stage siberian flood volcanism at 250 0 0 3 million years ago volcanogenic sulfate aerosols and the dynamic effects of the siberian plume likely contributed to environmental extrema that led to the mass extinctions

global triassic tetrapod biostratigraphy and biochronology abstract eight temporally successive assemblage zones of tetrapod fossils provide the basis for dividing triassic time into eight land vertebrate faunachrons these land vertebrate faunachrons their type assemblage zones and their approximate correlation to the standard global chronostratigraphic scale are ascending order 1 lootsbergian lystrosaurus assemblage zone balfour katberg and burgersdorp formations karoo basin south africa late dorashamian induan 2 nonesian cynognathus assemblage zone burgersdorp formation karoo basin south africa olenikian 3 perovkan shansiodon assemblage zone donguz formation russian urals anisian 4 berdyankian mastodonsaurus assemblage zone bukobay formation russian urals ladinian early carnian 5 otischalkian paleorhinus assemblage zone chinle group chinle basin usa late early to early late carnian 6 adamanian rutiodon assemblage zone chinle group chinle basin usa latest carnian 7 revueltian pseudopalatus assemblage zone chinle group chinle basin usa norian 8 apachean redondasaurus assemblage zone chinle group chinle basin usa rhaetian the triassic land vertebrate faunachrons provide a framework for the correlation of triassic nonmarine deposits with a temporal resolution comparable to the seven triassic stage ages of the standard global chronostratigraphic scale

heat induced moisture movement in a clay barrier ii computational modelling and comparison with experimental results the paper presents the application of a galerkin finite element technique for the numerical solution of the differential equations governing coupled heat flow and moisture movement in a clay buffer attention is focussed on the axisymmetric modelling of the hygro thermal processes encountered in the single borehole emplacement configuration developed for laboratory simulation the numerical results derived for the time dependent temperature distributions within the granite block and the residual moisture distribution within the buffer are compared with the respective experimental results

investigation of desaturation in an old tunnel and new galleries at an argillaceous site a numerical investigation of the desaturation process at the argillaceous tournemire site has been carried out this desaturation is initialized by the contact of the saturated rock with the ambient air in excavated openings the used hydraulical model is based on the richards approximation for unsaturated one phase flow coupled with the deformation of a porous medium with anisotropic linearly elastic behavior in relation to the extent of the desaturated zone around an excavated opening the intrinsic permeability and the relative permeability have been identified to be the most important model parameters the mechanical deformation process itself the seasonal influences and the tunnel lining are less important for the formation of the desaturated zone the comparison with measured saturation values bares some difficulties but indicates the principle capacity of the applied finite element codes to simulate the desaturation process the consideration of seasonal changes in humidity in the ambient air results in a constantly recurring desaturation resaturation cycle in the near field of the openings this seasonally influenced zone amount 1 2 m and is nearly independent from time and from a variation of model parameters within a reasonable range the possibility of material weakening in this zone is of special interest since claystone is a potential host rock for the disposal of radioactive waste

newly discovered fish faunas from the early triassic karoo basin south africa and their correlative implications recent collecting in exposures of the lowermost burgersdorp formation beaufort group of the karoo basin of south africa has revealed a previously unknown fish fauna from the early triassic scythian lowermost cynognathus assemblage zone caz which forms an important component of the total vertebrate assemblage the newly discovered fish material includes lungfish saurichthyids and a large microfauna that includes numerous isolated chondrichthyan teeth two fin spine fragments and actinopterygian scales and teeth the latest fish finds together with the lowermost cynognathus assemblage zone vertebrate faunas make this karoo basin assemblage zone one of the most diverse early triassic faunal assemblages comparable in faunal diversity to those from the czatkowice formation poland and the arcadia formation australia the presence of the lungfish ptychoceratodus phillipsi in the early middle triassic cynognathus assemblage zone subzone b and in the underlying latest early triassic cynognathus assemblage zone subzone a indicates that these lungfish could serve as range index fossils within the caz and thus are potentially useful biostratigraphic markers across the early middle triassic boundary furthermore the new fish fauna provides a vital marine realm link in particular with the faunas of madagascar and australia that is unavailable using the tetrapod faunal elements of the lower caz

an early triassic polar predator ecosystem revealed by vertebrate coprolites from the bulgo sandstone sydney basin of southeastern australia abstract vertebrate trace fossils often provide a measure of cryptic biodiversity and are especially pertinent when skeletal remnants are exceptionally rare the lower triassic lower olenekian bulgo sandstone at long reef in the sydney basin of southeastern australia constitutes just such a deposit having yielded isolated bones of giant capitosaurian temnospondyls and proterosuchid archosauriforms together with abundant coprolites that are geochemically rich in elemental phosphate and carbon denoting vertebrate predators microstructural analysis of these preserved droppings reveals occasional bone fragments fish scales insect cuticles plant material and bacterial traces pseudomorph voids as well as silicate mineral particles ree concentrations indicate that burial and early diagenesis occurred explicitly within fluvial sediments furthermore external morphological characterization permits attribution of spiral coprolites to chondrichthyan or osteichthyan fishes polygonal ovoid spherical and typically flattened feces to temnospondyls and conspicuously large cylindrical droppings to archosauriforms or other amniote apex predators collectively the bulgo sandstone coprolite assemblage thus offers new insights into ecosystem structure and palaeoenvironment in what was an earliest triassic near polar setting such data compliments the documented skeletal record but indicates a greater range of aquatic and possibly terrestrial carnivores the latter being enigmatically sparse in the australian triassic and yet detected here via the hitherto underexplored trace fossil evidence of their ecological presence

on the long term migration of uranyl in bentonite barrier for high level radioactive waste repositories the effect of different host rocks abstract repositories for high level radioactive waste hosted in argillite or granite with bentonite backfill are the two disposal concepts that been extensively studied a general perception is that granite has very low sorption capacity and therefore is disadvantageous in retarding the migration of radionuclides in comparison with argillite however when there is bentonite backfill does the sorption capacity of granite really matter for the migration of radionuclides how different host rocks would affect the migration of u vi through the bentonite backfill of an engineered barrier system ebs and which properties of the host rocks cause those differences in migration given that migration of radionuclides is a critical measure in assessing the performance of a repository here we present two coupled thermal hydrological and chemical models for the transport of u vi each with an identical setup except for the type of host rock argillite vs granite rock comparisons between our models show that the different host rocks exert their influence on migration of u vi via regulating the chemical conditions in the bentonite which affect the concentration of u vi at the source and the adsorption of u vi in the bentonite the key chemical conditions are ph ca and hco3 concentration in pore water which are strongly affected by soluble carbonate minerals our models also show the occurrence of illitization dissolution of smectite and precipitation of illite in the bentonite which affects the migration of u vi through changing ph and the quantity of adsorbents although generalization of current model results for granite and argillite should be done carefully the simulations highlight the importance of pore water chemistry in host rock as well as bentonite host rock interactions when assessing the performance of a repository in comparison to properties such as thermal conductivity permeability and adsorption capacity properties that have been studied intensively the pore water chemistry of host rocks deserve equal or even more attention because of its strong influence on radionuclide migration

thermo hydro mechanical response of granite to temperature changes this paper examines the thermo hydro mechanical behaviour of a granitic rock the cylindrical sample of granite contained a sealed fluid filled cavity which was subjected to a cycle of temperature changes on its outer surface the temperature and fluid pressure changes in the fluid filled cavity were measured since the measurement of fluid pressure and temperature in the sealed cavity is experimentally feasible the technique is a common feature in thermo hydro mechanical experiments however it was observed that regardless of how precisely the cavity was filled with de aired water air bubbles can still exist in the cavity and influence the fluid pressure changes a novel technique is suggested for taking into account the influence of the volume of trapped air and eliminating its effect in the estimation of permeability the experiment was computationally modelled using the finite element code comsol multiphysics and the experimental results were compared with the computational estimates

conceptual uncertainties in modelling the interaction between engineered and natural barriers of nuclear waste repositories in crystalline rocks nuclear waste disposal in geological formations relies on a multi barrier concept that includes engineered components which in many cases include a bentonite buffer surrounding waste packages and the host rock contrasts in materials together with gradients across the interface between the engineered and natural barriers lead to complex interactions between these two subsystems numerical modelling combined with monitoring and testing data can be used to improve our overall understanding of rock bentonite interactions and to predict the performance of this coupled system although established methods exist to examine the prediction uncertainties due to uncertainties in the input parameters the impact of conceptual model decisions on the quantitative and qualitative modelling results is more difficult to assess a swedish nuclear fuel and waste management company task force project facilitated such an assessment in this project 11 teams used different conceptualizations and modelling tools to analyse the bentonite rock interaction experiment brie conducted at the aspo hard rock laboratory in sweden the exercise showed that prior system understanding along with the features implemented in the available simulators affect the processes included in the conceptual model for some of these features sufficient characterization data are available to obtain defensible results and interpretations whereas others are less supported the exercise also helped to identify the conceptual uncertainties that led to different assessments of the relative importance of the engineered and natural barrier subsystems the range of predicted bentonite wetting times encompassed by the ensemble results were considerably larger than the ranges derived from individual models this is a consequence of conceptual uncertainties demonstrating the relevance of using a multi model approach involving alternative conceptualizations

hydraulic testing of low permeability silurian and ordovician strata michigan basin southwestern ontario summary straddle packer hydraulic testing was performed in 31 silurian intervals and 66 ordovician intervals in six deep boreholes at the bruce nuclear site located near tiverton ontario as part of site characterization activities for a proposed deep geologic repository dgr for low and intermediate level radioactive waste the straddle packer assembly incorporated a hydraulic piston to initiate in situ pulse tests within low hydraulic conductivity horizontal hydraulic conductivities of the silurian test intervals range from approximately 4e 14 to 4e 8 m s the average horizontal hydraulic conductivities of the ordovician intervals range from 2e 16 to 2e 10 m s the lower member of the cobourg formation the proposed host formation of the dgr between 660 and 688 meters below ground surface was found to have a horizontal hydraulic conductivity of 4e 15 to 3e 14 m s the formation pressures inferred from the hydraulic testing confirmed by long term monitoring show that the upper ordovician and middle ordovician trenton group are significantly underpressured relative to a density compensated hydrostatic condition and relative to the overlying silurian strata and underlying black river group and cambrian strata these underpressures could not persist if hydraulic conductivities were not as low as those measured