morphology faunas and genesis of ordovician hardgrounds from southern ontario canada abstract we have used associations of different microfacies to define facies or microfacies associations which form reasonably well defined sequences which we infer from analogies with recent and ancient carbonate environments to have been deposited in a shelf environment characterized by small scale topographic differentiation into shoal slope and basinal environments shoal environments are characterized by typically cross bedded well sorted bioclastic sands with intershoal areas consisting of interbedded bioclastic sands and heavily bioturbated finer grained carbonates slope and basinal environments are typically represented by proximal and distal cycles respectively these we compare with deposits of carbonate ramp bypass channels and with the more thoroughly studied deep water clastic submarine fans many of the strong variations in environmental energy in these proximal and distal cycles can be attributed to migration of channels on the fans and the effect of funnelling of storm surges down the channels although hardground morphology and faunas are mostly related to local effects such as intensity of scouring time of exposure topographic differentiation of the surface and other factors differing hardground types tend to be found in different environments smooth and rolling hardgrounds occur in the deeper distal environments where the beds were subject to only slight scour and often limited exposure before renewed sedimentation hummocky and undercut hardgrounds are characteristic of the middle parts of proximal cycles where they developed marginally to the main bypass channel and in intershoal areas both these areas are sites of intermittent sedimentation and moderate turbulence where cemented beds may be exposed for some time in environments optimal for attached benthos these hardgrounds usually contain the most diverse hardground biotas pebbly and reworked hardgrounds occur in coarse basal units of proximal cycles which are interpreted as the grain flow fillings of the central parts of bypass channels though isolated examples occur in intershoal areas and in the higher parts of proximal channels these hardgrounds contain low diversity faunas reflecting the stresses imposed by intermittent or constant abrasion though some contain more diverse faunal assemblages formed after redeposition

deep arid system hydrodynamics 1 equilibrium states and response times in thick desert vadose zones 1 quantifying moisture fluxes through deep desert soils remains difficult because of the small magnitude of the fluxes and the lack of a comprehensive model to describe flow and transport through such dry material a particular challenge for such a model is reproducing both observed matric potential and chloride profiles we propose a conceptual model for flow in desert vadose zones that includes isothermal and nonisothermal vapor transport and the role of desert vegetation in supporting a net upward moisture flux below the root zone numerical simulations incorporating this conceptual model match typical matric potential and chloride profiles the modeling approach thereby reconciles the paradox between the recognized importance of plants upward driving forces and vapor flow processes in desert vadose zones and the inadequacy of the downward only liquid flow assumption of the conventional chloride mass balance approach our work shows that water transport in thick desert vadose zones at steady state is usually dominated by upward vapor flow and that long response times of the order of 104 105 years are required to equilibrate to existing arid surface conditions simulation results indicate that most thick desert vadose zones have been locked in slow drying transients that began in response to a climate shift and establishment of desert vegetation many thousands of years ago

disturbances of temperature depth profiles due to surface climate change and subsurface water flow 2 an effect of step increase in surface temperature caused by forest clearing in southwest western australia a series of type curves is presented for estimating vertical groundwater fluxes under the condition of a step increase in surface temperature the depths of minimum groundwater temperature in temperature depth profiles are used as an indicator of the magnitude of the downward groundwater fluxes the type curve method has been applied to the subsurface thermal regime observed in experimental catchments in the collie river basin in southwest western australia to estimate the vertical groundwater fluxes under the condition of surface warming caused by land cover change from forest to agriculture the groundwater fluxes obtained from the type curves and the depths of minimum groundwater temperature in temperature depth profiles agree well with the values obtained from the other studies

chloride as a signature indicator of soil textural and hydrologic stratigraphies in variable charge deep profiles soil properties that influence water movement through profiles are important for determining flow paths reactions between soil and solute and the ultimate destination of solutes this is particularly important in high rainfall environments for highly weathered deep profiles we hypothesize that abrupt changes in the distribution of the quotient qt silt sand clay reflect the boundaries between textural units or textural ts and hydrologic hs stratigraphies as a result qt can be used as a parameter to characterize ts and as a surrogate for hs secondly we propose that if chloride distributions were correlated with qt under non limiting anion exchange then chloride distributions can be used as a signature indicator of ts and hs soil cores to a depth of 12 5 in were taken from 16 locations in the wet tropical johnstone river catchment of northeast queensland australia the cores belong to nine variable charge soil types and were under sugarcane saccharun officinarum s production which included the use of potassium chloride for several decades the cores were segmented at i m depth increments and subsamples were analysed for chloride ph soil water content theta clay silt and sand contents selected bores were capped to serve as piezometers to monitor groundwater dynamics depth incremented qt theta and chloride correlated each individually significantly with the corresponding profile depth increments indicating the presence of textural hydrologic and chloride gradients in profiles however rapid increases in qt down the profile indicated abrupt changes in ts suggesting that qt can be used as a parameter to characterize ts and as a surrogate for hs abrupt changes in chloride distributions were similar to qt suggesting that chloride distributions can be used as a signature indicator of qt ts and hs groundwater data indicated that chloride distributions depended at least partially on groundwater dynamics providing further support to our hypothesis that chloride distribution can be used as a signature indicator of hs copyright c 2005 john wiley sons ltd

distribution of environmental chloride in relation to subsurface hydrology abstract chloride distributions in 32 deeply weathered profiles up to 39 m deep were used to investigate the subsurface hydrology typical of the saline landscapes of the south west of western australia studies took place in two forested areas of differing rainfall and landform to compare the processes of water movement a steady state model of water and chloride movement which included the effects of diffusion was used to estimate vertical soil water flux density q w from observed concentrations of chloride these patterns of water flow were compared to the physical properties of the profiles a great deal of variability was found between profiles and there was a marked difference in the magnitude of q w between the areas of different rainfall however consistent patterns of subsurface water movement can be identified thin coarse textured surface soils are well leached by rainfall but in the clayey unsaturated zone below vertical soil water flux densities are very small due to the uptake of water by the eucalyptus forest where rainfall was 800 mm yr 1 q w was typically of the order 0 4 mm yr 1 and in the area of 1150 mm yr 1 rainfall q w was 2 5 mm yr 1 rates of recharge to groundwater estimated from chloride concentration in the saturated zone were as much as two orders of magnitude greater than q w above the water table it is concluded that preferred water flow in structural and textural heterogeneities within the regolith is the dominant mechanism of recharge the preferred flow paths are distributed throughout the landscape but only constitute a small proportion of it

simple predictions of maximum transport rate in unsaturated soil and rock 1 in contrast with the extreme variability expected for water and contaminant fluxes in the unsaturated zone evidence from 64 field tests of preferential flow indicates that the maximum transport speed vmax adjusted for episodicity of infiltration deviates little from a geometric mean of 13 m d a model based on constant speed travel during infiltration pulses of actual or estimated duration can predict vmax with approximate order of magnitude accuracy irrespective of medium or travel distance thereby facilitating such problems as the prediction of worst case contaminant traveltimes the lesser variability suggests that preferential flow is subject to rate limiting mechanisms analogous to those that impose a terminal velocity on objects in free fall and to rate compensating mechanisms analogous to le chatlier s principle a critical feature allowing such mechanisms to dominate may be the presence of interfacial boundaries confined by neither solid material nor capillary forces

interactions between perched and saprolite aquifers on a small salt affected and deeply weathered hillslope a small hillslope was chosen to investigate the role of throughflow as a mechanism responsible for the movement of soil water and solutes towards a saline seep and as a source of recharge to a permanent regional aquifer at depth the hydraulic properties chemical characteristics and physical responses of both systems were studied on a deeply weathered salt affected hillslope additional data were also obtained from other sites in south western australia regional groundwater flow occurred in a variably textured deeply weathered material in which the hydraulic conductivity varied from 0 001 to 0 14m day 1 perched groundwater flow throughflow occurred in the higher permeability 1 5 m day 1 near surface soil materials throughflow occurred throughout winter contributing approximately 530 m3 of fresh 160 mg l 1 cl water to a saline seep by contrast the deep aquifer discharged approximately 1100 m3 of waters with salt concentrations of 2000 6000 mg l 1 cl recharge and discharge rates to and from the deep aquifer were estimated to be of the order of 5 20 mm a 1 and 50 300 mm a 1 respectively saturated conditions existed throughout winter within the seep and the immediately adjacent non saline area with up to 60 per cent of the hillslope soils becoming saturated after major rainfall events 20 mm day 1 in the mid slopes in particular along a central depression saturation of the shallow soils caused macropore channel recharge to take place through the clay textured subsoils water level responses suggest that approximately 25 30 per cent of annual recharge occurred from one storm studied in september 1984 recharge through macropore channels is a significant mechanism in the concave slope areas on the hillslope throughflow was found to be a major source of water but not salt contributing to the saline seep in general the contribution of throughflow was found to decrease further inland at other sites studied however at inland sites where perennial perched aquifers have developed in deep sands saline areas have been caused by throughflow and not by deep aquifer discharge

development of the tanakura strike slip basin in japan during the opening of the sea of japan constraints from zircon u pb and fission track ages abstract the tanakura basin was formed by strike slip movement of the tanakura fault during the opening of the sea of japan in the early to middle miocene in this study we conducted u pb and fission track ft double dating of pyroclastic rocks from two stratigraphic units in the tanakura basin using these ages we constructed a detailed chronostratigraphy and discuss the evolution of the tanakura basin with respect to regional tectonics and the opening of the sea of japan we obtained new ages of 17 1 0 6 ma for the middle part of the asakawa formation and 17 4 0 9 ma for the lower part of the nawashiroda formation based on a comparison of the ages from this study and previously published data we clarify the ages of each formation of the miocene basin fill we suggest that the tanakura basin was formed by sinistral movement on the tanakura fault between 17 2 and 16 7 ma followed by the development of lakes and the deposition of alluvial fans within the basin rapid tectonic subsidence and submarine dacite volcanism occurred just prior to 16 7 ma the basin then began to uplift due to dextral strike slip movement on the tanakura fault at ca 15 7 15 3 ma

paleosols as deep regolith implications for ground water recharge across a loessial climosequence abstract thick loess deposits consisting of paleosol sequences comprise the deep regolith of the palouse region in eastern washington and northern idaho ground water is the principal water supply for the palouse basin yet recharge mechanisms and rates through this regolith are poorly understood forecasting the sustainability of the water supply has been hampered because models that predict ground water recharge are complicated by deep regolith that has complex stratigraphy and in some instances multiple buried hydraulically restrictive horizons to assess water movement pore water cl and 18o distributions were measured to 6 m depths in three catchments representing a climosequence across the basin and interpreted using catchment and basin wide stratigraphic relationships vertical facies between dense and soft horizons coincide with variations in cl in the eastern basin pore water cl ranged from 15 to 150 mg l and increased with depth in addition shifts in isotopic signature of oxygen in pore water coincide with cl rich horizons and suggest long pore water residence times in contrast cl in the central and western basin ranges from 1 to 15 mg l and changes little with depth tracer profiles illustrate three major hydrostratigraphic units in the basin 1 uplands with relatively homogeneous regolith that has short pore water residence times 2 uplands with heterogeneous regolith that has long pore water residence times and 3 valleys with heterogeneous regolith that display dynamic hydraulic processes regional relationships between deep regolith and surface soils were established in order to use the ssurgo database to estimate the spatial extent of each hydrostratigraphic unit the degree of paleosol development mimics that of contemporary sola across the climosequence results indicate that recharge is less than 3 mm year 1 in 33 of the study area where precipitation is greatest and regolith is heterogeneous recharge increases to 10 mm year 1 in 37 of the study area where regolith is homogeneous valley positions having active hydraulic regimes constitute 10 of the basin

groundwater recharge through a heavy textured soil abstract this study was undertaken to outline the character of groundwater movement through the unsaturated and saturated zones of a glacial till using natural tritium a testhole was cored to a depth of 17 4 m below ground surface in southern alberta canada and 55 samples were collected from the cores at 0 3 m intervals the soil water was distilled from each sample and analyzed for natural tritium and the soil samples were analyzed for particle size distribution the upper 3 m of the stratigraphic section consists of coarse to heavy textured interbedded lacustrine deposits these units are underlain by a heavy textured weathered till the study site is a zone of groundwater recharge with the water table at 9 m below ground surface tritium data can be used to show that water which entered the subsurface environment from ground surface after 1953 has migrated to the lacustrine till contact via intergranular seepage and fracture flow and that fractures are transmitting post 1953 recharge water to depths within the underlying slowly permeable unsaturated and saturated till in addition diffusion of tritium from the fractures into the adjacent matrix material appears to occur both above and below the water table

impact of geologic heterogeneity on recharge estimation using environmental tracers numerical modeling investigation this paper presents a numerical modeling approach for assessing the impacts of geologic heterogeneity on groundwater recharge estimates derived from environmental tracers common to many of the environmental tracer methods used to infer recharge in arid environments is an assumption of one dimensional vertical downward flow of water and solutes however in recent years there has been a growing recognition that fluid flux rates through geologic materials can be spatially variable owing to heterogeneities in porous media properties previous studies have suggested that local flow directions are dependent upon the stratigraphic and sedimentologic characteristics of the medium and may not be vertical even when application of water at the surface is spatially uniform and hydraulic gradients are vertical consequently environmental tracer movement will also be spatially variable and the one dimensional assumption invoked to interpret unsaturated environmental tracer concentration profiles may be unrealistic two different numerical simulation experiments were performed to investigate the problems with using environmental tracers to infer recharge the first involves simulation of flow and tracer transport through heterogeneous flat lying media and the second considers dipping layered anisotropic media the results of these simulations show that recharge inferred using environmental tracer methods is also highly spatially variable and that recharge estimates obtained by tracer profiles tend to overestimate recharge and should be considered accurate only to within an order of magnitude particularly in situations with significant media heterogeneity consequently recharge estimates obtained from tracer profiles should be critically evaluated with regard to impacts of spatially variable flow

preferred water flow and localised recharge in a variable regolith abstract the mechanisms of water flow and recharge to groundwater were investigated in a deep clayey regolith in southwest western australia a 700 m2 area was intensively studied for a period of two years vertical distributions of natural chloride in thirteen profiles up to 31 m deep were used to estimate the distribution of vertical soil water flux density in the 16 m unsaturated zone and rates of recharge to groundwater groundwater dynamics were monitored using ten single and four multilevel piezometers the regolith showed marked heterogeneity over horizontal and vertical distances of only a few metres this resulted in complex patterns of water and solute movement through the profiles over most of the experimental area vertical water flux density below 5 m in the unsaturated zone was from 2 2 to 7 2 mm yr 1 however within a relatively small portion of the site vertical soil water flux density was 50 100 mm yr 1 throughout the unsaturated zone this flux more closely matched the apparent rate of recharge to groundwater the area of preferred flow is apparently due to a discontinuity within the regolith a groundwater mound was seen to develop below the localised recharge area within 12 14 h of intense rainstorms and then dissipated over a period of 2 4 days

response of input and output of water and chloride to clearing for agriculture five small forested catchments in the collie river basin in southwest western australia were instrumented to quantify the changes in the input and output of salt and water when land use changed from forest to agriculture the paired catchment approach was used with two adjacent catchments located in high rainfall 1200 mm yr 1 and a group of three located in a lower 800 mm yr 1 rainfall area the treatment of complete clearing was applied to one catchment in the high rainfall zone and to about half of one catchment in the lower rainfall zone after three years of calibration with the uncleared control catchments strategies of partial clearing were applied to the third catchment in the lower rainfall zone the catchment pairs were found to be well matched the yield of water and salt increased immediately after clearing in the higher rainfall catchment streamflow increased about four times to 48 of rainfall salt load increased to fifteen times the mean saltfall measured as chloride ion of 7 g m 2 yr 1 direct runoff increased fourfold to 16 of yearly streamflow due partly to the progressive increase in the area of soil saturated to the surface the perched groundwater system was the major source 77 in 1983 of streamflow though it was the route rather than the source of increased salt to the stream the mottled and pallid clay profile was the dominant source of salt transported by the deep groundwater system into the perched aquifer streamflow became perennial in the first postclearing year absolute increases in streamwater and salt output from partially cleared catchments in the lower rainfall location were about an order of magnitude less than for the higher rainfall catchment though the relative increases were similar the three catchments were found to be accumulating salt in the cleared catchments the rising potentiometric surface would establish a saline groundwater discharge zone in the valley and a net export of salt in all treated catchments reduced interception results in increased water availability at the soil surface for stormflow and infiltration the reduction in transpiration had an added effect in increasing recharge to groundwater a new equlibrium for water had not been achieved eight years after clearing but was estimated to precede the new salt equilibrium

marine airborne salts applied to trace evapotranspiration local recharge and lateral groundwater flow in western australia concentrations of dissolved cl br so4 na k ca and mg in ground waters of six study areas in the flat wheatbelt of western australia revealed a variations of several orders of magnitude of ion concentrations 40 63 000 mg c11 1 in ground waters encountered in wells 2 46 m deep b variations exceeding an order of magnitude in the salinity observed in depth profiles of individual wells c positive linear correlations between the concentrations of cl br na and mg observed in all the study areas and similar correlations also with ca k and so4 in part of these areas d marine like relative ionic concentration abundances of cl br na and mg in the six study areas and of ca k and so4 in part of the areas e concentrations of the various ions distinctly below saturation with halite br containing salts or gypsum observations of this nature are shown to provide a powerful tool to establish a lack of fractionation between the marine ions during the atmospheric transport b salt input dominated by marine airborne salts c operation of evapotranspiration from the regolith in calculable degrees that vary from one surface cell to another d lack of salt phases in the aquifer materials e dominance of local vertical recharge over remote lateral recharge f infiltration of active recharge through preferred pathways in the aerated zone g storage of ground water in local compartments h amount of annual recharge in each unit of area and i hydrochemical maturity of the local hydrological system rise of water tables as a result of forest clearing produces a different flow regime for water and solutes the depth of the aerated zone is drastically reduced saline interstitial water is mobilized from the aquifer the former aerated zone and previously productive land becomes degraded by excessive soil salinities

climatic controls on diffuse groundwater recharge in semiarid environments of the southwestern united states 1 although there is no diffuse groundwater recharge at many semiarid sites evidence for diffuse recharge exists at some locations where mean annual precipitation is much less than mean annual potential evapotranspiration particularly where soils are coarse and rainfall variable is substantial we investigate the climatic controls on diffuse recharge using a one dimensional variably saturated flow model the model is driven by a stochastic parameterization of climate that includes storm size distribution and seasonality of precipitation p and potential evapotranspiration pet constrained by data from 536 weather stations in the southwestern united states storm size distribution and seasonality determine the frequency and duration of intervals when p exceeds pet which controls the flux of water past the root zone for coarse soils climates with large infrequent storms yield recharge when exceeds 0 4 compared with 0 7 for a typical climate recharge through fine soils is insensitive to storm size and occurs at 0 8 seasonality has a stronger influence on recharge than storm size distribution and the effects are similar for coarse and fine soils recharge is relatively insensitive to rainfall seasonality in contrast the typical pet annual cycle lowers of the recharge threshold by 0 3 the relative timing of p and pet maxima is critical recharge occurs at values that are lower by 0 2 when the rainy season occurs during winter instead of summer over the range of climate and soils examined values at the recharge threshold varied from 0 2 to 0 7 therefore and alone are insufficient to predict where recharge will occur

palaeoecological evidence for early aragonite dissolution in ancient calcite seas it has been proposed that shallow carbonate seas of upper ordovician and jurassic ages precipitated calcite as the primary calcium carbonate phase1 3 unlike such settings today it is expected that such seas were undersaturated with respect to the more soluble aragonite so that aragonitic invertebrate skeletons would have tended to dissolve here we describe examples in which this seems to have been the case our evidence consists of submarine cemented horizons in which aragonite fossils have been dissolved out to leave open moulds the walls of the moulds are encrusted by contemporaneous organisms confirming the early timing of the aragonite dissolution

hiatal surfaces from the miocene globigerina limestone formation of malta biostratigraphy sedimentology trace fossils and early diagenesis article i nfo article history received 7 december 2006 accepted 24 january 2008 the miocene globigerina limestone of the maltese islands contains widespread omission surfaces with very different characteristics and origins the terminal lower globigerina limestone hardground tlglhg formed during a period of falling sea level coccolith assemblages suggest shallowness sedimentary structures and trace fossil assemblages indicate increasing frequency of storm events and erosional episodes towards the surface calcite cementation which took place around thalassinoides burrows and formed irregular nodules was followed by dissolution of aragonite it is suggested that lithification was linked to microbial reactions involving organic matter in contrast two later surfaces the terminal middle globigerina limestone omissionground tmglog which marks the lower to middle miocene boundary and the fomm ir rih local hardground firlhg both contain early diagenetic dolomite lithification took place in two phases the dolomite is interpreted to have formed beneath the sea floor it was subsequently exhumed and partially corroded as the precipitation of calcitic and phosphatic cements took place around burrows open to the circulation of sea water

environmental isotope hydrology of salinized experimental catchments deuterium oxygen 18 tritium and chloride concentrations were used in three salinized experimental catchments to gain insight into the mechanism of solute concentration and flow processes in the saturated and unsaturated zones the three experimental catchments were studied because of their location in different rainfall regions their status with respect to clearing of native vegetation and with respect to secondary salinization two uncleared catchments have average annual rainfalls of approximately 820 and 1220 mm respectively the third cleared catchment has an annual rainfall of 650 750 mm this catchment was in an advanced state of secondary salinization and displayed large areas of saline groundwater discharge with halite encrustation at the ground surface the stable isotope compositions of the solution phase in solute bulge profiles in the unsaturated zone showed a close agreement with the amount weighted mean isotopic composition of rainfall and only surficial evidence of isotopic enrichment due to evaporation evaporation from the soil surface plays a minor role as a mechanism of solute concentration in the unsaturated zone the dominant process of solute concentration in the unsaturated zone was ion exclusion during uptake of water by tree roots which was evidently a solute but not isotope fractionating process tritium analyses of unsaturated zone water and grondwater indicated movement of recent recharge to 7 10 m depth at the low rainfall site but over the full depth of the 15 m unsaturated zone at the higher rainfall site the variability in 18o and 2h values of groundwaters was used in association with chloride concentrations to provide information on mixing characteristics of groundwaters within the catchments

paleohydrologic implications of some deep soilwater chloride profiles murray basin south australia abstract a chloride mass balance approach to estimating soilwater ages and paleorecharge rates was tested in an area where considerable paleoclimatic data were available for comparison application of the method to data from four cores of the unsaturated zone taken in the western murray basin showed that the soil water at the base of the chloride build up or bulge associated with the root zone of the native mallee vegetation was emplaced during the last glacial interval at least 20 000 years bp furthermore recharge rates at this time were very low these observations agree with independent paleoclimate evidence that suggest that this time was colder windier and drier results are consistent with the notion that the root zone chloride bulge so typical of the murray mallee region developed in response to aridity that peaked during the last full glacial interval in australia the chloride method is a useful tool in paleohydrology especially when used in concert with other evidence

effects of forest clearing on groundwater abstract groundwater systems were studied in five catchments 0 8 3 5 km2 over ten years at the end of the third year forest vegetation was totally or partially cleared in three catchments the cleared areas were sown to pasture or crop in accord with conventional agricultural practice for the region permanent aquifers were encountered within a deeply 30 m weathered regolith derived from igneous basement rocks in the higher rainfall catchment pair aquifer boundaries corresponded reasonably well with the surface divide but permanent aquifers were encountered mainly in lower parts of the three catchments in the medium rainfall areas slug test measurements of hydraulic conductivity k varied by more than a factor 100 within a catchment but there was no significant difference between the geometric mean of k in each catchment which varied between 1 4 and 7 6 mm d 1 in the higher rainfall catchments the potentiometric surface under forest normally responded by 1 4 m after each winter wet season this indicates significant seasonal recharge on the basis of the number of piezometers exhibiting this behaviour seasonal recharge was widespread in this area by contrast the seasonal response of the potentiometric surface was rarely more than 1 m under forest in the medium rainfall catchments and at many sites there was no apparent recharge in several years of this study in areas fully cleared for agriculture the potentiometric surface moved upward at more than 2 6 m yr 1 averaged over several years this was equivalent to increased recharge estimated as 6 12 of rainfall depending on the specific yield used for the aquifer the potentiometric surface was observed to rise less rapidly 0 9 m yr 1 in areas subjected to partial clearing groundwater chloride concentrations exhibit no obvious spatial pattern in the catchments probability density functions of the chloride data have similar shapes in the higher and medium rainfall catchment areas with median values of 460 and 1000 mg 1 1 respectively chloride concentrations were essentially constant with time in some piezometers while in others concentrations varied with or without trend recorded changes in time and space are not consistent with the transport equation for solute in an aquifer leading to the conclusion that local variability of solution velocity may be important this is in accord with the observed variability of hydraulic conductivity in these aquifers