upper mantle anisotropy beneath the geoscope stations seismic anisotropy has been widely studied this last decade particularly by measuring splitting of vertically propagating core shear waves the main interest in this technique is to characterize upper mantle flow beneath seismic stations on the other hand the major restriction in this method is that a single station gives a single anisotropy measurement alternative methods have been developed in order to avoid this restriction an accurate determination of upper mantle seismic anisotropy beneath a seismic station may allow one by doing anisotropy correction to characterize remote or deeper anisotropy the geoscope network is ideal for this purpose because it is composed of a large set about 26 of high quality broadband seismometers globally distributed and because some of these stations have run for more than 10 years and most of them for more than 5 years we selected about 100 events at each site generally of magnitude mb 6 0 and we performed systematic measurements of the splitting parameters fast polarization direction and delay time t on sks skks and pks phases splitting on oceanic islands has been difficult to observe owing to the low quality of the signal but also perhaps owing to complex upper mantle structures beneath the stations station kip kipapa hawaii in the pacific is the only oceanic geoscope station with a clear anisotropy we determined well constrained splitting parameters for 10 of the 17 continental stations that may be explained by a single anisotropic layer the poor correlation between fast polarization directions and the absolute plate motion together with the apparent incoherence between the plate velocities and the observed delay times suggest that a simple drag induced asthenospheric flow alone fails to explain most of the observations for some stations located on or near major lithospheric structures tam tamanrasset algeria for instance we observe a good correlation between fast polarization directions and regional structures at station scz santa cruz california we found clear variations of the splitting parameters as a function of the event backazimuth compatible with two layers of anisotropy three stations can canberra hyb hyderabad india and ssb saint sauveur badole france seem to be devoid of detectable anisotropy

integrated hydrogeological and geophysical study of depression focused groundwater recharge in the canadian prairies 1 in the northern prairie region of north america numerous seasonal wetlands and ephemeral ponds form as snowmelt water is trapped in small topographical depressions a detailed hydrogeological investigation is combined with electrical resistivity imaging eri to evaluate the roles of the wetlands and ponds on depression focused groundwater recharge at the st denis national wildlife area in saskatchewan canada the analysis of groundwater samples indicated two distinct geochemical zones a zone of salt leaching under wetland 109 and zones of salt accumulation under the adjacent uplands two intermediate zones were identified as partially leached or mixed leached unleached and premodern or mixed saline nonsaline water the resistivity images of the areas around 109 were classified using the correlation between eri derived electrical conductivity ec and the groundwater ec the eri data clearly showed that depression focused recharge occurs under all depressions regardless of size leaching is observed to the depth of a regional intertill aquifer indicating that depression focused recharge contributes to the regional groundwater system the eri data also revealed the complex pattern of salt distribution that could not have been recognized by hydrogeological observations alone the complex distribution of salts appears to be caused by interaction between wetlands and variations in topography index terms 1829 hydrology groundwater hydrology 1045 geochemistry low temperature geochemistry keywords depression focused recharge electrical resistivity imaging groundwater recharge prairie wetland

chemical heterogeneity in diffusion dominated aquitards 1 high resolution measurements of the three dimensional 3 d variability in pore water electrical conductivity ec were obtained at a clay rich aquitard research site the king site 120 m 70 m area in southern saskatchewan canada using direct push probing technology n 35 boreholes these measurements revealed complex lateral heterogeneity in the subsurface salt distributions which raised questions on the validity of the commonly used approach of transposing chemical data from distributed piezometers onto 1 d depth profiles for interpretation and solute transport modeling two dimensional numerical modeling simulations demonstrated that distributed nonuniform salt inputs have existed at the top of the unoxidized till aquitard for the past 3 5 kyr the source of the nonuniform salt inputs is unclear but may be due to either variations in microtopography 0 5 m or variable penetration depth of surface fractures a suite of generic solutions was developed to estimate the critical depth required to obtain chemical homogeneity in aquitards with nonuniform solute inputs and diffusion as the dominant transport mechanism these solutions are presented for a range of sinusoidal input functions with varying amplitudes magnitudes and wavelengths the solutions indicate ec distributions at the king site should be laterally uniform below a depth of around 20 m bg which is consistent with observed ec values at the site this study shows that aquitards with nonuniform salt inputs at their upper boundary are chemically heterogeneous above some critical depth and thus require careful attention when modeling solute transport processes within them

field experiments in a fractured clay till 2 solute and colloid transport a field tracer experiment was conducted in a lateral flow field in the weathered and highly fractured upper 6 m of a 40 m thick clay rich till plain in southwestern ontario in the upper 3 m where fractures are closely spaced 5 m d simulations with a discrete fracture porous matrix flow and transport model which used the cubic law for flow in fractures showed that diffusion of the solutes but not the much larger colloids into the matrix pore water between fractures is sufficient to cause the observed difference in solute and colloid transport rates transport derived and hydraulic conductivity derived fracture aperture values were similar within a factor of 3 and falling mainly within a range of 5 40 m in the upper 3 m the solute tracers were evenly distributed between pore water in the fractures and the matrix and as a result solute transport can be closely approximated with an equivalent porous medium epm approach below this depth fractures are more widely spaced 0 13 to 1 m with concentration peaks tending to occur near visible fractures and solute transport cannot be adequately described with an epm approach

role of microtopography in the formation of sodic soils in the semi arid part of the indo gangetic plains india abstract in the northwestern part of the indo gangetic plains igp india non sodic and moderately sodic soils occur on microhigh mh and highly sodic soils on microlow ml positions under a semi arid climate the main soil forming processes have been clay illuviation deposition of pedogenic calcium carbonate and concomitant development of sodicity the microlows are repeatedly flooded with surface water during brief high intensity showers so the soils are subject to cycles of wetting and drying this provides a steady supply of alkalis by hydrolysis of feldspars leading to precipitation of calcium carbonate at high ph and development of subsoil sodicity this impairs the hydraulic conductivity of soils and eventually leads to the development of natrustalfs with exchangeable sodium percentages increasing rapidly up the profile the semi arid climate and topography interact to facilitate greater penetration of bicarbonate rich water in microlow than microhigh positions thin sections show deformational pedofeatures such as cross and reticulate striation of plasmic fabric disruption of clay pedofeatures and carbonate nodules and elongation of voids as a result of tectonic activity during the holocene in view of the persistent build up of stresses in the igp in general and the study area in particular it seems that the neotectonics have caused the microtopographical variations 0 5 1 m that control the formation of sodic soils

origin and movement of groundwater and major ions in a thick deposit of champlain sea clay near montreal at a site near montreal piezometers and core samples were used to assess the origin age and rate of groundwater movement in a 28 m thick deposit of champlain sea clay 3h occurs only within the upper 3 4 m which indicates that groundwater below this surficial weathered zone originated prior to 1952 concentrations of 18o na and cl in water from the deepest piezometer suggest that the deep clay was deposited in a mixture of about 33 seawater and 67 freshwater profiles of several major ions show a gradual increase in concentration with depth mathematical simulations of vertical migration of ca2 mg2 k na and cl provide close matches to the field profiles when only upward diffusion of these ions into the surficial freshwater zone is included in the model with a diffusion time of approximately 10 000 a when the downward advection rate of 0 13 cm a 1 obtained from field measurements of hydraulic gradient and hydraulic conductivity is included in the model the simulated major ion profile

impact of permeable conduits on solute transport in aquitards mathematical models and their application 1 the migration of contaminants through porous conduits for example sand layers in aquitards or any preferential flow feature within a low permeability matrix can be significantly retarded via diffusion into the matrix and processes such as sorption and decay previous solutions for simulating contaminant transport in these types of environments have been limited to a parallel plate approach such as that used in studies of fractured rock aquifers a major drawback of using these approaches is that they cannot account for the radial component of diffusion that occurs from circular or elliptical sectioned conduits we have developed solutions for both of the latter cases and compared results from generic simulations to those obtained with a conventional parallel plate model the results demonstrated using a circular conduit approach can produce concentration profiles for both the conduit and surrounding matrix that are up to several orders of magnitude lower than those predicted using parallel plate models the solutions for elliptical section conduits provide concentration profiles that are bounded by the circular and parallel plate models we also present several generic simulations to demonstrate the effects of conduit radius and average groundwater flow velocity on concentration profiles finally the circular conduit model is applied to a clay rich till aquitard in southern saskatchewan canada to provide insight into an anomalous dissolved chloride peak in the vertical pore water profile the model demonstrates that the source of the high cl could be as far as 10 100 km from the site although this distance may be unrealistic and allows estimation of the cl concentration at the source we envisage that the solutions for conduit diffusion will have far wider applications than just aquitard studies and future uses may include tracer tests in karstic and fractured aquifers

hydrogeology of two saskatchewan tills i fractures bulk permeability and spatial variability of downward flow groundwater flow patterns were compared and contrasted in two deposits of clayey till of different thicknesses both of which overlie regional aquifers in a flat upland recharge area analysis of 67 field and laboratory hydraulic conductivity determinations indicated that conductive fractures in the unoxidized zone of the thinner till dalmeny site give rise to an isotropic bulk permeability of approximately 5 10 9 ms 1 which is two orders of magnitude greater than the bulk permeability of unoxidized till in the thicker deposit warman site vertical pore water velocities estimated using hydraulic and isotopic evidence vary greatly at dalmeny and appear to be of the order of 8 m in 10 000 yr at warman the association of vertical groundwater flux depth to water table and depth of oxidized zone at a given location is referred to as the flow regime there spatially detailed water level monitoring and test drilling indicated substantial variation of the flow regime at dalmeny on a horizontal scale of tens of meters no such variation exists at warman the differentiation of the flow regime at dalmeny is due to higher till permeability which permits a spatially variable response to microtopographically focussed infiltration of surface water recognition of the causes and symptoms of flow regime variability beneath flat till landscapes has implications for environmental assessment procedures agricultural practices wetland management and waste disposal

stratification of the f 2 layer observed in southeast asia this paper describes the latitudinal variation in f2 stratification balan and bailey 1995 as observed by a number of oblique and vertical ionosondes operating in southeast asia during 1997 stratification of the f2 layer was seen at dip latitudes from 4 s to 18 s on the southern side of the magnetic equator but did not occur at the closest reflection point to the magnetic equator dip latitude 2 3 n the observed transient cusp vertical ionosonde or additional nose oblique ionosonde was defined as an f3 layer or an f1 5 layer depending on whether it occurred above or below the layer which maintained continuity with the normal f2 layer peak within the zone of occurrence the transient layer was commonly seen as an f3 layer at reflection points closest to the magnetic equator but invariably as an f1 5 layer at reflection points farther from the magnetic equator these observations suggest that the distortion in the equatorial electron density profile associated with the phenomenon moved toward the base of the f2 layer as magnetic field lines descended with increasing latitude stratification of the f2 layer commenced at the same local time e g 0845 lt in november 1997 throughout the longitudinal range of coverage and was associated with a rapid rise in f2 layer height following sunrise the stratification ended at times varying from 1300 lt to sunset and was associated with a fall in the height of f2 peak electron density the region of maximum f2 layer stratification lay between the magnetic equator and the peak of the southern equatorial anomaly

subduction induced strain in the upper mantle east of the mendocino triple junction california we observe splitting of teleseismic shear waves at five stations of the berkeley digital seismic network located east of the mendocino triple junction in northeastern california that is dependent on the arrival direction of the seismic phases the observed variations with back azimuth cannot be explained with laterally varying anisotropy with a horizontal symmetry axis and are attributed to the presence of fabric with an inclined symmetry axis we assume that the anisotropy is caused by the preferred alignment of olivine crystals a grid search over possible orientations of the olivine a axes reveals that south of the mendocino triple junction they dip to the east whereas north of the triple junction they dip to the northeast on the basis of a comparison of the ray paths of our data to the spatial distribution of fast and slow p wave velocity anomalies in the upper mantle we conclude that the anisotropy is located within seismically slow regions and that the directions are controlled by the geometry of a steeply dipping fast p wave velocity anomaly assuming that the fast p velocity anomaly represents subducted slab material we conclude that the fabric beneath the stations north of the triple junction is most likely caused by the differential motion between this rigid strong down going plate and the surrounding mantle south of the triple junction the fabric may have developed while subduction of the farallon plate was still ongoing in this region prior to 6 ma however we prefer to attribute the observations to more recent asthenospheric flow associated with the opening of a slabless window beneath the north american lithosphere the flow is modulated by the presence of rigid lithosphere to the north and east

use of vertical profiles of δ18o to constrain estimates of hydraulic conductivity in a thick unfractured aquitard vertical distributions of 18o were used to constrain hydraulic conductivity k in a thick unfractured aquitard previous investigations utilizing permeability tests at a variety of scales keller et al 1989 indicated that bulk k at the site ranges from 3 5 0 11 m s to 1 2 10 10 m s advective displacements calculated on the basis of these k values lead to a wide range of predicted distributions of natural tracers after 11 000 years comparison of 18o distributions and simulated advection diffusion profiles provide a more precise constraint on advective displacement and hence on k the simulations cast in terms of a peclet number p v2t d ranging in value from 0 to 12 indicate that transport is diffusion controlled and that k is actually less than 1 2 10 11 m s p greater than 0 1 k 1 2 10 11 m s overestimates transport this result indicates that conventional permeability tests in very tight media tend to overestimate k in practical terms advective transport at the site is negligible and transport can be simulated with diffusion only p o

an additional layer in the low latitude ionosphere in indian longitudes total electron content observations and modeling 1 the paper presents the observations and modeling of an additional layer in the low latitude ionosphere in indian longitudes the signatures of the additional layer are observed as ledges or humps between the equatorial ionization anomaly trough and crest eia in the latitudinal profiles of total electron content tec measured using a single ground based beacon receiver located at trivandrum 8 5 n 77 e dip 0 5 n in india the ground based ionograms also show the presence of the so called f 3 layer for a short duration corresponding to these signatures and the layer is found to drift upward to the topside ionosphere the study provides first observational evidence that the so called humps in the latitudinal variation of tec are nothing but the upward propagating f 3 layer this conclusion is supported by theoretical modeling using the sheffield university plasmasphere ionosphere model it is shown that upward exb drift and strong equatorward neutral wind perturbed by atmospheric waves can produce the humps in the latitudinal variation of tec through the reduction in the downward diffusion of ionization along geomagnetic field lines the model results also show that the f 3 layer drifts to the topside and forms topside ledges

additional stratifications in the equatorial f region at dawn and dusk during geomagnetic storms role of electrodynamics 1 the role of electrodynamics in producing additional stratifications in the equatorial f region f 3 layer at dawn and dusk during geomagnetic storms is discussed two cases of f 3 layer at dawn 0600 0730 lt on 5 october 2000 and 8 december 2000 and one case of f 3 layer at dusk 1600 1730 lt on 5 october 2000 are observed for the first time by the digital ionosonde at the equatorial station trivandrum 8 5 n 77 e dip 0 5 n in india the unusual f 3 layers occurred during the geomagnetic storms and are associated with southward turning of interplanetary magnetic field b z suggesting that eastward prompt penetration electric field could be the main cause of the f 3 layers the dawn f 3 layer on 5 october is modeled using the sheffield university plasmasphere ionosphere model by using the e x b drift estimated from the real height variation of the ionospheric peak during the morning period the model qualitatively reproduces the dawn f 3 layer while the existing f 2 layer rapidly drifts upward and forms the f 3 layer and topside ledge a new layer forming at lower heights develops into the normal f 2 layer

features of the f3 layer in the low latitude ionosphere at sunset the f 3 layer is a common feature within 10 degrees of the magnetic equatorial ionosphere in the daytime according to balan et al 1998 the f 3 layer occurs mainly during the morning noon period due to the combined effect of the upward e x b drift and the neutral wind that provides upward plasma drifts at and above the f 2 layer the f 3 layer occurrence rate is higher in summer and decreases with increasing solar activity in this study the characteristic of the sunset f 3 layer is first investigated using a solar cycle of ionosonde data 1995 2010 from the magnetic equatorial station at jicamarca and compared with the features derived from the four subtropical stations at sao luis fortaleza kwajalein and vanimo evidence shows that the local time distribution of the occurrence of the f 3 layer can extend to the postsunset time 1800 2100 local time the sunset f 3 layer has a strong seasonal dependence occurring mainly during the summertime unlike the daytime f 3 layer the occurrence of the sunset f 3 layer clearly increases and the virtual height of the bottom side of the f 3 layer statistically increases from 620 to 1000 km with increasing solar activity in addition the occurrence of the sunset f 3 layer at the other stations is much less than that at jicamarca these features of the dependence on the season solar activity and latitude are clearly related to the geomagnetic control of the evening prereversal enhancement of the equatorial zonal electric field and geomagnetic configuration

sources of radiogenic helium in a clay till aquitard and its use to evaluate the timing of geologic events abstract concentrations of dissolved gases he ne ar and n 2 were measured in pore waters collected from a pleistocene 0 80 m depth and cretaceous 80 156 m depth aged clay rich aquitard system using both a conventional copper tube method and in situ diffusion samplers both methods yielded similar results he data revealed a well defined increase in concentration with depth from 1 7 10 8 cm 3 he stp g 1 water near the water table at 2 3 m below ground surface to 6 9 10 6 cm 3 he stp g 1 water at 80 m below ground surface b g the concentration at depth greatly exceeded values for atmospheric solubility at in situ temperatures and could not be attributed to steady state production from decay of u and th within the aquitard system trends in he isotope ratios and concentrations suggest accumulation as a result of both release of residual 4 he from within the pleistocene clay rich till ca 87 and an ascending radiogenic helium flux from underlying cretaceous age sediments ca 13 one dimensional transport modeling of the he data suggests that between 15 ka and 25 ka were required to produce the observed profile this time frame agrees with studies utilizing isotope tracers i e d h and 14 c dic to estimate the timing of deposition for the till at this site our results demonstrate the utility of using helium a nonreactive tracer for delineating hydrogeologic processes in slow permeability geologic strata and also support the contention that thick clay rich surficial aquitards can provide long term containment of contaminants including hazardous wastes

hydrogeochemistry of a clayey till 1 spatial variability the spatial variability of hydrogeochemical processes was studied within an 18 m thick unit of clayey till beneath a flat prairie landscape models of major element mass transfer constrained by chemical mineralogical and isotopic measurements on waters and solids were developed for two end member water quality types occurring within the unit the observed pattern of chemical variation which is predominantly lateral on a scale of tens of meters is caused by microtopographically controlled differences in the ratio of vertical water flux to oxidation rate associated with depression focused recharge such variation is to be expected where dynamic flow regimes develop in thin surficial tills containing chemically reduced constituents observed depletions of major elements from oxidized zones of the till support the mass transfer models and demonstrate that the time scales of persistence of hydrogeochemical variability in the till and of water quality evolution in the aquifer beneath range from 104 to 105 year na and s concentrations in such aquifers will depend primarily on ratios of influxes of end member water quality types from the till above while ca mg and inorganic c concentrations will remain high as long as partial pressures of co2 in the till remain high co2 generation in the till is discussed in the companion paper keller this issue

seismic anisotropy of the mantle lithosphere beneath the swedish national seismological network snsn body wave analysis shear wave splitting and p travel time residuals detect anisotropic structure of the upper mantle beneath the swedish part of fennoscandia geographic variations of both the

multichannel analysis of shear wave splitting a multichannel analysis is introduced to constrain seismic anisotropy from the shear wave splitting of sks and skks this technique utilizes simultaneously a set of records coming from different azimuths the splitting intensity of sks waves measured by the amplitude of the transverse component depends on the angle between the back azimuth of the earthquake and the direction of the symmetry axis and on the delay time t between the two quasi shear waves it is shown that the splitting parameters can be determined from the azimuthal dependence of the splitting intensity which is given by the first right eigenvector of the matrix containing the transverse components of all the records alternatively the splitting intensity can be measured by projecting the transverse components on the radial components derivatives experiments on synthetic seismograms demonstrate that both approaches provide robust estimates of the splitting parameters however the projection approach gives measurements that are closer to the inputs and with smaller error bars which suggests that it should be preferred when the signal to noise ratio is low the new technique is applied to analyze shear wave splitting under stations bcao bangui central african republic and bdfb brasilia brazil the analysis of 75 seismograms recorded by station bcao gives a fast polarization direction in very close agreement with the present day motion direction of the african plate comparisons with the results of previous studies obtained with other techniques and smaller data sets suggest that some of the published measurements may be strongly biased the main limitation of the multichannel analysis is a good azimuthal distribution of the seismicity maps of the azimuthal coverage were determined and it is found that the most favorable regions to study anisotropy with sks waves are a latitudinal band that goes from south america to africa the eastern part of north america and india

super plasma fountain and equatorial ionization anomaly during penetration electric field 1 relative importance of diffusion electric field and neutral wind on equatorial plasma fountain and equatorial ionization anomaly eia during a strong daytime eastward prompt penetration electric field ppef event are evaluated using the sheffield university plasmasphere ionosphere model and the recorded ppef during the super geomagnetic storm of 9 november 2004 the fountain rapidly develops into a super fountain during the ppef event the super fountain becomes strong with less poleward turning of the velocity vectors in the presence of an equatorward wind that reduces or stops the downward velocity component due to diffusion and raises the ionosphere to high altitudes of reduced chemical loss the eia crests in peak electron density and total electron content shift rapidly to higher than normal latitudes during the ppef event however the crests become stronger than normal only in the presence of an equatorward wind the results suggest that the presence of an equatorward neutral wind is required to produce a strong positive ionospheric storm during a daytime eastward ppef event the equatorward neutral wind need not be a storm time wind though stronger wind can lead to stronger ionospheric storms

formation of cratonic mantle keels by arc accretion evidence from s receiver functions 1 delineating mantle interfaces can provide important clues for understanding the formation of continents we use s wave receiver functions to investigate lithospheric structure along a transect extending from vancouver island to baffin island observed sp converted waves allow for interpretation of boundaries in the depth range expected for tectonic plates receiver functions show a distinct negative amplitude feature interpreted as the lithosphere astbenosphere boundary at shallow depths beneath british columbia 85km deepening abruptly at the eastern edge of the cordillera to 260km beneath the canadian shield dipping mid lithospheric discontinuities extend beneath several giant ca 1 8 ga epicontinental magmatic arcs consistent with formation of cratonic lithosphere by arc accretion this model provides a plausible explanation for global mid lithospheric discontinuities within cratons and aids in understanding their formation

controls on the distribution of major ions in pore waters of a thick surficial aquitard transport and geochemical processes controlling the chemical and isotopic composition of pore waters in the upper 45 m of a thick surficial clay rich till battleford formation were studied the upper 3 m of the till is oxidized and fractured the remaining 77 m of the till the aquitard is nonfractured and unoxidized concentrations of total dissolved solids so42 na mg2 and k decrease with depth through the unoxidized zone to a depth of about 15 m below ground below which the concentrations remain constant a similar trend was observed for alkalinity however the decrease in concentration occurs over 20 m in contrast to these ions ca2 concentrations increase with depth through the upper 20 m unoxidized zone below which the concentrations remain relatively constant the distribution of dissolved ions shows the presence of two end members elevated solute concentrations in the oxidized zone attributed to geochemical weathering that occurred since the start of the holocene and connate pleistocene age water at depths between 20 and 45 m abiotic and biotic geochemical reaction rates in the aquitard were shown to be extremely slow or not occurring

attenuation of nitrate in aquitard sediments of southern ontario to examine nitrate persistence detailed geochemical profiling using core squeezed water and piezometer samples was carried out at five sites in southern ontario where groundwater is moving downward in silt rich aquitard sediments at rates of 16 to more than 20 cm year 1 elevated levels of no3 n 5 50 mg 1 1 that occur in the shallow groundwater as a result of agricultural activity were found to be consistently attenuated generally to very low levels 0 05 mg 1 1 n at the redoxcline the horizon marking the boundary between the surficial weathered brown sediments and the underlying unweathered grey sediments tritium dating suggests that groundwater at the redoxcline depths 3 5 m was recharged between 1970 and 1980 thus the n03 depletion appears to result from biodegradation reactions since no major landuse changes have occurred during this period the close association of the nitrate depletion zones with the redoxcline where in particular sediment sulphur contents increase abruptly and where also porewater so42 levels increase suggests that the dominant attenuation reaction is autotrophic denitrification using reduced sulphur compounds present in the unweathered sediment as the electron donor mass balance calculations suggest that the increase in the downward rate of migration of the redoxcline owing to added sulphur consumption from no3 contamination is only about 1 mm year 1 at these sites review of the literature indicates that most silt and clay rich sediments have s contents in the same range or higher than those investigated here thus in most cases where aquifers are overlain by several metres or more of unweathered confining sediments it is likely that a high degree of protection is afforded from surficial no3 contamination

neutral wind effect in producing a storm time ionospheric additional layer in the equatorial ionization anomaly region 1 a new type of the additional layer is predicted to occur in the low latitude f region ionosphere during evening hours of a major magnetic storm by using the coupled ncar thermosphere ionosphere electrodynamic general circulation model tiegcm and sheffield university plasmasphere ionosphere model supim runs during the major magnetic storm of 29 30 october 2003 we present a new type of additional layer which occurs at the equatorial ionization anomaly eia by a new physical mechanism this mechanism requires that storm time meridional neutral wind surges travel from high to low latitudes and cross into the opposite hemisphere the wind surges modify the field aligned plasma velocities in the eia regions significantly after uplift of the ionospheric layer by a penetration electric field and interact with the downward field aligned plasma velocities of the enhanced equatorial fountain the combined storm effects of the enhanced plasma fountain and the neutral wind surges result in plasma convergence in altitude and form the additional layers underneath the eia crests

first simultaneous observations of f3 layer and e b drift in indian sector and modeling 1 although the basic mechanism of an additional stratification of the daytime equatorial f region called the f3 layer has been explained two observational aspects that remain not so clear are its summer winter differences and simultaneous occurrences on either side of the geomagnetic equator in this paper we address these two aspects using simultaneous observations of the f3 layer and vertical e b drift velocity made for the first time in an indian station gadanki 6 5 n mag lat during the low solar activity period 2008 2009 and making model computations using the sheffield university plasmasphere ionosphere model the observations confirm the frequent occurrence of the f3 layer in summer months compared to winter months the observations also reveal the occasional occurrence of clear and distinct f3 layer in winter although such a layer is frequent in summer in addition a threshold vertical plasma velocity involving the e b drift and neutral wind and its time integrated value are found to be important for the formation of the f3 layer the model results qualitatively reproduce the observations and show that irrespective of season the formation of the f3 layer is centered on that side of the equator where the equatorward neutral wind reduces the downward field aligned flow of plasma and the latitude band of the layer can extend to the opposite hemisphere especially when the vertical plasma velocity is large

magnetic conjugate observation of the f3 layer using the sealion ionosonde network 1 results from the meridional ionosonde network located in southeast asia sealion demonstrate the interesting nature of the f3 layer showing its generation mechanism ionograms obtained on 16 november 2004 and 31 march 2005 at chiang mai cmu geographic latitude 18 8 n geographic longitude 98 9 e and magnetic latitude 13 2 n chumphon cpn 10 7 n 99 4 e and 3 2 n and kototabang ktb 0 2 s 100 3 e and 10 1 s showed significant differences between cpn near the magnetic equator and cmu and ktb in the magnetic low latitude region the simultaneous magnetic conjugate observations of the f3 layer achieved using the sealion ionosonde network data showed clear dependences of the f3 layer on the magnetic latitude it is suggested that these magnetic latitude dependences of the f3 layer can be explained by considering the plasma diffusion effects along the magnetic field lines in the magnetic low latitude region

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

f3 layer during penetration electric field 1 the occurrence of an additional layer called f3 layer in the equatorial ionosphere at american indian and australian longitudes during the super double geomagnetic storm of 7 11 november 2004 is presented using observations and modeling the observations show the occurrence reoccurrence and quick ascent to the topside ionosphere of unusually strong f3 layer in australian longitude during the first super storm 8 november and in indian longitude during the second super storm 10 november all with large reductions in peak electron density nmax and total electron content gps tec the unusual f3 layers can arise mainly from unusually strong fluctuations in the daytime vertical e b drift as indicated by the observations and modeling in american longitude the strongest upward e b drift or eastward prompt penetration electric field ppef ever recorded at jicamarca produces unusually strong f3 layer in the afternoon hours 1400 1600 lt of ppef with large reductions in nmax and tec the layer also reappears in the following evening 1700 1800 lt owing to an unusually large downward drift at night when the drift is unusually upward and strong the f region splits into two layers

shear wave splitting continental keels and patterns of mantle flow in this study we investigated the origin of seismic anisotropy in the mantle beneath north america in particular we evaluated whether shear wave splitting patterns in eastern north america are better explained by anisotropy caused by lithospheric deformation anisotropy due to mantle flow beneath the lithosphere or a combination of both we examined new measurements of shear wave splitting from the missouri to massachusetts broadband seismometer array moma the north american mantle anisotropy and discontinuity experiment nomad as well as splitting parameters from several previous studies we developed a simple finite difference model that approximates mantle flow around a complex three dimensional continental lithospheric keel to evaluate potential anisotropy from mantle flow beneath the lithosphere in eastern north america we compared shear wave splitting observations to predicted splitting parameters calculated using this mantle flow model our results indicate that a significant portion of observed shear wave splitting in eastern north america can be explained by mantle flow around the continental keel however shear wave splitting patterns in a few regions of eastern north america indicate that a component of lithospheric anisotropy must exist particularly in regions containing the largest keel thicknesses for eastern north america as well as for splitting observations in australia europe and south america we favor a model in which anisotropy is controlled by a combination of both lithospheric deformation and subcontinental mantle flow

lithospheric deformation inferred from teleseismic shear wave splitting observations in the united kingdom observations of splitting in teleseismic shear waves recorded at stations in the united kingdom uk seismic network operated by the british geological survey are related to the tectonic structures and history in the uk the combination of network density and tectonic variability in the uk permits an assessment to be made of the relationship between splitting and geology fast polarization directions are most commonly parallel to geologic features resulting from compressional or strike slip events and splitting delay times mirror the increasing involvement of basement in deformation as observed through field investigation different orogenic episodes may be distinguished in the splitting orientations a peak in delay times is suggested in the observations at the iapetus suture a site of paleozoic subduction now in the uk interior these observations are consistent with the idea that continental anisotropy arises through coherent deformation of the lithosphere and is preserved long after orogenic deformation ceases

aerosol size confines climate response to volcanic super eruptions extremely large volcanic eruptions have been linked to global climate change biotic turnover and for the younger toba tuff ytt eruption 74 000 years ago near extinction of modern humans one of the largest uncertainties of the climate effects involves evolution and growth of aerosol particles a huge atmospheric concentration of sulfate causes higher collision rates larger particle sizes and rapid fall out which in turn greatly affects radiative feedbacks we address this key process by incorporating the effects of aerosol microphysical processes into an earth system model the temperature response is shorter 9 10 years and three times weaker 3 5 k at maximum globally than estimated before although cooling could still have reached 12 k in some midlatitude continental regions after one year the smaller response plus its geographic patchiness suggests that most biota may have escaped threshold extinction pressures from the eruption

fracture permeability and groundwater flow in clayey till near saskatoon saskatchewan field and laboratory studies of a clayey unweathered glacial till have shown that its bulk permeability exceeds its matrix permeability by two orders of magnitude such findings are common for weathered till but are rare for unweathered till and have important implications for groundwater recharge and contaminant transport the till in question is 6 m thick and appears to be unweathered and unfractured it is overlain by 12 m of weathered and highly fractured till results of consolidation tests on the unweathered till indicate a mean vertical hydraulic conductivity of 3 5 10 11 m s 1 and a mean specific storage of 1 3 10 4 m 1 results of slug tests yield a horizontal hydraulic conductivity of about 5 10 9 m s 1 drawdowns in the till in response to pumping from the aquifer below indicate a vertical hydraulic diffusivity of 4 5 10 5m2 s 1 the slug test results combined with specific storage results from consolidation tests indicate a similar value for horizontal hydraulic diffusivity of 4 10

numerical studies of vertical cl δ2h and δ18o profiles in the aquifer aquitard system in the pearl river delta china sedimentation may have a significant effect on the transport of solutes and environmental isotopes in sediment the depth profiles of the cl 2h and 18o in a borehole in the aquifer aquitard system in the pearl river delta prd china were obtained by centrifuging the core sediment samples a one dimensional model based on the sedimentation and sea level changes of the prd during the holocene was built to investigate numerically the transport mechanisms of cl 2h and 18o the sedimentation process was modelled as a moving boundary problem with the moving rate equal to the sedimentation rate the model was calibrated and the parameters were obtained by comparing simulated and measured data very good agreement between all the three observed profiles and the simulated ones demonstrates the reliability of the model and the parameters simulation results show that the shapes of the curves are controlled by the combination of sedimentation and upper boundary conditions diffusion solely is adequate to reconstruct the observed profiles which indicates that diffusion is the dominant vertical transport mechanism the effective diffusion coefficients of the aquitard and the aquifer equal to 5 0 10 11 and 2 0 10 10 m2 s respectively the results of this study will help in understanding the transport mechanisms of solutes and environmental tracers in deltas with geology and hydrogeology similar to the prd copyright 2015 john wiley sons ltd

hydrogeology of two saskatchewan tills ii occurrence of sulfate and implications for soil salinity abstract the occurrence of sulfate salts in groundwater and solids was documented at two sites named dalmeny and warman where clayey tills overlie regional aquifers at dalmeny the till is thinner and approximately two orders of magnitude more permeable than at warman samples for sulfur and sulfate determinations were collected to depths of approximately 14 m and at horizontal spacings of a few tens of meters large numbers of indirect measurements of bulk salt content were obtained with a noncontacting earth conductivity meter results showed that the bulk sulfur and sulfate contents of solids could not in general be adequately characterized with point or grab samples from boreholes at dalmeny measurements representing larger averaging volumes revealed a spatially intricate pattern of sulfate abundance and depletion which extends vertically through the oxidized and unoxidized zones of the till to the underlying aquifer similar measurements at warman suggest that sulfate variability there is limited to the oxidized zone these findings and the observed coincidence of sulfate patterns with the groundwater flow patterns documented in part i2 show that the bulk permeability of the till controls the manner in which the subsurface sulfate reservoir is affected by microtopographic focussing of surface water input conceptual analysis of the responses of these systems to various land management practices indicates that where tills are relatively permeable these practices would primarily affect the quality of groundwater recharge to underlying aquifers where tills have low permeability the same practices would have no effect on aquifer water quality but they would affect the potential for surface and soil salinization

spatial and temporal dynamics of water flow and solute transport in a heterogeneous glacial till the application of high resolution profiles of δ18o and δ2h in pore waters summary the heterogeneity and dynamic of water flow and solute transport processes were investigated in the upper 6 m of a surficial glacial till in southern saskatchewan canada continuous core samples from three vertical sites located over a maximum spatial distance of 65 m were collected and analyzed for particle size distribution porosity and water content high resolution 0 2 m profiles of 18o and 2h in pore waters were also measured for the three sites on a seasonal basis depth profiles of all measured parameters indicate highly heterogeneous structures in the upper 6 m in two coreholes depleted water isotopes measured at different depths below ground 0 7 and 3 m were in the range of winter precipitation values suggesting preferential flow of meltwater in spring accompanied by a rising water table a one dimensional equilibrium flow and transport model failed to simulate the isotope depth distributions with depleted winter values and could not reproduce the measured values even when accounting for vertical preferential flow a conceptual model was created based on the consistency of all measured data and assuming preferential lateral flow as the controlling flow and transport mechanism after snowmelt in the model water from surface runoff after snowmelt drains into an ephemeral depression that crosses the study site as this water infiltrates it forms a water table mound that slowly propagates away from the depression as the water table propagates outwards dynamic vertical flow processes result in net upward and downward fluxes

daytime additional f layer stratification over low midlatitude station of the indian sector under geomagnetic disturbed conditions 1 in this paper the observations of additional f layer stratification are presented in a region which is situated at the outer edge of equatorial ionization anomaly eia zone the digital ionosonde data observed over delhi 28 6 n 77 2 e dip 42 44 n during march april 2001 has been used to carry out the present work the observational period was geomagnetically disturbed and represents the high solar activity phase of 23rd solar cycle the additional transient cusp is frequently observed in the considered months before the noon hours however in this paper only five prominent cases are presented from the analysis of ionograms it is observed that the transient additional cusp is formed between the pre existing f1 and f2 layer hence named as the cusp of f1 5 study reveals that the traveling atmospheric disturbances tads along with the vertical expansion of f layer provides the necessary condition for the existence of this transient feature the intensification of f1 layer along with increased altitude immediately after the disappearance of additional stratification remains one of the fascinating features of the present results the present investigation demonstrates that the daytime f1 and f2 region over low midlatitude station is strongly modulated by the passage of tids originating at high latitudes or by atmospheric disturbances of local origin during the high solar activity period the concurrent presence of tads and the associated disturbance composition appears to be plausible reason behind the present observations

equatorial plasma fountain and its effects over three locations evidence for an additional layer the f 3 layer the equatorial plasma fountain and equatorial anomaly in the ionospheres over jicamarca 77 w trivandrum 77 e and fortaleza 38 w are presented using the sheffield university plasmasphere ionosphere model under magnetically quiet equinoctial conditions at high solar activity the daytime plasma fountain and its effects in the regions outside the fountain lead to the formation of an additional layer the f3 layer at latitudes within about plus or minus 10 of the magnetic equator in each ionosphere the maximum plasma concentration of the f3 layer which occurs at about 550 km altitude becomes greater than that of the f2 layer for a short period of time before noon when the vertical e b drift is large within the f3 layer the plasma temperature decreases by as much as 100 k the ionograms recorded at fortaleza on january 15 1995 provide observational evidence for the development and decay of an f3 layer before noon the neutral wind which causes large north south asymmetries in the plasma fountain in each ionosphere during both daytime and nighttime becomes least effective during the prereversal strengthening of the upward drift during this time the plasma fountain is symmetrical with respect to the magnetic equator and rises to over 1200 km altitude at the equator with accompanying plasma density depletions in the bottomside of the underlying f region the north south asymmetries of the equatorial plasma fountain and equatorial anomaly are more strongly dependent upon the displacement of the geomagnetic and geographic equators jicamarca and trivandrum than on the magnetic declination angle fortaleza

paleostress reconstruction from kinematic indicators in the oslo graben southern norway new constraints on the mode of rifting abstract the oslo graben southern norway is a n s trending carboniferous permian rift system characterized by major mafic to silicic magmatism n s trending faults reactivation of preexisting precambrian faults and formation of half grabens magmatism is expressed by the presence of lavas dyke injections cauldron formation and the intrusion of batholiths paleostress analyses mainly based on slickensides have been performed in the area both within and outside the rift structure combined with the current tectono magmatic model of the oslo graben area the analyses show the following stress evolution from the caledonian orogeny with its compressional tectonics in the silurian to the late stages of the carboniferous permian rifting nw se compression occurred in silurian times due to the continental collision of the caledonian orogeny after a long period of a missing geological record the area was affected by n s compression during the late carboniferous a shallow sedimentary basin developed indicative for the pre and proto rift phases the transition from the proto rift phase to the initial rift phase is marked by a transition from a transpressional regime into a transtensional regime during the early permian the stress regime changed from pure extension to radial extension we suggest that the oslo graben can not simply be explained in terms of or passive or active rifting but that a combination of both evolving through time is more suitable to explain the observations we propose a model in which the oslo graben is initially triggered by far field stresses in the latest carboniferous and earliest permian which infers opening due to passive rifting these far field stresses are suggested to be linked to the hercynian orogeny active to the south in central europe in carboniferous times and the reorganisation of the pangea supercontinent in early permian times the stress regime caused radial extension indicative for uplift and a change to an active mode of rifting simultaneously with the radial extension large volumes of magma are emplaced at near surface levels despite all alternative models an anomalous thermal gradient is necessary to create these large volumes of magmatic material we propose therefore that shortly after the onset of rifting the dominant rifting mode becomes active plume related although far field stresses might still be present

characterizing the hydrogeology of a complex clay rich aquitard system using detailed vertical profiles of the stable isotopes of water abstract high resolution 1d profiles of the stable isotopes of porewater 2h and 18o obtained by direct porewater equilibration of core samples were used to identify hydrogeologic zones in a thick complex till aquitard system in saskatchewan canada detailed 1d isotope profiles revealed the presence of three distinct hydrogeological zones an upper 5 10 m an intermediate 10 30 m and a lower 30 62 5 m till zone the upper hydrogeological zone was controlled by a sand layer having a high hydraulic conductivity k the lack of vertical variability in the stable isotope data in the intermediate zone suggested groundwater flow and solute transport was controlled by a system of interconnected vertical fractures and lateral sand layers the curved shape of the isotope profile in the lower till zone suggested that solute transport in this zone was controlled mainly by molecular diffusion we show that high resolution vertical stable isotope profiles of porewater obtained from core samples and direct equilibration yield cost effective and invaluable hydrogeologic information on groundwater flow in aquitard systems that cannot be realistically obtained by construction of costly conventional piezometer bundles i e 2h and 18o analyses of water samples and k determinations further the direct equilibration approach overcomes the problem of piezometer leakage in low k aquitards

features of additional stratification in ionospheric f2 layer observed for half a solar cycle over indian low latitudes 1 the features of the additional stratification in the ionospheric f2 layer often referred to as the f3 layer observed over an indian low latitude station waltair 17 7 n 83 3 e magnetic latitude mag lat 8 2 n during the period 1997 2003 are presented along with the data from two other indian stations the observations grossly confirm those reported earlier in the occurrence and seasonal variability of the f3 layer from an analysis of half a solar cycle ionosonde data 1997 2003 it is observed that the layer appeared more frequently during the summer solstice months of low solar activity period and persisted for longer durations during this season compared with equinox and winter solstice the best stratification is seen between 10 12 hours ist the occurrence of the f3 layer does not seem to depend on magnetic activity but the percentage of occurrence decreased with increasing solar activity the solar activity dependence over waltair confirms the model predictions of balan et al 1998 that the layer becomes less distinct and less frequent as solar activity increases the ionosonde data for the same period 1997 2003 from an equatorial station trivandrum 8 4 n 76 9 e mag lat 0 47 n and another low latitude station shar 14 n 80 e mag lat 6 8 n are also analyzed with a view to examine the effect of the equatorial plasma dynamics on the occurrence of such events

evidence for early proterozoic plate tectonics from seismic reflection profiles in the baltic shield plate tectonics provides the linking framework for all tectonic and magmatic activity seen today but it is not known when plate tectonics first developed on earth new deep seismic reflection and

a statistical study of the response of the dayside equatorial f2 layer to the main phase of intense geomagnetic storms as an indicator of penetration electric field 1 the response of the dayside equatorial f2 layer to the main phases of the 22 intense geomagnetic storms dst 150 nt in 1998 2008 is investigated using the digital ionosonde data from the equatorial stations in brazilian indian and australian longitudes together with equatorial electrojet strength and imf bz the storms include 15 superstorms dst 200 nt the observations show that there is a period during all mps when the f2 layer peak rises and falls rapidly with large peak electron density nmax reduction the rise velocity strongly correlates with the intensity dst of the storms and the duration of the nmax reduction corresponds to that of strong eastward electrojet when imf bz remains highly negative the observations indicate the occurrence of strong eastward prompt penetration electric fields ppef during the rapid f2 layer response the ppef drives the f2 layer peak rapidly upward which reduces nmax due to vertical expansion and diffusion the results therefore suggest that the rapid f2 layer response rapid rise and fall of peak height hmax with large nmax reduction observed by ionosondes can be used to detect the occurrence of the daytime eastward ppef during intense geomagnetic storms irrespective of season and level of solar activity the data also show two rare events of strong daytime westward electric fields due to disturbance dynamo and or prompt penetration the results are important when radars are not available to monitor the occurrence of the ppef

peculiar features of ionospheric f 3 layer during prolonged solar minimum 2007 2009 we present the seasonal and local time occurrence of ionospheric f 3 layer over tirunelveli geographic longitude 77 8 e geographic latitude 8 7 n dip 0 7 during extremely low and prolonged solar activity period 2007 2009 canadian advanced digital ionosonde observations from this station are used in the present study we find that the occurrence of f 3 layer is nearly 3 times higher during 2009 48 as compared to that during 2007 16 the increase of this order just within the low solar activity period is unusual in earlier studies similar increase in f3 occurrence has been reported when solar activity changes from high f10 7 182 t o low f10 7 72 the other important feature is the presence of postnoon f3 layers which are observed dominantly during summer solstice of 2009 such occurrence of postnoon f3 layers was nearly absent during summer solstice of the previous solar minimum 1996 over nearby dip equatorial station trivandrum we take equatorial electrojet eej as a proxy for eastward electric field it is noticed that the eej strength and the maximum rate of change of eej are higher for f3 days as compared to those on non f3 days we find that the peak occurrence of prenoon f3 layer closely coincides with the time of maximum rate of change of eej it is in general accordance with the theory proposed by balan et al 1998 that suggests the formation of f3 through vertically upward e b drift in presence of equatorward neutral wind the present study reveals that the rate of change of eastward electric field de dt as well plays an important role in the formation of f3 layer

chloride and chlorine isotopes 36cl and δ37cl as tracers of solute migration in a thick clay rich aquitard system detailed vertical profiles of dissolved cl and its isotopes 36cl and 37cl provided new information on the origin and systematics of this conservative tracer in pore waters of a thick aquitard system the aquitard system consists of surficial quaternary clay rich till 80 m thick deposited 30 20 kyr b p overlying cretaceous marine clay 76 m thick deposited 71 ma the distribution of cl 37cl and br showed the presence of five distinct end members for cl the top of the unoxidized till a regional aquifer underlying the cretaceous clay two localized geological heterogeneities sand streaks in the till and glacial meltwater emplaced with the till and still present at depths of between 36 and 60 m numerical simulations of the transport of cl from the sand streaks indicated that this geochemical profile has been developing throughout most of the holocene the 36cl measurements showed that the age of the dissolved cl in the upper cretaceous clay is likely between 0 75 and 1 9 myr the 36cl measurements further suggested that the dissolved cl in the till was not directly derived from the underlying cretaceous clay finally it was not possible to quantify the effects of isotopic fractionation of 37cl relative to 35cl because of diffusion in this aquitard system

application of inverse methods to contaminant source identification from aquitard diffusion profiles at dover afb delaware this paper presents a refinement and expansion of our previously described efforts to estimate contaminant plume history from observed contaminant concentrations within a low permeability aquitard at the site of a field scale groundwater remediation experiment at dover air force base at this site a two layer aquitard has been contaminated with tetrachloroethene and trichloroethene through diffusive mass transfer from an overlying contaminated aquifer measurements of contaminant concentrations in the aquitard are used together with independently obtained information about the sorption and diffusion properties of the aquitard medium to estimate the timewise variation of the boundary concentration at the interface between the aquitard and aquifer thus providing evidence related to the overlying plume history in our refined analysis we assume the contaminant source history to be a function of time with unknown form and we supplement our interpretations with a second coring result at a different location the results demonstrate how forensic interpretations of this kind can provide useful and important information regarding the contaminant release history at sites of groundwater contamination and cleanup however the results also show that the forensic problem is a highly nonunique problem associated with potentially large uncertainty interpretation of the estimated results therefore requires careful consideration in the context of other available information

advection and diffusion in a variable salinity confining layer a numerical model that simulates groundwater flow and solute transport for cases in which fluid properties are variable was applied in one dimension vertical to the shallow low permeability clayey confining layer in donana national park in southwestern spain the salinity in the 80 m thick confining layer decreases from a brine near the land surface to fresh water near its base results of model simulations indicate that the system could be in or close to a steady state condition the model calibration was very sensitive to small variations in individual model parameters and was nonunique in the sense that equally good calibrations could be achieved by compensatory joint perturbations in the permeability diffusion coefficient and overall governing hydraulic gradient at present there is probably an upward flow of the order of 1 mm yr 1 to 1 cm yr 1 and a balance in the solute flux between upward advection and downward diffusion the time scale of calculated responses to changes in boundary conditions in this low permeability system ranges from thousands to hundreds of thousands of years when considering extremes within the range of uncertainty of values of the evaluated parameters

distribution of the rare earth elements in porewaters from a clay rich aquitard sequence saskatchewan canada a 91 4 m thick porewater profile of the rare earth elements rees is presented from a thick clay rich pleistocene till 0 80 m and cretaceous clay 80 156 m aquitard sequence saskatchewan canada the upper 3 4 m of till is weathered absolute aqueous concentrations of the rees vary by more than one order of magnitude aqueous ree concentrations decrease with depth through the weathered till to a depth of about 15 m below ground below which the concentrations in the unweathered till remain relatively consistent the only porewater sample from the clay 91 4 m has the highest total ree concentration elevated ree concentrations in the oxidized zone attributed to geochemical weathering there is no significant seasonal variation in aqueous ree concentrations within the water columns in the piezometers redox conditions and solution complexation reactions exert predominant controls on the aqueous ree concentrations the majority of ree patterns are coherent characterized by overall negatively fractionated ree with convex down profiles from la to pr or nd and convex up from nd to tb in the porewater sample from the clay the lrees are an exception with a flat normalized profile hree lree fractionations in the porewaters are depth dependent and are mainly controlled by solution complexation with dissolved sulfate phosphate free carbonate ions and doc porewaters in the unweathered till 5 76 2 m are characterized by negative ce anomalies which may reflect in part negative ce anomalies in the host till geochemistry the negative ce anomalies are magnified relative to the host tills during water rock interaction and ree transportation porewaters from the weathered till exhibit strong positive ce anomalies relative to paas the host rocks and their leachates the ce anomalies are predominantly controlled by the redox conditions and solution complexation the large positive ce anomalies in these porewaters are probably caused by the oxidation of ce iii to ce iv that was stabilized in solution through complexation with high contents of inorganic and organic ligands positive eu anomalies relative to paas the host rocks and leachates of the host rocks result from hydrolysis of plagioclase feldspar the limited depth profile for total dissolved rees across the weathered unweathered till boundary is retarded with respect to that previously established for na k mg2 so42 and tds suggesting that chemical reactions control the migration of dissolved rees

observations of daytime f2 layer stratification under the southern crest of the equatorial ionization anomaly region 1 ionospheric vertical sounding observations are being carried out at sao jose dos campos 23 2 s 45 9 w dip latitude 17 6 s brazil under the southern crest of the equatorial ionization anomaly eia since august 2000 in this paper we present and discuss the observations of daytime f2 layer stratification near the crest of eia for the first time under magnetically quiet high solar activity conditions three examples and a year of statistics are presented the f2 layer stratification and f3 layer were observed between 10 40 and 11 45 ut on 31 december 2000 between 13 30 and 14 30 ut on 1 january 2001 and between 13 15 and 15 15 ut on 11 february 2001 the statistics during september 2000 to august 2001 shows that the f3 layer occurs only for 66 days 18 occurrence and it occurs only during september february spring summer with maximum occurrence in september october and longest duration in february the f2 layer stratification seems to be associated with gravity waves gws which have periods of about 30 60 min downward phase velocities of about 60 140 m s and vertical wavelengths of about 200 500 km the presence of powerful gravity waves in a vertically extended f layer seems to stratify the f2 layer and produce the f3 layer because the stratifications are observed during geomagnetically quiet periods the source of the gravity waves are most likely to be associated with local tropospheric disturbances and not with high latitude disturbances

a plate tectonic scenario for the iapetus and rheic oceans abstract the tectonics dynamics and biogeographic landscape of the early paleozoic were dominated by the opening and expansion of one large ocean the rheic and the diminution to terminal closure of another iapetus an understanding of the evolution of these oceans is thus central to an understanding of the early paleozoic but their chronicle also presents a rich temporal profile of the wilson cycle illustrating continental scale rifting microcontinent formation ocean basin development arc accretion and continent continent collision nevertheless contemporary paleogeographic models of the iapetus and rheic oceans remain mostly schematic or spatiotemporally disjointed which limits their utility and hinders their testing moreover many of the important kinematic and dynamic aspects of the evolution of these oceans are impossible to unambiguously resolve from a conceptual perspective and the existing models unsurprisingly present a host of contradictory scenarios with the specific aim to resolve some of the uncertainties in the evolution of this early paleozoic domain and a broader aim to instigate the application of quantitative kinematic models to the early paleozoic i present a new plate tectonic model for the iapetus and rheic oceans the model has realistic tectonic plates which include oceanic lithosphere that are defined by explicit and rigorously managed plate boundaries the nature and kinematics of which are derived from geological evidence and plate tectonic principles accompanying the presentation and discussion of the plate model an extensive review of the underlying geological and paleogeographic data is also presented

anisotropic lithosphere under the fennoscandian shield from p receiver functions and sks waveforms of the polenet lapnet array abstract seismic azimuthal anisotropy is the key evidence of the past and present strains in the upper mantle the standard analysis of shear wave splitting with the sks techniques is useful in mapping lateral variations but it is insensitive to depth of anisotropy and to variations of anisotropy with depth to retrieve the depth localized anisotropy under the fennoscandian shield we inverted p wave receiver functions of the polenet lapnet array in northern finland jointly with sks recordings shear wave anisotropy of 2 5 with the fast direction of 40 60 in a depth range from the moho to 110 km is a robust result of the inversion the obtained direction is nearly normal to the azimuth of the maximum horizontal compressional stress in the lithosphere but a recent origin of this anisotropy is in doubt this anisotropy may be frozen since the precambrian but it shows no clear relation with the trends of the precambrian tectonics the upper anisotropic layer accounts for 40 of shear wave splitting in sks and to explain the rest another anisotropic layer is required the top of the second layer with a practically similar fast direction is found at a depth of 200 240 km this direction is close to the current apm direction of the lithosphere with implication that the inferred anisotropy may be related with the current plate motion and the anisotropic layer belongs to the asthenosphere the bottom of this layer is uncertain but it is at least 320 km deep in a depth range from 160 km to 200 240 km the fast anisotropy direction is 110 150 origin of this direction is unclear

chloride bromide δ11b systematics of a thick clay rich aquitard system boron cl and br concentrations and boron isotopic compositions 11b were used to provide insight into the sources and water sediment interactions of fossil water in a thick nonfractured aquitard system in saskatchewan canada the aquitard system consists of 80 m of late pleistocene clay rich till disconformably overlying 77 m of late cretaceous marine clay the clay is underlain by a regional sand aquifer variations in cl and br confirmed the presence of well defined conservative mixing relationships between four types of fluids present in the aquitard system 1 low cl water from the base of the fractured and oxidized till zone at 4 m depth 2 water characterized by an elevated cl peak 190 mg l at about 12 m 3 glacial meltwater present between 20 and 60 m depth and 4 more saline water cl up to 1000 mg l from the underlying cretaceous clay and sand aquifer glacial meltwater has low cl 11b 20 and cl br ratios 50 the low cl br ratio of the glacial meltwater is similar to that of modern inland precipitation which suggests that the br budget in the atmosphere 20 30 ka b p was similar to that of today and that br enrichment in the atmosphere may be a natural process the relatively low cl br ratio 150 and 11b values of the saline water in the sand aquifer 35 and 39 respectively and pore water in the cretaceous clay 25 6 and 32 6 respectively are not consistent with simple dilution of seawater but suggest dilution and modification of fifteenfold evaporated seawater with a low cl br and a high 11b value 39 this evaporitic seawater may have been entrapped in the cretaceous clay upon or after its deposition and subsequently flushed from the clay by fresher water we suggest that the refreshening process modified the original brine into na hco3 water type and extracted boron with 11b 39 from the adsorbed sites in contrast increase of cl in the upper section of the till the 12 m peak resulted in apparent depletion of dissolved boron and relative 11b enrichment which can be explained by adsorption processes the b 11b relationships can thus be used to trace water clay interactions in aquitard systems

origin age and movement of pore water in argillaceous quaternary deposits at four sites in southwestern ontario hydrogeologic information in the form of textural properties field and laboratory determined hydraulic conductivity values vertical hydraulic gradients from piezometer nests and major ion and isotopic contents 18o 2h 3h 13c 14c was obtained from four sites located in southwestern ontario on thick deposits of clayey till and glaciolacustrine clay at each site the piezometers were installed from the water table zone situated 1 4 m below the surface to a maximum depth between 20 and 35 m below the surface values of hydraulic conductivity determined in the laboratory by consolidometer and triaxial methods are in the order of 10 8 10 7 cm s and are similar to values calculated from rates of water level rise in piezometers mean values of average vertical groundwater velocity calculated with the measured values of hydraulic conductivity porosity and hydraulic gradient using the darcy equation for a saturated non fractured porous medium range from 0 13 to 0 26 cm yr tritiated pore waters only occur within 3 6 m of ground surface thereby indicating that groundwaters below this depth recharged prior to at least 1952 18o in the pore waters exhibit a distinctive regular shift with depth from water table values of 9 to 10 smow characteristic of present day precipitation to values between 14 and 17 at depths of 20 40 m which are characteristic of much cooler waters corrected 14c ages of the groundwater are greater than 8000 yr b p thereby suggesting that the groundwaters at depth entered these deposits during or after the formation of these deposits approximately 11 000 to 14 000 yr ago 18o 2h and cl concentration profiles were simulated with a one dimensional model for transport by advection and diffusion in a saturated porous medium reasonable agreement between the model and the field profiles was obtained with values of effective diffusion coefficients of 3 0 10 6 cm2 s for 18o 2h and cl and with groundwater velocities between 0 03 to 0 05 cm yr based on these results it is concluded that the pore water in these deposits is a mixture of late pleistocene and modern waters and that the distribution of 18c 2h and cl in these deposits is influenced predominantly by molecular diffusion apparently more so than by hydraulic flow

distribution of arsenic iii arsenic v and total inorganic arsenic in porewaters from a thick till and clay rich aquitard sequence saskatchewan canada abstract inorganic arsenic species were measured in the porewaters collected from eighteen piezometers installed between 3 and 91 4 m below ground in a thick till and clay rich aquitard sequence located in southern saskatchewan to investigate the distribution of and controls on arsenic speciation in the sequence aqueous concentrations of as v as iii and total as are in the range of 0 31 97 0 71 21 and 3 2 98 ppb respectively profiles of as iii and as v concentration distribution with depth broadly track that of total as erratic increases to 15 2 m then more uniform concentrations to 88 m aqueous arsenic is accumulated at the upper redox transition zone 6 14 m the alkaline porewater at 91 4 m contains the highest concentrations of as v and total as which might result from the facilitated desorption of arsenate from the host solid due to decrease of positive surface charge of the oxides in alkaline solution the ratio of as v as iii is greater than unity in the uppermost oxidized porewater 3 m less than unity from 4 6 to 71 6 m and greater than unity in the lowest four porewaters 76 2 to 91 4 m in the 3 m porewater low as iii but high as v as iii is due to the oxidized nature of the near surface weathered till the high as v as iii in the deepest porewater at 91 4 m likely results from the enhanced and heterogeneous oxidation of as iii to as v on clay mineral surfaces in the alkaline solution total as and arsenic speciation may not be controlled by as fe or mn concentrations in the host till or clay dissolved as v and total as positively covary with aqueous chloride whereas dissolved as iii is independent of aqueous chloride aqueous as iii and to a less extent as v and total as are positively correlated with dissolved mn in the till in the clay aqueous as v and total as show strong negative covariation with mn however aqueous as iii as v and total as exhibit almost no correlation with total dissolved fe in the till the as v as iii ratio has strong negative correlation with dissolved mn but positive covaration with dissolved chloride generally good agreement between the redox potentials eh calculated from aqueous as v and as iii concentrations and those measured by a pt electrode throughout most of the unoxidized till suggests the suitability of using as v as iii redox couple as a redox indicator for the studied aquitard system however large negative bias of the calculated eh from the measured eh in the oxidized till upper unoxidized till and the clay is attributed to errors associated with the field measurements of eh

physical mechanism and statistics of occurrence of an additional layer in the equatorial ionosphere a physical mechanism and the location and latitudinal extent of an additional layer called the f3 layer that exists in the equatorial ionosphere are presented a statistical analysis of the occurrence of the layer recorded at the equatorial station fortaleza 4 s 38 w dip 9 s in brazil is also presented the f3 layer forms during the morning noon period in that equatorial region where the combined effect of the upward e b drift and neutral wind provides a vertically upward plasma drift velocity at altitudes near and above the f2 peak this velocity causes the f2 peak to drift upward and form the f3 layer while the normal f2 layer develops at lower altitudes through the usual photochemical and dynamical effects of the equatorial region the peak electron density of the f3 layer can exceed that of the f2 layer the f3 layer is predicted to be distinct on the summer side of the geomagnetic equator during periods of low solar activity and to become less distinct as the solar activity increases ionograms recorded at fortaleza in 1995 show the existence of an f3 layer on 49 of the days with the occurrence being most frequent 75 and distinct in summer as expected during summer the layer occurs earlier and lasts longer compared to the other seasons on the average the layer occurs at around 0930 lt and lasts for about 3 hours the altitude of the layer is also high in summer with the mean peak virtual height being about 570 km however the critical frequency of the layer f0f3 exceeds that of the f2 layer f0f2 by the largest amounts in winter and equinox f0f3 exceeds f0f2 by a yearly average of about 1 3 mhz

shear wave splitting as a diagnostic of variable anisotropic structure of the upper mantle beneath central fennoscandia abstract we analyze splitting of shear waves recorded during the svekalapko passive seismic experiment in south central finland to study fabrics of the mantle lithosphere of the precambrian region and thus to bring information into a debate on existence of plate tectonics or its forms in the early stage of continent formation geographical variations of the splitting parameters and their distinct dependence on direction of wave propagation through the upper mantle allow us to identify six domains of the central fennoscandian mantle lithosphere including the proterozoic archean transition and to model their fabrics by joint inversion of body wave anisotropic parameters fabrics of the archean mantle lithosphere can be approximated by a peridotite aggregate with lineation a dipping to the ne on the other hand anisotropy of the proterozoic mantle lithosphere is weaker and we model its fabric by the a c foliations dipping to the se we present a 3d self consistent anisotropic model of the proterozoic and archean upper mantle along the sw ne profile in the south central finland boundaries of inter growing wedges of the proterozoic and archean mantle lithospheres explain the longitudinal and shear wave propagation and polarization mantle xenolith ages surface wave tomography and location of the upper mantle reflectors we interpret the six anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro continents assembled

water and solute transfer between a prairie wetland and adjacent uplands 2 chloride cycle the quality of water in lakes and wetlands depends on the exchange of solutes with adjacent uplands in many prairie wetlands the input of water is dominated by snowmelt runoff and the outputis dominated by groundwater flow we use chloride as a tracer to quantify the mass transfer processes associated with surface runoff and groundwater flow between a wetland in saskatchewan canada and the surrounding upland snowmelt runoff transports 4 5 kg yr 1 of chloride from the upland to the wetland most of this chloride infiltrates under the wetland and moves laterally to the upland with shallow groundwater under the upland chloride moves upward in the vadose zone with soil water and accumulates near the surface as water is consumed by evapotranspiration part of this chloride mixes with snowmelt runoff and moves back to the wetland therefore chloride is cycled between the wetland and the upland at an approximate rate of 5 kg yr 1 the chloride cycle occurs within 5 6 m of the ground surface a small amount of chloride escapes from the cycle with the downward flow of groundwater into the deep aquifer the estimated flux of chloride leaving the cycle is 0 1 0 6 kg yr 1 which is of the same order of magnitude as the rate at which the catchment receives atmospheric deposition of chloride because the atmospheric input is reasonably well known over the prairie region the concentration of chloride in groundwater under recharge wetlands can be used to estimate the recharge rate of deep aquifers

atypical nighttime spread f structure observed near the southern crest of the ionospheric equatorial ionization anomaly 1 an atypical nighttime spread f structure is observed on ionograms at or above the f2 trace near the crest of the ionospheric equatorial ionization anomaly eia region this ionospheric atypical spread f phenomenon was observed using two closed spaced 115 km ionospheric soundings stations located in sao jose dos campos 23 21 s 45 97 w and cachoeira paulista 22 70 s 45 01 w brazil in a low latitude station near the southern crest of the eia region during nighttime low solar activity and quiet geomagnetic conditions this structure in the initial phase appears in the ionogram as a faint spread f trace above or at the f2 layer peak height after a few minutes it develops into a strong spread f trace and afterwards it moves to altitudes below the f2 layer peak heights finally the atypical nighttime f layer trace structure may remain for a while between the f layer bottom side and peak height or can move to an altitude above the f layer peak height and then it disappears in order to have a comprehensive view of the ionospheric environment characterizing the phenomenon under study complementary data from six gps station were used to investigate the ionosphere environment conditions during both events the six gps stations used in this study are distributed from near the equatorial region to low latitudes and provide evidence that the atypical nighttime spread f structures are not related with large scale equatorial irregularities plasma bubbles

observations of ionospheric f layer quadruple stratification near equatorial region this paper presents and discusses the occurrence of f layer quadruple stratification stf 1 stf 2 stf 3 and stf 4 during southern hemisphere winter season june july and august 2002 and high solar activity condition which was observed at palmas 10 3 s 48 3 w dip latitude 5 5 s near equatorial region brazilian sector this is the first time that the formation of f layer quadruple stratification stf 1 stf 2 stf 3 and stf 4 has been reported in the south american sector the stf 4 has a short lifetime compared with triple stratification f3 layer and it is antecedent and followed by triple f3 layer stratification

revised global model of thermosphere winds using satellite and ground based observations thermospheric wind data obtained from the atmosphere explorer e and dynamics explorer 2 satellites have been combined with wind data for the lower and upper thermosphere from ground based incoherent scatter radar and fabry perot optical interferometers to generate a revision hwm90 of the hwm87 empirical model and extend its applicability to 100 km comparison of the various data sets with the aid of the model shows in general remarkable agreement particularly at mid and low latitudes the ground based data allow modeling of seasonal diurnal variations which are most distinct at mid latitudes while solar activity variations are now included they are found to be small and not always very clearly delineated by the current data they are most obvious at the higher latitudes the model describes the transition from predominately diurnal variations in the upper thermosphere to semidiurnal variations in the lower thermosphere and a transition from summer to winter flow above 140 km to winter to summer flow below significant altitude gradients in the wind are found to extend to 300 km at some local times and pose complications for interpretation of fabry perot observations

radar and satellite global equatorial f region vertical drift model we present the first global empirical model for the quiet time f region equatorial vertical drifts based on combined incoherent scatter radar observations at jicamarca and ion drift meter observations on board the atmospheric explorer e satellite this analytical model based on products of cubic b splines and with nearly conservative electric fields describes the diurnal and seasonal variations of the equatorial vertical drifts for a continuous range of all longitudes and solar flux values our results indicate that during solar minimum the evening prereversal velocity enhancement exhibits only small longitudinal variations during equinox with amplitudes of about 15 20 m s is observed only in the american sector during december solstice with amplitudes of about 5 10 m s and is absent at all longitudes during june solstice the solar minimum evening reversal times are fairly independent of longitude except during december solstice during solar maximum the evening upward vertical drifts and reversal times exhibit large longitudinal variations particularly during the solstices in this case for a solar flux index of 180 the june solstice evening peak drifts maximize in the pacific region with drift amplitudes of up to 35 m s whereas the december solstice velocities maximize in the american sector with comparable magnitudes the equinoctial peak velocities vary between about 35 and 45 m s the morning reversal times and the daytime drifts exhibit only small variations with the phase of the solar cycle the daytime drifts have largest amplitudes between about 0900 and 1100 lt with typical values of 25 30 m s we also show that our model results are in good agreement with other equatorial ground based observations over india brazil and kwajalein

origin of pore water and salinity in the lacustrine aquitard overlying the regional aquifer of mexico city abstract a series of six ancient connected lakes occupied the broad plain of the closed basin of mexico this study pertains to two of these lakes 18o 2h and chemical patterns in the pore water of the broad aquitard formed from sediment in these lakes indicate that the origin of this paleo lake water was local meteoric water which entered the ancient lakes as runoff and groundwater from springs evaporation of surface water in the former chalco lake caused concentration of dissolved salts and enrichment in the heavy isotopes 18o and 2h during high water periods the south easternmost ancient lake chalco fed partially evaporated water to the closed lake texcoco the lowest of the lakes where further evaporation occurred causing higher concentration of salts and enrichment of heavy isotopes these major ions and stable isotopes follow the evaporation trends characteristic of closed or nearly closed evaporatic basins elsewhere in the world paleo lake evaporation lines in lakes chalco and texcoco originated from the same starting water and developed as a consequence of the topographic position of the former lakes and local climatological conditions a modern evaporation line developed after the drainage of the lakes reflecting evaporation of modern infiltrating meteoric water the presence of brackish pore water in most of the chalco aquitard which has a maximum thickness of 300 m indicates that upward vertical groundwater flow has not been capable of displacing the paleo lake water this suggests that vertical advection was not significant throughout the hundreds of thousands of years of existence of the aquitard sediments one dimensional numerical simulations of the deeper part of the 18o profile representing the thicker part of the aquitard sediments 140 m showed that this profile was developed by molecular diffusion with a small upward advective flux where apparently the chalco aquitard always had enriched brackish water overlying the fresh water aquifer

an empirical model of the occurrence of an additional layer in the ionosphere from the occultation technique preliminary results about 8 year electron density profile edp data from the cosmic formosat 3 satellites radio occultation technique were used to investigate the additional stratification of the f2 the so called f3 layer layer over the equatorial and low latitude ionosphere on a global scale for both the bottomside and topside ionosphere the f3 layer was recognized through the altitude differential profile featured by two maxima existing from the selected edp profile there were 37 000 bottomside and 25 000 topside cases of f3 layer selected out of 1 27 million occultation events at equatorial and low latitude areas during the period of april 2006 to august 2014 the statistical results for the bottomside ionosphere resemble that reported in zhao et al 2011a while in the topside the highest occurrence of f3 layer shows a 3 4 h delay depending on the altitude range of the stratification the magnetic latitude distribution shows different dependence with a tendency to form a single crest toward high altitude also the seasonal variation is weaker in the topside ionosphere compared to the bottomside one especially in the high altitude then we build up an empirical model of the f3 layer occurrence using the bottomside statistics based on empirical orthogonal function eof decomposition as it gets the inherent characters inside the data set and converges quickly the model well grasps the main features of the f3 occurrence e g the f3 occurrence s sensitivity on the magnetic latitude further in order to accommodate the ground observation a corrected factor was introduced as f3 layer is an important phenomenon in the low latitude ionosphere we have made an attempt to describe its feature with a consecutive function although future work needs to be done for an overall expression of this structure

hydrogeology of a thick clay till and cretaceous clay sequence saskatchewan canada clay rich glacial till and cretaceous clay are common throughout the interior plains of north america quantifying groundwater flow through these aquitards has implications for solute transport in aquitards and protection of underlying aquifers groundwater flow through a two tiered aquitard system was investigated using laboratory and field methods at a test site in saskatchewan canada the aquitard system consists of 80 m of uniform plastic clay rich battleford till deposited 12 18 ka bp disconformably overlying 77 m of late cretaceous plastic marine clay snakebite member deposited 70 72 ma bp the upper 3 4 m of till is oxidized and fractured whereas the remainder is unoxidized for the scales investigated results suggested that hydraulic conductivity k is independent of scale for relatively thick till and clay bedrock deposits analysis of slug tests in the unoxidized till and laboratory tests on cores of unoxidized till yielded geometric mean k values of 5 4 10 11 and 2 7 10 11 m s res

numerical analysis of solute migration through fractured clayey deposits into underlying aquifers this study examines the degree to which vertically fractured clayey aquitards protect an underlying aquifer from near surface sources of contamination evidence from field studies indicates that many clayey aquitards previously assumed to be unfractured at depth have vertical fractures that actively transmit groundwater calculated groundwater velocities within these fractures can exceed several meters per day for apertures in the range of those reported to occur in clays if this is the case significant quantities of dissolved contaminants originating in near surface zones may move rapidly downward through the fracture network into underlying aquifers a two dimensional laplace transform galerkin finite element model sudicky and mclaren this issue was used to assess the importance of idealized planar vertical fractures on flow and solute transport through a 15 m thick aquitard and subsequent plume evolution within an underlying aquifer in which groundwater flows horizontally sensitivity analyses indicate that solute transport through the aquitard is strongly affected by downward flow in widely spaced deep fractures with apertures as small as 10 m and that a plume of large lateral extent and significant concentration forms within the underlying aquifer in a few tens of years for apertures of the order of 20 m or much sooner if the apertures are 50 m this finding suggests that small hydraulically active fractures that are very difficult to detect or identify within an otherwise protective clayey barrier may cause rapid and large scale contamination of groundwater beneath the barrier

global characteristics of occurrence of an additional layer in the ionosphere observed by cosmic formosat 3 global observations of electron density profile edp from the cosmic formosat 3 satellites were used to investigate for the first time the additional stratification of the f2 layer over the equatorial ionosphere on a global scale which is called f3 layer the f3 layer in edp was recognized through the altitude differential profile featured by two maxima existing from 220 km to the peak height of the electron density there were similar to 9 400 cases of f3 layer selected out of similar to 448 000 occultation events at low and equatorial areas during the period of april 2006 september 2010 statistical results show that the highest occurrence of f3 layer appears at dip latitude 7 similar to 8 degrees 7 similar to 8 degrees for northern southern hemisphere and is more pronounced during summer months at 10 00 14 00 lt the occurrence also has a clear longitude dependence during boreal summer with relatively higher occurrence at 80 similar to 100 degrees 20 similar to 20 degrees 80 similar to 120 degrees and 160 similar to 170 degrees longitudes that is possibly associated with the wavenumber 3 diurnal tide de3 the results support the principle of the f3 layer proposed by balan et al 1998 which in turn validate the accuracy of the retrieval of the cosmic edp data citation zhao b w wan x yue l liu z ren m he and j liu 2011 global characteristics of occurrence of an additional layer in the ionosphere observed by cosmic formosat 3 geophys res lett 38 l02101 doi 10 1029 2010gl045744

deep seismic expression of an ancient plate boundary in europe seismological results on the structure of the upper mantle below europe reveal a marked contrast in seismic properties between precambrian and younger parts of europe the precambrian craton in eastern europe is characterized by high shear wave velocities which can be explained by low temperatures the transition to low seismic velocities below phanerozoic europe coincides with the crustal boundary zone of the craton and exists to depths of at least 140 kilometers despite the long and complex tectonic history of the plate boundary zone the transition is remarkably sharp which rules out any significant lateral transport of asthenospheric material across the suture zone