palaeohydrogeological insights from natural tracer profiles in aquitard porewater great artesian basin australia 1 the value of using environmental tracer profiles in aquitards to quantify fluid flux and to reveal information about palaeohydrology is largely unknown for parts of the world that were not glaciated during the cenozoic we present deep continuous vertical profiles of aquitard pore water chloride concentration and 2h 18o composition from the western margin of the great artesian basin australia where upward leakage is the dominant groundwater discharge mechanism at the deeper of the two sites studied the cl and 2h profiles exhibit a distinctive s shape which we interpret as a shift in the upper concentration boundary condition over time numerical simulations are used to support an hypothesis that the shallow phreatic aquifer was more saline and more enriched in 2h compared to current conditions prior to 120 ka followed by an extended freshening phase from 120 to 20 ka then a saline phase similar to current conditions for the last 20 ka these timeframes correspond favorably with results of previous studies into the palaeohydrology of nearby playa lake eyre at the shallower site the tracer profiles decrease exponentially with depth we explore several models for the evolution of these profiles and adopt one of long term salt input at ground surface at both sites tracer concentrations for groundwater sampled from the underlying artesian aquifer provide conclusive evidence that recharge occurred within the last 10 20 ka chloride was a more useful tracer than 2h in this study primarily due to lack of recent glaciation in central australia to provide a dynamic 2h tracer signal

isotopic composition of old ground water from lake agassiz implications for late pleistocene climate a uniform oxygen isotope value of 25 per mil was obtained from old ground water at depths of 20 to 30 meters in a thick deposit of clay in the southern part of the glacial lake agassiz basin the lake occupied parts of north dakota and southern manitoba at the end of the last glacial maximum and received water from the ice margin and the interior plains region of canada ground water from thick late pleistocene age clay deposits elsewhere a till in southern saskatchewan and a glaciolacustrine deposit in northern ontario show the same value at similar depths these sites are at about 50 n latitude span a distance of 2000 kilometers and like the lake agassiz sites have a ground water velocity of less than a few millimeters per year the value of 25 per mil is characteristic of meltwater impounded in the southern basin of lake agassiz this value corresponds to an estimated air temperature of 16 c compared with the modern temperature of 0 c for this area

the great extinction that never happened the demise of the dinosaurs considered the concept of a sudden extinction of the dinosaurs consequent upon the impact of some extraterrestrial object is so dramatic that it has taken hold upon the imaginations of many scientists as w

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

evolution of the eastern waddington thrust belt and its relation to the mid cretaceous coast mountains arc western british columbia the eastern waddington thrust belt cuts the eastern margin of the coast mountains mid cretaceous magmatic arc thrust faults carried triassic rocks of the intermontane superterrane early cretaceous volcanic and clastic rocks and volcanic and plutonic rocks of the active arc to the northeast outward from the core of the arc minimum shortening across the thrust belt is estimated as 50 or 40 km synkinematic through postkinematic metamorphism produced an inverted metamorphic gradient with the structurally higher magmatic arc as the likely heat source radiometric thermochronologic and structural data indicate that the thrust belt was active at 84 ma and probably at 87 ma and suggest that the peak of postkinematic metamorphism occurred about 82 84 ma the thrust belt was intruded by postkinematic plutons in latest cretaceous and early tertiary time 68 ma and 58 ma the eastern waddington thrust belt is coeval with or slightly younger than a system of west directed thrusts in the western and southern parts of the coast mountains arc the prominence of these structures suggests that synmagmatic contraction played a major role in development of the arc the distribution and character of syn and postthrusting metamorphism indicate that this contraction rather than localized loading by magma produced the metamorphism

natural and anthropogenic levels of tritium in a canadian arctic ice core agassiz ice cap ellesmere island and comparison with other radionuclides

understanding and modelling dissolved gas transport in the bedrock of three fennoscandian sites summary the origin and transport of dissolved gases in the geosphere is of interest for assessment studies of nuclear waste repositories in this paper we analyse available field measurements of helium methane and hydrogen at three fennoscandian sites forsmark and laxemar in sweden and olkiluoto in finland the field data are interpreted using different analytical models all based on the one dimensional diffusion equation the results of the different models provide estimates about the amount of deep gas flux the in situ production and the groundwater residence time of the considered sites the computed helium fluxes which fall within the lower range of crustal degassing fluxes reported by torgersen 2010 are strictly related with the high tightness of the considered fracture media the very high estimates of groundwater residence time indicate that at the considered depths there are only very few flowing fractures while in the rest of the fractured domain groundwater has been almost motionless during a whole glacial cycle

tectonic history of the eastern edge of the alexander terrane southeast alaska rocks exposed west of the coast plutonic complex in southern southeast alaska form an imbricate thrust belt that overprints the tectonic boundary between two of the largest allochthonous crustal fragments in the north american cordillera the insular and intermontane composite terranes in the alexander terrane insular composite terrane lower paleozoic metavolcanic and metasedimentary rocks descon formation and dioritic plutons are unconformably overlain by lower devonian clastic strata karheen formation these rocks are overlain locally by upper triassic basalt rhyolite and marine clastic strata hyd group upper jurassic and lower cretaceous metavolcanic and metasedimentary strata of the gravina sequence unconformably overlie the alexander terrane the gravina sequence forms a structural package over 15 km thick and records intermittent arc volcanism along the eastern edge of the alexander terrane the gravina sequence is structurally overlain by upper paleozoic and lower mesozoic metamorphosed basaltic strata marble and argillite alava sequence and locally by lower paleozoic supracrustal rocks and orthogneiss kah shakes sequence together these constitute the taku terrane which we correlate with the intermontane composite terrane local unconformity of gravina sequence strata over the alava sequence demonstrates that the gravina sequence overlapped an earlier structural boundary between the intermontane and insular composite terranes the rocks were deformed in the mid cretaceous by west vergent thrusting that was was broadly coeval with arc magmatism deformation involved emplacement of west directed thrust nappes over the structurally intact and relatively unmetamorphosed alexander terrane basement mid cretaceous tonalite granodiorite and quartz diorite intrude rocks of the thrust belt and are locally affected by the deformation mid cretaceous deformation occurred during two episodes that were contemporaneous with the emplacement of large sill like plutons older structures record ductile southwest vergent folding and faulting regional metamorphism and development of axial planar foliation the second generation structures developed during the later stages of southwest directed thrust faulting which juxtaposed rocks of contrasting metamorphic pressures and temperatures structural stratigraphic and geochronologic data indicate that the two phases of regional thrusting in southeast alaska occurred between 113 ma and 89 ma rocks in the western part of the thrust belt were uplifted regionally by 70 ma deformation involved the collapse of a marginal basin s and a magmatic arc and overprinted the older tectonic boundary between the insular composite terrane and the late mesozoic western margin of north america at that time the intermontane composite terrane contractional deformation along the length of the thrust belt was broadly coeval with arc magmatism and thus records intra arc tectonism late paleocene to early eocene igneous activity and extensional deformation subsequently affected the thrust belt

application of 2d resistivity profiling for mapping and interpretation of geology in a till aquitard near luck lake southern saskatchewan canada in southern saskatchewan canada the clay rich till deposits are important as sites for waste disposal and as protective covers on regional aquifers due to their low hydraulic conductivity and great thickness in such case it is very important to fully understand the detailed distribution and the variation of the gravel areas in the glacial cap to study the infiltration speed in the subsoil resistivity measurements in the form of 1d schlumberger sounding and 2d wenner resistivity profiling were carried out in the area north of luck lake southern saskatchewan to map the extent of gravel substratums in the till cap and to investigate the impact of a known fault on the gravel and till in the area these measurements were controlled with depth and single point resistivity information from two boreholes drilled previously the analysis of the 2d inverted sections shows the importance of electrical resistivity techniques for mapping the lateral and vertical heterogeneities in the till deposits which are related to the hydraulic processes controlling groundwater recharge the 2d resistivity imaging sections show the major till units on both sides of the east west fault system the strong resistivity contrast between the upper part of the till 10 23 m and the basal part 150 m allows the mapping of a gravel layer in the lower parts this gravel substratum is better defined and more significant towards the ridge in the northern area due to its greater thickness and higher resistivity the lowland area is characterized by clay rich of glaciolacustrine deposits identified in a borehole and by low resistivities 20 m the resistivity of the cretaceous mudstone bedrock is low typically 10 m no gravel deposits are interpreted to the downside of the fault

magma emplacement in a convergent tectonic orogen southern revillagigedo island southeastern alaska the western metamorphic belt of the british columbia alaska coastal orogen consists of lithostratigraphic units assigned to the taku terrane and the gravina sequence on revillagigedo island and cleveland peninsula in the ketchikan quadrangle of southeastern alaska greenschist and amphibolite grade schists of the western metamorphic belt are intruded by mid cretaceous tonalite and leucotonalite plutons and sills a number of these igneous bodies are spatially associated with northwest trending shear zones developed along thrust faults that formed during the main phase of metamorphism of the schists observations of field relations and structural fabric in the igneous rocks and the country rock schist show the following i along the southern shore of revillagigedo island the moth bay pluton was emplaced along a shear zone magmatic and submagmatic flow foliation in the southern border zone of the pluton parallels foliations in the sheared country rock rocks in the interior of the pluton are general

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

dinosaurs of great britain and the role of the geological society of london in their discovery ornithischia completing our survey of british non avian dinosaurs we here review the ornithischians of britain heterodontosaurids are present in the lower cretaceous lulworth formation of dorset and a few earlier possible records imply a long presence in the region of this clade britain9s thyreophoran record is rich and includes the earliest well represented taxon scelidosaurus as well as middle jurassic stegosaurs and ankylosaurs including a reasonably good cretaceous record of polacanthids and nodosaurids cretaceous stegosaurs are known only from fragmentary remains but the proposal that stegosaurs were present as early as the rhaetian is rejected among british iguanodontian ornithopods the possible dryosaurid callovosaurus is the oldest global record whereas the proposed synonymy of cumnoria with camptosaurus requires confirmation iguanodon has become a taxonomic dumping ground for assorted iguanodontians and is in need of revision most of the british species referred to this genus are almost certainly not closely allied to the neotype species i bernissartensis and require new generic names fragmentary remains suggest the early presence of hadrosaurids in britain the only british record of marginocephalia the wessex formation skull roof named yaverlandia bitholus appears not to belong to this clade but seems to be from a maniraptoran theropod

preconsolidation of tills and intertill clays by glacial loading in southern saskatchewan canada preconsolidation of pre battleford tills and intertill clays resulted in a narrow range of effective pressures 1800 200 kpa at 10 sites along a 1300 km transect across southern saskatchewan these data suggest an almost invariant loading system that is independent of total ice thickness which ranged from 1150 to 2000 m the preconsolidation process apparently took place in a temperate glacier environment the loading system is characterized as a variable thickness of ice related to distance from the glacier terminus a steady hydraulic grade line sustained a potentiometric surface within the subglacial sediments at an elevation consistently 69 76 of the total ice thickness this mechanism maintains small fluctuations in effective stress

transport of the yakutat terrane southern alaska evidence from sediment petrology and detrital zircon fission track and u pb double dating abstract two hypotheses have been offered to account for the transport and accretion history of the yakutat terrane in southern alaska to investigate these two options we deconvolved fission track ft and u pb ages of detrital zircons from stratigraphically coordinated samples collected in the northern robinson mountains into component populations the strata of the yakutat terrane include the middle eocene kulthieth formation the lower oligocene to lower miocene poul creek formation and the miocene pleistocene yakataga formation the kulthieth and poul creek formations record erosion of a simple uniform long lived nonvolcanic source terrain that crystallized from 50 to 220 ma and cooled from 40 to 110 ma miocene cooling episodes recorded in the source to the kulthieth and poul creek formations are likely associated with plutons in the northern coast plutonic complex and the kuiu etoilin belt the upper miocene to pleistocene yakataga formation records erosion of rocks that crystallized from 5

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

geological and anthropogenic controls on the sampling of the terrestrial fossil record a case study from the dinosauria dinosaurs provide excellent opportunities to examine the impact of sampling biases on the palaeodiversity of terrestrial organisms the stratigraphical and geographical ranges of 847 dinosaurian species are analysed for palaeodiversity patterns and compared to several sampling metrics the observed diversity of dinosaurs theropoda sauropodomorpha and ornithischia are positively correlated with sampling at global and regional scales sampling metrics for the same region correlate with each other suggesting that different metrics often capture the same signal regional sampling metrics perform well as explanations for regional diversity patterns but correlations with global diversity are weaker residual diversity estimates indicate that sauropodomorphs diversified during the late triassic but major increases in the diversity of theropods and ornithischians did not occur until the early jurassic diversity increased during the jurassic but many groups underwent extinction during the late jurassic or at the jurassic cretaceous boundary although a recovery occurred during the cretaceous only sauropodomorphs display a long term upward trend the campanian maastrichtian diversity peak is largely a sampling artefact there is little evidence for a gradualistic decrease in diversity prior to the end cretaceous mass extinction except for ornithischians and when such decreases do occur they are small relative to those experienced earlier in dinosaur evolution the geological society of london 2011

helium accumulation in groundwater ii a model for the accumulation of the crustal 4he degassing flux abstract a model of 4 he accumulation in a confined aquifer is presented which includes in situ production and a crustal degassing flux of 4 he into the bottom of a confined aquifer the model is consistent with the measurements of 4 he concentration in the great artesian basin australia torgersen and clarke 1985 and also with the measurements of 4 he concentration in the auob sandstone of namibia heaton 1981 the measured value of the crustal degassing flux of 4 he from these two areas is comparable with the 4 he degassing flux calculated from the atmospheric budget of 4 he wasserburg et al 1963 ozima and podosek 1983 a literature review suggests that a crustal degassing 4 he source may account for the 4 he accumulation in many other groundwater systems it is concluded from the literature review the detailed modelling of 4 he accumulation in gab and the auob sandstone and the atmospheric budget that crustal degassing of 4 he may be a common and widespread phenomena

radiogenic helium in shallow groundwater within a clay till southwestern ontario 1 profiles of 4he in pore water were measured in clay aquitards in sw ontario the 4he distributions are consistent with groundwater velocities that are 70 of initial 4he for 50 to 60 ka prior to incorporation into the till

helium diffusivity and fluxes from a sedimentary basin permo carboniferous trough northern switzerland abstract abundances of radiogenic he and ar isotopes observed in ground waters of the permian carboniferous terrigenous sediments pct in northern switzerland exceed those in the overlaying muschelkalk and underlying crystalline basement aquifers eliminating external sources of these species in this case a comparison of the observed abundances with those in situ generated sheds light on mobility of noble gases generated in the pct detailed studies of the parent element and he isotope concentrations in the pct rocks mineral separates pore and ground waters along with the data on logging and porosity allow he isotope production and redistribution in the pct rock water system to be understood and quantified the pct shales generate most of 3he and 4he and both isotopes are almost completely released from the shales into pore space and migrate either into the aquifers with movable waters and further out of the pct or into gas fluid inclusions of the rock forming minerals quartz and plagioclase here we present a he concentration profile based on i helium measured concentrations in ground water samples from 5 aquifers available within the cross section studied ii helium concentrations in 15 pct pore water samples derived from the he partial pressure in gas fluid inclusions recovered by special extraction saturation experiments in order to estimates the rates of he migration through the pct we compare the produced and observed abundances within the frame of 1d diffusion model only two parameters the diffusion coefficient for the whole sequence dall 4 1 10 3 m2 year 1 and the rate of he removal from the crystalline aquifers cr 1 4 10 6 year 1 are required to obtained a good agreement between the observed and calculated he concentrations in pct waters the minimal square deviations are 2 to 3 10 8 mol cm 3 h2o comparable with the accuracy of measurements the following parameters were derived from the modeling the reduction factor dall d0 0 013 the he diffusion fluxes into the overlaying muschelkalk and underlying crystalline aquifers fmu 1 4 10 7 mol m 2 year 1 and fcr 0 24 10 7 mol m 2 year 1 respectively from these values we calculated the mean helium residence times in pct 120 ma and in muschelkalk aquifer 6 ka the relationships between he diffusivities of the pct and the underlying crystalline basement are discussed we further compare our results with other estimates of he mobility in low permeable sediments

a new ankylosaur dinosauria ankylosauria from the lower cretaceous cloverly formation of central montana a cranium and other associated skeletal elements representing a new ankylosaurid dinosaur tatankacephalus cooneyorum gen et sp nov possess several diagnostic features that indicate that this new taxon differs from the only other known ankylosaur from the cloverly formation sauropelta edwardsorum these features include a frontoparietal dome an enlarged nuchal ridge that obscures the occipital region a circular orbit ventral curvature in the posterolaterally directed paroccipital processes a posteroventrally directed foramen magnum and a number of features on the braincase the phylogenetic analysis positions tatankacephalus with ankylosauridae based on its sharing of several characters with other members of this clade including an enlarged nuchal segment that obscures the occiput in dorsal view a ventrally curving lateral profile of the cranium anterior to the orbit pyramidal postorbital boss laterally projecting pyramidal quadratojugal boss the presence of a postocular shelf the presence

geochemical and isotopic evidence for a genetic link between canadian shield brines dolomitization in the western canada sedimentary basin and devonian calcium chloridic seawater hypersaline brines of marine origin deep within fractured crystalline rocks of the canadian shield are characterized by calcium chloride compositions with relatively low concentrations of magnesi

a new ankylosaurid dinosauria ankylosauria from the lower cretaceous of china with comments on ankylosaurian relationships amongst the fossil material collected by the sino soviet expeditions 1959 1960 to the alshan desert china was a large virtually complete ankylosaur skeleton gobisaurus domoculus gen et sp n

magmatism and deformation southern revillagigedo island southeastern alaska the mid cretaceous cale alkaline lree enriched plutons on southern revillagigedo island southeastern alaska form two distinct groups 1 biotite epidote hornblende tonalite of the moth bay pluton and 2 biotite bearing hornblende absent leucotonalite higher total ree and lower na 2 o al 2 o 3 and sr distinguish the moth bay tonalite from the leucotonalite the plutons are surrounded by narrow contact metamorphic aureoles containing kyanite and staurolite pressure estimates for emplacement based on metamorphic conditions of contact rocks and from igneous amphibole compositions are 8 9 kbar detailed analyses of pluton host rock relationships indicate that pluton emplacement was synchronous with orogen deformation pre emplacement thrusting placed the metavolcanic and metasedimentary rocks of the taku terrane structurally above the younger metasedimentary rocks of the gravina belt the contact between these units was subsequently cut by the moth bay pluton the southern margin of the moth bay pluton has been transformed to blastomylonite contact metamorphic textures and undeformed dikes which cut the blastomylonite indicate that shearing did not outlast crystallization of the pluton a still later phase of deformation transposed the pluton related structures and generated a northeast dipping ductile thrust fault southern revillagigedo shear zone along the southern shore of revillagigedo island the shear zone and earlier structures all trend approximately northwest fission track age determinations and track length measurements in apatite were used to determine the cooling histories of the plutonic units fission track ages from the western part of the study area are 51 3 4 0 ma apatite 57 8 4 4 ma zircon and 69 8 4 2 ma sphene eastward toward the coast batholith fission track ages are 10 m y younger these younger ages may result from a tectonic thermal event associated with batholith emplacement this same event may have generated north trending structures that overprint older northwest trending structures on the east side of the study area

105 million years of igneous activity wrangell alaska to prince rupert british columbia the coast mountains orogen which lies along coastal british columbia and southeastern alaska records extensive mesozoic and cenozoic igneous activity here we focus on the two youngest periods 105 50 ma and 30 ma present the history of subduction orogen uplift and finally extension associated with this magmatic activity can be related to plate motion since the mid cretaceous the 105 50 ma period is related to terrane accretion and subduction the northwest southeast trending coast shear zone divides the resulting coast mountains calc alkaline continental margin batholith into a western 105 90 ma and an eastern 80 50 ma arc melting of hydrous mantle overlying a dehydrating slab generated the plutons of the western arc the plutons of the eastern arc show a wider range of compositions their origin consists of mantle melts modified by melts from lower crustal rocks of continental affinity and possibly amphibolitic hydrated basalt in both parts of the arc igneous bodies also resulted from crustal melting these are very abundant in the eastern arc during the younger period bi modal igneous suites consisting of mantle derived mafic magmas and coeval crustal melts are associated with crustal extension and block faulting

hylaeosaurus polacanthus and the systematics and stratigraphy of wealden armoured dinosaurs two genera of armoured dinosaurs ankylosauria are present in the lower cretaceous wealden beds of england polacanthus owencan be distinguished from hylaeosaurus mantell on the basis of significant differences in the pectoral girdle hindlimb and dermal armour a comprehensive review of the dinosaurs from the wealden series of england and contemporary basins of western europe adds further evidence of a biologicalseparation between lower wealden hastings beds containing hylaeosaurusarmatus and upper wealden faunas wealden group of the isle of wight containing polacanthus foxii and nearly equivalent units in belgium france germany and spain

north africa s first stegosaur implications for gondwanan thyreophoran dinosaur diversity abstract eurypoda the major radiation of armoured dinosaurs comprises the ankylosaurs and their sister group the stegosaurs as the earliest branching major clade of ornithischian dinosaurs the evolutionary history of eurypoda is significant for understanding both the palaeobiology of bird hipped dinosaurs and the composition of middle mesozoic ecosystems eurypodans were diverse and abundant throughout the late jurassic and cretaceous in laurasia in contrast their remains are extremely rare in gondwana herein we describe a new genus and species of stegosaur from the middle jurassic of morocco adratiklit boulahfa adratiklit is the first eurypodan from north africa and the oldest definitive stegosaur from anywhere in the world the genus is more closely related to the european stegosaurs dacentrurus and miragaia than it is to the southern african taxa kentrosaurus and paranthodon statistically significant correlations between the number of dinosaur bearing formations dinosaur bearing collections and eurypodan occurrences in gondwana indicates that their fossil record is biased by both geological and anthropogenic factors tantalizing but fragmentary remains and trackways suggest that eurypodan diversity in gondwana may have been as rich as that of laurasia and the prospects for future discoveries of new genera across gondwana are therefore very good

skull of a jurassic ankylosaur dinosauria the origin and early evolution of many major dinosaur groups are poorly known because specimens are rare one of these groups the ankylosauria or armour plated dinosaurs is best known from well preserved specimens from the upper cretaceous period of asia and north america here we describe a well preserved skull of an earlier late jurassic ankylosaur which will be important in clarifying the early history of this group the specimen gargoyleosaurus parkpini gen et sp nov was collected from the upper jurassic morrison formation of wyoming usa despite its geological age the skull shows features seen in late cretaceous ankylosaurs including fusion of bone armour to the surface of the skull and mandible and closure of two skull openings the antorbital and upper temporal fenestrae the new taxon also has characters common to the two ankylosaur families the ankylosauridae and nodosauridae1 2 3 4 supporting the proposal that the ankylosauria originated from a single ancestor2 3 4 nevertheless specialized characters place gargoyleosaurus as the most primitive or basal member of the ankylosauridae

structural and geochronologic relations along the western flank of the coast mountains batholith stikine river to cape fanshaw central southeastern alaska abstract geologic and u pb geochronologic studies in central southeastern alaska provide constraints on the mid cretaceous to mid tertiary deformation west of the coast mountains batholith the ne dipping sumdum and fanshaw faults record the w directed emplacement of the ruth assemblage yukon tanana terrane and taku terrane over the subjacent gravina belt and alexander terrane ductile fabrics of the sumdum fanshaw fault system truncate early formed foliation and thrust faults in albian and older gravina belt strata u pb age data from syn and post tectonic plutons suggest that deformation was ongoing at 92 9 3 0 ma but had mostly ceased by 90 ma the sumdum fanshaw fault system marks the tectonic boundary between the alexander wrangellia terrane and inboard yukon tanana and stikine terranes and lies within a thrust belt that extends from southern alaska to northern washington mid cretaceous structures are truncated to the east by ne dipping ductile fabrics of the coast shear zone sheet like paleocene tonalites were emplaced into and deformed within the shear zone undeformed mid eocene dikes cross cut the tonalites kinematic relations in the coast shear zone suggest a complex displacement history that includes both east side up reverse and west side up normal shear the shear zone probably accommodated the collapse of overthickened crust developed during mid cretaceous shortening

radioelements radiogenic helium and age relationships for groundwaters from the granites at stripa sweden abstract the solution of radioelements and radiogenic 4he by groundwaters in fractured rocks is dependent upon the radioelement distribution in the rock matrix and the extent of the rock water interface the 234 u 238 u activity ratio and the dissolved u rn and he contents of such groundwaters respond to changes in the flow regime with time although 234 u 238 u activity ratios change with groundwater residence time as a consequence of 234th recoil induced solution of 234u the activity ratio is strongly influenced by the u distribution within fractures by the extent of the rock water interface and by the amount of 238u in solution a model for the quantitative evaluation of these effects is presented groundwaters from depths up to 880 m in the stripa granite have variable dissolved uranium contents and 234 u 238 u activity ratios the uranium geochemistry is primarily determined by variations in flow path rather than by groundwater age dissolved radiogenic 4he in the groundwaters increases with their depth of origin and is dependent upon the u content of the granite and upon its fracture porosity it increases with groundwater residence time but movement of 4he by diffusion and transport processes make the actual groundwater age indeterminate

helium concentrations and isotope compositions in 10 km deep groundwaters abstract helium isotopes are useful for tracing terrestrial water movement and calculating residence times which have important implications for radioactive waste disposal and carbon capture and storage projects helium concentrations are generally measured directly in water samples however this is not always possible in this scenario the he concentration equilibrium between pore waters and he accessible volumes e g fluid inclusions hereafter hav in minerals e g quartz can be utilized to determine he concentrations in this study the he partial pressure was measured in havs of quartz grains collected from cores of the kola super deep borehole ksdb using isothermal he extraction saturation experiments a large fraction of he was released from these samples during the first interval of isothermal heating indicating a destruction of the unstable havs likely due to decrepitation of fluid inclusions we present a new approach to calculate he partial pressures using only the he fraction released from the stable havs this approach gives a he partial pressure phe of 1 5 atm at depths of 10 km when combined with solubility data this value suggests a high he concentration in the deep pore waters nearby the ksdb 1 3 10 6 mol cc h2o 1 indicating a long residence time of he atoms in a deep water mineral system close to the age of the regional metamorphism 1700 ma the 3he 4he in the deep ksdb quartz samples and the pore waters are 3 10 8 typical of radiogenic he generated in 10 km deep archean rocks of the ksdb importantly external fluxes are not needed to explain he isotope abundances in rocks minerals and pore waters at these depths

dating very old pore waters in impermeable rocks by noble gas isotopes the sup 4 he sup 40 ar and sup 136 xe content dissolved in the pore water of sedimentary rock samples was measured on samples from borehole cores near the repository for nuclear waste in morsleben germany due to the very low permeabilities of the rock formations conventional groundwater sampling was almost impossible hence the authors developed a new sampling method for noble gases in the pore water of freshly drilled rock cores this method provides vertical noble gas profiles in high depth resolution even in impermeable rocks by application of the new technique quantitative age information of groundwater and pore water have been derived the authors find palaeowaters from the last glaciation depleted in delta d and delta sup 18 o with a sup 4 he age of about 55 kyr the high saline pore solutions below are at least 6 mio years old this has been concluded from the profiles of radiogenic sup 4 he and sup 40 ar close to diffusion in steady state and from xenon isotopes produced by spontaneous fission of sup 238 u in the rocks a sup 4 he flux of 2 center dot 10 sup minus 7 cc stp cm sup 2 yr is derived from the profile which is due to local sup 4 he production within the investigatedmore sediments less

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

canadian shield brine from the con mine yellowknife nt canada noble gas evidence for an evaporated palaeozoic seawater origin mixed with glacial meltwater and holocene recharge abstract dissolved noble gas concentrations were measured in high salinity 270 g l ca na cl groundwaters from the con mine yellowknife canada in an effort to discriminate between two possible origins as either a brine generated by evaporative enrichment in a paleozoic inland sea or marine water concentrated by freezing during glacial times major ion and isotope geochemistry indicate that brines from the deepest level remain relatively undisturbed by mixing with modern water introduced by mining mixing calculations are used to quantify fractions of brine glacial meltwater and modern water from this noble gas concentrations were corrected for excess air with ne and normalized to 100 brine solution over pressuring of helium and argon in the brine provide age constraints based on the accumulation of geogenic 4he and 40ar radiogenic age calculations together with the local geological history suggest brine emplacement during early palaeozoic time likely during the devonian when evaporitic inland seas existed in this region the concentrations of the atmospherically derived noble gases in the brine fraction kr 1 4e 8 xe 8 5e 10 cc stp cc h 2 o are close to atmospheric equilibrium for brine at 25 c kr 7 3e 9 xe 8 0e 10 cc stp cc h 2 o but are far lower than would be expected for closed system concentration of seawater by freezing kr 2 8e 6 xe 4 2e 7 cc stp cc h 2 o thus despite the complicated mixing history of the brine the atmospheric and geogenic noble gases provide strong evidence for an origin as air equilibrated brine from evaporated paleozoic seawater which infiltrated via density displacement through existing fractures and faults into the canadian shield

mid cretaceous transtension in the canadian cordillera evidence from the rocky ridge volcanics of the skeena group the age relations geochemistry and sedimentology of the rocky ridge formation of the skeena group are used to test competing tectonic reconstructions for the mid cretaceous canadian cordillera as well as the timing and location of the accretion of the insular superterrane pollen and macrofossil assemblages indicate that these intrabasinal basalts were erupted along the southern margin of the bowser basin in the early albian to early cenomanian single crystal fusion and step heating 40ar 39ar dating of hornblendes in one basalt flow from the uppermost part of the formation yielded middle cenomanian ages of 94 3 0 4 95 6 1 6 and 95 0 1 6 ma vesicular basalt flows interbedded with crystal rich tuff breccias contain evidence for hot emplacement as pyroclastic flows individual eruptive centers are identified by their proximal facies paleoflow indicators within the lava flows paleoflow indicators within interbedded volcaniclastic fluvial deposits geochemical differences and geographic isolation of volcanic deposits major and trace element geochemistry from 20 sampled lava flows indicates an alkali basalt composition for the volcanics the basalts of the northern rocky ridge volcanic center show enrichment of light rare earth and large ion lithophile elements with strong negative nb ta anomalies whereas the basalts of the southern tahtsa lake volcanic center show depletion to slight enrichment of light rare earth elements slight enrichment of large ion lithophile elements with minimal negative nb ta anomalies the geochemistry combined with paleogeographic and regional tectonic reconstruction suggests a continental arc setting with intraarc extension the presence of deeper marine facies to the west and the lack of a western sediment source in the skeena group indicate that the technically active insular superterrane was not west of the study area during mid cretaceous time thus we reconsider the omineca belt as the main axis of a mid cretaceous continental arc placing the intermontane superterrane in the intraarc to forearc position with the rocky ridge volcanics erupted along the forearc side of the omineca arc coeval regional strike slip faulting and reconstructed oblique plate convergence suggest a transtensional setting for rocky ridge intraarc extension an electronic supplement of tables a1 a2 may be obtained on a diskette or anonymous ftp from kosmos agu org login to agu s ftp account using anonymous as the username and guest as the password go to the right directory by typing cd apend type ls to see what files are available type get and the name of the file to get it finally type exit to leave the system paper 95tc03496 mid cretaceous transtension in the canadian cordillera evidence from the rocky ridge volcanics of the skeena group kari n bassett and karen l kleinspehn diskette may be ordered from american geophysical union 2000 florida avenue n w washington dc 20009 15 00 payment must accompany order

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

geochemical evidence for efficient aquifer isolation over geological timeframes aquitards layers of rock having low permeability have been suggested as potential long term reservoirs for toxic materials such as nuclear or chemical waste but information about the isolation properties of aquitard layers is essential to evaluate whether they can indeed be used safely as reservoirs here we investigate the long term mobility of groundwaters between two aquifers surrounding an aquitard layer in the eastern recharge area of the paris basin france using helium isotopes as a geochemical tracer the deeper trias sandstone aquifer which lies above the crystalline basement accumulates radiogenic 4he and primordial 3he from large regions of the crust and mantle at rates comparable to the degassing of the whole crust1 and of mid ocean ridges2 we show that the overlying carbonate dogger aquifer which is separated from the trias aquifer by an aquitard layer consisting of a 600 m succession of shales and clays is stagnant and has been extremely well isolated from the trias over the past several million years this finding together with previous studies at the centre of the paris basin3 4 shows that diffusive mass transfer across aquitards is negligible and that cross formational flow in basins takes place preferentially in faulted areas

biostratigraphy and paleoecology of pleistocene deposits riddell member floral formation late rancholabrean saskatoon canada the pleistocene floral formation has been described from across central and southern saskatchewan in the saskatoon area it comprises four distinct lithological units a basal sand overlain by till and an upper sand overlain by till the upper sand here named the riddell member contains the rich vertebrate composite riddell fauna the fossils are sufficiently distinctive to date the riddell member as late rancholabrean this age is considerably younger than the age of the wascana creek ash and indicates that various deposits assigned to the floral formation are not correlative paleoecological analysis indicates that five ecological communities are represented in the composite riddell fauna the largest and most extensive habitat is the dry upland prairie the sympatry of the represented taxa is unusual for central saskatchewan and suggests that a temperate equable climate prevailed paleoenvironmental reconstruction implies that the riddell fauna is not synchronous with the echo lake fauna but may be

testing helium equilibrium between quartz and pore water as a method to determine pore water helium concentrations abstract the effectiveness of carbon capture and geologic storage depends on many factors including and especially the permeability of the reservoir s caprock while caprock integrity is generally assumed if petroleum has been preserved it is poorly constrained in reservoirs containing only saline waters and co2 leakage poses a potential risk to shallow aquifers naturally occurring he accumulates in pore waters over time with the concentration being strongly dependent on the long term flux of fluid through the caprock furthermore a small fraction of pore water he diffuses into quartz and this may be used as a proxy for he concentrations in pore water where dissolved gas samples are difficult to obtain such as in deep sedimentary basins in this paper he contained in quartz grains is measured and compared to previously measured pore water concentrations quartz was purified from core samples from the san juan basin new mexico and the great artesian basin south australia quartz separates were heated at 290 c to release he from the quartz the quartz from the san juan basin and high purity quartz from the spruce pine intrusion north carolina was repeatedly impregnated at varying pressures using pure he heated and analyzed to build he sorption isotherms the isotherms appear linear but vary between samples possibly due to fluid inclusions within the quartz grains as high purity quartz samples partition only 1 5 of he that partitions into san juan basin samples concentrations of he in the pore water were calculated using the he accessible volume of the quartz and the air water he solubility the mean san juan basin he pore water concentration was 2 10 5 cc stp he g water 400 times greater than atmospheric solubility great artesian basin samples contain a mean he concentration of 3 10 6 cc stp he g water or 65 times greater than atmospheric solubility however pore water he concentrations in both the san juan and great artesian basins differ by up to an order of magnitude compared to samples collected with an alternate method the reason for the offset is attributable to either partial saturation of the pore volume or a lack of he equilibrium between quartz and pore water coating of clay or other mineral phases on quartz grains which tends to reduce the effective diffusion coefficient may cause the latter this technique of assessing permeability is promising due to the abundance of existing core samples from numerous basins where carbon sequestration may ultimately occur

tracing deep thermal water circulation systems in the e w trending buyuk menderes graben western turkey abstract we present information on the spatial variation of helium isotope ratios and several conservative geochemical constituents that serve as natural tracers to identify thermal water flow systems along the e w trending buyuk menderes graben the air normalized r r a ratios where r sample 3 he 4 he and r a air 3 he 4 he of geothermal fluids in the graben range from 3 69 to 0 2 r r a ratios of the high temperature fluids display regular variation along the graben from high mantle values in the east to low crustal values in the west the highest r r a ratios showing significant mantle he signatures occur at the eastern segment of the graben in the central section r r a ratios are lower and vary between 1 82 and 1 14 the lowest ratio of 0 20 r a indicating a value of high crustal helium up to 98 was observed in the germencik field where one of the highest temperatures recorded was 232 c at the western segment of the graben a regional variation is also apparent in the co 2 he systematics mantle derived carbon proportions were found to be generally less than 2 but similar to the r r a ratios the higher mantle carbon proportions occur at the eastern segment of the graben the spatial distribution of all the data points over the entire extent of the graben shows a regularly decreasing trend of mantle derived he and co 2 contributions toward the west these results were interpreted as a progressive dilution process of mantle volatiles resulting from the systematic addition of 3 he depleted crustal co 2 components finally because the r r a ratios of geothermal fluids in the graben decrease continuously in e to w direction we propose a continuous dilution process involving the addition of crustal radiogenic 4 he associated with deep circulating fluid flow this conclusion is compatible with the b and cl concentrations of the thermal waters that show a westward increasing trend this trend appears to be controlled by water rock interaction and may be linked to a possible thermal water circulation system trending from e to w toward the aegean sea

natural tracer profiles across argillaceous formations argillaceous formations generally act as aquitards because of their low hydraulic conductivities this property together with the large retention capacity of clays for cationic contaminants has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste in several countries programmes are under way to characterise the detailed transport properties of such formations at depth in this context the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large scale and long term transport behaviour of these formations here tracer profile data obtained by various methods of pore water extraction for nine sites in central europe are compiled data at each site comprise some or all of the conservative tracers anions cl br water isotopes delta 18 o delta 2 h and noble gases mainly he based on a careful evaluation of the palaeo hydrogeological evolution at each site model scenarios are derived for initial and boundary pore water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites using transport parameters derived from laboratory or in situ tests the comprehensive results from this project have been reported in mazurek et al 2009 here the results for three sites are presented in detail but the conclusions are based on model interpretations of the entire data set in essentially all cases the shapes of the profiles can be explained by diffusion acting as the dominant transport process over periods of several thousands to several millions of years and at the length scales of the profiles transport by advection has a negligible influence on the observed profiles at most sites as can be shown by estimating the maximum advection velocities that still give acceptable fits of the model with the data the advantages and disadvantages of different conservative tracers are also assessed the anion cl is well suited as a natural tracer in aquitards because its concentration varies considerably in environmental waters it can easily be measured although the uncertainty regarding the fraction of the pore space that is accessible to anions in clays remains an issue the stable water isotopes are also well suited but they are more difficult to measure and their values generally exhibit a smaller relative range of variation chlorine isotopes delta 37 cl and he are more difficult to interpret because initial and boundary conditions cannot easily be constrained by independent evidence it is also shown that the existence of perturbing events such as the activation of aquifers due to uplift and erosion leading to relatively sharp changes of boundary conditions can be considered as a pre requisite to obtain well interpretable tracer signatures on the other hand gradual changes of boundary conditions are more difficult to parameterise and so may preclude a clear interpretation

helium isotope fluxes and groundwater ages in the dogger aquifer paris basin the dogger aquifer of the paris basin has been shown to be first order homogeneous in its helium concentration and its helium isotopic ratio although slight differences are noted in relation to specific chemical water types the helium isotopic composition of the dogger aquifer contains a small component of mantle helium that is associated with a magmatic input although the heat accompanying this magma is small constraints on the age of the overlying albien aquifer are used to calculate the flux of helium out of the dogger this constraint allows a calculation of the residence time of waters in the dogger aquifer of 4 myr 50 which is significantly longer than estimates derived from hydrologic models and hydrologic testing it is possible that the hydrologic ages and the helium ages can be reconciled by a vertically layered dogger aquifer with gradients in he salinity and fluid flow vertical profiles of fluid composition helium concentration and permeability are required in the paris basin to resolve this question

two phase evolution of accretionary margins examples from the north american cordillera abstract the coast mountains orogen southeastern alaska and the salmon river suture zone western idaho record the accretion of oceanic crustal fragments to the north american cordilleran margin structural elements associated with these boundaries include a western accretion related thrust belt and steeply dipping post accretionary shear zone the shear zones the coast shear zone southeastern alaska and western idaho shear zone idaho are steeply dipping crustal scale structures characterized by steep isotopic and geophysical gradients the presence of syndeformational tabular calc alkaline tonalitic plutons concordant with shear zone fabrics locally preserved dextral strike slip indicators and pervasive down dip mineral and elongation lineations are consistent with an intra arc transpressional origin for both structures in addition to strike slip translation the structures accommodated exhumation of high pressure moderate temperature metamorphic rocks within the thrust belt to the west and moderate pressure high temperature batholithic rocks to the east similarities between the structures in alaska and idaho suggest that the observed two stage history of underthrusting of accreting crustal fragments followed by modification by intra arc transpressional shear zones is a common tectonic process our analysis implies that recognition of processes active during the accretion of crustal fragments to continental or cratonal margins is commonly inhibited by post accretion deformation and provides insight into lower crustal processes presently operative under modern strike slip accretionary boundaries in addition the intra arc transpressional shear zones e g the coast and western idaho shear zones are structures that could have accommodated paleomagnetically determined large magnitude transcurrent displacements

two stage exhumation of midcrustal arc rocks coast mountains british columbia 1 new geologic data from the central gneiss complex along douglas channel help delineate the burial and exhumation of the late cretaceous to eocene coast mountains magmatic arc arc plutonism was on going between 90 and 60 ma replaced by formation of dikes to 52 ma supracrustal rocks were buried to midcrustal levels by 90 ma and garnet and kyanite grew from 90 through 70 ma subsequent exhumation was nearly isothermal and took place in two stages the first occurred from 70 to 59 ma as the arc contracted obliquely and sillimanite replaced kyanite exhumation was slow 0 5 mm yr probably accomplished by erosion aided by coaxial crustal thinning exhumation rates about doubled in the second stage of exhumation after 59 ma and before 52 ma penetrative deformation ended prior to intrusion of the quottoon pluton at 59 ma and 6 5 kbar production of cordierite rims on garnet at 4 5 kbar and 700 c signaled the end of near isothermal decompression prior to 52 ma rapid cooling 100 c 106 years of the central gneiss complex followed cordierite growth temperatures dropped to 250 by 48 ma the increase in exhumation rate and the subsequent rapid cooling are attributed to excision of 6 km of crust on a detachment system on the northeastern side of the central gneiss complex comparison to other parts of the coast mountains arc the sierra nevada and fiordland new zealand shows that the amount and tempo of exhumation vary greatly within and between arcs suggesting that the processes accommodating exhumation vary significantly

a reappraisal of the ornithischian dinosaur amtosaurus magnus kurzanov and tumanova 1978 with comments on the status of a archibaldi averianov 2002 a fragmentary braincase from the baynshirenskaya svita cenomanian turonian of amtgay omnogov people s republic of mongolia was described as the holotype specimen of the ankylosaurid dinosaur amtosaurus magnus kurzanov and tumanova 1978 however the validity of this genus has been questioned by several authors recently a second species based on a fragmentary specimen consisting of a braincase and partial skull roof was assigned to amtosaurus as a archibaldi averianov 2002 here we re assess the status of amtosaurus and of the referred species a archibaldi we conclude that amtosaurus magnus is a nomen dubium that should be regarded as ornithischia indeterminate however a archibaldi is a valid taxon characterized by an autapomorphic feature of the skull roof and we refer this species to the new genus bissektipelta

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

exhumation and tilting of the western metamorphic belt of the coast orogen in southern southeastern alaska the uplift history of the western metamorphic belt in southern southeastern alaska can be traced using emplacement depths and cooling ages of mid cretaceous plutons which intruded the metamorphic belt during the period 101 ma to 89 ma during the period 101 ma to 94 ma the rocks of the metamorphic belt now at the surface were buried to a depth of approximately 30 km pressure data indicate that by 89 ma the western portion of the metamorphic belt was at a shallower crustal level 23 km within the study area while the eastern side remained at a depth of approximately 30 km cooling curves constructed from minerals in mid cretaceous plutonic rocks indicate that the western side of the metamorphic belt cooled earlier than the eastern side an observation consistent with the inferred uplift history southwestward transport of metamorphic belt rocks within the hanging walls of thrust and high angle faults may have provided one mechanism for uplift during mid to late cretaceous time the eastern portion of the western metamorphic belt cooled rapidly at 55 ma probably in response to a period of rapid uplift the coast shear zone an early tertiary high angle fault with west side up displacement bounds the east side of the metamorphic belt we suggest tertiary uplift occurred by tilting of the metamorphic belt due to movement along this fault

batholith emplacement at mid crustal levels and its exhumation within an obliquely convergent margin abstract emplacement of the central part of the coast mountains batholith of northern coastal british columbia occurred within a regime characterized by oblique convergence between the farallon kula and north american plates we use new structural kinematic and u pb isotopic data to show that the locations geometry and mechanisms of pluton emplacement within this batholith were controlled by displacements within a network of normal faults and transtensional shear zones these data also show that the most active period of pluton emplacement from 67 to 51 ma coincided with a change in style of deformation within the batholith prior to 67 ma plutons were emplaced within an arc dominated by regional scale contractional shear zones in contrast emplacement of 67 51 ma plutons occurred in an arc increasingly dominated by normal faults with arc parallel to oblique displacement and by sinistral transtensional shear zones we have identified and mapped the structure of three plutonic complexes composed of 67 to 51 ma plutons the khyex sill complex arden lake plutonic complex and quottoon plutonic complex shear zone controlled emplacement of plutons within the batholith accounts for the widely different orientations and structural features that characterize plutons within these three complexes during and after this latest cretaceous paleogene period of intense plutonic activity and accompanying deformation the deep roots of the batholith were rapidly unroofed by ductile normal faulting prior to 50 ma

using excess 4he to quantify variability in aquitard leakage summary fluid flux through aquitards controls the rate of recharge discharge cross formational fluid flow and contaminant transport in subsurface systems in this paper concentrations of 4 he are used to investigate the spatial distribution of vertical fluid flux through the regionally extensive great artesian basin aquitard system in northern south australia two vertical profiles of 4 he concentration in aquitard pore water augmented with regional sampling of aquifers above and below the aquitard were used to estimate fluid flux at multiple locations over a large spatial area 4 he concentrations in the shallow aquifer above the great artesian basin range from atmospheric equilibrium to 1000 times enriched over atmosphere fluid flux through the aquitard was estimated by fitting observed helium concentrations at each sampling site with a 1 d model of helium transport through the aquitard estimated fluid fluxes through the aquitard vary over three orders of magnitude across the study area in areas of competent aquitard fluid fluxes are less than 0 003 mm yr and mass transport of helium is dominated by molecular diffusion preferential discharge zones are clearly identifiable with fluid fluxes up to 3 mm yr our results show that fluid flux through a regionally extensive aquitard can be highly variable at large spatial scales and that 4 he concentrations in aquifers bounding the aquitard system provide a convenient and sensitive method for investigating aquitard flux at the regional scale

on the first partial skull of an ankylosaurian dinosaur from the lower cretaceous of the isle of wight southern england the specimen is identified as the partial cranium of a nodosaurid ankylosaur ornithischia thyreophora on the basis of the presence of bone which is fused to the dorsal surface of the skull and has secondarily closed the upper temporal fenestrae the only unequivocally nodosaurid material recovered from the isle of wight to date comes from wealden facies and has been referred to the genus polacanthus it is considered highly probable that this new skull is referable to the same genus despite having undergone abrasion through post emergence water rolling the skull and cranial walls have proved to be relatively informative of the general anatomy of the braincase and the neural and vascular anatomy of this part of the head the anatomy of the braincase of most ankylosaurs with the notable exception of the juvenile specimens of the ankylosaurid pinacosaurus is surprisingly poorly known despite the relative abundance of cranial material in north american and asian collections the cranial neural and vascular anatomy is well shown in this specimen and enables the first detailed description of nodosaurid endocranial structures the general form of the brain can be outlined from the structure of the endocast and the principal lobes can be identified the majority of the cranial nerves have been identified and a significant component of the associated vascular system is also visible in most respects the endocast shows a neural anatomy which is common to that known in most dinosaurs when compared to their nearest relatives the ankylosaurid ankylosaurs euoplocephalus the nodosaurid endocranial cast shows a more pronounced cerebral flexure a forebrain which is broader and more expanded dorsally and a more prominent cerebellum although there is no evidence for a floccular lobe there are minor differences in the arrangement of the cranial nerves and the dorsal portions of the vascular system are better shown because of erosion the olfactory lobes of this specimen of cf polacanthus are not preserved and cannot be compared to those of ankylosaurid ankylosaurs the latter are unusual in the strong separation of the lobes reflected in the divergent olfactory stalks this feature may be associated with the very complex passages within the nasal region of the skull which are lacking in the nodosaurids described to date