permeability and fracture patterns in extrusive volcanic rocks implications from the welded santana tuff trans pecos texas the santana tuff of trans pecos texas is a nonwelded to thoroughly welded fractured vitric crystal tuff the unsaturated welded portions of the santana tuff were examined to determine its matrix permeability and fracture patterns more than 1 100 permeability measurements on tuff surfaces were taken with a gas minipermeameter independent variables included the degree of surficial weathering the presence of rock varnish and the orientation of the surface with respect to direction of emplacement and flattening the mean permeabilities for fresh weathered and varnished surfaces were 55 33 md 5 03 md and 3 31 md respectively the fresh surface measurements are significantly different from the other two surface types both of which were from statistically equivalent populations analyses on cut surfaces showed about a 30 decrease in permeability perpendicular to flow direction and flattening this trend was also evident on the varnished and weathered surfaces weathering rinds including the varnish decrease the permeability in thin section the rinds exhibit a thin layer of dark minerals mostly fe oxides sem photographs of the weathered and varnished surfaces show a lamellate texture indicative of coating by smectitic clay particles fracture patterns were examined at six outcrops spanning 9 km a pavement was mapped at one outcrop rose diagrams and stereonets were prepared from more than 300 observations although the composite data show two main orientations of nearly vertical cooling fractures the fracture trends vary considerably even between out crops in proximity to each other field observations indicate that fractures are continuous across individual flow boundaries at the mapped outcrop the fracture density and trace length are fractal between the 0 5 m and 3 m range the fractal dimension of fracture density was 1 44 and the length of the fracture was scale dependent but a fractal dimension of fracture lengths was not able to be determined a lower percentage of abutting fractures was observed here than has been noted in similar studies in nevada this study demonstrates that weathering along fractures reduces fracture matrix interactions in such rocks and that fracture patterns on a regional scale may be difficult to characterize

coupling ground and airborne geophysical data with upscaling techniques for regional groundwater modeling of heterogeneous aquifers case study of a sedimentary aquifer intruded by volcanic dykes in northern ireland in highly heterogeneous aquifer systems conceptualization of regional groundwater flow models frequently results in the generalization or negligence of aquifer heterogeneities both of which may result in erroneous model outputs the calculation of equivalence related to hydrogeological parameters and applied to upscaling provides a means of accounting for measurement scale information but at regional scale in this study the permo triassic lagan valley strategic aquifer in northern ireland is observed to be heterogeneous if not discontinuous due to subvertical trending low permeability tertiary dolerite dykes interpretation of ground and aerial magnetic surveys produces a deterministic solution to dyke locations by measuring relative permeabilities of both the dykes and the sedimentary host rock equivalent directional permeabilities that determine anisotropy calculated as a function of dyke density are obtained this provides parameters for larger scale equivalent blocks which can be directly imported to numerical groundwater flow models different conceptual models with different degrees of upscaling are numerically tested and results compared to regional flow observations simulation results show that the upscaled permeabilities from geophysical data allow one to properly account for the observed spatial variations of groundwater flow without requiring artificial distribution of aquifer properties it is also found that an intermediate degree of upscaling between accounting for mapped field scale dykes and accounting for one regional anisotropy value maximum upscaling provides results the closest to the observations at the regional scale

linked thrust and strike slip faulting during late cretaceous terrane accretion in the san juan thrust system northwest cascades orogen washington the san juan thrust system makes up the western elements of the late cretaceous northwest cascades orogen of washington a stack of metamorphic nappes with terranes ranging in age from early paleozoic to middle cretaceous the tectonic development of the nappes is an unresolved issue important to understanding plate convergent processes operating in the north american cordillera in the creta ceous as well as at other times two terrane bounding fault zones were studied in this project the lopez and the rosario fault zones the fault zone rocks were affected by two cataclastic plastic late cretaceous deformational events d1 and d2 that included accretion and lateral motion during blueschist facies metamorphic conditions d1 produced upright folds and a subvertical axial planar s1 foliation fabric in the lopez fault zone and southwest vergent folds and gently northeast dipping axial planar s1 foliation in the rosario fault zone in the lopez fault zone d2 produced northwest striking and subvertical strike slip shear zones s2 with dominant sinistral displacements whereas in the rosario fault zone d2 generated low angle s2 shear zones and various slip crenulation fabrics formed by northwest directed thrust motion the d1 fabrics are inferred to be related to initiation of subduction related accretion of the nappes by orogen normal southwest northeast shortening and accretionary tectonics the subsequent d2 fabrics developed as temporally overlapping subduction related low angle thrusts in the rosario fault zone and high angle sinistral strike slip faults in the lopez fault zone in an overall transpressive setting due to oblique convergence this model suggests that the high angle lopez fault zone d2 was located above a gently northeast dipping thrust detachment s2 expressed by the rosario fault zone that allowed the accreted nappes to move parallel to the orogen the kinematic model cannot validate regional scale dextral terrane translation of the san juan thrust system as inferred by paleomagnetic data elsewhere in the western united states but addresses important tectonic processes caused by oblique subduction and changing plate conditions

the assessment of ree patterns and 143nd 144nd ratios in fish remains abstract the ree content and isotopic composition of sr and nd have been determined in fish teeth ranging in age from the trias to the present and from various localities mostly around the atlantic these measurements have been carried out on selachian and teleost remains from the same locality in togo and show no appreciable difference which suggests with the help of a mass balance calculation of the ce anomaly that diagenetic effects are not responsible for the ree enrichment of biogenic phosphates one group of fossil teeth has about 3 times the ree abundances of shale and a shale normalized pattern with a minimum at sm it is thought to reflect deposition in the open sea environment a second group has ree concentration about 10 times higher than the first group with either a regular light ree enrichment or more frequently a maximum in the middle ree both being probably indicative of deposition in estuarine or near shore conditions the shape of the ree spectra and the size of the ce anomaly can be used semi quantitatively to determine the depth of deposition the results presented here on late cretaceous eocene fish teeth samples from morocco reflect an increasing influx of deep waters with a lowla yb ratio and strong negative ce anomaly which agrees well with the evolution of sediment chemistry and microfauna associations in contrast nd is typical of the water mass in which the fish debris decayed examples of nearly isolated basins identified with nd isotopes include the south atlantic prior to the lutetian nd 13 5 the miocene persian gulf nd 3 1 and bolivia during the late cretaceous nd 12 8 togo and guinea bissau results suggest that in the south atlantic the meridional oceanic circulation had not started before 45 ma ago combination of ree and nd data suggests that the assignment of jurassic cretaceous samples measured so far to open sea water masses is still ambiguous

lithostratigraphy and deep water setting of the upper nanaimo group upper cretaceous outer gulf islands of southwestern british columbia the upper cretaceous nanaimo group consists of extensive shaly units and lenticular bodies of sandstone and conglomerate deposited in neritic to bathyal marine paleoenvironments single sandstone and conglomerate lenses cannot be traced throughout the basin but instead tend to concentrate at particular stratigraphic levels defining crudely sheet like composite units of coarse grained rocks many of the lenticular coarse grained units rest in major channels as deep as about 550 m sand and gravel were generally transported to the west and northwest by sediment gravity flows through these channels into the basin centre recognition of widespread channeling is critical to the definition of formal lithostratigraphic units four formations and two informal members are defined here for the upper nanaimo group the top of the nanaimo group is probably truncated by a major unconformity with local relief of at least 2 km the effect of the unconformity can only be seen by mapping the orientation of offshore rid

diet preferences and climate inferred from oxygen and carbon isotopes of tooth enamel of tarbosaurus bataar nemegt formation upper cretaceous mongolia abstract stable isotopes of oxygen and carbon of tooth enamel are increasingly being used as tracers to study palaeoecology and the diet preferences of fossil vertebrates we serially sampled tooth enamel carbonate along the growth axes of five early maastrichtian carnivorous dinosaur teeth tarbosaurus bataar tyrannosaurid from the nemegt formation mongolia in order to identify seasonal climatic variations and determine the diet of this apex predator additional bulk samples of dentine bone and surrounding sediment were analyzed in order to exclude diagenetic obfuscation of the isotopic record enamel samples of potential prey species for dietary studies were also analyzed in the case of the largest specimens the sampled teeth usually recorded annual cycles ranging between two thirds and a full year fluctuations in 18o values in tyrannosaurid teeth suggest seasonality high annual temperatures with distinct precipitation humidity maxima during summer months with mean annual temperatures mat ten degrees higher than those of present day mongolia the seasonal pattern of 18o shows similarities to that of the modern day shijiazhuang global network of isotopes in precipitation station northern china and suggests that the nemegt biota flourished when exposed to a cool temperate monsoon influenced climate herbivore and carnivore carbon isotopes 13c values from tooth enamel imply the presence of a woodland ecosystem dominated by coniferous trees such as araucariaceae and are consistent with the hypothesis that large sauropods and hadrosaurids were the preferred prey of tarbosaurus mean annual precipitation map based on the relationship between modern day c3 gymnosperms and local average map is estimated at 775 835 mm yr these results show that large theropod teeth can serve as valuable archives for palaeoenvironmental studies

pseudofaults resulting from compartmentalized liesegang bands update liesegang bands with apparent offset along fractures are common in some calcisiltite beds thin sections show however that primary laminations are not offset along the fractures following the development of fracture sets in the calcisiltite the fractures were cemented by calcite this formed polyhedral compartments of low permeability calcisiltite bounded by impermeable walls of calcite liesegang bands formed when oxygen in ground water diffused into polyhedra containing soluble ferrous iron in pore water each joint bounded polyhedral compartment behaved as an independent diffusion cell liesegang bands with nearly the same pattern and thickness tended to develop in adjacent compartments but not at the same stratigraphic level this resulted in the formation of pseudofaults

development of complex sub vertical layering in the cortaderas gabbro intrusion central chile abstract the cortaderas intrusion is a small gabbroic unit spatially associated with the lower cretaceous felsic illapel plutonic suite of central chile it is unmetamorphosed largely unaltered and not significantly tilted most of the intrusion has well developed vertical to steep layering dominantly defined by variations in abundance in plagioclase and amphibole in some places the layers are regular and rhythmic with a spacing of about 0 5 2 cm but elsewhere layering is more complex with solitary plagioclase rich bands 1 cm wide in some areas layers are convoluted sometimes with channel like structures apparent cross cutting relationships and balloon like structures pegmatoids occur as patches and layers in some places with miarolitic cavities plagioclase and amphibole dominate the mineralogy with minor clinopyroxene as relicts in amphibole and minor olivine chemical and isotopic data from different samples cannot be linked by any single simple process and several different magma sources are necessary we propose that the intrusion is a fossil conduit originally linking magma sources possibly associated with the base of the illapel plutonic suite to basaltic andesite to andesitic volcanism the first magmas flowed along a major fault heated the host rocks and solidified as unlayered gabbros later magmas flowed up the same structure but cooled slowly in the preheated host rocks producing the layered parts of the intrusion layering was produced by non dynamic processes perhaps similar to that which produces liesegang banding plagioclase and pyroxene crystallised first to produce a loose framework close to the walls of the conduit latent heat from growth of amphibole may have facilitated equilibration by development of layering and coarsening the channel like and cross cutting structures may have resulted from interactions of chemical diffusion waves with discontinuities in permeability of the crystal framework during the development of the crystal framework the interstitial silicate liquid became enriched in water partly dissolving earlier structures and crystallising as pegmatoids some with miarolitic cavities

palaeoenvironments of the late triassic rhaetian sea implications from oxygen and strontium isotopes of hybodont shark teeth the oxygen and strontium isotopic composition of 125 teeth of the hybodont sharks lissodus and hybodus from various late triassic rhaetian bone bed localities in the central european basin are used as environmental and ecological tracers for the shallow epicontinental rhaetian sea the preservation of tooth enameloid was ascertained by cathodoluminescence microscopy mean 18op values differ regionally across the rhaetian sea with values of 18 6 0 6 near the western gate 16 1 0 8 in the east 15 4 0 6 in the southeast and 17 7 0 9 in the south the 18op values in the eastern rhaetian sea are 4 5 lower relative to tethyan seawater while teeth from the southern and western parts close to the marine gates are less fractionated the strontium isotopic composition of teeth from most localities is more radiogenic in comparison to late triassic seawater the observed spatial 18op trend in the rhaetian sea indicates a shift from marine to brackish conditions in the south and west towards extensively brackish conditions with salinities of less than 16 in the east thus confirming the existence of two marine gates brackish conditions persisted throughout early rhaetian times and were maintained by increased fluvial discharge from the vindelician bohemian and fennoscandian highs as a result of enhanced atmospheric moisture availability in the course of the rhaetian transgression the 18op values of lissodus and hybodus indicate euryhaline behaviour of rhaetian hybodonts by exceeding modern shark intraspecific variability the lack of accordance in 18op values between different isotopically conspicuous localities in the rhaetian sea contradicts a basin wide migration pattern differences between co site taxa might indicate some degree of niche partitioning

liesegang blocks from sandstone beds of the hojedk formation kerman iran abstract three types of liesegang blocks sandstone blocks with liesegang patterns are present in sandstone beds of the hojedk formation near sowlat abad located in the kerman province of iran the liesegang blocks are mostly 6 to 12 cm by 4 to 8 cm in area in beds with a mean thickness of 10 cm the liesegang blocks are best developed along the drainages and vanish laterally to the sides and vertically beneath they are formed in sandstone blocks bound by the tectonically induced joints and fractures at the periphery and the bedding plane at the bottom each liesegang block is composed of a core and alternating iron poor shells intermediate shells and iron rich shells iron shells the shells follow the configuration of the outer shape of the block the most important factors involved in transformation of a sandstone bed into liesegang blocks are a condensed grid of joint polygons surface water the appropriate topographic site of exposure and the composition and thickness of the sandstone bed microscopic studies and the study of gains and losses of elements suggest two opposing diffusion direction trends in the course of liesegang block formation the effect of recent tectonic movements on the liesegang blocks manifested itself in various forms of interest is partial replacement of the earlier liesegang patterns by the later patterns along joints and formation of compound liesegang blocks liesegang blocks with more than one set of liesegang patterns from the study of liesegang patterns within the compound liesegang blocks the configuration of the joint polygon related to each liesegang pattern and thereby the sense of stress field migration in the area can be deduced

the incorporation of uranium into diagenetic phosphorite abstract the behavior of u during the diagenetic formation of marine phosphorite has been modelled the model examines a dissolution reprecipitation replacement of skeletal hydroxyapatite calcium carbonate and earlier generated francolite by francolite the amount of organic matter consumed relative to the mass of francolite formed the replacement reaction progress and the concentration of u in the replaced phases are the important parameters which dictate the concentration of u in the phosphate rock a partition coefficient between apatite and interstitial solution was calculated and is u f 0 57 natural phosphorites have been examined and are discussed in the light of the proposed model the u mass balance in a recent phosphorite is in good accord with theoretical predictions differences in u concentrations between sea floor phosphorites are explained either by the original variation in the organic matter distribution in the corresponding sediments and or by mineralogical differences caco3 vs hydroxyapatite therein senonian phosphate rocks which were formed via the francolite francolite transformation demonstrate that during that process the organic matter content in the sediment was approximately 50 the model supports the idea that phosphorite rock formation is a multistage process

petrologic evolution and paleogeography of the late cretaceous nanaimo basin washington and british columbia implications for cretaceous tectonics systematic variations in sandstone petrofacies of the upper cretaceous nanaimo group are related to basin evolution and uplift of surrounding tectonic provinces a subaerially exposed horst partially separated southern and northeastern portions of the nanaimo basin volcaniclastic and arkosic sediment was derived from this horst the horst subsided below wave base during very early evolution of the nanaimo basin but it controlled sediment dispersal throughout basin development lower units of the nanaimo group in the southern nanaimo basin are chert rich and were derived largely from terranes of the san juan islands and north cascades basaltic and plutonic debris from the insular belt was deposited into the northwestern nanaimo basin during early basin development minor deposition of arkosic debris from the coastal plutonic belt also occurred upper units of the nanaimo group contain abundant plagioclase rich sediment derived from the coastal plutonic belt rocks along the southeastern margin of the basin however reflect continued sedimentation from terranes of the san juan islands and north cascades arkosic and dacitic debris from insular belt sources is recognized in the northwestern nanaimo basin the nanaimo basin may have developed as a pull apart basin within a broad zone of normal and transcurrent faulting in response to oblique convergence or transform faulting between the kula plate and the pacific margin of washington and british columbia

feedbacks between deformation hydrothermal reaction and permeability evolution in the crust experimental insights abstract in this paper we present experiments that explore the interaction between crustal deformation hydrothermal reaction and permeability evolution we postulate that deformation should result in changes to mineral surface area which will either favour or inhibit water rock reactions involving the formation of secondary minerals mineral precipitation can greatly affect hydrologic properties such as permeability so it is therefore crucial that the controlling parameters are well constrained experiments were conducted using a paterson gas apparatus capable of independently controlling confining pressure p c pore pressure p p and axial load most experiments were conducted at p c 100 mpa and p p 50 mpa with temperatures of 200 600 c using a fine grained granitic rock in the experiments permeability evolution was measured under different stress regimes ranging from the isostatic to the shear failure case we find that permeability decreases with time by a well defined exponential function with a rate constant r representing the duration of the transient in permeability the rate constant is lowest when the specimen is in the compactional regime where mineral surface areas are minimized conversely the permeability reaction rate constant changes at the greatest rate when the specimen is stressed into the dilatant regime or undergoes shear failure these stress states result in the generation of fresh reactive mineral surface areas leading to enhanced reaction and a rapid associated change in permeability results from this study suggest that in natural systems a negative feedback effect might be operative in which enhanced mineral precipitation moderates permeability generated during episodes of deformation this feedback is likely to be important in dynamic environments such as fault zones or injection sites intended as emerging hydrothermal energy sources

cathodoluminescence tools provide clues to depositional history in miocene and pliocene mammalian teeth abstract this paper presents the results of a study which used cathodoluminescence cl observations optical images and sem spectra as a tool for assessing diagenetic processes during fossilisation of continental mammalian teeth the study was performed on fossil teeth of large mammals gomphotheriidae rhinocerotidae and hippopotamidae from namibia and from kenya with ages from the lower and middle miocene to pliocene the fossil sites are distinguished by their environmental conditions they include floodplain deposits fluvial deposits of the proto orange river and aeolianite deposits in namibia and fluvio lacustrine deposits of different ages in kenya optical cl provides information about the sites environments and diagenetic processes related to those environments a blue intrinsic luminescence for the aeolianite deposits and purple to yellowish for floodplain or fluvial deposits the cl spectra of these samples show sharp emission bands which are classically related to late recent incorporation of rare earth elements ree substituting in the ca 2 sites high resolution mapping of the distribution of these ree shows a gradient from the enamel interior low concentrations to the outer enamel margin high concentrations

a conceptual model for the preservation of thick transgressive shoreline successions examples from the forearc nanaimo basin british columbia canada abstract sequence stratigraphic models derived from passive margins and foreland basins characterize transgressive shorelines excluding incised valleys as recording periods of sediment starvation and are commonly represented as thin 10 m are more likely to be developed in active tectonic settings e g forearc and rift basins which generally experience high sedimentation rates and relatively rapid changes in base level settings with high sedimentation rates and moderate base level rise lead to progradational trends despite overall transgression of the shoreline in settings where changes in eustatic sea level mainly control the resulting stratigraphic architecture e g passive margins thin transgressive successions 1 10 m are more likely to be produced finally in settings defined by relatively slow base level change e g foreland basins the resultant transgressive succession typically comprises a lag 1 m overlain by offshore mudstones this conceptual model highlights the importance of the interplay between sedimentation rates and base level rise and is intended as a guide for the predictive modeling of sedimentary basins

climatic depositional and burial controls on diagenesis of appalachian carboniferous sandstones qualitative and quantitative methods abstract carboniferous quartz lithic and feldspar rich sandstones from different stratigraphic intervals within the central appalachian basin contain evidence for eogenetic and mesogenetic diagenesis important eogenetic products include fe oxide oxyhydroxide siderite kaolinite chlorite and calcite whereas quartz albite illite sericite fe carbonate and secondary porosity are the most important mesogenetic components correspondence and detrended correspondence analysis of the framework grain and diagenetic mineral data set has guided diagenetic interpretations and leads to two major conclusions first minerals that formed early appear to have been influenced by stratigraphic position the distribution of siderite and iron oxide oxyhydroxide is considered to reflect a second order paleoclimatic signature recognized throughout the carboniferous where siderite formed during everwet periods and iron oxide oxyhydroxide during semi arid conditions reflecting differences in redox second framework grain composition controlled the distribution of diagenetic products in the burial environment lithic arenites are deficient in authigenic quartz yet have undergone various degrees of illitization quartz deficiency is attributed to compaction related loss of primary porosity relatively early which inhibited sufficient fluid flow to account for much higher concentrations of quartz cement in the more competent quartz rich sandstones

remagnetization during cretaceous normal superchron in eastern san juan islands wa implications for tectonic history abstract the eastern san juan islands expose an island arc ophiolite sequence and one or more ocean floor terranes cover rocks of the former including red radiolarian tuff and arc derived sandstone have no penetrative fabric and lack high pressure minerals in contrast pillow basalts and ribbon cherts of the latter are strongly deformed and the overlying metagraywacke is folded with a penetrative axial plane cleavage all ocean floor rocks have aragonite in veins indicative of higher pressure conditions than experienced by the island arc rocks a downward magnetization is common to the ocean floor rocks consistent with widespread remagnetization during the cretaceous normal superchron this magnetization is carried by magnetite and in red rocks by hematite fluid flow during or after deformation and high p metamorphism likely facilitated remagnetization at low temperature the magnetic directions are somewhat scattered but most are moderately to steeply down to the southeast they are far from directions expected with or without northward transport of baja bc rotation of observed directions into agreement with those expected for either present or more southerly locations also rotate structural elements in the host rocks three alternative rotation histories explored here all produce structural reconstructions that differ considerably from the present structure a tectonic history of the eastern san juan islands based on any of these reconstructions would be superior to one based on present attitudes of structures this is because at least a constraint that the restored paleomagnetic directions match a paleomagnetic field direction is satisfied choices among alternative reconstructions would become clearer with better understanding of relative ages of specific structures and their magnetizations improved geologic understanding of the regional setting where the rocks could have been deformed and remagnetized would also help

revised ages of blueschist metamorphism and the youngest pre thrusting rocks in the san juan islands washington new ages of rocks in the san juan islands northwest washington significantly change our understanding of the evolution of the san juan islands thrust system re examination of foraminifera bearing mudstones at richardson on lopez island indicates a late aptian 112 115 ma not late albian 100 ma age as currently presented in the literature the age brackets of thrusting marked by these pre thrusting mudstones and 84 ma post thrusting sedimentary rocks span a much longer period than previously thought diminishing controls on rates of displacement in the thrust system and the timing of regional deformation in western washington new 40 ar 39 ar plateau ages of phengite in blueschist facies meta volcanic rock also at richardson are 124 0 7 ma 2 late barremian these blueschist facies volcanic rocks are in fault contact with the fossiliferous mudstones therefore the blueschist facies metamorphism at richardson previously inferred to be associated with the thrusting now appears to have occurred prior to thrusting further the ar ages demonstrate that blueschist facies fabric formed earlier than the thrust event and is therefore not directly useful in analyzing the thrusting kinematics the richardson 40 ar 39 ar age is similar to isotopic ages found in the eastern san juan islands and in the shuksan blueschist terrane in the northwest cascades and thus fits into an emerging regional age pattern of blueschist facies metamorphism during late jurassic early cretaceous up to barremian but not late albian cenomanian if this pattern is more broadly confirmed for the san juan islands all the blueschist facies metamorphism can be regarded as having formed in subduction zones elsewhere along the continental margin rather than in the anomalous setting of an on land thrust system as in the san juan islands resume de nouveaux ges pour les roches des iles san juan dans le nord ouest de l etat de washington changent profondement notre comprehension de l evolution du systeme de chevauchement san juan un reexamen des mudstones foraminiferes a richardson sur l ile lopez indique un ge aptien tardif 112 115 ma et non albien tardif 100 ma tel qu indique actuellement dans la litterature les plages d ges pour le chevauchement marquees par ces mudstones precedant le chevauchement et des roches sedimentaires 84 ma posterieures au chevauchement couvrent une periode beaucoup plus grande que stipulee anterieurement diminuant les controles sur les taux de deplacement dans le systeme de chevauchement et le moment de la deformation regionale dans l ouest de l etat de washington de nouveaux ges plateaux 40 ar 39 ar de la phengite dans des roches volcaniques au facies des schistes bleus aussi a richardson datent

magmatic life at low reynolds number the extremely high viscosities of high silica liquids mean that intermediate and high silica magmas exist deep within the laminar range of fluid behavior many common interpretations of layering in plutonic rocks rely on analogies with sedimentation in water but for such high viscosity liquids including interstitial liquid in partially crystallized intermediate magmas these analogies cannot be correct particle reynolds numbers for high silica liquids are exceedingly small on the order of 10 6 or less in such a regime inertia is negligible and everyday experience is inapplicable layering and other pseudo sedimentary structures in granodiorites and granites likely arise from processes such as chemical diffusion self organization and crystal ripening

ecological and physiological variability of sr ca and ba ca in mammals of west european mid wurmian food webs the middle to upper paleolithic transition in western europe is characterized from an ecological point of view by large ungulate communities adapted to cold climatic conditions the aim of this study is to reconstruct the trophic relationships prevailing in these paleoecosystems which have no equivalent in the modern world bone and dentine remains representing five mammalian assemblages dated around 35 ka bp one of which included a neandertal specimen are investigated for sr ca and ba ca of bioapatites examination of the n content and u ree luminescence of bulk material ca p ratios and mn and ca contents of purified samples demonstrates that the sr ca and the ba ca ratios of bone and dentine samples are not significantly altered by diagenesis as a consequence of the biological discrimination of sr and ba in relation to ca sr ca and ba ca values are impoverished with increasing trophic position and are strongly correlated within a trophic web the slopes of the linear regressions between sr ca and ba ca are consistent with modern variability furthermore a statistical difference was found between ba ca of foregut and hindgut herbivores when coexisting collagen is preserved the sr ba ca and 15n are strongly correlated the distribution of values suggests that the 15n range is mainly controlled by the variability of soil conditions whereas the 13c range may be related to resource availability

porosity and permeability variations in fractured and liesegang banded breathitt sandstones middle pennsylvanian eastern kentucky diagenetic controls and implications for modeling dual porosity systems abstract middle pennsylvanian fluvial sandstones in eastern kentucky breathitt group manifest visible evidence of alteration related to fluid flow localized through near vertical joints fracture related alterations involve both physical and chemical modifications that together create dramatic permeabilisty variations at the outcrop scale on the fracture surface infiltered detritus combined with mineral and organic coatings have reduced pore sizes and hence permeabilities 0 03 0 44 md by an order of magnitude over values characteristic of the adjacent sandstone 0 32 1 53 md prominent zones of orange brown discoloration contain evidence of oxidation reactions and form an envelope of variable thickness around the fractures authigenic iron oxides are not uniformly distributed within these zones but rather are concentrated as local bands of pervasive mineralization commonly known as liesegang bands petrographic evidence suggests that most of the iron that now resides in oxidized authigenic phases was derived from solutes mobilized through dissolution of older iron bearing authigenic minerals permeability and pore sizes within the oxidation zone are bimodal and vary from high values similar to those in adjacent unoxidized sandstone to low values associated with the zones of pervasive mineralization that approach those values observed for the fracture skin the large magnitude of permeability variation around fracture systems in these sandstones documents the presence of a dual porosity system and suggests that fluid and contaminant transport cannot be realistically modeled using average rock properties

diffusion of rare earth elements in fish teeth from deep sea sediments the distribution of rare earth elements rees in biogenic phosphate phases in sediments such as the remains of fish teeth has been proposed as an indicator of the depositional environment in the water column recording for example palaeo redox conditions1 and isotope geochemical2 5 and hydrothermal6 7 processes enrichment of these phases in rees takes place only during early diagenesis8 9 for which reason the ree signal has often been assumed to represent the unfractionated record of ree distribution in the water column overlying the sediment surface1 4 5 10 here we report on studies of ree zoning in fish teeth from pacific sediments from which we extract a ree diffusion coefficient of 70 mm2 myr 1 this value suggests that diffusion of rees from sea water into the fish teeth before burial is too slow to produce the enrichments observed instead the ree distributions must derive from the surrounding sediment pore fluids the use of these distributions as palaeoceanographic indicators is therefore called into question

the ree and end of 40 70 ma old fish debris from the west african platform ree concentrations and nd isotopic compositions have been determined in late cretaceous early cenozoic fish debris from west african and israeli platform sediments and show a strong regional control independent of time except for those from the northern morocco it is suggested that although diagenetic fluids do not contribute ree s directly to the phosphatic debris they may significantly change the ce anomaly and the end t value of the epicontinental seas which in turn control the ree in marine phosphates it is shown that over the investigated period the north moroccan shelf seawater was progressively flushed by deep north atlantic water

luminescence of uranium bearing opals origin and use as a ph record abstract fluorescence of minerals has been long used for u exploration it is proposed here that opal fluorescence can be used as a probe of the ph of the formation solution bringing constraints for modeling u speciation and sequestration at the earth s surface we present a study of fluorescence spectroscopy of u in opals resulting from low temperature 29 c alteration of mineralized rhyolitic lavas nopal i u deposit sierra pena blanca mexico these opals show green fluorescence with a concentric distribution at microscopic scale which is unambiguously assigned to uranyl groups oxidized form of u spectra appear typical of uranyl in opal as reported in literature for other localities according to peak positions when considering also the lifetime of fluorescence spectra with time resolved laser fluorescence spectroscopy fingerprinting indicates that uranyl occurs either as phosphate or hydroxo polynuclear complexes trapped onto the opal internal surface data are indicative of a ph of opal formation around 8 as derived from both conditions of laboratory experiments and reference to calculated diagrams of speciation this ph value is consistent with the nopal geological formations that were potentially in contact with the aquifer involved in the hydrothermal process in addition the microscopic zoning of u suggests that the speciation has been stable since opal formation more than 50 ka ago which allows the record of ph that prevailed at that time

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

precipitation sealing and diagenesis 1 experimental results during burial and diagenesis of granular aggregates significant permeability reduction may be induced by the formation of low temperature authigenic minerals to quantitatively assess the importance of this process we have conducted a series of hydrothermal flow through experiments using deionized water and labradorite quartz sand all experiments were conducted in a modified triaxial apparatus configured to allow continuous permeability measurements under most of the conditions tested significant permeability reduction is observed with no concurrent decrease in porosity the overall permeability reduction sometimes exceeds 1 order of magnitude over 4 days and is positively correlated to temperature and deviatoric stress scanning electron microscope observations together with data from additional experiments show that the observed permeability reduction is entirely a result of secondary mineral growth si and al concentrations in the postexperiment fluids are also correlated to temperature and stress confirming the link between the chemical state of the system and permeability behavior in all experiments permeability reduction is fastest early and levels off in the late stages to explain the permeability behavior as a function of time a conceptual model is developed in which precipitation of authigenic minerals is rapid at early times while dissolution of quartz and labradorite is most active as the system approaches equilibrium the components necessary for secondary mineral formation are liberated at a lower rate thereby causing precipitation to slow although authigenic mineral formation does not reduce total pore space in these experiments there is a reduction in effective porosity which results in permeability reduction

convergent radial dispersion in a double porosity aquifer with fracture skin analytical solution and application to a field experiment in fractured chalk an exact laplace transform solution to the problem of dispersion advection and adsorption of a tracer due to its injection in a steady horizontal radially convergent flow field in a densely fractured porous formation double porosity aquifer is presented the porous blocks were assumed to be covered with a layer of material fracture skin of negligible volume and storage capacity that provides a resistance to diffusion in the rock matrix longitudinal dispersion advection and adsorption dominate transport of the tracer in the fractures and diffusion and adsorption dominate movement of the tracer in the blocks dimensionless breakthrough curves are used to illustrate the influence of various aquifer and tracer properties in support of the model a detailed analysis is performed of a published multitracer field test conducted in a layer of densely fractured chalk in bethune france of the three tracers analyzed two are nonsorptive but have widely different free water diffusion coefficients and one is slightly sorptive analysis of measured breakthrough curves matched by trial and error to theoretical responses reveals that by allowing for fracture skin on block surfaces one can obtain 1 pure advection arrival times that are independent of the tracer used 2 values of mass recovery consistent with measured values and 3 relative values of effective diffusion coefficients that are consistent with known free water diffusion coefficients for the separate tracers reasonable estimates of longitudinal dispersivity and fracture porosity are also obtained

impact of coating and weathering on the properties of chalk fracture surfaces the surface topography of a natural fracture intersecting a chalk formation was mapped using a high resolution laser scanning device and its roughness was evaluated using five different criteria two coated and two uncoated slices of the natural fracture surface were encased in flow cells and exposed to short 24 and 8 hours interactions with percolating synthetic rainwater and industrial wastewater followed by long drying periods weeks these flow experiments simulated the intermittent infiltration of surface runoff and industrial effluents typical of the study area and resulted in erosion of the fracture surfaces and modification of their roughness the temporal variations in surface roughness were evaluated using three commonly used criteria standard deviation from mean heights differences between maximum and minimum heights and the root mean square roughness and two newly developed measures namely the slopes on the surfaces and a calculated roughness related ratio rrr the mean slope maps and rrr calculations were found to be good criteria for evaluating surface topography and its uniformity across the fracture surface the coated surfaces were significantly rougher had greater relief more heterogeneous topography and a larger surface area than the uncoated surfaces the results suggest that coating and fast weathering caused by intermittent flow events significantly change roughness surface area relief and the heterogeneity of a fracture surface these in turn may affect the spatial distribution of flow paths across that fracture surface consequently when exploring the properties of fracture surfaces and fracture flow the impact of surface skin and variations of the surface properties over short timescales should be taken into account

chemical diagenetic constraints on the timing of cataclasis in deformed sandstone along the pine mountain overthrust eastern kentucky abstract cathodoluminescence imaging reveals that sandstones of the middle pennsylvanian lee formation and breathitt group along the pine mountain overthrust pmo contain inter and intra granular authigenic quartz in proportions that differ markedly between samples of contrasting deformational state fracture surfaces generated during fault movement provided nucleation substrates favorable for the emplacement of substantial amounts of intragranular quartz up to 11 volume percent in the lee formation relatively undeformed sandstones contain cement that is dominantly intergranular whereas sandstones from highly deformed cataclasites along the trace of the pmo contain cement that is dominantly localized within intragranular fractures therefore the chemical diagenetic histories of different samples of breathitt and lee sandstones diverged markedly as a consequence of differing deformational histories and the cementation history thus constitutes a record that is relevant to deciphering the timing of deformation the small quantities of early formed intergranular cement within the cataclasites average 3 7 volume percent show evidence of breakage and accordingly must have largely pre dated the deformation quartz cementation modeling touchstone suggests that emplacement of this pre deformational intergranular cement within these deformed rocks can be bracketed within a period from approximately 280 to 260 ma an interpretation of fault movement that shortly post dates this initial period of quartz cementation is consistent with other estimates for the timing of the alleghanian orogeny because of their protracted period of burial rocks in the vicinity of the pmo remained at temperatures amenable to continued quartz cementation until the middle cenozoic and thus most of the quartz cementation in the cataclasites and also in the surrounding undeformed sandstones post dates movement on the fault

concentric fe oxyhydroxide bands in dacite cobbles rates of buffering chemical reactions abstract liesegang patterns rinds and bands are commonly observed in nature and form by self organised periodic precipitation of fe oxyhydroxide following a nonlinear reaction diffusion process although strictly liesegang patterns consist of bands that increase in width with increasing distance from the source of the fe that precipitated as fe oxyhydroxide regular banded patterns are also sometimes observed that are otherwise similar to liesegang patterns however the detailed process and time scale of regular fe oxyhydroxide bands development is still not fully understood here we describe an example of regular fe oxyhydroxide bands formed within dacite cobbles iron that was provided to the outer surfaces of the cobbles by acidic water that diffused towards the cobbles cores the spatial distributions of ca and fe within the fe oxyhydroxide bands across the cobbles show that the rhythmic fe oxyhydroxide precipitation was controlled by ph buffering the width of each band l and the expected diffusion coefficient of the rock matrix d provide the rate of reaction v and allow us to estimate the duration of fe oxyhydroxide band formation a diffusion reaction cross plot implies that the rhythmic fe oxyhydroxide patterns formed very rapidly within an order of 102 103 years considerably faster than previously estimated the simplified model can be applied to estimate the reaction time in any similar rock if regular fe oxyhydroxide bands are observed

luminescence of uranium and rare earth elements in apatite of fossil fish teeth abstract time delayed laser induced luminescence of uranium and rare earth elements ree in apatite of fossil fish teeth from the phosphorites of the senonian mishash formation israel were investigated before and after thermal treatment the unheated samples show luminescence of uo 2 2 luminescence of ree 3 sm eu pr is observed only after heating the samples at 1100 k in air the spectral properties indicate that uo 2 2 in the unheated samples is located in two different positions as aqua complexes of uranyl ions and associated with organic matter the ree in the unheated samples are accommodated in non luminescent form after heating the ree 3 sm eu pr are located in the ca 2 ii site presumably due to thermal diffusion

diagenetic heterogeneity in sandstone at the outcrop scale breathitt formation pennsylvanian eastern kentucky twenty seven samples of feldspathic phyllarenite were obtained from three 1 m grids in a large homogeneous distributary bar sand stone body with the goal of elucidating bed scale diagenetic het erogeneity significant variability in the content of both detrital and diagenetic components is present in the sample set this variation is within the range of values predicted from comparison with a large regional data set from the same formation but nonetheless it is large enough to preclude successful prediction of diagenetic prop erties from consideration of average composition and thermal his tory alone grain size is one important local control on the overall abundances of cement and porosity grain size operates to control the overall degree of cementation in these particular rocks indi rectly through its influence on lithic grain content and hence on compaction relatively minor carbonate cement is an exception to this trend and appears to be distributed somewhat randomly with out regard to the size or composition of the detrital components diagenetic heterogeneity of the magnitude documented in this example is correlated to differences in porosity and permeability and therefore has implications for reservoir simulation and explo ration risk assessment prediction of rock properties through dia genetic modeling is more successful if the textural controls on dia genetic heterogeneity are considered

oxygen and strontium isotopes from fossil shark teeth environmental and ecological implications for late palaeozoic european basins article i nfo fossil shark remains occur in both marine and nonmarine late palaeozoic deposits therefore their palaeo ecology is controversial the oxygen and strontium isotopic composition of biogenic fluorapatite in 179 teeth scales and spines predominantly of hybodontid lissodus and xenacanthiform orthacanthus xenacanthus bohemiacanthus triodus sharks from various late carboniferous moscovian to early permian artinskian basins of europe are used as ecological tracers to decipher diadromous or obligate freshwater lifestyle of the investigated taxa the 18 op values of the different shark teeth range from 11 7 to 20 2 within the different basins with mean values of 16 9 0 5 for the bohemian massif 16 2 0 8 for eastern germany 18 2 1 0 for southwestern germany 18 5 0 7 for southern central spain 17 6 0 4 for