novel 3d centimetre to nano scale quantification of an organic rich mudstone the carboniferous bowland shale northern england x ray computed tomography and serial block face scanning electron microscopy imaging techniques were used to produce 3d images with a resolution spanning three orders of magnitude from 7 7 m to 7 nm for one typical bowland shale sample from northern england identified as the largest potential shale gas reservoir in the uk these images were used to quantitatively assess the size geometry and connectivity of pores and organic matter the data revealed four types of porosity intra organic pores organic interface pores intra and inter mineral pores pore sizes are bimodal with peaks at 0 2 m and 0 04 m corresponding to pores located at organic mineral interfaces and within organic matter respectively these pore size distributions were validated by nitrogen adsorption data the multi scale imaging of the four pore types shows that there is no connected visible porosity at these scales with equivalent diameter of 20 nm or larger in this sample however organic matter and clay minerals are connected and so the meso porosity 20 nm within these phases provides possible diffusion transport pathways for gas this work confirms multi scale 3d imaging as a powerful quantification method for shale reservoir characterisation allowing the representative volumes of pores organic and mineral phases to be defined to model shale systems the absence of connected porosity at scales greater than 20 nm indicates the likely importance of the organic matter network and associated smaller scale pores in controlling hydrocarbon transport the application of these techniques to shale gas plays more widely should lead to a greater understanding of properties in the low permeability systems

application of microfocus computed tomography in carbonate reservoir characterization possibilities and limitations normally thin section petrography by which observations are made in two dimensions forms the basis of sedimentpetrological reservoir appraisal studies in reservoir characterization however insight in the three dimensional mineral and porosity distribution is necessary in this study microfocus computed tomography ct which is a non destructive technique has been used for 3d characterization of the mineral phases i e calcite dolomite anhydrite and porosity in carbonate reservoir rocks in order to obtain quantitative information on density and atomic number of the scanned reservoir samples as well as about their rock texture a dual energy scanning technique has been used additional beam artifact correction and a segmentation algorithm focused on differentiating calcite dolomite and anhydrite have been implemented to validate the developed methodology thin sections of scanned samples of the khuff formation oman have also been analyzed petrographically and compared to corresponding ct sections and to the results of the dual energy algorithms despite the lower resolution when compared to thin section analysis the accuracy of the dual energy technique is in the range of the standard point counting technique and estimations can be made concerning the microporosity of the samples since the developed dual energy methodology provides a fast and objective determination of the percentages of the mineralogical phases ct becomes a very powerful tool in the evaluation of the reservoir potential and in the quantification of mineralogical changes in sedimentary systems e g cycles in addition images are acquired visualizing and quantifying the spatial distribution of these phases in three dimensions which is a major advantage compared to classic 2d thin section petrography

clay microporosity in reservoir sandstones an application of quantitative electron microscopy in petrophysical evaluation clay mineral microporosity in sandstones is measured using computer assisted image analysis of back scattered electron micrographs of petrographic sections diagenetic kaolinite has a variety of textures with microporosity values ranging from 15 to 61 diagenetic chlorite has a generally uniform grain coating texture and microporosity of about 50 fibrous illitic clays are difficult to characterize by the same method an average value of 63 microporosity was recorded but analysis of stereo pair micrographs from scanning electron microscopy analyses reveals that illite commonly has microporosity of approximately 90 clay microporosity data are used to calculate effective pore volumes and volumes of clay bound water for clay minerals in sandstones converting from wei ht percent clay to volume percent clay is important microporosity data are valuable input to vshale evaluation where water saturation is associated with clay mineral type texture and volume

quantitative analysis of reservoir rocks by microfocus x ray computerised tomography abstract microfocus computer tomography ct is a non destructive imaging technique that allows visualisation of internal features within non transparent objects such as sedimentary rocks with resolution as good as 10 m in three dimensions this technique is highly superior to medical ct widely used in geology and material sciences superior resolution is achieved by decreasing the x ray spot size which allows a decrease in the penumbra effect and an increase in primary magnification by placing the sample close to the x ray source since polychromatic x ray sources are used the technique is not free of artefacts application of filtering techniques is recommended to circumvent these artefacts and to achieve good quality images for quantitative analysis application of a dual energy approach allows quantification of density as well as effective atomic number distribution of internal features as the technique acquires data in 3d ct provides an ideal tool to link 2d thin section petrography to 3d petrophysical measurements or to be used within an upscaling approach a number of applications and the use of dual energy density and effective atomic number characterisations are presented attention is also paid to some of the limitations of this technique

a comparison of micro ct and thin section analysis of lateglacial glaciolacustrine varves from glen roy scotland abstract despite the prevalence of thin section analysis in studies of quaternary sediments there are limitations associated with the production of thin sections sediment modification and the inherently 2d view that a thin section affords non destructive and rapid scanning technologies such as x ray computed microtomography ct enable material samples to be visualised and analysed in 3d in a quaternary context however such techniques are in their infancy this paper assesses the optimum approach to ct analysis of quaternary sediments applying the method on lateglacial glaciolacustrine varves from glen roy scotland scan datasets are examined at each stage of the thin section process and comparisons are made between 2d ct images and thin sections for the recognition of 2d sediment features with further appraisal of 3d models to identify 3d sediment structures comparable sediment features are observed in 2d ct images and thin sections however the ct imaging resolution determines the precision of microfacies descriptions additional 3d structures are distinguished from volumetric models that are otherwise impossible to identify in thin section slides these 3d structures can locally alter sediment properties e g layer thickness as seen in 2d thin sections and or digital images although such variation cannot be detected with these media it has been demonstrated that clear benefits exist in understanding the 3d structure of quaternary sediments both prior to thin sectioning to avoid complicating e g deformation structures and after thin sectioning to establish the complex 3d context of 2d datasets it is recommended that ct and thin section techniques are applied in parallel in future studies which will profit from the integration of true 3d data it is also advised that samples are scanned soon after field sampling due to the significant modification of in situ sediment structures that can occur during thin section processing

automated statistical method to align 2d chemical maps with 3d x ray computed micro tomographic images of soils abstract recent 2 dimensional measurements reveal that soils are chemically very heterogeneous at nanometric and micrometric scales direct measurement techniques are still lacking to extend these observations to 3 dimensions sequential sectioning of soils followed by 2 dimensional mapping of chemical elements and geometric interpolation to 3d appears to be the only available alternative unfortunately sectioning of soil samples suffers from geometric distortions that are difficult to avoid in practise in this regard the objective of the research described in this article was to develop a procedure enabling one to locate in a 3d x ray microtomographic image of a soil sample a physical surface that is obtained by sectioning and for which a number of chemical maps are available this procedure involves three steps 1 the reconstitution of the physical structure of the soil layer surface 2 the alignment of the chemical maps with the reconstituted soil surface image and 3 the 3d alignment of the 2d chemical maps with the internal structure of the soil cube visual comparison of the c and si maps and of the reconstituted ct images of the layer surfaces suggests a good correspondence between them which is supported by pearson correlation coefficients of 0 57 0 58 0 45 and 0 43 for the different surfaces and elements considered relative to the original 3d x ray ct image of the soil sample the planes associated with the c and si maps respectively are nearly superposed which further confirms the validity of the alignment procedure

tomography based characterization of ice air interface dynamics of temperature gradient snow metamorphism under advective conditions snow at or close to the surface commonly undergoes temperature gradient metamorphism under advective flow which alters its microstructure and physical properties a functional understanding of this process is essential for many disciplines from modeling the effects of snow on regional and global climate to assessing avalanche formation time lapse x ray microtomography was applied to investigate the structural dynamics of temperature gradient snow metamorphism exposed to an advective airflow in controlled laboratory conditions experiments specifically analyzed sublimation and deposition of water vapor on the ice structure in addition an analysis of the ice air interface dynamics was carried out using a macroscopic equivalent model of heat and water vapor transport through a snow layer the results indicate that sublimation of the ice matrix dominated for flow rates 10 6 m3 s 1 while during increased mass flow rates the water vapor deposition supplied by the advective flow counteracted sublimation a flow rate dependence of water vapor deposition at the ice interface was observed asymptotically approaching an average estimated maximum deposition rate on the whole sample of 1 05 10 4 kg m 3 s 1 the growth of microsized whisker like crystals on larger ice crystals was detected on microscope photographs leading to an increase of the specific surface area and thus suggest a change of the physical and optical properties of the snow the estimated values of the curvature effect of the ice crystals and the interface kinetic coefficient are in good agreement with previously published values

exploration of soil micromorphology to identify coarse sized om assemblages in x ray ct images of undisturbed cultivated soil cores abstract we proposed to use micromorphology to help identify coarse sized organic matter om in x ray computed tomography ct images of fresh undisturbed soil cores we sampled three soil columns 5 cm diameter 5 cm height in the interfurrows that mainly contain macroporosity and straw residues of the ploughed horizon of a silt loamy albeluvisol two of the samples were x ray scanned at 68 and 88 m voxel resolution and three thin sections were performed in one of the scanned columns retention curve was measured on the third soil column micromorphology observations showed macropores from very fine to coarse size and numerous mesopores were heterogeneously distributed in the soil matrix and concentrations of om of increasing stages of decomposition within and around the macroporosity ct images easily detected coarse sized om concentrations and recovered part of the discontinuous pattern of the coarse sized om fragments in the macroporosity we defined a table of correspondence between the structural features porosity and organo mineral features of size down to about 40 m and the grey level values of the scanned image the values of the thresholds were adjusted from the micromorphological observations and the porosities of the 3d segmented images compared well with the measured porosity of the third soil column the main limitation of the method was in choosing the threshold values separating pores and coarse sized om in order to recover the porosity of the zones containing the coarse sized om features the proposed method is a preliminary work that showed to be well suited for undisturbed soil samples containing large pieces of straw residues incompletely mixed with soil matrix but cannot be applied to the identification of fine sized om

the temperature gradient metamorphism of snow vapour diffusion model and application to tomographic images a simple physical model describing the temperature gradient metamorphism of snow is presented this model based on kelvin s equation and fick s law takes into account the local variation of the saturating vapour pressure with temperature it can determine locally whether the ice is condensing or subliming depending on both the pressure and temperature fields in the snow structure this model can also explain the formation of facets that occurs during the metamorphism using x ray microtomo graphic images of snow samples obtained under low to moderate temperature gradient conditions this model has been tested and compared to the reaction limited model proposed in a previous work

beam hardening artifact reduction in microfocus computed tomography for improved quantitative coal characterization microfocus computed tomography ct is a non destructive technique allowing visualization of the internal microstructure of objects this technique can be used to quantify the maceral content and to define the cleat system within coal samples however a number of artifacts intrinsic to the technique hamper the optimal quantitative use of ct one of the most important artifacts is beam hardening which generates streaks on the images near dense inclusions such as ankerite or pyrite and makes the border of the sample appear denser than in reality these artifacts can be minimized by using a dual energy method in which two sets of scans taken at a different energy level are combined in this study existing dual energy methods are combined into a new technique and adapted to be more ideally suitable for coal samples the method is calibrated with an artificial sample made of a plexiglas cylinder in which two aluminum rods are built in plexiglas and aluminum were selected since their x ray attenuation properties are similar to those of vitrinite and dense phases such as ankerite respectively the method is tested on a coal sample bearing relatively high percentages of iron minerals the corrected and uncorrected images from one representative slice through the sample are compared with reflected light microscopy images from the corresponding polished surface the results show that the applied approach creates images in which the border does not appear denser than in reality and in which the artificial streaks near dense inclusions are removed in addition size measurements of the ankerite veins and grains in the sample are much more accurate based on the corrected images it is therefore assumed that the proposed dual energy algorithm minimizes the beam hardening artifact however the corrected images have a lower signal to noise ratio than the uncorrected images consequently this approach magnifies to some extent other artifacts noise scatter and partial volume effect which are also present in the uncorrected images some solutions to correct for these artifacts and to improve the developed dual energy method are proposed

seasonal changes in the shell microstructure of the bloody clam scapharca broughtonii mollusca bivalvia arcidae article in this study seasonally controlled changes in shell microstructures in scapharca broughtonii s broughtonii mollusca bivalvia were demonstrated we observed shell microstructures and analyzed stable oxygen isotope ratios to reveal the factors controlling cyclical microstructural changes in s broughtonii t he speci mens examined were collected alive from three localities in japan the outer layer of s broughtonii was subdivided into a composite prismatic structure on the exterior side and a crossed lamellar structure on the interior side relative thickness of these two structures in the outer layer changed cyclically with ontog eny major growth breaks were formed immediately after thickening of the crossed lamellar layer in most specimens growth breaks were also marked by thickening of the composite prismatic structure fluctua tions in the relative thickness of the two microstructures were synchronized with those of the shell oxygen isotope ratios that indicated the seasonality of water temperature the crossed lamellar structure thickened at high water temperatures in summer shell oxygen isotope records indicated that the clams can form their shells at temperature higher than approximately 12 c with no record of lower winter temperatures growth breaks observed after the peaks of high water temperatures may have formed as a result of spawning because the breaks corresponded to the spawning season the proportion of the thickness of the shell microstructures can directly indicate fluctuations in the water temperature the methods used in this study can contribute to age determination the characterization of seasonal shell growth and an understanding paleotemperature changes in coastal regions

a bonding process between grains in mechanically disaggregated snow collections of disaggregated snow particles were examined in a temperature controlled microscope stage in addition to necks that appeared to sinter in a manner congruent with the two particle model there also appeared unanticipated dendritic growth which developed on some grains and grew into the pore space these branches developed preferentially only on part of and in different directions on individual grains some of these grew enough to join with adjacent grains that were in close proximity but not initially in contact while the surface of the adjacent grains did not show measurable growth or loss growth orientation is hypothesized to be due to crystal habit dependence on temperature columnar growth was observed at 5 c and plate like at 15 c the random growth orientation is in contrast to observed source and sink development aligned with a temperature gradient imposed using a gradient stage in this case a source to sink directionality across the pore was apparent in which faceted crystals grew at the expense of neighboring source grains the process of mechanically disaggregating snow produces numerous broken shards and sharp edged fracture surfaces we hypothesize that it is the sublimation of these high surface energy regions that provides the excess vapor to facilitate the diffusion limited dendritic growth observed in this equitemperature mechanically processed snow

new research in the methods and applications of sclerochronology abstract because the instrumental record is short and does not extend to periods before the initiation of significant human impacts full understanding of the processes and dynamics involved in the modern phase of very rapid global change depends on the interpretation of high resolution and precisely dated proxy archives the identification of very long lived species of bivalve mollusc in the extratropical marine environment has been a crucial recent advance these molluscs form patterns of periodic usually annual banding in their shells that are synchronous within populations so that long centennial and millennial stacked chronologies can be built by crossdating from live collected to fossil shells the variable growth rates and precisely dated geochemical data from the shell material provide long term real world data that can in principle be used to constrain climate models and to define long baselines for environmental monitoring however the signals in these data usually result from the complex interaction of multiple influences and the deconvolution and understanding of these influences is a major target of the scientific field of sclerochronology this special issue presents some of the latest research into the sclerochronology of mollusc shells it includes contributions to our understanding of shell growth including the identification of endogenous non environmental growth rhythms that persist throughout ontogeny and analysis in two papers of variability through ontogeny in the season of growth and the implications of such variability for temperature reconstruction one paper presents a new network of bivalve chronologies for uk waters with a 200 year seawater temperature reconstruction three papers cover trace element geochemistry including a novel approach to sampling for la icp ms that enables giant clam shells to be sampled at daily resolution an attempt to identify an independent temperature proxy for coastal waters using limpet shells and a detailed study of the drivers of variability in sr ca and ba ca ratios one study looks at shell microstructure as a temperature proxy finding a coherent temperature response in the shape of the prisms

measurement of aperture distribution capillary pressure relative permeability and in situ saturation in a rock fracture using computed tomography scanning we develop an experimental technique that uses computed tomography ct scanning to provide high resolution measurements of aperture distribution and in situ saturation along with capillary pressure and relative permeability for the same rough walled fracture we apply this technique to an induced fracture in a cylindrical basalt core undergoing water drainage we find that the sum of the water and gas relative permeabilities is much 1 at intermediate saturations and the water relative permeability shows a sharp change over a narrow range of average water saturation in situ saturation maps show channeling of gas and significant retention of the wetting phase water the capillary pressure initially increased and then decreased with decreasing water saturation although this type of capillary behavior is atypical for unsaturated flows we find that the sizes of the gas filled apertures are consistent with the measured capillary pressure

aggradation and carbonate accumulation of holocene norwegian cold water coral reefs cold water coral ecosystems present common carbonate factories along the atlantic continental margins where they can form large reef structures there is increasing knowledge on their ecology molecular genetics environmental controls and threats available however information on their carbo nate production and accumulation is still very limited even though this information is essential for their evaluation as carbonate sinks the aim of this study is to provide high resolution reef aggradation and carbonate accumulation rates for norwegian cold water coral reefs from various settings sunds inner shelf and shelf margin furthermore it introduces a new approach for the evaluation of the cold water coral preservation within cold water coral deposits by computed tomography analysis this approach allows the differentiation of various kinds of cold water coral deposits by their macrofossil clast size and orientation signature the obtained results suggest that preservation of cold water coral frameworks in living position is favoured by high reef aggradation rates while preservation of coral rubble prevails by moderate aggradation rates a high degree of macrofossil fragmentation indicates condensed intervals or unconformities the observed aggradation rates with up to 1500 cm kyr 1 exhibit the highest rates from cold water coral reefs so far reef aggradation within the studied cores was restricted to the early and late holocene available datings of norwegian cold water corals support this age pattern for other fjords while on the shelf cold water coral ages are reported additionally from the early middle holocene the obtained mean carbonate accumulation rates of up to 103 g cm 2 kyr 1 exceed previous estimates of cold water coral reefs by a factor of two to three and by almost one order of magnitude to adjacent sedimentary environments shelf slope and deep sea only fjord basins locally exhibit carbonate accumulation rates in the range of the cold water coral reefs furthermore cold water coral reef carbonate accumulation rates are in the range of tropical reef carbonate accumulation rates these results clearly suggest the importance of cold water coral reefs as local maybe regional to global carbonate sinks

climatic optimum during the holocene and the distribution of warm water mollusks in the sea of japan abstract the geographical distribution of warm water mollusks has been analyzed and the paleobiogeographical significance of the climatic optimum during the holocene in the formation of the shallow water malacofauna in the sea of japan has been assessed the shift of the southern boundary of the pacific boreal region was 700 800 km to the north compared to its present day position based on bivalve mollusks on the continental coast of the sea of japan this boundary is observed in peter the great bay 43 n and on the japanese side it seems to be at the central part of hokkaido it can be concluded that a temperature increase of the surface water mass of 0 1 0 2 c can cause a shift of about 100 km of the northern boundary of the area of warm water mollusks

quantitative 3d petrography using x ray tomography application to bishop tuff pumice clasts abstract textures are traditionally studied using the petrographic microscope which limits observations to 2d sections of 3d objects given the difficulty in retrieving information on shapes sizes and spatial distribution of objects in 3d from random sections a method that can yield observations in 3d is highly desirable x ray tomography yields a 3d map of the linear x ray attenuation coefficient which is a function of the atomic number and density of the material and the x ray energy used based on the compositional contrasts between different phases various phases can be identified in a rock pumice clasts characterized by isolated crystals surrounded by a low density matrix are ideal for the application of this technique we present our first results obtained using x ray tomography for pumice clasts from the bishop tuff samples studied are from units f7 and f8 and are representative of the variability in density and crystal contents observed in the early erupted bishop tuff data were collected on the geosoilenvironcars beamline at the advanced photon source argonne national laboratory using a 22 kev monochromatic x ray beam image analysis was performed using the software blob3d brightness contrasts in the resulting images allow the separation of magnetite sanidine quartz including minor plagioclase glass and vesicles crystals smaller than 5 voxels in diameter cannot be quantified properly mostly due to noise in the images this constrains the spatial resolution of the resulting images such that there is a trade off between sample size and spatial resolution we employed two runs with samples of varying sizes 5 and 10 mm to obtain adequate resolution voxel sizes ca 8 and 17 m we have previously studied quartz size distributions in bishop pumice clasts using a crushing sieving and winnowing procedure the agreement between our new and previous results is excellent quartz size distributions obtained using the tomography data are concave upward on population density vs size plots and resemble the size distributions for all quartz crystals including both whole crystals and fragments these size distributions were probably generated by fragmentation through which large crystals were converted in a larger number of small crystals petrographic observations suggest fragmentation occurred mostly under magmatic conditions sanidine size distributions are similar to those observed for quartz magnetite size distributions are typically linear indicating a simple magmatic history in contrast with the tektosilicates

computed tomography scan imaging of natural open fractures in a porous rock geometry and fluid flow computed tomography scan imaging techniques have been used on core samples to investigate the effect of natural open fractures on reservoir flow in the snohvit gas condensate field firstly computed tomography ct scanning was used to describe the 3d geometrical properties of the fracture network including orientation and fracture density two types of fractures were observed f1 fractures are short and stylolite related and f2 fractures are longer cross cutting the core and without any obvious relationship to stylolites secondly monitoring of single and two phase flow experiments on samples containing these two types of natural open fractures was performed under 10 and 80 bar net confining pressure while using ct scanning 1 phase miscible flooding experiment shows approximately 3 times higher flooding velocity in an open f2 fracture than in the matrix 2 phase flooding by gas injection into a 100 water saturated core gave early gas breakthrough due to flow in the fracture and thereafter very little water production the flow experiments showed that the presence of open fractures has a significant local effect on fluid flow even in a case with relatively high matrix porosity 200 300 md the sample containing f1 fractures showed a complex flow pattern influenced both by open fractures and stylolites the ct scan data enables an exact representation of the fracture network in core scale simulation models and therefore improves the understanding of fracture influence on flow in a fractured porous medium ct scanning of core samples provides an effective tool for integrating geology and fluid flow properties of a porous fractured medium

experimental and numerical investigation of the sintering rate of snow sintering rates in snow were investigated by measuring changes in penetration resistance with time and by using a numerical snow metamorphism model periodic snow micro penetrometer smp measurements were performed on uniform snow samples covering a wide range of densities the mean penetration resistance of snow increased with time according to a power law with an average exponent of 0 18 simulated changes in the bond to grain ratio for simplified spherical ice grains followed a power law with an average exponent of 0 18 showing that the mean penetration resistance as measured with the smp closely relates to bond to grain ratio in snow for lower density snow samples consisting mostly of dendritic snow morphologies the measured increase in penetration resistance was lower this is likely the result of two competing processes 1 strengthening of the snow sample due to the creation and growth of bonds and 2 weakening of the snow sample due to the formation of unbonded small rounded particles at the expense of larger dendritic forms on the other hand the rate of increase in penetration resistance for snow samples consisting of closely packed depth hoar was similar to that of rounded grains

palaeo climate controlled diagenesis of the westphalian c d fluvial sandstones in the campine basin north east belgium the westphalian c and d fluvial sandstones in the campine basin north east belgium are potential reservoirs for the sequestration of co2 and interesting analogues of the hydrocarbon reservoirs in the southern north sea although these sandstones were deposited in a relatively short period of time their reservoir properties and mineralogical compositions are very different a petrographic study complemented with stable isotope analyses fluid inclusion microthermometry and x ray diffraction analyses of the clay fractions of the sandstones which were sampled from deep boreholes 1000 m in the campine basin revealed that these differences are related mainly to the climate at the time of deposition the most important eogenetic processes affecting the westphalian sandstones were the generation of a pseudomatrix by physical compaction of al silicates and lithic fragments that were strongly altered by extensive meteoric leaching kaolinitization of unstable silicates and precipitation of siderite these processes had a detrimental influence on the reservoir properties of westphalian c sandstones but their impact on the westphalian d sandstones was minimal the difference is assumed to be related to the climate at the time of deposition which changed from tropical humid in the westphalian c to semi arid arid during the late westphalian d both the westphalian c and d sandstones were affected by similar mesogenetic processes mesogenetic quartz cementation resulted from chemical compaction and illitization of kaolinite k feldspar and smectitic clays illitization of kaolinite was controlled by the available quantities of co existing kaolinite and k feldspar and mainly affected the westphalian d sandstones illitization of k feldspar was controlled by the k feldspar content it had a much larger impact on the reservoir properties of the westphalian d as in these sandstones k feldspar was less affected by eogenetic alteration the illitization of smectitic clays resulted in illite quartz and ankerite cementation in both reservoirs this process had a more important impact on the westphalian c reservoir since cementation here also resulted from smectite to illite conversion in the interbedded and underlying shales the effect of mesogenetic alterations on the reservoir properties was much less drastic than the impact of eodiagenesis mesogenetic alterations do exert a significant control on the properties of the westphalian d the vast impact of eodiagenesis on the westphalian c sandstones made them less susceptible to mesogenetic alteration the effect of telogenetic processes on the porosity and permeability of the westphalian sandstones was small and restricted to the top reservoir intervals that directly underlie the cimmerian unconformity no significant telogenetic alterations related to the variscan unconformity were observed

the 3d microscopic signature of strain within glacial sediments revealed using x ray computed microtomography abstract x ray computed microtomography ct a non destructive analytical technique was used to create volumetric three dimensional 3d models representing the internal composition and structure of undisturbed pro and subglacial soft sediment sample plugs for the purposes of identifying and analysing kinematic indicators the technique is introduced and a methodology is presented addressing specific issues relating to the investigation of unlithified polymineralic sediments six samples were selected based on their proximity to type brittle and ductile deformation structures or because of their perceived suitability for successful application of the technique analysis of a proglacial ideal specimen permitted the 3d geometry of a suite of micro faults and folds to be investigated and the strain history of the sample reconstructed the poor contrast achieved in scanning a diamicton of glaciomarine origin is attributable to overconsolidation under normal loading the sediment demonstrated to have undergone subsequent subglacial deformation another overconsolidated diamicton contains an extensive small scale the subglacial sample evidence indicates that complex polyphase brittle ductile deformation histories are common in such diamictic soft sediments and that the local micro scale environment composition structure shear forces and effective pressure controls rheology the sediment void ratio is a key indicator of strain three of the samples are tentatively placed at different points on the strain cycle for subglacially deforming soft sediment based on their void ratio characteristics and distribution it has been demonstrated that ct offers significant potential for elucidating glacial soft sediment kinematics the ability of the technique to both test a variety of hypotheses pertaining to mechanisms operating within the subglacial environment and evaluate efforts to replicate those processes under controlled laboratory conditions is therefore discussed along with solutions to the problems encountered within this project ct also permits the seamless linking of analytical techniques applied at the hand specimen mm micromorphological m mm scanning electron microscopy and x ray diffraction fluorescence nm m scales and the archiving duplication and dissemination of sample volumetric 3d data

three dimensional grain fabric measurements using high resolution x ray computed tomography abstract high resolution x ray computed tomography hrxct provides detailed imagery of the interiors of rocks up to hand sample size non destructively and in three dimensions new tools described here allow these data to be used for analysis of grain fabrics two separate sets of measurement techniques have been developed the first concentrates on quantifying individual crystals phenocrysts porphyroblasts or other discrete objects or void spaces within a sample quantifiable properties include location size shape orientation and contact relationships with adjacent objects the second set of techniques performs a more general fabric analysis on any distinguishable component in a sample a fabric tensor can be computed based on a number of metrics including the star volume distribution svd star length distribution sld and mean intercept length mil methods the fabric tensors provide principal component directions and magnitudes which in turn provide a measure of degree of anisotropy and shape indices because the svd and sld measure only the material of interest whereas the mil is also influenced by spatial distribution results can be divergent for sparse phases also introduced is a three dimensional rose diagram that can be viewed interactively and inspected to reveal further details about non orthogonal directional components these techniques are demonstrated through analysis of a garnet kyanite schist from mica dam british columbia

thermal dependency of shell growth microstructure and stable isotopes in laboratory reared scapharca broughtonii mollusca bivalvia we experimentally examined the growth microstructure and chemistry of shells of the bloody clam scapharca broughtonii mollusca bivalvia reared at five temperatures 13 17 21 25 and 29 c with a constant pco2 condition 450 atm in this species the exterior side of the shell is characterized by a composite prismatic structure on the interior side it has a crossed lamellar structure on the interior surface we previously found a negative correlation between temperature and the relative thickness of the composite prismatic structure in field collected specimens in the reared specimens the relationship curve between temperature and the growth increment of the composite prismatic structure was humped shaped with a maximum at 17 c which was compatible with the results obtained in the field collected specimens in contrast the thickness of the crossed lamellar structure was constant over the temperature range tested these results suggest that the composite prismatic structure principally accounts for the thermal dependency of shell growth and this inference was supported by the finding that shell growth rates were significantly correlated with the thickness of the composite prismatic structure we also found a negative relationship between the rearing temperature and 18o of the shell margin in close quantitative agreement with previous reports the findings presented here will contribute to the improved age determination of fossil and recent clams based on seasonal microstructural records

ice crystals grown from vapor onto an orientated substrate application to snow depth hoar development and gas inclusions in lake ice a laboratory experiment was conducted in which new ice crystals were nucleated from the vapor phase onto large existing ice crystals obtained from antarctic lake ice flat smooth ice crystal surfaces were prepared with c axes oriented either vertically or horizontally when these were subjected to a supersaturated vapor environment multiple individual crystals nucleated onto the substrates adopting the same crystallographic orientation as the parent a dominant grain growth scenario for kinetic growth metamorphism in snow which in some ways is analogous to the oriented morphologies in lake ice is hypothesized in the lake ice growth scenario optimally oriented crystals will grow at the expense of those less preferentially positioned the proposed dominant grain growth theory for snow is in agreement with the observed decrease in the number of grains and the proximal similarity of crystal habit in kinetic growth metamorphism in snow similarly kinetic crystal growth on the interior of gas inclusions in antarctic lake ice will also acquire the crystallographic orientation of the substrate ice these small faceted interior crystals significantly influence light scattering and penetration in the lake ice cover

three dimensional miarolitic cavity distribution in the kakkonda granite from borehole wd 1a using x ray computerized tomography abstract three dimensional imaging of a granite core from the borehole wd 1a drilled at the kakkonda geothermal field ne japan was performed by x ray computerized tomography ct the ct images displayed miarolitic cavities possible geothermal reservoir felsic minerals mafic minerals and enclaves in the granite voxels with ct numbers less than 1500 were estimated to be the miarolitic cavities on the basis of i the ct imaging of the synthetic glass tubes and ii the detailed comparison between the ct image and the cut surface of the rock sample a three dimensional distribution of miarolitic cavities was reconstructed from a set of contiguous two dimensional ct images and showed a spatially heterogeneous distribution with a boundary that strikes n 20 e this trend is probably important as the regional distribution of the geothermal reservoir which demonstrates that x ray ct is a powerful tool in geothermal studies chemical fluctuations of na and k were found around the miarolitic cavity zone this may be useful for finding miarolitic cavity zones without coring

holocene coastal carbonates and evaporites of the southern arabian gulf and their ancient analogues abstract the holocene sediments of the coast of the united arab emirates in the southeastern arabian gulf are frequently cited in the literature as type examples for analogous assemblages of carbonates evaporites and siliciclastics throughout the geologic record this paper is intended as a convenient single source for the description of sediments of this region providing information on how to reach the classic localities and some of the analogs the holocene sediments of the region accumulate over an area that is 500 km long and up to 60 km wide the sediments collecting offshore are predominantly pelecypod sands mixed with lime and argillaceous mud with these latter fine sediments increasing as the water deepens the pelecypod rich sediments also collect east of abu dhabi island both in the deeper tidal channels between the barrier island lagoons and in deeper portions of the protected lagoons west of abu dhabi island the shallow water margin is the site of coral reefs and coralgal sands whereas to the east oolites accumulate on the tidal deltas of channels located between barrier islands grapestones accumulate to the lee of the reefs and the oolite shoals where cementation becomes more common they are particularly common on the less protected shallow water margins of the lagoons west of abu dhabi island pelleted lime muds accumulate in the lagoons in the lee of the barrier islands of the eastern abu dhabi lining the inner shores of the protected lagoons of abu dhabi and on other islands to the west are cyano bacterial mats and mangrove swamps landward of these a prograding north facing shoreline is formed by supratidal salt flats sabkhas in which evaporite minerals are accumulating this paper describes the localities associated with 1 the mangrove swamps of the west side of the al dhabaiya peninsula 2 the indurated cemented carbonate crusts cyanobacterial flats and sabkha evaporites on the shore of the khor al bazam south of qanatir island 3 the reef and oolitic sand flats on the coast just east of jebel dhana and 4 the marine travertine and aragonite coats associated with the beach sediments in a small bay south of jebel dhana and 5 the sabkha mutti between jebel barakah and al sila similar sedimentological associations of carbonate and evaporites to those of the holocene of the united arab emirates are to be found in the tertiary and mesozoic sedimentary rocks of the immediate subsurface in the arabian gulf other analogs to this setting include the paleozoic carbonates of the western usa europe and asia mesozoic carbonates of the gulf of mexico europe and middle east and tertiary sedimentary rocks in the middle east

development of a fracture network in crystalline rocks during weathering study of bishop creek chronosequence using x ray computed tomography and 14c pmma impregnation method the progressive development of porosity during subsoil weathering of granodiorite clasts was studied at the bishop creek moraine chronosequence in east central california fractures and other pores were examined using two complementary imaging techniques x ray computed tomography xrct and a 14c pmma 14c polymethylmethacrylate method the well known xrct method allows the investigation of three dimensional 3 d pore space 14c pmma is a less known method based on the complete impregnation of pore space with 14c doped pmma and subsequent autoradiograph of a rock section these imaging methods allow us to decipher the evolution of pore space in the granodiorite during the 120 k y weathering period the 14c pmma imaging technique was found to be more suitable for following the evolution of the whole sequence from intact bedrock to saprock in terms of crack density porosity and aperture working with hand specimens this method was adapted to detect both the low aperture fractures microcracks and macrocracks only a slight and progressive increase in total fracture density was observed during the whole weathering period however this trend does not hold if macrocracks and microcracks are separated microcrack density slightly decreases whereas macrocrack density increases due to a progressive expansion of microcracks the total porosity of the rock increases during weathering and is correlated to the progressive aperture increase of all types of cracks this evolution is accompanied by a change of crack morphology and connectivity and an overall increase in intragranular porosity of biotite and plagioclase aggregates

paragenesis of cretaceous to eocene carbonate reservoirs in the ionian fold and thrust belt albania relation between tectonism and fluid flow this paper examines the diagenetic history of dual i e matrix and fracture porosity reservoir lithologies in cretaceous to eocene carbonate turbidites of the ionian fold and thrust belt close to the oil producing centre of fier ballsh central albania the first major diagenetic event controlling reservoir quality was early cementation by isopachous and syntaxial low mg calcite these cements formed primarily around crinoid and rudist fragments which acted as nucleation sites in sediments in which these bioclasts are the major rock constituent this cement can make up 30 of the rock volume resulting in low effective porosity in strata in which these bioclasts are mixed with reworkedmicrite isopachous syntaxial cements stabilized the framework and matrixporosity is around 15 the volumetric importance of these cements their optical and luminescence character distribution and dull orange luminescence and stable isotopic signal 18o and 13c averaging respectively 0 5 vpdb and 2 vpdb all support a marine phreatic origin within these turbidites and debris flows several generations of fractures alternated with episodes of cementation a detailed reconstruction of this history was based on cross cutting relationships of fractures and compactional and layer parallel shortening lps stylolites the prefolding calcite veins possess orange cathodoluminescence similar to that of the host rock their stable isotope signatures 18o of 3 86 to 0 85 vpdb and 13c of 0 14 to 2 98 vpdb support a closed diagenetic rock buffered system a similar closed system accounts for the selectively reopened and subsequently calcite cemented lps stylolites 18o of 1 81 to 1 14 vpdb and 13c of 1 52 to 2 56 vpdb within the prefolding veins brecciated host rock fragments and complex textures such as crack and seal features resulted from hydraulic fracturing they reflect expulsion of overpressured fluids within the footwall of the frontal thrusts after folding and thrust sheet emplacement some calcite veins are still rock buffered 18o of 0 96 to 0 2 vpdb and 13c of 0 79 to 1 37 vpdb whereas others reflect external i e extraformational and thus large scale fluid fluxes some of these veins are linked to basement derived fluid circulation or originated from fluid flow along evaporitic decollement horizons 18o around 3 0 vpdb and 13c around 1 5 vpdb others are related to the maturation of hydrocarbons in the system 18o around 7 1 vpdb and 13c around 9 3 vpdb an open joint system reflecting an extensional stress regime developed during or after the final folding stage this joint system enhanced vertical connectivity this open joint network can be explained by the high palaeotopographical position and the folding of the reservoir analogue within the deformational front the joint system is pre burdigalian in age based upon a dated karstified discordance contact sediment filled karst cavity development is linked to meteoric water infiltration during emergence of some of the structures despite its sediment fill the karst network is locally an important contributor to reservoir matrix porosity in otherwise tight lithologies development of secondary porosity along bed parallel and bed perpendicular i e layer parallel shortening stylolites is interpreted as a late stage diagenetic event associated with migration of acidic fluids during hydrocarbon maturation development of porosity along the lps system enhanced the vertical reservoir connectivity

quantitative analysis of the joint variability of rock texture and composition in thin section the generalized griffiths descriptor and its application to sediment generation from granitoids abstract the general protocol for quantitative petrographic description of clastic sediments envisioned by j c griffiths approximately 60 years ago is built on specification of the following five statistically independent fundamental properties of aggregates modal composition spatial arrangement size distributions shape distributions and orientation distributions of the elements each element is represented by a grain falling into one of an exhaustive set of petrographic classes we introduce the so called generalized griffiths descriptor ggd which extends this protocol to igneous and metamorphic rocks statistical independence of the fundamental properties permits rigorous testing of petrogenetic hypotheses as well as simulation of rocks based on any conceivable combination of them the benefits of a unifying scheme for description of crystalline parent rocks and their weathering products are illustrated by exploratory analysis of a petrographic data set derived from five granodiorites from across north america comprising the parent rocks and three size fractions coarse medium and fine of their detritus compositional data analysis is used to estimate sediment generation and evolution sge trajectories for each of the plutons sampled the bulk mineral composition and the mineral composition of the rock fragment assemblage display a common trend of relative depletion of quartz and k feldspar with decreasing grain size compensated for by relative enrichment of biotite and accessory minerals the evolution of crystal interface composition suggests that the balance between chemical and mechanical weathering may be reflected in relative stabilities of crystal interfaces we propose a computationally efficient stereological inversion procedure for estimating the parameters of crystal size probability distributions in rocks based on the assumption of lognormality the lognormal distribution is an acceptable default model for crystal size in granitoids at the level of individual thin sections about 87 passes the tests for lognormality but less so at the level of entire plutons only 62 success ratio the current implementation of the ggd is not yet complete because it deals explicitly with the first three fundamental properties only as a consequence of adopting the simplifying assumption that all elements which make up a rock are spherical shape and orientation distributions may be included in future implementations of the ggd dedicated data sets comprising sediments generated from a single parent rock under different conditions will be needed to advance sge studies by shedding more light on the balance between chemical and mechanical weathering

3d quantification of mineral components and porosity distribution in westphalian c sandstone by microfocus x ray computed tomography abstract microfocus x ray computed tomography ct measurements were performed on deltaic sandstone samples from the diagenetically altered westphalian c strata campine basin north east belgium in order to collect three dimensional data on mineral quartz kaolinite ankerite etc and porosity distribution the acquired ct data were compared with point counting results of stained impregnated thin sections to qualify the sensitivity of ct comparison between techniques shows positive results with regard to the quantification of main mineral phases such as quartz and ankerite and porosity distribution however major discrepancies exist when studying the clay minerals this can be explained by the influence of microporosity associated with these clay minerals resulting in partial volume effects

microfabric and anisotropy of elastic waves in sandstone an observation using high resolution x ray microtomography abstract petrophysical experiments using acoustic velocities to characterise anisotropies of mechanical behaviour of rocks are of essential relevance to understand the geomechanical behaviour of sandstone reservoirs under changing stress fields here we present high resolution x ray microtomography ct as a supplementary research tool to interpret anisotropic ultrasound velocities in sandstones with variation of isotopic stress specimens of two lower cretaceous sandstones localities bentheim and obernkirchen both germany have been used in petrophysical laboratory experiments under dry conditions to study ultrasonic sound velocities frequency of signal input 1 mhz subsequently oriented micro plugs drilled from the sandstone samples were investigated using high resolution x ray microtomography by means of image processing of the reconstructed scan images geometric attributes such as mean structural thickness orientation and tortuosity were evaluated from the ct data for both pore space and grain skeleton our observations clearly indicate the different roles of pore space and grain skeleton in regard to the propagation of ultrasonic waves because the pores do not transmit the waves it was sufficient to investigate the average thickness of this fabric element in contrast as the ultrasonic waves traverse the rock via the adjacent grains it was necessary to survey the actual travel lengths of seismic waves in the sandstone grain skeleton

microcomputed tomography and shock microdeformation studies on shatter cones one of the aspects of impact cratering that are still not fully understood is the formation of shatter cones and related fracturing phenomena yet shatter cones have been applied as an impact diagnostic criterion for decades without the role of shock waves and target rock defects in their formation having been elucidated ever we have tested the application of the nondestructive microcomputed tomography ct method to visualize the interior of shatter cones in order to possibly resolve links between fracture patterns and shatter cone surface features striations and intervening valleys shatter coned samples from different impact sites and in different lithologies were investigated for their ct suitability with a shatter cone in sandstone from the serra da cangalha impact structure brazil remaining as the most promising candidate because of the fracture resolution achieved to validate the obtained ct data the scanned specimen was cut into three orthogonal sets of thin sections scans with 13 m resolution were obtained ct scans and microscopic analysis unraveled an orientation of subplanar fractures and related fluid inclusion trails and planar fracture pf orientations in the interior of shatter cones planar deformation features pdf were observed predominantly near the shatter cone surface previously undescribed varieties of feather features ff in the form of lamellae emanating from curviplanar and curved fractures as well as an arrowhead like ff development with microlamellae originating from both sides of a pf were observed the timing of shatter cone formation was investigated by establishing temporal relations to the generation of various shock microscopic effects shatter cones are thus generated post or syn formation of pf ff subplanar fractures and pdf the earliest possible time for shatter cone formation is during the late stage of the compressional phase that is shock wave passage of an impact event

computer axial tomography in geosciences an overview abstract computer axial tomography cat is one of the most adequate non destructive techniques for the investigation of the internal structure of a large category of objects this method based on the attenuation of x or gamma ray generates digital images which map the numerical values of the linear attenuation coefficient of a section or of the entire volume of the investigated sample depending on the energy of the utilized radiation as well as on the effective atomic number of the sample cat can furnish with a spatial resolution of 0 01 0 5 mm quantitative as well as qualitative information concerning local density or chemical composition of the sample in geosciences cat has been successfully applied to the investigation of bulk density moisture content or macroporosity of the soil soil plant water system oil sand or shales small scale heterogeneities in siltstone or sandstone diamonds in kimberlite mineralization layers in manganese nodules local structure of marine sediments or coal composition the method has also been used for the investigation of the rock mechanical properties rock permeability fracture network two or three phase flow or residual oil distribution in carbonate cores a review of the actual applications of cat in soil science sedimentology coal geology as well as rock mechanics is presented all these applications reveal the great potential of cat in geoscience investigations

changes of shell microstructural characteristics of cerastoderma edule bivalvia a novel proxy for water temperature abstract shells of bivalves potentially provide an excellent archive for high resolution paleoclimate studies however quantification of environmental variables specifically water temperature remains a very challenging task here we explore the possibility to infer water temperature from changes of microstructural characteristics of shells of the common cockle cerastoderma edule the size and elongation of individual microstructural units i e prisms in the outer shell layer of seven three to five year old specimens collected alive from the intertidal zone of the north sea near texel the netherlands and schillig germany were measured by means of automatic image processing growth patterns circatidal ciralunidian and fortnightly increments and lines shell oxygen isotope values and mark and recovery experiments were used to place the shell record in a precise temporal context irrespective of the locality and ontogenetic age size and elongation of the prisms increased non linearly with water temperature small 0 12 0 05 m 2 and round prisms elongation 2 42 0 31 were formed at temperatures of ca 10 c late april whereas larger 0 33 0 11 m 2 and more elongated prisms 3 26 0 28 occurred during hot summer ca 22 c no clear cut or consistent correlation existed between microstructural characteristics and growth rate as well as a variety of other environmental variables such as salinity chlorophyll a and turbidity based on these findings a model was constructed from three shells at texel that enables reconstruction of water temperature with a precision of 1 7 1 0 c from prism size and elongation sst 9 02 17 25 p s 1 10 p e this model was successfully tested at four shells from schillig the new temperature proxy can be of particular interest for paleoclimate studies in nearshore settings when non recrystallized c edule shells are available future studies are required to verify our findings and check if other species with the same and different microstructures show similar relationships with water temperature