classification of huminite iccp system 1994 abstract in the new classification iccp system 1994 the maceral group huminite has been revised from the previous classification iccp 1971 int handbook coal petr suppl to 2nd ed to accommodate the nomenclature to changes in the other maceral groups especially the changes in the vitrinite classification iccp 1998 the new vitrinite classification iccp system 1994 fuel 77 349 358 the vitrinite and huminite systems have been correlated so that down to the level of sub maceral groups the two systems can be used in parallel at the level of macerals and for finer classifications the analyst now has according to the nature of the coal and the purpose of the analysis a choice of using either of the two classification systems for huminite and vitrinite this is in accordance with the new iso coal classification that covers low rank coals as well and allows for the simultaneous use of the huminite and vitrinite nomenclature for low rank coals

mechanical interactions between rigid particles in a deforming ductile matrix analogue experiments in simple shear flow abstract the mechanical interaction between two or more particles is investigated in newtonian simple shear flow the experimental models allow observation of both the particle rotation and the deformation pattern around the particles the finite and instantaneous strain patterns around rigid particles are strongly heterogeneous and asymmetric with high finite strain zones aligned to the direction of maximum finite stretch these correspond to local flow with low vorticity number heterogeneous strain patterns around rigid particles spread over a distance of 1 2 times the particle length and this distance increases with increasing bulk strain where rigid particles are more concentrated these patterns coalesce and the overall pattern is then strongly controlled by the particles and cannot be simply related to the external boundary conditions in rocks the characteristic asymmetric strain pattern around rigid isolated particles is a reliable shear criterion which becomes unreliable with high concentrations of rigid particles particle rotation is significantly disturbed when the distance between adjacent particles of equal size is shorter than their length that is only in very concentrated suspensions of rigid particles in a composite shape fabric the development of the sub fabric corresponding to the smaller minerals will be more disturbed

evolution of mica fish in mylonitic rocks abstract mineral fish are lozenge shaped porphyroclasts single crystals in a finer grained matrix which occur in ductile shear zones and which are commonly used as shear sense indicators mineral fish of biotite tourmaline k feldspar garnet hypersthene and quartz occur in mylonites but most common are white mica fish these mica fish can be subdivided into six morphological groups that develop by different mechanisms determined by different initial shapes and orientations the principal mechanisms of formation are intracrystalline deformation combined with rigid body rotation concomitant selective grain size reduction occurs by recrystallisation cataclastic separation pressure solution and diffusional mass transfer microboudinage has been proposed for the breakdown of large mica fish into smaller ones but many mica fish undergo shortening rather than extension along their long axes evidence is presented for an alternative process in which the tips of mica fish are isoclinally folded and then break off along the hinge of these microfolds all the presented fish shaped porphyroclasts or mineral fish have a specific shape preferred orientation with their long axis at a small antithetic angle with respect to the foliation they represent a special group of objects with a stable orientation due to flow partitioning into narrow shear bands

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

climate impacts of an ice sheet in east siberia during the last glacial maximum abstract recent evaluations of geomorphological evidence in east siberia strongly suggest that no ice sheet existed on the east siberian arctic shelf during the last glacial maximum lgm contrary to the hypothesis of some authors because most general circulation model gcm simulations of the lgm have included such an ice sheet the impact of an east siberian ice sheet is crucial for understanding previous model simulations of the lgm the experiments in this study use the global environmental and ecological simulation of interactive systems genesis 2 0 gcm and the equilibrium vegetation ecology eve vegetation model to simulate the lgm climate with previously published simulation and without new simulation an east siberian ice sheet most lgm simulations have shown increased southerly advection into beringia resulting from the dynamics of the continental ice sheets which acts to alleviate the hemispheric glacial cooling in beringia the east siberian ice sheet provides a secondary source of warm air advection into beringia in the simulation with an east siberian ice sheet a glacial anticyclone develops over the ice sheet during winter resulting in subsidence of air flowing off the ice sheet increased southerly advection along the western margin of the ice sheet and warming to the south of the ice sheet during summer the ice sheet blocks northerly flow from the arctic also resulting in warming south of the ice sheet the primary vegetation difference is in the ratio of tundra to polar desert the more mild climate with the ice sheet present produces more tundra and less polar desert

2 d rotation behavior of a rigid ellipse in confined viscous simple shear numerical experiments using fem abstract the rotation behavior of rigid elliptical inclusions adherent to the viscous matrix in simple shear flow is investigated using a 2 d finite element numerical model several simulations were performed using different ratios s between shear zone width and inclusion s least principal axis a computational strategy was devised to calculate pressure and viscous forces exerted on the inclusion and deduce its angular velocity for large s values results agree remarkably well with theoretical predictions while for small s values results deviate significantly from theory but are in agreement with previous analogue experiments the numerical model provided detailed and coherent information about the physical parameters involved in the process e g pressure strain rate and vorticity distributions within the model

origin of minerals in joint and cleat systems of the pottsville formation black warrior basin alabama implications for coalbed methane generation and production coalbed methane is produced from naturally fractured strata in the lower pennsylvanian pottsville formation in the eastern part of the black warrior basin alabama major fracture systems include orthogonal fractures which consist of systematic joints in siliciclastic strata and face cleats in coal that strike northeast throughout the basin calcite and minor amounts of pyrite commonly fill joints in sandstone and shale and less commonly cleats in coal joint fill calcite postdates most pyrite and is a weakly ferroan coarse crystalline variety that formed during a period of uplift and erosion late in the burial history pyrite forms fine to coarse euhedral crystals that line joint walls or are complexly intergrown with calcite stable isotope data reveal large variations in the carbon isotope composition of joint and cleat fill calcite 10 3 to 24 3 peedee belemnite pdb but only a relatively narrow range in the oxygen isotope composition of this calcite 16 2 to 4 1 pdb negative carbon values can be attributed to 13c depleted co2 derived from the oxidation of organic matter and moderately to highly positive carbon values can be attributed to bacterial methanogenesis assuming crystallization temperatures of 2050c most joint and cleat fill calcite precipitated from fluids with 18o ratios ranging from about 11 to 2 standard mean ocean water smow uplift and unroofing since the mesozoic led to meteoric recharge of pottsville strata and development of freshwater plumes that were fed by meteoric recharge along the structurally upturned southeastern margin of the basin influxes of fresh water into the basin via faults and coalbeds facilitated late stage bacterial methanogenesis which accounts for the high gas content in coal and the carbonate cementation of joints and cleats diagenetic and epigenetic minerals can affect the transmissivity and storage capacity of joints and cleats and they appear to contribute significantly to interwell heterogeneity in the pottsville formation in highly productive coalbed methane fields joint and cleat fill calcite have strongly positive 13c values whereas calcite fill has lower 13c values in fields that are shut in or abandoned petrographic analysis and stable isotope geochemistry of joint and cleat fill cements provide insight into coalbed methane reservoir quality and the nature and extent of reservoir compartmentalization which are important factors governing methane production

bioassay for estimating the biogenic methane generating potential of coal samples abstract generation of secondary biogenic methane in coal beds is likely controlled by a combination of factors such as the bioavailability of coal carbon the presence of a microbial community to convert coal carbon to methane and an environment supporting microbial growth and methanogenesis a set of treatments and controls was developed to bioassay the bioavailability of coal for conversion to methane under defined laboratory conditions treatments included adding a well characterized consortium of bacteria and methanogens enriched from modern wetland sediments and providing conditions to support endemic microbial activity the contribution of desorbed methane in the bioassays was determined in treatments with bromoethane sulfonic acid an inhibitor of microbial methanogenesis the bioassay compared 16 subbituminous coal samples collected from beds in texas tx wyoming wy and alaska ak and two bituminous coal samples from pennsylvania pa new biogenic methane was observed in several samples of subbituminous coal with the microbial consortium added but endemic activity was less commonly observed the highest methane generation 80 mol methane g coal 56 scf ton or 1 75 cm 3 g was from a south tx coal sample that was collected from a non gas producing well subbituminous coals from the powder river basin wy and north slope borough ak contained more sorbed original methane than the tx coal sample and generated 0 23 mol g up to 16 scf ton or 0 5 cm 3 g new biogenic methane in the bioassay standard indicators of thermal maturity such as burial depth nitrogen content and calorific value did not explain differences in biogenic methane among subbituminous coal samples no original methane was observed in two bituminous samples from pa nor was any new methane generated in bioassays of these samples the bioassay offers a new tool for assessing the potential of coal for biogenic methane generation and provides a platform for studying the mechanisms involved in this economically important activity

zircon geochronology and ca 400 ma exhumation of norwegian ultrahigh pressure rocks an ion microprobe and chemical abrasion study understanding the formation and exhumation of the remarkable ultrahigh pressure uhp rocks of the western gneiss region norway hinges on precise determination of the time of eclogite recrystallization we conducted detailed thermal ionization mass spectrometry chemical abrasion analysis and sensitive high resolution ion microprobe analysis of zircons from four ultrahigh and high pressure hp rocks ion microprobe analyses from the flatraket eclogite yielded a broad range of apparently concordant caledonian ages suggesting long term growth in contrast higher precision thermal ionization mass spectrometry analysis of zircon subject to combined thermal annealing and multi step chemical abrasion yielded moderate pb loss from the first lowest temperature abrasion step possible minor pb loss or minor growth at 400 ma from the second step and a 407 404 ma cluster of slightly discordant 206pb 238u ages most likely free from pb loss from the remaining abrasion steps we interpret the latter to reflect zircon crystallization at 405 400 ma with minor discordance from inherited cores zircon crystallization occurred at eclogite facies possibly post peak conditions based on compositions of garnet inclusions in zircon as well as nearly flat hree profiles and lack of eu anomalies in zircon fractions subjected to chemical abrasion these ages are significantly younger than the 425 ma age often cited for western norway eclogite recrystallization implying faster rates of exhumation 2 5 8 5 km myr and coeval formation of eclogites across the uhp portion of the western gneiss region

development of web based organic petrology photomicrograph atlases and internet resources for professionals and students abstract with advances in web applications organic petrography and other related disciplines are in need of updated online resources and educational tools to aid professionals and students in the identification and interpretation of macerals the u s geological survey usgs organic petrology laboratory along with usgs eastern energy resources science center information technology staff have developed five web atlases containing images of organic matter in geologic materials 1 an american society for testing and materials astm atlas 2 an organic petrology taxonomy for international classification optic of coal macerals atlas 3 an interactive gulf coast photomicrograph web atlas i map 4 an organic material in shales atlas shale and 5 an interactive blue white ultraviolet uv light atlas light each web atlas contains images of macerals with associated sample and petrographic data collected by the usgs these webpages will provide means to preserve and circulate petrographic data collected by the usgs for coal and shale samples from all over the world

the genesis of coal from the viewpoint of coal petrology abstract the genesis of the microscopic constituents of coal macerals and of maceral associations microlithotypes representing various coal facies is discussed in the light of recent advances that have been made in the study of coals and modern peats peat microscopy especially promoted the understanding of humification and biological gelification both of which are decisive for the genesis of huminites vitrinites in brown coals and hard coals respectively microbial activity during peatification has been documented by chemists microbiologists and petrologists and recently by electron microscopical observations in coals this activity leads to the incorporation of lipid substances into the humic matter and later influences the chemical physical and technological properties of vitrinites geochemical gelification transforms the huminites of brown coals into the vitrinites of bituminous coals and is probably caused by the onset of bitumen generation in coal in this process the hydrogel brown coal is transformed to the bitumogel bituminous coal coal as a source rock for oil has become an important research subject for coal petrologists and oil exploration the formation of more or less liquid bitumen and its later cracking to gaseous hydrocarbons leads to the coalification jumps of the macerals especially liptinites and vitrinites and to the generation of secondary macerals like exsudatinite bitumen and micrinite dead carbon bituminization in coal has been revealed by the use of fluorescence microscopy which also found the presence of new liptinite macerals bituminite fluorinite and exsudatinite and suggests a higher proportion of algal material in coals than was thought earlier the genesis of various types of inertinite macerals will probably become an increasingly important subject of research especially with regard to rank inertinites that seem to attain their high inertinitic reflectance initially during coalification besides the origin of macerals the origin of various coal facies in terms of maceral associations is considered in relation to the palaeogeographic depositional milieu the peat forming vegetation palaeoclimate water and nutrient supply acidity marine and calcareous influence and fire with examples from euramerican carboniferous coals gondwana coals and tertiary brown coals vegetation water and oxygen supply eh conditions are most important for the generation of coal facies vegetation has been reconstructed with the help of palaeobotany including palynology cuticular analysis and wood anatomy in brown coals and with the study of petrified permineralized peats preserved in coal balls the microscopical investigations of botanically recognizable plant remains isolated from coals or accompanying rocks has been especially informative however the results of palynological and cuticular analyses should be evaluated with caution considering the varying resistance of palynomorphs and cuticles and in the case of palynomorphs their possible extrapaludal origin microscopical studies of modern peats that were derived from different types of vegetation growing in different hydrological environments have been very helpful in interpreting coal facies especially in brown coals the much disputed origin of brown coal lithotypes is considered in detail for hard coals there seems to be agreement that coal layers rich in vitrites and liptinite poor clarite were deposited in wet forest swamps that microlayered liptinite rich clarites are sub aquatic humic muds and that inertinite rich durites represent oxidized peats the origin of liptinite rich durites is controversial either subaquatic muds or oxidized peats the latter perhaps from raised bogs a recent trend in the literature is the assumption that many if not all mineable coal seams have been deposited in raised bogs under ombrogenous oligotrophic conditions although raised bogs with a dense arborescent vegetation are known from borneo it seems not probable that most seams which were deposited in foredeeps or steadily sinking graben zones are of ombrogenous origin although a succession from relatively wet and eutrophic to relatively dry and oligotrophic conditions may be true for occasional seams but as in modern peats striking changes of coal facies are commonly caused by hydrological events e g inundations as a consequences of crevasses or of fires that burned the peat the origin of the inertinite rich gondwana coals is discussed in relation to their specific climatic conditions and a comparison with sub arctic peats is recommended coals influenced by marine and calcareous conditions are characterized by high contents of sulfur and pyrite as well as by hydrogen rich vitrinites with a relatively low reflectance and high fluorescence all due to a strong bacterial activity in peats of low acidity proposals for further research are made in the conclusions

strain and fabric analyses based on porphyroclast interaction abstract two dimensional computer models of the interaction of elliptical clasts in a variety of kinematic conditions are used to study how clast imbrication and shape fabric development relate to strain and strain history the models provide templates for a known clast density and clast ellipticity that correlate clast imbrication angle of collision and clast shape fabric to strain and kinematics of deformed rocks modeling also shows that the mode of clast interaction plays a significant role in the accumulation of imbricated clasts and the development of shape fabric upon collision between clasts the trains formed can remain fixed or rotate if they rotate imbricated clasts can become independent when they are no longer forced together by the flow based upon the mode of clast and train rotation using the march rotation of passive lines and the jeffery rotation of rigid particles as end members three models are defined in an attempt to simulate the conditions of clast interaction under varying conditions the march fixed train march rotating train and jeffery rotating train models simulate solid state intermediate and magmatic conditions respectively modeling shows that the two march models produce similar results but the jeffery model of train rotation always produces a lower proportion of imbricated clasts and a much weaker shape fabric application of the modeling to the study of a syntectonic granite in the sierra nevada suggests that deformation was dominated by simple shear some k feldspar imbrication and fabric development took place initially in the magmatic stage and culminated in the solid state to produce a large proportion of imbricated k feldspar porphyroclasts which define a strong shape fabric this type of analysis provides a rationale to determine syn vs post emplacement deformation in the granite

coupled hydrology and biogeochemistry of paleocene eocene coal beds northern gulf of mexico thirty six formation waters gas and microbial samples were collected and analyzed from natural gas and oil wells producing from the paleocene to eocene wilcox group coal beds and adjacent sandstones in north central louisiana usa to investigate the role hydrology plays on the generation and distribution of microbial methane major ion chemistry and cl br relations of wilcox group formation waters suggest mixing of freshwater with halite derived brines high alkalinities up to 47 8 meq l no detectable so4 and elevated 13c values of dissolved inorganic carbon up to 20 5 vienna peedee belemnite vpdb and co2 up to 17 67 vpdb in the wilcox group coals and adjacent sandstones indicate the dominance of microbial methanogenesis the 13c and d values of ch4 and carbon isotope fractionation of co2 and ch4 suggest co2 reduction is the major methanogenic pathway geochemical indicators for methanogenesis drop off significantly at chloride concentrations above 1 7 mol l suggesting that high salinities inhibit microbial activity at depths greater than 1 6 km formation waters in the wilcox group contain up to 1 6 modern carbon a14c to at least 1690 m depth the covariance of d values of co produced h2o and ch4 indicate that the microbial methane was generated in situ with these late pleistocene or younger waters the most enriched carbon isotope values for dissolved inorganic carbon dic and co2 and highest alkalinities were detected in wilcox group sandstone reservoirs that were co2 flooded in the 1980s for enhanced oil recovery leading to the intriguing hypothesis that co2 sequestration may actually enhance methanogenesis in organic rich formations

evolution of caledonian deformation fabrics under eclogite and amphibolite facies at vardalsneset western gneiss region norway the vardalsneset eclogite situated in the western gneiss region sw norway is a well preserved tectonite giving information about the deformation regimes active in the lower crust during crustal thickening and subsequent exhumation the eclogite constitutes layers and lenses variably retrograded to amphibolite and is composed of garnet and omphacite with varying amounts of barroisite actinolite clinozoisite kyanite quartz paragonite phengite and rutile the rocks record a five stage evolution connected to caledonian burial and subsequent exhumation 1 a prograde evolution through amphibolite facies t 490 63 c is inferred from garnet cores with amphibole inclusions and bell shaped mn profile 2 formation of l s tectonite eclogite t 680 20 c p 16 2 kbar related to the subduction of conti nental crust during the caledonian orogeny lack of asymmetrical fabrics and orientation of eclogite facies extensional veins indicate that the deformation regime during formation of the l s fabric was coaxial 3 formation of sub horizontal eclogite facies foliation in which the finite stretching direction had changed by approximately 90 disruption of eclogite lenses and layers between symmetric shear zones characterizes the dominantly coaxial deformation regime of stage 3 locally occurring mylonitic eclogites t 690 20 c p 15 1 5 kbar with top w kinematics may indicate however that non coaxial deformation was also active at eclogite facies conditions 4 development of a widespread regional amphibolite facies foliation t 564 44 c p 10 3 8 1 kbar quartz veins and development of conju gate shear zones indicate that coaxial vertical shortening and sub horizontal stretching were active during exhumation from eclogite to amphibolite facies conditions 5 amphibolite facies mylonites mainly formed under non coaxial top w movement are related to large scale movement on the extensional detachments active during the late orogenic extension of the caledonides the structural and metamorphic evolution of the vardalsneset eclogite and related areas support the exhumation model including an extensional detachment in the upper crust and overall coaxial deformation in the lower crust

effect of shape and orientation on rigid particle rotation and matrix deformation in simple shear flow the rotation behaviour of rigid particles from a wide range of symmetry classes was analysed in a series of three dimensional analogue experiments in which the particles were embedded in a transparent linear viscous matrix deformed to large shear strains comparison of the measured trajectories with theoretical periodic paths for rigid ellipsoids shows that quadratic slightly orthorhombic and monoclinic particles have trajectory paths and rotation rates closest to theory orthorhombic and monoclinic particles with a minimum aspect ratio 1 5 develop non periodic trajectories the results establish that the simplified theoretical model for ellipsoidal forms is a good approximation for a wide range of natural particle shapes the relationship between the rotation of a rigid particle and deformation of the adjacent matrix was also determined in a series of experiments by placing the particle at different depths relative to an imprinted grid the results are well illustrated by the surface passing through the centre of the particle and initially parallel to the shear plane two deformed regions in the matrix are recognised in the first region the matrix rotates with the particle together forming an approximately ellipsoidal object the second region is dominated by folds of limited extent along the rotation axis and greatest extent in a direction that rotates asymptotically toward the shear direction the folds rotate more slowly than the principal direction of maximum finite stretch

organic petrology and coalbed gas content wilcox group paleocene eocene northern louisiana abstract wilcox group paleocene eocene coal and carbonaceous shale samples collected from four coalbed methane test wells in northern louisiana were characterized through an integrated analytical program organic petrographic analyses gas desorption and adsorption isotherm measurements and proximate ultimate analyses were conducted to provide insight into conditions of peat deposition and the relationships between coal composition rank and coalbed gas storage characteristics the results of petrographic analyses indicate that woody precursor materials were more abundant in stratigraphically higher coal zones in one of the cbm wells consistent with progradation of a deltaic depositional system holly springs delta complex into the gulf of mexico during the paleocene eocene comparison of petrographic analyses with gas desorption measurements suggests that there is not a direct relationship between coal type sensu maceral composition and coalbed gas storage moisture as a function of coal rank lignite subbituminous a exhibits an inverse relationship with measured gas content this result may be due to higher moisture content competing for adsorption space with coalbed gas in shallower lower rank samples shallower 600 m coal samples containing less moisture range from under to oversaturated with respect to their ch4 adsorption capacity

influence of a permanent low friction boundary on rotation and flow in rigid inclusion viscous matrix systems from an analogue perspective abstract natural occurrences and recent experimental work show that a low friction inclusion matrix boundary can be responsible for antithetical rotation and development of stable shape preferred orientations in simple shear the flow of a viscous matrix around a rigid inclusion to which it may or may not be adherent is still not well studied but it is relevant to the understanding of the behaviour of structural elements in mylonite zones we used two dimensional 2 d analogue experiments to address these issues the experimental results with a permanent low friction inclusion matrix boundary nonadherent mode show the following 1 the rotation behaviour of inclusions in this mode is markedly different from the theoretical predictions and experimental results for the adherent mode 2 inclusions with aspect ratio equal to 1 rotate synthetically at a rate that depends upon inclusion shape and orientation 3 ellipse rectangle and lozenge shaped inclusions rotate antithetically when starting with their greatest axis parallel to the shear direction 4 back rotation is limited in all cases studied and the angle between the inclusion greatest axis and the shear direction represents a stable orientation which depends on inclusion aspect ratio and shape 5 a metastable orientation exists which is strongly dependent upon inclusion shape and aspect ratio and separates fields of antithetic and synthetic rotation our experimental results show that the overall flow pattern is bow tie shaped in adherent and nonadherent modes however there are major differences in the way the matrix flows near the inclusion i in the nonadherent mode the nearby matrix flows past the inclusion whereas in the adherent mode the nearby matrix flows with and follows the inclusion therefore in the adherent mode passive marker lines parallel to the shear direction and streamlines show considerable deflections at the inclusion crests in marked contrast with their straight character in the nonadherent mode ii stagnation points or closed flow lines near the inclusion were not observed in the nonadherent mode which means that there is no closed separatrix around the inclusion in this mode despite the fact that the overall flow shape is bow tie iii in the adherent mode the line of flow reversal is stable throughout deformation but in the nonadherent mode it changes position and orientation with progressive shearing this shifting of the line of flow reversal can be an important factor controlling rotation behaviour in the nonadherent mode iv in the nonadherent mode the inclusion behaviour is similar to that observed in confined flow v the flow pattern in the nonadherent mode provides an explanation for the observed lack of drag folds associated with small scale rigid inclusions in mylonites

organic geochemistry and petrology of subsurface paleocene eocene wilcox and claiborne group coal beds zavala county maverick basin texas usa abstract coal samples from a coalbed methane exploration well in northern zavala county maverick basin texas were characterized through an integrated analytical program the well was drilled in february 2006 and shut in after coal core desorption indicated negligible gas content cuttings samples from two levels in the eocene claiborne group were evaluated by way of petrographic techniques and rock eval pyrolysis core samples from the paleocene eocene indio formation wilcox group were characterized via proximate ultimate analysis in addition to petrography and pyrolysis two indio formation coal samples were selected for detailed evaluation via gas chromatography and fourier transform infrared ftir and 13c cpmas nmr spectroscopy samples are subbituminous rank as determined from multiple thermal maturity parameters elevated rank relative to similar age coal beds elsewhere in the gulf coast basin in the study area is interpreted to be a result of stratigraphic and or structural thickening related to laramide compression and construction of the sierra madre oriental to the southwest vitrinite reflectance data along with extant data suggest the presence of an erosional unconformity or change in regional heat flow between the cretaceous and tertiary sections and erosion of up to 5 km over the cretaceous the presence of liptinite rich coals in the claiborne at the well site may indicate moderately persistent or recurring coal forming paleoenvironments interpreted as perennially submerged peat in shallow ephemeral lakes with herbaceous and or flotant vegetation however significant continuity of individual eocene coal beds in the subsurface is not suggested indio formation coal samples contain abundant telovitrinite interpreted to be preserved from arborescent above ground woody vegetation that developed during the middle portion of mire development in forested swamps other petrographic criteria suggest enhanced biological chemical and physical degradation at the beginning and end of indio mire development fluorescence spectra of sporinite and resinite are consistent and distinctly different from each other attributed to the presence of a greater proportion of complex asphaltene and polar molecules in resinite gas chromatography of resinite rich coal shows sesquiterpenoid and diterpenoid peaks in the c14 17 range which are not present in resinite poor coal quantities of extracts suggest bitumen concentration below the threshold for effective source rocks 30 50 mg hydrocarbon g total organic carbon hc g toc saturate aromatic and pristane phytane pr ph ratios are different from values for nearby tertiary reservoired crude oil suggesting that the indio coals are too immature to source liquid hydrocarbons in the area however moderately high hi values 200 400 mg hc g rock may suggest some potential for naphthenic paraffinic oil generation where buried more deeply down stratigraphic structural dip extractable phenols and c20 alkanes are suggested as possible intermediates for acetate fermentation in microbial methanogenesis which may however be limited by poor nutrient supply related to low rainfall and meteoric recharge rate or high local sulfate concentration

geological controls on gas content distribution of coal seams in the kinik coalfield soma basin turkey abstract the miocene soma coal basin may be one of the most promising areas for low rank coalbed methane in turkey so far the coalbed methane potential of the coal seams in the kinik coalfield soma basin has not been adequately studied a systematic investigation was performed on the gas content distribution of the kp1 and km2 coal seams and its geological controls which has been based on the geological data and the experimental results of 84 coal samples taken from 37 coal exploration wells in the kinik coalfield soma basin samples were analyzed in terms of coal properties and gas content the gas content was measured by the direct method based on the canister desorption test the gas content of the kp1 and km2 coal seams range from 0 90 to 2 61 m3 t and 0 51 to 3 86 m3 t respectively on as received basis with increasing trend from west to east areas in both seams diffusivity values of the kp1 and km2 coal seams vary from 2 84 10 5 min 1 to 56 4 10 5 min 1 and from 0 64 10 5 min 1 to 54 3 10 5 min 1 respectively the gas content of the kp1 seam has not been correlated with the coal properties whereas the gas content of the km2 seam has positive correlation with fixed carbon content and gross calorific value and negative correlation with moisture and ash content normal faults are well developed in the study area play an important role at gas migration causing gas dissipation and reduced gas content of each coal seam in the northern part the low gas content may result from the combined effects of the geological structure thickness of overlying unit burial depth and coal thickness in the southern part the gas content of coal seams is controlled by the combined effects of relatively favorable factors including fewer normal faults thicker overlying unit high burial depth and thick coal seam the variation of the gas content for the coal seams is a comprehensive reflection of geological factors with each coal seam has its own pattern of gas distribution and this should be considered for the future coalbed methane exploration and development studies in soma basin

shape fabrics of particles in low concentration suspensions 2d analogue experiments and application to tiling in magma abstract jeffery s equations ascribe a theoretical cyclic nature to the shape fabric of non interacting rigid particles immersed in a viscous fluid undergoing simple shear flow this theoretical behaviour is confirmed at low shear strains 5 first experiment 134 identical particles or 1 second experiment 178 particles with two size classes then become stable at 17 first experiment and at more than 50 second experiment of the population of particles due to the contribution of the tiled particles the shape fabric becomes asymmetrical in its orientation distribution with a maximum lying above the shear plane the latter result provides a new shear sense indicator in addition to the statistical determination of the tiled features the study also suggests that crystalline fabrics in magmas could be acquired at high melt fractions i e early in the crystallization history of the magma

applications of inclusion behaviour models to a major shear zone system the nordfjord sogn detachment zone in western norway rigid inclusion models have reached a stage where one should be able to use them to obtain quantitative values from ductile shear zones we used natural data collected in three sites and combined analogue and theoretical modelling to assess vorticity strain nature of rigid inclusion matrix interface and confinement in the large scale ductile nordfjord sogn detachment zone nsdz of the caledonides of western norway our study shows that 1 the observed shape preferred orientation spo at higher structural levels of the nsdz at site 1 gjervika can be explained by simple shear pure shear simple shear ratio sr 0 associated with a slipping inclusion matrix interface 2 the observed spo at deeper structural levels of the nsdz at site 2 near sandane can be produced by simple shear associated with a significant amount of shortening across the shear zone sr z 1 acting upon rigid inclusions in slipping contact with the enclosing matrix 3 observed back rotated boudins deeper in the nsdz at site 3 biskjelneset can form in confined flow associated with a considerable amount of shortening across the shear zone sr 0 4 4 the observed tails of porphyroclasts indicate a minimum at least local strain of ca g z 20 5 the clasts in the studied shear zones strongly depart from jeffery s model jeffery g b 1922 the motion of ellipsoidal particles immersed in a viscous fluid proceedings of the royal society of london a102 161e179 the large scale extensional nsdz under investigation shows evidence of strain partitioning rocks vary from protomylonites to ultramylonites and the simple shear and pure shear components are heterogeneously distributed therefore we conclude that flow in the nsdz was very heterogeneous both at the kilometre and the metre scale however the present study suggests that the amount of shortening across the shear plane throughout the nsdz increases with depth and the flattening component contributes to exhumation of the eclogite facies rocks in its footwall 2007 elsevier ltd all rights reserved

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

carboniferous coals of the zonguldak basin northwest turkey implications for coalbed methane potential we investigated the carboniferous coals in the zonguldak basin northwest turkey using a multidisciplinary approach including petrographical and geochemical analyses gas adsorption and gas content measurements artificial maturation experiments on selected coals and one dimensional 1 d modeling of the basin evolution and hydrocarbon generation the main emphasis was set on the definition of coalbed methane cbm generation capability and adsorption capacity of the coals considering these properties of coals and the amount and composition of gas within the coal seams we carried out a comprehensive evaluation of the cbm potential of the basin three areas in the basin namely armutcuk zonguldak and amasra were investigated separately for their cbm potential from the standpoint of petroleum oil and or gas generation the coals in the armutcuk and amasra areas are located within the oil generation window the coals of the zonguldak area are located within the oil and gas generation window computer aided basin modeling using a basin specific kinetic data set of hydrocarbon generation from coals suggests that significant quantities of gas have been generated only in the zonguldak area modeling results also indicate that major gas generation from the base of the westphalian a kozlu formation in the zonguldak area occurred between 80 and 42 ma during the late cretaceous early eocene prior to basin inversion that started at 42 ma and continues at present the predicted amount of generated coalbed gas from coal seams in the gas generation zone is several times higher than the adsorption capacity of the respective seams a certain amount of this gas controlled by the adsorption capacity is stored within the coal seams where it is generated gas generated in excess of storage capacity obviously would have been expelled from the coal part of the expelled gas is accumulated in coal seams located above the gas generation zone however the coal seams within and above the gas generation zone are undersaturated with respect to their adsorption capacity the undersaturation is probably caused by remigration of gas that is desorbed because of pressure decrease during basin inversion of more than 2500 m 8203 ft over the last 42 m y the rest of the gas generated within the coal seams and expelled first because of the overflow of adsorption capacity and then because of the desorption during basin inversion has either migrated to source conventional gas reservoirs or has been lost to the surface during basin inversion because the basin has not been explored for conventional gas reservoirs a conclusive mass balance cannot yet be performed despite basin inversion and remigration of gas some coal seams still contain gas amounts of up to 10 cm 3 g of coal indicating a cbm potential

exhuming norwegian ultrahigh pressure rocks overprinting extensional structures and the role of the nordfjord sogn detachment zone 1 the nordfjord sogn detachment zone nsdz is widely cited as one of the primary structures responsible for the exhumation of norwegian ultra high pressure uhp rocks here we review data from the considerable volume of research describing this shear zone and compile a strikeparallel cross section along the nsdz from the solund basin in the south to the soroyane uhp domain in the north this cross section highlights several previously unrecognized patterns revealing a shear zone with top to the west asymmetric fabrics that 1 initiated at amphibolite facies 2 overprints metamorphic breaks and tectonostratigraphic contacts and 3 has a gradational continuum of muscovite cooling ages these patterns constrain the kinematic evolution of the nsdz and suggest a new three step model for the exhumation of norwegian u hp rocks the initial stages of exhumation were characterized by the rise of crustal rocks from u hp depths to the base of the crust by buoyancydriven mechanisms not specified in this paper mantle exhumation was followed by top to thewest normal sense displacement within a broad noncoaxial ductile shear zone near the base of the crust that overprinted tectonostratigraphic contacts formed previously during mantle exhumation in the final stages of crustal exhumation top w brittleductile detachments soled into and partially excised this ductile shear zone dropping the devonian basins into contact with rocks of varying tectonostratigraphic levels this new interpretation of the nsdz is significant as it accounts for the extreme crustal excision observed in western norway using three sequentially overprinting structures active at different stages of uhp rock exhumation citation johnston s m b r hacker and t b andersen 2007 exhuming norwegian ultrahigh pressure rocks overprinting extensional structures and the role of the nordfjord sogn detachment zone tectonics 26 tc5001

rotation of rigid elliptical cylinders in viscous simple shear flow analogue experiments we used experiments to investigate the behaviour of rigid elliptical cylinders embedded in a viscous fluid of finite thickness and for very small ratios s between shear zone width z and the shortest principal axis e2 of the ellipse that constitutes the base of the elliptical cylinder 3 5 s z e2 1 2 former theoretical and experimental work on the rotation of rigid inclusions immersed in a viscous matrix considered infinite shear zone thickness and or a very large ratio between shear zone thickness and inclusion size s 1 and concluded that inclusions rotate continuously and synthetically with the applied bulk simple shear flow except for inclusions with infinite axial ratio our results depart greatly from the analytical predictions experiments were carried out at constant shear zone thickness but variable s and degree of coupling at the inclusion matrix interface the results show that 1 confined inclusion rotation always deviates from theoretical predictions for infinite shear zone thickness even for synthetic rotation 2 the deviation in the angular velocity and or in the sense of rotation increases as s approaches 1 and antithetic rotation is possible from a position with ellipse longest axis parallel to the shear plane and 3 a slipping inclusion matrix interface greatly enhances deviation from theoretical predictions with antithetic rotations to as much as 20

heat flow in the gulf coastal plain forty four new heat flow values from panhandle florida southwestern georgia southern alabama mississippi and louisiana range from 13 mw m sup 2 0 3 hfu 1 hfu 1 mu cal cm sup 2 s sup 1 41 8 mw m sup 2 in florida and alabama to 88 mw m sup 2 2 1 hfu in northern louisiana in general the values depict the eastern gulf coastal plain as an area with low to normal continental heat flow that increases from east to west anomalously low heat flow 13 33 mw m sup 2 0 3 0 8 hfu characterizes northcentral florida southwestern georgia and southern alabama while in northern louisiana 13 measurement sites yield values ranging from 50 mw m sup 2 1 2 hfu to 88 mw m sup 2 2 1 hfu distinctive disruptions in the temperature depth profiles attributed to convective effects within aquifers are limited in magnitude and extent and do not alter the geothermal gradient computations the region of relatively high heat flux in northern louisiana is coincident with an area underlain by cenozoic alkalic igneous rocks of the monroe uplift and an abnormal concentration of radiogenic heat sources within that body is postulated as the cause of the thermal anomaly

fate of injected co2 in the wilcox group louisiana gulf coast basin chemical and isotopic tracers of microbial brine rock co2 interactions the 2800 sandstone of the olla oil field is an oil and gas producing reservoir in a coal bearing interval of the paleocene eocene wilcox group in north central louisiana usa in the 1980s this producing unit was flooded with co2 in an enhanced oil recovery eor project leaving 30 of the injected co2 in the 2800 sandstone post injection this study utilizes isotopic and geochemical tracers from co produced natural gas oil and brine to determine the fate of the injected co2 including the possibility of enhanced microbial conversion of co2 to ch4 via methanogenesis stable carbon isotopes of co2 ch4 and dic together with mol co2 show that 4 out of 17 wells sampled in the 2800 sandstone are still producing injected co2 the dominant fate of the injected co2 appears to be dissolution in formation fluids and gas phase trapping there is some isotopic and geochemical evidence for enhanced microbial methanogenesis in 2 samples however the co2 spread unevenly throughout the reservoir and thus cannot explain the elevated indicators for methanogenesis observed across the entire field vertical migration out of the target 2800 sandstone reservoir is also apparent in 3 samples located stratigraphically above the target sand reservoirs comparable to the 2800 sandstone located along a 90 km transect were also sampled to investigate regional trends in gas composition brine chemistry and microbial activity microbial methane likely sourced from biodegradation of organic substrates within the formation was found in all oil fields sampled while indicators of methanogenesis e g high alkalinity 13c co2 and 13c dic values and oxidation of propane were greatest in the olla field likely due to its more ideal environmental conditions i e suitable range of ph temperature salinity sulfate and iron concentrations

organic geochemical and petrographic characteristics of tertiary coals in the northwest sarawak malaysia implications for palaeoenvironmental conditions and hydrocarbon generation potential abstract tertiary coals from mukah and balingian coalfields in the northwest sarawak malaysia were investigated to evaluate their regional rank variation petroleum generative potential and to reconstruct the palaeoenvironment conditions during peat accumulation the tertiary coals are characterized by high total organic carbon contents toc and yield of bitumen extraction ranging from 31 3 to 55 9 wt and 25 724 9 92 143 7 ppm respectively meet the standard as a good source rock potential the mukah and balingian coals were generally plotted in an area of type iii kerogen and mixed type ii iii kerogens with hi values between 90 and 289 mg hc g toc whereby the coals were derived from plant materials of terrigenous origin this shows that the balingian coals are dominated by type iii terrigenous kerogen while mukah coals are dominated by type ii iii kerogens and are thus considered to be generate mainly gas prone and limited oil prone this is also supported by macerals composition and open system pyrolysis gas chromatography py gc the mukah and balingian coals are thermally immature in rang from lignite to sub bituminous c rank possessing huminite reflectance in the range of 0 26 0 39 this immaturity has a considerable influence on the proximate analysis particularly on relatively high moisture and volatile matter contents and relatively low fixed carbon content petrographically it was observed that the mukah and balingian coals are dominated by huminite with low to high amounts of liptinite and relatively low amounts of inertinite pointing to predominantly anaerobic deposition conditions in the paleomires with limited thermal and oxidative tissue destruction the palaeoenvironment conditions of the coals are generally interpreted as a lower deltaic plain wet peat swamp depositional setting which are generally characterised by low tpi and high gi values and are plotted on the marsh field of the diessel s diagram this is usually consistent with generate relatively high ash yield as is the case of the mukah and balingian coals

relationship between petrographic and chemical properties and coal seam geometry hance seam breathitt formation southeastern kentucky the upper hance coal seam in southeastern kentucy was used as a template to examine the spatial distribution of ash yield sulfur content and petrographic constituents relative to the geometry of the deposit geometric characteristics include thinning and splitting of the two main benches leaders and riders analytical data showed the thick non split portions of the coal body to be low in ash and sulfur as well as vitrinite content whereas the thinned and split margins were higher in ash sulfur and vitrinite content these relationships suggest that thick non split portions of the upper hance peat accumulated in areas isolated from detrital influx while thinner marginal peat was subject to intermittent flooding from adjacent channels marginal peat was derived from larger trees which flourished at the mire s edge in the presence of adequate nutrients whereas only stunted vegetation subsisting in the nutrient depleted center contributed to interior peat accumulation ponds formed on the sparsely vegetated mature surface of the bog s interior the petrographic and chemical character of the hance coal body is analogous to ombrogenous domed peats which characteristically contain higher concentrations of inorganics at the periphery of the deposit

pore characteristics of wilcox group coal u s gulf coast region implications for the occurrence of coalbed gas abstract pore characteristics of 27 subbituminous coal samples 16 mesh splits from the paleocene eocene wilcox group of north louisiana ouachita and caldwell parishes and south texas zavala county were examined in relation to desorbed gas content coal gas of the wilcox group is primarily biogenic in origin thermogenic gas also may be present in some areas on an as received basis desorbed gas contents range from 0 59 to 1 28 m 3 t for ouachita parish samples 0 37 to 5 19 m 3 t for the caldwell parish samples and 0 02 to 0 06 m 3 t for the zavala county samples for louisiana coal samples micropore surface area and volume are correlated to the desorbed gas content of the wilcox group coal correlations r 0 50 and 0 47 respectively suggesting that micropore surface area and volume are important in terms of gas holding capacity adsorption by micropores appears to be the primary form of gas storage for the louisiana coal samples micropore surface area and volumes also are strongly correlated with the carbon ash yield ratio r 0 97 and 0 94 respectively indicating that gas sorption occurs primarily on organic matter mineral matter appears to reduce the sorption capacity of the coal micropore width decreases with depth r 0 63 probably as the result of increasing pressure and coal rank with depth for the louisiana coal samples mesopore surface area is negatively correlated with the carbon ash yield ratio r 0 70 suggesting that mesopores are preferentially associated with mineral matter average mesopore size is correlated with desorbed gas r 0 80 for the relatively shallow ouachita parish samples average depth 441 m 1446 ft these results suggest that the permeability of the wilcox coal is greater in the shallow stratigraphic intervals compared to deeper intervals additionally mesopore size decreases with depth r 0 80 for ouachita parish coal samples negative correlations of gas with mesopore surface area r 0 74 and mesopore volume r 0 56 strongly suggest that gas is not adsorbed in mesopores and that free gas may be present in larger mesopores macropores or fractures of the wilcox coal results also suggest that moisture in ouachita parish samples is present in mesopores moisture in mesopores may have blocked gas adsorption the low gas south texas samples average depth 313 m 1026 ft are markedly different from the louisiana samples specifically micropore surface area and micropore volume are negatively correlated with desorbed gas for the texas samples r 0 21 and 0 36 respectively geologic or environmental conditions probably were not conducive to the generation or storage of microbial gas in the zavala county coals the geologic settings i e salinity of formation water groundwater recharge permeability of coal of each study area are important factors that need to be considered in relation to the potential for generation or storage of microbial gas in south texas tectonic stress may have led to a reduction in permeability in the wilcox group coal creating an unfavorable environment for the generation or preservation of microbial gas the subbituminous rank of the zavala coals is also too low for significant thermogenic gas generation to have occurred

stable positions of rigid objects in non coaxial flow a study in vorticity analysis abstract distortions of a homogeneous fabric which occur around rigid objects in rocks deformed by non coaxial ductile flow are useful to determine the sense of shear but also contain information on other aspects of the flow rigid objects in a non coaxial flow fall into two categories those which are permanently rotating and those which can reach stable positions at high finite strain the orientation of such immobilized objects with respect to eigenvectors of instantaneous flow is a function of the vorticity number of the flow the ratio of instantaneous stretches and the axial ratio of the object in naturally deformed rocks immobilized rigid objects may be recognized from the geometry of the surrounding fabric tails of recrystallized material around porphyroclasts in a mylonite rotate towards parallellism with the extensional eigenvector of the flow and the shape of tails reflects the rotational behaviour of the porphyroclast the axial ratio of immobilized porphyroclasts and their orientation with respect to the tails can theoretically be used to determine the vorticity number of the flow and deviations from isochoric plane strain in practice such an analysis is as yet difficult but a tentative example is given of the way in which the vorticity number can be calculated from a population of feldspar porphyroclasts in a quartzite mylonite from the french pyrenees

analogue modelling of the influence of shape and particle matrix interface lubrication on the rotational behaviour of rigid particles in simple shear abstract the rotational behaviour of a rigid particle embedded in a linear viscous matrix undergoing cylindrical simple shear couette flow was studied in 2d rock analogue experiments the influence of particle shape elliptical vs monoclinic aspect ratio and the nature of the matrix particle interface lubricated vs unlubricated was investigated both matrix pdms and lubricant liquid soap were linear viscous with a viscosity ratio of ca 10 4 without lubricant the rotational behaviour of all particles closely approximates the jeffery theory lubricated monoclinic particles with the long diagonal initially parallel to the shear direction show back rotation and approach a stable position lubricated elliptical particles initially parallel to the shear direction also show back rotation but only transiently stabilize weak planar zones in the matrix adjacent to unlubricated elliptical particles do not induce backward rotation in general for elliptical particles rotation rate as a function of orientation depends on axial ratio and thickness of the lubricant mantle for thick mantles initially 10 of the volume of the particle rotation rates are faster than jeffery theory for very thin mantles they are markedly slower compared with thick mantles particularly when the long axis is nearly parallel to the shear direction rotation rates are never strictly zero so true stabilization does not occur however for more elongate particles axial ratio 6 rotation rates are so slow that a very strong shape preferred orientation would develop in a lubricated elliptical particle population in experiments the volume of lubricant is constant and the thickness adjacent to the long side of the particle progressively decreases with increasing strain in natural examples of porphyroclast systems the weak mantle continually develops by recrystallization and or cataclasis of the rigid clast core and a steady state between production and thinning could be attained potentially leading to true stabilization for particles with a high axial ratio

rotation behaviour of rigid inclusions in multiple association insights from experimental and theoretical models many rocks are representative of inclusion matrix systems where rigid inclusions float on a ductile matrix the geological analogues of such inclusion matrix systems are theoretically modelled with the help of jeffery s 1922 theory in recent years there have been a number of reinvestigations on the rotational motion of rigid inclusions to account for some geological observations that are not yet predicted in models based on jeffery s theory adding to this effort this paper investigates the effects of 1 inclusion concentration and 2 the degree of coherence at the inclusion matrix interface on the rotation behaviour of rigid inclusions in a multiple inclusion system during simple shear deformation shear box experiments were run on models containing multiple identical elliptic cylinders of wax mimicking rigid inclusion embedded within putty representing ductile matrix two sets of experiments were performed with and without lubrication at the inclusion matrix interfaces each model had an isolated inclusion to reveal the variation of rotations of single and multiple inclusions increase in inclusion concentration results in contrasting rotation behaviour of isolated and multiple inclusions initially oriented parallel to the shear direction when the interfaces were not lubricated inclusions in multiple association rotated antithetically whereas the isolated one almost remained stationary in models wherein the inclusion matrix interfaces were lubricated with liquid soap both isolated and multiple inclusions rotated antithetically but the isolated inclusion rotated at a lower rate with increasing inclusion concentration the difference in the rates of antithetic rotation between isolated and multiple inclusions tended to be larger in both lubricated and non lubricated conditions the sense of rotation of isolated as well as multiple inclusions initially oriented perpendicular to the shear direction was always synthetic irrespective of the nature of the interface lubricated or non lubricated however the instantaneous rotation rates of inclusions in multiple association were higher than that of the isolated inclusions disposed in the same orientation rotation of inclusion in an inclusion matrix system is basically induced by the traction exerted by the flowing matrix on the surface of the inclusion during deformation employing a hydrodynamic model it is shown that mutual mechanical interaction among inclusions which is a function of inclusion concentration modifies the stresses at the inclusion matrix interface to a large extent moment calculations reveal that inclusions oriented parallel to the shear direction experience an antithetic moment in response to the normal stress components the magnitude of which increases with increasing inclusion concentration this implies that rotation of shear parallel inclusions in antithetic sense is favoured by higher inclusion concentration on the other hand inclusions oriented perpendicular to shear direction experience a moment that induces synthetic rotation the magnitude of the synthetic moment is larger for larger inclusion concentration leading to increase in the rate of synthetic rotation using the theoretical model the moments are calculated as a function of the aspect ratio of inclusions and the inferences based on this moment calculation are complemented with experimental findings

variation in permeability with lithotype and maceral composition of cretaceous coals of the canadian cordillera abstract the permeability of high and medium volatile bituminous cretaceous coal at the megascopic and microscopic scale is investigated utilizing a pressure decay permeameter the order of decreasing permeability with lithotype is bright average 4 1 md banded 0 79 md fibrous 0 50 md banded dull 0 14 md and dull 0 016 md bright coals are the most permeable because of associated macro fracturing cleat banded dull coal permeability generally increases with increasing vitrinite content the lowest permeabilities occur in dull coals with a high mineral and inertinite content fibrous coal has a higher permeability than dull coal of the same rank due to the abundance of macroporous fusinite in fibrous coal dull coal permeability decreases with an increase in rank but these results are overshadowed by compositional variability between samples pressure decay measurements are more reliable for dull lithotypes as these lithotypes do not fracture as easily during sample preparation although measured permeabilities are optimistic due to the relaxation of stress upon exposure of coal to atmospheric pressure the results obtained are representative of the range of permeabilities of coal lithotypes and provide insight into the variability in permeability that may exist at high effective stress in the subsurface

deformation around rigid particles the influence of slip at the particle matrix interface abstract theoretical and previous experimental studies of rigid particle structures have only considered the behaviour of rigid particles for which the interface between particle and matrix is coherent in natural rocks the boundary behaviour may cover the whole range from free slip to complete coherence examples where slip may be promoted include crack seal deformation during the development of pressure shadows core mantle structures where the mantle is composed of much weaker fine recrystallized material and crystallizing magmas or partially molten rocks where grain boundaries are lubricated by the melt phase analogue scale model experiments have been performed under pure shear and simple shear conditions to compare the particle rotation and the flow in the matrix for both slipping and non slipping particle matrix interfaces when slip does occur particles rotate faster in pure shear and slower in simple shear than for non slip leading to the more rapid development of a shape preferred orientation the preferred orientation tends to be bimodal in simple shear flow the flow and finite strain patterns in the matrix are also strongly influenced by slip at the interface and porphyroclast systems can develop geometries with ambiguous or contradictory shear senses dependent on the original particle orientation in multi particle experiments slip on the interfaces enhances strong strain localization in non linear viscous material to produce patterns very similar to natural s c fabrics

controls on methane sorption capacity of indian coals details of methane sorption properties of some indian coals ranging in rank from high volatile bituminous c 0 62 ro max to medium volatile bituminous coal 1 46 ro max were investigated to determine the major factors influencing gas adsorption capacity and desorption rate variables studied included moisture content mineral matter content rank and coal type maceral composition adsorption isotherm analysis of dry coals showed that adsorption capacity followed a second order polynomial trend with rank equilibrium moist samples showed a linear increase in adsorption capacity with rank and had a significantly reduced adsorption capacity compared to the dry coals with the reduction being related to the moisture content mineral matter acted as a simple diluent to the gas adsorption capacity of the coals and was found to be nonadsorbent adsorption capacity moist was reduced by 0 32 cm3 g 10 ft3 gas t for every 1 increase in the ash yield bright and dull coal lithotypes showed strong separation in their adsorption capacities on an as analyzed basis with the bright coals adsorbing greater quantities of gas on a dmmf basis however no relationship was observed between coal type and gas storage capacity comparison of maceral composition with adsorption capacity dry confirmed this observation effective diffusivity de of methane through the coal was seen to be affected by coal type and rank effective diffusivity de decreased as rank increased which is related to the increasing microporous nature of the coal bulk coals tested had 2 3 times larger effective diffusivities than bright coals and dull coals had intermediate rates the larger de values for the bulk coals may be related to the presence of collodetrinite coupled with mineral matter which acts as higher permeability pathways for the gas compared with the high ash dull coals dominated by inertinite macerals differences were noted with similar age permian australian coals where methane adsorption capacities were larger and coal type had a stronger influence on adsorption capacity begin page 202

influence of lamprophyre sills on coal metamorphism coalbed gas composition and coalbed gas occurrence in the tongxin minefield datong coalfield china abstract magmatic intrusions in coal bearing strata can significantly change the physical and chemical properties of the intruded coal lamprophyre intrusions are extensive in coal seams 3 5 and 8 of the carboniferous permian coal bearing strata in the southeastern and southwestern regions of the tongxin minefield datong coalfield china they appear primarily as sills of varying magnitudes with thicknesses ranging from 0 15 to 23 51 m in this area coals can be classified as unaffected normal geothermal gradient and intrusion affected unaffected coals are of high volatile bituminous rank with values of maximum vitrinite reflectance ranging from 0 7 to 0 9 whereas intrusion affected coals have values of maximum vitrinite reflectance ranging from 0 9 to 7 2 a marked decrease in the degree of coalification can be observed with increasing distance from the lamprophyre intrusions near the intrusion coal contacts high volatile bituminous coals have been thermally altered to form natural coke the carbonate contents in intrusion affected coals 0 2 46 1 are significantly higher than those of the unaffected coal 0 2 0 the coalbed gases of coal seams 3 5 and 8 are highly variable in both their molecular compositions and overall gas contents their co2 volumes vary from 0 01 to 6 55 m3 t daf higher co2 values are found in the coals affected by intrusions and roughly decrease with increasing distance from the lamprophyre igneous intrusions toward the central region of the minefield these variations in gas compositions are mainly related to magmatic activity the coalbed gas contents in coal seams 3 5 and 8 range from 1 48 to 16 43 m3 t on a dry ash free basis the positive correlation observed between gas content and the ratio of co2 ch4 co2 occurs only in intrusion affected coals lamprophyre intrusions have negative effects on ch4 content in the study area since co2 has a higher adsorption capacity than ch4 c2h6 and n2 the injection of gaseous co2 derived from magmatic intrusions can effectively displace ch4 rich reservoir gas in addition there is a positive correlation between ash content and gas content on a dry ash free basis ash content is positively correlated with the ratio of co2 ch4 co2 occurring only in intrusion affected coals massive secondary carbonates that filled in the cleats act as small scale impermeable seals which provide a sealing effect both on gas contents and gas compositions during uplift

the producibility of coalbed methane from wilcox coals in louisiana abstract the producibility model for coalbed methane contains six controls they are 1 gas content 2 permeability 3 tectonic and structural setting 4 depositional setting 5 hydrology and 6 coal rank and gas generation gas content in central louisiana coalbed methane basin celcom coals was proven in 1989 when the torch operating company perforated the no 3 greer well sec 21 t14n r4e the well immediately began flowing gas 50 000 cfg d and 65 bbls water d the 3 greer flowed approximately 2 8 mmcfg over a three month period and was plugged permeability is indicated by the separation approximately 2 ohms of the 16 short normal and the 40 conductivity curves in most but not all e logs strongly developed spontaneous self potential sp in many e logs further indicates permeability tectonic and structural setting the celcom is situated between the sabine uplift and lasalle arch on the west southwest the d arbonne platform on the northwest and the monroe uplift on the northeast this location effected control on the wilcox depositional environments depositional setting the coals of the celcom were likely deposited on top of abandoned delta sequences prograding gulfward hydrology the coals of the celcom do not outcrop at the surface and therefore are not recharged with percolating ground water which must be removed during production the thick cane river shale section overlying the wilcox separates the brackish and fresh water sands of the sparta and cockfield from the saline waters of the wilcox the coals have been compacted through the burial process and the amount and type of contained water is not known although it is probably salt water coal rank and gas generation cores taken in equivalent sections in concordia parish louisiana reveal a vitrinite reflectance value of ro 0 45 a coal rank of bituminous

coalbed methane characteristics of gates formation coals northeastern british columbia effect of maceral composition the majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite rich coals however western canadian coals are more inertinite rich than those of the western united states and are shown to differ in gas adsorption characteristics the influence of maceral composition upon gas adsorption characteristics of medium volatile coal samples from the middle cretaceous gates formation of northeastern british columbia was investigated lithotype coal facies samples were analyzed for surface area maceral and mineral composition and methane adsorption standard coal analyses were also performed proximate low temperature ash and equilibrium moisture the vitrinite content of the samples analyzed ranges from 18 to 95 vol min ral matter free the ash yield varies from 4 4 to 33 7 wt both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms on a mineral matter free basis the amount of methane adsorbed generally increases with vitrinite enrichment the lowest methane adsorption occurs in the sample with the highest inertinite content carbon dioxide surface areas of the lithotypes range from 87 to 176 m2 g on a raw coal basis and from 99 to 184 m2 g on a mineral matter free basis surface area generally decreases with increased mineral matter content and increases with increased vitrinite content the increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite vitrinite is predominantly microporous whereas inertinite is meso to macroporous the monolayer volumes of carbon dioxide as calculated from the dubininradushkevich equation are higher than those of methane as determined from the langmuir equation but are correlated the methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit

the characteristics of coal reservoir pores and coal facies in liulin district hedong coal field of china the composition rank coal facies and coal pore structure characteristics of 15 coal samples were investigated systemically using methods of lithotype analysis maceral analysis proximate analysis mercury porosimetry analysis and nitrogen adsorption analysis these samples were directly collected from the working faces of no 4 8 9 seams in liulin district eastern margin ordos basin china four types of paleoenvironment including a wet forest swamp an intergradation forest swamp a drained forest swamp and a fresh water peat swamp were distinguished by lithotype and merceral analysis an r cluster analysis was performed to demonstrate the correlations between the coal facies and the pore structures the results showed that coal rank is the primary factor affecting the development of micropores and transition pores whereas coal facies control the development of seepage pores in similar coalification conditions especially in a local district and in a seam this work suggests that the vertical variations observed in coal properties macerals vitrinite reflectance mineral matters porosity bet specific area pore size distributions and pores connectivity were controlled by groundwater level fluctuations indicated by variations in the ground water index gwi in the ancient mires due to different accommodation and peat accumulation rates comparison of the porosity characteristics of various coal reservoirs developed in various coal facies indicates that wet forest swamp facies is favorable to the formation of a coalbed methane reservoir because of reasonable pore structure and good connectivity intergradation forest swamp facies rank the second and drained forest swamp facies are less advantageous

experimental observations on the effect of interface slip on rotation and stabilisation of rigid particles in simple shear and a comparison with natural mylonites for axial ratios r not vert similar3 porphyroclasts from three mylonites all show a very strong spo with the long axis of the best fit ellipse at an antithetic angle of 5 10 to the shear direction this is more consistent with a stable end orientation than with the transient fabrics predicted by theory for elliptical rigid particles in simple shear the cause of this divergence is investigated in a series of high simple shear strain 15 analogue experiments performed in a ring shear machine couette flow using a linear viscous matrix pdms the rotational behaviour of elongate r not vert similar5 rigid particles with elliptical and rhomboidal shapes comparable with the natural examples is modelled for both coherent and slipping particle matrix interfaces interface slip causes a dramatic reduction in the rotation rate of the elliptical particle compared with theory when the long axis is close to the shear direction but not stabilisation interface slip does result in stabilisation of the rhomboidal particle with the long diagonal oriented at a small antithetic angle to the shear direction for monoclinic particles mirror image shapes referred to here as types 1 and 2 show different rotational behaviour for the type 1 particle with a shape comparable to porphyroclast systems and mica fish the long side rotates asymptotically into parallelism with the shear direction natural examples of type 1 particles such as hornblende and olivine porphyroclasts measured from the finero mylonites southern alps show a very strong preferred orientation for r not vert similar3 with the long side parallel or at a small 5 antithetic angle to the mylonitic foliation for type 2 particles the short side stabilises close to the shear direction or at a small synthetic angle as also observed for sillimanite porphyroclasts from the mont mary mylonites western alps in this natural case stabilisation of the short sides is against an extensional crenulation cleavage rather than the mylonitic foliation the analogue experiments establish that interface slip is one mechanism for stabilisation of elongate rhomboidal particles in natural examples decoupling from the matrix may be affected by extensional crenulation cleavage or c planes in s c fabrics

kinematic behaviour of an interface and competence contrast analogue models with different degrees of bonding between deformable inclusions and their matrix abstract in a system composed of a ductile matrix with a particle included in it the deformation of the matrix the displacement field and the rotation and the deformation of the block are related to the viscosity ratio between block and matrix and also to the degree of bonding between the matrix and the block in this paper belemnites from the lower lias of the alps provide a natural example of moderately deformed objects included in a slaty matrix they are compared with analogue models made of paraffin in which a long block of a more competent paraffin is included depending on the degree of bonding between matrix and object the same block appears to be deformable or quite rigid with a high degree of bonding the strain refraction observed corresponds to the viscosity ratio between the block and the matrix when the degree of bonding is weak the block is quite undeformed its rotation is great and the deviation of the strain in the matrix is analogous to that observed around a fault the kinematic conditions appear to have a greater effect on the finite strain than the viscosity ratio of the materials

bituminite a tem view abstract an illinois coal high volatile bituminous b of carboniferous age containing typical bituminite has been examined by transmission electron microscopy tem to supplement observations with the light microscope with tem the bituminite has a fine fairly regular structure including voids of a characteristic shape this structure is almost certainly inherited from a botanical precursor and is thought to represent much altered remains of former colonies of algae probably green algae the present remains contain abundant lipid rich globules and probably also include matter of algal and bacterial origin which cannot be resolved even at tem resolutions

geological controls on coalbed methane reservoir capacity and gas content the influence of coal composition and rank on coalbed methane reservoir capacity gas content and gas saturation have been investigated for a series of australian canadian and united states coals globally there is no or little correlation between coal rank and methane adsorption capacity as commonly assumed although in particular basins there are general trends with rank and composition micropore1 capacity and surface area determined from low pressure carbon dioxide adsorption isotherms 0 c decrease and then increase with rank passing through a minimum in the high volatile bituminous coal rank there is no consistent variation in modal micropore size or size distribution with rank for suites of isorank coals there is a poor permian bulli and wongawilli seams australia to good positive correlation gates formation coal seams lower cretaceous canada between vitrinite content and methane adsorption capacity dry ash free and as received bases for each isorank coal suite there is a good correlation between micropore capacity and abundance of vitrinite and high pressure methane adsorption capacity comparison of coals of similar composition but from different isorank suites indicates however that the coals with the highest methane adsorption capacity do not necessarily have the highest micropore capacity such results are counterintuitive most pore volume available for methane adsorption is generally assumed to be microporosity it is suspected that moisture prevents methane from accessing some microporosity or competes with methane for adsorption space carbon dioxide micropore capacity which is performed on a dry basis may thus not reflect the microporosity available for gas adsorption in moisture equilibrated coals alternatively because of differing physical and chemical properties of carbon dioxide and methane apparent microporosity available to carbon dioxide due to greater energy of adsorption may not be available to methane total desorbed gas from canister analyses of sydney basin australian coals suggests that most coals are under saturated for a small data set the degree of saturation is negatively correlated with permeability r 0 78 suggesting preferential gas leakage from the higher permeability coals which are vitrite rich some degree of under saturation is probably the result of increased reservoir capacity as a consequence of uplift of the coal seams and thus lower temperatures following gas generation rates of desorption are correlated with total gas content r 0 79 but do not correlate with rank or any compositional parameter

the influence of depositional environments on coal petrographic composition of the lower kittaning seam western pennsylvania abstract lateral variations in maceral composition of the lower kittanning seam can be explained in terms of differential preservation of plant materials which is influenced by the ph eh of water within the peat swamp and by the rate of subsidence within the central part of the basin high telocollinite contents are observed this type of vitrinite represents large well preserved pieces of woody tissue whose preservation was favored by rapid burial towards the margins of the basin high desmocollinite contents are seen slower burial combined with the influx of neutral oxygenated fresh water permitted decomposition of the precursor materials producing this highly degraded type of vitrinite vertical variations in telocollinite and desmocollinite content can also be related to burial rates and ph eh conditions within the swamp throughout the basin high telocollinate contents observed in the lower part of the seam resulted from rapid burial under relatively low ph conditions continued high rates of subsidence led to an influx of neutral ph oxidizing waters associated with the encroaching marine environment under these new conditions more degradation of plant tissues occurred producing the high desmocollinite contents observed in the upper part of the seam this effect was most pronounced in the center of the basin an alternative explanation would be a change in vegetation type in response to the changing conditions the high desmocollinite content would then reflect a shift to a community dominated by smaller possibly herbaceous plants in addition to a change in vitrinite type towards the top of the seam a decrease in total vitrinite content and increases in total liptinite and inertinite contents are observed the increase in liptinite content is due to either 1 the higher resistance to decomposition of liptinite precursor materials when compared to vitrinite precursors in the more neutral conditions or 2 a change from a dominantly arborescent vegetation to a more herbaceous one the increase in inertinite results from an increase in transported material inertodetrinite and or an increase in the formation of inertinite macerals such as degrado fusinite possibly in response to the encroaching marine conditions an additional control on maceral composition is the level of metamorphism of the coal total liptinite content decreases towards the southeast in this area the coal has attained a sufficiently high rank that the reflectance of liptinite macerals approaches that of vitrinite thus making their identification difficult

biogenic origin of coalbed gas in the northern gulf of mexico coastal plain u s a new coal gas exploration and production in northern louisiana and south central mississippi gulf of mexico basin is focused on the wilcox group paleocene eocene where the depth to targeted subbituminous c to high volatile c bituminous coal beds ranges from 300 to 1680 m and individual coal beds have a maximum thickness of about 6 m total gas content generally excluding residual gas of the coal beds ranges from less than 0 37 cm3 g as analyzed or raw basis 1 2 cm3 g dry ash free basis daf at depths less than 400 m to greater than 7 3 cm3 g as analyzed basis 8 76 cm3 g daf in deeper 1 500 m parts of the basin about 20 wilcox coal gas wells in northern louisiana produce from 200 to 6485 m3 of gas day and cumulative gas production from these wells is approximately 25 million m3 as of december 2006 u s geological survey assessment of undiscovered technically recoverable gas resources in the gulf of mexico coastal plain including northern and south central mississippi indicates that coal beds of the wilcox group contain an estimated mean total 109 3 million m3 3 86 trillion ft3 of producible natural gas to determine the origin of the wilcox group coal gases in northern louisiana samples of gas water and oil were collected from wilcox coal and sandstone reservoirs and from under and overlying late cretaceous and eocene carbonate and sandstone reservoirs isotopic data from wilcox coal gas samples have an average 13cch4 value of 62 6 vpdb relative to vienna peedee belemnite and an average dch4 value of 199 9 vsmow relative to vienna standard mean ocean water values of 13cco2 range from 25 4 to 3 42 vpdb produced wilcox saline water collected from oil conventional gas and coalbed gas wells have dh2o values that range from 27 3 to 18 0 vsmow these data suggest that the coal gases primarily are generated in saline formation water by bacterial reduction of co2 shallow 150 m wilcox coal beds containing freshwater have little or no biogenic gas molecular and isotopic analyses of gas samples collected from conventional gas and oil wells suggests that both biogenic and thermogenic gases are present in and adjacent to the wilcox intervals that contain biogenic coal gases oil probably sourced from thermally mature down structural dip parts of the wilcox group is produced from sandstones within the coal bearing interval gas chromatograms of c10 saturated hydrocarbons from wilcox oils show a depletion of n alkanes probably resulting from biodegradation of the oil isotopic composition of the gases associated with the oils is of mixed themogenic and biogenic origin average 13cch4 44 4 vpdb and average dch4 182 4 vsmow

influence of a low viscosity layer between rigid inclusion and viscous matrix on inclusion rotation and matrix flow a numerical study abstract we have used 2 d finite element modelling to investigate the influence of a permanent low viscosity layer between matrix and inclusion on matrix flow and inclusion rotation under viscous simple shear flow rigid inclusions of different shape circle square ellipse lozenge rectangle and skewed rectangles and aspect ratio r were used the calculated matrix flow pattern is neither bow tie nor eye shaped it is a new flow pattern that we call cat eyes shaped which is characterized by i straight streamlines that slightly bend inwards at the inclusion s crests ii elongate eye shaped streamlines on each side of the inclusion iii stagnation points in the centre of the eyes iv absence of closed streamlines surrounding the inclusion v changes in flow configuration with inclusion orientation the lines of flow reversal bend and tilt closed streamline circuits may disappear and streamlines may bend outwards at the inclusion s crests concerning inclusion rotation the numerical results show that i a low viscosity layer lvl makes inclusions with r 1 rotate synthetically but the rotation rate depends upon shape circle or square and orientation therefore shape matters in the slipping mode ii all studied shapes with r 1 rotate antithetically when starting with the greatest principal axis e 1 parallel to the shear direction 0 iii rotation is limited because there is a stable equilibrium orientation se for all studied shapes with r 1 iii there is also an unstable equilibrium orientation ue and both se and ue depend upon inclusion s r and shape the present numerical results closely agree with previous results of analogue experiments with a permanent low viscosity interface only minor deviations related with small shape differences were detected

controls on the geometry of tails around rigid circular inclusions insights from analogue modelling in simple shear abstract we used analogue modelling to investigate the factors controlling tail geometry in porphyroclast systems results show that 1 inclusions can develop in both slipping and non slipping modes but inclusions only form in the latter 2 inclusions develop when the mantle production rate is constant and the mantle is transected by the separatrix inclusions form when the mantle is initially outside the separatrix and later comes inside this line 3 in the slipping mode the wedge shaped tail of inclusions always has a straight external surface parallel to the shear plane whereas in the non slipping mode the external surface is curved inwards external embayments 4 together with earlier theoretical results and inclusions always show stair stepping of tails when embedded in a viscous matrix under homogeneous simple shear deformation 5 maximum stair stepping occurs in the slipping mode and is at least equal to the inclusion diameter if our models bear significant similarity to nature then i the straight or curved character of inclusions could mean that they had respectively a slipping or non slipping interface with the surrounding recrystallized matrix and ii inclusions may result from shear deformation under retrogressive metamorphic conditions in thrust systems

the middle devonian basins of western norway sedimentary response to large scale transtensional tectonics abstract the devonian basins of western norway were formed during late to post orogenic extension of overthickened caledonian crust the basins are situated in the hanging wall of the extensional nordfjord sogn detachment zone nsdz and display extensional half graben geometries in sections parallel to the local direction of principal extension based on overall facies configurations paleocurrent patterns and intrabasinal structures we infer an anticlockwise rotation of the syndepositional extension direction from nw se in the south solund basin to wsw ene in the north hornelen basin the axes of folds that are roughly parallel to the local extension direction are rotated correspondingly the kvamshesten basin is located between the solund and hornelen basins sedimentological and structural data show evidence of an early southeastwards tilt direction followed by a more eastwards tilt and associated e w flowing paleodrainage correspondingly nw se trending folds and reverse faults are superposed by e w trending ones at low to intermediate stratigraphic levels the variations in apparent tilt direction for the basins together with variations in intrabasinal structure is interpreted to reflect an anticlockwise rotation of the regional syndepositional strain field the above observations and inferences indicate that the devonian basins in western norway formed in a strain field dominated by regional transtension accommodated by extension along the nsdz and sinistral strike slip along orogen parallel shear zones and faults to the north of the basins alternatively nw directed extension preceded the introduction of a sinistral strike slip component the models are in accordance with recent work carried out in the footwall of the nsdz and illustrates the tectono sedimentary response to a complex interplay between extension and strike slip that appears to have been fundamental in the late stage disintegration of the caledonian orogen

effect of mechanical interactions on the development of shape preferred orientations a two dimensional experimental approach abstract modifications in the development of preferred orientations of rigid particles due to mechanical interactions between particles are studied experimentally in two dimensions experiments in both pure shear and simple shear were performed and the results analysed using an easy and fast new automatic method for increased concentration of rigid particles the rotation of individual particles may be slowed down or even stopped due to collisions or disturbance of the flow in the matrix caused by neighbours in coaxial flow the fabric intensity is consequently reduced in simple shear flow the fabric evolution is no longer cyclic the intensity is on average weaker and the fabric axis rotates asymptotically toward the shear plane in the case of preferred orientations of particles having a low aspect ratio 2 5 the fabric rotates through the shear plane then undergoes a reverse rotation and rotates toward the shear plane again in the light of these experimental results we emphasize that quantification of finite strain based on such fabrics may lead to significant underestimates and calculated values should be taken as minimum estimates the kinematic significance of concentrated rigid particle preferred orientations in rocks is modified by interactions between particles techniques for qualitative or quantitative kinematic analysis may become unreliable for simple shear flows the concentrated population fabrics show an angular behaviour close to that of passive markers they tend to align parallel to the shear plane in simple shear flow