snowdrift landscape patterns an arctic investigation between 2012 and 2018 we mapped near peak seasonal snow depths across two swaths covering 126 km in northern alaska using aerial structure from motion photogrammetry and lidar surveys the surveys

fault zone architecture of the san jacinto fault zone in horse canyon southern california a model for focused post seismic fluid flow and heat transfer in the shallow crust abstract we report results of a new study of the architecture of the san jacinto fault zone in horse canyon california where stream incision has exposed a nearly continuous outcrop of the fault zone at 0 4 km depth the fault zone at this location consists of a fault core transition zone damage zone and tonalitic wall rocks we collected and analyzed samples for their bulk and grain density geochemical data clay mineralogy and textural and modal mineralogy progressive deformation within the fault zone is characterized by mode i cracking subsequent shearing of already fractured rock and cataclastic flow grain comminution advances towards the strongly indurated cataclasite fault core damage progression towards the core is accompanied by a decrease in bulk and grain density and an increase in porosity and dilational volumetric strain palygorskite and mixed layer illite smectite clay minerals are present in the damage and transition zones and are the result of hydrolysis reactions the estimated percentage of illite in illite smectite increases towards the fault core where the illite smectite to illite conversion is complete suggesting elevated temperatures that may have reached 150 c chemical alteration and elemental mass changes are observed throughout the fault zone and are most pronounced in the fault core we conclude that the observed chemical and mineralogical changes can only be produced by the interaction of fractured wall rocks and chemically active fluids that are mobilized through the fault zone by thermo pressurization during and after seismic events based on the high element mobility and absence of illite smectite in the fault core we expect that the greatest water rock ratios occur within the fault core these results indicate that hot pore fluids circulate upwards through the fractured fault core and into the surrounding damage zone though difficult to constrain we speculate that the site studied during this investigation may represent the top of a narrow ephemeral hydrothermal circulation cell that dissipates heat generated from rupture events at deeper levels 4 km

wind borne redistribution of snow across an antarctic ice rise redistribution of snow by the wind can drive spatial and temporal variations in snow accumulation that may affect the reconstruction of paleoclimate records from ice cores in this paper we investigate how spatial variations in snow accumulation along a 13 km transect across lyddan ice rise antarctica are related to wind borne snow redistribution lyddan ice rise is an approximately two dimensional ridge which rises about 130 m above the surrounding ice shelves local slopes on its flanks never exceed 0 04 despite this very smooth profile there is a pronounced gradient in snow accumulation across the feature accumulation is highest on the ice shelf to the east climatologically upwind of the ice rise and decreases moving westward with the lowest accumulation seen to the west climatologically downwind of the ice rise crest superimposed on this broad scale gradient are large 20 30 localized variations in accumulation on a scale of around 1 km that appear to be associated with local variations in surface slope of less than 0 01 the broad scale accumulation gradient is consistent with estimates of wind borne redistribution of snow made using wind speed observations from three automatic weather stations the small scale variability in accumulation is reproduced quite well using a snow transport model driven by surface winds obtained from an airflow model providing that both the wind shear and static stability of the upwind flow are taken into account we conclude that great care needs to be exercised in selecting ice core sites in order to avoid the possibility of blowing snow transport confounding climate reconstructions

continuous hydrocarbon accumulation over a large area as a distinguishing characteristic of unconventional petroleum the ordos basin north central china abstract global petroleum exploration is currently undergoing a strategic shift from conventional to unconventional hydrocarbon resources unconventional hydrocarbons in tight reservoirs show characteristics distinct from those of conventional hydrocarbon sources hosted in structural and stratigraphic traps the characteristic features include the following a hydrocarbon source and reservoir coexist porosity and permeability are ultra low nano pore throats are widely distributed hydrocarbon bearing reservoir bodies are continuously distributed there is no obvious trap boundary buoyancy and hydrodynamics have only a minor effect and darcy s law does not apply phase separation is poor there is no uniform oil gas water interface or pressure system and oil or gas saturation varies examples of unconventional hydrocarbon accumulations are the mesozoic tight sandstone oil province and the upper paleozoic tight sandstone gas province in the ordos basin north central china generally continuous hydrocarbon accumulation over a large area is a distinguishing characteristic of unconventional hydrocarbon sources because of the great potential of unconventional petroleum resources it is believed that research on such resources will be at the forefront of the future development of petroleum geology

nanocoatings of clay and creep of the san andreas fault at parkfield california mudrock samples were investigated from two fault zones at 3066 m and 3296 m measured depth md located outside and within the main damage zone of the san andreas fault observatory at depth safod drillhole at parkfield california all studied fault rocks show features typical of those reported across creep zones with variably spaced and interconnected networks of polished displacement surfaces coated by abundant polished films and occasional striations electron microscopy and x ray diffraction study of the surfaces reveal the occurrence of neocrystallized thin film clay coatings containing illite smectite i s and chlorite smectite c s minerals 40 ar 39 ar dating of the illitic mix layered coatings demonstrated miocene to pliocene crystallization and revealed an older fault strand 8 1 3 ma at 3066 m md and a probably younger fault strand 4 4 9 ma at 3296 m md today the younger strand is the site of active creep behavior reflecting a possible re activation of these clay weakened zones we propose that the majority of slow fault creep is controlled by the high density of thin

patterns of mineral transformations in clay gouge with examples from low angle normal fault rocks in the western usa abstract neoformed minerals in shallow fault rocks are increasingly recognized as key to the behavior of faults in the elasto frictional regime but neither the conditions nor the processes which wall rock is transformed into clay minerals are well understood yet understanding of these mineral transformations is required to predict the mechanical and seismogenic behavior of faults we therefore present a systematic study of clay gouge mineralogy from 30 outcrops of 17 low angle normal faults lanf s in the american cordillera to demonstrate the range and type of clay transformations in natural fault gouges the sampled faults juxtapose a wide and representative range of wall rock types including sedimentary metamorphic and igneous rocks under shallow crustal conditions clay mineral transformations were observed in all but one of 28 faults one fault contains only mechanically derived clay rich gouge which formed entirely by cataclasis clay mineral transformations observed in gouges show four general patterns 1 growth of authigenic 1m d illite either by transformation of fragmental 2m 1 illite or muscovite or growth after the dissolution of k feldspar illitization of fragmental illite smectite is observed in lanf gouges but is less common than reported from faults with sedimentary wall rocks 2 retrograde diagenesis of an early mechanically derived chlorite rich gouge to authigenic chlorite smectite and saponite mg rich tri octahedral smectite 3 reaction of mechanically derived chlorite rich gouges with mg rich fluids at low temperatures 50 150 c to produce localized lenses of one of two assemblages sepiolite saponite talc lizardite or palygorskite chlorite quartz and 4 growth of authigenic di octahedral smectite from alteration of acidic volcanic wall rocks these transformation groups are consistent with patterns observed in fault rocks elsewhere the main controls for the type of neoformed clay in gouge appear to be wall rock chemistry and fluid chemistry and temperatures in the range of 60 180 c

origins and fates of h2s in the cambrian and ordovician in tazhong area evidence from sulfur isotopes fluid inclusions and production data abstract gases oils solid bitumen samples and fluid inclusions were analyzed for chemical composition and 13 c and 34 s values and production data were collated to elucidate the origin and fates of the h 2 s in the tazhong area the h 2 s in the ordovician was measured to have 34 s values from 12 1 to 23 4 which are significantly lighter than the counterpart in the cambrian 33 0 indicating that the h 2 s did not migrate from the cambrian but may have been derived from thermochemical sulfate reduction in situ as partially supported by 12 c rich co 2 in fluid inclusions and tsr calcites with 13 c values from 3 6 to 17 7 in the ordovician the h 2 s rich gas subsequently mixed with h 2 s poor 13 c rich methane dominated gas as indicated by the roughly negative correlations of h 2 s content to dryness and gas oil ratio and ch 4 from fluid inclusions having 13 c values 1 2 3 6 lighter than the associated free gas the h 2 s has been dissolved in formation water precipitated as pyrite and incorporated into oils and solid bitumens resulting in the generation of alkylthiolanes alkylthiols and alkyl 2 thiaadamantanes and increase in 34 s values and s c ratios of the solid bitumen the content of h 2 s produced from the water intervals or petroleum water transition zones is significantly contributed from exsolved gas and thus higher than that of the gas cap gas in the reservoirs thus h 2 s contents cannot be used to indicate tsr extents in the ordovician however in the cambrian whole oil and saturates show positive shifts in 13 c values with increasing h 2 s contents indicating that the h 2 s in the cambrian was derived from tsr by liquid hydrocarbons

impact driven subduction on the hadean earth impacts could have driven transient subduction events on the hadean earth according to numerical simulations the scenario reconciles evidence for tectonic activity with that for an otherwise tectonically stagnant early earth

geochemical comparison between gas in fluid inclusions and gas produced from the upper triassic xujiahe formation sichuan basin sw china abstract natural gas in the xujiahe formation of the sichuan basin is dominated by hydrocarbon hc gas with 78 79 methane and 2 19 c2 hc its dryness coefficient c1 c1 5 is mostly

petroleum inclusions atop unayzah gas condensate reservoir signpost for an undocumented chapter of the arabian basin filling history abstract the carboniferous permian unayzah gas condensate reservoir of the ghazal field in eastern saudi arabia contains abundant oil inclusions indicative of a palaeo oil column the molecular composition of a fluid inclusion rich zone at the top of the reservoir revealed a mid mature biomarker distribution 0 80 vitrinite reflectance equivalent vre that is considerably lower than that of the co occurring reservoired fluid 1 41 vre side chain cracking of the triaromatic steroids evident in the produced condensate is significantly less advanced in the inclusion oil as is also reflected in their alkylnaphthalene distributions the lower maturity signal in the inclusion oil is combined with calcareous related biomarkers that include relatively abundant 30 nor 17 hopane c24 tetracyclic terpane and alkyldibenzothiophenes in contrast to the reservoir hydrocarbon fluid derived from the lower silurian qusaiba shale inclusion gas is enriched in the higher hydrocarbons which might be attributed to a high proportion of oil or wet gas inclusions fluid inclusion ethane and propane 13c are very close to the mean of the produced gases but carbon dioxide 13c is about 5 and methane 13c 2 less negative than the average of the produced ghazal gases which may signify more than one hydrocarbon generation population within the fluid inclusions an earlier contribution into the unayzah reservoir from a non qusaiba source may therefore be inferred to have had preceded the volumetrically more significant and more mature qusaiba charges further research is needed to elucidate the source of this oil charge and its extent which could include deep cambrian or neoproterozoic sources that might be present in the region

evidence for deeply buried oil prone source rocks in the baiyun depression pearl river mouth basin northern south china sea carbon isotope analyses of fluid inclusion gases trapped in quartz grains in nine sandstone core samples from eight wells in the baiyun depression and the panyu lower uplift were performed to determine the source and thermal maturity of the paleo natural gases two dimension thermal and hydrocarbon generation history modelling of the source rocks coupled with the carbon isotopic results of the fluid inclusion gases were used to understand the natural gas accumulation process and to locate the active gas source rocks in the baiyun depression the fluid inclusion gases were generated from high thermal maturity oil prone wenchang formation source rocks 1 7 3 1 ro with most ro values between 2 1 ro and 2 7 ro the mixing of high thermal maturity wenchang formation sourced gas with relatively low thermal maturity enping formation sourced oil associated gas resulted in relatively lighter carbon isotopes of the reservoired gases compared with the fluid inclusions gases gas mixing could have occurred during the main enping formation sourced oil charge period based on the hydrocarbon generation history modeling results this study confirms the presence of oil prone semi deep water and deep water lacustrine facies source rocks in the wenchang formation of the baiyun depression which are widely developed with great thicknesses based on the seismic facies interpretations however successful oil and gas exploration in the deep water area should consider the distribution of active gas source rocks in the wenchang formation because the depth of the base of the active source rock greatly decreases from shallow water to deep water areas which increases exploration risk in deep water and ultra deepwater areas

geochemistry of oil in fluid inclusions in a middle proterozoic igneous intrusion implications for the source of hydrocarbons in crystalline rocks abstract the ca 1280 ma dolerite sill within the mesoproterozoic roper group in the roper superbasin australia contains evidence for at least two episodes of hydrocarbon migration represented respectively by solid bitumen with a ketone rich extract and a mixture of a high maturity gas condensate and a lower maturity oil within oil bearing fluid inclusions the ketone isomers are formed by flash pyrolysis of kerogen during the intrusion of the dolerite sill org geochem 21 1994 829 and represent the first and oldest phase of hydrocarbon migration the gas condensate and oil were subsequently trapped as a mixture within fluid inclusions at diagenetic temperatures and pressures of around 110 c and 250 bars significantly after cooling of the sill and likely during the neoproterozoic reactivation of the roper superbasin either 1 these fluids migrated together and mixed in the reservoir or 2 an earlier oil charge was flushed by a later condensate charge and the oil condensate mixture was trapped within single fluid inclusions oil inclusions occur chiefly within albitised zones of labradorite laths within the dolerite matrix and within transcrystalline microfractures cutting vein calcite and rarely vein quartz oil inclusions trapped in the vein calcite are accompanied by hypersaline ca mg brines gas chromatography mass spectrometry of oil extracted from inclusions within the dolerite matrix shows that the oil is non biodegraded and was therefore trapped relatively quickly within the host minerals trace amounts of biomarkers indicate that the inclusion oil is of a biogenic origin and excludes any abiotic processes that are apparent sources of hydrocarbons in many crystalline rocks monomethylalkanes pentacyclic terpanes chiefly comprising hopanes and diahopanes and very low concentrations of steranes and diasteranes indicate input from cyanobacterial organic matter with a minor contribution from eukaryotes the hydrocarbons are likely derived from proterozoic source rocks such as the directly overlying velkerri formation and or the underlying barney creek formation from the mcarthur group the study has implications for the source of hydrocarbons in non sedimentary rocks and suggests that fluid inclusions can be used not only to distinguish between biogenic and abiogenic sources of hydrocarbons but also to provide critical information about the composition of the biomass fluid migration events and conditions under which hydrocarbons in different geological settings are trapped

variability of petroleum inclusions in vein fossil and vug cements a geochemical study in the barrandian basin lower palaeozoic czech republic abstract although no commercial oil or gas occurrences have been found in the barrandian basin residual oils and petroleum inclusions give evidence about the petroleum history of this lower palaeozoic basin petroleum inclusions are hosted in six generations of calcite and quartz cements that can be attributed to different stages of a basinal cycle and associated diagenetic events they were analysed using an on line crushing and an off line crush and leach approach five different groups pi a to pi e and intermediate mixtures pi m could be differentiated based on the relative distribution of n alkanes all oils had a calculated aromatic maturity rc ranging between 0 9 and 1 6 pi a shows a molecular weight maximum in the range of n c8 11 with a constant attenuation towards higher carbon numbered n alkanes this distribution is interpreted as the pristine precursor oil for other petroleum inclusion groups pi b has a maximum weight abundance at n c15 20 the genetic relationship between pi b and pi a can tentatively be explained by mixing effects or by gas stripping pi c is bimodal and characterised by a molecular weight maximum at n c32 34 and also a molecular weight maximum at n c15 20 similar to that of group pi b pi d shows a normally distributed molecular weight maximum in the range n c25 28 and is interpreted as a wax precipitate from ascending gas saturated in n alkanes pi e contains predominantly gaseous compounds with only a few higher hydrocarbons thompson s aromaticity values are elevated for condensates of group pi e and also for group pi c that is dominated by long chained n alkanes this gives evidence that fault bound petroleum migration in the barrandian basin was associated with evaporative fractionation for group pi c and pi e samples of group pi e yielded gas range compounds only and all come from a last generation of vein filling whitish calcite that was formed in a late uplift phase of the basin for other petroleum inclusion groups only a vague preferential occurrence in specific mineralisation phases or stratigraphic intervals of the host rock has been found this reflects the predominance of fracture bound migration in the barrandian basin aromatic maturity values also showed no correlation between either crystal type or pi group in six of the investigated petroleum inclusion samples alk 1 enes are present these terminal olefins are interpreted to be the result of the natural pyrolysis of petroleum due to the intrusion of volcanic dykes or hydrothermal processes an artificial generation of olefins during sample work up and analysis is unlikely the preservation of alk 1 enes from palaeozoic times was possible due to the protecting environment of petroleum inclusions

faulting processes in active faults evidences from tcdp and safod drill core samples abstract the microstructures mineralogy and chemistry of representative samples collected from the cores of the san andreas fault drill hole safod and the taiwan chelungpu fault drilling project tcdp have been studied using optical microscopy tem sem xrd and xrf analyses safod samples provide a transect across undeformed host rock the fault damage zone and currently active deforming zones of the san andreas fault tcdp samples are retrieved from the principal slip zone psz and from the surrounding damage zone of the chelungpu fault substantial differences exist in the clay mineralogy of safod and tcdp fault gouge samples amorphous material has been observed in safod as well as tcdp samples in line with previous publications we propose that melt observed in tcdp black gouge samples was produced by seismic slip melt origin whereas amorphous material in safod samples was formed by comminution of grains crush origin rather than by melting dauphine twins in quartz grains of safod and tcdp samples may indicate high seismic stress the differences in the crystallographic preferred orientation of calcite between safod and tcdp samples are significant microstructures resulting from dissolution precipitation processes were observed in both faults but are more frequently found in safod samples than in tcdp fault rocks as already described for many other fault zones clay gouge fabrics are quite weak in safod and tcdp samples clay clast aggregates ccas proposed to indicate frictional heating and thermal pressurization occur in material taken from the psz of the chelungpu fault as well as within and outside of the safod deforming zones indicating that these microstructures were formed over a wide range of slip rates

two dimensional numerical modelling of surface wind velocity and associated snowdrift effects over complex mountainous topography a new experimental software for blowing snow sytron2 is pre sented it takes advantage of the previous limited realization sytron1andof the entire real time operational environment of the automatic chain safran crocus mepra scm it runs presently on a rectangular grid with a mesh size of about 45m covering an area of 3 0 3 0km 2 around the observation test site col du lac blanc french alps 2700m a s l near the alpe d huez ski resort sytron2 is initialized with a realistic snowpack representation derived fromthe scmoutputs andcoupledto awind fieldcom puted by the new samver model the final aim is to build a fully embedded tool sui table for representing snowdrift effects with a better resolution at different specific locations the different tools and operators used are described as well as the field valida tion processes which are based on remote identification of the eroded and accumulated areas using digital pictures

fluid inclusion and stable isotope constraints on the origin of wernecke breccia and associated iron oxide copper gold mineralization yukon iron oxide cu au u co iocg mineralization is associated with numerous proterozoic breccia bodies collectively known as wernecke breccia in yukon territory canada multiphase breccia zones occur in areas underlain by paleoproterozoic wernecke supergroup metasedimentary rocks and are associated with widespread sodic potassic and carbonate alteration assemblages fluid inclusion data indicate syn breccia fluids were hot 185 350 c saline 24 42 wt nacl equivalent nacl cacl2 h2o brines estimates of fluid pressure vary from 0 4 to 2 4 kbar 1 kbar 100 mpa carbon and oxygen isotopic compositions of breccia related carbonates range from 11 to 1 5 pee dee belemnite pdb and 2 to 20 vienna standard mean ocean water v smow 18owater 8 to 15 respectively 13c and 18o values for host wernecke supergroup limestone dolostone vary from 2 to 1 6 and 12 to 25 respectively sulfur isotopic compositions of hydrothermal sulfides and sulfate vary from 12 to 13 and

influence of natural fractures on gas accumulation in the upper triassic tight gas sandstones in the northwestern sichuan basin china abstract the upper triassic xujiahe formation in the northwestern sichuan basin china is a typical tight gas sandstone reservoir that contains natural fractures and has an average porosity of 1 10 and air permeability less than 0 1 md because of compaction and cementation according to outcrops cores and image logs three types of natural fractures namely tectonic diagenetic and overpressure related fractures have developed in the tight gas sandstones the tectonic fractures include small faults intraformational shear fractures and horizontal shear fractures whereas the diagenetic fractures mainly include bed parallel fractures according to thin sections the microfractures also include tectonic diagenetic and overpressure related microfractures the diagenetic microfractures consist of transgranular intragranular and grain boundary fractures among these fractures intraformational shear fractures horizontal shear fractures and small faults are predominant and significant for fluid movement based on the monte carlo method these intraformational shear fractures and horizontal shear fractures improve the reservoir porosity and permeability thus serving as an important storage space and primary fluid flow channels in the tight sandstones the small faults may provide seepage channels in adjacent layers by cutting through layers in addition these intragranular and grain boundary fractures increase the connectivity of the tight gas sandstones by linking tiny pores the tectonic microfractures improve the seepage capability of the tight gas sandstones to some extent low dip angle fractures are more abundant in the t 3 x 3 member than in the t 3 x 2 and t 3 x 4 members the fracture intensities of the sandstones in the t 3 x 3 member are greater than those in the t 3 x 2 and t 3 x 4 members the fracture intensities do not always decrease with increasing bed thickness for the tight sandstones when the bed thickness of the tight sandstones is less than 1 0 m the fracture intensities increase with increasing bed thickness in the t 3 x 3 member fluid inclusion evidence and burial history analysis indicate that the tectonic fractures developed over three periods the first period was at the end of the triassic to the early jurassic the tectonic fractures developed during oil generation but before the matrix s porosity and permeability reduced which suggests that these tectonic fractures could provide seepage channels for oil migration and accumulation the second period was at the end of the cretaceous after the matrix s porosity and permeability reduced but during peak gas generation which indicates that gas mainly migrated and accumulated in the tectonic fractures the third period was at the end of the eogene to the early neogene the tectonic fractures could provide seepage channels for secondary gas migration and accumulation from the upper triassic xujiahe formation into the overlying jurassic formation

distribution of snow drifts on ridge slopes measurements and theoretical approximations during several winters the positions and magnitudes of excess snow deposits or denudation zones caused by wind have been evaluated on the flanks of regular elongated mountain ridges the surveys were carried out by conventional measurements of mass balance according to angle of slope 10 to 35 shape of crest hump or wedge shaped and orientation to the wind various patterns of snow deposition may be found it is shown that on ridges oriented perpendicularly to the main wind direction north west during snow storms near periodic snow deposits may be expected on the lee slope on the windward side there is a denudation zone near the crest the measurements indicate that lee slopes of mean slope angle are buried in mid winter under twice as much snow as the adjacent windward slopes however the ridge system as a whole accumulates the same amounts of snow as do areas of flat terrain theoretical approximations based on theories of potential flow and semi empi rical plume models are used to simulate the presumed dispersion of snow the model calculations intended as diagnostic tools suggest that snow may be diffused and deposited on lee slopes in a plume like manner similar to other particulate matter snowfall together with low level blowing snow as an additional source of suspended particles appears to increase the snow deposits mainly on the foot of steeper ridges

an approach to modelling the impact of snow drift on glaciation in the cairngorm mountains scotland this paper uses a geographical information system gis to develop a rule based model of the effect of snow drifting on glacier growth in the cairngorm mountains scotland during the younger dryas interval we develop a qualitative model of snow drift that uses a number of simple heuristics to generate a map of relative accumulation at a 50 m resolution over the massif relative susceptibility to snow drifting is then compared for a number of different zones under varying wind directions we conclude that under the conditions tested in our model glaciation of the cairngorms during the younger dryas was confined to the high corries and that the pattern of snow drifting suggested by our model points to dominant southerly winds copyright 1999 john wiley sons ltd

structural geology natural fault lubricants motion along faults can occur in sudden earthquakes or through steady aseismic creep rock samples retrieved by drilling deep into a creeping section of the san andreas fault show that clay minerals in fault rock promote creep behaviour

stable carbon isotopes of alkane gases from the xujiahe coal measures and implication for gas source correlation in the sichuan basin sw china abstract the upper triassic xujiahe formation in the sichuan basin sw china consists of a series of coal measures the first third and fifth members of this formation are dominated by gas prone dark mudstones and coals the mudstones contain type ii and iii kerogens with average organic carbon contents around 1 96 these source rocks are mature in the central sichuan and highly mature in the western sichuan basin characterized by gas generation with subordinate amounts of light oil or condensate oils the source rocks are intercalated with the sandstone dominated second fourth and sixth members of the xujiahe formation thus leading to three separate self contained petroleum systems in the region the proven gas reserves in the xujiahe formation are only less than that of the triassic feixianguan formation and the xujiahe formation has the second largest gas field guang an gas field in the basin gases derived from the xujiahe formation coals generally show a normal stable carbon isotopic trend for c1 c4 n alkanes with the highest 13c2 values among the nine gas pay zones in the basin 20 7 to 28 3 and 13c1 values as low as 43 0 in the central sichuan gas accumulations with an oil leg have also been found in the eastern and southern sichuan where the thickness of the xujiahe formation is significantly reduced gases in these accumulations tend to show low 13c2 values 30 0 to 36 3 characteristic of oil prone source rocks

experimental constraints on the relationship between clay abundance clay fabric and frictional behavior for the central deforming zone of the san andreas fault the presence of smectite saponite in fault gouge from the central deforming zone of the san andreas fault at parkfield ca has been linked to low mechanical strength and aseismic slip however the precise relationship between clay mineral structure fabric development fault strength and the stability of frictional sliding is not well understood we address these questions through the integration of laboratory friction tests and fib sem analysis of fault rock recovered from the san andreas fault observatory at depth safod borehole intact fault rock was compared with experimentally sheared fault gouge and different proportions of either quartz clasts or safod clasts extracted from the sample nano textural measurements show the development of localized clay particle alignment along shear folia developed within synthetic gouges such slip planes have multiples of random distribution mrd values of 3 0 4 9 the mrd values measured are higher than previous estimates mrd 1 5 that show lower degrees of shear localization and clay alignment averaged over larger volumes the intact fault rock exhibits less well developed nano clay fabrics than the experimentally sheared materials and mrd values decrease with smectite content we show that the abundance strength and shape of clasts all influence fabric evolution via strain localization quartz clasts yield more strongly developed clay fabrics than serpentine dominated safod clasts our results suggest that 1 both clay abundance and the development of nano scale fabrics play a role in fault zone weakening and 2 aseismic creep is promoted by slip along clay shears with 20 wt smectite content and mrd values 2 7

stable carbon and hydrogen isotopes of natural gases sourced from the xujiahe formation in the sichuan basin china abstract the compound specific hydrogen and carbon stable isotope ratios of alkanes in natural gases from the xujiahe and jurassic formations in the western sichuan basin were investigated to distinguish between coal derived and oil associated gases all gases were determined to be coal derived and sourced from the xujiahe formation thermal maturities of the source rocks are expected to vary from 0 8 1 8 vitrinite reflectance ro according to the empirical relationship between the measured 13cch4 values and ro which is within the scope of the maturities of source rocks 0 7 2 1 in particular c1 3 alkanes of primary coal derived gases which have not undergone any secondary alteration become more enriched in deuterium with increasing molecular mass and the dch4 values increase with increasing thermal maturity of source rocks in the sichuan basin d values of coal derived gases sourced from terrigenous source rocks of the xujiahe formation are more negative than those of oil associated gases sourced from marine organic matter of the sinian permian and triassic formations

an eulerian equation for snow accumulation downstream of an object this study investigated the form of the governing equation for the particle distribution by focusing on the particle motion processes rather than flow regime and particle characteristics a linear erosion term for a fetch eddy effect was introduced to the advection dispersion equation the equation formulated in this paper described most of the particle deposit patterns behind an object including porous and solid snow fences and a tree this theory may enable us to estimate particle motion parameters such as diffusion drift and erosion coefficients from field observed particle distributions snow stratigraphy observed by ground penetrating radar gpr was used verify to result of the modeled theoretical snow redistribution these analyses confirmed the effectiveness of the linear erosion term at explaining the particle deposition patterns due to eddys around a porous snow fence this article is protected by copyright all rights reserved

back analysis of drifting snow measurements over an instrumented mountainous site the nemo numerical model of drifting snow whose general outlines are presented in this paper is based on a physical model for saltation and turbulent diffusion the model needs a set of input parameters including fall velocity threshold shear velocity shear velocity mass concentration and roughness which are obtained from empirical formulae and wind speed measured at a given height to better determine the required field data in an alpine context our experimental site col du lac blanc 2700 m a s l french alps was first equipped with one anemometer and blowing snow acoustic sensors which proved not to be accurate enough for research purposes in the current state of development even though a new calibration curve was used we therefore set up a snow particle counter and we returned to the traditional robust mechanical traps and a 10 m mast with six anemometers two temperature sensors and a depth sensor to better determine friction velocity and aerodynamic roughness based on the studied drifting snow events we conclude 1 the proportionality of the aerodynamic roughness to the square of the friction velocity was confirmed but with a varying proportionality ratio depending on the snowdrift event 2 values of s u f were relatively well approximated by empirical formulae from data originating from antarctica and 3 snowdrift concentration profiles obtained by pomeroy s semi empirical formulae for the saltation layer coupled with a theoretical approach for the diffusion layer overestimated the concentration profiles for the studied blowing snow event

using vegetation to characterize the avalanche of canal del roc roig vall de nuria eastern pyrenees spain avalanche hazard maps of high accuracy are difficult to produce for land use planning and management purposes a good knowledge of extreme run out zones and frequencies of avalanches is required in the present work vegetation recognition especially focused on pinus uncinata trees and dendrochronological techniques are used to characterize avalanches that have occurred in historical times helping to determine both the extent of large or extreme avalanches and their occurrence in time vegetation was studied at the canal del roc roig eastern pyrenees spain avalanche path the avalanches descending this path affect the railway that reaches the vall de nuria resort and the run up to the opposite slope during winter 1996 two important avalanches affect ing this path were well documented these are compared with the results of the vegetation study consisting of an inventory of flora the recording of vegetation damages along eight transverse profiles at different altitudes on the path and a dendrochronological sampling campaign the data obtained contributed to a characterization of the predominant snow accumulation in the starting zone the 1996 avalanches and the range of frequencies of large avalanches also traces of avalanches that increase the path mapped in the avalanche paths map published by the institut cartogra fic de catalunya in 2000 were identified improving the initial existing information

co seismic and or a seismic microstructures of jfast 343 core samples from the japan trench abstract the microstructures mineralogy and chemistry of four representative samples collected from cores extracted from the japan trench during integrated ocean drilling project expedition 343 the japan trench fast drilling project jfast have been studied using optical microscopy tem sem xrf xrd and microprobe analyses the samples provide a transect from relatively undeformed marine sediments in the hanging wall to the undeformed footwall material crossing the thrust interface between the pacific and north american plate where the fault slipped during the march 2011 tohoku oki earthquake our preliminary results suggest that the low strength of jfast fault gouge material is caused by the high amount of clay minerals 60 smectite 14 illite clay minerals in the decollement gouge sample are partly replaced by newly formed manganese oxide which precipitated from hydrothermal fluids dauphine twins were found in quartz grains of the decollement sample suggesting local high stress possible during seismic loading other microstructures cannot be assigned unambiguously to co seismic or a seismic faulting processes the observed scaly clay fabric is consistent with observations in many other plate boundary fault zones significant grain size reduction was found in the fault decollement zone sample but a change in lithology of the fault material cannot be ruled out microstructures typical for a seismic deformation like dissolution precipitation features e g dissolved grain boundaries mineral alteration occur in all jfast core samples but more frequently in the decollement sample

diagenetic characteristics evolution controlling factors of diagenetic system and their impacts on reservoir quality in tight deltaic sandstones typical example from the xujiahe formation in western sichuan foreland basin sw china abstract deeply buried 3000 5000 m deltaic sandstones of the upper triassic xujiahe formation are important tight gas reservoirs in the sichuan foreland basin china the diagenesis of these tight sandstones was examined using a variety of petrographic and geochemical techniques including thin section description x ray diffraction xrd whole rock chemical analysis scanning electron microscopy sem cathodoluminescence cl imaging electron probe analysis fluid inclusions and isotopic analysis these integrated petrographic and geochemical techniques were used to determine the diagenetic history of the sandstones and its impact on the reservoir quality the tight deltaic sandstones of the t3x2 and t3x4 second and fourth members of xujiahe formation have undergone a significant and complicated series of diagenetic alterations and changes in geochemical composition strong mechanical and chemical compaction together with carbonate cementation destroyed almost all the primary pores and the secondary dissolution pores now dominate the pore space the t3x4 sandstones experienced a more open diagenetic system at near surface and eodiagensis resulted in higher porosity than seen in the t3x2 sandstones both the t3x2 and t3x4 sandstones experienced closed system diagenesis during middle late mesodiagenesis the early diagenetic dissolution which mainly occurred in the open geochemical system produced secondary pores and provided kaolinite and some k needed for the subsequent illitization of kaolinite and k feldspar the late dissolution of k feldspar and illitization of k feldspar in t3x4 sandstones and t3x2 sandstones during the mesodiagenesis produced some effective secondary pores in the closed geochemical system or in the focused fluid flow zone along fractures the diagenetic characteristics size and evolution of open vs closed diagenetic system which were constrained by the depositional environment deep burial depth and tectonic activity can be used to predict the reservoir quality ahead of drilling