prediction of lithofacies and reservoir quality using well logs late cretaceous williams fork formation mamm creek field piceance basin colorado understanding the controls and distribution of reservoir quality is important for the economic success of tight gas reservoirs in which diagenesis interacts with primary depositional variations in environment and texture to exert a strong control on pore networks rock mechanical properties and natural fractures in the upper cretaceous williams fork formation of the piceance basin framework grain composition is a major control on compaction and the occurrence of authigenic phases alteration of volcanic grains in the upper williams fork led to grain coating clay precipitation ferroan dolomite cement is found only in the deeper marine influenced intervals in which dolostone fragments are present this study shows that careful petrographic assessment of lithofacies heterogeneity can be upscaled by correlation with log properties to yield tools for field scale reservoir quality prediction twelve lithofacies are identified based on sand grain populations cement types and clay matrix content sandstones of the highest reservoir quality are those with grain coating clays that inhibit quartz cementation these sandstones can be identified based on high density porosity log values sandstones with the poorest reservoir qualities are tightly cemented with carbonate and quartz cement or are rich in clay matrix carbonate cemented intervals are identified by low density porosity clay matrix rich samples have high gamma ray and low density porosity values the presence of abundant potassium feldspar in the upper intervals results in high gamma ray readings even in the clean clay matrix free sandstone

flow variability at the continental shelf break of the mackenzie shelf in the beaufort sea observations from four yearlong current meter deployments made in 1987 1988 near the shelf break in the canadian beaufort sea are analyzed by statistical and spectral methods to characterize the structure and variability vertical and horizontal of the velocity field and to compare measurements obtained during summer ice free and winter ice covered conditions three main frequency bands are defined low frequencies 0 01 0 07 cpd intermediate or synoptic scale frequencies 0 07 0 7 cpd and high frequencies 0 7 cpd including tides and inertial currents within this division about 65 of the kinetic energy is in the low frequency band 15 in the intermediate band and 20 is in the high frequency band the latter is dominated by tidal motions low frequency variability is well correlated both vertically and horizontally along the shelf for separation distances exceeding 200 km variability in this band appears to be related to wind forcing and topographic wave propagation over large horizontal scales low frequency variability is highest during october and november in association with the occurrence of intense autumn storms and lowest during periods of ice cover due to wind shielding and increased frictional damping by ice cover intermediate scale motions have significant correlation in the vertical but poor correlation in the horizontal motions in this frequency band appear to be associated with mesoscale eddies advected by the mean flow there is also evidence of local generation of intermediate frequency current fluctuations by storms in late autumn and again an apparent damping during winter periods of ice cover finally high frequency motions show significant peaks in diurnal and semidiurnal tidal bands which are well correlated horizontally and vertically however other high frequency motions in this band show no significant correlation in either the vertical or horizontal direction there is no clear evidence in the current meter records of coupling between high frequency motions and direct atmospheric forcing

a reaction transport mechanical approach to modeling the interrelationships among gas generation overpressuring and fracturing implications for the upper cretaceous natural gas reservoirs of the piceance basin colorado predicting reservoir characteristics in tight gas sandstone reservoirs such as those of the upper cretaceous units of the piceance basin is difficult due to the interactions of multiple processes acting on sediments during basin development to better understand the dynamics of these systems a forward numerical model which accounts for compaction fracturing hydrocarbon generation and multiphase flow basinrtm is used in a one dimensional simulation of the u s department of energy s multiwell experiment mwx site in the piceance basin of particular interest is the effect of gas generation on the dynamics of the system

halocline structure in the canada basin of the arctic ocean 1 we examine the varieties and spatial distributions of pacific and eastern arctic origin halocline waters in the canada basin using 2002 2003 hydrographic data the halocline structure in the canada basin is different from the eastern arctic halocline because it includes fresher pacific winter waters that form a cold halostad which lies above the eastern arctic origin lower halocline waters the structure of the halostad in the canada basin however is not spatially uniform and depends on the pathway and history of the source water pacific winter water entering through the bering strait becomes salty due to sea ice formation and this in turn is dependent on the occurrence and distribution of polynyas in particular saline water from the eastern chukchi sea forms thick halostad and causes depression of the isohalines in the southern canada basin this depression influences thermohaline structure of the oceanic beaufort gyre

arctic ocean circulation patterns revealed by grace abstractmeasurements of ocean bottom pressure obp anomalies from the satellite mission gravity recovery and climate experiment grace complemented by information from two ocean models are used to investigate the variations and distribution of the arctic ocean mass from 2002 through 2011 the forcing and dynamics associated with the observed obp changes are explored major findings are the identification of three primary temporal spatial modes of obp variability at monthly to interannual time scales with the following characteristics mode 1 50 of the variance is a wintertime basin coherent arctic mass change forced by southerly winds through fram strait and to a lesser extent through bering strait these winds generate northward geostrophic current anomalies that increase the mass in the arctic ocean mode 2 20 reveals a mass change along the siberian shelves driven by surface ekman transport and associated with the arctic oscillation mode 3 10 reveals a mass dipole with mass decreasing

origin and timing of dauphine twins in quartz cement in fractured sandstones from diagenetic environments insight from fluid inclusions abstract electron backscattered diffraction techniques ebsd show that dauphine twins in quartz are widespread in many tectonometamorphic environments our study documents that under diagenetic temperatures

upwelling in the alaskan beaufort sea atmospheric forcing and local versus non local response abstract the spin up and relaxation of an autumn upwelling event on the beaufort slope is investigated using a combination of oceanic and atmospheric data and numerical models the event occurred in november 2002 and was driven by an aleutian low storm the wind field was strongly influenced by the pack ice distribution resulting in enhanced winds over the open water of the chukchi sea flow distortion due to the brooks mountain range was also evident mooring observations east of barrow canyon show that the beaufort shelfbreak jet reversed to the west under strong easterly winds followed by upwelling of atlantic water onto the shelf after the winds subsided a deep eastward jet of atlantic water developed centered at 250 m depth an idealized numerical model reproduces these results and suggests that the oceanic response to the local winds is modulated by a propagating signal from the western edge of the storm the disparity in wave speeds between the sea surface height signal traveling at the fast barotropic shelf wave speed versus the interior density signal traveling at the slow baroclinic wave speed leads to the deep eastward jet the broad scale response to the storm over the chukchi sea is investigated using a regional numerical model the strong gradient in windspeed at the ice edge results in convergence of the offshore ekman transport leading to the establishment of an anti cyclonic gyre in the northern chukchi sea accordingly the chukchi shelfbreak jet accelerates to the east into the wind during the storm and no upwelling occurs west of barrow canyon hence the storm response is fundamentally different on the beaufort slope upwelling versus the chukchi slope no upwelling the regional numerical model results are supported by additional mooring data in the chukchi sea

propagation velocity of a natural hydraulic fracture in a poroelastic medium the propagation rate of a natural hydraulic fracture is limited by the rate that fluid flows from the saturated rock into the void space created by fracture growth unlike induced hydraulic fractures natural hydraulic fractures can not be modeled by specifying rates of fracture growth or fluid flow into the fracture as boundary conditions numerical solutions of the governing equations for natural hydraulic fracture growth in a poroelastic medium indicate that growth rates are primarily controlled by the hydraulic conductivity the storage sp and the initial flaw length 2 o computationally more efficient models which partially and completely decouple material stresses from fluid pressures give similar results results for several rock types indicate that although the rate of fracture propagation is limited by fluid flow fracture growth still accelerates results are generalized in dimensionless plots of fracture length versus time for various values of the dimensionless parameter 1 gsp where g is the shear modulus and is the drained poisson s ratio

formation of winter water on the canadian beaufort shelf new insight from observations during 2009 2011 the arctic halocline forms a cold stratified barrier between the seasonally modified near surface layers and deeper atlantic derived waters its low temperature is maintained by intrusions of cold water formed over arctic shelves in winter surprisingly cold salty 33 water capable of halocline ventilation beaufort sea winter water bsww has been observed in the beaufort sea during some winters despite the low salinity 20 25 of shelf waters there in summer this study uses year round data from moored instruments on the beaufort shelf and slope during 2009 2011 to investigate the mechanisms involved our analysis reveals that four air sea interaction processes contribute to the formation of bsww flushing of the low salinity surface water from the shelf via ekman transport in late summer and early fall compensatory upwelling of more saline halocline water onto the shelf net seaward ice drift that promotes ice production by maintaining a flaw lead and entrainment of dense upwelled water into the freezing surface layer on the inner shelf this work moves beyond earlier studies in revealing that while weather conditions were more favorable to bsww formation in the winter of 2010 2011 than in 2009 2010 the difference was more strongly influenced by ekman transport offshore at the surface onshore at the seabed than by differences in cumulative brine injection from ice growth the strength of the ekman circulation over the canadian beaufort shelf in winter and its interannual variation have significance for surface nutrient renewal and for the cross shelf transport of pollutants at the surface and the seabed

nonseasonal fluctuations of the arctic ocean mass observed by the grace satellites 1 time variable gravity observations from the grace satellites reveal strong nonseasonal fluctuations of bottom pressure in the arctic ocean on the time scales from 2 to 6 months and a record high bottom pressure anomaly in february of 2011 here we examine the nature and driving forces behind those fluctuations we find that the nonseasonal variability of the arctic ocean mass is strongly coupled to wind forcing the zonal wind pattern is correlated with a dipole pattern of arctic ocean mass changes westerly wind intensification over the north atlantic at about 60 n as well as over the russian arctic continental shelf break cause the ocean mass to decrease in the nordic seas and in the central arctic and to increase over the russian arctic shelf basin wide arctic ocean mass fluctuations are correlated with northward wind anomalies over the northeastern north atlantic and nordic seas and over the bering sea we show that positive negative arctic ocean mass anomalies are associated with anticyclonic cyclonic anomalies of the large scale ocean circulation pattern based on ocean model simulations we conclude that the observed nonseasonal arctic ocean mass variability is mostly explained by the net horizontal wind driven transports and the contribution of fresh water fluxes is negligible we demonstrate that transport anomalies across both the atlantic and pacific gateways were equally important for generating large arctic ocean mass anomalies in 2011

flow of winter transformed pacific water into the western arctic abstract the dynamics of the flow of dense water through barrow canyon is investigated using data from a hydrographic survey in summer 2002 the focus is on the winter transformed bering water the highest volumetric mode of winter water in the chukchi sea which drains northward through the canyon in spring and summer the transport of this water mass during the time of the survey was 0 2 0 3 sv as the layer flowed from the head of the canyon to the mouth it sank decelerated and stretched strong cyclonic relative vorticity was generated on the seaward side of the jet which compensated for the stretching this adjustment was incomplete however in that it did not extend across the entire current possibly because of internal mixing due to shear instabilities the resulting vorticity structure of the flow at the canyon mouth was conducive for baroclinic instability and eddy formation multiple eddies of winter transformed bering water were observed along the chukchi beaufort shelfbreak those to the west of barrow canyon were in the process of being spawned by the eastward flowing shelfbreak current emanating from herald canyon while the single eddy observed to the east originated from the barrow canyon outflow it is argued that such an eddy formation is a major source of the ubiquitous cold core anti cyclones observed historically throughout the canada basin implications for the ventilation of the upper halocline of the western arctic are discussed

prediction of the error induced by topography in satellite microwave radiometric observations a numerical simulator of satellite microwave radiometric observations of mountainous scenes developed in a previous study has been used to predict the relief effects on the measurements of a spaceborne radiometer for this purpose the trends of the error due to topography i e the difference between the antenna temperature calculated for a topographically variable surface and that computed for a flat terrain versus the parameters representing the relief have been analyzed the analysis has been mainly performed for a mountainous area in the alps by assuming a simplified land cover scenario consisting of bare terrain with two roughness conditions smooth and rough soils and considering l and c bands i e those most suitable for soil moisture retrieval the results have revealed that the error in satellite microwave radiometric observations is particularly correlated to the mean values of the height and slope of the radiometric pixel as well as to the standard deviations of the aspect angle and local incidence angle both a regression analysis and a neural network approach have been applied to estimate the error as a function of the parameters representing the relief using the simulator to build training and test sets the prediction of the topography effects and their correction in radiometric images have turned out to be feasible at least for the scenarios considered in this study

relationship of p wave seismic attributes azimuthal anisotropy and commercial gas pay in 3 d p wave multiazimuth data rulison field piceance basin colorado this case history is one of three field projects funded by the us department of energy as part of its ongoing research effort aimed to expand current levels of drilling and production efficiency in naturally fractured tight gas reservoirs the original stated goal for the 3 d p wave seismic survey was to evaluate and map fracture azimuth and relative fracture density throughout a naturally fractured gas reservoir interval at rulison field this interval is the cretaceous mesaverde approximately 2500 ft 760 m of lenticular sands silts and shales three dimensional full azimuth p wave data were acquired for the evaluation of azimuthal anisotropy and the relationship of the anisotropy to commercial pay in the target interval the methodology is based on the evaluation of two restricted azimuth orthogonal source receiver azimuth 3 d p wave volumes aligned with the natural principal axes of the azimuthal anisotropy as estimated from velocity analysis of multiazimuth prestack gathers the dix interval

seasonal variation of upwelling in the alaskan beaufort sea impact of sea ice cover 1 data from a mooring array deployed from august 2002 to september 2004 are used to characterize differences in upwelling near the shelf break in the alaskan beaufort sea due to varying sea ice conditions the record is divided into three ice seasons open water partial ice and full ice the basic response is the same in each of the seasons roughly 8 h after the onset of easterly winds the shelf break jet reverses followed approximately 10 h later by upwelling of saltier water which is cold near the shelf break pacific winter water and warm at depth atlantic water the secondary circulation at the outer shelf is to first order consistent with a two dimensional ekman balance of offshore flow in the upper layer and onshore flow at depth there are however important seasonal differences in the upwelling overall the response is strongest in the partial ice season and weakest in the full ice season it is believed that these differences are dictated by the degree to which wind stress is transmitted through the pack ice as the strength of the wind forcing was comparable over the three seasons an eof based upwelling index is constructed using information about the primary flow secondary flow and hydrography the ability to predict upwelling using the wind record alone is explored which demonstrates that 90 of easterly wind events exceeding 9 5 m s 1 drive significant upwelling during certain periods the ice cover on the shelf became landfast which altered the upwelling and circulation patterns near the shelf break

high temperature hydrothermal origin for fractured carbonate reservoirs in the blackburn oil field nevada geologic note 1 preliminary petrographic and fluid inclusion studies of drill cuttings and core from the blackburn oil field reveal that many of the oil saturated fractures veinlets and breccias in the dolomite reservoir rock may be of high temperature hydrothermal origin textures of the earliest formed fracture veinlet networks and breccias suggest development by explosive hydrothermal fracturing the veinlets themselves preserve evidence that high temperature fluids favorable for such natural hydrothermal rock rupture once circulated in these rocks primary fluid inclusion homogenization temperatures indicate that early vein dolomite precipitated from hydrothermal brines at temperatures exceeding 350 degrees c 662 degrees f younger quartz sphalerite galena veinlets developed from dilute aqueous solutions at temperature of more than 225 degrees c 437 degrees f the high paleotemperatures recorded by early vein dolomite in the now much cooler about 120 degrees c or 248 degrees f blackburn reservoir rock imply an ancient magmatic heat source in this case almost certainly a small granodiorite stock tertiary adjoining and possibly underlying the field other carbonate hosted petroleum reservoirs in eastern nevada are also intimately associated with felsic intrusives we propose that igneous related high temperature hydrothermal fracturing could have created reservoir porosity and permeability at some or all of these fields and that future petroleum exploration in the basin and range might profitably incorporate the search for concealed plutons

natural fractures in tight oil sandstones a case study of the upper triassic yanchang formation in the southwestern ordos basin china natural fractures are important storage spaces and fluid flow channels in tight oil sandstones intraformational open fractures are the major channels for fluid flow in tight oil sandstones small faults may provide fluid flow channels across different layers according to analogous outcrops cores and borehole image logs small faults and intraformational open fractures are developed in the tight oil sandstones of the upper triassic yanchang formation in the southwestern ordos basin china among them high dip angle intraformational open fractures are the most abundant northeast southwest trending fractures are the principal fractures for fluid flow because that is the present day maximum horizontal compressive stress direction combined with production data horizontal wells striking normal to or at a large angle relative to the major flow pathways are beneficial for tight oil production improvement fractures with high dip angles are the main factor that influences initial oil production linkage and tip damage zones are more favorable for oil production improvement than wall damage zones this study provides an example of natural fracture characterization and unravels fracture contributions to reservoir physical properties and oil production of tight oil sandstones which could provide a geological basis for oil exploration and development in tight sandstones

fracture parameter estimation from well log data we evaluated a method of deriving seismic fracture parameters from vertical well log data with the assumption that the fractured medium is transversely isotropic with a horizontal axis of symmetry hti one approximation we used is that the observed vertical p wave velocity is the same as the background isotropic p wave velocity of the hti medium another assumption was that the fractures and cracks are noninteractive and penny shaped using these approximations we generated the fracture compliance matrix for each layer fracture parameters were then derived by constructing the hti stiffness matrix for those layers we tested our method using vertical well log data from a tight sand reservoir in colorado usa thomsen style parameters were derived and gas filled fractures were identified on this log the identified gas filled fractures were compared to the production log data the fracture density was also obtained at the well location within the depth of interest we also found some problems and limitations caused by approximating vertical p wave velocity the same as the background isotropic p wave velocity

a late cenozoic regional mesofracture system in southern england and northern france the upper cretaceous and palaeogene rocks of s england and n france are cut by a nw trending system of fractures characterized by swarms of vertical extension joints accompanied by conjugate sets of hybrid and shear joints and normal mesofaults many major photolineaments exhibit the same nw trend as the fractures and are particularly conspicuous in n france where they are coincident with rectilinear drainage channels suggesting a relationship between fracture orientation and physiography in s england this relationship is absent possibly because of the influence of additional fracture systems related to major flexures trending obliquely to the nw se direction these major e w trending flexures and associated fracture systems were formed during the oligocene to early miocene 9helvetic9 phase of deformation and are cross cut obliquely by fractures in the nw trending system the nw trending fractures and lineaments are parallel to neotectonic normal faults in the lower rhine embayment and become less well developed to the west with increasing distance from these major structures the lower rhine faults were reactivated and propagated into the quaternary cover as a consequence of ne sw regional tension generated during the late neogene to recent 9jura9 phase of nw se alpine convergence the nw trending extensional structures in s england and n france are considered to be of about the same age and related to the same stress regime as the neotectonic normal faults of the lower rhine embayment however because fractures of the nw system cutting palaeogene sediments in se england are truncated by the erosion surface beneath the plio pleistocene red crag deposits it is possible that in england fracture initiation did not continue into quaternary times

fractures in the low porosity and ultra low permeability glutenite reservoirs a case study of the late eocene hetaoyuan formation in the anpeng oilfield nanxiang basin china the naxiang basin located within the qin and dabie mountains orogenic belt in central china is a small intermountain faulted basin in which the late eocene hetaoyuan formation in the anpeng oilfield is the low porosity and ultra low permeability glutenite reservoirs the large scale fractures are mainly developed in the thick bedded conglomerates and gravel bearing gritstones the small scale jointed fractures bounded by layer are mainly developed in the medium granular and fine sandstones between the conglomerates or gravel bearing gritstones there also developed three kinds of micro fractures namely intergranular fractures intragranular fractures and transgranular fractures in the tight glutenites the fractures in the glutenite reservoirs are of chiefly high dip angles they assume chiefly the e w strikes next are the ne sw and nw se strikes on the log curve fractures usually show such responses as a decrease of the deep and shallow lateral resistivities an increase of the acoustic time difference a reduction of the density an increase of the compensation neutrons an occurrence of middle and high gamma ray and an expansion of the calipers fractures make contributions to the low porosity and ultra low permeability glutenite reservoirs by improving the permeability and then porosity micro fractures are the important channels connecting intergranular and intragranular solution pores thereby making better the connectivity within the tight glutenite reservoirs the small and medium scale fractures serve as the flow channels within the layers of fine and medium granular sandstones while the large scale fractures serve as the main flow channels for the whole reservoir under the impact of the present day stress the ne sw fractures perpendicular to the minimum principal stress assume a tensile state and have good connectivity large apertures and high permeability and are the major direction for fluid flow thereby providing a major basis for a further development

atmospheric controls on sea ice motion in the southern beaufort sea 1 the beaufort sea ice gyre is characterized in winter months by an anticyclonic regime associated with sea level pressure slp highs previous studies have shown instances of a reversal in this regime in summer months with the arrival of slp lows over the beaufort sea while also demonstrating a link to variations in lower stratospheric potential vorticity in this study we examine the role of relative vorticity in describing dynamic variability on weekly timescales from the surface to the middle stratosphere results from this analysis show that the beaufort gyre is characterized predominantly by anticyclonic activity throughout the year for the time interval considered from 1979 to 2000 with a summer reversal to cyclonic activity whose strength and duration varies between years these reversals coincide with reversals in slp based on a correlation analysis comparison of ice and atmospheric relative vorticity fields in the beaufort sea region bsr for all weeks from 1979 to 2000 indicates that sea ice and lower tropospheric processes are anticorrelated at zero time lag this is in contrast to relative vorticity fields at 10 mbar which exhibit maximum correlation between stratospheric and sea ice responses when 10 mbar leads ice relative vorticity by 2 6 weeks

identification characterization and change of the near surface temperature maximum in the canada basin 1993 2008 1 sea ice in the canada basin of the arctic ocean has decreased significantly in recent years and this will likely change the properties of the surface waters a near surface temperature maximum nstm at typical depths of 25 35 m has been previously described however its formation mechanisms seasonal evolution and interannual variability have not been established based on summertime conductivity temperature and depth surveys and year round ice tethered profiler data from 2005 to 2008 we found that the nstm forms when sufficient solar radiation warms the upper ocean a seasonal halocline forms in summer once enough sea ice melt has accumulated to separate the surface mixed layer from the nstm the nstm becomes trapped below the summer halocline thereby storing heat from solar radiation this heat can be stored year round in the canada basin if the halocline is strong enough to persist through winter in addition energy from storm driven mixing can weaken the summer halocline and entrain the nstm thereby melting sea ice in winter throughout this cycle ekman pumping within the convergent beaufort gyre acts to deepen the nstm from 1993 through 2007 the nstm warmed and expanded northward and both the nstm and the summer halocline formed at successively shallower depths north of 75 n the temperature of the nstm increased from 2004 to 2007 by 0 13 c yr and the nstm and summer halocline shoaled by 2 1 m yr and 1 7 m yr respectively from 1997 to 2007 the formation and dynamics of the nstm are manifestations of both the ice albedo feedback effect and changes to the freshwater cycle in the canada basin

characteristics of the beaufort sea high abstract characteristics of the arctic ocean s beaufort sea high are examined using fields from the ncep ncar reanalysis at a 2 hpa contour interval the beaufort sea high appears as a closed anticyclone in the long term annual mean sea level pressure field and in spring in winter the beaufort sea region is influenced by a pressure ridge at sea level extending from the siberian high to the yukon high over northwestern canada as assessed from 6 hourly surface winds the mean frequency of anticyclonic surface winds over the beaufort sea region is fairly constant through the year while for all seasons a strong closed high can be interpreted as the surface expression of an amplified western north american ridge at 500 hpa there is some suggestion of a split flow where the ridge linked to the surface high is separated from the ridge to the south that lies within the main belt of westerlies the aleutian low in the north pacific tends to be deeper than normal when there is a strong beaufort sea high in

analysis of states of stress between provinces of constant stress recent studies have indicated the existence of crustal provinces or domains within which the state of stress shows little apparent horizontal variation between provinces the state of stress may undergo substantial changes often over remarkably short distances as analyzed here the transition in stress state between adjacent domains is caused by shear tractions acting on the base of the elastic brittle layer and is mediated by a stress field within a zone between the provinces that can be determined by solving the equations of force equilibrium and stress compatibility the component of horizontal stress oriented perpendicular to the provincial boundary changes smoothly across the transition zone from one province to the other whereas the horizontal stress oriented parallel to the boundary shows smaller but discontinuous changes the horizontal component of shear stress is unlikely to change from one province to another because of the implausible nature of the required basal traction thus in this regard states of stress in adjacent domains appear to be coupled the coincidence of a number of stress transition zones with boundaries defined by heat flow suggests that in many cases the basal tractions are the result of thermally induced mass transport below the elastic brittle layer in the direction of increasing horizontal compressive stress this analysis provides a quantitative relationship between changes in the stress field measured in the upper portion of the crust and shear stresses acting on the base of the elastic brittle layer

natural hydraulic fracturing of tight gas sandstone reservoirs piceance basin colorado natural fractures form preferred pathways for basinal fluid flow and associated heat and mass transport in gas sandstone reservoirs with low matrix permeability fractures provide flow pathways between organic rich source and reservoir layers during gas charge and between matrix pores hydraulic fractures and the well bore during production while the formation of natural fractures has previously been associated with gas generation and pore fluid pressure increase through a process referred to as natural hydraulic fracturing other driving mechanisms such as stress changes by tectonic or exhumation processes remained viable alternatives to test whether these mechanisms contributed to fracture development we investigated the spatial and temporal distribution of fracture formation and its relationship to gas generation migration and charge in sandstone of the cretaceous mesaverde group across the entire production interval on a basinwide scale using fluid inclusion microthermometry of crack seal fracture cement formed concurrently with fracture opening we observed temperature trends that when compared with temperature evolution models of the formation date fracture formation between 41 and 6 ma in the northern and between 39 and 6 ma in the southern piceance basin the onset of fracture formation 20 30 m y prior to maximum burial eliminates changes in stress state associated with exhumation as a mechanism for triggering the onset of fracture formation instead calculated paleo pore fluid pressures of 40 90 mpa 5800 13 000 psi during fracture opening and the presence of methane rich inclusions in fracture cement suggest that fracture formation was aided by high pore fluid pressures during gas generation in organic rich shales and coals and associated charging of adjacent and interlayered sandstone reservoirs a 10 20 m y age progression in the onset of fracture formation from deeper to shallower horizons of the mesaverde group is consistent with gas generation and onset of fracture formation activated by burial temperature with limited upward migration of gas at this stage of reservoir evolution this age progression with depth is inconsistent with fracture formation triggered by changes in stress conditions associated with tectonic or structural processes expected to affect the entire formation synchronously our observations are thus most consistent with fracture formation by natural hydraulic fracturing in response to gas generation in interbedded source layers and reservoir charge based on widespread observations of fractures with similar structural and diagenetic attributes we consider natural hydraulic fracture formation in response to thermocatalytic gas generation to be a fundamental mode of brittle failure in otherwise structurally quiescent basins

diverse fracture properties and their impact on performance in conventional and tight gas reservoirs saudi arabia the unayzah south haradh case study the upper permian carboniferous unayzah formation in south haradh saudi arabia includes two major mechanical and petrophysical layers that are separated by shale rich zones open tectonic fracture clusters are rare and not essential for fluid flow in the unayzah a zone which has high porosity and permeability however such fracture clusters are essential to and impact the production performance in the unayzah b c tight gas reservoir the occurrence of the tectonic fractures in the unayzah formation is linked to the rock mechanical properties which vary with porosity shale volume cement type and texture the b c unit is more fractured than the a unit but its layers vary in the degree of fracturing the variation in fracture development within the b c unit results in differences in fracture enhanced permeability based on production profiles where flow is restricted to preferentially fractured mechanical layers that lack effective vertical fluid communication with other layers we identify two tectonic fracture systems an older subordinate fully mineralized system and a younger primary mostly open system early extensional fractures including joints and faults developed parallel to the basement faults during the opening of the neotethys these are fully mineralized and have little or no function as fluid conduits the younger system includes open fracture clusters that are predominantly parallel or nearly parallel to the regional east northeast west southwest maximum horizontal stress of the zagros that has been active since the late cretaceous and is independent of local structures therefore these fractures are controlled by remote stresses instead of the basement rooted forced folds and faults in this article we demonstrate that in the unayzah b c natural fractures are essential to permeability and in some areas to porosity and thence to reservoir performance the results of this study are being implemented in well placement and completion design to optimize the intersection of open fracture clusters with positive preliminary results

tracing pacific water in the north atlantic ocean 1 in the arctic ocean pacific source water can be distinguished from atlantic source water by nitrate phosphate concentration relationships with pacific water having higher phosphate concentrations relative to those of nitrate furthermore pacific water originally from the inflow through bering strait is clearly recognizable in the outflows of low salinity waters from the arctic ocean to the northern north atlantic ocean through the canadian arctic archipelago and through fram strait in the canadian arctic archipelago we observe that almost all of the waters flowing through lancaster and jones sounds most of the water in the top 100 m in smith sound containing the flow through nares strait and possibly all waters in hudson bay contain no water of atlantic origin significant amounts of pacific water are also observed along the western coast of baffin bay along the coast of labrador and above the 200 m isobath of the grand banks there is a clear signal of pacific water flowing south through fram strait and along the east coast of greenland extending at least as far south as denmark strait pacific water signature can be seen near the east coast of greenland at 66 n but not in data at 60 n temporal variability in the concentrations of pacific water has been observed at several locations where multiple year observations are available

testing the basin centered gas accumulation model using fluid inclusion observations southern piceance basin colorado the upper cretaceous mesaverde group in the piceance basin colorado is considered a continuous basin centered gas accumulation in which gas charge of the low permeability sandstone occurs under high pore fluid pressure in response to gas generation high gas pressure favors formation of pervasive systems of opening mode fractures this view contrasts with thatofothermodelsoflow permeabilitygasreservoirsinwhich gas migrates by buoyant drive and accumulates in conventional traps with fractures an incidental attribute of these reservoirs we tested the aspects of the basin centered gas accumulation model as it applies to the piceance basin by determining the timing of fracturegrowth and associated temperature pressure and fluid composition conditions using microthermometry and raman microspectrometry of fluid inclusions trapped in fracture cement that formed during fracture growth trapping temperatures of methane saturated aqueous fluid inclusions record systematic temperature trends that increase from approximately 140 to 185 c and then decrease to approximately 158 c over time which indicates fracture growth during maximum burial conditions calculated pore fluid pressures for methanerich aqueous inclusions of 55 to 110 mpa 7977 15 954 psi indicate fracture growth under near lithostatic pressure conditions consistent with fracture growth during active gas maturation and charge lack of systematic pore fluid pressure trends

upwelling on the continental slope of the alaskan beaufort sea storms ice and oceanographic response 1 the characteristics of pacific born storms that cause upwelling along the beaufort sea continental slope the oceanographic response and the modulation of the response due to sea ice are investigated in fall 2002 a mooring array located near 152w measured 11 significant upwelling events that brought warm and salty atlantic water to shallow depths when comparing the storms that caused these events to other aleutian lows that did not induce upwelling interesting trends emerged upwelling occurred most frequently when storms were located in a region near the eastern end of the aleutian island arc and alaskan peninsula not only were these storms deep but they generally had northward tending trajectories while the steering flow aloft aided this northward progression the occurrence of lee cyclogenesis due to the orography of alaska seems to play a role as well in expanding the meridional influence of the storms in late fall and early winter both the intensity and frequency of the upwelling diminished significantly at the array site it is argued that the reduction in amplitude was due to the onset of heavy pack ice while the decreased frequency was due to two different upper level atmospheric blocking patterns inhibiting the far field influence of the storms

regional fractures ii fracturing of mesaverde reservoirs in the piceance basin colorado 1 cretaceous strata in the east central piceance basin of northwestern colorado were subjected to several phases of stress due to horizontal tectonic compression burial and uplift these rocks contain a regional set of west northwest extension fractures observed in abundant vertical and deviated core from the u s department of energy s multiwell experiment and slant hole completion test wells time depth relationships fracture orientation and fluid inclusion analyses indicate that the fractures formed at about 36 40 ma during a phase of increased laramide west northwest compression and in a pressure temperature regime compatible with the geologically reconstructed maximum burial depths this regional fracturing is an example of load parallel extension fracturing and basinwide dilatancy at depth under conditions of high pore pressure and anisotropic tectonically created horizontal stress

experimental stretching of fluid inclusions in calcite implications for diagenetic studies homogenization temperatures of fluid inclusions trapped in calcite crystals may change with increased heating beyond the homogenization temperature fluid inclusions trapped in calcite during basin subsidence will tend to yield homogenization temperatures approaching maximum burial temperatures diagenetic studies that depend on these data will be biased coarse crystalline calcite containing saline fluid inclusions was used to examine the influence of increased temperatures and pressures on measured homogenization temperatures stepped heating experiments were conducted at 1 atm over a temperature range of 90 to 245 c along with hydrothermal experiments at confining pressures of 173 and 691 bar and temperatures of 160 250 and 350 c in all cases significant increases in the homogenization temperatures of the inclusion population were recorded presumably stresses generated during heating of the fluid inclusions exceeded the combined strength of the calcite crystal and the external pore pressure and thus caused fluid inclusion stretching size is a secondary factor that controls fluid inclusion reequilibration

the canada basin 1989 1995 upstream events and far field effects of the barents sea 1 the effects of upstream events on southern canada basin waters were examined using physical and geochemical data collected at one location between 1989 and 1995 these events included atlantic layer warming relocation of the atlantic pacific water mass boundary and increased ventilation of boundary current waters early signals of change in the canada basin first appeared in 1993 along the continental margin and by 1995 were evident in the basin interior and farther downstream differences in physical and geochemical properties nutrients oxygen 129i and cfcs were observed between 150 and 1600 m of the water column by 1995 the boundary between pacific and atlantic origin water was shallower and atlantic origin water occupied more of the canada basin water column atlantic origin lower halocline water was colder and more ventilated fram strait branch water was colder fresher and more ventilated and barents sea branch water was warmer fresher more ventilated and occupied a larger volume of the water column than in previous years water mass analysis showed that the composition of atlantic origin water in the canada basin in 1995 included 20 more water from the barents sea two related events upstream appear to be the source of this change an atmospheric regime shift in 1989 that increased cyclonic circulation a transition unprecedented within the latter half of the 20th century in magnitude geographic reach and apparent oceanographic impacts and a large volume of dense water flowed from the barents sea to the arctic ocean between 1988 and 1989 these two phenomena illustrate the close relationship between atmospheric and oceanic events whose combined influence was evident 6 years later and 5100 km downstream in the canada basin at depths 1000 m

late laramide thrust related and evaporite domed anticlines in the southern piceance basin northeastern colorado plateau new seismic and gravity data across the hydrocarbon producing divide creek and wolf creek anticlines in the southern piceance basin reveal contrasting styles of deformation within two widely separated time frames seismic data indicate that prebasin paleozoic deformation resulted in block faulting of the precambrian crystalline basement rocks and overlying cambrian through middle pennsylvanian strata movement along these block faults throughout much of pennsylvanian time during northeast southwest crustal extension likely influenced distribution of the middle pennsylvanian desmoinesian evaporite rich facies younger rocks including the thick succession of cenozoic basin strata then buried the paleozoic structures tectonic reconfiguration of the basin s eastern margin occurred during late laramide northeast southwest compression when a basement involved thrust block whose surface expression is the grand hogback monocline moved into the piceance basin a decollement developed in front of the thrust block within the mechanically weak desmoinesian evaporites and splayed out basinward as small scale imbricate thrusts in the upper cretaceous mancos shale the divide creek anticline formed above these splays as thrusting locally overthickened the shale and repeated the sandstone units between it and the evaporites the wolf creek anticline to the east however is due to both depositional and tectonic thickening of the evaporite section along the decollement gravity data confirm that excess mater al of relatively low density exists beneath the wolf creek structure whereas material of relatively higher density overthickened shale is found beneath the divide creek anticline thrust related basin margins and intrabasin folds structurally analogous to the divide creek and wolf creek anticlines may be more common than presently recognized in the rocky mountain foreland one well documented example is the pinedale anticline in the northern green river basin wyoming which like the divide creek anticline developed above a zone of splay faults from a decollement in front of a large thrust block

evidence for a petroleum subsystem in the frontier formation of the uinta piceance basin petroleum province anomalous carbonate horizons with intercrystalline hydrocarbon residue cone in cone structures and calcite beef veins in adjacent sandstone beds record potential evidence for hydrocarbon generation and seepage in the middle to upper turonian frontier formation from the uinta basin utah and colorado eight carbonate occurrences all encountered within distal delta front facies thin bedded sandstones and siltstones were sampled at outcrop locations from the southern and eastern margins of dinosaur national monument seven petrographic facies pf1 pf7 were identified using standard petrographic and cathodoluminescence microscopy pf1 large and small botryoids and fans pf2 yellow brown spherules pf3 microcrystalline spar cement pf4 blocky spar pf5 prismatic spar pf6 drusy mosaic spar and pf7 dolomite facies pf1 pf3 are synsedimentary phases comprising a large percentage of carbonate horizon volume whereas pf4 pf7 are late stage fabrics the 13c values of pf1 pf3 9 9 to 20 0 are consistent with contributions from biogenic methane seepage during deposition and early diagenesis brecciated pf1 fabrics and blowout depressions within sandstone horizons further indicate significant methane generation during deposition and early burial late stage fabrics contain 13c 8 0 to 17 3 and 18o 6 5 to 13 5 values consistent with progressive burial during which intercrystalline hydrocarbon residue cone in cone structures and calcite beef veins were formed by the thermal maturation of organic matter from enclosing distal delta front facies together these features reveal the potential for the thin bedded facies of the frontier formation distal delta front to serve as a potentially viable petroleum subsystem previously unrecognized in the uinta piceance petroleum province

distribution of atlantic and pacific waters in the upper arctic ocean implications for circulation the atlantic and pacific oceans provide source waters for the arctic ocean that can be distinguished by their differing nitrate and phosphate concentration relationships using these relationships we estimate the amount of atlantic and pacific waters in the surface layer top 30 m of the arctic ocean atlantic source water is dominant in most of the eurasian basin and is present in significant amounts in the makarov basin north of the east siberian sea pacific source water is dominant in most of the canadian basin and is present in significant amounts in the amundsen basin north of greenland we deduce circulation patterns from the distributions of atlantic and pacific source waters in the surface layer of the arctic ocean and conclude that the flow within the surface layer differs from ice drift along the north american and european boundaries of the polar basin

sedimentological controls on the fracture distribution and network development in mesaverde group sandstone lithofacies uinta basin utah usa the mesaverde group uinta basin utah is the source of current significant natural gas production and contains several trillion cubic feet of undiscovered natural gas resources to evaluate and model the potential connectivity of hydraulically induced fractures to natural fractures in the subsurface the natural fracture network was examined using scanline sampling image and well logs core and microstructural analyses regional fracture sets include subvertical fractures with dominant orientations of north south 006 0158 ne 045 0598 nnw 326 3428 and a wnw 271 2868 sedimentologic and diagenetic characteristics of seven sandstone lithofacies control the fracture development and distribution in the group key sedimentologic and diagenetic influences on fracture distribution include bed thickness stratigraphic architecture the degree of cementation and the type of cement from these sedimentologic controls on the character of natural fractures lithofacies can potentially predict fracture distribution within the mesaverde group based on environments of deposition the presence of nw trending discontinuous sandstone reservoirs deposited in meandering fluvial environments that are highly fractured by a pervasive wnw striking fracture set helps to explain fairways of prolific natural gas production within

fractures in sandstone reservoirs with ultra low permeability a case study of the upper triassic yanchang formation in the ordos basin china the upper triassic yanchang formation in the ordos basin central china is a typical sandstone reservoir with an ultra low permeability high angle tectonic fractures and diagenetic fractures such as near horizontal bedding fractures intragranular fractures and grain boundary fractures are abundant fractures are major pathways and enhance fluid flow in sandstone reservoirs with ultra low permeability because of their weak lateral continuity and their small apertures under lithostatic pressure bedding fractures make a relatively small contribution to the overall permeability of reservoirs as they are both of small size and low permeability intragranular fractures and grain boundary fractures mainly improve the connectivity of reservoirs by connecting the matrix pores high angle tectonic fractures control the fluid movement in the ultra low permeability reservoirs under the effect of different successive tectonic stress fields four assemblages of high angle tectonic fractures developed in the sandstone reservoirs under the present day stress differently oriented fractures have different connectivities apertures and permeabilities the northeast southwest fractures parallel to the maximum principal stress have a good connectivity large apertures and a high permeability forming the dominant flow paths knowledge of these paths can be used for optimizing well placement because of their sensitivity to pressure fractures in different directions will show varying apertures as the formation pressure decreases therefore the permeability of the fractures of different orientations and its impact on reservoirs vary at different developmental stages

wind forced upwelling and internal kelvin wave generation in mackenzie canyon beaufort sea low frequency current temperature and salinity variations over the shelf break in the southeastern beaufort sea mackenzie shelf are examined to determine the response of seasonally ice free waters to wind forcing and the role of submarine canyons in upwelling events and shelf circulation upwelling events were found to be statistically correlated to northeasterly winds which transport surface waters offshore and draw up water from deeper layers the response to alongshore wind stress is significantly amplified in mackenzie canyon where isopycnal displacements of over 400 m are observed such displacements are then observed to propagate eastward at a phase velocity near 0 6 m s 1 the canyon is thus a site of intense upwelling while the collapse of displaced isopycnals subsequent to cessation of wind forcing creates a disturbance propagating northeast along shelf as a free internal kelvin wave

mapping permeable subsurface fracture networks a case study on the cooper basin australia abstract the spatial distribution of permeable fracture networks is constrained in the subsurface cooper basin australia through the integration of most positive curvature k analysis of five three dimensional 3d seismic surveys wellbore fracture data and geomechanical modelling the k provides the likely distribution of subsurface extensional fractures based on the stress redistribution along the outer arc of an anticline these results are reprocessed into the semblance similarity attribute to improve the signal noise ratio prior to being extracted along the gas rich and low permeability patchawarra formation the subsurface fracture distribution maps show the geometry and density of extensional fractures that have been shown to facilitate fluid migration in this province particularly those striking se nw and e w as these are properly oriented to undergo tensile reactivation the density of these permeable se nw and e w striking fracture sets is predicted to significantly increase along e w elongate anticlines and may contribute to improved hydrocarbon recovery in this low permeability stratigraphic interval we show that wellbore fracture data n 917 in the patchawarra formation presents a close relationship to k results and can be used to generate high density structural data in this basin with the methodology applicable to other subsurface and offshore provinces

the western arctic boundary current at 152 w structure variability and transport abstract from august 2002 to september 2004 a high resolution mooring array was maintained across the western arctic boundary current in the beaufort sea north of alaska the array consisted of profiling instrumentation providing a timeseries of vertical sections of the current here we present the first year velocity measurements with emphasis on the pacific water component of the current the mean flow is characterized as a bottom intensified jet of o 15 cm s 1 directed to the east trapped to the shelfbreak near 100 m depth its width scale is only 10 15 km seasonally the flow has distinct configurations during summer it becomes surface intensified as it advects buoyant alaskan coastal water in fall and winter the current often reverses flows westward under upwelling favorable winds between the storms as the eastward flow re establishes the current develops a deep extension to depths exceeding 700 m in spring the bottom trapped flow advects winter transformed pacific water emanating from the chukchi sea the year long mean volume transport of pacific water is 0 13 0 08 sv to the east which is less than 20 of the long term mean bering strait inflow this implies that most of the pacific water entering the arctic goes elsewhere contrary to expected dynamics and previous modeling results possible reasons for this are discussed the mean atlantic water transport to 800 m depth is 0 047 0 026 sv also smaller than anticipated

water mass structure and boundaries in the mackenzie shelf estuary the mackenzie shelf is a broad estuarine region bordering the southeastern beaufort sea in the arctic ocean its fields of temperature and salinity result from the modification of offshore water masses by river inflow ice melting and freezing solar insolation and air sea exchange we here relate water masses resident on the mackenzie shelf to the large scale oceanography of the arctic mediterranean the summertime exchange between the shelf and open ocean is largely confined to waters lying above the main halocline s 34 2 psu cross shelf property distributions show that individual water masses maintain their structural identity i e core properties and buoyancy frequency as they move across the shelf and participate in the estuarine circulation shelf waters are strongly influenced by river inflow however the concept of a single plume issuing from the incoming river and forming a strictly two layered structure over uniform shelf water is misleading since a variety of temperature salinity and turbidity fronts co exist on the shelf at any given time

wind forced downwelling slope currents a numerical study abstract a study is made of the dynamics of slope currents that arise from a steady constant alongshore wind over a uniform shelf over the first 10 20 days the evolution of the downwelled system on an f plane is qualitatively described by linear coastal trapped wave dynamics after this time the thermal wind shear associated with the bottom mixed layer becomes important in the evolution of the undercurrent uc which is shown to be driven by the alongshore pressure gradient due to sea level as the uc over the slope evolves the bottom ekman transport becomes small and negative leading to the detachment of flow near the shelf break localized spreading of isopycnals and further intensification of the uc in contrast to results obtained without bottom drag bottom friction and boundary layer transport are shown to lead to a two to threefold increase in cross shelf interior transport downwelling and thermal wind shear by day 60 the resultant uc has speeds of up to 15 cm s 1 and a net transport of

deciphering fracturing and fluid migration histories in northern appalachian basin an integrated structural and geochemical analysis of mineralized faults and fractures revealed that the most widespread fracture systems in the northern appalachian basin resulted from two periods of post alleghenian deformation fluid inclusion homogenization measurements on calcite samples from pre syn and post kinematic structural settings bracketed the temperature ranges predominantly a function of depth of burial for each period of fracturing the first period of deformation produced northwest west northwest and east northeast fractures and related faults that experienced recurrent strike slip movements during a cooling event from 176 to 120 c 349 to 248 f this cooling episode was associated with the waning of an elevated thermal grad ent attained during dewatering caused by late paleozoic burial metamorphism at depths of 3 to 3 5 km 9 800 to 11 500 ft later normal faulting reopened the earlier strike slip fault zones during subsequent cooling of the system from 112 c 234 f to below 76 c 169 f this second cooling stage resulted from the 1 to 2 km 3 300 to 6 600 ft of uplift and erosion that occurred throughout the eastern united states during the cretaceous the ubiquitous occurrence of carbonate silicate and sulfide epigenetic mineralization in many environments allows for widespread application of the dating techniques demonstrated in this study basic to this approach is the analysis of mineral assemblages deposited during increases in hydrothermal circulation resulting from enhanc d permeability associated with periods of faulting and fracturing the presence of different mineral assemblages representing a range of ages and crystallization environments on various generations of brittle structures provides a means for developing detailed faulting and circulation histories and the determination of approximate as well as precise relative ages for each event

analogue simulation of natural orthogonal joint set formation in brittle varnish abstract two orthogonal joint sets are commonly observed in exposed sedimentary rocks with a wide variety of abutting and cross cutting relationships brittle varnish analogue models are carried out in conjunction with field studies in order to classify the different orthogonal fracture patterns and constrain the mechanical basis of orthogonal joint development the results suggest that the stress which creates the second joint set can result from i relaxation effects ii slight tension due to warping of the bands defined by the first parallel fractures and iii local and or regional reversals between 2 and 3 a ladder pattern formed by the combination of an initial set of long parallel joints and associated non cross cutting joints of the second set is obtained if the shear strength of the initial joints is low during the development of the second set a grid pattern where both sets mutually cross cut occurs when the shear strength of the initial joint set is high possibly the result of a high normal stress or healing and could result from two independent stress events an intermediate pattern comprising cross cutting and abutting orthogonal cross joints can form if the shear strength of the initial joints was intermediate and or variable during the development of the second set mutually abutting joint sets are observed within each pattern and could result from stress reversals or low differential stress during the final stages of joint development the classical presentation of joint data using rose diagrams cannot distinguish between the wide variety of orthogonal joint patterns maps of fracture intersections should compliment the orientation data we discuss methods to estimate the joint pattern where intersection data are absent

coal cleat domains and domain boundaries in the allegheny plateau of west virginia regional face cleats cutting pennsylvanian and permian coal seams in the allegheny plateau of west virginia can be divided into domains separated by boundaries that are sharply defined along most of their lengths domains and domain boundaries are established based on cleat trends number of regional cleat sets and relative chronology of cleat set development regional cleats of each set show a common trend and abutting relationships between multiple sets within a domain describe a progressive history of changing stress fields and cleat development boundaries dividing the in situ directions of horizontal principal stress are coincident with cleat domain boundaries suggesting a common and persistent controlling factor uniform trends of face cleats within domains and ab upt changes in cleat signature across domain boundaries can be spatially related to regional basement structures and a depositional hinge line within the coal bearing and underlying mississippian rocks in addition fold structures in coal and underlying sedimentary rocks across the allegheny plateau commonly terminate or change trend abruptly at joint domain boundaries in some cases regions of common fold trends in coal bearing rocks are contained within specific domains face cleat trends commonly differ from joint trends in rocks immediately bounding coal seams however one domain boundary in coal can be traced into mississippian rocks through the unconformity at the base of the pennsylvanian section in this case mississippian and pennsylvanian joint trends differ it follows tha joint domain boundaries can extend downward through rocks of different lithologies as well as coincide with conformable and unconformable stratigraphic boundaries

regional joint sets in the arabian platform as indicators of intraplate processes the eastern part of the saudi arabian craton is a platform underlain by gently tilted and horizontal mesozoic cenozoic sedimentary rocks everywhere more than 250 km distant from the zagros deformation front despite its tectonic simplicity the platform contains several laterally extensive but subdued structures and lineaments belonging to more than one system of fault zones and flexures new microtectonic observations of dominant sets of extension and conjugate hybrid joints permit regionally significant extension directions to be inferred and the origin of the macrostructures to be assessed the central arabian arch the e w crest of which coincides with an axis of mesozoic subsidence developed during the late cretaceous to eocene when the basin inverted as a consequence of the emplacement of ophiolite bearing nappes on the zagros and oman margins during arching there was strike parallel elongation of beds at the same time as the arch amplified the central arabian graben system evolved as a result of the northward displacement of an east arabian block or sheet that became detached across an arcuate separation zone which in the south is coincident with the crest of the arch an important neogene response in the arabian platform to ne sw shortening in the zagros ranges was the formation of a swarm of ne striking master joints and lineaments these structures reflect the diffuse and peripheral expansion of the foreland beyond the zagros deformation front

inferring paleostresses from natural fracture patterns a new method we introduce a method to infer the remote differential stress magnitude from the curvature of overlapping echelon fracture traces the curving paths of overlapping echelon cracks imply the predominance of local crack induced stresses over remote stresses during propagation nearly straight crack paths imply the controlling influence of a remote compressive crack parallel differential stress this method is used to interpret complex joint patterns mapped in sedimentary rock it is also applied to the problem of fracture pattern generation using computer models

two configurations of the western arctic shelfbreak current in summer abstractdata from a closely spaced array of moorings situated across the beaufort sea shelfbreak at 152 w are used to study the western arctic shelfbreak current with emphasis on its configuration during the summer season two dynamically distinct states of the current are revealed in the absence of wind with each lasting approximately one month the first is a surface intensified shelfbreak jet transporting warm and buoyant alaskan coastal water in late summer this is the eastward continuation of the alaskan coastal current it is both baroclinically and barotropically unstable and hence capable of forming the surface intensified warm core eddies observed in the southern beaufort sea the second configuration present during early summer is a bottom intensified shelfbreak current advecting weakly stratified chukchi summer water it is baroclinically unstable and likely forms the middepth warm core eddies present in the interior basin the mesoscale instabilities extract energy from the mean flow such

hydrocarbon generation as a mechanism for overpressuring in rocky mountain region overpressured reservoirs are present in the deeper parts of most basins in the rocky mountain region a variety of conditions can cause overpressuring however most high pressures in the region are caused by present day or recently active oil and gas generation or generation in the last few million years in low permeability rock successions that still contain organic matter capable of yielding thermally generated hydrocarbons rocks with above normal pressure range from devonian to tertiary and commonly are associated with low permeability tight reservoirs most of the overpressuring occurs in cretaceous and tertiary rocks overpressuring in rocks older than cretaceous is rare and where present only occurs in strata with very rich hydrocarbon source beds such as the d vonian mississippian bakken formation most organically lean pre cretaceous source beds are no longer capable of yielding enough hydrocarbons to maintain abnormal pressure nearly all overpressured reservoirs and source rocks have temperatures of approximately 200 f 93 c or higher in addition available data indicate that hydrocarbon related overpressuring does not generally occur if vitrinite reflectance ro values are less than 0 6 in oil prone strata or less than 0 7 in gas prone strata overpressured gas bearing strata generally have ro values of 0 8 or higher maximum reservoir pressures are about equal to the fracture gradient pressure in the reservoir rocks some vertical fractures in reservoir rocks are probably caused by rapid expulsion of hydrocarbons from the source beds high pressures in the rocky mountain region means that the rock succession is gas or oil saturated and discrete hydrocarbon water contacts are generally not present classical concepts of hydrodynamics do not appear to be applicable to these overpressured successions the optimum depths for exploration are generally the upper 1 000 2 000 ft 305 610 m of the overpressured succession

correlation between deformation lamellae microfractures macrofractures and in situ stress measurements white river uplift colorado dynamic analyses of quartz deformation lamellae and microfractures in lower paleozoic quartzites from the white river uplift record a northwest direction of compression which can be related to joint and fault orientations and in situ stress determinations crystallographic orientations of deformation lamellae resemble those formed in the subbasal i relatively nonselective domain microfractures in quartz grains form orthogonal sets of generally north northeast and west northwest trending fracutres which are approximately normal to bedding the strongest set of microfractures in most samples lies in the 2 plane deduced from deformation lamellae analyses suggesting that the microfractures are extensional features maxima of microfractures correspond to maxima of joints measured at adjacent locations the strikes of prominent west northwest sets of microfractures and joints are subparellel to the dominant northwest strike of faults on the uplift in situ stress measurements conducted in the piceance basin and rangely colorado areas indicate principal stress orientations similar to those determined from quartz deformation lamellae microfractures and joints which are pre uplift to early uplift late laramide fabric elements

circulation of summer pacific halocline water in the arctic ocean 1 we present an analysis of arctic ocean hydrographic and sea ice observations from the 1990s with a focus on the circulation of water that originates in the north pacific ocean previous studies have shown the presence of two varieties of relatively warm summer halocline water in the vicinity of the chukchi sea i e the relatively fresh alaskan coastal water acw and the relatively saltier summer bering sea water sbsw here we extend these studies by tracing the circulation of these waters downstream into the arctic ocean we find that acw is generally most evident in the southern beaufort gyre while sbsw is strongest in the northern portion of the beaufort gyre and along the transpolar drift stream we find that this separation is most extreme during the early mid 1990s when the arctic oscillation was at historically high index values this leads us to speculate that the outflow to the north atlantic ocean through the canadian archipelago and fram strait may be similarly separated as arctic oscillation index values fell during the later 1990s acw and sbsw began to overlap in their regions of influence these changes are evident in the area north of ellesmere island where the influence of sbsw is highly correlated with a 3 year lag with the arctic oscillation index we also note the presence of winter bering sea water wbsw which underlies the summer varieties all together this brings the number of distinct pacific water types in our arctic ocean inventory to three acw sbsw and wbsw

mechanics of monoclinal systems in the colorado plateau during the laramide orogeny monoclines developed in the colorado plateau region during the laramide orogeny are divided into western and eastern groups by a broad nnw trending antiform through the central part of the plateau in the western group the major monoclines verge to the east whereas in the eastern group the major monoclines verge to the west paleogeographic reconstruction based on paleocurrent indicators and sedimentary facies distribution suggests that the broad antiform was developed during the laramide orogeny and was coeval with the formation of the monoclines in the plateau this relationship implies that the monoclines were drag folds verging towards the center of the plateau as a response to the antiformal warping of the plateau to simulate the warping of the plateau region and the stress distribution that produced the variable trends of the monoclines an elastic thin plate model considering in plane stress was developed this model assumes that 1 sedimentation in the laramide basins provided vertical loading along the edge of the plateau region 2 frictional sliding was operating along the laramide faults on the northern and eastern boundaries and 3 the greatest regional compressive stress was oriented in the n60 e direction and was applied uniformly along the western and southwestern sides of the plateau buoyancy due to instantaneous isostatic adjustment of crustal thickening or magmatic addition was also considered the result of the model suggests that the frictional strength of the uinta thrust system on the northern side of the plateau is at least 2 times greater than that along the park range and sangre de cristo thrust systems on the eastern side of the plateau in order to explain the observed monoclinal trends and the warping pattern within the plateau during the laramide orogeny

laramide orogeny related controls on coal mine ground instability in cretaceous coal seams southern rocky mountain foreland abstract investigation of ground conditions in nine coal mines located in the structurally complex southern rocky mountain foreland tectonic province suggest that structural compression associated with the late cretaceous eocene laramide orogeny caused deformation of cretaceous aged coal seams structures include low angle bedding plane faults and drag folds that are indicative of bedding plane faulting other structures include high angle joints and faults the pattern of structural geologic features documented during mine mapping is similar to the local trends of regionally extensive thrust faults fold axes and basement cored uplifts that formed during the laramide orogeny this suggests that the observed structural geologic features in mines developed in cretaceous coal seams reflect regional deformation that occurred in response to the laramide orogeny the geologic structures documented in colorado new mexico and utah coal mines were commonly associated with major instances of ground failure the recognition of regional tectonic controls on relatively localized geologic structures has important implications for the prediction of degraded ground conditions in advance of mining because the structural discontinuities observed in coal mine immediate roof strata formed in response to regional stress conditions during orogenic activity they can often be simply characterized as linear zones that are relatively continuous along strike at the mine scale once recognized the structural zones can be projected in advance of mining so that section crews can be forewarned of potentially adverse ground conditions and be prepared to install appropriate supplemental support and local modifications to pillar design can be implemented to enhance long term stability thus geologic hazard mapping that incorporates structural geologic features as part of an integrated geologic characterization should be an appropriate method for ground control planning

topographic signatures in aquarius radiometer and scatterometer response theory suggests that topography large scale roughness will affect thermal emission at l band and could impact remote sensing of surface parameters such as soil moisture from space evidence is presented here for the existence of effects due to topography using data from the l band radiometers and scatterometer aboard the recently launched aquarius the correlation with the slope standard deviation at the topographic scale is presented for data over north africa and australia in the case of the radiometer brightness temperature is observed to increase at horizontal polarization and decrease at vertical polarization in the case of the scatterometer an increase with topographic roughness is observed for both polarizations the presence of the scatterometer provides an independent verification that the behavior observed is due to topography and the observations are consistent with predictions based on monte carlo simulations

mechanisms of pacific summer water variability in the arctic s central canada basin pacific water flows northward through bering strait and penetrates the arctic ocean halocline throughout the canadian basin sector of the arctic in summer pacific summer water psw is modified by surface buoyancy fluxes and mixing as it crosses the shallow chukchi sea before entering the deep ocean measurements from ice tethered profilers moorings and hydrographic surveys between 2003 and 2013 reveal spatial and temporal variability in the psw component of the halocline in the central canada basin with increasing trends in integrated heat and freshwater content a consequence of psw layer thickening as well as layer freshening and warming it is shown here how properties in the chukchi sea in summer control the temperature salinity properties of psw in the interior by subduction at isopycnals that outcrop in the chukchi sea results of an ocean model forced by idealized winds provide support to the mechanism of surface ocean ekman transport convergence maintaining psw ventilation of the halocline

atmospheric forcing of the beaufort sea ice gyre surface pressure climatology and sea ice motion 1 the beaufort gyre bg typically rotates anticyclonically and exerts an important control on arctic sea ice dynamics previous studies have shown reversals in the bg to rotate cyclonically during summer months and in recent decades throughout the annual cycle in this investigation we explore the synoptic climatology of atmospheric forcing and its relationship to sea ice motion and bg reversals a catalog of daily synoptic weather types is generated for the beaufort sea region covering the period 1979 to 2006 using ncep ncar reanalysis mean sea level pressure data principle components and k means cluster analyses mean synoptic type frequency persistence and duration values are calculated for each synoptic type and contrasted between the summer and winter seasons daily synoptic types are linked to changes in sea ice vorticity by using correlation analysis on lagged sea ice vorticity data lag correlations are found between synoptic types and sea ice vorticity smoothed over a 12 week running mean and show that cyclonic types which promote southerly or easterly atmospheric circulation over the southern beaufort sea commonly precede summer reversals furthermore significant seasonal within type variability in sea ice vorticity is detected within the synoptic types illustrating the importance of seasonal variability on these processes

origin of fracture porosity example from altamont field utah the occurrence of natural fracture systems in subsurface rock can be predicted if careful evaluation is made of the geologic processes that affect sedimentary strata during their cycle of burial diagenesis uplift and erosional unloading variations in the state of stress within rock arise for example from changes in temperature pore pressure weight of overburden or tectonic loading hence geologic processes acting on a sedimentary unit should be analyzed for their several contributions to the state of stress and this information used to compute a stress history from this stress history predictions may be made as to when in the burial cycle to expect fracture joint formation what type of fractures extension or shear may occur and which geologic factors are most favorable to development of fractures a stress history is computed for strata of the naturally fractured altamont oil field in utah s uinta basin calculations suggest that fractures formed in extension that the well cemented rocks are those most likely to be fractured that fractures began to develop only after strata were buried to great depth and that the fracture system continued to develop as strata were uplifted and denuded of overburden geologic evidence on fracture genesis and development is in accord with the stress history prediction stress history can be useful in evaluating a sedimentary basin for naturally fractured reservoir exploration plays

quality assessment of a satellite altimetry data product in the nordic barents and kara seas 1 satellite altimetry provides high quality sea surface height data that have been successfully used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales however the high latitude regions have traditionally been avoided due to the persistent sea ice cover most of the validation studies have focused on the areas below the polar circles in this paper we examine the quality and performance of a gridded satellite altimetry product in the nordic barents and kara seas the altimetric sea level in coastal areas is validated using available tide gauge records we show that at most locations in the nordic seas the altimetry and tide gauge measurements are in a good agreement in terms of the root mean square differences and the amplitudes and phases of the seasonal cycle the agreement deteriorates in the shallow areas of the barents and kara seas subject to the seasonal presence of sea ice and where the altimetry data are contaminated by the residual aliasing of unresolved high frequency signals the comparison of linear trends at the locations of tide gauges reveals discrepancies that need to be taken into account when interpreting long term changes of sea level in the region away from the coast the altimetry data are compared to drifter trajectories corrected for ekman currents the drifter trajectories are found consistent with the mesoscale variability of the altimetric sea level this study provides the first comprehensive validation of a gridded satellite altimetry data product in the high latitude seas

moment tensor inversion of microseisms from the b sand propped hydrofracture m site colorado abstract we apply a moment tensor inversion algorithm to microseismic events generated by hydrofracturing our dataset consists of microseismic events associated with a hydraulic fracturing experiment conducted at the gri doe m site near rifle colorado the event recordings were from a vertical string of 3 component accelerometer pods that are cemented in a borehole the accelerograms clearly show p and s waves which can be rotated into the sh and sv components to invert the p and s amplitudes for moment tensors we use just the first two peaks after the first arrival using this amplitude information and the average pulse width we formed a symmetric stylized pulse for integration and we inverted for the moment tensor resolution tests revealed that with the source microseism to receiver geometry we have at the m site where all receivers are in one borehole and at the same azimuth from the source we can extract the five deviatoric components of the moment tensor using combinations of p sh and sv amplitudes for example a minimum data set of 3 p wave 2 sv wave and 1 sh wave amplitudes to obtain the sixth component which is the isotropic component requires amplitude information from receivers at another azimuth we studied seven high quality events in detail and tested their results against two alternative source geometries these microseismic events tend to have a major double couple nodal plane aligned parallel to the main hydrofracture plane rather than have their tension t axes aligned parallel to the regional minimum principal compressive stress direction the events have seismic moments m0 on the order of 10 5 nm and moment magnitudes mw of about 2 5

puzzling over the dynamics of the lofoten basin a sub arctic hot spot of ocean variability 1 a sub arctic hot spot of intense synoptic scale variability is observed in the lofoten basin lb of the norwegian sea using ers 1 2 and envisat satellite altimetry measurements we discover a cyclonic propagation of the synoptic scale sea surface height anomalies around the center of the lb surface drifter trajectories do not reveal an associated coherent near surface cyclonic flow suggesting that the propagating signals have a wavelike nature we identify a dipole and a quadrupole wave modes rotating around the center of the lb obtain analytic dispersion relations for these modes and demonstrate that the observed propagation is a manifestation of topographic rossby waves most of the observed waves have a wavelength of about 500 km and phase speeds ranging from 2 to 10 km day we show that these waves are largely responsible for the localization and amplification of sea surface height variability in the center of the lb

aperture size scaling variations in a low strain opening mode fracture set cozzette sandstone colorado the aperture size distribution of a set of opening mode fractures in the cozzette sandstone is complex and cannot be described uniquely by a single equation this study of horizontal core includes aperture size data of macrofractures measured using a hand lens and microfractures measured using scanning electron microscope based cathodoluminescence sem cl macrofractures are poorly cemented and total fracture strain is an order of magnitude lower than the smallest strain values of most previously described vein sets macrofractures in this set therefore resemble typical joints as opposed to veins in most respects although intragranular microfractures compose about 98 of the microfracture population orientation fracture fill and fracture trace characteristics suggest that only transgranular microfractures can be shown to be genetically related to macrofractures aperture size data below 0 012 mm and above 1 mm follow a log normal distribution intermediate size data though relatively sparse suggest a power law aperture size distribution these results support the notion that this fracture set is an intermediate case between typical veins and joints the results also suggest that processes leading to size distributions commonly associated with veins i e power laws may be present in joint sets but over a more limited range bound at small size scales by grain scale effects and above by mechanical layering effects

scaling relationships of joint and vein arrays from the burren co clare ireland abstract we present a study of the systematics of veins and joints in carboniferous limestones of the burren ireland scaling relationships were established for fracture arrays mapped from low elevation aerial photographs that image fractures on numerous limestone pavements for areas up to ca 1 km2 the veins and joints occur in the same sequence but have contrasting scaling properties the veins strike north south and cut many beds to form vertically persistent non stratabound arrays they are strongly clustered and have scale invariant geometric properties vein geometries suggest they grew sub critically under relatively high differential stresses during north south directed variscan compression the joints form stratabound arrays with regular spacings that scale with bed thickness they show greater strike variation than the veins and have lognormal length distributions the joints formed during uplift under low differential stress conditions the contrasting scaling properties of the joints and veins are attributed to different overburden stresses at the time of formation the veins formed at greater depths than the joints in conditions that favoured fracture propagation across mechanical discontinuities resulting in the development of non stratabound scaling properties

shelfbreak current over the canadian beaufort sea continental slope wind driven events in january 2005 the shelfbreak current over the beaufort sea continental slope is known to be one of the most energetic features of the beaufort sea hydrography in january 2005 three oceanographic moorings deployed over the canadian eastern beaufort sea continental slope simultaneously recorded two consecutive shelfbreak current events with along slope eastward bottom intensified flow up to 120 cm s 1 both events were generated by the local wind forcing associated with two pacific born cyclones passing north of the beaufort sea continental slope toward the canadian archipelago over the mooring array the associated westerly wind exceeded 15 m s 1 these two cyclones generated storm surges along the beaufort sea coast with sea surface height ssh rising up to 1 4 m following the two westerly wind maxima we suggest that the westerly along slope wind generated a surface ekman onshore transport the associated ssh increase over the shelf produced a cross slope pressure gradient that drove an along slope eastward geostrophic current in the same direction as the wind this wind driven barotropic flow was superimposed on the background baroclinic bottom intensified shelfbreak current that consequently amplified summer fall satellite altimetry data for 1992 2013 show that the ssh gradient in the southeastern beaufort sea is enhanced over the upper continental slope in response to frequent storm surge events because the local wind forcing and or sea ice drift could not explain the reduction of sea ice concentration over the beaufort sea continental slope in january 2005 we speculate that wind driven sea level fluctuations may impact the sea ice cover in winter

regional fractures i a mechanism for the formation of regional fractures at depth in flat lying reservoirs 1 regional fractures may form slowly at depth in extension and parallel to regional horizontal tectonic compression such fracture sets can be common in reservoirs despite the absence of flexure of the strata and are commonly important contributors to reservoir permeability such fractures make good targets for deviated wells high formation pore pressure is crucial to creating low effective confining stresses and brittle rock properties in the reservoirs conditions conducive to fracturing despite deep burial but pore pressure does not exceed the least principal stress and does not cause tensile fracturing the mechanism of natural hydraulic fracturing is incompatible with the characteristics of most regional fracture sets rather many regional fractures form duri g far field compression initiate at locally induced tensile stresses caused by flaws in the rock and propagate in the plane of the maximum and intermediate compressive stresses the differential stress required for initiation and propagation of regional fractures is well below that necessary for shear failure in the presence of high pore pressure fractures can be held open at depth by a tectonic basinwide dilatancy of the strata and the open void space commonly becomes mineralized

kugmallit valley as a conduit for cross shelf exchange on the mackenzie shelf in the beaufort sea 1 kugmallit valley spans the midsection of a transect across the mackenzie shelf of the beaufort sea its greatest relief is 20 m and its width is 20 km using a yearlong record of ice drift ocean current temperature and salinity acquired near the center of the valley we describe a pattern of flow that is correlated with wind stress and ice motion and discuss its similarity to flow within larger submarine canyons that cut through the shelf break as in such canyons there is enhanced cross shelf transport within kugmallit valley during upwelling favorable surface stress the data also document the down valley flow of dense water from a flaw lead

laramide crustal thickening event in the rocky mountain foreland and great plains the rocky mountain foreland and great plains of the western united states were formerly part of a continental platform adjusted by erosion and deposition in cambrian through jurassic time to near mean sea level and therefore to a near uniform crustal thickness of approximately 33 km today the region stands at regional elevations up to 2 km isostatically supported by a crust exceeding 50 km in thickness reasonable estimates of tertiary sedimentation and laramide strain do not account for more than 15 of the implied thickening however from approximately 70 40 m y b p this region was underlain by a horizontally subducting slab of farallon plate lithosphere moving northeast this slab could have been the cause of the thickening finite difference thermal models with specified kinematics show only a temporary cooling of the base of the north american lithosphere by this slab the excess weight of the slab would have depressed the region plate bending calculations show a quantitative agreement of predicted depression with upper cretaceous isopachs since depression by this slab lasted until the eocene at least the latest cretaceous regression was probably caused by a laramide crustal thickening event the farallon slab might have caused crustal thickening in two ways its excess weight would have drawn in ductile lower crust from surrounding regions however calculations show that this effect is too slow too local and too reversible to explain most of the crustal thickening therefore it seems likely that ductile lower crust was transported from sw to ne by shear stresses which the farallon plate exerted on the base of the north american lithosphere a preliminary finite element calculation based on this hypothesis shows the correct general pattern of crustal thickening an unexpected but encouraging result is that predicted principal compression directions are orthogonal to many laramide basement uplifts

seasonal variability of water mass distribution in the southeastern beaufort sea determined by total alkalinity and δ18o 1 we examined the seasonal variability of water mass distributions in the southeastern beaufort sea from data collected between september 2003 and august 2004 salinity total alkalinity ta and isotopic composition 18o of seawater were used together as tracers of freshwater input i e meteoric water and sea ice meltwater we used an optimum multiparameter analysis to identify the different water masses including the mackenzie river sea ice melt sim winter polar mixed layer pml upper halocline water uhw with core salinity of 33 1 psu pacific origin and atlantic water computed values of co2 fugacity in seawater fco2 sw show that the surface mixed layer sml remains mostly undersaturated 328 55 atm n 552 with respect to the average atmospheric co2 concentration 380 5 atm over the study period the influence of the mackenzie river fco2 sw 500 atm was relatively small in the southeastern beaufort sea and significant fractions were only observed on the inner mackenzie shelf the contribution of sea ice melt fco2 sw 600 atm was usually located between 120 and 180 m depth but could contribute to the sml during wind driven upwelling events in summer and autumn and during brine driven eddies in winter

circulation dense water formation and outflow on the northeast chukchi shelf we investigated circulation and water mass modification processes in the chukchi sea using 1 temperature salinity and velocity data collected between september 1991 and september 1992 from moorings in bering strait and the northeast shelf and 2 meteorological data and ice concentrations derived from special sensor microwave imager ssm i imagery in october 1991 and from february to august 1992 the mean monthly circulation was steady and northward from november to january strong northeast winds diverted the low salinity bering inflow onto the western shelf and weakened and reversed flow over the northeast shelf the winds also opened extensive polynyas wherein cold hypersaline salinity 34 waters formed the fall winter circulation enhanced dense water formation by diverting low salinity waters away from and prolonging the residence time of water within the polynyas alongshore convergence of the coastal flow swept some of the cold hypersaline water offshore across isobaths but the coastal current carried most of it into the arctic ocean through barrow canyon the dense outflow mixed little during its descent through the upper canyon where bottom friction and rotation but not entrainment were important in the plume momentum balance if the outflow is not diluted by mixing in the lower canyon where theory suggests this will occur then the densest shelf waters can ventilate layers deeper than the halocline salt rejection estimates using ssm i data and surface heat budget calculations agree within a factor of 2 with independent estimates from the mooring hence remote sensing techniques can monitor winter salt rejection rates in the chukchi sea

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

simulating topographic effects on spaceborne radiometric observations between l and x frequency bands a numerical simulator of satellite microwave radiometric observations of orographically complex scenes at various frequencies and observation angles has been developed the simulator of topographic artefacts in microwave radiometry stamira exploits the information on the relief extracted from a digital elevation model and has been applied to a test case concerning a mountainous area in the alps by assuming a simplified land cover scenario consisting of bare terrain with two kinds of roughness smooth and rough soils the 1 10 ghz range has been considered to determine scattering and emission of soil and a nonscattering atmosphere has been supposed the simulations have shown the large impact of the rotation of the polarization plane and of the brightness temperature enhancement occurring for facets illuminated by radiation from the surrounding elevated terrain with respect to flat surfaces which scatter atmospheric downward radiation only by considering also the antenna pattern integration and the dependence of surface emissivity on the local observation angle we have found that for our case study the brightness temperature is larger than that measured observing a flat terrain at horizontal polarization at vertical polarization the opposite occurs these differences are analyzed and quantified

comparison of slope estimates from low resolution dems scaling issues and a fractal method for their solution five different algorithms for calculating slope from digital elevation models dems have been compared from regional to global scales though different methods produce different results the most significant outcome is that slope varies inversely with the dem grid size thus slopes estimated from coarse resolution data can be considered to produce significant underestimates of the true slope a fractal theory is adapted to solve this problem the variogram technique for the definition of fractal parameters is demonstrated to provide a relationship between slope and the spatial resolution of measurement the variation of fractal parameters is discussed at various scales and a model is developed to estimate the high resolution slope based on the coarse resolution dem by using fractal parameters the fractal parameters are estimated from the standard deviation of elevation in a 3 3 window of the dem to account for local variability in the surface standard deviation of elevation is found to be the most invariant property of different scale dems of the same area the model is validated using different resolution dems in southern spain and it is used to estimate the high resolution slope values at global scales based on a coarse resolution dem the slopes estimated using the technique outlined are a significant improvement on those estimated directly from the coarse resolution data slopes estimated in this way allow the more effective use of available coarse resolution data in regional and global scale modelling studies copyright 1999 john wiley sons ltd

fracture of summer perennial sea ice by ocean swell as a result of arctic storms 1 the arctic summer minimum sea ice extent has experienced a decreasing trend since 1979 with an extreme minimum extent of 4 27 106 km2 in september 2007 and a similar minimum in 2011 large expanses of open water in the siberian laptev chukchi and beaufort seas result from declining summer sea ice cover and consequently introduce long fetch within the arctic basin strong winds from migratory cyclones coupled with increasing fetch generate large waves which can propagate into the pack ice and break it up on 06 september 2009 we observed the intrusion of large swells into the multiyear pack ice approximately 250 km from the ice edge these large swells induced nearly instantaneous widespread fracturing of the multiyear pack ice reducing the large 1 km diameter parent ice floes to small 100 150 m diameter floes this process increased the total ice floe perimeter exposed to the open ocean allowing for more efficient distribution of energy from ocean heat fluxes and incoming radiation into the floes thereby enhancing lateral melting this process of sea ice decay is therefore presented as a potential positive feedback process that will accelerate the loss of arctic sea ice

circulation in the vicinity of mackenzie canyon from a year long mooring array abstract data from a five mooring array extending from the inner shelf to the continental slope in the vicinity of mackenzie canyon beaufort sea are analyzed to elucidate the components of the boundary current system and their variability the array part of the marine arctic ecosystem study mares was deployed from october 2016 to september 2017 four distinct currents were identified an eastward directed flow adjacent to the coast a westward flowing surface intensified current centered on the outer shelf a bottom intensified shelfbreak jet flowing to the east and a recirculation at the base of the continental slope within the canyon the shelf current transports 0 12 0 03 sv in the mean and is primarily wind driven the response is modulated by the presence of ice with little to no signal during periods of nearly immobile ice cover and maximum response when there is partial ice cover the shelfbreak jet transports 0 03 0 02 sv in the mean compared to 0 08 0 02 sv measured upstream in the alaskan beaufort sea over the same time period the loss of transport is consistent with a previous energetics analysis and the lack of pacific origin summer water downstream the recirculation in the canyon appears to be the result of local dynamics whereby a portion of the westward flowing southern limb of the beaufort gyre is diverted up the canyon across isobaths this interpretation is supported by the fact that the low frequency variability of the recirculation is correlated with the wind stress curl in the canada basin which drives the beaufort gyre