crustal velocity structure of the omineca belt southeastern canadian cordillera travel time inversion and amplitude modeling of a 350 km lithoprobe seismic refraction wide angle reflection profile determined the velocity structure of the crust and upper mantle along strike in the omineca belt of the canadian cordillera the upper crust to 12 18 km depth has velocities from 5 6 to 6 2 km s 1 and two shear zones the monashee decollement and gwillim creek shear zone are imaged by the wide angle reflections and velocity trends minor velocity differences on either side of the monashee decollement may be related to separate rock origins prominent reflections define the boundaries of a low velocity midcrustal layer from 10 15 km to 20 25 km depth with velocities less than 6 1 km s 1 the low velocities of the midcrust associated with high electrical conductivities and high heat flow may be considered as support for the hypothesis of fluids in the cordilleran crust though other possibilities such as the effect of high temperatures on rock velocities are possible in the lower crust velocities range from 6 4 6 5 km s 1 at the top of the lower crust to 6 6 6 8 km s 1 at its base the moho is very clearly defined by the refraction wide angle reflection data and has a gentle southerly dip crustal thicknesses are 35 37 km a thin crust mantle transition zone of 1 2 km thickness in which velocities vary between 7 6 and 7 7 km s 1 is consistent with coincident reflection data upper mantle velocities range from 7 9 to 8 1 km s 1 with indications from the data of upper mantle layering in comparison with neighboring regions the omineca belt has an anomalously thin crust low crustal velocities and a low velocity upper mantle similar only to the basin and range province the velocity structure may partly mirror the temperature profile which has overprinted the geological signature of the region as measured by the seismic refraction method the characteristics of a thin crust and lithosphere along with low velocities from midcrust to mantle suggests that both the basin and range and the southern canadian cordillera are currently being heated from a source within the mantle

a hydrocarbon exploration model for the cretaceous ferron sandstone member of the mancos shale and the dakota group in the wasatch plateau and castle valley of east central utah with emphasis on post 1980 subsurface data ofr 160

sedimentology and organic properties of lower tertiary lacustrine source rocks lunpola basin central tibetan plateau implications for hydrocarbon potential abstract the tertiary lacustrine niubao formation is well exposed in the middle western part of the lunpola basin central tibetan plateau where crude oil was once discovered during drilling campaigns sedimentological organic petrographic and geochemical work was performed on the upper and middle members of this formation in order to investigate its hydrocarbon source rock potential sedimentological analyses indicate that both members were deposited in relatively deep lake conditions away from the influence of big stream system with the upper niubao formation unf having higher sand content the two members contain abundant high quality type i kerogen derived mainly from plankton algae and bacteria compared with samples of the middle niubao formation mnf unf samples also contain more type ii and type iii kerogens of terrestrial origin biomarkers of source rock extracts suggest that a long standing anoxic stratified and saline ancient lake occupid the basin during deposition of the two members which was conducive to the preservation of organic matter however higher gammacerane content and the presence of carotane in mnf samples imply a more saline lake condition rock eval t max and biomarker parameters reveal marginal maturity and immaturity for samples from mnf and unf respectively therefore mnf has better source rocks of higher maturity might be the main hydrocarbon generating member of the basin similar diagnostic biomarkers and biomarker parameters reported in the crude oil also imply its affiliation with the source rocks of mnf

formation of internally drained contractional basins by aridity limited bedrock incision 1 low internal relief aridity and internal drainage characterize the puna altiplano plateau and the tibetan plateau and the tarim basin structurally these areas are reverse fault bounded terrains with intervening wedge top basins that store thick accumulations of sediment for millions of years orographic barriers along the margins of these basins are oriented normal to moisture bearing winds resulting in regional aridity the combination of this aridity rapid shortening and uplift rates and resistant exposed lithologies coincides with the location of these internally drained basins we hypothesize that these large internally drained areas persist indefinitely when uplift overwhelms the fluvial systems and defeats the channel network to test this hypothesis we developed models of channel defeat to examine the threshold conditions required to fragment the channel network the results of these models suggest that low erodibility rocks moderate to high uplift rates and low precipitation favor defeat of orogen traversing channels most coupled tectonic landscape development models prevent the development of internal drainage and so may overestimate the voracity of erosion in regimes that favor internal drainage profoundly influencing predicted orogenic growth patterns

correlation between the depth to the lower crustal high conductive layer and heat flow in the canadian cordillera abstract in much of the southern canadian cordillera the top of the lower crustal electrical conductor coexists with the 450 c isotherm a statistical correlation between the depth to the top of the lower crustal electrical conductor heat flow and 450 c isotherm are shown based on mt and heat flow results in southern british columbia canada the depth to the lower crustal conductor and the depth to the 450 c isotherm vary from 20 35 km in western b c insular belt coast plutonic complex intermontane belt to less than 10 km in the eastern part of the canadian cordillera omineca belt the largest depths are in the insular belt 35 km the coexistence of the top of the lower crustal electrical conductor top of the zone of lower crustal seismic reflectors and 450 c isotherm supports the hypothesis that the 450 c isotherm defines the top of the zone over which interconnected fluid can exist in the lower crust

evaluation of undiscovered natural gas in the upper cretaceous ferron coal wasatch plateau total petroleum system wasatch plateau and castle valley utah abstract the total petroleum system approach was used to estimate undiscovered gas potential of the wasatch plateau and castle valley central utah the ferron coal wasatch plateau total petroleum system was geologically defined and subdivided into seven assessment units six of which were formally evaluated geologic data considered in defining the assessment unit boundaries included thermal maturity coal presence and thickness overburden thickness and faulting intensity historical production data were also used to estimate volumes of gas from undrilled areas the one conventional assessment unit includes almost the entire area of the petroleum system and is characterized by known accumulations that occur in structural or combination traps in sandstone reservoirs the estimated undiscovered conventional producible gas that may be added to reserves of this unit ranges from a low f95 of 14 8 billion cubic feet bcfg 419 million cubic meters mm 3 of gas to a high f5 of 82 bcfg 2321 mm 3 and a mean value of 39 9 bcfg 1130 mm 3 continuous gas accumulations are those in which the entire assessment unit is considered to be gas charged within these assessment units there may be wells drilled that are not economic successes but all are expected to contain gas coalbed gas is in this continuous category mean estimates of undiscovered gas for the five continuous assessment units are 1 northern coal fairway drunkards wash 752 3 bcfg 21 323 mm 3 2 central coal fairway buzzard bench 536 7 bcfg 15 194 mm 3 3 southern coal fairway 152 6 bcfg 4320 mm 3 4 deep 6000 feet plus coal and sandstone 59 1 bcfg 1673 mm 3 5 southern coal outcrop 10 6 bcfg 300 mm 3 and joes valley and musinia grabens not assessed the mean estimate of undiscovered gas for the entire tps is 1551 2 bcfg 43 914 mm 3 there is a 95 chance that at least 855 7 bcfg 24 225 mm 3 and a 5 chance that at least 2504 bcfg 70 888 mm 3 of undiscovered producible gas remain in the tps

broadside wide angle seismic studies and three dimensional structure of the crust in the southeast canadian cordillera broadside or fan recordings of a lithoprobe seismic refraction wide angle reflection experiment in the southeastern canadian cordillera show several features further illuminating the crustal structure beyond that previously derived from score 90 southern cordillera refraction experiment of 1990 in line data analysis of a nearly in line profile centred on castlegar british columbia shows lower velocities in the upper crust associated with the purcell anticlinorium as well as velocity variations that may have some association with the purcell fault zone the depth to moho is almost 38 km somewhat deeper and on trend with the structure that has been established farther north the broadside records show high signal to noise ratio pmp arrivals i e reflections from the bottom of the crust these pmp fan picks were analysed in regions away from in line profiles providing further measurements of the depth to moho in the southeastern cordillera the analysis of the broadside records combined with t

how flat is tibet high resolution digital topography three arc second grid for most of tibet provides new information to characterize the relief of the highest and largest plateau on earth the arid to semiarid central and northern part of the plateau interior has low relief average slopes of over 250 m windows and a mean elevation of 5023 m above sea level at moderate wavelengths of m relief is or less for most of tibet as opposed to the much higher relief of up to 6 km on the plateau edges where glacial and fluvial dissection is greater because of higher levels of precipitation the only faults manifesting significant topographic relief are the relatively small scale generally north trending graben systems primarily in southern tibet and several large scale fault systems near the edges of tibet the flatness of tibet implies that 1 there has been little deformation especially shortening of the uppermost crust north of the graben systems during the late cenozoic and 2 shallow crustal isostatic compensation has been acting to level the surface of the plateau

paleocene eocene foreland basin evolution in the himalaya of southern tibet and nepal implications for the age of initial india asia collision siliciclastic sedimentary rocks derived from the southern lhasa terrane sitting depositionally upon rocks of the northern indian passive continental margin provide an estimate of the age of initial contact between the continental parts of the indian and asian plates we report sedimentological sedimentary petrological and geochronological data from upper cretaceous paleocene strata in the sangdanlin section located along the southern flank of the indus yarlung suture zone in southern tibet this is probably the most proximal and therefore the oldest record of the india asia collision these strata were deposited by high density turbidity currents or concentrated density flows and suspension settling of pelagic biogenic debris in a deep marine setting an abrupt change from quartz arenitic to feldspatholithic sandstone compositions marks the transition from indian to asian sediment provenance the abrupt compositional change is accompanied by changes in u pb ages of detrital zircons diagnostic of a sediment provenance reversal from indian to asian sources the timing of the transition is bracketed between 60 ma and 58 5 0 6 ma by detrital zircon u pb ages and zircon u pb ages from a tuffaceous bed in the upper part of the section in the context of a palinspastically restored regional paleogeographic framework data from the sangdanlin section combined with previously published data from the northern tethyan himalaya and the frontal nepalese lesser himalaya and subhimalaya suggest that a flexural wave migrated 1300 km southward across what is now the himalayan thrust belt from paleocene time to the present

crustal velocity structure in the eastern insular and southernmost coast belts canadian cordillera seismic refraction data recorded along a 330 km cross strike profile through the eastern insular and southernmost coast belts of the canadian cordillera are interpreted using an iterative combination of traveltime inversion and amplitude forward modelling the resultant model is characterized by large lateral variations in velocity the most significant of these variations is a decrease in upper and middle crustal velocities to the east of the surface trace of the harrison fault which likely represents the transition from crust of the insular superterrane to that of the intermontane superterrane this interpretation is consistent with some present geological models that place the possible probable location of the suture between the two superterranes less than 20 km east of the harrison fault velocities at the base of the upper crust average 6 4 and 6 2 km s west and east of the fault respectively mid crustal velocities average 6 6 6 9 km s to the west and 6 35 6 45 km s to the east of the fault low

conditions for flow in the continental crust 1 earthquake focal depth distributions and effective elastic thickness variations on the continents suggest that in old cold regions such as shields the lower continental crust can be stronger than the upper mantle and imply that the upper mantle can flow even when the lower crust does not however in other places substantial flow in the lower crust does occur particularly near extensional metamorphic core complexes we suggest that the lower crust only flows when its viscosity is significantly reduced either by heating from igneous intrusions or by the addition of water in both cases the important characteristics of the flow are a consequence of the limited time over which the viscosity reduction occurs the timescale is controlled either by conductive cooling of intrusions or by the separation of melt from its matrix which removes the water

inversion of three dimensional wide angle seismic data from the southwestern canadian cordillera seismic refraction wide angle reflection data were recorded on a triangular array in southwestern british columbia centered on the boundary between the coast belt to the southwest and the intermontane belt to the northeast the experiment part of the lithoprobe southern cordillera transect enabled determination of the three dimensional 3 d velocity structure of the crust and upper mantle an algorithm for the inversion of wide angle seismic data to determine 3 d velocity structure and depth to reflecting interfaces is developed the algorithm is based on existing procedures for the inversion and forward modeling of first arrival travel times and forward modeling of reflection travel times including 1 forward modeling using a 3 d finite difference algorithm and 2 a simple velocity model parameterization for the inversion which eliminates the need to solve a large system of equations the existing procedure is extended to allow 1 the inversion of reflection times to solve for depth to a reflecting interface and or velocity structure 2 the inversion of first arrival travel times to solve for depth to a refracting interface and 3 layer stripping application of the algorithm to southern cordillera data uses pg to constrain upper crustal velocity structure pmp to constrain lower crustal velocity structure and depth to moho and pn to constrain upper mantle velocities and depth to moho the 3 d velocity model for the southwestern canadian cordillera is characterized by 1 significant lateral velocity variations at all depths that do not in general correlate with surface geological features or gravity data 2 a relatively high velocity middle and lower crust in the southwestern part of the study area which correlates with a strong relative gravity high and outlines the eastern extent of lower wrangellia an accreted terrane forming the insular belt to the west 3 a narrow zone of slower velocity in the lower crust and change in crustal thickness associated with the fraser fault system lending additional support to the view that it is a crustal penetrating fault 4 an average upper mantle velocity of 7 85 km s and 5 a depth to moho of 33 36 km in the intermontane belt and 36 38 km throughout most of the coast belt decreasing in the west to 33 km near the insular coast contact horizontal velocity structure slices and an interpreted cross section based on these and other results show the complexity of crustal structure in the region

tectonic and sedimentary basin evolution of the eastern bangong nujiang zone tibet a reading cycle the ophiolite bearing bangong nujiang zone bnz traversing central tibet from east to west separates the qiangtang block in the north from the lhasa block in the south their stratigraphic development indicates that both blocks once formed a continuous continental platform until the late triassic following late paleozoic triassic rifting ocean crust formed between both blocks during the late triassic creating the dongqiao naqu basin dnb among other basins yu et al 1991 the analysis of the rift flank sequences reveals that rifting was dominated by transtension the basin was shortened by post mid cretaceous transpression thus the overall basin evolution represents a reading cycle despite some active margin processes which gave this cycle a special imprint major basin parts were preserved despite transpressional shortening suggesting that the eastern bnz represents a remnant basin our understanding of the dnb solves the prior problem of viewing the bnz as a mid late jurassic collisional suture although typical collision related deformation thickening mountain building as well as related molasse formation are lacking our model also explains the scattered linear ophiolite distribution by local transpression of remnant oceanic basin floor without having to consider problematic long range ophiolite thrusting

small scale convection at a continental back arc to craton transition application to the southern canadian cordillera a step in the depth of the lithosphere base associated with lateral variations in the upper mantle temperature structure can trigger mantle flow that is referred to as edge driven convection this paper aims at outlining the implications of such edge driven flow at a lateral temperature transition from a hot and thin to a cold and thick lithosphere of a continental back arc this configuration finds application in the southern canadian cordillera where a hot and thin back arc is adjacent to the cold and thick north american craton a series of geodynamical models tested the thermodynamical behavior of the lithosphere and upper mantle induced by a step in lithosphere thickness the mantle flow patterns thickness and heat flow evolution of the lithosphere and surface topography are examined we find that the lateral temperature transition shifts cratonward due to the vigorous edge driven mantle flow that erodes the craton edge unless the craton has a distinct high viscosity mantle lithosphere the mantle lithosphere viscosity structure determines the impact of edge driven flow on crustal deformation and surface heat flow a dry olivine rheology for the craton prevents the edge from migrating and supports a persistent surface heat flow contrast these phenomena are well illustrated at the transition from the hot canadian cordillera to craton that is supported by a rheological change and that coincides with a lateral change in surface heat flow fast seismic wave velocities observed in the upper mantle cratonward of the step can be explained as downwellings induced by the edge driven flow

crustal velocity structure in the southern coast belt british columbia we applied an iterative combination of two dimensional traveltime inversion and amplitude forward modelling to seismic refraction data along a 350 km along strike profile in the coast belt of the southern canadian cordillera to determine crust and upper mantle p wave velocity structure the crustal model features a thin 0 5 3 0 km near surface layer with an average velocity of 4 4 km s and upper middle and lower crustal strata which are each approximately 10 km thick and have velocities ranging from 6 2 to 6 7 km s the moho appears as a 2 km thick transitional layer with an average depth of 35 km and overlies an upper mantle with a poorly constrained velocity of over 8 km s other interpretations indicate that this profile lies within a collision zone between the insular superterrane and the ancient north american margin and propose two collision zone models i crustal delamination whereby the insular superterrane was displaced along east vergent faults over the terranes below and ii crustal

production waters associated with the ferron coalbed methane fields central utah chemical and isotopic composition and volumes this study investigated the composition of water co produced with coalbed methane cbm from the upper cretaceous ferron sandstone member of the mancos shale in east central utah to better understand coalbed methane reservoirs the ferron coalbed methane play currently has more than 600 wells producing an average of 240 bbl day well water water samples collected from 28 wellheads in three fields buzzards bench drunkards wash and helper state of the northeast southwest trending play were analyzed for chemical and stable isotopic composition water produced from coalbed methane wells is a na cl hco3 type water from the drunkards wash field has the lowest total dissolved solids tds 6300 mg l increasing in value to the southeast and northeast in the helper state field about 6 miles northeast water has the highest total dissolved solids 43 000 mg l and major ion abundance indicates the possible influence of evaporite dissolution or mixing with a saline brine in the southern buzzards bench field water has variable total dissolved solids that are not correlated with depth or spatial distance significant differences in the relative compositions are present between the three fields implying varying origins of solutes and or different water rock interactions along multiple flow paths stable isotopic values of water from the ferron range from 0 9 to 11 4 18o and 32 to 90 2h and plot below the global meteoric water line gmwl on a line near but above values of present day meteoric water isotopic values of ferron water are consistent with modification of meteoric water along a flow path by mixing with an evolved seawater brine and or interaction with carbonate minerals analysis of isotopic values versus chloride conservative element and total dissolved solids concentrations indicates that recharge water in the buzzards bench area is distinct from recharge water in drunkards wash and is about 3 c warmer these variations in isotopes along with compositional variations imply that the ferron reservoir is heterogeneous and compartmentalized and that multiple flow paths may exist

suppressed vitrinite reflectance in the ferron coalbed gas fairway central utah possible influence of overpressure chemical and thermoplastic properties of coals in the ferron coalbed methane fairway indicate that coals in the north are of higher rank than coals in the south measured vitrinite reflectance does not accurately show this variation of coal rank although vitrinite reflectance in the southern and central part of the fairway is consistent with other measures of coal rank suppressed vitrinite reflectance is observed in the north where methane contents are relatively high this coincidence of suppressed reflectance and relatively high coalbed methane yields may be significant we speculate that the suppressed reflectance values result from a burial history where overpressure developed during the early stages of coalification and persisted until recent uplift and cooling such instances may be diagnostic of prospective coalbed methane targets elsewhere

crust and upper mantle velocity structure of the intermontane belt southern canadian cordillera as part of the lithoprobe southern cordillera transect seismic refraction data were recorded along a 330 km long strike profile in the intermontane belt an iterative combination of two dimensional traveltime inversion and amplitude forward modelling was used to interpret crust and upper mantle p wave velocity structure this region is characterized by i a thin near surface layer with large variations in velocity between 2 8 and 5 4 km s and low velocity regions that correlate well with surface expressions of tertiary sedimentary and volcanic rocks ii an upper and middle crust with low average velocity gradient possibly a weak low velocity zone and lateral velocity variations between 6 0 and 6 4 km s iii a distinctive lower crust characterized by significantly higher average velocities relative to midcrustal values beginning at 23 km depth approximately 8 km thick with average velocities of 6 5 and 6 7 km s at top and base iv a depth to moho as defined by wide angle reflections that aver

early cretaceous gangdese retroarc foreland basin evolution in the selin co basin central tibet evidence from sedimentology and detrital zircon geochronology the selin co basin in the northern lhasa terrane includes more than 3000 m of upward coarsening lower cretaceous strata and the sedimentary sequence from the flysch to the molasse indicates the evolution of a foreland basin petrographic analysis shows that sandstones are rich in volcanic and sedimentary lithics and most of them fall into recycled orogen and magmatic arc uranium lead u pb ages were determined for 435 detrital zircons from the lower cretaceous strata in the selin co basin relative probability of detrital zircon ages shows the eshaerbu formation was rich in zircon grains with the age of 125 140 and 160 180 ma and the duoni formation was dominated by one main age cluster of 125 150 ma analysis of the potential provenances suggests the early cretaceous zircon grains were primarily derived from the gangdese magmatic arc to the south the youngest zircon ages in the lowermost exposure of the eshaerbru formation are c 130 ma providing a maximum depositional age of sediments in the selin

large scale crustal deformation of the tibetan plateau the topography velocity and strain fields calculated from a three dimensional newtonian viscous model for large scale crustal deformation are generally in good agreement with results from geological geodetic and earthquake studies in and around the tibetan plateau provided that the model rheology incorporates a weak zone within the deep crust beneath the plateau equivalent to a viscosity of 1012 pa s within a 250 m thick channel or 1018 pa s within a 15 km thick channel model studies and observations show a plateau at 5 km elevation with steep topographic gradients across the southern and northern plateau margins and more gentle gradients across the southeastern and northeastern margins rapid shortening strain is concentrated along the lower portions of the northern and southern plateau margins at rates 20 mm yr model results show north south shortening 10 mm yr in reasonable agreement with gps data 5 8 mm yr of north south shortening across the northern two thirds of the plateau and east west stretching 10 15 mm yr across the eastern half of the high plateau in reasonable agreement with seismic geologic and gps data upper crustal material moves eastward from the plateau proper into a lobe of elevated topography that extends to the south and east clockwise rotation of material around the east himalayan syntaxis at rates up to 10 mm yr occurs partly as a result of dextral shear between indian and asian mantle at depth and partly as a result of gravitational spreading from the high plateau to the south and east there is little difference in model surface deformation for assumptions of moderately weak or extremely weak lower crust except in southern and northern tibet where margin perpendicular extension occurs only for the case of an extremely weak lower crust our results suggest that the tibetan plateau is likely to have gone through a two stage development the first stage produced a long narrow high orogen whose height may have been comparable to the modern plateau the second stage produced a plateau that grew progressively to the north and east east west stretching eastward plateau growth and dextral rotation around the east himalayan syntaxis probably did not begin until well into the second stage of plateau growth perhaps becoming significant after 20 m y of convergence

the geological evolution of the tibetan plateau the geological evolution of the tibetan plateau is best viewed in a context broader than the india eurasia collision zone after collision about 50 million years ago crust was shortened in western and central tibet while large fragments of lithosphere moved from the collision zone toward areas of trench rollback in the western pacific and indonesia cessation of rapid pacific trench migration 15 to 20 million years ago coincided with a slowing of fragment extrusion beyond the plateau and probably contributed to the onset of rapid surface uplift and crustal thickening in eastern tibet the latter appear to result from rapid eastward flow of the deep crust probably within crustal channels imaged seismically beneath eastern tibet these events mark a transition to the modern structural system that currently accommodates deformation within tibet

lithospheric structure in the southern canadian cordillera from a network of seismic refraction lines lithospheric velocity structure and its relationship to regional tectonics and development of the southern canadian cordillera are derived from a synthesis of interpretations from nine in line seismic refraction wide angle reflection profiles and broadside data recorded during the lithoprobe southern cordillera refraction experiment score and other refraction experiments across southern british columbia and one profile in northwestern washington consistency of the score two dimensional models at their intersection positions is achieved through application of a simultaneous inversion of all relevant traveltime data the cross sectional and map presentations demonstrate the strong degree of three dimensional heterogeneity within the crust and upper mantle a first order characteristic is the continuous increase in crustal velocities westward from the foreland belt to the insular belt the variations do not correlate with the morphogeological belts they do correspond with large scale geological and or

organic matter accumulation of the lacustrine lunpola oil shale central tibetan plateau controlled by the paleoclimate provenance and drainage system abstract the cenozoic lacustrine lunpola oil shale located in the central tibetan plateau has received little research interest in its depositional history although it is estimated to be a huge resource reserve this study investigates the palaeoclimate provenance and regional drainage system of the ancient lakes using a combined analysis of element geochemistry and stratigraphy to elucidate the depositional history of the lunpola oil shale most of the samples in the lower part of the section have chemical index of alteration cia values between 65 and 75 reflecting a moderate weathered source while samples in the upper part the section have cia values between 60 and 65 which indicate relatively weak chemical weathering in the source area this stratigraphic grouping suggests a paleoclimate transition from a relatively warm or humid period to a cold or dry period the zr sc and th sc ratios of the samples reveal that sorting and recycling were minor during deposition of the oil shale the geochemical results al2o3 cao na2o k2o a cn k diagrams high contents of th plots of co th la sc and cr th sc th demonstrate that the sedimentary sources were felsic rocks plots of la th sc th sc zr 10 th co zr 10 and ti zr versus la sc illustrate that the source rocks were from continental arc and active continental margin the baingoin batholiths to the south of the lunpola basin consisting mainly of cretaceous granodiorite and adamellite are likely responsible for supplying materials to the lunpola oil shale similar special ree patterns further suggest the affiliation of the oil shale with the batholiths provenance analyses indicate a main river from the south moreover stratigraphic study confirms an upstream ancient baingoin lake between the source area and the ancient lunpola lake in this drainage system paleoclimate clearly restricted the development of rivers around the lakes although terrestrial organic matter higher plants dominated the drainage area the main river originating from the south could only bring a certain amount of them to the lakes moreover considering the filtration of the upstream ancient baingoin lake minor terrestrial organic matter could be carried and deposited in the ancient lunpola lake therefore lacustrine algae could proliferate as the main organic source and preserve in the stratified hypersaline lake to form the largest oil shale resource in tibet

crustal velocity structure of the omineca and intermontane belts southeastern canadian cordillera we provide information on the physical properties across two important morphogeological regions of the southeastern canadian cordillera the omineca and intermontane belts and tie together two previously interpreted wide angle seismic lines which have separately probed each zone along strike the data analyzed here line 7 of lithoprobe s 1990 southern cordillera refraction experiment in southern british columbia is along a 410 km profile from the fraser river to radium hot springs near the rocky mountain trench iterative forward and inverse modeling of the seismic travel times constrained by seismic amplitude characteristics and earlier cross line interpretations defines a thin crust with relatively low velocities the upper crust has an average thickness of 15 3 km and an average p wave velocity of less than 6 1 km s 1 with velocities at the bottom reaching 6 2 6 3 km s 1 it is further characterized by velocity gradients which decrease markedly with depth and by low velocity trends which correlate with the traces of crustal scale shear zones a high velocity region at the west end of the profile is coincident with a major uplift structure the midcrust has an average thickness of 9 2 km with velocities below 6 1 km s 1 except for the extreme west end of the profile this defines a midcrustal low velocity zone lvz in the omineca belt and partly in the intermontane belt the lower crust from 24 km to 34 km depth has velocities averaging 6 6 6 7 km s 1 higher velocities in the deep crust may mark the westward extent of north american cratonic rocks at the okanagan valley the upper mantle velocity has an average 8 0 km 5 increasing to 8 2 km s 1 at the maximum depth of ray penetration at 48 km the model presented here compliments well the earlier interpretations of vertical incidence seismic reflection profiles the velocity structure of the crust especially the lvz closely correlates with the regional isotherms while there seems to be no well defined velocity boundary between the intermontane and omineca belts there are distinct velocity differences between the intermontane and neighboring coast plutonic complex to the west the low velocity characteristics of the omineca and much of the intermontane belts may be a consequence of temperature control of the physical parameters of the crust the lithosphere in the southeastern canadian cordillera is clearly anomalous with respect to much of northwest north america and in terms of crustal thickness and velocity structure it is similar only to the basin and range province of the united states

upper cretaceous ferron sandstone major coalbed methane play in central utah recent drilling for coalbed gas in the upper cretaceous ferron sandstone member of central utah has resulted in one of the most successful plays of this kind exploration to date has resulted in three fields and a potential fairway 6 10 mi 10 16 km wide and 20 60 mi 32 96 km long corresponding to shallow coal occurrence at depths of about 1800 3500 ft 545 1060 m in the ferron a sequence of interbedded fluvial deltaic sandstone shale and coal in the lower part of the cretaceous mancos shale coalbed methane cbm reservoirs in this interval consist of thin to moderately thick 3 10 ft 1 3 m coal beds of relatively low rank high volatile b bituminous and variable gas content ranging from 100 scf ton or less in the south to as high as 500 600 scf ton in the north productive wells have averaged more than 500 mcf day and after several years continue to typically show negative production declines in the major productive area drunkards wash unit the first 33 producers averaged 974 mcf and 85 bbl of water per day after five years of continuous production estimated ultimate recoverable reserves for individual wells in this unit range from 1 5 to 4 bcf based on several criteria including gas content thermal maturity and chronostratigraphy the play is divided into northern and southern parts the northern part is characterized by coals that have the following characteristics 1 high gas contents 2 moderate thermal maturity e g vitrinite reflectance ro values of 0 6 0 8 3 good permeabilities 5 20 md 4 lack of exposure and 5 overpressuring due to artesian conditions southern coals have much lower average gas contents 100 scf ton and lower thermal maturity ro 0 4 0 6 and they are exposed along an extensive 35 mi 56 km outcrop belt that may have allowed a degree of flushing these coals however are also thicker and more extensive than those to the north and thus may retain significant begin page 200 potential northern coals appear to contain a mixture of gas from three sources in situ thermogenic methane migrated thermogenic methane from more mature sources and late stage biogenic gas current development is focused on the northern part of the stated fairway where well control and an existing infrastructure are present indications are that cbm exploration in the ferron will expand considerably in the near future

strong lateral strength contrasts in the mantle lithosphere of continents a case study from the hot sw canadian cordillera abstract this study aims at quantifying the 3 d variability in lithosphere strength of the south eastern canadian cordillera and adjacent craton to the east strength is calculated in a forward manner starting from rheological laws of brittle and ductile deformation the work flow calculates a temperature model based on a multi layer compositional model and subsequently estimates the strength distribution from both the compositional and temperature models the temperature modeling involves numerical inversion and cubic spline algorithms which enable to impose boundary conditions that account better for strong lateral variations in lithosphere thickness and lateral heat flow this addresses the lithosphere structure between the canadian cordillera and craton the canadian cordillera is marked by a hot and thin lithosphere of 60 km thickness that stands in contrast to a cold and thick craton of 170 km thickness to the east which consequently results in pronounced changes in bulk lithosphere strength the high surface heat flow of the cordillera interior and its contrast with the foreland basin can be reproduced by temperature models that combine elevated mantle heat flow due to the thin lithosphere and higher crustal heat production from magmatic intrusions a series of rheological models which examines the role of different temperature input models composition and strain rate shows that the first order strength pattern is persistent for the hot canadian cordillera strength resides for 80 in the upper crust and with integrated lithosphere strength of 2 0 3 5 106 mpa m for the cold craton the upper mantle provides 75 of the integrated strength with values of 4 0 8 0 106 mpa m for the crust and 20 65 106 mpa m for the lithosphere effective elastic thickness is estimated between 5 and 15 km for the cordillera and 40 80 km for the craton this illustrates the cordillera to craton transition as a prominent rheological feature for upper mantle flow dynamics and spatial seismicity trends