application of carbon isotopes to detect seepage out of coalbed natural gas produced water impoundments abstract coalbed natural gas cbng production from coal bed aquifers requires large volumes of produced water to be pumped from the subsurface the produced water ranges from high quality that meets state and federal drinking water standards to low quality due to increased salinity and or sodicity the powder river basin of northeastern wyoming is a major coalbed natural gas producing region where water quality generally decreases moving from the southeastern portion of the basin towards the center most produced water in wyoming is disposed into impoundments and other surface drainages where it may infiltrate into shallow groundwater groundwater degradation caused by infiltration of cbng produced water holding impoundments into arid soluble salt rich soils is an issue of immense importance because groundwater is a major source for stock water irrigation and drinking water for many small communities in these areas this study examines the potential of using stable c isotope signatures of dissolved inorganic c 13 c dic to track the fate of cbng produced water after it is discharged into the impoundments other geochemical proxies like the major cations and major anions were used in conjunction with field water quality measurements to understand the geochemical differences between cbng produced waters and ambient waters in the study area samples were collected from the cbng discharge outfalls produced water holding impoundments and monitoring wells from different parts of the powder river basin and analyzed for 13 c dic the cbng produced waters from outfalls and impoundments have positive 13 c dic values that fall within the range of 12 to 22 distinct from the ambient regional surface and groundwaters with 13 c dic values ranging from 10 to 14 the results from the study demonstrate that these contrasting 13 c dic signatures can be used to trace seepage out of cbng produced water impoundments into shallow groundwaters

stable isotope paleoaltimetry and the evolution of landscapes and life abstract reconstructing topography of our planet not only advances our knowledge of the geodynamic processes that shape the earth s surface equally important it adds a key element towards understanding long term continental moisture transport atmospheric circulation and the distribution of biomes and biodiversity stable isotope paleoaltimetry exploits systematic decreases in the oxygen 18o or hydrogen d isotopic composition of precipitation along a mountain front when the interaction of topography and advected moist air masses induces orographic precipitation these changes in 18o or d can be recovered from the geologic record and recent geochemical and modeling advances allow a broad range of proxy materials to be evaluated over the last 10 yr stable isotope paleoaltimetry has witnessed rapidly expanding research activities and has produced a broad array of fascinating tectonic and geomorphologic studies many of which have concentrated on determining the elevation history of continental plateau regions these single site studies have greatly expanded what used to be very sparse global paleoaltimetric data the challenge now lies in disentangling the surface uplift component from the impact of climate change on 18o and d in precipitation the robustness of stable isotope paleoaltimetry can be enhanced when high elevation 18o or d data are referenced against low elevation sites that track climate modulated sea level 18o or d of precipitation through time approach analysis of central andean paleosols documents that differences in 18o of soil carbonate between the subandean foreland and the bolivian altiplano are small between 11 and 7 ma but rise rapidly to ca 2 9 after 7 ma corroborating the magnitude of late miocene change in 18o on the altiplano future advances in stable isotope paleoaltimetry will greatly benefit from addressing four key challenges 1 identifying topographically induced changes in atmospheric circulation and associated teleconnections in the global climate system that affect 18o or d of precipitation 2 evaluating on a case by case basis if temporal and spatial changes in isotope lapse rates influence interpretations of paleoelevation 3 interfacing with phylogenetic techniques to evaluate competing hypotheses with respect to the timing of surface uplift and the diversification of lineages 4 characterizing feedbacks between changes in surface elevation and atmospheric circulation as these are likely to be equally important to the diversification of lineages than changes in surface elevation alone tackling these challenges will benefit from the accelerating pace of improved data model comparisons and rapidly evolving geochemical techniques for reconstructing precipitation patterns most importantly stable isotope paleoaltimetry has the potential to develop into a truly interdisciplinary field if innovative tectonic paleoclimatic and evolutionary biology phylogenetic approaches are integrated into a common research framework it therefore opens new avenues to study the long term evolution of landscapes and life

a multi isotope approach for understanding sources of water carbon and sulfur in natural springs of the central appalachian region natural springs have been reliable sources of domestic water and have allowed for the development of recreational facilities and resorts in the central appalachians the structural history of this area is complex and it is unknown whether these natural springs receive significant recharge from modern precipitation or whether they discharge old water recharged over geological times scales the main objective of this study was to use stable isotopes of water delta 18 text o text h 2 text o and delta 2 text h text h 2 text o dissolved inorganic carbon delta 13 text c text dic and dissolved sulfate delta 34 text s text so 4 and delta 18 text o text so 4 to delineate sources of water carbon and sulfur in several natural springs of the region our preliminary isotope data indicate that all springs are being recharged by modern precipitation the oxygen isotope composition indicates that waters in thermal springs did not encounter the high temperatures required for o isotope exchange between the water and silicate carbonate minerals and or the residence time of water in the aquifers was short due to high flow rates the carbon isotopic composition of dissolved inorganic carbon and sulfur oxygen isotopic composition of dissolved sulfate provide evidence of low temperature water rock interactions and various biogeochemical transformations these waters have undergone along their flow path

three dimensional effects in high drag state flows over long ridges abstract numerical simulations of nonrotating flow with uniform basic wind and stability past long three dimensional 3d ridges are compared to the corresponding two dimensional 2d limit to reveal the importance of 3d effects for mountain heights smaller than the threshold for breaking waves the low level flow over the interior of the ridge is well described by 2d theory when the horizontal aspect ratio is roughly 10 or greater by contrast in flows with wave breaking significant discrepancies between 2d and 3d results remain apparent even for 12 it is found that the onset of wave breaking and the transition to the high drag state is accompanied in 3d by an abrupt increase in deflection of the low level flow around the ridge the increased flow deflection is produced at least in part by upstream propagating columnar disturbances forced by the transition to the high drag state the deflection of the incident flow reduces the amplitude of the mountain wave aloft relative to 2d and acts as a neg

instability of amuay cliffside this paper presents a case study of cliffside instability geotechnical analyses employing field measurements and laboratory test results obtained over a 30 yr period indicate that rising pore pressures trigger slides along the cliff visual observation surveys and field exploration show that most of the landslides have wedge type failure geometry shear occurs through a nearly horizontal stratum of weak clay brown fat clay the strength of the fat clay decreases with deformation fluids generated by domestic and industrial activities have resulted in a perched water layer above the stratum of fat clay for more than two decades the pore pressure on top of the fat clay has risen a wedge type of stability analysis can give the correct factor of safety i e 1 0 for the slides which have occured asce

empirical relationships between elevation and the stable isotope composition of precipitation and surface waters considerations for studies of paleoelevation change a compilation of 68 studies from throughout many of the world s mountain belts reveals an empirically consistent and linear relationship between change in elevation and change in the isotopic composition of precipitation along altitudinal transects the isotopic composition of precipitation decreases linearly with increasing elevation in most regions of the world except in the himalayas and at elevations 5000 m there are no significant differences in isotopic lapse rates from most regions of the world 0 28 permil 100 m except at the extreme latitudes where isotopic lapse rates are higher given information on past changes in the isotopic composition of precipitation preserved in pedogenic or authigenic minerals this global isotopic lapse rate can be used to place numerical constraints on the topo graphic development of some ancient mountain belts or plateaus there are many complicating factors that can confound interpretation of paleoel evation change based on stable isotopes and many of these are unique to specific mountain belts or time periods relevant to all stable isotope based paleoelevation change studies is the temperature dependent isotope fractionation between a pedo genic or authigenic mineral and the water from which it forms in cases where isotopic proxy minerals are sampled from localities where temperature will change simulta neously with elevation change the apparent change in the isotopic composition of precipitation may be dampened by several permil this suggests that samples taken from the rainshadow side of an emerging orographic barrier may be more likely to preserve isotopic changes resulting from mountain uplift than samples taken from atop a rising mountain range or plateau

embankment failures at vernon british columbia a section of highway 97 west of vernon b c is located over a soft to firm compressible silty clay subsoil in addition to an extensive site investigation the performance of two test embankments was observed for 2 years before construction was begun on the highway grade between them when the highway fill reached a maximum thickness of about 10 m a failure occurred the design was then changed to include berms on either side but a second failure occurred when the grade was rebuilt an undrained back analysis of the first failure shows the influence of various variables on the factor of safety and illustrates the difficulty of choosing appropriate strength values for design when the site has a strong crust overlying a weaker layer and there is potential for progressive failure observations of settlements pore pressures and lateral movements in the subsoil describe the performance of the embankment during construction and reveal the importance of strain softening as a factor in the failures compa

stable isotope evidence for rapid uplift of the central apennines since the late pliocene abstract the central apennines an accretionary wedge overlying an area of slab detachment are characterized by prominent topography active normal faulting and high uplift rates however previous studies have failed to resolve the surface uplift history complicating efforts to link the topographic evolution with underlying geodynamic processes we aim to better quantify orographic changes by using stable oxygen isotope paleoaltimetry modern surface water 18 o are 5 lower at high elevation than at sea level reflecting orographic rainout over the apennines we present 262 new lacustrine and paleosol carbonate 18 o measurements collected from ten extensional intermontane basins spanning both high and low elevations and combine these with 1 166 published 18 o data permitting us to constrain changes in 18 o both spatially and temporally since the pliocene 18 o in present day high elevation basins has continuously decreased even as 18 o in lowland basins has remained constant over time we attribute this continuous 5 shift to increased orographic rainout as the central apennines were uplifted we estimate an increase in mean elevation of approximately 1 2 km since the late pliocene and these estimates match the suggested timing and expected amplitude of slab break off related uplift this supports the hypothesis that the opening of the adriatic slab window and associated mantle flow contributed significantly to building topography in the central apennines

the strontium isotopic evolution of marcellus formation produced waters southwestern pennsylvania abstract the production of natural gas and natural gas liquids from unconventional tight shale formations involves hydraulic fracturing and subsequent removal of fluids co produced with the gas the chemistry of the returning fluid reflects the original composition of the injection water mobilized constituents in the shale formation and co mingled formation waters liberated by hydraulic fracturing produced water from unconventional gas wells tapping the middle devonian marcellus formation is characterized by high total dissolved solids tds including very high strontium concentrations in this study the strontium isotope composition 87 sr 86 sr was measured in produced waters from four horizontally drilled hydraulically fractured marcellus shale gas wells in southwestern pennsylvania sampled from the first day after commencement of flowback to as much as 27 months later the 87 sr 86 sr of the waters tended to change rapidly over the first few days of water return and then approached but did not reach a constant range of values from 0 7113 to 0 7114 which appears to be characteristic of this part of the marcellus play in contrast the concentration of sr rose more slowly and appeared to hit a steady state value up to 3000 mg l by the end of the first year taken together with results from earlier work these data suggest mixing between injected frac fluid and high tds formation water highly enriched in sr and isotopically relatively uniform throughout the marcellus shale gas play this brine could exist within porous lenses of organic matter in the shale in pre existing fractures within the shale and or originate from fluids that migrated from adjacent formations at some point during the post depositional history of the basin

genetic and temporal relations between formation waters and biogenic methane upper devonian antrim shale michigan basin usa abstract controversy remains regarding how well geochemical criteria can distinguish microbial from thermogenic methane natural gas in most conventional deposits has migrated from a source rock to a reservoir rarely remaining associated with the original or cogenetic formation waters we investigated an unusual gas reservoir the late devonian antrim shale in which large volumes of variably saline water are coproduced with gas the antrim shale is organic rich of relatively low thermal maturity extensively fractured and is both source and reservoir for methane that is generated dominantly by microbial activity this hydrogeologic setting permits integration of chemical and isotopic compositions of coproduced water and gas providing a unique opportunity to characterize methane generating mechanisms the well developed fracture network provides a conduit for gas and water mass transport within the antrim shale and allows invasion of meteoric water from overlying aquifers in the glacial drift steep regional concentration gradients in chemical and isotopic data are observed for formation waters and gases dilute waters grade into dense brines 300 000 ppm over lateral distances of less than 30 km radiogenic 14c and 3h and stable isotope 18o and d analyses of shallow antrim shale formation waters and glacial drift groundwaters indicate recharge times from modern to 20 000 yr bp carbon isotope compositions of methane from antrim shale wells are typical of the established range for thermogenic or mixed gas 13c 47 to 56 however the unusually high 13c values of co2 coproduced with methane 22 and dissolved inorganic carbon dic in formation waters 28 require bacterial mediation the d values of methane and coproduced formation water provide the strongest evidence of bacterial methanogenesis methane ethane propane ratios and 13c values for ethane indicate 1 the presence of a thermogenic gas component that increases basinward and 2 progressive bacterial oxidation of ethane as the antrim shale subcrop is approached multiple episodes of pleistocene glaciation over northern michigan appear critical to the development of these gas deposits loading of thick ice sheets may have provided hydraulic head that enhanced dilation of preexisting fractures and influx of meteoric water the physical erosion cycle of repeated glacial advances and retreats exhumed the antrim shale around the northern margin of the michigan basin subjecting it to near surface physiochemical and biochemical processes the chemical and hydrologic relations demonstrated in the antrim shale reservoir suggest a dynamic connection between pleistocene glacial history of the midcontinent region and development of recoverable microbially generated natural gas reserves

the cenozoic climatic and topographic evolution of the western north american cordillera herein we present oxygen isotope records from cretaceous to recent terrestrial sediments in the western north american cordillera the purpose of this analysis is to use oxygen isotope records to understand the coupled surface elevation and climate histories of this region through the cenozoic to do this we constructed 18o maps of surface waters for time intervals that trace the development of topography of western north america these maps are based on 4861 oxygen isotope analyses from both published 4478 and new 383 data we determined the 18o values of surface waters using paleotemperatures derived previously from floral assemblages and the appropriate isotope fractionation factors these data suggest that in the late cretaceous to early eocene the sevier hinterland formed a plateau of unknown height around 50 ma a topographic wave developed in british columbia and eastern washington that swept southward reaching northeastern nevada at 40 to 38 ma and southern nevada 23 ma this southward encroachment of an eocene plateau sweep caused reorganization of drainage patterns such that the intraforeland basins of wyoming and utah drainages extended deep within the sevier hinterland as the wave swept southward the landscape within the sevier hinterland developed into a rugged and high mountain range with the hypsometric mean elevation of 4 km and relief of 1 5 km this eocene highland was bordered on the west by a high sierra nevada ramp and on the east by the intraforeland basins that captured water draining these growing highlands the spatial and temporal evolution of this highland correlates with the timing of volcanism and extension these observations support tectonic models that call for north to south removal of the farallon slab or piecemeal removal of mantle lithosphere the isotopic data show that prior to growth of this highland the north american monsoon nam penetrated much farther north in the paleocene eocene than today the combined effects of global cooling increasing latitudinal temperature gradients and the generation of the orographic barrier created by the growing north to south highland produced a southward migration of the nam front by the oligocene the hydrologic regime that we observe today was in place it has been modified since then as a result of basin and range extension and collapse of the highlands in the mid miocene this collapse allowed the nam to penetrate farther north into the great basin of nevada and utah

thermogenic and secondary biogenic gases san juan basin colorado and new mexico implications for coalbed gas producibility the san juan basin is the most prolific coalbed gas basin in the world with 1992 production exceeding 440 gcf footnote 12 4 billion m3 resources of approximately 50 tcf 1 4 trillion m3 and proved reserves of over 6 tcf 170 billion m3 coalbed gas wells with the highest production initial potential greater than 10 mcf day or 0 28 million m3 day occur in the overpressured north central part of the basin hydrologic analysis indicates that overpressure in the fruitland formation is artesian in origin and represents repressuring that developed during the middle pliocene highly permeable laterally continuous coal beds override abandoned shoreline pictured cliffs sandstones and extend to the elevated recharge area in he northern basin to form a dynamic regionally interconnected aquifer system coal rank and basin hydrodynamics control the composition of fruitland coalbed gases which varies significantly across the basin chemically dry gases in the north central part of the basin coincide with meteoric recharge and regional overpressure the consistency of methane dgr13c values across the basin the presence of isotopically heavy carbon dioxide in coalbed gases and bicarbonate in formation waters and biodegraded n alkane distributions of some coal extracts indicate that coalbed gases in the north central basin are a mixture of thermogenic 25 50 secondary biogenic 15 30 and migrated thermogenic 12 60 gases migrated conventionally and hydrodynamically trapped gases in situ generated secondary biogenic gases and solution gases result in gas content that plot on or above the coal sorption isotherm bacteria transported basinward in groundwater flowing from the elevated northern basin margins metabolized wet gas components n alkanes and organic compounds in the coal and generated secondary biogenic methane and carbon dioxide subsequent to coalification uplift erosion and cooling these gases may be limited to basin margins where shallow depths and structural deformation result in higher permeability or may extend more than 35 mi 56 km basinward from the recharge zone the presence of appreciable secondary biogenic gas indicates an active dynamic flow system with overall permeability sufficient for high productivity basin hydrogeology reservoir heterogeneity location of permeability barriers no flow boundaries and the timing of biogenic gas generation and trap devel pment are critical for exploration and development of unconventional gas resources in organic rich rocks

orographic precipitation isotopic ratios in stratified atmospheric flows implications for paleoelevation studies an idealized fully nonlinear atmospheric model was used to evaluate the effects of stratified atmospheric flows on orographic precipitation isotopic ratios with the aim of improving the foundation for interpreting proxy records used for paleoelevation studies orographic precipitation isotopic ratios can be understood in terms of two nondimensional parameters the flow parameter nh u where n is the moist brunt vaisala frequency a measure of atmospheric stratification h is the large scale relief and u is the upstream horizontal wind speed perpendicular to the orogen and the horizontal aspect ratio the ratio of the along strike length of the orogen to its across strike width existing rayleigh condensation models for paleoaltimetry studies are only strictly applicable when nh u 0 much of the time high values of both nh u and favor precipitation upstream of the terrain leading to isotopic ratios that are more depleted than predicted by the rayleigh model high nh u and low favor low level deflection of winds around the terrain which substantially reduces lifting and condensation leading to precipitation isotopic ratios in that are less depleted than predicted by the simple rayleigh model changes in climate or the horizontal terrain aspect ratio can change precipitation isotopic ratios at least as much as changes in surface elevation and surface uplift need not always affect precipitation isotopic ratios suggesting that proxy records must be interpreted within a broad context of climate variability and landscape evolution

thermochronological analysis of the dynamics of the southern alps new zealand the isotopic ages of material exposed close to the alpine fault in the southern alps new zealand vary in a consistent fashion along the orogen for the k ar system muscovite and biotite ages display two distinct spatial trends that meet in the area of fox glacier where a strong relationship is observed between k ar age and altitude excess argon is present in samples between mount kinnaird and haast pass in the southwest of the southern alps giving unrealistically old inconsistent k ar ages across this region incorporation of excess argon appears to be highly variable however and minimization of its influence on dynamical interpretations of thermochronology is possible through considering only the youngest age from a given area such treatment indicates that excess argon contamination does not play an important role in the systematic k ar age variation identified along the southern alps the observed age distribution is consistent with estimates of the modern rapid uplift and exhumation of the southern alps beginning ca 5 ma k ar mica ages older than this south of the copland valley indicate that substantial late cenozoic exhumation occurred along the southern alps prior to the development of the modern tectonic regime but at rates lower than at present total exhumation during the current phase of tectonism in the southern alps decreases from the whataroa river southward north of fox glacier the southern alps have attained a dynamical steady state such that the observed distribution of exhumation will not change significantly with further deformation and denudation under current conditions

inorganic carbon dynamics and co2 flux associated with coal mine drainage sites in blythedale pa and lambert wv usa drainage from coal mines where carbonate dissolution is driven by sulfuric acid can result in a net transfer of geologically bound carbon to the atmosphere the flux and downstream evolution of dissolved inorganic carbon dic is presented for two coal mine sites that discharge high concentrations of dic 3 7 4 5 mm c producing a total flux of dic from the mine from 13 to 249 kg c year 18 364 metric tons of co2 year more than 65 of the total dic is lost via co2 evasion with the remaining dic is exported downstream as dissolved species the fate of the dic depends upon the ph of the water which is controlled by evasion of co2 the concentration of pre existing alkalinity carbonate precipitation and dissolution and metal hydrolysis reactions the co2 concentrations and fluxes from the study sites are comparable to those estimated from literature data for other coal mine sites in the appalachian region the total flux estimated from a dataset of 140 coal mines was comparable in magnitude to the co2 emissions from a small coal fired power plant the extent of co2 degassing from mine waters is poorly constrained because 1 flux estimates can be biased low when acid waters are excluded in alkalinity based estimates 2 flux estimates can be biased high if non carbonate alkalinity is present in the mine waters and 3 mine waters react rapidly following discharge hampering the measurement process the study sites presented illustrate the impact of coal mining as an anthropogenic influence on carbon cycling however more data are necessary to fully estimate the importance of this impact on regional scales

determination of free co2 in emergent groundwaters using a commercial beverage carbonation meter summary dissolved co 2 in groundwater is frequently supersaturated relative to its equilibrium with atmospheric partial pressure and will degas when it is conveyed to the surface estimates of dissolved co 2 concentrations can vary widely between different hydrochemical facies because they have different sources of error e g rapid degassing low alkalinity non carbonate alkalinity we sampled 60 natural spring and mine waters using a beverage industry carbonation meter which measures dissolved co 2 based on temperature and pressure changes as the sample volume is expanded using a modified field protocol the meter was found to be highly accurate in the range 0 2 35 mm co 2 the meter provided rapid accurate and precise measurements of dissolved co 2 in natural waters for a range of hydrochemical facies dissolved co 2 concentrations measured in the field with the carbonation meter were similar to co 2 determined using the ph alkalinity approach but provided immediate results and avoided errors from alkalinity and ph determination the portability and ease of use of the carbonation meter in the field made it well suited to sampling in difficult terrain the carbonation meter has proven useful in the study of aquatic systems where co 2 degassing drives geochemical changes that result in surficial mineral precipitation and deposition such as tufa travertine and mine drainage deposits

atmospheric flow patterns around the southern alps of new zealand and implications for paleoaltimetry the development of relief may generate leeside rain shadows where precipitation 18o values are lower due to rainout on the windward side the magnitude of lowering in paleo 18o sampled from the leeside of a mountain range should at least in principle be related to the elevation of the mountain range in order for leeside proxies to record the highest elevations the majority of air masses need to travel up and over the ridge crest before raining out on the leeside if atmospheric flow patterns around the mountain range are dominated by flow deflection air masses that reach the leeside are less likely to record the highest elevations using the weather research and forecasting model and hybrid single particle lagrangian integrated trajectory hysplit model we demonstrate that modern atmospheric flow patterns in the southern alps of new zealand are not dominated by flow deflection the lack of flow deflection around the southern alps and the relatively low relief throughout the uplift history supports the use of leeside isotope records to constrain the timing of uplift and that uplift likely occurred 5 ma based on leeside isotope records in contrast orogens that are characterized by high elevations and strong flow deflection like the sierra nevada of california may not be good candidates for leeside isotope based paleoaltimetry studies ideal candidates for such studies should be characterized by relatively low elevations low atmospheric flow deflection and relatively low relief throughout the period of uplift

hydrogeology and redox geochemistry of ch4 in a late wisconsinan till and loess sequence in central iowa the hydrogeology and redox geochemistry of ch4 in two hydrogeological settings within a late wisconsinan till and loess sequence in central iowa were investigated using ch4 eh dissolved o2 no3 n nh4 n dissolved fe so4 h2s dissolved organic carbon doc particulate organic carbon poc 13c ch4 2h ch4 13c of dissolved inorganic carbon dic and 14c ch4 depleted 13c ch4 and 2h ch4 values enriched 13c dic values and the lack of higher hydrocarbons suggest that the ch4 is microbial and is formed by co2 reduction carbon 14 dates of ch4 indicate that 14 000 to 17 000 year old poc and doc in the 1oess and till compose the substrate for methanogenesis production of ch4 probably began after deglaciation at about 12 000 years b p and has continued to the present groundwater recharge particularly in the upland topographic position at the site has decreased ch4 concentrations in the upper part of the till

stable isotopic evidence for a pre middle miocene rain shadow in the western basin and range implications for the paleotopography of the sierra nevada 1 a recently proposed method for approximating the paleorelief of mountain belts makes use of the predictable relationship between the isotopic depletion of precipitation and the net elevation of an orographic barrier over which an air mass rises this rain shadow effect often creates desert regions on the lee side of mountain belts in which precipitation is isotopically light changes in the isotopic composition of precipitation can be estimated from the isotopic composition of authigenic or pedogenic minerals which can then be used to infer both the development of relief during orogenesis as well as the stability of a rain shadow formed by developing mountains the 18o of smectites formed from the weathering of middle miocene to late pliocene volcanic ashes currently exposed in the rain shadow of the modern sierra nevada of california show no indication of large scale late cenozoic surface uplift of the sierra and corresponding regional rain shadow development rather smectite isotope data tentatively suggest that elevations may have decreased over this time by as much as 2000 m toward the southern end of the range and 700 m in regions farther north this suggests that the modern rain shadow cast over the western basin and range has been in existence since pre middle miocene and that the sierra nevada have been a prominent orographic barrier since before this time these interpretations are in accord with several recent studies also suggesting a possible cenozoic elevation loss of an already developed sierra nevada mountain range

the evolution of hydroclimate in asia over the cenozoic a stable isotope perspective abstract links between tectonics and regional climate have been extensively studied in asia however despite decades of research the relative roles of tectonics and global climate in pacing the long term evolution of climate in asia remain disputed today climate in asia is characterized by large scale monsoonal circulation over india and southern china and exceptionally arid deserts across much of central asia that to the north yield to the wetter conditions of the steppe and taiga how why and if these boundaries have changed during the cenozoic has been limited by the lack of paleoclimate proxy data that can be broadly applied over space and time we use a large compilation of pedogenic and lacustrine carbonate stable oxygen 18o and carbon 13c isotope data 7 700 samples which record large scale atmospheric circulation and primary productivity respectively to reconstruct cenozoic hydroclimate in asia and delineate the boundaries through time of monsoonal and mid latitude westerly moisture the 18o data indicate that atmospheric circulation has remained similar to today for at least 55 million years southern tibet has always received southerly likely monsoonal moisture and this southerly moisture has likely rarely extended northward of the central tibetan plateau in contrast northern tibet and central asia have received moisture dominantly via the mid latitude westerlies which have maintained a semi arid to arid climate in central asia since the early eocene thus the spatial extent of large scale atmospheric circulation appears largely unperturbed by contemporaneous changes in india asia collisional tectonics extent of the paratethys and in global climate the 13c data support this interpretation but yield additional details particularly low 13c across a wide swath of eastern china during the eocene suggests greater primary productivity due to a strengthened east asia monsoon perhaps driven by high atmospheric pco2 and globally warm temperatures consistently higher 13c in central asia indicates that central asia has remained more arid than surrounding regions such as northern india and southern china which have received abundant precipitation due to the presence of monsoonal moisture however increases in 13c across much of central asia throughout the cenozoic including particularly pronounced increases in mongolia and kazakhstan during the neogene imply that primary productivity has declined across much of asia this large scale de greening is attributable to the combined effects of cenozoic global cooling and the late cenozoic uplift of the tian shan and altai mountains which block westerly moisture the uplift of these ranges in the late miocene is supported by decreasing neogene 18o in eastern kazakhstan and sharply increasing 13c in the lee of the altai these regional data demonstrate that the tian shan and altai reached sufficient elevations to interact with the westerly jet by the late miocene establishing a substantial rain shadow and shifting the seasonality of precipitation in western central asia we conclude that paleoclimatic changes during the cenozoic in central asia are more tightly controlled by global climate and by the interaction of the mid latitude westerlies with the tian shan and altai rather than by changes in the height or extent of the tibetan plateau or paratethys

geochemical analysis of atlantic rim water carbon county wyoming new applications for characterizing coalbed natural gas reservoirs coalbed natural gas cbng production typically requires the extraction of large volumes of water from target formations thereby influencing any associated reservoir systems we describe isotopic tracers that provide immediate data on the presence or absence of biogenic natural gas and the identify methane containing reservoirs are hydrologically confined isotopes of dissolved inorganic carbon and strontium along with water quality data were used to characterize the cbng reservoirs and hydrogeologic systems of wyoming s atlantic rim water was analyzed from a stream springs and cbng wells strontium isotopic composition and major ion geochemistry identify two groups of surface water samples muddy creek and mesaverde group spring samples are ca mg so4 type water with higher 87sr 86sr reflecting relatively young groundwater recharged from precipitation in the sierra madre groundwaters emitted from the lewis shale springs are na hco3 type waters with lower 87sr 86sr reflecting sulfate reduction and more extensive water rock interaction to distinguish coalbed waters methanogenically enriched was used from other natural waters enriched between 3 6 and 13 3 identified spring water that likely originates from mesaverde coalbed reservoirs strongly positive between 12 6 and 22 8 identified those coalbed reservoirs that are confined whereas lower between 0 0 and 9 9 identified wells within unconfined reservoir systems these results demonstrate that analysis provides immediate data to help identify atlantic rim groundwater sources hydraulic reservoir confinement springs associated with methanogenic coalbed reservoirs areas of peak methanogenic activity and to help assess gas potential and promote efficient cbng production

carbonate minerals in the global carbon cycle abstract carbonate minerals constitute earth s largest c reservoir this reservoir is considered unimportant to the global c cycle over long periods of time e g 10 6 yrs because it provides balanced sources and sinks of atmospheric co 2 as carbonate minerals precipitate and dissolve from carbonic acid respectively however carbonate mineral reactions may impact the carbon cycle at short time scales 10 2 to 10 5 yrs particularly when atmospheric pco 2 changes by several hundred ppm as exemplified by the paleocene eocene thermal maximum at transitions between glacial interglacial times and over the past century from anthropogenic inputs here i review recent literature about mechanisms in which carbonate minerals may impact the global carbon cycle carbonate mineral dissolution which increases dissolved inorganic carbon dic concentrations may represent a net atmospheric co 2 sink as primary productivity consumes dic resulting in organic c burial in fluvial systems of carbonate terrains alternatively carbonate minerals dissolved by sulfuric and nitric acids may represent an atmospheric source of co 2 with no rapid balancing atmospheric sink sulfuric acid dissolves carbonate minerals of modern carbonate platform sediments and water filled sinkholes and in the deep sea at the base of carbonate platform scarps in terrestrial landscapes sulfuric acid dissolves carbonate minerals of karst terrains hypogene caves and in comminuted glacial sediments nitric acid forms from oxidation of reactive n which has doubled in the past hundred years as humans fix atmospheric n 2 similar to some reactions involving sulfuric acid nitric acid dissolution of carbonate minerals represents a net source of atmospheric co 2 this source is concentrated in fertilized agricultural fields in carbonate terrains each of these processes represents a small flux relative to major c exchanges such as volcanic sources and silicate mineral weathering but collectively they could impact the c cycle at magnitudes similar to these major processes these impacts may increase as humans further alter elemental cycles of s and n

isotopic evidence of enhanced carbonate dissolution at a coal mine drainage site in allegheny county pennsylvania usa stable isotopes were used to determine the sources and fate of dissolved inorganic c dic in the circumneutral ph drainage from an abandoned bituminous coal mine in western pennsylvania the c isotope signatures of dic 13cdic were intermediate between local carbonate and organic c sources but were higher than those of contemporaneous pennsylvanian age groundwaters in the region this suggests a significant contribution of c enriched in 13c due to enhanced carbonate dissolution associated with the release of h2so4 from pyrite oxidation the sr isotopic signature of the drainage was similar to other regional mine waters associated with the same coal seam and reflected contributions from limestone dissolution and cation exchange with clay minerals the relatively high 34sso4 and 18oso4 isotopic signatures of the mine drainage and the presence of presumptive so4 reducing bacteria suggest that so4 reduction activity also contributes c depleted in 13c isotope to the total dic pool with distance downstream from the mine portal c isotope signatures in the drainage increased accompanied by decreased total dic concentrations and increased ph these data are consistent with h2so4 dissolution of carbonate rocks enhanced by cation exchange and c release to the atmosphere via co2 outgassing

topographic development of the southern alps recorded by the isotopic composition of authigenic clay minerals south island new zealand abstract the southern alps are developing as a consequence of oblique collision between the pacific and australian plates the southern alps lie on the west side of the south island of new zealand and create a massive rain shadow where greater than 12 m year of rain falls on the west coast and semiarid conditions exist to the east the rain out effect across the mountains causes precipitation west of the southern alps to have d and 18 o values averaging 30 and 5 5 whereas precipitation in the rain shadow to the east is isotopically lighter d 72 and 18 o 9 8 such large differences in the isotopic composition of precipitation would not have existed prior to the development of significant topography we have examined the topographic evolution of the southern alps using oxygen isotope analyses of authigenic kaolinites formed in the rain shadow to the east of the mountains between the cretaceous low topography and the pleistocene changes in the isotopic composition of authigenic clay minerals forming in equilibrium with meteoric water in the stratigraphic sequence record the development of southern alps topography and the resultant rain shadow our oxygen isotope analyses of authigenic kaolinites show a 5 6 decrease in the early pliocene from 18 2 in older rocks to 12 3 in younger rocks in addition smectite is abundant in all samples from the late miocene to recent but is conspicuously absent in most older rocks suggesting a change to a generally drier climate roughly coincident with the isotopic shift in kaolinites this method may be useful in unraveling timing of development of mountain belts elsewhere in the world

stable isotope constraints on the elevation history of the sierra nevada mountains california research on the uplift history of the sierra nevada mountain range has yielded seemingly conflicting results some studies argue for substantial uplift within the past 3 5 m y others suggest that high elevations may have existed since the cretaceous the rain shadow across the sierra nevada is associated with a strong isotopic gradient with lower 18o values in precipitation on the leeward side of the range reconstruction of the 18o value of meteoric water as a monitor of paleoelevation has focused mainly on the leeward side of the sierras but interpretation of the results of these studies may be complicated by shifts in global climate and regional moisture sources we address these concerns by analyzing the 18o value of tooth enamel bioapatite from contemporaneous mammalian fossils on either side of the present sierra range by sampling across the range 18o differences induced by a rain shadow can be isolated from other complicating factors our results indicate that the sierra rain shadow has existed since at least 16 ma which is an important constraint on models for the tectonic evolution of the western united states unfortunately temporal resolution for localities is too coarse to differentiate between glacial and interglacial localities during the past 2 m y so we cannot evaluate if there was a latest cenozoic pulse of uplift or elevation loss

fourth canadian geotechnical colloquium strength and slope stability in canadian soft clay deposits it is generally admitted that the long term stability of clay slopes should be analysed in terms of effective stresses which necessitates the knowledge of the pore pressure conditions and of the relationship between the shear strength and the effective stresses this paper deals with the determination of shear strength for stability analysis of clay slopes in eastern canada first the various concepts pertinent to slope stability in soft clay are examined and a certain justification of the use of the post peak or large strain strength is demonstrated in a second part 14 case records of natural slopes or permanent excavation slopes are presented and analysed in terms of the post peak strength finally values of post peak strength determined in the laboratory for more than 30 sites are presented and it is attempted to derive correlations by which the shear strength parameters could be readily approximated from other properties such as the apparent preconsolidation pressure or the vane strength

geochemistry and stable isotope investigation of acid mine drainage associated with abandoned coal mines in central montana usa the great falls lewistown coal field gflcf in central montana contains over 400 abandoned underground coal mines many of which are discharging acidic water with serious environmental consequences areas of the mines that are completely submerged by groundwater have circum neutral ph and relatively low concentrations of metals whereas areas that are only partially flooded or freely draining have acidic ph 3 and high concentrations of metals the ph of the mine drains either decreases or increases after discharging to the surface depending on the initial ratio of acidity mainly al and fe2 to alkalinity mainly hco3 in acidic fe rich waters oxidation of fe2 after exposure to air is microbially catalyzed and follows zero order kinetics with computed rate constants falling in the range of 0 97 to 1 25 mmol l 1 h 1 in contrast fe2 oxidation in near neutral ph waters appears to be first order with respect to fe2 concentration although insufficient data were collected to constrain the rate law expression rates of fe2 oxidation in the field are dependent on temperature such that lower fe2 concentrations were measured in down gradient waters during the day and higher concentrations at night diel cycles in dissolved concentrations of zn and other trace metals mn ni were also noted for down gradient waters that were net alkaline but not in the acidic drains the coal seams of the gflcf and overlying cretaceous sandstones form a perched aquifer that lies 50 m above the regional water table situated in the underlying madison limestone the d and 18o values of flooded mine waters suggest local derivation from meteoric water that has been partially evaporated in agricultural soils overlying the coal mines the s and o isotopic composition of dissolved sulfate in the low ph mine drains is consistent with oxidation of biogenic pyrite in coal under aerated conditions a clear distinction exists between the isotopic composition of sulfate in the acid mine waters and sulfate in the adjacent sedimentary aquifers making it theoretically possible to determine if acid drainage from the coal mines has leaked into the underlying madison aquifer

late cenozoic surface uplift of the southern sierra nevada california usa a paleoclimate perspective on lee side stable isotope paleoaltimetry late cenozoic surface uplift of the southern sierra nevada sierra california united states is widely debated recent interpretations of lee side isotope records from the southern sierra suggest that the elevation of the southern sierra has been sufficiently high to induce atmospheric flow patterns similar to modern patterns since the mid miocene at ca 12 ma the tendency for flow to deflect around a topographic barrier can be determined by the atmospheric stability barrier height and incoming wind speed we test the sensitivity of flow deflection to elevation to determine what elevation would have been sufficiently high to establish modern flow patterns in the mid miocene using global paleoclimate models and idealized regional weather models we find that the miocene atmosphere was more stable than modern we suggest that in a miocene climate flow patterns similar to modern pat terns could have been achieved for elevations as low as 2 km and that while miocene lee side isotope records from the southern sierra may indicate that the southern sierra has been a longstanding topographic feature they may not have changed significantly in response to proposed late cenozoic surface uplift of the southern sierra

refining paleoaltimetry reconstructions of the sierra nevada california using air parcel trajectories stable isotope paleoaltimetry studies often implicitly assume that atmospheric flow interactions with topography can be simply modeled as a rayleigh distillation process in which air parcels consistently ascend topographic barriers we present a modern a d 1979 2010 air parcel trajectory analysis using the hybrid single particle lagrangian integrated trajectory hysplit model that shows that this fundamental assumption is often violated in the sierra nevada region of the western united states observed trajectory patterns and scaling calculations indicate that windward orographic blocking frequently occurs when trajectories encounter high elevations 2 5 km in the central and southern sierra nevada as a result trajectories reaching the sierran lee commonly travel around rather than over the highest range elevations redirection effects are particularly pronounced at leeward sites distal 150 km to the sierran crest but are also evident in trajectory patterns in the northern sierra nevada this trajectory analysis improves the interpretability of regional meteoric water and proxy isotopic records and has particular relevance to stable isotope based reconstructions of sierran paleoelevations specifically stable isotope methods alone provide only limited insight into the elevation history of the sierra nevada and are likely insufficient to resolve proposed late cenozoic elevation gains on the order of 1 2 km that may have raised the sierra to its modern elevations

tracing the interaction of acid mine drainage with coal utilization byproducts in a grouted mine strontium isotope study of the inactive omega coal mine west virginia usa abstract in order to ameliorate acidic discharge the inactive omega coal mine west virginia was partially filled by injection of a grout consisting of 98 coal utilization byproducts cub including fluidized bed combustion ash and fly ash and 2 portland cement in this study discharge chemistry and sr isotope ratios were determined to identify and quantify the extent of interaction between mine waters and the cub cement grout eight sampling sites were monitored around the downdip perimeter of the mine the major and trace element chemistry of the discharges was generally not sufficient to distinguish between discharges that interacted with grout and those that did not elements that showed the most separation include k and as which were elevated in some waters that interacted with cub cement grout in contrast the sr isotope ratios clearly distinguished discharges from grouted and non grouted areas discharges that bypassed the grouted portions had 87 sr 86 sr ratios ranging from 0 71510 to 0 71594 while two discharges that interacted with grout had ratios in the range of 0 71401 0 71456 the treatment inlet which includes both grouted and ungrouted discharges yielded intermediate isotopic ratios leaching experiments on cub cement grout coal and surrounding rocks are consistent with the isotopic trends observed in the discharges based on these results waters that interacted with grout received 30 40 of their sr from the cub cement grout material these results suggest that the grout material is chemically eroding at a rate of approximately 0 04 per year this novel application of the sr isotope system illustrates its ability to sensitively track and quantify fluid interaction with coal and cub based grout

carbon fluxes pco2 and substrate weathering in a large northern river basin canada carbon isotope perspectives abstract isotopic composition of dissolved inorganic carbon 13 c dic in the ottawa river basin is about 8 and 16 for lowland carbonate and upland silicate tributaries respectively this suggests that 1 the source of dic to the ottawa river is soil respiration and carbonate weathering 2 exchange with the atmosphere is unidirectional or volumetrically unimportant and 3 in river respiration and photosynthesis are not significant influences on the river carbon budget accepting these constraints chemical and isotopic data are used to reconstitute soil pco2 for tributary catchments averages for upland silicate mixed and lowland carbonate basins are calculated to be roughly 2000 5000 and 30 000 ppm respectively these values are used as input to model the pathway of carbon through the watershed rain water to soil water to river water the flux of carbon from the ottawa river as dic is calculated to be 4 3 1010 mol c a utilizing carbon isotopes 75 and 25 of the ca2 mg2 flux is calculated to originate from carbonate and silicate weathering respectively and 61 of the dic is calculated to originate from organic respiration the latter represents some 6 of respired carbon in the basin assuming an average respiration rate of 0 5 mmol c m 2 h 1 based on a diffusion model co2 evasion to the atmosphere from the ottawa river and its tributaries is estimated to be 1 3 1010 mol c a or 30 of the dic flux

biogeochemistry of the forest city basin coalbed methane play abstract hydrogeochemical and microbial analyses of co produced formation waters and gas in the forest city basin were coupled to determine the origin of methane in shallow coal seams and make comparisons to commercial shale and coal gas plays in the adjacent illinois michigan and cherokee basins forest city basin coals contain dilute meteoric waters cl

attenuation and diel cycling of coal mine drainage constituents in a passive treatment wetland a case study from lambert run west virginia usa abstract this study reports changes in coal mine drainage constituent concentrations through a passive treatment wetland and over diel cycles the purpose of the study was to determine what physiochemical mechanisms control attenuation of metals and if they varied by location and through time the source water was slightly acidic average ph 5 43 downstream degassing of co2 contributed to an increase in ph prior to discharge from the site average ph 7 05 aluminum fe rare earth elements ree and y were removed to a greater extent than were mn co and ni at acidic ph the ree and y were generally complexed by so4 at higher ph carbonate complexes became more important the ree and y concentrations were normalized to the north american shale composite standard the normalized patterns were coherent near the source but anomalies of ce and y were present further downstream indicating oxidation and sorption processes four sets of diel based samples were collected one from a shallow surface flow wetland and three from a deeper newly constructed wetland well defined diel cycles were observed for concentrations of si mn fe co ni as ree and y in the shallow wetland in all cases the concentrations increased up to 863 during night and decreased during the day these cycles had an inverse relationship with the temperature cycle ph had no discernable cycle the consistency of concentration cycles suggests a common mechanism most likely associated with the formation of fe oxyhydroxides the increased rate of fe2 oxidation in warm water can account for the cycles in fe scavenging of the other elements by the fe precipitate can account for the consistency of the cycles even though the elements include cations anions h 2 aso 4 or haso 4 2 and neutral species h 4 sio 4 0 while ree and y had clear cycles in the constructed wetland the other elements did not this is partially due to the lower elemental concentrations including fe but the cycles may also be damped by the deeper slower moving water this study illustrates the dynamic nature of metal removal in passive treatment systems furthermore it suggests that grab samples collected during daytime hours may underestimate the concentrations and flux of metals in these systems

reconstructing the paleotopography of mountain belts from the isotopic composition of authigenic minerals the paleorelief of mountain belts can be estimated from the 18 o value of authigenic minerals development of relief during mountain building often creates lee side rain shadows in which precipitation is depleted in 18 o and d the magnitude of this rain shadow effect is strongly correlated to relief a compilation of 18 o data from surface waters throughout the globe shows a linear relationship between net elevation change and 18 o r 2 0 79 through the use of this relationship we investigated the timing and magnitude of elevation change in the southern alps of new zealand and the sierra nevada of california the 18 o values of kaolinites from new zealand show an 6 decrease in the early pliocene that corresponds to an 2 km elevation change in the southern alps the 18 o of smectites from the sierra nevada show little change since 16 ma suggesting that these mountains have been a long standing topographic feature

an approach for assessing engineering risk from shale gas wells in the united states in response to a series of energy crises in the 1970s the united states government began investigating the potential of unconventional domestic sources of energy to offset imported oil hydraulic fracturing applied to vertical tight sand and coal bed methane wells achieved some degree of success during a period of high energy prices in the early 1980s but shale gas remained largely untapped until the late 1990s with the application of directional drilling a mature technology adapted from deepwater offshore platforms that allowed horizontal wells to penetrate kilometers of organic rich shale and staged hydraulic fracturing which created high permeability flowpaths from the horizontal wells into a much greater volume of the target formations than previous completion methods these new engineering techniques opened up vast unconventional natural gas and oil reserves but also raised concerns about potential environmental impacts these include short term and long term impacts to air and water quality from rig operations potential migration of gas fluids and chemicals through the ground and effects on small watersheds and landscapes from roads pads and other surface structures engineering risk assessment commonly uses integrated assessment models iams which define sources of risk from features events and processes the risk from each system element is assessed using high fidelity models output from these is simplified into reduced order models so that a large integrated site performance assessment can be run using the iam the technique has been applied to engineered systems in geologic settings for sequestering carbon dioxide and it is also applicable to shale gas albeit with some modifications of the various system elements preliminary findings indicate that shale gas well drilling and hydraulic fracturing techniques are generally safe when properly applied incident reports recorded by state environmental agencies suggest that human error resulting from the disregard of prescribed practices is the greatest cause of environmental incidents this can only be addressed through education regulations and enforcement

stable isotope composition of waters in the great basin united states 1 air mass trajectories 1 isentropic trajectories calculated using the noaa climate monitoring and diagnostics laboratory s isentropic transport model were used to determine air parcel origins and the influence of air mass trajectories on the isotopic composition of precipitation events that occurred between october 1991 and september 1993 at cedar city utah and winnemucca nevada examination of trajectories that trace the position of air parcels backward in time for 10 days indicated five distinct regions of water vapor origin 1 gulf of alaska and north pacific 2 central pacific 3 tropical pacific 4 gulf of mexico and 5 continental land mass deuterium d and oxygen 18 18o analyses were made of precipitation representing 99 of all cedar city events similar analyses were made on precipitation representing 66 of the precipitation falling at winnemucca during the same period the average isotopic composition of precipitation derived from each water vapor source was determined more than half of the precipitation that fell at both sites during the study period originated in the tropical pacific and traveled northeast to the great basin only a small proportion traversed the sierra nevada the isotopic composition of precipitation is determined by air mass origin and its track to the collection station mechanism of droplet formation reequilibration within clouds and evaporation during its passage from cloud to ground the rayleigh distillation model can explain the changes in isotopic composition of precipitation as an air mass is cooled pseudo adiabatically during uplift however the complicated processes that take place in the rapidly convecting environment of cumulonimbus and other clouds that are common in the great basin especially in summer require modification of this model because raindrops that form in the lower portion of those clouds undergo isotopic change as they are elevated to upper levels of the clouds from where they eventually drop to the ground

worldwide distribution of continental rock lithology implications for the atmospheric soil co2 uptake by continental weathering and alkalinity river transport to the oceans 1 the silicate rock weathering followed by the formation of carbonate rocks in the ocean transfers co2 from the atmosphere to the lithosphere this co2 uptake plays a major role in the regulation of atmospheric co2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks this leads us to develop the first world lithological map with a grid resolution of 1 1 this paper analyzes the spatial distribution of the six main rock types by latitude continents and ocean drainage basins and for 49 large river basins coupling our digital map with the gem co2 model we have also calculated the amount of atmospheric soil co2 consumed by rock weathering and alkalinity river transport to the ocean among all silicate rocks shales and basalts appear to have a significant influence on the amount of co2 uptake by chemical weathering

origin of methane in the elk valley coalfield southeastern british columbia canada coalbead methane is part of the non conventional gas reservoirs and makes a significant contribution to gas production in some parts of the world initially it was assumed that coalbed methane was of thermogenic origin but most recent studies based on isotope and chemical data and taking into account the hydrogeology of the basin have demonstrated that secondary biogenic gases are formed in many coal bearing basins this study using a similar approach evaluated the origin of the gas in the elk valley coalfield located in british columbia canada isotope data in methane samples collected from testhole wells and piezometers show a range that varies from 51 8 to 65 4 and 303 to 415 for 13c and 2h respectively the 2h data which are among the most depleted data reported for coalbed methane have to be related to the very depleted 2h values of the groundwater 148 to 163 isotope and chemical data collected from dic show a trend of increasing 13c values 11 9 to 34 9 associated with an increase in dic concentration 216 to 1650 mg l the most 13c depleted dic and low dic waters are found in the shallow groundwater flow system representing conditions close to recharge areas while the most 13c enriched dic and high concentration dic waters are found in the discharge areas associated with a deep groundwater flow system the dic pattern which is typical for methanogenic aquifers and the isotope data obtained in methane samples clearly indicate that the gas found in the elk valley coalfield is mainly biogenic in origin this study reaffirms that an approach that combines an evaluation of the groundwater flow system the isotopic characterization and concentration pattern of the main carbon pools ch4 and dic and the isotopic characterization of the groundwater is needed to fully evaluate the origin of gases in coal basins

linking orogeny and orography in the southern alps of new zealand new observations from detrital fission track thermochronology of the waiho 1 borehole abstract numerical modeling coupling erosion with crustal deformation predicts that development of an orographic rain shadow may explain the asymmetric exhumation of convergent plate boundary orogens this prediction is consistent with observations from the southern alps of new zealand where bedrock thermochronology indicates crustal exhumation has been concentrated along the wet windward side of the mountains while the spatial correspondence of exhumation and precipitation patterns is compelling a robust evaluation of the link between orographic and orogenic processes further requires a temporal comparison between exhumation history plate reconstructions and paleoclimatic records we present a detailed exhumation history of the southern alps from detrital apatite and zircon fission track thermochronology of the waiho 1 borehole a 3 6 km thick sequence of proximal foreland basin sediments inverse thermal modeling of a 2062 grain dataset predicts two periods of rapid exhumation in the early and late miocene rapid exhumation in the early miocene was synchronous with the development of transpression along the alpine fault and a ca 20 22 ma pulse of exhumation may reflect cooling during inversion of preexisting extensional basins rapid exhumation in the late miocene was not synchronous with a discrete change in plate convergence but increased exhumation rates after 7 4 ma may instead reflect localization of plate boundary deformation along the alpine fault as orographic precipitation concentrated exhumation in the alpine fault hanging wall we propose that similar to prior interpretations from bedrock thermochronology detrital thermochronology of the southern alps foreland basin is consistent with numerical model predictions linking asymmetric exhumation of the orogen to the growth of an orographic rain shadow

residual shear strength mobilized in first time slope failures this paper presents a review of long term stability of stiff clay and clay shale slopes and detailed reanalyses of 99 case histories of slope failures in 36 soft clays to stiff clays and clay shales we analyzed 107 sections using the observed actual slip surface in a first time slope failure in clay or shale part or all of the slip surface is unsheared prior to the occurrence of the landslide most stiff clays and clay shales contain stratigraphic discontinuities such as bedding planes and laminations the fully softened shear strength is shown to be the lower bound for mobilized shear strength in first time slope failures in homogeneous soft to stiff clays and on the slip surfaces cutting across bedding planes and laminations for many of the first time slope failures it appears that part of the slip surface is at the residual condition for excavated slopes the residual condition could be present before the final slope is formed or it may develop in response to excavation by progressive deformation along nearly horizontal surfaces including bedding planes or laminations in addition to the permeability dependent rise in porewater pressure and softening delayed first time failure of slopes in stiff clays and clay shales is caused by propagation of the residual condition into the slope on horizontal or subhorizontal surfaces including stratigraphic discontinuities the residual condition is present on the entire surface of reactivated landslides

lias clay slope sections and their implications for the prediction of limiting or threshold slope angles a series of previously published engineering studies of lias clay slopes in the east midlands is summarized along with the description of some further slope sections all the slopes studied show evidence of landsliding though some of it may be of periglacial origin the very disparate nature of the different landslides suggest that various different erosion regimes were responsible for the original slope formation it is believed that the smaller landslides are more typical of the area piezometric observations show that at the present day maximum pore pressures are proportionately less in the larger landslides the average value of the pore pressure parameter ru varying between 0 48 for shallow landslides to 0 32 in the largest stability analyses show that the residual strength is strongly stress dependent r c r 0 varying from 16 in shallow landslides to 10 in the case of the largest these and other factors have important implications for the often used practice of combining laboratory measurements of residual strength with the infinite slope method of stability analysis to predict threshold slope inclinations for landsliding