the origin and mechanisms of salinization of the lower jordan river the chemical and isotopic 87 sr 86 sr 11 b 34 ssulfate 18 owater 15 nnitrate compositions of water from the lower jordan river and its major tributaries between the sea of galilee and the dead sea were determined in order to reveal the origin of the salinity of the jordan river we identified three separate hydrological zones along the flow of the river 1 a northern section 20 km downstream of its source where the base flow composed of diverted saline and wastewaters is modified due to discharge of shallow sulfate rich groundwater characterized by low 87 sr 86 sr 0 7072 34 ssulfate 2 high 11 b 36 15 nnitrate 15 and high 18 owater 2 to 3 values the shallow groundwater is derived from agricultural drainage water mixed with natural saline groundwater and discharges to both the jordan and yarmouk rivers the contribution of the groundwater component in the jordan river flow deduced from mixing relationships of solutes and strontium isotopes varies from 20 to 50 of the total flow 2 a central zone 20 50 km downstream from its source where salt variations are minimal and the rise of 87 sr 86 sr and so4 cl ratios reflects predominance of eastern surface water flows 3 a southern section 50 100 km downstream of its source where the total dissolved solids of the jordan river increase particularly during the spring 70 80 km and summer 80 100 km to values as high as 11 1 g l variations in the chemical and isotopic compositions of river water along the southern section suggest that the zarqa river 87 sr 86 sr0 70865 11 b25 has a negligible affect on the jordan river instead the river quality is influenced primarily by groundwater discharge composed of sulfate rich saline groundwater cl 31 180 mm so4 cl0 2 0 5 br cl2 310 3 87 sr 86 sr0 70805 11 b30 15 nnitrate 17 34 ssulfate4 10 and ca chloride rift valley brines cl 846 1500 mm br cl 6 8 10 3 87 sr 86 sr0 7080 11 b40 34 ssulfate4 10 mixing calculations indicate that the groundwater discharged to the river is composed of varying proportions of brines and sulfate rich saline groundwater solute mass balance calculations point to a 10 contribution of saline groundwater cl282 to 564 mm to the river a high nitrate level up to 2 5 mm in the groundwater suggests that drainage of wastewater derived irrigation water is an important source for the groundwater this irrigation water appears to leach pleistocene sediments of the jordan valley resulting in elevated sulfate contents and altered strontium and boron isotopic compo sitions of the groundwater that in turn impacts the water quality of the lower jordan river copyright 2004 elsevier ltd

the upper ordovician black shales of southern quebec canada and their significance for naturally occurring hydrocarbons in shallow groundwater abstract shale gas exploration in the st lawrence platform of southern quebec eastern canada focussed on the upper ordovician utica shale from 2006 to 2010 during which 28 wells were drilled 18 of which were fracked the st lawrence platform is thus considered as a pristine geological domain where potential environmental effects of fracking can be evaluated relative to the natural baseline conditions of the shallow aquifers in the saint edouard area southwest of quebec city it has been shown that groundwater carries variable and locally high levels of naturally occurring dissolved hydrocarbons in which thermogenic ethane and propane can be found fifteen shallow 30 147 m wells were drilled into bedrock and sampled cores and cuttings with the purpose of characterizing the shallow bedrock in a shale gas pre development context the shallow bedrock geology is made of three upper ordovician clastic formations the lotbiniere and les fonds formations are time and facies correlative with the utica shale present at a depth of 1 5 to 2 km in this area they are dominated by calcareous black shales with minor siltstone and micrite beds the nicolet formation is the youngest unit of the area and consists of gray to dark gray shales with locally abundant thick siltstone and fine grained sandstone beds the organic matter in the lotbiniere and les fonds formations is represented by solid bitumen with subordinate liptinite algae graptolites and chitinozoans representing normal marine type ii kerogen both formations are at the post peak hydrocarbon generation as indicated by the equivalent random vitrinite reflectance of 0 94 to 1 04 rock eval data support the type ii nature of the kerogen and the late oil window maturation level hydrocarbon extracts from the three formations have yielded high to low concentrations of c1 to c6 for all units an upward decrease in total volatiles c1 c2 c3 together with an increase in the gas dryness ratio c1 c2 c3 is recorded the transitions occurring at depths shallower than 50 m where the shales are more fractured the upward increase in the gas dryness ratio results from the more significant reduction of ethane and propane concentrations compared to that of methane consistent with the dryness ratio trend the 13 c vpdb values of methane change from thermogenic values 50 for deeper samples to more biogenic negative values 2 h vsmow trend of more negative values at shallower depths is noted the 13 c vpdb and 2 h vsmow values of rock hosted methane indicate that samples at shallow depth recorded a microbial influence it is proposed that diffusion and some microbial degradation of hydrocarbons are responsible for the decrease of rock volatiles and the in situ generation of biogenic methane in the shales at shallow depths to mix with the in situ thermogenic methane the utica shale is a very good source rock with high generation potential however thermogenic volatiles can also originate from shallower units with much shorter migration pathways the mixed thermogenic and biogenic methane in the groundwater results from fracture enhanced diffusion and biodegradation of volatiles at shallow depths

geochemistry of groundwater in the saint edouard area quebec canada and its influence on the distribution of methane in shallow aquifers abstract shale gas and tight oil production has undergone a tremendous increase in the last decade in north america which was accompanied by animated scientific debate and local public uproar concerning environmental issues especially the risks of contamination for shallow groundwater resources in quebec eastern canada public concerns led to a de facto moratorium on hydraulic fracturing in 2010 for the st lawrence lowlands where the underlying utica shale is known to contain significant gas resources as only a few exploration gas wells have been drilled this vast area may still be considered virgin in 2012 a 4 year project was initiated by the geological survey of canada which aimed at characterizing aquifer vulnerability to deep industrial activities in the saint edouard region located close to quebec city in the st lawrence lowlands as part of this project a baseline study of hydrocarbons and other geochemical parameters was conducted in shallow aquifers this paper presents groundwater geochemical characteristics in the region and assesses the geological hydrogeological and geochemical controls on methane distribution results show that methane is present in 96 of the 48 sampling points over the 500 km2 study area and that concentrations are highly variable from undetected

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

late glacial and holocene vegetational history from two sites in the western cordillera of southwestern ecuador the deciphering of the late glacial and holocene vegetation glacial geological and climatic history of cajas national park in southwestern ecuador is undertaken focusing on close interval sampling of sediment cores from two high elevations lakes lagunas chorreras 3700 m and pallcacocha 4060 m this study involves extensive dating both accelerator mass spectrometry and tephra palynological and sediment analyses of lakes and bogs basal dates for the two cores analyzed for pollen range from about 17 000 to about 15 500 cal yr bp vegetation surveys and surface sample pollen and spore analyses were accomplished for two transects in the western cordillera one began east of the main divide near cuenca ecuador and the other began at the crest of the western cordillera descending towards the pacific ocean these vegetation surveys coupled with pollen analyses of surface samples were used to establish pollen analogues to help in the interpretation of the fossil pollen records the results of the pollen analyses from the two lake cores indicate two major climatic periods 1 the late glacial pollen record beginning about 17 000 yr bp and ending near 11 000 is characterized by an herb paramo dominated by pteridophytes primarily huperzia spp with asteraceae assumed to be woody species and puya spp the climate inferred from these pollen records was cooler and moister than today the sediments for this time period are characterized by low loss on ignition percentages and high magnetic susceptibility values with secondary peaks between 12 000 and 13 000 yr bp low concentrations of charcoal fragments indicate a low incidence of fire and several pronounced fluctuations in pollen assemblages could be interpreted as changes in the prevailing wind direction and or climate 2 the beginning of the holocene as represented in the pollen record is characterized by the disappearance of puya pollen vastly diminished huperzia representation high charcoal concentrations and the expansion of moist montane forest pollen asteraceae possibly gynoxys are replaced as dominant timberline taxa by polylepis dominated timberline forest the charcoal record suggests that fires were much more prevalent during the early to middle holocene than during the late glacial changes in isoe tes concentrations and trends in upland vegetation may be related to fluctuations in lake levels and precipitation

geochemical evidence for possible natural migration of marcellus formation brine to shallow aquifers in pennsylvania the debate surrounding the safety of shale gas development in the appalachian basin has generated increased awareness of drinking water quality in rural communities concerns include the potential for migration of stray gas metal rich formation brines and hydraulic fracturing and or flowback fluids to drinking water aquifers a critical question common to these environmental risks is the hydraulic connectivity between the shale gas formations and the overlying shallow drinking water aquifers we present geochemical evidence from northeastern pennsylvania showing that pathways unrelated to recent drilling activities exist in some locations between deep underlying formations and shallow drinking water aquifers integration of chemical data br cl na ba sr and li and isotopic ratios 87sr 86sr 2h h 18o 16o and 228ra 226ra from this and previous studies in 426 shallow groundwater samples and 83 northern appalachian brine samples suggest that mixing relationships between shallow ground water and a deep formation brine causes groundwater salinization in some locations the strong geochemical fingerprint in the salinized cl 20 mg l groundwater sampled from the alluvium catskill and lock haven aquifers suggests possible migration of marcellus brine through naturally occurring pathways the occurrences of saline water do not correlate with the location of shale gas wells and are consistent with reported data before rapid shale gas development in the region however the presence of these fluids suggests conductive pathways and specific geostructural and or hydrodynamic regimes in northeastern pennsylvania that are at increased risk for contamination of shallow drinking water resources particularly by fugitive gases because of natural hydraulic connections to deeper formations

the utica shale and gas play in southern quebec geological and hydrogeological syntheses and methodological approaches to groundwater risk evaluation abstract the risk of groundwater contamination from shale gas exploration and development is a major societal concern especially in populated areas where groundwater is an essential source of drinking water and for agricultural or industrial use since groundwater decontamination is difficult or nearly impossible it is essential to evaluate exploration and production conditions that would prevent or at least minimize risks of groundwater contamination the current consensus in recent literature is that these risks are primarily related to engineering issues including casing integrity and surface activities such as truck traffic equipment and fluid haulage waste management mainly drill cuttings and water storage and treatment when hydraulic fracturing is utilized concerns have also been raised with respect to groundwater contamination that could result from potential fracture or fault interconnections between the shale unit and surficial aquifers which would allow fracturing fluids and methane to reach the surface away from the wellbore despite the fact that groundwater resources are relatively well characterized in some regions there is currently no recognized method to evaluate the vulnerability or risks to aquifers resulting from hydrocarbon industry operations carried out at great depths this paper focuses on the utica shale of the st lawrence platform quebec where an environmental study aiming to evaluate potential risks for aquifers related to shale gas development has been initiated to provide the context of these research efforts this paper describes the regional tectono stratigraphic evolution and current stress regime of the cambrian ordovician st lawrence platform as well as the utica shale internal stratigraphy mineralogy and thermal maturation then the hydrogeological context of the st lawrence platform is discussed finally the methodology for this environmental study based on geological geophysical geomechanical hydrogeological and geochemical data is presented

origin distribution and hydrogeochemical controls on methane occurrences in shallow aquifers southwestern ontario canada abstract natural gas reservoirs in organic rich shales in the appalachian and michigan basins in the united states are currently being produced via hydraulic fracturing stratigraphically equivalent shales occur in the canadian portion of the basins in southwestern ontario with anecdotal evidence of gas shows yet there has been no commercial shale gas production to date to provide baseline data in the case of future environmental issues related to hydraulic fracturing and shale gas production such as leakage of natural gas saline water and or hydraulic fracturing fluids and to evaluate hydrogeochemical controls on natural gas accumulations in shallow groundwater in general this study investigates the origin and distribution of natural gas and brine in shallow aquifers across southwestern ontario an extensive geochemical database of major ion and trace metal chemistry and methane concentrations of 1010 groundwater samples from shallow domestic wells in bedrock and overburden aquifers throughout southwestern ontario was utilized in addition select wells n 36 were resampled for detailed dissolved gas composition 13 c of ch 4 c 2 c 3 and co 2 and d of ch 4 dissolved gases in groundwater from bedrock and overburden wells were composed primarily of ch 4 29 7 98 6 mol of total gas volume n 2 0 8 66 2 mol ar o 2 0 2 3 4 mol and co 2 0 1 2 mol ethane was detected but only in low concentrations 100 in situ saturation were found in bedrock wells completed in the upper devonian kettle point formation middle devonian hamilton group and dundee formation and in surficial aquifers overlying these organic rich shale bearing formations indicating that bedrock geology is the primary control on methane occurrences a few n 40 samples showed na cl br evidence of brine mixing with dilute groundwater however only one of these samples contained high 60 in situ saturation ch 4 the relatively low 13 c values of ch 4 89 9 to 57 3 covariance of d values of ch 4 and h 2 o positive correlation between 13 c values of ch 4 and co 2 and lack of higher chain hydrocarbons c 3 in all but one dissolved gas sample indicates that the methane in groundwater throughout the study area is primarily microbial in origin the presence or absence of alternative electron acceptors e g dissolved oxygen fe no 3 so 4 in addition to organic substrates controls the occurrence of microbial ch 4 in shallow aquifers microbial methane has likely been accumulating in the study area since at least the late pleistocene to the present as indicated by the co variance and range of d values of ch 4 314 to 263 and associated groundwater 19 to 6 d h 2 o

hydraulic fracturing not responsible for methane migration although osborn et al 1 provided important geochemical measurements of dissolved methane in a portion of the appalachian basin their report does not fully appreciate the geologic history of this region and misrepresents potential risks of modern drilling and completion techniques used to develop shale gas resources the fear that hydraulic fracturing is responsible for methane migration from the marcellus shale into shallow groundwater is contrasted by direct observations in microseismic studies that even the longest fractures induced by the hydraulic fracturing process remain thousands of feet below groundwater resources 2

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

pre drilling water quality data of groundwater prior to shale gas drilling in the appalachian basin analysis of the chesapeake energy corporation dataset abstract unconventional natural gas production in the marcellus and utica formations of the northeastern united states raises concerns about potential impacts to shallow groundwater we examined and interpreted 13 040 analyses from pre drilling groundwater samples from domestic water wells in northeastern ne pennsylvania and 8004 samples from water wells in the western area which includes southwest pennsylvania eastern ohio and north central west virginia these samples were acquired on behalf of chesapeake energy corporation as part of its local pre drilling water supply monitoring program we evaluated concentrations of major ions and metals relative to federal drinking water quality standards upon which regulatory decisions are often based chesapeake s dataset the most comprehensive for these areas shows that exceedance of at least one water quality standard occurs in 63 of water well samples in ne pennsylvania and 87 in the western area in ne pennsylvania 10 of the samples exceeded one or more of the united states environmental protection agency s usepa primary maximum contaminant levels mcls for drinking water supplies 46 1 of the samples exceeded one or more of usepa secondary maximum contaminant levels smcls and another 7 exceeded one or more of usepa health advisory or regional screening levels for tap water in the western area 8 of samples exceeded one or more mcls 65 exceeded one or more smcls and 15 exceeded one or more health advisory or regional screening levels for tap water chesapeake s dataset orders of magnitude larger than any in previously published literature shows that water quality exceedances relate to factors such as where the sample occurs within the groundwater flow system the natural groundwater chemical type hydrochemical facies the geologic unit producing the water and or the topographic position valley versus upland our comparison of these results to historical groundwater data from ne pennsylvania which pre dates most unconventional shale gas development shows that the recent pre drilling geochemical data is similar to historical data we see no broad changes in variability of chemical quality in this large dataset to suggest any unusual salinization caused by possible release of produced waters from oil and gas operations even after thousands of gas wells have been drilled among tens of thousands of domestic wells within the two areas studied our evaluation also agrees with early researchers such as piper 1933 and lohman 1939 1937 who found that the saline waters in both areas underlie fresher groundwater the saline water is naturally occurring connate brine or salt water which has not been flushed by circulating meteoric water rather than vertical migration of salt water from deep strata such as the marcellus shale as suggested by warner et al 2012 elevated metals concentrations particularly iron and manganese partly relate to sample turbidity dissolved metals would provide a more accurate measurement of metals in shallow groundwater than does the total metals analysis typically required by regulations

vegetation history of pleasant island southeastern alaska since 13 000 yr b p abstract a 13 000 year history of late quaternary vegetational and climatic change has been derived from lacustrine sediments from pleasant island in the glacier bay region of southeastern alaska early arrival of lodgepole pine and mountain hemlock indicated by the presence of pollen and conifer stomata suggests expansion from refugia in the alexander archipelago a short term climatic reversal possibly correlated with the european younger dryas is inferred from the expansion of tundra elements and deposition of inorganic sediments between 10 600 and 9900 14 c yr b p two peat cores from the lake catchment verify holocene vegetation changes and aid in the separation of biogenic from climatic forces affecting vegetation history differences in pollen representation among the three cores illustrate the variation among pollen collecting substrates as well as the spatial heterogeneity of peatland development and its dependence on local hydrology initial peat accumulation and soil paludification occasioned by increases in temperature and precipitation in the early holocene allowed western and mountain hemlock to replace sitka spruce 8500 8000 yr b p open muskeg became widespread about 7000 yr b p and allowed lodgepole pine to reinvade the region after a 2000 yr absence the extensive replacement of fen elements by bog taxa at 3400 yr b p suggests increased paludification due to changing hydrologic conditions its correlation with the upland expansion of tsuga heterophylla suggests the onset of a cooler wetter neoglacial climate in southeastern alaska

late neoproterozoic to permian tectonic evolution of the quebec appalachians canada abstract due to the unique location of the quebec appalachians in a re entrant of the paleo north american margin and to the fact that the area largely escaped late paleozoic deformation this segment of the orogen preserves evidence of the early orogenic stages that are partly obscured elsewhere despite diachronicity both along and across strike of the orogen five tectonic events of regional significance are recognized 1 the earliest event is mainly recorded by neoproterozoic to early ordovician normal faults associated with extension of the laurentian craton and the establishment of a passive continental margin 2 the second event the ordovician taconian orogeny is marked by foreland directed deformation and corresponds to the principal deformational and metamorphic events recorded by the laurentian margin 3 the third event early salinic is early silurian it is restricted to the southern part of the quebec appalachians and consists of hinterland se directed thrusts folds and retrograde metamorphism 4 the fourth event late salinic is recorded by regional scale late silurian to early devonian normal or transtensional faults and is associated with the formation of the connecticut valley gaspe trough and 5 the last event the devonian acadian orogeny affects with variable intensity all the pre carboniferous lithologies this tectonic synthesis implies that the subdivision of the peri laurentian oceanic tracts proposed in other segments of the appalachians should be applied with caution in quebec and that the structural style the number of oceanic domains and possibly the vergence of subduction change along the strike of the orogen in particular the similarities of the thetford mines and boil mountain ophiolitic complexes and sedimentary covers and the lack of evidence for a major intervening suture are consistent with the maximum allochtony hypothesis i e the assumption that the southern quebec ophiolites are rooted east of the chain lake massif a geodynamic model involving the taconian obduction of a large ophiolitic nappe s the docking of a peri gondwanan gander medial new england terrane in early salinic the formation of large sedimentary basins connecticut valley gaspe and merrimack troughs due to trench rollback and or delamination during the late salinic event and collision at the outer margin of composite laurentia during the acadian orogeny can account for the protracted structural and metamorphic history of the quebec appalachians

the quaternary of ecuador abstract ecuador is composed of three major regions the coast the cordillera and the oriente or amazon in the eastern amazonic lowlands the quaternary begins with the deposition of the mera mesa formation composed of coarse and medium grained sediments that unit was sedimented during a dry climate forming two large alluvial fans an erosive episode followed with formation of pediments at a later stage the humid climate appeared in the late pleistocene with formation of a landscape of round convex hills and narrow valleys the last important event in the region was the deposition of a thick ash mantle in the early holocene the quaternary of the cordillera is characterized by important volcanic activity glacial processes and the occurrence of cangahua a loess like aeolian silt composed of piroclastic materials lahars debris avalanches and related phenomena are common the coastal region during the quaternary underwent the influence of mud flows debris avalanches and other cordilleran phenomena which aggradated the area san tadeo formation and other units sea level oscillations deposited tidal sediments in several areas during the middle holocene and the occurrence of el nino produced alterations in the oceanic and coastal regime during the late holocene

carbon and hydrogen isotopic evidence for the origin of combustible gases in water supply wells in north central pennsylvania abstract the origin of the combustible gases in groundwater from glacial outwash and fractured bedrock aquifers was investigated in northern tioga county pennsylvania thermogenic methane ch4 and ethane c2h6 and microbial ch4 were found microbial ch4 is from natural in situ processes in the shale bedrock and occurs chiefly in the bedrock aquifer the 13c values of ch4 and c2h6 for the majority of thermogenic gases from water wells either matched or were between values for the samples of non native storage field gas from injection wells and the samples of gas from storage field observation wells traces of c2h6 with microbial ch4 and a range of c and h isotopic compositions of ch4 indicate gases of different origins are mixing in sub surface pathways gas mixtures are present in groundwater pathways for gas migration and a specific source of the gases were not identified processes responsible for the presence of microbial gases in groundwater could be elucidated with further geochemical study

multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system summary the study of groundwater hydrogeochemistry of the paleozoic basses laurentides sedimentary rock aquifer system in quebec produced a large geochemical dataset groundwater samples were collected at 153 sites over a 1500 km2 study area and analyzed for major and minor ions the large number of data can lead to difficulties in the integration interpretation and representation of the results two multivariate statistical methods hierarchical cluster analysis hca and principal components analysis pca were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry this subgroup consisted of 144 samples and 14 parameters ca2 mg2 na k hco 3 cl so 4 2 fe2 mn2 br sr2 f ba2 hs seven geochemically distinct clusters c1 c7 resulted from the hca samples from clusters c3 c4 c6 and c7 are mostly located in preferential recharge areas the majority of these samples have ca mg hco3 recharge groundwater c3 c6 c7 and na hco3 evolved groundwater c4 samples from the other three clusters c1 c2 c5 are characteristic of an aquifer system under confined conditions the majority of these samples have na hco3 evolved groundwater c1 c5 and na cl ancient groundwater that exhibits elevated concentrations in br c2 in addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry the distribution of clusters also showed the importance of the geological formations on minor and trace elements such as fe2 mn2 sr2 f and ba2 the first five components of the pca account for 78 3 of the total variance in the dataset component 1 is defined by highly positive loadings in na cl and br and is related to groundwater mixing with champlain sea water and solute diffusion from the marine clay aquitard the high positive loadings in ca2 and mg2 of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system from their characteristic loadings the first two components are defined as the salinity and hardness components respectively components 3 5 are related to more local and geological effects the integration of the hca and the pca with conventional classification of groundwater types as well as with the hydrogeological and geological contexts allowed the division of the region into four main geochemical areas providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater the following factors were recognized as influencing the evolution of groundwater identified in every geochemical area 1 geological characteristics including sedimentary rock type and till mineralogy 2 hydrogeological characteristics represented by the level of confinement and the hydraulic gradient and 3 the geological history including the latest glaciation and the champlain sea invasion with its integrated approach this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems and provides an example of the long term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion

capillary tension and imbibition sequester frack fluid in marcellus gas shale in a recent issue of pnas warner et al 1 interpreted local ground water chemistry in the appalachian basin as a signal for cross formational pathways where natural migration of brine from the deep formations may be ongoing today the implication of this paper is that the marcellus is leaking now naturally without any human assistance and that if water based fluid is injected into these cross formational pathways that leakage which is already contaminating the aquifers with salt could be made much worse

late quaternary vegetational change in the central peruvian andes abstract new fossil pollen records from the central peruvian andes at elevations above 4000 m including pollen concentration data and additional radiocarbon dates provide information on late quaternary vegetation change for the region a pollen assemblage typical of superpuna plus low pollen concentrations and organics in the late glacial section of laguna tuctua indicate a cold dry climate but strong evidence for a late glacial climate reversal i e the younger dryas is not presently confirmed an abrupt increase in urticales pollen as compositae and polylepis acaena type pollen decline signals the beginning of the holocene subsequent increases in urticales and plantago rigida type pollen point to increased moisture as well as higher temperatures from about 11 000 to 7000 yr b p a possible correlation exists between the rapid expansion of puna and closed continuous forest and the rise in importance of camelids in the early holocene in the mid holocene plantago rigida cushion bogs and continuous montane forest elements decline suggesting a drier climate grasses and cheno ams then increase reaching maxima about 4000 yr b p pastoralism and agriculture are thought to have developed at this time according to ethnobotanical studies from this area and pollen evidence seems to support these findings between 3000 and 2000 yr b p pollen percentages of poaceae plantago rigida type and other local taxa decline as glacial activity was renewed in the higher mountains zea mays is present by 2000 yr b p and pollen of weeds and secondary successional plants associated with increasing agricultural disturbance are evident

numerical simulation of the environmental impact of hydraulic fracturing of tight shale gas reservoirs on near surface groundwater background base cases shallow reservoirs short term gas and water transport hydrocarbon production from unconventional resources and the use of reservoir stimulation techniques such as hydraulic fracturing has grown explosively over the last decade however concerns have arisen that reservoir stimulation creates significant environmental threats through the creation of permeable pathways connecting the stimulated reservoir with shallower freshwater aquifers thus resulting in the contamination of potable groundwater by escaping hydrocarbons or other reservoir fluids this study investigates by numerical simulation gas and water transport between a shallow tight gas reservoir and a shallower overlying freshwater aquifer following hydraulic fracturing operations if such a connecting pathway has been created we focus on two general failure scenarios 1 communication between the reservoir and aquifer via a connecting fracture or fault and 2 communication via a deteriorated preexisting nearby well we conclude that the key factors driving short term transport of gas include high permeability for the connecting pathway and the overall volume of the connecting feature production from the reservoir is likely to mitigate release through reduction of available free gas and lowering of reservoir pressure and not producing may increase the potential for release we also find that hydrostatic tight gas reservoirs are unlikely to act as a continuing source of migrating gas as gas contained within the newly formed hydraulic fracture is the primary source for potential contamination such incidents of gas escape are likely to be limited in duration and scope for hydrostatic reservoirs reliable field and laboratory data must be acquired to constrain the factors and determine the likelihood of these outcomes

using cl br ratios and other indicators to assess potential impacts on groundwater quality from septic systems a review and examples from principal aquifers in the united states summary a detailed review was made of chemical indicators used to identify impacts from septic tanks on groundwater quality potential impacts from septic tank leachate on groundwater quality were assessed using the mass ratio of chloride bromide cl br concentrations of selected chemical constituents and ancillary information land use census data well depth soil characteristics for wells in principal aquifers of the united states chemical data were evaluated from 1848 domestic wells in 19 aquifers 121 public supply wells in 6 aquifers and associated monitoring wells in four aquifers and their overlying hydrogeologic units based on previously reported cl br ratios statistical comparisons between targeted wells where cl br ratios range from 400 to 1100 and cl concentrations range from 20 to 100 mg l and non targeted wells indicated that shallow targeted monitoring and domestic wells 0 5 mg l shallow groundwater from target domestic wells relative to non target wells 1 5 mg l corresponded to significantly higher potassium boron chloride dissolved organic carbon and sulfate concentrations which may also indicate the influence of septic tank effluent impacts on groundwater quality from septic systems were most evident for the eastern glacial deposits aquifer and the northern high plains aquifer that were associated with the number of housing units using septic tanks high permeability of overlying sediments mostly oxic conditions and shallow wells overall little or no influence from septic systems were found for water samples from the deeper public supply wells the cl br ratio is a useful first level screening tool for assessing possible septic tank influence in water from shallow wells

recent cross formational fluid flow and mixing in the shallow michigan basin ground water with total dissolved solids tds ranging from 10 to 50 g l exists at depths between 90 and 140 m in devonian oil bearing formations in the shallow michigan basin of southwestern ontario these formations comprise mainly limestone and dolomite and the sources of the saline ground water have not been identified previously isotopic and major ion data from ground water from devonian oil bearing formations in southwestern ontario indicate that the highest salinity fluids were emplaced locally from depths of several hundred meters during the later stages of or following the wisconsinan glaciation saline water and petroleum were also emplaced into overlying pleistocene clay rich glacial deposits isostatic rebound leading to fracturing and enhanced formation permeability due to matrix expansion was probably the primary mechanism that enabled these saline fluids to migrate into discrete areas of the devonian and pleistocene formations the geochemical data presented here support a model involving cross formational fluid flow from depth occurring vertically on the scale of several hundred meters since glaciation the hydrogeologic regime in this shallow basinal system must therefore be viewed as dynamic rather than static to depths of at least 500 m over a time frame of 100 000 yr 54 refs 10more figs 2 tabs less

methane contamination of drinking water caused by hydraulic fracturing remains unproven shale gas extraction involves the drilling of organic rich low permeability shale and then stimulation of hydraulic fractures that allows gas to be produced methane in aquifers located above the shale strata for instance in pennsylvania united states has been attributed by some to be the result of contamination caused by the hydraulic fracturing process the work by osborn et al 1 described geochemical data from 68 drinking water wells in northeastern pennsylvania and upstate new york and evaluated whether the aquifers that the water wells penetrated were contaminated with thermogenic methane sourced from the underlying marcellus and utica shale formations the work by osborn et al 1 concluded that contamination had occurred and that the contamination accompanied gas well drilling and hydraulic fracturing the inference from the text and title of the paper is clear hydraulic fracturing had a role however the evidential basis for implicating this specific process is not sound and needs to be closely scrutinized

origin and formation of methane in groundwater of glacial origin from the cambrian vendian aquifer system in estonia abstract groundwater in the cambrian vendian aquifer system in estonia is characterised by the most depleted isotopic composition known in europe 18o down to 23 the water most likely originates from glacial meltwater recharge from the fennoscandian ice sheet in the pleistocene the aquifer system is characterised by relative high methane concentrations up to 50 of dissolved gases estimated absolute concentration up to 1600 mol l 1 the origin of which has so far remained unclear in this paper we focus on the origin of methane the factors controlling its spatial distribution and its isotope geochemistry in the aquifer system the data reveal a large spatial variability in methane concentration 13cch4 and 2hch4 values from 6 to 105 and from 220 to 420 respectively we show that local oxidation processes rather than different pathways of methane formation have affected the initial isotopic composition of methane using the least modified 13cch4 values from 85 to 105 we conclude that methane most likely originates from the organic material overridden by the fennoscandian ice shield during the late weichselian glaciation that was carried into the aquifer system with infiltrating glacial meltwater the estimated 18o values of the water where the methane was formed are 17 1 5 supporting the inference that the methane was formed during the middle weichselian interstadial the study shows that groundwater of glacial origin in the cambrian vendian aquifer system can serve as an alternative palaeoenvironmental archive to be used for studying the variations in climatic and environmental conditions in northern europe during glacial interglacial cycles of the pleistocene

glacial and postglacial pollen records from the ecuadorian andes and amazon abstract a long pollen record is derived from sediments of a lake dammed behind a low moraine of the last glaciation at 3 s latitude in the ecuadorian andes and is compared with a glacial age pollen record from the amazon rainforest immediately below lake surucucho llaviucu lies at 3180 m on the amazonian flank of the andes and above the glacial age pollen record from san juan bosco at 970 m the surucucho pollen record is interpreted as showing treeless vegetation in glacial times advance of treeline in late glacial time and holocene development of modern andean forests combining the surucucho and san juan bosco records shows that andean vegetation was affected by glacial cooling at all elevations vegetation did not move up and down slope as belts rather plant associations were reformed as temperature sensitive species found different centers of distribution with changing temperature

postglacial vegetation and fire history in the chirripo paramo of costa rica abstract pollen and charcoal analysis of a 5 6 m sediment core from lago de las morrenas 9 29 n 83 29 w 3480 m provides evidence of postglacial vegetation and fire history in the highlands of the cordillera de talamanca costa rica the site is presently surrounded by treeless paramo vegetation and apparently has been so since deglaciation about 10 000 yr b p pollen spectra suggest no pronounced changes in vegetation since ice retreat fires set by people or lightning have burned the paramo repeatedly with fire activity probably highest during the late holocene but these fires have not carved paramo from forest pollen percentages for gramineae and other paramo taxa decline upward whereas percentages for certain subalpine lower montane and lowland forest taxa increase slightly these changes may reflect the impact of prehistoric human activity or slight upslope migrations of forest taxa owing to climatic warming there is no clear evidence of higher timberlines during the mid holocene

taconian melanges in the parautochthonous zone of the quebec appalachians revisited implications for foreland basin and thrust belt evolution in the quebec appalachians disruption imbrication and thrusting of the taconian foreland basin sequence are responsible for the development of chaotic units within the turbiditic sequence of the caradocian sainte rosalie group the main lithologic assemblage of the parautochthonous zone these chaotic units have been termed olistostromes or tectonosomes on the basis of field criteria and following pini s 1999 classification olistostromal units containing blocks of the middle mudstone utica shale and upper turbidite units ste rosalie group of the foreland basin and spanning the caradocian n gracilis c americanus o ruedemanni and c spiniferus graptolite zones were deposited and incorporated into the sainte rosalie group disruption of more competent beds of the flyschic sequence and fault stacking and slicing of older rock units occurred along major thrust faults and now form structurally aligned corridors or tectonosomes graptolites and new chitinozoan data from both olistostromes and tec

desalination of a sedimentary rock aquifer system invaded by pleistocene champlain sea water and processes controlling groundwater geochemistry the objective of this study was to identify geochemical processes and quaternary geological events responsible for the variations in groundwater geochemistry observed in a sedimentary rock aquifer system including brackish to saline groundwater inorganic constituents and environmental isotopes were analyzed for 146 groundwater samples dissolution of carbonates dominates in recharge areas resulting in ca mg hco3 groundwater further along flow paths under confined conditions ca2 na ion exchange causes groundwater evolution to na hco3 type na cl groundwater is also found and it falls on a seawater mixing line using conservative tracers cl and br the original champlain sea water is shown to have been in the region a mixture of about 34 seawater and 66 freshwater a composition still retained by some groundwater na cl groundwater thus results from mixing with former champlain sea water and also from solute diffusion from overlying marine clay the system is thus found to be at different stages of desalinization from the original champlain sea water still present in hydraulically stagnant areas of the aquifer to fully flushed conditions in parts where more flow occurs especially in recharge zones the geochemical processes are integrated within the hydrogeological context to produce a conceptual geochemical evolution model for groundwater of the aquifer system

sr c and o isotope geochemistry of ordovician brachiopods a major isotopic event around the middle late ordovician transition here we present sr c and o isotope curves for ordovician marine calcite based on analyses of 206 calcitic brachiopods from 10 localities worldwide these are the first ordovician wide isotope curves that can be placed within the newly emerging global biostratigraphic framework a total of 182 brachiopods were selected for c and o isotope analysis and 122 were selected for sr isotope analysis seawater 87sr 86sr decreased from 0 7090 to 0 7078 during the ordovician with a major quite rapid fall around the middle late ordovician transition most probably caused by a combination of low continental erosion rates and increased submarine hydrothermal exchange rates mean 18o values increase from 10 to 3 through the ordovician with an additional short lived increase of 2 to 3 during the latest ordovician due to glaciation although diagenetic alteration may have lowered 18o in some samples particularly those from the lower ordovician maximum 18o values which are less likely to be altered increase by more than 3 through the ordovician in both our data and literature data we consider that this long term rise in calcite 18o records the effect of decreasing tropical seawater temperatures across the middle late ordovician transition superimposed on seawater 18o that was steadily increasing from 3 standard mean ocean water smow by contrast 13c variation seems to have been relatively modest during most of the ordovician with the exception of the globally documented but short lived latest ordovician 13c excursion up to 7 nevertheless an underlying trend in mean 13c can be discerned changing from moderately negative values in the early ordovician to moderately positive values by the latest ordovician these new isotopic data confirm a major reorganization of ocean chemistry and the surface environment around 465 to 455 ma the juxtaposition of the greatest recorded swings in phanerozoic seawater 87sr 86sr and 18o at the same time as one of the largest marine transgressions in phanerozoic earth history suggests a causal link between tectonic and climatic change and emphasizes an endogenic control on the o isotope budget during the early paleozoic better isotopic and biostratigraphic constraints are still required if we are to understand the true significance of these changes we recommend that future work on ordovician isotope stratigraphy focus on this outstanding middle late ordovician event

hydraulic fracturing in unconventional gas reservoirs risks in the geological system part 2 hydraulic fracturing is a method used for the production of unconventional gas resources huge amounts of so called fracturing fluid 10 000 20 000 m3 are injected into a gas reservoir to create fractures in solid rock formations upon which mobilised methane fills the pore space and the fracturing fluid is withdrawn hydraulic fracturing may pose a threat to groundwater resources if fracturing fluid or brine can migrate through fault zones into shallow aquifers diffuse methane emissions from the gas reservoir may not only contaminate shallow groundwater aquifers but also escape into the atmosphere where methane acts as a greenhouse gas the working group risks in the geological system as part of exxonmobil s hydrofracking dialogue and information dissemination processes was tasked with the assessment of possible hazards posed by migrating fluids as a result of hydraulic fracturing activities in this work several flow paths for fracturing fluid brine and methane are identified and scenarios are set up to qualitatively estimate under what circumstances these fluids would leak into shallower layers the parametrisation for potential hydraulic fracturing sites in north rhine westphalia and lower saxony both in germany is derived from literature using upper and lower bounds of hydraulic parameters the results show that a significant fluid migration is only possible if a combination of several conservative assumptions is met by a scenario

pollen studies in the junin area central peruvian andes laguna junin is a large lake 675 km long but only 4 m deep located in the grass covered altiplano at an altitude of 4 100 m northeast of lima pollen analysis of a 30 m core indicates that from about 12 000 yr ago until some time after 3 000 yr ago about 30 of the pollen was carried in by easterly winds from the east andean forests which today are at least 600 m lower in elevation contemporaneous pollen deposition in lakes on moraines of the last glaciation west of the junin plain was dominated by local grassland types and had little contribution from this easterly source at some time after 3 000 yr ago perhaps about 1 200 yr ago the pollen influx to laguna junin from this distant forest source greatly diminished perhaps because of deforestation by increased human populations between about 12 000 and 24 000 yr ago in the junin core the sparse pollen concentration was dominated by grassland types supplemented by polylepis acaena alnus and compositae blown in from the sub puna shrublands that may have occupied much of the east andean slopes in place of the humid forest that occurs there today the silty sediment in this section of the core is interpreted as outwash from piedmont glaciers that invaded the plain especially from the cordillera to the west these glaciers left a distinctive pattern of moraines and outwash fans which served to dam tine lake basin an unconformity in the sediment covers the time from about 24 000 to 39 000 yr ago when the lake was probably dry before this time the silty sediment and the dominance of grassland and shrubland pollen types indicates an earlier interval of glaciation recorded on the landscape by an older set of moraines and outwash fans which initially dammed the lake basin

assessing potential impacts of shale gas development on shallow aquifers through upward fluid migration a multi disciplinary approach applied to the utica shale in eastern canada abstract potential impacts of shale gas development on shallow aquifers has raised concerns especially regarding groundwater contamination the intermediate zone separating shallow aquifers from shale gas reservoirs plays a critical role in aquifer vulnerability to fluid upflow but the assessment of such vulnerability is challenging due to the general paucity of data in this intermediate zone the ultimate goal of the project reported here was to develop a holistic multi geoscience methodology to assess potential impacts of unconventional hydrocarbon development on fresh water aquifers related to upward migration through natural pathways the study area is located in the st lawrence lowlands southern quebec canada where limited oil and gas exploration and no shale gas production have taken place a large set of data was collected over a 500 km2 area near a horizontal shale gas exploration well completed and fracked into the utica shale at a depth of 2 km to investigate the intermediate zone integrity this project integrated research results from multiple sources in order to obtain a better understanding of the system hydrodynamics including geology hydrogeology deep and shallow geophysics soil rock and groundwater geochemistry and geomechanics the combined interpretation of the multi disciplinary dataset demonstrates that there is no evidence of and a very limited potential for upward fluid migration from the utica shale reservoir to the shallow aquifer microbial and thermogenic methane in groundwater of this region appear to come from the shallow organic rich fractured sedimentary rocks making up the regional aquifer nonetheless diluted brines present in a few shallow wells close to and downstream of a normal fault revealed that some upward groundwater migration occurs but only over a few hundred meters from the surface based on the isotopic signature of methane the methodology developed should help support regulations related to shale gas development aiming to protect groundwater

comment on hydraulic fracturing in faulted sedimentary basins numerical simulation of potential contamination of shallow aquifers over long time scales by claire gassiat et al

an overview of canadian shale gas production and environmental concerns abstract production of hydrocarbons from canadian shales started slowly in 2005 and has significantly increased since natural gas is mainly being produced from devonian shales in the horn river basin and from the triassic montney shales and siltstones both located in northeastern british columbia and to a lesser extent in the devonian duvernay formation in alberta western canada other shales with natural gas potential are currently being evaluated including the upper ordovician utica shale in southern quebec and the mississippian frederick brook shale in new brunswick eastern canada this paper describes the status of shale gas exploration and production in canada including discussions on geological contexts of the main shale formations containing natural gas water use for hydraulic fracturing the types of hydraulic fracturing public concerns and on going research efforts as the environmental debate concerning the shale gas industry is rather intense in quebec the utica shale context is presented in more detail