surface wave studies of some south carolina earthquakes long period surface waves generated by three south carolina earthquakes are used to infer focal mechanisms and seismic moments of the events the 3 february 1972 bowman south carolina earthquake is found to be shallow and to require an almost strike slip focal mechanism with pressure axes trending northeast southwest the 22 november 1974 charleston south carolina earthquake was smaller and was recorded by only three long period wwssn stations for this earthquake only an estimate of the seismic moment and focal depth were possible the focal mechanism of the 2 august 1974 clarkhill reservoir earthquake indicated motion on a northwest striking almost vertical dip slip fault in order to specify preferred motions on the nodal planes full waveform modeling of the long period traces at atl was necessary the results are not without ambiguity but represent the best estimates of source parameters for these earthquakes

stress field constraints on intraplate seismicity in eastern north america focal mechanisms of 32 north american midplate earthquakes mo 3 8 6 5 were evaluated to determine if slip is compatible with a broad scale regional stress field derived from plate driving forces and if so under what conditions stress regime pore pressure and frictional coefficient using independent information on in situ stress orientations from well bore breakout and hydraulic fracturing data and assuming that the regional principal stresses are in approximately horizontal and vertical planes 10o the constraint that the slip vector represents the direction of maximum resolved shear stress on the fault plane was used to calculate relative stress magnitudes defined by the parameterb s2 s3 s s3 from the fault stress geometry as long as the focal mechanism has a component of oblique slip i e the b axis does not coincide with the intermediate principal stress direction this calculation identifies which of the two nodal planes is a geometrically possible slip plane gephart 1985 slip in a majority of the earthquakes 25 of 32 was found to be geometrically compatible with reactivation of favorably oriented preexisting fault planes in response to the broad scale uniform regional stress field slip in five events was clearly inconsistent with the regional stress field and appears to require a localized stress anomaly to explain the seismicity significantly all five of these events occurred prior to 1970 when many regional networks were installed and their focal mechanisms are inconsistent with more recent solutions of nearby smaller events the frictional likelihood of the geometrically possible slip on the selected fault planes was evaluated in the context of conventional frictional faulting theory the ratio of shear to normal stress on the fault planes at hypocentral depth was calculated relative to an assumed regional stress field regional stress magnitudes were determined from 1 s s3 ratios based on the frictional strength of optimally oriented faults the basis for the linear brittle portion of lithospheric strength profiles 2 the computed relative stress magnitude b values and 3 a vertical principal stress assumed equal to the lithostat two end member possibilities were examined to explain the observed slip in these less than optimally oriented fault planes first the frictional coefficient was held constant on all faults hydrostatic pore pressure was assumed regionally and the fault zone pore pressure was determined since pore pressure is a measurable quantity with real limits in the crust p0 s3 this end member case was used to determine which of the geometrically possible slip planes were frictionally likely slip planes alternately pore pressure was fixed at hydrostatic everywhere and the required relative lowered frictional coefficient of the fault zone was computed slip in 23 of the 25 geometrically compatible earthquakes was determined to also be frictionally likely in response to an approximately horizontal and vertical regional stress field derived from plate driving forces whose magnitudes are constrained by the frictional strength of optimally oriented faults assuming hydrostatic pore pressure regionally the conditions for slip on these 23 relatively well oriented earthquake faults were determined relative to this regional crustal strength model and require only moderate increases in pore pressure between about 0 4 0 8 of lithostatic hydrostatic is about 0 37 of lithostatic or alternately moderate lowering 50 of the frictional coefficient on the faults which slipped superlithostatic pore pressures are not required focal mechanisms for the two other earthquakes with slip vectors geometrically consistent with the regional stress field however did require pore pressures far exceeding the least principal stress or extremely low coefficients of friction these events may reflect either local stress rotations undetected with current sampling or poorly constrained focal mechanisms the analysis also confirmed a roughly north to south contrast in stress regime between the central eastern united states and southeastern canada previously inferred from a contrast in focal mecha nisms between the two areas most central eastern united states earthquakes occur in response to a strike slip stress regime whereas the southeastern canadian events require a thrust faulting stress regime this contrast in stress regime with a constant maximum horizontal stress orientation determined by far field plate driving forces requires a systematic lateral variation in relative stress magnitudes superposition of stresses due to simple flexural models of glacial rebound stresses are of the correct sense to explain the observed lateral variation but maximum computed rebound related stress magnitude changes are quite small about 10 mpa and do not appear large enough to account for the stress regime change if commonly assumed stress magnitudes determined from frictional strength apply to the crust at seismogenic depths

the microbial input in carbonate anhydrite facies of a sabkha palaeoenvironment from guatemala a molecular approach abstract nine representative rock samplesincluding four anhydrites an oil stained dolomite and a laminated mudstone source rock from a sabkha type palaeoenvironment la felicidad 1 well guatemala have been compared in order to tentatively characterize each facies by a geochemical signature each sample has been studied by using basic parameters toc rock eval pyrolysis yields and analyses of alkanes and aromatics by computerized gc ms the following families of compounds have been reviewed n alkanes branched and cyclic alkanes n alkylbenzenes benzohopanes monoaromatic steroids d ring aromatic 8 14 secohopanoids alkylnaphthalenes alkylphenanthrenes alkyldibenzothiophenes and triaromatic steroids despite close geochemical relationships of all the sample a more in depth investigation taking into account molecular patterns and semi quantitative data reveals significant differences among the samples anhydrites may be differentiated from carbonates which illustrates the efficiency of organic geochemistry in environmental palaeoreconstruction even in organiccarbon lean sediments toc 0 04 0 08 in anhydrites in these anoxic marginally mature sediments the strong predominance of triterpanes over steranes tt to st 20 associated with other molecular features leads to the conclusion that the main contribution to the organic matter of all facies is by bacteria several prominent components including novel families iso c23 and iso c27 alkanes tetracyclic terpanes d ring aromatic 8 14 secohopanoids 1 phenylpentadecane undecylnaphathalene and their mono and dimethylated counterparts have been interpreted as derived from halophilic bacteria these conclusions may be extended to all crude oils from the same area which may be considered as true bacterially derived petroleums the la felicidad 1 well data are discussed with reference to other palaeosabkha type sequences from the sw aquitaine basin france in which the bacterial input is less important however in these sabkha sequences 1 phenylpentadecane undecylnaphthalene and related structures have also been identified

anaerobic methane oxidation and a deep h2s sink generate isotopically heavy sulfides in black sea sediments the main terminal processes of organic matter mineralization in anoxic black sea sediments underlying the sulfidic water column are sulfate reduction in the upper 2 4 m and methanogenesis below the sulfate zone the modern marine deposits comprise a ca 1 m deep layer of coccolith ooze and underlying sapropel below which sea water ions penetrate deep down into the limnic pleistocene deposits from 9000 years bp sulfate reduction rates have a subsurface maximum at the so42 ch4 transition where h2s reaches maximum concentration because of an excess of reactive iron in the deep limnic deposits most of the methane derived h2s is drawn downward to a sulfidization front where it reacts with fe iii and with fe2 diffusing up from below the h2s fe2 transition is marked by a black band of amorphous iron sulfide above which distinct horizons of greigite and pyrite formation occur the pore water gradients respond dynamically to environmental changes in the black sea with relatively short time constants of ca 500 yr for so42 and 10 yr for h2s whereas the fes in the black band has taken ca 3000 yr to accumulate the dual diffusion interfaces of so42 ch4 and h2s fe2 cause the trapping of isotopically heavy iron sulfide with 34s 15 to 33 at the sulfidization front a diffusion model for sulfur isotopes shows that the so42 diffusing downward into the so42 ch4 transition has an isotopic composition of 19 close to the 23 of h2s diffusing upward these isotopic compositions are however very different from the porewater so42 43 and h2s 15 at the same depth the model explains how methane driven sulfate reduction combined with a deep h2s sink leads to isotopically heavy pyrite in a sediment open to diffusion these results have general implications for the marine sulfur cycle and for the interpretation of sulfur isotopic data in modern sediments and in sedimentary rocks throughout earth s history

the baseflow and storm flow hydrology of a precambrian shield headwater peatland a hydrological investigation was conducted in a small headwater peatland located in the experimental lakes area north western ontario canada to determine the subsurface and surface flow paths within the peatland and between the peatland and an adjacent forested upland during baseflow and storm flow conditions distinct zones of groundwater recharge and discharge were observed within the peatland these zones are similar to those found in much larger flow systems even though the peatland was only influenced by local groundwater flow groundwater emerging in seeps and flowing beneath the peatland sustained the surface wetness of the peatland and maintained a constant baseflow the response of the peatland stream to summer rain events was controlled by peatland water table position when the basin was dry and antecedent moisture storage on the uplands when the basin was wet the magnitude and timing of peak runoa during wet conditions were controlled by the degree of hydrological connectivity between the surrounding upland terrain and the peatland 1998 john wiley sons ltd hydrol process vol 12 57 72 1998

abundance anomalies of aromatic biomarkers in the permian triassic boundary section at meishan china evidence of end permian terrestrial ecosystem collapse several aromatic biomarkers detected in solvent extracts and kerogen pyrolysates from samples of the global stratotype section and point gssp for the permian triassic boundary at meishan china show distinctive relative abundance anomalies that may be related to the end permian biotic crisis on land enrichment of dibenzofuran homologues across the permian triassic boundary may corroborate the concept of excessive soil erosion following loss of rooted vegetation enrichment of alkylphenol entities occurs just below the main marine mass extinction horizon and prior to the characteristic end permian 13c decline the alkylphenols were probably derived from lignin and may provide a molecular record of dieback of woody vegetation highly decreased relative abundances of dibenzothiophenes could be indicative of excessive supply of fe2 it is suggested that fe2 was land derived and may have originated from soils in addition to the permian triassic boundary interval biomarker abundance anomalies also occur around the wuchiapingian changhsingian boundary in the basal part of the meishan section

development of a largely anoxic stratified ocean and its temporary massive mixing at the permian triassic boundary supported by the sulfur isotopic record systematic sulfur isotope data for whole rock sulfides have been obtained from the chert dominated continuous pelagic sedimentary sequences spanning the permian triassic p tr boundary at tenjinmaru in the chichibu terrane and at sasayama in the tanba terrane in japan the p tr boundary is characterized by the occurrence of siliceous shales in association with a carbonaceous black mudstone which is similar in appearance to the worldwide distributed cretaceous tertiary k t boundary claystone the observed data clearly demonstrate a significant bimodalism the 34s 32s ratios with respect to cdt are generally low throughout the middle permian ca 39 to 25 0 and show a remarkable increase beginning in the lower upper permian and persisting into the lower triassic ca 20 to 2 0 with a temporary and drastic negative shift down to roughly the same isotopic level as in the middle permian just at the suspected p tr boundary ca 41 to 23 0 interestingly the mode of isotopic excursion across the p tr boundary is in striking contrast to that across the k t boundary which was recently described at kawaruppu in hokkado japan the apparent extent of fractionation with respect to contemporaneous seawater sulfate in the high 34s 32s group lies within the range of 25 10 0 which is quantitatively equivalent to the currently confirmed range of kinetic isotope effect during bacterial dissimilatory sulfate reduction and that in the low 34s 32s group mostly exceeds this range giving the values typically in the range of 45 10 0 which is similar to what is generally observed in the present day oceanic sediments the present data would provide strong evidence for the development of a largely stagnant anoxic stratified ocean which presumably began to form in the lower upper permian and persisted into the lower triassic and for a brief episode of its temporary massive mixing just at the suspected p tr boundary such an oceanic oxic anoxic history may account to some extent for the relatively high enrichments of chalcophile elements in basal triassic sediments in the world and add a significant constraint to the current arguments on the cause and consequence of the terminal permian mass extinction

the permo triassic extinction the end permian mass extinction brought the palaeozoic great experiment in marine life to a close during an interval of intense climatic tectonic and geochemical change improved knowledge of latest permian faunas coupled with recent advances in isotopic studies and biostratigraphy have greatly enhanced our understanding of the events of 250 million years ago and have begun to provide answers to many questions about the causes of extinction

an integrated biomarker isotopic and palaeoenvironmental study through the late permian event at lusitaniadalen spitsbergen abstract the largest extinction of the phanerozoic occurred near the permian triassic p tr boundary some 252 ma ago several scenarios and drivers have been proposed for this event here we report for the first time an integrated study comprising sedimentological data biomarker distributions abundances and selected stable carbon and hydrogen isotopes along with bulk isotopes 34spyrite 13ccarb 13corg for a late permian section from lusitaniadalen spitsbergen norway sedimentological and geochemical data support a marine transgression and collapse of the marine ecosystem in the late permian strong evidence for waxing and waning of photic zone euxinia throughout the late permian is provided by chlorobiaceae derived biomarkers including 13c data and 34spyrite implying multiple phases of h2s outgassing and potentially several pulses of extinction a rapid decrease in abundance of various land plant biomarkers prior to the marine collapse event indicates a dramatic decline of land plants during the late permian and or increasing distance from palaeoshoreline as a consequence of sea level rise changes in d of selected biomarkers also suggest a change in source of organic matter om or sea level rise we also found biomarker and isotopic evidence for a phytoplanktonic bloom triggered by eutrophication as a consequence of the marine collapse compound specific isotope analyses csia of algal and land plant derived biomarkers as well as 13c of carbonate and bulk om provide strong evidence for synchronous changes in 13c of marine and atmospheric co2 attributed to a 13c depleted source the source could be associated with isotopically depleted methane released from the melting of gas clathrates and or from respired om due to collapse of the marine ecosystem

close up of the end permian mass extinction horizon recorded in the meishan section south china sedimentary elemental and biotic characterization and a negative shift of sulfate sulfur isotope ratio abstract the permian triassic p tr boundary beds of the meishan section south china have been re studied in detail based on complete samples across the p tr transition under the microscope the end permian mass extinction horizon is calibrated to a 12 mm stratal interval the top being 19 mm below the top of bed 24e of the changhsing formation this abrupt disappearance of skeletal fragments of major benthos characterizes the end permian extinction event suggesting a catastrophic event an abrupt decrease in the 34s 32s ratios of seawater sulfate is confirmed to coincide with the end permian event horizon the sulfur isotope event is thought to have been caused by an overturn of a stratified ocean dominated by h2s implying coincidence of the oceanic mixing and the mass extinction coincident siberian flood volcanism may have triggered a long term 103 years cooling leading an ocean mixing a presumed comet impact to the ocean could have directly caused ocean mixing and the mass extinction

groundwater flow patterns in a large peatland abstract groundwater flow patterns and geochemistry were studied in the mer bleue bog near ottawa ontario canada groundwater flow patterns alternated between recharge i e head gradients producing flow from the surface of the peatland to the deeper peat and discharge i e head gradients indicating flow from the deeper peat towards the surface of the peatland during the summer of 1998 the patterns were controlled by changes in precipitation evapotranspiration and the differential head response of catotelm peat lower layer to changes in water table elevation above average rainfall in the spring created recharge patterns of groundwater flow in the peatland evapotranspiration exceeded precipitation for a three week period in mid summer decreasing head at the water table and reversing flow from recharge to discharge a sustained moisture deficit maintained a flow reversal for 32 days until a 46 mm rainfall raised the water table reversing the vertical hydraulic gradients and restoring recharge flow the mixing of meteoric water and deeper groundwater controls geochemical profiles diffusion modeling shows that the peatland is a long term recharge system however electrical conductivity and cation concentrations in peat pore waters increase up to 60 during a flow reversal and then decrease when recharge conditions are re established the redistribution of substrates from reversed flow is likely important to peatland biogeochemical function

holocene development of parabolic dunes in the central st lawrence lowland quebec abstract stabilized parabolic dunes in the central st lawrence lowland are oriented ne sw in the postulated direction of dune building winds coming from anticyclonic air circulation induced by the retreating laurentide ice sheet about 10 000 yr ago the eolian chronology reconstructed from several sections in mixed dune peatland environments indicates that postglacial plant colonization characterized by a fortuitous assemblage of arctic subarctic and boreal elements preceded dune formation during champlain sea regression around 10 000 yr b p confined peatlands and small forests were buried by eolian sands between 10 000 and 7500 yr b p under dry and temperate conditions this eolian episode lasted about 2500 14 c yr and ended when cyclonic air circulation similar to the present humid climatic regime was established following the breakup and disappearance of the laurentide ice sheet over hudson bay and peripheral areas dune stabilization through paludification of well drained eolian sands about 7500 yr b p suggests a major shift in climate toward wetter conditions that have been characteristic during most of the holocene in eastern north america minor eolian erosion induced by wildfire was recorded during late holocene time about 1250 yr b p anthropogenic perturbation logging and agriculture practice was also responsible for recent very local eolian activity

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

carbon sulfur oxygen and strontium isotope records organic geochemistry and biostratigraphy across the permian triassic boundary in abadeh iran pelagic deposits at abadeh represent a complete biostratigraphic record across the permian triassic boundary ptb the presumed water depth during deposition of these sediments was between 60 and 90 m similar to other permian triassic boundary sections the succession at abadeh is characterised by a negative carbon isotope shift of approximately 4 the values start to decrease in the lower c changxingensis c deflecta s l zone reach 0 12 v pdb in the uppermost permian just below the ptb remain low to the early i isarcica zone 0 32 and increase subsequently in the upper i isarcica zone for the time interval of the ptb negative carbon isotope excursion between the c iranica and the i isarcica zones no correlation exists between the 13ccarb and the 18ocarb the above observations argue against the conclusion of heydari et al 2001 that the carbon isotope event at the p t transition is an alteration artefact and not a global signal the decrease in 13ccarb is accompanied by a 5 and potentially up to 10 increase in 34ssss together these features are thought to reflect a complex global event notably the development of widespread anoxic oceans with anoxic bottom layers rising onto the shelves for the carbon isotope drop other factors such as the collapse of ocean primary productivity may also have played a role the 87sr 86sr ratios of dzhulfian seawater show only a minor increase from 0 70705 to 0 70710 reaching 0 70720 in the dorashamian the increase becomes steeper in the early triassic reaching 0 70754 in the n dieneri zone the rise of the strontium isotope values is thought to be related to enhanced continental weathering under humid climatic conditions in the uppermost permian c meishanensis h praeparvus zone and the lack of a dense land vegetation in the early triassic prior to the spathian upper olenekian

shallow groundwater surface water interactions in pond peatland complexes along a boreal plains topographic gradient shallow pond peatland complexes are important water resources and waterbird habitat on the boreal plains of canada and are potentially threatened by accelerated resource development we examined two shallow pond peatland complexes located in contrasting topographic positions within a clay rich till region one on a moraine and one on a lowland clay plain to evaluate the influence of landscape position on wetland groundwater surface water interactions hydrologic function and potential response to disturbance hydrometric and geochemical measurements indicated that precipitation and evaporation dominated the annual water balance of both ponds forested mineral uplands adjacent to the pond peatland complexes contributed no runoff inputs small recharge rates 5 mm year 1 from the ponds through low permeable clay to the underlying aquifer were measured at both topographic locations shallow groundwater fluxes to from the pond were controlled by water storage in and exchange with the adjacent riparian peatlands shallow groundwater fluxes may have contributed as much as 23 of inputs and outputs and influenced pond chemistry and permanence shallow groundwater exchange between the pond and adjacent peatlands varied seasonally and differed between the moraine and lowland complex groundwater flow reversals occurred around the entire perimeter of the moraine pond recharge from the moraine pond to the peatland during dry periods was off set by discharge to the pond from the peatland during wet periods in contrast shallow groundwater flow through conditions were observed at the lowland pond for most of the study however during a high rainfall event a groundwater flow reversal within the outflow peatland initiated discharge back into the pond these results suggest that the hydrologic regimes of some pond peatland complexes in clay rich till within the boreal plains will be more sensitive to local scale disturbances that impact flow dynamics and storage of near shore peatlands rather than larger scale disturbances of mineral upland regions

changes in biomarker abundances and sulfur isotopes of pyrite across the permian triassic p tr schuchert dal section east greenland abstract in this study we report on biomarker abundances through parts of the permian triassic boundary ptb of schuchert dal east greenland that contains rich marine faunal records and excellent terrestrial palynological records biomarker abundances and sulfur isotopes are used to correlate the series of events including changes in element cycling and associated redox conditions of the ocean surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on earth during a mass extinction episode the upper schuchert dal formation contains a low diversity palynological assemblage ascribed to arborescent cordiaite conifer pteridosperm vegetation samples from this pre collapse interval are characterised by high abundances of dibenzofuran dbf dibenzothiophene dbt and biphenyl since these compounds have similar base structures and show comparable abundance curves it is plausible that they probably derive from a common source we propose that phenolic compounds of lignin of the woody plants present during this period could be the source for dbf dbt and biphenyl the redox conditions during this period of time also support the formation of dbf and dbt just above the extinction interval there is a dramatic decrease in the abundances of dbf and dbt which occurs at the same time as a sudden change in the stable sulfur isotopic composition 34s of pyrite indicating a change in redox conditions from oxic to anoxic euxinic conditions 34s values leading up to the extinction are highly depleted in the heavy sulfur isotope about 40 vs vcdt whilst shortly after the extinction interval much more positive isotope values are observed about 25 an inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections it is suggested that two processes are operating closely here 1 changes in redox conditions and 2 extinction and or transgression accounting for the absence of woody material

rapid and synchronous collapse of marine and terrestrial ecosystems during the end permian biotic crisis a newly studied permian triassic p tr boundary section in jameson land east greenland contains an abundant and well preserved marine fauna as well as terrestrial palynomorphs for the first time it is possible to compare the biotic crises of the marine and terrestrial realms using the same samples from the same section the sediments record a negative excursion in 13 c carb values of 8 9 and in 13 c org values of 10 11 the presence of the conodont hindeodus parvus combined with the 13 c carb record enables correlation with the proposed global stratotype section at meishan this shows that the greenland section is the most expanded p tr section known collapse of the marine and terrestrial ecosystems took between 10 and 60 k y it took a further few hundred thousand years for the final disappearance of permian floral elements collapse of the terrestrial and marine ecosystems began at the same stratigraphic level and preceded the sharp negative excursion in the 13 c record

algal and archaeal polyisoprenoids in a recent marine sediment molecular isotopic evidence for anaerobic oxidation of methane 1 analyses of 13c contents of individual organic molecules in a marine sediment show that crocetane 2 6 11 15 tetramethylhexadecane an isomer of phytane is produced by microorganisms that use methane as their main source of carbon the sediments lie at a water depth of 68 m in the kattegat the strait between denmark and sweden crocetane appears first 185 cm below the sediment water interface in the zone marking the transition from sulfate reduction to methanogenesis its 13c value is 90 10 versus vienna pee dee belemnite vpdb its structure which includes four isoprene units arranged symmetrically around a tail to tail linkage suggests that it is produced by a member of the archaea growing at the intersection of the diffusion gradients for sulfate and methane in sedimentary pore waters the source organism apparently functions as a methane consuming member of the microbial consortium responsible for the anaerobic oxidation of methane hoehler et al 1994 in which as first demonstrated quantitatively in these sediments iversen and jorgensen 1985 electrons are transferred from methane to sulfate the presence of archaeal biomass throughout the sediment section is indicated by significant concentrations of 2 6 10 15 19 pentamethylicosane pmi and of ether bound phytane and biphytane the pmi reaches a minimum value of 47 well below the transition zone its isotopic depletion could reflect either methanogenic or methanotrophic sources the ether bound lipids are isotopically uniform throughout the section and are presumed to derive from archaea that utilize a carbon source unaffected by the oxidation of methane

effect of groundwater abstraction on fen ecosystems summary quantifying the effects of groundwater abstraction on fen ecosystems located in discharge areas can be complicated the water level in fens is close to the terrain surface most of the year and it is controlled by a relatively constant groundwater exfiltration it is difficult to measure the exfiltration fluxes and thus water level data is typically used to evaluate if the ecosystem is affected the paper presents collected data and analysis from a case study where the hydrological effect of groundwater abstraction on rich fens and springs in a danish river valley has been studied the natural hydrological conditions have been monitored intensively since march 2007 in the early spring 2009 two full scale pumping test were conducted in the regional high yield limestone aquifer the evaluation focuses on three isolated fens covering an area of approximately 5000 m 2 each and two natural springs all within a distance of 1 5 km to a planned well field in the river valley the interaction between groundwater and surface water is strongly affected by low permeable sediments these sediments reduce the direct discharge to the river and have a large impact on the functioning and presence of the rich fen and spring habitats continuous water level data from deep and shallow wells in the fens reflect the hydrological conditions large differences in water level drawdown during dry summer periods have been observed in the monitored fens and it is hypothesised that these differences are directly related to the groundwater seepage rate two pumping tests with duration of 3 weeks were performed at two different locations and the effects were monitored with 20 pressure transducers in monitoring wells and by continuous flow logging in springs in the area a significant reduction of the flow in the springs has been measured while the on the water level in the fens is difficult to distinguish from the natural variations it is concluded that hydrological modelling is a necessary tool in order to predict the long term effects of pumping in the fen areas the collected data gives valuable knowledge on the hydrology of the monitored ecosystems and the response towards groundwater abstraction and forms a solid foundation for hydrological modelling

results of recent south carolina seismological studies abstract understanding of the south carolina seismic zone and the 1886 charleston earthquake is much improved today as a result of seismological studies which began in 1973 a permanent seismic network was installed in 1974 in south carolina between charleston on the atlantic coast and columbia in the central part of the state temporary field networks of portable instruments were established in the epicentral areas of earthquakes near reservoirs in the northwest part of the state the seismic network data have provided precise hypocenter determinations in previously known zones of continuing activity near middleton place and summerville bowman and in a newly identified source of seismicity near adams run several new composite focal mechanisms were determined and abundant aftershock data were acquired results of recent geophysical and geological studies when combined with the seismological results indicate two seismic regimes in south carolina the first regime covers the buried basement structure of the middle and lower coastal plain province which has been shown by geophysical studies to be quite unlike piedmont province structures to the northwest the middleton place summerville and bowman seismic zones are associated with buried early mesozoic basins and large elongate mafic intrusives inferred from coincident positive aeromagnetic and gravity anomalies the current seismicity is concentrated in clusters rather than distributed along a northwest trending fault zone as suggested earlier by various workers the second regime covers the exposed piedmont province and the upper coastal plain earthquake activity may be associated with strain release on or near mapped faults or contacts between metamorphic belts in particular studies of aftershock and microearthquake activity in the vicinity of reservoirs indicates that in areas of high ambient stress the seismicity appears to be induced by fluctuations in the impounded water and pore pressure at depth

a regional crustal velocity model for the southeastern united states arrival time data from a southeastern united states earthquake are analyzed to formulate an average regional crustal velocity model the event studied is the magnitude 3 7 mb shallow earthquake 2 km depth that occurred on 26 august 1979 near the lake jocassee reservoir in northwestern south carolina over 90 seismograms were collected and read by at least two independent interpreters some 250 phases have been timed including 60 pn 80 pg 50 sn and 70 sg lg arrival times the arrival time data can be interpreted in terms of a single layer crust with average velocities of 6 25 0 04 km sec for compressional waves and 3 65 0 11 km sec for shear waves the average upper mantle velocities are 8 11 0 19 km sec p waves and 4 59 0 13 km sec s waves the mohorovic ic discontinuity is found to lie at varying average depths throughout the region 31 km coastal plain 33 km piedmont 40 km valley and ridge central united states a regional velocity model derived from the above results has the aforementioned average velocities a crustal thickness of 40 km and a set of time corrections for mantle refraction phases coastal plain pn 1 68 sec sn 2 74 sec piedmont pn 1 40 sec sn 2 28 sec valley and ridge and central united states no corrections this new velocity model is tested for precision by relocating several regional earthquakes and comparing the resulting travel time residuals with those from the earlier locations the tests demonstrate that the new model can be used to develop good results

simulating vertical flow in large peatlands ground water flow simulations are used to evaluate the importance of three parameters on vertical flow in peatlands regional slope permeability of the mineral soil underlying the peat and peatland topography our results indicate that the extent of vertical ground water flow in peatlands is primarily controlled by mineral soil permeability local ground water flow cells that form under small water table mounds at bog domes can drive peat pore water into permeable mineral soil however when peat forms over low permeability mineral soil vertical movement of peat pore water becomes negligible and lateral flow of water in the upper portion of the peat column dominates the peatland hydrology this effect is not due to the low permeability of humified peat layers as is commonly assumed in many peatland studies field data from the hudson bay lowland canada and the glacial lake agassiz peatlands of northern minnesota confirm the validity of these models these results are relevant in settings other than peatlands where relief is low and small topographic mounds exist

surface wave propagation in central asia observations of scattering and multipathing with the kyrgyzstan broadband array we studied the propagation of rayleigh waves at regional distances in central asia using a combination of array processing techniques and surface wave analysis we present results from the detailed analysis of three representative events recorded by a 10 station broadband network that has been running in the central asian country of kyrgyzstan since 1991 an ms 5 1 event near ashkhabad turkmenistan an ms 5 8 event in south central tibet and the october 7 1994 nuclear explosion at lop nor we find there is a remarkable difference in the propagation characteristics of surface waves along these three paths the path from the event in turkmenistan is simple and is well approximated by propagation through a laterally homogeneous medium array processing shows the entire rayleigh wave train stacks coherently and arrives from an azimuth close to that predicted by a great circle path furthermore estimates of dispersion curves and fundamental mode signals determined for individual stations show little variation across the array the tibet and lop nor paths are completely different we find strong evidence for complicated multipathing and scattering effects along both of these paths we observe a three stage pattern in the tibet case 1 the early lowest frequency part of the rayleigh wave packet arrives as a coherent signal from close to the great circle path azimuth 2 this is overpowered in the period range around 20 s by a strong multipath signal that propagates across the array from a much more southerly azimuth and 3 periods below 20 s rapidly become incoherent and the signal does not have a well defined direction of propagation the lop nor path shows similar complexity on this path there is little dispersion for measurable periods greater than 10 s so the low frequency energy arrives in an airy phase the airy phase stacks somewhat coherently it stacks but significant power is lost in the best beam and slowness analysis shows it arrives from an azimuth 14 north of the great circle path azimuth like the tibet event the direction of propagation of the shorter periods cannot be resolved these results are consistent with crustal structure in central asia the multipathing and scattering from the tibet and lop nor events are not surprising given these waves propagate across highly variable crust and high topography resulting from the collision of india with eurasia the relative simplicity of the turkmenistan event path reinforces this as almost all of that path traverses the relatively undeformed turan platform of uzbekistan

groundwater surface water interaction between an esker aquifer and a drained fen summary groundwater discharge from an esker aquifer to a fen was studied to understand relevant hydrological processes for groundwater surface water interaction in an esker peatland hillslope piezometric levels of the peat layer and esker sand layer were continuously monitored and compared to climate data groundwater exfiltration points were spatially mapped and related to peat depth the study showed a clear interaction between fen surface water and sand esker groundwater although the hydraulic conductivity of peat was low and the peat depth thick in the artesian aquifer beneath the fen the piezometric head showed a clear response to precipitation and evapotranspiration wetting of the peat is rapidly seen as pressure increase in the confined aquifer this provides new information on hydraulics of wetlands found in aquifer discharge areas groundwater exfiltrated through thick peat layers in vertical preferential point discharges demonstrating how double porosity provides flow through the peat layer with low hydraulic conductivity in the peat matrix the pipe flow channels were found in the deep peat area in the transition zones from deep peat to shallow peat diffuse seepage through the ditch bottom was found where ditches cut into the sand layer increased discharge through the ditch bed reduced the flow resistance at the aquifer boundary which can lower the groundwater level in the esker the results show new processes in the groundwater discharge zone that are useful for groundwater modelling and policy development for future groundwater protection

growth and demise of permian biogenic chert along northwest pangea evidence for end permian collapse of thermohaline circulation abstract the permian chert event pce was a 30 ma long episode of unusual chert accumulation along the northwest margin of pangea and possibly worldwide the onset of the pce occurred at about the sakmarian artinskian boundary in the sverdrup basin canadian arctic where it coincides with a maximum flooding event the ending of high frequency high amplitude shelf cyclicity the onset of massive biogenic chert deposition in deep water distal areas and a long term shift from warm to cool water carbonate sedimentation in shallow water proximal areas a similar and coeval shift is observed from the barents sea to the northwestern usa a landward and southward expansion of silica factories occurred during the middle and late permian at which time warm water carbonate producers disappeared completely from the northwest margin of pangea biotically impoverished and increasingly narrow cold water carbonate factories characterised by non cemented bioclasts of sponges bryozoans echinoderms and brachiopods were then progressively replaced by silica factories by late permian time little carbonate sediments accumulated in the barents sea and in the sverdrup basin where the deep to shallow water sedimentary spectrum was occupied by siliceous sponge spicules by that time biogenic silica sedimentation was common throughout the world silica factories collapsed in the late permian abruptly bringing the pce to an end in northwest pangea the end permian collapse of the pce was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions chert deposition resumed in the distal oceanic areas during the early middle triassic anisian after a 8 10 ma interruption early triassic chert gap the conditions necessary for the onset expansion and zenith of the pce were provided by the thermohaline circulation of nutrient rich cold waters along the northwestern and western margin of pangea and possibly throughout the world oceans these conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area created a nutrient and oxygen rich environment favouring siliceous biogenic productivity established cold sea floor conditions hindering silica dissolution while increasing calcium carbonate solubility and provided conditions adverse to organic and inorganic carbonate production the northwest margin of pangea was for nearly 30 ma bathed by cold waters presumably derived from the seasonal melting of northern sea ice the assumed engine for thermohaline circulation this process started near the sakmarian artinskian boundary intensified throughout middle and late permian time and ceased suddenly in latest permian time it led to oceanic conditions much colder than normally expected from the palaeolatitudes and the influence of cold northerly derived water was felt as far south southern nevada the demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warmer marine environment accompanied by sluggish circulation and perhaps a reduced input of dissolved silica to the ocean complete thawing of northern sea ice would have ended thermohaline circulation and led to warm and sluggish oceanic conditions inimical to the production accumulation and preservation of biogenic silica

changes in palaeoenvironmental conditions during deposition of the permian kupferschiefer lower rhine basin northwest germany inferred from molecular and isotopic compositions of biomarker components abstract biomarker distributions based on gc and gc ms data supplemented by stable carbon isotopic compositions based on irm isotope ratio monitoring gc ms data have been used to investigate changes in depositional conditions in a number of samples from a 2 m core rheinberger heide covering the entire deposition of the permian kupferschiefer lower rhine basin northwest germany compound classes investigated are aliphatic and aromatic hydrocarbons and maleimides 1h pyrrole 2 5 diones the core has been previously divided into four sections ti tiia tiib and tiii based on lithology the biomarker distributions and the 13c values of components indicate contributions from cyanobacteria algae green sulphur bacteria and higher plants minor throughout kupferschiefer deposition all of the phytoplanktonic components show 13c enrichment in the lowest section suggesting a greater productivity the occurrence of components derived from green sulphur bacteria chlorobiaceae indicates that the entire deposition was characterised by periods of photic zone anoxia such conditions were rapidly established after the initial transgression of the zechstein sea and may have been productivity driven but were less prevalent during deposition of the upper core sections

a unique geochemical record at the permian triassic boundary a 330 metre core drilled through the marine permian triassic boundary in the carnic alps of austria allows closely correlated studies of geochemistry petrography and palaeontology across the boundary the isotope shifts and metal concentrations are extended multiple and complex and do not resemble those seen at the cretaceous tertiary boundary both the carbon isotope shifts and the chemical events including an indium anomaly may have causes related to a major regression of the sea

large and rapid climate variability during the messinian salinity crisis evidence from deuterium concentrations of individual biomarkers during the messinian 6 m y ago massive sea level fall and widespread deposition of evaporites occurred in the mediterranean sea when it became isolated from the world oceans here we present the first hydrogen isotope data from individual sedimentary biomarkers n alkanes and isoprenoids that tracked climatically driven hydrographic changes in response to extreme evaporation during the messinian salinity crisis the stable hydrogen and carbon isotope compositions of these biomarkers show a range of 160 in d values and 14 in 13 c values and roughly covary this indicates that the source waters of the biomarkers were therefore in some cases extremely enriched in deuterium having average d as great as 66 vsmow vienna standard mean ocean water such values are only known from desert climates today because the offset between the d values of n alkanes and isoprenoids preserved in the miocene sedimentary rocks is similar to the offset found in modern biological samples we conclude that diagenesis did not significantly affect the primary deuterium concentrations

post fire ecohydrological conditions at peatland margins in different hydrogeological settings of the boreal plain in the boreal plain of canada the margins of peatland ecosystems that regulate solute and nutrient fluxes between peatlands and adjacent mineral uplands are prone to deep peat burning whether post fire carbon accumulation is able to offset large carbon losses associated with the deep burning at peatland margins is unknown for this reason we examined how post fire hydrological conditions i e water table depth and periodicity soil tension and surface moisture content and depth of burn were associated with moss recolonization at the peatland margins of three sites we then interpreted these findings using a hydrogeological systems approach given the importance of groundwater in determining conditions in the soil plant atmosphere continuum in peatlands peatland margins dominated by local groundwater flow from adjacent peatland middles were characterized by dynamic hydrological conditions that when coupled with lowered peatland margin surface elevations due to deep burning produced two common hydrological states 1 flooding during wet periods and 2 rapid water table declines during dry periods these dynamic hydrological states were unfavorable to peatland moss recolonization and bryophytes typical of post fire recovery in mineral uplands became established in contrast at a peatland margin where post fire hydrological conditions were moderated by larger scale groundwater flow flooding and rapid water table declines were infrequent and subsequently greater peatland dwelling moss recolonization was observed we argue that peatland margins poorly connected to larger scale groundwater flow are not only prone to deep burning but also lags in post fire moss recovery consequently an associated reduction in post fire peat accumulation may occur and negatively affect the net carbon sink status and ecohydrological and biogeochemical function of these peatlands

aquifer peatland connectivity in southern quebec canada in areas where peatlands are abundant they are likely to play a significant role in the hydrological and hydrogeological dynamics of a watershed although individual case studies are reported in the literature there is a large range of aquifer peatland interactions and there is a need to understand the controls of these interactions the objectives of this study were 1 to better understand aquifer peatland connections and how these may be predicted by geology and geomorphic location and 2 to provide a variety of reference sites for glacial geological settings slope and depression peatlands were studied in the abitibi temiscamingue region and in the st lawrence lowlands two contrasting regions of southern quebec a total of 12 transects that span a shallow aquifer peatland interface were instrumented with piezometers field investigations included peatland characterization monthly water level monitoring and continuous hydraulic head measurements with pressure transducers the results indicate that 7 of the 12 transects receive groundwater from the surrounding shallow aquifer at the peatland margin four lateral flow patterns were identified and associated with slope peatlands parallel inflow and divergent flow and with depression peatlands convergent flow and parallel outflow vertical hydraulic gradients suggest that water flows mainly downwards i e from the peatland to the underlying mineral deposits vertical connectivity appears to decrease as the distance from the peatland margin increases all of these exchanges are important components in the sustainability of peatland hydrogeological functions the regional comparison of aquifer peatland flow dynamics performed in this study provides a new set of referenced data for the assessment of aquifer peatland connectivity