spatial variability of hydraulic conductivity and bulk density along a blanket peatland hillslope this article presents the results of a field investigation of saturated hydraulic conductivity ksat and bulk density bd in an atlantic blanket bog in the southwest of ireland starting at a peatland stream and moving along an uphill transect toward the peatland interior bd and ksat were examined at regular intervals saturated horizontal hydraulic conductivity khsat and vertical kvsat was estimated at two depths 10 20 and 30 40 cm below the peat surface whereas bd was estimated for the full profile we consider two separate zones one a riparian zone extending 10 m from the stream and a second zone in the bog interior we found that the ksat was higher 10 5 m s 1 in the bog interior than that in the riparian zone 10 6 m s 1 whereas the converse applied to bulk density with lowest density 0 055 g cm 3 at the interior and highest 0 11 g cm 3 at the riparian zone in general we found khsat to be approximately twice the kvsat these results support the idea that the lower ksat at the margins control the hydrology of blanket peatlands it is therefore important that the spatial variation of these two key properties be accommodated in hydrological models if the correct rainfall runoff characteristics are to be correctly modelled stream flow analysis over 3 years at the peatland catchment outlet showed that the stream runoff was composed of 8 base flow and 92 flood flow suggesting that this blanket peatland is a source rather than a sink for floodwaters copyright 2011 john wiley sons ltd

the geochemistry of major and selected trace elements in a forested peat bog kalimantan se asia and its implications for past atmospheric dust deposition abstract biogeochemical processes in a forested tropical peat deposit and its record of past atmospheric dust deposition were assessed using the vertical distribution of lithophilic and plant essential elements in a dated core profile from borneo se asia peat formation started 22 120 14c yr before present bp and ca mg mass ratios of the solid peat and very low ash contents indicate a strongly ombrotrophic character throughout the deposit implying that most of the inorganic fraction has been supplied exclusively by atmospheric inputs concentration profiles of mn sr and ca suggest a very minor influence of chemical diagenesis in the underlying sediments silicon ca mg p s and k show a strong and extended zone of enrichment in the top 200 cm of the profile indicating that biological accumulation mechanisms are much more extensive than in temperate peat bogs in the lower core sections where the element distribution is dominated solely by past atmospheric deposition average al ti ratios are similar to the upper continental crust ucc whereas fe is slightly enriched and si is strongly depleted this condition favors highly weathered tropical soil dust as the main inorganic mineral source significant correlation of al fe si s ca and ti with the lithophilic elements y and zr suggests that the distribution of these elements is controlled by sources of atmospheric mineral dust the ca mg ca k and mg k ratios of the collected rainwater samples are similar to the global average of continental rainwater and suggest a continental character for the site this is supported by the similarity of the average concentration of br mg ca and s to that in temperate continental and maritime bogs in switzerland and scotland the concentration profiles of si fe al and ti show distinct peaks within the profile implying enhanced dust deposition reduced rates of peat accumulation or possibly both owing to climatic changes during the holocene enhanced dust deposition between 10 830 and 9060 14c yr bp is tentatively interpreted as a younger dryas like event with dust fluxes of 10 8 mg m2 yr the variations in al ti and fe ti profiles suggest that mineral dust sources have been changing constantly during the holocene with local sources being dominant between 7820 and 9500 14c yr bp and long range transport derived most likely from china being important during the late pleistocene and early holocene and from 7820 14c yr bp to the present

investigating peatland stratigraphy and hydrogeology using integrated electrical geophysics hydrology has been suggested as the mechanism controlling vegetation and related surficial pore water chemistry in large peatlands peatland hydrology influences the carbon dynamics within these large carbon reservoirs and will influence their response to global warming a geophysical survey was completed in caribou bog a large peatland in maine to evaluate peatland stratigraphy and hydrology geophysical measurements were integrated with direct measurements of peat stratigraphy from probing fluid chemistry and vegetation patterns in the peatland consistent with previous field studies ground penetrating radar gpr was an excellent method for delineating peatland stratigraphy prominent reflectors from the peat lake sediment and lake sediment mineral soil contacts were precisely recorded up to 8 m deep two dimensional resistivity and induced polarization imaging were used to investigate stratigraphy beneath the mineral soil beyond the range of gpr we observe that the peat is chargeable and that ip imaging is an alternative method for defining peat thickness the chargeability of peat is attributed to the high surface charge density on partially decomposed organic matter the electrical conductivity imaging resolved glaciomarine sediment thickness a confining layer and its variability across the basin comparison of the bulk conductivity images with peatland vegetation revealed a correlation between confining layer thickness and dominant vegetation type suggesting that stratigraphy exerts a control on hydrogeology and vegetation distribution within this peatland terrain conductivity measured with a geonics em31 meter correlated with confining glaciomarine sediment thickness and was an effective method for estimating variability in glaciomarine sediment thickness over approximately 18 km 2 our understanding of the hydrogeology stratigraphy and controls on vegetation growth in this peatland was much enhanced from the geophysical study

controls of extreme isotopic enrichment in modern microbialites and associated abiogenic carbonates abstract microbialites and abiogenic carbonates of the closed basin hypersaline lake laguna negra catamarca province argentina are highly enriched in both 13c and 18o these carbonates precipitate in the zone of recharge where lake water mixes with groundwater we examined the processes controlling the isotopic evolution of input waters in order to better interpret the isotopic compositions of the carbonates large enrichments of 13c in dissolved inorganic carbon and 18o in water occur as input groundwater chemically evolves these enrichments can be explained through the abiotic processes of water equilibration evaporation degassing and carbonate precipitation the 13c and 18o contents of lake carbonates are consistent with equilibrium precipitation from lake water indicating that the currently ongoing processes can explain the isotopic patterns observed in carbonates isotopic compositions of these microbialites are largely unrelated to the biological processes controlling microbialite formation a pattern that may be generalizable to other settings however the isotopic compositions of these microbialites record information about their depositional environment

facies dependent δ13c variation and diagenetic overprinting at the onset of the sturtian glaciation in north east greenland abstract time significant surfaces are used to construct a stratigraphic test of the intrabasinal reproducibility of a 16 neoproterozoic carbon isotope 13c anomaly in the ne greenland caledonides the 13c excursion from 6 to 10 occurs in the carbonate dominated andree land group and lies below glacial diamictites of the tillite group commonly correlated as sturtian in age 720 ma and has been widely interpreted to record a global isotopic event reflecting a perturbation in the carbon cycle preceding the initiation of the snowball ice age 13c stratigraphic patterns were determined in two strike sections with relatively shallow platform deposits at kap weber and slope deposits on ella o preserved directly below the first evidence for glaciation the top and bottom of the 13c profile was bounded by contiguous chronostratigraphic surfaces including an unconformity sequence boundary at the base recognisable in both sections and a subaerial exposure surface with a basinal correlative conformity at the top the 13c profile at kap weber shows 13c values of 6 that drop to 8 in fine grained slope deposits before returning to 6 in platform carbonates at the base of the glacial diamictite the slope section on ella o shows similar values for platformal carbonates of 6 with a similar drop to 10 in slope deposits but this section lacks the return to platform deposits evident at kap weber beneath the diamictite as well as a return to positive 13c values the absence of the platformal sediments and positive 13c values on ella o cannot be attributed to erosional truncation because the contact in this section shows a conformable interbedded transition into the glacial deposits indicating that a continuous record is preserved this disparity in 13c values below the base of the tillite group suggests that the most negative 13c values recorded in slope mudstone facies 10 occur near synchronously with values of 6 on the platform elemental mapping of the mudstone facies indicates that carbonate is largely pore filling and authigenic representing a secondary phase that is unlikely to record a seawater value elevated 13c values in shallow inner ramp carbonate intervals may record locally modified seawater enriched in 13c by photosynthesis and evaporation the excursion in 13c values in the upper andree land group is therefore interpreted to result from a shift in facies from platform carbonates to carbonate cemented and diagenetically overprinted mudstone and does not record the secular change in seawater 13c used for correlation or interpretation of biogeochemical events preceding the snowball ice age

hydrological modeling in swelling shrinking peat soils 1 peatlands respond to natural hydrologic cycles of precipitation and evapotranspiration with reversible deformations due to variations of water content in both the unsaturated and saturated zone this phenomenon results in short term vertical displacements of the soil surface that superimpose to the irreversible long term subsidence naturally occurring in drained cropped peatlands because of bio oxidation of the organic matter these processes cause changes in the peat structure in particular soil density and void ratio the consequential changes in the hydrological parameters need to be incorporated in water flow dynamical models in this paper we present a new constitutive relationship for the soil shrinkage characteristic ssc in peats by describing the variation of porosity with moisture content this model based on simple physical considerations is valid for both anisotropic and isotropic three dimensional peat deformations the capability of the proposed ssc to accurately describe the deformation dynamics has been assessed by comparison against a set of laboratory experimental results recently published the constitutive relationship has been implemented into a richards equation based numerical code and applied for the simulation of the peat soil dynamics as observed in a peatland south of the venice lagoon italy in an ad hoc field experiment where the relevant parameters are continuously measured the modeling results match well a large set of field data encompassing a period of more than 50 days and demonstrate that the proposed approach allows for a reliable reproduction of the soil vertical displacement dynamics as well as the hydrological behavior in terms of for example water flow moisture content and suction

hydrological management of a cutover peatland mechanisms for preserving the hydrological balance of thorne moors national nature reserve nnr while allowing peat extraction to continue in the surrounding peatland are examined three strategies exist for modifying seepage losses from the nnr i re direction of pump drainage waters from the peat extraction areas ii provision of a hydrological buffer zone around the nnr and iii mechanical compaction of the boundaries of the buffer zone strategy ii increased width of the buffer zone should be used together with strategy iii compaction for the maximum reduction of seepage losses from the nnr if strategy i water level manipulation is also adopted it may be possible to reduce the width of the hydrological buffer zone around the nnr

flow path oscillations in transient ground water simulations of large peatland systems abstract transient numerical simulations of the glacial lake agassiz peatland near the red lakes in northern minnesota were constructed to evaluate observed reversals in vertical ground water flow seasonal weather changes were introduced to a ground water flow model by varying evapotranspiration and recharge over time vertical hydraulic reversals driven by changes in recharge and evapotranspiration were produced in the simulated peat layer these simulations indicate that the high specific storage associated with the peat is an important control on hydraulic reversals seasonally driven vertical flow is on the order of centimeters in the deep peat suggesting that seasonal vertical advective fluxes are not significant and that ground water flow into the deep peat likely occurs on decadal or longer time scales particles tracked within the ground water flow model oscillate over time suggesting that seasonal flow reversals will enhance vertical mixing in the peat column the amplitude of flow path oscillations increased with increasing peat storativity with amplitudes of about 5 cm occurring when peat specific storativity was set to about 0 05 m 1

pool patterning in a northern peatland geophysical evidence for the role of postglacial landforms a hydrogeophysical study conducted in a 2200 ha peatland in central maine shows evidence that a laterally continuous esker deposit extends below the peat soil following the direction of glacier retreat and coinciding with the presence of a pool system ground penetrating radar gpr electrical resistivity er imaging and terrain conductivity measurements were constrained with limited hydrological measurements direct sampling of inorganic sediments and radiocarbon dating of peat soils to develop a conceptual model for pool formation that could explain the unique pool patterning observed in other northern peatlands gpr profiles revealed three dimensional images of two esker crests below the easternmost edge of the pool area gpr data was supported by er imaging and terrain conductivity data and allowed for facies differentiation to infer processes related to esker formation during the glacier front retreat hydrologic data showed preferential flow of groundwater towards the esker suggesting that pools may persist as a result of enhanced peat decomposition and carbon loss due to oxygenation and or upward supply of alternative electron acceptors from the mineral soil along narrow permeable inorganic esker crests variations in pool depths and radiocarbon dating of peat samples from the pool bottom support a model whereby pools originate at a focus centered along the two esker crests and subsequently spread laterally outwards

simulating holocene carbon accumulation in a western siberian watershed mire using a three dimensional dynamic modeling approach 1 the vast undisturbed mires in western siberia formed a significant sink of atmospheric carbon dioxide during the holocene however the lack of spatially resolved simulation models hampers the quantification of holocene carbon accumulation of the entire mire systems here we developed a three dimensional dynamic model based on a hydrological approach we applied the model to a large mire complex in western siberia to simulate its holocene development and to quantify the long term carbon accumulation rate lorca our model simulated a lorca with a spatial variation of 10 85 g c m 2 yr 1 the average over the holocene was 16 2 g c m 2 yr 1 simulation scenarios for the 21st century show that the average lorca dropped to 5 2 g c m 2 yr 1 because of oxidation and decomposition of peat following mire drainage after the 1950s even in the undrained parts of the mire complex the lorca is lowered substantially because of the dropped water table and resulting decrease in peat growth our results show that carbon accumulation in western siberian watershed mires will continue in the future thus these mires might remain a significant sink of carbon

linear amplitude patterns in corpus christi bay frio subbasin south texas interpretive pitfalls or depositional features linear amplitude patterns on stratal slices in the corpus christi bay area of texas are important seismic geomorphological features that reflect sediment dispersal patterns these amplitude patterns are oriented in both strike and dip directions some of the linear amplitude patterns are related to faults however most are related to orientation of sandstone bodies faulting may make the depositionally related linear amplitude patterns more fragmented but faults do not destroy the overall orientation or geomorphologic significance of these patterns amplitude patterns on stratal slices should be interpreted as unbiased general sediment dispersal patterns unless the patterns can be tied directly to a structural feature in depth understanding of structural and depositionally related amplitude patterns leads to more accurate stratal slicing interpretation in facies reservoir prediction using poststack 3d seismic data

effect of mine dewatering on the peatlands of the james bay lowland the role of marine sediments on mitigating peatland drainage the wetlands of the james bay lowland comprise one of largest wetland complexes in the world in part due to the properties thickness and hydraulic conductivity of the marine sediment ms that underlay them dewatering of an open pit diamond mine is depressurizing the surrounding silurian bedrock below the ms prior to mining it was assumed that these ms would largely isolate the overlying peatlands from the depressurized regional bedrock aquifer to assess this isolation we instrumented a 1 5 km long transect of wells and piezometers located within the zone of the mine s influence that crossed a sequence of bogs fens and bedrock outcrops bioherms results were differentiated between those areas with no ms near bioherms and those underlain by ms non bioherm along the transect between 2007 and 2010 at near bioherm and non bioherm locations average peat water tables declined 71 and 31 cm and hydraulic head declined 66 and 32 cm in bioherm and non bioherm locations respectively gradients varied from near zero 0 001 at the start of dewatering to 0 03 after 5 years in non bioherm areas and from 0 20 to 0 45 in near bioherm areas these gradients corresponded to fluxes groundwater recharge of approximately 0 26 mm day and 2 1 mm day in non and near bioherm areas respectively specific discharge recharge determined using the known mine dewatering rate and drawdown cone heads and areas corresponded well with measured recharge determined in the non bioherm transect locations a simple rearrangement of darcy s law used to calculate the specific discharge highlighted how the ratio of hydraulic conductivity to the thickness of the ms can be used to assess vulnerable areas therefore given the increasing development in ontario s far north considerable attention must be given to both the thickness and hydraulic conductivity of ms copyright 2013 john wiley sons ltd

a major perturbation of the carbon cycle before the ghaub glaciation neoproterozoic in namibia prelude to snowball earth 1 a large 11 15 negative shift in 13c is observed in shallow water carbonates directly beneath neoproterozoic glacial deposits or correlative disconformity in northwest namibia ascribed to a snowball earth reproducibility and stratigraphic concordance of this anomaly in 16 sections across the ancient continental shelf support a primary origin and field relations show it predates the fall in sea level associated with the ghaub glaciation we crudely estimate the duration of the isotopic shift as 0 6 106 years from a simple thermal subsidence model similar or larger 13c anomalies are found directly beneath neoproterozoic glacial units in australia canada china scotland and svalbard after considering conventional interpretations for negative 13c anomalies we conclude that a prolonged methane release to the atmosphere is most consistent with the timescale magnitude and geological context of the anomaly in namibia counterintuitively an anomalous methane flux that is sustained for 100s kyr may be consistent with a snowball glaciation

controls of soil pipe frequency in upland blanket peat 1 soil pipes were surveyed in 160 british blanket peat catchments using consistent application of ground penetrating radar soil pipes were found in all catchments the mean frequency of piping was 69 per kilometer of surveyed transect land management moorland gripping appears to exert the most important control on hillslope pipe frequency in blanket peats management practice in peatlands may therefore induce more rapid subsurface erosion carbon loss and landform denudation via enhanced preferential flow topographic position is also important with topslopes having greater pipe frequencies than footslopes followed by midslopes with lowest frequencies slope gradient however is not a significant factor in controlling blanket peat pipe frequency i propose that peat structural properties inherited from the way a blanket peat develops on a hillslope strongly control pipe network development this is manifested in the way slope position appears to control pipe frequency aspect appears not to influence pipe frequency in blanket peats except that it does play a weak role in catchments with annual precipitation 1500 mm here southwesterly facing slopes tend to have more frequent piping

a hydrologic assessment of a saline spring fen in the athabasca oil sands region alberta canada a potential analogue for oil sands reclamation canada s post mined oil sands will have a higher concentration of salts compared with freshwater peatlands that dominate the landscape while rare naturally occurring saline wetlands do exist in alberta s boreal plains and may function as analogues for reclamation however little is known about their hydrology this paper investigates the geochemical and hydrologic characteristics of a natural saline spring peatland in alberta s oil sands region the fen is located within a saline groundwater discharge area connected to the erosional edge of the grand rapids formation na 195 25 680 mgl 1 and cl 1785 56 249 mg l 1 were the dominant salts and the fen transitioned sharply to freshwater along its margins because in part of subsurface mineral ridges that restricted shallow groundwater exchange salinity decreased from hypersaline to brackish along the local groundwater flow path but no active spring outlets were observed over the two year study vertical groundwater discharge was minimal because of the very low permeability of the underlying sediments subsurface storage was exceeded during periods of high flow resulting in flooding and surface runoff that was enhanced by the ephemerally connected pond network these findings have implications for reclamation as mechanisms such as subsurface mineral ridges may function as effective saline groundwater control structures in the post mined environment incorporating saline wetlands into regional monitoring networks will help to better quantify natural discharge which has implications for belowground wastewater storage related to in situ bitumen extraction copyright 2015 john wiley sons ltd

metal binding to dissolved organic matter and adsorption to ferrihydrite in shallow peat groundwaters application to diamond exploration in the james bay lowlands canada the speciation and solubility of kimberlite pathfinder metals ni nd ba and k in shallow peat groundwaters is investigated over the yankee zulu and golf kimberlites in the attawapiskat region james bay lowlands canada the purpose of this study is to examine the relationship between dissolved organic matter dom complexation with kimberlite pathfinder metals and determine the spatial distribution of those metals in shallow peat groundwaters along sampling transects over subcropping kimberlites nickel nd ba and k complexation with dom and the adsorption of these metals onto ferrihydrite were calculated using visual minteq 3 0 and the nica donnan database calculations predict almost 100 of soluble nd ni and ba form complexes with dom at sampling sites with little to no contribution from upwelling groundwater i e dissolved organic c doc concentrations 40 132 mg l ph 3 9 5 5 and log ionic strength 6 3 in only the most ombrotrophic peat groundwater conditions does a majority fraction of k bind to dom by contrast under conditions with large contributions from upwelling groundwaters i e doc concentrations 640 mg l ph 5 5 6 5 and log ionic strength 3t o 2 as little as 10 of nd and ni and 0 k and ba are predicted to complex with dom the modeling calculations suggest the dominant control on metal dom complexation particularly with respect to ni and nd is competitive effects for dom binding sites due to elevated ionic strength where there is evidence of strong groundwater upwelling visual minteq modeling of metal adsorption on ferrihydrite surfaces predicts that under strong upwelling conditions ni and nd are scavenged from solution due to increased ferrihydrite precipitation and decreased fractions of metals complexed with dom analytical geochemical data are consistent with model predictions of metal adsorption on ferrihydrite total dissolved ni and nd concentrations at sites of strong upwelling are up to five times lower than waters with little to no upwelling and log ferrihydrite saturation indices logsi ferr indicate precipitation values up to 5 at sites of strong groundwater upwelling where the majority of ni and nd complex with dom and ferrihydrite is highly under saturated logsiferr 18 to 5 the concentrations of total ni and nd are elevated compared to other sites along sampling transects metal complexation with dom effectively inhibits metal scavenging from solution via adsorption and or from forming secondary mineral precipitates also because alkaline earth metals do not compete strongly with ni and nd for adsorption sites on ferrihydrite surfaces but do compete strongly for insoluble organic sites ni and nd are more likely to adsorb onto ferrihydrite

characteristics distribution and morphogenesis of subtidal microbial systems in shark bay australia abstract the distribution nature and extent of microbial deposits in hamelin pool shark bay have been investigated and mapped with emphasis on the occurrence external morphologies internal fabrics constructional mechanisms microbial communities growth rates and sediment associations in the intertidal and previously little researched subtidal zone detailed georeferenced substrate mapping revealed extensive subtidal microbial deposits occupying approximately 300 km 2 of the total holocene 1400 km 2 area of hamelin pool the microbial pavement covers 227 km 2 of the subtidal substrate that together with columnar structures reveals a subtidal microbial habitat which occupies an area 10 times larger than the area of the intertidal deposits microbial carbonate is composed of aragonite 80 98 that reveals high positive values of 13 c 4 46 to 5 88 and 18 o 3 06 to 3 88 as a characteristic of the highly evaporative environment with extensive microbial activity oldest dated heads are 1915 and 1680 14 c years bp and the overall system was deposited in two stages the first between 2000 and 1200 and the last from 900 years bp to the present slow growth rates vary from less than 0 1 mm year to 0 5 mm year different internal fabrics were constructed according to their position in relation to the littoral zone by distinct microbial communities and lateral fabric relations have been established evidence of shallowing upward fabric sequences of microbial origin reflects relative falling sea levels during the late holocene and is likely useful in ancient environmental interpretation a sequence of events and mechanisms are described emphasizing differences between the stromatolitic thrombolitic and cryptomicrobial deposits in shark bay the new substrate map and depositional history for this distinctive and peculiar microbial habitat establish the significance of subtidal structures and emphasize the geoscientific importance of hamelin pool especially with respect to early life studies and ancient analogues for understanding microbial activity deposit characteristics fenestral fabrics and distribution

measuring physical and hydraulic properties of peat from x ray tomography abstract organic soils cover a large percentage of the canadian land mass in the form of peatlands 14 and other organic terrains including arctic and alpine tundra and taiga 25 sphagnum mosses are the dominant peat forming species in all of these terrains understanding the processes by which this material conducts retains and redistributes moisture and energy is crucial to the successful development of physically based methods of measuring and modelling their hydrological response sphagnum peat was sampled from scotty creek in the wetland dominated zone of discontinuous permafrost near fort simpson northwest territories canada physical properties of the peat samples were measured from standard methods and x ray tomographic images of sub samples were obtained at 5 levels of volumetric moisture content between 0 4 and 0 7 the volumetric moisture content measured using the tomographic images closely approximated the gravimetric measurements properties of the pore spaces were measured in both two and three dimensions the active porosities measured in 2d and 3d were very similar and matched closely with values reported in the literature specific surface area 3d however was larger than the specific perimeter 2d the 2d analysis suggests a relatively gradual transition from small to large pores while in 3d the distribution is dominated by a single large pore space whose volume and surface area are 3 orders of magnitude larger than the next largest pore and 99 of the total inter particle pore volume this single large pore space contains the flow network this study elucidated the volume and configuration of this network for discrete ranges of soil water pressure that typically occur in the field the flow network diminished from 17 6 to 9 0 of a sample volume as its volumetric moisture content lowered from 0 65 to 0 42 this volume loss was accommodated by the thinning and disaggregation of moisture films although as the sample lost moisture the flow network maintained a relatively even spatial distribution

chemical dilation and the dual porosity of humified bog peat abstract hydrochloric acid and calcium and sodium chloride salt solutions were passed through humified bog peat cores of 1 m length to determine values for the material properties governing solute transport hydraulic conductivity effective porosity and dispersivity chloride passed through the bulk peat cores about twice as fast as predicted from chloride breakthrough curves measured by selective ion probes inserted into the peat 30 cm downgradient from the source with continued experimentation chloride dispersion increased chloride also passed through the peat up to 12 times slower than predicted by conservative advection the retardation of the chloride fronts the faster bulk transport and the asymmetry of the breakthrough curves all indicate that humified bog peat is a dual porosity medium solutes both move preferentially through active macropore spaces and diffuse into dead pore space in the peat matrix neither the effective porosity nor the dispersivity of the peat could be precisely determined from the breakthrough curves because the hydraulic conductivity and discharge rates through the peat increased as much as five times when the chloride tracer solutions passed through the cores in initial experiments the shapes of the breakthrough curves were generally consistent with dispersivities of the order of centimeters similar to that observed for granular soils at the same length scale meters whereas they flattened considerably during later experiments suggesting dispersivities in the range of tens of centimeters we hypothesize that the interaction of the chloride tracer solutions with organic acid functional groups may cause macropores to dilate and micropores to close off

methane derived authigenic carbonate from the lower doushantuo formation of south china implications for seawater sulfate concentration and global carbon cycle in the early ediacaran ocean authigenic carbonate associated with anaerobic oxidation of methane aom usually via microbial sulfate reduction msr or ferric iron reduction is generally characterized by extremely low 13c values 30 vpdb this has been used as one of the major diagnostic features for the recognition of hydrocarbon seep carbonate in the geological past previous reports on precambrian authigenic carbonates are rare limiting our understanding of the effects of their deposition on the earth s carbon isotopic mass balance in this study mainly based on petrographic features and pronounced negative 13c values as low as 38 1 we discovered authigenic calcite cement immediately above the cap dolostone in the basal ediacaran doushantuo formation in the jiulongwan section yangtze gorges area south china our observations not only provide direct evidence for the involvement of aom during carbonate precipitation in the early ediacaran 635 ma but also suggest that the seawater sulfate concentrations in the early ediacaran may have been higher than previously thought

subsidence and degradation of agricultural peatlands in the fenlands of norfolk uk historical drainage of peatlands across the east anglian fenlands has led to subsidence and degradation of the vast majority of the regional peat resource to the extent that many areas can no longer be classified as peatland water table management strategies have been introduced to reduce the rate at which these peatlands subside and physically and biochemically degrade we assessed the rate of subsidence and extent of peat soil degradation across an intensively farmed peatland where such water management measures have been introduced when compared against historical reports of subsidence across the east anglian fenlands the rate of subsidence does appear to have reduced over the last two decades the rate of subsidence does however vary spatially and is dependent on the geographical distribution of peat types and underlying mineral deposits the rate of subsidence and peat degradation has been greater in soil profiles which had a higher proportion of semi fibrous and fibrous peats in 1982 3 compared against those with a higher proportion of humified peat in 1982 3 over the last 22 years the proportion of more fibrous peat in all peat deposits has decreased to the extent that areas once classified as fibrous peat are now dominated by humified peat this suggests that future subsidence will be less influenced by shrinkage and controlled by biochemical processes where fen clay underlies a peat deposit it acts as an impermeable boundary thus keeping the overlying peat more saturated and reducing the degree of peat consolidation however the presence of fen clay also increases the degree of biochemical degradation of overlying fibrous peat horizons indeed where drains have been laid within such mineral strata there is an increase in soil acidity during autumnal drainage operations the environment is therefore optimised for sulfate reducing bacteria resulting in acid sulfate soils with increased rates of degradation

measurement of anisotropic hydraulic conductivity in unconsolidated sands a case study from a shoreface deposit oyster virginia in this study an integrated field and laboratory method which can be used to evaluate the magnitude and distribution of anisotropic hydraulic conductivity at the scale of bedding structures in unconsolidated sediment is demonstrated undisturbed sediment cores 10 16 cm in diameter and 18 25 cm long are obtained using a split barrel core sampler two undisturbed 5 72 cm diameter 7 90 cm long subcores oriented parallel and perpendicular to the primary bedding structures are then obtained from each field core the hydraulic conductivities of the subcores are then measured with a constant head permeameter the sampling and experimental procedures are designed to minimize potential sources of error sixty four 10 16 cm cores were sampled in a coastal sand outcrop located 300 m from a subsurface injection experiment near oyster virginia four distinct lithologies were sampled in horizontal transects with a spacing of 0 5 m between core locations in addition iron oxide bands which were prevalent throughout the exposure were sampled from both ends of the outcrop the average hydraulic conductivity values are consistent with the observable geologic features grain size sorting and iron oxide banding hydraulic conductivity is greater in the parallel oriented subcore for 90 of the core pairs and mean hydraulic conductivity ratios of parallel to perpendicular oriented subcores k k for the different lithologies ranged from 1 33 to 1 57 the major control on the anisotropy in this sediment is interpreted to be preferential grain orientations resulting from depositional processes with additional influences from the prominence of the bedding structures and secondary features such as hydrous iron oxide banding

descent into the cryogenian abstract the cryogenian period brackets an interval of profound glaciation commonly referred to by the evocative epithet snowball earth according to its recent redefinition the cryogenian began before the onset of low latitude glaciation ca 717 ma and ended during its final and catastrophic melting phase ca 635 5 ma pending future ratification of a global stratotype section and point or gssp the onset of the cryogenian period is estimated at about 720 ma however no consensus has yet been reached concerning the best section or criteria for its definition the articles in this special issue represent the state of the art in tonian cryogenian transition stratigraphy around the world and will contribute to the selection of the future gssp

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

hydraulic reversals and episodic methane emissions during drought cycles in mires reversals in hydraulic head and extensive methane losses were identified during a drought cycle from changes in hydraulic head and dissolved methane profiles in peat glacial lake agassiz peatlands northern minnesota united states during the summer 1990 drought regional groundwater discharged from the mineral soil underlying the peat to raised bogs concentrations of dissolved ch sub 4 in pore water showed that much of the peat column was supersaturated with respect to a reference standard of 1 atm partial pressure ch sub 4 by the summer of 1991 the severity of the drought lessened and the upper peat column was resaturated with precipitation derived water groundwater flow was then controlled by local precipitation driven recharge flow systems and the regional groundwater that was discharged affected only the peat immediately above the mineral soil peat interface in contrast during the summer of 1991 concentrations of dissolved ch sub 4 in pore water were all undersaturated with respect to 1 atm partial pressure ch sub 4 23 refs 5 figs

effect of mine dewatering on peatlands of the james bay lowland the role of bioherms the james bay lowland host one of the largest wetland complexes in the world in part due to the low permeability of marine sediments that suppress groundwater seepage losses dewatering of an open pit diamond mine in the area has depressurized the regional bedrock aquifer bioherms fractured limestone outcroppings formed from ancient coral reefs that protrude to the peatland surface lack this mantle of low permeability sediments and provide a direct connection between the peatland surficial and the regional bedrock aquifers well transects and piezometer nests were installed around seven bioherms in the depressurized zone and one in a non affected zone control to monitor the water table drawdown and change in hydraulic gradients around the bioherms water tables in the affected bioherms decreased between 2 and 4 m in the first 4 years of dewatering the drawdown in the bioherms caused a localized water table drawdown in the peat surrounding the bioherms that extended to approximately 30 m from the edge of the bioherm during a dry period under wet conditions drawdown was similar to that at the control site hydraulic gradients in the peat which typically are very small increased over the field seasons and in a few locations exceeded 1 these gradients represented significant losses to the local near bioherm system as at many of the locations surrounding the bioherms vertical seepage losses ranged between 1 and 4 mm day which are similar to the seasonal average evaporative water loss of 3 mm day the bioherms are acting as efficient drainage nodes however their influence is localized to the peat immediately 30 m surrounding them copyright 2012 john wiley sons ltd

disseminated jigsaw piece dolomite in upper jurassic shelf sandstones central north sea an example of cement growth during bioturbation unusual textural and chemical characteristics of disseminated dolomite in upper jurassic shelf sediments of the north sea have provided the basis for a proposed new interpretation of early diagenetic dolomite authigenesis in highly bioturbated marine sandstones the dolomite is present throughout the franklin sandstone formation of the franklin and elgin fields as discrete non ferroan generally unzoned subhedral to highly anhedral jigsaw piece crystals these are of a similar size to the detrital silicate grains and typically account for 5 of the rock volume the dolomite crystals are never seen to form polycrystalline aggregates or concretions or ever to envelop the adjacent silicate grains they are uniformly dispersed throughout the sandstones irrespective of detrital grain size or clay content dolomite authigenesis predated all the other significant diagenetic events visible in thin section the dolomite is overgrown by late diagenetic ankerite and bulk samples display stable isotope compositions that lie on a mixing trend between these components extrapolation of this trend suggests that the dolomite has near marine delta18o values and low positive delta13c values the unusual textural and chemical characteristics of this dolomite can all be reconciled if it formed in the near surface zone of active bioturbation sea water provided a plentiful reservoir of mg and a pore fluid of regionally consistent delta18o labile bioclastic debris e g aragonite mg calcite supplied isotopically positive carbon to the pore fluids during shallow burial dissolution such dissolution took place in response to the ambient calcite sea conditions but may have been catalysed by organic matter oxidation reactions bioturbation not only ensured that the dissolving carbonate was dispersed throughout the sandstones but also prohibited coalescence of the dolomite crystals and consequent cementation of the grain framework continued exchange of mg2 and ca2 with the sea water reservoir maintained a sufficient mg ca ratio for dolomite rather than calcite to form irregular crystal shapes resulted from dissolution of both the dolomite and the enclosed fine calcitic shell debris before ankerite precipitation during deep burial diagenesis

field methods for measuring hydraulic properties of peat deposits new field techniques were developed and tested to evaluate peat storativity and hydraulic conductivity in a boreal fen enclosed drainage tests and pumping tests were successfully completed in the thawed peat above an impermeable frozen layer and then repeated when the peat was fully thawed a loading test experiment constrained values of vertical hydraulic conductivity within an order of magnitude for the peat below a depth of 2 m an inherent advantage of these tests is that volumes of undisturbed peat on the scale of cubic metres may be characterized storativity of the fen peat as determined by enclosed drainage tests ranged from about 1 0 at the peat surface to 0 35 at a water table depth of 0 15 m laboratory drainage tests of peat cores gave similar but widely scattered results hydraulic conductivity near the surface was as high as 9 0 x 10 3 ms 1 determined with pumping tests and in the range of 10 6 to 10 5 ms 1 below a depth of 2 m estimated with the loading test slug tests gave similar results pumping tests enclosed storativity tests and loading tests are practical large scale field tests for determining peat properties

laboratory testing and in situ behaviour of peat as embankment foundation reply intact block samples of fibrous peat have been obtained using special equipment from two different sites in the james bay territory in quebec instrumented test fills were subsequently built at those two sites and the observed behaviour was used to check the laboratory data the laboratory testing program has included standard 24 h incremental tests and stage creep tests where constant loads were applied for periods of about 30 d pore pressure and direct permeability measurements were conducted in most of the tests the tests have been interpreted using the classical e log p curves or the tangent modulus approach the evaluation of compression with time under a constant load has allowed the distinction between primary and secondary consolidation a certain lag in pore pressure response has been observed and related to incomplete saturation the coefficient of permeability decreases rapidly with compression as indicated by direct measurements and pore pressure dissipation the comparison with field observ

structure of peat soils and implications for water storage flow and solute transport a review update for geochemists abstract global peatlands are a valuable but vulnerable resource they represent a significant carbon and energy reservoir and play major roles in water and biogeochemical cycles peat soils are highly complex porous media with distinct characteristic physical and hydraulic properties pore sizes in undecomposed peat can exceed 5 mm but significant shrinkage occurs during dewatering compression and decomposition reducing pore sizes the structure of peat soil consists of pores that are open and connected dead ended or isolated the resulting dual porosity nature of peat soils affects water flow and solute migration which influence reactive transport processes and biogeochemical functions advective movement of aqueous and colloidal species is restricted to the hydrologically active or mobile fraction of the total porosity i e the open and connected pores peat may attenuate solute migration through molecular diffusion into the closed and dead end pores and for reactive species also through sorption and degradation reactions slow diffusion limited solute exchanges between the mobile and immobile regions may give rise to pore scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils while new information on the diversity and functionalities of peat microbial communities is rapidly accumulating the significance of the geochemical and geomicrobial study on peat stands to benefit from a basic understanding of the physical structure of peat soils in this paper we review the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and briefly discuss their implications for water storage flow and the migration of solutes this paper is intended to narrow the gap between the ecohydrological and biogeochemical research communities working on peat soils

modelling two dimensional steady state groundwater flow and flow sensitivity to boundary conditions in blanket peat complexes this study used a two dimensional steady state finite element groundwater flow model to simulate groundwater flow in two newfoundland blanket peat complexes and to examine flow system sensitivity to changes in water table recharge and aquifer properties the modelling results were examined within the context of peat forming processes in the two complexes modelled flow compared favourably with observed flow the sensitivity analyses suggested that more highly decomposed bog peat along bog margins probably has had a positive impact on net peat accumulation within bog interiors peat with lower hydraulic conductivity along bog margins effectively impedes lateral drainage localizes water table drawdown to extreme bog margins and elevates water tables along bog interiors peat formation and elevated water tables in adjacent poor fens laggs currently rely on placic and ortstein horizons impeding vertical drainage and water flow inputs from adjacent bogs modest reductions in atmospheric recharge were found to govern bog flow system geometries in a way that would adversely affect paludification processes in adjacent fens laggs copyright 2004 john wiley sons ltd

carbon isotope variability across the ediacaran yangtze platform in south china implications for a large surface to deep ocean δ13c gradient new isotope data obtained from relatively conformable carbonate rich strata of the ediacaran yangtze platform in south china reveal substantial 13 c variability in platform sections four negative 13 c anomalies with a nadir down to 8 pdb are present in the interval between the cap carbonate level 635 ma and the precambrian cambrian boundary 542 ma while in slope and basinal sections 13 c values are negative through the entire doushantuo formation 635 551 ma if these 13 c values are close to their primary seawater signature they imply a strong 10 surface to deep ocean 13 c gradient that is consistent with long term deep ocean anoxia and the presence of a large dissolved organic carbon doc reservoir the two prominent negative 13 c excursions within the doushantuo formation above the cap carbonate level are associated with shoaling and local exposure of the platform the anomalies may thus record remineralization of a large oceanic doc pool via sulfate reduction that transferred 13 c depleted carbon from the oceanic doc reservoir to the surface ocean during regression inconsistencies in ediacaran 13 c profiles globally and variations in south china in particular highlight the need for further evaluation of local departures in 13 c from an inferred average seawater signature

anisotropy and depth related heterogeneity of hydraulic conductivity in a bog peat ii modelling the effects on groundwater flow anisotropy and heterogeneity of hydraulic conductivity k are seldom considered in models of mire hydrology we investigated the effect of anisotropy and heterogeneity on groundwater flow in bog peat using a steady state groundwater model in five model simulations four sets of k data were used the first set comprised measured k values from an anisotropic and heterogeneous bog peat these data were aggregated to produce the following simplified data sets an isotropic and heterogeneous distribution of k an isotropic and homogeneous distribution and an anisotropic and homogeneous distribution we demonstrate that where anisotropy and heterogeneity exist groundwater flow in bog peat is complex fine scale variations in k have the potential to influence patterns and rates of groundwater flow however for our data at least it is heterogeneity and not anisotropy that has the greater influence on producing complex patterns of groundwater flow we also demonstrate that patterns and rates of groundwater flow are simplified and reduced when measured k values are aggregated to create a more uniform distribution of k for example when measured k values are aggregated to produce isotropy and homogeneity the rate of modelled seepage is reduced by 28 we also show that when measured k values are used the presence of a drainage ditch can increase seepage through a modelled cross section our work has implications for the accurate interpretation of hydraulic head data obtained from peat soils and also the understanding of the effect of drainage ditches on patterns and rates of groundwater flow

variations in free phase gases in peat landforms determined by ground penetrating radar 1 the spatial variability of biogenic gas produced by methanogenic archaea is difficult to assess within saturated peat soils and is often poorly quantified this study uses ground penetrating radar to noninvasively estimate the vertical distribution of biogenic free phase gas fpg in two distinct peat landform types in the glacial lake agassiz peatland minnesota a near crest bog and a midslope lawn i e both as defined by surface vegetation communities ground penetrating radar velocities retrieved from common midpoint surveys were modeled using the complex refractive index model to estimate free phase gas volumes along one dimensional vertical profiles near crest bog landforms are characterized by vertical variability in gas content with accumulations along the peat column up to 24 by volume of fpg localized within the deep peat e g 2 4 m depth midslope lawn sites show lower total volumes up to 12 free phase gas and less variability that result in a more even free phase gas distribution throughout the vertical profile high resolution data also suggests the presence of thinner layers 1 m containing up to 40 free phase gas at a near crest site our results suggest that spatial distribution of free phase gas along the peat column may vary in the glacial lake agassiz peatlands depending on peat landform statistical analysis supports vertical variability of ground penetrating radar velocity data with a 95 confidence limit our results could potentially be upscaled using surface vegetation communities to estimate landscape scale gas storage potential in peat landforms

the stable carbon isotopic composition of organic material in platform derived sediments implications for reconstructing the global carbon cycle in pelagic carbonate sediments the degree to which the 13c values of inorganic and organic fractions co vary has been used to interpret rates of production burial and decomposition of organic carbon this relationship is relatively consistent through time permitting estimates of organic carbon production and preservation however as the majority of pelagic sediments older than 200 myr have been subducted carbonate sediments deposited in epeiric seas and platforms are often substituted for pelagic carbonates in analyses of ancient global carbon cycling there are well known pitfalls to using shallow marine carbonate materials including diagenesis semi isolation of depositional environments and input of different types of sediments with varying inorganic 13c 13cinorganic values which can obscure any global signatures one method used to assess whether global changes in 13c are accurately represented by 13cinorganic records is to examine variations in the 13c of co occurring organic material 13corganic if a 13corganic record co varies with a co occurring 13cinorganic record it is argued that the signals must be related to variations in the global carbon cycle this assumption has been investigated by analysing the isotopic composition of the organic carbon preserved in the uppermost 150 m of periplatform sediments recovered during odp leg 166 from the western margin of great bahama bank the 13corganic values measured in this study were compared to previously published 13cinorganic records measured on identical samples thus allowing a study of the correlation between the two records through time these analyses showed that the correlation coefficient between 13cinorganic and 13corganic increased from the proximal location site 1005 r2 0 1 to the distal site site 1006 r2 0 63 the importance of platform derived carbonate and organic material at the proximal location site 1005 is reflected in the absence of a co variation between inorganic and organic 13c records which exhibit no correlation on the platform itself in contrast the co variance in 13c values at the basinal location site 1006 is explained by a two point mixing model which demonstrates the importance of both pelagic and platform derived carbonate and organic carbon in generating the positive correlation between the organic and inorganic 13c values this results in a correlation between 13cinorganic and 13corganic records at site 1006 that is unrelated to global carbon cycling such data question the applicability of using 13corganic values to support the ability of 13cinorganic values to record global carbon cycling in carbonates recovered from environments where multiple sources of carbonate and organic carbon contribute to the bulk 13c signal

role and character of seasonal peat soil deformation on the hydrology of undisturbed and cutover peatlands 1 this paper describes the nature and magnitude of peat soil volume changes and its relation to seasonal changes in water table at an undisturbed bog peatland and on two cutover sections of the same peatland and its effect on hydraulic conductivity in the latter two sites operations had ceased 2 and 7 years prior to this study respectively the water table dropped to a maximum depth of 40 50 and 68 cm respectively at the undisturbed 2 year and 7 year abandoned sites and a resulted in subsidence of 0 96 3 84 and 2 65 cm m 1 respectively at the undisturbed site surface elevation changes did not always correspond to water table changes but peat underwent a period of swelling even as the water table fell probably due to the accumulation of methane in soil pores at all sites most volume change occurred in the upper 50 cm layer with maximum strain of 5 15 and 5 at the undisturbed 2 year and 7 year abandoned sites respectively and was strongly related to water table decline a model of peat deformation in the zone of saturation 100 cm depth based on changes in saturated soil moisture 6 grossly overestimated strain 1 in the saturated zone and again methane accumulation was the suspected cause of the soil moisture decrease peat compression and perhaps methane accumulation caused hydraulic conductivity to decrease over two orders of magnitude at 75 125 and 170 cm depth the decrease in hydraulic conductivity as a peatland dries may be an important self preservation mechanism i e against further water loss

hydrological hotspots in blanket peatlands spatial variation in peat permeability around a natural soil pipe 1 measurements were made of the hydraulic conductivity k of peat around a natural soil pipe in a blanket bog this is the first investigation of decimeter scale variability in both vertical k and horizontal k in blanket peats which were found to be higher than indicated by previous research this information suggests that it may be appropriate to reconsider i the spatial sampling strategies employed to investigate subsurface flow in blanket peatlands and ii how field data are used to parameterize flow models critically there was spatial structure in the heterogeneity with a wedge of high k peat directly above the pipe forming a hydrological conduit between near surface peat and the perennially flowing pipe there was also significantly greater horizontal k parallel to the pipe s orientation compared with horizontal k perpendicular to the pipe determinations of the triaxial anisotropy of k undertaken for the first time in peat soils revealed substantial directional variations in k the k around the pipe peat interface was investigated however sample length dependency of k for peat samples precluded the investigation of a hypothesized low k skin around the pipe

authigenic dolomites in the eocene oligocene organic carbon rich shales from the polish outer carpathians evidence of past gas production and possible gas hydrate formation in the silesian basin abstract eocene oligocene dolomite concretions and beds from the grybow and dukla units of the polish outer carpathians were studied these rocks occur in the organic carbon rich marine and fine grained deposits of hemipelagic or turbiditic origin mineralogic elemental and stable c and o isotopic composition of the dolomites was determined results indicate that the rocks were formed by precipitation of predominantly fe rich dolomite cement close to the sediment water interface prior to significant compaction the main source of bicarbonate for dolomite formation was bacterial methanogenesis as evidenced by the high 13c values up to 16 6 the main source of alkalinity was probably weathering of silicate minerals which might have also liberated ca and mg ions for the dolomites to form the distribution of these dolomites indicates that microbial methane production was widespread in the silesian basin moreover formation of some dolomites in the eastern part of the dukla unit was probably associated with gas hydrates as suggested by the elemental and oxygen isotopic composition of dolomitic matrix therefore the dolomites may serve as a proxy of areas where biogenic methane was produced where the rocks had high hydrocarbon potential and where hydrates could have existed detailed mineralogic and petrographic analyses allowed for the reconstruction of the diagenetic sequence and the evolution of pore fluids textural relationships between successive cement generations indicate that the central parts of the composite dolomite crystals experienced corrosion and that the latest ankerite cement filled the secondary intragranular cavities within those crystals this observation shows that reconstructions of pore fluid evolution based on core to rim analyses of such composite crystals may lead to wrong interpretations septarian cracks developed in the dolomites are often filled with multistage cements the earliest generations are ferroan dolomite and ankerite cements which precipitated within the cracks simultaneously to the ferroan dolomite and ankerite cements from the matrix of the dolomitic rocks which shows that septarian cracking occurred very early during the final stages of concretionary formation these cements were followed by the late diagenetic precipitates mainly quartz kaolinite and blocky calcite this calcite is commonly associated with bitumen which shows that it precipitated during or after oil migration in the decarboxylation zone

neoproterozoic chemostratigraphy and correlation of the port askaig glaciation dalradian supergroup of scotland the 13 c of preglacial carbonates beneath the glaciogenic port askaig formation falls from 5 to negative values while least altered 87 sr 86 sr values are close to 0 7067 postglacial cap carbonates of the bonahaven formation begin with negative 13 c carb values jumping sharply to 11 7 near the top which we correlate with excursions above the elbobreen wilsonbreen glaciations of svalbard and putative sturtian not varanger glaciations elsewhere dated at c 720 ma much of the succeeding terminal neoproterozoic is missing in ne svalbard and east greenland raising doubts about their use for global sr and c isotope curves in the neoproterozoic

karst hydrogeology within a subarctic peatland attawapiskat river hudson bay lowland canada abstract the attawapiskat river has cut through 30 m of mid silurian limestone 90 km west of james bay in the hudson bay lowland limestone cliffs of 12 15 m provide local relief along the river but inland the terrain is flat covered by 1 5 m or more of peat the area emerged from the tyrrell sea 4400 yr b p since that time two karst hydrogeological zones have become established these are 1 a vadose fluvio karst zone in the exposed limestone along the river represented by disappearing lakes and streams and 2 an organo karst zone represented by sinkholes on or next to limestone bioherms within the peat mantle they occupy 16 and 13 of the study area respectively

aggregate scale spatial heterogeneity in reductive transformation of ferrihydrite resulting from coupled biogeochemical and physical processes abstract iron hydr oxides are ubiquitous in soils and sediments and play a dominant role in the geochemistry of surface and subsurface environments their fate depends on local environmental conditions which in structured soils may vary significantly over short distances due to mass transfer limitations on solute delivery and metabolite removal in the present study artificial soil aggregates were used to investigate the coupling of physical and biogeochemical processes affecting the spatial distribution of iron fe phases resulting from reductive transformation of ferrihydrite spherical aggregates made of ferrihydrite coated sand were inoculated with the dissimilatory fe reducing bacterium shewanella putrefaciens strain cn 32 and placed into a flow reactor the reaction cell simulates a diffusion dominated soil aggregate surrounded by an advective flow domain the spatial and temporal evolution of secondary mineralization products resulting from dissimilatory fe reduction of ferrihydrite were followed within the aggregates in response to a range of flow rates and lactate concentrations strong radial variations in the distribution of secondary phases were observed owing to diffusively controlled delivery of lactate and efflux of fe ii and bicarbonate in the aggregate cortex only limited formation of secondary fe phases were observed over 30 d of reaction despite high rates of ferrihydrite reduction under all flow conditions tested ferrihydrite transformation was limited in the cortex 70 85 mol fe remained as ferrihydrite because metabolites such as fe ii and bicarbonate were efficiently removed in outflow solutes in contrast within the inner fractions of the aggregate limited mass transfer results in metabolite fe ii and bicarbonate build up and the consummate transformation of ferrihydrite only 15 40 mol fe remained as ferrihydrite after 30 d of reaction goethite lepidocrocite and minor amounts of magnetite formed in the aggregate mid section and interior at low lactate concentration 0 3 mm after 30 d of reaction under high lactate 3 mm concentration magnetite was observed only as a transitory phase and rather goethite lepidocrocite and siderite were the dominant secondary mineralization products our results illustrate the importance of slow diffusive transport of both electron donor and metabolites concentrations and concomitant biogeochemical reactions within soils and sediments giving rise to heterogeneous products over small spatial m scale

exploring pathways to late holocene increased surface wetness in subarctic peatlands of eastern canada the poor fens of the laforge region northeastern canada have developed under subarctic conditions they are characterized by a microtopography of large pools and low narrow strings paleorecords suggest some of these systems were once ombrotrophic and relatively dry taking account of their current bioclimatic position we aimed to explore the possible pathways towards the current wet state a process referred to as aqualysis we combined paleoecological methods applied to a peat core with conceptual modelling to identify factors that might plausibly explain aqualysis reconstructions showed the abeille peatland became minerotrophic with high water tables between 2400 and 2100 cal yr bp conceptual modelling supported by simulations using the numerical digibog model allowed us to identify the effects of cooling and increased precipitation on productivity decay peat hydraulic conductivity and vertical peat accumulation both cooling and increased precipitation were required for aqualysis to occur and for wet surface conditions to persist to the present day increased recharge from the catchment which also restricted drainage from the peatland center laterally was likely critical for the development of minerotrophic conditions the scenario of cooling and wetting in these peatlands is supported by available paleoclimate records for eastern canada

the role of recharge and evapotranspiration as hydraulic drivers of ion concentrations in shallow groundwater on everglades tree islands florida usa recently evapotranspiration has been hypothesized to promote the secondary formation of calcium carbonate year round on tree islands in the everglades by influencing groundwater ions concentrations however the role of recharge and evapotranspiration as drivers of shallow groundwater ion accumulation has not been investigated the goal of this study is to develop a hydrologic model that predicts the chloride concentrations of shallow tree island groundwater and to determine the influence of overlying biomass and underlying geologic material on these concentrations groundwater and surface water levels and chloride concentrations were monitored on eight constructed tree islands at the loxahatchee impoundment landscape assessment lila from 2007 to 2010 the tree islands at lila were constructed predominately of peat or of peat and limestone and were planted with saplings of native tree species in 2006 and 2007 the model predicted low shallow groundwater chloride concentrations when inputs of regional groundwater and evapotranspiration to recharge rates were elevated while low evapotranspiration to recharge rates resulted in a substantial increase of the chloride concentrations of the shallow groundwater modeling results indicated that evapotranspiration typically exceeded recharge on the older tree islands and those with a limestone lithology which resulted in greater inputs of regional groundwater a sensitivity analysis indicated the shallow groundwater chloride concentrations were most sensitive to alterations in specific yield during the wet season and hydraulic conductivity in the dry season in conclusion the inputs of rainfall underlying hydrologic properties of tree islands sediments and forest structure may explain the variation in ion concentration seen across everglades tree islands copyright 2012 john wiley sons ltd

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

anisotropy and depth related heterogeneity of hydraulic conductivity in a bog peat i laboratory measurements anisotropy and heterogeneity of hydraulic conductivity k are suspected of greatly affecting rates and patterns of ground water seepage in peats a new laboratory method termed here the modified cube method was used to measure horizontal and vertical hydraulic conductivity kh and kv of 400 samples of bog peat the new method avoids many of the problems associated with existing field and laboratory methods and is shown to give relatively precise measurements of k in the majority of samples tested kh was much greater than kv indicating that the bog peat was strongly anisotropic log10kh log10kv and log10 kh kv were found to vary significantly with depth although none of the relationships was simple we comment on the scale dependency of our measurements

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

was the ediacaran shuram excursion a globally synchronized early diagenetic event insights from methane derived authigenic carbonates in the uppermost doushantuo formation south china abstract the ediacaran period is characterized by the most profound negative carbon isotope 13c excursion in earth history the shuram excursion various hypotheses including the massive oxidation of dissolved organic carbon doc in the oceans the weathering of terrestrial organic carbon or the release and oxidation of methane hydrates and or expelled petroleum from the subsurface have been proposed as sources of the 13c depleted carbon more recently it has been suggested that global scale precipitation of early authigenic carbonates driven by anaerobic microbial metabolism in unconsolidated sediments may have caused the shuram excursion but empirical evidence is lacking here we present a comprehensive analysis of a shuram associated interval from the uppermost doushantuo formation in south china our study reveals petrographic evidence of methane derived authigenic calcite formed as early diagenetic cements and nodules that are remarkably depleted in 13c suggesting a buildup of alkalinity in pore fluids through the anaerobic oxidation of methane aom and systematically depleted in 18o relative to co occurring dolomite early authigenesis of these minerals is likely to be driven by increased microbial sulfate reduction triggered by enhanced continental weathering in the context of a marked rise in atmospheric oxygen levels in light of the finding of methane derived authigenic carbonates at zhongling and based on our basin scale stratigraphic correlation we hypothesize that the marked 13c and 18o depletion including their co variation noted worldwide in the shuram excursion may reflect an episode of authigenesis occurring within a sulfate methane transition zone smtz if true the shuram excursion was then a global biogeochemical response to enhanced seawater sulfate concentration in the ediacaran ocean driven by the neoproterozoic oxidation of surface environments this paleo oceanographic transition may have therefore paved the way for subsequent evolution and diversification of animals our study highlights the significance of an integrated approach that combines petrography mineralogy and texture specific micro drilling geochemistry in chemostratigraphic studies

stable isotopes of water show deep seasonal recharge in northern bogs and fens ground water recharge is assumed to occur primarily at raised bog crests in northern peatlands which are globally significant terrestrial carbon reservoirs we synoptically surveyed vertical profiles of peat pore water 18o and 2h from a range of bog and fen landforms across the glacial lake agassiz peatlands northern minnesota contrary to our expectations we find that local scale recharge penetrates to not only the basal peat at topographically high bog crests but also transitional sphagnum lawns and low lying fen water tracks surface landscape characteristics appear to control the isotopic composition of the deeper pore waters depths 0 5 m which are partitioned into discrete ranges of 18o on the basis of landform type mean standard deviation for bog crests 11 9 0 4 lawns 10 6 0 1 fen water tracks 8 8 1 0 fen water tracks have a shallow free water surface that is seasonally enriched by isotope fractionating evaporation fingerprinting recharge to underlying pore waters at depths 3 m isotope mass balance calculations indicate on average 12 of the waters we sampled from the basal peat of the fen water tracks was lost to surface evaporation which occurred prior to advection and dispersion into the underlying formation these new data provide direct support for the hypothesis that methane production in deeper peat strata is fuelled by the downward transport of labile carbon substrates from the surface of northern peat basins copyright 2013 john wiley sons ltd

site specific sequence stratigraphic section benchmark charts are key to regional chronostratigraphic systems tract analysis in growth faulted basins subbasins composing a larger basin can have similar appearing sediment fills that are diachronous it is important to construct a chronostratigraphic section for each subbasin to correctly correlate between subbasins a methodology is presented that incorporates the sequence stratigraphic interpretation of each subbasin which improves correlation of systems tracts between adjacent and widely separated subbasins the growth faulted subbasins in the corpus christi bay area along the western margin of the gulf of mexico are used to demonstrate this methodology a composite wire line log created by splicing unfaulted and relatively conformable log segments from the deepest wells in an area provides a stratigraphic record that captures a complete succession of depositional and cyclic history site specific sequence stratigraphic section s5 benchmark charts are composite logs containing additional data that summarize available geologic information for a subbasin site specific area color coded sequences and component systems tracts are basic information displayed on s5 benchmark charts this physical framework can then be calibrated with ages ma of sequences and bounding surfaces ages are based on geologic time charts representing latest consensus from isotopic polarity and microfossil integration sequence bounding unconformities and internal maximum flooding surfaces delineated on s5 benchmark charts when correlated with other wire line logs and placed into the seismic time domain produce a chronostratigraphic framework for an area comparison of s5 benchmark charts among adjacent widely spaced or isolated sites facilitates correlation of diachronous lithostratigraphic units

a field scale natural gradient solute transport experiment in peat at a newfoundland blanket bog a field scale natural gradient solute transport experiment conducted at a newfoundland blanket bog resulted in an asymmetrical plume owing to solute retardation in the dual porosity matrix an order of magnitude decrease in hydraulic conductivity 10 20 m downslope of the spill caused the transport rate to decrease and lateral dispersion to increase most transport occurred near the watertable and the transport rate increased as the watertable rose hydraulic conductivity between a depth of 0 and 0 2 m was 1 6 10 2 m s 1 whereas at a depth of 0 5 m it was 5 6 orders of magnitude lower owing to greater compaction and humification of the peat with depth at a depth of 0 4 0 45 m diffusion may have become the dominant transport mechanism in spite of the retardation process the solute front s rate of movement was relatively high about 2 3 m day 1 owing to a combination of the high watertable during the study and a relatively steep hydraulic gradient of 0 055 rain caused dilution and mixing of solute near the watertable evaporation did not have an appreciable effect on solute concentration which is attributable to the high transport rate

in situ characterization of preferential flow by combining plot and point scale infiltration experiments on a hillslope abstract this study focuses on the identification of the lateral preferential flow at the hillslope scale and the estimation of the saturated hydraulic conductivity for the fast flow region k s f based on infiltration experiments carried out at different spatial scales point and plot scales and at different soil depths the discrepancies between the considered scales were mainly attributed to macropore flow and the difficulty in adequately embodying the macropore network on small sampled soil volumes conversely at the plot scale the sampled volume was sufficient to activate the macropore network this information helped establish the usability of a given technique to determine the parameters describing the hydraulic properties of the soil in the matrix and fast flow regions while k s data obtained from the beerkan method with the beerkan estimation of soil transfer best parameter algorithm point scale were used to describe the matrix k s m the saturated hydraulic conductivity for the fast flow region was estimated using the soil block method plot scale estimated k s f values were one to three orders of magnitude higher than k s m the overall decrease of k s f with the soil depth supported the hypothesis that the macropore density decreased as a function of depth yielding higher macropore flow variability the soil block method in association with the beerkan infiltration runs allowed the estimation of the saturated hydraulic conductivity for the fast flow region based on a relatively simple field procedure

groundwater hydrology of boreal peatlands above a bedrock tunnel drainage impacts and surface water groundwater interactions summary little attention has been given to the pattern of hydrological connectivity between peatlands and water bearing fracture zones in crystalline bedrock the construction of the railway tunnel romeriksporten provided an opportunity for studying impacts of bedrock tunnelling on peatland hydrology and the hydraulic connectivity between peat deposits and deeper layers in an area with fractured precambrian gneisses exposed bedrock and surficial covers of thin till deposits and peatsoils above the tunnel the water level in peat wells fluctuated with maximum depths up to 3 m and water that otherwise would have generated surface runoff infiltrated in the peat drawdowns of the groundwater table in peatlands were observed as far as 340 m away from the tunnel trace the deep drainage base provided prolonged water table drawdowns in peatlands in dry periods and differential settlements in drained peatsoils resulted in secondary changes in patterns of surface water storage and flow the groundwater drawdowns were influenced by the balance between tunnel leakage and water supplies from catchments and the wetland position within the groundwater flow system deep and simultaneous lowering and fluctuations of hydraulic heads in wells in the peat the subpeat sediments and the bedrock above the tunnel demonstrated hydraulic connectivity between the peat layers and the bedrock and revealed vertical flow even through highly humified peat layers in the catotelm this shows that in peatlands with a subsurface of a relatively thin till cover above fractured crystalline bedrock favourable conditions for groundwater flow from peatsoils to rock are not always restricted to a few specific sites and indicates that attention should be given to the influence of peat water bedrock water connectivity on impacts of groundwater exploitation droughts and climate changes in such areas

peat porewaters have contrasting geochemical fingerprints for groundwater recharge and discharge due to matrix diffusion in a large northern bog fen complex abstract although northern peatlands represent a globally significant reservoir for carbon considerable uncertainty exists concerning solute transport systems within large 1000 km 2 peat deposits we therefore delineated geochemical gradients linked to groundwater recharge and discharge along a 6 km transect within the 1200 km 2 red lake peatland of northwestern minnesota we used ratios of ca mg and 87 sr 86 sr to distinguish discharge of calcareous groundwater 1 4 and 0 7155 respectively to the peatland from the mineral substratum along a topographic gradient from a bog crest downslope to an internal fen water track and bog islands in contrast the stable isotopes of the porewaters 18 o from 12 8 to 7 8 show that the active pore spaces in these peat profiles have been flushed by recharge from the near surface peat we hypothesize that back diffusion of groundwater derived solutes from the peat matrix to active pore spaces has allowed the geochemical signal from paleo hydrogeologic discharge to persist into the current regime of dilute recharge this effect has not been observed previously on the landform scale and has important implications for carbon cycling in peatlands

the origin and development of a minerotrophic soak on an irish raised bog an interpretation of depth profiles of hydrochemistry and peat chemistry the peat and pore water biogeochemistry of an irish oceanic raised bog are reported with a view to understanding the origin and development of a minerotrophic soak contained within an ombrotrophic bog depth profiles of electrical conductivity pore water chemistry and peat chemistry were recorded from the mire surface down to a maximum depth of 10 m approximately 1 m into the underlying mineral soil from the centre of lough roe a minerotrophic soak on clara bog in the irish midlands and from a location in the surrounding bog distinct differences in the hydrochemistry and peat chemistry between both sites are evident in the upper 5 m of the profile indicating that conditions differed during the latter development of the mire despite both sites being located on the apex of the raised bog dome as expected the profiles recorded from the ombrotrophic bog are characterised by low ionic concentrations in the upper bog peat with an increase in the concentration of calcium and other ions in the lower fen peat from 5 5 m depth at the lough roe site the profile shows relatively high concentrations of calcium and other ions in the upper part of the profile to our knowledge this is the first report of such detailed minerotrophic chemical profiles from the central area of a raised bog dome we hypothesize that the relevant minerals originate from the underlying clay layer and fen peat within the basin of the bog and the minerals prevailed within the soak because of 1 the generation of a flow of water from the developing bog through the minerotrophic fen peat towards the soak during its early development and 2 increased rates of decomposition within the soak throughout its existence the implications for the future conservation management of the site are discussed the author s 2009

wildfire effects on vadose zone hydrology in forested boreal peatland microforms summary peatland vulnerability to wildfire disturbance has been shown to vary as a function of hummock and hollow microforms and vadose zone hydrology with low lying hollow microforms most susceptible to deep combustion of peat to better understand how this microform induced pattern of burning alters vadose water storage pore water pressure and water table relationships we examined a paired burned and unburned peatland in the boreal plain region of north central alberta water table response to rain events increased significantly after wildfire resulting in a more variable unsaturated zone thickness that was more responsive to smaller rain events water storage losses in the vadose zone occurred primarily at depths greater than 15 cm large peat surface water loss occurred in hummock microforms in the early spring due to the presence of unsaturated frozen peat at depth likely a result of a vapour gradient from the unfrozen peat into the frozen peat underneath during this period the loss of water storage in the vadose zone satisfied up to 25 of daily evaporative demand compared to only 3 5 during ice free periods a similar but less severe drying was observed late in summer with burned hummocks the most vulnerable with high pore water pressures the enhanced surface drying observed is a precursor to high pore water pressure conditions that inhibit sphagnum regeneration our observations point to a paradox where the hummocks being most resistant to combustion are themselves most prone to high pore water pressures following wildfire the harsher hummock environment may contribute to the observed delay in post fire sphagnum regeneration in hummocks compared to hollows

shallow horizontal groundwater flow in peatlands is reduced by bacteriogenic gas production 1 we tested the extent to which horizontal hydraulic conductivity kh below the water table in near surface peats is affected by the accumulation of biogenic gas bubbles we found 1 immediately after water table rise the peat is not saturated levels of initial undersaturation were between 1 and 9 percent 2 the production of biogenic gas bubbles below the water table causes large reductions typically more than a factor of two in kh

soil water flow dynamics in a managed cutover peat field quebec field and laboratory investigations in this paper concerned with soil water dynamics in a managed cutover peat field the microscale hydrological processes and parameters governing water flow and storage through variably saturated peat are investigated an open water ditch reservoir enhanced wetting of adjacent cutover peat maintaining the water table depth above 43 cm during the summer surface soil moisture above 45 and water tension in the surface layer above 245 mbar desaturation of pores was noted in the 22 and 210 cm depths but at 230 and 250 cm a decrease in moisture content of several percent was associated with compression of the peat as the water table dropped air entry occurred only at pressures below 215 mbar seasonal subsidence resulted in cumulative vertical displacement in excess of 10 cm during the study period typical settlements in the peat ranged between 11 and 23 of the lowering of the water table considerable hysteresis was observed and vertical displacement was 5 times greater in response to water loss compared to rewetting the specific storage s s in the 180 cm thick deposit averaged 9 4 3 10 24 cm 21 during drying periods but averaged only 2 6 3 10 24 cm 21 on rewetting s s was more important than specific yield sy in the overall aquifer storativity transient hydraulic properties resulted from the shifting soil structure the increase in peat bulk density caused by drying increased the water retention capacity and decreased hydraulic conductivity mean saturated hydraulic conductivity was 15 cm d 21 and decreased 2 orders of magnitude as the degree of saturation dropped from 1 to 0 4 the horizontal vertical anisotropy ratio was 4 the changing surface elevation in response to seasonal subsidence had a profound influence on the nature of the storage changes and hydraulic parameters of the peat soil

the nature of the δ13c of periplatform sediments implications for stratigraphy and the global carbon cycle the carbon isotopic composition y 13 c of bulk carbonates obtained from a transect of sites drilled through platform and periplatform sediments of holocene to early miocene age has been compared to ascertain whether changes in the y 13 c can be correlated between sediments of equivalent ages and whether such changes can be related to global changes in the y 13 c of the dissolved inorganic carbon in the oceans over this time period five of the sites were drilled during leg 166 of the ocean drilling project 1003 1007 in a transect ranging from five km to 25 km away from the platform margin and penetrating sediments of holocene to oligocene age that are contained in 17 depositional sequences a q two shallow water sites clino and unda were situated on a extension of the same transect on great bahama bank in a water depth of 10 15 m with the exception of unda and clino the y 13 c of the carbonates ranges from 5x in the younger sequences to 1x in the early miocene in each of the sites the y 13 c is strongly positively correlated with the percentage of aragonite as a consequence the y 13 c of sequences a through f is strongly correlated reflecting the decreasing amount of aragonite with increasing depth in the two platform sites the y 13 c is significantly lower in the younger portions of the cores as a result of the influences of meteoric diagenesis during repeated exposure during the pleistocene although the y 13 c of the individual sequences can be correlated in most instances between the odp holes the changes are not related to global changes in the y 13 c of the oceans which in contrast to the y 13 c of the platform sediments become isotopically lower towards the present day instead variations in the y 13 c appear to be related to varying mixtures of y 13 c rich banktop sediments and pelagic material

mapping sediment dispersal patterns and associated systems tracts in fourth and fifth order sequences using seismic sedimentology example from corpus christi bay texas a seismic sedimentologic study was performed to map fourth and fifth order systems tracts in oligocene frio strata in corpus christi bay south texas guided by third order sequence stratigraphic correlations from seismic and wire line log data we prepared stratal slices from a three dimensional seismic volume to reveal high resolution 10 m 33 ft levels sediment dispersal patterns and associated systems tracts in a relative geologic time domain on average 1200 m 3940 ft of sediments were deposited in the third order lowstand expansion cycle and at least 16 higher order sequences fourth and fifth order sequences were recognized three types of depositional systems were identified in the frio stratigraphic section 1 offshelf lowstand slope fans that are best characterized by submarine channel and levee systems inside and outside incised submarine channels and by fan shaped sand body geometry 2 lowstand prograding deltaic systems that are composed of strike oriented and lobate deltaic sand bodies and 3 highstand systems that are represented by onshelf barrier lagoon and deltaic systems higher order sequence development was controlled by the interaction of relative sea level change sediment supply and gravity tectonics the top of sediment ridges was eroded or decapitated during many of the higher order sequences sand dispersal patterns are primarily controlled by accommodation resulting from rollover topography associated with growth faulting between the boundary fault and the hinge line atop rollover structures strike oriented sandstone bodies dominate within submarine channels and incised valleys and beyond the hinge line to the distal basin dip oriented sandstone bodies prevail sandstone thickness and dispersal patterns can be predicted by integrating wire line log measurements and seismic amplitude patterns

modeling of water balance cracking and subsidence of clay soils abstract a general procedure has been developed to model water balance cracking and subsidence of clay soils the main feature of this procedure is the introduction of the shrinkage characteristic in addition to the water retention and hydraulic conductivity curves into simulation models the proposed procedure enables direct calculation of volume changes in dependance on moisture transport with appropriate assumptions for geometry of swelling and shrinkage these volume changes are converted into cracking and subsidence taking into account the calculated area of shrinkage cracks at the soil surface together with the maximum infiltration rate of the soil matrix and the rainfall intensity rainfall is dynamically partitioned in matrix and crack infiltration in this way bypass flow and resulting rapid rises of groundwater levels in cracked soils can be simulated the procedure was validated by adapting a model for calculation of transient moisture flow in soils flowex into a version applicable on clay soils flocr computations with flocr of subsidence cracking groundwater level and top layer wetness of a dutch basin clay soil during 1985 were in good agreement with field observations moreover the proposed method of bypass calculation is supported by good correspondence between measured and simulated rapid rises of groundwater levels

facies dependent δ13c variation from a cryogenian platform margin south australia evidence for stratified neoproterozoic oceans abstract analysis of a cryogenian interglacial platform margin in the adelaide geosyncline reveals a strong carbonate 13 c facies relationship detailed chronostratigraphic correlation between sections ranging from shallow platform facies to deep basinal facies indicates the presence of a carbon isotopic gradient of between 8 and 11 in time equivalent strata shallow water back reef facies have 13 c values up to 8 2 while equivalent basinal sediments have 13 c values between 3 and 0 allochthonous blocks that have been transported from the platform margin into basinal environments retain their heavy 13 c values 4 9 and are surrounded by basinal calcareous shales with light 13 c values ave 0 8 the regional and stratigraphic consistency of these 13 c trends suggests a primary marine origin we interpret this 13 c facies correlation to be the result of ocean stratification stagnation that significantly reduced the rate of deep ocean ventilation and produced a large deep water organically derived carbon reservoir we suggest that stratification may have been a persistent feature of the global ocean throughout much of neoproterozoic time ocean stratification may explain many of the unusual features that characterise the sedimentary record of this era including large scale 13 c variation extreme climatic fluctuations and the presence of cap carbonates a highly variable climatic regime would be expected with the development of a large deep water carbon reservoir small changes in ocean circulation could rapidly transfer or remove large volumes of carbon to and from the surface ocean and atmospheric reservoirs leading to intense greenhouse or icehouse conditions respectively

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

seasonal changes in peatland surface elevation recorded at gps stations in the red lake peatlands northern minnesota usa 1 northern peatlands appear to hold large volumes of free phase gas e g ch4 and co2 which has been detected by surface deformations pore pressure profiles and electromagnetic surveys determining the gas content and its impact in peat is challenging because gas storage depends on both the elastic properties of the peat matrix and the buoyant forces exerted by pore fluids we therefore used a viscoelastic deformation model to estimate these variables by adjusting model runs to reproduce observed changes in peat surface elevation within a 1300 km2 peatland a local gps network documented significant changes in surface elevations throughout the year with the greatest vertical displacements associated with rapid changes in peat water content and unloadings due to melting of the winter snowpack these changes were coherent with changes in water table elevation and also abnormal pore pressure changes measured by nests of instrumented piezometers the deformation model reproduced these changes when the gas content was adjusted to 10 of peat volume and young s modulus was varied between 5 and 100 kpa as the peat profile shifted from tension to compression in contrast the model predicted little peat deformation when the gas content was 3 or lower these model simulations are consistent with previous estimates of gas volume in northern peatlands and suggest an upper limit of gas storage controlled by the elastic moduli of the peat fabric

detecting biotic and hydrogeochemical processes in large peat basins with landsat tm imagery a survey was made of three large peat basins in boreal north america with landsat tm imagery and field sampling false color composites composed of bands 2 3 and 4 are particularly effective in discriminating the major vegetation types and the important hydrogeochemical processes in these peatlands this imagery indicates that the discharge of alkaline groundwater provides one of the most important regional and local controls on peatland development

climatic and topographic limits to the abundance of bog pools on patterned peatlands open water pools develop within a matrix of terrestrial vegetation ridges regional patterns in the distribution of ridge pool complexes suggest that the relative cover of these two surface types is controlled in part by climate wetness but landscape topography must also be an important controlling factor in this paper a functional model that relates relative cover of ridges and pools to climate and surface gradient was developed and tested the model was formulated in terms of a water budget based on the differential effects of ridges and pools on losses by evapotranspiration and subsurface flow it predicts a positive relationship between surface gradient and ridge proportion with a linear effect related to water supply and ridge hydraulic conductivity modified at high ridge proportion by differences in evapotranspiration between ridges and pools the limit to patterned peatland distribution occurs where the surface is completely covered by ridges the model may be sensitive or insensitive to climate differences between localities depending on whether hydraulic characteristics of ridge peat co vary with water supply to distinguish between these alternative hypotheses surface gradient and ridge proportion were surveyed along 20 transects in each of three localities in scotland that differ threefold in net precipitation to pools the results of the field survey served to reject the climate sensitive hypothesis but were consistent with the climate insensitive hypothesis analysis of the residuals suggested that variation within localities was related more to topographic control of water supply than to ridge hydraulic conductivity or developmental stage hence within this maritime climate region the distribution of ridge pool complexes and the relative abundance of pools are controlled mainly by topographic variables field surveys across both maritime and continental regions are required to confirm a subtle climatic effect that allows pools to occur on higher gradients in drier climates than in wetter climates further development and testing of the functional model will provide a stronger basis for assessing potential feedback between climate change peatland surface structure and methane emission from pools copyright 2006 john wiley sons ltd

unsaturated hydraulic properties of sphagnum moss and peat reveal trimodal pore size distributions in ombrotrophic peatlands the moisture content of the vadose zone acrotelm controls oxygen diffusion rates redox state and the turnover of organic matter whether peatlands act as sinks or sources of atmospheric carbon thus relies on variably saturated flow processes the richards equation is the standard model for water flow in soils but it is not clear whether it can be applied to simulate water flow in live sphagnum moss transient laboratory evaporation experiments were conducted to observe evaporative water fluxes in the acrotelm containing living sphagnum moss and a deeper layer containing decomposed moss peat the experimental data were evaluated by inverse modeling using the richards equation as process model for variably saturated flow it was tested whether water fluxes and time series of measured pressure heads during evaporation could be simulated the results showed that the measurements could be matched very well providing the hydraulic properties are represented by a suitable model for this a trimodal parametrization of the underlying pore size distribution was necessary which reflects three distinct pore systems of the sphagnum constituted by inter intra and inner plant water while the traditional van genuchten mualem model led to great discrepancies the physically more comprehensive peters durner iden model which accounts for capillary and noncapillary flow led to a more consistent description of the observations we conclude that the richards equation is a valid process description for variably saturated moisture fluxes over a wide pressure range in peatlands supporting the conceptualization of the live moss as part of the vadose zone

a laboratory method to determine the hydraulic conductivity of mountain forest soils using undisturbed soil samples determination of infiltration properties of soils under laboratory conditions necessitates the collection of soil samples in a way that maintains their natural physical properties mountain forest soils containing rock fragments root systems and a significant amount of organic matter make it extremely difficult to test their hydraulic conductivity using both laboratory and field methods a widely used technique of sampling by driving a cylinder into the ground in this type of soils causes damage to their structure resulting from the displacement of root systems and rock fragments as well as reduction of soil porosity thus subsequent results contain an error that is difficult to estimate the aim of the present research was 1 to develop a laboratory method for testing the hydraulic conductivity of mountain forest soils and in particular a method of collection of undisturbed soil samples 2 to determine the influence of the applied method of collecting samples on the thickening of their peripheral layer and on elimination of increased infiltration at the boundary between the soil medium and the cylinder 3 to determine the extent of the impact of the irregular shape of a sample on its hydraulic conductivity and 4 to develop an empirical method for determining the actual values of hydraulic conductivity taking into account the error associated with the flow of water through samples with different shapes the method of soil sampling consists in gradual formation of a cylindrical soil monolith and filling the free space between the monolith and the tri cylindrical container with low pressure assembly foam this method ensures preservation of the natural physical properties of the examined samples and elimination of errors during the measurement of the hydraulic conductivity caused by increased infiltration at the boundary between the soil medium and the cylinder it was shown that the mean error of hydraulic conductivity determination related to the irregular shape of samples amounts to 11 57 the error may be eliminated by the application of conversion coefficients

peat hydraulic conductivity in cold regions and its relation to pore size and geometry subsurface flow through peat plays a critical role in the hydrology of organic covered permafrost terrains which occupy a large part the continental arctic sub arctic and boreal regions hillslope drainage in these terrains occurs predominantly through the active flow zone between the relatively impermeable frost table and the water table above it the hydraulic conductivity profile within this zone controls the subsurface drainage of snowmelt and storm water peat hydraulic conductivity profiles were examined at three sites in north western canada each representing a widely occurring organic covered permafrost terrain type three independent measures of saturated hydraulic conductivity were used tracer tests constant head well permeameter tests and laboratory measurements of undisturbed samples at all three sites the conductivity profiles contained very high values 10 1000 m d 1 within the top ca 0 1 m where the peat is only lightly decomposed a large reduction with increasing depth below the ground surface in the transition zone and relatively low values in a narrow range 0 5 5 m d 1 below ca 0 2 m depth where the peat is in an advanced state of decomposition digital image analysis of resin impregnated peat samples showed that hydraulic conductivity is essentially controlled by pore hydraulic radius the strong dependence of hydraulic conductivity on hydraulic radius implies that peat soils subjected to similar degrees of decomposition and compaction have a similar hydraulic conductivity regardless of the location this explains the similarity of the depth conductivity profiles among all three terrain types copyright 2008 john wiley sons ltd

application of 1d paleo fluvial process modelling at a basin scale to augment sparse borehole data example of a permian formation in the galilee basin australia