dune recovery after storm erosion on a high energy beach vougot beach brittany france abstract on 10th march 2008 the high energy storm johanna hit the french atlantic coast generating severe dune erosion on vougot beach brittany france in this paper the recovery of the dune of vougot beach is analysed through a survey of morphological changes and hydrodynamic conditions data collection focused on the period immediately following storm johanna until july 2010 i e over two and a half years results showed that the dune retreated by a maximum of almost 6 m where storm surge and wave attack were the most energetic dune retreat led to the creation of accommodation space for the storage of sediment by widening and elevating space between the pre and post storm dune toe and reducing impacts of the storm surge dune recovery started in the month following the storm event and is still ongoing it is characterised by the construction of secondary embryo dunes which recovered at an average rate of 4 4 5 cm per month although average monthly volume changes varied from 1 to 2 m 3 m 1 these embryo dunes accreted due to a large aeolian sand supply from the upper tidal beach to the existing foredune these dune construction processes were facilitated by growth of vegetation on low profile embryo dunes promoting backshore accretion after more than two years of survey the sediment budget of the beach dune system showed that more than 10 000 m 3 has been lost by the upper tidal beach we suggest that seaward return currents generated during the storm of 10th march 2008 are responsible for offshore sediment transport reconstitution of the equilibrium beach profile following the storm event may therefore have generated cross shore sediment redistribution inducing net erosion in the tidal zone

lithofacies microfacies and depositional environments of upper cretaceous oceanic red beds chuangde formation in southern tibet the gyangze basin located in southern tibet is one of the representative areas for cretaceous oceanic red beds corbs we investigated and inter correlated several new corb outcrops in the western and southeastern part of the gyangze area in addition to the previously described chuangde section the corbs in the gyangze basin mainly consist of shales thin bedded marls re sedimented limestones and clasts supported conglomerates breccias planktonic foraminifers in the carbonate rocks within corbs belong to the globotruncana ventricosa and globotruncanita calcarata zones indicative of middle campanian age the facies assemblages in the different sections indicate that the depositional environments of corbs range from outer base of slope apron to basin zones within carbonates we observed microfacies types characteristic of basin open deep shelf margin or toe of slope environments gravity transport resulted from the steepening of the sea floor in the gyangze basin owing to subduction during the campanian relatively oxic bottom water conditions prevailed below the toe of slope environment in the gyangze basin during corb deposition however the presence of gray clasts within a multicoloured matrix suggests less oxic conditions at shallower water depths within the basin c 2010 elsevier b v all rights reserved

mid cretaceous oceanic red beds in the umbria marche basin central italy constraints on paleoceanography and paleoclimate abstract detailed studies of the mid cretaceous sedimentary strata in the umbria marche basin in italy revealed that aside from several well known organic rich black shale horizons that record oaes several varicolored mainly reddish horizons indicate oxic conditions at the ocean bottom eight such horizons have been identified in aptian cenomanian sequences in the umbria marche basin the dysoxic oxic beds alternate regularly but not cyclically and seem to be the result of non random processes their occurrence is not a completely random process the duration of deposition of these oceanic red beds orbs varies from 0 13 my orb4 recorded in the ticinella primula zone to 4 54 my for orb1 which spans the globigerinelloides ferreolensis zone to the ticinella bejaouaensis zone in the piobbico core mid cretaceous orbs are not a local phenomenon because they occur in the tethyan deposits in the southern and austrian alps the carpathians the northern caucasus the central north atlantic in northeastern england and in the western himalayas they provide evidence for periodic changes in redox conditions at the ocean bottom such changes could have been caused by changes in bioproductivity basin geometry sedimentation rates paleocirculation and or production of bottom waters with higher content of dissolved oxygen in response to changes in paleoclimate we suggest that the periodic inflow of colder more oxygenated bottom waters was the probable cause of orbs development either as a result of changes in the ocean bottom topography or as a result of brief cool climate periods however reliable proxies for changes in deep ocean circulation are still lacking if orbs were the result of the paleoclimate and therefore indirectly caused by changes in co2 in atmosphere they document the increased sensitivity and instability of the mid cretaceous climate thus changes in ocean dynamics were on a scale of several hundred thousand years to several million years which has not been considered by most theories of co2 cycling mid cretaceous greenhouse paleoclimate and paleocean dynamics

implications of pore space characteristics on diffusive transport in basalts and granites a detailed characterization of the pore space is crucial for understanding of transport and element transfer in rocks here the effect of differences in texture and content of secondary minerals on transport in pore systems was determined for two rocks of widespread occurrence mid ocean ridge basalts morb and granites pore space characteristics were analyzed by hg porosimetry intrusion of a molten alloy and synchrotron based x ray tomographic microscopy for evaluating the role of pore space characteristics for the prediction of diffusive transport data on porosity and the effective diffusion coefficient deff were compared extended connective pore systems due to cracks and mineral dissolution are present in samples of both rocks indicating high internal specific surface area uneven pore size distributions in altered morb samples can be assigned to secondary minerals pore spaces determined by x ray tomography used to determine main direction of pores in the 3 d orthogonal system suggest a slight anisotropy in log log plots both rocks show roughly a linear dependence of deff for h2o and compounds with comparable diffusivities d2o monovalent cations and anions on porosity but at same porosity deff is clearly higher in granitic than in basaltic samples this difference is increasing with decreasing porosity indicating that at low porosities the efficiency of element transport in basaltic samples is diminished mainly inherited by the presence of small pores slowing down diffusion the fact that diffusive transport in basaltic rocks is stronger dependent on porosity than in granitic rocks shows that also other rock characteristics such as pore size distribution and tortuosity of the pore network highly affected by the alteration degree can markedly affect transport and reactivity of pore solution

use of vertical profiles of δ18o to constrain estimates of hydraulic conductivity in a thick unfractured aquitard vertical distributions of 18o were used to constrain hydraulic conductivity k in a thick unfractured aquitard previous investigations utilizing permeability tests at a variety of scales keller et al 1989 indicated that bulk k at the site ranges from 3 5 0 11 m s to 1 2 10 10 m s advective displacements calculated on the basis of these k values lead to a wide range of predicted distributions of natural tracers after 11 000 years comparison of 18o distributions and simulated advection diffusion profiles provide a more precise constraint on advective displacement and hence on k the simulations cast in terms of a peclet number p v2t d ranging in value from 0 to 12 indicate that transport is diffusion controlled and that k is actually less than 1 2 10 11 m s p greater than 0 1 k 1 2 10 11 m s overestimates transport this result indicates that conventional permeability tests in very tight media tend to overestimate k in practical terms advective transport at the site is negligible and transport can be simulated with diffusion only p o

modeling the impact of groundwater depletion on the hydrochemical characteristic of groundwater within mullusi carbonate aquifer west iraq the study of groundwater impact on the hydrochemical characteristic of groundwater within mullusi aquifer west iraq was conducted using the chemical analysis results in 14 production wells and groundwater levels observation in 17 water wells the interpretation of hydrochemical phenomena related to ions sources was determined based on spatial analysis maps of various hydrochemical ratios using arcgis software the study also determined the relation of groundwater velocity and static water levels with the hydrochemical ratios using statistical application of curve expert v1 3 program the variations of ion concentration were examined using the statistical significant differences for chemical constituents of water within mullusi aquifer the impact of dewatering due to high exploitation was explained by increasing the magnesium and chloride concentrations and lowering static water levels magnesium and chloride concentration may reach their maximum limits for drinking at a groundwater level of 485 m asl accordingly any decline in the water level of mullusi aquifer that occurs from 4 5 to 30 5 m may cause deterioration in groundwater quality this study modeled the effect of groundwater depletion on the groundwater quality in a theoretical equations approach

palaeomagnetism of cretaceous to tertiary sediments from southern tibet evidence for the extent of the northern margin of india prior to the collision with eurasia abstract palaeomagnetic studies have been carried out on mid cretaceous to latest palaeocene sediments from the tethyan himalaya on the northern margin of the indian plate near the localities of gamba 28 3 n 88 5 e and duela 28 0 n 89 2 e in southern tibet a total of 61 sites more than 700 cores have been sampled mainly from limestones zongshan formation jidula formation member ii zongpu formation sandstones jidula formation member iii and graywackes gamba group member ii with ages well defined from detailed lithological and biostratigraphic analyses carriers of characteristic remanences are magnetite in limestones and graywackes and hematite in sandstones reliable palaeodirections were obtained from 35 sites 356 specimens positive fold tests antiparallel normal and reverse polarities a northward trend of the palaeolatitudes with decreasing age and absence of any metamorphic overprint indicate a primary origin for the characteristic remanences the results have been compared with expected palaeodirections according to available data for the indian subcontinent based on its present day geometry the late maastrichtian sites fourteen sites 156 specimens and the middle late palaeocene sites fourteen sites 113 specimens yield palaeolatitudes of 5 7 s and 4 0 n for the sampling localities in southern tibet respectively these palaeolatitudes are much further north than expected and imply that crustal shortening between the tethyan himalaya and the indian shield since the time of india eurasia collision has occurred on the order of 1500 km at the longitude of gamba duela comparison of our observed palaeolatitudes with palaeolatitudes for the lhasa block during cretaceous and palaeocene times indicate that initial contact of the northern indian margin with the lhasa block was already established at 65 60 ma with suturing completed at about 55 50 ma

carbonate apron models alternatives to the submarine fan model for paleoenvironmental analysis and hydrocarbon exploration sediment gravity flow deposition along the deep water flanks of carbonate platforms typically does not produce submarine fans rather wedge shaped carbonate aprons develop parallel to the adjacent shelf slope break the major difference between submarine fans and carbonate aprons is a point source with channelized sedimentation on fans versus a line source with sheet flow sedimentation on aprons two types of carbonate aprons may develop along relatively gentle 4 platform margin slopes aprons form immediately adjacent to the shallow water platform and are referred to as carbonate slope aprons along relatively steep 4 15 platform margin slopes redeposited limestones accumulate in a base of slope setting by passing an upper slope via a multitude of small submarine canyons and are referred to as carbonate base of slope aprons both apron types are further subdivided into inner and outer facies belts inner apron sediments consist of thick mud supported conglomerates and megabreccias facies f as well as thick coarse grained turbidites facies a interbedded with subordinate amounts of fine grained peri platform ooze facies g outer apron sediments consist of thinner grain supported conglomerates and turbidites facies a as well as classical turbidites facies c with recognizable bouma divisions interbedded with approximately equal proportions of peri platform ooze facies g seaward aprons grade laterally into basinal facies of thin base cut out carbonate turbidites facies d that are subordinate to peri platform oozes facies g carbonate base of slope aprons grade shelfward into an upper slope facies of fine grained peri platform ooze facies g cut by numerous small canyons that are filled with coarse debris as well as intraformational truncation surfaces which result from submarine sliding in contrast slope aprons grade shelfward immediately into shoal water platform margin facies without an intervening by pass slope the two carbonate apron models presented here offer alternatives to the submarine fan model for paleoenvironmental analysis and hydrocarbon exploration for mass transported carbonate facies

saline leachate migration through clay a comparative laboratory and field investigation the migration of salt solutions nacl through remoulded compacted clay in a laboratory physical model is compared with field migration through a similar but undisturbed clay located below a domestic waste landfill in both the laboratory and field systems the salt profiles indicated that migration was dominated by diffusion after 12 years of leachate exposure at the landfill site both na and cl had migrated about 1 5 m from the soil refuse interface compared to an estimated advance of the seepage front of only 3 4 cm the pore water na and cl values versus depth exhibited considerable scatter requiring data from three boreholes to delineate the concentration boundaries of the vertical migration diffusion coefficients d were obtained using an analytical solution to the one dimensional dispersion convection equation laboratory values of d corrected to the estimated field temperature were similar to field values the d values of 3 to 6 10 6 cm2 s for cl and 2 5 10 6 cm2 s for na appear su

3d static reservoir modeling by geostatistical techniques used for reservoir characterization and data integration to remove some of the ambiguities in a heterogeneous oil reservoir a three dimensional model of the reservoir would be constructed by application of newly introduced methods the aim of this study is to define an accurate and efficient model of a complex reservoir in southwest of iran and accurately derive the geological and geometrical properties of the reservoir for well location proposal seismic data in addition to well logs were used for that purpose a corner point grid was used in this study and a generic global scale up method was combined with previous result for reservoir simulation the final model pointed out the heterogeneous characterization of the reservoir and proved the advantage of combining these methods in constructing accurate and efficient reservoir models according to these models it is concluded that the reservoir has different productive zones in different members that was not cleared in the previous models

sedimentary history of the tethyan basin in the tibetan himalayas after an epicontinental phase the sedimentary rocks in the tibetan himalayas document a complete wilson cycle of the neo tethyan tethys ill evolution between the gondwana supercontinent and its northward drifting margin lhasa block from the late permian to the eocene during the triassic rift stage the basin was filled with a huge clastic dominated sediment wedge with up to 5 000 m of flysch in the northern zone widespread deltaic clastics and shallow water carbonates of late norian to earliest jurassic age in the southern zone mark in conjunction with decreasing tectonic subsidence the transition to the drift stage some 4 500 m of jurassic and early cretaceous shallow water carbonates and siliciclastics accumulated on the tethyan indian passive margin deepening upward sequences with condensed beds at their tops alternate with repeated progradational packages of shelf sediments extensive abyssal sediments with basaltic volcanics in the northern deep water zone reflect continued ocean spreading and thermal subsidence paleomagnetic data gained separately for the northern indian plate and the lhasa block indicate that the neo tethys reached its maximum width about 110 ma ago with a spreading rate of 4 8 cm year before it commenced to close again during the remnant basin stage in the late cretaceous and paleogene a shallowing upward megasequence capped by a carbonate platform developed in the southern inner shelf realm in the northern slope basin plain zone turbidites and chaotic sediments derived from both the acretionary wedge and the steepening slope of the passive margin accumulated the depositional center of the remnant basin shifted southward as a result of flexural subsidence and southward overthrusting the sediments from the triassic to the paleogene are tentatively subdivided into five mega sequences which are controlled mainly by regional tectonics climatic influence e g carbonate deposition due to northward plate motion is partially subdued by terrigenous input and or increased water depth during the oligocene and miocene crustal shortening led to rapid uplift and the deposition of fluvial molasse in limited basins

ecomorphodynamic feedbacks and barrier island response to disturbance insights from the virginia barrier islands mid atlantic bight usa abstract ecomorphodynamic feedbacks play an important role in the susceptibility and response of barrier islands to disturbance by overwash dune building grasses like ammophila breviligulata can help to restore areas of high relief after overwash events i e resist disturbance if overwash recurs before dunes have reestablished however overwash adapted maintainer species like spartina patens upright variety may preferentially survive maintainer species help to preserve low flat topography thereby increasing the likelihood of future overwash i e reinforcing disturbance under frequent disturbance conditions this positive feedback may lead to overwash persistence we explore the potential influence of the maintainer feedback on two morphologically distinct barrier islands in the virginia coast reserve vcr located in the mid atlantic bight of the u s east coast combined topographic and vegetation surveys show that on hog island high relief rotating where dunes dominated by a breviligulata are ubiquitous overwash zones are currently limited in extent and related to beach width rather than dominance by s patens historical aerial photos and stratigraphic evidence ground penetrating radar cores indicate that gradual recovery has taken place following overwash events on hog island except where the beach is narrow and eroding conversely on metompkin island low relief transgressing overwash is widespread and dominated by s patens particularly along the rapidly migrating northern half of the island where shell armoring is also common overwash has generally been more prevalent and persistent here than on hog island we present a new conceptual model of the response of barrier islands to disturbance incorporating ecological and physical processes our findings suggest that in barrier systems where both dune building grasses and overwash adapted maintainer species are common like the vcr the maintainer feedback is likely to be a more important dynamic on islands already susceptible to frequent disturbance because of physical factors the maintainer feedback therefore has the potential to accelerate large scale shifts from dune dominated to overwash dominated barrier morphologies as the effects of climate change increased storm intensity sea level rise cause overwash to become more frequent

foredunes and blowouts initiation geomorphology and dynamics this paper reviews the initiation dynamics geomorphology and evolution of incipient foredunes established foredunes and blowouts incipient foredunes may be initiated in a variety of ways leading to the formation of ramps terraces or ridges depending on progradation rates vegetation type and cover sediment transport rates and scale of erosional processes vegetation cover morphology growth rates and types combine with aerodynamic processes to determine dune and swale morphology established foredunes are classified into five morpho ecological types and the flow behaviour over two types is detailed a new model of foredune evolutionary paths at various possible time scales is presented blowout initiation dynamics and sediment transport and evolution is examined throughout the review the gaps in present understanding of dune processes and a range of ideas for new research possibilities are provided

vegetation dynamics on eroding to accreting beach foredune systems florida panhandle vegetation surveys were conducted on a variety of coastal foredunes in a largely natural region along the gulf county region of the florida panhandle species presence absence and percentage cover were surveyed on 12 foredune profiles during different seasons the vegetation data were analyzed using the shannon wiener diversity index and sorensen index uniola sp and andropgon sp were the dominant species on foredunes uniola sp was found predominantly on the gulfward facing or stoss slopes and andropgon sp was found to be dominant on the inland or lee slopes of foredunes while they are present on all foredunes their presence and percentage cover are dominant on rapidly prograding coasts prograding accretional beaches had higher sorensen index values i e higher similarities than did the foredune vegetation profiles on eroding beaches diversity as indicated by the shannon wiener analysis h is greatest on the highest and generally eroding dunes foredune diversity increased with foredune height and the tallest foredunes were found on shorelines with relatively low erosion rates where dunes were slowly translating landwards cannibalizing older dunes and moving into areas colonized by late successional species such as quercus sp these observations of foredune species richness diversity profile similarities and the use of ecological indices can provide excellent proxy evidence of shoreline dynamics and in particular the degree of beach erosion and accretion in the absence of historical erosion accretion data copyright 2013 john wiley sons ltd

geochemical and climatic effects of increased marine organic carbon burial at the cenomanian turonian boundary perhaps the most significant event in the cretaceous record of the carbon isotope composition of carbonate1 2 other than the 1 2 5 negative shift in the carbon isotope composition of calcareous plankton at the cretaceous tertiary boundary3 is the rapid global positive excursion of 2 13c enrichment which took place between 91 5 myr and 90 3 myr late cenomanian to earliest turonian c t boundary event 1 4 5 this excursion has been attributed to a change in the isotope composition of the marine total dissolved carbon tdc reservoir resulting from an increase in rate of burial of 13c depleted organic carbon which coincided with a major global rise in sea level5 during the so called c t oceanic anoxic event oae 6 here we present new data from nine localities which demonstrate that a positive excursion in the carbon isotope composition of organic carbon at or near the c t boundary7 8 is nearly synchronous with that for carbonate and is widespread throughout the tethys and atlantic basins fig 1 as well as in more high latitude epicontinental seas the postulated increase in the rate of burial of organic carbon may have had a significant effect on co2 and o2 concentrations in the oceans and atmosphere and consequent effects on global climate and sedimentary facies

various types of olistostromes in a closing ocean basin tethyan himalaya cretaceous tibet abstract the cretaceous rocks of the central tethyan himalayas display different types of deep sea olistostromes and chaotic deposits which are accompanied by turbidites the deposits were incorporated into an accretionary prism and more or less deformed according to the composition and provenance of their clasts we distinguish four types of olistostromes 1 p type derived from the passive indian continental margin 2 po type derived from both the passive indian margin and ocean floor pelagic sediments and oceanic crust 3 poa type with clasts from the same sources as the po type but also containing material from the active margin along the lhasa block and 4 a and oa type mainly derived from the active margin accretionary prism and magmatic arc the occurrence of these different types of deep sea chaotic deposits in space and time is closely related to the evolution of the neo tethyan basin from a wide open ocean basin to a narrowing remnant and trench basin prior to collision whereas pure p type olistostromes formed when the basin was still wide predominating a type deposits characterize a late stage of basin evolution prior to collision mixed type olistostromes record an intermediate stage of basin evolution and require specific syn sedimentary tectonic activity

diffusion as the main process for mass transport in very low water content argillites 2 fluid flow and mass transport modeling 1 on the basis of chloride concentrations of pore water in the tournemire massif part 1 a conceptual model for mass transport in argillites by diffusion is proposed from this conceptual model and current knowledge of the geological history of the massif one dimensional numerical simulations are formulated for chloride transport in tournemire massif over the past 53 ma good agreement between experimental data and calculated values for both diffusion coefficients and concentrations of chloride confirms that diffusion is the main process for mass transport in the massif this model is also tested using deuterium contents of pore water applying variable concentrations to meteoric water circulating in system boundary layers based on the thermal dependency of its isotopic composition these simulations reveal the likely important role of lithologic heterogeneities such as fractures in the horizontal distribution of tracer concentrations

vegetation and sedimentation on coastal foredunes on a timescale of years to decades vegetated foredunes may show various modes of morphological development vegetation is one of the factors that determine the sedimentation pattern and thus morphology on the foredune in turn the vegetation pattern may be controlled by the sedimentation pattern although these effects have been quantified for short timescales there is relatively little information on the interaction between vegetation and sedimentation for timescales of over a year for the island of ameland the netherlands elevation measurements and aerial photographs between 2002 and 2012 were used to derive changes in elevation and vegetation patterns on a year to year basis this was done for a range of stable to accreting foredunes sedimentation increases from the beach to a maximum halfway up the seaward slope of the foredune and then decreases again when going landward this trend is further modified by the vegetation s spatial pattern on a timescale of years there is no correlation between the density of vegetation cover and the amount of accretion however by accounting for the gradual depletion of the sand load over the foredune a relationship can be defined between vegetation cover and its trapping efficiency foredune vegetation spreads mainly by lateral expansion of existing patches no strong effect was found of the sedimentation balance on the expansion of vegetation it is suggested that other growth limiting factors are of similar importance masking any possible dependency of vegetation growth on sand accretion

foredune vegetation patterns and alongshore environmental gradients mocambique beach santa catarina island brazil this paper examines patterns of foredune vegetation along an embayment in southern brazil and the relationships between variations in percent cover and diversity and environmental factors such as beach surfzone type and exposure to wind and wave energy the study was conducted on mocambique beach brazil which displays significant alongshore variations in exposure to the prevailing winds and waves beach surfzone morphodynamic type type and dimensions of the dune systems and foredune vegetation cover and diversity two vegetation surveys were carried out in contiguous 1 m2 quadrats across the foredune the presence absence percent cover of the species diversity and similarity between the vegetation of the profiles surveyed and their relation with environmental conditions are examined the results show that the vegetation cover decreases from south to north possibly reflecting the increasing exposure to wind and wave energy distinct patterns of species distributions occur along mocambique beach such that different plant species are dominant on the southern middle and northern ends of the beach a cluster analysis demonstrated two associations the first one is represented by the profiles located in the lower energy zone of the beach and the second association is represented by the profiles more exposed to wind and wave energy sediment deposition and salt spray the diversity of species decreases northwards possibly influenced by the surfzone type number of breaking waves and degree of aeolian transport the presence absence of the species and the vegetation cover on the foredune reflect the varying levels of exposure of the beach and foredune to the winds and waves and also reflect the volume of sediment deposition on the foredune and the beach mobility determined by the morphodynamic beach surfzone type copyright 2008 john wiley sons ltd

origin age and movement of pore water in argillaceous quaternary deposits at four sites in southwestern ontario hydrogeologic information in the form of textural properties field and laboratory determined hydraulic conductivity values vertical hydraulic gradients from piezometer nests and major ion and isotopic contents 18o 2h 3h 13c 14c was obtained from four sites located in southwestern ontario on thick deposits of clayey till and glaciolacustrine clay at each site the piezometers were installed from the water table zone situated 1 4 m below the surface to a maximum depth between 20 and 35 m below the surface values of hydraulic conductivity determined in the laboratory by consolidometer and triaxial methods are in the order of 10 8 10 7 cm s and are similar to values calculated from rates of water level rise in piezometers mean values of average vertical groundwater velocity calculated with the measured values of hydraulic conductivity porosity and hydraulic gradient using the darcy equation for a saturated non fractured porous medium range from 0 13 to 0 26 cm yr tritiated pore waters only occur within 3 6 m of ground surface thereby indicating that groundwaters below this depth recharged prior to at least 1952 18o in the pore waters exhibit a distinctive regular shift with depth from water table values of 9 to 10 smow characteristic of present day precipitation to values between 14 and 17 at depths of 20 40 m which are characteristic of much cooler waters corrected 14c ages of the groundwater are greater than 8000 yr b p thereby suggesting that the groundwaters at depth entered these deposits during or after the formation of these deposits approximately 11 000 to 14 000 yr ago 18o 2h and cl concentration profiles were simulated with a one dimensional model for transport by advection and diffusion in a saturated porous medium reasonable agreement between the model and the field profiles was obtained with values of effective diffusion coefficients of 3 0 10 6 cm2 s for 18o 2h and cl and with groundwater velocities between 0 03 to 0 05 cm yr based on these results it is concluded that the pore water in these deposits is a mixture of late pleistocene and modern waters and that the distribution of 18c 2h and cl in these deposits is influenced predominantly by molecular diffusion apparently more so than by hydraulic flow

the effect of heterogeneity of diffusion parameters on chloride transport in low permeability argillites understanding flow and transport in low permeability media is very important in the context of nuclear waste disposal oil and gas reservoirs and long term evolution of groundwater systems in low permeability media transport by diffusion is often the most important mass transport process this study investigates the effect of the heterogeneity of diffusion parameters on mass transport in low permeability media a geostatistical approach for integrating heterogeneity of diffusion parameters in groundwater flow and transport models is proposed and applied to the toarcian argillites in france which are studied in the framework of feasibility of storing radioactive waste in deep clayey massifs stochastic fields of the diffusion parameters of the toarcian argillites france are generated based on 64 measured values of diffusion coefficient and diffusion accessible porosity and used as input for a 3d local scale groundwater flow and transport model the chloride concentrations computed by these heterogeneous models are compared to the measured chloride concentrations and to concentrations calculated with a model in which the toarcian argillites are subdivided into several homogeneous zones the heterogeneous simulations result in a slightly better correspondence between measured and calculated values and have the additional advantage that the measured diffusion coefficient values in the toarcian are perfectly honored in the model this study shows that small scale variability of diffusion parameters has a significant effect on solute concentrations and omitting this heterogeneity may be a problem in transport calculations in low permeability media depending on the specific setting and objectives of the study

timing of diagenetic haematite growth in red pelagic limestones from gubbio italy abstract magnetite haematite and to a minor extent maghaemite are recognised in the cretaceous and paleocene red pelagic limestones at gubbio the magnetite is detrital or biological whereas the haematite grew during diagenesis from a goethitic precursor thermal and af demagnetization of samples collected from close to reversal boundaries indicate that the various magnetization components do not record the polarity reversal at exactly the same stratigraphic level in the few tens of centimetersbelow a recorded geomagnetic reversal defined by the magnetite magnetization some of the haematite grains are magnetized in the post reversal field the blocking temperature spectra of this haematite fraction with post reversal magnetization are found to shift toward higher temperatures as the reversal boundary is approached the blocking temperature spectra reflect the grain size spectra of the haematite which we interpret as arising by the continual nucleation of grains down to a certain burial depth where the conditions are no longer conducive to further haematite growth the depth below reversal boundaries to which haematite with post reversal magnetization can occur is estimated to be about 60 cm after compaction and is equivalent to a time of about 105 years for these particular sediments a detailed study of the magnetization components at reversal boundaries indicates that the first diagenetic growth of haematite through the single domain critical volume occurs prior to the mechanical fixation of the detrital or biological magnetite subsequently the diagenetic haematite grains do not rotate in response to the ambient geomagnetic field polarity as easily as the magnetite because of their occurrence as pigmentary coatings on larger non magnetic grains

37cl 35cl variations in a diffusion controlled groundwater system abstract groundwaters in the low permeability quaternary glacial deposits of southwestern ontario commonly exhibit increasing cl concentrations with depth because these deposits were formed in a freshwater glacial environment and because cl is not derived from weathering of these deposits previous investigations hypothesized that upward diffusion of saline formation waters from the shallow bedrock caused this cl trend this hypothesis was tested by measuring 37 cl 35 cl ratios in the groundwaters from two typical sites and comparing the results with theoretically derived isotopic distributions produced by diffusion 37cl measurements expressed relative to standard mean ocean chloride smoc ranged from 0 8 to 2 2 and vertical profiles showed a gradual enrichment in 35cl relative to 37cl with increasing distance upward from the bedrock till interface 537cl distributions were simulated with a mathematical solute transport model incorporating the effects of kinetic isotopic partitioning a sensitivity analysis indicated that the model results were affected by the groundwater velocity the isotope enrichment factor and diffusion times agreement between the simulated and observed cl isotope profiles was obtained using a groundwater velocity of 0 an isotopic enrichment factor of 1 0012 and diffusion times ranging from 14 000 to 16 000 years based on these results we conclude that the isotopic enrichment in 35cl was caused by upward diffusion over a period of about 15 000 years this diffusion period is consistent with what is known about the quaternary history of the area

natural tracer profiles across argillaceous formations argillaceous formations generally act as aquitards because of their low hydraulic conductivities this property together with the large retention capacity of clays for cationic contaminants has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste in several countries programmes are under way to characterise the detailed transport properties of such formations at depth in this context the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large scale and long term transport behaviour of these formations here tracer profile data obtained by various methods of pore water extraction for nine sites in central europe are compiled data at each site comprise some or all of the conservative tracers anions cl br water isotopes delta 18 o delta 2 h and noble gases mainly he based on a careful evaluation of the palaeo hydrogeological evolution at each site model scenarios are derived for initial and boundary pore water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites using transport parameters derived from laboratory or in situ tests the comprehensive results from this project have been reported in mazurek et al 2009 here the results for three sites are presented in detail but the conclusions are based on model interpretations of the entire data set in essentially all cases the shapes of the profiles can be explained by diffusion acting as the dominant transport process over periods of several thousands to several millions of years and at the length scales of the profiles transport by advection has a negligible influence on the observed profiles at most sites as can be shown by estimating the maximum advection velocities that still give acceptable fits of the model with the data the advantages and disadvantages of different conservative tracers are also assessed the anion cl is well suited as a natural tracer in aquitards because its concentration varies considerably in environmental waters it can easily be measured although the uncertainty regarding the fraction of the pore space that is accessible to anions in clays remains an issue the stable water isotopes are also well suited but they are more difficult to measure and their values generally exhibit a smaller relative range of variation chlorine isotopes delta 37 cl and he are more difficult to interpret because initial and boundary conditions cannot easily be constrained by independent evidence it is also shown that the existence of perturbing events such as the activation of aquifers due to uplift and erosion leading to relatively sharp changes of boundary conditions can be considered as a pre requisite to obtain well interpretable tracer signatures on the other hand gradual changes of boundary conditions are more difficult to parameterise and so may preclude a clear interpretation

a diffusion based interpretation of tetrachloroethene and trichloroethene concentration profiles in a groundwater aquitard analysis of subsurface soil cores from the site of a field scale groundwater remediation experiment at dover air force base delaware has revealed that tetrachloroethene pce and trichloroethene tce contamination extends into an aquitard underlying a groundwater aquifer the site location is well downgradient of the locations of contaminant release and the aquitard contamination is believed to have begun when contaminated groundwater first arrived in the overlying aquifer using independent estimates of sorption and diffusion properties in the aquitard layers mathematical modeling based on diffusion in laminate slabs has been used to make inferences regarding the historical concentration conditions in the overlying aquifer the results suggest that plume arrival occurred within the last two decades with some important differences in the inferred tce and pce plume histories the diffusion model was also applied toward predicting future aquitard concentrations and fluxes under scenarios based on the current condition as a starting point and hypothesized conditions of future groundwater cleanup the results demonstrate how aquitard sampling and diffusion modeling can provide essential information relevant to forensic analysis risk assessment and subsurface cleanup

patterns of early colonising species on eroding to prograding coasts implications for foredune plant communities on retreating coastlines abstract shoreline erosion is predicted to increase as the result of climate change yet the effects on foredune building species and associated dune processes remain poorly understood to predict the response of foredune plant communities to increased erosion we examined the abundance of six early colonising dune building species across 71 beach foredune sites in south east australia the assumption being that those species better adapted to shoreline retreat will be more frequent and have increased abundance on erosional coasts than species lacking the capacity to withstand or re establish following periods of storm induced erosion all species were frequently recorded regardless of the rate of shoreline progradation or erosion which ranged 3 8 to 2 2 m year 1 species presence was not related to erosion rates however there was a significant association between the rate of shoreline change and abundance for some of the studied species variation in traits related to tolerance to salinity and burial and the ability to establish following erosion appear to correspond to the observed patterns of species abundance while this study examined only six species it appears that species that are restricted to zones closer to the spring tide level that have a persistent rather than opportunistic growth history or that are limited in their ability to recolonise following erosion are more likely to be negatively impacted by increased rates of coastal erosion given the association between vegetation and foredune morphology these findings have important implications for the management of sandy coasts

modelling groundwater contamination above the asse 2 medium level nuclear waste repository germany the medium level radioactive waste deposited in the asse 2 salt mine germany has a total activity of 1 2 1015 bq 1 january 2002 the waste lies in a former mining chamber on the 511 m mining level close to the contact between the mesozoic country rock and the zechstein salt dome the mesozoic country rock is strongly faulted but the geometry of the fault pattern is incompletely known two tectonic cases are considered a pessimistic case which assumes that the radioactive source is linked to the surface by a single fault and an optimistic case which assumes that the radioactive source is not connected to any fault at all the potential groundwater contamination by radioactive fluids expelled from the cavity is simulated with the tough2 code for periods of up to 6 000 years when the potential contamination reaches its greatest vertical extent two types of driving forces are considered convergence of the rock salt surrounding the cavity and generation of h2 gas by the corrosion of iron steel and other metallic components of the waste at low o2 fugacities rock salt creep has the greatest potential impact as it leads to a radioactive plume whose 1 bq l activity contour rises up to 240 m below the surface in the pessimistic tectonic case the value of the model for the assessment of the environmental risk is limited the knowledge of the hydrogeological situation is incomplete and the pessimistic tectonic case may not be pessimistic enough for a realistic worst case scenario

evaluation of mineral precipitation potential in a spent nuclear fuel repository in this study the potential for mineral precipitation reactions to occur during the excavation disposal backfilling and closure of a deep geological repository for the final disposal of spent nuclear fuel was evaluated with the assistance of hydrogeochemical modelling four modelling exercises corresponding to the main expectable geochemical scenarios in the excavation damaged zone edz throughout repository evolution were carried out and the times for sealing of the discontinuities owing to mineral precipitation in each of them were evaluated and discussed the simulations show that mineral precipitation reactions are thermodynamically feasible in most of the studied cases the main mineral phases potentially responsible for the hydraulic sealing of the edz are calcite and ferric oxyhydroxides being the estimated volumes occupied by the precipitation of calcite between one and three orders of magnitude larger than the volume of precipitating ferric phases the estimated times for complete sealing of the edz may vary between several hundreds to more than 1 million years the shortest sealing times less than 3 000 years are obtained for the mixture of groundwaters from the repository depth with dilute infiltration waters

patterns of sand transport on vegetated foredunes the aeolian development of coastal foredunes is studied at two sites along the dutch coast amounts of sand transport are measured in cross sections over the foredunes and changes in surface height are monitored sand transport decreases rapidly landward of the vegetation boundary near the dunefoot changes in surface roughness and topography generate turbulence and upward flow causing a small part of the sand to be transported in suspension patterns of transport are found to be closely related to air flow which in turn is related to topography and vegetation density with steeper topography the amounts of sand transported landward from the dunefoot increase if vegetation density is low during oblique onshore winds most of the sand accumulates at the dune front during perpendicular onshore winds a large proportion of the sand is deposited landward of the slope when deflection of flow occurs landward transport of sand is interrupted

theoretical and experimental validation of mining enhanced permeability for simultaneous exploitation of coal and gas simultaneous recovery of coal and methane is a promising solution for making reasonable use of energy resources and preventing gas disasters coal mining produces an effect that enhances the permeability of coal and thus paradoxically enhances the ability to collect methane hence existing knowledge about permeability enhancement needs to be improved therefore a new parameter referred to as mining enhanced permeability is proposed to characterize the evolution of permeability for coal and other rocks a theoretical expression for the new parameter is deduced from the tablet fluid model to analyze the mining enhanced permeability of coal mass quantitatively a laboratory test was conducted to simulate the stress environment of the protected layers in protected coal seam mining at the same time a field test was conducted at a working face of mine no 10 at the pingdingshan coal mining group in china the evolution of the volumetric strain and mining enhanced permeability for both protective and protected layers were analyzed quantitatively the loading induced volumetric strain and permeability enhancement in the laboratory showed improvements of 1 59 and 72 26 respectively the mining induced volumetric strain and permeability enhancement also showed improvements of 0 14 and 7 77 respectively the evolution of enhanced permeability agreed with gas flow data observed in both laboratory and in situ tests namely a higher mining enhanced permeability led to high gas flow demonstrating the plausibility of mining enhanced permeability theory based on the tablet fluid model the theory describes the impact of mining on coal permeability and quantitatively captures the evolution of coal permeability in conclusion the proposed theory provides a strong foundation for designing systems to simultaneously recover coal and gas