a physical basis for the frictional melting of some rock forming minerals abstract under conditions of coseismic slip 0 1 2 0 m s 1 within the upper crust differences in the shear yield strengths fracture toughnesses melting points and to a lesser extent thermal conductivities of rock forming minerals result in a hierarchy of friction melting susceptibilities in many so called pseudotachylytes it is observed that phyllosilicates and amphiboles are preferentially consumed to form the melt phase whilst quartz and feldspar tend to survive as clasts this can be explained in terms of the disequilibrium flash melting of those mineral phases possessing the lower shear yield strengths fracture toughnesses and thermal conductivities rather than by eutectic melting that would otherwise generate equilibrium minimum melts indicative of igneous processes at high strain rates typical of coseismic faulting the mechanical behaviour of minerals is primarily controlled by their fracture toughnesses with progressive comminution during slip leading to fusion the friction melting dependence on the mechanical properties of minerals indicates that there may be an important relationship between wall rock lithology and earthquake magnitude if frictional melting results in fault lubrication

geochemical evolution of groundwater in the cambrian vendian aquifer system of the baltic basin abstract the shallowly buried marginal part of the cambrian vendian confined aquifer system of the baltic basin is characterised by fresh and low 18 o composition water whereas the deeply settled parts of the aquifer are characterized by typical na ca cl basinal brines spatial variation in water geochemistry and stable isotope composition suggests mixing origin of the diluted water of three end members glacial melt water of the weichselian ice age 115 000 10 000 bp na ca cl composition basin brine and modern meteoric water the mixing has occurred in two stages first the intrusion and mixing of isotopically depleted glacial waters with basinal brines occurred during the pleistocene glacial periods when the subglacial melt water with high hydraulic gradient penetrated into the aquifer the second stage of mixing takes place nowadays by intrusion of meteoric waters the freshened water at the northern margin of the basin has acquired a partial equilibrium with the weakly cemented rock matrix of the aquifer

planetary wave modelling of the middle atmosphere the importance of travelling wave components a linerized stationary planetary wave model is applied to mean data for a chosen quiescent winter month december 1979 comparison with observations from the stratosperic sounding unit on board noaa 6 shows that both the amplitude and height of propagation of wavenumber one are significantly underpredicted this behaviour is not substantially modified by extension to more sophisticated model formulation and representation of dissipative processes it is shown that the response to forcing varies appreciably with travelling wave frequency even at periods greater than one month and it is suggested that this sensitivity is a significant limitation on the applicability of stationary wave models based only on time mean behaviour

hydrological factors in the interpretation of stable isotopic proxy data present and past a european perspective in the context of this paper stable isotopic proxies are those preserving directly or via known or calculable fractionation factors a record of 18o 16o and or 2h 1h in the water which contributed to their growth suitable proxies include amongst others tree ring cellulose bone phosphate lake sediment minerals and speleothem fluid inclusions a principal aim of studying isotopic proxies is to gain more information about past climates through a knowledge of how rainfall isotope compositions have changed over time however converting back from proxy to rainfall is not necessarily straightforward because however well the isotopic fractionation due to proxy growth or formation is understood a variety of modifying processes may have intervened between this and the actual rainfall events three main reservoirs of environmental water may contribute to the isotopic compositions of terrestrial proxy indicators surface waters soil moisture and groundwater each of these can in principle be isotopically modified compared to rainfall in the locality this review examines these effects and how they may change under different european climate types at the present day it is concluded that while groundwater isotopic compositions typically represent closely the bulk composition of rainfall under a variety of climatic regimes soil and particularly lake waters require detailed study if their isotope systematics are to be adequately understood the review also finds that to a large extent the present is the key to the past in terms of recharge processes during the late pleistocene though glaciation may have had profound isotopic consequences in certain areas while a more general aridity led to the apparent absence of recharge in most areas for much of the late devensian

selective melting processes as inferred from experimentally generated pseudotachylytes abstract high speed friction experiments have been conducted on gabbros and granites to better constrain the process of frictional melting during seismogenic fault motion experiments were done on cylindrical specimens of 25 mm in diameter under a normal stress of 1 0 1 5 mpa and at slip rates up to 2 m s using a rotary shear high speed frictional testing machine the experimentally generated pseudotachylytes consist of a fused glassy matrix with abundant vesicles and angular or sub angular to rounded fragments these locally occur as injected network veins in the fractured rock x ray diffraction analysis has revealed the presence of as much as 40 70 wt glass the mineral contents of clasts in the experimental pseudotachylyte in granite as determined by x ray diffraction analysis indicate that quartz is the most resistant to melting biotite the least and feldspar is intermediate thus the sio2 depletion in natural pseudotachylyte glass is likely to be due to the selective melting of constituent materials during frictional melting

redox zonation and organic matter oxidation in palaeogroundwater of glacial origin from the baltic artesian basin abstract ordovician cambrian aquifer system o cm in the northern part of the baltic artesian basin bab estonia is part of a unique groundwater reservoir where groundwater originating from glacial meltwater recharge from the scandinavian ice sheet is preserved the distribution of redox zones in the anoxic o cm aquifer system is unusual strongly reducing conditions are found near the modern recharge area characterized by low concentrations of sulphate

microstructural and chemical changes associated with cataclasis and frictional melting at shallow crustal levels the cataclasite pseudotachylyte connection in pelitic schists of the nason terrane of washington state pseudotachylyte can be demonstrated to have developed subsequent to the formation of foliation parallel cataclasite zones numerous microstructural lines of evidence point to a genetic link between pseudotachylyte and cataclasite and chemical evidence indicates that cataclasis played an important role in controlling pseudotachylyte chemistry besides optical and textural differences between the cataclasite and pseudotachylyte which may occur together there is unambiguous evidence of a melt origin for the pseudotachylyte while such evidence within the cataclasite is absent tem evidence indicates that glass is present in at least some of the veins as demonstrated by a lack of electron diffraction microlites present in the glass lack dislocations high temperature microlites of a mineralogy and composition not present in the host schist occur in various habits which depend on the distance from the vein margin also present are assimilation textures apparently quenched sulfide droplets and vesicles and amygdules in a pseudotachylyte vein studied in detail five microstructural domains occur these include vein margin cataclasite a transitional dark pseudotachylyte vein interior glass opaque and sulfide rich blebs and translucent haloes surrounding some of the blebs the cryptocrystalline cataclasite matrix grades into the dark pseudotachylyte which optically grades into the glass after adjustment for silica the host schist and cataclasite matrix are chemically very similar the dark pseudotachylyte and glass with the exception of na2o and cao are chemically quite similar to the cataclasite matrix the main difference may be the result of the segregation of the opaque plagioclase blebs thus the pseudotachylyte chemistry is strongly dependent upon the chemistry of the material comprising the cataclasite matrix which in turn is dependent on mineral susceptibility to incorporation into the cataclasite matrix fluids infiltrated along the cataclasite zones prior to pseudotachylyte generation as recorded by hydration reactions sulfide veining na2o loss and fluid inclusions this demonstrates that pseudotachylytes can form under fluid rich conditions as opposed to the commonly assumed dry conditions

reconstruction of past climate conditions over central europe from groundwater data abstract here we present a 30 000 years low resolution climate record reconstructed from groundwater data the investigated site is located in the bohemian cretaceous basin in the corridor between the scandinavian ice sheet and the alpine ice field noble gas temperatures ngt obtained from groundwater data preserved multicentennial temperature variability and indicated a cooling of at least 5 7 c during the last glacial maximum lgm this is further confirmed by the depleted 18 o and 2 h values at the lgm high excess air ne at the end of the pleistocene is possibly related to abrupt changes in recharge dynamics due to progression and retreat of ice covers and permafrost these results agree with the fact that during the lgm permafrost and small glaciers developed in the inner valleys of the giant mountains located in the watershed of the aquifers a temporal decrease of deuterium excess from the pre industrial holocene to present days is linked to an increase of the air temperatures and probably also to an increase of water pressure at the source region of precipitation over the past few hundred years

subglacial hydrology in north western germany during the last glaciation groundwater flow tunnel valleys and hydrological cycles abstract numerical modelling of groundwater dynamics in an overpressured system of subglacial aquifers and aquitards under the marginal portion of the scandinavian ice sheet in northwestern germany has been coupled with calculations of basal meltwater production rates and with field evidence of meltwater erosional features largely fine grained subglacial sediments with relatively low hydraulic conductivities had a capacity to drain only about 25 of all basal meltwater produced in the relevant subglacial catchment area the rest of the meltwater was evacuated through tunnel valleys in spontaneous outburst events subglacial drainage cycles are proposed in which each cycle begins with meltwater drainage through the substratum groundwater flow followed by water ponding at the ice bed interface and ends in catastrophic meltwater releases through tunnel valleys

understanding the salinisation process for groundwater in an area of south eastern australia using hydrochemical and isotopic evidence abstract increases in groundwater salinity down gradient are a common occurrence in catchments throughout australia exacerbating the effects of dryland salinisation in discharge areas groundwater hydrochemical and isotopic data from the willaura catchment in south eastern australia which is affected by both primary natural and secondary human induced salinity allowed the factors that cause the down gradient trend in salinisation within this catchment to be determined the overall salinity of the groundwater 0 8 70 ms cm is controlled by evapotranspiration which concentrates cyclic salts in the unsaturated zone greatly increasing the salinity of the soil water to 3700 6400 mg l cl the progressive addition of this saline soil water to fresher groundwaters recharged on the catchment margins causes a gradual increase in salinity down gradient the groundwater stable isotope compositions show that most recharge occurs in winter and spring groundwater salinities increase around the saline lakes of the discharge zone due to direct evaporation from shallow watertables and minor dissolution of halite as indicated by cl br ratios mineral water interactions within the aquifers cause a slight overall reduction in salinity conversion of kaolinite to smectite and illite and cation exchange of na for ca2 on smectites cause na cl mg2 cl k cl si cl and hco3 cl ratios to progressively decline and ph to gradually increase down gradient oxidation of organic matter causes a strong decrease in the redox potential of the groundwaters down gradient the groundwater ages increase from modern containing tritium on the catchment margins to 8000 years based on 14c dating at the end of the 25 km flow path the older groundwaters are isotopically heavier than the younger waters probably due to recharge during a wetter climate in the early holocene the groundwater ages show clearly that the progressive addition of saline soil water causing groundwaters to become more saline down gradient has occurred throughout the holocene and may explain the occurrence of primary salinisation within many australian catchments

mis 3 mammoth remains from sweden implications for faunal history palaeoclimate and glaciation chronology the distribution of low arctic megafaunal remains in time and space from the area previously covered by the scandinavian ice sheet sis suggests the presence of breeding mammoth populations in the circum baltic region during the time interval from 44 to 26 ka ago the transport history of 30 mammoth teeth and bones from southern and north central sweden was estimated and the remains were subjected to osteological analyses and 14c dating oxygen isotope analyses of tooth enamel indicate a palaeoclimate considerably more homogenous than that experienced in sweden today showing moderate north south gradients in the d18o value of precipitation and temperature in general the results support the model of restricted ice sheet distribution during the second half of the middle weichselian the clear discrepancy in the inferred absence of glaciation in the central swedish uplands and the baltic basin as evidenced by the swedish mammoth data versus the danish osl based glaciation chronology in the period from 40 to 30 ka ago is discussed in the light of radiocarbon calibration and glacial dynamics r 2007 published by elsevier ltd less

sudbury breccia at whitefish falls ontario evidence for an impact origin sudbury breccias are unusual clast matrix rock bodies formed in abundance around the sudbury igneous complex the most obvious manifestation of a major impact event at sudbury at whitefish falls 70 km southwest of sudbury similar breccias consisting of clasts of argillite and amphibolite dyke enclosed in a fine grained matrix of host rock are developed in metamorphosed argillites of the huronian supergroup pre brecciation brittle textures in the host argillite and breccia clasts such as layer parallel foliation offset by cataclastic fractures suggest that the host rock was entirely competent prior to brecciation one composite penetrative foliation and its associated ductile folding were also formed in the argillite host prior to brecciation post brecciation ductile deformation produced a regionally dominant east west trending foliation and two late stage folding events and indicate a syn penokean age of brecciation the breccias at whitefish falls are enriched in ferromagnesian minerals compare

tunnel valley formation in northwest germany geology mechanisms of formation and subglacial bed conditions for the bornhoved tunnel valley the bornhoved tunnel valley consists of a relatively broad elongated depression filled primarily with tills and a narrow channel in the axial part filled with outwash glaciolacustrine sediments and tills the tunnel valley is at least 13 km long 222 m deep bottom at 191 m b s l and extends parallel to the axis of a peripheral sink between two permian salt diapirs in the substratum it is suggested that the initiation of the tunnel valley was controlled by a differential response of the bed materials to ice overriding on top of and between the salt structures the bornhoved tunnel valley is a polygenetic feature that resulted from different erosional processes throughout all three main glaciations in northern germany during the elsterian glaciation glaciotectonic squeezing occurred to be later replaced by subglacial meltwater erosion during the ice retreat and the holsteinian interglacial the valley was filled with fine grained glaciolacustrine and marine sediments which were subsequently removed and redeposited further down ice as a 200 m thick glaciotectonic melange by the first saalian advance the second saalian advance caused only minor changes and the tunnel valley was reactivated as a subglacial channel during the weichselian glaciation it is suggested that at the time of the first weichselian ice advance a large subglacial water reservoir developed in the area of the baltic sea basin and caused a rapid surge like ice movement as the ice sheet advanced out of the baltic sea basin drainage of the water reservoir was prevented by the ice toe overriding the permafrost on the saalian highlands during the ice retreat frozen ground was left beyond the ice margin and subglacial meltwater catastrophically drained through the tunnel valley with a discharge roughly estimated at about 3 75 103 m3 s it seems possible that drainage of the subglacial water collector through the bornhoved tunnel valley and other similar channels south of the baltic sea led to increased ice sheet basal friction and was one reason for successively smaller extents of the subsequent weichselian advances evidence against pervasively deforming bed materials in the vicinity of the bornhoved tunnel valley in the weichselian glaciation indicates that the valley served as an efficient drainage path for porewater from the subglacial sediments

using 81kr and noble gases to characterize and date groundwater and brines in the baltic artesian basin on the one million year timescale abstract analyses for 81 kr and noble gases on groundwater from the deepest aquifer system of the baltic artesian basin bab were performed to determine groundwater ages and uncover the flow dynamics of the system on a timescale of several hundred thousand years we find that the system is controlled by mixing of three distinct water masses interglacial or recent meteoric water 18 o 10 4 with a poorly evolved chemical and noble gas signature glacial meltwater 18 o 18 with elevated noble gas concentrations and an old high salinity brine component 18 o 4 5 90 g cl l with strongly depleted atmospheric noble gas concentrations the 81 kr measurements are interpreted within this mixing framework to estimate the age of the end members deconvoluted 81 kr ages range from 300 ka to 1 3 ma for interglacial or recent meteoric water and glacial meltwater for the brine component ages exceed the dating range of the atta 3 instrument of 1 3 ma the radiogenic noble gas components 4 he and 40 ar are less conclusive but also support an age of 1 ma for the brine based on the chemical and noble gas concentrations and the dating results we conclude that the brine originates from evaporated seawater that has been modified by later water rock interaction as the obtained tracer ages cover several glacial cycles we discuss the impact of the glacial cycles on flow patterns in the studied aquifer system

sudbury type breccias in the huronian gowganda formation near whitefish falls ontario products of diabase intrusion into incompletely consolidated sediments sudbury breccias are commonly attributed to meteoritic impact at about 1 85 ga in the vicinity of the sudbury igneous complex in the whitefish falls area about 75 km southwest of sudbury similar

carbon isotope systematics of the cambrian vendian aquifer system in the northern baltic basin implications to the age and evolution of groundwater groundwater in the cambrian vendian aquifer system has a strongly depleted stable isotope composition 18o values of about 22 and a low radiocarbon concentration which suggests that the water is of glacial origin from the last ice age the aim of this paper was to elucidate the timing of infiltration of glacial waters and to understand the geochemical evolution of this groundwater the composition of the dissolved inorganic c dic in cambrian vendian groundwater is influenced by complex reactions and isotope exchange processes between water organic materials and rock matrix the 13c composition of dissolved inorganic c in cambrian vendian water also indicates a bacterial modification of the isotope system the corrected radiocarbon ages of groundwater are between 14 000 and 27 000 radiocarbon years which is coeval with the advance of the weichselian glacier in the area

roundness of clasts in pseudotachylytes and cataclastic rocks as an indicator of frictional melting abstract we examine the roundness rd of clasts derived from fault rocks and discuss its possible application as an indicator for fracturing and chipping or frictional melting the roundness of quartz and feldspathic clasts derived from four frictional melting originated pseudotachylytes and one crushing without melting originated pseudotachylyte as well as three cataclastic rocks was measured between 230 and 270 clasts 10 m in size were measured for each sample the analyses show that rd is lower than 0 4 in all the clasts included in the cataclastic rocks and crushing originated pseudotachylyte whereas it varies from 0 1 to 1 0 and 35 90 of clasts have a roundness 0 4 in the melting originated pseudotachylyte it is suggested that the clasts having a roundness 0 4 were rounded by frictional melting rather than by fracturing or chipping in pseudotachylytes and that the roundness of clasts may be used as a special index of disintegration attributed to attrition and melting

friction melt distribution in a multi ring impact basin it is generally accepted that multi ring basins are the consequence of very large impacts but the mechanism by which they form is still a matter of contention1 2 most of what is currently known about multi ring basins is based on remote studies of the moon3 5 and to a lesser extent mars and mercury4 6 but at least two multi ring impact basins have been recognized on earth7 the sudbury8 canada and vredefort9 south africa impact structures providing an opportunity to study their properties directly here we describe the distribution of friction melt pseudotachylyte in the floor of the sudbury impact basin although the veins and dykes of pseudotachylyte decrease in both thickness and frequency of occurrence towards the basin periphery the greatest volumes of friction melt appear to define four rings around the central impact melt sheet field evidence indicates that the rings originated as zones of large displacement which facilitated localized frictional melting of the basin floor during the modification collapse stage of the cratering process by analogy we argue that the rings of other multi ring impact basins are also likely to be the remnants of such large displacement fault zones

mechanisms of subglacial groundwater recharge as derived from noble gas 14c and stable isotopic data abstract noble gas stable isotope and 14c data from samples collected along groundwater flow path within a confined paleozoic aquifer in northeastern wisconsin usa are used to deduce the effect of the laurentide ice sheet lis on the underlying groundwater and its recharge dynamics during the last glacial maximum the investigated area was near the center of the green bay lobe of the lis 14c ages that extend to 26 k a and low 18o derived temperatures during the time that the lis was present indicate that aquifer recharge continued when ice covered the area 18o values as low as 17 5 and 2h values as low as 127 7 indicate that a significant portion of aquifer recharge was derived from glacial meltwater that maintained its glacial isotopic signature during melting and subsequent recharge noble gas temperatures that remain above freezing at a constant 3 c unusually high excess air ne values and noble gas fractionation patterns indicate that recharge occurred across a very dynamic water table located within the ice sheet this englacial hydrologic system experienced recharge heads of as much as 7 8 m evidence for direct recharge of basal meltwater into the aquifer is not seen to the authors knowledge this is the first time that noble gas and isotope tracers have been used to deduce the provenance of aquifer water beneath continental ice sheets

evolution of groundwater systems at the european coastline an overview is given of the status and origin of fresh and saline groundwaters in the sedimentary aquifers at or near the present european coastline results are presented as six regional maps summarizing as far as possible the conditions likely to have existed at the end of the pleistocene after the impact of glaciation when groundwaters might be expected to have reached their maximum offshore evolution prior to the encroachment of sea water during the holocene marine transgression in the eastern baltic the groundwater evolution was different to other european regions in that freshwater heads were higher than the present day promoting recharge during much of the late pleistocene near the north sea coasts there is generally evidence of freshwater movement to depths of 100 150 m but the absence of deeper freshwater palaeowater storage may relate to the low hydraulic gradients in the north sea basin in the southeastern part of the north sea brackish palaeowater is found between tertiary marine sediments c 300 m below the island of rcmo l 0 km off the danish west coast freshwater of pleistocene and holocene ages is found in aquifers at the english channel coast in several areas to depths in excess of 300 m offshore flow in the late pleistocene took place towards the central palaeovalley and some of this groundwater may be preserved off the present coastline in the two atlantic coastal areas of france and portugal spain a contrast exists due to the proximity of the continental margin and different hydraulic gradients in portugal freshwaters are found at the coastline and probably offshore that contain evidence of recharge during the lowered sea levels in most of the southwestern atlantic coast of spain fresh recent groundwater discharges along and beyond the coastline while in the old estuary of the guadalquivir river saline holocene water still encroaches the sediments on the mediterranean coast of france and spain some salinity encroachment took place during sea level rise in most of the spanish aquifers fresh recent groundwater has substituted for palaeowater except for the low lying areas ebro delta inca sa pobla plain where brackish holocene water is still present

pleistocene hydrology of north america the role of ice sheets in reorganizing groundwater flow systems 1 while the geomorphic consequences of pleistocene megafloods have been known for some time it has been only in the past 2 decades that hydrogeologists and glaciologists alike have begun to appreciate the important impact that ice sheet aquifer interactions have had in controlling subsurface flow patterns recharge rates and the distribution of fresh water in confined aquifer systems across north america in this paper we document the numerous lines of geochemical isotopic and geomechanical evidence of ice sheet hydrogeology across north america we also review the mechanical thermal and hydrologic processes that control subsurface fluid migration beneath ice sheets finite element models of subsurface fluid flow permafrost formation and ice sheet loading are presented to investigate the coupled nature of transport processes during glaciation deglaciation these indicate that recharge rates as high as 10 times modern values occurred as the laurentide ice sheet overran the margins of sedimentary basins the effects of ice sheet loading and permafrost formation result in complex transient flow patterns within aquifers and confining units alike using geochemical and environmental isotopic data we estimate that the volume of glacial meltwater emplaced at the margins of sedimentary basins overrun by the laurentide ice sheet totals about 3 7 104 km3 which is about 0 2 of the volume of the laurentide ice sheet subglacial infiltration estimates based on continental scale hydrologic models are even higher 5 10 of meltwater generated these studies in sum call into question the widely held notion that groundwater flow patterns within confined aquifer systems are controlled primarily by the water table configuration during the pleistocene rather groundwater flow patterns were likely much more complex and transient in nature than has previously been thought because pleistocene recharge rates are believed to be highly variable these studies have profound implications for water resource managers charged with determining sustainable pumping rates from confined aquifers that host ice sheet meltwater

tunnel valleys concepts and controversies a review abstract although erosion of valleys by subglacial meltwater was first proposed more than 100 years ago the processes that produced these valleys under past ice sheets have remained a topic of vigorous debate the most commonly hypothesized mechanisms have included gradual formation by sediment deformation into the incipient valleys under steady state conditions and subsequent transport by meltwater to the ice margin time transgressive formation along a retreating ice margin by drainage of surface meltwater to the bed or release of impounded meltwater behind a marginal permafrost wedge probably catastrophically and rapid erosion during widespread catastrophic basal sheetflood events recent application of new and enhanced imaging techniques has led to the identification of many new tunnel valleys both on land and offshore throughout the regions glaciated during former ice ages in addition new advances in understanding of subglacial hydrology both from modelling and field instrumentation have helped to constrain the drainage of meltwater from past ice sheet beds this work elucidates the role of subglacial groundwater flow systems in evacuating meltwater from the bed but also shows that groundwater flow alone was not enough to maintain ice bed meltwater pore pressures below the level of ice flotation both modelling and field observations indicate that subglacial conduits oriented parallel to glacial flow lines reorganize groundwater flow systems into basins containing lateral flow toward conduits cut upward into the ice or downward into the bed because of the inability of groundwater flow to account for all the meltwater produced by basal melting other drainage mechanisms involving both non channelized and channelized meltwater flow have been proposed the notion of catastrophic drainage of impounded basal meltwater is still favored by many and the discovery of hundreds of subglacial lakes beneath the antarctic ice sheet and the likelihood of similar lakes beneath pleistocene ice sheets provides a source of water for those advocating catastrophic formation for tunnel valleys proponents of catastrophic drainage consider the valleys to be channels reflecting the width and perhaps depths of flows that formed them tunnel valleys produced by the scandinavian ice sheet have been described and mapped on land as well as on the sea bed valleys and networks of valleys some of which are totally buried have been linked to 3 or more glaciations tunnel valley networks from the last weichselian glaciation in denmark can be related to specific ice margins developed during ice retreat in north america most research has focused on tunnel valleys associated with ice margins formed by the last wisconsin glaciation along the southern margin of the laurentide ice sheet

drainage beneath ice sheets groundwater channel coupling and the origin of esker systems from former ice sheets abstract the nature of the drainage system beneath ice sheets is crucial to their dynamic behaviour but remains problematic an experimentally based theory of coupling between groundwater and major channel systems is applied to the esker systems in the area occupied the last ice sheet in europe which we regard as a fossil imprint of major longitudinal drainage channels we conclude that the large scale distribution and spacing of major eskers is consistent with the theory of groundwater control in which esker spacing is partly controlled by the transmissivity of the bed it is concluded that esker patterns reflect the large scale organisation of the subglacial drainage pattern in which channel development is coupled to groundwater flow and to the ice sheet s dynamic regime the theory is then used to deduce basal meltwater recharge rates and their spatial variability from esker spacing in an area in which the ice sheet was actively streaming during its final retreat patterns of palaeo groundwater flow and head distribution and the seasonally varying magnitude of discharge from stream tunnels at the retreating ice sheet margin major channel esker systems appear to have been stable at least over several hundred of years during the retreat of the ice sheet although major dynamic events are demonstrably associated with major shifts in the hydraulic regime modelling suggests that glaciation can stimulate deep groundwater circulation cells that are spatially linked to channel locations with groundwater flow predominantly transverse to ice flow that the circulation pattern has the potential to create large scale anomalies in groundwater chemistry and that the spacing of channels will change through the glacial cycle influencing water pressures in stream tunnels subglacial hydraulic gradients and effective pressure if the latter is reduced sufficiently it could trigger enhanced bed deformation thus coupling drainage to ice sheet movement it suggests the possibility of distinctive phases of sediment deformation and drumlin mobilisation during a glacial cycle

the ribe formation in western denmark holocene and pleistocene groundwaters in a coastal miocene sand aquifer the ribe formation is a regionally extensive miocene sand aquifer that is present in western denmark at depths ranging from 100 to 300 m below ground surface groundwater chemistry and isotope data collected from more than 40 wells show that the ribe formation mainly contains high quality ca bicarbonate type groundwater of holocene age 100 10 000 a bp pleistocene age groundwaters identified on the basis of stable isotopes noble gases and corrected 14c values are present below the island of r0m in discharge areas near the coast and in hydraulically isolated inland areas the groundwater age distribution in the ribe formation was successfully simulated with a numerical groundwater flow model and particle tracking only when the 14c content in groundwater was corrected for both geochemical reactions and diffusion the results indicate that geochemical and physical processes significantly influence the 14c content of groundwater and that the correction factors required for the two processes are of the same magnitude flow modelling results indicate that pleistocene groundwaters were emplaced at depth within the ribe fromation under low base level conditions that prevailed throughout the late pleistocene near the coast these waters are essentially isolated from the present flow system and pleistocene freshwater may be present offshore seismic surveys show that conditions offshore are favourable for the presence of pleistocene freshwater within the ribe formation and other aquifers

latest development of radiokrypton dating a tool to find and study paleogroundwater abstract the study of paleogroundwater on a timescale of several thousands to a million years is interesting both in terms of understanding the aquifer system itself and water resource management it may also provide valuable information about the paleoclimate in their seminal work loosli and oeschger 1969 identified 81kr as an ideal age tracer for paleogroundwater up to one million years old since then radiokrypton dating has been a desirable tool recent developments in the atom trap trace analysis method have made radiokrypton dating available to the earth science community at large in this paper we will show the current status for radiokrypton dating with an emphasis on sample size reduction the latest advancements have allowed analysis with only 20 kg of water moreover we will review selected studies that have been carried out on some large aquifers with old groundwater around the world using this new tool

a u pb age for mineralized nipissing diabase gowganda ontario concordant baddeleyite and rutile analyses from mineralized nipissing diabase at gowganda s castle mine yield a u pb age of baddeleyite is a primary phase of the diabase therefore the age dates the magmatic emplacement the genesis of rutile is less certain rutile could have formed during an episode of alteration veining and ag mineralization in which case the u pb age would also date the secondary event and demonstrate that ag mineralization was related to the nipissing magmatism however a primary magmatic origin of the rutile cannot be completely excluded for now thus the u pb age may not constrain the time of ag mineralization further research is needed to clarify this point

groundwater and climate dynamics derived from noble gas 14c and stable isotope data noble gas data in conjunction with stable isotopes and 14 c ages of groundwater samples from southeastern wisconsin usa indicate a soil cooling of at least 6 5 7 c during the last glacial period compared with modern soil temperatures because stable isotope and excess ne data indicate that none of the samples contains any significant portions of glacial meltwater samples with 14 c ages between 12 and 26 ka b p which is the time when the study area was ice covered most likely infiltrated during short periods of ice retreat or represent recharge containing a significant proportion of precipitation rather than subglacial meltwater recharge further all samples except for those recharged before the last glacial period show a strong correlation between noble gas temperature and 18 o by contrast 18 o values of samples older than ca 28 ka b p are too heavy with respect to their noble gas temperatures this might be due to a stronger influence of an isotopically enriched moisture source from the gulf of mexico the amount of excess air which is closely linked to the magnitude of groundwater table fluctuations increases shortly before and at the beginning of the last glacial period suggesting that recharge dynamics changed considerably during that time period

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

dating of glacial palaeogroundwater in the ordovician cambrian aquifer system northern baltic artesian basin abstract the ordovician cambrian aquifer system in the northern baltic artesian basin contains glacial palaeogroundwater that originates from the scandinavian ice sheet that covered the study area in the pleistocene previously no absolute dating of this palaeogroundwater has been attempted in this multi tracer study we use 3h 14c 4he and stable isotopes of water to constrain the age distribution of groundwater we apply the geochemical modelling approach developed by van der kemp et al 2000 and blaser et al 2010 to calculate the theoretical composition of recharge waters in three hypothetical conditions modern glacial and interstadial for 14c model age calculations in the second phase of the geochemical modelling the calculated recharge water compositions are used to calculate the 14c model ages using a series of inverse models developed with netpath the calculated 14c model ages show that the groundwater in the aquifer system originates from three different climatic periods 1 the post glacial period 2 the late glacial maximum lgm and 3 the pre lgm period a larger pre lgm component seems to be present in the southern and north eastern parts of the aquifer system where the radiogenic 4he concentrations are higher from 3 0 10 5 to 5 5 10 4 cc g 1 and the stable isotopic composition of water is heavier 18o from 13 5 to 17 3 glacial palaeogroundwater from the north western part of the aquifer system is younger and has 14c model ages that coincide with the end of the lgm period it is also characterized by lower radiogenic 4he concentrations 2 0 10 5 cc g 1 and lighter stable isotopic composition 18o from 17 7 to 22 4 relations between radiogenic 4he and 14c model ages and between radiogenic 4he and cl concentration show that groundwater in the aquifer system does not have a single well defined age rather the groundwater age distribution has been influenced by mixing between waters originating from end members with strongly differing ages overall the results suggest that in the shallower northern part of the aquifer system significant changes in groundwater composition can be brought about by glacial meltwater intrusion during a single glaciation however multiple cycles of glacial advance and retreat are needed to transport glacial meltwater to the deeper parts of the aquifer system

occurrences of pseudotachylyte at the east bull lake and shakespeare dunlop intrusions ontario canada pseudotachylyte bodies were recently identified within and adjacent to the early proterozoic east bull lake and shakespeare dunlop intrusions located approximately 25 40 km west southwest of the western margin of the sudbury igneous complex these breccia like bodies locally form extensive vein networks and are preferentially developed along the contact between the intrusions and older archean granitoid rocks the pseudotachylyte veins comprise variable proportions of locally derived rock fragments and an aphanitic to fine grained crystalline matrix that commonly displays flow textures the veins appear to have formed by intense cataclasis and or frictional melting these occurrences are very similar in appearance to sudbury breccia dykes that are observed at a radial distance of up to 80 km from the sudbury igneous complex sudbury breccia is widely believed to have formed as a result of the sudbury event a cataclysmic explosion that occurred at 1 85 ga the location of the pseudotachylyte veins descr

groundwater flow under a paleo ice stream of the scandinavian ice sheet and its implications for the formation of stargard drumlin field nw poland

sulphur isotope composition of dissolved sulphate in the cambrian vendian aquifer system in the northern part of the baltic artesian basin abstract the groundwater in the cambrian vendian aquifer system with its 18 o water values of about 22 vsmow and a low radiocarbon concentration is of glacial origin from the last ice age earlier surveys have highlighted a negative co variance of sulphate and bicarbonate content in the groundwater of the cambrian vendian aquifer system whereas the most depleted dissolved inorganic carbon 13 c values have been measured mainly in groundwater samples with the lowest sulphate concentrations in this paper we studied the origin of sulphate and the factors controlling the sulphur and carbon isotope geochemistry in the aquifer system direct sources of sulphate were not found but relying upon 18 o so 4 measurements we suggest that the sulphate originates from oxidation of sulphide minerals whereas the 34 s of the dissolved so 4 2 in the groundwater is more enriched than the 34 s of the surrounding rocks we show that bacterial activity may have caused the enrichment of 34 s of sulphate

the interglacial glacial cycle and geochemical evolution of canadian and fennoscandian shield groundwaters abstract results from cryogenic column experiments are compared with the geochemical data collected in the canadian and fennoscandian shields over the past 25 years to investigate the relative influence of the glacial interglacial cycle specifically the impact of continental glaciers permafrost and methane hydrate on the evolution of groundwater from crystalline shield environments several different geochemical indicators of freezing processes either glacial or permafrost related were utilized comparisons of na cl and br cl ratios 18 o and 2 h values and 18 o values and cl concentration during freezing fluids with different dominant cations follow distinctly different linear trends when na cl and br cl ratios are compared significantly none of the freezing trends follows the trend hypothesized by herut et al 1990 for the evolution of seawater chemistry during freezing intrusion of glacial meltwater and in situ freezing i e permafrost formation result in a similar end member when comparing 18 o values and cl concentration the geochemical influence of a freezing process on fresh brackish and some saline fluids was identified at some but not all canadian shield sites regardless of site location with respect to modern day permafrost appreciably physical and geochemical data do not support the formation of brines through any freezing process in the canadian and fennoscandian shields as hypothesized by starinsky and katz 2003 rather on all diagnostic freezing plots brines are an end member indicating a different evolutionary pathway significant depletions in 18 o with respect to modern precipitation an indication of either glacial meltwater or a freezing process were identified at depths of up to 1 km at some sites in the canadian shield and to shallower depths in the fennoscandian shield the potential of this fluid to reach such depths could be attributable to artificial gradients and mixing glacial recharge permafrost or paleo permafrost formation or methane hydrate or paleo methane hydrate formation at most locations it was not possible to distinguish between the different scenarios using the current geochemical database

melt origin of fault generated pseudotachylytes demonstrated by textures a petrographic and electron microprobe study of fault generated pseudotachylytes from the outer hebrides thrust zone scotland demonstrates that the textures have resulted from the primary crystallization of a clast laden melt rather than the devitrification of a glass or by crushing and cataclasis the observations are consistent with these pseudotachylytes having formed by frictional fusion followed by rapid quenching implying faulting at shallow crustal depths

using stable isotopes to characterize the conditions of groundwater formation on the eastern slope of the baltic shield nw russia abstract repeated continental glaciations and marine transgressions had a strong influence on the geochemical evolution of groundwater systems of the eastern slope of the baltic shield arkhangelsk region russia the spectrum from modern fresh waters to very old brines is distributed from the surface to a depth of 1 km in quaternary and vendian ediacaran sediments the purpose of this study was to i assess the isotopic composition of various types of groundwater ii assess the degree of participation of glacial melt and meteoric waters in the processes of dilution of seawater and brines according to isotope geochemical data and iii employ the use of stable isotopes to clarify previously performed groundwater dating it has been established that the salty water in the upper part of the vendian aquifer near the modern sea coast has maximum enrichment by heavy isotopes 18o 7 7 and 2h 98 9 on average it is a mixture of 19 51 glacial meltwater and 49 81 seawater the age of the marine component is 115 130 ka and the age of the glacial water is similar to that of the middle pleistocene the relict brackish water in the middle part of the vendian aquifer has the most depleted isotope composition 18o 14 1 and 2h 106 7 on average it is a mixture of 3 brine 8 19 glacial and 78 89 interglacial water and was formed in the range of 35 3 22 3 ka late pleistocene the maximum brine content 10 17 is characteristic of salt water in the lower part of the vendian aquifer the isotope composition of the fresh water is close to the weighted annual composition of modern precipitations 18o 13 2 and 2h 98 9 fresh water is a mixture of about 2 seawater up to 16 glacial water and 84 100 holocene water the age of this water is in the range from the present day to 11 8 1 6 ka the maximum depth of penetration of melt glacial waters of the middle pleistocene is assumed to be 600 m

the recharge of glacial meltwater and its influence on the geochemical evolution of groundwater in the ordovician cambrian aquifer system northern part of the baltic artesian basin abstract the geochemical evolution of groundwater in the ordovician cambrian aquifer system in the northern part of the baltic artesian basin bab illustrates how continental glaciations have influenced groundwater systems in proglacial areas the aquifer system contains water that has originated from various end members recent meteoric water glacial meltwater and relict na cl brine the saline formation water that occupied the aquifer system prior to the glacial meltwater intrusion has been diluted by meltwaters of advancing retreating ice sheets the diversity in the origin of groundwater in the aquifer system is illustrated by a wide variety in 18 o values that range from 11 to 22 5 these values are mostly depleted with respect to values found in modern precipitation in the area the chemical and isotopic composition of groundwater has been influenced by mixing between waters originating from different end members in addition the freshening of a previously saline water aquifer due to glacial meltwater intrusion has initiated various types of water rock interaction e g ion exchange carbonate mineral dissolution

pseudotachylyte petrogenesis constraints from the sudbury impact structure pseudotachylytes and their host rocks from the north range of the 1 85 ga sudbury impact structure have been investigated using analytical scanning electron microscopy electron microprobe analysis and xrf spectrometry the results show that the pseudotachylytes were produced in high speed slip zones by the frictional comminution and selective melting of wall rock lithologies the preferential assimilation of hydrous ferromagnesian phases during frictional melting produced relatively basic melts leaving the more mechanically resistant quartz and to a lesser extent plagioclase as included mineral clasts three distinct assemblages are identified within the pseudotachylytes a pre impact 1 85 ga rock and mineral clasts derived from host lithologies b a syn to immediately post impact 1 85 ga rapidly cooled quartz sanidine labradorite phlogopitic biotite matrix assemblage formed due to crystallization from a melt at 800 900 c and c a post impact 1 85 ga retrograde assemblage which overprints both clasts and matrices field evidence indicates that most pseudotachylyte formed in large displacement fault systems during gravitational collapse of the impact generated transient cavity the sudbury pseudotachylytes like endogenic pseudotachylytes were generated by frictional melting on fault surfaces the difference is primarily one of scale large km displacements occurring on impact induced ring faults can generate immense volumes of friction melt resulting in spectacular pseudotachylyte bodies up to 0 5 km thick and more than 10 km long

barium anomaly in the cambrian vendian aquifer system in north estonia a barium anomaly with a maximum ba2 concentration of 6 37 mg l was distinguished in a cambrian vendian cm v aquifer system that is widely used as a drinking water source in the towns kunda rakvere and kohtla jarve of north estonia the modelling results show that at low sulphate concentrations below 3 mg l ba2 contents can exceed the limit values for drinking water such as 2 mg l set by us epa bicarbonate ions in their common concentration range in groundwater cannot limit ba2 at its content below 10 mg l the probable natural sources of the anomaly are the crystalline basement and its weathering zone groundwater in the clayey weathering core is hydraulically connected with the overlying cm v aquifer system thus the upconing of deeper seated groundwater caused by intensive exploitation of wells is possible

transpressive tectonism in the eastern penokean orogen canada consequences for proterozoic crustal kinematics and continental fragmentation abstract results of a structural analysis of archean basement huronian cover and various igneous rocks in the sudbury area ontario and regional tectonometamorphic correlations suggest that structures in the eastern penokean orogen formed dominantly by dextral transpression bulk horizontal shortening started with the ca 2 4 to 2 2 ga blezardian orogeny and was accompanied by peak metamorphism and local granitoid magmatism during the 1 89 to 1 83 ga penokean orogeny horizontal dextral shear parallel to the curved axis of the eastern penokean orogen gained in importance and is most likely related to docking of proterozoic magmatic arc terranes to the superior province margin this tectonic activity led to distributed heterogeneous deformation of archean basement rocks and exhumation of deep crustal rocks in the sudbury area and the kapuskasing structural zone but may have failed to accrete paleoproterozoic terranes in the lake huron area the lack of evidence for horizontal extension following blezardian and penokean contraction suggests that crustal fragmentation of the archean supercontinent started at 2 45 ga finally the great lakes tectonic zone and the murray fault master dislocations in the penokean orogen may have acted as crustal weakness zones which influenced the orientation and development of 1 1 ga midcontinent rift segments

regional cross section of the southern province adjacent to lake huron ontario implications for the tectonic significance of the murray fault zone the southern province in the lake huron area of ontario and the penokean fold belt of minnesota wisconsin and michigan have the earmarks of a collisional orogen the huronian supergroup a southerly facing passive margin sequence was deposited during early aphebian early proterozoic crustal stretching and ocean basin formation along the southern margin of the superior province archean craton it accumulated as four unconformity bounded northerly tapering onlapping clastic wedges megacycles the thickness and facies variations reflect syndepositional down to the basin south normal faulting that controlled the accumulation and preservation of the lower three huronian megacycles these are overlapped northward by the youngest megacycle an extensive sheet of clastic sediments recording post stretching regional subsidence of the cratonic margin due to cooling and thermal contraction soft sediment folds in the rocks of the youngest megaycycle to the extreme south probably indicate southward slu

hydrogeological implications of glacial landscape evolution at skeiðararsandur se iceland abstract patterns of groundwater recharge and flow in present day and palaeo glacial environments are governed by both geomorphology and subsurface sedimentology this paper assesses the hydrogeological implications of glacial landscape evolution and develops a conceptual model of glacial landscape evolution and hydrogeological interaction the ice marginal zone of skei ararsandur se iceland was selected as a case study of a temperate actively receding glacier landsystem that is affected by both surging behaviour and periodic glacier outburst floods jokulhlaups the groundwater table elevation was measured approximately every 2 5 days throughout two six week summer field seasons in 2000 and 2001 and once in march 2001 using a network of shallow piezometers and hydraulic conductivity was calculated based on grain size distribution analysis of sampled aquifer materials the hydraulic conductivity of the near surface aquifer at the study site spans three orders of magnitude and is highest and most varied in areas inundated by the november 1996 jokulhlaup the shallow water table in the study area responds dynamically to precipitation events with the greatest fluctuation in an enclosed moraine lake basin with a perched aquifer underlain by ice and in a zone of outwash fans proximal to the ice margin the seasonal decline in water table is greatest at the ice margin reflecting the reduced winter recharge from the stagnant ice zone landsystems with morainic relief are associated with localised moraine precipitation fed groundwater systems these localised groundwater systems are superimposed on the intermediate regional scale groundwater systems that discharge further down sandur and offshore and are dominated by the gently sloping geomorphologically uniform outwash plain groundwater fed lakes formed in depressions from ice blocks deposited during jokulhlaups may provide important ecological niches the investigations at this site demonstrate that glacial outburst floods and glacier margin fluctuations produce a suite of sediments landforms and environments that affect the hydrogeological system