the representation of flows to partially penetrating rivers from layered and anisotropic aquifers abstract it has previously been shown that it is possible to represent the flow of water from a homogeneous isotropic aquifer to a river or drain by using a dupuit forcheimer groundwater flow model coupled with equations to calculate the magnitude of the flow to the river this work has now been extended to include anisotropic and layered aquifers results obtained from two dimensional free surface seepage models are used to assess the accuracy of the results from the dupuit forcheimer models it is shown that such models can be used to accurately estimate the flow to a river for a wide variety of situations

the late devensian glaciation along the western margin of the cheshire shroshire iowland the glacial succession in the western part of the cheshire shropshire lowland records the advance coalescence and subsequent uncoupling of irish sea and welsh ice sheets during the late devensian stage during advance a discontinuous sheet of basal till was emplaced across the floor of the region by subglacial lodgement on retreat compression of the irish sea ice sheet against bedrock obstruction generated a zone of supraglacial sedimentation resulting in the creation of the wrexham ellesmere wem whitchurch moraine system and the formation of a wide range of sedimentary environments including ice marginal sandur troughs ice front alluvial fans proglacial ribbon sandur and subglacial ice contact and proglacial lakes the geometry of sedimentary units and their lithologic and geomorphic characteristics display spatially ordered patterns of sediment landform assemblage which show that the statigraphic succession is a response to rapidly changing depositional conditions at a retreating supraglacial ice margin punctuated by minor still stands and ice front oscillations

preseismic hydrogen gas anomalies caused by stress corrosion process preceding earthquakes simultaneous monitoring of he h2 ar n2 ch4 and rn in gas bubbles of groundwater from the 1 500 m deep nagashima well in the active yoro fault zone central japan reveals that three microearthquakes with m 1 6 2 6 in the fault zone are accompanied and preceded by increases of h2 as is a moderately large event with m 5 4 in the same fault zone all the focal distances of the earthquakes are within 25 km no comparable anomalies were seen in the gas species other than h2 we suggest that the selective and preseimic increases of h2 in groundwater gas bubbles are geochemical signals of the earthquake nucleation process of stress corrosion mechanism aseismic slips preceding earthquakes in the active fault zone are likely to have enhanced h2 production by mechanochemical reaction of fractured rock surface with water in pre existing fault planes as groundwater conduits

the history of the major rivers of southern britain during the tertiary the evolution of the drainage system of lowland britain is discussed on the basis of available geological evidence including that from terrestrial sites and that which has more recently become available from offshore exploration of the north sea the english and bristol channels and the irish sea tertiary stratigraphy throws considerable light on landform and river development paleocene destruction of a chalk cover which seems to have been incomplete in western britain was accompanied by basin sedimentation under a tropical climate the major elements the thames solent hampshire proto avon river irish sea river and possibly an early trent river existed almost throughout the cenozoic the influence of atlantic rifting and thermal doming in nw britain appears to have been stronger and more temporally focused than the persistent flexuring that determined and maintained tertiary drainage lines in the se here also the folded mesozoic terrains on the surface contrast with the more dominant block faulted relief of the palaeozoic oldlands the rivers of the se can be shown to have extended or reduced their lengths in response to relative sea level change and gentle warping drainage antecedence the destruction of the solent system and the breaching of the english channel are also evident by contrast the major river systems of the west are now entirely submerged long term stability of the drainage pattern reflects a persistent tectonic regime in the south with a subdued low relief landscape having a weathered regolith and dense vegetation cover meandering river channels and alluvial styles predominated although channel forms varied according to sediment load slope and discharge variability coarse gravel dominated accumulations are rare and localized chemically stable lithologies dominate the clastic component throughout it is apparent that the deeply incised river valleys seen today are related to high predominantly coarse sediment yields encouraged by substantial rapid climate changes in the pleistocene this emphasizes the significance of mechanical compared with chemical weathering for the rate and nature of landscape dissection and the modifications that have arisen as a result of glaciation frost climate weathering rapidly changing climates and sea levels the stratigraphical evidence here reviewed is at variance with older largely geomorphologically based landform evolution models denudational chronology but gives considerable support to the recent proposals emphasizing the significance of paleocene erosion and enduring low relief landscapes and drainage systems evolving alongside fold development during the paleogene given the depobasin evidence now available postulated fluvially active episodes can and must be linked to contemporaneous deposition some at least of the many controversies involving the identity of erosion surfaces the dating of them using only residual deposits and weathering mantles and the selection of particular tertiary episodes as ones of landscape development can now be resolved

the pleistocene succession of the severn estuary a revised model based upon amino acid racemization studies this paper reports the results and stratigraphic implications of amino acid racemization studies of fresh and or inter tidal molluscs from i the important pleistocene sequences of kenn church new blind yeo drain yew tree farm and kenn pier avon county ii the previously undescribed pleistocene beach deposits beneath the llanwern steel mill south wales and iii re prepared and re analysed shells from the th u series dated beach deposits in belle houge cave jersey channel islands these studies indicate the complexity of sea level change in the area in amino acid group ii oxygen isotope stage 5e 120 000 130 000 years bp sea level reached 4 5 m od and possibly 12 m od this episode is correlated with similar group ii beach deposits on the gower coast and freshwater deposits in sw and se britain the data suggest these group ii deposits are different in age from the ipswichian interglacial inter tidal deposits at selsey a group iv age is attributed to freshwater deposits at yew tree farm and kenn pier which collected just above a contemporary sea level or included re worked earlier inter tidal rocky shore faunas these are provisionally correlated with the group iv deposits in the thames estuary at purfleet c 400 000 600 000 years bp since these deposits are thought at post date glacial deposits previously identified at kenn and court hill avon this glacial episode is now regarded as being much older than the wolstonian glacial stage with which it had been correlated previously

palaeogeography europe cut adrift the floor of the english channel provides evidence for two catastrophic floods arising from the drainage of huge glacial lakes in the area of the southern north sea these megafloods made britain what it is today britain became geographically isolated from continental europe when high interglacial seas flooded the shallow english channel and north sea shelf areas but a tenuous link remained the weald artois chalk ridge between southeast england and northwest france just how this isthmus was breached making britain an island has been a matter of conjecture a new bathymetric map of the sea floor may solve the mystery it reveals a large bedrock floored valley containing landforms including grooves and streamlined islands consistent with a megaflood event caused when a rock dam at the dover strait breached draining a large pro glacial lake in the north sea basin

the offshore quaternary sediment bodies of the english channel and its western approaches after a short review of present day surficial sediments on the sea floor of the english channel and its western approaches this paper summarises recent results on the present quaternary sandy accumulations tidal bank systems based on sea floor imaging very high resolution seismic surveys and a few piston cores the english channel a typical funnel shaped tidal shelf is presently starved of terrigenous sediments most of mobile sediments at the sea floor are autochthonous either skeletal carbonates or siliciclastic sands reworked from old littoral deposits or incised valley fills three zones are considered 1 the central and western central channel which is a bedload parting zone characterised by a pebbly lag making up the sole of the quaternary sediments throughout the shelf area 2 the eastern channel a flood dominated area characterised by medium to fine siliciclastic sands mainly of aeolian periglacial origin 3 the western approaches an ebb dominated area with a polygenic sediment cover characterised by coarse carbonate rich gravelly to muddy sands of marine to glaciomarine origin with a diachronous faunal content these sediments are sourced by reworking of a former littoral barrier or incised valley fills the seismic stratigraphy of quaternary sediment accumulations 10 50 m points to the predominant control of tidal dynamics together with the general interplay between the channel morphology and the sea level story the thickest deposits in the eastern channel and western approaches are built up into bank systems whereas the interpretation of the active eastern channel banks finds a general agreement the moribund banks in the western approaches i e the southern celtic banks remains under debate owing to the lack of long cores in our hypothesis both systems were built up during the last post glacial sea level rise the celtic banks would represent the tidal transgressive systems tract whereas the eastern channel banks correspond to the highstand systems tract the architecture of both bank systems is studied from two examples the bassure de baas bank in the eastern channel and the kaiser bank in the western approaches both examples show transgressive features the bassure de baas exhibits from base to top an estuarine mouth barrier a wave erosion surface a shoreface bank and finally a classic tidal bank by contrast the kaiser bank consists of the offshore reworking of fully marine deposits its base would correspond to the amalgamation of the last glacial sea level fall with a strong tidal ravinement surface from base to top the bank underwent tidal bar accretion very large dune field aggradation perched channels incision storm erosion and deposition

dynamic cycles ice streams and their impact on the extent chronology and deglaciation of the british irish ice sheet we present results from a suite of forward transient numerical modelling experiments of the british and irish ice sheet biis consisting of scottish welsh and irish accumulation centres spanning the last glacial period from 38 to 10 ka bp the 3d thermomechanical model employed uses higher order physics to solve longitudinal membrane stresses and to reproduce grounding line dynamics surface mass balance is derived using a distributed degree day calculation based on a reference climatology from mean 1961 1990 precipitation and temperature patterns the model is perturbed from this reference state by a scaled ngrip oxygen isotope curve and the specmap sea level reconstruction isostatic response to ice loading is computed using an elastic lithosphere relaxed asthenosphere scheme a suite of 350 simulations were designed to explore the parameter space of model uncertainties and sensitivities to yield a subset of experiments that showed close correspondence to offshore and onshore ice directional indicators broad biis chronology and the relative sea level record three of these simulations are described in further detail and indicate that the separate ice centres of the modelled biis complex are dynamically interdependent during the build up to maximum conditions but remain largely independent throughout much of the simulation the modelled biis is extremely dynamic drained mainly by a number of transient but recurrent ice streams which dynamically switch and fluctuate in extent and intensity on a centennial time scale a series of binge purge advance retreat cycles are identified which correspond to alternating periods of relatively cold based ice associated with a high aspect ratio and net growth and wet based ice with a lower aspect ratio characterised by streaming the timing and dynamics of these events are determined through a combination of basal thermomechanical switching spatially propagated and amplified through longitudinal coupling but are modulated and phase lagged to the oscillations within the ngrip record of climate forcing phases of predominant streaming activity coincide with periods of maximum ice extent and are triggered by abrupt transitions from a cold to relatively warm climate resulting in major iceberg melt discharge events into the north sea and atlantic ocean the broad chronology of the modelled biis indicates a maximum extent at 20 ka with fast flowing ice across its western and northern sectors that extended to the continental shelf edge fast flowing streams also dominate the irish sea and north sea basin sectors and impinge onto sw england and east anglia from 19 ka bp deglaciation is achieved in less than 2000 years discharging the freshwater equivalent of 2 m global sea level rise a much reduced ice sheet centred on scotland undergoes subsequent retrenchment and a series of advance retreat cycles into the north sea basin from 17 ka onwards culminating in a sustained younger dryas event from 13 to 11 5 ka bp modelled ice cover is persistent across the western and central highlands until the last remnant glaciers disappear around 10 5 ka bp

rapid thinning of the welsh ice cap at 20 19 ka based on 10be ages abstract new 10 be ages from the summits of three mountain areas of north wales reveal a very similar exposure timing as the welsh ice cap thinned after the global last glacial maximum eight bedrock and one boulder sample gave a combined arithmetic mean exposure age of 19 08 0 80 ka 4 2 1 similar exposure ages over a 320 m vertical range 824 to 581 m altitude show that ice cap thinning was very rapid and spatially uniform using the same production rate and scaling scheme we recalculated six published 10 be exposure ages from the nearby arans which also covered a similar elevation range from 608 to 901 m and obtained an arithmetic mean of 19 41 1 45 ka 7 5 1 the average exposure age of all 15 accepted deglaciation ages is 19 21 1 07 5 6 1 the complete dataset from north wales provides very strong evidence indicating that these summits became exposed as nunataks at 20 19 ka this result provides important insight to the magnitude of ice surface lowering and behavior of the welsh ice cap during the last deglaciation that can be compared to other ice masses that made up the british irish ice sheet

controls on groundwater rn 222 concentrations in fractured rock approximately 150 rn 222 analyses from groundwater wells in fractured lithologies of eastern connecticut were made to evaluate the intralithologic and interlithologic variability although there is a control of rn 222 activity in porefluids by uranium radium concentration in the host rock the variability of local rn 222 is dominated by site specific rock properties these are with their contribution to the variability i the specific fracture surface area 10 sup 3 times which is functionally dependent on crack width ii the emission efficiency 10 sup 2 times which is functionally related to the fracture spacing and iii the enrichment of uranium ra 226 on the fracture surface 10 sup 2 times thus the activity of radon in fractured lithologies is difficult to predict and the measurement of radon activity does not uniquely constrain the geometry of the rock or the chemical inhomogeneity

timing of massive fleuve manche discharges over the last 350 kyr insights into the european ice sheet oscillations and the european drainage network from mis 10 to 2 continuous high resolution mass accumulation rates mar and x ray fluorescence xrf measurements from marine sediment records in the bay of biscay ne atlantic have allowed the determination of the timing and the amplitude of the fleuve manche channel river discharges during glacial stages mis 10 mis 8 mis 6 and mis 4 2 these results have yielded detailed insight into the middle and late pleistocene glaciations in europe and the drainage network of the western and central european rivers over the last 350 kyr this study provides clear evidence that the fleuve manche connected the southern north sea basin with the bay of biscay during each glacial period and reveals that fleuve manche activity during the glaciations mis 10 and mis 8 was significantly less than during mis 6 and mis 2 we correlate the significant fleuve manche activity detected during mis 6 and mis 2 with the extensive saalian drenthe substage and the weichselian glaciations respectively confirming that the major elsterian glaciation precedes the glacial mis 10 in detail massive fleuve manche discharges occurred at ca 155 ka mid mis 6 and during termination i while no significant discharges are found during termination ii it is assumed that a substantial retreat of the european ice sheet at ca 155 kyr followed by the formation of ice free conditions between the british isles and scandinavia until termination ii allowed meltwater to flow northwards through the north sea basin during the second part of the mis 6 we assume that this glacial pattern corresponds to the warthe substage glacial maximum therefore indicating that the data presented here equates to the drenthe and the warthe glacial advances at ca 175 160 ka and ca 150 140 ka respectively finally the correlation of our records with odp site 980 reveals that massive fleuve manche discharges related to partial or complete melting of the european ice masses were synchronous with strong decreases in both the rate of deep water formation and the strength of the atlantic thermohaline circulation fleuve manche discharges over the last 350 kyr probably participated with other meltwater sources in the collapse of the thermohaline circulation by freshening the northern atlantic surface water

bayesian modelling the retreat of the irish sea ice stream we present an 8000 year history spanning 650km of ice margin retreat for the largest marine terminating ice stream draining the former british irish ice sheet bayesian modelling of the geochronological data shows the isis expanded 34 0 25 3ka accelerating into the celtic sea to reach maximum limits 25 3 24 5ka before a collapse with rapid marginal retreat to the northern irish sea basin isb this retreat was rapid and driven by climatic warming sea level rise mega tidal amplitudes and reactivation of meridional circulation in the north atlantic the retreat though rapid is uneven with the stepped retreat pattern possibly a function of the passage of the ice stream between normal and adverse ice bed gradients and changing ice stream geometry initially wide calving margins and adverse slopes encouraged rapid retreat 550m a 1 that slowed 100m a 1 at the topographic constriction and bathymetric high between southern ireland and wales before rates increased 200m a 1 across adverse bed slopes and wider and deeper basin configuration in the northern isb these data point to the importance of the ice bed slope and lateral extent in predicting the longer term 1000 a patterns and rates of ice marginal retreat during phases of rapid collapse which has implications for the modelling of projected rapid retreat of present day ice streams copyright 2013 john wiley sons ltd

the first estimation of fleuve manche palaeoriver discharge during the last deglaciation evidence for fennoscandian ice sheet meltwater flow in the english channel ca 20 18 ka ago the fleuve manche english channel palaeoriver represents the largest river system that drained the european continent during pleistocene lowstands particularly during the elsterian marine isotope stage 12 and saalian drenthe mis 6 glaciations when extensive ice advances into the north sea area forced the central european rivers to flow southwards to the bay of biscay ne atlantic numerous long piston cores and high resolution acoustic data from the northern bay of biscay have been correlated using a well constrained chronostratigraphical framework and for the first time allow the estimation of the discharge of the fleuve manche palaeoriver at the end of the last glacial period i e weichselian our results discussed in the light of relationships between river loads and drainage area characteristics strongly suggest that the bay of biscay collected sediment laden meltwater from the northern european lowlands and the southern part of the fennoscandian ice sheet at the end of the last glacial period and particularly during the paroxysmal phase of the european deglaciation ca 20 18 ka ago this demonstrates that the fleuve manche drainage area at that time was equivalent to those dating from the major elsterian and saalian drenthe glaciations based on our data we propose a revision of the palaeogeographical and palaeoglaciological evolution of the north sea area while showing that the british and fennoscandian ice sheets entered the north sea basin until ca 18 ka initiating isostatic adjustment of the basin this allowed the north sea fluvial system to flow southwards through the dover strait finally we discuss the fleuve manche freshwater discharge during the maximum european ice sheet retreat ca 18 ka the estimated discharge at this time appears important and sufficiently sustained to possibly contribute to the profound destabilisation of the thermohaline circulation recognised in the north atlantic from ca 18 to 16 ka

quaternary river terraces in england forms sediments and processes abstract flights of quaternary river terraces in south and east england have common characteristics involving low gradient planed or irregular bedrock surfaces and single or multi storey gravel deposits rather than depending on warm cold or cold warm transitions it is suggested that bedrock planation working depths of gravel and later stage relatively shallow aggradations are all dominantly of cold climate origin basal sediments show active incorporation of plucked and periglacially shattered materials whilst super incumbent units incorporating up catchment and slope derived materials demonstrate later cold stage sediment influx and consequent cessation of active bedrock erosion channel activity effecting both planation and deposition are reviewed together with the detailed sedimentology of gravelly sediments which show evidence of both autogenic processes bar migration channel switching and infilling and truncation of upper sedimentation units cold climate indicators turbation ice wedge casts and frozen block transport and specifically for the last glacial interglacial cycle varying sediment flux as climates changed both interglacial and transitional activities are believed to be of lesser morphological significance whilst prior uplift is taken as enabling rather than being a generator of terrace within the timescale of a glacial interglacial cycle variations within cold stage climates varying sediment influx and channel belt bedrock erosion are stressed as dominating mid catchment and mid latitude quaternary terracing at the glacial interglacial scale

the representation of flows to partially penetrating rivers using groundwater flow models abstract although partially penetrating rivers have been successfully represented in groundwater flow models the assessment of the resistance coefficient in the equation used to calculate the flow between the aquifer and the river has always been a problem various methods have previously been presented but their derivations contain major assumptions in this paper the various methods are reviewed tested and found to be inaccurate a new more accurate method is presented and modifications are made to the existing methods to improve their accuracy finally a practical example of the use of the methods is given which shows that they can be applied to field problems with confidence

amino acid geochronology of raised beaches in south west britain abstract based on 1 the epimerization of l isoleucine to d alloisoleucine d l ratios in patella vulgata littorina littorea l littoralis l saxatilis littorina species and nucella lapillus from raised beaches in south west britain 2 statistical analysis of the d l ratios and 3 lithostratigraphic and geomorphic evaluation three d l stages are proposed the d l ratios for all the species measured are converted to a patella vulgata standard the three d l stages are 1 1 the minchin hole d l stage d l ratios 0 175 0 014 defined at a stratotype in minchin hole cave gower wales 2 2 a provisionally defined but as yet unamed d l stage because of the current unavailability of a suitable stratotype with d l ratios of 0 135 0 014 3 3 the pennard d l stage d l ratios 0 105 0 016 defined at a stratotype in minchin hole cave gower wales two geochronological models of the three high sea level events representing the d l stages are constrained by uranium series age determinations on stalagmite interbedded with marine beds in minchin hole and bacon hole caves gower wales a potential fixed point in model evaluation is an age determination which is equivalent to oxygen isotope sub stage 5e 122 ka the two models are oxygen isotope stage and age ka bp d l stage d l ratio model 1a model 1b model 2 pennard 0 105 0 016 5a ca 80 5e 122 5e 122 5c ca 100 unnamed 0 135 0 014 5e 122 7 194 minchin hole 0 175 0 014 7 186 245 7 186 245 7 216 the ages of the raised beaches are used to constrain the timing and extent of glaciation in the area the extent of the late devensian glaciation is fixed by reference to localities where raised beaches of the pennard d l stage outcrop as well as by using unpublished data on molluscs incorporated into glacial deposits two pre devensian glaciations antedate the minchin hole d l stage the irish sea glaciation of the bristol channel irish sea older drift of south wales fremington till of north devon is ascribed to oxygen isotope 10 or earlier while the paviland welsh glaciation is ascribed to oxygen isotope stage 8 or earlier an earlier glaciation berwyn glaciation is inferred from erratics of known welsh provenance in essex

late flandrian coastal change and tidal palaeochannel development at hills flats severn estuary sw britain an eclectic range of stratigraphical sedimentological geochemical archaeological and historical evidence relating to a tidal palaeochannel exposed at a deep erosional level in the modern intertidal zone on the avon gloucestershire border demonstrates that tidal wetlands reclaimed during the roman period ranged much further seaward than the modern coastline vigorous late medieval early modern erosion linked to the cool disturbed conditions of the little ice age forced the coastline by the mid seventeenth century to a location inland of its present line a possible medieval landing place was destroyed and it was necessary to set back the flood defences as the result of renewed mudflat marsh growth the coast at hills flats has built outward during modern times but in three distinct stages and by no means as far seaward as its likely roman position

age of pleistocene faunas from bacon hole wales at present it is difficult to match british early upper pleistocene vertebrate faunas with the growing evidence for complex climatic change at this time derived from the oceanic oxygen isotope record and from long pollen cores however we report here new analyses of dated faunal assemblages from bacon hole wales which indicate that the ipswichian interglacial fauna dated at 125 kyr bp was followed by a devensian interstadial fauna dated at 81 kyr bp which still supported some supposedly typical inter glacial mammals combined with evidence of an intervening cold fauna from stump cross cave dated at more than 83 kyr bp these indications of complexity in faunal change at the ipswichian devensian transition are more consistent with the oxygen isotope and pollen core data than traditional views

the tectonic evolution of the north celtic sea and cardigan bay basins with special reference to basin inversion abstract the morphology and structural evolution of the north celtic sea basin ncsb and cardigan bay basin cbb are in large part controlled by reactivation of basement features of caledonian and possibly variscan origin from earliest triassic until maastrichtian times sedimentation was almost continuous initially in a rapidly subsiding rift system and finally in a progressive passive sag phase at the onset of the alpine orogeny both basins experienced spectacular inversion along readily identifiable axes the inversion takes the form of a compressive reactivation and reversal of the pre existing growth faults and a broad regional upwarping of the cretaceous depocentre the amount of inversion varies depending on the location within the basin but values in excess of 1000 m are possible by utilising regional seismic data the timing of inversion can be estimated as occurring between maastrichtian and eocene times which correlates with the so called laramide pulse of the alpine orogeny

horizontal and vertical components of flow deduced from groundwater heads abstract this paper which supplements that of connorton 1985 shows how velocity components can be deduced from information about the groundwater head even though the groundwater head remains constant with depth it is possible to estimate both the vertical and horizontal flow components from the groundwater head distribution the accuracy of these calculated flow components can be assessed by comparing with results obtained from solutions in terms of the groundwater potential which is a function of both horizontal and vertical co ordinates examples considered include confined and unconfined aquifers aquifers having a sloping base and time variant behaviour a study of an aquifer with a horizontal band of lower hydraulic conductivity shows that in this situation the groundwater head approximation may not be acceptable

sea level changes in the holocene over the last 30 years the emphasis in studies of the recovery from low last glaciation sea levels has changed significantly the search for a eustatic sea level curve having global relevance has ended studies into the rheology of the earth s crust and recognition that the geoid has not remained stable over time have resulted in the recognition that there must have been regional differences in eustatic response to deglaciation as a part of this re appraisal there has been a growing appreciation that crustal isostatic response to the removal of the weight of ice sheets has been accompanied by a consequential hydro isostatic response particularly in the areas of the shelf seas in the later part of the post war period attention has additionally been focussed on the much greater potential for error over the whole field of palaeoenvironmental reconstruction in the holocene including not only errors in dating but also a large number of possible sources of errors in heighting as a result of this an increasing number of scientists are withholding judgement on the nature of sea level rise and more particularly on the problem of higher than present late holocene eustatic sea levels the problems outstanding in the early 1960s have not yet been resolved but the bases of uncertainty have changed

the quaternary channel river seismic stratigraphy of its palaeo valleys and deeps based on the interpretation of geophysical data very high resolution seismic data combined with em1000 swath bathymetry this paper reviews the history of the channel river throughout the late cenozoic new evidence does illustrate how the interplay of tectonics eustacy and climate have influenced this northwest european drainage system the concepts of sequence stratigraphy allow the subdivision of the sedimentary record into depositional sequences bounded by unconformities resulting from globally synchronous sea level changes however the recognition of eustatic sea level changes in a cold climate environment is very difficult because of the interplay of additional phenomena such as glacio isostatic sea level changes with glacio eustatic changes for our interpretation it was necessary to adjust these concepts with the relative importance of geomorphological processes determining the behaviour of rivers and steering their evolution the foundations of the modern drainage system were laid after the oligocene channel inversion in general these early rivers occupied shallow valleys the pleistocene cold climates resulted in fluvial incision through time the channel river has adopted a drainage system that can be divided into three parts i the drainage basin comprising the southern bight the eastern channel and the london and paris basins ii the river zone itself which begins at the cotentin peninsula and passes through the hurd deep before reaching the continental shelf break in the celtic sea iii the depositional basin represented by the celtic banks complex and by the deep sea fans located at the foot of shamrock and black mud canyons during important lowstands marine oxygen isotope stages 22 16 10 6 and 2 the channel river seems to have reached the shelf break as indicated by the internal structure of the banks copyright 2003 john wiley sons ltd

10be and 26al exposure age dating of bedrock surfaces on the aran ridge wales evidence for a thick welsh ice cap at the last glacial maximum this paper presents results of the analysis of paired cosmogenic isotopes 10be and 26al from eight quartz rich samples collected from ice moulded bedrock on the aran ridge the highest land in the british isles south of snowdon on the aran ridge comprising the summits of aran fawddwy 905 m a s l and aran benllyn 885 m a s l 26al and 10be ages indicate complete ice coverage and glacial erosion at the global last glacial maximum lgm six samples from the summit ridge above 750 800 m a s l yielded paired 10be and 26al ages ranging from 17 2 to 34 4 ka respectively four of these samples are very close in age 10be ages of 17 5 0 6 17 5 0 7 19 7 0 8 and 20 0 0 7 ka and are interpreted as representing the exposure age of the summit ridge two other summit samples are much older 10be ages of 27 5 1 0 and 33 9 1 2 ka and these results may indicate nuclide inheritance the 26al 10be ratios for all samples are indistinguishable within one sigma uncertainty from the production rate ratio line indicating that there is no evidence for a complex exposure history these results indicate that the last welsh ice cap was thick enough to completely cover the aran ridge and achieve glacial erosion at the lgm however between c 20 and 17 ka ridge summits were exposed as nunataks at a time when glacial erosion at lower elevations below 750 800 m a s l was achieved by large outlet glaciers in the valleys surrounding the mountains copyright 2011 john wiley sons ltd

ice sheet extension to the celtic sea shelf edge at the last glacial maximum previous reconstructions of the british irish ice sheet biis envisage ice streaming from the irish sea to the celtic sea at the last glacial maximum to a limit on the mid shelf of the irish uk sectors we present evidence from sediment cores and geophysical profiles that the biis extended 150 km farther seaward to reach the continental shelf edge three cores recently acquired from the flank of outer cockburn bank a shelf crossing sediment ridge terminated in an eroded glacigenic layer including two facies overconsolidated stratified diamicts and finely bedded muddy sand containing micro and macrofossil species of cold water affinities we interpret these facies to result from subglacial deformation and glacimarine deposition from turbid meltwater plumes a date of 24 265 195 cal bp on a chipped but unabraded mollusc valve in the glacimarine sediments indicates withdrawal of a tidewater ice sheet margin from the shelf edge by this time consistent with evidence from deep sea cores for ice rafted debris peaks of celtic sea provenance between 25 5 and 23 4 ka bp together with terrestrial evidence this supports rapid ca 2 ka purging of the biis by an ice stream that advanced from the irish sea to the shelf edge and collapsed back during heinrich event 2

radon in groundwater as a tracer to assess flow velocities two test cases from israel two test cases from israel are presented herein employing the decay rate of radon along the flow path to assess groundwater flow velocities groundwater flow reaching the fault zone emerges in several places along the rift fault zone as thermal springs because of deep water confinement the high water temperature of the surface is indicative of high vertical flow velocities which maintains the original high temperatures knowing the rn content at a source point and at a given down gradient and assuming no rn addition from the water itself or along the flow path one can calculate the flow velocity based on the rn half life time the decay of rn in western galilee was found to be 570 150 pci l and in the dead sea area from 5000 2000 pci l along a respective flow path of 1000 and 200 m based on the above the calculated flow velocities were compared with those obtained from pumping tests in the study area the method is applicable because of the short rn half life to cases of high rn contents short distances and high flow velocities

radiocarbon constraints on the age of the maximum advance of the british irish ice sheet in the celtic sea reconstructions of the british irish ice sheet biis during the last glacial maximum lgm in the celtic sea and southern ireland have been hampered by a paucity of well dated stratigraphic records as a result the timing of the last advance of the largest outlet of the biis the irish sea ice stream to its maximum limit in the celtic sea has been variously proposed as being pre last glaciation early devensian and lgm the irish sea till was deposited by the irish sea ice stream during its last advance into the celtic sea we present 26 stratigraphically well constrained new ams radiocarbon dates on glacially transported marine shells from the irish sea till in southern ireland which constrain the maximum age of this advance the youngest of these dates indicate that the biis advanced to its overall maximum limit in the celtic sea after 26 000 20 000 14c yr bp thus during the last glaciation the most extensive phase of biis growth therefore appears to have occurred during the lgm at least along the celtic sea and irish margins these data further demonstrate that the uppermost inland glacial tills from the area of supposed older drift in southern ireland a region previously regarded as having been unglaciated during the lgm also date from the last glaciation thus most of southern ireland was ice covered at the lgm advance of the biis to its maximum southern limit in the celtic sea may have been a short lived glaciodynamic response facilitated by subglacial bed conditions rather than a steady state response to climate forcing alone

environmental reconstructions of a late devensian terrace sequence some preliminary findings facies analysis of severn main terrace sediments at eardington shropshire is instructive in determining aspects of the sedimentary environment at a proximal location in the terrace evaluation of the structural and directional properties of the gravels indicates that the terrace is a composite feature comprising two units the lower unit is notable for the widespread occurrence of large sandy facies a near absence of massive gravel facies and the presence of large locally derived lithoclasts in excess of 1 m in diameter facies associations observed indicate the existence of in channel bars and large channels with bedforms at the dune plane bed transition the directional properties of the unit indicate flows parallel to the main valley axis and although the unit is unlike previously reported examples it is interpreted as being the product of a proximal low sinuosity environment the upper unit is composed mainly of multistorey coarse massive gravel units with limited interbedded sand facies fabric analysis indicates progradation of the unit from the west the facies sequence is similar to those encompassed by facies models proposed for proximal alluvial fan deposits and therefore on structural and directional grounds the upper unit is interpreted as an alluvial fan deposit which prograded into the main severn valley from the adjacent mor brook tributary the implications of the composite nature of the terrace at this point are considered both in terms of terrace correlation and palaeohyrological estimation

groundwater radon anomalies associated with earthquakes abstract earthquake related changes in groundwater radon have been detected at a sensitive observation site located right on a major active fault in northeast japan a time series analysis based on bayesian statistics was successfully applied to remove background variations from the observed radon data enabling us to examine the earthquake related changes in detail we set a simple criterion of amplitude and duration for an anomaly observed in our radon data we define an anomaly as a radon change that kept its level beyond 2 a standard deviation over the whole observation period during a period longer than one day we have observed 20 radon anomalies that satisfied this criterion from january 1984 to december 1988 most of these anomalies have turned out to be related to large earthquakes that occurred in east japan and its surrounding area we have identified 12 post seismic and 2 pre seismic radon anomalies out of a total of 30 earthquakes with magnitude m 6 0 and hypocentral distance d 1000 km the typical pattern of the post seismic anomalies is a radon decrease which started just after an earthquake lasting for periods ranging from a few days to more than one week the amplitude of the post seismic anomalies depends on both magnitude and hypocentral distance and can in general be expressed by a simple magnitude distance relationships a possible pre seismic anomaly was observed about one week before the largest earthquake that occurred in this region during the observation period march 6 1984 m 7 9 d 1000 km another possible pre seismic anomaly was observed about three days before two nearby large earthquakes that occurred at almost the same place in a time interval of 53 min february 6 1987 m 6 4 and m 6 7 d 130 km

detectability and significance of 12 hr barometric tide in radon 222 signal dripwater flow rate air temperature and carbon dioxide concentration in an underground tunnel summary searching for small periodic signals such as the 12 hr s2 barometric tide and monitoring their amplitude as a function of time can provide important clues on the complex processes affecting fluid transport in unsaturated fractured media under multiple influences here first we show that a modified spectrogram analysis msa is more efficient than simple fourier transform to reveal weak periodic signals secondly we show how transient periodic signals can be monitored as a function of time using spectrograms these methods are applied to time series of radon and carbon dioxide concentration dripwater flow rates and air temperature measured during several years in the roselend dead end tunnel located in the french alps near an artificial lake a weak s2 line is evidenced in radon concentration with enhanced amplitude during transient radon bursts similarly the s2 line is observed using msa in dripwater flow rates which sample mainly fracture flow as suggested by a hydrochemical analysis while it is not seen in dripwater flow rates sampling matrix flow in the absence of a strong 24 hr line the presence of a s2 line suggests sensitivity to barometric pressure and thus a significant advective contribution in radon and some dripwater transport no s2 line is observed in the carbon dioxide time series the temporal structure of the s2 component however is not similar in the radon concentration and the dripwater flow rates suggesting in particular that dripwater does not play a significant role in the generation of radon bursts temperature time series exhibit a significant s2 contribution induced by atmospheric pressure spatially organised in the tunnel decreasing vertically upwards a remarkable transient temperature inversion during radon bursts suggests that the additional advective air contributions responsible for the radon bursts occur from the non saturated rocks below the tunnel

time variable response characteristics of groundwater radon to earthquakes a clear coseismic anomaly of groundwater radon was observed for a magnitude 5 6 earthquake that occurred on may 11 1992 the coseismic radon anomaly was observed at a station which is located right on a major active fault in northeast japan and about 140 km away from the hypocenter this was the first time that an earthquake with m 6 had ever been accompanied by a clear radon anomaly at the station although we had observed 12 similar coseismic radon anomalies at the station during the observation period from 1984 to 1987 all of the earthquakes that were accompanied by radon anomalies in that period had been with magnitude 6 0 and over surprisingly the radon concentration has become more sensitive to show coseismic anomalies even for m 5 earthquakes since october 1992 this enhancement of sensitivity of the coseismic radon response may be attributed to the progress of micro crack formation in the fracture zone of the active fault which could be related to unusual stress accumulation in the region

a critical review of the glaciomarine model for irish sea deglaciation evidence from southern britain the celtic shelf and adjacent continental slope in support of their glaciomarine model for the deglaciation of the irish sea basin eyles and mccabe cited the occurrence of distal glaciomarine mud drapes onshore in the isles of scilly and north devon and of arctic beach face gravels and sands around the shores of the celtic sea glacial and sea level data from the southern part of the irish sea in the terminal zone of the ice stream and the adjacent continental slope are reviewed here to test this aspect of the model the suggestion that the glacial sequences of both the isles of scilly and fremington in north devon are glaciomarine mud drapes is rejected an actively calving tidewater margin only occurred early in the deglacial sequence close to the terminal zone in the south central celtic sea relative sea levels were lower and therefore glacio isostatic depression less than envisaged in the glaciomarine model geochronological sedimentological and biostratigraphical data indicate that the raised beach sequences around the shores of the celtic sea and english channel were deposited at or during regression soon after interglacial eustatic highstands evidence for ice rafting at a time of high relative sea levels is restricted to a phase s earlier than the late devensian these data indicate that the raised beach sequences have no bearing on the style of irish sea deglaciation copyright 2001 john wiley sons ltd

river terrace sequences templates for quaternary geochronology and marine terrestrial correlation fluvial sequences particularly terrace staircases represent archives of quaternary palaeoclimatic fluctuation and can serve as stratigraphical frameworks for geochronology and for correlation with other depositional environments in particular the global marine oxygen isotope record fluvial lithostratigraphical frameworks also provide contexts for records from fossils and artefacts of faunal evolution and human occupation conversely both records can be means of relative dating of riverine sequences three fluvial sequences are examined as case studies first is the severn avon system in the english midlands which has biostratgraphical evidence and an amino acid geochronology together with marker inputs from three different glaciations the somme sequence of northern france famous for its palaeolithic artefact assemblages again has biostratigraphy and an amino acid geochronology and has also been dated with reference to overlying loess palaeosols sequences the fluvial terraces of the river arun the final case study lack dating evidence but are interspersed within the sussex raised beach staircase although various lines of evidence suggest that the rivers discussed have formed terraces in response to climatic fluctuation an intriguing difference is that interglacial sediments occur at the bases of terrace formations in the severn avon whereas in the somme they occur at the tops of sequences beneath loessic overburden

a stratigraphical basis for the last glacial maximum lgm abstract the last glacial maximum lgm is widely used to refer to the episode when global ice volume last reached its maximum and associated sea levels were at their lowest however the boundaries of the interval are ill defined and the term and acronym have no formal stratigraphical basis this is despite a previous proposal to define it as a chronozone in the marine records on the basis of oxygen isotopes and sea levels spanning the interval 23 19 or 24 18 ka and centred on 21 ka in terrestrial records the lgm is poorly represented since many sequences show a diachronous response to global climate changes during the last glacial cycle for example glaciers and ice sheets reached their maximum extents at widely differing times in different places in fact most terrestrial records display spatial variation in response to global climate fluctuations and changes recorded on land are often diachronous asynchronous or both leading to difficulties in global correlation however variations in the global hydrological system during glacial cycles are recorded by atmospheric dust flux and this provides a signal of terrestrial changes whilst regional dust accumulation is recorded in loess deposits global dust flux is best recorded in high resolution polar ice core records providing an opportunity to define the lgm on land and establish a clear stratigraphical basis for its definition on this basis one option is to define the global lgm as an event between the top end of greenland interstadial 3 and the base onset of greenland interstadial 2 spanning the interval 27 540 23 340 ka greenland stadial 3 this corresponds closely to the peak dust concentration in both the greenland and antarctic ice cores and to records of the global sea level minima this suggests that this definition includes not just the coldest and driest part of the last glacial cycle but also the peak in global ice volume the later part of the lgm event is marked by heinrich event 2 which reflects the onset of the collapse of the laurentide at c 24 ka together with other ice sheets in the north atlantic region a longer and later span for the lgm may be desirable although defining this in chronostratigraphical terms is problematic whichever formal definition is chosen this requires the contribution of the wider quaternary community

mathematical model of shallow water flow over porous media a conjunctive mathematical model for a surface subsurface flow system is developed the unsteady surface flow is explored by a set of one dimensional dynamic wave equations for shallow water which are solved by using a four point implicit finite difference scheme the transient subsurface flow is two dimensional with potential gradients in the vertical direction as well as the surface flow direction the porous medium may be saturated or unsaturated or both and it can be nonhomogeneous and anisotropic the subsurface flow equation is solved by employing a successive line over relaxation implicit finite difference scheme the surface and subsurface flow components are coupled at the ground surface considering the mass conservation and pressure relationships the model is verified by using existing experimental data and analytical solutions for special cases

ground water radon anomaly before the kobe earthquake in japan radon concentration in ground water increased for several months before the 1995 southern hyogo prefecture kobe earthquake on 17 january 1995 from late october 1994 the beginning of the observation to the end of december 1994 radon concentration increased about fourfold on 8 january 9 days before the earthquake the radon concentration reached a peak of more than 10 times that at the beginning of the observation before starting to decrease these radon changes are likely to be precursory phenomena of the disastrous earthquake

radon as an anthropogenic indoor air pollutant as exemplified by radium dial watches and other uranium and radium containing artefacts radon is generally regarded as a naturally occurring radiological hazard but we report here measurements of significant hazardous radon concentrations that arise from man made sources e g radium dial watches this study is an examination and assessment of health risks from radium and uranium found in historical artefacts and the radon that emanates from them this includes radium dial watches the main focus plus clocks aircraft instruments and ornaments and artefacts made of uranium glass uranium glazed such objects were very popular in the 1930s and 1940s and are still readily available today a collection of 30 radium dial pocket and wrist watches was measured and shown to be capable of giving rise to radon concentrations two orders of magnitude greater than the uk domestic action level of 200 bq m 3 in unventilated or poorly ventilated rooms furthermore individual watches are capable of giving rise to radon concentrations in excess of the uk domestic action level we also highlight a gap in remediation protocols which are focused on preventing radon entering buildings from outside with regard to internally generated radon hazards radon as arising from man made objects such as radium dial watches should be considered appropriately in radon protocols and guidelines

new age constraints for the limit of the british irish ice sheet on the isles of scilly the southernmost terrestrial extent of the irish sea ice stream isis which drained a large proportion of the last british irish ice sheet impinged on to the isles of scilly during marine isotope stage 2 however the age of this ice limit has been contested and the interpretation that this occurred during the last glacial maximum lgm remains controversial this study reports new ages using optically stimulated luminescence osl dating of outwash sediments at battery tresco 25 5 1 5 ka and terrestrial cosmogenic nuclide exposure dating of boulders overlying till on scilly rock 25 9 1 6 ka which confirm that the isis reached the isles of scilly during the lgm the ages demonstrate this ice advance on to the northern isles of scilly occurred at 26 ka around the time of increased ice rafted debris in the adjacent marine record from the continental margin which coincided with heinrich event 2 at 24 ka osl dating 19 6 1 5 ka of the post glacial hell bay gravel at battery suggests there was then an 5 ka delay between primary deposition and aeolian reworking of the glacigenic sediment during a time when the isis ice front was oscillating on and around the ll n peninsula 390 km to the north

coupling of groundwater and open channel flow abstract the paper describes an approach to incorporating drainage and the interaction of groundwater and open channel flow in a physically based hydrologic response model two classes of exchange are distinguished the first is concerned with the influence of minor conduits which require too much refinement to be modelled on an individual basis but amalgamated make an important contribution to the water budget of a region on an areal basis the second class of exchange is direct seepage from or into the larger waterways in which the flow is significant and is modelled as a distinct hydrologic process in the first part of the paper a theory for treating the exchange phenomena is developed the basis is formed by the hooghoudt ernst formula of drainage design and the theory of additional seepage resistances the remainder of the paper is devoted to the technical implementation of this theory a number of practical steps to limit the data and organization required are outlined the main technical hurdle dealt with is the coupling of the two fundamentally incompatible numerical schemes for groundwater and open channel flow in such a way that a conservative water balance is maintained details of the complete hydrologic response model are presented as an appendix

new insights into the quaternary evolution of the bristol channel uk a synthesis of new publically available borehole and bathymetric data combined with a wealth of other existing disparate data sources reveals new insights into the quaternary history of the bristol channel area sediment boreholes throughout the bristol channel confirm the area was glaciated in the pleistocene till is present below marine deposits and in some areas is visible morphologically as submerged moraines in the central and eastern bristol channel the submerged valley course of the palaeo severn is very clear in new high resolution bathymetric surveys this former river course and associated tributaries cross cut through glacial sediments in the bristol channel at least three phases of glaciation are recorded in the bristol channel one related to the southern limits of a late devensian substage marine isotope stage mis 2 welsh ice cap which reached into swansea bay an earlier devensian mis 4 3 glaciation associated with irish sea ice and another older glaciation that is associated with ice that filled the entire outer and central bristol channel the age of the older bristol channel glaciation is still open although it pre dates the devensian late pleistocene and must date to the middle pleistocene it is therefore evident that pleistocene glacial and fluvial activity combined with subsequent post glacial sea transgression directly account for current morphometries of the bristol channel and severn estuary and the current geography of the sw british isles

an anomalous radon decrease in groundwater prior to an m6 0 earthquake a possible precursor a significant decrease in the radon concentration of artesian groundwater was observed at a well established observation site in northeast japan about two days before an m 6 0 earthquake occurred about 200 km from the site on the basis of a concurrent in situ minus 126 m temperature drop of the groundwater the authors infer that precursory changes in regional stress were locally amplified near this site and resulted in the temporary mixing of cooler radon poor groundwater into the normal artesian flow

new data for the last glacial maximum in great britain and ireland abstract understanding the history of the british and irish ice sheet biis at the last glacial maximum lgm has been advanced by new approaches in particular by cosmogenic nuclide surface exposure dating aminostratigraphy of shelly glacial deposits ams radiocarbon dating and the evidence from continental margin marine cores all of which supersede the previously weak geochronologic control it was formerly believed that great britain and ireland was largely ice free between the last interglacial oxygen isotope sub stage 5e and the late devensian when the lgm occurred as such the biis was effectively out of phase with laurentide and scandinavian ice sheets as well as inferences of ice volume from oxygen isotope stratigraphy the biis during the late devensian maximum was also perceived as having been relatively stationary new evidence shows that the lgm was an important event during the evolution of an earlier biis when the extent of ice was greater repeated iceberg rafting events over the past 50 ka are shown by marine cores while the derivative inference of numerous corresponding glacial advances is supported by several clusters of 36 cl ages on glaciated surfaces and glacial boulders that are indicative of deglacial events between 40 and 12 ka these appear to be associated with heinrich events the earliest being inferred as heinrich 4 at about 40 ka during this advance the biis and scandinavian ice sheet sis were in contact and all of ireland was glaciated the ice sheet appears to have fluctuated several times between 40 and 25 ka although evidence for this is poorly preserved but the 36 cl and 14 c evidence is clear that the biis reached its lgm maximum size about 22 ka soon after heinrich event 2 when the biis and sis were not in contact one cluster of 36 cl and 14 c ages at 21 4 1 3 ka records an initial pulse of deglaciation that was followed by extensive deglaciation about 17 4 0 4 ka just before heinrich event 1 when the ice sheet readvanced contrary to previous views the biis probably existed throughout much of devensian time as a mobile and sensitive ice sheet during which the lgm advance was but one important event in places glacial deposits of the earlier devensian glaciation have previously been incorrectly identified as products of the later lgm glaciation

the glaciation of dartmoor the southernmost independent pleistocene ice cap in the british isles the granite uplands of dartmoor have traditionally been considered to be relict permafrost and periglacial landscapes that lay beyond the limits of quaternary glaciations but a variety of landform evidence indicates that a plateau icefield existed on the northern part of the moor constituting the southernmost independent ice cap in the british isles overdeepened or weakly u shaped valley segments fringing north dartmoor document an early extensive phase of glaciation but the most convincing landform evidence relates to more recent valley based glacier occupancy a moraine ridge on the slipper stones represents the most unequivocal palaeo glacier on north dartmoor with a palaeo ela of c 460 m above sea level asl although this relates to the youngest and most restricted phase of glaciation a longer term ela is likely to be represented by the corn ridge proto cirque at 370 410 m asl more extensive valley glaciers are recorded in each of the major drainage basins of north dartmoor by arcuate and linear bouldery ridges and hummocky valley floor drift which are interpreted as latero frontal moraines deposited by outlet lobes of a plateau icefield recession of these lobes is marked by inset sequences of such ridges and occasional meltwater channels plateau ice was predominantly thin and protective and snowblow and preferential accumulation in valley heads facilitated the modest glacial erosion and debris transport recorded in the landforms and sediments it is proposed that the highest plateaux have been occupied by ice for the longest cumulative period of time throughout the quaternary average glacial conditions explaining the distribution of different tor types on northern dartmoor this also explains the lack of tors on the most expansive of the highest plateau terrain ice dispersal centres as the product of a average glacial conditions preferentially removing tors or dampening their production rates b the survival of high relief type 1 tors during glaciation if they occupy summits too narrow to develop significant plateau icefields and or ridges that are bypassed by faster moving ice in adjacent deep valleys and c the survival of subdued type 2 tors in areas glaciated less regularly during the quaternary simple ice flow modelling indicates that a plateau icefield type glaciation is required for significant ice flow to occur and confirms thin ice cover in particular on narrow summits thereby supporting the explanation of tor class distribution the modelling allows us to spatially correlate the geomorphological evidence of margin positions into two major stages and further indicates a strong altitude mass balance feedback leading to an ice cap that is not in balance with its climate and with an extent that is limited by the length of the cold phases rather than their severity

the morphodynamics and internal structure of intertidal fine gravel dunes hills flats severn estuary uk in the macrotidal severn estuary uk the dynamics of intertidal fine gravel dunes were investigated these dunes are migrating across a bedrock platform systematic observations were made of hydraulic climate geometry migration rates and internal sedimentary structures of the dunes during spring tides the ebb flow is dominant dunes grow in height and have ebb orientated geometry with bedrock floors in the troughs during neap tides a weak flood flow may dominate dunes then are flood orientated or symmetrical neap dune heights decrease and the eroded sediment is stored in the dune troughs where the bedrock becomes blanketed by muddy gravel during spring tides instantaneous bed shear stresses reach 8 n m 2 sufficient to disrupt a 9 mm gravel armour layer however a sustained bed shear stress of 4 n m 2 is required to initiate dune migration at which time the critical depth mean velocity is 1 m s 1 ebb and flood inequalities in the bed shear stress explain the changes in dune asymmetry and internal structures during flood tides the crests of the dunes reverse such that very mobile sedimentary caps overlie a more stable dune core because ebb tides dominate internal structures of the caps often are characterised by ebb orientated steep open work foresets developed by strong tidal currents and some lower angle crossbeds deposited as weaker currents degrade foresets the foresets forming the caps may be grouped into cosets tidal bundles and are separated from mud infused cores of crossbeds that lie below by reactivation and erosion surfaces blanketed by discontinuous mud drapes the cores often exhibit distinctive muddy toe sets that define the spacing of tidal cosets

pleistocene geology of the lower severn valley u k abstract the lower severn valley contains a sequence of fluvial glaciofluvial and glaciogenic deposits of pleistocene age which is divided into two formations glaciogenic sediments are correlated with members of the wolston formation anglian a new formation the severn valley formation which consists of fluvial deposits is defined it is sub divided into six members the four oldest of which are considered in this paper the oldest deposits in the lower severn basin are the till and glaciofluvial outwash gravels of the woolridge member the till is correlated with the thrussington member of the wolston formation which is correlated with the lowestoft formation of the anglian stage oxygen isotope stage 12 the oldest member of the severn valley formation the spring hill member is provisionally correlated with oi stage 10 the bushley green member represents deposition during oi stages 9 and 8 the basal fossiliferous sediments bushley green fossil bed are correlated with oi stage 9 by amino acid geochronology the kidderminster station member records a significant input of lithologies not seen in quantity in the higher members and evidence is presented which suggests that this is a response to renewed glaciation in the upper basin this glaciation was responsible for the deposition of the ridgacre formation of the birmingham area amino acid geochronology and chlorine 36 ages from erratic boulders show that the kidderminster station member and ridgacre formation are of oi stage 6 warthe age the basal deposits of the holt heath member include the stourbridge fossil bed with a temperate fauna believed to be ipswichian last interglacial oi substage 5e and the upton warren fossil bed oi substage 5a most of the holt heath member consists of outwash from an irish sea ice sheet which entered the severn basin during the late devensian oi stage 2

catastrophic flooding origin of shelf valley systems in the english channel britain became geographically isolated from continental europe when high interglacial seas flooded the shallow english channel and north sea shelf areas but a tenuous link remained the weald artois chalk ridge between southeast england and northwest france just how this isthmus was breached making britain an island has been a matter of conjecture a new bathymetric map of the sea floor may solve the mystery it reveals a large bedrock floored valley containing landforms including grooves and streamlined islands consistent with a megaflood event caused when a rock dam at the dover strait breached draining a large pro glacial lake in the north sea basin a hypothesis for the permanent isolation of britain from mainland europe during interglacial high sea levels has been confirmed gupta et al analysed a new regional bathymetric map of part of the area finding a valley with landforms indicating large scale subaerial erosion by high magnitude water discharges they suggest breaching of a rock dam at the dover strait instigated drainage of a large lake in the north sea basin megaflood events involving sudden discharges of exceptionally large volumes of water are rare but can significantly affect landscape evolution continental scale drainage patterns and climate change1 it has been proposed that a significant flood event eroded a network of large ancient valleys on the floor of the english channel the narrow seaway between england and france2 3 4 this hypothesis has remained untested through lack of direct evidence and alternative non catastrophist ideas have been entertained for valley formation5 6 here we analyse a new regional bathymetric map of part of the english channel derived from high resolution sonar data which shows the morphology of the valley in unprecedented detail we observe a large bedrock floored valley that contains a distinct assemblage of landforms including streamlined islands and longitudinal erosional grooves which are indicative of large scale subaerial erosion by high magnitude water discharges our observations support the megaflood model in which breaching of a rock dam at the dover strait instigated catastrophic drainage of a large pro glacial lake in the southern north sea basin2 we suggest that megaflooding provides an explanation for the permanent isolation of britain from mainland europe during interglacial high sea level stands7 and consequently for patterns of early human colonisation of britain together with the large scale reorganization of palaeodrainage in northwest europe4

paired 26al and 10be exposure ages from lundy new evidence for the extent and timing of devensian glaciation in the southern british isles lundy lies in a strategic geographical position for understanding the glacial history of the british isles the island bears evidence of glaciation largely in the form of ice moulded bedrock and glaciallytransported boulders e an unusual occurrence this far south in the british isles irish sea ice penetrated the western bristol channel overriding lundy from the northwest during the last phase of glaciation in this area the results of paired terrestrial cosmogenic nuclide analyses 26al 10be constrain the timing of this extensive glaciation and provide for the first time an age for the exposure of lundy granite following deglaciation the results from nine paired samples yield 26al 10be exposure ages of 31 4e48 8 ka 10be and 31 7e60 0 ka 26al this challenges the view that any glaciation this far south must belong to middle pleistocene glaciations such as the anglian stage c 480e420 ka and a devensian age for the last glaciation is consistent with findings from the isles of scilly further south however the findings suggest early mid devensian marine isotope stage mis 4e3 glaciation of lundy it also implies that the island was exposed or covered for a short time by non erosive cold based ice at the global last glacial maximum lgm during mis 2 26e21 ka the potential exposure of the island throughout mis 2 contrasts with the evidence from the isles of scilly and the celtic sea which were glaciated at the lgm

precursory analysis of gps time series for seismic hazard assessment we discuss the use of fractal analysis of geophysical big data as a precursory method for the estimation of current seismic hazard we begin by analyzing gps time series of land surface displacements recorded in various regions of the planet exhibiting different degrees of seismic activity we show how the quantitative measure of chaoticity based on a modified detrended fluctuation analysis dfa method can be used to distinguish critical and noncritical regimes of evolution of the earth s crust having established the reference values for the measure of chaoticity we then choose california as the case study region and apply modified dfa to over 1200 time series for determining local areas currently exposed to higher seismic hazard we comprehensively analyze the results obtained and compare them with those produced by conventional risk assessment methods we demonstrate consistency of our results and yet discover that the suggested approach allows us to quantify two qualitatively different mechanisms involved in the growth of seismic hazards we propose a hypothesis which relates these mechanisms to the known mechanisms of earthquake generation that evince a growth of collective behavior in the earth s crust on the eve of an earthquake in order to verify the hypothesis we analyze the same gps data by an independent statistical method canonical coherence analysis cca which permits us to quantify the degree of synchronized behavior of constituents of the earth s crust the cca method confirms our previously obtained estimates thus supporting fractal analysis of gps time series as a suitable precursory method for current seismic hazard assessment

radon health and natural hazards a signpost for assessment and protection in the 21st century this volume draws together the final outputs of the five year unesco iugs igcp project 571 and presents new data on radon in the built and natural environments radon as a diagnostic tool of geophysical phenomena reflections and recommendations on the future of radon research and a critique of radon s asserted use as a therapy in recent years there has been an increasing interest in radon from a range of different aspects and we would suggest that radon science has the potential to be a useful tool in understanding our environment as well as its impacts on human health

the pleistocene rivers of the english channel region the pleistocene history of river systems that enter the english channel from northern france and southern england is reviewed during periods of low sea level cold stages these streams were tributaries of the channel river in southern england the largest the river solent is an axial stream that has drained the hampshire basin from the early pleistocene or late pliocene other streams of southern england may be of similar antiquity but their records are generally short and their sedimentary history have been destroyed as in northern brittany by coastal erosion and valley deepening as a consequence of tectonic uplift in northern france the seine and somme rivers have very well developed terrace systems recording incision that began at around 1 ma the uplift rate deduced from the study of these terrace systems is of 55 to 60 m myr 1 since the end of the early pleistocene generally the facies and sedimentary structures indicate that the bulk of the deposits in these rivers accumulated in braided river environments under periglacial climates in all the area around the channel evolution of the rivers reflects their responses to climatic change local geological structure and long term tectonic activity in this context the middle somme valley is characterised by a regular pattern in which incision occurs at the beginning of each glacial period within a general background of uplift nevertheless the response of the different rivers to climatic variations uplift and sea level changes is complex and variable according to the different parts of the river courses copyright 2003 john wiley sons ltd

soil gas radon emissions and volcanic activity at el hierro canary islands the 2011 2012 submarine eruption 1 soil gas radon 222rn and thoron 220rn activities have been continuously measured during the period of the recent volcanic unrest that occurred at el hierro canary islands at two different monitoring stations namely hie02 and hie03 significant increases in soil 222rn activity and 222rn 220rn ratio from the soil were observed at both stations prior to the 2011 2012 submarine eruption off the coast of el hierro showing the highest increases before the eruption onset and before the occurrence of the strongest seismic event m 4 6 statistical analysis showed that the long term temporal trend of filtered radon data matched closely that of seismic energy release during the volcanic unrest the observed increases of 222rn are related to the rock fracturing processes seismic activity and the magmatic co2 outflow increase as observed in hie03 station

the fleuve manche the submarine sedimentary features from the outer shelf to the deep sea fans bathymetric seismic and coring surveys have been carried out since the beginning of the 1990s on the outer shelf the slope and the continental rise of the western approaches margin most of the sedimentary features studied belong to a sedimentary system built up since the oligocene and fed by a palaeoriver the fleuve manche that flowed in the english channel during eustatic lowstands a geomorphological map details the spatial distributions of the palaeovalleys on the outer shelf the drainage basin like organised canyons on the slope and the channel levee and lobe complexes on the rise the obvious channel canyon connections and the assessed palaeovalley canyon links demonstrate that the fleuve manche was the single source for terrigeneous fluxes of the armorican deep sea fan when it was one of two sources of the celtic deep sea fan amongst parameters controlling the sedimentation two factors play a major role i subsidence controlled the possibly messinian riverine incision the turbidite activities during lowstands as well as marine infilling of the seawards part of the fleuve manche ii quaternary sedimentary supplies were influenced by the melting ice sheets and the connections with the onshore catchment basins copyright 2003 john wiley sons ltd

denudation of the continental shelf between britain and france at the glacial interglacial timescale the erosional morphology preserved at the sea bed in the eastern english channel dominantly records denudation of the continental shelf by fluvial processes over multiple glacial interglacial sea level cycles rather than by catastrophic flooding through the straits of dover during the mid quaternary here through the integration of multibeam bathymetry and shallow sub bottom 2d seismic reflection profiles calibrated with vibrocore records the first stratigraphic model of erosion and deposition on the eastern english channel continental shelf is presented published optical stimulated luminescence osl and 14c ages were used to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with major climatic sea level periods five major erosion surfaces overlain by discrete sediment packages have been identified the continental shelf in the eastern english channel preserves a record of processes operating from marine isotope stage mis 6 to mis 1 planar and channelised erosion surfaces were formed by fluvial incision during lowstands or relative sea level fall the depth and lateral extent of incision was partly conditioned by underlying geology rock type and tectonic structure climatic conditions and changes in water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers in northwest europe evidence for major erosion during or prior to mis 6 is preserved fluvial sediments of mis 2 age were identified within the northern palaeovalley providing insights into the scale of erosion by normal fluvial regimes seismic and sedimentary facies indicate that deposition predominantly occurred during transgression when accommodation was created in palaeovalleys to allow discrete sediment bodies to form sediment reworking over multiple sea level cycles saalian eemian early weichselian by fluvial coastal and marine processes created a multi lateral multi storey succession of palaeovalley fills that are preserved as a strath terrace the data presented here reveal a composite erosional and depositional record that has undergone a high degree of reworking over multiple sea level cycles leading to the preferential preservation of sediments associated with the most recent glacial interglacial period

significant annual and sub annual cycles in indoor radon concentrations seasonal variation and correction the majority of radon measurements in the built environment are made over sub year periods and are then generally seasonally corrected i e scaled by an appropriate seasonal correction factor scf to estimate the annual average radon concentration scfs are statistically derived and assume an underlying annual cycle reflecting the widely observed seasonal variation in indoor radon concentrations in the uk public health england has pioneered the calculation and use of a national scf set using an annual sinusoidal model for variations in radon concentration and averaging across the entire country to test the validity of that model a four year record of weekly radon data from four houses in brixworth northamptonshire uk was analysed in conjunction with corresponding weather data for the period from a nearby weather station the radon data showed a statistically significant annual cycle comprising both annual sinusoidal and second harmonic i e six month period terms two sets of scfs were calculated first using a conventional annual sinusoidal model which explained 21 2 of the variance in the radon data second a second harmonic term was included in the model which explained 24 6 of the variance this represents an improvement of 3 4 percentage points 15 9 and thus will result in better scfs