provenance and depositional environments of quaternary sediments from the western north sea basin as the majority of the data on quaternary sediments from the north sea basin are seismostratigraphical we analysed the elsterian swarte bank formation the late saalian fisher formation and the late weichselian dimlington stadial bolders bank formation in order to determine genesis and provenance the swarte bank formation is a subglacial till containing palynomorphs from the moray forth and the northeastern north sea and metamorphic heavy minerals from the scottish highlands the fisher formation was sampled from the northern and central north sea in the north it is interpreted as a subglacial till with glaciomarine sediments cropping out further south these sediments exhibit a provenance signature consistent with the midland valley of scotland the eocene of the north sea basin the grampian highlands and northeast scotland the bolders bank formation is a subglacial till containing palynomorphs from the midland valley of scotland northern britain and a metamorphic heavy mineral suite indicative of the grampian highlands southern uplands and northeast scotland these data demonstrate that there was repeated glaciation of the north sea basin during the middle and late pleistocene with ice sheets originating in northern scotland there was no evidence for a scandinavian ice sheet in the western north sea basin

the late devensian 22 000 bp irish sea basin the sedimentary record of a collapsed ice sheet margin the late devensian 20 ka bp glacial geology of the irish sea basin 4000 km2 is an event stratigraphy recording the entry of marine waters into a glacio isostatically depressed basin and the rapid retreat of the irish sea glacier as a tidewater ice margin marine limits occur up to 140 m o d across much of the central basin the ice margin was uncoupled from its bed exposing a subglacially scoured topography to glaciomarine processes the irish sea glacier was a major drainage conduit of the last british ice sheet calving of the marine ice margin resulted in fast flow surging of ice streams recorded by drumlin fields around the northern basin margin and tunnel valleys rapid evacuation of the basin may have stranded large areas of dead ice in peripheral zones e g cheshire shropshire lowlands and initiated the collapse of the ice sheet thick wedges of ice contact glaciomarine sediments were deposited during ice retreat as morainal bank complexes by successive tidewater ice margins stabilized at pinning points around the irish sea coast where morainal banks occur on the seaward side of drumlin swarms there is a clear sequential relationship between rapid ice loss from calving ice margins the development of fast flowing ice streams drumlinization and the pumping of subglacial sediment to tidewater raised delta complexes are locally associated with marine limits along the high relief coastal margins of wales east central ireland and the lake district associated valley infill complexes record downslope resedimentation of heterogenous sediments into the marine environment during ice retreat co eval offshore deposits are represented by well stratified glaciomarine complexes that infill a subglacially scoured topography that shows networks of tunnel valleys glaciomarine mud drapes occur well to the south of the maximum limit of grounded ice in the basin e g north devon scilly islands southern ireland the age of these distal sediments previously mapped as pre devensian tills is constrained by amino acid ratios basin rebound following deglaciation was rapid with over 100 m recovery in 3 ka and was followed by a low marine still stand peat accumulating in offshore areas now as much as 55 m below sea level has been drowned by the postglacial eustatic rise in sea level the glacio sedimentary model identified in this paper involving rapid ice retreat and related sedimentation triggered by rising relative sea level suggests that isotatic downwarping is an important mechanism for deglaciating continental shelves

statistical analysis of the induced basel 2006 earthquake sequence introducing a probability based monitoring approach for enhanced geothermal systems summary geothermal energy is becoming an important clean energy source however the stimulation of a reservoir for an enhanced geothermal system egs is associated with seismic risk due to induced seismicity seismicity occurring due to the water injection at depth have to be well recorded and monitored to mitigate the seismic risk of a damaging event an appropriate alarm system needs to be in place for each individual experiment in recent experiments the so called traffic light alarm system based on public response local magnitude and peak ground velocity was used we aim to improve the pre defined alarm system by introducing a probability based approach we retrospectively model the ongoing seismicity in real time with multiple statistical forecast models and then translate the forecast to seismic hazard in terms of probabilities of exceeding a ground motion intensity level one class of models accounts for the water injection rate the main parameter that can be controlled by the operators during an experiment by translating the models into time varying probabilities of exceeding various intensity levels we provide tools which are well understood by the decision makers and can be used to determine thresholds non exceedance during a reservoir stimulation this however remains an entrepreneurial or political decision of the responsible project coordinators we introduce forecast models based on the data set of an egs experiment in the city of basel between 2006 december 2 and 8 approximately 11500 m 3 of water was injected into a 5km deep well at high pressures a six sensor borehole array was installed by the company geothermal explorers limited gel at depths between 300 and 2700 m around the well to monitor the induced seismicity the network recorded approximately 11200 events during the injection phase more than 3500 of which were located with the traffic light system actions where implemented after an ml 2 7 event the water injection was reduced and then stopped after another ml 2 5 event a few hours later an earthquake with ml 3 4 felt within the city occurred which led to bleed off of the well a risk study was later issued with the outcome that the experiment could not be resumed we analyse the statistical features of the sequence and show that the sequence is well modelled with the omori utsu law following the termination of water injection based on this model the sequence will last 31 29 14 years to reach the background level we introduce statistical models based on reasenberg and jones and epidemic type aftershock sequence etas models commonly used to model aftershock sequences we compare and test different model setups to simulate the sequences varying the number of fixed and free parameters for one class of the etas models we account for the flow rate at the injection borehole we test the models against the observed data with standard likelihood tests and find the etas model accounting for the on flow rate to perform best such a model may in future serve as a valuable tool for designing probabilistic alarm systems for egs experiments

middle to late devensian glaciation of north east scotland implications for the north eastern quadrant of the last british irish ice sheet we present a review of over 175 years of research into the middle to late devensian weichselian glaciation of north east scotland based crucially on both its lithostratigraphic and geomorphic records the location of the region and surrounding seabed makes this unusually detailed record significant for deciphering the former interactions and dynamics of scottish and scandinavian ice within the north sea basin nsb which continue to be controversial a twelve stage event stratigraphy is proposed based on a parsimonious interpretation of stratigraphic relationships till lithology and regional clast fabrics striae subglacial bedforms ice marginal features and published geochronometry at critical sites the record of regional glaciation supports converging evidence that the north eastern quadrant of the last british and irish ice sheet biis reached its maximum spatial extent in the late middle to early late devensian and later re expanded following widespread internal glacial reorganisations marine transgression and partial retreat from the central nsb retreat was interrupted by several glacial readvances of limited extent field captured data helps identify important events that are not clearly resolved from remote sensing alone particularly regarding growth phases of the last glaciation

glaciomarine deltaic deposition and ice marginal tectonics the loch don sand moraine isle of mull scotland detailed descriptions are given of sediments exposed in the loch don sand moraine isle of mull scotland two distinct sediment landform associations occur within the moraine i a gilbert type glaciomarine delta complex graded to ca 34 m ordnance datum and ii thrust moraines consisting of deformed sands and silts whereas previous studies have attributed the moraine to a single glacial readvance this paper shows that the delta and the thrust moraines formed during ice sheet deglaciation and the loch lomond readvance respectively depositional conditions and the palaeoenvironment for each stage of moraine formation are reconstructed during the loch lomond readvance till deposition and thrust moraine formation appear to have been controlled by drainage conditions in the marginal zone of the glacier

a glacio isostatic facies model and amino acid stratigraphy for late quaternary events in spitsbergen and the arctic strong early holocene crustal uplift over the spitsbergen archipelago reflects disappearance of an ice mass centred just north east of the archipelago and which decayed rapidly just after 10 000 bp after a maximum extension between 12 600 and 10 000 bp from the lithofacies distributions associated with these events a glacio isostatic facies model can be defined which combined with analyses of amino acid racemization provides a valuable stratigraphic method for correlating pre holocene glacio isostatic events these are correlated with events in greenland and both are contrasted with weichselian glacial events at the southern margins of the two great northern hemisphere ice sheets and with contemporary water mass changes in the north atlantic and norwegian sea the geographical variation in glacier response through time is explained by three principal climatic circulation patterns

late quaternary marine mollusca as palaeoenvironmental proxies a compilation and assessment of basic numerical data for ne atlantic species found in shallow water abstract temperature salinity and depth limits are given for selected molluscs from boreal and arctic regions of the ne atlantic and adjacent shelf seas the significance of the data for palaeoenviromental analysis is briefly discussed

interlaminated ice proximal glacimarine sediments in muir inlet alaska muir inlet in glacier bay alaska is a glacial fjord receiving a tremendous volume of sediment annually the rate of sediment accumulation is greatest proximal to muir glacier about 9 m yr 1 and decreases away from the glacier the primary sediment sources are meltwater streams discharging at subglacial and ice marginal positions to form overflows interflows and underflows continuous turbidity currents overflows and interflows interact with diurnal tidal currents and their volume and sediment concentration varies diurnally and annually with meltwater discharge these effects produce cyclic deposits of a thin fine grained sand or silt lamina that grades normally to a thicker poorly to very poorly sorted mud lamina this lamina couplet is termed a cyclopel underflows are suggested to occur in this glacimarine environment because of conditions unique to subglacial fluvial systems underflow deposits occur only in proximal positions 0 5 km from glacier face and are coarse grained reverse to normal graded and exhibit an increase in sorting and sand content up layer ice rafted debris identified as particles 177 m is ubiquitous though low 5 by weight and occurs as isolated particles frozen pellets or as lenses that in cores may have a lamina appearance proximally ice rafted debris is difficult to identify because proximal sediment is often as coarse grained deposited sediment may be reworked by tidal currents and sediment gravity flows depositional processes operating in muir inlet produce interlaminated sand silt clay that characterizes sediment proximal to a glacier and fines seaward to mud sediment is classified into one of three sediment types 1 1 type i sediment is very fine grained mean 8 65 7 17 o low in sand 0 1 11 2 and very poorly to poorly sorted it is the dominant sediment type in muir inlet and is transported by plumes and deposited by suspension settling 2 2 type ii sediment is fine to coarse grained mean 6 70 3 12 o low to high in sand 5 1 86 6 and very poorly to moderately sorted it represents reworked sediment proximal plume deposits or coarse grained laminae of cyclopels 3 3 type iii sediment is coarse grained mean 3 89 2 38 o high in sand 58 0 100 0 and poorly to well sorted it is deposited by sediment gravity flows or underflows

glacial deposits at the boyne bay limestone quarry portsoy and their place in the late pleistocene history of northeast scotland the glacial deposits at the boyne bay limestone quarry near portsoy a key quaternary site of special scientific interest comprise i a sandy partly weathered diamicton craig of boyne till formation cbtf resting on decomposed bedrock ii a central variably glaciotectonised assemblage of dark clay diamicton and sand with rafts of sand and weathered diamicton whitehills glacigenic formation wgf and iii an upper dark sandy diamicton old hythe till formation ohtf the cbtf was probably derived from the west or southwest and the wgf from seawards structures within the ohtf conform to deposition by east or southeast moving ice from the moray firth but some erratics indicate derivation from the south the cbtf is believed to pre date the last lpswichian interglacial but the wgf and ohtf both post date the early middle devensian and are probably of late devensian age it is proposed that the ohtf was deposited by ice from inland which was directed eastwards near the coast by a vigorous glacier in the moray firth and that the complex late devensian glacial history of the south coast of the moray firth as a whole is the result of the interplay of these two contemporary ice masses british geological survey nerc 2000

palaeoseismic liquefaction event in late quaternary lake sediment at glen roy scotland late quaternary lake sediment deposits from a former ice dammed lake at glen roy scotland contain deformation structures indicative of liquefaction the distribution of deformation styles reflects a concentric pattern of the degree of liquefaction a possible fault rupture and several landslides are also observed in the central area the liquefaction structures the zonation of the sediment deformation and the association of deformation with landsliding can most simply be interpreted in terms of ground shaking during a major earthquake occurring at the end of the last glacial episode in scotland c 10 000 bp

geological and environmental management of ceramic clay quarries a review this paper shows a contribution to the knowledge of the geological management of ceramic raw material we have mainly focussed on the clays with a ceramic interest the article begins with an introduction to the mineralogical determining factor of the ceramic sector then it shows a development of the main steps that take place in the geological prospecting and it concludes with the criteria that must be followed when selecting the outcrops geographical and environmental conditions 1 legislation 2 market and technology 3 mineralogical and technological characterisation and 4 geological and mining characterisation

sedimentology of a late pleistocene submarine moraine complex county down northern ireland the killard point moraine formed when late pleistocene ice grounded on the isostatically depressed coastal lowlands of county down northern ireland at a time of relatively high sea level the moraine consists of three major lithologic associations which prograded for about 1 km from the ice grounding zone into a glaciomarine environment at the base of the succession a diamicton association is characterized by massive and stratified diamictons that are mainly debris flows it contains a minor ice rafted debris component the overlying sand association was deposited from sediment gravity flows of low to intermediate viscosity the gravel association was deposited by high density sediment gravity flows massive mud beds or drapes occur throughout the sequence and are related to low density turbidity or contour currents sequences of this type are more common in the geological record than the literature suggests and are often explained in terms of terrestrial based deglacial models this calls for a sedimentological reappraisal of many glacigenic deposits which accumulated in areas subject to deep isostatic depression during the late pleistocene

the high level marine shell bearing deposits of clava inverness shire and their origin as glacial rafts abstract the enigmatic high level till covered cold water marine shell bearing deposits at clava inverness shire are described systematically in the light of new observations made at sites documented in the literature the marine deposits named here as the clava shelly formation include three members the unfossiliferous clava sand the underlying clava shelly clay and a shelly diamicton known as the clava shelly till the first two members form a conformable coarsening upwards sequence containing a shallow water high boreal to low arctic fauna and flora the clava shelly till is essentially glacially re sedimented glaciomarine clay containing a sparse fauna but its stratigraphic relationship and age are not absolutely clear the shelly clay is ascribed to a mid devensian interstadial episode on the basis of amino acid dating it is concluded that the clava shelly clay and several discrete masses of clava sand and shelly till are glacially transported allochthons derived from the great glen the rafts were probably detached as a result of high pore water pressure building up in laterally restricted aquifers beneath a confined glacier that flowed north eastwards across the loch ness basin this glacier was deflected eastwards and upwards towards clava by ice flowing from the northern highlands along the beauly firth during the build up of the last scottish ice sheet the rafts were stacked at the ice margin when the glacier entered the nairn valley before being overriden by the expanding ice sheet

the northern sector of the last british ice sheet maximum extent and demise abstract strongly divided opinion has led to competing apparently contradictory views on the timing extent flow configuration and decay mechanism of the last british ice sheet we review the existing literature and reconcile some of these differences using remarkable new sea bed imagery this bathymetric data provides unprecedented empirical evidence of confluence and subsequent separation of the last british and fennoscandian ice sheets critically it also allows a viable pattern of ice sheet disintegration to be proposed for the first time covering the continental shelf around the northern united kingdom extensive echosounder data reveals striking geomorphic evidence in the form of tunnel valleys and moraines relating to the former british and fennoscandian ice sheets the pattern of tunnel valleys in the northern north sea basin and the presence of large moraines on the west shetland shelf coupled with stratigraphic evidence from the witch ground basin all suggest that at its maximum extent a grounded ice sheet flowed from se to nw across the northern north sea basin terminating at the continental shelf edge the zone of confluence between the british and much larger fennoscandian ice sheets was probably across the northern orkney islands with fast flowing ice in the fair isle channel focusing sediment delivery to the rona and foula wedges this period of maximum confluent glaciation c 30 25 ka bp was followed by a remarkable period of large scale ice sheet re organisation we present evidence suggesting that as sea level rose a large marine embayment opened in the northern north sea basin as far south as the witch ground basin forcing the two ice sheets to decouple rapidly along a north south axis east of shetland as a result both ice sheets rapidly adjusted to new quasi stable margin positions forming a second distinct set of moraines c 24 18 ka bp the lobate overprinted morphology of these moraines on the mid shelf west of orkney and shetland indicates that the re organisation of the british ice sheet was extremely dynamic probably dominated by a series of internally forced readvances critically much of the ice in the low lying north sea basin may have disintegrated catastrophically as decoupling progressed in response to rising sea levels final stage deglaciation was marked by near shore ice streaming and increasing topographic control on ice flow direction punctuated retreat of the british ice sheet continued until c 16 ka bp when following the north atlantic iceberg discharge event heinrich 1 ice was situated at the present day coastline in nw scotland

glacial deposits in great britain and ireland with the increasing awareness of environmental problems there is a growing desire for a de tailed understanding of superficial deposits in general and glacial deposits in particular this is because these sediments have a profound influence on groundwater protection waste management and nature conservation they are also of vital importance to civil engineering because they provide the foundation for as well as the materials extracted to build our roads and buildings the greater part of the british isles was glaciated at least once during the quater nary era in the regions subjected to glaciation glacial deposits underlie much of the present land surface although there have been many recent publica tions on various quaternary geological topics the present volume is the first dedicated to a detailed assessment of the glacial deposits of britain and ireland after introductory chapters presenting the glacial history the sedimentary sequences in 24 critical regions are discussed these regions include all of ireland the gla ciated area of great britain and the adjoining offshore region of the north sea the controver sial evolution of the irish sea basin during the last glaciation is discussed from various view points a collection of critical topics presented in the later part of the book range from the classification of glacigenic landforms and de posits to the results of geophysical geotechnical and geochemical analyses the book includes 368 figures 40 tables and 51 colour photographs a detailed index and a list of over 1000 references with 45 contributions by 48 scientists this volume represents a truly contemporary view of this field of research to gether with its companion volume the glacial deposits in north west europe this book pro vides an excellent textbook for the advanced student or the amateur as well as an indispen sible source and guidebook for the professional scientist

real time discrimination of earthquake foreshocks and aftershocks immediately after a large earthquake the main question asked by the public and decision makers is whether it was the mainshock or a foreshock to an even stronger event yet to come so far scientists can only offer empirical evidence from statistical compilations of past sequences arguing that normally the aftershock sequence will decay gradually whereas the occurrence of a forthcoming larger event has a probability of a few per cent here we analyse the average size distribution of aftershocks of the recent amatrice norcia and kumamoto earthquake sequences and we suggest that in many cases it may be possible to discriminate whether an ongoing sequence represents a decaying aftershock sequence or foreshocks to an upcoming large event we propose a simple traffic light classification to assess in real time the level of concern about a subsequent larger event and test it against 58 sequences achieving a classification accuracy of 95 per cent

sedimentary processes of canadian arctic fjords abstract conceptual models of circulation and sedimentation in arctic fjords are presented to illustrate the current understanding of these environments circulation is a vigorous process in these fjords and is enhanced by the loss of the freshwater cap during the long winter period of near zero inflow the process of brine rejection during the formation of sea ice and the role of glaciers and icebergs injecting freshwater at depth on the other hand the presence of sea ice blocks reduces the mixing action of wind which may otherwise represent the largest input of energy to fjord circulation it also provides a freshwater layer on melting and may in some circumstances damp the amplitude of tides during summer large loads of glacial sediment entering arctic fjords are separated into streams of overflowing suspended load and bed load in the presence of salt water as the concentrations of suspended load in the freshwater are normally much less than required to overcome the density of the salt water deposition occurs throughout the fjord by rapid settling of flocculated particles from the overflowing brackish water and from grain flows in the proximal environment created as the fluvial traction carpet moves over the delta foreset slope after sediment has been deposited it may be remobilized by slides which in turn may develop into fully turbulent flows as they move down the fjord floor a range of deposits from slump debris to minor turbidites are postulated to occur with the flocculated muds although not all have yet been examined in the arctic fjord stratigraphic record sea ice is an important sedimentological agent in arctic fjords it passively carries fluvial aeolian and colluvial material which is subsequently released from the ice during the stage of puddle draining at break up sea ice also actively incorporates fine and coarse sediments up to large boulders during freezing along the shores in winter and by wave and tidal current washing controlled by the presence of the ice during break up

geological mineralogical and chemical characterization of devonian kaolinite bearing sediments for further applications in the ceramic tiles industry in la paz bolivia clay minerals are widely distributed in bolivia among them illitic clays are most common in the altiplano where they are mined for use in the ceramic industry that has been growing in the last few years in addition to illitic sediments kaolinitic sediments have been recently discovered in sedimentary units in the bolivian altiplano residual ball clay occurrences in devonian sedimentary units were studied as part of this work geological mapping and geophysical studies ert and gpr were done for better understanding the origin of the deposits and were part of a preliminary study of the mineral potential to define the relationship with the host rock chemical and mineralogical techniques such as x ray diffraction scanning electron microscopy and inductively coupled plasma analyses were performed in samples from the studied area to verify the presence of kaolinite atterberg limits and behaviour of the raw material in ceramic specimens supported by chemical analyses show that this material is suitable for manufacturing tile ceramics this study provides fundamental knowledge for deposit exploitation and future generation of an alternative source of employment for the inhabitants of micaya

characterization of some nonmetallic resources in bolivia an overview of their potentiality and their application in specialized formulations bolivia has several nonmetallic occurrences widespread in the country unfortunately they are poorly studied and slightly characterized in the present work several nonmetallic occurrences locate

push moraines and glacier contact fans in marine and terrestrial environments the local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts which in turn determine the sediments and landforms produced at the glacier front many modern glaciers undergoing overall retreat in areas of maritime climate produce winter push moraines during a late winter readvance followed by a summer retreat whilst in more continental regions no significant winter readvance occurs and annual push moraines are absent the frontal dynamics which lead to these changes are analysed and the form structure sequence and field relations of both terrestrial and marine push moraines are described from iceland spitsbergen and baffin island long term changes in mass balance leading to major glacier advances or readvances also generate large push moraines in terrestrial environments push moraine formation is accompanied by uplift rejuvenation and down cutting of outwash systems whose sediments become closely associated with glaciotectonic structures which permit pre syn and post tectonic sequences to be identified the development of ice marginal fan moraine complexes is modelled as a function of the relative magnitude of two parameters the velocity of ice movement and the calving rate a high ice velocity just exceeded by the calving rate gives closely spaced push moraines and confluent ice marginal fans a high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans a low ice velocity in combination with a high calving rate results in well separated and feebly developed push moraines while a low ice velocity and a low calving rate produces feeble push moraines and coalescent fans

exploring the ingredients required to successfully model the placement generation and evolution of ice streams in the british irish ice sheet abstract ice stream evolution is a major uncertainty in projections of the future of the greenland and antarctic ice sheets accurate simulation of ice stream evolution requires an understanding of a number of ingredients that control the location and behaviour of ice stream flow here we test the influence of geothermal heat flux grid resolution and bed hydrology on simulated ice streaming the palaeo record provides snapshots of ice stream evolution with a particularly well constrained ice sheet being the british irish ice sheet biis we implement a new basal sliding scheme coupled with thermo mechanics into the bisicles ice sheet model to simulate the evolution of the biis ice streams we find that the simulated location and spacing of ice streams matches well with the empirical reconstructions of ice stream flow in terms of position and direction when simple bed hydrology is included we show that the new basal sliding scheme allows the accurate simulation for the majority of biis ice streams the extensive empirical record of the biis has allowed the testing of model inputs and has helped demonstrate the skill of the ice sheet model in simulating the evolution of the location spacing and migration of ice streams through millennia simulated ice streams also prompt new empirical mapping of features indicative of streaming in the north channel region ice sheet model development has allowed accurate simulation of the palaeo record and allows for improved modelling of future ice stream behaviour

middle and late weichselian devensian glaciation history of south western norway north sea and eastern uk data from eastern england scotland the northern north sea and western norway have been compiled in order to outline our current knowledge of the middle and late weichselian glacial history of this region radiometric dates and their geological context from key sites in the region are presented and discussed based on the available information the following conclusions can be made i prior to 39 cal ka and most likely after ca 50 cal ka scotland and southern norway were extensively glaciated most likely the central north sea was not glaciated at this time and grounded ice did not reach the shelf edge ii during the time interval between 29 and 39 ka periods with ameliorated climate including the alesund sandnes and tolsta interstadials alternated with periods of restricted glaciation in scotland and western norway iii between 29 and 25 ka maximum weichselian glaciation of the region occurred with the fennoscandian and british ice sheets coalescing in the central north sea iv decoupling of the ice sheets had occurred at 25 ka with development of a marine embayment in the northern north sea v between 22 and 19 ka glacial ice expanded westwards from scandinavia onto the north sea plateau in the tampen readvance vi the last major expansion of glacial ice in the offshore areas was between 17 5 and 15 5 ka at this time ice expanded in the north western part of the region onto the maloy plateau from norway and across caithness and orkney and to east of shetland from the moray firth the norwegian channel ice stream ncis which drained major parts of the south western fennoscandian ice sheet was active at several occasions between 29 and 18 ka

timing and depositional environments of a middle pleistocene glaciation of northeast england new evidence from warren house gill county durham at various times during the quaternary north eastern england was a zone of confluence between dynamic ice lobes sourced from the pennines northern scotland the cheviots and scandinavia the region thus has some of the most complex exposures of middle to late pleistocene sediments in britain with both interglacial and glacial sediments deposited in terrestrial and marine settings we investigated sedimentary sequences exposed on the coastline of county durham at warren house gill and present a new model of british and fennoscandian ice sheet interaction in the north sea basin during the middle pleistocene the stratigraphy at warren house gill consists of a lower diamicton and upper estuarine sediments both part of the warren house formation they are separated from the overlying weichselian blackhall and horden tills by a substantial unconformity the lower diamicton of the warren house formation is re interpreted here as an mis 8 to 12 glaciomarine deposit containing ice rafted lithics from north eastern scotland and the northeast north sea and is renamed the ash gill member it is dated by lithological comparison to the easington raised beach middle pleistocene amino acid racemisation values and indirectly by optically stimulated luminescence the overlying shallow subaqueous sediments were deposited in an estuarine environment by suspension settling and bottom current activity they are named the whitesides member and form the uppermost member of the warren house formation during glaciation ice rafted material was deposited in a marine embayment there is no evidence of a grounded onshore scandinavian ice sheet in county durham during mis 6 which has long been held as the accepted stratigraphy this has major implications for the currently accepted british quaternary stratigraphy combined with recent work on the middle pleistocene north sea drift from norfolk which is now suggested to have been deposited by a scottish ice sheet the presence of a scandinavian ice sheet in eastern england at any time during the quaternary is becoming increasingly doubtful

spatial variability of seismicity parameters in aftershock zones the spatial variability of the b value of the frequency magnitude relationship and the decay rate of aftershocks as described by the p value of the modified omori law is investigated by using dense spatial grids we map out the distribution of b and p values within the landers northridge morgan hill and kobe aftershock sequences considerable spatial variability is found with b values of independent subvolumes ranging from 0 6 to 1 4 and p values ranging from 0 6 to 1 8 these systematic and statistically highly significant differences argue that it is an oversimplification to assign one single p and b value to an aftershock sequence that extends up to 100 km the spatial distribution of these two parameters is compared with the slip distribution during the mainshock suggesting that the areas of largest slip release correlate with high b value regions we hypothesize that the frictional heat created during the event may influence the p value distribution within an aftershock zone while applied shear stress crack density and pore pressure govern the frequency magnitude distribution by investigating the frequency magnitude distribution separately for preseismic and postseismic periods for the morgan hill mainshock we find that only the volume in the vicinity of the highest slip release shows a significant increase in the b value which decays to premainshock values within a year surrounding areas of the aftershock zone show an approximately constant b value with time because the aftershock hazard after a mainshock depends strongly on both the b and p value we propose that aftershock hazard assessment can be improved by taking into account the spatial distribution of the parameters

quaternary stratigraphy of the fladen area central north sea a multidisciplinary study based on detailed stratigraphic investigations on a 200 6m long core bgs borehole no 81 26 from the fladen ground area british sector core material from the sleipner field norwegian sector and shallow seismic profiles between the core sites the following conclusions are drawn 1 the north sea was glaciated sometime during th elaterpart of matuyama reversed period a complete glacial interglacial glacial cycle is recorded in these sediments 2 in a period of marine sedimentation in the middle pleistocene a transgression regression cycle under boreal arctic regime is recorded 3 the fladen area has subsided between 0 9 and 0 6 m ka through the later parts of the quaternary 4 a major glacial event dated at between 130 and 200 ka is recorded as a thick till unit in 81 26 this till which was deposited by ice moving from the southwest scotland probably represents a period when the scandinavian and british ice sheets coalesced in the north sea 5 based on the seismic data and the stratigraphy of the sleipner core an ice free open embayment dry land is favoured for the central north sea during the late weichselian 6 from the amino acid data it is shown that there has been an episodic style of sedimentation through the quaternary 7 of the investigated sediments which span the last 1 mill year ca 98 have been deposited under arctic to boreal arctic conditions

geomorphic and sedimentary signatures of early holocene deglaciation in high arctic fiords ellesmere island canada implications for deglacial ice dynamics and thermal regime integrated studies of glacial geomorphology sedimentology marine limit elevations and radiocarbon dating in two adjacent fiords on southwestern ellesmere island indicate that early holocene regional deglaciation was characterized by a two step retreat pattern where initial rapid breakup of marine based ice preceded slower terrestrial retreat these data also indicate interfiord variations in early holocene deglacial thermal regime and illustrate the role of fiord topography as a control on glacier retreat in starfish bay deglacial landform sediment associations are preferentially located at fiord side topographic irregularities and record ice proximal glaciomarine sedimentation during stillstands at pinning points abundant fine grained subaquatic outwash indicates that the retreating trunk glacier was characterized by a warm based thermal regime the discrete location of these deposits and associated radiocarbon dates suggest rapid early holocene deglaciation of the outer and middle fiord inter

earthquake hazard after a mainshock in california after a strong earthquake the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures a stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock the probabilities depend strongly on the model parameters which are estimated with bayesian statistics from both the ongoing aftershock sequence and from a suite of historic california aftershock sequences probabilities for damaging aftershocks and greater mainshocks are typically well constrained after the first day of the sequence with accuracy increasing with time

a 7600 year sedimentary record of climatic instability in dunnet bay north scotland abstract we present a partial reconstruction of ne atlantic climatic variability the first based on stratigraphic evidence obtained from a vegetated dune system of the northern scottish coast the dune system at dunnet bay is fringed by prominent submerged peat deposits exposed only at low tide which record stable climatic periods when lower energy wind regimes prevailed allowing the formation of organic soils by contrast periods of sand influx are associated with high energy conditions the majority of sand material tested had a narrow range of particle sizes and major element composition supporting the interpretation of a common aeolian origin sand layers were dated with optically stimulated luminescence osl and peat layers were 14 c dated in four cores c1 c4 and seven sample sections s1 s7 the results from the two master sections s1 and s2 1 km apart indicate synchronous episodes of climatic stability 7650 6310 4340 4000 2690 2290 100 0 cal a bp and instability 6310 4340 4000 2690 2290 2000 170 100 cal a bp in spite of very different mean accumulation rates at the two sites 1 mm a 1 at s1 and 0 2 mm a 1 at s2 phases of sand deposition i e aeolian activity at dunnet tend to be associated with high average levels of chloride in the greenland ice sheet project 2 ice core gisp2 phases of peat development show a fairly good correspondence with low ice rafting activity in the ne atlantic and with indicators of wetness measured from a peat bog in sw sweden by contrast comparison of the dunnet depositional timeline with other regional studies e g hebrides and orkney shows little synchronicity this suggests that a local scale variables have a strong effect on regional patterns of dune instability and b the geological and geographic settings of dunnet bay mean that only large climatic regime shifts in the ne atlantic are capable of triggering instability and being preserved in the depositional record

aftershock sequence parameters in new zealand abstract regional generic models describing the temporal and magnitude distribution of aftershocks are routinely used in california to assess aftershock hazard this note applies the reasenberg and jones 1989 formulation of aftershock parameters to 17 new zealand earthquake sequences of m 5 5 from 1987 through 1995 the median values of the aftershock parameters are similar to those obtained for california

aftershocks of nuclear explosions compared to natural aftershocks abstract aftershocks of seven large nuclear explosions that were detonated at the nevada test site nts from 1968 through 1976 have been modeled with with different aftershock decay functions four natural aftershock sequences from the area have also been studied the aftershocks of nuclear explosions are different from most natural aftershocks because they decay more rapidly and their decay is more often fit by variants of exponential functions the aftershocks of nuclear explosions generally have shallower focus than natural aftershocks in keeping with the relatively shallow depths at which the nuclear explosions were detonated rapid decay is also observed in shallow focus aftershocks of natural earthquakes near the nevada test site suggesting that conditions at the hypocenters of the aftershocks influence the temporal decay of aftershocks a theory of aftershock decay proposed by dieterich 1994 predicts more rapid decay at shallow depths and offers one possible explanation of the results because aftershocks of nuclear explosions decay rapidly the activity currently observed in the nevada test site has most likely decayed fully and so the current level of activity should persist into the future

ice proximal glaciomarine sedimentation and sea level change in the inverness area scotland a review of the deglaciation of a major ice stream of the british late devensian ice sheet abstract evidence of both rising and falling relative sea levels and glacitectonic movements is preserved in two formations of raised glaciomarine deposits that were laid down in front of an oscillating grounded tidewater glacier in the inverness firth these changes occurred during the latter stages of the disintegration of the moray firth ice stream one of the major ice streams that drained the british main late devensian ice sheet most of the glaciomarine deposits antedate a sequence of glacio isostatically tilted late devensian marine shorelines and associated littoral and estuarine deposits the shorelines began forming at about 13 000 bp and record a progressive fall in relative sea level a new model for the deglaciation of the moray firth region is proposed after a critical appraisal of published accounts of both onshore and offshore quaternary sequences the disintegration of the moray firth ice stream involved several rapid phases of retreat to pinning points caused by iceberg calving and triggered by rising global sea level each retreat was followed by minor readvances or stillstands possibly caused by short lived accelerated periods of glacio isostatic rebound and concomitant temporary falls in relative sea level two such events occurred in the inverness firth the ardersier oscillation and the alturlie stillstand substantial differences lower relative sea levels later deglaciation are apparent between the pattern of ice retreat in the moray firth region and published accounts of the deglaciation of the irish sea basin these differences require a reassessment of some current hypotheses concerning the disintegration of major ice streams associated with high relative sea levels furthermore geological and geomorphological evidence suggesting both rising and falling sea levels in the inverness area prior to ca 13 500 bp is not fully compatible with recently published computer simulations of the dissolution of the british main late devensian ice sheet

glacial rebound and sea level change in the british isles observations of sea levels around the coastline of the british isles for the past 10 000 15 000 years exhibit a major regional variation and provide an important data base for testing models of glacial rebound as well as models of the late devensian ice sheet a high resolution rebound model has been developed which is consistent with both the spatial and temporal patterns of sea level change and which demonstrates that the observations are the result of i the glacio isostatic crustal rebound in response to the unloading of the ice sheet over britain and to a lesser degree of the ice sheet over fennoscandia and ii the rise in sea level from the melting late pleistocene ice sheets including the response of the crust to the water loading the hydro isostatic effect the agreement between model and observations is such that there is no need to invoke vertical crustal movements for great britain and ireland of other than glacio hydro isostatic origin the rebound contributions are important throughout the region and nowhere is it sufficiently small for the sea level change to approximate the eustatic sea level rise the observational data distribution around the periphery as well as from sites near the centre of the former ice sheet is sufficient to permit constraints to be established on both earth model parameters specifying the mantle viscosity and lithospheric thickness and the extent and volume of the ice sheet at the time of the last glaciation preliminary solutions are presented which indicate an upper mantle viscosity of 3 5 1020 pas a lithospheric thickness of about 100 km or less and an ice model that was not confluent with the scandinavian ice sheet during the last glaciation and whose maximum thickness over scotland is unlikely to have exceeded about 1500 m

morphological characteristics formation and glaciological significance of rogen moraine in northern scotland rogen moraine are enigmatic landforms whose exact origin is still debated we use nextmap digital surface models and aerial photographs to map the distribution of previously unreported fields of rogen moraine in the vicinity of loch shin northern scotland existing models of formation are tested against detailed morphological rogen moraine characteristics obtained from the remote sensing data and field observations detailed morphometric analyses combined with their geographical setting lead us to postulate a likely mechanism of formation rogen moraine appear to have formed in areas where there were strong basal ice flow velocity gradients thrusting by compression or fracturing by extension of preexisting partially frozen sediment probably occurred in these areas resulting in rogen moraine formation a general down ice increase in ridge crest spacing suggests that the latter process may have been dominant and is consistent with the location of rogen moraine in the lee of topographic obstructions in areas that experienced overall extensional ice flow we also suggest that at least one field of rogen moraine formed where lateral basal ice flow velocity gradients were strongest possibly in a subglacial shear margin setting given their location the landforms may be consistent with formation during headward scavenging of the moray firth palaeo ice stream into a shrinking core of cold based ice

properties of the aftershock sequence of the 1999 mw 7 1 hector mine earthquake implications for aftershock hazard we investigate the spatial and temporal seismicity parameters and the related probabilistic aftershock hazard for the aftershock sequence of the 1999 m w 7 1 hector mine mainshock and compare it with the neighboring 1992 m w 7 3 landers sequence using a catalog of 11 000 earthquakes we determine the earthquake size distribution b value the aftershock decay rate p value and the seismic activity rate a value the b values are high b 1 2 within the rupture area significantly lower b 0 7 north of the rupture area and increase with time since the mainshock probabilistic aftershock hazard maps computed automatically as early as 4 days after the mainshock identified the northernmost part of the sequence as the highest hazard region these maps show a good agreement between the forecasts and the recorded large aftershocks based on the asymmetrical b value and hazard patterns for both the hector mine and landers sequences we hypothesize that the mainshock rupture directivity and slip distribution influence aftershock hazard current static or dynamic stress triggering models cannot resolve this spatial and temporal evolution of the hazard stress tensor inversions of 1400 relocated first motion focal mechanisms show predominantly a strike slip stress state with a sw ne trend of the greatest principal stress the heterogeneity of the stress field is unusually high near the hector mine and landers mainshock ruptures particularly near patches of large slip

evidence for heinrich event 1 in the british isles in the north irish sea basin isb sedimentary successions constrained by ams 14c dates obtained from marine microfaunas record three major palaeoenvironmental shifts during the last deglacial cycle i marine muds cooley point interstadial dated to between 16 7 and 14 7 14c kyr bp record a major deglaciation of the isb following the late glacial maximum lgm ii terminal outwash and ice contact landforms killard point stadial were deposited during an extensive ice readvance which occurred after 14 7 14c kyr bp and reached a maximum extent at ca 14 14c kyr bp at this time the lowlands surrounding the north isb were drumlinised coeval flowlines reconstructed from these bedforms end at prominent moraines killard point bride st bees and indicate contemporaneity of drumlinisation from separate ice dispersal centres substrate erosion by fast ice flow and subglacial sediment transfer to ice sheet margins in north central ireland bed reorganisation associated with this fast ice flow phase involved overprinting and drumlinisation of earlier transverse ridges rogen type moraines by headward erosion along ice streams that exited through tidewater ice margins this is the first direct terrestrial evidence that the british ice sheet bis participated in heinrich event 1 h1 iii regional mud drapes directly overlying drumlins record high relative sea level rsl with stagnation zone retreat after 13 7 14c kyr bp rough island interstadial elsewhere in lowland areas of northern britain ice marginal sediments and morainic belts record millennial scale oscillations of the bis which post date the lgm advance on to the continental shelf and pre date the loch lomond stadial younger dryas advance in the highlands of western scotland ca 11 10 14c kyr bp in western northwestern and northern ireland killard point stadial h1 ice limits are reconstructed from ice flow lines that are coeval with those in the north isb and end at prominent moraines on the scottish continental shelf possible h1 age ice limits are reconstructed from dated marine muds and associated ice marginal moraines it is argued that the last major offshore ice expansion from the scottish mountains post dated ca 15 14c kyr bp and is therefore part of the h1 event in eastern england the stratigraphic significance of the dimlington silts is re evaluated because evidence shows that there was only one major ice oscillation post dating ca 18 14c kyr bp in these lowlands in a wider context the sequence of deglacial events in the isb widespread deglaciation of southern part of the bis major readvance during h1 ice sheet collapse is similar to records of ice sheet variability from the southern margins of the laurentide ice sheet lis well dated ice marginal records however show that during the killard point readvance the bis was at its maximum position when retreat of the lis was well underway this phasing relationship supports the idea that the bis readvance was a response to north atlantic cooling induced by collapse of the lis 1998 john wiley sons ltd

glaciotectonic structures as useful ice movement indicators in glacial deposits four canadian case studies glaciotectonic deformation structures are useful directional indicators of ice movement but are rarely reported by north american authors being three dimensional they are commonly conspicuous in cleaned sections measuring just a few of them can provide accurate ice movement directions at a site and they assist in deciphering the interaction of past glaciers and their substrata this paper concentrates on structures generally less than 10 m long in unconsolidated sediments that were induced by overriding glacial ice examples and interpretations of various types of structures are presented in four new canadian case studies from british columbia and southern ontario that illustrate different deformational circumstances in sediments of various ages

glacimarine processes and inductive lithofacies modelling of ice shelf and tidewater glacier sediments based on quaternary examples abstract three variables control the type of glacial debris source and where and when debris is introduced to an ocean 1 type of glacial ice source ice sheet or valley glacier 2 condition of a grounded glacier melting freezing or frozen base and cold or warm internal ice and 3 type of glacier front ice shelf or tidewater using these variables in different combinations eight glacimarine regimes are postulated to exist by integrating information from holocene sediment and pleistocene glacimarine sequences with the eight inductive regimes lithofacies relationships are predicted and modelled the models show a complexity of glacimarine lithofacies the importance of recognizing this complexity lies in realistic interpretations of ancient sequences ice shelf sediment may be limited in the geologic record because of tectonic and climatic constraints required for ice shelf formation alternatively in some tidewater glacier regimes larger volumes of glacimarine sediment are produced than in ice shelf regimes ice proximal sediment is distinctive especially near subglacial meltwater stream effluxes ice shelves and tidewater glaciers may produce similar ice proximal lithofacies e g morainal bank associations and laminites in certain regimes however details of lithofacies may aid in distinguishing ice shelf from tidewater regimes ice shelf and tidewater iceberg zone sediment can be distinguished from each other if basal and high level englacial debris can be distinguished ice shelf zone sediment out from the grounding line has a basal debris source high level englacial debris is deposited in more distal ice shelf zones resulting in sediment by pass in corresponding positions of a tidewater glacier regime iceberg rafted debris comprises mixed basal and high level englacial debris deeper water zones receive large volumes of sediment when a melting freezing base grounding line is at the edge of a continental shelf when the grounding line retreats sediment supply may be drastically reduced because of a back sloping continental shelf and trapping by morainal banks cool water bioclastic carbonates may accumulate once a grounding line has retreated although ice shelf iceberg zones are more extensive than those in tidewater regimes ice shelf icebergs have low debris content and resulting ice rafted debris may be scarce the smallest volume of sediment is produced by a frozen base ice sheet ending as a tidewater front and the largest volume by a melting freezing base valley tidewater glacier glacimarine sediment has a relatively high preservation potential near continental interiors or margins however at continental margins mass flow olistostrome and tectonic melange deposits may be preserved with glacimarine diamictites these deposits may be difficult to distinguish from each other especially if metamorphosed such as at a convergent margin the models presented do not fully represent the glacimarine environment because many other variables are omitted however the principal concepts of generating glacimarine lithofacies associations are considered continued research will verify if each regime exists and will provide data on those regimes that exist today to compare and modify these models

global to local scale parameters determining relative sea level changes and the post glacial isostatic adjustment of great britain abstract observations of relative sea level rsl change in great britain since 16 kyr bp and models of post glacial isostatic adjustment provide constraints on reconstructions of the british and antarctic ice sheets from the last glacial maximum to the present we use the global model from an earlier investigation modified ice 4g vm2 with lithospheric thickness 90 km which gives good rsl fits globally as well as for much of the british data a revised ice model for great britain that fits with recently published observations on ice limits and heights fails to explain all the misfits between rsl observations and predictions much more significant improvements result from models that incorporate a different chronology for the partial deglaciation of antarctica while keeping the total ice melt 17 m the same as in ice 4g vm2 the results suggest antarctic melting of 3 m ice equivalent sea level by 15 kyr bp only 1 m contribution to the 24 m rise of mwp1a with the major melting 12 5 kyr bp and a small amount of melting 1 0 0 3 m between then and 3 or 2 kyr bp these modifications produce rsl predictions for barbados that show the major changes in rate of sea level rise but with an offset up to 1 kyr compared to the observations possible explanations that remain to be investigated further are a delay in the melting of ice from some other region a reduction in the total melt derived from antarctica and a refinement of the 1 kyr temporal resolution assumed in the construction of the theoretical solution

the mode and mechanism of the last deglaciation oceanic evidence changes in ocean temperature carbonate productivity and ice rafted detritus in the north atlantic suggest that half of the northern hemisphere ice volume at the last glacial maximum had disappeared by 13 000 yr b p despite the still extensive limits of the ice sheets this early thinning of the ice sheets occurred during a time when summer insolation values were slowly rising but when pollen evidence south of the ice margins indicates cold dry air masses we infer that this rapid early ice disintegration 16 000 13 000 yr b p was caused by oceanic mechanisms 1 rising sea level causing increased calving along ice margins 2 the chilling of the sea surface by icebergs and meltwater reducing moisture extraction by the atmosphere and transport to the ice sheets and 3 winter freezing of the low salinity meltwater layer suppressing local moisture extraction and the regional influx of moisture bearing storms from lower latitudes in winter and hence starving the ice sheets these oceanic feedback mechanisms were strongest from 16 000 to 13 000 yr b p and weaker but still active from that date until the end of deglaciation at 6000 yr b p

postglacial tectonics of the scottish glacio isostatic uplift centre new evidence combined with a detailed re evaluation of postglacial fault movements seismic activity and shoreline sequences suggests that the period of deglaciation and the early holocene was more seismically active than the mid to late holocene it is proposed that the large scale lateral displacements formerly proposed can not be justified rather all postglacial fault movements appear to be limited to metre scale vertical movements along pre existing fault lines in addition it is argued that the younger dryas ice advance may have produced localised crustal redepression but not the more widespread impact formerly proposed both tectonic and postglacial rebound stresses however may be needed to explain the contemporary seismotectonics of the scottish highlands

the carstairs kames lanarkshire scotland morphology sedimentology and formation the carstairs kames have been the subject of debate for over 150 yr a synthesis of previous work along with new sedimentological data is used to reappraise this classic british esker locality three morphological elements are recognised i large sinuous and anastomosing ridges ii large irregular linear mounds and iii small low and irregular mounds the main ridge system is composed of a core of boulder gravel with sand pebble gravel above and adjacent to the core the large linear mounds contain a varied facies range which include glaciolacustrine sediments deltaic sequences laminites and dropstones debris flows and glaciofluvial channel systems all the deposits both in the main ridges and in the adjacent linear mounds contain syn and post depositional subsidence structures including normal faults synclinal folds and growth faults a range of potential origins for these landforms is reviewed and it is suggested that glaciofluvial sedimentation in a supraglacial environment controlled by a topography of ice cored ridges is the most appropriate depositional model 1997 john wiley sons ltd

facies characteristics of middle pleistocene saalian ice margin subaqueous fan and delta deposits glacial lake leine nw germany abstract the blocking of major river valleys in the leinebergland area by the early saalian scandinavian ice sheet led to the formation of a large glacial lake referred to as glacial lake leine where most of the sediment was deposited by meltwater at the initial stage the level of glacial lake leine was approx 110 m a s l the lake level then rose by as much as 100 m to a highstand of approx 200 m a s l two genetically distinct ice margin depositional systems are described that formed on the northern margin of glacial lake leine in front of the retreating scandinavian ice sheet the bornhausen delta is up to 15 m thick and characterized by a large scale tangential geometry with dip angles from 10 28 reflecting high angle foreset deposition on a steep delta slope foreset beds consist of massive clast supported gravel and pebbly sand alternating with planar parallel stratified pebbly sand deposited from cohesionless debris flows sandy debris flows and high density turbidity flows the finer grained sandy material moved further downslope where it was deposited from low density turbidity currents to form massive or ripple cross laminated sand in the toeset area the freden ice margin depositional system shows a more complex architecture characterized by two laterally stacked sediment bodies the lower part of the section records deposition on a subaqueous ice contact fan the upper part of the freden section is interpreted to represent delta slope deposits beds display low to high angle bedding 3 30 and consist of planar and trough cross stratified pebbly sand and climbing ripple cross laminated sand the supply of meltwater transported sediment to the delta slope was from steady seasonal flows during higher energy conditions 2 d and 3 d dunes formed migrating downslope and passing into ripples during lower energy flow conditions thick climbing ripple cross laminated sand beds accumulated also on higher parts of the delta slope

structural and depositional evidence for repeated ice marginal oscillation along the eastern margin of the late devensian irish sea ice stream abstract late devensian glacigenic sediments and landforms along the north west coast of wales document the advance and subsequent retreat of the eastern margin of an irish sea ice stream that met coalesced and ultimately uncoupled from ice radiating outwards from the adjacent welsh ice cap centred over snowdonia across the boundary between the two former ice masses is a set of sediment landform assemblages that reflect rapidly changing erosional and depositional conditions during ice interaction from the inner part of the ice stream the assemblages range outwards from a subglacial depositional assemblage characterised by drumlin swarms through a subglacial erosional assemblage marked by prominent bedrock scours and large subglacial rock channels through an ice marginal assemblage identified by closely spaced glaciotectonised push moraines and intervening marginal sandur troughs into a freely expanding proglacial sandur and lacustrine delta assemblage the ice marginal assemblage provides evidence for numerous oscillatory episodes during retreat and at least 20 ice marginal limits can be identified at least 11 of these display multiple criteria for identifying readvance and in the ideal case is characterised by a moraine form built by localised tectonic stacking of diamict to the rear fronted by a clastic wedge of ice front alluvial fan gravel and intercalated flow till the distribution of sediment landform assemblages suggests a highly dynamic convergent ice stream flow pattern with high ice velocity a sharply delineated lateral shear margin pervasive ice marginal glaciotectonic deformation and a tightly focused ice marginal sediment delivery system all signature characteristics of contemporary ice streams

flow pattern evolution of the last british ice sheet we present a 10 stage reconstruction of the evolution in ice flow patterns of the last british ice sheet from build up to demise derived from geomorphological evidence 100 flowsets identified in the subglacial bedform record drumlins mega scale glacial lineations and ribbed moraine are combined with ancillary evidence erratic transport paths absolute dates and a semi independently reconstructed retreat pattern to define flow patterns ice divides and ice sheet margins during build up maximum glaciation and retreat overprinting and cross cutting of landform assemblages are used to define the relative chronology of flow patterns and a tentative absolute chronology is presented based on a collation of available dates for ice advance and retreat the ice flow configuration of the last british ice sheet was not static some ice divides were remarkably stable persisting through multiple stages of the ice sheet evolution whereas others were transient features existing for a short time and or shifting in position 10s km the 10 reconstructed stages of ice sheet geometry capture two main modes of operation first as an integrated ice sheet with a broadly n s orientated ice divide and second as a multi domed ice sheet orientated parallel with the shelf edge a thick integrated ice sheet developed as ice expanded out of source areas in scotland to envelop southerly ice caps in northern england and wales and connect with the irish ice sheet to the west and the scandinavian ice sheet across the north sea following break up of ice over the north sea ice streaming probably drove mass loss and ice sheet thinning to create a more complex divide structure where ice flow patterns were largely controlled by the form of the underlying topography ice surface lowering occurred before separation of and retreat to multiple ice centres centred over high ground we consider this 10 stage reconstruction of the evolution in ice sheet configuration to be the simplest palaeo glaciological interpretation of the flowsets identified from the geomorphological record and their relative timing this empirically based reconstruction of flow pattern geometry provides a framework for more detailed local and regional studies and numerical modelling to provide robust explanations of the observed changes in ice sheet structure in terms of climate and glacial dynamics as a minimum numerical model outputs should be able to reproduce the identified flowset patterns in space and satisfy their chronological order

seismicity analysis through point process modeling a review the occurrence times of earthquakes can be considered to be a point process and suitable modeling of the conditional intensity function of a point process is useful for the investigation of various statistical features of seismic activity this manuscript summarizes likelihood based methods of analysis of point processes and reviews useful models for particular analyses of seismicity most of the analyses can be implemented by the computer programs published by the author and collaborators

the quaternary deposits and landforms of scotland and the neighbouring shelves a review abstract a thick sequence of quaternary sediments up to 1000 m has been deposited in the north sea basin and perhaps five major glacial episodes the first occurring prior to ca 1 8 2 1 ma bp and the last during the late devensian can be recognised between the glacial events periods of low salinity arctic marine or glacio marine sedimentation have been dominant although episodes of ameliorated climate when north atlantic drift waters had access to the north sea have been identified a number of horizons in separate boreholes have been correlated with the last interglacial oxygen isotope stage 5e and a sequence of water mass movements around the scottish coasts can be reconstructed for the last ca 125 ka on land sequences of quaternary deposits relating to several glacial and non glacial terrestrial and marine events occur in different areas but due to poor dating correlation between these sequences cannot yet be achieved in particular north east scotland has a complex glacial history with evidence for ice sheet glaciation on at least four occasions evidence from the outer hebrides north east scotland and the north sea basin indicates that the late devensian scottish ice sheet had a rather restricted extent only reaching a short distance offshore along much of the east and west coasts at this time ice free areas existed in north east scotland on the isle of lewis and probably in caithness and orkney whilst part of the outer shelf around st kilda was dry land a marine embayment extended down the east coast of scotland between the scottish and scandinavian ice sheets and independent ice caps existed on the outer hebrides and probably on shetland deglaciation of the greater part of the country took place prior to ca 13 ka bp whilst the climate was still very cold the ice retreat appears to have been orderly with stagnant ice masses being trapped only in topographically suitable locations a number of retreat stages or minor readvances occurred during the general deglaciation the firth of clyde was one of the last areas outside the highlands to be deglaciated and this occurred in a rapid possibly catastrophic fashion shortly prior to ca 13 ka bp despite the mild climate at the start of the lateglacial interstadial it is not known if there was complete deglaciation prior to the loch lomond readvance the readvance glaciers however may have started to advance during the latter part of the interstadial when declining terrestrial temperatures coincided with a period of mild marine conditions the loch lomond readvance maximum can only be dated to some time after ca 10 9 ka bp and it is likely that final ice free conditions were not achieved until the earliest holocene

extent and deglacial chronology of the last british irish ice sheet implications of exposure dating using cosmogenic isotopes over 160 10be and 36cl exposure ages pertaining to the extent and chronology of the last british irish ice sheet biis are critically reviewed despite uncertainties inherent in the use of exposure ages this approach has demonstrated that at the last glacial maximum lgm ca 26 21 ka the biis extended over all low ground in scotland and all or almost all of ireland consistent with recent models depicting extension of the last biis to the atlantic shelf edge all exposure ages obtained for high level sites above trimlines on the mountains of northwestern scotland and ireland pre date the lgm this finding confirms that high plateaux in these areas escaped significant glacial erosion probably under a protective cover of cold based glacier ice that remained frozen to the underlying substrate in terms of deglaciation chronology the southern irish sea basin was probably deglaciated by 19 18 ka with extensive deglaciation of low ground in ireland and northeastern scotland prior to ca 14 5 ka ice cover on low ground in northwestern scotland apparently persisted after 14 0 ka suggesting survival of ice in favourable locations during the lateglacial interstade ca 14 5 12 9 ka attempts to date readvances have had mixed success the wester ross readvance in northwestern scotland was initially dated to ca 16 3 ka but more recent research implies a much younger age ca 14 0 13 5 ka exposure ages indicating a prolonged stillstand during ice sheet retreat in the cairngorms at ca 14 5 14 0 ka conflict with ages obtained on postglacial rockslides and basal radiocarbon dates which indicate deglaciation before ca 15 5 15 0 ka exposure dating has been successfully employed to confirm a loch lomond stadial ca 12 9 11 5 ka age for moraines in several mountain areas and to constrain the minimum altitude of the ice cap that extended over the western grampians at that time copyright 2009 john wiley sons ltd

the history of quaternary sedimentation in the uk sector of the north sea basin reconnaissance seismic and sampling surveys have shown that up to 500 m of lower and early middle pleistocene deltaic sediments are preserved in the uk sector of the north sea the distributions of delta related facies record the progressive expansion of peripheral delta systems northwards across the southern north sea during the early pleistocene a late middle pleistocene unconformity is present throughout the uk sector and sedimentation above the unconformity was dominated by glacial erosional and depositional processes a complex system of deeply incised valleys was eroded during each of three regional middle and upper pleistocene glaciations and the valleys have been filled or partially filled by glaciolacustrine or glaciomarine and interglacial marine sediments the valleys of the earliest elsterian glaciation are up to 400 m deep in the southern north sea the saalian and weichselian valleys are commonly more than 100 m deep they are eroded through their contemporary tills nearshore but occur well beyond the limits of these tills offshore the origins of these valleys are attributed to a combination of fluvial subglacial and periglacial processes

rhythmically bedded glaciomarine sediments on whidbey island washington abstract several facies of late pleistocene glaciomarine sediments on whidbey island washington are rhythmically bedded the first consists of stratified silty sand which fines upward transitionally into pebbly mud several successions each approximately 0 6 m thick comprise a proximal meltwater facies thought to have been deposited in a shallow 10 m submarine fan environment both the positive lobe shape morphology of the exposure and the inferred depositional processes support this view underflow currents either high concentration turbidity currents or grain flows are thought to have deposited the silty sand while flocculation settling from turbid overflow and or interflow plumes and ice rafting were responsible for pebbly mud deposition such inferences are based on text ral analysis and observations of sedimentary structures the rhythmic interbedding is explained by invoking seasonal fluctuations of meltwater discharge this caused a variation of depositional process in areas proximal to meltwater input into the basin rhythmic interbedding is also observed within a channelized sequence of gravel sand and mud which comprise a fining upwards succession that includes turbidites laminations of sand and silt found in the upper portion of this section closely resemble the type of varved bedding commonly reported from glaciolacustrine sequences

kaolin a most diverse rock in genesis texture physical properties and uses the rock kaolin exhibits wider diversity in genesis texture physical properties and uses than probably any other common rock its diverse textures shown in scanning electron micrographs are correlative with and indicative of genesis and industrial use of kaolin kaolin originates by weathering by hydrothermal alteration or by crystallization from colloid size sediment whose chemical composition is congruent with that of kaolinite some kaolins freely slake into clay sized particles when wetted with water and likewise develop natural plasticity their texture is characterized by loosely expanded and packed crystals industrial uses of this type of kaolin exploit its free slaking property other kaolins of diametrically opposite properties do not slake and do not become plastic when immersed in water their texture is one of compact tightly interlocking crystals they are appropriately used in industry where selected size shape and original bulk density in crushed clay particles must be maintained despite wetting

pattern and timing of retreat of the last british irish ice sheet during the last glacial the ice sheet that subsumed most of britain ireland and the north sea attained its maximum extent by 27 ka bp and with an ice volume sufficient to raise global sea level by ca 2 5 m when it melted we reconstruct the demise of this british irish ice sheet biis and present palaeo glaciological maps of retreat stages between 27 and 15 ka bp the whole land area was investigated using remote sensing data and we present maps of moraines meltwater channels eskers and drumlins and a methodology of how to interpret and bring them together for the continental shelf numerous large moraines were discovered recording an extensive pattern of retreat stretching from sw ireland to the shetland isles from an integration of this new mapping of glacial geomorphology 26 000 landforms with previously published evidence compiled in the britice database we derive a pattern of retreat for the whole biis we review and compile relevant dates 881 examples that constrain the timing of retreat all data are held within a geographic information system gis and are deciphered to produce a best estimate of the combined pattern and timing of retreat pattern information reveals an ice sheet mainly comprised of a shelf parallel configuration from sw ireland to ne scotland but it spread far enough to the south to incorporate outlying ice domes over wales the lake district and kerry final disintegration was into a number of separate ice caps rather than reduction as a single mass and paradoxically retreat was not always back to high ground by 23 ka bp ice withdrew along its northern boundaries at the same time as the southern margins were expanding including transient ice streaming down the irish sea and advances of lobes in the cheshire basin vale of york and east coast of england ice divides migrated south by 19 ka the ice sheet was in crisis with widespread marine based ice losses particularly in the northern north sea and the irish sea considerable dynamic thinning occurred during this phase final collapse of all marine sectors occurred by 17 ka bp and with most margins beginning to back step onshore disintegration of the north sea ice bridge between britain and norway remains loosely constrained in time but the possibility of catastrophic collapse of this sector is highlighted the north channel and irish sea ice streams had finally cleaved the ice sheet into separate irish and scottish ice sheets by 16 ka bp rates of ice loss were found to vary widely over space and time e g 65 260 km3 per year the role of ice streams and calving losses of marine based sectors are examined retreat rates of up to ca 150 ma 1 were found for some ice stream margins that large parts 2 3 of the biis were marine based drained by ice streams and possibly with fringing ice shelves in places makes it a useful analogue for the west antarctic ice sheet wais this is especially so because the biis deglaciated in response to rising temperatures and a rising sea level driven by melting of other ice masses which are the current forcings that might cause collapse of the wais our reconstruction when viewed from the opposite perspective documents when fresh land became exposed for exploitation by plants animals and man and records for how long such land has been available for soil and geochemical development and ecological succession

loch lomond stadial and flandrian shorelines in the inner moray firth area scotland morphological mapping and stratigraphical investigations have identified surface and buried relict marine features in the inner moray firth area the features consist of a buried gravel layer formed during the loch lomond stadial a buried beach of early flandrian age and surface beaches and estuarine flats of mid late flandrian age analysis of the altitudes of morphological features has identified two buried and five possibly six surface glacio isostatically tilted raised shorelines the steepest shoreline is associated with the buried gravel layer and slopes down towards n20 e at a gradient of 0 20m km younger shorelines have lower gradients between 0 16 0 03m km the shoreline sequence combined with published data defines relative sea level movements in the area during the last 11000 years the inner moray firth shorelines are correlated with similar features in other areas of scotland which include the main lateglacial main buried and main postglacial shorelines

glacial rebound of the british isles ii a high resolution high precision model summary observations of ice movements across the british isles and of sea level changes around the shorelines during late devensian time after about 25 000 yr bp have been used to establish a high spatial and temporal resolution model for the rebound of great britain and associated sea level change the sea level observations include sites within the margins of the former ice sheet as well as observations outside the glaciated regions such that it has been possible to separate unknown earth model parameters from some ice sheet model parameters in the inversion of the glaciohydro isostatic equations the mantle viscosity profile is approximated by a number of radially symmetric layers representing the lithosphere the upper mantle as two layers from the base of the lithosphere to the phase transition boundary at 400 km the transition zone down to 670 km depth and the lower mantle no evidence is found to support a strong layering in viscosity above 670 km other than the high viscosity lithospheric layer models with a low viscosity zone in the upper mantle or models with a marked higher viscosity in the transition zone are less satisfactory than models in which the viscosity is constant from the base of the lithosphere to the 670 km boundary in contrast a marked increase in viscosity is required across this latter boundary the optimum effective parameters for the mantle beneath great britain are a lithospheric thickness of about 65 km a mantle viscosity above 670 km of about 4 5 lo2 pa s and a viscosity below 670 km greater than 4 x lo2 pas

the altitude and age of the main postglacial shoreline in eastern scotland abstract this paper discusses the patterns of altitude and age variation of the main postglacial shoreline in eastern scotland from the firth of forth to the dornoch firth for reasons of comparability attention is confined to the carseland areas the mean altitude of the shoreline declines eastwards from 14 8 m to 6 1 m od in the forth area from 11 2 m to 8 1 m in the earn tay area and northwards up the coast from the tay area to ca 6 4 m in the montrose basin area ca 3 9 m around the ythan estuary and ca 2 0 m near fraserburgh in the beauly firth inner moray firth area it declines northeastwards from ca 9 m to 7 1 7 9 m and declines to 5 7 m in the dornoch firth the isobase pattern for eastern scotland as represented by a quadratic trend surface conceals a significant regional variation in the tay area the age of the shoreline has been investigated at 14 sites grouped in 8 locations at varying distances from the centre of uplift the ages range from ca 6800 14c years bp in the upper forth carselands to 6095 75 5700 90 bp near fraserburgh with the exception of one site the data are consistent with the hypothesis that the shoreline is measurably diachronous having been abandoned progressively later with increasing distance from the centre of uplift the implications of these findings for understanding isostatic eustatic relationships are discussed

palaeoglaciology of the welsh sector of the british irish ice sheet this palaeoglaciological reconstruction based on the distribution of glacial lineations interpreted from satellite imagery considers the extent thickness and dynamics of the welsh ice cap and its interaction with the british irish ice sheet two major ice flow events were identified the oldest phase of ice flow event i is characterized by ice flowing from an ice dispersal centre situated over the higher terrain in north central wales and by ice thick enough to cover the mountain summits at this time the interior of the ice cap is inferred to have been dominated by cold based ice during the growth of the welsh ice cap it became confluent with the british irish ice sheet the welsh ice cap at this time was again sufficiently thick to submerge the highest mountain summits the youngest detected phase of ice flow event ii was marked by an abrupt change in the dynamics of the welsh ice cap during event ii the welsh ice cap was drained by at least four ice streams which followed major troughs in northern and eastern wales

glacial rebound of the british isles i preliminary model results summary observations of sea level change from localities around the british coastline indicate that major spatial and temporal variations have occurred over the past 15000 10000yr these observations provide a valuable data set for testing models of glacial rebound and for estimating the earth s response to surface loading as well as for placing broad constraints on models of the ice sheet over the northern british isles in late devensian time simple models have been developed to examine the criteria required for a high precision rebound model suitable for an inversion of the observations of sea level change for earth and ice model parameters for such a model to have a precision of better than 1 m these requirements include 1 introduction of the fennoscandian and more distant ice sheets into the model both as contributions to the sea level rise and to the crustal deformation of the associated changing ice and water loads 2 an expansion of the ice and meltwater loads to very high spherical harmonic degree including terms up to about 240 for the water load term 3 the development of higher iteration solutions of the sea level equation in order to model accurately the meltwater load contribution to sea level change 4 the introduction of loading cycles before the attainment of the last glacial maximum for both the british ice sheet and the other major but more distant ice sheets and 5 the introduction of time dependent coastlines during the period of rapid global sea level rise the sea level predictions are strongly dependent on both earth model and ice model parameters but because observations are available from a wide range of locations within and beyond the former ice sheet margins some separation of the two types of parameters is possible for example the models exclude the possibility that a substantial ice load occurred over the north sea between scotland and norway in late devensian time and that the maximum ice thickness over northern great britain is unlikely to have exceeded about 1500 m during the last glacial maximum the earth model parameters that can be resolved are the lithospheric thickness and the upper mantle viscosity a high resolution model incorporating the above model criteria and used to infer ice and earth model parameters from the observations of sea level change is developed in the accom panying paper

metastable mantle phase transformations and deep earthquakes in subducting oceanic lithosphere earth s deepest earthquakes occur as a population in subducting or previously subducted lithosphere at depths ranging from about 325 to 690 km this depth interval closely brackets the mantle transition zone characterized by rapid seismic velocity increases resulting from the transformation of upper mantle minerals to higher pressure phases deep earthquakes thus provide the primary direct evidence for subduction of the lithosphere to these depths and allow us to investigate the deep thermal thermodynamic and mechanical ferment inside slabs numerical simulations of reaction rates show that the olivine spinel transformation should be kinetically hindered in old cold slabs descending into the transition zone thus wedge shaped zones of metastable peridotite probably persist to depths of more than 600 km laboratory deformation experiments on some metastable minerals display a shear instability called transformational faulting this instability involves sudden failure by localized superplasticity in thin shear zones where the metastable host mineral transforms to a denser finer grained phase hence in cold slabs such faulting is expected for the polymorphic reactions in which olivine transforms to the spinel structure and clinoenstatite transforms to ilmenite it is thus natural to hypothesize that deep earthquakes result from transformational faulting in metastable peridotite wedges within cold slabs this consideration of the mineralogical states of slabs augments the traditional largely thermal view of slab processes and explains some previously enigmatic slab features it explains why deep seismicity occurs only in the approximate depth range of the mantle transition zone where minerals in downgoing slabs should transform to spinel and ilmenite structures the onset of deep shocks at about 325 km is consistent with the onset of metastability near the equilibrium phase boundary in the slab even if a slab penetrates into the lower mantle earthquakes should cease at depths near 700 km because the seismogenic phase transformations in the slab are completed or can no longer occur substantial metastability is expected only in old cold slabs consistent with the observed restriction of deep earthquakes to those settings earthquakes should be restricted to the cold cores of slabs as in any model in which the seismicity is temperature controlled via the distribution of metastability however the geometries of recent large deep earthquakes pose a challenge for any such models transformational faulting may give insight into why deep shocks lack appreciable aftershocks and why their source characteristics including focal mechanisms indicating localized shear failure rather than implosive deformation are so similar to those of shallow earthquakes finally metastable phase changes in slabs would produce an internal source of stress in addition to those due to the weight of the sinking slab such internal stresses may explain the occurrence of earthquakes in portions of lithosphere which have foundered to the bottom of the transition zone and or are detached from subducting slabs metastability in downgoing slabs could have considerable geodynamic significance metastable wedges would reduce the negative buoyancy of slabs decrease the driving force for subduction and influence the state of stress in slabs heat released by metastable phase changes would raise temperatures within slabs and facilitate the transformation of spinel to the lower mantle mineral assemblage causing slabs to equilibrate more rapidly with the ambient mantle and thus contribute to the cessation of deep seismicity because wedge formation should occur only for fast subducting slabs it may act as a parachute and contribute to regulating plate speeds wedge formation would also have consequences for mantle evolution because the density of a slab stagnated near the bottom of the transition zone would increase as it heats up and the wedge transforms to denser spinel favoring the subsequent sinking of the slab into the lower mantle