silurian turbidite provenance on the northern avalonian margin the windermere supergroup of nw england was deposited in a foreland basin on the northern margin of eastern avalonia and preserves an almost complete ashgill to poidoli sequence it was ideally positioned to record provenance changes associated with the closure of the iapetus ocean petrographic geochemical and nd isotopic parameters show distinct and concordant temporal trends the late ashgill to early llandovery is characterized by progressive hemipelagic dilution of material derived from the underlying borrowdale volcanic group from the llandovery onward petrographic and geochemical data indicate supply from a recycled orogen source input from the scandian orogen may be inferred no conclusive evidence is recorded of laurentian input into the basin by the late wenlock a unified sedimentary system probably spanned the iapetus ocean an abrupt reversal in provenance trends towards the end of the ludlow records basin inversion the occlusion of the iapetus seaway and concomitant cannibalization of older foreland basin sediments provenance data derived from upper wenlock to poidoli sediments aid the characterization of marine foreland basins

quick clay a case study of chemical perspective in southwest sweden quick clay a soil that changes from normal firm ground to a liquid mass when it is disturbed has been involved in most of the large and serious clay slides in sweden norway and canada the location time of occurrence and size of quick clay slides are difficult to predict and large slides may cause great devastation some geochemical studies of swedish quick clay were done in the 1960s and early 1970s but no systematic studies of the interrelationships of pore water chemistry mineralogy geotechnical properties and other parameters on quick clays in sweden have been published such studies are of national and general interest because of the many combinations of rock flour source areas and sedimentation conditions that occurred across central sweden and into the baltic sea area during deglaciation in this study geotechnical properties related to the in situ chemistry at one quick clay site were extensively studied and spot sampling was conducted at two other locations in southwest sweden in this area the clay minerals mainly are non expanding phyllosilicate minerals illite and primary minerals quartz feldspar which is consistent with previous studies of quick clay mineralogy extensive leaching has occurred at all three locations at the extensively studied site surte the lowest salinity was found at the greatest depth inferring that the leaching by fresh water was accomplished by water movement upward and laterally through the sediment from the underlying bedrock this is consistent with the local setting where bedrock hills rise sharply to over 100 m above the marine sediment surface an artesian pressure would also be anticipated at this location there is a correlation negative between sensitivity and salinity but there is an indication that the maximum salinity or electrical conductivity consistent with the quick clay behaviour is higher than reported elsewhere however for high sensitivities the salinity is about the same as reported elsewhere in the deepest part of the borehole there is a higher content of fe and al in the pore water indicating reduced state further work is needed to confirm the difference in salinity and to investigate the possible interplay of salinity and potential dispersing agents such as the role of anoxic conditions in this region further work is especially needed in the locations where the sediment accumulation occurred under lower salinity conditions at all three locations high remoulded shear strength and low sensitivity have been seen near the surface together with a decrease in pore water cation concentrations

relationship between electrical resistivity and basic geotechnical parameters for marine clays recently considerable efforts have been made in the attempt to map quick clay areas using electrical resistivity measurements however there is a lack of understanding regarding which soil parameters control the measured resistivity values to address this issue inverted resistivity values from 15 marine clay sites in norway have been compared with basic geotechnical index properties it was found that the resistivity value is strongly controlled by the salt content of the pore fluid resistivity decreases rapidly with increasing salt content there is also a relatively clear trend of decreasing resistivity with increasing clay content and plasticity index resistivity values become very low 5 m for high clay content 50 medium to high plasticity ip 20 materials with salt content values greater than about 8 g l or corresponding remoulded shear strength values greater than 4 kpa for the range of values studied there is poor correlation between resistivity and bulk density and between r

groundwater surface waters interactions at slope and catchment scales implications for landsliding in clay rich slopes understanding water infiltration and transfer in soft clay shales slopes is an important scientific issue especially for landsliding geochemical investigations are carried out at the super sauze and draix laval landslides both developed in the callovo oxfordian black marls with the objective to define the origin of the groundwater in situ investigations soil leaching experiments and geochemical modeling are combined to identify the boundaries of the hydrological systems at super sauze the observations indicate that an external water flow occurs in the upper part of the landslide at the contact between the weathered black marls and the overlying formations or at the landslide basement through a fault network such external origin of water is not observed at the local scale of the draix laval landslide but is detected at the catchment scale with the influence of deep waters in the streamwater quality of low river flows hydrogeological conceptual models are proposed emphasizing the role of the interactions between local slope and regional catchment flow systems the observations suggest that this situation is a common case in the alpine area expected consequences of the regional flows on slope stability are discussed in term of rise of pore water pressures and physicochemical weathering of the clay shales

potential field imaging of palaeozoic orogenic structure in northern and central europe abstract the trans european suture zone tesz is the most fundamental lithospheric boundary in europe separating the ancient crust of the fennoscandian shield east european craton from the younger crust of central europe and extending deep into the mantle geophysical potential field images provide an overview of the entire palaeozoic orogenic system of northern and central europe for the first time the tesz is largely concealed by sedimentary basins of permian cenozoic age geological observations are largely restricted to local basement highs and deep boreholes and the coverage of deep seismic surveys is widely spaced despite experiments recently acquired within the europrobe programme by contrast the potential field data offer a relatively detailed coverage of standardised observations throughout the tesz while some features of the images may be sourced in the near surface particularly in the gravity image much of their content reflects the structure of the underlying palaeozoic basement at the scale presented the images highlight the most fundamental features of the crustal structure of the tesz these include the strong contrast between the highly magnetic crust of the east european craton and the less magnetic palaeozoic accreted terranes of central europe the lateral continuity of terranes and their internal structure particularly where arc magmatic complexes are involved and the location and geometry of the terrane boundaries oceanic sutures and strike slip zones that separate them

mineralogy chemistry and physical properties interrelationships of some sensitive clays from eastern canada this paper describes the use of quantitative mineralogy and specific surface area in interpreting the index properties of clayey soils from nine sites in eastern canada samples representative of t

an acadian mountain front in the english lake district the westmorland monocline the structure of the southern and central english lake district is that of a southeast facing monocline named here the westmorland monocline this 10 km wide zone of highly cleaved southeast dipping rocks separates gently dipping poorly cleaved borrowdale volcanic group to the north from extensively folded but regionally subhorizontal windermere group foreland basin rocks to the south the monocline formed early in the local acadian deformation sequence and accommodates at least 8 km of uplift it coincides with the steep concealed margin of the lake district batholith a major northwest dipping shear zone is revealed in the deepest levels now exposed within the monocline in the skiddaw group rocks of the black combe inlier the monocline has the characteristics of a mountain front providing significant tectonic elevation across a foreland dipping panel of rocks with no hinterland dipping thrust visible at the surface we interpret the uplift as the consequence of a southeast vergent thrust with a gently northwest dipping ramp beneath the central lake district continuing southeastwards as a flat detachment beneath the windermere group a displacement up the ramp of about 20 km is accommodated by backthrusting within the monocline and by shortening within the windermere group of the hangingwall southeast of the monocline the tip lies beyond the limit of the lower palaeozoic inlier beneath carboniferous cover

towards a general model of quick clay development abstract within the clear definition of a quick clay as being a soil which has a sensitivity greater than 30 and a remoulded strength less than 0 5 kpa a general model for quick clay development is presented based on the influences of various material properties and natural processes on the sensitivity and remoulded strength the influences are separated according to depositional requirements and post depositional factors and according to whether the influence is to increase the undisturbed strength or to decrease the remoulded strength depositional factors are the requirements for a flocculated structure and the dominance of low activity minerals post depositional factors are cementation and slow load increase which increase the undisturbed strength and little consolidation leaching and dispersants which decrease the remoulded strength the application of the model to marine brackish water and freshwater sediments is discussed

slump folds and gravity slide structures in a lower palaeozoic marginal basin sequence the skiddaw group nw england major folds with associated thrust faults and a major olistostrome are described from the skiddaw group a lower ordovician turbidite sequence in the lake district of nw england the style and geometry of the structures are shown to be compatible with their generation as submarine slumps or slide masses although they are much larger than any slump structures hitherto described from britain the predominant strain is shown to be simple shear spatial and temporal variations in strain permit a developmental model to be erected the opposing vergence of the structures across the mapped area indicates a relatively narrow probably fault controlled depositional basin

oblique reflection of turbidity currents turbidity currents meeting obstacles for example the margins of a confined basin are subject to reflection the consequent change in flow direction is expressed in the sequence of depositional structures of the resulting bed of sediment putative examples of orthogonal reflection have been described based on 180 opposed current directions we present field evidence for the more general case of oblique reflection of turbidites and we report the results of flume experiments indicating a mechanism involving generation of internal solitary waves at an oblique ramp these propagate normal to the ramp regardless of the angle of incidence flow directions in reflected turbidites may indicate the orientation of reflecting surfaces such as basin margin slopes and thus may be of considerable help in paleogeographic and tectonic reconstructions

palaeozoic terranes and their lithospheric boundaries within the trans european suture zone tesz a review the trans european suture zone tesz is a broad and complex zone of terrane accretion separating ancient lithosphere of the baltic shield and east european craton eec from the younger lithosphere of western and southern europe there is debate about the number of terranes involved and their origins the most significant terrane boundaries originally oceanic sutures are poorly exposed and are defined using faunal provinciality prominent geophysical lineaments may represent sub terrane boundaries within composite terranes the avalonia composite terrane was amalgamated to baltica in latest ician time the provenance of the malopolska and moravo silesian terranes whose neoproterozoic basement is suspect with respect to baltica but with which they nonetheless share faunal affinities is still debated the extent of the variscide rhenohercynian zone defines the southern limit of the early palaeozoic accreted terranes terranes within the bohemian massif exhibit hp metamorphism recording subduction driven collision prior to incorporation in the tesz collage itself associated with a hp event in romania the saxothuringian zone and rheic suture are directly juxtaposed with the eec and the crustal structure of the tesz has been much modified by post palaeozoic tectonism deep seismic reflection data where available show that the oceanic sutures are frequently associated with inclined reflectivity zones irz in the lithospheric mantle here inferred to mark relict subduction zones interpreting the age of subduction is complicated by offset of originally coplanar mantle and crustal segments of the irz resulting from early orogenic lithospheric delamination at the moho interface and or post orogenic reordering processes the mantle irz appear to indicate a n directed polarity for early palaeozoic subduction apparently incompatible with the geological evidence which indicates subduction of the tornquist sea beneath avalonia and a large amount of underthrusting of avalonia by baltica possible explanations for these apparently incompatible observations are evaluated

palaeomagnetism of the ross of mull granite complex western scotland lower palaeozoic apparent polar wander of the orthotectonic caledonides the ross of mull granite complex was emplaced near the western margin of the orthotectonic caledonides of scotland in early mid silurian times anisotropy of magnetic susceptibility reflects the post tectonic character of the pluton and contrasts with magnetic fabrics in adjoining country rocks which record the regional d3 deformation palaeomagnetic study identifies two dominant magnetizations an a component is magnetite resident with distributed blocking temperatures 100 500 c and normal polarity d i 339 50 30 samples 95 5 6 palaeomagnetic pole at 12 e 1 s dp dm 5 0 7 5 it was probably acquired during initial cooling a b magnetization unblocking temperatures 500 580 c d i 195 21 40 samples 95 4 3 palaeomagnetic pole at 339 e 22 s dp dm 2 4 4 5 is of dual polarity and comparable to magnetizations widely recorded in the younger granite suite of the scottish caledonides it does not correlate with the timing of regional isotopic closure as defined by k ar thermochron ages and appears to have been imparted during a regional thermochemical event at low temperatures 250 150 c and a late stage of cooling of the orogen 420 410 ma metamorphic facies in the aureole and adjoining country rocks record examples of both a and b magnetizations together with a low blocking temperature 0 350 c component acquired during late palaeozoic early mesozoic rifting in the hebridean basin palaeomagnetic poles from the orthotectonic caledonides define a late to post tectonic magnetization record equivalent to a general east to west apparent polar wander trend of late ordovician lower devonian age a short term reversal of this trend is identified during the earlier part of silurian times so that mid late silurian poles are located in a similar position to late ordovician poles the overall path coincides with the contemporaneous record from the paratectonic caledonides of england and wales from c 455 ma it is therefore concluded that the three plate model of the caledonides incorporating the collision of laurentia and baltica in mid ordovician times to produce the orthotectonic caledonides and the closure of the iapetus ocean between baltica laurentia and avalonia in late ordovician times to produce the paratectonic caledonides was unified prior to the oldest magnetizations preserved in the orthotectonic caledonides certain second order discrepancies remain and may either reflect the incompleteness of the present database or the effects of subsequent regional rotation and strike slip movements prior to full welding of the orogen by late lower devonian times

resistivity measurements as a tool for outlining quick clay extent and valley fill stratigraphy a feasibility study from buvika central norway resistivity measurements as a tool for outlining quick clay extents and valley fill stratigraphy feasability study from buvika central norway

palaeomagnetism of palaeozoic peel sandstones and langness conglomerate formation isle of man implications for the age and regional diagenesis of manx red beds

the deep structure of northern england and the iapetus suture zone from birps deep seismic reflection profiles the nec deep seismic reflection profile images structures in the lower crust which represent the iapetus suture zone beneath southern scotland and northern england on the basis of reflectivity characteristics of the lower crust and reflection moho we recognize four different crustal zones which correspond to four crustal terrane types midland valley zone a a sub continental subduction complex zone b lake district zone c and midland platform zone d the junctions between each of these zones are interpreted as being tectonic a and b originate from the northern continental margin of the iapetus ocean and are separated from c and d which are derived from a southern continent by strong northerly dipping reflections between approximately 15 and 30 km deep in the crust the structure responsible for these reflections does not displace the reflection moho north of the ab cd junction the base of zone b and base of the reflective crust is marked by a pair of parallel reflectors persistent for a horizontal length of about 55 km these reflectors are interpreted as the top and bottom of a slice of remnant oceanic crust at their northerly limit the deepest of the two parallel reflectors transects the moho to a depth of 6 7 km into the uppermost mantle we suggest that their termination delimits the northerly extent of a decollement or shear zone at the present continental moho the shear zone was active during the late stages of caledonian collision when mantle originally from beneath the southern continent underthrust old and newly created crust of the collision zone

relationship between metamorphism and structure in the skiddaw group english lake district regional variation of white mica illite crystallinity in the skiddaw group is set against the structural interpretation of hughes cooper stone 1993 this issue in which early or pre ludlow deformation and slaty cleavage development s1 were succeeded by southward thrusting and an associated development of s1 and s1 crenulation cleavages possibly during early devonian times kubier index ki values are plotted in relation to geological structure for a major part of the skiddaw group and cross sections constructed the pattern is interpreted in terms of three processes 1 diagenetic to low anchizonal burial metamorphism under a relatively high geothermal gradient during the late arc stage early to mid silurian which preceded the orogenic phase and formation of s1 2 upper anchizonal to epizonal metamorphism due to tectonic thickening and slaty cleavage development during the early to pre ludlow orogenic phase following closure of iapetus 3 late tectonic uplift of already metamorphosed rocks by southward directed movement on the loweswater gasgale gill and causey pike thrusts possibly during early devonian time an analogous interpretation is made for the skiddaw area though with the addition of major post s1 contact metamorphism

a model for the crustal evolution of southern scotland in the late silurian southern scotland was a mature accretionary active margin of sumatra type on the southeastern edge of north america while england was on a passive margin on the opposite side of the iapetus ocean southward subduction below england during the middle ordovician produced a magmatic arc which now lies close to the iapetus suture and thus argues for a missing forearc terrane tectonic erosion or strike slip removal may be responsible for some of this missing terrane to the north of the lake district but we now suggest that underthrusting below southern scotland may also be an important cause if the ordovician forearc terrane of northern england is now below the southern uplands we would have an explanation for the evidence for similar lower crustal foundations on either side of the surface trace of the iapetus suture velocity structure from the lispb study sr u pb isotopic signatures and geophysical attributes of the c 400 ma granites the under thrusting model still leaves room for considerable modification of both margins by large strike slip faults seismic refraction profiles of modern accretionary active margins sumatra sw japan allow us to propose a likely velocity profile for late silurian southern scotland we choose a mesozoic forearc truncated by strike slip faulting the queen charlotte islands margin of the ne pacific as an analogue for the late silurian southern iapetus margin following previous suggestions of highly oblique and slow convergence during the final stages of closure of iapetus we combine the two profiles by under thrusting the southern margin to produce a model which involves minimal shortening in the collision zone the crustal profile resulting from such a collision would be very similar to the modern southern scotland profile both in terms of the scale of the tectono stratigraphic terranes involved and of the resulting crustal velocity structure the cessation of accretion after the mid wenlock may be related to impingement of the english continental crust against the scottish trench subsequent uplift of the southern uplands may be connected with the appearance of coarse detritus in the lake district during the silurian

geologic control on soil composition and properties lake ojibway clay plain matagami quebec varved clays deposited in proglacial lake ojibway at matagami quebec were derived from two source areas carbonate deficient precambrian crystalline igneous rocks from new quebec to the east and

short paper the subaerial setting of the ordovician borrowdale volcanic group english lake district most ordovician volcanic rocks of southern britain were produced in volcanic island settings and the borrowdale volcanic group bvg of the lake district has traditionally been interpreted in this way however a review of lithofacies associations in the bvg indicates a subaerial environment pyroclastic surge deposits thin welded tuff beds lava flow morphologies abundant erosional unconformities and fluviatile and laharic facies indicate widespread subaerial emplacement volcano tectonic subsidence aided preservation of subaerial facies although a preservation bias favoured lacustrine deposits erosional unconformities above subaerial aggradational volcanic sequences are to be expected so the sub windermere group unconformity does not necessarily imply tectonic uplift

turbidite to storm transition in a migrating foreland basin the kendal group upper silurian northwest england the uppermost windermere supergroup kendal group of northwest england records the passage from wenlock and lower ludlow deep water flysch deposits to upper ludlow and p idoli shallower water molasse deposits within an evolving foreland basin an upwards progression is preserved from oxygen poor basin slope turbidite deposits through more oxygenated bioturbated dilute density flow deposits to storm and wave influenced sediments the storm influenced sediments display hummocky cross stratification a skolithos ichnofacies shelly lags and symmetrical wave ripple cross lamination convolute lamination increases in magnitude and frequency in the upper part of the sequence apparently nucleated above ripple crests tropical hurricanes probably controlled storm deposition as suggested by late silurian palaeogeographic reconstructions structures in the heterolithic muddy siltstones suggest deposition in a lower energy wave influenced setting mud drapes short wavelength symmetrical ripples and multi directional ripple cross lamination are common the kendal group shows a regional palaeocurrent distribution consistent with an arcuate basin geometry bounded to the northwest and northeast by topographic slopes as well as a temporal trend facies and faunal diachroneity imply a southwards migration of the foreland basin depocentre through ludlow and p idoli time probably ahead of a rising mountain front to the north the increase in pre lithification sediment disturbance may reflect greater earthquake activity as this mountain front advanced and the basin began to invert

gravity anomalies flexure of the indian plate and the structure support and evolution of the himalaya and ganga basin bouguer gravity anomalies along four profiles across the western himalaya and ganga basin show large deviations from local isostatic equilibrium a deficit of mass characterizes the ganga basin and an excess underlies the lesser himalaya both can be understood if the indian plate is flexed down by the distributed load of part of the mountains the cross sectional shape of the ganga basin seems to be controlled by the deflection of the indian plate which we compute assuming the indian plate to overlie an inviscid fluid from the shapes of both bouguer anomaly profiles and the basement topography we place bounds on the flexural rigidity of such a plate if the ganga basin is a steady state feature then the age of the basal sediments in a given locality should be proportional to the distance of that locality from the southern edge of the basin if the rate of convergence of india and the himalaya were constant that rate should equal the distance divided by the corresponding age we find a rate of 10 to 15 mm a for the last 15 to 20 ma which is consistent with a large part of the 50 mm a rate of convergence between india and eurasia being absorbed by the eastward extrusion of parts of tibet profiles of bouguer gravity anomalies show only a small peak or plateau over the southern edge of the lesser himalaya implying that the boundary between the light sediments of the ganga basin and the heavier crustal rocks of the lesser himalaya is not sharp and that there exists some light material beneath the range we infer that some sediment deposited in the ganga basin has been underthrust beneath the lesser himalaya but the quantity is small most of this sediment probably is scraped off the indian plate to make the foothills of the range we find that the load of the high himalaya is too large to be supported solely by elastic stress in the indian plate if the flexural rigidity of the plate is constant and if no other external forces act on the plate the observed gradient in bouguer gravity anomalies increases from an average of about 1 mgal km over the ganga basin and lesser himalaya to about 2 mgal km over the high himalaya this increase in the gravity gradient implies that the moho dips more steeply 10 15 beneath the high himalaya than beneath the lesser himalaya 2 3 we interpret this steepening of the moho to be due to a weakening of the plate which allows it to bend more sharply beneath the high himalaya than farther south with the inclusion of a weak segment of indian plate beneath the high himalaya calculated anomalies show a somewhat increased gradient beneath the high himalaya but when the weight of the entire himalaya is used as a load on the plate calculated anomalies are more negative than observed therefore an external force system is needed to support much of the weight of the high himalaya as well as to bend the plate sufficiently beneath the high himalaya the magnitudes of the bending moment and the force per unit length that must be applied to the end of the plate are compatible with their sources being gravity acting on a part of india s mantle lithosphere stripped of its crust and underthrust beneath southern tibet

style scale and significance of sand bodies in the northern and central belts southwest southern uplands sedimentological and biostratigraphical data from the rhinns of galloway and adjacent areas in sw scotland confirm that deep water depositional systems consistently operated along and were sourced from the northwestern margin of an asymmetrical basin during the late ordovician and early silurian while pelagic facies accumulated simultaneously to the se providing a scenario analogous to many modern trench systems most of the observed sedimentological anomalies with regard to this general model can be explained within the context of the varied styles of trench filling depositional systems briefly reviewed here and the major stratigraphic and sedimentologic features can be best explained in terms of a geotectonically evolving fore arc region two main phases of development are recognized a llandeilo late ashgill during this time interval the fore arc trench region was tectonically juxtaposed against an active continental margin arc small to medium scale se prograding sand rich fans were formed within a relatively narrow trench leading to axial diversion of the fans initially to ne but later mainly to sw simultaneously a coarse volcanilithic sediment apron flanking the arc migrated gradually northeastwards probably in response to relative fault displacement of the arc and trench b llandovery during this time interval the fore arc trench region was dominated by a variety of mainly fan type depositional systems which were exclusively sourced at least until the uppermost llandovery from the northwestern margin the juxtaposition of coeval depositional systems differing significantly in sedimentological style and composition strongly suggests that the llandovery sedimentation in this region occurred in several structurally separated sub basins within the main trench system

foreland basin development and tectonics on the northwest margin of eastern avalonia the early palaeozoic convergence of avalonia and laurentia created a foreland basin at the suture zone of the former lapetus ocean sedimentological and stratigraphic evidence of shallowing and contemporaneous shortening suggests that the southern part of the basin the windermere group became detached from its basement in the late ludlow and began to invert the detachment beneath the basin rooted into a northwest dipping mid crustal thrust system contemporaneous uplift to the north of the late silurian basin involved shortening of the avalonian foreland basement by thrusting basin inversion occurred ahead of a southeastward advancing mountain front we postulate a foreland southeast prograding sequence of thrusting through the ludlow in the lake district the basin continued to migrate onto the avalonian foreland through the early devonian ahead of an advancing orogenic wedge finally coming to a stop in the emsian

subsidence analysis of eastern avalonian sequences implications for iapetus closure basin subsidence analysis employing the backstripping method indicates that fundamentally different basin generating mechanisms controlled silurian basin development in northern england and in wales accelerating subsidence with time suggests that the dominant control on basin formation in northern england was flexure of the eastern avalonian lithosphere mid wales however displays dominantly decelerating subsidence suggesting an extensional control the errors involved with the backstripping method particularly concerning lower palaeozoic application have been addressed in conjunction with sedimentological and tectonic data the subsidence patterns for the windermere supergroup indicate deposition in a flexurally loaded foreland basin which migrated southwards with time similar data for the powys supergroup of mid wales imply an extensional control on silurian deposition possibly in a strike slip setting however later poidoli and early devonian welsh sedimentation may represent the onset of foreland basin deposition the new data are consistent with a diachronous closure of the iapetus ocean related to rotational collision of eastern avalonia with laurentia during the early silurian early silurian oblique collision produced transtension in wales subsequent rotation of eastern avalonia produced more orthogonal collision thus continental flexure was felt initially in northern england in late wenlock times followed by migration of the resultant foreland basin to the southeast into wales in early devonian times the versatility of the backstripping method is shown by this application to lower palaeozoic sequences

palynofacies in a late silurian regressive sequence in the welsh borderland and wales the upper whitcliffe and lower part of the downton castle sandstone formations ludlow and pridoli series have been sampled from sequences distributed over an area roughly 4800 square km in west central england and wales ludfordian age rocks have been interpreted as the deposits of shelf and basin environments and those of the lower downton group as near shore to beach sections sampled from the shelf area are in the ludlow type area and in the usk may hill and woolhope inliers basin sediments were sampled at knighton the long mountain capel horeb and kington the samples were analysed for their palynological content and all the organic walled microfossils were studied together with the fragmentary remains of larger plants and animals using a series of ratios between different groups of microfossils it is apparent that there are consistent changes through time in both the palynomorph assemblages and in the structured and unstructured organic material dominance of some microplanktic groups taxa is used to define a new microphytoplanktic phase concept and to compare the sequence of palynoevents depositional environments inferred from palynofacies interpretation of the ludlow type area are closely comparable with those proposed previously from sedimentological data palynofacies sequences differ for the shelf and basin areas but show similar trends we have also recognized a dramatic shift in palynofacies at a level within the downton castle sandstone formation and its correlatives in both shelf and basin areas this change is tentatively interpreted as a storm event

a sequential back arc and foreland basin thrust duplex model for the southern uplands of scotland thrust imbrication of ordovician and silurian submarine fan sequences overlapping pelagic deposits in the southern uplands has been interpreted in terms of an accretionary prism formed above a nw directed subduction zone structural features invoked to support accretion are not definitive and could be explained in terms of a thin skinned thrusting model new palaeocurrent and compositional evidence from llandeilo to mid llandovery age turbidites in the northern part of the southern uplands proves interdigitation of sediments with strongly contrasting petrography turbidites derived from the south contain significant quantities of fresh andesitic detritus whereas those from the north form more mature quartz rich formations this implies a back arc situation the turbidites being deposited in a basin with a relatively mature continental landmass to the north and a rifted continental fragment containing an active volcanic arc to the south oblique collision of the opposing continental margins of the iapetus ocean during the llandovery caused the cessation of subduction underthrusting of the southern margin initiated a se propagating thrust stack which deformed the back arc basin sequence and may eventually have ramped over the eroded and faulted remains of the volcanic arc a southward migrating foreland basin formed ahead of the rising thrust stack and is now represented by the late llandovery hawick group and wenlock sequences mid to end silurian sinistral strike slip resulted from oblique collision and produced a transpressional regime during which reactivation of deep seated structures allowed the intrusion of lamprophyre dykes and granites

the lachenaie clay deposit some geochemical and geotechnical properties in relation to the salt leaching process this paper summarizes a detailed geotechnical and geochemical characterization program for the champlain clay deposit in lachenaie quebec presently the clay pore water is saline the main objective of the testing program was to study the leaching of the clay saline pore water since its deposition four issues are discussed in this paper first the deposit is shown to comprise two distinct clay layers with contrasting geotechnical properties the liquid limit and grain size distribution are the properties that best distinguish the two materials the upper layer is more plastic while the lower one is relatively silty the occurrence of these two layers is shown to be in agreement with some recent findings in quaternary geology second the relatively high pre consolidation pressures of the clay in the lachenaie area are shown to be coherent with an erosion scenario and the elevation of a neighbouring bluff previously interpreted as an erosion terrace third the relatively constant hydraulic conductivit

dynamic earth system and ecological controls of rainfall initiated landslides abstract rainfall initiated landslides continue to inflict damages and loss of life throughout the world processes and mechanisms revealed from hydrological geomorphic geotechnical pedological geological hydrochemical and biological investigations have advanced our understanding of these effects on slope stability however the interactions amongst these processes and attributes as they affect the initiation and propagation of landslides are not as well understood too often landslide studies are conducted from only one or at most two of these perspectives moreover while precipitation and hydrology are recognized as dynamic influences the earth system and ecological effects are often assumed to be static we assess the interplay of these processes related to landslides triggered by positive pore water accretion and loss of soil suction each of these conditions arguably requires a different view on the processes that cause slope failure and predictive approaches this review starts from the perspective of dynamic adapting earth and ecological systems and discusses how these attributes relate to landslide initiation mode location and timing specifically the role that large and small scale preferential flow plays in both contributing to and mitigating instability is elucidated including effects of bedrock exfiltration we also examine how and under what conditions these pathways manifest in different soils lithology and landforms the multiple effects of rhizosphere processes on slope stability are discussed including root reinforcement evaporation from canopies and litter layers transpiration and the role of root structure affecting preferential flow paths rainfall initiated landslides involve highly dynamic hydrologic earth surface and ecological processes that persist over a range of spatial and temporal scales however guidance for overcoming these challenges has been elusive a conceptual framework is presented to shed light on these dynamic and interactive processes that should lend insights into why and when certain slopes fail during storms while other seemingly similar slopes do not fail such advances will benefit landslide hazard assessments and disaster responsiveness protocols

the iapetus suture zone in england scotland and eastern ireland a reconciliation of geological and deep seismic data deep seismic profiles in the irish and north seas have successfully imaged crustal structure across the iapetus suture zone a problem with current interpretations is that the reflectors chosen as the suture project to the top of the basement well to the south of the solway line the palaeontologically defined trace of the suture we present a revised interpretation in which a reflectivity boundary common to all the profiles is identified as the leading edge of imbricated avalonian crust in effect the footwall of the suture zone this projects to the surface close to the solway line obviating the need to invoke northward backthrusting of the suture

the magnetic soils of brazil abstract certain brazilian latosols show a spontaneous magnetization of the clay size fraction in excess of 1 j t kg they can be picked up by a hand magnet magnetization is a good indicator of soil type being greatest in those soils derived from mafic or itabiritic rocks which have been little influenced by xanthization the soil yellowing process the magnetic phase is fully oxidized titanomaghemite which is inherited directly from weathered bedrock simple magnetic measurements are recommended as an aid in classifying tropical latosols

u pb chronology of the ennerdale and eskdale intrusions supports sub volcanic relationships with the borrowdale volcanic group ordovician english lake district u pb analyses of zircons from the ennerdale granitic intrusion and eskdale granite english lake district give ages of 452 4 ma and 450 3 ma respectively these data confirm the sub volcanic association of these intrusions and show that previously published rb sr whole rock and k ar mineral ages do not correspond to the emplacement and cooling of these igneous bodies the new ages show that only two phases of acid magmatism can now be linked to the exposed parts of the lake district batholith the caradoc late ordovician phase was caused by the subductionrelated processes which gave rise to volcanism and was followed by a separate early devonian phase of granite emplacement

reply to discussion on no exploits back arc basin in the iapetus suture zone of ireland journal of the geological society london 172 740 747 we thank van staal winchester 2017 for their discussion of our paper mcconnell et al 2015 and their concise summary of the evolution of the popelogan victoria arc tetagouche exploits basin and ganderian margin in the northern appalachians they make the case that we have failed to recognize the same tectonic elements and geological history in ireland they propose that we in concluding there was no exploits basin equivalent in ireland have an absence of evidence rather than evidence of absence we have documented a stratigraphical sequence that provides evidence of a 10 myr gap in volcanism at bellewstown c 474 464 ma at a time when the tetagouche exploits basin was actively opening further to the west along the orogen we have placed that observation in the regional context of a middle late ordovician stratigraphical and faunal linkage to the leinster terrane parkes harper 1996 where volcanism demonstrates continued subduction under a north facing volcanic arc on the ganderian margin mcconnell 2000 we concede that the bellewstown succession if taken in isolation could represent deposits on the passive margin of the tetagouche exploits basin but the darriwilian sandbian volcanic rocks of north leinster are too voluminous too young and geochemically incompatible with representing remnants of the passive margin of a tetagouche exploits basin aged rifted arc basin

geophysical characterization of areas prone to quick clay landslides using radio magnetotelluric and seismic methods landslides attributed to quick clays have not only considerable influences on surface geomorphology they have caused delays in transportation systems environmental problems and human fatalities

geophysical and geotechnical studies of geology and sediment properties at a quick clay landslide site at esp trondheim norway abstract increased urbanisation and development in previous marginal areas have led to the need to protect the population the environment and infrastructure from hazards such as quick clay landslides in this paper the opportunity which was presented following the gathering of a large amount of data in the area of the quick clay landslide at esp trondheim norway in 2012 is explored the data is of particular interest given the availability of frequency domain helicopter borne electromagnetic data fhem and extensive lidar imaging as well as a full range of in situ geophysical and geotechnical soundings and samples the ground conditions in the area are shown to be complex and it is clear that a multi disciplinary type approach combining geophysical geomorphological and geotechnical investigations is necessary in order to understand the hazards posed by potential quick clay landslides the investigation shows that very good overview mapping of the area can be obtained from fhem and that the data obtained from local electrical resistivity tomography ert and resistivity cone rcptu are consistent with each other and with the fhem data use of ert immediately after the landslide was particularly useful in delineating further risk areas and as an aid for assessment of evacuation of the local population lidar data is particularly useful in understanding the landslide trigger mechanisms the depth of the landslide the form of the run out and the nature of the material in the run out geotechnical data collected in the area is characteristic of that of soft sensitive norwegian marine clays and the various geotechnical and geophysical parameters correlate well with one another and also follow well established patterns the data shows that no single investigative method is available to accurately define quick clay layers but that a number of complimentary in situ and laboratory techniques are necessary for that purpose

nd isotope study of provenance patterns across the british sector of the iapetus suture the southern uplands greywacke succession scotland accumulated at the laurentian margin of the iapetus ocean it was sequentially incorporated into an imbricate accretionary thrust complex until closure of the ocean thereafter the thrust belt propagated across the suture zone as a foreland thrust belt directed towards the hinterland of avalonia a foreland basin migrating ahead of the thrust belt was the depositional site for the southernmost southern uplands units and the windermere supergroup english lake district a nd isotope study has shown that juvenile ophiolitic detritus was introduced into the oldest mid ordovician southern uplands greywackes before two distinct provenance areas evolved one supply ing juvenile andesitic detritus in addition to a quartzo feldspathic component the other proterozoic and exclusively quartzo feldspathic bimodal composition continued into the early silurian but was overlapped from late in the ordovician by greywackes with intermediate nd isotope composition this was not a sim ple mixing effect since the andesitic component is not represented and the necessary juvenile component comes from granodioritic and felsitic lithologies intermediate end values are then a consistent feature through the silurian both in the younger strata of the southern uplands and in the earliest foreland basin tur bidites of the windermere supergroup the transition suggests cessation of volcanicity and erosion of deeper levels of the provenance terrane s possibly linked to the evolution of the basin system from active margin accretion related to a foreland setting to the north of the southern uplands terrane beyond the southern upland fault a caradoc to wenlock turbidite sequence occupies inliers within the midland valley the older greywackes contain abundant juvenile ophiolite and plutonic detritus in addition to a quartzo feldspathic metamorphic component there are similarities with the most northerly part of the southern uplands from the late ordovician end values systematically decline so that early llandovery midland valley greywackes are exclusively quartzo feldspathic derived from an ancient source indistinguishable in isotopic terms from that periodically supplying the southern uplands in general the llandovery midland valley provenance was significantly more mature than that contemporaneously supplying the southern uplands thereafter the midland valley latest llandovery and early wenlock greywackes contain a higher proportion of a juvenile component and by the early wenlock greywackes from the midland valley southern uplands and lake district terranes are similar in terms of end a common provenance seems likely and suggests that by the mid silurian all three terrenes were in close proximity