regional neogene exhumation of britain and the western north sea tertiary exhumation of britain and the western north sea is interpreted to have taken place in two episodes each with amplitudes of about 1 km a palaeogene phase that principally affected the present onshore britain west of the present extent of the late cretaceous danian chalk group and a neogene phase that affected both onshore areas and the western north sea consequently maximum burial of mesozoic and older rocks in the present onshore areas generally occurred in the palaeocene c 60 ma in the western north sea the preservation of the chalk group today suggests relatively stable conditions prevailed immediately after its deposition rather than substantial palaeocene exhumation in this area maximum burial is interpreted to have occurred in the neogene the proposal is consistent with published exhumation estimates based on studies of sediment compaction offshore and of fission tracks onshore it also does away with unlikely high burial rates which are implied in the latest cretaceous earliest tertiary if removal of overburden from the chalk is assumed to have occurred in the palaeocene

evidence for cenozoic tectonic deformation in se ireland and near offshore 1 an integrated study of topography bathymetry high resolution aeromagnetic data and structural observations demonstrates significant cenozoic fault activity in se ireland tectonically generated knickpoints and reddened fault breccias along topographic escarpments that are underlain by greywacke bedrock and trend oblique to the regional caledonian strike provide evidence for fault displacement near offshore faults with similar geometry produce present day bathymetric scarps and localized tectonic topography in the inverted kish bank basin the integration of offshore high resolution aeromagnetic data and structural interpretation of the kish bank basin provides evidence for dextral transtension on nnw trending faults and sinistral transpression on ene trending faults bounding a lower paleozoic to carboniferous basement block these faults correlate onshore with previously recognized caledonian faults producing topographic offsets and surface uplift to the north offshore structures can be traced onshore and cut exposures of the caledonian leinster granite structural analysis of these outcrops indicates post variscan deformation a major fault on the nw margin of the batholith cuts a major erosion surface developed on carboniferous carbonate rocks and nonmarine miocene deposits are preserved above this surface fault kinematics provide evidence of two paleostress systems 1 nw se 1 subvertical 2 and ne sw 3 followed by 2 a clockwise swing of 1 to nnw sse timing of deformation in both stress systems is probably post oligocene age the mechanism driving this deformation is likely ridge push much is already known about cenozoic tectonics and exhumation from offshore basins this study shows that onshore ireland has also been affected by significant tectonic activity and exhumation during the cenozoic

the post variscan thermal and denudational history of ireland the thermal and denudational history of ireland is evaluated using an extensive new apatite fission track aft dataset derived from surface samples modelled thermal histories are used to construct maps of denudation for a number of time slices from triassic time to 10 ma using a time dependent palaeogeotherm the maps illustrate the spatial variability of denudation and subsidence within each time slice the patterns of denudation are complex showing considerable variability at the length scale of 101 102 km with especially high denudation rates found over known igneous centres such as the mournes of county down based on the onshore aft data alone there is no definitive signature of an irish sea dome extending significantly across ireland in early tertiary time the cumulative amount of denudation during tertiary time varies depending on the aft annealing model used but is generally in the region between 1 and 2 km and without clear spatial trends high amounts of denudation have been mapped over the tertiary intrusions in county down reflecting their unroofing since emplacement in paleocene time the cumulative denudation from triassic time to 10 ma shows relatively low amounts of denudation 2 km in the irish midlands and the extreme ne of the island consistent with the observation that mesozoic tertiary sediments and igneous products are preserved in the ulster basin the western flank of ireland and the region between dublin and county down show high cumulative amounts of denudation 4 km the latter being consistent with the high amounts of denudation interpreted for the irish sea region this denudation pattern explains in part the outcrop of precambrian and lower palaeozoic rocks in these areas the spatial integration of the denudation over the entire landmass gives the average denudation rate and the sediment discharge from ireland as a function of time average denudation rates are moderately high in triassic time falling to low values in cretaceous time and increasing substantially in tertiary time however the total volumetric discharge of sediment in tertiary time is an order of magnitude smaller than the preserved solid volume of tertiary sediment in the basins offshore western ireland

long term landscape evolution early miocene and modern rivers in southern new south wales australia basaltic lavas that flowed into river valleys draining westward from the uplands of southern new south wales have preserved the early miocene landscape to a remarkable degree the reconstruction of this landscape shows that the major topographic features of the highest part of the australian continent had taken on essentially their present form by the mid tertiary and that some of these features were formed during the mesozoic plateau surfaces have been lowered by only about 2 to 5 m ma and most major streams have incised by only about 5 to 18 m ma with a maximum incision of 30 m ma since the early miocene despite the passage of 20 ma stream gradients have not waned nor have major breaks in profiles been eliminated on the contrary the modern stream profiles are strikingly similar to their early miocene counterparts suggesting that the evolution of the profiles has been determined mainly by variations in stream power rather than by the headward retreat of nickpoints through the drainage system

tertiary uplift and inversion history in the north celtic sea basin and its influence on source rock maturity abstract tertiary uplift and basin inversion have been widely recognized in the area of the north celtic sea basin offshore ireland but the magnitude and timing of the various events have not been well documented an understanding of these events is important because recent basin history generally has a major influence on hydrocarbon source rock maturity levels a multi disciplinary approach was used to investigate the timing and nature of uplift in the north celtic sea basin involving seismic data interpretation well log correlation vitrinite reflectance measurement apatite fission track analysis and a cretaceous chalk group isopach and velocity study both regional uplift and compressive inversion can be interpreted to have occurred based on missing geological section compressive reactivation of earlier normal faults and basin centred uplift two tertiary erosion events are recognized a regional uplift in the palaeocene and compressive inversion characterized by basin doming and fault reversal probably associated with an oligo miocene phase of the alpine orogeny separating these was a period of basinal deposition in the eocene to oligocene a map of the magnitude of erosion generated as a result of the two events shows that the amount of uplift is quite variable in the northeast part of the basin where the later event was most severe uplift was as much as 1100 m reconstruction of the basin geometry before inversion together with thermal modelling at selected well locations suggests that upper jurassic source rocks reached maturity for oil generation only in the central portion of the basin whereas lower jurassic source rocks entered the gas window in much of the basin prior to tertiary uplift

cenozoic postrift domal uplift of north atlantic margins an asthenospheric diapirism model postrift domal uplifts are a distinct feature of the northern north atlantic rifted margins uplifted regions southern norway finnmark svalbard northern united kingdom occur with a typical spacing of 900 km the amount of domal uplift is substantial 1 2 km thermochronological geomorphological and seismic stratigraphic data suggest a coincident neogene onset of uplift postdating north atlantic breakup and predating onset of glaciation the norwegian domes are characterized by strongly negative gravity anomalies and reduced mantle p wave and s wave velocities previous models for uplift around the north atlantic e g glacial erosion intraplate stresses secondary convection fail to explain the above characteristics we present an asthenospheric diapir model based on a rayleigh taylor instability wherein a hot icelandic asthenosphere layer meets cold cratonic lithosphere the generated asthenospheric diapirs and associated partial melting offer a viable explanation for updoming application of this model to the south norwegian dome succesfully explains most of the currently available data

a continent wide map of 1 hz lg coda q variation across eurasia and its relation to lithospheric evolution 1 we present new maps of lg coda q qo and its frequency dependence at 1 hz that cover virtually all of eurasia qo is relatively high up to 650 or more in the east european siberian indian and kazakh platforms but is surprisingly low 300 500 in the arabian platform and western portion of the siberian platform as well as in great britain and the northwestern portion of mainland europe it is generally low throughout the tethysides orogenic belt but there too it displays substantial regional variations 150 400 most qo anomalies appear to be related to the tectonic history of the eurasian crust the four regions with lowest values coincide with four of eurasia s most active concentrations of earthquake activity observed eurasian qo values are consistent with a previously determined empirical plot of global values in which qo in any region is proportional to the time elapsed since the most recent episode of tectonic or orogenic activity there comparisons of the new qo map with maps of rayleigh wave velocity temperature subducted lithosphere and seismicity lead us to infer that lg coda wave attenuation is most easily explained by energy lost in moving fluids through permeable rock or in being scattered from fluid enhanced zones the fluids are likely to have originated by hydrothermal release from subducting lithosphere or other upper mantle heat sources anomalies in qo and other lithospheric properties in some cases extend well outside the tethysides belt and other regions where upper mantle heat sources are known to occur possible explanations include earlier episodes of subduction activity crustal deformation due to collision of the afro arabian and indian plates or broader than expected back arc activity beneath eurasia

plate reorganization a cause of rapid late neogene subsidence and sedimentation around the north atlantic subsidence analysis of wells in the central north sea and labrador grand banks and oft the west greenland scotian shelf and united states atlantic margin shows distinct quantitative stratigraphic correlation patterns of circum north atlantic sites a significant departure from the overall decrease in subsidence for the pliocene occurs in many wells when the rate is found to have increased one or more orders of magnitude from oligocence miocene rates wells were selected along transects from shore to basin to find if relative basin position is influenced by differential basin subsidence although stratigraphic resolution is not detailed more basinward sites experienced up to four times larger subsidence rates in the late neogene than in the oligocene miocene with a peak in the pliocene wells at the basin edge experienced much less subsidence or showed uplift the observations are consistent with a rapid change of intraplate stress at the cause for this observed transition in neogene subsidence major reorganizations of spreading direction and rate occurred during the pliocene along the entire atlantic spreading system possibly in conjunction with more global changes in plate motions we propose that the associated changes in intraplate stress caused the excess margin subsidence relative uplift along basin edges is consistent with this mechanism of relative movement and may explain apparent eustatic changes in sea level

mid to late cenozoic sedimentation on the continental margin off nw britain the present morphological expression of the continental margin off nw britain is a mid to late cenozoic phenomenon initiated by a major phase of rapid subsidence in the rockall trough and hatton rockall basin during the early late eocene this led to a deepening of the basins and the onset of bottom current activity in this region on seismic reflection profiles this basin subsidence event is manifest in the form of a widespread deep water unconformity caused by bottom current erosion this boundary is particularly enhanced at the basin margins and adjacent to the axial seamounts of rosemary bank and anton dohrn where the downwarped and eroded surface of lower upper eocene and older strata is onlapped by middle to upper cenozoic sediments the latter comprise two megasequences of late eocene to mid miocene and mid miocene to holocene age which consist predominantly of deep marine contourites both in the rockall trough and the hatton rockall basin although a clastic wedge has built out along the hebridean shelf margin since the mid miocene these megasequences reflect a gross two stage depositional history a response to intra plate tectonism which modified sedimentation patterns and palaeoceanographic circulation the development of the bounding unconformities early late eocene and mid miocene was coincident with major phases of regional tectonism

tortoises and hares dissolution erosion and isostasy in landscape evolution denudation mechanisms differ fundamentally between limestone and silicate rock types which are subject to very different rate thresholds and enhancers inhibitors silicates are removed largely by erosion the mechanical entrainment and transport of particles this is a relatively high energy and highly episodic process which occurs only when a minimum threshold flow velocity is exceeded it is inhibited by vegetation cover and favoured by strongly seasonal runoff limestone is removed largely by chemical dissolution at a rate directly proportional to runoff dissolution is a relatively low energy process that can occur at any flow velocity or in static water in general it is enhanced by vegetation cover and non seasonality of runoff these contrasting factors in the denudation of silicates versus limestone can produce strikingly uneven rates of surface lowering across a landscape sometimes akin to the well known tortoise and hare race where the slow and steady denudation of limestones may in the long term exceed the sometimes rapid but often localized and episodic erosion of silicates prolonged exposure of limestone to a humid temperate climate in a tectonically stable environment produces lowrelief corrosion plains in which limestone uplands are anomalous and in most instances due to recent unroofing from beneath a siliciclastic cover in a highly seasonal or semi arid climate almost the exact inverse may develop with flashy runoff and sparse vegetation favouring erosion rather than dissolution even under a constant humid climate progressive unroofing of a thick limestone unit within folded siliciclastics may lead to a topographic inversion over time with the limestone outcrop always forming a topographic low flanked by siliciclastic uplands valleys will be initiated on anticlinal crests where the limestone is first unroofed but progressive lowering of the limestone causes these valleys to migrate to their final position in the synclinal troughs in humid climates isostatic compensation in response to slow but continuous denudation of extensive limestone outcrops may be a significant factor in the development of relief on adjacent more slowly eroding silicate outcrops copyright 2004 john wiley sons ltd

late cenozoic uplift and volcanism on spitsbergen caused by mantle convection regional tectonic uplift heat flow measurements and p t estimates on upper mantle xenoliths associated with neogene volcanic rocks indicate a strongly thinned 50 km thick lithosphere beneath svalbard 650 km north of scandinavia data on neogene volcanic rocks and xenoliths indicate an 50 c temperature anomaly in the underlying asthenosphere together with volatile rich conditions in the upper mantle the svalbard uplift is one of several cenozoic epeirogenic uplifts along the margins of the north atlantic boundary processes occurring where hot spot influenced asthenosphere abuts cold deep continental lithosphere seem to be likely explanations for the uplifts

constraints on the age of the british tertiary volcanic province from ion microprobe u pb shrimp ages for acid igneous rocks from ne ireland using the sensitive high resolution ion microprobe shrimp u pb ages have been determined for zircons separated from rhyolitic obsidian from the tardree sandy braes rhyolite centre and granites of the mourne mountains and slieve gullion central igneous complexes of the british tertiary volcanic province these ages tardree 58 4 0 7 ma mourne 56 4 1 4 ma and 55 3 0 8 ma and slieve gullion 56 5 1 3 ma are in close agreement within error with results from independent dating methods rb sr k ar and 40 ar 39 ar and are interpreted as crystallization ages the euhedral clear bipyramidal nature of all separated zircons is indicative of a magmatic origin and combined with the paucity of zircon grains with any history of inheritance has implications for granite petrogenesis when considered with recently published high precision 40 ar 39 ar ages for sanidine separates from the hebrides these data help to establish a timeframe for tertiary magmatism in the nw british sector of the north atlantic tertiary volcanic province and show that central complex magmatism in ne ireland was confined to the later stages of activity

controls on syndepositional fracture patterns devonian reef complexes canning basin western australia abstract syndepositional fractures are an important feature of high relief carbonate systems and exert a profound control on many facets of platform evolution and reservoir development based on data collected from the canning basin s devonian reef complexes this study characterizes syndepositional fracture patterns as a function of variations in lithofacies depositional position stratigraphic architecture and mechanical stratigraphy fracture parameters such as extension and fracture intensity are documented to vary strongly as a function of lithofacies the highest syndepositional extension values occurring in the microbial facies of the famennian platform margin with extension values three times higher than observed in equivalent frasnian strata position along the depositional profile exerts a strong control on fracture patterns with an approximate two fold increase in syndepositional extension and fracture intensity typically observed from the platform interior to the platform margin syndepositional fracture intensity is shown to vary systematically with changes in platform margin trajectory with high fracture intensities observed in strongly progradational platforms and decreased fracture development in aggradational and retrogradational platforms evidence for the temporal evolution of the mechanical stratigraphy of the devonian reef complexes is presented with early lithified strata effectively behaving as a single large scale 50 150 m mechanical unit during syndepositional fracture development while secondary fractures become increasingly affected by bed scale 0 25 5 m mechanical heterogeneity introduced by progressive diagenesis the results presented here potentially provide a tool for predicting fracture characteristics e g intensity orientation location and vertical extent from limited subsurface data and provide a method for characterizing syndepositional deformation in other systems

palaeogene dyke swarm nw wales evidence for cenozoic sinistral fault movement the berw and aber dinlle faults represent the brittle manifestation of a major lineament the menai strait fault system which is known to have been active intermittently since late precambrian times documentation of historical seismicity in this area provides information on the most recent activity along this structure although there is a paucity of field evidence to support conclusively cenozoic or later movements this work documents data from three separate aeromagnetic datasets combined with field relationships which reveal a well defined cenozoic dyke swarm traversing anglesey and snowdonia showing clear sinistral offset up to 1 5 km along the berw fault the most northwesterly component of the menai strait fault system these data provide conclusive evidence of cenozoic

meso cenozoic morphotectonic evolution of southern norway neogene domal uplift inferred from apatite fission track thermochronology apatite fission track aft thermochronology of precambrian and paleozoic basement samples from southern norway reveals a post paleozoic exhumation history related to offshore mesozoic and cenozoic extensional basin development the data indicate two major phases of rapid exhumation a first mesozoic phase started in the triassic 220 ma in the east and south of the study area and migrated to the west where jurassic 160 ma ages of exhumation predominate a second event is indicated by thermal history modeling of aft ages and track length distributions it is inferred to be neogene in age initiated at about 30 ma and it produced a domal pattern of aft isochrons which follow present day topographic elevation youngest aft ages 100 ma are encountered at sealevel in the inner fjords near the areas of highest topography ages increase radially outward to the mountain peaks and the coastlines forward modeling of age elevation patterns suggests that mesozoic geothermal gradients were 10 15 c km higher than the present value of 20 c km during the triassic and jurassic a total of 1 3 3 5 km of overburden was removed from the study area assuming a 30 c km geothermal gradient for that period we attribute this to rift margin erosion as a result of erosional base level lowering and flank uplift as evidenced by thick continental clastic sequences deposited in triassic jurassic half grabens in the north sea basins we propose that 1 5 2 5 km of neogene exhumation were a result of late stage domal uplift this is supported by basinward dipping pre neogene strata in the basins surrounding southern norway and the infill of a 1 to 2 km thick neogene sediment wedge containing various internal unconformities domal uplift probably started in the late oligocene may have been amplified in the pliocene and was overprinted by plio pleistocene glacial erosion maximum neogene tectonic uplift is estimated at approximately 1 1 5 km radially decreasing outward to a value 500 m near the shoreline neogene domal uplift is coincident with oligocene and pliocene plate reorganizations in the north atlantic similar neogene domes are found around the norwegian greenland sea i e svalbard and the barents sea northern norway east greenland suggesting a regional tectonic cause the onset of neogene uplift postdates major volcanism and continental breakup by 25 m y and predates plio pleistocene glaciations its origin is possibly a combination of induced mantle convection resulting in thermal erosion of the lithosphere and the operation of intraplate stresses

the development of irish offshore sedimentary basins a variety of ensialic mesozoic and cenozoic sedimentary basins surround ireland three main periods of basin development occurred the first in the permo triassic produced a series of small rift basins which nucleated along reactivated generally caledonian structures the second in the mid and late jurassic represents a period of crustal extension and rifting the third phase reflects thermal subsidence of cretaceous and tertiary age and coincides with seafloor spreading in the north atlantic the basins developed in response to general east west extension simple extensional structures accompanied by crustal thinning dominated in the north south trending porcupine basin the ne sw oriented basins in the celtic sea slyne erris donegal and rockall areas developed in a transtensional setting until early cretaceous times the goban spur basins at the confluence of regional structural trends and adjacent to the continent ocean boundary are dominated by transtensional structures the effects of early tertiary alpine compression are seen especially in the celtic sea basins the basins whilst having some broad geological similarities which reflect eustatic sea level variations differ in their detailed evolution each basin experienced unique facets of local structural control tectonic history and facies distribution

configurational thermodynamics of fe ni alloys at earth s core conditions by means of ab initio calculations we perform an analysis of the configurational thermodynamics effects of disorder and structural energy differences in fe ni alloys at the pressure and temperat

short scale variations of tectonic regimes in the western european stress province north of the alps and pyrenees the data of the european part of the world stress map wsm are used to study the western european stress province north of the alps and pyrenees the study area is characterised by an almost homogeneous n 145 degrees e orientation of the maximum horizont

origins of the european regional stress field abstract we present a study of the origins of the european regional stress field intraplate stresses due to various plate boundary forces and intraplate stress sources were predicted using an elastic finite element analysis the finite element mesh consists of about 1629 nodes in a network of 3117 triangular elements which provide a spatial resolution of about 1 the study builds on the previous modelling studies through consideration of a wide range of plausible forces acting along the collisional eastern and southern plate boundaries and importantly through the inclusion of forces due to other lateral density variations within the lithosphere such as those associated with the continental margins and high topography the modelling was constrained by more than 1800 stress indicators from the world stress map project which provide information about the orientation of the observed maximum horizontal compressive stress sh the torque associated with the ridge push force is well constrained and the principal source of uncertainty relates to the boundary conditions used to represent the collisional resistance acting along the eastern and southern boundaries a gradient in the collisional resistance increasing in magnitude from west to east is assumed to act along the southern plate boundary whereas the eastern boundary is modelled as a pinned margin at 46 e the sh orientation and magnitude of the regional stress field was found to be largely invariant to the boundary conditions used to represent the tectonic forces acting along the eastern and southern margins and is characterized by a nearly uniform nw se compression with a magnitude in the range of 10 20 mpa averaged over a 100 km thick lithosphere lateral density variations within the continental areas of europe were found to reduce the magnitude of the predicted stresses but do not have a significant effect on the orientation of the regional stress field

palaeogene alpine tectonics and icelandic plume related magmatism and deformation in northern ireland the cenozoic tectonic history of nw europe is generally attributed to some combination of three principal controlling factors north atlantic opening alpine collision and formation of the icelandic mantle plume using constraints from the high resolution tellus aeromagnetic survey of northern ireland we show that palaeogene tectonics can be attributed to approximately north south alpine related compression forming nnw sse trending dextral and ene wsw trending sinistral conjugate strike slip faults with the latter defined by kilometre scale displacements along reactivated caledonian or carboniferous faults this tectonism was however punctuated by pulsed magmatic intrusive and extrusive events including four distinct dyke swarms that are attributed to ne sw to east west directed plume related extension although this evidence shows for the first time that north south alpine compression was periodically overwhelmed by the dynamic stresses and uplift associated with pulsed mantle plume related deformation associated strike slip faulting may have controlled the locus of volcanic activity and central igneous complexes and the location of sedimentary depocentres

dating and rhythmicity from the last deglacial cycle in the british isles in northern britain glaciotectonically thickened sediment piles represent the sediment flux transferred to ice margins by phases of fast ice flow and drumlin streamlining during the last deglacial cycle radiocarbon dating of marine faunas within deglacial muds age constrain phases of drumlinisation shaping to between 19 and 14 5 ka bp individual phases of drumlinization can be correlated with millennial time scale discharge events documented from the circum north atlantic which are probably climate driven the overall deglacial cycle records at least five major millennial time scale ice margin oscillations and phases of sediment sequence rhythmicity

gravity gradients and upper crustal tectonic fabrics ireland gravity gradients derived from an updated bouguer anomaly map of ireland reveal large scale lineaments many of which can be related to geological structures and tectonic development first horizontal derivatives of the anomaly calculated at various azimuths accentuate linear trends in different directions while the second derivative helps resolve near surface structure the dominant ne sw caledonian trending lineaments are interpreted as due to fault boundaries and folds in pre carboniferous basement and caledonian fault reactivation during the variscan orogeny subsidiary nne ssw trending lineaments are present as well as weaker nw se trending lineaments the largest negative anomalies are produced by late caledonian granites and widespread buried granitic rock in the middle to upper crust is proposed both exposed and inferred granites appear to be spatially related to intersections of ne sw with nne ssw and nw se trending lineaments the orientation of the dominant gravity trend changes from ne sw towards ene wsw going westwards across ireland and forms part of a more regional change in the caledonian gravity fabric recognised throughout the northeast atlantic region variscan e w gravity trends in the south of ireland overlay the caledonian trends relationships between gravity lineaments and anomalies support a thin skinned model for the variscan cover

the transition between the erris and the rockall basins new evidence from wide angle seismic data abstract the rockall trough is a deep water basin west of britain and ireland the origin of the basin and the nature of the crust beneath it is controversial a series of seismic wide angle experiments carried out during 1988 and 1990 help to clarify the crustal and upper mantle structure in the region results for the crustal structure from a profile which straddles the shelf break between the basin and the irish shelf are discussed here these data together with the available geological information indicate that the basin probably formed in the late palaeozoic to early mesozoic as part of a regionally linked basin assemblage which includes the hatton basin and the shallow sea basins surrounding ireland and britain good data quality has allowed the transition between the relatively unstretched crust of the irish and british mainland defined by previous onshore seismic refraction experiments to be well resolved the erris trough one of the small late palaeozoic to early mesozoic basins which fringe the mainland shelf region north of the porcupine basin is a half graben its major bounding fault is located on its western margin and the basin is divided from the rockall trough by a narrow horst the erris ridge the shelf trajectory along the western flank of the horst deepens smoothly towards the trough centre where the crust thins to 5 km near the trough margin below a sedimentary and water column 8 km thick surprisingly the crustal thickness is slightly greater over a 150 km broad zone at the trough centre i e ca 6 km this change in crustal thickness may be due to lateral strain migration to the warmer basin margins as its centre cooled during the deformation the crustal structure beneath the sediment pile at the trough centre is two layered as opposed to the three layered seismic refraction structure found onshore however the basic character of the lower crust present in onshore ireland in particular the presence of a gradient zone defining the crust mantle transition is still preserved in the trough this similarity in structure precludes the presence of magmatic underplating the crustal structure observed in the rockall trough can be formed by differential stretching of the lithosphere in this model the lower ductile crust and mantle lithosphere are stretched over a wide region by 2 2 3 strain focusing into a much narrower region of brittle upper crust generates severe amounts of crustal thinning 1 8 10 and is responsible for the fusing of the upper and mid crustal seismic refraction layers found beneath onshore ireland and britain mediating detachment surfaces sited at the brittle ductile transition at any time served to relay the strain from the lower lithosphere into the upper crust syntectonic heat loss plays an important role in controlling the deformation pattern

evidence for kilometre scale neogene exhumation driven by compressional deformation in the irish sea basin system simon p holford paul f green jonathan p turner gareth a williams richard r hillis david r tappin ian r duddy

evidence for post early eocene tectonic activity in southeastern ireland the role played by cenozoic deformation in denudation and landscape development in ireland has historically been difficult to assess because of the lack of widespread pre glacial cenozoic deposits onshore here we combine analysis of apatite fission track data and geomorphic observations to place constraints on the timing kinematics and magnitude of onshore deformation in southeastern ireland relationships between apatite fission track central age and elevation for samples from the wicklow and blackstairs mountains and tullow lowland suggest that these rocks record an exhumed apatite partial annealing zone which after cooling was dismembered by differential vertical displacements of up to several hundred metres we use inverted models of sample thermal history to show that samples across the region experienced very similar thermal histories up to and including a cooling event in late paleocene or early eocene time this effectively rules out strongly spatially heterogeneous denudation and implies that differential rock uplift occurred in post early eocene time the central age elevation relationships define at least three spatial domains with internally consistent apatite fission track data separated by known faults or topographic escarpments geomorphic analysis of these structures shows that patterns of catchment incision and sinuosity as well as the presence of antecedent drainage are best explained by differential vertical displacements at or near the domain boundaries the kinematics and magnitudes of these displacements are consistent with those implied by the apatite fission track results and are compatible with other examples of known cenozoic deformation from ireland and the adjacent continental margin

finite element modelling of stress patterns along the mid norwegian continental margin 62 to 68 n the inferred nature of the regional intraplate stress field off the coast of norway is based primarily on borehole breakout information and earthquake focal mechanisms the stress indicators reveal a slightly clockwise rotation of the orientation of the principal horizontal stress sh to the northwest with respect to the dominant e w orientation observed in the northern north sea the stress regime is predominantly strike slip and thrust fault although two normal faulting events have occurred on the shelf and shelf edge within the mid norwegian margin segment 62 to 68 n the tr0ndelag platform exhibits large variations of observed sn orientations this may be due to an almost isotropic horizontal stress state sh sh resulting from the superposition of local and regional stress sources this paper presents the predicted tectonic stresses along the mid norwegian margin based on a 3 d finite element analysis the two principal modelling objectives are to elaborate the effects of 1 changes in the regional stress magnitude sh and 2 variations in rock properties i e young s modulus on the horizontal stress anisotropy hsa of the v0ring basin and the tr0ndelag platform the model incorporates simplified mainland topography the tr0ndelag platform the voring basin the v0ring plateau and the lofoten basin our modelling results indicate that horizontal stress anisotropy hsa and the regional sh magnitude within the various structural units is dependent on their strike with respect to the orientation of the present day regional stress field specifically we find 1 a near isotropic horizontal stress magnitude configuration for the southern part of the v0ring basin where the gradient of topography across the mid norwegian margin is oriented oblique to the regional trend of sh 2 a maximum horizontal stress anisotropy hsa in the southern part of the tr0ndelag platform this local hsa maximum bordering the hsa minimum of the voting basin 3 a narrow band of high hsa at the eastern edge of the tr0ndelag platform imposed by compressive gravitational stresses related to the elevated topography of mainland norway 4 a low hsa at the western margin of the tr0ndelag platform related to spreading stresses associated with the topographic lowering towards the v0ring basin and 5 in case of a far field stress of sh 1 1sh the modelling results predict exchanged principal horizontal stresses sh and sh at the western margin of the tr0ndelag platform

crystal structure prediction for iron as inner core material in heavy terrestrial planets abstract the relative stability of different crystal structures for pure fe under applied pressure is calculated from quantum mechanics using the highly accurate apw lo method in the pressure range of 0 100 tpa we corroborate the prediction that iron adopts subsequently the bcc hcp fcc hcp and bcc structures in contrast to previous studies we identify a family of stacking fault structures that are competing with the ground state structure at all pressures implications for the properties of the inner core of the earth and heavy terrestrial exoplanets are discussed

late devonian carbonate margins and foreslopes of the lennard shelf canning basin western australia part b development during progradation and across the frasnian famennian biotic crisis abstract many studies document the occurrence of carbonate progradational successions that are driven by overall accommodation limited conditions and represent periods when substantial volumes of sediment are stored in slope settings however few have reported on the detailed internal anatomy and components of prograding clinothems and furthermore little is known about how environmental parameters affect the development of carbonate margins and slopes when superimposed on the long term low accommodation signal upper devonian frasnian and famennian carbonate outcrop exposures along the lennard shelf northeast canning basin western australia offer the examination of reefal margin and foreslope development in a variety of settings one of which is long term 10 ma progradation during the late frasnian and famennian in the early phases of progradation a global biotic crisis and faunal overturn occurred around the frasnian famennian f f boundary and indications of global climatic cooling are interpreted at points throughout the late devonian these extrinsic and intrinsic controls provide ecologic context and a stratigraphic framework to assess carbonate margin and foreslope architectures and facies distributions in order to better characterize and predict their complex heterogeneity the outcrop dataset collected includes measured sections tied to interpreted photomosaics and detailed mapping using aerial photographs from the south lawford range windjana gorge and dingo gap areas the outcrop observations highlight distinctive changes in margin style foreslope composition stratigraphic packaging and strike variability within the contexts of the f f biotic crisis long term highstand hst progradation and late devonian climatic changes intervals before and after the f f boundary exhibit notable increases in downslope calcimicrobial boundstone encrustation and evidence for waning foreslope contributions from other previously flourishing carbonate factories reflecting stressed ecological conditions and consequent calcimicrobial opportunism during gradual buildup and recovery periods that bracket the extinction the famennian slope post effects related to the f f crisis can be subdivided into a calcimicrobial boundstone dominated upper slope with a highly complex downdip transition into a mixed debris and grain dominated middle slope and a silt dominated lower slope to toe of slope and exhibits a highly complex lateral heterogeneity associated with multiple contributing sediment factories and temporal partitioning of resedimentation a repeated stacking pattern is observable in the famennian middle slope setting consisting of upward successions of debris followed by a gradation from silt dominated deposits into grain dominated deposits we here interpret these as the expression of high frequency sequences superimposed upon the longer term progradation and a function of transitional greenhouse to icehouse climates these findings offer predictive relationships that link the internal depositional heterogeneity of prograding slope systems to the interplay of long term accommodation drivers ecological conditions affecting carbonate sediment factories and climatic conditions that control the development of high frequency sequences

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous

timing and mechanisms of north atlantic cenozoic uplift evidence for mantle upwelling postrift domal uplift patterns are a distinct feauture of northern north atlantic margins on the basis of apatite fission track data offshore seismic stratigraphy geomorphology gravity and seismic tomography we argue that southern norway is characterized by predominantly neogene domal uplift currently available data suggest similar processes for other uplifted regions such as spitsbergen northern norway the british isles aad parts of east greenland

the inner inner core of the earth texturing of iron crystals from three dimensional seismic anisotropy abstract we present a three dimensional model of the seismic anisotropy and texturing of iron crystals in the inner core the form of the anisotropy changes suddenly at slightly less than half of the inner core radius the outer part is composed of iron crystals of a single phase with different degrees of preferred alignment along the spin axis of the earth the inner part may be composed of a different phase of crystalline iron or have a different pattern of alignment

tertiary compressional structures on the faroe rockall plateau in relation to northeast atlantic ridge push and alpine foreland stresses abstract a number of compressional anticlinal structures are identified in the western and northern part of the faroe rockall plateau these structures occur on that part of the faroe rockall plateau which was above sea level during the latest phase of paleocene plateau basalt extrusion three post basalt compressional phases have affected the plateau most of the compressional structures in the northern part of the plateau are related to ne sw to ene wsw oriented stress which we date to late paleocene early eocene the oligocene phase is interpreted as resulting from n s directed compressional stress which also mainly affected the compressional structures on the northern part of the plateau compressional stress from the northwest seemed to affect the whole of the faroe rockall plateau and we suggest it to be of miocene age it is proposed that during the late paleocene early eocene phase of compression local structure and anomalously oriented gravitational ridge push from the now extinct aegir axis contributed to a local ne sw compressional stress system the two later deformation phases were apparently connected to the regional northwest european stress system with small local modifications