late pleistocene and holocene depositional systems and the palaeogeography of the dogger bank north sea 3d seismic data from the dogger bank north sea allow the mapping of late pleistocene and holocene depositional systems in unprecedented detail the data demonstrate that glacial processes resulted in the development of incised tunnel valley systems during the weichselian and that these were subsequently modified by fluvial processes in a pro glacial setting subsequently the dogger bank formed an emergent plain during the holocene with a complex meandering river system associated tributary or distributary channels and lakes dominating the region prior to the sea level rising sufficiently to submerge the dogger bank around 7500 yr ago the meandering river system was replaced by a dendritic channel network of potential fluvial estuarine or intertidal origin as the holocene depositional features bear no systematic relationship to the bathymetry this study demonstrates that previously published bathymetry based models for the holocene palaeogeographic development of the north sea require modification

very high resolution 3d marine seismic data processing for geotechnical applications the processing of a small scale very high resolution vhr shallow marine 3d data volume is described the data were acquired over a small clay diapir on the river schelde in 1990 using an array of 12 dual channel microstreamers towed from a catamaran a network of 1 m 1 m bins could be produced over an area of 50 m 180 m 100 m penetration positioning was performed with an auto tracking laser ranging system assuring an absolute accuracy of a few decimetres preliminary processing steps included tidal correction and multiple removal an important step concerned the application of 3d prestack kirchhoff depth migration indeed this processing allows easy handling of the exact positions of both source and receivers as the latter were not set out on a conventional regular grid due to navigation difficulties because of the restricted data volume and the more or less stratified medium a 1d velocity model could be used this allowed a considerable simplification of the migration algorithm based on summation traveltimes were calculated only once using a 2d time grid with 0 1 m intervals this migration method proved very efficient greatly improving the seismic image and involved only limited cpu time on a small computer sparc 10 workstation it clearly demonstrates that advanced seismic processing can form a valuable and economically feasible tool for vhr shallow subsurface 3d seismics as long as the velocity field is not too complex this method should therefore no longer be restricted to large computers and hydrocarbon exploration but should also become a routine for vhr 3d shallow seismic work

buried late quaternary channel systems in the danish north sea genesis and geological evolution abstract the danish north sea has been subject to extensive seismic surveying both 2d and 3d during the past four decades the 3d seismic data from the area has mainly been used for hydrocarbon exploration but in the last decade it has also been utilized for investigating the quaternary sediments and especially buried incised valleys the erosional and depositional processes involved in forming such valleys are important in paleolandscape reconstruction but are often difficult to determine since sediment deposited by flowing water displays ambiguous geometric structures in this study we combine the analysis of infill geometries from high resolution 2d seismic data with plan view morphology analysis from 3d seismic data and lithological data from borehole reports in order to constrain the origin of buried channels in the danish north sea this data integration makes differentiations of a subaerial vs subglacial origin more robust the study focusses on analyzing a proglacial to fluvial channel system which was initiated as a subglacial tunnel valley system during the last glacial maximum and subsequently evolved as a fluvial system after deglaciation the channel system was active in a marsh environment during a period of subaerial exposure in the late weichselian to early holocene during the holocene transgression the system was gradually flooded leaving estuarine tidal deposits in the underfilled channels once the area was completely flooded the channel system was buried under marine sands

the blanketing effect of sediments in basins formed by extension a numerical model application to the gulf of lion and viking graben abstract a numerical finite difference model is employed to reconstruct the time temperature history of sediments in basins formed by extension in which crustal thinning by stretching as well as the effects associated with sedimentation and compaction are taken into account two extreme cases of basins were investigated to identify the scale of this mechanism the gulf of lion illustrates a case of a young basin in which the average sedimentation rate is high 620 m ma and the viking graben in the north sea offers a case of a basin formed in the triassic but where average sedimentation rate is much less 37 m ma in the former the sediments absorb 30 of the surface heat flow while in the latter the effect is only 10

tension gash like back arc basin opening and its control on subduction rollback inferred from tertiary faulting in sardinia 1 the tertiary reactivation of the paleozoic basement in ne sardinia is shown to reflect transtensional back arc tectonics related to the western mediterranean subduction rollback during the algero provencal basin opening the left lateral nuoro fault which is the prevailing structure in central sardinia operated as radial transfer between the west sardinian rift and northern tyrrhenian basin subsequently it contributed to a tension gash like opening of the southern tyrrhenian basin as conjugate fault to a right lateral fault set in se sardinia resulting antithetic rotations with respect to the arc are revealed by reoriented dikes in the basement the tension gash like opening of the southern tyrrhenian basin determined the gulf shape of the east sardinian margin and the arc shape of its calabrian counterpart this structural control on the southern tyrrhenian rollback scenario suggests that tension gash like opening of back arc basins represents an intrinsic aspect of subduction rollback

episodic and short lived granitic pulses in a post collisional setting evidence from precise u pb zircon dating through a crustal cross section in corsica abstract in western corsica a large granitoid batholith was emplaced during carboniferous and permian times these rocks display an evolution through time from high mg k calc alkaline to calc alkaline then alkaline affinities moreover the magmatic processes can be observed at different crustal levels new and precise isotope dilution and thermo ionisation mass spectrometry id tims u pb dating suggests that granite magmatism in corsica did not simply reflect the continuous thermal evolution of a thickened crust a precise timing for the post collisional magmatism is documented with four distinct short lived episodes respectively at 345 338 305 and 280 ma separated by periods of inactivity these four magma pulses display variable nd isotopic signatures related to mantle crust interactions granite magma generation and emplacement is strongly connected to the thermal and tectonic activity of the lithosphere an increasing contribution of a depleted mantle to the magmatic processes is documented for the last igneous event this is interpreted to reflect the emplacement of depleted mantle materials in the lower crust which enhanced heat flow and triggered partial melting of previously underplated mafic rocks this increasing contribution of mantle materials marks the onset of a new geodynamic cycle characterised by an extensional tectonic regime preluding to the opening of the alpine orogenic tract

palaeomagnetism of nw scotland syenites in relation to local and regional tectonics summary a detailed thermal demagnetization study has been carried out on a number of syenitic intrusions from north of the great glen fault in scotland multicomponent remanences of normal and reversed polarity have been recognized these define a series of palaeomagnetic poles from which an ordovician to silurian apparent polar wander path for northern scotland is deduced comparison of this apparent polar wander path with the established path for britain throws new light on the sequence of thrusting and magmatic activity in the nw highlands and precludes large scale 1500 km movement along the great glen fault later than the ordovician the data emphasize previously published discrepancies between the apparent polar wander paths of britain baltica and laurentia and are consistent with the suggestion that britain was among a set of intracratonic microplates which underwent complicated distinct movements throughout the caledonian orogeny

longitudinal facies architectural changes of a middle holocene anastomosing distributary system rhine meuse delta central netherlands abstract longitudinal changes in channel planform and facies architecture occur over a 22 km long reach of an anastomosing middle holocene distributary system in the rhine meuse delta central netherlands a geological map and a sequence of cross sections show that the channel belt is characterized by sand body width thickness ratios which decrease within the study area from approximately 25 upstream to well below 10 downstream accompanied by a change in channel planform as indicated by a downstream increase of the number of crevasse splays the lithological composition of the sand body is relatively homogeneous but there is always a well developed fining upward sequence from sandy channel deposits to clayey natural levee deposits within channel vertical aggradation appears to have been restricted during most of the period of activity of the distributary system and since lateral accretion was also limited especially in the downstream part rapid accumulation of channel deposits seems to have occurred predominantly during the avulsion stage leaving a narrow and shallow residual channel as the last remnant the longitudinal change in channel pattern is mainly attributed to a downstream increase in the rate of ground water level rise that resulted from holocene sea level rise in the rhine meuse delta a rate of ground water level rise of 1 5 mm yr 1 is required for the creation of fully developed anastomosing fluvial systems ribbons with a width thickness ratio of

a model for drowned terrestrial habitats with associated archeological remains in the northwestern gulf of maine usa abstract marine geophysical techniques and geological measurement of sea level change allow detailed mapping of seafloor archeological sites and development of models in the northwestern gulf of maine the lowstand of sea level is only at 60 m depth but a prolonged stasis during the late quaternary sea level rise herein termed the slowstand occurred between 11 500 and 7500 calibrated years before present cal yr bp at depths of 15 25 m this slowdown caused substantial erosion of glacial deposits and formed terrestrial beaches wetlands and lakes these landforms attracted people whose tools were later discovered during present day scallop fishing activities our study areas at the green islands and bass harbor are within the lowstand and slowstand depth ranges but at highly exposed and sheltered sites respectively the green islands site has lost most of its former terrestrial sediment and there is no longer any context for recovered artifacts at the protected bass harbor site the remains of eroded moraines are associated with drowned spits and a former lacustrine estuarine basin cores at the bass harbor location encountered freshwater peat deposits and numerous shallow subtidal shell and plant fossils all deposited during the slowstand the two most important controls on the preservation of terrestrial landforms and associated human artifacts in the northwestern gulf of maine are the rate of sea level rise and degree of shelter of the site from waves

between warm and cold impact of the younger dryas on human behavior in central europe abstract following a thorough review of high resolution environmental archives this paper aims at discriminating the factors determining the heterogeneous repercussion of the lateglacial younger dryas in central europe when examining the archaeological implications of human adaptation to the subsequent changes in the natural environment two divergent biotic regions are of special interest the north european plain and adjacent areas and the alpine foothills and surrounding mountain ranges in these regions two different archaeological technocomplexes traditions are found the tanged point complex and the curve backed point groups considering the distribution of the archaeological sites witnessing changes in the material culture and subsistence pattern the intensity of the environmental changes caused by the younger dryas is a decisive element settlement discontinuity during the younger dryas is questioned moreover the potential existence of established social networks between the two regions expressed by comparable developments such as microlithization is considered finally the authors assess whether the younger dryas acted as an accelerator or a brake in the process of regional diversification prior to the early mesolithic

plate and intraplate processes of hercynian europe during the late paleozoic abstract it is speculated that until late carboniferous time the region of hercynian europe was occupied by an elongated island arc system underlain by a segment of continental crust in the upper carboniferous two subduction zones are assumed to have extended from the north and south beneath hercynian europe an extensive zone of hot partially molten upper mantle lay above and between these and diapiric uprise of portions of this material led to separation of mafic magmas widespread partial melting in the lower and middle crust high temperature low pressure metamorphism in crustal rocks and regional uplift and extension of the crust as indicated by intermontane troughs and their associated volcanic rocks in visean to westphalian time hercynian europe collided with both the large neighbouring plates north america europe and africa during these diachronous collisions and owing to reduced rigidity of the relatively hot island arc crust the irregular continental margins of the larger and thicker continental plates induced oroclinal bending of hercynian europe after the collision processes had been terminated processes of upper mantle activity continued causing further crustal uplift and even enhanced crustal extension for several tens of million years into the lower permian decline of the upper mantle activity beneath hercynian europe is indicated by crustal subsidence and formation of a peneplain in permian time followed by the upper permian transgression of both the zechstein sea and the tethys sea which mark the end of the hercynian geodynamic cycle

early permian 90 clockwise rotation of the maures esterel corsica sardinia block confirmed by new palaeomagnetic data and followed by a triassic 60 clockwise rotation

younger dryas event recorded by the mirabilite deposition in huahai lake hexi corridor nw china abstract deposits from the huahai ancient lake in the hexi corridor were dated using conventional and ams 14c a 2500a carbon storage effect was defined at 9 25 m depth according to the 14c age difference between a plant macrofragment and detrital organic matter from the same layer the chronology of this strata indicated that the mirabilite layer at the depth of 8 05 m 9 15 m had formed during the younger dryas yd event the formation of the mirabilite layer indicated that the mean annual temperature in the hexi corridor dropped by 11 c during the yd event compared with today the lowest cold event occurred early in the yd which is consistent with what has been revealed by other high resolution records such as those of arctic ice cores and stalagmites in mid latitude regions

variscan orogeny in corsica new structural and geochronological insights and its place in the variscan geodynamic framework in western corsica remnants of pre batholitic lithological and metamorphic assemblages are preserved as km scale septa enclosed within lower carboniferous to early permian plutons two groups of septa were recognized 1 the argentella and agriates tenda fragments correspond to neoproterozoic rocks deformed and metamorphosed during the cadomian panafrican orogeny and 2 the zicavo porto vecchio solenzara fautea belgodere topiti and vignola fragments consist of variscan metamorphic rocks the lithological content and the main ductile deformation events for each septum are presented in the zicavo porto vecchio and topiti septa a top to the sw ductile shearing d1 event coeval with an amphibolite facies metamorphism is responsible for crustal thickening at ca 360 ma this main event was preceded by eclogite and granulite facies metamorphic events preserved as restites within migmatites dated at ca 345 330 ma a top to the se ductile shearing d2 event coeval with the crustal melting accommodated the exhumation of the d1 event in contrast the belgodere segment is peculiar as it exhibits a top to the e vergence although retrogressed high pressure rocks are also recognized the pre permian fragments are arranged in four nw se striking stripes that define a sw ne zoning with 1 a western domain in topiti vignola zicavo porto vecchio and solenzara fautea 2 a neoproterozoic basement with its unconformable early paleozoic sedimentary cover in argentella 3 an eastern metamorphic domain in belgodere 4 another neoproterozoic basement with its upper paleozoic sedimentary cover in agriates tenda the argentella basement is separated from the western and eastern domains by two sutures s1 and s2 the variscan corsica represents the eastern part of the sardinia corsica maures segment the comparison of this segment with other variscan domains allows us to propose some possible correlations we argue that the western domain argentella belgodere and agriates tenda domains can be compared with the southern variscan belt exposed in french massif central southern massif armoricain armorica microblock leon block respectively

the hattian bala rock avalanche and associated landslides triggered by the kashmir earthquake of 8 october 2005 the kashmir earthquake of the 8 october killed an estimated 87 350 people 25 500 through co seismic landslides the largest landslide associated with the earthquake was the 68 106 m3 hattian bala rock avalanche that destroyed a village and killed around 1000 people the deposit blocks the valley to a depth of 130 m impounding a lake that reached the dam crest in april 2007 an outburst flood now threatens a major settlement 3 km downstream a series of space images reveals landslide clusters in the rock avalanche source area prior to the earthquake the images also reveal a large slow moving landslide with its toe in the lake failure of this landslide may induce dam failure through overtopping and scour eighty five landslides in the hattian bala catchment predate the shaking of 8 october 2005 a further 73 are co seismic with the main shock and 21 postdate it in the period up to october 2006 landslide magnitude frequency distribution plots derived from satellite images allow an assessment of the contribution of seismically triggered events as compared to background rates of activity

origin and timing of the post variscan gabbro granite complex of porto western corsica the post variscan complex of porto consists of metaluminous to slightly peraluminous a type biotite granites mingled with gabbro dioritic rocks and late dykes with basaltic to trachyandesitic composition u pb zircon dating by la icp ms on two mafic intrusive samples constrains the time of the gabbro granite crystallisation at 281 3 ma and 283 2 ma hornblende 40ar 39ar ages from a late trachyandesite dyke date the dyking event at 280 2 ma which is within error the u pb zircon ages of the intrusives biotite granites show variable major and trace element compositions and similar initial end 0 3 to 0 9 whole rock chemistry variations and trace element compositions of plagioclase and allanite indicate that the granites are genetically linked essentially through fractional crystallisation of feldspars and minor allanite on the basis of whole rock chemistry e g initial end 4 9 to 1 7 and trace element clinopyroxene compositions we have ascertained that the mafic intrusives and basic dykes formed from isotopically depleted mantle source derived melts with similar trace element signature these basic melts experienced slightly different evolutionary histories controlled by fractional crystallisation and crustal contamination mainly by the acid magma that gave rise to the associated biotite granites but also by the enclosing older variscan granitoids u pb zircon data suggest that the porto complex was affected by hydrothermal fluid circulation at 259 9 ma

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

no relative rotation detected between corsica and sardinia forty dikes of upper paleozoic age have been investigated paleomagnetically on both sides of the straits of bonifacio to detect a possible rotation of sardinia relative to corsica a primary component of magnetization has been isolated after thermal and alternating field cleaning eleven sites in corsica yield a paleomagnetic mean of d 134 7 i 11 3 95 6 8 while 11 sites from sardinia showed a paleomagnetic mean of d 132 7 i 1 6 95 7 3 the two directions are not significantly different at the 95 confidence level no relative rotation between corsica and sardinia occurred across the bonifacio straits and the two islands maintained the present spatial relationship since the upper paleozoic a mean paleomagnetic direction of d 133 7 i 6 5 95 5 1 for the sardo corso massif yield a corresponding virtual mean pole position at 249 4 e 33 7 n coincident with upper paleozoic data of the mediterranean region this data implies about 70 of counterclockwise rotation of the block respect stable europe

genesis of a variscan batholith field petrological and mineralogical evidence from the corsica sardinia batholith abstract the genesis of the corsica sardinia batholith csb can be explained in a continental collision setting during the time of construction of the batholith which is dated at about 70 ma three magmatic associations were emplaced mg k calc alkaline u1 composite mafic silicic calc alkaline u2 and post collisional alkaline u3 in addition the level of intrusion became progressively shallower from 5 6 kbar for u1 to less than ikbar for u3 in a large scale uplift associations u1 and u2 exhibit non cogenetic mafic and felsic components the processes and products of interaction between mantle and crustal derived melts are however different and may be related to the thickness of the crust which controls both the parameters t pco2 ph2o andptot and the time of mingling of the products of anatexis and basaltic melts both u1 and u2 granitoids were formed by crystallization of a magma derived by fusion of a source of greywacke composition the melting occurred successively under granulitic u1 and amphibolite facies conditions u2 in association u1 basaltic melts displaying potassic lamprophyre like composition up to 8 k2o are of uncertain affinity furthermore crustal interaction with the basic magma precludes precise definition of the source in the u2 composite association the primary tholeiitic character of the mantle derived basic rocks is constrained by both mineralogical and geochemical data dry and hydrated subunits are distinguished among the basic rocks associated with the granitoids no hybridization processes have been identified in the core of the mafic complexes of the dry subunits but they are recognized at the level of emplacement at the margins at the contact with the granitoids contamination in the mafic hydrated subunit is due to the increase in water content of crustal origin in the magma during the ascent and emplacement of the basic complexes leading to the development of abundant green amphibole extensive hybridization is restricted to the base of the crust where it led to incomplete mixing yielding granodiorites and enclaves the genesis and emplacement of the composite calc alkaline u2 association took place in an extensional setting in an uplifting basement postdating a collisional event during the devonian an eastern austro alpine block was thrust onto the western ebro balearic continent the u1 mg k granitoids resulted from anatexis under conditions of pco2 ph2o this took place at the base of the austro alpine crust which was undergoing fusion due to its adiabatic ascent the u2 calc alkaline granitoid rocks were derived in a hydrated environment by fusion of the same austro alpine crust in corsica and of the ebro balearic crust on sardinia and in the pyrenees the conditions of interaction between mafic and felsic magmas may serve as a geodynamic marker providing information on the thickness of the crust in time and space and on the genesis of continental crust the persistence during the palaeozoic of dominantly tholeiitic mafic magmatism suggests that hot spot activity occurred in this area of southwestern europe during pre variscan and variscan times up to the time of opening of the liguro piedmontese ocean birthplace of the alpine orogen

assessing marine gas emission activity and contribution to the atmospheric methane inventory a multidisciplinary approach from the dutch dogger bank seep area north sea abstract we present a comprehensive study showing new results from a shallow gas seep area in 40 m water depth located in the north sea netherlands sector b13 that we call dutch dogger bank seep area it has been postulated that methane presumably originating from a gas reservoir in 600 m depth below the seafloor is naturally leaking to the seafloor our ship based subbottom echosounder data indicate that the migrating gas is trapped in numerous gas pockets in the shallow sediments the gas pockets are located at the boundary between the top of the late pliocene section and overlying fine grained sediments which were deposited during the early holocene marine transgression after the last glaciation we mapped gas emissions during three r v heincke cruises in 2014 2015 and 2016 and repeatedly observed up to 850 flares in the study area most of them 80 were concentrated at five flare clusters our repeated analysis revealed spatial similarities of seep clusters but also heterogeneities in emission intensities a first calculation of the methane released from these clusters into the water column revealed a flow rate of 277 l min sd5140 with two clusters emitting 132 and 142 l min representing the most significant seepage sites above these two flare clusters elevated methane concentrations were recorded in atmospheric measurements our results illustrate the effective transport of methane via gas bubbles through a 40 m water column and furthermore provide an estimate of the emission rate needed to allow for a contribution to the atmospheric methane concentration

paleomagnetism of jurassic carbonate rocks from sardinia no indication of post jurassic internal block rotations 1 several paleomagnetic studies on carboniferous and permian sedimentary and volcanic rocks from sardinia and corsica have recently demonstrated 1 the tectonic coherence between southern corsica and northern sardinia and 2 significant rotations between individual crustal blocks within sardinia itself the geodynamic significance of these rotations however is not clearly understood mainly because of uncertainties in defining their timing and causes in order to contribute to these issues a pioneering paleomagnetic study on jurassic carbonates from the baronie supramonte region of eastern central sardinia has been extended regionally and stratigraphically a total of 280 oriented drill cores were taken from 44 sites of middle and late jurassic age in the nurra baronie supramonte barbagia sarcidano and sulcis regions despite generally weak remanent magnetization intensities on the order of less than 1 ma m thermal and alternating field demagnetizations were successfully applied to define a characteristic remanent magnetization component in about 60 of the samples site mean directions show rather good agreement after correction for bedding tilt and yield middle and late jurassic overall mean directions of d 269 7 and i 45 0 95 8 0 k 14 and n 25 sites and d 275 5 and i 50 7 95 7 2 k 45 3 and n 10 sites positive regional and local fold and reversal tests demonstrate the primary character of the natural magnetic remanence which is carried by magnetite these results indicate only insignificant amounts 10 of post jurassic rotations within the island of sardinia the resulting middle and late jurassic paleopoles latitude lat 16 5 longitude long 299 1 dp 6 4 and dm 10 1 and lat 23 4 long 301 2 dp 6 5 and dm 9 7 corrected for the opening of 1 the liguro provencal basin and 2 the bay of biscay using rotation parameters from the literature fall near the coeval segment of the european apparent polar wander path these results constrain the timing of large differential block rotations found in late carboniferous permian rocks to a pre middle jurassic age and lead us to exclude tectonics related to the alpine orogeny for such rotations

exploring sea country through high resolution 3d seismic imaging of australia s nw shelf resolving early coastal landscapes and preservation of underwater cultural heritage abstract almost 2 million square km of australia s continental shelf was flooded following the termination of the last glacial maximum and with it the cultural heritage of the first arrival and coastal occupation of australia beginning some 65 000 years ago in order to prospect for this missing cultural record we must first identify submerged coastal landscapes and landforms that likely provided favourable environments for occupation and resource use however this task is challenged by the sheer size of the australian continental margin to help address this we use industry 3d seismic datasets that cover vast areas of australia s continental shelf to map seafloor bathymetry at high resolution 10 25 m our study focuses an area of 6500 square km on the mid outer shelf regions proximal to barrow island the 3d seismic bathymetry revealed a highly complex and geomorphically mature coastal landscape preserved at depths of 70 75 m below sea level including coastal barrier dunes lagoonal systems tidal flats and estuarine channels based on the depth of the submerged shorelines and reconstructed sea level curves the age range of these coastal landforms is constrained to marine isotope stage 3 57 29 ka which overlaps with the known onset of occupation at barrow island and the wider carnarvon bioregion and the adjacent pilbara such feature preservation has significant geoheritage value but also allows for human behavioural ecology modelling and provides targets for future dating and site survey

the role of discharge variability in the formation and preservation of alluvial sediment bodies abstract extant planform based facies models for alluvial deposits are not fully fit for purpose because they over emphasise plan form whereas there is little in the alluvial rock record that is distinctive of any particular planform and because the planform of individual rivers vary in both time and space accordingly existing facies models have limited predictive capability in this paper we explore the role of inter annual peak discharge variability as a possible control on the character of the preserved alluvial record data from a suite of modern rivers for which long term gauging records are available and for which there are published descriptions of subsurface sedimentary architecture are analysed the selected rivers are categorized according to their variance in peak discharge or the coefficient of variation cvqp standard deviation of the annual peak flood discharge over the mean annual peak flood discharge this parameter ranges over the rivers studied between 0 18 and 1 22 allowing classification of rivers as having very low 0 90 annual peak discharge variance deposits of rivers with very low and low peak discharge variability are dominated by cross bedding on various scales and preserve macroform bedding structure allowing the interpretation of bar construction processes rivers with moderate values preserve mostly cross bedding but records of macroform processes are in places muted and considerably modified by reworking rivers with high and very high values of annual peak discharge variability show a wide range of bedding structures commonly including critical and supercritical flow structures abundant in situ trees and transported large woody debris and their deposits contain pedogenically modified mud partings and generally lack macroform structure such a facies assemblage is distinctively different from the conventional fluvial style recorded in published facies models but is widely developed both in modern and ancient alluvial deposits this high peak variance style is also distinctive of rivers that are undergoing contraction in discharge over time because of the gradual annexation of the channel belt by the establishment of woody vegetation we propose that discharge variability both inter annual peak variation and flashiness may be a more reliable basis for classifying the alluvial rock record than planform and we provide some examples of three classes of alluvial sediment bodies representing low intermediate and high very high discharge variability from the rock record that illustrate this point

late paleozoic rotations of corsica and sardinia new evidence from paleomagnetic and k ar studies abstract a detailed paleomagnetic investigation of so called permian volcanics was undertaken in southeastern and northwestern sardinia k ar dating on separate minerals representing 30 sites on corsica and sardinia showed that the first calc alkaline cycle had taken place in westphalo stephanian times and the second alkaline one at the end of the stephanian 246 paleomagnetic specimens from 28 sites of southeastern sardinia and 2 sites from the northwest were demagnetized by alternating field and thermal processes the directions of characteristic magnetizations are d 85 i 6 95 5 for the volcanics of southeastern sardinia and d 126 i 1 for the nurra samples these mean directions differ from those of northwestern corsica and northern sardinia gallura the paleomagnetic results display good grouping for each volcanic complex but exhibit a geographical dispersion of the mean directions this scattering suggests significant motions in late hercynian times

an ultrahigh resolution 3 d survey of the shallow subsurface on the continental shelf of new jersey regional seismic surveys have identified a wedge of late quaternary sediment extending 150 km south from the hudson river apron along the edge of the continental shelf off new jersey the bottom of the sediment wedge is defined by a prominent reflector that is assumed to be an erosional surface carved during a lowstand of sea level probably corresponding to the wisconsin maximum glaciation about 18 000 years ago an extremely high resolution 3 d seismic reflection survey of the southern part of the wedge figure 1 was carried out in 1993 as part of the strataform strata formation on margins initiative funded by the u s office of naval research

the devastating muzaffarabad earthquake of 8 october 2005 new insights into himalayan seismicity and tectonics abstract the recent earthquake of 8 october 2005 in the muzaffarabad region in western himalaya destroyed several parts of pakistan and the north indian state of jammu and kashmir the earthquake of magnitude 7 6 claimed more than 80 000 lives clearly exposing the poor standards of building construction a major challenge facing the highly populated earthquake prone third world nations today in this paper we examine variations in the stress field seismicity patterns seismic source character tectonic setting plate motion velocities gps results and the geodynamic factors relating to the geometry of the underlying subsurface structure and its role in generation of very large earthquakes focal mechanism solutions of the muzaffarabad earthquake and its aftershocks are found to have steep dip angles comparable to the indian intra plate shield earthquakes rather than the typical himalayan earthquakes that are characterized by shallow angle northward dips a low p value of 0 9 is obtained for this earthquake from the decay pattern of 110 aftershocks which is comparable to that of the 1993 latur earthquake in the indian shield the deadliest stable continental region scr earthquake till date inversion of focal mechanisms of the harvard cmt catalogue indicates distinct stress patterns in the muzaffarabad region seemingly governed by an overturned himalayan thrust belt configuration that envelops this region adjoined by the pamir and hindukush regions recent developments in application of seismological tools like the receiver function technique have enabled accurate mapping of the dipping trends of the moho and lithosphere asthenosphere boundary lab of indian lithosphere beneath southern tibet these have significantly improved our understanding of the collision process the mechanism of himalayan orogeny and uplift of the tibetan plateau besides providing vital constraints on the seismic hazard threat posed by the himalaya new ideas have also emerged through gps macroseismic investigations paleoseismology and numerical modeling approaches while many researchers suggest that the himalayan front is already overdue for several 8 0 magnitude earthquakes some opine that most of the front may not really be capable of sustaining the stress accumulation required for generation of great earthquakes we propose that the occurrence of great earthquakes like those of 1897 in shillong and 1950 in assam have a strong correlation with their proximity to multiple plate junctions conducive for enormous stress build up like the eastern himalayan syntaxis comprising the junction of the india eurasia plates and the burma sunda micro plates

preservation of a drowned gravel barrier complex a landscape evolution study from the north eastern english channel abstract landscape response to post glacial relative sea level during the quaternary is documented using an integrated dataset of multibeam bathymetry and 2d seismic reflection profiles from the hastings bank area in the north eastern english channel mapping of nine seismic stratigraphic units calibrated to lithological information from multiple vibrocores has enabled the interpretation of fluvial shoreface barrier washover fan back barrier and tidal environments of deposition the interpreted landscape evolution is as follows i fluvial incision of bedrock during sea level lowstand ii progradation of a shoreline and then development of a barrier complex as sea level rose iii recycling and breaching of the barrier iv rapid drowning of the barrier complex v landward migration of the shoreline through continued sea level rise and vi complete abandonment and submarine preservation of the barrier complex during sea level highstand the previously undocumented yet exceptionally well preserved drowned barrier complex at hastings bank records phases of barrier initiation breakdown and retreat and documents coastal response to high rates of relative sea level rise initial development of the barrier complex required a sufficient supply of sediment maintained by offshore sources to keep pace with rising sea level which permitted progradation of a shoreline and development of a barrier complex inherited topography in the north eastern english channel is an important factor in the development of the barrier complex phases of barrier breakdown occur when sediment supply is outpaced by a rapid increase in accommodation controlled by existing basement morphology and rising sea levels subsequently the barrier responds through internal reorganisation by breaching and reworking of existing sediment bodies barrier retreat is characterised by a phase of sediment surplus overstepping under rapid rates of sea level rise where increased water depths limit wave reworking followed by a phase of discontinuous retreat where the shoreline steps back through sediment deficit overstepping hastings bank presents a rare opportunity to examine the conditions and processes that control barrier response to sea level rise and to assess the preservation potential of barrier deposits as a function of the style of retreat

phased occupation and retreat of the last british irish ice sheet in the southern north sea geomorphic and seismostratigraphic evidence of a dynamic ice lobe along the terrestrial margin of the southern north sea previous studies of the mis 2 glaciation impacting eastern britain have played a significant role in the development of principles relating to ice sheet dynamics e g deformable beds and the practice of reconstructing the style timing and spatial configuration of palaeo ice sheets these detailed terrestrially based findings have however relied on observations made from only the outer edges of the former ice mass as the north sea lobe nsl of the british irish ice sheet biis occupied an area that is now almost entirely submarine c 21 15 ka compounded by the fact that marine acquired data have been primarily of insufficient quality and density the configuration and behaviour of the last biis in the southern north sea remains surprisingly poorly constrained this paper presents analysis of a new integrated set of extensive seabed geomorphological and seismo stratigraphic observations that both advances the principles developed previously onshore e g multiple advance and retreat cycles and provides a more detailed and accurate reconstruction of the biis at its southern most extent in the north sea a new bathymetry compilation of the region reveals a series of broad sedimentary wedges and associated moraines that represent several terminal positions of the nsl these former still stand ice margins 1 4 are also found to relate to newly identified architectural patterns shallow stacked sedimentary wedges in the region s seismic stratigraphy previously mapped singularly as the bolders bank formation with ground truthing constraint provided by sediment cores these wedges are interpreted as sub marginal till wedges formed by complex subglacial accretionary processes that resulted in till thickening towards the former ice sheet margins the newly sub divided shallow seismic stratigraphy at least five units also provides an indication of the relative event chronology of the nsl while there is a general record of south to north retreat seismic data also indicate episodes of ice sheet re advance suggestive of an oscillating margin e g mis 2 maximum not related to first incursion of ice into region demonstrating further landform interdependence geographically grouped sets of tunnel valleys are shown to be genetically related to these individual ice margins providing clear insight into how meltwater drainage was organised at the evolving termini of this dynamic ice lobe the newly reconstructed offshore ice margins are found to be well correlated with previously observed terrestrial limits in lincolnshire and e yorkshire holderness e g mis 2 maximum and withernsea till this reconstruction will hopefully provide a useful framework for studies targeting the climatic mass balance and external glaciological factors i e fennoscandian ice sheet that influenced late stage advance and deglaciation important for accurately characterising both modern and palaeo ice sheets

reddish metagranites from the gennargentu igneous complex sardinia italy insight into metasomatism induced by magma mingling the recrystallization of quartz and plagioclase to higher calcium concentrations the progressive increase in the mgo mgo feo of chlorite closer to the contact indicates that this phase also recrystallized the iron released during chlorite recrystallization was buffered by hematite formation in the pores of metasomatic k feldspar the gennargentu metagranites provide evidence that metasomatic fluids can play a major role in driving metamorphic reactions in contact aureoles for instance the expected increase of ca in plagioclase owing to thermal equilibration was not achieved in the high t zone of the aureole because of fluid assisted removal of cations we conclude that caution should be taken when interpreting the processes that underpin contact metamorphism in terms of thermally driven ionic diffusion alone because the role of fluids may be significant if not overwhelming in the domains closest to the magmatic source

geochronological and structural study of tertiary and quaternary dikes in southern france and sardinia an example of the utilization of dike swarms as paleostress indicators ancient dikes swarms which are datable by geochronological methods can be used as paleostress indicators this study defines criteria by which suitable dike swarms can be selected this paper deals with tertiary and quaternary dike swarms of the french and sardinian peri alpine platform the results of geochronological and structural analysis show that the general trends of dikes ranging from nw se to n s intruded during the last 8 ma on the border of massif central and in languedoc parallel the general trajectories of the present stress field plane 1 2 as deduced from in situ measurements and from focal mechanism determination of earthquakes in detail dike swarms dated between 8 and 6 ma the region of coiron aubrac velay and causses in southern france possess a nw se orientation however those dated between 3 4 and 0 7 ma the region of logudoro montiferro and monte arci in sardinia and the region of escandorgue lodevois and agde in southern france are oriented roughly n s in southern france the stress orientations cannot be deduced from geophysical data with sufficient precision to determine whether the plane 1 2 orientation recorded by the dike propagation varies systematically in time or space nevertheless the fact that the oldest dike swarms 8 6 ma are oriented nw se indicate that the stress field may have been modified since that time

paleomagnetic data from late paleozoic dykes of sardinia evidence for block rotations and implications for the intra pangea megashear system paleomagnetic studies of dyke swarms from the variscan belt of europe can be used to reconstruct internal postorogenic rotations within the fold belt here we present paleomagnetic data from 13 late variscan dykes from sardinia ranging in age from 298 5 to 270 10 ma the dykes can be grouped on the basis of their different directions in strike in a northern a central eastern and a south eastern province paleomagnetic component directions have been obtained using thermal and alternating field demagnetization techniques which give reproducible results the paleomagnetic mean directions differ significantly between northern sardinia and south eastern and central eastern sardinia the latter two regions yielding statistically similar paleomagnetic mean directions these results indicate that sardinia fragmented into two arguably three crustal blocks after emplacement of the dykes which experienced differential relative rotations as is also indicated by the differences in overall strike directions the determination of timing sense and magnitude of these rotations has major implications for the reconstruction of the geodynamic evolution of the region in post carboniferous times we argue that the observed block rotations occurred during the permian as the result of post variscan intra pangea mobility possibly related to the transformation of an early permian pangea b to a late permian pangea a

paleomagnetic results of tertiary sediments from corsica evidence of post eocene rotation vi iotti l and kent dv 1990 paleomagnetic results of tertiary sediments from corsica evidence of post eocene rotation phys earth planet inter 62 97 108 middle eocene lutetian and lower to middle miocene burdigalian langhian sediments from corsica have been investigated in a paleomagnetic study to constrain the amount and timing of tectonic rotation of the corsican block with respect to sardinia and stable eurasia the sediments are generally characterized by weak and unstable magnetization and only five eocene and five miocene sites out of 23 sites sampled provided interpretable data our best estimate for the eocene paleomagnetic field for corsica suggests 370 of counter clockwise rotation and no latitudinal change with respect to stable eurasia in post eocene time this is similar to the amount of tectonic rotation documented from oligo miocene volcanics from sardinia which is therefore consistent with corsica and sardinia being part of the same tectonic block since at least the early to middle tertiary paleomagnetic results from the miocene sites may represent remagnetizations but the presence of reversed polarity magnetization at three of the five accepted sites indicates acquisition before the late pleistocene the final rotation history of corsica nevertheless is left unresolved

bridging the gap a terrestrial view of shallow marine sequences and the importance of the transition zone the shallow shelf area around the coast of the uk contains an important record of maritime and potentially prehistoric archaeology increasingly this area is the focus of anthropogenic activity such as gravel extraction and cable laying in advance of which it is increasingly common practice to investigate the archaeological potential of the sequences regions well structured approaches have been developed for the investigation of maritime wrecks and the latest prehistoric remains however the palaeolithic archaeological potential of these regions is less clear this is partly due to the depth of burial of archaeological material and the rather more fragmentary nature of the sequences present where consideration of the palaeolithic archaeology has been undertaken models and presumptions derived from terrestrial situations have been extrapolated across the near shore zone where often there is no data and into the maritime area within the maritime area these models have been used to interpret seismic data and scarce offshore core data for making regional reconstructions here we consider some of the issues in reconstruction and highlight the difficultly in extrapolating between terrestrial and maritime situations without careful investigation in the transition zone in particular we argue that rather than assuming similarities between patterns of landscape evolution between the on and off systems we should anticipate dissimilarity of patterns missing sequences and different landscape formation processes particularly in those areas of the shallow shelf area formerly occupied by drainage basins during sea level low stands

interaction between basic and acid magmas during the latest stages of the post collisional variscan evolution clues from the gabbro granite association of ota corsica sardinia batholith abstract the intrusive association of ota post variscan corsica sardinia batholith consists of mafic rocks and granites displaying mingling relations the mafic rocks are olivine gabbros to quartz diorites and the granites are subsolvus and characterised by biotite as the only mafic phase minor amounts of amphibole bearing granodiorites to granites develop along the contacts between mafic rocks and granites the rather high initial e nd 4 5 of the most primitive mafic sample indicates that parental basic melts had an extensive contribution from a depleted mantle source in the mafic rocks the decrease of initial e nd to 2 1 is associated with an increase of th and u concentrations in clinopyroxene thus indicating that the ota basic melts underwent a process of crustal contamination associated biotite granites have low initial e nd 0 4 and high th and u concentrations the chemical evolution of ota basic melts most likely occurred through fractional crystallisation and concomitant contamination with the acid magma that gave rise to associated biotite granites the incompatible element signature of late stage anhedral amphibole from variably evolved mafic rocks is similar thus suggesting that the whole ota mafic sequence recorded the contamination process possibly by percolation within the gabbroic crystal mush of a melt contaminated by the acid magma hybridisation between basic and acid magmas is also documented by contact amphibole bearing granitoids in particular major and trace element zoning of amphibole from granodiorites reveals that such a hybridisation was associated with reactions between crystals from the basic magma amphibole and clinopyroxene and the acid melt the occurrence of chemically homogeneous amphiboles in associated granites suggests that contact hybridisation comprised also a process of gradient induced chemical diffusion

the gross structure of the crust under corsica and sardinia as part of the european geotraverse project egt a number of international cooperative seismic refraction surveys were carried out along the n s segment from the ligurian sea across the islands of corsica and sardinia to the sardinian channel between sardinia and north africa from 1982 to 1985 for all the experiments offshore explosions served as energy sources ranging from 200 to 1125 kg the main result is that the crust in the ligurian sea is of transitional type with a thickness of only 18 km the two continental blocks of corsica and sardinia have a maximum crustal thickness of 33 and 34 km with average crustal velocities of 6 4 and 6 3 km s respectively other results are that the internal crustal structure as derived from the available data in both islands is rather undifferentiated with only local evidence for a more steplike interface in the lower crust corsica 6 3 to 6 6 km s sardinia 6 5 to 6 8 km s there are also indications of a slight velocity inversion under the southwestern part of sardinia farther south in the sardinian channel the crustal thickness decreases again to 20 km a significant feature is the observed pn velocity this parameter increases from the relatively low value of 7 5 km s in the north ligurian sea to 7 7 km s and 7 9 km s for corsica and sardinia and finally to 8 0 km s under the sardinian channel these values reflect the tectonic evolution of that part of the mediterranean sea

paleomagnetic evolution of the central massif france during the carboniferous the present paper aims to synthesize results of a systematic paleomagnetic investigation performed on metamorphic plutonic and volcanic series from the central massif detailed thermal and alternating field demagnetizations yield a large set of paleomagnetic directions several groups of directions corresponding to different age intervals are identified the group d mean direction d 288 i 57 37 s 110 e characterizes late devonian early carboniferous metamorphic and plutonic rocks from limousin the group c directions d 301 i 24 30 s 79 e represent late visean namurian magnetizations present in the major investigated areas the group b directions d 249 i 7 12 n 111 e exist not only in the whole central massif but also in other paleozoic outcrops of the variscan belt they were acquired during the namurian westphalian the group a a directions are the only typically european magnetic directions they have taken place in stephanian autunian times mainly during the kiaman reversed interval interpretation of these directions in terms of geodynamics leads to a probable large s n drift of the massif during the latest devonian early carboniferous followed by two important rotation phases first in the middle carboniferous then at the end of the westphalian these rotations have also affected other massifs of the variscan belt

a refined apparent polar wander curve for the transdanubian central mountains and its bearing on the mediterranean tectonic history abstract recently obtained palaeomagnetic data have given a fairly detailed apparent polar wander a p w curve for the mesozoic of the transdanubian central mountains which has been compared with other a p w curves from the mediterranean area the similarity of the a p w curves enabled a unified a p w curve to be constructed for the central mediterranean region it has been shown that the new mediterranean a p w curve is in full agreement even in details with the updated a p w curve for africa this confirms the existence during the entire mesozoic of a single central mediterranean megatectonic unit rigidly attached to africa its positions with respect to the pole can now be traced back in more detail than before

permian clockwise rotations of the ebro and corso sardinian blocks during iberian armorican oroclinal bending preliminary paleomagnetic data from the catalan coastal range ne spain abstract paleomagnetic investigations of early permian and triassic magmatic rocks from catalan coastal ranges provide three magnetic directions which are interpreted as primary magnetizations and partly as overprints the succession of magnetic directions is interpreted in terms of a succession of large scale clockwise rotations which bring the whole assembly of pyrenees catalonia corsica sardinia and maures esterel massifs from the southeast of the massif central to the west during permian this major movement is associated with clockwise rotation of northern limb of the iberian orocline during latest carboniferous and early permian 305 290 ma subsequently permian large scale dextral transtensional extensional shearing operated along aquitanian shear belt between the massif central in the northeast and the iberian variscan massifs in the southwest the latest phase of the rotation in the late permian early triassic is associated with alkaline magmatism probably linked to neo tethys opening activity in western europe

towards high resolution 3d marine seismic surveying using boomer sources the use of boomer sources for 3d seismic imaging of shallow marine structures was investigated in a feasibility study boomers show sufficient stability to be used in multichannel seismic surveys the acquisition of a high frequency densely sampled seismic data volume was successfully performed in the baltic sea a pleistocene fluvial channel system and shallow gas accumulations were revealed beneath the unconsolidated sediments which constitute the sea floor in the southern kiel bay

palaeogeographical changes in response to glacial interglacial cycles as recorded in middle and late pleistocene seismic stratigraphy southern north sea offshore stratigraphic records from the north sea contain information to reconstruct palaeo ice sheet extent and understand sedimentary processes and landscape response to pleistocene glacial interglacial cycles we document three major middle to late pleistocene stratigraphic packages over a 401 km2 area norfolk vanguard boreas offshore wind farm offshore east anglia uk through the integration of 2d seismic borehole and cone penetration test data the lowermost unit is predominantly fluviatile yarmouth roads formation marine isotope stage mis 19 13 including three northward draining valleys the middle unit swarte bank formation records the southernmost extent of tunnel valley fills in this area of the north sea providing evidence for subglacial conditions most likely during the anglian stage mis 12 glaciation the yarmouth roads and swarte bank deposits are truncated and overlain by low energy estuarine silts and clays brown bank formation mis 5d 4 smaller scale features including dune scale bedforms and abrupt changes in cone penetration test parameters provide evidence for episodic changes in relative sea level within mis 5 the landscape evolution recorded in deposits of mis 19 5 are strongly related to glacial interglacial cycles although a distinctive aspect of this low relief ice marginal setting are opposing sediment transport directions under contrasting sedimentary process regimes

how a river submerges into the sea a geological record of changing a fluvial to a marine paleoenvironment during early holocene sea level rise

geomorphometric characteristics of new zealand landslide dams abstract this study presents results from a quantitative analysis of a new inventory of n 232 landslide dam occurrences in new zealand previously published data were expanded by documentation of recent events and evidence from a regional air photo reconnaissance focused on the upland regions of southwestern south island additional geomorphometric data on landslide dams associated lakes and contributing catchment characteristics were extracted from a 25 m digital elevation model dem augmented by limited ground truthing and compiled in a gis based inventory the new zealand case examples fall into the global trend although they contain both two extremely large features in terms of landslide dam volume vd and lake volume vl analysis suggests that landslide dam height hd landslide dam volume vd lake volume vl contributing catchment area ac and local relief hr are key variables for assessing landslide dam stability independently from other catchment parameters such as lithology climate or dam sedimentology they may be provisionally used as representative characteristics of landslide dams irrespective of environmental boundary conditions such as climate geology or site specific valley geomorphometry three newly proposed dimensionless indices i e the backstow index is basin index ia and relief index ir based on landslide dam height hd allow limited yet promising preliminary assessments of landslide dam stability compared with worldwide examples they also demonstrate a much narrower conditional range for the formation of stable landslide dams in new zealand catchment parameters such as maximum elevation emax upstream relief hr contributing catchment area ac and relief ratio rr are significantly different at sites of former and existing landslide dammed lakes and may be used as independent variables in future terrain based classification schemes generally data are incomplete with underreporting of small and ephemeral landslide dams and over representation of earthquake case studies nonparametric correlation highlights the statistical interdependence between geomorphometric variables as an artefact of initial data calculation while varying accuracy poses a significant drawback for complex multivariate statistical techniques such as principal component cluster or discriminant analyses

a new gis approach for reconstructing and mapping dynamic late holocene coastal plain palaeogeography the geomorphological development of holocene coastal plains around the world has been studied since the beginning of the twentieth century from various disciplines resulting in large amounts of data however the overwhelming quantities and heterogeneous nature of this data have caused the divided knowledge to remain inconsistent and fragmented to keep improving the understanding of coastal plain geomorphology and geology cataloguing of data and integration of knowledge are essential in this paper we present a gis that incorporates the accumulated data of the netherlands coastal plain and functions as a storage and integration tool for coastal plain mapped data the gis stores redigitised architectural elements beach barriers tidal channels intertidal flats supratidal flats and coastal fresh water peat from earlier mappings in separate map layers a coupled catalogue style database stores the dating information of these elements besides references to source studies and annotations regarding changed insights using scripts the system automatically establishes palaeogeographical maps for any chosen moment combining the above mapping and dating information in our approach we strip the information to architectural element level and we separate mapping from dating information serving the automatic generation of time slice maps it enables a workflow in which the maker can iteratively regenerate maps which speeds up fine tuning and thus the quality of palaeogeographical reconstruction the gis currently covers the late holocene coastal plain development of the netherlands this period witnessed widespread renewed flooding along the southern north sea coast coinciding with large scale reclamation and human occupation our gis method is generic and can be expanded and adapted to allow faster integrated processing of growing amounts of data for many coastal areas and other large urbanising lowlands around the world it allows maintaining actual data overview and facilitates new ways of analysis at national regional and local scales 2016 elsevier b v

a mass movement origin for cirques the glacial process of cirque initiation whereby small initial hillslope hollows grow by nivation until snow can form glacier ice and ice motion then enlarges the hollow to a fully developed cirque appears to have difficulty explaining the creation of large cirques in the time available during quaternary glaciations at the rates at which glaciers are reported to erode rock and in rapidly uplifting mountain ranges it also has difficulty explaining the striking proliferation of cirques in fiordland south island new zealand an area of harder rock and less glaciation than the nearby cirque poor area of south westland here we show that cirques can be initiated as large deep seated often coseismic rock slope failure source area depressions in which snow may accumulate to form cirque glaciers which can then remove detritus from smooth and enlarge the cirque we present an example of a classically shaped cirque that has never held a glacier we show that many similarities between the locations sizes and shapes of rock slope failure source area depressions and cirques are understandable on this basis as is the occurrence of cirques in presently aseismic intraplate locations and their relative paucity in actively uplifting ranges the extent to which cirques may be of mass movement origin has implications for their value as palaeoclimatic indicators copyright 2006 john wiley sons ltd

late quaternary evolution of the upper reaches of the solent river southern england based upon marine geophysical evidence geological evidence suggests that during the late quaternary a river system the solent river drained a large part of central southern england its upper reaches flowed in a west east direction flanked to the south by a chalk ridge the purbeck isle of wight chalk ridge today only part of the upper reaches of the river9s tributary channels remain as the area was inundated during the flandrian transgression forming an embayment system poole and christchurch bays in order to map the offshore buried channels of the upper reaches of the solent river an extensive set of shallow marine geophysical data was analysed and interpreted the results of this investigation show that the solent river system was disrupted irreversibly by southerly capture of its upstream section before the flandrian transgression this disruption was the result of the fluvial breaching of the southern barrier of the system the purbeck isle of wight ridge at three points probably during late devensian time poole bay was first to be submerged during the transgression the estuaries which resulted from the drowning of the fluvial palaeovalleys of poole bay were infilled with transgressive facies sequences which have been preserved within the buried palaeovalleys in contrast christchurch bay was submerged at a later time but because of the abrupt manner of its inundation no transgressive facies have been preserved within its buried palaeovalleys

late palaeozoic palaeomagnetic and tectonic constraints for amalgamation of pangea supercontinent in the european variscan belt abstract this paper provides a review of the evolution of palaeomagnetic directions and sequence of tectonic events in the european variscan belt during late palaeozoic times these data are correlated with palaeomagnetic records from gondwana and baltica in order to provide a large scale geodynamic framework during the carboniferous to permian the early carboniferous palaeomagnetic records reported mainly from the rhenohercynian and saxothuringian magmatic arcs indicate a 70 anticlockwise rotation while late carboniferous to permian magnetic directions from various rocks of western and central europe are consistent with 120 clockwise rotation of the eastern and central parts of the variscan belt our review of the chronology of tectonic events is based on a robust database of geochronologically constrained deformation metamorphic and magmatic events which allow discretizing the 80 ma long orogenic evolution into five principal events in this scenario the variscan belt can be regarded as a linear sub plate isolated from gondwana and laurussia by the rhenohercynian and palaeotethysian oceans during devonian times this linear composite belt was segmented by transform faults and boundaries in the late devonian to early carboniferous times 360 335 ma during progressive e w closure of rhenohercynian ocean synchronously with collision between saxothuringian and moldanubian blocks subsequent relocation of subduction to the northern boundary palaeotethysian ocean was responsible for n s shortening almost orthogonal to the ancient sub plate n s elongation at around 335 325 ma this deformation resulted in dextral reactivation of transform boundaries associated with anticlockwise rotation of intermittent blocks at the end of this rotation the faults were parallelized to the teysseire tornquist zone the southern margin of baltica while the lozenge shaped blocks of the former variscan sub plate were further shortened during continuous contraction this evolution can fully explain the 70 anticlockwise rotation from cn3 to cn2 palaeomagnetic directions which are regarded as successive carboniferous magnetizations subsequently the variscan belt suffered a giant transtensional event from 325 to 310 ma that was related to the development of extensional syn magmatic core complexes over the whole belt and significant dextral reactivation of earlier nw se trending transform faults this extensional event was associated with important tilts recorded by cp magnetic overprint resulting from a major thermally induced remagnetization during this event new sets of sinistral transfer nne ssw trending faults originated that partly reactivated boundaries of the principal tectonic zones blocks delimited by second order sinistral and first order dextral faults then rotated in a clockwise manner by 80 the whole system subsequently suffered a period of nne ssw shortening that affected the variscan belt namely along the former laurussian and former variscan sub plate contact in the north and in the south where the giant cantabrian orocline developed at around 310 300 ma due to hard collision with gondwana this deformation is associated with the clockwise rotation of laurussia together with the accreted northern sector of the variscan belt and the anticlockwise of gondwana this clockwise 30 rotation is achieved by a1 remagnetizations while the southern part of iberia suffered anticlockwise rotation the final stage of rapid clockwise rotation affecting the northern limb of the iberian arc including corsica and sardinia is attributed to giant n s extension affecting the whole variscan belt at the onset of permo triassic opening of the tethys ocean this complex evolution is regarded as a result of the readjustment of inhomogeneous and thermally and mechanically instable mobile space in between reorganizing the gondwana and laurussia megaplates and the opening of the palaeotethys ocean during the final stages of formation of the pangea supercontinent finally the palaeomagnetically constrained rotations and tectonic evolution of the variscan belt are explained using a pinned model of internal and external rotations of blocks driven by activation of dextral shear zones by n s compression and e w transtension in particular

depositional patterns following the 1870s avulsion of the saskatchewan river cumberland marshes saskatchewan canada abstract the avulsion of the saskatchewan river cumberland marshes east central saskatchewan canada has resulted in new floodplain deposition over an area of more than 500 km2 since beginning in the 1870s the avulsion deposits are predominantly fine grained and could be otherwise classifiable as overbank sediments in alluvial floodplains presumed to be supplied by intermittent flooding of dominant master channels the north angling and cadotte channels are older pre existing channels that were intercepted and appropriated by the expanding avulsion following annexation of the north angling channel stable cohesive banks inhibited channel enlargement and crevassing forcing the increasing discharges to be accommodated by overbank flow and in the process enhancing new levee aggradation these levee deposits coarsen upward and thin downstream as a result of greater competence and higher proximal deposition rates brought on by the larger flows in contrast the cadotte channel responded to increasing discharges by levee breaching giving rise to splay progradation and floodbasin filling the cadotte splay complex formed from the avulsively annexed cadotte channel represents a small but typical area of the avulsion belt facies characteristics and interrelationships examined from auger borings and vibracores are presented to illustrate patterns of deposition and floodplain development avulsive flooding initially raised local water surface elevations deepening small existing lakes and creating new shallow 1 2 m deep lakes on the floodplain surface deposition began when levees of the cadotte channel were breached allowing water and coarser sediment to spread as sheet like flows while finer sediment was carried and deposited farther into the basin later as the proximal splay sheets coalesced and grew basinward flows became channelized and progradation of mouth bars into marshes and shallow lakes together with deposition of interchannel fines became dominant forming coarsening upward sequences further floodplain aggradation developed by overbank flooding when splay channels became stabilized and bordered by levees gradual abandonment was accompanied by deposition of organic rich fine grained sediment on top of the progradational sequences throughout the avulsion the north angling channel has stood as an older alluvial ridge separating two broad areas of avulsive deposition its recent levee deposits now grade basinward into these new floodplain sediments composed of thicker heterogeneous predominantly upward coarsening and rapidly deposited facies of the avulsion

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

rapid ice sheet retreat triggered by ice stream debuttressing evidence from the north sea using high resolution bathymetric and shallow seismic data from the north sea we have mapped hitherto unknown glacial landforms that connect and resolve longstanding gaps in the quaternary geological history of the basin we use these data combined with published information and dates from sediment cores to reconstruct the extent of the fennoscandian and british ice sheets fis and bis in the north sea during the last phases of the last glacial stage it is concluded that the bis occupied a much larger part of the north sea than previously suggested and that north sea ice underwent a dramatic disintegration 18 500 yr ago this was triggered by grounding line retreat of the norwegian channel ice stream which debuttressed adjacent ice masses and led to an unzipping of the bis and fis accompanied by drainage of a large ice dammed lake our reconstruction of events provides an opportunity to improve understanding and modeling of the disintegration of marine based ice sheets and the complex interplay between ocean circulation and the cryosphere

the quaternary geology of the north sea basin the north sea is a shallow 50 400 m deep 500 km wide marine embayment that separates the uk from scandinavia and northern europe fig 1 this epicontinental shelf area has had a long and complex geological history with its present day structural configuration largely being the result of rifting during the jurassic early cretaceous followed by thermal subsidence glennie and underhill 1998 zanella and coward 2003 since the middle cenozoic the central graben region of the north sea basin has accumulated up to 3000 m of oligocene to holocene sediments which locally includes more than 800 m of quaternary sediments caston 1977 1979 gatliff et al 1994 although a detailed understanding of the depositional history recorded by this sedimentary succession is yet to be fully established these sediments preserve evidence for the advance and retreat of several ice sheets into the north sea from the adjacent landmasses at different times during the quaternary these ice masses not only resulted in periodic erosion but also made a significant depositional contribution to the infill of the basin

mise en evidence par le paleomagnetisme d une importante rotation antihoraire des vosges meridionales entre le viseen terminal et le westphalien superieur the volcano sedimentary formations from the southern vosges are subdivided in two main series a lower visean series characterized by a volcanism of spilite keratophyre type and an upper visean series which includes a normal volcanic association of shoshonitic tendency paleomagnetic study of 50 sites sampled in both series but mostly in the upper one yields three types of directions of characteristic magnetizations the first type corresponds to tertiary and quaternary remagnetizations with low apparent blocking temperatures 350 500 c titano maghemites the second group is formed by remagnetizations which have taken place during late carboniferous early permian times and which show high blocking temperatures of magnetite and mostly titano haematites the mean direction is d 16 i 7 95 9 for 13 sites 43 n 165 e the last group is represented by primary magnetizations of latest visean age and post sudetic remagnetizations with blocking temperatures of magnetite and haematite the mean direction d 323 i 17 95 9 for 18 sites 25 n 228 e deviates from about 60 from the theoretical direction calculated with the early carboniferous european pole position this deviation is interpreted as resulting from a counterclockwise rotation of the southern vosges between late visean and westphalian times one consequence may be the formation of the variscan v due to the anticlockwise rotation of the eastern branch of the chain the northwesterly directions show a variation of the inclinations which may indicate that the rotation was preceded by a relatively significant drift of the vosges to the north

sequential extension as a record of corsica rotation during apennines slab roll back the mediterranean geodynamic system is an exceptional natural laboratory to study the complexities of back arc extension during subduction rollback corsica is a key locality that recorded the alpine subduction collision history followed by 30 ma of the apennines slab rollback responsible for the successive opening from west to east of the liguro provencal basin and the tyrrhenian sea the overall strain pattern of the alpine metamorphic units of alpine corsica is studied through a synthesis of i available geological maps ii geochronological data and iii newly acquired structural data relative to successive events of ductile and brittle extension three main stages of extension are recorded 1 syn metamorphic oligocene extension accommodated by n140 trending ductile shear zones that correspond to the reactivation of a major alpine thrust 2 burdigalian ramp flat extension with n60 70 trending fault zones that controlled the deposition of onshore piggy back basins e g st florent basin and 3 serravalian n s trending fault zones from a geodynamical point of view these successive extensional deformations in alpine corsica can be correlated to the history of the apennines slab rollback the two first stages are related to a southeastward rollback of the appennines slab that successively triggered 1 continental rifting in oligocene leading to the opening of the liguro provencal basin and 2 burdigalian extension with n60 70 trending fault zone oblique to the alpine thrust that after a counterclockwise rotation of the corso sardinian block became unable to accommodate extension finally the third stage that gave ns trending fault zones developed in serravalian at the onset of tyrrhenian rifting related to an eastward rollback of the apennines slab as a response of slab tearing in sicily

ice marginal dynamics of the last british irish ice sheet in the southern north sea ice limits timing and the influence of the dogger bank the southern north sea is a particularly important area for understanding the behaviour of the british irish ice sheet biis during the last glacial cycle it preserves a record of the maximum extent of the eastern sector of the biis as well as evidence for multiple different ice flow phases and the dynamic re organisation of the biis however to date the known ice sheet history and geochronology of this region is predominantly derived from onshore geological evidence and the offshore imprint and dynamic history of the last ice sheet remain largely unknown using new data collected by the britice chrono project this paper explores the origin and age of the dogger bank re assesses the extent and age of the glaciogenic deposits across the shallow areas of the north sea between the dogger bank and the north norfolk coast and re examines the dynamic behaviour of the biis in the southern north sea between 31 6 and 21 5 ka this paper shows the core of the dogger bank to be composed glaciolacustrine sediment deposited between 31 6 and 25 8 ka following its formation the western end of the dogger lake was overridden with ice reaching 54 n where the ice margin is co incident with the southerly extent of subglacial tills previously mapped as bolders bank fm this initial ice override and retreat northwards back across the dogger lake was complete by 23 1 ka but resulted in widespread compressive glaciotectonism of the lake sediments and the formation of thrust moraine complexes along the northern edge of the bank moraines are on lapped by later phase glaciolacustrine and marine sediments but do not show evidence of subsequent ice override the shallow seafloor to the west and southwest of the dogger bank records several later phases of ice advance and retreat as the north sea lobe flowed between the dogger bank and the yorkshire lincolnshire coasts and reached north norfolk new optically stimulated luminescence osl ages from garrett hill on outwash limit the arrival of the biis on the norfolk coast to 22 8 21 5 ka multiple till sheets and chains of moraines on the seafloor north of norfolk mark dynamic oscillation of the north sea lobe margin as it retreated northwards this pattern of behaviour is broadly synchronous with the terrestrial record of deposition of subglacial glaciofluvial and glaciolacustrine sediments along the yorkshire coast which relate to post dimlington stadial ice marginal oscillations after 21 5 ka with respect to forcing mechanisms it is likely that during the early phases of the last glacial maximum 30 23ka the interaction between the southern margin of the biis and the dogger lake was critical in influencing flow instability and rapid ice advance and retreat however during the latter part of the last glacial maximum 22 21 ka late phase ice advance in the southern north sea became restricted to the western side of the dogger bank which was a substantial topographic feature by this time this topographic confinement in addition to decoupling of the biis and the fennoscandian ice sheet fis further north enabled ice to reach the north norfolk coast overprinting the seabed with late phase tills of the bolders bank fm

paleopositions of the western europe hercynides during the late carboniferous deduced from paleomagnetic data consequences for stable europe abstract paleomagnetic investigations have been carried out in different areas of the variscan belt armorican massif central massif ardenne vosges and the black forest in order to unravel the paleogeographic evolution of the hercynides during the carboniferous subsequent to important southerly or northerly drifts the central massif and vosges underwent a large rotation of a still undetermined direction in latest visean namurian times during the namurian westphalian the whole belt was oriented n s all investigated areas yield wsw ene directions for that period these directions question the validity of carboniferous mean poles available for stable europe a european plate rotated counterclockwise by about 40 relative to its permian position would be more consistent with these results during the latest westphalian stephanian period i e within the 310 290 ma timespan the western europe hercynides rotated clockwise by 40 50 perhaps together with the whole of europe late variscan strike slip faulting and overthrusting probably result from that rotation

3 d seismic discontinuity for faults and stratigraphic features the coherence cube seismic data are usually acquired and processed for imaging reflections this paper describes a method of processing seismic data for imaging discontinuities e g faults and stratigraphic features one application of this nontraditional process is a 3 d volume or cube of coherence coefficients within which faults are revealed as numerically separated surfaces figure 1 compares a traditional 3 d reflection amplitude time slice with the results of the new method to our knowledge this is the first published method of revealing fault surfaces within a 3 d volume for which no fault reflections have been recorded

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

drowned coastal deposits with associated archaeological remains from a sea level slowstand northwestern gulf of maine usa drowned terrestrial wetland environments such as lakes marshes and beaches were thought to be rare in formerly glaciated regions like the gulf of maine united states in the northwestern gulf of maine postglacial relative sea level changes include a slowstand between 11 5 ka and 7 5 ka when the ocean rose 5 m this period of sea level stability permitted erosion of glacial materials and concomitant construction of spits and sheltered wetland habitats attractive to human occupation between 17 m and 22 m below modern sea level this work underscores the importance of a well constructed sea level chronology to predict the location of drowned terrestrial environments and associated cultural resources

tributary distributary and other fluvial patterns what really represents the norm in the continental rock record abstract this paper evaluates the recent claim made by weissmann et al 2010 that deposits of distributive fluvial systems dfs may form the bulk of the continental fluvial record weissmann et al 2010 define dfs as a pattern of channel and floodplain deposits that radiate outward from an apex that is located where the river enters the sedimentary basin as such dfs are fan like systems on which multiple channels coexist and distribute water and sediment across the fan published criteria for the recognition of dfs weissmann et al 2010 are 1 a radial pattern of channels from the dfs apex 2 downslope decreases in channel size 3 down dfs grain size decreases and 4 a lack of lateral channel confinement however in weissmann et al 2010 and subsequent papers only the first of these criteria is applied rigorously thus allowing a variety of types of fluvial system including avulsive incised anabranching and coastal plain distributary systems to potentially be classified uncritically as dfs an ancient succession formed by dfs should preserve mostly small channel bodies with a limited range of dimensions and no outsized channel bodies channel bodies in dfs dominated successions should also decrease in size in a down palaeoslope direction and show palaeocurrent relationships indicative of radial dispersal in order for the term dfs to be applied these characteristics should also be established within stratigraphic bodies that formed coevally however very few examples have yet been published that satisfy these criteria if the claim that dfs dominate the alluvial stratigraphic record is valid then few if any sedimentary bodies formed by large channels should be preserved a review of published research demonstrates however that the alluvial stratigraphic record contains a broad diversity of fluvial network styles including abundant representatives of tributary avulsive anabranching and incised in addition to distributary types it is also clear that the deposits of large main stem rivers that are comparable to the big rivers of the modern world are abundantly preserved in the stratigraphic record an analysis of the planimetric area of modern tributary and distributary fluvial systems is presented demonstrating that tributary systems are also likely to represent a far larger proportion of the ancient sedimentary record than dfs the body of evidence presented herein from modern and ancient alluvial systems thus suggests that the hypothesis of weissmann et al 2010 should be wholly rejected dfs do not dominate the continental stratigraphic record

crustal exhumation during ongoing compression in the variscan maures tanneron massif france geological and thermo mechanical aspects abstract the maures tanneron massif mtm together with corsica and sardinia represent the southeastern branch of the huge european variscan belt a continuous evolution from continental collision to exhumation is described from ca 350 ma to ca 320 ma based on an extended compilation of available geological and geochronological data this geological compilation is complemented with thermo mechanical modelling that tests the conditions under which deep seated hp units can melt and exhume massively during continued convergence we simulate in two dimensions the development of gravitational instabilities in a partially melting crust depending on rheological layering and heat sources and accounting for temperature dependent elasto visco plastic rheologies in order to reproduce pt exhumation patterns in the mtm over the appropriate time scale 20 my and spatial extent 100 km a best fit was obtained with a convergence rate of 0 5 cm yr and moderate diffusive surface processes the contribution of radiogenic heating in the pre stacked felsic crustal units is crucial a lateral alternation with mafic units is also required in order to prevent lateral spreading of the orogen a low viscosity partially molten crust 1020 pa s thus rather felsic accompanies crustal exhumation in a decoupled mode from the deeper mantle a shallow asthenosphere below the orogen lab at 70 km depth e g shallow slab break off produces too warm and sudden exhumation as opposed to a competent mantle lithosphere 120 km depth lab that restrains it the mtm witnesses the typical competition between far field plate convergence and internal body forces and our study pleads for a progressive evolution of transpression towards perpendicular extension from ca 320 ma

the pb zn ag vein system at montevecchio ingurtosu southwestern sardinia italy a summary of previous knowledge and new mineralogical fluid inclusion and isotopic data abstract the montevecchio ingurtosu district sw sardinia was among the largest historical pb zn producers of italy with significant ag output and yields of metallic byproducts such as cd co cu bi sb ge in and ga despite this importance detailed descriptions of orebodies and mineral assemblages are surprisingly scarce and old here we summarize all previously available information and contribute new textural microchemical fluid inclusion and c o isotopic data deriving from a recent sampling of currently exposed orebodies mineralization occurs as steeply dipping veins extending for almost 20 km at the northern and western flanks of the variscan arbus pluton veins are hosted in phyllites of the arburese unit close to the thermometamorphic aureole ore enrichments range from massive to coarsely nodular stockwork and brecciated vein filling consists of siderite locally zn rich quartz sphalerite galena remarkably rich in micro inclusions with accessory chalcopyrite fahlore bournonite barite and ni co sulfarsenides vein assemblages may vary even within a single vein from sphalerite to galena dominated cu rich assemblages fahlore chalcopyrite were locally observed wallrock is affected by silicification sericitization and pyrite dissemination sphalerite shows a complex mineral chemistry with marked variations in fe 0 08 to 8 9 mol fes and in cd contents from 1 wt trace element analyses la icp ms document the presence of measurable amounts of ga ge in ag ni co tl and mo fahlore varies from the sb tetrahedrite and the as tennantite endmembers with ag rich compositions corresponding to sb endmembers the occurrence of cd rich tetrahedrite up to 14 5 wt is remarkable fluid inclusion studies on sphalerite and quartz are in agreement with previous literature data and indicate comparatively low in the range 90 130 c homogenization temperatures th and high salinities 14 to 25 equiv mass nacl both microthermometric data and sem eds analyses of decrepitated inclusions indicate the presence of ca and k beside na pressure correction to th is presumably low in the order of 10 c considering a hydrostatic pressure regime application of the sphalerite based ggimfis thermometer provided temperatures in excellent agreement with fluid inclusion data for the montevecchio mineralization isotopic data on montevecchio carbonates define mildy negative 13cpdb values between 1 and 5 per mil and a larger spread of 18osmow values between 14 and 20 per mil other isotopic data from literature include a limited set of 34s values for galena sphalerite and pyrite and a fairly large body of pb isotopic data on galena comparatively narrow ranges for sulfur isotope signatures suggest a homogeneous possibly igneous sulfur source whereas the large spread in pb isotope signatures reflects the large scale character of the hydrothermal process and indicates that the arbus pluton may have been just one of the sources of ore lead the montevecchio vein system shows affinities with other late to post variscan european deposits the nature of the mineralizing fluids at montevecchio is analogous to low temperature basinal brines and typical of several regional scale late to post variscan hydrothermal events across europe mineralization at montevecchio obviously postdates the emplacement of the arbus plutonic complex but its exact age remains unknown

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

paleomagnetic investigations and k ar dating on the variscan plutonic massif of the champ du feu and its volcanic sedimentary environment northern vosges france abstract paleomagnetic investigations have been carried out on samples from the plutonic series of the champ du feu massif and the devonian ordovician host rocks in order to date the different phases of magnetization a series of samples has been selected for k ar analysis on micas amphiboles and feldspars the diorites granodiorites diabases and hornfelses are characterized by high susceptibilities of up to 10 1 si thermal demagnetization reveals several groups of directions of characteristic magnetization the a direction d 202 i 23 49 n 153 e is consistent with the permian virtual geomagnetic pole for europe the b 1 direction d 59 i 22 11 n 128 5 e was obtained from the effusive parts of the kagenfels granite dated at 284 ma diorites microdiorites and volcanics emplaced a short time after the intrusion of the natzwiller granite dated at 344 and 351 ma display three groups of directions the c 1 direction d 328 i 15 27 n 223 5 e the c 2 d 323 i 38 13 s 222 e and the c 3 d 272 i 41 16 s 260 e the c 1 and c 2 directions agree well with those obtained previously for visean volcanics from the southern vosges in the host rocks we have identified b and c overprintings despite the lack of tectonic control the paleomagnetic data demonstrate at least two important motions of the vosges first a rotation of undetermined direction relative to stable europe which affected the variscan belt between the late visean and 320 ma and second a clockwise rotation which occurred during the stephanian autunian in late variscan time

a paleomagnetic study of permian and triassic rocks from the toulon cuers basin se france evidence for intra pangea block rotations in the permian 1 the identification of a massive shear zone separating gondwana from laurasia during late palaeozoic times is one of the prerequisites for the controversial pangea b to a transition here we present new paleomagnetic data from permian and triassic sediments and volcanic rocks from the toulon cuers basin se france likely to be situated within this intra pangea shear zone a total of 150 samples from 14 sites were collected in the field 108 samples yielded reliable paleomagnetic component directions based on stepwise thermal demagnetization up to maximum temperatures of 690 c after removal of an initial viscous magnetic component from room temperature up to 200 c a second component of reverse polarity oriented to the south and up was identified in almost all samples of permian age the triassic samples behave similarly with the notable difference that here two polarities of magnetization are present positive field tests suggest the primary character of this characteristic magnetization the latitudes of the resulting early to mid permian paleopoles agree well with the corresponding segment of the apparent polar wander path apwp for europe whereas the longitudes are strung out along a small circle segment indicating relative rotations between the sampled regions and stable europe the triassic poles instead plot close to the triassic segment of the european apwp and provide an upper time limit for the observed rotations these results suggest a wrench faulting event associated with intra pangea crustal instability and transformation during the permian

the evolution of the dogger bank north sea a complex history of terrestrial glacial and marine environmental change this paper presents a summary of the results of a detailed multidisciplinary study of the near surface geology of the dogger bank in the southern central north sea forming part of a site investigation for a major windfarm development undertaken by the forewind consortium it has revealed that the dogger bank is internally complex rather than comprising a simple layer cake of the quaternary sediments as previously thought regional and high resolution seismic surveys have enabled a revised stratigraphic framework to be established for the upper part of this sequence which comprises the eem oldest dogger bank bolders bank formations and botney cut formation youngest overlain by a typically thin holocene sequence detailed mapping of key horizons identified on the high resolution seismic profiles has led to the recognition of a series of buried palaeo landsystems which are characterised by a range of features including glacial glacifluvial and fluvial channels a large scale glacitectonic thrust moraine complex with intervening ice marginal basins a lacustrine basin and marine ravinement surfaces interpretation of these buried landscapes has enabled the development of an environmental change model to explain the evolution of the dogger bank this evolution was driven by the complex interplay between climate change ice sheet dynamics and sea level change associated with the growth and subsequent demise of the british and irish and fennoscandian ice sheets during the weichselian glaciation following the decay of these ice sheets the dogger bank entered a period of significant climatic and environmental flux which saw a terrestrial landscape being progressively inundated as sea levels rose during the holocene