palaeomagnetism and magnetostiatigraphy of triassic strata in the sangre de cristo mountains and tucumcari basin new mexico usa summary we report palaeomagnetic data and a composite magnetic polarity sequence for middle and upper triassic rocks assigned to the anton chico member of the moenkopi formation and chinle group respectively exposed along the eastern flank of the sangre de cristo mountains and in the tucumcari basin of eastern and northeastern new mexico thermal demagnetization isolates a well defined dual polarity characteristic magnetization carried in most cases by haematite and interpreted as an early acquired chemical remanent magnetization crm characteristic magnetizations from 74 palaeomagnetic sites one site one bed are used to define a magnetic polarity sequence which we correlate with previously published triassic data obtained from both marine and non marine rocks preliminary correlation suggests that the resolution of magnetostratigraphic data derived from continental strata is not necessarily of lesser quality than that from marine rocks on the basis of the magnetostratigraphic data a profound unconformity is believed to separate lower middle norian and upper norian rhaetian strata of the chinle group palaeomagnetic poles derived from selected sites in steeply dipping 85 strata for the middle triassic anisian 240 ma 50 n 121 e n 8 late carman early norian 225 ma 53 n 104 e n 16 and late norian rhaetian 208 ma 59 n 77 e n 8 are in relatively good agreement with previously published data for the moenkopi formation and chinle group and related strata in southwest north america none the less comparison with palaeomagnetic poles obtained from gently dipping or flat lying triassic strata from this study anisian 46 n 112 e n 13 late carnian 54 n 87 e n 12 and previously published triassic poles in southwest north america suggest that a modest apparent rotation not greater than about 5 affects declinations from steeply dipping rocks the distribution of palaeomagnetic poles indicates 25 angular distance of apparent polar wander between about 240 and 208 ma

carnian norian biomagnetostratigraphy at silicka brezova slovakia correlation to other tethyan sections and to the newark basin correlations of upper triassic magnetic stratigraphies from tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy and discontinuous sedimentation particularly in the hallstatt limestones of turkey and austria the magnetic stratigraphy and conodont biostratigraphy from the upper carnian to upper norian limestones exposed at silickabrezova slovakia can be correlated to other tethyan sections and to the continental succession in the newark basin the resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations and result in a revised correlation to north american terrestrial vertebrate and palynological zones the correlations imply that the norian rhaetian boundary lies within newark polarity zone e17r at v207 ma the carnian norian boundary lies close to the base of newark polarity zone e7r at v226 ma this implies durations for the norian and rhaetian stages of 19 myr and 7 myr respectively 2002 elsevier science b v all rights reserved

integrated upper carnian to lower norian biochronology and implications for the upper triassic magnetic polarity time scale abstract we summarize the ammonoid conodont and halobiid biochronology of the upper carnian to lower norian based on a discussion of data in the alps sicily balkans turkey himalayas and timor with this integrated biostratigraphic scale the pizzo mondello section sicily can be recalibrated and the carnian norian boundary more precisely located there as a result the magnetostratigraphy of this section is now in good agreement with previous results from turkey although the latter series are more condensed cross correlation of available magnetostratigraphic data from marine tethyan sections allow us to construct a composite upper carnian to upper norian geomagnetic polarity time scale gpts this gpts leads us to question previously proposed magnetobiostratigraphic and chronostratigraphic correlations within the upper triassic newark non marine sedimentary sequence

upb la mc icp ms dating of rutile new reference materials and applications to sedimentary provenance in response to the general lack of sufficiently abundant and high quality rutile usingle bondpb reference materials for in situ geochronology we have characterised two new potential rutile 1 8 ga reference materials sugluk 4 and pca s207 from granulite facies belts of the canadian shield namely the northern cape smith belt of quebec and the snowbird tectonic zone sasatchewan characterisation includes id tims and la icp ms usingle bondpb dating imaging and trace element analysis we compare these materials with existing rutiles used already r19 and r10 luvizotto et al 2009 and zack et al 2011 and show that the measured usingle bondpb compositions i e including any common pb of our rutiles are considerably more homogeneous this makes possible a usingle bondpb normalisation procedure not reliant upon a common pb correction that results in a significant decrease in the uncertainty contribution from the common pb correction and better reproducibility of reference materials and unknowns for provenance analysis and other applications the reproducibility is 2 4 2rsd for 206pb 238u and 207pb 206pb only slightly greater than long term data for zircon reference materials we show in a rutile provenance study from young orogens bhutan himalaya and canadian cordillera that the sensitivity of our analytical set up allows dating of 90 of rutiles in a sediment using a 50 m laser ablation spotsize within samples containing rutile as young as 10 20 ma and obviates the requirement for u concentration pre screening thus reducing or eliminating rutile selection bias unsuccessful analyses are due to poor quality rutiles with predominant common pb 207pb signal below detection or u content below 1 2 ppm we have used the 207pb method using the tera wasserburg diagram to correct for substantial common pb in very young and or very low u rutiles rather than developing an on line correction since rutile ages reflect mainly the time of cooling rutile is a sensitive recorder of metamorphic thermochronological information and therefore is an excellent complement to detrital zircon u207pb data the contrast between zircon and rutile signatures in himalayan samples with rutile as young as 10 ma is shown to be very dramatic most zircons from the same sample are 480 ma with only a few grains or metamorphic rims reflecting miocene metamorphism as such rutile provides complementary information about the thermal events within the source regions of the grains rutile usingle bondpb dating is an underexploited provenance method with wide applicability to sedimentary provenance studies

interpretation and significance of combined trace element and u pb isotopic data of detrital rutile a case study from late ordovician sedimentary rocks of saxo thuringia germany the u pb age and trace element composition of detrital rutile provide information about the metamorphic history of the source region that cannot be constrained by traditional u pb dating of detrital zircon previous provenance investigations focussed on only one of these methods based on a large la icp ms trace element and u pb isotopic dataset of detrital rutile and u pb isotopic data of detrital zircon from late ordovician sedimentary rocks of saxo thuringia germany this paper discusses the application and significance of combining these methods in provenance investigations u pb age spectra from the detrital zircons analysed show multiple age components multimodal age spectra in all samples this is in contrast with the detrital rutile data as only one sample yielded a multimodal u pb age distribution multimodal age spectra of detrital rutile are most likely preserved in sediments from large catchment areas with complex geological histories they may also be related to specific sedimentation events such as glacial washout during the retreat of large ice shields e g the hirnantian glaciation of gondwana unimodal age spectra are however not restricted to small catchment areas if the provenance region is characterized by a pervasive thermal overprint such as the pan african orogeny throughout gondwana unimodal age distributions may further consist of overlapping age cluster detectable by different trace element composition of the detrital rutile grains the combined u pb age and trace element data from detrital rutile grains demonstrate that rutile sourced from metapelitic rocks yield reliable and precise u pb ages in contrast detrital rutile classified to be of metamafic origin generally has too low uranium concentrations to be dated reliably by la icp ms detrital rutile records low to medium grade metamorphic events in the source region and therefore has the potential to better constrain the maximum depositional age of sedimentary rocks in comparison to u pb dating of detrital zircon

aspects of pre tertiary paleomagnetism of spitsbergen and their tectonic implications abstract paleomagnetic investigations were carried out on cretaceous dolente dykes and sills permian limestones permo carboniferous limestones and lower devonian sandstones from different parts of spitsbergen detailed rock magnetic studies showed that the main magnetic minerals in dolentes limestones and sandstones are titanomagnetite magnetite and hematite respectively the rocks were demagnetized thermally and in alternating fields vector analysis of the demagnetization path separates the different components of nrm and establishes a characteristic remanence the paleomagnetic poles for cretaceous dolentes permo carboniferous limestones and lower devonian sandstones from spitsbergen are respectively 65 n 222 e 34 n 140 e and 12 n 135 e when compared with the european and north american apparent polar wander paths all spitsbergen poles he at a distance from both apwps suggesting that spitsbergen has been rotated and even translated in relation to europe during the opening of the labrador sea and greenland norwegian sea

detrital zircon populations in quartzites of the krkonose jizera massif implications for pre collisional history of the saxothuringian domain in the bohemian massif age spectra of detrital zircons from metamorphosed quartzites of the krkonose jizera massif in the northeastern part of the saxothuringian domain were obtained by u pb laser ablation inductively coupled plasma mass spectrometry dating the zircon ages cluster in the intervals of 450 530 ma and 550 670 ma and show individual data between 1 6 and 3 1 ga zircons in the analysed samples are predominantly of cambrian ordovician and neoproterozoic age and the marked peak at c 525 500 ma suggests a late cambrian maximum age for the sedimentary protolith detritus of the quartzites probably originated from the erosion of cambrian ordovician granitoids and their neoproterozoic meta sedimentary or magmatic country rocks the lack of neoproterozoic meta sedimentary rocks in the central and eastern part of the krkonose jizera massif suggests that the country rocks to voluminous cambrian ordovician magmatic bodies were largely eroded during the formation of early palaeozoic rift basins along the southeast passive margin of the saxothuringian domain the detrital zircon age spectra confirm the previous interpretation that the exposed basement dominated by neoproterozoic to cambrian ordovician granitoids was overthrust during devonian carboniferous subduction collision processes by nappes composed of metamorphosed equivalents of the uppermost cambrian devonian passive margin sedimentary formations only a negligible number of mesoproterozoic ages typically from the grenvillian event supports the interpretation that the saxothuringian neoproterozoic basement has an affinity to the west african craton of the northwestern margin of gondwana

organic matter apatite pyrite relationships in the botneheia formation middle triassic of eastern svalbard relevance to the formation of petroleum source rocks in the nw barents sea shelf abstract the middle triassic botneheia formation of eastern svalbard edgeoya and barentsoya comprises an organic carbon rich fine grained clastic succession 100 m thick that makes the best petroleum source rock horizon in the nw barents sea shelf the succession records a transgressive regressive interplay between the prodelta depositional system sourced in the southern barents sea shelf black shale facies of the lower and middle parts of the muen member and the open shelf phosphogenic system related to upwelling and nutrient supply from the panthalassic ocean phosphogenic black shale facies of the upper part of the muen member and the blanknuten member the relationships between organic matter authigenic apatite and pyrite in these facies allow to characterize the relative roles of redox conditions and oceanic productivity in the organic carbon preservation the accumulation of terrestrial and autochthonous marine organic matter in the black shale facies occurred under dominating oxic conditions and increasing upward productivity related to early transgressive phase and retrogradation of the prodelta system the phosphogenic black shale facies deposited in an oxygen minimum zone omz of the open shelf environment during the late transgressive to regressive phases under conditions of high biological productivity suppressed sedimentation rates and changing bottom redox the phosphatic black shales occurring in the lower and upper parts of the phosphogenic succession reveal depositional conditions indicative of the shallower part of omz including high input of autochthonous organic matter into sediment oxic to dysoxic episodically suboxic and or anoxic conditions intense phosphogenesis and recurrent reworking of the seabed the massive phosphatic mudstone occurring in the middle of the phosphogenic succession reflects the development of euxinia in the deeper part of omz during high stand of the sea high input of autochthonous organic matter in this environment was coupled with mineral starvation and intermittent phosphogenesis in mature sections in eastern svalbard the petroleum potential of the botneheia formation rises from moderate to good in the black shale facies and from good to very good in the phosphogenic black shale facies attaining maximum in the massive phosphatic mudstone

petrology and geochronology of rutile rutile tio2 is an important accessory mineral that when present offers a rich source of information about the rock units in which it is incorporated it occurs in a variety of specific microstructural settings contains significant amounts of several trace elements and is one of the classical minerals used for u pb age determination here we focus on information obtainable from rutile in its original textural context we do not present an exhaustive review on detrital rutile in clastic sediments but note that an understanding of the petrochronology of rutile in its source rocks will aid interpretation of data obtained from detrital rutile for further information on the important role of rutile in provenance studies the reader is referred to previous reviews e g zack et al 2004b meinhold 2010 triebold et al 2012 coarse rutile is the only stable tio2 polymorph under all crustal and upper mantle conditions with the exception of certain hydrothermal environments smith et al 2009 as such we will focus on rutile rather than the polymorphs brookite anatase and ultrahigh pressure modifications in this chapter we first review rutile occurrences trace element geochemistry and u pb geochronology individually to illustrate the insights that can be gained from microstructures chemistry and ages then in the spirit of petrochronology we show the interpretational power of combining these approaches using the ivrea zone italy as a case study finally we suggest some areas of future research that would improve petrochronologic research using rutile rutile is a characteristic mineral in moderate to high pressure metapelitic rocks in high pressure metamorphosed mafic rocks and in sedimentary rocks e g force 1980 frost 1991 zack et al 2004b triebold et al 2012 rutile also occurs rarely in magmatic rocks e g anorthosites as well as in some hydrothermal systems coarse grained

biota and palaeoenvironment of a high middle latitude late triassic peat forming ecosystem from hopen svalbard archipelago a siliceous permineralized peat block recovered from hopen in the svalbard archipelago hosts a low diversity late triassic flora dominated by autochthonous roots and stems of bennettitaleans and lycophytes and parautochthonous leaves sporangia spores and pollen from a small range of pteridophytes and gymnosperms some parenchymatous bennettitalean root cells show interactions with chytrid fungi and bacteria the remains of other fungi and fungi like organisms are dispersed within the peat s detrital matrix cavities excavated through some roots and compacted detritus contain abundant coprolites probably derived from sapro xylophagous oribatid mites although no body fossils have yet been identified sparse larger coprolites containing leaf fragments attest to the presence of invertebrate folivores in the ancient ecosystem the low diversity flora relatively few trophic levels and simple nutritional web together with sedimentological aspects of the host formation and the peat structure collectively favour accumulation of the organic mass as a fibric root dominated peat within a temperate high middle latitude well aerated mire

paleomagnetism of permian through early triassic sequences in central spitsbergen implications for paleogeography upper carboniferous through lower triassic sediments from spitsbergen have yielded paleomagnetic results with those for the late gzhelian early permian being the more reliable the corresponding pole 38 n 171 e is fully concordant with the early permian segment of the apparent polar wander path for baltica it does not support hypotheses about post carboniferous mobilism of spitsbergen with respect to stable europe neither mesozoic nor later rifting processes changed the position of spitsbergen considerably in relation to the stable europe

drilling induced remanence in carbonate rocks occurrence stability and grain size dependence summary a strong grouping of the directions of natural remanent magnetization in a collection of ordovician limestones and dolomites prior to correction for the in situ orientation of the samples led us to suspect the presence of a substantial spurious magnetization acquired during sample collection and preparation a close correspondence between the directions of the remanence vectors and the direction of the ambient magnetic field during sawing and drilling of the samples suggested that the remanence was dominated by a component acquired during cutting of the samples ten specimens of the camp nelson limestone and shakopee dolomite were demagnetized to 100 mt given an anhysteretic remanence along their axes and then sawed again a substantial magnetization parallel to the ambient field during cutting was acquired by all of the specimens and the resultant directions deviated by 7 70 from the direction of the anhysteretic magnetization stepwise alternating field and thermal cleaning to 60 mt and 400 c respectively failed to remove preferentially the cutting induced magnetic contamination since the fraction of magnetite grains cut during drilling and sawing must be a linear function of grain size modified lowrie fuller tests were carried out and the results are interpreted to indicate the presence of a multidomain magnetite fraction in the shakopee dolomite camp nelson limestone and oregon dolomite ratios of initial to anhysteretic susceptibility dxarm correlate well with the angular deviation of magnetic directions produced by sawing this indicates that acquisition of drilling induced remanence is a function of magnetite grain size compatible with the notion that the drillinginduced component resides in large magnetite grains which have been cut

calculating ice volumes and ice flux to constrain the dimensions of a 440 ma north african ice sheet abstract geological evidence indicates that the sahara was glaciated by a large ice sheet c 440 ma ago two end member theories have been proposed for the large scale configuration of this ice mass in the large ice sheet hypothesis the sahara was covered by a continuous ice sheet that straddled north africa arabia south africa and south america in the small ice sheet hypothesis it has been argued that separate ice sheets developed in each of these areas taking these end members and an ice sheet of intermediate dimensions we investigate this problem calculating likely ice volumes and the flux of ice to the ice margin we find that the small ice sheet adequately accounts for the estimated magnitude of post glacial transgression c 45 80 m associated with ice mass decay additionally the notion of a north african arabian ice sheet within the small ice sheet hypothesis is supported by an analysis of ice stream fluxes across the sahara accounting for widespread heterogeneous flow within the ice sheet this paper provides an independent check on the likely size and extent of late ordovician ice masses with potential application to other palaeozoic ice sheet reconstructions

zr and hf diffusion in rutile abstract chemical diffusion of zr and hf under anhydrous conditions has been measured in synthetic and natural rutile the sources of diffusant used were hafnon or zircon powders or a hafnon rutile mixture experiments were run in crimped pt capsules in air or in sealed silica glass capsules with solid buffers to buffer at nno or qfm rutherford backscattering spectrometry rbs was used to measure zr and hf diffusion profiles from these measurements the following arrhenius relations were obtained for zr diffusion parallel to c over the temperature range 750 1100 c d zr c 9 8 10 15 exp 170 30 kj mol 1 rt m 2 s 1 for hf diffusion parallel to c over the temperature range 800 1000 c d hf c 9 1 10 15 exp 169 36 kj mol 1 rt m 2 s 1 for hf diffusion normal to c over the temperature range 750 1050 c d hf c 2 5 10 12 exp 227 62 kj mol 1 rt m 2 s 1 diffusivities for experiments buffered at qfm and nno are similar to those run in air diffusivities in synthetic and natural rutile are likewise similar indicating that these findings can be applied directly in determining zr diffusivities in rutile in natural systems these data indicate that rutile should be moderately retentive of zr chemical signatures with zr diffusivities within an order of magnitude of those for pb in rutile over most geologic conditions when applied in evaluation of the relative robustness of the recently developed zr in rutile geothermometer t zack r moraes a kronz temperature dependence of zr in rutile empirical calibration of a rutile thermometer contributions to mineralogy and petrology 148 2004 471 488 e b watson d a wark j b thomas crystallization thermometers for zircon and rutile contributions to mineralogy and petrology 151 2006 413 433 these findings suggest that zr concentrations in rutile will be somewhat more likely to be affected by later thermal disturbance than the geothermometer based on zr concentrations in titanite l hayden e b watson d a wark a thermobarometer for sphene abstract 16th v m goldschmidt conference 2006 and much less resistant to diffusional alteration subsequent to crystallization than the ti in zircon geothermometer e b watson d a wark j b thomas crystallization thermometers for zircon and rutile contributions to mineralogy and petrology 151 2006 413 433 e b watson t m harrison zircon thermometer reveals minimum melting conditions on earliest earth science 308 2005 841 844

deducing source rock lithology from detrital rutile geochemistry an example from the erzgebirge germany abstract this study evaluates the applicability of rutile trace element geochemistry to provenance studies the study area is the erzgebirge in eastern germany where metamorphic rocks ranging from lower greenschist facies conditions up to granulite facies conditions are exposed we collected sand and rock samples from small catchment areas for a comparative analysis of rutile geochemistry using wavelength dispersive electron microprobe our results show that rutile geochemistry is a powerful tool in provenance studies allowing for the identification of source lithologies and an evaluation of the host orogen s metamorphic history the log cr nb ratio has proven to be decisive in discriminating between mafic and metapelitic lithologies it is also useful for identifying different source rocks when plotted versus a third element or proxy furthermore our results suggest that rutile thermometry can be applied to a much wider range of lithologies than previously assumed a quantification of temperature populations within single sand samples shows that at high grade metamorphic conditions such as those found in the erzgebirge more than 65 of rutiles do not re equilibrate during retrograde metamorphism and thus retain their peak temperature chemistry such samples which have equilibrated at recent metamorphic conditions can be identified by their 2 standard deviations of less than 120 c below 550 600 c no complete equilibration is reached rutiles from greenschist facies and lower metamorphic conditions in the erzgebirge still inherit relict temperatures from a former metamorphic cycle they partly record very high temperatures 950 c and supposedly derive from erosion of the west african craton in ordovician time

an empirical evaluation of the argon diffusion geometry in muscovite the temperature time significance of 40ar 39ar muscovite ages is difficult to evaluate quantitatively because of ambiguities in the choice of an appropriate model diffusion geometry the effective diffusion dimension and large uncertainties in experimentally determined diffusion parameters laser 40ar 39ar studies of natural 40ar concentration gradients suggest that argon loss in muscovite occurs primarily via cylindrical volume diffusion commonly with an effective diffusion dimension equal to the crystal diameter the present study tests the cylinder model geometry and the control of physical grain size on the effective diffusion dimension by measuring the anisotropy of a natural40ar diffusion gradient parallel and perpendicular to 001 in a single euhedral muscovite phenocryst the new data combined with previous studies clearly indicate loss of 40ar via cylindrical volume diffusion and strongly suggest that loss of 40ar across the 001 sheets slab diffusion geometry is minimal in undeformed crystals

origin of the magnetization of permo carboniferous sediments of spitsbergen svalbard archipelago rock magnetic investigations of permo carboniferous carbonate sediments from two areas on spitsbergen are described conducted to identify the carriers of the nrm in these rocks since microscopic and magnetic separation techniques could not profitably be applied the nature of magnetic minerals was investigated by thermal demagnetization of the nrm and decay of saturation isothermal remanence irs during heating to 600 c as well as by the distribution of the median destructive fields of the nrm and observation of magnetic susceptibility after subsequent heatings the results show that the nrm of these limestones resides mainly in magnetite but creation of magnetic pyrrhotite and of fresh magnetite is observed during heating to 600 c presence of sulphides indicates that magnetite is an oxidation product of pyrite or of non magnetic pyrrhotite examination of rock magnetic properties of limestones leads to the conclusion that most of the magnetite in the rocks of the bellsund area is of detrital origin whereas the rocks at festningen contain magnetite derived from pyrite probably during an early stage of the diagenetic process

linear and planar structure in ordered multivariate data as applied to progressive demagnetization of palaeomagnetic remanence summary consider a sequence of say 10 to 20 vector observations in threedimensional space it is suspected that a few subsets of consecutive observations are made up of collinear points the purpose of this paper is to construct a statistically based algorithm to find such linear segments and to assess their accuracy a similar assessment is made for coplanar sets of points this algorithm is applied here to palaeomagnetic data and is claimed to be superior to previous methods of palaeomagnetic analysis in terms of completeness and balance of analysis treatment of measurement errors and other sources of scatter criteria for identification of linear and planar sets of points and statistical rigour stability spectra with statistically based confidence limits are obtained as a by product 1 palaeomagnetic analysis background to the geometrical problem the natural remanent magnetization nrm in rocks is known in general to have originated in one or more relatively short time intervals during their formation and subsequent history i e during rock forming or metamorphic events during which nrm is frozen in stabilized by falling temperature grain growth etc the nrm acquired during each such event is a single vector magnetization parallel to the then prevailing geomagnetic field and is called a component of nrm rocks which have suffered more than one event of this kind are therefore liable to carry multi component nrm in the laboratory these components can be identified by demagnetizing the rock step by step usually by thermal alternating field or chemical demagnetization which involves the analysis of the distribution of blocking rzmperature coercivity and chemical leaching respectively resistance to these treatments is called stability of remanence and the range of treatment over which a particular component is removed is called the stability range of the component the various discrete

pre mesozoic alpine basements their place in the european paleozoic framework prior to their alpine overprinting most of the pre mesozoic basement areas in alpine orogenic structures shared a complex evolution starting with neoproterozoic sediments that are thought to have received detrital input from both west and east gondwanan cratonic sources a subsequent neoproterozoic cambrian active margin setting at the gondwana margin was followed by a cambrian ordovician rifting period including an ordovician cordillera like active margin setting during the late ordovician and silurian periods the future alpine domains recorded crustal extension along the gondwana margin announcing the future opening of the paleotethys oceanic domain most areas then underwent variscan orogenic events including continental subduction and collisions with avalonian type basement areas along laurussia and the juxtaposition and the duplication of terrane assemblages during strike slip accompanied by contemporaneous crustal shortening and the subduction of paleotethys under laurussia thereafter the final pangea assemblage underwent triassic and jurassic extension followed by tertiary shortening and leading to the buildup of the alpine mountain chain recent plate tectonic reconstructions place the alpine domains in their supposed initial cambrian ordovician positions in the eastern part of the gondwana margin where a stronger interference with the chinese blocks is proposed at least from the ordovician onward for the visean time of the variscan continental collision the distinction of the former tectonic lower plate situation is traceable but becomes blurred through the subsequent oblique subduction of paleotethys under laurussia accompanied by large scale strike slip since the pennsylvanian this global collisional scenario has been replaced by subsequent and ongoing shortening and strike slip under rising geothermal conditions and all of this occurred before all these puzzle elements underwent the complex alpine reorganization

the apparent polar wander path of the european plate in upper triassic lower jurassic times and the liassic intraplate fracturing of pangaea new palaeomagnetic constraints from nw france and sw germany summary in order to constrain the european plate motions during triassic lower jurassic times new palaeomagnetic data were acquired from various triassic liassic sediments of northeastern france and southwestern germany a carnian palaeopole 49 n 131 e k 193 a95 7 n 4 was obtained for keuper marls with consistent directions of normal and reversed polarities rhaetian sandstones also with both polarities and carnian dolomites with a magnetization of probable secondary origin provide a mean pole 51 n 112 e k 109 a95 6 n 6 more westerly than that given above the lower hettangian sampled in limestones of the xeuilley quarry near nancy shows a n r n polarity sequence with well defined anti parallel directions the mean hettangian pole is 55 n 100 e k 123 a95 11 n 3 induan sandstones from the northern vosges show two distinct overprints one consistent with the ladinian carnian magnetizations already observed in the same region the second consistent with the recalculated mean lower jurassic pole of europe five other sites with different rock types also exhibit late overprints with lower jurassic directions the mean pole calculated from these overprints is 74 n 124 e k 125 a95 6 n 6 the revised apparent polar wander path apwp presented here shows that for the mid permian to the earliest jurassic the palaeopoles of europe stayed around 50 latitude while the longitudes drifted from 185 e to 100 e the previously established upper triassic lower jurassic loop of the apwp is shifted westwards by about 25 the revised apwp involves the following plate motions after the late alleghanian tectonic phase which marked the end of the variscan orogeny central western europe rotated counterclockwise during about 70 myr up to the earliest jurassic the south north drift in latitude by 35 nearly 4000 km remained regular from 320 to 205 ma with a constant rate of 3 4cm yr 1 around 205 ma this motion ceased probably because of a collision somewhere in the north of eurasia then in the lower liassic the plate underwent a rapid counterclockwise rotation with a eulerian pole located in northeastern asia synchronous with fracturing in the atlantic and the neotethys areas it is proposed that the intraplate fracturing of pangaea was initiated by the rapid change of the megacontinent motion at the end of the trias

inclination flattening and the geocentric axial dipole hypothesis abstract william gilbert first articulated what has come to be known as the geocentric axial dipole hypothesis the gad hypothesis is the principle on which paleogeographic reconstructions rely to constrain paleolatitude for decades there have been calls for permanent non dipole contributions to the time averaged field recently these have demanded large contributions of the axial octupole which if valid would call into question the general utility of the gad hypothesis in the process of geological recording of the geomagnetic field earth filters distort the directions many processes for example sedimentary inclination flattening and random tilting can lead to a net shallowing of the observed direction therefore inclinations that are shallower than expected from gad can be explained by recording biases northward transport or non dipole geomagnetic fields using paleomagnetic data from the last 5 million years from well constrained lava flow data allows the construction of a statistical geomagnetic field model such a model can predict not only the average expected direction for a given latitude but also the shape of the distribution of directions produced by secular variation the elongation of predicted directions varies as a function of latitude from significantly elongate in the up down direction at the equator to circularly symmetric at the poles sedimentary inclination flattening also works in a predictable manner producing elongations that are stretched side to side and the degree of flattening depending on the inclination of the applied field and a flattening factor f the twin tools of the predicted elongation inclination relationship characteristic of the geomagnetic field for the past 5 million years and the distortion of the directions predicted from sedimentary inclination flattening allows us to find the flattening factor that yields corrected directions with an elongation and average inclination consistent with the statistical field model the method can be tested using sediments deposited in a known field application of the elongation inclination correction method to two magnetostratigraphic data sets from red beds in asia and pakistan brings the inclinations into agreement with those predicted from modern gps measurements and from global paleomagnetic data there appears to be no compelling reason at this time to abandon the geocentric dipole hypothesis which has provided such an excellent working model for so long

depositional history of the upper triassic kapp toscana group on svalbard norway inferred from palynofacies analysis and organic geochemistry abstract upper triassic sediments in the svalbard archipelago were deposited in several transgressive regressive cycles understanding their deposition and distribution is of vital importance because of their potential as hydrocarbon reservoir rocks in this study we integrate palynofacies with organic geochemistry in order to reconstruct the depositional environment of the upper botneheia fm up to the lower the knorringfjellet fm from two sections located in central spitsbergen for which distinctive palynofacies zones have been distinguished these are mainly terrestrially dominated but occasionally contain amorphous organic matter and marine palynomorphs rock eval pyrolysis reveals overall mature kerogen type iii iv samples our results indicate that at least partially restricted marine conditions prevailed during deposition of the botneheia fm the botneheia fm is overlain by a regressive cycle from the lower part of the tschermakfjellet fm up to the top of the de geerdalen fm with terrestrially dominated palynofacies assemblages the knorringfjellet fm contains increased marine palynofacies and marine dinoflagellate cysts which is in accordance with a transgression at the base of this unit this study integrates for the first time in the spitsbergen area quantitative palynofacies and sedimentary organic matter characterization and shows the generally accepted paleo environmental development for the svalbard archipelago

climate variations in the boreal triassic inferred from palynological records from the barents sea this paper presents palynological evidence from the late early triassic late smithian to the late triassic rhaetian of the barents sea area a continuous palynological succession from an exploration well 7228 7 1a in the nordkapp basin sw barents sea and palynological data from a series of shallow cores drilled at the svalis dome central barents sea representing selected triassic intervals these fully marine sediments are independently dated by marine faunas both records show significant shifts in the distribution of the main floral elements changing ratios of spore pollen taxa grouped as hygrophytes versus xerophytes and spores versus pollen reveal major changes of the floras within the studied interval one distinct turnover coincides with the smithian spathian boundary where lycopsid and pteridophyte spores dominated assemblages change to pollen pteridosperms and conifers dominated assemblages lower middle triassic assemblages are again dominated by lycopsid spores while the assemblages from the upper part of the middle triassic and the lower part of the late triassic are characterised by dominance of coniferous pollen and show the decline of pteridosperms in the latest triassic fern spores are abundant and diverse in contrast to the middle triassic the pollen assemblages are characterized by cycadophytes and araucariacites these distribution patterns are interpreted to reflect climatic changes the presented results from norwegian boreal areas confirm the significant differences between quantitative distribution of specific taxa as well as diversity of major groups in plant assemblages from low and mid latitudes the present survey opens new perspectives for more detailed comparisons and climatic interpretations of floras from the triassic period a time during which mesozoic vegetation established the major changes in the dominance of specific floral elements especially the diversification and spreading of the conifers can probably be related to climatic changes

palynological correlation of carnian humid pulses throughout western tethys abstract the carnian pluvial event is an upper triassic swing toward increased rainfall best documented in the tethys tropical belt and mainly recognized on its effects on sedimentary systems as the demise of carbonate platforms and the enhanced siliciclastic supply in some portions of western tethys and particularly in the raibler schichten of the northern calcareous alps and in the dolomites the carnian pluvial event is recorded by four discrete siliciclastic pulses in the raibler schichten three siliciclastic intervals are documented and take the name of first second and third shale in order to correlate these pulses at the basinal scale the study of the palynological assemblages in a section of the raibler schichten near rubland austria and of the classical succession of the lunz nappe have been carried out more than eighty palynomorph species are recorded most of them correspond to typical carnian morphospecies of the carnian pluvial event in europe on the base of their stratigraphic distribution three different palynomorph assemblages are described aulisporites astigmosus assemblage lagenella martinii assemblage and granuloperculatipollis rudis assemblage a fourth older assemblage is also informally defined a palynostratigraphic correlation between the nca the germanic basin and the dolomites has been obtained the four siliciclastic pulses recognized in the raibler schichten and lunz are also found in the dolomites and yield the same palynological associations the base of the schilfsandstein that record the carnian pluvial event in the germanic basin is correlated to the second or third siliciclastic pulse first or second shale of the raibler schichten siliciclastic pulses are thus correlated throughout western tethys and can thus be interpreted as short lived humid climate wiggles within the carnian pluvial event a quantitative analysis of the carnian successions of the nca highlights a shift toward hygrophytic elements in the uppermost julian and an abrupt return to xerophytic associations in the lower tuvalian the palynological hygrophytic associations that characterize the aulisporites astigmosus and lagenella martinii assemblages are present in many other parts of europe and middle east suggesting that the carnian pluvial event determined a humid climate perturbation in a wide area of the northern hemisphere spanning from tropical to high latitudes

palaeomagnetic argument for a stationary spitsbergen relative to the british isles western europe since late devonian and its bearing on north atlantic reconstruction abstract palaeomagnetic results from the devonian of central spitsbergen mimer valley formation billefjorden suggest an average palaeofield direction for the late devonian early carboniferous with declination 227 5 inclination 30 6 corresponding to a relative pole position at lat 24 s long 325 e this magnetization which is post tectonic is regarded as acquired chemically linked with the upper devonian svalbardian phase of deformation this result together with some recent data from central spitsbergen defines a devonian polar wander segment that accords extremely well with corresponding british data we interpret this in terms of no major displacement of central spitsbergen as compared with western europe since devonian time svalbard and the barents sea region have probably formed a fairly stable platform since the early devonian on the balance of available geological and palaeomagnetic evidence from spitsbergen the british isles and newfoundland the north atlantic region does not appear to have been subjected to strike slip motions in the order of thousands of kilometers in or since the late devonian

integrated stratigraphy and palaeoclimate history of the carnian pluvial event in the boreal realm new data from the upper triassic kapp toscana group in central spitsbergen norway the late triassic climate is characterized by arid conditions interrupted by a humid phase known as the carnian pluvial event cpe this wet phase is well documented in the tethyan realm but evidence from the boreal realm is scarce here we present evidence from quantitative palynology for the cpe from the kapp toscana group on central spitsbergen integrated with organic carbon isotope data linked to the geomagnetic polarity time scale our data reveal an early to mid julian 1 age for the tschermakfjellet formation the transition to the julian 2 is located in the de geerdalen formation and the isfjorden member is confirmed as mostly tuvalian 3 in age the aulisporites astigmosus pollen assemblage zone that marks the base of the cpe in the tethys realm at the base of the julian 2 is assigned to the julian 1 in the boreal region palaeoclimate proxy data inferred from principal component analysis indicate wetter conditions from the julian 2 onwards which is in agreement with the establishment of local swamp vegetation on top of a delta plain the palaeotemperature curve indicates a period of cooler climate during the early julian 1 followed by warming during the late julian 1 supplementary materials a list of all identified morphotaxa of pollen spores and aquatic palynomorphs is available at http www geolsoc org uk sup18879

genesis of a regionally widespread celadonitic chert ironstone bed overlying upper lias manganese deposits hungary abstract mineralogy and chemical composition are presented for a chert ironstone bed that overlies the urkut mn deposit this bed is mottled green brown in its lower and upper parts which are composed of quartz goethite and celadonite these parts of the bed are interpreted to be strongly altered tuffs reflecting oxidic low temperature alteration of a hydrated fe rich al poor tuff and k and mg uptake from seawater the middle part of the bed is a mineralized bacterial mat quartz goethite textures resembling bacterial cells and colonies are common with wavy bulbous laminations composed of mounds overlying a mesh work stromatolite like texture constructed of micrometre size fe oxides this bed is concordant with the underlying mn deposit and marks the termination of mn accumulation although no genetic connection exists between the two the rocks adjacent to the contact record the oceanographic and bottom water conditions extant when accumulation of one of the major mn deposits of europe ended when the transdanubian range was located in the middle of the adria apulian microcontinent between the neotethys and atlantic ligurian seaways a pyroclastic origin for part of the bed has significance for the toarcian of central europe because evidence of volcanism occurring at that time is otherwise sparse

trace element systematics in granulite facies rutile implications for zr geothermometry and provenance studies metamorphic rutile from granulite facies metapelitic rocks of the archean pikwitonei granulite domain pgd manitoba canada provides constraints on the systematics of trace elements in rutile during high temperature conditions and subsequent slow cooling compositional profiles and maps of the zr concentrations in rutile grains 120 600 m from three metapelitic gneisses were acquired by electron probe micro analysis using a spatial resolution of down to 2 m simultaneously profiles were analysed for nb cr and v which have significantly different diffusion characteristics in rutile the profiles of all elements show relatively homogeneous concentrations within most grains but significant inter grain differences even within a single thin section some rutile grains display a slight concentration decrease from a neighbouring garnet towards the matrix for all measured elements the lack of diffusion profiles for all analysed elements shows that these are highly immobile in rutile and that distributions of these elements are primary and preserve prograde information the nb and cr concentrations overlap with ranges that are ascribed to different provenances indicating that source discrimination based on these elements is not possible in all cases high retentiveness for zr implies that the zr in rutile geothermometer is highly robust to diffusive re equilibration even during very slow cooling 2 c ma 1 from granulite facies conditions most grains have high zr contents 3000 4600 ppm differences between high zr contents suggest that during growth under vapour absent conditions there may not be saturation of zr in rutile even if zircon is present therefore several rutile grains need to be analysed in a sample to obtain a useful minimum peak temperature the highest zr concentrations correspond to 900 c this is significantly higher than previous peak temperature estimates of 820 c based on two feldspar thermometry on a regional scale this implies that part of the pgd was affected by ultra high temperature uht metamorphism it also implies that rutile is able to preserve primary compositions even to uht conditions this study shows that if combined with textural information zr in rutile has the potential to be a very useful tool for estimating rutile crystallization temperatures and peak metamorphic conditions for granulite facies rocks zr in rutile yields more reliable peak metamorphic temperatures than most other exchange geothermometers which tend to partially re equilibrate by diffusion during cooling

a recipe for the use of rutile in sedimentary provenance analysis abstract rutile has received considerable attention in the last decade as a valuable petrogenetic indicator mineral based on both new and previously published data we carve out advantages and pitfalls regarding tio 2 minerals in sedimentary provenance analysis this results in a recipe for the use of rutile in provenance studies the main points are rutile geochemistry from different grain size fractions does not differ systematically and hence rutiles should be extracted from the fraction containing the most rutile grains usually 63 200 m similarly different magnetic susceptibility of rutile does not systematically imply different trace element composition before interpretation of tio 2 mineral data it is important to determine the polymorph type rutile anatase and brookite appear to differ systematically in trace element composition as an alternative to raman spectroscopy chemical classification according to nb cr sn fe v and zr concentrations can be applied for rutile a new host lithology discrimination scheme based on cr nb systematics is introduced x 5 nb ppm 500 cr ppm which leads to better classification results than previously published discrimination methods according to this equation metamafic rutiles have negative values of x while metapelitic rutiles have positive values evaluation of the growth temperature calculations of metamorphic rutile after different authors shows that the equations given by tomkins et al 2007 should be applied to both metamafic and metapelitic rutiles although there is a pressure effect on the zr incorporation in rutile the pressure range for most rutiles of 5 15 kbar introduces an uncertainty in calculated temperature of no more than 35 c the distribution of calculated temperatures from detrital rutiles is crucial only well defined temperature populations should be used for thermometry interpretation

a middle triassic paleomagnetic pole for the eurasian plate from heming france the paleomagnetic study of middle triassic limestones 91 cores 160 samples from a 40 m thick section in heming france yields a paleomagnetic pole for stable europe at lat 53 5 n lon 140 8 e dp 2 3 dm 3 9 this pole fills an important gap of the apparent polar wander path apwp of the eurasian plate the comparison of this pole with available data shows a standstill of the eurasian plate from the late paleozoic to the middle triassic followed by a rapid drift until the lower jurassic the beginning of the rapid drift is contemporaneous with the initiation of main rifting processes in the tethyan oceans

magnetostratigraphy and biostratigraphy of the carnian norian boundary interval from the pizzo mondello section sicani mountains sicily the 146 5 m thick upper triassic limestone section at pizzo mondello in the sicani mountains of western sicily is characterized by high quality of exposure accessibility and stratigraphic continuity magnetostratigraphic results delineate 12 normal and reverse polarity magnetozones labelled successively from the base upwards as pm1n pm1r pm6n pm6r the carnian norian boundary based on conodont biostratigraphy falls somewhere in the pm3n to pm5n interval which corresponds to the e14n to e16n magnetozone interval in the newark reference sequence of polarity reversals comparison of magnetobiostratigraphic data from the newark basin pizzo mondello and other late triassic marine sections available from the literature suggests the existence of a reduction in sedimentation rate in the tethyan marine domain at around the carnian norian boundary although the newark and the expanded pizzo mondello sections correlate well with each other correlation with the condensed kavur tepe and scheiblkogel sections is unsatisfactory a re interpretation of the kavur tepe results suggests that the section is younger than its previous correlation with the newark section and that it was deposited in the northern instead of the southern hemisphere most of the condensed tethyan marine sections are seen to be highly discontinuous as evidenced by concantenated conodont total range zones q 2001 elsevier science b v all rights reserved

nb and zr behavior in rutile during high grade metamorphism and retrogression an example from the ivrea verbano zone abstract detailed textural observations and in situ analyses emp sims and la icp ms are used to characterize trace element behavior during prograde and retrograde metamorphic reactions involving rutile the ivrea verbano zone is a classic granulite area and rocks from the strona and d ossola valleys are an example of the amphibolite to granulite facies transition although different rock types occur in the area detailed sampling and petrographic work show that rutile only occurs in granulite facies paragneisses these rocks show a rich inventory of textures that allow not only for the investigation of trace element behavior in response to prograde rutile growth but also for the effect of post peak processes on rutile chemistry nb concentrations in rutile from lower grade samples show a larger spread from 500 to 5000 ppm within one sample when compared to those from higher grades this pattern can be modeled using prograde rutile growth formed from biotite breakdown zr concentrations in rutile are characterized by an anomalously large spread and a bimodal distribution maximum zr concentrations increase according to the general metamorphic gradient known for this area temperatures from zr in rutile thermometry although feasible are considerably higher than previous calculations increasing from ca 850 to 930 c a second cluster of zr concentrations in rutile occurs at rather constant concentrations ca 1000 ppm for all localities and is interpreted to be related to intense fluid influx at high temperature and or to post peak diffusional resetting favored by slow cooling rates alteration textures characterized by a complex network of micro veins are evidence for the late fluid influx the fluid strongly affected the rutiles which is evidenced by corrosion of older rutile grains and formation of rutile veinlets

rutile chemistry and thermometry as provenance indicator an example from chios island greece abstract in the present study we focused on detrital rutile separated from 12 psammitic samples that belong to three different sedimentary successions carboniferous permo carboniferous permo triassic occurring on chios island greece the ti cr al fe nb zr si and v contents of the rutiles were obtained by electron microprobe analyses to trace their provenance the cr and nb concentrations of the analysed rutile grains show a wide range and indicate that this mineral in the carboniferous succession is mainly derived from metamafic rocks whereas in the permo carboniferous and permo triassic successions stem from a metapelitic source the calculated formation temperatures using the zr in rutile thermometer range from ca 520 to 850 c with hotter rutile being encountered in the permo carboniferous and permo triassic successions this feature together with the rutile chemistry indicate a change in source rock lithology through time which could either reflect an increasing depth of erosion of an exhumed variscan nappe pile of heterogeneous composition in the hinterland or a change in the style of accretion and erosion of different terranes at the southern margin of laurussia during the subduction of a branch of the palaeotethys ocean in the late palaeozoic in general this study underscores the importance of rutile chemistry and thermometry in quantitative single mineral provenance analysis and in chemostratigraphic analysis of clastic sedimentary rocks

magneto biostratigraphy of the middle to upper triassic transition central spitsbergen arctic norway palaeomagnetic and biostratigraphic data were obtained for the latest ladinian and most of the carnian botneheia formation to basal kapp toscana group from two sections in central spitsbergen svalbard archipelago thermal and alternating field af demagnetization reveals a magnetization of both normal and reversed polarities the mean directions pass reversal and fold tests and are similar to other european late triassic palaeopoles one of the sections displays 15 of vertical axis clockwise tectonic rotation on a decollement in the underlying botneheia formation the magnetostratigraphy is dominated by normal polarity in the uppermost botneheia formation and into the tschermakfjellet and basal de geerdalen formations a substantial hiatus characterizes the ladinian carnian boundary in central spitsbergen so reverse magnetozones identified in tethyan sections near this boundary are absent magnetostratigraphic correlation along with palynostratigraphic constraints indicates that most of the de geerdalen formation is lower carnian the magnetostratigraphy and palynology indicates that the isfjorden member upper unit of the de geerdalen formation is probably mid carnian in age change in the lithological architecture in the isfjorden member compared with the underlying parts of the de geerdalen fm suggests a hiatus near the base of the member which may represent a mid carnian unconformity not previously recognized on spitsbergen

a paleomagnetic pole position of late jurassic early cretaceous dolerites from hinlopenstretet svalbard and its tectonic implications abstract paleomagnetic examination of late jurassic early cretaceous dolerites hinlopenstretet reveal a mean paleofield direction d 181 i 71 95 4 2 k 117 9 17 sites 96 samples which is argued to represent a deuteric magnetization formed at the time of cooling the resultant paleopole 66 n 200 e dp 7 dm 8 accords with paleomagnetic poles of similar age for north america after taking into account post jurassic continental separation the result from the present study is interpreted to represent a late jurassic early cretaceous paleopole for eurasia the similarity of the paleopoles from cratonic north america and eurasia in its pre drift configuration at about 145 ma makes it reasonable to conclude that relative displacement due to extension between eurasia and north america prior to the onset of sea floor spreading must have taken place after 145 ma and before the start of sea floor creation in the cretaceous

palaeomagnetic rock magnetic and mineralogical investigations of the lower triassic vardebukta formation from the southern part of the west spitsbergen fold and thrust beltk dudzisz and otherspalaeomagnetism of triassic rocks spitsbergen

tethyan magnetostratigraphy from pizzo mondello sicily and correlation to the late triassic newark astrochronological polarity time scale we present the magnetostratigraphy and stable isotope stratigraphy from an expanded 430 m thick upper triassic marine limestone section at pizzo mondello sicily and review published biostratigraphic information that can be used to defi ne the location of the conodont carnian norian and norianrhaetian boundaries in this section pizzo mondello offers good potential for magnetostratigraphic correlation of marine biostratigraphic and chemostratigraphic data with the continental newark astrochronological polarity time scale apts for development of an integrated late triassic time scale the relatively stable average values of 18 o centered on 0 are a strong indication that the cherty limestone at pizzo mondello suffered very little diagenetic overprinting the conodont carnian norian boundary is located 12 5 m above a positive shift of 13 c a statistical approach was applied to evaluate various pizzo mondello to newark magnetostratigraphic correlations two correlation options have the highest correlation coeffi cients in option 1 the base of pizzo mondello correlates with the middle part of the newark apts whereas in option 2 the base of pizzo mondello starts toward the early part of the newark apts we prefer option 2 in which the carnian norian boundary based on conodonts as well as its closely associated positive 13 c shift correspond to newark magnetozone e7 at ca 228 227 ma adopting newark astrochronology implying a long norian with a duration of 20 m y and a rhaetian of 6 m y duration these ages are in fact not inconsistent with the few high quality radiometric dates that are available for late triassic time scale calibration based on its good exposure accessibility stratigraphic thickness and continuity and multiple chronostratigraphic correlation possibilities we propose pizzo mondello as global stratigraphic section and point for the base of the norian

magnetostratigraphy of the mayerling section austria and erenkolu mezarlik turkey section improvement of the carnian late triassic magnetic polarity time scale abstract we present a magnetostratigraphic study of two carnian late triassic pelagic limestone sections from the northern calcareous alps mayerling section and southwestern turkey erenkolu mezarlik section biostratigraphic control is based on conodont zonation for the mayerling section and both on conodonts and ammonoids for the erenkolu mezarlik section in both sections the characteristic magnetization is essentially carried by a mineral of the magnetite family eight magnetic intervals are obtained from the mayerling section and fourteen from erenkolu mezarlik when these results are compared to the carnian magnetostratigraphic sequence obtained from the bolucektasi tepe section satisfactory correlations are observed and a composite carnian magnetic polarity time scale containing 24 intervals can be proposed by combining all these results the lower part of the upper carnian is however missing tuvalian 1 zone and lower part of the tuvalian 2 zone no clear correlation is observed between our composite sequence and the other published magnetostratigraphic data of carnian age the satisfactory correlation observed between the mayerling and the bolucektasi tepe sections indicates that both sections were deposited in the northern hemisphere thus providing constraints on the origin of the antalya nappes

reconstructions of the continents around the north atlantic at about the 60th parallel abstract late carboniferous early tertiary apparent polar wander apw paths 300 40 ma for north america and europe have been tested in various reconstructions these paths demonstrate that the 500 fathom bullard et al fit is excellent from late carboniferous to late triassic times but the continental configuration in northern pangea changed systematically between the late triassic ca 214 ma and the mid jurassic ca 170 ma due to pre drift extension best fit north atlantic reconstructions minimize differences in the late carboniferous early jurassic and late cretaceous tertiary segments of the apw paths but an enigmatic difference exists in the paths for most of the jurassic whereas for the early cretaceous the data from europe are nearly non existent greenland s position is problematic in a bullard et al fit because of a late triassic early jurassic regime of compression 300 km that would be inherently required for the norwegian shelf and the barents sea but which is geologically not defensible we suggest a radically new fit for greenland in between europe and north america in the early mesozoic this fit keeps greenland locked to europe for the late paleozoic early mesozoic and maintains a reconstruction that better complies with the offshore geological history of the norwegian shelf and the barents sea pre drift a24 extension amounted to approximately 450 km on the mid norwegian shelf but with peak extension in the late cretaceous

upper anisian to lower carnian magnetostratigraphy from the northern calcareous alps austria we present a magnetostratigraphic study of three pelagic limestone sections gamsstein mendlingbach and mayerling from the eastern part of the northern calcareous alps together these sections which contain a rich conodont fauna yield a sedimentary record encompassing the uppermost anisian the ladinian and the lower carnian thermal demagnetization and isothermal remanent magnetization experiments indicate that the magnetization is essentially carried by a mineral of the magnetite family the high unblocking temperature components isolated from the three sections provide clear magnetic polarity zonations correlations between these results based on the biostratigraphic data and tephrochronology allow the construction of a composite magnetic polarity sequence from the illyrian substage upper anisian to the julian 2 zone lower carnian this sequence contains 17 well defined polarity reversals and eight more poorly defined intervals correlations can be suggested between the new data and other magnetostratigraphic results previously obtained from marine sections we estimate that the magnetic reversal frequency was 2 5 to 3 6 reversals per million years during the ladinian

global warming leads to early triassic nutrient stress across northern pangea the largest extinction in earth history in the latest permian was followed throughout most of the early triassic by a prolonged period of ecologic recovery what factors delayed biotic recovery are still under debate and partly revolve around impacts of global warming on primary marine productivity we examined n isotope records from the festningen section on spitsbergen to examine changes in nutrient availability through the early to middle triassic along the northern margin of pangea our results show progressive decline in n availability throughout the griesbachian leading to severe nutrient limitations through the remainder of the early triassic until returning to a highly productive continental margin in middle triassic time these results are consistent with other studies from northern and western pangea and thus show regional nutrient limitations occurred in what should have been the main zone of marine primary productivity such nutrient limitation likely stressed primary production and consequently contributed to prolonged marine recovery we suggest this was driven by high ocean temperatures depressing the marine nutricline

pb diffusion in rutile diffusion of pb was measured in natural and synthetic rutile under dry 1 atmosphere conditions using mixtures of pb titanate or pb sulfide and tio2 as the sources of diffusant pb depth profiles were then measured with rutherford backscattering spectrometry rbs over the temperature range 700 1100 c the following arrhenius relation was obtained for the synthetic rutile d 3 9 10 10exp 250 12 kj mol 1 rt m2s 1 results for diffusion in natural and synthetic rutile were quite similar despite significant differences in trace element compositions mean closure temperatures calculated from the diffusion parameters are around 600 c for rutile grains of 100 m size this is about 100 c higher than rutile closure temperature determinations from past field based studies suggesting that rutile is more resistant to pb loss through volume diffusion than previously thought

the early palaeozoic break up of northern gondwana sedimentology physical volcanology and geochemistry of a submarine volcanic complex in the bavarian facies association saxothuringian basin germany abstract ordovician volcano sedimentary successions of the bavarian facies association in the saxothuringian basin record the continental rift phase of the separation of the saxothuringian terrane from gondwana an 80 m succession from the vogtendorf beds and randschiefer series arenig middle ordovician exposed along the northern margin of the munchberg gneiss massif in northeast bavaria were subjected to a study of their sedimentology physical volcanology and geochemistry the randschiefer series previously has been interpreted as lavas tuffs sandstones and turbidites but the studied ordovician units include four main lithological associations mature sandstones and slates pillowed alkali basalts and derivative mass flow deposits trachyandesitic lavas and submarine pyroclastic flow deposits interbedded with turbidites eight lithofacies have been distinguished based on relict sedimentary structures and textures which indicate deposition on a continental shelf below wave base the explosive phase that generated the pyroclastic succession was associated with the intrusion of dykes and sills and was succeeded by the eruption of pillowed basalts debris flow deposits overlie the basalts ordovician volcanism in this region therefore alternated between effusive and explosive phases of submarine intermediate to mafic volcanism based on geochemical data the volcanic and pyroclastic rocks are classified as basalts and trachyandesites according to their geochemical characteristics especially to their variable concentrations of incompatible elements such as the high field strength elements hfse they can be divided into three groups group i which is formed by massive lavas at the base of the succession has extraordinarily high contents of hfse the magmas of this group were probably derived from a mantle source in the garnet stability field by low ca 1 degrees of partial melting and subsequent fractionation group ii which comprises the pillow lavas at the top of the sequence displays moderate enrichment of hfse this can be explained by a slightly higher degree of melting ca 1 6 for the primary magma group i and ii melts fractionated from their parental magmas in different magma chambers the eruption centres of groups i and ii therefore cannot be the same and the volcanic rocks must have originated from different vents the sills and pyroclastic flow deposits of group iii stem at least partly from the same source as group i rocks of group i most likely mixed together with group ii components during the formation of the group iii flows which became hybridised during eruption transportation and emplacement the sedimentological and geochemical data best support a rift as the tectonic setting of this volcanism analogous to modern continental rift zones hence the rift associated volcanic activity preserved in the vogtendorf beds and randschiefer series represents an early ordovician stage of rift volcanism when the separation of the saxothuringian terrane from gondwana had just commenced

slow subduction of a thick ultrahigh pressure terrane 1 high precision lu hf and sm nd ages reported here cover a large portion of the western gneiss region wgr ultrahigh pressure uhp terrane norway and range from 413 9 3 7 to 397 1 4 8 ma collectively new and existing geochronologic data for eclogites demonstrate that eclogite facies metamorphism occurred over a large area 60 000 km2 for an unexpectedly long period of 20 ma a thermal model using slow subduction 2 4 mm a 1 of a relatively warm and thick slab can reproduce the observed p t t history of the wgr uhp terrane indicating that large uhp terranes with protracted peak or near peak histories probably reflect slow subduction of relatively thick crustal sections

la icp ms u pb dating of detrital rutile and zircon from the reynolds range a window into the palaeoproterozoic tectonosedimentary evolution of the north australian craton abstract the palaeoproterozoic reynolds range of the arunta region central australia comprises a series of shallow marine clastic sediments reynolds range group which overlies deeper water sequences of turbidites lander rock formation and minor sandstones unnamed sandstone u pb age data collected from detrital rutile and zircon in these rocks indicates these sequences contain very similar age spectra although with a notable and important shift to younger ages within the stratigraphically younger reynolds range group detrital zircons from the unnamed sandstone directly underlying the unconformity with the reynolds range group contain a major age component at ca 1860 ma together with a wide spread of ages between ca 3 2 and 2 0 ga and a minor age component of 1830 1805 ma detrital rutile from the same rock yield a unimodal age spectrum with a mean age of ca 1840 ma the detrital zircon age spectrum from the reynolds range group is similar although the youngest cluster of ages is younger and dates to between 1800 ma and 1780 ma detrital rutile from these rocks yield a unimodal age spectrum with a mean age of ca 1790 ma although the observed differences in ages are subtle we suggest these nevertheless mark a significant change in provenance we attribute the predominance of 1860 1820 ma detrital zircon and 1840 ma detrital rutile within the unnamed sandstone and the characteristic ca 1860 ma detrital zircon age cluster in previously published provenance studies from the lander rock formation to uplift and erosion of the halls creek pine creek orogen this orogenic belt marks collision between the north australian and kimberley cratons an event dated to between 1835 ma and 1810 ma and which incorporates marginally older rocks dating to 1860 ma from the foreland of the kimberley craton by contrast we attribute the influx of younger rutile and zircon together with a distinct facies change observed with the onset of the deposition of the reynolds range group to a shift in provenance region to the yapungku orogen which marks the collision between the west australian and north australian cratons and is dated to ca 1800 1765 ma a change in provenance is additionally consistent with significant differences in rutile trace element composition the lander rock formation and the reynolds range group are stratigraphically correlated with sedimentary rocks that overly large parts of the north australian craton we suggest this indicates spatially continuous basinal conditions within the north australian craton between ca 1840 ma and 1780 ma although the erosion and drainage systems feeding this basin were strongly influenced by the collision and orogenesis along the northwest and southwest margins of the north australian craton

biomagnetostratigraphy of the vikinghogda formation svalbard arctic norway and the geomagnetic polarity timescale for the lower triassic a bio magnetostratigraphy for the lower triassic is constructed using the ammonoid biostratigraphy from arctic boreal successions combined thermal and alternating field demagnetisation determines the triassic magnetic field polarity in 86 of specimens with 36 showing linear trajectory line fits and the remainder great circle trends towards the characteristic magnetisation mean pole directions for the deltadalen 50 159 dp dm 3 9 5 1 lusitaniadalen 56 163 dp dm 4 4 5 4 and vendomdalen 57 143 dp dm 4 4 5 4 members fall close to the european lower triassic apparent polar wander path mean directions for two of these member means pass the reversal test the remanence is predominantly carried by magnetite the polarity stratigraphy when integrated with the ammonoid and meager conodont data is similar to that determined from successions in the sverdrup basin canada the permian triassic boundary post dates a pronounced palynofloral turnover and pre dates a short duration reverse magnetozone lt1n 1r in the correlated shangsi section in s china lt1n 1r occurs after the fad of h parvus but in the arctic is within the otoceras boreale zone the late griesbachian to early smithian is mostly reverse polarity with three normal polarity intervals overlain by mid and late smithian normal polarity the spathian contains four reverse polarity intervals the oldest one within the early spathian with the remainder in the late spathian transition into the anisian is within the uppermost reverse magnetozone a feature documented in other sections of this age the polarity pattern is correlated to other marine sections indicating the robustness of the bio magnetostratigraphic composite and its utility in calibrating lower triassic time

the direction correction tilt test an all purpose tilt fold test for paleomagnetic studies abstract the tilt or fold test in paleomagnetism is used to infer whether paleomagnetic remanence was acquired before or after tectonic tilting while several tilt test formulations have been proposed none fully satisfies the requirements of statistical validity applicability to all bedding geometries and ease of use this paper introduces the direction correction dc test which examines the relationship between the paleomagnetic site mean directions and their corresponding bedding tilt corrections the dc test is similar to mcfadden s correlation test because both test whether or not the site directions contain information about the bedding tilts however the dc test gives greater weight to sites with greater counter bedding the dc test is similar to watson s numerical tilt tests because they determine the degree of untilting which gives optimal concentration of site directions however the dc test uses analytical rather than numerical methods graphical output aids the researcher in recognizing problem sites using both real and simulated data the dc test is demonstrated to be more discriminating than other tilt test formulations for all bedding geometries the simulations show that the power of the tilt test is inversely proportional to the 95 confidence interval 95 of the overall mean as a rule of thumb paleomagnetists should attempt to sample sufficient sites to obtain an 95 less than 1 6 of the bedding attitude difference