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

paleomagnetism of triassic bedded chert from japan for determining the age of an impact ejecta layer deposited on peri equatorial latitudes of the paleo pacific ocean a preliminary analysis abstract bedded chert samples from the norian upper triassic sakahogi section of the mino terrane in the inuyama area southwest japan have been collected for paleomagnetic study in order to determine the age of an impact ejecta layer interbedded within it and the paleolatitude of its deposition thermal demagnetization of the bedded chert samples revealed four distinct remanent magnetization components the last demagnetized component with both polarities is interpreted to be the primary magnetization which produced the first magnetostratigraphic data of the middle to upper norian from panthalassa consistent with tethyan magnetostratigraphic sections tie points were derived from paleomagnetic and paleontological data from which the stratigraphic position of the ejecta layer was compared with the astronomically tuned geomagnetic polarity time scale apts the age of ejecta layer is estimated to be about 212 ma this magnetostratigraphic age is consistent with the radiometric age of the manicouagan impact that formed the second largest known crater in the phanerozoic at quebec canada the results of this study as well as previous studies suggest that the chert section which includes the ejecta layer was deposited within a paleolatitude range of 0 3 14 4 n this indicates that the material ejected by the manicouagan impact event reached near the equatorial region of the paleo pacific ocean

new evidence for block and thrust sheet rotations in the central northern calcareous alps deduced from two pervasive remagnetization events 1 we present 81 paleomagnetic sites early triassic to early cretaceous from the central sector of the northern calcareous alps nca eastern alps austria and germany stepwise thermal demagnetization defines three magnetic directions mostly carried by low unblocking temperature and low coercivity minerals j3 350 j2 500 j1 575 and 680 j3 and j2 show positive inclinations whereas j1 very seldom is of dual polarity the fold tests show that a j3 can be interpreted as a postfolding and posttilting remagnetization and j2 as a postfolding and pre syn tilting j1 can be considered as primary because of the occurrence of two polarities and evidence presented by other authors in the area all three components show a systematic and significant clockwise rotation after comparing with the expected european references j2 or j1 are marked by higher rotation values than j3 j2 shows different inclinations depending on the structural position north or southward dips considering the structural evolution and the observed inclinations the first postfolding and pretilting remagnetization event j2 could have taken place between late cretaceous and eocene times but certainly before the thrusting of the nca over the rhenodanubian flysch and northward tilting caused by the stacking of the lower austroalpine nappes the second postfolding and posttilting remagnetization j3 would have been acquired after the final thrusting of the nca over penninic units from then the nca behaved as a set of rigid blocks recording the main stage of vertical axis clockwise rotation 65 in average associated with the continental collision the variable degree of rotation in the different positions from 40 to 134 can be explained by individual vertical axis rotation in a block system trying to adjust to space problems the constant declination differences between j2 and j3 25 in average would reflect the rotation related with the lateral differences of shortening during the oblique thrust of the austroalpine units over the penninic units

salinity bias on the foraminifera mg ca thermometry correction procedure and implications for past ocean hydrographic reconstructions 1 mg ca in foraminiferal calcite has recently been extensively used to estimate past oceanic temperatures here we show however that the mg ca temperature relationship of the planktonic species globigerinoides ruber is significantly affected by seawater salinity with a 1 psu change in salinity resulting in a 1 6 c bias in mg ca temperature calculations if not accounted for such a bias could lead for instance to systematic overestimations of mg ca temperatures during glacial periods when global ocean salinity had significantly increased compared to today we present here a correction procedure to derive unbiased sea surface temperatures sst and 18osw from g ruber tmg ca and 18of measurements this correction procedure was applied to a sedimentary record to reconstruct hydrographic changes since the last glacial maximum lgm in the western pacific warm pool while uncorrected tmg ca data indicate a 3 c warming of the western pacific warm pool since the lgm the salinity corrected sst result in a stronger warming of 4 c

new constraints on the end triassic upper norian rhaetian magnetostratigraphy abstract the end triassic was marked by one of the five important phanerozoic global mass extinctions the construction of a detailed magnetic polarity time scale for this period that would integrate data from marine and terrestrial realms is thus of particular interest we report new magnetostratigraphic data from the oyuklu section located in southwestern turkey which allow one to propose a complete late upper norian sevatian 2 to rhaetian magnetic polarity sequence two correlations are discussed between the new tethyan marine sequence and the continental magnetic polarity record previously determined from the newark basin in eastern north america both options suggest that the rhaetian is at least partly missing in the newark basin which would reconcile most late triassic magnetostratigraphic results and biotic features obtained from marine and continental environments following our preferred correlation the rhaetian would have a duration as short as 2 myr and 4 5 myr if the sevatian 2 zone is included as part of the rhaetian

a mesozoic time scale we present an integrated geomagnetic polarity and stratigraphic time scale for the triassic jurassic and cretaceous periods of the mesozoic era with age estimates and uncertainty limits for stage boundaries the time scale uses a suite of 324 radiomenc dates including high resolution 40 ar 39 ar age estimates this framework involves the observed ties between 1 radiometric dates biozones and stage boundaries and 2 between biozones and magnetic reversals on the seafloor and in sediments interpolation techniques include maximum likelihood estimation smoothing cubic spline fitting and magnetochronology

norian magnetostratigraphy from the scheiblkogel section austria constraint on the origin of the antalya nappes turkey abstract late triassic magnetostratigraphic investigations in southwestern turkey have suggested that parts of the antalya nappes are constituted of a melange of blocks originally deposited either in the vicinity of the northern tip of arabia or more surprisingly directly north of india in the southern hemisphere in order to ascertain this result more clearly we have correlated the turkish series with austrian sections of corresponding age from the northern calcareous alps for which the hemisphere of deposition is beyond doubt the new magnetostratigraphic results obtained from the scheiblkogel section austria confirm the previously suggested middle to late norian magnetic polarity sequence and support the heterogeneous character of the antalya nappes

new magnetostratigraphic and 40ar39ar dating results from the suva marl fiji calibration of the early pliocene geomagnetic polarity time scale abstract the suva marl fiji provides a rare opportunity to integrate early pliocene biostratigraphic magnetostratigraphic and chronostratigraphic data we present new paleomagnetic data that extend the previously reported magnetostratigraphy p rodda i mcdougall r a cassie d a falvey r todd j a wilcoxon isotopic ages magnetostratigraphy and biostratigraphy from the early pliocene suva marl fiji geol soc am bull 96 1985 529 538 of the suva marl down section and suggest a revision of the original correlation with the geomagnetic polarity time scale gpts 40 ar 39 ar laser incremental heating analyses of mineral separates from the interbedded tuffs yield refined age constraints for previously reported k ar dates for the suva marl polarity reversals the new dates and the new magnetostratigraphic data are most consistently interpreted as supporting the revised early pliocene polarity time scale w a berggren d v kent c c swisher iii m p aubry a revised cenozoic geochronology and chronostratigraphy in w a berggren d v kent m p aubry j hardenbol eds geochronology time scales and global stratigraphic correlation soc econ paleontol mineral spec publ 54 1996 129 212 the ages of the suva marl reversals derived from the 40 ar 39 ar dates provide a revised direct calibration of the early pliocene gpts bringing it in synch with those calibrations produced by orbital tuning of milankovitch cycles astronomical time scale

magnetostratigraphy of the kavur tepe section southwestern turkey a magnetic polarity time scale for the norian we present the magnetostratigraphy of the late triassic pelagic kavur tepe section from the taurides southwestern turkey the section investigated is about 30 m thick and consists of fine grained whitish limestones the biostratigraphy based on the conodont zonation gives an age from the lacian 2 zone lower norian to the sevatian 2 zone upper norian the paleomagnetic analyses indicate very favourable behaviour with two magnetic components which can be isolated both by thermal and af demagnetization the magnetization is carried by magnetite and goethite which are clearly evident in irm experiments the first component of normal magnetic polarity has roughly the direction of the present day field the high unblocking temperature component shows directions of both polarities in total fifteen magnetic polarity intervals are observed within the kavur tepe section the characteristic calculated fisherian mean direction is particularly tightly grouped d 220 2 and i 32 1 with k 40 9 95 1 7 and nsamp 179 after bedding correction polarity correlations with two other sections in turkey and in austria northern calcareous alps show that the kavur tepe sediments were deposited in the southern hemisphere by combining the magnetostratigraphic results from the bolucektasi tepe 1 and the kavur tepe sections an almost complete norian magnetic polarity sequence is established showing 30 magnetic intervals that are well calibrated with the conodont and ammonoid zonations a magnetic reversal frequency close to about 2 7 reversals myr is derived for the norian this medium frequency is in agreement with the hypothesis of a long time constant 150 200 myr in the changes of the magnetic reversal frequency since the kiaman reversed superchron

magnetostratigraphic dating of the proposed rhaetian gssp at steinbergkogel upper triassic austria implications for the late triassic time scale the global stratotype section and point gssp for the rhaetian stage has recently been proposed at steinbergkogel in austria we re sampled the steinbergkogel sections stk a and stk b c in high resolution to establish a robust magnetostratigraphy that allows global correlation the palaeomagnetic signal at steinbergkogel is composed of three components which can be separated by thermal demagnetization the highest temperature component revealed between 280 300 and maximum 600 c is of dual polarity and is interpreted as primary rock magnetic experiments showed that the signal is carried by magnetite our results allow correlation between the two individual steinbergkogel outcrops subsequently we correlate the two key biostratigraphic horizons for the base of the rhaetian the fo of m hernsteini and the fad of m post hernsteini to other sections of the tethys domain the correlation to the astronomically dated continental successions of the newark basin indicates that these positions for the base of the rhaetian are most likely determined in chrons e16n and e16r respectively this correlation is confirmed by cyclostratigraphic control on the marine pizzo mondello italy section where a combination of long period milankovitch cycles 175 myr and short eccentricity cycles 100 kyr provide additional correlation constraints respectively supporting a long duration of the rhaetian our study implies that the norian and rhaetian stages have durations of 17 and 9 myr

improving the upper triassic numerical time scale from cross correlation between tethyan marine sections and the continental newark basin sequence abstract magnetostratigraphic cross correlations between biochronologically well dated tethyan marine sections and the astronomically tuned sedimentary sequence from the continental newark basin eastern north america help to improve the upper triassic time scale we show here that the most recent radiometric results constraining the age of the base and top of the upper triassic 237 and 200 ma respectively strengthen the chronostratigraphic calibration of the newark sedimentary sequence proposed by krystyn et al earth planet sci lett 203 2002 343 351 these results allow one to reconcile the milankovitch based cyclostratigraphy from the newark sequence the magnetostratigraphic data from both marine and continental environments and upper triassic biostratigraphy including data on tethyan marine faunas and on terrestrial vertebrates according to this calibration the successive upper triassic stages would have very different durations 10 myr for the carnian 237 227 ma 25 myr for the norian 227 202 ma and 2 myr for the rhaetian 202 200 ma but only if the entire rhaetian is recorded in the newark sequence we further show that the biozone durations in the upper triassic would have been highly variable and as a whole would have lasted much longer than in the lower and middle triassic

seismic and potential field imaging of the guichon creek batholith british columbia canada to delineate structures hosting porphyry copper deposits the guichon creek batholith gcb located in south central british columbia contains several large low grade copper deposits of considerable economic importance the surface geology of the guichon batholith and its surrounding region have been well mapped however little information about subsurface features is available the batholith consists of four major phases emplaced radially outward which can be separated on the basis of their texture and composition previous interpretation of gravity data suggests a mushroom shaped structure for the batholith data from lithoprobe seismic reflection line 88 11 acquired across the batholith in 1988 reveal weakly coherent east dipping reflections on the west side and west dipping reflections on the east in the upper 10 km to determine if these are related to structures associated with the batholith we reprocessed the upper 6 s with particular emphasis on applications of signal enhancement techniques e g pattern recognition methods refraction statics

mesozoic paleogeography of the northern calcareous alps evidence from paleomagnetism and facies analysis the northern calcareous alps are generally thought to have been part of the same southern tethyan continental margin as the southern alps during late jurassic and early cretaceous time contrasting liassic paleomagnetic data from the northern calcareous alps and the southern alps can be explained by large scale clockwise rotation during late cretaceous and tertiary tectonic emplacement of the northern calcareous alps onto the european continental margin alternatively the data can be reconciled by postulating that the northern calcareous alps did not undergo the african mesozoic rotational history seen in the southern alps and were separated from the southern alps by a short lived branch of jurassic ocean facies analysis in the karwendel thiersee syncline of the northern calcareous alps indicates that the jurassic basin sediments in this area were deposited in an east west oriented sinistral strike slip fault system in the southern alps and central austroalpine complex coeval basin sedimentation was controlled by north south oriented normal faults this contrasting basin evolution and evidence for a source of ophiolitic detritus south of the northern calcareous alps argue for a short lived ocean basin south of the northern calcareous alps that was closed by early cretaceous time

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

seasonality of u k 37 temperature estimates as inferred from sediment trap data abstract the seasonality of sea surface temperatures sst estimated from the alkenone u k 37 index has been a debated issue since the development of the proxy using a compilation of sediment trap time series data from 34 sampling locations we show that the seasonality of maximum alkenone flux in sediment traps varies markedly across the oceans depending not only on latitude and light availability but also on local oceanographic conditions the seasonality of the alkenone flux to sediments may also be shaped by the complexity of sedimentation processes and a consistent globally applicable seasonal pattern is not apparent nevertheless u k 37 values display a world ocean scale correlation with mean annual ssts 0 m that closely resembles the standard calibration equation now established for modern surface sediment records thus with a few notable exceptions at oceanographic locations proximate to major hydrographic fronts it can be concluded that the integrated sedimentation patterns for u k 37 measured in sediment trap time series provide a measure of annual mean sst

late pliocene to early pleistocene changes in the north atlantic current and suborbital scale sea surface temperature variability the strength and latitudinal position of the north atlantic current nac determines the position of the arctic front and heat transport to the high northern latitudes with potentially important consequences for northern hemisphere glaciation a southward shift in the nac and reduced poleward heat transport is hypothesized to have triggered the last major climate transition in earth s history late pliocene intensification of northern hemisphere glaciation inhg in turn inhg is hypothesized to have led to the amplification of climate variability on suborbital time scales to date however only a handful of adequately resolved records are available to test these two hypotheses here we present a new late pliocene to earliest pleistocene record from integrated ocean drilling program site u1313 north atlantic 41 n 2 9 to 2 4 ma we use mg ca derived paleotemperature records in planktic foraminiferal calcite to investigate changes in summer sea surface temperatures sst on orbital and suborbital time scales our results call into question the suggestion that significant weakening and or southward shift of the nac served as a trigger for northern hemisphere cooling and intensified continental ice sheet growth across inhg in contrast to the late pleistocene during inhg we find that the position of the nac and arctic front probably lay well to the north of site u1313 and that the amplitude of suborbital sst variability did not change on glacial interglacial time scales conservative estimates of late pliocene to earliest pleistocene interglacial summer ssts in our record are up to 3 c warmer than present while glacial summer ssts are only 2 c to 3 c cooler in fact our interglacial summer ssts are remarkably similar to those of the mid pliocene our findings indicate that inhg must have involved amplifying feedback mechanisms that are tightly coupled to ice sheet growth but that these processes were insufficiently developed by the late pliocene earliest pleistocene to have triggered large amplitude changes in suborbital climate in the midlatitude north atlantic

oxygen isotopic evidence for late triassic monsoonal upwelling in the northwestern tethys the oxygen isotopic composition of conodonts from the pizzo mondello section in the sicani basin sicily italy on the northwestern tethys margin has been used to reconstruct regional paleoseawater conditions the 18 o phos values 21 21 9 measured by sensitive high resolution ion microprobe shrimp ii are consistent with previously published 18 o phos data from the contemporaneous marginal hallstatt meliata basin 20 3 22 5 located farther north but are distinctly higher than those previously reported from the open ocean setting of the nearby lagonegro basin 18 7 20 0 this 2 offset represents a temperature differential of 8 c suggesting that sea surface temperatures along the northwestern margin sicani and hallstatt meliata basins of the tethys ocean were lower than in the open ocean lagonegro basin during the late carnian tuvalian 2 to early norian lacian we interpret the cooler waters of the marginal basins to reflect coastal upwelling driven by strong monsoonal systems as predicted by existing paleoclimate models for this region

paleomagnetism and paleogeography of the northern calcareous alps austria prefolding magnetization components have been resolved at 38 sites of liassic adnet limestones in the central northern calcareous alps nca and at one site in the drauzug the site mean directions are northeasterly and down and are closer to coeval european directions than to southern alpine african directions the western end of both the nca and of the drauzug yield different site mean directions and negative fold tests indicating remagnetization the sampling localities have been rotated relative to one another during thrusting however comparison of paleomagnetic poles with the european apparent polar wander path implies an average clockwise rotation of about 30 for the nca relative to europe larger scale clockwise rotations in excess of 80 relative to the southern alps are implied by comparison with the southern alpine african polar wander path facies analysis of jurassic and lower cretaceous basinal sediments in the central part of the nca suggests that liassic subsidence was related to presently e w sinistral strike slip faults whereas malm berriasian subsidence was controlled by presently e w south dipping normal faults both paleomagnetic and facies data tend to indicate that the nca did not undergo the african rotation seen in southern alpine paleomagnetic data this implies the existence of a short lived tract of triassic jurassic ocean floor between the nca and the southern alps which linked the pindos ocean to the ligurian trough and allowed adria to rotate independently from the nca during the late jurassic eo alpine deformation and metamorphism are associated with the early cretaceous closure of this hallstatt trough

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

magnetostratigraphy and biostratigraphy of the middle triassic margon section southern alps italy abstract a magnetostratigraphic study has been performed on the paleontologically well constrained pelagic middle triassic lower upper ladinian boundary section at margon trento southern alps italy rock magnetic investigations indicate the presence of both high and low coercivity minerals specimens subjected to progressive thermal demagnetization procedures show that nearly all of them exhibit a low temperature magnetization component parallel to the present day field before bedding correction and a high temperature one characterized by either positive or negative and opposite polarity considered as the characteristic triassic magnetization the comparison of the margon magnetic polarity zonation with those of two coeval sections poses some problems when ammonoid and conodont based stratigraphies have to be correlated however good correlation has been obtained for the recognized middle triassic ammonoid biozones in the tethyan realm valuable data to the construction of a standard magnetostratigraphic and paleontological scale are contributed by the results from the margon section

the late pliocene benguela upwelling status revisited by means of multiple temperature proxies as compared to the late pleistocene alkenone based sea surface temperature sst in the benguela region revealed relatively warm and stable sst recorded between approximate to 3 5 and 2 0 ma and coincide with a period of increasing biological productivity as revealed by increasing deposition of biogenic opal we assess how the hydrological patterns recorded in sst proxies are embedded in the geological record by performing a proxy proxy comparison we used laser ablation inductively coupled plasma mass spectrometry to measure the mg ca on the planktonic foraminifera species globigerina bulloides allowing in situ measurements of mg ca on individual foraminiferal tests mg ca derived temperatures provide much colder temperatures than alkenone derived sst by up to 10 degrees c we build a scenario involving contrasting sensitivities of paleothermometers upon the annual cycle namely alkenones preferentially capturing sst when the surface ocean is warmer than the mean annual average sst and g bulloides capturing sst when upwelling intensifies multichamber analysis also suggests that g bulloides migrates below the sea surface while calcifying its last chambers prior to gametogenesis allowing the extraction of both surface and subsurface temperature from mg ca measured on different chambers the range of temperatures recorded between our multiple sst proxies is supported by the range of temperatures simulated with a general circulation model when different seasons different water depth and different orbital configurations occurring during the late pliocene are considered a greater seasonal cycle in sst during the pliocene can account for alkenone and mg ca derived temperature contrast pointing to a radically different mode of upwelling activity in the benguela region compared to today

magnetostratigraphy of the kavaalani section southwestern turkey consequence for the origin of the antalya calcareous nappes turkey and for the norian late triassic magnetic polarity timescale a magnetostratigraphic study of the kavaalani section of uppermost carnian to upper norian age located in the antalya calcareous nappes southwestern turkey reveals nineteen polarity intervals this pattern correlates very well with two other polarity sequences obtained from the same nappe system bolucektasi tepe and kavur tepe if these sections were deposited in the same northern hemisphere this new interpretation changes our previous conclusions regarding the southern hemisphere origin of the magnetic remanence of the kavur tepe section the paleomagnetic data obtained from the kavur tepe and the kavaalani sections therefore reflect large 180 internal rotations within the antalya nappes these nappes were likely formed close to the northern tip of the arabian promontory we propose a revised yet still preliminary version of the norian magnetic polarity sequence

pervasive palaeogene remagnetization of the central taurides fold and thrust belt southern turkey and implications for rotations in the isparta angle the turkish anatolide tauride block rifted away from the northern margin of gondwana in the triassic which gave way to the opening of the southern neo tethys by the late palaeocene to eocene it collided with the southern eurasian margin leading to the closure of the northern neo tethys ocean to determine the position of the anatolide tauride block with respect to the african and eurasian margin we carried out a palaeomagnetic study in the central taurides belt which constitutes the eastern limb of the isparta angle the sampled sections comprise carboniferous to palaeocene rocks mainly limestones our data suggest that all sampled rocks are remagnetized during the late palaeocene to eocene phase of folding and thrusting event related to the collision of the anatolide tauride block with eurasia to further test the possibility of remagnetization we use a novel end member modelling approach on 174 acquired isothermal remanent magnetization irm curves we argue that the preferred three end member model confirms the proposed remagnetization of the rocks comparing our data to the post eocene declination pattern in the central tauride belt we conclude that our clockwise rotations are in agreement with data from other studies after combining our results with previously published data from the isparta angle that includes our study area we have reasons to cast doubt on the spatial and temporal extent of an earlier reported early to middle miocene remagnetization event we argue that the earlier reported remagnetized directions from triassic rocks in tilt corrected coordinates from the southwestern antalya nappes western taurides are in good agreement with other studies from the area that show a primary origin of their characteristic remanent magnetization this implies that we document a clockwise rotation for the southwestern antalya nappes since the triassic that is remarkably similar to the post eocene 40 rotation of the central taurides for the previously published results that are clearly remagnetized we argue that their remagnetization has occurred in the palaeocene to eocene

what do we know about the evolution of mg to ca ratios in seawater 1 although most reconstructions of the evolution of the mg to ca ratio in seawater conclude that it has increased during the course of the cenozoic they disagree widely regarding the magnitude of this change on the basis of fluid inclusion and caco3 mineralogy observations the increase was at least threefold on the basis of mg content of foraminifera shells it was only a factor of 1 7 a recently published reconstruction based on the mg content of calcite fillings of voids in ridge flank basalts lends support to the conclusion that the change was severalfold but as it is very difficult to come up with a plausible geologic scenario which could account for such a large change we lean toward the smaller estimate based on the magnesium content of foraminifera shells

paleomagnetic reconnaissance of early mesozoic carbonates from williston lake northeastern british columbia canada evidence for late mesozoic remagnetization three classic sections of middle and late triassic fossiliferous limestones cropping out around williston lake in british columbia canada were sampled for paleomagnetic study the objective was to test the suitability of these units for detailed magnetobiostratigraphic study with the aim of improving the reference triassic geomagnetic polarity time scale the williston lake characteristic magnetizations differ however from any triassic north america cratonic reference directions a satisfactory agreement is found instead with cretaceous early cenozoic north america cratonic reference directions the exclusive occurrence of normal polarity suggests that remagnetization likely occurred during the cretaceous long normal superchron remagnetizations may have been triggered by connate brines which moved along aquifers of porous sandstones and carbonates in the early stages of laramide folding resume trois sections fossiliferes classiques de calcaires trias moyen et tardif affleurant autour du lac williston en colombie britannique ont ete echantillonnees pour une etude paleomagnetique l objectif etait de s assurer de la pertinence de ces unites pour une etude magneto bio stratigraphique detaillee visant a ameliorer l echelle referentielle de temps de la polarite geomagnetique au trias les magnetisations caracteristiques du lac williston different toutefois de toute direction cratonique referentielle au trias en amerique du nord toutefois une correlation satisfaisante est etablie avec les directions cratoniques referentielles du cretace cenozoique precoce en amerique du nord l occurrence exclusive d une polarite normale suggere qu il y eut probablement une remagnetisation au cours du long superchron normal du cretace les remagnetisations peuvent avoir ete declenchees par des saumures connees qui se sont deplacees le long d aquiferes de gres et de carbonates poreux dans les premieres phases du plissement laramide

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