calibrating the end permian mass extinction the end permian mass extinction was the most severe biodiversity crisis in earth history to better constrain the timing and ultimately the causes of this event we collected a suite of geochronologic isotopic and biostratigraphic data on several well preserved sedimentary sections in south china high precision u pb dating reveals that the extinction peak occurred just before 252 28 0 08 million years ago after a decline of 2 per mil in 13c over 90 000 years and coincided with a 13c excursion of 5 that is estimated to have lasted 20 000 years the extinction interval was less than 200 000 years and synchronous in marine and terrestrial realms associated charcoal rich and soot bearing layers indicate widespread wildfires on land a massive release of thermogenic carbon dioxide and or methane may have caused the catastrophic extinction

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

permian to early triassic magnetostratigraphy from the central european basin in poland implications on regional and worldwide correlations abstract permian early triassic rocks sampled in 15 outcrops 93 hand samples and 11 unoriented boreholes 630 hand samples from the polish part of the central european basin were studied paleomagnetically in spite of extensive remagnetization affecting 50 of samples from the boreholes a magnetic polarity sequence was compiled the polarity pattern is not only common for many sections from the investigated area but also convergent with the global synthetic magnetostratigraphic scale the lower rotliegend early permian rocks contain a reversed polarity record while the upper rotliegend late permian early triassic sediments are characterized by mixed polarity magnetization within the buntsandstein part of that mixed megazone 14 magnetic zones were found buntsandstein sedimentation started with a normal polarity zone which may be compared with that of early griesbachian defined in several places in the world the polarity record noted in the middle buntsandstein sediments could indicate significant stratigraphic gaps or condensations near the middle buntsandstein and rot boundary the comparison of the upper buntsandstein polarity with the early middle triassic magnetostratigraphic data from other basins suggests that the majority or even all the rot sediments should be included in the anisian

paleomagnetism of the dewey lake formation late permian northwest texas end of the kiaman superchron in north america the remanent magnetization of red beds of the late permian dewey lake formation from northwest texas was investigated using thermal chemical and alternating field demagnetization after removal of a small present day viscous overprint the dewey lake shows univectorial decay of the remanence revealing a dual polarity characteristic direction of d 152 4 i 11 1 k 39 5 95 5 9 n 16 sites three polarity transitions were observed defining at least four polarity zones the observed polarity zones are roughly layer parallel and may correlate with the illawarra magnetozone at the end of the kiaman if this is so k ar age determinations of an interbedded ash layer kolker and fracasso 1985 suggest that the kiaman superchron ended before 251 4 ma the paleopole located at 51 4 n 126 2 e confirms the reliability of previously reported late permian poles from southwest united states which fall significantly off the late permian segment of the paleomagnetic euler pole pep track of gordon et al 1984 this implies that a more segmented set of small circles is required to model the north american apparent polar wander path diminishing the usefulness of the pep method

palaeomagnetism and magnetostratigraphy of uppermost permian strata southeast new mexico usa correlation of the permian triassic boundary in non marine environments summary continental red sandstone and siltstone rocks of the dewey lake quartermaster formation at maroon cliffs near carlsbad new mexico are characterized by two components of magnetization with partially overlapping laboratory unblocking temperature spectra both magnetizations display high coercivities 100 mt probably residing in haematite a north directed magnetization with steep positive inclination unblocks between 100 and 650 c isolating a predominantly northwest directed magnetization with shallow inclination of near uniform normal polarity and maximum unblocking temperatures of 680 c we collected samples from 24 palaeomagnetic sites i e individual beds from a 60 m thick section of flat lying strata disconformably overlying carbonate and evaporite rocks of the rustler formation the upper member of the rustler formation contains a late permian early changxingian marine invertebrate and conodont fauna of the sampled sites four yield only steep magnetizations interpreted to be recent overprints eight sites did not yield well grouped site means and were excluded from the final calculations the formation mean dec 337 7 inc 9 2 k 31 6 a 95 7 8 n 12 sites defines a palaeomagnetic pole located at 55 2 n 117 5 e in good agreement with other late permian north american cratonic poles correlation of the short polarity sequence of this section of dewey lake strata is unambiguous compared with the polarity stratigraphy of marine sections in asia and supported by isotopic age determinations on a widespread bentonite bed in dewey lake strata in west texas approximately 251 ma and fossil data for the underlying rustler formation the magnetostratigraphy is consistent with deposition of the dewey lake formation during the latest changxingian late permian stage

magnetostratigraphy of the lower triassic beds from chaohu china and its implications for the induan olenekian stage boundary a magnetostratigraphic study was performed on the lower 44 m of the west pingdingshan section near chaohu city anhui province china in order to provide a magnetic polarity scale for the early triassic data from 295 paleomagnetic samples are integrated with a detailed biostratigraphy and lithostratigraphy the tilt corrected mean direction from the west pingdingshan section passes the reversal and fold tests the overall mean direction after tilt correction is d 299 9 i 18 3 305 2 95 1 9 n 19 the inferred paleolatitude of the sampling sites 31 6 n 117 8 e is about 9 4 consistent with the stable south china block scb though the declinations indicate some 101 counter clockwise rotations with respect to the stable scb since the lower triassic low field anisotropy of magnetic susceptibility indicates evidence of weak strain the lower part of the yinkeng formation is dominated by reversed polarity with four normal polarity magnetozones wp2n to wp5n with evidence of some thinner 0 5 m thick normal magnetozones the continuous magnetostratigraphy from the yinkeng formation provides additional high resolution details of the polarity pattern through the later parts of the induan into the lowest olenekian the magnetostratigraphic and biostratigraphic data show that the conodont marker for the base of the olenekian first presence of neospathodus waageni is shortly prior to the base of normal magnetozone wp5n this provides a secondary marker for mapping the base of the olenekian into successions without conodonts this section provides the only well integrated study from a tethyan section across this boundary but problems remain in definitively relating this boundary into boreal sections with magnetostratigraphy

palaeoecology of the conodonts hindeodus and clarkina during the permian triassic transitional period abstract detailed investigation of the distributions of the hindeodus and clarkina neogondolella conodont faunas has been undertaken on the p t boundary strata of the meishan section zhejiang province south china in association with detailed facies analysis this reveals that hindeodus increased and clarkina sharply declined in abundance during a phase of relative sea level rise which began at the end permian bed 25 and extended into early triassic this was associated with the development of anoxic conditions this distribution does not accord with previous suggestions that hindeodus was a nearshore shallow water taxon the decline of the supposed deeper water genus clarkina is also somewhat surprising but it may relate to the inhibition of a nektobenthic genus by dysoxic anoxic bottom waters the widespread facies and geographic distribution of hindeodus suggests it was a pelagic type unaffected by anoxic bottom waters hence the hindeodus lineage provides a reliable criterion for identification of the permian triassic boundary

geochemistry of permian triassic shales in the salt range pakistan implications for provenance and tectonism at the gondwana margin abstract upper permian and lower triassic griesbachian dienerian smithian and spathian shales in the salt range pakistan were deposited at the margin of gondwana during a time of active rifting xrf and inaa major element trace element and rare earth element ree analyses of shales exhibit progressive change in chemistry from upper permian to spathian sio 2 al 2 o 3 decreases upsection and k 2 o na 2 o increases together with an increase in the chemical index of alteration cia hfs elements are enriched relative to paas at the base of the sequence but are progressively depleted upward most compatible elements are depleted throughout relative to paas sc however is relatively enriched producing a general decline in th sc upward with the exception of a single sample at the base of the sequence ree shows little variation from upper permian to smithian ranging from 159 to 146 but increases to 206 in the spathian chondrite normalised la n yb n also increases upsection from 9 0 to 12 8 eu eu values are 0 48 0 54 in the upper permian dienerian sequence but anomalies become smaller 0 53 0 65 and more similar to paas 0 66 in the smithian and spathian such values are typical of continentally derived sediments but the slight decrease upward suggests a small influx of more mafic material this and decreasing th sc contrasts with increasing la n yb n and ree which imply an increasingly felsic source these anomalies may be resolved by modeling potential sources using the ree and th sc the modeling suggests that the permian dienerian sediments could have been derived from a source of upper proterozoic crust upc phanerozoic granite pg and amphibolite amp in ratios around 60 38 2 in the smithian and spathian proportions change to 76 20 4 and 68 28 4 respectively although the increase in the amp component is small when combined with increase in upc at the expense of pg it is sufficient to approximate the changes in th sc and eu eu la n yb n ratios in the permian dienerian may be influenced by concentrations of hree enriched garnet and zircon cia indices and a cn k relations show that source weathering conditions oscillated between non steady state permian dienerian smithian and steady state griesbachian spathian indicative of episodic uplift at the gondwana margin cia ratios in the spathian are greatest in the spathian indicative of more intense weathering at that time however a cn k relations ree contents and the modeled upc pg amp mix in the spathian could also have been produced by recycling of smithian sediments

magnetostratigraphic correlations in two cores from the late triassic lunde formation beryl field northern north sea uk the magnetostratigraphy of two cores from the late triassic lunde formation of the northern north sea are compatible with the calibrated magnetostratigraphy for the norian stage determined by gallet et al 1993 from tethyan carbonates the polarities of the cores indicate a lower to upper norian age for core 9 13a 36 and lower to middle norian age for core 9 13a a45 the isolated characteristic magnetizations are due to a triassic detrital remanent magnetization which is partially overprinted with a drilling induced remanence of two origins the drilling induced remanences are associated with 1 the main coring procedure producing an overprint which is oriented downcore and 2 the subsample coring procedure which produces an overprint parallel to the subsample core axis and directed outwards from the main core axis the elimination of those specimens with a significant drilling induced remanence is important for the determination of the magnetostratigraphy in these cores

the katmai scientific drilling project surface phase investigation of an exceptional igneous system explosive volcanism is the response of magma to rapid decompression inherent complexity of volcanoes and lack of observations at depth in young systems are impediments to proper understanding of this important phenomenon the katmai scientific drilling project is an interdisciplinary surface and drilling investigation of an exceptionally large and relatively simple explosive volcanic event that occurred in alaska s aleutian range in 1912 the surface phase of the project is now largely complete and results are presented in the papers that follow

chemical and thermal constraints on models of thermal springs valley of ten thousand smokes alaska thermal 15 30 c springs issuing from 1912 ash flow tuff in the mid valley region of the valley of ten thousand smokes consist of meteoric water that may have been heated by an incompletely cooled lens of welded tuff upvalley from the springs conductive cooling of the thermal waters along the flow path is the likely cause for the difference between the observed spring temperatures and the source temperature inferred from chemical geothermometry conductive cooling alone can not easily account for the seasonal fluctuations in spring temperatures however mixing of the thermal waters with cold meteoric waters would seem a likely possibility but thermal water chemistry is constant indicating that mixing does not occur after the water leaves the zone of heating even if mixing occurred simple mixing models do not account totally for the observed temperature differences of the springs from late spring to summer the geochemical and thermal data argue for a complex hydrological and thermal regime

far travelled permian chert of the north fork terrane klamath mountains california permian chert in the north fork terrane and correlative rocks of the klamath mountains province has a remanent magnetization that is prefolding and presumably primary paleomagnetic results indicate that the chert formed at a paleolatitude of 8 6 2 5 but in which hemisphere remains uncertain this finding requires that these rocks have undergone at least 8 6 4 4 of northward transport relative to permian north america since their deposition paleontological evidence suggests that the permian limestone of the eastern klamath terrane originated thousands of kilometers distant from north america the limestone of the north fork terrane may have formed at a similar or even greater distance as suggested by its faunal affinity to the eastern klamath terrane and more westerly position available evidence indicates that convergence of the north fork and composite central metamorphic eastern klamath terranes occurred during triassic or early jurassic time and that their joining together was a middle jurassic event primary and secondary magnetizations indicate that the new composite terrane containing these and other rocks of the western paleozoic and triassic belt behaved as a single rigid block that has been latitudinally concordant with the north american craton since middle jurassic time

magnetostratigraphy and high resolution lithostratigraphy of the permian triassic boundary interval in central germany abstract a comprehensive lithostratigraphic and magnetostratigraphic study was carried out in order to provide a magnetic polarity scale for the lower buntsandstein of the classic germanic trias in its type area of central germany the 300 m thick lower buntsandstein consists of 20 small scale fining upward cycles they can be correlated over large parts of the central european basin using a combination of high resolution cyclic stratigraphy and gamma ray logging on the basis of this robust lithostratigraphic framework a very precise positioning and correlation of paleomagnetic results has been realized eight outcrops and one completely cored well were collected yielding a total of 900 paleomagnetic samples from about 80 of them a characteristic remanence was obtained the consistent correlation of lithostratigraphic units and magnetozones supports an early acquisition of the characteristic magnetizations in both the magnetite bearing gray lithologies as well as the hematite bearing red brown lithologies the inter section correlation of all investigated profiles allows the creation of a well defined composite magnetic polarity scale the uppermost zechstein comprises one normal znz and two reversed zry zrz magnetozones in the overlying lower buntsandstein are delineated three normal sn1 to sn3 and three reversed sr1 to sr3 well documented magnetozones which can be correlated with magnetic records from the boreal and tethyan realms the combination of magnetostratigraphic and biostratigraphic data suggests the base of the oolite alpha 2 within the beds of the so called graubankbereich lower buntsandstein as the position of the hindeodus parvus calibrated permian triassic boundary within the germanic trias it is situated within the lowermost part of a remarkable thick normal magnetozone sn1 which is a distinctive feature occurring in virtually all magnetic records across the permian triassic boundary

geochemistry of waters in the valley of ten thousand smokes region alaska abstract meteoric waters from cold springs and streams outside of the 1912 eruptive deposits filling the valley of ten thousand smokes vtts and in the upper parts of the two major rivers draining the 1912 deposits have similar chemical trends thermal springs issue in the mid valley area along a 300 m lateral section of ash flow tuff and range in temperature from 21 to 29 8 c in early summer and from 15 to 17 c in mid summer concentrations of major and minor chemical constituents in the thermal waters are nearly identical regardless of temperature waters in the downvalley parts of the rivers draining the 1912 deposits are mainly mixtures of cold meteoric waters and thermal waters of which the mid valley thermal spring waters are representative the weathering reactions of cold waters with the 1912 deposits appear to have stabilized and add only subordinate amounts of chemical constituents to the rivers relative to those contributed by the thermal waters isotopic data indicate that the mid valley thermal spring waters are meteoric but data is inconclusive regarding the heat source the thermal waters could be either from a shallow part of a hydrothermal system beneath the 1912 vent region or from an incompletely cooled welded tuff lens deep in the 1912 ash flow sheet of the upper river lethe area bicarbonate sulfate waters resulting from interaction of near surface waters and the cooling 1953 1968 southwest trident plug issue from thermal springs south of katmai pass and near mageik creek although the mageik creek spring waters are from a well established more deeply circulating hydrothermal system katmai caldera lake waters are a result of acid gases from vigorous drowned fumaroles dissolving in lake waters composed of snowmelt and precipitation

late permian to late triassic palaeomagnetic data from iran constraints on the migration of the iranian block through the tethyan ocean and initial destruction of pangaea summary a palaeomagnetic study of late permian to early jurassic rocks from the alborz and sanandaj sirjan zones in iran and a compilation of selected palaeopoles from the carboniferous to the present provide an updated history of the motion of the iranian block within the tethys ocean the iran assemblage part of gondwana during the palaeozoic rifted away by the end of the permian we ascertain the southernhemisphere palaeoposition of iran at that time using magnetostratigraphy and show that it was situated close to arabia near to its relative position today a northward transit of this block during the triassic is shown with an estimated expansion rate of the neotethyan ridge of 100 140 km myr 1 the northward convergence with respect to eurasia ended during the ladinian middle triassic and is marked by a collision in the northern hemisphere with the turan platform which was the southern margin of the eurasian continent at that time no north south component of shortening is evidenced north of iran afterwards an analysis of the declinations from the late permian to the present shows diverent large rotations emphasizing the important tectonic phases suvered since the triassic finally we propose palaeomagnetic reconstructions of the tethys area during the late permian and the late triassic showing that the palaeotethys ocean was narrower than previously thought and did not widen its gate to the panthalassa before the triassic period

a pure dipole analysis of the gondwana apparent polar wander path paleogeographic implications in the evolution of pangea the paleogeography of prebreakup pangea at the beginning of the atlantic spreading has been a subject of debate for the past 50 years reconciling this debate involves theoretical corrections that cast doubt on available data and paleomagnetism as an effective tool for performing paleoreconstructions this 50 year old debate focuses specifically on magnetic remanence and its ability to correctly record the inclination of the paleomagnetic field in this paper a selection of paleopoles was made to find the great circles containing the paleomagnetic pole and the respective sampling site the true dipole pole tdp was then calculated by intersecting these great circles effectively avoiding nondipolar contributions and inclination shallowing in an innovative method the great circle distance between each of these tdps and the paleomagnetic means show the accuracy of paleomagnetic determinations in the context of a dominantly geocentric axial and dipolar geomagnetic field the tdps calculated allowed a bootstrap analysis to be performed to further consider the flattening factor that should be applied to the sedimentary derived paleopoles it is argued that the application of a single theoretical correction factor for clastic sedimentary derived records could lead to a bias in the paleolatitude calculation and therefore to incorrect paleogeographic reconstructions the unbiased apwp makes it necessary to slide laurentia to the west in relation to gondwana in a b type pangea during the upper carboniferous later evolving during the early permian to reach the final a type pangea configuration of the upper permian 2017 american geophysical union all rights reserved

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

paleomagnetic constraints on the permian triassic boundary in terrestrial strata of the karoo supergroup south africa implications for causes of the end permian extinction event the closure of the palaeozoic witnessed the greatest biotic crisis in earth history surprisingly little is known about the effects and timing of the terrestrial counterpart of the well described end permian mass extinction from known marine successions worldwide in the present study reliable paleomagnetic results were obtained from a pt boundary section in the terrestrial karoo basin of south africa permo triassic aged mudstones from a locality in the eastern cape province yielded two magnetic chrons reverse followed by normal with the boundary possibly close to the reversal this extends to results from a previous study thereby jointly identifying a r n r polarity pattern for this boundary interval the ptb interval is constrained below the red mudstones of the beaufort group at the present locality and within reverse magnetised green mudstone implying a diachronic relation between the marine and terrestrial end permian mass extinction events

new constraints on the upper permian and lower triassic geomagnetic polarity timescale from the abadeh section central iran we present the magnetostratigraphy of the abadeh section central iran thermal demagnetization shows two magnetic components one at low unblocking temperatures which corresponds to a present day field direction and another at high temperatures this second component which contains both polarities is interpreted as a primary magnetization acquired during sediment deposition at a paleolatitude of about 7 7 s a sequence of 14 magnetic polarity zones is obtained in the intervals during the upper dzhulfian lower changhsingian upper permian and during the griesbachian lower triassic combining data from south china canada pakistan and iran we propose a composite but still uncomplete upper permian and lower triassic geomagnetic polarity timescale

illawarra reversal the fingerprint of a superplume that triggered pangean breakup and the end guadalupian permian mass extinction abstract the permian magnetostratigraphic record demonstrates that a remarkable change in geomagnetism occurred in the late guadalupian middle permian ca 265 ma from the long term stable kiaman reverse superchron throughout the late carboniferous and early middle permian to the permian triassic mixed superchron with frequent polarity changes in the late permian and triassic this unique episode called the illawarra reversal probably reflects a significant change in the geodynamo in the outer core of the planet after a 50 million years of stable geomagnetism the illawarra reversal was likely led by the appearance of a thermal instability at the 2900 km deep core mantle boundary in connection with mantle superplume activity the illawarra reversal and the guadalupian lopingian boundary event record the significant transition processes from the paleozoic to mesozoic modern world one of the major global environmental changes in the phanerozoic occurred almost simultaneously in the latest guadalupian as recorded in 1 mass extinction 2 ocean redox change 3 sharp isotopic excursions c and sr 4 sea level drop and 5 plume related volcanism in addition to the claimed possible links between the above listed environmental changes and mantle superplume activity i propose here an extra explanation that a change in the core s geodynamo may have played an important role in determining the course of the earth s surface climate and biotic extinction evolution when a superplume is launched from the core mantle boundary the resultant thermal instability makes the geodynamo s dipole of the outer core unstable and lowers the geomagnetic intensity being modulated by the geo and heliomagnetism the galactic cosmic ray flux into the earth s atmosphere changes with time the more cosmic rays penetrate through the atmosphere the more clouds develop to increase the albedo thus enhancing cooling of the earth s surface the illawarra reversal the kamura cooling event and other unique geologic phenomena in the late guadalupian are all concordantly explained as consequences of the superplume activity that initially triggered the breakup of pangea the secular change in cosmic radiation may explain not only the extinction related global climatic changes in the end guadalupian but also the long term global warming cooling trend in earth s history in terms of cloud coverage over the planet

permian triassic boundary magnetostratigraphy from the southern alps italy palaeomagnetic investigations of permian triassic boundary sections in the dolomites provided a magnetostratigraphy for the uppermost part of the permian bellerophon formation to the lower triassic werfen formation magnetite was the dominant magnetic component in most of the samples while the presence of hematite was characteristic for the tesero horizon which is regarded as the immediate permian triassic boundary layer the palaeomagnetic results are consistent with earlier studies of permian and triassic sediments and volcanites in the southern alps the mean characteristic remanence directions indicate deposition and remanence acquisition at a shallow northerly palaeolatitude and a counterclockwise rotation a zone of reversed polarity occurs at the top of the permian sequence and a polarity change from reverse to normal polarity shortly above the base of the werfen formation the onset of a tectonically controlled sedimentary cycle marks the beginning of the basal triassic normal polarity zone which corresponds to most of griesbachian time the record of geomagnetic polarity across the permian triassic boundary confirms the apparent continuity as found by sedimentologic biostratigraphic investigations which emphasise a gradual lithic transition with no evidence for a time gap at the boundary

permian and triassic paleomagnetism of the southwestern tien shan timing and mode of tectonic rotations abstract volcanic rocks of the lower permian luchob formation and sedimentary rocks of the presumed upper permian hanaka and middle upper triassic madighen formations were studied in three localities in the southwestern tien shan primary magnetizations were isolated in lower permian and triassic rocks whereas the remanence of reversed polarity in the hanaka formation acquired during the kiaman superchron may be slightly younger than the rock age inclinations in all three formations agree with the european reference data but declinations are deflected westward we argue that these deflections are due to the late permian late triassic but pre rhaetian counterclockwise rotations and partly due to late cenozoic counterclockwise rotations inclinations in permian and lower triassic rocks throughout the tien shan foldbelt the junggar basin and north tarim are also in agreement with the reference data implying that within the error limits this part of central asia was already welded together with kazakhstan and the european plate in the permian westward deflected declinations throughout this region are accounted for not by movements of large blocks such as the tarim but by domino fashion late permian triassic rotations by strike slip

paleomagnetic results from the upper permian of the eastern qiangtang terrane of tibet and their tectonic implications abstract paleomagnetic samples were collected from red intercalations within the upper permian tuoba formation from the eastern qiangtang terrane of tibet progressive thermal demagnetization has revealed a prefolding possibly primary characteristic remanent magnetization chrm which yields a tilt corrected mean direction ofd i 25 2 6 7 95 8 6 the equatorial paleolatitude for the qiangtang terrane indicated by this result and the similarity of late permian fauna and flora shared by the qiangtang terrane and south china block scb suggest that the two terranes were in close proximity during the late permian a late permian paleogeographic reconstruction involving the major terranes of the present day east asia is constructed in which the songpan garze sea is surrounded by laurasia the north china block ncb the scb and the qiangtang terrane the permian development of the songpan garze sea appears to be related to the rifting of the qiangtang terrane off the scb its triassic evolution may resemble that of the solomon sea today in the southwestern pacific

streamflow anomaly patterns in the u s a and southern canada 1951 1970 abstract the map patterns of streamflow conditions in the u s a and southern canada are examined by means of a principal components analysis of the monthly flow records of 102 streams the analysis reveals the basic anomaly patterns of streamflow and also describes the variation of these patterns through time the basic anomaly patterns are of large spatial scale and vary slowly through time reflecting the temporal and spatial scale of the controlling climatic anomalies an extension of the analysis allows the gaging stations to be assigned to homogeneous hydrologic regions

a palaeomagnetic reconnaissance of northeastern baluchistan pakistan a total of 560 samples from three areas in northeastern baluchistan the southern sulaiman range the central loralai range and the northern kirthar range were analyzed using thermal demagnetization techniques thirteen formations of late palaeozoic to early tertiary age were studied palaeomagnetically inclinations of the obtained results show a general affinity with the indian apparent polar wander path deviating declinations from the loralai range indicate a clockwise rotation over 50 with respect to the indian shield secondary magnetization components probably of late palaeocene to early eocene age were consistently present in the samples from the kirthar range and the sulaiman range but were not observed in samples from the loralai range acquisition of these components is attributed to crustal upwarping during the palaeocene which is tentatively related to initial collision of continental indo pakistan with an island arc off south central asia the baluchistan data support recent palaeomagnetic results from the indus tsangpo suture zone in ladakh nw himalaya which indicate that such an initial collision took place at very low northern palaeolatitudes

syntectonic magnetization of the mid palaeozoic sierra grande formation further constraints on the tectonic evolution of patagonia a palaeomagnetic study was carried out in the silurian devonian clastic sedimentary rocks of the sierra grande formation exposed in northeastern patagonia 41 6 s 65 3 w thirteen sites n 88 were located on opposite limbs of a syncline anticline structure stepwise thermal demagnetization permitted the identification of a very stable magnetic component of reversed polarity carried by hematite stepwise performance of the fold test yielded negative results both in situ and after 100 bedding correction but positive after partial unfolding 19 this indicates a syntectonic origin for the isolated magnetization a pole position was computed for the partially 19 corrected remanence sg3 77 3 s 310 7 e p 7 7 m 6 6 n 13 its position is coincident with late early to late permian palaeomagnetic poles from south america suggesting that age for the previously undated folding of the sierra grande sequence and therefore for the main tectonic event that affected the northern boundary of patagonia palaeozoic palaeomagnetic poles from patagonia obtained to date agree with those from gondwana of devonian or younger age suggesting that patagonia did not undergo important displacements relative to south america since those times this and the permian age of deformation determined in this study invalidates tectonic models involving collision of a far travelled patagonia with gondwana in the mid or late palaeozoic

correlation and comparison of seawater δ34ssulfate records at the permian triassic transition abstract correlation of carbonate associated sulfate cas 34 s analysed permian triassic p tr sections via conodont biostratigraphy and sequence stratigraphy shows distinct phases in the oceanic 34 s sulfate evolution during the period 1 million years m y either side of the p tr boundary a 34 s sulfate rise in the changhsingian prior to the end permian mass extinction is followed by a period of about 350 000 years of erratic and substantial 34 s sulfate movements range 1 to 28 the mass extinction occurring in the middle of this period the sharp swings in this phase indicate severe changes in the oceanic sulfur geochemistry and perhaps stages of ocean inhomogeneity low 34 s sulfate values coincide with the mass extinction horizon suggesting the extinction is related to an input of relatively 32 s enriched sulfur into the oceanic sulfate reservoir the source of this sulfur most likely being h 2 s from euxinic waters after the erratic 34 s sulfate phase there is a stabilisation of 34 s sulfate values 17 until the later griesbachian however there is a possibility of discrepant panthalassan and tethyan data sets during the early to mid griesbachian but this requires further work for confirmation 34 s sulfate values are erratic in the late griesbachian to early dienerian suggesting further perturbation of the sulfur cycle the poorly age constrained smithian record shows a wide range of 34 s sulfate values probably indicating swings during that time also the 34 s sulfate movements from the changhsingian to smithian indicate the permian triassic transition is a time of intense changes in the sulfur fluxes to and from the oceans and perhaps stages of ocean inhomogeneity

the permian triassic boundary in the central european basin magnetostratigraphic constraints some stratigraphic interpretations concerning correlation of the permian triasssic transition beds from the central european boreal and tethyan basins are inconsistent with the existing magnetostratigraphic data in addition the suggestion that the permian triassic boundary is located in the lower part of the calvorde formation of the central european basin cannot be supported by magnetostratigraphic data results of magnetostratigraphic correlation show that in the polish part of the central european basin the permian triassic boundary is close to the boundary between the uppermost zechstein and the lower buntsandstein it is located within the reversed magnetozone pzr1 identified in the upper part of the rewal formation in the german part of the central european basin the permian triassic boundary can be located within the reversed magnetozone zrz that covers most of the brockelschiefer a higher stratigraphic location of this boundatry i e inside the lowermost buntsandstein requires a reversed polarity record to be found within the basal triassic normal polarity zone

permo triassic palaeomagnetism in the emei mountain region southwest china summary a palaeomagnetic study has been made of samples collected from permo triassic type sections in the emei mountain region of southwest china no results were obtained from the lower permian qixia formation limestones or the lower upper permian maokou formation limestones the upper permian longtanian emeishan basalt formation shows excellent stability to both alternating field and thermal demagnetization results from 24 flows 125 samples are all of normal polarity have a positive fold test cretaceous or tertiary folding and give a pole position at 54 5 n 254 3 e with dp 1 8 dm 3 5 the basalts were thus presumably extruded after the end of the kiaman reversed superchron the overlying upper permian xuanwei formation of red mudstones and sandstones changxingian in age also shows a positive fold test from n 12 samples after thermal treatment and has a positive reversals test at level c the pole position is close to that of the emeishan basalt and lies at 57 0 n 260 9 e with dp 4 3 dm 8 5 the lower triassic griesbachian to mid nammalian feixianguan formation is primarily a red sandstone sequence at this locality thermal treatment of the collection of 114 samples reveals two main components the a component is always observed below 600 c and probably represents a drm either from magnetite or specular haematite the 5 component resides in haematite and is often of the opposite polarity superimposed on the a component it is revealed only above 600 c and is a crm acquired during diagenesis although normal components dominate both the a and b components also have reverse polarities the normal a and normal b components are statistically indistinguishable and the normal b component shows a positive fold test the reverse b component is however not quite antiparallel to the normal b component and may therefore be a second crm acquired at a slightly different time to the normal b component all these components are thought to have arisen during deposition and diagenesis over a few million years as has been observed in other studies of redbeds the dominance of normal components is consistent with the observation that the earlier part of the griesbachian stage of the lower triassic is mainly a normal polarity chron the overall mean of the n 101 both normal and reverse a and 5 components is considered to be the best estimate of the palaeofield in the early triassic giving a pole position at 56 2 n 227 6 e with dp 1 t dm 3 4 this pole lies 15 2 away from the emeishan basalt pole suggesting a polar shift occurred near the permo triassic boundary a review of late permian and early triassic poles from the south china block shows a similar polar shift

magnetostratigraphic correlations of permian triassic marine to terrestrial sections from china abstract we have studied three permian triassic pt localities from china as part of a combined magnetostratigraphic 40ar 39ar and u pb radioisotopic and biostratigraphic study aimed at resolving the temporal relations between terrestrial and marine records across the permo triassic boundary as well as the rate of the biotic recovery in the early triassic the studied sections from shangsi sichuan province langdai guihzou province and the junggar basin xinjiang province span marine paralic and terrestrial pt environments respectively each of these sections was logged in detail in order to place geochronologic paleomagnetic geochemical conodont and palynologic samples within a common stratigraphic context here we present rock magnetic paleomagnetic and magnetostratigraphic results from the three localities at shangsi northern sichuan province we sampled three sections spanning permo triassic marine carbonates magnetostratigraphic results from the three sections indicate that the composite section contains at least eight polarity chrons and that the pt boundary occurs within a normal polarity chron a short distance above the mass extinction level and a reversed to normal r n polarity reversal furthermore the onset of the illawarra mixed interval lies below the sampled section indicating that the uppermost permian changhsingian and at least part of the wuchiapingian stages postdate the end of the kiaman permo carboniferous reversed superchron at langdai guizhou province we studied magnetostratigraphy of pt paralic mudstone and carbonate sediments in two sections the composite section spans an r n polarity sequence section mean directions pass a fold test at the 95 confidence level and the section mean poles are close to the mean pt pole for the south china block based on biostratigraphic constraints the r n transition recorded at langdai is consistent with that at shangsi and demonstrates that the pt boundary occurred within a normal polarity chron a short distance above the mass extinction level in the southern junggar basin xinjiang province in northwest china we determined the magnetostratigraphy of three sections of a terrestrial sequence normal and reversed polarity directions are roughly antipodal and magnetostratigraphies from the three sections are highly consistent combined bio and magneto stratigraphy used to correlate this sequence to other pt sequences suggests that the previously proposed biostratigraphic pt boundary in the junggar sections was most likely misplaced by earlier workers suggesting that further work is necessary to confidently place the pt boundary there

fossil and active fumaroles in the 1912 eruptive deposits valley of ten thousand smokes alaska fumaroles in the ash flow sheet emplaced during the 1912 eruption of novarupta were intensely active throughout the valley of ten thousand smokes vtts when first studied in 1917 fumarole temperatures recorded in 1919 were as hot as 645 c influx of surface waters into the hot ash flow sheet provided the fluid flow to sustain the fumaroles but also enhanced cooling so that by the mid 1930 s vigorous activity survived only in the vent region configuration and distribution of high temperature fissure fumaroles tens of meters long that are prevalent in the middle and upper vtts were controlled largely by sintering and degree of welding which in turn controlled fracturing and permeability of the ash flow tuff one fracture type developed parallel to the enclosing valley walls during compaction of the ash flow sheet another type extends across the vtts nearly perpendicular to the flow direction a third type of randomly oriented fractures developed as cooling contraction cracks during vapor phase devitrification in distal parts of the ash flow sheet where the tuff is nonwelded prominent fumaroles have irregular funnel shaped morphologies fumarole distribution in the nonwelded part of the ash flow sheet is concentrated above pre emplacement river channels the hottest longest lived fumaroles occurred in the upper vtts near the 1912 vent where the ash flow sheet is thicker more indurated and on average more mafic richer in dacite and andesite in contrast to the thinner nonwelded rhyolitic tuff in the distal part of the sheet fumarolic activity was less intense in the distal part of the tuff because of lower emplacement temperatures more diffuse fumarole conduits in the nonwelded tuff and the thinness of the ash flow sheet chemical leaching of ash flow tuff by hot rising fluids took place adjacent to fumarolic conduits in deep parts of the fumaroles deposition of incrustation minerals the components of which were carried upward by fumarolic gases took place in the upper part of the ejecta mostly in the fallout layers the permeability difference between the ash flow tuff and the overlying coarse dacite fallout was a critical factor in promoting the abrupt gradients in temperature pressure and fo2 that resulted in deposition of minerals from the fumarolic gases the permeability difference between nonwelded ash flow tuff and overlying fine grained fall layers in the lower vtts is less pronounced the total mass of fumarolically deposited minerals appears large at first glance owing to the conspicuous coloration by fe minerals the mass is appreciably less than is apparent however because most incrustations are composed largely of ejecta coated or cemented by fine grained fumarolic minerals a large mass of unstable incrustation minerals mainly chlorides and sulfates reported during the 1917 1919 studies have since been removed by dissolution and weathering in the vent region argillic alteration that followed high temperature degassing is localized along arcuate subsidence fractures in fallback ejecta at widely scattered residual orifices fumarolic gases presently are near neutral steam and temperatures are as hot as 90 c

the valley of ten thousand smokes katmai klaska a unique geochemistry laboratory abstract during june 6 8 1912 a new vent novarupta near mt katmai in the aleutian range of alaska released the largest volcanic eruption of this century and the largest rhyolitic eruption in nearly twenty centuries spectacular fumaroles developed in the ash flow sheet prompting robert f griggs who discovered the steaming valley in 1916 to name it the valley of ten thousand smokes vtts the katmai scientific drilling project was developed to advance understanding of the physical and chemical processes involved with explosive volcanism through an interdisciplinary investigation of the novarupta vent and fissure fumaroles present in the ash flow sheet novarupta vent represents a unique target for subsurface geophysical and coring studies of structures and lithologies produced by explosive volcanism panel on volcanic studies at katmai national academy of sciences 1989 scientific expeditions sponsored by the department of energy the national science foundation and the u s geological survey were conducted during the summers of 1989 and 1990 most of the surface studies are now complete and drilling is planned for 1994 contingent on successful completion of the national environmental policy act process one of the main objectives of this ambitious study is to determine the source mechanisms and thermal and chemical conditions of the fumarolic transport of elements that occurred following ash flow emplacement as part of the surface investigation prior to drilling a detailed geochemical study has been initiated involving the mass flux of nearly fifty major minor and trace elements using samples from fumarolic deposits located in distal rhyolitic and proximal dacitic and andesitic portions of the ash flow sheet significant enrichments are observed in s br cl f zn pb cu sn cr ni as sb and au in various portions of the fossil fumaroles these enrichments correlate well with those determined in active high temperature fumarolic sublimates and indicate that most of these elements were transported to the surface early in the vapor phase

magnetostratigraphy of the permo triassic boundary section at shangsi guangyuan sichuan province china continous marine sedimentation characterizes many late permian to early triassic sections on the yangtze terrane in south china the permo triassic p tr boundary section at shangsi sichuan province consists of limestones intercalated with clays and mudstones which belong to the wuchiapingian and changxingian upper permian and the griesbachian and dienerian lower triassic stages the p tr boundary is formed by a clay horizon with an unusually high iridium concentration the intensity of natural remanent magnetization is very low with a mean of 0 15 ma m 1 about 40 of the samples contain secondary or unstable magnetization components only whereas the remaining samples carry a characteristic remanent magnetization thought to reflect the polarity of the geomagnetic field during deposition with sufficient accuracy normal and reversed polarity of the characteristic magnetization constitute a pattern of at least six polarity zones the p tr boundary being situated very close to the transition from a reversed to a normal polarity zone the shangsi polarity sequence represents part of the illawarra interval of mixed polarity the exact beginning of which has still to be determined

authigenic heavy minerals a clue to unravel supergene and hypogene alteration of marine and continental sediments of triassic to cretaceous age se germany abstract siliciclastic continental marine sediments of triassic through jurassic age resting unconformably on the crystalline rocks of the central european variscides and marine deltaic sediments of cretaceous age deposited in a narrow embankment are well exposed in the wackersdorf area se germany these sediments were investigated for their variegated spectrum of authigenic heavy minerals hm and heavy mineral hm aggregates the majority of which belongs to the semi opaque group of minerals using petrographic and ore microscopy supplemented by sem edx and by empa these hms originated from supergene weathering diagenesis and hypogene alteration hydrothermal processes related to faults and unconformities the physical and chemical conditions during which these authigenic minerals developed are discussed by means of eh ph diagrams under different temperature conditions ilmenite pseudorutile anatase series may be used as a measure for the intensity of supergene alteration under rising oxygen fugacity pseudorutile and anatase also formed during hypogene alteration and developed different crystal morphologies compared with their supergene counterparts found in the above series the authigenic hm fluorite barite niccolite acanthite silver bravoite ni marcasite pyrite sphalerite galena chalcopyrite chalcocite and rhabdophane ce were produced by hypogene hydrothermal processes the hypogene mineralization in the mesozoic foreland sediments belongs to two types 1 epi mesothermal ree f mineralization controlled by the structural reactivation along a deep seated lineamentary fault zone and 2 epithermal ni cu zn as s mineralization related to the geohydraulic plane of the late variscan unconformity permo triassic peneplain

multidisciplinary high resolution correlation of the permian triassic boundary abstract biostratigraphic correlation of the ten most important permian triassic boundary sections throughout tethys enables establishment of four conodont and ammonoid subdivisions within a stratigraphic interval one to a few metres thick representing less than 1 ma in ascending order they are conodonts clarkina changxingensis c deflecta zone hindeodus typicalis interval isarcicella parva zone and i isarcica zone and ammonoids pseudotirolites pleuronodoceras zone lower otoceras zone upper otoceras zone and ophiceras zone most of them can be traced to north america and the arctic region carbon isotope investigations of 24 sections along tethys and in greenland and spitzbergen confirm the consistency of 13c negative excursions at the permian triassic boundary together with an inconsistent ir anomaly eight sections show that in most cases there is a succession of ir anomaly denoting the end permian catastrophic environment 13c excursion biomass loss extinction p t boundary origination of newcomers potentially capable of intercontinental correlation within that short time interval there is an intercontinental sequence boundary at the top of the permian and a transgressive surface at the p t boundary followed shortly by a maximum flooding surface an intercontinental anoxia event accompanied the transgression three delineations of the mass extinction phases and three population explosions have been recognized and can be more or less correlated in south china and the southern alps radiometric dating of the volcanogenic boundary clays of meishan shangsi and the main stage siberian tunguss traps give an almost identical age of 250 ma thus implying a synchronous interregional volcanic event there are a few palaeomagnetic transforms within the ptb strata thus multidisciplinary research of the p t boundary strata allows subdivision of this short interval into more than ten intercontinentally correlatable parts each subdivision averages less than 100 ka in duration this may be the highest resolution obtained so far in pre cretaceous rocks high frequency milankovitch type cyclic deposits within the p t boundary beds enable correlation of even higher resolution in the lower yangtze area this high resolution is made possible because the p t transition is a time of saltation and catastrophy in geological history causality of the aggregation of events merits further investigation

a reconnaissance 40ar39ar geochronologic study of ore bearing and related rocks siberian russia abstract 40 ar 39 ar age spectra of biotite from a mineralized vein in the ore bearing noril sk i intrusion and from picritic like gabbrodolerite from the weakly mineralized lower talnakh intrusion show that these bodies were emplaced at 249 2 ma which is not significantly different from the age of the permian triassic boundary the ore bearing intrusions postdate the lower third of the flood basalt sequence in the noril sk area and on the basis of geochemistry can best be correlated with lavas slightly younger than those which they cut thus flood basalt was erupted at the time of the permian triassic mass extinction event although its role in this event is as yet ill defined additional new 40 ar 39 ar age data for a group of intrusive and extrusive rocks on the western margin of the siberian craton indicate that mafic magmatism extended over a period of several tens of million years whereas paleomagnetic data suggest that the bulk of the siberian flood basalt sequence near noril sk has been erupted in only a million years or so 40 ar 39 ar ages of plagioclase from early flood basalt flows are about 2 younger than those obtained for biotite from the crosscutting noril sk i intrusion probably because of slight alteration and argon loss from the plagioclase

magnetostratigraphy of the lower triassic volcanics from deep drill sg6 in western siberia evidence for long lasting permo triassic volcanic activity summary the deep drill hole sg6 in western siberia 66 n 78 5 e penetrated 1 1 km of lower triassic basalts which are possibly an extension of the central siberian permo triassic flood basalt province about 300 samples of these basalts were progressively demagnetized and measured principal component analysis often shows multiple magnetizations carried by haematite and magnetite the corrected mean inclinations are 77 and 77 for the haematite component a magnetostratigraphic scale was derived and showed a n r n r n succession this is quite diverent from the noril sk and taimyr typical polarity scale r n the basalts found in the sg6 deep drill hole are slightly younger than those of central siberia and taimyr they correspond to middle upper induan age whereas the noril sk and taimyr sections correspond to an uppermost permian and lower induan age altogether they indicate that after a high output rate of volcanic material near the permo triassic boundary this activity slowed down drastically on the siberian platform and taimyr but persisted for several million years in western siberia

further palaeomagnetic data from chitral eastern hindukush evidence for an early india asia contact the eastern hindukush forms part of an elongate belt central domain collage of cimmerian microcontinents that encircles the northern part of the indian subcontinent a gondwanan origin is commonly assumed for this belt but a laurasian origin for the chitral region has been argued on palaeontological talent and mawson 1979 and palaeomagnetic klootwijk and conaghan 1979 grounds the laurasian view was based on a pilot study we undertook of upper devonian pisolitic ironstones from a thrust sheet at kur gh spur in chitral preliminary results showed a characteristic magnetization component d 318 i 6 5 n 7 block samples k 14 95 16 5 indicating an equatorial palaeoposition this component was thought to be of primary origin and was interpreted in terms of a late devonian laurasian affinity of the kur gh spur rocks this controversial conclusion has been tested in the present more comprehensive study of the thrust pile of sedimentary rocks in the resh n kur gh b ni region of chitral and the primary origin of the characteristic magnetization component refuted thermal demagnetization of 333 block samples from middle to upper devonian variegated sediments permian quartz flysch permo triassic carbonates and mid cretaceous redbeds showed two interpretable components a softer component of recent origin a and a harder characteristic component b of both normal and reverse polarity whose mean direction d 314 1 i 6 0 n 4 thrust sheets k 198 2 95 6 5 is comparable to the characteristic component observed in our preliminary study however the universal presence of this component throughout the thrust pile proves its overprint origin which we attribute to initial india asia contact palaeomagnetic information pertinent to the controversy of a laurasian versus a gondwanan origin of the chitral region has not been obtained in this further study because primary magnetizations could not be identified beyond doubt hence we retract herewith our original conclusion of a late devonian laurasian affinity of the chitral region on the basis of the palaeomagnetic evidence the secondary component b comprises a suite of secondary magnetizations acquired at equatorial to low northern palaeolatitudes and is attributed to initial contact between greater india and southern asia component b has been observed previously in the himalayan tibetan region both north and south of the indus tsangpo suture zone identification is herein extended to the hindukush region north of the northern kohistan or shyok suture zone which is a western continuation of the indus tsangpo suture comparison of this suite of collision at tributed equatorial palaeolatitude data from the india asia convergence zone with new palaeolatitude constraints from the ninetyeast ridge on the northward movement of the indian plate constrained additionally by a recent minimal estimate of the palaeogeographic northern extent of greater india indicates that initial contact between northwestern greater india and southern asia was established at or before the cretaceous tertiary boundary the overprint origin of component b at about this time is further supported by observations by zeitler 1985 on rocks from the sampled area in chitral of partially reset zircon fission track ages around 68 55 ma the nw se declination axis of component b indicates a 60 70 counterclockwise rotation of the sampled thrust pile with respect to eurasia and a counterclockwise rotation between 10 and 30 with respect to india some of the recent field components a show a comparable rotation and indicate that the tectonic activity that led to the formation of the hindukush pamir karakorum syntaxial zone has continued into recent times

paleomagnetic results from saudi arabia and the permo triassic pangea configuration the pangea configuration for the interval of late carboniferous to early jurassic is still debated was it similar to the well known wegenerian pangea or did gondwanaland move with respect to laurussia along a major right lateral lineament of several thousand kilometres during the triassic as suggested by irving we try here to answer this important question with the paleomagnetic study of well dated permo triassic sediments from a borehole in saudi arabia sediments of the same age have also been sampled at the surface but proved to be remagnetized probably by a strong desert alteration the paleomagnetic study of the bore hole core yielded a high temperature component magnetization thought to be of primary origin carried either by magnetite late permian limestones or hematite early triassic red shales with antipodal normal and reversed inclinations its co latitude and pole directions compare well with those from a selection of south american african madagascar and moroccan poles a new reliable pole west gondwana with a mean age of 244 11 m y is derived 53 4 n 259 4 e a95 3 6 in west african coordinates and its comparison with the laurussian poles of same age window strongly suggests a pangea in which the northern part of south america was facing the east of north america pangea b of irving at the permo triassic boundary a large right lateral strike slip movement of some 3500 km during the triassic is thus required to reconstruct pangea to its jurassic pre atlantic opening position

a geomagnetic polarity timescale for the permian calibrated to stage boundaries the reverse polarity kiaman superchron has strong evidence for at least three or prob ably four normal magnetochrons during the early permian normal magnetochrons are during the early asselian base ci1r 1n at 297 94 0 33 ma late artinskian ci2n at 281 24 2 3 ma mid kungurian ci3n at 275 86 2 0 ma and roadian ci3r an at 269 54 1 6 ma the mixed polarity illawarra superchron begins in the early wordian at 266 66 0 76 ma the wordian capitanian interval is biased to normal polarity but the basal wuchiapingian begins the beginning of a significant reverse polarity magnetochron lp0r with an overlying mixed polarity interval through the later lopingian no significant magnetostratigraphic data gaps exist in the permian geomagnetic polarity record the early cisuralian magnetochrons are calibrated to a succession of fusulinid zones the later cisuralian and guadalupian to a conodont and fusulinid biostratigraphy and lopingian magnetochrons to conodont zonations age calibration of the magnetochrons is obtained through a bayesian approach using 35 radiometric dates and 95 confidence intervals on the ages and chron durations are obtained the dating control points are most numerous in the gzhelian asselian wordian and changhsingian intervals this significant advance should provide a framework for better correlation and dating of the marine and non marine permian

permian triassic magnetostratigraphy new results from south china abstract continuous marine sediments of permian to triassic age are widely distributed over large areas in southern china they offer the potential for developing magnetostratigraphic columns to investigate the polarity status of the palaeomagnetic field three carbonate sections on the yangtze platform which represent mainly the upper permian but also parts of the lower triassic and possibly parts of the uppermost lower permian contain a long term main r n r n r polarity succession throughout the permian this signal is hidden under strong overprint magnetizations of variable origin and can be mostly obtained only from directional trends of the natural remanent magnetization during demagnetization rather than from clear stable end point directions the new chinese polarity sequences are in accord with magnetostratigraphic records from the former ussr and pakistan depending on stratigraphic assignment of the lithological formations studied either they include the boundary between the lower and upper permian and give evidence that the kiaman reversed polarity superchron had ended before the upper permian or the formations all belong stratigraphically to the upper permian with the oldest reversed interval to be correlated with the reversed zone in the midian stage of the palaeontologically well dated nammal section in pakistan this zone is preceded by at least one normal polarity zone at nammal so that the end of the kiaman superchron would not be observed in the new chinese sections

the middle triassic magnetostratigraphy from the peri tethys basin in poland abstract the paper presents the first complete magnetic polarity scale obtained for the middle triassic of the northern peri tethys area the roetian and muschelkalk deposits of southern poland upper silesia the holy cross mountains were studied paleomagnetically the obtained paleopole a 52 n 143 e fits well to the middle triassic ca 240 ma segment of the stable european apwp a set of various quality characteristic directions isolated in 106 samples was used for construction of the composite polarity scale this peritethyan scale has been tied with conodont zonation and referred to the scale erected earlier in the tethyan realm comparison of both scales indicates that the whole roetian succession in the southern polish basin should be correlated with the latest olenekian the normal marine sedimentation ceased in the polish basin as early as in the late fassanian time the obtained magnetostratigraphic scale combined with the sequence stratigraphic framework enables a reliable chronological correlation of the late olenekian ladinian succession over the entire peri tethys basin

late permian to early triassic magnetostratigraphy a late permian to early triassic magnetostratigraphic reference section is presented the lower triassic part is based on results from marine limestone sections in south china published earlier 1 2 reliable new permian data are added here which have been collected in the nammal gorge salt range northwest pakistan where marine sediments have been deposited quasi continuously with occasional minor hiatuses during the late palaeozoic to early mesozoic about 50 of the permian samples from the nammal section contain hidden beneath a strong recent or tertiary overprint a characteristic remanent magnetization chrm which is very likely of permian age this component which was imprinted on the southern hemisphere has normal as well as reversed polarity with a normal mean direction decl 289 3 incl 50 3 95 4 3 n 113 which is in close agreement with the palaeofield direction expected for a site belonging to the indian plate as part of gondwanaland during the permian in the lower upper permian several normal polarity zones are recognized this contradicts the current assumption that rocks of this age belong to the long reversely polarized kiaman hyperzone the kiaman interval must end and the illawarra hyperzone of mixed polarity must begin in or prior to the lowermost upper permian the permian triassic boundary at nammal as well as in the chinese sections is situated very close to a transition from a reversed to a normal polarity zone the upper permian at nammal together with the lower triassic south china sections is estimated to cover about 20 ma nearly 30 polarity changes are observed which result in an average reversal frequency very similar to that observed during the early tertiary the reversal rate after the end of the long lasting reversed kiaman hyperchron apparently increases in a manner similar to that after the end of the cretaceous long normal superchron only a few polarity zones are found in the lower upper permian while progressively more frequent reversals follow in the lower triassic

new time constraints on lithospheric scale oroclinal bending of the ibero armorican arc a palaeomagnetic study of earliest permian rocks from iberia abstract the palaeozoic variscan orogeny was a large scale collisional event that involved amalgamation of multiple continents and microcontinents previous palaeomagnetic and structural analyses of the western variscan orogen notably the ibero armorican arc suggest that this region underwent oroclinal bending of an originally near linear orogen during the latest stages of variscan deformation in the late palaeozoic these analyses necessitate a two stage tectonic history with east west compression forming a linear belt in the carboniferous followed by a change in regional compression directions resulting in crustal block rotation and formation of the present day arc this study presents new palaeomagnetic analyses of early permian samples from the sotres and cabranes formations 41 3 n 222 5 w 95 13 1 in the northern inner limb and the viar basin 51 8 n 199 2 w 95 6 7 in the southern outer limb of the arc both locations yield expected early permian palaeomagnetic pole positions for stable iberia implying that measured magnetizations have undergone no significant vertical axis rotation since acquisition and thus were acquired subsequent to oroclinal bending this new result places a time constraint of about 10 ma for oroclinal bending of the ibero armorican arc which agrees well with recent geodynamical models that relate oroclinal bending to lithospheric delamination in this region

abrupt and gradual extinction among late permian land vertebrates in the karoo basin south africa the karoo basin of south africa exposes a succession of upper permian to lower triassic terrestrial strata containing abundant terrestrial vertebrate fossils paleomagnetic magnetostratigraphic and carbon isotope data allow sections to be correlated across the basin with this stratigraphy the vertebrate fossil data show a gradual extinction in the upper permian punctuated by an enhanced extinction pulse at the permian triassic boundary interval particularly among the dicynodont therapsids coinciding with negative carbon isotope anomalies

end of the kiaman superchron in the permian of sw england magnetostratigraphy of the aylesbeare mudstone and exeter groups the chronology of permian strata in sw england is fragmentary and largely based on radiometric dating of associated volcanic units magnetostratigraphy from the c 2 km of sediments in the exeter and aylesbeare mudstone groups was undertaken to define a detailed chronology using the end of the kiaman superchron and the overlying reverse and normal polarity in the middle and upper permian as age constraints the palaeomagnetic directions are consistent with other european permian palaeopoles with data passing fold and reversal tests the end of the kiaman superchron in the wordian occurs in the uppermost part of the exeter group the overlying aylesbeare mudstone group is early capitanian to latest wuchiapingian in age the changhsingian and most of the lower triassic sequence is absent magnetostratigraphic comparison with the southern permian basin shows that the exeter and aylesbeare mudstone groups are closely comparable in age with the havel and elbe subgroups of the rotliegend ii succession the altmark unconformities in these successions appear similar in age to the sequence boundaries in sw england indicating that both may be climate controlled clasts in the exeter group from unroofing of the dartmoor granite first occurred at a minimum of c 8 myr after formation of the granite supplementary material additional sampling magnetic fabric and palaeomagnetic data are available at http doi org 10 6084 m9 figshare c 3283400

magnetostratigraphy of the hettangian langmoos section adnet austria evidence for time delayed phases of magnetization summary study of the magnetostratigraphy of the earliest jurassic mainly hettangian section of langmoos near adnet in austria northern calcareous alps provides a sequence of 10 magnetic polarity intervals these intervals are often evident in the natural remanent magnetization however rather than a true magnetostratigraphic sequence palaeomagnetic analyses reveal evidence for successive phases of magnetization within the section evidence includes 1 changes in lithology associated with changes in magnetic polarity 2 different combinations of components of both polarities and 3 largely non antipodal directions considering the palaeomagnetic directions we suggest that the apparent magnetostratigraphy is the result of two or three phases of magnetization which occurred at different stages of the tectonic emplacement of the northern calcareous alps

18 o 16 o studies of fossil fissure fumaroles from the valley of ten thousand smokes alaska at three sample sites where there are good exposures of the upper 15 m of the 1912 ash flow sheet in the valley of ten thousand smokes vtts alaska 18o 16o studies indicate that fumarolic activity produced a very wide range of 18o values 0 1 to 12 6 n 32 in the groundmass adjacent to fossil fissure fumaroles this contrasts sharply with the uniformity of 18o in the groundmass away from fumarolic conduits 18o 5 9 to 7 1 n 7 and in all of the feldspar phenocrysts 18o 6 11 to 7 5 1 for 11 samples from this study and hildreth 1987 independent of whether these were collected from fossil fumaroles or from unaltered tuff only one sample contained feldspars that were even slightly 18o enriched relative to the others cloudy plagioclase 18o 8 45 and this sample also contained the most 180 enriched groundmass of any of those analyzed 18o 12 6 this preservation of primary magmatic 18o values in the vtts feldspar phenocrysts is clearly a consequence of the extremely short time span i e 1912 to 1923 of vigorous high temperature fumarolic activity in the 1912 ash flow sheet these 18o l6o systematica are strikingly similar to those discovered in the 2 8 ma intracaldera chegem tuff gazis et al 1996 and in the fossil fumaroles in the outflow sheet of the 0 76 ma bishop tuff holt and taylor 1998 thus confirming that a similar type of fumarolic meteoric hydro thermal activity occurred above the zone of intense welding in all three of these ash flow tuffs this is particularly important because it provides a direct linkage between the older tuffs and the actual observations at the vtts of steam chemistry water rock interaction circulation geometry flow velocities and fumarolic temperatures up to 645 c the 18o l6o effects in the vtts can all be explained in terms of a two stage history a an early 10 to 15 year long high temperature 450 c fumarolic 18o depletion event groundmass 18o 0 1 to 4 8 and b a subsequent much longer lived low temperature 150 c 18o enrichment episode groundmass as high as 18o 12 6 steam in these low temperature fumaroles probably passed through various parts of the same hydrothermal system associated with the earlier higher temperature fumarolic activity and a weakened form of this low temperature hydrothermal circulation continues to the present day keith et al 1992 lowell and keith 1991 this low temperature 18o 16o exchange probably occurred in combination with mineralogical alteration of both the groundmass and the calcium rich portions of feldspar phenocrysts during the waning 150 c stages of fumarolic activity spilde et al 1993 the slight 18o enrichment of apparently pristine transparent feldspar phenocrysts 18o 7 51 in one of the 18o depleted meteoric hydrothermally altered fumarolic samples whole rock 18o 4 8 probably indicates that this sample was incipiently altered at low temperatures as fumarolic activity waned and thus may have had a whole rock 18o value much lower than 4 87 prior to 1923

paleomagnetism and electron microscopy of the emeishan basalts yunnan china abstract many normal and a few reversed characteristic directions of magnetization have been obtained by predominantly thermal demagnetization from ten sites of the late permian emeishan basalts collected near kunming yunnan province the normal magnetization directions pass a fold test at the 99 confidence level and yield declination inclination 26 12 k 46 95 6 and a paleopole at 50 n 241 e however the reversed polarity directions with declination inclination at 244 3 are not antipodal to the normal ones which is also noted in other studies of the emeishan basalts of the yangtze paraplatform of the south china block speculations about the cause of this lack of antipodality center on 1 1 local relative rotations 2 2 incomplete demagnetization 3 3 unusually large non dipole fields secular variation or asymmetric reversals in the late permian 4 4 errors in sample orientation 5 5 later remagnetization represented by one or the other polarity group the first two causes are ruled out by our observations and the third cannot be tested with data from china alone but is unlikely because it has not been observed elsewhere errors in sample orientation may be present in those studies that used a magnetic compass because sample intensities of magnetization are on the high side however for the normal polarity directions a solar compass has been used in some of the studies and all normal polarity directions observed in the area are in agreement thus sample orientation errors can be invoked only for the reversed polarity directions in order to test cause 5 we have examined the magnetic carriers in eight samples with scanning electron microscopy titanium poor to titanium rich magnetite commonly cruciform in crystal habit indicates primary igneous crystallization in two samples that have ne and wsw declinations in contrast six normal polarity samples with nne declinations show pervasive replacement of original titanomagnetite by titanium free magnetite and sphene indicating a high degree of alteration we ascribe this alteration to late hydrothermal circulation and argue that it has caused remagnetization in post permian times this study suggests therefore that the ne sw directions are more likely to be representative of the late permian paleomagnetic field than the nne directions

chemical components of the martian soil melt degassing hydrothermal alteration and chondritic debris on the basis of measurements by the viking and soviet phobos missions the fine grained surficial drift material on mars is enriched in moderately volatile and mobile elements such as s cl k and br the compounds of these elements may amount to as much as 16 wt of the soil while the bulk of the soil appears to consist primarily of crustal material whose composition is similar to that of the basaltic mars meteorites clark 1993 three possible geochemical sources melt degassing hydrothermal alteration and accretion of chondritic material may have contributed to the enrichments we have evaluated possible chemical signatures for these sources by examining the relative abundances of chemical elements in the different components to the measured k abundance in the mars soil and have identified characteristic elements for each component the relative abundances of mobile elements in the different components are much less variable than their absolute abundances which strongly depend on conditions such as temperature and water composition the volatility controlled elemental signature of the melt degassing process includes enrichments of zn mo cd ba and w relative to the elemental abundances in the other components and martian meteorites hydrothermal alteration of minerals and glass controlled by low temperature solubility makes up a second component with a characteristic lithium enrichment signature a chondritic component is enriched in siderophile and chalcophile elements including ni compared to material derived from the martian mantle which was depleted in siderophile elements due to core formation unfortunately the existing data for the mars soil do not include any of these key signature elements and the uncertainties for the viking analyses could allow large amounts of each of these elements the mars pathfinder inorganic analysis experiment and the 2001 orbital gamma ray experiment have the potential to determine some of these characteristic elements and to reveal the possible contributions to the soil the enriched components of the soil especially cd and pb could also be a potential hazard for future martian explorers who will be exposed to the dust carried into their habitats on their space suits

new tertiary paleomagnetic poles from mongolia and siberia at 40 30 20 and 13 ma clues on the inclination shallowing problem in central asia we report results of a paleomagnetic study of 490 cores from 59 sites corresponding to 52 distinct basaltic flows from mongolia and siberia khaton sudal 39 4 ma 44 5 n 101 4 e taatsyn gol 1 31 5 ma 45 4 n 101 3 e 2 28 0 ma 45 5 n 101 1 e ust bokson 19 9 ma 52 1 n 100 3 e and taatsyn gol 3 12 7 ma 45 5 n 101 0 e stepwise thermal and alternating field demagnetizations isolated a stable high temperature component htc of magnetization in most specimens which we interpret as the primary magnetization of these basaltic lava flows the four corresponding paleopoles appear consistent with coeval paleopoles from other asian effusive formations however except for the 12 7 ma paleopole the paleopoles are systematically far sided from the european apparent polar wander path apwp with respect to site locations corresponding to anomalously shallow inclinations in tertiary asian effusive formations in the hypothesis of a dipolar magnetic field in the tertiary this indicates a 1000 1500 km position of the siberia craton and amuria block farther south than expected at 40 and 30 ma tectonically this interpretation implies decoupling and relative rotations between the western and eastern parts of eurasia between the cretaceous and present we show that if siberia were located more to the south the 15 20 paleolatitude anomaly generally observed in sedimentary formations from central asia reduces to a more reasonable average value of 7 which could result from the superimposition of shallowing mechanisms due to sedimentary processes and northward motion of asian blocks under the effect of ongoing penetration of india into eurasia in the tertiary

paleomagnetism and magnetostratigraphy of the traps from western taimyr northern siberia and the permo triassic crisis abstract the siberian traps were emplaced near the permo triassic boundary and are among the largest continental igneous provinces a 1750 m thick section of traps from the western taimyr 72 9 n 84 e has been sampled this section is equivalent to the lower and middle part of the total siberian traps section thirty one oriented hand samples were studied and demagnetised by alternating fields and heating cycles a stable characteristic component passes the fold test and is thought to be primary the mean direction is d 84 i 75 with 95 10 n 29 and the corresponding pole is 59 n 150 e the bottom part 660 m is of reversed polarity the middle part 900 m is normal and the uppermost level 150 m is mixed correlations with reference permo triassic magnetostratigraphic timescales are discussed the most probable correlation indicates an age quite close to the permian triassic boundary and a duration for the volcanism of less than 1 m y the data are therefore consistent with the hypothesis that this volcanism triggered the permian triassic crisis

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

response of bankfull flood magnitudes to holocene climate change uinta mountains northeastern utah long term variations in holocene fl ood magnitude were quantifi ed from the bankfull dimensions of abandoned channels preserved on flsurfaces in the northern uinta mountains of northeastern utah cross sectional areas of abandoned channels were reconstructed and relationships derived from the modern gage records were used to estimate bankfull discharges from bankfull cross section areas the results indicate systematic nonrandom variations of bankfull fl oods in the northern uinta mountains large fl oods as much as 10 15 greater than modern dominated from 8500 to 5000 calendar yr b p and again from 2800 to 1000 cal yr b p small fl oods as much as 15 20 less than modern characterize the periods from 5000 to 2800 cal yr b p and from 1000 cal yr b p to near present the middle and late holocene record of bankfull fl ood magnitude compares well with independent evidence for climatic variation in the area the early holocene record indicates that larger than modern bankfull fl oods coincide with warmer than modern mean annual temperature we hypothesize that an increased range of magnitude for seasonal solar radiation during the early holocene favored the accumulation and rapid melting of deep snowpacks in the high uinta mountains thus producing large fl oods despite warmer mean annual temperatures the episode of smaller than modern bankfull fl oods between 5000 and 2800 cal yr b p coincides with records of increased forest fi re frequency in the northern uintas larger than modern fl oods from 2800 to 1000 cal yr b p coincide with a local decrease in forest fi re frequency and evidence for minor local glacial readvances the decrease in fl magnitudes following 1000 cal yr b p corresponds to numerous local and regional records of warming during the medieval climatic anomaly

tree ring based streamfiow reconstruction for ashley creek northeastern utah implications for palaeohydrology of the southern uinta mountains two ring width chronologies from douglas fir pseudotsuga menzeisii and one from pinyon pine pinus edulis were used to reconstruct mean annual discharge of ashley creek in the uinta mountains utah for the years ad 1637 1970 a backward elimination multiple linear regression model identified six statistically significant variables including annual lags ranging from 1t o 2 years the final model explains 71 of variability r 2 adjusted for degrees of freedom lost when regressed against the annual discharges recorded for 1915 72 statistical analysis of the model reconstruction using the reduction of error statistic the durbin watson statistic and the hypergeometric distri bution all indicate fidelity of the model for reconstructing discharge the lilliefors test indicates that years of extreme discharge greater than the 90th percentile or less than the 10th percentile are non randomly distributed between 1637 and 1970 persistent years of above median discharge as well as non random clustering of years above the 90th percentile occurred from 1692 1704 and 1898 1945 analysis of the modern gauge data set shows that mean annual discharge on ashley creek explains between 81 and 91 of the variations of mean annual discharge on the other main stream in the southern uinta mountains indicating that reconstructed mean annual discharge on ashley creek is representative of palaeohydrologic conditions across the south flank of the range these data suggest that the southern uinta mountains experienced persistent below median discharge for 1741 1897 through the peak of the little ice age as identified in numerous surrounding mountain ranges in the central rockies this interpretation agrees with lichenometric evidence for extremely limited little ice age glacial activity in the uintas indicating that the range experienced unusually warm dry conditions at this time