plate boundary observatory and related networks gps data analysis methods and geodetic products the geodesy advancing geosciences and earthscope gage facility global positioning system gps data analysis centers produce position times series velocities and other parameters for approximately two thousand continuously operating gps receivers spanning a quadrant of earth s surface encompassing the high arctic north america and caribbean the purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite tradeoffs involved with combination of results gage gps analysis involves formal merging within a kalman filter of two independent loosely constrained solutions one is based on precise point positioning produced with the gps inferred positioning system orbit analysis simulation gipsy oasis software at central washington university cwu and the other is a network solution based on phase and range double differencing produced with the gps at mit gamit software at new mexico institute of mining and technology nmt the primary products generated are the position time series that show motions relative to a north america reference frame and secular motions of the stations represented in the velocity field the position time series themselves contain a multitude of signals in addition to the secular motions co seismic and post seismic signals seasonal signals from hydrology and transient events some understood and other not yet fully explained are all evident in the time series and ready for further analysis and interpretation we explore the impact of analysis assumptions on the reference frame realization and on the final solutions and we compare within the gage solutions and with others

the end permian mass extinction a rapid volcanic co2 and ch4 climatic catastrophe abstract the end of the permian was a time of crisis that culminated in the earth s greatest mass extinction there is much speculation as to the cause for this catastrophe here we provide a full suite of high resolution and coeval geochemical results trace and rare earth elements carbon oxygen strontium and clumped isotopes reflecting ambient seawater chemistry and water quality parameters leading up to the end permian crisis preserved brachiopod low mg calcite based seawater chemistry supplemented by data from various localities documents a sequence of interrelated primary events such as coeval flows of siberian trap continental flood basalts and emission of carbon dioxide leading to warm and extreme greenhouse conditions with sea surface temperatures sst of 36 c for the late permian although anoxia has been advanced as a cause for the mass extinction most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling but not a general cause instead we suggest that renewed and increased end permian siberian trap volcanic activity about 2000 years prior to the extinction event released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extreme global warming and increased continental weathering eventually these rapidly discharged greenhouse gas emissions less than 1000 years before the event ushered in a global hothouse period leading to extreme tropical ssts of 39 c and higher based on these sea surface temperatures atmospheric co 2 concentrations were about 1400 ppmv and 3000 ppmv for the late and end permian respectively leading up to the mass extinction there was a brief interruption of the global warming trend when sst dropped concurrent with a slight but significant recovery in biodiversity in the western tethys it is possible that emission of volcanic sulfate aerosols resulted in brief cooling just after the onset of intensified warming during the end of the permian after aerosol deposition global warming resumed and the biotic decline proceeded and was accompanied by suboxia in places of the surface ocean which culminated in the greatest mass extinction in earth history

changhsingian conodont succession and the end permian mass extinction event at the daijiagou section in chongqing southwest china abstract previous studies suggested rapid evolution of conodonts across the permian triassic boundary ptb and the end permian mass extinction pattern varies in different sections in south china here we document a high resolution conodont succession from a carbonate facies of the changhsingian stage and across the ptb at the daijiagou section about 35 km north to chongqing city southwest china two genera and twelve species are identified seven conodont zones are recognized from the uppermost part of the lungtan formation to the lowest feixianguan formation they are the clarkina liangshanensis c wangi c subcarinata c changxingensis c yini c meishanensis and hindeodus parvus zones in ascending order based on the high resolution biostratigraphical framework at daijiagou the end permian mass extinction was rapid and it began in the base of the clarkina meishanensis zone associated with the extinction a negative excursion of 13 c carb started in the middle part of clarkina yini zone with a progressive shift of 1 6 to the middle part of the clarkina meishanensis followed by a sharp shift of 3 51 from the clarkina meishanensis zone to the hindeodus parvus zone our study also suggests that the triassic index species hindeodus parvus co occurred with hindeodus changxingensis and clarkina zhejiangensis and directly overlies the clarkina meishanensis zone at the daijiagou section all these data from the daijiagou section and some previous studies of other sections in sichuan guizhou provinces and chongqing city suggest that the first occurrences of hindeodus parvus are slightly earlier than the sharp negative excursion of 13 c carb and the fad at the meishan gssp section we consider that the slight difference of the end permian mass extinction chemostratigraphy and conodont biostratigraphy at daijiagou and its adjacent areas is most likely subject to different lithofacies fossil preservation and the constraint on the stratigraphic resolution rather than a different tempo of the end permian mass extinction in a global sense the whole changhsingian conodont succession at daijiagou provides a high resolution correlation with other equivalent sections in the palaeotethys the controversial results of biostratigraphy and chemostratigraphy between the sections investigated in this paper and the meishan gssp section also provide some important implications that accurate chronocorrelation requires the evaluation of multiple varied stratigraphcal signals rather than relying solely on the fad of the triassic index species hindeodus parvus for recognizing the permian triassic boundary ptb growth series of abundant specimens for each species are figured the taxonomy of some hindeodus species in the ptb interval is updated

carbon isotope stratigraphy across the permian triassic boundary a review abstract the palaeozoic mesozoic transition is marked by distinct perturbations in the global carbon cycle resulting in a prominent negative carbon isotope excursion at the permian triassic p t boundary well known from a plethora of marine and continental sediments potential causes for this negative 13 c trend and their links to the latest permian mass extinction have been intensively debated in the literature in order to draw conclusions regarding causation a general 13 c curve was defined after consideration of all available datasets and with due reference to the biostratigraphic background the most important features of the p t carbon isotope trend are the following the 4 7 13 c decline lasting 500 000 years is gradual and began in the changhsingian at the stratigraphic level of the c bachmanni zone the decreasing trend is interrupted by a short term positive event that starts at about the latest permian low latitude marine main extinction event horizon eh indicating that the extinction itself cannot have caused the negative carbon isotope excursion after this short term positive excursion the 13 c decline continues to a first minimum at about the p t boundary a subsequent slight increase is followed by a second occasionally two peaked minimum in the lower and middle i isarcica zone the negative carbon isotope excursion was most likely a consequence of a combination of different causes that may include 1 direct and indirect effects of the siberian trap and contemporaneous volcanism and 2 anoxic deep waters occasionally reaching very shallow sea levels a sudden release of isotopically light methane from oceanic sediment piles or permafrost soils as a source for the negative carbon isotope trend is questionable at least for the time span a little below the eh and somewhat above the p t boundary

tracking magma volume recovery at okmok volcano using gps and an unscented kalman filter 1 changes beneath a volcano can be observed through position changes in a gps network but distinguishing the source of site motion is not always straightforward the records of continuous gps sites provide a favorable data set for tracking magma migration dense campaign observations usually provide a better spatial picture of the overall deformation field at the expense of an episodic temporal record combining these observations provides the best of both worlds a kalman filter provides a means for integrating discrete and continuous measurements and for interpreting subtle signals the unscented kalman filter ukf is a nonlinear method for time dependent observations we demonstrate the application of this technique to deformation data by applying it to gps data collected at okmok volcano seven years of gps observations at okmok are analyzed using a mogi source model and the ukf the deformation source at okmok is relatively stable at 2 5 km depth below sea level located beneath the center of the caldera which means the surface deformation is caused by changes in the strength of the source during the 7 years of gps observations more than 0 5 m of uplift has occurred a majority of that during the time period january 2003 to july 2004 the total volume recovery at okmok since the last eruption in 1997 is 60 80 the ukf allows us to solve simultaneously for the time dependence of the source strength and for the location without a priori information about the source

current perspectives on the permian triassic boundary and end permian mass extinction preface abstract the end permian mass extinction is now robustly dated at 252 6 0 2 ma u pb and the permian triassic p t gssp level is dated by interpolation at 252 5 ma an isotopic geochronological timescale for the late permian early triassic based on recent accurate high precision u pb single zircon dating of volcanic ashes together with calibrated conodont zonation schemes is presented the duration of the early triassic induan olenekian stages is estimated at only 5 5 million years the duration of the induan stage griesbachian dienerian sub stages is estimated at ca one million years and the early olenekian smithian sub stage at 0 7 million years duration considering this timescale the delayed recovery following the end permian mass extinction may not in fact have been particularly protracted in the light of the severity of the extinction conodonts evolved rapidly in the first 1 million years following the mass extinction leading to recognition of high resolution conodont zones continued episodic global environmental and climatic stress following the extinction is recognized by multiple carbon isotope excursions further faunal turnover and peculiar sedimentary and biotic facies e g microbialites the end permian mass extinction is interpreted to be synchronous globally and between marine and non marine environments the nature of the double phased late permian extinction at the guadalupian lopingian boundary and the p t boundary linked to large igneous provinces suggests a primary role for superplume activity that involved geomagnetic polarity change and massive volcanism

conodont biostratigraphic control on transitional marine to non marine permian triassic boundary sequences in yunnan guizhou china the recovery of conodonts associated with ash beds and magnetostratigraphy in the key zhongzhai section near langdai liuzhi guizhou province provides precise and definitive control on the position of the permian triassic boundary in the transition from marine to non marine facies of western guizhou and eastern yunnan provinces of southwestern china in the zhongzhai section the boundary interval consists of a lower limestone 20 cm thick that contains fragments of hindeodus sp and clarkina sp this is overlain by a 50 cm thick black shale bed containing an abundant brachiopod fauna but only a single conodont fragment this bed is in turn overlain by a 23 cm thick limestone that contains clarkina meishanensis merrillina ultima hindeodus changxingensis h praeparvus and h eurypyge directly over this limestone is a 5 cm thick ash bed followed by a 10 cm thick black shale which is overlain by a second upper ash bed that is 3 cm thick on top of the upper ash bed is a 20 cm thick silty limestone containing an abundant dwarf conodont fauna dominated by hindeodus and containing h parvus but also including clarkina tulongensis the permian triassic boundary is placed at the level of the black shale located between the two ash beds 2007 elsevier b v all rights reserved

early triassic conodont palynological biostratigraphy of the meishan d section in changxing zhejiang province south china the lower triassic consisting of the yinkeng fm helongshan fm and the lower part of the nanlinghu fm is well developed at the meishan d section of changxing county zhejiang province south china based on detailed study of the conodont biostratigraphy from the interval of the permian triassic boundary and the lower triassic in the meishan d section 8 conodont zones are recognized in ascending order as follows the neogondolella changxingensis yini hindeodus praeparvus zone beds 24a 24e top of the changxing fm the neogondolella meishanensis meishanensis hindeodus eurypyge zone beds 25 27b base of the yinkeng fm the hindeodus parvus zone beds 27c 27d first conodont zone of triassic the global index for the base of triassic the isarcicella staeschei zone beds 28 29a lower part of the yinkeng fm i isarcica zone beds 29b 51 lower part of the yinkeng fm the neogondolella tulongensis n planata zone beds 52 72 from upper part of the yinkeng fm to lower part of the helongshan fm the neospathodus kummeli zone beds 73 92 middle part of the helongshan fm and the neospathodus cristagalli n dieneri zone beds 93 111 from upper part of the helongshan fm to the base of the nanlinghu fm at the meishan d section the palynological biostratigraphy is also studied herein the palynological assemblage of lundbladispora taeniaesporites equisetosporites is found in the intervals which contain the conodont isarcicella isarcica zone and the lower part of the neogondolella tulongensis n planata zone

postseismic relaxation following the 1992 m7 3 landers and 1999 m7 1 hector mine earthquakes southern california 1 postseismic relaxation measured postseismic deformation less the deformation that would have occurred at the preseismic rate has been monitored at the same 10 monuments over 6 years following both the 1992 landers and the 1999 hector mine earthquakes for both earthquakes the displacement components of the observed relaxation are well described by i if1 t where i and i are constants peculiar to each component at each monument t is the time after the earthquake and f1 t is a temporal function common to all components and all monuments for that earthquake the temporal function f1 t can be approximated by bt c loge 1 t where 38 7 15 2 days and 25 6 7 7 days for the landers and hector mine relaxations respectively because the estimated values of do not differ significantly the transient term loge 1 t in the temporal function may be the same for both earthquakes the asymptotic t relaxation rates ib are only a few mm a and do not appear to be significantly different following the two earthquakes the asymptotic deformation rates appear to be slightly greater than the preseismic deformation rates but the preseismic rates were not measured directly thus the deformations of the landers array measured over the first 5 6 years following the landers earthquake and over the first 6 4 years following the hector mine earthquake are generally consistent with a simple model in which the transient postearthquake relaxation depends upon time as loge 1 t with 28 5 days and the asymptotic postseismic speeds of the monuments exceed the preseismic speeds by at most only a few millimeters per annum

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

upper permian and lower triassic conodonts high precision u pb zircon ages and the permian triassic boundary in the malay peninsula abstract conodont biostratigraphic and high precision u pb isotope data are presented for the permian triassic transition in three limestone hills gua bama gua panjang and gua sei in the malay peninsula gua bama yielded conodonts representating the clarkina orientalis clarkina wangi and clarkina subcarinata zones and the wuchiapingian changhsingian stage boundary is identified for the first time in malaysia the wuchiapingian subspecies hindeodus julfensis wardlawi kozur is elevated to species level h wardlawi and evolved to the changhsingian species hindeodus julfensis sweet and then hindeodus changxingensis wang distinguishing features and a new phylogeny of species of the genera hindeodus and isarcicella in the late permian early triassic are presented a new ca tims high precision u pb age of 253 70 0 06 ma for zircon from a tuff layer 6 5 m above the wuchiapingian changhsingian boundary and in the lower part of the clarkina subcarinata zone is reported conodont faunas from gua panjang represent the clarkina changxingensis hindeodus praeparvus clarkina yini clarkina zhangi and hindeodus parvus zones and the ptb is placed at approximately 12 m in the studied 19 m thick sequence three tuff layers in the lower part of gua panjang contain zircon grains with ca tims u pb ages of 252 23 0 07 ma 252 47 0 12 ma and 252 16 0 16 ma maximum age respectively conodont faunas from gua sei represent the upper permian changhsingian clarkina hauschei hindeodus latidentatus zone and the basal triassic lower induan griesbachian hindeodus parvus and isarcicella staeschei zones the ptb is placed at 30 m above the base of the gua sei sequence

new species of the conodont genus hindeodus and the conodont biostratigraphy of the permian triassic boundary interval abstract four new species of the conodont genus hindeodus hindeodus eurypyge sp nov hindeodus inflatus sp nov hindeodus sp nov a and hindeodus sp nov b are described from the permian triassic transition in south china our study confirms the first appearance of hindeodus parvus at the gssp level base of bed 27c at meishan however at shangsi the first occurrence of h parvus is about 4 5 m above the event boundary analysis of conodont biostratigraphy of the meishan d section and the shangsi section suggest significant differences between the two sections these include the absence of h changxingensis wang from the shangsi section and the approximately 4 5 m of the shangsi section that contains h priscus kozur h latidentatus kozur and h eurypyge n sp below the first occurrence of h parvus these differences may be accounted for most easily by suggesting that there is a minor depositional hiatus at the permian triassic boundary gssp level as based on the first appearance of the conodont hindeodus parvus in meishan section d taxonomic re evaluation of hindeodus pa elements indicates that species of the genus can be broadly separated into two groups based on the morphology of the posterior portion of the element and on growth patterns the stable pa element morphology of hindeodus first developed in the carboniferous was replaced by a complex of rapid evolutionary change in the latest permian and early triassic with as many as 11 valid species of the genus in the permian triassic boundary interval which are probably descendants of only two species h typicalis and h n sp b we suggest that the dramatic change in conodont biofacies observed at the p t boundary in south china from neogondolella dominated faunas to hindeodus dominated faunas was caused by the introduction of a high component of silt beginning in bed 27 at meishan and bed 28 at shangsi that tipped the environmental balance in favor of hindeodus and isarcicella over neogondolella clarkina species we contend that hindeodus species were adaptable to higher levels of turbidity than neogondolella clarkina species and hence at meishan and shangsi it was not a matter of a drastic increase in the abundance of hindeodus but an exclusion of neogondolella

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

biostratigraphy and sedimentology of upper permian and lower triassic strata at masore western slovenia abstract upper permian and lowermost triassic strata of the masore section in western slovenia have been restudied by means of bio and lithostratigraphy this section is mainly characterized by a carbonate succession of the bellerophon formation deposited in a shallow marine ramp environment that was located in the western part of the paleotethys the permian triassic boundary ptb transition is marked by laminated microbialites stromatolites interpreted to reflect a deeper ramp environment the conodont elements recovered enabled the recognition of the hindeodus praeparvus zone of the uppermost permian upper changhsingian in the bellerophon formation gondolellids are documented in the ptb transitional interval with microbial microfacies whereas the isarcicella isarcica zone lower griesbachian lower triassic is recognized in the tectonically separated werfen formation just above the microbial microfacies part of the section the lowermost part of the microbialites is characterized by late permian species of foraminifers indicating that at least this part of the section is still upper permian

contrasting microbial community changes during mass extinctions at the middle late permian and permian triassic boundaries abstract microbial communities are known to expand as a result of environmental deterioration during mass extinctions but differences in microbial community changes between extinction events and their underlying causes have received little study to date here we present a systematic investigation of microbial lipid biomarkers spanning 20 myr middle permian to early triassic at shangsi south china to contrast microbial changes associated with the guadalupian lopingian boundary glb and permian triassic boundary ptb mass extinctions high resolution analysis of the ptb crisis interval reveals a distinct succession of microbial communities based on secular variation in moretanes 2 methylhopanes aryl isoprenoids steranes n alkyl cyclohexanes and other biomarkers the first episode of the ptb mass extinction me1 was associated with increases in red algae and nitrogen fixing bacteria along with evidence for enhanced wildfires and elevated soil erosion whereas the second episode was associated with expansions of green sulfur bacteria nitrogen fixing bacteria and acritarchs coinciding with climatic hyperwarming ocean stratification and seawater acidification this pattern of microbial community change suggests that marine environmental deterioration was greater during the second extinction episode me2 the glb shows more limited changes in microbial community composition and more limited environmental deterioration than the ptb consistent with differences in species level extinction rates 71 vs 90 respectively microbial biomarker records have the potential to refine our understanding of the nature of these crises and to provide insights concerning possible outcomes of present day anthropogenic stresses on earth s ecosystems

comment on u pb calcite age of the late permian castile formation delaware basin a constraint on the age of the permian triassic boundary by m l becker et al earth planet sci lett 203 2002 681 689

conodont biostratigraphy of a new permo triassic boundary section at wenbudangsang north tibet abstract the wenbudangsang section is a newly discovered continuous succession of marine carbonates that straddles the permian triassic boundary ptb extending from the late permian to the earliest triassic induan the section is located in the wenbudangsang area of geji county northern tibet and tectonically sits within the northern gangdise stratigraphic division conodonts are abundant throughout this section except being comparatively rare and less diverse in the permian strata below the distinctive ptb clay bed the conodonts are mainly represented by hindeodus isarcicella pa elements neogondolella pa elements and ramiform elements with few neospathodus pa elements present at the top of the section two conodont zonal successions have thus been determined based on hindeodus isarcicella and neogondolella species the hindeodus isarcicella succession includes the uppermost permian hindeodus julfensis zone hindeodus praeparvus zone and the lowermost triassic hindeodus parvus zone isarcicella staeschei zone isarcicella isarcica zone and hindeodus postparvus zone the neogondolella succession consists of the upper permian neogondolella changxingensis neogondolella deflecta neogondolella postwangi zone neogondolella yini neogondolella zhangi zone neogondolella meishanensis zone the neogondolella taylorae zone that crosses the ptb and the lowermost triassic neogondolella krystyni zone and neogondolella prediscreta n sp zone the top of the section is defined by the neospathodus kummeli zone and neospathodus cristagalli zone two new species hindeodus microdentatus n sp and n prediscreta n sp are established and described in this paper the ptb conodont successions recognised in the new wenbudangsang section have been closely correlated herein with other well known ptb sections the gssp meishan section of south china sections in abadeh in iran and sections at spiti in india importantly the conodont faunas from wenbudangsang now provide an opportunity to effectively correlate the ptb hindeodid and gondolellid zonal schemes given the high abundance of both assemblages which is unique to this section

environmental signal propagation in sedimentary systems across timescales abstract earth surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales the geomorphic and stratigraphic products of this source to sink sediment transfer record signals of external environmental forcings as well as internal or autogenic dynamics of the sedimentary system here we evaluate environmental signal propagation across sediment routing systems with emphasis on sediment supply qs as the carrier of up system forcings we review experimental numerical and natural examples of source to sink sediment routing and signal propagation during three timescales 1 historic which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries 2 centuries to several millions of years referred to as intermediate timescale and 3 deep time we discuss issues related to autogenic dynamics of sediment transport transient storage and release that can introduce noise lags and or completely mask signals of external environmental forcings we provide a set of conceptual and practical tools for evaluating sediment supply within a source to sink context which can inform interpretations of signals from the sedimentary record these tools include stratigraphic and sediment routing system characterization sediment budgets geochronology detrital mineral analysis e g thermochronology comparative analog approaches and modeling techniques to measure calculate or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment routing systems

complete biotic and sedimentary records of the permian triassic transition from meishan section south china ecologically assessing mass extinction and its aftermath abstract the meishan section south china is the global stratotype section and point gssp for the permian triassic boundary ptb and is also well known for the best record demonstrating the permian triassic mass extinction ptme all over the world this section has also been studied using multidisciplinary approaches to reveal the possible causes for the greatest phanerozoic biocrisis of life on earth many important scenarios interpreting the great dying have been proposed on the basis of data from meishan nevertheless debates on biotic extinction patterns and possible killers still continue this paper reviews all fossil and sedimentary records from the permo triassic p tr transition based on previously published data and our newly obtained data from meishan and assesses ecologically the ptme and its aftermath to determine the biotic response to climatic and environmental extremes associated with the biocrisis eight updated conodont zones clarkina yini clarkina meishanensis hindeodus changxingensis clarkina taylorae hindeodus parvus isarcicella staeschei isarcicella isarcica and clarkina planata zones are proposed for the ptb beds at meishan major turnover in fossil fragment contents and ichnodiversity occurs across the boundary between bed 24e 5 and bed 24e 6 suggesting an extinction horizon in a thin stratigraphic interval the irregular surface in the middle of bed 27 is re interpreted as a firmground of glossifungites ichnofacies rather than the previously proposed submarine dissolution surface or hardground surface both fossil fragment contents and ichnodiversity underwent dramatic declines in beds 25 26a coinciding with metazoan mass extinction fossil fragment content ichnodiversity and all ichnofabric proxies including burrow size tiering level bioturbation level indicate that the p tr ecologic crisis comprises two discrete stages coinciding with the first and second phases of the ptme in meishan ecologic crisis lagged behind biodiversity decline during the ptme pyrite framboid size variations suggest that depositional redox condition was anoxic to euxinic in the latest changhsingian became euxinic in beds 25 26a turned dysoxic in bed 27 then varied from euxinic to anoxic through most of the griesbachian the 9 c increase in seawater surface temperature from bed 24e to bed 27 at meishan seems to result in dramatic declines in biodiversity and fossil fragment contents in beds 25 26a but had little effect on all ecologic proxies both metazoans and infauna seem not to have been affected by the pre extinction anoxic euxinic condition the anoxic event associated with the ptme may have occurred in a much shorter period than previously thought and is only recorded in beds 25 26a at meishan fossil fragment contents ichnofaunas ichnofabrics and pyrite framboid size all show that no signs of oceanic acidification and anoxia existed in bed 27 the early griesbachian anoxia may have resulted in rarity of ichnofauna and metazoans in the lower yinkeng formation in which the ichnofauna is characterized by small simple horizontal burrows of planolites and metazoan faunas are characterized by low diversity high abundance opportunist dominated communities the rapid increase of 9 c in sea surface temperature and a short anoxia or acidification coincided with the first pulse biocrisis while a prolonged and widespread anoxia probably due to a long period of high seawater temperate condition may be crucial in mortality of most organisms in the second pulse ptme marine ecosystems started to recover coupled with environmental amelioration in the late griesbachian

magmatic inflation at a dormant stratovolcano 1996 1998 activity at mount peulik volcano alaska revealed by satellite radar interferometry 1 a series of ers radar interferograms that collectively span the time interval from july 1992 to august 2000 reveal that a presumed magma body located 6 6 0 5 km beneath the southwest flank of the mount peulik volcano inflated 0 051 0 005 km3 between october 1996 and september 1998 peulik has been active only twice during historical time in 1814 and 1852 and the volcano was otherwise quiescent during the 1990s the inflation episode spanned at least several months because separate interferograms show that the associated ground deformation was progressive the average inflation rate of the magma body was 0 003 km3 month from october 1996 to september 1997 peaked at 0 005 km3 month from 26 june to 9 october 1997 and dropped to 0 001 km3 month from october 1997 to september 1998 an intense earthquake swarm including three ml 4 8 5 2 events began on 8 may 1998 near becharof lake 30 km northwest of peulik more than 400 earthquakes with a cumulative moment of 7 15 1017 n m were recorded in the area through 19 october 1998 although the inflation and earthquake swarm occurred at about the same time the static stress changes that we calculated in the epicentral area due to inflation beneath peulik appear too small to provide a causal link the 1996 1998 inflation episode at peulik confirms that satellite radar interferometry can be used to detect magma accumulation beneath dormant volcanoes at least several months before other signs of unrest are apparent this application represents a first step toward understanding the eruption cycle at peulik and other stratovolcanoes with characteristically long repose periods

restudy of conodont biostratigraphy of the permian triassic boundary section in zhongzhai southwestern guizhou province south china abstract new conodont samples have been systematically collected at high stratigraphic resolution from the upper part of the longtan formation through to the lower part of the yelang formation at the zhongzhai section southwestern guizhou province south china in an effort to verify the first local occurrence of hindeodus parvus in relation to the permian triassic boundary at this section the resampled conodont fauna from the permian triassic boundary interval comprises five identified species and two undetermined species in hindeodus and clarkina most importantly the first local occurrence of hindeodus parvus is found for the first time from the bottom of bed 28a 18 cm lower than the previously reported first local occurrence of this species at this section considering the previously accepted ptb at the zhongzhai section well calibrated by conodont biostratigraphy geochronology and carbon isotope chemostratigraphy this lower earlier occurrence of h parvus suggests that this critical species could occur below the permian triassic boundary as such this paper provides evidence that 1 the first local occurrences of h parvus are diachronous in different sections with respect to the ptb defined by the first appearance datum fad of this species at its gssp section in meishan china and that 2 the lower stratigraphic range of h parvus should now be extended to latest permian

the timing and extent of the eruption of the siberian traps large igneous province implications for the end permian environmental crisis we present new high precision 40ar 39ar ages on feldspar and biotite separates to establish the age duration and extent of the larger siberian traps volcanic province samples include basalts and gabbros from noril sk the lower tunguska area on the siberian craton the taimyr peninsula the kuznetsk basin vorkuta in the polar urals and from chelyabinsk in the southern urals most of the ages except for those from chelyabinsk are indistinguishable from those found at noril sk cessation of activity at noril sk is constrained by a 40ar 39ar age of 250 3 1 1 ma for the uppermost kumginsky suite the new 40ar 39ar data confirm that the bulk of siberian volcanism occurred at 250 ma during a period of less than 2 ma extending over an area of up to 5 million km2 the resolution of the data allows us to confidently conclude that the main stage of volcanism either immediately predates or is synchronous with the end permian mass extinction further strengthening an association between volcanism and the end permian crisis a sanidine age of 249 25 0 14 ma from bed 28 tuff at the global section and stratotype at meishan china allows us to bracket the p tr boundary to 0 58 0 21 myr and enables a direct comparison between the 40ar 39ar age of the traps and the permo triassic boundary section younger ages 243 ma obtained for basalts from chelyabinsk indicate that volcanism in at least the southern part of the province continued into the triassic

deposition in the kuznetsk basin siberia insights into the permian triassic transition and the mesozoic evolution of central asia abstract this paper describes the permian mesozoic stratigraphy of the kuznetsk basin southern siberia which is adjacent to the vast and hydrocarbon rich west siberian basin and on the edge of the siberian flood basalts the basin fill is permian to cretaceous in age and is dominated by non marine siliciclastics up to 7 km thick palaeocurrent indicators show dominant flow to the north northeast during the permian to jurassic fourteen lithofacies are grouped in three facies associations fluvial channel belt overbank and floodplain floodplain pond coal bearing permian siliciclastics are interpreted as meandering river deposits in a foreland basin with subsidence generated by thrust sheet loading from at least three basin margins these sediments pass abruptly but conformably upwards into coal barren sandstones and conglomerates and siltstones interpreted as braided river deposits two basalt flows occur within the coal barren succession a recently published precise ar ar age of 250 3 0 7 ma for the lower of these basalts

uppermost permian to lower triassic conodont successions from the enshi area western hubei province south china abstract we present recent study results of the lower triassic conodont succession from the ganxi and jianshi areas of enshi city western hubei province south china which were situated on a carbonate ramp at the northeastern margin of the upper yangtze platform therein the uppermost permian to lower triassic succession is well exposed and yielded abundant conodonts a total of nine conodont zones are differentiated 1 clarkina yini zone 2 clarkina meishanensis zone 3 hindeodus changxingensis zone 4 hindeodus parvus zone 5 hindeodus postparvus zone 6 clarkina planata zone 7 neoclarkina aff discreta zone 8 neospathodus dieneri zone and 9 novispathodus waageni zone the ns dieneri m1 ns dieneri m2 and ns dieneri m3 subzones have also been distinguished within the ns dieneri zone and the nv waageni eowaageni and nv waageni waageni subzones are recognizable within the nv waageni zone in jianshi most of the zones occur in succession but the c planata zone is a local ecozone reflecting deeper water biofacies during h postparvus zone time in the jianshi section the permian triassic boundary is placed at bed 136 2 based on the appearance of hindeodus parvus immediately above the disappearance of changhsingian taxa while the induan olenekian boundary iob is drawn at bed 225 40 cm based on the first appearance of nv waageni eowaageni within the upper range of the ns dieneri zone indices the enshi conodont zones overall correlate well with those recognized elsewhere in south china and worldwide

transient signal detection using gps measurements transient inflation at akutan volcano alaska during early 2008 1 continuous global positioning system gps networks record station position changes with millimeter level accuracy and have revealed transient deformations on various spatial and temporal scales however the transient deformation may not be easily identified from the position time series because of the large number of sites in a network low signal to noise ratios snr and correlated noise in space and time here we apply state estimation and principal component analysis to the daily gps position time series measured in alaska sites of the plate boundary observatory network our algorithm detects a transient signal whose maximum displacement is 9 mm in horizontal and 11 mm in vertical that occurred at akutan volcano during the first half of 2008 a simple mogi source inversion suggests inflation at shallow depth 3 9 km beneath the volcano although the detection was not easy because the signal was aseismic non eruptive and weak not apparent in raw daily time series our detection method improves the snr and therefore provides higher resolution for detecting the transient signal

present day kinematics of the eastern tibetan plateau and sichuan basin implications for lower crustal rheology d s stamps was funded in part by the nsf ear postdoctoral fellowship program grant ear1249295 x rui was funded in part by the cea spark program xh15038

data adaptive detection of transient deformation in geodetic networks author s walwer d calais e ghil m abstract 2016 american geophysical union all rights reserved the recent development of dense and continuously operating global navigation satellite system gnss networks worldwide has led to a significant increase in geodetic data sets that sometimes capture transient deformation signals it is challenging however to extract such transients of geophysical origin from the background noise inherent to gnss time series and even more so to separate them from other signals such as seasonal redistributions of geophysical fluid mass loads in addition because of the very large number of continuously recording gnss stations now available it has become impossible to systematically inspect each time series and visually compare them at all neighboring sites here we show that multichannel singular spectrum analysis m ssa a method derived from the analysis of dynamical systems can be used to extract transient deformations seasonal oscillations and background noise present in gnss time series m ssa is a multivariate nonparametric statistical method that simultaneously exploits the spatial and temporal correlations of geophysical fields the method allows for the extraction of common modes of variability such as trends with nonconstant slopes and oscillations shared across time series without a priori hypotheses about their spatiotemporal structure or their noise characteristics we illustrate this method using synthetic examples and show applications to actual gps data from alaska to detect seasonal signals and microdeformation at the akutan active volcano the geophysically coherent spatiotemporal patterns of uplift and subsidence thus detected are compared to the results of an idealized model of such processes in the presence of a magma chamber source

noise in gps displacement measurements from southern california and southern nevada 1 time series of position changes estimated from data from 236 continuously recording gps receivers operating in southern california and southern nevada are evaluated for noise models that characterize their temporal correlations the lengths of the time series range between 3 5 and 10 years after adjusting these data for postseismic deformation offsets and annual periodicities i find that about one half of the time series have temporal correlations that are categorized as either flicker or random walk noise the remaining time series can be best categorized as either a combination of flicker and random walk power law noise first order gauss markov plus random walk noise or power law plus broadband seasonal noise a variety of geodetic monuments are used in southern california and nevada including deeply braced designs cement piers pins drilled in outcrop and buildings when i evaluate the noise for each time series in terms of an estimate of the standard error in velocity i find that the sites with the smallest errors are those located in nevada using deeply braced monuments sites that are installed within regions of active pumping both for groundwater and oil had the largest standard errors in velocity comparison of monument stability as measured by standard error in rate with average annual rainfall nearby indicates a marginally significant correlation in addition even though regional filtering removed much of the common mode signals in these time series there still remains a common mode seasonal signal which can and should be removed

conodont biostratigraphy across the permian triassic boundary at chaotian in northern sichuan china abstract detailed conodont biostratigraphy of the permian triassic boundary ptb interval was analyzed at the fossiliferous chaotian section in northern sichuan china the ptb interval at chaotian is composed of the uppermost permian mudstone limestone of the dalong formation and the lowermost triassic marl limestone of the feixianguan formation both representing deep basinal facies the ptb interval is enriched in ammonoids and conodonts and is divided into 6 conodont zones including 1 clarkina changxingensis changxingensis c subcarinata assemblage zone 2 c postwangi c sp b assemblage zone 3 c taylorae c zhejiangensis c changxingensis yini assemblage zone 4 barren intra zone 5 hindeodus parvus zone and 6 isarcicella zone in ascending order the first four zones correspond to the changhsingian whereas the latter two to the lower induan griesbachian the first occurrence fo of h parvus in the lowermost feixianguan formation is regarded as the conodont biostratigraphic boundary from the uppermost dalong formation various taxa of the genus clarkina occurred abundantly and suddenly disappeared at the top of the dalong formation therefore the top of the dalong formation is interpreted as a horizon of the eventostratigraphic boundary on the basis of conodont zones the chaotian section is correlated with the shangsi and meishan gssp of the ptb sections in south china and the zal section in iran

size variation of conodont elements of the hindeodus isarcicella clade during the permian triassic transition in south china and its implication for mass extinction abstract based on the analysis of thousands of conodont specimens from the permian triassic p t transition at meishan the gssp of p t boundary and shangsi sections in south china this study investigates the size variation of hindeodus and isarcicella p1 elements during the mass extinction interval the results demonstrate that hindeodus isarcicella underwent 4 episodes of distinct size reduction during the p t transition at the meishan section and 2 episodes of size reduction in the earliest triassic at shangsi the size reductions at meishan took place at the junctions of beds 24d 24e 25 26 27b 27c and 28 29 and at the junctions of beds 28 29c and 30d 31a at shangsi the two earliest triassic size reduction episodes were correlative between the two sections these changes coincide with some important geological events such as eustatic sea level changes anoxic events carbon isotope oscillations miniaturization of brachiopods and microbial changes through detailed investigation of the palaeoenvironment and the palaeoecology of hindeodus isarcicella the authors propose that the main causes of the size reduction was a sharp decline of food availability because of the mass extinction and the anoxic event during the p t transition the pattern of size reduction supports suggestions that the end permian mass extinction was multi episodal consisting of 3 extinction events rather than a single catastrophic event

computer aided detection of transient inflation events at alaskan volcanoes using gps measurements from 2005 2015 abstract analysis of transient deformation events in time series data observed via networks of continuous global positioning system gps ground stations provide insight into the magmatic and tectonic processes that drive volcanic activity typical analyses of spatial positions originating from each station require careful tuning of algorithmic parameters and selection of time and spatial regions of interest to observe possible transient events this iterative manual process is tedious when attempting to make new discoveries and does not easily scale with the number of stations addressing this challenge we introduce a novel approach based on a computer aided discovery system that facilitates the discovery of such potential transient events the advantages of this approach are demonstrated by actual detections of transient deformation events at volcanoes selected from the alaska volcano observatory database using data recorded by gps stations from the plate boundary observatory network our technique successfully reproduces the analysis of a transient signal detected in the first half of 2008 at akutan volcano and is also directly applicable to 3 additional volcanoes in alaska with the new detection of 2 previously unnoticed inflation events in early 2011 at westdahl and in early 2013 at shishaldin this study also discusses the benefits of our computer aided discovery approach for volcanology in general advantages include the rapid analysis on multi scale resolutions of transient deformation events at a large number of sites of interest and the capability to enhance reusability and reproducibility in volcano studies

conodont diversity and evolution through the latest permian and early triassic upheavals abstract a study of latest permian and early triassic multielement conodonts identifies eight steps in their evolutionary history during an interval when earth s biosphere was highly stressed these steps are 1 gradual decline of families and genera through the changhsingian up to the late griesbachian 2 conodont biofacies change and extinction of tethyan endemic species close to the permian triassic boundary ptb 3 faunal turnover with extinction and origination in the late griesbachian 4 initial radiation in gondolellids and diversification in apparatuses during the dienerian 5 explosive radiation in the early middle smithian 6 major extinction in the late smithian 7 major radiation early in the spathian 8 gradual turnover and decline in the late spathian through early anisian conodontophorids were reduced from five families at the beginning of the changhsingian to three by the ptb and to two late in the griesbachian from the changhsingian to the late griesbachian there was a single multielement apparatus represented in the gondolellidae whereas by the olenekian there were at least twelve given absolute age constraints the conodont recovery in the aftermath of the ptb was extraordinary conodont evolution during the dienerian remains obscure but was very significant in terms of changes in multielement apparatuses in spite of induan extinctions generic diversity generally increased from the ptb up to the late smithian in terms of species genera and multielement apparatuses the acme of triassic conodonts was in the middle smithian and the biggest extinction was in the late smithian after this extinction generic and apparatus diversity quickly returned to high levels marking a significant spathian recovery gradual decline characterized the late spathian and persisted into the early anisian a synthetic summary of the temporal distribution and proposed relationships amongst all known lower triassic conodonts provide an improved foundation for biostratigraphic and biochronologic studies extinction and radiation trends correlate well with sea level changes and sequence boundaries faunal turnovers correspond to lowstands in the late griesbachian late smithian and late spathian and radiations correspond to transgressions in the early griesbachian early smithian and early spathian the trends also correlate with perturbations in the carbon cycle with lower triassic 13c minima corresponding to extinction and faunal turnover and positive values generally occurring during radiations however middle triassic recovery of marine benthos follows a positive maxima and an overall decline in conodont diversity new taxa borinella chowadensis b megacuspa neogondolella griesbachensis and n mongeri are described

impact of hydrothermal activity on organic matter quantity and quality during deposition in the permian dalong formation southern china abstract the very high temperature at the center of a hydrothermal system is detrimental for the deposition of organic rich sediments however it s not known how the petroleum source rock develops at the boundary of a hydrothermal system where the seawater temperature was only slightly elevated the petroleum generation potential using pyrolysis gc gc ms and ft icr ms techniques of eight organic rich permian shale samples from shangsi section china were systematically investigated principal component analysis reveals that the quantity and quality of the organic matter in the shale is dominated by biomass productivity the redox condition and terrestrial organic matter input rare earth element distribution pattern reveals that the two samples with highest toc contents show a slight eu anomaly which indicates the sample was influenced by a hydrothermal system to some degree a depositional model showing how the influences from hydrothermal event promote the development of petroleum source rock is summarized 1 at the edge of a hydrothermal system the seawater temperature can be elevated by 5 10 c which further promotes the development of phytoplankton and zooplankton 2 an upwelling can be intrigued and chemical weathering will be accelerated which both introduce excessive nutrients and increase the biota productivity 3 flux with the terrestrial advanced plant can also be accelerated to the shelf area by the volcano induced climate change 4 the consumption of the extensive biomass induced by the hydrothermal activity would expand the oxygen minimum zone and further enable more organic matter to be preserved in shale

episodic inflation events at akutan volcano alaska during 2005 2017 detection of weak volcano deformation helps constrain characteristics of eruption cycles we have developed a signal detection technique called the targeted projection operator tpo to monitor surface deformation with global positioning system gps data we have applied the tpo to gps data collected at akutan volcano from june 2005 to march 2017 and detected four inflation events that occurred in 2008 2011 2014 and 2016 with inflation rates of about 8 22 mm yr above the background trend at a near source site av13 numerical modeling suggests that the events should be driven by closely located sources or a single source in a shallow magma chamber at a depth of about 4 km the inflation events suggest that magma has episodically accumulated in a shallow magma chamber

permian ice volume and palaeoclimate history oxygen isotope proxies revisited abstract a high resolution oxygen isotope record based on 356 measurements of conodont apatite from several low latitudinal sections in south china usa and iran was composed in order to unravel permian palaeotemperature and ice volume history the conodont apatite 18 o record is compared to published brachiopod calcite 18 o records brachiopods and conodonts from different palaeocontinents show significantly different 18 o values suggesting differences in local climatic conditions e g evaporation precipitation ratio as a consequence secular changes in palaeotemperature and oxygen isotope composition of permian sea water cannot be reconstructed from records combined from different areas but have to be based on records from a specific area oxygen isotope analyses of different conodont taxa suggest that streptognathodus and hindeodus lived in near surface seawater and recorded surface water temperature whereas the habitat of gondolellid genera was variable depending on sea level with both near surface and deeper waters as potential life habitat the oxygen isotope record measured on conodonts from south china exhibits relative high values between 22 and 23 vsmow during the glaciated early permian translating into warm seawater temperature between 26 and 30 c assuming that the late palaeozoic ice volumes were comparable to the pleistocene glacial maxima in contrast to the earlier view that the late palaeozoic ice age lpia terminated in the late sakmarian the south china conodont apatite oxygen isotope record suggests waning of the ice sheets in the kungurian ice melting is indicated by a pronounced decrease in 18 o of 2 vsmow which is interpreted as reflecting the combined effect of climatic warming and glacial ice melting significant temperature fluctuations 4 c warming succeeded by 6 to 8 c cooling are observed during the guadalupian lopingian transition interpreted as combined climate changes induced by emeishan volcanism and changes in habitat depth of gondolellid conodonts oxygen isotope values increase to 22 vsmow in the changhsingian which suggests climate cooling and clarkina moving to deeper waters because of the changhsingian sea level rise across the permian triassic boundary 18 o values decrease from 22 to 19 vsmow parallel to the significant negative carbon isotope excursion and the eruption of the siberian traps the latter is pointing to a cause effect relationship as a consequence of the massive release of volcanic greenhouse gases derived from the siberian volcanism and related processes

triggered tremor sweet spots in alaska 1 to better understand what controls fault slip along plate boundaries we have exploited the abundance of seismic and geodetic data available from the richly varied tectonic environments composing alaska a search for tremor triggered by 11 large earthquakes throughout all of seismically monitored alaska reveals two tremor sweet spots regions where large amplitude seismic waves repeatedly triggered tremor between 2006 and 2012 the two sweet spots locate in very different tectonic environments one just trenchward and between the aleutian islands of unalaska and akutan and the other in central mainland alaska the unalaska akutan spot corroborates previous evidence that the region is ripe for tremor perhaps because it is located where plate interface frictional properties transition between stick slip and stably sliding in both the dip direction and laterally the mainland sweet spot coincides with a region of complex and uncertain plate interactions and where no slow slip events or major crustal faults have been noted previously analyses showed that larger triggering wave amplitudes and perhaps lower frequencies 0 03 hz may enhance the probability of triggering tremor however neither the maximum amplitude in the time domain or in a particular frequency band nor the geometric relationship of the wavefield to the tremor source faults alone ensures a high probability of triggering triggered tremor at the two sweet spots also does not occur during slow slip events visually detectable in gps data although slow slip below the detection threshold may have facilitated tremor triggering

episodic inflation and complex surface deformation of akutan volcano alaska revealed from gps time series abstract akutan is one of the most active volcanoes in the aleutian island arc studies involving seismic gps and insar data have observed activity and deformation on the island since 1996 in this study we inverted measurements of volcanic deformation observed using three components of motions at 12 continuous gps sites to define magma source parameters using mogi point source okada dislocation and yang spheroid and ellipsoid models in order to analyze the evolution of this magma source we split the gps data into five consecutive time periods and one period that incorporates all available data these time periods were designed around two inflation events in 2008 and 2014 when a sudden and significant increase in vertical velocity was observed inversion of these time periods independently allowed us to create a magma volume time series that is related to the physical migration of magma defined by the estimated source parameters the best fit model parameters resulting from these inversions describes magma storage in the form of an oblate spheroid centered on the northeastern rim of the caldera of akutan volcano extending from a depth of 7 km to 8 km with a length of 3 5 km a strike of n165 e and a dip of 63 from the horizontal to the southwest our model results were compared with seismic studies and found to support previous interpretations of episodic inflation beneath akutan volcano with complicated magma storage at intermediate depths the inflation event observed in 2008 was estimated to be the result of an injection of magma of 0 08 km 3 that was followed in 2014 by an additional increase in volume of 0 06 km 3 no periods of deflation were observed in the gps data after these events and we believe the total volume of magma accumulated in this region 0 2 km 3 remains in a shallow storage system beneath akutan volcano

postearthquake relaxation after the 2004 m6 parkfield california earthquake and rate and state friction 1 an unusually complete set of measurements including rapid rate gps over the first 10 days of postseismic deformation is available at 12 continuous gps stations located close to the epicenter of the 2004 m6 0 parkfield earthquake the principal component modes for the relaxation of the ensemble of those 12 gps stations were determined the first mode alone furnishes an adequate approximation to the data thus the relaxation at all stations can be represented by the product of a common temporal function and distinct amplitudes for each component north or east of relaxation at each station the distribution in space of the amplitudes indicates that the relaxation is dominantly strike slip the temporal function which spans times from about 5 min to 900 days postearthquake can be fit by a superposition of three creep terms each of the form l loge 1 t l with characteristic times l 4 06 0 11 and 0 0001 days it seems likely that what is actually involved is a broad spectrum of characteristic times the individual components of which arise from afterslip on different fault patches perfettini and avouac 2004 have shown that an individual creep term can be explained by the spring slider model with rate dependent no state variable friction the observed temporal function can also be explained using a single spring slider model i e single fault patch that includes rate and state dependent friction a single state variable and either of the two commonly used aging and slip state evolution laws in the latter fits the rate and state friction parameter b is negative

age and timing of the permian mass extinctions u pb dating of closed system zircons the age and timing of the permian triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts zircons from nine ash beds within the shangsi and meishan sections china pretreated by annealing followed by partial attack with hydrofluoric acid result in suites of consistent and concordant uranium lead u pb ages eliminating the effects of lead loss the u pb age of the main pulse of the extinction is 252 6 0 2 million years synchronous with the siberian flood volcanism and it occurred within the quoted uncertainty

the spatial nearshore offshore distribution of latest permian phytoplankton from the yangtze block south china abstract in order to analyze the spatial paleoecological distribution of the organic walled microphytoplankton in the late permian five sections from the yangtze block south china displaying different sediment facies types from neritic to offshore paleoenvironments including basinal facies have been investigated palynologically based on the diversity and relative abundance of acritarch species and genera the new data from the permian provide similar patterns as those described from other geological periods 1 low diversities with 2 to 4 acritarch species occur in nearshore environments whereas the higher diversities more than ten acritarch species appear in the offshore environments 2 at the generic level the genera leiosphaeridia reduviasporonites and micrhystridium are distributed widely from nearshore facies corresponding to shallow water environments to offshore facies corresponding to deeper water settings whereas some genera such as dictyotidium and veryhachium have a narrower distribution occurring on the continental shelf and towards the basin indicating open marine environments 3 the genus schizosporis only occurs around the permian triassic boundary ptb when the sea level declined probably indicating nearshore environments with shallow water settings 4 at the specific level the species micrhystridium breve displaying short spines and leiosphaeridia minutissima are indicative of neritic facies whereas the other species of micrhystridium and veryhachium with longer spines e g micrhystridium stellatum and veryhachium hyalodermum and leiosphaeridia microgranifera indicate more open marine environments big spherical acritarch species over 80 m in diameter such as dictyotidium reticulatum indicate shallow water environments and 5 in the ptb strata the relative abundance of the enigmatic reduviasporonites interpreted by some authors as a fungal spore is not higher than 14 in every sample indicating that a spike of reduviasporonites does not occur in the yangtze area reduviasporonites chalastus 40 m in length obviously dominates in shelf environments of shallow water whereas the smaller reduviasporonites catenulatus 15 m in length are more common in deeper water

discovery of shallow marine biofacies conodonts in a bioherm within the carboniferous permian transition in the omolon massif ne russia near the north paleo pole correlation with a warming spike in the southern hemisphere the conodont genera hindeodus and streptognathodus are reported for the first time within the carboniferous permian transition in the northern high latitudes of the paren river omolon massif ne russia several fossil groups including brachiopods bivalves scaphopods and microgastropods were found to be prolific in the invertebrate dominated bioherms these bioherms occur within predominantly siliciclastic sequences with extremely poor fauna whereas in the studied bioherms the diversity of the bivalves and brachiopods exceeded observed diversity elsewhere in coeval facies in ne russia the bioherms are biostratigraphically constrained as uppermost pennsylvanian to lowermost cisuralian based on ammonoids the very unusual peak of bivalve and brachiopod diversity and the occurrence of conodonts that require minimum sea water temperatures of at least 10 12 c indicate a short lived but significant warming event at that time at least of provincial significance this event most likely corresponds with a short lived warming event recently discovered in the east of the southern hemisphere in timor and australia thus the event is possibly of global significance

reply to the comment on quantitative biochronology of the permian triassic boundary in south china based on conodont unitary associations 1 introduction in their comment jiang et al 2016 claim that the discordance between our zonation brosse et al 2016 and the interval zones does not rest on the use of the unitary association method guex 1991 and guex et al 2015 per se but on our failure to use the most recent published conodont ranges from some key chinese sections they add that our analysis is based on unreliable taxonomic data sets with unjustified taxonomic re assessments and hence that we did not demonstrate that the unitary association method performs better than traditional interval zones additionally the comment by jiang et al 2016 contains misunderstandings pertaining to the method used in our study brosse et al 2016 our goal was to apply the unitary association method on a dataset of conodont distributions from south china around the permian triassic boundary ptb in order to reassess the quality of the corresponding data and to provide a discrete and robust alternative zonation to the continuous first occurrence based interval zones such interval zones are routinely utilized in permian and triassic conodont biostratigraphy regardless of their abundant internal contradictions three categories of points of contention can be extracted from the comment of jiang et al 2016 method selection of data and taxonomy and illustrations each of these is addressed separately below 2 method fig 1 complies with the recommendation of jiang et al 2016 and takes into account all the recent literature summarizing the most recent published conodont ranges from the relevant sections the reader will immediately observe that the sequences of first occurrences fos used in the most recently published interval zones occupy contradictory positions between the different sections this is precisely the main criticism expressed in our work this problem cannot be solved by simply standardizing the taxonomy of the considered taxa many contradictions do persist after taxonomic homogenization as conceded by jiang et al 2016 fos are prone to diachronism but contrary to what jiang et al 2016 suggest sampling effort is not the only nor the main reason for such diachronism and ptb sections from south china are no exceptions in this respect fig 9 of brosse et al 2016 demonstrates the contrary ironically enough jiang et al 2016 acknowledge that last occurrences los can be diachronous because of local ecological differences but they exclude that fos can be affected in reality these authors unduly equate every local fo with an alleged instantaneous spreading of a species across all sections incidentally such an unwarranted assumption also deliberately ignores that speciation is an intrinsically space restricted evolutionary process

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

pcaim joint inversion of insar and ground based geodetic time series application to monitoring magmatic inflation beneath the long valley caldera this study demonstrates the interest of using a principal component analysis based inversion method pcaim to analyze jointly insar and ground based geodetic time series of crustal deformation a major advantage of this approach is that the insar tropospheric biases are naturally filtered out provided they do not introduce correlated or high amplitude noise in the input times series this approach yields source models which are well constrained both in time and space due to the temporal resolution of the ground based geodetic data and the spatial resolution of the insar data the technique is computationally inexpensive allowing for the inversion of large datasets to demonstrate the performance of this approach we apply it to the 1997 98 magmatic inflation event in the long valley caldera california

conodont biostratigraphy across the permian triassic boundary at the dawen section great bank of guizhou guizhou province south china implications for the late permian extinction and correlation with meishan several continuous permian triassic boundary ptb sections are well exposed in the interior of the great bank of guizhou gbg on the east limb of the bianyang syncline luodian county guizhou province south china fourteen conodont taxa are identified including clarkina kazi clarkina lehrmanni n sp clarkina taylorae clarkina zhejiangensis hindeodus eurypyge hindeodus inflatus hindeodus sxlatidentatus hindeodus parvus erectus hindeodus parvus parvus hindeodus postparvus hindeodus praeparvus hindeodus typicalis isarcicella staeschei and merrillina ultima based on a detailed study of the permian triassic interval at the dawen section the first occurrence fo of h parvus parvus in the lower daye formation at about 7 45 m above the contact surface between the upper permian skeletal packstone and a calcimicrobial framestone unit is correlated with the permian triassic boundary the occurrence of h eurypyge h praeparvus and m ultima immediately below and h postparvus above the interval supports this interpretation a morphometric analysis of 31 hindeodus specimens helped distinguish h parvus erectus from h parvus parvus and h postparvus correlation with the meishan section ptb gssp using both conodont biostratigraphy and carbon isotopes indicates that the major extinction at the two localities is simultaneous and coincides with the top of the skeletal packstone at dawen the contact between the skeletal packstone and the calcimicrobialite is very irregular and has previously been interpreted as a dissolution surface and correlated with a surface in the lower part of bed 27 at meishan our results confirm this interpretation and reveal that the dissolution event postdated the extinction

near real time monitoring of volcanic surface deformation from gps measurements at long valley caldera california 1 long valley caldera in eastern california is an active volcanic area and has shown continued unrest in the last three decades we have monitored surface deformation from global positioning system gps data by using a projection method that we call targeted projection operator tpo tpo projects residual time series with secular rates and periodic terms removed onto a predefined spatial pattern we used the 2009 2010 slow deflation as a target spatial pattern the resulting tpo time series shows a detailed deformation history including the 2007 2009 inflation the 2009 2010 deflation and a recent inflation that started in late 2011 and is continuing at the present time november 2012 the recent inflation event is about four times faster than the previous 2007 2009 event a mogi source of the recent event is located beneath the resurgent dome at about 6 6 km depth at a rate of 0 009 km3 yr volume change tpo is simple and fast and can provide a near real time continuous monitoring tool without directly looking at all the data from many gps sites in this potentially eruptive volcanic system

identifying globally synchronous permian triassic boundary levels in successions in china and vietnam using graphic correlation abstract understanding the timing and correlation of significant global events in earth history is facilitated by the global boundary stratotype section and point gssp concept along with multi proxy correlation techniques as an example the permian triassic boundary ptb gssp is used herein to correlate three ptb successions in east and southeast asia the ptb is defined using the first appearance datum fad of the conodont hindeodus parvus at the meishan d section in china by definition then meishan d is the only section on earth where the fad of h parvus represents the beginning of the triassic at 251 88 ma and thus the end of the permian therefore when correlating strata in any other section back to the ptb using biostratigraphic data the local lowest observed occurrence point loop of h parvus will probably not equate precisely to the defined fad gssp level the ptb for the beginning of the triassic at meishan d the graphic correlation method applied to ptb sites in china and vietnam is used herein to demonstrate that loops of h parvus in other successions are not equivalent in time to the ptb fad the loop and highest observed occurrence point hoop for conodont data at two other successions studied huangzhishan in china and lung cam in vietnam are used to determine the approximate level where the triassic begins in these successions resulting in high resolution correlation among the sections and correlation back to the ptb gssp level it is demonstrated that when critical biostratigraphic data are missing multiple proxy correlation techniques geochemical geophysical and in some regional instances unique lithostratigraphic information such as coeval ash beds can be used to aid in locating the boundary in successions that are not the defining gssp loop and hoop data are used to establish a line of correlation to differentiate between a defining ptb h parvus fad versus the h parvus loop in secondary successions and to project the ptb fad into secondary sections to define the ptb at these localities in addition the timing of h parvus arrivals at these sections is used to establish rough dispersal rates and patterns in the region

inverting geodetic time series with a principal component analysis based inversion method 1 the global positioning system gps system now makes it possible to monitor deformation of the earth s surface along plate boundaries with unprecedented accuracy in theory the spatiotemporal evolution of slip on the plate boundary at depth associated with either seismic or aseismic slip can be inferred from these measurements through some inversion procedure based on the theory of dislocations in an elastic half space we describe and test a principal component analysis based inversion method pcaim an inversion strategy that relies on principal component analysis of the surface displacement time series we prove that the fault slip history can be recovered from the inversion of each principal component because pcaim does not require externally imposed temporal filtering it can deal with any kind of time variation of fault slip we test the approach by applying the technique to synthetic geodetic time series to show that a complicated slip history combining coseismic postseismic and nonstationary interseismic slip can be retrieved from this approach pcaim produces slip models comparable to those obtained from standard inversion techniques with less computational complexity we also compare an afterslip model derived from the pcaim inversion of postseismic displacements following the 2005 8 6 nias earthquake with another solution obtained from the extended network inversion filter enif we introduce several extensions of the algorithm to allow statistically rigorous integration of multiple data sources e g both gps and interferometric synthetic aperture radar time series over multiple timescales pcaim can be generalized to any linear inversion algorithm

crustal structure along the aleutian island arc new insights from receiver functions constrained by active source data 1 moho depth and vp vs estimates from stacking phases of receiver functions along the aleutian island arc give new constraints on its composition and structure they expand on the current understanding of island arcs and their relationship to continental crust production we also present an approach for including constraints from active source data in receiver function analysis in a region with sparse data coverage to complement this analysis moho depth averages 37 5 km with an average uncertainty of 2 5 km along the entire arc excluding the westernmost island of attu yields an average crustal thickness of 38 5 2 9 km the vp vs ratio decreases moving eastward along the arc with an average value of 1 80 in the western and central portion of the arc built on oceanic crust but 1 63 in the eastern section built on continental crust this may reflect tectonic and compositional changes along the arc however overall the arc appears more mafic than continental crust near constant crustal thickness despite significant compositional changes may indicate that nonmagmatic processes such as erosion and isostasy act to regulate arc thickness additionally strong conversions from an upper crustal magma chamber are observed beneath akutan island confirming and clarifying the geometry of the magma body inferred from other techniques they indicate a volcanic body much larger than the eruptive edifice a feature that must persist between eruptive cycles

quantitative biochronology of the permian triassic boundary in south china based on conodont unitary associations abstract the biochronological characterization of the permian triassic boundary ptb is here improved by means of conodont unitary associations zones uazs the selected data set comprises the six best documented sections in south china including the meishan global stratotype section and point of the ptb this new biochronological zonation has a much higher accuracy than previous schemes which were based on continuous interval zones we show how traditional interval zones around the ptb in south china suffer from diachronous boundaries that cross each other as the result of sampling effort intensity and density and of geographical or ecological exclusion of zonal index taxa inclusive of the first occurrence of the base triassic index species hindeodus parvus our quantitative and robust approach produces a discrete sequence comprising six uazs in the closest agreement with the position of the ptb in meishan the ptb falls here in the interval of separation between uaz 2 and uaz 3 in meishan this interval of separation corresponds to the stratigraphic interval above bed 25 and below bed 27 which also includes the formational boundary between the changhsing and the yinkeng formations we provide a new and independent support for this placement by showing that it correlates with the main turnover of conodont species within the analysed time interval as previously documented the main extinction interval ranged from bed 25 to bed 28 in meishan which are here assigned to uaz 2 and to uaz 4 respectively therefore the main extinction episode is not of end permian age but straddles the ptb previous claims for two distinct extinction pulses bracketing the ptb in south china were based on traditional conodont interval zones and are not supported by the new ua zonation the oldest triassic uaz 3 is identified by the characteristic species hindeodus pisai and by any of the ten characteristic pairs of species neogondolella zhejiangensis or neogondolella tulongensis associated with hindeodus changxingensis hindeodus parvus neogondolella planata neogondolella taylorae or isarcicella huckriedei separate analyses of anchignathodontids and neogondolellids sub data sets show that the base of the triassic is unambiguously defined by the occurrences of the characteristic species h changxingensis isarcicella prisca and i huckriedei in shallow water settings and of two characteristic species n planata and n taylorae in deep water settings moreover we document uncoupled diversity trends across the ptb for each of these two clades a substantial diversification phase of anchignathodontids spans the interval from uaz 3 to uaz 5 it is followed by a drastic 50 reduction of the number of species between uaz 5 and uaz 6 on the other hand neogondolellids show a protracted extinction from uaz 4 to uaz 6 in south china correlations are proposed for the microbialite bearing sections and deeper water ptb sections the ua method also highlights which parts of the conodont record are still insufficiently documented for reliable correlations biochronological correlations with meishan and its u pb radio isotopic ages allow inferring a maximal duration of 61 48 ka for the gap at the base of the triassic microbial limestone at dajiang a time interval that also corresponds to the duration of the main extinction episode in meishan

an integrated biostratigraphy conodonts and foraminifers and chronostratigraphy paleomagnetic reversals magnetic susceptibility elemental chemistry carbon isotopes and geochronology for the permian upper triassic strata of guandao section nanpanjiang basin south china abstract the chronostratigraphy of guandao section has served as the foundation for numerous studies of the end permian extinction and biotic recovery in south china guandao section is continuous from the permian triassic boundary to the upper triassic conodonts enable broad delineation of stage and substage boundaries and calibration of foraminifer biostratigraphy as follows changhsingian griesbachian first hindeodus parvus and first appearance of foraminifers postcladella kalhori and earlandia sp griesbachian dienerian first neospathodus dieneri and last appearance of foraminifer p grandis dienerian smithian first novispathodus waageni and late dienerian first appearance of foraminifer hoyenella ex gr sinensis smithian spathian first nv crassatus and last appearance of foraminifers arenovidalina n sp and glomospirella cf vulgaris spathian aegean first chiosella timorensis and first appearance of foraminifer meandrospira dinarica aegean bithynian first nicoraella germanica and first appearance of foraminifer pilammina densa bithynian pelsonian after last neogondolella regalis prior to first paragondolella bulgarica and first appearance of foraminifer aulotortus eotriasicus pelsonian illyrian first pg excelsa and last appearance of foraminifers meandrospira deformata and pilamminella grandis illyrian fassanian first budurovignathus truempyi and first appearance of foraminifers abriolina mediterranea and paleolituonella meridionalis fassanian longobardian first bv mungoensis and last appearance of foraminifer a mediterranea longobardian cordevolian first quadralella polygnathiformis and last appearance of foraminifers turriglomina mesotriasica and endotriadella wirzi the section contains primary magnetic signature with frequent reversals occurring around the permian triassic olenekian anisian and anisian ladinian boundaries predominantly normal polarity occurs in the lower smithian bithynian and longobardian cordevolian predominantly reversed polarity occurs in the upper griesbachian induan olenekian pelsonian and lower illyrian reversals match well with the gpts large amplitude carbon isotope excursions attaining values as low as 2 9 13c and high as 5 7 13c characterize the lower triassic and basal anisian values stabilize around 2 13c through the anisian to carnian similar signatures have been reported globally magnetic susceptibility and synthetic gamma ray logs show large fluctuations in the lower triassic and an overall decline in magnitude of fluctuation through the middle and upper triassic the largest spikes in magnetic susceptibility and gamma ray indicating greater terrestrial lithogenic flux correspond to positive 13c excursions high precision u pb analysis of zircons from volcanic ash beds provide a robust age of 247 28 0 12 ma for the olenekian anisian boundary at guandao and an age of 251 985 0 097 ma for the permian triassic boundary at taiping together the new u pb geochronology from the guandao and taiping sections suggest an estimated duration of 4 71 0 15 ma for the early triassic epoch

the end permian regression in south china and its implication on mass extinction abstract records of more than 20 permian triassic boundary ptb sections from south china show that widespread end permian regression took place in whole south china timing of the low ebb of this regression was pinpointed to the clarkina meishanensis and hindeodus changxingensis zones biostratigraphic and paleogeographic studies at conodont zonation level reveal that the yangtze carbonate platform and isolated small carbonate platforms in the hunan guizhou guangxi hgg basin experienced sedimentary hiatus during these two zones which lasted about 50 100 kya meanwhile the basinal areas namely the northern marginal basin of yangtze platform and the hunan guizhou guangxi basin have continuous conodont zonation with silicious and ashbed deposits the basinal areas show two negative 13c shifts during the ptb interval from clarkina yini zone to isarcicella isarcica zone while on the platforms there is usually only one negative shift because the early shift at c meishanensis zone was lost during hiatus the end permian regression and successive rapid transgression taking place at the ptb casted important effects to the pattern and process of the ptb mass extinction the depositional hiatus hitherto underestimated will necessitate reassessment of some interpretations on the causes and results of that extinction

expansion of photic zone euxinia during the permian triassic biotic crisis and its causes microbial biomarker records the incursion of euxinic waters into the ocean surface layer is hypothesized to have been an important killing agent during the end permian mass extinction however both the causes and extent of oceanic euxinia during this crisis remain poorly known making assessment of its role in the mass extinction difficult here we document the distribution of aryl isoprenoids ais which are biomarkers of obligate anaerobic green sulfur bacteria chlorobiaceae that are indicative of photic zone euxinia in 12 permian triassic boundary ptb sections with a wide distribution globally profiles of ai abundance for the 12 study sections show significant spatio temporal variation no ais were identified in the shallowest sections but ais are present both prior to and following the mass extinction in intermediate depth sections and following the mass extinction in deep water sections this pattern suggests a combination of upward and oceanward expansion of photic zone euxinia during the ptb crisis possibly fueled by elevated riverine nutrient fluxes as a consequence of climatic warming terrestrial ecosystem destruction and enhanced erosion this hypothesis is supported by the close association of ais with elevated abundances of moretanes and dibenzofuran dbf which are biomarkers for terrestrial erosion expansion of oceanic euxinia at intermediate water depths may have established a long term reservoir that fed episodic incursions of h2s bearing waters into shallow marine environments delaying the recovery of marine ecosystems during the early triassic the biomarker records of the present study thus provide significant evidence of terrestrial marine linkage during the ptb crisis

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

early triassic terrestrial tetrapod fauna a review abstract the permian triassic mass extinction ptme ca 252 mya was one of the most severe biotic crises of the phanerozoic eliminating 90 of marine and terrestrial species this was followed by a long period of recovery in the early and middle triassic which revolutionised the structure of both marine and terrestrial ecosystems triggering the new ecosystem structure of the mesozoic and cenozoic entire new clades emerged after the mass extinction including decapods and marine reptiles in the oceans and new tetrapods on land in both marine and terrestrial ecosystems the recovery is interpreted as stepwise and slow from a combination of continuing environmental perturbations and complex multilevel interaction between species in the new environments as ecosystems reconstructed themselves here we present a review of early triassic terrestrial tetrapod faunas geological formations and outcrops around the world and provide a semi quantitative analysis of a data set of early triassic terrestrial tetrapods we identify a marked regionalisation of early triassic terrestrial tetrapods with faunas varying in both taxonomic composition and relative abundance according to palaeolatitudinal belt we reject the alleged uniformity of faunas around pangaea suggested in the literature as a result of the hot house climate in addition we can restrict the tetrapod gap of terrestrial life in the early triassic to palaeolatitudes between 15 n and about 31 s in contrast to the earlier suggestion of total absence of tetrapod taxa between 30 n and 40 s there was fairly strong provincialism following the ptme according to cluster analysis of a taxon presence matrix entirely consistent with early triassic palaeobiogeography unexpectedly the overall pattern for early triassic terrestrial tetrapod faunas largely reflects that of the late permian suggesting that the recovery faunas in the early triassic retained some kind of imprint of tetrapod distributions according to palaeogeography and palaeoclimate despite the near total extinction of life through the ptme

evolutionary dynamics of the permian triassic foraminifer size evidence for lilliput effect in the end permian mass extinction and its aftermath abstract there is growing evidence of the lilliput effect in the end permian mass extinction and its aftermath however very little has been published on assessing the lilliput effect on protozoans in the early triassic based on quantitative analysis of a great quantity of samples from outcrop sections this study investigates foraminiferal test size variations through the changhsingian to the olenekian based on fossil records from three outcrop sections in south china the sharp reduction in foraminifer sizes coincides with the first or main episode of the end permian mass extinction foraminifers remained small in sizes in the early induan their body sizes increased slowly in the late induan to olenekian but never recovered to the pre extinction test size levels the lilliput effect on foraminifera in the aftermath of the end permian crisis is indicated by the extinction of large taxa decrease in size for surviving taxa and rise of small sized new forms physiological reactions of various foraminifer groups reveal that several defaunation events such as anoxia ocean acidification and global warming that prevailed through the permian triassic interval may be responsible for both the end permian crisis and the lilliput effect

integrative timescale for the lopingian late permian a review and update from shangsi south china abstract the lopingian is the uppermost series of the paleozoic and it is bracketed by two major biological events including the pre lopingian crisis and the end permian mass extinction epme a high resolution temporal framework is essential to understand the patterns and causes of the extinction lopingian strata of south china have been intensively studied because three gssps have been defined in the region based on the review and updates to data from the shangsi section as well as correlation with the meishan section the time framework for the lopingian is revised including biostratigraphy chemostratigraphy magnetostratigraphy cyclostratigraphy and geochronology the temporal framework is constrained by both precise geochronologic data and a high resolution conodont succession and provides the possibility that the current high resolution marine international standard can also be applied to nonmarine strata by means of geochronology magnetostratigraphy and cyclostratigraphy the entire lopingian high resolution conodont succession is for the first time since the lopingian series was adopted as the international standard recognized at a single section in south china and the succession correlates very well with the lopingian gssp sections at penglaitan and meishan the permian triassic boundary ptb of the shangsi section is constrained to the basal 6 cm interval of bed 28b in view of ammonoids bivalves conodonts u pb ages and the epme the mass extinction interval is between bed 27 and lower bed 28a according to the epme pattern at the shangsi section and the alternative interval between extinct permian species and new triassic species is from upper bed 28a to lower bed 28b unitary association ua analysis of lopingian conodonts reveals 15 unitary association zones uazs based on seven important lopingian sections of south china most of the uazs correlate well with the standard biozonation except for uaz 3 to uaz 5 and uaz 12 the correspondence between uazs and standard conodont biozones at the shangsi section provides a practical example to understand controls on conodont uaz determination the lopingian conodont succession is temporally calibrated by geochronologic ages identified 405 kyr eccentricity cycles and a monte carlo analysis at the shangsi and meishan sections updated ages for the base of the lopingian and base of the changhsingian are provided

end permian extinction and volcanism induced environmental stress the permian triassic boundary interval of lower slope facies at chaotian south china abstract in order to reveal environmental changes across the permo triassic boundary ptb the detailed lithostratigraphy of the ptb interval is analyzed at chaotian in northern sichuan china the studied section is composed of the changhsingian upper permian dalong formation and the induan lower triassic feixianguan formation of a lower slope facies deposited on the northwestern margin of the yangtze carbonate platform the 12 m thick interval across the ptb consists mainly of bedded carbonates and mudstone and is lithologically divided into 7 units i e units a to g in ascending order the main extinction horizon of permian taxa is recognized at the unit d e boundary where various fossil metazoans and protists such as ammonoids brachiopods bivalves conodonts and radiolarians rapidly disappeared or became scarce the complete disappearance of radiolarians at the unit d e boundary emphasizes that the ptb extinction affected not only various late permian benthic and free swimming metazoans but also planktonic protozoans the lowest induan index conodont hindeodus parvus first occurs at the base of unit f marking the biostratigraphically defined ptb horizon unit e composed of unique bedded marl between the main extinction horizon and the first occurrence of triassic taxon represents a period of strong environmental stresses that suppressed productivity both of silica and carbonate secreting organisms by changing their size radiolarians reacted most sensitively to the environmental change that already started in the late changhsingian appreciably before the final extinction event the frequent intercalation of rhyo dacitic tuff beds particularly in unit d and the lower part of unit e across the main extinction horizon suggests that intermittent felsic volcanism and relevant environmental change may have been responsible for the mass extinction of the permian taxa and for the prolonged post extinction lag time before the initial recovery the frequent ash falls during the late changhsingian indicate that the volcanism induced environmental change had already started earlier than the main extinction all the biological production carbonate silica and organic matter collapsed at the unit d e boundary when the environmental stresses may have passed a critical threshold for maintaining ecological stability the ptb interval between the extinction and the first appearance of triassic taxon at chaotian is ca 1 4 m thick apparently almost eight times thicker than that at the global stratotype section and point of ptb in meishan 19 cm the chaotian section as well as the neighboring shangsi section in northern sichuan may provide a better chance for high resolution chemostratigraphic analyses that may allow detection and correlation of subtle environmental changes across the ptb

early triassic conodonts of jiarong nanpanjiang basin southern guizhou province south china abstract jiarong huishui county guizhou province south china is a key locality for the study of the early triassic recovery after the end permian mass extinction the size reduction of conodonts at the smithian spathian transition was first documented in jiarong and it is also a locality that contributes to the documentation of the early triassic paleo seawater temperatures in the jiarong sections thirteen conodont zones were identified for the early triassic in ascending order they are hindeodus parvus zone hindeodus sosioensis zone clarkina krystyni zone neoclarkina discreta zone neospathodus cristagalli eurygnathodus costatus assemblage zone novispathodus waageni eowaageni zone novispathodus waageni waageni zone discretella discreta zone pachycladina parachirognathus assemblage zone novispathodus pingdingshanensis zone icriospathodus collinsoni zone triassospathodus homeri zone triassospathodus triangularis zone these conodont zones in the jiarong sections improve the global correlation of early triassic sections and also provide better regional age constraints in an area that is important for studies of recovery from the extinction based on the first appearance of nv waageni eowaageni the induan olenekian boundary is recognized at 3 6 m above the base of the jiarong iii section the dominance of blade shaped segminate conodonts was replaced by gondola shaped segminiplanate conodonts twice the first time was in the late griesbachian and the second time was in the early spathian the dominance of segminiplanate conodonts probably indicates that the deeper seawater environment became more oxygenated during the late griesbachian and early spathian for short time intervals as it is believed that the griesbachian segminiplanate conodonts favored deeper oxygenated water habitats a new genus spathogondolella gen nov and a new species spathogondolella jiarongensis sp nov have been recognized

marine productivity changes during the end permian crisis and early triassic recovery abstract the latest permian mass extinction lpme coincided with major changes in the composition of marine plankton communities yet little is known about concurrent changes in primary productivity earlier studies have inferred both decreased and increased productivity in marine ecosystems immediately following the end permian crisis here we assess secular and regional patterns of productivity variation during the crisis through an analysis of the burial fluxes of three elemental proxies total organic carbon toc phosphorus p and biogenic barium babio primary productivity rates appear to have increased from the pre crisis late permian through the early triassic in many parts of the world although the south china craton is unusual in exhibiting a pronounced decline at that time most of the 14 permian triassic study sections show concurrent increases in sediment bulk accumulation rates suggesting two possible influences linked to subaerial weathering rate changes 1 intensified chemical weathering resulting in an increased riverine flux of nutrients that stimulated marine productivity and 2 intensified physical weathering leading to higher fluxes of particulate detrital sediment to continental shelves thus enhancing the preservation of organic matter in marine sediments an additional factor especially in the south china region may have been the intensified recycling of bacterioplankton derived organic matter in the ocean surface layer reducing the export flux rather than primary productivity per se the ecosystem stresses imposed by elevated fluxes of nutrients and particulate sediment as well as by locally reduced export fluxes of organic matter may have been important factors in the 2 to 5 million year long delay in the recovery of early triassic marine ecosystems

an intercalibrated triassic conodont succession and carbonate carbon isotope profile kamura japan abstract the kamura section located in the chichibu belt of kyushu island in southern japan contains a succession of uppermost permian to upper triassic shallow marine atoll sediments from the mid panthalassic ocean in the present study carbonate microfacies conodont biostratigraphy and carbonate carbon isotopes were analyzed making it possible to construct a detailed biochronological framework for the triassic of the central panthalassic region a total of 14 conodont zones are recognized from the uppermost changhsingian to the upper norian the lower triassic contains the hindeodus parvus isarcicella isarcica and h postparvus zones griesbachian the neospathodus dieneri zone dienerian and the novispathodus ex gr waageni parachirognathus zone smithian while no evidence of the upper lower triassic spathian substage was recovered at kamura the overlying middle triassic section consists of the chiosella ex gr timorensis cratognathus paragondolella ex gr alpina pg ex gr excelsa budurovignathus hungaricus and b mungoensis zones followed in the upper triassic by the quadralella tadpole gladigondolella malayensis q lobata q carpathica primatella cf orchardi pr permica epigondolella rigoi pg hallstattensis and e ex gr bidentata norigondolella steinbergensis zones the exact stratigraphic intervals present at kamura were refined through intercalibration of the conodont biozonation data with its 13ccarb profile which shows a characteristic series of negative and positive excursions that correspond to well established global reference profiles the permian triassic boundary is placed 0 20 m above the mitai kamura formation contact a reference datum corresponding to the end permian extinction horizon 0 m based on the first appearance of h parvus and the olenekian anisian boundary is placed 17 60 m above the reference datum based on the first appearance of ch ex gr timorensis kamura carbonates were assigned to six fabric types and 17 microfacies the microfacies succession records a deepening immediately following the end permian mass extinction a strong shallowing during the mid to late smithian development of an unconformity spanning the entire spathian and minor sea level fluctuations during the middle and late triassic the spathian unconformity is attributed to a eustatic fall related to a sharp cooling event at or close to the smithian spathian boundary that exposed the kamura atoll the subsequent resumption of shallow marine sedimentation in the earliest middle triassic was probably due to continued thermal subsidence of the oceanic crustal basement beneath the atoll the present work is the most complete analysis to date of the conodont biostratigraphic carbon isotope chemostratigraphic and eustatic records of the triassic system in the central panthalassic ocean and should serve as a regional reference standard in the future

pyrite framboid study of marine permian triassic boundary sections a complex anoxic event and its relationship to contemporaneous mass extinction size analysis of pyrite framboids has been undertaken on epicontinental permian triassic boundary sections throughout the world in order to evaluate the intensity and duration of anoxia mid paleolatitude sections from the margins of the boreal spitsbergen greenland and neotethyan oceans western australia reveal intense anoxia throughout the permian triassic boundary interval with euxinic conditions frequently developing and dysoxia encountered even in relatively shallow water settings above storm wave base at equatorial paleolatitudes weakly oxygenated dysoxic conditions are widely developed in a broad range of water depths including those shallow enough to produce oolite deposition although euxinia was rare western and eastern tethyan locations re veal a complex and unstable redox history anoxia in the hindeodus praeparvus zone was replaced by oxygenated facies in the permian triassic boundary interval h changxingensis to h parvus zones oxygen poor deposition returned during the succeeding isarcicella isarcica zone the more persistent and intense development of oxygen restriction in cooler water mid paleolatitude sections argues against warming and dissolved oxygen decline as the key cause of permian triassic bound ary anoxia in higher paleolatitudes the ben thic invertebrate extinctions occurred during a prolonged phase of oxygen poor deposition while in equatorial tethyan locations benthic losses occurred at the end of the fi rst anoxic phase in the late h praeparvus zone

conodonts radiolarians and ostracodes in the permian e lert formation loei fold belt indochina terrane thailand conodonts are rare in the permian carbonates of indochina but abundant conodonts and ostracodes have been obtained from turbiditic limestones of the permian e lert formation along with radiolarians from overlying cherts all deposited on the margins of the interplatform nam duk basin conodonts are typically tethyan and are very similar to faunas from sicily and south china they include hindeodus gulloides pseudohindeodus oertlii mesogondolella siciliensis and sweetognathus subsymmetricus which indicate a probable late kungurian roadian age range although a wordian age cannot be excluded m siciliensis which has a high blade and small cusp supposedly typical of warm water conodonts is found in deep 500 m carbonate turbidites in thailand and in very deep deposits in oman and sicily but generally not in shallow water tropical limestones in thailand oman and sicily the chert sequence yields a radiolarian fauna consisting of 11 confidently assigned species of which albaillella asymmetrica a sinuata tormentum delicatum and latentifistula patagilaterata suggest a latest kungurian earliest roadian age deposited at a palaeodepth of c 500 m ostracodes consist of 16 genera and 23 species which belong to shivaella paraberounella carinaknightina paraparchites shemonaella bairdia cryptobairdia bairdiacypris spinocypris pseudobythocypris baschkirina microcheilinella basslerella polycope and cyathus of which shivaella elertensis sp nov chitnarin is newly described the ostracodes are a palaeoecologically mixed assemblage comprising external platform and deeper water forms suggesting that the limestone turbidites were deposited on the proximal part of the slope cyathus caperata and c elliptica show a palaeobiogeographic link to south china

high resolution sims oxygen isotope analysis on conodont apatite from south china and implications for the end permian mass extinction abstract understanding the interplay of climatic and biological events in deep time requires resolving the precise timing and pattern of paleotemperature changes and their temporal relationship with carbon cycle variations and biodiversity fluctuations in situ oxygen isotope analyses of conodont apatite from south china enables us to reconstruct high resolution seawater temperature records across the permian triassic boundary ptb intervals in the upper slope meishan lower slope shangsi and carbonate platform daijiagou and liangfengya settings constrained by the latest high precision geochronological dates and high resolution conodont biozones we can establish the temporal and spatial patterns of seawater temperature changes and assess their potential connections with the carbon cycle disruption and biodiversity decline we find a rapid warming of 10 c during the latest permian earliest triassic that postdated the onset of the negative shift in 13ccarb by 81 kyr thousand years the abrupt decline in 13ccarb by 32 kyr and the onset of mass extinction by 23 kyr which contradicts previous claims that the extreme temperature rise started immediately before or coincided with the onset of mass extinction our new evidence indicates that climate warming was most likely not a direct cause for the main pulse of the end permian mass extinction epme but rather a later participant or a catalyst that increased the pace of the biodiversity decline in addition a prominent cooling is recorded in the earliest changhsingian with the main phase a drop of 8 c in 0 2 ma confined to the lower part of the clarkina wangi zone and synchronous with the positive limb of the carbon isotope excursion cie around the wuchiapingian changhsingian boundary wcb in meishan and shangsi further long term and high resolution studies from other sections are needed to confirm the full contexts and underlying dynamics of the wcb cooling event

determination of sediment provenance at drift sites using hydrogen isotopes and unsaturation ratios in alkenones the large 20 hydrogen isotopic gradient in surface waters of the northwest atlantic ocean is exploited to track changes in the source of alkenones to the bermuda rise sediment drift cultures of the predominant alkenone producing coccolithophorid e huxleyi were grown in deuterium enriched seawater and shown to possess alkenones with a d h ratio that closely tracked the water d h ratio r 2 0 999 n 5 isotopic enrichments with a fractionation factor between 0 732 and 0 775 a hydrogen isotopic depletion of 193 3 n 9 was measured in alkenones from suspended particles relative to seawater in the subpolar and subtropical northwest atlantic ocean this value was used to calculate the water d values in which alkenones from bermuda rise sediment were synthesized and by extension the water mass in which they were produced applying this technique we find that 60 to 100 of the alkenones in late holocene bermuda rise sediment were produced in deuterium depleted subpolar water to the northwest of the drift to reconcile values of the alkenone unsaturation ratio u k 37 a widely used proxy for sea surface temperature with the d values of alkenones in late holocene sediments from the bermuda rise at least three sources of sediment must be invoked a cold very isotopically depleted source almost certain to be the scotian margin a warm moderately isotopically depleted source likely to be the northwestern edge of the subtropical gyre and a cold isotopically enriched source which we hypothesize to be the subpolar waters overlying the main branch of north atlantic deep water flowing southwest from the nordic seas copyright 2005 elsevier ltd paleoclimate records with sufficient length and temporal resolution to study the occurrence and causal mechanisms of abrupt climate change are exceedingly rare rapidly deposited ocean sediments provide the best archive for studying these events through geologic time but such sites in the open ocean are limited to sediment drift deposits such as the bermuda rise in the northwest atlantic using multiple climate proxies in a single core is becoming more common in high resolution pa leoclimate investigations but a major potential concern for this approach arises from the possibility that the fine fraction of sediment e g 63 m and the climate proxies within it may represent conditions far from the deposition site here we propose and test the hypothesis that hydrogen isotope ratios of alkenones a class of lipids from phytoplankton may provide insight into the source of fine grained sediment because of their restricted sources broad geographic distri bution and excellent preservation properties alkenones are of particular interest in the emerging field of compound specific hydrogen isotopic analysis the sedimentary abundances ex tents of unsaturations and isotopic compositions of alkenones provide quantitative and near continuous records we isolated alkenones from cultured unicellular algae haptophyte emil iania huxleyi surface ocean particulate material and open ocean sediments to determine the extent and variability of hydrogen isotopic fractionation in the di tri and tetraunsat urated c37 compounds we then compared the d values of the alkenones in surface sediments between the bermuda rise and the scotian margin above which a large 20 d gradient exists we determined the fractionation between alkenones from suspended particulate samples and the water in which the phytoplanton lived and examined the variability of alkenone d values during the medieval warm period little ice age climate transition cf keigwin 1996 at the bermuda rise

southern california permanent gps geodetic array spatial filtering of daily positions for estimating coseismic and postseismic displacements induced by the 1992 landers earthquake the june 28 1992 m w 7 3 landers california earthquake was the first earthquake to be surveyed by a continuously operating global positioning system gps array the coordinate time series of seven sites are evaluated for station displacements during an interval of 100 days centered on the day of the earthquake we employ a new spatial filtering technique that removes common mode errors from the coordinate time series this approach provides precise estimates of site specific displacements compared to the cumbersome method of analyzing baselines between pairs of stations all sites indicate significant coseismic horizontal displacements of 5 65 mm with uncertainties of 1 2 mm horizontal displacements are in general agreement with elastic dislocation models in particular for sites closer to the epicenter vertical displacements range from 13 to 7 mm with uncertainties of 2 4 mm the observed vertical displacements in all cases show 5 10 mm more subsidence than expected from geodetic and seismic geologic models significant postseismic horizontal displacements totaling 6 2 mm 10 20 of the coseismic displacement are detected at the three sites closest to the epicenter these displacements are modeled as a short term exponential relaxation with a decay time of 22 10 days superimposed on a longer term linear interseismic trend scaling the observed coseismic and postseismic displacements at one of the sites with the distance to the epicenter provides a measure of site strain which agrees well with the direction and magnitude determined from more precise laser strain meter data the time series do not show any detectable preseismic displacements

southern california permanent gps geodetic array error analysis of daily position estimates and site velocities we analyze time series of daily positions estimated from data collected by 10 continuously monitoring global positioning system gps sites in southern california during the 19 month period between the june 28 1992 mw 7 3 landers and january 17 1994 mw 6 7 northridge earthquakes each time series exhibits a linear tectonic signal and significant colored noise spectral power at frequencies in the range 5 yr 1 to 0 5 d 1 is dominated by white noise or possibly fractal white noise and is several orders of magnitude higher than what would be expected from random walk noise in this short period range attributed by others to geodetic monument motions estimating a single slope for the time series power spectra suggests fractal white noise processes with spectral indices of about 0 4 site velocity uncertainties assuming this fractal white noise model are 2 4 times larger than uncertainties obtained assuming a purely white noise model a combination white noise plus flicker noise spectral index of 1 model also fits the data and suggests that the velocity uncertainties should be 3 6 times larger than for the white noise model we cannot adequately distinguish between these two noise models nor can we rule out the possibility of a random walk signal at the lowest frequencies these questions await the analysis of longer time series in any case reducing the magnitude of low frequency colored noise is critical and appears to be best accomplished by building sites with deeply anchored and braced monuments otherwise rate uncertainties estimated from continuous gps measurements may not be improved significantly compared to those estimated from infrequent campaign mode measurements

toward a unified science of the earth s surface opportunities for synthesis among hydrology geomorphology geochemistry and ecology 1 the earth s surface is shaped by the interaction of tectonics water sediment solutes and biota over a wide range of spatial and temporal scales and across diverse environments development of a predictive science of earth surface dynamics integrates many disciplines and approaches including hydrology geomorphology ocean and atmospheric science sedimentary and structural geology geochemistry and ecology this paper discusses challenges opportunities and a few example problems that can serve as pathways toward this integration

stratigraphy biostratigraphy and c isotopes of the permian triassic non marine sequence at dalongkou and lucaogou xinjiang province china abstract measured lithostratigraphic sections of the classic permian triassic non marine transitional sequences covering the upper quanzijie wutonggou guodikeng and lower jiucaiyuan formations at dalongkou and lucaogou xinjiang province china are presented these measured sections form the framework and reference sections for a range of multi disciplinary studies of the p t transition in this large ancient lake basin including palynostratigraphy vertebrate biostratigraphy chemostratigraphy and magnetostratigraphy the 121 m thick wutonggou formation at dalongkou includes 12 sandstone units ranging in thickness from 0 5 to 10 5 m that represent cyclical coarse terrigenous input to the lake basin during the late permian the rhythmically bedded mudstone dominated guodikeng formation is 197 m and 209 m thick on the north and south limbs of the dalongkou anticline respectively and 129 m thick at lucaogou based on limited palynological data the permian triassic boundary was previously placed approximately 50 m below the top of this formation at dalongkou this boundary does not coincide with any mappable lithologic unit such as the basal sandstones of the overlying jiucaiyuan formation assigned to the early triassic the presence of multiple organic 13c isotope excursions mutant pollen and multiple algal and conchostracan blooms in this formation together with late permian palynomorphs suggests that the guodikeng formation records multiple climatic perturbation signals representing environmental stress during the late permian mass extinction interval the overlap between the vertebrates dicynodon and lystrosaurus in the upper part of this formation and the occurrence of late permian spores and the latest permian to earliest triassic megaspore otynisporites eotriassicus is consistent with a latest permian age for at least part of the guodikeng formation palynostratigrahic placement of the permian triassic boundary in the junggar basin remains problematic because key miospore taxa such as aratrisporites spp are not present palynomorphs from the guodikeng are assigned to two assemblages the youngest from the upper 100 m of the formation and the overlying jiucaiyuan formation contains both typical permian elements and distinctive taxa that elsewhere are known from the early triassic of canada greenland norway and russia the latter include spores assigned to pechorosporites disertus lundbladispora foveota naumovaspora striata decussatisporites mulstrigatus and leptolepidites jonkerii while the presence of devonian and carboniferous spores and early permian pollen demonstrate reworking is occurring in the guodikeng assemblages the sometimes common occurrence of scutasporites sp cf scutasporites unicus and other pollen suggests that the late permian elements are in place and that the upper assemblage derives from a genuine transitional flora of early triassic aspect in the junggar basin biostratigraphic data and magnetostratigraphic data indicate that the permian triassic boundary gssp level is in the middle to upper guodikeng formation and perhaps as high as the formational contact with the overlying jiucaiyuan formation

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

seismicity and structure of akutan and makushin volcanoes alaska using joint body and surface wave tomography joint inversions of seismic data recover models that simultaneously fit multiple constraints while playing upon the strengths of each data type here we jointly invert 14 years of local earthquake body wave arrival times from the alaska volcano observatory catalog and rayleigh wave dispersion curves based upon ambient noise measurements for local vp vs and hypocentral locations at akutan and makushin volcanoes using a new joint inversion algorithm the velocity structure and relocated seismicity of both volcanoes are significantly more complex than many other volcanoes studied using similar techniques seismicity is distributed among several areas beneath or beyond the flanks of both volcanoes illuminating a variety of volcanic and tectonic features the velocity structures of the two volcanoes are exemplified by the presence of narrow high vp features in the near surface indicating likely current or remnant pathways of magma to the surface a single broad low vp region beneath each volcano is slightly offset from each summit and centered at approximately 7 km depth indicating a potential magma chamber where magma is stored over longer time periods differing recovery capabilities of the vp and vs data sets indicate that the results of these types of joint inversions must be interpreted carefully

ground deformation associated with the march 1996 earthquake swarm at akutan volcano alaska revealed by satellite radar interferometry in march 1996 an intense swarm of volcano tectonic earthquakes 3000 felt by local residents mmax 5 1 cumulative moment of 2 7 1018 n m beneath akutan island in the aleutian volcanic arc alaska produced extensive ground cracks but no eruption of akutan volcano synthetic aperture radar interferograms that span the time of the swarm reveal complex island wide deformation the western part of the island including akutan volcano moved upward while the eastern part moved downward the axis of the deformation approximately aligns with new ground cracks on the western part of the island and with holocene normal faults that were reactivated during the swarm on the eastern part of the island the axis is also roughly parallel to the direction of greatest compressional stress in the region no ground movements greater than 2 83 cm were observed outside the volcano s summit caldera for periods of 4 years before or 2 years after the swarm we modeled the deformation primarily as the emplacement of a shallow east west trending north dipping dike plus inflation of a deep mogi type magma body beneath the volcano the pattern of subsidence on the eastern part of the island is poorly constrained it might have been produced by extensional tectonic strain that both reactivated preexisting faults on the eastern part of the island and facilitated magma movement beneath the western part alternatively magma intrusion beneath the volcano might have been the cause of extension and subsidence in the eastern part of the island we attribute localized subsidence in an area of active fumaroles within the akutan caldera by as much as 10 cm during 1992 1993 and 1996 1998 to fluid withdrawal or depressurization of the shallow hydrothermal system

recurrent biotic rebounds during the early triassic biostratigraphy and temporal size variation of conodonts from the nanpanjiang basin south china eleven conodont zones are established for the lower triassic of the motianling section in the nanpanjiang basin south china detailed size measurements on 2244 p1 conodont elements demonstrate dynamic size variation patterns during the early triassic that are calibrated to the early triassic timescale and conodont zonation correlation of conodont size variation with various environmental indicators shows that these size changes are primarily controlled by rapidly changing and episodic environmental conditions and ecological recovery in the aftermath of the end permian mass extinction decreasing size trends occur in the early griesbachian late griesbachian and at the smithian spathian boundary episodes of size increase rebounds occur in the middle griesbachian induan olenekian boundary and middle late spathian the observed temporal size variations indicate that conodont animals were significantly affected by rapidly changing environmental conditions mainly temperature and redox conditions during the early triassic and recurrent size increases rebounds occurred during periods of environmental and climatic amelioration climatic cooling and oxygenation demonstrating a complicated recovery history of marine ecosystems in the aftermath of the largest phanerozoic biotic crisis supplementary material data for all species are available at https doi org 10 6084 m9 figshare c 4528616

first record of hindeodus isarcicella population in lower triassic of slovenia abstract this study documents the permian triassic boundary in the iri area of western slovenia a paleontological study of the lukac section northwest of iri resulted in the recovery of a variety of microfossils this report documents the conodont fauna recovered from the section this is the first report of the hindeodus isarcicella population in slovenia and it provides important new biostratigraphic data for the definition of the permian triassic boundary hindeodus parvus has been recovered and its first appearance in the lowermost werfen formation indicates the base of the triassic period based on the conodont taxa h parvus hindeodus typicalis hindeodus sp isarcicella isarcica isarcicella lobata isarcicella staeschei isarcicella turgida and isarcicella sp a at least three faunas can be distinguished and they make possible a worldwide correlation