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

late permian changhsingian conodont biozonation and the basal boundary ganxi section western hubei province south china four neogondolellid conodont interval zones were recognized across the changhsingian stage at ganxi section western hubei province south china they are in ascending order the clarkina wangi zone the clarkina changxingensis changxingensis zone the clarkina changxingensis yini zone and the clarkina meishanensis meishanensis zone the present study suggests that the base of the changhsingian can be defined by the first appearance datum fad of clarkina wangi within an evolutionary lineage from clarkina longicuspidata to clarkina wangi the wuchiapingian changhsingian boundary can be placed at the base of bed 104 at ganxi section south china because of the first occurrence of clarkina wangi

climate warming in the latest permian and the permian triassic mass extinction high resolution oxygen isotope records document the timing and magnitude of global warming across the permian triassic p tr boundary oxygen isotope ratios measured on phosphate bound oxygen in conodont apatite from the meishan and shangsi sections south china decrease by 2 in the latest permian translating into low latitude surface water warming of 8 c the oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates suggesting that the addition of isotopically light carbon to the ocean atmosphere system by siberian traps volcanism and related processes resulted in higher greenhouse gas levels and global warming the major temperature rise started immediately before the main extinction phase with maximum and harmful temperatures documented in the latest permian meishan bed 27 the coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems in addition very warm climate conditions in the early triassic may have played a major role in the delayed recovery in the aftermath of the permian triassic crisis

radioisotopic and biostratigraphic constraints on the classical middle upper permian succession and tetrapod fauna of the moscow syneclise russia

did the great dying of life take 700 k y evidence from global astronomical correlation of the permian triassic boundary interval the cause of the great permian triassic p t boundary mass extinctions remains unknown a crucial step in identifying the cause involves a precise timing of the mass extinction interval mei in order to reconstruct the pattern of biotic evolution and the chronologic record of potential triggers here we present an estimate of the p t boundary mei duration based on astronomical tuning of multiple cyclic sedimentary records magnetic susceptibility data from shangsi southern china provide evidence for strong 405 k y orbital eccentricity forcing throughout the p t boundary interval radioisotope dating combined with 405 k y tuning provides an absolute time scale through the p t boundary interval at unprecedented high resolution an estimated 700 k y duration for the mei at shangsi is supported by eccentricity tuned estimates of four other sections in china and austria in addition at shangsi the onset of mass extinction occurred shortly following a coincidence of minima in the observed 1 5 m y 405 k y and 100 k y cycles a change in the magnetic susceptibility response to astronomical forcing occurred just prior to the onset of extinction with reduced 100 k y scale cyclicity continuing into the early triassic for more than 2 m y

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

revised conodont based integrated high resolution timescale for the changhsingian stage and end permian extinction interval at the meishan sections south china abstract meishan section d with the wuchiapingian changhsingian and permian triassic gssps has become the most intensively studied section because it records the whole process of the largest biological extinction during the phanerozoic numerous data including high precision geochronology multiple isotope chemostratigraphy magnetostratigraphy and high resolution multiple fossil biostratigraphy have been determined during the last decade conodonts are very abundant in the changhsingian stage at the meishan sections and their biostratigraphy together with geochronologic and multiple geochemical data provide a basic temporal framework to calibrate the end permian mass extinction and realize global correlation between sections at meishan and those in other regions of the world however major discrepancies exist in various previous studies of conodonts from the meishan sections many different authors have documented very different species ranges based on different concepts and approaches of taxonomy we here employ a sample population approach to revise and refine the high resolution conodont biostratigraphic framework for the changhsingian stage and end permian mass extinction interval across the permian triassic boundary ptb at the meishan sections eight zones are recognized from the latest wuchiapingian to the basal triassic they are in ascending order the clarkina longicuspidata zone in the uppermost wuchiapingian the clarkina wangi zone clarkina subcarinata zone clarkina changxingensis zone clarkina yini zone clarkina meishanensis zone clarkina zhejiangensis hindeodus changxingensis zone in the changhsingian stage and the hindeodus parvus zone in the basal triassic conodont evolutionary lineages for the whole changhsingian are also tentatively established all species are described in detail and growth series of different specimens for valid species are figured as completely as possible the temporal relationship of each conodont zone with geochemical excursions geochronologic calibration and magnetostratigraphical polarity zones are provided which is critical to understand the tempo of the end permian mass extinction

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

late guadalupian to lopingian permian carbon and strontium isotopic chemostratigraphy in the abadeh section central iran abstract the abadeh section well exposed in the hambast valley in central iran has long been one of the most extensively studied sections because of its continuous carbonate dominated strata from lower permian to lower triassic however biostratigraphy and correlation with the equivalent sequences in other regions remain controversial in this paper both carbon isotope excursion 13 c carb and strontium isotope ratio 87 sr 86 sr based on bulk carbonate samples have been measured to serve as chemostratigraphical proxies to estimate the three different chronostratigraphical boundaries in the lopingian at the abadeh section including the permian triassic event pteb the guadalupian lopingian glb and the wuchiapingian changhsingian boundaries wcb these three boundaries are important for understanding the marine biological evolution around this critical interval based on the 13 c excursions the rising trend of 87 sr 86 sr and the value around 0 7073 and the occurrence of microbialite beds the permian triassic event boundary bed 25 at the meishan section is suggested at 0 5 m below the base of the main microbialite bed the glb is suggested at 46 5 m based on the position of the minor 13 c carb negative depletion coupled with the values between 0 7069 and 0 7070 of 87 sr 86 sr and its beginning point of the rising trend which is above the lowest value 0 7068 of 87 sr 86 sr ratio in the paleozoic the relationship between section thickness and their high resolution depositional age projecting age is interpolated for the whole lopingian using locally weighted regression scatter plot smoother lowess of strontium isotopic ratio based on the negative 13 c excursion and the value 0 7072 of 87 sr 86 sr ratio the wcb is estimated at 1 m above the lithologic boundary between unit 6 and unit 7 much lower than the boundary defined by previous conodont biostratigraphy but similar to other index fossils this boundary is projected as ca 254 6 ma in 87 sr 86 sr age projecting model and is close to zircon u pb dating age from south china

oceanic redox evolution across the end permian mass extinction at shangsi south china abstract the end permian mass extinction epme was the most severe extinction event of the phanerozoic to investigate oceanic redox conditions around the epme we conducted a series of geochemical analyses including iron speciation trace element geochemistry total organic carbon toc and nitrogen isotopes of kerogen 15nkero around the epme at the shangsi section south china three intervals with different redox conditions can be distinguished based on iron speciation during the first interval early and middle changhsingian bottom waters were pervasively euxinic in the second interval late changhsingian and the epme bottom water fluctuated between oxic and anoxic but non sulfidic conditions with the oxic mode becoming increasingly predominant over time during the third interval following the epme bottom waters appeared to have been consistently anoxic although again not pervasively euxinic this redox history is supported by enrichments in the authigenic fraction of redox sensitive elements these relatively high 15nkero values 1 0 corresponding with changhsingian euxinia suggest reducing bottom waters did not impinge on the photic zone the shift to values near 0 within and above the epme indicates an ecological expansion of diazotrophs stratigraphic trends of nixs cdxs pxs and toc indicate that primary productivity was highest in the first interval coinciding with euxinic bottom water then decreased during the lower part of interval 2 and remained at low level through the remainder of the studied section the temporal relationship between redox condition and primary productivity suggests that euxinia was supported by high productivity and carbon export in the early changhsingian the expansion of n2 fixation coincides closely with the previously documented warming of the ocean surface at shangsi and may be related to reduced oceanic circulation and suppressed vertical mixing the temporal distribution of deepwater anoxia and euxinia suggests that they were not primary causes for the extinction of benthos at shangsi

experimental determination of elastic constants of oshima granite barre granite and chelmsford granite employing polyhedral specimens longitudinal and shear wave velocities were measured in various directions of propagation and polarization sound velocities showed orthorhombic elasticity in all of the rocks with the assumption of orthorhombic elasticity the nine stiffness constants of all samples were determined by the sound velocities under atmospheric pressure and kelvin christoffel s equation twenty one stiffness constants of oshima granite determined without assuming any symmetry also showed orthorhombic features directions of the symmetry axes agreed well with the orientation of the preexisting cracks akaike s information criterion showed that the orthorhombic model with nine nonzero elastic stiffnesses was better than the model having 21 nonzero elastic stiffnesses for oshima granite the polyhedrons of two granitic rocks were loaded under hydrostatic pressure all components of the stiffness constants increased with pressure under pressure of more than 120 mpa two granitic rocks were approximately isotropic the results show that oriented microcracks are mainly responsible for the orthorhombic elasticity of the granitic rocks and also indicate that dry oriented cracks can not be a cause for the anisotropic elasticity of granites at depths of more than 6 8 km

the permian triassic boundary event a geochemical study of three chinese sections abstract trace elements were determined in two well documented chinese permian triassic p tr boundary sections meishan and shangsi and in a new section liangfenya iridium concentrations range from 3 to 87 pg g at or below levels in common sedimentary rocks the results contrast with previous reports of high ir concentration in the meishan and shangsi sections and offer no support to suggestions of a major meteoroid impact at the end of the permian a notable feature in each of these widely separated p tr sections 500 1500 km is the existence of 2 5 light colored clay layers at and near the boundary these clay layers are strongly enriched in cs zr hf ta and th and depleted in cr co and ir indicating that they are altered ash apparently from the same massive silicic volcanic eruptions we estimate the magnitude of these eruptions to be a few thousand km3 of magma a volume comparable to the great toba eruption

the marnet radiolinked seismometer network spanning the marmara sea and the seismicity of western turkey summary the marnet telemetered seismic network spanning the marmara sea supplements the isk network of conventional seismic stations and increases the resolution for monitoring the seismicity in western turkey seismicity maps for the period 1976 to 1981 display pronounced swarm type activity where small earthquakes cluster in the same locality three types of seismic activity can be identified and related to present day tectonic deformation normal earthquake episodes associated with the main line of the north anatolian fault continuous swarm activity but with marked fluctuations and bursts of activity in the tensional regime south of a line from izmir to adapazari and continuous activity with only minor fluctuations within the marmara region as it is sheared by the westward movement of the main anatolian plate

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

a delayed end permian extinction in deep water locations and its relationship to temperature trends bianyang guizhou province south china new collecting at a biostratigraphically highly resolved deep water section in south china reveals a brief a few tens of thousands of years but measurable delay in extinction timing relative to contemporaneous shallower water sections foraminifers and conodonts in the bianyang section show a sharp extinction at the top of hindeodus changxingensis zone whilst in shallower sections such as the well known meishan gssp location these taxa have a major extinction pulse at the top of the preceding clarkina yini zone the main end permian extinction coincides with the onset of a negative carbon isotope excursion whilst the deep water extinctions occur around the lowpoint of the carbon isotope curve rapidly increasing surface water temperatures and the effects of deep water anoxia were all important during the crisis although it is noteworthy that regression and extinction also show a close temporal link

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

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

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

the effects of crack anisotropy on the hypocentral locations of local earthquakes summary exact modelling of the earthquake location process in regions of dilatancy anisotropy shows that failure to take account of the velocity anisotropy in the determination of local hypocentres can result in erroneous and misleading locations in particular the locations can indicate spurious migrations of foci from the true epicentral positions and the true depths of foci these spurious locations may indicate planes of hypocentres deviating from the true fault plane observations of such phenomena have been noted several times in the literature however once the anisotropic model is known a simple location program incorporating the anisotropic velocity variations permits accurate location of local earthquakes using p and first s wave arrival times

earthquake prediction a new physical basis summary subcritical crack growth in the laboratory occurs slowly but progressively in solids subjected to low stresses at low strain rates the cracks tend to grow parallel to the maximum compressive stress so that when this stress is aligned over a large enough region the cracks will also be aligned and possess effective seismic anisotropy it is suggested that such subcritical crack growth produces extensive dilatancy anisotropy eda throughout earthquake preparation zones this process is a possible driving mechanism for earthquake precursors observed at substantial distances from impending focal zones and provides in the shear wave splitting which has been observed in several seismic regions a possible technique for monitoring the build up of stress before earthquakes

evaluation of anisotropy by shear wave splitting the polarizations of three component shear wavetrains carry unique information about the internal structure of the rock through which they pass specifically commonly observed shear wave splitting may contain information about the orientation of crack distributions this information cannot usually be recovered from shear waves recorded at the free surface because of interference with the interaction of the shear wave with the surface even for nearly vertical incidence however shear wave splitting in synthetic three component vertical seismic profiles in some cases may be interpreted directly in terms of the direction of strike of vertical cracks because the human eye is not skilled at identifying the phase relationships between three component seismograms played out conventionally as parallel time series the polarizations are displayed in orthogonal sections of the particle displacements to facilitate recognition and evaluation of the shear wave splitting estimating the orientations of cracks an

shear wave polarizations near the north anatolian fault i evidence for anisotropy induced shear wave splitting summary the turkish dilatancy projects tdp1 in 1979 and tdp2 in 1980 recorded small earthquakes near the north anatolian fault with closely spaced networks of three component seismometers in order to investigate the possibility of diagnosing dilatancy from its effects of shear wave propagation this paper examines the polarizations of shear wavetrains recorded in the shear wave window immediately above the earthquake foci abrupt changes in the orientation and or ellipticity of the shear wave polarizations are almost always observed during the first few cycles following the initial shear wave arrival on each seismogram the horizontal projections of the polarizations of the first shear wave arrivals at any given station show nearly parallel alignments with approximately the same orientations at each of the recording sites with one exception it is difficult to explain this uniform alignment over a wide area in terms of scattering at the irregular surface topography or by earthquake focal mechanisms we demonstrate that the shear wave splitting is likely to be the result of anisotropy in the region above the earthquake foci which could produce polarizations displaying the observed alignments the temporal change of the azimuth of alignment observed at one locality between 1979 and 1980 may be due to the release of a local stress anomaly by a very near earthquake

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

changes in the global carbon cycle occurred as two episodes during the permian triassic crisis coeval records of ocean atmosphere and terrestrial change are crucial to understanding the pattern and causes of global mass extinction across the permian triassic boundary ptb however relationships among changes in different settings remain largely unclear primarily due to the challenges associated with the correlation among disparate records here we compare marine carbon isotopic records with marine and terrestrial environmental and biotic events recorded in sediments from the meishan ptb section of south china time scaled carbonate carbon isotopes exhibit two gradual major shifts across the ptb at meishan and these are duplicable elsewhere around the tethys ocean the two shifts are associated with two episodes of enhanced terrestrial weathering indicated by an increased abundance of 13 c enriched moretanes relative to hopanes and an elevated abundance of black carbon fragments key marine events previously reported for the ptb including photic zone euxinia faunal mass extinction and cyanobacterial expansion also occur as two episodes coinciding with both of the progressive shifts to negative 13 c values and enhanced weathering the temporal sequence of the duplicable events suggests that the biotic crisis was a consequence of prolonged and episodic changes in the marine and continental systems and argues against an extraterrestrial impact as the main cause

effects of the free surface on shear wavetrains summary the behaviour of shear waves is of great importance in identifying and investigating seismic anisotropy in the earth however shear wavetrains recorded at the earth s surface do not always reflect the motion at depth introducing practical problems of interpretation shear wavetrains incident on the surface of an isotropic half space at angles less than critical about 35 are broadly preserved but at greater angles substantial distortions can occur for stations situated close to the source as in local earthquake studies the local sp phase a radially polarized precursor to s may occur the behaviour at the surface of an anisotropic half space is further complicated by the divergence of phase and energy propagation vectors all of these complications suggest that detailed seismogram modelling is essential to any study of shear wave propagation in the earth and in particular to investigations of anisotropy induced shear wave splitting

timing of the permian triassic biotic crisis implications from new zircon u pb age data and their limitations abstract the most profound biotic crisis in the earth s history causing the near extinction of both terrestrial and marine life occurred at the end of the permian period about 253 myr ago and marks the paleozoic mesozoic era boundary the cause of this event is still a matter of vigorous debate with both brief and catastrophic as well as gradual mechanisms having been proposed similar to a recent landmark study this study uses the u pb method on zircons from the uppermost permian lowermost triassic ash fall deposits at meishan zhejiang province se china in order to examine time and rate constraints for these events the results of both this study and previous work show that for these ash layers the effects of pb loss are combined with varying amounts and sources of inheritance resulting in an age scatter which prohibits the extraction of a statistically robust age in many cases though the effects of pb loss on the zircons analyzed in this study were reduced by leaching the grains in hydrofluoric acid as opposed to commonly applied air abrasion prior to analysis the presence within a single ash layer of multiple generations of older xenocrysts in many cases only slightly older than the depositional age has made quantitative interpretation even more difficult when these combined phenomena bias individual zircon ages by less than a percent they are extremely difficult to deconvolute and if multi grain analyses are used can become impossible to recognize because of the resulting age averaging monte carlo simulations using actual measurements of individual zircon crystals show that age excursions due to pb loss and xenocrystic contamination for the meishan bentonites are easily homogenized to the point of undetectability when replicate analyses of multi grain zircon samples are compared thus this study uses only high precision analyses of single crystals whether from our work or that of previous studies three main conclusions have emerged first our data require a significant increase in the age of the permian triassic boundary by more than 2 myr compared to the previous study which shifts the age to a value older than 253 ma second neither our data nor those from previous work can confirm or negate the possibility of a very abrupt biotic crisis third even large suites of very high quality single zircon u pb analyses for these tuffs cannot in most cases yield objective reliable and robust dates with accuracies at the sub myr level though the temptation to perform arbitrary selection of subsets of the analyses for that purpose is almost irresistible the last conclusion is not an indictment of zircon u pb dating in general other rocks and other zircon populations can and do behave very differently and further technical advances will likely improve our ability to prepare grains or sub grains of adequately enhanced quality for analysis consequently the results of the present study strongly suggest that for problems requiring time scale accuracy inferences from zircon u pb dating must be based on sufficiently large suites of single crystal or crystal domain high precision analyses

shift in the paradigm for gssp boundary definition abstract for over 200 years the use of biotic events as the basis for the establishment of chronostratigraphic boundaries has been the only approach successfully utilized for international and national chronostratigraphy the traditional biostratigraphic method provides relatively high resolution averaging 1 ma or sometimes less this biochronological evolutionary approach to the global boundary stratotype section and point gssp utilizes biotic primary markers pm with a few exceptions encompasses the integrated pm and other non pm markers as the general principles for defining gssp boundaries and is a reasonably reliable mechanism for global correlation and a relatively stable international geologic time scale igts the biotic pm s however possessed several serious restrictions the nature of biological taxonomy climatic sedimentary environmental and directly applicable within the tropics subtropics only biotic evolution and radiogenic isotopes are the only systems in geologic time that encompass the direction of time the latter possessed less restrictions than the former the recent tendency to define gssp s utilizing magnetic chrons climatic events and geochemistry may work in the cenozoic but is useless in the mesozoic and older sediments because their cyclic nature repeatedness and the need for a second directional in time index biostratigraphic or radioisotopic to place the pm in the right position within the scale i propose here to utilize volcanic ash beds as the best primary marker in geologic chronostratigraphy the u pb system is one of the most dependable of the geochronologic systems because it relies on a simple and non interpretive radioisotopic decay constant the ash bed gssp as a lithological horizon is universal for the gssp definition and can be correlated as an age in any facies marine lagoon and continental regardless of paleoclimatic zones paleoceanographic geochemical and most other geological factors even moderate level metamorphism 900 does not affect the u pb dating of zircons the gssp at the base of a volcanic ash bed primary marker could be established in a short working time and these ash beds can be integrated with the existing as well as new biostratigraphic geochemical magnetostratigraphic and astronomical data secondary markers to create a robust accurate and highly useable time scale several potential gssp s that could be established with the volcanic ash beds close to the traditional and or historical boundaries serve as examples for this approach and include devonian carboniferous moscovian kasimovian kasimovian gzhelian and sakmarian artinskian boundaries

evolution of a plume influenced source to sink system an example from the coupled central emeishan large igneous province and adjacent western yangtze cratonic basin in the late permian sw china abstract source to sink paleogeography in a time constrained sequence stratigraphic framework has been reconstructed for the non marine to marine transitional lopingian strata late permian in the western yangtze cratonic basin wycb and the adjacent inner zone of the emeishan large igneous province elip in order to reveal the evolution of a mantle plume influenced cratonic basin the lopingian coal bearing strata can be subdivided into seventeen 4th order sequences and three 3rd order composite sequences representing 6 76 myr paleogeographic reconstructions of the wycb demonstrate the existence of n s trending terrestrial transitional and marine facies belts distributed west to east away from the central elip geomorphological analysis indicates that the western boundary of the source area coincided with the major axis of the uplifted central elip based on sediment flux estimates and modeling bqart model relief of the central elip increased from near sea level in the earliest late permian and reached equilibrium at about 200 m in the latest permian sediment volume backfilling analysis indicates that total tectonic uplift of the central elip in the late permian was more than 500 m evolution of the coupled central elip and wycb can be subdivided into three stages pre eruptive uplift stage pre and syn eruptive subsidence stage and syn and post eruptive uplift stage post eruptive basin filling was controlled by sediment supply that was related to tectonic uplift drainage topography and climate change and basin accommodation that was related to sea level fluctuations and plume induced syn sedimentary tectonics

stresses and pressures at the quartz to coesite phase transformation in shear deformation experiments coesite was found in quartz aggregates experimentally deformed at confining pressures of 1 0 1 5 gpa and temperatures between 600 c and 900 c the confining pressure pc and in most cases the mean stress m of the experiments were below those of the quartz to coesite phase transformation yet coesite formed when the maximum principal stress 1 was within the p t range of the coesite stability field in one sample the euhedral coesite grains were corroded indicating that coesite started to transform back to quartz it is inferred that this sample started to deform with 1 above the quartz to coesite phase transformation and with on going deformation 1 decreased to values in the quartz stability field due to strain weakening in all cases 1 triggered the quartz to coesite reaction as well as the reverse reaction suggesting that 1 is the critical parameter for the quartz to coesite transformation not pc or m with progressive deformation the coesite laths rotated towards the shear plane as more rigid particles with the sense of shear in case of back reaction new quartz grains exhibit no systematic crystallographic relationship with respect to old coesite the experiments cover different degrees of pressure overstepping different temperatures and different experimental durations at p and t and deformation always enhances the reaction kinetics the observation that 1 is critical for a pressure dependent phase transformation also for reversals poses questions for the thermodynamic treatment of such phase transformations

neotectonics of the marmara sea region of turkey seismological investigations in western anatolia nw turkey have identified linear patterns of earthquake epicentres outlining a wedge shaped block in the area of the marmara sea this block shows different seismic characteristics from the rest of western anatolia and appears to act as a separate tectonic unit earthquake fault plane mechanisms show that the marmara block is being rotated and sheared in order to accommodate the right lateral motion of the north anatolian fault and the extensional tectonics of the southwestern anatolia investigations of the behaviour of seismic shear waves suggest that neotectonic stress aligns water filled microcracks throughout the upper brittle 10 20 km of the crust and that in situ stress directions can be monitored by analysis of shear waves recorded on three component instuments

low latitudinal standard permian radiolarian biostratigraphy for multiple purposes with unitary association graphic correlation and bayesian inference methods abstract the ideal goal of biostratigraphic studies is to make stratigraphic ranges of all species clear and to fix globally synchronous biohorizons as age controls however it is difficult to achieve this goal in simple traditional ways and so a new solution is proposed for permian radiolarian biostratigraphy to achieve this goal including to establish a globally applicable biostratigraphy to estimate the numerical age of biohorizons and to determine stratigraphic ranges at species level all 400 known permian radiolarian species approximately 70 stratigraphic sections and 1560 samples from 350 previously published papers about the low latitude tethys and panthalassa oceans were analyzed issues of permian studies are summarized and a solution is proposed from the cenozoic point of view considering traditional methods as well as successful methods in cenozoic radiolarian studies here we implement newly proposed methods that have never been used for permian radiolarian studies unitary association method uam minimum disordered biohorizon algorithm mdba graphic correlation gc and reiteration estimation rounds rer of these our proposed rer is a new method to predict the probability of the estimated age for a sample by bayesian inference and joint probability both statistical methods as these four methods are applicable to any biostratigraphic study the principals and practical applications of these methods are carefully explained so non specialists can understand the logical procedure as a result 15 unitary association zones uazs are established for the entire permian biostratigraphic scheme by uam the numerical ages of 42 first occurrences fos are estimated from non parametric data from the middle guadalupian middle permian to the uppermost lopingian uppermost permian by mdba and gc and the statistical likelihood uaz ranges of 165 species in the entire permian were obtained using the rer procedure a usability test of our uazs shows that 97 96 of the 933 tested samples from previously published papers are well correlated and without contradiction within the statistical error of cenozoic synchronous biohorizons at 1 4 myr 23 of 42 fos are potentially regarded as synchronous events as the statistical likelihoods of uaz ranges are estimated by bayesian inference these ranges can be updated by anyone

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

analysis of records of local earthquakes the turkish dilatancy projects tdp1 and tdp2 summary this is the introduction to a series of papers analysing records from three component seismometers immediately above a swarm of small earthquakes near the north anatolian fault in turkey the networks were set up to investigate the possibility of estimating dilatancy induced adisotropy by monitoring shear wave splitting in shear waves from local earthquakes as suggested by the hypothesis of extensive dilatancy anisotropy eda these networks were among the first closely spaced digital three component seismometers to be deployed in the shear wave window immediately over a seismic source zone where the polarizations of incident shear waves can be recognized from surface recordings consequently the seismograms display several new phenomena that have not been previously observed 1 the polarizations of almost all shear waves arriving within the shear wave window showed abrupt changes in direction characteristic of shear wave splitting in synthetic seismograms modelling wave propagation through anisotropic rocks 2 the polarizations of the faster split shear waves are in patterns characteristic of propagation through distributions of cracks aligned by the principal axes of stress but not characteristic sf shear waves propagating through isotropic rock from a double couple source oriented by the same stress axes 3 many characteristics of the observed polarization patterns are similar to synthetic polarization diagrams for wave propagation through vertical parallel cracks 4 the orientation of the anisotropy derived from the shear wave polarizations is consistent with the common axes of stress of the fault plane mechanisms 5 the orientation of the shear wave anisotropy is also similar to the orientation of the anisotropy derived independently from inverting p and s wave arrival times and 6 there is some indication of a temporal change in polarization in one locality such as might be expected if a change in a local stress anomaly altered the crack geometry

a refined succession of changhsingian and griesbachian neogondolellid conodonts from the meishan section candidate of the global stratotype section and point of the permian triassic boundary abstract a detailed study of new conodont collections from the changxing formation at the meishan section has resulted in taxonomic refinement of several important neogondolellid species most of the previously erected species are much more strictly redefined mainly based on the denticulation of the holotypes and the stratigraphic ranges attributed to key conodont taxa are modified three new species and two new subspecies all of which are form species are tentatively erected and described mainly for the purpose of taxonomic explanation as a result of the taxonomic refinement six neogondolellid conodont zones are recognized for the changxing formation and the permian triassic boundary interval

comment on quantitative biochronology of the permian triassic boundary in south china based on conodont unitary associations by brosse et al 2016 recently brosse et al 2016 have proposed the use of conodont unitary associations zones uazs to substantially modify the biostratigraphy of the permian triassic transition and to redefine the permian triassic boundary ptb however in our opinion the uaz analysis presented by brosse et al 2016 is based on unreliable taxonomic data sets with unjustified taxonomic re assessments no evidence shows that the uaz approach improves the biozone biostratigraphy currently used to date the ptb

tectonics of the marmara sea region of turkey new evidence from micro earthquake fault plane solutions summary composite and single event fault plane solutions for microearthquakes in the izmit bay area of the marmara sea indicate right lateral strike slip motion and tension on this extension of the north anatolian fault this interpretation is consistent with teleseismically determined fault plane solutions obtained for larger earthquakes on the marmara sea seismic lineation consideration of the microplate geometry of north western turkey inferred from seismicity as well as earthquake mechanisms suggests that the region comprises two seismotectonic units with differing styles of deformation the anatolid structures of south and central western anatolia are undergoing major extension whereas the pontid structures of the marmara sea region are being sheared resulting in a mixed regime of both strike slip and extensional faulting

quantitative stratigraphic correlation of the lower triassic in south china based on conodont unitary associations abstract unitary association method uam analyses of conodont faunas from 28 sections spanning the biggest phanerozoic end permian mass extinction and significant global environmental and ecosystem perturbations during the succeeding early triassic are presented based on 72 conodont species 26 unitary association zones uazs are established for the latest permian to earliest middle triassic of south china these uazs provide quantitative high resolution tools to correlate sequences in the early triassic of south china and to compare and test high resolution conodont biostratigraphy based on interval conodont zones developed over the past three decades our quantitative analyses provide insights on ongoing debates relating to the first appearance datum fad of the conodont hindeodus parvus which is used to place and subsequently correlate the golden spike defining the base of the triassic permian triassic boundary at the base of bed 27c at the gssp meishan d section previous proposals that suggested potential earlier occurrences of h parvus below its fad at meishan section are not supported by our results in deep water sections the first occurrence fo of h parvus lies at the base of uaz 5 at the bianyang section while it lies within uaz 6 at the meishan section this indicates that the earliest occurrence of h parvus in south china is in the bianyang section but this conclusion needs further testing due to the reliance on spot data by the uam anomalously high occurrences of hindeodus in the mingtang section close to the bianyang section further suggests that the bianyang mingtang area may have provided a temporally extended habitable zone for anchignathodontid conodonts stage boundaries currently proposed or established using interval conodont zones locate within or between uazs and are difficult to correlate with carbon isotope curves uazs are useful in helping to define gssps by recognizing which correlations are most robust and in the selection of the most appropriate species and level for gssps

early wuchiapingian cooling linked to emeishan basaltic weathering abstract the last glaciation during the late paleozoic ice age commenced at around the guadalupian lopingian g l boundary and is synchronous with the emplacement of the emeishan large igneous province using ca tims zircon u pb dating we obtained an age of 259 51 0 21 ma for the uppermost tuff from the puan volcanic sequence in the eastern emeishan large igneous province constraining the timing of emeishan volcanism and providing another candidate age for the g l boundary in addition we determined an age of 259 69 0 72 ma for a basal claystone in the immediately overlying longtan formation from a drill core section in southwest south china these ages along with source weathering trends of mudstones from the lower longtan formation and compiled paleotemperature records indicate an earliest wuchiapingian cooling coinciding with the onset of the last permian glaciation this global cooling is associated with positive shifts in both organic and carbonate carbon isotopic records and likely a decrease in atmospheric pco2 a hypothesised causal linkage is proposed in which the rapid post eruptive basaltic weathering of the emeishan province in an equatorial humid belt may accelerate the atmospheric co2 consumption and lead to climate cooling our work supports the long term climate cooling effects of large igneous provinces

high precision u pb zircon age constraints on the guadalupian in west texas usa abstract the guadalupian epoch was characterized by major changes in paleogeography paleoclimate and biodiversity yet the paucity of precise and accurate radioisotopic dates from the guadalupian stages in their type area guadalupe mountains national park in west texas has rendered their calibration inadequate in this study we report high precision u pb zircon geochronology by the ca id tims method from three ash beds 2 internal errors only in the rader member of the bell canyon formation at the back ridge section 262 127 0 097 ma mswd 0 89 n 3 the lower pinery member of the bell canyon formation at the frijole section 264 23 0 13 ma mswd 0 89 n 8 and the basal south wells member of the cherry canyon formation at the monolith canyon section 266 525 0 078 ma mswd 0 62 n 5 the bayesian interpolation statistics method is used to establish an age stratigraphy model that estimates the base of the capitanian to be 264 28 0 16 ma serving as the best age estimate for the capitanian stage at present in addition we review the existing geochronology from the guadalupian series in west texas and seek to propose more precise temporal estimates of guadalupian geological and biological events these data constrain the high frequency sequences of the cherry canyon and bell canyon formations in the guadalupe mountains national park area accordingly the base of the wordian is estimated at 266 9 0 4 ma and the illawarra geomagnetic polarity reversal in west texas at 267 4 0 4 ma to 266 5 0 3 ma the global end guadalupian extinction began in the conodont zone of jinogondolella altudaensis above the base of the reef trail member of the bell canyon formation and might continue to the clarkina postbitteri postbitteri zone in the earliest wuchiapingian the conodonts display a rapid evolutionary rate during this interval this constrains the biotic crisis from ca 260 ma to 259 ma based on our conodont age estimation the emplacement of the emeishan large igneous province elip in south china has been constrained to ca 260 ma to 257 4 ma based on zircon u pb geochronology by the ca id tims method overlapping with the end guadalupian extinction which provides support for the temporal relationship between them additionally the elip persisted into the early wuchiapingian and may have hampered ecosystem restoration during the post extinction interval

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

evolution of permian conodont provincialism and its significance in global correlation and paleoclimate implication the main components of asselian through artinskian conodont faunas found around the world are basically the same and the provincialism is indicated only by less common endemic elements such as gondolelloides and new genus a henderson in north pangea sweetognathus bucaramangus around the equator and vjalovognathus in eastern gondwana provincialism is marked by differences at the species level of mesogondolella neostreptognathodus and sweetognathus during the kungurian and becomes very distinct with differences at the genus level during the guadalupian and lopingian three provinces of permian conodonts referred to as the north cool water province ncwp the equatorial warm water province ewwp and the peri gondwana cool water province gcwp are recognized the ncwp is marked by gondolelloides in the early cisuralian dominance of neostreptognathodus and no or rare sweetognathus in the late cisuralian dominance of merrillina and mesogondolella and absence of sweetognathus in the guadalupian and dominance of merrillina and mesogondolella and absence of iranognathus in the lopingian the ewwp is characterized by the absence of gondolelloides and vjalovognathus in the cisuralian abundance of sweetognathus and pseudosweetognathus in the kungurian late cisuralian jinogondolella and sweetognathus in the guadalupian and clarkina and iranognathus in the lopingian the gcwp is marked by vjalovognathus merrillina in the cisuralian vjalovognathus merrillina and mesogondolella in the guadalupian and vjalovognathus and merrillina in the lopingian mixed faunas are recognized in regions bordering between the ewwp and gcwp including western timor during the artinskian pamirs during the kungurian and the salt range during the guadalupian and lopingian three different conodont zonations are proposed one for each of the three conodont provinces four potential horizons for inter provincial correlation of permian conodonts are recognized they are in ascending order 1 the first appearance of sweetognathus whitei which is closely related to the last occurrence of carboniferous type conodonts such as streptognathodus and adetognathus 2 the first appearance of neostreptognathodus pequopensis 3 the base of the jinogondolella nankingensis zone and 4 the base of the clarkina postbitteri iranognathus erwini zone the spatial and temporal distribution pattern of permian conodonts suggests that temperature is the primary controlling factor evolution of permian conodont provincialism reveals a glaciation during the asselian and sakmarian a global warming during the artinskian a climate cooling in north pangea during the kungurian a continuation of kungurian climate trends in the guadalupian a relatively minor warming during the wuchiapingian a returned cooling in the changhsingian and lower and middle griesbachian and a global warming in the late griesbachian which ended the permian conodont lineage

cyclostratigraphy and astrochronology case studies from china abstract a high precision geologic time scale is the essential key for understanding the earth s evolutionary history and geologic processes astronomical tuning of orbitally forced stratigraphic records to construct high resolution astronomical time scales ats has led to a progressive refinement of the geologic time scale over the past two decades in turn these studies provide new insights regarding the durations and rates of major earth events evolutionary processes and climate changes all of which provide a scientific basis for contextualizing and predicting future global change trends south china hosts some of the best exposed and well dated neoproterozoic through mesozoic stratigraphic sections in the world many of which are suitable for cyclostratigraphy and calibrating the geologic time scale in north china several cenozoic oil bearing basins have deep boreholes with continuous sampling and or well logging that enable derivation of astronomically tuned time scales for an improved understanding of basin evolution and hydrocarbon generation this special issue focuses on case studies of astrochronology and applied cyclostratigraphy research using reference sections within china in this introductory overview we 1 summarize all existing astrochronology studies of the neoproterozoic through cenozoic sections within china that have been used to enhance the international geologic time scale 2 examine briefly the astronomically forced paleoclimate information recorded in various depositional systems and the modern techniques employed to analyze the periodicity of these signals encoded within the sedimentary record and 3 summarize the 20 contributions to this special issue of palaeogeography palaeoclimatology palaeoecology on cyclostratigraphy and astrochronology case studies from china

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

geochronological constraints on post extinction recovery of the ammonoids and carbon cycle perturbations during the early jurassic abstract this paper presents the first quantitative study of the early jurassic recovery of ammonoids after the end triassic mass extinction based on detailed u pb id tims isotope dilution thermal ionization mass spectrometry geochronology from ash bed zircons placed within a clear phylogenetical and biochronological framework at the subzonal and species level this study was triggered by the discovery of a rich peruvian succession of ammonites deposited concomitantly with an unusually large number of ash beds two major phases of rediversification are observed during the psiloceras spelae and angulaticeras zones that correspond to positive peaks in the 13corg curve providing a possible link between biodiversity and the global carbon cycle in the case of the post extinction recovery the development of the earliest hettangian ammonites occurs within the genus psiloceras which begins with the occurrence of p spelae and then explodes into worldwide development of smooth psiloceratids of the psiloceras planorbis group s l this rapid biodiversification likely occurred less than 100 ka after the end triassic crisis the genus psiloceras occupied all the possible ecological niches worldwide from the pacific deep waters to the nw european shallow deposits and also in some rare tethyan occurrences like at germig in tibet this global dispersion allowed the differentiation of the group in several major phyla the schlotheimiidae discamphiceratinae arietitidae and lytocerataceae which were the roots of all other jurassic and cretaceous ammonites

abundance variation of iridium and trace elements at the permian triassic boundary at shangsi in china despite recent searches for anomalous iridium ir concentrations at the permian triassic boundary p tr of marine sediments1 3 no ir above a level of 0 5 p p b parts per 109 has been found detailed event stratigraphical research has revealed a comparatively high platinum group enrichment and geochemical anomalies of trace elements in the p tr boundary clay at meishan changxing county zhejiang province china4 we report here an investigation of ir and trace element abundances in the p tr boundary layer of shangsi section guangyuan county sichuan province fig 1 an ir value of 2 p p b detected in the boundary layer supports the occurrence of an extraterrestrial event at the end of the permian

high resolution δ13ccarb chemostratigraphy from latest guadalupian through earliest triassic in south china and iran large carbon cycle perturbations are associated with the end permian mass extinction and subsequent recovery but late permian lopingian carbon cycle dynamics prior to the mass extinction event remain poorly documented here we present a high resolution 13ccarb chemostratigraphic framework from latest guadalupian to earliest triassic time calibrated with high resolution conodont biostratigraphy and high precision geochronology we observe two large negative excursions in 13ccarb the first in uppermost guadalupian strata and the second at the end of the changhsingian stage and between these events distinctive excursions from the middle wuchiapingian to the early changhsingian the end changhsingian excursion represents a major reorganization of the global carbon cycle associated with the end permian mass extinction however the extent to which the end guadalupian and wuchiapingian changhsingian boundary excursions result from local versus global controls remains unresolved regardless of their underlying causes these three excursions provide chemostratigraphic markers for global correlation of lopingian strata

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

deep borehole log evidence for fractal distribution of fractures in crystalline rock summary sonic velocity and electrical resistivity logs run to a depth of 3 5 km in crystalline rock near the san andreas fault at cajon pass in southern california correlate over scale lengths both small sub metre and large tens to hundreds of metres no such correlations are seen with the more lithologically sensitive natural gamma intensity log the correlation between the sonic velocity and electrical resistivity logs suggests that a non lithologic property of the crystalline rock controls fluctuations in situ fracture intensity is a logical candidate for the controlling rock property the fluctuations of the individual sonic velocity and electrical resistivity logs are examined with the hurst rescaled range parameter over borehole log intervals 1 5 m l 1500 m for log fluctuations arising from a scale invariant physical process the hurst rescaled range scales with data interval as lh 0 h 1 a purely random sequence of in situ fractures produces a scaling exponent h 0 50 fluctuations in the cajon pass sonic velocity and electrical resistivity logs yield h 0 70 evidence that in situ fracture sets tend to occur in clusters rather than at purely random intervals the tendency for fracture clustering over log intervals 1 5 m l 1500 m suggests that fracture formation is a fractal process independent of length scale in which larger fracture intervals form from clustering of numerous smaller fracture intervals seismic reflectivity derived from the borehole sonic velocity log is also scale independent over the range of data intervals 1 5m l 1500 m with a hurst exponent h 0 21 if we associate fracture clustering with crustal fault formation the cajon pass borehole sonic velocity and electrical resistivity logs predict that crustal faults scale fractally with fractal dimension d 2 30 the equivalent b value for earthquake size distribution is b d 2 1 15 on this hypothesis observed b values 1 15 indicate a tendency for earthquakes to cluster on existing weak faults a scale independent mechanics for crystalline rock fracture formation in which larger scale fractures form as clusters of smaller scale fractures provides a mechanical link between the small pervasive stress aligned flaws cracks and microfractures which can impart anisotropy to crystalline rock and the larger scale fractures associated with finite strain and faulting thus in crustal regions of active but low strain fracture anisotropy is observed to be aligned with the inferred maximum principal stress while in actively faulted crust fracture anisotropy is observed to be more nearly fault parallel as if the fractures are aligned by the finite strain faulting process

the wuchiapingian changhsingian boundary upper permian at meishan of changxing county south china abstract section d at meishan changxing county in the zhejiang province china has been extensively studied in various aspects of the stratigraphy during the past 20 years it was ratified by the international union of geological sciences iugs as the global standard stratotype section and point gssp for the permian triassic boundary in 2000 and is also a potential stratotype for the wuchiapingian changhsingian boundary however the contact relationship between the longtan wuchiapingian and changxing chainghsingian formations has been a controversial subject for years recent studies on section c about 300 m west of section d at meishan confirm a complete depositional succession around the boundary and suggest that the proposed boundary level the fad of clarkina wangi within the lineage from c longicuspidata to c wangi is consistent with the first appearance of the index changhsingian fusulinid palaeofusulina sinensis and tapashanitid ammonoids

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

azimuthal variations in p wave travel times and shear wave splitting in the charlevoix seismic zone abstract a significant drop of up to 1 in the seismic p travel times recorded from controlled explosions occurred in the charlevoix seismic zone csz between 1979 and 1980 the travel time data exhibited variations not only with distance but also with azimuth these variations are interpreted in terms of extensive dilatancy anisotropy eda in 1984 and 1985 shear wave splitting was observed in the csz on micro earthquake seismograms under the assumption of eda the observations are interpreted in terms of a dominant crack orientation of about 36 and a crack density of around 0 05 to 0 02 the observations from the p and s waves are not incompatible with one another

astronomical tuning of the end permian extinction and the early triassic epoch of south china and germany abstract the timing of the end permian mass extinction and subsequent prolonged recovery during the early triassic epoch can be established from astronomically controlled climate cycles recorded in continuous marine sedimentary sections astronomical cycle tuning of spectral gamma ray logs from biostratigraphically constrained cyclic stratigraphy through marine sections at meishan chaohu daxiakou and guandao in south china yields an integrated time scale for the early triassic which is consistent with scaling of magnetostratigraphy from climatic cycles in continental deposits of the germanic basin the main marine mass extinction interval at meishan is constrained to less than 40 of a 100 kyr kilo year cycle i e c 13 is estimated to have lasted c 13 from 2 to 4 across the smithian spathian boundary at chaohu was completed in 50 kyr the earliest marine reptiles in the mesozoic at chaohu that are considered to represent a significant recovery of marine ecosystems did not appear until 4 7 myr million years after the end permian extinction the durations of the griesbachian dienerian smithian and spathian substages including the uncertainty in placement of widely used conodont biostratigraphic datums for their boundaries are 1 4 0 1 0 6 0 1 1 7 0 1 and 1 4 0 1 myr implying a total span for the early triassic of 5 1 0 1 myr therefore relative to an assigned 251 902 0 024 ma for the permian triassic boundary from the meishan gssp the ages for these substage boundaries are 250 5 0 1 ma for base dienerian 249 9 0 1 ma for base smithian base of olenekian stage 248 2 0 1 ma for base spathian and 246 8 0 1 ma for the base of the anisian stage this astronomical calibrated timescale provides rates for the recurrent carbon isotope excursions and for trends in sedimentation accumulation through the early triassic of studied sections in south china

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

magnetostratigraphic constraints on two stage eruptions of the emeishan continental flood basalts temporal and spatial variations of high and low contents of ti basalts in the permian emeishan large igneous province elip of southwest china and vietnam are crucial for modeling of continental basalt formation and the nature of mantle lithosphere interaction a combined geochemical and magnetostratigraphic study was carried out at yanyuan in the inner zone of the elip geochemical results indicate that the basalts are low ti lt basalts ti y 484 2 511 4 in the luomapu section and high ti ht basalts ti y 558 2 658 9 in the gongmushan section systematic paleomagnetic sampling and stepwise thermal demagnetization demonstrate that the higher temperature component shows two distinct characteristic remanent magnetizations with northeasterly upward and sww downward directions these results indicate a simple magnetostratigraphic normal and reversed polarity pattern from the lower and upper parts of the section respectively by comparing with available magnetostratigraphic and paleomagnetic data carried out in the elip these results imply that the eruption of the emeishan basalts can be divided into early normal polarity subchron and late reversal subchron stages the early stage included lt basalts in the inner zone and most of the ht basalts in the intermediate and outer zones and the late stage contained a part of lt and ht basalts in the upper parts of the sections in the inner zone and a few in the intermediate zone of the elip correlating with available middle late permian magnetostratigraphy and the permian magnetic time scale the new magnetic polarity sequence result suggests that the elip formed over a very short time interval 1 myr

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

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

migration controls extinction and survival patterns of foraminifers during the permian triassic crisis in south china abstract the permian triassic mass extinction the greatest biotic crisis in earth history triggered the complete replacement of ecosystems with the 5 10 surviving species giving rise to the mesozoic fauna despite a long history of systematic studies on permian triassic foraminifera there have been few investigations into spatial and temporal patterns of survivorship and evolution during this critical interval we interrogate a high resolution data set comprising newly obtained and previously published foraminiferal data including 13 422 specimens in 173 species in 62 genera from seven well studied permian triassic successions that record a transect of platform to basin facies in south china shallow water settings seen at the cili and dajiang sections suffered a single pulse sudden extinction with high extinction rates at the end of the palaeofusulina sinensis zone deeper water and slope environments seen at liangfengya and meishan experienced a two pulse extinction in the clarkina yini and isarcicella staeschei zones basinal settings seen at shangsi gujiao and sidazhai record a single less devastating extinction pulse in and slightly above the c yini zone in the late permian foraminiferal diversity was greatest on the shallow platforms where 76 4 of species recorded in our study lived the two pulses of the permian triassic extinction prompted this foraminiferal diversity hotspot to move to deeper slope settings comprising 75 6 of contemporary species and finally basinal settings comprising 88 8 of species we propose that foraminifera migrated to deeper water to avoid overheating and toxicity in shallow waters that were driven by the emplacement of the siberian traps and coeval volcanic activities around the paleotethys ocean this study provides a methodological framework for investigating survival mechanisms for foraminifers and other taxonomic groups during mass extinction events

carbon isotopic evidence for chemocline upward excursions during the end permian event abstract a negative shift in marine inorganic carbon isotope composition 13 c carb during the end permian mass extinction has been used as evidence for several different extinction mechanisms changes to the 13 c of organic matter and the difference between it and 13 c carb 13 c 13 c carb 13 c org have been examined at few locations with conflicting interpretations we examine the changes to both organic and inorganic carbon isotopes across the permian triassic boundary at two marine sections from south china meishan and shangsi and compare these to data from other previously published sections through these analyses we demonstrate that a decrease in 13 c occurred during the extinction event throughout the paleo tethys ocean the extent and intensity of the decrease varies by location averaging a negative shift of 5 several possibilities as to the cause of this shift exist including siberian trap volcanism a change in the terrestrial marine organic carbon input to the system or a change in the dominant marine biota brought about through environmental changes such as widespread ocean anoxia euxinia the decrease in 13 c observed at many of these sections across the event horizon is here interpreted to represent a shift from algae cyanobacteria to less fractionating phototrophic sulfur bacteria in marine shelf environments resulting from upward excursions of the chemocline these chemocline upward excursions would release euxinic water to the photic zone allowing phototrophic sulfur bacteria to thrive the limited available biomarker data are consistent with this interpretation

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

dynamic palaeogeographic reconstructions of the wuchiapingian stage lopingian late permian for the south china block abstract as an important tool in natural resource exploration palaeogeography provides a portrayal of deep time earth the south china block located in the eastern palaeotethys includes multiple natural resources e g coal shale gas bauxite etc in the permian which are well known for their important economic significance in this paper data gathered from literature amount to 431 stratigraphic sections of wuchiapingian age from south china these data were quantitatively analyzed and dynamically reconstructed in the global context under the revised plate motion model by gplates software for the first time a schematic 3 d model was constructed based on the high resolution reconstructions in this paper showing two relatively large highlands developed in the south china block during the wuchiapingian including the kangdian highland in the west and the cathaysia highland in the east and a small yunkai highland in the south a broad platform dominated depositional system with small uplifts and depressions was developed between these two highlands these reconstructions show great potential to explore enriched coal seams and shale gas in the peripheral areas of the two ancient highlands in the west and east of the south china block based on the dynamic evolution of this depositional system south china experienced an overall sea level rise with frequent secondary transgressions and regressions during the wuchiapingian this is in contrast to the widespread continental and evaporite deposits on much of pangea and its surrounding margins after the end guadalupian global regression compilation of conodont biostratigraphic data suggest that the temporal and spatial constraints on the unconformity across the guadalupian lopingian boundary glb resulted from dongwu uplift movement the regression began during the jinogondolella shannoni zone and ended in the clarkina leveni zone but the response time varies in different localities of south china these results provide detailed information about sea level eustacy tectonic uplift sedimentary hiatus resource accumulation and palaeoclimate change from the south china block during the wuchiapingian

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

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

sulfur isotopic evidence for chemocline upward excursions during the end permian mass extinction the latest permian was a time of major change in ocean chemistry accompanying the greatest mass extinction of the phanerozoic to examine the nature of these changes samples from two well studied marine sections that span the permian triassic boundary have been analyzed the meishan and shangsi sections located in southern china isotopic analysis of the carbonate associated sulfate in these samples provides a detailed record of several isotopic shifts in 34scas approaching and across the ptb ranging from 30 to 15 vcdt with repeated asynchronous fluctuations at the two locations we interpret the patterns of isotopic shifts in conjunction with other data to indicate a shallow unstable chemocline overlying euxinic deep water which periodically upwelled into the photic zone these chemocline upward excursion events introduced sulfide to the photic zone stimulating a bloom of phototrophic sulfur oxidizing bacteria we hypothesize that elemental sulfur globules produced by these organisms and 34s depleted pyrite produced in the euxinic water column were deposited in the sediment later oxidation led to incorporation as cas this created the large changes to the 34scas observed in the latest permian at these locations

osmium isotope evidence for volcanism across the wuchiapingian changhsingian boundary interval abstract two negative carbon isotope excursions 3 5 6 5 across the wuchiapingian changhsingian boundary wcb are observed globally sections in china canada and iran however the causative mechanism of these excursions is debated here high resolution osmium isotope 187os 188os or osi chemostratigraphy of four globally correlated wcb sections 3 in china meishan shangsi and lianyuan and 1 in canada buchanan lake show two separate osi excursions to less radiogenic compositions that are coincident with the carbon isotope shifts for two of the south china sections lianyuan meishan in contrast only a single osi excursion to less radiogenic compositions coinciding with the earliest changhsingian carbon isotope shift is observed for the shangsi and buchanan lake sections the osi shift is interpreted to reflect increased unradiogenic os input from basaltic magmatism in south china possibly related to the emeishan large igneous province lip however 187os 188os data suggest that only the earliest changhsingian volcanism had global impact on both the ocean and atmosphere the lack of any evidence for a biotic event associated with the wcb therefore may have been due to the more regional rather than global impact of volcanism during the latest wuchiapingian in contrast during the earliest changhsingian volcanism was sufficient to cause a more global signal in the ocean osmium record but was inadequate or too prolonged to drive any significant environmental change volcanism however may have provided the isotopically light carbon that drove the negative carbon isotope excursions across the wcb

evidence for shallow and pervasive seismic anisotropy in the wellington region new zealand the shear waves of local earthquakes were recorded during a 5 month deployment of seven three component digital seismographs on the wellington peninsula new zealand the seismographs were spaced an average of less than 5 km apart and over 300 local earthquakes were recorded with phase arrivals within the shear wave window a significant number 37 of the earthquakes recorded showed clear evidence of shear wave splitting identifiable fast and slow shear wave arrivals with similar pulse shapes consistent polarization directions at particular stations were also observed even when poor signal to noise ratio or scattering meant that no slow shear wave arrival could be identified however there were large station to station differences in the polarization directions correcting for the observed shear wave splitting improved the fit between the measured shear wave polarizations and those calculated assuming a double couple focal mechanism the cause of the observed shear wave splitting is therefore most likely to be seismic anisotropy large station to station differences in the polarization alignments ranging from 61 24 to 137 18 suggest that most anisotropy is confined to the top 2 3 km of the crust however there is evidence from one station for a small amount of pervasive anisotropy if such a trend existed on the other stations it could not be identified because of the large scatter in the data points the measured delay times between split shear waves vary from 0 02 to 0 22 s with a mean value of 0 1 0 06 s this translates to a near surface shear wave velocity anisotropy of about 10 with up to 2 pervasive anisotropy possible throughout the crust this data set indicates that extensive dilatancy anisotropy cannot be the sole cause of crustal seismic anisotropy and that foliations in the rock fabric and the fracture zones of active faults may also be important there is no evidence for temporal change in the shear wave splitting parameters during the period of the experiment

two pulses of extinction during the permian triassic crisis over 90 of marine species were lost during the end permian extinction fossil data show that the crisis in china was marked by two distinct phases of marine extinction separated by a 180 000 year recovery period

twelve years of geophysical research in the charlevoix seismic zone abstract various and extensive geophysical monitoring began in 1974 in the charlevoix seismic zone csz the historical record and a major earthquake in 1925 characterize this zone as the likely site of a future damaging earthquake i e m 5 5 or larger and the aim of the monitoring was to develop the capability of predicting such earthquakes the parameters studied included microseismicity seismic travel times electrical impedance vertical movement horizontal movement tilt gravity change and strain through water well level changes although no clear precursor was detected in the months before the largest seismic event that occurred during the observation period m 5 0 the multiparameter experiment provided new insights into the structure and the mechanics of this active region observations of several hundred well located microearthquakes have permitted the delineation of ancient rift faults that are now being activated by high horizontal compression the geographical extent of the zone is sharply defined by the microseismicity which occurs in an area of 35 km 80 km straddling the st lawrence river observation of p waves from accurately timed explosions and s waves from earthquakes support the hypothesis of extensive dilatancy anisotropy eda involving saturated parallel cracks in the crust the data have permitted an estimate of both crack density and the direction for the principal compressive stress in the region n 30 e changes in electrical parameters with periods of months to years were detected at five of the six magnetotelluric stations installed in the region changes in the polarization angle of the earth s electrical telluric field correlated well for seven years with calculated groundwater accumulation levels at one site electric impedance changes showed no clear correlation from station to station but changes at one station appear to correlate with a seismic p wave travel time change anomaly and with the disappearance of a negative gravity anomaly at the time of an unusual number of earthquakes in the range m 2 to 3 from mid 1976 to mid 1977 it is suggested that these correlated changes could be related to aseismic stress redistribution and fluid flow along one of the ne striking rift faults about two years before the m 5 0 earthquake in 1979 continuous monitoring of tilt surface and borehole and well water levels was carried out at a single site charlevoix geophysical observatory although there were unexplained near surface tilts of the order of the earth tide amplitude within two or three days before some earthquakes they were either not spatially coherent or were related to small unexplained temperature changes in the tiltmeter vault no intermediate term one week to one year precursors were seen against a noise level of 1 3 rad rms for near surface tilt observations and a noise level of 0 2 0 3 rad rms for borehole tilt measurements at a depth of 50 100 m the threshold of detectable tidal tilt admittance changes for the borehole tiltmeters was lowered to 2 but no significant changes were seen four coseismic changes in the levels of water in boreholes were observed all were drops in water level which were much larger than expected on the basis of elastic dislocation theory it is suggested that these could be explained either by the collapse of a dilatant zone around the respective hypocentres or by triggered aseisnuc movement on a nearby active fault borehole water level tides observed from 1980 to 1986 exhibit significant variations in amplitude and phase which are thought to be the result of time varying elastic properties in a nearby structure some constraints can now be placed on the long term deformation of the csz as a whole from tiltmeter levelling and horizontal surveys data from a levelling array observed from 1976 to 1986 puts a limit of 0 54 rad yr on the secular tilt rate at the observatory a further limit of 0 1 rad yr is provided by borehole tilt measurements over the period 1983 1986 a limit of 2 cm is placed on vertical movements northwest of the st lawrence river by levelling surveys in 1965 1978 1980 and 1982 no significant 90 confidence deviatoric strain has been detected across the csz from horizontal control surveys carried out in 1912 1919 1965 1978 and 1983 the maximum allowable long term strain rate across the csz from 1919 to 1983 is 0 16 strain yr

a shear wave polarization study in the wellington region new zealand a month of digital data from two three component seismograph stations near wellington new zealand was analyzed as part of a feasibility study for a major project to investigate shear wave splitting although the total number of earthquakes studies was small 14 some suggestive results were obtained almost all events recorded within the shear wave window showed a phase reversal of the horizontal components after one or two shear wave cycles suggesting that there are actually two shear wave arrivals the measured polarization of the first shear wave arrivals was n 31 plus minus 11 e this polarization alignment cannot be explained by focal mechanisms and it is unlikely to be due to topography because of the station to station correlation the present evidence suggests the most likely cause is crustal anistropy due to the geological structure at shallow depth rather than stress aligned micro cracks

biogeochemical evidence for euxinic oceans and ecological disturbance presaging the end permian mass extinction event article i nfo the permian triassic boundary event at 252 2 ma marks the largest extinction of marine fauna in the phanerozoic and there is a wide consensus that the extinction coincided with an intense oceanic anoxic event thestratotypeofthechanghsingianstage preciselyconstrainedbytheptbglobalstratotypesectionandpoint gssp and the gssp for the wuchiapingian changhsingian boundary both at meishan in southern china is well documented in respect to geochronology and the pattern of extinction here we report secular trends in bulk isotopic parameters and lipid biomarkers in a core spanning 214 m of stratigraphic section across the ptb and through the entire changhsingian interval our analysis of these data viewed in the context of relative sea level change and strontium isotopes reveals distinct shifts in paleoenvironmental conditions and profound changes in plankton ecology well before and following the biological extinction event specifically patterns of steroids and triterpenoids indicate a marine plankton community that was heavily dominated by bacteria during the late wuchiapingian middle changhsingian and early griesbachian stages secular trends in aromatic hydrocarbons diagnostic for anoxygenic green sulphur bacteria chlorobiaceae identify periods when euxinic conditions extended into the photic zone during the entire changhsingian stage here also the 15

shear wave polarizations near the north anatolian fault ii interpretation in terms of crack induced anisotropy summary the polarizations of shear waves recorded by networks of digital thxee component seismometers immediately above small earthquakes near the north anatolian fault in turkey display shear wave splitting on almost all shear wave seismograms recorded within the shear wave window this splitting is incompatible with source radiation patterns propagating through simple isotropic structures but is compatible with effective anisotropy of the internal structure of the rock along the ray paths this paper interprets the phenomena in terms of widespread crack induced anisotropy distributions of stress induced cracks model many features of the observations and synthetic polarization diagrams calculated for propagation through simulated cracked rock are similar to the observed patterns this evidence for widespread crack induced anisotropy lends strong support to the hypothesis of extensive dilatancy anisotropy eda suggested by laboratory experiments in subcritical crack growth the crucial evidence confirming some form of eda would be observations of temporal changes in shear wave splitting as the stress field alters the crack density and crack geometry there is some weak evidence for such temporal changes at one site but further analysis of suitable digital three component seismometer networks in seismic areas is required to confirm eda

the variation of delays in stress induced anisotropic polarization anomalies summary polarization anomalies in seismic shear wavetrains diagnostic of propagation through anisotropic media have now been observed in dilatancy zones in seismic regions stress induced dilatancy will open cracks with preferred orientations which will be effectively anisotropic to short period seismic waves the polarization anomalies are due to the shear waves splitting in propagation through anisotropic media into components with different polarizations and different velocities this writes characteristic signatures into the shear wavetrains the paper examines ways in which the differential shear wave anisotropy the delay between the split shear waves varies with direction by plotting stereograms of the relative delays and their polarizations for possible dilatancy symmetry systems it seems likely that if sufficient observations of these anomalies can be obtained at each stage of the dilatancy episode it will be possible to estimate the symmetry directions of the dilatancy and the geometry of the stress induced crack system as well as monitoring the progress of the dilatancy episode