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

the fallacy of the shallow water problem in marine csem exploration the recent explosion of activity in offshore controlled source electromagnetic csem exploration has shown both theoretically and in practice for the time harmonic case that shallow water environments depths less than say 300 m can pose a significant challenge for detection and characterization of thin resistive targets in the subsurface because the weakly attenuated atmospheric response overprints the weaker target response as an alternative the transient csem experiment is considered to explore the nature of the airwave signature when viewed from the perspective of csem time series the signature of a thin isolated resistive horizon is computed by using the quasi analytic solution for a 1d earth in response to excitation by a horizontal electric dipole antenna that signature clearly seen in the transient data generally lies in the time interval between the arrivalof the airwave and the late time seawater response the fact that either decreasing the water depth or increasing the source r

stromatolites near the permian triassic boundary in chongyang hubei province south china a geobiological window into palaeo oceanic fluctuations following the end permian extinction abstract stromatolites just after the end permian extinction are exceptionally well developed in the chongyang area of hubei province south china the stromatolites include endolithic coccoidal microbes and exhibit three growth forms columnar layered pseudo columnar and columnar each located in different stratigraphic horizons the columnar type is the most conspicuous and provides key information on the mode of their construction in this paper we describe the mega to microscopic features of these stromatolites together with interpretations of their construction the columnar type typically comprises alternations of lighter and darker laminae with intercalations of dense micritic laminae the lighter laminae are composed of fine to coarse calcite cement and fine dolomite whereas the darker laminae are composed of micrite and microspar endolithic coccoids are sporadic in these laminae in contrast the dense micritic laminae consist of micrite with abundant endolithic coccoids accentuating the laminae of stromatolites the columnar stromatolites were formed under deteriorating conditions after the end permian mass extinction as follows 1 the alternating development of lighter and darker laminae due to the colonization of different microbial communities in lower energy shallow to deep subtidal settings 2 carbonate precipitation within each microbial community through microbial metabolic activity and degradation of extracellular polymeric substances eps leading to the alternations of lighter and darker laminae 3 episodic interruption of the growth of the lighter and darker laminae by endolithic coccoidal activity and 4 high levels of endolithic activity accompanied by the precipitation of carbonate within boreholes to produce the dense micritic laminae in contrast the columnar layered and pseudo columnar types comprise alternations of lighter and darker laminae composed mainly of fine to coarse calcite cement fine dolomite micrite peloids and microspar with sporadic endolithic coccoids the dense micritic laminae are absent or rare in these stromatolites these types were essentially produced by the repetition of processes 1 and 2 documented in the columnar type the finely alternating laminae of these stromatolites are therefore the product of the repeated initiation and cessation of growth of relevant microbial communities in response to changing environmental conditions the stromatolites were formed immediately after the end permian extinction and persisted intermittently throughout the early triassic the chongyang stromatolites are undoubtedly some of the best developed stromatolites near the permian triassic boundary and retain a high resolution record of microbial successions and palaeo oceanic perturbations immediately following the end permian extinction

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

a newly discovered earliest triassic chert at gaimao section guizhou southwestern china abstract the permian triassic ptb boundary section at gaimao huaxi district guiyang guizhou province records a unique lithological transition between the permian and triassic in south china thus bioclastic limestones of the changxing formation are overlain by radiolarian bearing siliceous rocks of the dalong formation and ultimately limestone mudstone alternations of the shabaowan formation conodont sampling of the section revealed well preserved elements that enabled a conodont biostratigraphy to be established the occurrences of hindeodus julfensis and hindeodus typicalis in changxing formation bioclastic limestone indicate a late permian age four conodont zones have been established in dalong and shabaowan formations in ascending order those are the isarcicella isarcica zone neogondolella or clarkina planata zone neogondolella krystyni zone and neospathodus dieneri zone the presence of typical griesbachian conodonts i isarcica and isarcicella staeschei in upper dalong formation indicates that this formation s radiolarian bearing siliceous mudrocks are of earliest triassic age and not restricted to the permian as previously thought thin section analysis reveals that the upper dalong formation contains spheroidal radiolarians but not a diverse assemblage of permian holdover taxa the new data proves that following the end permian mass extinction of radiolarian the abundance of these siliceous planktons was maintained at least locally enabling chert deposition to persist thus the gaimao section provides an exception to the early triassic chert gap the first of its kind in palaeo tethys and indicates that the end of chert deposition does not always mark the end permian mass extinction

early triassic seawater sulfate drawdown abstract the marine sulfur cycle is intimately linked to global carbon fluxes atmospheric composition and climate yet relatively little is known about how it responded to the end permian biocrisis the largest mass extinction of the phanerozoic here we analyze carbonate associated sulfate cas from three permo triassic sections in south china in order to document the behavior of the c s cycle and its relationship to marine environmental changes during the mass extinction and its aftermath we find that 34 s cas varied from 9 to 44 at rates up to 100 myr 1 during the griesbachian smithian substages of the early triassic we model the marine sulfur cycle to demonstrate that such rapid variation required drawdown of seawater sulfate concentrations to 4 mm and a reduction in its residence time to 200 kyr this shorter residence time resulted in positive covariation with 13 c carb due to strong coupling of the organic carbon and pyrite burial fluxes carbon and sulfur isotopic shifts were associated with contemporaneous changes in climate marine productivity and microbial sulfate reduction rates with negative shifts in 13 c carb and 34 s cas linked to warming decreased productivity and reduced sulfate reduction sustained cooling during the spathian re invigorated oceanic overturning circulation reduced marine anoxia and limited pyrite burial as seawater sulfate built to higher concentrations during the spathian the coupling of the marine c and s cycles came to an end and a general amelioration of marine environmental conditions set the stage for a recovery of invertebrate faunas variation in seawater sulfate during the early triassic was probably controlled by climate change possibly linked to major eruptive phases of the siberian traps

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

anomalous diffusion of electromagnetic eddy currents in geological formations controlled source electromagnetic em induction in some geological formations isshown here to be compactly described by an anomalous subdiffusion process such aprocess which is not universal is governed by a fractional diffusion equation oralternatively the convolutional form of ohm s law a subdiffusing eddy current vortex or electromagnetic smoke ring propagates in such a way that its position of medianintensity overruns its position of peak intensity this behavior is not allowed in classicaldiffusion but is a simple consequence of diffusion within a stationary fractal medium a similar analysis has been applied to understand heavy tailed traveltime distributions thatappear in certain hydrological time series the tell tale signature of anomalouselectromagnetic diffusion is a slope b of the magnetic zero crossing moveout curve that isconstant with transmitter receiver rx offset and significantly different from unity neither lateral heterogeneity nor unixial anisotropy can generate such a constant slopemoveout curve with an economy of model parameters controlled source em data fromtwo sites in texas and one in new mexico are used in this study to test the eddy currentsubdiffusion hypothesis

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

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

revised sm nd systematics of kambalda greenstones western australia sm nd isotope systematics in mafic ultramafic lavas from the norseman wiluna greenstone belt western australia have been reinvestigated a previous age based on mixing lavas and granites is not confirmed instead a sm nd age of 3 262 44 myr is indicated for the lavas 400 myr older than intruding granites and predating gneisses that have been proposed as basement rocks

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

onset development and cessation of basal early triassic microbialites betm in the nanpanjiang pull apart basin south china block abstract new investigations in the nanpanjiang basin indicate that the onset of the iconic microbialites associated with the paleozoic mesozoic boundary was early triassic in age bathymetry water agitation oxygenation light penetration and clastic load are shown to have exerted a direct control on the growth of microbialites carbonate supersaturation is also required for the deposition of the microbialites bathymetric control is further corroborated by the inheritance of the topography of a latest permian pull apart basin into early triassic times with a distribution of basal early triassic microbialites betm restricted to uplifted blocks and the accumulation of carbonaceous black shales in adjacent troughs the geographically most extensive nanpanjiang betm bloomed on a large nw se trending uplifted block exceeding 12 000 km 2 luolou platform centered on northwestern guangxi post triassic displacements along the youjiang fault obscure the paleogeographic relation of betm exposed west of this fault triassic foraminifers occur in the basal most betm episode which is locally bracketed by high energy grainstones made of reworked permian foraminifers therefore the permian triassic boundary ptb is within the unconformity that separates the late permian heshan fm from the basal most betm where accommodation space was sufficient up to five event surfaces are associated with the unconformity microfacies analysis supports chemical dissolution but did not reveal evidence for subaerial erosion although intercalated grainstone made of permian foraminifers indicate reworking chemical dissolution and mechanical erosion both conceivably contributed to the genesis of the unconformity the upward shift from tabulated to domical microbial build ups is accompanied by accumulation of coquinoid lenses between domes which indicates deepening of the luolou platform betm the main drowning resulting from both regional tectonic subsidence and a global sea level rise led to the cessation of the betm that were buried under predominant fine siliciclastics any concomitant change in sea water chemistry appears unlikely

geological noise in near surface electromagnetic induction data 1 controlled source electromagnetic induction is a geophysical technique used to identify anthropogenic and natural features such as unexploded ordnance or fluid pathways in the shallow subsurface however electromagnetic responses are difficult to interpret owing to the complexity of the underlying electrical conductivity structure we show here that electromagnetic responses are fractal signals reflecting a very rough distribution of electrical conductivity apparent conductivity profiles across a floodplain and a fractured sandstone aquifer both show that the fractal properties of the surface response depend on the complexity of the causative geological structure small scale fluctuations in the response due to geological noise are inherently reproducible and are not caused by random instrumental or atmospheric effects as often assumed new approaches to modeling are required to take full advantage of the rich information content of near surface electromagnetic data

abrupt warming in the latest permian detected using high resolution in situ oxygen isotopes of conodont apatite from abadeh central iran abstract climate warming probably as a result of massive degassing of greenhouse gases from the siberian traps magmatism has often been acclaimed as a major cause of the end permian mass extinction indeed several studies have documented a sudden rise in seawater temperatures during the latest permian earliest triassic as evidenced by oxygen isotopic records measured on conodont apatite however whether such a rapid increase in seawater temperatures occurred before during or after the mass extinction remains controversial moreover the pattern of this rise in seawater temperatures and its timing relative to the latest permian earliest triassic carbon cycle disruption mass extinction as well as the siberian traps magmatism still need to be rigorously examined in various regions in this study we present high resolution oxygen isotopic records of conodont apatite 18oapatite from the upper permian lowermost triassic interval at the abadeh section central iran that are analyzed with in situ secondary ion mass spectrometry sims method the 18oapatite results from abadeh demonstrate a clear pattern consisting of three phases 1 from the lower wuchiapingian clarkina dukouensis zone to the end permian mass extinction horizon 18oapatite values are relatively stable fluctuating in the range of 18 28 20 15 with an average of 19 44 2 18oapatite value remains high as 19 26 at the mass extinction horizon above this horizon a sudden decrease occurs in the clarkina hauschkei zone and reaches a low value of 17 05 close to the permian triassic boundary 3 in the lowermost triassic 18oapatite values maintain a low baseline in the range of 16 92 17 39 with an average of 17 11 overall the most dramatic change in 18oapatite values i e a decrease of 2 converting into an abrupt warming of 10 c occurred above the mass extinction horizon and below the permian triassic boundary at abadeh the abadeh 18oapatite record is consistent with previous results documented in south china iran and armenia in terms of the timing and magnitude of a substantial warming and therefore represents a global signature if applying the high precision temporal framework established in the well dated meishan gssp section to abadeh the abrupt warming of 10 c took only a maximum duration of 37 kyr thousand years by projecting the carbon cycle change temperature rise mass extinction at the abadeh and meishan sections and the temporal evolution of the siberian traps magmatism onto a unified timescale the temporal correlation strongly suggests that the switch from dominantly extrusive eruptions to widespread sill intrusions is probably the most annihilating phase of the siberian traps magmatism and is temporally consistent with the end permian mass extinction

remote sensing of geomorphology and facies patterns on a modern carbonate ramp arabian gulf dubai u a e abstract the occurrence of power law relationships in the spatial distribution of sedimentary lithotopes has been identified in both modern and ancient carbonate depositional bodies in this study facies patterns and their spatial relationships are investigated quantitatively in an arabian gulf shallow subtidal carbonate ramp setting using a synergy of ikonos satellite imagery and vessel based acoustic bathymetry survey three dimensional reconstruction of the facies distribution on the seabed enabled quantification of relationships between eight dominant facies classes and the association of particular lithotopes to water depth fractal behavior was investigated using a combination of boundary and patch based metrics and the spatial distribution of early diagenetically cemented hardgrounds and unconsolidated carbonate sand were shown to display strong fractal properties in contrast we show that landscape scale processes can be treated as essentially deterministic and facies neighborhood patterns are strongly probabilistic identifying that the heterogeneity of shallow subtidal carbonate facies scales with a power law within certain thresholds has the potential to serve as a tool in environmental reconstruction in the ancient where information on the lateral persistence of facies units is difficult to obtain the findings are relevant to the interpretation of stratigraphic sequences and paleo depth analysis

a multidimensional horizontal loop controlled source electromagnetic inversion method and its use to characterize heterogeneity in aquiferous fractured crystalline rocks summary the controlled source dual horizontal loop harmonic electromagnetic hlem profiling method is well suited to the problem of investigating fracture zones in crystalline rocks but there are still limitations in the way that experimental data are currently interpreted the use of 1 d data inversion leads to inaccurate determination of geological structure to allow accurate characterization of zones of fractured rock especially underneath heterogeneous overburden we have developed an efficient 2 5 d regularized inversion method for reconstructing subsurface electrical resistivity distributions from multifrequency hlem data with the forward problem solved in 3 d using a staggered grid finite difference method the inversion method is validated using a synthetic example and practical data sets from four borehole sites in a granitic terrain in northeast brazil an appraisal of our results for sites with boreholes sited using conventional data analysis procedures shows that we can distinguish between optimally located productive wells in fracture zone lineaments and those with diminished yields in weathered layer with no major underlying fracture zones we suggest that 2 5 d inversion can aid in developing better strategies for sustainable groundwater resource development in the basement terrains

sm nd studies of archaean metasediments and metavolcanics from west greenland and their implications for the earth s early history metasedimentary and metavolcanic rocks from the archaean of west greenland have been examined for evidence of crustal components greater than 3 8 ga in age and for their compatibility with the presently adopted bulk earth sm nd parameters sm nd isotopic data have been obtained for the garbenschiefer metagabbro unit metasediments from the isua supracrustal belt gneisses interior to the isua belt and metasediments from the malene supracrustal belt using estimates of emplacement age t of between 3 77 and 3 67 ga for the parental volcanics to the garbenschiefer unit initial143nd 144nd ratios yield positiveendt values between 1 0 and 3 1 relative to the chur parameters for seven out of eight samples model sm nd ages for the isua gneisses and metasediments are only compatible with their estimated stratigraphic ages if their sources were ca 2end relative to chur at those times similarly model sm nd ages for the malene samples are only compatible with stratigraphic age constraints when based on a source evolution with positiveendt implications of these results for the early development of the earth s mantle are discussed

growth and differentiation of the continental crust declining radiogenic heat production since the archaean has resulted in a secular evolution from a regime of numerous fast moving small thin torsionally weak plates to the present regime of larger thicker torsionally stronger plates moving at an average rate of less than one sixth of the archaean rate this has been accompanied by episodic changes in geological effects by 2500 ma b p about 85 of the present crustal mass had grown by the addition and amalgamation of mafic and calc alkaline rocks in oceanic arcs at an average rate of 11 17 pg a during the early proterozoic the first large cratons were stabilized and locally thickened and differentiated the proterozoic was an era of little continental growth falling average sea level and intracontinental deformation by 700 ma b p cratons had become much more stable marginal accretionary terrians had begun to develop with an average phanerozoic growth rate of 1 64 pg a and blueschists and ophiolites sensu stricto witness the advent of the extant plate tectonic regime

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

end permian mass extinction in the oceans an ancient analog for the twenty first century the greatest loss of biodiversity in the history of animal life occurred at the end of the permian period 252 million years ago this biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of earth s largest continental flood basalt provinces the siberian traps volatile release from basaltic magma and sedimentary strata during emplacement of the siberian traps can account for most end permian paleontological and geochemical observations climate change and perhaps destruction of the ozone layer can explain extinctions on land whereas changes in ocean oxygen levels co2 ph and temperature can account for extinction selectivity across marine animals these emerging insights from geology geochemistry and paleobiology suggest that the end permian extinction may serve as an important ancient analog for twenty first century oceans

anachronistic facies and carbon isotopes during the end permian biocrisis evidence from the mid tethys kisejin iran abstract late permian mass extinction lpme research has focused primarily on tethyan sections because it is believed that these successions are more complete than those from other localities and provide a more comprehensive record of the largest most devastating extinction event in earth history the kisejin section a previously undocumented mid tethyan upper permian lower triassic succession located in the central iran plate the kisejin section contains a continuous permian triassic sequence with only small breaks in sedimentation and was examined in order to determine sedimentologic biostratigraphic and carbon isotopic trends across the permian triassic transition abnormal anachronistic carbonates developed in the study area following the lpme and include microbialites edgewise conglomerates sparitic microspheres and microbially coated grains microbialites occur as thrombolites stromatolites and as agglutinated forms renalcis type calcimicrobes are documented for the first time from permian triassic boundary microbialites ptbms of iran coated grains fall into two groups and include pre ptbm ooids which are dense and cloudy and possibly microbial in origin and post ptbm cortoids with destructive and constructive micrite envelopes latest permian conodonts h praeparvus m ultima coupled with carbon isotopic values place the permian triassic boundary within the lowermost thrombolite unit about 2 1 m above the boundary between the nessen formation and the elika formation and indicate that microbialite growth began during the latest permian our study of this previously unknown section shows that unlike other well known ptb sections from iran the microbialite pattern is complicated and is more similar to ptbm successions from turkey in addition we note a similarity between the unusual facies of the kisejin section and those of eastern tethyan sections from china i e sparry microspheres and renalcis type calcimicrobes these unusual facies have not been previously reported from other well known iranian sections including julfa and abadeh which are thick and have been extensively studied

natural assemblages of the conodont clarkina in lowermost triassic deep sea black claystone from northeastern japan with probable soft tissue impressions abstract we report the first discovery of lower triassic clarkina assemblages four natural conodont assemblages from lower triassic pelagic black claystones of the north kitakami belt in northeastern japan akkamori section the fossils were obtained from the 2 5 m horizon level above the black claystone base which is assigned to the end permian mass extinction event this horizon has been dated to the earliest triassic griesbachian by the occurrence of hindeodus parvus which is the index species for the base of the triassic in the same and subjacent horizons these four fossil assemblages include a paired segminiplanate formed p1 element which was identified as the genus clarkina and have fully or partially preserved the original components of conodont elements the most complete assemblage among them includes 15 distinctive elements namely s0 and pairs of m s1 s2 s3 s4 p1 and p2 it is noteworthy that these fossil assemblages preserve probable impressions of eyes which were replaced by aggregations of silicate phosphate and sulphide minerals the occurrence of several sets of fossils that retain the original positioning of the conodonts elemental apparatuses as well as the original presence of soft tissue may be attributed to the process by which the conodonts bodies were transported to the deep seafloor and by which the activity of agents of decomposition was inhibited in near abiotic sediments under anoxic conditions in the pelagic deep sea during the earliest triassic

permian continental paleoenvironments in southeastern asia new insights from the luang prabang basin laos in laos southeastern asia late paleozoic sediments were identified by early french explorations across indochina during the late 19th century pavie missions but little work was undertaken to characterize the sedimentological and stratigraphical context until now from detailed sedimentological and paleontological studies we propose an interpretation of the depositional environment and of the stratigraphic context of series located on the right bank of the mekong river in the luang prabang basin where three main formations were described the silicoclastic red claystone formation attributed to alluvial plain environment contains large fragments of unidentified dicynodonts the limestones and sandstones formation preserves a new macrofloral assemblage displaying affinities with middle to late permian cathaysian floras of south china this assemblage occurs as an intercalation within marine calcareous sandstones that have yielded a marine fauna including the ammonoid pseudotirolites sp which indicates a late permian changhsingian age the well developed purple claystones formation yielded an abundant and well preserved late permian fauna composed of a carnivorous amphibian and numerous dicynodon cranial and postcranial elements this formation shows a vertical evolution from braided river to alluvial plain with sheet flood sand bed and bed load rivers with a constant supply of volcanic clasts results from the analysis of the paleontological associations in the luang prabang basin suggest that a continental communication between laurussia and the indochina block existed during the permian allowing for migration of the terrestrial dicynodon fauna

the construction and development of shrimp i an historical outline abstract in 1973 bill compston advocated the building of an ion microprobe at the research school of earth sciences rses at the australian national university anu the commercial ion probes available at this time were too small to have sufficient sensitivity for trace element analysis and too low in mass resolution to avoid molecular interferences the project commenced in 1974 with the appointment of a former anu phd student steve clement who had expertise in beam transport theory to achieve high sensitivity and high mass resolution beam transport theory indicated that a much larger magnet than in any commercially available mass spectrometer would be required clement chose an ion optical design by professor matsuda of osaka university in 1974 which had the required combination of high mass resolution and high transmission clement s job was to produce the detailed scientific designs and machine drawings for the new instrument as well as testing the completed instrument clement coined the term shrimp sensitive high resolution ion microprobe by the end of 1977 nearly all the components had been manufactured and the big electromagnet had been successfully tested in the following year the secondary mass analyzer was assembled and tested using a thermal ionization source and showed great promise with flat topped peaks at 5000 resolution and 50 transmission with 50 v energy spread at this stage the machine had far exceeded the specifications for the available commercial ion probes continued development during 1981 to the point where the original design specifications were fully realized was time consuming since learning how to use the entirely novel instrument was no simple task no one else had an instrument like shrimp the application of the instrument to zircon u pb geochronology established the necessary operating conditions for measuring pb isotopic compositions and the elemental ratios pb u and u zr from 20 m diameter spots on single zircon grains application of this in the early 1980s started a revolution in precambrian geology by the ability to produce rapidly accurate and precise age determinations on structurally complex zircon samples

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

global perturbation of the marine calcium cycle during the permian triassic transition a negative shift in the calcium isotopic composition of marine carbonate rocks spanning the end permian extinction horizon in south china has been used to argue for an ocean acidification event coincident with mass extinction this interpretation has proven controversial both because the excursion has not been demonstrated across multiple widely separated localities and because modeling results of coupled carbon and calcium isotope records illustrate that calcium cycle imbalances alone cannot account for the full magnitude of the isotope excursion here we further test potential controls on the permian triassic calcium isotope record by measuring calcium isotope ratios from shallow marine carbonate successions spanning the permian triassic boundary in turkey italy and oman all measured sections display negative shifts in 44 40ca of up to 0 6 consistency in the direction magnitude and timing of the calcium isotope excursion across these widely separated localities implies a primary and global 44 40ca signature based on the results of a coupled box model of the geological carbon and calcium cycles we interpret the excursion to reflect a series of consequences arising from volcanic co2 release including a temporary decrease in seawater 44 40ca due to short lived ocean acidification and a more protracted increase in calcium isotope fractionation associated with a shift toward more primary aragonite in the sediment and potentially subsequently elevated carbonate saturation states caused by the persistence of elevated co2 delivery from volcanism locally changing balances between aragonite and calcite production are sufficient to account for the calcium isotope excursions but this effect alone does not explain the globally observed negative excursion in the 13c values of carbonate sediments and organic matter as well only a carbon release event and related geochemical consequences are consistent both with calcium and carbon isotope data the carbon release scenario can also account for oxygen isotope evidence for dramatic and protracted global warming as well as paleontological evidence for the preferential extinction of marine animals most susceptible to acidification warming and anoxia

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

controls on facies architecture of a large triassic carbonate platform the great bank of guizhou nanpanjiang basin south china abstract the great bank of guizhou gbg is an exceptionally well exposed isolated triassic platform in the nanpanjiang basin of south china the platform is exhumed with its depositional profile preserved and is dissected by a faulted syncline that exposes a complete and uncomplicated cross section providing a unique opportunity to evaluate mechanisms involved in its birth evolution and demise the gbg formed near the southern margin of the yangtze platform during a deepening event that expanded the nanpanjiang basin and drowned the region surrounding the gbg in the latest permian initial accumulation of the gbg began in the latest permian with small reef mounds and open marine skeletal packstones following the end permian extinction cyanobacterial boundstones grew over the bank top during the early triassic the gbg developed a low relief bank profile with mobile oolite shoals at the margin shallow subtidal and peritidal deposits in the interior and gentle slopes dominated by pelagics debris flow deposits and turbidites at the basin margin in the middle triassic anisian the gbg developed a progressively steepening profile rimmed with massive tubiphytes reefs the platform was flat topped with tidal flat deposits across the interior basin margin deposition was dominated by turbidites and debris flow deposits but eventually shifted to avalanche and rock fall deposits as the slopes steepened to the angle of repose in the middle triassic ladinian an erosional escarpment up to 1700 m high developed at the margin platform margin strata are bedded packstones similar to interior strata whereas breccias at the basin margin contain coral boundstone clasts suggesting erosion of reefs from the escarpment a restricted subtidal lagoon formed in the interior producing an atoll like morphology later a flat topped profile was restored as tidal flats spread across the interior in the beginning of the late triassic deepening contributed to termination of the gbg before siliciclastic turbidites and shales were deposited over the platform in contrast with the well known platforms of the dolomites of northern italy the gbg contains abundant muddy carbonates and a progressively steepening bank to reef rimmed and escarpment architecture the italian platforms contain little mud and have angle of repose pinnacle geometries the gbg s larger size increased mud production and protected it from extensive winnowing of mud which in turn resulted in off bank shedding of muddy sediments that were stable on relatively gentle basin margin slopes which progressively steepened and ultimately led to avalanche deposits and a high relief erosional escarpment in contrast the lesser mud content of the dolomites platforms forced avalanche and talus deposition to dominate throughout deposition of basin margins which in turn produced their angle of repose geometries

calcium isotope constraints on the end permian mass extinction the end permian mass extinction horizon is marked by an abrupt shift in style of carbonate sedimentation and a negative excursion in the carbon isotope 13c composition of carbonate minerals several extinction scenarios consistent with these observations have been put forward secular variation in the calcium isotope 44 40ca composition of marine sediments provides a tool for distinguishing among these possibilities and thereby constraining the causes of mass extinction here we report 44 40ca across the permian triassic boundary from marine limestone in south china the 44 40ca exhibits a transient negative excursion of 0 3 over a few hundred thousand years or less which we interpret to reflect a change in the global 44 40ca composition of seawater co2 driven ocean acidification best explains the coincidence of the 44 40ca excursion with negative excursions in the 13c of carbonates and organic matter and the preferential extinction of heavily calcified marine animals calcium isotope constraints on carbon cycle calculations suggest that the average 13c of co2 released was heavier than 28 and more likely near 15 these values indicate a source containing substantial amounts of mantle or carbonate derived carbon collectively the results point toward siberian trap volcanism as the trigger of mass extinction

early earth closing the gap the age of the oldest jack hills zircons earth s oldest minerals is contentious atomic scale mapping of the distribution of radiogenic isotopes within a jack hills zircon confirms that the oldest known continental crust formed just after the earth moon system

factors controlling carbonate platform asymmetry preliminary results from the great bank of guizhou an isolated permian triassic platform in the nanpanjiang basin south china abstract a well exposed isolated carbonate platform the great bank of guizhou in the nanpanjiang basin of south china developed from the latest permian to the earliest late triassic platform strata are dissected by a faulted syncline exposing a complete cross section through the interior margins and flanks enabling a detailed assessment of depositional controls previous studies portrayed the platform as having a relatively symmetrical architecture even though much of the former work was focused on the platform interior and northern margin basin transition our research reveals five aspects of the southern margin facies and stratigraphy that are significantly different from those of the northern margin 1 subaerial exposure and unconformity developed on top of the upper permian sponge boundstone and in the overlying lower triassic strata 2 permian and triassic clasts chaotically admixed within early triassic breccias 3 lower triassic strata remarkably thinner on the southern margin 4 a much narrower tubiphytes reef facies preserved along the southern margin in the middle triassic and 5 large scallop shaped reentrants at the southern margin evident in satellite images three end member models may explain the asymmetry 1 antecedent topography of the underlying upper permian reef rimmed margin coupled with eustatic sea level fluctuation 2 differential tectonic uplift and 3 large scale submarine collapse of the platform margin subaerial exposure and admixing of permian and triassic clasts observed at yungan section is best explained by the tectonic uplift model however the submarine collapse model also explains several of the observations if it is associated with uplift s or sea level fall s submarine collapse is supported by large concave erosional reentrants scallops visible in satellite images taken together our observations suggest that a combination of tectonic uplift and margin collapse contributed to platform asymmetry further work promises to further constrain the details and timing of processes that contributed to the asymmetry

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

large perturbations of the carbon cycle during recovery from the end permian extinction high resolution carbon isotope measurements of multiple stratigraphic sections in south china demonstrate that the pronounced carbon isotopic excursion at the permian triassic boundary was not an isolated event but the first in a series of large fluctuations that continued throughout the early triassic before ending abruptly early in the middle triassic the unusual behavior of the carbon cycle coincides with the delayed recovery from end permian extinction recorded by fossils suggesting a direct relationship between earth system function and biological rediversification in the aftermath of earth s most devastating mass extinction

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

fractal nature of stratigraphic sequences orders of stratigraphic sequences are being used loosely and with widely varying definitions the orders seem to be subdivisions of convenience rather than an indication of natural structure it is proposed that at least at time scales of 103 106 yr sequences and systems tracts are scale invariant fractal features in which units bounded by exposure surfaces and units bounded by flooding surfaces are about equally likely support for this conceptual model derives from the well known facts that 1 sediment architecture is largely scale invariant over a wide range of scales in time and space 2 first order trends of sea level movements and sedimentation rates are fractal on all geologically relevant time scales and 3 detailed studies in carbonates indicate approximately equal abundance of flooding surfaces and demonstrable exposure surfaces among unit boundaries finally traces of prograding shelf edges that step up and step down in response to sea level changes are demonstrated in this study to have a fractal nature

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

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

roles apparent resistivity amplitude and phase play in an aquifer s electrical hydraulic conductivity correlation 1 this paper argues how the spectral characteristics of two borehole apparent resistivity traces further corroborate two statistically significant electrical hydraulic eh conductivity correlations previously reported in nevada s fractured welded tuffs even though the eh conductivity correlation is positive in one borehole and negative in the other as explained by low pore water electrical conductivity and the absence or presence of alteration minerals both apparent resistivity amplitude spectra are identically power law structured this is interpreted to mean that eh flow is occurring along rock fractures of a common regional fractal dimension furthermore both apparent resistivity phase spectra are strikingly linear as mandated by the condition of incompressible fluids linear phase implies a groundwater flow that is geostatistically nonstationary in the wide sense a complication normally not considered by hydrogeologists

growth of correlated pore scale structures in sedimentary rocks a dynamical model this report explores statistical models and geochemical observations to determine new insights into the formation of sedimentary rock

a gelation analogy of crustal formation derived from fractal conductive structures 1 the statistical evaluation of numerical random media models and of electromagnetic array data provides evidence of fractal conductive structures in the middle and lower crust during the search for an electrical conduction mechanism that is compatible with the geophysical anomalies in the middle and lower crust random resistor networks were developed these networks contain two types of resistors representing the rock matrix and the conductive phase here we demonstrate that random resistor network models can also explain the statistical properties of the electric field distortion measured in large scale electromagnetic array experiments correspondence between measured and modeled distortion statistics is obtained if the structures formed by the two resistor types in the networks have a fractal geometry this can indicate that the natural conductive networks also have a fractal geometry and stay close to a percolation threshold a simple scale model of crust formation mechanics is considered in order to find an analog medium and an analog process that creates such a geometry we suggest gelation as a rheological analogy that allows for a coexistence of ductile and brittle behavior of material in the lower crust this process forms fractal structures in the host matrix and fractal conductive networks provided that conductive material is available at that time of crustal evolution the statistical evaluation of the field data provides evidence for a fractal structure with an upper bound of the size of fennoscandia

global oolite deposits across the permian triassic boundary a synthesis and implications for palaeoceanography immediately after the end permian biocrisis abstract the permian triassic mass extinction ptme is not only a dramatic loss in biodiversity and major change in ecosystem structures but also coincided with the formation of abundant unusual sedimentary structures of these ooids were widespread in shallow marine carbonate settings during the permian triassic p tr transition and giant ooids occurred more frequently at this critical period than any time during the phanerozoic global review of 43 oolite bearing permian triassic boundary ptb sections with reliable biostratigraphic controls indicates that ooids occurred mostly in coincidence with the latest permian extinction lpe and its immediate aftermath ooids became widespread over extensive regions just after the lpe during the interval corresponding to the conodont hindeodus changxingensis zone they persisted into the earliest triassic until the conodont isarcicella isarcica zone in addition oolites are often found in association with microbialites in low latitude shallow marine settings proliferation of ooids over the p tr transition indicates an extensive range of warm waters with high level of carbonate saturation state that prevailed in the oceans during that time the latest permian ooids were usually small 0 3 to 0 7 mm in diameter aragonitic poorly preserved and recrystallized while moderately to well preserved morphology bimineralic and oversized forms usually occurred in the i isarcica zone of the earliest triassic and afterwards widespread aragonitic ooids in the end of the permian reinforce the scenario that an aragonite sea period may have resulted in the dramatic losses of skeletal organisms that precipitated low mg calcite and hampered their recovery in the aftermath the anomalous primary mineralogy of lower triassic ooids implies that previously assumed stable seawater composition during the early triassic needs to be revaluated

electric dipole fields over an anisotropic seafloor theory and application to the structure of 40 ma pacific ocean lithosphere summary seismic anisotropy has been detected in the oceanic crust and upper mantle and likewise it is geologically reasonable to expect that a certain amount of lateral anisotropy exists in sea oor electrical properties anisotropy in earth properties can often lead to surprising eiects on geophysical responses that are not anticipated from simple isotropic theories here we investigate the eiects of lateral anisotropy on the frequency domain controlled source electromagnetic csem response of a uniaxially conducting non magnetic sea oor excited by a horizontal electric dipole whose moment is oriented obliquely with respect to the electrical strike direction a paradox of anisotropy is observed in which the sea oor electric eld strength is enhanced in the most conductive direction of the sea oor this enhancement is opposite to what one would expect based on naive isotropic theory we also show that it is possible in certain circumstances to extract the along strike electrical conductivity from marine controlled source electromagnetic data using only isotropic modelling the extraction of across strike conductivity however requires full anisotropic modelling the physical insight into electromagnetic induction in uniaxial media that is presented here should greatly assist the geological interpretation of marine csem experimental data applying our algorithm to the pegasus data set csem data collected over 40 ma paci c ocean lithosphere produces a model with conductivity in the fossil spreading direction that is seven times greater than the conductivity perpendicular to spreading strain aligned mineralogical fabric as predicted by tectonic modelling would explain our result with enhanced conductivities caused by hydrogen conduction along the olivine a axis or connected accumulations of trace conductors such as graphite or magnetite

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

conodont zonation across the permian triassic boundary at the xiakou section yichang city hubei province and its correlation with the global stratotype section and point of the ptb xiakou section is situated north of the central yangtze platform with successive late permian to early triassic strata thicker than the global stratotype section and point gssp of the permian triassic boundary ptb we recognized three conodont zones across the ptb in this section by high precision biostratigraphy they are the hindeodus latidentatus clarkina meishanensis zone hindeodus parvus zone and isarcicella isarcica zone in ascending order which correspond well with the gssp the present biostratigraphic work on xiakou section certainly confirmed the conodont zonation through the ptb at the gssp and also testified to the correctness of the ptb demarcation in xiakou section based on this precise demarcation of the ptb the appearance of a clay layer bed zsji266 just beneath the ptb should be an important advantage over the gssp because this clay layer approaches to the ptb much in contrast with those two clay layers bed 26 and bed 28 in the gssp therefore the radiometric isotopic da

evolution of oceanic redox conditions during the permo triassic transition evidence from deepwater radiolarian facies abstract the 90 biodiversity loss among marine invertebrate species during the end permian mass extinction the most severe phanerozoic biocrisis has been attributed to widespread oceanic anoxia superanoxia recent studies of the lithofacies inorganic geochemistry and biomarkers of permian triassic boundary ptb sections have yielded an inferred pattern of oceanic redox changes that is complex and sometimes inconsistent in this contribution we review the ecology of radiolarians an important microzooplankton group during the permo triassic transition and consider its implications for contemporaneous changes in paleoceanographic conditions our analysis shows that 1 late permian radiolarian faunas were cosmopolitan with different orders having specific depth preferences i e albaillellarians favoring deeper waters and spherical forms entactinarians and spumellarians shallower waters 2 deep water taxa declined earlier than shallow water taxa 3 many paleozoic type taxa survived into the early triassic but went extinct during a second crisis in the dienerian dead clade walking followed by the appearance or expansion of mesozoic type taxa during the olenekian and 4 the survival of paleozoic type taxa during the early triassic was greater at higher paleolatitudes than in the tropics these observations are consistent with a first order redox control on radiolarian faunal distributions specifically a shallowing and poleward expansion of the oceanic oxygen minimum zone during the ptb crisis the consequent adaptation of some deepwater taxa to shallower environments resulted in early triassic radiolarian faunas in continental basins becoming more similar to those in pelagic settings enhanced survival of paleozoic type taxa in high latitude regions indicates that the main stressor on permo triassic radiolarian communities was reduced oceanic oxygen levels stronger in the tropics rather than climatic warming stronger at the poles

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

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

evidence of hierarchy in the complex fractured system of geropotamos crete greece as extracted from transient electromagnetic responses the essential goals of this paper are to test the transient electromagnetic tem response in a fractured geological complex medium and to better understand the physics introduced by associating a roughness parameter to the geological formation an anomalous fractional diffusion approach is incorporated to describe the electromagnetic induction in rough multi scaled geological structures the multi scaling characteristics of geropotamos basin in crete are revealed through the analysis of transient step off response of an em loop antenna the semi empirical parameters derived from late time tem measurements are correlated with the multi scale heterogeneities of the medium certain interesting properties of the late time slope and the power law of near surface resistivity distribution as extracted from tem inversion for different depth are presented the analysis of the parameter which scales the induced voltage in the loop in the late stage of the electromagnetic response leads to a different view of the em geophysical data interpretation we show that it is strongly correlated with areas of high fracture density within the geological formations of the geropotamos area for that reason it is proposed as a local multi scaling empirical index the results of this paper suggest that anomalous diffusion could be a viable physical mechanism for the fractal transport of charge carriers explaining observed late time tem responses across a variety of natural geological settings

a permian triassic boundary microbialite deposit from the eastern yangtze platform jiangxi province south china geobiologic features ecosystem composition and redox conditions abstract a permian triassic p tr boundary microbialite ptb microbialite deposit occurs near xiushui on the southern margin of the eastern yangtze platform south china this 2 m thick microbialite overlies uppermost permian bioclastic limestone with a 5 cm thick oolite like grainstone layer at the contact this ptb microbialite consists of lower thrombolite 1 5 m thick and an upper dendrolite 0 5 m thick the thrombolite interval is characterized by a clotted texture of reddish sparitic patches embedded in a gray micritic matrix whereas the dendrolite texture consists of brownish sparitic patches embedded within a yellow micritic matrix abundant calcified microbes occur in both the thrombolite and the dendrolite including 1 columnar and clustered fabrics which are especially rich in the thrombolite assigned as products of gakhumella or related microorganisms and 2 microspheroids 40 60 m in diameter with different interior structures these calcimicrobes are considered to have played an important role in constructing the xiushui ptb microbialite the demise of the microbialite was likely due to a sea level fall during the early griesbachian lowermost triassic which resulted in a lowering of the wave base thereby destroying the microbialite frameworks and facilitating the deposition of winnowed skeletal grainstone metazoan community structures within the microbialite changed sharply across the end permian extinction horizon which is placed at a sharp negative shift in 13 c carb quantitative analyses show that the xiushui microbialite community is similar to that of chongyang and cili microbialites this is probably because all of these microbialites grew along the margins of the lower yangtze region during the p tr transition however unlike other ptb microbialites the xiushui ecosystem contains fairly abundant metazoans which are dominated by ostracods with minor occurrences of foraminifers microgastropods and microconchids both the ostracod assemblage and the pyrite framboid analyses indicate an upper dysoxic zone to a well oxygenated condition for the xiushui microbialite this implies that some ptb microbialite ecosystems developed in conditions that were not always harsh instead some were hospitable for some metazoans to survive immediately after the end permian crisis considering that the redox conditions indicated by ptb microbialites are quite variable we infer that oxygen levels probably were not the crucial factor affecting the growth of the ptb microbialites

erosional truncation of uppermost permian shallow marine carbonates and implications for permian triassic boundary events on shallow marine carbonate buildups in south china turkey and japan uppermost permian skeletal limestones are truncated by an erosional surface that exhibits as much as 10 cm of topography including overhanging relief sedimentary facies microfabrics carbon isotopes and cements together suggest that erosion occurred in a submarine setting moreover biostratigraphic data from south china demonstrate that the surface postdates the uppermost permian sequence boundary at the global stratotype section and truncates strata within the youngest known permian conodont zone the occurrences of similar truncation surfaces at the mass extinction horizon on carbonate platforms across the global tropics each overlain by microbial buildups and their association with a large negative excursion in 13 c further suggest a causal link between erosion of shallow marine carbonates and mass extinction previously proposed to account for marine extinctions the hypothesis of rapid carbon release from sedimentary reservoirs or the deep ocean can also explain the petrographic observations rapid unbuffered carbon release would cause submarine carbonate dissolution accounting for erosion of uppermost permian skeletal carbonates and would be followed by a pulse of high carbonate saturation explaining the precipitation of microbial limestones containing upwardgrowing carbonate crystal fans models for other carbon release events suggest that at least 5 10 18 g of carbon released in 100 k y would be required of previously hypothesized permian triassic boundary scenarios thermogenic methane production from heating of coals during siberian traps emplacement best accounts for petrographic characteristics and depositional environment of the truncation surface and overlying microbial limestone as well as an associated carbon isotope excursion and physiologically selective extinction in the marine realm

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

rapid expansion of oceanic anoxia immediately before the end permian mass extinction tive of an expansion of oceanic anoxia and higher th u ratios from 0 06 to 0 42 indicative of drawdown of u concentrations in seawater using a mass balance model we estimate that this isotopic shift represents a sixfold increase in the flux of u to anoxic facies implying a corresponding increase in the extent of oceanic anoxia the intensification of oceanic anoxia coincided with or slightly preceded the eh and persisted for an interval of at least 40 000 to 50 000 y following the eh these findings challenge previous hypotheses of an extended period of whole ocean anoxia prior to the end permian extinction

death in guizhou late triassic drowning of the yangtze carbonate platform abstract the yangtze platform in south china formed a stable palaeogeographic element from the late proterozoic to the end of the middle triassic with deposition of shallow water carbonates during much of this time a portion of the yangtze platform in south central guizhou drowned at the transition from permian to triassic as the south adjacent nanpanjiang basin encroached about 100 km northward but a new stable platform margin was established that persisted through the early and middle triassic this long history as a stable carbonate platform ended at the transition from the ladinian to the carnian the latest ladinian rocks the yangliujing formation are 490 m of shoaling upward carbonate cycles of grapestone and bioclastic grainstone fenestral limestone and stromatolitic dolomudstone commonly overprinted by extensive subaerial diagenesis the beginning of the carnian is marked by a rapid transition to medium dark grey nodular lime mudstones containing ammonoids conodonts and thin shelled bivalves the zhuganpo formation the upper part of this thin pelagic limestone contains many muddy intraclasts some slightly bored and encrusted indicating incipient cementation the overlying wayao formation is a condensed black shale with thin interbeds of dark grey manganiferous lime mudstone near the base ammonoids conodonts thin shelled bivalves and articulated crinoid stems are abundant fine grained greywacke with sole marks forms prominent bundles within grey calcareous shale in the overlying laishike formation ammonoids and thin shelled bivalves occur sporadically in this 810 m thick unit calcareous shale with thicker shelled bivalves and packages of cleaner coarser grained sandstone characterize the banan formation 460 m thick the sandstone units generally coarsen and thicken upward with ripples medium scale trough cross beds and rare u tube burrows quartzose coal bearing siliciclastics 690 m thick form the overlying huobachong formation thick bedded cross stratified sandstone and conglomerates are amalgamated into thinning and fining upward intervals separated by blocky mudstones this fining upward motif continues into the overlying erqiao formation but coals are lacking at the beginning of the late triassic carnian the previously stable yangtze platform on which peritidal limestones were forming was drowned and covered by dark lime mud that was cemented into intraclasts and nodular lime mudstone black shale and manganiferous pelagic limestone formed a condensed interval recording maximum submergence turbidite sandstone and shale of the laishike flysch filled the accommodation space of 800 m created during drowning of the yangtze platform leading to deposition of shoaling upward shelf and paralic sandstones and shales but without significant carbonate production the succeeding fining upward siliciclastics are interpreted as braided stream deposits with coals that mark minor marine incursions the shallow shelf and braided stream deposits form a molasse 1500 m thick it was apparently derived from the west in contrast to the underlying flysch where palaeocurrent directions are from the north or northeast the entire yangtze platform became emergent during the late triassic and was never submerged again subtle local differences in the drowning sequences indicate differential subsidence and suggest that tectonics played a role in the death of the yangtze platform

evidence for end permian ocean acidification from calcium isotopes in biogenic apatite c record of carbonate rocks 13 c carb for the selective extinction of heavily calcifi ed marine animals and for the abrupt transition in carbonate facies across the extinction horizon an additional proxy is necessary to distinguish among these options calcium isotopes hold promise for differentiating between suggested scenarios for change in seawater carbonate chemistry linked with the end permian extinction the calcium cycle is linked to the carbon cycle through the weathering of limestone and the deposition of calcium carbonate sediments calcium isotopes fractionate by 0 6 and 1 3 in calcite and aragonite respectively during the precipitation of modern carbonate minerals meaning carbonate sediments are enriched in the lighter isotope relative to the seawater from which they precipitated skulan et al 1997 tang et al 2008 imbalances between calcium delivery and burial fl uxes and changes in the magnitude of fractionation during carbonate deposition will result in changes in the 44 40 ca of seawater and will be recorded in marine sediments depaolo 2004 farkao et al 2007 therefore variation in the

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

structural features of an active strike slip fault on the sliding flank of mt etna italy abstract the strike slip pernicana fault system pfs was activated along the eastern flank of mt etna during an earthquake in september 2002 and one month later during the eruption of the ne rift structural and volcanological data suggest that the pfs was activated as a result of the slide of the ne flank of etna this activation produced surface fracturing on walls and on paved and unpaved roads the segments of the pfs arranged in a right stepping en echelon configuration show a an inverse proportion between length and frequency b fractal behavior over scales of 10 2 10 1 m between their length overstep and overlap c consistent strike with regard to their fault array and d a progressive eastward decrease in the displacement along the smallest faults the consistent geometric and kinematic features of the pfs related to the sector collapse of etna are similar to those of faults in strike slip settings

the lower triassic of south china abstract the permian triassic boundary of south china has been well known and well studied for decades but what is relatively less noticed is that there are also many excellent marine lower triassic sequences in the region covering various paleogeographic lithofacies this paper presents an outline of the various lower triassic stratigraphic sequences in south china and provides a reference to the application of the lower triassic subdivision and stages the early triassic marine basin of south china is subdivided into five sedimentary provinces cathaysia lower yangtze upper yangtze youjiang and lijiang provinces each province has an interrelated distribution of lithofacies and stratigraphy the lower triassic biostratigraphic sequences of bivalves ammonoids and conodonts are summarized in the various sedimentary facies and provinces of south china the chinese twofold subdivision of the lower triassic is primarily demonstrated as well in this paper

stepwise and large magnitude negative shift in δ13ccarb preceded the main marine mass extinction of the permian triassic crisis interval abstract large perturbations to the global carbon cycle occurred during the permian triassic boundary mass extinction the largest extinction event of the phanerozoic eon 542 ma to present controversy concerning the pattern and mechanism of variations in the marine carbonate carbon isotope record of the permian triassic crisis interval ptci and their relationship to the marine mass extinction has not been resolved to date herein high resolution carbonate carbon isotope profiles 13ccarb accompanied by lithofacies were generated for four sections with microbialite taiping zuodeng cili and chongyang in south china to better constrain patterns and controls on 13ccarb variation in the ptci and to test hypotheses about the temporal relationship between perturbations to the global carbon cycle and the marine mass extinction event all four study sections exhibit a stepwise negative shift in 13ccarb during the late permian early triassic with the shift preceding the end permian crisis being larger 3 than that following it 1 2 the pre crisis shifts in 13ccarb are widely correlatable and hence represent perturbations to the global carbon cycle the comparatively smaller shifts following the crisis demonstrate that the marine mass extinction event itself had at most limited influence on the global carbon cycle and that both late permian 13ccarb shifts and the mass extinction must be attributed to some other cause their origin cannot be uniquely determined from c isotopic data alone but appears to be most compatible with a mechanism based on episodic volcanism in combination with collapse of terrestrial ecosystems and soil erosion

effect of a hadean terrestrial magma ocean on crust and mantle evolution this paper presents a model for the thermal and chemical evolution of a global magma ocean created by impact heating during the earth s accretion detailed calculations are given for a melt depth of 120 km for end member picritic and peridotitic compositions application of fluid mechanics and heat transfer principles shows as a first approximation that the chemical evolution can be portrayed by idealized fractional crystallization occurring only on the the bottom of the magma ocean the fractional crystallization sequence for the picritic model is 90 km of mafics overlain by 15 km of ol sp gabbronorite and topped by 15 km of iron rich leucodiorite whereas the peridotite sequence consists of 99 km of dunite harzburgite and websterite overlain by 5 km of ol sp gabbronorite and capped by 16 km of ferroleucogabbronorite although subsolidus convection would rehomoginize all but the felsic layers of the picritic model the layers of the peridotite would remain intact owing to their stable density profile the mineralogy of the felsic layers is largly independent of the basic model assumptions however the composition of the mafic layers is model dependent the most likely results for the mafic mafic layers lherzolite or primitive mantle peridotite are similar to mantle xenoliths suggesting that a terrestrial magma ocean may have existed however comparison of the chemistry of the calculated upper felsic layer with that of the canadian shield shows that crystallization of a global magma ocean would not directly produce the archean continental crust multiple melting and differentiation of the fe leucodiorite to fe leucogabbronorite layer and of the underlying primitive mantle would be required to form an archean granitoid crust

stable carbon isotope stratigraphy across the permian triassic boundary in shallow marine carbonate platforms nanpanjiang basin south china a distinct negative 13c excursion is documented in two permian triassic sections heping and taiping in shallow marine carbonate platform deposits in the nanpanjiang basin south china these sections span from the changhsingian to the dienerian and are characterized by a distinct marine boundary facies change from massive skeletal lime packstone in the changhsingian to distinctive calcimicrobial framestone in the griesbachian hindeodus parvus zone the 13corg and 13ccarb excursions occur directly after the onset of the calcimicrobial framestone herein termed the permian triassic boundary event and before the first occurrence of h parvus the isotope shifts are associated with a sharp drop in species abundance and diversity and coincide with a decrease in total organic carbon toc content the shift towards depleted values in 13corg and 13ccarb at the permian triassic boundary event together with low toc contents persists throughout the griesbachian h parvus zone these data document a corresponding negative shift of 13corg and 13ccarb values and low toc contents with the onset of growth of calcified microbial framestones a postextinction disaster facies immediately below the base of the griesbachian h parvus zone based on paleontological evidence the first occurrence of the disaster facies follows the extinction event which implies that the 13c depleted values above this facies postdate the event this suggests that two separate events had to account for the initiation of the extinction and the 13c excursion however the consequences that led to the negative isotopic shift might be linked to the intriguing recovery lag of early triassic ecosystems based on data from ptb sections worldwide of a greater 13c offset in high compared with low latitudes we propose that methane eruptions from thermal destabilization of high latitude clathrate deposits may have led to the negative 13c shift and may have caused long term adverse ecological conditions

major perturbation of ocean chemistry and a strangelove ocean after the end permian mass extinction the severe mass extinction of marine and terrestrial organisms at the end of the permian period c 251 ma was accompanied by a rapid 1 ma decrease in sedimentary burial of organic carbon in the early triassic

iron and sulfur in the pre biologic ocean tentative geochemical cycles for the pre biologic earth are developed by comparing the relative fluxes of oxygen dissolved iron and sulfide to the atmosphere and ocean the flux of iron is found to exceed both the oxygen and the sulfide fluxes because of the insolubility of iron oxides and sulfides the implication is that dissolved iron was fairly abundant and that oxygen and sulfide were rare in the atmosphere and ocean sulfate produced by the oxidation of volcanogenic sulfur gases was the most abundant sulfur species in the ocean but its concentration was low by modern standards because of the absence of the river borne flux of dissolved sulfate produced by oxidative weathering of the continents these findings are consistent with the geologic record of the isotopic composition of sedimentary sulfates and sulfides except in restricted environments the sulfur metabolism of the earliest organisms probably involved oxidized sulfur species not sulfide

permian triassic extinction pattern revealed by foraminifers and geochemical records in the central persian gulf southern iran abstract permian triassic boundary ptb foraminifers are studied from the upper part of the dalan formation and the base of the kangan formation in four wells a b e f on and near the qatar arc persian gulf iran isotope studies including 13c and 18o values from wells b and e and 87sr 86sr ratios in wells b e and f have also been carried out to possibly provide a high resolution extinction pattern of foraminifers in the ptb interval the latter has been thoroughly investigated in iran turkey south china vietnam slovenia carnic alps and bukk mountains kashmir greenland and serbia the distribution of the last appearance of foraminiferal genera from the ptb interval in all of the wells is very similar featuring a stepwise extinction from 3 to 2 m before the boundary and compares to that observed in some of the sections from elsewhere i e south china vietnam slovenia and serbia the 13c value in wells b and e shows a negative shift at the base of a thrombolite unit immediately after the considered ptb and another negative shift at about 11 m below it in well e the thrombolite unit is assumed as earliest triassic but questionable with no supportive conodonts the 18o isotope values in wells b and e demonstrate the same negative upward trend due to dysoxic or anoxic conditions in the end permian oceans the uniform reduction without any sharp incline in the 18o profile suggests concurrent global warming the highest 87sr 86sr ratio fluctuations in wells b e and f coincide with the appearance of thrombolites changes in the profiles of carbon oxygen and strontium isotopes close to the ptb in wells b e and f seem to correspond to lithofacies variations from limestone to dolostone and a reduction in foraminiferal diversity these changes substantiate a clear perturbation in the marine environmental and global geochemistry elements through the ptb interval the 13c 18o and 87sr 86sr values obtained from the studied wells are comparable to those in other ptb stratigraphic sections in the paleo tethyan region

changhsingian late permian conodonts from son la northwest vietnam and their stratigraphic and tectonic implications abstract late permian conodonts are for the first time reported from vietnam pa sa sb sc and m elements of the changhsingian conodont species hindeodus julfensis sweet are reported from a 40 cm thick limestone in the middle part of the yenduyet formation near son la nw vietnam the occurrence of h julfensis indicates a changhsingian age that is consistent with an interpreted early changhsingian age for a brachiopod fauna slightly higher in the sampled section the son la section is located in the song da rift zone and overlies basaltic volcanics considered equivalent to the emeishan large igneous province basalts that are plume related the permian triassic boundary in vietnam is yet to be precisely located biostratigraphically but proxy chemostratigraphic data indicate its likely position in sections at nhi tao and lung cam n vietnam and correlation with the global stratotype section and point at meishan south china the recovered conodonts have a conodont colour alteration index of 5 and have been heated to c 600 c but they do not show any evidence of textural alteration due to regional metamorphism such as micro folding or stretching that would indicate any direct effects of the compressional indosinian orogeny

detection of near surface horizontal anisotropy in a weathered metamorphic schist at llano uplift texas by transient electromagnetic induction abstract the use of transient controlled source electromagnetic prospecting to detect buried steeply dipping foliation in metamorphic rocks is illustrated with data acquired over the precambrian packsaddle schist in the llano uplift of central texas the azimuthal variation of the transient voltage at a given transmitter receiver separation about a fixed central point is consistent with the forward model response of a homogeneous halfspace exhibiting horizontal electrical anisotropy the loop loop exploration configuration is ideally suited to probe horizontal anisotropy a quantitative match of the forward response to the observed data produces reasonable electrical conductivity values and coefficient of anisotropy for resistive crystalline geological materials the most conductive direction consistently lies within a few degrees of the geologically mapped foliation strike direction the electrical anisotropy is strongest below the near surface weathered layer within the more competent bedrock the agent responsible for generating the anistropy cannot be definitively determined because it is likely to be a combination of geological factors such as weathering compositional banding and microcracking all of which enhance electrical conductivity parallel to the plane of foliation the transient electromagnetics is supplemented by dc resistivity and seismic surveys the elastic anisotropy is evident in the near surface weathered layer but it may not persist very deep into the underlying competent schist the exposure of foliated schist at the surface is not sufficient to rule out a possible role for systematically aligned macrofracture sets as a secondary cause of the observed anisotropy

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

evidence for a diachronous late permian marine crisis from the canadian arctic region a high resolution chemostratigraphic study of a 24 m thick section at west blind fiord on ellesmere island canadian arctic documents stepwise environmental deterioration in the marine sverdrup basin during the late changhsingian late late permian as a result of volcanic disturbances to surrounding landmasses a horizon within the upper lindstrom formation datum a is characterized by increased fe oxyhydroxide fl uxes and weathering intensity as well as modest shifts toward more reducing watermass conditions and higher marine productivity recording an initial disturbance that washed soils into the marine environment the contact between chert of the lindstrom formation and silty shale of the overlying blind fiord formation which is 1 6 m higher and 50 k y younger than datum a records a large increase in detrital sediment fl ux more strongly enhanced marine productivity and a regional extinction of siliceous sponges herein termed the arctic extinction event the horizon equivalent to the latest permian mass extinction of tethyan shallow marine sections is 5 6 m higher and 100 k y younger than the arctic extinction event demonstrating the diachronous nature of the marine biotic and environmental crisis at a global scale it is associated with intensifi ed anoxia and possible changes in phytoplankton community composition in the study section marine environmental deterioration in the sverdrup basin probably triggered by terrestrial ecosystem deterioration and elevated detrital sediment fl uxes was under way by the early part of the late changhsingian well before the onset of main stage siberian traps fl ood basalt volcanism the event sequence at west blind fiord may record the deleterious effects of early stage explosive silicic eruptions that affected the boreal region possibly through deposition of toxic gas and ash within a restricted latitudinal band while having little impact on marine ecosystems in the peri equatorial tethyan region