io hot spots in 1991 results from europa occultation photometry and infrared imaging abstract during the winter of 1991 an unusually favorable series of occultations of io by europa took place we obtained infrared photometry of four of these events at the united kingdom infrared telescope at wavelengths of 5 0 or 3 4 m in order to investigate the nature and distribution of volcanism on io by observing the occultation of the volcanic hot spots by the limb of europa observations at 3 4 m on 1991 01 08 detected a possible small hot spot in the northern hemisphere observations at 5 0 m on 1991 02 27 detected and resolved the major hot spot loki which had a diameter of 170 km and had three times its voyager 1 flux and also detected the voyager hot spot pele at about half its voyager 1 flux a 5 0 m occultation of pele on 1991 03 06 when loki was not occulted indicated no significant flux change since the week before infrared images of io obtained at the nasa infrared telescope facility between october 1990 and april 1991 show that the europa occultations occurred during a period of unusually high activity at loki loki showed very little thermal emission in observations between 1990 10 12 and 1990 11 27 but increased in flux by a factor of 10 in 32 days by 1991 12 29 loki then remained bright in all observations until 1991 03 26 but had begun to fade on 1991 04 09 such rapid variations in flux over such a large area are remarkable multiwavelength observations indicate that loki increased in temperature during the brightening and that materials hotter than 630 k were exposed at loki the possible pele type volcanoes surt and aten unlike pele were not detected with 3 8 m flux upper limits of about 8 gw m 1 str 1

postapocalyptic greenhouse paleoclimate revealed by earliest triassic paleosols in the sydney basin australia the permian triassic boundary in the sydney basin of australia is coincident with a pronounced decrease in 13 c isotopic values of organic carbon the last coals anywhere in the world for all of the early triassic ca 6 m y time and extirpation of the glossopteris flora at the top of the illawarra and newcastle coal measures coal bearing paleosols of the latest permian represent extensive swamplands of the seasonally deciduous glossopteris flora in a humid cold temperate lowland southwest of an andean style volcanic arc stone rolls large ribs of floor rock up into the coal within some of the uppermost coals of the permian coal measures can be interpreted as string bogs of a kind now found in cold climates at latitudes of 68 70 which is compatible with a paleomagnetically estimated paleolatitude of 65 85 s for the sydney basin paleolatitude was not much different for earliest triassic time but paleosols of that age include inceptisols and entisols showing substantial chemical and textural weathering more like soils now forming at latitudes of 40 58 than those within polar circles this anomalous high latitude warmth set in at the permian triassic boundary sedimentation rates increased at the boundary marked by geochemically unusual acidification of clay and a dramatic carbon isotopic excursion these changes in environments and ecosystems can be explained by soil erosion following deforestation implied by the plant extinctions and abundant fungal remains at the permian triassic boundary evidence from paleosols can now be added to that from paleontological and isotopic studies showing that disruption of the carbon cycle at the permian triassic boundary resulted in a co 2 or ch 4 post apocalyptic greenhouse paleoclimate

carbon and oxygen isotope stratigraphy of the lower mississippian kinderhookian lower osagean western united states implications for seawater chemistry and glaciation a positive carbon isotope 1 3 c excursion has been recognized in upper kinderhookian and early osagean carbonates in three sections in southeast idaho and nevada the oldest 1 3 c peak 7 is dated to the isostichaconodont zone and a younger peak occurs in the typicus zone the shifts are recorded in a range of carbonate lithofacies representing various water depths along the shelf lithofacies sampled for 1 3 c and 1 8 o at the samaria mountain section in southeast idaho record the shallowest water conditions indicated by cross bedded skeletal and peloidal grainstones the deepest water conditions are present in the pahranagat range section in eastern nevada which consists mainly of bioturbated lime mudstone and skeletal wackestone the 1 3 c values from these widely separated sedimentary basins show a consistent trend that correlates with early mississippian curves generated from brachiopod calcite in western europe and the midcontinent of north america as well as dolomites in utah and wyoming 1 8 o values become more positive up section generally paralleling the positive trend in 1 3 c during the late kinderhookian no subaerial exposure surfaces are recognized in the sections examined in southeast idaho and nevada and at least the 1 3 c trends are interpreted as primary seawater fluctuations sea level changes occurred near the beginning of the late kinderhookian 1 3 c shift early to middle parts of the isosticha zone and within the peak of the 1 3 c excursion kinderhookian osagean boundary although tectonic changes associated with the antler orogeny have likely modified the eustatic signature

multi phase volcanic resurfacing at loki patera on io the jovian moon io hosts the most powerful persistently active volcano in the solar system loki patera the interior of this volcanic caldera like feature is composed of a warm dark floor covering 21 500 square kilometres surrounding a much cooler central island the temperature gradient seen across areas of the patera indicates a systematic resurfacing process which has been seen to occur typically every one to three years since the 1980s analysis of past data has indicated that the resurfacing progressed around the patera in an anti clockwise direction at a rate of one to two kilometres per day and that it is caused either by episodic eruptions that emplace voluminous lava flows or by a cyclically overturning lava lake contained within the patera however spacecraft and telescope observations have been unable to map the emission from the entire patera floor at sufficient spatial resolution to establish the physical processes at play here we report temperature and lava cooling age maps of the entire patera floor at a spatial sampling of about two kilometres derived from ground based interferometric imaging of thermal emission from loki patera obtained on 8 march 2015 ut as the limb of europa occulted io our results indicate that loki patera is resurfaced by a multi phase process in which two waves propagate and converge around the central island the different velocities and start times of the waves indicate a non uniformity in the lava gas content and or crust bulk density across the patera

transient investigation of saltwater upconing in laboratory scale coastal aquifer abstract the objective of this research was to examine the response of seawater intrusion and retreat to freshwater abstraction from a well in laboratory scale coastal aquifer under transient conditions this has been done experimentally and numerically through qualitative and quantitative analysis the laboratory experiments were completed in a two dimensional laboratory tank for two beads sizes namely 1090 m and 780 m the seawat code was used for the numerical simulations the experimental results showed that the vulnerability of the pumping well to salinization was higher for the low permeability aquifer whereby the saltwater upconing process was observed at an abstraction rate 40 smaller in the lower permeability aquifer compared to the high permeability aquifer in the lower permeability scenario the inland penetration of the saline plume was up to 41 larger than in the higher permeability scenario for an equivalent pumping rate increment in addition the process of decay after the abstraction had ceased of the wedge was slower in the lower permeability aquifer which suggests a slower retreat of the wedge the qualitative comparison of the shape of the saline plume and the quantitative comparison of the transient toe length data between experimental and numerical results showed excellent agreement the flow velocity field analysis revealed that the local reduction of the magnitude of the flow velocity along the upper part of the interface was a major factor contributing to the saltwater upconing mechanism

loki io a periodic volcano loki is the most powerful volcano in the solar system it has been observed to be in continuous though variable activity since 1979 synthesis of more than a decade of groundbased data suggests that loki eruptions are cyclic with a 540 day period application of a simple lava cooling model to temperatures in loki patera and eruption start and end times implies that brightenings are due to a resurfacing wave propagating across the patera the data are most consistent with lava lake overturn but resurfacing by lava flows cannot be ruled out a porosity gradient in the lake crust could cause lava lake overturn to occur periodically on the timescale observed

palaeoenvironments and faunal recovery after the end permian mass extinction abstract strata of the lower triassic werfen formation dolomites northern italy record deposition in a wide range of palaeoenvironments from peritidal to outer ramp settings this enables accurate assessment of faunal recovery following the end permian mass extinction by eliminating facies related effects extinction of the shelly taxa appears to be rapid and occurs in the latest permian tesero oolite horizon disappearance of the various trace fossil taxa appears to be more gradual following the extinction the lower and middle griesbachian are characterised by laminated sediments containing low diversity bedding plane assemblages ichnological geochemical and sedimentological data show evidence of widespread low oxygen conditions normally oxygenated waters return in the late griesbachian and there is a moderate increase in tiering above and below the surface macrofaunal and ichnofossil diversity decrease markedly during the smithian with the appearance of more terrigenous strata possibly reflecting an increased run off and more brackish conditions complete recovery begins in the basal spathian with an increase in tiering above and below the substrate crinoids and ammonoids appear for the first time in the werfen formation and the ichnogenus rhizocorallium re appears global correlation is hindered by poor biostratigraphy in the dolomites region however on a broad scale it appears as though many of the palaeoenvironmental changes are repeated worldwide current available data suggest that the re appearance of some trace fossil taxa e g diplocraterion rhizocorallium may be globally synchronous

biotic impacts of temperature before during and after the end permian extinction a multi metric and multi scale approach to modeling extinction and recovery dynamics abstract extinction and delayed recovery during the end permian extinction and early triassic has been linked to environmental instability brought on by volcanic outgassing and greenhouse conditions but the relative importance of the myriad of environmental stressors at this time on recovery dynamics is not well understood previous workers have documented both overall delayed biotic recovery for the entirety of the early triassic but also incipient recoveries that appear to occur relatively early after the initial extinction event here we explore the patterns of extinction and recovery using several metrics of ecological complexity in marine benthic communities using a global dataset and compare several multiple regression models to determine which set of abiotic factors best predicts extinction and recovery dynamics we additionally test the importance of temporal scale of analysis in interpretations of recovery dynamics and modeling results by including analyses at the epoch stage and substage scales bracketing the interval of extinction and recovery we find differences in mode of recovery between the ecological metrics analyzed with some metrics exhibiting an early triassic recovery lag while others recover continuously or immediately following the initial extinction event we also find evidence of a global dienerian minimum with overall levels of community complexity significantly lower than earlier griesbachian communities suggesting a synchronous disturbance to the progression of recovery at this time the regression model with 18oapatite mean values as the response variable is most often found to be the best fit model across all time scales analyzed though proxies of rock record fidelity and paleontological sampling effort become more important in finer timescale analyses likely due to dwindling sample numbers out of the models tested these results suggest that global ocean temperatures best predict patterns of extinction and recovery across several ecological metrics and that thermal episodes during the initial extinction event and subsequently in the early triassic recovery period significantly suppressed benthic marine community health

carbon isotope record of the p t boundary and the lower triassic in the southern alps evidence for rapid changes in storage of organic carbon abstract the carbonate carbon isotope record of lower triassic shelf sediments was investigated in the pufels and l om picol uomo sections of the western central dolomites to derive a complete record from the permian triassic transition to the uppermost lower triassic from the western tethys the carbon isotope record shows the well studied decrease at the permian triassic boundary ptb followed by an increase to about 1 5 at the dienerian smithian boundary the 13c values increase to a pronounced 6 maximum a steady rapid drop until the upper smithian below 2 follows this 13c peak at the smithian spathian transition a steep rise to positive values is documented the positive carbon isotope peak is interpreted to reflect an interval of enhanced burial of organic carbon whereas the isotopic minima provide evidence of periods of oxidation of organic matter and or release of isotopically light carbon this may be ascribed to quickly changing environmental conditions which have already been postulated by paleontologists due to the delayed biotic recovery from the permian triassic extinction event because of the short time interval these positive isotope excursions represent their generation by burial of organic carbon in periods of high productivity and or anoxia appears plausible concurrent carbon isotopic excursions are reported from iran pakistan and oman as well as from southern china which indicate an at least tethys wide event if the excursion proves to be of global significance dark shale deposited in the pelagic panthalassa ocean may have acted as sink for organic carbon supporting the hypothesis of a periodically stratified ocean in the lower triassic

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

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

sudden and extreme hyperthermals low oxygen and sediment influx drove community phase shifts following the end permian mass extinction abstract we present a correlated record of carbon isotope geochemistry and sedimentological analysis for the lower triassic werfen formation from the italian dolomites macro and mid sized fossil diversity ecology and climate sensitivity are included to provide an integrated account of the benthic response to paleoenvironmental change novel communities developed in the wake of the mass extinction during pervasive fluctuations in environmental conditions in the sedimentary sequences of the werfen formation of the italian dolomites microbialites microconchids foraminifera and ubiquitous flat clams formed a complex community within the first 500 000 years later increased sea surface temperatures and inundation of the seafloor with siliciclastic sediments favored infaunal bivalves and microgastropods persistent trends in the environment can produce directional often irreversible community shifts defined here as phase shifts phase shifts in ecosystem structure can be driven by environmental shifts across threshold boundaries to produce an abrupt and dramatic novel community composition a phenomenon readily observed during the early triassic previously described disaster forms including flat clams microconchids foraminifera and microbialites are re envisioned as a phase shift community we hypothesize that the unique persistent and reoccurring microbialite and mid sized fauna assemblages observed during the initial recovery from the end permian mass extinction and re appearing throughout the early triassic typify a phase shift community in the smithian infaunal bivalves and microgastropods represent a second phase shift community developed in response to a persistent directional rise in sea surface temperatures and enhanced sediment influx we compare and contrast phase shifts with other models for ecosystem recovery including trophic competition and earth system succession

temperature age and crust thickness distributions of loki patera on io from galileo nims data implications for resurfacing mechanism 1 a high spatial resolution multi wavelength observation by the galileo nims instrument has been analysed to determine the temperature and area distribution of a large portion of the ionian volcano loki patera the temperatures of the cooler components from a two temperature fit to the data can be used to determine ages of the surface the age of the floor along a profile across the floor of the caldera ranges from 10 to 80 days this puts the start of the resurfacing in july early august 2001 yielding a resurfacing rate of approximately 1 km day with the new lava spreading from the sw corner of the caldera in a ne direction this rate is consistent with resurfacing by foundering of the crust on a lava lake however the temperature distribution may also result from the emplacement of flows implied crust thicknesses derived using a lava cooling model range from 2 6 to 0 9 m

carbon isotope compositions of the late permian carbonate rocks in southern china their variations between the wujiaping and changxing formations abstract the carbon isotope compositions of the upper permian marine carbonate rocks in southern and eastern guizhou and central guangxi of southern china have been investigated the results reveal a 13c anomaly at the boundary between the wujiaping and changxing formations of the upper permian the 13c values in limestones of the wujiaping formation are mostly within the range of 3 5 and 5 0 whereas the 13c values in limestones of the changxing formation are mostly less than 3 0 ranging from 0 2 to 3 1 the carbon isotope negative excursion at the boundary between these two formations is helpful to differentiate the two stages wuchiapian and changxingian of the late permian in southern china if substantiated by sufficient fossil materials this also means that the 13c values of the carbonates were decreasing throughout the late permian and this change was accompanied by some rapid falls such as those in the permian triassic boundary and possibly in the wujiapingian and changxingian boundary during the late permian the consumption of organic carbon by the oxidation of the previously formed coals as a result of dry climates and tectonic uplifting must have exceeded the burial of organic carbon as in coal in addition lack of coal deposits during the late tatarian on the gondwana fragments suggests a global reduced coal accumulation consequently more 12c rich co2 was released into the atmosphere which might contribute to the 13c depletion seen in upper permian marine carbonates

experimental observations of saltwater up coning summary the proper management of coastal aquifers commonly requires an understanding of the behaviour of saltwater plumes underlying production wells the current understanding of saltwater up coning i e the pumping induced rise in the freshwater saltwater interface is based predominantly on theoretical constructs of salinity and flow responses to groundwater pumping plus a limited number of field scale and laboratory investigations there is a need to produce direct observations of saltwater up coning given the considerable and inherent uncertainties associated with the prediction of density dependent flow and dispersive solute transport behaviour in this study time series observations of saltwater up coning were made using controlled sand tank experiments of a two dimensional aquifer cross section a range of mixed convection ratios was tested by invoking different groundwater abstraction rates and saltwater densities the temporal development of up coning was characterised in terms of the height of the interface apex the width of the salt plume and the salinity of the pumping well experimental results were compared to an existing sharp interface analytical solution and close agreement was obtained for two of the cases higher freshwater saltwater density differences and lower pumping appeared to induce the largest deviations from theoretical up coning dispersive transport processes dominated during phases of near well up coning causing gradual increases in pumped water salinity although plumes became non dispersive after the interface made contact with the bore an interesting departure from the classical up coning shape was obtained for the situation of highest saltwater density and lowest pumping in which up coning occurred as an almost horizontal interface for the majority of the experiment eventually producing a double apex shape as the interface neared the well the experimental results could form a useful basis for the testing of density dependent groundwater flow and transport models since they offer controlled laboratory analogues of saltwater up coning

io s volcanism thermo physical models of silicate lava compared with observations of thermal emission abstract analyses of thermal infrared outbursts from the jovian satellite io indicate that at least some of these volcanic events are due to silicate lava analysis of the january 9 1990 outburst indicates that this was an active eruption consisting of a large lava flow with mass eruption rate of order 10 5 m 3 sec 1 and a sustained area at silicate liquidus temperatures this is interpreted as a series of fire fountains along a rift zone a possible alternative scenario is that of an overflowing lava lake with extensive fire fountaining the january 9 1990 event is unique as multispectral observations with respect to time were obtained in this paper a model is presented for the thermal energy lost by active and cooling silicate lava flows and lakes on io the model thermal emission is compared with earth based observations and voyager iris data the model a provides an explanation of the thermal anomalies on io s surface b provides constraints on flow behavior and extent and infers some flow parameters and c determines flow geometry and change in flow size with time and the temperature of each part of the flow or lava lake surface as a function of its age models of heat output from active lava flows or inactive but recently emplaced lava flows or overturning lava lakes alone are unable to reproduce the observations if the january 9 1990 event is the emplacement of a lava flow the equivalent of 27 such events per year would yield a volume of material sufficient if uniformly distributed to resurface all of io at a rate of 1 cm year

analytical solution for determining the critical condition of saltwater upconing in a leaky artesian aquifer saltwater upconing that occurs in an aquifer overlain by a leaky confining unit is described by an analytical model that assumes the existence of a sharp interface between the freshwater and saltwater and the occurrence of a critical rise in the interface above which only an unstable cone can exist at the critical rise the pressure on the freshwater side of the interface is equal to the pressure on the saltwater side of the interface also the curve for pressure versus depth on the freshwater side of the interface is tangent to the curve for pressure versus depth on the saltwater side of the interface at the critical condition and thus the slopes of the freshwater and saltwater pressure distribution curves are equal these two conditions equality of pressures and equality of pressure gradients are used to derive two equations that can be solved simultaneously for the critical interface rise and the associated critical pumping rate instead of assuming a fixed value for the critical rise of the interface its location is calculated using an analytical equation expressed in terms of aquifer and confining unit properties and well geometry the associated critical pumping rate is calculated as a function of aquifer and confining unit properties well geometry and the critical interface rise ratio for field conditions the critical rise of the interface and critical pumping rate can be calculated analytically or graphically in an example calculation the critical interface rise ratio which is the ratio of the critical interface rise divided by the distance from the original location of the interface to the bottom of the pumped well is calculated to be 0 710 and the critical pumping rate is calculated to be 3 72 104 m3 day

development of a largely anoxic stratified ocean and its temporary massive mixing at the permian triassic boundary supported by the sulfur isotopic record systematic sulfur isotope data for whole rock sulfides have been obtained from the chert dominated continuous pelagic sedimentary sequences spanning the permian triassic p tr boundary at tenjinmaru in the chichibu terrane and at sasayama in the tanba terrane in japan the p tr boundary is characterized by the occurrence of siliceous shales in association with a carbonaceous black mudstone which is similar in appearance to the worldwide distributed cretaceous tertiary k t boundary claystone the observed data clearly demonstrate a significant bimodalism the 34s 32s ratios with respect to cdt are generally low throughout the middle permian ca 39 to 25 0 and show a remarkable increase beginning in the lower upper permian and persisting into the lower triassic ca 20 to 2 0 with a temporary and drastic negative shift down to roughly the same isotopic level as in the middle permian just at the suspected p tr boundary ca 41 to 23 0 interestingly the mode of isotopic excursion across the p tr boundary is in striking contrast to that across the k t boundary which was recently described at kawaruppu in hokkado japan the apparent extent of fractionation with respect to contemporaneous seawater sulfate in the high 34s 32s group lies within the range of 25 10 0 which is quantitatively equivalent to the currently confirmed range of kinetic isotope effect during bacterial dissimilatory sulfate reduction and that in the low 34s 32s group mostly exceeds this range giving the values typically in the range of 45 10 0 which is similar to what is generally observed in the present day oceanic sediments the present data would provide strong evidence for the development of a largely stagnant anoxic stratified ocean which presumably began to form in the lower upper permian and persisted into the lower triassic and for a brief episode of its temporary massive mixing just at the suspected p tr boundary such an oceanic oxic anoxic history may account to some extent for the relatively high enrichments of chalcophile elements in basal triassic sediments in the world and add a significant constraint to the current arguments on the cause and consequence of the terminal permian mass extinction

interpreting carbon isotope excursions strangelove oceans large negative excursions in marine carbonate delta sup 13 c are commonly associated with period boundaries and mass extinctions explanations for these events must be consistent with limitations imposed by carbon isotope mass balance at steady state i e for excursions lasting more than 10 sup 5 yr the surface ocean delta sup 13 c is set by the organic fraction of the total carbon burial rate and the magnitude of the photosynthetic isotope effect the delta sup 13 c of the deep ocean and the surface to deep isotope gradient are set by both the organic fraction of the ocean s remineralized particulate flux and the magnitude of the isotope effect thus it is the carbon isotope composition of the deep ocean that is most reflective of internal oceanic processes the surface ocean records changes in the longer term throughput of carbon in the system the cessation of organic export from the surface ocean such as is presumed to have caused the strangelove ocean condition of the cretaceous tertiary k t boundary leads to an isotopically homogeneous ocean in decades to centuries if this condition persists the ocean s isotopic composition approaches that of the riverine weathering input in 10 sup 5 yr failure to approach this value during the k t event suggests continued production andmore burial of organic carbon dominantly in either terrestrial or shallow marine environments less

sequencing events across the permian triassic boundary guryul ravine kashmir india abstract the permian triassic boundary ptb section at guryul ravine kashmir india comprises a 100 m thick apparently conformable succession of mixed siliciclastic carbonate sediments deposited in a deep shelf or ramp setting this section although long important in debates concerning placement of the ptb has not previously been the focus of an integrated chemostratigraphic study in the present study samples from a 20 m thick interval straddling the ptb were analyzed for major and trace element concentrations toc tic rees and organic 13c 15n to investigate contemporaneous environmental changes the guryul ravine section exhibits a sequence of discrete events that provide potentially important information about the character and cause s of the ptb two transient negative c isotopic excursions within the upper changxingensis zone predate the late permian event horizon lpeh i e the global mass extinction event by 200 400 kyr and are associated with the onset of a major eustatic rise and with secondary extinction peaks these excursions may record minor environmental disturbances prior to the main end permian crisis supporting an intrinsic mechanism such as volcanism and climate change rather than an extrinsic mechanism such as a bolide impact the onset of a large 4 0 to 4 5 sustained negative c isotope shift marks the lpeh which is located at the zewan khunamuh formation contact 260 cm below the biostratigraphically defined ptb the guryul ravine section exhibits a stepwise extinction pattern with the largest peak between the lpeh and ptb and a secondary peak just above the ptb a pattern similar to that observed in the meishan d gssp

evidence for recurrent changes in lower triassic oceanic circulation of the tethys the δ13c record from marine sections in iran abstract stable carbon isotope curves derived from lower triassic carbonate rocks from three iranian sections are established to investigate changes in the carbon cycle during the early triassic in this area the sections are located in the south center abadeh north amol and northwest zal of iran all three curves show a similar pattern starting out with high 13 c values in the uppermost permian decreasing across the permian triassic boundary an increase toward more positive values during the griesbachian that slowly increase further up during the dienerian followed by a positive excursion to values as high as 8 near the dienerian smithian boundary during the smithian values return to below 0 whereas second positive excursion to values higher than 3 is recorded at the smithian spathian boundary again followed by a drop in 13 c into the spathian and a final excursion to positive values at the spathian anisian boundary the results from these iranian sections are consistent with previous studies from italy and china thus strongly suggesting that the recorded 13 c variability represents at least tethys wide geochemical signals moreover the new curves reveal evidence of high amplitude frequent oscillations pointing toward rapid and profound changes in the global carbon cycle during the lower triassic stratification of the ocean interrupted by episodic overturning transporting deep water to the ocean surface is a viable mechanism to account for the recorded isotope variations provided that the 13 c curve is representative of the global lower triassic ocean it has high potential for accurately dating sedimentary successions via chemostratigraphy

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

permian deposits and the permian triassic boundary in croatia palaeoclimatic implications based on palaeontological and geochemical data

impact of layered heterogeneity on transient saltwater upconing in coastal aquifers abstract this research investigated the effect of layered heterogeneity on transient saltwater upconing in a laboratory scale coastal aquifer the experiments were conducted in a 2d laboratory flow tank and the response of the saltwater wedge to pumping was analysed in a heterogeneous aquifer system where a low permeability layer was constructed in the middle of the aquifer the seawat code was used for validation and to perform additional simulations to explore the sensitivity of the critical pumping rate and the critical time to the main parameters characterising the low permeability layer which included its permeability thickness and position the experimental results showed that the presence of layered heterogeneity noticeably altered the shape and the intrusion length of the upconing wedge without inducing a change in the abstraction rate triggering saltwater upconing mechanism compared to the homogeneous case the numerical results of the layered aquifer provided excellent agreement with the experimental data for both the transient toe length and the shape of the steady state saltwater wedges the sensitivity analysis revealed that the critical pumping rate and the critical time was found to decrease considerably with decreasing hydraulic conductivity and thickness of the middle layer which evidences the higher vulnerability of such layered aquifer systems to the saltwater upconing in comparison to idealised homogeneous systems the results nonetheless showed that varying the position of the interlayer induced very little change on the critical pumping rate but the critical time would tend to decrease as the low permeability layer was moved deeper away from the pumping well particularly for smaller middle layer thickness

the influence of seawater carbonate chemistry mineralogy and diagenesis on calcium isotope variations in lower middle triassic carbonate rocks abstract the geological calcium cycle is linked to the geological carbon cycle through the weathering and burial of carbonate rocks as a result calcium ca isotope ratios 44ca 40ca expressed as 44 40ca can help to constrain ancient carbon cycle dynamics if ca cycle behavior can be reconstructed however the 44 40ca of carbonate rocks is influenced not only by the 44 40ca of seawater but also by diagenetic processes and fractionation associated with carbonate precipitation in this study we investigate the dominant controls on carbonate 44 40ca in upper permian to middle triassic limestones ca 253 to 244 ma from south china and turkey this time interval is ideal for assessing controls on ca isotope ratios in carbonate rocks because fluctuations in seawater 44 40ca may be expected based on several large carbon isotope 13c excursions ranging from 2 to 8 parallel negative 13c and 44 40ca excursions were previously identified across the end permian extinction horizon here we find a second negative excursion in 44 40ca of 0 2 within lower triassic strata in both south china and turkey however this excursion is not synchronous between regions and thus cannot be interpreted to reflect secular change in the 44 40ca of global seawater additionally 44 40ca values from turkey are consistently 0 3 lower than contemporaneous samples from south china providing further support for local or regional influences by measuring 44 40ca and sr concentrations sr in two stratigraphic sections located at opposite margins of the paleo tethys ocean we can determine whether the data represent global conditions e g secular variations in the 44 40ca of seawater versus local controls e g original mineralogy or diagenetic alteration the sr and 44 40ca data from this study are best described statistically by a log linear correlation that also exists in many previously published datasets of various geological ages using a model of early marine diagenetic water rock interaction we illustrate that this general correlation can be explained by the chemical evolution of bulk carbonate sediment samples with different initial mineralogical compositions that subsequently underwent recrystallization although early diagenetic resetting and carbonate mineralogy strongly influence the carbonate 44 40ca values the relationship between sr and 44 40ca holds potential for reconstructing first order secular changes in seawater 44 40ca composition

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

trace fossils and the aftermath of the permo triassic mass extinction evidence from northern italy abstract the duration of early triassic anoxia in the carbonate ramp settings of the werfen formation dolomites northern italy has been constrained using ichnofabric and sedimentological data this includes fine lamination and abundant pyrite framboids commonly reworked into lags by storm events the anoxic event spanned the entire griesbachian stage and extended from deep waters into extraordinarily shallow water settings evidence for oxygen deficiency can be found in mid and inner ramp facies the extent and duration of this event may at least partially explain the magnitude of the permo triassic mass extinction normal benthic conditions returned rapidly in the dienerian stage and pervasively bioturbated distal ramp facies testify to the ventilation of the deeper water areas of the region in post griesbachian times a post mass extinction radiation is not particularly well displayed in either trace fossil or body fossil diversity compilations from the dolomites moderate low levels of trace fossil diversity are maintained throughout the post griesbachian werfen formation whilst the body fossil data shows a moderate increase from the mid smithian stage there is thus a curious lag period spanning the dienerian to mid smithian when environmental conditions were apparently normal but the marine fauna failed to show any recovery

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

the final galileo ssi observations of io orbits g28 i33 abstract we present the observations of io acquired by the solid state imaging ssi experiment during the galileo millennium mission gmm and the strategy we used to plan the exploration of io despite galileo s tight restrictions on data volume and downlink capability and several spacecraft and camera anomalies due to the intense radiation close to jupiter there were many successful ssi observations during gmm four giant high latitude plumes including the largest plume ever observed on io were documented over a period of eight months only faint evidence of such plumes had been seen since the voyager 2 encounter despite monitoring by galileo during the previous five years moreover the source of one of the plumes was tvashtar catena demonstrating that a single site can exhibit remarkably diverse eruption styles from a curtain of lava fountains to extensive surface flows and finally a 400 km high plume over a relatively short period of time 13 months between orbits i25 and g29 despite this substantial activity no evidence of any truly new volcanic center was seen during the six years of galileo observations the recent observations also revealed details of mass wasting processes acting on io slumping and landsliding dominate and occur in close proximity to each other demonstrating spatial variation in material properties over distances of several kilometers however despite the ubiquitous evidence for mass wasting the rate of volcanic resurfacing seems to dominate the floors of paterae in proximity to mountains are generally free of debris finally the highest resolution observations obtained during galileo s final encounters with io provided further evidence for a wide diversity of surface processes at work on io

io loki patera as a magma sea 1 we develop a physical model for loki patera as a magma sea we calculate the total volume of magma moving through the loki patera volcanic system every resurfacing cycle 540 days and the resulting variation in thermal emission the rate of magma solidification at times reaches 3 106 kg s 1 with a total solidified volume averaging 100 km3 yr 1 a simulation of gas physical chemistry evolution yields the crust porosity profile and the timescale when it will become dense enough to founder in a manner consistent with observations the loki patera surface temperature distribution shows that different areas are at different life cycle stages on a regional scale however there can be coordinated activity indicated by the wave of thermal change which progresses from loki patera s sw quadrant toward the ne at a rate of 1 km d 1 using the observed surface temperature distribution we test several mechanisms for resurfacing loki patera finding that resurfacing with lava flows is not realistic only the crustal foundering process is consistent with observations these tests also discovered that sinking crust has a heat deficit which promotes the solidification of additional magma onto the sinking plate bulking up in the limiting case the mass of sinking material can increase to a mass of 3 times that of the foundering plate with all this solid matter sinking there is a compensating upward motion in the liquid magma this can be in excess of 2 m yr 1 in this manner solid liquid convection is occurring in the sea

geochemical evidence from bio apatite for multiple oceanic anoxic events during permian triassic transition and the link with end permian extinction and recovery abstract a detailed 20 myr redox history of permian to triassic oceans changhsingian to carnian stages has been constructed using ce anomaly ce and th u ratios from conodont albid crown apatite material the results show that the well established phenomenon of intense ocean anoxia coincident with the end permian mass extinction is faithfully recorded in conodont ce and th u data extending this conodont redox record shows that end permian anoxia persisted possibly into the earliest dienerian stage and that two intense oceanic anoxic events also occurred later in the early triassic earliest smithian earliest spathian and middle spathian followed by a weaker manifestation of anoxia in the anisian stage seen in ce data marine benthic radiation following the end permian mass extinction began after the smithian earliest spathian anoxic event suggesting a suppression of evolution prior to this due to these inimical conditions the failure of the middle spathian anoxic event to retard the evolutionary rebound implies shallow shelf seas remained well ventilated at this time even if the oceans did not other attributes of the early triassic record also closely coincide with redox fluctuations phases of anoxia intensification saw the proliferation of microbial carbonates and major negative carbon isotope swings that can be attributed to chemocline shallowing causing alkalinity pulses and enrichment in light remineralised carbon and or indicate a trigger meachnaims related to increased fluxes of light c from siberian volcanic sources

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

massive volcanism at the permian triassic boundary and its impact on the isotopic composition of the ocean and atmosphere abstract bulk carbonate and conodonts from three permian triassic p t boundary sections at guryul ravine kashmir abadeh central iran and pufels bula bulla italy were investigated for 13 c and 18 o carbon isotope data highlight environmental changes across the p t boundary and show the following features 1 a gradual decrease of 4 to more than 7 starting in the late permian changhsingian c bachmanni zone with two superimposed transient positive excursions in the c meishanensis h praeparvus and the m ultima s mostleri zones 2 two 13 c minima the first at the p t boundary and a higher occasionally double minimum in the lower i isarcica zone it is unlikely that the short lived phenomena such as a breakdown in biological productivity due to catastrophic mass extinction a sudden release of oceanic methane hydrates or meteorite impact s could have been the main control on the latest permian carbon isotope curve because of its prolonged 0 5 ma duration gradual decrease and the existence of a 1 positive shift at the main extinction horizon the p t boundary 13 c trend matches in time and magnitude the eruption of the siberian traps and other contemporaneous volcanism suggesting that volcanogenic effects such as outgassed co 2 from volcanism and even more thermal metamorphism of organic rich sediments as the likely cause of the negative trend

spatial characterization of the seawater upconing process in a coastal mediterranean aquifer plana de castellon spain evolution and controls in this contribution we describe the formation and evolution of the upconing process in a mediterranean coastal aquifer the study area has experienced severe salinization over the last 40 years because of intensive exploitation of groundwater we used historical and current records of piezometric levels and chloride concentrations to trace the development of the salinization of the aquifer we defined the 3d shape of the saline wedge from the spatial distribution of chloride concentrations and vertical well logs of electrical conductivity using monitoring network data upconing first appeared in the early 90s and has continued until the present day in this study we examined the intensity of the upconing process dry periods and the associated increases in pumping caused the advance of seawater intrusion the sharp reduction in groundwater withdrawals over the last 10 years has caused the saline wedge to move backwards although the ongoing pumping and the climate conditions mean that this retreat is quite slow

isotope shifts in the late permian of the delaware basin texas precisely timed by varved sediments closely spaced samples 285 in number of varved sediments from the upper permian in delaware basin texas have been analyzed for 13ccarb 13corg 18ocarb corg ccarb and calcite dolomite 13c records a dramatic rise from 2 8 to 5 7 in only 4400 years detected in three sections across the basin extrapolating smoothly through a 600 year interruption by a local west side of the basin fresh water inflow evidenced by low 18o this continuity and low corg within the basin both indicate that the excess net deposition of corg necessary to generate the rise in 13c took place in the ocean external to the delaware basin correlation with similar records from the zechstein basin suggest that the event was world wide although this poses obvious difficulties for the carbon cycle the rate of rise of 13c and its sustained high level must imply conversions of oxidized carbon to reduced carbon that are very large depending on which reservoirs were involved

analysis of saltwater upconing beneath a pumping well abstract aquifer systems that contain freshwater and saltwater are usually stratified with the more dense saltwater underlying the freshwater a groundwater well discharging from the freshwater zone causes the saltwater to move upwards towards the well this phenomenon is known as saltwater upconing two methods of analysis the sharp interface method and the fluid density dependent solute transport method are used to simulate saltwater upconing numerical experiments including comparisons of the two methods indicate 1 for low to moderate pumpages the 50 isochlor and sharp interface correlate well 2 the well can discharge significant concentrations of saltwater even though a stable cone according to the sharp interface method exists below the well screen 3 an almost linear relationship exists between the well discharge rate and the concentration of the discharge at low pumping rates that maintain a stable cone and 4 upconing is sensitive to transverse dispersivity whereas it is insensitive to longitudinal dispersivity a simulation of upconing at test site no 4 truro cape cod massachusetts indicates that the appropriate field value of transverse dispersivity is very small this supports the validity of the sharp interface assumption for analyzing the behavior of systems with thin saltwater freshwater transition zones

extraterrestrial lava lakes abstract active lava lakes are rare on earth with only ten documented examples all formed by lavas of basaltic composition and housed inside summit craters or calderas the existence of lava lakes on other planetary bodies may imply similarities in either composition or volcano tectonic settings and so has important implications for understanding the link between melt production and volcanism we review lava lakes on earth and other planets particularly active caldera like features interpreted to be currently containing active lava lakes on jupiter s moon io and features interpreted as remnants of lava lakes on venus and mars mercury and the moon do not boast the major calderas or shield volcanoes of their larger rocky neighbors partly due to a horizontally compressive tectonic regime arising from global contraction that makes it difficult to move melts through the upper crust we discuss the evidence for active lava lakes on io and show how modeling based on terrestrial lava lakes can reveal how these phenomena differ on both bodies the superficial similarities do not necessarily imply that the plumbing is similar observations of the largest lava lake on io loki patera provide insight into the nature of ionian lava lakes in general which may be more similar to eruptive episodes on the east pacific rise on earth which lead to temporary lava lakes although temporal data for io s lava lake activity are scarce studies of temporal variability of lava lakes on earth are useful for providing ground truth for comparisons future studies of earth by remote sensing and field observations and of io by both ground based observations and future missions are needed to answer many questions including why lava lakes rare on earth appear to be common on io

mercury anomalies associated with three extinction events capitanian crisis latest permian extinction and the smithian spathian extinction in nw pangea strata of permian early triassic age that include a record of three major extinction events capitanian crisis latest permian extinction and the smithian spathian extinction were examined at the festningen section spitsbergen over the c 12 ma record examined mercury in the sediments shows relatively constant background values of 0 005 0 010 g g 1 however there are notable spikes in hg concentration over an order of magnitude above background associated with the three extinctions the hg total organic carbon toc ratio shows similar large spikes indicating that they represent a true increase in hg loading to the environment we argue that these represent hg loading events associated with enhanced hg emissions from large igneous province lip events that are synchronous with the extinctions the hg anomalies are consistent across the nw margin of pangea indicating that widespread mercury loading occurred while this provides utility as a chemostratigraphic marker the hg spikes may also indicate loading of toxic metals to the environment a contributing cause to the mass extinction events

saltwater upconing in unconfined aquifers the need for skimming of fresh groundwater above a saline water body without producing an unacceptable contamination in the pumped water calls for the investigations carried out in this research work two axisymmetric models namely the steady state and the transient upconing models are developed with the assumption of an abrupt interface finite element method with an iterative scheme is employed in solving the steady state model whereas a method of finite element in space and finite differences in time is used with iterative schemes for the transient model the models are calibrated with the analytical solutions for the case of radial flow to a fully penetrating well in an unconfined aquifer a method of superimposing the effects of hydrodynamic dispersion on the upconing is discussed the simulation results of both models together with the technique of dimensional analysis provide information for establishing design criteria for optimal pumping or choice of well depth or both

the nature of the volcanic activity at loki insights from galileo nims and ppr data abstract loki is the largest patera and the most energetic hotspot on jupiter s moon io in turn the most volcanically active body in the solar system but the nature of the activity remains enigmatic we present detailed analysis of galileo near infrared mapping spectrometer nims and photopolarimeter radiometer ppr observations covering the 1 5 100 m wavelength range during the i24 i27 and i32 flybys the general pattern of activity during these flybys is consistent with previously proposed models of a resurfacing wave periodically crossing a silicate lava lake in particular our analysis of the i32 nims observations shows over much of the observed patera surface temperatures and implied ages closely matching those expected for a wave advancing counterclockwise at 0 94 1 38 km day the age pattern is different than other published analyses which do not show as clearly this azimuthal pattern our analysis also shows two additional distinctly different patera surfaces the first is located along the inner and outer margins where components with a 3 00 4 70 m color temperature of 425 k exist the second is located at the southwestern margin where components with a 550 k color temperature exist although the high temperatures could be caused by disruption of a lava lake crust some additional mechanism is required to explain why the southwest margin is different from the inner or outer ones finally analysis of the temperature profiles across the patera reveal a smoothness that is difficult to explain by simple lava cooling models paradoxically at a subpixel level wide temperature distributions exist which may be difficult to explain by just the presence of hot cracks in the lava crust the resurfacing wave and lava cooling models explain well the overall characteristics of the observations however additional physical processes perhaps involving heat transport by volatiles are needed to explain the more subtle features

the changing climate framework and depositional dynamics of triassic carbonate platforms from the dolomites abstract the triassic of the dolomites offers a valuable opportunity to investigate the relationships between climate fluctuations and the changing depositional dynamics of carbonate platforms the reconstruction of the large palaeoclimatic modification is based on the synthesis of multiple sedimentological palaeobotanical pedological and geochemical proxies the triassic climate fluctuations were generally fast in nature and were probably associated with a latitudinal shift of the monsoon belts during the triassic the dolomites were placed at an intertropical northern latitude of about 16 18 and were generally dominated by dry climate and elevated temperature at least five pulses toward moister climate are however documented dated to early olenekian middle anisian late ladinian middle carnian and late norian times within this variable climatic scenario the carbonate systems record a global evolutionary trend from late permian early triassic regional shelves rich in loose micrites and bio calcarenites to anisian ladinian synsedimentary cemented steep sided 35 40 high relief platforms and back to carnian low angle ramps moist transgressive episodes were surprisingly prone to the spreading of corals and other colonial reef organisms probably because of the reduced space competition by syndepositional cementation structures the permo triassic boundary extinction dramatically impacted on the calcified organism communities but the carbonate depositional architecture nevertheless stayed almost unaffected through the boundary the early triassic and earliest anisian were commonly associated with hyperhaline sometimes evaporitic conditions intervals of moister climate and efficient river discharge are however documented by earliest induan and early olenekian sediments the latter terrigenous deposits matched a crisis in the carbonate production after a return to arid conditions during the anisian a fluctuation toward moister climate developed associated to a massive continental vegetation cover the anisian tectonic activation of the region fragmented the previous carbonate shelf triggering the development of three generations of fast prograding but globally backstepping isolated platforms recording an increasing role of the synsedimentary cementation a dry climate dominated the late anisian and early ladinian interval at the time a fast subsidence pulse was associated with platform drowning and basinal anoxia only a few aggrading pinnacles were able to survive providing the nuclei for larger prograding platforms during a dry climate interval massive syndepositional cementation generated a major source of carbonate carbonate production stayed active through the ladinian magmatic phase but the onset of volcanism was associated with a large modification in the platform carbonate facies which became dominated by automicrites moist climate phases are well documented again during the late ladinian followed by a return to dry conditions the late ladinian early carnian platforms prograded toward the eastern dolomites depocentre eventually infilling almost the whole of the accommodation space the middle portion of the carnian recorded renewed sharply moist phases associated with the demise of the rimmed platforms and with the return to loose sediment ramps at least four separated humid fluctuations can be identified in this carnian interval alone climate then returned to persistent aridity until the late norian moist phase

a close up look at io from galileo s near infrared mapping spectrometer infrared spectral images of jupiter s volcanic moon io acquired during the october and november 1999 and february 2000 flybys of the galileo spacecraft were used to study the thermal structure and sulfur dioxide distribution of active volcanoes loki patera the solar system s most powerful known volcano exhibits large expanses of dark cooling lava on its caldera floor prometheus the site of long lived plume activity has two major areas of thermal emission which support ideas of plume migration sulfur dioxide deposits were mapped at local scales and show a more complex relationship to surface colors than previously thought indicating the presence of other sulfur compounds

io s loki patera modeling of three brightening events in 2013 2016 abstract loki patera is one of the most dramatically time variable volcanic features on io exhibiting episodic brightening events every 1 3 years that may produce over 15 of io s global heat flow we observed three such brightening events with adaptive optics imaging at the keck and gemini n telescopes over the course of 70 nights of observation in 2013 2016 the high cadence and multi wavelength nature of the observations provides constraints on models for activity at loki patera the matson et al 2006 model for loki patera as an overturning basaltic magma sea is adapted to fit the observations of all three events in particular we adjust the details of the overturn progression and modify the lava thermal properties to include dependencies on temperature and porosity to improve the fit to the data the preferred models find overturn front propagation velocities of 1 2 1 7 km day corresponding to resurfacing rates of 1500 2200 m2 s the time intervals of 440 540 days between successive events are roughly consistent with the 540 day period calculated by rathbun et al 2002 for events prior to 2001 the best coverage was obtained for the 2016 brightening model fits to this event require a lava bulk thermal conductivity of 0 55 0 75 w m k with the best fit obtained for a value of 0 7 w m k and an average porosity that decreases during cooling for all three events the overturn front appears to propagate around the patera in the clockwise direction opposite to what has been inferred for past brightening events there is evidence that the overturn may be more complex than a single propagating wave perhaps involving multiple simultaneous resurfacing waves as well as portions of the patera that are active even after the nominal bright phase has ended the measured intensities are anomalously low when loki patera is viewed at high emission angles suggestive of topographic shadowing due to a raised area or the edge of the depression in which the magma sea resides

lower triassic δ13c isotope curve from shallow marine carbonates in japan panthalassa realm confirmation of the tethys δ13c curve abstract 13 c data from tethyan sections provide evidence of profound changes in the carbon cycle during the lower triassic sections from the panthalassa realm were investigated to establish whether these variations are also present there in the jurassic accretionary wedges in japan exotic blocks having a panthalassan affinity have been incorporated the majority of the blocks are pelagic cherts but rare shallow water carbonates are also present we present a 13 c study on the lower triassic of a shallow water carbonate succession deposited on a mid oceanic seamount and accreted to the chichibu belt japan two sections have been measured at kamura central kyushu island the carbon isotope curve shows depleted values across the permian triassic boundary ptb subsequently followed by an increase to heavier values into the dienerian culminating in a maximum of almost 4 v pdb before a steep drop at a stratigraphic gap low values are recorded in the smithian but rise to enriched 13 c values 3 5 near the smithian spathian boundary the observed trend of the stable carbon isotope curve from japanese sediments mirrors the curves derived from sections in the tethys e g italy iran turkey oman and the south china nanpanjing basin our results support the interpretation of this curve as representing a global trend across the ptb and in the lower triassic although some distinct features are absent around the dienerian smithian boundary profound variations of the carbon isotope curve in the lower triassic are presented for the first time from a marine section outside of the tethys they indicate severe global changes in the lower triassic carbon cycle and the causative processes must have significantly contributed to the delayed biotic recovery after the ptb large amounts of carbon were shifted between carbon reservoirs most probably between shallow and deep ocean waters and or ocean and sediment anoxia followed by overturn of the ocean water masses may have been the mechanism which quickly altered ecological conditions in the ocean leading to variable availability of nutrients and oxygen and changes in isotope composition of the available carbon in the surface waters that was incorporated in the precipitated carbonate

climatic and oceanographic isotopic signals from the carbonate rock record and their preservation stable isotopic data from marine limestones and their constituent fossils and marine cements can provide quantitative evidence for changes in global climate and ocean circulation oxygen isotopic data can indicate changes in temperature and ocean composition whereas stratigraphic variation in carbon isotope ratios may reflect changes in the carbon cycle that can be linked to changes in oceanic productivity and atmospheric greenhouse gases terrestrial carbonates meteoric cements calcretes and speleothems similarly offer significant potential for understanding the evolution of terrestrial climates by providing evidence for the composition of rainwater and the nature of vegetative cover primary environmental isotopic signals may be obscured by the effects of post depositional diagenetic alteration cementation and replacement reactions can take place in a wide range of diagenetic environments the diagenetic history of an individual limestone is determined by a combination of its mineralogical diagenetic potential and depositional setting together with subsequent changes in relative sea level and burial history carbon isotopic values are less prone to alteration during diagenesis than oxygen values but shifts can be significant where organogenic carbon is incorporated linear covariation of carbon and oxygen values is not a reliable indicator of diagenetic alteration water rock interaction and fluid mixing may produce non linear distributions attempts to determine long term changes in climatic and oceanographie conditions through isotope stratigraphy of shallow water limestones must include an assessment of the diagenetic history of the materials analysed petrographic examination using conventional microscopy backed up where appropriate by cathodoluminescence and scanning electron microscopy together with elemental and strontium isotopic analysis can help to identify the effects of diagenetic alteration where material with a range of different degrees of alteration is preserved in the same sediment it may be possible to compare patterns of isotopic and elemental variation and to attempt to unravel the effects of diagenesis in order to determine primary environmental isotopic signals recent research has shown that these techniques can be successfully employed in both phanerozoic and precambrian sediments

evolutionary models in the early triassic marine realm abstract the relative influences of extrinsic compared to intrinsic drivers of evolutionary change have long been theorized and debated in the fossil record ecological recoveries from mass extinction events present records in which to examine these contrasts competition in a low diversity world reproductive strategy reconstruction of trophic systems and ecological specialization represent possible intrinsic controls on diversification feedback between diversity and abundance shifts of marine organisms with biogeochemical cycling and environmental conditions act as extrinsic controls on recovery process and rate disentangling these evolutionary pressures is a major challenge for understanding evolutionary recovery from mass extinction the end permian mass extinction 251 88 ma represents the largest mass extinction in earth history and led to an extended recovery interval which lasted the duration of the early triassic 4 8 myr and beyond recent analyses suggest that the survivors of the mass extinction were biased toward organisms with higher metabolic rates that were more resilient against the volatile environmental changes that pervaded the early triassic including extreme temperature events low ph and low oxygen conditions we use the early triassic recovery of gastropods echinoids and ammonoids to examine the processes of taxonomic and ecological evolution in response to or in spite of extrinsic environmental perturbations the case studies of benthic gastropods and echinoids when compared to pelagic ammonoids reflect similarities and differences in recovery following the end permian mass extinction gastropods and echinoids exhibit evidence of strong extrinsic environmental limitations which implicate the availability of refugia as a control on recovery low initial taxonomic diversity of survivors may have also limited the evolutionary recovery of both clades abundant and diverse microgastropod assemblages are interpreted as an adaptation to extreme environmental conditions the morphological diversity of disarticulated echinoid spines and plates described in the southwestern united states and examination of phylogenetic ghost lineages hints at a significant hidden diversity of early triassic echinoids ammonoids experienced taxonomic resets but are shown to be resilient to repeated environmental perturbations in the boreal ocean over the duration of the early triassic ammonoids may have adapted to persistent latitudinal temperature gradients and oxygen minimum zones that developed in the early triassic ocean basins

a unique geochemical record at the permian triassic boundary a 330 metre core drilled through the marine permian triassic boundary in the carnic alps of austria allows closely correlated studies of geochemistry petrography and palaeontology across the boundary the isotope shifts and metal concentrations are extended multiple and complex and do not resemble those seen at the cretaceous tertiary boundary both the carbon isotope shifts and the chemical events including an indium anomaly may have causes related to a major regression of the sea

some aspects of the permian triassic boundary ptb and of the possible causes for the biotic crisis around this boundary abstract the first appearance datum fad of hindeodus parvus is an excellent datum very close to the base of the otoceras woodwardi zone priority base of the triassic for the first time it allows an exact correlation of the ptb in all marine facies and faunal realms the following features of the extinction and recovery patterns near the ptb are most important for the search for causes of the ptb biotic crisis 1 most strongly affected were the siliceous plankton radiolarians and the warm water benthos and nekton 2 most of the cold water faunas were not significantly affected 3 the recovery of the warm water benthos and siliceous plankton occurred only after an unusually long time during the late olenekian and middle triassic 4 the productivity of the terrestrial plants dropped strongly and the recovery was mainly in the upper olenekian and in the middle triassic 5 several terrestrial extinction events occurred at different levels within the upper permian considerable before the marine ptb at or close to the fad of lystrosaurus no extinction event in the terrestrial faunas can be observed 6 terrestrial faunal elements that survived the dzhulfian dorashamian extinctions were able to survive some months of extreme climatic conditions by hibernation like life stages vertebrates or by dry and freezing resistant eggs conchostracans 7 about 50 of the genera that disappeared at the ptb re appeared in the olenekian middle triassic interval lazarus taxa or in this time interval genera appeared that had undoubtedly evolved from genera that had disappeared at the ptb and 8 the ptb is preceded by mass occurrences of marine and continental fungi and the fungal spike ends abruptly a little before the ptb a scenario for the ptb biotic crisis is elaborated that takes into consideration the real not interpolated diversity patterns of different marine and continental fossil groups the exact correlation of bioevents in different faunal realms and facies the strong biotic crisis in the tethyan warm water faunas in contrast to the much weaker biotic event in cold water faunas the severe dzhulfian dorashamian climate in many parts of the world caused by the continent ocean configuration and by siberian trap volcanism the cooling of the boreal area by the northward drift of pangaea that interrupted the exchange of warm water benthos between the tethys and western north america during the guadalupian the extinction event at the guadalupian lopingian boundary that restricted most of the affected warm water faunas to the tethys the importance of lower scythian anoxia that reached an unusually shallow level and above all the effects of the contemporaneous huge volcanic events about 250 m y ago on the siberian platform and in the eastern tethys that caused a 3 6 months lasting volcanic winter with strong cooling in low latitudes followed by a strong global warming

high productivity in the earliest triassic ocean black shales southwest japan abstract bedded cherts containing the permian triassic p t boundary exposed in the tanba and chichibu belts southwest japan contain interbedded organic rich black shales the organic carbon concentration of black shales before thermal maturation was evaluated to be about 3 average considering their maturity levels kerogens do not contain any debris of higher plant origins but are mostly composed of structureless amorphous kerogen black shales comprise organic matter derived mainly from plankton with additional organic matter derived from bacterial activity showing that the high primary production took place intermittently in the earliest triassic a stratified ocean with a well developed oxygen minimum layer rich in nutrients was intermittently disturbed due to tectonically and or climatically induced active ocean current systems in the earliest triassic resulting in upwelling causing remarkably high primary production to form organic rich black shales

parallel trends in organic and inorganic carbon isotopes across the permian triassic boundary stable carbon isotope ratios in both inorganic and organic reservoirs have been widely applied to model environmental and sedimentological changes on a global scale most studies dealing with major extinction events have used the record of inorganic carbon in this paper the authors report the relation between shifts in carbon 13 content of organic matter and coexisting carbonate fractions at a major extinction event the permian triassic boundary they found that both delta sup 13 c sub carb and delta sup 13 c sub org of the surface ocean varied dramatically across the boundary but the fractionation delta sup 13 c between organic matter and carbonate remained constant this result appreciably restricts the interpretation of changes in the carbon cycle during this critical interval the new data are best explained by a combination of two mechanisms for variation in delta sup 13 c sub carb 1 burial and erosion of organic carbon with a long time constant and 2 sequestration of organic carbon into shallow and deep oceanic reservoirs with a shorter time constant for application to their case the first mechanism is limited by possible buildup of marine pco sub 2 which would increase the isotopic fractionation factor the second mechanism is limited in application to short term transient variations in delta sup 13 c modelingmore of the carbon cycle and its variations of delta sup 13 c must take both mechanisms into account less

post solidification cooling and the age of io s lava flows abstract the modeling of thermal emission from active lava flows must account for the cooling of the lava after solidification models of lava cooling applied to data collected by the galileo spacecraft have until now not taken this into consideration this is a flaw as lava flows on io are thought to be relatively thin with a range in thickness from 1 to 13 m once a flow is completely solidified a rapid process on a geological time scale the surface cools faster than the surface of a partially molten flow cooling via the base of the lava flow is also important and accelerates the solidification of the flow compared to the rate for the semi infinite approximation which is only valid for very deep lava bodies we introduce a new model which incorporates the solidification and basal cooling features this model gives a superior reproduction of the cooling of the 1997 pillan lava flows on io observed by the galileo spacecraft we also use the new model to determine what observations are necessary to constrain lava emplacement style at loki patera flows exhibit different cooling profiles from that expected from a lava lake we model cooling with a finite element code and make quantitative predictions for the behavior of lava flows and other lava bodies that can be tested against observations both on io and earth for example a 10 m thick ultramafic flow like those emplaced at pillan patera in 1997 solidifies in 450 days at which point the surface temperature has cooled to 280 k and takes another 390 days to cool to 249 k observations over a sufficient period of time reveal divergent cooling trends for different lava bodies examples lava flows and lava lakes have different cooling trends after the flow has solidified flows cool faster thin flows solidify and cool faster than flows of greater thickness the model can therefore be used as a diagnostic tool for constraining possible emplacement mechanisms and compositions of bodies of lava in remote sensing data

synchrony and causal relations between permian triassic boundary crises and siberian flood volcanism the permian triassic boundary records the most severe mass extinctions in earth9s history siberian flood volcanism the most profuse known such subaerial event produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less analysis of 40 ar 39 ar data from two tuffs in southern china yielded a date of 250 0 0 2 million years ago for the permian triassic boundary which is comparable to the inception of main stage siberian flood volcanism at 250 0 0 3 million years ago volcanogenic sulfate aerosols and the dynamic effects of the siberian plume likely contributed to environmental extrema that led to the mass extinctions

io heat flow from dark paterae abstract dark paterae on the jovian satellite io are evidence of recent volcanic activity some paterae appear to be entirely filled with dark volcanic material while others have only partially darkened floors dark paterae have area and heat flow longitudinal distributions that are bimodal as well as anti correlated with the longitudinal distribution of mountains on io at a global scale as part of our study of io s total heat flow we have examined the darkest paterae and quantified their thermal emission in order to assess their contribution this is the first time that the areas of the dark material in these paterae have been measured with such precision and correlated with their thermal emission dark paterae yield a significantly larger contribution to io s heat flow than dark volcanic fields dark paterae including loki patera yield at least 4 10 13 w or 40 of io s total heat flow in comparison dark flow fields yield 10 13 w or 10 of io s total heat flow of the total heat loss from dark paterae loki patera alone yields 10 13 w or 10 of io s total thermal emission

io s thermal emission from the galileo photopolarimeter radiometer galileo s photopolarimeter radiometer instrument mapped io s thermal emission during the i24 i25 and i27 flybys with a spatial resolution of 2 2 to 300 kilometers mapping of loki in i24 shows uniform temperatures for most of loki patera and high temperatures in the southwest corner probably resulting from an eruption that began 1 month before the observation most of loki patera was resurfaced before i27 pele s caldera floor has a low temperature of 160 kelvin whereas flows at pillan and zamama have temperatures of up to 200 kelvin global maps of nighttime temperatures provide a means for estimating global heat flow

constraints on early triassic carbon cycle dynamics from paired organic and inorganic carbon isotope records abstract large 13c excursions anomalous carbonate precipitates low diversity assemblages of small fossils and evidence for marine euxinia in uppermost permian and lower triassic strata bear more similarity to neoproterozoic carbonates than to the remainders of the permian and triassic systems middle triassic diversification of marine ecosystems coincided with the waning of anoxia and stabilization of the global carbon cycle suggesting that environment ecosystem linkages were important to biological recovery however the earth system behavior responsible for these large 13c excursions remains poorly constrained here we present a continuous early triassic 13corg record from south china and use it to test the extent to which early triassic excursions in 13ccarb record changes in the 13c of marine dissolved inorganic carbon dic regression analysis demonstrates a significant positive correlation between 13corg and 13ccarb across multiple sections that span a paleoenvironmental gradient such a correlation is incompatible with diagenetic alteration because no likely mechanism will alter both 13corg and 13ccarb records in parallel and therefore strongly indicates a primary depositional origin a simple explanation for this correlation is that a substantial portion of the preserved corg was derived from the contemporaneous dic pool implying that the observed excursions reflect variation in the 13c of the exogenic carbon reservoir ocean atmosphere biomass these findings support existing evidence that large 13c excursions are primary and therefore strengthen the case that large scale changes to the carbon cycle were mechanistically linked to the low diversity and small size of early triassic fossils associated sedimentary and biogeochemical phenomena further suggest that similar associations in neoproterozoic and cambrian strata may reflect the same underlying controls

permo triassic boundary superanoxia and stratified superocean records from lost deep sea pelagic cherts of japan and british columbia canada recorded a long term and worldwide deep sea anoxic oxygen depleted event across the permo triassic or paleozoic and mesozoic boundary 251 2 million years ago the symmetry in lithostratigraphy and redox condition of the boundary sections suggest that the superocean panthalassa became totally stratified for nearly 20 million years across the boundary the timing of onset climax and termination of the oceanic stratification correspond to global biotic events including the end guadalupian decline the end permian extinction and mid triassic recovery

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

geochemical events documented in inorganic carbon isotopes abstract screening of sampling and analytical data is crucial for the detection of real global shifts in marine 13c against the noise of diagenesis the real global shifts of 13c are of two types 1 long term secular shifts caused by changes in the fractional burial of organic carbon and 2 transient shifts caused by abrupt changes of biological productivity in the surface photic zone both are applicable to stratigraphic correlation but differ in their application to modelling of changes in oceanographic or atmospheric composition a recent compilation found 34 carbon isotope events in the phanerozoic and neoproterozoic equally distributed among positive and negative shifts this in itself attests to a variety of proximate causes of the shifts

controls on the formation of microbially induced sedimentary structures and biotic recovery in the lower triassic of arctic canada microbially induced sedimentary structures miss are reportedly widespread in the early triassic and their occurrence is attributed to either the extinction of marine grazers allowing mat preservation during the permo triassic mass extinction or the suppression of grazing due to harsh oxygen poor conditions in its aftermath here we report on the abundant occurrence of miss in the lower triassic blind fiord formation of the sverdrup basin arctic canada sedimentological analysis shows that mid shelf settings were dominated by deposition from cohesive sand mud flows that produced heterolithic rippled sandstone facies that pass down dip into laminated siltstones and ultimately basinal mudrocks the absence of storm beds and any other event beds points to an unusual climatic regime of humid quiet conditions characterized by near continuous run off geochemical proxies for oxygenation mo al th u and pyrite framboid analysis indicate that lower dysoxic conditions prevailed in the basin for much of the early triassic the resultant lack of bioturbation allowed the development and preservation of miss including wrinkle structures and bubble textures the microbial mats responsible for these structures are envisaged to have thrived on sandy substrates within the photic zone in oxygen poor conditions the dysoxic history was punctuated by better oxygenated phases which coincide with the loss of miss thus permo triassic boundary and griesbachian mudrocks from the deepest water settings have common benthos and a well developed tiered burrow profile dominated by phycosiphon the presence of the intense burrowing in the earliest triassic contradicts the notion that bioturbation was severely suppressed at this time due to extinction losses at the end of the permian the notion that early triassic miss preservation was caused by the extinction of mat grazers is not tenable

lower triassic large sea floor carbonate cements their origin and a mechanism for the prolonged biotic recovery from the end permian mass extinction precipitation of inorganic calcium carbonate is a common occurrence in both modern and ancient marine environments however synsedimentary growth of large 5 10 cm crystalline carbonate cements directly onto the sea floor has been thought to be limited to the proterozoic when seawaters were highly oversaturated with calcium carbonate compared to average phanerozoic values outer shelf to slope deposits of the lower triassic union wash formation in east central california deposited in oxygen restricted settings contain crystalline calcium carbonate cements that appear to have grown directly on the sea floor paleoenvironmental analyses indicate that these large calcium carbonate cements grew under conditions that were similar to those proposed for the precipitation of inorganic calcite in the black sea sulfate reduction of organic matter led to an increase in the amount of bicarbonate ion in deep waters and a concomitant increase in co 2 and alkalinity mixing with surface waters led to co 2 degassing and precipitation of cements from waters supersaturated with calcium carbonate the presence of these cements and associated facies thus provides evidence of harsh environmental conditions in the early triassic at the regional level which may have acted in concert with biotic effects of the end permian mass extinction as well as similar deleterious conditions e g shelf anoxia in other regions to produce a prolonged as well as temporally and geographically variable biotic recovery from this mass extinction