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

permian and triassic greenhouse crises paleoclimatic time series from permian and triassic paleosols reveal transient episodes of unusually warm and wet conditions interrupting long periods of cool and dry conditions usual for calcareous red paleosols some of these paleoclimatic events are known from stomatal index of fossil lepidopteris leaves to have been episodes of elevated global atmospheric co2 the magnitude of 19 known permian and triassic greenhouse crises varied considerably and they offer new evidence for the relationship between paleoclimate and atmospheric co2 levels these greenhouse crises also had marked effects on global lowland vegetation introducing frost sensitive tropical lycopsids to high latitudes and drought tolerant conifers to low latitude lowlands greenhouse events punctuate phases in plant evolution ottokaria callipteris plumsteadia rufloria lidgettonia tatarina pleuromeia and dicroidium scytophyllum floras greenhouse events also punctuate the evolution of reptilian dynasties successive pelycosaur dinocephalian dicynodont rhynchosaur and dinosaur faunas and respiratory adaptations such as enlarged bony secondary palate greenhouse crises of the late and middle permian were the most severe known and suggest a role for atmospheric pollution with ch4 and co2 in those mass extinction events probably from thermogenic cracking of coals by intrusive feeder dikes of flood basalts because of formalities in boundary definition these mass extinctions are neither end permian nor end guadalupian but upper changhsingian and mid capitanian respectively

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

stable isotope and trace element stratigraphy across the permian triassic transition a redefinition of the boundary in the velebit mountain croatia article i nfo stable isotopes of carbonates 13 ccarb 18 ocarb organic matter 13 corg 15 norg and major trace and rare earth element ree compositions of marine carbonate rocks of late permian to early triassic age were used to establish the position of the permian triassic boundary ptb at two continuous sections in the velebit mountain croatia the chosen sections rizvanusa and brezimenjaca are composed of two lithostratigraphic units the upper permian transitional dolomite and the overlying sandy dolomite the contact between these units characterized by the erosional features and sudden occurrence of ooids and siliciclastic grains was previously considered as the chronostratigraphic ptb the sandy dolomite is characterized by high content of non carbonate material up to 30 wt insoluble residue originated from erosion of the uplifted hinterland a relatively rich assemblage of permian fossils including geinitzina globivalvulina hemigordius b ioclasts of gastropods ostracods and brachiopods was found for the first time in sandy dolomite 5 m above the lithologic boundary in the rizvanusa section a rather abrupt negative 13 ccarb excursion in both sections appears in rocks showing no recognizable facies change within the sandy dolomite 2 at rizvanus aa nd 1 2 at brezimenjaca 11 m and 0 2 m above the lithologic contact respectively this level within the lower part of the sandy dolomite is proposed as the chemostratigraphic ptb in the rizvanus as ection the 13 corg values decline gradually from 25 in the upper permian to 29 in the lower triassic the first negative 13 corg

pennsylvanian early triassic stratigraphy in the alborz mountains iran new fieldwork was carried out in the central and eastern alborz addressing the sedimentary succession from the pennsylvanian to the early triassic a regional synthesis is proposed based on sedimentary analysis and a wide collection of new palaeontological data the moscovian qezelqaleh formation deposited in a mixed coastal marine and alluvial setting is present in a restricted area of the eastern alborz transgressing on the lower carboniferous mobarak and dozdehband formations the late gzhelian early sakmarian dorud group is instead distributed over most of the studied area being absent only in a narrow belt to the se the dorud group is typically tripartite with a terrigenous unit in the lower part toyeh formation a carbonate intermediate part emarat and ghosnavi formations the former particularly rich in fusulinids and a terrigenous upper unit shah zeid formation which however seems to be confined to the central alborz a major gap in sedimentation occurred before the deposition of the overlying ruteh limestone a thick package of packstone wackestone interpreted as a carbonate ramp of middle permian age wordian capitanian the ruteh limestone is absent in the eastern part of the range and everywhere ends with an emersion surface that may be karstified or covered by a lateritic soil the late permian transgression was directed southwards in the central alborz where marine facies nesen formation are more common time equivalent alluvial fans with marsh intercalations and lateritic soils qeshlaq formation are present in the east towards the end of the permian most of the alborz emerged the marine facies being restricted to a small area on the caspian side of the central alborz there the permo triassic boundary interval is somewhat similar to the abadeh shahreza belt in central iran and contains oolites flat microbialites and domal stromatolites forming the base of the elikah formation the p t boundary is established on the basis of conodonts small foraminifera and stable isotope data the development of the lower and middle part of the elikah formation still early triassic in age contains vermicular bioturbated mudstone wackestone and anachronostic facies like gastropod oolites and flat pebble conglomerates three major factors control the sedimentary evolution the succession is in phase with global sea level curve in the moscovian and from the middle permian upwards it is out of phase around the carboniferous permian boundary when the dorud group was deposited during a global lowstand of sealevel when the global deglaciation started in the sakmarian sedimentation stopped in the alborz and the area emerged therefore there is a consistent geodynamic control from the middle permian upwards passive margin conditions control the sedimentary evolution of the basin which had its depocentre s to the north climate also had a significant role as the alborz drifted quickly northwards with other central iran blocks towards the turan active margin it passed from a southern latitude through the aridity belt in the middle permian across the equatorial humid belt in the late permian and reached the northern arid tropical belt in the triassic

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

is mid late paleozoic ocean water chemistry coupled with epeiric seawater isotope records isotopes of epeiric sea carbonates are used to construct seawater records for modeling global changes in paleozoic ocean chemistry climate and for intercontinental correlation we present for the first time geochemical results of paleozoic brachiopods biogenic low mg calcite blmc from open ocean permian carboniferous seamounts of japan situated in the tropical mid panthalassic ocean strontium isotope values of blmc from the panthalassic and paleotethys oceans are coupled with those of coeval specimens from epeiric seas of north america europe and russia p 0 393 but not with those of epeiric sea whole rocks matrix aragonite calcite mac p 0 029 and conodonts biogenic apatite ba p 0 031 oxygen isotope values of blmc from the panthalassic and paleotethys exhibit mixed results with studies of counterparts from epeiric seas p 0 596 reflecting overprinting of local environmental conditions on global trends carbon isotope values of blmc and mac from the panthalassic and paleotethys oceans are generally dissimilar to those of coeval material from epeiric seas of north america europe and russia p 0 001 and 0 002 respectively factors such as water mass stratification evaporation dilution depth temperature carbon burial and or oxidation variations and syndepositional diagenesis within the local environment probably influenced the chemistry of the fauna and accumulating sediments this decoupling of carbon and oxygen isotope values from the open ocean with those from epeiric seas makes questionable the use of isotope results from epeiric seas for international correlation constructing global seawater records determining fluxes in the global carbon cycle and for modeling climate changes and subsequently atmospheric carbon dioxide levels

isotope excursions and palaeotemperature estimates from the permian triassic boundary in the southern alps italy abstract the end permian mass extinction event coincides with a dramatic negative shift in both the 13c and the 18o isotope record at or near the extinction horizon from multiple marine and terrestrial sections round the globe this study has identified the isotope excursions in a shallow water carbonate dominated section at val brutta in the southern alps high resolution bulk rock sampling revealed that there is an average 13ccarb negative shift of 4 and a 18ocarb shift of 6 this is similar to the isotope record at other nearby localities this section like many others shows a degree of recrystallisation which hampers absolute palaeotemperature calculations however some brachiopod fossils including specimens of comelicania and janiceps found within the beds that contain the bulk rock anomaly appear to be remarkably well preserved and still retain their internal structure and the primary isotopic variation across the shell as such they have been successfully analysed and the data used to produce a palaeotemperature estimate at the time of the isotope anomaly of between 26 and 29 c for latest permian

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

heterogeneity cyclicity and diagenesis in a mississippian brachiopod shell of palaeoequatorial britain a shell of gigantoproductus okensis shows twenty growth lines with marked changes of fabric indicating periodical reduction of growth rates caused by environmental perturbations the number of growth lines suggests a lifespan of 20 years in agreement with the survival rates of extant brachiopods and with spiral deviation analysis geochemical analyses across the growth profile show a heterogeneous distribution of stable isotopes and trace elements it is possible to distinguish primary from altered carbonate and to interpret the isotopic data the oxygen isotope signal in the unaltered parts is periodical and annual with oscillation of 1 1 the higher values are at the growth lines winter and therefore most likely related to monsoon circulation during the visean the annual periodicity seems also present in the altered part of the shell suggesting that diagenesis could have reset the primary values but preserved their cyclicity

interpreting benthic oxygen levels in mudrocks a new approach quantified paleoecology and gamma ray spectrometry have been applied in the analysis of the kimmeridge clay a highly organic rich british jurassic mudrock decreasing benthic oxygen trends are reflected in decreasing species richness and dominance diversity values similarly the degree of fragmentation of the benthos reflects the benthic energy levels and covaries with benthic oxygen the calculation of authigenic uranium values from data gathered by gamma ray spectrometry shows enrichment in more oxygen deficient environments the good correlation between the independently derived paleoecological and authigenic u data indicates the importance of these techniques in environmental analysis of marine petroleum source rocks

geochemistry of modern brachiopods applications and implications for oceanography and paleoceanography abstract modern rhynchonellida terebratulida thecideida and a few inarticulated brachiopods were collected live or soon after death at 30 locations from depths of 2 3940 m from the equator to high latitudes covering the atlantic pacific indian caribbean and mediterranean oceans seas well preserved fibers of the secondary layer combined with sr 450 1928 mg kg mn 1 199 mg kg and fe 1 610 mg kg contents confirm with few exceptions the excellent preservation of the modern brachiopod material evaluation of the stable isotope compositions was conducted on 276 specimens and on 374 published samples for a total database of 650 samples from 80 locations it revealed that oxygen isotope incorporation into shell calcite secondary layer of modern articulated brachiopods in most cases occurs in equilibrium with the ambient water and as such reflects surrounding environmental conditions thecideida as a group shallow water and low latitude incorporate oxygen isotopes 3 04 to 0 35 into shell calcite in equilibrium with their ambient water a large majority of genera and species of the terebratulida shallow water and low mid latitude also incorporate oxygen 2 30 to 3 48 into shell calcite in isotopic equilibrium with their surrounding water in contrast equilibrium incorporation of oxygen isotopes into shell calcite by the rhynchonellida is uncertain but a vital effect probably applies to the craniida the question of equilibrium disequilibrium incorporation of carbon isotopes into shell calcite of modern brachiopods remains unresolved at this time isotope compositions range up to 4 5 5 6 and 1 5 for 13 c and up to 5 5 5 9 and 0 3 for 18 o for shallow water low mid and high latitude brachiopods respectively strontium isotopes of modern brachiopods as expected show no significant variation with location latitude water depth temperature salinity and general water conditions once local habitat and ecological influences of fossil brachiopods from similar latitudes are considered their isotopic elemental values should be valuable diagenetic indicators and important oceanographic chemostratigraphic proxies

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

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

palaeoclimate interpretation of stable isotope data from lake sediment archives the isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments this article reviews the controls on the isotope composition of lacustrine skeletal and non skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature precipitation patterns evaporation and the carbon cycle it highlights the differences in the palaeoclimate potential of a wide range of lakes ranging from open to closed lake basins a large number of the case histories but not all are drawn from studies of temperate lakes from europe large closed lake systems in the tropics and elsewhere lose water predominantly through evaporation and contain sediments with variable and generally high 18o values fluctuations in the isotope composition of authigenic or biogenic minerals are mainly a function of long term changes in the precipitation evaporation ratio in contrast small open lakes which have a degree of through flow typically contain sediments with 18o values that vary by no more than a few these variations are generally ascribed to variations in temperature or the isotope composition of precipitation p from which either an annual or seasonally specific signal can be gained these types of lakes are common in northern europe and at high altitudes the interpretation of isotope data from a lacustrine succession requires a knowledge of the local processes that might control and modify the signal their effects need to be quantified and a robust calibration using the modern lake system is necessary to establish the relationship between the measured signal the isotopic composition of the host waters and climate

δ18o and δ13c values of modern brachiopod shells abstract researchers have not rigorously tested the hypothesis that calcite from modern brachiopod shells is precipitated in oxygen isotope equilibrium with ambient seawater isotopic variability at the intraspecimen and intertaxon levels has not been examined without such data for modern brachiopods similar data from ancient brachiopods cannot be accurately interpreted in this study a survey is made of 18 o and 13 c values of terebratulid rhynchonellid thecideidine and craniacean brachiopods from antarctica the bay of fundy curacao japan new zealand norway puget sound palau sicily and south africa this suite of samples provides a wide range of taxonomic levels temperatures salinities and depositional environments for evaluating the degree of isotopic equilibrium attained during precipitation of brachiopod calcite new data indicate that modem brachiopod calcite is not always precipitated in oxygen and carbon isotope equilibrium with ambient seawater calcite from the primary layer and specialized shell structures hinge brachidium foramen interarea muscle scars are depleted in both 18 o and 13 c a characteristic of biological fractionation or vital effects often found in other calcerous marine organisms our findings suggest that these portions of the brachiopod shell should be avoided during sampling of ancient brachiopods secondary layer calcite the material most often analyzed in ancient brachiopods has higher 18 o and 13 c values which approach and sometimes correspond with predicted equilibrium values therefore secondary layer calcite is the most suitable portion of the brachiopod shell for use as an ancient seawater proxy although near equilibrium precipitation in secondary layer calcite is encouraging to those studying the isotopic composition of ancient oceans these data come with caveats large intraspecimen variability in the 18 o values of secondary layer calcite 1 in some samples limits the use of brachiopods as precise indicators of the 18 o value or temperature of ancient seawater the 18 o and 13 c values of secondary layer calcite deviate from predicted equilibrium values toward the lower values of the primary layer and specialized shell structures indicating a measurable vital effect in most cases measured 18 o values are lower than the calculated equilibrium values dictated by seasonal variations in the 18 o value and temperature of seawater ontogenetic variations in the 13 c values of secondary layer calcite have also been measured and must be assessed when interpreting ancient data modern brachiopods occur in a wide range of seawater salinities and temperatures therefore the relation between salinity and the 18 o value of seawater must be known to correctly calculate the temperature of calcite precipitation from secondary layer 18 o values errors of up to 15 c are found if ambient seawater is assumed to have a constant 18 o value e g 0 smow and the 18 o values of secondary layer calcite are used to calculate temperature coupled with vital effects and intraspecimen variability these errors can obscure the resolution of secular variations in the rock record

a biogeographically mixed late guadalupian late middle permian brachiopod fauna from an exotic limestone block at xiukang in lhaze county tibet a total of 17 brachiopod species belonging to 15 genera are recorded from a limestone block of about 3 4 km2 in the indus tsangbo suture zone at xiukang in lhaze county of tibet the brachiopod fauna generally indicates a late guadalupian age late wordian capitanian late middle permian based on its association with the timorites bearing ammonoid fauna and the presence of the brachiopod urushtenoidea crenulata palaeobiogeographically the fauna exhibits transitional mixed characters between the warm water cathaysian and cold to temperate gondwanan faunas and may have developed on a carbonate build up or seamount on the oceanic crust

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

palaeotethys seawater temperature rise and an intensified hydrological cycle following the end permian mass extinction abstract the end permian mass extinction has been associated with severe global warming main stage volcanism of the siberian traps occurred at or near the extinction interval and has been proposed as a likely greenhouse catalyst in this study a high resolution 18o record is established using diagenetically resistant apatite of conodonts and low mg calcite of brachiopods from stratigraphically well constrained permian triassic p tr boundary successions in northwestern iran a new evaluation is made for previously published conodont 18o values from south china and revised palaeotemperatures are presented together with new data from wuchiapingian to griesbachian sections in iran 18o data from p tr sections in iran document tropical sea surface temperatures sst of 27 33 c during the changhsingian with a negative shift in 18o starting at the extinction horizon translating into a warming of ssts to over 35 c the results are consistent with re calculated ssts of the south chinese sections warming was associated with an enhanced hydrological cycle involving increased tropical precipitation and monsoonal activity in the tethys sea global warming intensification of the hydrological cycle and associated processes vertical water column stratification eutrophication and subsequent local anoxia may all have facilitated an extinction event

chemical diagenesis of a multicomponent carbonate system 2 stable isotopes abstract this study examines the oxygen and carbon isotopic distribution in the brachiopods crinoids rugose corals and matrix cement from the mississippian burlington limestone iowa and missouri and the silurian read bay formation arctic canada the isotopic data can be reconciled with textural and trace element observations only if the 18o content of ancient oceans differed from that of the present oceans this postulated secular variation in the 18o content of seawater requires a separate evaluation of the mississippian and silurian carbonate components examination of the 18o content of the least altered low mg calcite fossil components of the two formations suggests that the 18o of mississippian seawater was on average about 1 5 lighter and that of silurian seawater was about 5 5 lighter than the 18o of present day ocean water the average diagenetic shift in 18o for the read bay formation which stabilized in a partly closed diagenetic phreatic meteoric system is about 1 for the original low mg calcite and about 2 for the original high mg calcite and aragonite components conversely for the burlington limestone which stabilized in an open diagenetic phreatic meteoric system the average diagenetic shift in 18o is about 3 for the original low mg calcite and about 4 f r the original high mg calcite components the 13c values of the originally low mg calcite or high mg calcite with less than 7 mole mgco3 brachiopods and rugose corals the originally high mg calcite crinoids and the originally aragonite lime mud of the burlington limestone and read bay formation are bimodally distributed this bimodal 13c distribution is independent of geologic age inferred original mineralogy of the component degree of diagenetic alteration and the type of diagenetic meteoric system with components from both the read bay formation and burlington limestone contributing to both 13c groups the mode of the light 13c group is 0 25 and for the heavy 13c group it is 3 25 pdb both 13c groups also show a decrease in 13c of about 1 with increasing diagenetic alteration stabilization

carbon oxygen and strontium isotopes in paleozoic carbonate components an evaluation of original seawater chemistry proxies abstract brachiopods trilobites cements and whole rock matrix material were evaluated for their reliability as proxies of original seawater carbon oxygen and strontium isotope chemistry in this process coeval material was evaluated from individual horizons of formations spanning the permian to cambrian unaltered shells of low mg calcite articulated brachiopods retain original seawater oxygen carbon and strontium isotope compositions as old as late ordovician assessments of older specimens are hampered by a lack of suitable material coeval brachiopod whole rock sets a definitive assessment of cement marine chemistry is difficult due to the paucity of material but despite this caveat cements hold some promise for retaining original carbon and possibly strontium isotope seawater values in contrast the potential of whole rock material as a proxy of original seawater chemistry is quite complex in some but not all instances the carbon isotopic composition of whole rock after detailed scrutiny and evaluation appears to represent an original seawater chemistry signal in a few instances their oxygen isotope compositions reflect original seawater values unlike the stable isotope compositions the strontium isotopes of all studied whole rock material permian to upper cambrian appear not to reflect original seawater chemistry values thus the potential for retaining original seawater isotope chemistry and serving as specific proxies in order of decreasing reliability are 1 unaltered low mg calcite brachiopods c o and sr isotopes 2 pristine marine cements c and sr isotopes and 3 whole rock material c isotopes carbon oxygen and strontium isotope compositions of ordovician trilobites mirror those of coeval unaltered brachiopods cambrian trilobites hold significant promise as an important proxy of original seawater isotope chemistry but further studies are needed to ascertain their full potential the survey of isotopes in some ordovician and cambrian intermediate low mg calcite trilobites demonstrates their potential as an important proxy of original seawater chemistry

brachiopod fabric classes and biogeochemistry implications for the reconstruction and interpretation of seawater carbon isotope curves and records abstract shell calcite of modern and ancient brachiopods is an important proxy in reconstructing oceanographic conditions of seawater our investigation reveals significant magnesium and carbon isotope relationships between two classes of ancient brachiopods brachiopods of the extinct class strophomenata constructed two or three layer shells with a primary layer of randomized granular calcite a secondary layer of cross bladed laminar calcite and at times a tertiary layer of large prismatic calcite contemporaneous but extant rhynchonellata also have two or three layer shells but their secondary layer consists of calcite fibers instead of cross bladed laminar calcite furthermore inter crystalline space is limited in between the fibers of the secondary layer of the rhynchonellata but higher in the laminar secondary layer of strophomenata 18 o values of the two classes of brachiopods from the same stratigraphic interval of the lopingian nesen formation of north iran show a considerable overlap with no significant difference p 0 263 in contrast carbon isotope values are significantly different p 0 001 between contemporaneous strophomenata mean 2 18 and rhynchonellata mean 4 13 an evaluation of literature data of permian asselian and carboniferous visean and serpukhovian strophomenata mean 2 32 n 59 and rhynchonellata mean 4 94 n 105 confirms a similar differentiation in their carbon isotope values its higher magnesium contents suggest that the strophomenata probably secreted shell calcite at a faster rate than their coeval rhynchonellata this process may account for the 13 c differentiation observed between specimens of these two brachiopod classes however the different amount and composition of the organic matter of the strophomenata may also play a role in shaping their more negative carbon isotope signature thus the class of brachiopod and their associated different fabric must be adjusted for in their 13 c results and taken into consideration during the reconstruction of paleozoic global 13 c carbonate based seawater curves invariably in some earlier studies undetected impacts imposed by the class fabric on 13 c may account for some of the variation or trends documented in deep time seawater 13 c curves reconstructed with brachiopod populations from north america europe and russia

micromorphology and differential preservation of upper permian brachiopod low mg calcite abstract calcareous shells of rhynchonelliform brachiopods from the nesen formation late permian of iran were studied by scanning electron microscope cathodoluminescence and trace element chemistry to define their microstructure and state of preservation in the strophomenata shell succession the secondary layer consists of cross bladed laminar calcite and in a few species there is a tertiary layer of prisms in the rhynchonellata shell succession the secondary layer consists of elongated fibers and the tertiary layer of prisms all specimens were classified into six micromorphological types based on the fabric of the layer and the morphology of their microstructural units laminae fibres and prisms shell micromorphology and enclosing whole rock were further analyzed by cathodoluminescence and trace chemistry to assess preservation of brachiopod low mg calcite and specifically of their layers and microstructural units relative color frequencies were determined for each morphological type and degree of luminescence based on the lithology of the host rocks to evaluate the main factors that affect shell preservation results suggest that diagenetic alteration may depend on shell fabric and taxonomy as well as lithology of the host rock but it appears that the first and the second features are the most important factors in determining the degree of brachiopod low mg calcite preservation in general the fibrous secondary layer is likely more often and better preserved than its laminar counterpart irrespective of host rock lithology furthermore tertiary layers tend to be better preserved than secondary ones in rhynchonellata low mg calcite shells whereas no preferential preservation of either layer over the other was observed in the shells of strophomenata this information is important when selecting fossil brachiopod low mg calcite shells as geochemical proxies for paleoclimatic paleoecologic paleoenvironmental and other studies

δ18o and δ13c of permian brachiopods a record of seawater evolution and continental glaciation abstract two hundred sixty four 18 o and 13 c values of permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined these were then utilized for construction of baseline oxygen and carbon isotope curves for the permian interval in addition 21 13 c whole rock values are reported for the wordian and capitanian the early permian asselian to artinskian times are characterized by 2 5 decrease in oxygen isotope values from 0 7 to 3 3 v pdb this is attributed to a 4 7 c increase in temperature in the southern urals concomitant with the retreat of the permo carboniferous ice sheets and return of the 18 o depleted melt water into the oceans the late permian samples from iran jolfa at kuh e ali bashi and china meishan yield 18 o values and presumably temperatures similar to those that followed the termination of the large scale glaciation in the lower permian in between the upper kungurian to capitanian samples from the delaware basin guadalupe mountains are enriched in 18 o at 1 5 to 3 we have no definitive explanation for these data but tentatively suggest that the anomaly can potentially be a result of evaporative enrichment of seawater in 18 o due to intracratonic arid setting of the basin the 18 o enriched nature of the zechstein samples 1 2 to 2 5 on the other hand is in all probability a reflection of the high evaporation rates in the zechstein sea the permian interval is characterized by a relatively constant 13 c at about 4 the exceptions are again the brachiopods from the delaware basin guadalupe mountains which show 1 6 increase in the guadalupian to values of up to 5 9 in the wordian a tentative explanation as in the case of oxygen is based on the proposition that the semi enclosed delaware basin was likely stratified with sequestration of the 13 c depleted carbon to the deeper water layers and a complementary 13 c enrichment in the upper oxygenated layer the coeval open ocean water dic may have been similar to that of the remainder of the permian interval at 4 as indicated by whole rock carbonate samples from oman sicily and iran in the latest permian the trend mimics the well known 13 c drop at the permian triassic boundary

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

biochemostratigraphy of the upper frasnian in the namur dinant basin belgium implications for a global frasnian famennian pre event the upper frasnian sequence of the namur dinant basin in southern belgium consists of mixed siliclastic carbonate succession of a ramp setting where the sequence spans the rhenana linguiformis conodont zones earlier studies investigated the chemostratigraphic variations during the frasnian famennian event but little has been yet known about the nature of the counterpart variations that immediately preceded that time interval despite the scarcity of well preserved brachiopods sixty one calcitic shells were collected mainly from beds of the neuville and les valisettes formations lower and upper rhenana zones to investigate biochemostratigraphic profiles of oxygen carbon isotope and rare earth element ree variations of the time interval immediately before the frasnian famennian boundary the 18o and 13c values of the well preserved shells range from 9 5 to 5 6 vpdb 7 7 1 1 n 33 and from 1 8 to 3 8 vpdb 1 1 1 7 n 33 respectively which are within the documented global values the c and o isotope profiles exhibit parallel shifts particularly at the top of the neuville formation top of the lower rhenana zone which are associated with a sea level rise and shrinkage in the brachiopod community also the th u 0 9 0 6 n 16 and ce ce 2 2 0 5 n 16 ratios suggest deposition under reducing conditions consistent with sea transgression

shallow water redox conditions from the permian triassic boundary microbialite the rare earth element and iodine geochemistry of carbonates from turkey and south china redox sensitive elements serve as useful proxies of the oxygenation state of ancient environments but their interpretation may not always be straightforward to evaluate the inherent complexities rare earths and yttrium rey iodine and major element concentrations are determined in two carbonate sections spanning the permian triassic p tr transition in demirtas turkey and cili south china we use major oxides to identify non seawater rey sources such as siliciclastics fe oxides phosphates and diagenetic fluids additionally we employ y ho ratio la anomaly and light rare earth element depletion to identify which samples preserve a seawater like reysn distribution in contrast to past interpretations we find that the p tr boundary microbialites in both sections contain rey signatures indicative of deposition in an oxic environment these boundary microbialites have their base at the extinction horizon and are widespread within the tethyan region in the cili section the underlying permian limestone also preserves a seawater like rey signature with a negative ce anomaly this indicates that the water column was oxygenated both before and after the extinction event the permian limestone in the demirtas section does not preserve a seawater like reysn distribution so the absence of a ce anomaly cannot be used to distinguish prevailing redox conditions during deposition however in these samples we find the presence of a diverse permian benthic community sufficient to identify deposition in an oxic environment the geochemical evidence for a continuously oxic environment during the deposition of the boundary microbialite presented in this study strongly supports work done using ostracods as redox indicators within the boundary microbialite in south china the microbialite has been proposed as a disaster facies in part resulting from the exclusion of grazers although anoxia is one of the suggested mechanisms for the exclusion of grazers we find that it is not supported by geochemical and biotic evidence

carbon sinks in small sahelian lakes as an unexpected effect of land use changes since the 1960s saga gorou and dallol bosso sw niger for several decades global change has resulted in an increase in runoff in the sahelian belt provoking major changes in the quality and quantity of sediments transported by drainage networks one of the astonishing consequences is the establishment of numerous permanent lakes the origins of particulate organic matter om preserved within lacustrine sediments of three lakes were investigated by coupling optical observations palynofacies and bulk geochemistry rock eval 6 pyrolysis an initial estimate of particulate organic carbon oc stored in these lacustrine sediments was assessed soil organic matter som was sampled from the surface 0 10 cm of various land use and land cover areas and was characterized and compared with sedimentary organic matter our results reveal that lake tankalawal is subjected to high autochthonous organic sedimentation toc ranges between 3 0 and 10 0 wt while lakes bangou kirey and bi are characterized by weak sedimentation of non indigenous om originating from the soil erosion and shore vegetation toc 3 0 wt in sediments the effects of early diagenesis on the om induce not only a loss of labile and aquatic om but also a significant loss of terrestrial om which is supposed to be more resistant than its aquatic counterpart both the preservation of om in top sediments and the relative preservation of terrestrial om impact the oc storage in lakes indeed oc storage in lacustrine sediments lake bangou kirey was two to seven times higher than the oc storage in sahelian soils where greater contributions of terrestrial om to sedimentary om are associated with lower oc storage in lacustrine sediments for lakes bangou kirey and bi oc accumulation rates were also assessed due to the identification of a sedimentary limit corresponding to the establishment of permanent lakes dated earlier 1960s high oc fluxes were estimated and ranged between 104 and 213 g oc m 2 yr 1 compared with other oc accumulation rates for various african lakes these high values are similar to those calculated for reservoirs and are related to anthropogenic pressure soil textures favoring erosion and proper physical and chemical conditions for om preservation in sediments accordingly in these sahelian environments that are generally viewed as non efficient in storing oc we claim that global change could promote a new oc sink if other similar studies reinforce our assertion then regional c budgets should be revisited

brachiopods recording seawater temperature a matter of class or maturation calcite fibres of the innermost secondary layer of low magnesium calcite brachiopod shells are in oxygen isotope equilibrium with ambient seawater previous work on terebratalia transversa indicates that the first formed calcite fibres of the secondary layer are not in isotopic equilibrium while the later fibres of mature valves are in oxygen isotope equilibrium with seawater here secondary ion mass spectrometry sims analyses reveal that this trend of oxygen isotope equilibrium being attained towards the innermost shell rather than being a feature throughout the secondary layer occurs in brachiopods from two orders and two sub orders this suggests a general pattern among brachiopods with low magnesium calcite shells and leads to the recommendation that only the innermost fibres of mature valves be included in proxy calculations of seawater temperature although the trend is common in the three species studied here the extent of the isotopic range is much less marked in the species that lacks punctae

neotethys seawater chemistry and temperature at the dawn of the end permian mass extinction abstract the end of the permian was a time of great death and massive upheaval in the biosphere atmosphere and hydrosphere over the last decades many causes have been suggested to be responsible for that catastrophe such as global warming anoxia and acidification the gyanyima limestone block was an open ocean seamount in the southern neotethys at subtropical latitude and it affords us insight into open ocean oceanographic changes during the end of the permian after careful screening using multiple tests we reconstructed carbonate seawater curves from the geochemical data stored in pristine brachiopod shell archives from the shallow water limestone of the changhsingian gyanyima formation of tibet the reconstructed strontium isotope curve and data for the late changhsingian are relatively invariant about 0 707013 but in the upper part of the succession the values become more radiogenic climaxing at about 0 707244 the 87 sr 86 sr curve and trend are similar to those observed for the upper permian succession in northern italy but dissimilar less radiogenic to whole rock results from austria iran china and spitsbergen the ce ce anomaly results ranging from 0 310 to 0 577 for the brachiopods and from 0 237 to 0 655 for the coeval whole rock before the event and of 0 276 for whole rock during the extinction event suggest normal redox conditions these ce values are typical of normal open ocean oxic water quality conditions observed in modern and other ancient counterparts the biota and ce information clearly discounts global anoxia as a primary cause for the end permian biotic crisis carbon isotopes from brachiopod shells and whole rock are relatively invariant for most of the latest permian interval which is in stark contrast to the distinct negative carbon isotope excursion observed near and about the event estimates of seawater temperature at shallow depth fluctuated from 22 2 to 29 0 c up to unit 8 2 and then gradually rise from 29 7 c in unit 8 13 to values exceeding 35 c at a stratigraphic level about 120 ky before the permian triassic boundary and just before the onset of the extinction interval this dramatic increase in seawater temperature has been observed in global successions from tropical to mid latitude and from restricted to open ocean localities e g northern italy iran the brachiopod archive and its geochemical proxies from tibet support the paradigm that global warming must have been an important factor of the biotic crisis for the terrestrial and marine faunas and floras of the late paleozoic world

sea surface temperature and salinity variability at bermuda during the end of the little ice age 1 we use geochemical and isotope measurements on a 225 year old brain coral diploria labyrinthiformis from the south shore of bermuda 64 w 32 n to construct a record of decadal to centennial scale climate variability the coral was collected alive and annual density bands visible in x radiographs delineate cold and warm seasons allowing for precise dating coral skeletons incorporate strontium sr and calcium ca in relative proportions inversely to the sea surface temperature sst in which the skeleton is secreted previous studies on this and other coral colonies from this region document the ability to reconstruct mean annual and wintertime sst using sr ca measurements goodkin et al 2007 2005 the coral based records of sst for the past 2 centuries show abrupt shifts at both decadal and centennial timescales and suggest that sst at the end of the little ice age between 1840 and 1860 was 1 5 0 4 c colder than today 1990s coral reconstructed sst has a greater magnitude change than does a gridded instrumental sst record from this region this may result from several physical processes including high rates of mesoscale eddy propagation in this region oxygen isotope values 18o of the coral skeleton reflect changes in both temperature and the 18o of seawater ow where ow is proportional to sea surface salinity sss we show in this study that mean annual and wintertime 18o of the carbonate oc are correlated to both sst and sss but a robust quantitative measure of sss is not found with present calibration data in combination however the sr ca and oc qualitatively reconstruct lower salinities at the end of the little ice age relative to modern day temperature changes agree with other records from the bermuda region radiative and atmospheric forcing may explain some of the sst variability but the scales of implied changes in sst and sss indicate large scale ocean circulation impacts as well

catastrophic dispersion of coal fly ash into oceans during the latest permian extinction the eruption of the siberian trap flood basalts resulted in the heating and combustion of coals and organic rich sediments at the time of the permian mass extinction the presence of char in distant lake sediments linked to the eruption suggests that fly ash could have been generated by the coal combustion and then dispersed globally creating toxic marine conditions

paleobathymetry of a silurian shelf based on brachiopod assemblages an oxygen isotope test primary 18 o signals of 97 brachiopod shells from the lower silurian llandovery carbonate succession of anticosti island were used to test the hypothesis of water depth and water temperature gradient for the silurian onshore offshore benthic assemblages ba1 ba5 the analyzed shells were from the pentamerus palaformis pentamerus oblongus stricklandia planirostrata ehlersella davidsonii and triplesia anticostiensis communities which have been interpreted to occupy different water depths screening of the shells using petrographic and chemical criteria confirmed good preservation of original material shells of p palaformis p oblongus e davidsonii and t anticostiensis have very similar mean 18 o values 5 vienna peedee belemnite vpdb while shells of s planirostrata have a somewhat lighter value 5 6 the 18 o values in corroboration with taphonomic and paleoecologic data suggest the following 1 that the water mass of the anticosti carbonate shelf was warm and well mixed vertically during the early silurian 2 that the pentamerid brachiopod paleocommunities that lived at 20 90 m of water depth show little 18 o differentiation in their shell composition and 3 that the pentamerus stricklandia and triplesia communities need to be investigated at the species level as both taphonomic and oxygen isotopic data indicate that the stricklandia planirostrata community most likely lived in a notably warmer shallower water than the pentamerus palaformis community and that triplesia anticostiensis ba5 lived at water temperature comparable to that of the pentamerus habitat ba3 this may suggest either that at the generic level the pentamerus stricklandia and triplesia clorinda equivalent communities may have had substantial overlap in their spatial distribution in the ba3 ba4 paleobathymetric settings or that the isotope signals are too faint to record water depth differences on a tropical shelf

biogenic and abiogenic low mg calcite blmc and almc evaluation of seawater ree composition water masses and carbonate diagenesis the ree and shale normalized paas reesn values of modern brachiopods biogenic low mg calcite blmc represented by several species from high to low latitudes from shallow to deep waters and from warm and cold water environments define three distinct average seawater trends the warm and cold water brachiopods define two indistinguishable p 0 050 groups that mimic open ocean seawater ree chemistry exhibiting the typical lree enrichment with a slightly positive to negative ce anomaly followed by an otherwise invariant series other recent brachiopods from an essentially siliciclastic seabed environment are distinct in both ree and reesn trends from the previous two populations showing a slight enrichment in the mrees and an increasing trend in the hrees other groups of modern brachiopods are characterized by elevated reesn trends relative to the normal groups as well as by complexity of the series trends the most characteristic feature is the decrease in the hrees in these brachiopods from areas of unusual productivity i e such as upwelling currents fluvial input and aerosol dust deposition preserved brachiopods from the eocene and silurian exhibit reesn trends and ce anomalies similar to that of the open ocean modern brachiopods although their enriched ree concentrations suggest precipitation of blmc influenced by extrinsic environmental conditions preservation of the blmc was tested by comparing the ree and reesn trends of preserved eocene brachiopods to those of oligocene brachiopods that were altered in an open diagenetic system in the presence of phreatic meteoric water the altered blmc is enriched by approximately one order of magnitude in both ree and reesn trends relative to that in blmc of their preserved counterparts similarly the ree and reesn of preserved silurian brachiopod blmc were compared to those of their enclosing altered lime mudstone which exhibits features of partly closed system phreatic meteoric water diagenesis despite these differences in the diagenetic alteration systems and processes the rees and reesn trends of the blmc of altered brachiopods and of originally mixed mineralogy lime mudstones now diagenetic low mg calcite are enriched by about one order of magnitude relative to those observed in the coeval and preserved blmc in contrast to the changes in ree and reesn of carbonates exposed to phreatic meteoric water diagenesis are the ree compositions of late burial calcite cements precipitated in diagenetically open systems from burial fluids the ree and reesn trends of the burial cements mimic those of their host lime mudstone with all showing slight lree enrichment and slight hree depletion exhibiting a chevron pattern of the reesn trends the overall enrichment or depletion of the cement reesn trends relative to that of their respective host rock material reflects not only the openness of the diagenetic system but also strong differences in the elemental and ree compositions of the burial fluids evaluation of the ce ce sn and la pr pr sn anomalies suggests precipitation of the burial calcite cements essentially in equilibrium with their source fluids

multiphase partial and selective dolomitization of carnian reef limestone transdanubian range hungary partially dolomitized carbonate successions provide a good opportunity to understand the commonly multistage process of dolomitization petrographic methods fluid inclusion microthermometry and stable isotope measurements were applied to reconstruct the diagenetic evolution and dolomitization of a partially dolomitized carnian reef limestone from the transdanubian range hungary the diagenetic history began with reef diagenesis and formation of dolomite micro aggregates in microbial fabric elements this was followed by the development of euhedral porphyrotopic dolomite crystals through overgrowths around the previously formed dolomite micro aggregates during the earliest burial stage increasing burial resulted in the extension of the dolomite patches via formation of finely crystalline replacement dolomite from the late norian when the carnian reef carbonates reached the depth of 1 0 to 1 8 km the diagenetic evolution continued in an intermediate to deep burial setting contemporaneously an extensional regime was established leading to fracturing the progressive burial resulted in the recrystallization of the pre existing dolomite with increasing temperature while saddle dolomite cement was precipitated in fractures in connection with the alpine orogeny intense denudation took place during the late cretaceous accompanied by fracturing similar tectonically controlled denudation and fracturing occurred in several stages during the cenozoic as a result of these processes the studied carnian carbonates were raised to a near surface position or became subaerially exposed leading to dedolomitization of the last dolomite phase and precipitation of calcite cement in cavities and fractures this study revealed that by investigating partially and selectively dolomitized rock types it is possible to document and understand those stages of the multiple dolomitization process which can barely be detected in the completely dolomitized rock bodies recognition of the dolomitization phases could provide the basis for the analysis of their relations with the depositional diagenetic and tectonic processes and stages of basin evolution

fabric retentive non luminescent brachiopods as indicators of original delta 13 c and delta 18 o composition a test abstract fabric retentive non luminescent helderbergian brachiopods from open marine deposits analogous to brachiopods used in other studies to determine paleo oceanic stable isotopic composition exhibit depleted 13c values immediately below the erosional contact and more enriched values of 13c at greater stratigraphic distances below this surface in addition 13c values of these brachiopods display a marked shift across the erosional surface and values above it are essentially the same as those 30 m or more beneath the surface complementing these trends whole rock analyses metastable high agnesian calcite constituents echinoderms as well as early equant calcite cement also exhibit an increased depletion trend in 13c values as the helderberg oriskany contact is approached from below fabric retentive luminescent as well as obviously recrystallized brachiopods display stable isotopic values similar to those of fabric retentive non luminescent brachiopods thus best preserved fabric retentive non luminescent brachiopods exhibit values similar to obviously recrystallized brachiopods diagenetically altered metastable constituents echinoderms stable early meteoric cements and whole rock samples helderberg strata of new york state were affected by early meteoric diagenesis during a siegenian exposure event prior to deposition of the overlying marine oriskany sandstone meteoric diagenesis during this exposure gave rise to a characteristic carbon isotopic depletion trend approaching the helderberg oriskany contact all of the skeletal constituents underwent isotopic exchange during early diagenetic exposure to meteoric waters consequently the practice of using fabric retentive non luminescent brachiopods as indicators of their original chemistry and by extension paleo oceanic chemistry is questioned

diagenetic evaluation of a pennsylvanian carbonate succession bird spring formation arrow canyon nevada u s a 1 brachiopod and whole rock comparison abstract diagenetic evaluation of the pennsylvanian bird spring formation arrow canyon nevada u s a involved the detailed petrographic and geochemical examination of its brachiopod and whole rock components 13 c 18 o and 87 sr 86 sr of whole rock wr statistically p 0 0001 do not agree with isotope values of coeval brachiopod low mg calcite lmc more importantly a detailed investigation of the best preserved fine grained whole rock material demonstrates that it does not universally preserve its carbon isotope values in contrast with hypothetical predictions furthermore lumped trace chemistry or stable isotope tests do not unequivocally identify brachiopod or whole rock fine to coarse grained samples that carry an original seawater signal instead diagenetic evaluation involving as many screening tests as possible on a horizon by horizon level to compensate for spatial and temporal variations is necessary to identify the sample s that carries an original seawater signature many brachiopods from the bird spring formation are blue to non luminescent and carry microstructures and trace element contents similar to those of their modern tropical counterparts concurrence of chemical results between well preserved brachiopods and whole rock if originally low mg calcite is achieved in 22 of coeval samples for 13 c blmc wr with natural limits of 0 25 in 20 of samples for 18 o blmc wr with natural limits of 0 25 and in 9 of samples for 87 sr blmc wr with global limits of 0 000025 after an adjustment for mineralogical fractionation if whole rock is considered originally aragonite the concurrence of 13 c blmc wr drops to 0 and for 18 o blmc wr it drops to 6 furthermore comparison of stable isotopes of our well preserved brachiopods with those of preserved whole rock from the literature suggests that they are significantly different p 0 0001 with results of the latter dataset being more negative by about 0 77 2 57 with mineralogical adjustment for 13 c pdb and 1 31 2 11 for 18 o pdb thus our integrated screening and comparative tests indicate that 1 an overwhelming number of the whole rock samples from the bird spring formation carry a diagenetic instead of a primary signal for both carbon and oxygen isotopes and 2 many of the biogenic low mg calcite brachiopods in this succession carry an original chemical signal suitable for the reconstruction of high resolution seawater isotope curves representative of the pennsylvanian north american epeiric sea and potentially of the global oceans

climate forced change in hudson bay seawater composition and temperature arctic canada abstract global climate change impacts marine ecosystems directly and indirectly especially in the arctic and antarctic we show the first long term 1920 2011 time series of oceanographic change in hudson bay an arctic marine ecosystem based on coupled brachiopod calcite stable and clumped isotope results long term decrease in brachiopod 13c parallels that of seawater dic in hudson bay and after considering its seasonal sea ice coverage it is similar to that of the 13c suess effect observed in the north atlantic and other regions acidification of hudson bay seawater leads warming by about 10 20 years and with intensified warming from the 1970s to 2010s closely coupled to earlier sea ice breakup post industrial warming of hudson bay is initially slow but in later years faster and of greater magnitude than of the coeval global oceans our observations for the past 90 years suggest that climate forced change contributed to an average increase of about 0 1 c and 3 6 c in sea surface water temperature of hudson bay over the first 50 and subsequent 40 years respectively this 3 7 c post industrial warming of hudson bay seawater is about six times the 0 67 c increase observed during the past 100 years in global ocean sea surface temperature which is about double the postulated increase of about 2 c for polar regions our results are consistent with the general notion that polar marine environments such as hudson bay can serve as sensitive indicators of change in climate and of change still to come for lower latitude ecosystems

sampling species abundance and the stratigraphic signature of mass extinction a test using holocene tidal flat molluscs assume that a catastrophe caused the sudden extinction of the molluscan biota of a holocene tidal flat would this event be recorded accurately in the stratigraphic record how accurately would the extinction of rare species be recorded how would sudden gradual and stepwise patterns of extinction compare bivalve and gastropod species occurrences were recorded from eight tidal channel sediment cores up to 70 cm long from bahia la choya northern gulf of california the distribution of last occurrences of 45 species suggests that a sudden extinction would appear to be gradual in the stratigraphic record due to error in biostratigraphic range end points signor lipps effect extinction is typically not accurately recorded for species with less than 15 stratigraphic abundance i e occurring in less than 15 of the sample intervals 71 of the species the data were subjected to simulations of stepwise and gradual extinction differences between the sudden stepwise and gradual scenarios are apparent in 1 frequency distributions of biostratigraphic last occurrences 2 graphic relations between stratigraphic abundance and last occurrence and 3 patterns of apparent diversity decline below the extinction boundary extinction studies in outcrops and cores could utilize last occurrence and stratigraphic abundance data readily available in the fossil record to distinguish among sudden stepwise and gradual patterns of extinction

stratigraphic imprint of the late palaeozoic ice age in eastern australia a record of alternating glacial and nonglacial climate regime stratigraphic and sedimentological data from new south wales and queensland eastern australia indicate that the late palaeozoic ice age comprised at least eight discrete glacial intervals each 1 8 ma in duration here termed glaciations separated by nonglacial intervals of comparable duration these events spanned an interval from mid carboniferous c 327 ma to the early late permian c 260 ma and illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the late early permian followed by an opposite trend towards the final demise of glaciation in the late permian the alternating glacial nonglacial motif suggests that the late palaeozoic ice age was considerably more dynamic than previously thought these patterns are remarkably consistent with recent interpretations of palaeofloral change eustatic sea level fluctuations and co 2 climate glaciation relationships for this interval of time the detailed record of alternating glacial and nonglacial climate mode disclosed herein may facilitate more closely resolved evaluations of stratigraphic records elsewhere notably in far field ice distal northern hemisphere successions

shell structure patterns and trends of oxygen and carbon stable isotopes in modern brachiopod shells this study investigates 13c and 18o variations in the shells of modern brachiopods representing all extant groups of calcite precipitating brachiopods collected live from 8 locations sem examinations determined the ultrastructural characteristics of each species prior to isotope analyses 13c and 18o analyses of shell carbonate were carried out with samples representing disparate morphological features and ultrastructural shell layers of both ventral and dorsal valves generally 18o values from the fibrous secondary or prismatic tertiary shell layers of the articulated terebratulida and rhynchonellida species were in oxygen isotopic equilibrium with ambient seawater isotopic temperatures extrapolated from these values are close to measured annual mean seawater temperatures 18o values were relatively unaffected by shell specialisation the only exception was antarctic species liothyrella uva which did not have a complete tertiary shell layer typical of this genus and had 18o values of the innermost layer strongly correlated with 13c and mostly not in oxygen isotopic equilibrium with ambient seawater with the exception of the rhynchonellid notosaria nigricans the outer primary layer material was depleted in 13c and 18o and highly variable inclusion of this material even as part of a whole shell sample could lead to misinterpretation of seawater temperature therefore only fossil secondary layer material should be used the anomalous articulated thecideidine brachiopod thecidellina barretti is composed of mainly primary shell material and was not in oxygen isotope equilibrium 18o values from the laminar secondary layer material of the inarticulated craniida are highly variable therefore these species are not recommended for use as palaeoenvironmental proxies this study suggests caution when employing fossil brachiopod shells with similar ultrastructures to modern craniid and thecideidine brachiopods the carbon isotope composition is highly variable in all of the brachiopods studied analysis of samples from specialised regions of the secondary shell layer show a pattern of depletion in 13c relative to non specialised secondary material the carbon isotope variability is independent of 18o and is repeated in most of the articulated species regardless of geographical location this is possibly a vital effect produced by metabolic prioritisation

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

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

the permian triassic boundary in western slovenia idrijca valley section magnetostratigraphy stable isotopes and elemental variations stable isotope analyses of carbonate 13ccarb and total organic carbon toc 13corg together with geochemical analyses of 54 major minor and trace elements and magnetic susceptibility measurements were carried out on whole rock samples of the undisturbed permian triassic p tr limestone boundary sequence in the idrijca valley w slovenia at the p tr boundary there is a 0 8 cm thick clayey marl layer ptb showing a characteristic magnetic susceptibility pulse and considerable enrichment in most major minor and trace elements the p tr transition is characterized by 1 an abrupt decrease in sedimentation rate from 32 to 5 cm 100 ka 2 a well known prominent negative excursion of 13ccarb and 13corg reflecting global perturbations in the carbon cycle and 3 the drastic disappearance of typically upper permian marine fauna although the shape of the 13ccarb curve indicates gradual long term change across the p tr boundary the sharp negative 13corg anomaly within an interval from 30 cm below to 6 cm above the boundary suggests an interruption of those gradual processes our observations for selected redox sensitive elements mo u v and zn abundances for organic carbon and sulphur and the rare earth elements ree distribution in the boundary sequence as well as the shape of the ce ce curve suggest that oceanic anoxia was typical of the upper permian and that the transition to oxygenated conditions occurred at the p tr boundary oxygenation at the p tr transition is coincidental with the terminal phase of the upper permian marine regression the shape of the ce ce curve indicates that the redox environmental conditions changed again in the earliest triassic resulting once more in oxygen deficient conditions

siberian gas venting and the end permian environmental crisis abstract the end of the permian period is marked by global warming and the biggest known mass extinction on earth the crisis is commonly attributed to the formation of the siberian traps large igneous province although the causal mechanisms remain disputed we show that heating of tunguska basin sediments by the ascending magma played a key role in triggering the crisis our conclusions are based on extensive field work in siberia in 2004 and 2006 heating of organic rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated 100 000 gt co2 the gases were released to the end permian atmosphere partly through spectacular pipe structures with kilometre sized craters dating of a sill intrusion by the u pb method shows that the gas release occurred at 252 0 0 4 million years ago overlapping in time with the end permian global warming and mass extinction heating experiments to 275 c on petroleum bearing rock salt from siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases the results indicate that global warming and ozone depletion were the two main drivers for the end permian environmental crisis we demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a large igneous provinces causes an environmental crisis or not we propose that a similar mechanism could have been responsible for the triassic jurassic 200 ma global warming and mass extinction based on the presence of thick sill intrusions in the evaporite deposits of the amazon basin in brazil

boron isotope geochemistry of paleozoic brachiopod calcite implications for a secular change in the boron isotope geochemistry of seawater over the phanerozoic abstract boron isotope composition of marine carbonates has been proposed as a paleo ph proxy and potential tool to reconstruct atmospheric pco2 the precise knowledge of the boron isotopic composition of ancient seawater represents the fundamental prerequisite for any paleo ph reconstruction this contribution presents boron isotope values for silurian to permian brachiopod calcite that might be used to reconstruct ph or boron isotope composition of past oceans all brachiopod shells were screened for diagenetic recrystallization by means of cathodoluminescence microscopy trace element geochemistry b fe mn sr as well as sem only nonluminescent shells revealing well preserved microstructures high strontium and boron concentrations as well as low iron and manganese contents were accepted for boron isotope analysis the boron isotope ratios of silurian devonian pennsylvanian and permian brachiopod calcite range from 6 8 to 11 0 7 3 to 14 9 12 4 to 15 8 and 10 1 to 11 7 respectively these 11b values are significantly lower in comparison to 11b values of modern biogenic carbonates and indicate that the paleozoic oceans were depleted in 11b by up to 10 box modeling of the boron geochemical cycle suggests that the significant depletion of 11b in the oceanic reservoir may have been initiated by an enhanced continental boron discharge our data support the earlier made conclusion that boron isotopes may not be used in the geological past as reliable paleo ph proxy unless the boron isotopic composition of ancient oceans can be constrained by further studies

early permian pangea b to late permian pangea a the pre drift wegenerian model of pangea is almost universally accepted but debate exists on its pre jurassic configuration since tedirving introd ucedpangea b by placing gond wana farther to the east by v3000 km with respect to laurasia on the basis of paleomagnetic data new paleomagnetic data from radiometrically dated early permian volcanic rocks from parts of adria that are tectonically coherent with africa gondwana integrated with published coeval data from gondwana and laurasia again only from igneous rocks fully support a pangea b configuration in the early permian the use of paleomagnetic data strictly from igneous rocks excludes artifacts from sedimentary inclination error as a contributing explanation for pangea b the ultimate option to reject pangea b is to abandon the geocentric axial dipole hypothesis by introducing a significant non dipole zonal octupole component in the late paleozoic time averaged geomagnetic field we demonstrate however by using a dataset consisting entirely of paleomagnetic directions with low inclinations from sampling sites confined to one hemisphere from gondwana as well as laurasia that the effects of a zonal octupole field contribution would not explain away the paleomagnetic evidence for pangea b in the early permian we therefore regard the paleomagnetic evidence for an early permian pangea b as robust the transformation from pangea b to pangea a took place during the permian because late permian paleomagnetic data allow a pangea a configuration we therefore review geological evidence from the literature in support of an intra pangea dextral megashear system the transformation occurred after the cooling of the variscan mega suture andlasted v20 myr in this interval the neotethys ocean opened between india arabia and the cimmerian microcontinents in the east while widespread lithospheric wrenching and magmatism took place in the west around the adriatic promontory the general distribution of plate boundaries and resulting driving forces are qualitatively consistent with a right lateral shear couple between gondwana and laurasia during the permian transcurrent plate boundaries associated with the pangea transformation reactivated variscan shear zones andwere subsequently exploitedby the opening of western neotethyan seaways in the jurassic

shell succession assemblage and species dependent effects on the c o isotopic composition of brachiopods examples from the silurian of gotland brachiopods are the most widely used biological constituents for the determination of stable c and o isotopic compositions in paleozoic sediments in the present study critical precautions for obtaining reliable isotope values and maximum possible reliability are discussed samples were taken in the tectonically undisturbed and exceptionally well preserved silurian sequence on gotland sweden the state of preservation of brachiopod shells was examined by cathodoluminescence cl microscopy and by comparison of shell ultrastructures with those of recent brachiopods nine types of ultrastructure are distinguished and attributed either to biological differences or to diagenetic alterations for isotope analyses only largely unaltered areas of the secondary fibrous shell layer should be used shell layers with other types of ultrastructure primary tertiary laminar may have isotopic compositions different from the assumed seawater value even when diagenetically unaltered only brachiopod taxa with a shell succession that includes a sufficiently thick secondary shell layer e g spiriferida rhynchonellida orthida give reliable mutually corresponding isotope values indicating that the shell calcite precipitated at or near equilibrium with ambient seawater brachiopods with other kinds of shell successions strophomenida pentamerida as well as other calcite shelled organisms trilobites ostracodes give non equilibrium isotopic results and therefore should not be used by restricting the samples to one species or to a group of closely related species even minor differences in primary isotopic composition can be excluded in the silurian of gotland the stratigraphically widely distributed spiriferid atrypa reticularis was selected for study considering the type of record four different taphonomic assemblages are defined in autochthonous assemblages of specimens which lived contemporarily original values of carbon as well as oxygen isotopes can be evaluated with a reliability of 0 4 this allows the recognition of minor hydrographically produced differences between neighbouring contemporary facies areas and the determination of small 1 isotopic excursions thus besides being indicators of hydrographic conditions in ancient oceans stable carbon and oxygen isotope compositions can be used as a stratigraphic tool that provides correlations sometimes even within biozones

clumped isotope signatures in modern brachiopod carbonate abstract we present a temperature to 47 relationship for naturally occurring modern brachiopods which was established using a suite of thirteen brachiopod specimens from twelve sampling localities that span a mean annual seawater temperature range of 0 8 to 29 0 c sample locations and depths were selected to maximize the range of temperatures covered by the calibration while minimizing the seasonal temperature variability impacting the samples linear least squares regression analysis yields the following relationship expressed using the ghosh et al 2006 reference frame 47 0 0478 0 0099 10 6 t 2 0 1164 0 1203 n 13 r 2 0 91 95 ci this equation lies within the 95 confidence interval of the original relationship determined using synthetic calcite ghosh et al 2006 but is in better agreement with the newly revised calibration of zaarur et al 2013 however despite this broad agreement our equation has a shallower slope than the equations for synthetic calcites and yields temperatures at the warm end of the calibration temperature range 47 0 640 that are as much as 3 1 c offset from those predicted using the equation of zaarur et al 2013 on the other hand our new equation has a steeper slope than the henkes et al 2013 equation for modern brachiopods and mollusks this finding is consistent with the hypothesis that differences in the protocols employed by laboratories that use different temperatures of phosphoric acid digestion cause the observed discrepancies between the 47 values reported by various laboratories