petroleum systems of the oldest gas field in china neoproterozoic gas pools in the weiyuan gas field sichuan basin abstract weiyuan the oldest gas field in china is a rare example of the giant neoproterozoic gas pools this field is located in southwestern sichuan basin with a proven in place gas reserve around 40 billion cubic meters bcm or 1 41 trillion cubic feet tcf in reservoirs of the sinian dengying formation this field is almost depleted now with a cumulative gas production of 14 4 bcm and a recovery factor of around 36 the neoproterozoic gas pools are also geographically overlapped by gas pools in the lower permian maokou formation with an additional proven in place gas reserve about 0 861 bcm or 30 2 bcf gases in the sinian reservoirs are relatively rich in nitrogen co 2 h 2 s helium and argon with gaseous alkanes showing l 3 c 1 13 c 2 and l3 c 1

middle late permian mass extinction on land the end permian mass extinction has been envisaged as the nadir of biodiversity decline due to increasing volcanic gas emissions over some 9 million years we propose a different tempo and mechanism of extinction because we recognize two separate but geologically abrupt mass extinctions on land one terminating the middle permian guadalupian at 260 4 ma and a later one ending the permian period at 251 ma our evidence comes from new paleobotanical paleopedological and carbon isotopic studies of portal mountain antarctica and comparable studies in the karoo basin south africa extinctions have long been apparent among marine invertebrates at both the end of the guadalupian and end of the permian which were also times of warm wet greenhouse climatic transients marked soil erosion transition from high to low sinuosity and braided streams soil stagnation in wetlands and profound negative carbon isotope anomalies both mass extinctions may have resulted from catastrophic methane outbursts to the atmosphere from coal intruded by feeder dikes to flood basalts such as the end guadalupian emeishan basalt and end permian siberian traps

high precision dating of the kalkarindji large igneous province australia and synchrony with the early middle cambrian stage 4 5 extinction the voluminous kalkarindji flood basalts erupted in australia during the cambrian and covered 2 x 10 6 km 2 new u pb and ar 40 ar 39 age data from intrusive rocks and lava flows yielded statistically indistinguishable ages at ca 511 ma suggesting a relatively brief emplacement for this province a zircon age of 510 7 0 6 ma shows that this province is temporally indistinguishable at the few hundred thousand year level from the early middle cambrian stage 4 5 boundary age of 510 1 ma which marks the first severe extinction of the phanerozoic and an extended marine anoxia period sulfur concentration measurements ranging from 50 to 1900 mu g g and fractal analysis of extensive explosive volcanic breccias suggest that blasts and phreatomagmatic explosions have contributed to injection of large amounts of sulfur into the stratosphere in addition magma intrusions in oil gas and sulfate deposits may have generated significant emission of ch4 and so2 which along with volcanic gases would have combined to cause an oscillation of the climate and led to the cambrian extinction less

paleomagnetism of trap intrusions east siberia implications to flood basalt emplacement and the permo triassic crisis of biosphere article history despite decades of concentrated studies large igneous provinces lips are still among the most enigmatic phenomena of the earth evolution among the myriad questions facing researchers the duration of eruptive magmatic activity and its distribution through time are probably the most mysterious ones although the accuracy of modern dating techniques offers relatively high resolution it is impossible to discriminate whether magmatic activity was more or less uniform or concentrated in few powerful outbursts consequently many trap related questions from their origin to possible impact on the biosphere still cannot be answered some of the above questions can be addressed with paleomagnetic data as have been effectively done in the case of the end cretaceous deccan traps the siberian traps are one of the largest lips in the phanerozoic and are thought by some to be the triggering event for the end permian mass extinction we conducted a paleomagnetic study of trap intrusions along two long profiles in the eastern part of the province and found that most site mean directions are grouped several times tighter than is common for the data on thick lava series and dyke swarms similar over grouping is found in other parts of the siberian trap province too we argue that this phenomenon is the most likely related to nearly simultaneous emplacement of trap intrusions over areas of several ten to few hundred kilometers in dimension for few millenniums or even faster moreover such brief events account for all or nearly all magmatism in each area how such events correlate over the entire siberian lip however remains an open question still our data together with paleomagnetic results on thick lava series in siberia strongly indicate that magmatic activity consisted of a number of brief pulses in comparison to the other lips the siberian one is underlain by the thickest succession of carbonates evaporites and coal bearing clastics that are capable of producing huge amount of green house and poisonous gases we hypothesize that these very fast injections of magma into thick underlying sediments and the unique geological setting of the siberian lip are the major reasons for the permo triassic mass extinction being

eruptive history of the karoo lava flows and their impact on early jurassic environmental change this paper reports new paleomagnetic and geochronologic data from a 1500 m thick composite section belonging to the drakensberg group the thickest remnant of the karoo lavas in northern lesotho flow by flow analysis of paleomagnetic directions reveals twenty one magnetic directional groups dg corresponding to single eruptive events see and sixteen individual lava flows the new age determinations of lava flows range from 180 1 1 4 to 182 8 2 6 ma these data combined with previous results allow us to propose that the main part of the drakensberg group and the karoo intrusive complex dated around 181 183 ma may have been erupted over a period as short as 250 kyr and may have coincided with the two main phases of extinction in the early toarcian this scenario agrees well with the discontinuous rhythm of environmental and biotic perturbations in the late pliensbachian toarcian interval

determination of rapid deccan eruptions across the cretaceous tertiary boundary using paleomagnetic secular variation 2 constraints from analysis of eight new sections and synthesis for a 3500 m thick composite section 1 the present paper completes a restudy of the main lava pile in the deccan flood basalt province trap of india chenet et al 2008 reported results from the upper third and this paper reports the lower two thirds of the 3500 m thick composite section the methods employed are the same i e combined use of petrology volcanology chemostratigraphy morphology k ar absolute dating study of sedimentary alteration horizons and as the main correlation tool analysis of detailed paleomagnetic remanence directions the thickness and volume of the flood basalt province studied in this way are therefore tripled a total of 169 sites from eight new sections are reported in this paper together with the results of chenet et al 2008 these data represent in total 70 of the 3500 m combined section of the main deccan traps province this lava pile was erupted in some 30 major eruptive periods or single eruptive events see each with volumes ranging from 1000 to 20 000 km3 and 41 individual lava units with a typical volume of 1300 km3 paleomagnetic analysis shows that some sees with thicknesses attaining 200 m were emplaced over distances in excess of 100 km both likely underestimates due to outcrop conditions and up to 800 km the total time of emission of all combined sees could have been much less than 10 ka with most of the time recorded in a very small number of intervening alteration levels marking periods of volcanic quiescence so called big red boles the number of boles thickness of the pulses and morphology of the traps suggest that eruptive fluxes and volumes were larger in the older formations and slowed down with more and longer quiescence periods in the end on the basis of geochronologic results published by chenet et al 2007 and paleontological results from keller et al 2008 we propose that volcanism occurred in three rather short discrete phases or megapulses an early one at 67 5 1 ma near the c30r c30n transition and the two largest around 65 1 ma one entirely within c29r just before the k t boundary the other shortly afterward spanning the c29r c29n reversal we next estimate sulfur dioxide likely a major agent of environmental stress amounts and fluxes released by sees they would have ranged from 5 to 100 gt and 0 1 to 1 gt a respectively over durations possibly as short as 100 years for each see the chemical input of the chicxulub impact would have been on the same order as that of a very large single pulse the impact therefore appears as important but incremental neither the sole nor main cause of the cretaceous tertiary mass extinctions

paleoatmospheric pco2 fluctuations across the cretaceous tertiary boundary recorded from paleosol carbonates in ne china abstract a dramatic change in atmospheric composition has been postulated because of global carbon cycle disruption during the cretaceous k tertiary t transition following the chicxulub impact and deccan trap eruptions here pedogenic carbonates were collected from drill core of a borehole sk 1 n straddling the late cretaceous and early paleocene strata in the songliao basin northeast china to reconstruct atmospheric co 2 concentrations using a paleosol paleobarometer our estimates for atmospheric pco 2 from paleosol carbonates range between 277 115 ppmv and 837 164 ppmv between 67 8 ma and 63 1 ma one large 66 65 5 ma and several small co 2 spikes 64 7 64 2 ma during the latest maastrichtian to earliest danian are reported here and incorporated with previously published pco 2 estimates also estimated from paleosol carbonates these co 2 spikes are attributed to one million year long emplacement of the large deccan flood basalts along with the extraterrestrial impact at the k t boundary

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

an attempt to constrain the age duration and eruptive history of the karoo flood basalt naude s nek section south africa we have carried out paleomagnetic sampling of a similar to 750 m sequence of the karoo large igneous province naude s nek pass south africa k ar dating cassignol gillot has been performed on four samples from the 650 m upper unit mean age 179 2 1 8 ma and a sample from the lower unit 184 8 2 6 ma a succession of two phases of volcanism is suggested the lower 25 flows 115 m thick have recorded a reversed polarity the next 23 flows 135 m thick are transitional and contribute a detailed record of the van zijl 1962 jurassic reversal the upper 38 flows 500 m thick have normal polarity directional groups dgs of lava flows with quasi identical remanence directions indicate eruption durations too short to have recorded geomagnetic secular variation and hence are interpreted as single eruptive events altogether 19 dgs and 10 sheet lobes yield a sequence of 29 distinct directions this could correspond to a total eruptive activity shorter than 3000 years less than one per mil of the total duration over which the section was emplaced we obtain a new paleomagnetic pole for south africa at similar to 180 ma lambda 75 2 degrees n phi 276 4 degrees e a 95 5 8 degrees n 19 which is consistent with earlier reports

carbon isotope signatures of pedogenic carbonates from se china rapid atmospheric pco2 changes during middle late early cretaceous time lower cretaceous pedogenic carbonates exposed in se china have been dated by u pb isotope measurements on single zircons taken from intercalated volcanic rocks and the ages integrated with existing stratigraphy 13 c values of calcretes range from 7 0 to 3 0 and can be grouped into five episodes of increasing decreasing values the carbon isotope proxy derived from these palaeosol carbonates suggests p co 2 mostly in the range 1000 2000 parts per million by volume ppmv at s z co 2 contributed by soil respiration 2500 ppmv and 25 c during the hauterivian albian interval c 30 ma duration such atmospheric co 2 levels are 4 8 times pre industrial values almost double those estimated by geochemical modelling and much higher than those established from stomatal indices in fossil plants rapid rises in p co 2 are identified for early hauterivian middle barremian late aptian early albian and middle albian time and rapid falls for intervening periods these episodic cyclic changes in p co 2 are not attributed to local tectonism and volcanism but rather to global changes the relationship between reconstructed p co 2 and the development of large igneous provinces lips remains unclear although large scale extrusion of basalt may well be responsible for relatively high atmospheric levels of this greenhouse gas suggested levels of relatively low p co 2 correspond in timing to intervals of regional to global enrichment of marine carbon in sediments and negative carbon isotope 13 c excursions characteristic of the oceanic anoxic events oae1a selli event kilian and paquier events constituting part of the oae 1b cluster and oae1d short term episodes of high p co 2 coincide with negligible carbon isotope excursions associated with the faraoni event and the jacob event given that episodes of regional organic carbon burial would draw down co 2 and negative 13 c excursions indicate the addition of isotopically light carbon to the ocean atmosphere system controls on the carbon cycle in controlling p co 2 during early cretaceous time were clearly complex and made more so by atmospheric composition also being affected by changes in silicate weathering intensity

constraining the cause of the end guadalupian extinction with coupled records of carbon and calcium isotopes abstract a negative c 13 excursion in carbonate sediments near the guadalupian lopingian middle late permian boundary has been interpreted to have resulted from a large carbon cycle disturbance during the end guadalupian extinction event ca 260 ma however the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbation to the global carbon cycle calcium isotopes can be used to further constrain the cause of a carbon isotope excursion because the carbon and calcium cycles are coupled via caco3 burial in this study we present coupled carbon and calcium isotope records from three guadalupian lopingian g l sections in china penglaitan and chaotian and turkey koserelik tepe the c 13 and ca 44 40 records differ among our studied sections and do not co vary in the same manner no section shows c 13 and ca 44 40 changes consistent with massive rapid volcanic co2 emissions or methane clathrate destabilization additionally many sections with large 3 changes in c 13 exhibit o 18 evidence for diagenetic alteration only one section exhibits a large excursion in the ca 44 40 of limestone but the absence of a similar excursion in the ca 44 40 of conodont apatite suggests that the limestone excursion reflects a mineralogical control rather than a perturbation to the global calcium cycle hence we interpret the large isotopic changes observed in some sections to have resulted from local burial conditions or diagenetic effects rather than from a large carbon and calcium cycle disturbance perturbations to the global carbon and calcium cycles across the g l transition were much less intense than the disturbances that occurred across the subsequent permian triassic boundary this finding is consistent with the much smaller magnitude of the end guadalupian extinction relative to the end permian

no evidence for thermogenic methane release in coal from the karoo ferrar large igneous province abstract the early jurassic toarcian oceanic anoxic event t oae and concurrent negative carbon isotope 13 c excursion have recently been attributed to either the release of methane ch 4 clathrates or thermogenic ch 4 gas associated with the karoo ferrar large igneous province lip into coals and organic rich shales 12 c enriched thermogenic ch 4 production associated with the karoo ferrar would result in residual material being 12 c depleted nearer the intrusions in this study geochemical analyses carbon isotopes volatile matter vm vitrinite reflectance r o are reported for two coal transects associated with dykes intruding the no 4l coal in the highveld coalfield karoo basin south africa vm decreases from over 35 to around 15 in one transect and the second transect shows a less pronounced decrease from 25 to 16 accompanying the decrease in vm content is an increase in r o from background levels of around 0 7 to over 4 adjacent to the dyke used as a palaeo geothermometer r o values indicate background temperatures of 100 c increasing to 300 c close to the contact despite changes in vm and r o there are no significant changes in 13 c certainly not of the magnitude that would be expected associated with large scale thermogenic ch 4 generation these and other gondwanan coals have low vitrinite and liptinite contents components more prone to ch 4 generation in part explaining the modest decreases in vm adjacent to the dykes this combined with the relatively narrow metamorphic aureole surrounding the intrusions and the likelihood that at least some of the volatiles generated by the intrusion were trapped as coalbed ch 4 or condensed as pyrolytic carbon suggests only limited ch 4 release in addition based on original estimates of moisture contents in these coals and the depth at time of intrusion 1 000 2 000 m the dykes would have lost most of their energy heating and evaporating water thus having very little remaining energy to generate thermogenic ch 4

rapid eruption of silicic magmas from the parana magmatic province brazil did not trigger the valanginian event the valanginian stage is marked by a period of global positive 13c carbon cycle perturba tion and biotic crises which are collectively referred to as the valanginian event ve many attempts have been made to link the parana etendeka large igneous province volcanism with the ve however currently there is no conclusive proof to support this hypothesis since the timing and duration of the volcanic activity are not known with suf cient precision in this study we signi cantly revise the time scales of magmatism and environmental impact of the parana magmatic province pmp in brazil with new high precision zircon u pb ages from the low ti palmas and high ti chapeco sequences our data demonstrate that signi cant volumes of low ti silicic rocks from the pmp erupted rapidly at ca 133 6 ma within 0 12 0 11 k y the age of the high ti chapeco sequence from central pmp is constrained at ca 132 9 ma and thus extends the duration of magmatic activity by 700 k y our new ages are systematically younger than previous ages and postdate the major positive carbon isotope excursion indicating that pmp silicic magmatism did not trigger the ve but could have contributed to extending its duration within the framework of the stratigraphic column of the pmp the earliest low ti basalts could have been responsible for the ve if they are at least 0 5 m y older than the low ti silicic rocks dated herein

sulfur and chlorine in late cretaceous deccan magmas and eruptive gas release large volume p hoehoe lava flows erupted 67 to 65 million years ago forming the deccan traps india the impact of these flood basalt eruptions on the global atmosphere and the coeval end cretaceous mass extinction has been uncertain to assess the potential gas release from this volcanism we measured sulfur and chlorine concentrations in rare glass inclusions inside crystals and on glassy selvages preserved within lavas concentrations range from 1400 parts per million of s and 900 parts per million of cl in inclusions down to a few hundred parts per million in the lava these data indicate that eruptions of deccan lavas could have released at most 0 103 weight of s yielding up to 5 4 teragrams of so2 per cubic kilometer of lava a more conservative estimate is 0 07 weight of s and 0 04 weight of cl yielding 3 5 teragrams of so2 and 1 teragram of hcl for every cubic kilometer of lava erupted the flows were very large in volume and these results imply that huge amounts of s and cl gases were released the environmental impact from even individual eruptions during past flood basalt activity was probably severe

carbon dioxide emissions from deccan volcanism and a k t boundary greenhouse effect a greenhouse warming caused by increased emissions of carbon dioxide from the deccan traps volcanism has been suggested as the cause of the terminal cretaceous extinctions on land and in the sea we estimate total eruptive and noneruptive co2 output by the deccan eruptions from 6 to 20 1016 moles over a period of several hundred thousand years based on best estimates of the co2 weight fraction of the original basalts and basaltic melts the fraction of co2 degassed and the volume of the deccan traps eruptions results of a model designed to estimate the effects of increased co2 on climate and ocean chemistry suggest that increases in atmospheric pco2 due to deccan traps co2 emissions would have been less than 75 ppm leading to a predicted global warming of less than 1 c over several hundred thousand years we conclude that the direct climate effects of co2 emissions from the deccan eruptions would have been too weak to be an important factor in the end cretaceous mass extinctions

a temporal link between the emeishan large igneous province sw china and the end guadalupian mass extinction abstract previous studies have suggested that there were two mass extinction events in the late permian one that occurred at the permo triassic p t boundary 251 ma and a second smaller mass extinction that occurred 5 8 myr earlier at the end of the guadalupian many workers have argued that there is a causal relationship between large scale volcanic activity and mass extinctions the major mass extinction event at the p t boundary coincides with the outpouring of huge quantities of lava that formed the siberian flood basalt province in russia courtillot et al earth planet sci lett 166 1999 177 195 and wignall earth sci rev 53 2001 1 33 suggested that the earlier late permian mass extinction coincided with the eruption of the lavas that formed the emeishan flood basalt efb province in sw china however the age of eruption of the efb lavas is poorly constrained using the sensitive high resolution ion microprobe to analyze zircons we have established the age of the xinjie intrusion believed to be a feeder to the main phase of efb volcanism to be 259 3 ma hence the formation of the efb is coincident with a proposed extinction event at 256 259 ma this result supports a temporal link between the emeishan large igneous province and the end guadalupian mass extinction

gas emissions due to magma sediment interactions during flood magmatism at the siberian traps gas dispersion and environmental consequences we estimate the fluxes of extremely reduced gas emissions produced during the emplacement of the siberian traps large igneous province due to magma intrusion in the coaliferous sediments of the tunguska basin using the results of a companion paper iacono marziano et al submitted to epsl and a recent work about low temperature interaction between magma and organic matter svensen et al 2009 we calculate co ch4 dominated gas emission rates of 7 1015 2 1016 g yr for a single magmatic volcanic event these fluxes are 7 to 20 times higher than those calculated for purely magmatic gas emissions in the absence of interaction with organic matter rich sediments we investigate by means of atmospheric modelling employing present geography of siberia the short and mid term dispersion of these gas emissions into the atmosphere the lateral propagation of co and ch4 leads to an important perturbation of the atmosphere chemistry consisting in a strong reduction of the radical oh concentration as a consequence both co and ch4 lifetimes in the lower atmosphere are enhanced by a factor of at least 3 at the continental scale as a consequence of 30 days of magmatic activity the short term effect of the injection of carbon monoxide and methane into the atmosphere is therefore to increase the residence times of these two species and in turn their capacity of geographic expansion the estimated co and ch4 volume mixing ratios i e the number of molecules of co or ch4 per cm3 divided by the total number of molecules per cm3 in the low atmosphere are 2 5 ppmv at the continental scale and locally higher than 50 ppmv the dimension of the area affected by these high volume mixing ratios decreases in the presence of a lava flow accompanying magma intrusion at depth complementary calculations for a 10 year duration of the magmatic activity suggest i an increase in the mean ch4 volume mixing ratio of the whole atmosphere up to values 3 to 15 times higher than the current one and ii recovery times of 100 years to bring back the atmospheric volume mixing ratio of ch4 to the pre magmatic value thermogenic methane emissions from the siberian traps has already been proposed to crucially contribute to end permian early triassic global warming and to the negative carbon isotopic shift observed globally in both marine and terrestrial sediments our results corroborate these hypotheses and suggest that concurrent high temperature co emissions also played a key role by contributing to increase i the radiative forcing of methane and therefore in its global warming potential and ii the input of isotopically light carbon into the atmosphere that generated the isotopic excursion we also speculate a poisoning effect of high carbon monoxide concentrations on end permian fauna at a local scale

contact metamorphism and thermogenic gas generation in the voring and more basins offshore norway during the paleocene eocene thermal maximum voluminous volcanic intrusive activity took place in the voring and more basins at the paleocene eocene boundary at about 56 ma this event caused thermal maturation of cretaceous sedimentary rocks in the basins we have estimated the resulting thermogenic gas generation potential from contact metamorphism using numerical simulations calibrated using borehole data the borehole 6607 5 2 from the utgard sill complex in the voring basin contains two c 100 m thick sills and is used as a case study we present both new and compiled data showing that 1 the bulk organic content is reduced towards the sill intrusions 2 a c 1 km thick stratigraphic interval is thermally affected based on vitrinite reflectance data 3 relative emplacement timing can affect the gas yield by up to 25 and 4 some of the thermogenic methane is still present in the aureoles the numerical model is calibrated using data from 11 wells we estimate that the total gas generation potential for the two utgard sills equals that of the troll field c 10 gt ch 4 the largest producing gas field offshore norway we show that in the voring and more basins the total gas generation potential is up to 1500 gt ch 4 c 1100 gt c even from the relatively organic poor cretaceous source rocks with c 1 wt organic carbon with implications for the carbon cycle at the paleocene eocene boundary

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

phanerozoic large igneous provinces lips heatt haline euxinic acidic thermal transgression episodes and mass extinctions abstract the phanerozoic consists of three mutually exclusive climate states icehouse greenhouse and hothouse the greenhouse is the default state representing 70 of the phanerozoic it is characterized by a weak thermal mode pole driven deep water formation with little or no continental sea ice and weakly oxic cool water sinking near the poles nitrogen limitation characterizes greenhouse oceans in which ammonium may be the dominant bioavailable form of nitrogen the steady state greenhouse default must be forced to produce either of the other two states continent continent collision produces the intense chemical weathering that draws down atmospheric co2 and results in the icehouse state that comprises 20 25 of the phanerozoic icehouses have ice caps in contact with the ocean that produce icebergs and foster sea ice formation sea ice formation fills the ocean with highly oxic phosphorus limited icewater except for a thin layer of warm surface water in the tropics of the 23 most conspicuous mass extinctions of the phanerozoic including the late ediacaran 4 are associated with ice volume related regressions and 3 are problematic we suggest that the other 16 mass extinctions occurred when greenhouse climate was forced to hothouse climate large igneous provinces lips can trigger the heatt haline euxinic acidic thermal transgression mechanism which can force greenhouse climate to a hothouse climate state the rapid voluminous co2 emissions of lips cause a series of events that result in very slow but pronounced haline mode circulation mid latitude driven deep water formation that produces warm saline bottom water at very dry hot subtropical and middle latitudes this water upwells at the poles causing warm and moist equable climate hothouse development promotes deep sea anoxia that is generated in concert with co2 buildup and warming the spread of anoxia favors reduced nitrogen over nitrate and limited iron dust curtails nitrogen fixation this leads to dominance of primary productivity by primitive green algae and or cyanobacteria progression to euxinia that reaches the photic zone severely curtails primary productivity via poisoning even as availability of usable nitrogen plummets the result is eukaryotic mass extinction we suggest that the 16 phanerozoic mass extinctions referred to above resulted at least in part from the heatt process evidence for this relationship at 11 of the most severe extinctions is convincing data sets for the other 5 are strongly suggestive of heatt related mass extinction but do not yet have enough documentation to reliably characterize them as heatt episodes

intracrystalline site preference of oxygen isotopes in goethite a single mineral paleothermometer abstract the crystal structure of goethite feo oh has two distinct oxygen sites one with exclusively fe o bonds the other with bonds to both iron and hydrogen we developed a method to assess the oxygen isotope contrast between these sites by measuring both the bulk goethite and the oxygen released in the conversion of goethite to hematite the method involves collecting the water released by dehydroxylation fluorinating that population of extracted atoms and measuring the resulting oxygen isotope composition extracted o 18 then on a separate aliquot all structural oxygen is fluorinated and measured bulk o 18 using synthetic goethite precipitates grown under controlled environmental conditions we found significant temperature dependent fractionation e bulk extracted 5 51 0 26 10 6 t 2 44 5 2 8 t in kelvin this intracrystalline fractionation forms the basis of a single phase paleothermometer with an estimated uncertainty of 2 3 c the temperature dependence appears to be independent of the isotopic composition of the parent fluid from which the goethite formed and the ph of that fluid this intracrystalline thermometer can be used to simultaneously determine the formation temperature of a goethite and the isotopic composition of the water from which it formed natural goethites analyzed with this technique yield geologically reasonable formation temperatures of between 15 and 41 c

how contact metamorphism can trigger global climate changes modeling gas generation around igneous sills in sedimentary basins abstract large volumes of greenhouse gases such as ch4 and co2 form by contact metamorphism of organic rich sediments in aureoles around sill intrusions in sedimentary basins thermogenic gas generation and dehydration reactions in shale are treated numerically in order to quantify basin scale devolatilization we show that aureole thicknesses defined as the zone of elevated metamorphism relative to the background level vary within 30 250 of the sill thickness depending on the temperature of the host rock and intrusion besides the sill thickness in shales with total organic carbon content of 5 wt ch4 is the dominant volatile 85 135 kg m3 generated through organic cracking relative to h2o generation from dehydration reactions 30 110 kg m3 even using conservative estimates of melt volumes extrapolation of our results to the scale of sill complexes in a sedimentary basin indicates that devolatilization can have generated 2700 16200 gt ch4 in the karoo basin south africa and 600 3500 gt ch4 in the voring and more basins offshore norway the generation of volatiles is occurring on a time scale of 10 1000 years within an aureole of a single sill which makes the rate of sill emplacement the time constraining factor on a basin scale this study demonstrates that thousands of gigatons of potent greenhouse gases like methane can be generated during emplacement of large igneous provinces in sedimentary basins

sulfur isotopic studies of continental flood basalts in the noril sk region implications for the association between lavas and ore bearing intrusions previous studies of both ore and non ore bearing intrusives in the permo triassic flood basalts of the siberian platform in the noril sk area have shown that high grade ni cu platinum group elements pge mineralization is associated with anomalously high 34s values of 8 to 12 in addition several researchers have proposed that observed depletions in the cu ni and pge content of basaltic lavas of the nadezhdinsky nd formation are related to diffusional exchange with and upgrading in metal tenor of sulfides in the volcanic conduit system sulfur isotopic studies of the lavas at noril sk were initiated to determine if interaction with crustally derived sulfur in the conduit system was evident and if the nd lavas in particular were characterized by an anomalous isotopic signature 34s values of the lavas range from 4 5 to 8 7 vienna canon diablo troilite vcdt with s concentrations from 40 to 1373 ppm the majority of 34s values range from 0 to 4 and are similar to those from s poor intrusions in the noril sk area although textural data are not supportive of early sulfide saturation and the presence of immiscible sulfide droplets in the lavas recrystallization may have erased expected mineralogical and textural evidence mineralogical data indicate that hydrothermal alteration of the lavas has occurred but s redistribution has been restricted to localized areas and 34s values have not been affected the relatively low s concentrations of the lavas are thought to be due in large part to degassing of the lavas in the shallow conduit system and during eruption our calculations are consistent with the premise that degassing of basaltic magmas at temperatures in excess of 900 c at qfm leads to only minor 34s depletion of sulfur remaining in the melt and decreases in 34s values of less than 2 at 90 degassing for this reason all lavas with 34s values in excess of 2 require a contribution of 34s enriched country rock sulfur because of the high s content and 34s value 16 20 of evaporites in the country rocks at noril sk contamination of less than 0 5 is required to explain the most 34s enriched lavas the nd lavas have an average 34s of 2 9 but show no difference in s isotopic composition relative to the other lavas suggesting that metal depletion involved only limited s transfer or that exchange between mantle derived s and s of crustal origin buffered 34s values to less than 5 anomalously positive 34s values similar to those of the ore bearing intrusives in the noril sk region are not consistently found in low s rocks either lavas or intrusives although the mechanism for the derivation of sulfide in the ore bearing intrusions remain speculative it is clear that the formation of sulfide ores characterized by high metal tenors proceeded only in the presence of sulfur of crustal origin

does large igneous province volcanism always perturb the mercury cycle comparing the records of oceanic anoxic event 2 and the end cretaceous to other mesozoic events mercury hg is increasingly being used as a sedimentary tracer of large igneous province lip volcanism and supports hypotheses of a coincidence between the formation of several lips and episodes of mass extinction and major environmental perturbation however numerous important questions remain to be answered before hg can be claimed as an unequivocal fingerprint of lip volcanism as well as an understanding of why some sedimentary records document clear hg enrichment signals whilst others do not of particular importance is evaluating the impact of different volcanic styles on the global mercury cycle as well as the role played by depositional processes in recording global hg cycle perturbations here new mercury records of cretaceous oceanic anoxic event 2 oae 2 94 ma and the latest cretaceous 67 66 0 ma are presented oae 2 is associated with the emplacement of multiple predominantly submarine lips the latest cretaceous with subaerial volcanism of the deccan traps both of these connections are strongly supported by previously published trends towards unradiogenic osmium os isotope values in globally distributed sedimentary records hg data from both events show considerable variation between different locations attributed to the effectiveness of different sediment types in registering the hg signal with lithologically homogeneous records documenting more clear hg enrichments than sections with major changes in lithology such as limestones to claystones or organic rich shales crucially there is no geographically consistent signal of sedimentary hg enrichment in stratigraphic records of either oae 2 or the latest cretaceous that matches os isotope evidence for lip emplacement indicating that volcanism did not cause a global hg perturbation throughout the entire eruptive history of the lips formed at those times it is suggested that the discrepancy between os isotope and hg trends in records of oae 2 is caused by the limited dispersal range of hg emitted from submarine volcanoes compared to the global scale distribution of os a similar lack of correlation between these two proxies in uppermost cretaceous strata indicates that although subaerial volcanism can perturb the global hg cycle not all subaerial eruptions will do so these results highlight the variable impact of different volcanogenic processes on the efficiency of hg dispersal across the globe factors that could influence the impact of lip eruptions on the global mercury cycle include submarine versus subaerial volcanism volcanic intensity or explosivity and the potential contribution of thermogenic mercury from reactions between ascending magma and surrounding organic rich sediments

climate changes caused by degassing of sediments during the emplacement of large igneous provinces most mass extinctions during the last 500 m y coincide with eruptions of large igneous provinces lips the cretaceous tertiary extinction was synchronous with the deccan flood volcanism the permian triassic extinction with the eruption of the enormous siberian traps and the end guadalupian extinction with the emeishan volcanic province the causal link remains disputed however and many lips apparently had no significant impact on the biosphere here we show that a key control on the destructive consequences of lip emplacement is the type of sedimentary rock in basins beneath the flood basalts contact metamorphism around intrusions in dolomite evaporite coal or organic rich shale generates large quantities of greenhouse and toxic gases co 2 ch 4 so 2 which subsequently vent to the atmosphere and cause global warming and mass extinctions the release of sediment derived gases had a far greater impact on the environment than the emission of magmatic gases

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

evaluating episodic hydrothermal activity in south china during the early cambrian implications for biotic evolution abstract the early cambrian 541 514 ma was a crucial interval for the evolution of life on earth popularly known as the cambrian explosion here we report the timing of changes in hydrothermal and depositional inputs as well as paleo redox state which may have influenced biogeochemical changes according to high resolution petrology fossil distributions isotopic records and inorganic geochemistry the lower cambrian of the south china can be subdivided into four intervals the lowermost cambrian zhujiaqing formation cam i the cambrian stage 2 shiyantou formation cam ii the lower part of the cambrian stage 3 yu anshan formation cam iii and the mid upper cambrian stage 3 and the middle upper part of the yu anshan formation continuing into the canglangpu formation cam iv hydrothermal events are detected during the early cam i cam ii and cam iii intervals during the early cam i and cam ii intervals these events coincided with extensive bottom water euxinia which in turn may have restricted the spread or proliferation of ediacaran fauna and small shelly fauna through the whole cam iii interval further hydrothermal events occurred concurrently with euxinic and ferruginous conditions probably within a single spatially stratified water column again plausibly restricting the spread of aerobic organisms in conjunction with the cessation of hydrothermal events and the gradual lowering of sea level during the late cam iii oxic water environments gradually spread into relatively deep water regions concurrent with the emergence of the chengjiang and qingjiang faunas these data suggest that periodic hydrothermal events may have had a significant impact on the spread radiation and extinction of macroscopic fauna during the early cambrian in south china

the mid capitanian middle permian mass extinction and carbon isotope record of south china abstract conodont c isotope and fossil and facies data are presented for the capitanian middle permian mass extinction record seen in platform carbonates maokou and wuchiaping formations of south china where limestones interdigitate with the volcanic succession of the emeishan large igneous province the maokou formation provides an extinction record marked by the loss of keriothecal walled fusulinaceans and a turnover in calcareous algae in sections within the emeishan province this crisis occurs at the base of the oldest record of volcanism from the jinogondolella altudaensis conodont zone of mid capitanian age around the periphery of the emeishan province this extinction level lies within the upper part of the maokou formation at a level where platform carbonate deposition was frequently interrupted by thick volcanic ash depositional events the assemblages of the uppermost maokou formation are characterised by typical late permian taxa although these levels still lie within the middle permian guadalupian series disaster taxa such as earlandia and diplosphaerina are locally prolifically abundant in the aftermath of the mass extinction the crisis is particularly noteworthy amongst photosynthetic taxa such as calcareous algae and fusulinaceans that probably harboured photosymbionts therefore a kill mechanism involving cooling from explosive volcanism and potentially acid rain from sulphate aerosols appears appropriate a composite 13ccarb curve calibrated against a high resolution conodont biostratigraphy reveals a major intra capitanian negative excursion of 5 superimposed on typically heavy 4 5 middle permian values this curve can also be recognised in panthalassan seamount carbonates of japan although this requires reassignment of apparently upper permian limestones to the middle permian in both china and japan the capitanian mass extinction occurs during the early stage of this major intra capitanian negative excursion assuming typical platform carbonate accumulation rates the records of the maokou formation suggest 13ccarb values fell at 0 01 kyr suggesting a catastrophic origin such as gas hydrate destabilisation is unlikely although a volcanic source is possible

the relationship between the east asian summer monsoon and el nino southern oscillation revealed by reconstructions and a control simulation for millennium abstract proxy based reconstructions of the asian summer monsoon exhibit variability over multiple scales from inter annual to centennial the relationship between east asia summer monsoon easm variability and the el nino southern oscillation enso over the last millennium remains unclear and a focus of current research this study investigates this relationship using observations reanalysis data proxy based reconstructions and a control simulation using the community earth system model cesm the results derived from both the observation reanalysis proxy based reconstruction and the simulation show consistently that the relationship between easm strength and nino3 4 sst is divergent the observation reanalysis data illustrate strong negative correlations between nino3 4 sst and easm strength at an annual scale in the 1920s 1930s and 1980s 1990s with weak correlations during other periods the proxy based reconstruction demonstrates strong negative correlations at inter decadal scales from the 1360s to the 1530s with either weak correlations or positive correlations during other periods moreover the simulations reveal positive correlations in some periods and negative or weak correlations in other periods the simulations demonstrate that the divergent relationship may be derived from multi decadal variations in pacific sst caused by internal variability in the climate system likely due to the inter decadal pacific oscillation ipo the easm variation is usually in out of phase with nino3 4 sst during the positive negative phase of the ipo in the positive phase of the ipo there is a tripolar pattern expressed in a cyclone anticyclone cyclone arrangement at pressure level of 850 hpa from the tropics to mid latitudes over the northwest pacific warming of the nino3 4 strengthens the tropical cyclone by weakening the trade winds and subsequently strengthening the subtropical anticyclone leading to a strong meiyu front which suggests a strong easm however in the negative phase of the ipo a huge cyclone occupies the northwest pacific warming of the nino3 4 strengthens the cyclone by weakening the trade winds which leads to a weak meiyu front which suggests a weak easm these results may be helpful in further understanding the mechanisms through which the enso and ipo impact the atmospheric circulations in the asian pacific especially regarding the long term variations in easm at inter annual to inter decadal scales

detailed dem analysis of a rockslide scar to characterize the basal sliding surface of active rockslides 1 the basal sliding surfaces in large rockslides are often composed of several surfaces and possess a complex geometry the exact morphology and location in three dimensions of the sliding surface remains generally unknown in spite of extensive field and subsurface investigations such as those at the aknes rockslide western norway this knowledge is crucial for volume estimations failure mechanisms and numerical slope stability modeling this paper focuses on the geomorphologic characterization of the basal sliding surface of a postglacial rockslide scar in the vicinity of aknes this scar displays a stepped basal sliding surface formed by dip slopes of the gneiss foliation linked together by steeply dipping fractures a detailed characterization of the rockslide scar by means of high resolution digital elevation models permits statistical parameters of dip angle spacing persistence and roughness of foliation surfaces and step fractures to be obtained the characteristics are used for stochastic simulations of stepped basal sliding surfaces at the aknes rockslide these findings are compared with previous models based on geophysical investigations this study discusses the investigation of rockslide scars and rock outcrops for a better understanding of potential rockslides this work identifies possible basal sliding surface locations which is a valuable input for volume estimates design and location of monitoring instrumentation and numerical slope stability modeling

volatile fluxes during flood basalt eruptions and potential effects on the global environment a deccan perspective abstract we examine the role that flood basalt eruptions may have played during times of mass extinction through the release of volcanic gases continental flood basalt provinces have formed by numerous eruptions over a short period of geologic time characteristically a few million years within this period a short lived climactic phase that lasts about 1 ma typically emplaces a large proportion of the lava volume this phase consists of a series of huge eruptions each yielding 10 3 10 4 km 3 of magma each eruption lasted on the order of a decade or more and built an immense p hoehoe dominated lava flow field by eruptive activity along fissures tens to hundreds of km long high fire fountains emanating from vents along the fissures at times sustained eruption columns that lofted gas and ash into the upper troposphere and lower stratosphere while the lava flows covered huge areas the combination of large eruption magnitudes maintained high effusion rates during eruptions and the repeated nature of the characteristic large scale eruptive activity occurs in earth history only during periods of flood basalt volcanism based on recent analogs and determination of volatile contents of ancient flood basalt lavas we estimate that individual eruptions were capable of releasing 10 000 tg of so 2 resulting in atmospheric loadings of 1000 tg a 1 during a sustained decade long eruptive event we apply this model of flood basalt volcanism to estimate the potential mass of co 2 and so 2 released during formation of the 65 ma deccan province the deccan lava pile contains the record of hundreds of enormous p hoehoe flow fields erupted within a period of about 1 ma consequently atmospheric perturbations associated with so 2 emissions from just one of these long lasting eruptions were likely to have been severe and constantly augmented over a decade or longer by contrast the amounts of co 2 released would have been small compared with the mass already present in the atmosphere and thus much more limited in effect individual eruptions were followed by hiatuses of hundreds to thousands of years during which the gas contributions to the atmosphere would be recycled it is clear that the nature and potential atmospheric impact of a series of huge volume repeated long term degassing events requires further investigation in conjunction with appropriate climate models

no link between the panjal traps kashmir and the late permian mass extinctions 1 voluminous late permian flood basalt eruptions are contemporaneous with the mid capitanian 260 ma and end permian 251 ma mass extinction events the panjal traps of kashmir are thought to be correlative to the mid capitanian mass extinction however no radiometric age has been determined we report a single zircon u pb laser ablation icp ms date of a rhyolite from the lower middle part of the volcanic sequence twenty four individual zircon crystals yield a mean 206u 238pb age of 289 3 ma the results show that the panjal traps are considerably older than previously interpreted and not correlative to post neo tethys rifting of the gondwanan margin or the mid capitanian mass extinction and are in fact correlative to the opening of the neo tethys ocean in contrast to other similarly size large igneous provinces the panjal traps are not coincident with a mass extinction event and therefore casts doubt on the direct relationship between continental flood basalt volcanism and ecosystem collapse

are late permian carbon isotope excursions of local or of global significance we present a new biostratigraphically calibrated organic and inorganic c isotope record spanning the basal late permian to earliest triassic from southern guizhou nanpanjiang basin south china after fluctuations of a likely diagenetic overprint are removed three negative carbon isotope excursions cies persist these include a short lived cie during the early wuchiapingian a protracted cie ending shortly after the wuchiapingian changhsingian boundary and a third cie straddling the permian triassic boundary comparison of our new c isotope record with others from the same basin suggests that influences of local bathymetry and of the amount of buried terrestrial organic matter are of importance comparison with other coeval time series outside of south china also highlights that only the negative cie at the permian triassic boundary is a global signal these differences can be explained by the different volumes of erupted basalts between the late permian emeishan and the younger siberian large igneous provinces and their distinct eruptive modalities emeishan volcanism was largely submarine implying that sea water was an efficient buffer against atmospheric propagation of volatiles the equatorial position of emeishan was also an additional obstacle for volatiles to reach the stratosphere and benefit from an efficient global distribution consequently the local significance of these cies calls into question global correlations based on c isotope chemostratigraphy during the late permian the timing of the late permian chinese cies is also not reflected in changes in species diversity or ecology unlike the sudden and global permian triassic boundary crisis and subsequent early triassic upheavals

contact metamorphic devolatilization of shales in the karoo basin south africa and the effects of multiple sill intrusions abstract quantification of fluid generation during contact metamorphism of shale is important for the understanding of metamorphic processes fluid flow in sedimentary basins and perturbations of the global carbon cycle in this study we provide geochemical and numerical analyses from the organic rich ecca group in the karoo basin south africa which was affected by contact metamorphism from multiple sill intrusions in the early jurassic organic matter was efficiently converted to hydrocarbons during contact metamorphism and complete loss of organic carbon in the innermost aureole is common mineral dehydration reactions are evident from the occurrence of metamorphic minerals like biotite and loss of the clay fraction towards the intrusive contact we have developed a numerical model in order to quantify fluid production from both inorganic and organic reactions during contact metamorphism the modelling results are constrained by data from two case studies in the karoo basin in order to obtain reliable estimates of the carbon loss from metamorphism of shale we show that single thin 15 m thick sills have a gas production potential of several gigatons of methane ch4 if emplaced over a 1000 km2 area furthermore the vertical spacing between simultaneously emplaced sills has an important influence on the gas generation potential when two sills are emplaced with a vertical spacing of 7 times the intrusion thickness the total ch4 generation is up to 35 more than for two separate sills data and modelling from five sills emplaced within the ecca group show hydrocarbon generation throughout the organic rich section with total carbon loss next to the sills this has implications for the fluid production and metamorphism in volcanic basins where multiple sills are common

potential links between ocean plateau volcanism and global ocean anoxia at the cenomanian turonian boundary the cenomanian turonian boundary is marked globally by the extinction of marine invertebrates and an increase in the accumulation and preservation of organic carbon rich sediments black shales the timing of this boundary also coincides with large scale volcanism from at least three large igneous provinces the caribbean and ontong java oceanic plateaus and the madagascar flood basalts in this paper we assess the possibility that hydrothermalism associated with large scale submarine magmatism was responsible for the reduction of dissolved o 2 in the oceans we investigate two potential mechanisms the oxidation of reduced material in hydrothermal effluents and the stimulation of primary productivity in the water column due to the injection of hydrothermal fe into surface waters with the first mechanism we find that a 10 000 km 3 submarine basalt eruption three orders of magnitude larger than recent midocean ridge eruptions could release enough reduced hydrothermal material to consume at least 6 percent of the dissolved o 2 in seawater in a well ventilated ocean such as the present ocean with the second mechanism we calculate that even a small percentage of the hydrothermal fe released from a single large flow could have led to a significant increase in primary productivity in areas where fe was the biolimiting nutrient such as open ocean areas in the pacific the potential impact of both of these o 2 reducing mechanisms at the cenomanian turonian boundary would have been significantly greater if cretaceous oceans were less well ventilated than the present oceans

methane release from igneous intrusion of coal during late permian extinction events abstract unusually large and locally variable carbon isotope excursions coincident with mass extinctions at the end of the permian period 253 ma and guadalupian epoch 260 ma can be attributed to methane outbursts to the atmosphere methane has isotopic values 13c low enough to reduce to feasible amounts the carbon required for isotopic mass balance the duration of the carbon isotopic excursions and inferred methane releases are here constrained to 10 000 yr by counting annual varves in lake deposits and by estimating peat accumulation rates on paleogeographic maps the most marked carbon isotope excursions form linear arrays back to plausible methane sources end permian siberian traps and longwood bluff intrusions of new zealand and end guadalupian emeishan traps of china intrusion of coal seams by feeder dikes to flood basalts could create successive thermogenic methane outbursts of the observed timing and magnitude but these are unreasonably short times for replenishment of marine or permaf

hydrothermal venting of greenhouse gases triggering early jurassic global warming abstract the climate change in the toarcian early jurassic was characterized by a major perturbation of the global carbon cycle the event lasted for approximately 200 000 years and was manifested by a global warming of 6 c anoxic conditions in the oceans and extinction of marine species the triggering mechanisms for the perturbation and environmental change are however strongly debated here we present evidence for a rapid formation and transport of greenhouse gases from the deep sedimentary reservoirs in the karoo basin south africa magmatic sills were emplaced during the initial stages of formation of the early jurassic karoo large igneous province and had a profound influence on the fate of light elements in the organic rich sedimentary host rocks total organic carbon contents and vitrinite reflectivity data from contact aureoles around the sills show that organic carbon was lost from the country rocks during heating we present data from a new type of geological structures termed breccia pipes rooted in the aureoles within the shale of the western karoo basin the breccia pipes are cylindrical structures up to 150 meters in diameter and are mainly comprised of brecciated and baked black shale thousands of breccia pipes were formed due to gas pressure build up during metamorphism of the shales resulting in venting of greenhouse gases to the toarcian atmosphere mass balance calculations constrained by new aureole data show that up to 1800 gt of co2 was formed from organic material in the western karoo basin about 15 times this amount of co2 27 400 gt may have formed in the entire basin during the intrusive event u pb dating of zircons from a sill related to many of the pipes demonstrates that the magma was emplaced 182 5 0 4 million years ago this supports a causal relationship between the intrusive volcanism the gas venting and the toarcian global warming

a tale of two extinctions converging end permian and end triassic scenarios the end permian c 252 ma and end triassic c 201 ma mass extinction events are commonly linked to the emplacement of the large igneous provinces of the siberia traps and central atlantic magmatic province respectively accordingly scenarios for both extinctions are increasingly convergent and cross fertilization of ideas has become important here we present a synthesis of extinction scenarios based on a critical assessment of the available palaeontological sedimentological geochemical and geophysical evidence how similar were the extinction events what gaps exist in our understanding and how can a comparison of the events enhance our understanding of each event individually our focus is on the most important proximate kill mechanisms including climate change and atmospheric pollution increased soil erosion weathering and runoff forest dieback and the spread of pathogens and ocean temperature changes anoxia and acidification there is substantial evidence to suggest that very similar kill mechanisms acted upon late permian as well as late triassic ecosystems strengthening the hypothesis that the ultimate causes of the mass extinction events were similar

multiple phases of carbon cycle disturbance from large igneous province formation at the triassic jurassic transition the end triassic mass extinction ca 201 4 ma coincided with a major carbon cycle perturbation based on an 5 6 negative excursion in 13 c toc total organic carbon records both events coincided directly with the onset of massive flood basalt volcanism in the central atlantic magmatic province camp organic carbon isotope data from the western tethys ocean austria and the germanic basin uk and germany however demonstrate earlier disruption of the global carbon cycle preceding camp eruptions a 2 3 late rhaetian precursor negative excursion in marine and continental 13 c toc records is matched by a negative perturbation in 13 c leaf data suggesting multiple events of rhaetian atmospheric 13 c depletion intruding dike and sill systems preceding camp eruptive volcanic activity may have released 3000 7000 gt of isotopically light carbon as thermogenic methane from subsurface organic rich strata this possibly caused an end triassic atmospheric p co 2 increase and reduced ecosystem stability before the actual onset of eruptive volcanic activity in the camp region we present a model that identifies three phases of disturbances in global biogeochemical cycles related to the formation of this large igneous province

three fe ti oxide ore bearing gabbro granitoid complexes in the panxi region of the permian emeishan large igneous province sw china the permian 260 ma emeishan large igneous province of sw china contains three nearly identical gabbro granitoid complexes that host giant fe ti oxide deposits the fe ti oxide deposits are within the lower portions of evolved layered gabbroic intrusions and are spatially and temporally associated with a type granitic plutons the 264 3 ma taihe layered gabbroic intrusion hosts a large magmatic fe ti oxide deposit and is coeval with the taihe peralkaline a type granitic pluton which is dated at 261 2 ma within the a type granitic pluton are microgranular enclaves which have compositions intermediate between the gabbro and host granite primitive mantle normalized incompatible element plots show corresponding reciprocal patterns between the mafic and felsic rocks the chondrite normalized ree patterns show eu anomalies changing from positive eu eu 1 5 to 5 9 in the gabbroic intrusion to negative in the enclaves eu eu 0 4 to 0 6 and granites eu eu 0 2 to 0 5 whole rock end t values of the gabbroic intrusion end t 2 5 to 3 3 are similar to those of the enclaves end t 1 0 to 2 0 and granite end t 1 5 to 1 9 whereas the zircon ehf t values of the gabbro ehf t 8 1 0 8 are indistinguishable from those of the granites ehf t 9 2 1 0 suggesting that the parent magmas for all rock types originated from the same mantle source geochemical modeling indicates that the gabbros and granites can be generated by fractional crystallization of a common parental magma similar to high ti emeishan flood basalt the compositional jump from the gabbro to the enclaves is attributed to the crystallization of fe ti oxide minerals the results of this study and other studies suggest that the magmatic conditions for example pressure composition fo2 which led to the formation of at least three fe ti oxide bearing gabbro granitoid complexes were relatively common during the development of the emeishan large igneous province

transition into a hothouse world at the permian triassic boundary a model study abstract the permian triassic boundary ptb 252 3 ma marks the largest mass extinction of the phanerozoic with a loss of more than 90 of marine organisms and is characterized by lethally hot surface temperatures the ptb global warming has been linked to greenhouse gas emissions from the siberian traps and associated coal bed intrusions and likely led to severe environmental consequences such as ocean acidification a decline in the marine productivity and extensive hypoxia in order to understand these changes feedbacks in the climate system have been explored with sensitivity climate simulations and compared to temperature proxies from the sedimentary record the response of the ptb ocean circulation to an atmospheric perturbation of 5000 pg c comparable to earth s total fossil fuel inventory leads to a global temperature increase by 3 4 c and an increase in ocean stratification the pole to equator temperature gradient decreases by 2 c with an increase in co2 radiative forcing predominately due to snow albedo feedbacks over gondwana the greenhouse induced warming would have led to a weakening of the hadley cell and an associated decrease in the trade winds and equatorial primary productivity these climatic changes might have been amplified by cloud feedback processes a reduced concentration of cloud condensation nuclei due to a biologic decline of dimethylsulfide caused by the temperature stress or changes in airborne mineral particles could have reduced the cloud albedo particularly in high latitudes results from a climate simulation with reduced cloud albedo suggest a polar warming of up to 7 c and a reduction of the pole to equator temperature gradient by 4 c in addition to the reduction caused by the increase in greenhouse induced radiative forcing the scenario with reduced cloud albedo further leads to an increase in ocean stratification and widespread low oxygen concentrations in the panthalassa during the early triassic

progress problems and prospects an overview of the guadalupian series of south china and north america abstract the guadalupian epoch is marked by the formation of the pangean supercontinent global sea level change rifting and drifting of the cimmerian continents formation of large igneous provinces and dramatic biotic changes a high resolution biostratigraphic chemostratigraphic and high precision geochronologic framework of this critical transition is fundamental to understanding these events extensive studies of the latest cisuralian and guadalupian series in both south china and north america reveal the same conodont lineages but the conodont interval zones based on jinogondolella within the guadalupian series are slightly diachronous high precision u pb geochronological studies ca id tims method calibrate the base of the guadalupian series base roadian at 273 01 0 14 ma a previously reported age from an ash bed overlying the emeishan flood basalts 259 51 0 21 ma is adopted for the guadalupian lopingian boundary glb based on recently published geochronology and bayesian age modeling from the guadalupian series the base of the capitanian is constrained at 264 28 0 16 ma and the base of the wordian is interpolated to be 266 9 0 4 ma the illawarra reversal is of early middle wordian age both north america and south china possess a distinct negative 13ccarb excursion of 3 5 at the latest kungurian and early roadian lk er cie which coincides with the early stages of a significant 3rd order sea level rise the large end guadalupian 13ccarb negative excursion may have been affected by post depositional diagenesis or a warming event associated with the emeishan volcanism the 87sr 86sr ratios in both regions declined from the latest kungurian to the late capitanian but have different ratios and reveal several fluctuations in the middle guadalupian measured 18oapatite values suggest that the delaware basin was 3 4 c cooler than the eastern yangtze block analysis of a new high resolution database of marine taxa indicates only a minor pre lopingian diversity drop from 261 04 ma to 259 98 ma which coincides with the peak emeishan volcanism the widely perceived end guadalupian mass extinction in north america is evidently masked by and possibly an artefact of a stratigraphic truncation effect due to rapid lithofacies changes from limestone to laminated evaporites with the closure of the west texas basins

climate changes caused by degassing of sediments during the emplacement of large igneous provinces comment many mass extinctions and biotic crises coincide with eruptions of large igneous provinces lips but a causal link remains disputed because many lips apparently had no severe deleterious impact on the biosphere wignall 2005 1 ganino and arndt 2009 2 presented exciting data showing that

contact metamorphism of organic rich mudstones and carbon release around a magmatic sill in the basque cantabrian basin western pyrenees abstract recent studies have documented the expulsion of methane and oil to the albian paleoseabed in the basque cantabrian basin they interpret that hydrocarbon generation and expulsion were triggered by seismically recorded magmatic intrusions which metamorphosed organic rich host sediments an outcrop within the basin was selected to investigate organic matter evolution and sediment degassing due to an igneous body this intrusion is a 5 m thick late albian basaltic sill that intruded mudstones of the black flysch group near gorliz north iberia vitrinite and bitumen reflectance profiles and metamorphic mineral distribution in the overburden indicate that the sill produced a thermal effect that increases toward the intrusion defining a 2 m thick minimum contact aureole geochemical profiles of toc s1 s2 hi and pc show a gradual decrease toward the sill indicating organic carbon loss and increase in the thermal maturity of the organic matter in the same direction concordantly gas chromatograms show a loss of n alkanes and a predominance of the shorter chain length homologues adjacent to the sill tmax and pi s1 s1 s2 values increase toward the sill which suggests an increase in the thermal stress and in the extent of kerogen pyrolysis respectively organic carbon loss in the aureole was the result of carbon devolatilization and formation of co2 and ch4 gases the newly formed co2 reacted with pore waters to precipitate 13c depleted carbonate minerals in the aureole and in sill fractures ch4 escaped from the aureole via hydrofractures to the paleoseabed where methane derived authigenic carbonates were formed

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

new 40ar 39ar and k ar ages of the viluy traps eastern siberia further evidence for a relationship with the frasnian famennian mass extinction abstract we present here new ages combining both k ar and 40 ar 39 ar techniques reinforcing the possible link between the viluy traps eastern siberia with the late devonian mass extinctions the viluy traps also referred to as the yakutsk large igneous province are associated with the breakup of the eastern margin of the siberian platform as a triple junction rift system with volcanic outcropping along the lena markha and viluy rivers and an initial volume of volcanic products of about one million cubic kilometers k ar ages obtained on seven samples from the viluy rift display values ranging from 366 5 to 381 5 ma with a mean age of 374 5 ma our new 40 ar 39 ar results display well defined step heating plateau ages ranging from 362 3 3 4 to 379 7 3 5 ma although most k ar and 40 ar 39 ar ages agree within about 1 uncertainty which reinforces the validity of the k ar ages obtained with the cassignol and gillot unspiked technique even in the paleozoic a slightly clearer scenario appears when only the 40 ar 39 ar ages are considered effectively they cluster in two different groups with weighted mean ages of 364 4 1 7 and 376 7 1 7 ma these ages support a multi phases emplacement of the viluy traps as is the case for many continental flood basalts because the age of the first volcanic phase is undistinguishable from recent determinations of the age of the frasnian famennian boundary our results further strengthen the hypothesis of a causal relationship between the two events the second phase of emplacement of the viluy traps occurred at the end of the devonian apparently slightly before the devonian carboniferous boundary finally except for the ordovician silurian extinction which remains to be associated with a volcanic province all major phanerozoic mass extinctions have been correlated with the emplacement of a cfb thereby reinforcing the possible causal link between these events

thermochemistry of monazite la and dissakisite la implications for monazite and allanite stability in metapelites thermochemical properties have been either measured or estimated for synthetic monazite lapo4 and dissakisite calamgal2 sio4 3oh the mg equivalent of allanite a dissakisite formation enthalpy of 6 976 5 10 0 kj mol 1 was derived from high temperature drop solution measurements in lead borate at 975 k a third law entropy value of 104 9 1 6 j mol 1 k 1 was retrieved from low temperature heat capacity c p measured on synthetic lapo4 with an adiabatic calorimeter in the 30 300 k range the c p values of lanthanum phases were measured in the 143 723 k range by differential scanning calorimetry in this study la oh 3 appeared as suitable for drop solution in lead borate and represents an attractive alternative to la2o3 pseudo sections were calculated with the theriak domino software using the thermochemical data retrieved here for a simplified metapelitic composition la ree y and considering monazite and fe free epidotes along the dissakisite clinozoisite join as the only ree bearing minerals calculation shows a stability window for dissakisite clinozoisite epidotes t between 250 and 550 c and p between 1 and 16 kbar included in a wide monazite field the p t extension of this stability window depends on the bulk rock ca content assuming that synthetic lapo4 and dissakisite la are good analogues of natural monazite and allanite these results are consistent with the ree mineralogy sequence observed in metapelites where 1 monazite is found to be stable below 250 c 2 around 250 450 c depending on the pressure allanite forms at the expense of monazite and 3 towards amphibolite conditions monazite reappears at the expense of allanite

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago