mass mortality and its environmental and evolutionary consequences the latest mesozoic and earliest tertiary sediments at deep sea drilling project site 524 provide an amplified record of environmental and biostratographic changes at the end of cretaceous closely spaced samples representing time intervals as short as 102 or 103 years were analyzed for their bulk carbonate and trace metal compositions and for oxygen and carbon isotopic compositions the data indicate that at the end of cretaceous when a high proportion of the ocean9s planktic organisms were eliminated an associated reduction in productivity led to a partial transfer of dissolved carbon dioxide from the oceans to the atmosphere this resulted in a large increase of the atmospheric carbon dioxide during the next 50 000 years which is believed to have caused a temperature rise revealed by the oxygen isotope data the lowermost tertiary sediments at site 524 include fossils with cretaceous affinities which may include both reworked individuals and some forms that survived for a while after the catastrophe our data indicate that many of the cretaceous pelagic organisms became extinct over a period of a few tens of thousands of years and do not contradict the scenario of cometary impact as a cause of mass mortality in the oceans as suggested by an iridium anomaly at the cretaceous tertiary boundary

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

the role of microphysical and chemical processes in prolonging the climate forcing of the toba eruption the mega eruption of toba sumatra occurred around 73 ka ago during the onset of a glaciation of the late quaternary this coincidence combined with the unprecedented amount of sulphur released by this volcano has led to the hypothesis that toba sulphate aerosols caused a transient surface cooling which may have contributed to a shift of the climate system because of the self limiting effect of gravitational sedimentation the climatic impact of extremely large sulphur injections into the stratosphere are thought to be rather limited here we present model calculations combining microphysical and chemical feedbacks which show that the eruption could instead have led to the formation of a long lasting volcanic aerosol layer although the concentrations of radiatively active species such as o3 or so2 could also have been considerably perturbed the resulting forcings should have only slightly moderated the aerosol cooling effect during the first few years following the eruption according to our results extremely high stratospheric sulphur loading could lead to a more prolonged effect on the climate than previously assumed

la fossa caldera breaching and submarine erosion vulcano island italy abstract la fossa caldera lfc on vulcano island in the aeolian archipelago italy is a multi collapse caldera whose north eastern part lies underwater through the integration of marine geophysical surveys and sampling carried out in the last decade its submarine extension and offshore areas have been reconstructed in unprecedented detail strong erosive processes breached the submarine portion of lfc and gradually dismantled the caldera rims and infill leading to the emplacement of a wide volcaniclastic fan from the base of lfc down to over 1000 m the bathy morphologic setting seismoacoustic facies and analyses of sediment samples from the fan together with volumetric considerations suggest that this feature is the pathway deposit of submarine unconfined gravity flows and turbidity currents deriving from the gradual dismantling of lfc submarine erosive processes are still active and the progressive erosion of the northern caldera sector threatens the stability of the active la fossa cone and the nearby coastal settlements

late cretaceous restructuring of terrestrial communities facilitated the end cretaceous mass extinction in north america the sudden environmental catastrophe in the wake of the end cretaceous asteroid impact had drastic effects that rippled through animal communities to explore how these effects may have been exacerbated by prior ecological changes we used a food web model to simulate the effects of primary productivity disruptions such as those predicted to result from an asteroid impact on ten campanian and seven maastrichtian terrestrial localities in north america our analysis documents that a shift in trophic structure between campanian and maastrichtian communities in north america led maastrichtian communities to experience more secondary extinction at lower levels of primary production shutdown and possess a lower collapse threshold than campanian communities of particular note is the fact that changes in dinosaur richness had a negative impact on the robustness of maastrichtian ecosystems against environmental perturbations therefore earlier ecological restructuring may have exacerbated the impact and severity of the end cretaceous extinction at least in north america

atmospheric and oceanic impacts of antarctic glaciation across the eocene oligocene transition the glaciation of antarctica at the eocene oligocene transition approx 34 million years ago was a major shift in the earth s climate system but the mechanisms that caused the glaciation and its effects remain highly debated a number of recent studies have used coupled atmosphere ocean climate models to assess the climatic effects of antarctic glacial inception with often contrasting results here using the hadcm3l model we show that the global atmosphere and ocean response to growth of the antarctic ice sheet is sensitive to subtle variations in palaeogeography using two reconstructions representing eocene and oligocene geological stages the earlier stage eocene priabonian which has a relatively constricted tasman seaway shows a major increase in sea surface temperature over the pacific sector of the southern ocean in response to the ice sheet this response does not occur for the later stage oligocene rupelian which has a more open tasman seaway this difference in temperature response is attributed to reorganization of ocean currents between the stages following ice sheet expansion in the earlier stage the large ross sea gyre circulation decreases in size stronger zonal flow through the tasman seaway allows salinities to increase in the ross sea deep water formation initiates and multiple feedbacks then occur amplifying the temperature response this is potentially a model dependent result but it highlights the sensitive nature of model simulations to subtle variations in palaeogeography and highlights the need for coupled ice sheet climate simulations to properly represent and investigate feedback processes acting on these time scales

rapid short term cooling following the chicxulub impact at the cretaceous paleogene boundary the mass extinction at the cretaceous paleogene boundary 66 ma is thought to be caused by the impact of an asteroid at chicxulub present day mexico although the precise mechanisms that led to this mass extinction remain enigmatic most postulated scenarios involve a short lived global cooling a so called impact winter phase here we document a major decline in sea surface temperature during the first months to decades following the impact event using tex86 paleothermometry of sediments from the brazos river section texas we interpret this cold spell to reflect to our knowledge the first direct evidence for the effects of the formation of dust and aerosols by the impact and their injection in the stratosphere blocking incoming solar radiation this impact winter was likely a major driver of mass extinction because of the resulting global decimation of marine and continental photosynthesis

global warming and ocean stratification a potential result of large extraterrestrial impacts we acknowledge the support of resources provided by uk national centre for atmospheric science ncas the high performance computing cluster supported by the research and specialist computing support service at the university of east anglia uk natural environment research council nerc grants cpe ne k014757 1 and paleopolar ne i005722 1 data can be obtained from mj on request acm acknowledges support from an axa postdoctoral fellowship and the erc acci grant project no 267760 and nerc grant ne m018199 1

effects of soil surface components on soil hydrological behaviour in a dry mediterranean environment southern spain abstract various researchers have studied the spatial pattern of soil surface components such as vegetation rock fragments bare soil litter and surface crusts as a key factor of hydrological behaviour in mediterranean settings with heterogeneous patches of vegetation cover and strong human impact the studies indicate that there is a mosaic of patches that generate run off or infiltrate overland flow distributed in various ways along hillslopes few of these studies however have looked at areas underlain by metamorphic rocks such as phyllites or schists this study analysed the temporal and spatial variability of the effects of soil surface components on hydrological processes in a small dry mediterranean catchment underlain by metamorphic rocks a systematic sampling of multiple sites throughout a hydrological year was carried out we related the hydrological behaviour of soil surface components to 1 their position along the hillslope 2 the distance of existing vegetation tussocks from the line of run off 3 rainfall intensity and 4 the main physical chemical soil properties affecting infiltration processes statistical analysis was used to check the validity of the relationships the results show that soil surface components have highly variable effects in both space and time on soil hydrological behaviour these effects particularly depend on the location along the line of maximum slope and the intensity of preceding rainfall whose interaction defines soil hydrological status these results are similar to those for other mediterranean settings with different lithology in that the succession of contributing patches are hydrologically interconnected along a hillslope the variables used and the grouping of explanatory variables through principal component analyses were found to be suitable for discussing the spatial distribution of soil surface components in the hydrologically dynamic environment of the study area

the chicxulub asteroid impact and mass extinction at the cretaceous paleogene boundary the cretaceous paleogene boundary similar to 65 5 million years ago marks one of the three largest mass extinctions in the past 500 million years the extinction event coincided with a large asteroid impact at chicxulub mexico and occurred within the time of deccan flood basalt volcanism in india here we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction notably a single ejecta rich deposit compositionally linked to the chicxulub impact is globally distributed at the cretaceous paleogene boundary the temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations for example darkness and cooling lead us to conclude that the chicxulub impact triggered the mass extinction

asteroid impact not volcanism caused the end cretaceous dinosaur extinction the cretaceous paleogene mass extinction 66 ma included the demise of non avian dinosaurs intense debate has focused on the relative roles of deccan volcanism and the chicxulub asteroid impact as kill mechanisms for this event here we combine fossil occurrence data with paleoclimate and habitat suitability models to evaluate dinosaur habitability in the wake of various asteroid impact and deccan volcanism scenarios asteroid impact models generate a prolonged cold winter that suppresses potential global dinosaur habitats conversely long term forcing from deccan volcanism carbon dioxide co2 induced warming leads to increased habitat suitability short term aerosol cooling volcanism still allows equatorial habitability these results support the asteroid impact as the main driver of the non avian dinosaur extinction by contrast induced warming from volcanism mitigated the most extreme effects of asteroid impact potentially reducing the extinction severity

selective environmental stress from sulphur emitted by continental flood basalt eruptions several biotic crises during the past 300 million years have been linked to episodes of continental flood basalt volcanism and in particular to the release of massive quantities of magmatic sulphur gas species flood basalt provinces were typically formed by numerous individual eruptions each lasting years to decades however the environmental impact of these eruptions may have been limited by the occurrence of quiescent periods that lasted hundreds to thousands of years here we use a global aerosol model to quantify the sulphur induced environmental effects of individual decade long flood basalt eruptions representative of the columbia river basalt group 16 5 14 5 million years ago and the deccan traps 65 million years ago for a decade long eruption of deccan scale we calculate a decadal mean reduction in global surface temperature of 4 5 k which would recover within 50 years after an eruption ceased unless climate feedbacks were very different in deep time climates acid mists and fogs could have caused immediate damage to vegetation in some regions but acid sensitive land and marine ecosystems were well buffered against volcanic sulphur deposition effects even during century long eruptions we conclude that magmatic sulphur from flood basalt eruptions would have caused a biotic crisis only if eruption frequencies and lava discharge rates had been high and sustained for several centuries at a time

impact production of co2 by the cretaceous tertiary extinction bolide and the resultant heating of the earth evidence at the cretaceous tertiary boundary suggests that the proposed extinction bolide struck a continental or shallow marine terrane this evidence includes shocked quartz and feldspar grains found in the boundary layer inherited from a range of rock types a high 87 sr 86 sr ratio in some planktonic fossils which could reflect continental derived sr ref 5 and evidence that the platinum group element rich clay layer is underlain at some localities by a deposit of possible tsunamic origin these observations and data demonstrate that sea level at the end of the cretaceous was 150 200 m higher than at present suggesting the possibility that the extinction bolide struck a shallow marine carbonate rich sedimentary section here we show that the impact of such a bolide 5km in radius onto a carbonate rich terrane would increase the co 2 content of the atmosphere by a factor of two to ten additional dissolution of co 2 from the ocean s photic zone could release much larger quantities of co 2 the impact induced release of co 2 by itself would enhance atmospheric greenhouse heating and give rise to a worldwide increase in temperature from 2 k to 10 k for periods of 10 4 to 10 5 years

cretaceous extinctions multiple causes figure 1 deccan plateau basalts lava from deccan volcanism formed distinct layering credit gsfc nasa in the review the chicxulub asteroid impact and mass extinction at the cretaceous paleogene boundary p schulte et al 5 march p 1214 2 the terminal cretaceous

rapid recovery of life at ground zero of the end cretaceous mass extinction the cretaceous palaeogene mass extinction eradicated 76 of species on earth1 2 it was caused by the impact of an asteroid3 4 on the yucatan carbonate platform in the southern gulf of mexico 66 million years ago 5 forming the chicxulub impact crater6 7 after the mass extinction the recovery of the global marine ecosystem measured as primary productivity was geographically heterogeneous 8 export production in the gulf of mexico and north atlantic western tethys was slower than in most other regions8 11 taking 300 thousand years kyr to return to levels similar to those of the late cretaceous period delayed recovery of marine productivity closer to the crater implies an impact related environmental control such as toxic metal poisoning 12 on recovery times if no such geographic pattern exists the best explanation for the observed heterogeneity is a combination of ecological factors trophic interactions 13 species incumbency and competitive exclusion by opportunists 14 and chance 8 15 16 the question of whether the post impact recovery of marine productivity was delayed closer to the crater has a bearing on the predictability of future patterns of recovery in anthropogenically perturbed ecosystems if there is a relationship between the distance from the impact and the recovery of marine productivity we would expect recovery rates to be slowest in the crater itself here we present a record of foraminifera calcareous nannoplankton trace fossils and elemental abundance data from within the chicxulub crater dated to approximately the first 200 kyr of the palaeocene we show that life reappeared in the basin just years after the impact and a high productivity ecosystem was established within 30 kyr which indicates that proximity to the impact did not delay recovery and that there was therefore no impact related environmental control on recovery ecological processes probably controlled the recovery of productivity after the cretaceous palaeogene mass extinction and are therefore likely to be important for the response of the ocean ecosystem to other rapid extinction events

on impact and volcanism across the cretaceous paleogene boundary the cause of the end cretaceous mass extinction is vigorously debated owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing impact and extinction we used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing we found support for major outgassing beginning and ending distinctly before the impact with only the impact coinciding with mass extinction and biologically amplified carbon cycle change our models show that these extinction related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide thus limiting the global warming otherwise expected from postextinction volcanism

modeling climatic effects of carbon dioxide emissions from deccan traps volcanic eruptions around the cretaceous paleogene boundary abstract warming events observed in paleotemperature proxy records within 500 kyr of the cretaceous paleogene k pg boundary have often been attributed to atmospheric co 2 increases due to deccan traps flood volcanism currently there is uncertainty in the size nature and timing of the deccan eruptions all of which lead to uncertainty in the likely climatic effects modeling the impact of deccan traps eruption on climate is complicated by the discrepancy between the lifetimes of emitted gasses and the length of the total eruptive sequence though so 2 emissions can have important climatic effects the short atmospheric lifetimes of so 2 and resulting aerosols mean these effects are unlikely to be recognized in the proxy record here we focus on the co 2 emissions and attempt to match paleotemperature proxy records with plausible emissions scenarios we also test the relevance for climate of the number length and arrangement e g increasing or decreasing size of individual eruptions as well as the total duration and size of the overall eruptive sequence we find that the number and length of individual eruptions are largely unimportant to co 2 based based climate effects but that the pattern and duration of eruption have measureable effects unsurprisingly the total emitted co 2 from the deccan traps exerts a strong control on climatic effects and better constraints on the volume of emitted gas are necessary at the high end of the uncertainty range the deccan traps eruptions are capable of generating warming events recorded in the proxy record but rates of silicate weathering above modern rates are necessary to draw down co 2 in accordance with those records

the eruptive tempo of deccan volcanism in relation to the cretaceous paleogene boundary late cretaceous records of environmental change suggest that deccan traps dt volcanism contributed to the cretaceous paleogene boundary kpb ecosystem crisis however testing this hypothesis requires identification of the kpb in the dt we constrain the location of the kpb with high precision argon 40 argon 39 data to be coincident with changes in the magmatic plumbing system we also found that the dt did not erupt in three discrete large pulses and that 90 of dt volume erupted in 1 million years with 75 emplaced post kpb late cretaceous records of climate change coincide temporally with the eruption of the smallest dt phases suggesting that either the release of climate modifying gases is not directly related to eruptive volume or dt volcanism was not the source of late cretaceous climate change

impact winter and the cretaceous tertiary extinctions results of a chicxulub asteroid impact model abstract the chicxulub impact crater in mexico is the site of the impact purported to have caused mass extinctions at the cretaceous tertiary k t boundary 2 d hydrocode modeling of the impact coupled with studies of the impact site geology indicate that between 0 4 and 7 0 1017 g of sulfur were vaporized by the impact into anhydrite target rocks a small portion of the sulfur was released as so3 or so4 which converted rapidly into h2so4 aerosol and fell as acid rain a radiative transfer model coupled with a model of coagulation indicates that the aerosol prolonged the initial blackout period caused by impact dust only if the aerosol contained impurities a larger portion of sulfur was released as so2 which converted to aerosol slowly due to the rate limiting oxidation of so2 our radiative transfer calculations combined with rates of acid production coagulation and diffusion indicate that solar transmission was reduced to 10 20 of normal for a period of 8 13 yr this reduction produced a climate forcing cooling of 300 wm 2 which far exceeded the 8 wm 2 greenhouse warming caused by the co2 released through the vaporization of carbonates and therefore produced a decade of freezing and near freezing temperatures several decades of moderate warming followed the decade of severe cooling due to the long residence time of co2 the prolonged impact winter may have been a major cause of the k t extinctions

baby it s cold outside climate model simulations of the effects of the asteroid impact at the end of the cretaceous sixty six million years ago the end cretaceous mass extinction ended the reign of the dinosaurs flood basalt eruptions and an asteroid impact are widely discussed causes yet their contributions remain debated modeling the environmental changes after the chicxulub impact can shed light on this question existing studies however focused on the effect of dust or used one dimensional noncoupled atmosphere models here we explore the longer lasting cooling due to sulfate aerosols using a coupled climate model depending on aerosol stratospheric residence time global annual mean surface air temperature decreased by at least 26 c with 3 to 16 years subfreezing temperatures and a recovery time larger than 30 years the surface cooling triggered vigorous ocean mixing which could have resulted in a plankton bloom due to upwelling of nutrients these dramatic environmental changes suggest a pivotal role of the impact in the end cretaceous extinction

submarine silicic volcanism of the healy caldera southern kermadec arc sw pacific i volcanology and eruption mechanisms the submarine healy volcano southern kermadec arc with a 2 2 5 km wide caldera is pervasively mantled with highly vesicular silicic pumice within a water depth of 1 150 1 800 m pumices comprise type 1 white light grey pumice with 30 mm vesicles and weak moderate foliation type 2 grey pumice with millimetre scale laminae flow banded foliation including stretched vesicles 55 mm in length and a minor finely vesicular type 3 pumice all types are sparsely porphyritic with undevitrified glassy groundmass 68 70 sio2 which is microlite and lithic free coexisting pyroxenes yield magma temperatures of 950 c pumice density is 0 5 g cm 3 and vesicularity is 78 83 vesicle size distributions for types 1 and 2 pumice range from 20 m to 20 mm with a strong power law relation with d 2 5 0 4 for vesicles 9 mpa will limit vesicularity to less than the observed 78 83 whereas pressure 6 mpa require a more shallower reconstruction of the edifice and larger volume syn eruptive collapse uniformly high vesicularity is interpreted as evidence of insulation within an eruption column comprising steam and hot pyroclasts most pyroclasts cool condensing and ingesting water into steam inflated vesicles and then sink progression into pyroclastic mode would expand the eruption column displace ambient water reduce the hydrostatic load and further promote vesiculation and fragmentation pyroclasts within the column would quench at these reduced pressures we argue that healy eruptions deeper than 1 000 m cannot be pyroclastic volumes for the lower and upper bounds of edifice size are 2 36 and 3 58 km3 respectively but do not account for intra caldera pumice fill these volumes are considered to be predominantly primary eruption output as shown by a dearth of accessory lithics in all pumice yielding at an average 81 vesicularity eruptive pumice volumes of between 10 and 15 km3 some pyroclasts may have risen to the sea surface and be a correlative of the sea rafted loisels pumice the latter occurs in some new zealand holocene beach sequences and has a estimated age of 590 80 calendar years

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

trajectories and distribution of material ejected from the chicxulub impact crater implications for postimpact wildfires 1 the trajectories of low and high energy ejecta from the chicxulub impact crater have been computed using a numerical code and compared with analyses of debris deposited in k t boundary sections these calculations indicate that low energy ejecta produces centimeter to meter thick deposits within 4000 km of the point of impact although its azimuthal distribution depends on the incident angle of the projectile with the surface of the earth the high energy ejecta or vapor plume rises through the atmosphere and isotropically expands at the top of the atmosphere the velocity of this ejecta increases as it rises approximately 12 of the high energy ejecta is lost because it reaches escape velocities while 25 of the material reaccretes within 2 hours 55 reaccretes within 8 hours and 85 reaccretes within 72 hours this ejecta is distributed globally but it is concentrated around the chicxulub impact site and at the antipode corresponding to india and the indian ocean 65 million years ago it is also slightly smeared in a longitudinal direction because of earth s rotation because this debris does not reaccrete all at once the collisional shock heating of the atmosphere will be drawn out over a period of a few days and will occur in pulses this could be an important factor when calculating postimpact chemical reactions in the stratosphere the calculations also indicate the ejecta would have ignited wildfires on several continents around the world although the distribution of those fires depends partly on the trajectory of the projectile

quantifying the release of climate active gases by large meteorite impacts with a case study of chicxulub potentially hazardous asteroids and comets have hit earth throughout its history with catastrophic consequences in the case of the chicxulub impact here we reexamine one of the mechanisms that allow an impact to have a global effect the release of climate active gases from sedimentary rocks we use the sova hydrocode and model ejected materials for a sufficient time after impact to quantify the volume of gases that reach high enough altitudes 25 km to have global consequences we vary impact angle sediment thickness and porosity water depth and shock pressure for devolatilization and present the results in a dimensionless form so that the released gases can be estimated for any impact into a sedimentary target using new constraints on the chicxulub impact angle and target composition we estimate that 325 130 gt of sulfur and 425 160 gt co2 were ejected and produced severe changes to the global climate

volcanism impact and mass extinctions incredible or credible coincidences massive continental volcanism and or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years the end permian end cretaceous and end triassic extinctions however reevaluation of the frequency of bolide impacts and plume related flood basalt provinces indicates that both types of event occur much more frequently than mass extinctions and so in isolation may not be responsible for the largest extinctions furthermore the kill mechanisms associated with either flood basalts or impacts do not appear to be sufficiently powerful to cause worldwide collapse of ecosystems leading to the largest mass extinctions contemporaneous flood basalts and bolide impact may be prerequisites for the largest mass extinctions we present a statistical analysis of the probability of coincidence between volcanism and impact and show that three random coincidences of these events in the last 300 m y are likely no causal relationship between impact and volcanism is necessary the lesser mass extinctions on the other hand may not require juxtaposition of two such catastrophic events such coincidences occurring on more than three occasions during the last 300 m y become increasingly unlikely d 2004 elsevier b v all rights reserved

deccan volcanism induced high stress environment during the cretaceous paleogene transition at zumaia spain evidence from magnetic mineralogical and biostratigraphic records abstract we conducted detailed rock magnetic mineralogical and geochemical mercury analyses spanning the cretaceous paleogene boundary kpb at zumaia spain to unravel the signature of deccan induced climate and environmental changes in the marine sedimentary record our biostratigraphic results show that zumaia is not complete and lacks the typical boundary clay zone p0 and the base of zone p1a 1 in the basal danian presence of an unusual 1m thick interval spanning the kpb is characterized by very low detrital magnetite and magnetosome biogenic magnetite contents and by the occurrence of akaganeite a very rare mineral on earth in oxidizing acidic and hyper chlorinated environments compatible with volcanic settings these benchmarks correlate with higher abundance of the opportunist guembelitria cretacea species detrital magnetite depletion is not linked to significant lithological changes suggesting that iron oxide dissolution by acidification is the most probable explanation the concomitant decrease in magnetosomes produced by magnetotactic bacteria at the anoxic oxic boundary is interpreted as the result of changes in seawater chemistry induced by surficial ocean acidification mercury peaks up to 20 50 ppb are common during the last 100 kyr of the maastrichtian zone cf1 but only one significant anomaly is present in the early danian which is likely due to the missing interval absence of correlation between mercury content r2 0 009 and total organic carbon r2 0 006 suggest that the former originated from the deccan traps eruptions no clear relation between the stratigraphic position of the mercury peaks and the magnetite depleted interval is observed although the frequency of the mercury peaks tends to increase close to the kpg boundary in contrast to bidart france and gubbio italy where magnetite depletion and akaganeite feature within a 50cm thick interval located 5 cm below the kpg boundary the same benchmarks are observed in a 1m thick interval encompassing the kpg boundary at zumaia results reinforce the synchronism of the major eruptions of the deccan traps magmatic province with the cretaceous paleogene kpg mass extinction and provide new clues to better correlate the deccan imprint of the global sedimentary record

the stratigraphy of mass extinctions and recoveries interpretations of the tempo of mass extinctions and recoveries often rely on the distribution of fossils in a stratigraphic column these interpretations are generally compromised when they are no

submarine volcanic morphology of the western galapagos based on em300 bathymetry and mr1 side scan sonar 1 a compilation of high resolution em300 multibeam bathymetric and existing mr1 side scan sonar data was used to investigate the volcanic morphology of the flanks of the western galapagos islands the data portray an assortment of constructional volcanic features on the shallow to deep submarine flanks of fernandina isabela and santiago islands including rift zones and groups of cones that are considered to be the primary elements in constructing the archipelagic apron ten submarine rift zones were mapped ranging in length from 5 to 20 km comparable in length to western canary island rift zones but significantly shorter than hawaiian submarine rift zones a detailed analysis of the northwestern fernandina submarine rift including calculated magnetization from a surface towed magnetic study suggests that the most recent volcanism has focused at the shallow end of the rift small submarine volcanic cones with various morphologies e g pointed cratered and occasionally breached are common in the submarine western galapagos both on rift zones and on the island flanks where no rifts are present at depths greater than 3000 m large lava flow fields in regions of low bathymetric relief have been previously identified as a common seafloor feature in the western galapagos by geist et al 2006 however their source s remained enigmatic the new em300 data show that a number of the deep lava flows originate from small cones along the mid lower portion of the nw submarine rift of fernandina suggesting that the deep flows owe their origin at least in part to submarine rift zone volcanism

u pb constraints on pulsed eruption of the deccan traps across the end cretaceous mass extinction temporal correlation between some continental flood basalt eruptions and mass extinctions has been proposed to indicate causality with eruptive volatile release driving environmental degradation and extinction we tested this model for the deccan traps flood basalt province which along with the chicxulub bolide impact is implicated in the cretaceous paleogene k pg extinction approximately 66 million years ago we estimated deccan eruption rates with uranium lead u pb zircon geochronology and resolved four high volume eruptive periods according to this model maximum eruption rates occurred before and after the k pg extinction with one such pulse initiating tens of thousands of years prior to both the bolide impact and extinction these findings support extinction models that incorporate both catastrophic events as drivers of environmental deterioration associated with the k pg extinction and its aftermath

energy volatile production and climatic effects of the chicxulub cretaceous tertiary impact a comprehensive analysis of volatiles in the chicxulub impact strongly supports the hypothesis that impact generated sulfate aerosols caused over a decade of global cooling acid rain and disruption of ocean circulation which contributed to the mass extinction at the cretaceous tertiary k t boundary the crater size meteoritic content of the k t boundary clay and impact models indicate that the chicxulub crater was formed by a short period comet or an asteroid impact that released 0 7 3 4 x 10 31 ergs of energy impact models and experiments combined with estimates of volatiles in the projectile and target rocks predict that over 200 gigatons gt each of so2 and water vapor and over 500 gt of co2 were globally distributed in the stratosphere by the impact additional volatiles may have been produced on a global or regional scale that formed sulfate aerosols rapidly in cooler parts of the vapor plume causing an early intense pulse of sulfuric acid rain estimates of the conversion rate of stratospheric so2 and water vapor to sulfate aerosol based on volcanic production of sulfate aerosols coupled with calculations of diffusion coagulation and sedimentation demonstrate that the 200 gt stratospheric so2 and water vapor reservoir would produce sulfate aerosols for 12 years these sulfate aerosols caused a second pulse of acid rain that was global radiative transfer modeling of the aerosol clouds demonstrates 1 that if the initial rapid pulse of sulfate aerosols was global photosynthesis may have been shut down for 6 months and 2 that for the second prolonged aerosol cloud solar transmission dropped 80 by the end of first year and remained 50 below normal for 9 years as a result global average surface temperatures probably dropped between 5 degrees and 31 degrees k suggesting that global near freezing conditions may have been reached impact generated co2 caused less than 1 degree k greenhouse warming and therefore was insignificant compare to the sulfate cooling the magnitude of sulfate cooling depends largely upon the rate of ocean mixing as surface waters cool sink and are replaced by upwelling of deep ocean water this upwelling apparently drastically altered ocean stratification and circulation which may explain the global collapse of the delta 13c gradient between surface and deep ocean waters at the k t boundary

response cretaceous extinctions the letters by archibald et al keller et al and courtillot and fluteau question our conclusion that the cretaceous paleogene mass extinction was caused by the asteroid impact at chicxulub all three letters stress that deccan flood basalt volcanism played a major role in the extinction keller