early jurassic late pliensbachian co2 concentrations based on stomatal analysis of fossil conifer leaves from eastern australia the stomatal index a measure of stomatal density of an extinct australian early jurassic araucariacean conifer species allocladus helgei jansson is used to reconstruct the atmospheric carbon dioxide concentration pco 2 in the early jurassic the fossil leaves are preserved in a single bed palynologically dated to late pliensbachian similar to 185 183 mya atmospheric pco 2 is estimated from the ratios between the stomatal index of a helgei and the stomatal indices of three modern analogs nearest living equivalent plants co2 concentration in the range of similar to 750 975 ppm was calibrated from the fossil material with a best estimated mean of similar to 900 ppm the new average pco 2 determined for the late pliensbachian is thus similar to although similar to 10 lower than previously inferred minimum concentrations of similar to 1000 based on data from the northern hemisphere but may help constrain pco 2 during this period our results are the first pco 2 estimates produced using jurassic leaves from the southern hemisphere and show that i paleo atmospheric pco 2 estimates are consistent at a global scale though more investigations of southern hemisphere material are required and ii the stomatal proxy method can now be used without the context of relative change in pco 2 when applying the correct methodology c 2014 the authors published by elsevier b v on behalf of international association for gondwana research less

oak leaves as biosensors of late neogene and early pleistocene paleoatmospheric co2 concentrations abstract complementary to the interpretation of 13 c values of biogenic carbonate and sedimentary organic carbon in marine sediments paleoatmospheric co 2 levels can be estimated by considering the inverse relationship between atmospheric co 2 concentration and stomatal parameters frequency size on leaves of land plants in woody plants the significance of this species specific physiological response to changing co 2 regimes is now repeatedly confirmed both experimentally and from historical sequences of leaves collected since the onset of industrialization a corollary of this relationship is that analysis of stomatal parameters on fossil leaves has the potential of determining changes in paleoatmospheric co 2 levels at different time scales well preserved cuticle remains of oak leaves from late miocene pliocene and early pleistocene sediments of the lower rhine embayment germany the netherlands give promise of extending the record of stomatal frequency response to the last 10 ma during intervals with warm temperate to subtropical climatic conditions oak leaves are characterized by a high stomatal resistance or low conductance to co 2 diffusion and low stomatal frequencies during cooler intervals we observe an opposite picture comparison with historical relations between co 2 concentration and stomatal properties suggests that paleoatmospheric co 2 concentrations were not significantly higher than during the last 200 years and fluctuated several times between 280 and 370 ppmv in covariation with contrasting regional climatic conditions on a global scale intervals with reduced co 2 levels match glacial pulses characterized by the occurrence of ice rafted detritus in high latitude oceanic sediments

fungal proliferation at the cretaceous tertiary boundary we have found that a fungal spike occurs between the diverse late cretaceous palynoflora and the low diversity fern dominated early paleocene assemblages in a new zealand section the fungal layer is coincident with the ir anomaly marking the extinction event

new constraints on atmospheric co2 concentration for the phanerozoic earth s atmospheric co2 concentration ca for the phanerozoic eon is estimated from proxies and geochemical carbon cycle models most estimates come with large sometimes unbounded uncertainty here we calculate tightly constrained estimates of ca using a universal equation for leaf gas exchange with key variables obtained directly from the carbon isotope composition and stomatal anatomy of fossil leaves our new estimates validated against ice cores and direct measurements of ca are less than 1000 ppm for most of the phanerozoic from the devonian to the present coincident with the appearance and global proliferation of forests uncertainties obtained from monte carlo simulations are typically less than for ca estimates from other approaches these results provide critical new empirical support for the emerging view that large 2000 3000 ppm long term swings in ca do not characterize the post devonian and that earth s long term climate sensitivity to ca is greater than originally thought key points a novel co2 proxy calculates past atmospheric co2 with improved certainty co2 is unlikely to have exceeded 1000 ppm for extended periods post devonian earth s long term climate sensitivity to co2 is greater than originally thought

carbon sequestration activated by a volcanic co 2 pulse during ocean anoxic event 2 ninety four million years ago during ocean anoxic event 2 there was a marked increase in the burial of organic carbon in marine sediments measurements of stomata in fossil leaves show that the two main pulses of carbon burial were associated with a decline in atmospheric co2 levels of up to 26 the cretaceous ocean anoxic event 2 about 94 million years ago is thought to be linked to extensive volcanism which triggered a biogeochemical chain of events that eventually led to widespread marine anoxia and a remarkable increase in carbon burial in marine sediments1 2 3 it has been suggested that the event was accompanied by a substantial decrease in atmospheric co2 concentrations4 but the quantification of the drawdown remains controversial5 6 here we reconstruct atmospheric co2 concentrations throughout the ocean anoxic event from counts of the stomata in fossil leaves and use terrestrial carbon isotopes to link the reconstruction to marine records of the event7 8 we find that before the onset of ocean anoxia atmospheric co2 concentrations increased by 20 over background levels of 370 100 70 ppm this was part of a long term rise in atmospheric co2 levels presumably caused by volcanism which reached a peak of 500 400 180 ppm however two pulses of extensive carbon burial during the ocean anoxic event as indicated by positive carbon isotope excursions are associated with decreased atmospheric co2 concentrations we conclude that the sequestration of marine organic carbon led to a decrease in atmospheric co2 concentration of up to 26 during ocean anoxic event 2

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

global trends of pco2 across the cretaceous paleogene boundary supported by the first southern hemisphere stomatal proxy based pco2 reconstruction reliable reconstructions of atmospheric carbon dioxide concentrations pco2 are required at higher resolution than currently available to help resolve the relationship between mass extinctions and changes in palaeo pco2 levels such reconstructions are needed 1 at a high temporal resolution for constraining the pre and post extinction atmospheres and 2 at a sufficient spatial resolution to constrain potential inter hemispheric differences here we estimate pco2 based on fossil lauraceae leaf cuticle specimens derived from three localities with strata spanning the latest cretaceous to the mid paleocene including a new cretaceous paleogene boundary k pg locality in new zealand we use two independent methods of stomatal density based pco2 reconstructions a transfer function calibrated using herbarium material and the stomatal ratio method producing three calibration sets our results based on the mean values of each of the three calibration methods indicate pco2 ranging between ca 460 and 650 ppm during the latest cretaceous falling precipitously to average values between ca 360 and 430 ppm across the k pg boundary and further to ca 305 320 ppm in the mid paleocene a spike of extremely high pco2 at the k pg could not be confirmed but our results are nonetheless consistent with previously published pco2 records from the northern hemisphere and show that stomatal density worldwide was responding to significant changes in pco2 across the k pg

production of sulphate rich vapour during the chicxulub impact and implications for ocean acidification following the chicxulub impact many foraminifera in near surface waters perished but bottom dwelling species survived impact experiments suggest that sulphate in chicxulubs target rocks was released as predominantly sulphur trioxide which would have been converted to sulphuric acid in the atmosphere and swept down swiftly by larger particles acidifying the ocean surface

geochemistry in the lung reaction path modeling and experimental examination of rock forming minerals under physiologic conditions a novel and promising application of a geochemical tool adapted to medical science is the thermodynamic and kinetic modeling of the behavior of minerals in fluids similar to lung fluids or simulated lung fluids slf reaction path modeling for chrysotile anorthite k feldspar talc muscovite kaolinite albite and quartz under physiologic conditions in slf gives dissolution times for these minerals as chrysotile anorthite k feldspar talc muscovite kaolinite albite quartz for the reaction of these minerals with slf hydroxylapatite a mineral initially supersaturated in slf and several other secondary minerals were predicted to form e g mesolite is predicted to precipitate during dissolution reactions of other al 3 containing minerals batch experiments using slf and a brucite chrysotile mineral mixture confirm that hydroxylapatite forms during reactions in slf potentially a function of having a seed crystal in the brucite chrysotile or hydromagnesite predicted to form from brucite dissolution present moreover sem analysis of lung tissue also confirms the formation of calcium phosphates e g hydroxylapatite reaction path modeling of minerals under physiologic conditions provides insight into mineral behavior in the body predicted mineralization pathways associated with pleural plaques and the predicted formation of al3 bearing minerals during reaction path modeling deserve attention when considering pathologies in the body

chemostratigraphic evidence of deccan volcanism from the marine osmium isotope record continental flood basalt cfb volcanism is hypothesized to have played a causative role in global climate change and mass extinctions uncertainties associated with radiometric dating preclude a clear chronological assessment of the environmental consequences of cfb volcanism our results document a 25 decline in the marine 187 os 188 os record that predates the cretaceous tertiary boundary ktb and coincides with late maastrichtian warming we argue that this decline provides a chemostratigraphic marker of deccan volcanism and thus constitutes compelling evidence that the main environmental consequence of deccan volcanism was a transient global warming event of 3 to 5 c that is fully resolved from the ktb mass extinction

reconstruction of atmospheric co2 during the early middle eocene by application of a gas exchange model to fossil plants from the messel formation germany abstract in this study atmospheric co 2 during the early middle eocene 47 ma is reconstructed using fossil plants from the messel formation close to darmstadt germany co 2 concentration is calculated using a mechanistic model of gas exchange which optimizes co 2 uptake by photosynthesis against water vapor loss by transpiration a strategy that is commonly realized in land plants input data for the model are stomatal data density and pore length paleoclimate data obtained by two different approaches and biochemical parameters of photosynthesis leaves from three taxa belonging to two different families were studied laurophyllum lanigeroides daphnogene crebrigranosa both lauraceae and rhodomyrtophyllum sinuatum myrtaceae the results suggest that co 2 was between 853 and 1033 ppm during the development of the messel formation stomatal data therefore indicate a co 2 concentration that was substantially higher than today the reconstructed range of co 2 concentration is close to data provided by geochemical modeling results and conforms to various data that indicate a warm and ice free climate during this time interval

greenhouse crises of the past 300 million years proxies of past co 2 and climate over the past 300 m y now reveal multiple global climate change events in unprecedented detail evidence for past co 2 spikes comes from expanded and refined data on stomatal index of fossil ginkgo and related leaves new evidence for synchronous climatic change comes from paleosols in montana utah and neighboring states each co 2 spike was coeval with unusually clayey red and decalcified paleosols which can be traced throughout the colorado plateau spikes in atmospheric co 2 also were coeval with increases in paleosol alkali depletion as an indication of high temperature and spikes in paleosol base depletion and depth to calcic horizons as indications of high precipitation in the colorado plateau times of warmer climate were also more humid perhaps due to greater moisture potential of warmer air seasonality of climate did not increase during warm wet spikes the mesozoic greenhouse was not persistently hot with cool spells but warm with hot flashes these data furnish power laws predicting the sensitivity and magnitude of change in mean annual temperature mat and mean annual precipitation map due to rising co 2 in a mid latitude mid continental region the magnitude of the coming anthropogenic greenhouse pales in comparison with past greenhouse spikes at times of global mass extinctions

multiproxy analysis of a new terrestrial and a marine cretaceous paleogene k pg boundary site from new zealand an integrated study of palynology mossbauer spectroscopy mineralogy and osmium isotopes has led to the detection of the first k pg boundary clay layer in a southern hemisphere terrestrial setting the k pg boundary layer was independently identified at centimetre resolution by all the above mentioned methods at the marine k pg boundary site of mid waipara and the terrestrial site of compressor creek greymouth coal field new zealand mossbauer spectroscopy shows an anomaly of fe containing particles in both k pg boundary sections jarosite at mid waipara and goethite at compressor creek this anomaly coincides with a turnover in vegetation indicated by an interval dominated by fern spores and extinction of key pollen species in both sections in addition to the terrestrial floristic changes the mid waipara section reveals a turnover in the dinoflagellate assemblages and the appearance of global earliest danian index species geochemical data reveal relatively small iridium enrichments in the boundary layers of 321 pg g at mid waipara and 176 pg g at compressor creek unradiogenic os 187 os 188 values of the boundary clay reveal the presence of a significant extraterrestrial component we interpret the accumulation of fe nano phases at the boundary as originating from both the impactor and the crystalline basement target rock the goethite and jarosite are interpreted as secondary phases formed by weathering and diagenesis the primary phases were probably controlled by the initial composition of the vapor plume and condensation kinetics rather than condensation thermodynamics this investigation indicates that identification of fe in nano phases by mossbauer spectroscopy is an accurate and cost effective method for identifying impact event horizons and it efficiently complements widely used biostratigraphic and geochemical methods c 2010 elsevier ltd all rights reserved less

the distinct foliar physiognomy of the late cretaceous forests of new zealand probably deciduous abstract three features of leaf physiognomy craspedodromous venation compound teeth and a lobed leaf outline figure prominently in the late cretaceous vegetation of southern new zealand these make it distinctly different from typical extant predominantly evergreen forests and some deciduous vegetation the physiognomy of the late cretaceous vegetation at the assemblage level shows more similarity with predominantly deciduous forests of the northern hemisphere in terms of the proportions of these characters in the flora at the taxon level combinations of characters found in fossils are very similar to and in some cases restricted to widespread extant northern hemisphere deciduous taxa but also to rarer components of evergreen forests it may not be possible to categorically determine whether any one fossil was deciduous the distinctly different assemblage level foliar physiognomy implies a distinctly different lifestyle for the new zealand forests that bordered gondwana in the late cretaceous it is highly likely that this physiognomy reflects an important deciduous component this is unexpected as for at least part of this time new zealand was apparently below north of the polar circle with a temperate and everwet climate

erosion of deccan traps determined by river geochemistry impact on the global climate and the 87sr 86sr ratio of seawater abstract the impact of the deccan traps on chemical weathering and atmospheric co2 consumption on earth is evaluated based on the study of major elements strontium and 87sr 86sr isotopic ratios of the main rivers flowing through the traps using a numerical model which describes the coupled evolution of the chemical cycles of carbon alkalinity and strontium and allows one to compute the variations in atmospheric pco2 mean global temperature and the 87sr 86sr isotopic ratio of seawater in response to deccan trap emplacement the results suggest that the rate of chemical weathering of deccan traps 21 63 t km2 yr and associated atmospheric co2 consumption 0 58 2 54 106 mol c km2 yr are relatively high compared to those linked to other basaltic regions our results on the deccan and available data from other basaltic regions show that runoff and temperature are the two main parameters which control the rate of co2 consumption during weathering of basalts according to the relationship f r f c 0 exp ea r 1 t 1 298 where f is the specific co2 consumption rate mol km2 yr rf is runoff mm yr c0 is a constant 1764 mol l ea represents an apparent activation energy for basalt weathering with a value of 42 3 kj mol determined in the present study r is the gas constant and t is the absolute temperature k modelling results show that emplacement and weathering of deccan traps basalts played an important role in the geochemical cycles of carbon and strontium in particular the traps led to a change in weathering rate of both carbonates and silicates in carbonate deposition on seafloor in sr isotopic composition of the riverine flux and hence a change in marine sr isotopic composition as a result deccan traps emplacement was responsible for a strong increase of atmospheric pco2 by 1050 ppmv followed by a new steady state pco2 lower than that in pre deccan times by 57 ppmv implying that pre industrial atmospheric pco2 would have been 20 higher in the absence of deccan basalts pco2 evolution was accompanied by a rapid warming of 4 c followed after 1 myr by a global cooling of 0 55 c during the warming phase continental silicate weathering is increased globally since weathering of continental silicate rocks provides radiogenic sr to the ocean the model predicts a peak in the 87sr 86sr ratio of seawater following the deccan traps emplacement the amplitude and duration of this spike in the sr isotopic signal are comparable to those observed at the cretaceous tertiary boundary the results of this study demonstrate the important control exerted by the emplacement and weathering of large basaltic provinces on the geochemical and climatic changes on earth

late glacial and early holocene variations in atmospheric co2 concentration indicated by high resolution stomatal index data data from ice cores suggest that late glacial and early holocene atmospheric co2 variations were rather conservative the most important change being a gradual younger dryas increase by contrast palaeo co2 records based on the inverse relationship between co2 partial pressure and stomatal frequency of terrestrial plant leaves reflect a more dynamic co2 evolution including an abrupt decrease at the allerod younger dryas transition here we present a late glacial and early holocene co2 record based on stomatal index data from leaves preserved in the sediments of a small lake in southwestern sweden three independent records constructed from stomatal index data of salix polaris salix herbacea and betula nana leaves were combined to form a high resolution co2 reconstruction for the period 12 800 10 800 cal yr bp atmospheric co2 concentrations were found to have decreased rapidly from c 260 ppmv to 210 215 ppmv within 200 years during the allerod gi 1 younger dryas gs 1 transition after 100 200 years co2 concentration started to gradually increase to 270 290 ppmv at the end of the younger dryas stadial gs 1 co2 concentrations were relatively stable during the early holocene except for a short lived period of lower 240 250 ppmv values c 11350 11200 cal yr bp this late glacial and early holocene co2 evolution partly resembles previous stomatal based co2 reconstructions and the overall trend is almost identical to that seen in ice core records the amplitude of change is however markedly higher in the swedish stomatal based record compared to the ice cores this difference may partly be accounted for by the inherent smoothing of ice core co2 records caused by diffusion but a major part of the difference in amplitude between ice core and stomatal based records still remains to be explained based on our reconstruction atmospheric co2 may have played an important role in climate dynamics during the last deglaciation c 2003 elsevier b v all rights reserved less

a vertical exposure of the 1999 surface rupture of the chelungpu fault at wufeng western taiwan structural and paleoseismic implications for an active thrust fault we mapped and analyzed two vertical exposures exposed on the walls of a 3 to 5 m deep 70 m long excavation and a smaller 3 m deep 10 m long excavation across the 1999 rupture of the chelungpu fault the primary exposure revealed a broad anticlinal fold with a 2 5 m high west facing principal thrust scarp contained in fluvial cobbly gravel beds and overlying fine grained overbank deposits sequential restoration of the principal rupture requires initial failure on the basal east dipping thrust plane followed by wedge thrusting and pop up of an overlying symmetrical anticline between two opposing secondary thrust faults net vertical offset is about 2 2 m across the principal fault zone from line length changes we estimate about 3 3 m of horizontal shortening normal to fault strike the ratio of these values yields a total slip of 4 0 m and an estimate of about 34 for the dip of the fault plane below the excavation this value is nearly the same as the 35 average dip of the fault plane from the surface to the hypocenter restoration of the exposed gravelly strata and adjacent overbank sediments deposited prior to the 1999 event around the principal rupture suggests the possible existence of a prior event a buried 30 m wide anticlinal warp beneath the uplifted crest of the 1999 event is associated with three buried reverse faults that we interpret as evidence for an earlier episode of folding and faulting in the site the prior event is also recorded in the smaller excavation which is located 40 m south and is oriented parallel to the larger excavation radiocarbon dating of samples within the exposed section did not place tight constraints on the date of the previous event available data are interpreted as indicating that the previous event occurred before the deposition of the less than 200 14 c yr b p overbank sands and after the deposition of the much older fluvial gravels we interpret the previous event as the penultimate event relative to the 1999 chi chi earthquake we estimated the long term slip rate of the chelungpu fault to be 10 15 mm yr during the last 1 ma based on previously published retrodeformable cross sections this rate is however significantly higher than geodetic rates of shortening across the chelungpu thrust where two pairs of permanent global positioning system stations suggest 7 10 mm yr of shortening across the fault given the 4 m of average slip the long term slip rate yields an interseismic interval of between 267 and 400 yr for the chelungpu fault

atmospheric co2 from the late oligocene to early miocene based on photosynthesis data and fossil leaf characteristics abstract the late oligocene represents a comparatively cool phase followed by a warming event the so called late oligocene warming that predates the mi 1 glacial event at the oligocene miocene transition there is evidence that these climate events were linked to level changes in atmospheric co2 in this study atmospheric co2 from the late oligocene to the early miocene is reconstructed by a terrestrial proxy stomatal parameters of angiosperm leaves fossil leaves of six plant species were considered laurophyllum pseudoprinceps l acutimontanum both lauraceae platanus neptuni platanaceae eotrigonobalanus furcinervis quercus rhenana and q praerhenana all fagaceae the plant material originates from various sites in germany late oligocene to the early miocene and austria early miocene a mechanistic theoretical approach based on stomatal data photosynthesis and gas exchange control was used since this approach also requires climate data as input parameters for calculating assimilation and transpiration rates palaeoclimate of these sites were also derived in detail considerable differences were found between results obtained by the two lauraceae taxa and all other taxa with the lauraceae indicating a high co2 level if lauraceae are included a co2 level of about 700 ppm for the late and latest oligocene is obtained and about 500 ppm for the early miocene all non lauraceae taxa belonging to different families indicate a consistently lower level of co2 of about 400 ppm for all considered sites and time slices a value of 400 ppm is also consistent with other proxy data that are available for that time period a steady level of 400 ppm would indicate a decoupling of co2 and cooling warming events from the late oligocene to the early miocene more data provided by different proxies are desirable to unravel the interactions between atmosphere and climate for the late oligocene and the early miocene

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

trace element concentrations in the mexico belize ejecta layer a link between the chicxulub impact and the global cretaceous paleogene boundary four exposures of chicxulub impact ejecta along the mexico belize border have been sampled and analyzed for major and trace element abundances the ejecta deposits consist of a lower spheroid bed containing clay and dolomite spheroids and an upper diamictite bed with boulders and clasts of limestone and dolomite the matrix of both beds is composed of clay and micritic dolomite the rare earth element ree compositions in the matrix of both units show strong similarities in concentrations and pattern furthermore the zr tio2 scatter plot shows a linear correlation indicating one source these results indicate that the basal spheroid bed has the same source and was generated during the same event as the overlying diamictite bed which lends support to a single impact scenario for the albion formation ejecta deposits the elevated concentrations of non meteoritic elements such as sb as u and zn in the matrix of the lower spheroid bed are regarded to have been derived from the sedimentary target rocks at the chicxulub impact site the positive eu and ce anomalies in clay concretion and in the matrix of the lower part of the spheroid bed in albion island quarry is probably related to processes involved in the impact such as high temperature and oxidizing conditions analogous trace element anomalies have been reported from the distal cretaceous paleogene k t boundary clay layer at different sites thus the trace element signals reported herein are regarded to support a genetic link between the chicxulub impact the ejecta deposits along the mexico belize border and the global k t boundary layer

vertebrate extinctions and survival across the cretaceous tertiary boundary abstract a critical analysis of the fossil vertebrate record across the cretaceous tertiary boundary shows that the available evidence is far less accurate than that concerning invertebrates and microfossils far reaching conclusions have been drawn from generalisations about vertebrate extinctions in the continental realm based on the local record from western north america but little is known about patterns of terminal cretaceous vertebrate extinctions in other parts of the world and even the western north american record is ambiguous despite this unsatisfactory record it clearly appears that terminal cretaceous vertebrate extinctions were highly selective with some groups e g dinosaurs becoming completely extinct whereas others seem to be virtually unaffected this argues against devastating catastrophes of the kind postulated by some recent impact scenarios however the survival of groups known to be sensitive to climatic deterioration such as crocodilians and other non dinosaurian reptiles indicates that alternative hypotheses involving gradual but fairly important climatic changes on a world wide scale are not convincing either the pattern of extinction and survival among vertebrates across the cretaceous tertiary boundary may be explained as a consequence of the disruption of some food chains following a crisis in the plant kingdom which itself may have been the result of the atmospheric consequences of unusual extraterrestrial or internal events

quantification of amphibole content in expanded vermiculite products from libby montana u s a using powder x ray diffraction five expanded vermiculite samples known to have originated from the former vermiculite mine near libby montana were analyzed using powder xrd to quantify their amphibole content an expanded vermiculite with no detectable amphibole based on our xrd methods discussed herein was spiked with 100 500 1000 2500 5000 7500 and 10 000 ppm libby amphiboles to determine the detection limit of xrd and to develop a calibration method the 110 amphibole peaks were not detectable in the 100 and 500 ppm samples thus defi ning the detection limit the 110 peak areas for the remaining samples were measured and used to form a calibration curve relating peak area to ppm amphibole of the fi ve libby samples each had detectable levels of amphibole and their amphibole content ranged from 1171 to 9218 ppm the xrd method provides a bulk measurement of the total amphibole content to determine the amount of asbestiform amphiboles morphological considerations obtained by microscopy techniques are required from the results of a previous polarized light microscopy study the fi ve expanded vermiculites in this study would contain from 390 to 3073 ppm asbestiform amphiboles and not be subject to regulation on the basis of the 1 rule used by regulatory agencies in the u s a

quantifying carbon fixation in trace minerals from processed kimberlite a comparative study of quantitative methods using x ray powder diffraction data with applications to the diavik diamond mine northwest territories canada abstract the capacity of mine waste to trap co2 is in some cases much larger than the greenhouse gas production of a mining operation in mine tailings the presence of secondary carbonate minerals that trap co2 can therefore represent substantial fixation of this greenhouse gas the abilities of three methods of quantitative phase analysis to measure trace nesquehonite mgco3 3h2o in samples of processed kimberlite have been assessed the method of reference intensity ratios rir the internal standard method and the rietveld method with x ray powder diffraction data tests on synthetic mixtures made to resemble processed kimberlite indicate that both the rir and rietveld methods can be used accurately to quantify nesquehonite to a lower limit of approximately 0 5 wt for conditions used in the laboratory below this value estimates can be made to a limit of approximately 0 1 wt using a calibration curve according to the internal standard method the rir method becomes increasingly unreliable with decreasing abundance of nesquehonite primarily as a result of an unpredictable decline in preferred orientation of crystallites for rietveld refinements structureless pattern fitting was used to account for planar disorder in lizardite by considering it as an amorphous phase rietveld refinement of data collected from specimens that were serrated to minimize preferred orientation of crystallites gives rise to systematic overestimates of refined abundances for lizardite and underestimates for other phases the resulting pattern of misestimates may be mistaken for the effect of amorphous and or nanocrystalline material in samples this effect is mitigated by collecting data from non serrated specimens which typically give relative errors on refined abundances for major and minor phases in the range of 5 20 however relative error can increase rapidly for abundances less than 5 wt nonetheless absolute errors are sufficiently small that estimates can be made for the amount of co2 stored in secondary nesquehonite using the rir method or the rietveld method for abundances 0 5 wt and a calibration curve for abundances

mid cretaceous pco2 based on stomata of the extinct conifer pseudofrenelopsis cheirolepidiaceae stomatal characteristics of an extinct cretaceous conifer pseudofrenelopsis parceramosa fontaine watson are used to reconstruct atmospheric carbon dioxide p co 2 over a time previously inferred to exhibit major fluctuations in this greenhouse gas samples are from nonmarine to marine strata of the wealden and lower greensand groups of england and the potomac group of the eastern united states of hauterivian to albian age 136 100 ma atmospheric p co 2 is estimated from the ratios between stomatal indices of fossil cuticles and those from four modern analogs nearest living equivalent plants using this approach and two calibration methods to explore ranges results show relatively low and only slightly varying p co 2 over the hauterivian albian interval a low of 560 960 ppm in the early barremian and a high of 620 1200 ppm in the albian data from the barremian wealden group yield p co 2 values indistinguishable from a soil carbonate based estimate from the same beds the new p co 2 estimates are compatible with sedimentological and oxygen isotope evidence for relatively cool mid cretaceous climates

nano particles as the primary cause for long term sunlight suppression at high southern latitudes following the chicxulub impact evidence from ejecta deposits in belize and mexico life on earth was sharply disrupted 66 ma ago as an asteroid hit the sea floor in what is today yucatan peninsula mexico approximately 600 km 3 of sedimentary rock were vapourized ejected into the atmosphere and subsequently deposited globally as an ejecta apron and fallout layer proximal ejecta deposits occur in belize and southern mexico where the so called albion island spheroid bed is superimposed on the target rock the barton creek formation we analysed the spheroid bed via mossbauer spectroscopy petrology xrd and palynology at several sites similar to 350 500 km distance from the crater centre our results show that the relative concentrations of fe in nano phase goethite alpha feooh are very high in the spheroid bed samples from albion island belize and from ramonal south mexico but are low to absent in the spheroid bed at ramonal north and in the cretaceous target rock moreover our study shows that goethite and haematite are the dominant fe oxide nano phases and the xrd results show that the target rock consists of both calcite and dolomite we suggest that the heterogeneous composition of the spheroid bed between the various sites reflects the different types of target rocks that were dispersed within the rapidly expanding vapour plume and the complex sorting processes involved in the formation of the ejecta blanket the distribution of the vapourized target rock strongly influenced life on earth at the close of the mesozoic however the comparatively thin k pg boundary clay in high latitude gondwanan successions combined with evidence of catastrophic changes to the biota in this region implies that the long term sunlight suppression in the southern hemisphere was mainly governed by the large quantities of hydrous aerosols nucleated around sulphuric acid droplets or nano sized particles such as the nano phase fe oxides c 2014 the authors published by elsevier b v on behalf of international association for gondwana research less

a high resolution marine 187os 188os record for the late maastrichtian distinguishing the chemical fingerprints of deccan volcanism and the kp impact event abstract a composite late maastrichtian 65 5 to 68 5 ma marine osmium os isotope record based on samples from the southern ocean odp site 690 the tropical pacific ocean dsdp site 577 the south atlantic dsdp site 525 and the paleo tethys ocean demonstrates that subaerially exposed pelagic carbonates can record seawater os isotope variations with a fidelity comparable to sediments recovered from the seafloor new results provide robust evidence of a 20 decline in seawater 187os 188os over a period of about 200 kyr early in magnetochron c29r well below the cretaceous paleogene boundary kpb confirming previously reported low resolution data from the south atlantic ocean new results also confirm a second more rapid decline in 187os 188os associated with the kpb that is accompanied by a significant increase in os concentrations complementary platinum pt and iridium ir concentration data indicate that the length scale of diagenetic remobilization of platinum group elements from the kpb is less than 1 m and does not obscure the pre kpb decline in 187os 188os increases in bulk sediment ir concentrations and decreases in bulk carbonate content that coincide with the os isotope shift suggest that carbonate burial flux may have been lower during the initial decline in 187os 188os we speculate that diminished carbonate burial rate may have been the result of ocean acidification caused by deccan volcanism