tectonic setting and timing of the final deccan flood basalt eruptions the role of extensional tectonics in the generation of basaltic melt and eruption of continental flood basalts is controversial and yet it remains crucial to understanding the origin and cause of these large volume eruptions establishing the timing of lithospheric extension continental rifting and the onset of continental flood basalt volcanism is therefore of importance to petrogenetic models detailed mapping along the mumbai coast india reveals three chemically distinct sets of dikes which together with high precision 40 ar 39 ar dating demonstrate the temporal relationship between lithospheric extension and deccan volcanism the east west extension evident along the west coast of india which led to the separation of the seychelles from the indian plate only began during the final phases of the basalt eruptions and cannot have initiated the large volume eruptions of the deccan flood basalt province

the stable isotopic composition of modern soil carbonate and its relationship to climate the oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water the carbon isotopic cycle for co 2 in soils can be described in terms of the proportion of biomass using the c 4 photosynthetic pathway and the co 2 respiration rate of the soil at low soil respiration rates significant atmospheric co 2 mixing can occur in general the carbon isotopic composition of soil carbonate is related to the proportion of c 4 biomass present in soil but soils that freeze to the depth of carbonate formation often have a significant atmospheric component this suggests that freezing of the soil solution should be considered as another important mechanism for soil carbonate formation because of these relationships the isotopic composition of soil carbonate may be a paleoclimatic and paleoecologic indicator in cases in which diagenetic alteration has not occurred

hydrocode simulation of the chicxulub impact event and the production of climatically active gases we constructed a numerical model of the chicxulub impact event using the chart d squared csq code coupled with the analytic equation of state aneos package in the simulations we utilized a target stratigraphy based on borehole data and employed newly developed equations of state for the materials that are believed to play a crucial role in the impact related extinction hypothesis carbonates calcite and evaporites anhydrite simulations explored the effects of different projectile sizes 10 to 30 km in diameter and porosity 0 to 50 the effect of impact speed is addressed by doing simulations of asteroid impacts vi 20 km s and comet impacts vi 50 km s the masses of climatically important species injected into the upper atmosphere by the impact increase with the energy of the impact event ranging from 350 to 3500 gt for co2 from 40 to 560 gt for s and from 200 to 1400 gt for water vapor while our results are in good agreement with those of ivanov et al 1996 our estimated co2 production is 1 to 2 orders of magnitude lower than the results of takata and ahrens 1994 indicating that the impact event enhanced the end cretaceous atmospheric co2 inventory by at most 40 consequently sulfur may have been the most important climatically active gas injected into the stratosphere the amount of s released by the impact is several orders of magnitude higher than any known volcanic eruption and with h2o is high enough to produce a sudden and significant perturbation of earth s climate

multiple impacts across the cretaceous tertiary boundary abstract the stratigraphy and age of altered impact glass microtektites microkrystites ejecta layers from the chicxulub crater are documented in late maastrichtian and early danian sediments in mexico guatemala belize and haiti in northeastern mexico two to four ejecta layers are present in zone cf1 which spans the last 300 ky of the maastrichtian the oldest ejecta layer is dated at 65 27 0 03 ma based on sediment accumulation rates and extrapolated magnetostratigraphy all younger ejecta layers from the maastrichtian and early danian parvularugoglobigerina eugubina zone pla l may represent repeated episodes of reworking of the oldest layer at times of sea level changes and tectonic activity the k t boundary impact event 65 0 ma is not well represented in this area due to widespread erosion an early danian pla l ir anomaly is present in five localities bochil actela coxquihui trinitaria and haiti and is tentatively identified as a third impact event at about 64 9 ma a multiimpact scenario is most consistent with the impact ejecta evidence the first impact is associated with major deccan volcanism and likely contributed to the rapid global warming of 3 4 c in intermediate waters between 65 4 and 65 2 ma decrease in primary productivity and onset of terminal decline in planktic foraminiferal populations the k t boundary impact marks a major drop in primary productivity and the extinction of all tropical and subtropical species the early danian impact may have contributed to the delayed recovery in productivity and evolutionary diversity

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

constraints on the thermal energy released from the chicxulub impactor new evidence from multi method charcoal analysis it has been suggested by various workers that an extraterrestrial impact at the k t boundary delivered sufficient thermal power to ignite globally extensive wildfires numerous models have sought to predict the amount of thermal power released by the impact but none have considered the distribution of wildfire indicators in k t rocks probably the most distinctive product from combustion of biomass is charcoal the abundance of charcoal across the k t boundary at eight non marine sites in north america stretching from colorado in the south to saskatchewan in the north is recorded using three separate methods that allow quantitative analyses of microscopic to macroscopic charcoal particles this study not only provides the first extensive study of charcoals across the k t boundary but also uses the presence or absence of charred material to predict the extent and severity of the thermal pulse released by the k t impact across the area predicted to have suffered the most extreme environmental effects the k t rocks contain on average between four and eight times according to the method used less charcoal than the cretaceous rock record and non charred plant remains are abundant in the k t rocks the below background charcoal abundance and the high proportion of noncharred material in the k t and lowermost tertiary rocks across the western interior of north america suggest that there were no significant wildfires in this area associated with the k t event although soot and polyaromatic hydrocarbons pahs have been reported in the k t rocks we suggest that the soot morphology and pah types are more consistent with a source from the vaporization of hydrocarbons rather than biomass for spontaneous ignition of vegetation temperatures 545 c are necessary whereas smouldering will begin at 325 c the below background levels of charcoal in the k t rocks allow the ground temperatures following the k t impact to be constrained to between no more than 545 c at any point and not above 325 c for any significant period this implies a maximum irradiance of 2 at the ground surface and that no more than 6 kw m 2 of thermal power was delivered to the ground for more than a few hours therefore our results show that the fossil record indicates that the impact at chixculub did not generate sufficient thermal power to ignite extensive wildfires

relationship between mass extinction and iridium across the cretaceous paleogene boundary in new jersey we directly link iridium ir anomalies in new jersey to the mass extinction of marine plankton marking the cretaceous paleogene k pg boundary we confirm previous reports of an ir anomaly 20 cm below the extinction of cretaceous macrofauna the pinna bed with new results from a muddy sand section from tighe park freehold new jersey united states but we also show that ir anomalies correlate with marine mass extinctions at three other clay rich new jersey sections thus we attribute the anomaly at freehold to the downward movement of ir and reaffirm the link between impact and mass extinction

model tests on single piles in soft clay laboratory model tests in soft clay were conducted to investigate the behaviour of single piles subjected to lateral soil movements passive pile and to determine the ultimate soil pressure acting along the pile shaft a specially designed apparatus for the tests was manufactured and calibrated reasonably consistent soil samples were prepared for the tests by a consolidometer the limiting soil pressures acting along the model pile shaft were measured by pressure transducers the ultimate soil pressure was then determined based on the maximum value of the limiting soil pressures acting along the pile shaft the ultimate soil pressure obtained from the single passive pile tests was 10 6su where su is the undrained shear strength of the clay and agreed well with those from the literature key words pile foundation lateral soil movement clay model test

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

phanerozoic atmospheric co2 change evaluating geochemical and paleobiological approaches abstract the theory and use of geochemical modeling of the long term carbon cycle and four paleo pco 2 proxies are reviewed and discussed in order to discern the best applications for each method geochemical models provide pco 2 predictions for the entire phanerozoic but most existing models present 5 10 m y means and so often do not resolve short term excursions error estimates based on sensitivity analyses range from 75 200 ppmv for the tertiary to as much as 3000 ppmv during the early paleozoic the 13 c of pedogenic carbonates provide the best proxy based pco 2 estimates for the pre tertiary with error estimates ranging from 500 1000 ppmv pre devonian estimates should be treated cautiously error estimates for tertiary reconstructions via this proxy are higher than other proxies and models 400 500 ppmv and should not be solely relied upon we also show the importance of measuring the 13 c of coexisting organic matter instead of inferring its value from marine carbonates the 13 c of the organic remains of phytoplankton from sediment cores provide high temporal resolution up to 10 3 10 4 year high precision 25 100 ppmv for the tertiary to 150 200 ppmv for the cretaceous pco 2 estimates that can be near continuous for most of the tertiary its high temporal resolution and availability of continuous sequences is advantageous for studies aiming to discern short term excursions this method however must correct for changes in growth rate and oxygen level at elevated pco 2 750 1250 ppmv this proxy loses its sensitivity and is not useful the stomatal density and stomatal index of land plants also provide high temporal resolution 2 year high precision 10 40 ppmv for the tertiary and possibly cretaceous pco 2 estimates and so also is ideal for discerning short term excursions unfortunately this proxy also loses sensitivity at some level of pco 2 above 350 ppmv which currently is largely undetermined our analysis of the recently developed 11 b technique shows that it currently is not yet well constrained most importantly it requires the assumption that the boron isotopic composition of the ocean remains nearly constant through time in addition it assumes that there are no biological or temperature effects and that diagenetic alteration of the boron isotopic composition does not occur a fifth co 2 proxy based on the redox chemistry of marine cerium has several fundamental flaws and is not discussed in detail here

carbon isotopic evidence for biomass burning at the k t boundary a new interpretation of existing carbon isotopic data combined with results from a biogeochemical model suggests that burning of terrestrial biomass occurred on a global scale at the cretaceous tertiary k t boundary carbon isotopic ratios from planktonic and benthic microfossils across the k t boundary reveal not only a breakdown in the normal surface water to deep water gradient of 13 c 12 c but also a reversal at the boundary this reversal cannot be explained by the cessation off primary production alone we propose that combustion of terrestrial biomass with subsequent transfer of isotopically light carbon to surface waters is the most likely cause of this anomaly a biogeochemical model is used to quantify the extent of burning at the boundary combustion of roughly 25 of the above ground biomass at the end of the cretaceous is necessary to account for the observed isotopic signal

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

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

a complete high resolution paleocene benthic stable isotope record for the central pacific odp site 1209 1 we have compiled the first stratigraphically continuous high resolution benthic foraminiferal stable isotope record for the paleocene from a single site utilizing cores recovered at pacific odp site 1209 the long term trend in the benthic isotope record suggests a close coupling of volcanic co2 input and deep sea warming over the short term the record is characterized by slow excursions with a pronounced periodic beat related to the short 100 kyr and long 405 kyr eccentricity cycle the phase relationship between the benthic isotope record and eccentricity is similar to patterns documented for the oligocene and miocene confirming the role of orbital forcing as the pace maker for paleoclimatic variability on milankovitch time scales in addition the record documents an unusual transient warming of 2 c coeval with a 0 6 carbon isotope excursion and a decrease in carbonate content at 61 75 ma this event which bears some resemblance to eocene hyperthermals marks the onset of a long term decline in 13c the timing indicates it might be related to the initiation of volcanism along greenland margin

the chicxulub impact event and its environmental consequences at the cretaceous tertiary boundary abstract an impact mass extinction hypothesis for the cretaceous tertiary k t boundary transition has been confirmed with multiple lines of evidence beginning with the discovery of impact derived ir in k t boundary sediments and culminating in the discovery of the chicxulub impact crater likewise a link between the chicxulub impact crater and k t boundary sediments has been confirmed with multiple lines of evidence including stratigraphic petrological geochemical and isotopic data the environmental effects of the chicxulub impact event were global in their extent largely because of the interaction of ejected impact debris with the atmosphere the environmental consequences of the chicxulub impact event and their association with the k t boundary mass extinction event indicate that impact cratering processes can affect both the geologic and biologic evolution of our planet

fire across the k t boundary initial results from the sugarite coal new mexico usa abstract it has been hypothesized that major global fires occurred following a bolide impact at the cretaceous tertiary boundary evidence for this has been mainly from soot or black carbon at a number of marine boundary sites as well as the occurrence of inertinites fusinite in coals above the boundary in addition the occurrence of fossil charcoal inertinites in potential tsunami deposits has been used to strengthen this idea however fire is known to have been widespread throughout the cretaceous based on the distribution of fossil charcoal and it is necessary to evaluate the claims for a global fire at the k t boundary within the context of this more extensive record of ancient fires the occurrence of the k t boundary within the sugarite coal sequence in the raton basin new mexico offers the opportunity to assess the incidence of fire in local peat forming vegetation in the latest cretaceous across the cretaceous tertiary boundary interval and in the earliest tertiary the distribution of fire products i e fossil charcoal is assessed using a combination of inertinite group macerals in polished blocks of coal and plant particles released by chemical maceration of coal inertinite group macerals fusinite semifusinite inertodetrinite which represent fossil charcoal and particles of charcoal in maceration residues are abundant throughout the sugarite coal sequence both before during and after the k t boundary event samples from below the boundary yield inertinites that constitute more than 20 of the coal three horizons are inertinite rich 50 fire was obviously an important element of the terrestrial environment during the latest cretaceous high inertinite values and abundant charcoal particles characterize the latest cretaceous part of the coal the carbonaceous shale just below the boundary the boundary interval itself and tertiary coals and carbonaceous shales above the boundary charcoal in mineral rich units of the latest cretaceous immediately below the boundary in the boundary interval and in the tertiary is dominated by small inertodetrinite particles these might have been wind blown from regional fires or they may reflect reworking during erosion which led to sediment input into the mire in either case the charcoal signature in these units is the same irrespective of their position in the sequence our data combined with that from two other sites in terrestrial sequences in north america show that fires were an integral part of mire ecosystems through the latest cretaceous and into the early tertiary therefore evidence for distinctive global wildfires at the cretaceous tertiary boundary would have to be sought from careful consideration of other aspects of charcoal deposition including flux rates for charcoal and soot

chronology of the terrestrial upper cretaceous in the songliao basin northeast asia the cretaceous was a period of great environmental biological and geodynamical change but a paucity of an accurate time frame for continental strata has prevented our understanding of the terrestrial processes and the integration of marine and terrestrial records here we present an integrated chronology for the terrestrial upper cretaceous in east asia based on new high resolution magnetostratigraphic results and previously published sims u pb zircon analyses of the cretaceous continental scientific drilling borehole sequence from the songliao basin in northeast china hereafter termed ccsd sk i which consists of a sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m correlation to the geomagnetic polarity timescale was achieved by combining magnetostratigraphic and sims u pb zircon geochronologic data and lithostratigraphy our correlation suggests that the ccsd sk i sedimentary sequence spans from the upper chron c34n to chron c29r the age of the sedimentary sequence from the upper quantou formation k2q to the mingshui formation k2m in the songliao basin can thus be constrained to an interval from the turonian to the maastrichtian ages in addition our correlation puts the cretaceous paleogene boundary in the upper part of member 2 of the mingshui formation k2m2 the constructed comprehensive chronology allows the precise correlation of the terrestrial upper cretaceous of the songliao basin to marine strata as well as other continental sequences

determining terrestrial paleotemperatures using the oxygen isotopic composition of pedogenic carbonate abstract quantifying terrestrial paleotemperatures has proven to be a challenging endeavor this paper explores the use of the oxygen isotopic composition of pedogenic calcite for terrestrial paleotemperature reconstructions we generate three paleotemperature equations two of them derived by simultaneous solution of equations that describe the fractionation of oxygen isotopes in the exogenic cycle while the third equation is derived using a linear regression through modern 18occ mat oxygen isotopic composition of pedogenic calcite versus mean annual temperature data we use the paleotemperature equations to evaluate climate change across the k t boundary by analyzing the oxygen isotopic composition of pedogenic carbonates from a series of stacked paleosols in west texas the fabrics in the calcite nodules were evaluated in order to identify soil carbonate components that have the best chance of containing isotopic information that represents ancient pedogenic conditions the average temperature for west texas during the time period studied is 18 0 5 c two temperature excursions are recognized prior to the k t boundary in which terrestrial temperatures increase by about 4 c for relatively short periods of time these short greenhouse events documented in west texas correlate with changes in marine temperatures as well as terrestrial temperatures in north dakota during the same time period latitudinal temperature gradients generated using the west texas and north dakota data indicate that the spatial simultaneous solution yields the most reliable temperature reconstructions of the three equations considered in this study

correlation of the deccan and rajahmundry trap lavas are these the longest and largest lava flows on earth abstract we propose that the rajahmundry trap lavas found near the east coast of peninsular india are remnants of the longest lava flows yet recognized on earth 1000 km long these outlying deccan like lavas are shown to belong to the main deccan traps several previous studies have already suggested this correlation but have not demonstrated it categorically the exposed rajahmundry lavas are interpreted to be the distal parts of two very large volume p hoehoe flow fields one each from the ambenali and mahabaleshwar formations of the wai sub group in the deccan basalt group eruptive conditions required to emplace such long flows are met by plausible values for cooling and eruption rates and this is shown by applying a model for the formation of inflated p hoehoe sheet flow lobes the model predicts flow lobe thicknesses similar to those observed in the rajahmundry lavas for the last 400 km of flow the lava flows were confined to the pre existing krishna valley drainage system that existed in the basement beyond the edge of the gradually expanding deccan lava field allowing the flows to extend across the subcontinent to the eastern margin where they were emplaced into a littoral and or shallow marine environment these lavas and other individual flow fields in the wai sub group may exceed eruptive volumes of 5000 km3 which would place them amongst the largest magnitude effusive eruptive units yet known we suggest that the length of flood basalt lava flows on earth is restricted mainly by the size of land masses and topography in the case of the rajahmundry lavas the flows reached estuaries and the sea where their advance was perhaps effectively terminated by cooling and or disruption however it is only during large igneous province basaltic volcanism that such huge volumes of lava are erupted in single events and when the magma supply rate is sufficiently high and maintained to allow the formation of very long lava flows the rajahmundry lava fields were emplaced around 65 ma during the later times of deccan volcanism probably just after the k t environmental crisis however many lava forming eruptions of similar magnitude and style straddled the k t boundary

fish tooth δ18o revising late cretaceous meridional upper ocean water temperature gradients the oxygen isotope composition of fossil fi sh teeth a paleo upper ocean temperature proxy exceptionally resistant to diagenetic alteration provides new insight on the evolution of the low to middlelatitude thermal gradient between the middle cretaceous climatic optimum and the cooler latest cretaceous period the new middle cretaceous low to middle latitude thermal gradient agrees with that previously inferred from planktonic foraminifera 18o recovered from deep sea drilling project and ocean drilling program drilling sites although the isotopic temperatures derived from 18o of fish teeth are uniformly higher by 3 4 c in contrast our new latest cretaceous thermal gradient is markedly steeper than those previously published for this period fish tooth 18o data demonstrate that low to middle latitude thermal gradients of the middle cretaceous climatic optimum and of the cooler latest cretaceous are similar to the modern one despite a cooling of 7 c between the two periods our new results imply that no drastic changes in meridional heat transport are required to explain the late cretaceous climate based on climate models such a cooling without any change in the low to middle latitude thermal gradient supports an atmospheric co2 decrease as the primary driver of the climatic evolution recorded during the late cretaceous

modelling the primary control of paleogeography on cretaceous climate the low thermal gradients and clement winters characterizing climates of the cretaceous period reveal that the climate system has modes of behaviour quite different from the present recent proxy data analyses suggest that some aspects of climate change within the cretaceous appear to be decoupled from co2 evolution at the geological time scale here we investigate the impact of paleogeography on the global climate with the climate model foam using a early mid and late cretaceous continental configuration we find that changes in geography from the early to mid to late cretaceous cause a large decrease of the seasonal cycle first order identified processes are the decreased continentality of the mid to high latitudes from the mid cretaceous and the increase of the latent heat transport into the winter hemisphere which induce a wetter and a cloudier atmosphere capable of diminishing the winter cooling of the continents owing to the modifications of the seasonal cycle in response to the tectonic forcing the equator to pole thermal gradient is reduced from the early to mid to late cretaceous we nevertheless still do not succeed in simulating warm enough polar temperatures and a definitive theory still waits for an integrated approach explicitly accounting for each factor influencing the thermal gradient ocean dynamics stratospheric clouds and vegetation our study also suggests a mechanism that can weaken the correlation between co2 and climate changes during the cretaceous as evolving geography from the early to late cretaceous through the response of the water cycle and the changes in the thermal gradient results in a 3 8 c global warming at a constant atmospheric co2 level this demonstrates that the paleogeography may affect the relation between pco2 and the climate history and consequently has to be accounted for when linking the atmospheric co2 evolution and the climate record at geological time scales

an application of the coda methodology for moment rate spectra using broadband stations in turkey a recently developed coda magnitude methodology was applied to selected broadband stations in turkey for the purpose of testing the coda method in a large laterally complex region as found in other albeit smaller regions coda envelope amplitude measurements are significantly less variable than distance corrected direct wave measurements i e l sub g and surface waves by roughly a factor 3 to 4 despite strong lateral crustal heterogeneity in turkey they found that the region could be adequately modeled assuming a simple 1 d radially symmetric path correction after calibrating the stations isp iskb and malt for local and regional distances single station moment magnitude estimates m sub w derived from the coda spectra were in excellent agreement with those determined from multistation waveform modeling inversions exhibiting a data standard deviation of 0 17 though the calibration was validated using large events the results of the calibration will extend m sub w estimates to significantly smaller events which could not otherwise be waveform modeled the successful application of the method is remarkable considering the significant lateral complexity in turkey and the simple assumptions used in the coda method

oxygen and hydrogen isotope compositions of permian pedogenic phyllosilicates development of modern surface domain arrays and implications for paleotemperature reconstructions abstract mineralogic chemical and oxygen and hydrogen isotope compositions of 15 different phyllosilicate samples from permo pennsylvanian age paleosols of the eastern shelf of the midland basin of texas and the southern anadarko basin are presented mixtures of 2 1 phyllosilicates and kaolinite dominate most samples although some samples consist of relatively pure 2 1 phyllosilicates chemical and mineralogic data are used in conjunction with published thermodynamic data to calculate hydrogen and oxygen isotope fractionation factors for each sample in turn application of measured oxygen and hydrogen isotope compositions of the phyllosilicates to temperature dependent fractionation equations are used to calculate paleotemperatures of crystallization the d values of the phyllosilicates range from 69 to 55 the 18 o values range from 19 5 to 22 7 if these samples preserve a record of equilibrium with paleo meteoric waters the isotopic compositions of the phyllosilicates correspond to paleotemperatures of phyllosilicate crystallization ranging from 22 3 c to 35 3 c in particular the stratigraphic trend of calculated temperatures from midland basin samples suggests that early permian surface temperatures may have been up to 10 c warmer than those of the latest pennsylvanian

geochemical model of δ18o of pedogenic calcite versus latitude and its application to cretaceous palaeoclimate abstract in the absence of a systematic global data base on the 18 o composition of modern soil calcite predicted isotopic values are calculated as a function of latitude between 60 and 20 using 18 o of summer and winter meteoric water ambient soil temperature equal to either measured values in asia or mean annual temperature and 0 10 20 and 30 evaporation of soil water the results show overall higher isotopic values for summer versus winter precipitation but steeper positive slopes for the winter precipitation curves where soil temperature is equated to mean annual temperature the summer precipitation curves are nearly flat at high latitudes and have a negative slope at low latitudes in all cases the 18 o values increase with increasing percent evaporation of soil water oxygen isotopic data for early aptian and late maastrichtian cretaceous palaeosol calcite as a function of palaeolatitude of the western interior of north america plot in the modern winter precipitation field which along with vertic features may suggest a winter wet palaeoclimate steeper positive slopes for the cretaceous curves compared to the modern curves may be attributable to greater latitudinal gradients in mean annual temperature and soil temperature in the cretaceous compared to today and or to a greater degree of evaporation in cretaceous soils at low latitudes compared to the modern earth distinguishing between these possibilities will require a more complete understanding of the variables that affect oxygen isotopes in pedogenic calcite as well as better cretaceous terrestrial palaeoclimate proxies with which to compare the isotopic data

atmospheric pco2 and depositional environment from stable isotope geochemistry of calcrete nodules barremian lower cretaceous wealden beds england abstract nodular soil carbonates calcretes are present in overbank facies of lower cretaceous non marine wealden beds wessex formation of southern england field evidence suggests that these calcretes formed mostly under semi arid mediterranean type climatic conditions typical calcrete fabrics identified petrographically include floating detrital grains corroded grain margins and circumgranular cracks defining peds localized alteration of primary micrites is mainly associated with large cracks where early non ferroan diagenetic cementation and neomorphism was focused diagenetic ferroan calcites occur as void fills and yield relatively light carbon isotope and oxygen isotope compositions 13 c 15 0 18 o 6 3 compared to well preserved micrite 13 c 10 2 18 o 4 0 precise definition of 13 c values for well preserved micrites allow estimation of partial pressure of atmospheric co 2 p co 2 for the early barremian of 560 ppmv using a published diffusion reaction model the data suggest that atmospheric co 2 was low during the mid early cretaceous before rising to a previously defined mid cretaceous high data from calcretes in the weald clay highlight the need for selection of appropriate material and careful evaluation before p co 2 calculations are attempted the weald clay samples come from marshy palaeoenvironments where ingress of atmospheric co 2 into the soil zone was either reduced or prevented

the calcareous nannofossil response to the end cretaceous warm event in the tropical pacific abstract the response of calcareous nannofossils to the end cretaceous warming is investigated in the tropical pacific dsdp site 577a shatsky rise through the record of species richness shannon diversity distribution patterns and statistical treatments this event is marked by a strong acme of the tropical species micula murus and is accompanied by a decrease of placozygus spiralis the disappearance of biscutum constans and a decrease in bulk 13c indicative of a decrease in primary productivity an increase in abundance of other micula species at site 577a and a drop in species richness recorded in all sites of shatsky rise suggest stressed environmental conditions coincident with the end cretaceous warming the acme of m murus at shatsky rise and in the atlantic ocean is recorded within magnetochron c29r and correlates 1 with the intense warming as expressed in intermediate waters through the 18o of benthic foraminifera and in surface waters through poleward migration reduced diversity and dwarfism in planktonic foraminifer assemblages 2 with a sharp decline in marine 187os 188os chemical marker of deccan volcanic activity and 3 with a rise in the atmospheric pco2 record of terrestrial plants in texas usa probably triggered by deccan volcanic degassing however a drop of calcareous nannofossil cool water taxa in the equatorial and south atlantic as well as a first rise in abundance of m murus in the south atlantic and tropical pacific occur in the topmost part of chron c30n and correlates with the rise in palaeotemperature record of terrestrial plants in north dakota usa this suggests that initiation of the warming in the atmosphere and surface waters may predate the striking warming of intermediate water masses by 150 200 kyr the coincidence and the links between climate change volcanism geochemical and biotic events at the end of the maastrichtian thus remain to be fully elucidated

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

cretaceous tertiary palynofloral perturbations and extinctions within the aquilapollenites phytogeographic province a combination of detailed intermediate and large scale stratigraphic perspectives is necessary to understand the driving mechanisms for floral change across the cretaceous tertiary k t boundary because short term physical and biotic events occur within longer term trends most maastrichtian palynofloral extinctions have been identified within the northern circumpolar supra continental aquilapollenites province in mid continental north america the presence of a physically defined k t boundary provides opportunities to examine contemporaneous terrestrial palynofloras over a latitudinal also approximately paleolatitudinal distance of 3200 km seventy five percent of last appearances occur before the k t boundary at high latitudes and must have been caused by ongoing terrestrial processes palynofloral events directly associated with the k t boundary include both local last appearances and inferred extinctions and synchronous and diachronous changes in relative abundances two different styles of factors are reflected in these events the first possibly attributable to chemical or other profound atmospheric perturbations associated with the worldwide distribution of the fireball layer of the k t claystone resulted in extinctions of angiosperm with a zoophilous pollination strategy the second factor possibly reflecting energy released during the deposition of ballistically transported impact debris or hackly ejecta layer of the boundary claystone resulted in the selective northward attenuating removal of the canopy vegetation best documented for southwestern canada which was succeeded by a fern dominated vegetation in mid continental north america these consequences of the boundary event were mediated by independent preexisting circumstances climate regional and through time local depositional environment and ongoing background extinctions and origins

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

micromorphology submicroscopy and microprobe study of carbonate pedofeatures in a vertisol gilgai soil complex south russia abstract carbonate nodules and soft masses were studied in a gilgai soil complex in the north caucasus south russia microrelief with an amplitude about 30 cm resulted in a wetter environment with stronger leaching in the microlow and a drier pedoenvironment with carbonate accumulation in the microhigh various macroforms of carbonate nodules and soft masses were identified in soil pits and sampled for micromorphology scanning electron microscopy sem and microprobe analyses to better characterize them and elucidate their pedogenesis common and unique attributes were described for carbonate pedofeatures depending on loci in gilgai soil complex the most probable hypothesis for their formation is as follows nodules represent early pedogenic products that were initiated before gilgai formation modern hydrology resulted in variability of dissolution recrystallization of the nodules along the gilgai microtopography the variability in degree of impregnation aggregation into pellets and presence of hard nodular cores reflects several generations of soft masses

upper cretaceous stable carbon isotope stratigraphy of terrestrial organic matter from sakhalin russian far east a proxy for the isotopic composition of paleoatmospheric co2 abstract time stratigraphic patterns of stable carbon isotopic ratios recorded in terrestrial organic matter from cenomanian maastrichtian successions for the russian far east can be correlated to those of carbonate carbon from well studied successions for other parts of the world age indicative biostratigraphy based on regional ammonoids and inoceramid bivalves are well established in japan and can be applied to the whole cretaceous succession except for the upper cenomanian lower turonian and the upper part of the maastrichtian zones lacking macrofossils globally correlative carbon isotopic events previously documented with carbonate carbon from europe and with carbonate carbon and marine organic matter from the u s western interior are recognized with similar magnitude through uppermost cenomanian lower campanian in ascending order these events are positive spike across the cenomanian turonian boundary step like leveled segment followed by negative shift lower middle turonian trough like negative excursion middle upper turonian positive rebound coupled with following broad peak coniacian and positive peak basal campanian followed by modest negative excursion the parallel fluctuation of the 13 c value between the terrestrial organic matter and carbonate suggests carbon isotopic equilibrium between surface seawater and atmospheric co 2 and demonstrates that the isotopic curve of terrestrial organic carbon can be used to monitor carbon isotopic fluctuations of co 2 in the ocean atmosphere system in the upper campanian and maastrichtian a negative 13 c excursion within chron 33r and a following rapid rebound can be correlated with the same distinctive carbon isotopic feature of carbonate observed in the deep sea cores from south and north atlantic the indian and the pacific oceans within this interval the 13 c value of terrestrial organic matter also reflects carbon isotopic fluctuation of the global co 2 reservoir with relatively minor regional local noise

geochemical evidence for suppression of pelagic marine productivity at the cretaceous tertiary boundary the normal biologically productive ocean is characterized by a gradient of the 13c 12c ratio from surface to deep waters here we present stable isotope data from planktonic and benthic micro fossils across the cretaceous tertiary boundary in the north pacific which reveal a rapid and complete breakdown in this biologically mediated gradient the fluxes of barium a proxy for organic carbon and caco3 also decrease significantly at the time of the major marine plankton extinctions the implied substantial reduction in oceanic primary productivity persisted for 0 5 myr before the carbon isotope gradient was gradually re established in addition the stable isotope and preservational data indicate that environmental change including cooling began at least 200 kyr before the cretaceous tertiary boundary and a peak warming of 3 c occurred 600 kyr after the boundary event

environmental change in the great plains an isotopic record from fossil horses abstract carbon and oxygen isotope ratios of fossil horse tooth enamel from nebraska and texas show evidence for late neogene environmental changes in the great plains the earliest unambiguous c4 dietary signal among texas equids coincides with the age of the classic late hemphillian age coffee ranch fauna which we suggest is 6 6 ma based on volcanic ash correlations c4 vegetation was present in the diets of a small fraction of late hemphillian equids in nebraska and was thereafter ordinary in the diets of both nebraska and texas equids there is no unequivocal evidence for abundant c4 vegetation in the diets of pre late hemphillian equids and we suggest that the ensuing dietary change reflects c4 biomass expansion in the latest miocene carbon isotope ratios of post hemphillian horses in nebraska can be divided into two statistically distinct populations on the basis of whether tortoise remains co occur with horse remains indicating that the two proxies carbon isotopes and presence absence of tort

the destruction of paleoclimatic isotopic signals in pleistocene carbonate soil nodules of western australia stable carbon and oxygen isotopic analyses were conducted on small 10 mm spherical pleistocene carbonate soil nodules from 53 different levels in a 9 15 m soil auger collected in northern western australia the 13c and 18o values range from 4 to 0 and 9 to 6 pee dee belemnite standard respectively comparison of these values to the 13c values of coexisting soil organic matter som reveals marked differences between the two records the som values record an enrichment of 16 through the section whereas the carbonate values record only a 4 variability application of a diffusion production model to the data indicates isotopic disequilibrium between the two carbon records one possible interpretation of the apparent isotopic disequilibrium is that the nodules formed at depths of 1 cm but this interpretation is not supported by field observations an alternative is that the soil organic matter currently in the profile was emplaced after nodule formation such a scenario would have to have occurred numerous times during the late pleistocene as the nodules grew below different soil zones through time a third explanation is that diagenetic alteration of the carbonates in the presence of dissolved inorganic groundwater carbon has occurred this interpretation is consistent with the widely fluctuating regional groundwater table it is also supported by petrographic fabrics and heterogeneous cathodoluminescence patterns indicative of initial pedogenic development of the nodules and then at least one dissolution event multiple precipitation events prolonged nodule growth by displacive spars and microspars cementation and recrystallization of some micrite the results illustrate potential problems for 1 the use of some pedogenic carbonate isotopic records as proxies for environmental change and 2 the use of altered 18o values and unaltered 13c values as screening tools for the presence or absence of diagenesis the results highlight the necessity of understanding regional environmental conditions and diagenetic histories prior to using pedogenic carbonates in paleoreconstructions

carbon isotope fractionation during decomposition of organic matter in soils and paleosols implications for paleoecological interpretations of paleosols abstract stable isotope ratios reported as 13c of organic carbon preserved in paleosols have potential utility as a valuable paleoecological indicator if the isotopic composition of paleobiomass is preserved in the paleosol organic carbon without fractionation however soil organic matter is in a constant state of decomposition in an open system and frequently decomposes further during alteration after burial of the paleosol during this decomposition kinetic fractionation of 13c 12c in an open system results in concentration of 13c in the residual organic matter preserved in the soil and paleosol this paper summarizes studies of modern soils which show that this 13c enrichment follows a rayleigh distillation process whereby the 13c 12c ratio is a function of the natural logarithm of the fraction of remaining soil organic carbon leaving soil organic carbon 13c enriched by up to 6 with respect to the original biomass if the fraction of original biomass carbon remaining during these decomposition processes deviates significantly from 1 the soil organic carbon can be 13c enriched by several per mil and thus not a good paleoecological indicator of the 13c value of the original biomass therefore effective paleoecological studies of 13c preserved in paleosol organic carbon must therefore demonstrate that the measured concentration of organic carbon in the paleosol is near its maximum concentration during soil formation or that the paleosol organic matter does not include the 13c enriched products of microbial decomposition suggestions are made for interpreting the effects of carbon isotope fractionation of organic matter and for materials and methods most useful for paleoecological studies from bulk paleosol organic carbon

geochemistry of late archaean metagreywackes from the western dharwar craton south india implications for provenance and nature of the late archaean crust abstract late archaean metagreywackes of the ranibennur formation dharwar supergroup in the dharwar shimoga schist belt of the western dharwar craton wdc are texturally and mineralogically immature of the quartz intermediate type the sio 2 content in them ranges from 60 58 to 65 26 wt chemical index of weathering ciw values varies between 50 and 65 4 indicating a low degree of chemical alteration of the provenance rocks a high degree of correlation between k 2 o and al 2 o 3 r 0 73 and low rb sr ratios also suggest a low degree of alteration of provenance rocks abundances of transition group elements cr 118 221 n 89 154 v 89 192 and sc 11 16 ppm as well zr 132 191 ppm suggest a mixed mafic felsic provenance for the metagreywackes low hree and y content and low tb yb ratios 0 23 0 41 suggest the presence of tonalite as an important component in the provenance areas values of eu eu 0 78 and th sc 0 55 suggest that the granodioritic upper crust had evolved prior to serving as the provenance mixing calculations suggest 50 55 vol tonalite 20 25 vol granite 18 20 vol basalt and 5 vol komatiite composition for the provenance geochemical characteristics of the ranibennur metagreywackes suggest that sedimentary basin formed in the vicinity of a magmatic arc in a continental island arc setting and the detritus were shed from the arc rock

development of asian monsoon revealed by marked ecological shift during the latest miocene in northern pakistan carbon isotopes from soil carbonate1 4 and soil organic matter5 6 yield palaeoecological information because the carbon in the soil carbonate forms in isotopic equilibrium with local soil co2 refs 1 7 the isotopic composition of which is in turn determined by local plant cover siwalik group sediments in northern pakistan contain a well exposed palaeosol record spanning the past 18 myr here we report on stable carbon isotope results from associated pedogenic carbonate which indicate a dramatic ecological shift from to dominated floodplain biomass beginning 7 4 7 0 myr ago the earlier c3 floodplain biomasses were probably mainly composed of trees and shrubs whereas c4 grasslands dominated in the plio pleistocene oxygen isotopes also exhibit a shift in the latest miocene probably corresponding to a major climate change which may have induced the forest to grassland transition this dramatic ecological shift in the latest miocene may mark the inception or a marked strengthening of the asian monsoon system

multi proxy paleosol evidence for middle and late triassic climate trends in eastern utah abstract prior investigations suggest that alluvial lowlands of pangea in the southwestern u s a during the middle to late triassic experienced an arid to semiarid climate with significant seasonality our investigation finds evidence for a global pluvial episode from paleosols in the middle to late triassic section of eastern utah multi proxy paleosol evidence is used to quantify rainfall amounts ambient temperatures and atmospheric co 2 concentrations and infer associated plant formations related to ecosystem persistence rainfall estimates are derived from geochemical molecular weathering ratios temperature and atmospheric co 2 levels from stable oxygen and carbon isotopes of pedogenic carbonate respectively and ecosystem reconstruction by a combination of climate indexes and paleosol characteristics eight pedotypes were identified and include poorly drained aquic entisols fisher well drained non aquic entisols salt valley calcic aridisols castle valley calcic inceptisols moab cambic ute and calcic la sal vertisols dystric inceptisols kokopeli and argillic alfisols slickrock the middle triassic moenkopi formation anisian was dominated by castle valley paleosols with mean annual rainfall between 300 and 400 mm and mean annual temperature between 13 and 23 c mesic to hyperthermic based on these climate indexes and root traces the associated plant formation was most likely desert shrub or dry woodland the lower chinle formation carnian contains a succession of ute and la sal paleosols that changed up section to kokopeli fisher and slickrock paleosols in accordance with geochemical and isotopic signatures from these pedotypes rainfall amounts initially increased to between 700 and 900 mm and then to between 1300 and 1400 mm temperatures estimated from the la sal paleosol are approximately 18 c thermic at this time the lower chinle marks a transition from dry woodland to open forest that appears to correlate with the formation of the petrified forest member in arizona the upper chinle formation carnian norian reveals a return to semiarid to subhumid conditions and the formation of castle valley moab and salt valley paleosols all of which appear to have supported desert shrub or dry woodlands rainfall amounts decreased to between 400 and 600 mm with temperatures eventually increasing to 29 c hyperthermic using the paleosol isotopic barometer atmospheric co 2 estimates generally correlate with other proxy for the triassic the well developed alfisols and noncalcareous inceptisols identified during the carnian of the lower chinle correlate with a previously identified global pluvial episode based on sedimentological and marine isotopic evidence possibly in response to rifting of pangea it should not be assumed that the middle to late triassic in continental alluvial lowlands supported a uniform semiarid to arid climate with strong seasonality

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

new palaeomagnetic data from the mahabaleshwar plateau deccan flood basalt province india implications for the volcanostratigraphic architecture of continental flood basalt provinces abstract new magnetostratigraphic data from seven western ghats sections in the deccan volcanic province are presented these are combined with an established geochemically defined stratigraphy and volcanological logs to provide a correlated chronological eruptive framework we identify two magnetic polarities in five of the sections and these are assigned to chrons 29r and 29n importantly the reversal boundary represents an identifiable isochronous surface within the volcanic pile this surface occurs at different elevations as does the altitude of the geochemically defined formation boundary i e ambenali mahabaleshwar fms which defines a second isochronous surface inspection reveals significant differences in the number and thickness of lava units preserved between these two surfaces this indicates that there was significant local topography c 80 m across deccan volcanic province lava fields during their development an interpretation consistent with topographies observed across modern and historical examples e g hawaii iceland these data also indicate that the geochemical stratigraphies of continental flood basalt provinces can mask local and sub regional detail in lava stacking patterns when applied at smaller spatial scales 2 10 4 m finally transitional r n directions preserved in some eruptive units place constraints upon the rates of eruption and indicate c 2 ka periods of volcanic repose

paleosol barometer indicates extreme fluctuations in atmospheric co2 across the cretaceous tertiary boundary we present an atmospheric p co 2 p is partial pressure curve showing extreme fluctuations for the interval between ca 77 and 63 ma in southern alberta canada using a paleosol barometer paleosol carbonate nodules micrite were collected from 40 bk horizons among 6 stratigraphic sections for stable carbon isotope analysis based on results from the study area declining atmospheric p co 2 from 1200 ppmv v is volume in the campanian to 780 ppmv in the maastrichtian correlates with late cretaceous climate cooling and falling sea level as documented in global records the remarkable rise in atmospheric p co 2 near 65 5 ma 1440 ppmv correlates with volcanic activity associated with the deccan traps rising sea level and warmer global climates the decline in atmospheric p co 2 760 ppmv at the cretaceous tertiary boundary and subsequent sharp rise into the danian 1000 ppmv occurred during static terrestrial temperatures and sea level this work provides compelling evidence that atmospheric p co 2 curves modeled for the phanerozoic do not offer the resolution needed to understand environmental conditions during catastrophic events in earth9s history

atmospheric carbon dioxide linked with mesozoic and early cenozoic climate change carbon isotopes of fossil plants and model simulations suggest that atmospheric carbon dioxide levels were variable during the period 200 to 60 million years ago the large decreases in the partial pressure of co2 coincide with glaciations providing evidence against climate co2 decoupling during the mesozoic

terrestrial palynomorph biostratigraphy of the cypress hills wood mountain and turtle mountain areas upper cretaceous paleocene of western canada three cored test holes were drilled to study the stratigraphic interval spanning the cretaceous tertiary boundary one in the western cypress hills near elkwater alberta a second in the eastern portion of the wood mountain area near killdeer saskatchewan and a third on the western edge of turtle mountain near goodlands manitoba the terrestrial elements of the palynological assemblages are discussed the maastrichtian assemblages encompassed the scollardia trapaformis zone and two new subzones myrtipites scabratus aquilapollenites delicatus var collaris and porosipollis porosus aquilapollenites notabile within the wodehouseia spinata zone the paleocene zones encountered include the aquilapollenites reticulatus subzone of the w spinata zone the previously described wodehouseia fimbriata and momipites wyomingensis zones and the newly defined tricolporopollenites kruschii zone these provide a biostratigraphy for the cored intervals which can be related to polarity chrons the observations mad

highly heterogeneous precambrian basement under the central deccan traps india direct evidence from xenoliths in dykes abstract crustal or mantle xenoliths are not common in evolved tholeiitic flood basalts that cover huge areas of the precambrian shields yet the occasional occurrences provide the most direct and unequivocal evidence on basement composition few xenolith occurrences are known from the deccan traps india and inferences about the deccan basement have necessarily depended on geophysical studies and geochemistry of deccan lavas and intrusions here we report two basalt dykes rajmane and talwade dykes from the central deccan traps that are extremely rich in crustal xenoliths of great lithological variety gneisses quartzites granite mylonite felsic granulite carbonate rock tuff because the dykes are parallel and only 4 km apart and only a few kilometres long the xenoliths provide clear evidence for high small scale lithological heterogeneity and strong tectonic deformation in the precambrian indian crust beneath measured 87sr 86sr ratios in the xenoliths range from 0 70935 carbonate to 0 78479 granite mylonite the rajmane dyke sampled away from any of the xenoliths shows a present day 87sr 86sr ratio of 0 70465 and initial at 66 ma ratio of 0 70445 the dyke is subalkalic and fairly evolved mg no 44 1 and broadly similar in its sr isotopic and elemental composition to some of the lavas of the mahabaleshwar formation the xenoliths are comparable lithologically and geochemically to basement rocks from the archaean dharwar craton forming much of southern india as several lines of evidence suggest the dharwar craton may extend at least 350 400 km north under the deccan lava cover this is significant for precambrian crustal evolution of india besides continental reconstructions

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

combustion of fossil organic matter at the cretaceous paleogene k p boundary recognition of elevated concentrations of aciniform soot in cretaceous paleogene k p boundary sediments worldwide led to the hypothesis that global scale forest wildfires could have been generated by the k p boundary bolide impact and might have contributed directly to the extinction event the wildfires are estimated to have injected 10 13 t of co 2 into the atmosphere resulting in an interval of greenhouse warming yet minimal amounts of charred plant remains and abundant noncharred material occur in various k p boundary locations across north america this refutes the inference that wildfires occurred on a global scale and requires an alternative explanation for the aciniform soot here we describe significant concentrations of carbon cenospheres in k p boundary sediments from new zealand denmark and canada carbon cenospheres are thought to derive solely from incomplete combustion of pulverized coal or fuel oil droplets which suggests that the impact may have combusted organic rich target crust the chicxulub impact crater is located adjacent to the cantarell oil reservoir one of the most productive oil fields on earth this indicates that abundance of organic carbon in the chicxulub target crust was likely to have been above global mean values but even if we discount chicxulub9s organic rich locality the global mean crustal abundance for fossil organic matter is more than adequate to account for observed concentrations of both carbon cenospheres and aciniform soot therefore making the global wildfire hypothesis unnecessary

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

ocean overturning since the late cretaceous inferences from a new benthic foraminiferal isotope compilation 1 benthic foraminiferal oxygen isotopic d 18 o and carbon isotopic d 13 c trends constructed from compilations of data series from multiple ocean sites provide one of the primary means of reconstructing changes in the ocean interior these records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records we present new benthic foraminiferal d 18 o and d 13 c compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to 80ma andtentatively to 110ma first order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the late cretaceous 65 ma to early paleogene 35 65 ma homogeneity and a return to heterogeneity in the late paleogene early neogene 35 0 ma we propose that these transitions reflect alterations in a first order characteristic of ocean circulation the ability of winds to make water in the deep ocean circulate we document the initiation of large interbasinal d 18 o gradients in the early oligocene and link the variations in interbasinal d 18 o gradients from the middle eocene to oligocene with the increasing influence of wind driven mixing due to the gradual tectonic opening of southern ocean passages and initiation and strengthening of the antarctic circumpolar current the role of wind driven upwelling possibly associated with a tethyan circumequatorial current in controlling late cretaceous interior ocean heterogeneity should be the subject of further research

late cretaceous chronology of large rapid sea level changes glacioeustasy during the greenhouse world we provide a record of global sea level eustatic variations of the late cretaceous 99 65 ma greenhouse world ocean drilling program leg 174ax provided a record of 11 14 upper cretaceous sequences in the new jersey coastal plain that were dated by in tegrating sr isotopic stratigraphy and biostratigraphy backstripping yielded a late cre taceous eustatic estimate for these sequences taking into account sediment loading com paction paleowater depth and basin subsidence we show that late cretaceous sea level changes were large 25 m and rapid k1 m y suggesting a glacioeustatic control three large d 18 o increases are linked to sequence boundaries others lack sufficient d 18 o data consistent with a glacioeustatic cause and with the development of small 10 6 km 3 ephemeral ice sheets in antarctica our sequence boundaries correlate with sea level falls recorded by exxon production research and sections from northwest europe and russia indicating a global cause although the exxon record differs from backstripped estimates in amplitude and shape

global fire at the cretaceous tertiary boundary cretaceous tertiary k t boundary clays from five sites in europe and new zealand are 102 104 fold enriched in elemental c mainly soot which is isotopically uniform and apparently comes from a single global fire the soot layer coincides with the ir layer suggesting that the fire was triggered by meteorite impact and began before the ejecta had settled