stable isotopic composition of soil carbon dioxide in the tucson basin arizona u s a abstract most models to correct 14c groundwater ages require the 13c value of soil co2 in the recharge areas of the aquifer at the time of recharge ninety one soil gas samples were collected at three long term sites in the tucson area from july 1980 to june 1981 to determine the extent of seasonal variations and the influence of vegetation on the 13c and co2 concentration of soil gases variations were observed in both 13c and co2 concentrations the highest co2 concentrations up to 1 3 at 60 cm depth were observed during march and april the lowest 0 1 co2 at 12 cm depth were observed during the winter months the 13c values varied by 5 during the sampling period the lowest 13c contents were found in early spring and summer part of the 13c variation is due to exchange with atmospheric co2 other causes could be decomposition of organic matter with different isotopic composition and different decay rates and or to a seasonal displacement of the period of maximum activity among different varieties of plants the mean 13c for samples at the long term sites was 18 in addition fifteen soil gas samples were collected in the bottom of washes which are the assumed recharge areas of the tucson aquifer both co2 and 13c concentrations showed changes with time and location high concentrations of co2 of up to 4 8 were found the mean 13c for these samples was 20 a major source of co2 in the riverbeds is believed to be decomposition of organic matter carried out by the runoff water during the periodic flooding of the washes

ten years of natural ageing of calcareous stones abstract in the recent years as aesthetic criteria are predominant over structural criteria and the knowledge of stone materials is considered negligible sometimes a stone is used on a building facade that after a few years shows structural problems decreasing decay resistance in fact can show itself by means of evident signals such as fractures and bowing that can compromise a building s structural stability in this work nine different kinds of calcareous stone slabs exposed for ten years to natural weathering in turin northern italy have been studied petrographic characteristics and an enhanced petrographic analysis of adjacent grains aga were compared with the physical and mechanical properties of slabs exposed stone durability was detected by means of the following test methods ultrasonic pulse velocity upv water absorption superficial water absorption by means of a contact sponge flexural strength bowing measurements and image analysis from the comparison of the results obtained to detect the decay with the different techniques it is possible to assert that the upv measurement best correlates with flexural strength after ten years of natural weathering the decrease of mechanical resistance of calcitic stones with similar grain size is inversely proportional to the value of aga the same tests are performed after various thermal and moisture cycles according the recent en 16306 european standard comparison of natural weathering and artificial ageing by means of image analysis suggests that the natural external factors cause different types and degrees of porosity than artificial ageing

factors of paleosol formation in a late cretaceous eolian sand sheet paleoenvironment marilia formation southeastern brazil abstract the marilia formation which crops out in southeastern brazil is interpreted as a late cretaceous eolian sand sheet area the sedimentary succession ca 110 m thick is characterized by alternating strata of eolian deposits and paleosols the paleosols constitute more than 66 of the thickness and are an important element in the interpretation of the paleoenvironmental controlling factors which affected the soil formation in this eolian sand sheet in this paper six paleosol profiles are described and assigned to two pedotypes itaja and apore the itaja pedotype is constituted of a sequence of five superimposed polygenetic profiles which show different phases of clay illuviation and carbonate precipitation and it has been classified as aridisol the apore pedotype overlies the itaja pedotype this pedotype shows an increase in leaching cia k ratios reddening and illuvial clay features in respect to itaja and has been classified as alfisol the analysis of the factors which controlled the soil formation revealed that both pedotypes formed on a stable landscape probably covered by a community of low stature plants in which the soils had sufficient time to develop very mature profiles the changes in soil forming processes were driven principally by variations in available soil moisture from precipitation using depth to carbonate functions from bk and cia k proxy from bt horizons of the itaja pedotype mean annual precipitation map estimates range from 240 to 1078 mm yr respectively these contrasting climatic conditions resulted in the superimposition of arid or semi arid with more humid climates and determined the considerable change in the pedogenic features with many horizons showing the interlacing of calcite and clay features in the apore pedotype cia k proxy from bt horizons estimates that averaged map was around 900 mm yr and the prevalent humid conditions can be attested by soil properties and abundance and depth of root traces our results show that the diversity in pedotypes is mainly attributed to differences in paleoclimatic conditions during maastrichtian time and that eolian sedimentation was restricted to periods of harsh arid conditions as in semi arid climates with map estimates around 240 mm yr the formation of soils with well developed calcic horizons was possible

physical weathering of marbles caused by anisotropic thermal expansion marbles as building stones as well as in their natural environments show complex weathering phenomena the most important damage scenario is based on the highly anisotropic thermal expansion coefficient of calcite i e extreme expansion parallel and contraction normal to the crystallographic c axis therefore the rock fabric and especially the lattice preferred orientation texture of calcite and or dolomite as the predominant mineral phases in marbles have a significant influence on the mechanical weathering the textures of marbles from five different locations vary from a more or less perfect prolate to moderate oblate shape of the 006 pole figure tensor accordingly the texture derived bulk thermal dilatation anisotropy covers a broad range from 0 048 to 0 680 the modelled thermal dilatations correlate with those obtained from experimental measurements the difference in magnitude is basically explained by the microcrack fabrics which was not considered in the computations all samples show a deterioration due to thermal treatment regardless of the strength of texture the directional dependence of a the total magnitude of the thermal dilatation coefficient and b of the residual strain is highest in marbles with a strong texture whereas the carrara marble with a weak texture exhibits a uniform crack formation the progressive loss of cohesion along grain boundaries due to dilatancy may serve as an example for the initial stage of physical weathering

stable carbon isotope stratigraphy of the paleogene pedogenic series of southern france as a basis for continental marine correlation the upper cretaceous lower paleogene formations in the aix en provence basin are characterized by interfingering lacustrine carbonates and flood plain alluvium the deposits from both environments display numerous horizons of carbonate rich paleosols by using a combined magnetostratigraphy and carbon isotope stratigraphy for the pedogenic carbonate glaebules we constructed a detailed integrated stratigraphy for the entire lower paleogene this method provides a way to correlate marine and terrestrial sequences when c3 plants dominated the environment both long term and short term 13 c variations were identified in the provence series 1 the uniform carbon isotope record established through the end of the maastrichtian followed by the abruptly negative carbon isotope excursion in the lowermost paleocene provides a marker for the precise location of the cretaceous tertiary boundary in this basin 5 m below the calcaire de vitrolles formation 2 a gradual 13 c increase through the middle upper paleocene similar in amplitude to that of the marine realm 3 a short term negative 13 c excursion in the latest paleocene as seen within the calcaire de st marc formation and 4 a slow decrease during the late paleocene to early eocene with a probable hiatus in the sedimentary record the provence mammal site of palette is shown to be stratigraphically younger than the late paleocene negative 13 c excursion

systematic variations in the carbon and oxygen isotopic composition of pedogenic carbonate along elevation transects in the southern great basin united states stable carbon and oxygen isotope variations in holocene soil carbonates that formed in the unsaturated zone were examined along several elevation transects in the southern great basin united states a region with a semi arid climate our intent was to study the relationship between the stable isotopic composition of pedogenic carbonates and climate ecological variations differences in parent material and soil depth 13 c of pedogenic carbonate in three different soil profiles from different elevations decreases with soil depth indicating a decrease in the ratio of atmospheric to plantderived co 2 downprofile pedogenic carbonate at the soil air interface approaches a 13 c value in equilibrium with atmospheric co 2 in all three soils observed 13 c profiles for pedogenic carbonate can be described using a one dimensional model for 12 co 2 and 13 co 2 assuming isotopic equilibrium between soil co 2 and soil carbonate the modeled best fit to observed isotopic profiles suggests that the profile differences in part result from differing soil respiration rates at each site 13 c in deep pedogenic carbonate 50 cm varies by about 12 per mil over a 2 440 m elevation range being enriched in 13 c at the lowest elevations the slope of 13 c for these carbonates versus elevation is very similar for soils developed on carbonate and on noncarbonate parent materials depletion by 4 6 to 4 7 per mil per 1 000 m increase in altitude between 300 to 2 740 m above mean sea level for the localities studied this concordance makes it likely that there has been complete isotopic exchange between hco 3 in solution and soil co 2 prior to carbonate precipitation soil co 2 and soil respiration rates increase systematically with elevation the plantderived component of soil co 2 indicates that c 3 plants dominate the biomass at most measured sites in agreement with plant surveys calculated equilibrium fractionation factors between soil co 2 and soil carbonate are very similar to those observed again indicating complete isotopic exchange between carbon species in all the soil co 2 and soil carbonate data suggest that the 13 c variation with elevation observed in the soil carbonates results from differing soil respiration rates at each site as well as from variations in the proportion of c 3 to c 4 and cam plants in each site9s surface biomass 18 o values in pedogenic carbonates are higher at lower elevations due in part to the more positive 18 o values for meteoric waters at lower elevations the average 18 o value of deep 50 cm pedogenic carbonate at all sites however is enriched 2 4 to 3 7 per mil with respect to values we predict should be in equilibrium with the isotopic composition of local meteoric waters this suggests that evaporative isotopic enrichment of soil waters may have occurred at all elevations prior to precipitation of carbonate or that seasonal differences in the isotopic composition of meteoric waters coupled with differential infiltration may be taking place one or both of these processes also may explain the 18 o decrease in soil carbonate with depth observed in two of three soil profiles

paleosols spanning the cretaceous paleogene transition eastern montana and western north dakota paleosols occur in exposures of the latest cretaceous hell creek and paleocene tullock ludlow formations in montana and western north dakota these units are composed mainly of interbedded siltstones and sandstones of meandering fluvial origin the paleosols indicate that changes in ancient soil development occurred concomitantly with the better known faunal transition in order of decreasing abundance silty soils sandy soils organic soils and volcanic soils are preserved pedogenic features present in these soils include roots microscopic segregations of amorphous material birefringence fabric and soil structures the features suggest that throughout the cretaceous paleogene transition pedogenic processes in the region produced immature profiles an observation consistent with the unstable fluvial setting in which the ancient soils formed gleization was a dominant process in this setting and podzolization modified some sandy soils the association of the features enables recognition of o a e btg bhs bg bc cg and c horizons during middle hell creek time soils formed in a poorly drained setting that was only stable enough to permit incipient pedogenesis the bulk of the pedogenesis occurred in levee and flood plain deposits soils also occurred on point bar and crevasse splay deposits in topographically depressed regions organic accumulations formed with minimal soil development matted plant debris is the product of this environment gley features and segregations of iron oxides around voids suggest fluctuation of the water table by latest hell creek time the mean level of the water table rose and in the lowest tullock ludlow exposures extensive ponded deposits are preserved vegetation accumulated at a rate sufficient for coal formation the amount of fluctuation apparently was reduced and pedogenesis was further inhibited as indicated by the virtual absence of illuviated clays in the sediments

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

carbon isotopes in continental weathering environments and variations in ancient atmospheric co2 pressure abstract abundance and carbon isotope data from an fe co3 oh component in apparent solid solution in oolitic goethites have been used to infer ancient atmospheric co2 pressures a test of the validity of these estimates might be comparisons of the carbon isotope compositions of fe co3 oh in oolitic goethites with time equivalent pedogenic calcites temporal trends of the oolitic goethite and pedogenic calcite 13c values are generally similar but time equivalent samples from each of these two groups are not common in the existing data to facilitate discussion of the concept comparisons were made of available goethite and calcite samples even though ages of the compared samples in each pair were not identical in four out of the five comparisons fe co3 oh abundance and 13c data were combined with pedogenic calcite 13c data to calculate physically reasonable soil co2 concentrations for the ancient calcitic soids this suggests that the compared oolitic goethite and pedogenic calcite systems were responding to the same global scale phenomenon i e atmospheric co2 atmospheric pco2 as determined from the goethites in these four well behaved cases ranged from values indistinguishable from modern within analytical uncertainty to values up to approximately 16 time modern modern atmospheric pco2 was taken to be 10 3 5 atm one interpretation of the fifth anomalous comparison is that atmospheric co2 levels increased from about 3 times modern to about 18 times modern from the triassic into the early jurassic this inferred value for the pco2 of the early jurassic atmosphere is not uniquely constrained by the existing data and needs to be substantiated however even considerably lower early jurassic atmospheric pco2 values of 6 to 9 times modern i e 1 3 to 1 2 of the estimated value of 18 times modern would still indicate significant differences between the global carbon cycles then and now these results highlight the need for more research on the behavior of the atmosphere during and after the triassic jurassic transition

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

paleo co2 variation trends and the cretaceous greenhouse climate the cretaceous was one of the most remarkable periods in geological history with a greenhouse climate and several important geological events reconstructions of atmospheric co2 using proxies are crucial for understanding the cretaceous greenhouse in this paper we summarize the major approaches for reconstructing co2 based on paleobotanical or geochemical data and synthesize the co2 variations throughout the cretaceous the results show that atmospheric co2 levels remained relatively high throughout the cretaceous but were lower in the early cretaceous highest in the mid cretaceous and gradually declined during the late cretaceous however this overall trend was interrupted by several rapid changes associated with ocean anoxic events oaes and the end cretaceous catastrophic event new data on paleo co2 levels from paleobotanical and paleosol evidences support not only the overall trends indicated by geochemical models but provide more precise records of the short term fluctuations related to brief episodes of climate change temporal resolution within the long quiet magnetic period in the middle cretaceous is one of the obstacles preventing us from a more comprehensive understanding of the co2 climate linkage but new paleo co2 determinations and climatic data from stratigraphic sections of sediments intercalated with datable volcanic rocks will allow a better understanding of the relationships between fluctuations of atmospheric co2 climate change and geological events

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

palaeoecology of late cretaceous polar vegetation preserved in the hansen point volcanics nw ellesmere island canada abstract mesozoic polar forests represent an extinct biome subject to a polar light regime and elevated atmospheric co2 levels in this paper new cretaceous fossil plant assemblages are reported from nw ellesmere island canada at a paleolatitude of 75 n these occur in a campanian maastrichtian aged interval of the hansen point volcanics a unit interpreted as a coastal plain peat mire complex within an active volcanic setting studies of palynomorphs sterile and fertile foliage and wood indicate that mire environments were dominated by amber producing taxodiaceous conifers with other conifers ginkgos cycads angiosperms ferns lycopsids and bryophytes occurring in subordinate numbers leaf physiognomic studies imply that most vegetation was deciduous occurrence of traumatic rings in the woods together with a high year to year variability in ring width indicates disturbed growing conditions possibly linked to a combination of frosts volcanic eruptions and flooding abundant charcoal remains indicate that an additional important disturbance process was wildfire results of this study compare closely with those from coeval circum arctic fossil sites and augment our knowledge of the community scale ecology of the cretaceous polar biome

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

geologic history of seawater a magic approach to carbon chemistry and ocean ventilation abstract we explore the relationship between atmospheric o 2 and co 2 evolution and seawater chemistry with particular focus on the co 2 carbonic acid system and ocean ventilation over the phanerozoic eon using a coupled biogeochemical earth system model magic this model describes the biogeochemical cycles involving the major components of seawater ca mg na k cl so 4 co 2 hco 3 co 3 as well as components o 2 fe p organic c reduced s central to long term ecosystem productivity the magic calculations show that the first order input fluxes from weathering of continental rocks of ca mg and dissolved inorganic carbon dic to the ocean varied in a cyclical manner over the phanerozoic the cyclicity is mainly the result of the impact of changing atmospheric co 2 levels and hence temperature and runoff on these fluxes reflecting the nature of hothouse greenhouse high co 2 and warm versus icehouse low co 2 cool and continental glaciation conditions during the phanerozoic uptake of dic by seafloor basalt seawater reactions also varied in a corresponding fashion to the weathering fluxes the fluxes of ca mg dic and other seawater constituents removed in oceanic sinks were also calculated and hence with calculated inputs and outputs of seawater constituents the changes in seawater chemistry through phanerozoic time could be obtained seawater ph increased irregularly during the phanerozoic from just above 7 in the cambrian period approaching modern average values in the most recent several millions of years calcite saturation state also increased with decreasing age both ph and calcite saturation state trends exhibited a cyclic overprint of hothouse and icehouse environmental conditions dissolved sulfate changed in a cyclical manner reflecting mainly variations in weathering and accretion rates and redox conditions whereas dissolved potassium exhibited little variation in concentration using our standard model results for the chemistry of seawater and changes in atmospheric co 2 and o 2 as the basis for a series of sensitivity experiments we vary the ventilation rate of the global ocean and quantify the resulting changes in terms of processes such as net primary production organic carbon burial and oxidation pyrite weathering and sulfate reduction we use these preliminary results to discuss how changes in ocean ventilation affect atmospheric co 2 and o 2 and in turn exert changes in the sulfur organic carbon and inorganic carbon systems we postulate that periods of slow plate accretion rates associated with lower atmospheric co 2 vigorous deep water formation cooler drier climatic conditions and greater poleward temperature gradients are more likely to be associated with a strong thermohaline circulation and thus enhanced global ocean mixing conversely periods of higher accretion rates higher co 2 higher average global temperatures with more equable poleward gradients and higher sea levels resulting in extensive continental inundation would be more likely to be coincident with times of reduced mixing of the global ocean it is important to recognize that the scale of these changes depends on how major tectonic cycles controlling chemical weathering co 2 and temperature in turn affect nutrient supply global ocean productivity and global ocean thermohaline circulation the key to elucidating these changes lies in an understanding of the relationship between long term tectonic evolution which leads to changes in climate sea level and the global distribution of continental landmasses and the sedimentary environments they host and the circulation of the global ocean

benthic foraminiferal turnover across the cretaceous paleogene boundary at agost southeastern spain paleoenvironmental inferences abstract we studied upper cretaceous and lower paleogene benthic foraminifera from the agost section southeastern spain to infer paleobathymetrical changes and paleoenvironmental turnover across the cretaceous paleogene k p transition benthic foraminifera indicate uppermost bathyal depths at agost during the abathomphalus mayaroensis biochron from about 400 kyr before the k p boundary through the early plummerita hantkeninoides biochron about 120 150 kyr before that boundary the depth increased to middle bathyal for the remainder of the cretaceous and remained so for the danian part of the studied section parasubbotina pseudobulloides biochron at least 200 kyr after the k p boundary there were no perceivable bathymetrical changes at the k p boundary where 5 of the species became extinct and the species composition of the benthic foraminiferal fauna changed considerably below the boundary infaunal morphogroups constitute up to 65 73 of the faunas directly above the boundary in the black clays of the lower guembelitria cretacea biozone benthic foraminifera are rare several opportunistic taxa e g the agglutinant haplophragmoides sp have short peaks in relative abundance possibly reflecting low oxygen conditions as well as environmental instability with benthos receiving food from short lived local blooms of primary producers above the clays through the end of the studied interval epifaunal morphogroups dominate up to 70 of the assemblages or there is an even mixture or epifaunal and infaunal morphogroups infaunal groups do not recover to pre extinction relative abundances indicating that the food supply to the benthos did not recover fully over the studied interval about 200 kyr after the k p boundary the benthic foraminiferal faunal changes are compatible with the direct and indirect effects of an asteroid impact which severely destabilized primary producers and the oceanic food web that was dependent upon them

climate model predictions for the latest cretaceous an evaluation using climatically sensitive sediments as proxy indicators to date many general circulation model gcm experiments have failed to reproduce the warm high latitude temperatures suggested for the cretaceous by geological proxy climate indicators especially for the northern hemisphere and within continental interiors the vast majority of these proxies are biologically based and it is important to determine whether alternative sedimentologically based proxies indicate similar cold biases in models therefore we have performed an evaluation of the very latest generation of climate model predictions for terrestrial sites using climatically sensitive sediments as palaeoclimate indicators evidence from the geological record comprising coal peat evaporites bauxite and laterite deposits are portrayed on a series of palaeoclimate data maps these are then compared with the global distributions of potential deposits generated from model simulations of the maastrichtian using versions of the hadley centre climate model the maastrichtian was chosen because of the greater range and sophistication of gcms adapted for its climate simulation and sediment prediction than for other cretaceous stages this thus represents the first attempt at comparing such state of the art models to lithological climate indicators and quantifying their relative performances for peat coal there is generally good correspondence between maastrichtian model predictions for predicted potential deposits and the observed record for evaporites there is also very close agreement between predictions by the models and the geological record minor differences between the individual model versions resulting from their differing levels of atmospheric co2 and the different palaeogeographical representations of intracontinental seaways in the northern hemisphere for bauxites and laterites the models predict less than half of the documented deposits successfully portraying equatorial accumulations but omitting the majority of mid to high latitude deposits the main discrepancy is therefore identified as the failure of all models to predict bauxite and laterite deposits corresponding with recorded accumulations within the mid to high latitudes of europe and asia in many cases the effects of co2 have minimal impact on the skill of model prediction however for evaporite distributions the low co2 model is appreciably worse in general the best match across the geological data and models is achieved by the simulation with open northern hemisphere seaways overall these results confirm those inferred from biological proxies showing that climate models have a serious cold bias in high latitudes and continental interiors during the cretaceous and that the latest generation of climate models still produces results which are incompatible with the geological data levels of atmospheric co2 and uncertainties in palaeogeography cannot explain the discrepancy the cold bias is common to many climate models and suggests that a process or mechanism is poorly represented or omitted in the current generation of climate models or that we are failing to recognise a major boundary condition change in the cretaceous if the former this implies that we may be underestimating the extent of extreme future climate change at high latitudes and in continental interiors

paleoclimate estimates and fire ecology immediately prior to the end cretaceous mass extinction in the frenchman formation 66ma saskatchewan canada abstract the fossil rich deposits of the uppermost maastrichtian 66 ma frenchman formation of southern saskatchewan canada provide a detailed continuous record of terrestrial ecosystem dynamics during the last half million years leading up to the end cretaceous mass extinction paleoenvironmental interpretations for the frenchman formation are here refined by the first absolute paleoclimate estimates for the late cretaceous of saskatchewan and by the placement of these climate estimates within a north american context climate estimates were calculated using leaf margin analysis and the climate leaf analysis multivariate program clamp derived from two independent plant macrofossil assemblages collected from the frenchman formation climate parameter estimates indicate that the maastrichtian climate of southern saskatchewan was subtropical to warm temperate with mean annual temperatures between 12 c and 14 c and with marked seasonality these results are comparable with estimates derived from other late campanian and maastrichtian paleofloras in the western interior basin although small variations among coeval localities were noted or determined overall the plant fossil assemblages from the two study localities support the paleoenvironmental interpretation of the frenchman formation as a swampy to lowland forest system with canopy forming deciduous conifers and a diverse angiosperm dominated mid canopy and understory an unexpected marked disparity in plant diversity was found between the two paleofloras despite the plant assemblages returning similar paleoclimate parameter estimates abundant in situ inertinite fossil charcoal deposits were found in association with the less diverse paleofloral site which contained only angiosperm fossils inertinite was absent from the deposits containing the more diverse paleoflora which contained a different composition of angiosperm and gymnosperm fossils fire is known to be a prevalent feature of late cretaceous deposits worldwide and modern angiosperm plants typically are the first to recover following fire disturbances we suggest that the two frenchman formation paleofloras represent different stages of secondary ecological succession following a disturbance by fire the identification of fire ecology in the fossil record may have important implications for understanding biodiversity patterns on small spatial and temporal scales immediately prior to the cretaceous mass extinction

influence of changing hydrology on pedogenic calcite precipitation in vertisols dance bayou brazoria county texas u s a implications for estimating paleoatmospheric pco2 the 13 c values of pedogenic soil formed calcite preserved in the sedimentary record have been used to estimate atmospheric pco 2 using the paleosol calcite paleobarometer a fundamental assumption for applying this paleobarometer is that atmospheric co 2 concentrations have a direct influence on the measured pedogenic calcite 13 c values as a result of open system exchange between atmospheric and soil respired co 2 here we address the timing of calcite precipitation in relation to the soil saturation state and soil atmosphere connectivity in a modern vertisol smectitic clay rich soil seasonally saturated in brazoria county texas u s a luminescent phases of calcite growth under cathodoluminescence microscopy have more negative 13 c values 13 c 11 1 vpdb 0 78 1 than the non luminescent phases 13 c 2 53 vpdb 1 41 1 the luminescent phase of calcite formed during the water saturated portion of the year thereby minimizing the incorporation of atmospheric co 2 and negating its use for pco 2 estimations the non luminescent phase formed during the well drained portion of the year when atmospheric co 2 mixed with soil respired co 2 and is therefore useful for pco 2 estimation from these results we present a model to independently test the saturation state of a paleosol at the time of pedogenic carbonate precipitation finally we calculate soil respired co 2 concentrations that are an order of magnitude lower than those that are typically assumed in the soil carbonate paleobarometer equation

a new high resolution chronology for the late maastrichtian warming event establishing robust temporal links with the onset of deccan volcanism the late maastrichtian warming event was defined by a global temperature increase of 2 5 5 c that occurred 150 300 k y before the cretaceous paleogene k pg mass extinction this transient warming event has traditionally been associated with a major pulse of deccan traps west central india volcanism however large uncertainties associated with radiogenic dating methods have long hampered a definitive correlation here we present a new high resolution single species benthic stable isotope record from the south atlantic calibrated to an updated orbitally tuned age model to provide a revised chronology of the event which we then correlate to the latest radiogenic dates of the main deccan traps eruption phases our data reveal that the initiation of deep sea warming coincides within uncertainty with the onset of the main phase of deccan volcanism strongly suggesting a causal link the onset of deep sea warming is synchronous with a 405 k y eccentricity minimum excluding a control by orbital forcing alone although amplified carbon cycle sensitivity to orbital precession is evident during the greenhouse warming a more precise understanding of deccan induced climate change paves the way for future work focusing on the fundamental role of these precursor climate shifts in the k pg mass extinction

physico chemical environment of pedogenic carbonate formation in devonian vertic palaeosols central appalachians usa the morphology and geochemistry of pedogenic carbonate found in vertic claystone palaeosols in the devonian catskill formation in central pennsylvania preserve a record of the physical and chemical environment of carbonate precipitation the carbonate is characterized by three distinct petrographic generations pedogenic rhizoliths and nodules are the earliest precipitated generation and typically consist of dull red brown luminescent micrite clear equant calcite spar cement fills voids in the centres of rhizoliths as well as circumgranular cracks and septarian voids in nodules early spar cements are nonluminescent to dull luminescent whereas later spar cements exhibit bright yellow orange luminescence late stage pedogenic fractures are always occluded with very bright yellow orange luminescent spar cements the incorporation of progressively higher concentrations of mn up to 34 000 ppm into successively younger calcite spar cements without concomitant increases in fe suggests carbonate precipitation from an evolving meteoric water in which mn2 became increasingly mobile over time the increased mobility is possibly due to decreasing eh resulting from oxidation of organic matter after rapid soil burial on the floodplain the amount of fe2 available for incorporation into calcite was limited because most iron was immobile having been earlier oxidized and bound to the palaeosol clay matrix as a poorly crystallized ferric oxide or oxyhydroxide mineral carbon isotope compositions of pedogenic carbonate correlate with the inferred depth of carbonate precipitation rhizoliths preserved below the lowest stratigraphic occurrences of pedogenic slickensides are consistently depleted in 3c relative to nodules which formed stratigraphically higher within the zone of active soil shrink and swell processes nodular carbonate precipitated in proximity to deep cracks in the soil is enriched due to increased gas exchange with isotopically heavy atmospheric c02 accordingly rhizolith compositions will most accurately estimate palaeoatmospheric levels of c02 the use of nodule compositions may result in overestimation of pco by as much as 30

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

paleoclimate reconstruction of the prince creek formation arctic alaska during maastrichtian global warming abstract the upper cretaceous maastrichtian prince creek formation of arctic alaska 82 85 n paleolatitude preserves successions of alluvial paleosols that are used to estimate mean annual precipitation map mean annual temperature mat and meteoric water oxygen isotope composition for the prince creek formation the highest map estimates range between 1000 and 3900 mm yr and the lowest range between 350 and 1200 mm yr the precipitation variability derived from stable carbon isotope analysis occurs on a time scale of 104 years map values agree with previous interpretations from fossil pollen pedological features soil types vegetation composition sedimentological indicators and clamp estimates that suggest high precipitation amounts and high humidity despite the considerable uncertainty with mat proxies our values are consistent with warm month mean temperatures obtained previously from paleobotanical data the 18o of smectite from bentonite beds clusters around 5 0 vsmow the 18o of meteoric water calculated from bentonitic smectite is 23 vsmow assuming a mean annual temperature of 6 3 c which is slightly more 18o depleted than meteoric water calculated from pedogenic siderite in stratigraphically younger beds closer to the brooks range chronostratigraphic correlation with the lower cantwell formation denali national park alaska 64 n paleolatitude suggests higher precipitation rates and highly 18o depleted precipitation in the late cretaceous paleo arctic compared to central alaska these data are consistent with previous studies that suggest a warmer and moister greenhouse earth and an intensified hydrological cycle that enhanced latent heat transport resulting in increased rainout effects

magnetostratigraphy of the canadian continental drilling program cretaceous tertiary k t boundary project core holes western canada the canadian continental drilling program ccdp cretaceous tertiary boundary project cored three holes to 160 188 and 170 m in southern alberta saskatchewan and manitoba respectively to int

geologic constraints on the glacial amplification of phanerozoic climate sensitivity the long term carbon cycle depends on many feedbacks silicate weathering consumes atmospheric co2 but is also enhanced by the increased temperatures brought about by this important greenhouse gas the long term sensitivity t2x of climate to co2 doubling modulates the strength of this negative feedback we update the model experiment of royer and others 2007 by estimating an empirical probability density function pdf of t2x for the phanerozoic by using an improved geocarbsulf carbon cycle model to predict a larger recalibrated set of proxy co2 measurements from the present day to 420 ma the new geocarbsulf parameterizes the rapid weathering of volcanic rocks relative to plutonic rocks updates to the carbon cycle model and the proxy co2 data set induce opposing model responses as a result our experiment maintains an agreement with t2x estimates based on numerical climate models and late cenozoic paleoclimate for a climate sensitivity t2x that is uniform throughout the phanerozoic the most probable value is 3 to 4 c geocarbsulf fits the proxy co2 data equally well and with far more parameter choices if t2x is amplified by at least a factor of two during the glacial intervals of the paleozoic 260 340 ma and cenozoic 0 40 ma relative to non glacial intervals of earth history for glacial amplification of two the empirical pdfs for glacial climate sensitivity predict t2x g 2 0 c with 99 percent probability t2x g 3 4 c with 95 percent probability and t2x g 4 4 c with 90 percent probability the most probable values are t2x g 6 to 8 c this result supports the notion that the response of earth9s present day surface temperature will be amplified by the millennial and longer term waxing and waning of ice sheets

north american nonmarine climates and vegetation during the late cretaceous abstract analyses of physiognomy of late cretaceous leaf assemblages and of structural adaptations of late cretaceous dicotyledonous woods indicate that megathermal vegetation was an open canopy broad leaved evergreen woodland that existed under low to moderate amounts of rainfall evenly distributed through the year with a moderate increase at about 40 45 n many dicotyledons were probably large massive trees but the tallest trees were evergreen conifers megathermal climate extended up to paleolatitude 45 50 n mesothermal vegetation was at least partially an open broad leaved evergreen woodland perhaps a mosaic of woodland and forest but the evapotranspirational stress was less than in megathermal climate some dicotyledons were large trees but most were shrubs or small trees evergreen conifers were the major tree element some mild seasonality is evidenced in mesothermal woods precipitational levels probably varied markedly from year to year northward of approximately paleolatitude 65 n evergreen vegetation was replaced by predominantly deciduous vegetation this replacement is presumably related primarily to seasonality of light the southern part of the deciduous vegetation probably existed under mesothermal climate comparisons to leaf and wood assemblages from other continents are generally consistent with the vegetational climatic patterns suggested from north american data limited data from equatorial regions suggest low rainfall late cretaceous climates except probably those of the cenomanian had only moderate change through time temperatures generally appear to have warmed into the santonian cooled slightly into the campanian and more markedly into the maastrichtian and then returned to santonian values by the late maastrichtian the early eocene was probably warmer than any period of the late cretaceous latitudinal temperature gradients were lower than at present for the campanian and maastrichtian a gradient of about 0 3 c 1 latitude is inferred equability was high a mean annual range of temperature of about 8 c is inferred for paleolatitude 51 56 n during the campanian most late cretaceous plants evolved in a climate characterized by absence of freezing and low to moderate amounts of precipitation a brief low temperature excursion and a major long lasting increase in precipitation occurred at the cretaceous tertiary boundary in megathermal climates these events selected for plants that could exist in rainforest environments in mesothermal climates deciduousness and contamitant structural adaptations were selected the events at the cretaceous tertiary boundary had a major and long lasting impact on the evolution of land plants and their ecosystems low precipitation at low to middle late cretaceous latitudes is suggested to be the result of high levels of atmospheric co2 which in turn are probably related to inability of warm saline oceans to store large amounts of carbon conditions appear to have rapidly changed at the cretaceous tertiary boundary when oceanic circulation and stratification may have been fundamentally altered after the boundary the oceans were apparently able to store much greater amounts of carbon and the oceans withdrew large amounts of co2 from the atmosphere in turn more precipitation fell at low to middle latitudes the resulting high biomass vegetation formed a second major carbon reservoir to keep atmospheric co2 low relative to the late cretaceous changes in oceanic and atmospheric circulation probably resulted from some factor external to the ocean atmosphere system

tectonic stratigraphic and sedimentologic significance of a regional discontinuity in the upper judith river group belly river wedge of southern alberta saskatchewan and northern montana the lithostratigraphic interval between the taber and lethbridge coal zones in the upper portion of the nonmarine judith river group of southeastern alberta is divisible into two lithostratigraphic units separated by a regionally extensive and diachronous discontinuity the lower unit referred to here as the oldman formation is characterized by very fine grained to fine grained sandstones that contain fewer than 2 volcanic rock fragments sandstone bodies with numerous sets of horizontally stratified sandstone showing little or no evidence of lateral accretion siliceous paleosols ganisters and a relatively high gamma ray signal in the upper half of the formation the oldman formation comprises deposits of a low sinuosity perhaps ephemeral fluvial system that originated in the southern cordillera of canada and northern montana and flowed northeastward perpendicular to the axis of the alberta basin the upper unit is assigned to a new formation the dinosaur park formation and is characterized by

modern soil system constraints on reconstructing deep time atmospheric co2 abstract paleosol carbonate based estimates of paleo atmospheric co 2 play a prominent role in constraining radiative forcing and climate sensitivity in the deep time large uncertainty in paleo co 2 estimates made using the paleosol carbonate co 2 barometer however arises primarily from their sensitivity to soil respired co 2 s z this parameter is poorly constrained due to a paucity of soil co 2 measurements during carbonate formation in modern soils and a lack of widely applicable proxies of paleo soil co 2 here the 13 c values of carbonate and soil organic matter som pairs from 130 holocene soils are applied to a two component co 2 mixing equation to define soil order specific ranges of soil co 2 applicable for constraining s z in their corresponding paleosol analogs equilibrium carbonate som pairs characterized by 13 c carb som values of 12 2 15 8 define a mean effective fractionation of 14 1 and overall inferred total soil co 2 contents during calcite formation of s z during calcite formation is 1500 2000 ppmv range of 500 2500 ppmv overall higher values 2000 5000 ppmv are indicated by the subset of these soils characterized by higher moisture content and productivity near atmospheric levels 400 200 ppmv of estimated s z are indicated by immature soils recording their low soil productivity vertisols define the largest range in total soil co 2 25 000 ppmv reflecting their seasonally driven dynamic hydrochemistry a s z range of 1000 10 000 ppmv is suggested for paleo vertisols for which calcite precipitation can be constrained to have occurred in an open system with two component co 2 mixing with a best estimate of 2000 ppmv 1000 ppmv appropriate for paleo vertisols for which evidence of protracted water saturation is lacking mollisol pairs define a best estimate of s z of 2500 ppmv range of 600 4000 ppmv for late cretaceous and cenozoic analogs non equilibrium pairs with 13 c values 16 make up 51 of the dataset lending support to the hypothesis that pedogenic carbonate precipitation occurs during periods of low productivity in a soil atmosphere with a large component of atmospheric co 2 predictable scaling between estimated soil co 2 and the difference in 13 c between measured pedogenic carbonate and that predicted to have formed from soil respired co 2 inferred from measured som can be used to further constrain appropriate ranges of s z for reconstruction of paleo atmospheric p co 2 soil co 2 estimates are poorly correlated to mean annual precipitation likely reflecting that for carbonate bearing soils where moisture limits co 2 production total soil co 2 is most strongly influenced by actual evapotranspiration

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

palaeoclimate and palaeovegetation in central india during the upper cretaceous based on stable isotope composition of the palaeosol carbonates abstract the oxygen isotope compositions of the pedogenic carbonates formed on the sediments of the lameta formation of central india during the upper cretaceous range from 6 7 to 8 9 estimates of the oxygen isotope composition of the soil water in equilibrium with the carbonates suggest average meteoric water composition of 8 this value is considerably lighter compared to the modern precipitation in central india 3 the lighter oxygen isotope composition can be explained in terms of cumulative effects of highly seasonal monsoon like climatic regime in a rain shadow zone and a more pronounced continental effect due to a bigger size of cretaceous india the carbon isotopic compositions of the lameta carbonates range from 7 1 to 10 7 with an average of 9 1 suggesting pedogenesis in soils dominated by c 3 type of vegetation the estimated average composition of the vegetation is about 3 enriched compared to the modern day c 3 vegetation this is probably due to atmospheric influence contributing about 15 of the total co 2 in the soil an analysis of this contribution using the model of cerling 1991 indicates that the partial pressure of co 2 in the late cretaceous atmosphere was 800 12 000 ppmv

late pliocene to early pleistocene changes in the north atlantic current and suborbital scale sea surface temperature variability the strength and latitudinal position of the north atlantic current nac determines the position of the arctic front and heat transport to the high northern latitudes with potentially important consequences for northern hemisphere glaciation a southward shift in the nac and reduced poleward heat transport is hypothesized to have triggered the last major climate transition in earth s history late pliocene intensification of northern hemisphere glaciation inhg in turn inhg is hypothesized to have led to the amplification of climate variability on suborbital time scales to date however only a handful of adequately resolved records are available to test these two hypotheses here we present a new late pliocene to earliest pleistocene record from integrated ocean drilling program site u1313 north atlantic 41 n 2 9 to 2 4 ma we use mg ca derived paleotemperature records in planktic foraminiferal calcite to investigate changes in summer sea surface temperatures sst on orbital and suborbital time scales our results call into question the suggestion that significant weakening and or southward shift of the nac served as a trigger for northern hemisphere cooling and intensified continental ice sheet growth across inhg in contrast to the late pleistocene during inhg we find that the position of the nac and arctic front probably lay well to the north of site u1313 and that the amplitude of suborbital sst variability did not change on glacial interglacial time scales conservative estimates of late pliocene to earliest pleistocene interglacial summer ssts in our record are up to 3 c warmer than present while glacial summer ssts are only 2 c to 3 c cooler in fact our interglacial summer ssts are remarkably similar to those of the mid pliocene our findings indicate that inhg must have involved amplifying feedback mechanisms that are tightly coupled to ice sheet growth but that these processes were insufficiently developed by the late pliocene earliest pleistocene to have triggered large amplitude changes in suborbital climate in the midlatitude north atlantic

concentration of carbon dioxide in the late cretaceous atmosphere stable carbon isotope data from late cretaceous maastrichtian palaeosols in india are used to estimate the concentration of carbon dioxide in the late cretaceous atmosphere we show that the maastrichtian atmosphere is unlikely to have contained more than about 1300 ppm by volume of co 2 this value agrees with an independently modeled value of co 2 in the late cretaceous atmosphere a low concentration of the greenhouse gas carbon dioxide in the maastrichtian atmosphere relative to concentrations in the earlier cretaceous is consistent with palaeotemperature information from terrestrial plant and marine fossils which suggest that the global climate cooled toward the end of the cretaceous period

u pb zircon age constraints on the earliest eruptions of the deccan large igneous province malwa plateau india abstract climate instability driven by emission of volatiles during emplacement of large igneous provinces lips is frequently invoked as a potential cause of mass extinctions however documenting this process in the geologic record requires a holistic understanding of eruption rates the location of eruptive centers and potential sources of climate changing volatiles we present new chemical abrasion isotope dilution thermal ionization mass spectrometry ca id tims u pb zircon geochronology from malwa plateau basalts on the northern margin of the deccan lip india these basalts have been previously interpreted as either an extension of the province s main volcanic stratigraphy or as an independent eruptive center active up to millions of years prior to the main eruptive phase our data instead demonstrate that the lower malwa plateau basalts are temporally correlative with the first pulse of deccan volcanism and provide new constraints on its initiation and duration paleomagnetic data further indicate that upper malwa plateau basalts may be age equivalent to the second third and fourth pulses of deccan volcanism the relative thicknesses of age equivalent packages of basalt are consistent with eruption of the deccan lip from a southward migrating eruptive center the first eruptive pulse is coeval with a 200 kyr late maastrichtian warming event preserved globally in contemporaneous stratigraphic sections we propose that the first pulse of deccan magmatism was more voluminous in the north where it erupted through organic rich sedimentary rocks of the narmada tapti rift basin thermal metamorphism of these sediments could have been a source of sufficient co2 to drive the late maastrichtian warming event which if true would reconcile the apparent dampened warming signals associated with later deccan eruptive pulses

a pedotype approach to latest cretaceous and earliest tertiary paleosols in eastern montana a pedotype approach to the study of paleosols emphasizes individual profiles it is an alternative approach to the study of geosols which are laterally extensive suites of paleosols or pedofacies which are pedogenically distinctive sedimentary facies this is the first pedotype study of paleosols across the cretaceous tertiary boundary in eastern montana pedotypes allow assessment of sedimentation and fossilization the sequence of paleosols across the cretaceous tertiary boundary at bug creek is one of high temporal resolution because most available geological time can be accounted for by differing degree of development inferred for each pedotype paleosols at bug creek include pedotypes that preserve plant fossils well but were unfavorable for preservation of fossil vertebrates pedotypes also allow reassessment of ecosystem change despite indications of catastrophe at the cretaceous tertiary boundary the array of paleocene and cretaceous pedotypes are not strikingly different the upper cretaceous hell creek formation includes pedotypes interpreted as gleyed alfisols inceptisols and entisols probably formed under seasonally water logged forest and mean annual rainfall of the order of 900 1200 mm most paleosols of the lower paleocene tullock formation were histosols but some can be interpreted as gleyed inceptisols and entisols probably formed under bald cypress swamps in a humid climate with 1200 mm mean annual rainfall broadly comparable pedotypes were present before and after the cretaceous tertiary boundary although paleocene flood plain forest lived in paleosols chemically a little more oligotrophic than cretaceous paleosols this modest difference supports the idea that change to coaly facies in the earliest paleocene was a local shift in sedimentary environment such local changes do not begin to account for profound disruption in specific composition of plant and animal communities at the cretaceous tertiary boundary in eastern montana

climate change during the last 150 million years reconstruction from a carbon cycle model variations of the atmospheric co2 level and the global mean surface temperature during the last 150 ma are reconstructed by using a carbon cycle model with high resolution input data in this model the organic carbon budget and the co2 degassing from the mantle both of which would characterize the carbon cycle during the cretaceous are considered and the silicate weathering process is formulated consistently with an abrupt increase in the marine strontium isotope record for the last 40 ma the second order variations of the atmospheric co2 level and the global mean surface temperature in addition to the first order cooling trend are obtained by using high resolution data of carbon isotopic composition of marine limestone seafloor spreading rate and production rate of oceanic plateau basalt the results obtained from this model are in good agreement with the previous estimates of palaeo co2 level and palaeoclimate inferred from geological biogeochemical and palaeontological models and records the system analyses of the carbon cycle model to understand the cause of the climate change show that the dominant controlling factors for the first order cooling trend of climate change during the last 150 ma are tectonic forcing such as decrease in volcanic activity and the formation and uplift of the himalayas and the tibetan plateau and to a lesser extent biological forcing such as the increase in the soil biological activity the mid cretaceous was very warm because of the high co2 level 4 5 pal maintained by the enhanced co2 degassing rate due to the increased mantle plume activities and seafloor spreading rates at that time although the enhanced organic carbon burial would have a tendency to decrease the co2 level effectively at that period the variation of organic carbon burial rate may have been responsible for the second order climate change during the last 150 ma

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

deccan volcanism caused coupled pco2 and terrestrial temperature rises and pre impact extinctions in northern china evaluating the terrestrial climate record provides a critical test of the roles of chicxulub impact and deccan traps volcanism during the cretaceous paleogene k pg mass extinction most evidence came from marine records but our new clumped isotopes data from paleosol carbonates in the songliao basin provide a terrestrial climate history from northern china this reveals there was a pre impact warming caused by the onset of deccan traps volcanism whereas the following short term cooling then another warming episode were likely caused by chicxulub impact and post boundary volcanism our study suggests that the pco levels were probably the main control on the latest cretaceous cooling and the climatic fluctuations across the k pg boundary interval in northern china in the songliao basin the pre impact deccan traps volcanism links to losses of half of the lacustrine algae species charophytes and almost all of the lacustrine ostracodes this suggests that the deccan traps volcanism had already destabilized the ecosystem and caused extinctions prior to the chicxulub impact

an early pleistocene atmospheric co2 record based on pedogenic carbonate from the chinese loess deposits abstract the tight coupling between temperature and atmospheric co2 is shown by ice core records for the past 0 8 million years myr however the modern atmospheric partial pressure of co2 pco2 has exceeded previous interglacial pco2 levels over the past 0 8 myr suggesting that the earlier part of the pleistocene and pliocene might be a better analog of today s radiative forcing of co2 the early pleistocene experienced a constant cooling characterized by the intensification of northern hemisphere glaciations existing pco2 records developed from marine organic matter and inorganic precipitates however disagree with the trends and absolute values of co2 over this time interval here we present quantitative interglacial pco2 estimates from 2 6 0 9 myr using the stable carbon isotopic compositions of pedogenic carbonates collected from the chinese loess plateau clp our pco2 records provide the first documentation of pco2 from continental sedimentary deposits over the early pleistocene the successive decrease of our pco2 records is broadly consistent with the increase in deep sea o 18 and the overall decline of sea surface temperature sst at this time but in contrast with the increasing peak interglacial pco2 recorded in ice cores for the last 0 8 myr

maastrichtian paleocene foreland basin stratigraphies western canada a reciprocal sequence architecture palynological and magnetostratigraphic chronostratigraphic correlations of lower maastrichtian to paleocene strata along an east west western canada basin transect allow for the recognition of a reciprocal sequence architecture in nonmarine strata reference sections include three canadian continental drilling program cretaceous tertiary boundary project core holes and outcrops in alberta southern saskatchewan and north central montana the spatial and temporal position of the third order sequences provides evidence for the correlation of proximal sector regional disconformities and sedimentary wedges with distal sector sedimentary wedges and regional disconformities respectively the boundary between the two sectors is represented by a hingeline which separates the foreland basin syncline from the peripheral bulge the stratigraphies defined by reciprocal third order sequences are complicated by fourth order boundaries developed within proximal sedimentary wedges and with no correlative distal strata these results support tectonic control on foreland basin sedimentation a model for interpreting the various types of sequences in terms of foreland basin evolution vertical tectonics and orogenic cycles is provided it is argued that nonmarine sequence boundaries times of maximum uplift in the foreland region may be expressed as disconformities incised valleys top of mature paleosol levels or base of fluvial channels whereas nonmarine equivalents of marine maximum flooding surfaces times of maximum basinal subsidence may be indicated by extensive coal seams and or lacustrine sediments resume les correlations palynologiques magnetostratigraphiques et chronostratigraphiques des strates echelonnees du maastrichtien inferieur au paleocene le long du transect est ouest du bassin de la cordillere occidentale au canada permettent la reconnaissance d une ordonnance architecturale de sequences reciproques dans les strates continentales les coupes de reference incluent trois trous de forage carottes du canadian continental drilling program cretaceous tertiary boundary project et des affleurements localises en alberta dans le sud de la saskatchewan et dans le centre nord du montana la position spatiale et temporelle des sequences de troisieme ordre plaide pour la mise en correlation des discordances regionales et des depots sedimentaires en coin dans le secteur proximal avec les depots sedimentaires en coin et les discordances regionales dans le secteur distal respectivement une ligne de jonction represente la limite entre les deux secteurs qui separe le bassin d avant pays en forme de cuvette du bombement peripherique les stratigraphies definies par les sequences de troisieme ordre reciproques sont embrouillees par les limites de quatrieme ordre developpees au sein des depots sedimentaires en coin proximaux sans la presence de strates distales correlatives ces resultats appuient la these d un controle tectonique sur le bassin sedimentaire d avant pays on presente ici un modele interpretant les divers types de sequences en termes d evolution d un bassin d avant pays de tectonique verticale et de cycles orogeniques nous tentons de demontrer que les discordances les vallees entaillees les horizons sommitaux de paleosols matures ou la base des chenaux fluviaux peuvent aider a definir les limites des sequences continentales periodes de soulevement maximum dans la region de l avant pays tandis que les couches de charbon etendues et ou les sediments lacustres representent plutot les equivalents continentaux des aires d inondation maximale periodes de subsidence maximum du bassin traduit par la redaction catuneanu and sweet 703

sedimentological and palynological evidence of regional climatic changes in the campanian to paleocene sediments of the rocky mountain foothills canada abstract evidence of paleoclimatic variations in the upper campanian to lower paleocene post wapiabi sequence of strata is visible both laterally between the central and southern foothills and vertically in the stratigraphic record these differences are expressed by the distribution of climatically sensitive sediments i e coal and caliche and associated palynological assemblages within floodplain facies as well as by changes in the style of fluvial channels the interpretation of a semi arid environment for mature caliche paleosols is supported by the impoverished character of the associated palynological assemblages both in terms of diversity and the number of specimens recovered and by the conspicuous presence of classopollis the lateral extent of the semiarid floodplain facies and associated broad and mobile channel deposits is limited to the southern part of the basin no signs of a caliche facies have been found in the post wapiabi strata of the central foothills instead some of the floodplain deposits associated with meandering streams in this part of the basin contain numerous thick coal bearing intervals the relative climatic differences between the more humid central part and the drier southern part of the basin prevailed throughout the entire post wapiabi interval as this cannot be satisfactorily explained by the position of the sea shore or by orographic influences alone there was probably another external factor this could have been the pattern of atmospheric circulation such as that responsible for the present day climatic differences existing between the southern and central foothills semiarid floodplain facies occur at two levels in the stratigraphic column of the southern foothills in the late campanian belly river formation and in the upper maastrichtian to lower paleocene willow creek formation they correspond to regressive episodes of the epicontinental seaway intervening between these semiarid floodplain facies are the marine shales of the bearpaw formation and both overlying and underlying them thin coal beds these represent recurrent periods of swamp growth and peat accumulation in back barrier environments lagoon fill and supratidal marsh respectively because of the proximity of these swamps to the sea shore it is difficult to assess the influence of climate on the relative humidity of these settings on strictly sedimentological grounds however the terrestrial components of the palynological assemblages recovered from these marginal marine settings and correlative lacustrine sediments containing fresh water stromatolites but no coal in the central foothills are in sharp contrast with the impoverished assemblages known from the caliche facies the former are prolific diverse and contain a number of triprojectate pollen species which indicate a relatively humid climate during the latest campanian time

atmospheric pco2 perturbations associated with the central atlantic magmatic province the effects of a large igneous province on the concentration of atmospheric carbon dioxide pco2 are mostly unknown in this study we estimate pco2 from stable isotopic values of pedogenic carbonates interbedded with volcanics of the central atlantic magmatic province camp in the newark basin eastern north america we find pre camp pco2 values of 2000 parts per million ppm increasing to 4400 ppm immediately after the first volcanic unit followed by a steady decrease toward pre eruptive levels over the subsequent 300 thousand years a pattern that is repeated after the second and third flow units we interpret each pco2 increase as a direct response to magmatic activity primary outgassing or contact metamorphism the systematic decreases in pco2 after each magmatic episode probably reflect consumption of atmospheric co2 by weathering of silicates stimulated by fresh camp volcanics

dinosaur eggshell isotope geochemistry as tools of palaeoenvironmental reconstruction for the upper cretaceous from the tremp formation southern pyrenees abstract the isotopic compositions 13 c and 18 o of dinosaur eggshells have been widely used in palaeoenvironmental studies although the geochemical signatures of eggshells are not usually contrasted with other proxies in this work the isotopic signatures of eggshells from a large maastrichtian succession from the tremp formation southern pyrenees spain are compared to those of carbonate pedogenic nodules occurring in the same levels the isotopic signatures of eggshells vary according to the stratigraphic unit and geographical location a group of samples from several localities corresponding to eggshells without significant diagenetic imprints has isotopic values differing from the associated nodules the late cretaceous isotopic composition record from the tremp fm is consistent that is the eggshells have distinct primary signatures preserved however the eggshells from another locality which exhibit neomorphed textures display isotopic signatures similar to the associated pedogenic carbonate which suggests a diagenetic isotopic signature and confirms alteration in the eggshells both microscopic and geochemical data suggest that an early meteoric diagenesis pedogenesis is responsible for the secondary signatures the 13 c values in the carbonate pedogenic nodules indicate a carbon isotopic composition typical of c3 plants although the slight difference in 13 c between the palaeosol carbonate of coeval successions may be due to slightly different palaeoenvironmental conditions the small discrepancy in the 13 c calculated for c3 plants from carbonate nodules and from eggshells may be because the palaeosol carbonate gives the isotopic composition of the vegetation grown at a local site whereas the 13 c from eggshells is a proxy for the ingested food in the area in which the dinosaurs lived the oxygen isotopic compositions from palaeosol carbonate nodules have been used for calculation of the air temperature and we may conclude that the mean air temperature in the studied area during the late cretaceous was approximately 21 c the use of this temperature gives rational results in the calculation of the oxygen isotopic composition of palaeosol carbonate by means of the isotopic composition of the eggshell carbonate additionally a relatively continuous isotopic record of nodules shows an overall vertical trend towards negative 13 c values and a high relative and steady 18 o content throughout the maastrichtian the k pg boundary was recorded by a negative excursion in 13 c in the carbonate nodules

paleoenvironmental conditions in the late paleogene sumatra indonesia abstract a stratified paleosol sequence exposed in an open pit mine in central sumatra provides a record of the paleoenvironmental conditions in the lower reaches of a large river system in the late paleogene latest eocene or oligocene morphological geochemical and stable isotope data suggest that the sequence represents a mosaic of local environmental conditions changing from estuarine to riverine up section weakly expressed soils formed on low lying estuary surfaces while more well expressed soils formed on higher better drained surfaces peatlands coal with clayey subsoils were along the estuary margins well expressed soils with evidence of clay translocation and chemical weathering become more common higher in the section where alluvial deposits associated with a meandering river are dominant stable carbon isotope ratios support a paleolandscape dominated by c 3 plants with input by c 4 vegetation limited to a few intervals finally whole rock geochemistry suggests moderate chemical weathering consistent with a tropical locality this multi proxy paleoenvironmental reconstruction suggests a highly productive lowland forest environment at this locality in the late paleogene and provides the first direct examination of the terrestrial environment in sumatra at this time the limited fossil record in island southeast asia during this time period is likely a result of poor bone and shell preservation in tropical forest environments combined with a general lack of systematic prospecting however our continuing work in this area has produced a relatively diverse assemblage of fossil vertebrates now including fishes amphibians turtles crocodiles and mammals as well as a growing diversity of fossil plants

modelling equable climates of the late cretaceous can new boundary conditions resolve data model discrepancies late cretaceous maastrichtian climate and vegetation is modelled using the hadcm3l fully coupled atmosphere ocean model and the triffid dynamic vegetation model we investigate data model inconsistencies in the high latitudes and continental interiors by exploring the sensitivity of modelled terrestrial climate to vegetation treatment changing atmospheric pco2 levels and the representation of arctic seaway connections we expand on previous work by using millennial scale gcm runs with dynamic vegetation to allow for improved representations of ocean heat transport and terrestrial boundary conditions incorporating realistic vegetation drives high latitude warming particularly during summer through reductions in surface albedo and induced atmosphere ocean feedbacks resulting regional warming can exceed 10 c as pco2 rises some regions cool as deciduous to evergreen change increases albedo incorporating enhanced arctic connectivity reconfigured ocean heat transport drives widespread terrestrial warming of 3 c and 5 c regionally applying sensitivities in combination significant palaeobotanical data model inconsistencies in the northern high latitudes and continental interiors remain further work is required to resolve climate and vegetation model deficiencies and improve the interpretation and geographic distribution of quantitative climate sensitive geological proxies

declining atmospheric co2 during the late middle eocene climate transition the transition from the extreme greenhouse of the early paleogene 52 ma to the present day icehouse is the most prominent change in earth s cenozoic climate history during the late middle eocene climate transition 42 38 ma which preceded the onset of long lived continental scale ice sheets there is concor dant evidence for brief pulses 1 m y in length of global warmth and ice sheet growth but few constraints on atmospheric co 2 here we estimate the concentration of atmospheric co 2 during this critical interval using stomatal indices of fossil metasequoia needles from ten levels in an exceptionally well preserved core from the giraffe kimberlite locality in northwestern canada reconstructed co 2 concentra tions are mainly between 700 to 1000 ppm but include a secular decline to 450 ppm towards the top of the investigated section because the co 2 threshold for nucleating continental ice sheets at this time was 500 to 750 ppm the co 2 decline is compatible with a rapid 10 4 yrs transition from warm largely ice free conditions to cooler climates with ice sheets these fossils provide direct evidence that high latitude deciduous forests thrived in the geological past under co 2 concentrations that will likely be reached within the 21 st century 500 1000 ppm

late cretaceous to early tertiary magnetostratigraphy of a continental sequence red deer valley alberta canada the red deer valley exposes a conformable 350 m thick late campanian to early paleocene fluvial deltaic coal bearing sequence named the edmonton group systematic sampling and paleomagnetic analysis of the dominant lithologies mudstones sandstones and shales were carried out over five sections correlated by coal seams to provide some 500 sites stratigraphic levels primary detrital remanent magnetization directions after alternating field cleaning produce a polarity reversal pattern correlatable to sea floor magnetic anomalies 29 33 the campanian maastrichtian boundary based upon the first appearance of wodehouseia and the maastrichtian paleocene cretaceous tertiary boundary based upon an ir anomaly associated with dinosaur and cretaceous palynofloral extinctions correlate closely magnetostratigraphically with the marine foraminiferal section at gubbio italy radiometric dating of bentonites has indicated the ages of these boundaries to be approximately 71 and 64 ma respectively

the influence of rock fabric in the durability of two sandstones used in the andalusian architectural heritage montoro and ronda spain abstract natural stone has been a popular and reliable building material throughout history appearing in many historic monuments and in more recent buildings research into the intrinsic properties of specific stones is important because it gives us a greater understanding of the factors that limit and act on them this can help prevent serious problems from occurring in our buildings bringing both esthetic benefits and financial savings to this end the main objective of this research has been to study the influence of the fabric and the mineral composition of two types of sandstone on their durability the first is a red continental sandstone from the buntsandstein age called molinaza roja which is quarried in montoro cordoba the second is quarried in ronda malaga and is sold under the trade name of arenisca ronda it is a light pink whitish calcarenite deposited during the late tortonian to late messinian we characterized their petrological and petrophysical properties by studying their rock fabrics porous systems and mechanical properties in order to obtain a complete vision of the behavior of their rock fabrics we also carried out two decay tests the salt crystallization and the freeze thaw tests we then measured the effects on the textures of the altered samples during and after the decay tests and we evaluated the changes in the porous system by comparing the results between intact and altered samples we found that arenisca ronda is less durable because it has a high quantity of expandable clays smectites and a high percentage of pores in the 0 1 1 m range in which the pressure produced by salt crystallization is strongest in molinaza roja the decay agents caused significant sanding due to loss of cohesion between the clasts especially during the salt crystallization test in both stones the anisotropies oriented textures have an important role in their hydric and dynamic behavior and also affect their mechanical properties especially in the compression resistance no changes in color were detected

climatic and environmental indications of carbon and oxygen isotopes from the lower cretaceous calcrete and lacustrine carbonates in southeast and northwest china abstract carbon and oxygen isotopic ratios were determined from 100 lower cretaceous samples from four carbonate bearing facies in southeast se and northwest nw china for palaeoclimatic and palaeoenvironmental analyses the samples were interpreted as sediments within sublithofacies of distal alluvial ponds sf1 open shallow lakes sf2 littoral lakes sf3 and marshes sf4 results of analyses show in se china 13c values range between 5 0 and 3 0 with a negative trend through time and 18o values are all negative 19 3 7 4 in nw china 13c values range from 4 0 to 4 0 with periodic change and 18o values range between 18 0 and 1 5 both relatively heavy values and pronounced covariances of most 13c and 18o indicate semiarid climate and domination of closed brackish lakes marshes and ponds in nw and se china during the early cretaceous of them positive 13c 0 0 to 4 0 and relatively heavy 18o 5 0 to 1 5 values suggest interruptions of arid evaporation in intermittences of the early hauterivian in sw fujian of the middle aptian in west jiuquan basin of the late aptian in sw ordos basin and of the late aptian early albian in liupanshan basin in a short interval of the early aptian the hot and humid climate occurred in local sw zhejiang by high kaolinite content and in west jiuquan basin by warm flora could be an exception particularly extremely negative 18o values mainly 19 0 9 0 indicate relatively low temperature in se fujian in the berriasian barremian in liupanshan basin in the late aptian in sw ordos basin in the late albian and in west jiuquan basin in the mid late aptian which is supposed to attribute to the presence of 2500 m 4500 m in elevation more positive values and more covariance ratios of 13c and 18o in nw china than in se china and in mainland china than in america indicate a arider climate in former than in later probably attributing to the palaeogeography in distance to sea a tentative correlation of the early cretaceous 13c value excursion of calcretes shows a good compatibility between marine oaes and terrestrial carbonate sediments and between nw china and america continents implying a global response to carbon cycle in both marine and terrestrial environments the feature suggests the potential of global correlation and application of terrestrial calcrete 13c excursions in pre cenozoic