salt inclusions in polar ice core location and chemical form of water soluble impurities abstract ice cores retrieved from ice sheets provide the most detailed records of climate over the past several hundred thousand years for example water soluble impurities have been used as proxies for atmospheric chemistry however numerical models warned that the distributions of the trace constituents are significantly altered by rapid diffusion through liquid veins along triple junctions during ice sheet flow although these calculations assumed that the trace constituents are preferentially confined to grain boundaries and form a vein network this assumption has not been confirmed experimentally using micro raman spectroscopy here we show that most of the soluble impurities are confined as salt inclusions within grains these inclusions are mainly composed of the sulfate salts na 2 so 4 10h 2 o mgso 4 12h 2 o and caso 4 2h 2 o we also found that methane sulfonate salts and other complex salts exist only in the glacial period ice our findings imply that these salts form within 185 m of the ice surface and then preserve their composition as the ice is pushed to greater depths this means that depth profiles of the trace constituents should be preserved in deep ice cores as reliable proxies for past climate

lateglacial climate development in nw romania comparative results from three quantitative pollen based methods abstract this paper provides quantitative reconstructions of the lateglacial changes in four climate parameters from two fine resolution pollen profiles in the gutaiului mountains nw romania climate estimates are based on two modern analogue techniques with and without considering vegetation types and weighted averaging partial least squares regression wa pls giving evidence for several climatic fluctuations during the period from 14 700 to 11 500 cal yr bp the comparative results of the two modern analogue techniques show consistent trends of climate changes that are also coherent at both sites but these results appear to largely disagree compared with climate reconstruction provided by wa pls the modern analogue techniques revealed four intervals with low temperatures prior to 14 700 cal yr bp between 13 950 and 13 800 13 400 and 13 200 and 12 700 and 11 700 cal yr bp the temperature declines were more pronounced for winter than for summer suggesting an intensification of seasonality which together with a drop in precipitation indicates an increase in continentality the younger dryas is the most pronounced cooling phase with winter temperatures 14 16 c colder than modern conditions annual and summer temperatures 2 5 c and 2 c respectively below present ones precipitation was 400 500 mm half that of present during the bolling and allerod summer temperatures were close to modern values 13 to 17 c whereas winter 6 to 12 c and annual temperatures 0 5 to 6 c as well as precipitation were 550 to 700 mm lower indicating more continental conditions compared to the present day climate

upheavals during the late maastrichtian volcanism climate and faunal events preceding the end cretaceous mass extinction abstract the late maastrichtian was a time of major climate evolution and extinction extremes rapid climate warming of 2 3 c in intermediate waters between 69 5 and 68 ma top c31r to base c30n accompanied maximum evolutionary diversification 43 increase zone cf5 to low cf4 in planktic foraminiferal history followed immediately by a cluster of extinctions during the last 250 ky of the maastrichtian c29r zones cf2 cf1 rapid warming of 4 c in intermediate waters and 8 c on land resulted in high stress environments ending in the mass extinction the end cretaceous mass extinction is recorded in sediments between massive deccan lava flows in india and attributed to so 2 and co 2 outgassing leading to ocean acidification the early late maastrichtian climate and faunal upheavals are not well known here we document the faunal similarities of both events from the indian ocean through the tethys and gulf of mexico results show that both extreme warm events are marked by high stress environments characterized by decreased abundance and diversity of large specialized species and dwarfing high abundance of low oxygen tolerant species and disaster opportunist surface dweller guembelitria blooms the similarity in faunal response with the deccan warming of c29r cf2 cf1 suggests that volcanism was also responsible for the warming and faunal upheaval of the early late maastrichtian major volcanic activity at this time included the onset of deccan eruptions and ninetyeast ridge volcanism the role of the chicxulub impact appears to have been a contributing rather than causal factor in the mass extinction

methodology of the last climatic cycle reconstruction in france from pollen data abstract a numerical method has been devised to reconstruct the climate of the last climatic cycle from pollen data reliable annual reconstructions have been published recently for the two french long sequences of la grande pile and les echets covering the last 140 millennia this paper gives more details on the method used it proposes new reconstructions based on an extended modern pollen data base these reconstructions are consistent with the previous ones especially detailed information is obtained on the seasonal characteristics of climate computations of gcm on the climate variations from 125 kyr to 115 kyr b p are confirmed for western europe the insolation variations have induced at that time a decrease of seasonality accompanied by an increased cyclonic activity in winter this has been the beginning of the first ice growth after the last interglacial other glacier growth phases are detected at the end of substage 5c and particularly at the end of substage 5a

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

robust multi proxy data integration using late cretaceous paleotemperature records as a case study abstract in paleoclimate studies multiple temperature records are often compared and combined to evaluate temperature trends yet no standardized approach for integrating proxy derived paleotemperature records exists in addition paleotemperature data are often reported without uncertainty estimates prediction errors and raw data are not always available this complicates the quantification of for example temperature trends and the magnitude of warming events here we propose a robust quantitative approach for multi proxy analysis in paleoclimate studies to demonstrate this we study the latest maastrichtian warming event lmwe in the odp 174ax bass river core new jersey and integrate five independent paleotemperature proxies covering the last million years of the cretaceous our integrated temperature reconstruction suggests that after a climatically stable period a latest cretaceous warming of 3 9 1 1 c occurred between 450 and 100 kyr before the k pg boundary the error on this reconstructed temperature should be considered the absolute minimum error as poorly constrained or unknown uncertainties cannot be fully propagated the warming event was followed by a gradual cooling to pre warming conditions towards the end of the cretaceous furthermore the record suggests multiple warming pulses during the lmwe the results of this integrated approach are consistent with other latest cretaceous temperature records suggesting that the trend described here represents a global signal

inferring geothermal heat flux from an ice borehole temperature profile at law dome east antarctica geothermal heat flux ghf is an important control on the dynamics of antarctica s ice sheet because it controls basal melt and internal deformation however it is hard to estimate because of a lack of in situ measurements estimating ghf from ice borehole temperature profiles is possible by combining a heat transfer equation and the physical properties of the ice sheet in a numerical model in this study we truncate ice borehole temperature profiles to determine the minimum ratio of temperature profile depth to ice sheet thickness required to produce acceptable ghf estimations for law dome a temperature profile that is within 60 of the local ice thickness is sufficient for an estimation that is within approximately one median absolute deviation of the whole profile ghf estimation this result is compared with the temperature profiles at dome fuji and the west antarctic ice sheet divide which require a temperature profile that is 80 and more than 91 of the ice thickness respectively for comparable accuracy in deriving ghf median estimations from truncated temperature profiles it is possible to discriminate between available ghf models this is valuable for assessing and constraining future ghf models

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

astronomical calibration of the danian stage early paleocene revisited settling chronologies of sedimentary records across the atlantic and pacific oceans abstract astronomical tuning of sedimentary records to precise orbital solutions has led to unprecedented resolution in the geological time scale however the construction of a consistent astronomical time scale for the paleocene is controversial due to uncertainties in the recognition of the exact number of 405 kyr eccentricity cycles and accurate correlation between key records here we present a new danian integrated stratigraphic framework using the land based zumaia and sopelana hemipelagic sections from the basque basin and deep sea records drilled during ocean drilling program odp legs 198 shatsky rise north pacific and 208 walvis ridge south atlantic that solves previous discrepancies the new coherent stratigraphy utilises composite images from odp cores a new whole rock 13c isotope record at zumaia and new magnetostratigraphic data from sopelana we consistently observe 11 405 kyr eccentricity cycles in all studied danian successions we achieve a robust correlation of bioevents and stable isotope events between all studied sections at the 100 kyr short eccentricity level a prerequisite for paleoclimatic interpretations comparison with and subsequent tuning of the records to the latest orbital solution la2011 provides astronomically calibrated ages of 66 022 0 040 ma and 61 607 0 040 ma for the cretaceous paleogene k pg and danian selandian d s boundaries respectively low sedimentation rates appear common in all records in the mid danian interval including conspicuous condensed intervals in the oceanic records that in the past have hampered the proper identification of cycles the comprehensive interbasinal approach applied here reveals pitfalls in time scale construction filtering techniques in particular and indicates that some caution and scrutiny has to be applied when building orbital chronologies finally the zumaia section already hosting the selandian global boundary stratotype section and point gssp could serve as the global danian unit stratotype in the future

abrupt changes of temperature and water chemistry in the late pleistocene and early holocene black sea new mg ca sr ca and published stable oxygen isotope and 87sr 86sr data obtained on ostracods from gravity cores located on the northwestern black sea slope were used to infer changes in the black sea hydrology and water chemistry for the period between 30 to 8 ka b p calibrated radiocarbon years the period prior to 16 5 ka b p was characterized by stable conditions in all records until a distinct drop in 18o values combined with a sharp increase in 87sr 86sr occurred between 16 5 and 14 8 ka b p this event is attributed to an increased runoff from the northern drainage area of the black sea between heinrich event 1 and the onset of the bolling warm period while the mg ca and sr ca records remained rather unaffected by this inflow they show an abrupt rise with the onset of the bolling allerod warm period this rise was caused by calcite precipitation in the surface water which led to a sudden increase of the sr ca and mg ca ratios of the black sea water the stable oxygen isotopes also start to increase around 15 ka b p although in a more gradual manner due to isotopically enriched meteoric precipitation while sr ca remains constant during the following interval of the younger dryas cold period a decrease in the mg ca ratio implies that the intermediate water masses of the black sea temporarily cooled by 1 2 c during the younger dryas the 87sr 86sr values drop after the cessation of the water inflow at 15 ka b p to a lower level until the younger dryas where they reach values similar to those observed during the last glacial maximum this might point to a potential outflow to the mediterranean sea via the sea of marmara during this period the inflow of mediterranean water started around 9 3 ka b p which is clearly detectable in the abruptly increasing mg ca sr ca and 87sr 86sr values the accompanying increase in the 18o record is less pronounced and would fit to an inflow lasting 100 a

forty seven new subglacial lakes in the 0 110 e sector of east antarctica during the summer field seasons of 1987 91 studies of central east antarctica by airborne radio echo sounding commenced this scientific work continued in the 1990s in the vostok subglacial lake area and along the traverse route from mirny and led to the discovery of 16 new subglacial water cavities in the areas of domes fuji and argus and the prince charles mountains twenty nine subglacial water cavities were revealed in the area near vostok along with a feature we believe to be a subglacial river two subglacial lakes were discovered along the mirny vostok traverse route these are located 50 km north of komsomolskaya station and under pionerskaya station we find high geothermal heat flux in the vicinity of the largest of the subglacial lakes and suggest this may be due to their location over deep faults where additional mantle heat is available

stable climate in india during deccan volcanism suggests limited influence on k pg extinction abstract large igneous provinces lips have been temporally correlated to mass extinctions throughout the phanerozoic including the emplacement of the deccan volcanic province dvp 66 3 65 6 ma in western and central india which has been invoked as either a cause or exacerbating factor in the cretaceous paleogene k pg extinction however relatively little is known about local paleoclimatic and paleoenvironmental responses to volcanism to investigate the dvp s role as a driver of local environmental change and to provide climatic background for known ecological shifts new inter basaltic paleosol profiles at the eastern edge of the dvp are used in conjunction with profiles from the literature to reconstruct paleoclimate and terrestrial environments before and after the k pg these profiles provide a novel opportunity to study the sediments within basalt flows before during and after a mass extinction event and in the midst of a lip emplacement event paleoclimate proxies and the floral humidity province proxy reflect little long term change in either climate or environment across the k pg with stable precipitation values and temperatures accompanied by a constant forest signal these interpretations are corroborated by macrofloral records and sedimentology from india which suggest some environmental turnover but generally support a forested fluvio lacustrine environment throughout the duration of volcanism our results support the possibility of rapid recovery times for terrestrial ecosystems during volcanism and suggest that while dvp eruptions may have exacerbated long term environmental perturbation the emplacement of the dvp is not likely to have caused the terrestrial mass extinction at the k pg boundary

calcareous nannofossil extinction and survivorship across the cretaceous paleogene boundary at walvis ridge odp hole 1262c south atlantic ocean abstract site 1262 in the south atlantic ocean has provided a stratigraphically continuous deep cretaceous paleogene boundary sequence high resolution calcareous nannofossil quantitative analyses were carried out across the k p boundary and provided a remarkable record of the abrupt and catastrophic extinction the calcareous nannofossil assemblages are abundant and well preserved allowing to obtain a precise bioevent sequence and to document in detail the survivors and victims and the subsequent recovery across the k p boundary late maastrichtian diversity and absolute abundance is high and no decrease towards the boundary has been observed the relative abundance of cretaceous species does not suffer important changes during the latest maastrichtian however the increase in abundance of cool water taxa paralleled with a decrease of warm water taxa in the uppermost 2 cm of the maastrichtian revealed a pulse of surface water cooling the k p boundary is marked by an important decrease in calcareous nannofossil absolute abundance the increase of cretaceous persistent species such as cyclagelosphaera reinhardtii together with the dinoflagellate cysts of thoracosphaera operculata and the appearance of the new paleocene taxa cyclagelosphaera alta and biantholithus sparsus these events are followed by the successive relative abundance increases of other cretaceous survivors as zeugrhabdotus sigmoides markalius inversus and biscutum recognized as r selected taxa adapted to eutrophic and cold water environments in the early danian several first occurrences of small new paleocene species have been observed calcareous nannoplankton evolutionary attempts to colonize vacant niches left by the extinct cretaceous species only some forms succeed and become ancestors to the cenozoic assemblages the other disappear in few kiloyear the presence of a reworking mixing interval above the k p boundary hampered to unequivocally interpret if the few cretaceous vanishing taxa may have survived for a very short time after the k p extinction

an astronomically dated record of earth s climate and its predictability over the last 66 million years much of our understanding of earth s past climate comes from the measurement of oxygen and carbon isotope variations in deep sea benthic foraminifera yet long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the cenozoic era and to study their dynamics here we present a new highly resolved astronomically dated continuous composite of benthic foraminifer isotope records developed in our laboratories four climate states hothouse warmhouse coolhouse icehouse are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of cenozoic climate dynamics

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

abrupt deep sea warming at the end of the cretaceous climatic and oceanographic variations during the last 2 m y of the maastrichtian inferred from high resolution 10 k y stable isotope analysis of the mid latitude south atlantic deep sea drilling project site 525 reveal a major warm pulse followed by rapid cooling prior to the cretaceous tertiary boundary between 66 85 and 65 52 ma cool but fluctuating temperatures average 9 9 and 15 4 c in intermediate and surface waters respectively this interval is followed by an abrupt short term warming between 65 45 and 65 11 ma which increased temperatures by 2 3 c in intermediate waters and decreased the vertical thermal gradient to an average of 2 7 c this warm pulse may be linked to increased atmospheric pco 2 increased poleward heat transport and the switch of an intermediate water source from high to lowmiddle latitudes during the last 100 k y of the maastrichtian intermediate and surface temperatures decreased by an average of 2 1 and 1 4 c respectively compared to the maximum temperature between 65 32 and 65 24 ma

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

a 135 000 year vostok specmap common temporal framework the object of the present study is to introduce a means of comparing the vostok and marine chronologies our strategy has been to use the 18o of atmospheric o2 denoted 18oatm from the vostok ice core as a proxy for the 18o of seawater denoted 18osw our underlying premise in using 18oatm as a proxy for 18osw is that past variations in 18osw an indicator of continental ice volume have been transmitted to the atmospheric o2 reservoir by photosynthesizing organisms in the surface waters of the world s oceans we compare our record of 18oatm to the 18osw record which has been developed from studies of the isotopic composition of biogenic calcite 18oforam in deep sea cores we have tied our 18oatm record from vostok to the specmap timescale throughout the last 135 kyr by correlating 18oatm with a 18osw record from v19 30 results of the correlation indicate that 77 of the variance is shared between these two records we observed differences between the 18oatm and the 18osw records during the coldest periods which indicate that there have been subtle changes in the factors which regulate 18oatm other than 18osw our use of 18oatm as a proxy for 18osw must therefore be considered tentative especially during these periods by correlating 18oatm with 18osw we provide a common temporal framework for comparing phase relationships between atmospheric records from ice cores and oceanographic records constructed from deep sea cores our correlated age depth relation for the vostok core should not be considered an absolute vostok timescale we consider it to be the preferred timescale for comparing vostok climate records with marine climate records which have been placed on the specmap timescale we have examined the fidelity of this common temporal framework by comparing sea surface temperature sst records from sediment cores with an antarctic temperature record from the vostok ice core we have demonstrated that when the southern ocean sst and antarctic temperature records are compared on this common temporal framework they show a high degree of similarity we interpret this result as supporting our use of the common temporal framework for comparing other climate records from the vostok ice core with any climate record that has been correlated into the specmap chronology

40k 40ar dating of the main deccan large igneous province further evidence of ktb age and short duration most mass extinctions coincide in time with outpourings of continental flood basalts cfb some 20 years ago it was shown courtillot v besse j vandamme d montigny r jaeger j j cappetta h 1986 deccan flood basalts at the cretaceous tertiary boundary earth planet sci lett 80 361 374 courtillot v feraud g maluski h vandamme d moreau m g besse j 1988 deccan flood basalts and the cretaceous tertiary boundary nature 333 843 846 duncan r a pyle d g 1988 rapid eruption of the deccan flood basalts at the cretaceous tertiary boundary nature 333 841 843 that the age of the deccan traps was close to the cretaceous tertiary kt boundary and its duration under 1 myr we have undertaken a new geochronological study using the unconventional 40k 40ar cassignol gillot technique which is particularly well suited to the potassium poor deccan lavas the mean of 4 determinations from the topmost ambenali and mahabaleshwar formations is 64 5 0 6 ma they straddle the c29r c29n reversal boundary for which they provide a new constraint the mean age of 3 determinations from the oldest jawhar formation is 64 8 0 6 ma the difference in age between top and bottom of a 3500 m composite section probably comprising 80 of the total deccan volume is statistically insignificant with the overall mean age being 64 7 0 6 ma n 7 our results are consistent with the most recent 40ar 39ar determinations knight k b renne p r halkett a white n 2003 40ar 39ar dating of the rajahmundry traps eastern india and their relationship to the deccan traps earth planet sci lett 208 85 99 knight k b renne p r baker j waight t white n 2005 reply to 40ar 39ar dating of the rajahmundry traps eastern india and their relationship to the deccan traps discussion by a k baksi earth planet sci lett 239 374 382 confirming that there should be no systematic difference between the two methods when they are used in an optimal way an earlier smaller but significant pulse of volcanism between 68 and 67 ma extending over at least 500 km in latitude in the northern part of the deccan cfb has also been identified after 2 to 3 ma of quiescence the second major phase of volcanism occurred near 65 ma expanding over most of the area covered by the first pulse and another 500 km to the south consistent with drift of india by 300 to 450 km at not vert similar 150 mm yr during the quiescence period new paleontological data from the remote rajahmundry section keller g adatte t gardin s bartolini a bajpai s humler e in prep the cretaceous tertiary boundary in deccan traps of the krishna godavari basin of southeastern india epsl to be submitted suggest that this second pulse can itself be divided into two major pulses one starting in c29r and ending at the kt boundary the second starting in the upper part of c29r and ending within c29n

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

characteristics of salt inclusions in polar ice from dome fuji east antarctica 1 we studied the depth profile of the chemical properties number concentration and average diameter of micro inclusions in antarctic ice from dome fuji analysis of the data indicated that the distribution of inclusions was not significantly modified during ice sheet flow although a main constituent na2so4 10h2o changed into another solid phase in the deep ice in the chemical form sodium sulfate and magnesium sulfate were dominant in the interglacial and early glacial ice but were not detected in the glacial maximum ice instead the sulfate in the glacial maximum ice was mainly in the form of calcium sulfate this is strong support for the hypothesis that the neutralization regime of acid aerosols in the atmosphere and snowpack dramatically changed from chemical reaction with sea salt to that with dust during glacial maxima

humid glacials arid interglacials critical thoughts on pedogenesis and paleoclimate based on multi proxy analyses of the loess paleosol sequence crvenka northern serbia abstract loess paleosol sequences lps provide unique terrestrial archives for past environmental and climate changes the loess units are generally interpreted to reflect more arid conditions whereas paleosols are thought to document more humid conditions this paradigm may however deserve to be challenged in some regions because it does not take into account past changes in dust accumulation rates here we present a multi proxy sedimentological and geochemical characterization of the lps crvenka serbia spanning the last 140 ka commonly used analyses such as magnetic susceptibility organic carbon content grain size and weathering indices allow the quantification of the intensity of pedogenesis however loess accumulation rates were much higher during glacials than during interglacials so that it is not trivial to infer past rates of pedogenesis and related paleoclimate conditions novel proxies based for example on lipid biomarkers and their isotopic composition are not so directly affected by changes in loess accumulation rates and might provide interesting new insights long chain plant derived n alkanes in the lps crvenka suggest a minor but non negligible contribution of deciduous trees and shrubs c27 and c29 during mis 1 2 4 and 6 whereas grasses and herbs c31 and c33 dominate the alkane input during mis 3 and 5 this is in agreement with the notion that parts of southeast europe served as refugia for deciduous trees during glacials on the other hand edaphic conditions on the drought prone loess plateaus seem to have been more arid during mis 3 and 5 compound specific d analyses on the alkanes show only little changes on glacial interglacial timescale when compared with the isotopic enrichment of the mediterranean sea during the last glacial this likely indicates a complex combination of reduced temperatures increased rainfall reduced evapotranspiration and more advection of north atlantic moisture although disentangling these factors is difficult interpretation in terms of humid glacials and more arid interglacials seems to be supported also by other novel lipid biomarkers so called gdgts glycerol dialkyl glycerol tetraethers

warm younger dryas summers and early late glacial spread of temperate deciduous trees in the pannonian basin during the last glacial termination 20 9 kyr cal bp abstract this paper focuses on the last glacial termination vegetation and climate reorganization of the eastern pannonian plain via the multi proxy paleoecological analysis of kokad mire in eastern hungary grains size sediment chemistry and magnetic susceptibility records are compared with the pollen and plant macrofossil records on the basis of which biome and quantitative summer mean temperature reconstructions are provided and discussed with other climate records of the region biome assignments indicated graminoid and forb tundra vegetation from 19 440 cal yr bp with the local presence of betula pendula b pubescens b nana and pinus sylvestris a rapid biome shift to cool coniferous forest took place at 16 200 cal yr bp and a second biome shift was identified at 14 740 cal yr bp when cool mixed forest developed and persisted into the early holocene the most prominent feature of the record was the early post last glacial maximum lgm establishment 17 700 cal yr bp and expansion 14 700 cal yr bp of elm ulmus and hazel corylus supporting the phylogeographical evidence for extra mediterranean refugia in the pannonian basin the fungal spore record indicated the presence of large grazing mammals locally after the lgm until 16 780 cal yr bp their disappearance predated the biome shift to cold coniferous forest and the final increase of forest fires pollen based summer temperature reconstruction suggested relatively warm summers 14 5 c by 19 440 cal yr bp and buffered july mean temperature fluctuations throughout the last glacial termination in this region with

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

antarctic subglacial conditions inferred from a hybrid ice sheet ice stream model abstract subglacial conditions of large polar ice sheets remain poorly understood despite recent advances in satellite observation major uncertainties related to basal conditions such as the temperature field are due to an insufficient knowledge of geothermal heat flow here a hybrid method is presented that combines numerical modeling of the ice sheet thermodynamics with a priori information using a simple assimilation technique additional data are essentially vertical temperature profiles measured in the ice sheet at selected spots as well as the distribution of subglacial lakes in this way geothermal heat flow datasets are improved to yield calculated temperatures in accord with observations in areas where information is available results of the sensitivity experiments show that 55 of the grounded part of the antarctic ice sheet is at pressure melting point calculated basal melt rates are approximately 65 gt year 1 which is 3 of the total surface accumulation although these sensitivity experiments exhibit small variations in basal melt rates the impact on the ice age of basal layers is quite important in areas that are characterized by relatively low melt rates this may lead to standard deviations up to 50 in a model run over a period of 10 6 years subglacial water flow is concentrated underneath the large outlet glaciers of antarctica the larger subglacial lakes are perched at the head of these subglacial water systems an exception however is the lake system of the recovery ice stream catchment that receives a substantial amount of subglacial melt water from the upstream catchment

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

a new concept for the paleoceanographic evolution of heinrich event 1 in the north atlantic new records of planktonic foraminiferal 18o and lithic and foraminiferal counts from eirik drift are combined with published data from the nordic seas and the ice rafted debris ird belt to portray a sequence of events through heinrich event 1 h1 these events progressed from an onset of meltwater release at not vert similar19 ka bp through the conventional h1 ird deposition phase in the ird belt starting from not vert similar17 5 ka bp to a final phase between 16 5 and not vert similar15 ka bp that was characterised by a pooling of freshwater in the nordic seas which we suggest was hyperpycnally injected into that basin after not vert similar15 ka bp this freshwater was purged from the nordic seas into the north atlantic which preconditioned the nordic seas for convective deep water formation this allowed an abrupt re start of north atlantic deep water nadw formation in the nordic seas at the bolling warming 14 6 ka bp in contrast to previous estimates for the duration of h1 i e 1000 years to only a century or two the total combined composite h1 signal presented here had a duration of over 4000 yrs not vert similar19 14 6 ka bp which spanned the entire period of nadw collapse it appears that deep water formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead the location of meltwater injections may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

north atlantic control on precipitation pattern in the eastern mediterranean black sea region during the last glacial based on proxy records from western black sea cores we provide a comprehensive study of climate change during the last glacial maximum and late glacial period in the black sea region for the first time we present a record of relative changes in precipitation for nw anatolia based on variations in the terrigenous supply expressed as detrital carbonate concentration the good correspondence between reconstructed rainfall intensity in nw anatolia and past western mediterranean sea surface temperatures ssts implies that during the glacial period the precipitation variability was controlled like today by mediterranean cyclonic disturbances periods of reduced precipitation correlate well with low ssts in the mediterranean related to heinrich events h1 and h2 stable oxygen isotopes and lithological and mineralogical data point to a significant modification in the dominant freshwater sediment source concomitant to the meltwater inflow after 16 4 cal ka bp this change implies intensification of the northern sediment source and with other records from the mediterranean region consistently suggests a reorganization of the atmospheric circulation pattern affecting the hydrology of the european continent the early deglacial northward retreat of both atmospheric and oceanic polar fronts was responsible for the warming in the mediterranean region leading simultaneously to more humid conditions in central and northern europe

spatial variations in heat at the base of the antarctic ice sheet from analysis of the thermal regime above subglacial lakes antarctic subglacial lakes provide an important boundary condition for thermal analysis of the ice sheet in that the basal ice temperature over lakes may be assumed to be at the pressure melting point we have used a one dimensional vertical heat transfer equation to determine theoretical temperature values for the ice sheet base above 77 subglacial lakes identified from airborne radio echo sounding data covering 50 of antarctica variations in our temperature results to below the pressure melting temperature over lakes are due to either our estimate of the geothermal heat flux or a neglect of heat derived from a internal ice deformation and b basal sliding in the thermal model our results indicate that when the geothermal heat flux is set at 54 mw m 2 the ice sheet base above 70 of the known antarctic subglacial lakes is calculated to be at the pressure melting value these lakes are located mainly around dome c ridge b and vostok station for the ice sheet above subglacial lakes located hundreds of kilometres from the ice divide using the same thermal model loss of heat due to vertical advection is calculated to be relatively high in such regions if the ice sheet base is at the pressure melting point heat lost due to vertical advection must be supplemented by heat from other sources for the three lakes beneath terre adelie and george v land for instance the basal thermal gradient calculated to produce pressure melting at the ice sheet base is equivalent to 1 5 2 times the value obtained when 54 mw m 2 of geothermal heat is used as the sole basal thermal component we suggest that as distance from the ice divide increases so too does the amount of heat due to internal ice deformation and basal sliding moreover by considering the ice sheet basal thermal characteristics above subglacial lakes which lie on the same ice flowline we demonstrate empirically that the heat due to these horizontal ice motion terms varies pseudo exponentially with distance from the ice divide the location along a flowline where a rapid increase in the basal heat gradient is calculated may correspond to the onset of large scale basal sliding

constraints on the volume and rate of deccan traps flood basalt eruptions using a combination of high resolution terrestrial mercury records and geochemical box models abstract deccan traps continental flood basalt eruptions spanned the cretaceous paleogene mass extinction erupting over a million cubic kilometers of basalt over a total duration of approximately a million years the environmental consequences of flood basalt eruptions depend on the timing and amount of volatile release eruption rates are thus needed to evaluate their potential to cause climate change radioisotopic dates are not currently sufficient to resolve sub ten thousand year eruptive tempos necessary for constraining the effects of short lifetime volatiles including sulfur dioxide recent studies have demonstrated that increases in mercury concentration in sedimentary records correlate with flood basalt eruptions under some circumstances however mercury concentrations have primarily been used to show the presence or absence of flood basalt eruptions we show that this proxy can be used to quantitatively estimate eruptive rates using a mercury geochemical cycle framework we illustrate this using new mercury chemostratigraphic records from terrestrial cretaceous paleogene boundary sections in eastern montana usa with multiple high resolution chronologic constraints we estimate that deccan eruptions lasted on the order of centuries and released 500 3000 megagrams mg of mercury per year corresponding to 50 250 km3 a of lava the box model framework highlights the importance of carefully accounting for differences in sedimentation rate and sampling resolution when comparing mercury records from different locations and depositional environments while there are uncertainties in the box model estimates due to possible variation in flood basalt mercury emissions and sedimentation rates they provide a useful framework to quantitatively evaluate the global mercury budget change indicated by changing concentration in sedimentary records eruptions of the estimated size would have released enough so2 if it reached the stratosphere to cause significant cooling for the duration of the eruption however given our constraints on the duration of individual eruptions these colder periods are likely too brief to be clearly visible in most existing paleoclimate records

orbital forcing of the paleocene and eocene carbon cycle multimillion year proxy records across the paleocene and eocene show prominent variations on orbital time scales the cycles which have been identified at various sites across the globe preferentially concentrate spectral power at eccentricity and precessional frequencies it is evident that these cycles are an expression of changes in global climate and carbon cycling paced by astronomical forcing however little is currently known about the link between orbital forcing and the carbon cycle climate system and the amplitude of associated atmospheric co2 variations here we use simple and complex carbon cycle models to explore the basic effect of different orbital forcing schemes and noise on the carbon cycle our primary modeling target is the high resolution 7 7 myr long benthic isotope record at ocean drilling program site 1262 in the south atlantic for direct insolation forcing as opposed to artificial eccentricity tilt precession one major challenge is understanding how the system transfers spectral power from high to low frequencies we discuss feasible solutions including insolation transformations analogous to electronic ac dc conversion dc ing regarding mechanisms we focus on tropical insolation and a long term carbon imbalance in terrestrial organic burial oxidation but do not rule out other scenarios our analysis shows that high latitude mechanisms are unlikely drivers of orbitally paced changes in the late paleocene early eocene lpee earth system furthermore we provide constraints on the origin and isotopic composition of a possible lpee cyclic carbon imbalance source responding to astronomical forcing our simulations also reveal a mechanism for the large 13c eccentricity lag at the 400 kyr period observed in paleocene oligocene and miocene sections we present the first estimates of orbital scale variations in atmospheric co2 during the late paleocene and early eocene

synchronous climate changes in antarctica and the north atlantic central greenland ice cores provide evidence of abrupt changes in climate over the past 100 000 years many of these changes have also been identified in sedimentary and geochemical signatures in deep sea sediment cores from the north atlantic confirming the link between millennial scale climate variability and ocean thermohaline circulation it is shown here that two of the most prominent north atlantic events the rapid warming that marks the end of the last glacial period and the bolling allerod younger dryas oscillation are also recorded in an ice core from taylor dome in the western ross sea sector of antarctica this result contrasts with evidence from ice cores in other regions of antarctica which show an asynchronous response between the northern and southern hemispheres

improving the ginkgo co2 barometer implications for the early cenozoic atmosphere abstract stomatal properties of fossil ginkgo have been used widely to infer the atmospheric concentration of co2 in the geological past paleo pco2 many of these estimates of paleo pco2 have relied on the inverse correlation between pco2 and stomatal index si the proportion of epidermal cells that are stomata observed in recent ginkgo biloba and therefore depend on the accuracy of this relationship the si p co2 relationship in g biloba has not been well documented however here we present new measurements of si for leaves of g biloba that grew under pco2 from 290 to 430 ppm we prepared and imaged all specimens using a consistent procedure and photo documented each count as in prior studies we found a significant inverse relationship between si and pco2 however the relationship is more linear has a shallower slope and a lower correlation coefficient than previously reported we examined leaves of g biloba grown under pco2 of 1500 ppm but found they had highly variable si and a large proportion of malformed stomata we also measured stomatal dimensions stomatal density and the carbon isotope composition of g biloba leaves in order to test a mechanistic model for inferring pco2 this model overestimated observed pco2 performing less well than the si method between 290 and 430 ppm we used our revised si pco2 response curve and new observations of selected fossils to estimate late cretaceous and cenozoic pco2 from fossil ginkgo adiantoides all but one of the new estimates is below 800 ppm and together they show little long term change in pco2 or relation to global temperature the low paleogene pco2 levels indicated by the ginkgo si proxy are not consistent with the high pco2 inferred by some climate and carbon cycle models we cannot currently resolve the discrepancy but greater agreement between proxy data and models may come from a better understanding of the stomatal response of g biloba to elevated pco2 better counts and measurements of fossil ginkgo or models that can simulate greenhouse climates at lower pco2

rapid development of anisotropic ice crystal alignment fabrics inferred from englacial radar polarimetry central west antarctica 1 anisotropy in englacial radar power was measured using 60 mhz and 179 mhz copolarized pulse modulated radar at 19 sites in central west antarctica the study region is a 100 300 km2area near the west antarctic ice sheet divide that separates ice flow toward the ross and amundsen embayments the frequency dependence of the returned power indicates that most of the radar data are affected by vertical variations in the crystal orientation fabric cof though the 60 mhz data are more affected by acidity contrasts in the top 1000 m significant polarimetric variations occur at most sites likely due to effects of the anisotropic cof patterns more anisotropic variations occur at sites with significant horizontal strain whereas more isotropic variations occur at sites where vertical compression dominates azimuthal shifts with depth of the principal axes of cof were found in shallow ice near the current flow divide and at greater depths over locations of rough bed the former indicates that the divide has differentially migrated resulting in a rotation of the principal cof axes nevertheless the regionally consistent radar signatures suggest that the first order ice properties in this area have remained constant and that no major changes in the strain configuration or ice topography have occurred for the past five to eight thousand years we conclude that shallow polarimetric features can be related to the current strain configurations and that englacial polarimetric features can help constrain current ice rheology and evolution of the ice topography

the effect of geographic range and climate on extinction risk in the deep time amphibian fossil record abstract geographic range is of crucial importance concerning the extinction risk of species however our understanding of how the influence of this trait on extinction risk has varied through earth history and across different climate regimes is still rather unexplored this is especially true for taxa that are currently of strong interest in conservation biology displaying a strong mismatch between paleontological studies and modern efforts to quantify the extinction risk of threatened species we herein calculated a continuous measure for the connection of geographic range and extinction risk in the deep time amphibian fossil record furthermore we evaluated the impact of climate on this connection using two climate proxies derived from oxygen isotope data global relative temperature change and variations in the latitudinal temperature gradient we show that geographic ranges tended to be larger during times of comparatively small latitudinal temperature gradients moreover the strength of geographic range influencing extinction risk fluctuated temporally but remained positive at all times the variation in range size impact on extinction risk showed a strong connection with the latitudinal temperature gradient our findings indicate that geographic range persists as a factor influencing species extinction risk through all times however geographic range seemed less important during times of higher environmental variability reasons might be the restriction of species ranges due to environmental constraints causing ranges to become more similar and therefore lose relative importance in buffering for extinction risk while other factors gain in importance simultaneously similar ranges might be more prone to alteration by e g conservation biases related to sedimentary deposition and fossilization in relation to their real range size resulting in a smaller signal to noise ratio potentially affecting the correlation strength we show that trait extinction risk dynamics can vary in their intensity and that specifically the observed impact of geographic range on extinction risk can vary with climatic changes

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

magnesium methanesulfonate salt found in the dome fuji antarctica ice core using micro raman spectroscopy we identified the chemical forms of methanesulfonate salt particles in reference samples of the dome fuji antarctica ice core we found only ch3so3 2mgnh2o among methanesulfonate salts and this salt particle is most prevalent in the last glacial maximum lgm ice we suggest that during the lgm ch3so3 2mgnh2o may have formed in the atmosphere through the chemical reaction of ch3so3h with sea salts but probably not in the firn and ice due to the neutralization of acid in lgm ice of inland antarctica

latest cretaceous climatic and environmental change in the south atlantic region latest maastrichtian climate change caused by deccan volcanism has been invoked as a cause of mass extinction at the cretaceous paleogene k pg boundary 66 0 ma yet late maastrichtian climate and ecological changes are poorly documented in particular on the southern hemisphere here we present upper maastrichtian lower danian climate and biotic records from the bajada del jaguel bj shelf site neuquen basin argentina employing the tex86 paleothermometer marine palynology dinoflagellate cysts and micropaleontology foraminifera these records are correlated to the astronomically tuned ocean drilling program site 1262 walvis ridge collectively we use these records to assess climatic and ecological effects of deccan volcanism in the southern atlantic region both the tex86 based sea surface temperature sst record at bj and the bulk carbonate 18o based sst record of site 1262 show a latest maastrichtian warming of 2 5 4 c at 450 to 150 kyr before the k pg boundary coinciding with the a large deccan outpouring phase benthic foraminiferal and dinocyst assemblage changes indicate that this warming resulted in enhanced runoff and stratification of the water column likely resulting from more humid climate conditions in the neuquen basin these climate conditions could have been caused by an expanding and strengthening thermal low over the south american continent biotic changes in response to late maastrichtian environmental changes are rather limited when compared to the major turnovers observed at many k pg boundary sites worldwide this suggests that environmental perturbations during the latest maastrichtian warming event were less severe than those following the k pg boundary impact

late quaternary dynamics of the tisza river evidence of climatic and tectonic controls abstract the focus of this study is to understand a dramatic avulsion event on the tisza river during the late pleistocene the river course switched by about 80 km from the east to west of the great hungarian plain ghp through the zahony bend to its present meander belt the aim of this study is to date this zahony avulsion based upon radiocarbon and pollen samples from six cores in the polgar study area situated in the west of the ghp at the middle course of the tisza river in addition a grain size composition and heavy mineral analysis has been performed the results of these analyses reveal a sequence of paleochannels and have been plotted on a high resolution digital elevation model illustrating the paleochannel form and age relationships the study suggests that the age of this major avulsion event is significantly older than it was previously supposed instead of 10 to 11 ka it is according to our new data 16 18 ka and definitely predates the last glacial maximum lgm the river cut into the previous contiguous surface and formed at least one climatic terrace then drifted gradually westward as a response to a tilt or the differential subsidence of tectonic origin

younger dryas to mid holocene environmental history of the lowlands of nw transylvania romania pollen micro charcoal and total carbon analyses on sediments from the turbuta palaeolake in the transylvanian basin of nw romania reveal younger dryas to mid holocene environmental changes the chronostratigraphy relies on ams 14c measurements on organic matter and u th tims datings of snail shells results indicate the presence of pinus and betula open woodlands with small populations of picea ulmus alnus and salix before 12 000 cal yr bp a fairly abrupt replacement of pinus and betula by ulmus dominated woodlands at ca 11 900 cal yr bp likely represents competition effects of vegetation driven by climate warming at the onset of the holocene by 11 000 cal yr bp the woodlands were increasingly diverse and dense with the expansion of quercus fraxinus and tilia the establishment of corylus and the decline of upland herbaceous and shrubs taxa the marked expansion of quercus accompanied by tilia between 10 500 and 8000 cal yr bp could be the result of low effective moisture associated with both low elevation of the site and with regional change towards a drier climate at 10 000 cal yr bp corylus spread across the region and by 8000 cal yr bp it replaced quercus as a dominant forest constituent with only little representation of picea abies carpinus became established around 5500 cal yr bp but it was only a minor constituent in local woodlands until ca 5000 cal yr bp results from this study also indicate that the woodlands in the lowlands of turbuta were never closed

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

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

large arctic temperature change at the wisconsin holocene glacial transition analysis of borehole temperature and greenland ice sheet project ii ice core isotopic composition reveals that the warming from average glacial conditions to the holocene in central greenland was large approximately 15 c this is at least three times the coincident temperature change in the tropics and mid latitudes the coldest periods of the last glacial were probably 21 c colder than at present over the greenland ice sheet

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

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

formation of air clathrate hydrates in polar ice sheets heterogeneous nucleation induced by micro inclusions to investigate factors influencing nucleation of air clathrate hydrates in polar ice sheets we have performed high resolution mapping of the distributions of soluble impurities air bubbles and air hydrate crystals versus depth in the dome fuji antarctic ice significant correlation observed between the concentrations of air inclusions and impurities in ice along with frequent occurrence of impurities inside hydrate crystals suggest that micro inclusions promote hydrate nucleation in the ice matrix our observations also show that the diffusive macroscopic scale redistribution of air constituents in ice in the bubble hydrate transition zone is controlled by the original sedimentary layering of soluble impurities acting as nucleation helpers the results of this study are important for the correct interpretation of high resolution gas analyses of ice cores and for better understanding the global bubble to hydrate transformation process in polar ice sheets

a high resolution benthic stable isotope record for the south atlantic implications for orbital scale changes in late paleocene early eocene climate and carbon cycling abstract the late paleocene and early eocene were characterized by warm greenhouse climates punctuated by a series of rapid warming and ocean acidification events known as hyperthermals thought to have been paced or triggered by orbital cycles while these hyperthermals such as the paleocene eocene thermal maximum petm have been studied in great detail the background low amplitude cycles seen in carbon and oxygen isotope records throughout the paleocene eocene have hitherto not been resolved here we present a 7 7 million year myr long high resolution orbitally tuned benthic foraminiferal stable isotope record spanning the late paleocene and early eocene interval 52 5 60 5 ma from ocean drilling program odp site 1262 south atlantic this high resolution 2 4 kyr record allows the changing character and phasing of orbitally modulated cycles to be studied in unprecedented detail as it reflects the long term trend in carbon cycle and climate over this interval the main pacemaker in the benthic oxygen isotope 18 o and carbon isotope 13 c records from odp site 1262 are the long 405 kyr and short 100 kyr eccentricity cycles and precession 21 kyr obliquity 41 kyr is almost absent throughout the section except for a few brief intervals where it has a relatively weak influence during the course of the early paleogene record and particularly in the latest paleocene eccentricity paced negative carbon isotope excursions 13 c cies and coeval negative oxygen isotope 18 o excursions correspond to low carbonate caco 3 and coarse fraction cf values due to increased carbonate dissolution suggesting shoaling of the lysocline and accompanied changes in the global exogenic carbon cycle these negative cies and 18 o events coincide with maxima in eccentricity with changes in 18 o leading changes in 13 c by 6 5 kyr in the 405 kyr band and by 3 1 kyr in the higher frequency 100 kyr band on average however these phase lags are not constant with the lag in the 405 kyr band extending from 4 5 kyr to 21 2 kyr from the late paleocene to the early eocene suggesting a progressively weaker coupling of climate and the carbon cycle with time the higher amplitude 405 kyr cycles in the latest paleocene are associated with changes in bottom water temperature of 2 4 c while the most prominent 100 kyr paced cycles can be accompanied by changes of up to 1 5 c comparison of the 1262 record with a lower resolution but orbitally tuned benthic record for site 1209 in the pacific allows for verification of key features of the benthic isotope records which are global in scale including a key warming step at 57 7 ma

dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle dust deposition and climate in the carpathian basin over an independently dated last glacial interglacial cycle

sea surface temperature variability in the subpolar atlantic over the last two millennia 1 a decadal resolution time series of sea surface temperature sst spanning the last two millennia is reconstructed by combining a proxy record from a new sediment sequence with previously published data from core md99 2275 north of iceland the alkenone based sst reconstruction is validated with historic observational data and compared to a new similar temporal resolution reconstruction obtained from sediment core rapid21 3k in the subpolar north atlantic the two sst paleorecords show consistent multidecadal scale coolings throughout the interval and similar expressions during the contrasted climatic periods colloquially known as the medieval climatic anomaly mca and little ice age lia in order to further understand the temporal and spatial sst variations and investigate the influence of natural forcings on the observed sst changes during the last millennium we compare our time series to simulations using the institut pierre simon laplace ipslcm4 v2 climate model this comparison highlights the potential importance of volcanism as a natural forcing driving coherent abrupt cooling events captured in the subpolar north atlantic records

ice core age dating and paleothermometer calibration based on isotope and temperature profiles from deep boreholes at vostok station east antarctica an interpretation of the deuterium profile measured along the vostok east antarctica ice core down to 2755 m has been attempted on the basis of the borehole temperature analysis an inverse problem is solved to infer a local geophysical metronome the orbital signal in the surface temperature oscillations expressed as a sum of harmonics of milankovich periods by correlating the smoothed isotopic temperature record to the metronome a chronostratigraphy of the vostok ice core is derived with an accuracy of 3 0 4 5 kyr the developed timescale predicts an age of 241 kyr at a depth of 2760 m the ratio 13d 13t i between deuterium content and cloud temperature fluctuations at the top of the inversion layer is examined by fitting simulated and measured borehole temperature profiles the conventional estimate of the deuterium temperature slope corresponding to the present day spatial ratio 9 per mil oc is confirmed in general however the mismatch between modeled and measured borehole temperatures decreases noticeably if we allow surface temperature responsible for the thermal state of the ice sheet to undergo more intensive precession oscillations than those of the inversion temperature traced by isotope record with this assumption we obtain the long term temporal deuterium temperature slope to be 5 8 6 5 per mil oc which implies that the glacial interglacial temperature increase over central antarctica was about 15oc in the surface temperature and 10oc in the inversion temperature past variations of the accumulation rate and the corresponding changes in the ice sheet surface elevation are simultaneously simulated

insights into continental temperatures in the northwestern black sea area during the last glacial period using branched tetraether lipids abstract in the continental realm continuous quantitative temperature reconstructions spanning the last glacial are rare especially in central and eastern europe here we provide a reconstruction from the northwestern black sea catchment spanning 40 to 9 ka bp from a study of the relative distribution of branched glycerol dialkyl glycerol tetraethers brgdgts in black sea lacustrine sediments first the origins of brgdgts are discussed the comparison of geochemical proxies from the same core supports a dominant terrestrial origin for brgdgts during the last glacial and a strong decrease in the soil derived brgdgt proportion toward the holocene since the lowering of soil vs lacustrine derived brgdgts is prone to bias the temperature signal that is reconstructed using a soil calibration a correction for in situ production is applied the corrected signal is compared to independent discrete temperature records from the study area the brgdgt temperature relative evolution reconstructed in this work provides additional insight regarding millennial scale climate variability in central and eastern europe notably the imprints of heinrich event cold spells and lateglacial climatic oscillations are consistent with other regional paleorecords from the northern hemisphere