planktic foraminiferal turnover and δ13c isotopes across the paleocene eocene transition at caravaca and zumaya spain abstract biostratigraphic and faunal analysis of planktic foraminifera and benthic foraminiferal isotopes at zumaya and caravaca sections in spain indicate that zumaya has a continuous record with high sediment accumulation rates across the paleocene eocene transition whereas caravaca has a hiatus with the uppermost zone p4 zone p5 and the lower part of zone p6 missing both sections contain nearly continuous and expanded records of the global 13c excursion at zumaya and caravaca respectively the 13c excursion is associated with dark grey shale deposition in a dysaerobic benthic environment this 13c event is associated with a major planktic foraminiferal turnover marked by the gradual extinction and evolution of 33 and 18 of the species respectively a rapid change in the relative abundances of these taxa occurs at the 13c excursion coincident with the extinction of 50 of the small benthic foraminiferal taxa the entire water column was affected by this faunal turnover surface intermediate deep dwellers but in contrast to benthic foraminifera there was no net loss of habitats since species extinctions of planktic foraminifera were largely replaced by originations

stability and change in tethyan planktic foraminifera across the paleocene eocene transition abstract examination of planktic foraminifera in the tethys basin during the paleocene eocene transition reveals two stasis intervals that are separated by a major saltation event coincident with the p e short term perturbation in global climate and oceanography changes occurred at many spatial and temporal scales as well as many taxonomic and ecologic hierarchical levels though with various rates and magnitudes the stasis intervals are marked by slow changes at the species level and account for 50 of the observed first and last appearances during a 2 5 myr interval the saltation event is marked by rapid changes at the species and morpho guild levels and accounts for the remaining 50 of first and last appearances during an interval of about 100 200 kyr despite these changes many taxonomic and ecologic units such as the depth assemblages and genera and faunal parameters such as species richness and turnover rates are stable with respect to the p e perturbation this coexistence of change and stability marks the crisis of tethyan planktic foraminifera across the p e transition and reveals the possible dynamics of ecological evolution

stable isotopes of carbon and sulphur as indicators of environmental change past and present stable isotopes of carbon 12 c and 13 c and sulphur 32 s and 34 s are fractionated during some of the transformations between reservoirs in the global carbon and sulphur cycles the main processes controlling the isotopic composition of earth surface reservoirs are for carbon photosynthesis respiration and equilibration between oceanic dissolved inorganic carbon and atmospheric co 2 and for sulphur bacterial sulphate reduction and sulphide reoxidation thus the different reservoirs of carbon and sulphur in the global cycles attain characteristic isotopic compositions that can be used as a fingerprint for different carbon and sulphur sources and to track changes in the balance of carbon and sulphur stored in different reservoirs these isotopic signals can be used both to examine contemporary anthropogenic impacts on the cycling of carbon and sulphur and where isotopic compositions are faithfully preserved in ancient sediments to examine historical changes in global geochemical cycles through geological time a number of case studies are discussed to illustrate how isotopic techniques represent one of the most powerful and important tools available in the study of both the causes and affects of ancient and modern global environmental change

climate and bioproductivity control on carbonate turbidite sedimentation paleocene to earliest eocene gulf of biscay zumaia spain abstract the paleocene to lowermost eocene zumaia series situated along the basque coast northern spain consists of pelagic limestones and marlstones with interbedded mixed calcarenite turbidites we have compared the composition and frequency of turbidite beds in time as well as the clay mineral and bulk rock carbon isotope composition of the pelagic beds to discern the factors controlling turbidite deposition the pelagic beds are coccolithic mudstones with mainly planktic foraminifera the sources of detrital material to turbidites were the carbonate producing shelves bearing foramol associations around the evolving bay of biscay and to a minor extent the incipient pyrenean chain for siliciclastic components we have found close relationships between variations of turbidite facies and depositional rates with clay mineral assemblages and carbon isotopes in the pelagic beds the latter are in line with global trends it appears that in the early bay of biscay climate and nutrient availability controlled turbidite sedimentation the bulk rock late paleocene np 5 np 9 positive carbon isotope excursion coincides with a period of relatively cool and dry climate characterized by the highest frequency of turbidity flow we propose that during this period globally enhanced latitudinal temperature gradients and strong thermohaline ocean circulation increased bioproductivity in surface waters by upwelling and or by wind driven ekman pumping in contrast warm perennially wet periods such as the early paleocene np 1 np 4 and the paleocene eocene transition upper np 9 np 10 are characterized by low frequency of turbidity flow in the basin this may have been caused by sluggish thermohaline circulation and low carbonate productivity during this time period

early paleogene climate and productivity of the eastern equatorial atlantic off the western coast of ghana early paleogene warmth is consistent with global observation although temperature reconstructions were characterized by some degree of uncertainty in spite of applied corrections the suggested epifaunal benthic foraminifera maximum temperature range 23 65 30 36 c was still above the proposed maximum tropical sea surface temperature of 27 c confirming that foraminiferally derived temperatures are strongly dependent on assumptions paleoclimate and paleoproductivity of the eastern equatorial atlantic were poorly correlated r2 0 due to major anomalies 13c isotopic signatures have been largely and independently used to resolve discrepancies in eight anomalous depths identified in this study in view of overlapping 18o isotopic signatures the last three anomalies are consistent with the dramatic onset of global cooling which occurred during this interval the first five still remain anomalous challenging the conventional view that glacial oceans are more productive than interglacial oceans discrepancies in these anomalous depths could have been due to artifacts preservation biases related to dissolution and or shell thickening or encrustation however this study suggests extratropical variability and climate dynamics reflecting regional anomalies due to upwelling or feedback mechanisms of poleward heat transport which are prevalent in the eastern equatorial atlantic

facies analysis and palaeoclimatic significance of ironstones formed during the eocene greenhouse lower and middle eocene ironstone sequences of the naqb and qazzun formations from the north east bahariya depression western desert egypt represent a proxy for early palaeogene climate and sea level changes these sequences represent the only palaeogene economic ooidal ironstone record of the southern tethys these ironstone sequences rest unconformably on three structurally controlled cenomanian palaeohighs for example the gedida harra and ghorabi mines and formed on the inner ramp of a carbonate platform these palaeohighs were exposed and subjected to subaerial lateritic weathering from the cenomanian to early eocene the lower and middle eocene ironstone sequences consist of quiet water ironstone facies overlain by higher energy ironstone facies the distribution of low energy ironstone facies is controlled by depositional relief these deposits consist of lagoonal burrow mottled mud ironstone and laterally equivalent tidal flat stromatolitic ironstones the agitated water ironstone facies consist of shallow subtidal intertidal nummulitic ooidal oncoidal and back barrier storm generated fossiliferous ironstones the formation of these marginal marine sequences was associated with major marine transgressive regressive megacycles that separated by subaerial exposure and lateritic weathering the formation of lateritic palaeosols with their characteristic dissolution and reprecipitation features such as colloform texture and alveolar voids implies periods of humid and warm climate followed major marine regressions the formation of the lower to middle eocene ironstone succession and the associated lateritic palaeosols can be linked to the early palaeogene global warming and eustatic sea level changes the reworking of the middle eocene palaeosol and the deposition of the upper eocene phosphate rich glauconitic sandstones of the overlying hamra formation may record the initial stages of the palaeoclimatic transition from greenhouse to icehouse conditions

origin of glauconite in the recent bottom sediments of the ocean abstract there are two general types of sedimentary glauconite in recent ocean sediments terrigenous allogenic and authigenic glauconite recent sediments of the oceans contain mainly terrigenous allogenic glauconite shelf and continental slope which is formed from ancient glauconite bearing rocks on coasts islands and the ocean floor the age of terrigenous allogenic glauconite ranges from 2 to 70 m y 8 samples from the atlantic ocean 13 from the pacific ocean 1 from the indian ocean the area of terrigenous allogenic glauconite distribution correlates very well with the area of distribution of glauconite bearing rocks on land and does not correlate with the climate and bathymetry authigenic glauconite is seldom found in recent ocean sediments the sediments with authigenic glauconite form transition zones between sediments with organic carbon h 2 s and sulphide near coasts and oxidized sediments of the ocean floor red clay and others the areas of authigenic glauconite distribution are not yet well known the formation of authigenic glauconite occurs mainly during diagenesis of sediments by synthesis from interstitial solutions and or alteration of clay minerals

the temporal distribution of evolutionary and migrational events in pelagic systems episodic or continuous the evolutionary and ecological dynamics of origination immigration and extinction emigration patterns of two pelagic groups planktic foraminifera and calcareous nannofossils within two paleoceanographic regions over the past 40 m y are compared with predictions of the turnover pulse hypothesis that speciation extinction and migration are pulsed or episodic and synchronous with change in the physical environment the specific species dynamics examined of the records of 918 species include expected time to extinction origination immigration as a function of geologic time extinction emigration as a function of biologic age and geologic time and the interactive effects of time of origination immigration and geologic time on the probability of extinction emigration overall there is little empirical support for times of evolutionary quiescence or ecological stability rather the dominant pattern is one of continuous rather than episodic evolutionary and ecological activity there is little evidence of synchroneity of response among cohorts or with major change in the physical environment coeval species experience the same time periods differently in terms of the probability of speciation immigration and extinction emigration the empirical patterns support the hypothesis that at this taxonomic and temporal resolution the controlling factors on evolutionary and ecological turnover are more omnipresent than pulsed or episodic

integrating palynological and geochemical data in a new approach to palaeoecological studies upper cretaceous of the banterwick barn chalk borehole berkshire uk abstract the dinoflagellate cyst record from an upper cretaceous uppermost cenomanian upper coniacian chalk core drilled at banterwick barn berkshire is described and statistically correlated with elemental and stable isotope bulk sediment geochemical data from the same core seventy two dinocyst species and subspecies are recorded and stable carbon and oxygen isotopic 13 c 18 o trends are documented lithostratigraphy and chemostratigraphic correlation of the 13 c curve with an expanded section at dover kent are used to identify stratigraphically significant marls and determine the positions of macrofossil zones and stage boundaries in the banterwick barn core these data indicate that 30 m of chalk at dover are represented by senoniasphaera rotundata alveolata is proposed which has a fad in the lower turonian and last appears lad in the lower coniacian senoniasphaera rotundata rotundata autonym herein has its fad in the middle turonian first common occurrence in the uppermost turonian and lad in the upper coniacian an extremely impoverished assemblage of dinocysts in the highest cenomanian to lowest turonian is considered to be largely a preservational artefact of intraclastic nodular and calcarenitic chalks and is not related directly to the well documented global oceanic anoxic event oae2 occurring at that time 93 5 ma a sharp increase in dinocyst abundance in the lower turonian corresponds with a change in lithology to more marly chalks a gradual decrease in the number of species is observed through the middle turonian to upper coniacian 18 o records show that this was associated with global climatic cooling cluster analysis of the dinocyst abundance record with geochemical data indicates four distinct species groups with characteristic geochemical associations i e groups 1 4 groups 1 and 2 are associated with phases of increased siliciclastic supply a positive correlation with higher 13 c values differentiates the latter group 3 is independent of carbonate and detrital input and group 4 is associated with high carbonate flux and low detrital supply these groupings suggest that cyst forming dinoflagellates exhibited a range of ecological niches in the late cretaceous although the relationship between the encystment process and the geochemical associations is unclear key environmental factors are likely to be sea level and climate related including water depth turbidity nutrient supply sea surface temperature and environmental stability predictability integrated geochemical and palynological studies have great potential for inter regional correlation and palaeoenvironmental interpretation

paleogene stable isotope events the oxygen isotope record in paleogene benthic foraminifera shows that at the base of the paleogene the ocean deep waters had a temperature of about 10 c rising to about 12 c at the base of the eocene and cooling between 51 ma and 49 ma to about 9 c the most dramatic event occurred just after the eocene oligocene boundary at about 35 8 ma when ocean deep waters cooled by several degrees within 104 105 yr probably in association with temporary glaciation in the antarctic region another more intense glacial event in antarctica may have occurred later in the oligocene at about 31 ma and a third near the top of the oligocene at 24 ma in the marine carbon isotope record a very rapid negative excursion occurred precisely at the cretaceous tertiary boundary a recovery to unusually positive values in the late paleocene was followed by a second negative excursion close to the paleocene eocene boundary that was even more extreme in magnitude although it was not as rapid these major carbon isotope events permit very accurate stratigraphic correlation there are many other smaller features in the carbon isotope record that will also prove useful for this purpose

the multiple impacts hypothesis for mass extinction a comparison of the late devonian and the late eocene abstract application of the lag time multiple impacts hypothesis poag 1997b palaios 12 582 590 poag et al 2001 columbia univ press to the late devonian leads to the prediction that the frasnian famennian pulsed extinctions were triggered by a rapid drop in global temperature that followed an impact produced anomalous warm interval which interrupted the global cooling trend from the middle devonian greenhouse to the early carboniferous icehouse in actualistic comparison with the late eocene the lag time multiple impacts hypothesis would predict that a frasnian interval of multiple impacts should have occurred between 367 7 and 366 7 ma the fact that three impacts the alamo siljan and flynn creek do occur either within this predicted interval or close to it in time is corroborative evidence that the lag time multiple impacts hypothesis may indeed provide the causal mechanism for the frasnian famennian mass extinction based on the application of the lag time multiple impacts hypothesis to the frasnian famennian mass extinction it is here suggested that future searches for evidence of impact events in the late devonian be concentrated in strata that occur in the frasnian transitans to early hassi zonal interval and not in strata immediately below or above the frasnian famennian boundary

faunal turnover of intermediate water benthic foraminifera during the paleogene in new zealand abstract analysis of benthic foraminifera in upper cretaceous through oligocene bathyal sediments from east coast north island new zealand demonstrates that the catastrophic extinction event of intermediate water 100 1000 m taxa occurred approximately 58 57 ma during the latest paleocene early eocene global warming the following middle eocene cooling produced stepwise origination events signifying the greatest turnover of the fauna most of the extinct species are aerobic forms whereas the surviving taxa are dysaerobic forms this interpretation suggests that a change of environment to low oxygen conditions was the main cause of the extinction following the extinction event a dysaerobic fauna occupied the intermediate water for about one million years the stepwise appearance of new aerobic species in the middle eocene indicates a gradual increase of dissolved oxygen in the intermediate water

mammalian generic diversity and turnover in the late paleocene and early eocene of the bighorn and crazy mountains basins wyoming and montana usa abstract patterns of mammalian generic turnover richness and faunal composition were investigated for faunas from 17 biostratigraphic zones in middle paleocene through early eocene deposits of the bighorn and clarks fork basins of northern wyoming and the crazy mountains basin of south central montana significance of turnover was evaluated 1 by comparison of observed turnover to expected turnover calculated from the multiple regression of turnover on zone duration and generic richness and 2 by comparison of observed turnover to a bootstrapped turnover distribution patterns of turnover and richness also were assessed in light of relative sampling quality of each faunal zone the analysis identified four intervals of significant faunal change the torrejonian tiffanian transition the late tiffanian the earliest wasatchian and the middle to late wasatchian the first interval was characterized by a high number of last occurrences in the latest torrejonian resulting in a decrease in standing generic richness in the earliest tiffanian but no major changes in ordinal composition during the next interval of significant turnover the late tiffanian higher than expected first occurrences resulted in an increase in standing richness and a change in faunal composition most probably reflecting the immigration of taxa from outside north america the third and most dramatic interval of significant generic turnover took place in the earliest wasatchian and was distinguished by a high number of first occurrences but relatively few last occurrences this led to a marked increase in generic richness a pattern similar to that for the early wasatchian of north america as a whole the major change in faunal composition as in the late tiffanian was largely composed of immigrants from other continents the pattern of faunal change during the early wasatchian of the bighorn basin along with evidence for global warming at the paleocene eocene boundary supports previous interpretations associating this episode in mammalian evolution with the opening of high latitude intercontinental dispersal routes during the fourth interval of interest the middle to late wasatchian the bighorn basin fossil record shows a drop in generic richness this differs from the overall north american pattern and may be in part an artifact of still inadequate sampling for the latest part of the stratigraphic sequence in the bighorn basin

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

conflicting isotopic and biotic evidence for tropical sea surface temperatures during the tertiary abstract the biotic evidence from a varied group of shallow water organisms including mangroves zooxanthellate corals mainly reefal and larger foraminifera suggests that sea surface temperatures at low latitudes during the tertiary from at least the early eocene to the middle miocene were subtropical to tropical in nature and similar to temperatures prevailing at low latitudes at the present day 20 28 c in a recent paper shackleton 1984 the suggestion is made on the basis of oxygen isotope studies of foraminiferal shells that low latitude sea surface temperatures during the palaeogene and much of the neogene were invariably lower than those in similar regions today with a stable temperature of around 18 c this paper discusses the conflicting evidence for sea surface temperatures obtained from palaeontological and isotopic sources and suggests that palaeotemperatures derived from some isotopic studies are too low to account for the distribution and diversity of many tertiary tropical and subtropical biotas

δ13c values of miocene pacific benthic foraminifera correlations with sea level and biological productivity 13 c 12 c ratios of miocene benthic foraminifera from 22 pacific ocean sites vary with time but are similar at almost all sites in any restricted interval 13 c values are correlated with sea levels inferred from onlap offlap curves reflecting the deposition of greater amounts of organic matter on the continental shelves during transgressions differences in 13 c between sites are correlated with local differences in biological productivity in the overlying surface waters 13 c 12 c values of benthic foraminifera show promise as indicators of marine paleoproductivity

high resolution 104 years deep sea foraminiferal stable isotope records of the eocene oligocene climate transition we have constructed high resolution 104 105 years benthic foraminiferal 13c and 18o records for the upper eocene through lower oligocene of two pelagic sequences deep sea drilling project dsdp site 522 in the angola basin south atlantic ocean and ocean drilling program odp site 744 in the southern indian ocean these records provide improved constraints on both the timing and magnitude of marine oxygen and carbon isotope events from 30 to 35 ma the oxygen isotope records indicate that the ubiquitous 18o increase oi 1 which marks the rapid expansion of continental ice sheets and a minimum of 3 to 4 c of cooling of bottom waters in the earliest oligocene 33 6 ma occurred in 350 kyr more than half the transition occurred over the final 40 50 kyr this period of lower temperatures and widespread continental glaciation persisted for roughly 400 kyr i e the duration of magnetochron c13n these records also indicate that this interval was characterized by at least two 100 kyr waxing and waning cycles oi 1a and oi 1b and possibly several higher frequency events the benthic foraminiferal 13c records show a positive 0 8 excursion that is nearly isochronous with the oi 1 oxygen isotope increase similar magnitude 13c increases at other sites indicate this was a global phenomenon suggestive of an unusually large perturbation to the carbon cycle this excursion was followed by smaller amplitude 13c oscillations with periods of roughly 400 kyr we suspect that the ubiquitous oi 1 13c excursion resulted from a brief but substantial increase in export production and carbon burial

fossil plants record an atmospheric 12co2 and temperature spike across the palaeocene eocene transition in nw europe the large negative excursion of carbon isotope composition 13 c recorded from foraminifera and bulk carbonates indicates a major anomaly in the operation of the global carbon cycle across the palaeocene eocene boundary therefore we sought terrestrial evidence for the transfer of isotopically light carbon 12 co 2 from the ocean to the atmosphere by making systematic 13 c measurements or well dated sequences of fossil pollen from nw europe the results indicate an atmospheric 12 co 2 spike of c 2 between 58 and 55 ma coincident with the ocean isotopic anomalies pollen spectra from these sequences suggest a marked shift in dominance from mixed mesophytic to paratropical forests synchronous with the terrestrial isotope excursion

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

assessing offsets between the δ13c of sedimentary components and the global exogenic carbon pool across early paleogene carbon cycle perturbations 1 negative stable carbon isotope excursions cies across the paleocene eocene thermal maximum petm 56 ma range between 2 and 7 even after discounting sections with truncated records individual carbon isotope records differ in shape and magnitude from variations in the global exogenic carbon cycle through changes in 1 the relative abundance of mixed components with different 13c within a measured substrate 2 isotope fractionation through physiological change and 3 the isotope composition of the carbon source all three factors likely influence many early paleogene 13c records especially across the petm and other hyperthermal events we apply these concepts to late paleocene early eocene 58 52 ma records from lomonosov ridge arctic ocean linear regression analyses show correlations between the 13c of total organic carbon toc and two proxies for the relative contribution of terrestrial organic components to sediment toc the branched and isoprenoid tetraether index and palynomorphs we use these correlations to subtract the terrestrial component from 13ctoc and calculate marine organic matter 13c the results show that the magnitude of the cie in 13ctoc across the petm is exaggerated relative to the magnitude of the cie in 13cmom by 3 due to increased contributions of terrestrial organic carbon during the event collectively all carbon isotope records across the petm and other major climate carbon cycle perturbations in earth s history are potentially biased through one or more of the above factors indeed it is highly unlikely that any 13c record shows the true shape and magnitude of the cie for the global exogenic carbon cycle for the petm we conclude that cie in the exogenic carbon cycle is likely 4 but it will take additional analyses and modeling to obtain an accurate value for this cie

substantial iron sequestration during green clay authigenesis in modern deep sea sediments pyrite formation has been considered a key iron sink in organic rich marine sediments analyses of sediments from the ivory coast ghana marginal ridge demonstrate that iron can be buried at greater rates during green clay formation

syndepositional shallow water precipitation of glauconitic minerals abstract numerous studies have demonstrated that glauconitic minerals predominantly form in water depths of mid shelf to upper slope in modern oceans these areas tend to have slow sedimentation rates another commonly cited requisite for glauconitic mineral precipitation cambro ordovician strata from the southwestern us are rich in glauconitic minerals stratigraphic sedimentological and petrographic constraints indicate that the glauconitic minerals are autochthonous in marked contrast to the modern environments of deposition these cambro ordovician strata formed under very shallow water to tidal flat conditions the trough cross stratified deposits of the most glauconitic mineral rich accumulations glaucarenites indicate a high energy environment and probably a normal to high rate of sedimentation the presence of fibroradiated rims of glauconitic minerals on glauconitic mineral pellets echinoderm fragments and quartz grains demonstrates that the cambro ordovician glauconitic minerals precipitated on or in close proximity to the sea floor and prior to calcite precipitation consequently glauconitic minerals must have formed under markedly different conditions in the lower paleozoic than they do today thus the occurrence of glauconitic minerals in the rock record cannot be used a priori as an environmental indicator of either mid shelf and deeper water and or a slow rate of sedimentation

stable isotope stratigraphy and paleoclimatology of the paleogene bighorn basin wyoming usa abstract climatic warming from the late paleocene into the early eocene had profound effects on atmospheric and marine circulation marine thermal gradients and benthic biota in addition marine carbon isotope values decreased substantially in both surface and deep waters because carbon is rapidly exchanged between reservoirs at the earth s surface such as marine surface water the atmosphere land plants and materials that obtain carbon from plants e g soil minerals and herbivores carbon isotope fluctuations provide time lines linking the marine and continental records we analyzed the carbon isotope composition of paleosol carbonates and mammalian tooth enamel from stratigraphic sections in northwestern wyoming carbon isotope correlation demonstrates that a short interval of extreme high latitude warming coincided precisely with the first appearance of several important modern mammalian orders in addition oxygen isotope analyses of fossils and paleosol carbonates provide information about climatic conditions on land in the paleogene we reconstructed the oxygen isotope composition of local meteoric water using biogenic minerals paleocene eocene meteoric water was significantly 18 o depleted indicating substantial loss of water vapor during its transport to the region soil temperature was calculated as a proxy for mean annual temperature assuming oxygen isotope equilibrium between soil carbonate and meteoric water calculated temperatures were plausible 10 25 c but highly variable prohibiting high resolution analysis of local temperature variations in response to global climatic warming

terrestrial records of a regional weathering profile at the paleocene eocene boundary in the williston basin of north dakota the orange zone within the bear den member of the golden valley formation williston basin north dakota represents a terrestrial weathering profile formed by intense pedogenesis during an ancient ca 55 ma global warming event referred to as the paleocene eocene thermal maximum distinctive features of the orange zone include 1 high abundances of kaolinite 2 a strongly leached character with a bright orange iron enriched horizon 3 poor organic carbon preservation and 4 ferric pans pisoliths at its basal contact equivalent to modern lateritic materials though conclusive evidence such as a distinctive paleocene eocene thermal maximum flora and or definitive carbon isotope excursion is lacking the stratigraphic succession of palynofloral datums preserved within the upper part of the bear den orange zone is similar to that associated with the later stages of other terrestrial paleocene eocene thermal maximum records from the u s western interior bulk 13 c org ratios decrease through the orange zone as well but the magnitude of this isotopic decrease is less than that of the carbon isotope excursion thus the collective evidence indicates that the early initial stages of the paleocene eocene thermal maximum are either preserved within the barren condensed interval of the lower orange zone or are missing altogether from the williston basin stratigraphy and that the orange zone likely developed during the later recovery stages of the paleocene eocene thermal maximum the williston basin records generally agree with the tenet that continental weathering intensified during the paleocene eocene thermal maximum moreover these records indicate that the paleohydrology of the basin varied markedly and that sequestration of terrestrial organic carbon was greatly reduced as this transient global warming event unfolded

the paleocene eocene transition in the antarctic indian ocean inference from planktic foraminifera isotopic depth stratification and relative abundance studies of planktic foraminifera at odp site 738 reveal three major faunal turnovers during the latest paleocene and early eocene reflecting the climatic and structural changes in the antarctic surface ocean faunal event 1 occurred near the paleocene eocene boundary and is characterized by a faunal turnover in deep dwellers decreased relative abundance in intermediate dwellers and increased relative abundance in surface dwellers this event marks a temporary elimination of the vertical structure in the surface ocean over a period of more than 63 000 years that is apparently associated with the sudden shutdown of the antarctic intermediate water production the appearance of morozovellids before this event suggests that polar warming is the cause for the shutdown in the production of this water mass at this time warm saline deep water may have formed at low latitudes faunal event 2 occurred near the ap5a ap5b subzonal boundary and is characterized by a faunal turnover in deep dwellers with no apparent change in surface and intermediate dwellers increased individual size wall thickness and relative abundance in deep dwelling chiloguembelinids suggests the formation of a deep oxygen minima in the antarctic oceans during the maximum polar warming possibly as a result of upwelling of nutrient rich deep water faunal event 3 occurred in subzone ap6 and is characterized by a faunal turnover in surface dwellers and a delayed diversification in deep dwellers this event marks the onset of antarctic cooling a drastic decrease in the 13c 18o values of the deep assemblage in zone ap7 suggests an intensified thermocline and reduced upwelling following the polar cooling

late paleocene to eocene paleoceanography of the equatorial pacific ocean stable isotopes recorded at ocean drilling program site 865 allison guyot an expanded and largely complete upper paleocene to upper eocene section was recovered from the pelagic cap overlying allison guyot mid pacific mountains at ocean drilling program odp site 865 18o26 n 179o33 w paleodepth 1300 1500 m reconstructions show that the site was within a few degrees of the equator during the paleogene because no other paleogene sections have been recovered in the pacific ocean at such a low latitude site 865 provides a unique record of equatorial pacific paleoceanography detailed stable isotopic investigations were conducted on three planktonic foraminiferal taxa species of acarinina morozovella and subbotina we studied benthic foraminiferal isotopes at much lower resolution on species of cibicidoides and lenticulina nuttallides truernpyi and gavelinella beccariiformis because of their exceptional rarity the 5180 and 513c stratigraphies from site 865 are generally similar to those derived from other paleocene and eocene sections the planktonic foraminiferal records at site 865 however include significantly less short term single sample variability than those from higher latitude sites indicating that this tropical oligotrophic location had a comparatively stable water column structure with a deep mixed layer and less seasonal variability low amplitude 0 1 0 8 o oscillations on timescales of 250 000 to 300 000 years correlate between the 513c records of all planktonic taxa and may represent fluctuations in the mixing intensity of surface waters peak sea surface temperatures of 24o 25oc occurred in the earliest eocene followed by a rapid cooling of 3 6oc in the late early eocene temperatures remained cool and stable through the middle eocene in the late eocene surface water temperatures decreased further vertical temperature gradients decreased dramatically in the late paleocene and were relatively constant through much of the eocene but increased markedly in the late eocene intermediate waters warmed through the late paleocene reaching a maximum temperature of 10oc in the early eocene cooling in the middle and late eocene paralleled that of surface waters with latest eocene temperatures below 5oc extinction patterns of benthic foraminifera in the latest paleocene were similar to those observed at other pacific sites and were coeval with a short term very rapid negative excursion in 513c values in planktonic and benthic taxa as at other sites during this excursion benthic foraminiferal 5180 values decreased markedly indicating warming of 4 to 6oc for tropical intermediate waters while planktonic taxa show slight warming 1 oc followed by 2oc of cooling convergence of 5180 values of planktonic and benthic foraminifera suggests that thermal gradients in the water column in this tropical location collapsed during the excursion these data are consistent with the hypothesis that equatorial pacific surface waters were a potential source of warm higher salinity waters which filled portions of the deep ocean in the latest paleocene oxygen isotopic data indicate that equator to high southern latitude sea surface thermal gradients decreased to as little as 4oc at the peak of the excursion suggesting some fundamental change in global heat transport

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

organic rich sedimentation in the south pacific ocean associated with late paleocene climatic cooling abstract a distinctive organic rich marine mudstone of late paleocene age occurs in most of new zealand s sedimentary basins and has been identified as a potential source rock for oil and gas identified as the waipawa formation in the east coast basin and the tartan formation in the great south and canterbury basins the unit is a relatively uniform massive mudstone that varies greatly in thickness 2 70 m and grades laterally into distinctive facies equivalents notably greensand and a thin bedded siliceous mudstone all these facies are characterised by relatively high toc 0 5 10 wt and 13 c enrichment 13 c toc 24 and we refer to them collectively as waipawa organofacies our detailed stratigraphic and geochemical studies refine the age 58 7 to 59 4 ma distribution and nature of the waipawa organofacies we have determined that deposition occurred in continental margin settings throughout much of the southwest pacific under cool dysoxic conditions associated with a significant influx of terrestrial organic matter high marine productivity a global fall in sea level and a regional unconformity across shallow and deep marine settings the combination of cool temperatures lowered sea level and bathyal erosion suggests that deposition was linked to short lived growth of an antarctic ice sheet in the earliest late paleocene 59 ma

sedimentological evidence for the formation of an east antarctic ice sheet in eocene oligocene time middle eocene to late oligocene sediments recovered at ocean drilling program sites 689 and 690 on maud rise in the southernmost atlantic ocean and at sites 738 and 744 on kerguellen plateau in the southernmost indian ocean were analysed in order to study the depositional environment and the palaeoclimate special emphasis was placed on the reconstruction of the formation of a cryosphere on the antarctic continent the investigations include quantifications of carbonate and opal contents grain size analyses and studies of clay mineral assemblages the sedimentary sequence at all sites under investigation is highly pelagic with nannofossil oozes and chalks dominant the first indication of probable glacierization at sea level is in the form of isolated gravel and terrigenous sand grains which indicate ice rafting from middle eocene time at c 45 5 ma this is supported by enhanced concentrations of detrital chlorite and reworked kaolinite probably some glaciers reached the sea while most of the continent remained under the influence of a humid and warm to temperate climate the growth of the inland ice resulted in enhanced physical weathering and in increased contents of detrital chlorite and kaolinite from about 40 ma a strengthening of the glacial conditions and the onset of continental east antarctic glaciation is recorded in early oligocene sediments with an age of 36 ma all major sediment parameters document this event the clay mineralogy changed between c 36 3 ma and c 35 5 ma from smectite dominated assemblages to illite and chlorite dominated assemblages the latter being indicative of physical weathering under cooler climates large quantities of ice rafted gravel and sand accumulated on the kerguelen plateau between 36 0 ma and 35 8 ma at the same time an increase in opal content occurred as well as a decrease in carbonate the sediment parameters imply that the east antarctic continent was more or less totally buried beneath the ice during oligocene time the ice sheet however probably did not have a polar but a temperate character as indicated by the occurrence of nothofagus and relatively warm surface water temperatures prohibiting the long distance transport of debris by icebergs

did photosymbiont bleaching lead to the demise of planktic foraminifer morozovella at the early eocene climatic optimum the symbiont bearing mixed layer planktic foraminiferal genera morozovella and acarinina were among the most important calcifiers of early paleogene tropical subtropical oceans a marked and permanent switch in the abundance of these genera is known to have occurred at low latitude sites at the beginning of the early eocene climatic optimum eeco such that the relative abundance of morozovella permanently and significantly decreased along with a progressive reduction in the number of species concomitantly the genus acarinina almost doubled its abundance and diversified here we examine planktic foraminiferal assemblages and stable isotope compositions of their tests at ocean drilling program site 1051 northwest atlantic to detail the timing of this biotic event to document its details at the species level and to test a potential cause the loss of photosymbionts bleaching we also provide stable isotope measurements of bulk carbonate to refine the stratigraphy at site 1051 and to determine when changes in morozovella species composition and their test size occurred we demonstrate that the switch in morozovella and acarinina abundance occurred rapidly and in coincidence with a negative carbon isotope excursion known as the j event 53 ma which marks the start of the eeco we provide evidence of photosymbiont loss after the j event from a size restricted 13c analysis however such inferred bleaching was transitory and also occurred in the acarininids the geologically rapid switch in planktic foraminiferal genera during the early eocene was a major evolutionary change within marine biota but loss of photosymbionts was not the primary causal mechanism

linked silurian carbon cycle perturbations bursts of pinnacle reef growth extreme sea level oscillations and evaporite deposition michigan basin usa abstract integration of sedimentologic chemostratigraphic biostratigraphic and geochronologic data identifies the profound influence that sudden bursts of carbonate sedimentation sea level oscillation and hypersalinity associated with ireviken and mulde carbon cycle perturbations had on the evolution of the michigan basin during the silurian conodonts and carbon isotope 13ccarb stratigraphy of the lockport and engadine dolomites constrain the rapid build up and progradation of a thick biohermal wedge along the basin margins to the sheinwoodian age ireviken excursion a recently identified period of global reef growth this event significantly changed the hydrologic architecture of the basin ultimately resulting in restricted seawater exchange that drove evaporite deposition zircon u pb ages of 428 ma from bentonites near the base of the evaporite bearing salina group together with 13ccarb profiles transecting the basin constrain the onset of hypersalinity to initiation of the late homerian mulde excursion importantly the double 13ccarb peak of this event parallels a complex pattern of dramatic sea level oscillations on the order of 100 m recorded within the a 0 to a 2 evaporites and associated pinnacle reefs ascending 13ccarb values were accompanied by sea level fall karstification and the formation of evaporites in the basin center intra excursion sea level rebounds triggered exceptionally rapid upward pinnacle reef growth subsequent sea level fall again exposed the ramp and pinnacle reefs resulting in basin wide restriction and massive salt deposition that ultimately encased the reefs in salt the return to baseline 13ccarb values was accompanied by flooding and carbonate sedimentation our integrated approach with high resolution 13ccarb stratigraphy from closely spaced intra basinal sections as a central component enables finely tuned chronostratigraphic correlation recognition of unconformity bound facies packages i e systems tracts and constrains variations in sea level and sedimentation rates these findings have immediate applications to predictive static reservoir models for the evaluation of the reefs as repositories for anthropogenic co2 sequestration gas storage reservoirs and hydrocarbon exploration ultimately our findings demonstrate that a cascade of rapid environmental changes including pulses of carbonate sedimentation high amplitude sea level oscillations and evaporite deposition were associated with the ireviken and mulde perturbations of the silurian carbon cycle

manganese deposition through geological time dominance of the post eocene deep sea environment abstract the total terrestrial manganese ore deposits amount to about 6 4 10 9 tonnes of which 5 3 10 9 tonnes 82 are precambrian and 1 1 10 9 tonnes 18 mesozoic and cenozoic deep sea manganese nodules formed since the lower miocene unconformity 12 ma b p hold about 10 11 tonnes mn about 16 times the manganese in terrestrial deposits the development of deep sea manganese nodules is a reflection of global cooling and resulted from the transition of the sluggish cretaceous ocean with warm saline bottom water to the post eocene ocean with cold well oxygenated bottom curents important climatic and oceanographic events occurred at the eocene oligocene boundary and more particularly at the lower miocene unconformity which marks the period of increased antarctic bottom water circulation by contrast the giant shallow water manganese deposits of the lower jurassic to oligocene are associated with anoxia and high sea level stands the two types of deposit reflect different oceanographic conditions and tend not to be contemporaneous mass balance considerations suggest that the present day input of manganese into the oceans is in balance with its deposition in manganese nodules and sediments with perhaps 90 of the input being from hydrothermal sources although this is speculative the scale of present day deep sea manganese nodule formation suggests that we live in the manganese era

middle eocene through early oligocene climate history and paleoceanography in the southern ocean stable oxygen and carbon isotopes from odp sites on maud rise and kerguelen plateau mackensen a and ehrman w u 1992 middle eocene through early oligocene climate history and paleoceanography in the southern ocean stable oxygen and carbon isotopes from odp sites on maud rise and kerguelen plateau mar geol 108 l 27 paleogene stable oxygen and carbon isotopes were measured in foraminifera from odp sites 689 and 690 at maud rise in the atlantic ocean sector of the southern ocean and from sites 738 744 748 and 749 at the southern kerguelen plateau in the indian ocean sector these data were compared with sedimentological data from the same sample set both benthic and planktic 6180 values document a cooling trend beginning around 49 5 ma at all sites during the late middle eocene planktic lso values indicate a steepening latitudinal temperature gradient from 14 c at the northern sites towards 10 c at the southernmost sites terrigeneous sand grains of probably ice rafted origin and clay mineral assemblages point to the existence of a limited east antarctic ice cap with some glaciers reaching sea level as early as middle eocene time around 45 5 ma between 45 and 40 ma average paleotemperatures were between 5 and 7 c in deep and intermediate water masses while near surface water masses ranged between 6 and io c during the late eocene between 40 and 36 ma average temperatures further decreased to 4 5 c in the deep and intermediate water masses and to 5 8 c near the sea surface abruptly increasing 61so values at approximately 35 9 ma exactly correlate with a sharp pulse in the deposition of icerafted material on the kerguelen plateau a dramatic change in clay mineral composition and an altered southern ocean circulation indicated by a differentiation of benthic 61 c values between sites increasing opal concentrations and decreasing carbonate contents for planktic and benthic foraminifera this 80 increase ranges between 1 0 and 1 3 o and between 0 9 and 1 4 o respectively we favour a hypothesis that explains most of the 61so shift at 35 9 ma with a buildup of a continental east antarctic ice sheet consequently relatively warm oligocene antarctic surface water temperatures probably are explained by a temperate wet based nature of the ice sheet this would also aid in the fast build up of an ice sheet by enhancing the moisture transport on to the continent

paleoceanographic significance of late paleocene dysaerobia at the shelf slope break around new zealand abstract a geochemical and micropaleontological study of the waipawa formation in new zealand was undertaken to investigate its depositional setting and possible relationship to major changes in the marine environment the organic rich formation was deposited in the late paleocene during a third order eustatic sea level rise precise age control is lacking but deposition can be placed between a climatic cooling at 59 1 ma and a thermal maximum at 55 5 ma during the transition from cold to warm saline deep water circulation in the south pacific deposition occurred around most of the land mass generally near the shelf break and microfaunal evidence suggests dysaerobic conditions there appears to have been no contemporaneous organic rich sedimentation on the shelf so the widespread high phytoplanktonic productivity which is reflected in positive excursions in kerogen 13c to 20 was probably caused by regional upwelling however the paleodistribution of the formation cannot be readily accounted for by wind driven upwelling alone there is strong positive correlation between organic content kerogen 13c values and unusually high abundance of 24 n propylcholestanes 20 55 of c27 c30 regular steranes surface water conditions favoured a particular group of phytoplankton that preferentially synthesised the precursor c30 sterols and there is microfaunal evidence for warming carbonate oxygen isotopic data are also consistent with warming but may be affected by diagenetic alteration the waipawa formation may result from regional upwelling of warm saline oxygen depleted nutrient rich deep water in what appears to be an earlier and longer term but geographically more restricted event than that responsible for the benthonic extinction event at 55 5 ma

a critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for late cretaceous global correlation abstract climate variability is driven by a complex interplay of global scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter regional correlation which in most cases cannot be obtained with biostratigraphic methods alone chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high resolution correlation over large distances but complications arise from a multitude of possible influences from local differences in biological diagenetic and physico chemical factors on individual 13c records that can mask the global signal to better assess the global versus local contribution in a 13c record it is necessary to compare numerous isotopic records on a global scale as a contribution to this objective this paper reviews bulk sediment 13ccarb records from the late cretaceous in order to identify differences and similarities in secular 13c trends that help establish a global reference 13c record for this period the study presents a global scale comparison of twenty 13c records from sections representing various palaeo latitudes in both hemispheres and different oceanic settings from the boreal tethys western interior indian ocean and pacific ocean and with various diagenetic overprinting the isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute 13c values and variation in amplitude between the sites these differences reflect the varying local influences e g from depositional settings bottom water age and diagenetic history whereas the concordant patterns in 13c shifts might represent 13c fluctuations in the global seawater dissolved inorganic carbon the latter is modulated by variations in organic matter burial relative to re mineralization in the global scale formation of authigenic carbonate and in partitioning of carbon between organic carbon and carbonate sinks these variations are mainly controlled by changes in climate and eustasy additionally some globally synchronous shifts in the bulk 13ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and thus can be globally synchronized by fluctuations in eustasy atmospheric and oceanic oxygen levels or in large scale oceanic circulation because the influence of early diagenetic cements on the bulk 13ccarb signal can but need not be synchronized chemostratigraphy should not be used as a stand alone method for trans continental correlation and especially minor isotopic shifts have to be interpreted with utmost care nevertheless the observed consistency of the 13c correlations confirms global scale applicability of bulk sediment 13c chemostratigraphy for the late cretaceous including sediments that underwent lithification and burial diagenesis such as the sediments from the himalayan and alpine sections limitations arise from increased uncertainties 1 in sediments with very low carbonate content 2 from larger 13c variability in sediments from very shallow marine environments 3 from unrecognized hiatuses or strong changes in sedimentation rates and 4 in sections with short stratigraphic coverage or with few biostratigraphic marker horizons the combination of chemostratigraphy with biostratigraphy and magnetostratigraphy substantially increases the precision and temporal resolution of inter regional correlations and helps overcome problems that arise from differences in biostratigraphic schemes facies or provincialism of key fossils by using an iterative approach to stepwise increase precision of the correlations isochroneity of first and last occurrences of marker species versus chemostratigraphy is tested which helps to improve biostratigraphic zonations to assess zonal boundary ages and to identify useful criteria for defining late cretaceous stage boundaries many of which are still not formally defined the presented correlations indicate a consistent position for most planktic foraminifer zonal boundaries relative to corresponding isotope shifts during the mid cretaceous sea level high whereas diachroneity appears to be more pronounced during the late campanian and maastrichtian global sea level fall a similar pattern is observed for trans continental consistency in the 13c shifts graphic correlation of isotopic shifts magnetostratigraphic and biostratigraphic events among the compared sections is used to detect hiatuses or relative changes sediment accumulation rates and visualizes consistency or offsets of individual biostratigraphic markers relative to chemo and magnetostratigraphy finally an attempt of a global average 13c stack is presented for the turonian through maastrichtian

c and o isotope compositions of modern fresh water mollusc shells and river waters from the himalaya and ganga plain the aim of this paper is to unfold the relationship between the o and c isotope compositions of modern fresh water mollusc shells and water in order to refine the basis of interpretation for paleoenvironnemental reconstruction in the sub himalayan river basins large number of mollusc shells and associated host water from both running water and closed body of water were analysed including intra shell variability in a few cases the o isotopic compositions of river waters in the himalaya and ganga plain have a large range from 18 in the north of the high range up to 8 to 4 in the ganga plain 18o of rivers are also seasonally variable especially in foothills rivers whereas the seasonal contrast is smoothed out for the main himalayan rivers having large catchments o isotopic compositions of bulk shells aragonite vary between 15 and 5 average 18oara values are consistent with precipitation at equilibrium with host waters at a temperature range of 20 25 c suggesting that shell growth may be favoured during non monsoon conditions shells collected along the main himalayan rivers have 18o values uniformly distributed within 11 and 6 reflecting the minimal seasonal contrast shown by these rivers in contrast o isotopic compositions of shells from foothills rivers vary only by 4 this shows that depending on the type of river where the molluscs grow the information in term of 18o amplitude will be different for identical climatic conditions in closed or pond water bodies significant enrichment in 18o due to evaporation is observed the c isotopic compositions of river dissolved inorganic carbon dic decrease downstream from 0 to 10 reflecting input of soil derived alkalinity and plant productivity in the river 13c of shells are systematically lower than compositions calculated for equilibrium with river dic indicating that in addition to dic a significant fraction of carbon is derived from metabolic sources intra shell 13c are stable compared to the seasonal variability of dic suggesting that the pool of organic carbon changes throughout year

environmental impact of volcanic margin formation late rift stage uplift and subsequent massive transient volcanism during breakup of rifted volcanic continental margins constrain paleoenvironments by modifying basin geometry and the composition of the atmosphere hydrosphere and thus biosphere on regional and global scales the early tertiary north atlantic breakup history shows that lava emplacement was accompanied by regional ashfalls and that extrusive complexes influenced paleogene oceanic and continental margin circulation and sedimentation temporal correspondence with the terminal paleocene deep sea extinction event and the earliest eocene greenhouse suggests a global impact possibly by enhanced atmospheric co 2 levels leading to polar warming and thereby changing patterns of deep water formation in this context transient subaerial volcanism at continental margins should be considered with the much discussed continental flood basalt provinces and oceanic plateaus

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

a new zealand record of sea level rise and environmental change during the paleocene eocene thermal maximum abstract the global warming associated with the paleocene eocene thermal maximum petm ca 55 5 myr ago is the most dramatic identified short term temperature increase of the cenozoic one direct consequence of a warming world is a rise in sea level due primarily to the thermal expansion of water as oceans warmed the kumara 2 core south island new zealand spans the paleocene eocene transition and provides a rare southern hemisphere continental margin record of the petm lithology palynology and compound specific stable isotope compositions of higher plant leaf wax n alkanes reveal a 4 85 m petm and a carbon isotope excursion cie of ca 4 5 larger than the 2 5 to 3 5 cies generally recorded by deep sea foraminifera there is a shift from a terrestrial to a marine potentially anoxic sedimentary depositional environment at the base of the petm interpreted as being the result of a local sea level rise coincident with the onset of the cie is the appearance of pollen associated with thermophilic conditions and the development of nypa mangrove swamps moreover there is a reorganisation of the angiosperm pollen assemblage during the petm and an initial increase in fern spores and decrease in gymnosperms crucially all of these changes occur below the horizon characterised by the most negative 13c values suggesting that 1 the recorded negative excursion of 4 5 may indeed reflect the shift in atmospheric co2 isotopic composition and 2 that the large input of 13c depleted carbon into the ocean atmosphere system was not geologically instantaneous with at least some of the added carbon lagging warming sea level rise and vegetation change furthermore compound specific hydrogen isotope analyses show a large degree of variability both directly before and during the cie suggesting that the petm in new zealand was characterised by complex and transient changes in the hydrological regime similar to those reported in north america the arctic and eastern africa thus the new petm record from kumara 2 reveals local climatic and biotic responses driven by a combination of global warming and the consequential change in local depositional environment induced by sea level rise

global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events rea d k zachos j c owen r m and gingerich p d 1990 global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events palaeogeogr palaeoclimatol palaeoecol 79 117 128 events of the paleocene eocene boundary provide the clearest example to date of how a tectonic event may have global climatic consequences recent advances permit well constrained stratigraphic determination of several events that occurred at that boundary in chron c24r a many fold increase in sea floor hydrothermal activity a global warming a reduction in the intensity of atmospheric circulation a conversion to salinity driven deep ocean circulation a marked lightening of oceanic 313c values extinction and evolution of both benthic foraminifera and land mammals and important plate boundary reorganizations including the outpouring of the east greenland volcanics and the initiation of the oceanic rift between norway and greenland we hypothesize that enhanced sea floor hydrothermal activity occasioned by global tectonism resulted in a flooding of the atmosphere with coz causing a reduced pole to equator temperature gradient and increased evaporation at low latitudes increased formation of warm salty probably low nutrient waters coupled with the warm temperatures at high latitudes occasioned a salinity driven rather than temperature driven deep water circulation this newly evolved ocean circulation pattern changed the apportionment of global heat transport from the atmosphere to the ocean with concomitant changes in the circulation intensity of both reduced intensity of atmospheric circulation resulted in lower oceanic biological productivity and enhanced seasonality of climate on the continents a major extinction event among benthic foraminifera was probably a response to the new low nutrient and chemically changed bottom waters and endemism following rapid evolution and dispersal of mammalian orders may have been in response to the new continental climate regime

understanding long term carbon cycle trends the late paleocene through the early eocene 1 the late paleocene to the early eocene 58 52 ma was marked by significant changes in global climate and carbon cycling the evidence for these changes includes stable isotope records that reveal prominent decreases in i 18 oa ndi 13 c suggesting a rise in earth s surface temperature 4 i c and a drop in net carbon output from the ocean and atmosphere concurrently deep sea carbonate records at several sites indicate a deepening of the calcite compensation depth ccd here we investigate possible causes e g increased volcanic degassing or decreased net organic burial for these observations but from a new perspective the basic model employed is a modified version of geocarb iii however we have coupled this well known geochemical model to loscar long term ocean atmosphere sediment carbon cycle reservoir model which enables simulation of seawater carbonate chemistry the ccd and ocean i 13 c we have also added a capacitor in this case represented by gas hydrates that can store and release 13 c depleted carbon to and from the shallow geosphere over millions of years we further consider accurate input data e g i 13 c of carbonate on a currently accepted timescale that spans an interval much longer than the perturbation several different scenarios are investigated with the goal of consistency amongst inferred changes in temperature the ccd and surface ocean and deep ocean i 13 c the results strongly suggest that a decrease in net organic carbon burial drove carbon cycle changes during the late paleocene and early eocene although an increase in volcanic activity might have contributed importantly a drop in net organic carbon burial may represent increased oxidation of previously deposited organic carbon such as stored in peat or gas hydrates the model successfully recreates trends in earth surface warming as inferred from i 18 o records the ccd and i 13 c at the moment however our coupled modeling effort cannot reproduce the magnitude of change in all these records collectively similar problems have arisen in simulations of short term hyperthermal events during the early paleogene paleocene eocene thermal maximum suggesting one or more basic issues with data interpretation or geochemical modeling remain

effect of aridity and rainfall seasonality on vegetation in the southern tropics of east africa during the pleistocene holocene transition fossil pollen analyses from northern lake malawi southeast africa provide a high resolution record of vegetation change during the pleistocene holocene transition 18 9 ka recent studies of local vegetation from lowland sites have reported contrasting rainfall signals during the younger dryas yd the lake malawi record tracks regional vegetation changes and allows comparison with other tropical african records identifying vegetation opening and local forest maintenance during the yd our record shows a gradual decline of afromontane vegetation at 18 ka around 14 5 ka tropical seasonal forest and zambezian miombo woodland became established at 13 ka drier more open formations gradually became prevalent although tropical seasonal forest taxa were still present in the watershed during the yd this drought intolerant forest type was likely restricted to areas of favorable edaphic conditions along permanent waterways the establishment of drought tolerant vegetation followed the reinforcement of southeasterly tradewinds resulting in a more pronounced dry winter season after 11 8 ka the onset of the driest most open vegetation type was coincident with a lake low stand at the beginning of the holocene this study demonstrates the importance of global climate forcing and local geomorphological conditions in controlling vegetation distribution

long term 105 or short term 103 δ13c excursion near the palaeocene eocene transition evidence from the tethys expanded sedimentary records from the tethys reveal unique faunal and isotopic changes across the palaeocene eocene p e transition unlike in the open oceans the tethys exhibits a gradual decrease of 1 5 in 13c values prior to the rapid 13c excursion associated with the 613c excursion is a decrease in calcite burial increase in detrital content and appearance of a unique opportunistic planktic foraminifera1 assemblage e g compressed acarininids the existence of a prelude decrease in 13c values in the tethys suggests that the p e 13c excursion may have occurred in two steps and over a few hundred thousand years rather than as one step over a few thousand years as previously suggested this slower excursion rate is readily explained by changing organic carbon weathering or burial rates and avoids the need of invoking ad hoc scenarios

phanerozoic history of deep sea trace fossils the phanerozoic diversity of deep sea trace fossils based on 151 flysch formations displays distinct non linear changes through the phanerozoic with peaks in the ordovician early silurian and early carboniferous lowered in the permian older late jurassic a peak in the tithonian aptian lowered in the albian and the maximum in the eocene the contribution of graphoglyptids in trace fossil assemblages rises gradually up to the end of the cretaceous shows a peak in the palaeocene eocene but a depression in the oligocene all the changes were probably influenced by competition for food and food supply bottom water temperatures and oxygenation and frequency of flysch habitats there is no clear influence of major biotic crises ordovician silurian cretaceous tertiary palaeocene eocene on the diversity of deep trace fossils except the eocene oligocene crisis

oligocene miocene biostratigraphy magnetostratigraphy and isotopic stratigraphy of the western north atlantic magnetostratigraphic records from western north atlantic deep sea drilling project dsdp sites 563 and 558 are correlated with the geomagnetic polarity time scale gpts berggren et ai 1984a 1984b using marine magnetic anomalies and selected biostratigraphic datum levels the magnetochronology established is used to make direct magnetobiostratigraphic correlations that agree with previous oligocene early miocene studies however we show that zones nn8 partim and nn9 and associated epoch 11 correlate with magnetic anomaly 5 chron csn this contrasts with previous indirect correlations of epoch 11 with anomaly sa and requires an upward adjustment of 1 5 2 0 m y for middle late miocene calcareous nannofossil zones we correlate the middle late miocene boundary with zone nn8 and earliest chron csn 10 4 ma

carbon and oxygen isotope stratigraphy of the english chalk and italian scaglia and its palaeoclimatic significance a detailed carbon and oxygen isotope stratigraphy has been generated from upper cretaceous coastal chalk sections in southern england east kent culver cliff isle of wight eastbourne and seaford head sussex norfolk coast and the british geological survey bgs trunch borehole norfolk data are also presented from a section through the scaglia facies exposed near gubbio italian apennines wherever possible the sampling interval has been one metre or less both the chalk and scaglia carbon isotopic curves show minor positive excursions in the mid cenomanian mid and high turonian basal coniacian and highest santonian lowest campanian there is a negative excursion high in the campanian in chalk sections that span that interval the well documented cenomanian turonian boundary spike is also well displayed as is a broad positive excursion centred on the upper coniacian a number of these positive excursions correlate with records of organic carbon rich deposition in the atlantic ocean and elsewhere the remarkable similarity in the carbon isotope curves from england and italy enables cross referencing of macrofossil and microfossil zones and pinpoints considerable discrepancy in the relative positions of the turonian coniacian and santonian stages the oxygen isotope values of the various chalk sections although showing different absolute values that are presumably diagenesis dependent show nonetheless a consistent trend the east kent section which is very poorly lithified indicates a warming up to the cenomanian turonian boundary interval then cooling thereafter regional organic carbon burial documented for this period is credited with causing drawdown of co 2 and initiating climatic deterioration inverse greenhouse effect data from other parts of the world are consistent with the hypothesis that the cenomanian turonian temperature optimum was a global phenomenon and that this interval represents a major turning point in the climatic history of the earth

middle oligocene cooling from equatorial pacific dsdp site 77b an apparently complete 150 m oligocene sequence of pelagic sediment at equatorial pacific deep sea drilling project site 77b has been analyzed for stable isotope and quantitative planktonic foraminiferal studies lower abundance of inferred warm water species and enrichment of 18 o and 12 c in foraminiferal tests during the interval 29 to 32 m y ago suggest cooler climate lowered sea level and significant volume of continental ice compared to earlier and later times in the oligocene

large terrestrial and marine carbon and hydrogen isotope excursions in a new paleocene eocene boundary section from tanzania recent onshore drilling expeditions in tanzania have yielded sediments spanning much of the late cretaceous and paleogene which show exceptionally good preservation of both calcareous microfossils and organic matter the interval of the paleocene eocene thermal maximum petm was recovered at tanzania drilling project tdp site 14 in 2004 the petm interval was identified using planktonic foraminifer and nannofossil biostratigraphy carbon isotopic measurements of planktonic foraminifera from the genus subbotina show a maximum measured negative shift in 13c values of approximately 4 5 which is significantly larger than has been observed for most deep sea foraminifer records higher plant derived n alkanes yield a ca 6 5 negative shift through the same interval as carbon isotope fractionation in higher plants varies amongst taxa and is influenced by humidity it is possible that this remarkably large shift in the n alkane 13c values records environmental and vegetation changes as well as changes in the 13c value of the ocean atmosphere reservoir however dramatic increases in humidity appear to be unlikely as higher plant biomarker d values shift to higher rather than lower values taken together the records suggest that the magnitude of the carbon isotope excursion cie in the ocean atmosphere reservoir may have been larger than has generally been accepted this has important implications for the source and quantity of 13c depleted carbon released at the petm

tertiary paleoceanic chemical variability unintended consequences of simple geochemical models five lines of concrete quantitative evidence about oceanic chemical composition during the past 65 m y can provide insights into the controlling processes and their temporal variations but the system constraints are not yet fully understood the calcium carbonate compensation depth mean carbon isotopic ratio and strontium isotopic ratio have all changed significantly during this time while changes in lithium to calcium and strontium to calcium ratios have been much smaller when these tracers are considered separately simple scenarios of changes in geochemical and geological factors can be used to explain the historical records these factors include 1 increases in continental chemical weathering rates and net continental fluxes to the oceans 2 changes in the isotopic composition of material weathered from continents to the oceans 3 decreases in the proportion of calcium carbonate deposited on continental shelves 4 changes in the deposition or weathering rates of certain types of sediments and 5 changes in hydrothermal circulation because these geochemical cycles are linked to each other and to others such as nutrients and global atmospheric carbon dioxide an explanation invoked for one tracer must satisfy the direction magnitude and timing of the patterns for all the tracers several simple scenarios for geochemical variations have been evaluated for their consequences both intended and unintended and compared to the historical records despite the attractiveness and possible justifications of some simple hypotheses for example decreases in organic carbon burial rates increases in carbonate weathering rates on the continents or increases in all continental weathering rates no one simple scenario appears to be consistent with both the timing and magnitude of the changes observed during the past 65 m y for all tracers considered the contradictions uncovered can be useful in defining what knowledge is crucial to further understanding of oceanic chemical history better knowledge is needed of absolute deep ocean sediment accumulation rates and their temporal variability of the extent and time scale of variability in the net carbon isotope input to the ocean from continental weathering of steady state fluxes for oceanic mass balances and the extent to which these mass balances approach steady state behavior and of the links and interactions between the geochemical cycles of various elements

unusual occurrence of glauconite in a shallow lagoonal environment lower cretaceous northern aquitaine basin sw france some minerals are considered to be representative of specific natural environments among them glauconite is considered to be formed in marine deep platform conditions however the term glauconitic is misused to designate green minerals formed in marine outer shelf environments x ray diffraction scanning electron microscopy and energy dispersive x ray analyses of individual green materials were carried out leading to the identification of glauconite in the purbeckian facies green glauconite grains predominantly occur as burrow fills and occasionally as faecal pellet replacements two depositional environments have been identified from bottom to top of the succession 1 an argillaceous dolomitic lagoonal sediment formed in saline shallow water 2 a marl limestone alternation deposited in a brackish water estuary the crystallochemical properties of the glauconites change abruptly these findings show that glauconite may form in coastal environments and not only in mid shelf to upper deep water platform environments as classically assumed moreover the glauconite composition changes with the chemical conditions imposed by the local environment

stable δ13c δ18o and strontium isotopes through the paleocene at gebel aweina eastern tethyan region abstract stable 13 c 18 o and strontium 87 sr 86 sr isotopic records have been established through the paleocene section at gebel aweina in the eastern desert egypt the section has been formed in a shelf upper bathyal environment and spans the interval from planktonic foraminiferal zones p1d to p6a or p6b integrated evaluation of isotopic results and scanning electron microscope observations suggest that strontium and whole rock 13 c records reflect primarily original isotopic trends whereas 18 o and foraminiferal 13 c values have been severely affected by diagenesis the whole rock 13 c record exhibits a continuous increase of 4 from the early paleocene to middle late paleocene the increase is followed by a stepwise 13 c decrease of the same magnitude through the late late paleocene and onwards the gross trends of this 13 c record have earlier been registered in many coeval deep sea sections but there are also some significant disparities at aweina for example the paleocene carbon isotopic changes have a higher amplitude in the deep sea the mid to late paleocene 13 c increase has been interpreted to reflect high biological productivity and or changes in the global carbon mass balance the 13 c decrease in the upper part of the aweina section can be identified as the paleocene eocene transitional long term 10 3 kyr negative 13 c shift which may reflect a major reorganisation in global oceanic circulation patterns the well known latest paleocene deep sea benthic foraminiferal extinction event has been found in the upper part of the aweina section and coincides with a distinct and rapid 13 c decrease of 1 5 the benthic extinction event and the associated 13 c anomaly thus represent important stratigraphic markers also in more shallow environments the gebel aweina 13 c record shows considerably lower values compared to the global 13 c record during early and early late paleocene and in the latest paleocene in the early late paleocene foraminiferal zones p3a to the base of p4 the aweina 13 c values increase rapidly by 1 5 and converge with the global record thereafter the two records covary up to the benthic extinction event after which they diverge the convergence between the records may reflect sea level rise and more open water mass exchange between the eastern tethys and the world ocean the similarity of pilot 13 c records from greece and tunisia with the aweina record support this interpretation diagenetic processes however cannot be ruled out and further studies are required to determine the significance of the 13 c depletions in the eastern tethyan sediments the 87 sr 86 sr ratios through the paleocene at gebel aweina are remarkably invariable close to a value of 0 7077 this is the same trend that has been reported in some earlier detailed studies conducted on well preserved calcitic material from the paleocene indicating original sr isotopic signatures at gebel aweina the homogeneity of sr isotopic ratios throughout the paleocene contrasts with the prominent changes observed in the carbon isotope record indicating a decoupling of the mechanisms regulating the mass fluxes of these elements the invariable sr isotopic ratios suggest stable conditions as regards to relative changes in mass fluxes of riverine and or hydrothermal sr during the paleocene

end cretaceous mass extinction event argument for terrestrial causation the end cretaceous mass extinctions were not a geologically instantaneous event and were selective in character these features are incompatible with the original alvarez hypothesis of their being caused by a single asteroid impact that produced a world embracing dust cloud with devastating environmental consequences by analysis of physical and chemical evidence from the stratigraphic record it is shown that a modified extraterrestrial model in which stepwise extinctions resulted from encounter with a comet shower is less plausible than one intrinsic to the earth involving significant disturbance in the mantle

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

milankovitch cyclicity and the boom clay formation an oligocene siliciclastic shelf sequence in belgium the boom clay formation of northeast belgium consists of a sequence of alternating laterally persistent beds of silt and clay power spectral analysis of grain size variations indicates regular sedimentary cycles with wavelengths of about 100 and 46cm that had periods of 124 and 57 thousand years ka or less the lateral continuity ofthe beds combined with the regularity and estimated periods of the cycles suggests an indirect link to the 100 and 41 ka orbital milankovitch cycles the variations in meangrain size were caused by changing bottom water turbulence as controlled by storms and or glacio eustatic water depth fluctuations this study confirms that certain marinesiliciclastic sequences can provide proxy records of palaeoclimatic variance

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

comparative paleoecology of paleogene and neogene mammalian faunas trophic structure and composition abstract trophic structure and composition are examined in two important biotic records one the paleogene of wyoming and montana and the other from the neogene of pakistan the paleogene sequence spans approximately 10 million years and encompasses four north american land mammal ages torrejonian tiffanian clarkforkian and wasatchian the neogene sequence spans approximately 17 m y and includes most of the miocene and pliocene with the best documented interval spanning from 16 to 7 ma five basic trophic categories primary consumers herbivores frugivores omnivores secondary consumers insectivores carnivores are recognized for paleogene and neogene mammals based on tooth morphology body size and analogy with modern mammalian groups the paleogene mammalian biota is characterized as one in which both trophic structure and taxonomic composition change through the history of the record the neogene mammalian biota maintains a relatively consistent trophic structure through most of the record although taxonomic composition changes substantially through time based on comparisons of trophic structure from the paleogene and neogene records with that of selected modern mammalian faunas paleogene habitats fluctuated between closed humid forests and more open drier woodlands neogene trophic structure indicates that savanna woodlands were the typical habitat present through most of the sequence only after 7 ma did these woodlands give way to more open grasslands in pakistan

oligocene climate dynamics a planktonic and benthic foraminiferal stable isotope stratigraphy of the oligocene equatorial pacific ocean drilling program site 1218 was generated at 6 kyr resolution between magnetochrons c9n and c11n 2n 26 4 30 ma on a newly developed astronomically calibrated timescale our data allow a detailed examination of oligocene paleoceanography the evolution of the early cryosphere and the influence of orbital forcing on glacioeustatic sea level variations spectral analysis reveals power and coherency for obliquity 40 kyr period and eccentricity 110 405 kyr orbital bands with an additional strong imprint of the eccentricity and 1 2 myr obliquity amplitude cycle driving ice sheet oscillations in the southern hemisphere planktonic and benthic foraminifera 18o are used to constrain the magnitude and timing of major fluctuations in ice volume and global sea level change glacial episodes related to obliquity and eccentricity variations occurred at 29 16 27 91 and 26 76 ma corresponding to glacioeustatic sea level fluctuations of 50 65 m alteration of high latitude temperatures and antarctic ice volume had a significant impact on the global carbon burial and equatorial productivity as cyclic variations are also recorded in the carbon isotope signal of planktonic and benthic foraminifera the water column carbon isotope gradient and estimated percent carbonate of bulk sediment we also investigate the implications of a close correspondence between oxygen and carbon isotope events and long term amplitude envelope extrema in astronomical calculations during the oligocene and develop a new naming scheme for stable isotope events on the basis of the 405 kyr eccentricity cycle count

thermal excursions in the ocean at the cretaceous tertiary boundary northern morocco δ18o record of phosphatic fish debris c lecuyer p grandjean j r o neil h cappetta and f martineau 1993 thermal excursions in the ocean at the cretaceous tertiary boundary northern morocco c lso record of phosphatic fish debris palaeogeogr palaeoclimatol palaeoecol 105 235 243 high precision oxygen isotope analyses were made of phosphate extracted from 17 samples of nektonic and benthic fish debris sampled across the stratigraphic cretaceous tertiary boundary in northern morocco a refinement of the silver phosphate method was used to isolate phosphate from biogenic materials measured 180 values of 18 6 20 5 o are interpreted as reflecting high resolution thermal variations that affected the ocean water column of the western tethys the warm 27 c water masses that characterized maastrichtian times underwent rapid cooling and stabilized at an average temperature of 19 c during the dano montian and thanetian this period of constant and cool temperature was followed by a relatively rapid but more gradual warming to about 25 c achieved in the middle ypresian significant small shifts in 6180 values between nektonic and benthic fauna recorded only during the stages of rapid warming or cooling may correspond to averaged thermal differences within the water column that developed in response to global climatic changes the indicated temperature distribution could have been caused by thermal changes in the atmosphere rather than some signal carried by deep ocean currents the oxygen isotope data coupled with previous measurements of ree and end ti on the same samples support the suggestion that paleo pacific westward currents progressed as far as the northwestern part of the african platform at the end of the cretaceous period

growth ring analysis of early tertiary conifer woods from the canadian high arctic and its paleoclimatic interpretation abstract fossil forests where petrified stumps were preserved in growth position have been found within early tertiary sediments near strathcona fiord ellesmere island canadian arctic archipelago these fossil forests are obvious evidence for early tertiary climate much warmer than that of today we analyzed the growth rings of petrified woods from two fossil forest sites one in middle paleocene and the other in late early eocene to extract information on climate change the woods consist most abundantly of metasequoia and cf glyptostrobus suggesting that these forests grew in similar environments of warm to cool temperate climates mean ring width mean sensitivity and power spectrum were calculated for ring width sequences although significant difference in the mean ring width between the two forests was found a comparison with living trees suggests that the difference can be attributed to the specific difference between the forests so that a significant climate change may not necessarily be invoked we found little significant difference in the mean sensitivity and power spectrum between the forests neither did we find any strong indication of periodicities consideration of all features suggests that there was no significant difference in climate of middle paleocene and late early eocene time in the high arctic however the mean ring widths of these forests were significantly smaller than that reported for mid cretaceous high arctic fossil forest

mid paleocene dropstones in the whangai formation new zealand evidence of mid paleocene cold climate abstract sedimentological micropalaeontological and organic geochemical rock eval pyrolysis criteria suggest that calving glaciers probably from antarctica likely reached the sea and floated by new zealand during the middle paleocene dropping angular coarse detritus into marine mud the dropstone event coincides with marked shifts in organic geochemistry of the associated marine shale as well as changes in foraminiferal productivity the implied cool climate event may have only been a short term climatic oscillation perhaps of only thousands of years however it was significant enough to have affected the biota and organic matter in the water column the dropstones may represent a deep water example of a correlative conformity referred to in sequence stratigraphy literature although the dropstones are easily recognizable in the sediments the interpretation relies on associated palaeontological and organic geochemical data sea level curves presented elsewhere in the literature show mid paleocene sea level falls which approximately coincide with the time when the dropstones in eastern new zealand were deposited

tempo and scale of late paleocene and early eocene carbon isotope cycles implications for the origin of hyperthermals abstract the upper paleocene and lower eocene are marked by several prominent 1 carbon isotope 13c excursions cie that coincide with transient global warmings or thermal maxima including the paleocene eocene thermal maximum petm the cie which are recorded mainly in marine sedimentary sequences have also been identified in continental sequences occurred episodically and yet appear to be paced or triggered by orbital forcing to constrain the timing and scale of the cie relative to long term baseline variability we have constructed a 4 52 million year myr long high resolution 3 kyr bulk sediment carbon isotope record spanning the lower eocene to upper paleocene c25r c24n from a pelagic sediment section recovered at odp site 1262 in the southeast atlantic this section which was orbitally tuned utilizing high resolution core log physical property and geochemical records is the most stratigraphically complete upper paleocene to lower eocene sequence recovered to date time series analysis of the carbon isotope record along with a high resolution fe intensity record obtained by xrf core scanner reveal cyclicity with variance concentrated primarily in the precession 21 kyr and eccentricity bands 100 and 400 kyr throughout the upper paleocene lower eocene in general minima in 13c correspond with peaks in fe i e carbonate dissolution both of which appear to be in phase with maxima in eccentricity this covariance is consistent with excess oceanic uptake of isotopically depleted carbon resulting in lower carbonate saturation during periods of high eccentricity this relationship includes all late paleocene and early eocene cie confirming pacing by orbital forcing the lone exception is the petm which appears to be out of phase with the 400 kyr cycle though possibly in phase with the 100 kyr cycle reinforcing the notion that a mechanism other than orbital forcing and or an additional source of carbon is required to account for the occurrence and unusual scale of this event