extreme warming of tropical waters during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm ca 56 ma was a major global environmental perturbation attributed to a rapid rise in the concentration of greenhouse gases in the atmosphere geochemical records of tropical sea surface temperatures ssts from the petm are rare and are typically affected by post depositional diagenesis to circumvent this issue we have analyzed oxygen isotope ratios 18o of single specimens of exceptionally well preserved planktonic foraminifera from the petm in tanzania 19 s paleolatitude which yield extremely low 18o down to 3 c during the petm and may have exceeded 40 c calcareous plankton are absent from a large part of the tanzania petm record extreme environmental change may have temporarily caused foraminiferal exclusion

evidence for preindustrial variations in the marine surface water carbonate system from coralline sponges 1 coralline sponge skeletons are excellent tools for reconstructing the carbon isotope history of dissolved inorganic carbon dic in tropical surface waters carbon isotope records from coralline sponges clearly reflect the industrial 12c increase in atmospheric co2 with a precision that permits quantitative interpretations we find from a set of 13c records of four caribbean sponge specimens that the isotopic response of surface water dic to the changing isotopic composition of atmospheric co2 varied dynamically during the last century depending on the rate of atmospheric change three of our sponges provide 600 year long 13c records for the first time we can reconstruct surface water 13cdic for the full history of the industrial co2 release as well as the preceding preindustrial period back to the beginning of the little ice age this provides a well founded estimate of the anthropogenically uninfluenced preindustrial background level of surface water 13c 12c ratios our records show small but systematic variations that appear to be linked to the climate fluctuations of the little ice age

enhanced terrestrial weathering runoff and surface ocean carbonate production during the recovery stages of the paleocene eocene thermal maximum 1 the carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the paleocene eocene thermal maximum petm circa 55 ma the rapid release of large quantities of carbon into the ocean atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion cie the brevity 120 220 kyr of the petm reflects the rapid enhancement of negative feedback mechanisms within earth s exogenic carbon cycle that served the dual function of buffering ocean ph and reducing atmospheric greenhouse gas levels detailed study of the petm stratigraphy from ocean drilling program site 690 weddell sea reveals that the cie recovery period which postdates the cie onset by 80 kyr is represented by an expanded 2 5 m thick interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate collectively the micropaleontological and sedimentological changes preserved within the cie recovery interval reflect a transient state when ocean atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths a prominent peak in the abundance of the clay mineral kaolinite is associated with the cie recovery interval indicating that continental weathering runoff intensified at this time as well robert and kennett 1994 such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering runoff and carbonate precipitation helped sequester carbon during the petm recovery period e g dickens et al 1997 zachos et al 2005

origin of limestone conglomerates in the choson supergroup cambro ordovician mid east korea abstract the choson supergroup cambro ordovician of mid east korea consists mainly of shallow marine carbonates and contains a variety of limestone conglomerates these conglomerates are largely comprised of oligomictic rounded lime mudstone clasts of various size and shape equant oval discoidal tabular and irregular and dolomitic shale matrices most clasts are characterized by jigsaw fit mosaic disorganized or edgewise fabric and autoclastic lithology each conglomerate layer is commonly interbedded with limestone dolomitic shale couplets and occasionally underlain by fractured limestone layer capped by calcareous shale limestone conglomerates in the choson supergroup consist of 1 disorganized polymictic conglomerate cd 2 horizontally stratified conglomerate cs 3 mosaic conglomerate cm and 4 disorganized edgewise oligomictic conglomerate cd e these conglomerates are either depositional cd and cs or diagenetic cm and cd e in origin diagenetic conglomerates formed under the conditions of 1 alternating deposition and preservation of carbonate rich and carbonate poor layers and 2 early differential cementation of carbonate rich layers in situ fragmentation may result from brittle fracturing and ductile deformation due to compaction and dewatering enhanced by dissolution processes fluidization is promoted by the overlying impermeable calcareous shale beds and has probably reinforced in situ fragmentation of the underlying limestone beds in situ fragmentation and rounding process is important whereby earlier semiconsolidated portions of limestone are incorporated into the still fluid portion which can be termed autoconglomeration process a synthesis of 145 beds of limestone conglomerates in the choson supergroup suggests that less than about 7 of the conglomerate layers 10 145 are depositional whereas the rest more than 93 135 145 are identified as diagenetic conglomerates the common occurrence of diagenetic conglomerates warrants further study on limestone conglomerates elsewhere in the world

dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the paleocene isotopic records across the latest paleocene thermal maximum lptm indicate that bottom water temperature increased by more than 4 c during a brief time interval 104 years of the latest paleocene 55 6 ma there also was a coeval 2 to 3 excursion in the 13c of the ocean atmosphere inorganic carbon reservoir given the large mass of this reservoir a rapid 13c shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere however a direct consequence of warming bottom water temperature from 11 to 15 c over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic ch4 hydrate at locations with intermediate water depths in terms of the present day oceanic ch4 hydrate reservoir thermal dissociation of oceanic ch4 hydrate during the lptm could have released greater than 1 1 to 2 1 1018 g of carbon with a 13c of approximately 60 the release and subsequent oxidation of this amount of carbon is sufficient to explain a 2 to 3 excursion in 13c across the lptm fate of ch4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the lptm

eocene carbonate accumulation in the north central pacific ocean new insights from ocean drilling program site 1209 shatsky rise abstract major climate transitions and perturbations in global carbon cycle are known to have occurred during the eocene between 56 and 34 million years ago ma a series of carbon isotope excursions cies mark variations in the global carbon cycle and changes in climate through early eocene paleocene eocene thermal maximum petm ca 56 ma is the most pronounced and well documented of these events expressed as a clay rich layer in many deep sea sections resulting from widespread carbonate dissolution on the seafloor which is in turn related to shoaling of the carbonate compensation depth ccd and lysocline other cies of early eocene had similar response however response of these geologically instantaneous hyperthermals differ from long term warmth multi million year time scale of the early eocene climate optimum eeco in terms of sea floor carbonate accumulation following the termination of eeco earth s climate transitioned into long term cooling pronounced fluctuations in ccd of equatorial pacific are known to have occurred during middle late eocene as well whose global extent and origin are still unresolved most proxy records either span the interval of early eocene or document particular climatic events in eocene which significantly limits visualizing the long term eocene climate change and response of open marine carbonate preservation the present study documents change in carbonate dissolution and carbonate mass accumulation rate through the entire eocene 56 34 ma at odp site 1209 on shatsky rise north central pacific and ties it to a stable carbon and oxygen isotope record our study determines the correlation between deep sea carbonate dissolution and carbon cycling process during the dynamic climate regime of eocene a strong correlation between magnitude of cies and intensity of dissolution for early eocene hyperthermal events appears to significantly weaken for multiple dissolution events in middle late eocene thereby indicating fundamental difference in their causal mechanism

high latitude hydrological changes during the eocene thermal maximum 2 abstract the eocene hyperthermals including the paleocene eocene thermal maximum petm and eocene thermal maximum 2 etm2 represent extreme global warming events 56 and 54 million years ago associated with rapid increases in atmospheric greenhouse gas concentrations an initial study on petm characteristics in the arctic region argued for intensification of the hydrological cycle and a substantial increase in poleward moisture transport during global warming based on compound specific carbon and hydrogen isotopic 2h 1h records from sedimentary leaf wax lipids in this study we apply this isotopic and hydrological approach on sediments deposited during etm2 from the lomonosov ridge integrated ocean drilling program expedition 302 our results show similar 2h 1h changes during etm2 as during the petm with a period of 2h enrichment 20 relative to pre event values just prior to the negative carbon isotope shift cie that is often taken as the onset of the hyperthermal and more negative lipid 2h values 15 during peak warming notably lipid 2h enrichment at the base of the event is coeval with colder tex 86 h temperatures if 2h 1h values of leaf waxes primarily reflect the hydrogen isotopic composition of precipitation the observed local relationship between temperature and 2h 1h values for the body of etm2 is precisely the opposite of what would be predicted using a simple rayleigh isotope distillation model assuming a meridional vapor trajectory and a reduction in equator pole temperature gradients overall a negative correlation exists between the average chain length of n alkanes and 2h 1h suggesting that local changes in ecology could have impacted the hydrogen isotopic compositions of leaf waxes the negative correlation falls across three separate intervals the base of the event the initial cie and during the h2 hyperthermal of which the assignment is not fully certain three possible mechanisms potentially explain 2h enriched signals at the base of the event including 1 intense local drying and cooling leading to evaporative 2h enrichment 2 changes in frequency intensity of storm events and its impact on high latitude amount effects and 3 changes in low latitude temperatures evidence for hydrological shifts at the base of both hyperthermals suggests that hydrological change or the factors promoting hydrological change played a role in triggering the release of greenhouse gases generation of similar high resolution isotopic and temperature records at other latitudes is crucial for understanding the causal links between temperature and hydrological changes and may help constrain the source and mechanism of carbon release that triggered the early eocene hyperthermals

high resolution records of the late paleocene thermal maximum and circum caribbean volcanism is there a causal link two recently drilled caribbean sites contain expanded sedimentary records of the late paleocene thermal maximum a dramatic global warming event that occurred at ca 55 ma the records document significant environmental changes including deep water oxygen deficiency and a mass extinction of deep sea fauna intertwined with evidence for a major episode of explosive volcanism we postulate that this volcanism initiated a reordering of ocean circulation that resulted in rapid global warming and dramatic changes in the earth s environment

high resolution deep sea carbon and oxygen isotope records of eocene thermal maximum 2 and h2 eocene thermal maximum 2 etm2 and h2 were two short lived global warming events that occurred 2 m y after the paleocene eocene thermal maximum petm ca 56 ma we have generated benthic foraminiferal stable carbon and oxygen isotope records of four sites along a depth transect on walvis ridge 3 5 1 5 km paleodepth southeast atlantic ocean and one site on maud rise weddell sea to constrain the pattern and magnitude of their carbon isotope excursions cies and deep sea warming at all sites etm2 is characterized by 3 c warming and a 1 4 cie the h2 event that occurred 100 k y later is associated with 2 c warming and a 0 8 cie the magnitudes of the 13 c and 18 o excursions of both events are signifi cantly smaller than those during the petm but their coherent relation indicates that the 13 c change of the exogenic carbon pool was similarly related to warming during these events despite the much more gradual and transitioned onset of etm2 and h2

recovering the true size of an eocene hyperthermal from the marine sedimentary record 1 hyperthermals episodes of abrupt global warming associated with the massive injection of carbon into the oceans and atmosphere represent possible analogs for future climate change however uncertainties in their magnitude rate and duration arising as a result of mixing processes and changes in carbonate preservation as the sediment record is formed complicate their use in constraining climate sensitivity and the role of carbon cycle feedbacks here we use cgenie an earth system model of intermediate complexity to assess likely magnitude and rate of carbon input taking a small hyperthermal event from the early middle eocene c22nh3 49 2ma as a case study we develop an iterative method combined with a sediment model simulating the formation and mixing of deep sea sediments to converge on an estimate for the true magnitude of the carbon cycle perturbation in the atmosphere and ocean that drives the event in inverting the 0 95 benthic 13 cexcursion recorded atocean drilling program site 1258 we obtain an estimate of at least 1 45 for the atmospheric co2 13 c excursion that drove event c22nh3 we also assess controls on intersite variation of event shape in model sediments and find that sedimentation rate is the strongest determinant of modeled event size with higher sedimentation rate sites recording the atmospheric signal more accurately our revised estimate for the size of c22nh3 implies a total carbon input almost two thirds higher than would be deduced if the recorded 13 c excursion magnitude was taken at face value

new evidence for subtropical warming during the late paleocene thermal maximum stable isotopes from deep sea drilling project site 527 walvis ridge the late paleocene thermal maximum lptm was a dramatic short term global warming event that occurred 55 ma warming of high latitude surface waters and global deep waters during the lptm has been well documented however current data suggest that subtropical and tropical sea surface temperatures ssts did not change during the event conventional paradigms of global climate change such as co2 induced greenhouse warming predict greater warming in the high latitudes than in the tropics or subtropics but nonetheless cannot account for the stable tropical subtropical ssts we measured the stable isotope values of well preserved late paleocene to early eocene planktonic foraminifera from south atlantic deep sea drilling project dsdp site 527 to evaluate the subtropical response to the climatic and environmental changes of the lptm planktonic foraminiferal 18o values at site 527 decrease by 0 94 from pre lptm to excursion values providing the first evidence for subtropical warming during the lptm we estimate that subtropical south atlantic ssts warmed by at least 1 4 c on the basis of possible changes in evaporation and precipitation the new evidence for subtropical sst warming supports a greenhouse mechanism for global warming involving elevated atmospheric co2 levels

carbonate saturation dynamics during the paleocene eocene thermal maximum bathyal constraints from odp sites 689 and 690 in the weddell sea south atlantic abstract spatiotemporal patterns of carbonate dissolution provide a critical constraint on carbon input during an ancient 55 5 ma global warming event known as the paleocene eocene thermal maximum petm yet the magnitude of lysocline shoaling in the southern ocean is poorly constrained due to limited spatial coverage in the circum antarctic region this shortcoming is partially addressed by comparing patterns of carbonate sedimentation at the site 690 petm reference section to those herein reconstructed for nearby site 689 biochemostratigraphic correlation of the two records reveals that the first 36 ka of the carbon isotope excursion cie signaling petm conditions is captured by the site 689 section while the remainder of the cie interval and nearly all of the cie recovery are missing due to a coring gap a relatively expanded stratigraphy and higher carbonate content at mid bathyal site 689 indicate that dissolution was less severe than at site 690 thus the bathymetric transect delimited by these two petm records indicates that the lysocline shoaled above site 689 1 100 m while the calcite compensation depth remained below site 690 1 900 m in the weddell sea region the ensuing recovery of carbonate sedimentation conforms to a bathymetric trend best explained by gradual lysocline deepening as negative feedback mechanisms neutralized ocean acidification further biochemostratigraphic evidence indicates the tail end of the cie recovery interval at both sites has been truncated by a hiatus most likely related to vigorous production and advection of intermediate waters

evidence of dynamic recrystallization in polar firn 1 microstructural analyses have been performed on polar firn from the european project for ice coring in antarctica drilling site in dronning maud land antarctica the results derived from images of the firn structure in microscopic resolution indicate that dynamic recrystallization is active in firn at all depths and it dominates the evolution of the microstructure when the firn density exceeds a critical value of 730 kg m3 overburden snow load 0 2 mpa at the firn ice transition density 820 kg m3 the microstructure is characterized by many small grains and bulged or irregularly shaped grain boundaries more than half of all grains show subgrain boundaries thus strain induced boundary migration is an essential feature to describe the irregular grain structure in agreement with previous studies significant grain growth has been observed with depth for the largest grains in the samples however our microscopic analysis reveals that the grain growth with depth in fact vanishes if all grains larger than 65 m in diameter are taken into account this result reflects the fact that the growth of the largest grains is counteracted by grain size reduction by shrinking and subdivision of old grains as well as production of new grains consequently previous conclusions that grain growth in polar firn is essentially analogous to normal grain growth in metallic and ceramic sinters and that the stored strain energy is small in comparison with grain boundary energy can no longer be supported additionally our observations show that the incipience of dynamic recrystallization in polar ice sheets is not as sensitive to temperature as supposed so far a discussion of the change of the mean grain size due to the measuring technique is imperative

response of larger benthic foraminifera to the paleocene eocene thermal maximum and the position of the paleocene eocene boundary in the tethyan shallow benthic zones evidence from south tibet

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

structure and magnitude of the carbon isotope excursion during the paleocene eocene thermal maximum abstract the paleocene eocene thermal maximum petm was a geologically rapid and transient warming event that occurred ca 56 million years ago ma it was associated with a pronounced negative carbon isotope excursion cie and with profound changes in the atmosphere hydrosphere and biosphere this event reflects injections of large amounts of carbon into the atmosphere ocean system but whether single or multiple episodes of carbon release caused this event is uncertain here we present carbon isotope data of bulk carbonate from two parallel limestone sections at tingri south tibet where the limestone was deposited on a tropical carbonate ramp during the petm carbon isotope data of bulk carbonate from both sections are almost identical displaying an expanded stepped cie profile with large magnitude the stepped cie profile consists of three discrete intervals of decreasing carbon isotope values which can be correlated on an inter regional scale between sections from different depositional environments lake carbonate ramp continental slope and open ocean the consistency of these correlations implies occurrence of at least three carbon releases within the cie and indicates complex processes of carbon injection during the petm moreover the cie magnitude of 7 recorded at tingri is tentatively interpreted to reflect carbon isotope changes in the atmosphere and the surface ocean which is larger than the generally accepted value of 4 but is still within the range of some previous records

constraints on ocean acidification associated with rapid and massive carbon injections the early paleogene record at ocean drilling program site 1215 equatorial pacific ocean massive amounts of 13c depleted carbon rapidly entered the ocean more than once during the early paleogene providing a geological framework for understanding future perturbations in carbon cycling

the palaeocene eocene carbon isotope excursion constraints from individual shell planktonic foraminifer records the palaeocene eocene thermal maximum petm is characterized by a global negative carbon isotope excursion cie and widespread dissolution of seafloor carbonate sediments the latter feature supports the hypothesis that the petm and cie were caused by the rapid release of a large mass greater than 2000gt c of 12c enriched carbon the source of this carbon however remains a mystery possible sources include volcanically driven thermal combustion of organic rich sediment dissociation of seafloor methane hydrates and desiccation and oxidation of soil sediment organics a key constraint on the source s is the rate at which the carbon was released fast rates would be consistent with a catastrophic event e g massive methane hydrate dissociation whereas slower rates might implicate other processes the petm carbon flux is currently constrained by high resolution marine and terrestrial records of the cie in pelagic bulk carbonate records the onset of the cie is often expressed as a single or multiple step excursion extending over 10 4 years individual planktonic shell records in contrast always show a single step cie with either pre excursion or excursion isotope values but no transition values benthic foraminifera records which are less complete owing to extinction and diminutive assemblages show a delayed excursion here we compile and evaluate the individual planktonic shell isotope data from several localities we find that the most expanded records consistently show a bimodal isotope distribution pattern regardless of location water depth or depositional facies this suggests one of several possibilities i the isotopic composition of the surface ocean atmosphere declined in a geologic instant 500yr ii that during the onset of the cie most shells of mixed layer planktonic foraminifera were dissolved or iii the abundances or shell production of these species temporarily declined possibly due to initial ph changes

a blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

evolutionary consequences of the latest paleocene thermal maximum for tropical planktonic foraminifera study of planktonic foraminiferal assemblages preserved in the central equatorial pacific odp site 865 reveal that genera which inhabited the near surface mixed layer diversified during the latest paleocene thermal maximum lptm this transient diversification gave rise to a suite of short lived 50 to several 100 ka distinctive morphotypes morozovella allisonensis sp nov m africana and acarinina sibaiyaensis that are restricted to the lptm interval parallel morphometric and stable isotopic data have been recorded from individual shells of members of the m velascoensis m allisonensis and a soldadoensis a sibaiyaensis lineages the single specimen isotope data confirm that m allisonensis and a sibaiyaensis are indeed stratigraphically restricted to the lptm carbon isotope excursion all specimens recorded anomalously low 13c values a stratigraphic succession of single specimen isotope data from within the 13c excursion interval was used to reconstruct the complex population dynamics which mediated the rapid 10 ka evolution of the lptm taxa these data reveal that local populations of ancestral m velascoensis temporarily collapsed with the descendant m allisonensis suddenly originating from a peripherally isolated population this pattern is most consistent with peripatric speciation overall the evolutionary transition from acarinina soldadoensis to a sibaiyaensis is most consistent with sympatric speciation although certain elements of this transition are suggestive of a parapatric mechanism we postulate that the rapid evolution of the lptm taxa a sibaiyaensis and m allisonensis was fostered by a deepening of the nutrient depleted mixed layer alternatively the lptm morphotypes m allisonensis and a sibaiyaensis may have been extreme ecophenotypic variants arrayed along an intensified ecological gradient support for this latter interpretation is derived from the morphometric data which clearly show the morphological intergradation of the lptm taxa with their respective ancestors thus the morphologic diversification seen during the lptm may represent failed speciations both scenarios invoke a temporary steepening of clinal gradients in response to intensified oligotrophy the strong size dependencies displayed by the 18o and 13c signatures of m allisonensis and a sibaiyaensis suggest that photosymbiosis facilitated the evolutionary success of the morozovellids and acarininids during the lptm

the late palaeocene early eocene and toarcian early jurassic carbon isotope excursions a comparison of their time scales associated environmental changes causes and consequences although the earth9s environment is constantly changing there have been a few unusual episodes over the last c 200 ma when change was extreme in terms of its rapidity severity long lasting consequences and unpredictability the geochemical and biotic records for two of these episodes the palaeocene eocene thermal maximum and the toarcian oceanic anoxic event early jurassic possess many significant similarities each event was associated with a major carbon isotope excursion significant levels of biotic extinctions severe global warming an enhanced hydrological cycle and evidence for widespread seawater anoxia both carbon isotope excursions can be subdivided into distinct stages with broadly similar characteristics and durations based on a detailed comparison the palaeocene eocene thermal maximum may have been an incipient oceanic anoxic event the geochemical and biotic changes during these two events are most readily explained by the abrupt large scale dissociation of methane hydrate that followed a period of more gradual environmental change linked to the emplacement of a large igneous province carbon release rates at those times were of the same order of magnitude as the current anthropogenic release rate of carbon to the atmosphere indicating that ancient events such as these may usefully serve as analogues for present day environmental change

response of calcareous nannofossils to the paleocene eocene thermal maximum observations on composition preservation and calcification in sediments from odp site 1263 walvis ridge sw atlantic abstract in this study we present the results of a detailed analysis on calcareous nannofossil assemblages from sediment cores of odp site 1263 southern east atlantic walvis ridge this section represents one of the few complete deep sea sections that document the paleocene eocene thermal maximum petm in the pelagic realm the petm transient event was characterized by a brief but intense interval of global warming a global negative carbon isotope excursion cie and widespread dissolution of seafloor carbonate sediments paired analysis at polarizing light microscope lm and scanning electron microscope sem documents the different behavior of nannofossils through the different phases of the petm at the onset of cie within the cie and during the recovery interval the presence of anomalous specimens and morphotypes within some nannofossil taxa recorded during previous lm high resolution analyses has been further investigated in selected samples at the sem besides the known representatives of the cie petm excursion nanno flora as rhomboaster calcitrapa group and discoaster anartios the analysis revealed the presence of peculiar morphotypes of fasciculithus and deformed specimens of discoaster nobilis group discoaster mediosus and discoaster multiradiatus that are considered related to the anomalous amount of co2 in the ocean atmosphere system during the early phase of petm comparative analyses were performed in few selected samples from other petm sections located at different latitudes in the atlantic and pacific oceans although the anomalous geochemical conditions during the petm cie interval seem to have had some influence on the nannofossil production calcification and assemblage composition it results that local productivity together with post depositional diagenetic conditions were additional important controlling factors on nannofossil assemblages preliminary data from eocene thermal maximum 2 etm2 or elmo suggest that nannofossil malformations are not exclusive of the petm and are associated to other episodes of perturbation of the c cycle

late paleocene early eocene tethyan carbonate platform evolution a response to long and short term paleoclimatic change abstract the early paleogene experienced the most pronounced long term warming trend of the cenozoic superimposed by transient warming events such as the paleocene eocene thermal maximum petm the consequences of climatic perturbations and associated changes on the evolution of carbonate platforms are relatively unexplored today modern carbonate platforms especially coral reefs are highly sensitive to environmental and climatic change which raises the question how sub tropical reef systems of the early paleogene reacted to gradual and sudden global warming eutrophication of shelf areas enhanced co 2 levels in an ocean with low mg ca ratios the answer to this question may help to investigate the fate of modern coral reef systems in times of global warming and rising co 2 levels here we present a synthesis of tethyan carbonate platform evolution in the early paleogene 59 55 ma concentrating on coral reefs and larger foraminifera two important organism groups during this time interval we discuss and evaluate the importance of the intrinsic and extrinsic factors leading to the dissimilar evolution of both groups during the early paleogene detailed analyses of two carbonate platform areas at low egypt and middle spain paleolatitudes and comparison with faunal patterns of coeval platforms retrieved from the literature led to the distinction of three evolutionary stages in the late paleocene to early eocene tethys stage i late paleocene coralgal dominated platforms at low to middle paleolatitudes stage ii a transitional latest paleocene platform stage with coralgal reefs dominating at middle paleolatitudes and larger foraminifera dominated miscellanea ranikothalia assilina platforms at low paleolatitudes and stage iii early eocene larger foraminifera dominated alveolina orbitolites nummulites platforms at low to middle paleolatitudes the onset of the latter prominent larger foraminifera dominated platform correlates with the paleocene eocene thermal maximum the causes for the change from coral dominated platforms to larger foraminifera dominated platforms are multilayered the decline of coralgal reefs in low latitudes during platform stage ii is related to overall warming leading to sea surface temperatures in the tropics beyond the maximum temperature range of corals the overall low occurrence of coral reefs in the paleogene might be related to the presence of a calcite sea at the same time larger foraminifera started to flourish after their near extinction at the cretaceous paleogene boundary the demise of coralgal reefs at all studied paleolatitudes in platform stage iii can be founded on the effects of the petm resulting in short term warming eutrophic conditions on the shelves and acidification of the oceans hampering the growth of aragonitic corals while calcitic larger foraminifera flourished in the absence of other successful carbonate producing organisms larger foraminifera were able to take over the role as the dominant carbonate platform inhabitant leading to a stepwise tethyan platform stage evolution around the paleocene eocene boundary this szenario might be also effective for threatened coral reef sites

climate and sea level perturbations during the incipient eocene thermal maximum evidence from siliciclastic units in the basque basin ermua zumaia and trabakua pass northern spain abstract based on carbon isotope stratigraphy and lithology a revised high resolution correlation is proposed between sections spanning the incipient eocene thermal maximum ietm in the basque region northern spain in three studied sections the ietm event is represented by a prominent non to low calcareous siliciclastic unit su 4 20 5 m thick during formation of the su sedimentation rates for siliciclastic material increased by a factor of two to five whereas detrital grain size decreased significantly kaolinite and chlorite became more abundant in the clay fraction and calcite dissolution in the water column intensified the su reflects a significant change in climate and hydrological regime towards a warmer and seasonally drier climate the drying caused perennial vegetation cover to collapse and led to increased continental erosion but also to reduced hydrodynamic energy of freshwater debouching into the oceans a coeval relative sea level fall probably related to tectonic uplift or doming affecting major parts of western europe increased the land sea slope and further enhanced erosion rates palynological studies support periodic vegetation during seasonal rain instead of permanent conifer forests prominent caliche soils in coeval continental deposits in northern spain also support warm semiarid conditions during the ietm event net evaporation increased under the subtropical high pressure cells including the basque region whereas more northerly latitudes became more wet the su has a similar origin as detrital units previously assigned to the early palaeogene so called siderolithic discharge in other parts of western europe

dynamic response of the shallow marine benthic ecosystem to regional and pan tethyan environmental change at the paleocene eocene boundary the indus basin of pakistan preserves a record of a late paleocene early eocene shallow marine carbonate ecosystem in the east tethys and of its response to an interval of marked climate change and regional tectonic reconfiguration local palaeoecological conditions and or the tethyan latitudinal temperature gradient favoured meso oligotrophic biotic assemblages of mainly larger benthic foraminifera lbfs and dasycladacean algae in the late paleocene early thanetian of east tethys whereas coral algal assemblages dominated west tethys the appearance of oligotrophic lbfs miscellanids and ranikothalids in the indus basin during latest paleocene late thanetian time is comparable with west tethys and suggests a pan tethyan response to long term early paleogene warming however the response of the shallow marine biota to profound earliest eocene environmental change in east tethys was remarkably different from that apparent in the west the larger foraminifer turnover lft and rapid radiation of typical eocene lbfs e g alveolina nummulites and orbitolites seen in the west does not occur in the east during the earliest eocene a relict late paleocene fauna mainly miscellanids and ranikothalids persisted in east tethys but this shows profound morphological and ecological modifications with palaeo depth ranges compressed to shallower environments the delayed lft in the indus basin indicates the complex response of the shallow marine biota to the earliest eocene climate perturbation in the east india asia collision at the paleocene eocene boundary may have produced local biogeographic barriers increased seasonal runoff and altered oceanic gateways and oceanic circulation delaying the lft later in the early eocene pan tethyan environmental conditions were restored and alveolina and nummulites migrated east

paleocene eocene thermal maximum environmental change in the new jersey coastal plain benthic foraminiferal biotic events abstract the environmental impact of the paleocene eocene thermal maximum petm has been intensively studied in the new jersey coastal plain but the benthic foraminiferal response reflecting bottom water conditions has not been documented at high resolution we use benthic foraminiferal data across the paleocene eocene boundary in cores from wilson lake wl and bass river br to recognize 5 foraminiferal associations based on species clusters their varying abundances allow the identification of a stratigraphic succession of 8 distinct biofacies across the studied interval uppermost paleocene biofacies 1 corresponds to the glauconitic sands of the vincentown formation and contains rare small planktic foraminifera and a diverse benthic fauna sediments accumulated slowly in a sufficiently oxygenated outer neritic setting depth 100 110 m at wl 140 150 m at br under fairly oligotrophic conditions the embayment was storm dominated and influenced by strong currents inhibiting deposition of suspended fine particles e g planktic foraminifera clay and enhancing re suspension no significant pre petm environmental changes are detected in the benthic foraminiferal assemblages deposition of the fine grained silty clays of the marlboro clay started at the onset of the petm with transitional lithology present at wilson lake gavelinella beccariiformis common at deep shelfal to bathyal abyssal depths is the only taxon to become extinct at this level water depth increased during the petm to a maximum of 130 150 m at wl planktic foraminifera increased strongly in abundance while the benthic foraminiferal assemblage changed to a more opportunistic less diverse assemblage dominated by stress tolerant taxa tappanina selmensis pulsiphonina prima and anomalinoides acutus biofacies 2 increased riverine influence may have reduced vertical mixing initiating stratification of the water column and establishment of a continuously dysoxic mud belt benthic diversity then gradually increased indicating environmental recovery biofacies 3 and 4 40 95 kyr post petm onset riverine influence probably became more variable generating peak abundances of specialized taxa in a mud belt system with increased accumulation rates the latest petm biofacies 5 95 kyr post onset contains a poorly diverse bulimina callahani assemblage indicative of reoxygenated but still eutrophic bottom water conditions with renewed vertical mixing the lower eocene glauconitic sandy clays of the manasquan formation contain an outer neritic benthic fauna biofacies 6 8 depth 100 135 m at wl indicative of persistent high primary production with return of more vigorous currents higher abundances of buliminids may have been triggered by upwelling along frontal zones our environmental interpretations indicate relatively stable benthic foraminiferal ecosystems at persistently outer neritic water depths 100 150 m despite distinct temporary changes during the petm including eustatic sea level rise of up to 30 m and widespread establishment of dysoxic conditions

response of antarctic odp site 690 planktonic foraminifera to the paleocene eocene thermal maximum faunal evidence for ocean climate change 1 high resolution study of antarctic planktonic foraminiferal assemblages ocean drilling program site 690 weddell sea shows that these microplankton underwent a stepwise series of changes during the paleocene eocene thermal maximum petm initiation of this response coincides with the onset of the carbon isotope excursion cie but precedes the benthic foraminiferal mass extinction the top to bottom succession in the biotic response indicates that the surface ocean atmosphere was affected before the deep sea the earliest stage of the faunal response entailed a conspicuous turnover within the shallow dwelling genus acarinina and a succession of stratigraphic first appearances the genus morozovella large 180 m biserial planktonics and a wilcoxensis are all restricted to the lower cie within this petm section acarininid populations crashed as the ocean climate system ameliorated during the cie recovery reflecting atypical surface water conditions this transient decline in acarininids is paralleled by a marked increase in carbonate content of sediments it is postulated that this interval of carbonate enrichment and its unusual microfauna reflects enhanced carbon storage within reservoirs of the global carbon cycle other than the marine carbonate system sensu broecker et al 1993 ravizza et al 2001

warming the fuel for the fire evidence for the thermal dissociation of methane hydrate during the paleocene eocene thermal maximum dramatic warming and upheaval of the carbon system at the end of the paleocene epoch have been linked to massive dissociation of sedimentary methane hydrate however testing the paleocene eocene thermal maximum hydrate dissociation hypothesis has been hindered by the inability of available proxy records to resolve the initial sequence of events the cause of the paleocene eocene thermal maximum carbon isotope excursion remains speculative primarily due to uncertainties in the timing and duration of the paleocene eocene thermal maximum we present new high resolution stable isotope records based on analyses of single planktonic and benthic foraminiferal shells from ocean drilling program site 690 weddell sea southern ocean demonstrating that the initial carbon isotope excursion was geologically instantaneous and was preceded by a brief period of gradual surface water warming both of these findings support the thermal dissociation of methane hydrate as the cause of the paleocene eocene thermal maximum carbon isotope excursion furthermore the data reveal that the methane derived carbon was mixed from the surface ocean downward suggesting that a significant fraction of the initial dissociated hydrate methane reached the atmosphere prior to oxidation

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

coherent pattern and timing of the carbon isotope excursion and warming during eocene thermal maximum 2 as recorded in planktic and benthic foraminifera 1 eocene thermal maximum 2 etm2 53 7 ma occurred approximately 2 myr after the paleocene eocene thermal maximum 55 5 ma and was characterized by a deep sea warming of 3 c associated with massive release of carbon into the ocean atmosphere system we performed single specimen stable isotope analyses of the planktic foraminiferal genera acarinina surface dweller and subbotina thermocline dweller from ocean drilling program sites 1265 1267 and 1263 walvis ridge se atlantic ocean and compared high resolution planktic and benthic stable isotope records to constrain the surface warming and the bathymetric pathway of the carbon isotope excursion during etm2 tests of the thermocline dweller subbotina are absent from sediment deposited during the peak of etm2 the acarinina carbon and oxygen isotope records of sites 1263 1265 and 1267 are strikingly similar despite some test recrystallization and large differences in burial depths sea surface temperature sst estimates based on d 18 o isotope values of acarinina indicate a sst increase of 2 c significantly less than the 3 c estimated for bottom water warming the maximum negative carbon isotope excursion for acarinina was 1 7 slightly more than in the deep sea 1 4 the planktic and benthic isotope records do not show time lags indicating that during etm2 the isotopically depleted carbon injected into the ocean atmosphere system was rapidly mixed within all oceanic carbon reservoirs

climate sensitivity to arctic seaway restriction during the early paleogene abstract the opening and closing of ocean gateways affects the global distribution of heat salt and moisture potentially driving climatic change on regional to global scales between 65 and 45 million years ago ma during the early paleogene exchange between the arctic and global oceans occurred through two narrow and shallow seaways the greenland norway seaway and the turgai strait sediments from the arctic ocean suggest that during this interval the surface ocean was warm brackish and episodically enabled the freshwater fern azolla to bloom the precise mechanisms responsible for the development of these conditions in the paleogene arctic remain uncertain here we show results from an isotope enabled atmosphere ocean general circulation model which indicate that northern hemisphere climate would have been very sensitive to the degree of oceanic exchange through the arctic seaways we also present modelled estimates of seawater and calcite 18o for the paleogene by restricting these seaways we simulate freshening of the surface arctic ocean to 6 psu and warming of sea surface temperatures by 2 c in the north atlantic and 5 10 c in the labrador sea our results may help explain the occurrence of low salinity tolerant taxa in the arctic ocean during the eocene and provide a mechanism for enhanced warmth in the north western atlantic we propose that the formation of a volcanic land bridge between greenland and europe could have caused increased ocean convection and warming of intermediate waters in the atlantic if true this result is consistent with the theory that bathymetry changes may have caused thermal destabilisation of methane clathrates and supports a tectonic trigger hypothesis for the paleocene eocene thermal maximum petm

climate model and proxy data constraints on ocean warming across the paleocene eocene thermal maximum article constraining the greenhouse gas forcing climatic warming and estimates of climate sensitivity across ancient large transient warming events is a major challenge to the palaeoclimate research community here we provide a new compilation and synthesis of the available marine proxy temperature data across the largest of these hyperthermals the paleocene eocene thermal maximum petm this includes the application of consistent temperature calibrations to all data including the most recent set of calibrations for archaeal lipid derived palaeothermometry this compilation provides the basis for an informed discussion of the likely range of petm warming the biases present in the existing record and an initial assessment of the geographical pattern of petm ocean warming to aid interpretation of the geographic variability of the proxy derived estimates of petm warming we present a comparison of this data with the patterns of warming produced by high pco2 sim ulations of eocene climates using the hadley centre atmosphere ocean general circulation model aogcm hadcm3l on the basis of this comparison and taking into account the patterns of intermediate water warming we estimate that the global mean surface temperature anomaly for the petm is within the range of 4 to 5 c

climate model sensitivity to atmospheric co2 levels in the early middle paleogene this study examines the sensitivity of the slab ocean version of the national center for atmospheric research climate system model with revised eocene geography orography and vegetation to changing carbon dioxide co2 levels we compare model results with temperature proxies from the geologic record for the early middle paleogene we ran three modeling experiments with co2 levels at 500 1000 and 2000 ppm and all with atmospheric methane levels of 3 5 ppm surface temperatures in the two higher co2 scenarios are warmer than those of the 500 ppm scenario the largest warming with increasing co2 occurred in the high latitudes particularly in the northern hemisphere during the wintertime compared to the 500 ppm case arctic wintertime temperatures increased by 10 c for the 1000 ppm scenario and 20 c for the 2000 ppm scenario the 1000 and 2000 ppm scenarios produced mean annual and cold month mean temperatures in mid and high latitudes that are much more compatible with the climate interpretations from eocene flora especially for data from the southern hemisphere tropical sea surface temperatures ssts in the 2000 ppm scenario however are still 4 c higher than the warmest temperatures inferred from proxy data the better match between temperatures in the high co2 modeling scenario and high latitude climate interpretations is consistent with the idea that the co2 levels during the eocene were high at least 3 4 times the pre industrial value of 280 ppm but the discrepancies in the tropics suggest that sst estimates from proxies are too low or that the models lack some tropical cooling mechanism that was important at this time

cyanobacteria proliferation in the cenomanian turonian boundary interval of the apennine carbonate platform immediate response to the environmental perturbations associated with oae 2

reversed deep sea carbonate ion basin gradient during paleocene eocene thermal maximum 1 the paleocene eocene thermal maximum petm 55 ma ago was marked by widespread caco3 dissolution in deep sea sediments a process that has been attributed to massive release of carbon into the ocean atmosphere system the pattern of carbonate dissolution is key to reconstructing changes in deep sea carbonate chemistry and ultimately the rate magnitude and location of carbon input here we show that during the petm the deep sea undersaturation was not homogeneous among the different ocean basins application of a sediment model to a suite of data records from different sites and ocean basins shows that a globally uniform decrease in deep sea carbonate ion concentration co32 is inconsistent with the data rather we demonstrate that deep sea co32 increased from the atlantic through the southern ocean into the pacific our results show that the petm deep sea co32 basin gradient during dissolution was reversed relative to the modern

latest paleocene benthic extinction event on the southern tethyan shelf egypt foraminiferal stable isotopic δ13c δ18o records the dramatic global extinction of 35 50 of benthic foraminifera species in the deep sea in the latest paleocene and associated negative excursions in 13 c and 18 o may be related to spreading of warm saline bottom water from subtropical tethyan shallow regions over the sea floor worldwide our study of neritic sections in egypt shows that in the southern shallow tethys a prominent long term change in bottom water chemistry sedimentation and benthic foraminifera fauna was initiated at the time when the deep sea benthic extinction event bee took place bottom water 13 c values on the tethyan shelf show a sudden 3 0 negative shift at this event however contrary to the deep sea in which the 13 c excursion was of short duration tethyan 13 c values did not fully return to preboundary values but remained depressed by 1 5 for at least 1 m y the 13 c values at the egyptian shelf during the bee are much lower than would be expected if this was a source region for global deep water the 18 o values indicate no significant change in bottom water salinity or temperature at the bee the long lasting environmental changes that began on the egyptian shelf at the bee may be related to for example gateway reorganization along the tethyan seaway paleogeographic changes possibly also triggered a change in the loci of global deep water formation however these loci must be sought in another part of the tethys

an alternative age model for the paleocene eocene thermal maximum using extraterrestrial 3he a continuous age model for the brief climate excursion at the paleocene eocene boundary has been constructed by assuming a constant flux of extraterrestrial 3he 3he et to the seafloor 3he et measurements from odp site 690 provide quantitative evidence for the rapid onset few kyr and short duration 120 kyr of global warming and of the associated disturbance to the earth s surficial carbon budget at this time these observations support astronomically calibrated age models indicating extremely rapid release of isotopically light carbon possibly from seafloor methane hydrate as the proximal cause of the event however the 3he et technique indicates a previously unrecognized and extreme increase in sedimentation rate coincident with the return of climate proxies to pre event values the 3he et based age model thus suggests a far more rapid recovery from the climatic perturbation than previously proposed or predicted on the basis of the modern carbon cycle and so may indicate additional or accelerated mechanisms of carbon removal from the ocean atmosphere system during this period 3he et was also measured at odp site 1051 to test the validity of the site 690 chronology comparison of these data sets seems to require removal of several tens of kyr of sediment within the climatic excursion at site 1051 an observation consistent with sediment structures and previous age modeling efforts the site 1051 age model shows a 30 kyr period in which climate proxies return toward pre event values after which they remain invariant for 80 kyr if this rise represents the recovery interval identified at site 690 then the 3he et based age models of the two sites are in good agreement however alternative interpretations are possible and work on less disrupted sites is required to evaluate the reliability of the proposed new chronology of the climate excursion regardless of these details this work shows that the 3he et technique can provide useful independent evidence for the development and testing of astronomically calibrated age models

beyond methane towards a theory for the paleocene eocene thermal maximum abstract extreme global warmth and an abrupt negative carbon isotope excursion during the paleocene eocene thermal maximum petm have been attributed to a massive release of methane hydrate from sediments on the continental slope 1 however the magnitude of the warming 5 to 6 c 2 3 and rise in the depth of the ccd 2 km 4 indicate that the size of the carbon addition was larger than can be accounted for by the methane hydrate hypothesis additional carbon sources associated with methane hydrate release e g pore water venting and turbidite oxidation are also insufficient we find that the oxidation of at least 5000 gt c of organic carbon is the most likely explanation for the observed geochemical and climatic changes during the petm for which there are several potential mechanisms production of thermogenic ch4 and co2 during contact metamorphism associated with the intrusion of a large igneous province into organic rich sediments 5 is capable of supplying large amounts of carbon but is inconsistent with the lack of extensive carbon loss in metamorphosed sediments as well as the abrupt onset and termination of carbon release during the petm a global conflagration of paleocene peatlands 6 highlights a large terrestrial carbon source but massive carbon release by fire seems unlikely as it would require that all peatlands burn at once and then for only 10 to 30 ky in addition this hypothesis requires an order of magnitude increase in the amount of carbon stored in peat the isolation of a large epicontinental seaway by tectonic uplift associated with volcanism or continental collision followed by desiccation and bacterial respiration of the aerated organic matter is another potential mechanism for the rapid release of large amounts of co2 in addition to the oxidation of the underlying marine sediments the desiccation of a major epicontinental seaway would remove a large source of moisture for the continental interior resulting in the desiccation and bacterial oxidation of adjacent terrestrial wetlands

co2 driven ocean circulation changes as an amplifier of paleocene eocene thermal maximum hydrate destabilization changes in ocean circulation have been proposed as a trigger mechanism for the large coupled climate and carbon cycle perturbations at the paleocene eocene thermal maximum petm ca 55 ma an abrupt warming of oceanic intermediate waters could have initiated the thermal destabilization of sediment hosted methane gas hydrates and potentially triggered sediment slumps and slides in an ensemble of fully coupled atmosphere ocean general circulation model aogcm simulations of the late paleocene and early eocene we identify such a circulation driven enhanced intermediate water warming critically we find an approximate twofold amplification of atlantic intermediate water warming when co2 levels are doubled from 2x to 4x preindustrial co2 compared to when they are doubled from 1x to 2x this warming is largely focused on the equatorial and south atlantic and is driven by a significant reduction in deep water formation from the southern ocean this scenario is consistent with altered petm circulation patterns inferred from benthic carbon isotope data and the intensity of deep sea carbonate dissolution in the south atlantic the linkage between intermediate water warming and gas hydrate destabilization could provide an important feedback in the establishment of peak petm warmth

impact of dissolution on the sedimentary record of the paleocene eocene thermal maximum the input of massive amounts of carbon to the atmosphere and ocean at the paleocene eocene thermal maximum petm 55 53 ma resulted in pervasive carbonate dissolution at the seafloor at many sites this dissolution also penetrated into the underlying sediment column the magnitude of dissolution at and below the seafloor a process known as chemical erosion and its effect on the stratigraphy of the petm are notoriously difficult to constrain here we illuminate the impact of dissolution by analyzing the complete spectrum of sedimentological grain sizes across the petm at three deep sea sites characterized by a range of bottom water dissolution intensity we show that the grain size spectrum provides a measure of the sediment fraction lost during dissolution we compare these data with dissolution and other proxy records electron micrograph observations of samples and lithology the complete data set indicates that the two sites with slower carbonate accumulation and less active bioturbation are characterized by significant chemical erosion at the third site higher carbonate accumulation rates more active bioturbation and possibly winnowing have limited the impacts of dissolution however grain size data suggest that bioturbation and winnowing were not sufficiently intense to diminish the fidelity of isotopic and microfossil assemblage records

the spread of marine anoxia on the northern tethys margin during the paleocene eocene thermal maximum records of the paleoenvironmental changes that occurred during the paleocene eocene thermal maximum petm are preserved in sedimentary rocks along the margins of the former tethys ocean and peri tethys this paper presents new geochemical data that constrain paleoproductivity sediment delivery and seawater redox conditions from three sites that were located in the peri tethys region trace and major element iron speciation and biomarker data indicate that water column anoxia was established during episodes when inputs of land derived higher plant organic carbon and highly weathered detrital clays and silts became relatively higher anoxic conditions are likely to have been initially caused by two primary processes i oxygen consumption by high rates of marine productivity initially stimulated by the rapid delivery of terrestrially derived organic matter and nutrients and ii phosphorus regeneration from seafloor sediments the role of the latter process requires further investigation before its influence on the spread of deoxygenated seawater during the petm can be properly discerned other oxygen forcing processes such as temperature salinity driven water column stratification and or methane oxidation are considered to have been relatively less important in the study region organic carbon enrichments occur only during the initial stages of the petm as defined by the negative carbon isotope excursions at each site the lack of observed terminal stage organic carbon enrichment does not support a link between petm climate recovery and the sequestration of excess atmospheric co2 as organic carbon in this region such a feedback may however have been important in the early stages of the petm

a transient rise in tropical sea surface temperature during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been attributed to a rapid rise in greenhouse gas levels if so warming should have occurred at all latitudes although amplified toward the poles existing records reveal an increase in high latitude sea surface temperatures ssts 8 to 10 c and in bottom water temperatures 4 to 5 c to date however the character of the tropical sst response during this event remains unconstrained here we address this deficiency by using paired oxygen isotope and minor element magnesium calcium ratios of planktonic foraminifera from a tropical pacific core to estimate changes in sst using mixed layer foraminifera we found that the combined proxies imply a 4 to 5 c rise in pacific sst during the petm these results would necessitate a rise in atmospheric pco 2 to levels three to four times as high as those estimated for the late paleocene

the paleocene eocene thermal maximum how much carbon is enough the paleocene eocene thermal maximum petm 55 53 million years before present was an abrupt warming event that involved profound changes in the carbon cycle and led to major perturbations of marine and terrestrial ecosystems the petm was triggered by the release of a massive amount of carbon and thus the event provides an analog for future climate and environmental changes given the current anthropogenic co2 emissions previous attempts to constrain the amount of carbon released have produced widely diverging results between 2000 and 10 000 gigatons carbon gtc here we use the uvic earth system climate model in conjunction with a recently published compilation of petm temperatures to constrain the initial atmospheric co2 concentration as well as the total mass of carbon released during the event thirty six simulations were initialized with varying ocean alkalinity river runoff and ocean sediment cover simulating various combinations of pre petm co2 levels 840 1680 and 2520 ppm and total carbon releases 3000 4500 7000 and 10 000 gtc we find that both the 840 ppm plus 7000 gtc and 1680 ppm plus 7000 10 000 gtc scenarios agree best with temperature reconstructions bottom waters outside the arctic and north atlantic oceans remain well oxygenated in all of our simulations while the recovery time and rates are highly dependent on ocean alkalinity and sediment cover the maximum temperature anomaly used here to constrain the amount of carbon released is less dependent on this slow acting feedback

atmospheric methane from organic carbon mobilization in sedimentary basins the sleeping giant abstract the mass of organic carbon in sedimentary basins amounts to a staggering 1016 t dwarfing the mass contained in coal oil gas and all living systems by ten thousand fold the evolution of this giant mass during subsidence and uplift via chemical physical and biological processes not only controls fossil energy resource occurrence worldwide but also has the capacity for driving global climate only a tiny change in the degree of leakage particularly if focused through the hydrate cycle can result in globally significant greenhouse gas emissions to date neither climate models nor atmospheric co2 budget estimates have quantitatively included methane from thermal or microbial cracking of sedimentary organic matter deep in sedimentary basins recent estimates of average low latitude eocene surface temperatures beyond 30 c require extreme levels of atmospheric co2 methane degassing from sedimentary basins may be a mechanism to explain increases of atmospheric co2 to values as much as 20 times higher than pre industrial values increased natural gas emission could have been set in motion either by global tectonic processes such as pulses of activity in the global alpine fold belt leading to increased basin subsidence and maturation rates in the prolific jurassic and cretaceous organic rich sediments or by increased magmatic activity such as observed in the northern atlantic around the paleocene eocene boundary increased natural gas emission would have led to global warming that was accentuated by long lasting positive feedback effects through temperature transfer from the surface into sedimentary basins massive gas hydrate dissociation may have been an additional positive feedback factor during hyperthermals superimposed on long term warming such as the paleocene eocene thermal maximum petm as geologic sources may have contributed over one third of global atmospheric methane in pre industrial time variability in methane flux from sedimentary basins may have driven global climate not only at time scales of millions of years but also over geologically short periods of time earth system models linking atmospheric ocean and earth surface processes at different timescales with the sedimentary organic carbon cycle are the tools that need to be developed in order to investigate the role of methane from sedimentary basins in earth s climate

testing the impact of diagenesis on the δ18o and δ13c of benthic foraminiferal calcite from a sediment burial depth transect in the equatorial pacific stable oxygen and carbon isotope 18o and 13c values measured in foraminiferal calcite are one of the primary tools used in paleoceanography diagenetic recrystallisation of foraminiferal calcite can act to reset primary isotopic values but its effects are typically poorly quantified here we test the impact of early stage diagenesis on stable isotope records generated from a suite of drill sites in the equatorial pacific ocean recovered during ocean drilling program odp leg 199 and integrated ocean drilling program iodp expedition 320 our selected sites form paleowater and burial depth transects with excellent stratigraphic control allowing us to confidently correlate our records we observe large inter site differences in the preservation state of benthic foraminiferal calcite implying very different recrystallisation histories but negligible inter site offsets in benthic 18o and 13c values we infer that diagenetic alteration of benthic foraminiferal calcite in sedimentary oozes must predominantly occur at shallow burial depths 100 m where offsets in both the temperature and isotopic composition of waters in which the foraminifera calcified and pore waters in which diagenesis occurs are small our results suggest that even extensive recrystallisation of benthic foraminiferal calcite results in minimal shifts from primary 18o and 13c values this finding supports the long held suspicion that diagenetic alteration of foraminiferal calcite is less problematic in benthic than in planktic foraminifera and that in deep sea sediments routinely employed for palaeoceanographic studies benthic foraminifera are robust recorders of stable isotope values in the fossil record

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

anthropogenic carbon release rate unprecedented during the past 66 million years carbon release rates during the palaeocene eocene thermal maximum are difficult to constrain comparing relative rates of carbon cycle and climate change at the event s onset suggests emissions were much slower than anthropogenic emissions

rapid diversification of planktonic foraminifera in the tropical pacific odp site 865 during the late paleocene thermal maximum the planktonic foraminiferal generamorozovellaandacarininarapidly in 10 k y diversified during the late paleocene thermal maximum lptm giving rise to such morphotypes asm allisonensis new species m africana anda sibaiyaensis single specimen isotopicanalysisconfirmsthatm allisonensisanda sibaiyaensisarerestrictedtothelptm carbon isotope excursion recorded at ocean drilling program site 865 equatorial pacific ocean the short lived 50 to several 100 k y excursion taxa attest to the ephemeral effectsofthelptmonthecalcareousplankton single specimenoxygenisotopedatashow that evolution of m allisonensis and a sibaiyaensis was accompanied by migration to deeper water depths ancestralm velascoensisanda soldadoensiswere extremely rare or absent during the early stages of the lptm but immigrated back into the study area to coexist with their descendants in later lptm horizons photosymbiosis may have facilitatedthemorozovellidandacarininiddiversificationsduringtheoligotrophicconditionsof the lptm

statistical constraints on el nino southern oscillation reconstructions using individual foraminifera a sensitivity analysis recent investigations of submillennial paleoceanographic variability have attempted to resolve high frequency climate signals such as the el nino southern oscillation enso using the population statistics of individual planktic foraminiferal 18o analyses this approach is complicated by the relatively short lifespan of individual foraminifers 2 4 weeks compared to the time represented by a typical marine sediment sample decades to millennia here we investigate the uncertainty associated with individual foraminiferal analyses ifa through simulations on forward modeled 18ocarbonate first focusing on the nino3 4 region of the tropical pacific ocean a bootstrap monte carlo algorithm is developed to constrain the uncertainty on ifa statistics subsequently to test the sensitivity of ifa to changes in seasonal cycle amplitude enso amplitude and enso frequency synthetic time series of 18ocarbonate with differing variability are constructed and tested with our algorithm the probabilities of the ifa technique in detecting changes in enso amplitude and seasonal cycle amplitude or a combination of both for the surface ocean and thermocline at different locations in the tropical pacific are quantified we find that the uncertainty in the standard deviation is smaller than the range that the ifa signal is insensitive to enso frequency and at certain locations the seasonal cycle may dominate enso ifa sensitivity towards enso is highest at the central equatorial pacific surface ocean and the eastern equatorial pacific eep thermocline whereas sensitivity towards the seasonal cycle is highest at the eep surface ocean our results suggest that rigorous uncertainty quantification should become standard practice for accurately interpreting ifa data

kimberlite eruptions as triggers for early cenozoic hyperthermals 1 the early cenozoic experienced at least three short but major hyperthermals associated with disruptions of the global carbon cycle the largest among those the paleocene eocene thermal maximum was associated with a negative carbon isotopic excursion of 2 5 that appears to be best explained by the thermal dissociation of methane hydrates due to an initial period of warming the cause of the initial warming has been attributed to a massive injection of carbon co2 and or ch4 into the atmosphere however the source of the carbon is as yet unknown the emplacement of a large cluster of kimberlite pipes at 56 ma in the lac de gras region of northern canada may have provided the carbon that triggered early warming in the form of exsolved magmatic co2 our calculations indicate that the estimated 900 1100 pg of carbon required for the initial 3 c of ocean water warming associated with the paleocene eocene thermal maximum could have been released during the emplacement of a large kimberlite cluster the coeval ages of two other kimberlite clusters in the lac de gras field and two other early cenozoic hyperthermals indicate that co2 degassing during kimberlite emplacement is a plausible source of the co2 responsible for these sudden global warming events

could changing ocean circulation have destabilized methane hydrate at the paleocene eocene boundary 1 during the paleocene eocene thermal maximum petm 55 ma marine and terrestrial carbon isotope values exhibit a negative shift of at least 2 5 indicative of massive destabilization of marine methane hydrates releasing 2000 gigatons of methane carbon the cause of the hydrate destabilization is unknown but has been speculated to be warming due to a change from high latitude to low latitude deepwater formation here we present results from a numerical ocean model indicating that a sudden switch of deepwater formation from southern to northern high latitudes caused middepth and deep ocean warming of 3 5 c the switch is caused by a slow increase in the intensity of the atmospheric hydrologic cycle as expected under increasing temperatures and consistent with petm sedimentary evidence deepened subtropical subduction prior to the thermohaline circulation switch causes warming of 1 4 c in limited areas at thermocline through upper intermediate depths which could destabilize methane hydrates gradually and at progressively greater depths warming accompanying a south to north switch in deepwater formation would produce sufficient warming to destabilize seafloor gas hydrates over most of the world ocean to a water depth of at least 1900 m

extreme warming of mid latitude coastal ocean during the paleocene eocene thermal maximum inferences from tex86 and isotope data changes in sea surface temperature sst during the paleocene eocene thermal max imum petm have been estimated primarily from oxygen isotope and mg ca records generated from deep sea cores here we present a record of sea surface temperature change across the paleocene eocene boundary for a nearshore shallow marine section located on the eastern margin of north america the sst record as inferred from tex86 data indicates a minimum of 8 c of warming with peak temperatures in excess of 33 c similar ssts are estimated from planktonic foraminifer oxygen isotope records al though the excursion is slightly larger the slight offset in the oxygen isotope record may reflect on seasonally higher runoff and lower salinity

latest paleocene benthic foraminiferal extinction and environmental changes at tawanui new zealand a major extinction of intermediate water 500 1000 m benthic foraminiferal species coincided with a major decrease in 13c 2 8 of terrestrial organic matter n c29 alkane and 34s 20 of whole rock sulfide in a continuous siltstone sequence in the tawanui section 46 s paleolatitude along the akitio river southeastern north island new zealand in the middle part of the uppermost paleocene nannofossil zone cp8 the benthic extinction 25 of species occurred over 3 kyr at 55 5 ma increases in kaolinite illite and kaolinite smectite ratios and in terrestrial organic carbon percentages started 3 kyr before the major benthic extinctions lasted over 40 kyr and probably reflect warmer climate and increased rainfall the productivity of planktonic foraminifera and calcareous nannoplankton decreased 3 kyr prior to the major extinctions and recovered at the time of benthic extinctions these events that started 3 kyr before the extinction can be best explained by warming increased rainfall reduced salinity of surface waters and increased influence of warm saline deep water wsdw benthic foraminiferal oxygen indices indicate a strong decrease in dissolved oxygen levels within the intermediate water from low oxic 1 5 3 0 ml l o2 to suboxic 0 3 1 5 ml l o2 conditions coinciding with the benthic extinctions increases in total organic carbon toc and in the hydrocarbon generating potential of kerogen measured as the hydrogen index hi agree with the interpretation of decreased dissolved oxygen levels of the intermediate water the lowest oxygen conditions lasted 40 kyr and coincided with a decrease in calcareous benthic foraminiferal productivity highest toc levels and lowest 13c of terrestrial organic carbon dominant formation of wsdw or sluggish intermediate water circulation caused by warming and high rainfall in high latitude areas most likely led to the 3 kyr time lag between events on land and in surface waters preceeding the extinction and the development of dysaerobia in the sea coinciding with the major benthic extinction and decrease in 13c and 34s in new zealand global warming of deep and intermediate waters may have caused decomposition of methane hydrate in sediments resulting in a strongly decreased 13c of marine carbonates promoting dysaerobia in the ocean and warming global climate by increased methane concentrations in the atmosphere upwelling of wsdw occurring soon after it became dominant in high latitude areas is likely responsible for the recovery of normal salinity and the concomitant recovery of planktonic foraminifera and calcareous nannoplankton productivity in high latitude surface waters minor benthic foraminiferal extinctions 9 of species occurred 40 kyr after the major extinctions lasted 6 kyr and coincided with the initiation of environmental recovery

a palaeogene perspective on climate sensitivity and methane hydrate instability the palaeoceneeocene thermal maximum petm a rapid global warming event and carbon cycle perturbation of the early palaeogene provides a unique test of climate and carbon cycle models as well as

release of methane from a volcanic basin as a mechanism for initial eocene global warming a 200 000 yr interval of extreme global warming marked the start of the eocene epoch about 55 million years ago negative carbon and oxygen isotope excursions in marine and terrestrial sediments show that this event was linked to a massive and rapid approximately 10 000 yr input of isotopically depleted carbon it has been suggested previously that extensive melting of gas hydrates buried in marine sediments may represent the carbon source and has caused the global climate change large scale hydrate melting however requires a hitherto unknown triggering mechanism here we present evidence for the presence of thousands of hydrothermal vent complexes identified on seismic reflection profiles from the voring and more basins in the norwegian sea we propose that intrusion of voluminous mantle derived melts in carbon rich sedimentary strata in the northeast atlantic may have caused an explosive release of methane transported to the ocean or atmosphere through the vent complexes close to the palaeocene eocene boundary similar volcanic and metamorphic processes may explain climate events associated with other large igneous provinces such as the siberian traps approximately 250 million years ago and the karoo igneous province approximately 183 million years ago