response of nannoplankton to early eocene ocean destratification abstract nannoplankton play a significant role in the global carbon cycle changes in the composition of the assemblage can influence primary productivity carbon burial and ultimately climate here counts of nannofossils in eocene samples document one of the largest nannoplankton assemblage turnovers of the cenozoic era this event is marked by the global expansion of reticulofenestra at the termination of the early eocene climatic optimum eeco and continues through the progressive cooling to the earliest oligocene glaciation to understand the mechanisms driving this assemblage shift we use multivariate statistical techniques and carbon and oxygen isotope records from localities worldwide we find that the turnover in the global nannofossil assemblage is tied to thermal destratification of the ocean and a coincident decrease in the efficiency of the oceanic biologic pump at the height of the eeco we propose that increased vertical mixing and increased nutrient supply to surface waters during the eeco caused a shift in the trophic structure towards enhanced productivity influencing the global nannoplankton population

global dinoflagellate event associated with the late paleocene thermal maximum the late paleocene thermal maximum or lptm ca 55 ma represents a geologically brief time interval 220 k y characterized by profound global warming and associated environmental change the lptm is marked by a prominent negative carbon isotope excursion cie interpreted to reflect a massive and abrupt input of 12 c enriched carbon to the ocean atmosphere reservoir possibly as a result of catastrophic gas hydrate release on time scales equivalent to present day rates of anthropogenic carbon input the lptm corresponds to important changes in the global distribution of biota including mass extinction of marine benthic organisms the dinoflagellate cyst record indicates that surface dwelling marine plankton in marginal seas also underwent significant perturbations during the lptm we report on the dramatic response of representatives of the genus apectodinium from two upper paleocene lower eocene sections in the southern new zealand and northern austria hemispheres where the dinoflagellate records are directly correlated with the cie benthic foraminifera extinction event and calcareous nannofossil zonation the results indicate that the inception of apectodinium dominated assemblages appears to be synchronous on a global scale and that the event is precisely coincident with the beginning of the lptm apectodinium markedly declined in abundance near the end of the lptm this apectodinium event may be associated with 1 exceptionally high global sea surface temperatures and or 2 a significant increase in marginal marine surface water productivity such a globally synchronous acme of dinoflagellate cysts is unprecedented within the dinoflagellate cyst fossil record

nannoplankton origination events and environmental changes in the late paleocene and early eocene the origination of six nannoplankton species in the late paleocene to middle eocene involves significant change in the entire nannofossil assemblage the change began at the first occurrence and accelerates at the increase in abundance of the new species the changes in the environment generally reflect the preferred ecology of the originating species the species that originated in the late paleocene to early eocene outside of the paleocene eocene thermal maximum petm are generally thought to be oligotrophic taxa adapted to warm water conditions during this long interval temperatures were generally increasing and nutrient availability was decreasing conditions that would have been advantageous for the originating taxa conversely the species that originated in the middle eocene are generally thought to be mesotrophs adapted to colder water conditions these taxa were selected for during a time of generally increasing nutrient availability and decreasing temperature orbital stratigraphy indicates that the first occurrences of three paleocene taxa are time transgressive by up to 400 kyr the only event that appears to be synchronous is the abundance increase of zygrhablithus bijugatus during the petm this species is thought to be mesotrophic and replaces the genus fasciculithus at a time when nutrient availability was likely increasing rapidly

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

sedimentary trace element constraints on the role of north atlantic igneous province volcanism in late paleocene early eocene environmental change abstract a growing body of geologic evidence suggests that emplacement of the north atlantic igneous province naip played a major role in global warming during the early paleogene as well as in the transient paleocene eocene thermal maximum petm event a 5 million year record of major and trace element abundances spanning 56 to 51 ma at deep sea drilling project sites 401 and 549 confirms that the majority of naip volcanism occurred as subaerial flows thus the trace element records provide constraints on the nature and scope of the environmental impact of the naip during the late paleocene early eocene interval subaerial volcanism would have injected mantle co2 directly into the atmosphere resulting in a more immediate increase in atmospheric greenhouse gas abundances than co2 input through submarine volcanism the lack of significant hydrothermalism contradicts recently proposed mechanisms for thermally destabilizing methane hydrate reservoirs during the petm any connection between naip volcanism and petm warming had to occur through the atmosphere

late paleocene to middle eocene calcareous nannofossil biochronology from the shatsky rise walvis ridge and italy abstract the precision of late paleocene to middle eocene nannofossil datums is investigated by means of quantitative methods and correlated to the magnetic polarity stratigraphy using sequences from the northwest pacific southeast atlantic and italy it is the rule rather than the exception to find tails of very reduced abundances prior to or after a range of consistent and higher abundances the absolutely first or final occurrence of a species therefore seldom provides a synchronous datum when material from different geographic areas are compared on the other hand synchroneity is often confirmed when the initial sharp rise or the final sharp decline in abundance is used as datum level the use of datums not employed in the two principal existing nannofossil zonal schemes can substantially improve the biostratigraphic resolution two established zonal markers show abundance patterns making them unsuitable as datums the first occurrences of ellipsolithus macellus base np4 diachronous and tribrachiatus nunnii base np10 and paleocene eocene boundary too rare and too short range in open ocean sections the first occurrence of either fasciculithus spp or sphenolithus spp is a better marker near the base of np4 the first occurrence of discoaster diastypus at 56 6 ma represents a suitable replacement for recognition of the paleocene eocene boundary

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

response of calcareous nannofossils to the paleocene eocene thermal maximum from a shelf section in jordan abstract the paleocene eocene thermal maximum petm is known as an approximately 200 kyr long lasting interval of extreme global warming accompanied by major alterations in the ocean atmosphere system these include a negative carbon isotope excursion intense carbonate dissolution and biotic changes of marine floras and faunas the current study reports the response of calcareous nannofossils across the paleocene eocene boundary in a paleoshelf setting in jordan core os 28 clearly marked by a negative 13 c org excursion and the occurrence of characteristic excursion taxa e g discoaster araneus rhomboaster spp coccolithus bownii while this section suffers from intense dissolution at the onset of the event and the peak of the isotopic excursion it retains well preserved diverse nannofossil assemblages from the pre petm petm recovery and post petm intervals these assemblages are dominated by two taxa of inferred mesotrophic affinities coccolithus pelagicus toweius spp and show only low abundances of oligotrophic taxa discoaster spp fasciculithus spp sphenolithus spp overall there appear to be only relatively low level changes in the general assemblage composition across the petm during the post petm however there was a gradual decrease in relative abundance of c pelagicus and toweius spp this decline co coccured with a relative increase of coccolithus bownii and coccolithus foraminis and in its later phase was accompanied by an increase in the relative abundance of sphenolithus spp these changes indicate a possible shift towards less fertile conditions following the hyperthermal event the relatively muted signal of biotic change associated with the petm interval at this site was partly a consequence of poor preservation within the key sequence of the studied core on the other hand the low signal may also be indicative for local environment processes such as variations in riverine sourced nutrients salinity turbidity operating on a regional scale these local factors overrode the direct and indirect temperature signals that are the dominant control on nannofossil communities across the petm in open ocean sites finally the assemblages from the jordan section highlight further the overall spatial heterogeneity in reported responses of shelf area communities to the petm interval these heterogeneities have been observed in shelf assemblages from tanzania new jersey and the tethyan margins which again points to the strong influence of regional controls like river input in more marginal settings

changes in calcareous nannofossil assemblages during the middle eocene climatic optimum clues from the central western tethys alano section ne italy we present a study focused on changes in calcareous nannofossil assemblages of the alano section during the middle eocene climatic optimum meco this warming event is characterized by a prominent perturbation both in oxygen and carbon stable isotopes around the chron c18r c18n transition ca 40 ma and lasting ca 500 600 kyr semi quantitative analyses on calcareous nannofossil assemblages have been carried out our results show that the meco interval coincides with a significant shift in the relative abundance of calcareous nannofossil taxa suggesting a relationship between biotic changes and stable isotope shifts paleoecological studies at species level and or based on morphometric criteria i e small placoliths sometimes show the opposite behaviour between changes observed at the genus level and those observed at lower taxonomic levels for instance a taxon thought to be better adapted to oligotrophic warm waters e g sphenolithus shows a prominent decrease if analyzed at genus level but an increase was instead recorded for s spiniger moreover taxa preferentially thriving in eutrophic cold waters as for instance small reticulofenestrids increase remarkably in abundance during this warming phase while medium large placoliths do not show any significant trend an increase in reworked mainly cretaceous specimens is also observed during the meco these lines of evidence are consistent with a transient enrichment in dissolved nutrients in warmer sea surface waters suggesting that an enhanced nutrient availability could have driven the make up of the calcareous nannofossil assemblages the increase in reworking may indicate an increase in terrigenous input due to increased chemical weathering likely produced by an enhanced hydrological cycle

biogeographic gradients of middle eocene oligocene calcareous nannoplankton in the south atlantic ocean middle eocene oligocene calcareous nannoplankton have been analyzed quantitatively for eight dsdp and odp sites ranging from the equatorial zone to 65 s latitude in the south atlantic ocean there is a general decrease in calcareous nannoplankton species diversity from the middle eocene through the oligocene and species diversity also decreases towards the higher latitudes similar to findings of other studies the drop of the species diversity of calcareous nannoplankton across the eocene oligocene boundary is not drastic delineation of latitudinal distribution patterns of individual species or groups and r mode cluser analysis permit the classification of warm water taxa coccolithus formosus discoasters helicosphaerids and sphenoliths temperate water taxa coccoliths pelagicus cyclicargoliths floridanus group reticulofenestra bisecta reticulofenestra samodurovii reticulofenestra umbilica and cool water taxa chiasmoliths isthmolithus recurvus and reticulofenestra daviesii the abundance of warm water taxa plummets whereas the abundance of cool water taxa sharply increases across the eocene oligocene boundary at the middle and high latitude sites reflecting a profound cooling event in these areas polar ordination and similarity analyses reveal that steep latitudinal biogeographic gradients had been established at least by the middle eocene the gradient greatly increases near the eocene oligocene boundary indicating more severe and permanent cooling at the high latitudes the biogeographic gradient data of this study conflict with the widely accepted inference from the oxygen isotopic data that the thermal gradients between mid latitudes and high latitudes are low or nearly flat for the paleogene oceans lower surface water salinities in the high latitudes may have lowered the 18o values of the planktonic microfossils but apparently did not have significant effect on latitudinal distribution patterns of calcareous nannoplankton which offers an independent means for estimating latitudinal thermal gradients

similarities between planktonic and larger foraminiferal evolutionary trends through paleogene paleoceanographic changes abstract the paleogene evolutionary records of planktonic foraminifera and larger benthic foraminifera show parallel patterns in development that may in part reflect changes in nutrient flux to surface waters following the terminal cretaceous extinctions faunas were dominated by a few cosmopolitan opportunistic species more specialized k strategists in both groups diversified during the paleocene dominating into the early eocene consistent with he globally mild climatic regime and probable limited rates of nutrient flux to surface waters high latitude cooling intensified in the middle eocene promoting diversification of less specialized taxa characteristic of cooler and deeper waters higher latitudes meridional upwelling zones and boundary currents geographic ranges of warm water taxa diminished and fragmented yet many species survived thus global diversities during the middle eocene were the highest in the cenozoic as cooling and increased rates of nutrient flux further intensified in the late eocene extinction rates of warm water planktonic and larger benthic species exceeded origination rates of cooler water and less specialized forms so diversity dropped to intermediate levels where it remained through the late eocene and oligocene previous observations that planktonic foraminiferal faunas dominated by warm water taxa are often replaced by cool water faunas even though oxygen isotopes only recorded relatively minor cooling can be reconciled by the explanation that the biotic communities responded to changes in trophic resources and euphotic habitats that accompany the temperature reduction as well as to temperature change itself

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

provincialism associated with the paleocene eocene thermal maximum temporal constraint sudden global warming 55 ma is associated with remarkable biotic events among both terrestrial and marine organisms the marine microplankton were especially affected with a rapid diversification among tropical planktonic foraminifera a global acme of the dinoflagellate apectodinium complex and sudden changes in abundance patterns among the calcareous nannoplankton additionally and in contrast with the former two groups the latter group showed marked provincialism with the distinctive rhomboaster spp discoaster araneus association rd restricted to a broadly crescent shaped area extending through the tethys seaway and the north and south atlantic oceans we show here that this geographically restricted association was also temporally restricted the stratigraphic occurrence of the rhomboaster spp d araneus association is correlative with the earliest eocene carbon isotope excursion the relative abundance of this association is highest in the interval of minimum 13c values and sharply decreases as the 13c increases toward preexcursion values we propose that the rhomboaster spp d araneus association constitutes a stratigraphic proxy for the carbon isotope excursion and represents an unique response to the paleocene eocene thermal maximum petm with a temporal span on the order of 175 kyr

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

middle eocene to late oligocene antarctic glaciation deglaciation and southern ocean productivity during the eocene oligocene transition earth cooled significantly from a greenhouse to an icehouse climate nannofossil assemblages from southern ocean sites enable evaluation of paleoceanographic changes and hence of the oceanic response to antarctic ice sheet evolution during the eocene and oligocene a combination of environmental factors such as sea surface temperature and nutrient availability is recorded by the nannofossil assemblages of and can be interpreted as responses to the following changes a cooling trend started in the middle eocene was interrupted by warming during the middle eocene climatic optimum and by short cooling episodes the cooling episode at 39 6 ma preceded a shift toward an interval that was dominated by oligotrophic nannofossil assemblages from 39 1 to 36 2 ma we suggest that oligotrophic conditions were associated with increased water mass stratification low nutrient contents and high efficiency of the oceanic biological pump that in turn promoted sequestration of carbon from surface waters which favored cooling after 36 2 ma we document a large synchronous surface water productivity turnover with a dominant eutrophic nannofossil assemblage that was accompanied by a pronounced increase in magnetotactic bacterial abundance this turnover reflects a response of coccolithophorids to changed nutrient inputs that was likely related to partial deglaciation of a transient antarctic ice sheet and or to iron delivery to the sea surface eutrophic conditions were maintained throughout the oligocene which was characterized by a nannofossil assemblage shift toward cool conditions at the eocene oligocene transition finally a warm nannofossil assemblage in the late oligocene indicates a warming phase

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

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

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

a benthic foraminiferal record of paleocene sea level and trophic redox conditions at gebel aweina egypt we quantitatively analyzed benthic foraminiferal assemblages in order to reveal biotic and paleoenvironmental trends in the paleocene section of gebel aweina egypt on the southern tethyan shelf the first correspondence axis ranks taxa along an empirically derived bathymetric gradient with neritic taxa e g discorbis duwi and haplophragmoides walteri opposed to bathyal taxa e g nuttallides truempyi and gavelinella beccari ormis the estimated paleodepth as reflected by the various assemblages was mostly 200 m but varied between 50 m p3a np4 and 300 m p4 n p8 the resultant four relative sea level cycles appear to be at least of regional extent and may in part be eustatically controlled the second correspondence axis reflects trends in trophic and redox development low food high oxygen conditions prevailed during biochrons plc p3b np4 np5 and late p4 np8 when assemblages were mostly dominated by cibicidoides spp most oligotrophic conditions coincided with maximum paleodepth intermediate trophic levels were established during middle p4 np6 and early p5 np9 from the level of the latest paleocene benthic extinction event bee middle p5 and np9 onwards until biochron p6a np10 assemblages dominated by buliminids marked increased trophic levels and reduced ventilation probably resulting from enhanced surface productivity enhanced surface productivity along the southern tethyan margin started during biochron p4 and at least on some shelves intensified after the bee increasing productivity during the latest paleocene contrasts with global trends this may be expected during climatic warming and an expanding trophic resource continuum leading to regionally intensified eutrophy and oligotrophy high productivity through upwelling along the southern tethyan provides support for gcm predictions of intense wind stress in this region during the warm late to latest paleocene 1998 elsevier science b v

variations to calcareous nannofossil caco 3 content during the middle eocene c21r h6 hyperthermal event 47 4 ma in the gorrondatxe section bay of biscay western pyrenees abstract the carbonate content of calcareous nannofossils is dependent on seawater composition one of the factors that affect seawater chemistry and consequently the degree of calcification in coccolithophores is temperature as seen in present day warming oceans the depth at which carbonates are dissolved calcite compensation depth ccd can rise due to an increase in hco 3 and decrease in ph leading to a major dissolution on the seabed and burndown similar processes have also been deduced for eocene hyperthermal events such as the petm and etm2 this study reports changes in coccolith carbonate mass from a hemipelagic setting gorrondatxe at 1500 m paleodepth during the core of a minor eocene hyperthermal event namely the c21r h6 event 47 44 47 32 ma image analysis techniques were used to determine differences in the carbonate mass of selected calcareous nannofossil taxa revealing species specific patterns the caco 3 mass of chiasmolithus solitus decreased by 50 over the course of the c21r h6 event and many specimens also lost their crossed central bars an additional indication of mass loss reticulofenestra sp 3 5 m showed a similar trend but the percentage of mass lost was lower toweius pertusus interpreted as being reworked mirrored the behaviour of chiasmolithus solitus suggesting that the caco 3 mass loss may have occurred on the seabed rather than in the water column in general it can be concluded that the lysocline rose to 1500 m paleobathymetry in the bay of biscay during the c21r h6 event formation of corrosive bottom water in the north atlantic ocean is regarded as being responsible for the rise in the lysocline

middle eocene late oligocene climate variability calcareous nannofossil response at kerguelen plateau site 748 a major deterioration in global climate occurred through the eocene oligocene time interval characterized by long term cooling in both terrestrial and marine environments during this long term cooling trend however recent studies have documented several short lived warming and cooling phases in order to further investigate high latitude climate during these events we developed a high resolution calcareous nannofossil record from odp site 748 hole b for the interval spanning the late middle eocene to the late oligocene 42 to 26 ma the primary goals of this study were to construct a detailed biostratigraphic record and to use nannofossil assemblage variations to interpret short term changes in surface water temperature and nutrient conditions the principal nannofossil assemblage variations are identified using a temperate warm water taxa index twwt from which three warming and five cooling events are identified within the middle eocene to the earliest oligocene interval among these climatic trends the cooling event at 39 ma cooling event b is recorded here for the first time variations in fine fraction 18o values at site 748 are associated with changes in the twwt index supporting the idea that significant short term variability in surface water conditions occurred in the kerguelen plateau area during the middle and late eocene furthermore odp site 748 calcareous nannofossil paleoecology confirms the utility of these microfossils for biostratigraphic paleoclimatic and paleoceanographic reconstructions at southern ocean sites during the paleogene

antarctic subtropical humid episode at the paleocene eocene boundary clay mineral evidence clay mineral assemblages from east antarctica have been analyzed at high stratigraphic resolution 20 to 1 ka throughout the interval from 55 6 to 55 0 ma which includes the terminal paleocene isotopic excursion in ocean drilling program site 690b on maud rise lat 65 s in the weddell sea region changes in the clay associations reflect a major increase in chemical weathering caused by increased temperature and or rainfall in at least this sector of east antarctica for a brief 270 ka interval in the latest paleocene this represents the most intense warming known for the cenozoic this high latitude climatic episode is recorded synchronously by stable isotopes and clay minerals a progression is evident in the clay assemblages during the latest paleocene that apparently reflects changing relations between temperature and precipitation this sequence began with the interval of rapid temperature increase that marks the beginning of the oxygen isotopic excursion a brief increase in kaolinite at the inception of the excursion suggests a temporary increase in year round precipitation in antarctica in response to an increased continent to ocean temperature gradient this kaolinite spike was followed by almost total dominance by smectite for the remainder of the isotopic excursion 120 ka suggesting that warmer southern ocean surface temperatures of 18 to 22 c were associated with seasonal precipitation alternating wet and dry seasons claymineral variations on antarctica during the isotopic excursion reflect a tight coupling between oceanic and continental climate change immediately following the excursion at 55 22 ma kaolinite percentages increased to values similar to modern subtropical tropical areas for 150 ka a remarkable event for the antarctic abundant kaolinite suggests perennial rainfall and minimum soil temperatures of 15 c during at least part of the year the kaolinite increased during a time of lower southern ocean surface water temperatures suggesting increased atmospheric heat transport toward the poles a temporary change in atmospheric circulation is suggested from dominantly zonal to meridional

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

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

clay mineralogy of phyllic and intermediate argillic alteration at bingham utah the earliest alteration mineral zones in the porphyry cu mo au ore deposit at bingham utah include the outermost propylitic and inner potassic alteration of igneous rocks innermost phyllic and intermediate argillic alteration is superimposed on propylitic and potassic alteration petrographic x ray diffraction and electron microprobe analyses are used to characterize the clay mineralogy of phyllic and intermediate argillic alteration phyllic alteration affects monzonite near the contact with the quartz monzonite porphyry in the southwest and northeast portions of the deposit and consists primarily of veins and vein selvages of illite interstratified with an average of 7 percent smectite r 3 ordering the veins and selvages also contain small amounts of smectite and kaolinite the illite smectite interstratification is a mixture of 1m and 2m polytypes structural formulas for the illite show less k and al and more si than muscovite octahedral mg and both a tetrahhedral and an octahedral layer charge the kubler crystallinity index and smectite content increase systematically as particle size decreases consistent with an increase in smectite in the interstratification in the smaller size fractions intermediate argillic alteration consists of smectite illite and kaolinite that occur primarily as a replacement of plagioclase phenocrysts a few veins of intermediate argillic minerals are present in the quartz monzonite porphyry illite is interstratified with an average of 6 percent smectite r 3 ordering but a few samples contain a regular interstratification of illite with 40 to 50 percent smectite r1 ordering the smectite replacing plagioclase is montmorillonite and smectite that occurs in one vein is beidellite statistical trends in intermediate argillic alteration mineralogy within the quartz monzonite porphyry show that illite and kaolinite abundances increase generally upward and toward the northeast smectite abundance increases generally downward and toward the southwest in a cross section near the center of the deposit abundances of kaolinite and illite decrease as abundance of smectite increases with increasing depth the occurrence of interstratified illite smectite averaging 6 to 7 percent smectite together with discreet smectite suggest formation near 200 c a temperature difference between phyllic and intermediate argillic alteration could not be resolved from the mineralogy temperature estimates from fluid inclusions for phyllic alteration at other porphyry copper deposits generally range from 200 to 350 c the activity ratio of na k for the fluid calculated from na k in illite averages 5 0 for a phyllic vein that crosscuts propylitic alteration 1 4 for a phyllic vein that crosscuts potassic alteration and 2 8 for intermediate argillic alteration superimposed on potassic alteration log f h 2 o f hf of the hydrothermal fluid computed from the fluorine content of illite averages 6 1 for a phyllic vein that crosscuts propylitic alteration 5 8 for a phyllic vein that crosscuts potassic alteration and 5 7 for intermediate argillic alteration log f h 2 o f hf of fluids forming late stage biotite is about 5 0 intermediate argillic alteration could not be correlated with sulfides in the quartz monzonite porphyry an increase in illite upward and toward the northeast may correlate with massive sulfides in sediments recently discovered in that region

new chronology for the late paleocene thermal maximum and its environmental implications the late paleocene thermal maximum lptm is associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle we have developed a new orbital chronology for ocean drilling program odp site 690 weddell sea southern ocean by using spectral analysis of high resolution geochemical records the lptm interval spans 11 precessional cycles yielding a duration of 210 to 220 k y the 13 c anomaly associated with the lptm has a magnitude of about 2 5 to 3 we show that about 2 of the excursion occurs within two steps that each were less than 1000 yr in duration the remainder developed through a series of steps over 52 k y the timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial further we are able to correlate the records between odp sites 690 and 1051 western north atlantic on the scale of 21 k y cycles which demonstrates that the details of the 13 c excursion are recognizable between distant sites comparison of cycle records at sites 690 and 1051 suggests that sediment representing the interval 30 k y just prior to and at the onset of the lptm are missing in the latter location this unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k y of the start of the lptm

correlation between isotope records in marine and continental carbon reservoirs near the palaeocene eocene boundary changes in the isotope content of the large marine carbon reservoir can force shifts in that of the smaller carbon pools in the atmosphere and on land the carbon isotope compositions of marine carbonate sediments from the late palaeocene vary considerably exhibiting a sudden decrease close to the palaeocene eocene boundary which coincides with deep sea benthic extinctions1 and with changes in ocean circulation here we report that these fluctuations in the marine carbon isotope record are closely tracked by the terrestrial records provided by palaeosol carbonates and mammalian tooth enamel in using palaeosol carbonates to reconstruct the co2 content of the ancient atmosphere2 isotope shifts of this sort will have to be taken into account the sharp decrease in 13c 12c ratios in the late palaeocene provides a datum for precise correlation of marine and continental records and suggests that abrupt climate warming at this time may have played an important role in the evolution of land mammals

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

deep sea ostracode turnovers through the paleocene eocene thermal maximum in dsdp site 401 bay of biscay north atlantic abstract previous low resolution studies suggest that ostracodes in contrast with deep sea foraminifera largely survived the massive environmental changes of the paleocene eocene thermal maximum petm in a new high resolution study from the continental slope 1800 m paleodepth ne atlantic we also find extensive survivorship of ostracode faunas but this is accompanied by a temporary drop in species diversity and ecological diversity during the petm there are 12 common ostracode species before the petm that are reduced to only two species at the same time as the benthic foraminiferal extinction event all but three species reappear in the later parts of the petm and statistical analysis suggests that most of the apparent lazarus species might be found with sufficient sampling of petm faunas we find no evidence for an excursion fauna of ostracodes as has been detected in calcareous nannofossils planktic foraminifera and benthic foraminifera however the ostracode assemblages changed from a relatively diverse ecological assemblage before and after the petm to one dominated by infaunal species typical of low oxygen conditions during the petm the absence of major extinction and the temporary nature of species disappearances are comparable to turnovers in shallow marine ostracodes and stands in sharp contrast to the 50 species level extinction in benthic foraminifers

changes in calcareous nannofossil assemblages across the paleocene eocene transition from the paleo equatorial pacific ocean quantitative analyses of selected calcareous nannofossils in deep sea sections recovered from the paleo equatorial pacific odp leg 199 provide new information about biostratigraphy biochronology and the evolutionary history of calcareous nannofossils across the paleocene eocene transition interval the sediment cores from odp leg 199 represent the first continuous paleocene eocene boundary sections ever to be sampled in the central equatorial pacific ocean calcareous nannofossil assemblages are studied to document the distribution of biostratigraphically useful taxa such as ericsonia discoaster fasciculithus rhomboaster and tribrachiatus focus is given to the evolution of the rhomboaster tribrachiatus lineage in the lower eocene interval at site 1215 and on the stratigraphic relationship of these taxa relative to species in the genus fasciculithus critical intervals of north atlantic dsdp site 550 have also been re examined the tribrachiatus digitalis morphotype was described at site 550 from an interval affected by down hole contamination partly originating from within the tribrachiatus orthostylus range the t digitalis morphotype represents an evolutionary transitional form between t contortus and t orthostylus entering the stratigraphic record within the range of the former species and disappearing within the lower part of the range of the latter species the subzonal subdivision of zone np10 hence collapses lithological and colour variability reflecting orbital cyclicity occur in the lower eocene of site 1215 permitting a relative astronomical age calibration of the tribrachiatus taxa the distinct rhomboaster spp discoaster araneus association also occurs in the paleo equatorial pacific ocean together with a marked decrease in diversity of fasciculithus spp site 1220 reveals a short peak abundance of thoracosphaera spp just above the p e boundary interval which probably reflects a stressed surface water environment

the paleocene eocene transition in the marginal northeastern tethys kazakhstan and uzbekistan we studied two sections that accumulated during the paleocene eocene transition in shelf waters in the northeastern tethys stable carbon isotopic compositions of marine and terrestrial biomarkers are consistent with a 13c depletion in the oceanic and atmospheric carbon dioxide pools during the late paleocene thermal maximum lptm subzone p5b the 2 3 negative 13c excursion in planktic foraminifera coincides with minimum 18o values an incursion of transient subtropical planktic foraminiferal fauna and the occurrence of an organic rich sapropelite unit in uzbekistan which accumulated at the onset of a transgressive event biomarker distributions and hydrogen indices indicate that marine algae and bacteria were the major organic matter sources during the late paleocene subzones p4 and p5a the marginal northeastern tethys experienced a temperate to warm climate with wet and arid seasons most likely warm and humid climate initiated during the lptm subzone p5b and subsequently extended during the eocene zone p6 onto adjacent land areas of the marginal northeastern tethys

detrital zircon geochronology of a conglomerate in the northeastern cape breton highlands implications for the relationships between terranes in cape breton island the canadian appalachians cape breton island has been interpreted as consisting of four zones of pre carboniferous rocks but the relationships among them are controversial to help resolve the controversy we have dated detrital zircons from a conglomerate part of the cheticamp lake gneiss in the aspy terrane in the northeastern cape breton highlands using the u pb method the following ages were obtained 462 2 ma middle ordovician 492 488 ma 6 ages early ordovician 552 3 ma latest precambrian early cambrian 620 13 and 687 4 ma cadomian and 809 17 1423 10 1462 12 1605 14 1644 4 and 1911 5 ma proterozoic the middle ordovician age sets a maximum age limit for deposition of the conglomerate and supports an ordovician silurian age for the cheticamp lake gneiss the early ordovician latest precambrian early cambrian and cadomian ages match published ages from the bras d or terrane and its correlatives and the mira terrane and its correlatives and indicate provenance of the conglomer

calcareous nannofossil changes in response to the spreading of the south china sea basin during eocene oligocene abstract numerous models have been proposed to constrain the process of the south china sea formation yet the paleogene paleoenvironmental researches are hindered by the paucity of long continuous well dated geological records in this work eocene to oligocene nannofossil biostratigraphy and assemblage changes in a sediment section from the northern south china sea were studied to shed light on these issues we established an age model to confine the studied section between 40 and 22 ma based on 17 calcareous nannofossil datum levels the age model enabled to date the most prominent seismic reflector t60 centered at 26 8 ma a regional tectonic event interpreted as corresponding to the ridge jump event in the early phase of south china sea spreading changes in nannofossil abundance and assemblage compositions imply continuous transgression and deepening of water depth from the late eocene to early miocene during the late eocene the studied area was a neritic sea with relatively eutrophic conditions supporting abundant r lockeri group and c pelagicus from 34 ma to 27 ma during the oligocene the earlier neritic environment was replaced by relative warm and oligotrophic conditions in a shallow sea as indicated by higher concentration of c floridanus sphenolithus spp and helicosphaera spp since 26 ma pelagic conditions prevailed small reticulofenestra

paleoenvironmental signature of the selandian thanetian transition event stte and early late paleocene event elpe in the contessa road section western neo tethys abstract sedimentary records of the early cenozoic indicate a series of events with climatic and carbon cycle variability known as hyperthermals a 350 kyr long event of environmental disruption during the paleocene not described before and here named selandian thanetian transition event stte has been recognized and well constrained in the western tethys contessa road section gubbio italy through high resolution biostratigraphic geochemical and rock magnetic data the stte exhibits peculiar stressed ecological responses among calcareous nannofossils and foraminifera which highlight marked environmental perturbation affecting the biosphere the environmental instability is not confined within the photic zone but extends to the seafloor leading to little more trophic conditions of the sea surface waters with an enhanced but of short measure nutrient availability on the seafloor conditions and marked rise of lysocline magnetic susceptibly ms is dominantly controlled by the balance between carbonate productivity and detrital supply as evidenced by the strong correlation between ms and caco3 r2 0 72 however we also document two components in the isothermal remanent magnetization irm and first order reversal curves forc diagrams that prove the occurrence of biogenic magnetite throughout the stte systematic variations in bio geochemical and magnetic parameters show the relative abundance of carbonate production or inversely dissolution of carbonate versus detrital supply during the stte which induced higher populations of magnetotactic bacteria through increased terrigenous input and therefore increased nutrient supply noteworthy the uppermost part of the stte includes the equivalent of the suspected hyperthermal short lived early late paleocene event elpe the elpe event shows an episode of increase in magnetic properties of the sediments including an increase in magnetofossil concentration as indicated by irm components and forc diagrams the comparison of biotic and abiotic records throughout the stte at contessa road section with available data across the elpe from former investigated ocean and land based sites provides lines of evidence that this latter event might be indeed only the terminal part of a long lasting environmental change than hitherto supposed

shelf and open ocean calcareous phytoplankton assemblages across the paleocene eocene thermal maximum implications for global productivity gradients abrupt global warming and profound perturbation of the carbon cycle during the paleocene eocene thermal maximum petm ca 55 ma have been linked to a massive release of carbon into the ocean atmosphere system increased phytoplankton productivity has been invoked to cause subsequent co2 drawdown cooling and environmental recovery however interpretations of geochemical and biotic data differ on when and where this increased productivity occurred here we present high resolution nannofossil assemblage data from a shelf section the u s geological survey usgs drill hole at wilson lake new jersey and an open ocean location ocean drilling program odp site 1209 paleoequatorial pacific these data combined with published biotic records indicate a transient steepening of shelf offshelf trophic gradients across the petm onset and peak with a decrease in open ocean productivity coeval with increased nutrient availability in shelf areas productivity levels recovered in the open ocean during the later stages of the event which coupled with intensified continental weathering rates may have played an important role in carbon sequestration and co2 drawdown

nannofossil assemblage fluctuations during the paleocene eocene thermal maximum at sites 213 indian ocean and 401 north atlantic ocean palaeoceanographic implications the paleocene eocene thermal maximum petm was an abrupt global warming event at f55 ma this event had profound effects on the biosphere quantitative investigations of calcareous nannofossil assemblages were performed across the petm at deep sea drilling project site 213 in the tropical indian ocean and site 401 in the bay of biscay north atlantic ocean at a temperate latitude calcareous nannofossil assemblages from both sites show major changes before during and after the petm fluctuations at site 213 are affected by selective dissolution of the least robust taxa by contrast assemblages in the lower part of the petm at site 401 show less diagenetic alteration and display high abundances of genera such as discoaster fasciculithus and ericsonia these taxa reflect relatively warm and probably oligotrophic surface waters abundances of the genus chiasmolithus an indicator of relatively cool and eutrophic waters decreased dramatically the upper portion of the petm is characterized by an increase in the abundance of toweius spp and zygrhablithus bijugatus interpreted as a return to cooler and more eutrophic conditions the elimination of fasciculithus was probably due to competition with the holococcolith species z bijugatus which occupied the same ecological niche the occurrences of long armed and asymmetrical discoaster species such as discoaster araneus discoaster anartios and discoaster okadai and rhomboaster species such as rhomboaster calcitrapa and rhomboaster cuspis are characteristic of the petm interval d 2004 elsevier b v all rights reserved

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

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

evidence of surface water oligotrophy during the paleocene eocene thermal maximum nannofossil assemblage data from ocean drilling program site 690 maud rise weddell sea 1 nannoplankton assemblages at ocean drilling program site 690 maud rise weddell sea experienced an abrupt and dramatic transformation at the onset of the paleocene eocene thermal maximum petm at 55 m y the major assemblage shift suggests a change from colder more productive surface waters to warmer more oligotrophic conditions significant restructuring of assemblages during the later part of the petm indicates that nannoplankton communities were not stable and that surface water conditions changed although they remained warm and oligotrophic combined with benthic foraminiferal assemblage data nannoplankton assemblage results suggest increased sequestration of nutrients in shelf environments and starvation of the open ocean although the petm was a short lived event it appears to have had long term effects on nannoplankton leading to the extinction of fasciculithus a dominant paleocene genus

calcareous nannoplankton changes across the early toarcian oceanic anoxic event in the western tethys 1 calcareous nannoplankton were profoundly affected by environmental perturbations coincident with the early toarcian oceanic anoxic event t oae we quantify the abundance of nannofossils across the t oae at three locations in western europe where the event is marked by a prominent negative carbon isotope excursion cie data were treated by statistical analysis and the shannon diversity index was applied in order to describe nannofossil assemblage changes related to paleoenvironmental evolution in the basal toarcian before the t oae high proportions of taxa with an affinity for low temperature e g p liasicus t patulus bussonius occurred this observation is consistent with interpretations of published oxygen isotope records during the t oae the lowest abundance of nannofossils is observed but there is a peak of a coccolith calyculus from an organism that probably thrived in low saline surface waters depleted of nitrate at the end of the perturbation the lowest diversities of nannofossils occurred and assemblages are dominated by crepidolithus crassus a deep dweller this interval corresponded to progressive reoxygenation of deep water and the reoccupation of the deep photic zone by nannoplankton the highest abundance of nannofossils is recorded above the cie and testifies to the recovery of the entire nannoplankton community the t oae was widespread perhaps global and probably linked to major changes in the atmosphere and hydrosphere however the record of this event varies in the basins surrounding the western tethys suggesting regional imprints on the global signal the regional variability may attest to establishment of effective connections between the arctic and tethys oceans which allowed cool low saline water formed at high latitudes to stream toward the western tethys

an osmium isotope excursion associated with the late paleocene thermal maximum evidence of intensified chemical weathering in the latest paleocene an abrupt shift to more negative 13c values has been documented at numerous marine and terrestrial sites bralower et al 1997 cramer et al 1999 kaiho et al 1996 kennett and stott 1991 koch et al 1992 stott et al 1996 thomas and shackleton 1996 zachos et al 1993 this carbon isotope event cie is coincident with oxygen isotope data that indicate warming of surface waters at high latitudes of nearly 4 6 c kennett and stott 1991 and more moderate warming in the subtropics thomas et al 1999 here we report 187os 188os isotope records from the north atlantic and indian oceans which demonstrate a 10 increase in the 187os 188os ratio of seawater coincident with the late paleocene cie this excursion to higher 187os 188os ratios is consistent with a global increase in weathering rates the inference of increased chemical weathering during this interval of unusual warmth is significant because it provides empirical evidence supporting the operation of a feedback between chemical weathering rates and warm global climate which acts to stabilize earth s climate walker et al 1981 estimates of the duration of late paleocene cie bains et al 1999 bralower et al 1997 norris and rohl 1999 rohl et al 2000 in conjunction with the os isotope data imply that intensified chemical weathering in response to warm humid climates can occur on timescales of 104 105 years this interpretation requires that the late paleocene thermal maximum os isotope excursion be produced mainly by increased os flux to the ocean rather than a transient excursion to higher 187os 188os ratios in river runoff although we argue that the former is more likely than the latter we cannot rule out significant changes in the 187os 188os ratio of rivers

calcareous plankton evolution and the paleocene eocene thermal maximum event new evidence from tanzania the biotic response of calcareous microplankton at the paleocene eocene thermal maximum petm climate event principally comprised poleward migrations the appearance of excursion taxa and elevated turnover in calcareous nannoplankton here we examine whether this relatively muted evolutionary signal may be due to the quality of the stratigraphic and fossil record by analysing exceptionally well preserved microfossils from an expanded hemipelagic petm section in southern tanzania tdp site 14 both nannofossils and planktonic foraminifera show major abundance declines at the onset of the petm that are not explained by dilution or dissolution the petm onset is also marked by the extinction of eight nannofossil species possibly as many as 12 and the intra petm assemblages are quite distinct from background and dominated by coccolithus including the excursion taxon c bownii this biotic response is not clearly biased in favour of particular ecological groups although the nannofossil excursion taxa were all warm water favouring and there was a net diversity loss within cool water favouring eutrophic groups a shift from toweius to coccolithus dominated assemblages is suggestive of increased oligotrophy although the presence of abundant gladiolithus indicates upper photic zone oligotrophy throughout the time interval represented by the tdp site 14 section the significant plankton assemblage shifts diversity decline and possible reduction of calcareous plankton production and or export suggest the rapid onset of highly disruptive environmental change at the petm onset this change must have included rapid temperature increase and heat stress may have played a role in shaping the petm assemblage compositions causing a limited number of extinctions and favouring taxa from warmer areas of the groups ecological range however the muted evolutionary response in these plankton groups indicates that they were highly resilient to this environmental change and through adaptation to the new conditions e g the excursion taxa but probably principally through range shifts i e migration or simply the ability to acclimatize the vast majority of the biodiversity survived and thrived again once conditions returned to normal

implications of reduced turbidity current and landslide activity for the initial eocene thermal maximum evidence from two distal deep water sites previous studies propose that submarine landslides and turbidity currents may become more likely due to future rapid global warming determining whether global warming increases likelihood assists in assessment of landslide triggered tsunami hazards and risk to seafloor structures other studies propose that landslides helped to trigger past rapid climate change due to sudden release of gas hydrates two deep water turbidite records show prolonged hiatuses in turbidity current activity during the initial eocene thermal maximum ietm at 55 ma the ietm represents a possible proxy for future anthropogenically induced climate change it is likely that our records mainly represent large and fast moving disintegrative submarine landslides statistical analysis of long term 2 3 myr records shows that turbidity current frequency significantly decreased after the ietm our results indicate that rapid climate change does not necessarily cause increased turbidity current activity and do not provide evidence for landslides as a primary trigger for the ietm

the impact of paleocene eocene boundary events on middle neritic benthic foraminiferal assemblages from egypt abstract a 25 m upper paleocene to lower eocene marly sequence exposed at gebel duwi quseir red sea coast of egypt provides a good opportunity for studying paleocene eocene p e boundary stratigraphy and events various bio eco and isotope stratigraphic correlations accurately delineate the position of the p e boundary i e the level of stable isotopic excursions and deep sea benthic extinctions in the middle part of this section within zones p5 and np9 in this paper the impact of p e boundary environmental perturbations on benthic foraminiferal communities of the shallow tethyan shelf is examined benthic foraminiferal assemblages from gebel duwi characterized by large frondicularia phosphatica and f nakkadyi in addition to a number of other neritic taxa but without any typical outer neritic bathyal taxa suggest middle neritic 75 100 m deposition throughout the studied interval and only minor relative sea level variations perhaps some 10 20 m across the boundary sea level appears to have been stable yet a distinct faunal turnover marks the p e boundary of this shallow site which in contrast to deep sea records is less abrupt being preceded by a gradual diversity decrease starting some four meters below the boundary moreover most exits are either local or just temporary and thus not true extinctions many lazarus taxa reappear at some point above the boundary while all but one of the disappearing taxa are known from other lower eocene neritic deposits in egypt in general benthic foraminiferal assemblages display low diversities and high dominance values notably anomalinoides aegyptiacus up to 74 suggesting high levels of environmental stress at the sea floor in combination with occasionally very high p b ratio s up to 98 p and generally laminated sediments the character of the benthic assemblage points to a strong influence of recurrent dysoxia and or anoxia we suggest that these resulted from surface eutrophication by intermittent coastal upwelling and reduced ventilation of the bottom environment although these conditions prevailed during most of the time interval studied they were most severe during the latest paleocene and early eocene when eutrophication intensified and the organic carbon flux to the sea floor increased enhanced atmospheric contrasts between the tethys seaway and the african continent resulting in intensified longshore tradewinds may have controlled these changes at the p e boundary the bottom environment became minimally ventilated perhaps due to reduced oxygen advection from deeper waters three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual decrease of environmental stress and a return to more normal conditions although the organic carbon flux to the sea floor remained high

patterns and magnitude of deep sea carbonate dissolution during eocene thermal maximum 2 and h2 walvis ridge southeastern atlantic ocean 1 eocene thermal maximum 2 etm2 or h1 53 7 ma represents a short lived warming episode associated with the injection of a large mass of 13c depleted carbon into the ocean atmosphere system the mass of injected carbon the extent of deep sea dissolution and the amount of warming during etm2 appear to be approximately half of those documented for the paleocene eocene thermal maximum petm 55 5 ma but the pattern of lysocline migration during etm2 has not yet been documented sufficiently to decipher potential differences in carbon sources and sequestration mechanisms we present high resolution carbonate dissolution and bulk stable isotope records across etm2 and the successive h2 event 53 6 ma on a common age model for four sites along the walvis ridge depth transect 1500 to 3600 m paleowater depth to assess lysocline evolution the onset of etm2 is characterized by multiple depth dependent transitions of carbonate dissolution up to 96 of the total flux associated with rapid depletions in bulk carbonate carbon up to 1 1 5 and oxygen up to 0 7 1 5 isotope values h2 shows a 0 7 negative carbon isotope excursion with a coeval decrease in 18o of 0 5 and 80 of carbonate dissolution during etm2 the lysocline recovered within 30 ka we attribute this rapid recovery to terrestrial caco3 neutralization through enhanced chemical weathering of carbonates in soils and rocks according to theory carbonate dissolution was lower after recovery than prior to etm2 indicating carbonate ion oversaturation and a deeper position of the lysocline spectral analysis indicates that the changes in carbonate dissolution and 13c values were precession paced implying that weathering feedbacks and short term perturbations in the carbon cycle were important in determining early eocene background and hyperthermal ocean co32 conditions

the micropaleontological record of marine early eocene oil shales from jordan abstract core os 28 located in central jordan offers an expanded record of calcareous nannofossils and benthic foraminifera for the early eocene of the southern tethys the oil shale succession of the studied interval covers calcareous nannofossil biozones np10 np11 np12 and np13 microfossils document the biotic response of calcareous nannofossils and benthic foraminifera to short and long term warming trends of the early eocene following the paleocene eocene thermal maximum petm on a global scale two early eocene short term shifts to higher atmospheric co 2 concentration are recorded by negative 13 c excursions these are known as eocene thermal maximum 2 and 3 etm2 etm3 stable isotope records 13 c org 13 c carb 18 o carb from the study area do not show these negative excursions which elsewhere can be correlated with the two hyperthermal events known from early eocene successions the absence of negative 13 c signals otherwise typical for etm2 and etm3 is explained by a diagenetic alteration of the isotope signal after deposition high abundances of the nannofossil taxon sphenolithus spp in biozone np10 indicate less fertile conditions for this interval than for the overlying biozone np11 throughout biozones np11 to np13 coccolithus pelagicus and toweius spp are the dominant taxa of the assemblages suggesting a mesotrophic environment surface waters experienced a temperature change from warm to moderate warm the benthic foraminifera in calcareous nannofossils biozone np10 and in the lower part of np11 reflect oligo mesotrophic and moderate to well oxygenated bottom water conditions throughout the upper part of biozones np11 np12 and np13 the benthic foraminifera are characterized by an increasing abundance of anomalinoides zitteli lenticulina spp and valvulineria scrobiculata this coincides with enriched total organic matter content toc indicating a shift to mesotrophic conditions and a moderate oxygen supply of the bottom waters based on the micropaleontological observations made in core os 28 the early eocene is first characterized by an increase and subsequently by a decrease of nutrients and oxygen the composition of both benthic and planktic communities was rather controlled by variations of regional environmental parameters than by global ones these include strong runoff climatic variability and the architecture of the basin

mammalian community response to the latest paleocene thermal maximum an isotaphonomic study in the northern bighorn basin wyoming new stratigraphic and paleontological information from the mccullough peaks northern bighorn basin wyoming is incorporated into an isotaphonomic faunal database and used to investigate the impact of the latest paleocene thermal maximum and coincident earliest wasatchian immigration event on local mammalian community structure surface collections from willwood formation overbank deposits provide taphonomically consistent and stratigraphically resolved samples of the medium to large sized components of underlying mammalian communities rarefaction shows that the immigration event caused an abrupt and dramatic increase in species richness and evenness after this initial increase diversity tapered off to more typical wasatchian levels that were still higher than those in the preceding clarkforkian wasatchian immigrants were rapidly incorporated into the new community organization representing 20 of the taxa and 50 of the individuals immigrant taxa generally had larger body sizes and more herbivorous and frugivorous dietary habits compared to endemic taxa causing significant turnover in body size structure and trophic structure there was a significant short term body size decrease in many lineages that may have been prompted by the elevated temperatures and or decreased latitudinal thermal gradients during the latest paleocene thermal maximum rapid short term climatic change transient climates and associated biotic dispersal can have abrupt and long lasting effects on mammalian community evolution

the source and fate of massive carbon input during the latest paleocene thermal maximum lithologic faunal seismic and isotopic evidence from the blake nose subtropical western north atlantic links a massive release of biogenic methane 55 5 million years ago to a warming of deep ocean and high latitude surface waters a large perturbation in the combined ocean atmosphere carbon cycle the largest of the past 90 million years a mass extinction event in benthic faunas and a radiation of mammalian orders the deposition of a mud clast interval and seismic evidence for slope disturbance are associated with intermediate water warming massive carbon input to the global exogenic carbon cycle pelagic carbonate dissolution a decrease in dissolved oxygen and a benthic foraminiferal extinction event these events provide evidence to confirm the gas hydrate dissociation hypothesis and identify the blake nose as a site of methane release

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

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

calcareous nannofossil assemblage changes across the paleocene eocene thermal maximum evidence from a shelf setting article i nfo biotic response of calcareous nannoplankton to abrupt warming across the paleocene eocene boundary re flects a primary response to climatically induced parameters including increased continental runoff of fresh water global acidification of seawater high sedimentation rates and calcareous nannoplankton assemblage turnover we identify ecophenotypic nannofossil species adapted to low ph conditions discoaster anartios d araneus rhomboaster spp excursion taxa adapted to the extremely warm climatic conditions bomolithus supremus and coccolithus bownii three species of the genus toweius t serotinus t callosus t occultatus adapted to warm rather than cool water conditions opportunists adapted to high productivity conditions coronocyclus bramlettei neochiastozygus junctus and species adapted to oligotropic and or cool water con ditions that went into refugium during the petm zygrablithus bijugatus calcidiscus parvicrucis and chiasmolithus bidens discoaster anartios was adapted to meso to eutrophic rather than oligotrophic condi tions comparison of these data to previous work on sediments deposited on shelf settings suggests that local conditions such as high precipitation rates and possible increase in major storms such as hurricanes resulted in increased continental runoff and high sedimentation rates that affected assemblage response to the petm published by elsevier b v