tropical sea surface temperature reconstruction for the early paleogene using mg ca ratios of planktonic foraminifera 1 to understand the climate dynamics of hypothesized past greenhouse intervals it is essential to constrain tropical sea surface temperatures sst yet existing proxy records give conflicting results here we present the first mg ca based study of pre quaternary sst and investigate early paleogene late paleocene through late middle eocene 58 6 39 8 ma tropical temperatures using planktonic foraminifera belonging to the genus morozovella from ocean drilling program site 865 on allison guyot western central equatorial pacific ocean calcification temperatures similar to or warmer than modern tropical sst are calculated using a range of assumptions regarding diagenesis temperature calibration and seawater mg ca long term warming is observed into the early eocene 54 8 49 0 ma with peak sst between 51 and 48 ma and rapid cooling of 4 c beginning at 48 ma these findings are inconsistent with the 18o based sst previously estimated for this site

trace fossils after the k t boundary event from the agost section se spain palaeogene trace fossils penetrate the uppermost cretaceous sediments in the agost section betic cordillera se spain chondrites targionii zoophycos isp planolites isp a planolites isp b thalassinoides isp a thalassinoides isp b thalassinoides isp c alcyonidiopsis longobardiae and diplocraterion parallelum have been identified a well developed endobenthic tiering pattern is interpreted the uppermost tier a represents major benthic activity in the shallowest sediments at or just below the seafloor recorded as bioturbated background only discrete rare planolites the next upper tier b displays the highest trace fossil diversity with planolites in the shallow levels and thalassinoides and alcyonidiopsis at slightly deeper ones the intermediate tier c contains randomly distributed thalassinoides and alcyonidiopsis cross cut by zoophycos and large and medium sized chondrites the deepest tier d contains zoophycos cross cut by medium and mainly small sized chondrites two interpretations are proposed 1 vertical partitioning of a singled multi tiered community under steady stable conditions in well oxygenated water bottom reflecting gradual changes deep into the sediment with decreasing oxygen pore water and benthic food and increasing substrate consistency and 2 sequential colonization and community replacement reflecting the work of two successive communities the first community mainly represented by planolites alcyonidiopsis and thalassinoides was produced in a shallow oxygenated soft substrate probably related to decreasing oxygen content and benthic food availability this community was replaced by deeply burrowing organisms that produced zoophycos and chondrites this sequential colonization can be determined by changes in environmental parameters related to the cretaceous palaeogene k t event or may have resulted from normal ecological and early diagenetic processes

a field based study on variation in mg ca and sr ca in larger benthic foraminifera 1 the mg ca and sr ca ratios of foraminifera are used as proxies of paleotemperature although the mg ca is found to be related with temperature in planktonic foraminifera the reliability of this proxy in benthic foraminifera has yet to be established it is essential therefore to understand the minor elements composition and their relation to ambient water parameters in different benthic foraminiferal species in this study a systematic field based study was carried out on larger benthic foraminifera lbf of okinawa japan to assess if mg ca and sr ca in their tests could be used as proxies of seawater temperature five seasonal samples were collected from the reef flat to pick live specimens of amphistegina lessonii neorotalia calcar calcarina hispida calcarina gaudichaudii baculogypsina sphaerulata and marginopora kudakajimaensis the mg ca in a lessonii was 60 mmol mol while in the remaining five species the values were 200 mmol mol substantially higher than that recorded in planktonic and smaller benthic foraminifera interspecies and intraspecies mg ca variations were fairly large even in samples of the same season the sr ca were quite uniform 2 mmol mol across the species and seasons the correlations between test mg ca and sr ca and ambient water temperature and salinity were found to be poor the possible reasons are 1 the influence of biological activities particularly the photosynthesis respiration cycle of algal symbionts and 2 masking of the true relationship due to an averaging effect in whole test analysis of species having longer a life span in view of this it is suggested that the whole shell mg ca and sr ca of lbf is not an apt proxy of paleotemperature

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

eocene to oligocene benthic foraminiferal isotopic record in the bay of biscay we present here oxygen and carbon isotopic records of eocene to oligocene benthic f oraminif era from two bay of biscay deep sea drilling project dsdp sites 119 and 401 18o of benthic foraminifera increases 1 9 from a middle eocene minimum zones p10 p11 to an earliest oligocene maximum zone np21 approximately 1 4 of the increase in benthic foraminiferal 18o occurs during the late eocene to earliest oligocene zones p15 16 np21 previous results from other north atlantic dsdp sites 400a and 398 have significantly lower 18o values of benthic foraminifera some by as much as 2 refs 1 3 we believe that these differences result from diagenetic alteration of the sediments in the deeper buried sites 400a and 398

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

stable warm tropical climate through the eocene epoch earth s climate cooled from a period of extreme warmth in the early eocene epoch ca 50 ma to the early oligocene ca 33 ma when a large ice cap first appeared on antarctica evidence from the planktonic foraminifer oxygen isotope record in deep sea cores has suggested that tropical sea surface temperatures declined by 5 10 degrees over this interval eventually becoming much cooler than modern temperatures here we present paleotemperature estimates from foraminifer isotopes and the membrane lipids of marine crenarcheota from new drill cores in tanzania that indicate a warm and generally stable tropical climate over this period we reinterpret the previously published isotope records in the light of comparative textural analysis of the deep sea foraminifer shells which shows that in contrast to the tanzanian material they have been diagenetically recrystallized we suggest that increasingly severe alteration of the deep sea plankton shells through the eocene produced a diagenetic overprint on their oxygen isotope ratios that imparts the false appearance of a tropical sea surface cooling trend this implies that the long term eocene climatic cooling trend occurred mainly at the poles and had little effect at lower latitudes

oligocene plant ecological strategies in low latitude asia unraveled by leaf economics abstract the oligocene represents an important epoch in the history of the stepwise global climate evolution from a warm climate to a cooler climate the change probably introduced selective pressures influencing ecological strategies and caused the past ecosystems restructured however little is known about the paleoenvironment and adaptive plant ecological strategies in the terrestrial realm of the low latitudes here based on the plant fossils from the baigang formation of the baise basin low latitude china the paleoclimate paleovegetational type and paleoecological strategy are reconstructed using leaf physiognomic analyses integrated plant record and leaf economics spectrum respectively the results show that under a warm and wet sub tropical climate with low seasonality the oligocene baise flora was dominated by slow return maximized resource retention species but mixed with a considerable proportion of fast return rapid resource acquisition species these ecological strategies might promote the community to maximize the use of limited living resources and at the same time to better tolerate potential extreme situations these results allow us to examine which ecological strategies that fossil plants selected under a given paleoclimate condition and might potentially provide a clue to predict the direction of ecological strategy changes in a future climate change scenario

past co2 changes and tropical sea surface temperatures the relationship between past co2 variations and tropical climate change on time scales of millions of years is reviewed explanations for cretaceous and early cenozoic climate change often involve higher atmospheric co2 levels climate models predict that such increases should have been associated with warmer tropical sea surface temperatures ssts however sparse mid cretaceous 18o based sst estimates from low latitude calcareous plankton are 1 0 1 5 heavier than predicted initial evaluations indicate that changes in salinity may not alleviate model data discrepancies for calcareous 18o and that interpretation of altered latitudinal 18o gradients in terms of increased poleward heat transport due to warm saline bottom water wsbw formation would require very large levels of wsbw production at least 60 sv calcareous 18o records may not always record true sst patterns as 18o analyses from phosphatic groups which are less sensitive to diagenesis indicate ssts 5 c higher this latter conclusion is supported by a number of other fossil groups which indicate temperatures warmer than those estimated from calcareous 18o in order to more rigorously test the paleo co2 hypothesis and indeed the models used to forecast future climates it is desirable to intensify investigations of past climate change in low latitudes in order to determine whether these preliminary conclusions stand the test of further scrutiny

patterns of biodiversity and faunal rebound following the k t boundary extinction event in austral palaeocene molluscan faunas palaeocene molluscan faunas are characterised by complex evolutionary histories following the cretaceous tertiary k t boundary extinction event and exhibit dramatic distinct signatures of composition and biodiversity levels relating to extinction and post extinction recovery processes this paper is the first to document and survey the entire palaeocene record of the southern hemisphere which comprises at least 515 recorded molluscan taxa from australia new zealand chatham islands antarctica and south america the record is much richer than previously recognised the k t boundary event was a prime mechanism of change for the composition of palaeocene faunas but palaeocene diversity patterns were shaped also by the final break up of gondwana concomitant changes in climate and in oceanic circulation and faunal recovery processes the flip flop in diversity of bivalves and gastropods across the k t boundary stems from a rapid evolutionary burst of speciation in the danian for gastropods especially carnivorous forms with planktotrophic development which infilled ecospace vacated by the extinction in the southern hemisphere fossil record deposit feeders were less affected by the extinction event and seemingly more extinction resistant but other important factors related to stratigraphic range and spectrum of life habits habitats affected survivorship success suspension feeders especially epifaunal forms were hard hit by the extinction but had bounced back within a few million years by late danian time at the latest but at lower diversity than during the late cretaceous the extinction was not as marked in most southern regions as reflected in the antarctic record in the antarctic k t boundary interval diversity drops suddenly ca 50 m before the boundary and while suspension feeders remain at low diversity for at least 300 kyr gastropods still dominate the molluscan assemblages most of the k t boundary molluscan survivors were bivalve species 66 and all of these were members of representative genera that displayed extensive stratigraphic and geographic ranges in the cretaceous or earlier in the mesozoic the majority of earliest danian antarctic molluscs belong to newly evolved species within surviving genera 58 but by late danian time this trend had changed to a dominance of new species in new genera many new groups arose during the palaeocene especially by late danian time and these faunas are highly distinctive at both genus and species level for example the wangaloa formation fauna of late danian age ca 63 61 ma is dominated by new species in new genera ranging in values from 62 5 to 81 a systematic catalogue of all known palaeocene austral species is presented herein in the appendix for the first time with details of formation recorded age and inferred life habits

an oligocene multi species foraminiferal oxygen and carbon isotope record from odp hole 758a indian ocean paleoceanographic and paleo ecologic implications abstract an oligocene basal miocene zones p19 p22 n4 oxygen and carbon isotope stratigraphy is presented based on mixed benthic foraminiferal faunas and different species of planktic foraminifers from eastern indian ocean odp hole 758a lack of covariance in planktic and benthic 18 o ratios indicates that many oligocene sea level fluctuations including the major fall at 30 ma are not of glacio eustatic origin 18 o values suggest that test morphology is a poor indicator of preferred depth habitat of oligocene planktic foraminifers also some groups show considerable shifts in preferred depth habitat reconstructed surface water temperature was nearly constant during the investigated period but even assuming a large antarctic icecap values are unrealistically low 18 20 c most likely water masses with markedly different oxygen isotopic composition existed this poses great problems for quantitative temperature reconstructions planktic foraminiferal species show similar 13 c ratios indicating well mixed surface waters this contrasts with the strong oxygen isotopic gradient which suggests well stratified surface waters during the oligocene the difference in 13 c ratio between the average ratio of planktic foraminiferal species and the benthic foraminifers 13 c p b shows an inverse relation with the known circulation intensity record and thus with productivity this 13 c pattern is interpreted as being caused by the presence of younger bottom waters at this site during periods with lower temperatures and or larger antarctic ice sheets

turnover of larger foraminifera during the paleocene eocene thermal maximum and paleoclimatic control on the evolution of platform ecosystems the larger foraminifera turnover lft during the paleocene eocene transition constitutes an important step in paleogene larger foraminifera evolution involving a rapid increase in species diversity shell size and adult dimorphism a platform to basin transect in egypt provides new data on timing and causal mechanisms through correlation with planktic biozonations and through integration with regional paleoenvironmental data the lft coincides with the boundary between shallow benthic biozones sbz4 and sbz5 and closely correlates with the paleocene eocene thermal maximum petm enhanced oligotrophy from the late paleocene onward favored the diversification of k strategist larger foraminifera we suggest that a short term eutrophication during the petm led to a temporary decline of extreme k strategist larger foraminifera species providing opportunities for new taxa with different ecological strategies to develop during post petm oligotrophic conditions these new taxa were able to evolve rapidly and soon dominated early eocene larger foraminifera assemblages whereas many paleocene taxa gradually disappeared the success of larger foraminifera during the early paleogene appears climatically controlled because of the vulnerability of corals to high surface water temperatures the late paleocene to early eocene global warming may have favored larger foraminifera at the expense of corals as the main carbonate producing component on carbonate platforms at lower latitudes

bryozoan beds in northern italy as a shallow water expression of environmental changes during the oligocene isotope event 1 abstract shifts in carbonate producing biotic communities in the geological record provide evidence of past environmental changes in the neritic realm the shallow marine calcare di nago formation exposed in the san valentino section northern italy covers the late eocene and earliest oligocene the succession is characterized by the occurrence of light dependent biota such as coralline algae and larger benthic foraminifera in the uppermost part of the section however the fossil association is dominated by bryozoans which are filter feeder organisms this ca 12 m thick interval locally contains up to 86 bryozoans while coralline algae as well as larger benthic foraminifera are absent coralline algae and nummulitid foraminifera recover in the upper part of the bryozoan beds whereas orthophragminids do not recover the gradual disappearance of larger foraminifera and coralline algae within the bryozoan dominated deposits is coeval with a pronounced positive shift in 13c based on its biostratigraphic position this positive shift is interpreted to be linked to the positive shift in 13c recognized in deep sea records shortly above the eocene oligocene boundary which in turn is associated to the positive shift in 18o leading to the oi 1 oligocene isotope event 1 cooling phase total phosphorus content increases in the bryozoan beds suggesting enhanced nutrient supply to the neritic ecosystem this phosphorous peak is coeval with the globally recognized increment in ocean productivity around the oi 1 and 13c positive shift thus disappearance of light dependent biota and the dominance of bryozoans in the platform carbonates studied are interpreted to result not necessarily from a deepening of the depositional environment but from the combination of lower sea surface temperatures and the deterioration of underwater light conditions on account of elevated turbidity in surface waters resulting from enhanced primary productivity as bryozoan beds occur in several italian localities around the eocene oligocene boundary they are interpreted to represent the regional expression of neritic carbonate depositional systems to global environmental changes occurring at the dawn of an ice house earth

nutrient influence on fossil carbonate factories evidence from sedex extractions on burdigalian limestones miocene nw italy and s france abstract different miocene shallow water carbonate successions have been examined to test the potential of phosphorus sequential extraction sedex in studying palaeo nutrient levels and to investigate nutrient influence on carbonate factories during this epoch the coralline algal dominated sequence of the pietra da cantoni group nw italy and the bryozoan dominated sequence of the sommieres basin s france have been targeted for this study actually albeit they both developed during the burdigalian in the very same latitudinal zone they present remarkably different carbonate factories palaeontological analyses have investigated the distribution of the major groups of carbonate producing organisms throughout the successions these results have been compared with those of geochemical analyses on phosphorus and organic matter abundance testifying a clear relationship between the skeletal assemblage and the availability of nutrients as expected on the basis of modern oceanography and benthic ecology bioavailable phosphorus concentration was higher in the bryozoan dominated basin than in the coralline algal dominated basin this result strongly supports sedex sequential extraction as a viable instrument to investigate the nutrient supply in the geological record this also proves that the early miocene mediterranean carbonate factories were deeply controlled by nutrient influence with patterns similar to those observed in present day oceans moderate nutrient concentrations resulted in coralline algal dominance while high nutrient concentrations produced carbonate factories dominated by heterotrophs suspension feeders like bryozoans the euphotic zone producers which dominate in classical tropical associations were probably restricted to areas with low nutrient concentrations

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

an interpretation of cretaceous and tertiary biota in polar regions abstract rich fossil floras and vertebrate faunas lived within the arctic and atarctic circles during the cretaceous and paleogene these occurrences seem explicable by the nature of the thermal environments in polar regions and by the physiological responses of plants and animals allied to those that lived there there seems no need to invoke a lower tilt to the earth s axis to provide greater warmth and light in polar regions to account for these fossil records

estimating mediterranean oligocene miocene sea surface temperatures an approach based on coral taxonomic richness abstract during the oligocene and miocene shallow water carbonates of the mediterranean region were rich in scleractinian corals thriving within various depositional settings including different reef types their diversity patterns although related to a complex interplay between a suite of environmental factors and palaeobiogeography are considered to be strongly controlled by climate variability and changes in sea surface water temperature by using the quantitative relationship between present day coral taxonomic richness and prevailing sea water temperature underlined by the so called energy hypothesis we test zooxanthellate coral generic richness values from a selection of 102 oligocene miocene localities of the mediterranean region as a proxy for relative palaeotemperatures for each oligocene miocene stage generic richness values per z coral site are firstly examined together with variations of the mediterranean z coral generic pool for better testing the method and assessing its potential application patterns of generic richness and inferred palaeotemperatures are then compared with global palaeoclimatic curves based on marine oxygen stable isotopes data or other climate proxies such as palaeoclimatic records from european continental floras and from fossil coral linear extension rate results clearly show that fluctuations of coral richness derived palaeotemperatures correspond relatively well with global changes of sea water temperature especially for the entire oligocene the chattian aquitanian boundary and the late miocene the well known mid miocene climatic optimum however is not recorded suggesting that regional factors acting together with important palaeogeographical changes exerted a strong control on the generic richness of mediterranean z coral communities a remarkable decline of taxonomic richness is recorded after the burdigalian together with a gradual decrease of palaeotemperatures in the region from the middle miocene onwards to the messinian however an increase in the temperature range of z coral localities is clearly visible indicating that z coral communities were able to thrive and adapt to a wider temperature range as the mediterranean was gradually migrating northwards outside the tropical belt the energy hypothesis if used at global or regional scale can be considered a promising and reliable method for estimating cenozoic palaeotemperatures from coral or other suitable fossil assemblages of shallow water carbonates

climate changes in the early to middle miocene of the central paratethys and the origin of its echinoderm fauna abstract this study uses echinoderm diversity to assess climatic changes in the early to middle miocene of the central paratethys it is based mainly on a taxonomically standardised dataset of central paratethys echinoids supplemented by data on asteroid ophiuroid crinoid and holothuroid distributions potential constraints of the raw diversity data are explored and possible biases are identified these include a heterogeneous rock record in terms of outcrop area and facies of the preserved sedimentary rocks stage duration and sampling bias the latter was overcome by utilising rarefaction analysis to investigate species richness these analyses show that the patterns observed in the raw data are robust and not severely biased by sampling intensity the potential influence of a heterogeneous rock record was assessed by comparing surface outcrop areas of the various stages to standing diversity a second bias involving a heterogeneous rock record the non preservation of distinct habitats was overcome by carrying out within habitat comparison of standing diversity and faunal composition the observed patterns were therefore established as true signals rather than artefacts produced by various biases consequently echinoderm diversity is used to evaluate climate changes during the neogene of the central paratethys as well as to interpret minimum winter and summer sea surface temperatures in the badenian middle miocene climatic conditions during the deposition of the badenian leitha limestone were addressed along with the presence of n s gradients within the central paratethys the presently available data suggest warm temperate conditions for the late eggenburgian early burdigalian followed by a brief temperature drop in the ottnangian early late burdigalian temperatures increased again in the karpatian and a climatic optimum was reached in the early badenian a slight cooling during the middle badenian was reflected by the southwards shift of predominantly temperate genera from the northern fringes of the central paratethys in the early badenian to the central parts in the late badenian the faunal gradients observed in the early badenian of the central paratethys suggest that the boundary between the warm temperate and tropical zone lay somewhere within the paratethys at that time considering the more southerly position of the study area about 34 palaeolatitude in the early middle miocene this implies that the tropical climate zone was much wider during the early middle miocene than today biogeographic investigations of the central paratethyan echinoid faunas show that the overwhelming part of the central paratethys echinoid species are immigrants from the mediterranean area immigration occurred in three distinct waves during the late eggenburgian the karpatian and early badenian while no common echinoid species were identified between the boreal region and the central paratethys two species of asteroids from the northern most fringes of the central paratethys also occur in the north sea basin endemism is low in most of the stages except for the ottnangian when geodynamic processes and global cooling resulted in a large scale re organisation of central paratethyan faunas

the eocene expansion of nautilids to high latitudes abstract a short term return of environmental conditions similar to those of the end cretaceous is marked by the reappearance of nautiloid cephalopods in the lower middle eocene la meseta formation of seymour island antarctic peninsula previous findings have been supplemented by a collections of 33 specimens the nautiloids come from several horizons the oldest sample apparently being located close to the base of the formation telm1 the most numerous coming from the cucullaea bed of telm2 and 3 a few specimens were collected from telm4 6 the la meseta formation nautiloid assemblages developed apparently in response to one of the eocene warmings and resulting transgression of a warm sea the incursion of nautiloids into southern high latitudes was roughly coeval with their expansion to the northern european seas and the succession of faunas was parallel in both regions based on the analogy with the lower eocene london clay nautiloid assemblages an estimate of bathymetric evolution of the environment can be made by the presence of a relatively shallow water form similar to cimomia imperialis close to the base of the lower middle eocene la meseta formation telm1 marks the beginning of the marine transgression the dominant la meseta species euciphoceras argentinae was apparently an analogue of the english e regale the occurrence of which in the london clay corresponds to the highest sea level stand the presence of aturia in the higher part telm4 and 5 of the la meseta formation suggests that cold oceanic waters possibly entered the area accompanied by a sea level drop the last nautiloid telm6 is an euciphoceras sp interpreted to be indicative of shallower habitat depth limits both incursion of the nautiloids to and their disappearance from the eocene high latitudes were connected with a fundamental rearrangement of the geographic distribution of particular lineages

carbon and oxygen isotopic disequilibria of recent deep sea benthic foraminifera abstract the carbon and oxygen isotopic compositions of 149 samples of benthic foraminifera from deep sea core tops indicate that none of the nine species studied secrete calcium carbonate in isotopic equilibrium with ambient bottom water uvigerina pyrgo murrhina and oridorsalis tener are the closest to 18o equilibrium with average deviations about 0 4 while planulina wuellerstorfi and p murrhina are the closest to 13c equilibrium with average deviations about 1 p wuellerstorfi shows the most systematic relationship between 13c and bottom water apparent oxygen utilization the intraspecific variabilities in 18o and 13c suggest that estimates of bottom water paleotemperatures can be made to a precision of 0 7 c while estimates of past apparent oxygen utilization aou can be made to 35 mol kg based on intraspecific comparisons of the recent samples with fossils no temporal changes in the degree of either 18o or 13c disequilibrium have been detected for planulina wuellerstorfi uvigerina oridorsalis tener and globocassidulina subglobosa

early paleogene temperature history of the southwest pacific ocean reconciling proxies and models we present a new multiproxy tex86 18o and mg ca marine temperature history for canterbury basin eastern new zealand that extends from middle paleocene to middle eocene including the paleocene eocene thermal maximum petm and early eocene climatic optimum eeco in light of concerns that proxy based sea surface temperature sst estimates are untenably warm for the southwest pacific during the eocene we review the assumptions that underlie the proxies and develop a preliminary paleo calibration for tex86 that is based on four multiproxy eocene records that represent an sst range of 15 34 c for the southwest pacific paleogene we show that tex86l exhibits the best fit with the eocene paleo calibration ssts derived from related proxies tex86h 1 tex86 exhibit a systematic warm bias that increases as tex86 values decrease a warm bias of 4 7 c where tex86 0 7 the tex86l proxy indicates that southwest pacific sst increased by 10 c from middle paleocene to early eocene with sst maxima of 26 28 c tropical during the petm and eeco and an sst minimum of 13 16 c cool warm temperate at the middle late paleocene transition 58 7 ma the base of the eeco is poorly defined in these records but the top is well defined in canterbury basin by a 2 5 c decrease in sst and bottom water temperature bwt in the latest early eocene 49 3 ma bwt falls from a maximum of 18 20 c in the eeco to 12 14 c in the middle eocene overall cooler temperatures are recorded in the mid waipara section which may reflect a deeper 500 m water depth and less neritic depositional setting compared with hampden and odp 1172 200 m water depth the high ssts and bwts inferred for the petm and eeco can be reconciled with eocene coupled climate model results if the proxies are biased towards seasonal maxima and the likely effect of a proto east australian current is taken into account

new pollen evidence from nariani georgia for delayed postglacial forest expansion in the south caucasus the nature and timing of environmental changes throughout the last glacial interglacial transition in the south caucasus and more widely in eastern europe are still not fully understood according to certain pollen records forest expansion occurred in many areas several millennia after what is considered worldwide as the onset of the holocene the current problem we face is that the time lag in forest expansion varies from one sequence to another sometimes with no delay at all moreover the potential forcing controlling factors behind this complex pattern contrary to the almost synchronous global holocene warming are still a matter for debate accordingly we revisit the issue of forest expansion through vegetation history obtained in the south caucasus using a new pollen record retrieved from the nariani paleolake south georgia these data attest to a steppic phase initially dominated by amaranthaceae chenopodiaceae 12 700 10 500 cal yr bp then by poaceae 10 500 9000 cal yr bp culminating with a more forested phase 9000 5000 calyrbp although some palaeoclimatic regional reconstructions show a wet early holocene we interpret the delay in forest expansion recorded in nariani 2500 years as the result of reduced spring precipitation which would have limited forest development at that time

foraminiferal biofacies in a silica rich neritic sediment late eocene south australia abstract the highly siliceous blanche point formation accumulated during the late eocene zones p15 p16 in the st vincent basin when the climate was warm it differs from shelly neritic carbonates above it and below it by higher but fluctuating numbers of benthonic foraminifera of the family uvigerinidae and by high dominance in different horizons of infaunal crustacean traces and of infaunal gastropods within the blanche point formation changes from a banded siliceous opal ct sediment to a homogeneous spongolite are paralleled by biofacies changes high numbers of uvigerinidae and in part of the formation high numbers of robertinacea bolivinidae sphaeroidina cassidulina are more consistent with generally lowered levels of oxygen at the sediment surface than with other forms of environmental stress the study is consistent with a recent conclusion based on mineralogy that the abundant silica came from volcanic ash it suggests too that restricted circulation permitted biogenic and other mechanisms of fix the silica in the st vincent basin whilst silica was being flushed away from more open environments facing the nascent southern ocean

ichnofossils and rhizoliths of the nearshore fluvial jebel qatrani formation oligocene fayum province egypt abstract the ichnofossils and rhizoliths of the oligocene jebel qatrani formation of egypt are among the best preserved most diverse in form and most abundant of such structures yet recognized in fluvial rocks twenty one forms are described the ichnofauna contains traces domichnia fodinichnia cubichnia of probable annelid insect crustacean and vertebrate origin these include the first described fossil nest structures and gallery systems of subterranean termites isoptera the first examples of ophiomorpha from wholly fluvial rocks and the first fossil vertebrate burrows from the african tertiary rhizoliths associated with the ichnofauna and those occurring elsewhere document a variety of small wetland plants coastal mangroves and much larger trees the environment suggested by these traces is consistent with the coastal tropical to subtropical monsoonal rain forest with adjacent more open areas that is indicated by independent evidence of sedimentology paleontology and paleopedology

tropical sea temperatures in the high latitude south pacific during the eocene sea surface temperature sst estimates of 30 c from planktic foraminifera and archaeal membrane lipids in bathyal sediments in the canterbury basin new zealand support paleontological evidence for a warm subtropical to tropical climate in the early eocene high latitude 55 s southwest pacific such warm ssts call into question previous estimates based on oxygen isotopes and present a major challenge to climate modelers even under hypergreenhouse conditions 2240 ppm co2 modeled summer ssts for the new zealand region do not exceed 20 c

facies analysis and sequence stratigraphy of a miocene warm temperate carbonate ramp montagna della maiella italy abstract the uppermost oligocene lower miocene to upper miocene ramp carbonates from montagna della maiella italy form a supersequence bounded by deeply incised truncation surfaces this supersequence is subdivided into four sequences each sequence is composed of skeletal limestones in its lower part and marly limestones in its upper part the lower parts of the sequences are foramol limestones which suggest deposition in the warm temperate climate zone changes in climate oceanography and relative sea level combined to control sedimentation in the four sequences in the lower parts of the two older sequences the skeletal sands built dunes suggesting high energy conditions the dominant skeletal grains in the oldest sequence are larger foraminifers and in the next sequence they are bryozoans this change reflects cooling around the time of the aquitanian burdigalian boundary in the lower parts of the two younger sequences of middle and late miocene age sediment sheets with red algal bryozoan oncoids suggest deposition under calmer conditions transgressive and highstand systems tracts are recognized in all sequences a shelf margin systems tract may be exposed in the second oldest sequence in contrast to the situation that exists when warm water carbonates are deposited sedimentation of the foramol limestones on this isolated ramp was unable to balance accommodation during sea level rise this led to hemipelagic sedimentation during sea level highstands conglomerates resulted from reworking along flooding surfaces

tertiary ice sheet dynamics the snow gun hypothesis we observe strong negative correlation between tertiary low to mid latitude planktonic foraminiferal 18o and the difference between these data and coeval benthic foraminiferal 18o late quaternary data do not show this correlation coupling statistical model 18o comparisons and evidence for antarctic ice and ocean temperature variation we infer that tertiary ice volume recorded by tropical planktonic 18o increased as the deep ocean warmed because the isotopic signatures of deepwater temperature variation and ice volume change were of opposite sign the sum of these signals in tertiary benthic 18o became lost in the noise this renders low correlation between tertiary planktonic and benthic 18o time series compared to late quaternary data we contend that tertiary ice sheet growth was commonly driven by warming of deep water from low to mid latitude marginal seas snow gun hypothesis in contrast late quaternary ice sheets grew as deep water formed at high latitude cooled because tectonic forcing and orbital forcing at low latitude primarily controlled production and temperature variations of this warm saline deep water these influences largely dictated tertiary ice volume fluctuations through the tertiary we infer ice volume fluctuations to be an important component of sea level history on timescales between 103 and 107 years

petrology and palaeoenvironmental significance of glaucony in the eocene succession at whitecliff bay hampshire basin uk following the investigations of odin and others into the distribution of green granules glaucony has been widely assumed to be a reliable indicator of a fully marine open shelf environment with a low sedimentation rate we have investigated the value of glaucony as a palaeoenvironmental indicator through an investigation of the pellets and their distribution and reworking in the predominantly brackish to shallow marine tertiary sediments of the hampshire basin together with a re evaluation of the sedimentology glaucony has apparently formed in situ in all lithofacies from shallow marine to estuarine of the three highest glaucony concentrations all dominated by in situ glaucony two occur within highstand system tracts the third is at a sequence boundary several important surfaces do not have more than a few percent glaucony with very variable proportions of mature and in situ pellets the correlation between glaucony concentration and sequence stratigraphy is most obvious in the london clay and wittering formations where least reworking of pellets has occurred in the barton group there are no major concentrations of glaucony at any of the important stratal surfaces we believe this more random glaucony distribution is due to limited glaucony formation and reworking of older glaucony in these sediments ideal conditions for glaucony formation are interpreted to have been fully marine 10 30 m water depth a warm temperature plus low sedimentation rate with periodic winnowing to concentrate the pellets although most of these conditions for glaucony formation occurred in the selsey formation and barton group a factor or factors mitigated against glauconitization we suggest that this was lowering of the water temperature the london clay and wittering formations were deposited relatively rapidly 50 60 m ma 1 and include intervals of estuarine sedimentation both factors that we believe inhibited glaucony formation glaucony maturity reflects the minimum length of time spent in surface sediments close to the oxic sub oxic interface point count data and chemical data for glaucony indicate widespread reworking and an overall increase in reworking with time possibly due to uplift on the isle of wight monocline the apparently wide range of conditions in which glaucony will form and the frequency with which it is reworked suggest that it is a less useful indicator palaeo environmental indicator than is commonly supposed

environmental factors influencing skeletal grain sediment associations a critical review of miocene examples from the western mediterranean the presence of foramol rhodalgal and bryomol skeletal grain associations in ancient shallow marine limestones is commonly interpreted as evidence for non tropical palaeoclimate despite temperature being only one of several factors influencing skeletal grain associations such interpretations neglect the multitude of factors other than temperature that influence carbonate producing biota these include nutrients water energy water transparency depth of the sea floor salinity oxygen ca2 and co2 concentrations mg ca ratio alkalinity substrate requirements competitive displacement as well as biological and evolutionary trends this uniformitarian approach also disregards the probability that conditions of present day biological systems may not be representative of past conditions of analogous systems here the importance of considering these other factors is illustrated through two examples of carbonate platforms in the western mediterranean these platforms are dominated by foramol rhodalgal and bryomol associations of miocene age in spite of having formed in tropical conditions the platforms discussed are 1 the lower tortonian ramp on menorca balearic islands and 2 the lower middle miocene ramps of the central apennines italy evidence for tropical conditions in the mediterranean during the period of growth of these platforms is provided by species of red algae and larger foraminifera by data from coeval continental basins and by global oxygen isotope data

paleo oceanographic and tectonic settings of early miocene reefs and associated carbonates of offshore southeast asia the late oligocene to early middle miocene was a period of widespread reef and associated carbonate deposition over a wide latitudinal range in the offshore region of southeast asia a generally rising eustatic sea level during this period allowed the accumulation of thick reefal units an expansion of the coral algal regional facies belt north to japan and south to new zealand occurred during the early miocene as the result of a reduced oceanic latitudinal temperature gradient an episode of enhanced organic carbon burial is reflected in a positive dgr13c excursion from 17 5 to 13 5 ma increasing paleo oceanographic equability may have resulted in reduced ocean circulation with the resultant development of an expanded oxygen minimum zone marine oil prone or anic carbon was deposited in silled anoxic basins both bounded by and within island arc systems a combination of tectonic and paleo oceanographic factors therefore created conditions that favored contemporaneous deposition of organic carbon rich source beds and reef reservoirs during the latest early to early middle miocene paleogeographic and facies reconstructions for an 18 m y interval indicate that deposition occurred in three tectonic settings 1 passive continental margins 2 convergent plate boundaries and 3 obliquely convergent plate boundaries in all these settings the vertical motion histories of fault bounded blocks and of larger tectonic elements within which they are contained directly controlled the geographical distribution of carbonate buildups their scal and morphology duration diagenesis and relationship to siliciclastics

bivalve molluscs and cenozoic paleoclimatic events in the northwestern pacific ocean abstract a new method for the calculation of cenozoic paleotemperatures is proposed which is based on the statistical relation between the august ta and annual ty temperature of surface water and the coefficient of thermotropy ct the coefficient presents the percentage ratio of the number of species of bivalve molluscs from temperate and warm water genera to the total number of species in a definite region for the northwestern pacific at 1 1 ct 92 1 the most adequate temperature estimations gave the equations t y 3 836 1 014 ct and t a 10 998 1 009 ct paleotemperatures in the vicinity of western tochilinsky key section and eastern korfa gulf key section kamchatka south sakhalin makarovsky key section and a number of areas of hokkaido and honshu japan have been reconstructed using the proposed procedure an early middle miocene around 16 ma temperature maximum which is of high climatic stratigraphic value has been found to be present in all areas studied and to correspond to the level of the kakertian horizon of western kamchatka the takinoue lower togeshita horizon of hokkaido and the nishikurosawa formation of north honshu the average annual surface water temperatures at that time were 7 1 c up to 9 6 c and 11 5 c respectively in close similarity to the northern areas of the atlantic haq 1982 a four fold advancement of temperate faunistic complexes toward higher latitudes has been observed near western kamchatka specified as the kuluvenian kakertian ilynian early and late etolonian temperature maxima the paleoceanological situation near western kamchatka during these maxima is assumed to be sufficiently close to that presently existing in peter the great bay and in more southerly areas of the sea of japan the basic paleotemperature trends which turn out to be similar for all regions studied and for the main neogene north pacific paleoclimatic events tsuchi 1989 1990 1992 suggest the validity and suitability of the proposed method for the determination of paleotemperatures using the coefficient of thermotropy this is also evidenced by the agreement between the paleotemperature estimates obtained here and the oxygen isotope values

ecology of extant nummulitids and other larger benthic foraminifera applications in palaeoenvironmental analysis abstract larger benthic foraminifera lbf are important contributors to modern and ancient tropical shallow marine sediments over the past 30 years a substantial body of literature has built up on the ecology of modern lbf especially in terms of their environmentally sensitive depth distribution reproductive strategy and morphology and the symbiotic relationship between many larger foraminifera and photosynthetic algae over the same period the extinct genus nummulites which is abundant in eocene sediments of southern europe north africa and the arabian peninsula has increasingly been studied principally because significant volumes of hydrocarbons have been discovered reservoired within nummulitic limestones offshore tunisia and libya the modern ecological studies of lbf provide a powerful tool with which to develop palaeoecological models for fossil nummulites and other symbiont bearing larger foraminifera in the rock record

orbitally forced climate change in late mid eocene time at blake nose leg 171b evidence from stable isotopes in foraminifera previous stable oxygen isotopic data from surface dwelling foraminifera indicate that eocene tropical sea surface temperatures ssts were significantly lower than at present here we show that stable isotopic analyses 180 13c of the late mid eocene mixed layer dweller morozovella spinulosa are consistent with in mid eocene mid latitudes ssts close to or slightly lower than modern temperatures at blake nose western north atlantic in contrast isotopic analyses of the benthic foraminiter nuttalides truempyi reveal a gradual fall in mean bottom water temperatures from 8 to 7 c over c 500 ka years these deep intermediate water temperatures are significantly higher than modern ones and are similar to intermediate and bottom water temperatures recorded from earlier in palaeogene and late cretaceous time large shifts arc seen in the 18o and 13c values of the planktonic foraminifers of up to 1 and 2 6 respectively that probably reflect temperature and nutrient fluctuations controlled by regional changes in upwelling intensity and runoff the surface to benthos 18o gradient decreases from 3 pdb to a minimum of c 0 5 pdb over 400 ka which could relate to the intensity of upwelling spectral analysis reveals precessional forcing in the foraminiferal 18o records which shows the direct influence of low latitude insolation on surface water stratification monsoonal wind systems may have forced the upwelling cycles and or freshwater input the benthic foraminifer 18o record also contains the obliquity cycle in addition to the precessional cycles indicating the inheritance of mid and high latitude forcing to subtropical deep waters

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

environmental change in the subtropics during the late middle eocene greenhouse and global implications 1 oxygen isotope records from odp site 1052 blake nose subtropical north atlantic ocean indicate significant short term high amplitude variability up to 1 4 in about 2500 to 4000 years during the late middle eocene 37 9 37 5 ma these variations reflect a combination of changes in sea surface temperature and the oxygen isotope composition of the regional seawater in order to independently evaluate the magnitude of sst changes at blake nose and better understand the nature of environmental change during the late middle eocene we present planktonic foraminiferal mg ca data combined with 18o data from the same samples the calculated mg ca paleotemperatures indicate a decrease in ssts over the study interval from 33 to 28 c at the same time that previously published foraminiferal 18ocalcite values from the same samples also decrease thus the 18ocalcite values must reflect a significant component of seawater 18o change in order to reconcile the opposite paleotemperature trends reflected by both proxies calculated 18oseawater values decreased from 3 at 37 83 ma to 2 at 37 6 ma the combined trends of the sst and 18oseawater cannot be explained by an increase of continental ice over this time interval instead the data favor an overall weakening of the hydrological cycle as global climate transitioned from the greenhouse to icehouse

scleractinian assemblages under sediment input their characteristics and relation to the nutrient input concept abstract in the geological record scleractinian dominated turbid water bioconstructions that accumulated under substantial terrigenous input along with shallow neritic marls rich in well preserved corals are common these occurrences indicate that beyond some threshold the ecologic and taphonomic effects of sedimentation prevail over the effects of nutrification field data and experiments on recent corals show that some taxa cope well with terrigenous turbidity and sedimentation and acclimate to increased heterotrophy colonial corals resilient to sediment input commonly are massive to platy forms of high skeletal plasticity and with large polypars to effectively reject sediment or are branched species providing a very small sedimentation area cleaned by feeble currents or small polyped massive taxa that tolerate intermittent veneering by sediment these corals may comprise siltation assemblages of recent turbid water reefs and level bottoms in siliciclastic environments conversely excess input of even low amounts of dissolved inorganic nutrients into clear waters adversely affects many coral species fossil turbid water bioconstructions twb were situated in inner shelf to shore zone settings or near storm wave base on shelves or ramps did not stack into reef complexes mostly show a cluster to segment fabric are scarce in or devoid of frame pores with marine cement and lacked a high carbonate slope relative to fossil clear water buildups preserved in pure limestone successions fossil twb contain moderately diverse coral assemblages with an increased proportion of sediment resistant forms aside from coral behaviour that is elusive in fossils the sediment resistance of corals was mainly determined by colony shape and polypar size but small polyped sediment tolerant corals became common since the early cretaceous late jurassic to cretaceous turbid water coral assemblages are dominated by plocoid or thamnasterioid forms corresponding cainozoic assemblages consist mainly of cerioid and plocoid taxa in fossil twb bioerosion and encrustation are similar or higher than in contemporaneous clear water buildups under higher sediment input accumulation of discrete twb was quenched and level bottoms of both corals and soft substrate biota formed in the resulting coral marls depending on turbidity sedimentation and substrate stability the coral fauna consists largely of both solitary corals and mainly sediment resistant pseudocolonial colonial forms or is dominated by solitary corals many corals show growth anomalies resulting from partial mortality due to episodic rapid sedimentation and unstable substrate in coral marl environments because of terrigenous input nutrient levels probably were elevated yet macroboring and encrustation are very scarce beyond some threshold of terrigenous sediment input and accumulation the ecologic and taphonomic effects of sedimentation and unstable substrate prevail over the effects of nutrient enrichment during the meso cainozoic evolution of scleractinians increasing photoautotrophy and progressive invasion of oligotrophic environments is in contrast to a late cretaceous to cainozoic increase in the relative number of reefs in marginal marine siliciclastic settings this trend may be explained by second order sea level fall and shrinking of epicontinental carbonate seas and isolated platforms driving corals to more narrow attached shelves and by a wider total trophic range in which distinct coral assemblages can thrive as a result of coral evolution and diversification

evidence for seasonality in early eocene high latitude sea surface temperatures abstract specific challenges still exist in our understanding of past greenhouse climate states whilst climate model simulations using atmospheric co2 concentrations consistent with proxy estimates broadly align with lower latitude proxy temperature estimates they struggle to reproduce the warming implied by proxies at higher latitudes especially in the marine realm this inconsistency has often led to the conclusion that climate models are insufficiently sensitive here we analyse the distribution of photozoan and heterozoan carbonates which provide important constraints for latitudinal sea surface temperature sst gradients to assess data model mismatches for the early eocene climatic optimum the carbonate facies distribution is compared against quantitative geochemical proxy temperature estimates 18 o mg ca clumped isotopes and tex86 and a new hadcm3l climate simulation good correspondence exists between the simulated cold month ssts and photozoan carbonates indicating hadcm3l is effectively reconstructing meridional temperature gradients into mid latitudes whilst there is good agreement between simulated mean annual ssts and geochemical proxy estimates in low latitudes the 18 o mg ca and tex86 estimates instead align with warm month ssts at higher latitudes in light of the carbonate facies evidence and consistency between our simulation and available terrestrial proxy temperature estimates this study supports previous claims that a warm season bias exists in many middle and high latitude sst estimates this helps resolve the discrepancy between climate simulations and marine proxies and shows that climate models and data might be more closely aligned than is appreciated further we demonstrate that simple and widely available proxies can play a fundamental role in contextualising wider paleoclimate uncertainties

a comparison of eocene climate model results to quantified paleoclimatic interpretations abstract the integration of climate model results and geologic information offers considerable potential for deriving greater insight into the geologic record in this study climate model results and quantified climatic interpretations derived from proxy data are compared to assess model capabilities and to examine proxy data interpretations atmospheric general circulation model experiments were used to produce a range of possible representative eocene climate states based on current knowledge of the eocene record the climate model experiments incorporate two idealized endmembers of eocene ocean surface temperature distributions characterized by very different latitudinal gradients model results are compared to quantified interpretations of the climate of early eocene north america in an attempt to identify one of the sea surface temperature distributions as more likely to have existed during the eocene the comparisons do not produce a conclusive match between inferred paleoclimatic information and any single case of model results but some interesting insights become apparent model predictions of mean annual temperature and mean annual precipitation compare favorably to interpretations from geologic evidence but there are large differences between model results and interpreted paleoclimatic parameters of minimum surface temperature and mean annual temperature range several possible causes for these differences are discussed

thermal evolution of cretaceous tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels 1 the evolution of subtropical 30 35 n upper ocean temperatures through the cretaceous is inferred from the oxygen isotope compositions of 64 fish teeth enamel coming from the western tethyan platform mean 18o values of 22 at the berriasian valanginian boundary decrease with oscillations to 18 5 around the cenomanian turonian boundary and progressively increase to 21 5 by the end of the cretaceous the similarity of this oxygen isotope curve for bioapatites from platform environments with those for foraminifera and bulk carbonates that were deposited in deeper waters and at other paleolatitudes indicates that they record global climatic signals major cooling events at the million year scale can be distinguished 1 at the berriasian valanginian boundary and 2 during the earliest late valanginian a third cooling event is detected during the earliest aptian these events already proposed as icehouse interludes during the lower cretaceous are also recorded at subtropical latitudes a progressive warming is identified from the aptian to the cenomanian turonian interval that corresponds to a thermal optimum and then upper ocean temperatures decreased to the maastrichtian minimum isotopic temperatures range from 15 c to 28 c assuming a 18oseawater of 1 for an ice free world taking more realistic 18oseawater values of 0 for tropical waters during glacial periods within the berriasian valanginian interval and earliest aptian or with above average salinities possibly the maastrichtian temperatures are increased by 4 5 c temperature differences between climatic extremes of the valanginian and cenomanian turonian are estimated to have been 10 c latitudinal thermal gradients for the albian cenomanian turonian and maastrichtian were 0 2 0 3 c latitude and thus weaker than modern oceanic values at about 0 4 c latitude

reevaluation of conflicting eocene tropical temperature estimates molluskan oxygen isotope evidence for warm low latitudes oxygen isotope data from planktonic foraminifera for the warm eocene epoch suggest that tropical sea surface temperatures ssts may have been cooler than at present such data have stimulated various explanations involving e g major changes in ocean heat transport however the planktonic data disagree with terrestrial climate proxies which suggest significantly warmer low latitude temperatures we examined this discrepancy by analyzing seasonal oxygen isotope variations in shallow marine mollusks from the mississippi embayment results indicate that mean annual ssts decreased from 26 27 c in the early eocene to 22 23 c in the oligocene agreeing well with temperatures inferred from terrestrial climate proxies these cooling trends with more significant winter cooling 5 c than summer cooling 3 c are consistent with the predicted consequences of decreasing atmospheric co 2 concentration through the paleogene suggesting that atmospheric co 2 change was a major controlling factor for paleogene climate change that winter sst estimates from the mollusks agree well with the foraminiferal sst estimates suggests that planktonic foraminiferal growth in low latitudes occurred mainly during the cooler winter months throughout the eocene we hypothesize that the unusual hydrography of eocene oceans shifted foraminiferal productivity primarily to winter biasing foraminiferal sst estimates of mean annual ssts