a cenozoic record of the equatorial pacific carbonate compensation depth atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks these feedbacks involve the erosion of silicate rocks and organic carbon bearing rocks the integrated effect of these processes is reflected in the calcium carbonate compensation depth which is the oceanic depth at which calcium carbonate is dissolved here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial pacific ocean the carbonate compensation depth tracks long term ocean cooling deepening from 3 0 3 5 kilometres during the early cenozoic approximately 55 million years ago to 4 6 kilometres at present consistent with an overall cenozoic increase in weathering we find large superimposed fluctuations in carbonate compensation depth during the middle and late eocene using earth system models we identify changes in weathering and the mode of organic carbon delivery as two key processes to explain these large scale eocene fluctuations of the carbonate compensation depth

middle miocene ocean climate transition high resolution oxygen and carbon isotopic records from deep sea drilling project site 588a southwest pacific high resolution stable isotopic records are presented for the epi benthic foraminifer cibicidoides the inferred shallow dwelling planktonic globigerinoides quadrilobatus and the inferred deep dwelling planktonic globoquadrina dehiscens from the middle miocene 16 12 ma of deep sea drilling project site 588a lord howe rise southwest pacific high resolution multiple species oxygen and carbon isotopic data define the timing and character of the well known middle miocene climatic oceanographic transition with a resolution comparable to quaternary records the benthic foraminiferal 18o record is marked by several large fluctuations from 16 to 14 8 ma followed by a series of rapid 50 kyr 18o increases that suggest a new state of the ocean climate system after 14 8 ma the total middle miocene benthic oxygen isotopic increase of 1 2 is largely incorporated in two steps an increase of 0 8 from 14 5 to 14 0 ma and a second increase of 0 7 from 13 45 to 12 45 ma each step is comprised of a series of marked 18o increases indicative of rapid east antarctic ice sheet growth and contemporaneous deepwater cooling a strong covariance of 0 7 between the benthic and deep dwelling planktonic species from 14 5 to 14 0 ma including a rapid increase from 14 1 to 14 05 ma suggests a 0 7 increase in the 18o composition of seawater 18osw because of east antarctic ice sheet growth comparison of the 18o record of gs quadrilobatus suggests that surface waters warmed at this site by 3 c from 14 1 to 13 6 ma carbon isotopic time series for each species generally covary throughout the early to middle miocene interval 16 12 ma confirming that 13c variations in this interval largely represent reservoir changes high resolution 13c data allow improved resolution of the latter five of six 13c maxima within the well known early to middle miocene carbon isotopic excursion the monterey carbon isotopic excursion from 17 0 to 13 5 ma this is useful for global correlation the last of these maxima ends with a 1 decrease centered from 13 9 to 13 7 ma 300 kyr after the 18o increase considered to reflect east antarctic ice growth covariance between benthic 18o and 13c from 16 to 13 8 ma suggests a sensitive relation between global carbon cycling and the ocean climate system prior to 13 8 ma episodic increases in organic carbon burial may have contributed to deep sea benthic 13c maxima and synchronous global cooling the positive relationship ended at 13 8 ma indicative of changing relations between global carbon cycling and the ocean climate system brought on by the increased stability of the east antarctic ice sheet after a major growth phase from 14 5 to 14 0 ma

middle miocene southern ocean cooling and antarctic cryosphere expansion magnesium calcium data from southern ocean planktonic foraminifera demonstrate that high latitude similar to55degreess southwest pacific sea surface temperatures ssts cooled 6degrees to 7degreesc during the middle miocene climate transition 14 2 to 13 8 million years ago stepwise surface cooling is paced by eccentricity forcing and precedes antarctic cryosphere expansion by similar to60 thousand years suggesting the involvement of additional feedbacks during this interval of inferred low atmospheric partial pressure of co2 pco 2 comparing ssts and global carbon cycling proxies challenges the notion that episodic pco2 drawdown drove this major cenozoic climate transition sst salinity and ice volume trends suggest instead that orbitally paced ocean circulation changes altered meridional heat vapor transport triggering ice growth and global cooling

a middle miocene relative paleointensity record from the equatorial pacific abstract we present a high resolution magnetostratigraphy and relative paleointensity rpi record derived from the upper 85 m of iodp site u1336 an equatorial pacific early to middle miocene succession recovered during expedition 320 321 the magnetostratigraphy is well resolved with reversals typically located to within a few centimeters resulting in a well constrained age model the lowest normal polarity interval from 85 to 74 87 m is interpreted as the later part of chron c6n 18 614 19 599 ma thirty three other magnetozones occur from 74 87 to 0 85 m which are interpreted to represent the continuous sequence of chrons onset of chron c5er 18 748 ma to the end of chron c5an 1n 12 014 ma we identify three putative previously unrecognized subchrons within chron c5cn 1n chron 5bn 1r and c5abn sedimentation rates vary from about 7 to 15 m myr with a mean of about 10 m myr we observe rapid apparent changes in the sedimentation rate at geomagnetic reversals between 16 and 19 ma that indicate a calibration error in geomagnetic polarity timescale atnts2004 the remanence is carried mainly by non interacting particles of fine grained magnetite which have forc distributions characteristic of biogenic magnetite given the relative homogeneity of the remanence carriers throughout the 85 m thick succession and the fidelity with which the remanence is recorded we have constructed a relative paleointensity rpi record that provides new insights into middle miocene geomagnetic field behavior the rpi record indicates a gradual decline in field strength between 18 5 ma and 14 5 ma and indicates no discernible link between rpi and either chron duration or polarity state

effects of diagenesis on the isotopic record of late paleogene tropical sea surface temperatures abstract oxygen isotope records of planktonic foraminifera indicate that late eocene and oligocene tropical sea surface temperatures were as much as 8 c lower than present at a time when high latitude sea surface temperatures were higher than present using a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate the effects of diagenesis on bulk carbonate 18 o records for the cenozoic are quantified for four tropical sites most of the observed variations in measured 18 o values at all sites can be accounted for by diagenetic effects there are no systematic trends that support substantial variations in tropical sea surface temperatures beyond diagenetic effects with the possible exception of the early eocene for which the data are consistent with slightly higher sea surface temperatures reconstructions based on oxygen isotope records of planktonic foraminifera which indicate cooler tropical sea surface temperatures for the eocene and oligocene may be artifacts of diagenetic recrystallization as such records are particularly sensitive to diagenetic effects

the importance of atmospheric dynamics in the northern hemisphere wintertime climate response to changes in the earth s orbit milankovitch proposed that variations in the earth s orbit cause climate variability through a local thermodynamic response to changes in insolation this hypothesis is tested by examining variability in an atmospheric general circulation model coupled to an ocean mixed layer model subjected to the orbital forcing of the past 165 000 yr during northern hemisphere summer the model s response conforms to milankovitch s hypothesis with high low insolation generating warm cold temperatures throughout the hemisphere however during northern hemisphere winter the climate variations stemming from orbital forcing cannot be solely understood as a local thermodynamic response to radiation anomalies instead orbital forcing perturbs the atmospheric circulation in a pattern bearing a striking resemblance to the northern annular mode the primary mode of simulated and observed unforced atmospheric variability the hypothesized reason for this similarity is that the circulation response to orbital forcing reflects the same dynamics generating unforced variability these circulation anomalies are in turn responsible for significant fluctuations in other climate variables most of the simulated orbital signatures in wintertime surface air temperature over midlatitude continents are directly traceable not to local radiative forcing but to orbital excitation of the northern annular mode this has paleoclimate implications during the point of the model integration corresponding to the last interglacial eemian period the orbital excitation of this mode generates a 1 2 c warm surface air temperature anomaly over europe providing an explanation for the warm anomaly of comparable magnitude implied by the paleoclimate proxy record the results imply that interpretations of the paleoclimate record must account for changes in surface temperature driven not only by changes in insolation but also by perturbations in atmospheric dynamics

the loess record in sections at koblenz metternich and tonchesberg in the middle rhine area abstract the loess palaeosol sequences of the middle rhine area provide a relatively detailed and continuous terrestrial record of climate and environment change for the past 200 000 years loess palaeosol sequences are generally well preserved in inter and intra crater depressions of late middle pleistocene scoria cones in the east eifel volcanic field and on fluvial terraces of the lower middle terrace of the rivers rhine and moselle stratigraphic and chronological investigations of loess palaeosol sequences from sections at tonchesberg and koblenz metternich in the middle rhine area indicate that the last interglacial and glacial cycle is preserved in much more detail than previously thought in both sections the last interglacial soil is covered by at least ten palaeosols postdating the eemian oxygen isotope sub stage ois 5e brown forest soil

microstructural and geochemical perspectives on planktic foraminiferal preservation glassy versus frosty in recent years it has become apparent that the cool tropic paradox of paleogene and cretaceous greenhouse climates arises because of the diagenetic alteration of tropical planktic foraminiferal calcite near the seafloor yielding artificially high 18o values because the mg ca compositions of foraminiferal and inorganic calcite are thought to be quite different mg ca measurements should be a sensitive way of monitoring diagenetic alteration here we examine the extent of diagenetic alteration of eocene planktic foraminiferal calcite using scanning electron microscope imaging of foraminiferal test microstructures and geochemical 18o and mg ca analyses we compare microstructural and geochemical characteristics between given species exhibiting two contrasting states of preservation those that appear frosty under reflected light and those that appear glassy microstructural evidence reveals extensive diagenetic alteration of frosty foraminiferal tests at the micron scale while 18o analyses document consistently higher 18o and therefore lower paleotemperatures in this material yet we find that 18o offsets between species in these frosty foraminiferal assemblages appear to be generally preserved suggesting that frosty foraminifera remain valuable for generating relatively short approximately 1 myr paleoceanographic time series that do not demand absolute estimates of paleotemperature we also find that the observed increase in mg ca for planktic foraminifera exhibiting diagenetic alteration compared to glassy taphonomies is far smaller than would be expected from the addition of inorganic calcite based on laboratory derived mg2 partition coefficients our findings imply that a much lower mg2 partition coefficient controls inorganic calcite formation in deep sea sedimentary sections in accordance with the findings of baker et al 1982

was there an abrupt cold climatic event in the middle eemian pollen record from a palaeolake at the hieronimowo site ne poland abstract seventy samples of lacustrine sediments from a palaeolake at the hieronimowo site ne poland were investigated by pollen analysis method the obtained results indicate that the examined sequence spans the whole eemian interglacial mis 5e the beginning of the early vistulian weichselian mis 5d and some undefined period of the plenivistulian middle weichselian mis 2 4 the specific feature of the studied profile is the great thickness of deposits representing the hornbeam phase of the eemian interglacial e5 r paz which was the younger part of the climatic optimum of this interglacial and the very well developed pollen record of this phase that is absent in other profiles in ne poland due to this our study allowed for the first time in ne poland the detailed reconstruction of changes in the vegetation and in the mean january and july temperature during the middle part of the eemian interglacial this reconstruction unequivocally rules out the existence of an abrupt short lasting cold event at that time only a gradual slight increase in temperature was apparent during the older part of the hornbeam phase to 21 c for july and to 0 c for january and gradual decrease during its younger part to 17 c for july and to 5 c and

the heartbeat of the oligocene climate system a 13 million year continuous record of oligocene climate from the equatorial pacific reveals a pronounced heartbeat in the global carbon cycle and periodicity of glaciations this heartbeat consists of 405 000 127 000 and 96 000 year eccentricity cycles and 1 2 million year obliquity cycles in periodically recurring glacial and carbon cycle events that climate system response to intricate orbital variations suggests a fundamental interaction of the carbon cycle solar forcing and glacial events box modeling shows that the interaction of the carbon cycle and solar forcing modulates deep ocean acidity as well as the production and burial of global biomass the pronounced 405 000 year eccentricity cycle is amplified by the long residence time of carbon in the oceans

variability of carbonate diagenesis in equatorial pacific sediments deduced from radiogenic and stable sr isotopes the recrystallisation dissolution precipitation of carbonate sediments has been successfully modelled to explain profiles of pore water sr concentration and radiogenic sr isotope composition at different locations of the global ocean however there have been few systematic studies trying to better understand the relative importance of factors influencing the variability of carbonate recrystallisation here we present results from a multi component study of recrystallisation in sediments from the integrated ocean drilling program iodp expedition 320 321 pacific equatorial age transect peat where sediments of similar initial composition have been subjected to different diagenetic histories the peat sites investigated exhibit variable pore water sr concentrations gradients with the largest gradients in the youngest sites radiogenic sr isotopes suggest recrystallisation was relative rapid consistent with modelling of other sediment columns as the 87sr 86sr ratios are indistinguishable within 2 uncertainties from contemporaneous seawater 87sr 86sr ratios bulk carbonate leachates and associated pore waters of site u1336 have lower 87sr 86sr ratios than contemporaneous seawater in sediments older than 20 2 ma most likely resulting from the upward diffusion of sr from older recrystallised carbonates it seems that recrystallisation at site u1336 may still be on going at depths below 102 5 rmcd revised metres composite depth suggesting a late phase of recrystallisation furthermore the lower sr ca ratios of bulk carbonates of site u1336 compared to the other peat sites suggest more extensive diagenetic alteration as less sr is incorporated into secondary calcite compared to the other peat sites u1336 has an inferred greater thermal gradient and a higher carbonate content the enhanced thermal gradient seems to have made these sediments more reactive and enhanced recrystallisation in this study we investigate stable sr isotopes from carbonate rich deep sea sediments for the first time pore water 88 86sr increases with depth from 0 428 to values reaching up to 0 700 at site u1336 documenting an isotope fractionation process during recrystallisation secondary calcite preferentially incorporates the lighter sr isotope 86sr leaving pore waters isotopically heavy the 88 86sr values of the carbonates themselves show more uniform values with no detectable change with depth carbonates have a much higher sr content and total sr inventory than the pore waters meaning pore waters are much more sensitive to fractionation processes than the carbonates the 88 86sr results indicate that pore water stable sr isotopes have the potential to indicate the recrystallisation of carbonate sediments

the transition from temperate phases to stadials in the long upper pleistocene sequence from les echets france abstract from two sections of the long sequence of les echets corresponding to the end of the eemian and to the end of st germain ii interstadial respectively detailed pollen diagrams have been established which provide information about the climatic conditions prevailing during the transitions from very temperate periods to the following cold stadials

minimal influence of recrystallization on middle miocene benthic foraminiferal stable isotope stratigraphy in the eastern equatorial pacific stable carbon and oxygen isotopes 13c and 18o of foraminiferal tests are amongst the most important tools in paleoceanography but the extent to which recrystallization can alter the isotopic composition of the tests is not well known here we compare three middle miocene 16 13 ma benthic foraminiferal stable isotope records from eastern equatorial pacific sites with different diagenetic histories to investigate the effect of recrystallization to test an extreme case we analyzed stable isotope compositions of benthic foraminifera from integrated ocean drilling program site u1336 for which the geochemistry of bulk carbonates and associated pore waters indicates continued diagenetic alteration in sediments 14 7 ma despite this diagenetic overprinting the amplitudes and absolute values of the analyzed u1336 stable isotopes agree well with high resolution records from better preserved sites u1337 and u1338 nearby our results suggest that although benthic foraminiferal tests of all three sites show some degree of textural changes due to recrystallization they have retained their original stable isotope signatures the good agreement of the benthic foraminiferal stable isotope records demonstrates that recrystallization occurred extremely rapidly 100 kyr after deposition this is confirmed by the preservation of orbital cyclicities in u1336 stable isotope data and 18o values being different to inorganic calcite that would precipitate from u1336 pore waters during late recrystallization the close similarity of the benthic foraminiferal stable isotope records between the sites allows the well resolved paleomagnetic results of site u1336 to be transferred to sites u1337 and u1338 improving the global geological timescale

vegetation patterns under climate changes in the eemian and early weichselian in central europe inferred from a palynological sequence from ustkow central poland abstract this paper presents a fresh examination of a pollen profile from ustkow central poland which after preliminary results was thought to span a period between the early eemian mis 5e and the upper pleni weichselian mis 3 the newly obtained results confirmed the age assessment of the bottom series but revealed a much older age for the uppermost part of the profile as far back as the rederstall stadial mis 5b palynological research showed slightly different patterns of vegetation in comparison to other sites located in central europe among them were an early ulmus maximum coinciding with the betula optimum in the early eemian a relatively late optimum of taxus baccata during the decline of the middle eemian and a distinct division of the older part of the late eemian into phases of abies picea and picea pinus forest domination the herning stadial mis 5d falls into a typical bipartition reflected by heathland domination during its older part and the prevalence of juniperus thickets and artemisia poaceae steppe during its younger part which makes this succession similar to those from northern germany the pollen spectra reflecting the brorup interstadial mis 5c distinctly revealed an intra brorup cold oscillation rarely detected in profiles from central europe and a period of larix dominated forests during the latest part of the interstadial extraordinarily high percentages exceeding 15 of the total pollen sum local pollen taxa together with the lithological composition of deposits revealed that there was a water body in the area during the periods of the late saalian early eemian transition middle eemian the decline of the tilia phase the herning stadial mis 5d the early brorup interstadial mis 5c and the rederstall stadial mis 5b between these time intervals a poor and or rich fen and or bog functioned

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

variations in the strontium isotope composition of seawater during the paleocene and early eocene from odp leg 208 walvis ridge we refined the strontium isotope seawater curve for the paleocene and early eocene by analysis of samples recovered from the walvis ridge during ocean drilling project odp leg 208 the highest sr 87 sr 86 values occurred in the earliest paleocene at similar to 65 ma and generally decreased throughout the paleocene reaching minimum values between 53 and 51 ma in the early eocene before beginning to increase again at similar to 50 ma a plausible explanation for the sr 87 sr 86 decrease between 65 and 51 ma is increased rates of hydrothermal activity and or the eruption and weathering of large igneous provinces e g deccan traps and north atlantic strontium isotope variations closely parallel sea level and benthic delta o 18 changes during the late paleocene and early eocene supporting previous studies linking tectonic reorganization and increased volcanism to high sea level high co2 and warm global temperatures

sedimentary evidence of landscape and climate history since the end of mis 3 in the krkonose mountains czech republic abstract a sedimentary core recovered from the cirque basin of labsk d l valley 1039 m a s l in the krkonose mountains reflects the environmental history for approximately the last 30 000 years analyses of magnetic susceptibility carbon content pollen assemblages and macrofossil data in a 15 m thick sediment sequence provide the first continuous record of lateglacial and holocene vegetation history in sudetes region of the czech republic the succession of sedimentary units in the lower part of the core suggests that the cirque was ice free before the onset of the last glaciation at the beginning of marine isotope stage 2 highly variable climate prevailed during this period with cold conditions culminating about 18 cal ka bp cold climates persisted until the lateglacial period evidenced by an identified warming and subsequent cooling event correlated with the younger dryas period sparse treeless vegetation dominated in the catchment area at that time the sequence of interrupted thinly laminated silts reflects the retreat and temporary readvance of a local glacier in the cirque during 12 5 10 8 cal ka bp subsequently the alpine treeline ecotone gradually shifted above the cirque floor palaeoclimatic conditions in the early holocene fluctuated strongly whereas since 5 1 cal ka bp conditions have been more stable pollen based climate reconstructions suggest significant cooling at around 9 8 9 3 7 7 7 5 and 4 0 3 3 cal ka bp spruce forests have dominated the site since 5 0 cal ka bp when the vegetation became similar to the modern one two phases of increased sedimentation were identified within the holocene culminating about 9 2 7 5 cal ka bp and 5 8 5 5 cal ka bp sediment yield was as high as 2 4 mm yr 1 during the period reflecting environmental changes during the atlantic sub boreal transition

low frequency pliocene climate variability in the eastern nordic seas the pliocene 5 3 2 6 ma is often described as a relatively stable climatic period with warm temperatures characterizing high latitudes new suborbital resolved stable isotope records from ocean drilling program hole 642b in the eastern nordic seas document that the pliocene was not a stable period characterized by one climate rather seven distinct climate phases each lasting between 150 000 and 400 000 years are identified and characterized in the time interval 5 1 3 1 ma four of the transitions between the defined climate phases occurred close to an eccentricity minimum and a minimum in amplitude of change for northern hemisphere summer insolation while two occurred around an eccentricity maximum and a maximum in amplitude in insolation change hence a low frequency response of the nordic seas to insolation forcing is indicated in addition paleogeographic and related paleoceanographic changes expansion of the arctic sea ice cover and onset of northern hemisphere glaciation were important factors behind the evolving pliocene low frequency variability in the eastern nordic seas it is likely that the identified climate phases and transitions are important beyond the nordic seas due to their association with changes to both insolation and paleogeography however a strong and variable degree of diagenetic calcite overgrowth is documented for the planktic foraminifera especially influencing the planktic 18o results the absolute values and amplitude of change cannot be taken at face value

a cromerian complex stalagmite from the mendip hills england in order to provide a better chronological constraint on a british middle pleistocene interglacial a large stalagmite boss from the mendip hills was selected for palaeoclimate data using pollen analysis dating analyses by thermal ionisation mass spectrometry tims of uranium thorium ratios and by magnetostratigraphy constrain the age of the sample to 450 780 ka the isotopic consistency of the tims analyses plus the presence of luminescence laminations suggest that the sample has been preserved under closed system conditions pollen assemblages have been recovered from the speleothems despite the fact that the ph of calcite deposition is usually greater than 7 furthermore the evidence presented here indicates that the pollen was probably transported by the speleothem feedwater rather than entering the cave aerially the pollen record contained within the stalagmite is interpreted as early mid interglacial but does not have clear cromerian affinity 1997 john wiley sons ltd

cenozoic deep sea temperatures and global ice volumes from mg ca in benthic foraminiferal calcite a deep sea temperature record for the past 50 million years has been produced from the magnesium calcium ratio mg ca in benthic foraminiferal calcite the record is strikingly similar in form to the corresponding benthic oxygen isotope 18o record and defines an overall cooling of about 12 c in the deep oceans with four main cooling periods used in conjunction with the benthic 18o record the magnesium temperature record indicates that the first major accumulation of antarctic ice occurred rapidly in the earliest oligocene 34 million years ago and was not accompanied by a decrease in deep sea temperatures

orbital forcing and role of the latitudinal insolation temperature gradient orbital forcing of the climate system is clearly shown in the earths record of glacial interglacial cycles but the mechanism underlying this forcing is poorly understood traditional milankovitch theory suggests that these cycles are driven by changes in high latitude summer insolation yet this forcing is dominated by precession and cannot account for the importance of obliquity in the ice age record here we investigate an alternative forcing based on the latitudinal insolation gradient lig which is dominated by both obliquity in summer and precession in winter the insolation gradient acts on the climate system through differential solar heating which creates the earths latitudinal temperature gradient ltg that drives the atmospheric and ocean circulation a new pollen based reconstruction of the ltg during the holocene is used to demonstrate that the ltg may be much more sensitive to changes in the lig than previously thought from this it is shown how lig forcing of the ltg may help explain the propagation of orbital signatures throughout the climate system including the monsoon arctic oscillation and ocean circulation these relationships are validated over the last eemian interglacial which occurred under a different orbital configuration to the holocene we conclude that lig forcing of the ltg explains many criticisms of classic milankovitch theory while being poorly represented in climate models

an analysis of eemian climate in western and central europe on the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the last interglacial eemian climatic history in western and central europe the main tool for this analysis is the climatic indicator species method only selected woody species are used for the quantification of data partial climatic range diagrams are presented for abies alba acer monspessulanum acer tataricum buxus sempervirens tilia tomentosa the problem of time correlation and pollen zonation of the eemian is discussed the climatic analysis itself is based on an improved version of the indicator species method in this version not every site is analysed for its climatic values instead maps and tables on the migrational history of hedera ilex buxus abies and species of acer tilia and abies are the basis for climatic maps showing respectively january and july isotherms for the periods of the corylus zone e4a and the carpinus zone e5 it is concluded that mean january temperatures were as much as 3 c higher at amsterdam the netherlands than at present and mean temperatures in july were 2 c higher however the thermal maximum in winter was later zone e5 than the summer thermal maximum zone e4a winter temperatures changed parallel to rise and fall of global sea level precipitation changes are more difficult to estimate in the first part of the eemian precipitation must have been relatively low but from zone e4b onward it increased to higher values reaching 800 mm and probably substantially more in zones e5 and e6 hence the eemian climate was in its beginning relatively more contintental and later from e4b onward more oceanic however as compared with the holocene the eemian climate was generally speaking more oceanic

uniform geothermal gradient and heat flow in the qiongdongnan and pearl river mouth basins of the south china sea abstract the pearl river mouth basin prmb and qiongdongnan basin qdnb are oil and gas bearing basins in the northern margin of the south china sea scs geothermal survey is an important tool in petroleum exploration a large data set comprised of 199 thermal conductivities 40 radioactive heat productions 543 measured geothermal gradient values and 224 heat flow values has been obtained from the two basins however the measured geothermal gradient data originated from diverse depth range make spatial comparison a challenging task taking into account the variation of conductivity and heat production of rocks we use a uniform geothermal gradient to characterize the geothermal gradient distribution of the prmb and qdnb results show that in the depth interval of 0 5 km the uniform geothermal gradient in the prmb varies from 17 8 c km to 50 2 c km with an average of 32 1 6 0 c km in comparison the qdnb has an average uniform geothermal gradient of 31 9 5 6 c km and a range between 19 7 c km and 39 5 c km heat flows in the prmb and qdnb are 71 3 13 5 mw m 2 and 72 9 14 2 mw m 2 respectively the heat flow and geothermal gradient of the prmb and qdnb tend to increase from the continental shelf to continental slope owing to the lithosphereic crustal thinning in the cenozoic

the middle miocene climatic transition east antarctic ice sheet development deep ocean circulation and global carbon cycling abstract the middle miocene represents a major change in state in cenozoic climatic evolution following the climax of neogene warmth in the late early miocene at 16 ma the early stage of this climatic transition from 16 to 14 8 ma was marked by major short term variations in global climates east antarctic ice sheet eais volume sea level and deep ocean circulation in the later stage from 14 8 to 12 9 ma climatic developments included major growth of the eais and associated antarctic cooling a distinct increase in the meridional temperature gradient large fluctuations in sea level followed by a global sea level fall and important changes in deep water circulation including increased production of southern component water east antarctic ice sheet growth and polar cooling also had large effects on global carbon cycling and on the terrestrial biosphere including aridification of mid latitude continental regions increased stability of the eais after 14 8 ma represents a crucial step in the establishment of late neogene global climate systems what controlled these changes in polar climates and the east antarctic ice sheet deep ocean circulation changes probably played a major role in the evolution and variation in polar climates as they have throughout the cenozoic oxygen and carbon isotopic evidence for warm saline deep water production in the eastern tethyan northern indian ocean indicates that meridional heat transport to the antarctic inhibited cenozoic polar cooling and eais growth during the early middle miocene from 16 to 14 8 ma inferred competition between warm low latitude sources derived from the eastern tethyan northern indian ocean and a cold high latitude source southern component water from 16 to 14 8 ma may have been associated with instability in the antarctic climate and cryosphere reduction of warm saline deep water flow to the southern ocean at 14 8 ma may have decreased meridional heat transport to the antarctic cooling the region and leading to increased production of southern component water these middle miocene climatic and cryospheric changes in the antarctic had profound effects on marine and terrestrial climates as the meridional surface temperature gradient increased boundaries between climatic zones strengthened leading to increased aridification of mid latitude continental regions in australia africa and north and south america enhancing the development of grasslands and stimulating the evolution of grazing mammals

synchronous mid miocene upper and deep oceanic δ13c changes in the east equatorial pacific linked to ocean cooling and ice sheet expansion abstract we present mid miocene 12 0 16 0 ma high resolution 3 8 kyr deep thermocline planktonic foraminiferal 18 o and 13 c records at iodp site u1337 from the eastern equatorial pacific the benthic and planktonic 18 o records of site u1337 have a similar long term cooling trend but display obvious amplitude differences of glacial interglacial cycles after 13 9 ma planktonic 18 o cycles are usually larger than 1 0 nearly 2 times those of the benthic 18 o the post 13 9 ma change is probably caused by intensified upwelling along with ocean cooling but may include upper ocean circulation changes both the benthic and planktonic 13 c records at site u1337 reveal marked 400 kyr carbon isotope cycles during the mmco middle miocene climate optimum with a trend toward lower 13 c from 16 0 ma to 12 0 ma the similarity in response between surface and deep carbon isotopes indicates that the mid miocene carbon excursions in the east equatorial pacific involved the whole ocean basin water column and thus are a global signal box model simulations reveal that the long eccentricity 400 kyr paced carbon inputs from weathering changed the burial ratio of carbonates to organic carbon and helped to produce the significant 400 kyr cycles in oceanic 13 c the increased weathering of carbonate silicate and kerogen rocks are the major factors controlling the long term decrease in oceanic 13 c after 16 0 ma

late pleistocene evolution of the rhine meuse system in the southern north sea basin imprints of climate change sea level oscillation and glacio isostacy high resolution continuous core material geophysical measurements and hundreds of archived core descriptions enabled to identify 13 late pleistocene rhine meuse sedimentary units in the infill of the southern part of the north sea basin the netherlands northwestern europe this sediment record and a large set of optical stimulated luminescence dates 14c dates and biostratigraphical data allowed to establish detailed relationships between climate change sea level oscillation glaciation history and the sedimentary development of the rhine fluvial system during the last glacial cycle marine isotope stages 5e 2 eemian weichselian a well preserved eemian sediment record was encountered as the infill of a late saalian mis6 subglacial basin part of this record reflects groundwater rise controlled fine grained sedimentation as a result of postglacial early eemian sea level rise it shows strong analogy to developments known from the holocene rhine meuse delta outside of the glacial depressions near coastal deposits are only fragmentarily preserved the early glacial rhine sediment record is dominated by organic debris and peat layers marking landscape stability and low fluvial activity part of this record may have been formed under near coastal conditions significant amounts of reworked marine biomarkers in the lag deposits of early pleniglacial mis4 fluvial systems indicate that this period is characterized by extensive reworking of older mis5 near coastal sediments despite the marked early pleniglacial climatic cooling input of new sediment from the drainage basin was relatively low a feature that is related to the presence of regolith protective relic soil complexes in the basin during the early middle pleniglacial a major rhine avulsion indicates the system was in an aggrading mode and that sediment supply into the lower reaches of the rhine had strongly increased this increase in sediment supply coincided with the timing of major climate cooling that occurred from 50 to 45 ka onwards the increase in sediment supply is related to final breakup of the soil complexes in the drainage basin after 24 ka a strong input of coarse grained gravelly sediments was observed which indicates a strong increase in physical weathering processes and periglacial controlled supply of bedload sediment in the catchment a time delay between climate change 30 ka and channel belt aggradation 24 ka is explained as a result of transport path length between source and sink and or effects of higher continental runoff rates after 22 ka the late middle pleniglacial late pleniglacial and lateglacial rhine meuse record testifies for strong influence of glacio isostatic controlled differential upwarping of the study area glacio isostatic controlled forebulge upwarping and lateral valley tilting is shown to have deflected rhine meuse channel belts after 35 ka glacio isostatic upwarping is seen as the main cause for strong incision during the first phase of the late pleniglacial 30 24 ka at later stage glacio isostatic controlled incision was overruled due to high climate controlled sediment input from the catchment and probably initial glacio isostatic subsidence migration of channel belts towards the direction of the former centre of glacio isostatic uplift indicates that glacio isostacy influenced rhine meuse paleogeography until far into the lateglacial 2007 elsevier ltd all rights reserved

last interglacial eemian hydrographic conditions in the southwestern baltic sea based on dinoflagellate cysts from ristinge klint denmark a dinoflagellate cyst record with strong mediterranean lusitanian affinities is described from marine deposits of eemian age last interglacial late pleistocene at ristinge klint denmark revealing new information about the hydrographic evolution of the southwestern baltic sea a revised correlation of the pollen record at ristinge klint with that of the annually laminated site at bispingen in northern germany provides temporal control approximately the first quarter of eemian time is represented a marine ingression into a lake took place during the quercus rise about 300years into the interglacial and is marked by low c 3 psu salinities at the base of the cyprina clay that increased progressively an abrupt and significant rise in the inflow of warm saline waters from the north sea occurred at about 750 years into the interglacial the corylus rise and at about 1900 years into the interglacial strongly stratified waters developed higher in the cyprina clay and continuing to its top at nearly 3000 years into the interglacial more open marine waters are indicated although fully marine conditions were not reached the dinoflagellate record throughout the cyprina clay at ristinge klint is therefore one of increasing marine influence summer sea surface temperatures approached and may have exceeded 26 28 c during early eemian time indicating temperatures at least 5 c warmer than at present these warm conditions persisted to the top of the record at ristinge klint no evidence exists at ristinge klint for the influence of arctic watermasses and the paucity of cold water species throughout the section reflects mild winter temperatures in the southwestern baltic sea the new species spiniferites ristingensis is formally described and the name operculodinium centrocarpum var cezare de vernal goyette rodrigues 1989 is validated

pliocene switch in orbital scale carbon cycle climate dynamics the high frequency periods of 105 years relationship between carbon and oxygen isotopes in benthic foraminifera the two proxies most extensively used to reconstruct past changes in earth s carbon cycle and climate shows two distinct patterns across the cenozoic the first glacial style pattern associates negative excursions in 13c with positive excursions in 18o indicative of relatively cold temperatures and greater ice volume the second hyperthermal style pattern associates negative excursions in 13c with negative excursions in 18o indicative of warming here i assess the coherence and phasing of these high frequency orbital scale cycles in particular the 100 kyr eccentricity period in 13c and 18o from multiple high resolution benthic foraminiferal records spanning the last 65 million years of earth history in order to identify which of these patterns is most persistent across the cenozoic and when the switch between these patterns occurred i find that the glacial style 13c 18o pattern is a feature restricted to the plio pleistocene suggesting a fundamental change in the interplay between the carbon cycle and climate associated with the onset of northern hemisphere glaciation this relative stability of the high frequency relationship between 13c and 18o across most of the cenozoic persists despite significant secular changes in climate and may suggest a dichotomous response of terrestrial carbon cycle dynamics to orbital forcing with a switch occurring in the last 5 myr

fluid flow in deep sea carbonates estimates based on porewater sr abstract fluid flow of up to 200 m myr is documented in thick about 500 m deep sea carbonate sections by numerical modeling of the porewater sr 2 and 87 sr 86 sr profiles at dsdp sites 572 573 and 574 these sites were selected as likely candidates for significant fluid flow in the sedimentary part of the section because it had already been shown that they are underlain by rapidly flowing fresh seawater in the basaltic basement the nature of the exercise is to fit the porewater sr properties at these sites by finding a common rate of sr exchange as a function of sediment age and a local rate of vertical fluid flow the flow rates determined in this way are 20 m myr upwards at site 574 20 m myr downwards at site 573 and 200 m myr downwards at site 572 because of uncertainties of about a factor of 2 in the assumption of a common rate of sr exchange at all sites and trade offs between the sr exchange and fluid flow in determining the shape of sr 2 and 87 sr 86 sr profiles at a given site the precision of the method is of the order of 10 m myr thus at least at site 572 the sr properties of the interstitial waters provide a convincing measure of vertical fluid flow through a thick carbonate section

evidence for last interglacial chronology and environmental change from southern europe establishing phase relationships between earth system components during periods of rapid global change is vital to understanding the underlying processes it requires records of each component with independent and accurate chronologies until now no continental record extending from the present to the penultimate glacial had such a chronology to our knowledge here we present such a record from the annually laminated sediments of lago grande di monticchio southern italy using this record we determine the duration 17 70 0 20 ka and age of onset 127 20 1 60 ka b p of the last interglacial as reflected by terrestrial ecosystems this record also reveals that the transitions at the beginning and end of the interglacial spanned only 100 and 150 years respectively comparison with records of other earth system components reveals complex leads and lags during the penultimate deglaciation phase relationships are similar to those during the most recent deglaciation peaks in antarctic warming and atmospheric methane both leading northern hemisphere terrestrial warming it is notable however that there is no evidence at monticchio of a younger dryas like oscillation during the penultimate deglaciation warming into the first major interstadial event after the last interglacial is characterized by markedly different phase relationships to those of the deglaciations warming at monticchio coinciding with antarctic warming and leading the atmospheric methane increase diachroneity is seen at the end of the interglacial several global proxies indicate progressive cooling after 115 ka b p whereas the main terrestrial response in the mediterranean region is abrupt and occurs at 109 50 1 40 ka b p

in situ δ18o and mg ca analyses of diagenetic and planktic foraminiferal calcite preserved in a deep sea record of the paleocene eocene thermal maximum we report 18o and minor element mg ca sr ca data acquired by high resolution in situ secondary ion mass spectrometry sims from planktic foraminiferal shells and 100 500 m sized diagenetic crystallites recovered from a deep sea record odp site 865 of the paleocene eocene thermal maximum petm the 18o of crystallites 1 2 pee dee belemnite pdb is 4 8 higher than that of planktic foraminiferal calcite 3 6 pdb while crystallite mg ca and sr ca ratios are slightly higher and substantially lower than in planktic foraminiferal calcite respectively the focused stratigraphic distribution of the crystallites signals an association with petm conditions hence we attribute their formation to early diagenesis initially sourced by seafloor dissolution burndown ensued by reprecipitation at higher carbonate saturation the mg ca ratios of the crystallites are an order of magnitude lower than those predicted by inorganic precipitation experiments which may reflect a degree of inheritance from donor phases of biogenic calcite that underwent solution in the sediment column in addition sims 18o and electron microprobe mg ca analyses that were taken within a planktic foraminiferal shell yield parallel increases along traverses that coincide with muricae blades on the chamber wall the parallel 18o and mg ca increases indicate a diagenetic origin for the blades but their 18o value 0 5 pdb is lower than that of crystallites suggesting that these two phases of diagenetic carbonate formed at different times finally we posit that elevated levels of early diagenesis acted in concert with sediment mixing and carbonate dissolution to attenuate the 18o decrease signaling petm warming in whole shell records published for site 865

paleoceanographic changes across the latest danian event in the south atlantic ocean and planktic foraminiferal response abstract a number of short warming events occurred during paleocene and eocene of which the paleocene eocene thermal maximum petm 56 ma is the most severe and most investigated event the less known latest danian event lde at 62 2 ma represents a 200 ky lasting warming phase superimposed on a long term cooling trend after the early paleocene south atlantic odp site 1262 data covering 1 myr indicate a warming of the entire water column by 1 5 2 6 c accompanying a prominent negative carbon isotope excursion 0 9 1 1 and a long term re organization of the planktic foraminiferal fauna associated with the lde this study unravels a different paleoceanographic evolution of the upper ocean structure compared to results from pacific odp site 1210 unlike the pacific the atlantic site lacks an apparent change of stratification as well as an overall dominance of thermocline dwelling planktic foraminifera species and a low abundance of surface dwelling photosymbiotic foraminifera within the lde indications for a slightly enhanced stratification of the upper water column and transient warming were indicated when surface dwelling planktic foraminifera became temporarily more abundant the long term evolution in planktic foraminifera with the disappearance of praemurica at the lde onset and a contemporaneous rise in morozovella is similar to the trends reported from shatsky rise odp site 1210

strontium and its isotopic composition in interstitial waters of marine carbonate sediments abstract the concentrations and isotopic compositions of strontium in interstitial waters from several dsdp sites where sediments consist chiefly of carbonate oozes and chalks are used as indicators of carbonate diagenesis by reference to a recently produced curve showing detailed variations in the87sr 86sr ratio of seawater with time carbonate sediments of the walvis ridge show increases in interstitial sr2 concentrations in the upper carbonate ooze sections with the highest concentrations near the ooze chalk boundary where maximum rates of carbonate recrystallization occur below this in situ production of sr2 diminishes and there is a diffusive flux of sr to an underlying sink presumably volcanogenic sediments or basalts leading to sr isotopic disequilibrium between carbonates and interstitial waters in some other sites however there is no apparent sr sink at depth and isotopic equilibrium is retained overall diffusive smoothing of profiles exerts an important control on the87sr 86sr ratios although lower ratios than contemporaneous seawater values in the carbonate oozes often correlate with zones of mg2 loss and reflect a combination of a flux of sr2 from the zone of maximum recrystallization rates together with a contribution from the in situ alteration of volcanic matter

quantification of climate and vegetation from southern african middle stone age sites an application using late pleistocene plant material from sibudu south africa abstract in southern africa numerous middle stone age msa sites document important steps in technological and behavioural development leading to significant changes in the lifeways of modern humans to assess whether these cultural changes and developments may be related to environmental changes we need to ascertain past environments to do this we apply a new quantitative method the gis based coexistence approach cagis on fossil plant material from the msa site sibudu kwazulu natal south africa previous qualitative environmental interpretations of the fossil fauna and flora of the site remain ambiguous because much of the material is anthropogenically introduced it is difficult to distinguish between the effects of natural changes in the local vegetation and behavioural changes of the people that inhabited the shelter cagis can be applied to such biased assemblages and seems to be an adequate method to directly quantify palaeoclimate and vegetation parameters at an archaeological site the cagis analysis shows that during the howiesons poort hp industry winters were slightly colder and drier than present whereas during summer temperatures and precipitation were similar to today post hp winters were drier and colder than present presumably colder than during the hp summer temperatures remained the same but summer precipitation decreased from the hp to post hp vegetation cover was less than today may be even less than during the hp the late msa was observably warmer than the older periods especially during winter at the same time summer precipitation slightly increased and vegetation became more dense but still remained generally open similar to today s anthropogenic landscape generally climatic changes are most pronouncedly reflected in winter temperature parameters especially in minimum winter temperatures and to a lesser extent by changes in summer precipitation the observed ecological trends seem to be affected mainly by variations through time in winter temperatures this refinement of interpretation was not discernible using previous methods for analysing the sibudu data

an attempt at correlation between the velay pollen sequence and the middle pleistocene stratigraphy from central europe abstract long continuous lacustrine sequences constitute on the continent a precious tool for coupling the long term continental environmental changes with deep sea and ice core records using the count from the top method moreover they can contribute to long distance correlation on the continent itself and thus help to classify discontinuous sedimentary records palynostratigraphical correlation is proposed here between the velay long sequence and the late middle pleistocene series from central europe with special attention to temperate episodes the similarities between the praclaux and the holsteinian interglacial suggest that they are both contemporaneous with marine isotopic stage mis 11 even if absolute dates are still divergent the evidence of two major warm periods with an interglacial type of vegetation between the holsteinian and the eemian is confirmed by the velay record

mid miocene isotope stratigraphy in the deep sea high resolution correlations paleoclimatic cycles and sediment preservation mid miocene pelagic sedimentary sections can be correlated using intermediate and high resolution oxygen and carbon isotopic records of benthic foraminifera precision of a few tens of thousands of years is readily achievable at sites with high sedimentation rates for example deep sea drilling project sites 289 and 574 the mid miocene carbon isotope records are characterized by an interval of high 13c values between 17 and 13 5 ma the monterey excursion of vincent and berger 1985 upon which are superimposed a series of periodic or quasi periodic fluctuations in 13c values these fluctuations have a period of approximately 440 kyr suggestive of the 413 kyr cycle predicted by milankovitch theory vincent and berger proposed that the monterey excursion was the result of increased organic carbon burial in continental margins sediments the increased 13c values called 13c maxima superimposed on the generally high mid miocene signal coincide with increases in 18o values suggesting that periods of cooling and or ice buildup were associated with exceptionally rapid burial of organic carbon and lowered atmospheric co2 levels it is likely that during the monterey excursion the ocean atmosphere system became progressively more sensitive to small changes in insolation ultimately leading to major cooling of deep water and expansion of continental ice we have assigned an absolute chronology based on biostratigraphic and magneto biostratigraphic datum levels to the isotope stratigraphy and have used that chronology to correlate unconformities seismic reflectors carbonate minima and dissolution intervals intervals of sediment containing 13c maxima are usually better preserved than the overlying and underlying sediments indicating that the 13c values of tco2 in deep water and the corrosiveness of seawater are inversely correlated this again suggests that the 13c maxima were associated with rapid burial of organic carbon and reduced levels of atmospheric co2 the absolute chronology we have assigned to the isotopic record indicates that the major mid miocene deepwater cooling ice volume expansion took 2 m y and was not abrupt as had been reported previously the cooling appears abrupt at many sites because the interval is characterized by a number of dissolution intervals the cooling was not monotonic and the 2 m y interval included an episode of especially rapid cooling as well as a brief return to warmer conditions before the final phase of the cooling period the increase in 18o values of benthic foraminifera between 14 9 and 12 9 ma was greatest at deeper water sites and at sites closest to antarctica the data suggest that the 18o value of seawater increased by no more than about 1 1 per mil during this interval and that the remainder of the change in benthic 18o values resulted from cooling in antarctic regions of deepwater formation equatorial planktonic foraminifera from sites 237 and 289 exhibit a series of 0 4 per mil steplike increases in 13c values only one of these increases in planktonic 13c is correlated with any of the features in the mid miocene benthic carbon isotope record

ocean overturning since the late cretaceous inferences from a new benthic foraminiferal isotope compilation 1 benthic foraminiferal oxygen isotopic d 18 o and carbon isotopic d 13 c trends constructed from compilations of data series from multiple ocean sites provide one of the primary means of reconstructing changes in the ocean interior these records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records we present new benthic foraminiferal d 18 o and d 13 c compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to 80ma andtentatively to 110ma first order variations ininterbasinal isotopicgradients delineate transitions from interior ocean heterogeneity during the late cretaceous 65 ma to early paleogene 35 65 ma homogeneity and a return to heterogeneity in the late paleogene early neogene 35 0 ma we propose that these transitions reflect alterations in a first order characteristic of ocean circulation the ability of winds to make water in the deep ocean circulate we document the initiation of large interbasinal d 18 o gradients in the early oligocene and link the variations in interbasinal d 18 o gradients from the middle eocene to oligocene with the increasing influence of wind driven mixing due to the gradual tectonic opening of southern ocean passages and initiation and strengthening of the antarctic circumpolar current the role of wind driven upwelling possibly associated with a tethyan circumequatorial current in controlling late cretaceous interior ocean heterogeneity should be the subject of further research

middle to late miocene stepwise climate cooling evidence from a high resolution deep water isotope curve spanning 8 million years 1 we present high resolution 2 3 kyr benthic foraminiferal stable isotopes in a continuous well preserved sedimentary archive from the west pacific ocean ocean drilling program site 1146 which track climate evolution in unprecedented resolution over the period 12 9 to 8 4 ma we developed an astronomically tuned chronology over this interval and integrated our new records with published isotope data from the same location to reconstruct long term climate and ocean circulation development between 16 4 and 8 4 ma this extended perspective reveals that the long eccentricity 400 kyr cycle is prominently encoded in the 13c signal over most of the record reflecting long term fluctuations in the carbon cycle the 18o signal closely follows variations in short eccentricity 100 kyr and obliquity 41 kyr in particular the obliquity cycle is prominent from 14 6 to 14 1 ma and from 9 8 to 9 2 ma when high amplitude variability in obliquity is congruent with low amplitude variability in short eccentricity the 18o curve is additionally characterized by a series of incremental steps at 14 6 13 9 13 1 10 6 9 9 and 9 0 ma which we attribute to progressive deep water cooling and or glaciation episodes following the end of the miocene climatic optimum on the basis of 18o amplitudes we find that climate variability decreased substantially after 13 ma except for a remarkable warming episode at 10 8 10 7 ma at peak insolation during eccentricity maxima 100 and 400 kyr this transient warming associated with a massive negative carbon isotope shift is reminiscent of intense global warming events at eccentricity maxima during the miocene climatic optimum

interglacial and glacial climate oscillations in a marine shelf sequence from northern denmark a multidisciplinary study abstract a 22 5 m long marine shelf sequence in northern denmark covers the climatic shifts from glacial environments through interglacial and into early glacial conditions the interglacial was interrupted by two cool intervals also the early glacial succession experienced oscillations of the climate and a period with ameliorated temperature conditions has been separated as an interstadial these results are based on a multidisciplinary high resolution study of lithology foraminifera ostracods macrofauna diatoms and stable isotopes in a silty clay sequence from a borehole at norre lyngby 70 5 48 0 m depth the lithostratigraphy and the variations in depositional environment in the area is supported by a reflection seismic profile across the core site the chronostratigraphy is discussed on the basis of biostratigraphical correlation and seismostratigraphy as well as optically stimulated luminescence osl dating and amino acid measurements the biostratigraphy and the osl dates suggest an eemian age for the interglacial while amino acid results point to an older age if the interglacial is confirmed as eemian we believe that the succeeding interstadial period is likely to be correlated with the brorup interstadial the climatic changes in this eastern part of the north sea region are closely linked with changes in the north atlantic circulation pattern and the environmental fluctuations at norre lyngby are therefore believed to reflect fluctuations in the past regional climatic and oceanic system

preservation of benthic foraminifera and reliability of deep sea temperature records importance of sedimentation rates lithology and the need to examine test wall structure preservation of planktic foraminiferal calcite has received widespread attention in recent years but the taphonomy of benthic foraminiferal calcite and its influence on the deep sea palaeotemperature record have gone comparatively unreported numerical modeling indicates that the carbonate recrystallization histories of deep sea sections are dominated by events in their early burial history meaning that the degree of exchange between sediments and pore fluids during the early postburial phase holds the key to determining the palaeotemperature significance of diagenetic alteration of benthic foraminifera postburial sedimentation rate and lithology are likely to be important determinants of the paleoceanographic significance of this sediment pore fluid interaction here we report an investigation of the impact of extreme change in sedimentation rate a prolonged and widespread upper cretaceous hiatus in the north atlantic ocean on the preservation and 18o of benthic foraminifera of middle cretaceous age nannofossil zone nc10 uppermost albian lowermost cenomanian 99 ma ago from multiple drill sites at sites where this hiatus immediately overlies nc10 benthic foraminifera appear to display at least moderate preservation of the whole test however on closer inspection these tests are shown to be extremely poorly preserved internally and yield 18o values substantially higher than those from contemporaneous better preserved benthic foraminifera at sites without an immediately overlying hiatus these high 18o values are interpreted to indicate alteration close to the seafloor in cooler waters during the late cretaceous hiatus intersite differences in lithology modulate the diagenetic impact of this extreme change in sedimentation rate our results highlight the importance of thorough examination of benthic foraminiferal wall structures and lend support to the view that sedimentation rate and lithology are key factors controlling the paleoceanographic significance of diagenetic alteration of biogenic carbonates

eastern equatorial pacific benthic foraminiferal distribution and deep water temperature changes during the early to middle miocene abstract we investigate changes in benthic foraminiferal assemblages and estimate bottom water temperatures bwt based on mg ca ratios of oridorsalis umbonatus over three selected intervals of major climate change during the late early to middle miocene at integrated ocean drilling program iodp sites u1337 4463 m water depth and u1338 4200 m water depth eastern equatorial pacific ocean the targeted intervals are 1 the onset of the miocene climatic optimum mco at 16 9 ma and associated carbon cycle perturbation site u1337 2 the episode of peak warmth within the mco centered at 15 6 ma site u1338 3 the major cooling step at 13 8 ma related to east antarctic ice sheet expansion site u1338 assemblages from these three intervals are mainly composed of cosmopolitan long ranging e g paleogene to recent lower bathyal to abyssal species including calcareous elongated forms that became extinct during the middle pleistocene the onset of the mco and interval of peak warmth had little impact on benthic foraminiferal accumulation rates bfar abundances and assemblage composition a transient bwt warming of 2 6 c at the onset of the interval of peak warmth concurred with a benthic stable oxygen isotope 18 o decrease of 1 suggesting that the 18 o decrease was largely controlled by bwt changes a substantial increase in bfar and in the abundances of epistominella exigua and epifaunal taxa after 13 83 ma coincides with increased opal accumulation rates reflecting enhanced and seasonally pulsed organic carbon c org flux to the seafloor during the global cooling step during this interval bwt decrease by 1 7 c concurrent with a 1 0 increase in the stable oxygen isotope composition of seawater 18 o sw comparable trends at ocean drilling program odp site 1146 in the south china sea with a 2 2 c cooling and 0 9 increase in 18 o sw at 13 8 ma further support that the benthic 18 o increase during the major cooling step was largely controlled by ice volume changes

a chronology for the long pollen record from lake wangoom western victoria australia as derived from uranium thorium disequilibrium dating the chronology of a long pollen record from lake wangoom one of the few long palaeoenvironmental records from southeastern australia is discussed in light of the acquisition of new uranium thorium disequilibrium utd dates of crucial importance has been the estimation of ages for two major pre holocene phases of forest expansion recorded in the sequence with implications for the timing of periods of high effective precipitation in the region the new utd ages indicate that the oldest forest phase falls within the penultimate interglacial whereas the later phase corresponds with the last interglacial this is older than indicated by previously reported utd and radiocarbon dates but confirms a chronology based on direct correlation with the pollen record from marine core e55 6 the new chronology of the lake wangoom sequence provides evidence that phases of sustained forest development in southeast australia relate to interglacial periods in comparison interstadial periods appear to be characterised by only minor arboreal development marked differences in the pattern of vegetation development evident in each of the interglacials are thought to reflect varying climatic and anthropogenic influences copyright 2002 john wiley sons ltd

evolution of palaeolake environment in poland during the eemian interglacial based on oxygen and carbon isotope data from lacustrine carbonates abstract the results of oxygen and carbon stable isotope investigations of eight eemian lacustrine sediments from poland are presented the values of 18o changed from ca 11 to 1 and 13c values oscillated between 3 5 and 7 0 the isotopic record correlated well with pollen cladoceran and diatom data the evolution of the palaeolakes in poland was reconstructed the palaeolakes originated during the final phase of the wartanian late saalian glaciation the 18o and 13c values of that time reflect the input of detrital carbonates into the basins the boundary between the glaciation and the interglacial period is expressed by a significant decrease in 18o and 13c values during the early eemian a positive trend in 18o values confirms the gradual climatic changes the eemian optimum is characterized by constant 18o and 13c values during the early vistulian weichselian glaciation the palaeolake declined the varying 18o values likely reflect frequent changes in water balance between precipitation and evaporation associated with an influence of marine circulation the fluctuations of the isotopic curves in the upper parts of the successions the post optimum were caused by a shallowing of the basin by infilling with sediments the observed shifts in the isotopic curves are due to the proximity of the baltic sea and earlier strong oceanic influences

ca isotopes in carbonate sediment and pore fluid from odp site 807a the ca2 aq calcite equilibrium fractionation factor and calcite recrystallization rates in pleistocene sediments abstract the calcium isotopic compositions 44ca of 30 high purity nannofossil ooze and chalk and 7 pore fluid samples from odp site 807a ontong java plateau are used in conjunction with numerical models to determine the equilibrium calcium isotope fractionation factor s f between calcite and dissolved ca2 and the rates of post depositional recrystallization in deep sea carbonate ooze the value of s f at equilibrium in the marine sedimentary section is 1 0000 0 0001 which is significantly different from the value 0 9987 0 0002 found in laboratory experiments of calcite precipitation and in the formation of biogenic calcite in the surface ocean we hypothesize that this fractionation factor is relevant to calcite precipitation in any system at equilibrium and that this equilibrium fractionation factor has implications for the mechanisms responsible for ca isotope fractionation during calcite precipitation we describe a steady state model that offers a unified framework for explaining ca isotope fractionation across the observed precipitation rate range of 14 orders of magnitude the model attributes ca isotope fractionation to the relative balance between the attachment and detachment fluxes at the calcite crystal surface this model represents our hypothesis for the mechanism responsible for isotope fractionation during calcite precipitation the ca isotope data provide evidence that the bulk rate of calcite recrystallization in freshly deposited carbonate ooze is 30 40 myr and decreases with age to about 2 myr in 2 3 million year old sediment the recrystallization rates determined from ca isotopes for pleistocene sediments are higher than those previously inferred from pore fluid sr concentration and are consistent with rates derived for late pleistocene siliciclastic sediments using uranium isotopes combining our results for the equilibrium fractionation factor and recrystallization rates we evaluate the effect of diagenesis on the ca isotopic composition of marine carbonates at site 807a since calcite precipitation rates in the sedimentary column are many orders of magnitude slower than laboratory experiments and the pore fluids are only slightly oversaturated with respect to calcite the isotopic composition of diagenetic calcite is likely to reflect equilibrium precipitation accordingly diagenesis produces a maximum shift in 44ca of 0 15 for site 807a sediments but will have a larger impact where sedimentation rates are low seawater circulates through the sediment pile or there are prolonged depositional hiatuses

rock magnetic properties of eemian maar lake sediments from massif central france a climatic signature the hypothesis of a climate variability within the last interglacial eemian suggested by oxygen isotope data of a greenland ice core grip was later supported by magnetic susceptibility organic matter and pollen signatures in the eemian lake sediments of the lac du bouchet france in the present paper we analyse in detail the rock magnetic properties of these sediments in order to determine the origin of the magnetic susceptibility variations furthermore in order to verify the empirical relation between magnetic susceptibility and climate we studied two eemian sequences from neighbouring lakes lac st front and ribains maar lake rock magnetic investigations mainly consisted of analyses of anhysteretic and isothermal remanent magnetizations along with hysteresis measurements carried out on pilot samples lac du bouchet susceptibility variations are at least partly affected by postdepositional magnetite dissolution lac st front sediments show a complex behaviour resulting in partly contradicting interpretations of rock magnetic parameters possible explanations may be the presence of a very fine grained magnetite or the presence of maghemite ribains maar lake sediments show a homogeneous magnetic mineralogy without major variations in most of the rock magnetic parameters susceptibility records of the three lakes were compared under the simplified assumption that magnetic susceptibility mainly reflects variations of the detrital titano magnetite input only a poor correlation between the three eemian susceptibility sequences is observed suggesting that local effects including dissolution and dilution effects may have altered the original detrital climatic signal the purely detrital origin of the lac du bouchet eemian susceptibility variations must thus be questioned but it nevertheless appears to be the only lake whose susceptibility variations can tentatively be correlated with the grip eemian oxygen isotope record

high resolution palynological record off the iberian margin direct land sea correlation for the last interglacial complex abstract we present high resolution pollen dinocyst and isotopic data for the last interglacial complex from marine core md952042 southwestern margin of the iberian peninsula 37 48 n 10 10 w 3148 m direct land sea correlation from this core indicates that during this period north atlantic sea surface temperatures were in phase with iberian climate our palynological analysis suggests a younger dryas like event at the marine isotope stage mis 6 5 transition the analysis also indicates that the eemian spans from the lightest isotopic values of mis 5e ca 126 ky bp to the heavier isotopic values towards the mis 5e 5d transition therefore the eemian is not entirely equivalent to mis 5e pollen analysis identifies four climatic phases of low amplitude during the eemian a mediterranean climate in southwestern europe is gradually replaced by oceanic conditions the middle of the eemian is characterized by an increase in precipitation on the land and ocean associated with a slight cooling this seems to be the result of a displacement of the polar front as far south as southern europe during this period after the eemian three relatively short climatic phases on land melisey i st germain ia and montaigu cold event occurred contemporaneously with three shifts of sea surface temperatures the montaigu event first identified in terrestrial pollen sequences is therefore also recorded in core md952042 on the basis of pollen dinocyst and planktonic isotopic data our results also show that the warm periods of mis 5 are not characterized by similar climatic conditions on land

strontium isotope fractionation of planktic foraminifera and inorganic calcite we have investigated the strontium isotope fractionation 88 86srcarb aq between inorganic calcite and aqueous sr2 ions by precipitation experiments at a constant temperature of 25 c and precipitation rates r ranging from 102 3 to 104 2 mol m2 h strontium isotope ratios were measured using the 87sr 84sr double spike technique it was found that strontium isotope fractionation in these calcites is strongly dependent on the precipitation rate view the mathml source the measured 88 86sr values are significantly correlated with previously measured 44 40ca and sr ca values of the same calcite samples 88 86srcarb aq 0 18 44 40cacarb aq 0 01 view the mathml source the slope of 88sr 86sr versus 44ca 40ca fractionation is 0 18 0 04 and compatible with a kinetic fractionation during dehydration of the strontium and calcium ions but not with isotope fractionation in a diffusive boundary layer using published equilibrium 44 40cacarb aq and view the mathml source values we estimate the equilibrium isotope fractionation of strontium to be very close to zero 88 86sreq carb aq 0 01 0 06 this estimate is confirmed by strontium isotope values of natural inorganic calcites that precipitated very slowly in basalts of the ocean crust the results from the inorganic calcites are used to explain strontium isotope fractionation of planktic foraminifera specimens of two warm water species globigerinoides ruber and globigerinoides sacculifer were picked from the holocene section of a caribbean sediment core we found no significant difference in 88 86sr between the two species in addition g ruber specimens from marine isotope stage 2 in the same core show 88 86sr values identical to the holocene specimens the strontium isotopes of both foraminifera species are strongly fractionated 88 86srcarb aq 0 248 0 005 when compared to published data of other major marine calcifiers applying the results from the inorganic precipitation experiments we find that the strong foraminiferal strontium isotope fractionation can be explained by calcification in a largely open system at high precipitation rates comparable in magnitude to rates known from scleractinian reef corals this interpretation is in good agreement with the kinetic calcification model for planktic foraminifera by kisakurek et al 2011 which was based on calcium isotopes and elemental sr ca ratios

reconstructing past sea surface temperatures correcting for diagenesis of bulk marine carbonate abstract a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate is used to obtain information on how sea surface temperatures have varied in the past by correcting measured 18o values of bulk carbonate for diagenetic overprinting comparison of bulk carbonate and planktonic foraminiferal 18o records from odp site 677a indicates that the oxygen isotopic composition of bulk carbonate does reflect changes in sea surface temperature and 18o at odp site 690 we calculate that diagenetic effects are small and that both bulk carbonate and planktonic foraminiferal 18o records accurately reflect paleogene warming of high latitude surface oceans biased from diagenesis by no more than 1 c the same is likely to be true for other high latitude sites where sedimentation rates are low at dsdp sites 516 and 525 the effects of diagenesis are more significant measured 18o values of eocene bulk carbonates are more than 2 lower at deeply buried site 516 than at site 525 consistent with the model prediction that the effects of diagenesis should be proportional to sedimentation rate model corrections reconcile the differences in the data between the two sites the resulting paleotemperature reconstruction indicates a 4 c cooling of mid latitude surface oceans since the eocene at low latitudes the contrast in temperature between the ocean surface and bottom makes the carbonate 180 values particularly sensitive to diagenetic effects most of the observed variations in measured 18o values are accounted for by diagenetic effects rather than by sea surface temperature variations we show that the data are consistent with constant equatorial sea surface temperatures through most of the cenozoic with the possible exception of the early eocene when slightly higher temperatures are indicated we suggest that the lower equatorial sea surface temperatures for the eocene and oligocene reported in other oxygen isotope studies are artifacts of diagenetic recrystallization and that it is impossible to reconstruct accurately equatorial sea surface temperatures without explicitly accounting for diagenetic overprinting

the beginning of the ice age in europe and its major subdivisions abstract the time range of the quaternary is discussed in terms of the view that this period is essentially the one in the earth s history in which during certain intervals inland ice developed in the northern hemisphere this process first became evident about 2 3 ma bp since then the quaternary thus defined has witnessed many climatic variations although for practical reasons it is not feasible to assign the status of stage to each distinclty warm or cold phase climatic change is nevertheless the most appropriate basis for world wide correlation it seems possible to use both climatic change and other correlation parameters to arrive at a practicable subdivision of the quaternary period into stages before about 1 ma vegetational succession during interglacials in western europe differed from that seen in later times a possible cause for this divergence is discussed in the later part of the quaternary after about 1 ma two distinct types of warm temperate intervals occurred one associated with high sea levels and an oceanic climate the other showing lower sea levels and a cooler and more continental climate the difference between these two types is shown by comparison of the distribution of abies during these time intervals

climate response to orbital forcing across the oligocene miocene boundary spectral analyses of an uninterrupted 5 5 million year my long chronology of late oligocene early miocene climate and ocean carbon chemistry from two deep sea cores recovered in the western equatorial atlantic reveal variance concentrated at all milankovitch frequencies exceptional spectral power in climate is recorded at the 406 thousand year ky period eccentricity band over a 3 4 million year period 20 to 23 4 my ago ma as well as in the 125 and 95 ky bands over a 1 3 million year period 21 7 to 23 0 ma of suspected low greenhouse gas levels moreover a major transient glaciation at the epoch boundary approximately 23 ma mi 1 corresponds with a rare orbital congruence involving obliquity and eccentricity the anomaly which consists of low amplitude variance in obliquity a node and a minimum in eccentricity results in an extended period approximately 200 ky of low seasonality orbits favorable to ice sheet expansion on antarctica

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

eemian crustal deformation in the eastern baltic area in the light of the new sites at peski russia and pohja uhtju estonia abstract several eemian mikulino marine deposits are known from the northwestern part of russia and from estonia the best known deposits are situated at mga russia and at prangli estonia two new sites with clayey and silty deposits covered by till were studied for pollen and diatoms at peski russia and pohja uhtju estonia at peski the deposit representing the eemian interglacial is 3 8 m thick at the depth of 13 4 9 6 m above present sea level at pohja uhtju the deposit representing the eemian is 3 5 m thick at the depth of 47 9 51 4 m below present sea level although peski is situated at a higher altitude than pohja uhtju at present the diatom stratigraphy at these sites indicates deeper and more saline conditions in the peski area than at pohja uhtju during the eemian this result is similar to some previous studies which indicate that although the russian deposits e g peski mga are now at a higher altitude than those in estonia pohja uhtju and prangli the diatoms in the russian deposits are indicative of a considerable depth of water during the time of deposition these deposits suggest that the eemian shore levels ascend from estonia eastwards while the late weichselian and holocene shorelines tilt downwards in the same general direction the present material from estonia and northwestern part of russia shows marked differences between the eemian and late weichselian holocene crustal deformations which probably resulted from different ice loads during the final glaciation phases and probably also from different deglaciation patterns during the saalian and late weichselian

eccentricity pacing of eastern equatorial pacific carbonate dissolution cycles during the miocene climatic optimum the miocene climatic optimum mco similar to 16 9 to 14 7ma provides an outstanding opportunity to investigate climate carbon cycle dynamics during a geologically recent interval of global warmth we present benthic stable oxygen o 18 and carbon c 13 isotope records 5 12kyr time resolution spanning the late early to middle miocene interval 18 to 13ma at integrated ocean drilling program iodp site u1335 eastern equatorial pacific ocean the u1335 stable isotope series track the onset and development of the mco as well as the transitional climatic phase culminating with global cooling and expansion of the east antarctic ice sheet at similar to 13 8ma we integrate these new data with published stable isotope geomagnetic polarity and x ray fluorescence xrf scanner derived carbonate records from iodp sites u1335 u1336 u1337 and u1338 on a consistent astronomically tuned timescale benthic isotope and xrf scanner derived caco3 records depict prominent 100kyr variability with 400kyr cyclicity additionally imprinted on c 13 and caco3 records pointing to a tight coupling between the marine carbon cycle and climate variations our intersite comparison further indicates that the lysocline behaved in highly dynamic manner throughout the mco with 75 carbonate loss occurring at paleodepths ranging from similar to 3 4 to similar to 4km in the eastern equatorial pacific ocean carbonate dissolution maxima coincide with warm phases o 18 minima and c 13 decreases implying that climate carbon cycle feedbacks fundamentally differed from the late pleistocene glacial interglacial pattern where dissolution maxima correspond to c 13 maxima and o 18 minima carbonate dissolution cycles during the mco were thus more similar to paleogene hyperthermal patterns

foraminifer test preservation and diagenesis comparison of high latitude eocene sites foraminifer tests are prone to diagenetic recrystallization on a micron scale that can affect their geochemical composition hence it is important to identify fossil material that is well preserved here we illustrate the textures of tests from several high latitude eocene sites using a combination of reflected light microscopy and high resolution scanning electron microscopy the sites are ocean drilling program odp site 647 in the labrador sea 53 n odp site 689 at maud rise in the weddell sea 64 s odp site 1135 kerguelen plateau c 59 s and outcrop samples from hampden beach new zealand palaeolatitude c 55 s the foraminifera studied from site 647 and hampden beach have glassy transparent tests that show only minor signs of diagenetic alteration whereas the foraminifera from sites 690 and 1135 are opaque and recrystallized we associate the better state of foraminifer preservation at the former sites with the high clay content of the sediments our observations suggest that site 647 and hampden beach may be useful for the establishment of high latitude sea surface temperatures and hence global temperature gradients in the eocene

impacts of orbital forcing and atmospheric carbon dioxide on miocene ice sheet expansion the processes causing the middle miocene global cooling which marked the earth s final transition into an icehouse climate about 13 9 million years ago myr ago 1 4 remain enigmatic tectonically driven circulation changes 5 6 and variations in atmospheric carbon dioxide levels 7 8 have been suggested as driving mechanisms but the lack of adequately preserved sedimentary successions has made rigorous testing of these hypotheses difficult here we present high resolution climate proxy records covering the period from 14 7 to 12 7 million years ago from two complete sediment cores from the northwest and southeast subtropical pacific ocean using new chronologies through the correlation to the latest orbital model 9 we find relatively constant low summer insolation over antarctica coincident with declining atmospheric carbon dioxide levels at the time of antarctic ice sheet expansion and global cooling suggesting a causal link we surmise that the thermal isolation of antarctica played a role in providing sustained long term climatic boundary conditions propitious for ice sheet formation our data document that antarctic glaciation was rapid taking place within two obliquity cycles and coincided with a striking transition from obliquity to eccentricity as the drivers of climatic change

middle miocene ice sheet dynamics deep sea temperatures and carbon cycling a southern ocean perspective 1 relative contributions of ice volume and temperature change to the global 1 18o increase at 14 ma are required for understanding feedbacks involved in this major cenozoic climate transition a 3 ma benthic foraminifer mg ca record of southern ocean temperatures across the middle miocene climate transition reveals 2 2 c cooling 14 2 13 8 ma indicating that 70 of the increase relates to ice growth seawater 18o calculated from mg ca and 18o suggests that at 15 ma antarctica s cryosphere entered an interval of apparent eccentricity paced expansion glaciations increased in intensity revealing a central role for internal climate feedbacks comparison of ice volume and ocean temperature records with inferred pco2 levels indicates that middle miocene cryosphere expansion commenced during an interval of southern ocean warmth and low atmospheric pco2 the antarctic system appears sensitive to changes in heat moisture supply when atmospheric pco2 was low suggesting the importance of internal feedbacks in this climate transition

cenozoic benthic foraminiferal mg ca and li ca records toward unlocking temperatures and saturation states the sensitivities of benthic foraminiferal mg ca and li ca to bottom water temperature and carbonate saturation state have recently been assessed here we present a new approach that uses paired mg ca and li ca records to calculate simultaneous changes in temperature and saturation state using previously published records we first use this approach to document a cooling of deep ocean waters associated with the establishment of the antarctic ice sheet at the eocene oligocene climate transition we then apply this approach to new records of the middle miocene climate transition from odp site 761 to estimate variations in bottom water temperature and the oxygen isotopic composition of seawater we estimate that the oxygen isotopic composition of seawater varied by 1 between the deglacial extreme of the miocene climatic optimum and the glacial maximum following the middle miocene climate transition indicating large amplitude variations in ice volume however the longer term change between 15 3 and 12 5 ma is marked by a 1 c cooling of deep waters and an increase in the oxygen isotopic composition of seawater of 0 6 we find that bottom water saturation state increased in the lead up to the middle miocene climate transition and decreased shortly after this supports decreasing pco2 as a driver for global cooling and ice sheet expansion in agreement with existing boron isotope and leaf stomatal index co2 records but in contrast to the published alkenone co2 records

global perturbation of the carbon cycle at the onset of the miocene climatic optimum the miocene climatic optimum mco ca 17 14 7 ma represents one of several major interruptions in the long term cooling trend of the past 50 m y to date the processes driving high amplitude climate variability and sustaining global warmth during this remarkable interval remain highly enigmatic we present high resolution benthic foraminiferal and bulk carbonate stable isotope records in an exceptional continuous carbonate rich sedimentary archive integrated ocean drilling program site u1337 eastern equatorial pacific ocean which offer a new view of climate evolution over the onset of the mco a sharp decline in delta o 18 and delta c 13 at ca 16 9 ma contemporaneous with a massive increase in carbonate dissolution demonstrates that abrupt warming was coupled to an intense perturbation of the carbon cycle the rapid recovery in delta c 13 at ca 16 7 ma similar to 250 k y after the beginning of the mco marks the onset of the first carbon isotope maximum within the long lasting monterey excursion these results lend support to the notion that atmospheric pco 2 variations drove profound changes in the global carbon reservoir through the mco implying a delicate balance between changing co2 fluxes rates of silicate weathering and global carbon sequestration comparison with a high resolution delta c 13 record spanning the onset of the cretaceous oceanic anoxic event 1a similar to 120 m y ago reveals common forcing factors and climatic responses providing a long term perspective to understand climate carbon cycle feedbacks during warmer periods of earth s climate with markedly different atmospheric co2 concentrations

late quaternary climatic change in france estimated from multivariate pollen time series abstract in regions like southern france where usual analytical techniques are unsatisfactory due to the heavy influence of human activity and the existence of a complex climate the quantitative reconstruction of climate from pollen is particularly difficult that is why an original method has been performed the first step of the method based on best analogs estimation and multiple regression is to calculate a relationship between climate monthly temperature and precipitation and modern pollen spectra for data from 182 sites the result is called the analog climate the second step of the method an original combination of canonical correlation and principal components analyses extracts the common information from several fossil pollen sequences to produce a so called paleobioclimate this step removes the effects of local differences in the vegetation among nearby sites and also reduces the effects of human disturbance in the third step the signals obtained from the first two steps are merged by kalman filter into a final reconstruction where the noise is reduced by around 37 the results presented with a 95 confidence level suggest that the pleni wurm was 7 to 13 c colder than present and had 20 to 60 less precipitation than today this large confidence takes into account the climatic diversity of the region at 13 000 yr b p the climate reached the modern level of precipitation but the temperature was just less than present the subsequent decrease of precipitation is less important than that of temperature this fact may explain the advance of alpine glaciers during the younger dryas preboreal warming was abrupt 3 to 4 c per 500 yr and precipitation increased more slowly

obliquity and long eccentricity pacing of the middle miocene climate transition 1 the middle miocene east antarctic ice sheet expansion eaie which is indicated by an abrupt 1 increase in global benthic foraminiferal 18o at 13 8 ma marks the middle miocene climate transition mmct and has been related to astronomically modulated changes in the global carbon cycle here we present high resolution 3 4 kyr benthic foraminiferal 18o and 13c records from iodp site u1337 in the central equatorial pacific which spans the period 12 2 15 8 ma the isotopic records clearly demonstrate significant imprints from periodic variations in the earth s orbital parameters particularly the obliquity 40 kyr and the long eccentricity 400 kyr cycles while the benthic 18o and 13c exhibit nearly identical amplitudes for glacial interglacial cycles from 15 8 to 12 2 ma the long term trends in the benthic 18o and 13c had started to reverse after the beginning of the eaie within the 400 kyr band the benthic 18o and 13c displays a constant phase relationship between 15 8 and 12 2 ma at the 41 kyr band however a phase reversal reaching 180 between 18o and 13c occurs from 13 8 ma to 14 0 ma during the period of the eaie a similar phase relationship of benthic foraminiferal 18o and 13c at the 400 kyr band and the 41 kyr band is also observed at odp site 1146 from the northern south china sea this phase jump occurs when the long term trends in 18o and 13c split suggesting a decoupling of the global ice volume and ocean carbon reservoir changes during the middle miocene

eemian sea level highstand in the eastern baltic sea linked to long duration white sea connection abstract revised diatom and new dinoflagellate cyst and benthic foraminiferal data from the eastern baltic sea have refined our understanding of eemian last interglacial 131 119 5 ka sea level change on the russian karelia a former seaway linking the baltic to the white sea results from peski eastern baltic show the initiation of marine conditions just before 131 ka in the latest saalian after the opening of a connection to the north sea following the onset of the eemian marine highstand and the opening of the white sea connection at around 130 25 ka near fully marine conditions persisted in the eastern baltic area for ca 6 kyr until ca 124 ka for most of the eemian a strong thermal stratification in the eastern baltic resulted from an arctic and possible north atlantic water component from the white sea merging with warmer waters from the north sea from ca 124 ka decreasing salinity indicates the end of the marine highstand and a simultaneous closure of the baltic sea white sea connection i e a duration of ca 6 kyr for this seaway the main influence of white sea inflow appears to be restricted to the eastern baltic area although a large submerged area in the russian karelia associated with temperate atlantic waters could have assisted in creating a more oceanic climate for central europe

eemian and vistulian weichselian development of the meltout depression on the watershed between the mroga and mrozyca rivers central poland based on lithological and pollen analysis the lithological and palaeobotanical research conducted in a closed drainage depression located in the watershed zone between the mroga and mrozyca rivers central poland allowed for the reconstruction of its palaeogeography in the period subsequent to the retreat of the last ice sheet wartanian stage of the odranian glaciation the purpose of this article is to gather and synthesise the obtained results as well as to reconstruct the processes of development and filling in the studied depression over the last 135 000 years the post glacial evolution of the relief was recorded in the mineral and biogenic sediments deposited on glacial formations the modern closed drainage depression is a trace of a fossil extensive glacial meltout depression the post glacial development of the land relief within the depression involved three stages dominated by different types of morphogenesis i e the deglaciation stage during the wartanian stage of the odranian glaciation the eemian interglacial early vistulian aggradation stage and the vistulian aggradation denudation stage high thickness of the identified biogenic sediments suggests considerable transformations of the relief of the watershed during the two cycles of temperate climate the eemian interglacial and the holocene the thickness of the mineral sediments suggest low dynamics of the environment during the last glacial maximum lgm and undermine the hypotheses on the determining effect of periglacial conditions on the character of the relief of central poland the obtained results constitute an inspiration and starting point for another research project concerning the reconstruction of the watersheds in central poland

differential response at the seafloor during palaeocene and eocene ocean warming events at walvis ridge atlantic ocean odp site 1262

unlocking the ice house oligocene miocene oxygen isotopes eustasy and margin erosion oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental ice sheets on antarctica since the earliest oligocene circa 35 ma the growth and decay of ice sheets during the oligocene to modern ice house world caused glacioeustatic sea level changes the early eocene was an ice free greenhouse world but it is not clear if ice sheets existed during the middle to late eocene doubt house world benthic foraminiferal 18o records place limits on the history of glaciation suggesting the presence of ice sheets at least intermittently since the earliest oligocene the best indicator of ice growth is a coeval increase in global benthic and western equatorial planktonic 18o records although planktonic isotope records from the western equatorial regions are limited subtropical planktonic foraminifera may also record such ice volume changes it is difficult to apply these established principles to the cenozoic 18o record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events we improved oligocene to miocene correlations of 18o records and erected eight oxygen isotope zones oi1 oi2 mi1 mi6 benthic foraminiferal 18o increases which are associated with the bases of zones oil circa 35 8 ma oi2 circa 32 5 ma and mil circa 23 5 ma can be linked with 18o increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near antarctica our new correlations of middle miocene benthic and western equatorial planktonic 18o records show remarkable agreement in timing and amplitude we interpret benthic planktonic covariance to reflect substantial ice volume increases near the bases of zones mi2 circa 16 1 ma mi3 circa 13 6 ma and possibly mi5 circa 11 3 ma possible glacioeustatic lowerings are associated with the 18o increases which culminated with the bases of zone mi4 circa 12 6 ma and mi6 circa 9 6 ma although low latitude planktonic 18o records are required to test this these inferred glacioeustatic lowerings can be linked to seismic and rock disconformities for example we link 12 oligocene early late miocene inferred glacioeustatic lowerings with 12 of the sequence boundaries inferred eustatic lowerings of haq et al 1987

core top evaluation of benthic foraminiferal isotopic ratios for paleo oceanographic interpretations abstract the benthic foraminifera cibicides wuellerstrofi oridforsalis tener and pyrgo rotalaria from twelve core tops in the norwegian greenland sea and c wuellerstorfi o tener and o umbonatus from four core tops on the rio grande rise were analysed for oxygen and carbon isotopes the norwegian greenland sea data yield statistically discrete means for both 18o and 13c for each species the interregional comparison of our data to published data from the east pacific rise shows that c wuellerstorfi 18o and 13c variations reflect oceanographic differences between sites whereas the data on oridorsalis and pyrgo do not we conclude that c wuellerstorfi is a reliable sensor of bottom water conditions whereas other taxa are of unproven utility supportive biological studies and the lack of positive covariance of 18o to 13c among deep sea benthic taxa lead us to reject models calling for incorporation of metabolic co2 to explain the isotopic variation among deep sea benthic foraminifera we propose a within sediment microhabitat hypothesis to explain the 13c variations among taxa

the δ13c in benthic foraminiferal tests of fontbotia wuellerstorfi schwager relative to the δ13c of dissolved inorganic carbon in southern ocean deep water implications for glacial ocean circulation models on a transect between 20 and 70 s in the eastern atlantic ocean and weddell sea water samples from 19 hydrographic stations and bottom water from 55 surface sediment samples taken with a multiple corer were investigated for the stable carbon isotopic composition of the total dissolved inorganic carbon 13c co2 these measurements were compared to 13c values determined on live specimens of the benthic foraminifer fontbotia wuellerstorfi and closely related genera from the same stations in addition at 16 stations the stable carbon isotope composition of sedimentary organic carbon was measured general deepwater and bottom water mass circulation patterns as inferred from the 13c co2 are in close agreement with those known from other nonconservative tracers very low 13c values of upper circumpolar deep water 0 3 pee dee belemnite pdb in the polar front region and the eastern limb of the weddell gyre coincide with nutrient maxima however a significant decoupling of the dissolved phosphate signal from the 13c co2 signal is indicated in the abyssal weddell sea we attribute this to temperature dependent fractionation processes during gas exchange of surface waters with the atmosphere at sites of bottom water formation multiple corer water from the sediment water interface is slightly 13c depleted relative to deepwater and bottom water 13 co2 the surface sediment organic carbon 13c is 3 to 4 lower south of the polar front than north of it and the 13corg in freshly accumulated phytodetritus is 3 to 4 lower than surface sediment organic carbon 13c comparison of live f wuellerstorfi 13c and related genera with bottom water 13c co2 exhibits at most stations between the subtropical front 41 s and the southern boundary of the antarctic circumpolar current 55 s a significant lowering of foraminiferal 13c values compilation of a mean last glacial interglacial 13c amplitude 13c from six published southern ocean cores results in a shift of 0 99 0 13 pdb this shift is greater than that in all other regions however all of these cores are from positions close to recent oceanic fronts thus for these peripheral areas of the southern ocean we suggest about half of the glacial interglacial shift can be explained by varying frontal zone positions and widths accompanied by a change in mode and height of export production

sr isotopes in interstitial waters of marine sediments from deep sea drilling project cores sr isotopic compositions of interstitial sea waters have been documented in detail with cores from 37 deep sea drilling project sites the 87sr 86sr ratios are sensitive indicators of diagenetic reactions involving alteration of volcanic matter dispersed in sediments and recrystallization of carbonates effects of basalt alteration reactions except possibly for hydrothermal signals and of alteration of continental debris are minimal carbonate recrystallization has a significant effect on the geochemical mass balance of sr but diffusion of unradiogenic strontium from interstitial waters has only a small effect on the 87sr 86sr ratio of ocean water

orbitally paced climate evolution during the middle miocene monterey carbon isotope excursion one of the most enigmatic features of cenozoic long term climate evolution is the long lasting positive carbon isotope excursion or monterey excursion which started during a period of global warmth after 16 9 ma and ended at similar to 13 5 ma approximately 400 kyr after major expansion of the antarctic ice sheet we present high resolution 1 9 kyr astronomically tuned climate proxy records in two complete sedimentary successions from the northwestern and southeastern pacific odp sites 1146 and 1237 which shed new light on the middle miocene carbon isotope excursion and associated climatic transition over the interval 17 1 12 7 ma we recog nize three distinct climate phases with different imprints of orbital variations into the climatic signals 1146 and 123 7 delta 18 o delta 13 c 1237 xrt fe fraction 63 pm 1 climate optimum prior to 14 7 ma characterized by minimum ice volume and prominent 100 and 400 kyr variability 2 long term cooling from 14 7 to 13 9 ma principally driven by obliquity and culminating with rapid cryosphere expansion and global cooling at the onset of the last and most pronounced delta 13 c increase 3 icehouse mode after 13 9 ma with distinct 100 kyr variability and improved ventilation of the deep pacific the monterey carbon isotope excursion 16 9 13 5 ma consists overall of nine 400 kyr cycles which show high coherence with the long eccentricity period superposed on these low frequency oscillations are high frequency variations 100 kyr which closely track the amplitude modulation of the short eccentricity period in contrast to delta 13 c the delta 18 o signal additionally shows significant power in the 41 kyr band and the 1 2 myr amplitude modulation of the obliquity cycle is clearly imprinted in the 1146 delta 18 o signal our results suggest that eccentricity was a prime pacemaker of middle miocene climate evolution through the modulation of long term carbon budgets and that obliquity paced changes in high latitude seasonality favored the transition into the icehouse climate c 2007 elsevier b v all rights reserved

a paleogene calcareous microfossil konservat lagerstatte from the kilwa group of coastal tanzania microfossil assemblages and their shell geochemistry are widely used in paleocean ography but they can be significantly altered by subtle variations in preservation state clay rich hemipelagic sediments of the paleogene kilwa group of coastal tanzania host calcareous microfossils that are exceptionally preserved as evidenced by morphological taxonomic and geochemical data the planktonic foraminifera are preserved as glassy translucent tests with original microgranular wall textures that resemble well preserved modern specimens and they arguably yield geochemical values that are relatively unaffected by recrystallization the calcareous nannofossils are extraordinarily diverse and represented by unique assemblage compositions that include dissolution susceptible taxa especially holo coccoliths and rhabdoliths and fragile and very small 3 mu m heterococcoliths many of which are new taxa notably the extant deep photic zone taxon gladiolithus is documented for the first time in the pre quaternary fossil record the kilwa group calcareous nannofossil diversities are consistently higher than all coeval assemblages and provide a benchmark against which to compare other paleogene biodiversity data highest diversities are preserved in hemipelagic clay rich lithologies and the greatest losses occur in lithified carbonate rich sediments most of the lost diversity however is confined to distinct taxonomic groups holococcoliths and syracosphaerales and in general the preservational potential of paleogene coccolithophores was greater than in the modern oceans because a larger proportion of the biodiversity fell within the larger size fractions for both foraminifera and coccolithophores incorporation into impermeable clay rich sediments that have never been deeply buried appears to have been critical in producing this konservat lagerstatte preservation

middle miocene climate cooling linked to intensification of eastern equatorial pacific upwelling during the middle miocene earth s climate transitioned from a relatively warm phase miocene climatic optimum to a colder mode with reestablishment of permanent ice sheets on antarctica thus marking a fundamental step in cenozoic cooling carbon sequestration and atmospheric co2 drawdown through increased terrestrial and or marine productivity have been proposed as the main drivers of this fundamental transition we integrate high resolution 1 3 k y benthic stable isotope data with x ray fluorescence scanner derived biogenic silica and carbonate accumulation estimates in an exceptionally well preserved sedimentary archive recovered at integrated ocean drilling program site u1338 to reconstruct eastern equatorial pacific productivity variations and to investigate temporal links between high and low latitude climate change over the interval 16 13 ma our records show that the climatic optimum 16 8 14 7 ma was characterized by high amplitude climate variations marked by intense perturbations of the carbon cycle episodes of peak warmth at southern hemisphere insolation maxima coincided with transient shoaling of the carbonate compensation depth and enhanced carbonate dissolution in the deep ocean a switch to obliquity paced climate variability after 14 7 ma concurred with a general improvement in carbonate preservation and the onset of step wise global cooling culminating with extensive ice growth over antarctica ca 13 8 ma we find that two massive increases in opal accumulation ca 14 0 and ca 13 8 ma occurred just before and during the final and most prominent cooling step supporting the hypothesis that enhanced siliceous productivity in the eastern equatorial pacific contributed to co2 drawdown

simulation of long eccentricity 400 kyr cycle in ocean carbon reservoir during miocene climate optimum weathering and nutrient response to orbital change 1 deep sea foraminiferal 13c records contain abundant 400 kyr cycles indicating a link between eccentricity forcing and ocean carbon reservoir change here we simulate the oceanic 13c maxima events forced by the earth s orbital geometry during the miocene climate optimum mco 17 14 ma using a box model the simulated results of both surface and deep water 13c display co varying 400 kyr cycle modulated by orbital parameters weathering induced carbon input will change the burial ratio of carbonates to organic carbon and further result in periodic changes in the oceanic 13c the increase of riverine nutrient input which is synchronous with riverine carbon input often stimulates primary productivity and burial of organic carbon our results support that eccentricity maxima minima enhance reduce weathering intensity and nutrient supply which lead to minima maxima of 13c the prominent 400 kyr cycle of ocean carbon reservoir is interpreted as likely caused by a long memory of carbon in the ocean

an explanation of the effect of seawater carbonate concentration on foraminiferal oxygen isotopes abstract stable oxygen isotope ratios of foraminiferal calcite are widely used in paleoceanography to provide a chronology of temperature changes during ocean history it was recently demonstrated that the stable oxygen isotope ratios in planktonic foraminifera are affected by changes of the seawater chemistry carbonate system the 18 o of the foraminiferal calcite decreases with increasing co 3 2 concentration or p h this paper provides a simple explanation for seawater chemistry dependent stable oxygen isotope variations in the planktonic foraminifera orbulina universa which is derived from oxygen isotope partitioning during inorganic precipitation the oxygen isotope fractionation between water and the dissolved carbonate species s h 2 co 3 hco 3 co 3 2 decreases with increasing p h provided that calcium carbonate is formed from a mixture of the carbonate species in proportion to their relative contribution to s the oxygen isotopic composition of caco 3 also decreases with increasing p h the slope of shell 18 o vs co 3 2 of orbulina universa observed in culture experiments is 0 0022 mol kg 1 1 spero et al 1997 whereas the slope derived from inorganic precipitation is 0 0024 mol kg 1 the theory also provides an explanation of the nonequilibrium fractionation effects in synthetic carbonates described by kim and o neil 1997 which can be understood in terms of equilibrium fractionation at different p h the results presented here emphasize that the oxygen isotope fractionation between calcium carbonate and water does not only depend on the temperature but also on the p h of the solution from which it is formed

vegetation and climate during warmer intervals in the late pleistocene of western and central europe abstract many warmer intervals occurred during the last interglacial glacial cycle 130 10 ka in europe the vegetational record shows several types of such intervals among which the forest periods of the eemian interglacial and the amersfoort brorup interstadials of the early weichselian are of special interest a series of map reconstructions is used to present some of the relevant vegetational and paleoclimatic characterizations they represent two types of temperate intervals occurring in the late pleistocene in europe one with a rather uniform distribution of vegetation types a warmer oceanic climate and a high sea level the other type shows strong vegetation gradients both north south and east west a more continental climate and a relatively low sea level inland ice probably persisted in the far north during this last type of interval it is suggested that these two types of interglacial occurred throughout the pleistocene

quantitative reconstruction of climate variability during the eemian merkinė and weichselian nemunas in lithuania abstract little is known concerning climate changes in the eastern baltic region during the last interglacial glacial cycle and in particular climate changes during the weichselian in this study a quantitative reconstruction of the mean january and july temperature for the medininkai 117 site in lithuania is presented the reconstruction is based on pollen and plant macrofossils from this site which reveal that the vegetation was characteristic of many northern europe sites during the eemian and early weichselian gradual evolution of the vegetation suggests that relatively uniform climate conditions existed during the eemian our reconstructions support the view of a relatively stable eemian with short cooling phases of low amplitude a strong increase in temperature was apparent during the beginning of the interglacial and decrease during the transition to the weichselian reconstructed july temperatures of the eemian interglacial were approximately 2 c higher than today 18 5 c today 16 2 c and were similar to today for january 5 2 c today 5 1 c july temperatures during the early weichselian were only 2 c lower than during the eemian whereas the january temperatures gradually decreased winter temperatures were relatively high above 10 c during the early weichselian

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