precipitation driven decadal scale decline and recovery of wetlands of lake pannon during the tortonian high resolution pollen and dinoflagellate analyses were performed on a continuous 98 cm long core from tortonian deposits of lake pannon in the styrian basin in austria the sample distance of 1 cm corresponds to a resolution of roughly one decade allowing insights into environmental and climatic changes over a millennium of late miocene time shifts in lake level surface water productivity on a decadal to centennial scale can be explained by variations of rainfall during the tortonian climatic optimum related to negative fine scale shifts of mean annual precipitation shoreline vegetation belts reacted in an immediate replacement of poaceae by cyperaceae as dominant grasses in the marshes fringing the lake in contrast to such near synchronous ecosystem responses to precipitation a delayed lake level rise of 4 6 decades is evident in the hydrological budget of lake pannon this transgression caused by a precipitation increase up to 1200 mm yr resulted in a complete dieback of marshes simultaneously open water dinoflagellates such as impagidinium took over in the brackish lagoon and fresh water dinoflagellates disappeared as soon as the rainfall switched back to moderate levels of 1100 1200 mm yr the rise of the lake level slowed down the marsh plants could keep up again and the former vegetation belts became re established thus mean annual precipitation more than temperature was the main driving force for high frequency fluctuations in the tortonian wetlands and surface water conditions of lake pannon such high resolution studies focusing on tortonian decadal to centennial climate change will be crucial to test climate models which try to compare the tortonian models with predictions for future climate change

quantifying the eocene to pleistocene topographic evolution of the soutwestern alps france and italy we evaluate the topographic evolution of the southwestern alps using eocene to pleistocene pollen data combined with existing sedimentological petrographic and detrital geo and thermochronological data we report 32 new pollen analyses from 10 sites completed by an existing dataset of 83 samples from 14 localities situated across the southwestern alps including both the pro and the retro foreland basins the presence of microthermic tree pollen mainly abies picea indicates that this part of the mountain belt attained elevations over 1900 m as early as the oligocene inferred rapid surface uplift during the mid oligocene coincided with a previously documented brief phase of rapid erosional exhumation when maximum erosion rates may have reached values of up to 1 5 2km myr slower long term average exhumation rates of 0 3km myr since the late oligocene helped maintaining the high alpine topography of the southwestern alps until today the relative abundances of meso microthermic tree pollen cathaya cedrusand tsuga and microthermic tree pollen abies picea in the pro and retro foreland basin deposits indicate that the present day asymmetric topography with a relatively gentle western flank and steeper eastern flank was established early in the southwestern alps at least since

isotopic paleoecology of mammals and the middle miocene cooling event in the madrid basin spain abstract the middle miocene underwent profound climatic perturbations detected in worldwide marine and continental records the miocene climatic optimum 17 to 14 ma a warm and humid period was followed by the middle miocene cooling 14 13 8 ma characterized by a sharp drop in temperatures and an increase in aridity triggered by the reestablishment of the eastern antarctica ice sheet the madrid basin located in the central iberian peninsula has furnished a considerable number of miocene fossil sites with a very complete succession of localities from the lower middle miocene to the upper middle miocene middle and upper aragonian mn5 and mn6 local zones db to g mammalian fossil tooth enamel of different taxa including rhinoceros equids gomphothere suids and ruminants from 16 fossil sites spanning from 15 9 ma to 13 2 ma were analyzed for 13c 18oco3 and 18opo4 values with the aim of determining regional paleoecological paleoenvironmental and paleoclimatic changes across this important climate transition the 13c values vary between 11 9 and 6 4 vpdb indicating a c3 environment ranging from woodlands to more open conditions the rhinoceros alicornops simorrense and hoploaceratherium tetradactylum the gomphothere gomphotherium angustidens the cervid heteroprox moralesi and the paleomerycid triceromeryx pachecoi may be regarded as browsers inhabiting more closed environments whereas the equid anchitherium the rhinoceros hispanotherium matritense and the bovid tethytragus langai show a mixed feeding diet related to more open conditions furthermore the variation in 13c values across the fossil sites and local zones indicates drier conditions in local zones db and dc 15 9 14 8 ma a more humid period in local zone dd 14 8 14 1 ma before a return to a drier environment in local zones e f and g 14 1 13 2 ma the 18oco3 and 18opo4 values and calculated 18ow values all track a declining trend from local zones db to dd 15 9 14 1 ma with minimum values in local zone e 18oco3 26 5 2 1 18opo4 18 4 2 4 and 18ow 5 3 2 9 the minimum in 18o values in local zone e 14 1 13 7 ma appears to coincide with a drop in temperature at the time of the middle miocene cooling 14 13 8 ma after this minimum 18oco3 18opo4 and 18ow values recover in local zones f and g 13 7 13 2 ma the calculation of 13cleaf values allowed us to determine plausible biomes that might have existed in the madrid basin during the middle miocene i e a tropical rain forest a tropical deciduous forest a temperate evergreen forest and a xeric woodland scrubland although this method was not able to detect more savanna like environments finally 13cdiet meq values were used to infer mean annual precipitation with values ranging from 250 mm yr local zone dc to 670 mm yr local zone dd which are in accordance with the proposed biomes suggested by the 13cleaf values and fossil mammal assemblages

formation of tectonic peperites from alkaline magmas intruded into wet sediments in the beiya area western yunnan china tertiary 3 78 ma to 3 65 ma biotite k feldspar porphyritic bodies intrude tertiary poorly consolidated lacustrine sedimentary rocks in the beiya mineral district in southwestern china the intrusives are characterized by a microcrystalline and vitreous cryptocrystalline groundmass by replacement of some tabular k feldspar phenocrysts with microcrystalline chlorite and calcite and by fe rich rings surrounding biotite phenocrysts peculiar structures such as contemporary contact faults and slickensides ductile shear zones and flow folds foliation and lineations tension fractures and banded and boudin peperites are developed along the contact zones of the intrusives these features are related to the forceful intrusion of the alkaline magmas into the wet tertiary sediments the partially consolidated magmas were deformed and flattened by continued forceful magma intrusion that produced boudinaged and banded peperites these peperites characterized by containing oriented deformation fabrics are classified as tectonic peperites as a new type of peperite and formation of these tectonic peperites was related to fracturing of magmas caused by forceful intrusion and shear deformation and to contemporary migration and injection of fluidized sediments along fractures that dismembered the porphyritic magma emplacement of the magma into the wet sediments in the beiya area is interpreted to be related to a large pressure difference rather than to the buoyancy force

global vegetation dynamics and latitudinal temperature gradients during the mid to late miocene 15 97 5 33 ma a 617 site palaeobotanical dataset for the mid to late miocene is presented this dataset is internally consistent and provides a comprehensive overview of vegetational change from 15 97 to 5 33 ma the palaeobotanical dataset has been translated into the biome4 classification scheme to enable direct comparison with climate model outputs the vegetation change throughout the langhian seravallian tortonian and messinian is discussed the data shows that the langhian which includes the end of the mid miocene climatic optimum represents a world significantly warmer than today the high northern latitudes were characterised by cool temperate forests the mid latitudes by warm temperate mixed forests the tropics by tropical evergreen broadleaf forests and antarctica by tundra shrub vegetation cool temperate mixed forest existed during the seravallian in the high northern latitudes a reduction in warm temperate mixed forests in the mid latitudes and a loss of tundra on antarctica was noted tortonian vegetation distribution indicates that further cooling had occurred since the seravallian the major changes in vegetation include the first evidence for cold taiga forest in the high northern latitudes and a further reduction of warm temperate mixed forests by the messinian this cooling trend had eliminated warm temperate mixed forests from the western usa and australia and had formed mid latitude deserts despite the cooling trend throughout the mid to late miocene the vegetation distribution of all four reconstructed stages reflect the vegetation of a world warmer than the pre industrial conditions the latitudinal distribution of bioclimatic zones suggests that the latitudinal temperature gradient for the langhian would have been significantly shallower than at present and has gradually but asymmetrically become more modern towards the end of the miocene first the southern hemisphere distribution of bioclimatic zones became more modern probably due to the climatic effects of a fully glaciated antarctica the northern hemisphere bioclimatic zone gradient continued to be shallower than modern throughout the miocene and slowly became more modern by the messinian

climatic comparison of miocene pollen floras from northern east china and south central alaska usa abstract the shanwang area of shandong china lat 36 5 n and the nenana coal field southern central alaska lat 63 9 n have very different vegetation and climate types today however during the late early to early middle miocene pollen floras of the two areas were rather similar though they represent different subregions of deciduous forest vegetation more than half the genera and families of the two floras are held in common and some trees with modern asian affinities appear in both fossil floras pollen and leaf data imply that during the first half of the miocene the fossil floras of south central alaska were closely related to those in northeastern asia a summer wet climate existed at both fossil locations the shanwang flora records a mean annual temperature mat about like that of the present about 13 c but winters were warmer probably above zero in contrast we estimate that the alaskan suntrana flora records a mat of 7 9 c about 10 12 c warmer than now winters average probably higher than 5 to 11 c were considerably warmer and summers average probably 16 18 c were somewhat warmer the difference in mat between sites 27 in latitude apart suggests a latitudinal temperature gradient of about or less than 0 3 c per degree latitude by comparison the average latitudinal temperature gradient for the northern hemisphere between latitude 35 and 65 is about 0 7 c at least twice as steep as that for the early to middle miocene interval at these sites the comparatively low temperature gradient is a quantitative estimate of warmth in the north polar region in the early neogene

palaeoenvironment palaeoclimate and age of the brassington formation miocene of derbyshire uk the brassington formation is the most extensive miocene sedimentary succession onshore in the uk because of its unique position at the margin of nw europe the pollen from this lithostratigraphical unit provides evidence on the development of vegetation affected by north atlantic currents and hypothesized atmospheric circulation changes during the middle to late miocene climate cooling palynostratigraphy suggests that the uppermost kenslow member of the brassington formation is not coeval previously all occurrences of the kenslow member were assumed to be contemporary the oldest pollen assemblage is from the more southern bees nest pit which represents a subtropical conifer dominated forest of late serravallian age c 12 ma a younger assemblage was observed from the more northern kenslow top pit this indicates that a subtropical mixed forest was present during the early tortonian 11 6 9 ma the shift from a conifer dominated to a mixed forest was related to precipitation although the total precipitation did not change between the two assemblages the younger assemblage had more uniform rainfall throughout the year the diachronous nature of the kenslow member means that the depositional model of the brassington formation needs revising and this will have implications for neogene to recent uplift of the southern pennines supplementary material all valid formally defined palynomorph taxa below the generic level that are mentioned in this paper with full author citations are available at http www geolsoc org uk sup18889

integrated stratigraphy of the early miocene lacustrine deposits of pag island sw croatia palaeovegetation and environmental changes in the dinaride lake system article i nfo an integrated stratigraphic study of a neogene lacustrine succession on the pag island croatia combining quantitative pollen analysis magnetostratigraphy cyclostratigraphy biostratigraphy and gamma ray measurements provides new insights into orbitally controlled variations in palaeo vegetation and depositional patterns in the dinaride lake system the quantitative palynological record shows a cyclical pattern of vegetation changes that closely corresponds to sedimentological patterns the intervals with a high abundance of thermophilous and xeric indicators suggesting a warm and dry climate generally coincide with intervals of frequent lignite deposition and shallow lake facies this suggests that both records are dominantly controlled by variations in past climatic conditions and lake level our data show two large scale warming and shallowing upward cycles which are interpreted to be forced by the 100 kyr eccentricity cycle of the earth s orbit magnetostratigraphic data of the examined section reveal a long 113 m reversed polarity interval followed by a 7 m thick interval of normal polarity at the top the inferred depositional rate of 0 3 mm yr combined with biostratigraphic constraints by mollusks suggests that the most logical correlation of the reversed interval is to chron c5cr this indicates that the pag succession was deposited between 17 1 and 16 7 ma and that it corresponds to the burdigalian stage of the early miocene and the regional karpatian stage of the central paratethys the high relative percentage of thermophilous pollen taxa engelhardia and taxodium type being the most prominent generally indicates a subtropical humid climate for the sw croatian part of the dinaride lake system the observed warming trend is possibly related to the onset of the miocene climatic optimum

biogeographic provincialism in rodent faunas from the iberoccitanian region southwestern europe generates severe diachrony within the mammalian neogene mn biochronologic scale during the late miocene abstract in order to develop paleoecological studies involving many fossil sites there is a need to establish a consistent time framework which enables us to arrange the fossil associations according to a sequence of biotic events and subsequently to test a relationship with paleoenvironmental changes the nature of the continental fossil record has given rise to much controversy with regard to the establishment of general biostratigraphical scales additionally biochronological scales are sometimes all that can be proposed the primary goal of the present paper is to present a time arrangement for the iberoccitanian micromammalian fossil sites from the latest middle miocene to the mio pliocene boundary spanning around 7 million years approximately 12 61 4 95 ma herein we study over one hundred faunal lists of rodents from the iberoccitanian region compiled from the literature previous research has described two biogeographical provinces in our study area a northern one valles penedes and southeast france and a southern one all the iberian basins except the valles penedes we therefore conducted alroy s maximum likelihood appearance event ordination ml aeo methodology applying it to the database compiled for each province finally using available numerical dates for a quarter of the sites we obtained a calibrated ordination for all localities in each analysis the results obtained are roughly coherent with the mammalian neogene units mn and allow estimation of the numerical ages for the entire set of fossil sites included in the study nevertheless our results show severe diachrony between the two biogeographic provinces of the iberoccitanian region in relation to the mn boundaries which might be linked to the existence of a refuge area associated with more humid environments in the northern province

miocene pollen record of kc 1 core in the qaidam basin ne tibetan plateau and implications for evolution of the east asian monsoon abstract thick cenozoic deposits in the qaidam basin provide great potential for understanding the tectonic history paleoclimatic changes and evolution of the east asian monsoon this study examines the pollen record from the kc 1 core for the interval covering the later early to late miocene 18 5 ma thermophilic taxa percentages are high between 18 and 14 ma and decrease after this time a pattern which fits well with the middle miocene climatic optimum mmco between 18 and 14 ma and global climatic cooling after 14 ma during the same period xerophytic taxa percentages gradually increase and those of the conifers gradually decrease suggesting an aridification process in the qaidam region driven by the gradual strengthening of the east asian winter monsoon eawm and weakening of the east asian summer monsoon easm the global climate cooling process appears to have driven the climatic development of the qaidam basin region throughout the miocene but the uplift of the tibetan plateau also contributed

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

middle miocene climate and vegetation models and their validation with proxy data abstract the miocene is a relatively recent epoch of the earth s history with warmer climate than today particularly during the middle miocene climatic optimum mmco approximately 17 15 ma although the cause of the warming is probably not only attributable to co2 but also to changes in orography and configuration of ocean gateways this time interval represents an ideal case study to test the ability of climate models to simulate warm climates comparable to those that the earth may experience in the near future however even with higher than present day co2 concentrations the mmco warming inferred from terrestrial proxy data has been difficult to reproduce in climate models since fossil flora do not provide direct information on climate but on flora and vegetation climate model results are generally compared to climate reconstructions obtained from the fossil flora in this study we apply an alternative method by simulating palaeovegetation from the outputs of the climate model using a dynamic vegetation model model vegetation reconstruction can then be compared to the vegetation cover indicated by the fossil flora record at the various localities provided that a common classification of plant functional types pfts is used for the data and the model here we reconstruct the vegetation of the middle miocene with the global dynamic vegetation model caraib using the climatologies derived from five atmospheric general circulation models the reliability of the simulations is examined on a presence absence basis of pfts by comparison of vegetation reconstructions to palaeoflora data recorded in the northern hemisphere and the tropics this comparison provides an overall agreement around 60 between model and data when all sites and tree types are considered three model simulations out of five show to be better at predicting the absence than the presence the presence of warm temperate mixed forests in the middle latitudes dominated by broadleaved deciduous warm temperate and subtropical trees is generally well reproduced in caraib simulations however poor agreement is obtained for the presence of tropical pfts out of the tropics and for warm pfts at latitudes northward of 50 n where climate models remain too cold to produce assemblages of trees consistent with the data nevertheless the model data comparison performed here highlights several mismatches that could result not only from missing feedbacks in the climate simulations but also from the data the results of the likelihood analysis on presence absence of pfts illustrate the uncertainties in the pft classification of the neogene floral records the coexistence of some pfts in the palaeovegetation data is impossible to reproduce in the vegetation model simulations because of the climatic definition of the modern pfts this result indicates either a bias in the identification of modern analogues for fossil plant taxa or a possible evolution of environmental requirements of certain plants

vegetation and climate changes during the late pliocene and early pleistocene in sw anatolia turkey abstract pollen analysis was done on lacustrine sedimentary sequences dated by micromammals as late pliocene early pleistocene that outcrop in two neogene graben basins from sw turkey this study shows vegetation changes from steppe like to more forested environments very similar to the cyclic oscillations related to late pleistocene glacial interglacial climate changes artemisia was abundant during cold arid periods indicating that this species was already widespread in this area during the latest pliocene and the beginning of the pleistocene a review of pollen records from anatolia agrees with this study suggesting that the spreading of this arid species occurred during a major climatic change the beginning of the first glaciations and probably a change in seasonality towards summer aridity artemisia temporarily disappeared from the region during warm wet periods and thus we suggest that glacial interglacial type oscillations already occurred in the area during the late pliocene early pleistocene

migration history of air breathing fishes reveals neogene atmospheric circulation patterns the migration history of an air breathing fish group channidae snakehead fishes is used for reconstructing neogene eurasian precipitation and atmospheric circulation patterns the study shows that snakeheads are sensitive indicators of summer precipitation maxima in subtropical and temperate regions and are present regularly if the wettest month exceeds 150 mm precipitation and 20 8c mean temperature the analysis of 515 fossil freshwater fish deposits of the past 50 m y from africa and eurasia shows two continental scale migration events from the snakeheads center of origin in the south himalayan region events that can be related to changes in the northern hemisphere circulation pattern the first migration ca 17 5 ma into western and central eurasia may have been caused by a northward shift of the intertropical convergence zone that brought western eurasia under the influence of trade winds that produced a zonal and meridional precipitation gradient in europe during the second migration between 8 and 4 ma into africa and east asia snakeheads reached their present day distribution this migration could have been related to the intensification of the asian monsoon that brought summer precipitation to their migratory pathways in east africa arabia and east asia

high resolution palynological analysis in late early middle miocene core from the pannonian basin hungary climatic changes astronomical forcing and eustatic fluctuations in the central paratethys high resolution palynological analysis in the karpatian sarmatian late early middle miocene interval of the borehole tengelic 2 hungary reveals the existence of a forest organized in altitudinal belts developed in a subtropical warm temperate humid climate reflecting the so called miocene climatic optimum pollen changes from the late early miocene to the middle miocene are related to climatic variations values of mean annual temperature ta between 18 and 20 8c and mean annual precipitation pa between 1200 and 1400 mm have been estimated bclimatic amplitude methodq for the badenian decreasing during late badenian and sarmatian ta and pa about 16 8c and 1100 mm have been interpreted as a climatic cooling correlated with the bmonterey cooling eventq and related to the development of the east antarctic ice sheet eais alternation in pollen taxa thermophilous vs altitudinal elements reflects the astronomical forcing on temperature and precipitation and then on vegetation where obliquity and eccentricity cycles dominated eustatic changes determine pinus and pinaceae and dinocyst variations

palynological evidence for miocene climate change in the forecarpathian basin central paratethys nw bulgaria abstract we reconstruct quantitatively the middle to upper miocene climate evolution in the southern forecarpathian basin central paratethys area northwest bulgaria by applying the coexistence approach to 101 well dated palynofloras isolated from three cores the climatic evolution is compared with changes in vegetation and palaeogeography the middle miocene was a period of a subtropical warm temperate humid climate with mean annual temperature mat between 16 and 18 c and mean annual precipitation map between 1100 and 1300 mm thereby during the entire middle miocene a trend of slightly decreasing temperatures is observed and only small climate fluctuations occur which are presumably related to palaeogeographic reorganisations the vegetation shows a corresponding trend with a decrease in abundance of palaeotropic and thermophilous elements the upper miocene is characterised by more diverse climatic conditions probably depending on palaeogeographic and global climatic transformations the beginning of this period is marked by a slight cooling and a significant drying of the climate with mat 13 3 17 c and map 652 759 mm after that fluctuations of all palaeoclimate parameters occur displaying cycles of humid dryer and warmer cooler conditions which are again well reflected in the vegetation our study provides a first quantitative model of the middle upper miocene palaeoclimate evolution in southeastern europe and is characterised by a relatively high precision and resolution with respect to the climate data and stratigraphy

the use of pollen floras as a tool to estimate palaeoaltitude of mountains the eastern pyrenees in the late neogene a case study northern hemisphere vegetation is generally zoned as a consequence of latitudinal and altitudinal gradients temperature reconstruction from three successive pollen floral assemblages of tortonian messinian and zanclean age from the eastern pyrenees has been used to estimate the altitudinal evolution of the uplifted cerdanya basin and its surrounding massifs a new method has been developed for the uplifted basins which completes that already applied to pollen floras from coastal marine deposits close to mountains in contrast to previous hypotheses it seems that the eastern pyrenees occurred at a lower altitude in the late miocene before continuous uplift began 10 ma ago the rate of this uplift ranged between 0 06 and 0 12 mm yr

tertiary palaeogeography and tectonostratigraphic evolution of the northern and southern peri tethys platforms and the intermediate domains of the african eurasian convergent plate boundary zone abstract the increasing effects of african eurasian convergence during the tertiary resulted in the uplift and emergence of the northern and southern peri tethys platforms palaeogeographic maps covering six selected time slices including the middle eocene late early oligocene late early miocene early middle miocene early late miocene and middle to late pliocene illustrate that environmental and depositional differentiations on the northern platform and along the bordering domains of the convergence zone were more pronounced than on the southern platform and its adjacent areas the tectonic evolution of the northern platform included an overall eastward directed trend in the onset of basin uplift and emergence which started at about the eocene oligocene transition at 34 ma tectonostratigraphic analyses indicate a striking contemporaneity of the events which defined the temporal and spatial development of both the domains of the convergent plate boundary zone and the bordering platforms five episodes of major regional change in palaeogeographic and tectonic setting are distinguished they occurred in the late eocene 37 34 ma early late oligocene 30 27 ma latest early to earliest middle miocene 17 15 ma early late miocene 9 8 ma and late early to early middle pliocene 4 3 ma these episodes encompassed changes which were most probably induced by geodynamic events primarily related to the relative motions of the african arabian and eurasian plates in turn the plate motions are assumed to have triggered discrete steps in the regional kinematics and geodynamics that governed the palaeogeographic evolution of the peri tethys platforms and the intermediate domains of the african eurasian plate boundary zone

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

seawater paleotemperature and paleosalinity evolution in neritic environments of the mediterranean margin insights from isotope analysis of bivalve shells the first step of ice sheet build up on antarctica at the eocene oligocene boundary was followed by a phase of climate instability culminating during the miocene with a warming event called the middle miocene climate optimum mmco that ended with a marked cooling phase identified as the middle miocene climate transition mmct while numerous benthic foraminifera 18o and mg ca data have been used to capture the global climate evolution during this interval of climate and ice sheet instability geochemical records from shallow water carbonates still remain scarce yet such records are crucial to capture the diversity of regional environmental responses to global climate changes and thus to better understand the behavior of our climate system during this critical interval in this work we test the potential of a multi proxy approach 18o clumped isotope 47 strontium isotopes 87sr 86sr applied to bivalves recovered from the liguro provencal basin and rhodano provencal basin northwestern of the mediterranean sea to reconstruct the evolution of shallow seawater temperature and salinity in this region over the latest oligocene to middle miocene interval 10 myrs our results highlight a local cooling in the northwestern mediterranean sea during the mmco that contrasts with the warming observed in other regions with seawater temperatures inferred from 47 analyses in the 13 18 c range these cool seawater temperatures recorded in the studied region during the mmco are much cooler than those recorded in the open oceans but are in agreement with the proliferation of bryozoan observed in the castillon du gard area during this interval low bivalve 18o values 3 24 in average are recorded during this episode are interpreted to reflect enhanced freshwater inputs lowering local salinity and seawater 18o such enhanced freshwater inputs point to a phase of enhanced hydrological cycle in the studied region possibly linked to the global mid miocene warming event bivalve 87sr 86sr data mostly fall within the global seawater sr isotope reference curve but remain compatible with enhanced freshwater inputs during the aquitanian and during the langhian as these inputs were probably not important enough to induce a large departure from the seawater curve at a regional scale

palaeoenvironments of the late miocene pruedo basin implications for the uplift of the central pyrenees the nature structure and extent of a palaeo basin sedimentary infill exposed in the aran valley central pyrenees was studied by combining stratigraphical and biostratigraphical analyses and an audio magnetotelluric survey the basin developed on top of a pre existing peneplain and was formed by the north maladeta fault activity the fluvio palustrine sequence filling the basin was at least 100 m thick specimens of the taxon hippuris cf parvicarpa nikitin were identified for the first time in a european palaeoflora the palynological and carpological analyses allowed us to 1 constrain the age of the basin infill as vallesian 11 1 8 7 ma 2 characterize the vegetation of the belt surrounding the basin as a mainly temperate to warm temperate assemblage and 3 estimate the palaeoaltitude of the site at between 700 and 1000 m which leads to an altitude change of 900 1200 m for the north maladeta fault downthrown block and 1640 1640 m for the upthrown block these data allowed us to estimate the regional uplift of the area at between 0 08 and 0 19 mm a 1 the different exhumation values obtained by other researchers for sites located at both sides of the north maladeta fault are in agreement with its activity as a normal fault since the late miocene supplementary materials details of the data acquisition processing and modelling for the porera profile are available at www geolsoc org uk sup18551

benchmark data of a changing sea palaeogeography palaeobiogeography and events in the central paratethys during the miocene abstract the reconstruction and interpretation of terrestrial ecosystems and vegetational patterns in the central european miocene have to take into account the influence of a vast landlocked water body namely the paratethys sea as a northern appendage of the early mediterranean sea it spanned a north south gradient of at least 4 latitude and has been suggested to represent some kind of palaeothermometer which reflected slight expansions or restrictions of climatic belts due to its vulnerable marine connections it was also highly susceptible to major global sea level fluctuations which are reflected in phases of endemism hence a fairly continuous record of marine nearshore assemblages throughout the miocene reflects an extraordinary interplay of sea level fluctuations changes in climate immigrations and blooms in autochthonous elements whilst biostratigraphic implications of these patterns were recognised early in palaeontology a biogeographic model is still lacking the intermingling of palaeogeographic terms with those restricted to biogeography is still commonly used a situation which can be overcome by integrating data from different biota into a new palaeobiogeographic scheme herein a data set of 1809 species level taxa gastropoda and foraminifera serves as the base for interpretations gastropods in particular turned out to be of greatest value for the differentiation of palaeobiogeographic units due to sensitive reactions to all environmental parameters and occupying a wide range of ecological niches based on the excellent gastropod record the proto danubian province early danubian p danubian p balatonian p and a proto caspian subprovince are defined the biogeographic reorganisations are associated with five major biotic events within the gastropod faunas these big five comprise four extinctions the late ottnangian extinction event loee the mid badenian extinction event mbee the badenian sarmatian extinction event bsee the sarmatian pannonian extinction event spee and one exceptional immigration origination event termed the early badenian build up event ebbe foraminifera are less valuable for palaeobiogeographic purposes in the area and time slice studied endemisms are generally lower and turn over rates less dramatic they are however very useful for stratigraphic correlations with the mediterranean and atlantic areas this fairly well calibrated marine biostratigraphy of the central paratethys serves as stratigraphic backbone and control for continental stratigraphy

halimeda dominance in the coastal wedge of pietra di finale ligurian alps italy the role of trophic conditions the middle to late miocene mixed carbonate siliciclastic coastal wedge of the pietra di finale unconformably overlying the ligurian alps succession displays a carbonate portion dominated by halimeda and porites fragments that fall in the photozoan assemblages photozoan assemblages typically develop under tropical and oligotrophic conditions while hetorozoan assemblages tend to thrive in high nutrient settings the pietra di finale formation shows however that high weathering and an increase of nutrient inputs related to alpine uplift and humid climatic conditions promoted halimeda over the seagrass carbonate factory in the photic zone the successful halimeda proliferation was due to its efficient competition for nutrients especially nitrogen thus the pietra di finale formation represents an interesting counter intuitive example in which increased nutrient concentrations promoted instead of inhibited a photozoan over a seagrass related heterozoan carbonate production

late miocene and early pliocene environments in the southwestern black sea region from high resolution palynology of dsdp site 380a leg 42b a high resolution palynological study has been performed on late miocene messinian and early pliocene zanclean sediments cored at dsdp site 380a leg 42b a late miocene coastal vegetation has been identified in association with a delta environment the pliocene is characterised by competition between the two most important vegetation components namely humid thermophilous forests and dry steppes with changes driven by large amplitude climatic variations these variations are linked to other european reference pollen records and to the global temperature evolution for the early pliocene and result in climatostratigraphic relationships at large geographic scale an orbital tuning is proposed with respect to new data clarifying time control on the section the black sea appears to have dried up in response to the messinian salinity crisis in the mediterranean with which it might have been connected during periods of high sea level

how much did climate force the messinian salinity crisis quantified climatic conditions from pollen records in the mediterranean region the latest miocene 5 96 to 5 33 ma is characterised by an outstanding event the desiccation of the mediterranean sea messinian salinity crisis it has been suggested that this was caused by a tectonic event with no climatic change playing a role in desiccation quantifying the climate of the region during this period will help support or refute this hypothesis an effective method for reconstructing the climate from neogene pollen data is the climatic amplitude method based on the modern climatic requirements of plants to interpret fossil data it has been conceived especially for periods devoid of modern vegetation analogue twenty messinian to lower zanclean pollen sequences are now available in the peri mediterranean region most of them do not cover the whole messinian interval particularly those along the mediterranean shorelines where sedimentation was interrupted during the sea s desiccation in contrast sedimentation was almost continuous in such areas as the atlantic side of morocco along the adriatic coast including the po valley and to a lesser extent the black sea the mediterranean sites nonetheless provide a reliable if not a discontinuous record of vegetation variability in time and space a first examination of the pollen diagrams reveals a high regional variability controlled by local conditions and throughout the interval a southward increase in herb pollen frequency in contrast to the tree pollen frequency this indicates that open and probably dry environments existed in the southern mediterranean region prior to during and after the salinity crisis trees developed in areas close to mountains such as in the po valley in cerdanya and in the black sea region most variations observed in the pollen diagrams are constrained by fluctuations of pinus pollen amounts indicating eustatic variations climatic quantification from pollen data does not show obvious climatic changes due to the desiccation of the mediterranean sea especially in the dry and warm southwestern mediterranean area sicily southern spain and north africa at maccarone along the adriatic sea a decrease in temperatures of the coldest month and less importantly a decrease in mean annual temperatures corresponding to a drastic vegetation change are reconstructed these temperature variations are assumed to be controlled by regional environmental changes massive arrival of waters in this basin rather than to reflect cooling because some authors link the second phase of evaporite deposition to a period of global warming some migrations of plants probably occurred as a response to mediterranean desiccation but the climatic contrast which has probably existed at that time between the central mediterranean and the peripheral areas might be amplified climatic reconstruction from pollen data in the western mediterranean area shows that climate is not the direct cause of the mediterranean desiccation as the mediterranean region had experienced continuously high evaporation long before the crisis therefore the main factor leading to this event seems to be the successive closures of the betic and rifian corridors isolating the mediterranean sea from the atlantic ocean

the neogene of eurasia spatial gradients and temporal trends the second synthesis of neclime article i nfo this volume represents the second synthesis of the international open research network neclime neogene climate evolution in eurasia that was established in 2000 to study climate change in eurasia during the neogene and its impact on ecosystems the main objectives of neclime research are 1 proxy data based quantitative reconstructions of neogene climate in eurasia by means of standardised techniques 2 the modelling of atmospheric and oceanic circulation and of biomes using neogene boundary conditions and 3 the analysis of the interaction between palaeogeography vegetation and climate presently 94 scientists from 34 countries are neclime members contributing with their published data to a collective data base integrating proxies from various sources such as palaeobotany vertebrate palaeontology and geology the following core topics are addressed in the volume precipitation patterns and landscape opening the asian monsoon systems the potential of past climates for the evaluation of future climate change scenarios as well as short term change and variability of climate highlights of the single contributions are summarised in a proxy data section and in a modelling section respectively it is shown that the integrative approach presented in this volume brings about a much better and much more detailed understanding of neogene climate dynamics in eurasia than previously achieved even though neogene climate changes may have regional aspects differing considerably from each other and from the general global trend the results from the various proxy and modelling studies consistently show that later neogene cooling implicated more pronounced latitudinal and longitudinal gradients on the other hand the issue reveals a number of problems and questions resulting from the contrary nature of palaeozoological and palaeobotanical palaeoclimate proxies and modelling results mainly at a more regional level the models can not yet explain the relatively warm high latitudes during the neogene and we still do not sufficiently understand the role of the various boundary conditions such as co2 palaeogeography and palaeovegetation in the observed neogene climate change and its regional differentiation these apparent uncertainties underline the importance of the study of palaeo scenarios in order to enhance the reliability of future climate projections

a method for climatic reconstruction of the mediterranean pliocene using pollen data pollen data from numerous sites around the mediterranean sea indicate that several important vegetation and climatic changes occurred during the pliocene these data are in good agreement with pollen records from northwest europe and with 18o curves from mediterranean and atlantic deep sea cores quantitative palaeoclimatic reconstructions from pliocene pollen data of the mediterranean region cannot be based on conventional modern analogue techniques as individual pliocene pollen spectra contain taxa representing temperate warm temperate and subtropical plants that do not grow together today instead we propose a new method that uses a climatic amplitude method modified to take partially into account the relative abundances of the taxa we applied this method to the pliocene garraf 1 palynological sequence from catalonia which provides a long continuous record of climatic change from 5 3 ma to the early pleistocene we estimate that annual temperatures were 1 to 5 c higher than today and the annual precipitation 400 to 1000 mm higher than today prior to the beginning of the late cenozoic glacial interglacial cycles in contrast temperature and precipitation both fell sharply during the glacial phases of the earliest glacial interglacial cycles

palynomorphs from a lacustrine sequence provide evidence for palaeoenvironmental changes during the early miocene in central anatolia turkey pollen samples belonging to 54 plant taxa from 32 intervals in a 59 m thick lacustrine sequence in the harami open pit lignite mine in konya province turkey were studied to evaluate early miocene aquitanian changes in vegetation climate and environments in central anatolia the regional vegetation consisted of forests whose composition changed through time an abundance of sub tropical and warm temperate mainly deciduous trees in the lower part of harami section indicates a warm and humid climate in the region during the earliest miocene a trend towards cooler and drier conditions driven by a combination of regional and local factors is reflected by the sequential establishment of two kinds of coniferous forests a cedar cedrus dominated forest in the middle part of the section followed by a mixed cedar and pine pinus forest in the upper part of the section the high percentages of cedrus in the middle and upper portions of the harami section suggest that high elevation coniferous forests

multiproxy reconstruction of the palaeoclimate and palaeoenvironment of the middle miocene somosaguas site madrid spain using herbivore dental enamel profound palaeoclimatic changes took place during the middle miocene the miocene climatic optimum 20 to 14 13 5 ma was followed by a sudden 200 ka decrease in temperature and an increase in aridity around the world as a consequence of the reestablishment of the ice cap in antarctica somosaguas palaeontological site madrid basin spain has provided a rich record of mammal remains coincident with this global event middle miocene biozone e 14 1 13 8 ma it contains four fossiliferous levels t1 t3 1 t3 2 and t3 3 with t1 being the oldest that span an estimated time of 105 125 ka scanning electron microscope sem and rare earth element ree analyses performed on herbivore tooth enamel gomphotherium angustidens anchitherium cf a cursor conohyus simorrensis prosantorhinus douvillei and ruminants indicate that diagenetic processes have not been intense enough as to obscure the original geochemical signal stable isotope 18oco3 13cco3 and 18opo4 analyses have been measured on the herbivore tooth enamel across these levels with the aim of determining to what extent the global cooling and aridity pattern is recorded at this site a decrease in 18oco3 and 18opo4 has been detected from t1 to t3 3 and t3 1 to t3 3 respectively indicating a progressive drop of about 6 c from around 18 c to 12 c in mean annual temperatures within t3 tooth enamel 13c values experience an increase from t3 1 to t3 3 suggesting an increase in aridity ba ca analyses have also been performed on the tooth enamel in order to detect changes in the palaeoecology of the studied taxa this ratio allows the establishment of particular feeding patterns such as a more browsing habit in the case of gomphotherium angustidens compared to anchitherium cf a cursor as suggested by higher ba ca values in the latter trace elements do not support any significant change across the succession in the dietary behaviour of the species analyzed despite the stable isotopes evidence of an important palaeoclimatic shift from t1 to t3 3

carbon and oxygen isotopic variability in neogene paleosol carbonates constraints on the evolution of the c4 grasslands of the great plains usa abstract understanding the development of grassland ecosystems is critical for understanding the evolution of their associated vertebrate faunas we focus on the central and southern portions of the great plains which is the largest continuous grassland in north america and has a well documented mammalian fossil record modern biomass in this region is dominated by c4 grasses but paleontological evidence indicates the region was forested prior to the middle miocene implying the region was formerly dominated by c3 plants we examine long and short term variations in the abundance of c4 grasses and climatic conditions in the central and southern great plains using the stable carbon and oxygen isotope composition of paleosol carbonates from 28 sections of 11 lithostratigraphic units in the region the carbon isotope composition 13c of paleosol carbonate reflects the proportion of c3 and c4 plants that grew in an ancient soil the long term pattern of 13c values indicates that the percentage of c4 grasses in the great plains was moderate ca 20 throughout most of the miocene increased from 6 4 to 4 0 ma and reached modern levels by 2 5 ma based on the range in 13c values within sections and the mean 13c values for different carbonate morphologies that reflect different intervals of carbonate accumulation the abundance of c4 biomass did not vary substantially on short time scales the variability in c4 biomass on short time scales does not correlate with age of section latitude longitude or the mean percentage of c4 biomass the oxygen isotope composition 18o of soil carbonate is controlled by soil temperature and the 18o value of soil water great plains paleosol 18o values vary considerably in relation to time and latitude removing the variation due to latitude with least squares linear regression reveals a temporal pattern that is consistent with the global pattern of neogene climate change quantitative interpretation of the 18o record is difficult without independent control on temperature or the oxygen isotope composition of soil water both of which have probably varied with long term climate change comparisons of measured 18o values for each section with predicted values based on modern temperature data and estimated modern meteoric water 18o values suggest that 1 most miocene sections have 18o values consistent with warmer temperatures and more positively shifted soil water 18o values than today 2 three miocene sections in western nebraska probably had soil water compositions that were more negative than similar aged localities in the region and 3 the plio pleistocene sections have 18o values consistent with cooler temperatures and more negative soil water 18o values than today the paleosol 13c values do not correlate strongly with the pattern of climate change recorded by the 18o values suggesting that long term change in mean temperature is not the main control on the abundance of 13c biomass in the great plains we propose two testable hypotheses to account for our data and other published data that bear on the evolution of the great plains ecosystem

miocene deepwater oceanography a global synthesis of miocene benthic foraminiferal carbon and oxygen isotopic and faunal abundance data indicates that miocene thermohaline circulation evolved through three regimes corresponding approximately to early middle and late miocene times there is evidence for major qualitative differences between the circulation of the modern ocean and the miocene ocean prior to 11 ma the 13c 12c ratios of the benthic foraminifera cibicidoides are interpreted in terms of water mass aging i e the progressive depletion of dissolved o2 and lowering of 13c values as the result of oxidation of organic matter as water flows further from its sources at the surface of the oceans both isotopic and faunal data indicate that the early miocene regime from 22 to 15 ma was the most different from today s during that interval intermediate and deep waters of both the atlantic and the pacific oceans aged in a northward direction and the intermediate waters of the indian the south atlantic and the south pacific oceans were consistently the youngest in the global ocean we speculate that early miocene global thermohaline circulation may have been strongly influenced by the influx of warm saline water tethyan indian saline water from the tethys into the northern indian ocean the isotopic and faunal data suggest that flow from the tethyan region into the indian ocean diminished or terminated at about 14 ma isotopic and faunal data give no evidence for north atlantic deep water nadw formation prior to about 14 5 ma with the exception of a brief episode in the early miocene from 14 5 to 11 ma nadw formation was weak and circumpolar and antarctic water flooded the deep south atlantic and south pacific as the antarctic ice cap grew from about 10 ma to the end of the miocene thermohaline circulation resembled the modern circulation in many ways in latest miocene time 6 to 5 ma circulation patterns were very similar to today s except that nadw formation was greatly diminished the distribution pattern of siliceous oozes in miocene sediments is consistent with our proposed reconstruction of thermohaline circulation major changes which occurred in circulation during the middle miocene were probably related to the closing of the tethys and may have contributed to rapid middle miocene growth of the antarctic ice cap appendices 1 4 6 and 7 are available withentire article on microfiche order fromamerican geophysical union 2000 floridaavenue n w washington dc 20009 document 88p 002 5 00 payment mustaccompany order

growth of subtropical forests in miocene europe the roles of carbon dioxide and antarctic ice volume the middle miocene is a crucial period for the evolution of apes and it corresponds to their appearance in europe the dispersion of apes was made possible by tectonic changes and the expansion of their habitat sub tropical forest in europe the context in which the middle miocene climatic optimum occurred still lacks constraints in terms of atmospheric p co 2 and ice sheet volume and extent using a coupled atmosphere ocean general circulation model gcm and dynamic vegetation model we investigated the sensitivity of miocene climate and vegetation to p co 2 levels and antarctic ice sheet configurations our results indicate that higher than present p co 2 is necessary to simulate subtropical forest in western and central europe during the middle miocene but that a threshold at high p co 2 makes subtropical forest partly collapse moreover removing ice over antarctica modifies oceanic circulation and induces warmer and slightly wetter conditions in europe which are consistent with the expansion of subtropical forest these results suggest that a small east antarctic ice sheet 25 of present day ice volume together with higher than present p co 2 values are in better agreement with available european middle miocene data

coral microbialite environment in a middle miocene reef of hungary abstract the presence of microbial crusts microbialites is reported here for the first time from a middle miocene badenian coral reef in hungary the succession of initiation and development of the microbial crusts is described in relation to the reef architecture the main features of the palaeoenvironment are discussed with focus on the associated invertebrate faunas mostly corals molluscs bryozoans and crabs we conclude that the microbial crusts developed under normal marine conditions and were a significant contributor to reef framework development including its strengthening through calcification of the microbial organisms microbialites are anticipated in other early and middle miocene coral reef occurrences of the mediterranean paratethys realm and to date may have simply escaped positive recognition

high resolution analysis of upper miocene lake deposits evidence for the influence of gleissberg band solar forcing article i nfo a high resolution multi proxy analysis was conducted on a 1 5 m long core of tortonian age 10 5 ma late miocene from austria europe the lake sediments were studied with a 1 cm resolution to detect all small scale variations based on palynomorphs pollen and dinoflagellate cysts ostracod abundance geochemistry carbon and sulfur and geophysics magnetic susceptibility and natural gamma radiation based on an already established age model for a longer interval of the same core this sequence can be limited to approx two millennia of late miocene time with a resolution of 13 7 years per sample the previous study documented the presence of solar forcing which was verified within various proxies on this 1 5 m core by a combination of redfit spectra and gaussian filters significant repetitive signals ranged in two discrete intervals corresponding roughly to 55 82 and 110 123 years fitting well within the lower and upper gleissberg cycle ranges based on these results the environmental changes along the 2000 year late miocene sequence are discussed no major ecological turnovers are expected in this very short interval nonetheless even within this brief time span dinoflagellates document rapid changes between oligotrophic and eutrophic conditions which are frequently coupled with lake stratification and dysoxic bottom waters these phases prevented ostracods and molluscs from settling and promoted the activity of sulfur bacteria the pollen record indicates rather stable wetland vegetation with a forested hinterland shifts in the pollen spectra can be mainly attributed to variations in transport mechanisms these are represented by a few phases of fluvial input but mainly by changes in wind intensity and probably also wind direction such influence is most likely caused by solar cycles leading to a change in source area for the input into the lake furthermore these solar induced variations seem to be modulated by longer solar cycles the filtered data display comparable patterns and modulations which seem to be forced by the 1000 year and 1500 year cycles the 1000 year cycle modulated especially the lake surface proxies whereas the 1500 year cycle is mainly reflected in hinterland proxies indicating strong influence on transport mechanisms

dissolved iron and iron ii distributions beneath the pack ice in the east antarctic 120 e during the winter spring transition distributions of dissolved iron dfe and its reduced form fe ii to a depth of 1000 m were investigated under the seasonal pack ice off east antarctica during the sea ice physics and ecosystem experiment sipex 2 sea ice voyage in september october 2012 concentrations of dfe were elevated up to five fold relative to southern ocean background concentrations and were spatially variable the mean dfe concentration was 0 44 0 4 nm with a range from 0 09 to 3 05 nm profiles of dfe were more variable within and among stations than were macronutrients suggesting that coupling between these biologically essential elements was weak at the time of the study brine rejection and drainage from sea ice are estimated to be the dominant contributors to elevated dfe concentrations in the mixed layer but mass budget considerations indicate that estimated dfe fluxes from brine input alone are insufficient to account for all observed dfe melting icebergs and shelf sediments are suspected to provide the additional dfe fe ii was mostly below the detection limit but elevated at depth near the continental shelf implying that benthic processes are a source of reduced fe in bottom waters the data indicate that dfe builds up under the seasonal sea ice cover during winter and that reduction of fe may be hampered in early spring by several factors such as lack of electron donors low biological productivity and inadequate light below the sea ice the accumulated dfe pool in the mixed layer is expected to contribute to the formation of the spring bloom as the ice retreats

mid neogene mediterranean marine continental correlations an alternative interpretation recent revised magnetostratigraphic and astrochronologic calibrations of several calcareous planktonic microfossil datum events in particular coccolithus miopelagicus and neogloboquadrina acostaensis combined with our magnetobiostratigraphic investigation of a 10 m thick section at ecotet near lyon france in which terrestrial micromammals vallesian zone mn9 are intercalated with calcareous nannoplankton and planktonic foraminifera belonging to zones nn6 nn8 and n14 15 m11 and m12 respectively lead us to question the recent recalibration by krijgsman et al 1996 eart planet sci lett 142 367 380 of the aragonian vallesian mn7 8 mn9 boundary with chron c5r 1r v11 1 ma and the lower upper vallesian mn9 10 boundary with chron c4ar 2n v9 6 9 7 ma ecotet with a uniform reverse polarity is shown to be assignable uniquely to chron c5r interregional correlation of ecotet with mediterranean terrestrial stratigraphies indicates that progonomys whose first occurrence fo has been traditionally placed in mediterranean mammal zone mn10 was already present in mediterranean zone mn9 at v11 4 ma and did not experience a 2 million year delay in its putative prochoresis from asia

middle miocene latitudinal climatic gradient in western europe evidence from pollen records abstract pollen analysis of sections spanning the middle miocene langhian and serravallian from southern spain to switzerland has been carried out with the aim of reconstructing the existing latitudinal environmental gradient floral assemblages indicate a tropical subtropical to warm temperate climate for the entire area during the middle miocene the presence in all pollen spectra of taxa with high temperature requirements demonstrates that the latitudinal gradient in temperature was relatively low the development of a diverse subarid flora in southern spain including neurada lygeum prosopis calligonum nitraria caesalpiniaceae etc points to a very dry climate with a marked seasonality these features clearly indicate that a very warm and dry climate i e a steppe environment was already present during the langhian in the northwestern mediterranean area on the other hand milder conditions are progressively inferred towards the north as subdesertic elements gradually disappeared and taxa with higher water requirements increased the latter dominates the pollen assemblages in the eastern central part of france and switzerland thus precipitations would have been evenly distributed throughout the year we interpret this gradient from subdesertic vegetation in the south to humidity adapted plant environments in the north as the result of a latitudinal gradient in precipitation

deciphering temperature and salinity from biogenic phosphates the δ18o of coexisting fishes and mammals of the middle miocene sea of western france abstract this study examines the possibility of estimating the oxygen isotopic composition and temperature of seawater by using a combination of 18o values of phosphate from coexisting fishes and mammals of the middle miocene sea of western france teeth of different species of teleosteans and selachians and rib fragments of metaxytherium medium related to modern dugongs were sampled in the langhian seravallian calcareous sediments of eastern brittany and touraine 18o values of fishes range from 21 4 to 22 7 while those of mammals range from 20 1 to 21 7 the variability in 18o values of miocene fishes is not related either to sampling localities or taxa oxygen isotope analyses were also carried out on living dugong dugon from djibouti 18 o 19 6 20 3 and on hydrodamalis gigas which lived two hundred years ago in the low salinity waters of the bering strait 18 o 17 3 the results show that the slope of the oxygen isotope fractionation curve between the dugongids and water is probably close to 1 18o variations within miocene fish and mammal populations are similar and close to or slightly higher than 1 this variation may be attributed mainly to a 18o change in the ambient seawater composition the miocene shallow water masses in western france were thus characterized by varying 18o values as well as average salinities equal to or higher than the contemporaneous open world ocean calculated average temperatures of 20 2 c are compatible with a sub tropical climate local and global causes for this variation in the oxygen isotope composition of miocene seawater are discussed