himalayan forelands palaeontological evidence for oligocene detrital deposits in the bugti hills balochistan pakistan in the southwestern sulaiman geological province balochistan pakistan terrestrial detri tal facies from the bugti hills region have yielded the richest tertiary vertebrate faunas to be found in asia thus far new fossils from five successive and distinct bone beds bridge the supposed oligocene sedimentary hiatus within the sulaiman geological province the lowermost continental levels of the previously described miocene chitarwata formation known as the bugti member are oligocene in age in the bugti area neither a mixture of heterochronic faunal elements nor endemism of any fauna is evident in this area additional microfaunal material from the bugti member constrains an oligocene age for the lower chitarwata formation in zinda pir northeast of the bugti hills this oligocene transition between the marine kirthar eocene and continental siwalik miocene deposits consists of a regressive fluvio deltaic system occupying a vast floodplain it represents an early stage molasse in the palaeo indus basin which drained western orogenic highlands resulting from the colli sion between the indian and eurasian plates

habitat tracking range dynamics and palaeoclimatic significance of eurasian giant salamanders cryptobranchidae indications for elevated central asian humidity during cenozoic global warm periods article i nfo environmental fluctuations are a driving force in vertebrate evolution but cryptobranchids giant salamanders show little morphologic change since the jurassic here we analyze their fossil distribution in the cenozoic of eurasia and show that morphologic stasis is also maintained by stable environments making giant salamanders an ideal proxy group for environmental and palaeoclimatic studies the climate space of recent and fossil cryptobranchids is best characterized by high humidity with mean annual precipitation values over 900 mm the recorded patchiness of their fossil record can be explained by habitat tracking and or range expansion from higher altitudes into lowland settings during humid periods with increased basinal relief in central asia cryptobranchids are recorded from five intervals four of them are global warm periods paleocene eocene thermal maximum late oligocene warming miocene climate optimum and mio pliocene transition this distribution suggests that during global warmth the asian cold high pressure zone during winter months may be weak or absent thus moist westerly winds penetrate far into the continent the presence of cryptobranchids also indicates that the aridification across the eocene oligocene boundary as reported from mongolia and northwestern china does not occur in the zaysan basin probably due to increased upslope precipitation in the rising altai mountains

oxygen isotope calibration of the onset of ice rafting and history of glaciation in the north atlantic region we report here that dsdp site 552a cored with the hydraulic piston corer on the west flank of rockall bank recovered an undisturbed sequence of alternating white deep sea carbonate oozes and dark coloured layers that are rich in glacial debris oxygen isotope analysis of the sequence together with detailed nannofossil and palaeomagnetic stratigraphy shows that the first major horizon of ice rafting occurred at about 2 4 myr and was preceded by a minor pulse of ice rafting at about 2 5 myr the carbon isotope record shows that the site has been bathed by a water mass of similar characteristics to present day north atlantic deep water at least since 3 5 myr

origin and development of artemisia asteraceae in asia and its implications for the uplift history of the tibetan plateau a review abstract the spatial and temporal evolution of artemisia and its relationship with the tibetan plateau tp uplift are examined by summarizing pollen data from 122 sites across china the pollen morphological data reveal that artemisia may have originated from the arid semiarid middle latitudes of asia in the late eocene and spread west and east in the oligocene as the result of early uplift of the tibetan plateau and the global cooling during the miocene artemisia reached the southeastern part of the tp and became common in the western tp due to the high elevation in these regions at the same time the asian monsoon prevented the spread of artemisia to the southern part of the tp since the pliocene especially in the pleistocene artemisia distribution was very similar to its current distribution which indicates that the topography of the tp and the paleoenvironmental conditions in the east asia became more like today thus the cenozoic origin and evolution of artemisia in the asia was strongly influenced by the uplift of the tp global cooling as well as monsoon development

holarctic correlation of non marine palaeocene eocene boundary strata using mammals a new biostratigraphic correlation is suggested for the palaeocene eocene boundary strata in the holarctic great significance is attached to the thanetian hiatus which has critical importance in the placing of the palaeocene eocene boundary in western europe intercontinental correlation of the palaeocene eocene boundary in non marine strata by means of mammals reveals the duration of the thanetian hiatus in the paris basin it corresponds almost entirely to the clarkforkian land mammal age of north america and possibly to the zhigden and naran members of the naran bulak formation of mongolia which suggests a palaeocene age for the clark9s fork fauna the gray bull and bumban faunas appear to be practically contemporaneous and are correlated with the sparnacian fauna of west european meudon the palaeocene eocene boundary in north america is thus traced beneath the gray bull zone wasatchian land mammal age while in central asia it is believed to underlie the bumban member of the naran bulak sections where there is evidence of the simultaneous appearance of perissodactyls primates omomyidae rodents condylarths of the genus hyopsodus and others

paleogene mammals from the iwaki formation in japan their implications for the geologic age and paleobiogeography of this formation abstract the mammalian fauna and geologic age of the iwaki formation of the paleogene shiramizu group iwaki southern fukushima northeastern japan are reviewed and previously undescribed specimens are described the iwaki mammalian fauna consists of three artiodactyl species bothriogenys sp cf b hui anthracotheriidae entelodon gobiensis entelodontidae and cf notomeryx sp ruminantia these three genera indicate an ergilian asian land mamma age late eocene priabonian equivalent correlation for the iwaki formation demonstrating that the eocene oligocene boundary exists within the shiramizu group these three genera have never co occurred in a single formation although in asia they have been recorded only in the late eocene in asia bothriogenys has been recorded in the southern and middle regions entelodon has been mostly recorded in the northern and middle regions with one exception from the southern region and notomeryx has been recorded in the southern region the co occurrence of these three genera in the iwaki formation implies that bothriogenys entelodon and perhaps also notomeryx can be useful late eocene indicators in terrestrial eastern asia it also suggests that the iwaki mammalian fauna is paleobiogeographically located between the northern and southern late eocene faunas of eastern asia showing some faunal mixture the iwaki fauna is also unique in comprising diverse faunas of marine sharks and seashore birds together with terrestrial mammals the iwaki vertebrate fauna is key for reconstructing the faunas of the eastern coastal margin of the asian continent during the late eocene

palaeoclimate when the world turned cold as massive ice sheets grew on antarctica during the first major glaciation of the cenozoic era the northern continents cooled and dried the coincidence in timing implies that the cause was global rather than regional

magnetostratigraphic constraints on the fossiliferous ulantatal sequence in inner mongolia china implications for asian aridification and faunal turnover before the eocene oligocene boundary abstract the transition from eocene to oligocene and its implications in the terrestrial realm has been a focal target for cenozoic climate and environment research as it is widely considered the most dramatic climatic shift of the past 50 million years tibetan plateau and proximal areas have been of utmost interest since the biogeographic relationships and understanding of the depositional environments in the region have remained unsettled during and after the eocene oligocene transition eot this study derives a first chronostratigraphic framework for ulantatal a fossiliferous area in inner mongolia china based on paleomagnetic reversal stratigraphy and the constraints of faunal correlations the time spanned in the strata is between ca 35 and 27 ma thus exposing a long sedimentary succession ranging from the latest eocene to late oligocene the lithological characteristics reveal these extensive fine grained sediments mainly originate from eolian dust deposition the onset of which is constrained at the latest eocene ca 34 8 ma the presence of post mongolian remodeling fauna already in the late eocene of ulantatal demonstrates unequivocally that the major faunal turnover preceded the eocene oligocene boundary earlier to what has been recorded from other east asian localities the faunal composition predominated by rodents and lagomorphs remains strikingly stable across the eocene oligocene boundary suggesting the eot related change in the animal communities was gradual or stepwise rather than abrupt moreover the turnover into this environment dominated by small mammals can be linked with eocene aridification of asia highlighting the dynamic responses of terrestrial systems to changing environment and climate associated with the eot

taphonomy of vertebrate assemblages from the paleogene of northwestern wyoming and the neogene of northern pakistan abstract we compare the taphonomy of vertebrate assemblages from two long continental records the early paleogene of the bighorn basin wyoming and the neogene siwalik sequence of northern pakistan both sequences contain a similar array of fluvial facies and the abundance of these facies differs among formations we document environments of preservation of vertebrate localities over time to determine comparability of fossil assemblages within and between sequences changes in sample size and species richness are noted to reveal potential sampling effects on patterns of faunal turnover preservational history determined the environment sample size quality of specimens taxonomic composition and spatial and temporal resolution of fossil assemblages and thereby the quality of the fossil record and its suitability for further analyses in both sequences changes in prevailing taphonomic processes reflect changes in lithofacies and habitat distribution correlated changes are found in fossil productivity species richness and faunal composition both sequences contain some episodes of apparent faunal change in which appearances and disappearances of rare taxa can be attributed principally to changes in sample size the paleogene record has high taxonomic resolution i e to genus or species for most mammalian fossil remains temporal and spatial averaging of paleogene fossil assemblages changes with lithofacies the neogene record has higher taxonomic resolution for remains of small mammals different preservational circumstances impose different constraints on paleocological and evolutionary analyses the best opportunities for paleocommunity reconstruction are provided by high taxonomic resolution large samples nd varied environments of preservation these circumstances are found in limited portions of each record the best opportunities for documenting evolution within lineages and species replacement patterns are provided by high taxonomic resolution high temporal resolution and consistent preservational context these taphonomic attributes pertain to the more common paleogene mammals particularly from the rich paleosol localities of the willwood formation and to the more common neogene small mammals from abandoned channel fills of the siwalik record

discovery of the oldest european ruminant in the late eocene of bulgaria did tectonics influence the diachronic development of the grande coupure abstract we describe the oldest known european ruminant bachitherium thraciensis sp nov from late eocene latest bartonian or early priabonian strata in bulgaria the new specimen which possesses the most primitive dental morphology known in the bachitheriidae family predates its western european relatives by at least 4 5 myr the discovery suggests that ruminants dispersed into europe in a series of east to west waves preceding and following the eocene oligocene boundary probably originating from asia the oldest ruminant reported here migrated into southeastern europe during a second wave comprising the grand coupure dispersal event ruminants moved into western europe at the eocene oligocene boundary a third wave composed by bachitheriidae and tragulidae arrived in western europe 2 myr later in the earliest oligocene the origin of this east to west diachronism was probably facilitated by orogenesis that episodically allowed dispersal of ruminants from asia through southeastern europe and into western europe in what we herein term the bachitherium dispersal event however none of the abundant perissodactyl fauna from southeastern europe migrated to western europe during this time because like their relatives in central asia they may not survive to terminal eocene cooling and aridity

step wise change of asian interior climate preceding the eocene oligocene transition eot abstract understanding the global climate change from greenhouse to icehouse conditions at the eocene oligocene transition eot 34 million years ago requires climatic records from oceanic as well as continental realms of the key late eocene doubthouse period preceding this switch here we report integrated stratigraphic results from well dated late eocene continental mudflat to saline lake paleoenvironments of the xining basin northeastern tibetan plateau western china recording regional and global change cyclostratigraphic analysis strongly suggests continuous dominance of the 41 kyr obliquity cycle in the whole late eocene interval down to the base of polarity chron c18n 2n at 39 ma with additional input of the 100 kyr eccentricity cycle up to the base of chron c13r at 34 7 ma this might imply that high latitude climates dominated the area long before the eot probably related to incipient ice volume fluctuations furthermore our results reveal two paleoenvironmental deterioration steps preceding the eocene oligocene transition the first step occurs in the top of chron c17n 1n at 36 6 ma this age closely corresponds to 1 the high altitude pollen appearance in chron c16 2r at 36 4 ma in the same section 2 the recently dated final retreat of the tarim sea in western china and 3 a shift from precession to obliquity dominance in the atlantic ocean this near co occurrence suggests global change at this time we hypothesize this change is related to an increase in incipient ice sheet volume leading to passing threshold conditions for the high altitude pollen appearance and tarim sea retreat finally leading to decreased moisture availability in the xining basin at the second step in the base of chron c13r at 34 7 ma a substantial increase in clastic sedimentation rates is observed this might relate to increased climate variability preceding the greenhouse to icehouse transition at the eot that prevented landscapes to attain equilibrium configurations

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

late eocene sea retreat from the tarim basin west china and concomitant asian paleoenvironmental change the paleogene sediments of the southwest tarim basin along the west kunlun shan in western china include the remnants of the easternmost extent of a large epicontinental sea this shallow sea once extended across the eurasian continent before it retreated westward and eventually separated as the paratethys sea climate modeling results suggest that this sea retreat is an equally important forcing mechanism as the tibetan plateau uplift in the aridification of the asian continental interior and the intensification of the asian monsoon system the age and paleogeography of the retreat are poorly constrained hindering the understanding of its cause and paleoenvironmental impacts this study reports litho and biostratigraphic results from two sections recording the last major regression out of the tarim basin that is expressed by a regional transition from marine clastics and limestones to continental red beds rich micro and macrofossil assemblages including benthic foraminifera ostracods bivalves calcareous nannofossils and organic walled dinoflagellate cysts dinocysts indicate a shallow proximal and marine environment strong similarity to assemblages known from central asia and europe confirms that surface ocean connections extended across eurasia from the tarim basin to the western tethys during the latest eocene moreover the recovered fossil associations date the last marine sediments as earliest priabonian in age 37 ma overlap between dinoflagellate mps interval zone and calcareous nannofossil zone cp 14 the retreat of the sea from the tarim basin is time equivalent with the sea level lowstand at the bartonian priabonian boundary but pre dates both the oligocene miocene regional uplift of the pamir mountains and kunlun shan and the major eustatic sea level falls of the eocene oligocene transition 34 ma and mid oligocene 30 ma which are usually held responsible for the sea retreat furthermore a concomitant and significant aridification step occurs at 36 6 ma top of chron c17n 1n as recorded by regional sedimentary records of the xining basin along the northeastern tibetan plateau suggesting that the tarim sea served as a significant moisture contributor for the asian interior

early oligocene vegetation and climate of southwestern china inferred from palynology abstract the early oligocene represents the beginning of the modern icehouse world to better understand how vegetation and climate changed during this period we reconstruct quantitively the early oligocene vegetation and climate by analyzing fossil spore and pollen assemblages from luhe basin yunnan province in southwestern china the reconstructed paleoclimate using bioclimatic analysis shows that the mean annual temperature mat ranged from 14 4 to 15 4 c the mean annual precipitation map was 1070 1 1297 8 mm and the range of mean temperature of coldest quarter mtcq was 6 7 to 7 c lower than that of the present day 9 3 c the reconstructed regional vegetation indicates a deciduous broadleaved forest mixed with evergreen broadleaved elements considering other paleogene floras in yunnan deciduous broadleaved elements dominated in this area from the late eocene to the early oligocene the paleoclimate reconstruction suggests that this vegetation composition may have been controlled mainly by cold winter temperatures

revisiting the paleogene climate pattern of east asia a synthetic review abstract east asian paleogene climates have long been regarded as controlled by the planetary wind system which might result in a climate pattern with three latitudinally distributed zones two humid zones located separately in the north and south were lithologically designated by coals and oil shales while an arid zone in the middle was represented by red beds and evaporites because the middle arid zone was located along 30 n paleolatitude its presence had been further linked with a then subtropical high however this long standing model has recently been challenged by growing evidence from petrology sedimentology paleontology paleobiogeography paleoclimatology and climate modeling here we review the primary data from these disciplines and reinterpret their climate significances to revisit the east asian climate pattern during the paleogene petrologically while the occurrence of coals and or oil shales is accepted as an indicator for overall humid climates that of red beds and or evaporites is highly equivocal to exclusively indicate perennial arid climates unless their origins are carefully investigated in reality generic red beds merely represent an oxidizing environment not essentially associated with a single specific climate type meanwhile evaporites although typically precipitated in arid environments may be deposited in either perennial dry or seasonal monsoonal climates there is no solid evidence so far to convincingly support that the landscape of the so called middle arid zone was dominated by desert and or steppe under a then subtropical high during most of the paleogene the plant function type study additionally suggests that the middle arid zone appears to be lack of xerophytic vegetation even though some xerophytic or sclerophyllous plant taxa did sporadically occur interestingly paleozoological data show that the paleogene mammalian faunas were somewhat equably distributed over east asia strongly suggesting the evident absence of a critical biogeographical or climatic barrier stretched across the middle arid zone as the planetary wind model implied in contrast to the planetary wind model monsoonal or monsoon like paleogene climates have been broadly reported from the northern middle and southern east asia as well as adjacent regions of russia and kazakhstan if only the indicators for humid climates are considered simply due to the uncertainty of those for perennial arid climates east asia must have had a relatively dry region in the continental interior during the late eocene to oligocene transition likely caused by the continentality and or the rain shadow effect along with the global cooling the monsoonal interpretation is highly in agreement with the evidence from floras faunas basin analyses and modeling experiments and well explicates the paleogene climate distribution and seasonal dynamics of east asia however further studies will be largely needed to verify whether uniformly according to the modern criteria the paleogene climates of the east asia interior can be accurately attributed to the arid category

faunal turnovers of palaeogene mammals from the mongolian plateau most orders and many families of modern mammals were established during the palaeogene mammalian evolution during this period of time has been correlated with global climatic events1 2 3 4 although the timing mode and scale of such a climate evolution link remain debatable1 5 6 the palaeogene global climate was step punctuated by a warming across the palaeocene eocene boundary about 55 myr ago and a cool off throughout the late eocene and early oligocene epochs1 2 7 8 9 10 the most severe cooling was at 33 5 myr slightly after the eocene oligocene boundary and was characterized by a drop in the mean annual temperature and by changes in vegetation from eocene dense forests to oligocene more open country5 here we analyse 33 palaeogene mammal faunas from the mongolian plateau of china and mongolia there is a distinct pattern of faunal turnovers perissodactyl dominant faunas of the eocene were abruptly replaced by rodent lagomorph dominant faunas of the oligocene we interpret the turnovers as having been effected by global climatic shifts and name the prominent biotic reorganization across the eocene oligocene boundary the mongolian remodelling which correlates to the european grande coupure

tibetan uplift prior to the eocene oligocene climate transition evidence from pollen analysis of the xining basin uplift of the tibetan plateau and the himalayas since the onset of the indo asia collision is held responsible for asian aridifi cation and monsoon intensifi cation but may also have gradually cooled global climate leading to the 34 ma eocene oligocene transition to unravel the interplay between tibetan uplift and global climate proxy records of asian paleoenvironments constrained by accurate age models are needed for the paleogene period here we report the 38 ma appearance of high altitude vegetation recovered from palynological assemblages in precisely dated lacustrine sediments from the xining basin of the northeastern tibetan plateau region this result confi rms previous evidence for important regional uplift in the central and northern tibetan plateau regions during the early stage of the indo asia collision this is consistent with the idea that the associated increase in rock weathering and erosion contributed to lowering of atmospheric co 2 leading to the eocene oligocene transition

the geological events at the eocene oligocene boundary abstract at the end of the eocene series of geological events occurs on a worldwide scale of which the intensity is comparable to the one occurring at the cretaceous tertiary boundary oxygen and carbon isotopic variations in biogenic carbonates indicate a sudden drop in sea water temperature as well as a modification of oceanic chemistry which is corroborated by trace element analyses of the same carbonates simultaneously the c c d drops and the oceanic sedimentation rate is considerably reduced many genera disappear foraminifera nannoplankton dinoflagellates while on the continents the evolution of the microflora indicates a general cooling many groups among mammals become extinct before the oligocene faunal renewal the break of stehlin there is an important regression which explains that continuous sections are rare at the eocene oligocene boundary gaps are common in the deep oceanic domain these dramatic events started in europe at the boundary between the priabonian the ludian the lattorfian or the early tongrian and the stampian the rupelian or the late tongrian

eocene oligocene transition in central asia and its effects on mammalian evolution the eocene oligocene boundary eob marks a period of dramatic global climatic change correlated with pronounced mammalian faunal change the timing of these events is well constrained in north america and europe but the asian record has yet to produce a synthetic section linking environmental change mammalian fossils and precise geochronological dates here we present the first magnetostratigraphic section for the hsanda gol formation mongolia which yields significant oligocene fossils and also marks a pattern of aridification that is tightly correlated to the eob 33 9 ma supporting a broader pattern of aridification in the central asian plateau across the eob oligocene faunas of asia can now be confidently correlated to those of north america europe and africa these results suggest that mammalian faunal turnover within asia occurred slightly later than similar events within europe and question the influence of asian immigrants on the grande coupure faunal turnover

a new assemblage of stem pecoran ruminants from the oligocene chitarwata formation bugti hills baluchistan pakistan paleoenvironmental and paleobiogeographic implications abstract a new assemblage of stem pecoran ruminants from the oligocene chitarwata formation lower bugti member bugti hills pakistan consists of three identified genera and another indeterminate ruminant although limited the dental and postcranial material is sufficient to identify the genera amphitragulus and mosaicomeryx two common forms known from middle to late oligocene deposits of europe thus reinforcing the middle oligocene age of the lowermost chitarwata formation mosaicomeryx is reported for the first time from the indian subcontinent and this occurrence considerably expands its geographical distribution a new genus and species paalitherium gurki is erected on the basis of an unusual and unique association of characters on its lower molars the unclear definition and occurrences of gelocus gajensis pilgrim 1912 are re examined in the light of new data from the bugti and zinda pir areas pakistan the new ruminant fauna from paali is clearly distinctive from the early miocene assemblage known from bugti in accordance with other fossil evidence the ruminant fauna described here suggests the existence of a tropical forested environment under monsoonal regime with soft food supplies during the time of deposition of the lowermost chitarwata formation

onset of aridification by 34 ma across the eocene oligocene transition in central asia cenozoic climate has changed markedly from a warm wet climate to the present cool dry glacial interglacial cycles the largest of these cooling steps is thought to have taken place across the eocene oligocene transition terrestrial airborne eolian loess is a direct result of land aridification therefore the prolonged formation of thick eolian loess deposits provides a key to aridification history in the geological past however the oldest eolian loess in the asian interior has been dated to only 25 22 ma here we present new sedimentological geochemical and magnetostratigraphic data from cenozoic sections in southwestern mongolia to show that the earliest eolian dust accumulation occurred by 34 ma 10 m y earlier than currently believed we suggest that this oldest eolian dust accumulation provides direct evidence for enhanced aridification across the eocene oligocene transition in central asia this is explicable by reduced moisture transport caused by prevailing westerlies during retreat of the neotethys ocean these climatic changes were related to the changing regional plate configuration as well as to global cooling and ice sheet growth in antarctica

evolution within the charophyte genus harrisichara late paleogene southern england environmental and biostratigraphic implications the eocene oligocene transitional strata of the hampshire basin isle of wight provide a unique opportunity to study evolution and biotic turnover in the continental realm in relation to the global change occurring at this time gyrogonites of the charophyte genus harrisichara vary through the late paleogene and their abundance has enabled a rigorous morphometric study morphometric methodologies including eigenshape analysis have been used to best quantify evolution within the genus thirteen horizons from six isle of wight localities representing a time period of circa 3 5 million years have been used in this study results show a sharp morphological shift occurring within the genus harrisichara between the headon hill formation and the bembridge limestone formation the morphological evolution constitutes a doubling in the volume of the gyrogonites the observed morphological shift within the genus harrisichara is argued to be a functional response to the changing global climate and the associated increase in seasonality the results of the morphological shift have the potential effect of increasing both establishment and persistence rates within the genus harrisichara the timing of the observed shift coincides with mammal faunal turnover and this implies a wider biotic response to the inferred climate change at this time however harrisichara does not show evolutionary change across the grande coupure the earliest oligocene major mammalian faunal turnover event the timing of the morphological change is also coincident with the zonal boundary between the harrisichara vasiformis tuberculata zone and the harrisichara tuberculata superzone and the morphometric approach would represent a much more robust definition of the boundary biostratigraphy based on multiple morphometric studies of assemblages of individual charophyte taxa will facilitate superior correlation and should be more widely applied in charophyte biostratigraphy

expansion of open landscapes in northern china during the oligocene induced by dramatic climate changes paleoecological evidence abstract the mammalian faunas of the mongolian plateau were affected by an important turnover at the eocene oligocene transition caused by a global cooling and a local aridification which could have strongly affected the environment however paleoenvironmental indices remain scarce in this area during the oligocene the knowledge of the main paleoecological trends of mammals can thus constitute essential clues in order to better evaluate the impact of these climate changes on east asian environment variations as fossils of the primary consumer macro mammals are unavailable to reconstruct past environments we proposed to infer the feeding habits of well described rodent communities by studying their dental microwear patterns we assumed that their diet range reflected their past micro habitats 80 dental specimens of cricetidae and ctenodactylidae excavated from ulantatal sites inner mongolia china were investigated through the oligocene period our results reveal that the main wear features observed in their dental patterns are fine scratches which correspond to the ingestion of abrasive matter such as grasses or dust present in herbaceous to shrubby layers in addition to these plants they could also have consumed insects feeding behaviors which included a high component of abrasive intakes were probably linked to important environmental changes that occurred between the eocene and the oligocene that is stressed by the appearance and the relative expansion of open habitats involving mainly shrubs and probably to a lesser extent grasses these environmental changes are supported by some dental characteristics of the oligocene mammalian paleocommunities of the mongolian plateau e g high crown similarly oligocene paleoenvironmental records of the north american great plains indicate the presence of woodlands and savannas at the same latitudes including grasses although preliminary these results concur with the assumption of the diversification of grasses in open landscapes well before their expansion during the late miocene

the age of the grande coupure mammal turnover new constraints from the eocene oligocene record of the eastern ebro basin ne spain abstract the grande coupure represents a major terrestrial faunal turnover recorded in eurasia associated with the overall climate shift at the eocene oligocene transition during this event a large number of european eocene endemic mammals became extinct and new asian immigrants appeared the absolute age of the grande coupure however has remained controversial for decades the late eocene oligocene continental record of the eastern ebro basin ne spain constitutes a unique opportunity to build a robust magnetostratigraphy based chronostratigraphy which can contribute with independent age constraints for this important turnover this study presents new magnetostratigraphic data of a 495 m thick section moia santpedor that ranges from 36 1 ma to 33 3 ma the integration of the new results with previous litho bio and magnetostratigraphic records of the ebro basin yields accurate ages for the immediately pre and post grand coupure mammal fossil assemblages found in the study area bracketing the grande coupure to an age embracing the eocene oligocene transition with a maximum allowable lag of 0 5 myr with respect to this boundary the shift to drier conditions that accompanied the global cooling at the eocene oligocene transition probably determined the sedimentary trends in the eastern ebro basin the occurrence and expansion of an amalgamated channel sandstone unit is interpreted as the forced response of the fluvial fan system to the transient retraction of the central basin lake systems the new results from the ebro basin allow us to revisit correlations for the controversial eocene oligocene record of the hampshire basin isle of wight uk and their implications for the calibration of the mammal palaeogene reference levels mp18 to mp21

lithofacies and fluvial lacustrine environments of the palaeogene sevkhuul and ergil members ergiliin zoo formation south gobi mongolia the clastic sequence of the ergiliin zoo formation stretches along the mongolian chinese border in the southern gobi desert mongolia its members sevkhuul ergil exposed in the erdene sum region are well known for their vertebrate remains of late eocene and oligocene age based upon field work the continental red beds were subdivided into four units described as i prodelta mud sand flat ii delta front iii delta plain and iv calcretes all sub environments are in a fluvial lacustrine setting electronmicroprobe analysis in addition to conventional thin section examination was applied to shed some light on the complex mineral association made up of light minerals quartz plagioclase ternary feldspar orthoclase smectite illite rare palygorskite heavy minerals almandine pyrope solid solution series zoisite epidote s s s and abundant goethite and carbonate minerals calcite dolomite igneous rocks being exposed in the source area have contributed to the formation of carbonate minerals and mg bearing sheet silicates during diagenesis higher up on the delta plain transitional between distal alluvial and deltaic deposits fluids emerged from the distal alluvial fluvial deposits and formed calcareous duricrusts drawing conclusions from the rock colour the mineral assemblage and the palaeoecological data the climatic conditions may be described as alternating wet and dry seasons closely resembling those conditions of a modern savannah

link between global cooling and mammalian transformation across the eocene oligocene boundary in the continental interior of asia evidence in the world s ocean current system indicates an abrupt cooling from 34 1 to 33 6 ma across the eocene oligocene boundary at 33 9 ma the remarkable cooling period in the ocean called the eocene oligocene transition eot is correlated with pronounced mammalian faunal replacement as shown in terrestrial fossil records for the first time within asia a section is magnetostratigraphically dated that also produces mammalian fossils that span the late eocene early oligocene transition three fossil assemblages revealed through the eot 34 8 33 7 and 30 4 ma demonstrate that perissodactyl faunas were abruptly replaced by rodent lagomorph dominant faunas during climate cooling and that changes in mammalian communities were accelerated by aridification in central asia three fossil assemblages 34 8 33 7 and 30 4 ma within the north junggar basin burqin section tied to this magnetostratigraphically dated section reveal that perissodactyl faunas were abruptly replaced by rodent lagomorph dominant faunas during climate cooling and that changes in mammalian communities were accelerated by aridification in central asia the biotic reorganization events described in the burqin section are comparable to the grande coupure in europe and the mongolian remodeling of mammalian communities that is the faunal transition was nearly simultaneous all over the world and mirrored global climatic changes with regional factors playing only a secondary role

space geodetic measurement of crustal deformation in central and southern california 1984 1992 we estimate the velocity field in central and southern california using global positioning system gps observations from 1986 to 1992 and very long baseline interferometry vlbi observations from 1984 to 1991 our core network includes 12 gps sites spaced approximately 50 km apart mostly in the western transverse ranges and the coastal borderlands the precision and accuracy of the relative horizontal velocities estimated for these core stations are adequately described by a 95 confidence ellipse with a semiminor axis of approximately 2 mm yr oriented roughly north south and a semimajor axis of approximately 3 mm yr oriented east west

global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events rea d k zachos j c owen r m and gingerich p d 1990 global change at the paleocene eocene boundary climatic and evolutionary consequences of tectonic events palaeogeogr palaeoclimatol palaeoecol 79 117 128 events of the paleocene eocene boundary provide the clearest example to date of how a tectonic event may have global climatic consequences recent advances permit well constrained stratigraphic determination of several events that occurred at that boundary in chron c24r a many fold increase in sea floor hydrothermal activity a global warming a reduction in the intensity of atmospheric circulation a conversion to salinity driven deep ocean circulation a marked lightening of oceanic 313c values extinction and evolution of both benthic foraminifera and land mammals and important plate boundary reorganizations including the outpouring of the east greenland volcanics and the initiation of the oceanic rift between norway and greenland we hypothesize that enhanced sea floor hydrothermal activity occasioned by global tectonism resulted in a flooding of the atmosphere with coz causing a reduced pole to equator temperature gradient and increased evaporation at low latitudes increased formation of warm salty probably low nutrient waters coupled with the warm temperatures at high latitudes occasioned a salinity driven rather than temperature driven deep water circulation this newly evolved ocean circulation pattern changed the apportionment of global heat transport from the atmosphere to the ocean with concomitant changes in the circulation intensity of both reduced intensity of atmospheric circulation resulted in lower oceanic biological productivity and enhanced seasonality of climate on the continents a major extinction event among benthic foraminifera was probably a response to the new low nutrient and chemically changed bottom waters and endemism following rapid evolution and dispersal of mammalian orders may have been in response to the new continental climate regime

causes of rapid motions of the earth s pole analysis of new highly accurate geodetic data reveals rapid motions of the earth s pole with peak to peak variations of 0 002 to 0 020 seconds of arc fluctuating on timescales between two weeks and several months comparison with meteorological excitation estimates shows that these motions are at least partially driven by surface air pressure changes as modified by the response of sea level to atmospheric loading such geodetic measurements thus potentially provide a novel means of observing the dynamics of the atmosphere and oceans at very low spatial wavenumbers

geodetic measurement of deformation in the ventura basin region southern california we have measured the deformation in the ventura basin region southern california with global positioning system gps measurements carried out over 4 6 years between 1987 and 1992 the deformation within our network is spatically variable on scales of tens of kilometers with strain rates reaching 0 6 1 micro rad yr in the east central basin blocklike rotations are observed south and northwest of the basin where the maximum shear strain rates are an order of magnitude lower 0 06 1 micro rad yr to the south we also observed clockwise rotations of 1 deg 7 deg m y shear strain rates determined by comparing angle changes from historical triangulation spanning several decades and gps measurements give consistent though less precise results the geodetic rates of shortening across the basin and western transverse ranges are lower than those estimated from geological observations but the patterns of deformation from the two methods agree qualitatively

faunal stability during the early oligocene climatic crash abstract traditional neo darwinism views species as highly flexible entities which adapt to climatic change by gradually evolving new morphologies of the 177 species of mammals from the upper eocene lower oligocene 37 30 ma white river group in the high plains most species are static for 2 4 million years on average and some persist much longer only three examples of gradualism can be documented in the entire fauna and these are mostly size changes contrary to expectations most mammalian species show no change during the earliest oligocene climatic crash 33 2 ma in spite of the fact that the vegetation changed from dense forests to open forested grassland mean annual temperatures dropped 13 c and conditions got much drier and more seasonal only a few mammalian lineages speciated a few more went extinct and the vast majority 62 out of 70 persisted through this climatic event with no observable response whatsoever this evidence shows that organisms are much less responsive to the environment than short term neontological studies suggest

sub milliarcsecond determination of pole position using global positioning system data the determination of pole position variations from the analysis of 23 days of global positioning system gps data continuously collected with a globally distributed 21 station network is discussed the comparison of the estimated pole positions from these data with results from 11 very long baseline interferometry vlbi experiments conducted during this same interval yields weighted root mean square differences about the mean differences of 0 5 mas for both x and y pole position estimates from an analysis using single day arcs and 1 0 and 0 8 mas from an analysis using three weekly multiday arcs these results are of sufficient quality that gps could provide an alternative technique to vlbi and satellite laser ranging for regular monitoring of high time resolution variations in the position of the earth s rotation axis

precise determination of earth s center of mass using measurements from the global positioning system global positioning system gps data from a worldwide geodetic experiment were collected during a 3 week period early in 1991 geocentric station coordinates were estimated using the gps data thus defining a dynamically determined reference frame origin which should coincide with the earth center of mass or geocenter the 3 week gps average geocenter estimates agree to 7 13 cm with geocenter estimates determined from satellite laser ranging a well established technique the rms of daily gps geocenter estimates were 4 cm for x and y and 30 cm for z

chlorite chemical composition change in response to the eocene oligocene climate transition on the northeastern tibetan plateau abstract the eocene oligocene climate transition eoct at 34 ma is a pronounced environmental reorganization that occurred in the cenozoic era and has been extensively studied via marine archives however to date there is still a less well dated continental record across the eoct which can mostly be attributed to a lack of suitable proxies used in the varied continental settings in terms of sedimentary facies provenance and climate thus resulting in a poor understanding of the continental response to this transition located on the northeastern tibetan plateau the qaidam basin is filled with continuous and well exposed cenozoic fluvio lacustrine sediments cenozoic lacustrine sediment has been proven to be an ideal archive to study the continental climatic response to the eoct here we present the detailed mineralogical and elemental composition of chlorite a widespread clay mineral in continental sediments formed by rock weathering collected from a lacustrine sequence in the northern qaidam basin to constrain the onset of the eoct and the related climatic response the results show that chlorite abundance crystallinity indices intensity ratios of chlorite diagnostic peaks and chemical composition collectively exhibit remarkable changes at 34 3 ma to be more specific the well crystallized fe mg rich chlorites were characterized by a high fe content before the eoct and turned into high mg content mg chlorites with poor crystallinity the chlorite chemical composition change is assumed to have been related to regional drying after the eoct thus providing new insights into the continental paleoenvironmental change based on this novel proxy

an ecological response to the eocene oligocene transition revealed by the δ13ctoc record lanzhou basin ne tibetan plateau abstract the eocene oligocene e o transition corresponds to an abrupt global cooling thought to have been one of the greatest temperature changes in the mid cenozoic earth s history sparse studies have successfully reconstructed the terrestrial ecological response to this temperature change here we report results from the study of organic carbon isotopes 13ctoc together with n alkanes biomarker analysis in the yongdeng section lanzhou basin northwest china and discuss changes in 13ctoc and their mechanisms the results show that between 35 3 ma and 31 0 ma 13ctoc ranged from 26 72 to 21 27 the main change occurred at 33 4 ma when 13ctoc became heavier by 3 at this time the long chain n alkane members c27 c29 and c31 were dominant suggesting the most likely sources of organic matter were terrestrial plants combining these results with existing measurements of plant 13ctoc and sporopollen data in adjacent areas we infer that this change at 33 4 ma might have been caused by an increase in gymnosperm content especially coniferous trees adapted to cold climates which have a heavier 13ctoc than that of the angiosperms this would have been a response to the global cooling characteristic of this period

facies related diagenetic alteration in lacustrine deltaic red beds of the paleogene ergeliin zoo formation erdene sum area s gobi mongolia the late eocene ergeliin zoo formation mongolia was subdivided into four facies associations stratigraphic units which are characterized by various carbonate minerals 1 mud sand flat low fe dolomite high mg calcite 11 delta front high mn dolomite low mg calcite 111 delta plain high mn calcite low mg and moderate fe calcite iv calcretes high mg calcite besides carbonate minerals prevailing among the cement minerals some sheet silicates ca smectite palygorskite illite apatite and fe oxide hydroxides occur in the siliciclastics of these lacustrine deltaic red beds the prodelta mud sand flat deposits unit 1 were dolomitized and cemented by high mg calcite during evaporative pumping at times of low lake stand under redox conditions greater than 0 and intrastratal solutions of strong alkalinity manganoan dolomite is fairly widespread in the delta front sediments unit 11 the mn content of which is likely to have been derived from decomposition of vertebrate remains the mn fe ratio in the carbonate minerals was controlled by the redox conditions and the shallow burial depth in the porous delta front sediments eh values around zero and ph values slightly above 7 occurred as a result of basinward fluid movements high mn dolomite high fe dolomite low mg calcite fluid movement was locally impeded by finer grained delta plain deposits unit iii intertonguing with arenaceous aquifers low mg moderate fe calcite high mn calcite higher up on the delta plain with deposits laid down in an environment transitional between distal alluvial and deltaic unit iv closed lake basin conditions reappeared as fluids emerged from the distal alluvial fluvial deposits or were driven by capillary force to ascend and form calcretes abundant in mg bearing calcite the climatic conditions in the erdene sum area mongolia are likely to have been semi and transitional into arid c 2005 elsevier b v all rights reserved

eocene oligocene mammalian faunal turnover in the hampshire basin uk calibration to the global time scale and the major cooling event a new high resolution c 1 ma mammalian record in continental eocene oligocene strata in the hampshire basin is used to investigate the nature and timing of the major europe wide mammalian faunal turnover termed the grande coupure whether this was caused by climate change or by competition with taxa dispersing from asia is controversial the mammalian faunas in this record after rarefaction analysis show a sharp reduction in diversity only after the grande coupure improved correlation of nw european successions to global events confirms the grande coupure as earliest oligocene it shows that a c 350 ka hiatus interrupts the hampshire and paris basin sequences prior to the first record of post grande coupure asian taxa hiatus bridging faunas from elsewhere in europe record mainly post grande coupure taxa suggesting that the turnover occurred early in the hiatus minimizing bias to the turnover pattern a previously unrecorded second smaller turnover involving european mammals only immediately precedes the grande coupure in the hampshire basin coinciding with vegetational change this turnover is judged not to represent cooling it is concluded that the grande coupure coincides with the earliest oligocene oi 1 glaciation and that climate change combined with competition to produce the turnover

astronomically forced climate cooling across the eocene oligocene transition in the pearl river mouth basin northern south china sea abstract during the late eocene early oligocene major changes in the global climate and environment occurred including decreases in global temperature and the appearance of antarctic glaciation these changes marked the transition from early cenozoic greenhouse conditions to icehouse conditions research on this cooling trend in the atlantic and high latitude regions has increased but few reports have studied low latitude regions e g the northern south china sea and it remains unclear whether sediment records in these areas preserve signals related to this global cooling event in this study we studied records from a lacustrine well in the wenchang sag pearl river mouth basin prmb northern south china sea we conducted palynological and cyclostratigraphic analyses to reconstruct the depositional environment and assess the influence of orbital forcing the cyclostratigraphic analysis showed that depositional cycles including fining upwards and coarsening upwards sequences were controlled mainly by long eccentricity forcing the expansion and contraction of the lake system at 1 2 myr time intervals in addition changes in the pollen spore assemblage before and after the eocene oligocene e o transition show a dramatic shift from a moderately deep lake to a shallow lake with delta facies as recorded by the wenchang to enping formations in the wenchang sag prmb these findings suggest that the climate deteriorated in response to global cooling the amplification of obliquity forcing and the coevolution between obliquity power and global pco2 during the e o transition suggest that the low latitude sedimentary records from china contain a high latitude signal furthermore the low amplitudes of the precession obliquity and eccentricity cycles are coupled with the initial decreases in the global sea level and pco2 and a positive bias in the carbon oxygen isotopic compositions at 34 3 ma these results suggest that orbital forcing played a role in elevating pco2 across a critical threshold during the e o transition 33 9 ma

early rhinocerotids mammalia perissodactyla from south asia and a review of the holarctic paleogene rhinocerotid record the earliest rhinocerotids from south asia are identified on the basis of few dental remains originating from the late eocene of thailand wai lek mine krabi basin and the early oligocene of pakistan paali nala c2 bugti hills once synthesized the holarctic paleogene rhinocerotid record points out a westward diachronism of rhinocerotid first appearance data from north america to europe via asia throughout mid cenozoic times the faunal similarity among mammal localities from the late eocene and early oligocene of peninsular thailand southern china and pakistan suggests the existence of a single south asian paleoprovince during this interval and the persistence of a tropical subtropical climate substantial faunal changes recorded in eastern balochistan reveal a significant climatic deterioration from the middle part of the oligocene neither provinciality nor endemism is noticeable for rhinocerotoid taxa recognized in the oligocene of the indian subcontinent neither the himalayas nor the tibet plateau was a paleogeographic barrier for large mammals during this interval resume les plus anciens rhinocerotides d asie du sud sont identifies gr ce a quelques restes dentaires provenant de l eocene superieur de thailande mine de wai lek bassin de krabi et de l oligocene inferieur du pakistan paali nala c2 collines bugti la synthese du registre fossile paleogene holarctique des rhinocerotides revele un net diachronisme des premieres apparitions de rhinocerotides depuis l est amerique du nord vers l ouest asie puis europe au cours du cenozoique moyen la similarite des communautes de mammiferes entre les localites de l eocene superieur et de l oligocene inferieur de thailande peninsulaire de chine du sud et du pakistan suggere l existence d une seule paleoprovince sud asiatique pendant la periode consideree sous un climat tropical a subtropical les changements fauniques enregistres au balouchistan oriental revelent une deterioration climatique significative a partir du milieu de l oligocene aucun indice de provincialisme ou d endemisme n est releve pour les rhinocerotoides oligocenes du sous continent indien ni les himalayas ni le plateau du tibet ne constituaient a l epoque une barriere paleogeographique pour les grands mammiferes

tibetan plateau aridification linked to global cooling at the eocene oligocene transition the eocene oligocene transition about 33 5 million years ago was a major global climate event the end of the eocene was unusually warm with no significant ice on antarctica but the oligocene saw the arrival of a permanent antarctic ice sheet two papers this week relate to the continental effects of this global change dupont nivet et al examined sedimentary records from the tibetan plateau and find a drop in atmospheric water which caused cooling and aridification coincident with antarctic cooling previous studies attributed this phenomenon to the rapid uplift of the tibetan plateau but this new work suggests that regional tibetan climate was influenced by global events in an unrelated paper on the same climate transition zanazzi et al explore the cooling in north america at the time using stable isotope measurements from fossil teeth and bones to create a proxy temperature record they find a large drop in mean annual temperature of 8 2 c a greater fall than seen in the oceans this continental transition may explain why many cold blooded reptiles and amphibians became extinct whereas mammals able to regulate their body temperature escaped relatively unscathed precisely dated evidence details that aridification on the tibetan plateau occurred at the time of the eocene oligocene transition in the marine records this suggests a direct link between the palaeontological and palaeoenvironmental changes recorded in continental asia at the time and global climate cooling continental aridification and the intensification of the monsoons in asia are generally attributed to uplift of the tibetan plateau and to the land sea redistributions associated with the continental collision of india and asia1 2 3 whereas some studies suggest that past changes in asian environments are mainly governed by global climate4 5 6 the most dramatic climate event since the onset of the collision of india and asia is the eocene oligocene transition an abrupt cooling step associated with the onset of glaciation in antarctica 34 million years ago7 8 9 however the influence of this global event on asian environments is poorly understood here we use magnetostratigraphy and cyclostratigraphy to show that aridification which is indicated by the disappearance of playa lake deposits in the northeastern tibetan plateau occurred precisely at the time of the eocene oligocene transition our findings suggest that this global transition is linked to significant aridification and cooling in continental asia recorded by palaeontological and palaeoenvironmental changes10 11 12 and thus support the idea that global cooling is associated with the eocene oligocene transition13 14 15 we show that with sufficient age control on the sedimentary records global climate can be distinguished from tectonism and recognized as a major contributor to continental asian environments

geocenter location and variations in earth orientation using global positioning system measurements we have studied the use of global positioning system gps ground and flight tracking data to measure short period earth orientation variations and changes in earth s center of mass location the geocenter ground based gps estimates of daily and subdaily changes in earth orientation presently show centimeter level precision comparisons between gps estimated earth rotation variations ut1 utc and those calculated from ocean tide models suggest that observed subdaily variations in earth rotation are dominated by oceanic tidal effects our preliminary gps estimates for geocenter location from a 3 week experiment agree with an independent satellite laser ranging estimates to 10 15 cm covariance analysis predicts that temporal resolution of gps estimates for earth orientation and geocenter improves significantly when data collected from low earth orbiting satellites as well as from ground sites are combined the low earth gps tracking data enhance the accuracy and resolution for measuring high frequency global geodynamical signals over time scales less than 1 day low earth orbiters such as topex poseidon carrying gps flight receivers will provide opportunities to demonstrate these enhancements

δ18o and δ13c records from a cenozoic sedimentary sequence in the lanzhou basin northwestern china implications for palaeoenvironmental and palaeoecological changes abstract in northwestern china carbonate 18 o variation has been closely associated with evaporation and precipitation whereas the variation of carbonate 13 c generally reflects patterns of palaeovegetation located within the transitional zone between the chinese loess plateau and the tibetan plateau the lanzhou basin has developed a continuous sequence of cenozoic sediments which have been subjected to detailed sedimentological and high resolution magnetostratigraphic analyses in the present study pedogenic carbonate o and c isotopic analyses were obtained throughout the entire cenozoic sequence the 18 o record exhibits a general positive trend with several abrupt changes a dramatic positive shift in the 18 o record at 33 ma indicates the initiation of the aridification process within the basin which was likely associated with the late eocene westward retreat of the tethys sea and global cooling two significant positive shifts in the 18 o record at 22 ma and 3 5 ma are synchronous with major increases in aeolian dust deposition on the chinese loess plateau and in the north pacific ocean suggesting the intensified aridity of the asian interior which is likely related to the stepwise uplift of the tibetan plateau via the blocking of water vapour pathways the 13 c values exhibit a weak positive trend with a remarkable shift at 3 5 ma this trend is likely related to a decrease in vegetation density in response to the ongoing cenozoic aridification whereas the shift at 3 5 ma may reflect the large scale expansion of c 4 plants