variations in spruce picea sp distribution in the chinese loess plateau and surrounding areas during the holocene based on published pollen data from 44 sites in the loess plateau and surrounding areas we recalculate values of picea abundance digitized from the original diagrams and construct six isopoll maps to reconstruct the distribution of spruce forest at 2000 yr intervals during the holocene spruce forest gradually expanded from about 10 ka bp ago and reached its peak distribution around 8 ka bp it retained its maximum extent between 8 ka bp and 6 ka bp broadly covering the subalpine area and stretching to the valleys of the western loess plateau with high densities and even reaching the edges of the adjacent desert regions after 6 ka bp spruce forest began to retreat to higher elevations this trend was accelerated after 4 ka bp after 2 ka bp it disappeared completely from the loess plateau and most of its surrounding areas precipitation strongly dominated by the asian summer monsoon was the primary controlling factor in the distribution of spruce before 2 ka bp after about 2 ka bp the increasing intensity of human activity became the primary factor in the disappearance of spruce in the loess plateau resulting in an enormous impact on the present landscape

asian summer monsoon changes the pollen flow on the tibetan plateau abstract abundant evidence has revealed that the tibetan plateau s uplift influenced the evolution of the asian summer monsoon system pollen as fine powdery substance which can be easily transmitted by wind currents has great potential to be used as an indicator of the monsoon s intensity and flow direction and used for the detection and evaluation of the ancient monsoon on the tibetan plateau hence it is extremely important and necessary to achieve a better understanding of the modern pollen deposition model on the plateau however most of the previous studies mainly focused on the coupling of surface pollen deposition and regional vegetation and the establishment of the transfer function between pollen vegetation climate on the tibetan plateau but largely neglected the direct correlation of the modern surface pollen deposition and the monsoon s intensity and its current direction we have comprehensively analysed a dataset of the surface pollen on the tibetan plateau and discovered that 1 the surface pollen assemblage can reflect the alpine meadows steppe and desert vegetation which means that surface pollen data can be used to assess the deep time vegetation 2 most of the exotic pollen are from trees the spatial distribution trend of these tree pollen s relative abundance is highly coupled with the path of the asian summer monsoon and the extent to which it encroached on the tibetan plateau these results unambiguously demonstrate that tree pollen deposition on the tibetan plateau is dominated by the asian summer monsoon i e the upslope movement of the modern asian summer monsoon drives the spread of pollen rain from low altitude vegetation to high altitude areas if a similar scenario happened at different stages of the asian summer monsoon evolution and the tibetan plateau uplift the pollen buried in the sediments have the potential to reflect the current direction and intensity of the asian summer monsoon at that time moreover it would provide a simple and potentially practical proxy for the study of the evolutionary history of the asian summer monsoon e g wind direction and intensity under the influence of the plateau s uplift

stable isotope based paleoaltimetry abstractthe quantitative estimation of paleoaltitude has become an increasing focus of earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts as well as the influence of mountain belt growth on regional and global climate the general observation of decreasing 18o and 2h values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation these studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming in this review we provide a theory behind the application of stable isotope based approaches to paleoaltimetry we apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations examples of the application of paleoaltimetry techniques to himalaya tibet and the andes are discussed

sea level reconstructions from the peri vocontian zone south east france point to valanginian glacio eustasy the valanginian is a period of global environmental change as illustrated by sedimentary palaeontological geochemical and climatic perturbations a production crisis in most of the carbonate platforms suggests important changes in palaeoenvironmental conditions during the same time interval a major positive excursion in 13c the weissert event suggests perturbations of the carbon cycle from the latest early valanginian to the early hauterivian in order to better understand the link between these changes sea level fluctuations have been reconstructed in detail from the middle berriasian to the earliest hauterivian sections from the peri vocontian zone south east france have been investigated because of the good quality of outcrops on the carbonate platforms their margins and in the vocontian basin sections ranging from the most proximal zone swiss jura to the basin were interpreted in terms of sequence stratigraphy and cyclostratigraphy and correlated at high resolutions using the identified small medium and large scale sequences as well as depositional geometries sea level fluctuations were reconstructed two main trends are evidenced during the studied interval i the peak amplitude magnitude of the sea level fluctuations increased gradually from the middle berriasian to the early valanginian and reached a maximum more than 50 m from the middle early valanginian to the valanginian hauterivian boundary and ii sea level variations were quite symmetrical during the late berriasian slightly asymmetrical during the early valanginian and strongly asymmetrical fast sea level rise slow fall from the latest early valanginian to the earliest hauterivian moreover three orders of sea level fluctuations were recognized in the sedimentary rocks of the peri vocontian zone platform basin correlations and cyclostratigraphic interpretations of the basinal sections evidence an astronomical control on the sea level variations mainly by the two eccentricity cycles of 100 and 400 kyr the increase in the amplitude of the sea level fluctuations and their change from symmetrical to asymmetrical can be related to the onset of a major cooling event in the early valanginian fast transgressions followed by slower regressions would correspond to waxing and waning of high latitudinal ice during most of the valanginian especially from the latest early valanginian to the latest late valanginian glacio eustatic sea level fluctuations in tune with the 100 and 400 kyr eccentricity cycles are in agreement with glaciations during the valanginian

early miocene climate of central eurasia evidence from aquitanian floras of kazakhstan abstract the rich fossil record in kazakhstan documents that during the oligocene and early miocene this area in central eurasia was densely forested with warm temperate deciduous trees and shrubs of the so called turgayan flora twenty nine fossil floras leaf and pollen assemblages have been selected for a quantitative analysis of the aquitanian early early miocene climate in kazakhstan mean annual temperatures are estimated to have been around 15 c while values of mean annual precipitation are about 1000 mm in combination with several other climate parameters estimated temperatures of the warmest and coldest months precipitation of the wettest driest and warmest months these data reflect uniform climatic conditions over several thousands of square kilometres temperature parameter estimates show slight spatial differentiation with generally cooler mean annual temperatures and higher seasonality i e warmer summers and colder winters in the north eastern part of the study area compared with the southwestern area around lake aral as compared with palaeoclimate estimates for the european and east asian aquitanian the central part of the eurasian continent reveals higher seasonality and slightly increased continentality

magnetostratigraphy and depositional history of the miocene wushan basin on the ne tibetan plateau china implications for middle miocene tectonics of the west qinling fault zone abstract based on field mapping section measurement and magnetostratigraphy 1700 m of sedimentary rocks have accumulated in the wushan basin between 16 ma and 6 ma basin geometry sedimentation characteristics and the early syn depositional deformation along the northern margin of the basin indicate that formation of the wushan basin was related to tectonic deformation along the west qinling fault zone during the middle miocene a series of basins of similar age to the wushan basin were generated along and to the south of the west qinling fault zone while basalts also erupted in this region at this time we suggest that the middle miocene 16 ma may represent a change in kinematics and deformation style in the region along and to the south of the west qinling fault zone at this time there was a transition from nne ssw compressional deformation that dominated the region since the late paleogene to the development of wnw ese and or e w trending strike slip movement and associated transpressional and transtensional activity that continues today the miocene wushan basin may have developed in association with transpression along the west qinling fault zone whether this transition was related to the onset of strike slip along the east kunlun fault and related deformation transfer lower crustal flow or removal of mantle lithosphere the middle miocene provides direct evidence for a change in the kinematic style along the plateau margin

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

locomotive implication of a pliocene three toed horse skeleton from tibet and its paleo altimetry significance the tibetan plateau is the youngest and highest plateau on earth and its elevation reaches one third of the height of the troposphere with profound dynamic and thermal effects on atmospheric circulation and climate the uplift of the tibetan plateau was an important factor of global climate change during the late cenozoic and strongly influenced the development of the asian monsoon system however there have been heated debates about the history and process of tibetan plateau uplift especially the paleo altimetry in different geological ages here we report a well preserved skeleton of a 4 6 million y old three toed horse hipparion zandaense from the zanda basin southwestern tibet morphological features indicate that h zandaense was a cursorial horse that lived in alpine steppe habitats because this open landscape would be situated above the timberline on the steep southern margin of the tibetan plateau the elevation of the zanda basin at 4 6 ma was estimated to be 4 000 m above sea level using an adjustment to the paleo temperature in the middle pliocene as well as comparison with modern vegetation vertical zones thus we conclude that the southwestern tibetan plateau achieved the present day elevation in the mid pliocene

pollen evidence for an eocene to miocene elevation of central southern tibet predating the rise of the high himalaya quantifying the elevation history of the 2000 km wide tibetan plateau to an average elevation of 5 km is important for understanding key aspects of cenozoic global climate change collision tectonics and the evolution of the asian monsoon yet quantitative measures of cenozoic surface height change across tibet remain few and are sometimes contradictory here we report the first exploratory application of a modified co existence approach coa using previously published fossil pollen records to reconstruct quantitatively the cenozoic minimum palaeoaltitudes of gangdise nyainqentanglha area of the tibetan plateau gcm simulations were used to adjust eocene and miocene raw coa values for secular climate change and changes in palaeolatitude this modelled correction increased the coa derived altitudes by 895 96 m to give a minimum overall eocene altitude of 3295 3495 m the miocene correction factor of 481 25 m gave an overall minimum altitude estimate of 3000 3150 m for the holocene coa returns four equally likely elevations of 4800 4950 m 3800 3900 m 3000 3100 m and 2900 3000 m the first of these is indistinguishable from the present day regional average while the others suggest significant upslope pollen transport both the eocene and miocene palynologically derived height estimates are consistent with suggestions of significant core plateau elevation by the eocene but are likely to underestimate the true palaeoelevation due to pre himalayan upslope pollen transport

how old is the asian monsoon system palaeobotanical records from china the recent discovery of monsoon records in early miocene raised a question of the time when the east asian monsoon system initiated a distinguishing feature of the modern monsoon system is its geographic distribution which disturbs the zonal pattern indigenous to the planetary climate system and the appearance of the monsoonal climate pattern in the geological records should signify the onset of the monsoon system here we present the results of a compilation of palaeobotanical and lithological data from 125 sites over china that has revealed two completely different patterns of climate zones the palaeogene pattern with a broad belt of aridity stretched across china from west to east and the neogene pattern with the arid zone restricted to northwest of china which has persisted until today the reorganization of the climate system around the oligocene miocene boundary provides evidence for the establishment of the modern east asian monsoon since then the neogene has witnessed significant variations of the monsoon system including enhancement of aridity and monsoon intensity at about 15 13 my around 8 my and 3 my the new data do not support the onset of the asian monsoon system around 8 my rather the new data led to a hypothesis that the transition to the monsoon climate system in east asia occurred in the latest oligocene

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

multistratigraphic records of the lower cretaceous valanginian cenomanian puez key area in n italy abstract we present a stratigraphic investigation of a hauterivian to cenomanian hemipelagic succession from col puez in the dolomites southern alps northern italy a composite section of seven segments was studied with bio magneto and chemostratigraphy which enabled detailed and robust age calibration of the puez succession it also revealed the paleoceanographic history and helped identify the important global climatic events of that period the age of the lower cretaceous puez formation in the dolomites is refined as late hauterivian to early cenomanian ammonoids provide a detailed biostratigraphic subdivision that forms the basis for analyses of the faunal distribution and the paleoenvironmental evolution of basins and plateaus across the tethys the succession consists of facies similar to those of coeval units in the tethys apart from the late barremian to late aptian interval which is marked by a major hiatus followed by a few meters thick redbed of late aptian age the lower cretaceous was characterized by a weak 1 positive 13c trend punctuated by a positive shift in the late hauterivian corresponding to the faraoni level oxygen isotope values show a decreasing trend from the hauterivian to the albian cenomanian which mirrors a long term increasing trend in paleotemperatures from 15 18 c to 25 30 c this is in agreement with global paleotemperature reconstructions for this period representing the onset of mid cretaceous super greenhouse conditions nonetheless no black shale occurs at the intervals equivalent to aptian albian oceanic anoxic events oae suggesting unique paleoceanographic conditions enhanced current activity on a submarine height on the trento plateau area during the mid cretaceous

magnetostratigraphy of cenozoic sediments from the xining basin tectonic implications for the northeastern tibetan plateau 1 the xining subbasin of the longzhong basin holds the longest continuous cenozoic stratigraphic record at the margin of the northeastern tibetan plateau despite a rich biostratigraphic content including the xiejia mammal fauna the tectonic evolution of the basin is largely unconstrained in this study we present stratigraphic biostratigraphic and magnetostratigraphic results that provide a basis for reconstructing the cenozoic tectonic evolution of the xining basin with respect to adjacent regions of the northeastern tibetan plateau magnetostratigraphic analysis from three red bed sections in the xining basin indicates continuous deposition at low and nearly constant accumulation rates average 2 2 cm kyr from 52 0 to 17 0 ma we interpret this result to indicate that no major regional tectonic event implying large sediment accumulation variations has affected the xining basin deposition during this considerable time window in detail accumulation rate variations outline a three stage evolution with 1 8 cm kyr from 52 0 ma to 34 5 ma 4 1 cm kyr from 34 5 to 31 0 ma and 2 3 cm kyr from 31 0 to 17 0 ma the second order increase between 34 5 and 31 0 ma can be interpreted to result from either a distal tectonic event or to be of climatic origin although the region was tectonically quiescent for much of the cenozoic tectonic activity occurred during basin initiation or reactivation at circa 55 0 52 5 ma and during intense basin deformation after 17 0 ma

forcing of late cenozoic northern hemisphere climate by plateau uplift in southern asia and the american west geologic evidence indicates that net vertical uplift occurred on a large kilometer scale and at accelerating rates during the middle and late cenozoic in plateaus of southern asia and the american west based on this evidence general circulation model sensitivity tests were run to isolate the unique effects of plateau uplift on climate the experiments simulated significant climatic changes in many places some far from the uplifted regions the basic direction of most of these simulated responses to progressive uplift is borne out by changes found in the geologic record winter cooling of north america northern europe northern asia and the arctic ocean summer drying of the north american west coast the eurasian interior and the mediterranean winter drying of the north american northern plains and the interior of asia and changes over the north atlantic ocean conducive to increased formation of deep water the modeled changes result from increased orographic diversion of westerly winds from cyclonic and anticyclonic surface flow induced by summer heating and winter cooling of the uplifted plateaus and from the intensification of vertical circulation cells in the atmosphere caused by exchanges of mass between the summer heated and winter cooled plateaus and the mid latitude oceans disagreements between the geologic record and the model simulations in alaska and the southern rockies and plains may be related mainly to the lack of narrow mountain barriers in the model orography taken together the observed regional trends comprise much of the pattern of late cenozoic climatic deterioration in the northern hemisphere that culminated in the plio pleistocene ice ages the success of the uplift sensitivity experiment in simulating the correct pattern and sign of most of the observed regional climatic trends points to uplift as an important forcing function of late cenozoic climatic change in the northern hemisphere at time scales longer than orbital variations however the modest amplitude of the uplift induced cooling simulated at high latitudes indicates a probable need for additional climatic forcing

dominant control of the south asian monsoon by orographic insulation versus plateau heating heat emitted from the tibetan plateau as dry heat and water vapour has long been assumed to be the main driver of the south asian summer monsoon but new work suggests that in fact it is the neighbouring mountains that are the major influence william boos and zhiming kuang use an atmospheric model to show that flattening the tibetan plateau has little effect on the monsoon so long as the himalayas and surrounding mountain ranges remain the plateau does boost rainfall locally along its southern edge but it is the build up of hot moist air over india insulated from colder drier air by the himalayas that drives large scale monsoon circulation the elevation of the tibetan plateau is thought to cause its surface to serve as a heat source that drives the south asian summer monsoon potentially coupling uplift of the plateau to climate changes on geologic timescales here however an atmospheric model is used to show that flattening of the tibetan plateau has little effect on the monsoon provided that the narrow orography of the himalayas and adjacent mountain ranges is preserved the tibetan plateau like any landmass emits energy into the atmosphere in the form of dry heat and water vapour but its mean surface elevation is more than 5 km above sea level this elevation is widely held to cause the plateau to serve as a heat source that drives the south asian summer monsoon potentially coupling uplift of the plateau to climate changes on geologic timescales1 2 3 4 5 observations of the present climate however do not clearly establish the tibetan plateau as the dominant thermal forcing in the region peak upper tropospheric temperatures during boreal summer are located over continental india south of the plateau here we show that although tibetan plateau heating locally enhances rainfall along its southern edge in an atmospheric model the large scale south asian summer monsoon circulation is otherwise unaffected by removal of the plateau provided that the narrow orography of the himalayas and adjacent mountain ranges is preserved additional observational and model results suggest that these mountains produce a strong monsoon by insulating warm moist air over continental india from the cold and dry extratropics these results call for both a reinterpretation of how south asian climate may have responded to orographic uplift and a re evaluation of how this climate may respond to modified land surface and radiative forcings in coming decades

a late eocene palynological record of climate change and tibetan plateau uplift xining basin china climate models suggest that asian paleoenvironments monsoons and continental aridification were primarily governed by tectonic uplift and sea retreat since the eocene with potential contribution of global climate changes however the cause and timing of these paleoenvironmental changes remain poorly constrained the recently well dated continental mudflat to ephemeral saline lake sedimentary succession situated in the xining basin at the northeastern margin of the tibetan plateau nw china provides a unique opportunity to develop additional proxy successions in this area that are placed accurately in time here a palynological record from this succession is reported high abundances of desert and steppe desert taxa such as ephedripites and nitrariadites nitraripollis are found which can be differentiated by the presence of broad leaved deciduous forest taxa in the lower part of the section particularly up to 36 4 ma magnetochron c16r and a sudden increase of pinaceae pinuspollenites piceaepollenites and abiespollenites which is dated at 36 1 ma c16n 2n coexistence approach coa indicates that from 39 9 to 36 4 ma c17n 1n regional climate was warm and wet while from 36 4 to 33 5 ma c16n 2n c13r climate tends to be cooler and drier the data indicate that paleoenvironmental and palynological changes on the ne part of the tibetan plateau resulted from a combination of long term tectonic uplift forcing and long and short term climate changes the increase of taxa such as piceaepollenites and abiespollenites indicates not only a cooling and drying trend prior to the eocene oligocene e o boundary but also the existence of high altitude mountain habitats in the periphery of the xining basin the sudden pinaceae event correlates closely in time with a marked aridification step as viewed from the lithology of the xining basin that was linked to the sea retreat out of the tarim basin

a new approach to stable isotope based paleoaltimetry implications for paleoaltimetry and paleohypsometry of the high himalaya since the late miocene the change in oxygen isotopic composition of precipitation is modeled using equilibrium fractionation during rayleigh distillation linked to the thermodynamics of atmospheric ascent and water vapor condensation the primary controllers of the vertical variation in isotopic composition with elevation are the low elevation temperature and relative humidity as these control the vertical distribution of condensation an empirical fit of precipitation versus model condensation based on alpine stations is derived this fit is represented in the model as the weighted mean composition of condensation within a 1000 m thick air parcel 1500 500 m above the ground surface and is used for all other regions comparison of model versus observed modern precipitation reveals a close fit particularly of more highly elevated sites comparison of modern waters in the himalayas and southern tibet with model predictions particularly as revealed by comparison of observed and predicted hypsometry provides additional support to the validity of the model finally application of this model to estimates of paleo waters in the himalayas and southern tibet reveals that this region had already achieved its present hypsometry by the late miocene about 10 ma ago fl 2001 published by elsevier science b v

late cenozoic genus fupingopollenites development and its implications for the asian summer monsoon evolution an extinct palynomorph fupingopollenites was used as the basis for a discussion of the late cenozoic asian summer monsoon asm evolution and its possible driving forces based on the spatial and temporal variations in its percentages across inner and east asia we found that fupingopollenites mainly occurred in east asia with boundaries to the ne of ca 42 degrees n 135 degrees e and nw of ca 36 degrees n 103 degrees e during the early miocene ca 23 17 ma this region enlarged westwards reaching the eastern qaidam basin ca 36 degrees n 97 5 degrees e during the middle miocene ca 17 11 ma before noticeably retreating to a region bounded to the nw at ca 33 degrees n 105 degrees e during ca 11 5 3 ma the region then shrank further in the pliocene with the ne boundary shrinking southwards to about 35 degrees n 120 degrees e the area then almost disappeared during the pleistocene 2 6 0 ma the flourishing and subsequent extinction of fupingopollenites is indicative of a narrow ecological amplitude with a critical dependence on habitat humidity and temperature most likely mean annual precipitation map 1000 mm and mean annual temperature mat 10 degrees c therefore the fupingopollenites geographic distribution can indicate the humid asm evolution during the late cenozoic revealing that the strongest asm period occurred during the middle miocene climate optimum mmco similar to 17 14 ma after which the asm weakened coincident with global cooling we argue that the global cooling played a critical role in the asm evolution while the tibetan plateau uplifts made a relatively small contribution c 2015 international association for gondwana research published by elsevier b v all rights reserved

quantitative reconstruction of miocene climate patterns and evolution in southern china based on plant fossils abstract southern china especially yunnan has undergone high tectonic activity caused by the uplift of himalayan mountains during the neogene which led to a fast changing palaeogeography previous study shows that southern china has been influenced by the asian monsoon since at least the early miocene however it is yet not well understood how intense the miocene monsoon system was in the present study 63 fossil floras of 16 localities from southern china are compiled and evaluated for obtaining available information concerning floristic composition stratigraphic age sedimentology etc based on such reliable information selected mega and micro floras have been analysed with the coexistence approach to obtain quantitative palaeoclimate data visualization of climate results in maps shows a distinct spatial differentiation in southern china during the miocene higher seasonalities of temperature and precipitation occur in the north and south parts of southern china respectively during the miocene most regions of southern china and europe were both warm and humid central eurasia was likely to be an arid center which gradually spread westward and eastward our data provide information about miocene climate patterns in southern china and about the evolution of these patterns throughout the miocene and is also crucial to unravel and understand the climatic signals of global cooling and tectonic uplift

late quaternary monsoon patterns on the loess plateau of china china s loess plateau was formed under special conditions the tectonic movement topographical characteristics and monsoon patterns combined to create a favourable environment for the accumulation of thick loessic deposits the loess plateau itself is part of the monsoon triangle of china a region very susceptible to climatic changes throughout the upper pleistocene the palaeoenvironment on the loess plateau alternated from steppe to deciduous forest and coniferous forest in response to shifts in the atmospheric circulation three monsoon patterns appear to be indicated 1 a full glacial monsoon pattern 18000 15000 yr bp which induced a cold and dry climate favouring loess accumulation in steppe conditions 2 an interglacial monsoon pattern last interglacial and holocene in which a warm humid climate prevailed with deciduous forests leaving palaeosols interbedded within the loess sequence and 3 a transitional or interstadial monsoon pattern 50 000 23 000 yr bp in which the climate was cold and humid in the loess plateau encouraging the development of coniferous forest

late cenozoic deformation and uplift of the ne tibetan plateau evidence from high resolution magnetostratigraphy of the guide basin qinghai province china the cenozoic intramontane gonghe guide basin in qinghai province china is tectonically controlled by the sinistral strike slip framework of the kunlun and altyn tagh south qilian faults in the northeastern tibetan plateau the basin is filled with thick cenozoic clastic sedimentary formations which provide important evidence of the deformation of this part of the plateau although they have long lacked good age constraints detailed magnetostratigraphic and paleontologic investigations of five sections in the guide basin and their lithologic and sedimentary characteristics allow us to divide a formerly undifferentiated unit the guide group into six formations where ages are now magnetostratigraphically well established they are given in parentheses the amigang 1 8 2 6 ma ganjia 2 6 3 6 ma and herjia formations 3 6 to ca 7 0 7 8 ma and the older miocene ashigong garang and guidemen formations these rocks document a generally upward coarsening sequence characterized by increasing accumulation rates increasing gravel content and sizes of its components changes of bedding dips and source rock types and marginal growth faults collectively reflect accelerated deformation and uplift of the ne tibetan plateau after 8 ma punctuated by a sharp increase in sedimentation rate at ca 3 2 ma that reflects the boulder conglomerates of the ganjia formation interestingly much of the vergence of the compressional deformation in the basin is to the south accommodated by a sequence of six thrusts f1 f6 which become active one by one progressively later toward the south undoubtedly contributing to the uplift of this part of the plateau f1 likely initiated the guide basin due to crustal flexure in the oligocene f2 was active in the early miocene f4 and f5 at ca 3 6 ma and f6 was active in the early pleistocene the detailed late miocene and younger magnetostratigraphy allows us to place much improved time constraints on the deformation and hence uplift of northeastern tibet which when compared with ages for events on other parts of the plateau provides important boundary conditions for the geodynamical evolution of tibet

paleotemperatures and ice volume of the past 27 myr revisited with paired mg ca and 18o 16o measurements on benthic foraminifera 1 we explore the applicability of paired mg ca and 18o 16o measurements on benthic foraminifera from southern ocean site 747 to paleoceanographic reconstructions on pre pleistocene timescales we focus on the late oligocene through pleistocene 27 0 ma history of paleotemperatures and the evolution of the 18o values of seawater 18osw at a temporal resolution of 100 200 kyr absolute paleotemperature estimates depend on assumptions of how mg ca ratios of seawater have changed over the past 27 myr but relative changes that occur on geologically brief timescales are robust results indicate that at the oligocene to miocene boundary 23 8 ma temperatures lag the increase in global ice volume deduced from benthic foraminiferal 18o values but the smaller scale miocene glaciations are accompanied by ocean cooling of 1 c during the mid miocene phase of antarctic ice sheet growth 15 13 ma water temperatures cool by 3 c unlike the benthic foraminiferal 18o values which remain relatively constant thereafter temperatures vary by 3 c and reach maxima at 12 and 8 5 ma the onset of significant northern hemisphere glaciation during the late pliocene is synchronous with an 4 c cooling at site 747 a comparison of our 18osw curve to the haq et al 1987 sea level curve yields excellent agreement between sequence boundaries and times of increasing seawater 18o 16o ratios at 12 11 ma in particular when benthic foraminiferal 18o values do not support a further increase in ice volume the 18osw curve comes to a maximum that corresponds to a major mid miocene sea level regression the agreement between the character of our mg ca based 18osw curve and sequence stratigraphy demonstrates that benthic foramaniferal mg ca ratios can be used to trace the 18osw on pre pleistocene timescales despite a number of uncertainties related to poorly constrained temperature calibrations and paleoseawater mg ca ratios the mg ca record also highlights that deep ocean temperatures can vary independently and unexpectedly from ice volume changes which can lead to misinterpretations of the 18o record

predicting paleoelevation of tibet and the himalaya from δ18o vs altitude gradients in meteoric water across the nepal himalaya the 18o value of meteoric water varies with elevation providing a means to reconstruct paleoelevation if the 18o values of paleowater are known in this study we determined the 18o values of water 18omw from small tributaries along the seti river and kali gandaki in the nepal himalaya we found that 18omw values decrease with increasing altitude for both transects 18omw vs altitude along the kali gandaki in west central nepal fit a second order polynomial curve consistent with increasing depletion of 18o with increasing elevation as predicted by a rayleigh type fractionation process this modern 18omw vs altitude relationship can be used to constrain paleoelevation from the 18o values of miocene pliocene carbonate 18oc deposited in the thakkhola graben in the southern tibetan plateau paleoelevations of 3800 480 m to 5900 350 are predicted for the older tetang formation and 4500 430 m to 6300 330 m for the younger thakkhola formation these paleoelevation estimates suggest that by 11 ma the southern tibetan plateau was at a similar elevation to modern

the coexistence approach theoretical background and practical considerations of using plant fossils for climate quantification the coexistence approach was established by mosbrugger and utescher 1997 as a plant based method to reconstruct palaeoclimate by considering recent climatic distribution ranges of the nearest living relatives of each fossil taxon during its existence for over more than 15 years its basics have been tested and reviewed in comparison with other terrestrial and marine climate reconstruction techniques and climate modelling data however some controversies remain about its underlying data or its applicability in general in view of these controversies this paper discusses the power and limitations of the coexistence approach by summarising past results and new developments we give insights into the details and problems of each step of the application from the assignment of the fossil plant to the most suitable nearest living relative the crucial consideration of the usefulness of specific taxa towards their climatic values and the correct interpretation of the software based suggested palaeoclimatic intervals furthermore we reflect on the fundamental data integrated in the coexistence approach by explaining different concepts and usages of plant distribution information and the advantages and disadvantages of modern climatic maps additionally we elaborate on the importance of continually updating the information incorporated in the database due to new findings in e g palaeo botany meteorology and computer technology finally for a transparent and appropriate use we give certain guidelines for future applications and emphasize to users how to carefully consider and discuss their results we show the coexistence approach to be an adaptive method capable of yielding palaeoclimatic and palaeoenvironmental information through rime and space c 2014 elsevier b v all rights reserved

middle miocene paleoaltimetry of southern tibet implications for the role of mantle thickening and delamination in the himalayan orogen the stable isotope composition of pedogenic and early diagenetic carbonates from the oiyug basin of southern tibet allows model estimates of the paleoaltimetry of the tibetan plateau for the middle miocene pedogenic calcium carbonate nodules have average d 18 occ values of 219 6 whereas nodular lacustrine dolomites range in composition from 27 6 to 25 5 the most negative of the carbonate isotope values can be used to constrain the oxygen isotope composition of paleoprecipitation from which model estimates of paleoaltimetry can be made model results indicate that the southern tibetan plateau achieved elevations of 5200 11370 2605 m by at least 15 ma our results are identical within uncertainty to previous workers paleoelevation estimates based on oiyug basin fossil floral physiognomy this is the first time that two paleoaltimeters have been directly compared and are in accord collectively these data strongly support tectonic models in which thickening of mantle lithosphere beneath the domain of crustal thickening and subsequent detachment of the mantle lithosphere plays an indiscernible role in the elevation history of this part of the himalaya tibet orogenic system

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

what drove sea level fluctuations during the mid cretaceous greenhouse climate the major states in which earth s climate operates i e icehouse greenhouse and hothouse are epochs of tens of millions of years these states set long term boundary conditions that need to be considered for climate and sea level interpretations this paper summarizes the conceptual models for hydrological cycling derived from the characteristics of these three climate states while glacio eustatic forcing of sea level changes under icehouse climate conditions is fairly well understood the drivers of eustatic sea level fluctuations under greenhouse conditions remain enigmatic this lack of understanding may be related to incoherencies in the current ideas about the impact of accelerated hydrological cycling on sea level under greenhouse climate conditions as an example for a greenhouse climate we review evidences that link proxies for climate and sea level for the intensely studied but controversially discussed mid cretaceous sea level history based on sequence stratigraphy and a recently published high precision timescale we demonstrate that the late middle turonian pewsey 13c isotope maximum represents a major transgression not a regression as previously stated which conflicts with the interpretation of a co occurring 18o maximum to reflect a short glacial episode this contradiction can be solved by the concept presented here that dominance of aquifer eustasy characterized sea level forcing during the turonian greenhouse climate despite a possible though contentious sporadic presence of minor ice sheets the effects of temperature and ice volume both lead to a pronounced 18ocarb maximum during glacio eustatic regressions in contrast the opposing effects of temperature and groundwater volume on oxygen isotope fractionation lead to a 18ocarb maximum during aquifer eustatic transgressions we suggest that throughout earth history both aquifer eustatic and glacio eustatic forcing formed a combined sea level response with dominance of aquifer eustasy being typical for the greenhouse climate mode during the icehouse mode aquifer eustasy apparently remains active as a background process but is outpaced by the glacio eustatic effect

triassic vegetation and climate evolution on the northern margin of gondwana a palynological study from tulong southern xizang tibet china abstract we present vegetation reconstructions based on an almost complete succession through the triassic of tulong nyalam county southern xizang tibet china the permian and earliest triassic samples were barren of palynomorphs however in overlying strata we identified well preserved and diverse miospore assemblages seven pollen and spore zones spanning the olenekian to the rhaetian were recognized these palynological zones were amalgamated into three floral stages that comprise distinct vegetation types 1 an early olenekian lycophyte dominated flora with common pteridosperms indicative of a warm and dry climate 2 a late olenekian transitional flora composed of abundant conifers with low abundances of lycophytes signifying a decrease in temperature and increase in humidity 3 a middle to late triassic mature conifer dominated flora with diverse sphenophytes ferns and cycadophytes indicative of a stable temperate and humid climate the changes in vegetation and climate tentatively correlate with the rifting of northern gondwana suggesting that regional tectonics was a contributive driving factor to local floral community change

cenozoic continental climatic evolution of central europe continental climate evolution of central europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation and winter and summer temperatures although some regional effects occur the european cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments during the last 45 million years continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures correspondingly cenozoic cooling in central europe is directly associated with an increase of seasonality in contrast inferred cenozoic mean annual precipitation remained relatively stable indicating the importance of latent heat transport throughout the cenozoic moreover our data support the concept that changes in atmospheric co2 concentrations although linked to climate changes were not the major driving force of cenozoic cooling

early pliocene paleo altimetry of the zanda basin indicated by a sporopollen record abstract whether the uplift of the tibetan plateau tp led to the origin and development of the indian monsoon is still in dispute a helpful indicator would be greater knowledge about the chronological development of paleo altimetry the zanda basin located on the sw margin of the tp forms one of the most extensive cenozoic sedimentary basins in tibet the modern climate of this area is controlled by the indian monsoon circulation system it is thus an appropriate region for the study of paleo altimetry in addition to research into the relation between the tp and the indian monsoon sporopollen analyses of early pliocene lacustrine strata in the zanda basin show that gymnosperm pollen is dominant av 77 and mainly composed of picea av 27 2 and abies av 24 2 fern spores occupy a lesser proportion av 17 6 while angiosperm pollen including temperate sub tropical broadleaved trees shrubs and herbs accounts for only a small proportion of the assemblage this sporopollen assemblage suggests that sub alpine dark coniferous forests were distributed around the basin and grow in a cool and wet climate rather than in a modern alpine steppe environment these characteristics indicate that the zanda basin s altitude throughout the early pliocene was most probably lower than it is at present

cenozoic climate gradients in eurasia a palaeo perspective on future climate change abstract recent studies in the frame of the neclime neogene climate evolution in eurasia network provide a comprehensive inventory of continental palaeoclimate data for various time slices reconstructed from the palaeobotanical record the integrative analysis of spatial gradients and patterns observed from the proxy data together with data obtained from numeric modelling studies considerably improved our knowledge about the functioning of the climate system in the cenozoic when compared to the present an overall warmer more humid climate existed cenozoic climates are characterized by warm high latitudes shallow latitudinal and longitudinal gradients and wet continental interiors while concentration of greenhouse gases was about at the present day level or considerably higher thus these past climates potentially are valuable to better understand future climate change because they allow empirical access to climate situations that do not or not yet exist today in the present study continental climate data calculated from micro and macrofloras using the coexistence approach are analysed in order to compare past gradients and patterns and their anomalies relative to present day conditions with future climate change scenarios for the case study three time intervals are selected the mid eocene represents a very warm period of the cenozoic exemplifying greenhouse conditions with high atmospheric co 2 of over 1 100 ppmv the mid miocene is known as outstanding warm time interval as well the concentration of greenhouse gases is still controversially discussed but was certainly below the eocene level a third interval selected the tortonian represents a time span of subsequent cooling with the beginning of arctic glaciation for this period a pre industrial co 2 level is assumed it is shown that the study of past climate patterns provides important clues when evaluating modelling results for future scenarios anomalies predicted under global warming partly coincide with the palaeoclimate data sets as an example for greenhouse conditions the mid eocene data also show a strong warming of the high latitudes and a significant positive anomaly of winter temperatures in the continental interior as in the model study for the future scenario however for the tortonian where a pre industrial co 2 can be assumed data show the best agreement with predicted patterns

vegetation and climatic changes of sw china in response to the uplift of tibetan plateau abstract to understand the vegetation succession and climatic changes at the southeastern margin of the tibetan plateau in the neogene we reconstructed the middle miocene vegetation and climate based on palynological data from four localities which are at different latitudes along the ailao mountains in yunnan southwest china the palynological assemblages suggest that the vegetation there was composed of mixed evergreen and deciduous broad leaved forests growing under subtropical conditions based on the palynological data the palaeoclimatic parameters from the four localities are established the new parameters were compared with those of the late miocene of the late pliocene and of today the comparison revealed that the temperatures were obviously lower in the middle miocene than they are today this suggested that the ailao mountains were not high enough to block the asian winter monsoon in the middle miocene the middle miocene vegetation at the southeastern edge of the tibetan plateau was also compared to that of central tibet it would appear that the palaeoclimate at the southeastern edge of the tibetan plateau was warmer and wetter than in central tibet in contrast to the neogene cooling in central europe the climate at the southeastern edge of the tibetan plateau has gradually warmed since the middle miocene this phenomenon was most likely caused by the uplift of the tibetan plateau which has succeeded in blocking the asian winter monsoon since the middle miocene

chronological sequence and subdivision of chinese neogene mammalian faunas six land mammal ages are recognized for the neogene of east asia the ages are based upon updated large and small mammal faunas and replace or redefine the land mammal stages erected by li et al 1984 comparisons and correlations are made to faunas in europe northern and southern asia and north america in addition methods of utilizing mammalian faunal data to define and recognize geochronologic ages are discussed

orbital tuning of a lower cretaceous composite record maiolica formation central italy 1 a high resolution pelagic bulk carbonate stable isotope record from a central tethyan lower cretaceous composite section is presented three well exposed sedimentary sequences chiaserna monte acuto bosso and gorgo a cerbara sections central italy cropping out throughout the maiolica formation were correlated by a detailed magnetostratigraphy lithostratigraphy and calcareous plankton biostratigraphy in order to reconstruct a continuous composite record from the middle berriasian to the lower aptian the integrated stratigraphy of the three sequences provided an accurate time framework for the new high resolution c isotope curve which is presented in this study the composite 13c signal recorded in the depth domain was analyzed by combined lomb scargle periodogram and weighted wavelet z transform wwz weighted wavelet amplitudes wwa foster wavelet spectral methodologies both appropriate for unevenly sampled curves these tools allowed us to unravel the main frequencies modulating the record and their hypothetical shift in depth respectively the long term 400 000 and 2 400 000 years eccentricity cycles were consistently recorded throughout all the composite record once band pass filtered in these two periodicity bands and compared to the lithologic pattern cycles identified throughout the composite sequence the 13c signal was used as a valuable proxy record for a reliable construction of an orbital tuning of the early cretaceous an estimated age for all the different stratigraphic events recognized throughout the composite record was reported in particular the reestimated ages of the paleomagnetic chrons documented in the upper part of the record show differences with those reported by gradstein et al 2004 up to 2 m y the valanginian carbon shift present in the middle part of the composite sequence was estimated to be 2 3 m y long the good agreement between the estimated age of the base of this positive carbon isotope excursion 136 34 m y and the predominant volcanic phase associated to the parana etendeka large igneous province intrusion confirmed a possible cause effect link between the two events

eocene to pliocene exhumation history of the tianshui huicheng region determined by apatite fission track thermochronology implications for evolution of the northeastern tibetan plateau margin abstract this study presents new apatite fission track aft data from the tianshui huicheng region which is situated in the northeastern margin of the tibetan plateau aft results including 19 detrital and 13 bedrock samples show that deposition in the tianshui huicheng basin range from early eocene to late miocene pliocene and most of the apatites derived from the western qinling orogenic belt reflecting one rapid exhumation episode at 34 29 ma and two phases of volcanism at 23 18 ma and ca 13 ma the exhumation history of the tianshui huicheng region is likely related to episodic tectonic activity and directly linked to the kinematics of active deformation of the tibetan plateau active processes deciphered from the detritus indicate that deformation reached the northeastern tibetan plateau margin as early as ca 49 ma which is manifested by the initiation of the tianshui huicheng basin the 23 18 ma event linked to the lithosphere deformation of the western qinling and the neogene basin formation along the tianshui huicheng region by modeling the bedrock samples an 8 4 ma event was revealed which resulted from the intense deformation of the tianshui huicheng region

do fossil plants give a climatic signal the agreement in the pattern of major biomes with that of climatic zonation of the earth gives a strong indication that climate is the overriding influence controlling the distribution of plant communities three aspects of plants which may be preserved in the fossil state give a signal of the climatic conditions under which they grew 1 the present climatic association of their 9nearest living relative9 2 leaf physiognomy of arborescent plants 3 the character of their secondary xylem 9wood9 of ordinary usage reflecting by the presence or absence of growth rings the seasonality or lack of it in their environment and the potential for tree growth that it offered the significance and limitations of these 9palaeoclimatic signals9 as they may be read from the fossil plant record are reviewed and evaluated the recent demonstration that stomatal frequency of leaves is responsive to changes in ambient carbon dioxide partial pressure offers promise for direct palaeobotanical evidence for past changes in the level of this climatically significant atmospheric constituent

relationship between the tibetan plateau heating and east asian summer monsoon rainfall 1 this study reveals the close correspondence between the interannual variability of the dominant east asian summer rainfall pattern and the diabatic heating over the tibetan plateau in both spring and summer the heating fluctuation over the tibetan plateau is associated with two wave like circulation patterns which bear the characteristics of forced rossby wave emanating away from the deep heating the wave like pattern in turn affects the east asian summer rainfall because of the persistent heating over the tibetan plateau from spring to summer and its possible effect on the surrounding areas the heating index defined in this study can be used as a good predictor for the jja heating and precipitation distributions evidences shown suggest that external conditions other than the sst anomaly must be considered to understand the interannual variability of the east asian summer rainfall

sensitivity of climate to late cenozoic uplift in southern asia and the american west numerical experiments experiments with general circulation models with no mountains half mountains and full modern mountains show the sensitivity of atmospheric circulation patterns to progressive amounts of uplift the experiments were motivated by geologic evidence for large kilometer scale uplift in the late cenozoic in southern asia and the american west particularly within the last 10 m y in january the amplitude of the mid latitude upper tropospheric planetary waves increased with uplift and the low level winds were progressively blocked or diverted around the topographic features in july the progressive uplift caused monsoonlike circulations to develop in the vicinity of the colorado and tibetan plateaus atmospheric heating rates midtroposphere vertical motion and upper tropospheric planetary wave amplitudes varied approximately linearly with progressive uplift these results suggest that geologically recent kilometer scale uplift may have had climatic consequences comparable in magnitude and pattern to those of earlier stages of uplift comparison of the simulated climatic effects of uplift with the geologic evidence for late cenozoic climatic change especially for the last 10 m y is given in accompanying papers

late miocene quaternary rapid stepwise uplift of the ne tibetan plateau and its effects on climatic and environmental changes abstract the way in which the ne tibetan plateau uplifted and its impact on climatic change are crucial to understanding the evolution of the tibetan plateau and the development of the present geomorphology and climate of central and east asia this paper is not a comprehensive review of current thinking but instead synthesises our past decades of work together with a number of new findings the dating of late cenozoic basin sediments and the tectonic geomorphology of the ne tibetan plateau demonstrates that the rapid persistent rise of this plateau began 8 1 ma followed by stepwise accelerated rise at 3 6 ma 2 6 ma 1 8 1 7 ma 1 2 0 6 ma and 0 15 ma the yellow river basin developed at 1 7 ma and evolved to its present pattern through stepwise backward expansion toward its source area in response to the stepwise uplift of the plateau high resolution multi climatic proxy records from the basins and terrace sediments indicate a persistent stepwise accelerated enhancement of the east asian winter monsoon and drying of the asian interior coupled with the episodic tectonic uplift since 8 ma and later also with the global cooling since 3 2 ma suggesting a major role for tectonic forcing of the cooling

miocene pollen assemblages from the zeku basin northeastern tibetan plateau and their palaeoecological and palaeoaltimetric implications abstract a comprehensive understanding of the tectonic uplift history of the tibetan plateau tp a 2000 km wide region with a mean altitude of 4000 5000 m above sea level asl is crucial for interpreting global cenozoic climate change collisional tectonics and the evolution of the asian climatic system however the timing degree and extent of the uplift of the tp remain controversial here we report new palynological data from early to mid miocene lacustrine swamp sediments in the zeku basin northeastern tp the palynoflora includes 68 palynotaxa at a family or genus level comprising gymnosperms 16 2 angiosperms 77 9 pteridophytes 2 9 and others 2 9 and is suggestive of a mixed warm temperate forests of coniferous e g picea abies and tsuga and deciduous broadleaved trees e g ulmus zelkova betula and quercus with some subtropical elements e g carya and liquidambar three periods of vegetation succession can be recognized from the caergen section indicating a stepwise warming and drying trend from bottom to top the local palaeoclimatic parameters obtained by applying the coexistence approach coa to palynologic assemblages rendered mean annual temperature mat values of 14 2 16 1 c and mean annual precipitation map values of 797 1113 mm this study departs from the traditional application of the coa relying on published determination of plant climate relationships rather than on data derived from the paleoflora database which is currently not fully open access based on the difference in temperatures between the early to mid miocene and the present day and the temperature lapse rate corrected to take account of miocene global temperature differences the estimated palaeoaltitude of the zeku basin during the early to mid miocene was 1200 1400 m asl this palaeoaltitude estimate suggests that this basin has experienced about 2200 2500 m of uplift since the early to mid miocene findings therefore do not support previous hypotheses that the northeastern tp attained its present altitude before the miocene

tertiary structural evolution of the gangdese thrust system southeastern tibet structural and thermochronological investigations of southern tibet xizang suggest that intracontinental thrusting has been the dominant cause for formation of thickened crust in the southernmost tibetan plateau since late oligocene two thrust systems are documented in this study the north dipping gangdese system gts and the younger south dipping renbu zedong system rzt west of lhasa the gangdese thrust juxtaposes the late cretaceous forearc basin deposits of the lhasa block the xigaze group over the tethyan sedimentary rocks of the indian plate whereas east of lhasa the fault juxtaposes the late cretaceous eocene andean type arc the gangdese batholith over tethyan sedimentary rocks near zedong 150 km southeast of lhasa the gangdese thrust is marked by a 200 m thick mylonitic shear zone that consists of deformed granite and metasedimentary rocks a major south dipping backthrust in the hanging wall of the gangdese thrust puts the xigaze group over tertiary conglomerates and the gangdese plutonics north of xigaze and west of lhasa a lower age bound for the gangdese thrust of 18 3 0 5 ma is given by crosscutting relationships the timing of slip on the gangdese thrust is estimated to be 27 23 ma from 40 ar 39 ar thermochronology and a displacement of at least 46 9 km is indicated near zedong the age of the gangdese thrust gt is consistent with an upper age limit of 24 ma for the initiation of movement on the main central thrust in places the younger renbu zedong fault is thrust over the trace of the gt obscuring its exposure the rzt appears to have been active at circa 18 ma but had ceased movement by 8 1 ma the suture between india and asia has been complexly modified by development of the gts rzt and locally strike slip and normal fault systems

testing the climatic estimates from different palaeobotanical methods an example from the middle miocene shanwang flora of china the miocene shanwang biota from eastern china contains exceptionally well preserved plant fossils with abundant leaf fossils and palynomorphs co occurring at several levels in the sedimentary succession this has provided an ideal opportunity to undertake detailed comparative quantitative palaeoclimate reconstruction based on both mega and microfloral assemblages using various approaches namely the coexistence approach coa leaf margin analysis lma and climate leaf analysis multivariate programme clamp by applying these approaches to the same dataset and using multiple fossil assemblages from different levels we are able to compare results from the different methods of climate prediction clamp and lma give consistently lower temperature mean annual temperature mat predictions than the coa taking errors into account all methods indicate no overall climate change through the sequence studied results from coa show overall agreement in the palaeoclimate parameters obtained using both pollen and leaf datasets indicating a high degree of internal consistency with this method

miocene vegetation and climatic changes reconstructed from a sporopollen record of the tianshui basin ne tibetan plateau abstract the miocene vegetation and climate history of western china remains unclear however widely distributed miocene sediments of the tianshui basin in the ne tibetan plateau provide a great potential for deciphering the miocene vegetation and climate history of this region this paper presents first sporopollen record from these sediments covering the period from 17 1 to 6 1 ma sporopollen data reveal that temperate warm temperate broad leaved forest of quercus ulmus and betula dominated the tianshui region between 17 1 and 14 7 ma which was replaced by forest or forest steppe of ulmus artemisia and betula between 14 7 and 11 7 ma after a return to a broad leaved forest of betula and quercus during 11 7 8 5 ma the forest decreased rapidly and was replaced mostly by steppe vegetation mainly composed of artemisia chenopodiaceae and poaceae after 8 5 ma we interpret the observed vegetation changes as a result of global climate change which is characterized by global cooling development of arctic ice sheets and permanent el nino state after the middle miocene climatic optimum the rapid development of steppe at about 8 5 ma suggested a permanent drying of the asian interior at this time coinciding with the onset of the well known hipparion red clay deposition in north china

the late pliocene palaeoenvironments and palaeoclimates of the western iberian atlantic margin from the rio maior flora abstract using a revised chronology a new palynological study on the late pliocene piacenzian and earliest gelasian rio maior site of the tagus basin in western portugal has been undertaken from the f98 core combining light microscopy and scanning electron microscopy a total of 127 different pollen and spore taxa have been identified from the piacenzian lake and indicate the presence of a subtropical to warm temperate mixed forest during the majority of the piacenzian 3 6 2 8 ma it is only in the latest piacenzian after 2 8 ma that progressive extinctions of climate sensitive taxa and a drop in diversity indicate a cooling and drying climate trend that has also been recorded from high latitude localities by the earliest gelasian 2 58 ma a low diversity ericaceae and pinus dominated vegetation remained the piacenzian flora of rio maior also shows fluctuations in the presence of climate sensitive taxa and pollen spore diversity that may be related to piacenzian glaciations

early miocene vegetation and climate in weichang district north china abstract the early miocene palynological assemblage of guangfayong gfy in the weichang district hebei province china has been studied it consists of 48 palynomorphs belonging to 39 families with pollen and spores belonging to angiosperms 28 9 gymnosperms 59 9 ferns 10 8 and other elements 0 5 based on the palynological assemblages of gfy and wuluogong wlg another locality in the weichang district the early miocene vegetation of the weichang district was characterized by a mixed temperate forest of conifers e g pinus picea tsuga and broad leaved trees e g betula alnus with some subtropical plants e g carya the palaeoclimatic parameters of guangfayong were obtained by applying the coexistence approach the mean annual temperature from 7 8 to 14 9 c the difference of temperature between the coldest and warmest months from 14 2 to 23 c the mean temperature of the coldest month from 3 to 5 9 c the mean temperature of the warmest month from 23 5 to 25 4 c the mean annual precipitation from 658 7 to 1389 4 mm the minimum monthly precipitation from 7 6 to 16 4 mm and the maximum monthly precipitation from 161 4 to 205 9 mm it suggests a warm temperate to subtropical climate in weichang district similar to that of present day zhaojue city sichuan province in the yangtze river valley when the palaeoclimatic parameters were compared with those of middle miocene shanwang basin it would seem that the temperature and precipitation were a little higher in the middle miocene of eastern china however if the latitudinal temperature gradient at that time is considered the median temperature values of gfy of early miocene and shanwang of mid miocene were similar

palaeo altimetry of the late eocene to miocene lunpola basin central tibet the elevation history of the tibetan plateau provides direct insight into the tectonic processes associated with continent continent collisions here we present oxygen isotope based estimates of the palaeo altimetry of late eocene and younger deposits of the lunpola basin in the centre of the plateau which indicate that the surface of tibet has been at an elevation of more than 4 kilometres for at least the past 35 million years we conclude that crustal but not mantle thickening models combined with plate kinematic solutions of india asia convergence are compatible with palaeo elevation estimates across the tibetan plateau

onset of asian desertification by 22 myr ago inferred from loess deposits in china the initial desertification in the asian interior is thought to be one of the most prominent climate changes in the northern hemisphere during the cenozoic era1 2 3 4 but the dating of this transition is uncertain partly because desert sediments are usually scattered discontinuous and difficult to date here we report nearly continuous aeolian deposits covering the interval from 22 to 6 2 million years ago on the basis of palaeomagnetic measurements and fossil evidence a total of 231 visually definable aeolian layers occur as brownish loesses interbedded with reddish soils this new evidence indicates that large source areas of aeolian dust and energetic winter monsoon winds to transport the material must have existed in the interior of asia by the early miocene epoch at least 14 million years earlier than previously thought3 5 regional tectonic changes and ongoing global cooling are probable causes of these changes in aridity and circulation in asia

interactions between environmental change and shallow water carbonate buildup along the northern tethyan margin and their impact on the early cretaceous carbon isotope record 1 the evolution of the early cretaceous northern tethyan carbonate platform was not only influenced by changes in sea level detrital influx and surface water temperature but also by changes in trophic levels we distinguish between phases of carbonate production dominated by oligotrophic photozoan communities and by mesotrophic and eventually colder water heterozoan communities superimposed on this bimodal trend in platform evolution were phases of platform demise for which we provide improved age control based on ammonite biostratigraphy the initial phase of these episodes of platform demise corresponds in time to episodes of oceanic anoxic events and environmental change in general on the basis of a comparison between the temporal changes in an early cretaceous ammonite calibrated d 13 c record from southeastern france and coeval changes in the platform record we suggest that the history of carbon fractionation along the northern tethyan margin was not only influenced by changes in the oceanic carbon cycle such as in the rate of production and preservation of organic and carbonate carbon and in the size of the oceanic dissolved inorganic carbon reservoir but it was also influenced by the above mentioned changes in the ecology and geometry of the adjacent carbonate platform phases of photozoan carbonate production induced positive trends in the hemipelagic carbonate d 13 c record phases of heterozoan carbonate production pushed the d 13 c system toward more negative values platform drowning episodes implied an initial increase in d 13 c values followed by a longerterm decrease in d 13 c values

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

oligocene climate signals and forcings in eurasia revealed by plant macrofossil and modelling results abstract the oligocene represents a transitional time period from a warm climate to a cooler climate that is more representative of the modern day yet a general view of continental climate pattern and forcings are still lacking different proxies and models show striking disparities especially in mid high latitudes requiring validation of oligocene climate reconstruction in order to understand the large scale processes that drive the observed climate changes here we compiled 149 macrofossil floras in the mid high latitudes of eurasia then quantitatively reconstructed the oligocene climate using coexistence approach ca and combined previously published paleoclimate data during the oligocene eurasian mid high latitudes were mainly dominated by a humid subtropical climate mean annual temperature mat ranged between 5 4 c and 25 5 c with mean annual precipitation map ranging from 338 to 2453 mm three regions europe central eurasia and eastern asia indicate different climatic regimes with a generally warmer and wetter climate in europe and a colder and drier climate in central eurasia when compared to eastern asia no significant reorganization of climate was observed between the early and late oligocene the climate anomalies between the oligocene and present indicate that geographic changes e g retreat of the paratethys sea played an important role in shaping the climate pattern of eurasia by comparing the fossil data to a range of different hadcm3l model simulations of the oligocene with differing boundary conditions e g co2 and topography we demonstrate similar large scale climate spatial patterns between models and fossil data however models simulated much higher temperature seasonality lower simulated winter temperatures and higher simulated summer temperatures in eurasia mean annual temperature analysis indicates that simulations with 560 and 1120 ppmv co2 matched better with fossil data when compared to other simulations depending on the topography these results provide some constraints that should be considered for future paleoclimate modelling

the paleoaltimetry of tibet an isotopic perspective stable isotopes provide a valuable perspective on the timing of elevation change of the tibetan plateau we begin our paper by looking in depth at isotopic patterns in modern tibet we show that the 18 o value of surface waters decreases systematically up the himalayan front in central nepal by about 2 8 km in agreement with the patterns documented and modeled by previous research on the tibetan plateau itself there is no apparent correlation between elevation and the 18 o value of flowing surface waters both surface waters and soil carbonates display a northward increase in 18 o values of about 1 5 north of the himalayan crest even though elevation increases modestly the isotopic increase with latitude reduces the isotope elevation gradient for water in the northernmost plateau to 1 to 2 km carbonates in both soils and lakes form at higher temperatures than assumed by previous studies on the plateau temperature estimates from clumped isotope 47 analyses of modern soil carbonates significantly exceed mean annual air t and modeled maximum summer soil temperatures by 15 8 2 8 and 9 7 2 5 c respectively similarly elevated temperatures best account for the 18 o values observed in modern soil and lake carbonates we recalculated paleoelevations from previous studies on the plateau using both higher formation temperatures and latitude corrected isotopic values with one notable exception our revised model produces paleoelevation estimates very close to previous estimates the exception is the reconstruction from late eocene age deposits at xoh xil for which we calculate elevations that are higher and much closer to the current elevation than previously reconstructed therefore there is no evidence for northward progression through time of tibetan elevation change instead the available but admittedly very scanty evidence suggests that much of tibet attained its modern elevation by the mid eocene a truly robust test of the various geodynamic models of uplift await expansion and replication of isotopic records all across tibet especially in the center and north and for 15 ma

low latitude vegetation and climate dynamics at the paleocene eocene transition a study based on multiple proxies from the jathang section in northeastern india abstract we present a multi proxy study of an upper paleocene lower eocene succession from the paleo equatorial region the study is carried out on a coal bearing shallow marine succession exposed at jathang east khasi hills meghalaya northeastern india the succession was deposited in a low energy coastal marsh bay complex dinoflagellate cyst biostratigraphy yields a late paleocene to early eocene age for the section the deposits of the lower part of the succession represent a transgressive systems tract tst defined by seven parasequences each starting with bay sediments deposited during transgression followed by a shallowing upward bay fill marsh deposit in the vertical succession each parasequence acquires an increasingly marine character culminating in a maximum flooding surface at the paleocene eocene boundary it is followed by four shallowing upward parasequences deposited in a highstand systems tract hst enhanced chemical weathering and high terrestrial supply are testified by raised sio2 and al2o3 contents and high percentages of terrestrial palynomorphs the pollen flora recovered from the jathang section was used for quantitative paleoclimate and vegetation reconstructions the coexistence approach was applied based on nearest living relatives nlrs of sixty fossil species recorded at different stratigraphic levels seven climate variables were determined for the fossil assemblages and as a measure of the seasonality of climate the number of dry months was estimated our study shows that during the paleocene there existed warm seasonally dry tropical climate conditions with mean annual temperature at ca 24 26 c and mean annual precipitation at ca 700 1800 mm and with a dry season of 5 6 months particularly warm and wet perhumid climate conditions with 26 27 c and 2200 3200 mm mean annual precipitation with a dry period of 2 3 months were reconstructed for the latest paleocene earliest eocene interval the study shows a distinct vegetational turnover from palm dominated seasonally dry tropical forest during the paleocene to highly diversified dicotyledonous megathermal rainforest during the latest paleocene early eocene the present study demonstrates that the reduced duration of the dry period during the latest paleocene earliest eocene due to a more active hydrological cycle played a major role in determining the climate and shaping the vegetation cover in the paleo equatorial region there is evidence from our data that seasonality of rainfall is the determining factor for the tropical forest vegetation pattern of the equatorial region rather than mean annual rainfall condition as the main trigger for the observed step wise changes of the hydrology along the studied succession the fast northward movement of the indian plate is inferred

high and dry in central tibet during the late oligocene the time at which the tibetan plateau rose to its present high elevation remains controversial with estimates ranging from 40 ma to more recent than 7 ma new stable isotope analyses of modern and accurately dated ancient paleosol carbonate in the nima basin of central tibet point to an arid climate and high paleoelevation 4 5 5 km comparable to today s setting by 26 ma oxygen isotope values of ancient 26 ma soil carbonate are both very negative and indistinguishable after modest corrections for changes in global climate from the lowest least evaporated oxygen isotope values of modern soil carbonates in the area substantial enrichments in oxygen 18 in paleolacustrine carbonates as well as high carbon isotope values from paleosol carbonates indicate considerable lake evaporation and low soil respiration rates respectively and both are consistent with the present arid climate of the nima area blockage of tropical moisture by the himalaya and perhaps the gangdese shan probably has contributed strongly to the aridity and very negative oxygen isotope values of soil carbonate and surface water in the nima area since at least the late oligocene the maintenance of high elevation since at least 26 ma suggests that any flow of lower crust from beneath central tibet must have been balanced by coeval northward insertion of indian crust beneath the plateau