origin of maghaemite in chinese loess deposits aeolian or pedogenic maghaemite and magnetite common ferrimagnetic minerals in surficial soils have physical properties which are similar except for the thermal instability of the former utilising this exception a study of thermomagnetic properties has been made to systematically separate these two magnetic components in loess and palaeosol samples from the upper parts of the luochuan section of the central chinese loess plateau this investigation has shown that although maghaemite thermally unstable component occurs in greater amounts in palaeosols ms 0 0187 am2 kg 1 1 1 than in loess units ms 0 0156 am2 kg 1 1 1 in relative terms its contribution to the ferrimagnetic component of magnetisation is higher in the loess units ms 32 2 2 0 than the soils ms 23 5 3 7 such an observation suggests that much of the maghaemite component originates in the aeolian source area with some addition of pedogenic maghaemite occurring in the palaeosols

greatly expanded tropical warm pool and weakened hadley circulation in the early pliocene the pliocene warm interval has been difficult to explain we reconstructed the latitudinal distribution of sea surface temperature around 4 million years ago during the early pliocene our reconstruction shows that the meridional temperature gradient between the equator and subtropics was greatly reduced implying a vast poleward expansion of the ocean tropical warm pool corroborating evidence indicates that the pacific temperature contrast between the equator and 32 n has evolved from 2 c 4 million years ago to 8 c today the meridional warm pool expansion evidently had enormous impacts on the pliocene climate including a slowdown of the atmospheric hadley circulation and el nino like conditions in the equatorial region ultimately sustaining a climate state with weak tropical sea surface temperature gradients may require additional mechanisms of ocean heat uptake such as enhanced ocean vertical mixing

cool la nina during the warmth of the pliocene the role of el nino southern oscillation enso in greenhouse warming and climate change remains controversial during the warmth of the early mid pliocene we find evidence for enhanced thermocline tilt and cold upwelling in the equatorial pacific consistent with the prevalence of a la nina like state rather than the proposed persistent warm el nino like conditions our pliocene paleothermometer supports the idea of a dynamic ocean thermostat in which heating of the tropical pacific leads to a cooling of the east equatorial pacific and a la nina like state analogous to observations of a transient increasing east west sea surface temperature gradient in the 20th century tropical pacific

preliminary magnetostratigraphy of a thick eolian red clay loess sequence at lingtai the chinese loess plateau magnetic remanence and bulk susceptibility measurements are reported for a 305 m eolian loess red clay sequence at lingtai the chinese loess plateau polarity zonation defined by about 680 remanence data yields a basal age of about 7 05 ma for the section which represents the oldest wind blown dust deposited continuously in north central china during the late cenozoic the resultant magnetostratigraphic scheme implies a nearly linear accumulation rate about 2 98 cm ka of atmospheric dust on the loess plateau during the period of 7 05 to 2 58 ma comparison of the bulk susceptibility record with the pedogenic characteristics of the red clay observed in the field suggests that magnetic susceptibility in the red clay is not as useful as in the loess soil sequence to indicate summer monsoon variations

alkenone and boron based pliocene pco2 records abstract the pliocene period is the most recent time when the earth was globally significantly 3 c warmer than today however the existing pco2 data for the pliocene are sparse and there is little agreement between the various techniques used to reconstruct palaeo pco2 this disagreement coupled with the general low temporal resolution of the published records does not allow a robust assessment of the role of declining pco2 in the intensification of the northern hemisphere glaciation inhg and a direct comparison to other proxy records are lacking for the first time we use a combination of foraminiferal 11b and organic biomarker alkenone derived carbon isotopes proxies to determine the concentration of atmospheric co2 over the past 5 ma both proxy records show that during the warm pliocene pco2 was between 330 and 400 ppm i e similar to today the decrease to values similar to pre industrial times 275 285 ppm occurred between 3 2 ma and 2 8 ma coincident with the inhg and affirming the link between global climate the cryosphere and pco2

bentheimer sandstone revisited for experimental purposes abstract bentheimer sandstone outcrop samples are ideal for laboratory studies due to their lateral continuity and block scale homogeneous nature over the years they have been used to investigate reservoir topics ranging from passive and active properties of oil gas water rock interaction and processes to flow and transport this work shows an evaluation of bentheimer sandstone properties and their characteristics to advance understanding on the mineral accessory and the physical and electrical transport properties on the basis of the nature of depositional environments and diagenesis we measure and characterize spatial attributes of the matrix mainly by qualitative analysis laboratory and stereological measurements and statistical 2d 3d reconstructions the main contribution of this paper is the impact of mineral composition on the petrophysical quality and block scale homogeneity of the reservoir with 3d techniques reconstructions of the new rock grain framework pore structures have been created based on measurements a review of literature data and interpretation of variation between the outcrops and flow relevant parameters we conclude that bentheimer sandstone is a rock that shows constant mineralogy and is largely free of paramagnetic impurities in accordance with the results of 3d reconstructions techniques and in line with the depositional settings they show a well sorted grain framework and a pore network that can be used to calculate the permeability and resistivity without conducting any direct laboratory measurements of either parameter it presents a porosity with a range of 0 21 0 27 and permeabilities varying between 0 52 and 3 02 darcy based on our work and literature it is found that high permeability together with similar distribution of pore throats and bodies make the sandstone an attractive and easy obtainable candidate for comparative experimental studies moreover we state by comparing various techniques that the efficiency and resolution accuracy of the applied method must be taken into consideration when planning the measurements

magnetic susceptibility of loess in china abstract the low field susceptibility of the loess deposits in the chinese loess plateau is due to both paramagnetic and ferromagnetic minerals paramagnetism can be seen in the less to unweathered loess horizons where superparamagnetic contributions which arise from ultrafine magnetite particles are not as strongly developed as in the heavily weathered palaeosols frequency dependent susceptibility and minimum unblocking temperatures of low temperature thermoremanent magnetization generally indicate finer grain sizes in the palaeosols as compared to the loess beds this grain size difference and the fact that susceptibilities of the same stratigraphic palaeosol layer vary by an order of magnitude between the western and central regions of the plateau are considered as strong evidence that the ultrafine magnetite is not of detrital aeolian origin but was formedin situ the pedogenetic processes are clearly related to palaeoclimatic changes therefore the various susceptibility properties may serve for a detailed reconstruction of the continental palaeoclimatic conditions for the last 2 5 ma since the palaeomagnetically dated beginning of loess sedimentation in china

modelling pliocene warmth contribution of atmosphere oceans and cryosphere the relative role of the atmosphere oceans and cryosphere in contributing towards middle pliocene warmth ca 3 ma bp is investigated using the hadcm3 coupled ocean atmosphere general circulation model the model was initialised with boundary conditions from the usgs prism2 data set and a pliocene atmospheric co2 level of 400 ppmv and run for 300 simulated years the simulation resulted in a global surface temperature warming of 3degreesc compared to present day in contrast to earlier modelling experiments for the pliocene surface temperatures warmed in most areas including the tropics 1 5degreesc compared with present day the model predicts a general pattern of ocean warming 1 5degreesc in both hemispheres to a depth of 2000 m below which no significant differences are noted sea ice coverage is massively reduced up to 90 the flow of the gulf stream north atlantic drift is up to 100 mm s 1 greater in the pliocene case analysis of the model predicted meridional streamfunction suggests a global pattern of reduced outflow of antarctic bottom water aabw up to 5 sv a shallower depth for north atlantic deep water formation and weaker thermohaline circulation 3 sv the decrease in aabw occurs mainly in the pacific rather than atlantic ocean model diagnostics for heat transports indicate that neither the oceans nor the atmosphere are transporting significantly more heat in the pliocene scenario rather these results indicate that the major contributing mechanism to global pliocene warmth was the reduced extent of high latitude terrestrial ice sheets 50 reduction on greenland 33 reduction on antarctica and sea ice cover resulting in a strong ice albedo feedback these results highlight the need for further studies designed to improve our knowledge regarding pliocene terrestrial ice configurations

spatial and temporal patterns of grain size and chemical weathering of the chinese red clay formation and implications for east asian monsoon evolution abstract palaeoclimatic interpretation of the red clay in the chinese loess plateau is particularly important for understanding of the east asian monsoon evolution from pliocene to the quaternary in this study a n s transect involving five loess red clay sections across the loess plateau was selected for detailed investigation with analyses of grain size and major element geochemistry in order to address the spatial pattern results indicate that the red clay contains large amount of coarse 16 m fraction and shows a prominent n s decreasing gradient much similar to that of the overlying loess suggesting that the dust transport was dominantly by low level northerly northwesterly winds compared with overlying loess the red clay is markedly fine and rather constant through all the sections implying a distant and steady dust source area about 200 km further north during most of the pliocene time pedogenic leaching intensities inferred from geochemical data display a clear decreasing trend from south to north both for the red clay and the loess suggesting that the modern spatial pattern of the east asian monsoon regime has been maintained at least for the past 5 ma the n s spatial gradient however might be smaller during the pliocene than the quaternary period temporally two short periods of climatic deterioration implied by marked grain size coarsening and low weathering intensity occurred at 5 3 and 3 5 ma respectively which divide the pliocene into two major stages the 5 3 3 5 ma stage is characterized by a steady state climate through the entire region consistent with other records in the 3 5 2 7 ma stage the red clay in the jingbian section shows a noticeable coarsening in grain size than the previous stage indicating some southward extension of the deserts in agreement with mass accumulation rate record in the north pacific but the eolian dust deposition remained relatively stable in major part of the loess plateau until 2 7 ma the red clay deposition was then terminated by massive and coarse loess deposition in the entire region suggesting dramatic intensification of the winter monsoon in response to the onset of extensive glaciation of northern hemisphere

permanent el nino like conditions during the pliocene warm period during the warm early pliocene 4 5 to 3 0 million years ago the most recent interval with a climate warmer than today the eastern pacific thermocline was deep and the average west to east sea surface temperature difference across the equatorial pacific was only 1 5 0 9 c much like it is during a modern el nino event thus the modern strong sea surface temperature gradient across the equatorial pacific is not a stable and permanent feature sustained el nino like conditions including relatively weak zonal atmospheric walker circulation could be a consequence of and play an important role in determining global warmth

wind blown origin of the pliocene red clay formation in the central loess plateau china abstract in order to determine the depositional processes of the pliocene red clay formation deposited directly beneath the plio pleistocene loess in the chinese loess plateau four red clay sections spanning over 400 km are studied grain size analysis of closely spaced samples in the sections shows that the particles of the red clay are very fine with the sand fraction 63 m being negligible and that all the curves indicating changes in different grain size parameters have a similar pattern the grain size records in the upper part of the four sections are almost identical with the median grain size centered at 4 8 m the ree patterns of 28 samples from the jiaxian red clay section are all characterized by lree enrichments relatively flat hree and slight negative eu anomaly being similar to those of eolian loess and the average upper continental crust these lines of evidence point to a wind blown origin of the red clay deposits accumulation of the loess soil sequences in the chinese loess plateau during the past 2 6 ma can be therefore regarded as the continuation of the pliocene atmospheric dust deposition observations of spatial grain size changes in the loess plateau suggest that the eolian red clay might be transported mainly by the westerlies differing significantly from the overlying loess that was transported essentially by the east asia winter monsoonal winds

superparamagnetism of two modern soils from the northeastern pampean region argentina and its paleoclimatic indications summary the magnetic susceptibility carried by pedogenic fine grained ferrimagnets has been widely used as paleoclimatic proxy to elucidate long term paleoclimatic variations for windblown terrestrial loess paleosol sequences however the magnetic properties of the lithogenic parentmaterialcanmaskthepedogenicsignals inthisstudy wesystematicallyinvestigatedthe origin of the superparamagnetism of two modern soils from the northeastern humid pampean region argentina developed on loess materials of different mineralogical composition the samples were treated with the citrate bicarbonate dithionite cbd reagent which is known to dissolve the submicron pedogenic ferrimagnets while leaving unaltered the coarse grained ones the magnetic material accounting for the frequency dependent magnetic susceptibility peak at about 50 k remained in the residuals and is independent of the pedogenic processes in addition pedogenic ferrimagnetic particles in the two soils have a magnetic signature comparable to that of the soils from the chinese loess plateau it is also suggested that the for the bulk samples does not seem to be a reliable paleoclimatic proxy for the pampean soils investigated in this study instead the cbd soluble magnetic signals could be more useful to detect paleoenvironmental variations in this region these new findings provide improved understanding of the magnetic assemblage in the pampean loess soils and make it feasible to retrieve the paleoclimatic signals carried by the pedogenic cbd soluble iron oxides after removing the effects of the lithogenic inputs

estimates of arctic land surface temperatures during the early pliocene from two novel proxies during the pliocene 2 6 to 5 ma ago atmospheric co 2 levels have been estimated as similar to or slightly above present levels tripati et al 2009 pagani et al 2010 and yet earth s climate was considerably different recent evidence suggests that although global temperatures were 2 3 c warmer than pre industrial arctic warming may have been amplified during the pliocene thus precise temperature records of this interval are required to assess the sensitivity of earth s climate to persistent levels of co 2 between 365 and 415 ppm we present records of two independent proxies for terrestrial growing season temperatures at the early pliocene beaver pond site on ellesmere island 18 o values of cellulose from well preserved peat constrain the 18 o values of meteoric water to 20 7 0 3 which we combined with 18 ovalues of aragonitic freshwater molluscs found within the peat in order to calculate mollusc growth temperatures this approach results in an average growing season temperature of 14 2 1 3 c temperatures were independently derived by applying carbonate clumped isotope thermometry to mollusc shells from the same site indicating an average growing season temperature of 10 2 1 4 c a one way anova indicates that the differences between the two techniques are not significant as the difference in mean temperatures between both methods is no different than the difference between individual shells using a single technique both techniques indicate temperatures 11 16 c warmer than present may sept temperature 1 6 1 3 c and represent the first thermodynamic proxy results for early pliocene ellesmere island

spatial patterns of vegetation and climate on the chinese loess plateau since the last glacial maximum abstract in order to identify the spatial patterns of vegetation and climate on the chinese loess plateau since the last glacial maximum lgm pollen analysis was conducted for loess deposits from seven sites which constitute two north south and west east transects across the plateau results show that steppe prevailed both in the lgm and the holocene optimum during the lgm vegetation in the northwest mainly consisted of artemisia echinops type taraxacum type and chenopodiaceae and vegetation in the southeast was characterized by the same types but with a slight increase in poaceae during the holocene optimum vegetation was more diverse with poaceae artemisia echinops type and chenopodiaceae dominant in the northwest and pinus corylus poaceae artemisia and selaginella sinensis dominant in the southeast our records also show that from the lgm to the holocene optimum the presence of echinops type and taraxacum type pollen decreased while poaceae pollen became more prevalent as it has been found that most species of poaceae prefer relatively humid conditions and abundances of echinops type and taraxacum type increase in desert vegetation a new proxy poaceae echinops type taraxacum type ratio p e t was thus developed to compare the spatial differences in climate between the lgm and the holocene optimum with high p e t values indicating relatively warm and wet conditions the p e t ratio shows an overall southward and eastward increase for both the lgm and the holocene optimum furthermore it exhibits a prominent north south and west east gradient during the holocene optimum but displays a flat one during the lgm indicating more pronounced spatial contrasts in climate during the holocene than in the lgm this phenomenon may be attributed to the unique geographic location of the loess plateau which was located in the marginal zone of the east asian summer monsoon during interglacials but was dominated by the winter monsoon during glacials due to a southward displacement of climate zones

pedostratigraphy of chinese loess deposits and climatic cycles in the last 2 5 myr summary the pedostratigraphy and magnetostratigraphy of several sections in the loess plateau of north central china have been investigated and correlated the most complete and distinct loess paleosol sequence occurs in the baoji section of the southern part of the plateau thirty seven pedostratigraphic units are identifiable in the baoji section and correlated with those in other parts of the plateau the sequence represents thirty seven major cold to warm climatic cycles in the last 2 5 myr at about the time of the matuyama gauss magnetic reversal an abrupt climatic event occurred in north china represented by the shift of the well weathered red clay formation below the m g boundary to the alternating loess and paleosol units above marking the beginning of a new epoch in the course of climatic evolution in addition there are two other major shifts of dominant periods of climatic cycles recorded in the loess paleosol sequences one occurring at about 1 5 myr and another at about 0 8 myr the pedostratigraphy of loess deposits in north central china provides an independent measure of the world wide climatic fluctuations and is now the most complete and reliable record of the major climatic cycles in the last 2 5 myr

magnetostratigraphy and sedimentology of the jingchuan red clay section and correlation of the tertiary eolian red clay sediments of the chinese loess plateau a 325 m thick loess and red clay sequence was recently discovered at jingchuan which is situated about 45 km north of the previously studied lingtai section in the middle part of the chinese loess plateau the jingchuan section is composed of 199 m of pleistocene loess and 126 m of tertiary red clay deposits paleomagnetic studies show that the jingchuan red clay has a basal age of at least 7 7 ma which represents the oldest red clay deposits presently known in the loess plateau field observations and grain size analyses both suggest an eolian origin of the red clay thus extending available records of the eolian deposits in the loess plateau from about 7 0 ma to 7 7 ma correlation of both pedostratigraphy and magnetic susceptibility records suggests that the late cenozoic red clay records in the loess plateau have a general continuous nature thereby providing potential for deriving long term climatic evolution signals from this eolian loess and red clay sequence

magnetostratigraphy of the baoji loess paleosol section in the north central china loess plateau the baoji section is judged to be the most complete accessible quaternary loess paleosol section in the north central china loess plateau it is located 5 km north of the city of baoji it contains 37 paleosols and was recently named the type pedostratigraphic section the pedostratigraphic units geosols of the baoji section can be correlated throughout the loess plateau by a combination of magnetostratigraphy and character position and association of pedostratigraphic units magnetic properties were determined from 483 samples taken from 159 m of loess that overlies the red clay formation all major reversals that occurred in the last 2 5 ma were recorded the brunhes matuyama boundary occurs at a depth of 58 5 m within loess unit l8 the jaramillo subchron between 72 0 m in loess unit l10 and 76 4 m in paleosol s11 the olduvai subchron between 125 5 m in loess unit l25 and 131 5 m in loess unit l27 and the gauss matuyama boundary at 157 8 m within loess unit l33 just above the contact with the red clay formation this is the only known site where all major magnetic reversals are clearly defined in distinct field identifiable loess soil units in one section the magnetostratigraphy of the baoji section is thus recommended as the type section for the loess plateau

vegetation and climate changes in the western chinese loess plateau since the last glacial maximum abstract pollen analysis was conducted for loess deposits from three sites in the western chinese loess plateau i e the loess area west of the liupan mountains results show that during the last glacial maximum lgm in situ vegetation was dominated by artemisia and some drought tolerant species such as echinops type chenopodiaceae nitraria and ephedra while coniferous forest mainly picea flourished in nearby river valleys during the holocene optimum picea almost disappeared and echinops type chenopodiaceae nitraria and ephedra decreased vegetation was characterized by artemisia taraxacum type polygonaceae and leguminosae implying the climate was warmer and wetter than during the lgm during the late holocene chenopodiaceae indicator of human managed habitats increased in the study area indicating enhanced human activity the climate was warmer and more humid in the loess areas east of the liupan mountains than in the west during both the lgm and holocene optimum likewise a significant difference in specific plant types was observed between the east and west since the lgm during the lgm pinus and some broadleaf trees emerged but no picea forest grew while in the west vegetation was characterized by desert shrub and desert steppe in situ and by dark coniferous forests mainly picea in nearby river valleys during the holocene optimum treeline advanced upward as a result of increased temperature picea thus withdrew from the western loess areas therefore temperature is the major factor controlling the growth of picea in the chinese loess plateau

a strengthened east asian summer monsoon during pliocene warmth evidence from red clay sediments at pianguan northern china abstract the pliocene epoch 5 3 2 6 ma is the most recent geological interval in which atmospheric co2 levels were similar to those of the present day 400 ppmv this epoch is therefore considered to be the best ancient analog for predicting a future anthropogenic greenhouse world in order to determine the response of the east asian summer monsoon easm rainbelt during pliocene warmth a 71 9 m thick aeolian red clay sequence at pianguan was investigated rock magnetic experiments suggest that magnetite of pseudo single domain size is the dominant remanence carrier in the red clay sequence magnetostratigraphic data constrained by lithostratigraphy show that the polarity zones of the red clay section correlate with those between subchrons c2an 2r and c3an 2n of the geomagnetic polarity time scale gpts yielding an age range of 6 9 2 9 ma the red clay deposits exhibit enhanced weathering intensity over two time intervals namely 5 23 4 3 ma and 3 7 2 9 ma as evidenced by their well developed pedogenic characteristics as well as their high free to total fe2o3 ratios and high redness a values which in turn indicate an increased summer monsoon intensity during most of the pliocene furthermore the pedogenic characteristics of the well weathered pliocene soils were compared with those of paleosol unit s5 one of the best developed soil units found in pleistocene loess from the yulin luochuan and lantian sections which constitute a north south transect across the chinese loess plateau clp the pliocene soils at pianguan show a pedogenic development similar to the s5 0 5 ma at luochuan in the central plateau which is located some 3 7 latitude south of pianguan but this development is much stronger than that observed at yulin in the north and weaker than that seen at lantian in the south this may imply a more northerly penetration 400 km of the monsoon rainbelt during pliocene warmth compared with the pleistocene interglacial period 0 5 ma ago supporting the prediction that the easm rainbelt shifts northward in a warmer world in addition our results show that pliocene warmth was unlikely to have been characterized by a permanent el nino like state but was possibly influenced by a la nina like state

rock magnetism of late neogene and pleistocene deep sea sediments relationship to sediment source diagenetic processes and sediment lithology we use bivariate scatter plots to illustrate variations in selected rock magnetic properties low field susceptibility anhysteretic and isothermal remanence of late neogene and pleistocene deep sea sediments from 16 sites in the arctic ocean north atlantic equatorial atlantic and north pacific ocean and the arabian sea our intention is to examine the ability of the rock magnetic properties to differentiate the sediments according to factors such as lithology geographical area and the dominant mode of terrigenous sedimentation which at these sites is via ice rafting via bottom currents or via eolian processes overall correlations between sediment magnetic properties and gross lithology is poor and factors such as the source and transport path of terrigenous sediment and detrital magnetic minerals together with the action of reductive diagenetic processes are the major controls on the magnetic properties on the bivariate scatter plots sites with major ice rafted contributions tend to have high sedimentary ferrimagnetic mineral concentrations relatively coarse ferrimagnetic grain sizes and scattered sample point distributions in contrast sites where we infer significant bottom current supply of terrigenous material have tightly grouped sample point distributions carbonate sediments in which the terrigenous component is supplied by eolian processes tend to have a broad range of magnetic mineral concentration caused by glacial interglacial fluctuations in carbonate accumulation and eolian activity sediments containing significant volcanogenic material have high concentrations of relatively coarse grained ferrimagnetic material reductive diagenesis is a significant determinant of sediment magnetic properties in high productivity areas and has the effect of preferentially removing the fine grained ferrimagnetic fraction causing a coarsening of the ferrimagnetic grain size distribution and a rise in the antiferromagnetic ferrimagnetic ratio

iron geochemistry of loess and red clay deposits in the chinese loess plateau and implications for long term asian monsoon evolution in the last 7 0 ma abstract recently some groups of authors have demonstrated that the tertiary red clay deposits underlying the pleistocene loess paleosol sequence in the chinese loess plateau are wind blown in origin thus extending the eolian record in the plateau from 2 6 ma back to about 7 0 ma and providing a good opportunity to reconstruct long term monsoon changes as magnetic susceptibility the widely used paleomonsoon proxy of loess deposits is problematic in reconstructing the monsoon history recorded in the red clay the development of other proxies is urgently needed in this study we analyzed the ratios of citrate bicarbonate dithionite cbd extractable fe2o3 to total fe2o3 concentrations in four loess sections along a north south transect of the loess plateau and in the lingtai loess red clay sequence of 305 m thick the fe2o3 ratio in the loess sections clearly shows higher values in soil units than in loess horizons and a southward increase in this ratio is also remarkable along the transect these are in good agreement with the temporal spatial variations in the east asia summer monsoon intensity identified by other monsoon proxies and soil development observations the fe2o3 ratio thus attests to being a good proxy indicator of the summer monsoon evolution the lingtai fe2o3 ratio record shows high values over three time intervals 4 8 4 1 ma 3 4 2 6 ma and during the interglacial periods of the past 0 8 ma the increase in summer monsoon intensity over the three intervals also coincides with the well developed soil characteristics it is therefore concluded that the east asia summer monsoon has experienced a non linear evolution since the late miocene the occurrence of a monsoon prime at about 4 8 4 1 ma implies that the tibetan plateau one of the most important boundary conditions in maintaining the monsoon circulation must have been uplifted to a critical height at that time

a new magnetostratigraphic framework for late neogene hipparion red clay in the eastern loess plateau of china abstract mammalian fossils especially the hipparion fauna found in the red clay of the loess plateau are of immense value for reconstructing late neogene paleoecology and paleoclimatology in northern china the lack of a precise chronological framework for these fossil sites has impeded our understanding of the evolution of the chinese mammalian fauna their correlation with european mammalian units and the retrieval of paleoclimatic information in this study a field survey of regional stratigraphy in the baode area of shanxi was carried out and three profiles tanyugou yangjiagou i and yangjiagou ii of late neogene deposits were selected for detailed investigation a new chronological framework of the late neogene sequences in the baode area is established by means of paleomagnetism our results show that the red clay accumulation in the baode area began at least 7 23 ma ago deposition continued to the superposed jingle formation the most continuous and complete exposure of the jingle formation known to date was identified and dated to 2 72 5 34 ma a lithological distinction between the jingle formation and the underlying baode formation forms a clear boundary in the red clay that is not coincident with the miocene pliocene boundary documented elsewhere three rich fossil layers are found in the yangjiagou ii profile and dated to 6 43 6 54 ma 6 83 6 86 ma and 7 15 7 18 ma respectively with the application of three different demagnetization techniques the matuyama gauss geomagnetic reversal boundary was identified in a transitional unit between loess and typical red clay deposits a lock in depth of as large as 6 8 m corresponding to ca 65 ka was inferred but remains unexplained

carbonate leaching processes in the red clay formation chinese loess plateau fingerprinting east asian summer monsoon variability during the late miocene and pliocene 1 high resolution variations in carbonate minerals from the jiaxian red clay section located at the northern limit of the present east asian summer monsoon easm on chinese loess plateau were quantified using fourier transform infrared spectroscopy we analyzed a large quantity of sediments dated from the late miocene to pliocene 8 2 2 6 ma the carbonates in this interval show high frequency variations alternating between leached and calcareous horizons the low carbonate contents and high values of magnetic susceptibility and high rb sr ratios were found in the leached zones a pattern that is consistent with that observed in the overlying quaternary loess paleosol sequences this pattern suggests that east asian monsoon eam rainwater enhanced leaching and accumulation processes of carbonate minerals in the red clay formation in a way similar to the loess paleosol sequence seven alternating leached and calcareous zones are identified suggesting oscillations of the easm and east asian winter monsoon intervals the calcareous zones were also found to have high zr rb ratio these indications of shifts from a strong easm to east asian winter monsoon dominance correlate well with the cooling transition indicated by deep sea 18o isotopes this evidence suggests that the eam was active during the late miocene and pliocene and was similar to the quaternary monsoon the presence of a strong eam during the pliocene warm period also raises questions about the hypothesis that past and future warm climate conditions could produce a permanent el nino like state

new contributions to chinese plio pleistocene magnetostratigraphy abstract a new collection of over 500 orientated hand samples of which 180 are red clays from a 195 m loess red clay section near xian 109 12 e 34 12 n china has been dated by magnetic stratigraphy biostratigraphic and previous magnetostratigraphic investigations gave a maximum age for the chinese loess of 2 4 ma implying that the underlying red clay formation is pliocene in age the present study yields a clearly defined magnetic polarity stratigraphy in good agreement with a polarity time scale developed by earlier workers an interpretation of this magnetostratigraphy suggests a basal age for the loess series in this region of 2 5 ma and a minimum age for the base of the red clay formation which is also the base of the section of 5 0 ma

strengthened east asian summer monsoons during a period of high latitude warmth isotopic evidence from mio pliocene fossil mammals and soil carbonates from northern china the east asian monsoons have fluctuated in concert with high latitude warmth during the past several hundred thousand years with humid summer monsoon dominant climates characterizing warm intervals including interglacials and interstadials and arid winter monsoon dominant climates characterizing cool intervals including glacials and stadials of the states comprising the mid pleistocene to recent climatic regime interglacials are most similar in terms of high latitude ice volumes and temperatures to those extant during the late miocene and early pliocene thus an important question is whether mio pliocene climates in northern china were analogous to a hypothetical prolonged interglacial state with increased summer monsoon precipitation and expansion of forest and steppe environments at the expense of desert environments we utilize new and previously published carbon isotopic data from fossil teeth and soil carbonates to place constraints on paleovegetation distributions and to help infer the behavior of the monsoon system between 7 and 4 ma we find that plants using the c 4 photosynthetic pathway which today are largely grasses found in regions with warm season precipitation were present in northern china by late miocene time demonstrating that the c 4 expansion in china was not significantly delayed compared to the global c4 event during the late miocene early pliocene interval soil carbonate and tooth enamel 13 c data indicate 1 that nearly pure c 3 plant ecosystems existed in the southern chinese loess plateau clp and therefore ecosystems there were dominated by woody dicot herbaceous dicot or cool season grass vegetation or a combination of these and 2 that the clp was characterized by a pattern of northward increasing c 4 vegetation and aridity utilizing a broadened conceptual model for interpreting 13 c data and citing independent faunal floral and lithostratgraphic data we suggest that these patterns reflect northward expansion of forest and steppe ecosystems and relatively humid monsoon climates during the late miocene and early pliocene an important implication of this interpretation is that the forcing mechanism illuminated by the temporal correlation during the pleistocene between warm high latitudes and strong east asian summer monsoons is a robust feature of the eurasian tectonic climatic system that predates the plio pleistocene climatic reorganization

vegetation and climate changes during three interglacial periods represented in the luochuan loess paleosol section on the chinese loess plateau studies of vegetation successions related to climate changes during previous interglacial periods provide important insights into the mechanisms of climate change during the current interglacial and enable predictions of future climate impacts on ecosystems the chinese loess plateau clp which is particularly sensitive to climate warming presents an excellent site for such studies however few detailed records exist of vegetation and climate variations during interglacial periods on the clp this study obtained a series high resolution pollen records from the luochuan loess paleosol section on the clp and the paper discusses the vegetation and climate histories during three previous interglacial periods mis 9 mis 7 and mis 5 the artemisia chenopodiaceae steppe vegetation that covered this area between 342 ka and 312 ka changed to humulus chenopodiaceae steppe between 312 ka and 302 ka and then reverted to artemisia chenopodiaceae steppe after 302 ka from 250 ka to 237 ka the vegetation type remained artemisia chenopodiaceae steppe and then changed to artemisia humulus steppe between 237 ka and 227 ka between 227 ka and 195 ka the vegetation returned to artemisia chenopodiaceae steppe during mis 5 vegetation of the study area changed from pinus rosaceae chenopodiaceae forest steppe between 129 ka and 117 ka to artemisia humulus ranunculaceae steppe from 117 ka to 96 ka after 96 ka the vegetation types changed to pinus betula chenopodiaceae forest steppe comparing these pollen records with other climatic proxies from the clp and the oxygen isotope records from the pacific ocean suggests that vegetation and climate change features around the study site were synchronous with east asian monsoon variations near 65 n the regional tectonic uplift probably provided only a subordinate influence on vegetation and climate variation on the clp during mis 5