holocene relative sea level change and rate of sea level rise from coastal deposits in the toyooka basin western japan this study presents relative sea level rsl change from 11 200 to 500 cal bp in the toyooka basin western japan diatom assemblage and sedimentary sulfur analyses were performed for 32 sediment

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

mineralogical evidence of reduced east asian summer monsoon rainfall on the chinese loess plateau during the early pleistocene interglacials the east asian summer monsoon easm is an important component of the global climate system a better understanding of easm rainfall variability in the past can help constrain climate models and better predict the response of easm to ongoing global warming the warm early pleistocene a potential analog of future climate is an important period to study easm dynamics however existing monsoon proxies for reconstruction of easm rainfall during the early pleistocene fail to disentangle monsoon rainfall changes from temperature variations complicating the comparison of these monsoon records with climate models here we present three 2 6 million year long easm rainfall records from the chinese loess plateau clp based on carbonate dissolution a novel proxy for rainfall intensity these records show that the interglacial rainfall on the clp was lower during the early pleistocene and then gradually increased with global cooling during the middle and late pleistocene these results are contrary to previous suggestions that a warmer climate leads to higher monsoon rainfall on tectonic timescales we propose that the lower interglacial easm rainfall during the early pleistocene was caused by reduced sea surface temperature gradients across the equatorial pacific providing a testable hypothesis for climate models

oxygen isotope record of paleorainwater in authigenic carbonates of chinese loess paleosol sequences and its paleoclimatic significance abstract oxygen isotopic compositions of rhizoconcretions and land snail shells were measured to reconstruct the 18o profiles of paleorainwater 18op for well dated loess paleosols in luochuan china to assess the paleoclimatic significance of 18op factors that control the spatial and temporal 18o variations of rainwater in east asian monsoon regions were investigated modern records indicate that the spatial 18o variations of modern rainwater 18om are closely related to near surface temperature t and the amount of precipitation p in order to separate the effects of t and p on the 18om a linear relationship between 18om t and the natural logarithm of p is established by multiple regressing analyses 18 o m 1 070 0 326 t 2 041 ln p the 18o of paleorainwater over the past 130 ka in luochuan area is calculated by the modern spatial 18o t p relationship using estimated t and p from other paleoclimate records the calculated 18o match well to those reconstructed from the authigenic carbonates which implies that the spatial and temporal 18o variations of rainwater in east asian monsoon regions have similar 18o t p relationships and the authigenic carbonates in chinese loess paleosol sequences can serve as valid records of 18op as an application of the 18o t p relationship p variation in the past 130 ka in luochuan was evaluated the reconstructed p is in good agreement with other studies using different approaches our results suggest higher precipitation in marine isotope stages 1 3 and 5 reflecting intense summer monsoon influences during these periods of time

partly pedogenic origin of magnetic variations in chinese loess quaternary sequences of interbedded aeolian silts loess and buried soils palaeosols potentially provide one of the best terrestrial records of past climates1 5 magnetic susceptibility variations in loess and palaeosol sequences from china are strongly correlated with climate induced fluctuations of oxygen isotope ratios in deep sea sediments2 4 6 8 as an explanation of this correlation it has been suggested that the recorded variations in magnetic susceptibility depend primarily on the degree of dilution by non magnetic bulk loess constituents of a uniform magnetic assemblage derived from remote but unknown sources6 8 it has also been suggested that such a model involving changes in the accumulation rate of loess superimposed on a constant flux of magnetic particles provides a relative geological timescale through the control of loess deposition by astronomically modulated climate fluctuations7 here we report a preliminary test of this model using rock magnetic properties especially sensitive to variations in magnetic grain size our results show that palaeosols are characterized by much finer magnetic grain size assemblages than are the intervening loess units this suggests that a simple model based on constant magnetic influx and dilution by variable amounts of non magnetic loess is inadequate our magnetic measurements establish the close comparability of the fine grained magnetic minerals in the palaeosol samples to those in contemporary soils and thus point to a partially pedogenic origin for the magnetic mineral assemblages in the palaeosols

morphological characters and multi element isotopic signatures of carbonates from chinese loess paleosol sequences abstract morphological characters and multi element isotopic compositions of carbonates from the loess paleosol sequences in northwestern china are examined to explore the origin of the minerals samples are collected from various sections ranging from holocene to 0 9 ma within the sequences and fractions with grain sizes 45 and 45 m exhibit an almost perfect spherical shape while those 13 c and 18 o values between minerals and biologically originated samples indicates that the 206 pb 204 pb 207 pb 204 pb 208 pb 204 pb and 87 sr 86 sr these results suggest the utility of fine carbonate particles in the soil profile in reconstructing a potentially higher resolution 13 c and 18 o time series to elucidate the paleoclimatic fluctuation in the chinese loess plateau during pleistocene the discovery of the nano rod calcite in chinese loess together with previous findings of the similar mineral form in asian dust strongly suggests the possibility that these highly reactive caco 3 form may alter the aerosol properties during transport

origin of strontium and calcium in pedogenic needle fibre calcite nfc abstract strontium sr and calcium ca isotopic compositions and sr ca ratios have been analysed in different fractions of pedogenic needle fibre calcite nfc from the swiss jura mountains villiers neuch tel switzerland in order to determine their ca sources and to investigate the potential role of fungi in the origin of nfc 87sr 86sr ratios have been measured to trace the ca trapped within different pedogenic carbonate this ratio was compared for previously identified microscopic morphological groups of nfc the bulk soil fine earth

late quaternary climate in southern china deduced from sr nd isotopes of huguangyan maar sediments abstract the hydro climatic conditions that prevailed during the last glacial and early to mid holocene periods in south china are inferred from chemical compositions and sr nd isotope ratios of sediments from lake huguangyan maar and its vicinity the lake sediments are comprised of organic matter volcanic materials and aeolian input from nearby granitoid derived soils variations in 87sr 86sr ratios in the lake sediments indicate two modes of climate conditions wet intervals during which the lake sediments are mainly derived from the volcanic lake rim materials expressed in low 87sr 86sr ratios and dry intervals during which fine particles from the nearby granitic soils are windblown to the lake and supply local dust expressed in high 87sr 86sr ratios in the sediments these wet and dry intervals generally correspond to regional climate records e g speleothem 18 o profiles in southeast china and correlate with global climate events e g heinrich events while 18 o records of speleothems from southeast china caves are dominated by the precession signal the huguangyan maar sr record mainly correlates with obliquity this most likely reflects masking of the precession signal due to regional climate variability accentuating the obliquity signal these local effects may also account for some of the differences that have been observed between the various east asian monsoon records more importantly the masking of the precession signal reveals the direct influence of obliquity on the hydro climate regime in south china

variation of rb sr ratios in the loess paleosol sequences of central china during the last 130 000 years and their implications for monsoon paleoclimatology abstract rb sr and magnetic susceptibility have been measured in the last interglacial glacial loess profiles at luochuan and huanxian central china a high degree of similarity between the parameters in both profiles suggests that variations of rb sr ratios in the sequence can be regarded as an indicator of east asian summer monsoon strength matching the rb sr record with the specmap 18o curve suggests that the rb sr ratio responds sensitively to changes of the east asian monsoon induced by global ice volume variation

ice volume forcing of east asian winter monsoon variations in the past 800 000 years particle size measurements of some typical loess soil samples taken in different localities of the chinese loess plateau demonstrate that the grain size ratio of 10 m can be used as an indicator of variations in intensity of the east asian winter monsoon winds grain size curves of the baoji and weinan sections show that this proxy indicator is very sensitive to loess soil alterations analytical results also suggest that during soil forming periods eolian dust accumulation was still substantial and hence loess deposition can be regarded as a nearly continuous process during the quaternary period in this study we compared the baoji grain size time series with the specmap marine isotope record with the objective of elucidating the dynamic linkage between changes in global ice volume and the winter monsoon circulation both records show good agreement at both time and frequency domains in particular the winter monsoon variations are also dominated by a 100 000 yr period over the past 800 000 yr it is thus inferred that direct local insolation forcing could be less important in driving the east asian winter monsoon variability and alternatively variations in glacial age boundary conditions may have played a key role in modulating and pacing its strength and timing

integrated summer insolation forcing and 40 000 year glacial cycles the perspective from an ice sheet energy balance model although the origins of the 40 000 year glacial cycles during the early pleistocene are readily attributed to changes in earth s obliquity also having a 40 000 year period the lack of ice volume variability at precession periods 20 000 years is difficult to reconcile with most parameterizations of the insolation forcing it was recently proposed that precession s influence on glaciation is muted because variations in the intensity of summer insolation are counterbalanced by changes in the duration of the summertime but no climate model has yet been shown to generate obliquity period glacial cycles in response to the seasonal insolation forcing here we present a coupled ice sheet energy balance model that reproduces the seasonal cycle and when run over long time periods generates glacial variability in response to changes in earth s orbital configuration the model is forced by the full seasonal cycle in insolation and its response can be understood within the context of the integrated summer insolation forcing the simple fact that obliquity s period is roughly twice as long as that of precession results in a larger amplitude glacial response to obliquity however for the model to generate almost exclusively obliquity period glacial variability two other conditions must be met first the ice sheet s ablation zone must reside poleward of 60 n because insolation intensity is more sensitive to changes in earth s obliquity at high latitudes second the ablation season must be long enough for precession s opposing influences on summer and fall insolation intensity to counterbalance one another these conditions are consistent with a warm climate and a thin ice sheet where the latter is simulated as a response to subglacial sediment deformation if a colder climate is prescribed or in the absence of basal motion ice sheets tend to be larger and undergo greater precession period variability in keeping with proxy observations of late pleistocene glaciation

determination of temperature dependent stable strontium isotope 88sr 86sr fractionation via bracketing standard mc icp ms stable strontium isotopes here 88sr 86sr are introduced as a new member of the nontraditional stable isotopes we have developed a bracketing standard method for the determination of 88 86sr using an axiom mc icp ms and normalizing to strontium srm nbs987 for individual measurements the external reproducibility is better than about 25 ppm 1 rsd for the iapso seawater standard a 88 86sr value of 0 381 0 010 2sem was determined for the first time a temperature dependent strontium isotope fractionation during calcium carbonate precipitation could be shown aragonite samples inorganically precipitated under temperature control between 10 and 50 c revealed a 88 86sr temperature dependency of 0 0054 5 c r2 0 987 in contrast for natural coral samples pavona clavus from a proxy calibration study 23 to 27 c we did determine 0 033 5 c r2 0 955 the processes causing this sixfold stronger temperature dependency for the natural coral samples have to be studied in more detail in future studies in a first approach the different slopes can be interpreted as effects of kinetic fractionation of strontium ions with or without a hydrate shell of 22 to 29 water molecules

registration of precession signal in the last interglacial paleosol s1 on the chinese loess plateau solar insolation plays an essential role in driving orbital scale east asian monsoon eam variability unlike chinese speleothem 18o records characterized by dominant precessional cycles many loess proxies from the chinese loess plateau clp usually display damped precessional scale variability to reconcile the precessional monsoon variability recorded in two classic archives it s critical to investigate which factor can significantly affect the sensitivity of loess proxies to precessional forcing in this study we synthesize grain size gs and magnetic susceptibility results of 18 paleosol s1 profiles over the clp with effort to evaluating the relative impacts of sedimentation rate sr and pedogenesis on the precessional signal intensity psi during the last interglaciation based on unified grain size age models amplitude contrast between normalized gs and variations of five substages of the last interglaciation is employed to infer the psi the results indicate that precessional signals are evident in the gs records of the high sr loess profiles on the northern and western clp comparison of the psi variations with the sr and mean annual precipitation map changes suggests that the gs psi is positively correlated to the sr changes while the psi is negatively positively related to the sr map changes our results confirm that distinct precessional cycles in high resolution loess proxies permit a plausible reconciliation of monsoon variability recorded in chinese loess and speleothem

tracing changes in monsoonal precipitation using mg isotopes in chinese loess deposits abstract the widespread aeolian deposits on the chinese loess plateau clp have been investigated intensively as an outstanding archive of information on past variations of the east asian monsoon eam however differentiating the impacts of precipitation and temperature on loess based proxies is difficult and complex which hampers our ability to understand the variability and dynamics of the eam in this study we investigated the mg isotope composition 26mg of the secondary carbonates in fine grained loess samples from ten holocene profiles and a loess paleosol sequence as well as in the primary carbonates of nine loess source samples from the asian inland deserts our aim was to explore the potential of the 26mg values of secondary carbonates in tracing precipitation changes the results demonstrate that 26mg values are homogeneous 2 07 in primary carbonates from different loess sources but display large variations in secondary carbonates of loess increasing from 3 33 in the northwest clp to 1 80 in the southeast clp and from 3 58 during the last glacial to 1 65 during the last interglacial the variations were mainly controlled by eam precipitation via the migration of isotopically light mg because mg isotope fractionation during the formation of secondary carbonates is temperature insensitive and the primary carbonate in different loess sources has relatively constant 26mg values this conclusion is further supported by high correlation r2 0 84 between modern mean annual precipitation map and 26mg in the secondary carbonates of spatial loess samples based on this 26mg map relationship temporal variations in map were quantitatively estimated ranging from 670 mm during the last interglacial to 270 mm during the last glacial at the southern clp compared with previous estimates our map exhibits a larger amplitude of glacial interglacial fluctuations 400 mm with a less uncertainty 53 76 mm implying that 26mg values in secondary carbonates of loess can serve as a novel precipitation proxy to infer eam variability and dynamics

ice age terminations 230th dated oxygen isotope records of stalagmites from sanbao cave china characterize asian monsoon am precipitation through the ends of the third and fourthmost recent ice ages as a result am records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments establishing the timing and sequence of major events in all four cases observations are consistent with a classic northern hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets meltwater and icebergs entering the north atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon causing increases in atmospheric co2 and antarctic temperatures that drive the termination in the southern hemisphere increasing co2 and summer insolation drive recession of northern ice sheets with probable positive feedbacks between sea level and co2

the clumped isotope geothermometer in soil and paleosol carbonate we studied both modern soils and buried paleosols in order to understand the relationship of temperature t c 47 estimated from clumped isotope compositions 47 of soil carbonates to actual surface and burial temperatures carbonates from modern soils with differing rainfall seasonality were sampled from arizona nevada tibet pakistan and india t c 47 obtained from these soils shows that soil carbonate forms in the warmest months of the year in the late morning to afternoon and probably in response to intense soil dewatering t c 47 obtained from modern soil carbonate ranges from 10 8 to 39 5 c on average t c 47 exceeds mean annual temperature by 10 15 c due to summertime bias in soil carbonate formation and to summertime ground heating by incident solar radiation secondary controls on t c 47 are soil depth and shading site mean annual air temperature maat across a broad range 0 30 c of site temperatures is highly correlated with t c 47 from soils following the equation maat c 1 20 t c 47 0 21 72 r 2 0 92 where t c 47 0 is the effective air temperature at the site estimated from t c 47 the effective air temperature represents the air temperature required to account for the t c 47 at each site after consideration of variations in t c 47 with soil depth and ground heating the highly correlated relationship in this equation should now permit mean annual temperature in the past to be reconstructed from t c 47 in paleosol carbonate assuming one is studying paleosols that formed in environments generally similar in seasonality and ground cover to our calibration sites t c 47 0 decreases systematically with elevation gain in the himalaya following the equation elevation m 229 t c 47 0 9300 r 2 0 95 assuming that temperature varied similarly with elevation in the past this equation can be used to reconstruct paleoelevation from clumped isotope analysis of ancient soil carbonates we also measured t c 47 from long sequences of deeply buried 5 km paleosol carbonate in the himalayan foreland in order to evaluate potential diagenetic resetting of clumped isotope composition we found that paleosol carbonate faithfully records plausible soil t c 47 down to 2 5 4 km burial depth or 90 125 c deeper than this and above this temperature t c 47 in paleosol carbonate is reset to temperatures 40 c we observe 40 c as the upper limit for t c 47 in modern soils from soil depths 25 cm and therefore that t c 47 40 c obtained from ancient soil carbonate indicates substantially warmer climate regimes compared to the present or non primary temperatures produced by resetting during diagenesis if representative this limits the use of t c 47 to reconstruct ancient surface temperature to modestly buried 3 4 km paleosol carbonates despite diagenetic resetting of 47 values 18 o and 13 c values of the same deeply buried paleosol carbonate appear unaltered we conclude that solid state reordering or recrystallization of clumping of carbon and oxygen isotopes can occur in the absence of open system exchange of paleosol carbonate with significant quantities of water or other phases

high regional climate sensitivity over continental china constrained by glacial recent changes in temperature and the hydrological cycle the east asian monsoon is one of earth s most significant climatic phenomena and numerous paleoclimate archives have revealed that it exhibits variations on orbital and suborbital time scales quantitative constraints on the climate changes associated with these past variations are limited yet are needed to constrain sensitivity of the region to changes in greenhouse gas levels here we show central china is a region that experienced a much larger temperature change since the last glacial maximum than typically simulated by climate models we applied clumped isotope thermometry to carbonates from the central chinese loess plateau to reconstruct temperature and water isotope shifts from the last glacial maximum to present we find a summertime temperature change of 6 7 c that is reproduced by climate model simulations presented here proxy data reveal evidence for a shift to lighter isotopic composition of meteoric waters in glacial times which is also captured by our model analysis of model outputs suggests that glacial cooling over continental china is significantly amplified by the influence of stationary waves which in turn are enhanced by continental ice sheets these results not only support high regional climate sensitivity in central china but highlight the fundamental role of planetary scale atmospheric dynamics in the sensitivity of regional climates to continental glaciation changing greenhouse gas levels and insolation

timing of the brunhes matuyama magnetic polarity reversal in chinese loess using 10be in chinese loess the brunhes matuyama b m geomagnetic reversal occurs 25 k y prior to the age found in marine sediments this offset has been attributed by some to post depositional magnetic overprinting of loess while others have argued it is due to errors in the loess time scale here we solve this long standing debate by exploiting a new method to extract reproducible records of geomagnetic field intensity from loess with 10 be a proxy for global average geomagnetic field intensity and using it to show that a pronounced minimum in field intensity a requirement for dipole field reversal is recorded in two separate loess records at ca 780 3 kyr b p this timing is synchronous with the b m reversal timing seen in marine records verifying the standard loess time scale as correct but it is 25 k y younger than the age depth of the magnetic polarity reversal recorded in these same chinese loess sediments demonstrating that loess magnetic overprinting has occurred

astronomical timescale and palaeoclimatic implication of stacked 3 6 myr monsoon records from the chinese loess plateau abstract magnetic susceptibility and grain size records from two continuous red clay and loess palaeosol sequences on the chinese loess plateau have been generated to investigate the evolution and variability of the east asian monsoon eam during the late pliocene and pleistocene tuning the grain size records to orbital obliquity and precession yields an improved astronomical timescale for the loess palaeosol sequence 0 2 6 ma and an extended age model for the upper red clay formation 2 6 3 6 ma this timescale indicates older ages for a number of the magnetic polarity boundaries consistent with lock in depth offsets in loess sequences good site to site correlation enables generation of stacked grain size and susceptibility records spanning the last 3 6 myr these records indicate that monsoon evolution since the late pliocene can be subdivided into three phases 0 1 25 1 25 2 72 and 2 72 3 4 ma each phase is characterized by unique amplitude and frequency characteristics for both summer monsoon magnetic susceptibility and winter monsoon grain size spectral analyses of the stacked monsoon proxies indicate that characteristics of both the summer and winter monsoons are dominated mainly by variance in the eccentricity 410 and 100 kyr obliquity 41 kyr and precession 23 and 19 kyr bands over the past 3 4 myr implying a non linear response of the long term eam evolution to orbital and glacial forcing

magnetostratigraphy and palaeoclimatic significance of late tertiary aeolian sequences in the chinese loess plateau summary the aeolian red clay sequence in the central part of the chinese loess plateau was investigated in an attempt to obtain magnetostratigraphic and palaeoclimatic records from the results we deduce that aeolian dust accumulation and the related east asia palaeomonsoon system began at least 7 6 myr ago and that the tibetan plateau had reached a significant elevation by that time the late tertiary palaeoclimatic history of the red clay as reflected by magnetic susceptibility is reconstructed for the time period 7 6 2 5 ma increases in aeolian dust accumulation for the last 7 6 myr appear to have a close relation with the uplift processes of the tibetan plateau the remarkable increase of aeolian dust accumulation beginning at 3 2 ma appears to reflect the influence of an increasing global ice volume on the east asian monsoon and aeolian dust accumulation

indo pacific hydroclimate in response to changes of the intertropical convergence zone discrepancy on precession and obliquity bands over the last 410 kyr

the asian monsoon over the past 640 000 years and ice age terminations oxygen isotope records from chinese caves characterize changes in both the asian monsoon and global climate here using our new speleothem data we extend the chinese record to cover the full uranium thorium dating range that is the past 640 000 years the record s length and temporal precision allow us to test the idea that insolation changes caused by the earth s precession drove the terminations of each of the last seven ice ages as well as the millennia long intervals of reduced monsoon rainfall associated with each of the terminations on the basis of our record s timing the terminations are separated by four or five precession cycles supporting the idea that the 100 000 year ice age cycle is an average of discrete numbers of precession cycles furthermore the suborbital component of monsoon rainfall variability exhibits power in both the precession and obliquity bands and is nearly in anti phase with summer boreal insolation these observations indicate that insolation in part sets the pace of the occurrence of millennial scale events including those associated with terminations and unfinished terminations records of the asian monsoon have been extended to 640 000 years ago and confirm both that the 100 000 year ice age cycle results from integral numbers of precessional cycles and that insolation influences the pacing of major millennial scale climate events prior records of the asian monsoon have revealed cyclic variations over hundreds of thousands of years probably driven by variations in insolation caused by the precession of earth s orbit hai cheng and colleagues now provide a speleothem record from chinese cave samples that extends earlier records to 640 000 years ago close to the maximum age possible with uranium thorium dating this spectacular record confirms that the characteristic 100 000 year ice age cycle corresponds to an integral number four or five of precession cycles and that insolation influences millennial scale variations in monsoon strength

natural and anthropogenic sources of east asian dust nd sr isotopic signatures of loess modern dust and their potential source materials are systematically investigated to discriminate the natural and anthropogenic sources of eastern asian dust chinese loess is an eolian deposit that has accumulated over the past few million years and is characterized by a negative nd sr isotopic correlation that implies binary sources for the natural background of eastern asian dust loess in northeastern china shows the highest end 0 value while loess in western china has the lowest end 0 considering the nd sr isotopic signatures of the potential sources we propose that the high end 0 end member is derived from the arid lands around the northern boundary of china while the low end 0 end member originates from the deserts on the northern margin of the tibetan plateau chinese loess plateau deposits are dominated by northern margin tibetan plateau dust suggesting a strong link between the thick eolian deposit in this region and the evolution of the tibetan plateau the long range transported spring dust in both nanjing south china and japan has an nd sr isotopic composition similar to that of loess however spring dust in beijing north china has a much lower end 0 value indicating an additional anthropogenic contribution of low end 0 material possibly from the sandy lands in the adjacent north and west

asynchronous evolution of the isotopic composition and amount of precipitation in north china during the holocene revealed by a record of compound specific carbon and hydrogen isotopes of long chain n alkanes from an alpine lake both the timing of the maximum east asian summer monsoon easm intensity in monsoonal china and the environmental significance of the chinese stalagmite oxygen isotopic record delta o 18 have been debated here we present a ca 120 year resolution compound specific carbon delta c 13 and hydrogen sd isotopes of terrestrial long chain n alkanes extracted from a well dated sediment core from an alpine lake in north china our delta c 13 data together with previously reported pollen data from a parallel core demonstrate a humid mid holocene from ca 8 5 ka bp assuming that the climatic humidity of north china is an indicator of the easm intensity then the maximum easm intensity occurred in the mid holocene our sd data reveal a similar long term trend to the delta o 18 record from nearby lianhua cave indicating that the synchronous sd and delta o 18 records faithfully record the sd and delta o 18 of precipitation respectively the most negative sd and delta o 18 values occur in t he early mid holocene from ca 11 5 ka bp this contrast in the timing of isotopic variations demonstrates a complex relationship between the isotopic composition of precipitation and precipitation amount or easm intensity further comparisons indicate a possible linkage between the precipitation amount in north china and the west east thermal gradient in the equatorial pacific in addition the temperature of the moisture source area may play an important role in determining the isotopic composition of precipitation in monsoonal china c 2016 elsevier b v all rights reserved

late quaternary aeolian dust input variability on the chinese loess plateau inferences from unmixing of loess grain size records abstract the grain size distributions gsds of loess paleosol sequences may provide valuable information on provenance transport and paleoclimate variability and consequently a wide range of methods to extract genetic information from loess gsds has been proposed here it is shown that a genetically meaningful decomposition of a series of late quaternary loess grain size records extending across the chinese loess plateau can be accomplished with the end member modelling algorithm emma the unmixing results in conjunction with loess accumulation rate estimates reveal that two contrasting dust supply patterns were active over the loess plateau during the last glacial interglacial cycle i a background sedimentation pattern that was dominant during interglacial periods especially over the central and southern parts of the loess plateau is reflected by the constant flux of the fine grained loess component ii an episodic highly variable dust input pattern that was dominant during glacial periods throughout the loess plateau and noticeable during interglacial periods mainly over the northern loess plateau and almost disappearing over the southern loess plateau is reflected in the admixture of two coarse grained loess components a genetic interpretation and the paleoclimatic significance of the mixing model are provided by comparison of the modelled end members with modern dust samples in terms of their gsd and flux rates

influence of the intertropical convergence zone on the east asian monsoon a palaeoclimate record spanning the past 16 000 years with nearly annual time resolution has been obtained from lake huguang maar in china the magnetic properties and titanium content of the lake sediments are thought to reflect changes in the east asian winter monsoon strength thus providing a complement to palaeoclimate archives that record the strength of the rain bearing summer monsoon the records point to an anti correlation between winter and summer monsoon strength best explained by migration of the intertropical convergence zone itcz a belt of low pressure air at the equator interestingly the decline of china s tang dynasty and the mayan civilization broadly coincide with drought periods recorded in lake huguang maar and cariaco basin sediments respectively did major shifts in the position of the itcz catalyse simultaneous events in civilizations on opposite sides of the pacific ocean the asian australian monsoon is an important component of the earth s climate system that influences the societal and economic activity of roughly half the world s population the past strength of the rain bearing east asian summer monsoon can be reconstructed with archives such as cave deposits1 2 3 but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct here we present high resolution records of the magnetic properties and the titanium content of the sediments of lake huguang maar in coastal southeast china over the past 16 000 years which we use as proxies for the strength of the winter monsoon winds we find evidence for stronger winter monsoon winds before the bolling allerod warming during the younger dryas episode and during the middle and late holocene when cave stalagmites suggest weaker summer monsoons1 2 3 we conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone similar migrations of the intertropical convergence zone have been observed in central america for the period ad 700 to 900 refs 4 6 suggesting global climatic changes at that time from the coincidence in timing we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the tang dynasty in china and the classic maya in central america

temperature and leaf wax δ2h records demonstrate seasonal and regional controls on asian monsoon proxies orbital scale precipitation isotope records can elucidate climate forcing mechanisms and provide benchmarks for climate model validation the ability to differentiate the influence of temperature seasonality and vapor transport history on precipitation isotope proxies is critical to both objectives we present a 300 k y leaf wax hydrogen isotope record from the south china sea with the effects of local condensation temperature removed 2 h wax t 2 h wax t reflects annually integrated precipitation 2 h in the pearl river catchment of southeast china depleted 2 h wax t lags minimum precession p min by 1 0 0 7 k y reflecting the influence of maximum summer insolation and minimum winter insolation with a minor influence of global ice volume which lags p min by 3 3 0 4 k y in contrast annually integrated cave 18 o minima in central china 1000 km north of our site lag p min by 2 7 0 3 k y in phase with ice volume minima this phase indicates that precipitation 18 o in central china is more strongly influenced by ice volume forcing at the precession band with a lesser influence of northern hemisphere insolation our new 2 h wax t data demonstrate that precipitation isotopes in asia have strong regional variability interpreting water isotope records within the context of regionally varying temperature seasonality and sensitivity to changing glacial boundary conditions is imperative to understanding asian hydroclimatic change

bi hemispheric forcing for indo asian monsoon during glacial terminations abstract the drivers of the indo asian monsoon dynamics during terminations have recently emerged as a controversial issue cheng et al 2009 ice age terminations science 326 248 252 using east asian speleothem records proposed a strict northern hemisphere insolation control at the orbital timescale with weak monsoon intervals occurring at terminations on the contrary an et al 2011 glacial interglacial indian summer monsoon dynamics science 333 719 723 using a record from the hequing paleolake basin highlight the importance of the southern hemisphere climate forcings on indian summer monsoon dynamics at glacial interglacial timescale the purpose of this note is to propose an explanation of the weak monsoon intervals at terminations using a deep sea sediment stack monsoon record the mechanism involved is linked to interhemispheric interactions as proposed by an et al 2011 superimposed to the role of orbital forcing precession and obliquity parameters this explanation clarifies the combination of complex drivers acting on the indo asian monsoon dynamic at terminations

variation of east asian monsoon precipitation during the past 21 k y and potential co2 forcing paleoclimatic research can provide critical insight on causes of change in the east asian monsoon which influences the lives of 1 6 billion people today in this study we use paleoclimatic indexes from chinese loess deposits which have clear climatic implications and are independently dated to reconstruct the monsoon precipitation since 21 ka our results show that monsoon precipitation persistently decreased from 21 ka to ca 8 ka and increased after ca 8 ka with a precipitation peak at 8 3 ka these changes in east asian summer monsoon precipitation are synchronous with changes in high northern latitude ice volume ice cover and atmospheric co2 these new data suggest that variation of the monsoon precipitation was probably driven by co2 forced high northern latitude temperature changes shifting the location of the intertropical convergence zone that dominates monsoon precipitation our trace 21000 modeling experiment supports this interpretation

continued obliquity pacing of east asian summer precipitation after the mid pleistocene transition abstract records from natural archives show that the strength of the east asian summer monsoon easm strongly depends on the orbital configuration of the earth however the dominant orbital cycles driving easm have been found to be spatially different speleothem stable oxygen isotopic records from southern china which are believed to reflect large scale changes in the asian monsoon system are dominated by climatic precession cycles further north on the chinese loess plateau clp loess and paleosol sequences which are argued to be controlled by monsoon intensity are in pace with global ice volume changes dominated by obliquity and after the mid pleistocene transition by 100 kyr cycles to understand these critical discrepancies here we apply a novel proxy based on the trace metal compositions of pedogenic carbonate in the eolian deposits on the clp to reconstruct summer precipitation over the last 1 5 million years our reconstructions show that summer precipitation on the clp is dominantly forced by obliquity not in pace with the ice volume imprinted loess paleosol sequences before and after the mid pleistocene transition or with the precession paced speleothem oxygen isotopic records coupled with climate model results we suggest that the obliquity driven variations of summer precipitation may originate from the gradient of boreal insolation that modulates the thermal contrast between the asian continent and surrounding oceans

plio pleistocene ice volume antarctic climate and the global δ18o record we propose that from 3 to 1 million years ago ice volume changes occurred in both the northern and southern hemispheres each controlled by local summer insolation because earth9s orbital precession is out of phase between hemispheres 23 000 year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean 18 o or sea level leaving the in phase obliquity 41 000 years component of insolation to dominate those records only a modest ice mass change in antarctica is required to effectively cancel out a much larger northern ice volume signal at the mid pleistocene transition we propose that marine based ice sheet margins replaced terrestrial ice margins around the perimeter of east antarctica resulting in a shift to in phase behavior of northern and southern ice sheets as well as the strengthening of 23 000 year cyclicity in the marine 18 o record

dolomite as a tracer for the source regions of asian dust 1 the possibility of using dolomite as a source tracer for asian dust was assessed samples of potential dust sources were systematically collected from the arid semiarid areas in north china dolomite of detrital origin was detected only in samples taken from the regions on the north margin of tibetan plateau nmtp thus the nmtp originated dust can be detected by the presence of detrital dolomite and applications are performed for the modern dust in beijing and the ancient dust deposits of loess in north china contribution of the nmtp originated particles to the spring dust in beijing and the loess in chinese loess plateau and eastern tibetan plateau are suggested however dolomite cannot be detected in the studied dust storm dust and the loess in northeast china indicating their sources other than the nmtp regions

evolution of ocean temperature and ice volume through the mid pleistocene climate transition earth s climate underwent a fundamental change between 1250 and 700 thousand years ago the mid pleistocene transition mpt when the dominant periodicity of climate cycles changed from 41 thousand to 100 thousand years in the absence of substantial change in orbital forcing over this time an increase occurred in the amplitude of change of deep ocean foraminiferal oxygen isotopic ratios traditionally interpreted as defining the main rhythm of ice ages although containing large effects of changes in deep ocean temperature we have separated the effects of decreasing temperature and increasing global ice volume on oxygen isotope ratios our results suggest that the mpt was initiated by an abrupt increase in antarctic ice volume 900 thousand years ago we see no evidence of a pattern of gradual cooling but near freezing temperatures occur at every glacial maximum

late quaternary drainage evolution in response to fold growth in the northern chinese tian shan foreland abstract alluvial units are important in understanding the interactions of antecedent drainage evolution with fold growth along the flanks of active orogenic belts this is demonstrated by the anjihai river in the northern chinese tian shan foreland which at present flows northward cutting sequentially through the nananjihai anticline the huoerguos anticline and the anjihai anticline three episodes of alluviation designated as fans fa fb and fc are identified for the anjihai river these three alluvial terrain features comprise a series of terraces where the topographic characteristics geomorphologic structure and up warped longitudinal profiles indicate continuous uplift and lateral propagation of the halaande anticline and the anjihai anticline over the past 50 ky shortly after 3 6 ka when the oldest terrace during the period of the fan fb sedimentation was formed significant rock uplift at the overlapping zone of the anjihai anticline and the halaande anticline led to the eastward deflection of the antecedent anjihai river a series of local terraces with elevation decreasing eastward indicate the gradual eastward migration of the channel of the anjihai river during the period of the fan fc sedimentation finally the anjihai river occupied the previous course of the jingou river when the latter was deflected eastward in response to rock uplift of the anjihai anticline presently flowing across the eastern tip of the anjihai anticline

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

direct measurements of deglacial monsoon strength in a chinese stalagmite chinese speleothems cave deposits preserve a remarkable paleoclimate record in their oxygen isotope ratios 18 o the precise interpretation of this record has been the subject of stimulating discussion most studies link the 18 o variability in chinese speleothems to regional summer monsoon rainfall and or rainfall integrated between tropical sources and cave sites discussion has centered on mechanisms behind this link as well as the location and seasonality of hypothesized rainfall changes until now these hypotheses were not directly tested in speleothems because conventional drill sampling techniques are insufficient for measuring speleothem 18 o at seasonal resolution here we use an ion microprobe to analyze seasonal 18 o variability in an annually banded stalagmite from kulishu cave northeastern china that grew during the last deglaciation the new seasonal resolution data show that the stalagmite 18 o values record two aspects of regional monsoon dynamics 1 changes in the isotopic fractionation of water vapor sourced from both the indian and pacific oceans and 2 the annual proportion of summer monsoon rainfall which was systematically greater during the holocene and bolling allerod than during the younger dryas both relate to regional rainfall the isotopic fractionation changes also relate to rainfall integrated from tropical sources

modeling the time dependent response of the asian summer monsoon to obliquity forcing in a coupled gcm a phasemap sensitivity experiment to study the time dependent response of the asian summer monsoon to obliquity forcing we analyze a 284 000 year long transient simulation produced by a fully coupled global climate model gcm using a new phase mapping phasemap approach here we focus on understanding the phase response of monsoonal circulation to insolation forcing at the earth orbital obliquity band 41 kyr our results show that the east asian summer monsoon easm can be divided into two geographic regions the north east asian summer monsoon neasm and the south east asian summer monsoon seasm the indian summer monsoon ism and the seasm are in phase at the obliquity band strengthened with an increase in obliquity from obliquity minima omin to obliquity maxima omax the neasm is out of phase with the ism and seasm weakened with an increase in obliquity from omin to omax we hypothesize that the inverse phase between the neasm and the ism at the obliquity band results from an ism neasm teleconnection linked to the formation mechanism of the bonin high

late quaternary dust flow on the chinese loess plateau abstract the dust flux of over 25 g cm2 103yr was reached in the central part of the chinese loess plateau during the last glacial maximum this is more than three times higher than during the last interglacial and early glacial time the grain size of the pleniglacial dust reached a peak shortly after 20 000 years ago and testifies to the occurrence of strong winds and frequent dust storms

the long term paleomonsoon variation recorded by the loess paleosol sequence in central china abstract the loess paleosol sequence in central china during the last 2 5 ma is a good record of the asian monsoon variation which could be considered as the concrete realization of global paleoclimatic cycles the geological and biological evidence of the loess paleosol sequence indicates that the loess was mainly the dust deposits transported by the northerly wind of winter monsoons and also suffered to some extent from pedogenesis caused by weakened summer monsoons and that the paleosol accreted by the rather slow dust accumulation was closely related to strengthened summer monsoons an alternating occurrence of loess and paleosol in the luochuan section implies the variation history of warm humid climate with a summer monsoon dominance and cold dry climate with a winter monsoon dominance the magnetic susceptibility of loess and paleosol can be regarded as a proxy index of asian monsoon variation an analysis of the susceptibility curve and structure characters of luochuan section shows that the asian monsoon circulation was strengthened from early pleistocene to late pleistocene and the 500 ka bp point and 1200 ka bp point seem to be a threshold and a turning point respectively in terms of the long term paleomonsoon variation in asia

changes in the distribution of uvigerinidae species over the past 775 kyr implications for the paleoceanographic evolution of the japan sea abstract the distribution of benthic foraminifera of the uvigerinidae family which are abundant in middle to upper pleistocene samples from the yamoto basin in the japan sea have been analyzed quantitatively and used for paleoceanographic interpretations twenty three uvigerinidae species are reported from iodp site u1426 6 of which are present in at least three or more samples with 10 or more abundance and considered as dominant species the abundance and ecological preferences of dominant uvigerinidae species comprised of uvigerina mediterranea uvigerina yabei uvigerina sp 1 uvigerina peregrina suggest dysoxic conditions with high influx of organic matter between 775 and 475 ka in response to the enhanced flow of the tsushima warm current the end of mis 13 marked the onset of more extreme glacial interglacial climate cycles in the japan sea glacial interglacial alternations of uvigerina peregrina and trifarina angulosa from 475 ka to the holocene indicate major fluctuations in circulation and productivity within this semi enclosed basin both u peregrina and t angulosa respond to 100 kyr variability reflecting the paleoclimatic shift and global ice volume changes associated with the middle pleistocene transition

orbitally paced variations of water availability in the se asian monsoon region following the miocene climate transition abstract middle miocene earth had several boundary conditions similar to those predicted for future earth including similar atmospheric p co 2 and substantial antarctic ice cover but no northern hemisphere ice sheets we describe a 12 m outcrop of the terrestrial yanwan section in the tianshui basin gansu china following the miocene climate transition 13 9 13 7 ma it consists of 25 cm thick caco 3 cemented horizons that overprint siltstones every 1 m we suggest that stacked soils developed in siltstones under a seasonal climate with a fluctuating water table evidenced by roots clay films mottling presence of caco 3 nodules and stacked carbonate nodule 13 c and 18 o profiles that mimic modern soils we suggest that the caco 3 cemented horizons are capillary fringe carbonates that formed in an arid climate with a steady water table and high potential evapotranspiration rates pet evidenced by sharp upper and basal contacts micrite sparite and root pore cements the caco 3 of the cemented horizons and the carbonate nodules have similar mean 18 o and 13 c values but the cements have significantly smaller variance in 13 c and 18 o values and a different 18 o versus 13 c slope supporting the conclusion that these carbonates are from different populations the magneto stratigraphic age model indicates obliquity pacing of the arid conditions required to form the caco 3 cemented horizons suggesting an orbital control on water availability we suggest two possible drivers for the obliquity pacing of arid conditions 1 variability in the cross equatorial pressure gradient that controls summer monsoon asm strength and is influenced by obliquity paced variations of antarctic ice volume and 2 variability in western pacific ocean east asian continent pressure gradient controlled by the 25 45 n meridional insolation gradient we also suggest that variations in aridity were influenced by variations in pet and sensible heating of the regional land surface which are both influenced by precession controlled 35 n summer insolation we then use orbital configurations to predict lithology coincidence of obliquity minima strong asm and 35 n summer insolation maxima strong asm drives strong asm and high pet resulting in soil formation in an environment with relatively large seasonal changes in water availability coincidence of obliquity maxima weak asm and 35 n summer insolation maxima strong asm moderates the asm results in high pet and thus drives overprinting of soils by capillary fringe carbonates above a deepened and relatively stable water table coincidence of obliquity and insolation minima also moderates the asm but results in low pet and thus a high water table which explains the previously documented occurrence of aquatic plants in this section this context allows us to assign an orbital configuration to atmospheric p co 2 determined from the paleosols our best estimate of p co 2 during the times of intermediate ice volume is 475 650 230 ppmv median value with error reported as 84th 16th percentile values southern hemisphere control of asm variability during the middle miocene may have resulted in larger orbital scale water availability variations compared with the pleistocene

syntectonic growth strata and implications for late cenozoic tectonic uplift in the northern tian shan china abstract propagation of faults and folds in the foreland basins of tian shan is an important process accommodating cenozoic crustal shortening and mountain building but little is known about the accurate time of the cenozoic tectonic deformation based on growth strata and age determination we show that syntectonic growth strata began to develop in the middle part of tian shan since 6 ma ago geometry analysis indicates that formation of the growth strata is associated with progressive fold limb rotation formation of the growth strata is contemporaneous with the tectonic deformation in the thrusting and folding zones together with the remarkable increase of sedimentation rate as well as the accumulation of coarse molasse deposits we conclude that the late cenozoic crustal shortening and mountain building in the region initiated since about 6 ma and lasted to the early pleistocene as a consequence of intracontinental deformation within the india eurasia convergent system

chinese loess and the paleomonsoon abstract this paper presents a general review of the recent research advances of the east asian paleomonsoon based mainly on studies of the loess soil sequences in the chinese loess plateau in the last 2 6 million years the paleomonsoonal history may be divided into about 166 events on a time scale of the earth s orbital variations during the last glacial period millenial scale oscillations of the monsoon system were prominent which can be fairly well correlated with the dansgaard oeschger cycles recognized in the greenland ice cores the monsoonal rainfall belt has experienced a wide repeated advance retreat change during the glacial interglacial cycles of the pleistocene both temporal and spatial changes of the monsoon system in the quaternary could have been linked closely to global ice volume variations

summer monsoon intensity controls c4 c3 plant abundance during the last 35 ka in the chinese loess plateau carbon isotope evidence from bulk organic matter and individual leaf waxes the natural abundance of c3 and c4 plants is affected by multiple environmental factors including temperature moisture balance and atmospheric pco2 the relative importance of these factors is a subject of considerable debate and may vary in different natural ecosystems previous studies generally focus on single loess sequences in the chinese loess plateau and conflicting conclusions on c4 c3 have been reached when studying carbon isotope ratios in carbonate and organic matter in this paper we report a comprehensive carbon isotopic characterization of total organic carbon toc and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the chinese loess plateau clp the five coring sites encompass large gradients of annual mean temperature 9 2 13 9 c and precipitation 402 673 mm allowing us to assess the controlling mechanisms on c4 c3 plant ratios glacial interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility our results demonstrate that increased c4 c3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites we conclude c4 abundance increases from the last glacial to the holocene in response to greater monsoon activity and that the c4 expression is suppressed in the cold and drier intervals

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

incorporation of trace metals into microcodium as novel proxies for paleo precipitation abstract trace element compositions of microcodium are applied for the first time as possible paleo proxies based on a case study on the chinese loess plateau clp the mg ca and sr ca ratios of the microcodium picked from the holocene paleosol across the clp show distinct positive correlation over large range of nearly one order of magnitude higher mg ca and sr ca ratios of microcodium are recorded in the sites on the northwestern clp where less monsoonal rainfall is received similar large variation of the positively correlated mg ca and sr ca ratios has also been observed for the stream water on the clp with the same spatial pattern the mg ca and sr ca ratios of the microcodium seem to be largely controlled by the composition of soil solution as reflected by stream water rather than partition coefficient rayleigh distillation and thus evolving composition of soil solution as a result of progressive precipitation of secondary calcite is responsible for the large variation and positive correlation of the mg ca and sr ca ratios for both the microcodium and stream water we propose that the bio remains in chinese loess may become inactive when the soil water is extracted to a degree and then be calcified into microcodium by the infiltration of freshwater that is mixed with the highly evolved soil solutes thus the mg ca and sr ca ratios of microcodium may record the paleo precipitation amount by reflecting the mixing ratio between the highly evolved soil solutes with higher mg ca and sr ca ratios and the fresh soil water with lower mg ca and sr ca ratios

sr isotopic and elemental characteristics of calcites in the chinese deserts implications for eolian sr transport and seawater sr evolution abstract calcite content sr concentrations and isotopes of calcites in the chinese deserts are systematically studied in this paper calcite contents which are calculated according to acid soluble ca contents in the deserts are generally higher in the sandy deserts than in the sandy lands and decrease roughly from northwest to northeast of china acid soluble sr is well correlated with calcite in the chinese deserts implying acid soluble sr comes mainly from the calcite dissolution sr concentrations in calcites calculated on the basis of calcite contents and acid soluble sr concentrations in the deserts have an inverse relation to calcite contents essentially mirroring the degree of sr substitution for ca in the calcite development desert calcites have regional variations in sr isotopic ratios calcite sr isotopic ratios depend on geological settings and chemical weathering the badain jaran and tengger deserts are probably affected by additional factors such as the remote groundwater cycle or overturning of underlying sand deposits only four deserts taklimakan qaidam badain jaran and tengger appear to be potential sources of eolian deposits in the chinese loess plateau clp isotopic signatures of calcite sr and silicate nd further indicate that the tengger desert was not an important source for eolian deposits in the clp eolian calcite was probably enriched due to wind sorting from the potential sources to the clp and suffered weathering leaching after it accumulated in the clp sr isotopic compositions and ca sr molar ratios of calcites are different between the deserts and the lingtai profile due to the integrated effect of wind sorting and weathering leaching it is essential to calculate accurately the 87sr 86sr ratio and sr concentration of eolian calcite entering the oceans according to geochemical data of the chinese deserts because of the importance of the chinese deserts in the global dust cycle the calculated sr concentration and 87sr 86sr ratio of eolian calcite entering the north pacific ocean are 11 75 mol g and 0 71032 respectively the calculated values in this study are close to the recommended values by jacobson jacobson a d 2004 has the atmospheric supply of dissolved calcite dust to seawater influenced the evolution of marine 87sr 86sr ratios over the past 2 5 million years geochem geophys geosyst 5 12 1 9 q12002 doi 10 1029 2004gc000750 using the same model as that of jacobson 2004 the effect of asia dust on the evolution of seawater sr isotopes is evaluated 87sr 86sr seawater increases by 0 3 10 5 if the lower dust flux of 2 34 108 mol sr yr is used in the model suggesting the little effect of asian dust on the seawater sr record in the quaternary the increase in 87sr 86sr seawater is 1 5 10 5 if the higher value of 1 17 109 mol sr yr is used as observed in the quaternary sr record these results further support the suggestions of jacobson 2004

late quaternary faulting on the manas and hutubi reverse faults in the northern foreland basin of tian shan china abstract the tian shan range lies in the actively deforming part of the india asia collision zone in the northern foreland basin of tian shan the strata were intensively deformed by cenozoic folding and faulting slip rate studies along these faults are important for understanding the dynamics of crustal deformation and evaluating the seismic hazards in the region two reverse faults the manas and hutubi faults in the northern foreland basin were investigated due to past faulting events along these faults the terrace treads along the manas river were ruptured forming fault scarps several meters in height loess deposits were trapped and preserved at the surface ruptures along these scarps the thickness of the trapped loess is dependent on the size of the ruptures the minimum and maximum ages of these scarps are constrained by dating the loess preserved at the surface ruptures and the terrace treads respectively using the quartz optically stimulated luminescence osl dating technique our dating results suggest that the loess trapped at the ruptures was deposited from the early to mid holocene at the hutubi fault and from the mid to late holocene at the manas fault the vertical displacements of the faults were evaluated by measuring the topographic profiles across the investigated fault scarps using the differential global position system dgps our results suggest that during the late quaternary in the studied region the vertical slip rates of the manas fault were between 0 74 mm yr and 1 6 mm yr while the hutubi fault had a much lower vertical slip rate between 0 34 mm yr and 0 40 mm yr the tectonic implications of our results are discussed

late pleistocene shortening rate on the northern margin of the yanqi basin southeastern tian shan nw china abstract how strain is distributed and partitioned on individual faults and folds on the margins of intermontane basins remains poorly understood the haermodun ha anticline located along the northern margin of the intermontane yanqi basin on the southeastern flank of the tian shan preserves flights of passively deformed alluvial terraces these terraces cross the active anticline and can be used to constrain local crustal shortening and uplift rates geologic and geomorphic mapping in conjunction with high resolution dgps topographic surveys reveal that the terrace surfaces are perpendicular to the fold s strike and display increased rotation with age implying that the anticline has grown by progressive limb rotation combined with the open sinusoidal curve model and excess area method we calculated uplift and shortening values for each terrace since abandonment using the published exposure ages of each terrace we found the vertical uplift rate gradually decreased from 0 43 to 0 11 mm a whereas the shortening rate remained constant at 0 3 mm a since the anticline began to grow a fresh fault scarp 0 4 0 1 m high is visible along the southern portion of the ha anticline and is interpreted to be the most recent evidence of seismic activity using an estimated rupture area and the length of the fresh offset created by this earthquake we estimate that the main thrust underlying the ha anticline has generated moderate m

osl dating of offset streams across the altyn tagh fault channel deflection loess deposition and implication for the slip rate abstract two deflected streams flowing across the altyn tagh fault atf were investigated at the aksay segment nw china due to strike of the atf stream channels are deflected and elongated by adding new sections along the fault line after subsequent water erosion and fluvial refreshment banks of these deflected streams are overlain by aeolian loess geomorphological features suggest that stream deflections along the fault were developed as a result of faulting activities and displacements were progressively accumulated from multiple faulting cycles each faulting cycle is composed of faulting event triggered elongation of channels creation of stream banks or risers and subsequent aeolian loess deposition on the banks a model is proposed to illustrate the relationship between fault movement and loess deposition which is supported by osl dating of the loess on the offset stream channels our results demonstrated that 1 loess deposits along deflected streams can be used to trace fault slip history given specific geomorphic assumptions discussed in the text and 2 based on stream channel offsets and loess ages the holocene slip rate of the atf is estimated to be 11 2 mm year along the aksay segment

nd and sr isotopic characteristics of chinese deserts implications for the provenances of asian dust silicate nd sr isotopes of the fine grained fractions of the 10 major deserts and sandy lands in north china and the loess in chinese loess plateau were systematically investigated wide ranges in nd sr isotopic compositions have been observed the results of the 7 0 b the deserts on the northern margin of tibetan plateau with end 0 ranging from 11 9 to 7 4 and c the deserts on the ordos plateau with the lowest end 0 11 5 the distribution of the threes isotopic regions is controlled by the tectonic setting in north china which implies that the materials of the deserts are derived from the locally eroded rocks from the surrounding mountains and the nd sr isotopic signatures of these deserts could be quit stable over the past million years on the sub tectonic time scales if there is any desert at those times the nd sr isotopic compositions of the loess are mostly close to those of the deserts in isotopic region b suggesting that the main source regions of the last glacial loess in the chinese loess plateau are badain jaran desert tengger desert and qaidam desert also the comparison between the nd sr isotopes of the 5 lm silicate fractions of the deserts and the ancient dust falls in the north pacific and greenland show that the asian end members of these dust falls are derived most from the deserts in the isotopic region b and less from those in the isotopic region c

heterodynes dominate precipitation isotopes in the east asian monsoon region reflecting interaction of multiple climate factors abstract for the past decade east asian monsoon history has been interpreted in the context of an exceptionally well dated high resolution composite record of speleothem oxygen isotopes 18ocave from the yangtze river valley this record is characterized by a unique spectral response with variance concentrated predominantly within the precession band and an enigmatic lack of variance at the eccentricity and obliquity bands here we examine the spectral characteristics of all existing 250 kyr long terrestrial water isotope records in asia including a new water isotope record using leaf wax hydrogen isotope ratios from the chinese loess plateau there exist profound differences in spectral characteristics among all orbital scale asian water isotope records we demonstrate that these differences result from latitudinal gradients in the influence of the winter and summer monsoons both of which impact climate and water isotopes throughout east asia water isotope records therefore do not reflect precipitation during a single season or from a single circulation system rather water isotope records in east asia reflect the complex interplay of oceanic and continental moisture sources operating at multiple earth orbital periods these non linear interactions are reflected in water isotope spectra by the presence of heterodynes although complex we submit that water isotope records when paired with rapidly developing isotope enabled model simulations will have the potential to elucidate mechanisms causing seasonal precipitation variability and moisture source variability in east asia

delayed build up of arctic ice sheets during 400 000 year minima in insolation variability an east asian winter monsoon proxy record using grain size variations in chinese loess over the past 900 000 years shows that for up to 20 000 years after the interglacials at 400 000 year intervals the weak monsoon winds maintain a mild non glacial climate at high northern latitudes qingzhen hao and colleagues present a record of grain size variations in the chinese loess plateau a proxy of variations in the strength of the east asian winter monsoon and show that relatively high insolation at 400 000 year intervals held off the inception of the subsequent ice age for about 20 000 years relative to other glacial inceptions mechanistically the extension of warm conditions was probably linked to a weak siberian high pressure system associated with a delayed build up of northern ice and snow the authors speculate that these observations imply that arctic climate may remain in non glacial mode for more than 40 000 years even in the absence of anthropogenic greenhouse gases knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial1 may help to inform our understanding of future climate change unfortunately long term continuous records of ice sheet variability in the northern hemisphere only are scarce because records of benthic 18o content represent an integrated signal of changes in ice volume in both polar regions2 however variations in northern hemisphere ice sheets influence the siberian high3 an atmospheric pressure system so variations in the east asian winter monsoon eawm as recorded in the aeolian dust deposits on the chinese loess plateau can serve as a useful proxy of arctic climate variability before the ice core record begins here we present an eawm proxy record using grain size variations in two parallel loess sections representative of sequences across the whole of the chinese loess plateau over the past 900 000 years the results show that during periods of low eccentricity and precessional variability at approximately 400 000 year intervals the grain size inferred intensity of the eawm remains weak for up to 20 000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis in contrast there is a rapid increase in the eawm after the end of most other interglacials we conclude that for both the 400 000 year interglacials the weak eawm winds maintain a mild non glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records during these times the less severe summer insolation minima at 65 n ref 4 would have suppressed ice and snow accumulation leading to a weak siberian high and consequently weak eawm winds

microcodium in chinese loess as a recorder for the oxygen isotopic composition of monsoonal rainwater abstract records of asia summer monsoon asm from the chinese loess and the speleothem display distinct features the very different proxies that were applied to the two archives may be responsible for this discrepancy a direct comparison between the speleothem and the loess records under the same proxy system of rainwater 18o may help to resolve this puzzle here we show that the calcified microcodium in the loess deposits may record the oxygen isotopic composition of the summer rainwater a microcodium based 18o record covering the past 140 kyrs was generated which shows similar magnitude of the overall variation to that of the speleothem records however much weaker precession variability was registered in the microcodium record during the last interglacial period instead the microcodium 18o record is more consistent with the widely used summer monsoon proxy of magnetic susceptibility in the loess deposits with clear glacial interglacial pattern this similarity may originate from the low sedimentation rate of the interglacial paleosol layer that preferentially record the peak asm signals on the precession band it is also possible that the orbital variability of asm between the north china and south china is inherently different with more ice volume related influence in the north a longer microcodium 18o record in sequences of higher sedimentation rate and a reliable record of summer rainfall may help to resolve these possibilities

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

stable carbon and oxygen isotopic composition of modern land snails along a precipitation gradient in the mid latitude east asian monsoon region of china abstract the stable oxygen and carbon isotope composition 18oshell and 13cshell of land snail shells preserved in chinese eolian loess deposits have the potential to reconstruct past changes in the east asian summer monsoon easm since the late oligocene to assess the potential of 18oshell and 13cshell for the semi quantitative reconstruction of past variations of the easm we studied modern snails and the corresponding vegetation composition of three distinct ecosystems woodland grassland and mountains spanning a large rainfall gradient 178 1403 mm in the mid latitude east asian monsoon region the results show that different snail species in the three ecosystems have significantly different values of 18oshell and 13cshell the snails in woodland from the eastern plain area have significantly lower 18oshell and 13cshell values than those of snails in grassland from the chinese loess plateau and the snails from the qinba mountains region have values intermediate between the two systematic variations of the 13c of snail shells body tissues and local plants are evident along the rainfall gradient indicating that 13cshell is mainly influenced by the 13c of ingested plants which is controlled by the easm we confirm that 13cshell is a reliable precipitation proxy and we obtained a new empirical equation 13cshell 0 0030 0 0003 map 8 80 0 32 r 0 76 n 74 p

orbital scale timing and mechanisms driving late pleistocene indo asian summer monsoons reinterpreting cave speleothem δ18o 1 southeast china cave 18o often interpreted as a pure east asian summer monsoon proxy lags maximum northern hemisphere summer insolation by 2 9 0 3 kyrs at the precession cycle the arabian sea summer monsoon stack lags by 8 1 kyr consistent with 13 other indian and east asian summer monsoon proxies from marine lake and terrestrial archives this 5 kyr phase difference cannot be attributed to age control inadequacies in the marine chronology it requires reconciliation in the context of proxy interpretation both of these lags are incompatible with a direct response to northern hemisphere summer insolation implicating additional forcing mechanisms analysis of heterodynes in the cave 18o spectrum demonstrates that variance contained in the arabian sea summer monsoon proxies also resides in the cave 18o record this variance is subtracted from the cave 18o record yielding a residual that is highly coherent and in phase with precession minima reflecting the impact of winter temperature change on cave 18o meteorological precipitation under cold conditions thus we argue that the timing of light cave 18o peaks cannot be interpreted as reflecting the timing of strong summer monsoons alone the 2 9 kyr precession band phase lag of cave 18o reflects the combined influence of summer monsoon forcing with a phase lag of 8 kyrs relative to precession minima and winter temperature forcing that is in phase with precession minima this interpretation is consistent with modern seasonality in the amount and isotopic composition of rainfall in southeast china

molecular records of continental air temperature and monsoon precipitation variability in east asia spanning the past 130 000 years our current understanding of past changes in east asian summer monsoon easm precipitation intensity derives from several loess paleosol sequences and oxygen isotope 18o records of well dated stalagmites although temperature is generally presumed to have had minimal impact on easm records past air temperature dynamics over east asia are so far relatively poorly understood mainly due to the lack of tools to reconstruct continental paleotemperatures here we report a high resolution record of east asian air temperature over the past 130 000 years based on soil bacterial lipid signatures preserved in a loess paleosol sequence from the mangshan loess plateau in china we find that maximum local insolation is the main driver of air temperature although greenhouse gas concentrations and southern hemisphere climate may influence temperature at times when insolation is weak causing a decoupling with easm precipitation intensity direct comparison of our temperature record with precipitation induced changes in past soil ph derived from the same suite of lipids confirms this decoupling subsequent cross spectral analysis of the two molecular proxy records reveals that variations in monsoon precipitation consistently lag those in air temperature throughout the whole record at the dominant precession band the length of this lag is variable however and increases as glaciation develops this observation is consistent with an increasing influence of northern hemisphere ice sheets on the modulation of easm response to insolation forcing during ice ages

timing duration and transitions of the last interglacial asian monsoon thorium 230 ages and oxygen isotope ratios of stalagmites from dongge cave china characterize the asian monsoon and low latitude precipitation over the past 160 000 years numerous abrupt changes in 18o 16o values result from changes in tropical and subtropical precipitation driven by insolation and millennial scale circulation shifts the last interglacial monsoon lasted 9 7 1 1 thousand years beginning with an abrupt less than 200 years drop in 18o 16o values 129 3 0 9 thousand years ago and ending with an abrupt less than 300 years rise in 18o 16o values 119 6 0 6 thousand years ago the start coincides with insolation rise and measures of full interglacial conditions indicating that insolation triggered the final rise to full interglacial conditions

glacial interglacial indian summer monsoon dynamics the modern indian summer monsoon ism is characterized by exceptionally strong interhemispheric transport indicating the importance of both northern and southern hemisphere processes driving monsoon variability here we present a high resolution continental record from southwestern china that demonstrates the importance of interhemispheric forcing in driving ism variability at the glacial interglacial time scale as well interglacial ism maxima are dominated by an enhanced indian low associated with global ice volume minima in contrast the glacial ism reaches a minimum and actually begins to increase before global ice volume reaches a maximum we attribute this early strengthening to an increased cross equatorial pressure gradient derived from southern hemisphere high latitude cooling this mechanism explains much of the nonorbital scale variance in the pleistocene ism record