lateglacial and early holocene surface exposure ages of glacial boulders in the taiwanese high mountain range abstract glacial landforms and sediments mapped in three presently unglaciated mountain massifs the nanhuta shan the hsueh shan and the yushan support the concept of repeated multi stage glaciations in the taiwanese high mountain range during the late pleistocene new results from surface exposure dating using in situ produced cosmogenic 10 be measured in samples taken from erratic and moraine boulders in nanhuta shan at altitudes between 3100 and 3500 m are presented here the results confirm independent and previously reported optically stimulated luminescence osl ages and 10 be exposure ages from glacial deposits in the same area and suggest a lateglacial and early holocene glaciation the so called nanhuta glacier advance with two substages at about 12 15 ka and 9 5 ka bp the respective equilibrium line altitudes ela were calculated at 3340 m and 3440 m with corresponding ela depressions of 610 100 m and 510 100 m relative to the present day theoretical ela which is estimated to be at about 3950 100 m in taiwan large scale erosional landforms indicate a much wider glacier extent during an earlier stage which is not dated in nanhuta shan so far luminescence dating from near hsueh shan suggests an age of marine isotope stage mis 4 for this stage

genetic relationship between 1780 ma dykes and coeval volcanics in the lvliang area north china abstract the 1780 ma dykes and coeval volcanics constitute a large igneous province in the north china craton however whether these dykes and volcanic rocks of varying compositions originated from one or multiple sources remains controversial the ca 1780 ma lvliang dykes are characterized by widespread e w oriented dykes and minor n w oriented diabase dykes the e w oriented dykes are bimodal and comprise two subgroups one is dominated by acidic high silica dykes sio 2 63 wt while the other is dominated by mafic to intermediate relatively low silica dykes sio 2 sims u pb dating on zircons from one high silica dyke and a rhyolite volcanic layer yields 207 pb 206 pb ages of 1783 7 ma and 1776 6 ma respectively and sims u pb dating on baddeleyites from a low silica dyke yields a 207 pb 206 pb age of 1789 5 ma they are all tholeiitic in composition mgo 0 3 6 1 wt sio 2 51 74 wt enriched in light rare earth elements la yb n 7 9 20 2 and show negative anomalies in nb ta sr and eu eu eu 0 3 0 9 they also have similar in situ hf isotopes of baddeleyite zircon ehf values of 14 5 to 1 8 and bulk rock end 6 7 to 3 0 isotopes furthermore immiscible textures are identified from the xiaoliangling group volcanics which are characterized by some silica rich melts globules in the fe rich magma these spatiotemporal affinities and geochemical similarities as well as the identified immiscible textures reveal that the low silicate dykes are conduits for the basalt andesite with significant fractionation of clinopyroxene and plagioclase while the high silica dykes are conduits for the rhyolite dacite with distinct immiscible segregation prior to eruption in addition there is a sharp change of ehf values at 1780 1730 ma and their hf t dm ages are 2750 1950 ma as these rocks originated from the subcontinental lithospheric mantle this may indicate that the subcontinental lithospheric mantle was metasomatized during this time period possibly by a paleo plume event

holocene vegetation and climate of the alashan plateau nw china reconstructed from pollen data a set of 55 recent pollen spectra from the alashan plateau and the qilian mountains qilianshan northwestern china has been analyzed the established relationships between the pollen spectra and modern vegetation and precipitation patterns of the studied area have been applied to 65 fossil pollen spectra from a 825 cm long sediment record collected in the topographic depression formerly occupied by eastern juyan palaeolake 41 89 n 101 85 e 892 m a s l several qualitative approaches e g indicator plant species artemisia chenopodiaceae and ephedra fragilis type s l ephedra distachya type pollen ratios and quantitative methods of vegetation and climate reconstruction have been tested with the surface pollen and then applied to the eastern juyan pollen record fossil pollen data reveal pronounced environmental changes in the studied area of the alashan plateau between ca 10 700 and 1700 cal yr b p desert taxa as chenopodiaceae nitraria calligonum reaumuria were abundant in the vegetation cover around the study site through the whole record pollen spectra dated to ca 10 700 5400 cal yr b p are characterised by highest values of chenopodiaceae e fragilis type and other desert indicating taxa suggesting rather dry climate most favourable conditions are reconstructed between 5400 and 3900 cal year b p on the basis of relative increase in abundance of artemisia pollen a return to dry conditions occurred at about 3900 cal yr b p the lake finally desiccated after 1700 cal yr b p reconstructed dry climate oscillations between 5900 and 5400 and 3100 cal yr b p correlate well with similar events found in the published records from northern and western china and central mongolia however eastern juyan record does not show the early holocene humidity maximum as suggested by the sedimentary data from monsoon influenced areas of china

hydrogen isotopic ratios of plant wax n alkanes in a peat bog deposited in northeast china during the last 16 kyr abstract based on paleoclimatic reconstructions using various proxies the holocene climate optimum 10 5 6 ka has been characterized as a warmer and wetter period in most of east asia the summer monsoons associated with the east asian monsoon evidently intensified and extended further inland from the pacific ocean a source region of moisture a notable exception to this general pattern exists in northeast china where less wet conditions are recorded we determined molecular compositions of individual plant wax hydrocarbons and their hydrogen isotope compositions d values in a radiocarbon dated peat core recovered from the hani marsh in jilin province china and confirmed that the temperature dependent effective precipitation in northeast china decreased during the holocene climate optimum a combination of p aq an indicator of the relative contribution of aquatic to terrestrial plants and the difference in d between low c 23 c 25 and c 27 and high molecular weight c 31 n alkanes in the hani peat bog indicates a dramatic change in vegetation from the deglaciation to the holocene no significant differences were observed between the d values of low and high molecular weight n alkanes with relatively high d values and low p aq during the early holocene indicating that all n alkanes were produced by evapotranspiration sensitive terrestrial plants during that time however lower d values of mid chain n alkanes c 23 c 25 and c 27 relative to the long chain n alkane c 31 together with higher p aq values during the deglaciation 14 11 ka suggest an increase in the contribution of aquatic plants and a higher water level during the period the study demonstrates that northeast china was under a markedly wetter climate condition during the late deglaciation for the 16 kyr record in the hani peat sequence we infer that moisture delivery by the east asian monsoon was relatively invariable in northeast china but increased evaporation during the warmer holocene climate optimum reduced the effective precipitation defined by the balance between precipitation and evaporation

synchronism of holocene east asian monsoon variations and north atlantic drift ice tracers eighteen radiocarbon dated eolian and paleosol profiles within a 1500 km long belt along the arid to semi arid transition zone of north central china record variations in the extent and strength of the east asian summer monsoon during the holocene dated paleosols and peat layers represent intervals when the zone was dominated by a mild moist summer monsoon climate that favored pedogenesis and peat accumulation brief intervals of enhanced eolian activity that resulted in the deposition of loess and eolian sand were times when strengthened winter monsoon conditions produced a colder drier climate the monsoon variations correlate closely with variations in north atlantic drift ice tracers that represent episodic advection of drift ice and cold polar surface water southward and eastward into warmer subpolar water the correspondence of these records over the full span of holocene time implies a close relationship between north atlantic climate and the monsoon climate of central china

late quaternary aeolian activity in the mu us and otindag dune fields north china and lagged response to insolation forcing 1 dune fields in parts of northern china contain important stratigraphic records of late quaternary change in the east asian monsoon in this study 33 new optically stimulated luminescence osl ages and other measurements from aeolian sediment sections are used to reconstruct the timing of wet dry climate variation in the mu us and otindag dune fields of north china the results indicate dune activity and dry climate in the last few hundred years 14 ka to about 7 8 ka and 50 ka to 60 ka the dunes were mainly stable implying a wetter climate between about 7 8 ka and 2 4 ka these results imply a lag of several thousand years between peak summer insolation at 10 11 ka and high summer monsoon rainfall after 7 8 ka in the investigated regions the monsoon climate may not respond directly to orbital forcing over millennial time scales land surface feedbacks may account for lagged dune field response

a pollen record of holocene climatic changes from the dunde ice cap qinghai tibetan plateau pollen preserved in ice cores from the dunde ice cap provides a sensitive record of holocene climatic changes and vegetational response in the northern qinghai tibetan plateau at time scales ranging from millennia to centuries and decades pollen analysis of the annually resolvable ice layers for a 30 yr period 1957 1986 suggests that total pollen concentration is correlated positively with summer precipitation and negatively with summer temperature thus it is a sensitive indicator of moisture availability and vegetation density in the steppe and desert regions around dunde high pollen concentrations between 10 000 and 4800 yr b p suggest that the summer monsoon probably extended beyond its present limit to reach dunde and westernmost tibet in response to orbital forcing the summer monsoon retreated time transgressively across the qinghai tibetan plateau during the middle holocene relatively humid periods occurred at 2700 2200 1500 800 and 600 80 yr b p probably as a result of neoglacial cooling prominent pollen changes during the medieval warm period 790 620 yr b p and the little ice age 330 80 yr b p suggest that the vegetation in the qinghai tibetan plateau region is sensitive to abrupt century scale climatic changes such as those anticipated in scenarios of greenhouse warming

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

the holocene salinity history of bosten lake xinjiang china inferred from ostracod species assemblages and shell chemistry possible palaeoclimatic implications abstract a sediment core from bosten lake the largest freshwater lake in the tianshan mountains and in the northwesternmost province of china provided a high resolution record of environmental change covering the last 8500 cal a bp higher salinity levels of bosten lake were reconstructed from assemblages the stable isotope composition and sr ca and mg ca ratios of ostracod shells between 7800 and 5600 cal a bp a period of low and moderate salinities between 5600 and 4900 cal a bp was followed by the re establishment of higher salinities between 4900 and 4300 cal a bp since then bosten lake has recorded fluctuating conditions with a number of multi centennial phases of low and moderate salinities although the salinity lake level relationship of bosten lake is not fully understood a higher salinity at the core site seems to correspond to periods of higher lake levels this contradictory interpretation is explained tentatively by the changing distance of the core site to the freshwater providing river mouth with changing lake levels and potentially resulting lateral shifts of the salinity distribution pattern within the lake assuming this explanation is correct the record from bosten lake reflects higher moisture availability and a strong climatic influence of the indian monsoon in the early mid holocene until about 4000 cal a bp and more unstable drier conditions susceptible to minor changes in the regional circulation patterns and temperature variations afterwards

basin wide holocene environmental changes in the marginal area of the asian monsoon northwest china in arid regions because of spatial variability using single climate records is difficult to reconstruct the past climate change for the drainage basins holocene environmental records were collected from the upper middle and lower regions of the shiyang river drainage basin in the marginal area of the asian monsoon northwest china the main objective of this paper was to compare the records from the terminal lake and the middle and upper reaches of the basin to study the basin wide environmental changes during the early holocene the vegetation was sparse and the effective moisture was relatively low in the basin the holocene climatic optimum started between 7 0 and 8 0 cal ka bp during which the lake level reached the highest level in the terminal lake the vegetation density and the effective moisture reached the highest level during the holocene in the drainage basin from 4 7 cal ka bp the terminal lake began to shrink while the vegetation density decreased dramatically in the middle and upper regions of the drainage the effective moisture began to decrease since 3 5 cal ka bp and the arid tendency was earlier in the terminal lake than it was in the middle and upper regions of the drainage basin during the early holocene the relatively arid environment was affected by the gradually intensifying east asian monsoon and the dry westerly winds the mid holocene optimum benefited from the intensive east asian monsoon and the humid westerly winds then the east asian monsoon retreated since the late holocene in the basin the arid tendency may be related to the retracting of the east asian monsoon however the intensifying acidification after 1 5 cal ka bp may be correlated to the increasing dryness of the westerly winds

palynological evidence of climatic and oceanographic changes in the north sea during the last deglaciation abstract palynological analyses performed on cores from the norwegian channel troll 8903 led to reconstruction of the late glacial variations in sea surface conditions using dinoflagellate cyst data and permitted direct correlation with the vegetation history of northwestern europe derived from pollen assemblages by 15 000 yr b p ice rapidly receded from the norwegian shelf and relatively warm summer conditions prevailed in surface waters a first late glacial cooling marked by extensive seasonal sea ice cover is dated at ca 13 600 13 00014c yr b p which coincides with the oldest dryas interval during the bolling allerod interval a rise in sea surface temperature both in february up to 3 c and august up to 15 c led to the establishment of ice free conditions in the northern north sea while pollen data reveal a densification of the vegetation cover the beginning of the younger dryas interval is marked by an increase in nonarboreal pollen input indicative of the opening of the forest vegetation cover concomitant with a cooling of surface waters during winter and development of sea ice cover however sea surface conditions remained relatively warm in summer until about 10 300 yr b p when extremely cold conditions and extensive sea ice cover developed up to 7 months yr improving conditions are recorded in surface waters by 10 100 yr b p a few hundred years before the development of forest cover onshore as shown by the pollen record such a discrepancy between marine and terrestrial indicators at the end of younger dryas time suggests a delayed response of the vegetation to regional climate warming

the flickering switch of late pleistocene climate change polar ice contains a unique record of past climate variations previous greenland ice cores have documented relatively warm interstadial periods during the last glaciation and short centuryscale returns to colder conditions during the glacial to interglacial warming see for example ref 1 these climate features have also been observed to varying degrees in ocean sediment cores2 4 and terrestrial pollen and insect records5 7 here we report electrical conductivity measurements from a new greenland ice core which confirm these previous observations and also reveal a hitherto unrecognized mode of rapid climate variation fluctuations in ice conductivity on the scales of 5 20 years reflect rapid oscillations in the dust content of the atmosphere this flickering between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation

new views of tropical paleoclimates from corals abstract corals offer a rich archive of past climate variability in tropical ocean regions where instrumental data are limited and where our knowledge of multi decadal climate sensitivity is incomplete in the eastern equatorial pacific coral isotopic records track variations in enso related changes in sea surface temperature further west corals record variability in sea surface temperature and rainfall that accompanies zonal displacement of the indonesian low during enso events these multi century records reveal previously unrecognised enso variability on time scales of decades to centuries outside the enso sensitive equatorial pacific long term trends towards recent warmer wetter conditions suggest the tropics respond to global forcings new coral paleothermometers indicate that surface ocean temperatures in the tropical southwestern pacific were depressed by 4 6 c during the younger dryas climatic event and rose episodically during the next 4000 yr high temporal resolution measurements of sr ca and 18 o in corals provide information about the surface ocean hydrologic balance and can resolve the seasonal balance between precipitation and evaporation radiocarbon measurements in corals coupled with ocean circulation models may be used to reconstruct near surface ocean circulation past mixing rates and the distribution of fossil fuel co2 in the upper ocean most recently seasonal to interannual variations in the radiocarbon of corals from the equatorial pacific have been linked to the redistribution of surface waters associated with the enso

reconstruction of climate and vegetation changes of lake bayanchagan inner mongolia holocene variability of the east asian monsoon a high resolution pollen and pediastrum record spanning 12 500 yr is presented for lake bayanchagan 115 21 e 41 65 n and 1355 m a s l southern inner mongolia individual pollen taxa pt mat and the pft affinity scores pft mat were used for quantitative climatic reconstruction from pollen and algal data both techniques indicate that a cold and dry climate similar to that of today prevailed before 10 500 cal yr b p the wettest climate occurred between 10 500 and 6500 cal yr b p at which time annual precipitation was up to 30 60 higher than today the early holocene increases in temperature and precipitation occurred simultaneously but mid holocene cooling started at approximately 8000 cal yr b p 1500 yr earlier than the drying vegetation reconstruction was based on the objective assignment of pollen taxa to the plant functional type the results suggest that this region was dominated by steppe vegetation throughout the holocene except for the period 9200 to 6700 cal yr b p when forest patches were relatively common inner mongolia is situated at the limit of the present east asian monsoon and patterns of vegetation and climate changes in that region during the holocene probably reflect fluctuations in the monsoon s response to solar insolation variations the early to middle holocene monsoon undoubtedly extended to more northern latitudes than at present

lacustrine and eolian records of holocene climate changes in the mongolian plateau preliminary results abstract this study compares two pairs of adjacent lacustrine and eolian sections at sites in the southern and northern mongolian plateaus in order to test spatial climate variability during the holocene based on the lithology proxy data and 14 c dated and the interpolated ages the following observations can be made in the northern mongolian plateau a best developed holocene paleosol dated at 8672 14 c yr bp at the shaamar section and the carbonate rich laminated layer in the gun nuur lake core mark the interval of warmer and dryer climate during the early holocene younger paleosols at the shaamar section and corresponding organic rich layers in the gun nuur core were formed under distinctly cooler and more humid conditions the baahar nuur lake core in the southern mongolian plateau and the dingxi type section in the northern part of the western chinese loess plateau appear to indicate that a prolonged interval of maximum humidity prevailed in this region during the early and mid holocene 9000 4000 14 c yr bp by contrast in the northern mongolian plateau the most humid conditions seem to have occurred from 4500 to 2500 possibly to 1650 14 c yr bp this discrepancy implies that the concept of the holocene climatic optimum has limitations and may have to be reconsidered if it is intended to have a large scale connotation

linkage between c4 vegetation expansion and dune stabilization in the deserts of ne china during the late quaternary abstract knowledge of the role of c4 vegetation expansion in regulating dune stabilization during the late quaternary is important for understanding the evolution of the environment and climate in the climatically sensitive margin of the east asian summer monsoon however due to the lack of both reliable vegetation records and chronological control during episodes of dune activity the relationship between c4 vegetation expansion and dune stabilization in the deserts of ne china during the late quaternary remains unclear here we present a new regional compilation of late quaternary stable carbon isotopic data from organic matter together with dated records from sub aerial sedimentary deposits in the region our compilation of vegetation development and dune activity in these deserts suggests that c4 vegetation expansion with a main contribution from chenopodiaceae and a secondary contribution from poaceae and cyperaceae may have played a critical role in dune semi stabilization with a northwestward trend from 13 to 9 ka and dune stabilization throughout the entire study region from 9 to 5 ka in addition during the late holocene intensified millet cultivation or overgrazing and or climatic deterioration at 1 5 ka likely caused an increase in c4 vegetation abundance in the deserts of ne china which is associated with a dune mobilization episode in contrast after 2 5 ka decreased vegetation cover and dune mobilization in the mu us and hobq deserts were likely caused by poor land use practices and historically documented droughts overall c4 vegetation expansion was the main cause of dune stabilization in these deserts during the late quaternary

a transfer function model developed from an extensive surface pollen data set in northern china and its potential for palaeoclimate reconstructions a total of 237 surface soil pollen samples were collected from less disturbed zonal communities and a new surface pollen data set has been established in northern china pollen climate parameter transfer functions using weighted averaging regression and calibration partial least squares wa pls model as a tool to reconstruct past climate changes from pollen data were tested with this new surface pollen data set the results of cross validation showed that the method worked very well with precipitation r 0 94 r2jack 0 89 rmsepjack 69 mm the safe dynamic range of the reconstruction was 40 mm 800 mm and worked well with temperature tann r 0 84 r 2jack 0 71 rmsepjack 2 0 c the safe dynamic range of the reconstruction was 4 c 13 c mtwa r 0 79 r2jack 0 63 rmsepjack 2 5 c and the safe dynamic range of the reconstruction was 8 c 26 c indicating that the surface pollen data set and wa pls reconstruction technique in this paper have strong potential for palaeoclimatic reconstr

holocene climatic reconstructions from the fossil pollen record at qigai nuur in the southern mongolian plateau this study focuses on the reconstructions of vegetation and climate changes during the past 11 000 years on the basis of 222 fossil pollen samples from qigai nuur core qgn 2004 in the southern p

episode of strengthened summer monsoon climate of younger dryas age on the loess plateau of central china abstract the baxie loess section just east of the tibetan plateau contains evidence showing that the asian monsoon climate experienced an abrupt reversal near the end of the last glacial age rapid deposition of dust under cool dry full glacial conditions gave way to an interval of soil development and reduced dust influx attributed to a strengthening of the warm moist summer monsoon a subsequent abrupt increase in dust deposition a response to a weakening of the summer monsoon was later followed by renewed soil formation as summer monsoon circulation again intensified during the early holocene by one interpretation the thin upper loess is a manifestation of the european younger dryas oscillation however in this case the available 14c ages require either that 1 onset of loess deposition lagged the beginning of the younger dryas event in europe by as much as 2000 calibrated 14c years or 2 all the 14c ages are too young possibly due to contamination alternatively the late glacial paleosol the top of which is synchronous with the abrupt end of the late glacial 18o anomaly in the dye 3 greenland ice core records the younger dryas event such an interpretation is consistent with general circulation model simulations of younger dryas climate that show strong seasonality and a strengthened summer monsoon and with marine cores from the western pacific ocean that contain evidence of pronounced cooling of surface waters during younger dryas time

variability of monsoon climate in east asia at the end of the last glaciation abstract high resolution paleomonsoon proxy records from peat and eolian sand paleosol sequences at the desert loess transition zone in china denote a rapid oscillation from cold dry conditions 11 200 10 60014c yr b p to cool humid conditions 10 600 10 20014c yr b p followed by a return to cold dry climate 10 200 10 00014c yr b p variations in precipitation proxies suggest that significant climatic variability occurred in monsoonal eastern asia during the younger dryas interval late glacial climate in the chinese desert loess belt that lies downwind from europe was strongly influenced by cold air from high latitudes and from the north atlantic via the westerlies the inferred precipitation variations were likely caused by variations in the strength of the siberian high which influenced the pressure gradient between land and ocean and therefore influenced the position of the east asian monsoon front

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

timing of deglaciation from an oxygen isotope curve for atlantic deep sea sediments the exact timing of deglaciation is an important issue in the context of climatic feedback involving the deglacial rise in atmospheric co2 seen in ice cores1 4 we have produced evidence from box cores taken in the equatorial atlantic that the last deglaciation occurred in two major steps which were separated by a brief pause5 here we propose that this pause is equivalent to the period of glacial readvance known as younger dryas which lasted from about 11 to 10 kyr bp if our correlation is correct then the initiation of deglaciation occurred after 14 kyr bp which disagrees with most other deep sea timescales

holocene lake level changes of hurleg lake on northeastern qinghai tibetan plateau and possible forcing mechanism the palaeoshorelines of a lake are the direct geomorphic evidences to reflect past water levels and record information on palaeoclimatic changes previous research indicates that the timing and forcing mechanisms of climatic change on the northeastern qinghai tibetan plateau ne qtp are still controversial here we report quartz optically stimulated luminescence osl ages for beach deposits and accelerator mass spectrometry ams 14c age for plant remains shoreline features and geomorphic exposures that contribute to a reconstruction of the lake level history of hurleg lake on the ne qtp the results imply that 1 three high lake levels are dated to 6 8 6 4 5 0 4 7 and 2 2 1 4 kyr corresponding to relatively wet and stable climate from pollen records of sediment core in this lake during mid late holocene 2 the highest lake level period occurred at 5 0 4 7 kyr which is almost synchronous with the highest effective moisture phase from synthesized lake records influenced by the westerlies and 3

palynological evidence for holocene environmental change in the changjiang yangtze river delta china abstract holocene vegetation changes in response to climate fluctuations and human impacts are reviewed on the basis of pollen analyses from borehole cores taken from the changjiang yangtze river delta china and other previously reported data during the earliest holocene 10 930 9000 cal yr bp the climate was warm and wet allowing thermophilous hardwoods to occupy mid and low elevations surrounding a palaeo changjiang estuary the climate became gradually cooler and cool tolerant conifers grasses and ferns became dominant until 7600 cal yr bp when the estuary became a delta a mid holocene climatic optimum occurred between 7600 and 4800 cal yr bp when evergreen and broadleaved deciduous trees flourished at mid and low elevations surrounding the delta front prodelta after this time climate became cooler again until 1340 cal yr bp during this period evergreen and broadleaved deciduous trees were replaced by conifers and grasses inhabiting the inter subtidal flat delta front this development of conifer grassland vegetation was shortly interrupted between 3860 and 3200 cal yr bp when thermophilous tree cover increased and open vegetation with scattered conifers was reduced since 1340 cal yr bp the vegetation has been similar to that at present under warm wet conditions human impacts are recognized by the first appearance of fagopyrum and a sudden increase in herb pollen at 4500 and 1340 cal yr bp respectively

conceptual model of recharge to southeastern badain jaran desert groundwater and lakes from environmental tracers sources of groundwater recharge to the badain jaran desert in china have been investigated using geochemical and isotopic techniques stable isotope compositions 18o and 2h of shallow groundwater and surface water from oasis lakes evolve from a starting composition considerably depleted compared to local unsaturated zone moisture confirming inferences from chloride mass balance that direct infiltration of precipitation is not a volumetrically important source of recharge to the shallow aquifer in the study area shallow phreatic and deeper confined groundwater bodies appear unconnected based on chemical composition and radiocarbon activities hydrogeologic evidence points toward a bordering mountain range yabulai as a likely recharge zone which is consistent with tracer results a mean residence time in the range of 1 2 ka for the desert s southeastern margin is inferred from radiocarbon these results reveal that some replenishment to the desert aquifer is occurring but at a rate much lower than previously suggested which is relevant for water resources planning in this ecologically sensitive area

inputs of glacially derived dissolved and colloidal iron to the coastal ocean and implications for primary productivity 1 glacial meltwaters draining shield bedrock under the greenland ice sheet gis contain 0 4 m total dissolved fe tdfe with an average flow weighted concentration of 53 nm the concentrations of 0 03 and 0 03 0 4 m fe vary over the ablation period with weighted means for each of these fractions being respectively 22 4 nm and 30 8 nm these concentrations are lower estimates as an adjacent larger glacier a more representative source of glacial meltwater had higher dissolved fe concentrations and reactions of meltwaters with proglacial sediments could also enhance dissolved fe concentrations this source of tdfe is additional to the reactive oxyhydr oxide phases identified by raiswell et al 2006 that are also introduced to adjacent polar seas from glaciers the fe concentrations in the shield bedrock underlying the gis are lower than those of other crustal rocks 4 0 cf 6 2 but we argue that these fe concentrations are not limiting on the total dissolved fe concentrations we measure the biogeochemical weathering processes operating on the subglacial debris and suspended sediment in our catchment are likely to be similar to those in other glaciated catchments therefore the meltwater fe concentrations reported here can be used to give a first estimate of global fluxes of meltwater dissolved fe to coastal polar waters a lower estimate of the global flux of tdfe from glacial meltwaters is 75 106 moles fe a this glacial meltwater input of fe to adjacent polar waters will be greatest around greenland where there are highest annual meltwater discharges however the greatest impact of this source of glacial meltwater fe is anticipated to be in antarctic high nutrient low chlorophyll hnlc waters where phytoplankton productivity is typically limited by availability of fe for antarctic waters the estimated meltwater fe tdfe input is about 10 of that suggested to come from sea ice melting but glacial inputs continue throughout the austral summer ablation period after sea ice melt is complete

asynchronous evolution of the indian and east asian summer monsoon indicated by holocene moisture patterns in monsoonal central asia abstract the numerical meta analysis of 92 proxy records 72 sites of moisture and or temperature change confirms earlier findings that the dominant trends of climatic evolution in monsoonal central asia since the last glacial roughly parallel changes in northern hemisphere summer insolation i e the period following the last glacial maximum was characterized by dry and cold conditions until 15 cal kyr bp followed by a warm wet period coincident with the bolling allerod warm period and terminated by a cold dry reversal during the younger dryas period after an abrupt increase at the start of the holocene warm and wet conditions prevailed until ca 4 cal kyr bp when moisture levels and temperatures started to decrease ordination of moisture records reveals strong spatial heterogeneity in moisture evolution during the last 10 cal kyr the indian summer monsoon ism areas northern india tibetan plateau and southwest china exhibit maximum wet conditions during the early holocene while many records from the area of the east asian summer monsoon indicate relatively dry conditions especially in north central china where the maximum moisture levels occurred during the mid holocene we assign such phenomena to strengthened hadley circulation centered over the tibetan plateau during the early holocene which resulted in subsidence in the east asian monsoonal regions leading to relatively dry conditions our observations of the asynchronous nature of the two asian monsoon subsystems on millennial time scales have also been observed on annual time scales as well as implied through the spatial analysis of vertical air motion patterns after strong ascending airflows over the tibetan plateau area that were calculated from ncep ncar reanalysis data for the last 30 years analogous with the early holocene the enhancement of the ism in a future warming world will result in an increase in the asynchronous nature of the monsoon subsystems this trend is already observed in the meteorological data from the last 15 years

timing and structure of the younger dryas event in northern china a high resolution and absolute dated stalagmite record from kulishu cave beijing characterizes asian monsoon am history in northern china between ca 14 and 10 5 ka bp thousand yrs before present present 1950 including the entire younger dryas yd event using 230 th dates and counting of annual layers the shift into the yd began at 12 850 40 yr bp and took w340 yrs and the shift out of the yd began at 11 560 40 yr bp and took 38 yrs best estimate w20 yrs broadly similar to previously reported am records from central and southeastern china the more gradual nature of the start of the yd event as observed in the am records appears to contrast with the more abrupt beginning observed in the greenland ice records the total amplitude of the am yd event is also smaller than the amplitude of the am heinrich stadial 1 event in addition the general rising trend of the am during the bolling allerod period contrasts with the general cooling trend in greenland temperature during that time the influence of rising insolation on the am may explain this observation

a critical examination of evidence for a quaternary glaciation in mt laoshan eastern china abstract accurately determining how far south quaternary glaciers existed in eastern china has important implications for understanding global quaternary climate in this study we provide evidence for a colder paleoclimate in the late pleistocene of the laoshan range on the eastern shandong peninsula at 36 05 36 19 n latitude through documentation of erosional and depositional landforms that were possibly formed by glaciation we integrate field observations documenting and mapping the existence of typical glacial cirques glacial horns moraines aretes tarn lakes and other paleoglacial features in mt laoshan with a detailed digital elevation model dem created in an arcgis environment merged with landsat etm imagery to document the spatial relations of these features other features that may or may not be glacial in origin include large boulder fields that could be moraines or debris avalanches and potholes that could have formed beneath glaciers or in river systems additionally some features previously interpreted as glacial features are here re interpreted as weathering related phenomena although some of these features alone provide only weak to moderate evidence for glaciation together the suite of indicators provides strong evidence for sea level glaciation at 36 n in the late pleistocene of eastern china we further integrate the evidence of glaciation with the late pleistocene paleogeography and climate and suggest that the glaciers formed as a result of orographic effects from moist monsoonal breezes crossing a paleolake developed in north china then rising over mt laoshan and dropping their moisture there with a wide desert formed on the leeward side of the mountains

estimation of aeolian dust flux on cheju island korea during the mid to late holocene abstract aeolian dust flux was estimated from a maar sediment with bimodal grain size distribution on cheju island korea during the mid to late holocene the bimodal grain size distributions of chemically isolated aeolian quartz and lithogenic minerals were partitioned into fine and coarse components by a weibull function fitting method and fine and coarse aeolian dust fluxes were estimated estimates of coarse dust flux ecdf during the last 6500 years varied from 2 to 14 mg cm 2 yr and averaged 7 mg cm 2 yr ecdf were low during the period 6500 4000 cal yr bp increased from 4000 to 2000 cal yr bp and decreased again from 2000 to 1000 cal yr bp indicating a millennial scale variation the estimates of fine dust flux efdf varied from 1 to 11 mg cm 2 yr with an average of 3 mg cm 2 yr the variation of efdf was characterized by centennial scale fluctuations these results demonstrate that aeolian dust sediments in downwind areas including korea and japan were a mixture of fine and coarse dust components transported by the westerlies and winter monsoon surface winds respectively this suggests that these aeolian dust sediments should be interpreted in view of two dust components and two transporting winds

teleconnection of climatic events between east asia and polar high latitude areas during the last deglaciation abstract from observations of continuous aeolian and swamp sediment sequences augmented by a detailed 14 c chronology 13 c and organic c analyses we can demonstrate century to millennium scale fluctuations in east asian monsoon palaeoclimatic events we also infer significant precipitation variability within the last deglaciation the major climatic zones that have been recognised in europe and find counterparts in east asia are the bolling allerod 14 750 12 800 cal yr b p and the younger dryas 12 800 11 600 cal yr b p the last deglaciation sediment sequences are characterised by frequent facies changes reflecting climate instability these frequent abrupt climatic events correlate well with fluctuations recorded in high latitude and polar areas as represented by the greenland ice core gisp 2 and a core from the north sea this indicates a palaeoclimate teleconnection between the high latitude and polar areas and the east asian monsoon areas through cold air mass activity and the related atmospheric pressure system

holocene environmental changes in the central inner mongolia based on single aliquot quartz optical dating and multi proxy study of dune sands abstract alternating units of dune sands and paleosols in the central inner mongolia imply multiple episodes of dune building and stabilization in response to the waxing and waning of the east asian monsoon such eolian deposits were dated by using the single aliquot quartz optical dating method combined with the multi proxy study on the deposits the past environmental changes during the holocene have been reconstructed our results indicate that widespread eolian sand mobilization occurred in the studied region during the beginning of the early holocene from 11 5 ka to 9 ka the climate became warm and humid during the period between 9 ka and 5 6 ka holocene optimum after 5 6 ka the region again became arid as inferred from dune building however the environmental changes during the late holocene have been affected by both climate and human impacts and the presence of desert environment in such semiarid region is not only the result of climatic drought of the late holocene but also related to poor land use practices

climate changes in northern china since the late pleistocene and its response to global change abstract nine representative high resolution profiles with reliable 14c chronologies have been chosen from the monsoon sensitive areas in china winter monsoon from the north west and summer monsoon from the east to provide a comparative picture of climate change within these areas comprehensive analyses of stratigraphic sequences and climatic proxy data have been used to reconstruct a history of fluctuating dry and wet environmental conditions in these monsoon sensitive areas since the last deglaciation these records have also been compared with greenland ice core and guliya ice core data four major events representing these climate fluctuations e1 e4 are recognised among them e3 indicates an abrupt cooling event after the younger dryas interval this event has so far only been recognised in china and high latitude areas in the northern hemisphere it is proposed that century to millenial scale global temperature changes affect the intensity of monsoon circulation through ocean atmosphere interactions hence producing dry and wet climate fluctuations in monsoon sensitive areas in an era of global warming the overall picture presented by the sequences of wet dry periods recorded in chinese monsoon affected areas during the last deglaciation can be used as an historical analogue for future predictions of medium to long term climate change within these areas

chronology of holocene sediments from the archaeological salawusu site in the mu us desert in china and its palaeoenvironmental implications the archaeological salawusu site is located at the southeast margin of the mu us desert and in the northern marginal area of the east asian monsoon therefore its environment is sensitive to the changes of the east asian monsoon at the palaeolithic salawusu site most of the previous studies are concerned with the age of the palaeoanthropic fossils ages ranging from 30 to 120 ka and the climate change in the last glaciation period while studies on the chronology and climate change since the late glacial are very limited in the current study eight luminescence samples were collected from dishaogouwan dsg section and dated using quartz optically stimulated luminescence osl radiocarbon samples were also collected and the past environmental changes since the late glacial have been reconstructed based on stratigraphical and chronological data the results show that 1 the ams age of modern weed living under water is about 1550 35 a which is the current reservoir effect age and after reservoir effect subtraction the radiocarbon age of the shells is in agreement with the osl age while the radiocarbon age of the bulk sample is younger 2 aeolian sand mobilization occurred in the studied region before similar to 12 ka 3 within the holocene the wettest climate occurred during the onset of the holocene when an extensive palaolake existed in the study area marked by the development of lacustrine sediments at around similar to 12 ka 4 after similar to 12 ka the climate showed a trend of increasing aridity which led to a continuous shrinkage of the palaolake and its ultimate desiccation between 1 8 and 1 0 ka evidenced by the shift from lacustrine sediments to peat and finally to palaeosol 5 the dating results also show an enormous incision of about 60 m in about 1 75 ka by the salawusu river c 2011 elsevier ltd all rights reserved the archaeological salawusu site is located at the southeast margin of the mu us desert and in the northern marginal area of the east asian monsoon therefore its environment is sensitive to the changes of the east asian monsoon at the palaeolithic salawusu site most of the previous studies are concerned with the age of the palaeoanthropic fossils ages ranging from 30 to 120 ka and the climate change in the last glaciation period while studies on the chronology and climate change since the late glacial are very limited in the current study eight luminescence samples were collected from dishaogouwan dsg section and dated using quartz optically stimulated luminescence osl radiocarbon samples were also collected and the past environmental changes since the late glacial have been reconstructed based on stratigraphical and chronological data the results show that 1 the ams age of modern weed living under water is about 1550 35 a which is the current reservoir effect age and after reservoir effect subtraction the radiocarbon age of the shells is in agreement with the osl age while the radiocarbon age of the bulk sample is younger 2 aeolian sand mobilization occurred in the studied region before similar to 12 ka 3 within the holocene the wettest climate occurred during the onset of the holocene when an extensive palaolake existed in the study area marked by the development of lacustrine sediments at around similar to 12 ka 4 after similar to 12 ka the climate showed a trend of increasing aridity which led to a continuous shrinkage of the palaolake and its ultimate desiccation between 1 8 and 1 0 ka evidenced by the shift from lacustrine sediments to peat and finally to palaeosol 5 the dating results also show an enormous incision of about 60 m in about 1 75 ka by the salawusu river c 2011 elsevier ltd all rights reserved

timing and spatial distribution of mid holocene drying over northern china response to a southeastward retreat of the east asian monsoon 1 to determine the timing and spatial distribution of mid holocene drying over northern china the mineralogical and oxygen isotopic composition of authigenic carbonate from a closed lake at bayanchagan southern inner mongolia were measured further analysis and synthesis of the spatial geological data were performed results from lake bayanchagan show a significant drying at 6000 calendar years cal years b p indicated by dolomite precipitation and a striking rise in 18o values the synthesis of spatial data reveals a zonal distribution for timing of drying over northern china in the mid holocene which began at 9000 7000 cal years b p in deserts of north central china at 7000 5500 cal years b p drying extended into the desert steppe transitional zone and at 4500 cal years b p into northeastern and south central china this pattern indicates that the east asian summer monsoon has significantly retreated southeastward since the mid holocene which may be related to orbitally induced northern hemisphere insolation changes a retreat of 400 550 km is inferred for the front of the summer monsoon from 6500 to 4500 cal years b p

eolian environmental changes in the northern mongolian plateau during the past 35 000 yr abstract this study focuses on an eolian section shaamar section in the northern mongolian plateau and compares the eolian sequences in the northern mongolian plateau with those along the southern boundary of the gobi deserts to better understand the dynamics of the gobi deserts during the past 35 000 14c yr bp only a weak entisol like paleosol was formed around 29 000 14c yr bp in the exposed mis 3 portion at the shaamar section whereas an eolian colluvium paleosol sequence at nearby bureghkanga section exhibits three paleosols formed around 29 000 14c yr bp 31 000 14c yr bp 34 000 14c yr bp loess paleosol sequences in the western siberian lowland exhibit four paleosols formed from 40 000 to 25 000 14c yr bp i e mis 3 during mis 2 two mollisol like paleosols were formed from 25 000 to 21 000 14c yr bp and from 16 000 to 13 000 14c yr bp and one entisol like paleosol was formed around 9500 14c yr bp at the shaamar section the mis 2 was characterized primarily by silt deposition except for the interval between 21 000 and 16 000 14c yr bp that was dominated by sand deposition the holocene began with the mollisol like paleosol formation from 8600 to 7000 14c yr bp the mid holocene 7000 to 3000 14c yr bp was marked by a relatively poor vegetation cover and the late holocene since 3000 14c yr bp by the densest vegetation cover of the entire holocene in summary the maximal extent of hyperarid and arid areas gobi deserts and gobi like occurred twice 1 from 21 000 to 16 000 14c yr bp and from 13 000 to 8600 14c yr bp when the dominant eolian deposition conditions extended from 56 n to 33 n or even larger the extent of hyperarid and arid areas retreated to the area between 38 n and 48 n or even much smaller several times during mis 3 and during the early holocene considering the uncertainties of dates it seems that the holocene bioclimatic conditions might have changed more or less synchronously between the north and the south and that the bioclimatic conditions varied more frequently in the north than in the south during mis 3 two mollisol like paleosols iic 13 000 to 16 000 14c yr bp and iiia 21 000 to 25 000 14c yr bp were well developed during mis 2 in the north but no corresponding major paleosols were discovered in the south suggesting that the climate did not change synchronously during mis 2 the climates during the stadial interstadial mis 3 2 transition 25 000 to 21 000 14c yr bp and during the last glacial maximum deglacial transition 16 000 to 13 000 14c yr bp were much more humid in the north than in the south

eolian quartz flux variations in cheju island korea during the last 6500 yr and a possible sun monsoon linkage we have obtained a high resolution sedimentary record covering the last 6500 yr from a maar in cheju island korea in order to reconstruct the history of variations in the eolian quartz flux eqf and hence asian dust the long term variation of eqf reveals three intervals a period of high eqf 4000 2000 cal yr b p and two periods of low eqf 6500 4000 cal yr b p and 2000 cal yr b p to present which have been affected by the east asian monsoon due to insolation change and the cold air activity in high latitudes correlated with polar high pressure systems this long term variation is superimposed by millennial and centennial scale fluctuations with periodicities of 1137 739 214 162 137 127 and 111 yr implying drier conditions in the source areas in china the detrended eqf record correlates visually and statistically cross spectral analysis with the atmospheric d 14 c record solar proxy the centennial scale variability in eqf may be affected

late quaternary landscape evolution in a small catchment on the chinese loess plateau abstract late quaternary landscape evolution was analysed with reference to a small 0 08 km 2 drainage basin system in southeastern gansu province southwestern chinese loess plateau in this region v shaped valleys with broad valley floors are prominent landscape features whose basic shape already existed prior to mis 2 during mis 2 the valley bottoms were infilled with fluvially reworked loess today forming accumulation terraces infrared optically stimulated luminescence irsl dating of these loess like deposits assigned them to the time span ranging from 22 5 to 17 7 ka bp during the late holocene valley fills were partly eroded and the receiving stream channel was deepened by at least 25 m close to the confluence of the study site s channels these alternating erosion and accumulation phases were triggered by climatic factors or human impact in the most recent past the high landscape sensitivity of the chinese loess plateau has led to increasing soil conservation measures that have effectively confined surface erosion however the lack of drainage on the artificial terraces induces piping processes

late pleistocene intensification technologies in northern china intensification technologies used in late pleistocene northern china include microblades milling stones and pottery all of which have been implicated in development of agriculture in northern china perhaps influenced by the harsh climate of the younger dryas this paper examines the adaptive function of these technologies in the context of late pleistocene climate and environment it is proposed that microlithic technology was a tool of mobile foragers focused on hunting and the initial use of pottery was probably connected to bone grease production only milling stones were initially a plant oriented intensification technology but their sparse episodic appearance in the late pleistocene did not lead to persistent intensification involved in the development of agriculture it was only after the younger dryas in the context of improved holocene climate and greater primary productivity that these three technologies converged with changes in mobility to become part of the agricultural revolution in northern china

postglacial climate change record in biomarker lipid compositions of the hani peat sequence northeastern china abstract the peat sequence at hani in northeastern china accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system the molecular compositions of n alkanes n alkanols and n alkanoic acids extracted from the hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat forming vegetation long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n alkane distributions throughout the hani peat sequence the paleoclimate integrity of these biomarker molecules appears to be well preserved most of the n alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants in contrast n alkanoic acid distributions are dominated by secondary components that record the importance of post depositional microbial activity in this peat sequence which evidently can be extensive in a percolation mire elevated n alkane paq values and c23 c29 ratios which are both molecular proxies for water loving plants record an especially moist local climate in the bolling allerod 14 5 to 12 9 ka younger dryas 12 9 to 11 5 ka and pre boreal 11 5 to 10 5 ka portions of the hani peat sequence depressed paq values and c23 c29 ratios and larger n alkane average chain length values indicate that the holocene climatic optimum 10 5 to 6 ka was a period of warmer climate with lower effective precipitation which contrasts with evidence of wetter climates in most of east asia