climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

climate instability during the penultimate glaciation evidence from two high resolution loess records china the xinzhuangyuan and lijiayuan loess sections in the northwestern part of the chinese loess plateau were studied down to paleosol unit s2 which probably formed during marine oxygen isotopic stage 7 200 000 years b p the thickness of the loess soil sequence above s2 is 63 m at xinzhuangyuan and 43 m at lijiayuan a 2 cm sample spacing yields a mean depositional resolution of 50 80 years for the last and penultimate glacial loess units l1 and l2 and 200 years for the last interglacial soil unit sl thus enabling us to reconstruct high resolution climatic changes during the last two glacial interglacial cycles the grain size records of the two sections are regarded as a proxy for changes in the monsoon desert system over northern china results show that frequent large amplitude climatic oscillations on millennial timescales occurred during the penultimate glaciation in a manner similar to that during the last glaciation suggesting that suborbital scale climatic variations may be a common feature of the climate system during glacial periods of the pleistocene the last interglacial soil s1 is composed of three individual soils and two thin intervening loess horizons in both of the sections short term variations in grain size are not prominent within the soil complex implying the absence of strong millennial scale climatic oscillations during the last interglaciation in northern china

ice volume forcing of winter monsoon climate in the south china sea high resolution studies of a planktonic foraminifer core record from the south china sea scs 31kl 18 45 4 n 115 52 4 e water depth 3360 m reveal changes driven by ice volume forcings in the climate of the east asian monsoon in the western pacific marginal sea during the late quaternary the analyses of planktonic foraminifer faunal abundance data from the core indicate significant variations in the relative abundances of the dominant taxa over the past 100 000 years since the isotope stage 5 the transfer function estimates of faunal sea surface temperatures sst correlate well with a long term 104 105 years trend of global glaciation about 65 000 years ago there was an observable change in the mode of sst variability as many low latitude records have shown these findings suggest that the scs surface circulation and the east asian winter monsoon systems are mainly driven by variations in global glaciation levels the association of surface ocean cooling in the scs with global climatic events suggests that fluctuations in the strength of the east asian winter monsoon may be linked to shifts in the latitudinal position of the westerly winds and the siberian high pressure system

abrupt change of sediment records in the southern south china sea during the last glacial period and its environment significance abstract chemical compositions of sediments at core ns07 25 6 39 945 n 113 32 936 e water depth 2006 m are analyzed to discuss abrupt change of sediment records in the southern south china sea scs during the last glacial period and its environmental implications major and trace elements experienced three significant changes which occurred at 31 9 26 1 and 18 5 ka bp respectively at 31 9 ka bp when sea surface temperature remained relatively low terrigenous sediment flux increased but biogenic activities weakened greatly at 26 1 ka bp both terrigenous sediment flux and biogenic fractions number were steady however some elemental ratios changed noticeably at that time before 26 1 ka bp core sediments with low nb ta but high zr hf ratios were mainly derived from the paleo mekong and or molengraaff rivers exposed on the sunda shelf at that time after 26 1 ka bp sediments with high nb ta but low zr hf ratios probably relate to strengthened impact of deep water current since 18 5 ka bp sea level ascended rapidly from 110 m below the present terrigenous sediment flux decreased and biogenic activities strengthened continuously probably related with the east asian monsoon evolution

changes in sand content of loess deposits along a north south transect of the chinese loess plateau and the implications for desert variations geological records have shown that the deserts east of the helan mountains in northern china were covered by grass during the holocene optimum whereas during marine oxygen isotope stages 2 and 4 distribution of the deserts was almost the same as at present the wide advance retreat cycles of the deserts may have exerted an important control on grain size changes in the loess of the loess plateau by altering the distance between the source and the accumulation zone of the loess this challenges the widely accepted model that winter monsoon winds were the sole factor responsible for spatial and temporal changes in loess texture to observe spatial changes in sedimentological characteristics of loess during the last glacial interglacial cycle the texture of loess was measured along a north south transect of the loess plateau this transect consists of nine loess sections starting at yulin in the transitional region between the loess plateau and the mu us desert and ending at weinan in the southernmost part of the loess plateau southward changes in sand 63 m content along the transect suggest that variations in desert extent have indeed played a significant role in loess grain size distributions particularly in the northern part of the loess plateau it is proposed that sand content 63 m of loess in the loess desert transitional zone may be used as a proxy indicator for proximity to the desert margin

recent developments in element concentration and isotope ratio analysis of individual fluid inclusions by laser ablation single and multiple collector icp ms abstract laser ablation inductively coupled plasma mass spectrometry la icp ms has become a most powerful technique for the elemental analysis of individual polyphase inclusions completely enclosed in minerals be they solid or a solid liquid gas mixture at the time of measurement simultaneous accurate quantification of major to ultra trace element concentrations from li to u by well controlled ablation of the entire fluid or melt inclusion content and successful use of largely matrix independent external calibration protocols are unique features of this method this contribution reviews fluid inclusion fundamentals relevant for their bulk analysis by la icp ms and discusses key aspects of the analytical protocol emphasis is on figures of merit precision accuracy obtained from the analysis of individual inclusions and fluid inclusion assemblages and procedures and technical developments to improving data quality are elaborated a new equation for the calculation of detection limits for la icp ms analysis is presented which closely follows iupac conventions applications are reviewed with emphasis on the use of synthetic fluid inclusions in constraining metal solubility and distribution between co existing phases new data for natural bismuth fluid inclusions document the seamless transition to melt inclusion analysis by la icp ms thus highlighting the fact that the procedures presented here are generally applicable to the analysis of inclusions in complex host minerals isotope ratio analysis of individual fluid inclusions by multicollector icp ms mc icp ms is a recent development that requires fast transient signals to be accurately recorded by instrumentation designed for high precision static measurements of long lasting stable ion beams we address the general principles based on pb isotopes and review a first application to the bingham canyon porphyry cu au mo deposit a pilot study using about 50 synthetic fluid inclusions containing srm 987 sr and variable nacl ca and rb concentrations demonstrates that accurate 87 sr 86 sr isotope ratios can be obtained on an individual rb poor fluid inclusion at absolute 2 precisions of 0 0003 to 0 002 a residual trend in 87 sr 86 sr as a function of the rb sr abundance ratio in the fluid inclusions suggests that interference correction of 87 rb on mass 87 assuming identical mass bias coefficients for the two elements may be inaccurate however the offset can be accurately corrected for by regressing the data to zero 87 rb the versatility and detection power of la icp ms makes this technique the method of choice for solute abundance and isotope ratio analysis of individual fluid inclusions significant future progress can be achieved by improvements in ion production transmission and data recording efficiency and by further improving control on inclusion ablation by pulsed laser beams data quantification strategies may also have to be further refined to keep pace with instrumental progress and innovation

quaternary glacial history of the kanas valley chinese altai nw china constrained by electron spin resonance and optically stimulated luminescence datings abstract the chinese altai is located on the northern edge of central asia rich geological records of quaternary glaciations are preserved in this area however the glacial history in the chinese altai has hardly been investigated this study aims to rebuild the regional glacial history in the kanas valley of the chinese altai we present 14 electron spin resonance esr ages and 3 optically stimulated luminescence osl ages from glacial landforms by integrating with ages from previous studies five major glacial advances are identified during marine oxygen isotope stages mis 6 5 4 3 and 2 with ages of 167 0 16 0 123 0 18 0 ka 97 0 19 0 78 0 7 0 ka 76 0 16 0 73 1 6 6 ka 52 1 7 8 34 4 4 2 ka and 28 0 3 3 16 1 1 5 ka respectively the glacial advance during mis 5 is the local last glacial maximum and glaciers became successively more restricted from mis 5 to mis 2 in addition the extensive mis 3 glacial advance in the chinese altai contrasts with the absence of mis 3 glacial advance in the mongolia altai these glacial patterns reflect that precipitation brought by the westerlies might play a primary role on driving glacial advances during the last glacial in the chinese altai this glacial chronology is in reasonable agreement with existing glacial chronologies from other parts of the altai tian shan and pamir indicating similar climate controls on the patterns of quaternary glaciation across central asia highlands

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

color reflectance of chinese loess and its implications for climate gradient changes during the last two glacial interglacial cycles 1 to examine the relationship between color changes of loess deposits and paleoclimate conditions a north south transect consisting of twelve loess sections were studied color reflectance was measured on loess paleosol samples from the loess transect which accumulated over the last two glacial interglacial cycles the redness value a shows an overall southward increase for both loess and soil units coinciding with the pattern of a southerly increase in pedogenic development and the present north south climatic gradient the redness of loess deposits is linearly correlated with latitude values implying that this parameter is an efficient proxy for the weathering intensity of loess deposits the gradient of weathering intensity is much steeper during interglacials than in glacials by comparison of color records for different time interval

loess record of climatic changes during mis5 in the hexi corridor northwest china abstract the hexi corridor is adjacent to deserts that serve as one of the dust sources of chinese loess the rate of aeolian dust accumulation is higher in the corridor than those in central and western part of chinese loess plateau so the loess might have recorded more details of climate changes the approximately 12 m thick s1 paleosol sequence at the shagou loess section comprises five soils and four intervening loess horizons color index carbonate content and grain size variation within the loess paleosol sequence are used as proxies of the east asian monsoon and movement of the desert margin the eemian mis 5e equivalent lacks obvious variations in the shagou record a transition layer in this section indicates the complexity of the penultimate deglaciation during substage 5d 5a sub orbital fluctuations of monsoon and desert variations are recorded both in the proxies and stratrigraphy being coincident with cold events and warm interstadials in north atlantic and greenland our records suggest that the east asian monsoon was affected by polar and high latitude climate variations even in the last interglacial

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

timing of glacier expansion during the last glacial in the inner tien shan kyrgyz republic by osl dating abstract optically stimulated luminescence osl dating was applied to glacial sediments and adjacent loess from moraines in the teskey ala too and at bashy ranges in the inner tien shan kyrgyz republic kyrgyzstan two large glacier expansions during the last glacial were observed in the two study areas teskey terskey stages i and ii moraines were dated to marine isotope stage mis 4 early mis 3 and mis 2 and at bashy stage ii in the at bashy range dated to late mis 3 mis 2 the timing of the two expansions during the last glacial coincided with global cold periods and with advances of the major northern hemisphere ice sheets however the fact that the greater expansion occurred in mis 4 early mis 3 in the teskey ala too range suggests that climate during mis 4 early mis 3 was more humid than during mis 2 it is possible that the strengthened siberian high during mis 2 restricted the impact of the westerlies and this reduced precipitation in the study area

are chinese loess deposits essentially continuous 1 we conducted a paleomagnetic examination of the last glacial loess of three representative profiles along an east west transect in the central loess plateau in order to assess the continuity of chinese loess the results show that the xifeng and luochuan profiles record the laschamp geomagnetic excursion but with different morphologies together with the published results from weinan southern plateau our results suggest that sedimentation of the last glacial loess in the central southern plateau was continuous at the time scale equivalent to the duration of the laschamp excursion 2 kyr but probably episodic at finer time scales 2 kyr no geomagnetic excursion was found at the yichuan profile near the yellow river valley where loess accumulation may be strongly affected by local environmental changes and thus may have been discontinuous both site location and time scale therefore need to be considered when considering continuity of chinese loess

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

stable isotope and ostracode species assemblage evidence for lake level changes of nam co southern tibet during the past 600 years abstract ostracode species assemblages and stable oxygen and carbon isotopes of shells from two 210 pb dated short cores of 78 cm and 47 cm length taken from lake nam co southern tibet provide information about lake level history of the past approximately 600 years at decadal resolution a transfer function is applied to reconstruct paleo water depths from modern ostracodes ostracode assemblages and isotope data from five species allow a subdivision into phases of lake level evolution before 1600 ad relatively low oxygen isotope values and high abundances of deep water 30 m ostracodes i e leucocythere dorsotuberosa leucocythere dorsotuberosa f postilirata suggest a lake level 10 m higher than today between 1600 ad and 1800 ad more positive oxygen isotope values and higher abundances of shallow water ostracodes i e ilyocypris cf mongolica candona xizangensis suggest a lake level approximately 40 m below modern level between 1800 ad and 1920 ad oxygen isotopes are characterized by a trend to more negative values followed by a trend to more positive ones these trends are interrupted by several short term fluctuations but overall oxygen isotope values suggest a drop in lake level a clearer lake level picture is provided by species assemblages that suggest a continuously increasing lake level since 1900 ad precipitation data from meteorological stations nearby show an increase in precipitation in the last 30 years the low lake level between 1600 ad and 1800 ad is contemporary to the little ice age during that cold period meltwater input into the lake decreased this underlines the sensitivity of the level of lake nam co to temperature changes on the tibetan plateau

impact of late quaternary environmental changes on deep sea benthic foraminiferal faunas of the red sea abstract fluctuations in abundance diversity and species composition of benthic foraminifera from two sites of the northern and southern red sea indicate strong variability of deep sea ecosystems during the last four glacial to interglacial cycles in total five and four different benthic foraminiferal assemblages have been identified in the northern core and southern core respectively comparison with recent faunas from the red sea and adjacent oceans allowed the reconstruction of temporal changes in deep water ventilation salinity and food availability at the seafloor generally the abundance of infaunal and miliolid taxa increase during glacial intervals indicating increased organic matter fluxes oxygen decrease and salinity increase in deep waters during these times these fluctuations are attributed to enhanced oxygen consumption rates and temporarily reduced deep water formation in the northern red sea during glacial intervals the recorded environmental changes are a reflection of both high and low latitude climate changes the northern red sea is mainly influenced by glacio eustatic sea level fluctuations that control deep water formation rates and by mid latitude climate changes of the mediterranean region that control surface productivity in contrast deep sea ecosystem variability of the southern red sea is additionally influenced by low latitude climate changes attributed to the ne monsoon intensity that drives the inflow of nutrient rich surface waters from the gulf of aden these results demonstrate the high sensitivity of deep sea ecosystems of the red sea to both global and regional climate changes

impacts of post depositional processes on rapid monsoon signals recorded by the last glacial loess deposits of northern china abstract rapid east asian monsoon oscillations recorded by chinese loess are thought to be dynamically linked to north atlantic climate however few efforts have been made to assess the effects of post depositional processes e g surface mixing and pedogenesis on loess paleoclimatic records here a detailed optically stimulated luminescence dating of a thick loess sequence from the western loess plateau is presented offering a reliable chronology for last glacial deposits magnetic susceptibility and mean grain size records from three loess paleosol sequences along a northwest southeast transect are investigated to evaluate impacts of post depositional processes on these loess based proxy records our results indicate that 1 loess sequences developed within the flat tableland of the central and western loess plateau are nearly continuous during the last glaciation and 2 post depositional processes have distinct impacts on rapid monsoon signals recorded in loess sequences from different regions in the central loess plateau rapid monsoon signals have been attenuated to various degrees depending on the sedimentation rate and pedogenic intensity in the northwestern loess plateau however due to high sedimentation rate and relatively weak pedogenesis high resolution grain size oscillations reliably record rapid monsoon changes and can be well correlated to rapid climate changes recorded in the greenland ice core and hulu cave stalagmite

comparison of oxygen isotope records from the gisp2 and grip greenland ice cores recent results1 2 from the greenland ice core project grip summit ice core suggest that the climate in greenland has been remarkably stable during the holocene but was extremely unstable for the time period represented by the rest of the core spanning the last two glaciations and the intervening eemian inter glacial here we present the complete oxygen isotope record for the greenland ice sheet project 2 gisp2 core drilled 28 km west of the grip core we observe large rapid climate fluctuations throughout the last glacial period which closely match those reported for the grip core however in the bottom 10 of the cores spanning the eemian interglacial and the previous glacia tion there are significant differences between the two records it is possible that ice flow may have altered the chronological sequences of the stratigraphy for the bottom part of one or both of the cores considerable further work will be necessary to evaluate the likelihood of this and the extent to which it will still be possible to extract meaningful climate information from the lowest sections of the cores

impacts of grain size sorting and chemical weathering on the geochemistry of jingyuan loess in the northwestern chinese loess plateau abstract major and trace elemental compositions of loess samples collected from the jingyuan section in the northwestern chinese loess plateau clp were analyzed to investigate the potential impacts of grain size sorting and chemical weathering on the loess geochemistry and to extract appropriate geochemical indices for better evaluating the east asian monsoon variability based on variations of major and trace elements in different grain size fractions seventeen elements were classified into three types 1 si and na display higher contents with the increased particle sizes 2 al fe mg k mn zn rb cr v are mainly enriched in fine size fractions 3 ti ba zr p ca and sr show irregular variations among different size fractions comparison of al normalized elemental ratios with zr rb and rb sr ratios two commonly employed indicators for grain size sorting and pedogenic weathering indicates that si al zr al ti al variations match well with zr rb and grain size results whilst ca al sr al p al ratios display similar variability as that of rb sr ratio comparison of loess based proxies e g elemental ratios magnetic susceptibility grain size of jingyuan section with speleothem and ice core records confirms that elemental ratios of high resolution loess sequences developed in the northwestern clp can be employed to address fluctuations of the winter monsoon induced grain size sorting and summer monsoon related weathering and pedogenesis at glacial interglacial and millennial timescales

oxygen isotope record of sea level and climate variations in the sulu sea over the past 150 000 years the sulu sea is located in the warm pool of the western pacific ocean where mean annual temperatures are the highest of anywhere on earth because this large heat source supplies the atmosphere with a significant portion of its water vapour and latent heat understanding the climate history of the region is important for reconstructing global palaeoclimate and for predicting future climate change changes in the oxygen isotope composition of planktonic foraminifera from sulu sea sediments have previously been shown to reflect changes in the planetary ice volume at glacial interglacial and millenial timeseales and such records have been obtained for the late pleistocene epoch and the last deglaciation1 3 here i present results that extend the millenial time resolution record back to 150 000 years before present on timescales of around 10 000 years the sulu sea oxygen isotope record matches changes in sea level deduced from coral terraces on the huon peninsula4 this is particularly the case during isotope stage 3 an interglacial period 23 000 to 58 000 years ago where the sulu sea oxygen isotope record deviates from the specmap deep ocean oxygen isotope record5 thus these results support the idea4 6 that there were higher sea levels and less continental ice during stage 3 than the specmap record implies and that sea level during this interglacial was just 40 50 metres below present levels the subsequent rate of increase in continental ice volume during the return to full glacial conditions was correspondingly faster than previously thought

osl dating of glacier extent during the last glacial and the kanas lake basin formation in kanas river valley altai mountains china the kanas river originates on the southern slope of youyi peak the largest center of modern glaciers in altai mountains china three sets of moraines and associated glacial sediments are well preserved near the kanas lake outlet recording a complex history and landscape evolution during the last glacial dating the moraines allows the temporal and spatial glacier shift and climate during the last glacial to be determined and then constrains when and how the kanas lake basin was formed dating of the glacial tills was undertaken by utilizing the optically stimulated luminescence osl method results date four samples from the three sets of moraines to 28 0 34 4 38 1 and 49 9 ka and one sample from outwash sediment to 6 8 ka the kanas lake basin is a downfaulted basin and was eroded by glacier before 28 0 ka and the glacial moraines blocked the glacier melt water after the glacier retreat which made the present day kanas lake eventually form at least before 6 8 ka bp in altai mountains the glacier advance was more extensive in marine isotope stage mis 3 than mis 2 probably because the mid latitude westerlies shifted northward and or intensified during the mis 3 resulting in a more positive glacier mass balance nevertheless the siberian high dominated the altai mountains in mis 2 resulting in a relative decrease in precipitation

high resolution scanning xrf investigation of chinese loess and its implications for millennial scale monsoon variability millennial scale monsoon variability has been investigated intensively using loess based proxies however the amplitude and rhythms of millennial scale signals have seldom been disentangled from the background glacial interglacial changes here we present the results of high resolution scanning x ray fluorescence analysis of a 75 m thick loess sequence from the north western chinese loess plateau to address glacial interglacial to millennial monsoon variability over the last two climatic cycles variations of the si k fe k and ca k ratios are separated spectrally into low and high frequency components corresponding to glacial interglacial and millennial scale monsoon variability respectively the results indicate that the three elemental ratios exhibit similar glacial interglacial variability but with varying spectral densities at the 100 41 and 23 kyr periodicities millennial scale variability is quite similar between the three elemental ratios and comparable to those inferred from records of chinese speleothem 18o greenland palaeotemperature and north atlantic cooling events comparison of various proxies indicates the broad similar magnitudes of abrupt climate changes at least during the last two glacial interglacial cycles whereas the timing and amplitude of abrupt climatic events are not well correlated we suggest that refinement of loess chronology and intensive data model integration in the future are critical to decipher the characteristics and dynamics of rapid monsoon changes

variations of younger dryas atmospheric radiocarbon explicable without ocean circulation changes the concentration of radiocarbon 14c in the atmosphere depends on its production rate by cosmic rays and on the intensity of carbon exchange between the atmosphere and other reservoirs for example the deep oceans for the holocene the past 11 500 years it has been shown that fluctuations in atmospheric radiocarbon concentrations have been caused mostly by variations in the solar magnetic field1 2 3 recent progress in extending the radiocarbon record backwards in time4 5 6 7 8 9 10 has indicated especially high atmospheric radiocarbon concentrations in the younger dryas cold period between 12 700 and 11 500 years before the present these high concentrations have been interpreted as a result of a reduced exchange with the deep ocean reservoir caused by a drastic weakening of the deep ocean ventilation7 8 9 11 12 here we present a high resolution reconstruction of atmospheric radiocarbon concentrations derived from annually laminated sediments of two polish lakes lake go ciaz and lake perespilno these records indicate that the maximum in atmospheric radiocarbon concentrations in the early younger dryas was smaller than previously believed and might have been caused by variations in solar activity if so there is no indication that the deep ocean ventilation in the younger dryas was significantly different from today s

archean uplift of a subprovince boundary in the canadian shield revealed by magnetic fabrics abstract a high strain zone reported elsewhere as a subprovince or tectonic terrane boundary shows evidence of uplift during a penetrative d 1 event some outcrops reveal this by conventional l s petrofabric observations however all outcrops permit measurements of the anisotropy of low field magnetic susceptibility ams which here records the preferred crystallographic orientation of chlorite biotite and amphibole furthermore anisotropy of anhysteretic magnetic remanence aarm reflects the preferred orientation of ferromagnetic grains magnetite and pyrrhotite all three types of fabric show that the rocks were shortened in a north south direction perpendicular to the terrane boundary and stretched upwards in a nearly coaxial strain history a few anomalous magnetic fabrics may indicate some late d 1 subhorizontal e w extension compatible with transpression along the boundary we conclude that this boundary is a zone of high strain associated with the uplift of the high grade plutonic rocks of the winnipeg river subprovince with only slight evidence of minor components of late transpression during the penetrative d 1 fabrics

climatic implications of loess deposits from the beijing region variations in magnetostratigraphy pedostratigraphy grain size and magnetic suscep tibility of the loess deposits near beijing have been studied at two sections the sections are about 400 km east of the main loess deposits in china have a maximum thickness of 100 m and extend back to 1 1 ma the sequence consists of 14 loess palaeosol couplets s0 s14 which correlate well with sequences in the loess plateau susceptibility records from the sites near beijing are comparable to the xifeng luochuan and baoji sections located in the middle part of the loess plateau however the down core variations in the grain size in the upper lishi formation exhibit some differences the median grain size increases by about 25 30 m from l4 to l2 with the sandy grains 63 m increasing from 10 20 wt to 40 50 wt this implies that the depositional environment of the dust sources in the beijing loess section is different in some aspects from the loess plateau the beijing loess may have had a different dust source than the loess plateau copyright 2001 john wiley sons ltd journal of quaternary science

geochemical evidence of the chinese loess provenance during the late pleistocene abstract the provenance of chinese loess plateau sediments is an often posed question that has not been satisfactorily resolved elemental geochemistry characteristics of the deposition may provide important evidence in this regard to this end geochemical analyses were undertaken on densely sampled strata from four loess sections one of which is located in northwestern china at the desert margin and the other three on the loess plateau as well as sediments from the badain jaran desert it was found that loess deposition on the chinese loess plateau and the northern foot of the qilian mountains had strong geochemical similarity during the last glacial cycle but had remarkable differences with the badain jaran desert samples it is inferred that the desert was not the most important direct provider of dust material to the loess plateau rather one of the main source areas appears to have been the vast silt rich piedmont alluvial fan distributed at the northern foot of the qilian mountains

climate change loess and palaeosols proxy measures and resolution in north china the loess plateau of north china is a key region for the study of records of quaternary climatic change various techniques to abstract climatically sensitive data were first applied to the classic loess palaeosol site at luochuan and current views on climatic change in asia have been strongly moulded by results from this central part of the loess plateau data including the magnetic susceptibility granulometry mineralogy geochemistry micromorphology fossil content and inorganic and organic carbon content of asian loess palaeosol series have been used singly and in combination as surrogate measures of palaeoclimates to infer climatic changes with particular reference to changes in the asian monsoon some of this work is reviewed and the status of a number of parameters as climatic proxies is discussed some lithostratigraphic sequences from which proxy measures of climate have been derived are incomplete as shown by erosion surfaces water laminated zones and truncated palaeosol profiles while others provide records of relatively low resolution most descriptions of quaternary climatic changes based on studies of the loess emphasize alternations in the relative dominance of warm and moist v cool dry and dust laden monsoons some recent studies of the much higher resolution loess palaeosol successions on the western margins of the loess plateau have suggested that such changes may sometimes be out of phase with the inference that the current climate model is too simple means of testing this hypothesis are proposed

late quaternary glacial history of the nalati range central tian shan china investigated using 10be surface exposure dating we constrained glacial chronologies in three valleys on the southern slopes of the nalati range in the central tian shan china the takelakete aiken and sairenwuxunsala valleys using 10be surface exposure dating our 10be exposure ages constrain three glacial events during 72 8 3 8 59 9 3 5 ka 55 4 3 0 34 9 2 1 and 0 29 0 17 0 27 0 20 ka corresponding to marine oxygen isotope stages mis 4 and 3 and little ice age lia respectively glaciers have been restricted from composite valley glaciers and piedmont glaciers during mis 4 3 to confined valley glaciers during mis 3 to small valley glaciers during the lia and to hanging and cirque glaciers at present this pattern of glacial change is broadly consistent with other glaciated areas across the tian shan extensive glacial advances during mis 4 and 3 were probably driven by enhanced precipitation brought by the westerlies compared to mis 3 glacial advance lower temperature may counteract the effect of relatively lower precipitation to drive a similar or even larger glacial advance during mis 4 glacial advances were limited during mis 2 probably reflecting enhanced arid conditions in the tian shan caused by the weakened westerlies and strengthened siberian high

last glacial maximum climate inferences from integrated reconstruction of glacier equilibrium line altitude for the head of the urumqi river tianshan mountains abstract the relationship between climate and glacial equilibrium line altitude ela during the last glacial maximum lgm has recently received considerable interest however in the headwaters of urumqi river in northwest china a systematic reconstruction for the paleo elas had not been completed to permit regional and large scale paleoclimate inferences recent improvements in dating and understanding of glacial extents provide the possibility to use glacial reconstruction to infer the paleoclimate to improve the ability to obtain paleoclimate information the elas during the local lgm mis2 3 and modern time 1998 2004 were constructed by using an integrated method the regional tectonic uplift is considered when calculating the lgm elas in order to improve their precision and thus obtain a better estimate of the paleoclimate the estimated ela values were input into a robust equation to derive the forcing paleoclimatic conditions during the local lgm in the study area the ela was between 3420 and 3560 m a s l 493 633 m lower than modern ela considering energy and mass balance in the equation to account for the ela decrease during the lgm the temperature decreased by 5 42 6 30 c and the precipitation was 30 compared to the present

high resolution multi proxy climate records from chinese loess evidence for rapid climatic changes over the last 75 kyr the loess paleosol sequence in loess layer l1 malan loess is investigated in three regions of the western chinese loess plateau nine pedogenic layers are found in l1 and three proxy climate indices magnetic susceptibility ms grain size gs and caco3 content are measured at intervals of 0 2 kyr in order to recover records of monsoon climate variations time series of ms gs and caco3 content document the high resolution history of summer and winter monsoon climate variations over the last 75 kyr the records show a high degree of similarity to the warm interstadials recorded in ice cores from greenland and the antarctic and with heinrich events in the north atlantic during the last glacial cycle bond cycles are also recorded by the chinese loess records overall our results indicate that numerous rapid changes in climate occurred in china during the last glacial cycle but that the range of climate variations was smaller than recorded in greenland

magnetic anisotropy in natural amphibole crystals anisotropy of magnetic susceptibility ams is often used as a proxy for mineral fabric in deformed rocks to do so quantitatively it is necessary to quantify the intrinsic magnetic anisotropy of single crystals of rock forming minerals amphiboles are common in mafic igneous and metamorphic rocks and often define rock texture due to their general prismatic crystal habits amphiboles may dominate the magnetic anisotropy in intermediate to felsic igneous rocks and in some metamorphic rock types because they have a high fe concentration and they can develop a strong crystallographic preferred orientation in this study the ams is characterized in 28 single crystals and 1 crystal aggregate of compositionally diverse clino and ortho amphiboles high field methods were used to isolate the paramagnetic component of the anisotropy which is unaffected by ferromagnetic inclusions that often occur in amphibole crystals laue imaging laser ablation inductively coupled plasma mass spectrometry and mossbauer spectroscopy were performed to relate the magnetic anisotropy to crystal structure and fe concentration the minimum susceptibility is parallel to the crystallographic a axis and the maximum susceptibility is generally parallel to the crystallographic b axis in tremolite actinolite and hornblende gedrite has its minimum susceptibility along the a axis and maximum susceptibility aligned with c in richterite however the intermediate susceptibility is parallel to the b axis and the minimum and maximum susceptibility directions are distributed in the a c plane the degree of anisotropy k increases generally with fe concentration following a linear trend k 1 61 10 9 fe 1 17 10 9 m3 kg additionally it may depend on the fe2 fe3 ratio for most samples the degree of anisotropy increases by a factor of approximately 8 upon cooling from room temperature to 77 k ferroactinolite one pargasite crystal and riebeckite show a larger increase which is related to the onset of local ferromagnetic s l interactions below about 100 k this comprehensive data set increases our understanding of the magnetic structure of amphiboles and it is central to interpreting magnetic fabrics of rocks whose ams is controlled by amphibole minerals

millennial scale climatic oscillations during the last interglaciation in central china repeated southward excursions of north atlantic polar water during the last interglaciation 18 o stage 5 130 74 ka are recorded by planktonic foraminifera and ice rafted detritus in north atlantic sediment cores and greenland ice sheet cores display quasi synchronous fluctuations comparable high frequency variations in the east asian winter monsoon climate are discernible in three loess paleosol profiles in central china that span the last interglaciation peak values of the 40 m quartz fraction and bulk sediment samples from the s1 last interglacial accretionary paleosol complex reflect major dust flux events when winter monsoon winds strengthened frequent oscillations of the dust flux and nine significant dust events are recorded six events falling between ca 110 and 70 ka are correlated with cold peaks c19 24 identified in north atlantic cores two comparable dust peaks occur within paleosol s1ss3 substage 5e the older of these dating to ca 121 ka may correlate with a brief cold event recently recognized in high resolution marine and terrestrial climate proxy records

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

high resolution climate record from the beijing area during the last glacial interglacial cycle the zhaitang loess section located in the western suburbs of beijing has yielded a very high resolution magnetic susceptibility record for the last glacial and interglacial period all substages can be clearly defined in marine isotope stage mis 5 s1 and even also in substage 5a demonstrating comparable detail with vostok and parts of the grip ice record rapid climate shifts during the eemian period may have extended to continental asia but exerted only a weak influence on the zhaitang record abrupt climate transitions 5b 5c 5d 5e recorded in this section from the ne edge of the plateau show more detrial than most other chinese loess records these three well defined peaks in substage 5a imply sensitivity of the east asian monsoon to rapid hemisphere scale climate change and the prospect of finding more information on orbital and non orbital events in the loess sequence

east asian monsoon variation and climate changes in jeju island korea during the latest pleistocene to early holocene a 4 96 m long sediment core from the hanon paleo maar in jeju island korea was studied to investigate the paleoclimatic change and east asian monsoon variations during the latest pleistocene to early holocene 23 000 9000 cal yr bp high resolution toc content magnetic susceptibility and major element composition data indicate that jeju island experienced the coldest climate around 18 000 cal yr bp which corresponds to the last glacial maximum lgm further these multi proxy data show an abrupt shift in climatic regime from cold and arid to warm and humid conditions at around 14 000 cal yr bp which represents the commencement of the last major deglaciation after the last major deglaciation the toc content decreased from 13 300 to 12 000 cal yr bp and from 11 500 to 9800 cal yr bp thereby reflecting the weakening of the summer monsoon the lgm in jeju island occurred later in comparison with the chinese loess plateau such a disparity in climatic change events between central china and jeju island appears to be caused by the asynchrony between the coldest temperature event and the minimum precipitation event in central china and by the buffering effect of the pacific ocean

climatic signals in the chinese loess record for the last glacial the influence of northern high latitudes and the tropical pacific the high resolution shagou loess section near the northwest limit of the east asian summer monsoon northwest china was analyzed the timescale of this section was set up based on a grain size age model and age controls the record of the shagou section shows that the millennial scale oscillations are superimposed on an orbital scale trend which can be correlated with the variations found in greenland and the sulu sea differences in the corresponding dansgaard oeschger cycles between the records in greenland and the chinese loess sections including the orbital scale trend the timing and the amplitude suggest that the climatic signals in chinese loess might not be singularly regulated by the north atlantic the differences in trend and amplitude can be reasonably explained when compared with the sulu sea record this suggests that the western tropical pacific also exerted an important influence on climatic signals found in the chinese loess record possibly countering the impact of high latitude factors during the last glacial

asian summer monsoon instability during the past 60 000 years magnetic susceptibility and pedogenic evidence from the western chinese loess plateau abstract the 28 m high resolution shajinping loess section in lanzhou on the western chinese loess plateau records a 60 ka millennial summer monsoon variation the record shows that asian summer monsoons have rapid episodic pulse enhancements spanning only ca 1 2 ka in high frequency domain and having sub milankovitch cycles of progressive weakening in low frequency domain in the last glaciation soil formation seems to occur with a surprisingly fast response to these summer monsoon enhancements resulting in weakly or moderately developed paleosol sequences both the pattern and timing of the summer monsoon enhancements show that they can be correlated to most major warm dansgaard oeschger episodes and long term cooling bond cycles of the north atlantic climatic records indicating a possible teleconnection between tropic oceanic air masses and the north atlantic climatic system but differences exist for the transition of mis 2 3 and the holocene where extraordinarily heavy dust input events and fairly variable climatic fluctuations occur for the former and latter respectively a westerlies swing model is proposed to interpret this link

millennial scale summer monsoon oscillations over the last 260 ka revealed by high resolution elemental results of the mangshan loess palaeosol sequence from the southeastern chinese loess plateau abstract loess based proxies have been widely used to infer glacial interglacial to millennial scale changes of the east asian monsoon however the characteristic of millennial scale variability is still unclear during glacial interglacial cycles in loess palaeosol sequence here we present high resolution 5 cm elemental results of a 96 7 m thick mangshan loess palaeosol sequence on the southeastern chinese loess plateau to emphasize millennial monsoon changes we explore time series of loess proxies magnetic susceptibility caco3 content ca k fe k and rb sr ratios and speleothem 18o records and decompose these proxies into intrinsic components using the ensemble empirical mode decomposition method synthesized signals of low and high frequency components can track the monsoon variability at glacial interglcial and millennial timescales respectively the proportions of millennial components of the loess proxies vary from 9 4 13 4 less than that in chinese speleothem 18o record 24 4 among five loess proxies fe k ratio is the most sensitive indicator of millennial scale summer monsoon oscillations exhibiting abrupt changes similar to that of the chinese speleothem 18o record the amplitude of abrupt monsoon changes recorded in mangshan is larger during interglacials than glacials which is in line with gulang records implying the lower sensitivity of loess proxies to weak weathering during glacilals and an interglacial amplification of abrupt summer monsoon changes

east asian monsoon forcing of suborbital variability in the sulu sea during marine isotope stage 3 link to northern hemisphere climate 1 we have generated a new high resolution record of variations in planktonic foraminiferal oxygen isotopes 18o and mg ca from a sediment core images 97 2141 in the sulu sea located in the philippine archipelago of western tropical pacific this record reveals distinct suborbital scale 18o changes most notably during marine isotope stage 3 mis3 30 000 to 60 000 years b p the amplitudes of these 18o fluctuations 0 4 to 0 7 exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions in the same interval variations in planktonic foraminifera mg ca suggest that suborbital surface ocean temperature variations of 1 to 1 5 c in the sulu sea were not in phase with 18o combined this evidence indicates that the mis3 millennial 18o events in the sulu sea were primarily the result of changes in surface water salinity which today is directly related to the east asian monsoon eam and its influence on the balance between surface water contributions from the south china sea and western pacific warm pool wpwp within dating uncertainties the mis3 sulu sea 18o suborbital variability indicates that times of fresher surface conditions in the sulu sea coincide with similar conditions in the wpwp stott et al 2002 and also with intensifications of the summer eam as recorded in the u th dated chinese hulu cave speleothem 18o record wang et al 2001 and thus by inference with interstadials in the greenland ice core records combined these results indicate that pronounced suborbital variability in the summer eam and intertropical convergence zone itcz during mis3 was tightly coupled with climate conditions in the northern high latitudes

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr