magnetostratigraphy of chinese loess paleosol sequences abstract as one of the longest and most continuously deposited terrestrial sedimentary archives in the world chinese loess paleosol sequences record paleoclimatic and paleomagnetic variations at a range of time scales magnetostratigraphic studies provide a first order chronological framework for chinese loess sequences in this review we highlight recent developments in loess magnetostratigraphy including pedostratigraphy based on magnetic susceptibility variations we highlight progress in understanding the mechanisms by which the natural remanent magnetization nrm is acquired and discuss in detail the fidelity of paleomagnetic recording in loess records including the recording of magnetic polarity reversals excursions and relative paleointensity variations finally we discuss future prospects for studies of loess nrm

chronology and paleoenvironmental records of a drill core in the central tengger desert of china abstract the desertification history of inland asia provides most direct evidence for asian drying history but the formation ages of the most asian deserts are not clear due to the lack of outcrops the tengger desert one of the main proximal deserts of the chinese loess plateau clp is of special paleoclimatic significances for its dust emission and environmental affection here we report lithofacies paleomagnetic ages and paleoenvironmental proxy indexes of the first drill core wedp01 from the central tengger desert paleomagnetism measurements reveal that the core spans from 3 55 ma to present consistent with the electron spin resonance esr dating results the strata of the central desert consist of alluvial fluvial deposits lacustrine fluvial deposits mixed with dust and eolian sand from bottom to top sedimentary analysis reveals that continuous eolian sand started by 0 9 ma marking the initial formation of the tengger desert and the domination of eolian sand in the strata with similar characters of the modern desert appeared by 0 68 ma indicating expansion of the tengger desert the proximal deserts formation and simultaneous increase of dust accumulation in the clp and the north pacific ocean in mid pleistocene demonstrate the role of proximal deserts for the dust loading of northern china and even northern hemisphere our analysis suggests the uplift of tibetan plateau in the mid pleistocene probably played the main role for this drying event and desert formation while global cooling may strength the arid environment of the proximal deserts

stacked 2 6 ma grain size record from the chinese loess based on five sections and correlation with the deep sea δ18o record 1 this study aims to establish a stacked climate record of the quaternary period from the chinese loess sequence and to address the forcing mechanisms for the regional climate history of the loess plateau by correlating the stacked record with a composite 18o record in deep sea sediments a total of 18 352 samples were obtained from five loess sections located at baoji lingtai jingchuan puxian and pingliang in the southern and middle loess plateau these yielded high resolution grain size records between section correlation of these shows that although small depositional hiatuses are present in places within a single section most parts of the sections display near continuous dust deposition throughout the quaternary the grain size records were tuned simultaneously to the theoretical variations in obliquity and precession of the earth s orbit the grain size records plotted on their orbital timescales were then averaged to form a stacked loess grain size time series termed the chiloparts record this resolves most of the orbital timescale paleoclimate events buried in the loess soil sequences of the southern and middle loess plateau and can be used as a regional archive of the pleistocene climate history in the loess plateau comparison of the chiloparts record with a composite marine 18o record shows that for the past 1 8 ma the loess paleosol record can be correlated almost cycle by cycle with the marine record several discrepancies in the climatic events between the two records have also been identified implying that regional forcing mechanisms may have played a part in the climatic evolution of the chinese loess plateau

the environmental effects of the uplift of the qinghai xizang plateau the intense upheaval of the qinghai xizang plateau took place 2 ma bp the terraces of the yellow river in the lanzhou region and its upper sections provide a record of the uplift of the plateau the interaction of glaciation cycles resulting from climatic changes and pulsating tectonic upheavals are both involved in the record of environmental change across the plateau three tectonic climatic events which are termed respectively the qinghai xizang movement the huanghe yellow river movement and the gonghe movement occurred 2 1 5 1 0 and 0 15 ma bp the upheaval of the qinghai xizang plateau was the trigger mechanism of the asian monsoon the loess plateau was formed in the monsoon triangle of east asia human origins and human evolution may have been stimulated by the uplift of the qinghai xizang plateau

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

binary sources of loess on the chinese loess plateau revealed by u pb ages of zircon the age distribution of detrital zircon has been used to trace sediment sources existing datasets show great similarity of zircon ages between the loess on the chinese loess plateau clp and the sediments from the north tibetan plateau ntp implying that eolian dust is delivered from the ntp to the clp by westerly winds or via the yellow river however ntp dust can also be transported by northwesterly winds from the alxa arid lands aals where materials are received from both the ntp and the gobi altay mountains gams here we report u pb zircon ages for aals sands and ntp and clp loess the results show that the zircons in the aals are mixed from ntp and gams zircons ntp loess is mainly derived from local sources mixing of materials from the ntp and gams defines the zircon ages of the loess on the clp better than the pure ntp source no temporal and spatial heterogeneities of zircon ages have been observed for the loess on the clp which suggests that the well mixed materials in the aals likely have an eolian source

gradational quaternary benthic marine communities on the van diemen rise timor sea northern australia abstract quaternary benthic marine communities on the van diemen rise timor sea have an inherent patchiness diffuse boundaries and are not limited to specific depth zones as previously inferred for faunas of the timor sea statistical similarity of cluster groups on the van diemen rise are greater than that previously measured in the timor sea additional site specific faunal surveys in the region could incorrectly attribute the absence of the previously defined community groups to environmental disturbance rather than the inherent variability of the communities assemblages themselves the effects of potential disturbance associated with resource exploration activity should readily be distinguishable from the community groups identified in this study

provenance of loess material and formation of loess deposits on the chinese loess plateau abstract results of a multiple isotopic chemical and mineralogical analysis of loess from the three northwestern inland basins the junggar basin the tarim basin and the qaidam basin and the loess plateau region of china are summarized they suggest a qualification of the conventional views that the three northwestern basins were the important source areas of the loess plateau and that the sand deserts were the primary single source of the chinese loess it is argued that the gobi stony desert in southern mongolia and the adjoining gobi and sand deserts the badain jaran desert tengger desert ulan buh desert hobq desert and mu us desert in china rather than the three inland basins are the dominant source areas of the loess plateau however although these gobi and sand deserts are regarded as the main source regions they serve as dust and silt holding areas rather than dominant producers the mountain processes including glacial grinding frost weathering salt weathering tectonic processes and some fluvial comminution in the gobi altay mts hangayn mts and the qilian mts have played an important role in producing the vast amounts of loess sized material for forming the loess plateau

late quaternary palaeolake levels in tengger desert nw china comprehensive field investigations and laboratory analyses show that palaeolakes including the megalake tengger and other semi connected and isolated water bodies during late pleistocene covered an area of more than 20 000 km 2 this is an area more than half the size of the tengger desert in nw china stratigraphic correlations and chronological evidence indicate that the palaeolakes started to develop around 42 000 14 c year bp uncalibrated all throughout the paper but their extent was limited until 37 000 14 c year bp based on the chronology of representative lacustrine deposits it can be deduced that the megalake tengger was established around 35 000 14 c year bp and maintained until 22 000 14 c year bp leading to the formation of the baijian hu terraces which are regarded as firm evidence of the existence of palaeolakes the formation mechanism is unclear and the climate situation at the time is still an open question the holocene palaeolakes started to develop around 12 000 14 c year bp the baijian hu terraces indicate that the high water levels in the area occurred around 8500 5400 5100 3500 and 1860 1370 14 c year bp the extent of the holocene palaeolakes primarily migratory lakes was smaller than that of the late pleistocene palaeolakes d 2004 elsevier b v all rights reserved

artificial optical bleaching of the aluminium center in quartz implications to esr dating of sediments abstract electron spin resonance esr dating of quartz extracted from sediments may contribute to elaborate a neogene and quaternary chronostratigraphy especially in the case of azoic deposits when methods such as thermoluminescence or k ar cannot be applied the esr method is applicable for aeolian littoral and fluvial sediments when quartz is zeroed or bleached by an optical phenomenon photoelectric effect due mainly to uv solar rays in this case esr dating on bleached quartz is based on the presence of paramagnetic substituted atoms in the crystal lattice the al center can be optically bleached and its signal intensity decreases in fossil samples versus exposure to the solar light after a long time the esr intensity reaches a plateau value corresponding to the electrons which cannot be extracted by the light energy these electrons represent a residual dose which must be subtracted from the total equivalent dose in order to obtain the archaeological dose our kinetic study has the objectives of obtaining a new modelization and to establish a correct time of natural bleaching for using quartz sample as appropriate for dating we have investigated samples from a fossil fluvial sand from the creuse river terraces system france our experimental bleaching curve obtained is compared with that one previously proposed by walther and zilles quat sci rev 13 1994 611

alluvial sediment or playas what is the dominant source of sand and silt in desert soil vesicular a horizons southwest usa 1 vesicular a av soil horizons form beneath desert pavements from the accretion of aeolian sediment dust commonly thought to be derived primarily from desiccating pluvial lakes and playas with contributions from ephemeral washes and alluvial fans particle size distributions of av horizons are typically bimodal with primary modes of very fine silt and fine sand suggesting that the horizon matrix is derived from multiple sources here we conduct detailed chemical and physical analysis of both av horizon soil samples and potential sources of aeolian sediment to better constrain the relative contributions of dust associated with the development of av horizons geochemical data from both sand 125 250 m and silt 2 32 m fractions in av horizons and potential dust sources in the eastern mojave desert and western sonora desert usa point to large contributions from nearby sources including distal alluvial fans and washes and comparably lower contributions from regional sources such as playas the silt mode is derived from suspension transport of dust and the fine sand mode is derived from saltating sand the desiccation of pluvial lakes in the mojave desert is commonly believed to have driven episodes of aeolian activity contributing to sand dunes and av horizon formation we propose that alluvial fans and washes are underappreciated as desert dust sources and that pulses of dust from late pleistocene and holocene alluvial fans dwarfed pulses of dust from desiccating pluvial lakes in the eastern mojave desert

a 900 k y record of strath terrace formation during glacial interglacial transitions in northwest china the timing of the development of strath terraces with respect to climatic variability remains equivocal previous studies attribute strath terrace formation to glacial or interglacial climates or to variations in sediment and water fluxes that cause lateral erosion followed by vertical incision a chronology of strath terrace formation spanning similar to900 k y has been generated on the basis of loess paleosol couplets and paleomagnetic thermoluminescence and radiocarbon dating of strath terraces in the qilian shan of northeastern tibet repetitive stratigraphic and geomorphic patterns on each terrace indicate that they formed during glacial interglacial transitions long term bedrock incision rates and inferred rock uplift rates appear steady and unrelated to strath formation over the past 900 k y

temporal variations in pb isotopes and trace element concentrations within chinese eolian deposits during the past 8 ma implications for provenance change article i nfo the pb isotopes and trace element compositions of the silicate fraction of airborne dust from the chinese loess plateau were analyzed to infer provenance change during the past 8 ma the results indicate that the composition of eolian dust changed at 2 6 ma coincident with initiation of the northern hemisphere ice sheet the change in trace element composition at 2 6 ma indicates that a larger component of the eolian dust was derived from felsic rocks after this time pb isotopic evidence demonstrates that the source material of tertiary red clay differs to some extent from that of quaternary eolian deposits although chemical weathering may result in compositional changes in eolian deposits such a scenario is not supported by the present evidence given that glacial grinding and frost weathering processes have been active in the peaks of high mountains during the quaternary eolian dust of this age contains a large proportion of material derived from areas of high topographic relief and relatively little material from low lying cratonic regions such alpine processes played an important role in controlling the distinct changes in pb isotopes and trance element concentrations recorded at around 2 6 ma 2010 published by elsevier b v

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

late cenozoic eolian deposition in the north pacific asian drying tibetan uplift and cooling of the northern hemisphere a newly constructed record of eolian dust accumulation from the central north pacific shows that dust deposition increased by an order of magnitude quite rapidly at 3 6 ma we associate this sudden drying with the uplift of at least the northern portion of the tibetan plateau shutting off the indian ocean moisture source to central and western china this ten fold increase in atmospheric dust loading appears to be associated with the 1 m y long shift toward heavy 18o values that occurred at 3 6 2 6 ma the dust grain size record of wind intensity begins its late cenozoic coarsening a million years before the drying event at 4 5 ma the northern hemisphere cooling that results in intensification of the subpolar westerly winds may have as its ultimate cause the drawdown of atmospheric co2 in the latest miocene and the early pliocene closing of the panamanian seaway

magnetostratigraphic and radiometric constraints on salt formation in the qaidam basin ne tibetan plateau abstract the qaidam basin is the largest cenozoic intermontane basin within the northeast ne tibetan plateau it contains large amounts of nonmarine evaporite deposits formed during the pliocene quaternary even at present extensive salt deposits dominated by halite and potash are formed by solar driven concentration of brine water in the basin interior making it the most important industrial base for potash exploitation in china the formation of salt required an arid climatic appropriate hydrological and tectonic setting through geologic times and will do so in the future studying the salt formation in the qaidam basin will enhance our understanding of processes driven by saline lake evolution regional climate change and tectonic movements not only for the setting of the tibetan plateau reliable dating is crucial for assessing the time of salt formation in qaidam basin and the accumulation process yet no comprehensive scientific studies have been reported on this important issue until now in this paper we critically review and compile magnetostratigraphic and radiometric studies of the salt bearing strata within seven depressions of the basin we find that the ages of salt formation are very different in these depressions for the dalangtan yiliping chahansilatu and kunteyi depressions first salt deposits occurred at 3 90 0 02 ma 2 88 0 04 ma 2 24 0 01 ma and 1 18 0 02 ma respectively for the mahai gasikule and qarhan the ages of earliest salt formation are much younger i e 302 56 ka 608 38 ka and 54 24 ka respectively however the result from mahai has to be considered with caution the variability of ages suggests an older salt forming stage in the center of the western basin and a younger salt accumulation period along the basin margin in a regional view previous results from stratigraphy sedimentology geomorphology and tectonic history allow us to conclude that the salt formation in the qaidam basin was probably controlled by pulsed intrabasinal tectonic movements and the distribution and migration of paleo rivers during the pliocene quaternary however the climatic shift towards drier and colder conditions in the asian interior during this time also promoted salt formation

oxygen isotope signatures of quartz from major asian dust sources implications for changes in the provenance of chinese loess abstract we present a systematic investigation of the oxygen isotopic composition of quartz in both fine and coarse fractions 18 o values of both the fine and coarse fractions from the various sources are overlapped to varying degrees thus making it difficult to differentiate them nevertheless the quartz 18 o values of both fractions exhibit an increasing trend from the mongolian gobi to the northern chinese deserts and then to the taklimakan desert this implies that the geological settings of the source areas are different which in turn results in differing contributions of high temperature igneous rocks the combination of quartz 18 o results with other quartz based provenance tracers can clearly differentiate the three major source areas i e the taklimakan desert the mongolian gobi and the northern chinese deserts in addition comparison of our results with previous 18 o measurements of fine grained quartz from the luochuan loess sequence suggests the likely glacial interglacial fluctuations in dust provenance finally we suggest that the combination of quartz 18 o signatures and other dust provenance tracers can potentially improve the recognition of long term fluctuations in the provenance of chinese loess red clay deposits

formation and evolution of the badain jaran desert north china as revealed by a drill core from the desert centre and by geological survey abstract the deserts in north china are regarded as direct records of the process of inland asian aridification amongst these deserts those proximal to the chinese loess plateau clp are especially important because of their role as sediment source areas in order to investigate the formation history of the badain jaran desert the largest desert proximal to the clp a 310 m long drill core was obtained from the desert centre which reached the underlying basement rock the lithology of the core consists of an upper layer of aeolian sand with three intercalated layers of lacustrine sediments overlying alluvial fluvial deposits which are developed unconformably over red coloured basement rock a geological survey indicates that the lower red coloured basement rock is of late cretaceous age and is cut by a mesozoic erosion surface widely developed over the badain jaran area on the basis of optically stimulated luminescence and electron spin resonance dating and stratigraphic correlation a preliminary chronological framework was established which was improved by tuning the aeolian sand proportion of the drill core to earth orbital obliquity and precession this final chronology suggests that 1 the basal age of the desert strata is at least 1100 ka corresponding to the formation of the badain jaran desert and 2 that the formation of the erosion surface terminated and the surface had begun to subside by at least 1200 ka the formation of the desert can be summarized as follows the alluvial fluvial fan formed by the heihe river draining the qilian mountains provided sufficient sedimentary material to form the desert under an arid climate while the asian winter monsoon and the westerlies entrained the clastic sediments from the fan area which finally accumulated downwind more distant sediment transport was prevented by the intervening mountainous terrain these coupled processes were driven by tibetan plateau uplift and ongoing global climatic cooling after initial formation of the desert three humid phases occurred in mis 13 15 mis 5 and the holocene during which extensive lakes developed the sequential drying out of the lakes may reflect inter relationships between global climate and the intensity of the asian summer monsoon and the westerlies

lake evolution in the tengger desert northwestern china during the last 40 000 years climatic changes inferred from lacustrine deposits and lake level fluctuations in northwestern and central china are mainly based on paleoclimatic records from the tibetan plateau while there is still a lack of data relating to the semiarid arid desert regions of inner mongolia in the tengger desert different paleolake levels at baijian hu are documented by six paleoshorelines and stratified lake carbonates the highest lake level occurred ca 39 000 14c yr b p and prevailed over about 16 000 km2 from sediment structure geochemical composition and ostracods we infer humid cool conditions until 23 000 14c yr b p in the northern badanjilin desert at gaxan nur sogu nur high lake levels can be deduced from mollusc bearing paleobeaches and lake carbonates which have been dated to 34 000 14c yr b p and indicate a lake that covered some 32 000 km2 after ca 20 000 yr b p the climate became dry with increased eolian activity and decreasing lake levels reestablishment of wet conditions occurred ca 13 000 yr b p the holocene is represented by stratified lake deposits that alternate with fluvial and eolian deposits indicating a longterm oscillating trend toward arid conditions the existence of widespread freshwater lakes during the late pleistocene indicates a semihumid climate without an accompanying fall in temperature to arctic conditions

geochemical and isotopic studies of aeolian sediments in china the sr and nd isotopic rare earth element ree and major element compositions together with mineral and grain size proportions are reported for aeolian loess deposits and desert sands from several chinese localities the study was carried out in order to examine regional variations in the isotopic and geochemical features of these aeolian sediments and to constrain the provenance of chinese loess samples include loesses from the tarim and junggar basins and desert sands from the taklimakan desert in north west china loess from the ordos area and desert sands from the tengger and mu us deserts in north central china as well as loess and desert sands from the naiman area north east china ree distributions show minimal variation among the chinese loess deposits whereas those for the desert sands show regional variations new isotopic data document a latitudinal variation in sr and nd isotopic features for the loesses and desert sands the naiman and junggar loesses have distinctly lower 87sr 86sr ratios and higher end 0 values than the loesses from the tarim basin the ordos area and the loess plateau among the desert sands the naiman samples have higher end 0 values than the taklimakan tengger and mu us samples isotopic data suggest that loesses of the loess plateau were supplied from the tarim basin loesses and taklimakan desert sand and that the naiman loesses were supplied from the junggar basin loesses the latitudinal variation in the loesses and desert sands may be partly explained by isotopic variations reported previously for moraines from the tianshan and west kunlun mountains which are possible sources for the loesses and desert sands these inferences on the provenance of the loesses and desert sands are consistent with the dust transport pattern over east asia

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

esr dating of aeolian sand near tennant creek northern territory australia abstract electron spin resonance esr dating of aeolian sand in the northern territory of australia was carried out using the al centres in quartz grains as part of an attempt to date prehistoric faulting associated with the 1988 tennant creek earthquakes our experiments on optical bleaching of esr electron spin resonance signals show that sunlight does not completely bleach the esr signal from the al centre of quartz grains in this aeolian sand the total doses were determined from the acquired esr signal intensity however a correction to compensate for partial bleaching and the resultant inherited residual esr signal has to be carried out by using this technique the esr age estimates an increase with depth which suggests that nearly complete optical bleaching has occurred through this slice of geologic time for age estimates younger than 50 ka the esr ages are in generally good agreement with independently determined tl thermoluminescence data beyond 50 ka the esr ages are systematically older than the tl ages the oldest esr age estimate of 160 0 5 9 ka is from a sample at 228 cm depth and esr results from the vertical samplings yield an apparent sedimentation rate of 2 6 cm ka

quaternary paleoenvironmental evolution of the tengger desert and its implications for the provenance of the loess of the chinese loess plateau abstract the dust sources of the loess deposits of the chinese loess plateau clp are suggested to be the gobi deserts in north china and the tibetan plateau in southwest china the tengger desert td a major desert situated to the northeast of the tibetan plateau and to the northwest of the clp on the western margin of the present day asian summer monsoon domain is an ideal area for assessing which of these potential dust source areas may be dominant a 104 m long drill core bj14 was obtained from the northwestern td the magnetostratigraphy constrained by electron spin resonance dating in the upper part of the core includes the brunhes matuyama and beginning of the gauss polarity chrons with their boundaries at the depths of 44 57 m and 94 31 m respectively sedimentary facies analysis based on lithological grain size magnetic susceptibility and micropaleontological evidences indicates that the core is primarily composed of lacustrine deposits combined with the results of previous studies in the eastern td and the adjacent regions the sedimentary sequence of core bj14 indicates that lakes occupied the northern and eastern td during most of the early pleistocene and that the onset of a desert environment occurred at 0 9 ma our results suggest that the td may have contributed only a limited amount of dust to the clp during the early pleistocene

grain size distribution function of polymodal sediments in hydraulic and aeolian environments and numerical partitioning of the sedimentary components most continental sediments are polymodal composed of overlapping components of which the grain size generally obeys some type of natural distribution the grain size components and their function types can be determined from frequency and cumulative curve plots in order to define the function formula of the grain size distribution the function parameters can be estimated by fitting a defined function formula to the measured grain size data of the sample which simultaneously achieves numerical partitioning of the sedimentary components genetic analysis of grain size components of hydraulic and aeolian sediments demonstrates the following environmental implications fluvial sediment is composed of isolated saltation and suspension components the sediments in closed lake basins are dominated by a suspension silt clay component with a small proportion of saltation sand the fine sand component makes up the majority of desert sand overlapping with a small proportion of fine dust aeolian loess is composed of two overlapping components a short suspension time silt component and a long suspension time fine component aeolian material in the north pacific deep sea sediments is dominated by long suspension time fine dust the fine component in aeolian sediments shows a consistent grain size distribution and genetic connection from the desert sand loess of northern china to the north pacific ocean which is mainly transported by westerly winds and is dispersed in the atmosphere forming a background dust c 2002 elsevier science b v all rights reserved

the mid pleistocene climate transition onset of 100 ka cycle lags ice volume build up by 280 ka the mid pleistocene climate transition mpt is the complex climatic change which brought the late pleistocene ice ages we explore the mpt in the time and frequency domains by new methods of time series analysis high resolution oxygen isotope records reveal that the ice volume related increase in 18o mean amplitude 0 29 0 05 1 transition midpoint 922 12 ka duration 40 9 ka significantly preceded the abrupt increase in the amplitude of the 100 ka cycle at 641 9 ka this finding can be quantitatively simulated using a simple ice bedrock model in which due to the additional ice the calving threshold is exceeded the simulated calving events prior to 650 ka are separated by 77 ka whereas after 650 ka they occur pseudo periodically with a mean period of nearly 100 ka the cause for the delay of the 100 ka calving cycle was not a slow bedrock relaxation rather the coincidental combination of insolation existing ice mass and bedrock depression