geochemistry of loess deposits in northeastern china constraint on provenance and implication for disappearance of the large songliao palaeolake the harbin loess typical of the loess in ne china is located in the easternmost margin of the eurasian loess belt and was recently investigated from the perspective of an asian aeolian dust system before this study the geochemical composition and provenance of the harbin loess remained poorly understood more importantly the study of the harbin loess also provides a unique opportunity to understand the geomorphological evolution process of the large songliao palaeolake in the northeast plain this study presents the results on the geochemical characteristics major elements trace elements rare earth elements and sr nd isotope of the harbin loess there are markedly consistent geochemical compositions in and between the loess and palaeosol sediments revealing stable dust sources and identical sources for the loess and palaeosol various indicators illustrating weathering and recycling indicate that the harbin loess palaeosol sediments were derived from sources with a low degree of weathering and from material with first cycle alluvial lacustrine deposits combinations of various provenance tracing indicators indicate that the harbin loess has a strong geochemical affinity with the songnen sandy land and to a certain extent the horqin sandy land but not with the hulun buir sandy land which indicates that these loess deposits are derived from a mixed provenance with the dominant source being the neighbouring songnen sandy land and a second distal source being the horqin sandy land finally we advocate that the harbin loess accumulation could serve as the direct record of the songliao palaeolake disappearance supplementary material data for the ne sandy lands of china and full provenance discrimination diagrams are available at https doi org 10 6084 m9 figshare c 3835009

red soils with white net like veins and their climate significance in south china abstract the microstructure particle size distribution mineral and chemical compositions of both the white net like veins and the red matrix of the xuancheng laterite soil section in anhui south china in the middle to lower reaches of the yangtze river were investigated using x ray diffraction xrd x ray fluorescence spectrometry xrf polarized light microscopy observation and particle size distribution analysis there was more quartz while less clay minerals in the white veins relative to the red matrix in particle size distribution patterns the more abundant 5 20 m particle size component of the white veins resulted from their higher quartz content discrepancy in degree of weathering between the white veins and the red matrix was derived from the depletion of fe2o3 total and mno2 and the relative accumulation of sio2 in the white veins white veins across the lithological layers and inclusions of relict red matrix material in the white veins indicated that the net like soils originated from an initial uniform red soil the white spots or veins were derived from the long term modification of the pre existing soil or concurrent weathering soils hydrodynamic conditions of the groundwater exerted influence on the formation of white veins the formation process of the white net like veins was different from that of the red matrix suggesting that the white vein materials reflected a hydrological imprint upon the result of these conditions the net like soils in south china were compatible to the mottled soils in africa australia india and brazil however much more intense depletion of fe oxide and much better developed white veins in the net like soils of south china suggest probably even warmer and more humid palaeoclimatic conditions relative to those in africa australia india and brazil during the period

pedogenic modification of loess significance for palaeoclimatic reconstructions abstract this review considers the role of pedogenic processes in modifying wind blown dust loess concentrating particularly on the ways that resulting properties may be interpreted as indicators of past climatic conditions and changes emphasis is placed on the sequences of palaeosols developed within loess deposits that are frequently regarded as some of the best terrestrial equivalents of marine sediment records of long term global climatic change a palaeosol is generally interpreted in terms of the broad pedogenic processes and environments assumed to be currently responsible for that type of soil forming at the present surface even the very presence of a palaeosol may have palaeoclimatic significance however in that it is often taken to indicate a period of relative land surface stability and warmer and or moister conditions between cold and or arid phases of loess accumulation in reality it may be more useful to consider many loess palaeosol sequences in terms of changing balances between pedogenesis and loess accumulation over geological time in most regions it seems that the balance swings towards pedogenesis during interglacials or interstadials when sediment supply and transport are limited and the climate is warmer and or wetter where accumulation rates are still appreciable during these soil forming intervals however the soils and palaeosols may be accretionary with surface build up keeping pace with pedogenesis welding may also occur where covering sediments are insufficiently thick to isolate an underlying palaeosol from the effects of pedogenesis active at a new land surface further complications occur due to reworking of palaeosols and syndepositional pedogenic alteration of loess units generally such pedocomplexes can only be deciphered if the different pedogenic geomorphic and sedimentary processes are identified and ordered within a pedosedimentary reconstruction a recent trend has been to treat some loess palaeosol sequences as quasi continuous time series particularly when comparing depth functions of climatic proxy properties such as magnetic susceptibility and grain size with marine and ice core isotope curves

geochemistry of the pliocene red clay formation in the chinese loess plateau and implications for its origin source provenance and paleoclimate change abstract recent field observations and sedimentological studies suggest the eolian origin of the late tertiary red clay formation underlying the pleistocene loess soil sequence in the loess plateau thereby extending the wind blown record from 2 6 ma down to 7 0 ma in north central china to address the source provenance of the red clay major and trace element concentrations were analyzed on the samples from a north south loess transect of the loess plateau and a red clay section at jiaxian results show that there is a good agreement of both major and trace element compositions between the last glacial interglacial loess soil units and the jiaxian red clay record the ree distribution patterns of the loess soil and red clay samples are remarkably similar in shape with enriched lree and fairly flat hree profiles and clear negative eu anomaly the geochemical features of the red clay are also identical to those of upper continental crust these chemical characteristics provide further evidence for eolian sedimentation of the red clay from the relations both between na2o al2o3 and k2o al2o3 ratios and between u pb and th pb ratios the eolian loess and red clay materials must have been subject to thorough sedimentary differentiation and moderate chemical weathering in the source area the chemical similarity between soil unit s1 and the red clay implies that such an environment as occurred in the last interglacial period may have already formed in northwestern china during the late tertiary comparison of down section variations in elemental ratios with field observations of pedogenic development of the red clay suggests that cao al2o3 sr rb and sr ba are more sensitive to climate changes than magnetic susceptibility and can be used to reconstruct the climate history of the late cenozoic

the response of transitional pedogenic characteristics of loess in the yunxian basin to abrupt climatic events in the northern subtropics since the last glacial maximum abstract the transitional pedogenic characteristics of loess deposits in the yunxian basin have provided solid evidence for understanding the mechanisms of dust transportation deposition and detailed documentation of climate instability since the last glacial maximum lgm in the northern subtropics of china the heinrich stadial 1b hs 1b 16 9 14 7 ka b p event b lling aller d b a 13 9 13 ka b p period younger dryas yd 12 9 11 7 ka b p event and an environmental event 5 4 ka b p during the holocene optimum were imprinted by the high resolution multi proxy of loess paleosol in the yunxian basin china based on granularity and chemical analyses the loess in the yunxian basin can be classified as a fine clayey loess zone that experienced a moderate degree of chemical weathering the mechanism forming the transitional pedogenic characteristics was explained by the dust storm frequency data 1957 2007 particle size data and multi proxy records of chemical weathering extent which was mainly caused by the moderate transport distance from the common provenance and the transitional climatic characteristics of the northern subtropical zone

distribution provenance and onset of the xiashu loess in southeast china with paleoclimatic implications abstract loess deposits are important archives of past climate change in subtropical china where long term terrestrial records are scarce however only a few long term records with reliable dating were reported in jiangsu province where loess deposits in southeastern china were first discovered and designated as the xiashu loess moreover the provenance of the xiashu loess is still controversial this study presents the magnetostratigraphy and detrital zircon u pb age results of loess deposits at zhoujiashan in nanjing jiangsu province to date this section with basal age of approximately 0 88 ma may be the oldest loess deposits discovered in southeastern china based on the detrital zircon u pb ages of the zhoujiashan section together with published results of geochemistry geomorphology sedimentology and meteorology we propose that the xiashu loess has two mixed sources local materials derived from the yangtze river basin including exposed river lake beds floodplains and mountains served as a major contributor the distal eolian dust that originated from the arid areas of north china including deserts piedmont alluvial fans and drylands played a minor role in the formation process of the xiashu loess the nearly synchronous onset age approximately 0 88 0 85 ma of the xiashu loess was attributed to a regional environmental event during the middle pleistocene transition

middle pleistocene to holocene geochronology of the river aguas terrace sequence iberian peninsula fluvial response to mediterranean environmental change abstract our results from the river aguas basin suggest that fluvial archives travertine and slope deposits provide sensitive resolution records of environmental changes during the last 170 kyr from the chronostratigraphic data sets we have established a model of middle and late pleistocene river response for littoral basins on the southern iberian peninsula u th and osl dating indicate the major periods of travertine formation of the alfaix travertine platform which range from 169 to 26 kyr at least four incision events interrupted this aggradation period between 167 and 148 kyr between 148 and 110 kyr around 95 kyr and at 71 kyr aggradation ceased after 26 kyr and incision occurred during ois 2 subsequently the terraces t4a and t4b were deposited osl dating of the t4a channel deposit provides maximum ages of 28 20 and 18 kyr however short climatic events such as the younger dryas produced two more river incision episodes during ois 2 nonetheless for river systems influenced by tectonics climate and sea level changes it is difficult to assess the weight of each controlling factor regarding the three mechanisms of pleistocene river dynamics in middle size catchment areas of the littoral region of southeastern spain our results support the hypothesis that large scale tectonics triggered the general downcutting trend whereas the main aggradation and incision phases occurred during periods of major sea level changes over short time scales the influence of climate variability as documented by pollen records plays a decisive role thus the river responses to the three cyclic mechanisms operate at different time scales although synergetic processes should be considered with respect to the magnitude of abrupt incision aggradation events

elemental and sr nd isotopic compositional disparity of riverine sediments around the yellow sea constraints from grain size and chemical partitioning to obtain a better understanding of the source compositions of the river sediments around the yellow sea and their relationship with source rocks elements and strontium neodymium sr nd isotopes of different grain sizes silt and clay populations and chemical labile and residual phases fractionations in riverine sediments were studied extensively these results clearly revealed a systematic compositional disparity between korean river kr and chinese river cr sediments especially in the residual detrital fraction the geochemical dissimilarity between these might reflect inherited signatures of their source rocks but with minor control from chemical weathering in particular the remarkable enrichment of some elements iron fe and magnesium mg and the behavior of large ion lithophile elements e g barium ba potassium k and sr during weathering as well as less radiogenic sr isotopic compositions implies that cr sediments might be weathering products of relatively more mafic rocks with abundant ferromagnesian and plagioclase feldspar minerals compared with kr sediments derived from silicic granites with relatively higher quartz and potassium feldspar contents this different petrological rationale is clearly evident in an a cn k diagram which estimated the source rock of cr sediments as granodioritic a composition that reflects accurately the average composition of weathered continental crust in china the recognition of such geochemical systematics in two river sediments especially in grain size and chemically partitioned data may contribute to the establishment of provenance tracers for the yellow sea and east china sea sediments with multi sources as well the dust deposition in the western pacific c 2015 elsevier ltd all rights reserved

an estimate of ice drifted sediments based on the mud content of the ice cover at montmagny middle st lawrence estuary abstract recent measurements made at montmagny a locality on the south shore of the middle st lawrence estuary 70 km northeast of quebec city 47 n give an idea of the volume of fine grained sediments incorporated in the ice cover and allow an estimation of the annual load drifted by ice at this locality a mean thickness of 10 cm of mud was encountered in the ice cover over an area of approximately 20 km 2 thus the total load of fines may be as much as 4 10 6 tonnes t it is estimated that upon melting at break up about 15 of this load returns to the montmagny tidal flat while the remaining volume is carried to the offshore zone considering breakup characteristics it is estimated that about 1 5 2 10 6 t of fines return to the turbidity zone while the remaining load is ice drifted outside that zone since the shore area of the middle st lawrence estuary covered by ice during the winter is approximately 60 km 2 it is calculated that a load of 5 6 10 6 t of sediment incorporated in the ice cover could escape from the turbidity zone annually to this load should be added another 4 10 6 t of suspended matter which come from the freezing in situ of the turbid water in the offshore zone an annual output by ice drifting of 10 10 6 t of sediment is thus likely and is in great contrast to the output during the ice free season of approximately 1 10 6 t in the middle st lawrence estuary the annual output almost equals the input consequently the sediment budget is virtually in a state of equilibrium which helps to explain why there is very little permanent mud deposition in the shore and offshore zones today it is concluded that ice processes largely control the sedimentary budget of the turbidity zone of the middle st lawrence estuary a particular environment within a mid latitude inner continental shelf which is partly dominated by ice

soils as indicators of quaternary climatic change in mid latitude regions abstract soils result from changes to uppermost layers of the earth s crust occuring beneath stable land surfaces soil properties are determined by five factors or groups of factors climate organisms relief parent material and time quantitative climatic interpretation of soils depends upon mathematical relationships between individual soil properties and climatic factors i e climofunctions these are difficult to establish and often cannot be applied to diagenetically modified buried soils so most climatic interpretations of soils are qualitative or semi quantitative soil features formed by frost action are the most reliable climatic indicators most soils continue to develop over time however many soil dating techniques provide only a single date some time during the period of soil formation the beginning and end of a soil development period are best determined by reference to dated deposits over as large an area as possible but stratigraphical interpretation of soils is still impeded by imprecise definitions and procedures the soil chronosequences developed in the major loess deposits of europe and asia provide the best evidence for climatic change throughout the quaternary however only major glacial interglacial cycles are well expressed to obtain more detailed evidence of weaker interstadial cycles it is necessary to study chronosequences in mid latitude regions which were generally moister for much of the quaternary however these soils are less well preserved and present additional difficulties of interpretation because of greater variation in parent material relief and time as soil forming factors

molecular fossils in a pleistocene river terrace in southern china related to paleoclimate variation abstract the red paleosols oxisols in southern china provide a record of global climate oscillation during at least the last 0 80 ma here we present a correlation between the marine oxygen isotope record stage 11 21 and the paleosol molecular fossil signature in the fourth xiushui river terrace in southern china temporal variations seen in two molecular ratios c15 21 c22 33n alkanes and pristane to phytane pr ph down the paleosol profile are postulated to have arisen from variations in biological input and subsequent pedogenesis in response to the changing strength of the east asian summer monsoon climate the preliminary findings suggest strong couplings among the soil vegetation and climate and provide a basis for a correlation between the terrestrial and oceanic records

climate forcing of fluvial system development an evolution of ideas starting from traditional ideas on the climatic steering of fluvial system dynamics it appears that there are different kinds of climatic influences on system dynamics they vary from direct climatic forcing like peak precipitation to indirect like permafrost and partial forcing like vegetation vegetation or its absence and not directly climate is considered as the main cause of fluvial incision or deposition during temperate or cold periods however other external factors than climate and non climatic factors such as local basin characteristics like subsoil lithology and relief express their effects on the fluvial systems by their role in the energy balance of the river catchment finally internal factors in fluvial system evolution like thresholds and response time should not be neglected

chemical weathering of the loess deposits in the lower changjiang valley china and paleoclimatic implications abstract loess deposits xiashu loess are widely distributed in the lower changjiang valley east china and are considered to be of eolian origin with a similar provenance to the well documented loess of north central china the xiashu loess is characterized by strong dissolution of carbonate and considerable weathering of some silicate minerals especially plagioclase chemical mobility of ca sr na mg was observed in the xiashu loess sediments whilst most transition metals are relatively enriched chemical index of variation cia and element ratios of k na and k ca record several paleoclimate events in the lower changjiang valley during the mid late quaternary corresponding with isotopic records in deep sea sediments east china might be governed by stronger summer monsoons than north central china during interglacial periods of the mid late quaternary which may somewhat obscure the record of winter monsoons during glacial periods

volcanic sources and diagenetic alteration of permian triassic boundary k bentonites in guizhou province south china abstract terrestrial permian triassic boundary ptb sequences in south china usually contain one to three ash beds k bentonites which provide evidence of a possible trigger for the terrestrial mass extinction and are useful as a distinct marker for correlation of the ptb boundary interval from terrestrial to marine areas here we investigate the clay mineralogy and geochemistry of ash beds in the zhejue and jiucaichong sections representing paludal and lacustrine environments respectively in order to better understand the source s and preservation of these ash beds the two zhejue k bentonites exhibit similar compositions that are distinctly different from that of the jiucaichong k bentonite the former contain mainly clay minerals with minor quartz anatase and lepidocrocite and the clay minerals in these layers are mainly r1 and r3 mixed layer illite smectite i s and well crystallized to poorly crystallized kaolinite whereas the latter consists mainly of r3 i s with minor quartz feldspars and anatase the former have higher cia values 92 2 and 93 8 than the latter 79 4 indicating more intense chemical weathering that may have been related to deposition in a paludal setting with high organic acid concentrations in pore fluids these k bentonites also exhibit differences in major element chemistry mgo and k2o contents are higher at jiucaichong due to lesser weathering intensity and possibly early diagenetic uptake from pore fluids ree chemistry jiucaichong exhibits a larger eu anomaly and nd isotopic compositions zhejue k bentonites have 143nd 144nd ratios of 0 512436 and 0 512400 higher than the 0 512190 ratio for jiucaichong although some of these compositional differences may be related to the dissimilar chemical environments in which diagenesis occurred i e paludal vs lacustrine the differences in eu anomalies and nd isotopic compositions imply heterogeneous volcanic ash sources the source of these k bentonites was probably a continental volcanic arc located on the paleo southern margin of the south china craton within which multiple volcanic vents may have been active concurrently

ice rafting of fine grained sediment a sorting and transport mechanism beaufort sea alaska abstract the presence of turbid sediment rich fast ice in the arctic is a major factor affecting transport of fine grained sediment turbid ice was found to be present in a zone 10 to 20 km wide along the coast of the beaufort sea sediment concentrations observed in cores taken in seasonal fast ice ranged from 3 to more than 1 600 g m3 finely disseminated silt and clay sized particles dominated discoloring the upper segments of the cores in a layer up to 1 m thick in almost all of the cores the upper most 10 cm of ice was relatively less turbid and the relief at the base of the turbid layer was 10 to 20 cm over distances of 1 to 2 m observers have documented the widespread sporadic occurrence of sediment rich fast ice in both the beaufort and bering seas the known sources a d transport relations of suspended sediment did not explain this distribution of turbid ice the occurrence of sediment in only the upper part of the seasonal fast ice indicates that sediment rich ice forms early during ice growth the most likely mechanism for the formation of sediment laden ice and preferential sorting of fine sediments requires resuspension of nearshore bottom sediment during storms accompanied by formation of frazil ice and subsequent lateral advection before the fast ice is stabilized we estimate that the sediment incorporated in the beaufort ice canopy formed a significant proportion of the seasonal influx of terrigenous fine grained sediment the dominance of fine grained sediment suggests that in the arctic and sub arctic these size fractions may be ice rafted in greater volumes than the coarse fraction of traditionally recognized ice rafted sediment the incorporation and transport mechanism may be a significant factor in the transport of fine grained sediments in the arctic basin

bimodal grain size distribution of chinese loess and its palaeoclimatic implications grain size analysis indicates that chinese loess generally shows a bimodal distribution with a coarse and a fine component the coarse component comprising the main part of the loess has pronounced kurtosis and is well sorted which is interpreted to be the product of dust storms generated by low altitude northwesterly winds its grain size reflects the strength of the low altitude circulation in the dust seasons of the year and its percentage provides an indicator of the source area aridity and the frequency of dust storms conversely the fine component has a wide grain size range and is poorly sorted sedimentary illustrations based on the grain size distribution characteristics of bulk samples and of detrital quartz suggest that the fine component probably represents the background dust load of the atmosphere and is mainly transported by high altitude westerly airstreams its grain size provides an estimate of the westerly air stream intensity the coarse and fine components of a loess sample can be mathematically separated by fitting a designated mathematical distribution function to the measured grain size data and this procedure constitutes an approach for reconstructing the palaeowind system of northern china c 2003 elsevier b v all rights reserved

mixed layer illite vermiculite as a paleoclimatic indicator in the pleistocene red soil sediments in jiujiang southern china abstract the mineralogy and chemical composition of the jiujiang red soil sediments were investigated using x ray diffraction xrd x ray fluorescence xrf and inductively coupled plasma mass spectrometry icp ms mixed layer illite vermiculite i v was confirmed based on the conditions that a broad peak of 1 0 to 1 4 nm appeared in xrd after mg saturation and its d spacing did not change after glycol treatment but collapsed to 1 0 nm after heating owing to the loss of water and hydroxy cations from its interlayer the mixed layer i v contents fluctuate throughout the section but show a decreasing trend upwards suggesting decreased weathering towards the surface of the section the chemical index of alteration cia values and rb sr ratios also exhibit upward decreasing trends jointly revealing the climate shift from warm humid to cool dry from the middle to the late pleistocene although the general climate evolution can be evaluated by cia values and rb sr ratios sub climatic events within the jiujiang red soil sediments cannot be identified the sio2 al2o3 al2o3 fe2o3 and sio2 fe2o3 ratios clearly fluctuate along the section especially within the net like red soil sediments but they do not reveal multiple climate cycles this is because of an inhomogeneous distribution of sio2 al2o3 and fe2o3 in the white veins and the red matrix and also non uniform sampling the variation in the content of mixed layer i v show a strong positive correlation with changes in magnetic susceptibility of loess paleosol sediments and in marine oxygen isotope ratios revealing multiple sub climate cycles on a global scale since the middle pleistocene therefore the mixed layer i v contents not only reveal the whole climate trend documented in the red soil sediments since the middle pleistocene but also disclose the sub climate cycles related to the deposit pedogenesis process

environmental fluctuation impacted the evolution of early pleistocene non human primates biomarker and geochemical evidence from mohui cave bubing guangxi southern china abstract quaternary climate variability profoundly impacting the evolution and distribution of plants and animals across the globe has been reconstructed by many sediment archives here we track past changes of temperature rainfall and plant type by using the n alkane and glycerol dialkyl glycerol tetraethers gdgts as well as weathering and pedogenesis by mineralogical and geochemical proxies from a 250 cm deep soil sediment profile from the early pleistocene deposits in mohui cave southern china indices for weathering intensity such as mineral composition quartz feldspar and calcite major element proxies ti na al na al mg ti mg ciw pia cpa cia trace element proxies ba sr and rb sr and biomarker proxies oep lsr and cpi show similar secular trends revealing a three stage historical accumulation the high long chain n alkane ratios c31 c29 and c31 c33 c27 c29 indicate that the vegetation in the region had increases in percentage of woody plants and decreases in herbs during periods of relatively lower temperature and less precipitation which evidenced from gdgts consistent with a weak weathering process influenced by summer monsoon strength further we compared the distribution of these plant types with the taxonomic variation in the vertebrate paleontological fossils excavated from the same profile in mohui cave the distribution of lufengpithecus appears in only one interval but gigantopithecus blacki appears throughout the profile despite an environment that experienced transitional stages from grassland to woodland in relatively cooler and drier conditions we infer that in face of these climatic changes lufengpithecus may have preferred to emigrate from the region while gigantopithecus blacki may have stayed given that it was limited to staying in its core area

magnetic susceptibility evidence of monsoon variation on the loess plateau of central china during the last 130 000 years the magnetic susceptibility of loess and paleosols in central china represents a proxy climate index closely related to past changes of precipitation and vegetation and thus to summer monsoon intensity time series of magnetic susceptibility constructed for three loess paleosol sequences in the southern part of the chinese loess plateau document the history of summer monsoon variation during the last 130 000 yr they correlate closely with the oxygen isotope record of stages 1 to 5 in deep sea sediments soils were forming during intervals of strong summer monsoon whereas loess units were deposited at times of reduced monsoon intensity the chinese loess paleosol sequence can thus be viewed as a proxy record of asian monsoon variability extending over the last 2 5 myr

magnetic properties and geochemistry of the xiashu loess in the present subtropical area of china and their implications for pedogenic intensity variations in the magnetic susceptibility of chinese loess have been used to indicate pedogenic intensity and therefore past climate across the chinese loess plateau clp however the relationship between climate and magnetic properties has not been fully resolved and therefore a study of loess sections distributed over a wider climatic region is timely in this study we have investigated a 22 1 m loess section named the xiashu loess at dagang china by integrating both rock magnetic and geochemical proxies this loess profile is situated in a modern subtropical climate region with annual mean precipitation and temperature of 1100 mm and 15 4 c respectively and therefore has experienced a stronger weathering intensity due to its lower latitude higher temperature and rainfall geochemical and magnetic evidence indicate the same source area for the xiashu loess as for loess in northern china the magnetic mineral assemblage of the xiashu loess is dominated by a higher concentration of superparamagnetic sp single domain sd magnetite maghemite grains in strongly weathered paleosols than in the loess layers consistent with the production of fine grained ferrimagnetic minerals during pedogenic processes nevertheless compared to loess in the clp the xiashu loess shows 1 reduced contrasts in magnetic susceptibility hard isothermal remanent magnetization hirm and remanence of coercivity bcr between loess and paleosols units which indicates that the loess units have undergone stronger pedogenic alterations 2 lower peak values of hirm and in paleosols in addition the ratios sirm arm sirm where sirm and arm are saturation isothermal remanent magnetization and the susceptibility of anhysteretic remanent magnetization respectively and bcr are found to be significantly correlated with the quotient cao na2o mgo tio2 a geochemical indicator of pedogenic intensity overall it seems that pedogenic processes in the xiashu loess lead to a relative increase in fine grained ferrimagnetic sp sd grains but depletion of anti ferromagnetic minerals magnetic and geochemical proxies indicate strengthened east asia summer monsoon during marine isotope stages 13 11 and 5 which is in good agreement with the records from the clp and the south china sea 2007 elsevier b v all rights reserved

magnetic susceptibility of the quaternary red clay in subtropical china and its paleoenvironmental implications abstract magnetic susceptibility lf and other magnetic parameters of 11 typical profiles of quaternary red clay qrc in subtropical china were measured lf curves of the qrc profiles show similar vertical variations lf of the uppermost yellow brown earth ybe and uniform red clay urc of the profiles is high mostly ranging from 50 to 150 10 8 m 3 kg 1 that of the reticulate red clay rrc sharply decreases downwards especially in the lower rrc lrrc with dense reticulate pattern lf is often less than 10 10 8 m 3 kg 1 grain size characteristics and geochemical properties of the qrc suggest that the sharp decrease of lf in the rrc is not related to sudden change of parent materials but to the formation of the reticulate pattern further study indicates that pedogenic fine ferrimagnetic minerals fm superparamagnetic particles sp and or stable single domain ssd are the main magnetic carriers of the qrc the ybe and urc with higher lf show low coercivity and magnetic soft behavior the rrc especially the lrrc with weak magnetism shows high coercivity and magnetic hard behavior the temperature dependent susceptibility tds of the qrc suggests that the dominant type of fm in the ybe and urc is pedogenic maghemite the rrc especially the lrrc however contains little maghemite but a trace amount of lithogenic multi domain md magnetite inherited from the parent rock during post depositional hydromorphic processes pedogenic maghemite was more easily dissolved than hematite which caused the sharp decrease of lf in the rrc as lf of the qrc was mainly controlled by the intensity of hydromorphic processes rather than the weathering degree lf of the qrc in subtropical china cannot accurately indicate the paleoclimate during the quaternary period when the red clay was initially formed

neodymium and strontium isotopic constraints on soil sources in barbados west indies abstract neodymium and strontium isotopic compositions and sm nd ratios are used to constrain the sources of silicate rich soils developed on uplifted pleistocene coral reef limestones on barbados west indies the geographic and geologic setting of barbados facilitates the application of these tracers to the evaluation of the following soil sources 1 pleistocene reef limestone regolith 2 tertiary carbonate rocks sandstones and mudstones that are exposed in northeastern barbados 3 volcanic ash erupted from the lesser antilles arc 4 saharan dust transported by trade winds and 5 fertilizer the soils have nd values that range from 6 6 to 1 9 87 sr 86 sr values of 0 70890 to 0 71067 and sm nd ratios of 0 223 0 260 the pleistocene limestone component is the most significant source of sr in the soils and a negligible source of nd comparison of sm and nd concentrations and neodymium isotopic compositions of soil samples that are weathered to varying extents indicates that sm and nd are relatively unfractionated and retained in the soils during weathering nd and sm nd variations in the soils therefore primarily reflect the compositions and proportions of the silicate sources mass balance calculations based on sm nd systematics require that the silicate soil components contain between 30 85 volcanic ash with the remaining silicate fraction comprised of old continentally derived sediment in contrast to sm and nd sr is mobilized and removed from the soils during weathering strontium from volcanic and carbonate sources is preferentially removed relative to continental silicate sources the strontium isotopic compositions of the soils therefore reflect the combined effects of the degree of weathering and the compositions and proportions of the soil sources mass balance calculations indicate that at least 35 60 of the initial sr in the soils has been removed by weathering these results illustrate 1 the utility of radiogenic isotopes in identifying and quantifying soil sources and weathering processes 2 the compositional influence of numerous sources on soils even those developed in a relatively isolated area such as barbados and 3 the domination of barbados soil sm nd systematics by nonregolith eolian components

cenozoic climate change in eastern asia part i abstract this special issue provides new studies in the field of cenozoic climate change in eastern asia the papers in this volume are multidisciplinary in nature and examine a range of topics including paleovegetation sedimentology clay mineralogy geochemistry magnetostratigraphy and climate modelling the findings of these studies demonstrate that analysis of terrestrial paleoclimate changes in eastern asia may offer insights into the effects of tibetan plateau uplift and ultimately the dynamic processes of global change that took hold throughout the cenozoic the second part of this special issue to be published later will add a paleoecology component examining how cenozoic climate change has impacted floras and faunas in eastern asia

geochemistry and mineralogy of the 2 45 ga pronto paleosols ontario canada abstract the ontario canada pronto paleosols which formed around 2 45 ga on archean granite were studied through field observation mineralogical study by microscope and microprobe and chemical analyses of major and 45 trace elements including rare earth elements rees since the first full description of its mineralogy and chemistry of major elements by gay and grandstaff gay a l grandstaff d e 1980 chemistry and mineralogy of precambrian paleosols at elliot lake ontario canada precambrian res 12 349 373 the pronto paleosols are among the most cited paleosols of the archean early proterozoic era though several questions have been raised as to whether they are true in place ancient soils results of this study show that the studied section meets the criteria for being in place paleosols furthermore the profile has no explicit traces of being strongly affected by hydrothermal alteration the ree containing accessory minerals were destroyed through weathering and secondary phosphate minerals with rees formed all of these observations support the weathering origin of the pronto paleosols however the profile should be identified as a saprolith rather than paleosol as even the uppermost samples exhibit the granitic texture of the parent rock the samples in this study were collected mainly from two sites site i and site ii saprolith samples from site i show the retention of fe and increases of the fe iii fe ii ratios and the chemical index of alteration cia values toward the unconformity as for the site ii samples the fe ti ratios show slight decreases with increasing cia values in the upper part of section whereas these samples also show the same trend of increasing fe iii fe ii ratios as the samples from site i microprobe analyses show that fe from the parent rock distributes mainly in mafic minerals as hornblende biotite or chlorite which were completely destroyed during the early stages of weathering in the saprolith section fe is present in sericite aggregates in the form of obscure patches of iron oxide tens of micrometers in size all these characteristics indicate that i the fe was not lost during soil formation at site i and slight amount of fe was lost at site ii and ii ferrous fe was quantitatively transformed to ferric fe i e oxidation during soil formation in the samples from both sites the ratios of al ti and si ti decrease toward the top of the profile together with the destruction of minerals toward the unconformity such as apatite biotite and chlorite the depletion of al and si suggests that the parental granite was weathered by an acidic weathering solution during the archean early proterozoic era the high atmospheric partial pressure of co 2 p co 2 is the most probable candidate for producing the acidic weathering solution

mineralogical and clay mineralogical aspects of loess research abstract mineralogical and clay mineralogical investigations under certain circumstances allow conclusions regarding the rate and kind of pedogenetic weathering especially clay mineral formation together with soil physical and chemical and mainly micromorphological investigations paleoclimatic conclusions can be drawn in central european holocene and pleistocene loess soils as well as in relict loess soils in the central and northern part of the great plains of the u s a smectite is the dominant pedogenetically formed mineral in the fine clay fraction

paleomagnetism of the 1 1 ga umkondo large igneous province in southern africa 1 the umkondo dolerites are present over a wide area in the kalahari craton southern africa thirty nine sampling sites in botswana and south africa yielded tightly grouped paleomagnetic directions due south with shallow inclinations and three sites of opposite polarity the dolerites have u pb single crystal baddeleyite or zircon crystallization ages of 1112 0 5 to 1108 0 9 ma these results can be combined with published data from 39 additional umkondo sites and 33 sites in the grunehogna province of antarctica after restoring east antarctica to its position next to southern africa grouping the sites geographically yields 10 site mean poles with mean at 64 0 n 38 8 e a95 3 7 this umkondo pole can be correlated with keweenawan poles from laurentia because both sets of poles are precisely of the same age as well as predominantly of one polarity the relative orientation of the two cratons within the rodinia supercontinent is fixed this implies that the namaqua natal maud belt which rims the southern part of the kalahari craton faced away from laurentia the umkondo pole combined with published poles suggest that the kalahari craton remained distinctly south of the laurentian craton between 1 1 and 1 0 ga making it highly unlikely that the two cratons collided

the effect of weathering on the grain size distribution of red soils in south eastern china and its climatic implications abstract particle size analysis is a useful way to determine the source and deposition of sediments however there are inconsistencies when this method is used to constrain the origin of the red soils in south eastern china to address this problem we performed a detailed grain size analysis of two red soil sequences in xuancheng and qiliting located along the lower reaches of the yangtze river by comparing their particle size characteristics with those of the loess on the loess plateau in northern china we found that the aeolian samples plot in a particular zone in the c m grain size of the cumulative 1 versus median grain size plot and cluster nearer the lower left corner of the plot as their degree of weathering increases the grain size features suggest that the onset of large scale aeolian deposition along the lower reaches of the yangtze river occurred at approximately 0 8 ma although both sedimentary sorting and post depositional weathering control the grain size variations in the deposits the extremely strong weathering due to the humid warm climate along the lower reaches of the yangtze river primarily modified the grain size distributions of the primary red soil deposits strong weathering increased the very fine silt 2 5 m fraction and decreased the coarse 63 m fraction we also found that certain grain size parameters of the red soils varied with the weathering intensity which can be used as indicators of palaeoclimate variations the grain size variations in both the qiliting and xuancheng sequences suggest that the mid pleistocene climate transition mpt may have affected the lower reaches of the yangtze river at 0 9 ma

the influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern united states this paper reports systematic changes in mudrock composition through time on a single con tinental cmstal block the changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton the major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study major elements record sediment recycling processes as well as changing proportions of sedi mentary and first cycle source rocks with the exceptions of kzo which tends to increase and sioz and a o3 which show no trend most major oxides tend to decline in relative abundance in younger mud rocks patterns shown by the index of compositional variability fe03 kro naao cao mgo mno tiojialro and by k20 a1203 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material excursions from progressive trends marked by increases in mgo k20 and cao reflect episodes of large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift the chemistry of low solubility trace elements in contrast is not sensitive to recycling effects and reflects the composition of first cycle input incompatible elements are progressively enriched relative to compatible elements in younger mudrocks and values for chondrite normalised rare earth elements also increase in addition the eu anomaly becomes systematically more negative in younger samples these trends cmnot be explained by diagenetic or weathering processes and therefore indicate that the proportion of fnc tionated granitic first cycle detritus being added to the sedimentary system becomes greater with time these results confirm the importance of tectonic setting in controlling mudrock chemistry and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle

geochemical and detrital zircon u pb geochronological constraints on provenance of the xiaomei red earth sediments bose basin guangxi province southern china abstract the bose basin in southern china is within a region influenced by the winter westerly monsoon and thus potentially subject to eolian dust accumulation a red earth sequence developed on terraces of the youjiang river a branch of the pearl river records information about climate variation during the pleistocene and its relationship to contemporaneous global climate changes in this study geochemical characteristics and u pb geochronology of detrital zircons of the red earth sequence at xiaomei were investigated using x ray diffraction xrd x ray fluorescence xrf inductively coupled plasma mass spectrometry icp ms thermal ionization mass spectrometry tims and detrital zircon u pb dating analyses our results show that the red earth sediments are composed of quartz and clay minerals kaolinite illite and mixed layer illite vermiculite with minor hematite and goethite mobile elements such as cao mgo na2o k2o sr and ba are depleted and immobile elements such as tio2 al2o3 fe2o3 t and zr are enriched in comparison with loess paleosols of the chinese loess plateau clp the upper continental crust ucc and post archean australian shale paas these data indicate that the xiaomei red earth sediments have experienced intense chemical weathering similar to that of the xuancheng and jiujiang red earth sections on the middle to lower reaches of the yangtze river the xiaomei sediments have similar la th ratios u pb vs th pb relationships and rare earth element ree distributions to the clp ucc and paas and their low end 0 values are indicative of an upper crustal origin the 147sm 144nd and 87sr 86sr ratios of the xiaomei sediments are different from loess paleosols of the clp but similar to those of well mixed river sediments u pb dating of detrital zircons in the xiaomei sediments shows that crystals from different units have slightly different age distributions the full xiaomei section yields a distribution similar to that of upper permian triassic clastic rocks in the youjiang area and the distribution of the middle to upper xiaomei section additionally shows similarities to upper crust of the south china craton our results indicate that the xiaomei red earth sequence which dates to the late early to early middle pleistocene 1 0 0 6 ma accumulated predominantly from fluvially transported locally weathered materials and therefore that the sediment carrying capacity of the east asian winter monsoon has been overestimated in previous provenance studies of red earth sediments in south china

geochemical characterization of the luochuan loess paleosol sequence china and paleoclimatic implications abstract chemical major and trace element and isotopic sr nd analyses of the luochuan loess paleosol sequence in china were performed in order to examine the following problems 1 potential source heterogeneity 2 element behavior during pedogenesis 3 paleoclimatic implications and 4 the use of loess data to determine the average composition of the upper continental crust new results clearly indicate that rb sr u and ce abundances are severely depleted in paleosols relative to their parental loess the behavior of these elements is strongly controlled by the breakdown of primary minerals such as carbonate sr or by alteration processes in highly oxidizing environments ce and u the pattern of element variations through the upper section of the luochuan sequence mimics the magnetic susceptibility signal both in position and in intensity thus reinforcing the pedogenesic origin of the enhanced magnetic susceptibility in paleosols all loess samples display highly uniform ree patterns except for ce characterized by the upper continental crust ucc ratios la yb n 10 and eu eu 0 66 the paleosol ree patterns are similar to those of the loess with the same lree hree fractionation but they also show distinct and variable negative ce anomalies nd and sr isotopic compositions are rather uniform in both loess and paleosols and do not vary with stratigraphic position nd 10 5 to 9 2 87 sr 86 sr 0 715 to 0 719 the isotopic homogeneity in the luochuan sequence strongly suggests a uniform source region during the entire period of deposition since 800 ka ago to the present several conclusions may be drawn from the present study 1 1 no geochemical distinction can be made between loess layers l1 to l7 the sources and the dust storm trajectories must have been essendally the same for the last 800 ka 2 2 some elements e g ca rb sr u ce are strongly fractionated by pedogenesis between loess and paleosols ce mobility in soils is clearly demonstrated but the process responsible for this leaching is still poorly understood 3 3 systematic variations of element abundances and ratios between loess and paleosols can be used as chemical indicators for pedogenesic intensity and so for paleoclimatic change these chemical indicators serve a function similar to that of oxygen isotopes in deep sea sediments pelagic foraminifera or that of magnetic susceptibility in loess sequences they are different recorders of paleoclimatic change 4 4 the striking uniformity of ree patterns and la th ratios in the luochuan loess and paleosols as well as in loess worldwide is an excellent starting point for estimating the average composition of the upper continental crust

quantitative paleoenvironmental and paleoclimatic reconstruction using paleosols abstract paleosols fossil soils are preserved throughout the geologic record in depositional settings ranging from alluvial systems to between basalt flows until recently paleosols were studied using primarily qualitative methods in recent years paleopedology has shifted from a largely qualitative field based on comparisons with modern analogues to an increasingly quantitative endeavor some of this change has been a result of applying existing techniques to new materials but many of the innovations have been the result of applying new techniques to new materials including thermodynamic modeling of soil formation isotope geochemistry and applications of empirical relationships derived from modern soils a variety of semi quantitative and quantitative tools has been developed to examine past weathering and pedogenesis and to reconstruct both paleoenvironmental and paleoclimatic conditions at the time that the paleosols formed though it is often not possible to achieve the same temporal resolution as with marine records for paleoclimatic reconstructions proxies based on paleosols are potentially a much more direct means of making paleoclimatic reconstructions because soils form at the earth s surface in direct contact with the atmospheric and climatic conditions at the time of their formation paleoclimatic and environmental properties that may be reconstructed using the new proxies include provenance weathering intensity mean annual precipitation and temperature during pedogenesis nutrient fluxes into and out of the paleosols the atmospheric composition of important gases including co2 and o2 the moisture balance during pedogenesis the soil gas composition reconstructed vegetative covering and paleo altitude

grain size magnetic susceptibility and geochemical characteristics of the loess in the chaohu lake basin implications for the origin palaeoclimatic change and provenance abstract rare studies on the aeolian deposit located in north bank of the yantgze river are documented recently it is found in the field investigations and in bore sections that the loess in the chaohu lake basin has the largest thickness of over 40 m in this study the probability cumulative curves frequency distribution the grain size distributions and the discriminant function of the grain size suggest that the loess in the chaohu lake basin is of eolian origin the magnetic susceptibility curves of the loess in the basin coincide perfectly with those of the loess in the northern china and the marine isotope stages mis and show that paleoclimatic cycles and sub cycles were documented since l3 during middle late pleistocene in the basin the ms curve of paleosol s1 paleosol s2 and loess l3 in the basin coincide perfectly with mis5 mis 7 and mis 8 respectively the good correspondence indicates that the loess in the basin has given a sensitive response to the globe paleoclimatic change since l3 on the other hand the climate changes in some stages recorded by the loess has regional characteristics obviously which might be the result of the dual effect of globe climate changes and east asia monsoon climate changes the result of geochemical characteristics suggests that the loess in the basin has undergone moderate to strong chemical weathering most elements are mobilized during chemical weathering na and ca of the loess are markedly lost and the removal of k is also evident and chemical weathering doesn t evidently turn into the si removal stage the chemical weathering of the loess is more intensive than that of the loess deposits in northwestern china and the upper reaches of the yantgze river the intensive chemical weathering has been documented by the loess might be related to strong monsoon climate in chaohu lake basin the provenance of the loess also differs from that in northern china and is discussed firstly with the lithofacies palaeogeography the well developed alluvial lacustrine deposits in the huaihe floodplain seem to be the major source materials of the loess

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

microorganism induced weathering of clay minerals in a hydromorphic soil abstract in order to improve the understanding of factors influencing weathering in hydromorphic soils the clay mineral and chemical compositions iron hydr oxides organic compounds and sr and nd isotopic compositions of hydromorphic soils on the banks of the liangzi lake hubei province south china were investigated the b horizon in the lower profile exhibits a distinct net like pattern with abundant short white veins within the red brown matrix their various 87sr 86sr and 143nd 144nd isotopic compositions showed only small variations of 0 7270 0 7235 and 0 51200 0 51204 respectively consistent with the composition of yangtze river sediments indicating that the soils were all derived from alluvium from the catchment the white veins contained notably more sio2 al2o3 tio2 and mobile elements relative to the red brown matrix while they both showed similar values for the chemical index of alteration of 86 7 and 87 1 respectively and displayed similar degrees of weathering the clay minerals in a ae and e horizons of the soil profile were illite kaolinite and mixed layer illite smectite these same three clay minerals comprised the white net like veins in the soil b horizon whereas only illite and kaolinite were observed in the red brown matrix iron hydr oxides in a ae and e horizons of the soil profile were hematite and goethite whereas in the red brown matrix of the b horizon they were hematite goethite and ferrihydrite different organic compounds were observed for the white vein and the red brown matrix in the soil b horizon an 18 2 fatty acid biomarker for fungi in the net like vein but not in the red brown matrix compared with the red brown matrix the white net like vein also clearly contained more mono unsaturated fatty acids which are sometimes associated with bacteria that have the capacity to reduce fe iii thus migration of iron and the formation of the net like veins involved the participation of biota during the hydromorphic pedogenesis process as ferrihydrite is usually formed with the assistance of biota redoximorphic processes will chemically affect phyllosilicates by changing their charge and fe iii in illite may serve as electron acceptor for fe iii reducing microorganisms this leads to an increase in negative charge in the illite structure which could be neutralized by electrostatic displacement of interlayer cations and adsorption of protons thereby promoting transformation of illite to mixed layer illite smectite and dissolution of the pre existing illite mineral our results suggest that microorganisms brought about iron leaching and dominated the alteration of clay minerals by redox processes and different mineral volumes formed in the net like b horizon of the hydromorphic soil were attributed to the microorganism induced weathering process

an analysis of geomagnetic field reversals supports the validity of the geocentric axial dipole gad hypothesis in the precambrian abstract the geocentric axial dipole gad hypothesis has been regarded as the cornerstone of paleomagnetism for decades and disputes on its applicability have mostly dealt with the precambrian data one way to analyze the zonal harmonics of the geomagnetic field and the validity of gad hypothesis is based on the angular difference between the normal and reversed polarities also referred to as reversal asymmetry for this purpose a comprehensive compilation of the reversals of archaean and proterozoic geomagnetic field has been done using a novel paleomagnetic database with 3246 entries globally given the uncertainties prevailing in this type of analysis results from 106 reversal records show no dependence of the reversal asymmetry on paleolatitude thus supporting the outcome of our inclination frequency analysis of the precambrian field in addition to the inclination asymmetry the non antiparallelity between n and r also involves a declination asymmetry which is more difficult to determine and deals with the non zonal features of the field based on our dual polarity data we propose that the geocentric axial dipole gad is a viable approximation of the geomagnetic field throughout the precambrian

paleomagntism of archean rocks from northwestern ontario ii shelley lake granite quetico subprovince the 2580 20 ma shelley lake granite of the quetico gneiss belt in northwestern ontario preserves two distinct natural remanent magnetizations nrm s of different ages type 1 nrm of either normal 1n or reverse 1r polarity was isolated in 43 samples using three methods stable end point directions orthogonal vector plots and converging remagnetization circles the mean direction based on both 1n and 1r results is d 5 9 i 56 4 k 95 4 95 4 4 n 12 sites which is significantly different from both the present earth s field pef and axial dipole field directions at the site type 2 nrm either normal 2n or reverse 2r was successfully separated from 1n 1r in 13 samples its mean direction combining both polarities is d 70 3 i 27 8 k 20 1 95 9 4 n 13 samples the paleopole sl1 corresponding to 1n 1r falls at 65 8 e 77 6 n near track 6 of the laurentian apparent polar wander path apwp around 2600 ma this remanence is carried principally by primary multido

aeolian origin of the red earth in southeast china a clay like deposit known as red earth is widely distributed over the terraces and high lands of the yangtze river valley in southeast china its typical pedo stratigraphical features have attracted the interest of pedologists and geologists for many years although its origin is still debated here we report an analyses of the grain size distributions rare earth element bee patterns and upper continental crust ucc normalised major elemental composition of the red earth and compare them with those of the loess and other aeolian deposits in northern china the results show that the red earth in southeast china has two or three end member grain size distributions similar to the sedimentary characteristics and geochemical composition of aeolian deposits found in northern china together with other evidence from field observations these results suggest that the red earth is probably of acolian origin on the basis of these data we suggest that thick aeolian dusts were also deposited in the wet subtropics and that the effect of the winter monsoonal winds upon the dust transport in eastern china was more important than previously believed copyright c 2002 john wiley sons ltd

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

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

randomly interstratified illite vermiculite from weathering of illite in red earth sediments in xuancheng southeastern china abstract mixed layer illite vermiculite i v clays of the xuancheng red earth were investigated using x ray diffraction xrd fourier transform infrared ftir spectrometer and high resolution transmission electron microscopy hrtem methods the xrd results indicated that the mixed layer i v clays were characterized by the broad 10 14 a peak with a maximum intensity at 12 a in air dried sample which decomposed into two peaks at 10 a and 14 a peaks respectively after ethylene glycol treatment after k saturation the 14 a peak changed to 10 a which reverted back to 14 a after saturation with mg 2 with a notable decrease in intensity of the 10 a peak the broad 10 14 a peak collapsed to 10 a on heating to 400 c these suggested that the broad 10 14 a peak resulted from randomly interstratified illite vermiculite clays together with discrete illite and also vermiculite hrtem observation showed that straight 10 a illite layers were interstratified with 12 a vermiculite layers suggesting that transformation of illite to vermiculite involves an exchange of k by hydrated cations associated with a swelling of the illite the 060 spacing of i v clay is 1 50 a indicating a dioctahedral precursor of illite and thus reinforcing the transformation from illite to vermiculite ftir analysis suggested that most band positions of vermiculite and illite in mixed layer i v did not change in comparison with those of the discrete clay species indicating that the basic crystal structure of mixed layer illite vermiculite remains the same as the discrete clays the interlayer cations in the interlayer region of vermiculite layers of the i v clays are mainly ca and minor mg al and fe the abundant ca makes the i v clays to behave like i s on glycolated and thermal treatment while the mg al and fe complex ions in the interlayer region cause the vermiculite layer to lose its expandability and to behave like chlorite the mixed layer i v clays were widely formed in late quaternary alluvial fans in subtropical to tropical areas where the sediments experienced synchronous pedogenic modification the syndepositional pedogenesis process leads to an incomplete transformation of illite to vermiculite and causes the formation of metastable intermediates of mixed layer illite vermiculite

geochemistry of the xining xifeng and jixian sections loess plateau of china eolian dust provenance and paleosol evolution during the last 140 ka abstract loess and paleosol samples from three distant sections xining xifeng jixian of the chinese loess plateau were analyzed for chemical and nd sr isotopic compositions in order to obtain information about the paleoclimatic variation during the last 140 ka these three sections represent three different climatic conditions from arid in the west xining to more humid in the east jixian across the loess plateau isotopic analyses show that all the three sections display a restricted range of 143 nd 144 nd ratios or e nd 10 0 5 indicating the dominance of relatively young and uniform upper crustal sources for the eolian dust the loess and paleosol samples have typical upper crustal 87 sr 86 sr ratios 0 714 0 718 and their variation can partly be attributed to different carbonate silicate ratios in the samples ree data from the three sections are indistinguishable from each other they show typical upper crust patterns characterized by la yb n 10 and eu eu 0 65 the high degree of chemical and isotopic homogeneity suggests that the dust source region must have undergone multiple recycling and thorough sedimentary mixing processes various chemical indicators have been used to monitor the pedogenetic intensity in these sections although results for the jixian section agree reasonably well with the known climatic conditions on the loess plateau the other two sections yield results not in agreement with some well accepted proxies like magnetic susceptibility or grain size distribution some chemical proxy indicators established in our previous work on the luochuan section such as the systematic u depletion and negative ce anomalies in ree patterns in soils are not clearly recorded in the present case the discrepancy between different climatic proxies could be related to the effective soil water budget temperature as well as the rate of development of each proxy

palaeopedogenesis of red palaeosols in yunnan plateau southwestern china pedogenical geochemical and mineralogical evidences and palaeoenvironmental implication abstract red palaeosol as an important archive of ancient pedoenvironments effectively reflects the palaeoenvironmental change and tectonic uplift history of the plateau four red palaeosol profiles were collected at 2200 to 2400 m elevations from the yunnan plateau yp to investigate the pedogenic features chemical weathering process and mineral assemblages of soils pedological geochemical and mineralogical techniques were used to understand the palaeopedogenic palaeoenvironmental change and landscape evolution of the plateau pedologically the red palaeosols were characterized by the dark red color a hue of 5yr or redder strong acidity ph 50 g kg 1 and clay 50 contents the red palaeosols were enriched with fe 2 o 3 al 2 o 3 and tio 2 with very low contents of cao mgo na 2 o and k 2 o and slightly low contents of si 2 o and mno chemical weathering indices such as cia cia al 2 o 3 al 2 o 3 cao na 2 o k 2 o 100 sa sa sio 2 al 2 o 3 saf saf sio 2 al 2 o 3 fe 2 o 3 and a cn k diagram al 2 o 3 cao na 2 o k 2 o indicated that the red palaeosols had experienced strong chemical weathering processes scanning electron microscopy analyses revealed that quartz grains of the red palaeosols were characterized by a number of deep dissolution pits and cracks on their surfaces the clay minerals of the red palaeosols were composed of kaolinite gibbsite hematite and vermiculite in the order of abundance pedogenical geochemical and clay mineralogical evidences revealed that the red palaeosols were developed by palaeopedogenic processes under tropical climatic environments the presence of highly weathered soils at an altitude of 2200 2400 m indicated the influence of tectonic uplift on the soil vertical distribution it is estimated that the red palaeosols had uplifted about 1600 2000 m since their initial formation palaeopedogenesis of red palaeosols provides new insight into the palaeoclimatic and palaeoenvironmental reconstruct and tectonic movement of yp

ring structures made by shore ice in a muddy tidal flat st lawrence estuary canada abstract large size ring sedimentary structures occurring in a muddy tidal flat on the south shore of the st lawrence estuary are reported for the first time they range from 15 to 50 m in diameter and occur as isolated features or in groups of 3 to 5 in plan they form well defined circles scattered throughout the higher mud flat some structures are characterized by an inner ring and by a chaotic surface of alternating micro ridges and depressions the outer surrounding mud ridge is a few decimeters high and wide 25 60 cm ring structures occur at the emplacement of icefoot pustules and are related to vertical pressures exerted on the substrate by ice blocks moved up and down by tide motion icefoot pustules form every winter but not necessarily at the same location it is likely that the related ring structures can be fossilized and preserved in the sedimentary sequence consequently they can be of assistance in palaeoenvironmental interpretation

clay mineralogy and geochemistry and their palaeoclimatic interpretation of the pleistocene deposits in the xuancheng section southern china a red soil profile in xuancheng anhui province southern china in the middle to lower reaches of the yangtze river was investigated using x ray diffraction x ray fluorescence spec trometer and scanning electron microscopy the mobile components k2o and na2o and trace elements ba and sr of the xuancheng section exhibit a general trend of decrease downward along the red soil profile together with an increase downward of chemical index of alteration cia values suggesting more intense depletion in the lower portion than in the upper portion the major components sio2 a l 2o3 and fe2o3 as well as sio2 al2o3 sio2 fe2o3 and al2o3 fe2o3 ratios show notable fluctuations along the soil profile indicating intense climatic oscillations in the area during the pleistocene age the clay mineral assemblage of the xuancheng section can be generally subdivided into three groups suggesting a general trend of three stages of climate changes the lower portion of 10 4 6 3 m depth has a lower illite content and higher abundance of kaolinite and illite smectite i s clays indicating that a warm and wet climate prevailed over the episode of ca 600 350 ka bp a decrease in abundance of kaolinite and i s clays and increase in illite content at a depth of 6 3 2 2 m probably indicate a transition stage of climate change from warm humid to cool dry in the period ca 350 80 ka bp the higher illite content and lower abundance of kaolinite and i s clays in the upper portion of 2 2 0 m depth suggest that a relatively cool and dry climate dominated since ca 80 ka bp based on changes in clay mineralogy and chemical indices of the sediments seven warm cold fluctuations were determined in the area since the middle pleistocene climate changes documented in the xuancheng section are in agreement with the d 18 o records of sediments from the equatorial pacific core v28 238 and the loess palaeosol sequences in the loess plateau of northwestern china correlated to the episode of s4 and s5 soil units in the loess plateau the period of ca 600 350 ka bp in the xuancheng area was dominated by the particularly strong east asia summer monsoon as indicated by its most abundant kaolinite and i s clays fluctuations in clay mineralogy along the xuancheng soil profile were mainly controlled by both the east asia summer and winter monsoons in response to the global changes in the middle late pleistocene copyright 2009 john wiley sons ltd

sediment sources and east asian monsoon intensity over the last 450 ky mineralogical and geochemical investigations on south china sea sediments a coupled approach based on clay mineral assemblages and isotopic data sr and nd of sediment from ocean drilling program odp site 1145 has been used to trace the sources of sediment feeding the northern part of the south china sea and to investigate the evolution of east asian monsoon intensity over the last 450 ky clay mineral assemblages are dominated by illite and smectite with lesser abundance of chlorite and kaolinite 87 sr 86 sr and end 0 isotopic data combined with the smectite illite chlorite ratio indicate that the pearl river is the main contributor for detrital material to the northern margin of the scs with variable continental input of volcanic material derived from the erosion of the luzon arc these inputs follow the low latitude solar insolation with a 23 ky periodicity as recorded by a periodic change of the clay mineralogy for the first time this study presents a scs deep sea sediment high resolution record of climatic changes in the last 450 ky showing that smectite illite chlorite variations are mainly related to changes in the east asian summer monsoon intensity because the mineralogical record is independent of other external forcing phenomena such as global glacial interglacial oscillations the smectite illite chlorite ratio has been used here as a proxy to reconstruct past changes of the south east asian summer monsoon intensity d 2005 elsevier b v all rights reserved

sedimentology of an ice contact glaciomarine fan complex nastapoka hills eastern hudson bay northern quebec abstract emerged holocene coalescing glaciomarine fans are exposed along the nastapoka hills eastern hudson bay the fans form part of a regional stratified drift belt associated with terrestrial and submarine frontal moraines and other grounding lines deposits these thick extensive and in many cases coalescent sediment bodies were deposited during a stillstand of the quebec labrador sector qls of the laurentide ice sheet lis that pinned on the hills during eastward retreat from hudson bay the fans are composed of basal interbedded and interlaminated sand silt and silty clay facies association i fa i deposited by suspension settling from overflow plumes sediment gravity flows and ice rafting towards the ice contact zone fa i interfingers with diamict layers fa ii deposited by gravity flows and ice rafting these two sedimentary units are overlain by interbedded sand and gravel fa iii formed by reworking during subsequent emergence parts of fa i and fa ii were remobilized by submarine gravity flows which prevailed long after ice retreat the sedimentology of the nastapoka hills provides information on the processes operating near the grounding line of a temperate ice sheet reaching tidewater

geochemical evidence for provenance diversity of loess in southern china and its implications for glacial aridification of the northern subtropical region abstract the thick xiashu loess in southern china is distributed not only in the yangtze river valley but also and most extensively in the region between the qinling mountains and the lower reaches of the yangtze river however there are few studies of the provenance and climatic implications of the xiashu loess in this latter region here we present the results of a provenance study of last glacial loess samples from twenty two typical xiashu loess sections using the major and trace element composition as a provenance indicator seventeen of the sites are located to the north of the yangtze river and our primary aim was to determine the provenance of the xiashu loess within this region our results indicate that the alluvial plain located mainly in the present drainage area of the huai river was the primary dust source for the xiashu loess in this region the occurrence of multiple local dust sources within this alluvial plain suggested by their geochemical heterogeneity indicates that the alluvial plain experienced intensified aridity which caused it to become a dust source for local loess deposits in northern subtropical china during the last glacial our study provides strong evidence to challenge the long held view that the occurrence of xiashu loess resulted from the southward incursion of the clp loess deposits sourced from deserts of the asian interior and it confirms the substantial role of aridification of the present humid northern subtropical region for dust emission to the climate system during the last glacial

stable hydrogen and oxygen isotopes in mineral bound water and the indication for chemical weathering intensity abstract chemical weathering plays a key role in the long term climate change and global biogeochemical cycle in this study a 5 1 m long basalt developed weathering profile from hunan province china was selected for the analyses of major elements grain size ph total organic carbon thermogravimetric tg and differential thermogravimetric properties dtg as well as stable isotopes d and 18 o in mineral bound waters the major purpose is to distinguish different types of mineral bound water and to verify whether hydrogen and oxygen isotopes of mineral bound water can indicate chemical weathering intensity based on the tg and dtg results different types of mineral bound water were extracted by a sequential heating extraction technique 40 120 c 120 300 c 300 600 c and 600 900 c the mineral bound water lost below 120 c is absorbed water a mixture of interlayer and crystal waters occurs at 120 300 c and above 300 c is mostly constitution water hydrogen and oxygen isotopic ratios at top 2 m are subject to the influences of eolian and pedogenic processes the absorbed water has been exchanged and reached isotopic equilibrium with ambient soil water while the crystal water and interlayer water cannot be separated by heating method in this study hydrogen and oxygen isotopes of constitution water can indicate chemical weathering showing positive relationships with weathering intensity although the mechanism for their indication to chemical weathering remains further investigation we suggest that the isotopic fractionation between the formation of clay minerals and surface water should be taken into account this research sheds new light on mineral bound water phase and a potential proxy for tracing the process of chemical weathering

sedimentary structures made by shore ice in muddy tidal flat deposits st lawrence estuary quebec abstract well preserved sedimentary structures formed by shore ice are exposed in emergent muddy tidal flat deposits along the shoreline of the st lawrence estuary the sedimentary features are exposed in high marsh micro cliffs 1 to 2 m high features from two localities where they are the most abundant sainte anne de beaupre north shore and montmagny south shore are reported here two categories are distinguished first bowl shaped circular and elongated structures 30 to 100 cm across which are former scoured depressions subsequently filled by stratified mud fine sand and organic debris and second deformations folds a few decimeters to a few meters in size produced by ice block pressure pebble to boulder size dropstones are associated with these structures most features were observed in mud flat and low marsh units facies vertically exposed at these localities the age of these tidalite deposits ranges from about 200 to 600 years these ice made structures and deformations well preserved in a sequence of recent emerged tidal sediments suggest that similar features may be preserved in older rock formations consequently they can be considered as a promising tool for interpreting the former climatic conditions in which tidalites and other shallow marine and lacustrine formations may have been deposited

petrological and geochemical differentiation of lateritic iron crust profiles abstract lateritic iron crust profiles developed from metabasic rocks in west africa burkina faso were studied from a petrographical and geochemical point of view at the base of profiles a thick gray purple kaolinitic horizon occurs with frequent macroscopic preservation of original pre existing structures in such an horizon chemical balances clearly show that part of kaolinite crystals could be explained by an absolute accumulation from circulating solutions higher up in the profiles fe accumulation leads to two main facies purplered hematitic spots and nodules and yellow kaolinitic and goethitic spots mottled clay horizon hematite and goethite distribution in that horizon is regulated by water activity in microenvironments hematitic nodules form as kaolinite crystals are completely dissolved in goethitic spots fe accumulation is much less abundant and the first generation of well crystallized kaolinite is replaced by a poorly crystallized and smaller kaolinite crystals showing a greater substitution of al 3 for fe 3 in the upper part of profiles all the kaolinite is gradually dissolved and the maximum of ferruginous concretion formation leads to a hard and nodular iron crust

transparent heavy minerals and magnetite geochemical composition of the yangtze river sediments implication for provenance evolution of the yangtze delta abstract heavy mineral and detrital magnetite geochemistry were analyzed to extract sediment provenance indexes from different reaches of the modern yangtze river which were used to trace sediment source of the yangtze delta and to speculate its geomorphology change since the pliocene our results show that diagnostic heavy minerals of the upper yangtze sediment are characterized by clinopyroxene 12 on average and magnetite 7 on average the middle reaches by ilmenite zircon and tourmaline and the local small rivers by fluorite detrital magnetite composition of ti mg v and cr is high in the upper yangtze from the underlying basalt these diagnostic indexes are then used in the pliocene sediment core to extract provenance signal of different yangtze reaches analysis of core sediment of the yangtze delta reveals that sediment provenance of the pliocene was from local small rivers since the beginning of the pleistocene core sediments provenance was similar to that of the middle yangtze tributaries after 1 2 ma high content of pyroxene and magnetite grains that are rich in ti mg v cr imply sediment provenance signals from the upper yangtze sediment provenance shift from short distance sources to more distant sources indicates that the geomorphology of the yangtze delta region has undergone a great transformation since the pliocene this dramatic landform change is likely in response to continuous uplift of the tibetan plateau and accelerated subsidence of the east china coast since the pliocene

three component mixed layer illite smectite kaolinite i s k minerals in hydromorphic soils south china to understand clay mineral transformations in hydromorphic conditions in the red earth sediments in xuancheng south china clay mineralogy was investigated using x ray diffraction xrd and high resolution transmission electron microscopy hrtem the xrd results indicated that clay minerals in the hydromorphic soils were illite kaolinite smectite vermiculite and mixed layer illite smectite and illite smectite kaolinite changes of the kaolinitic reflections under the various conditions suggested that the kaolinitic phase is a mixed layer structure having kaolinite layers randomly interstratified with illite and smectite layers hrtem observation showed that 10 a illite layers interstratified with both 15 a smectite layers and 7 a kaolinite layers in clay particles confirming the occurrence of illite smectite kaolinite i s k three component mixed layer clays the lattice fringes of the i s k clays appeared corrugated and vanishing and also exhibited variable thickness along a lattice fringe which were consistent with changes from illite to smectite from smectite to kaolinite and from illite to kaolinite respectively hydromorphic conditions in the xuancheng soils led simultaneously to the direct transformation of illite to kaolinite and the transformation of illite to smectite to kaolinite in the pedogenic processes and the formation of i s k three component mixed layer clays as intermediate products of these processes

regional distribution of the quaternary red clay with aeolian dust characteristics in subtropical china and its paleoclimatic implications abstract grain size and geochemical characteristics of 18 quaternary red clay qrc profiles mainly located in the lower and middle reaches of the yangtze river in subtropical china were studied the results showed that all the qrc profiles can be classified into three types type a mainly distributed between 29 n and 31 n share the similar characteristics with the xiashu loess with the uniformity of grain size and elemental compositions and the enrichment of the basic dust fraction 10 m 63 m which may originate from aeolian dust deposits and is hence called a loess like qrc type b mainly distributed between 25 n and 28 n shows alluvial features with many coarse grains and large scale vertical variation of grain size and chemical compositions type ab distributed between type a and type b approximately 28 n 29 n shows double unit structure the upper part is similar to type a the lower however shows alluvial features like type b the loess like qrc is mainly distributed along the yangtze river but gradually declines southwards and is rarely seen south of 28 n the existence of the loess like qrc is strong evidence for the occurrence of heavy dustfalls in the modern red soil areas in subtropical china during the quaternary glacial periods the region distributed with the loess like qrc is at least 3 latitude south of the xiashu loess implying that the loess red clay boundary in the yangtze valley had once oscillated with the alternations between glacial and interglacial climates during the quaternary period the loess like qrc actually includes both glacial and interglacial paleoclimatic information we suggest that the yellow brown earth ybe in the upper qrc was formed during the last glacial period the underlying red clay with the aeolian dust characteristics but being strongly weathered was initially deposited during the second last glacial or earlier glacial stages but heavily weathered and rubefied in the subsequent interglacial events no multi cyclical paleoclimatic records were found in the qrc profiles due to the overlapped information but the weathering degree of the profiles clearly show a trend of decreasing upwards which suggests that the climate in the yangtze valley has become colder and drier since the late quaternary period

geochemical evidence for the provenance of middle pleistocene loess deposits in southern china the provenance of middle pleistocene loess in the middle and lower reaches of the yangtze river the most intensively investigated loess deposits outside the loess plateau region in china remains controversial identification of the provenance will provide crucial insight into the environmental implications of this valuable sedimentary archive and into the potential role of the east asian winter monsoon in transporting the dust from deserts in the asian interior in this study geochemistry was used to compare the provenance of loess in the lower reaches of the yangtze river in southern china with that inferred for loess deposits on the loess plateau in northern china compared with samples from the loess plateau the 20 mm fraction in the loess deposits of southern china has higher tio2 al2o3 zr nb zr al zr ti zr hf y al and lan smn ratios and lower eu eu th nb y nb and al nb ratios the clear distinction in immobile element ratios between samples from the two regions indicates that the loess deposits in the two regions have different provenances the inferred difference in source area is also supported by variations in the major element composition of bulk samples obtained in this study and collected from published data these lines of evidence indicate that the deserts in the asian interior are not the primary provenance for the southern loess it is suggested that the adjacent floodplains to the north of yangtze river are the dominant dust sources and the occurrence of sustained loess deposits in the lower reaches of the yangtze river currently an area of northern subtropical climate is an indication of local aridification and strengthened winter monsoon activity during glacial periods as a regional response to the middle pleistocene climate transition around 0 8 ma the role of the east asian winter monsoon in transporting the dust from northern deserts to southern china has been overestimated in previous studies

provenance of lithogenic surface sediments and pathways of riverine suspended matter in the eastern mediterranean sea evidence from 143nd 144nd and 87sr 86sr ratios in order to characterize the provenance of lithogenic surface sediments from the eastern mediterranean sea ems residual leached fraction of 34 surface samples have been analysed for their 143 nd 144 nd and 87 sr 86 sr isotope ratios the sample locations bracket all important entrances of riverine suspended matter into the ems as well as all sub basins of the ems the combined analyses of these two isotope ratios provide a precise characterization of the lithogenic fraction of surface sediments and record their dilution towards the central sub basins we reconstruct provenance and possible pathways of riverine dispersal and current redistribution assuming more or less homogenous isotopic signatures and flux rates of the eolian fraction over the ems lithogenic sediments entering the ionian sea from the calabrian arc and the adriatic sea are characterized by high 87 sr 86 sr isotope ratios and low end 0 values average 87 sr 86 sr 0 718005 and end 0 11 06 n 5 aegean sea terrigenous sediments show an average ratio of 87 sr 86 sr 0 713089 n 5 and values of end 0 7 89 n 5 the aegean isotopic signature is traceable up to the southwest south and southeast of crete the sediment loads entering the ems via the aegean sea are low and spread out mainly through the strait of casos east of crete surface sediments from the eastern levantine basin are marked by the highest end 0 values 3 3 n 6 and lowest 87 sr 86 sr isotope ratios average 0 709541 n 6 reflecting the predominant input of the nile sediment the influence of the nile sediment is traceable up to the ne trending eastern flank of the mediterranean ridge the characterization of the modern riverine dispersal and eolian flux based on isotope data may serve as a tool to reconstruct climate coupled variations of lithogenic sediment input into the ems d 2002 elsevier science b v all rights reserved

geochemical constraints on provenance of the mid pleistocene red earth sediments in subtropical china abstract the source of mid pleistocene red earth sediments in the middle to lower reaches of the yangtze changjiang river was investigated based on their geochemical characteristics the xuancheng and jiujiang red earth sediments have similar major and trace element distribution patterns compared to the loess and paleosol deposits of the chinese loess plateau the upper continental crust ucc and the post archean australian average shale paas the sediments display notable depletion of cao mgo na2o and accumulation of tio2 al2o3 and fe2o3 t the trace element distribution patterns of the red earth sediments are also different from those of loess and the paas but are similar to those of the loess deposits except for lower values of mobile trace elements sr ba and ni and higher values of zr and y the red earth samples have uniform la th ratios of 2 8 compatible with those of the ucc loess and paleosol they also have similar chondrite normalized ree patterns characterized by enriched lree and relatively flat hree profiles and consistent negative eu anomalies similar to those of the ucc the loess and paleosol and the yangtze deposits these results suggest that the red earth sediments have been subject to considerable mixing prior to deposition and strong subsequent chemical weathering the sediments have very uniform 143nd 144nd and 147sm 144nd ratios this points to well mixed and multi recycled sediments the 143nd 144nd and 87sr 86sr values of the red earth sediments match well with those of the deposits in the middle to lower reaches of the yangtze river but are different from those of the loess and paleosols this suggests that the red earth sediments are derived from the drainage basins of the middle to lower yangtze river and might have experienced more intense chemical weathering relative to the yangtze deposits as reflected by their higher rb sr ratios intense depletion of mobile elements and accumulation of immobile elements as well as their well developed net like structure

global changes during carboniferous permian glaciation of gondwana linking polar and equatorial climate evolution by geochemical proxies the most prevalent phanerozoic glaciation occurred during the carboniferous permian on the southern hemisphere gondwana supercontinent sediments from the pennsylvanian dwyka group deposited in the karoo basin of south africa provide a complete record of glaciation and deglaciation phases the direct correlation of glaciation events in southern gondwana basins with the well studied climate evolution of equatorial regions was previously hampered by lack of precise radiometric dating as dating has now become available for the karoo basin the gondwana glaciation can be viewed in a global paleoclimatic framework with high temporal resolution element geochemical proxies cia chemical index of alteration zr ti rb k v cr record three confined shifts in climate and paleoenvironment of the karoo basin these shifts were induced by changes in sea level weathering rate provenance and redox conditions because of the low availability and diagenetic overprint of carbonates ocean and atmosphere pco 2 variations had to be reconstructed from 1 3 c o r g values of marine organic matter the 1 3 c o r g signatures are affected by variable proportions of marine versus terrestrially derived organic matter and its state of preservation organic geochemical investigations toc total organic carbon c n lipid biomarkers indicate the organic matter in the central karoo basin was primarily of algal origin in agreement with element proxies the varying 1 3 c o r g values mirror shifts in pco 2 rather than variations of organic matter type a covariation trend between carbon isotope signatures of equatorial carbonates and 1 3 c o r g values from the karoo basin argues against local forcing factors and instead implies a global climate control mechanism the 5 7 m y duration of a complete glacial cycle is not in tune with any known orbital frequency processes such as changes in equator pole temperature gradients or newly developing atmosphere ocean circulation pathways can be regarded as controlling factors

geochemistry of sediments from the huaibei plain east china implications for provenance weathering and invasion of the yellow river into the huaihe river abstract the sediments of the huaibei plain in semi humid mid eastern china represent valuable geological records with respect to eolian fluvial interactions depositional environments and climate change in this region provenance and weathering conditions are often reconstructed using sedimentary geochemistry methods in this study an 8 m core from huainan and a set of loess samples from northern and southern china were analyzed for major trace and rare earth elements rees results were compared to determine the samples provenance the major trace rare earth elements contents and grain size distribution were found to fluctuate widely in the 2 8 m section of the huainan core and more narrowly closer to the surface 0 2 m this suggests a provenance shift at a depth of 2 m the tio 2 al 2 o 3 sio 2 al 2 o 3 th nb la nb values and ree patterns in the upper core 0 2 m are similar to those found in samples from the chinese loess plateau clp these results suggest that the clp in northern china is likely to be the primary origin of the upper part 0 2 m of the huainan core compared with clp samples the upper part of the huainan core exhibits lower k 2 o al 2 o 3 values and higher chemical alteration indices this is indicative of the material s substantial weathering during transportation and re deposition and implies that these sediments could reasonably be classified as typical recycled loess the sediments may have been transported from the clp to huainan as yellow river flood events probably during the last deglaciation 13 2 ka as a result of increased precipitation along with glacier and snow melt in the upper reaches of the yellow river catchment during this period this suggests that the yellow river may have migrated into the huaihe river catchment much earlier than the earliest historical records 361 bce suggest the implications of this would be profound with respect to chinese history

weathering and alteration of volcanic ashes in various depositional settings during the permian triassic transition in south china mineralogical elemental and isotopic approaches to better understand the alteration of volcanic ash in different depositional environments we measured the clay mineralogy major and trace element geochemistry and sr and nd isotopic composition of altered ashes in two permian triassic boundary ptb successions in southern china the pengda and xinmin sections in guizhou province represent different depositional settings allowing us to investigate the role of the early burial environment on authigenic clay formation the ptb ash beds in both sections consist predominantly of mixed layer illite smectite clays altered ashes in the relatively shallow pengda section contain predominantly r2 and r3 i s clays with 70 to 85 illite layers whereas their stratigraphic equivalents in the deeper xinmin section contain only r3 i s clays which are of two types with 88 and 99 illite layers respectively the two studied ash beds can be stratigraphically correlated between the pengda and xinmin sections and show similar 143nd 144nd ratios 0 511991 for pd 1 and 0 511983 for xm 1 0 512073 for pd 2 and 0 512074 for xm 2 ree distributions and immobile element cross plots are consistent in suggesting that the altered ashes may have originated via felsic volcanism altered ashes in the deep sea xinmin section have notably high 87sr 86sr ratios 0 764209 and 0 795921 relative to those from equivalent horizons in shallower environments 0 728455 and 0 749953 this difference in 87sr 86sr ratios is likely attributable to different degrees of chemical weathering elemental ratios such as sio2 al2o3 k2o al2o3 y sr and zr sr all support more intensive chemical leaching in deep water environments the altered ashes at xinmin contain substantially more k2o than those at pengda suggesting greater incorporation of k into clay minerals due to lower ph during early diagenesis clay mineral assemblages and stacking structures of i s clays in the altered ashes are consistent with a general sequence of smectite illitization during diagenesis and burial metamorphism in both sections

high resolution luminescence chronology for xiashu loess deposits of southeastern china abstract loess deposits in xiashu are representative of such deposits in southeastern china that are mainly distributed in the middle and lower reaches of the yangtze river valley these loess paleosol sequences provide a key archive of past climate change in humid subtropical regions however the ages of the sequences are not well constrained in this study the standard quartz single aliquot regenerative sar dose optically stimulated luminescence osl and k feldspar post infrared infrared stimulated luminescence post ir irsl pirir290 methods are used to date two loess sequences in nanjing region our results show that quartz sar osl and k feldspar pirir290 ages are more or less indistinguishable from one another up to 50 ka beyond this age the k feldspar pirir ages increased systematically with deposition depth agreeing well with the expected ages as far as 200 ka on the basis of a fully independently dated timescale we are therefore able to propose for the first time a new age model for the xiashu loess deposits accumulated since the penultimate interglacial period using our newly obtained luminescence dating ages we observe a marked difference between the loess accumulation rates in the two sequences potentially forced by regional depositional processes and loess preservation