characterization of high molecular weight organic matter in marls of the salt iv formation of the mulhouse basin high molecular weight organic matter of six marl samples of the mulhouse basin has been characterized the kerogen asphaltene and polar fractions were analysed by flash pyrolysis gc ms in addition sulphur rich geomacromolecules present in the polar fractions were also desulphurized with raney ni and the released hydrocarbons were characterized by gc ms the kerogen and asphaltene pyrolysates are dominated by linear and isoprenoid alkanes and alkenes most likely derived from aliphatic biopolymers of algae algaenans and contain moderate to low amounts of alkylated thiophenes marls deposited under hypersaline conditions contain more organically bound sulphur and less isoprenoid algaenans in their kerogen asphaltene fractions than marls deposited under less saline conditions high contributions of terrestrial organic matter are not revealed by abundant alkyl phenols in the pyrolysates desulphurization of sulphur rich geomacromolecules present in the polar fractions yields hydrocarbons with distributions different from those of the free saturated hydrocarbons but the amounts released are low relative to the hydrocarbons present as such

east asian monsoon variations during oxygen isotope stage 5 evidence from the northwestern margin of the chinese loess plateau abstract we present the results of high resolution multi proxy climate studies of the s1 palaeosol corresponding to oxygen isotope stage ois 5 from the northwestern margin of the chinese loess plateau area here s1 is much thicker ca 6 8 m than in the central loess plateau areas ca 2 m where most previous studies have been conducted hence much higher resolution stratigraphic studies are possible yielding more insight into the temporal variations of the east asian monsoon during mis 5 the frequency dependent magnetic susceptibility as well as the concentration of secondary carbonate is used as an indicator of the summer monsoon intensity and the median particle size as an indicator of the winter monsoon intensity the results suggest that the northwestern margin of the chinese loess plateau experienced the strongest summer monsoon intensity in sub stage oiss 5e and the weakest in oiss 5a among the three warmer periods during stage 5 the summer monsoon was weaker in oiss 5b than in oiss 5d a dusty interval interrupted the second warmer period 5c and a soil forming event interrupted the first colder period 5d the results also suggest that the directions of changes in the intensities of summer and winter monsoons may not always have been proportionately opposite for example the weakest summer monsoon occurred in oiss 5a during which the winter monsoon was not the strongest we further conclude that the winter monsoon during the last interglacial was probably driven by global ice volume fluctuations while the summer monsoon was primarily controlled by the northern hemisphere solar insolation and was probably modified by a feedback mechanism that is the climatic buffering effect of low latitudinal oceans may have distorted the response of the summer monsoon to insolation variations finally our results do not show the degree of climatic instability comparable to that recorded in the grip ice core for the last interglacial oiss 5e even though the study area is situated in a region which has been sensitive to climatic changes

early silurian telychian bryozoan reefs in the epeiric sea of south china are heterotrophic metazoan buildups promoted by internal waves abstract after the mass extinction at the end of the ordovician period metazoan reefs recovered and became widespread on the yangtze carbonate platform by the late aeronian as recorded by a diverse and complex reef system in the shihniulan formation in the overlying siliciclastic dominated hanchiatien formation the reefs declined in size and biodiversity along with a sudden facies change during the lower telychian without any phototrophic organisms small reefs were primarily built by abundant bryozoans which crop out in the lower part of this formation at the southern tip of chongqing southwest china these reefs occur as massive argillaceous limestones varying in size from 1 6 to 2 8 m in thickness and 6 to 16 m in diameter the reefs are surrounded by gray green shales and silty shales distinct vertical ecozonation is present and four growth stages have been recognized represented by four facies types from bottom to top 1 auloporid coral echinoderm bryozoan packstone floatstone 2 fenestrate bryozoan echinoderm bafflestone 3 fistulipora asperopora framestone and 4 fistulipora framestone in tropical mid to outer ramp settings these bryozoan reefs showcase an unusual reef community in heterozoan carbonates which were probably influenced by internal waves

stepwise expansions of c4 biomass and enhanced seasonal precipitation and regional aridity during the quaternary on the southern chinese loess plateau abstract the expansion of c 4 plants is one of the most prominent vegetation changes in the global ecosystem during the cenozoic era although c 4 plant expansions in the latest miocene have been widely reported factors driving the expansions are still in debate and the details of vegetation changes during the quaternary have not been well studied here we present high resolution carbon isotope time series of both organic matter and bulk carbonates covering the past 2 58 ma derived from the loess soil successions on the southern chinese loess plateau the organic matter 13 c values indicate stepwise c 4 plant expansions initiated at 1 6 and at 0 43 ma respectively we conclude that such tectonic time scale c 4 plant expansions are controlled by enhanced seasonality of precipitation relatively more precipitation in the warm growing season as well as regional aridity and this long term fluctuation superimposes on the orbital scale variations of c 4 plants while the latter appears phase locked with cyclical changes of summer monsoon circulations

δ13c values of loess total carbonate a sensitive proxy for asian summer monsoon in arid northwestern margin of the chinese loess plateau abstract we measured carbon isotope ratio of loess total carbonates 13 cic from the jingyuan loess profile in the arid northwestern portion of the chinese loess plateau clp in order to examine the effectiveness and sensitivity of loess total carbonate 13 cic values as a potential paleoenvironmental indicator the 13 cic record in the loess profile shows large variations ranging from 1 to 7 during the past 70 ka the most negative 13 cic peaks coincide with paleosol formation s 0 l 1 ss 1 and l 1 ss 2 which occurred under relatively wetter climatic conditions during middle holocene and marine 18 o stages 3 on the other hand the least negative 13 cic values responded to loess accumulation during relative drier phases of lgm and marine 18 o stages 4 while 13 cic variations in the loess profile in arid area demonstrate a clear correlation with changes of total organic carbon isotope 13 coc of bulk sediments which has been widely used as a proxy for the past monsoon precipitation intensity the 13 cic values in the loess profile are more sensitive to the changes of paleohabitat controlled by the asian monsoon variation in the arid area we propose that carbon isotope compositions of total carbonates in loess profile can serve as a sensitive and reliable proxy for the asian summer monsoon in the arid northwestern chinese loess plateau

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

hydrocarbon biomarkers of different lithofacies of the salt iv formation of the mulhouse basin france forty nine samples from an 11 m section of the salt iv formation of the tertiary mulhouse basin alsace france covering six different lithotypes marl nodular lenticular laminated and massive anhydrite halite were analysed for hydrocarbon biomarkers the hydrocarbon biomarker assemblages are dominated by acyclic isoprenoids especially phytane 0 13 pr ph 0 52 n alkanes with specific distribution patterns and steranes large differences in their distributions indicate significant changes in the palaeoenvironment the largest changes observed are those in the desmethyl and methylsterane distributions and are probably linked to an occasional reconnection of the evaporite basin with the sea leading to an input of dinoflagellate algae 3 methylsteranes are present in all samples studied and their carbon number distribution mimics that of the 5 desmethylsteranes in line with previous suggestions that they are diagenetic products of sterols with a sugar unit at c 3 biosynthesized from dietary sterols the increase in relative abundance of the 3 methylsteranes during periods of marine incursions suggests that these precursors are biosynthesized by marine organisms variations in biomarker composition between the different lithofacies are minor probably because the organic matter is mainly associated with the marl and all lithotypes contain a marl component detailed subsampling of two marl layers and subsequent analysis indicated that the changes on a small time scale are minor to those on a larger time scale

proxy of monsoon seasonality in carbon isotopes from paleosols of the southern chinese loess plateau soil organic matter som and soil carbonate sc are common constituents in soils and are directly related to plant growth som accumulates gradually from the decomposition of plant material over time whereas sc formation is biased to dry season soil dissolved co 2 that derives from plant respiration during a drying phase of the growing season in some mixed c 3 c 4 environments the peak of c 3 and c 4 plant metabolism differs seasonally and the carbon source that contributes to the som and sc can be different consequently 13 som values reflect an annual average of the floral biomass but 13 sc values reflect a seasonal aspect of the plant community the relationship between 13 c sc and 13 c som is mainly controlled by how different the seasonal conditions are our results suggest that the relationship is a seasonal proxy that can be used to differentiate the seasonality effects of indian east asian and siberian monsoons on the chinese loess plateau during the last interglacial glacial cycle

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

paleosol stable isotope evidence for early hominid occupation of east asian temperate environments hominids left africa and occupied mainland asia by 1 8 myr ago about 1 15 myr agohomo erectusand an associatedstegodon ailuropodafauna migrated from subtropical china across the qinling mountains into the temperate loess plateau this migration may be an evolutionary milestone in human adaptability because it may represent the first occupation of a nontropical environment loess paleosol stable isotope ratios from the last interglacial glacial cycle provide comparative data for reconstructing the hominid paleoenvironments the climate during gongwangling hominid occupation about 1 15 myr ago was influenced by both siberian mongolian winter and indian summer monsoon systems characterized as a cold cool dry winter and warm mild semihumid summer and fall the gongwangling hominids preyed mainly on warm climate adapted animals such asstegodon ailuropodafauna suggesting a warm season occupation the stable isotope ratios also indicate that the chenjiawo hominids occupied an environment similar to that of the gongwangling about 650 000 yr ago the associated fauna with a mixture of forest and steppe warm and cold cool climate adapted animal assemblage s suggests a permanent occupation by this time thus the reliable earliest and permanent occupation of temperate environments may have occurred 150 000 yr earlier in eastern asia rather than in europe

molecular isotopic characterisation of hydrocarbon biomarkers in palaeocene eocene evaporitic lacustrine source rocks from the jianghan basin china immature organic matter in lacustrine source rocks from the jianghan basin eastern china was studied for distributions and stable carbon isotopic compositions 13 c of hydrocarbon biomarkers all of the bitumens contain isorenieratane 13 c ca 17 indicating the presence of chlorobiaceae and thus periods of euxinic conditions extended into the photic zone aliphatic hydrocarbon fractions are dominated by pristane and phytane and contain relatively low amounts of 4a and 4 methylsteranes c 30 13 c ca 16 believed to originate from 4 methylsterols in dinoflagellates 13 c values of gammacerane ca 24 and c 30 17 21 h hopane ca 23 are consistent with an origin from bacterivorous ciliates that fed on chlorobiaceae the bitumens contain low relative amounts of organo sulphur compounds one rock contains c 37 and c 38 n alkanes 13 c ca 36 derived from alkadienes and alkenones of prymnesiophytes the distributions of hydrocarbon biomarkers suggest that they were initially sulphurised during early diagenesis and later released during early thermal maturation

predominance of archaea derived hydrocarbons in an early triassic microbialite abstract we investigated the distribution of lipids in lower triassic sedimentary rocks 252 247 myr from south china including a shallow water microbialite in the uppermost section of the outcrop archaeal derived hydrocarbons were the major constituents of the microbialite from the latest early triassic among these we detected i abundant c 40 acyclic and monocyclic biphytanes possibly derived from glycerol dialkyl glycerol tetraether lipids and their degradation products c 30 39 pseudohomologues and ii a c 25 head to tail linked regular isoprenoid hydrocarbon possibly derived from dialkyl glycerol diether lipids dgds and its degradation products c 21 24 pseudohomologues and abundant pristane and phytane through combination of compound specific stable carbon isotope analysis of isoprenoid hydrocarbons which had average 13 c values of 35 to 30 and their molecular distribution it was not possible to unambiguously define the archaeal source for the biphytanes in the microbialite the 13 c values for pristane and phytane were similar to those for head to tail linked c 21 25 isoprenoids potential source organisms for these compounds were halophilic archaea except for methane seep microbialites no other ancient or recent phototrophic microbialites have been reported to contain predominantly archaeal isoprenoid hydrocarbons our findings suggest the presence of a new type of microbialite

winter spring precipitation as the principal control on predominance of c3 plants in central asia over the past 1 77 myr evidence from δ13c of loess organic matter in tajikistan abstract although changes in atmospheric co2 levels are thought to be the major factor driving long term c3 c4 vegetation evolution recent studies tend to emphasize the effect of regional climate conditions on c3 c4 variations the middle latitudes 30 45 in which c3 c4 plants are highly sensitive to environmental changes provide an optimal basis for the investigation of the relative impacts of climate and pco2 on shifts in c3 c4 cover in order to assess the factors controlling these shifts as well as the complex interactions between environmental factors the carbon isotopic composition of bulk organic matter from the chashmanigar loess section southern tajikistan was measured for the past 1 77 myr in general the 13c record shows mostly negative values throughout the sequence almost all 13c values falling between 23 and 26 indicating a predominance of c3 plants in central asia over this time period despite the presence of numerous glacial interglacial cycles from 0 85 myr to the present the 13c values become increasingly positive reflecting a growing c4 signal however this c4 component is not detectable prior to 0 25 myr after which minor peaks are evident at 228 171 and 18 kyr the 13c record from chashmanigar indicates that winter spring precipitation i e mediterranean climatic conditions have characterized central asia throughout the past 1 77 myr leading to the predominance of c3 vegetation in the context of glacial interglacial scale changes in atmospheric co2 therefore it is climate rather than pco2 that controls c3 c4 variations in asia s middle latitudes the gradual increase in the c4 component since 0 85 myr especially the notable peaks after 0 25 myr may have been caused by an increase in summer precipitation due to an enhanced southward shift of the climate zones

impact of dia and catagenesis on sulphur and oxygen sequestration of biomarkers as revealed by artificial maturation of an immature sedimentary rock hydrous pyrolysis of an immature ro 0 25 sulphur rich marl from the gessoso solfifera formation messinian in the vena del gesso basin was carried out at 160 c t 330 c for 72 h to study the effect of progressive diagenesis and early catagenesis on the abundance and distribution of sulphur containing and sulphur and oxygen linked carbon skeletons in low molecular weight and high molecular weight fractions e g kerogen to this end compounds in the saturated hydrocarbon fraction monoaromatic hydrocarbon fraction polyaromatic hydrocarbon fraction alkylsulphide fraction and ketone fraction were quantified as well as compounds released after desulphurisation of the polar fraction and hilialh4 treatment of the desulphurised polar fraction sulphur bound phytane and 20r 5 14 17 h and 20r 5 14 17 h c27 c29 steranes in the polar fraction become less abundant with increasing maturation temperature whereas the amount of their corresponding hydrocarbons increases in the saturated hydrocarbon fraction carbon skeletons that are bound in the kerogen by multiple bonds e g c38n alkane and isorenieratane are first released into the polar fraction and then as free hydrocarbons these changes occur at relatively low levels of thermal maturity ro 0 6 as evidenced by the immature values of biomarker maturity parameters such as the c35 hopane ratio and the 22s 22s 22r 17 21 h c35 hopane ratio sulphur and oxygen bound moieties present in the polar fraction are not stable with increasing thermal maturation however alkylthiophenes ketones 1 2 di n alkylbenzenes and free n alkanes seem to be stable thermal degradation products of these sulphur and oxygen bound moieties thus apart from free n alkanes which are abundantly present in more mature sedimentary rocks and crude oils alkylthiophenes 1 2 di n alkylbenzenes and ketones can also be expected to occur the positions of the thiophene moiety and the carbonyl group coincide with the original positions of the functional groups of their precursors thus important information about palaeobiochemicals is retained throughout the sequestration degradation process

multiple expansions of c4 plant biomass in east asia since 7 ma coupled with strengthened monsoon circulation the expansion of plants using the c4 photosynthetic pathway is one of the most prominent changes in the global ecosystem during the cenozoic era a significant late miocene expansion is well documented however the existence and cause of subsequent expansions are still not clear owing in part to the lack of long continuous climate vegetation records here we present two high resolution carbon isotope time series covering the past 7 m y derived from eolian deposits on the chinese loess plateau the data indicate three intervals of significant c4 plant expansions within the semiarid monsoonal region of east asia ca 2 9 2 7 ma 1 3 0 9 ma and 0 6 ma present these expansions covary with strengthened east asian summer monsoon circulation we conclude that in east asia large scale late miocene c4 c3 vegetation changes in semiarid areas have been primarily driven by warm seasonal precipitation and temperature variations associated with changes in monsoon circulation

paleoclimatic significance of the mineral magnetic record of the chinese loess and paleosols the origins of the magnetic susceptibility variations of the chinese loess and paleosols are explored by scanning and transmission electron microscopy of magnetic extracts and by magnetic modeling of magnetic hysteresis data to provide quantified estimates of the major magnetic components microscopy identifies several distinct size and shape characteristics in the magnetic carriers lithogenic magnetites intact and abraded dominate the coarse grained magnetic fraction the smallest of the coarse grains is 2 i m the remaining magnetic materal is ultrafine in size with two types of magnetite particles present type a particles strongly resemble soil magnetites produced by inorganic precipitation type b particles which occur rarely are probably bacterial in origin quantitative modeling of these magnetic assemblages shows that over 90 of the susceptibility variations is accounted for by the superparamagnetic magnetite component compared to the loess units the paleosols are richer in magnetite particularly of superparamagnetic size and have a threefold higher ratio of magnetite to hematite we identify pedogenic formation of magnetite as the major contributor to the loess magnetic record matching this record against other paleoclimatic records we find an extremely high correlation with the standard 18o record the chinese loess sequences record a very high resolution magnetic stratigraphy directly related to changing climate

structure and significance of c30 4 methyl steranes in lacustrine shales and oils abstract the structure of the abundant c 30 4 methyl steranes of ancient freshwater lacustrine sediments and derived oils is of interest as their precursors the 4 methyl and in particular 4 23 24 trimethyl sterols dinosterols are reported to be specific to dinoflagellates this study employs a novel liquid crystal gc phase combined with gc ms and gc ms ms to separate and characterise mixtures of c 30 4 methyl sterane standards not resolvable on non polar phases this technique is then applied to identify the c 30 4 methyl steranes in an ancient freshwater sediment a freshwater lacustrine and a marine derived oil a comparison is also made with the 4 methyl steranes in marine sediments containing varying amounts of dinoflagellate cysts the c 30 4 methyl steranes of the freshwater lacustrine samples have been shown to possess a 4 methyl 24 ethylcholestane structure while both 4 methyl 24 ethylcholestanes and 4 23 24 trimethyl 5 h cholestanes dinosteranes were found in the marine dinoflagellate rich sediments while still indicative of dinoflagellates 4 methyl 24 ethyl sterols are generally not the major dinoflagellate sterol and alternative explanations for the abundance of 4 methyl 24 ethylcholestanes in ancient lacustrine sediments should be considered possibly ancient freshwater dinoflagellates synthesised principally the 4 methyl 24 ethyl form alternatively a source from an unrecognized algal class is possible while a source from bacteria which are known to synthesise certain 4 methylsterols is discussed

does δ13ccarb of the chinese loess indicate past c3 c4 abundance a review of research on stable carbon isotopes of the chinese loess current research on stable carbon isotopes of the chinese loess is reviewed the stable carbon isotopic composition of soil organic matter som 13corg of paleosols formed during interglacials is more positive than that within loess accumulated during glacials spatially it becomes progressively more negative from the eastern chinese loess plateau clp to the western however stable carbon isotopic composition of pedogenic carbonates 13ccarb from the same sequence produces an opposing trend both temporally and spatially and variation differs from expectations under conditions of equilibrium this indicates that 13ccarb in the chinese loess cannot be used to reconstruct the relative proportion of c3 c4 plants in past ecological communities furthermore use of 13ccarb to reconstruct the expansion of c4 plants in older tertiary red clay deposits is considered unreliable we believe 13ccarb may act as an indirect indicator of vegetation density following on changes in moisture supply controlled by the intensity of the asian summer monsoon but conclude that full understanding of the paleoclimatic significance of 13ccarb in the chinese loess and underlying tertiary red clay requires better understanding of modern isotopic processes

organofacies and paleoenvironment of the oligocene maikop series of angeharan eastern azerbaijan the maikop formation deposited in eastern azerbaijan during oligocene and early miocene times contains prolific source rocks with primarily type ii organic matter paleontological analyses of dinoflagellate cysts revealed a lower to upper oligocene age for the investigated succession near angeharan a major contribution of aquatic organisms diatoms green algae dinoflagellates chrysophyte algae and minor inputs from macrophytes and land plants to organic matter accumulation is indicated by n alkane distribution patterns composition of steroids and 13c of hydrocarbon biomarkers microbial communities included heterotrophic bacteria cyanobacteria chemoautotrophic bacteria as well as green sulfur bacteria higher inputs of terrigenous organic matter occurred during deposition of the upper oligocene units of the maikop formation from angeharan mountains the terpenoid hydrocarbon composition argues for angiosperm dominated vegetation in the shamakhy gobustan area high primary bioproductivity resulted in a stratified water column and the accumulation of organic matter rich sediments in the lower oligocene units of the maikop formation organic carbon accumulation during this period occurred in a permanently salinity stratified mesohaline environment with free h2s in the water column this is indicated by low pristane phytane ratios of all sediments varying from 0 37 0 69 lower methylated trimethyltridecyl chromans ratio in the lower units and their higher contents of aryl isoprenoids and highly branched isoprenoid thiophenes subsequently the depositional environment changed to normal marine conditions with oxygen deficient bottom water the retreat of the chemocline towards the sediment water interface and enhanced oxic respiration of om during deposition of the upper oligocene maikop sediments is proposed parallel depth trends in 13c of total om n alkanes isoprenoids and steranes argue for changes in the regional carbon cycle associated with the changing environmental conditions increased remineralisation of om in a more oxygenated water column is suggested to result in low toc and hydrocarbon contents as well as 15n enriched total nitrogen of the upper oligocene units

variations in abundances and distributions of isoprenoid chromans and long chain alkylbenzenes in sediments of the mulhouse basin a molecular sedimentary record of palaeosalinity abstract the abundances and distribution patterns of mono di and trimethylated 2 methyl 2 4 8 12 trimethyltridecyl chromans mttcs and long chain alkylbenzenes in extracts of marl 66 samples anhydrite 15 and halite 1 strata of the salt iv formation of the oligocene mulhouse basin are reported the distributions of the methylated mttcs indicate salinity changes of the upper part of a density stratified water column of the basin these variations are explained by a tectonically or climatically induced change in the supply of water of relative lower salinity to form a layer overlying the deeper water brine hence it is suggested that mesohaline 3 5 15 conditions in the surface waters were established as a result of periodic incursions of marine water and subsequent evaporation conversely during periods when the surface water was derived mainly from fresh water from the hinterland lower average salinity in the surface layer resulted the distributions of long chain alkylbenzenes also appear to record these changes

organic matter of the mulhouse basin france a synthesis the lower oligocene evaporite sequence of the mulhouse basin france contains organic matter rich marl deposits these marls display an overall cyclic variation of sedimentation rate organic carbon content hydrogen index and selected molecular parameters over a 30 m thick stratigraphic interval the integration of all sedimentological and geochemical parameters has allowed the reconstruction and characterization of the paleoenvironment of deposition the marls were deposited in a perennial lake that was at times connected to the sea two organic facies end members could be assigned to a lake stage with a marine connection and a lake stage that received dominantly continental water input the overall stratigraphic variation in the organic matter content is interpreted to reflect the adaptation of the oligocene flora to the changing paleoclimate and environmental conditions

stereochemical studies of acyclic isoprenoids xii lipids of methanogenic bacteria and possible contributions to sediments abstract abundant volatile lipids of methanobacterium thermoautotrophicum and methanosarcina barkeri include isoprenoid hydrocarbons c30 and c15 c20 and c25 isoprenoid alcohols m barkeri contains 2 6 10 15 19 pentamethyleicosane whose relative stereochemistry is the same as found in marine sediments indicating that it is a marker of methanogenic activity the c20 c30 and c25 alkenes in m thermoautotrophicum also have a preferred sterochemistry the latter have the 2 6 10 14 18 pentamethyleicosanyl skeleton suggesting that the alkane in marine sediments may derive from methanogens the stereochemistry of squalane in a marine sediment is also compatible with an origin in methanogens in contrast the stereochemistry of pristane in m thermoautotrophicum indicates a fossil fuel contaminant origin suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin there is therefore little evidence at present that the pristane in immature marine sediments originates in methanogens the c15 and c20 saturated alcohols in m thermoautotrophicum have mainly the all r configuration if this is generally true for methanogens the c20 alcohol in the messel shale may originate mainly from methanogens whereas that in the green river shale may originate mainly from photosynthetic organisms

palaeoenvironmental conditions during deposition of the upper cretaceous oil shale sequences in the songliao basin ne china implications from geochemical analysis abstract excellent hydrocarbon source rocks oil shales containing type i organic matter om were deposited in the continental songliao rift basin during the late cretaceous a major contribution of aquatic organisms dinoflagellates green algae botryococcus and minor input from macrophytes and land plants to om accumulation is indicated by n alkane distribution steroid composition and 13 c values of individual biomarkers microbial communities included heterotrophic bacteria cyanobacteria and chemoautotrophic bacteria as well as purple and green sulfur bacteria the presence of methanotrophic bacteria is indicated by 13 c depleted methyl hopane the sediments were deposited in a eutrophic alkaline palaeolake highly reducing saline bottom water conditions and a stratified water column existed during om accumulation of the qingshankou formation and member 1 of the nenjiang formation this is indicated by low pristane phytane gammacerane index and mttc ratios and the presence of carotane and aryl isoprenoids however an abrupt change in environmental conditions during deposition of member 2 of the nenjiang formation is indicated by significant changes in salinity and redox sensitive biomarker ratios a freshwater environment and suboxic conditions in the deep water prevailed during this period higher input of terrigenous om occurred during deposition of the upper nenjiang formation good oil to source rock correlation was obtained using biomarker fingerprints of oil stained sandstone from the quantou formation and oil shales from the qingshankou formation based on the extent of isomerisation of c 31 hopanes the oil was most probably derived from oil shales of the qingshankou formation in deeper parts of the basin

carbonate rhizoliths in loess and their implications for paleoenvironmental reconstruction revealed by isotopic composition δ13c 14c abstract loess paleosol sequences are important terrestrial archives for studying quaternary climate changes they often contain secondary carbonates including e g rhizoliths calcified roots these secondary carbonates are precipitated in isotopic equilibrium with root derived co2 and are therefore used to reconstruct the vegetation present during their formation based on stable carbon isotopic composition 13c usually the chronological context of secondary carbonates in general is not mentioned because it is assumed that they are formed synsedimentary with loess deposition the loess paleosol sequence at nussloch sw germany contains in its youngest part upper wurmian large carbonate rhizoliths with diameters of up to 5 cm and lengths of up to 1 m and more which have not been described in this profile so far we investigated rhizoliths as well as loess adjacent to and distant from rhizoliths for carbonatic carbon ccarb and organic carbon corg contents as well as their isotopic composition 13c radiocarbon dating to identify the rhizolith origin and the time frame of their formation considering the 13c fractionation by carbonate precipitation the 13ccarb values 10 9 0 1 revealed c3 plant origin of the rhizolith carbonate and the absence of large amounts of occluded primary loess carbonate similar 14c ages of rhizolith ccarb and corg 3788 59 years bp and 3150 59 years bp respectively argued for the absence of postsegregational alteration therefore they are suitable for the reconstruction of paleoenvironmental conditions after loess sedimentation the 14c ages clearly indicate that rhizoliths did not form synsedimentary roots penetrated the loess at nussloch after the deposition had ceased at 15 ka bp even in the loess adjacent to the rhizoliths up to a distance of 5 cm 13ccarb values indicate the presence of secondary carbonate deriving from postsedimentary organic matter of origin other than that of the reference loess material hence this postsedimentary input of younger root biomass might have masked the initial plant signal in loess paleosol sequences which could cause uncertainties for paleoenvironmental reconstructions based solely on loess organic matter

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

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

environmental magnetism a practical guide j walden f oldfield j and smith eds technical guide no 6 quaternary research association london 1999 243 pp price 17 00 9 00 to qra members isbn 0 907780 42 3

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

new chronology and organic matter paleoclimatic significance of nusloch loess sequence rhine valley germany due to its high accumulation rate the loess sequence of nu loch rhine valley germany is well suited to a high resolution study of continental paleoenvironmental changes over the last climatic cycle for northwestern europe as carbon isotope ratios of plants depend on environmental variations c of loess derived organic matter constitute reliable paleoclimatic proxies we present here a new chronology of nu loch loess sequence based on several c and tl dates our data show high correlations with global climate e ects vostok co or semi global gisp2 o and thus o er in this way a new approach to establish accurate chronologies in continental sequences furthermore using a deconvolution of the c signal would provide a quantitative proxy of moisture supply and permit paleoprecipitation reconstructions 2000 elsevier science ltd and inqua all rights reserved

microanalysis of primary fluid inclusions in halite constraints for an evaporitic sedimentation modeling application to the mulhouse basin france the chemistry of the waters from which the evaporitic minerals crystallized in the lower part of the salt iv unit of the mulhouse basin france has been investigated the lithological and fluid inclusion data have been compared to the output data of the mass transfer program newequi which simulates the change in brine composition during its evaporation advancement the results show that the evolution of the composition of the brine is compatible with the calculated sequence of evaporation of a parent water corresponding to a seawater modified by cacl2 rich hydrothermal water in the studied sequence fluid inclusion data provide useful constraints for reconstructing the paleoenvironment controlling the evaporitic sedimentation they also provide data on the water stratification in the basin and on its connectivity with the open sea and important parameters controlling the productivity possible sources for the nutrients and the preservation of organic matter in the sediment

dinoflagellate origin for sedimentary 4α methylsteroids and 5α h stanols biological marker compounds provide useful tools for evaluating the depositional environments of recent and ancient sediments and petroleums1 largely through established relationships between the organic matter of sediments and source organisms1 2 such relationships are best tested and explored by investigating the lipid components of natural populations of autochthonous biota that can be clearly recognized as contributors to underlying bottom sediments in this context we have studied the lipids of the freshwater dinoflagellate peridinlum lomnickii woloszynska order peridiniales class dinophyceae collected from the waters of priest pot3 a eutrophic lake in the english lake district its distributions of both 4 methylsterols and 4 methylstanones closely resemble those of the underlying bottom sediments demonstrating that dinoflagellates are important contributors of these sedimentary compounds the 4 methylsteroidal hydrocarbons found in ancient sediments and petroleums4 6 are presumably diagenetic products of such 4 methylsteroids and therefore reflect dino flagellate inputs to the original depositional environments furthermore the prominence of 5 h cholestan 3 ol in p lomnickii suggests that dinoflagellates may be the long sought direct biological source of sedimentary 5 h stanols

towards an orbital time scale for chinese loess deposits abstract in this study we analyzed the grain size of the baoji loess soil sequence at 10 cm intervals results show that grain size variations are very sensitive to loess soil alternations with loess units being much coarser than soils such a change in loess soil grains is interpreted as the result of the glacial interglacial cyclic variations in the intensity of the winter monsoon winds out of siberia the grain size record is thus employed as a proxy indicator of the winter monsoon circulation and tuned to the orbital records calculated recently by berger and loutre 1991 under the control of major magnetic reversals the tuning is independent of any correlation with 18o signals in the deep sea sediments the resulting grain size time scale is tightly constrained as suggested by the following facts 1 the filtered obliquity and precession components from the grain size data on the orbital time scale closely match the theoretical orbital records 2 ages of the major magnetic reversals estimated from the grain size time scale are in good agreement with the k ar dated ages 3 there is close coherence between the baoji grain size time series and the orbital variations at the orbital frequency bands over the entire 0 2 5 ma period and 4 the grain size record on the orbital time scale shows a close similarity to the orbitally tuned dsdp site 607 and odp site 677 18o records examination of time dependent characteristics of the grain size record suggests that there are two major shifts of dominant periodicities in the long term monsoonal cycles one occurring at about 0 8 ma bp and the other around 1 7 ma bp

branched tetraether membrane lipids associated with rhizoliths in loess rhizomicrobial overprinting of initial biomarker record abstract loess palaeosol sequences are considered important terrestrial archives for studying quaternary climate recent studies have shown that calcified roots rhizoliths can be significantly younger than surrounding terrestrial sediment loess and that loess organic matter may be contaminated with root derived carbon from post sedimentary deep rooting plants branched glycerol dialkyl glycerol tetraethers gdgts are membrane lipids produced by unknown bacteria in soil and are increasingly being used as palaeoclimate proxies the aim of this work was to examine the impact of the temporal decoupling between rhizoliths and loess on the abundance and composition of branched gdgts and consequently on the application of branched gdgts as proxies in loess deposits branched gdgts in rhizoliths and the surrounding sediment from a loess palaeosol sequence in nussloch sw germany were examined their composition varied between the rhizolith and loess which may reflect the fact that branched gdgts were biosynthesized at different times late pleistocene for loess and holocene for rhizoliths and therefore under different environmental conditions a large difference ca 7 c in branched gdgt reconstructed palaeotemperature was observed between rhizoliths and loess in addition the reconstructed temperatures were the opposite from those expected from the assumed depositional ages of branched gdgts this might be explained by the post sedimentary input of root associated microorganism derived branched gdgts to loess which might have led to an overprint of the initial branched gdgt signal in the sediment our results suggest that post sedimentary penetration of deep rooting plants in loess might entail uncertainty regarding the application of branched gdgt palaeoproxies and that caution should be exercised in interpreting temperature estimates derived from branched gdgts in loess palaeosol sequences this is of special importance for loess where rhizoliths are abundant and where non calcified root remains of different age from that of the sediment are possible in addition the gdgt concentration in rhizoliths and surrounding loess supports the hypothesis of a heterotrophic lifestyle for branched gdgt producing bacteria

variation and paleoclimatic significance of organic carbon isotopes of ili loess in arid central asia as an indicator for terrestrial paleovegetation the stable isotopic composition of total organic matter delta c 13 org in loess sediments has been widely used for paleoclimatic reconstruction in western europe the great plains of north america and the chinese loess plateau clp however little is known about the variation and paleoclimatic significance of the loess delta c 13 org in arid central asia aca we report delta c 13 org data from an axike axk loess paleosol profile from the eastern ili basin eastern central asia along the profile the delta c 13 org values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon toc consistent with results for western europe and the northwestern clp our results demonstrate that the loess delta c 13 org in this region documents mainly the response of delta c 13 of locally predominant c 3 plants to paleoclimatic variation especially paleoprecipitation our results also suggest that the loess delta c 13 org values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed delta c 13 org results from modern plants and surface soils in the future c 2013 elsevier ltd all rights reserved

handbook of environmental isotope geochemistry vol 1 the terrestrial environment a p fritz and j ch fontes editors elsevier amsterdam 1980 xii 532 pp u s 90 25 dfl 185 00

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

δ13c of loess organic matter as a potential proxy for paleoprecipitation paleoprecipitation reconstructions on the basis of pollen are well known but they do not provide high temporal resolution for glacial periods high resolution paleoprecipitation reconstructions for the last glaciation based on the isotopic record organic matter in loess from nussloch rhine valley germany are consistent with paleoprecipitation inferred from peat in the same area using an independant method thus 13c of loess organic matter can be used as a proxy for paleoprecipitation

lacustrine source rock deposition in response to co evolution of environments and organisms controlled by tectonic subsidence and climate bohai bay basin china three paleogene syn rift intervals from the bohai bay basin the most petroliferous basin in china were analyzed with sedimentological and geochemical techniques to characterize the lateral source rock heterogeneities to reveal the environmental and ecological changes through geologic time and to construct depositional models for lacustrine source rocks under different tectonic and climatic conditions the third es3 and first es1 members of the eocene shahejie formation and the oligocene dongying formation ed display widely variable total organic carbon contents hydrogen indices and visual kerogen compositions suggesting changes in organic facies from deep to marginal sediments carefully selected deep lake facies samples from any interval however display fairly uniform biomarker composition these three intervals have distinctly different biomarker assemblages which indicate weakly alkaline freshwater lakes with a moderately deep thermocline during es3 deposition alkaline saline lakes with shallow chemocline during es1 deposition and acidic freshwater lakes with deep unstable thermocline during the deposition of the dongying formation such environmental changes corresponded to changes in subsidence rate and paleoclimate from rapid subsidence and wet climate during es3 deposition through slow subsidence and arid climate during es1 deposition to rapid subsidence and wet climate during ed deposition and resulted in synchronous changes in terrigenous organic matter input phytoplankton community and primary productivity the co evolution of environments and organisms controlled by tectonic subsidence and climate accounted for the deposition and distribution of high quality lacustrine source rocks with distinctly different geochemical characteristics most rift basins experienced changes in subsidence rates and possibly changes in climates during their syn rift evolutions the models constructed in this paper may have important implications for source rock prediction in other lacustrine rift basins

dinosteranes 4 23 24 trimethylsteranes and other biological markers in dinoglagellate rich marine sediments of rhaetian age abstract alkane biological marker distributions and concentrations have been determined in 18 samples from a section of rhaetian age from the bristol trough and a quantitative micropalaeontological analysis carried out taking into account previous geological investigations of the sequence three end member depositional settings have been recognised from changes in total organic carbon content the biological markers and the micropalaeontological composition these depositional environments are attributed as follows the first which occurs in the lower part of the section corresponds to deposition in a supratidal sabkha type setting with the major organic input being of allochthonous origin the second also in the lower part of the section indicates the occurrence of periods of marine incursion with enhanced salinity resulting from evaporation in the upper part of the section marginal marine conditions are apparent with higher organic carbon biological marker and amorphous organic matter contents at the top suggesting the establishment of more stable conditions of oxygen depletion some sediments in the sequence are notable for containing an abundance of cysts of rhaetogonyaulax rhaetica one of the oldest marine dinoflagellates comparison of microfossil abundances with hydrocarbon abundances extends the circumstantial evidence for the dinophyceae being the major biological source of dinosteranes 4 23 24 trimethylcholestanes and some other 4 methyl steranes in marine sediments the presence of dinosteranes and their 24 ethyl counterparts extends the stratigraphic range of occurrence of such components back to the rhaetian c 31 methyl steranes in the sediments from the second depositional setting are tentatively assigned a 4 22 23 24 tetramethyl sterane skeleton and a dinoflagellate origin

high abundance of carotanes in the brackish saline lacustrine sediments a possible cyanobacteria source abstract the organic rich oil shales of low maturity and tight oils from the middle permian lucaogou formation were formed in a brackish saline lacustrine environment in the jimusaer sag junggar basin they are characterized by remarkably abundant carotane and carotane the biological sources and favourable sedimentary environments of carotanes formation remain obscure organic geochemical analyses of 17 oil shales and 20 tight oils from the jimusaer sag reveal that reducing evaporitic and carbonate rich shallow water environment is favourable for carotane accumulation geochemical studies show that carotane abundance is controlled by both source of organic matter and sedimentary environment rather than thermal maturity in the study area even though both higher plants and microalgae are reported to be precursors of carotanes cyanobacteria may be the main biological sources of carotanes in the lucaogou formation based on cyanobacteria derived biomarkers such as the c39 2 6 dimethyl benzene substituted isoprenoid 2 methylhopanes 7 and 8 monomethylhepadecanes the airborne volcanic ash containing ample elements e g mg and fe caused by the intermittent volcanic eruptions during the middle permian most likely contributed to the flourish of cyanobacteria in the study area

secular and environmental constraints on the occurrence of dinosterane in sediments abstract the distribution patterns of sedimentary a ring methylated steranes have changed markedly over geological time although dinosterane and its isomer 24 ethyl 4 methylcholestane have been tentatively identified in three proterozoic rock units they are either not detectable or occur in low abundance relative to 3 methyl steranes throughout most of the palaeozoic between permian and middle triassic times 260 220 ma ago 4 methyl sterane abundances in marine sediments increased markedly the presence of dinosterane in some middle triassic marine sediments is contemporaneous with the appearance of fossil cysts of uncontested dinoflagellate affinity 4 methyl steranes including dinosterane or their precursor sterenes and sterols then show a continuous presence often in high abundance in marine sediments from the late triassic through to the present day assemblages of 4 methyl steranes and their precursors but with dinosterane absent or in low relative abundance are often the predominant steroids in lacustrine sediments in the cainozoic dinosterane appears to arise predominantly from marine dinoflagellates and as a consequence is a useful biological marker for mesozoic and cainozoic marine organic matter the isomer 24 ethyl 4 methylcholestane is likely to have multiple origins although its very high abundance in tertiary lacustrine sediments and oils compared to older materials suggests that dinoflagellates could also be the source in these cases

novel cyclised and aromatised diagenetic products of β carotene in the green river shale abstract a suite of novel diagenetic products of carotene has been identified in an extract of a sample from the green river shale identification is mainly based on comparison of mass spectra with those of diagenetic products of another carotenoid isorenieratene these compounds were formed by i cyclisation and aromatisation of the polyene isoprenoid chain ii explusion of toluene and m xylene from the polyene isoprenoid chain and iii aromatisation of the 1 1 5 trimethylcyclohex 5 enyl moieties resulting in 1 2 dimethylbenzene end groups reduction of the double bonds of carotene is the most important diagenetic process however as judged from the high relative amount of carotane 63 of quantified diagenetic products of carotene these results indicate that the fossilisation potential of carotenoids is greater than previously thought

did an extensive forest ever develop on the chinese loess plateau during the past 130 ka a test using soil carbon isotopic signatures abstract pleistocene vegetation history on the chinese loess plateau has been traditionally investigated using palynological methods and questions remain regarding whether an extensive broadleaf deciduous forest ever developed on the loess table under favorable climatic conditions the authors have employed a c isotope approach to address this question by comparing 13 c values in soil organic matter from different loess ecological domains with known source vegetation to the c isotope values obtained from a paleosol section that can be dated back to 130 ka the c isotopic compositions of modern soils from the loess table and the loess desert transition gave 13 c values of 24 5 to 18 2 and 25 7 to 20 7 respectively these c isotopic ratios are consistent with the standing modern vegetation that is dominated by a mixture of c 3 and c 4 plants and can be distinguished from that in the patchy forest areas where exclusive c 3 trees yield a narrow 13 c value range from 26 9 to 25 average 26 1 obtained 13 c compositions from paleosols and loess sediments in the lantian and the luochuan profiles vary from 24 to 16 9 indicating a grass dominated steppe with shifting c 3 and c 4 contributions controlled mainly by paleoclimatic changes during the late pleistocene the present results suggest no extensive forest coverage on the loess table during the past 130 ka even under the most suitable conditions for forest development this conclusion supports the explanation of natural causes for the development of only patchy forests on the modern loess table and provides critical historical information toward the vegetation restoration project that is currently underway on the chinese loess plateau

vegetation variation of loess deposits in the southeastern inner mongolia ne china over the past 1 08 million years abstract the stable carbon isotopic composition of organic matter of aeolian silt deposits is regarded as an appropriate proxy index of paleovegetation especially in the chinese loess plateau in central china in this study a loess paleosol sequence in the southeastern inner mongolia autonomous region in northeastern ne china which is located outside the chinese loess plateau is chosen to reconstruct the vegetation history since 1 08 ma temperature exhibits a threshold value which determines the growth of c4 plants in this study area the organic matter of the samples is derived from two different vegetation types namely the mixed c3 and c4 plants and the pure c3 plants the 13c of the organic matter shows negative values in loess units and higher values in paleosol units this finding reflects the influence of temperature and summer monsoon intensity on the vegetation dynamics over glacial interglacial cycles on a longer time scale the 13c values are higher between 1 1 and 0 9 ma and after 0 35 ma and lower between 0 9 and 0 35 ma which may be attributed to a long term temperature variation our analysis shows that regional temperature is the most important limiting factor that forces vegetation changes at the glacial interglacial time scale in ne china

east asian monsoon evolution during the eemian as recorded in the western chinese loess plateau abstract we present a high resolution environmental magnetic record of the east asian summer monsoon spanning paleosol s1 corresponding to marine oxygen isotope mis 5 from the jiuzhoutai jzt loess section in lanzhou on the northwestern edge of the chinese loess plateau we use a chronology based on a sediment grain size age model frequently used for chinese loess the eemian is dated to 127 37 121 31 ka bp and can be divided into three sub stages based on variations in summer monsoon intensity early eemian 127 37 125 67 ka bp with an intermediate summer monsoon intensity mid eemian 125 67 124 24 ka bp with weakest summer monsoon intensity and late eemian 124 24 121 31 ka bp with the strongest summer monsoon intensity contrasting the winter monsoon weakened at the beginning of mis5e reached its weakest intensity during the late eemian 121 ka bp and then commenced an irreversible strengthening trend furthermore the eemian exhibits a similar climatic trend to the holocene optimum since both are divided into two parts by an intervening arid interval and the most humid period occurs in the secondary pedogenic stage therefore we suggest that the climate evolution during eemian and later may provide useful information about climate forecast in the future

evolving history of the east asian summer monsoon intensity during the mis5 inconsistent records from chinese stalagmites and loess deposits as an important component of the global monsoon system the intensity of east asian summer monsoon easm influences lives and economic development of more than 2 billion people the last interglacial period also known as marine isotope stage 5 mis 5 has been thoroughly investigated due to its similarity to the modern interglacial period mis 1 according to records from chinese stalagmites and loess deposits evolving history of easm intensity during mis5 can be divided into 5 sub stages i e 5a 5e however during the 3 warm sub stages 5a 5c and 5e evolving history of easm intensity recorded by chinese stalagmites and loess deposits is apparently different oxygen isotope 18o records of stalagmites demonstrate that the easm intensity during mis5e 5c and 5a is not obviously different on the other hand easm intensity apparently decreased from mis5e to 5c and 5a based on chinese loess deposits records the discrepancy between chinese stalagmite and loess deposits reveals that 18o records of stalagmites may not be a pure indicator of easm intensity the relationship between 18o and easm intensity is not linear based on 18o data of modern precipitation from 21 weather stations within major monsoon area in china mmac ca 110 e to 122 e 18 n to 41 n we speculate that chinese stalagmite 18o values recorded changes of 18o of summer precipitation as well as adjustment from 18o of winter precipitation inconsistent records from chinese stalagmites and loess deposits indicate that further investigations are needed to study the mechanism and fractionation of 18o in stalagmites collected in china

a molecular stratigraphic approach to palaeoenvironmental assessment and the recognition of changes in source inputs in marls of the mulhouse basin alsace france principal components analysis pca has been used to investigate changes in concentrations of the components of the hydrocarbon fractions extracted from 71 marl samples selected to cover two total organic carbon toc maxima in the lower part of the salt iv formation a lower oligocene evaporitic sequence from the mulhouse basin france the analysis indicates that the fractions can be ascribed as lying between two end member distributions the changes in these distributions are gradual suggesting that they resulted from fairly gradual changes in the depositional palaeoenvironment these changes are related to increased algal productivity associated with the evolution of a restricted lacustrine environment through to one with a greater marine influence systematic variations in the concentrations of selected components relative to the toc profile point to a repeated sequential evolution in the biological assemblage during deposition of the sequence

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

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

evidence for sulphide links in a crude oil asphaltene and kerogens from reductive cleavage by lithium in ethylamine abstract reduction of a sulphur rich asphaltene from a crude oil rozel point with lithium in ethylamine li etnh2 affords an alkane fraction similar to that obtained from desulphurisation with raney nickel but in higher yield using li etnd2 deuterium labelled alkanes were obtained thereby confirming the presence of sulphide linkages in the asphaltene fraction reduction of two sulphur rich kerogens with similar sulphur contents serpiano shale m triassic and jurf ed darawish jed u cretaceous afforded significant quantities of polar solvent extractable material both kerogens also yielded low amounts of hydrocarbons although the amount released from jed kerogen was significantly higher the results indicate that whereas the kerogens contain hydrocarbon moieties intermolecularly linked by sulphide bridges the distributions of the precursors lipids which were incorporated were different for example gc ms analysis of the labelled products from jed kerogen revealed them to be dominated by steranes of algal origin with the position s of deuterium labelling providing evidence of sulphide linking and cross linking on the other hand the labelled products from serpiano kerogen were dominated by hopanes of bacterial origin which were linked terminally via the side chain

pedogenesis and paleoclimate interpretation of the magnetic susceptibility record of chinese loess paleosol sequences in the chinese loess paleosol sequences from luochuan haanxi province china variations in the magnetic susceptibility have been accepted as an excellent proxy for paleoclimate and the standard interpretation is that climatic processes have enhanced the magnetic susceptibility of the paleosols beyond the base line level of the loess by using mineral magnetic properties and a soil chemistry extraction procedure we show that most of the magnetic susceptibility signal in both the paleosols and the loess is due to pedogenesis in effect loess deposition and pedogenesis are competing processes at all times and the presence of a paleosol simply indicates that the latter process was predominant these results imply that any interpretation of the paleoclimate record of loess paleosol sequences must recognize the pedogenic nature of the magnetic susceptibility signal and that the focus of future research must be on the critical role of climate in the development of the paleosols

rhizoliths in loess evidence for post sedimentary incorporation of root derived organic matter in terrestrial sediments as assessed from molecular proxies abstract loess palaeosol sequences are important terrestrial archives for studying quaternary climate change a major assumption for palaeoenvironmental reconstruction based on loess organic matter om is that it represents the signal of syn sedimentary incorporated plant biomass i e predominantly grass vegetation however recent studies on rhizoliths roots encrusted by secondary carbonate formed in loess reveal the possibility of post sedimentary penetration of loess palaeosol sequences by deeply rooting plants this likely led to incorporation of younger root derived om into surrounding loess potentially causing an overprinting of the initial plant derived signal of loess om to obtain information on the source vegetation of rhizoliths and surrounding loess om we examined rhizoliths and loess from nussloch sw germany using alkane and fatty acid fa molecular proxies moreover the lipid composition was compared in transects from rhizoliths via rhizosphere loess towards root free loess for a preliminary assessment towards quantifying the post sedimentary input of root derived om in loess loess om gave a combined signal from shoot and root biomass from grass vegetation confirming the assumption of deposition during glacial periods with scarce grass vegetation cover in contrast the lipid composition of rhizolith om reflected roots of woody vegetation indicating the post sedimentary character of rhizoliths stronger degradation of om together with a large content of microorganism derived fas in the former rhizosphere indicated rhizodeposition associated with high microbial activity in loess adjacent to rhizoliths at least up to a distance of 5 cm rhizosphere loess and reference loess at a distance of 50 70 cm showed a significantly different om composition thereby revealing the incorporation of considerable portions of root derived om into loess in the vicinity of roots further studies are necessary for an exact quantification of this potential overprint of the syn sedimentary loess om which might cause uncertainty in palaeoenvironmental studies

stable carbon and oxygen isotopic study of carbonate along a loess paleosol section in lantian county shaanxi province on the southeastern edge of the chinese loess plateau studies of carbonate carbon isotope of loess paleosol 13ccarb in the chinese loess plateau clp have shown 13ccarb less negative in loess and more negative in paleosol which is opposite to that of bulk organic matter although some mechanisms have been proposed to explain this inconsistency few studies have been conducted to investigate how carbonate migration could affect the reliability of utilizing 13ccarb as an effective indicator here a loess paleosol profile with a nodule horizon intercalated in the loess layer located on the southeastern edge of the clp was investigated to understand the influence of carbonate eluviation and reprecipitation on 13ccarb along the section the mean grain size and magnetic susceptibility generally conform to the field observed loess paleosol stratigraphy however carbonate content shows distinct differences in the two sides of the nodule horizon clearly indicating eluviation along the section the variation of carbon and oxygen isotopic compositions of soil carbonate 13csc and 18osc and nodule carbonate 13cnc and 18onc along the profile does not present a clearly meaningful picture generally 13csc and 18osc have a similar change trend along the profile and are positively correlated but there is no apparent relationship between 13cnc and 18onc more importantly 18onc values fall in the range of 18osc whereas 13cnc values are much more positive than 13csc detailed analyses of the data indicate migration of carbonate along the profile which is an important factor that determines that loess paleosol 13ccarb could not be employed as a high resolution paleovegetational and paleoenvironmental indicator in the clp at least on or below the glacial interglacial scales

variation in carbon isotopic composition over the past ca 46 000 yr in the loess paleosol sequence in central kazakhstan and paleoclimatic significance abstract we present a high resolution record of 13 c org variation from two loess sequences in central kazakhstan the variation shows that the vegetation was persistently dominated by c 3 plants over the past ca 46 000 yr the 13 c org signature was most likely an indicator of moisture and the moisture variation in central kazakhstan was associated with the precipitation in western europe the 13 c org indicated that moisture variation exhibited five stages decreasing during stage 1 ca 46 000 ca 31 500 yr bp increasing during stage 2 ca 31 500 ca 25 500 yr bp again decreasing during stage 3 ca 25 500 ca 19 000 yr bp fluctuating along a constant line during stage 4 ca 19 000 ca 5000 yr bp and increasing during stage 5 last ca 5000 yr our comparison demonstrated a general similarity between the 13 c org indicated moisture variation in central kazakhstan and the reconstructed precipitation variation in western europe the similarity implies that the moisture of the past ca 46 000 yr in central kazakhstan has been controlled or modulated by westerlies that brought water vapor from the north atlantic not only to western europe but also to central kazakhstan

isotopically heavy carbon in the c21 to c25 regular isoprenoids in halite rich deposits from the sdom formation dead sea basin israel abstract a series of miocene pliocene halite deposits with extremely low organic carbon contents from the sdom formation dead sea basin israel have been studied distributions and 13c contents of biomarkers have been determined using gc ms and irm gcms analyses respectively the hydrocarbon fractions consist mainly of pristane phytane and c21 to c25 regular isoprenoids the predominance of c21 regular isoprenoids in the dead sea halites and other hypersaline deposits indicate that these components could be derived from ether bound membrane lipids of halophilic archaea the lack of intact ether bound lipids in the polar fractions indirectly infers that such components have already been released at early stages of diagenesis their 13c contents are enriched in 13c by up to 7 compared to the biomarkers of presumed phytoplanktonic origin i e steranes and hopanes within the same sediment sample in agreement with a source other than algae and cyanobacteria thus tentatively assigned as halophilic archaea based on biomarker distributions 13c contents and mineral compositions these sediments appear to have been deposited in a salinity stratified water body with a bottom water brine continual evaporation and deposition of the higher salts i e carnallites are favourable conditions for the growth of halophilic archaeal communities

molecular isotopic evidence of environmental and ecological changes across the cenomanian turonian boundary in the levant platform of central jordan abstract we evaluated the structure of planktonic communities and paleoenvironmental conditions throughout the cenomanian turonian oceanic anoxic event oae2 by studying bulk geochemical properties and the molecular isotopic composition of source specific hydrocarbons from organic rich sediments deposited in an intrashelf basin at the levant platform central jordan high concentrations of desmethyl and 4 methylsteranes as well as dinosteranes indicate that marine algae including dinoflagellates were the main primary producing organisms the presence of 2 methylhopanes and 13 c enriched hopanes in addition to isotopically enriched aryl isoprenoids evidenced the contribution of cyanobacteria and green sulfur bacteria respectively additionally variable but fairly low 15 n values during oae2 suggest the occurrence of diazotrophy as a likely important process fueling primary production during oae2 in this stratified anoxic continental platform variations in the relative contribution of biomarkers revealed changes in planktonic communities associated with sea level change and water column stratification oae2 was characterized by strong stratification anoxic bottom waters and a deep chemocline as evidenced by high gammacerane and homohopane indices and the absence of photic zone euxinia pze markers respectively however the presence of isorenieratane and its derivatives in post oae black shales points to a shoaling of the chemocline and to pze this interval was also characterized by an exceptionally high abundance of chlorophyll derived pristane and phytane up to 2 mg g 1 toc likely as a result of highly enhanced primary production and organic matter preservation remarkably this high productivity event co occurs with an exceptionally high abundance of calcispheres reported elsewhere to be part of a global bio event

δ13c variations of loess organic matter as a record of the vegetation response to climatic changes during the weichselian this paper presents high resolution records of 13 c 12 c ratios of organic matter from two loess sequences in northwestern europe our analysis is the first attempt to use organic matter 13 c as a record of the response of vegetation to climatic variations in an area where climatic changes were not strong enough to induce a radical change in vegetation cover over the last climatic cycle the vegetation of the rhine valley showed a strong predominance of c3 plants thus the small 13 c variations with an amplitude of only 1 5 to 3 are interpreted as corresponding to fluctuations in water supply and atmospheric co 2 concentration variations rather than to the ratio of c4 to c3 vegetation furthermore loess sequences accumulated at high rates and allow high correlation with climatic proxy data like the greenland ice sheet project 2 gisp2 18 o and the variations in co 2 concentration recorded in the vostok ice core the 13 c constitutes a reliable and complementary proxy to study small climatic stresses endured by vegetation during the weichselian in northwestern europe moreover by using absolute age control and correlations between global vostok co 2 or semi global gisp2 18 o climate effects 13 c values of organic matter in loess sequences offer a new tool to establish a refined chronology in continental sequences

high resolution δ13ctoc and magnetic susceptibility data from the late early pleistocene southern margins of the chinese loess plateau abstract on the chinese loess plateau stable carbon isotope values for total organic matter 13ctoc from more than 10 loess paleosol sequences since the last glacial interglacial show generally consistent variations with enriched values normally occurring in paleosol layers the only exceptions are records from the westernmost and northwestern chinese loess plateau however both asian summer monsoon intensity and temperature have been suggested as the principal factor affecting these consistently similar 13ctoc variations until now 13ctoc records covering the whole quaternary have been relatively rare with problems including low resolution and conflicts in both the c4 expansion history and with related climatic interpretations in this paper we report on high resolution late early pleistocene low frequency magnetic susceptibility lf and 13ctoc data from yushan section on the southern margins of the chinese loess plateau our 13ctoc data present an abstruse relation with the glacial interglacial cycles represented by loess paleosol sequences with 13c enriched excursions in some paleosol layers and 13c depleted excursions in others furthermore our 13ctoc data shows negative and positive correlations with lf data using a threshold lf value of 70 10 8 m3 kg if the lf data are taken as an indicator of pedogenetic intensity and therefore an indicator of asian summer monsoon intensity there are two possible relations between chinese loess 13ctoc and asian summer monsoon intensity i e the chinese loess 13ctoc cannot simply be adopted as the sole indicator of asian summer monsoon intensity at least during the late early pleistocene on the southern margins of the chinese loess plateau our results demonstrate that c4 plants became a significant proportion of local vegetation cover only when asian summer monsoon intensity exceeded a certain degree for example in the surface vegetation for the s15 and s16 paleosol layers of the yushan section the relation between climate and chinese loess 13ctoc requires further detailed study

dinosterane and other steroidal hydrocarbons of dinoflagellate origin in sediments and petroleum abstract the steroidal alkanes of a selection of sediments and oils have been examined by gc ms with multiple metastable reaction monitoring specific 4 methyl sterane isomers have been identified by comparison with isomers synthesized from sterols isolated from dinoflagellates an immature marine oil shale and two mature marine oils of triassic to early cretaceous age contained high concentrations of c30 steranes comprising desmethyl 24 ethyl 4 methylcholestane and 4 23 24 trimethylcholestane dinosterane isomers an immature non marine oil shale and two non marine oils of cretaceous to eocene age contained stereoisomers of 24 ethyl 4 methylcholestane as the dominant c30 steranes reaction monitoring analyses in gc ms are particularly suited to unravelling complex distributions of homologous and stereoisomeric steroids encountered in oils and their source rocks

palaeoclimate controlled accumulation of organic matter in oligocene evaporite sediments of the mulhouse basin abstract marl beds of a 30 m thick interval of the oligocene evaporites of the mulhouse basin display a cyclic variation in their organic carbon content that is related to changes in sedimentation rate the construction of a time scale suggests a duration of 58 000 30 yr for the interval studied calculated accumulation rates for organic matter of aquatic origin are used to assess the fluctuation of palaeoproductivity of the system the observed variation of the accumulation rates of terrigenous organic matter throughout the studied interval is most likely linked to variations in palaeoclimate

climatic dependency of soil organic carbon isotopic composition along the s n transect from 34 n to 52 n in central east asia abstract we explored the relationships between surface soil 1 20 cm organic carbon isotopic signatures and associated climatic factors in central east asia in an attempt to develop transfer functions that can be used to retrieve the paleoclimatic information stored in the thick eolian paleosol sequences within the area our analysis shows that the negative correlation between the surface soil organic 13c values and the mean annual precipitation is robust r2 0 453 n 196 p

source rock potential of evaporitic environment examination of modern saline lakes solar evaporation ponds and lagoons shows that the evaporitic environment can be very productive of organic matter few species survive in the brines but those that do commonly exist in great profusion in a marine evaporitic embayment the flow of surface currents is persistently toward regions of highest salinity so that there is a continual supply and concentration of nutrients prolific growth of phytoplankton may be similar to that in areas of upwelling in modern oceans only carbonates precipitate in the mesosaline part 4 to 12 salinity of such an evaporitic environment and no great dilution of organic matter by clastic or biogenic sediments occurs because stratification of brine may occur and reducing conditions may be a sociated with the bottom waters much of the organic matter produced can be preserved upon maturation the result may be a rich carbonate source rock frequently unrecognized in the geologic column in the middle east mesosaline conditions are known to have occurred many times from the triassic to cretaceous and may be responsible for the vast reserves of petroleum in the area evaporitic conditions may also have played a part in the petroleum productivity of many other areas including the michigan and paradox basins

a coupled environmental system formed at about 2 5 ma in east asia abstract the somewhat abrupt commencement of loess deposition on a large scale in north central china is palaeomagnetically measured at about 2 5 ma the formation of the dynamical conditions responsible for windblown loess processes implies a reorganization of the atmospheric circulation over eastern asia it is speculated that at that time the accelerated uplift of the tibetan plateau had reached a threshold height giving rise to the intensification and northward shift of the siberian high and deepening of the cyclone in the lee of the tibetan plateau the uplift of tibet and the resulting reorganization of atmospheric circulation at about 2 5 ma would initiate a coupled environmental system tibetan plateau inland desert loess plateau in eastern asia that could be a key system in understanding the onset of glaciation in northern hemisphere and climatic change in the quaternary the climatic shift from near continuous warm condition before 2 5 ma to frequent and chaotic fluctuations after is speculated to be triggered to a significant extent by the uplift of the tibetan plateau an orography cold surge albedo temperature feedback mechanism is developed in explaining the harsher climate over east asia during glacial time and is thought to be one of the major contributors in promoting glacial development on the globe

the mulhouse basin evidence from porphyrin distributions for water column anoxia during deposition of marls abstract marls from the evaporitic mulhouse basin oligocene alsace france contain alkyl porphyrins dominated by nickel complexed species the presence in high relative abundance of a range of components with carbon numbers up to c 37 indicates that anaerobic photosynthetic bacteria made a significant contribution to the photosynthetic community in the palaeoenvironment and in turn that anoxic conditions extended into the photic zone of a stratified water column further evidence is given by the assignment by hplc coinjection with a standard of a c 34 component with the same carbon skeleton as one of the bacteriochlorophylls d of such bacteria significant differences in the nickel and vanadyl porphyrin distributions in one of the samples examined appear to result from changes in the depositional environment which are recorded with a stratigraphic resolution below that sampled or indicate derivation of these two porphyrin pools from different parts of the water column

climatically driven glacial interglacial variations in c3 and c4 plant proportions on the chinese loess plateau high resolution 13c records of bulk organic matter om from three loess paleosol successions from the central chinese loess plateau document systematic fluctuations in c3 and c4 plant abundance for certain intervals during the past 620 k y measured 13c values of om in paleosols are less negative by 0 5 4 and total organic carbon toc contents are higher by up to 0 5 wt relative to corresponding values in loess deposits the 13com and toc decrease from peak values in paleosols progressively into overlying and underlying loess deposits integrated 13com toc and magnetic susceptibility rec ords indicate an increase in c4 vegetation to 50 during peak paleosol formation and a decrease in c4 vegetation to 30 during loess deposition for three of the past glacial interglacial cycles these results indicate that c4 plant abundance declined during glacials in this mid latitude region driven primarily by a shift to enhanced winter precipitation and lower temperatures and further contribute to the rapidly growing body of evidence that low p co2 during pleistocene glacials was insufficient to trigger c4 plant expansion without coincident favorable climatic conditions

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

multiproxy evidence of middle and late pleistocene environmental changes in the loess paleosol sequence of bůhzdař czech republic abstract loess paleosol sequences preserve information that can be used to reconstruct paleoenvironments a dense network of reliably analyzed sequences from different geographic locations is crucial to address ecological and climatic trends which occurred during the pleistocene this paper focuses on a loess paleosol sequence in b hzda situated 9 km nw of prague czech republic geochemical approaches total organic carbon xrf elemental analyses xrd mineralogy 13c and 18o stable isotopes are combined with grain size distributions and optically stimulated luminescence osl to assess the climatic conditions at the time of formation of the strata the oldest loess at this location was formed circa 200 ka ago mis 7 making it the oldest loess in central bohemia for now the b hzda loess paleosol sequence was highly affected by several erosion events eemian paleosols mis 5e being completely missing the partly relocated paleosols situated at the lower part of the b hzda sequence represent a period of increased humidity during late mis 7 and mis 6 despite the fact that the b hzda profile is not particularly thick 5 m significant changes in paleoclimate reconstructions have been detected