the cr renazzo type carbonaceous chondrite group and its implications abstract a petrologic geochemical and oxygen isotopic study of eight meteorites identified as cr renazzo type chondrites reveals that they have a set of similar properties that distinguishes them from other chondrite groups and confirms cr as a carbonaceous chondrite group characteristics of the cr group include 1 1 abundant large multilayered fe ni metal rich type i chondrules 2 2 abundant matrix and dark inclusions di that contain microchondrules microfragments and magnetite framboids and platelets 3 3 unique assemblages of serpentine and chlorite rich phyllosilicates and ca carbonates 4 4 ca carbonate rims on chondrules 5 5 abundant fe ni metal with a positive ni vs co trend and a solar ni co ratio 6 6 low abundance of refractory rich inclusions 7 7 amoeboid olivine aggregates aoa with mn rich and mn poor forsterite and 8 8 oxygen isotopic compositions that form a unique mixing line the cr chondrites are breccias consisting of two major components the large layered chondrules and the matrix dark inclusions al rais is an anomalous member in having a higher abundance of the dark inclusion component 70 vol and this accounts for its having a higher volatile content than other members of the group the conditions that prevailed during aqueous alteration of the cr chondrites differed from those of other hydrated chondrite groups and may be the result of a higher temperature environment than that for the ci and cm chondrites the cr chondrite components chondrules matrix dark inclusions etc experienced aqueous alteration to differing degrees prior to assembly of the host chondrites and dark inclusions represent a lithology that was altered by water to a greater degree than the rest of the meteorite the overall degree of hydration in cr chondrites varies among meteorites with al rais being the most hydrated the oxygen isotopic variation of the whole rocks chondrules and matrices may be related to degree of hydration indicating that cr chondrites interacted with a water rich component having heavy oxygen and that was the same as ci and cm water

alkyldibenzofurans in terrestrial rocks influence of organic facies and maturation abstract dibenzofuran dbf dibenzothiophene dbt and phenanthrene phe have been determined along with their methyl derivatives mdbfs mdbts mps in coals carbonaceous shales and mudstones of lower cretaceous to upper carboniferous ages from the elmworth gas field canada and from the sakoa madagascar and ruhr coal germany basins the samples contained mainly terrestrial organic matter with thermal maturities in the 0 7 1 9 mean vitrinite reflectance rr range the pronounced predominance of mdbfs over mdbts in the sakoa samples is typical of plant debris deposited in lacustrine swamp environments onset of intense mdbf generation occurs at fairly low rank 0 77 rr as indicated by elevated concentrations of 50 120 g mdbfs g total organic carbon toc influences of lithology organic matter type and maturity on distributions of the target compounds were extracted from the molecular concentration data by multivariate statistical methods such as principal components analysis pca and fuzzy c means cluster analysis with nonlinear mapping nlm a specific source effect on 1 mdbt concentrations suggests that lichens contributed to the senescent coal forming forest in the sakoa coal basin alkyldibenzofurans hence are potential lichen biomarkers mdbfs can be used as maturity indicators only beyond 1 0 rr where ruhr coals displayed a distinct increase in the 1 4 mdbf ratio

the isolation occurrence and origin of fluorenones in crude oils and rock extracts abstract a rapid method for the analysis of fluorenones in crude oils and reservoir core extracts based on solid phase extraction and gc ms is described a detailed reservoir study involving analysis of both fluids and core extracts was performed and variations in the distributions of fluorenones between reservoir phases are discussed concentrations of fluorenones in reservoir core extracts are often very high which may reflect sorption processes after fluorenone production but in general fluorenone abundance in flowed oils seems to be sporadic and may be related to sample age and storage history with recent production oils having lower fluorenone concentrations than corresponding older drill stem test oils while a geochemical origin for fluorenones cannot be eliminated in some settings we are concerned that these compounds may be frequently formed sporadically as a result of post sampling oxidation

the physics of wind blown loess implications for grain size proxy interpretations in quaternary paleoclimate studies abstract loess deposits are recorders of aeolian activity during past glaciations since the size distribution of loess deposits depends on distance to the dust source and environmental conditions at the source during transport and at deposition loess particle size distributions and derived statistical measures are widely used proxies in quaternary paleoenvironmental studies however the interpretation of these proxies often only considers dust transport processes to move beyond such overly simplistic proxy interpretations and toward proxy interpretations that consider the range of environmental processes that determine loess particle size distribution variations we provide a comprehensive review on the physics of dust particle mobilization and deposition furthermore using high resolution bulk loess and quartz grain size datasets from a last glacial interglacial sequence we show that because grain size distributions are affected by multiple often stochastic processes changes in these distributions over time allow multiple interpretations for the driving processes consequently simplistic interpretations of proxy variations in terms of only one factor e g wind speed are likely to be inaccurate nonetheless using loess proxies to understand temporal changes in the dust cycle and environmental parameters requires i a careful site selection to minimize the effects of topography and source distance and ii the joint use of bulk and quartz grain size proxies together with high resolution mass accumulation rate calculations if possible

short climatic oscillations in a western european loess sequence kesselt belgium this new study of the loess section at kesselt is focused mainly on the reconstruction of palaeoenvironments of the last glacial period in the belgian dutch region detailed grain size analyses in combination with the study of the palaeosols and periglacial structures indicate the occurrence of climatic cycles during loess deposition permafrost development coincided with enhanced deposition of relatively coarse loess and alternated with permafrost degradation decreased deposition of finer loess and tundra soil formation a newly designated palaeosol lafelt soil is described in detail particularly in terms of its micromorphological properties it is a luvisol and its chronostratigraphical position is still open to debate but radiocarbon dating places it in the weichselian middle pleniglacial 1998 john wiley sons ltd

results of paleoecological studies in the loess region of szeged othalom se hungary abstract new results of sedimentological magnetic susceptibility geochemical radiocarbon and malacological analysis from a typical and an infusion loess section are presented from se hungary the geologic and geomorphologic value of the area is that aeolian typical loess accumulated on sand dunes that formed during mis3 while in the interdune depressions on the top of lacustrine deposit series infusion loess developed as the two types of loess interfinger it is the first demonstration that the two types of loess formed during the same time period isochron in different environments heterotype at the end of mis3 and during mis 2 between 33 000 13 000 cal bp a temperate steppe forest steppe environment characterized the loess surface of the se great hungarian plain during the first interstadial phase of mis2 a pinus sylvestris charcoal rich paleosol layer developed on the loess covered surface of a wind blown sand hummock while in the interdune depressions a pond phase developed after the formation of the paleosol layer on the surface of the loess covered wind blown sand hummock during the heinrich 2 event vertigo modesta vallonia tenuilabris indicate a cold steppe forest steppe environment and a deeper and colder lake phase in the interdune depressions after that a short microinterstadial phase developed and a pupilla triplicata chondrula tridens dominated temperate steppe forest steppe environment evolved on the terrestrial surface between 23 000 21 000 cal bp after 21 000 cal bp in the last glacial maximum lgm the environment completely changed the average dust accumulation accelerated and coarse silt 0 02 0 06 mm became dominant as a result the lake stage transformed to a marshy environment while on the land area shade loving including closed forest environment preferring mollusca taxa appeared such as vestia turgida vitrina pellucida and mastus venerabilis based on the mollusca fauna composition humidity increased during the cooling of the lgm horizon forestation started and a boreal forest steppe evolved at the study site during the post lgm the interdune depressions filled and aeolian loess layers developed formation of the infusion loess occurred between 24 000 17 000 cal bp loess formation lasted until the beginning of the late glacial maximum last permafrost maximum and ended in a forest steppe environment with boreal central european holarctic palearctic and continental mollusc fauna elements

noble gases in h chondrites and potential differences between antarctic and non antarctic meteorites abstract thirty one antarctic h chondrites from the allan hills have been analyzed for their noble gases seven of the specimens contain solar gases thirteen have a cosmic ray exposure age around 8 ma both fractions are as observed for h chondrites from the rest of the world scrutiny of the data for paired samples yields a minimum number of 17 independent falls with 6 falls required for the 8 ma peak of exposure age the distribution of exposure ages as well as that of radiogenic 4 he and 40 ar yield no evidence that h chondrites from the allan hills region represent a mixture of populations that is different from that brought to moderate latitudes of the earth in more recent times

loess palaeosol section in sarengrad croatia a qualitative discussion on the correlation of the geochemical and magnetic susceptibility data abstract the sarengrad loess section is located on the south bank of the danube river in the easternmost part of croatia the published lithostratigraphical results including grain size total organic content calcium carbonate content and luminescence dating results are complemented by geochemical content of major and trace elements and acidity and magnetic susceptibility studies throughout the section four palaeosols are intercalated in the loess the oldest hydromorphic one is covered by laminated alluvial sediments and loess the second palaeosol is an argillic dark brown soil with the highest value of the profile and the other two palaeosols are brownish and less developed geochemical characteristics and ms signals of the palaeosols explain both the main characteristics and degree of pedogenesis palaeosol horizons could be clearly distinguished from loess based on the content of major and trace elements and on weathering coefficients such as ba sr and cao na 2 o mgo k 2 o al 2 o 3 irsl age estimates of 86 6 8 6 and 55 3 5 5 ka indicate that most of the middle and upper pleniglacial loess record is missing at the sarengrad section however the loess palaeosol sequence at sarengrad has a very detailed record correlating with mis 4 5

rapid and cyclic aeolian deposition during the last glacial in european loess a high resolution record from nussloch germany abstract this paper reports the results of an investigation of the weichselian upper pleniglacial loess sequences of nussloch rhine valley germany based on stratigraphy palaeopedology sedimentology palynology malacology and geochemistry 13 c supported by radiocarbon tl and osl dating grain size and magnetic susceptibility records are taken at 5 cm intervals from the upper pleniglacial upg loess the data indicate cyclic variations in loess deposition between ca 34 and 17 ka when the sedimentation rate is especially high 1 0 1 2 m per ka for more than 10 m the grain size index gsi ratio of coarse silt versus fine silt and clay shows variations which are assumed to be an indirect measurement of wind intensity the sedimentation rate interpreted from the profiles indicates high values in loess loess events le 1 to le 7 and low or negligible values in tundra gley horizons g1 to g8 osl ages from the loess and 14 c dates from organic matter in the loess show that loess deposition was rapid but was interrupted by shorter periods of reduced aeolian sedimentation comparison between the data from nussloch and other european sequences demonstrates a progressive coarsening of the loess deposits between ca 30 and 22 ka this coarsening trend ends with a short but major grain size decrease and is followed by an increase to a new maximum at 20 2 ka w shape correlation between the loess gsi and the greenland ice core dust records suggests a global connection between north atlantic and western european global atmospheric circulation and wind regimes in addition the typical upper pleniglacial loess deposition begins at ca 30 31 ka close to heinrich event he 3 and the main period of loess sedimentation at about 25 2 ka is coeval to he 2 correlation of magnetic susceptibility and grain size records shows that the periods characterised by high gsi coincide with an increase in the amount of ferromagnetic minerals reworked from the rhine alluvial plain they suggest enhancement in the frequency of the storms from n nw these results are integrated within a palaeogeographical model of dust transport and deposition in western europe for the weichselian upper pleniglacial or late pleniglacial

acfer 182 and paired samples an iron rich carbonaceous chondrite similarities with alh85085 and relationship to cr chondrites three samples of a new fe rich chondrite were found in the sahara in 1990 and 1991 acfer 182 acfer 207 acfer 214 the samples are paired and the meteorite will be designated as acfer 182 the chondrite is chemically texturally and mineralogically similar to the allan hills meteorite alh85085 one important difference between the two meteorites is the smaller average chondrule size in alh85085 the major components of acfer 182 in decreasing abundance are 1 1 highly altered by terrestrial weathering matrix 2 2 mineral and polymineralic silicate fragments and aggregates 3 3 chondrule fragments 4 4 chondrules 5 5 metal 6 6 fine grained dark inclusions the abundance of chondrules is lower and the average chondrule size 90 m smaller than in most other chondrites chondrule fragments are often so large that they cannot be derived from the present chondrule population apparently size sorting has prevented accumulation of the larger parent chondrules several spectacular ca al rich inclusions were found rich in ca dialuminate hibonite or zr y sc bearing phases the chemical composition of acfer 182 and of alh85085 are almost indistinguishable major chemical signatures are 1 1 uniform enrichment of fe and other nonvolatile metals relative to ci chondrites by about 70 2 2 absence of enrichment in refractory lithophiles characteristic of most type 2 and 3 carbonaceous chondrites 3 3 strong depletion of volatile and moderately volatile elements based on the oxygen isotopic composition the chemical composition and the abundances of chondrules and matrix acfer 182 should be classified as a carbonaceous chondrite considering their affinity to carbonaceous chondrites and their high bulk iron content the two meteorites acfer 182 and alh85085 are designated as ch chondrites there are mineralogical and chemical similarities among acfer 182 alh85085 and cr chondrites which distinguish these meteorites from other types of carbonaceous chondrites 1 1 low feo contents of olivine and pyroxene and correspondingly high metal contents 2 2 high cr content in olivine 3 3 abundant fine grained dark inclusions 4 4 abundant ca dialuminate caal4o7 in cais 5 5 similarities in oxygen isotopic composition 6 6 low contents of moderately volatile elements 7 7 low refractory element contents 8 8 presence of a unique component of subsolar rare gases these observations suggest similar conditions of formation for the components of these meteorites a single common parent body is unlikely in view of the differences in chemical composition and in the size distribution of individual components

malacological and sedimentological evidence for warm glacial climate from the irig loess sequence vojvodina serbia four loess units and three paleosol layers are preserved in the irig brickyard vojvodina serbia amino acid geochronology provides stratigraphic correlations between loess units v l1 and v l2 at the irig section with loess of glacial cycles b and c respectively described from other central european localities luminescence dating results for the upper loess layers v l1l1 and v l1s1l1 confirm the geological interpretations although in samples below paleosol v l1s1s2 the age increase with depth is less than in our proposed age model magnetic susceptibility and sedimentological evidence from the irig loess paleosol sequence show general similarities with the mis 6 1 pattern of the specmap oxygen isotope curve malacogical investigations at the irig site reveal the continuous presence of the chondrula tridens and helicopsis striata faunal assemblages throughout the last glacial and final part of the penultimate glacial loess the loess snail fauna which is characterized by the complete absence of cold resistant species suggests a stable dry and relatively warm glacial climate compared with other central european loess localities furthermore these data suggest that the southern slope of fruska gora was a refugium for warm loving and xerophilus mollusc taxa during the otherwise unfavorable glacial climates of the late pleistocene

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

mis3 2 millennial oscillations in greenland dust and eurasian aeolian records a paleosol perspective abstract since their discovery the abrupt climate changes that punctuated the last glacial period 110 6 14 62 ka have attracted considerable attention originating in the north atlantic area these abrupt changes have been recorded in ice marine and terrestrial records all over the world but especially in the northern hemisphere with various environmental implications ice core records of unprecedented temporal resolution from northern greenland allow to specify the timing of these abrupt changes which are associated with sudden temperature increases in greenland over a few decades very precisely the continental records have so far been mainly interpreted in terms of temperature precipitation or vegetation changes between the relatively warm greenland interstadials gi and the cooler greenland stadials gs here we compare records from greenland ice and northwestern european eolian deposits in order to establish a link between gi and the soil development in european mid latitudes as recorded in loess sequences for the different types of observed paleosols we use the correlation with the greenland records to propose estimates of the maximum time lapses needed to achieve the different degrees of maturation and development to identify these time lapses more precisely we compare two independent ice core records 18 o and dust concentration indicating variations of atmospheric temperature and dustiness in the greenland area respectively our method slightly differs from the definition of a gi event duration applied in other studies where the sharp end of the 18 o decrease alone defines the end of a gi we apply the same methodology to both records i e the gis are defined to last from the beginning of the abrupt 18 o increase or dust concentration decrease until the time when 18 o or dust recur to their initial value before the gi onset determined both visually and algorithmically and compare them to published estimates of gi timing and duration the duration of the gi and consequently the maximum time for paleosol development varies between 200 and 4200 years when visually determined and between 200 and 4800 years when estimated algorithmically for gi 17 to 2 i e an interval running from 60 ka to 23 ka b2k age before 2000 ad furthermore we investigate the abruptness of the transition from stadial to interstadial conditions which initiates the paleosol development the average transition duration is 55 4 16 1 56 8 19 6 years when determined visually and 36 4 13 4 60 00 21 2 years when determined algorithmically for the 18 o dust concentration the 18 o increases correspond to a mean temperature difference of 11 8 c on the top of the greenland ice sheet associated with substantial reorganizations of the ecosystems in mid latitude europe

the effects of thermal maturity on distributions of dimethylnaphthalenes and trimethylnaphthalenes in some ancient sediments and petroleums abstract the distributions of di and trimethylnaphthalenes in two sedimentary sequences from western australia have been examined by capillary gas chromatography and combined gas chromatography mass spectrometry a general decrease was observed in the relative proportions of dimethylnaphthalenes and trimethylnaphthalenes with increasing thermal maturity similar trends were also observed for six crude oils which have very different ratios of ethylcholestane epimers indicating very different thermal histories these results suggest that changes in the relative abundances of certain methyl substituted naphthalenes may be useful indicators of thermal maturity of sedimentary organic matter and the use of a number of isomer ratios is illustrated

the size distribution of microparticles from selected segments of the greenland ice core project ice core representing different climatic periods the size distribution of insoluble microparticles dust in the particle size interval 0 4 6 0 m radius has been measured in more than 1400 samples from the greenland ice core project grip deep ice core from summit greenland the samples were taken from ice core segments representing 32 climatic periods including ice from the eem interglacial and ice from below the eemian ice the mean dust volume distributions from the climatic periods are compared and the relationship of total dust mass to the concentration of ca2 and to the stable isotopic composition 18o is investigated the dust volume distributions are found to be lognormal in the size interval 0 4 2 0 m with nearly identical shapes changes of the lognormal part of the volume distributions are found to be connected to the total dust mass in a systematic way the total dust mass is correlated to the ca2 concentration and data do not show any enrichment in ca2 from exposed continental shelves due to lower sea levels during the last glacial maximum the total dust mass is strongly connected to 18o the volume distribution of the particles in the size interval 2 0 6 0 m is found to be almost the same in most periods the exceptions are the cold periods in the last part of the last glacial period where the volume of these particles is higher than in most periods and the periods from the eemian and just above the eemian where the volume of these particles is lower the volume distributions of both the eemian warm periods and the cold eemian events are different from the distributions in ice from both below and above the eemian ice climate changes appear to have modified the processes of production transport modification and deposition of the dust aerosol in the same way over the last 120 000 years or more

paired renazzo type cr carbonaceous chondrites from the sahara ten chondrites with chemical and mineralogical similarities to the carbonaceous chondrite renazzo were recovered at two locations of the sahara acfer 059 087 097 114 139 186 187 209 270 and el djouf 001 although the el djouf location is more than 500 km away from the acfer location all samples appear to result from a single fall based on chemical and petrographic similarities and supported by light element stable isotope geochemistry noble gas record and similar 26al contents the acfer el djouf meteorite is classified as a cr renazzo type carbonaceous chondrite this group presently comprises three non antarctic members al rais renazzo acfer el djouf and five antarctic meteorites the major lithological components of the acfer el djouf meteorite are large chondrules up to 1 cm in size mean diameter 1 0 0 6 mm chondrule and mineral fragments ca al rich inclusions feni metal about 8 10 vol and dark inclusions embedded in a fine grained fragment bearing groundmass mineral compositions of the ten acfer el djouf samples are similar to those of other cr chondrites most of the ca al rich inclusions are below 300 m in size and rich in melilite and spinel in some cais the rare phase caal4o7 is dominant fo rich cr bearing olivine fa0 4 and enstatite fs0 4 are the major phases of the chondrite the meteorite is mildly shocked with a shock stage of s2 indicating a peak shock pressure of 5 10 gpa for the bulk meteorite the oxygen isotopic compositions and carbon and nitrogen stable isotope geochemistry of the acfer el djouf samples are very similar to those of the other cr type chondrites the major element composition of the acfer el djouf meteorite is indistinguishable from cr chondrites when compared to renazzo the acfer el djouf samples however have systematically lower contents of the moderately volatile elements zn ga as au sb and se and the highly volatile elements br c and n this is thought to reflect primary differences between renazzo and the acfer el djouf meteorite

on the reliability and comparability of laser diffraction grain size measurements of paleosols in loess records abstract laser diffraction grain size data and size distributions of paleosols are widely used in paleoenvironmental reconstructions as physicochemical alteration related proxies of past changes of the sedimentary environment different laser diffraction devices optical theories and optical settings are being applied nowadays and ignorance of several uncertainty factors and drawbacks of this indirect grain size characterization approach has led to poorly comparable and reproducible granulometric datasets here we present a detailed comparison of grain size results acquired by three state of the art widely used laser diffraction devices fritsch analysette 22 microtec plus horiba partica la 950 v2 and malvern mastersizer 3000 grain size distributions were calculated using both the fraunhofer and mie scattering theories and a wide variety of optical settings 68 different complex refractive indices 1 45 1 6 0 01i 1i for 10 samples from loess paleosol sequences of the carpathian basin our findings demonstrate that optical settings have significant effects on grain size distributions especially for the finest fractions clay and fine silt populations interestingly the selection of laser diffraction devices was an even more deterministic factor in grain size characterization as revealed by network analyses clustering of bulk and size fractionated grain size records was primarily determined by the device used and also by the applied optical settings at the same time the real physical differences of samples were found to be deterministic exclusively for the sand sized fraction as such these findings emphasize the importance of the accurate description of applied methodological details in research papers as comparability and reproducibility of granulometric datasets cannot be ensured with a lack of information about instrumental conditions and settings

the origin of chondritic macromolecular organic matter a carbon and nitrogen isotope study the n and c abundances and isotopic compositions of acid insoluble carbonaceous material in thirteen primitive chondrites five unequilibrated ordinary chondrites three cm chondrites three enstatite chondrites a ci chondrite and a cr chondrite have been measured by stepped combustion while the range of c isotopic compositions observed is only delta 13c 30 the n isotopes range from delta 15n approximately 40 to 260 after correction for metamorphism presolar nanodiamonds appear to have made up a fairly constant 3 4 wt of the insoluble c in all the chondrites studied the apparently similar initial presolar nanodiamond to organic c ratios and the correlations of elemental and isotopic compositions with metamorphic indicators in the ordinary and enstatite chondrites suggest that the chondrites all accreted similar organic material this original material probably most closely resembles that now found in renazzo and semarkona these two meteorites have almost m shaped n isotope release profiles that can be explained most simply by the super position of two components one with a composition between delta 15n 20 and 40 and a narrow combustion interval the other having a broader release profile and a composition of delta 15n approximately 260 although isotopically more subdued the ci and the three cm chondrites all appear to show vestiges of this m shaped profile how and where the components in the acid insoluble organics formed remains poorly constrained the small variation in nanodiamond to organic c ratio between the chondrite groups limits the local synthesis of organic matter in the various chondrite formation regions to at most 30 the most 15n rich material probably formed in the interstellar medium and the fraction of organic n in renazzo in this material ranges from 40 to 70 the isotopically light component may have formed in the solar system but the limited range in nanodiamond to total organic c ratios in the chondrite groups is consistent with most of the organic material being presolar

the preservation state of organic matter in meteorites from antarctica the recovery of large numbers of meteorites from antarctica has dramatically increased the amount of extraterrestrial material available for laboratory studies of solar system origin and evolution yet the great age of antarctic meteorites raises the concern that significant amounts of terrestrial weathering has corrupted their pre terrestrial record organic matter found in carbonaceous chondrites is one of the components most susceptible to alteration by terrestrial processes to assess the effects of antarctic weathering on both non antarctic and antarctic chondritic organic matter a number of cm chondrites have been analyzed mossbauer spectroscopy has been used to ascertain pre terrestrial and terrestrial oxidation levels while pyrolysis gas chromatography mass spectrometry was used to determine the constitution of any organic matter present increased oxidation levels for iron bearing minerals within the non antarctic chondrites are likely to be a response to increased amounts of parent body aqueous alteration parent body processing also appears to remove ether bonds from organic material and alkyl side chains from its constituent units the iron in antarctic chondrites is generally more oxidized than that in their non antarctic counterparts reflecting terrestrial weathering antarctic weathering of chondritic organic matter appears to proceed in a similar way to parent body aqueous alteration and simply enhances the organic responses observed in the non antarctic data set degradation of the record of preterrestrial processes in antarctic chondrites should be taken into account when interpreting data from these meteorites

quartz osl dating of late quaternary chinese and serbian loess a cross eurasian comparison of dust mass accumulation rates abstract reconstructing dust mass accumulation rate mar from loess deposits is critical to understanding past atmospheric mineral dust activity and requires accurate independent age models from loess deposits across europe and asia previous correlations of loess in europe and china have tended to focus on multi millennial timescales with no detailed examination of dust mar at the two ends of the eurasian loess belt on shorter sub orbital scales here we present a detailed quartz optically stimulated luminescence osl chronology from the serbian titel loess plateau veliki surduk loess core and the chinese loess plateau lingtai section the luminescence ages pass internal tests and show consistent increases in age with depth with no obvious major hiatuses however as reported before it seems the quartz osl technique is only capable of accurate age determination up to accrued doses of ca 150 gy ca 30 40 ka due to approaching field saturation of the quartz osl signal two age depth models were used to reconstruct dust mars where one utilises osl data solely and the other additionally makes assumptions about sedimentation rates although short term fluctuations in mar are model dependent general mar patterns between the two sites are very similar with peak mar occurring rather late in the last glacial ca 13 25 ka this suggests that at least broad scale trends in dust activity within the last glacial period may be similar at a continental scale

aqueous alteration in cr chondrites meteorite parent body processes as analogue for long term corrosion processes relevant for nuclear waste disposal aqueous alteration of carbonaceous chondrites is one of the fundamental processes on accreting planetesimals that changes pristine materials from the formation of the solar system the study of mineralogical petrological and chemical changes resulting from this alteration provides insight into the physical and chemical setting of forming planetesimals cr chondrites provide samples for all stages of aqueous alteration from type 3 to 1 entirely hydrated and are thus suited to study the alteration of pristine materials in a coherent sequence vitrification is a common way to store and stabilize fission products and minor actinides resulting from the reprocessing of nuclear spent fuel in a nuclear boro silica glass in steel containers the waste material has to be stored safely for a period of at least 105 106 years in a clay rich geological repository laboratory experiments being too short to follow the long term evolution of these materials we analyzed the mineralogical petrological and chemical changes in a series of cr chondrites renazzo cr2 al rais cr2 and gro 95577 cr1 to serve as analogues rims of secondary materials around metal grains in contact to the fine grained matrix serve as analogue to the interface between steel containment and the surrounding clay rich geological layer while chondrule glassy mesostasis is used as a proxy of the nuclear glass with increasing degree of aqueous alteration in the sequence renazzo al rais gro 95577 the size of the rims increase fe rich alteration rims are 10 m in thickness around metal grains in the fine grained matrix in renazzo in al rais multi layered structures of interchanging fe s and p ca rich layers appear with a thickness of up to 30 m in the highly altered gro 95577 extensive inner and external rims of secondary phases reach up to 200 m into the surrounding matrix in chondrules metal in contact with the altered mesostasis shows similar trends but with thinner alteration rims altered mesostasis is similar to the surrounding fine grained matrix consisting of serpentine and smectite however the chemistry has not completely equilibrated as indicated by e g a remaining high al contents 2 2 wt fine grained matrix and altered mesostasis show a trend towards decreasing fe with progressing alteration matrix is also the main source of s in the alteration system most of the dissolved species stays close to the source the main source for fe ni p and also ti cr and mn is the altered metal these findings confirm the model for long term corrosion of nuclear disposal sites alteration rims of iron oxides form around the steel containments whereas dissolved species fe al and si diffuse into the surroundings

normal alkanes in meteorites molecular δ13c values indicate an origin by terrestrial contamination in the time period since 1961 n alkanes straight chain hydrocarbons have been detected in varying amounts in many meteorites proposed origins for these compounds have included extraterrestrial biotic extraterrestrial abiotic and terrestrial contamination processes to help establish the source of these compounds we determined the carbon isotopic compositions of individual n alkanes in meteorites of several different classes and terrestrial histories orgueil ci1 cold bokkeveld cm2 murchison cm2 vigarano cv3 allende cv3 ornans co3 and bishunpur ll3 the efficiency of supercritical fluid extraction sfe was exploited to provide extractable non polar organic matter from the meteorites the n alkanes in these extracts were then identified with gas chromatography mass spectrometry gc ms and the carbon isotopic composition of individual molecules was determined using isotope ratio monitoring gas chromatography mass spectrometry irm gc ms n alkanes were found in all but one of the meteorites analysed allende but carbon number distributions varied between samples pristane and phytane were also detected in five of the seven meteorites 13c values for the individual n alkanes occupied a range from 25 3 to 38 7 the 13c values for the meteoritic n alkanes have a similar range as those for n alkanes measured from petroleum in the literature therefore the n alkanes in meteorites appear to be terrestrial contaminants which may have originated from fossil hydrocarbons or petroleum products this type of contamination is analogous to that which will be threatening future meteorite falls and the samples returned from spaceflight missions over the next two decades and beyond for falls already contaminated irm gc ms appears useful in discriminating between indigenous compounds and those introduced by terrestrial contamination

differences between antarctic and non antarctic meteorites an assessment abstract the discovery of a statistically significant number of meteorites in antarctica over the past 20 years has posed many questions one of the most intriguing suggestions that came up during the study of the antarctic samples was that there might be a difference between the parent populations of antarctic and non antarctic meteorites this interpretation was put forward after the detection of a significant difference in the abundances of volatile and mobile trace elements in h l and c chondrites and achondrites other major differences include the occurrence of previously rare or unknown meteorites different meteorite type frequencies petrographic characteristics oxygen isotopic compositions and smaller average masses in addition antarctic meteorites have greater terrestrial residence ages and have collected on the ice shield over several 10 5 years the reality of numerous such differences has now been established beyond doubt however the main question regarding the cause of these differences remains it seems that they have a wide variety of origins ranging from pre terrestrial traits to collection recovery effects and terrestrial weathering studies of terrestrial weathering have shown that over the long time the meteorites spend in and on the ice even subtle processes can produce substantial effects for future investigations it will be important to pay more attention to the weathering status of samples and to develop a more reliable and quantitative weathering index e g based on infrared reflectance spectrometry or differential scanning calorimetry not all differences between the antarctic and non antarctic meteorite populations can be explained by weathering pairing or different collection procedures variable trace element abundances and distinct differences in the thermal history and thermoluminescence characteristics have to be interpreted as being pre terrestrial in origin such differences imply the existence of meteoroid streams whose existence poses problems in the framework of our current knowledge of celestial mechanics however several independent studies support the existence of such meteoroid streams thus being consistent with the suggestion of a time variable influx of extraterrestrial material to earth the generally smaller average size of antarctic meteorites may be the cause for the different meteorite type frequency and the higher abundance of rare samples because smaller meteorites may come from a slightly different parent population in this paper we summarize the contributions in this series and provide a review of the current state of the question for the reality and cause of differences between antarctic and non antarctic meteorites

high resolution record of the last climatic cycle in the southern carpathian basin surduk vojvodina serbia abstract high resolution study of the surduk loess palaeosols sequence in serbia vojvodina has been performed within a research project eole focusing on the impact of rapid climatic changes during the last climatic cycle in the european loess belt the methodology used for this multidisciplinary approach is based on a continuous sampling column that allows a very accurate correlation between all studied proxies magnetic susceptibility grain size and organic carbon and the dated samples irsl 14 c according to the stratigraphical and sedimentological data the surduk loess sequence appears as a very complete record of the last climatic cycle 19 m and exhibits a similar pattern than other contemporaneous loess sequences from western central and eastern europe the main difference is the evidence of a drier environment all over the last climatic cycle sedimentological and palaeopedological data the high resolution grain size record 5 cm is well correlated with stratigraphical boundaries and highlights a strong variability within the loess deposition especially during the upper pleniglacial between ca 33 and 15 ka during the upper pleniglacial a succession of millennial timescale events characterised by the deposition of coarser loess are particularly well evidenced by grain size data as in some west european records finally an attempt to correlate the variations of grain size parameters at surduk with the greenland grip dust record is proposed according to this study millennial timescale climatic events that characterise the north atlantic area during the last climatic cycle have thus been recorded in the environments located at the southern border of the european loess belt

paleoenvironments from robust loess stratigraphy using high resolution color and grain size data of the last glacial krems wachtberg record ne austria abstract the complex interplay of dust sedimentation pedogenesis and erosion reworking in the formation of loess paleosol sequences lps challenges paleoenvironmental proxies here we show that color and grain size are essential parameters characterizing loess profiles and support robust stratigraphies as a basis for reconstructions in the context of local geo ecological and large scale paleoclimatic evolution detailed paleoenvironmental records from the period since the arrival of anatomically modern humans to the last glacial maximum are scarce in the alpine surroundings the c 7 5 m thick lps krems wachtberg ne austria known for its well preserved upper paleolithic context at a depth of 5 5 m formed between 40 and 20 ka bp by quasi continuous dust sedimentation interrupted by phases of incipient pedogenesis and local reworking the new kw2015 composite is based on three sections studied and sampled at 2 5 cm resolution color and grain size data support a robust stratigraphy for reconstructions of the pedosedimentary evolution the marked transition from oxidized to reduced paleosols of kw2015 around 34 35 ka corresponds to the middle to upper pleniglacial transition as part of a general cooling trend from marine isotope stage mis 3 to 2 intensely modulated by millennial scale climatic fluctuations as recorded in the greenland ice core data the distinct response of kw2015 to these trends highlights that reconstructing lps evolution based on a robust stratigraphy is a prerequisite to paleoenvironmental proxy interpretation

mineralogy and composition of matrix and chondrule rims in carbonaceous chondrites abstract the degree of compositional variation of fine grained minerals displayed by the members within any carbonaceous chondrite group i e ci cm cv cr is a direct reflection of the range of aqueous alteration assemblages present matrix and fine grained chondrule rims within any particular carbonaceous chondrite are mineralogically nearly identical to one another but not necessarily similar in bulk elemental composition even though they have subsequently experienced post accretional secondary processing aqueous alteration under identical conditions this may indicate preferential alteration of one component brecciation exchange of components between rims and matrix and or accretion of matrix and rims from mineralogically or compositionally distinct materials we propose that co chondrites experienced parent body conditions of low f o2 low water rock ratios and temperatures below 50 c cr chondrites experienced higher water rock ratios potentially higher temperatures 150 c and a wide range of f o2 the alteration mineralogy of cv chondrites indicates water rock ratios at the high end at least of the range for cr chondrites essebi and mac 87300 cm chondrites experienced temperatures below 50 c low f o2 and low water rock ratios except eet 83334 which probably experienced relatively higher f o2 and b 7904 and y 86720 which experienced postalteration temperatures in the range 500 700 c most ci chondrites experienced temperatures between 50 and 150 c relatively high water rock ratios and variable f o2 with a late stage increase in the latter due possibly to brecciation and consequent release of methane y 82162 witnessed post alteration heating possibly as high as 400 c

late pleistocene climatic variations at achenheim france based on a magnetic susceptibility and tl chronology of loess abstract new field investigations of the achenheim sequence alsace france allow for the characterization of variations in the low field magnetic susceptibility over most of the last climatic cycle i e the past 130 000 yr new stratigraphic data and thermoluminescence measurements permit reassessment of the previous chronological interpretation of the upper pleistocene at achenheim a high resolution analysis of magnetic susceptibility discloses the occurrence of a fine grained marker horizon which was also found recently in another section this horizon is interpreted as a small scale dust layer deposited prior to the main interval of loess deposition the horizon deposited at the marine isotope stage mis 5 4 boundary has been found in other loess sequences and is especially prevalent in central europe it is characterized by low susceptibility values and a grayish color new thermoluminescence dates indicate that the loess deposition took place after the mis 5 4 boundary i e after 70 000 yr these results are consistent with the greenland grip ice core dust record which also demonstrates a dusty atmosphere after 72 000 yr ago on a more regional scale the achenheim loess sequence demonstrates a reliable correlation between the western side of the eurasian loess belt and the dust record of the greenland ice cores

tropical oceanic rainfall and sea surface temperature structure parsing causation from correlation in the mjo abstractbased upon on the findings of y li and r e carbone the association of tropical rainfall with sst structure is further explored with emphasis on the mjo passband analyses include the tropical indian ocean maritime continent and tropical western pacific regions the authors examine the anomalies of and correlations between sst structure the frequency of rainfall events and rainfall amount based on detailed examination of a 49 month time series all findings are statistical inferences and interpretations consistent with established theory the statistical inferences are broadly consistent with a pivotal role played by the convergent laplacian of sst together with an expected but somewhat indirect role of sst itself the main role of sst in the mjo passband appears limited to production of moist static energy which is highly correlated with cumulative precipitation yet bears a decidedly conditional relationship to the occurrence of rainfall if rain occurs then more rain is likely over

abrupt millennial climatic changes from nussloch germany upper weichselian eolian records during the last glaciation abstract increasing attention has been focussed on the massive iceberg discharges in the north atlantic heinrich events during the last glaciation and their worldwide terrestrial counterparts however these events are particular episodes among more regular cyclic events named dansgaard oeschger events in ice cores or bond cycles in marine cores here we examine grain size 13c and magnetic susceptibility data from nussloch one of the most complete west european eolian sequence examined so far these indices indicate that during the 31 19 kyr interval using chronology provided by radiocarbon osl and tl dates millennial scale variations occurred affecting both precipitation and vegetation furthermore these are associated with oscillations in the wind strength matching the dust deposition rate in greenland as recorded in the grip ice core our study shows that the abrupt climatic changes the dansgaard oeschger events are also recorded in the west european loess sequences this implies an atmospheric mechanism linking dust deposition over greenland and europe which is probably connected to global climatic events during the last glaciation

geochemical investigations to explain iodine overabundances in antarctic meteorites abstract iodine bromine and chlorine concentrations were determined in different antarctic meteorite specimens eucrites high iron and low iron chondrites with isotope dilution mass spectrometry in all antarctic meteorites i overabundances have been analysed compared with the concentrations for non antarctic meteorites of the same class half of the antarctic specimens show especially high concentrations of more than 1 g a similarly high enrichment effect in antarctic meteorites was not found for br and cl but smaller cl excesses could be observed in some eucrites and high iron chondrites by analysing different types of antarctic rocks a significant decrease of the i concentration but not of the br and cl concentration was determined from the surfaces to the centers of the rocks this shows that atmospheric i compounds interact with the surfaces of antarctic rocks and therefore with those of antarctic meteorites as well analyses of atmospheric halogens show that the gaseous compound ch 3 i is probably responsible for the i overabundance in antarctic meteorites and rocks chloride and bromide are found in particles derived from sea spray in antarctic aerosols deposition of halogens in antarctic snow near the coast shows i cl ratios 10 190 higher than the average value for seawater the corresponding br cl ratios are in the same range as seawater on the basis of our results and of other reported data we construct a preliminary hypothesis for a geochemical i cycle in antarctica taking into consideration long distance and short distance transportation of different i compounds from the coast to inland antarctica

dust sources and deposition during the last glacial maximum and current climate a comparison of model results with paleodata from ice cores and marine sediments mineral dust aerosols in the atmosphere have the potential to affect the global climate by influencing the radiative balance of the atmosphere and the supply of micronutrients to the ocean ice and marine sediment cores indicate that dust deposition from the atmosphere was at some locations 2 20 times greater during glacial periods raising the possibility that mineral aerosols might have contributed to climate change on glacial interglacial time scales to address this question we have used linked terrestrial biosphere dust source and atmospheric transport models to simulate the dust cycle in the atmosphere for current and last glacial maximum lgm climates we obtain a 2 5 fold higher dust loading in the entire atmosphere and a twenty fold higher loading in high latitudes in lgm relative to present comparisons to a compilation of atmospheric dust deposition flux estimates for lgm and present in marine sediment and ice cores show that the simulated flux ratios are broadly in agreement with observations differences suggest where further improvements in the simple dust model could be made the simulated increase in high latitude dustiness depends on the expansion of unvegetated areas especially in the high latitudes and in central asia caused by a combination of increased aridity and low atmospheric co2 the existence of these dust source areas at the lgm is supported by pollen data and loess distribution in the northern continents these results point to a role for vegetation feedbacks including climate effects and physiological effects of low co2 in modulating the atmospheric distribution of dust

fossil redox conditions influence organic matter composition in loess paleosols the soil memory recorded in paleosols of loess paleosol sequences is an important contributor to our understanding of past climatic conditions molecular proxies based on the organic matter preserved in paleosols form an essential part of this record but the long term preservation of som is poorly understood especially for sediment traps and slope profiles this paper addresses the composition of organic material from the early weichselian a horizons of the rocourt paleosol a major paleostratigraphic marker for the eemian and early weichselian in western europe naoh extractable organic matter from an exceptionally thick rocourt profile in the kesselt quarry belgian loess belt was analyzed by pyrolysis gas chromatography mass spectrometry pyrolysis gc ms and the results evaluated against paleopedological data the molecular composition of the organic matter at kesselt was compared with reference samples from two nearby quarries including the type locality at veldwezelt hezerwater and to a sample from the contemporary nussloch sequence in germany the som composition found at the four sites indicated a large content of microbial matter and was dominated by carbohydrates and n compounds many of which were not reported before from som pyrolysates differences in the molecular composition between samples both within profiles and between sites coincided with differences in landscape position slope shoulder plateau and fossil redox conditions surface gleys samples form drier and more upland situations contained more burnt material while samples from slope profiles and surface gleys contained even more microbial material in particular chitin results therefore suggest that the admixture of microbial som is considerable in loess paleosols and that differences in edaphic conditions in particular slope position and soil moisture and occurrence of wildfires are important for the long term preservation of som these should therefore be considered when interpreting biogeochemical proxies

update on terrestrial ages of antarctic meteorites abstract cosmic ray produced 36 cl half life 3 01 10 5 years has been measured in 90 antarctic meteorites by accelerator mass spectrometry the terrestrial ages of the meteorites were calculated from the results after excluding possible paired objects 138 terrestrial ages from 18 different locations are available from 14 c 81 kr and 36 cl measurements for application to antarctic meteorite and glaciological studies the terrestrial ages of allan hills meteorites vary from 2000 years to 1 million years and are clearly longer than those of yamato meteorites and other antarctic meteorites the oldest allan hills meteorites were found close to the eastern edge and in the southeast of the main icefield among all antarctic meteorites measured to date only l and ll chondrites have terrestrial ages older than 370 000 years

late pleistocene landscape dynamics in saxony germany paleoenvironmental reconstruction using loess paleosol sequences abstract loess archives are of paramount importance for reconstructing regional paleoenvironmental conditions of past glacial periods the saxonian loess region is an area of transition between the western and the eastern european loess belt with this contribution a documented loess paleosol composite profile for the saxonian loess region is extended and a new chronostratigraphy established by high resolution osl dating of two profiles is described in addition for the first time osl age estimates for the loess paleosol sequence at seilitz are presented for the quartz and polymineral fine grain fraction based on the presented composite profile climatic and environmental conditions e g wind speed temperature are deduced based on high resolution osl dating it is possible to identify a hiatus spanning ca 30 ka this gap is located in the gleina complex where an underlying layer shows an age of ca 60 ka and the upper layer an age of ca 30 ka additionally two periods of strong loess accumulation with ages of ca 70 60 ka and 30 18 ka could be identified there is a general trend of grain size coarsening up towards the late glacial which shows a maximum at ca 21 ka correlations with french western german and polish loess sections are discussed

antarctic and non antarctic meteorites form different populations compared with non antarctic falls antarctic meteorites include many of hitherto rare unique or unknown type1 such as lunar and putative martian samples2 4 attention has not previously been paid to the more common sorts of antarctic meteorites and here we focus on the most frequently encountered h5 chondrites we find that compositional differences between antarctic and non antarctic specimens of this class especially those involving thermally sensitive trace and ultra trace elements are so substantial that it seems extremely doubtful that the two sample populations are derived from the same parent population this implies that the contemporary falls less than 200 years old and the substantially older on average 300 000 years for victoria land antarctic meteorites either differ in genetic history or sample different extraterrestrial parent populations or both

origin of metallic fe ni in renazzo and related chondrites abstract the anomalous positive co ni correlation among metal grains from the renazzo and al rais chondrites reported in previous studies has two components 1 1 a chondrule trend that extends up to 120 145 mg g ni probably reflects the mixing of fe rich and fe poor nebular metal and 2 2 a weak extrachondrule trend that spans a ni range from 40 70 mg g reflects fe introduction during mild metamorphism to assess the formation of this metal we determined ni and co zoning profiles in metallic fe ni from different petrographic sites chondrule interiors chondrule margins chondrule rims and matrix in renazzo al rais and the related chondrite macalpine hills 87320 metal from chondrule interiors shows flat ni and co concentrations and profiles moderately large grain to grain compositional variations even within chondrules and generally high ni and co nickel concentrations extend above the kamacite stability limit etching such martensite shows high ni domains in some cases but observed ni concentrations do not exceed 190 mg g metal from chondrule margins adjacent to matrix shows convex inverted u shaped ni and co zoning profiles the highest ni and co concentrations are at grain centers although the mean central ni and co concentrations in margin grains are much lower than those in metal from chondrule interiors about half of the matrix metal shows flat co and ni profiles like those from chondrule interiors the remainder are convex the differences in mean co and ni contents between chondrules and extrachondrule materials may reflect differential sampling of nebular metal grains having compositions that varied with particle size we interpret the low co and ni contents at the edges of grains in chondrule margins to reflect dilution by fe produced by feo reduction the reduction seems not to have occurred in the nebula but rather during a brief period of parent body metamorphism reduction of fine grained feo produced metallic fe that plated onto nearby metal grains although diffusive exchange between pentlandite and metal could produce the observed ni gradient it is doubtful that it could produce the similar gradient of co metal from chondrule interiors was inaccessible during the reduction event and retained the flat profiles established during chondrule formation

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

palaeotemperature reconstruction during the last glacial from δ18o of earthworm calcite granules from nussloch loess sequence germany abstract the nussloch loess palaeosol sequence rhine valley germany is considered to be one of the most complete records of the last glacial period in western europe due to its very high sedimentation rate and its good chronological control this sequence is therefore a good framework in which to develop new proxies for palaeoenvironmental reconstructions in this study we explore for the first time the potential of earthworm calcite granules as a new bio indicator and climatic proxy of absolute air and soil temperature in the context of last glacial loess these granules are composed of rhomboedric calcite crystals organized in a radial crystalline structure as these granules are individually generated by earthworms at a relative fast rate they are expected to record intra annual variations in the available sources of oxygen percolating waters of meteoric origin we extracted thirty earthworm calcite granules from 11 of 5 cm layers thick from tundra gley and brown soil horizons previously dated at 45 to 23 ka oxygen isotope ratios were measured on each individual granule the 18o of calcite granules and interlinked transfer functions between water cycle air and soil temperatures allowed us to estimate air temperatures ranging from 10 to 12 4 c which most likely reflect the warm periods of the year when earthworms were the most active

the effect of biodegradation and water washing on the occurrence of alkylphenols in crude oils abstract biodegraded oils from california and nigeria were analysed to assess the impact of biodegradation upon alkylphenol occurrence in crude oils the extent of biodegradation in the 13 californian samples ranged from very mild full n alkane distribution present to moderate complete degradation of c 15 n alkanes and significant reduction of acyclic isoprenoids corresponding to a range of n alkanes and acyclic isoprenoids stage 5 the data from the naturally degraded sample suites were compared to the results of an in vitro aerobic biodegradation experiment conducted with a north sea oil biodegradation resulted in significant reduction in total alkylphenol abundance and preferential depletion of c 3 and c 2 alkylated compounds in the nigerian and laboratory degraded samples these effects were most pronounced in oils in which the methylated naphthalenes had been biodegraded biodegradation stage 4 or 5 there was no clear relationship between alkylphenol abundance or molecular distributions and the extent of biodegradation in the californian samples although alkylphenol distributions in the biodegraded samples were generally dominated by the c 3 compounds simple oil water partition calculations showed that these distributions were consistent with the effects of water washing

structural deformation of the leoville chondrite foliations defined by alignment of elongated chondrules have been noted previously in chondrites but none displays this effect so well as leoville cv3 the shapes of leoville chondrules were produced by deformation in situ as indicated by inclusions and clasts with similar shapes and preferred orientations to those of chondrules similarities in the aspect ratios of apparent strain ellipses measured for chondrules alone 1 9 and 2 0 by several methods and for the whole meteorite 2 0 indicate either that leoville deformed homogeneously or that it deformed as a framework of touching chondrules this amount of strain corresponds to approximately 33 uniaxial shortening assuming constant volume because the strain ellipse was measured in only one orientation this strain value is a minimum estimate for the meteorite lack of correlation between foliation and either shock or thermal effects argues that impact or metamorphism are unlikely to have produced this deformation compaction due to overburden from progressive accretion on the chondrite parent body is suggested to have been its cause estimates of maximum deviatoric stresses in the interiors of asteroid sized bodies and constraints on maximum temperatures for cv3 chondrites are consistent with diffusional flow as the deformation mechanism for olivine in these chondrules diffusional flow is also suggested by the scarcity of observed lattice dislocations deformation of leoville olivines by this mechanism at geologically reasonable strain rates appears to require higher temperatures than those believed to have been experienced by this meteorite 600 c however differences in olivine grain size the presence of water or a more complex deformation history might explain this discrepancy

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

grain size of quartz as an indicator of winter monsoon strength on the loess plateau of central china during the last 130 000 yr the chinese loess paleosol sequence constitutes an important record of variations in asian monsoon climate over the past 2 4 myr magnetic susceptibility of loess and paleosols has been used as a proxy for summer monsoon intensity while median grain size has been regarded as a measure of the strength of winter monsoon winds that were responsible for most of the dust transport however median grain size is only an approximate index of winter monsoon strength because both paleosols and loess have been modified to various degrees by weathering processes that have produced pedogenic clay the quartz component of loess and paleosols is largely unaffected by weathering processes and therefore constitutes a more reliable proxy index of monsoon wind strength median grain size qmd and maximum grain size qmax values of monomineralic quartz isolated from the loess paleosol section at luochuan in the central loess plateau are characterized by two main intervals during the last ca 130 000 yr when these parameters were significantly greater than 9 and 85 m respectively and three main intervals when they were lower the data imply that the winter monsoon weakened during the intervals with low qmd and qmax values which coincide with marine oxygen isotope stages 5 3 and 1 and was strongest ca 67 000 and 20 000 yr ago during isotope stages 4 and 2 however both quartz grainsize records display second order high frequency high amplitude variations which are lacking in the magnetic susceptibility record that imply rapid and significant changes in atmospheric conditions that affect dust transport and deposition

weichselian upper pleniglacial environmental variability in north western europe reconstructed from terrestrial mollusc faunas and its relationship with the presence absence of human settlements abstract during the weichselian glaciation millennial timescale climatic changes are a major cause of environmental variability which influence the composition of large mammal fauna and the geographical distribution of human prehistoric populations nevertheless precise environmental contexts of archaeological artefacts may remain unknown due to an unclear stratigraphy and or to the bad preservation of paleoenvironmental proxies as pollen is badly preserved in glacial loess deposits a compilation of age constrained high resolution molluscan records is used to initiate the establishment of a canvas of millennial timescale spatial and temporal environmental changes in the european loess belt during the weichselian upper pleniglacial ca 37 20 ka to look for relationships with spatial distribution of human settlements in this study new terrestrial mollusc assemblages have been added to the database previously established for north western europe they strengthen the position of the limit between the two molluscan based biogeographical domains initially highlighted for north western europe a flat and poorly vegetated western domain extending around the channel and in belgium and a hilly domain with more diversified vegetation to the east the analysis of molluscan data shows the persistence of these two domains throughout alternations of loess deposition phases interstadial stadial transitions and stadial phases with phases of development and degradation of tundra gley horizon stadial interstadial transitions and interstadial phases the interpretation of malacofauna from both domains combined with associated pedological and sedimentological features climate modelling and comparisons with present tundra environments reveals a significant effect of both seasonality and snow cover along a longitudinal gradient between both domains but also between phases of loess deposition and phases of tundra gley development during interstadial phases the intense functioning of the active layer and the degradation of permafrost in north western europe led to more homogeneous environments which were less favourable for the diversity of both vegetation and terrestrial mollusc fauna presently uncertainties of numerical ages still preclude precise correlations of loess units and tundra gley horizons between different sites and with nonlocal prehistoric occupations however a first raw comparison of the molluscan data with spatial distributions of aurignacian gravettian and solutrean upper magdalenian lithic cultures reveals that the northern limit of the first two ones fits well with the south eastern border of the poorly vegetated western domain also characterised by well developed ice wedge networks during phases of permafrost installation later an important southward shift of human populations in western europe resulted from the extreme aridity of the last glacial maximum

chemical studies of h chondrites ii weathering effects in the victoria land antarctic population and comparison of two antarctic populations with non antarctic falls abstract we report rnaa data for 14 siderophile lithophile and chalcophile volatile mobile trace elements ag au bi cd co cs ga in sb se te tl u zn in interior portions of 45 different h4 6 chondrites 49 samples from victoria land antarctica and 5 h5 chondrites from the yamato mts antarctica relative to h5 chondrites of weathering types a and b all elements are depleted 10 at statistically significant levels in extensively weathered types b c and c samples probably by leaching on the ice sheet surface contents of 8 elements in extensively weathered samples may provide a qualitative ranking for terrestrial surface residence chondrites of weathering types a and b seem compositionally uncompromised and as useful as contemporary falls for trace element studies when data distributions for these 14 trace elements in non antarctic h chondrite falls and unpaired samples from victoria land and from the yamato mts queen maud land are compared statistically numerous significant differences are apparent concentrations of 8 elements differ significantly in the victoria land and non antarctic h5 chondrite populations essentially the same compositional differences and 53 mn content and shock history differences appear when h4 6 populations are compared contents of 8 elements differ when queen maud land and victoria land populations are compared and 5 for the queen maud land non antarctic comparison these and other differences give ample cause to doubt that the various sample populations derive from the same parent population the observed differences do not reflect weathering chance or other trivial causes a preterrestrial source must be responsible the least unlikely of these involves a temporal variation in the source regions from which meteoroids derive

moisture evolution in central asia since 26 ka insights from a kyrgyz loess section western tian shan abstract central asia ca is located in the hinterland of the eurasian continent and faces an extreme risk of continued aridification under the current global warming trend to predict future climate change in ca paleoclimate studies provide essential references however the mechanisms underlying climate changes in ca remain relatively poorly known here we investigate moisture variations in ca as recorded in a 6 m loess section in the western tian shan kyrgyzstan which has accumulated since 26 ka based on the radiometric ams 14c dating we reconstructed the evolution of the wind regime and moisture conditions in the western tian shan with a modified grain size index gsim and a new l proxy l while the frequency dependent magnetic susceptibility fd redness a and yellowness b did not provide reliable paleoclimatic indicators due to weak pedogenesis and other controlling factors the gsim records demonstrated a precipitation maximum in summer before 15 ka shifting to a maximum in spring after 15 ka probably associated with large scale modulation of the latitudinal climatic zones and atmospheric circulation in response to retreat of the northern hemisphere ice sheets based on the l records we place emphases on the important role of temperature modulated evaporation in moisture evolution across ca however this has only influenced moisture evolution in spring and summer with little effect on winter moisture conditions moreover the l records may also indicate that atmospheric humidity can partly affect the long term effective moisture variations

high resolution record of the last interglacial glacial cycle in the nussloch loess palaeosol sequences upper rhine area germany the nussloch loess sequences were sampled at close intervals 10 cm and documented in respect of their stratigraphy palaeopedology sedimentology palynology malacology and geochemistry and were dated using radiocarbon and osl methods for each stratigraphic unit the results of both the eld studies and the analytical and geochronological data obtained cast light upon the response of the loessic environment to global climatic variations during the last cycle the basal soil complex underwent a pedosedimentary evolution similar to those of the bordering area complex luvisol greyzem steppe soila which re ects the classic progression towards increased continentality of the environment between the end of the eemian 5d and the beginning of the full glacial stage pleniglacial the lower pleniglacial corresponds to an initially very arid phase dominated by the accumulation of loess followed by the deposition of strati ed niveo eolian sands the middle pleniglacial complex ca 55 30 is clearly characterised by the inhibited loessic sedimentation it is primarily marked by two phases of stabilisation recorded in the form of weathered horizons cambisols which are separated by a rather thin layer corresponding to loessic sedimentation with tundra gleys this intermediate phase brings together organic silt deposits which record an interstadial dated at 32 33 ka c bp the thick loessic accumulations of the upper pleniglacial 10 m which clearly began to accumulate before the oxygen isotope stage ois 3 2 boundary show evidence of vulnerability to considerable uctuations in response to variations in wind dynamics and the intensity of de ation in the rhine valley finally a proposed correlation of loess palaeosol stratigraphies from germany belgium and france spanning the entire last interglacial glacial cycle is presented 2001 elsevier science ltd and inqua all rights reserved

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

comparisons between antarctic and non antarctic meteorites based on carbon isotope geochemistry abstract the whole rock c isotopic composition of a suite of ordinary chondrites indicates that there is a difference between antarctic and non antarctic meteorites however this apparent distinction is not due to an inherent difference in the meteorite source populations but is rather a result of the presence of antarctic weathering products mainly bicarbonates which affect the overall 13 c of these meteorites when these weathering products are removed either by acid washing or combustion to 500 c the perceived division also disappears leading to the conclusion that ordinary chondrites both antarctic and non antarctic have similar 13 c values a similar effect is noted in data from three separate groups of achondrites the ureilites heds and sncs however here the weathering products do not influence total c data in the case of the ureilites this is readily understood since the indigenous c content is high the heds and sncs on the other hand with low indigenous c abundance contain relatively lower concentrations of weathering products compared to ordinary chondrites which can be removed by combustion to 200 c this suggests a different complement of weathering products in the achondritic and chondritic meteorites an effect which may be related to differences in chemistry or porosity the almost ubiquitous occurrence of weathering products with distinctive c isotopic composition highlights the importance of removing all terrestrial contaminants from meteorites with low indigenous c budgets before attempting any interpretation concerning their c abundance or isotopic composition the c chemistry of ci cm and cr chondrites is also subject to problematic interpretation whilst the indigenous c abundance is too high to be compromised by the addition of terrestrial weathering products the inhomogeneous distribution of an array of components with widely varying isotopic signatures leads to a random distribution of 13 c values analyses of individual components insoluble macromolecular material carbonates and silicon carbide reveal that there are no gross differences in c chemistry between antarctic and non antarctic chondrites the few distinctions that do exist might readily be explained by weathering or isotopic exchange in antarctic whilst not forming a separate population antarctic carbonaceous chondrites may extend the range of properties of non antarctic chondrites beyond the currently known limits

solid state cp mas 13 c nmr of the insoluble organic matter of the orgueil and murchison meteorites quantitative study solid state cp mas 13c nuclear magnetic resonance nmr study of the insoluble organic fraction isolated by hf hcl treatment under an inert atmosphere from the orgueil and murchison carbonaceous meteorites is reported based on these spectra eight different types of carbons aro and ali linked ch3 ch2 aliphatic c linked to heteroelements protonated and non protonated aromatic c carboxyls and carbonyls were identified their relative amounts were determined and theoretical nmr derived h c atomic ratios were calculated comparison of these h c ratios with those obtained from elemental analysis revealed that a large part of the carbons of the insoluble fraction of both meteorites are not detected by cp mas 13c nmr taking into account these undetected carbons the relative abundance of aromatic carbons as of the total carbons was calculated as between 69 and 78 in orgueil and 61 and 67 in murchison and thus shown to be much higher than previously thought in addition the nmr data allowed to calculate the ratio of non protonated and protonated aromatic carbons based on previous studies on chemical and thermal degradation the present nmr data were interpreted as reflecting the occurrence of highly substituted rather small aromatic moieties in these insoluble organic materials along with ftir data nmr results also pointed to a relatively high branching level in the aliphatic chains especially for murchison according to the above results the insoluble organic matter in these meteorites did not suffer a marked thermal maturation during the late hydrothermalism of the parent body its synthesis involved a statistical combination of all the possible bonds between ch3 ch2 and ch radicals producing both the aliphatic and the aromatic moieties this model explains not only the chemical features of the chondritic insoluble organic material but also the typical ftir signature of the interstellar medium therefore organic material found in the interstellar medium and that incorporated in the most primitive objects of the solar system seem to share a common organosynthesis

the history and nature of wind erosion in deserts recently the importance of wind erosion has been reevaluated many low angle surfaces developed on susceptible materials possess closed depressions pans and these often have a distinctive morphology and lunette dunes on their lee sides it has also become apparent that in drylands there are extensive areas of stone pavements some of which have been molded by deflation however it is now recognized that other horizontal sorting processes have played a role especially movement of fines by overland flow vertical sorting associated with wetting and drying salt heave bioturbation frost action and dust accretion have also played a role in hyperarid areas especially with unidirectional winds bedrock outcrops and old lake beds have been molded to give aerodynamic forms called yardangs the study of dust storms by analysis of climatological data and remote sensing has revealed the importance of deflation especially in hyperarid areas with centripetal drainage deflation hot spots such as the bo

a compilation of western european terrestrial records 60 8 ka bp towards an understanding of latitudinal climatic gradients terrestrial records of past climatic conditions such as lake sediments and speleothems provide data of great importance for understanding environmental changes however unlike marine and ice core records terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non specialist as a consequence many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations comparisons or modelling exercises here we present a compilation of western european terrestrial palaeo records covering entirely or partially the 60 8 ka intimate time period the compilation contains 56 natural archives including lake records speleothems ice cores and terrestrial proxies in marine records the compilation is limited to include records of high temporal resolution and or records that provide climate proxies or quantitative reconstructions of environmental parameters such as temperature or precipitation and that are of relevance and interest to a broader community we briefly review the different types of terrestrial archives their respective proxies their interpretation and their application for palaeoclimatic reconstructions we also discuss the importance of independent chronologies and the issue of record synchronization the aim of this exercise is to provide the wider palaeo community with a consistent compilation of high quality terrestrial records to facilitate model data comparisons and to identify key areas of interest for future investigations we use the compilation to investigate western european latitudinal climate gradients during the deglacial period and despite of poorly constrained chronologies for the older records we summarize the main results obtained from nw and sw european terrestrial records before the lgm

a multi proxy analysis of two loess paleosol sequences in the northern harz foreland germany two loess paleosol sequences from the northern harz foreland hecklingen and zilly have been investigated in general loess paleosol sequences represent valuable terrestrial archives of regional environmental and climatic conditions during past glacial periods the study area is part of the northern european loess belt and was in the vicinity of the scandinavian ice sheet during the weichselian aiming towards a better understanding of the paleoenvironmental conditions during the weichselian in an area close to the scandinavian ice sheet results from grain size geochemical xrf cns color and magnetic susceptibility measurements are combined the findings demonstrate an increased input of aeolian material during the last glacial maximum and the last cover loess period which is in accordance to the theory of drier and colder conditions during this time frame further data reveal a strong input not only of loess but also of coarser material coming from a shorter distance during the last glacial maximum in both profiles material of the last glacial maximum clearly indicates a shift of wind direction towards easterly winds in hecklingen an enhancement of coarser material has been observed within the recent soil and mis 3 soil material since soil material that dates back to the mis 3 is present in the profile it can be assumed that surface processes were less intrusive during the mis 3 and 2 than in e g the lower rhine embayment and saxony c 2016 elsevier b v all rights reserved

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

holocene loess deposition and soil formation as competing processes matanuska valley southern alaska although loess paleosol sequences are among the most important records of quaternary climate change and past dust deposition cycles few modern examples of such sedimentation systems have been studied stratigraphic studies and 22 new accelerator mass spectrometry radiocarbon ages from the matanuska valley in southern alaska show that loess deposition there began sometime after f6500 14 c yr b p and has continued to the present the silts are produced through grinding by the matanuska and knik glaciers deposited as outwash entrained by strong winds and redeposited as loess over a downwind distance of f40 km loess thickness sand content and sand pluscoarse silt content decrease whereas fine silt content increases loess deposition was episodic as shown by the presence of paleosols at distances 10 km from the outwash plain loess source stratigraphic complexity is at a maximum i e the greatest number of loesses and paleosols at intermediate 10 25 km distances from the loess source surface soils increase in degree of development with distance downwind from the source where sedimentation rates are lower proximal soils are entisols or inceptisols whereas distal soils are spodosols ratios of mobile cao k2o and fe2o3 to immobile tio2 show decreases in surface horizons with distance from the source thus as in china where loess deposition also takes place today eolian sedimentation and soil formation are competing processes study of loess and paleosols in southern alaska shows that particle size can vary over short distances loess deposition can be episodic over limited time intervals and soils developed in stabilized loess can show considerable variability under the same vegetation d 2004 university of washington all rights reserved

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

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

molecular and isotopic indicators of alteration in cr chondrites the cr group of carbonaceous chondrites may represent some of the most primitive extraterrestrial materials available for analysis however in contrast to other chondrite groups the cr organic fraction is poorly characterized the carbonaceous chondrite literature shows that relatively anhydrous thermal processing results in a condensed poorly alkylated o poor macromolecular material while for aqueous processing the converse is true such characteristics can be used to discern the alteration histories of the carbonaceous chondrites we have performed bulk elemental and isotopic analysis and flash pyrolysis on four cr chondrites renazzo al rais elephant moraine eet 87770 and yamato y 790112 to determine the nature of their organic component renazzo al rais and y 790112 release qualitatively similar pyrolysis products although there are some variations al rais macromolecular structure contains substantially higher relative abundances of alkylated and oxidized species and relatively lighter 15n suggesting that it has endured more extensive aqueous processing than the other cr chondrites renazzo appears relatively unprocessed with a low degree of alkylation a lack of detectable nitrogen bearing components and low methylnaphthalene ratio eet 87770 s low abundance of alkylated species suggests its macromolecular structure may be relatively condensed with condensation potentially assisted by a period of mild thermal alteration

investigating the variations in carbon and nitrogen isotopes in carbonaceous chondrites the carbonaceous chondrites contain significant amounts of carbon and nitrogen bearing components the most abundant of which is organic matter stepped combustion data of whole rock and hf hcl residues of carbonaceous chondrites reveal that the organic material can be subdivided operationally into three components 1 free organic matter fom which is readily extractable from whole rock meteorites and is enriched in 13c and 15n 2 labile organic matter lom which has a macromolecular structure but is liberated by hydrous pyrolysis lom is the parent structure for some fom and is also enriched in 13c and 15n and 3 refractory organic matter rom which is also macromolecular but is virtually unaffected by hydrous pyrolysis and is relatively depleted in 13c and 15n the macromolecular entities lom and rom are by far the most abundant organic components present and as such the relative abundances of the 13c and 15n enriched lom and the 13c and 15n depleted rom will have a major influence on the overall isotopic composition of the whole rock meteorite laboratory experiments designed to simulate the effects of parent body aqueous alteration indicate that this form of processing removes lom from the macromolecular material allowing rom to exert a stronger influence on the overall isotopic compositions hence aqueous alteration of macromolecular materials on the meteorite parent body may have a significant control on the stable isotopic compositions of whole rock carbonaceous chondrites the enstatite chondrites are also carbon rich but have been subjected to high levels of thermal metamorphism on their parent body stepped combustion data of hf hcl residues of enstatite chondrites indicate that if they and carbonaceous chondrites inherited a common organic progenitor metamorphism under reducing conditions appears to incorporate and preserve some of the 13c enrichments in lom during graphitisation however when metamorphism is at its most extreme the 15n enrichments in lom are lost

primary aerosol sea salt and soil dust deposited in greenland ice during the last climatic cycle comparison with east antarctic records ion chromatography data of ca mg cl and ca and coulter counter particle measurements are used to study the cycle of marine and continental primary aerosol reaching greenland in relation to climatic changes over the last 150 kyr a detailed comparison between greenland dome summit and antarctic vostok records provides new insight on a potential link between northern and southern patterns ca is a good indicator of continental input and is mainly emitted as caco3 an attempt is made to estimate the contribution of aluminosilicates using the concentration of insoluble particles greater than 0 5 m in diameter the relative abundance of non sea salt mg and ca and of aluminosilicate shows that the calcium content of continental background aerosol over greenland was much higher during the glacial age the neutralization capacity of carbonaceous aerosol is estimated the inverse relationship between 18o and continental input as well as the response of this input to the rapid climatic variations that have occurred during the second part of the glacial age are discussed in terms of source and transport modification in relation to the presence and the extent of the great laurentide ice cap the corresponding vostok profiles strongly suggest that some of the phenomena observed at high northern latitudes are of global concern the marine component of na nam is a good tracer of sea salt aerosol similarly to continental input it shows an inverse but more linear relationship with 18o the sensitivity of greenland and antarctic marine input to climate variations of small and large amplitude is compared and a corresponding estimation is made for the aeolian contribution the respective influence of atmospheric circulation and the water vapor cycle is discussed the chlorine to marine sodium weight ratio increases with temperature from values very close to the bulk seawater ratio during the last glacial maximum 18 20 kyr b p to values significantly higher during the holocene and warm eemian the corresponding excess of chloride hcl is discussed in terms of atmospheric transport taking into account the role of atmospheric acidity on sea salt fractionation processes owing to postdepositional phenomena similar vostok data must be considered cautiously nevertheless aerosol fractionation seems to have been much more important over the vostok site except during glacial extrema

link between european and north atlantic abrupt climate changes over the last glaciation 1 sub millennial timescale climate variations correlated with those in the north atlantic area are identified in the loess sequence from nussloch germany exceptionally developed over the interval between about 38 000 and 18 000 years ago the dansgaard oeschger do events 8 to 2 as well as some less pronounced warming episodes recorded in the greenland ice have their counterpart in the nussloch loess stratigraphy and in the variations of the loess grain size index gsi the north atlantic heinrich events 3 and 2 are expressed at nussloch as maxima of the gsi record the similarity of the fine variations in the nussloch loess and the greenland ice records points to an intimate link of climate changes in western europe with those in the north atlantic

isotopic composition of carbonaceous chondrite kerogen evidence for an interstellar origin of organic matter in meteorites abstract stepwise combustion has revealed systematic patterns of isotopic heterogeneity for c h and n in the insoluble organic fraction m kerogen from the orgueil and murray carbonaceous chondrites those patterns are essentially identical for both meteorites indicating a common source of m kerogen the data cannot be reconciled with a single mass fractionation process acting upon a single precursor composition this indicates either a multi path history of mass dependent processing or a significant nucleogenetic contribution or both if mass fractionation were the dominant process the magnitude of the observed isotopic variability strongly suggests that ion molecule reactions at very low temperatures probably in interstellar clouds were responsible in any case an interstellar rather than solar nebular origin for at least some of the meteoritic organic matter is indicated this has interesting implications for the origin of prebiotic molecules temperatures in the early solar system and the isotopic compositions of volatiles accreted by the terrestrial planets

continental biogenic species in the greenland ice core project ice core tracing back the biomass history of the north american continent ammonium nitrate and organic acid records from the greenland ice core project deep ice core are discussed all species have a continental biogenic source that is situated predominantly on the north american continent for species deposited in summit central greenland the record therefore can be used to trace back the biomass history of the north american continent difficulty in the interpretation of these records arises from their unknown transfer behavior in a more alkaline atmosphere which characterizes glacial time periods compared to interglacial stadials this may have implications not only for weak acids such as formate and acetate but also possibly for the transport and incorporation of hno3 into aerosols whereas ammonium is probably not affected by the alkalinity change of the atmosphere our approach is to compare samples with similar h concentrations throughout the record from the records we infer several significant fluctuations in the extent of the laurentide ice sheet during the last glaciation we find evidence against the occurrence of an extensive younger dryas event in north america

late pleistocene loess palaeosol sequences in poland and western ukraine abstract polish and nw ukrainian loess covers are situated along the northern margin of the central part of the european loess belt because of their intermediate geographic position they form a bridge for loess studies in eastern and western europe fifteen loess soil sequences representing the last interglacial glacial loess cycle were investigated using a new methodological approach elaborated for this purpose the thickness of the late pleistocene sequences ranges between 4 and 14 m all these profiles were sampled in vertical continuous sections at close intervals 5 10 cm and documented with respect to their sedimentology palaeopedology and stratigraphy the main litho and pedostratigraphic units were established during field investigations loess palaeosol sequences confirm the general instability of the last glacial climate the representative late pleistocene interfluve loess sequence in the study area consists of four units two polygenetic palaeosol complexes and two calcareous loess units within these loess units two generations of ice wedge casts indicate twofold expansion and disappearance of permafrost during the last glacial period this evidence confirms the correlation of main terrestrial events of the late pleistocene loess sequences with the marine record the last glacial loess sequences in poland and nw ukraine are of crucial importance for palaeogeographic reconstructions of european loess areas