petrographic constraints on the diversity of chondrule reservoirs in the protoplanetary disk abstract chondrules from different chondrite groups show characteristic properties including abundances of different chondrule textural types chondrule sizes oxygen isotope compositions chondrule bulk compositions and petrographic properties of type i and type ii chondrules including abundances of relict grains overall it can be argued that each chondrite group sampled a unique chondrule reservoir and that chondrite groups may represent fractions of larger reservoirs that are represented by chondrite classes these observations provide constraints for models of the early solar system in which it is necessary to establish multiple separate chondrule reservoirs and maintain them over extended time periods models for accretion of chondrite parent bodies must be able to account for localized accretion of chondrules that were formed in spatially or temporally separated reservoirs

spatial and temporal variation of geochemical properties and paleoceanographic implications in the south korea plateau east sea during the late quaternary geochemical opal total organic carbon toc and caco3 analyses of three sediment cores from the south korea plateau in the east sea japan sea revealed that the late quaternary 190 kyr bp to the present paleoceanographic conditions are characterized by the orbital variations of geochemical properties that have recorded the changes of surface and bottom water conditions chronostratigraphy of the sediment cores was accomplished by the direct correlation of l values to the well dated core md01 2407 in oki ridge supplement to the ams 14c dates well known lithostratigraphic and tephrostratigraphic markers biogenic opal concentrations are high during marine isotope stage mis 1 and mis 5 5 and low during the glacial period suggesting that diatom production was enhanced during the warm period when the surface water exchange between the east sea and adjacent marginal seas was active in contrast glacial opal paleoproductivity appears to have been depressed probably because of insufficient nutrient availability resulting from limited vertical ventilation overall toc contents follow the orbital variations high during the interglacial and relatively low during the glacial time however high resolution toc fluctuations are independent of opal concentration which may be attributed more to the preservation of organic matter rather than to the surface water production the high toc contents in the thin dark mud i e tl layers may be due to the enhanced surface water production as well as the intensified bottom water anoxia on the other hand high caco3 contents associated with the tl layers during the glacial and stadial period may be attributed to the reduced dissolution the temporal variations of these geochemical properties are likely to follow the global orbital cycles indicating the significant changes of surface and bottom water properties due to the eustatic sea level fluctuations between the interglacial and glacial period the comparable values of these geochemical properties among the sediment cores suggest that the spatial paleoceanographic conditions in the south korea plateau were consistent and uniform during the late quaternary in spite of a little local discrepancy in amounts of properties and timing of events

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

correlation of fluctuations in cladoceran planktonic littoral ratio between three cores from a small lake in southern finland holocene water level changes the main aim of the study was to test the cladoceran planktonic littoral p l method in holocene lake level studies with three cores from a small lake iso lehmalampi 60 21 n 24 36 e in south

crystal bearing lunar spherules impact melting of the moon s crust and implications for the origin of meteoritic chondrules crystal bearing lunar spherules clss in lunar breccia 14313 14315 14318 soil 68001 24105 and impact melt rock 62295 samples can be classified into two types feldspathic and olivine rich feldspathic clss contain equant tabular or acicular plagioclase grains set in glass or a pyroxene olivine mesostasis the less common olivine rich clss contain euhedral or skeletal olivine set in glass or possess a barred olivine texture bulk chemical and mineral chemical data strongly suggest that feldspathic clss formed by impact melting of mixtures of ferroan anorthosite and mg suite rocks that compose the feldspathic crust of the moon it is probable that olivine rich clss also formed by impact melting but some appear to have been derived from distinctively magnesian lunar materials atypical of the moon s crust some clss contain reversely zoned relic plagioclase grains that were not entirely melted during cls formation thin 5 m thick rims of troilite or phosphate and chemical gradients in glassy mesostases attributed to metasomatism in a volatile rich na k p rich environment crystal bearing lunar spherules were rimmed and metasomatized prior to brecciation compound cls objects are also present these formed by low velocity collisions in an environment probably an ejecta plume that contained numerous melt droplets factors other than composition were responsible for producing the crystallinity of the clss we agree with previous workers that relatively slow cooling rates and long ballistic travel times were critical features that enabled these impact melt droplets to partially or completely crystallize in free flight moreover incomplete melting of precursor materials formed nucleation sites that aided subsequent crystallization clearly clss do not resemble meteoritic chondrules in all ways the two types of objects had different precursors and did not experience identical rimming processes and vapor fractionation appears to have played a less important role in establishing the compositions of clss than of chondrules however the many detailed similarities between clss and chondrules indicate that it is more difficult to rule out an origin for some chondrules by impact melting than some have previously argued differences between clss chondrules and their host rocks possibly can be reconciled with an impact melt origin for some chondrules when different precursors the higher gravity of the moon compared to chondrite parent bodies and the likely presence of nebular gas during chondrule formation are taken into account

highly siderophile element and osmium isotope evidence for postcore formation magmatic and impact processes on the aubrite parent body abstract aubrites exhibit a wide range of highly siderophile element hse re os ir ru rh pt pd au concentrations and 187os 188os compositions their hse concentrations are one to three orders of magnitude less than chondrites with the exception of the shallowater and mt egerton samples while most aubrites show chondritic hse abundance ratios significant enrichments of pd and re relative to os ir and ru are observed in 12 of 16 samples present day 187os 188os ratios range from subchondritic values of 0 1174 to superchondritic values of up to 0 2263 half of the samples have 187os 188os ratios of 0 127 to 0 130 which is in the range of enstatite chondrites along with the brecciated nature of aubrites the hse and re os isotope systematics support a history of extensive postaccretion processing including core formation late addition of chondritic material and or core material and potential breakup and reassembly highly siderophile element signatures for some aubrites are consistent with a mixing of hse rich chondritic fragments with a hse free aubrite matrix the enrichments in incompatible hse such as pd and re observed in some aubrites reminiscent of terrestrial basalts suggest an extensive magmatic and impact history which is supported by both the 187re 187os isotope system and silicate hosted isotope systems rb sr k ar yielding young formation ages of 1 3 3 9 ga for a subset of samples compared with other differentiated achondrites derived from small planetary bodies aubrites show a wide range in hse concentrations and 187os 188os most similar to angrites while similarities exist between the diverse groups of achondrites formed early in solar system history the aubrite parent body ies clearly underwent a distinct evolution different from angrites brachinites ureilites howardites eucrites and diogenites

carbon isotopic compositions of long chain n alkanes in the japan sea sediments implications for paleoenvironmental changes over the past 85 kyr abstract carbon isotopic compositions of long chain n alkanes in cores kh 79 3 c 3 and l 3 taken from the oki ridge 37 04 n 134 42 e water depth 935 m in the japan sea were measured by gas chromatography isotope ratio mass spectrometry fluctuations in the carbon isotopic composition of terrestrially derived material as determined from 13 c n alkane weighted average of 13 c values for higher plant derived n c29 and n c31 alkanes range from 29 1 to 32 1 for the past 85 kyr in core kh 79 3 c 3 13 c n alkane values in colder climates 18 o stages 2 and 4 are depleted in 13 c by approximately 1 relative to those in warmer climates stages 1 3 and 5 1 this suggests that the temporal variations of the 13 c values for higher plant derived n alkanes exhibit a close relationship with glacial interglacial cycles the results over the past 30 kyr 14 c age reveal that the 13 c n alkane values shifted abruptly from 31 1 0 5 to 29 9 0 4 at around 10 kyr b p with the isotopic values remaining relatively constant thereafter this positive 1 2 shift in 13 c n alkane values can be attributed to one or both of the following factors i enhancement of primary productivity on land and ii change in vegetational types e g c4 c3 plants ratios and or changes in the species of c3 plants

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

climate change in southern illinois usa based on the age and δ13c of organic matter in cave sediments abstract matrix supported diamicton and uniform to laminated silty fine grained sediment deposited from about 42 500 to 27 600 cal yr b p under slackwater conditions nearly filled two caves in southwestern illinois at some point most of the sediment was flushed from the caves and from about 22 700 to 4000 cal yr b p floods deposited a drape of sandy and silty sediment on remnant slackwater successions cobbly alluvium and bedrock especially from 7700 to 4000 cal yr b p clay mineral analyses of the slackwater cave sediment reveal a provenance of chiefly petersburg silt a smectite and illite rich proglacial lacustrine unit present in the overlying illinois episode glacial succession today remnants of the ancient subterranean slackwater deposits nearly fill several secondary passages and in at least two locations cover a cobble mantled strath terrace 1 3 to 1 5 m above active stream channels slumping and sinkhole formation appear to have been important mechanisms for deposition of the ancient subterranean deposits slumping of these surficial deposits and associated vegetation can occur along the flanks of sinkholes in addition to sinkhole formation and enter caves however the finer organics some of them comminuted during transport into the caves become part of the cave alluvium this finer organic fraction is the modern analog of the humified organic matter disseminated in slackwater sediment dated in this investigation by radiocarbon methods twenty four 14c ages on humified organic matter provide chronologic control the 13c values of the organic matter reflect the proportion of c4 type to c3 type vegetation growing in and around swallets and sinkholes at the time of redeposition drought tolerant c4 type vegetation was more prevalent relative to c3 type vegetation from 42 500 to 31 200 cal yr b p compared to conditions from 28 800 cal yr b p to the present the 13c values are consistent with the results from other investigations of speleothems and organic matter from loessial paleosols

ubiquitous high feo silicates in enstatite chondrites our electron microprobe studies of four type 3 enstatite chondrites show that olivines and low ca pyroxenes with more than 3 wt feo are more abundant than previously recognized 4 8 of clear pyroxene grains and a higher proportion of dusty pyroxenes have fs 5 20 from scanning electron microscope and electron probe surveys of these four eh3 chondrites we discovered 542 objects that contain silicates very largely pyroxene with 3 wt feo 18 chondrules 381 rimmed or unrimmed grains and 143 mineral aggregates with fs 5 27 pyroxene or fa 3 14 olivine aggregates and grains may have been derived from chondrules by comminution rims of enstatite with fs 0 3 on many grains formed by reduction or growth in the nebula or parent body in two eh4 5 chondrites we identified 89 feo rich objects that are all enstatite grains with fs 1 10 having feo poor enstatite rims which grew during planetary metamorphism two of the 18 feo rich chondrules in eh3 chondrites have textures and mineral compositions that are consistent with crystallization of feo rich melts in others these textures are modified by nebula or planetary reduction along cracks and grain edges that formed low feo silicates and metallic fe ni however several feo rich chondrules contain crystals of both high and low feo silicates that appear to have igneous origins but could not have formed by closed system crystallization of chondrule melts these probably reflect either reduction of chondrule melts by the nebula during crystallization or collisions of partly molten chondrules having very different feo concentrations an origin involving partial melting of chondrule precursor grains seems less plausible

nonporphyritic chondrules and chondrule fragments in enstatite chondrites insights into their origin and secondary processing fil varela maria eugenia consejo nacional de investigaciones cienti ficas y tecnicas centro cientifico tecnologico san juan instituto de ciencias astronomicas de la tierra y del espacio argentina

the response of flood plain ecosystems to the late glacial and early holocene hydrological changes a case study from a small central european river valley abstract we use a range of environmental variables to explore the possible drivers influencing the biota especially the composition of aquatic invertebrates during the younger dryas yd and early holocene eh in different river valley sites a well developed meandering river and the confluence zone of headwater streams using pollen macrofossil cladoceran and chironomid as well as geochemical and lithological data as proxies for environmental factors i e water depth and temperature we attempt to show that these different sites display similar hydroclimatic signals especially floods the geochemical records in the studied valley are correlated with environmental factors such as the evolution of the vegetation the intensification phase of slope processes and fluvial activities cladocerans and chironomids potentially play important roles in the recognition of flood episodes in the study sites and any shift in their diversity and especially the co occurrence of planktonic sediment associated cladocerans with rheophilic chironomids could be valuable indicators of floods and flow episodes the variable changes in water levels at the sites reconstructed by the cladoceran based water depth model were positively associated with changes in lithophilic elements k na al mg and ti sio2 biog ter and fe mn and our estimates of the paleohydraulic parameters for the study sites are generally consistent with changes in the composition of aquatic invertebrates the recorded yd floods appear to be synchronous regardless of the size and the different geological and geomorphological settings of each part of the river catchment our investigation demonstrates that flood magnitude increases in the downstream direction along the valley the common increases in the water level at all study sites from the grabia river valley are significant from 12 400 to 12 200 and from 11 900 to 11 800 cal bp and are comparable with those from elsewhere in poland and europe

diopside bearing el6 eet 90102 insights from rare earth element distributions abstract eet 90102 is the first known diopside bearing el6 chondrite diopside occurs in most aubrites and is occasionally found as rare small grains in unequilibrated enstatite chondrites but is unknown from equilibrated enstatite chondrites we have carried out a study of the rare earth element ree distributions in eet 90102 with a specific emphasis on diopside in order to better understand its origin in this meteorite we also present data for ca rich pyroxenes from two unequilibrated eh3 enstatite chondrites for comparison our data show that diopside and other silicates in eet 90102 exhibit volatility related anomalies indicative of formation under highly reducing conditions such anomalies have not previously been observed in el6 chondrites although they are common in unequilibrated enstatite chondrites diopside in eet 90102 probably formed by metamorphic equilibration of enstatite and oldhamite the ree compositions of some grains in particular the presence of positive yb anomalies indicate that they inherited their ree characteristics largely from cas other grains have ree patterns that are more consistent with a derivation of diopside primarily from enstatite in contrast to other el6 chondrites which experienced slow cooling eet 90102 was quenched from high metamorphic temperatures thus there may have been insufficient time to completely homogenize diopside ree compositions the presence of diopside in eet 90102 simplifies one outstanding problem of aubrite formation melting of a diopside bearing enstatite chondrite protolith provides a source for the abundant diopside in aubrites without requiring the oxidation of oldhamite as suggested by previous research

feo rich silicates in the sahara 97159 eh3 enstatite chondrite mineralogy oxygen isotopic compositions and origin we report the mineralogy and oxygen isotopic compositions of feo rich silicates in the sahara 97159 eh3 chondrite this component is referred to as feo rich because it contains substantially more feo than the characteristic feo poor silicates in the highly reduced enstatite meteorites these feo rich silicates are mostly low ca pyroxene fs535 and their compositions suggest an origin under more oxidizing conditions like those for the ordinary chondrites however the mafic silicates in ordinary and carbonaceous chondrites are dominantly olivine and the feo rich silicates in the e chondrites are less commonly olivine the oxygen isotopic compositions of the feo rich silicates are indistinguishable from those of feo poor silicates in sahara 97159 these observations suggest that both the feo rich silicates and the feo poor silicates in eh chondrites formed from the same oxygen reservoir where redox conditions varied widely

sediment isotope tracers from lake saarikko finland and implications for holocene hydroclimatology abstract multi component isotopic analyses on a sediment core from lake saarikko finland give insight into holocene climate changes in northern europe oxygen isotopic records from aquatic cellulose and authigenic carbonate reflect consistent similar trends in hydrological balance and are employed jointly to infer relative changes in lake water temperature other geochemical and isotopic tracers shed light on fluctuations in lake level and nutrient cycling facilitating the interpretation of the oxygen isotopic archives in the early holocene 10 000 9000 cal yr bp the lake level was low and dry conditions prevailed despite low temperatures higher lake levels and depleted oxygen isotopic values 9000 7500 cal yr bp were probably caused by several factors higher effective humidity an isotopically depleted precipitation source a cold event around 8300 cal yr bp and increased spring snowmelt in contrast higher summer temperatures lower effective humidity lower lake levels and enriched oxygen isotopic values were experienced during the mid holocene 7500 3300 cal yr bp the occurrence of the warmest inferred lake water and the most enriched cellulose oxygen isotope values 6000 5000 cal yr bp is consistent with a summer temperature maximum inferred from other proxy sources from the region the late holocene was characterized by higher effective humidity and higher lake levels increase in spring snowmelt and colder temperatures most likely related to the little ice age induced a drastic change in the lake hydrology and probably caused the formation of its present outlet 800 cal yr bp changes in the lake hydrological balance and climate variables inferred from oxygen isotopic records can be related to atmospheric circulation most clearly to changes in the dominance and strength of westerly air flow as well as summertime anticyclonic circulation

compositional continuity of enstatite chondrites and implications for heterogeneous accretion of the enstatite chondrite parent body abstract chemical compositions of eleven enstatite chondrites 1 eh5 4 eh3 3 el3 i el5 and 2 el6 and their metal and nonmagnetic fractions determined by instrumental neutron activation analysis are reported the abundances of nonvolatile lithophile elements such as al sc and mg increase from eh to el while those of siderophile and moderately volatile elements decrease in the sequence of eh5 to eh3 el3 and el5 6 the continuity in compositions of enstatite chondrites and in particular the inverse variations of moderately volatile element abundances with petrographic type between eh and el groups demonstrate that enstatite chondrites have been derived from a common parent body the enstatite chondrite parent body formed by heterogeneous accretion of materials available in the accretional region metal was effectively accreted into the core where eh5 chondrites were derived and the abundances of metal decreased as accretion proceeded in complement silicate abundances gradually increased in the layers that accreted later the lack of correlation between volatile element abundances and metamorphic degree demonstrates that losses of moderately volatile elements from enstatite chondrites cannot have resulted from parent body processes furthermore it is expected that during accretion various components would mix and thus erase any early fractionation of moderately volatile elements of a single parent body variations of ambient gas temperatures during accretion are also impossible to produce the volatile element pattern of enstatite chondrites it is suggested that moderately volatile elements in the enstatite chondrites were lost during local heating the chondrule formation process formation of chondrules appears to have proceeded during the accretion of the enstatite chondrite parent body and lasted for a certain period the mineralogical and textural features of enstatite chondrites can be explained in terms of two stages of metamorphism the metamorphic trend from eh3 to eh5 resulted from internal heating whereas the trend from el3 to el6 was due to an external heat source it seems very likely that the eh chondrites were metamorphosed during accretion thus cooled rather rapidly activities of the early sun could serve as an energy source for the external heating

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

on the significance of diopside and oldhamite in enstatite chondrites and aubrites enstatite is the primary silicate phase of equilibrated enstatite chondrites eecs the cao contents of these enstatites lie close to or on the enstatite diopside phase boundary yet curiously diopside has always been absent from eec assemblages in contrast aubrites contain abundant diopside even though they are thought to be derived from an e chondrite like protolith a phase equilibrium analysis of the ca mg fe mn si o s system under reducing conditions solves this enigma and shows that diopside bearing eecs should commonly be found when s fugacity is sufficiently high e g fe fes buffer low o fugacity limits the stability of diopside in favor of oldhamite under such conditions the relative stability of diopside and oldhamite is described by the reaction camgsi2o6 mgs cas mg2si2o6 a large bulk compositional field exists where diopside and oldhamite are simultaneously stable the existence of oldhamite does not preclude the stability of diopside phase diagram topology demonstrates that bulk compositions lying in the enstatite oldhamite field and enstatite oldhamite alabandite field have enstatite cao contents nearly identical to that of enstatite in equilibrium with diopside alone this explains the high enstatite cao contents of all eecs that do not contain diopside this study also reports the discovery of the first eec to contain metamorphic diopside the antarctic meteorite eet 90102 elephant moraine 90102 has a typical el6 texture and contains the assemblage enstatite diopside albite kamacite troilite sinoite and graphite trace quantities of alabandite oldhamite and daubreelite are also present diopside is stable in eet 90102 because its bulk composition lies within either the enstatite diopside oldhamite alabandite or diopside alabandite enstatite stability fields in contrast all other eecs analyzed to date have bulk compositions lying in the enstatite oldhamite alabandite stability field the discovery of diopside in eet 90102 helps confirm the predictions of the phase equilibrium analysis elephant moraine 90102 experienced a high temperature metamorphic equilibration from which it was quenched the enstatite diopside cas in alabandite and fe in alabandite geothermometers yield temperatures of last equilibration of 900 c the absence of daubreelite and schreibersite along with high troilite cr contents and high kamacite p contents confirm a high temperature metamorphic quench the eet 90102 chondrite experienced a somewhat different cooling history and has a slightly different bulk composition than all other eecs studied to date however the close mineralogic petrologic and textural similarities between eet 90102 and nominal el6 chondrites signify that it should be classified as a diopside and sinoite bearing el6 chondrite assuming that the aubrites formed from an e chondrite like protolith a source rock similar to that of a diopside bearing eec offers a clear advantage for aubrite formation melting of a diopside saturated eec protolith would not require conversion of cas to achieve diopside saturation upon cooling

the palaeoecological development of the late medieval moat multiproxy research at rozprza central poland abstract the rozprza stronghold functioned as a seat of a noble family since at least the early14th century ad in the form of the motte and bailey residence the remains of the residence are situated in the central part of mid luci za river valley on the river terrace remnant adjoining a strongly expanding floodplain the situation and state of preservation give a unique opportunity to conduct research that explain the construction process detailed history of the medieval moat and palaeoenvironmental reconstruction of the valley floor radiocarbon and dendrochronological dating and analysis of artefacts confirmed 14th century age of the moat organic deposits gyttja peat and organic mud of moat fill allowed for a set of multiproxy analyses based on sediment cores the research results indicate shallow water with brief episodes of in wash in the first stage 13th 14th c ad followed by a transformation into telmatic habitat in the second phase of the moat development from 16th 17th c ad the deposition of overbank alluvium took place within the moat ditch system as late as the 18th and or 19th c ad we studied the development of this moat environment in the context of valley floor changes

long term vegetation change and controlling factors in donghae area korea over the past 40 000years abstract determining the effect of climate change since the last glacial maximum lgm in the east sea sea of japan coastal region of korea has been difficult owing to a dearth of suitable paleoclimate proxies a 40 000 year carbon isotope 13c record from cave deposits collected from cheongok cave korea reveals both long term change and superimposed shorter term isotopic excursions the 13c value of the sedimentary organic matter a proxy for past vegetation change varied from 25 to 21 with lower values during the lgm and higher values during the holocene a pattern that is generally consistent with trends in total organic carbon content toc and magnetic susceptibility from the lgm to the late holocene the c4 plant abundance mainly grasses estimated using a simple binary mixing model increased from 15 to 45 this long term change resembles trends in biogenic opal production in the east sea sea surface temperature and global sea level more than it does asian summer monsoon strength long term changes in c4 plant abundance in eastern coastal areas of korea over the last 40 000 years were probably affected most strongly by sea level driven ocean circulation changes in the east sea coupled with continental ice volume changes low pco2 during the lgm was not sufficient to cause the expansion of c4 plant coverage without favorable climatic conditions

metal and associated phases in bishunpur a highly unequilibrated ordinary chondrite it appears that the highly unequilibrated bishunpur ordinary chondrite preserves phase relations acquired during solar nebular processes to a relatively high degree metamorphic temperatures may not have exceeded 300 350 c the major categories of metal are 3 kinds of metal in the metal matrix three kinds in chondrule interiors and 2 kinds in chondrule rims the fine grained matrix metal is highly variable in composition the kamacite co content 7 8 2 0 mg g is within the l group range 6 7 8 2 mg g but extends well above and below its ni content 38 5 mg g is considerably lower than in more equilibrated chondrites and taenite is ni rich 450 mg g and unzoned these compositions imply equilibration at very low temperatures of about 300 350 c it seems unlikely that volume diffusion could account for the observed relatively unzoned phases a better model involves mass transport by grain boundary diffusion and grain growth at the indicated temperatures we find no evidence that the matrix was ever at higher temperatures large 50 650 m polycrystalline metal aggregates consisting of individually zoned crystals are also found in the matrix they probably represent clusters formed in the solar nebula a few large 50 250 m round monocrystalline grains are also present in the matrix metal bearing chondrules tend to be highly reduced they contain low ni metal that occasionally contains si and or cr silicates in these chondrules tend to have low feo feo mgo ratios the si rich metal grains are never in contact with silicates and are always surrounded by troilite with a poorly characterized ca cr sulfide at the metal troilite interface they appear to be high temperature nebular condensates that avoided oxidation even during the chondrule forming process silicon contents drop below our detection limit when the sulfide coating is absent much more common in chondrule interiors are si free spheroidal metal grains not associated with sulfides these have ni and co contents very similar to the si bearing grains and appear to be oxidized variants of the same material the third class of chondrule metal is fine 1 m dusty grains inside individual olivine grains these seem to reflect high temperature in situ reduction of feo from the olivine the composition of kamacite is different in sulfide rich and sulfide poor chondrule rims and in both cases it is dissimilar to the compositions in the chondrule interiors and matrix this indicates that chondrule rims could not have resulted from reactions with the matrix but are primary features acquired prior to accretton

formation of niningerite by silicate sulfidation in eh3 enstatite chondrites unequilibrated eh chondrites contain silica bearing chondrules with abundant niningerite mg fe mn s and troilite fes distinguishing them from the silica bearing chondrules in ordinary and carbonaceous chondrites the conventional explanation for the origin of niningerite and oldhamite cas is that they are condensates from c rich nebular gas however models of condensation from a solar gas with an elevated c o ratio predict mineralogy that is inconsistent with petrographic observations we report petrographic and chemical evidence from 45 silica bearing chondrules from the eh3 chondrites sahara 97072 and alan hills 84170 for formation of niningerite and oldhamite by sulfidation of ferromagnesian silicates the results indicate extensive thermal processing of the chondrules including melting before during and after sulfidation bulk compositions of chondrules exhibiting varied degrees of sulfidation suggest that depletion of mg and enrichment of fe mn and na accompany the reactions sulfidation of feo bearing silicates which formed at oxidizing conditions at least iw 3 can occur with exposure to a h poor c and s rich gaseous reservoir 6 8 fo2 log units below the iw buffer at temperatures high enough for partial melting of silicates physicochemical analysis of mineral reactions inferred from sulfidized chondrules suggests a melted metal sulfide assemblage in a h poor environment is capable of generating sufficient s vapor to drive sulfidation the reaction of silicates with the s gas will result in progressive extraction of fe ca and mg into sulfides with the stoichiometric amounts of silica either reacting with olivine to form enstatite or when olivine is exhausted precipitating as free silica the sulfidation environment drastically increases mg volatility resulting in evaporative loss until saturation in the ambient gas is reached the newly formed mg rich niningerite will tend to reach equilibrium composition by losing mg and gaining fe plus mn from the ambient gas consistent with the observed chemical fractionation in the sulfidized chondrules therefore sulfidation of ferromagnesian silicates can also explain the low bulk mg si ratios of the enstatite chondrites if the sulfidizing gas was lost before accretion of the enstatite chondrite parent body

chondrules in the qingzhen type 3 enstatite chondrite possible precursor components and comparison to ordinary chondrite chondrules abstract the qingzhen eh3 fall appears to be the least equilibrated enstatite chondrite mineral compositions vary widely from chondrule to chondrule and in some cases from grain to grain within individual chondrules as in ordinary chondrite oc chondrules most elements show appreciable ranges in concentration porphyritic olivine pyroxene pop chondrules are richer than porphyritic pyroxene pp and radial pyroxene rp chondrules in refractory lithophiles and siderophiles unlike oc chondrules qingzhen s rp and pp chondrules have similar bulk compositions elements in each of the following sets intercorrelate significantly probably because these elements were present in the same nebular components 1 1 fe co ni ir au 2 2 ca eu se 3 3 al sc hf 4 4 na ree 5 5 cl br several additional elements show no correlations set 1 elements were probably derived from a metal component as in oc chondrules set 3 elements which occur in higher concentrations in olivine bearing pop chondrules suggest the existence of a refractory lithophile rich olivine rich component similar to the one previously inferred for oc chondrules set 2 elements suggest a precursor component rich in oldhamite and set 4 elements suggest another refractory bearing component components 2 and 4 were not precursors of oc chondrules for some chondrules interelement ratios of refractory lithophiles such as ca al ti sc and ree are similar to ci ratios this indicates that these elements were probably derived from silicates we suggest that the earliest solid phases were refractory silicates that were sulfurized before chondrule formation some of these sulfurized components e g one rich in oldhamite were abundant in the region where the qingzhen chondrules formed

hydroclimatic variations over the last millennium in eastern finland disentangled by fossil cladocera abstract future climate warming is expected to alter atmospheric moisture balance and therefore paleoclimatic archives of past moisture and hydrological patterns may provide understanding of the magnitude speed and ecosystem responses to the regionally altered climatic regimes the present study aimed at disentangling millennial variation in hydroclimatic parameters including summer effective moisture lake levels and ice free season by using sedimentary cladoceran fossils we used a site specific cladoceran based inference model to reconstruct lake level fluctuations in a 1500 yr sediment record from lake pieni kauro eastern finland in the context of previously established paleoclimatic data of summer temperature and precipitation in addition we applied cladoceran planktonic littoral ratio mean body size and abundance of fossil ephippia as supplementary proxies for paleoclimatic interpretations the results showed that lake level was lower during the pre and early medieval climate anomaly mca around 500 1000 ad than at present and started to rise toward the culmination during the little ice age lia around 1600 1700 ad when the lake level was higher than at present pelagic cladoceran body size was larger and abundance of ephippia increased during the lia suggesting significant reduction in the length of the ice free season and lower water temperatures comparison of the lake level reconstruction with the previous paleoclimatic data suggested that effective moisture has had a long term negative relationship with temperature and positive relationship with summer precipitation in eastern finland the results indicated that the pre and early mca was warm and dry long ice free season low summer effective moisture and the culmination of the lia was cool and moist reduced ice free season increased summer effective moisture unraveling the seasonality of the multicentury hydroclimatic patterns in eastern finland may offer important insights in linking the large scale atmospheric circulation patterns to seasonal climate events

petrology and oxygen isotope compositions of chondrules in e3 chondrites chondrules in e3 chondrites differ from those in other chondrite groups many contain near pure endmember enstatite fs 1 some contain si bearing feni metal cr bearing troilite and in some cases mg mn and ca sulfides olivine and more feo rich pyroxene grains are present but much less common than in ordinary or carbonaceous chondrite chondrules in some cases the feo rich grains contain dusty inclusions of metal the oxygen three isotope ratios 18o 17o of olivine and pyroxene in chondrules from e3 chondrites which are measured using a multi collection sims show a wide range of values most enstatite data plots on the terrestrial fractionation tf line near whole rock values and some plot near the ordinary chondrite region on the 3 isotope diagram pyroxene with higher feo contents 2 10 wt feo generally plots on the tf line similar to enstatite suggesting it formed locally in the ec enstatite chondrite region and that oxidation reduction conditions varied within the e3 chondrite chondrule forming region olivine shows a wide range of correlated 18o and 17o values and data from two olivine bearing chondrules form a slope 1 mixing line which is approximately parallel to but distinct from the ccam carbonaceous chondrite anhydrous mixing line we refer to this as the ecm enstatite chondrite mixing line but it also may coincide with a line defined by chondrules from acfer 094 referred to as the pcm primitive chondrite mineral line ushikubo et al 2011 the range of o isotope compositions and mixing behavior in e3 chondrules is similar to that in o and c chondrite groups indicating similar chondrule forming processes solid gas mixing and possibly similar 16o rich precursors solids however e3 chondrules formed in a distinct oxygen reservoir internal oxygen isotope heterogeneity was found among minerals from some of the chondrules in e3 chondrites suggesting incomplete melting of the chondrules survival of minerals from previous generations of chondrules and chondrule recycling olivine possibly a relict grain in one chondrule has an r chondrite like oxygen isotope composition and may indicate limited mixing of materials from other reservoirs calcium aluminum rich inclusions cais in e3 chondrites have petrologic characteristics and oxygen isotope ratios similar to those in other chondrite groups however chondrules from e3 chondrites differ markedly from those in other chondrite groups from this we conclude that chondrule formation was a local event but cais may have all formed in one distinct place and time and were later redistributed to the various chondrule forming and parent body accretion regions this also implies that transport mechanisms were less active at the time of and following chondrule formation

c4 plant productivity and climate co2 variations in south central texas during the late quaternary abstract a continuous record of organic carbon 13c from a buried soil sequence in south central texas demonstrates 1 strong coupling between marine and adjacent continental ecosystems in the late pleistocene as a result of glacial meltwater entering the gulf of mexico and 2 ecosystem decoupling in the holocene associated with a reduction of meltwater and a shift in global circulation patterns in the late pleistocene reduction in c4 plant productivity correlates with two well documented glacial meltwater pulses 15 000 and 12 000 14c yr b p indicating a cooler than present adjacent continental environment increased c4 production between 11 000 and 10 000 14c yr b p suggests that the younger dryas was a warm interval responding to the diversion of glacial meltwater away from the mississippi river with waning meltwater flow c4 productivity generally increased throughout the holocene culminating in peak warm intervals at 5000 and 2000 14c yr b p shifts in the abundances of c3 c4 plants through the late quaternary show no correlation to ecophysiological responses to atmospheric co2 concentration

recent ecological change in a remote scottish mountain loch an evaluation of a cladocera based temperature transfer function recent ecological changes in a small scottish mountain loch loch coire fionnaraich lcfr were inferred using cladocera analysis and an application of a cladocera based temperature transfer function approach modern assemblages of cladocera from 68 mountain lakes in scotland and norway were used to derive the transfer function among 21 measured environmental variables mean summer lake surface water temperature lswt accounted for the highest 8 variation in a redundancy analysis of the modern data a quantitative inference model r2 0 72 rmsep 1 81 c for summer lswt was developed using linear partial least squares regression and calibration the resulting reconstructed summer lswt at lcfr was compared with local instrumental air temperature records over the last 20 yr and the central england temperature cet series over the last 110 yr the reconstruction showed a broadly similar pattern to the local instrumental temperature records however the relationship between the longer cet series and reconstructed summer lswt was poor suggesting that the site was relatively insensitive to temperature changes prior to the recent warming of the last few decades clear changes in cladoceran species diversity and relative abundance of littoral taxa coincident with the most recent period of climate warming recorded both locally and in the cet suggest that cladocera do respond to climate change however their response to temperature is complex and indirect the underlying mechanism leading to change in cladocera assemblages may involve changes in trophic status and habitat availability of the system it is concluded that understanding other factors such as atmospheric pollution controls of community dynamics of cladocera and the overall ecological complexity of mountain lakes is required before any reliance can be placed on a cladocera temperature transfer function for reconstructing climatic change crown copyright 2008

late weichselian and holocene record of the paleoenvironmental changes in a small river valley in central poland abstract the developmental history from the oldest dryas to the late holocene of a paleolake and mire located in a river valley in central poland was studied using high resolution records of pollen macrofossils cladocera sedimentology and geochemistry from a 14 c dated sediment core we inferred temperature and water level dynamics using cladocerans and palynological and geochemical methods were employed to investigate natural fluvial activity particularly for these elements that are difficult to find through sedimentological methods our research demonstrates how climate fluctuation in the late glacial and holocene periods influenced the development of a paleolake and mire in a small river valley and shows the importance of long term research to establish hydroclimatic conditions in biogenic sediments we propose that water level fluctuations were important in modifying biotic assemblages the results of our multiproxy analysis clearly suggest that the main driver of changes in aquatic and terrestrial ecosystems as well as in geomorphological processes in the valley was climate reconstructed temperatures generally follow the known trends showing an increase at the beginning of the bolling allerod and holocene and a decrease at the beginning of the oldest and younger dryas similarly periods of water level increase are synchronous with climatic changes however the local environmental forces were a significant factors affecting biotic diversity in the studied time span fish predation macrophyte structure ph and calcium content partly influence the results of the cladoceran based water depth reconstruction in particular interestingly the cladoceran inferred summer temperature reconstruction for pawlowa appear realistic although the temperature trends can be considered reliable our results indicate the important role of local factors which control the species composition of the subfossil assemblages

july mean temperature and annual precipitation trends during the holocene in the fennoscandian tree line area pollen based climate reconstructions july mean temperature and annual precipipation during the last 9900 cal yr bp were recon structed from pollen assemblages preserved in a sediment core from northern finland quantitative recon structions were performed using a modern pollen climate calibration model based on weighted averaging partial least squares regression the predictive ability of the model was evaluated against modern meteoro logical data using leave one out cross validation the prediction error for july mean temperature is c 1 0 c and for annual precipitation 340 mm the july mean temperatures during the earliest holocene were low c 1 1 0 c and annual precipitation was high c 600 800 mm between 8200 and 6700 cal yr bp july mean temperatures reached their maxima 12 5 13 0 c which are c 1 4 1 7 c higher than at present at the same time precipitation decreased during the late holocene july mean temperatures declined and the last 2000 years have been the coolest since the early holocene precipitation has slightly increased the spatial coherence between our results and of several other climate reconstructions from northern europe indicates that the holocene climate was strongly influenced by north atlantic oceanic and atmospheric circulation patterns we propose that the distinctly oceanic climate of the early holocene was due to enhanced westerly latitudinal airflow which was replaced at c 8200 cal yr bp by a more meridional flow pattern and by the development of predominantly anticyclonic summer conditions

the thermometry of enstatite chondrites a brief review and update due to the discoveries in antarctica the number of known enstatite chondrites has doubled in the last few years and many rare or previously unknown types have been collected most notably many el3 and eh3 chondrites we have applied the five major enstatite chondrite thermometers to the new and previously known enstatite chondrites the thermometers being 1 kamacite quartz enstatite oldhamite troilite kqeot 2 oldhamite 3 alabandite niningerite 4 sphalerite and 5 phosphide metal measured temperatures based on the kqeot and oldhamite systems are 800 c 1000 c with the type 3 enstatite chondrites having values similar to those of type 4 6 it seems likely that these temperatures relate to events prior to parent body metamorphism such as nebula condensation or chondrule formation and were not significantly reset by later events measured temperatures for alabandite niningerite metal phosphide and sphalerite in eh chondrites increase from 300 c 400 c to 600 c 800 c with petrographic indications of increasing metamorphism in contrast measured temperatures for all el chondrites including the most heavily metamorphosed are generally 400 c apparently el chondrites cooled more slowly than the eh chondrites regardless of metamorphism experienced measured temperatures for the alabandite niningerite metal phosphide and sphalerite are actually closure temperatures for the last thermal event suffered by the meteorite and the fast cooling rates indicated are most consistent with processes occurring in thick regoliths

late quaternary dust flow on the chinese loess plateau abstract the dust flux of over 25 g cm2 103yr was reached in the central part of the chinese loess plateau during the last glacial maximum this is more than three times higher than during the last interglacial and early glacial time the grain size of the pleniglacial dust reached a peak shortly after 20 000 years ago and testifies to the occurrence of strong winds and frequent dust storms

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

experimental study and tem characterization of dusty olivines in chondrites evidence for formation by in situ reduction an analytical transmission electron microscopy atem study was undertaken in order to better understand the formation conditions of dusty olivines i e olivines containing abundant tiny inclusions of fe ni metal in primitive meteorites dusty olivines from type i chondrules in the bishunpur chondrite ll3 1 and from synthetic samples obtained by reduction of san carlos olivines were examined in both natural and experimental samples micron size metal blebs observed in the dusty region often show preferential alignments along crystallographic directions of the olivine grains have low ni contents typically 2 wt and are frequently surrounded by a silica rich glass layer these features suggest that dusty olivines are formed by a sub solidus reduction of initially fayalitic olivines according to the following reaction fe2sio4 in olivine 2fe metal xsio2 in melt 1 x sioin gas 3 x 2o2 in gas some volatilization of siogas may account for the apparent excess of metal relative to silica rich glass observed in both experimental and natural samples comparison with experimentally produced dusty olivines suggests that time scales of the order of minutes usually inferred for chondrule formation are also adequate for the formation of dusty olivines these observations are in agreement with the hypothesis that at least part of the metal phase in chondrites originated from reduction during chondrule formation

sedimentary cladocera as indicators of past water level changes in shallow northern lakes the usability of subfossil cladocera assemblages in reconstructing long term changes in lake level was examined by testing the relationship between cladocera based planktonic littoral p l ratio and water level inference model in a surface sediment dataset and in a 2000 yr sediment record in finland the relationships between measured and inferred water levels and p l ratios were significant in the dataset implying that littoral taxa are primarily deposited in shallow littoral areas while planktonic cladocerans accumulate abundantly mainly in deepwater locations the 2000 yr water level reconstructions based on the water level inference model and p l ratio corresponded closely with each other and with a previously available midge inferred water level reconstruction from the same core showing a period of lower water level around ad 300 1000 and suggesting that the methods are valid for paleolimnological and climatological use

how cold was the little ice age a proxy based reconstruction from finland applying modern analogues of fossil midge assemblages climate dynamics during the past ca 700 years in southern finland were reconstructed using fossil midge diptera nematocera assemblages aiming to estimate quantitatively the temperature change that has occurred from the little ice age to the present midge stratigraphies of two sediment cores from eastern and southern finland were chosen to be examined for temperature inferences utilizing the modern analogue technique the new midge based temperature inference model had a coefficient of determination of 0 901 and a prediction error of 0 498 c showing improvement over the previous finnish models the combined curve of the inferred temperatures derived from both of the cores showed a decrease towards ca 1700 ad when temperatures were approximately 1 c cooler than the past 700 years average and almost 2 c colder than present the temperatures began to increase in southern finland from 1800 ad and in eastern finland from 1900 ad onwards the highest temperatures were reached at the top of the core representing the present climate warming although there was slight overestimation in the recent inferred values the reconstructed trends were in close correspondence with the previous proxy based historical and measured data that suggests that the reconstruction was realistic and reliable

properties of chondrules in el3 chondrites comparison with eh3 chondrites and the implications for the formation of enstatite chondrites the study of chondrules provides information about processes occurring in the early solar system in order to ascertain to what extent these processes played a role in determining the properties of the enstatite chondrites the physical and chemical properties of chondrules from three el3 chondrites and three eh3 chondrites have been examined by optical cathodoluminescence cl and electron microprobe techniques properties examined include size texture cl and composition of both individual phases and bulk chondrules the textures distribution of textures and composition of silicates of the el3 chondrules resemble those of eh3 chondrules however the chondrules from the two classes differ in that 1 the size distribution of the el chondrules is skewed to larger values than eh chondrules 2 the enstatite in el chondrules displays varying shades of red cl due to the presence of fine grained sulfides and metal in the silicates and 3 the mesostasis of eh chondrules is enriched in na relative to that of el chondrules the similarities between the chondrules of the two classes suggest similar precursor materials while the differences suggest that there was not a single reservoir of meteoritic chondrules but that their origin was fairly local the differences in the size distribution of chondrules in eh and el chondrites may be explained by aerodynamic and gravitational sorting during accumulation of the meteoric material while differences in cl and mesostasis properties may reflect differences in formation conditions and cooling rate following chondrule formation we argue that our observations are consistent with the formation of enstatite chondrites in a thick dynamic regolith on their parent body

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

reconstruction of the holocene palaeoenvironmental conditions accordingly to the multiproxy sedimentary records from lake pilvelis latvia abstract reconstruction of the holocene palaeoenvironment conditions in southeastern latvia is based on multiproxy records from lake pilvelis pollen plant macrofossil and microfossil analysis loss on ignition loi measurements 14 c dating humic substances content humification index and elemental composition of gyttja organic mass the data complex obtained in the result of multiproxy studies of sediments in lake pilvelis indicates significant changes in the depositional environment during the lake development data from lake pilvelis show that the start of organic rich sediments formation before approximately 9750 cal bp when birch pine forest dominated in the surrounding landscape diagrams and data sets show six remarkable comparatively short cooling periods during the holocene which are related to changes in temperature and water level and influenced values and variability of remains the investigation recognized the 8 4 ka bp and 4 6 ka bp cold events while other cooling events can be recognised conditionally during the events of 4 0 ka bp the water level decreased extremely and the climate was probably drier indicated by the comparison of records from lake pilvelis mazais svetinu bog and lake razna a comparison of pollen data from lake pilvelis with lake kurjanovas mazais svetinu bog and lake razna shows some similarities revealing features of cooler climatic conditions approximately at the time characterised by an increase of betula and herb pollen

multicentennial megadrought in northern europe coincided with a global el nino southern oscillation drought pattern during the medieval climate anomaly the el nino southern oscillation enso is a pacemaker of global climate and the accu rate prediction of future climate change requires an understanding of the enso variability recently much debated aspects of the enso have included its long term past and future changes and its associations with the north atlantic and european sectors potentially in inter action with the north atlantic oscillation and the atlantic multidecadal oscillation here we present the fi rst european dendroclimatic precipitation reconstruction that extends through the alternating climate phases of the medieval climate anomaly and the little ice age we show that northern europe underwent a severe precipitation defi cit during the medieval climate anomaly which was synchronous with droughts in various enso sensitive regions worldwide while the subsequent centuries during the little ice age were markedly wetter we attribute this drought primarily to an interaction between the enso and the north atlantic oscillation and to a lesser or negligible degree to an interaction between the enso and the atlantic multidecadal oscillation

the origin and history of the metal and sulfide components of chondrules abstract fourteen siderophile and other non lithophile elements determined in 31 semarkona ll3 0 chondrules by neutron activation analysis are severely fractionated relative to lithophile elements their chondrule whole rock abundance ratios vary by factors of up to 1000 the mean ratio is 0 2 non refractory siderophile abundance patterns in ni rich chondrules are smooth functions of volatility and in ni poor chondrules patterns are more irregular refractory siderophile elements are often fractionated from ni they covary confirming the presence of a refractory metal component the chalcophile element se correlates with br and siderophile elements zinc is uniformly low and uncorrelated with other elements most metal and sulfide in chondrules was probably present in the solar nebula before chondrule formation most siderophile and chalcophile elements were in these materials some fe was also in silicates as were minor amounts of ni co au ge and possibly se the amount of metal formed by reduction during chondrule melting was minor the common metal component in chondrules is similar to and may be the same as the common component involved in the metal silicate fractionation of the ordinary chondrite groups chondrules are depleted in metal chiefly because they sampled metal poor precursor assemblages metal segregation during the molten period and subsequent loss was a minor process that may be responsible for most surface craters on chondrules

temperature and effective moisture variability in southern finland during the holocene quantified with midge based calibration models effective moisture and temperature dynamics during the late glacial and holocene were reconstructed from fossil midge diptera nematocera assemblages in lake hirvijarvi southern finland quantitative inferences were performed using midge based transfer functions for water depth and mean july air temperature the aim was to identify major trends in holocene climate development the results were generally consistent with patterns found in previous investigations from nearby regions and indicated some distinct differences in palaeoclimate between southern and northern finland the results indicate that the region was characterised by a very cold late pleistocene cool and moist but drying early holocene warm and moist mid holocene and cool and moist late holocene a progressive trend of increasing lake levels from the early holocene towards the present was evident the results of this study provide implications for regional differences in effective moisture between southern and northern finland during the holocene copyright 2010 john wiley sons ltd

palaeoecological record of natural changes and human impact in a small river valley in central poland abstract the developmental history of a mire located in the grabia river valley central poland spanning the last 9000 years was investigated using high resolution records of pollen cladocera and geochemistry from a 14c dated core the study demonstrates the value of cladocera palynological and geochemical methods in research into human impact and natural fluvial activity particularly for those elements that are difficult to find through sedimentological methods our research shows the importance of long term reconstructions in establishing palaeohydroclimatic conditions and determining the human impact on the mire we propose that water level fluctuations were important in modifying biota assemblages periods with higher water levels are synchronous with climatic changes but in the subatlantic they also correspond to phases of human activity in the valley the probable phases of increased fluvial activity of the grabia river coincide in general with periods of wet climate deforestation and soil erosion the main phases that show increases in the water level in the lower part of grabia river valley are estimated at ca 5800 5500 bc 4500 4300 bc 4200 3800 bc and 400 ad the water level changes of 1300 ad 1500 ad and 1650 ad as well as those of the last century were most strongly influenced by a combination of natural and anthropogenic factors anthropogenic events were particularly significant during the middle ages and in the last century

first known el5 chondrite evidence for dual genetic sequence for enstatite chondrites the enstatite chondrites form two compositionally distinct groups the eh and el chondrites and four petrologic types types 3 6 where each type represents increasing degrees of metamorphic alteration1 2 prior to the recovery of the antarctic meteorite reckling peak a80259 the subject of the present report all known el chondrites were petrologic type 6 whereas all known eh chondrites were types 3 5 it has long been appreciated that the variations in bulk composition preclude a simple conversion of eh4 material into el6 material3 7 however complex models involving simultaneous variations in bulk composition and petrologic type have been discussed1 5 8 9 and may be implied by other classification schemes in common use that of anders keil type i intermediate type ii and that of van schmus and wood e3 e4 e5 e6 we report here the discovery of the first el5 chondrite an el5 breaks the eh3 4 eh5 el6 sequence and indicates that the enstatite chondrites constitute two discrete isochemical metamorphic sequences eh3 5 and el5 6

fine nickel poor fe ni grains in the olivine of unequilibrated ordinary chondrites abstract fine 2 m ni poor 10 mg g fe ni grains are common inclusions in the olivine in porphyritic chondrules in unequilibrated ordinary chondrites the olivine grains appear to be relicts that survived chondrule formation without melting the most common occurrence of this dusty metal is in the core of olivine grains having clear fe poor rims and surrounded either by small euhedral clear olivine grains zoned with feo increasing toward the border of the grains or by large elongated fe poor orthopyroxenes oriented parallel to the chondrule surface and enclosing small round olivine grains various amounts of ca al rich glass are always present the dusty metal is occasionally found in the rims of olivine grains either isolated in the matrix or included in chondrules a rare occurrence is as bands in highly deformed olivines this dusty metal appears to be the product of in situ reduction of feo from the host olivine among the possible reductants h2 or carbonaceous matter ch2 n seem the most likely hydrogen may have been implanted by solar wind or solar flare irradiation but this requires that dissipation of nebular gas occurred before the end of the chondrule formation process carbonaceous matter may have been implanted by shock less likely reductants are nebular co or c dissolved in the olivine lattice the large relict olivine grains may be nebular condensates or more likely fragments broken off earlier generations of chondrules

alkenone temperature estimates for the east sea during the last 190 000 years abstract the late quaternary records of alkenone based sea surface temperature sst from a core located in the western margin of the east sea japan sea showed that the estimated temperature fluctuated greatly the variability being consistent with orbital scale global climate records during the period of marine isotope stage mis 6 the alkenone temperatures were low 7 10 c whereas during mis 5 5 the temperature increased rapidly up to 21 c during the entire period of mis 5 the temperature decreased from 21 c to 13 c then the temperature fluctuated between 10 c and 15 c during miss 4 and 3 after that it continued to fluctuate between 15 c and 17 c variation in the east sea sst is considered to be closely related to changes in the east asian monsoon system and seawater transport by the tsushima warm current the glacial surface cooling could be associated with the strong winter monsoon and or weakened summer monsoon in east asia during the glacial period when the sea level was low the influx of warm water was restricted and this might have enhanced the lowering of the surface temperature these conditions most likely caused significant changes in surface water circulation a basin scale cyclonic gyre might have occurred in the east sea without the development of the subpolar front during the interglacial period the surface warming seems to be related to the intensified summer monsoon system the high stand of the sea level and climate change most likely caused the development of cyclonic and anti cyclonic gyres in the north and south respectively and the subpolar front in the central part of the sea

a multiproxy study of younger dryas and early holocene climatic conditions from the grabia river paleo oxbow lake central poland abstract a multi proxy reconstruction of water depth temperature and precipitation inferred from cladocera chironomidae and pollen assemblages has been obtained from wierczyna paleo oxbow central poland during the younger dryas yd and early holocene results suggest that the yd was relatively cold and comprised two main phases the first ca 12 500 12 000 cal yrs bp is characterized by a continental climatic regime and a decrease in winter temperatures and precipitation but an increase in spring summer precipitation the second phase ca 12 000 11 500 cal yrs bp was more mild with a variable continental climate an increase in summer and winter temperature a lengthening of the growing season and increased annual precipitation the reconstructed water level generally follows changes in spring and summer precipitation and length of growing season the frequency and timing of hydroclimatic oscillations at wierczyna show strong similarities to records from other sites in europe this confirms that oxbows and valley mire ecosystems respond to rapid climate change during the yd and early holocene this study therefore brings new insights into the effects of climate changes on river environments especially during the yd we also discuss the limitations of water depth temperature and precipitation reconstructions inferred from the studied biotic assemblages

evidence for relict grains in chondrules of qingzhen an e3 type enstatite chondrite abstract petrographic and chemical studies of the qingzhen chondrite strongly suggest that it is the most highly unequilibrated type 3 enstatite chondrite recognized so far qingzhen contains abundant well defined chondrules some of which were incompletely molten during the chondrule formation process the relict olivine grains within these chondrules contain dusty inclusions of almost pure metallic fe which appear to be the in situ reduction product of the fayalitic component of the olivine the reduction process presumably took place at the time of chondrule formation and the chondrule precursor material must have been more oxidized than average enstatite chondrite material we believe that this oxidized material may have formed at the enstatite chondrite formation location in the solar nebula provided fluctuations in the degree of oxidation of the nebular gas existed at such locations reheating of this material under more reducing conditions would lead to the observed reduction of the olivine igneous olivines within chondrules always contain detectable amounts of cao while relict olivines are essentially cao free this seems to suggest that the relict olivines did not originate during a previous igneous process of chondrule formation and might represent condensation products from the early solar nebula

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

ree and actinide microdistribution in sahara 97072 and alha77295 eh3 chondrites a combined cosmochemical and petrologic investigation abstract we report the results of rare earth elements rees and u th inventory of individual minerals oldhamite enstatite and niningerite in two of the most unequilibrated and primitive eh3 known so far alha77295 and sahara 97072 under the highly reducing condition that prevailed during the formation of enstatite chondrites rees are mainly chalcophile and concentrated in oldhamite the study is guided by detailed petrographic investigations of the individual minerals in chondrules complex sulfide metal clasts and enstatite dominated matrices we developed two textural parameters in order to resolve the evolution of oldhamite condensates and their residence in the solar gas prior to their accretion in the individual objects or in matrices and relate these textural features to the measured ree patterns of the individual oldhamite crystals these textural parameters are the crystal habit of oldhamite grains idiomorphic or anhedral and their host assemblages ree concentrations were measured by sims and la icpms oldhamite grains display ree enrichments 10 100 ci four types of ree patterns are encountered in oldhamite in alha77295 in general the ree distributions cannot be assigned to a specific oldhamite bearing assemblage the most represented ree pattern is characterized by both slight to large positive eu and yb anomalies and is enriched in light rees relative to heavy rees this pattern is present in 97 of oldhamite in sahara 97072 suggesting a different source region in the reduced part of the nebula or different parental eh asteroids for the two eh3 chondrites different parental asteroids are also supported by mgs fes zoning profiles in niningerite grains adjacent to troilite revealing both normal and reverse zoning trends and different mns contents the observed homogeneity of ree distribution in oldhamite grains in sahara 97072 is not related to the mild metamorphic event identified in this meteorite that caused breakdown of the major k and rb bearing sulfide djerfisherite ree concentrations in enstatite range between 0 2 and 8 ci hence enstatite is an important ree host next to oldhamite most patterns are characterized by negative eu and yb anomalies niningerites are negligible contributors to bulk eh3 ree inventory average positive eu and yb anomalies observed in most oldhamite are complimentary to the negative ones in enstatite thus explaining the flat patterns of the bulk meteorites the condensation calculations based on cosmic abundances predict that the first oldhamite condensates should have flat ree patterns with eu and yb depletions since eu and yb condense at lower temperature than other ree however this pattern is seen in enstatite our findings are at odds with the predicted negative eu and yb anomalies in oldhamite earliest condensates from a closed system in a reduced solar source our petrographic mineral chemistry and ree abundances of oldhamite enstatite and niningerite discards an origin of oldhamite by impact melting rubin et al 2009 our results do not support in first order the scenario of the incorporation of ree in the earth s core to explain 142nd excess in terrestrial samples relative to chondrites because oldhamite is the major ree carrier phase and has super chondritic sm nd ratios

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