seismic detection of the lunar core despite recent insight regarding the history and current state of the moon from satellite sensing and analyses of limited apollo era seismic data deficiencies remain in our understanding of the deep lunar interior we reanalyzed apollo lunar seismograms using array processing methods to search for the presence of reflected and converted seismic energy from the core our results suggest the presence of a solid inner and fluid outer core overlain by a partially molten boundary layer the relative sizes of the inner and outer core suggest that the core is 60 liquid by volume based on phase diagrams of iron alloys and the presence of partial melt the core probably contains less than 6 weight of lighter alloying components which is consistent with a volatile depleted interior

quantification of holocene asian monsoon rainfall from spatially separated cave records abstract a reconstruction of holocene rainfall is presented for southwest china an area prone to drought and flooding due to variability in the east asian monsoon the reconstruction is derived by comparing a new high resolution stalagmite 18 o record with an existing record from the same moisture transport pathway the new record is from heshang cave 30 27 n 110 25 e 294 m and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature heshang lies 600 km downwind from dongge cave which has a published high resolution 18 o record wang y j cheng h edwards r l he y q kong x g an z s wu j y kelly m j dykoski c a li x d 2005 the holocene asian monsoon links to solar changes and north atlantic climate science 308 854 857 by differencing co eval 18 o values for the two caves secondary controls on 18 o e g moisture source moisture transport non local rainfall temperature are circumvented and the resulting 18 o signal is controlled directly by the amount of rain falling between the two sites this is confirmed by comparison with rainfall data from the instrumental record which also allows a calibration of the 18 o proxy the calibrated 18 o record provides a quantitative history of rainfall in southwest china which demonstrates that rainfall was 8 higher than today during the holocene climatic optimum 6 ka but only 3 higher during the early holocene significant multi centennial variability also occurred with notable dry periods at 8 2 ka 4 8 4 1 ka 3 7 3 1 ka 1 4 1 0 ka and during the little ice age this holocene rainfall record provides a good target with which to test climate models the approach used here of combining stalagmite records from more than one location will also allow quantification of rainfall patterns for past times in other regions

comment on prediction of metal silicate partition coefficients for siderophile elements an update and assessment of pt conditions for metal silicate equilibrium during accretion of the earth by k righter epsl 304 2011 158 167 2011

lunar core formation new constraints from metal silicate partitioning of siderophile elements abstract analyses of apollo era seismograms lunar laser ranging data and the lunar moment of inertia suggest the presence of a small at least partially molten fe rich metallic core in the moon but the chemical composition and formation conditions of this core are not well constrained here we assess whether pressure temperature conditions can be found at which the lunar silicate mantle equilibrated with a fe rich metallic liquid during core formation to this end we combine measurements of the metal silicate partitioning behavior of siderophile elements with the estimated depletion due to core formation in those elements in the silicate mantle of the moon we also explore how the presence of the light element sulfur suggested by seismic models to be present in the core at concentrations of up to 6 wt in the lunar core affects core formation models we use published metal silicate partitioning data for ni co w mo p v and cr in the lunar pressure range 1 atm 5 gpa and characterize the dependence of the metal silicate partition coefficients d on temperature pressure oxygen fugacity and composition of the silicate melt and the metal if the core is assumed to consist of pure iron core mantle equilibration conditions that best satisfy lunar mantle depletions of five siderophile elements ni co w mo and p are a pressure of 4 5 0 5 gpa and a temperature of 2200 k the lunar mantle depletions of cr and v are also consistent with metal silicate equilibration in this pressure and temperature range if 6 wt s is incorporated into the lunar core our results therefore suggest that metal silicate equilibrium during lunar core formation occurred at depths close to the present day lunar core mantle boundary this provides independent support for both the existence of a deep magma ocean in the moon in its early history and the presence of significant amounts of sulfur in the lunar core

interior of the moon the presence of garnet in the primitive deep lunar mantle new trace element data have been generated by inductively coupled plasma mass spectrometry icp ms for 65 high and low ti mare basalts from the apollo 11 12 14 15 and 17 landing sites these data demonstrate that ratios of the high field strength elements and yttrium are generally chondritic in the mare source regions for the low ti basalts but nonchondritic in the high ti basalts and potassium rare earth elements and phosphorus kreep such differences can be explained by addition and subtraction respectively of ilmenite this interpretation is consistent with derivation of the basalts from lunar magma ocean lmo cumulates through which late stage ilmenite has sunk and mixed with earlier magma ocean products compositional differences between the mare basalts and volcanic glass beads suggest that at least some of the latter were derived from a garnet bearing source region siderophile and chalcophile element data suggest that the garnet bearing source escaped the lmo melting event and thus represents primitive moon material the remaining glasses are generally very low ti vlt and appear to have been derived from early lmo cumulates i e olivine and orthopyroxene similar to the vlt basalts the remaining glasses were derived from below the lmo cumulates and as the magmas rose they underwent sequential assimilation to varying degrees initially of an ilmenite rich cumulate followed by a kreep component this study presents geochemical evidence for the existence of garnet in a mare source and demonstrates the likelihood that the lmo was not whole moon thus preserving primitive lunar material which has acted as the source region for at least some of the volcanic glasses

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

the moon re examined abstract recent geochemical and geophysical data from the moon enable a revision of earlier interpretations regarding lunar origin structure and bulk composition earth and moon show many similarities among their isotopic compositions but they have evolved in totally dissimilar ways probably related to the deficiency of water in the moon as well as the vast differences in size and internal pressure although some global geochemical trends such as volatile depletion based on k u ratios have been established current lunar samples come from differentiated regions making the establishment of a bulk composition more reliant on bulk geophysical properties or isotopic similarities although it remains unclear how the latter relate to whole moon composition the lack of fractionation effects among the refractory and super refractory elements indicates that the proto lunar material seems unlikely to have been vaporized while the depletion of volatile elements may place lower limits on proto lunar temperatures the apparent lack of geochemical evidence of an impacting body enables other possible impactors such as comets to be considered

a 5200 year paleoecological and geochemical record of coastal environmental changes and shoreline fluctuations in southwestern louisiana implications for coastal sustainability abstract this study presents a 5200 year history of coastal environmental changes and shoreline fluctuations based on a multi proxy sedimentary record developed from the eastern end of louisiana s chenier plain palynological loss on ignition grain size and x ray fluorescence data for a 525 cm sedimentary core indicate five stages of ecosystem development in the rockefeller wildlife refuge since the mid holocene between 5190 and 4240 cal yr bp the relative sea level was much lower than the present level and our study area was occupied by a baldcypress swamp when the sale cypremont subdelta complex formed at a western position approximately 4600 years ago our study area was transformed to a maritime forest about 4240 3440 cal yr bp suggesting shoreline progradation when the mississippi river delta lobe switched to more easterly positions during the teche st bernard lafourche and plaquemine balize complexes our study site was transformed back to a freshwater swamp between 3440 and 1520 cal yr bp and then to a coastal marsh between 1520 and 300 cal yr bp after the atchafalaya wax lake subdelta complex formed at a more westerly position again the modern day beach form at 300 cal yr bp these coastal ecosystem developments suggest that shoreline retreat started at 3440 cal yr bp and persisted to the present day in addition evidence of at least four possible paleohurricane events was found during the late holocene our multi proxy record demonstrates that shoreline fluctuation in southwestern louisiana was tied to the mississippi river delta switch since the mid holocene shoreline progradation occurred during the sale cypremont subdelta phase 5200 3500 years ago when the sediment supply was high retrogradation occurred after 3500 cal yr bp when the mississippi river subdelta complexes occupied more easterly position resulting in diminished sediment supply a significant increase in the delivery of water and total suspended sediment load from the atchafalaya river to the gulf of mexico is needed in order to sustain the southwestern louisiana coastal wetlands

the lunar dynamo background it is unknown whether the moon has a fully differentiated and melted structure with a metallic core or retains a partially primordial unmelted interior the differentiation history of the moon is manifested by its record of past magnetism paleomagnetism although the moon today does not have a global magnetic field the discovery of remanent magnetization in lunar rocks and in the lunar crust demonstrated that there was a substantial lunar surface field billions of years ago however the origin intensity and lifetime of this field have been uncertain as a result it has been unclear whether this magnetization was produced by a dynamo in the moon s advecting metallic core or by fields generated externally to the moon establishing whether the moon formed a core dynamo would have major implications for understanding its interior structure thermal history and mechanism of formation as well for our understanding of the physics of planetary magnetic field generation the interior structure of the moon and the lunar dynamo new magnetic measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its advecting liquid metallic core innermost red shell this dynamo may have been driven by convection possibly powered by crystallization of the core innermost red sphere and or stirring from the solid mantle thick green shell the magnetic field was recorded as magnetization by rocks on the lunar surface image created by hernan canellas the interior structure of the moon and the lunar dynamo new magnetic measurements of lunar rocks have demonstrated that the ancient moon generated a dynamo magnetic field in its advecting liquid metallic core innermost red shell this dynamo may have been driven by convection possibly powered by crystallization of the core innermost red sphere and or stirring from the solid mantle thick green shell the magnetic field was recorded as magnetization by rocks on the lunar surface image created by hernan canellas advances a new generation of laboratory magnetic studies of lunar rocks and spacecraft measurements of lunar crustal magnetic fields have produced major advances in our understanding of the evolution of ancient magnetic fields on the moon it has now been established that a dynamo magnetic field likely existed on the moon from at least 4 5 billion to 3 56 billion years ago with an intensity similar to that at the surface of earth today the field then declined by at least an order of magnitude by 3 3 billion years ago the early epoch of high field intensities may require an exceptionally energetic power source such as mechanical stirring from mantle precession the extended history of the lunar dynamo appears to demand long lived power sources such as mantle precession and core crystallization outlook measurements of the intensity of the ancient lunar dynamo have shown that it was surprisingly intense and long lived the next phase of lunar magnetic exploration will be to obtain more accurate measurements of field paleointensities and to determine when the dynamo initiated and finally disappeared this will be coupled with the continued development of magnetohydrodynamic models for characterizing mechanical and other unusual dynamo mechanisms and further investigations into the thermal structural and geodynamical history of the lunar core and mantle the eventual availability of absolutely oriented samples and in situ spacecraft measurements of bedrock should enable the first measurements of the paleo orientation of lunar magnetic fields such directional data could determine the lunar field s geometry and reversal frequency as well as constrain ancient local and global scale tectonic events

holocene climate change and human impacts implied from the pollen records in anyang central china age constrained and high resolution pollen records from 12 000 cal bp to the late holocene from wangjiadian a site close to the yinxu and huanbei archaeological sites are presented and compared with archaeological data to reconstruct climate change and human impact during the holocene in the anyang region central china the pollen data demonstrate that the younger dryas event occurred between 11 500 and 10 000 cal bp and that the time between 8200 and 3400 cal bp was a period of warm temperature and high precipitation the megathermal period the pollen records also reflect human impact in this region since 3400 cal bp a sharp decrease in pinus pollen percentages as well as sharp increases in pollen abundance of ulmus ruderal species including planted poaceae and selaginella sinensis suggest forest clearance and selective felling associated with agriculture human impacts are also associated with changes in sedimentation as the palaeo soil ground surface was covered by yellow brown sandy silt at this time this might reflect anthropogenic soil erosion in anyang

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

core formation in earth s moon mars and vesta stimulated by new experimental results on metal silicate partitioning of elements at elevated temperatures and pressures we have revisited the question of core formation in earth s moon mars and vesta the probable source of the eucritic meteorites earlier studies suggested metal silicate equilibrium in mars but led to the paradox that mars accreted homogeneously while the earth accreted heterogeneously using new elevated pressure and temperature metal silicate partition coefficients we show that abundances of the moderately siderophile elements in the mantles of the moon mars and vesta are consistent with early magma oceans on these bodies the most successful model for explaining the lunar mantle siderophile element abundances requires a core of 5 of the mass of the moon 500 km radius siderophile element abundances in mars are consistent with intermediate pressure metal silicate equilibrium as has also been recently suggested for the earth the most successful model for explaining the martian siderophile element abundances requires a bulk planetary composition that has greater than ci chondritic abundances of the moderately siderophile elements and a core of 30 of the mass of mars siderophile element abundances in the mantle of vesta are consistent with low pressure liquid metal liquid silicate equilibrium as expected for an asteroid sized body and a core of 10 of the mass of vesta comparison of our best fit oxygen fugacities for vesta with thermodynamic calculations of oxygen fugacity for silicate bearing iron meteorites indicates that parts of the inner solar system were homogeneous with respect to redox state at 4 5 ga approximately 2 log fo2units below the fe feo buffer much higher than estimates for the solar nebula similar comparisons for mars and the earth indicate that these bodies have undergone oxidation since 4 5 ga because the oxygen fugacities associated with metal silicate equilibrium in both mars and the earth moon system are much lower than those recorded in martian and terrestrial basaltic and periodotitic samples the oxidation on mars is most likely due to atmospheric effects whereas earth s much wider range of oxygen fugacities must be due to both atmospheric and plate tectonic effects

forming a moon with an earth like composition via a giant impact in the giant impact theory the moon formed from debris ejected into an earth orbiting disk by the collision of a large planet with the early earth prior impact simulations predict that much of the disk material originates from the colliding planet however earth and the moon have essentially identical oxygen isotope compositions this has been a challenge for the impact theory because the impactor s composition would have likely differed from that of earth we simulated impacts involving larger impactors than previously considered we show that these can produce a disk with the same composition as the planet s mantle consistent with earth moon compositional similarities such impacts require subsequent removal of angular momentum from the earth moon system through a resonance with the sun as recently proposed

holocene east asian monsoon variability links to solar and tropical pacific forcing 1 sedimentary geochemical records from subalpine retreat lake subtropical taiwan document the unstable east asian monsoon eam climate over the past 10 300 years with a weak eam between 10 3 and 8 6 ky b p eam intensity peaks between 8 6 and 7 7 ky b p and then gradually decrease in response to summer insolation heat and moisture transport our proxy record reveals several weak monsoon intervals that correlate to low sea surface temperatures in the western tropical pacific and cold events in the north atlantic linking the tropical pacific north atlantic and polar climates because weak eam events at 8 2 5 4 and 4 5 2 1 ky b p also correspond to low values of atmospheric methane and periods of reduced north atlantic deep water formation we therefore suggest that centennial to millennial scale monsoon variability during the holocene in the northern subtropics is globally mediated via a sun ocean monsoon north atlantic linkage

partitioning behavior of ni co mo and w between basaltic liquid and ni rich metal implications for the origin of the moon and lunar core formation a recent model of the origin of the moon in a giant impact put forth by o neill 1991a and b states that the bulk abundances of siderophile elements in the moon would be provided by the impactor plus a late reduced veneer a small ni rich core would then separate setting the siderophile element abundance pattern in the lunar mantle i test this hypothesis using simple mass balance and the results of an experimental study that i have conducted on the partitioning of moderately siderophile elements between basalt and ni rich metal i find this hypothesis to be viable under a limited set of conditions

asynchronous evolution of the indian and east asian summer monsoon indicated by holocene moisture patterns in monsoonal central asia abstract the numerical meta analysis of 92 proxy records 72 sites of moisture and or temperature change confirms earlier findings that the dominant trends of climatic evolution in monsoonal central asia since the last glacial roughly parallel changes in northern hemisphere summer insolation i e the period following the last glacial maximum was characterized by dry and cold conditions until 15 cal kyr bp followed by a warm wet period coincident with the bolling allerod warm period and terminated by a cold dry reversal during the younger dryas period after an abrupt increase at the start of the holocene warm and wet conditions prevailed until ca 4 cal kyr bp when moisture levels and temperatures started to decrease ordination of moisture records reveals strong spatial heterogeneity in moisture evolution during the last 10 cal kyr the indian summer monsoon ism areas northern india tibetan plateau and southwest china exhibit maximum wet conditions during the early holocene while many records from the area of the east asian summer monsoon indicate relatively dry conditions especially in north central china where the maximum moisture levels occurred during the mid holocene we assign such phenomena to strengthened hadley circulation centered over the tibetan plateau during the early holocene which resulted in subsidence in the east asian monsoonal regions leading to relatively dry conditions our observations of the asynchronous nature of the two asian monsoon subsystems on millennial time scales have also been observed on annual time scales as well as implied through the spatial analysis of vertical air motion patterns after strong ascending airflows over the tibetan plateau area that were calculated from ncep ncar reanalysis data for the last 30 years analogous with the early holocene the enhancement of the ism in a future warming world will result in an increase in the asynchronous nature of the monsoon subsystems this trend is already observed in the meteorological data from the last 15 years

the dry holocene megathermal in inner mongolia the paleoclimate since 14 kyr bp 14c age was reconstructed based on a 16 22 m long sediment core collected from lake yanhaizi a saline lake located near the northern limit of the east asian summer monsoon in inner mongolia coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated these sediments have low organic carbon contents but high maturity indices indicating that they were deposited in an arid environment by contrast based on high organic contents and low maturity indices fine sediments were deposited during periods of high lake stand in a humid environment it was in general dry between 8 0 and 4 3 kyr bp the above dry and wet phases are consistent with those recovered from the arid semiarid transition zone elsewhere but are unlike the widely perceived humid holocene megathermal reported in east china and the newly reconstructed record in the alpine retreat lake in taiwan the discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon on the other hand much enhanced evaporation over higher monsoon precipitation at lake yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon this also accounts for the fact the high temperature holocene megathermal as revealed in the okinawa trough and the northern south china sea is correlated to the dry phases at lake yanhaizi conversely the 4 2 kyr bp coldest period in the holocene corresponds to a wet phase at lake yanhaizi

a model for linking grain size component to lake level status of a modern clastic lake abstract grain size distributions of fluvial eolian and marine sediments were explicated decades ago for lake sediments however there is still great uncertainty in explaining the genesis of grain size components due to the inherent complexity of their polymodal distributions in this study the grain size components of the surface sediments of daihai lake inner mongolia were partitioned using a lognormal distribution function and the relationship between the identity of each component and the specific sedimentary environment was investigated the data indicate that the modern clastic sediments of daihai lake contain five distinct unimodal grain size distributions representing five grain size components each of the components retains its identity including modal size manner of transportation and environment of deposition although the relative percentage varies with the hydraulic condition throughout the lake these components are specified from fine to coarse modes as long term suspension clay offshore suspension fine silt and medium to coarse silt and nearshore suspension fine sand and saltation medium sand the percentage of the components interpreted as an indication of nearshore environments displays a negative correlation with water depth across the modern lakebed suggesting a model for linking the nearshore components in sediment cores to the lake level status in the geological past the model was applied to a sediment core from the lake where high percentages of the nearshore components in the core sediments were correlated with low regional precipitations reconstructed on the pollen profile of the same core the coincidences between two independent proxies do not only demonstrate the validity of lognormal distribution function in partitioning polymodal sediments but also reveals the potential of the grain size component lake level status model for lake s paleohydrological reconstruction

quantitative precipitation estimates for the northeastern qinghai tibetan plateau over the last 18 000 years quantitative information regarding the long term variability of precipitation and vegetation during the period covering both the lateglacial and the holocene on the qinghai tibetan plateau qtp is scarce herein we provide new and numerical reconstructions for annual mean precipitation pann and vegetation history over the last 18 000 years using high resolution pollen data from lakes dalianhai and qinghai on the northeastern qtp hitherto five calibration techniques including weighted averaging wa weighted average partial least squares regression wa pls modern analogue technique mat locally weighted weighted averaging regression lwwa and maximum likelihood ml were firstly employed to construct robust inference models and to produce reliable pann estimates on the qtp the biomization method was applied for reconstructing the vegetation dynamics the study area was dominated by steppe and characterized with a highly variable relatively dry climate at 18 000 11 000 cal a b p pann increased since the early holocene obtained a maximum at 8000 3000 cal a b p with coniferous temperate mixed forest as the dominant biome and thereafter declined to present the pann reconstructions are broadly consistent with other proxy based paleoclimatic records from the northeastern qtp and the northern region of monsoonal china the possible mechanisms behind the precipitation changes may be tentatively attributed to the internal feedback processes of higher latitude e g north atlantic and lower latitude e g subtropical monsoon competing climatic regimes which are primarily modulated by solar energy output as the external driving force these findings may provide important insights into understanding the future asian precipitation dynamics under the projected global warming

a multi proxy quantitative record of holocene hydrological regime on the heixiazi island ne china indications for the evolution of east asian summer monsoon the holocene hydrological regime on the heixiazi island is critical for understanding the evolution of the east asian summer monsoon easm for the island s climate sensitive location on the northern fringe of the easm domain in this paper a marsh depression on the central island was selected to reconstruct the locally hydrological variation and to discuss its indications for the holocene easm evolution this work is based on multi proxy magnetic susceptibility grain size loss on ignition and carbonate content analyses of 22 modern sedimentary samples with a water level gradient of 0 66 cm and 100 cored sedimentary samples covering last 9 0 ka bp the proxies hydrological significance was previously interpreted by the 22 modern samples using linear regression equations to construct their relationships to water level changes among these proxies the magnetic susceptibility carbonate content as well as the md and sand fraction of grain size exhibit high level relationships against the water level changes with r2 0 6 thus these four proxies linear regression equations were selected and used on the 100 cored samples and the holocene water level changes in the studied depression were quantitatively reconstructed it shows that two relatively high water level stages with strengthened easm occurred during 8 0 4 5 ka bp and 3 0 1 4 ka bp which were alternated by three low water level stages with declined easm during 9 0 8 0 ka bp 4 5 3 0 ka bp and 1 4 0 ka bp respectively among these fluctuations the highest water level stage with most strengthened easm which is defined as the holocene monsoon maximum occurred during 6 4 4 5 ka bp such a new evolution pattern of the easm can be further supported by a large variety of records from monsoon margin regions we suggest the holocene easm evolution was generally associated with the thermal conditions in both the inner eurasia landmass and the west pacific ocean with an exception of the weak easm before 8 0 ka bp due to the enhanced siberia high with the dominance of the eurasia ice sheet in the early holocene

biomarker similarities between the saline lacustrine eocene green river and the paleoproterozoic barney creek formations abstract the paleoproterozoic barney creek formation which is currently interpreted as a restricted deep marine paleoenvironment plays a disproportionate role in our understanding of proterozoic ocean chemistry and the rise of complex life the barney creek formation hosts several unusual biomarker features specifically its methylhopane and carotenoid signatures herein we demonstrate that the saline lacustrine eocene green river formation shares a similar distribution of methylhopanes and carotenoids which is characteristic of saline lacustrine organic matter more generally these distinct methylhopane and carotenoid patterns are not observed together in marine organic matter of any geologic age these results imply a saline lacustrine depositional environment for the barney creek formation which agrees with earlier but now abandoned depositional models of this formation as a result models of proterozoic ocean chemistry and emergence of complex life that rely on a marine barney creek formation should be reexamined alternatively if paleoproterozoic marine biomarker signatures resemble those of younger saline lacustrine systems then this must be recognized to accurately interpret geologic biomarker and paleoenvironmental records

holocene vegetation and climate histories in the eastern tibetan plateau controls by insolation driven temperature or monsoon derived precipitation changes abstract the climates on the eastern tibetan plateau are strongly influenced by direct insolation heating as well as monsoon derived precipitation change however the moisture and temperature influences on regional vegetation and climate have not been well documented in paleoclimate studies here we present a well dated and high resolution loss on ignition peat property and fossil pollen record over the last 10 000 years from a sedge dominated fen peatland in the central zoige basin on the eastern tibetan plateau and discuss its ecological and climatic interpretations lithology results indicate that organic matter content is high at 60 80 between 10 and 3 ka 1 ka 1000 cal yr bp and shows large magnitude fluctuations in the last 3000 years ash free bulk density as a proxy of peat decomposition and peatland surface moisture conditions oscillates around a mean value of 0 1 g cm 3 with low values at 6 5 4 7 ka reflecting a wet interval and an increasing trend from 4 7 to 2 ka suggesting a drying trend the time averaged mean carbon accumulation rates are 30 6 gc m 2 yr for the last 10 000 years higher than that from many northern peatlands tree pollen mainly from picea mostly reflecting temperature change in this alpine meadow forest ecotonal region has variable values from 3 to 34 during the early holocene reaches the peak value during the mid holocene at 6 5 ka and then decreases until 2 ka the combined peat property and pollen data indicate that a warm and wet climate prevailed in the mid holocene 6 5 4 7 ka representing a monsoon maximum or optimum climate for the region the timing is consistent with recent paleo monsoon records from southern china and with the idea that the interplays of summer insolation and other extratropical large scale boundary conditions including sea surface temperature and sea level change control regional climate the cooling and drying trend since the mid holocene likely reflects the decrease in insolation heating and weakening of summer monsoons regional synthesis of five pollen records along a south north transect indicates that this climate pattern can be recognized all across the eastern tibetan plateau the peatland and vegetation changes in the late holocene suggest complex and dramatic responses of these lowland and upland ecosystems to changes in temperature and moisture conditions and human activities

graphite oxidation in the apollo 17 orange glass magma implications for the generation of a lunar volcanic gas phase abstract an apollo 17 picritic orange glass composition has been used to experimentally investigate the conditions at which graphite would oxidize to form a co rich gas and ultimately produce lunar fire fountain eruptions isothermal decompression experiments run above the a17 orange glass liquidus temperature 1350 c suggest that the initial co rich gas phase produced by graphite oxidation would be generated during magma ascent at a pressure of 40 mpa 8 5 km beneath the lunar surface additional experiments with 2000 ppm s and 1000 ppm cl showed that the presence of these dissolved gas species would not affect the depth of graphite oxidation verifying that the first volcanic gas phase would be generated by the oxidation of graphite a simple ideal chemical mixing model for calculating melt feo activity in a fe metal silicate melt system was tested with a series of 0 1 mpa controlled oxygen fugacity experiments agreement between the model and experiments allows the model to be used to calculate oxygen fugacity in picritic lunar glass compositions such as the a17 orange glass using this model in a reanalysis of chemical equilibria between the natural a17 orange glass melt and the metal spherules fe85ni14co1 trapped within the glass beads indicates a log oxygen fugacity of 11 2 0 7 log units more oxidized than previous estimates at the a17 orange glass liquidus temperature 1350 5 c this fo2 corresponds to a minimum pressure of 41 mpa on the graphite c o surface the fact that the same critical graphite oxidation pressure was determined in decompression experiments and from the fe feo activity model for the natural a17 orange glass metal assemblage strongly supports this pressure 8 5 km depth for volcanic gas formation in lunar basalts generation of a gas by oxidation of c in ascending magma is likely to have been important in getting dense lunar magmas to the surface as well as in generating fire fountain eruptions the vesicles common in many lunar basalts and the ubiquitous fe metal in these rocks are also likely generated by the oxidation of carbon the presence of carbon in the lunar basalts and the recent discovery of ppm levels of water in lunar basalts indicate that at least parts of the lunar interior still contained volatiles at 3 9 bybp

holocene flooding history of the lower tagus valley portugal the present paper aims to reconstruct the lower tagus valley flooding history for the last ca 6500 a to explore the suitability of pollen based local vegetation development in supporting the reconstruction of flooding history and to explain fluvial activity changes in terms of allogenic climate human impact and autogenic system intrinsic processes the flooding history has been determined by cored sedimentary records located 18 km apart in distal low energy backswamps on both sides of the tagus channel in these low energy backswamps fine grained sediment layers deposited from suspended load of overbank flood water reflect periods with multiple overbank floods by means of a multi proxy approach sedimentology magnetic susceptibility grain size loss on ignition carbonate content and pollen sedimentary and environmental changes were identified at both sites synchronous lithological intervals accumulated suggesting a common origin for the changes in fluvial activity since ca 6500 cal a bp based on lithological changes three phases of high fluvial activity 6500 5500 4900 3500 and 1000 0 cal a bp and two phases of low fluvial activity 5500 4900 and 3500 1000 cal a bp were identified two periods with dominant allogenic controls on fluvial activity in the lower tagus valley were identified relative sea level 6500 5500 cal a bp and human impact 1000 0 cal a bp during the intermediate period changes in fluvial activity may have been caused by climate 5500 1000 cal bp but unambiguous correlations are difficult to make this is due to the way allogenic controls are translated through the fluvial system the geomorphological differences between upstream and downstream studies and autogenic processes the comparison of local vegetation development and flooding phases as reconstructed using sedimentology shows a limited added value of using local palynology as a proxy for fluvial activity 2010 john wiley sons ltd

improved gravity field of the moon from lunar prospector an improved gravity model from doppler tracking of the lunar prospector lp spacecraft reveals three new large mass concentrations mascons on the nearside of the moon beneath the impact basins mare humboltianum mendel ryberg and schiller zucchius where the latter basin has no visible mare fill although there is no direct measurement of the lunar farside gravity lp partially resolves four mascons in the large farside basins of hertzsprung coulomb sarton freundlich sharonov and mare moscoviense the center of each of these basins contains a gravity maximum relative to the surrounding basin the improved normalized polar moment of inertia 0 3932 0 0002 is consistent with an iron core with a radius of 220 to 450 kilometers

the proto earth as a significant source of lunar material geochemical evidence continues to challenge giant impact models which predict that the moon formed from both proto earth and impactor material analyses of lunar samples reveal isotopic homogeneity in titanium a highly refractory element suggesting lunar material was derived predominantly from the mantle of the proto earth

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

reappraisal of hydrocarbon biomarkers in archean rocks hopanes and steranes found in archean rocks have been presented as key evidence supporting the early rise of oxygenic photosynthesis and eukaryotes but the syngeneity of these hydrocarbon biomarkers is controversial to resolve this debate we performed a multilaboratory study of new cores from the pilbara craton australia that were drilled and sampled using unprecedented hydrocarbon clean protocols hopanes and steranes in rock extracts and hydropyrolysates from these new cores were typically at or below our femtogram detection limit but when they were detectable they had total hopane 37 9 pg per gram of rock and total sterane 32 9 pg per gram of rock concentrations comparable to those measured in blanks and negative control samples in contrast hopanes and steranes measured in the exteriors of conventionally drilled and curated rocks of stratigraphic equivalence reach concentrations of 389 5 pg per gram of rock and 1 039 pg per gram of rock respectively polycyclic aromatic hydrocarbons and diamondoids which exceed blank concentrations exhibit individual concentrations up to 80 ng per gram of rock in rock extracts and up to 1 000 ng per gram of rock in hydropyrolysates from the ultraclean cores these results demonstrate that previously studied archean samples host mixtures of biomarker contaminants and indigenous overmature hydrocarbons therefore existing lipid biomarker evidence cannot be invoked to support the emergence of oxygenic photosynthesis and eukaryotes by 2 7 billion years ago although suitable proterozoic rocks exist no currently known archean strata lie within the appropriate thermal maturity window for syngenetic hydrocarbon biomarker preservation so future exploration for archean biomarkers should screen for rocks with milder thermal histories

terrestrial origin of the moon abundance patterns of siderophile elements in the earth s mantle have been determined by complex processes connected with internal segregation of a metallic core amounting to 32 of the earth s mass although the lunar core may be only 2 of the lunar mass and formed in very different conditions to the earth s core the lunar siderophile pattern is closely related to that of the earth s mantle implying that the material in the moon derived mainly from the earth s mantle after core formation new models for the accretion of the earth which require impacts by large planetesimals in the presence of a corotating primitive terrestrial atmosphere provide a mechanism for transferring material from the earth s mantle into geocentric orbit as a ring of proto lunarplanetesimals from which the moon later accreted

correlation between indian ocean summer monsoon and north atlantic climate during the holocene there has been a number of investigations for the correlation between the asia monsoon and the north atlantic climate for the last glacial however little research has been done for the present interglacial the holocene here we present for the first time a high resolution composite proxy record for the indian ocean summer monsoon spanning around 12 000 years based on the 13c time series of both a single plant species carex mulieensis remains cellulose and the total plant assemblage cellulose in the hongyuan peat bog from the tibet plateau the records show that the strength of the indian ocean summer monsoon had abrupt variations during the last 12 000 years the weakest monsoon occurred in the younger dryas period following rapid strengthening from around 11 200 to 10 800 a bp the monsoon kept a generally strong level for around 5300 years from around 5500 a bp onwards the monsoon strength tended to gradual decrease in addition there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales which superimpose the general tendency of the monsoon variation in every case when the ice rafted debris events in the north atlantic occurred the summer monsoon strength decreased correspondingly these evidences show that teleconnection between the indian ocean summer monsoon and the north atlantic climate is present not only in the last glacial but also in the holocene which may be linked to abrupt reorganizations of the ocean thermohaline circulation leading to redistribution of energy changing temperature and moisture gradient over the southern subtropical indian ocean and eventually controlling the variability of the indian ocean summer monsoon

a new view of lunar ferroan anorthosites postmagma ocean petrogenesis 1 new melting experiments in the range of 0 1 mpa to 4 7 gpa provide the basis for calculations of polybaric crystallization which show that both a 300 km deep magma ocean mo enriched in refractory elements and a 600 km deep magma ocean with refractory element concentrations similar to the earth s upper mantle produce sufficient amounts of differentiated residual liquid capable of crystallizing the troctolitic noritic mineral assemblages that are prevalent in lunar ferroan anorthosites lfa however the both oceans become saturated with augite after 20 30 crystallization of the plagioclase saturated residuum and thereafter are no longer capable of producing noritic assemblages a second set of melting experiments reveals the existence of a previously unrecognized equilibrium augite liquid pigeonite plagioclase and a thermal minimum on the pigeonite plagioclase liquidus surface at 0 6 gpa these equilibria will produce melts of mafic cumulates with lower wo content than those from which the cumulates originally formed in a postmagma ocean environment of overturning mafic cumulates melt thus formed and entrained in a buoyant segregation of plagioclase would then form diapiric masses that would crystallize troctolitic noritic assemblages after intruding upward diapiric intrusions could also provide the local deformational environment needed to produce the apparently high 95 plagioclase modes of the lfa an unstable density profile in the cumulate pile following crystallization of most of the mo should provide the impetus for overturn and the heat for partially remelting mafic cumulates

the constitution and structure of the lunar interior the current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period missions of the 1960s including the rangers surveyors and lunar orbiters as well as earth based telescopic studies laid the groundwork for the apollo program and provided a basic understanding of the surface its stratigraphy and chronology through a combination of remote sensing surface exploration and sample return the apollo missions provided a general picture of the lunar interior and spawned the concept of the lunar magma ocean in particular the discovery of anorthite clasts in the returned samples led to the view that a large portion of the moon was initially molten and that crystallization of this magma ocean gave rise to mafic cumulates that make up the mantle and plagioclase flotation cumulates that make up the crust smith et al 1970 wood et al 1970 this model is now generally accepted and is the framework that unifies our knowledge of the structure and composition of the moon the intention of this chapter is to review the major advances that have been made over the past decade regarding the constitution of the moon s interior much of this new knowledge is a direct result of data acquired from the successful clementine and lunar prospector missions as well as the analysis of new lunar meteorites as will be seen results from these studies have led to many fundamental amendments to the magma ocean model much of what we know from sample analyses has been previously summarized elsewhere and only their most important aspects will be discussed in this chapter the reader is referred to the relevant chapters in the books basaltic volcanism on the terrestrial planets basaltic volcanism study project 1981 the

the variation of summer monsoon precipitation in central china since the last deglaciation abstract two stalagmites c996 1 and c996 2 collected from the jiuxian cave in the shaanxi province in central china have been studied with u series dating and stable isotope analysis thirty eight 230 th dating results showed that the stalagmite c996 1 was continuously deposited through the last 8 5 ka bp thousand years before present present 1950 ad and c996 2 was deposited through the last 19 ka bp excluding two growth hiatuses between 8 3 and 5 7 ka bp and 15 4 and 11 9 ka bp with a relatively stable boundary condition we interpret the 18 o of speleothem calcite as most indicative of the amount of summer monsoon precipitation although temperature and other factors might have some minor impact the 18 o records show notable changes within the last glacial maximum lgm resembling other east asian monsoon records such as those from the hulu and sanbao caves suggesting that significant monsoonal climate changes occurred in eastern asia as far north as the qinling mountains during the lgm interval a comparison of our records to precisely dated contemporaneous speleothem records from other caves shows that the increasing trend of 18 o during the holocene commenced as early as 7 5 ka bp in the low latitude monsoonal area i e the hoti cave while at higher latitudes this shift occurred later such as 7 0 ka bp in the dongge cave 5 3 ka bp in the heshang cave 4 7 ka bp in the sanbao cave and 4 5 ka bp in the jiuxian cave these results imply an asynchronous change of the summer monsoon precipitation occurred in east asia during the holocene the asynchrony may be related to the responses of a coupled tropical and subtropical monsoon system to changes of the insolation and the differences in thermal forcing which result from the complex geographical configuration the variation of sea surface temperature sst in the western tropical pacific may also have important impacts on the summer monsoon precipitation changes in central and northern china because it affects the northwestern pacific subtropical high a monsoon front regulator more robust tests are needed to confirm this phenomenon and to evaluate the contribution of different factors in detail

quantifying the effect of solid phase composition and structure on solid liquid partitioning of siderophile and chalcophile elements in the iron sulfur system we report experimentally determined partition coefficients between solid and liquid phases for bulk compositions on either side of the fe fes eutectic for a suite of siderophile chalcophile and lithophile elements experiments were performed at conditions of 1 5 and 2 gpa in pressure p 1323 k in temperature t and virtually identical eutectic sulfide liquid compositions in equilibrium with either solid face centered cubic fe or solid fes this enabled isolation of the effect of solid phase composition and structure from pressure temperature melt composition effects solid phase liquid metal partition coefficients d values for ge re ni co cr mn v sn pb re and w differ significantly if partitioning occurs between identical metallic liquids but different solid phases whereas zn cu and mo are virtually unaffected for all elements except ge and sn measured solid fe liquid sulfide partition coefficients at 1 5 and 2 gpa are inconsistent with model predictions based on atmospheric pressure experiments indicating that such models may not be appropriate for modeling core crystallization processes at non ambient pressure the framework of a lattice strain based model of solid liquid metal partitioning stewart et al 2009 enables us to quantify the effect of the solid phase changing the solid phase from fe to fes leads to systematic increases in r0 from 1 54 to 1 65 a and apparent young s modulus e from 112 to 178 gpa these systematic changes can be used to predict element partitioning in eutectic solid fes bearing systems from measurements in eutectic solid fe bearing systems although changing the solid phase from face centered cubic fe to fes is an end member example our data suggest that changes with pressure in the structure e g to hexagonally close packed at high pressure and composition e g to higher s content at high pressure of solid iron could affect the partitioning of elements between fe and liquid metal during the solidification of planetary cores

reconstruction of climate and vegetation changes of lake bayanchagan inner mongolia holocene variability of the east asian monsoon a high resolution pollen and pediastrum record spanning 12 500 yr is presented for lake bayanchagan 115 21 e 41 65 n and 1355 m a s l southern inner mongolia individual pollen taxa pt mat and the pft affinity scores pft mat were used for quantitative climatic reconstruction from pollen and algal data both techniques indicate that a cold and dry climate similar to that of today prevailed before 10 500 cal yr b p the wettest climate occurred between 10 500 and 6500 cal yr b p at which time annual precipitation was up to 30 60 higher than today the early holocene increases in temperature and precipitation occurred simultaneously but mid holocene cooling started at approximately 8000 cal yr b p 1500 yr earlier than the drying vegetation reconstruction was based on the objective assignment of pollen taxa to the plant functional type the results suggest that this region was dominated by steppe vegetation throughout the holocene except for the period 9200 to 6700 cal yr b p when forest patches were relatively common inner mongolia is situated at the limit of the present east asian monsoon and patterns of vegetation and climate changes in that region during the holocene probably reflect fluctuations in the monsoon s response to solar insolation variations the early to middle holocene monsoon undoubtedly extended to more northern latitudes than at present

holocene moisture evolution in arid central asia and its out of phase relationship with asian monsoon history we synthesize palaeoclimate records from the mid latitude arid asian region dominated today by the westerlies arid central asia aca to evaluate spatial and temporal patterns of moisture changes during the holocene sediment records from i i takes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200 year time slices the proxies used in these records include pollen and diatom assemblages sediment lithology lake levels and geochemistry mainly isotope data the results of our synthesis show that aca as a whole experienced synchronous and coherent moisture changes during the holocene namely a dry early holocene a wetter less dry early to mid holocene and a moderately wet late holocene during the early holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka 1 ka 1000cal a bp hence the effective moisture history in aca is out of phase with that in monsoonal asia as documented by numerous palaeoclimate records in monsoonal asia a strong summer monsoon and humid climate characterized the early holocene and a weakened summer monsoon and drier climate prevailed during the late holocene which were mainly controlled by changes in low latitude summer insolation in contrast we propose that the pattern of holocene effective moisture evolution in the westerly dominated aca was mainly determined by north atlantic sea surface temperatures ssts and high latitude air temperatures that affect the availability amount and transport of water vapor also topography of the tibetan plateau and adjacent asian highlands could have contributed to the intensification of dry climate in aca during the early holocene as a result of strengthening the subsidence of dry air masses associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation summer insolation might have played a key role in directly controlling moisture conditions in aca but only after the northern hemisphere ice sheets had disappeared in the mid and late holocene c 2007 elsevier ltd all rights reserved

tungsten isotopes and the origin of the moon abstract the giant impact model of lunar origin predicts that the moon mainly consists of impactor material as a result the moon is expected to be isotopically distinct from the earth but it is not to account for this unexpected isotopic similarity of the earth and moon several solutions have been proposed including i post giant impact earth moon equilibration ii alternative models that make the moon predominantly out of proto earth mantle and iii formation of the earth and moon from an isotopically homogeneous disk reservoir here we use w isotope systematics of lunar samples to distinguish between these scenarios we report high precision 182w data for several low ti and high ti mare basalts as well as for mg suite sample 77215 and lunar meteorite kalahari 009 which complement data previously obtained for kreep rich samples in addition we utilize high precision hf isotope and ta w ratio measurements to empirically quantify the superimposed effects of secondary neutron capture on measured 182w compositions our results demonstrate that there are no resolvable radiogenic 182w variations within the moon implying that the moon differentiated later than 70 ma after solar system formation in addition we find that samples derived from different lunar sources have indistinguishable 182w excesses confirming that the moon is characterized by a small uniform 26 parts per million excess in 182w over the present day bulk silicate earth this 182w excess is most likely caused by disproportional late accretion to the earth and moon and after considering this effect the pre late veneer bulk silicate earth and the moon have indistinguishable 182w compositions mixing calculations demonstrate that this earth moon 182w similarity is an unlikely outcome of the giant impact which regardless of the amount of impactor material incorporated into the moon should have generated a significant 182w excess in the moon consequently our results imply that post giant impact processes might have modified 182w leading to the similar 182w compositions of the pre late veneer earth s mantle and the moon

geochemical constraints on the origin of the moon abstract hypotheses for the origin of the moon involve variants on capture double planet and fission processes double planet and fission hypotheses are examined in the light of siderophile trace elements the siderophile trace elements chosen w re mo p ga ge have well understood geochemical behavior such that appropriate metal silicate partition coefficients are available and their abundances in the lunar and terrestrial mantles 4 4 4 5 109 years ago may be reasonably inferred the fission hypothesis of ringwood 1979 is not consistent with the behavior of re mo and p the hybrid fission hypothesis of wanke et al 1983 overcomes many of the deficiencies of ringwood s hypothesis but is not readily reconcilable with the behavior of re and ir the double planet hypothesis as most recently advanced by newsom and drake 1982 1983 appears to be consistent with siderophile element behavior in the moon

estimation of trace element concentrations in the lunar magma ocean using mineral and metal silicate melt partition coefficients this study uses experimentally determined plagioclase melt d values to estimate the trace element concentrations of sr hf ga w mo ru pd au ni and co in a crystallizing lunar magma ocean at the point of plagioclase flotation similarly experimentally determined metal silicate partition experiments combined with a composition model for the moon are used to constrain the concentrations of w mo ru pd au ni and co in the lunar magma ocean at the time of core formation the metal silicate derived lunar mantle estimates are generally consistent with previous estimates for the concentration of these elements in the lunar mantle plagioclase melt derived concentrations for sr ga ru pd au ni and co are also consistent with prior estimates estimates for hf w and mo however are higher these elements may be concentrated in the residual liquid during fractional crystallization due to their incompatibility alternatively the apparent enrichment could reflect the inappropriate use of bulk anorthosite data rather than data for plagioclase separates

the influence of silicate melt composition on distribution of siderophile elements among metal and silicate liquids abstract liquid metal liquid silicate partitioning of fe ni co p ge w and mo among a carbon saturated metal and a variety of silicate melts magnesian tholeiitic siliceous aluminous aluminosiliceous basalts depends modestly to strongly upon silicate melt structure and composition low valency siderophile elements fe ni and co show a modest influence of silicate melt composition on partitioning germanium shows a moderate but consistent preference for the depolymerized magnesian melt high valency siderophile elements p mo and w show more than an order of magnitude decrease in metal silicate partition coefficients as the silicate melt becomes more depolymerized detailed inspection of our and other published w data shows that polymerization state temperature and pressure are more important controls on w partitioning than oxidation state for this to be true for a high and variable valence element implies a secondary role in general for oxidation state even though some role must be present equilibrium core segregation through a magma ocean of ultrabasic composition can provide a resolution to the excess abundances of ge p w and mo in the mantle but the mantle composition alone cannot explain the excess abundances of nickel and cobalt in chondritic proportions

thermodynamic properties of fe s alloys from molecular dynamics modeling implications for the lunar fluid core abstract density and sound velocity of fe s liquids for the p t parameters of the lunar core have not been constrained well from the analysis of seismic wave travel time weber et al 2011 proposed that the lunar core is composed of iron alloyed with 6 wt of light elements such as s a controversial issue in models of planetary core composition concerns whether fe s liquids under high pressure temperature conditions provide sound velocity and density data which match the seismic model here we report the results of molecular dynamics md simulations of iron sulfur alloys based on embedded atom model eam the results of calculations include caloric thermal and elastic properties of fe s alloys at concentrations of sulfur 0 18 at temperatures up to 2500 k and pressures up to 14 gpa the effect of sulfur on the elastic properties of fe rich melts is most evident in the notably decreased density with added s content in the md simulation the density and bulk modulus k t of liquid fe s decrease with increasing sulfur content while the bulk modulus k s decreases as a whole but has some fluctuations with increasing sulfur content the sound velocity increases with increasing pressure but depends weakly on temperature and the concentration of sulfur for a fluid fe s core of the moon 5 gpa 2000 k with 6 16 at s 3 5 10 wt the sound velocity and density may be estimated at the level of 4000 m s 1 and 6 25 7 0 g cm 3 comparison of thermodynamic calculations with the results of interpretation of seismic observations shows good agreement of p wave velocities in the liquid outer core while the core density does not match the seismic models at such concentrations of sulfur and a density by 20 35 higher than the model seismic density a radius for the fluid outer core should be less than about 330 km found by weber et al because at the specified mass and moment of inertia values of the moon an increase of the core density leads to a decrease of the core radius these results are important for modeling the current state and composition of the lunar core and can be applied to models of large satellites core properties

a chemical model for generating the sources of mare basalts combined equilibrium and fractional crystallization of the lunar magmasphere abstract it is generally considered that mare basalts were generated by the melting of a cumulate mantle formed in an early moon wide magma ocean or magmasphere however the nature and chemistry of this cumulate mantle and the logistics of its origin have remained elusive extensive studies of terrestrial layered mafic intrusions over the past sixty years have emphasized the imperfection of fractional crystallization and attendant crystal crystal and crystal liquid separation in a convecting magma chamber crystal liquid and crystal crystal separations were similarly inefficient during evolution of the lunar magma ocean lmo allowing for the trapping of interstitial liquid and entrainment of a small proportion of less dense plagioclase into the denser mafic cumulate mush indeed petrography of lunar highlands samples demonstrates this for anorthosites with 1 10 olivine the residual liquid after 80 90 crystallization was very evolved in fact kreepy and even in small proportions 1 5 would have a noticeable effect on the trace element chemistry of melts generated from these cumulates this trapped residual liquid would elevate total ree abundances in the cumulate pile while synchronously deepening the already negative eu anomaly essentially this trapped liquid will make the cumulate more fertile for melting to generate both kreep basalt and mare basalt magmas plagioclase entrained in the mafic cumulate pile adds an essential al component to the high ti basalt source and will moderate the requisite negative eu anomaly in the cumulate early in the evolution of the lunar mantle when the lmo still was largely liquid it is likely that vigorous convection was an important factor in crystallization such convection would allow crystals to remain suspended and in equilibrium with the lmo liquid for relatively long periods of time this extended period of equilibrium crystallization would then have been followed by fractional crystallization once plagioclase became a liquidus phase and began to float to form the lunar highlands crust previous authors have proposed a three component model for the evolution of high ti mare basalt source regions this model includes kreep early olivine rich high mg cumulates and late ilmeniterich low mg cumulates in various proportions however we propose a model for high ti basalt parent magmas which is in accord with studies of terrestrial layered intrusions this model for the high ti source includes trapped instantaneous residual liquid tirl 1 3 and entrainment of a small 2 5 proportion of plagioclase into the late stage cumulate pile in order to account for both the observed al compositions and trace element characteristics of high ti mare basalts melting of this relatively shallow ilmenite and clinopyroxene bearing late stage cumulate can generate high ti mare basalt magmas furthermore we are in agreement with other workers that only through a process of nonmodal melting will the high ti values for the parent magmas be realized large scale convective overturn of the cumulate pile and mixing of kreep with early and late stage cumulates is not required however localized overturn of the upper tenth of the cumulate pile is likely and in fact required to achieve an appropriate major element balance for the high ti mare basalt source region

corrigendum to holocene vegetation and climate dynamics of ne china based on the pollen record from sihailongwan maar lake quat sci rev 124 2015 275 289

a 3 d numerical study of the thermal evolution of the moon after cumulate mantle overturn the importance of rheology and core solidification 1 models in which the mantle of the moon evolves from an initially stratified state following magma ocean solidification and overturn have been applied to address important features of long term thermal evolution of the moon including convective instability of overturned ilmenite bearing cumulates ibc at the lunar core mantle boundary generation of mare basalts core sulfur content and inner core radius paleomagnetism and the present day mantle structure whether a dense overturned ibc rich layer at the bottom of the mantle can become thermally unstable to generate a single upwelling is controlled largely by the temperature dependence of viscosity the activation energy convective instability of the ibc rich layer controls the heat flux out the core and the presence of an internally generated magnetic field a long period of 700 ma high positive core mantle boundary cmb heat flux after the instability of the ibc rich layer is expected from our models present day deep mantle temperatures inferred from seismic and gravitational inversion constrain the magnitude of mantle viscosity from 5 1019 to 1 1021 pa s the cmb temperature and solidified inner core radius inferred from seismic reflection constrain the core sulfur content our evolution models with 5 10 wt sulfur content can produce the observed 240 km radius inner core at the present day the asymmetrical distribution of the deep moonquakes only in the nearside mantle could be explained as the remnant structure of the single chemical upwelling generated from ibc rich layer our evolution model after the overturn results in an early 0 55 km expansion in radius for 1000 ma due to the radiogenic heating associated with ibc in the deep mantle and may provide a simple explanation for the early expansion inferred from the gravity recovery and interior laboratory mission

metal silicate partitioning of tungsten at high pressure and temperature implications for equilibrium core formation in earth abstract tungsten partitioning between liquid metal and liquid silicate d w from 1723 2673 k 0 5 18 gpa and over a wide range of metal and silicate compositions provides constraints on planetary core formation models we find that w partitioning is extremely sensitive to the carbon content of the metal alloy becoming about an order of magnitude more siderophile at carbon saturation activity composition corrections based on interactions between w c and fe c in metal solution shift calculated d w to more lithophile values and calculated oxygen fugacities fo2 to more oxidizing values than uncorrected data w exists as a highly charged cation in silicate solution displaying a mixture of oxidation states from 4 to 6 in experiments at fo2 of 0 5 2 log units below the iron wustite buffer at constant fo2 the average calculated valence decreases with pressure from 5 5 at 0 5 gpa to 4 at 11 18 gpa as a result of its high oxidation state w partitioning is strongly dependent on silicate melt polymerization and fo2 in contrast to some previous results we find that d w may decrease slightly in response to increasing temperature in the pressure range of our experiments pressure exerts a non monotonic effect d w increases with pressure up to 3 to 4 gpa but decreases at higher pressures previous models for the effects of pressure and temperature on w partitioning that conflict with our results appear to result from a conflation of the intensive parameters of pressure temperature and carbon content the mantle abundance of w could have been set by single stage metal silicate equilibration along the liquidus in a deep peridotite magma ocean at pressures from 20 50 gpa and at oxygen fugacities consistent with the mantle s present iron budget iw 2 to 2 5 equilibration at higher pressure is viable if the core forming metal contained a significant but not unreasonable abundance of carbon 2 wt recent continuous accretion models involving multi stage metal silicate equilibration in a deepening magma ocean with progressive oxidation of the silicate remain permissible given our new treatment of w partitioning data

core formation in the earth and moon new experimental constraints from v cr and mn abstract the mantles of the earth and moon are similarly depleted in v cr and mn relative to the concentrations of these elements in chondritic meteorites the similar depletions have been used as evidence that the moon inherited its mantle from the earth after a giant impact event we have conducted liquid metal liquid silicate partitioning experiments for v cr and mn from 3 to 14 gpa and 1723 to 2573 k to understand the behavior of these elements during planetary core formation our experiments have included systematic studies of the effects of temperature silicate composition metallic s content metallic c content and pressure temperature has a significant effect on the partitioning of v cr mn with all three elements increasing their partitioning into the metallic liquid with increasing temperature in contrast pressure is not observed to affect the partitioning behavior the experimental results show the partitioning of cr and mn are hardly dependent on the silicate composition whereas v partitions more strongly into depolymerized silicate melts the addition of either s or c to the metallic liquid causes increased metal silicate partition coefficients for all three elements parameterizing and applying the experimental data we find that the earth s mantle depletions of v cr and possibly mn can be explained by core formation in a high temperature magma ocean under oxygen fugacity conditions about two log units below the iron wustite buffer though the depletion of mn may be due entirely to its volatility however more oxidizing conditions proposed in recent core formation models for the earth cannot account for any of the depletions additionally because we observe no pressure effect on the partitioning behavior the data do not require the mantle of the moon to be derived from the earth s mantle although this is not ruled out all that is required to create depletions of v cr and mn in a mantle is a planetary body that is hot enough and reducing enough during its core formation such conditions could have existed on the moon forming impactor

very preliminary reference moon model abstract the deep structure of the moon is a missing piece to understand the formation and evolution of the earth moon system despite the great amount of information brought by the apollo passive seismic experiment alsep the lunar structure below deep moonquakes which occur around 900 km depth remains largely unknown we construct a reference moon model which incorporates physical constraints and fits both geodesic lunar mass and polar moment of inertia and love numbers and seismological body wave arrivals measured by apollo network data in this model the core radius is constrained by the detection of s waves reflected from the core in a first step for each core radius a radial model of the lunar interior including p and s wave velocities and density is inverted from seismic and geodesic data in a second step the core radius is determined from the detection of shear waves reflected on the lunar core by waveform stacking of deep moonquake apollo records this detection has been made possible by careful data selection and processing including a correction of the gain of horizontal sensors based on the principle of energy equipartition inside the coda of lunar seismic records and a precise alignment of sh waveforms by a non linear inversion method the very preliminary reference moon model vpremoon obtained here has a core radius of 380 40 km and an average core mass density of 5200 1000 kg m 3 the large error bars on these estimates are due to the poorly constrained s wave velocity profile at the base of the mantle and to mislocation errors of deep moonquakes the detection of horizontally polarized s waves reflected from the core and the absence of detection of vertically polarized s waves favour a liquid state in the outermost part of the core all these results are consistent within their error bars with previous estimates based on lunar rotation dissipation williams et al 2001 and on lunar induced magnetic moment hood et al 1999

core mantle differentiation in mars 1 the physical and chemical conditions under which martian core formation took place are not well constrained we modeled the pressure temperature and oxygen fugacity conditions under which it would be possible to match the inferred depletions of moderately siderophile elements ni co w mo ga p and ge in the martian mantle using new constraints on their metal silicate partitioning behavior using literature metal silicate partitioning data we characterize the dependence of the metal silicate partition coefficients d on the temperature pressure oxygen fugacity and composition of the silicate melt and the metal using a uniform parameterization approach for each element our results show that it is impossible to simultaneously account for the martian mantle depletions of moderately siderophile elements if the martian core sulfur content exceeds 10 5 wt at reducing conditions 1 log unit below the iron wustite iw buffer at 10 5 wt core s the conditions that best satisfy martian mantle abundances of the seven siderophile elements are a mean pressure of 13 1 gpa at 2330 k corresponding to the presence of a magma ocean at least 1000 km deep during martian core formation more oxidizing conditions than the iron wustite buffer as suggested by iron meteorites are inconsistent with mantle siderophile element abundances extension of our approach to the highly siderophile elements ru pd re ir and pt shows that their martian mantle abundances are orders of magnitude too high to be accounted for by metal silicate equilibration at high pressure and high temperature in a magma ocean requiring a late veneer stage after core formation

a partially molten magma ocean model the properties of the lunar crust and upper mantle can be explained if the outer 300 400 km of the moon was initially only partially molten rather than fully molten the top of the partially molten region contained about 20 melt and decreased to 0 at 300 400 km depth nuclei of anorthositic crust formed over localized bodies of magma segregated from the partial melt then grew peripherally until they covered the moon throughout most of its growth period the anorthosite crust floated on a layer of magma a few km thick the thickness of this layer is regulated by the opposing forces of loss of material by fractional crystallization and addition of magma from the partial melt below concentrations of sr eu and sm in pristine ferroan anorthosites are found to be consistent with this model as are trends for the ferroan anorthosites and mg rich suites on a diagram of an in plagioclase vs mg in mafics clustering of eu sr and mg values found among pristine ferroan anorthosites are predicted by this model

apollo 15 green glass compositional distribution and petrogenesis abstract we have characterized a comprehensive suite of individual green glass beads from apollo 15 soil to determine interelement behavior and to constrain petrogenetic relationships we analyzed 365 particles for trace elements by instrumental neutron activation analysis and analyzed 52 of them selected to cover the compositional ranges observed for trace elements for major elements by electron microprobe analysis we confirm the observation of delano 1979 that the beads comprise discrete compositional groups although two of the groups he denned are further split on the basis of trace element compositions each of the resulting seven groups has distinct average rare earth abundances the coherence between major and trace element data was masked in previous studies by imprecision correlated error and nonrepresentative sampling of the different groups most of the compositional characteristics of the green glasses can be explained by a model for batch equilibrium melting of a nearly homogeneous ultramafic source region when the complicating effects of high pressure and low oxygen fugacity are taken into account the previously puzzling behavior of ni and co as apparently incompatible elements may arise from partial reduction of those elements to the zero oxidation state resulting in low mineral melt partition coefficients the model also offers explanations for why the green glasses form boomerang shaped trends on many two element variation diagrams and why certain compositions groups a and d are more abundant than glasses with other compositions

testing the model for linking grain size component to lake level status of modern clastic lakes a model was proposed recently for linking grain size component to lake level status based on investigations of daihai lake in inner mongolia to test this model grain size components of the surface sediments of dali lake 500 km northeast of daihai lake were partitioned and their relationships with the lake level status were examined in this study the data show that modern clastic sediments of dali lake contain five distinct grain size components representing specific depositional processes and sedimentary environments within the lake in common with daihai lake these components are specified as long term suspension clay offshore suspension fine silt offshore suspension medium to coarse silt nearshore suspension fine sand and nearshore saltation medium sand in dali lake by contrast the offshore suspension components are lacking in more samples from the nearshore zone the nearshore suspension and saltation components occur in more samples from the offshore and transitional zone respectively and two adjacent components are well separated these differences would result from higher energy hydraulics of dali lake generated by stronger and more frequent winds occurring in the lake region under this hydraulic condition clastic materials entering the lake and the resultant components would be reworked more seriously during transportation within the lake leading to further basin ward transportations of the major components and better separations of two adjacent components percentage of the nearshore components is negatively related to water depth suggesting the grain size component lake level status model for the lake this model was applied to a sediment core from the lake showing that high percentages of the nearshore components in the core coincide with low precipitations reconstructed on the pollen profile of the same core the coincidence of two independent proxies demonstrates the wide applicability of the grain size component lake level status model to lake s paleohydrological reconstruction

lunar magma ocean crystallization revisited bulk composition early cumulate mineralogy and the source regions of the highlands mg suite abstract crystallization of the lunar magma ocean lmo has been numerically modeled and its products inferred from sample observations but it has never been fully tested experimentally this study is a reexamination of the lmo hypothesis by means of the first experimental simulation of lunar differentiation two end member bulk moon compositions are considered one enriched in refractory lithophile elements relative to earth and one with no such enrichment a two stage model of magma ocean crystallization based on geophysical constraints is simulated and features early crystal suspension and equilibrium crystallization followed by fractional crystallization of the residual magma ocean an initially entirely molten moon is assumed part 1 of this study presented here focuses on stage 1 of this model and considers the early cumulates formed by equilibrium crystallization differences in mantle mineralogy resulting from different bulk moon compositions and implications for the source regions of the highlands mg suite refractory element enriched bulk moon compositions produce a deep mantle that contains garnet and trace cr spinel in addition to low ca pyroxene and olivine in contrast compositions without refractory element enrichment produce a deep dunitic mantle with low ca pyroxene but without an aluminous phase the differences in bulk composition are magnified in the residual melt the residual lmo from the refractory element enriched composition will likely produce plagioclase and ilmenite earlier and in greater quantities both compositions produce mg rich early cumulate piles that extend from the core mantle boundary to 355 km depth if 50 equilibrium crystallization and whole moon melting are assumed these early lmo cumulates provide good fits for the source regions for a component of the high mg ni and co poor parental magmas of the mg suite cumulates if certain conditions are called upon the olivine in early lmo cumulates produced by either bulk moon composition is far too rich in cr to be reasonable for the source regions of the mg suite meaning either core formation in the presence of s and or c must be invoked to deplete the lmo and the crystallizing olivine in cr or that current estimates of the bulk lunar cr content are too high we infer that melts meeting the criteria of the mg suite parents could be produced from early lmo cumulates by solid state kreep and plagioclase hybridization near the base of the crust and subsequent partial melting additionally we propose a revised model for mg suite petrogenesis

phase equilibria of a low s and c lunar core implications for an early lunar dynamo and physical state of the current core abstract multiple lines of geochemical and geophysical evidence suggest the moon has a small metallic core yet the composition of the core is poorly constrained the physical state of the core now or in the past depends on detailed knowledge of its composition and unfortunately there is little available data on relevant multicomponent systems i e fe ni s c at lunar interior conditions in particular there is a dearth of phase equilibrium data to elucidate whether a specific core composition could help to explain an early lunar geodynamo and magnetic field intensities or current solid inner core liquid outer core states we utilize geochemical information to estimate the ni s and c contents of the lunar core and then carry out phase equilibria experiments on several possible core compositions at the pressure and temperature conditions relevant to the lunar interior the first composition is 0 5 wt s and 0 375 wt c based on s and c contents of apollo glasses a second composition contains 1 wt each of s and c and assumes that the lunar mantle experienced degassing of up to 50 of its s and c finally a third composition contains c as the dominant light element phase equilibrium experiments were completed at 1 3 and 5 gpa using piston cylinder and multi anvil techniques the first composition has a liquidus near 1550 c and solidus near 1250 c the second composition has a narrower liquidus and solidus temperatures of 1400 and 1270 c respectively while the third composition is molten down to 1150 c as the composition crystallizes the residual liquid becomes enriched in s and c but s enrichment is greater due to the incorporation of c but not s into solid metallic feni comparison of these results to thermal models for the moon allow an evaluation of which composition is consistent with the geophysical data of an early dynamo and a currently solid inner and liquid outer core composition 1 has a high enough liquidus to start crystallizing early in lunar history 4 3 ga consistent with the possible core dynamo initiated by crystallization of a solid inner core composition 1 also stays partially molten throughout lunar history and could easily explain the seismic data composition 2 on the other hand can satisfy one or the other set of geophysical data but not both and thus seems like a poor candidate for a lunar core composition composition 3 remains molten to temperatures that are lower than current estimates for the lunar core thus ruling out the possibility of a c rich and s poor lunar core the s and c poor core composition studied here composition 1 is consistent with all available geochemical and geophysical data and provides a simple heat source and mechanism for a lunar core dynamo core crystallization that would obviate the need for other primary mechanisms such as impacts core mantle coupling or unusual thermal histories

a possible high temperature origin of the moon and its geochemical consequences abstract the formation of the moon is thought to be the result of a giant impact between a mercury to proto earth sized body and the proto earth however the initial thermal state of the moon following its accretion is not well constrained by geochemical data here we provide geochemical evidence that supports a high temperature origin of the moon by performing high temperature 1973 2873 k metal silicate partitioning experiments simulating core formation in the newly formed moon results indicate that the observed lunar mantle depletions of ni and co record extreme temperatures 2600 3700 k depending on assumptions about the composition of the lunar core during lunar core formation this temperature range is within range of the modeled silicate evaporation buffer in a synestia type environment our results provide independent geochemical support for a giant impact origin of the moon and show that lunar thermal models should start with a fully molten moon our results also provide quantitative constraints on the effects of high temperature lunar differentiation on the lunar mantle geochemistry of volatile and potentially siderophile elements cu zn ga ge se sn cd in te and pb at the extreme temperatures recorded by ni and co many of these elements behave insufficiently siderophile to explain their depletions by core formation only consistent with the inferred volatility related loss of cr cu zn ga and sn during the moon forming event and or subsequent magma ocean degassing

a long lived lunar dynamo powered by core crystallization the moon does not possess an internally generated magnetic field at the present day but extensive evidence shows that such a field existed between at least 4 2 and 3 56 ga ago the existence of a metallic lunar core is now firmly established and we investigate the influence of inner core growth on generating a lunar core dynamo we couple the results of a 3 d spherical thermochemical convection model of the lunar mantle to a 1 d thermodynamic model of its core the energy and entropy budget of the core are computed to determine the inner core growth rate and its efficiency to power a dynamo sulfur is considered to be the main alloying element and we investigate how different sulfur abundances and initial core temperatures affect the model outcomes for reasonable initial conditions a solid inner core between 100 and 200 km is always produced during its growth a surface magnetic field of about 0 3 t is generated and is predicted to last several billion years though most simulations predict the existence of a core dynamo at the present day one way to stop magnetic field generation when the inner core is growing is by a transition between a bottom up and top down core crystallization scheme when the sulfur content becomes high enough in the outer core according to this hypothesis a model with about 6 to 8 wt sulfur in the core would produce a 120 160 km inner core and explain the timing of the lunar dynamo as constrained by paleomagnetic data

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

pollen based quantitative reconstruction of holocene climate changes in the daihai lake area inner mongolia china vegetation around the daihai lake northern china is very sensitive to climate changes in this paper pollen based quantitative climate reconstructions using three methods weighted averaging partial least squares method wapls modern analog technique mat and pollen response surface method prs were conducted to obtain robust reconstructions of holocene climate changes in the daihai lake area the result obtained by the three methods all consistently show the annual precipitation to have been 50 100 mm lower in the early holocene 100 200 mm higher in the mid holocene and 50 100 mm lower again in the late holocene than at present the wapls and the mat methods also show quasi synchronous oscillations of the mean annual temperature ta 18 28c lower in the early holocene and 18 38c higher in the midholocene than today the time period from 6200 to 5100 cal yr bp was the wettest and the warmest interval with an annual precipitation pa greater than 550 mm and mean annual temperature ta higher than 6 58c several cold and dry events can be identified to occur about 8200 6000 and 4400 cal yr bp with an annual precipitation less than 400 mm and a mean annual temperature colder than 4 58c respectively the mean temperature of the warmest month tw as reconstructed using both wapls and mat methods was relatively stable during the holocene fluctuating about 628c relative to the present level but the prs method suggests more varied tw values in both amplitude and frequency after 1500 cal yr bp no consistent pattern can be observed from these three different analyses probably because of the impact of intensified human disturbances on the natural vegetation the fluctuations of annual precipitation pa correspond to that observed in dongge cave in southern china the differences might be linked to indian monsoon and east asia monsoon climates or caused by the different degree of dating precision different temporal resolution and different sensitive response of climate proxies to the climate variations

palaeosol development in the chinese loess plateau as an indicator of the strength of the east asian summer monsoon evidence for a mid holocene maximum the interpretation of the stalagmite delta o 18 record from southern china as an indicator of east asian summer monsoon easm rainfall amount or intensity is strongly debated soil development in the chinese loess plateau clp situated in the modern summer monsoon domain has long been treated as a direct and reliable easm proxy in this study we compiled 81 loess and 229 palaeosol dates from 77 profiles across the clp and synthesized the data statistically in order to investigate the easm history during the holocene the resulting history of holocene loess deposition and palaeosol development demonstrates that 1 loess deposition decreased and palaeosol formation increased across the clp after 11 5 ka 1 ka 1000 cal yr bp revealing a gradually intensified easm during the early holocene 2 numerous palaeosols developed in the clp between 8 8 ka and 3 4 ka indicating a generally strong easm during the mid holocene 3 the number of palaeosol dates decreased rapidly at around 3 ka suggesting a sudden retreat of the easm in the late holocene these trends of easm evolution are broadly consistent with variations in aeolian sand activity in the four main sandlands the mu us otindag horqin and hulun buir sandlands along the modern monsoon fringe in northern china and are supported by a wide range of independent evidence in addition we also found that high loess deposition and stronger aeolian activity occurred at similar to 5 ka representing a weak easm event within the context of an overall strong mid holocene easm the strong mid holocene easm revealed by palaeosol development in the clp and aeolian sand activity in the sandlands in northern china contrasts with the early holocene easm maximum suggested by stalagmite delta o 18 data from southern china our results are compatible with the proposal that the stalagmite delta o 18 variations in china do not result from changes in easm rainfall amount or intensity but instead reflect changes in moisture source driven by variations in atmospheric oceanic circulation c 2014 elsevier ltd and inqua all rights reserved

new ni and co metal silicate partitioning data and their relevance for an early terrestrial magma ocean abstract it is generally assumed that the abundances of the siderophile metal loving elements in the earth s mantle are the result of core formation in the early earth in the most popular model the low contents of siderophile elements in the earth s mantle are the result of metal silicate equilibration followed by metal accumulation at the base of a magma ocean this model is primarily based on the pressure dependence of ni and co metal silicate partition coefficients first determined by li and agee li j agee c b 1996 geochemistry of mantle core differentiation at high pressures nature 381 686 689 we have undertaken a further test of this hypothesis by performing a large number of additional partition experiments with the two key elements ni and co at a variety of temperatures and a pressure range extending from ambient pressure to 25 gpa 750 km depth in the earth the unexpected result of the new experiments is the recognition of two pressure regimes in the temperature and pressure dependences of ni fe and to a lesser extent of co fe exchange metal silicate partition coefficients k d ni fe and k d co fe the strong pressure and temperature dependences of k d ni fe and k d co fe at atmospheric pressure change below about 5 gpa to much weaker dependences at higher pressures as a consequence the pressure dependences of k d ni fe and k d co fe cannot be regressed with a single fit over the entire pressure range fits based on partition data obtained in this work and from the literature between 5 gpa and 25 gpa were extrapolated to pressures and temperatures to lower mantle liquidus conditions the co fe partition coefficients required to satisfy the present mantle composition is reached at about 35 gpa whereas the proper ni fe ratio requires 45 to 50 gpa at 55 gpa ni and co partition coefficients would be identical but the ni and co contents imposed on the earth s mantle by metal silicate equilibration would be too low this would exclude single stage magma ocean models for producing approximately chondritic ni co ratio in the earth s mantle however the accuracy of the experimental data obtained here and from the literature is not sufficient to unambiguously exclude single stage equilibration the results of this and other recent studies exclude that fe ni and co contents of the present upper mantle were established by metal silicate equilibration at upper mantle conditions

crystals stirred up 2 numerical insights into the formation of the earliest crust on the moon 1 this is the second paper in a two part series examining the fluid dynamics of crystal settling and flotation in the lunar magma ocean in the first paper we develop a direct numerical method for resolving the hydrodynamic interactions between crystals and their feedback on the flow field in magmatic liquid in this paper we use this computational technique to test the leading model for the formation of the earliest crust on the moon the anorthositic lithology of the lunar crust is thought to have been formed by the flotation of buoyant plagioclase crystals at a time when the lunar mantle was still wholly or largely molten this model is appealing from an observational point of view but its fluid dynamical validity is not obvious because 1 plagioclase probably started crystallizing very late i e when the magma ocean was already 80 solidified and 2 a significant portion of the shallow lunar crust consists of almost pure plagioclase 90 vol requiring very efficient plagioclase segregation the goal of this study is to better understand the fluid dynamical conditions that hinder or facilitate crystal settling or flotation our approach complements earlier studies by explicitly linking the petrological and fluid dynamical evolution and by focusing on the effect of increasing crystal fraction we find that crystal settling was probably possible throughout the entire solidification history of the lunar magma ocean as long as crystal sizes were sufficiently large r 1 mm and crystal fraction sufficiently low 13

compressibility change in iron rich melt and implications for core formation models abstract metallic iron in both solid and liquid states is the dominant component of earth s core density measurements of molten iron containing an appropriate amount of light elements 5 7 wt carbon identified a liquid liquid transition by a significant compressibility increase in the vicinity of the liquid triple point at 5 2 gpa this transition pressure coincides with a marked change in the pressure evolution of the distributions of nickel cobalt and tungsten between liquid metal and silicate melt that form a cornerstone of geochemical models of core formation the identification of a clear link between molten metal polymorphism and metal silicate element partitioning implies that reliable geochemical core formation models will need to incorporate the effects of these additional liquid metal transitions

co2 h2o and orbitally driven climate variability over central asia through the holocene small variations in earth s orbit have a direct impact on global climate with the greatest changes occurring over large land masses such as asia orbitally driven climate signals are therefore likely to be identifiable in climate proxy records derived from sediment sections in the continental interior proxy records derived from temperature dependent variables are also likely to display a signal due to temporal variability of atmospheric co2 and related climatic parameters such as water vapour content to determine the magnitude of climate anomalies associated with shortwave and longwave radiative forcing over asia a suite of numerical atmospheric simulations is performed that spans most of the holocene from 10 000 to 2500 years bp at 500 year intervals over central asia the amplitude of the summer winter seasonal cycle is greater than today in all simulations but exhibits two distinct maxima at 9000 and 6000 bp simulated precipitation and snow accumulation over central asia are markedly higher during the early mid holocene and are oscillatory exhibiting peaks at 8000 7500 and 4500 bp the atlantic and subboreal times respectively co2 h2o forcing and orbital forcing combine to drive temperature oscillations over central asia which in turn regulate relative humidity and changes in surface hydrology correlation between simulated results and proxy records from across asia suggest that co2 h2o and orbital forcing are dominant factors driving fluctuations of large scale central asian climate through the holocene

contributors to chromium isotope variation of meteorites we report the results of a comprehensive high precision survey of the cr isotopic compositions of primitive chondrites along with some differentiated meteorites to ensure complete dissolution of our samples they were first fused with lithium borate tetraborate at 1050 1000 c relative to the nist cr standard srm 3112a carbonaceous chondrites exhibit excesses in 54cr 52cr from 0 4 to 1 6e 1e 1 part in 10 000 and ordinary chondrites display a common 54cr 52cr deficit of 0 4e analyses of acid digestion residues of chondrites show that carbonaceous and ordinary chondrites share a common 54cr enriched carrier which is characterized by a large excess in 54cr 52cr up to 200e associated with a very small deficit in 53cr 52cr 2e we did not find 54cr anomalies in either bulk enstatite chondrites or in leachates of their acid digestion residues this either requires that the enstatite chondrite parent bodies did not incorporate the 54cr anomaly carrier phase during their accretion or the phase was destroyed by parent body metamorphism chromium in the terrestrial rocks and lunar samples analyzed here show no deviation from the nist srm 3112a cr standard the eucrite and martian meteorites studied exhibit small deficits in 54cr 52cr the 54cr 52cr variations among different meteorite classes suggest that there was a spatial and or temporal heterogeneity in the distribution of a 54cr rich component in the inner solar system we confirm the correlated excesses in 54cr 52cr and 53cr 52cr for bulk carbonaceous chondrites but the new data yield a steeper slope 6 6 than that reported in shukolyukov and lugmair 2006 the correlated excesses may affect the use of the mn cr chronometer in carbonaceous chondrites we could not confirm the bulk carbonaceous chondrite mn cr isochron reported by shukolyukov and lugmair 2006 and moynier et al 2007 mostly because we find much smaller total variations in e53cr 0 2 all bulk chondrites have small e53cr excesses up to 0 3 relative to the earth most likely reflecting the sub chondritic mn cr ratio of the earth the e53cr variations in chondrites do seem to grossly correlate with mn cr and yield an initial solar system 53mn 55mn value of 5 4 2 4 10 6 corresponding to an absolute age of 4566 4 2 2 ma nuclear interactions with cosmic rays result in coupled excesses in e54cr and e53cr with a 4 1 ratio in phases with high fe cr these are most dramatically demonstrated in the iron meteorite carbo showing excesses in e54cr of up to 140e these new results show that the mn cr chronometer should be used with caution in samples minerals with high fe cr and long cosmic ray exposure ages

chronological evidence that the moon is either young or did not have a global magma ocean a new age determination for a moon rock collected close to the site of the apollo 16 lander has yielded a surprisingly young age of around 4 360 million years this age would require either that the moon solidified some 200 million years after the formation of the solar system significantly later than is assumed by most lunar formation models or that the long held theory that the moon once had a primordial global magma ocean is flawed in the latter case much of the lunar crust could have been produced by non magma ocean processes such as serial magmatism chemical evolution of planetary bodies ranging from asteroids to the large rocky planets is thought to begin with differentiation through solidification of magma oceans many hundreds of kilometres in depth1 2 3 the earth s moon is the archetypical example of this type of differentiation evidence for a lunar magma ocean is derived largely from the widespread distribution compositional and mineralogical characteristics and ancient ages inferred for the ferroan anorthosite fan suite of lunar crustal rocks the fans are considered to be primary lunar flotation cumulate crust that crystallized in the latter stages of magma ocean solidification according to this theory fans represent the oldest lunar crustal rock type2 3 4 attempts to date this rock suite have yielded ambiguous results however because individual isochron measurements are typically incompatible with the geochemical make up of the samples and have not been confirmed by additional isotopic systems5 6 7 8 9 by making improvements to the standard isotopic techniques we report here the age of crystallization of fan 60025 using the 207pb 206pb 147sm 143nd and 146sm 142nd isotopic systems to be 4 360 3 million years this extraordinarily young age requires that either the moon solidified significantly later than most previous estimates or the long held assumption that fans are flotation cumulates of a primordial magma ocean is incorrect if the latter is correct then much of the lunar crust may have been produced by non magma ocean processes such as serial magmatism10

half precessional cycles recorded in chinese loess response to low latitude insolation forcing during the last interglaciation abstract chinese loess offers favourable conditions for identifying evidence for high resolution climatic changes previous studies have examined orbital scale climatic cycles and the other shorter time scale climatic oscillations similar to the recorded glacial instability in deep sea cores in this study we focus on examining the high resolution palaeoclimatic records in the northwestern loess plateau where the dust accumulation rate is high and the loess soil sequences are highly sensitive to the shifting pattern of the east asian monsoon system our results of magnetic susceptibility and particle size analysis from the northwestern loess plateau reveal well defined half precessional cycles during the last interglaciation culminating at approximately 122 000 111 000 100 000 88 000 and 79 000 yr these variations are a direct response to the low latitude forcing through its modulation on the east asian summer monsoon in this context the east asian summer monsoon has played an important role in conveying climatic signals from tropical pacific to the middle latitude areas

sedimentary sulfur geochemistry of the paleogene green river formation western usa implications for interpreting depositional and diagenetic processes in saline alkaline lakes abstract the sulfur geochemistry of the lacustrine paleogene green river formation colorado utah and wyoming usa is unlike that of most marine and other lacustrine rocks distinctive chemical isotopic and mineralogical characteristics of the formation are pyrrhotite and marcasite high contents of iron mineral sulfides strikingly enriched in 34 s cyclical trends in sulfur abundance and 34 s values and long term evolutionary trends in 34 s values analyses that identified and quantified these characteristics include carbonate free abundance of organic carbon 0 13 47 wt total iron 0 31 13 wt reactive iron 70 of total iron total sulfur 0 02 16 wt acid volatile monosulfide s av disulfide s di 70 of total sulfur sulfate s so 4 and organosulfur s org isotopic composition of separated sulfur phases 34 s di av up to 49 and mineralogy morphology and paragenesis of sulfide minerals mineralogy morphology 34 s di av and 34 s org have a distinctive relation reflecting variable and unique depositional and early diagenetic conditions in the green river lakes when the lakes were brackish dissimilatory sulfate reducing bacteria in the sediment produced h 2 s which initially reacted with labile iron to form pyrite framboids and more gradually with organic matter to form organosulfur compounds during a long lived stage of saline lake water the amount of sulfate supplied by inflow decreased and alkalinity and ph of lake waters increased substantially extensive bacterial sulfate reduction in the water column kept lake waters undersaturated with sulfate minerals a very high h 2 s so 4 ratio developed in stagnant bottom water aided by the high ph that kinetically inhibited iron sulfidization progressive removal of h 2 s by coeval formation of iron sulfides and organosulfur compounds caused the isotopic composition of the entire dissolved sulfur reservoir to evolve to 34 s values much greater than that of inflow sulfate which is estimated to have been 20 a six million year interval within lake uinta cores records this evolution as well as smaller systematic changes in 34 s interpreted to reflect 100 000 year lake level cycles when porewater was exceptionally reducing unstable fes phases eventually recrystallized to pyrrhotite during diagenesis a much later reaction related to weathering altered pyrrhotite to marcasite

the moon a personal recollection and memorial for professor lawrence a taylor an apollo stalwart abstract the first geochemical analysis of lunar samples returned by the apollo 11 mission revealed that the moon was highly differentiated and depleted in volatile elements stable isotope compositions show that earth and moon are closely related but they have evolved in totally dissimilar ways probably related to the deficiency of water in the moon as well as the vast differences in size currently available lunar samples come from cumulate source regions making the establishment of a bulk planetary composition more reliant on geophysical rather than geochemical properties

petrogenesis of picritic mare magmas constraints on the extent of early lunar differentiation calculations of isobaric batch polybaric batch and polybaric fractional melting have been carried out on a variety of proposed lunar and terrestrial source region compositions results show that magmas with a generally tholeiitic character plagioclase and high ca pyroxene crystallize before low ca pyroxene reflecting relatively high al2o3 concentrations 12 wt are the inevitable consequence of anhydrous partial melting of source regions composed primarily of olivine and two pyroxenes with an aluminous phase on the solidus low al2o3 magmas 10 wt as typified by the green picritic glasses in the lunar maria require deep 700 1000 km low al2o3 source regions without an aluminous phase the difference between primitive and depleted mantle beneath mid ocean ridges amounts to less than 0 1 wt al2o3 whereas formation of the green glass source region requires a net loss of between 1 5 and 2 5 wt al2o3 basalt extraction cannot account for fractionations of this magnitude accumulation of olivine and pyroxene at the base of a crystallizing magma ocean is however an effective method for producing the necessary al2o3 depletions both olivine rich and pyroxene rich source regions can produce the picritic magmas but mixing calculations show that both types of source region are likely to be hybrids consisting of an early to intermediate stage cumulate olivine plus enstatite and a later stage cumulate assemblage mass balance calculations show that refractory element enriched bulk moon compositions contain too much al2o3 to allow for the deep low al2o3 source regions even after extraction of an al2o3 rich 26 30 wt crust between 50 and 70 km thick

the effect of melt composition on metal silicate partitioning of siderophile elements and constraints on core formation in the angrite parent body we present 275 new metal silicate partition coefficients for p s v cr mn co ni ge mo and w obtained at moderate p 1 5 gpa and high t 1683 1883 k we investigate the effect of silicate melt composition using four end member silicate melt compositions we identify possible silicate melt dependencies of the metal silicate partitioning of lower valence elements ni ge and v elements that are usually assumed to remain unaffected by changes in silicate melt composition results for the other elements are consistent with the dependence of their metal silicate partition coefficients on the individual major oxide components of the silicate melt composition suggested by recently reported parameterizations and theoretical considerations using multiple linear regression we parameterize compiled metal silicate partitioning results including our new data and report revised expressions that predict their metal silicate partitioning behavior as a function of p t x fo2 we apply these results to constrain the conditions that prevailed during core formation in the angrite parent body apb our results suggest the siderophile element depletions in angrite meteorites are consistent with a cv bulk composition and constrain apb core formation to have occurred at mildly reducing conditions of 1 4 0 5 log units below the iron wustite buffer iw corresponding to a apb core mass of 18 11 the core mass range is constrained to 21 8 mass if light elements s and or c are assumed to reside in the apb core incorporation of light elements in the apb core does not yield significantly different redox states for apb core mantle differentiation the inferred redox state is in excellent agreement with independent fo2 estimates recorded by pyroxene and olivine in angrites

constraints on core formation in vesta from metal silicate partitioning of siderophile elements abstract it is now widely accepted that the asteroid 4 vesta has an fe rich metallic core but the composition of the core and the conditions prevailing during core mantle differentiation are poorly constrained in light of new constraints on vesta s geophysical and geochemical properties obtained by the dawn mission we have re examined the conditions at which core mantle differentiation in vesta may have occurred by linking the estimated mantle depletions of siderophile elements p co ni cu ga ge mo and w in the vestan mantle to newly derived predictive equations for core mantle partitioning of these elements we extend the number of elements previously considered in geochemical modeling of vestan core formation and use published metal silicate partitioning data obtained at low pressures to characterize the dependence of metal silicate partition coefficients d on pressure temperature oxygen fugacity and composition of the silicate and metallic melt in our modeling we implement newly derived mantle depletions of p co ni and ga through analysis of published hed meteorite analyses and assess two contrasting bulk compositional models for vesta modeling results using monte carlo simulations constrain vestan core formation to have occurred at mildly reducing conditions of approximately 2 log units below the iron wustite iw buffer iw 2 05 0 20 if the two most likely bulk compositions binary mixtures of h cm or h cv chondritic meteorites are considered assuming a temperature range between 1725 and 1850 k and a sulfur free pure fe core if the core is assumed to be sulfur rich 15 wt s as predicted by the latter bulk compositional models observed depletions for all eight siderophile elements can be simultaneously satisfied at iw 2 35 0 10 and 1725 1850 k for the h cv bulk composition and iw 2 30 0 15 and 1725 1850 k for the h cm bulk composition more reducing conditions are not consistent with the observed siderophile element depletions in the vestan mantle independent of the sulfur content of the vestan core and of the bulk compositional model chosen our analysis shows that a previously proposed shallow magma ocean on vesta during core formation is not consistent with the observed mantle depletion of ga for the two considered bulk compositions irrespective of core composition instead our results are consistent with the existence of a deep magma ocean during core formation on vesta requiring 50 100 mantle melting

euxinia and primary production in late cretaceous eastern equatorial atlantic surface waters fostered orbitally driven formation of marine black shales 1 oceanic anoxic events oae in the cretaceous represent major perturbations in the global climate and ocean system characterized by widespread deposition of organic carbon in the ocean the causes and effects of these events are poorly constrained mainly because of the lack of high resolution marine records here we report the distribution of molecular markers from a millennial scale record of coniacian santonian black shale oae 3 from ocean drilling program site 959 in the deep ivorian basin in the eastern equatorial atlantic highly branched isoprenoids and alkenone derived organic compounds indicate that diatoms and calcareous nanoplankton were important primary producers changes in redox sensitive trace metal accumulation and biomarkers of green sulfur bacteria provide evidence for extreme variations in redox conditions with intervals of lower photic zone euxinia pze accordingly oxygen in the coniacian santonian tropical atlantic was absent as during the cenomanian turonian boundary oae 2 but over more restricted geographic area and more limited time intervals we hypothesize that pze was a common phenomenon typical in large areas of tropical continental margins these conditions fostered sequestration of atmospheric co2 and thus helped cause the positive excursion in 13c of carbonate documented in higher latitude marine records

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

the grain size depositional process in wetlands of the sanjiang plain and its links with the east asian monsoon variations during the holocene abstract compared to the well studied the grain size depositional process in hydraulic and aeolian sediments the process in wetlands is still poorly understood in this study the grain size components of a well dated mud peat profile sj2 in the sanjiang plain were partitioned using a lognormal distribution function the results suggest that the lacustrine deposits contain four distinct unimodal grain size distributions c 1 through c 4 with their modal sizes ranging 0 7 1 6 2 4 8 7 15 7 27 8 and 380 2 529 6 m respectively only the c 1 and c 3 were identified in the peat layers a grain size depositional modal was introduced to explain the environmental meanings of the four components c 3 as a nearshore suspension component was the most sensitive component to the variation of local hydraulic conditions based on the variation of c 3 percentages of the profile sj2 the local hydraulic conditions were tentatively reconstructed and the results showed a close relation with the monsoon variations during the holocene accordingly we suggest the relative coarse component of the polymodal peat deposits in monsoonal regions can be used as a sensitive indicator for the hydraulic conditions and the monsoon circulations in the geological past

holocene vegetation and climate dynamics of ne china based on the pollen record from sihailongwan maar lake abstract high resolution palynological analysis on annually laminated sediments of sihailongwan maar lake shl provides new insights into the holocene vegetation and climate dynamics of ne china the robust chronology of the presented record is based on varve counting and ams radiocarbon dates from terrestrial plant macro remains in addition to the qualitative interpretation of the pollen data we provide quantitative reconstructions of vegetation and climate based on the method of biomization and weighted averaging partial least squares regression wa pls technique respectively power spectra were computed to investigate the frequency domain distribution of proxy signals and potential natural periodicities pollen assemblages pollen derived biome scores and climate variables as well as the cyclicity pattern indicate that ne china experienced significant changes in temperature and moisture conditions during the holocene within the earliest phase of the holocene a large scale reorganization of vegetation occurred reflecting the reconstructed shift towards higher temperatures and precipitation values and the initial holocene strengthening and northward expansion of the east asian summer monsoon easm afterwards summer temperatures remain at a high level whereas the reconstructed precipitation shows an increasing trend until approximately 4000 cal yr bp since 3500 cal yr bp temperature and precipitation values decline indicating moderate cooling and weakening of the easm a distinct periodicity of 550 600 years and evidence of a mid holocene transition from a temperature triggered to a predominantly moisture triggered climate regime are derived from the power spectra analysis the results obtained from shl are largely consistent with other palaeoenvironmental records from ne china substantiating the regional nature of the reconstructed vegetation and climate patterns however the reconstructed climate changes contrast with the moisture evolution recorded in s china and the mid latitude semi arid regions of n china whereas a clear insolation related trend of monsoon intensity over the holocene is lacking from the shl record variations in the coupled atmosphere pacific ocean system can largely explain the reconstructed changes in ne china

the timeline of the lunar bombardment revisited abstract the timeline of the lunar bombardment in the first gy of solar system history remains unclear basin forming impacts e g imbrium orientale occurred 3 9 3 7 gy ago i e 600 800 my after the formation of the moon itself many other basins formed before imbrium but their exact ages are not precisely known there is an intense debate between two possible interpretations of the data in the cataclysm scenario there was a surge in the impact rate approximately at the time of imbrium formation while in the accretion tail scenario the lunar bombardment declined since the era of planet formation and the latest basins formed in its tail end here we revisit the work of morbidelli et al 2012 that examined which scenario could be compatible with both the lunar crater record in the 3 4 gy period and the abundance of highly siderophile elements hse in the lunar mantle we use updated numerical simulations of the fluxes of asteroids comets and planetesimals leftover from the planet formation process under the traditional assumption that the hses track the total amount of material accreted by the moon since its formation we conclude that only the cataclysm scenario can explain the data the cataclysm should have started 3 95 gy ago however we also consider the possibility that hses are sequestered from the mantle of a planet during magma ocean crystallization due to iron sulfide exsolution o neil 1991 rubie et al 2016 we show that this is likely true also for the moon if mantle overturn is taken into account based on the hypothesis that the lunar magma ocean crystallized about 100 150 my after moon formation elkins tanton et al 2011 and therefore that hses accumulated in the lunar mantle only after this timespan we show that the bombardment in the 3 4 gy period can be explained in the accretion tail scenario this hypothesis would also explain why the moon appears so depleted in hses relative to the earth we also extend our analysis of the cataclysm and accretion tail scenarios to the case of mars the accretion tail scenario requires a global resurfacing event on mars 4 4 gy ago possibly associated with the formation of the borealis basin and it is consistent with the hse budget of the planet moreover it implies that the noachian and pre noachian terrains are 200 my older than usually considered

magma oceans in the inner solar system theory and observations point to the occurrence of magma ponds or oceans in the early evolution of terrestrial planets and in many early accreting planetesimals the apparent ubiquity of melting during giant accretionary impacts suggests that silicate and metallic material may be processed through multiple magma oceans before reaching solidity in a planet the processes of magma ocean formation and solidification therefore strongly influence the earliest compositional differentiation and volatile content of the terrestrial planets and they form the starting point for cooling to clement habitable conditions and for the onset of thermally driven mantle convection and plate tectonics this review focuses on evidence for magma oceans on planetesimals and planets and on research concerning the processes of compositional differentiation in the silicate magma ocean distribution and degassing of volatiles and cooling

asian monsoon oscillations in the northeastern qinghai tibet plateau since the late glacial as interpreted from visible reflectance of qinghai lake sediments abstract qinghai lake is a large saline lake on the qinghai tibetan plateau of central asia that is effected by both the indian and asian monsoons we used reflectance spectroscopy to characterize the sediments in a 795 cm long core taken from the southeastern part of the lake sediment redness which is related to iron oxide content seems to monitor paleoclimatic changes in the core iron oxides appear to be eroded from nearby red beds or loess deposits and are transported by fluvial means into the lake thus redness increases at times of increased precipitation that is as monsoon strength increases our redness monsoon proxy shows climate changes on several times scales on a millennial scale it records humid conditions during the early and mid holocene from about 4200 to 2300 yr bp low redness values suggest a two millennial long dry period which in the late holocene is followed by a more humid period on a centennial scale the redness proxy records not only the little ice age but also the medieval warm period the dark ages cool period and the roman warm period time series analysis of the redness record indicates a 200 yr frequency which corresponds to the de vries solar cycle suggesting that in addition to insolation changes resulting from orbital variations solar forcing also results from cyclic changes in the sun s luminosity