a model for the thermal and chemical evolution of the moon s interior implications for the onset of mare volcanism crystallization of the lunar magma ocean creates a chemically stratified moon consisting of an anorthositic crust and magma ocean cumulates overlying the primitive lunar interior within the magma ocean cumulates the last liquids to crystallize form dense ilmenite rich cumulates that contain high concentrations of incompatible radioactive elements the underlying olivine orthopyroxene cumulates are also stratified with later crystallized denser more fe rich compositions at the top this paper explores the chemical and thermal consequences of an internal evolution model accounting for the possible role of these sources of chemical buoyancy rayleigh taylor instability causes the dense ilmenite rich cumulate layer and underlying fe rich cumulates to sink toward the center of the moon forming a dense lunar core after this overturn radioactive heating within the ilmenite rich cumulate core heats the overlying mantle causing it to melt in this model the source region for high tio2 mare basalts is a convectively mixed layer above the core mantle boundary which would contain small and variable amounts of admixed ilmenite and kreep this deep high pressure melting as required for the generation of mare basalts occurs after a reasonable time interval to explain the onset of mare basalt volcanism if the content of radioactive elements in the core and the chemical density gradients above the core are sufficiently high but within a range of values that might have been present in the moon regardless of details implied by particular model parameters gravitational overturn driven by the high density of magma ocean fe rich cumulates should concentrate high tio2 mare basalt sources and probably a significant fraction of radioactive heating toward the center of the moon this will have important implications for both the thermal evolution of the moon and for mare basalt genesis

phytoliths indicators of grassland dynamics during the late holocene in intertropical africa abstract the reconstruction of african tropical grassland history during the late holocene can be carried out using phytolith analysis fossil phytolith assemblages from lake guiers in the sahelian region of senegal and from lake sinnda in the guineo congolian region of congo were investigated the results are interpreted on the basis of modern phytolith assemblages from the same regions and compared to pollen data previously obtained tall or short grass associations are discriminated by their phytolith index iph saddle cross dumbel saddle while the density of shrubs and trees is indicated by relative proportions of the dicotyledon phytoliths the phytolith data emphasize that in the guineo congolian region around lake sinnda the driest phase of the late holocene occurred between 4000 and 1200 yr b p commencing with the opening of the dense forest and its replacement by a short grass savanna from ca 1000 yr b p wetter climatic conditions developed as represented by the setting up of a tall grass savanna woodland the modern shrub and tall grass savanna was developed ca 700 yr b p in the sahelian region around lake guiers the driest phase occurred after about 2000 yr b p and has not been followed by moister conditions a tall grass savanna woodland was gradually replaced by a shrub and short grass savanna which still occurs a short period of development of swampy vegetation which can be related to a lake level change interrupted the semi arid adaptation of the vegetation between about 2000 yr b p and the present

representational bias in phytoliths from modern soils of central north america implications for paleovegetation reconstructions abstract understanding localized patterns and community compositions of vegetation in an environment is critical to the reconstruction of climatic and ecological conditions across all spatiotemporal scales one of the most accurate and useful ways to characterize vegetation and therefore to describe the climatic and ecological conditions of a location is through the plant fossil record phytoliths plant silica microfossils are often preserved in the absence of other paleobotanical data and are becoming more widely used for deep time vegetation reconstructions significant work has been done to standardize the analytical methodology of phytolith extraction statistical analysis and interpretation but more detailed investigations are needed to understand how well a given soil assemblage represents the actual aboveground plant biomass for a given ecosystem we present results from paired soil phytolith assemblages and local vegetation assemblages across the central united states including temperate forest grassland and rangeland scrubland ecosystems phytolith assemblages obtained via extractions from soil a horizons were compared to percent cover of species and plant biomass estimates obtained via in situ field observations and aerial estimates of tree cover to analyze differences in the relative abundance of forest woody vegetation vs grasses soil phytolith assemblages from all sites average a 29 bias toward the grass morphotypes as compared to actual aboveground biomass observations and comparisons to percent cover yielded broadly comparable bias figures percent bias estimates do not show significant correlations to most environmental factors temperature precipitation local elevation however an extremely strong correlation p

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

the origin and spread of grass dominated ecosystems in the late tertiary of north america preliminary results concerning the evolution of hypsodonty abstract sediment samples were collected in northwestern nebraska from the following lithologic units 1 the upper oligocene monroe creek formation the lower miocene harrison formation and upper harrison beds of the arikaree group and 2 the lower miocene runningwater formation and the dawes clay member box butte formation of the ogallala group the samples were processed using heavy liquid extraction and analyzed for siliceous plant microfossils phytoliths all samples yielded well preserved and diverse assemblages dominated by grass phytoliths but included phytoliths produced by woody and herbaceous dicotyledons palms and sedges the abundance of woody dicotyledons and palms decreased up section the grass assemblages consisted mainly of festucoid c3 phytolith morphotypes an index assessing the amount of tree cover d p the ratio of dicotyledon phytoliths to grass phytoliths was employed to interpret the data according to this analysis there was open c3 dominated grassland in the study area between 25 and 17 ma at least 7 ma before supposed adaptations to grasslands in ungulates hypsodonty originate

the spread of grass dominated habitats in turkey and surrounding areas during the cenozoic phytolith evidence abstract the arrival of hipparionine horses in the eastern mediterranean region around 11 ma was traditionally thought to mark the simultaneous westward expansion of savanna vegetation across eurasia however recent paleoecological reconstructions based on tooth wear carbon isotopes and functional morphology indicate that grasses played a minor role in late miocene ecosystems of the eastern mediterranean which were more likely dry woodlands or forests the scarcity of grass macrofossils and pollen in miocene floras of europe and asia minor has been used to support this interpretation based on the combined evidence it has therefore been suggested that late miocene ungulate faunal change in the eastern mediterranean signals increased aridity and landscape openness but not necessarily the development of grass dominated habitats to shed new light on the miocene evolution of eastern mediterranean ecosystems we used phytolith assemblages preserved in direct association with faunas as a proxy for paleovegetation structure grassland vs forest we extracted phytoliths and other biogenic silica from sediment samples from well known early to late miocene 20 7 ma faunal localities in greece turkey and iran in addition a middle eocene sample from turkey yielded phytoliths and served as a baseline comparison for vegetation inference phytolith analysis showed that the middle eocene assemblage consists of abundant grass phytoliths grass silica short cells interpreted as deriving from bambusoid grasses as well as diverse forest indicator phytoliths from dicotyledonous angiosperms and palms pointing to the presence of a woodland or forest with abundant bamboos in contrast the miocene assemblages are dominated by diverse silica short cells typical of pooid open habitat grasses forest indicator phytoliths are also present but are rare in the late miocene 9 7 ma assemblages our analysis of the miocene grass community composition is consistent with evidence from stable carbon isotopes from paleosols and ungulate tooth enamel showing that c4 grasses were rare in the mediterranean throughout the miocene these data indicate that relatively open habitats had become common in turkey and surrounding areas by at least the early miocene 20 ma 7 million years before hipparionine horses reached europe and arid conditions ensued as judged by faunal data

gas pressures in geothermal systems abstract the partial pressures of co2 h2s and h2 in geothermal reservoir waters are fixed by temperature dependent mineral equilibria the dissolved gases have a significant effect at which depth the rising hot waters start to boil if their temperature exceeds 250 c and particularly when it exceeds 300 c the following functions describe the temperature dependence of pco2 ph2s and ph2 respectively log p co 2 2 81 5012 7t 1 0 00919t 6 464 log t log p h 2 s s 18 75 24738 9t 1 0 10133t 43 170 log t log p h 2 s d 2 76 5758 2t 1 0 00850t 6 359 log t log p h 2 s 10 14 17763 1t 1 0 04084t 23 368 log t log p h 2 d 9 85 7290 3t 1 0 07202t 22 651 log t where p is partial pressure in bars abs and t is temperature in kelvins two functions are given for each of h2s and h2 one set indicated by subscript d is valid for all waters 300 c and waters in the range 200 300 c if containing 500 ppm cl it is considered that the temperature functions are valid for waters in basaltic to acidic volcanic rocks and also for some waters at least in sedimentary rocks the following function describes crudely total gas pressure plus ph2o in geothermal systems log p total 0 00543 621 4t 1

ultramafic impact melt sheet beneath the south pole aitken basin on the moon 1 the spectral profiler onboard the japanese lunar explorer kaguya conducted the first hyperspectral survey around the south pole aitken basin spa on the moon that is one of the largest impact structures in the solar system the radiative transfer modeling revealed that fresh crater central peaks inside spa are commonly composed of an ultramafic assemblage dominated by magnesium rich orthopyroxene suggesting a homogeneous layer buried under spa the extensive ultramafic layer could be a relic of a gigantic impact melt pool produced by the spa forming impact the preponderance of orthopyroxene could have resulted from significant fractional crystallization of the lunar magma ocean prior to the onset of plagioclase floatation

small scale spatial resolution of the soil phytolith record in a rainforest and a dry forest in costa rica applications to the deep time fossil phytolith record abstract phytolith analysis a well established tool in archaeology and quaternary paleoecology has become a source of data for deep time paleoecological studies only in the last 15 years recent years have also witnessed the publication of numerous soil phytolith inventories from extant vegetation types representing modern analogues however this work suffers from several methodological shortcomings limiting inter study comparisons and the development of a single and repeatable protocol for soil sample collection in this paper we focus on two fundamental methodological questions that must be answered before modern analogue studies can be meaningfully applied to deep time paleoecology 1 do phytoliths from the lower portion of the a horizon more commonly preserved in paleosols reflect standing vegetation equally well as the upper a horizon which is more commonly used in modern analogue studies but often truncated by erosion in paleosols 2 does a point soil sample usually collected from paleosols capture standing vegetation as accurately as a composite soil sample commonly used in modern analogue studies which is made from subsamples taken from a small area to address these questions we collected soil from 10 10 m quadrats in a rainforest la selva and a dry forest palo verde in costa rica and compared phytolith assemblages from upper vs lower soil a horizons and composites vs single phytolith assemblages at both sites phytolith assemblages from the lower vs upper a horizon and from single vs composite samples provide similar vegetation structure signal despite some compositional differences these results suggest that the typical approach in deep time paleoecology of taking point samples from the lower a horizon of paleosols is likely justifiable at least for paleosols reflecting rainforest and dry forest soils we discuss possible mechanisms driving differences between sites and future approaches to further expand and test our results

pyroxene spectroscopy revisited spectral compositional correlations and relationship to geothermometry the authors wish to thank the various agencies which have provided the necessary support for this project including grants in aid of research from sigma xi the scientific research society to e a c the geological society of america grant 3741 87 to e a c and nasa planetary geology and geophysics grant nagw 642 to m j g

compositional variations of the lunar crust results from radiative transfer modeling of central peak spectra 1 we present model mineralogy of impact crater central peaks combined with crustal thickness and crater central peak depth of origin models to report multiple perspectives of lunar crustal composition with depth here we report the analyses of 55 impact crater central peaks and how their compositions directly relate to the lunar highlands sample suite a radiative transfer model is used to analyze clementine visible plus near infrared spectra to place compositional constraints on these central peak materials central peaks analyzed are dominantly magnesian and plagioclase poor strong compositional similarities to lunar mg suite materials are evident relative to crustal thickness estimates central peak mineralogy becomes more plagioclase rich as the crust thickens relative to the crust mantle boundary the origin of peaks with dominantly mafic mineralogy are confined to the lower crust and primarily within the south pole aitken and procellarum kreep terranes pkt additionally central peaks with anorthositic mineralogy 60 vol plagioclase are transported to the surface from all depths in the crustal column and confined to the feldspathic highlands terrane fht the discovery of mafic and magnesian materials consistent with mg suite rocks of the sample collection in all lunar terranes suggests that the process and sources that give rise to these types of rocks is not unique to the pkt and not necessarily dependent on incompatible elements for formation the identification of ferroan and magnesian anorthositic material near the crust mantle boundary of the fht is also inconsistent with an increasing mafic feldspar ratio and mg with depth in the crust

reconstruction of the late pleistocene grassland of the columbia basin washington usa based on phytolith records in loess abstract silica phytoliths preserved in three loess sections in southeastern washington state revealed a 100 000 year history of the columbia basin grassland changes in the proportion of different morphotypes indicate large shifts in vegetation composition during the last 100 ka a low elevation section 677 m asl near the center of the basin provided a record of alternating xeric festuca poa and mesic festuca koeleria grassland the middle slope section 1095 m asl supported picea abies or pinus ponderosa forest or non analog parkland at different times some trees were present at or near the site even during the last glacial maximum the highest site 1220 m asl supported stipa festuca and poa dominated grassland with some artemisia shrub during most of the late pleistocene but supports a coniferous forest today variations in vegetation can be explained as a response to changes in large scale climatic controls grasslands and shrub steppe were apparently more widespread and forests more restricted than today during the marine isotope stages 2 and 4 probably as a result of cooler and drier conditions the three new records are well correlated with previously published paleo reconstructions based on phytolith cicada burrow and stable isotope data from a nearby kp 1 loess section carp lake pollen record and global ice volume variations

crustal thickness of the moon implications for farside basin structures 1 based on the latest selene lunar gravity and topography model obtained by kaguya mission we compute the lunar crustal thickness map to investigate differences between farside basin structures the thickest crust is located in the southern rim of the dirichlet jackson basin and the thinnest crust at the moscoviense basin the thickest crust corresponds to the highest topography and is consistent with airy isostasy the thinnest crust is due to an abnormally large mantle plug the crustal thicknesses at apollo 12 14 sites of our crustal thickness model are 45 1 and 49 9 km the crustal thickness map indicates that the differences between recently proposed type i and type ii basins are probably controlled by the ratio between pre impact crustal thickness and impact scale

lunar ferroan anorthosites and mare basalt sources the mixed connection global overturn of a hot gravitationally unstable lunar mantle immediately following the solidification of a magma ocean and essentially complete by 4 4 ga explains several characteristics of lunar petrology lunar mare basalt sources are inferred to be depleted in europium and alumina these depletions are consensually attributed to complementary plagioclase floating from a magma ocean however the connection cannot be so simple and direct in contrast to the mare basalt source parent magma the ferroan anorthosite parent magma was more evolved by virtue of its lower mg fe ratio and ni abundances although less evolved in its poverty of clinopyroxene constituents flat rare earth pattern and lower incompatible element abundances the europium anomaly in mare sources is inferred to be present at 400 km depth too deep to have been directly influenced by plagioclase crystallization massive overturning of the post magma ocean mantle would have carried down clinopyroxene ilmenite and phases containing fractionated rare earths europium anomalies and some heat producing radionuclides these phases contributed to deep mare basalt sources upward moving phases would have been magnesian mafic minerals their immediate melting on pressure release contributed the magnesian suite of plutonic norites and troctolites that post date the anorthosites in the highlands crust

distribution of materials excavated by the lunar crater bullialdus and implications for the geologic history of the nubium region abstract previous spectroscopic studies of the lunar crater bullialdus located in the nubium basin indicated an unusual stratigraphy of two gabbroic layers overlying a noritic unit the possible existence of a layered mafic pluton at bullialdus was suggested to investigate the geologic context with more detailed spatial information charge coupled device ccd images of bullialdus were obtained using eight filters 0 40 0 56 0 73 0 91 0 95 0 98 0 99 and 1 02 m a linear mixing model was used to investigate the fractional abundances of spectral end members chosen from within the multispectral image since the reflectance properties of lunar materials over this wavelength range are sensitive to variations in composition and soil maturity fractional abundance images were used to create a new geologic map of the crater the spatial relationships of the surface materials confirm the previously inferred stratigraphy and further reveal the central peaks to exhibit two distinct compositional units noritic anorthosite and anorthositic norite three models for the origin of the observed stratigraphy are considered bullialdus has excavated stratigraphic units containing 1 early mare basalt overlying anorthositic noritic crustal material 2 part of a layered mafic pluton and or 3 part of an impact melt sheet formed by the nubium basin impact event

vegetation response during the lead up to the middle miocene warming event in the northern rocky mountains usa abstract the mid miocene climatic optimum mmco initial warming beginning ca 18 ma and with peak warming ca 17 14 75 ma constitutes the earth s most recent greenhouse episode characterized by a transient shift to higher global atmospheric co 2 levels and warmer possibly wetter climatic conditions combined with the spread of grass dominated habitats it has been suggested that the mmco lead to significant turnover and modernization of fauna and flora however records documenting local vegetation change during the mmco are rare hence this hypothesis remains largely untested herein we combine phytolith assemblages and 13 c records from paleosol organic matter from the railroad canyon section rcs eastern idaho to provide the first direct detailed and continuous long term record of vegetation composition and structure in a single basin during the lead up to the mmco 22 9 15 2 ma late arikareean early barstovian phytolith assemblage analysis indicates that grasses primarily c 3 pooids dominated early middle miocene vegetation potential c 4 pacmad grasses were present by ca 21 6 20 7 ma late arikareean and vary in abundance 0 4 17 2 of diagnostic phytoliths through the section although relatively rare overall pacmad grasses decrease significantly through time in parallel with declining diatom abundances and an increase in pooid grasses in contrast paleosol 13 c org indicates 0 29 1 c 4 vegetation but no consistent temporal change where both phytolith and isotope based estimates are made from the same paleosol they are within error most 82 of the time thus the apparent discrepancy in temporal trends could either be due to differences in the resolution of the two records or could be explained if many pacmads were not c 4 grasses but instead water loving c 3 species overall these data suggest that open habitat mosaic vegetation with grass dominated grasslands and open woodlands occurred in the north rocky mountains usa by at least the early miocene more comparable to the timing for the spread of grass dominated habitats in the great plains than previously thought additionally phytolith data suggest that overall vegetation structure remained relatively stable throughout the rcs inconsistent with published paleosol morphology data this points to regionally unique floral patterns decoupled from global climate change leading into the mmco

compositional diversity and geologic insights of the aristarchus crater from moon mineralogy mapper data 1 the moon mineralogy mapper m3 acquired high spatial and spectral resolution data of the aristarchus plateau with 140 m pixel in 85 spectral bands from 0 43 to 3 0 m the data were collected as radiance and converted to reflectance using the observational constraints and a solar spectrum scaled to the moon sun distance summary spectral parameters for the area of mafic silicate 1 and 2 m bands were calculated from the m3 data and used to map the distribution of key units that were then analyzed in detail with the spectral data this analysis focuses on five key compositional units in the region 1 the central peaks are shown to be strongly enriched in feldspar and are likely from the upper plagioclase rich crust of the moon 2 the impact melt is compositionally diverse with clear signatures of feldspathic crust olivine and glass 3 the crater walls and ejecta show a high degree of spatial heterogeneity and evidence for massive breccia blocks 4 olivine strongly concentrated on the rim wall and exterior of the southeastern quadrant of the crater is commonly associated the impact melt 5 there are at least two types of glass deposits observed pyroclastic glass and impact glass

eocene vegetation and ecosystem fluctuations inferred from a high resolution phytolith record a thorough understanding of the ecosystem factors that can act as drivers of vegetation change an important factor for projecting impacts of future climate change requires adequately distinguishing between plant community changes that occur on the local scale or over ecological time scales and long term trends phytolith assemblages have the potential to provide this information but little work has been done so far to test their ability to do so in deep time we examined vegetation patterns inferred from phytoliths plant silica microfossils from a single section of the renova formation timberhills region montana dated to 39 2 3 ma late middle eocene the section is composed of fl uvial sediments overprinted by paleosols including alfi sols entisols inceptisols and composite paleosols phytolith assemblages from 27 paleosol samples were used to reconstruct a high resolution vegetation history for the area and were compared with paleosol data phytoliths are predominantly from forest plants and include tropical elements such as palms arecaceae and gingers zingiberales suggesting a paratropical forest the high resolution sampling records heterogeneous vegetation including shifts among closed forest moderately open forest forest gaps edges and woodland and grass dominated habitats grasses are interpreted as early open habitat plants tolerant of drier conditions but they appear to be replaced by forest vegetation with time resulting in poor correspondence between paleosol type and phytolith assemblage at some stratigraphic levels where paleosol morphology indicates a forest ecosystem and the phytolith assemblages indicate a changing grass forest mixture as a function of depth within the profi les this is the fi rst study that has used phytoliths to construct a high resolution record of vegetation from deep time and we demonstrate that dense sampling and multiproxy approaches to paleo environmental reconstruction are necessary to capture vegetation heterogeneity in time and across microhabitats

calibrating grass phytolith assemblages in climatic terms application to late pleistocene assemblages from kansas and nebraska abstract the use of modern phytolith assemblages for the interpretation of fossil phytolith assemblages demonstrates the utility of phytolith analysis in reconstructing grassland vegetation and climate in the great plains of north america the modern data presented are the typical average assemblages for 34 modern localities taken throughout the great plains modern assemblage variability across the region is substantial this variability shows a coherent geographical pattern consistent with modern grassland composition these modern phytolith assemblages are calibrated in terms of modern climate data specifically july mean temperature seven fossil assemblages from three late pleistocene localities in the central great plains are presented two alternative phytolith temperature regression models are applied to these fossil assemblages to estimate paleo temperature resulting estimates are consistent with other efforts to calculate late pleistocene temperature departures in the region ca 8 0 to 7 0 c the fossil data also show rapid change in grassland composition and climate during the pleistocene holocene transition these results demonstrate how phytolith analysis can complement or substitute for pollen analysis in the great plains of north america

evidence of early c 4 grasses habitat heterogeneity and faunal response during the miocene climatic optimum in the mojave region abstract major changes to landscapes climate and mammalian faunas occurred at the regional scale in western north america during the miocene climatic optimum mco between 17 and 14 ma but few studies have looked at how the mco affected basin scale environments paleoenvironmental reconstructions coupled with mammalian fossil assemblages from the crowder and cajon valley formations in the mojave desert california contribute insights into local scale 10s of kilometers responses to warming during the hemingfordian and barstovian north american land mammal ages by integrating lithological descriptions phytolith analyses carbon isotope composition of preserved soil organic matter 13csom and elemental geochemistry of paleosols we provide reconstructions of depositional environments vegetation and precipitation through the mco phytolith and 13csom evidence suggest that paleoenvironments were predominately c3 grasslands with the earliest potential presence of c4 grasses in the region found within the crowder formation at 17 ma based on elemental geochemistry of paleosols mean annual precipitation estimates are 807 182 mm yr 1 at 17 ma in the crowder formation and 740 800 182 mm yr 1 from 16 to 15 ma in the cajon valley formation our multiproxy approach indicates that the crowder and cajon valley basins were stable large scale braided stream and floodplain systems with intermittent paleosol development and heterogeneity in vegetation and moisture conditions across spatial scales overall we find a signal of local paleoenvironmental stability during the mco however a significant drying trend in the crowder formation does correspond with faunal turnover and reduction in the number of taxa present high species diversity within faunal assemblages especially among small mammals and fewer shared species between the crowder and cajon valley assemblages than expected based on bootstrap analysis indicate that peak mammal diversity was accommodated at both local and regional scales during sustained tectonic activity and the mco in western north america

paleoclimate simulations for north america over the past 21 000 years features of the simulated climate and comparisons with paleoenvironmental data maps of upper level and surface winds and of surface temperature and precipitation illustrate the results of a sequence of global paleoclimatic simulations spanning the past 21 000 years for north america we review a the large scale features of circulation temperature and precipitation that appear in the simulations from the ncar community climate model version 1 ccm 1 b the implications of the simulated climate for the past continental scale distributions of three plant taxa picea spp pseudotsuga menziesii and artemisia tridentata which are broadly representative of the vegetation across the continent and c the potential explanations in terms of atmospheric circulation or surface energy and water balance processes for mismatches between the simulations and observations most of the broad scale features of previous paleoclimatic simulations with the ncar ccm 0 for north america are present in the current simulations many of the elements of a conceptual model based on previous climate simulations that describes the controls of paleoclimatic variations across north america during the past 21 000 years are found in simulations reviewed here these include 1 displacement of the jet stream by the laurentide ice sheet to the south of its present position in both winter and summer 2 generation of a glacial anticyclone over the ice sheet at the lgm and the consequent induction of large scale sinking motions induced over eastern north america 3 changes in the strength of surface atmospheric circulation features through time including weakening of the aleutian low in winter and strengthening of the eastern pacific and bermuda high pressure systems in summer as the ice sheet decreased in size 4 development of a heat low at the surface and a strengthened ridge in the upper atmosphere over the continent at the time of the maximum summer insolation anomaly 5 increases in summer temperature earlier in regions remote from the ice sheet these increases appear earlier in the present ccm 1 simulations than in the previous ccm 0 ones however and 6 continuation of negative winter temperature anomalies into the middle holocene in general simulated surface conditions that are discordant with paleoenvironmental observations can be attributed to the simulation of particular atmospheric circulation patterns e g those that suppress precipitation or advect warm air into a region with these mismatches amplified in beringia and the southeastern united states by surface energy and water balance processes

classification of paleosols despite increased interest in paleosols during the past decade no satisfactory classification is in current use presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope the classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes organic matter content horizonation redox conditions in situ mineral alteration illuviation of insoluble minerals compounds and accumulation of soluble minerals the most prominent of these six features processes provides the key to classifying a paleosol into one of nine orders four of the order names are borrowed from soil taxonomy histosol spodosol oxisol vertisol whereas the other five order names are presented here for the first time calcisol gypsisol gleysol argillisol protosol the orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol the classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology

soil phytoliths from miombo woodlands in mozambique this paper describes topsoil phytolith assemblages from 25 loci underneath miombo woodlands on an eco transect intersecting the mozambican rift along a geographical altitudinal climatic and botanical gradient we provide the first comprehensive overview of the phytolith spectrum that defines northern mozambique s zambezian floristic zone our classifying criteria derive from comparison with previously described and quantified reference collections of trees and grasses growing in the study area we characterize the sedimentological and soil features of the matrices where phytoliths are found establishing correlation among geo edaphic variables and phytoliths descriptive statistics along with nonparametric and parametric statistical analyses evaluate phytolith grouping criteria variation robustness and membership from a taphonomic perspective we attest that topsoil phytolith assemblages are polygenic and do not represent an episodic snapshot of extant vegetation but a palimpsest from plants representing various disturbance episodes succession stages and ecological trends phytoliths retrieved from mozambican miombo soils do not seem to trace altitudinal temperature or precipitation gradients and no significant differences exist between highland and lowland phytolith assemblages this article provides a phytolith analog for woodland environments that can guide future paleoenvironmental research it also confirms that phytolith analysis is able to detect shifts in the woodland grassland interface

evolution of grasses and grassland ecosystems the evolution and subsequent ecological expansion of grasses poaceae since the late cretaceous have resulted in the establishment of one of earth s dominant biomes the temperate and tropical grasslands at the expense of forests in the past decades several new approaches have been applied to the fossil record of grasses to elucidate the patterns and processes of this ecosystem transformation the data indicate that the development of grassland ecosystems on most continents was a multistage process involving the paleogene appearance of c3 and c4 open habitat grasses the mid late cenozoic spread of c3 grass dominated habitats and finally the late neogene expansion of c4 grasses at tropical subtropical latitudes the evolution of herbivores adapted to grasslands did not necessarily coincide with the spread of open habitat grasses in addition the timing of these evolutionary and ecological events varied between regions consequently region by region investigations using both direct plant fossil

possible mantle origin of olivine around lunar impact basins detected by selene the composition structure and evolution of the moon s mantle is poorly constrained a global survey of the moon s surface using the spectral profiler onboard the lunar explorer selene kaguya identifies a number of exposures of olivine in concentric regions around lunar craters with a possible mantle origin

multi proxy evidence for tectonic control on the expansion of c4 grasses in northwest argentina the timing of the rise of c4 grasses and the climatic conditions driving their expansion are widely debated with recent studies suggesting that the expansion was more complex than previously thought proxy reconstructions from northwestern argentina record multiple increases and decreases in c4 abundance throughout the late miocene to early pliocene as well as variations in the timing of the spread of c4 grasses into the region here we present a multi proxy paleovegetation reconstruction of the proportions of c3 and c4 vegetation using organic carbon and phytoliths preserved in paleosols at entre rios in the santa maria basin of catamarca argentina between 6 2 and 3 3 ma both corg13 and phytolith assemblages indicate a c3 dominated ecosystem with no evidence for substantial amounts of c4 vegetation from the late miocene through mid pliocene despite their rise to dominance elsewhere during this time these data suggest that by 6 2 ma the santa maria basin floor was at an elevation high enough to create locally cool conditions that allowed c3 vegetation to outcompete c4 grasses phytolith assemblages show that later uplift of the sierra calchaquies and sierra aconquija ranges through the pliocene increased aridity and drove the expansion of c3 grasses at the expense of palms and other forest indicators this multi proxy paleovegetation reconstruction demonstrates that tectonics played an important role in controlling the late miocene expansion c4 grasses by suppressing their spread into northwest argentina

northern imbrium noritic anomaly 1 an analysis of the northern imbrium noritic nin region was conducted using clementine uvvis multispectral images and derived band parameters band parameters were used to map spatial variations in composition and to aid in general separation of compositional signatures from effects such as maturity and topography compositional trends in which the abundance of mafic materials relative to feldspathic materials increased were observed with depth in large craters with distance to the west and with distance from the center of the imbrium basin on average the region appears to have an anomalously mafic surface composition with a noritic upper unit overlying and grading into a more feldspathic layer that is exposed in the central peak of the largest crater in the region of several hypotheses that could explain these results we favor a scenario in which feldspathic crustal materials underlie moderately mafic south pole aitken antipodal ejecta which is covered by and mixed with mafic imbrium ejecta limitations of the clementine uvvis data preclude quantitative evaluation of these hypotheses but compositional information from new high resolution data sets should allow the direct comparisons needed to test these hypotheses

phytoliths as paleoenvironmental indicators west side middle awash valley ethiopia phytolith assemblage analysis offers the potential to refine our knowledge of paleoecosystems where grasses and sedges predominate in this work holocene and pleistocene sediments from an arid tropical region in ethiopia have been analyzed for their phytolith content presented as detailed counts and diagrams according to the twiss classification the aim is to test the usefulness of phytolith assemblages to indicate paleoenvironments at middle awash where fossil pollen grains are poorly preserved in sediments that yielded abundant archaeological remains the vegetation in the middle awash subdesertic valley is currently a shrub steppe dominated by c4 grasses adapted to arid conditions with a narrow riparian forest limited to the awash river our results show that modern surface samples holocene and pleistocene sediments contain well preserved and different phytolith assemblages and therefore that no translocation processes from modern soil to geological strata seem to occur fossil records and modern assemblages are interpreted using phytolith ratios to estimate the density of the tree cover the aridity and the proportion of c3 versus c4 grasses as applied to phytolith assemblages from north america and west africa the phytolith assemblages from modern soil samples correctly reflect the proportion of trees and shrubs versus grasses different in the riparian vegetation and the shrub steppe modern phytolith assemblages appear to be a mixed signature of local and regional vegetation phytolith analysis of the holocene sample suggests a grassland where the grass community is constituted by the chloridoideae subfamily adapted to warm and dry conditions and where c3 pooideae cover the highlands phytolith analysis of the pleistocene sample evidences grassland formation with scattered woody elements where c4 panicoideae grasses adapted to warm and humid conditions dominate the grass cover however these conclusions need to be confirmed by more complete study on phytolith assemblages from modern vegetation from ethiopia

regional scale variability in the spread of grasslands in the late miocene abstract a new paleovegetation reconstruction based on both phytolith and paleosol carbon isotopic data is presented for the middle late miocene 11 2 9 5 ma of southwestern montana both sources of data indicate an open habitat c3 grassland ecosystem with a small c4 component

radiative transfer modeling of lunar highlands spectral classes and relationship to lunar samples 1 tompkins and pieters 1999 identified eleven spectral classes present on the surface of the moon here we model these spectral classes to determine the compositions that define them we do this by mathematically matching spectral classes to radiative transfer computed spectra using spectral shape contrast and excursion parameters as defining characteristics model spectra are based upon known mineralogies mafic mineral mg s molar mg mg fe 100 and maturities we compare these compositional results to a compilation of 100 apollo samples to determine plausible representative samples for these spectra results indicate that unique mineralogic solutions for several spectral classes can be determined unambiguously however classes previously interpreted to be pyroxene rich are compositionally ambiguous results suggest these ambiguous mineral assemblages are not random but correlate with variations in absolute reflectance these data further suggest absolute reflectance is a compositionally diagnostic spectral parameter that should be used in conjunction with relative reflectance analysis to constrain mineralogy although absolute reflectance for the eleven spectral classes is not available to constrain their composition we detail mineral chemical i e mg and absolute reflectance variations of matching model relative reflectance spectra to narrow the possibilities this information is used in a pilot study of bullialdus crater for which clementine absolute reflectance is known results indicate bullialdus s central peak consists of tompkins and pieters spectral classes an agn and n bullialdus s spectra that match class n are roughly consistent with previous compositional interpretations however matches to classes an and agn indicate more mafic assemblages typical of mg suite norite gabbronorite rocks

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

taphonomy of phytoliths and macroplants in different soils from olduvai gorge tanzania and the application to plio pleistocene palaeoanthropological samples the abundance and types of phytoliths in the fossil record are taphonomically biased and do not correspond with the macroplant record to better understand the bias and improve the interpretation of samples from olduvai gorge tanzania we analysed the phytoliths from three sample sets modern grasses sedges palm and dicots in the area modern soils in the area and the fossil soils from the eastern palaeolake margin in lowermost bed ii fourier transform infrared spectrometry analyses were performed in parallel to compare the mineral composition of both modern soils and fossil soils we found that the abundance of phytoliths is greatly reduced in soil samples compared with modern plant material but the morphotypes can be reliably interpreted dicotyledonous wood bark phytoliths appear to be over represented in the soil types grass phytoliths and sedges to a lesser degree are preserved in the soils but in lower abundances resulting in these groups being under represented the macroplant fossils are fragments of grass and sedge aerial culms and dicotyledonous stems that are preserved in fluvial and lacustrine deposits it is suggested that phytoliths represent the continuous flora whereas macroplant fossils represent the more robust tissues of selected plants preserved under more catastrophic conditions a post depositional model is proposed and the palaeovegetation is reinterpreted as being richer and more complex than indicated by other fossil data

using phytolith assemblages to reconstruct the origin and spread of grass dominated habitats in the great plains of north america during the late eocene to early miocene abstract this paper outlines a general approach for analyzing siliceous microfossils from plants phytoliths in geologic sediments and uses this method to reconstruct the evolution of grasslands in the central great plains during the late tertiary phytolith assemblage analysis is widely employed for reconstructing vegetation types in pleistocene holocene paleoecology and archaeology but no standardized methodology is currently available published phytolith studies are often system specific and tailored after specific modern analogues as a result they vary in extraction technique classification scheme and method of inference for ancient phytolith assemblages whose modern analogues are not well understood a more general analytic approach is necessary this analytic approach includes studying all size fractions 2 250 mm using a classification scheme based on the available literature and a comprehensive modern phytolith reference collection and comparing relative frequencies through time of all diagnostic phytoliths to interpret changes in habitat structure this general method was applied to late eocene to early miocene sediment samples from northwestern nebraska to deduce vegetation history and the results were compared to those obtained using a more specific technique stromberg paleogeogr paleoclimatol paleoecol 177 2002 59 in both studies phytoliths were extracted by means of heavy liquid separation from the following lithostratigraphic units 1 the late eocene chadron formation and the early oligocene brule formation white river group 2 the late oligocene early miocene monroe creek formation the early miocene harrison formation and anderson ranch formation arikaree group and 3 the early miocene runningwater formation and box butte formation ogallala group the two techniques general vs specific produced results that differ markedly data from the general approach indicate the presence of relatively closed habitats in late eocene to early oligocene typified by the presence of phytoliths from bambusoid grasses woody and herbaceous dicotyledons and palms the introduction and spread of modern open habitat grasses such as pooids arundinoids and panicoids occurred between the late oligocene and early miocene this resulted in a savanna or woodland type habitat by the early miocene in contrast analysis using the specific method suggested the presence of open habitats in northwestern nebraska from the late eocene onward the difference in interpretation based on the two approaches is principally due to inclusion of phytoliths 50 mm and the use of an expanded reference collection in the current study general analytic approach these results point to the importance of methodological choices in phytolith analysis and emphasize the usefulness of phytoliths as paleoecological indicators in the fossil record

measuring moonlight an overview of the spatial properties lunar coverage selenolocation and related level 1b products of the moon mineralogy mapper 1 the moon mineralogy mapper m3 a high resolution high precision imaging spectrometer flew on board india s chandrayaan 1 mission from october 2008 through august 2009 this paper describes some of the spatial sampling aspects of the instrument the planned mission and the mission as flown we also outline the content and context of the resulting level 1b spatial products that form part of the m3 archive while designed and planned to operate for 2 years in a 100 km lunar orbit m3 was able to meet its lunar coverage requirements despite the shortened mission an increase of the orbit altitude to 200 km and several relevant problems with spacecraft attitude timing and ephemeris the unexpected spacecraft issues required us to invent a novel two step approach for selenolocation leveraging newly available lunar reconnaissance orbiter lunar orbiter laser altimeter lola topography and an improved spacecraft ephemeris we have created a method that permits us to bootstrap spacecraft attitude estimates from the image data themselves this process performs a nonlinear optimization to honor a set of data derived image to image tie points and image to lola control points error analysis of the final results suggests we have converged to a selenolocation result that has image to image root mean square rms errors less than 200 m and image to lola rms errors less than 450 m despite using data derived spacecraft attitude results the level 1b products include the lunar coordinates resulting from this inversion process and 10 relevant observational geometry parameters that fully characterize the ray tracing geometry on a pixel by pixel basis

early crustal building processes on the moon models for the petrogenesis of the magnesian suite abstract the plutonic rocks of the magnesian suite mg suite represent the period of lunar basaltic magmatism and crustal growth 4 46 to 4 1 ga that immediately followed the initial differentiation of the moon by magma ocean lmo formation and crystallization the volume and distribution of the mg suite and its petrogenetic relationship to latter stages of lunar magmatism mare basalts remains obscure these plutonic rocks exhibit a range of compositions and include ultramafics troctolites spinel troctolites norites and gabbronorites a distinguishing characteristic of this suite is that they contain some of the most magnesium rich phases fo95 90 that had crystallized from lunar magmas yet they also are significantly enriched in an incompatible element component referred to as kreep a late stage product of lmo crystallization containing abundant potassium k rare earth elements ree phosphorous p uranium and thorium ion microprobe analyses of individual mineral phases olivine pyroxene and plagioclase from the mg suite have shown some very unexpected characteristics that have profound implications on the origin of these basaltic magmas although the mg suite lithologies are typified by silicates with relatively high mg early liquidus phases such as olivine are fairly low in ni co and cr relative to more iron rich olivines in the younger mare basalts the high y and ti y in early phases such as olivine and orthopyroxene indicate that the parental basaltic melts were high in incompatible elements and contained an ilmenite fractionation signature however the y in olivine from many of the troctolites and ultramafic lithologies are only slightly greater than that of the olivine in the mare basalts whereas olivine in the norites gabbronorites and apollo 14 troctolites are exceedingly high the kreep component may have been added to the mg suite parent magmas by assimilation or mixing into the mantle source the volume of kreep required to be added to the parental magmas of the mg suite tends to favor the latter mechanism for kreep incorporation the extremely high abundances of kreep in the norites and gabbronorites are a product of substantial crystallization 40 to 70 of kreep enriched mg suite parental magmas basaltic magmatism associated with kreep extended for over 1 5 billion years and appears to have changed over time the early stages of this style of lunar magmatism mg suite appear to represent melting of early lmo cumulates with low abundances of ni co cr and v later stages of kreep rich basaltic magmatism seemed to clearly involve melting of a variety of lmo cumulate assemblages with higher incompatible element enrichment it appears that the heat derived from the kreep component was instrumental in at least initiating melting of the lunar mantle over this period of time

carbon and oxygen isotopic variability in neogene paleosol carbonates constraints on the evolution of the c4 grasslands of the great plains usa abstract understanding the development of grassland ecosystems is critical for understanding the evolution of their associated vertebrate faunas we focus on the central and southern portions of the great plains which is the largest continuous grassland in north america and has a well documented mammalian fossil record modern biomass in this region is dominated by c4 grasses but paleontological evidence indicates the region was forested prior to the middle miocene implying the region was formerly dominated by c3 plants we examine long and short term variations in the abundance of c4 grasses and climatic conditions in the central and southern great plains using the stable carbon and oxygen isotope composition of paleosol carbonates from 28 sections of 11 lithostratigraphic units in the region the carbon isotope composition 13c of paleosol carbonate reflects the proportion of c3 and c4 plants that grew in an ancient soil the long term pattern of 13c values indicates that the percentage of c4 grasses in the great plains was moderate ca 20 throughout most of the miocene increased from 6 4 to 4 0 ma and reached modern levels by 2 5 ma based on the range in 13c values within sections and the mean 13c values for different carbonate morphologies that reflect different intervals of carbonate accumulation the abundance of c4 biomass did not vary substantially on short time scales the variability in c4 biomass on short time scales does not correlate with age of section latitude longitude or the mean percentage of c4 biomass the oxygen isotope composition 18o of soil carbonate is controlled by soil temperature and the 18o value of soil water great plains paleosol 18o values vary considerably in relation to time and latitude removing the variation due to latitude with least squares linear regression reveals a temporal pattern that is consistent with the global pattern of neogene climate change quantitative interpretation of the 18o record is difficult without independent control on temperature or the oxygen isotope composition of soil water both of which have probably varied with long term climate change comparisons of measured 18o values for each section with predicted values based on modern temperature data and estimated modern meteoric water 18o values suggest that 1 most miocene sections have 18o values consistent with warmer temperatures and more positively shifted soil water 18o values than today 2 three miocene sections in western nebraska probably had soil water compositions that were more negative than similar aged localities in the region and 3 the plio pleistocene sections have 18o values consistent with cooler temperatures and more negative soil water 18o values than today the paleosol 13c values do not correlate strongly with the pattern of climate change recorded by the 18o values suggesting that long term change in mean temperature is not the main control on the abundance of 13c biomass in the great plains we propose two testable hypotheses to account for our data and other published data that bear on the evolution of the great plains ecosystem

terrestrial evidence for a two stage mid paleocene biotic event abstract marine records of the paleocene indicate a series of hyperthermal events characterized by significant climatic and carbon cycle variability but there are few comparable continental records the mid paleocene biotic event mpbe is a recently described interval defined by a rapid negative carbon isotope excursion and major short term changes in marine ecosystems but it is as yet unclear whether the event was globally important here we present the first terrestrial paleoenvironmental record of the mpbe based on paleosols that document rapid and short lived increases in temperature and precipitation and resultant shifts in plant assemblages concomitant with substantial carbon isotope excursions the new record indicates that carbon cycle changes during the early late paleocene may have resulted in a two stage transient hyperthermal event that caused a significant perturbation to both the regional climate and terrestrial ecology of south america in addition to the major biotic event mpbe previously recognized in marine records overall this suggests that the mpbe may have been a global climate event with far reaching environmental impacts in both the marine and terrestrial realms

mg spinel lithology a new rock type on the lunar farside 1 high resolution compositional data from moon mineralogy mapper m3 for the moscoviense region on the lunar farside reveal three unusual but distinctive rock types along the inner basin ring these are designated oos since they are dominated by high concentrations of orthopyroxene olivine and mg rich spinel respectively the oos occur as small areas each a few kilometers in size that are widely separated within the highly feldspathic setting of the basin rim although the abundance of plagioclase is not well constrained within the oos the mafic mineral content is exceptionally high and two of the rock types could approach pyroxenite and harzburgite in composition the third is a new rock type identified on the moon that is dominated by mg rich spinel with no other mafic minerals detectable 5 pyroxene olivine all oos surfaces are old and undisturbed since basin formation they are effectively invisible in image data and are only recognized by their distinctive composition identified spectroscopically the origin of these unusual lithologies appears to be linked to one or more magmatic intrusions into the lower crust perhaps near the crust mantle interface processes such as fractional crystallization and gravity settling within such intrusions may provide a mechanism for concentrating the mafic components within zones several kilometers in dimension the oos are embedded within highly anorthositic material from the lunar crust they may thus be near contemporaneous with crustal products from the cooling magma ocean

effects of rapid global warming at the paleocene eocene boundary on neotropical vegetation temperatures in tropical regions are estimated to have increased by 3 to 5 c compared with late paleocene values during the paleocene eocene thermal maximum petm 56 3 million years ago event we investigated the tropical forest response to this rapid warming by evaluating the palynological record of three stratigraphic sections in eastern colombia and western venezuela we observed a rapid and distinct increase in plant diversity and origination rates with a set of new taxa mostly angiosperms added to the existing stock of low diversity paleocene flora there is no evidence for enhanced aridity in the northern neotropics the tropical rainforest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide in contrast to speculations that tropical ecosystems were severely compromised by heat stress

new insights into lunar petrology distribution and composition of prominent low ca pyroxene exposures as observed by the moon mineralogy mapper m3 1 lunar geochemical groups such as mg suite ferroan anorthosite and alkali suite rocks are difficult to distinguish from orbit because they are defined by both modal mineralogy and elemental composition of their constituent minerals while modal mineralogy can be modeled only specific minerals or elements can be directly detected at near infrared nir wavelengths pyroxenes are among the most spectrally distinctive minerals and their absorption bands are sensitive to structure and composition pyroxenes thus provide important clues to distinguish these geochemical groups and to understand lunar crustal evolution using moon mineralogy mapper data we search for lithologies dominated by strong low calcium pyroxene lcp signatures we compare the nir absorptions of 20 lcps to a suite of synthetic pyroxenes to determine which lunar pyroxenes appear magnesian enough to be candidate mg suite norites we detail three prominent regions of lcp 1 in south pole aitken basin spa 2 south of mare frigoris and 3 north of mare frigoris the absorption band positions suggest that the lcps north of mare frigoris and those in spa are compositionally similar to one another and of mg50 75 implying that the mafic material excavated by the spa impact was relatively iron rich modified gaussian modeling results suggest that the apollo basin may have tapped different composition material than is exposed in much of spa the lcps located in the highlands south of mare frigoris exhibit absorption bands at short wavelengths consistent with mg 80 the coincidence of these mg rich lcps with the thorium measured by lunar prospector make them good candidates for kreep related mg suite pyroxenes

the expansion of c4 grasses and global change in the late miocene stable isotope evidence from the americas j3c values in paleosols and fossil teeth have been used to document the expansion of c plants in south asia africa and north america during the late miocene however the exact timing and rate of expansion of c vegetation is unclear outside the old world because of a lack of high resolution records we present a high resolution record from northwest argentina in which the s13c values of soil carbonate rise above a threshold of 8 0 suggesting the presence of c plants starting at 7 3 6 7 ma sr3c values of fossil teeth from well dated sections in south and north america display a concomitant increase of c plants in the diets of large herbivores these results show that the late miocene expansion of c plants was global but occurred at different rates in each region while it is has been suggested that declining pc0 levels during the late neogene caused c plant expansion climate change such as an increase in summer dominated rainfall regimes globally is an alternative explanation the 6 0 soil carbonate records from south asia east africa and now also northwest argentina all show an increase of at least 3 4 in the late neogene either the result of climate change or of greater evaporation in average grassland soils

modern calibration of phytolith carbon isotope signatures for c3 c4 paleograssland reconstruction abstract the carbon isotope signature of fossil phytoliths silica bodies produced in abundance in the tissue of grasses presents a promising tool for reconstructing the biogeography of c3 and c4 grasses during the neogene previously applied isotopic techniques such as the carbon isotope signatures of soil carbonate herbivore tooth enamel and leaf waxes are limited in that they cannot distinguish between c3 grasses and c3 shrubs trees as a result these records do not provide any information on the relative dominance of c3 vs c4 grasses phytolith carbon isotope ratios on the other hand have the potential to provide a direct record of the photosynthetic pathway c3 or c4 of grasses specifically because this technique is still in its infancy several modern calibration issues remain and are examined here through the presentation of some new data and the synthesis of existing published data on the 13c values of phytoliths from modern grasses and soils first fresh phytoliths extracted directly from grasses exhibit depleted isotopic values relative to the source plant and phytoliths from c4 grasses are more depleted than phytoliths from c3 grasses this difference in depletion is most likely the result of lipids present within phytoliths which are also generally more depleted in c4 plants than c3 plants relative to whole plant values second phytolith assemblages from modern soils do not share the same degree of isotopic depletion or compression as fresh phytoliths this suggests that soil phytolith assemblage 13c is affected by pedogenic or taphonomic processes the weight of current evidence suggests that pedogenic alteration is less of a concern while selective preservation taphonomic bias may play an important role even so comparison of the 13c values of phytolith assemblages with 13c values of soil organic matter som from modern soils indicates that phytoliths can record the c3 c4 contribution to the soil it appears that phytoliths retain a longer term smoothed record in contrast to the more rapid turnover of som pools that can be influenced by even recent land use changes third the interpretation of fossil phytolith 13c in terms of proportion of c3 and c4 grasses requires isotopic end member values end members from fresh phytoliths cannot be used because they fail to capture the range of soil phytolith assemblage data comparison of soil phytolith 13c values with som 13c yields empirically derived end member values that take into account any taphonomic effects these end members c3 26 8 c4 15 3 capture the range of observed values for soil and paleosol phytolith 13c values spanning the last 650 000 years the modern calibration work presented here provides the necessary groundwork for applying this technique to paleoecological reconstructions of neogene grasslands

long quaternary record in eastern washington u s a interpreted from multiple buried paleosols in loess loess that is from a few meters to 75 m thick covers an area of more than 20 000 km2 on the columbia plateau in washington idaho and oregon the region of deepest loess is in eastern washington and is called the palouse the palouse is downwind of the channeled scabland through which massive outburst floods from glacial lake missoula flowed repeatedly during glacial stages of the pleistocene the deepest stratigraphic section yet studied is in a remnant of the once continuous loess cover that is surrounded by scabland channels a normal over reverse magnetic polarity zonation in this section supports an age of more than 790 000 yr but 15 35 m of loess may be present beneath this section so a total of 1 5 2 million yr is possible upward fining of texture in some layers in the loess at this site and stratigraphic evidence at nearby sites suggest that at least some pulses of loess deposition were triggered by episodes of cataclysmic floods nineteen or more individual paleosols can be recognized in 26 m of section based on field morphology physical and chemical properties and micromorphology the paleosols consist of calcic petrocalcic and duripan horizons many of which are associated with cambic horizons less strongly developed soils in this and other sections have been obscured by partial overlap of soil development in an episodically rising loess landscape paleosols in the loess at other sites reflect a dry to moist climatic gradient from west to east across the region during the pleistocene that was grossly similar to today s accumulation of pedogenic carbonates and silica dominates in a western zone where the present day mean annual precipitation is less than about 450 mm translocation of silicate clays and leaching of carbonates dominate in a central steppe zone where precipitation is between 450 and about 700 mm fragipans are common in an eastern zone along the steppe forest transition at present day precipitation of over 700 mm reconnaissance study suggests that these climatic pedogenic zones have been somewhat stable during many of the episodes of soil development preserved in the loess although some paleosols have different features from the majority of the paleosols in that zone e g paleosols with fragipans in a sequence of paleosols with argillic horizons which suggests that some episodes of soil development took place under different climatic conditions

a photometric function for analysis of lunar images in the visual and infrared based on moon mineralogy mapper observations 1 changes in observed photometric intensity on a planetary surface are caused by variations in local viewing geometry defined by the radiance incidence emission and solar phase angle coupled with a wavelength dependent surface phase function f which is specific for a given terrain in this paper we provide preliminary empirical models based on data acquired inflight which enable the correction of moon mineralogy mapper m3 spectral images to a standard geometry with the effects of viewing geometry removed over the solar phase angle range for which the m3 data were acquired our models are accurate to a few percent particularly where thermal emission is not significant our models are expected to improve as additional refinements to the calibrations occur including improvements to the flatfield calibration improved scattered and stray light corrections improved thermal model corrections and the computation of more accurate local incident and emission angles based on surface topography