volatiles in lunar felsite clasts impact related delivery of hydrous material to an ancient dry lunar crust abstract in this detailed geochemical petrological and microstructural study of felsite clast materials contained in apollo breccia samples 12013 14321 and 15405 little evidence was found for relatively enriched reservoirs of endogenic lunar volatiles nanosims measurements have revealed very low volatile abundances 2 18 ppm hydrogen in nominally anhydrous minerals nams plagioclase potassic alkali feldspar and sio2 that make up a majority of these felsic lithologies yet these mineral assemblages and clast geochemistries on earth would normally yield relatively high volatiles contents in their nams 20 to 80 ppm hydrogen this difference is particularly notable in felsite 14321 1062 that exhibits extremely low volatile abundances 2 ppm hydrogen and a relatively low amount of microstructural evidence for shock metamorphism given that it is a clast of the most evolved 74 wt sio2 rock type returned from the moon if taken at face value wet felsic magmas 1 2 1 7 wt water are implied by the relatively high hydrogen contents of feldspar in felsite clasts in apollo samples 12013 and 15405 but these results are likely misleading these felsic clasts have microstructural features indicative of significantly higher shock stress than 14321 1062 these crustal lithologies likely obtained no more water from the lunar interior than the magma body producing 14321 1062 rather we suggest hydrogen was enriched in samples 12013 and 15405 by impact induced exchange and or partial assimilation of volatiles added to the surface of the moon by a hydrated impactor asteroid or comet or the solar wind thus the best estimate for magmatic water contents of felsic lunar magmas comes from 14321 1062 that leads to a calculated magmatic water content of 0 2 wt this dry felsic magma has a slightly greater but comparable water content to the ancient mafic magmas implied by the other lithologies that we have studied based on this and expanding evidence for a significantly dry ancient or early degassed moon it is likely that some recent estimates 100 s ppm of the water abundances in the lunar parental magma ocean have been overestimated

distinguishing between water column and sedimentary denitrification in the santa barbara basin using the stable isotopes of nitrate 1 below its sill depth the santa barbara basin sbb is commonly suboxic o2 3 m with only brief periods of ventilation associated with development of suboxia the concentration of nitrate decreases with depth into the basin without an associated decrease in phosphate indicating that a substantial fraction of the nitrate supplied to the basin is removed by denitrification coincident with the decrease in nitrate concentration across the redoxcline the interface between oxic and suboxic waters within the sbb there is an increase in the 15n 14n of that nitrate as would be anticipated from the isotopic fractionation associated with denitrification however the increase in 15n 14n of nitrate is much smaller than occurs in the open eastern tropical north pacific etnp for a comparable amount of nitrate loss both the concentrations of n species within the basin and measurements of nitrate 18o 16o suggest that the lower than expected 15n enrichment in the suboxic sbb involves denitrification rather than being due to some unknown source of low 15n 14n n to the deep sbb calculations with a range of models of nitrate supply and consumption indicate that the degree of nitrate consumption in the basin is too small for differences in water circulation to explain the isotopic differences between the santa barbara basin and the open etnp previous studies indicate that the isotope effect of sedimentary denitrification is negligible due to nitrate diffusion in sediment pore waters thus we infer that the small magnitude of the isotopic enrichment of sbb water column nitrate is due to the importance of sedimentary denitrification within the basin assuming that water column and sedimentary denitrification have isotope effects of 25 and 1 5 per mil respectively our results suggest that sedimentary denitrification accounts for more than 75 of the nitrate loss within the suboxic sbb

patterns of deglacial warming in the pacific ocean a review with emphasis on the time interval of heinrich event 1 abstract based on a compilation of currently available records of past sea surface temperature sst variability estimated from a variety of different proxies the regional scale deglacial sst development in the pacific ocean is tentatively classified into four endmember types the subtropical and tropical pacific is characterized by a continuous deglacial warming without marked interruption during the time interval of heinrich event 1 h1 whereas the subarctic north pacific exhibits centennial scale warm cold oscillations during this time interval sst records from marginal seas of the pacific show a deglacial warming interrupted by a cooling event coeval with h1 followed by a marked bolling sst increase a single sst record from the southwestern subantarctic pacific displays a continuous deglacial warming across h1 followed by an antarctic cold reversal type cooling during the allerod thus in contrast to the deglacial sst development in the atlantic which has been inferred to be overwhelmingly driven by the redistribution of heat through changes in the meridional overturning circulation moc none of the open oceanic pacific sst records reviewed here displays any obvious and or dominant response to the reduction of the moc and or the reorganization of atmospheric circulation during h1 within the limits of absolute chronologies all tropical and subtropical pacific sst records show an onset of deglacial warming at 19 1 ka coeval with the onset of the deglacial rise in sea level

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

petrography relationships and petrogenesis of the gabbroic lithologies in northwest africa 773 clan members northwest africa 773 2727 3160 3170 7007 and 10656

more surprises from the moon volcanic deposits on the moon are almost entirely composed of basaltic lava flows that make up the dark and extensive mare plains high resolution images and compositional data now reveal rare non mare volcanism on the moon s farside

evidence for explosive silicic volcanism on the moon from the extended distribution of thorium near the compton belkovich volcanic complex we reconstruct the abundance of thorium near the compton belkovich volcanic complex on the moon using data from the lunar prospector gamma ray spectrometer we enhance the resolution via a pixon image reconstruction technique and find that the thorium is distributed over a larger 40km 75 km area than the 25km 35 km high albedo region normally associated with compton belkovich our reconstructions show that inside this region the thorium concentration is 14 26ppm we also find additional thorium spread up to 300km eastward of the complex at 2 ppm the thorium must have been deposited during the formation of the volcanic complex because subsequent lateral transport mechanisms such as small impacts are unable to move sufficient material the morphology of the feature is consistent with pyroclastic dispersal and we conclude that the present distribution of thorium was likely created by the explosive eruption of silicic magma

composition of orientale basin deposits and implications for the lunar basin forming process the orientale basin on the lunar western limb has served as the prototype lunar multiring basin for many years in order to constrain possible models of the formation and excavation of basin ejecta we have studied the composition of orientale basin deposits using both earth based spectral reflectance and apollo orbital geochemical data results indicate that orientale basin ejecta are dominantly anorthositic with compositions ranging from pure anorthosite to noritic anorthosite although minor quantities of mare basalt and low k fra mauro basalt are present ultramafic and kreep components appear to be absent portions of the inner rings of the basin may be composed of anorthosite whose shock levels exceed 20 gpa 200 kbar in conjunction with photogeologic evidence for the preservation of prebasin topography and structure within the cordillera basin ring we suggest that the diameter of the excavation crater of the orientale basin is on the order of 500 to 600 km effective depths of excavation are probably less than about half the local crustal thickness which in this region is on the order of 100 km we find that the orientale impact excavated dominantly upper crustal rocks with a depth of excavation consistent with a proportional growth basin forming model

thorium abundances on the aristarchus plateau insights into the composition of the aristarchus pyroclastic glass deposits 1 thorium th data from the lunar prospector gamma ray spectrometer lp grs are used to constrain the composition of lunar pyroclastic glass deposits on top of the aristarchus plateau our goal is to use forward modeling of lp grs th data to measure the th abundances on the plateau and then to determine if the elevated th abundances on the plateau are associated with the pyroclastic deposits or with thorium rich ejecta from aristarchus crater we use a variety of remote sensing data to show that there is a large homogenous portion of the pyroclastics on the plateau that has seen little or no contamination from the th rich ejecta of aristarchus crater our results show that the uncontaminated pyroclastic glasses on aristarchus plateau have an average th content of 6 7 ppm and 7 wt tio2 these th and ti values are consistent with th rich intermediate ti yellow glasses from the lunar sample suite on the basis of this information we use petrologic equations and interelement correlations for the moon to estimate the composition of the source region from which the aristarchus glasses were derived we find that the source region for the aristarchus glasses contained high abundances of heat producing elements which most likely served as a thermal driver for the prolonged volcanic activity in this region of the moon

oxygen minimum zone expansion in the eastern tropical north pacific during deglaciation concentrations lamination preservation and d 15 n values from cores located between 540 750 m water depth in the gulf of tehuantepec southern mexico these results differ from similar proxies found even 5 n of the site where there is evidence for omz changes related to rapid climate change in the northern hemisphere instead omz expansion in the gulf was contemporaneous with changes in sea ice extent and zonal wind shifts around antarctica pointing to subantarctic mode water and antarctic intermediate water as likely sources of oxygen depleted water these observations reinforce the importance of the southern ocean as a primary modulator of northern hemisphere ocean climate as far as 15 n in the etnp citation hendy i l and t f pedersen 2006 oxygen minimum zone expansion in the eastern tropical north pacific during deglaciation geophys res lett 33 l20602 doi 10 1029 2006gl025975

silica polymorphs in lunar granite implications for granite petrogenesis on the moon granitic lunar samples largely consist of granophyric intergrowths of silica and k feldspar the identification of the silica polymorph present in the granophyre can clarify the petrogenesis of the lunar granites the presence of tridymite or cristobalite would indicate rapid crystallization at high temperature quartz would indicate crystallization at low temperature or perhaps intrusive slow crystallization allowing for the orderly transformation from high temperature silica polymorphs tridymite or cristobalite we identify the silica polymorphs present in four granitic lunar samples from the apollo 12 regolith using laser raman spectroscopy typically lunar silica occurs with a hackle fracture pattern we did an initial density calculation on the hackle fracture pattern of quartz and determined that the volume of quartz and fracture space is consistent with a molar volume contraction from tridymite or cristobalite both of which are less dense than quartz moreover we analyzed the silica in the granitic fragments from apollo 12 by electron probe microanalysis and found it contains up to 0 7 wt tio2 consistent with initial formation as the high temperature silica polymorphs which have more open crystal structures that can more readily accommodate cations other than si the silica in apollo 12 granitic samples crystallized rapidly as tridymite or cristobalite consistent with extrusive volcanism the silica then inverted to quartz at a later time causing it to contract and fracture a hackle fracture pattern is common in silica occurring in extrusive lunar lithologies e g mare basalt the extrusive nature of these granitic samples makes them excellent candidates to be similar to the rocks that compose positive relief silicic features such as the gruithuisen domes

a compositional study of the aristarchus region of the moon using near infrared reflectance spectroscopy newly obtained near infrared reflectance spectra for features on or near the aristarchus plateau demonstrate the diversity of compositions in the region highland units are of three probable compositions a feldspar and clinopyroxene assemblage a probable clinopyroxene olivine and possibly feldspar assemblage and an assemblage composed of olivine or olivine and feldspar the feldspar clinopyroxene assemblage is tentatively correlated with the major th anomaly centered on aristarchus crater the regional pyroclastic deposits on the plateau are composed of greater than 90 fe2 bearing glass the aristarchus cratering event fully penetrated any mare or pyroclastics in the target evidence for mare related material is found in the ejecta on the mare side of the mare plateau contact

compton belkovich volcanic complex cbvc an ash flow caldera on the moon abstract volcanic calderas are found on earth mars venus and io and are rare but unique volcanic structures in the solar system compton belkovich volcanic complex cbvc 60 5 n 99 5 e on the far side of the moon is a unique non mare feature due to its evolved lithology regional tectonic setting its location being near the north pole far from the procellarum kreep terrane pkt and its recent association with endogenic water high resolution remote sensing observations of several structural features at cbvc such as ring faults radial faults fractures manifested by various morphological features such as domes of varied sizes and shapes and pyroclastic ash flows characterize it to be a volcanic caldera the loading of humboldtianum basin with basalts and subsequent development of extensional structures outside it along with high thorium anomaly and resulting silicic volcanism at cbvc producing central collapsed caldera could be considered as an analogy to silicic calderas on earth formed in extensional tectonic regime even though the tectonic processes involved in these two cases are entirely different the former being impact related whereas the latter involves rifting or hotspot related activities associated with extensional plate tectonics presence of high reflectance feature and its extension to the east southeast of the topographic expression and its relation with pyroclastic dispersal have been supported by radar based mini rf observations and high resolution lroc nac imagery it suggests the presence of a late stage fine pyroclastic layer within the cbvc region the diverse volcanic features that exist at the studied site indicate a series of deformation and eruption events associated with silicic magmatism and thus cbvc could be considered as an ash flow caldera on the moon here we present a detailed appraisal of various volcanic and structural features detected at cbvc through high resolution optical as well as radar observations based on the previous and present studies an evolutionary model of the area has been proposed and the petrological implications of silicic magmatic activity its manifestation evolution and association with endogenic water have been discussed

petrogenesis and chronology of lunar meteorite northwest africa 4472 a kreepy regolith breccia from the moon northwest africa nwa 4472 is a polymict lunar regolith meteorite the sample is kreep rich high concentrations of potassium rare earth elements and phosphorus and comprises a heterogeneous array of lithic and mineral fragments these clasts and mineral fragments were sourced from a range of lunar rock types including the lunar high magnesian suite the high alkali suite kreep basalts mare basalts and a variety of impact crater environments the kreep rich nature of nwa 4472 indicates that the sample was ejected from regolith on the nearside of the moon in the procellarum kreep terrane and we have used lunar prospector gamma ray remote sensing data to show that the meteorite is most similar to and most likely sourced from regoliths adjacent to the imbrium impact basin u pb and pb pb age dates of nwa 4472 phosphate phases reveal that the breccia has sampled pre nectarian 4 35 ga rocks related to early episodes of kreep driven magmatism some younger phosphate u pb and pb pb age dates are likely indicative of impact resetting events at 3 9 4 ga consistent with the suggested timing of basin formation on the moon our study also shows that nwa 4472 has sampled impact melts and glass with an alkali depleted incompatible trace element rich high sc low rb th ratios low k compositional signature not related to typical apollo high k kreep or that sampled by kreepy lunar meteorite sayh al uhaymir sau 169 this provides evidence that there are numerous sources of kreep rich protoliths on the moon

metasomatic products of the lunar magma ocean the role of kreep dissemination the origin of the incompatible element rich lunar component kreep is in the lunar magma ocean lmo the fractionated residual melt after crystallization of the lmo represents urkreep after warren and wasson 1979 the percentage of this residual melt is low enough to be within the realm of silicate liquid immiscibility sli this process has the ability to split the kreep signature into k and reep fractions which are manifest as lunar granite k and phosphate phases present in highland lithologies or as quartz ferrotroctolite in lunar soils reep we envisage this as a localized but significant process since only a small portion of urkreep undergoes sli norms of experimental and apollo 15 basaltic immiscible glasses suggest that thevreep fraction found in the lunar highlands has undergone post sli fractionation of at least fayalite this significantly reduces the density of the reep fraction and coupled with its low viscosity 10 15 poise it can percolate upward metasomatizing the lunar crust the higher viscosity of the granitic melt 30000 poise inhibits its mobility and it forms pods in the lower rust as required for vhk basalt petrogenesis with the identification of kreepy components the composition of urkreep can be calculated using experimental evidence the kreep components may be recombined to give the pre sli composition or liquid liquid kd s can be used to calculate a pre sli composition from lunar granite both calculated urkreep compositions are lower in mgo and al2o3 and higher in feo and p2o5 than reported low and high k kreep compositions the calculated ree abundances are higher and the ree profiles are slightly more lree enriched than the previously reported kreep compositions however the ree profile calculated using liquid liquid kd s is concave upwards compared to the lree enriched profile produced by recombining the kreep components pre sli whitlockite apatite fractionation occurred prior to immiscibility in order to generate the concave upwards profile the lree enriched profile represents the pre sli magma prior to phosphate fractionation the presence of superkreepy rock types can be accounted for by k and reep fraction assimilation and the compositions of olivine vitrophyres can now be modeled using analyzed lunar rock types without the inference of a mythical high mg component other more widespread kreepy rocks e g apollo 14 breccias apollo 15 kreep basalts lkfm basalts are produced by incorporation of the more widespread pre sli urkreep component the splitting of kreep into identifiable lithological components allows the petrogenesis and role of kreep in lunar evolution to be better understood

non mare silicic volcanism on the lunar farside at compton belkovich non basaltic volcanism is rare on the moon and has been found predominantly on the lunar nearside analysis of lunar reconnaissance orbiter camera images and spectral data reveal the presence of compositionally evolved non basaltic volcanism on the lunar farside

geochemistry petrology and cooling history of 14161 7373 a plutonic lunar sample with textural evidence of granitic fraction separation by silicate liquid immiscibility we report new findings related to sample 14161 7373 the first analyzed lunar intrusive rock to show textural evidence for the formation of granitic material by silicate liquid immiscibility sli and geochemical evidence for separation of that material at least on a small scale from mafic residua ion microprobe analyses of rare earth element ree concentrations in silicates record the compositional evolution of this late stage assemblage for a sample whose bulk assemblage that of whitlockite monzogabbro has ree concentrations at 5 6 kreep levels the silicates have only moderately high ree concentrations the calculated ree concentrations of melt in equilibrium with pigeonite after re integration of pigeonite host and augite lamellae is approximately 2 high k kreep the high bulk ree concentrations of the assemblage are the result of a high proportion of whitlockite probably an excess i e the assemblage is a whitlockite cumulate variations in silicate ree concentrations reflect the co crystallization of whitlockite which we interpret to have begun crystallizing prior to the onset of late stage immiscibility of the felsic melt fraction calculated cooling rates based on a quantitative model of pyroxene exsolution reveal a two stage thermal history which involved initial crystallization at a minimum depth of 700 800 m during which the primary augite and pigeonite grains unmixed to form the observed host lamella pairs unusual compositional profiles close to the host lamella interface are consistent with a second stage of mild reheating followed by rapid cooling at a depth of 30 m most likely in an ejecta blanket the shallow depth of origin indicated for 14161 7373 is consistent with other studies of evolved lunar intrusive rocks supporting the interpretation that lunar qmd and granite as found among the apollo samples are late stage differentiates of high level intrusions and are not related to differentiation of deep crustal kreep reservoirs

the lassell massif a silicic lunar volcano abstract lunar surface volcanic processes are dominated by mare producing basaltic extrusions however spectral anomalies landform morphology and granitic or rhyolitic components found in the apollo sample suites indicate limited occurrences of non mare geochemically evolved si enriched volcanic deposits recent thermal infrared spectroscopy high resolution imagery and topographic data from the lunar reconnaissance orbiter lro show that most of the historic red spots and other less well known locations on the moon are indeed silica rich relative to basalt here we present a geologic investigation of the lassell massif 14 65 s 350 96 e near the center of alphonsus a basin in mare nubium where high silica thermal emission signals correspond with morphological indications of viscous possibly also explosive extrusion and small scale low reflectance deposits occur in a variety of stratigraphic relationships multiple layers with stair step lobate forms suggest different eruption events or pulsing within a single eruption absolute model ages derived from crater size frequency distributions csfds indicate that the northern parts of the massif were emplaced at 4 ga before the surrounding mare however csfds also indicate the possibility of more recent resurfacing events the complex resurfacing history might be explained by either continuous resurfacing due to mass wasting and or the emplacement of pyroclastics relatively low reflectance deposits are visible at meter scale resolutions below detection limits for compositional analysis at multiple locations across the massif suggestive of pyroclastic activity a quenched flow surface or late stage mafic materials compositional evidence from 7 band uv vis spectral data at the kilometer scale and morphologic evidence for possible caldera collapse and or explosive venting support the interpretation of a complex volcanic history for the lassell massif

the isotopic record of lunar volcanism abstract the timing and extent of lunar volcanism was determined primarily by the internal thermal evolution of the moon a late heavy bombardment produced most of the observable lunar basins easily recognized stratigraphic markers and also may have influenced lunar volcanism most of the nearside basins seem to have been produced 3 8 4 0 ga ago during a period often referred to as the lunar cataclysm the pre cataclysm period was characterized by formation of the lunar crust plutonic rocks within the crust and pre mare volcanism isotopic analysis of breccia clasts pre dating the cataclysm has yielded an outline of this period the isotopic record of post cataclysm mare volcanism is clear but incomplete because samples from the youngest mare areas are lacking specifically the isotopic data show that some lunar anorthosites formed 4 45 ga ago consistent with early formation of an anorthositic lunar crust some mg suite norites troctolites and dunites also formed approximately contemporaneously with the oldest anorthosites but others are up to 200 300 ma younger more evolved rocks granites and quartz monzodiorites also formed between 4 4 and 4 0 ga ago the earliest known pre mare volcanism at 4 25 ga ago included aluminous mare like basalts and an olivine gabbronorite similar to apollo 12 basalts kreep basalt volcanism began at least 4 1 ga ago approximately contemporaneously with that of the ancient mare like basalts and continued during the cataclysm recorded instances of high ti mare basalt volcanism began during or immediately after the cataclysm low ti mare basalt volcanism is the most recent for which samples are available the isotopic data record an early primary lunar differentiation during which mare basalt sources formed probably by crystallization of cumulus minerals from a lunar magma ocean the isotopic record of post cataclysm basalts indicates a heterogeneous lunar mantle and can be explained by partial melting of cumulate sources but more complex petrogenesis also has been suggested more complex petrogenetic processes including assimilation and assimilation fractional crystallization afc seem to be required for pre mare volcanics the isotopic data contain a hint that petrogenesis of the oldest pre mare volcanics may be linked to formation of the so called procellarum basin possibly the oldest and largest lunar basin such a basin would provide a geologic context for the pre mare volcanics and its formation may have been a defining moment in lunar history

intermittent existence of a southern californian upwelling cell during submillennial climate change of the last 60 kyr 1 application of a high resolution multiproxy approach to a sedimentary section drilled at ocean drilling program site 1017 located under a highly active upwelling cell off point conception california provides clear evidence for surface ocean productivity shifts on submillennial timescales during the last 60 kyr the proxies include bulk sediment major and minor elements organic carbon and carbonate concentrations 15n and planktonic foraminiferal species assemblage and carbon isotope determinations the collective results demonstrate that marine productivity in this area was not simply linearly related to cold and warm cycles except during the millennial scale climate oscillations of marine isotope stage mis 3 during that interval the upwelling cell and resulting high productivity were active during warm interstadial events and were largely inactive during cool stadial events however the last glacial maximum was also relatively productive productivity increased dramatically during the bolling warm interval while the allerod and younger dryas were much less productive high coccolithophorid abundance commenced during the earliest holocene after 10 ka the complexity of the productivity response was probably related to interplay between local winds as well as california undercurrent strength

space weathering effects in diviner lunar radiometer multispectral infrared measurements of the lunar christiansen feature characteristics and mitigation multispectral infrared measurements by the diviner lunar radiometer experiment on the lunar renaissance orbiter enable the characterization of the position of the christiansen feature a thermal infrared spectral feature that laboratory work has shown is proportional to the bulk silica content of lunar surface materials diviner measurements show that the position of this feature is also influenced by the changes in optical and physical properties of the lunar surface with exposure to space the process known as space weathering large rayed craters and lunar swirls show corresponding christiansen feature anomalies the space weathering effect is likely due to differences in thermal gradients in the optical surface imposed by the space weathering control of albedo however inspected at high resolution locations with extreme compositions and christiansen feature wavelength positions silica rich and olivine rich areas do not have extreme albedos and fall off the albedo christiansen feature wavelength position trend occupied by most of the moon these areas demonstrate that the christiansen feature wavelength position contains compositional information and is not solely dictated by albedo an optical maturity parameter derived from near ir measurements is used to partly correct diviner data for space weathering influences

silicic lunar volcanism testing the crustal melting model lunar silicic rocks were first identified by granitic fragments found in samples brought to earth by the apollo missions followed by the discovery of silicic domes on the lunar surface through remote sensing although these silicic lithologies are thought to make up a small portion of the lunar crust their presence indicates that lunar crustal evolution is more complex than originally thought models currently used to describe the formation of silicic lithologies on the moon include in situ differentiation of a magma magma differentiation with silicate liquid immiscibility and partial melting of the crust this study focuses on testing a crustal melting model through partial melting experiments on compositions representing lithologies spatially associated with the silicic domes the experiments were guided by the results of modeling melting temperatures and residual melt compositions of possible protoliths for lunar silicic rocks using the thermodynamic modeling software rhyolite melts rhyolite melts simulations predict liquidus temperatures of 950 1040 c for lunar granites under anhydrous conditions which guided the temperature range for the experiments monzogabbro alkali gabbronorite and kreep basalt were identified as potential protoliths due to their ages locations on the moon i e located near observed silicic domes chemically evolved compositions and the results from rhyolite melts modeling partial melting experiments using mixtures of reagent grade oxide powders representing bulk rock compositions of these rock types were carried out at atmospheric pressure over the temperature range of 900 1100 c because all lunar granite samples and remotely sensed domes have an elevated abundance of th some of the mixtures were doped with th to observe its partitioning behavior run products show that at temperatures of 1050 and 1100 c melts of the three protoliths are not silicic in nature i e they have 63 wt sio2 by 1000 c melts of both monzogabbro and alkali gabbronorite approach the composition of granite but are also characterized by immiscible si rich and fe rich liquids furthermore th strongly partitions into the fe rich and not the si rich glass in all experimental runs our work provides important constraints on the mechanism of silicic melt formation on the moon the observed high th content of lunar granite is difficult to explain by silicate liquid immiscibility because through this process th is not fractionated into the si rich phase results of our experiments and modeling suggests that silicic lunar rocks could be produced from monzogabbro and alkali gabbronorite protoliths by partial melting at t 1000 c additionally we speculate that at higher pressures p 0 005 gpa the observed immiscibility in the partial melting experiments would be suppressed

thermal infrared emissivity of felsic rich to mafic rich analogues of hot planetary regoliths abstract inner solar system bodies with absent or extremely tenuous atmospheres such as mercury and several high eccentricity near earth objects neos are subject to a wide range of surface temperatures here we show how the thermal expansion induced by strong diurnal insolation variations affects the thermal infrared spectra of felsic rich to mafic rich regoliths 1400 700 cm 1 spectra of granular plagioclase pyroxene mixtures were measured in the laboratory at four temperatures between 425 k and 725 k simulating different daily surface temperatures within the solar system at the same time we describe for the first time how two minerals with different thermal expansion coefficients combined in the same granular sample appear in a non ambient i e non 298 k thermal infrared spectrum the spectra of plagioclase rich analogues appear to be dominated by felsic features regardless of the daily surface temperature and do not exhibit any of the short wavelength absorptions of pyroxenes when detectable on the other hand the 870 cm 1 pyroxene absorption which is not affected by thermal variations functions instead as a proxy for the solid solution composition i e the mg fe relative contents in contrast indications of the plagioclase solid solution occurring at ambient temperatures i e ca na relative contents disappear at temperatures over 525 k christiansen feature position and spectral contrast which show a clear dependency on composition even at high temperatures require an accurate reproduction of the shallow thermal gradient in order to be used as indices in general in order to decipher planetary hyperspectral data surface temperature acquisition seems to be a prerequisite as well as a comparison with analogue spectra obtained under realistic environmental conditions

nitrogen isotopic evidence for micronutrient control of fractional no3 utilization in the equatorial pacific during the u s jgofs eqpac program variations in nitrogen isotopic ratio d15n and their control by relative no3 drawdown were examined in detail near surface d15n data clearly conform to rayleigh isotopic fractionation during phytoplankton utilization of no with a fractionation factor of about 5 this isotopic signal both propagates into particulate nitrogen pools and is a persistent large scale characteristic of the system decreasing near surface no3 with distance from the equator strongly correlates with increasing d15n in euphotic zone particulate organic matter pom as well as sinking particles during both surveys 1 el nino and 2 non el nino cruises despite a doubling of no3 accompanying relaxation of el nino conditions d15n values in near surface pom and deeply sinking particles as a function of latitude were similar for the two periods since d15n varies with relative nutrient drawdown and not its concentration this parameter appears to not have varied significantly in both cases about 50 of upwelled no3 was consumed in the immediate vicinity of the equator as estimated from the d15n data the moored sediment trap time series provided a more highly resolved temporal view of the 15n dynamics of this system at the equator and to the south there is little temporal variation in d15n and hence in relative no3 utilization over the 1 yr duration of the program at 28 and 58 n there is a large 5 decrease in d15n during the transition to non el nino conditions in response to the northward movement of no3 rich waters which probably reflects the intensification of the north equatorial current overall no3 utilization at the equator remained between 40 and 60 over the observation period despite large hydrographic and dynamical changes this observation implies a tight control of relative no3 utilization consistent with iron fe limitation since fe is supplied in this region by upwelling relative no3 utilization is likely determined by the product of the ratio of fe to no3 in upwelled waters and the no3 fe utilization ratio given no change in the chemistry of source waters increases in upwelling as observed during the transition away from el nino will affect surface no3 new and export production but it will not affect relative no3 utilization in this light downcore d15n records in the equatorial pacific should reflect past changes in the limitation of no3 drawdown by fe perhaps through changes in equatorial undercurrent chemistry

the basalts of mare frigoris this paper discusses the methodology and results of a detailed investigation of mare frigoris using remote sensing data from clementine lunar prospector and lunar reconnaissance orbiter with the objective of mapping and characterizing the compositions and eruptive history of its volcanic units with the exception of two units in the west mare frigoris and lacus mortis are filled with basalts having low tio2 to very low tio2 low feo and high al2o3 abundances these compositions indicate that most of the basalts in frigoris are high al basalts a potentially undersampled yet important group in the lunar sample collection for its clues about the heterogeneity of the lunar mantle thorium abundances of most of the mare basalts in frigoris are also low although much of the mare surface appears elevated due to contamination from impact gardening with the surrounding high th imbrium ejecta there are however a few regional thorium anomalies that are coincident with cryptomare units in the east the two youngest mare basalt units and some of the scattered pyroclastic deposits and volcanic constructs in addition mare frigoris lies directly over the northern extent of the major conduit for a magma plumbing system that fed many of the basalts that filled oceanus procellarum as interpreted by andrews hanna et al 2014 using data from the gravity recovery and interior laboratory mission the relationship between this deep reaching magma conduit and the largest extent of high al basalts on the moon makes mare frigoris an intriguing location for further investigation of the lunar mantle

the lunar gruithuisen silicic extrusive domes topographic configuration morphology ages and internal structure abstract the gruithuisen domes situated on the western portion of the imbrium basin rim form three tall mountains nw gamma delta totaling 780 km3 in volume the shapes of the domes are significantly different from that of mare type domes elsewhere on the moon we use data from the lunar reconnaissance orbiter lro and kaguya missions lro lunar orbiter laser altimeter lunar reconnaissance orbiter camera diviner and the kaguya imager to characterize the domes and assess models for their origin the configuration of the domes steep slopes up to 18 20 and their specific remote sensing characteristics strong downturn in the uv and results from the m3 and diviner instruments suggest that the domes formed by eruptions of highly viscous lava the estimated surface volumes of the domes vary from 20 km3 nw dome to 290 km3 gamma dome to 470 km3 delta dome the domes occur on the portion of the imbrium basin rim that is overlain by ejecta from the post imbrium iridum crater in some areas relatively high albedo smooth volcanic plains are seen within the iridum ejecta near the gruithuisen domes and low albedo mare deposits surround and embay the domes and iridum crater dating of different units and features by crater counts indicates that impact melts from the iridum basin are 3 9 ga old the domes gamma and delta are 3 8 ga and the ages of the plains near the domes vary from 2 3 to 3 6 ga a fresh impact crater exposes the internal structure of the gamma dome the most prominent features on the wall of the crater are rough blocky layers that are typical of volcanic plains in the highlands and maria around the domes the layers are interleaved with fine grained materials of higher and lower albedo and the visible orientation of the layers changes over short a few hundred meters distances these characteristics of the internal structure of the dome are consistent with eruptions of high viscosity lava rough layers that alternated with possible explosive activity fine grained materials the spatial association of the gruithuisen domes with the highland lava plains resembles the situation in which bimodal volcanism occur on earth the terrestrial association can be due to either fractional crystallization in basaltic magma reservoirs or remelting of high silica crustal materials in the first case the evolved melts appear in later stages of volcanic activity and in the second case these melts are formed near the beginning of evolution of the magmatic systems the age estimates of the gruithuisen domes and the surrounding volcanic plains are more consistent with the crustal remelting scenario however remelting of primary anorthositic crust cannot readily produce the silica rich melts and requires the presence of pre existing granite like materials formation of the domes by fractional crystallization avoids this difficulty but requires explanation of the older age of the domes relative to the volcanic plains in the surroundings a third option is that the domes are unrelated genetically to the mare deposits

the global surface temperatures of the moon as measured by the diviner lunar radiometer experiment abstract the diviner lunar radiometer experiment onboard the lunar reconnaissance orbiter lro has been acquiring solar reflectance and mid infrared radiance measurements nearly continuously since july of 2009 diviner is providing the most comprehensive view of how regoliths on airless bodies store and exchange thermal energy with the space environment approximately a quarter trillion calibrated radiance measurements of the moon acquired over 5 5 years by diviner have been compiled into a 0 5 resolution global dataset with a 0 25 h local time resolution maps generated with this dataset provide a global perspective of the surface energy balance of the moon and reveal the complex and extreme nature of the lunar surface thermal environment our achievable map resolution both spatially and temporally will continue to improve with further data acquisition daytime maximum temperatures are sensitive to the albedo of the surface and are 387 397 k at the equator dropping to 95 k just before sunrise though anomalously warm areas characterized by high rock abundances can be 50 k warmer than the zonal average nighttime temperatures an asymmetry is observed between the morning and afternoon temperatures due to the thermal inertia of the lunar regolith with the dusk terminator 30 k warmer than the dawn terminator at the equator an increase in albedo with incidence angle is required to explain the observed decrease in temperatures with latitude at incidence angles exceeding 40 topography and surface roughness influence temperatures resulting in increasing scatter in temperatures and anisothermality between diviner channels nighttime temperatures are sensitive to the thermophysical properties of the regolith high thermal inertia ti materials such as large rocks remain warmer during the long lunar night and result in anomalously warm nighttime temperatures and anisothermality in the diviner channels anomalous maximum and minimum temperatures are highlighted by subtracting the zonal mean temperatures from maps terrains can be characterized as low or high reflectance and low or high ti low maximum temperatures result from high reflectance surfaces while low minimum temperatures from low ti material conversely high maximum temperatures result from dark surface and high minimum temperatures from high ti materials impact craters are found to modify regolith properties over large distances the thermal signature of tycho is asymmetric consistent with an oblique impact coming from the west some prominent crater rays are visible in the thermal data and require material with a higher thermal inertial than nominal regolith the influence of the formation of the orientale basin on the regolith properties is observable over a substantial portion of the western hemisphere despite its age 3 8 gyr and may have contributed to mixing of highland and mare material on the southwest margin of oceanus procellarum where the gradient in radiative properties at the mare highland contact is broad 200 km

liquid fractionation part iv scale models for liquid fractionation of calc alkaline magmas abstract liquid fractionation has been modeled experimentally using scale theory the results confirm that under conditions of constant viscosity a low density magma can ascend as a coherent laminar layer along the vertical walls the results also suggest however that if viscosity increases with differentiation the fractionated liquid forms small centimetreized plumes not only along inclined and irregular walls and along the bottom of magma chambers but even on vertical walls the formation of plumes enhances the accumulation of rhyolitic magma and may increase the efficiency of fractionation

the distribution and origin of lunar light plains around orientale basin abstract lunar light plains are relatively flat smooth to gently rolling deposits that occur in crater floors and other topographic lows in the lunar highlands with albedo values comparable to surrounding highland terrain once interpreted to be the product of highland volcanism apollo 16 samples from the light plains of the cayley formation led to the interpretation that most light plains form from the deposition of fluidized basin ejecta conflicting relative age estimates suggest that light plains are ejecta from the orientale and imbrium basins or from a larger number of impact events combined with possible volcanic eruptions here we examine the distribution variability and origin of light plains associated with the orientale basin using data from the lunar reconnaissance orbiter camera lroc we find that the distribution composition and age of the light plains to the north and northwest of the orientale basin are consistent with an origin with the formation of orientale in this case the orientale basin forming impact significantly altered the surface within four basin radii from the rim

widespread distribution of oh h 2 o on the lunar surface inferred from spectral data remote sensing data from lunar orbiters have revealed spectral features consistent with the presence of oh or h2o on the lunar surface analyses of data from the moon mineralogy mapper spectrometer onboard the chandryaan 1 spacecraft have suggested that oh h2o is recycled on diurnal timescales and persists only at high latitudes however the spatial distribution and temporal variability of the oh h2o as well as its source remain uncertain here we incorporate a physics based thermal correction into analysis of reflectance spectra from the moon mineralogy mapper and find that prominent absorption features consistent with oh h2o can be present at all latitudes local times and surface types examined this suggests the widespread presence of oh h2o on the lunar surface without significant diurnal migration we suggest that the spectra are consistent with the production of oh in space weathered materials by the solar wind implantation of h and formation of oh at crystal defect sites as opposed to h2o sourced from the lunar interior regardless of the specific composition or formation mechanism we conclude that oh h2o can be present on the moon under thermal conditions more wide ranging than previously recognized

hansteen mons an lroc geological perspective abstract mons hansteen is a relatively high albedo well known lunar red spot located on the southern margin of oceanus procellarum 2 3 s 50 2 w it is an arrowhead shaped 25 km on a side two layer mesa with a small cone shaped massif on its north edge formed by three morphologically and compositionally distinct geologic units these units were emplaced in three phases over nearly 200 million years the oldest 3 74 ga hilly dissected unit composed of high silica and low feo content materials formed a low steep sided mesa the materials of this unit erupted mainly from vents along northeast and northwest trending sets of fractures the pitted unit which comprises the upper tier mesa is composed of high silica and even lower feo content materials this material was erupted at 3 5 ga from numerous closely spaced vents i e pits formed along closely spaced northeast southwest trending sets of fractures at nearly the same time eruptions of lower silica and higher feo materials occurred on the north flank of mons hansteen at the intersection of two major fractures to produce the north massif unit the eruptions that created the north massif units also produced materials that thinly blanketed small areas of the hilly dissected and pitted units on the north flank of mons hansteen also at nearly the same time i e 3 5 ga basalt flows formed the surrounding mare each unit of mons hansteen appears to be mantled by locally derived ash which only modestly contaminated the other units the morphology of mons hansteen especially the pitted unit suggests a style of volcanism where only a relatively small amount of material is explosively erupted from numerous closely spaced vents

petrology and geochemistry of lunar granite 12032 366 19 and implications for lunar granite petrogenesis apollo 12 sample 12032 366 19 is a 21 3 mg granite fragment that is distinct from any other lunar granite or felsite it is composed of barian k feldspar quartz sodic plagioclase hedenbergite fayalite and ilmenite with trace amounts of zirconolite baddeleyite apatite and merrillite the texture of 12032 366 19 is largely a micrographic intergrowth predominantly of k feldspar and quartz and to a lesser extent plagioclase and quartz hedenbergite fayalite and ilmenite are present in minor but significant quantities 6 0 3 1 and 1 7 wt respectively and are scattered throughout the feldspar quartz intergrowths trace amounts of zr bearing phases are found including zirconolite 0 6 wt and baddeleyite 0 04 wt incompatible trace element concentrations are high in 12032 366 19 particularly the high field strength elements e g zr sm and th 1500 25 and 61 g g respectively the chondrite normalized rare earth element concentrations form a v pattern that is characteristic of other lunar granitic material by modeling 12032 366 19 as a derivative from a kreep like parent melt the composition and mineral assemblage can be obtained by extended fractional crystallization combined with separation of the low density minerals plus trapped melt components prior to final solidification however this model cannot quantitatively account for the relatively sodic composition of the plagioclase an 34 50 and requires that the starting melt has na 2 o of 1 2 1 4 wt which is higher than most kreep compositions formation of this assemblage by silicate liquid immiscibility is neither required nor indicated by petrogenetic modeling

mapping the feo and tio2 content of the lunar surface with multispectral imagery the derivation of quantitative elemental concentrations from multispectral imaging of the moon has long been a goal of lunar remote sensing concentration maps at the spatial resolutions available from the recent clementine mission would provide a revolutionary new tool for understanding the origin and evolution of the lunar crust lucey et al 1995 presented a method for extracting the concentration of fe from multispectral imaging of the moon this paper examines and quantifies important aspects ofthat technique left unexamined by lucey et al which had the potential to severely limit its utility these aspects include the effects of maturity grain size mineralogy shading due to topography and the presence of glass we also present a new algorithm for derivation of tio2 from multispectral imaging of both mare and highland units we find that both techniques are only weakly sensitive to maturity and that they have about 1 wt accuracy based on examination of the spectral properties and compositions of resolved lunar sampling stations presented by blewett et al 1997 we also discuss these findings in the context of two contrasting views of the effect of composition on lunar spectral properties presented by pieters and coworkers and hapke and coworkers we find the view of hapke and coworkers to be more consistent with our observations using a global mosaic of clementine multispectral data and these element derivation algorithms we find that the global modal abundance of feo is 4 5 wt 1 wt and the global modal abundance of tio2 is 0 45 wt 1 wt

crater size frequency distribution measurements and age of the compton belkovich volcanic complex abstract the compton belkovich volcanic complex cbvc is a 25 35 km feature on the lunar farside marked by elevated topography high albedo high thorium concentration and high silica content morphologies indicate that the complex is volcanic in origin and compositions indicate that it represents rare silicic volcanism on the moon constraining the timing of silicic volcanism at the complex is necessary to better understand the development of evolved magmas and when they were active on the lunar surface we employ image analysis and crater size frequency distribution csfd measurements on several locations within the complex and at surrounding impact craters hayn 87 km diameter and compton 160 km diameter to determine relative and absolute model ages of regional events using csfd measurements we establish a chronology dating regional resurfacing events and the earliest possible onset of cbvc volcanism at 3 8 ga the formation of compton crater at 3 6 ga likely resurfacing by volcanism at the cbvc at 3 5 ga and the formation of hayn crater at 1 ga for the cbvc we find the most consistent results are obtained using craters larger than 300 m in diameter the small crater population is affected by their approach to an equilibrium condition and by the physical properties of regolith at the cbvc

glacial interglacial dynamics of the eastern equatorial pacific cold tongue intertropical convergence zone system reconstructed from oxygen isotope records record mean late holocene lh last glacial maximum lgm d 18 o amplitudes ranging between 1 0 and 1 3 we estimate that mean sea surface temperatures sst in this region during the lgm were on average 1 5 0 5 c lower than the lh larger d 18 o amplitudes are observed in sites north of the equator indicating a spatial pattern of reduced meridional sst gradient across the equator during the lgm this result is supported by comparison of mg ca sst reconstructions from two sites straddling the equator we interpret the reduction of this gradient during the lgm as evidence for a less intense cold tongue intertropical convergence zone itcz frontal system a more southerly position of the itcz and weaker southeast equatorial trades in the eep indexterms 1620 global change climate dynamics 3309 3339 meteorology and atmospheric dynamics ocean atmosphere interactions 0312 4504 3344 meteorology and atmospheric dynamics paleoclimatology 4231 oceanography general equatorial oceanography 4267 oceanography general paleoceanography keywords cold tongue itcz oxygen isotopes tropical pacific

the distribution of mg spinel across the moon and constraints on crustal origin a robust assessment is made of the distribution and spatially resolved geologic context for the newly identified rock type on the moon a mg spinel bearing anorthosite pink spinel anorthosite psa essential criteria for confirmed detection of mg spinel using spectroscopic techniques are presented and these criteria are applied to recent data from the moon mineralogy mapper altogether 23 regions containing confirmed exposures of the new mg spinel rock type are identified all exposures are in highly feldspathic terrain and are small a few hundred meters but distinct and verifiable most resulting from multiple measurements each confirmed detection is classified according to geologic context along with other lithologies identified in the same locale confirmed locations include areas along the inner rings of four mascon basins knobs within central peaks of a few craters and dispersed exposures within the terraced walls of several large craters unexpected detections of mg spinel are also found at a few areas of hypothesized non mare volcanism the small mg spinel exposures are shown to be global in distribution but generally associated with areas of thin crust confirmation of mg spinel exposures as part of the inner ring of four mascon basins indicates this psa rock type is principally of lower crust origin and predates the basin forming era

the temperatures of giordano bruno crater observed by the diviner lunar radiometer experiment application of an effective field of view model for a point based data set abstract point based planetary datasets are typically stored as discrete records that represent an infinitesimal location on the target body instrumental effects and spacecraft motion during integration time can cause single points to inadequately represent the total area on the target that contributes to an observation production of mapped data products from these data for scientific analysis proceeds by binning points onto rectangular grids empty bins occur where data coverage is insufficient relative to grid resolution a common problem at high latitudes in cylindrical projections and remedial interpolation can lead to high uncertainty areas and artifacts in maps to address such issues and make better use of available data we present a method to calculate the ground projected effective field of view efov for point based datasets using knowledge of instrumental characteristics and observation geometry we apply this approach to data from the lunar reconnaissance orbiter lro diviner lunar radiometer experiment a visible to far infrared multispectral radiometer which acquires radiometric measurements of reflected visible and emitted infrared radiation of the moon in 9 spectral channels between 0 35 and 400 m analysis of gridded radiance from crater giordano bruno a 22 km diameter rayed crater is used to demonstrate our gridding procedure diviner data with such processing reveals details of the surface that are seen in the high resolution lro camera nac images brightness temperatures and anisothermality observed in diviner s ir channels show the thermophysical properties of the crater ejecta to be very heterogeneous indicative of minimal mechanical disruption by micrometeoroid impacts consistent with a very young

constraining the source regions of lunar meteorites using orbital geochemical data lunar meteorites provide important new samples of the moon remote from regions visited by the apollo and luna sample return missions petrologic and geochemical analysis of these meteorites combined with orbital remote sensing measurements have enabled additional discoveries about the composition and age of the lunar surface on a global scale however the interpretation of these samples is limited by the fact that we do not know the source region of any individual lunar meteorite here we investigate the link between meteorite and source region on the moon using the lunar prospector gamma ray spectrometer remote sensing data set for the elements fe ti and th the approach has been validated using apollo and luna bulk regolith samples and we have applied it to 48 meteorites excluding paired stones our approach is able broadly to differentiate the best compositional matches as potential regions of origin for the various classes of lunar meteorites basaltic and intermediate fe regolith breccia meteorites are found to have the best constrained potential launch sites with some impact breccias and pristine mare basalts also having reasonably well defined potential source regions launch areas for highland feldspathic meteorites are much less well constrained and the addition of another element such as mg will probably be required to identify potential source regions for these

the neotectonic setting of puerto rico the island of puerto rico in the northeast caribbean lies within a broad deformation zone between the caribbean and north american plates the simplest model for the tectonic setting of puerto rico has major strike slip movement on nearly east west lines in the vicinity of the puerto rico trench coupled to a small counterclockwise rotation of a puerto rico block within the broader plate boundary zone this simple model is attractive because it predicts the tectonic regime south of puerto rico and provides an explanation for a possible component of extension across the puerto rico trench west of 65 5 w gloria long range sidescan sonar data and seismic reflection profiles have been used to test this model by mapping the major tectonic features across the plate boundary north and south of puerto rico to the north the new data help to resolve between conflicting models of underthrusting or strike slip motion at the puerto rico trench no direct evidence of compression is seen although evidence for normal and strike slip movement is abundant this combined with regional considerations leads us to conclude that the main east west trending part of the puerto rico trench between 65 5 w and 68 w lies within a strike slip regime although oblique convergence occurs both to the east and west where the plate boundary trends east southeast to the south of puerto rico underthrusting of the caribbean plate beneath the island decreases from west to east and it is ultimately replaced by extension in the virgin islands basin east of 65 w

variations in tropical convection as an amplifier of global climate change at the millennial scale the global expression of millennial scale climatic change during the glacial period and the persistence of this signal in holocene records point to atmospheric teleconnections as the mechanism propagating rapid climate variations we suggest rearrangements in the tropical convection system globally affected the concentration and location of atmospheric water vapour and modulated terrestrial and marine emissions of ch4 and n2o providing a tropical mechanism of amplifying and perpetuating millennial scale climate changes a multi proxy reconstruction reflecting various aspects of the intensity of the arabian sea summer monsoon shows strong millennial scale variability over the past 90 kyr in which low intensity is associated with a southern shift of the intertropical convergence zone itcz and an eastward shift in the equatorial convergence zone the monsoon reconstruction which is based on new data from a somali margin sediment core is supported by previously reported tropical paleoclimatic records and suggests that global scale millennial climatic variability is in part driven by modulations in the tropical hydrological cycle and tropical emissions of the greenhouse gases ch4 and n2o

highly silicic compositions on the moon using data from the diviner lunar radiometer experiment we show that four regions of the moon previously described as red spots exhibit mid infrared spectra best explained by quartz silica rich glass or alkali feldspar these lithologies are consistent with evolved rocks similar to lunar granites in the apollo samples the spectral character of these spots is distinct from surrounding mare and highlands material and from regions composed of pure plagioclase feldspar the variety of landforms associated with the silicic spectral character suggests that both extrusive and intrusive silicic magmatism occurred on the moon basaltic underplating is the preferred mechanism for silicic magma generation leading to the formation of extrusive landforms this mechanism or silicate liquid immiscibility could lead to the formation of intrusive bodies

bulk mineralogy of lunar crater central peaks via thermal infrared spectra from the diviner lunar radiometer a study of the moon s crustal composition at depth 1 the central peaks of lunar impact craters are thought to be composed of uplifted material originating from varying depths of the crustal column the interpreted crystallization sequence of the early lunar magma ocean resulted in an anorthositic upper crust that may become progressively more mafic as it approaches the olivine rich mantle emissivity spectra from the lunar reconnaissance orbiter lro diviner radiometer are used to derive the wavelength location of the christiansen feature cf which is sensitive to bulk silicate mineralogy here a survey of cf values has been performed for the central peaks of 135 complex craters providing global and regional observations of the heterogeneity of crustal compositions crustal thickness models give context to the preimpact depth of the central peak material and its proximity to the crust mantle boundary this study has identified six craters with potentially ultramafic compositions within their central peaks more common occurrences of mafic material found in a wide variety of crater central peaks show a silicate composition roughly similar to mare basalt or an olivine bearing gabbro the range of central peak cf values is similar to that of the rest of the lunar surface bulk mineralogy of the central peak material does not appear to be correlated with its crustal depth of origin suggesting both lateral and vertical heterogeneity in crustal composition rather than a gradual transition from felsic to mafic composition it is likely that the moon s extensive cratering history has continually overturned the original crust erasing any original systematic dependence of composition on depth or proximity to the mantle

large scale silicate liquid immiscibility during differentiation of tholeiitic basalt to granite and the origin of the daly gap the dearth of intermediate magmatic compositions at the earth s surface referred to as the daly gap remains a major issue in igneous petrology the initially favored explanation invoking silicate liquid immiscibility during evolution of basalt to rhyolite has lost support because of the absence of any firm geological evidence for separation of fe and si rich liquids in igneous rocks this work presents a record of large scale magmatic differentiation due to immiscibility in the tholeiitic sept iles intrusion canada one of the largest layered plutonic bodies on earth gabbroic cumulate rocks from the critical zone of this intrusion show a bimodal distribution in density and p2o5 content despite identical major element chemistry of the principal magmatic phases immiscibility is supported by the presence of contrasting fe rich and si rich melt inclusions trapped in cumulus apatite phase diagrams and well documented occurrences of small scale immiscibility confirm that liquid liquid unmixing and the separation of fe rich and si rich liquids may contribute significantly to the daly gap along the tholeiitic liquid line of descent

virtis emissivity of alpha regio venus with implications for tessera composition abstract the composition of venus tessera terrain is unknown the visible and infrared thermal imaging spectrometer virtis aboard venus express vex collects data that yields the surface emissivity at 1 m which contains information convolving a number of surface properties including composition we examine the variation of emissivity in the vicinity of alpha regio which is the largest exposure of tessera terrain imaged by virtis we find that the emissivity of alpha regio tessera is lower than adjacent plains materials and the deposits and flows of eve corona both of which have previously been interpreted to be basaltic the emissivity of the bulk of alpha is also lower than its western boundary which is interpreted to comprise plains structurally deformed to the same degree as tessera terrain this suggests that the lower emissivity of alpha is independent of structural elements macroscale roughness or local sedimentation processes and is due to material properties like composition or grain size the deviation of the emissivity of alpha from that of the plains for which a bulk basaltic composition is well supported corresponds to a significant difference in rock type or surface mineral assemblage the 1 m emissivity of alpha is consistent with rocks with low ferrous iron content this includes felsic igneous rocks like granitoids that form under either water rich or water poor conditions a water rich origin would require both a hydrosphere and a plate recycling mechanism and thus be limited to the lifetime of surface water on venus alternatively granitoids could form via the differentiation of basaltic melts the production of all tessera terrain by this mechanism would require the accumulation and preservation of felsic melts from a volume of mafic magma that exceeds what is preserved in the currently observed plains both mechanisms of granitoid formation would require that tessera terrain be formed prior to the emplacement of the plains consistent with their stratigraphic position anorthosites also satisfy the emissivity signature and can form from copious amounts of partial melting of a mafic source low emissivity values are also consistent with carbonates sulfates phyllosilicates and their dehydration products which may have formed via weathering of basalts under conditions of higher atmospheric p h2o all of these hypotheses suggest the mineralogy of alpha tessera records an extinct era of venus history and is a key target for future exploration

the mairan domes silicic volcanic constructs on the moon 1 the mairan domes are four features located in northern oceanus procellarum at 312 3e 41 4n on the moon high resolution visible imagery visible to mid ir spectra and lunar prospector th abundance data all indicate that these four domes have a composition that is consistent with derivation from a si rich highly evolved magma

abundance and distribution of iron on the moon the abundance and distribution of iron on the moon is derived from a near global data set from clementine the determined iron content of the lunar highlands crust 3 percent iron by weight supports the hypothesis that much of the lunar crust was derived from a magma ocean the iron content of lower crustal material exposed by the south pole aitken impact basin on the lunar farside is higher 7 to 8 percent by weight and consistent with a basaltic composition this composition supports earlier evidence that the lunar crust becomes more mafic with depth the data also suggest that the bulk composition of the moon differs from that of the earth9s mantle this difference excludes models for lunar origin that require the earth and moon to have the same compositions such as fission and coaccretion and favors giant impact and capture

global assessment of pure crystalline plagioclase across the moon and implications for the evolution of the primary crust recent advancements in visible to near infrared orbital measurements of the lunar surface have allowed the character and extent of the primary anorthositic crust to be studied at unprecedented spatial and spectral resolutions here we assess the lunar primary anorthositic crust in global context using a spectral parameter tool for moon mineralogy mapper data to identify and map fe bearing crystalline plagioclase based on its diagnostic 1 25 m absorption band this allows plagioclase dominated rocks specifically anorthosites to be unambiguously identified as well as distinguished from lithologies with minor to trace amounts of mafic minerals low spatial resolution global mosaics and high spatial resolution individual data strips covering more than 650 targeted craters were analyzed to identify and map the mineralogy of spectrally pure regions as small as 400 m in size spectrally pure plagioclase is identified in approximately 450 targets located across the lunar surface diviner thermal infrared tir data are analyzed for 37 of these nearly monomineralic regions in order to understand the compositional variability of plagioclase an in these areas the average an for each spectrally pure region is estimated using new laboratory measurements of a well characterized anorthite an96 sample diviner tir results suggest that the plagioclase composition across the lunar highlands is relatively uniform high in calcium content and consistent with plagioclase compositions found in the ferroan anorthosites an94 98 our results confirm that spectrally pure anorthosite is widely distributed across the lunar surface and most exposures of the ancient anorthositic crust are concentrated in regions of thicker crust surrounding impact basins on the lunar nearside and farside in addition the scale of the impact basins and the global nature and distribution of pure plagioclase requires a coherent zone of anorthosite of similar composition in the lunar crust supporting its formation from a single differentiation event like a magma ocean our identifications of pure anorthosite combined with the grail crustal thickness model suggest that pure anorthosite is currently observed at a range of crustal thickness values between 9 and 63 km and that the primary anorthositic crust must have been at least 30 km thick

interhemispheric leakage of isotopically heavy nitrate in the eastern tropical pacific during the last glacial period denitrification zone while the nicaragua site is at the southern boundary the d 15 n record from nicaragua shows an antarctic timing similar to denitrification changes observed off peru chile but is radically different from the northern records we attribute this to the leakage of isotopically heavy nitrate from the south pacific oxygen minimum zone omz into the nicaragua basin the nicaragua record leads the other eastern tropical north pacific etnp records by about 1000 years because denitrification peaks in the eastern tropical south pacific etsp before denitrification starts to increase in the northern hemisphere omz i e during warming episodes in antarctica we find that the influence of the heavy nitrate leakage from the etsp is still noticeable although attenuated in the gulf of tehuantepec record particularly at the end of the heinrich events and tends to alter the recording of millennial timescale denitrification changes in the etnp this implies 1 that sedimentary d 15 n records from the southern parts of the etnp cannot be used straightforwardly as a proxy for local denitrification and 2 that denitrification history in the etnp like in the arabian sea is synchronous with greenland temperature changes these observations reinforce the conclusion that on millennial timescales during the last ice age denitrification in the etnp is strongly influenced by climatic variations that originated in the highlatitude north atlantic region while commensurate changes in southern ocean hydrography more directly and slightly earlier affected oxygen concentrations in the etsp furthermore the d 15 n records imply ongoing physical communication across the equator in the shallow subsurface continuously over the last 50 70 ka citation pichevin l e r s ganeshram s francavilla e arellano torres t f pedersen and l beaufort 2010 interhemispheric leakage of isotopically heavy nitrate in the eastern tropical pacific during the last glacial period paleoceanography 25 pa1204 doi 10 1029 2009pa001754

a model for the dynamics of crater centered intrusion application to lunar floor fractured craters lunar floor fractured craters are a class of craters modified by post impact mechanisms they are defined by distinctive shallow floors that are convex or plate like sometimes with a wide floor moat bordering the wall region radial concentric and polygonal floor fractures suggest an endogenous process of modification two mechanisms have been proposed to account for such deformations viscous relaxation and spreading of a magma intrusion at depth below the crater to test the second assumption and bring more constraints on the intrusion process we develop a model for the dynamics of magma spreading below an elastic overlying layer with a crater like topography as predicted in earlier more qualitative studies the increase in lithostatic pressure at the crater wall zone prevents the intrusion from spreading laterally leading to the thickening of the intrusion additionally our model shows that the final crater floor appearance after the uplift which can be convex or flat with or without a circular moat bordering the wall zone depends on the elastic thickness of the layer overlying the intrusion and on the crater size our model provides a simple formula to derive the elastic thickness of the overlying layer hence a minimum estimate for the intrusion depth finally our model suggests that crust redistribution by cratering must have controlled magma ascent below most of these craters

large fluctuations of dissolved oxygen in the indian and pacific oceans during dansgaard oeschger oscillations caused by variations of north atlantic deep water subduction a s and s h were supported by the paleoclimate program of the national science foundation as part of the paleovar project atm 0602395

thermal history of apollo 12 granite and kreep rich rock clues from pb pb ages of zircon in lunar breccia 12013 abstract with the mafic to ultramafic petrology of the moon the presence of granite appears anomalous however fragments of rocks with a definite granitic textures and mineralogy have been recovered from the maria where their ages point to an ultimate origin in the highlands apollo 12 mare breccia 12013 is one of these unique lunar rocks containing abundant granitic components it consists of a black portion composed mainly of fragments of plagioclase and noritic rock with minor fragments of granitic rock and a gray portion that is dominated by an overall granitic component zircon grains from this breccia were studied by combining cathodoluminescence cl imaging and micron scale ion microprobe dating techniques zircon grains from the black portion have a large age variation 4 0 4 3 ga a few of them exhibit complex age zoning within individual grains corresponding to cl zoning zircon grains from the gray portion show no cl zoning features but also have a large age variation between different grains 4 2 4 3 ga in this study we suggest that the large age variations of zircon in 12013 among different grains and within individual grains were caused by post crystallization impact events and most of them are not original crystallization ages the 4 3 ga zircon age probably represents the minimum crystallization age of the granitic component in 12013 similar to lunar granites from the apollo 14 and 17 landing sites this old crystallization age also implies that various ree patterns of lunar granites might not be entirely related to their crystallization ages based on comparison with the 207pb 206pb ages for zircon from the apollo 12 14 and 17 landing sites we suggest that there was at least one pre 3 9 ga major impact event on the moon at 4 2 ga

thermal infrared 2 5 13 5 μm spectroscopic remote sensing of igneous rock types on particulate planetary surfaces fundamental molecular vibration bands are significantly diminished by scattering thus such bands in spectra of fine particulate regoliths i e dominated by 5 m particles or regoliths displaying a similar scale of porosity are difficult to use for mineralogical or rock type identification consequently other spectral features have been sought that may be more useful in spectroscopic remote sensing of composition we find that mineralogical information is retained in overtones and combination tones of the fundamental molecular vibrations in the 3 0 to 7 0 m region but that relatively few minerals have a sufficiently distinctive band structure to be unambiguously identified with currently available techniques more significantly identification of general rock type as defined by the scfm chemical index scfm sio2 sio2 cao feo mgo is possible using spectral features associated with the principal christiansen frequency and with a region of relative transparency between the si o stretching and bending bands however environmental factors may affect the appearance and wavelengths of these features finally prominent absorption bands may result from the presence of relatively small amounts of water hydroxyl or carbonate because absorption bands exhibited by these materials in the 2 7 to 4 0 m region where silicate spectra are otherwise featureless increase strongly in spectral contrast with decreasing particle size such materials are thus detectable in very small amounts in a particulate regolith composed predominantly of silicate minerals

glacial holocene δ15n record from the gulf of tehuantepec mexico implications for denitrification in the eastern equatorial pacific and changes in atmospheric n2o 1 the intensity of denitrification in the gulf of tehuantepec along the mexican margin of the eastern tropical north pacific etnp was reconstructed for the last 23 000 years using the nitrogen isotopic composition of sediment organic matter 15norg in conjunction with other geochemical tracers of water column productivity during the last glacial period 15norg values ranged from 6 5 to 8 6 with values increasing between 23 and 17 ka deglaciation was marked by an abrupt increase in 15norg with maximum values 9 9 occurring during the bolling allerod period and the earliest holocene a decline in 15norg values occurred over the last 10 000 years with late holocene values being similar to those of the glacial period our data suggest that denitrification in this region was minimal during the last glacial and is consistent with the deposition of bioturbated sediments at the study site the intensity of denitrification increased dramatically during deglaciation and the early holocene signaling the presence of a strong oxygen minimum zone this period is also marked by the deposition of laminated sediments in the region the 15norg records display similar temporal trends to those seen in the greenland ice core record of atmospheric n2o concentrations at present denitrification within the eastern tropical pacific and arabian sea accounts for a major portion of the global marine loss of fixed nitrogen and a significant fraction of the ocean atmosphere n2o flux originates from these areas large changes in n2o emissions from these regions in the past would have directly impacted global greenhouse gas concentrations

gruithuisen domes region a candidate for an extended nonmare volcanism unit on the moon small lunar areas known as red spots are thought to represent good candidates for nonmare volcanic units predating or contemporaneous with the period of mare volcanism in this study we present imaging telescopic and orbital clementine multispectral surveys of the gruithuisen region located in the northwestern border of mare imbrium which contains imbrian age domical features of likely viscous volcanic origin with spectral characteristics of red spot areas a rather spectrally homogeneous unit having typical characteristics of red spots is found to coincide with the material within the morphological boundaries of the gruithuisen delta gamma and northwest domes an extended dome like unit is identified spectrally and surrounds and extends to the west and the north of the domes this unit shows spectral characteristics close to those of the domes suggesting the presence of a significant amount of dome material extending many kilometers away from the domes themselves both the spectral characteristics of the dome and the dome like unit are clearly different from those of highlands and the surrounding mare basalts the spectral identification of a widespread dome like unit suggests that the specific style of eruption that is inferred for the formation of the domes i e viscous flows of possible more silicic composition might have occurred on a regional scale in this part of the moon prior to the iridum event about 3 8 gyr ago this volcanic style appears to be more widespread in the early part of lunar history than previously thought

radiative transfer modeling of compositions of lunar pyroclastic deposits 1 while over 100 lunar pyroclastic deposits have been identified remotely their compositions remain poorly constrained in this work we determine the compositions of three lunar regional pyroclastic deposits which are likely to contain large amounts of glass and for which we have high quality ground based spectra the aristarchus plateau mare humorum and sulpicius gallus we use radiative transfer theory and employ measured optical constants of glasses to predict the bidirectional reflectance of a particulate glass surface as a function of fe and ti concentration particle size and maturity in order to find the best spectral match to the remotely observed deposits tools are not available to model the optical effects of the unusual geometries of the ilmenite laths in the black beads so we address their effects on spectra of the regional pyroclastic deposits using computational mixing we find that model spectra of pure glass as opposed to devitrified black beads provide good matches to all three regions radiative transfer modeling predicts iron contents of 21 20 and 17 wt feo for aristarchus humorum and sulpicius gallus respectively and suggests that all three regions are low in titanium a result supported by lunar prospector neutron spectrometer data however we find that a moderate ti glass mixed with a small fraction of black beads cannot be ruled out for the sulpicius gallus region

lro observations of morphology and surface roughness of volcanic cones and lobate lava flows in the marius hills 1 the volcanic domes cones sinuous rilles and pyroclastic deposits of the marius hills region of the moon 13 4 n 304 6 e represent a significant episode of magmatic activity at or near the lunar surface that is still poorly understood comparisons between lroc nac block populations mini rf data and diviner derived rock abundances confirm that blocky lava flows comprise the domes of the marius hills 8 m features measured by diviner indicate that the domes are not rich in silica and are not significantly different than surrounding mare materials lroc observations indicate that some of the dome building lava flows originated directly from volcanic cones many of the cones are c shaped while others are irregularly shaped and local topography and lava eruptions affect cone shape in general the cones are morphologically similar to terrestrial cinder and lava cones and are composed of varying amounts of cinder spatter and lava many of the cones are found in local groupings or alignments the wide range of volcanic features from broad low domes to steep cones represents a range of variable eruption conditions complex morphologies and variable layering show that eruption conditions were variable over the plateau

isotopic constraints on glacial interglacial changes in the oceanic nitrogen budget early deglacial maximum in nitrate 15 n 14 n in suboxic zones and no significant glacialto late holocene change in global ocean nitrate 15 n 14 n consistent with the work of brandes and devol 2002 we find that the steady state 15 n 14 n of oceanic nitrate is controlled primarily by the fraction of total denitrification that occurs in the water column therefore a deglacial peak in the ratio of water column to sediment denitrification caused by either a strong feedback between water column denitrification and the n reservoir or by an increase in sediment denitrification due to sea level rise can explain the observed deglacial 15 n 14 n maximum in sediments underlying water column denitrification zones the total denitrification rate and the mean ocean nitrate concentration are also important determinants of steady state nitrate 15 n 14 n for this reason modeling a realistic deglacial 15 n 14 n maximum further requires that the combined negative feedbacks from n2 fixation and denitrification are relatively strong and n losses are relatively small our results suggest that the glacial oceanic n inventory was at most 30 greater than today s and probably less than 10 greater index terms 4267 oceanography general paleoceanography 4805 oceanography biological and chemical biogeochemical cycles 1615 4845 oceanography biological and chemical nutrients and nutrient cycling 4870 oceanography biological and chemical stable isotopes keywords feedback nitrogen isotopes paleoceanography

thorium abundances on the lunar surface measurements of absolute thorium abundances on the lunar surface are presented using both the high and low altitude data taken with the lunar prospector gamma ray spectrometer an analysis of the uncertainties shows that the measured uncertainties are 7 g g are likely small area regions 150 km 2 using lunar topographic data we have shown that the thorium abundances in the lunar high lands and portions of south pole aitken spa basin are larger for lower elevations we have also studied a number of regions with anomalously high thorium abundances such as the northwestern region of spa basin the crater arago in western tranquillitatis and the compton belkovich region in the northeastern highlands the compton belkovich region appears to be enriched with evolved rocks such as alkali anorthosite and currently represents the only such extended region on the moon that has been identified in contrast tycho crater has very low thorium abundances which suggests that kreep was not assimilated at depth in this portion of the moon

southern ocean control on the extent of denitrification in the southeast pacific over the last 70 ka abstract temporal changes in oceanic denitrification the bacterial reduction of nitrate under suboxic conditions highlight the potential importance of n inventory changes and the production of n 2 o on the climate system at the same time the cause of the globally observed variation in denitrification remains unclear high resolution benthic foraminiferal oxygen isotope and bulk sediment nitrogen isotope records from odp site 1234 on the chile margin record integrated denitrification changes within the peru chile upwelling system over the last 70 ka denitrification changes in the southeast pacific are coherent with antarctic climate changes recorded by the byrd ice core 18 o record and lead northern hemisphere climate events the southern hemisphere character of the chile margin 15 n record suggests that episodes of reduced denitrification in the se pacific represent times when more oxygen was supplied as the result of changes in the ventilation and preformed nutrient content of subantarctic mode water samw which forms in the subantarctic zone of the southern ocean and feeds into the low latitude thermocline

the relationship between radar scattering and surface roughness of lunar volcanic features lunar roughness measurements derived from the lunar orbiter laser altimeter are compared to 12 6 cm wavelength radar data collected by the miniature radio frequency instrument and 70 cm wavelength radar data collected by the arecibo observatory these data are compared to assess how surface and subsurface roughness are correlated and affected by parameters including age and composition at length scales between 0 1 and 100 m a range of features are analyzed including volcanic domes marius hills rumker hills gruithuisen and mairan domes mare imbrium serenitatis and oceanus procellarum pyroclastic dark mantle deposits sinus aestuum sulpicius gallus and mare vaporum and two young craters copernicus and tycho statistically significant positive correlations exist between topographic roughness and both p and s band circular polarization ratios the strongest correlation is observed at the longest length scales correlations weaken as length scales become less similar potentially due to distinct processes controlling surface modification roughness is not significantly correlated with local slope although the marius hills are compositionally distinct from the gruithuisen and mairan domes they are indistinguishable in roughness characteristics conversely the rumker hills mare and dark mantle deposits are smoother at the length scales examined possibly due to fine grained mantling of regolith or pyroclastic deposits the floor and ejecta of tycho are the roughest surfaces measured in this study while the floor and ejecta of copernicus overlap the roughness distribution of the volcanic features this study shows that many factors control the evolution of roughness over time on various length scales

constraints on olivine rich rock types on the moon as observed by diviner and m3 implications for the formation of the lunar crust we place upper limits on lunar olivine abundance using midinfrared 5 25 m data from the lunar reconnaissance orbiter diviner lunar radiometer experiment diviner along with effective emissivity spectra of mineral mixtures in a simulated lunar environment olivine bearing pyroxene poor lithologies have been identified on the lunar surface with visible near infrared vnir observations since the kaguya spectral profiler sp vnir survey of olivine rich regions is the most complete to date we focus this work on exposures identified by that study we first confirmed the locations with vnir data from the moon mineralogy mapper m3 instrument we then developed a diviner olivine index from our laboratory data which along with m3and lunar reconnaissance orbiter camera wide angle camera data was used to select the geographic area over which diviner emissivity data were extracted we calculate upper limits on olivine abundance for these areas using laboratory emissivity spectra of anorthite forsterite mixtures acquired under lunar like conditions we find that these exposures have widely varying olivine content in addition after applying an albedo based space weathering correction to the diviner data we find that none of the areas are unambiguously consistent with concentrations of forsterite exceeding 90 wt in contrast to the higher abundance estimates derived from vnir data 2016 american geophysical union

late quaternary variability of sedimentary nitrogen isotopes in the eastern south pacific ocean 1 we present high resolution bulk sedimentary 15n data from the southern edge of the present day oxygen minimum zone of the eastern south pacific the record is interpreted as representing changes in water column nitrogen removal during the last 70 000 years we found significant fluctuations in the isotopic signal that suggest major reorganizations of the oxygen minimum zone at millennial timescales these fluctuations were not related to other millennial scale changes like the northern hemisphere s dansgaard oeschger climate swings or local changes in primary productivity so appear to be dictated by the southern hemisphere s climate rhythm this is preliminarily corroborated by an overall agreement between our 15n data and the sedimentary proxy of ice sheet dynamics in patagonia which is in turn correlated with surface water properties at the midlatitude subduction region of the eastern south pacific intermediate waters finally potential implications on late quaternary changes in atmospheric co2 concentrations are discussed

climatically related millennial scale fluctuations in strength of california margin oxygen minimum zone during the past 60 k y a strong oxygen minimum zone omz currently exists along the california margin because of a combination of high surface water productivity and poor intermediate water ventilation however the strength of this omz may have been sensitive to late quaternary ocean circulation and productivity changes along the margin although sediment lamination strength has been used to trace ocean oxygenation changes in the past oxygen levels on the open margin are not sufficiently low for laminations to form in these regions benthic foraminifera are highly sensitive monitors of omz strength and their fossil assemblages can be used to reconstruct past fluctuations benthic foraminiferal assemblages from ocean drilling program site 1017 off point conception exhibit major and rapid faunal oscillations in response to late quaternary millennial scale climate change dansgaard oeschger cycles on the open central california margin these faunal oscillations can be correlated to and are apparently synchronous with those reported from santa barbara basin together they represent major fluctuations in the strength of the omz which were intimately associated with global climate change weakening perhaps disappearing during cool periods and strengthening during warm periods these rapid major omz strength fluctuations were apparently widespread on the northeast pacific margin and must have influenced the evolution of margin biota and altered biogeochemicalmore cycles with potential feedbacks to global climate change less

nitrogen isotope and productivity variations along the northeast pacific margin over the last 120 kyr surface and subsurface paleoceanography 1 glacial interglacial changes in sedimentary 15n over the last 120 kyr display a remarkably similar pattern in timing and amplitude in core records extending from the denitrification zone in the eastern tropical north pacific etnp where subsurface denitrification is active to the oregon margin where no denitrification occurs today low 15n values 4 6 generally characterize glacial stages 2 and 4 and higher 15n values 7 10 are representative of the holocene millennial scale periods within stage 3 and stage 5 the inferred synchroneity of 15n variations along the entire margin implies that the nitrate isotopic signal produced in the oxygen poor subsurface waters in the etnp is rapidly advected northward and recorded at sites far beyond the boundaries of the modern denitrification zone similar to 15n primary production indicators percent corg ba al and percent opal show glacial interglacial as well as millennial scale variations along the ne pacific margin with higher primary production during warm periods however the relative phasing between 15n and paleoproduction tracers within individual records changes latitudinally whereas 15n and primary production vary approximately synchronously in the midlatitudes production lags 15n in the etnp by several kiloyears this lag calls for a new understanding of the processes driving denitrification in the etnp we suggest that oxygen input by the equatorial undercurrent as well as local organic matter flux controls denitrification rates in the etnp moreover the differences in relative timing point to a time transgressive development of upwelling favorable winds along the ne pacific margin after the last glaciation with those in the north developing several kiloyears earlier

complex explosive volcanic activity on the moon within oppenheimer crater abstract oppenheimer crater is a floor fractured crater located within the south pole aitken basin on the moon and exhibits more than a dozen localized pyroclastic deposits associated with the fractures localized pyroclastic volcanism on the moon is thought to form as a result of intermittently explosive vulcanian eruptions under low effusion rates in contrast to the higher effusion rate hawaiian style fire fountaining inferred to form larger regional deposits we use lunar reconnaissance orbiter camera images and diviner radiometer mid infrared data chandrayaan 1 orbiter moon mineralogy mapper near infrared spectra and clementine orbiter ultraviolet visible camera images to test the hypothesis that the pyroclastic deposits in oppenheimer crater were emplaced via vulcanian activity by constraining their composition and mineralogy mineralogically we find that the deposits are variable mixtures of orthopyroxene and minor clinopyroxene sourced from the crater floor juvenile clinopyroxene and juvenile iron rich glass and that the mineralogy of the pyroclastics varies both across the oppenheimer deposits as a whole and within individual deposits we observe similar variability in the inferred iron content of pyroclastic glasses and note in particular that the northwest deposit associated with oppenheimer u crater contains the most iron rich volcanic glass thus far identified on the moon which could be a useful future resource we propose that this variability in mineralogy indicates variability in eruption style and that it cannot be explained by a simple vulcanian eruption a vulcanian eruption should cause significant country rock to be incorporated into the pyroclastic deposit however large areas within many of the deposits exhibit spectra consistent with high abundances of juvenile phases and very little floor material thus we propose that at least the most recent portion of these deposits must have erupted via a strombolian or more continuous fire fountaining eruption and in some cases may have included an effusive component these results suggest that localized lunar pyroclastic deposits may have a more complex origin and mode of emplacement than previously thought

global silicate mineralogy of the moon from the diviner lunar radiometer we obtained direct global measurements of the lunar surface using multispectral thermal emission mapping with the lunar reconnaissance orbiter diviner lunar radiometer experiment most lunar terrains have spectral signatures that are consistent with known lunar anorthosite and basalt compositions however the data have also revealed the presence of highly evolved silica rich lunar soils in kilometer scale and larger exposures expanded the compositional range of the anorthosites that dominate the lunar crust and shown that pristine lunar mantle is not exposed at the lunar surface at the kilometer scale together these observations provide compelling evidence that the moon is a complex body that has experienced a diverse set of igneous processes

thermal infrared emissivity measurements under a simulated lunar environment application to the diviner lunar radiometer experiment 1 we present new laboratory thermal infrared emissivity spectra of the major silicate minerals identified on the moon measured under lunar environmental conditions and evaluate their application to lunar remote sensing data sets thermal infrared spectral changes between ambient and lunar environmental conditions are characterized for the first time over the 400 1700 cm 1 6 25 m spectral range for a fine particulate mineral suite including plagioclase albite and anorthite pyroxene enstatite and augite and olivine forsterite the lunar environment introduces observable effects in thermal infrared emissivity spectra of fine particulate minerals which include 1 a shift in the christiansen feature cf position to higher wave numbers shorter wavelengths 2 an increase in the overall spectral contrast and 3 decreases in the spectral contrast of the reststrahlen bands and transparency features our new measurements demonstrate the high sensitivity of thermal infrared emissivity spectra to environmental conditions under which they are measured and provide important constraints for interpreting new thermal infrared data sets of the moon including the diviner lunar radiometer experiment onboard nasa s lunar reconnaissance orbiter full resolution laboratory mineral spectra convolved to diviner s three spectral channels show that spectral shape cf position and band ratios can be used to distinguish between individual mineral groups and lunar lithologies the integration of the thermal infrared cf position with near infrared spectral parameters allows for robust mineralogical identifications and provides a framework for future integrations of data sets across two different wavelength regimes

the lunar reconnaissance orbiter mission six years of science and exploration at the moon abstract since entering lunar orbit on june 23 2009 the lunar reconnaissance orbiter lro has made comprehensive measurements of the moon and its environment the seven lro instruments use a variety of primarily remote sensing techniques to obtain a unique set of observations these measurements provide new information regarding the physical properties of the lunar surface the lunar environment and the location of volatiles and other resources scientific interpretation of these observations improves our understanding of the geologic history of the moon its current state and what its history can tell us about the evolution of the solar system scientific results from lro observations overturned existing paradigms and deepened our appreciation of the complex nature of our nearest neighbor this paper summarizes the capabilities measurements and some of the science and exploration results of the first six years of the lro mission

geology and scientific significance of the rumker region in northern oceanus procellarum china s chang e 5 landing region the rumker region 41 45 n 49 69 w is located in northern oceanus procellarum of the moon mons rumker is the most distinctive geological feature in the area the region is characterized by prolonged lunar volcanism late imbrian period to eratosthenian period forming multiple geologic units in the area including very low ti to low ti mare basalts high ti mare basalts and volcanic complexes each geologic unit has distinct element composition and mineral assemblages the rumker region overlying the procellarum kreep terrain was selected as the landing region for china s chang e 5 lunar sample return mission prelanding analyses of the geologic context and scientific potential are reported in this contribution we conducted detailed geological mapping using image spectral and altimetry data fourteen geological units were defined a geologic map was constructed and the geologic history was outlined the western mare units im1 im2 and im3 are imbrian aged 3 4 3 5 ga representing the major stage of lunar mare eruptive volcanism the eastern young mare units em3 and em4 2 ga are among the youngest mare basalts on the moon they have never been explored in situ or studied in the laboratory we suggest that samples returned from the eastern mare unit em4 could answer many fundamental questions and that this unit should be listed as the top priority landing site for chang e 5 sample return mission

origin of the anomalously rocky appearance of tsiolkovskiy crater abstract rock abundance maps derived from the diviner lunar radiometer instrument on the lunar reconnaissance orbiter lro show tsiolkovskiy crater to have high surface rock abundance and relatively low regolith thickness the location of the enhanced rock abundance to the southeast of the crater is consistent with a massive well preserved impact melt deposit apparent in lro miniature radio frequency instrument circular polarization ratio data a new model crater age using lro lunar reconnaissance orbiter camera imagery suggests that while it originated in the late imbrian tsiolkovskiy may be the youngest lunar crater of its size 180 km diameter together these data show that tsiolkovskiy has a unique surface rock population and regolith properties for a crater of its size and age explanation of these observations requires mechanisms that produce more large blocks preserve boulders and large blocks from degradation to regolith and or uncover buried rocks these processes have important implications for formation of regolith on the moon

nonmare volcanism on the moon photometric evidence for the presence of evolved silicic materials abstract images and photometric data from the lunar reconnaissance orbiter camera lroc narrow angle cameras nacs are used to investigate regions of the moon inferred from previous remote sensing compositional studies to be associated with nonmare silicic volcanics specifically lroc nac imagery with photometry normalized to account for local slopes using nac digital terrain models dtms was used to investigate the exposed areas associated with the compton belkovich volcanic complex cbvc hansteen alpha volcanic complex havc lassell massif lm gruithuisen domes gd and ejecta of aristarchus crater ac photometric studies of spacecraft landing sites for which ground truth compositional data exist allow us to study the relationship between photometric properties of soils and their mineralogical and chemical compositions the silicic regions have high reflectance and single scattering albedos that are consistent with different proportions of highly reflective minerals including alkali feldspar and quartz and low concentrations of mafic minerals of the silicic sites studied the cbvc has the highest reflectance values and single scattering albedos silicic pyroclastic deposits may also occur at the cbvc and we present evidence from laboratory spectra that an addition of up to 20 wt glassy silicic materials to a highlands type regolith simulant can account for the increased reflectance of these volcanic regions reflectance variations across and within the sites can be explained by mixing of felsic mineral components evolved to intermediate silicic compositions and or silicic pyroclastic deposits

thorite in an apollo 12 granite fragment and age determination using the electron microprobe abstract we present the first quantitative compositional analysis of thorite in a lunar sample the sample a granitic assemblage also contains monazite and yttrobetafite grains all with concentrations of u th and pb sufficiently high to determine reliably with the electron microprobe the assemblage represents the first documented occurrence of these three minerals together and only the second reported occurrence of thorite in a lunar rock sample 12023 147 10 is a small monomict rock fragment recovered from an apollo 12 regolith sample it comprises graphic intergrowths of k feldspar and quartz and plagioclase and quartz along with minor or accessory hedenbergite fayalite ilmenite zircon yttrobetafite thorite monazite and fe metal thorite ideally thsio4 occurs in the assemblage adjacent to quartz and plagioclase and includes a 12 xenotime y hree po4 component from quantitative electron probe microanalysis epma of th u and pb in thorite assuming that all of the measured pb is radiogenic we calculate an age of 3 87 0 03 ga yttrobetafite and monazite which contain lesser concentrations of u th and pb than the thorite yield ages of 3 78 0 06 ga and 3 9 0 3 ga respectively these dates are consistent with formation of the granitic material around 3 8 3 9 ga possibly associated with or after the formation of the imbrium basin this age falls within a group of younger ages for granitic samples measured mainly by ion microprobe analysis of zircon compared to a suite of older ages ca 4 20 4 32 ga also from zircons meyer et al 1996 a 3 8 3 9 ga age may reflect an origin following the imbrium event whereby granitic melt formed as a result of heating and melting and was mobilized and emplaced along an imbrium related ring fracture system silicic volcanic or exposed intrusive materials occur in several circum imbrium locations such as the mairan and gruithuisen domes and in ejecta excavated by aristarchus crater perhaps sample 12023 147 10 and some of the other granitic materials sampled at the apollo 12 site represent rocks similar to the rocks that make up these large silicic rock occurrences

climatically linked oscillations in arabian sea denitrification over the past 1 m y implications for the marine n cycle water column and core top 15n data show that arabian sea denitrification produces large nitrogen isotopic enrichments that are regionally recorded with fidelity in the sediments these results facilitate interpretation of a 1 m y 15n record for ocean drilling program site 722b on the owen ridge in terms of climatically linked oscillations in denitrification at the major orbital periods as at present denitrification was greatest during interglacial periods and apparently was not active during most glacial intervals cross spectral analysis of 15n with foraminiferal 18o global climate sea level index and lithogenic grain size monsoon strength index suggests forcings by changes in hydrography and productivity acting through the extent and intensity of the oxygen minimum zone the data suggest that denitrification may be an internal forcing mechanism for climate change during major glacial interglacial transitions through influence on marine n inventory and atmospheric co2 however compensation or amplification may occur from other sinks sediment denitrification or sources nitrogen fixation

differentiation of the south pole aitken basin impact melt sheet implications for lunar exploration we modeled the differentiation of the south pole aitken spa impact melt sheet to determine whether noritic lithologies observed within spa formed as a result of the impact results indicate differentiation of spa impact melt can produce noritic layers that may accommodate observed surface compositions but only in specific scenarios one of nine modeled impact melt compositions yielded layers of noritic materials that account for observations of noritic lithologies at depths of 6 km in this scenario impact occurred before a hypothesized lunar magma ocean cumulate overturn the 50 km deep melt sheet would have formed an insulating quenched layer at the surface before differentiating the uppermost differentiated layers in this scenario have feo and tio2 contents consistent with orbital observations if they were subsequently mixed with the uppermost quenched melt layer and with less feo and tio2 enriched materials such as ejecta emplaced during younger impacts these results verify that noritic lithologies observed within spa could have formed as a direct result of the impact therefore locations within spa that contain noritic materials represent potential destinations for collecting samples that can be analyzed to determine the age of the spa impact potential destinations include central peaks of bhabha bose finsen and antoniadi craters as well as walls of leibnitz and schrodinger basins additionally potential remnants of the uppermost quenched melt may be preserved in gabbroic material exposed in mafic mound exploring and sampling these locations can constrain the absolute age of spa a task that ranks among the highest priorities in lunar science

the mons rumker volcanic complex of the moon a candidate landing site for the chang e 5 mission mons rumker is a large volcanic complex in oceanus procellarum on the moon and is a candidate landing site for china s chang e 5 sample return mission we conducted a comprehensive study of the topography geomorphology composition and stratigraphy of the mons rumker region with multi source remote sensing data in order to better understand the geology of the region and provide further support for the chang e 5 mission the results show that the rumker plateau stands 200 1300 m above the surrounding mare surface and 75 of the plateau has a slope of less than 3 at a baseline length of 30 m domes are the most prominent volcanic landforms in mons rumker and a total of 22 domes were identified and divided into two types that may represent different stages of volcanic activity spectral analyses indicated that mons rumker is covered by low ti basalt and the dominant mafic mineral is high calcium pyroxene though signs of mixing of highland materials and basalt have been found mons rumker has three main basalt units and their absolute model ages are 3 71 ga 3 58 ga and 3 51 ga respectively steep sided domes could be the youngest volcanic features on the plateau with indications that they were active until the eratosthenian a new geologic map of the study region was produced and used to interpret and discuss the geologic evolution of the region finally we propose two candidate landing sites for the chang e 5 mission