the shape and internal structure of the moon from the clementine mission global topographic and gravitational field models derived from data collected by the clementine spacecraft reveal a new picture of the shape and internal structure of the moon the moon exhibits a 16 kilometer range of elevation with the greatest topographic excursions occurring on the far side lunar highlands are in a state of near isostatic compensation whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age a global crustal thickness map reveals crustal thinning under all resolvable lunar basins the results indicate that the structure and thermal history of the moon are more complex than was previously believed

folsom drought and episodic drying on the southern high plains from 10 900 10 200 14c yr b p the paleoenvironments of late pleistocene and early holocene time on the southern high plains have been studied for decades but regionally extensive or long term easily recoverable proxy climate indicators are difficult to find the stratigraphy of valley fill and upland eolian deposits and stable carbon isotope data in addition to geographically limited paleontological data now provide clues to the environment during this time which includes the earliest or paleoindian period 11 200 8000 14c yr b p of human occupation during the clovis occupation 11 200 10 900 14c yr b p valleys contained perennial streams this was followed in folsom time 10 900 10 200 14c yr b p by an abrupt change to lakes and ponds with water levels fluctuating between several meters depth and no surface water and marshes and accumulation of sheet sands on uplands starting the earliest phase of construction of the regional dune fields these changing conditions indicate a shift from relatively wetter to relatively drier conditions with episodic drought stable c isotopes further indicate that warming characterized the clovis folsom transition during the rest of the paleoindian period the environment was relatively cool but fluctuated between wetter and drier conditions with an overall trend toward drying that resulted in further enlargement of the dune fields and culminated in the warm dry altithermal beginning 8000 14c yr b p clovis time probably was the wettest of any paleoindian period in terms of runoff and spring discharge the folsom period was drier and was the earliest episode of regional wind erosion and eolian deposition and may have been the warmest of paleoindian times evidence of a previously hypothesized clovis drought in this region is sparse

late quaternary alluvial stratigraphy of a low order tributary in central texas usa and its response to climate and sediment supply abstract this paper presents the first comprehensive late quaternary alluvial stratigraphic study of a low order tributary in central texas using cowhouse creek as a case study the late pleistocene jackson ja alluvium forms the elevated t2 terrace the entrenched holocene valley is filled with the buried georgetown gt alluvium approximately 11 000 to 8000 14 c yr b p and associated royalty paleosol and the surficially exposed fort hood fh alluvium approximately 7000 to 5000 14 c yr b p and west range wr alluvium approximately 4200 to 600 14 c yr b p forming the broad t1 terrace the ford fo alluvium 14 c yr b p forms the modern t0 floodplain entrenched into t1 conditioned by cooler and wetter climates cowhouse creek was characterized by relatively high base flow and low sediment supply during deposition of the ja and gt alluvium appreciable upland soil erosion ensued during the middle holocene in response to warmer climate conditions resulting in widespread valley filling by the fh alluvium deposition of the late holocene wr and f0 alluvium was characterized by diminished sediment storage during relatively stable climate conditions the temporal alluvial stratigraphic framework of the bedrock confined cowhouse creek valley is out of phase with the alluvial sequence in the larger brazos river valley

distribution and modes of occurrence of lunar anorthosite 1 we have utilized telescopic near infrared spectra and multispectral images of the moon provided by the galileo and clementine missions to determine the distribution and modes of occurrence of pure anorthosite anorthosites have now been identified in all portions of the nearside including the site of the putative procellarum basin anorthosite is associated with the rings of orientale grimaldi humorum nectaris nubium mutus vlaq and balmer basins major portions of the inner rings of grimaldi humorum crisium orientale and nectaris are composed of pure anorthosite the large spatial extent of these anorthosites appears to rule out an origin in the upper portions of discrete differentiated mg suite plutons in every instance the anorthosites were exposed from beneath a shallower near surface layer of more pyroxene rich material more mafic material also occurs beneath the pure anorthosite unit large expanses of the northern farside exhibit very low feo values this region contains abundant anorthosite and stands in stark contrast to the mafic composition exhibited by the interior of the south pole aitken basin spa the distribution of compositional units on large portions of the lunar farside as well as the southern portion of the lunar nearside appears to be largely attributable to the spa impact event the distribution and modes of occurrence of anorthosites clearly indicate that a thick global layer of anorthosite is present at various depths beneath most portions of the lunar surface this anorthosite layer dominated the upper portion of the primordial crust and was produced by plagioclase flotation in the global magma ocean

fluvial response to late quaternary climatic and environmental change edwards plateau texas abstract radiocarbon controlled late pleistocene to modern stratigraphic frameworks for fluvial systems that drain the edwards plateau westcentral texas coupled with reconstruction of climatic and environmental changes permit development of a model for the evolution of fluvial landscapes during the past 20 000 years during this time large valleys of the edwards plateau were characterized by channel aggradation and sediment storage from 20 to 14 000 yrs b p deep excavation of bedrock valleys from ca 14 to 11 000 yr b p and deposition of extensive and complex valley fills during the last 11 000 yr valley fills contain three distinct unconformity bounded allostratigraphic units representing episodes of channel aggradation and floodplain construction during the early to middle ca 11 000 5000 yr b p and late holocene ca 5000 1000 yr b p and development of the incised channels and associated narrow floodplains of the last 1000 years early to middle holocene alluvial deposits were derived from proximal sources within the respective drainage basins whereas late holocene deposits include sediments derived from distal sources sediment supply to major valleys axes has been extremely limited during the last 1000 years alluvial sequences of the edwards plateau record fluvial responses to climatically driven changes in discharge regimes and the concentration of sediments along valley axes allostratigraphic units define time periods when the concentration of sediment exceeded stream power resulting in sediment storage whereas unconformities record widespread morphological and sedimentary adjustments unconformities between late pleistocene alluvium and holocene valley fills record bedrock valley incision in response to decreased sediment loads associated with slope stability in the uplands by contrast unconformities within the holocene valley fill record floodplain abandonment accompanied by continued channel migration and sediment storage but little additional bedrock valley cutting episodes of floodplain abandonment occurred as a result of decreased flood magnitudes following shifts to drier climatic conditions at ca 5000 and 1000 yr b p fluvial responses to climatic change were conditioned by a progressive degradation of upland soils that caused increases through time in the flashiness of flood events which in turn led to changes in processes of floodplain construction flood events on late pleistocene and early to middle holocene rivers were for the most part contained within channel perimeters and floodplains were constructed by lateral migration by contrast late holocene rivers were characterized by deep overbank flooding and floodplain construction by vertical accretion high magnitude floods were most significant from ca 2500 to 1000 yr b p when large chute channels were cut and filled on floodplain surfaces and soils developed on previously stable terrace surfaces were buried by up to 2 m of fine sands and muds

isotope paleoecology of episodic mid to late holocene bison population expansions in the southern plains u s a abstract we used a xad purified ams radiocarbon method to date 62 bison specimens from different contexts on the very southern extent of the great plains of north america to produce a precise chronology of bison population expansions spanning the last 6000 years sixty one of these samples provide stable carbon and nitrogen isotope data indicating relative temperature and moisture conditions during intervals defined by the presence of bison within this time span this chronology indicates climatic conditions favorable to bison were present in the greater central texas area including the uplifted edwards plateau and extending to the coastal plain during periods from 5955 to 5815 3290 to 3130 2700 to 2150 and 650 to 530 cal bp however isotope results suggest climatic conditions differed for each period the earliest calf creek period was characterized by cool but dry conditions the later late archaic 1 2 periods were increasingly warmer and wetter and the latest toyah period was cooler and drier than the late archaic periods but warmer and wetter than calf creek both the calf creek and toyah periods had higher variability within these overall trends comparison with regional records suggests that these periods represent variation within generally cool dry climates human adaptive response to increased bison availability resulted in significant cultural changes across all four periods

stable carbon isotope record of middle to late holocene climate changes from land snail shells at hinds cave texas abstract stable carbon isotope ratios of shell carbonate and shell organic matter from land snails rabdotus alternatus from hinds cave texas are used to reconstruct the climate history of the drier western part of the southern great plains present mean annual rainfall of 400 mm over the last ca 5000 yr ams radiocarbon analyses of four individual shells from each of two strata indicate that there are no problems of reworking or age mixtures within strata however burning is evident in many shells amino acid composition and racemization were used to identify shells that had been significantly heated and these were rejected for isotopic analysis because of possible alteration of the isotopic signal fourteen samples of snails from hinds cave each consisting of 2 6 individual shells from the same provenience were radiocarbon dated by ams and analyzed for stable carbon isotopes in addition a sample collected alive ca ad 1890 from a nearby site was analyzed to represent modern conditions the shells show no decrease in organic content with age indicating good preservation of shell organic matter both the organic and carbonate isotope values show similar temporal trends the oldest samples 4100 4600 cal yr bp are relatively depleted in 13 c maximum 13 c values are reached at ca 3500 cal yr bp thereafter there is a regular depletion in 13 c with the recent sample showing the lowest 13 c value the change in the isotopic values over time is quite large range of 4 5 for organic matter and indicates substantial climatic changes the variations in isotopic values are interpreted as resulting primarily from changes in moisture conditions affecting the abundance of drought adapted cam crassulacean acid metabolism plant species enriched in 13 c thus relatively moist mid holocene conditions are indicated with increasingly dry conditions reaching a maximum at ca 3500 cal yr bp followed by progressively moister conditions through the late holocene

contributions of la nina and el nino to middle holocene drought and late holocene moisture in the american southwest eolian landforms in estancia basin central new mexico record two episodes of extreme drought and low groundwater levels during the middle holocene 7000 5400 1 4 c yr b p followed by a rise in the water table throughthe late holocene blowouts and associated lunettes formed when water levels fell below the desiccated floor of pluvial lake estancia allowing widespread deflation elevation of the water table in the basin is regulated by a balance between evaporation from playas that occupy the blowouts and recharge of aquifers in the adjacent manzano mountains isotopic analyses of modern precipitation and groundwater reveal that recharge originates primarily as winter moisture which is amplified during el ninos and diminished during la ninas thus changes in the elevation of a reconstructed holocene water table may reflect systematic changes in el nino southern oscillation enso circulation

isopycnal and diapycnal circulation of the upper equatorial atlantic ocean in 1983 1984 isopycnal circulation and diapycnal processes in the equatorial atlantic ocean are investigated using eight cruises from november 1982 to july 1984 an eastward decrease of the transport of the equatorial undercurrent is observed averaging 18 2 106 m3 s 1 at 35 w to 10 2 106 m3 s 1 at 4 w there is also a meridional convergence at the undercurrent level and a larger meridional divergence in the surface layer of 15 106 m3 s 1 between 35 w and 4 w in the eastern equatorial atlantic the undercurrent core density as well as the salinity above the undercurrent experience a large seasonal cycle during the season where the eastern atlantic thermocline is closest to the surface and surface waters are coldest the current peaks in denser waters and subsurface salinity maximum are weaker an analysis of the salinity on isopycnal surfaces indicates that there is significant diapycnal mixing in the upper thermocline in the eastern atlantic the upper thermocline vertical heat diffusivity coefficient scaled over 1 of latitude varies between 3 cm2 s 1 during the upwelling season and nearly 0 early in the year this seasonal mixing is an important element of undercurrent dynamics the turbulent heat flux at the base of the surface layer averages 50 w m 2 between 1 5 n and 1 5 s the surface layer heat budget implies an average oceanic gain of 60 w m 2 between 1 5 n and 1 5 s which could result from exchanges with the atmosphere the heat flux and fresh water seasonal cycles needed to close the budgets are not realistic however the eastern equatorial atlantic thermocline seasonal upwelling is associated with a large inflow into the surface layer over the two years this flow averaging 11 12 106 m3 s 1 originates from the upper thermocline and diapycnal transports near the core of the undercurrent or below are found to be small below the core of the undercurrent we also find that mixing is not intense for instance at 26 5 in the upper part of the thermostad vertical heat diffusivity is only 0 6 cm2 s 1 assuming that mixing takes place over 1 of latitude the uncertainties on these budgets are however large and assumptions on the dynamics that were used could not be checked

the clementine mission to the moon scientific overview in the course of 71 days in lunar orbit from 19 february to 3 may 1994 the clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths these data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side in addition laser ranging measurements provided the first view of the global topographic figure of the moon the topography of many ancient impact basins has been measured and a global map of the thickness of the lunar crust has been derived from the topography and gravity

lunar topographic roughness maps from lunar orbiter laser altimeter lola data scale dependence and correlation with geologic features and units we present maps of the topographic roughness of the moon at hectometer and kilometer scales the maps are derived from range profiles obtained by the lunar orbiter laser altimeter lola instrument onboard the lunar reconnaissance orbiter lro spacecraft as roughness measures we used the interquartile range of profile curvature at several baselines from 115 m to 1 8 km and plotted these in a global map format the maps provide a synoptic overview of variations of typical topographic textures and utilize the exceptional ranging precision of the lola instrument we found that hectometer scale roughness poorly correlates with kilometer scale roughness because they reflect different sets of processes and time scales hectometer scale roughness is controlled by regolith accumulation and modification processes and affected by the most recent events primarily geologically recent 1 2 ga meteoritic impacts kilometer scale roughness reflects major geological impact volcanic and tectonic events in earlier geological history young large impact craters are rough and their roughness decreases with age the global roughness maps revealed a few unusually dense clusters of hectometer and decameter size impact craters that differ in their morphology and settings from typical secondary crater clusters and chains the origin of these features is enigmatic the maps can assist in the geological mapping of the lunar maria by revealing contacts between volcanic plain units the global roughness maps also clearly reveal cryptomaria old volcanic plains superposed by younger materials primarily crater and basin ejecta

understanding the lunar surface and space moon interactions the surface of the moon is a critical boundary that shapes our understanding of the moon as a whole all geologic mapping and remote sensing techniques utilize only the outermost portion of the moon before leaving the moon for study in our laboratories all lunar samples that have been studied existed at or very near the surface with the exception of the deeply probing geophysical techniques our understanding of the interior of the moon is derived from surficial but not superficial information coupled with boundary of the lunar crust it is the lower boundary layer of the tenuous lunar atmosphere and constitutes both a source and a sink for atmospheric gases the surface is also where the moon interacts with the space environment causing changes in the physical nature of lunar materials and provides a laboratory for the study of processes that occur on all airless bodies the data obtained remotely by the galileo clementine and lunar prospector missions as well as data derived from lunar meteorites have resulted in major changes to our understanding of global distributions of chemistry and rocks this chapter summarizes the current understanding of this critical interface the surface of the moon in its role as the lower boundary of the lunar atmosphere the upper boundary of the crust and the window through which we view through remote sensing the composition of the crust and the history of the moon in this post lunar prospector time the view of the moon has changed lending new perspectives to lunar samples and lunar processes but the new view will likely remain in flux as we continue to digest the results from these recent space missions and move forward to a new era of lunar exploration despite the freshness of our perspective this is an important moment to capture

channel trenching and climatic change in the southern u s great plains fifteen alluvial sequences in texas and oklahoma exhibit the same late holocene record of channel trenching at 1 ka the erosion was preceded by slow alluvial sedimentation in most stream valleys resulting in the formation of a cumulic organic rich flood plain soil previously named the copan soil the soil formed during a period of regionally moister climate as indicated by pollen spectra molluscan faunas vertebrate faunas sedimentary structures and high alluvial water tables at 1 ka the regional climate changed from moist to dry coinciding with an episode of channel incision of valley floors throughout the southern great plains channel trenching occurred simultaneously in both small and large streams in drainage basins of the arkansas red trinity brazos and colorado rivers the sequences are the first documented example of widespread holocene incision accompanied by firm evidence for a synchronous change in regional climate

the effects of late quaternary climate and pco2 change on c4 plant abundance in the south central united states the late quaternary was a time of substantial environmental change with the past 70 000 years exhibiting global changes in climate atmospheric composition and terrestrial floral and faunal assemblages we use isotopic data and couple climate and vegetation models to assess the balance between c3 and c4 vegetation in texas during this period the carbon isotope composition of fossil bison mammoth and horse tooth enamel is used as a proxy for c3 versus c4 plant consumption and indicates that c4 plant biomass remained above 55 through most of texas from prior to the last glacial maximum lgm into the holocene these data also reveal that horses did not feed exclusively on herbaceous plants consequently isotopic data from horses are not reliable indicators of the c3 c4 balance in grassland biomes estimates of c4 percentages from coupled climate vegetation models illuminate the relative roles of climate and atmospheric carbon dioxide co2 concentrations in shaping the regional c4 signal c4 percentages estimated using observed modern climate vegetation relationships and late quaternary climate variables simulated by a global climate model are much lower than those indicated by carbon isotope values from fossils when the effect of atmospheric co2 concentration on the competitive balance between c3 and c4 plants is included in the numerical experiment however estimated c4 percentages show better agreement with isotopic estimates from late quaternary mammals and soils this result suggests that low atmospheric co2 levels played a role in the observed persistence of c4 plants throughout the late quaternary

on lunar asymmetries 2 origin and distribution of mare basalts and mascons 1 a novel mechanism is proposed for the emplacement of mare basalts and the formation of mascons that does not involve melting or remelting of the source region the source magmas are the remnants of the primordial lunar magma ocean and are rich in incompatible elements including radioactive isotopes potassium rare earth elements and phosphorus kreep and volatiles exsolution of volatiles as the magmas cooled and crystallized a process called second boiling produced overpressures which drove the dense basalts upward to the surface creating the mascons this process occurred preferentially beneath nearside mare basins where the crust is thinnest and lithostatic pressure is lowest the delay between impact and magmatic extrusion reflects the time needed for the volatile rich magma to cool to its second boiling point radioactive heating buffered the magmas against cooling and solidification allowing for an extended period of magmatism

middle holocene bison diet and mobility in the eastern great plains usa based on δ13c δ18o and 87sr 86sr analyses of tooth enamel carbonate during the holocene bison bison bison were key components of the great plains landscape this study utilizes serial stable isotope analyses tooth enamel carbonate of 29 individuals from five middle holocene 7 8 5 ka archaeological sites to address seasonal variability in movement patterns and grazing behavior of bison populations in the eastern great plains stable carbon isotopes 13 c indicate a bison diet that is similar to the c3 c4 composition of modern tallgrass prairies while 87 sr 86 sr values generally indicate very little seasonal movement 50 km and relatively limited inter annual movement 500 km over the course of 4 5 yr analyses of variability in serial stable oxygen isotope samples 18 o further substantiate a model of localized bison herds that adhered to upland areas of the eastern plains and prairie forest border

holocene bison in the great basin western usa bison bison bison were widespread in the eastern and northern parts of the great basin the area of internal drainage in the arid western usa during the late holocene particularly after 1600 14

stable isotopic evidence for latest pleistocene and holocene climatic change in north central texas abstract a paleoclimatic record for a southern great plains locality the aubrey clovis site in north central texas has been established using stable carbon and oxygen isotopes detailed composite stratigraphic sections constrained by 14 c ages place the age of these deposits between 14 200 and 1600 yr b p calcium carbonate samples of lacustrine and pedogenic origin were analyzed oxygen isotopic compositions of most of these in situ carbonates reflect equilibrium precipitation from local meteoric waters oxygen isotope values reflect changes in the composition of meteoric waters tied to changes in the isotopic composition of moisture derived from the gulf of mexico oxygen isotopic variability at the aubrey site is coincident with marine isotopic records from the gulf that vary due to changes in laurentide ice sheet volume and meltwater influx the stable carbon isotopic record reflecting changing biomass through time corroborates humid versus arid interpretations based on sedimentology and rates of alluviation a middle holocene arid period was in contrast to moist early and late holocene climate affirming interpretations of other workers studying southern great plains holocene climate history

wetter and cooler late holocene climate in the southwestern united states from mites preserved in stalagmites the presence of at least 12 species of well preserved mites in two late holocene stalagmites from hidden cave guadalupe mountains new mexico depicts changing climate over the past 3200 yr growth of both stalagmites determined by uranium series dating occurred from at least 3171 48 yr ago and ceased by 819 82 yr ago some of the 12 subfossil genera and species in the stalagmites are like those currently found in wetter and cooler climates northern like and distinctly different from those known in the cave n 16 and on the surface immediately around the cave n 32 the mismatch of genera and species in the stalagmites cave and surface near the cave argues for a wetter and cooler late holocene climate in the southwestern united states from ca 3200 to 800 yr ago

late quaternary vegetation and climate changes in central texas based on the isotopic composition of organic carbon stable carbon isotope analysis of organic carbon in alluvial deposits and soils of three streams in central texas reveals significant shifts in the ratio of c3 to c4 plant biomass production during the past 15 000 yr these temporal changes in vegetation appear to be in response to changes in climate during the late pleistocene c4 plants comprised only about 45 to 50 of the vegetative biomass in this area suggesting that conditions were cooler and wetter than at any time during the past 15 000 yr the time between 11 000 and 8000 yr b p is interpreted as transitional between late pleistocene conditions and warmer and drier holocene conditions based on a slight increase in the abundance of c4 plant biomass during the middle holocene between approximately 6000 and 5000 yr b p mixed c3 c4 plant communities were replaced almost completely by c4 dominated communities indicating prairie expansion and warmer and drier climatic conditions by 4000 yr b p the abundance of c4 plant biomass decreased to levels similar to the early holocene transitional period suggesting a return to cooler and wetter climatic conditions no significant shift in the ratio of c3 to c4 productivity has occurred during the last 4000 yr except for a slight increase in the abundance of c4 plant biomass around 2000 yr b p the results of this investigation correlate well with other regional late quaternary climatic interpretations for central and north texas the southern plains region and with other portions of the great plains

late quaternary sedimentology and geochronology of small playas on the southern high plains texas and new mexico u s a abstract playas are small circular basins forming a ubiquitous component of the southern high plains landscape they are filled with carbonaceous mud deposited since the terminal pleistocene the stratigraphy and geochronology of 30 playas was investigated to better understand the paleoenvironmental record of basin filling at the base of the fill in some playas is a well sorted eolian sand dated between 13 000 and 11 000 14c yr bp the beginning of mud deposition representing aggradation of eolian dust on a moist vegetated playa floor was largely between 12 000 and 10 500 14c yr bp playa filling slowed 9000 to 4000 14c yr bp probably due to dry conditions increased 4000 to 2000 14c yr bp then slowed again eolian sand and loam likely representing regional aridity accumulated in some basins episodically just prior to 10 700 14c yr bp between 8600 and 4700 14c yr bp and at 1300 14c yr bp stable c isotopes from one basin indicate that the playa was inundated only seasonally throughout the record beginning 11 500 14c yr bp the phytolith record in that basin indicates an abrupt shift toward cooling 11 400 to 11 200 14c yr bp and then increasing importance of xeric adapted c4 grasses through the holocene

timing and extent of late quaternary paleolakes in the trans pecos closed basin west texas and south central new mexico abstract the trans pecos closed basin is a hydrographically closed region covering 20 000 km 2 centered on salt basin 160 km east of el paso texas geomorphic and limnetic evidence have been used to identify four major highstands for lake king during the last glacial maximum lgm additional geomorphic features from a second recently identified paleolake lake sacramento have been found in the beargrass subbasin a nested subbasin approximately 75 km northwest of salt basin radiocarbon ages of the organic material in lake king sediments date four abrupt climate changes and rapid lacustrine transgressions during the lgm with a quasi periodicity of 2000 yr geomorphic evidence in the beargrass subbasin identifies lake cycles contemporaneous with those in lake king the dates for these transgressions correlate with the dates of freshening events identified by researchers in paleolake basins elsewhere in new mexico the quasi periodicity of the events approximates that of dansgaard oeschger events identified from greenland ice cores the contemporaneity of the trans pecos transgressions with transgressive events in other basins in the region suggests that paleolakes in the region were in phase with respect to abrupt climate changes during the latter stages of the lgm

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 south pole region of the moon as seen by clementine the clementine mission has provided the first comprehensive set of high resolution images of the south pole region of the moon within 5 of latitude of the pole an area of an estimated 30 000 square kilometers remained in shadow during a full lunar rotation and is a promising target for future exploration for ice deposits the schrodinger basin 320 kilometers in diameter centered at 75 s is one of the two youngest least modified great multiring impact basins on the moon a large maar type volcano localized along a graben within the schrodinger basin probably erupted between 1 and 2 billion years ago

late quaternary floodplain history of the brazos river in east central texas abstract the floodplain along a 75 km segment of the brazos river traversing the gulf coastal plain of texas has a complex late quaternary history from 18 000 to 8500 yr b p the brazos river was a competent meandering stream that migrated from one side of the floodplain to the other creating a thick layer of coarse grained lateral accretion deposits after 8500 yr b p the hydrologic regime of the brazos river changed the river became an underfit meandering stream that repeatedly became confined within narrow and unstable meander belts that would occasionally avulse avulsion occurred four times first at 8100 yr b p then at 2500 yr b p again around 500 yr b p and finally around 300 yr b p the depositional regime on the floodplain also changed after 8500 yr b p with floodplain construction dominated by vertical accretion most vertical accretion occurred from 8100 to 4200 yr b p and from 2500 to 1250 yr b p two major and three minor periods of soil formation are documented in the floodplain sequence the two most developed soils formed from 4200 to 2500 yr b p and from around 1250 to 500 yr b p these changes on the floodplain appear to be the result not of a single factor but of the complex interplay among changes in climate sediment yield and intrinsic floodplain variables over time

middle holocene drought on the southern high plains abstract the climate of the southern high plains during the middle holocene is indicated by data from a variety of sources stratigraphic geomorphic and pedologic research at six localities in draws several dune sites and one playa lake basin show that widespread eolian erosion and sedimentation began in some areas by 9000 yr b p and culminated 6000 4500 yr b p probably because of warmer drier conditions that reduced the vegetative cover archaeological investigations at three sites provide evidence for the excavation of wells at this time apparently because of a declining water table studies of a few vertebrate and invertebrate faunas also indicate warming and drying in the middle holocene climate models and very limited isotopic data from bison bone suggest that summers in the middle holocene were warmer than present with reduced effective precipitation all lines of evidence indicate that the southern high plains was subjected to prolonged drought in the middle holocene with a maximum between 6500 and 4500 yr b p conforming climatically and chronologically to the altithermal

spectral properties of the marius hills volcanic complex and implications for the formation of lunar domes and cones we have used multispectral data from the clementine uv visible camera to study the volcanic features of the marius hills complex and their comparison to other lunar domes and cones there are several mare units identified in the complex each with a unique ti content as indicated by their 415 750 nm value the domes in marius hills are spectrally identical to the mare plains of the complex supporting similar compositions in contrast most of the volcanic cones of the complex are lower in reflectance bluer in color and have weaker mafic absorptions than the mare and domes the spectral characteristics of the cones can best be explained by fine grained crystallization in the spatter that compose the cones other lunar cones such as mons esam in northern tranquillitatis have spectral properties similar to those at marius hills the rima parry cones and their associated dark mantle deposit appear redder with a stronger mafic absorption than the marius hills cones the cones isis and osiris in southern mare serenitatis the domes of rumker hills and several domes in northern mare tranquillitatis are spectrally similar to adjacent mare units the mairan and gruithuisen domes in northern oceanus procellarum have a feldspathic signature characteristic of highland material although they are redder and brighter than adjacent highland soils they appear to represent highland material that resembles domes rather than actual mare domes like those at marius and rumker hills the diversity of lunar volcanic features can best be explained by differences in accumulation rates and cooling of ejected clasts from various eruption styles mare domes may have formed at lower effusion rates thereby allowing lava to construct small shields with slopes 3 the steeper domes at marius hills require higher viscosities resulting from even lower effusion rates and enhanced crystallization in the magmas during the terminal stages of earlier eruptions that emplaced the mare cones like mons esam rima parry isis and osiris are aligned along linear rilles and are interpreted to result from degassing of near surface dikes in contrast the cones of marius hills show no linear alignment and may result from strombolian eruptions at the terminal stages of earlier effusive eruptions that emplaced the domes and mare in the complex

lunar regional dark mantle deposits geologic multispectral and modeling studies clementine five channel uv visible uvvis data have been used to study seven regional dark mantle deposits dmds on the moon the dmds were mapped in distribution to determine their extent and stratigraphic relationship to other geologic units based upon the spectral properties for each dmd the crystallization of the beads in each deposit was inferred and used to estimate cooling rates in the volcanic plumes that emplaced the deposits deposits with a high concentration of glasses reflect volcanic plumes that had low optical densities and high cooling rates whereas deposits dominated by crystallized beads indicate plumes with slower cooling rates due to higher optical densities spectral data from each of the regional dmds show that their glass crystallized bead ratio can be estimated based upon their 415 750 and 750 950 nm values and comparison to laboratory spectra for the beads patches of young dark mantle in the sinus aestuum dmd represent one extreme with the bluest color highest 415 750 and weakest glass band absorption lowest 750 950 of all the dmds at the other extreme is the aristarchus plateau dmd with the reddest color and strongest glass band absorption the other nearside dmds including taurus littrow sulpicius gallus rima bode and mare vaporum lie between these two extremes due to intermediate mixtures of the crystallized beads and glasses with other local soils the orientale ring dmd on the western limb is dominated by volcanic glasses and is spectrally similar to the localized dmds found in alphonsus crater we have identified a central vent for the orientale ring dmd and model the eruption as degassing of a near surface dike to produce a 20 km high umbrella shaped plume with ejection velocities of 360 m s and deposition of the glasses at an average radius of 80 km from the vent although we cannot identify the exact sources for the other regional dmds probably because they are buried beneath younger mare the eruptions most likely resulted from dikes breaching the surface and producing a volcanic plume dominated by larger greater than submillimeter hot clasts that formed mare and sinuous rules the small percent of clasts that form the volcanic beads are carried by the expanding gas cloud to large distances in some cases 100 km to produce the observed continuous regional dmds the lack of basalt samples that can be petrologically related to the volcanic glasses may be a result of their spatial separation with the basalts flowing into the basins while the beads are deposited both into the basins and on the adjacent highlands

withdrawn lithological and mineralogical investigation of the lunar surface with hyperspectral imaging evidence and implications for the evolution of the moon s primitive crust the publisher regrets that this article has been withdrawn as a similar article was simultaneously submitted to another journal http dx doi org 10 1016 j gsf 2016 03 005 therefore qualifying as a redundant publication the full elsevier policy on article withdrawal and redundant publication and can be found at https www elsevier com authors journal authors policies and ethics

lunar mare basalts in the aristarchus region implications for the stratigraphic sequence from clementine uvvis data the aristarchus region of oceanus procellarum is an area concentrated with lunar basalts which were mainly produced by the last major phase of lunar volcanism on the western nearside a group of lunar sample and remote sensing scientists have carried out the extensive task of characterization of lunar mare soils with regard to their mineralogical and chemical makeup and regional geologic mapping spectral parameters of the high spatial resolution clementine images are used to identify and define these basalts as different compositional and spectral units this endeavor is aimed at deciphering the subtle spectral characteristics of mare soils and validating the mapping technique used in this study together with making statistical analysis of the links between the basalt types with ages in order to provide a further understanding of material types and geologic evolution in the aristarchus region of the moon from the new perspective of mining geologic information in multivariable image spaces spectrally distinct 9 high ti and 11 low ti basalt reference spectra have been distinguished and as a result more than 70 spectrally and compositionally basaltic units which range in age from 1 20 b y to 3 74 b y have been identified to some extent a potential relationship between composition and relative age exists in the statistical analysis of the links between spectral types related with the clementine ratio colors of various basalts and ages in this study which suggests that composition with different states of maturity correlate with age to some extent the mineralogical characteristics and spectra age relationship in the marius hills region indicate that the early basalts may still be exposed at the surface deposit after prolonged volcanic activity in this region this may be a result of not being blanketed by later lava flows or lava extrusions of underlying low ti basalts in addition stratigraphic analysis also reveals and confirms that tio 2 concentrations appear to vary independently with time and generally eruptions of

an investigation of potential pyroclastic deposits on the southeast limb of the moon abstract we investigated the physical and spectral properties of potential dark mantling deposits pdmds previously and newly identified on the se limb of the moon near the craters humboldt and petavius the goals of this investigation were to constrain the composition and mode of emplacement of these poorly studied deposits to identify interdeposit variations and to use these results to draw conclusions about regional and subsurface geologic processes our investigation involved an assessment of both the physical properties size texture morphology and spectral properties albedo absorption bands color ratios utilizing remote sensing data from multiple lunar orbital missions we found that many of the se limb deposits previously identified as possibly pyroclastic in origin were likely effusively emplaced however we also identified several likely pyroclastic deposits including three not previously mapped we found that the volcanic deposits across the study area comprise three major spectral groups one similar to mare fecunditatis one similar to mare australe and one similar to known glassy pyroclastic deposits elsewhere on the moon we conclude that volcanism across the se limb was likely fed from at least two distinct magma source regions and that the type and extent of surface expression of this volcanic activity was possibly influenced by regional variations in crustal thickness our documentation and analysis of the complex volcanic history in this region of the moon supports ongoing efforts to develop increasingly detailed interpretations of the volcanic history of the entire moon

late holocene dune migration on the south texas sand sheet abstract there are a wide variety of vegetated eolian depositional landforms associated with the south texas sand sheet attesting to the past dominance of eolian processes mapping identified two sets of parabolic dunes elongating with winds from the southeast and the northwest parabolic dunes elongated by northwesterly winds are older than ca 200 years and may be associated with eolian depositional events ca 2700 and or 2000 years ago the latest dune migration event associated with southeasterly winds occurred ca 200 years ago and at one site is inset into northwesterly extended parabolic dunes this period of dune migration may be coincident with particularly severe drought identified in the tree ring record centered at ad 1790 when the palmer drought severity index was 4 a threshold of dune movement may have occurred ca in the 11th 15th and 20th centuries when there are two or more consecutive years with a palmer drought severity index of

mineralogy of the lunar crust results from clementine received 1997 december 5 accepted in revised form 1998 september 15 abstract the central peaks of 109 impact craters across the moon are examined with clementine ultraviolet visible uvvis camera multispectral data the craters range in diameter from 40 to 180 km and are believed to have exhumed material from 5 30 km beneath the surface to form the peaks including both upper and lower crustal rocks depending on whether craters have impacted into highlands or basins representative five color spectra from spectrally and spatially distinct areas within the peaks are classified using spectral parameters including key ratio which is related to mafic mineral abundance and spectral curvature linked to absorption band shape which distinguishes between low and high ca pyroxene and olivine the spectral parameters are correlated to mineralogical abundances related in turn to highland plutonic rock compositions the derived rock compositions for the various central peaks are presented in a global map from these results it is evident that the lunar crust is compositionally diverse both globally and at local 100 m scales found within individual sets of central peaks although the central peaks compositions imply a crust that is generally consistent with previous models of crustal structure they also indicate a more anorthositic crust than generally assumed with a bulk plagioclase content of 8 1 evolving from pure anorthosite near the surface towards more mafic low ca pyroxene rich compositions with depth comparable to anorthositic norite evidence for mafic plutons occurs in both highlands and basins and represent all mafic highland rock types however the lower crust is more compositionally diverse than the highlands with both a greater range of rock types and more diversity within individual sets of central peaks

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

paleoclimate and amerindians evidence from stable isotopes and atmospheric circulation two amerindian demographic shifts are attributed to climate change in the northwest plains of north america at 11 000 calendar years before present yr bp amerindian culture apparently split into foothills mountains vs plains biomes and from 8 000 5 000 yr bp scarce archaeological sites on the open plains suggest emigration during xeric altithermal conditions we reconstructed paleoclimates from stable isotopes in prehistoric bison bone and relations between weather and fractions of c4 plants in forage further we developed a climate change model that synthesized stable isotope existing qualitative evidence e g palynological erosional and global climate mechanisms affecting this midlatitude region our isotope data indicate significant warming from 12 400 to 11 900 yr bp supporting climate driven cultural separation however isotope evidence of apparently wet warm conditions at 7 300 yr bp refutes emigration to avoid xeric conditions scarcity of archaeological sites is best explained by rapid climate fluctuations after catastrophic draining of the laurentide lakes which disrupted north atlantic deep water production and subsequently altered monsoonal inputs to the open plains

analysis of chang e 2 brightness temperature data and production of high spatial resolution microwave maps of the moon abstract the microwave radiation passively emitted from the moon is valuable for investigating the physical properties of the lunar regolith microwave maps which can reveal subsurface characteristics at depths of centimeters to meters give clues to understanding the evolution of the lunar surface china s chang e 2 ce 2 spacecraft carried a microwave radiometer mrm and conducted passive microwave remote sensing of the moon at 3 7 8 19 35 and 37 ghz 10 3 84 1 55 and 0 81 cm wavelengths during 2010 2011 brightness temperature tb data derived from the mrm orbital observations cover the entire moon and the time coverage is over a complete lunation in this paper we use spherical harmonic fits to model the tb variation as functions of local time and latitude using these fits we normalized the day and nighttime tb data measured at various local times into noon time and midnight conditions the spatial sampling of the normalized tb maps is 6 km pixel much higher than ground based observations and higher resolution than the mrm maps derived from chang e 1 by removing the variation in tb related to local time and latitude we produced a series of microwave maps that reveal differences in the properties of the regolith across the lunar surface the microwave behavior of various lunar surface features can be explained primarily by differences in the microwave loss tangent of the materials for example we find that the high ti maria have high daytime tb and exhibit lower nighttime tb than the other maria as a result of the high dielectric loss tangent of ilmenite the ilmenite rich materials are less transparent to microwaves and hence emissions emerge from closer to the surface which is heated strongly in the day and cools quickly at night most fresh craters correspond to low tb spots in the nighttime microwave maps in contrast to their behavior as hot spots in nighttime infrared data suggesting that the higher loss tangent of rocks compared to soils suppresses microwave emission at night the aristarchus plateau has a lower loss tangent relative to its surroundings because it is blanketed by fine grained rock poor pyroclastic material the pyroclastic blanket is more transparent to microwaves than the nearby maria causing the plateau to have relatively cool daytime tb and warm nighttime tb as a consequence of microwave emissions that originate at greater depths the orientale basin is another prominent anomaly in the microwave maps indicating that orientale materials differ in thermophysical and or dielectric properties from typical highland lithologies brightness temperature differences among prominent rayed craters indicate that the very youngest crater rays e g giordano bruno have lower thermal inertia than older but still optically immature rays e g tycho

clementine observations of the aristarchus region of the moon multispectral and topographic data acquired by the clementine spacecraft provide information on the composition and geologic history of the aristarchus region of the moon altimetry profiles show the aristarchus plateau dipping about 1 to the north northwest and rising about 2 kilometers above the surrounding lavas of oceanus procellarum to the south dark reddish pyroclastic glass covers the plateau to average depths of 10 to 30 meters as determined from the estimated excavation depths of 100 to 1000 meter diameter craters that have exposed materials below the pyroclastics these craters and the walls of sinuous rilles also show that mare basalts underlie the pyroclastics across much of the plateau near infrared images of aristarchus crater reveal olivine rich materials and two kilometer sized outcrops of anorthosite in the central peaks the anorthosite could be either a derivative of local magnesium suite magmatism or a remnant of the ferroan anorthosite crust that formed over the primordial magma ocean

compositional analysis of the orientale basin using full resolution clementine data some preliminary results clementine imaged the moon globally in eleven different wavelengths we used these data to construct a full resolution 250 m pixel multispectral image of the orientale basin using this image in conjunction with other data sets such as earth based spectra we mapped the compositional units of the basin to obtain insights into its formation and evolution the basin ejecta units are largely uniform in composition with the inner montes rook formation being slightly more mafic than the outer hevelius formation the inner and outer rook mountains display many outcrops of pure anorthosite these and other findings are consistent with a three layer model for the lunar crust consisting of a mixed zone megaregolith tens of kilometres thick overlying a layer of anorthosite above a basaltic layer

a sharper view of impact craters from clementine data the ultraviolet visible camera on the clementine spacecraft obtained high spatial resolution images of the moon in five spectral channels impact craters mapped with these multispectral images show a scale of lithologic diversity that varies with crater size and target stratigraphy prominent lithologic variations feldspathic versus basaltic occur within the south wall of copernicus 93 kilometers in diameter on the scale of 1 to 2 kilometers lithologic diversity at tycho 85 kilometers in diameter is less apparent at this scale although the impact melt of these two large craters is remarkably similar in this spectral range the lunar surface within and around the smaller crater giordano bruno 22 kilometers in diameter is largely dominated by the mixing of freshly excavated material with surrounding older soils derived from a generally similar feldspathic lithology

surface drifter pathways originating in the equatorial atlantic cold tongue 1 subtropical cells stcs connect subduction zones of the eastern subtropics of both hemispheres to the equatorial current systems via equatorward flow in the thermocline some of this thermocline water is converted back into warm near surface water in the eastern equatorial cold tongue from whence it is exported poleward here we examine the export pathways from the cold tongue in the atlantic based on recently available near surface drifter data we find that similar to its pacific counterpart water upwelled in the atlantic cold tongue follows multiple pathways back into the subtropics but not directly to the subduction zones thus the subtropical cells are open to extensive influence from and exchange with the subtropical and midlatitude ocean

subsurface structures of buried features in the lunar procellarum region abstract the gravity recovery and interior laboratory grail mission unraveled numbers of features showing strong gravity anomalies without prominent topographic signatures in the lunar procellarum region these features located in different geologic units are considered to have complex subsurface structures reflecting different evolution processes by using the grail level 1 data we estimated the free air and bouguer gravity anomalies in several selected regions including such intriguing features with the three dimensional inversion technique we recovered subsurface density structures in these regions

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

discrimination between maturity and composition of lunar soils from integrated clementine uv visible near infrared data application to the aristarchus plateau the reflectance spectrum of a lunar soil is mainly dominated by the composition and the degree of exposure to space weathering processes such as micrometeorite bombardment and solar wind implantation the spectral alteration effects of space weathering should be removed for accurately investigating the composition of the lunar surface using remote sensing data in this paper we show that the integration of the clementine uv visible uvvis and near infrared nir channels provides an improved evaluation of the spectral alteration the depth of the mafic absorption feature at 0 95 m is also better defined by combining the uvvis and nir data laboratory spectra of lunar soil samples indicate that the continuum slope derived from the 1500 750 nm ratio is closely related to the concentration of fine grained submicroscopic iron is the continuum slope therefore provides an evaluation of the spectral alteration of the surface which can be subtracted from the 1 or 2 m absorption band depths to retrieve compositional information this method has been applied to the aristarchus plateau which exhibits a broad range of mineralogical composition and maturity a nine channel multispectral mosaic of 680 clementine images of the aristarchus plateau has been processed eight telescopic spectra have been used to check the validity of the reduction process for the near infrared bands the 1 m absorption band once corrected for spectral alteration provides an evaluation of the initial feo content in mafic silicates mafic iron lunar soil samples show that it is possible to quantitatively map mafic iron with this technique our results are in good agreement with those obtained using the algorithm of lucey et al 1995 1998a which is based on uvvis bands alone the mafic iron content and total iron content which can be derived from the combined uvvis and nir data sets are less sensitive to local slopes than that derived from lucey et al s method this new method could therefore be useful for investigating areas at middle to high latitudes removing spectral alteration from the 2000 1500 nm ratio also makes possible a better discrimination between olivine and pyroxene within identified mare basalts on the aristarchus plateau

oxygen extraction from lunar soils and pyroclastic glass we have conducted experiments on 16 lunar soils and three lunar pyroclastic glass samples to study the extraction of oxygen an important resource for a future lunar base the samples were chosen to span the range of composition mineralogy and maturity represented in the apollo sample collection each sample was reduced in flowing hydrogen for 3 hours at 1050 c the dominant effect was reduction of fe2 as feo in minerals and glass to iron metal with concomitant release of oxygen oxygen extraction was strongly correlated with initial fe2 abundance the data and supporting experiments also indicate extraction of oxygen from tio2 and sio2 no dependence of oxygen release on sample maturity could be identified oxygen was extracted in decreasing order of efficiency from ilmenite agglutinitic and pyroclastic glass olivine and pyroxene the experimental reduction of lunar soil provides a method for assessing the oxygen production potential for sites on the lunar surface from lunar orbit our results show that oxygen yield from the regolith can be predicted from knowledge of only one parameter total iron content this parameter can be measured from orbit by gamma ray spectrometry or multispectral imaging these experimental data also support the selection of feedstocks and operating parameters for a lunar oxygen plant

upwelling and primary production during the u s geotraces east pacific zonal transect the 2013 u s geotraces eastern pacific zonal transect epzt traversed the highly productive peruvian coastal upwelling pcu region in this work the flux of nitrate into the euphotic zone is derived for stations within the pcu using a previously developed method whereby dilution of the water column 7be inventory by upwelled 7be free water provides a means to infer upwelling rates furthermore with knowledge of upwelling rates 7be profiles are used to constrain vertical diffusivity within the upper thermocline these transport terms are applied to nitrate profiles to estimate net community production between 79 w and 104 w along the epzt which includes the zone of active upwelling to the edge of the oligotrophic gyre with a simple one dimensional model the calculated upwelling rates were inversely related to mixed layer temperature and ranged from 0 to 3 0 m d results using a depth dependent upwelling rate with a component of horizontal advection are also described vertical diffusivities near the base of the euphotic zone were in the range 1 7 4 5 10 4 m2 s these values are compared to those generated by analysis of temperature profiles net community production averaged 15 mmol c m2 d for stations between 84 w and 104 w and was 134 mmol c m2 d for the furthest inshore station at 79 w which displayed the lowest sst and greatest rate of upwelling

geomorphologic mapping of the lunar crater tycho and its impact melt deposits abstract using selene kaguya terrain camera and lunar reconnaissance orbiter camera lroc data we produced a new high resolution 10 m pixel geomorphological and impact melt distribution map for the lunar crater tycho the distal ejecta blanket and crater rays were investigated using lroc wide angle camera wac data 100 m pixel while the fine scale morphologies of individual units were documented using high resolution 0 5 m pixel lroc narrow angle camera nac frames in particular tycho shows a large coherent melt sheet on the crater floor melt pools and flows along the terraced walls and melt pools on the continuous ejecta blanket the crater floor of tycho exhibits three distinct units distinguishable by their elevation and hummocky surface morphology the distribution of impact melt pools and ejecta as well as topographic asymmetries support the formation of tycho as an oblique impact from the w sw the asymmetric ejecta blanket significantly reduced melt emplacement uprange and the depressed uprange crater rim at tycho suggest an impact angle of 25 45

on the evolution of the thermocline and subthermocline eastward currents in the equatorial atlantic 1 eastward currents in the thermocline and subthermocline layers of the tropical atlantic ocean are described using observations obtained during two boreal summer cruises covering the whole equatorial basin the analysis focuses on the eastward evolution of zonal currents in the thermocline and sub thermocline the equatorial undercurrent is not found close to the african coast in boreal summer 2000 maybe because of interannual variability as observed in the pacific the south and north equatorial undercurrents are shown to shift poleward from west to east and the two cruises indicate that the north equatorial undercurrent does not enter the gulf of guinea the south and north intermediate countercurrents are variable with longitude and contrarily to the observations in the eastern equatorial pacific are not found in the east of the guinea basin

stable isotope dietary analysis of bison bone samples from the hudson meng bonebed effects of paleotopography abstract selected fossil bison rib bones from the hudson meng bonebed early holocene age were studied in order to assess possible sources of isotopic variability along a north south transect which spans large variations in paleotopography and resulting hydrological conditions analyses performed on the specimens included microscopic examination in thin section determination of 13 c values in collagen and determination of 13 c and 18 o values in bone carbonate explanations for spatial trends in isotopic data centre around the effects of pre burial topography upon deposition and preservation of skeletal samples arguing for enhanced analysis and consideration to be given to site paleosurface characteristics during the selection of specimens for paleodietary and paleoclimate analysis all enamel and bone carbonate data suggest a diet 13 c value between 19 and 20 for these early holocene animals while most collagen values predict dietary 13 c values ranging from 21 to 24 5 two interpretations exist for the difference between the 13 c value of diet predicted from bone carbonate and the apparent 13 c value of the modern grass biomass available to grazers in a nearby location first that the grass biomass available to grazers in this area 9500 bp had a higher 13 c value and second that the bison diet consisted of a selective subset of species available in the environment

a description of the annual cycle in sea surface temperature and upper ocean heat in the equatorial atlantic abstract temperature and velocity time series obtained by surface moorings during the seasonal response of the equatorial atlantic experiment are used to investigate the role of ocean dynamics upon the annual cycle of equatorial sea surface temperature sst and upper ocean heat the annual cycle in sst is explained by different mechanisms each operant at different phases of the cycle the boreal springtime decrease in sst results from upwelling in response to the seasonal intensification of easterly wind stress this upwelling causes the seasonal formation of the cold tongue along the equator in the central and eastern portions of the basin an early summer increase in sst is attributed to the meridional convergence of reynolds heat flux associated with surface current instability generated waves after the instability waves abate sst and mixed layer depth remain relatively steady from late summer through fall when the advective terms are small and cancelling suggesting that surface heating is then

equatorial upwelling rates inferred from helium isotope data a novel approach 1 upwelling is one of the key processes to maintain the tropical atlantic cold tongue this feature is of special interest to climate research since its sst variability is significantly correlated with the west african monsoon direct measurements of the upwelling have been hampered by the small speeds involved instead vertical motion has to be estimated by indirect methods here we propose a novel approach to infer equatorial upwelling velocities by exploiting the helium isotope disequilibrium between atmosphere and equatorial oceanic mixed layer the data were collected during woce cruises a13 and a14 although the vertical and horizontal resolution of the helium data in the upper tropical oceans was too poor to support a detailed study it was sufficient to show the potential of the method

prospects for interregional correlations using wisconsin and holocene aridity episodes northern gulf of mexico coastal plain abstract luminescence dating of extensive dune fields and associated eolian sandsheets provided a chronology of recently recognized pleistocene and early holocene dry climate episodes in the currently humid warm temperate northern northeastern gulf of mexico region scattered parabolic dunes and clusters of intersecting parabolic dunes along with elongated shore transverse and shore parallel dunes developed these landforms occur in a 390 km long and 2 to 3 km wide semicontinuous belt in southeast alabama and northwestern florida dune elevations reach 22 m sangamon coastal barrier sectors were the primary source of the eolian sand deflation was coeval with early wisconsin to mid holocene marine low sea levels and associated distant shorelines early holocene dune dates were synchronous with indications of a hypsithermal dry interval in southeast louisiana the yucatan and the south atlantic seaboard overlapping with dry episodes in yucatan and the high plains texas dunes and louisiana and texas prairie mounds especially in the southwest texas coast still dominated by dry climate suggests intervals of early to late holocene drought the dates provide the basis for identifying and correlating wisconsin early and late holocene climate phases between currently semiarid and humid coastal and interior areas they contribute to future studies including interregional paleoclimate modeling although pleistocene coastal eolian deposition coincided with glaciation in the northern interior and with cooler temperatures of a reduced gulf of mexico holocene aridity phases may have been related to major variations in the position of high pressure cells storm tracks and branches of the jet stream and even to prolonged la nina conditions

accelerator radiocarbon dating at the molecular level molecular level 14c dating is the isolation of specific classes of molecules for their 14c dating by accelerator mass spectrometry ams complex matrices such as fossil bone are difficult to date due to their extreme chemical heterogeneity by isolating individual amino acids contaminants humates are removed and crystalline amino acids result bones with 0 1 0 2 n and collagenous compositions can be dated accurately because structural collagen is present contaminants are removable with xad resin bones with 0 1 n and non collagenous compositions yield dates hundreds to thousands of years too young because most of the preserved organic matter is exogenous accelerator 14c dates on collagenous and non collagenous bones are not comparable due to intrinsic dating inaccuracies ams 14c dating of amino acids demonstrated that 1 post 10 800 year ages for north american megafauna are due to sample contamination not holocene ages on extinct fauna 2 a clovis age 10 900 years was established for a human fossil from the anzick site montana 3 holocene ages cannot be established absolutely for many north american human fossils because the bones were non collagenous 4 accurate ages are attainable on vertebrate fossils as small as passerine birds from pacific island localities 5 well preserved bones are datable without their destruction by extracting protein with water at high temperatures and 6 stratigraphic anomalies to 45 000 years in european upper paleolithic rock shelters are recognizable by dating bone directly

tsiolkovsky crater a window into crustal processes on the lunar farside mineralogy and distribution of rock types in the tsiolkovsky region of the lunar farside are evaluated in terms of crustal stratigraphy and evolution calibrated multispectral images from five orbits of clementine data provide compositional information at a scale that allows diverse geologic features to be analyzed and compared the entire region is seen to be highly anorthositic with outcrops of relatively pure anorthosite quite common the crater itself has excavated blocks of anorthosite and noritic anorthosite from the near surface highland crust often in a mixed jumble the central peaks of tsiolkovsky which have exhumed much deeper material however are composed of relatively pure anorthosite with olivine rich zones concentrated near the ridge crests boundaries between the anorthosite and olivine rich zones are sharp but spatial relations suggest the coherent olivine rich zone is relatively thin 1 km the composition of the mare material filling tsiolkovsky is shown to be low titanium basalt smaller exposures of mare basalt occur about one crater radius from the rim the crustal structure to 25 km in this region prior to the tsiolkovsky impact appears to be top to bottom a few kilometers of anorthositic breccias comprising the megaregolith a zone of crystalline anorthosite with pockets of noritic anorthosite a zone of anorthosite devoid of iron bearing minerals and a zone of relatively pure anorthosite containing olivine rich material possibly emplaced as intrusions

galileo multispectral imaging of the north polar and eastern limb regions of the moon multispectral images obtained during the galileo probe s second encounter with the moon reveal the compositional nature of the north polar regions and the northeastern limb mare deposits in these regions are found to be primarily low to medium titanium lavas and as on the western limb show only slight spectral heterogeneity the northern light plains are found to have the spectral characteristics of highlands materials show little evidence for the presence of cryptomaria and were most likely emplaced by impact processes regardless of their age

remote sensing of lunar pyroclastic mantling deposits abstract mantling deposits on the moon are considered to be pyroclastic units emplaced on the lunar surface as a result of explosive fire fountaining these pyroclastic units are characterized as having low albedos having smooth fine textured surfaces and consisting in part of homogeneous febearing volcanic glass and partially crystallized spheres mantling units exhibit low returns on depolarized 3 8 cm radar maps indicating an absence of surface scatterers in the 1 to 50 cm size range a number of reflectance spectra from several regional pyroclastic deposits are presented for the first time these data support a previous interpretation that mantling units have a unique spectral signature which is indicative of the presence of a significant fe bearing volcanic glass component the rima bode region is discussed as an example of an area in which several types of remote sensing data including 3 8 cm radar spectral reflectance and multispectral vidicon data were used to reconstruct the geologic events surrounding the emplacement of a regional pyroclastic mantling deposit the recognition of numerous varieties of volcanic glass samples especially relatively high albedo e g green yellow glasses suggests the existence of additional unrecognized mantling deposits with albedos higher than those studied to date on the basis of the remote sensing data summarized and presented five new areas have been identified which may represent higher albedo regional pyroclastic deposits

large shield volcanoes on the moon 1 the volcanic style of the moon has long been understood to consist almost exclusively of flood basalts erupted from fissures along with minor pyroclastic activity large central vent shield volcanoes that characterize basaltic volcanism on the other terrestrial planets appeared to be absent small few kilometers diameter central vent constructs have long been recognized in the lunar maria and often are found clustered in fields throughout the lunar maria new global topographic data from the lola and lroc instruments on lro reveal that almost all of these volcanic complexes on the moon occur on large regional topographic rises in the lunar maria tens to hundreds of kilometers in extent and between several hundred to several thousand meters high we propose that these topographic swells are shield volcanoes and are the lunar equivalents of the large basaltic shields found on the earth venus and mars the newly recognized lunar shields are found peripheral to the large deeply flooded impact basins imbrium and serenitatis suggesting a genetic relation to those features loading of the lithosphere by these basalt filled basins may be responsible for inducing a combination of flexural and membrane stress inducing a pressure distribution on vertically oriented dikes favorable to magma ascent this condition would occur in a zone annular to the large circular loads produced by the basins where the shield volcanoes occur

composition of the lunar highland crust from near infrared spectroscopy near infrared reflectance spectra of the lunar highlands are synthesized to obtain global information about the composition of the lunar near side crust immature exposed surfaces from small fresh craters mountains and massifs and large craters with central peaks are included in a survey of rock types across the lunar near side compositions recognized in these data include anorthosite noritic gabbric and troctolitic mineral assemblages three quarters of the areas studied that represent samples from the upper 1 2 km of lunar crust exhibit noritic compositions with different amounts of pyroxene and or brecciation alteration norites are ubiquitous across the near side and show no spatial clustering associated with any of the major basins in contrast to this noritic megaregolith of the upper crust material representing stratigraphically deeper zones 5 15 km of the lunar crust is dominated by gabbros anorthosites and troctolites with less than a quarter of the areas studied exhibiting a noritic composition the origin of the noritic megaregolith and its relation to deeper crustal material is thus somewhat of an enigma the current limited statistics for areas identified as anorthosites and troctolites are insufficient to derive global spatial distributions gabbroic areas however are notably concentrated in the western hemisphere although incomplete for a global assessment of crustal materials these data demonstrate that the lunar near side crust is clearly mineralogically heterogeneous both laterally and vertically and not well mixed below 1 2 km

topographic compositional units on the moon and the early evolution of the lunar crust the distribution of elevations on the moon determined by clementine deviates strongly from a normal distribution suggesting that several geologic processes have influenced the topography the hypsograms for the near side and far side of the moon are distinctly different and these differences correlate with differences in composition as determined by apollo orbital geochemistry clementine global multispectral imaging and ground based spectroscopy the hypsograms and compositional data indicate the presence of at least five compositional altimetric units the lack of fill of the south pole aitken basin by mare basalts suggests poor production efficiency of mare basalt in the mantle of this area of the moon

the aristarchus impact event and the effects of target material the relatively well preserved 42 km diameter lunar impact crater aristarchus was excavated across the boundary between the aristarchus plateau and the mare plains previous geological mapping of the different ejecta facies associated with aristarchus has shown that there are distinct morphological differences between ejecta emplaced on either side of the fault scarp that separates the plateau from the mare one explanation of this observation is that ejecta behaved in different ways on emplacement depending on the original lithology of the excavated material to test this proposal we examine the pre aristarchus regional stratigraphy and identify the spectral signatures of each of the material s units by comparing these data with analysis of the geology and spectral characteristics of the ejecta units we are able to show the provenance of each of the mappable ejecta facies the conclusions are consistent with the concept of the crater ejecta asymmetry being related to bedrock characteristics using geological mapping spectral interpretation and present understanding of the impact cratering process we reconstruct the impact event and suggest how such techniques could be used further to interpret the moon s composition and history

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

human responses to middle holocene altithermal climates on the north american great plains abstract the climate of the great plains during the middle holocene varied considerably but overall it was marked by a north south gradient of increasingly warmer and drier conditions with a reduction in effective moisture surface water and resource abundance and an increase in resource patchiness sediment weathering erosion and aeolian activity pronounced drought conditions were most evident on the southern high plains understanding the human responses to middle holocene climates is complicated by a lack of archaeological data which is partly a result of geomorphic processes that removed or deeply buried sites of this age and by the varying adaptive responses of hunter gatherers during this period on the southern high plains where drought was most severe surface and groundwater sources dried and bison populations were diminished prompting substantial adaptive changes including local abandonment well digging to tap underground water and a widening of the diet breadth to incorporate higher cost lower return seed and plant resources sites of this age on the central and northern plains also show a possible increase in diet breadth with the incorporation of plant foods in the diet and perhaps changes in settlement mobility including possible shift into higher elevation areas or mapping on to extant rivers and springs but linking those changes to middle holocene drought is less straightforward

late pleistocene northward dispersing bison antiquus from the bighill creek formation gallelli gravel pit alberta canada and the fate of bison occidentalis late pleistocene bison skeletal remains from the gallelli gravel pit in the bighill creek formation at calgary alberta document at least two individuals including the largest postglacial bison r

a dual tracer approach to estimate upwelling velocity in coastal southern california abstract the distribution of the cosmogenic radionuclide 7be t 1 2 53 d in the surface ocean has previously been used to estimate upwelling velocity in the open ocean however the loss of 7be to particle export has limited this approach in high particle density environments like the continental margins in this study we combine a mass balance of 7be with a 234th budget in the surface ocean to constrain the loss of 7be to particle sinking at the san pedro ocean time series spot in the inner southern california bight during spring 2013 upwelling velocities all in m d 1 determined from the 7be mass balance were observed to increase from 0 5 0 6 in january to 2 5 1 3 in may then decrease to 1 2 0 5 in june these results agree within uncertainty with upwelling velocities derived from the monthly bakun upwelling index which ranged from 0 1 to 2 8 m d 1 supporting the pressure field based approach evidence from a heat budget and the nutrient distribution over the course of the study supports that the upwelling signal at spot 20 km offshore is not transported from coastal upwelling near shore but instead is dominantly a local signal likely driven by wind stress curl