new views of lunar geoscience an introduction and overview beyond the earth the moon is the only planetary body for which we have samples from known locations the analysis of these samples gives us ground truth for numerous remote sensing studies of the physical and chemical properties of the moon and they are invaluable for our fundamental understanding of lunar origin and evolution prior to the return of the apollo 11 samples the moon was thought by many to be a primitive undifferentiated body e g urey 1966 a concept shattered by the data returned from the apollo and luna missions ever since new data have helped to address some of our questions but of course they also produced new questions in this chapter we provide a summary of knowledge about lunar geologic processes and we describe major scientific advancements of the last decade that are mainly related to the most recent lunar missions such as galileo clementine and lunar prospector 1 1 the moon in the planetary context compared to terrestrial planets the moon is unique in terms of its bulk density its size and its origin fig 1 1a c all of which have profound effects on its thermal evolution and the formation of a secondary crust fig 1 1d numerous planetary scientists considered the moon as an endmember among the planetary bodies in our solar system because its lithosphere has been relatively cool rigid and intact throughout most of geological time a one plate planet and its surface has not been affected by plate recycling an atmosphere water or life therefore the moon recorded and preserved evidence for geologic processes that were active over the last 4 4 5 b y and offers us the unique opportunity to look back into geologic times for which evidence on earth has long been erased fig 1 1c d impact cratering an exterior process is considered the most important surface process on the moon internal

comparative soil development of quaternary paleosols of the central united states abstract buried soils in the central united states aid in deciphering stratigraphy and chronology by being stratigraphic markers such soils may provide a record of many quaternary events particularly that of climatic change interglacial soils like the sangamon soil may have formed for over 100 000 years during which the climate shifted from cold to warm to cold again interstadial soils formed under cooler conditions and for less time in this paper we review our knowledge of quaternary paleosols in the central united states with emphasis on indiana and through comparison with the type localities in indiana the sangamon soil is the most widespread buried soil of interglacial rank exposures of the sangamon soil reveal a range of characteristics that are related to soil forming factors jenny h 1941 factors of soil formation mcgraw hill new york 281 pp jenny h 1980 the soil resource origin and behavior ecological studies 37 springer new york the most important of these factors include parent materials soil drainage and the duration of soil development how long a buried soil formed may be determined by whether it is an interglacial or an interstadial soil thus the sangamon soil can serve as a standard to which other soils both interglacial and interstadial can be compared the most widespread interstadial soil in the central united states is the middle wisconsinan farmdale sidney soil exposures of this soil are less common than for the interglacial sangamon soil although enough data are available to provide an additional basis for evaluation of other soils based upon a semi quantitative ranking of soil development by an assemblage of characteristics we have numerically defined soil development for well developed moderately developed and weakly developed categories the most strongly developed buried soils in the central united states are the early pleistocene soils and the yarmouth soil both the yarmouth soil and the sangamon soil may be more strongly developed in indiana than in their respective type areas in iowa and illinois both the yarmouth soil and the sangamon soil are more strongly developed than the surface soil the primary reason seems to be the greater time intervals over which the yarmouth and sangamon soils developed as expected interstadial soils are much more weakly developed than interglacial soils soil development is also a function of soil drainage in general better drained profiles of the sangamon soil are the best developed soils

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

a 250 000 year record of lunette dune accumulation on the southern high plains usa and implications for past climates abstract a concentration of lake playa basins occurs on the southern high plains shp of northwest texas and eastern new mexico associated with these lake playas are lee side lunettes positioned on their southeast margins ranging in height from 1 5 to 10 m an osl dating program was applied to 30 samples from lunettes associated with large lakes and small playa basins samples were extracted from trenched dune sections or from deep cores earlier shp lunette investigations show depositional ages primarily in the late wisconsin and holocene this research extends the timing of lunette accretion to the middle pleistocene the earliest recorded deposition for these features the expanded chronology permitted investigation into dune morphology on nested lunettes built on contracting lake margins outer lunettes formed prior to inner dunes but simultaneous deposition occurred on downwind ridges as younger lee side dunes were constructed large lake lunettes were inactive during discreet shp pluvial episodes from early wisconsin to lgm conversely these lunettes accreted when climatic conditions promoted basin desiccation and aeolian deflation this suggests their mode of formation contrasts with lunette models recognized for other regions from post lgm to earliest holocene active lunette accretion occurred from 16 to 11 ka followed by a significant period of lunette construction during the mid holocene late holocene lunette deposition was interrupted by intervals of landscape stability lunette deposition between 1300s and 1700s corresponds with drought intervals recognized in tree ring records from adjacent regions recent lunette activity on the plateau is contemporary with the 1930 s dust bowl further insight into shp response to changing climatic conditions was given by comparing lunette depositional events with previous investigations on sedimentation intervals for draws lake playa basins and sand sheets

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

hf w chronometry of lunar metals and the age and early differentiation of the moon the use of hafnium tungsten chronometry to date the moon is hampered by cosmogenic tungsten 182 production mainly by neutron capture of tantalum 181 at the lunar surface we report tungsten isotope data for lunar metals which contain no 181 ta derived cosmogenic 182 w the data reveal differences in indigenous 182 w 184 w of lunar mantle reservoirs indicating crystallization of the lunar magma ocean 4 527 0 010 billion years ago this age is consistent with the giant impact hypothesis and defines the completion of the major stage of earth9s accretion

age genesis and paleoclimatic interpretation of the sangamon loveland complex in the lower mississippi valley u s a for more than a century the sangamon paleosol the sangamon has been an integral part of geologic and pedologic investigations in the central united states including the upper mississippi and lower missouri river valleys compositional pedologic micromorphologic stratigraphic and age data indicate that the prominent reddish paleosol developed in silt rich deposits of the lower mississippi valley from southernmost illinois to northwestern mississippi represents multiple periods of soil formation and is wholly or in part time equivalent to the sangamon of the central united states thermoluminescence data for localities where the sangamon developed in loess indicate that the primary period of loess deposition was from 190 to 130 ka oxygen isotope stage ois6 that loess deposition continued intermittently from 130 to 74 ka ois5 and that deposition was wholly or in part coeval with loveland loess deposition in the central united states beryllium 10 chemical and pedologic data indicate that in the lower mississippi valley 1 the sangamon represents a minimum time period of 60 80 k y 2 there were at least two periods of soil formation ca 130 90 ka and 74 58 ka ois4 and 3 rates of weathering and pedogenesis equaled or exceeded the net loess accumulation rate until at least 46 ka ois3 and resulted in development of a paleosol in the overlying basal roxana silt along a n s transect from southern illinois to western mississippi sangamon macroscopic characteristics as well as the micromorphology chemistry and mineralogy suggest a regional paleoclimate during periods of soil formation that 1 was warm to hot with a wider range in temperature precipitation and evapotranspiration than present 2 had seasonal to decadal or longer periods of drought and 3 had down valley southward trends of increasing temperature and precipitation and decreasing seasonality and variation in annual to decadal precipitation

modern sangamon and yarmouth soil development in loess of unglaciated southwestern illinois abstract the thebes section in unglaciated southwestern illinois contains a well preserved 500 kyr loess paleosol sequence with four loesses and three interglacial soils various magnetic mineralogical and elemental properties were analyzed and compared over the thickness of soil sola these proxies for soil development intensity have the following trend yarmouth geosol sangamon geosol modern soil quartz plagioclase zr sr and tio 2 na 2 o ratios were most sensitive to weathering frequency dependent magnetic susceptibility and anhysteretic remanent magnetization greatest in a horizons also correspond well with soil development intensity neoformed mixed layered kaolinite expandables suggestive of a warm humid climate were detected in the sangamon and yarmouth soil sola clay illuviation in soils was among the least sensitive indicators of soil development differences in properties among interglacial soils are interpreted to primarily reflect soil development duration with climatic effects being secondary assuming logarithmic decreases in weathering rates the observed weathering in the sangamon geosol is consistent with 50 kyr of interglacial weathering oxygen isotope stage 5 compared to 10 kyr for the modern soil oxygen isotope stage 1 we propose that the yarmouth geosol in the central midwest formed over 180 kyr of interglacial weathering including oxygen isotope stages 7 9 and 11

playa lake basins on the southern high plains of texas and new mexico part i hydrologic geomorphic and geologic evidence for their development playa lake basins of the southern high plains texas and new mexico may originate wherever water periodically can collect in a surficial depression they expand however by hydrologic and geomorphic processes including 1 dissolution of lithologic carbonates by infiltrating water 2 transport downward of fine grained clastic and organic material by the infiltrating ground water leading to continuing processes of oxidation and carbonate dissolution in the subsurface and 3 eolian removal of clastic material from the floor of playa lakes which at some sites appears to have deepened playa depressions evidence for largely hydrologic processes of playa basin development on the southern high plains includes 1 a geographic occurrence restricted to relatively flat areas of the high plains surface that have poorly developed fluvial drainage and which are underlain by generally unsaturated clastic and calcrete beds 2 a tendency to occur where water collects and infiltrates as along ephemeral streams and lineations suggestive of fracture systems and 3 hydrologic geochemical petrographic and bore hole data which suggest that recharge to the high plains aquifer is principally from playa lakes that various geochemical changes including carbonate dissolution and enhancement of secondary porosity occur as water moves downward through the unsaturated zone beneath playa lakes and that calcrete beds often are missing or significantly dissolved beneath playa floors

glacial and periglacial erosion of the appalachians abstract the marine 18 o record indicates that the first ice advance into the appalachians equivalent to that of the late wisconsin occurred in the pliocene at about 2 4 ma only periodic localized glacial and periglacial activity occurred in the northern appalachians from 2 33 to 0 85 ma after 0 85 ma middle to late pleistocene eight out of ten glaciations covered the northern appalachians and brought periglacial conditions to the southern appalachians during the last 850 000 years glaciation extended to the late wisconsin limit within the appalachians for 15 of the time and extended to the early wisconsin limit just north of the appalachians for 25 of the time pleistocene glacial erosion of the appalachians of 120 200 m is necessary to account for the estimated volume of pleistocene ocean sediment derived from the appalachians and the estimated volume of pliocene pleistocene glaciogenic ocean sediment derived from the entire laurentide ice sheet this amount of glacial erosion occurring over the maximum expectable duration of pliocene pleistocene ice cover of 247 000 years yields glacial erosion rates from 0 5 0 8 m ka 1 such depths of erosion by thick warm based ice streams were localized in the lowlands and estuaries of the northern appalachians in the maritimes the presence of thin cold based ice caused minimal erosion of uplands periglacial landforms and tundra boreal forest were distributed throughout the appalachian highlands and the northern coastal plain during the glacial maxima periglacial erosion of 0 15 0 30 m ka 1 near the ice in pennsylvania decline to 0 1 0 2 m ka 1 in the southern piedmont each cold period almost completely renewed the regolith by eroding slopes and filling valleys the cumulative effect of the eight to ten major cold events could have produced as much as a few ten s of meters of periglacial ridge top lowering during the pleistocene both estimated glacial and periglacial erosion rates greatly exceed estimated current fluvial erosion rates therefore glacial and periglacial processes should be considered the dominant processes in shaping the present appalachian landscape the northern appalachians may be evolving towards a form where the landscape provides just the shape necessary to permit the least work conveyance of the ice across the region during glacial maxima the southern appalachians may be evolving towards a form where the landscape provides just the hillslope form necessary to transport the debris provided by periglacial conditions

athens subepisode wisconsin episode non glacial and older glacial sediments in the subsurface of southwestern michigan usa abstract we describe the first complete sediment core to bedrock in southwestern michigan of a radiocarbon defined sequence of michigan subepisode marine oxygen isotope stage mis 2 glacial sediments athens subepisode mis 3 non glacial sediments and two older tills using sedimentological lithological and radiocarbon analyses organics from athens subepisode lacustrine and palustrine sediments yield radiocarbon ages of 41 920 42 950 and 43 630 45 340 and 43 500 14 c yr bp we propose the name port sheldon formation for these organic bearing sediments we interpret the underlying diamictons as two basal tills separated by glaciolacustrine fines the youngest till hemlock crossing till lying below the port sheldon formation is a dark gray gravel poor clay loam to loam with a mean kaolinite illite ratio of 0 98 0 04 the oldest till glenn shores till is a dark grayish brown gravel rich clay loam to sandy loam with mean kaolinite illite ratio of 1 22 0 08 about 130 water well records demonstrate that organic sediments and underlying diamictons are common in the subsurface of ottawa county these tills are likely illinois episode mis 6 or older but an ontario subepisode mis 4 age cannot be ruled out deep bedrock basins in lower michigan provide an untapped archive of pre michigan subepisode history

nonsynchronous episodic incision evidence of threshold exceedance and complex response as controls of terrace formation terrace sequences can represent regional or continental scale factors such as climatic fluctuations neotectonic activity and base level change however they can also reflect random incision events brought about by local scale geomorphic threshold exceedance and subsequent complex response this study explores the formative processes of three discontinuous but adjacent late pleistocene to late holocene step terrace sequences in southeastern australia correlation of river terrace fills was undertaken by comparing terrace remnants based on topography morphology sedimentology stratigraphy and chronology a geomorphic model of floodplain abandonment and terrace formation for this valley setting is presented most of southeastern australia has shown no evidence of tectonic uplift during the late quaternary bedrock bars on the hunter river isolate the study reach from downstream base level changes the nonsynchronous episodic behavior of incision events in this catchment strongly indicates that climate is not a dominant control on terrace formation with the exclusion of climatic fluctuations tectonic uplift and base level change as causes of incision catastrophic floods and the exceedance of geomorphic thresholds emerge as the dominant controls of terrace formation

osl dating of brazilian fluvial carbonates tufas using detrital quartz grains abstract robust chronologies for quaternary fluvial carbonate sediments tufas from brazil are still challenging we obtain optically stimulated luminescence osl ages of brazilian tufa deposits using the single aliquot regeneration sar dose protocol applied to single grains and multigrain aliquots of quartz extracted from tufa matrix additionally radiocarbon 14 c ages were obtained for the carbonate matrix and organic matter from tufas the methodology was applied in samples from tufa deposits in southwestern and southeastern regions with quaternary carbonate deposition equivalent doses distributions have overdispersion between 19 and 81 indicating that the studied samples comprise well bleached as well as poorly bleached sediments the quartz grains extracted from the studied tufas show an osl signal dominated by the fast component and reliable dose response curves with saturation doses 2 d 0 ranging from 35 to 210 gy most of the samples has low radiation dose rates 0 40 0 02 to 0 78 0 05 gy ka with variation in the water content due to compaction and matrix recrystallization being the major factors that could induce dose rate changes through time hard tufa samples with intense carbonate cementation show quartz osl ages from 51 9 4 8 to 150 3 35 9 years these ages are much older than the radiocarbon ages of the carbonate matrix and organic matter the osl ages of soft tufa samples related with the active fluvial system ranged from 0 8 0 1 to 5 5 0 4 years and are in the same interval of radiocarbon ages presented in the previous works we interpret that carbonate recrystallization or uptake of organic matter after tufa formation are responsible for the younger radiocarbon ages compared to quartz osl ages in the older tufa samples for these samples age differences vary up to tens of thousands years between deposition of quartz grains and the last episode of carbonate recrystallization or organic matter uptake consequently we believe that the obtained osl ages are the best estimates for the starting deposition time of the studied tufa samples

the application of radiocarbon age estimates to the dating of glacial sequences an example from the miami sublobe ohio u s a abstract despite the importance of dating glacial sequences little evidence has been available to highlight the stratigraphic issues associated with the interpretation of age analysis a compilation of radiocarbon data from the miami sublobe of the laurentide ice sheet provides a large enough data set more than 133 dates to identify at least two sources of error sample and unit variability and transportation problems analysis of different samples from the same stratigraphic level commonly differ by more than the reported one sigma error and 2 000 year differences do occur glacial entrainment and transportation emplace older organic material over younger in situ materials and this effect may also give age errors in the data set of up to 2 000 years at a minimum multiple radiocarbon ages from a sequence of units are necessary to assign a reliable age to events within a glacial sequence however representing multiple ages poses its own problems a graphical representation that combines the probability of each sample appears to be one solution

a rb sr and sm nd isotope geochronology and trace element study of lunar meteorite lapaz icefield 02205 abstract rubidium strontium and samarium neodymium isotopes of lunar meteorite lapaz icefield lap 02205 are consistent with derivation of the parent magma from a source region similar to that which produced the apollo 12 low ti olivine basalts followed by mixing of the magma with small amounts 1 2 wt of trace element enriched material similar to lunar kreep rich sample sau 169 the crystallization age of lap 02205 is most precisely dated by an internal rb sr isochron of 2991 14 ma with an initial 87sr 88sr at the time of crystallization of 0 699836 0 000010 leachable ree rich phosphate phases of lap 02205 do not plot on a sm nd mineral isochron indicating contamination or open system behavior of the phosphates excluding anomalous phases from the calculation of a sm nd isochron yields a crystallization age of 2992 85 initial e143nd 2 9 0 8 that is within error of the rb sr age and in agreement with other independent age determinations for lap 02205 from ar ar and u pb methods the calculated 147sm 144nd source ratios for lap 02205 various apollo 12 and 15 basalts and samples with strong affinities to kreep sau 169 nwa 773 15386 are uncorrelated with their crystallization ages this finding does not support the involvement of a common kreep component as a heat source for lunar melting events that occurred after crystallization of the lunar magma ocean

behavior of tungsten and hafnium in silicates a crystal chemical basis for understanding the early evolution of the terrestrial planets 1 the short lived isotopic system involving the decay of 182hf to 182w half life of 9 ma has been used to establish a time scale for planetary assembly and core formation the w isotope signature of lunar and martian basalts appears to be correlated to characteristics of their source on the moon the small amount of excess 182w is associated with basalts that may be derived from an ilmenite and clinopyroxene bearing mantle that was produced during late stages of lunar magma ocean crystallization on mars excess 182w is associated with a depleted mantle source our experimental measurements for the partitioning behavior of hf and w between silicates and melt suggest that the early fractionation of hf from w by phases such as ilmenite high ca clinopyroxene and garnet may be significant enough to account for the generation of all or part of the radiogenic w signatures in the mantle sources for these basalts the duration and nature of early mantle differentiation events on the moon and mars may be calculated by combining hf w fractionation with the extent of radiogenic w enrichment

tungsten isotopes in ferroan anorthosites implications for the age of the moon and lifetime of its magma ocean new w isotope data for ferroan anorthosites 60025 and 62255 and low ti mare basalt 15555 show that these samples contrary to previous reports lee d c et al 1997 science 278 1098 1103 lee d c et al 2002 earth planet sci lett 198 267 274 have a w isotope composition that is indistinguishable from kreep and other mare basalts this requires crust extraction on the moon later than 60 myr after cai formation consistent with 147sm 143nd ages for ferroan anorthosites the absence of 182hf induced 182w variations in the moon is consistent with formation of the moon at 62 10 90myr after cai formation that has been inferred based on the indistinguishable 182w 184w ratios of the bulk moon and the bulk silicate earth the uncertainties on the age of the moon and the age of the oldest lunar samples currently hamper a precise determination of the duration of magma ocean solidification and are consistent with both an almost immediate crystallization and a more protracted timescale of 100 myr

optical dating of tufa via in situ aeolian sand grains a case example from the southern high plains usa abstract precipitated carbonates commonly termed tufas or travertines maybe of considerable utility for palaeoenvironmental reconstruction their potential however for such reconstruction is commonly limited by difficulties associated with their absolute age control attempts to date such deposits via uranium series techniques have been complicated by their chemically open behaviour here we describe an alternative approach to date tufa deposits associated with ephemeral saline lake basins from the southern high plains usa we have optically dated sand grains of a mixed aeolian fluvial spring fed origin as the integrating dosimeter we assume that the grains are fully resetting prior to their incorporation into the tufa deposits and employ a time dependent disequilibrium dosimetric model to account for the build up of uranium series daughter products the approach was applied to a set of four samples with known stratigraphic association we obtained stratigraphically sensible optical ages ranging from 78 8 to 56 4 ka these data are consistent with existing palaeoenvironmental models of regional recharge

magmatic evolution of the moon although incomplete because of the imperfect and somewhat random sampling of rock types by the apollo and luna missions 1969 1976 the history of lunar magmatism has been reconstructed by numerous researchers over the past three decades these reconstructions have illustrated the continuous nature of lunar magmatism from 4 6 to approximately 2 0 ga and the large influence of early differentiation and catastrophic bombardment on lunar mantle dynamics magmatism and eruptive style in this review we group magmatism into multiple stages of activity based on sampled rock types and evaluate the models for each stage stage 1 is early lunar differentiation and associated magmatism partial melting of the moon soon after accretion was responsible for producing an anorthositic crust and a differentiated lunar interior the extent of lunar melting and mantle processing depends strongly on the mechanisms that induced melting estimates for the time over which melting and crystallization occurred range from tens to hundreds of millions of years stage 2 is the disruption of lunar magma ocean cumulates soon after the crystallization of most of the lunar magma ocean the cumulate pile experienced gravitational overturn this resulted in transport of late forming cumulates into the deep lunar mantle and mixing of magma ocean cumulates on a variety of scales stage 3 is the post magma ocean highland magmatism whereas the ferroan anorthositic crust was probably produced during the crystallization of a magma ocean the slightly younger mg suite and alkali suite plutonic rocks may have been generated by decompressional melting of early magma ocean cumulates during cumulate pile overturn a kreep and crustal signature was incorporated into these primitive basaltic magmas through assimilation near the base of the lunar crust or through melting of a hybridized mantle the alkali suite could represent either the differentiation products of mg suite parental magmas or a separate but contemporaneous episode of basaltic magmatism stage 4 is pre basin volcanism sample analysis and remote sensing data indicate that early lunar volcanism kreep basalts and high alumina basalts was contemporaneous with periods of highlands plutonism and catastrophic bombardment of the lunar surface the relationship between early stages of lunar volcanism and the contemporaneous plutonism is not clear the kreep basalts may be volcanic equivalents to both the mg suite and alkali suite stage 5 is the late remelting of magma ocean cumulates and eruption of mare basalts basin associated eruption of mare basalts occurred during and following the late stages of catastrophic bombardment this volcanic activity was possibly an extension of the thermal event that initiated pre basin volcanism mare basalts exhibit a wide range of composition resulting from near surface fractionation of chemically distinct primary basaltic magmas most likely mare basalts were produced by small to moderate degrees of partial melting of hybrid cumulate sources in the deep lunar mantle alternatively the mixed chemical signatures observed in many mare basalts may be interpreted as indicating assimilation of late stage evolved cumulates by melts produced deep in the cumulate pile the wide range of compositions exhibited by the mare basalts compared with earlier episodes of basaltic magmatism may reflect the thermal regime in the lunar mantle that limited the extent of partial melting and melt source homogenization

correlation of the eemian and the weichselian with deep sea oxygen isotope stratigraphy abstract the eemian interglacial was defined in the netherlands and is correlated all over northern europe it is now demonstrated that the eemian was the last interglacial in europe thus it is obvious that it should correlate with either the entire stage 5 in the deep sea oxygen isotope stratigraphy or with parts of stage 5 several observations prove that the eemian correlates with substage 5e the two other peaks in stage 5 correlates with the warm interstadials brorup and odderade in northern europe

a luminescence method for dating dirty pedogenic carbonates for paleoenvironmental reconstruction pedogenic carbonates are sensitive paleoclimatic and paleomonsoonal indicators stratigraphic markers and important sources and sinks in the global co budget establishing a chronology of such carbonates has been difficult due to their open system behaviour with respect to the radioisotopes used for dating a luminescence method for chronometric dating of carbonates is proposed which is less susceptible to post depositional changes and uses subtle changes in the radiation flux to a mineral grain on being carbonated this change is estimated by measuring luminescence signals of carbonated and uncarbonated mineral separates from the sediment strata and can be related to the age of the carbonate formation such ages of pedogenic carbonates from thar desert india conform with paleoclimatic and stable isotopic data and show that they formed in thar ca 17 ka 5 ka and 2 ka ago since the last glacial epoch

hf zr and ree partition coefficients between ilmenite and liquid implications for lunar petrogenesis hf zr and ree partition coefficients between ilmenite and coexisting liquid were determined under near lunar conditions ilmenite was synthesized at 1125 c under low oxygen fugacity fo2 10 12 4 from glass of a high ti mare basalt composition doped with 50 100 g g of ree and hf and 500 1000 g g of zr the partition coefficients d of ilmenite for hf and zr obtained by isotope dilution analysis are 0 41 and 0 33 respectively these values are significantly lower than those of ilmenite 3 0 and 1 8 respectively from a kimberlite megacryst fujimaki et al 1984a dree for the synthesized ilmenite are slightly smaller than those of ilmenite from the kimberlite megacryst and the dlu is 0 056 these results suggest that ilmenite may have played an important role in the lu hf evolution of lunar mare basalts using newly determined dlu and dhf for ilmenite the lu hf evolution or lunar cumulates and the coexisting magma was examined for several different crystallization sequences by a model calculation the lu hf variation trend of most high ti mare basalts is well explained by a small degree less than 5 of partial melting of the cumulates however a higher degree of partial melting is required to explain the variation of very low ti basalts green glass and apollo 12 low ti basalts apollo 15 low ti basalts could not be produced by simple partial melting but may require chromite crystallization as well

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

pristine lunar glasses criteria data and implications major element analyses of several thousand glasses from all of the apollo landing sites have resulted in the identification of 25 groups of pristine i e volcanic glass the nickel in these pristine glasses is shown to be indigenous not meteoritic contamination and to be correlated with mg the chemical data indicate that these glasses are consistently better candidates for primary magmas than the majority of crystalline mare basalts the pristine glasses support the view that assimilative processes ringwood and kesson 1976 involving two cumulate systems in the differentiated mantle operated during mare petrogenesis the reality of those assimilative interactions is evident by the occurrence of two linear arrays among the chemistries of the glasses data suggest that these cumulate components in the differentiated mantle persist for lateral distances of at least 1000 km and therefore appear to be products of a vast magma ocean that existed early in lunar history alternative hypotheses claiming that the highlands crust and mare source regions were produced by serial magmatism without a magma ocean have not yet considered all of the constraints derived from the pristine glasses

large lake basins of the southern high plains ground water control of their origin the origin of the 40 50 topographically large lake basins on the southern high plains of texas and new mexico has been an enigma previous workers have considered deflation or evaporite dissolution at depth and subsequent collapse as the most probable mechanisms however the eolian hypotheses have been unable to provide convincing arguments as to how the wind selectively erodes the thick deflation resistant calcrete caprock that is persistent over much of the southern high plains furthermore recent detailed studies on some of the basins show no significant evaporite dissolution at depth and neither mechanism offers a satisfactory explanation as to why the basins are almost universally associated with subsurface topographic highs or why they are absent where the high plains aquifer thickness exceeds 60 m we address these latter concerns and modify the deflation hypothesis by proposing that the calcrete caprock may never have been deposited in the areas now occupied by the basins the absence of calcrete deposition is proposed to have resulted from high water tables caused by an increase in hydraulic gradient where aquifers thinned above bedrock highs a high water table close to and or intersecting the surface prevents deposition of calcrete and thus the uncemented surface would be more susceptible to deflation than the surrounding calcrete covered areas after decline of the water table the rise in water table associated with bedrock highs is documented by numerical simulation using boundary conditions and hydrologic parameters representative of the southern high plains

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

new insights on illinoian deglaciation from deposits of glacial lake quincy central indiana abstract the deposits of glacial lake quincy overlie a diamicton associated with the classically defined illinoian limit in central indiana this lake covered at least 180 km 2 with a depth of 20 m and developed when the illinoian ice sheet retreated 15 km from the maximum limit causing lake impoundment against devore ridge overflow from glacial lake quincy eroded across the ridge forming a number of steeped walled outlets a section along mill creek exposes a sedimentologic sequence associated with glacial lake quincy from a subglacial diamicton to ice proximal to ice distal glacial lacustrine sediments we report new optical ages by multiple aliquot regenerative dose procedure for the fine grained rhythmically bedded sediments presumed to represent the lowest energy depositional facies dominated by suspension settling which maximized sunlight exposure in turn optical ages were determined on the fine grained 4 11 m polymineral and quartz fractions under infrared and blue excitation which yielded statistically similar ages optical ages span from ca 170 to 108 ka with the average of 16 optical ages indicating deglaciation at ca 135 ka generally coincident with marine oxygen isotope stage 6 to 5 transition and rise in global sea level

evidence for a naturally occurring post glacial acid sulfate weathering event in northwestern indiana usa abstract we review the evidence for a naturally occurring acid sulfate weathering event along the southern shore of lake michigan that was initiated 15 000 years bp before present at the close of the wisconsin glaciation the evidence includes 1 unproductive black soils that were encountered when settlers drained the wetlands in the area for agriculture 2 areas of soils that have anomalously low base saturation and are classified into ultic subgroups in a region where typic subgroups are the norm 3 unexpectedly high arsenic concentrations in streambed sediments of the kankakee river 4 pyrite jarosite and gypsum in cobbles from outwash deposits in the areas and 5 identification of a modern day unproductive black soil with a surface soil ph of 2 1 we propose that the acid sulfate weathering event was initiated when the lake michigan lobe of the wisconsin glacier eroded pyrite rich bedrock and deposited it in an outwash fan in front of the valparaiso moraine where sorting by water depleted calcium carbonate rich fine material relative to pyrite rich coarse material acid sulfate weathering on the higher landscape positions led to well drained soils depleted of calcium and magnesium and resulted in anomalously low base saturation and soils now classified into ultic subgroups calcium iron and sulfate moved to adjacent wetlands in the lower lying landscape positions where reduction of iron and sulfate resulted in the precipitation of secondary pyrite in the accumulating organic material drainage of these wetlands for agriculture beginning in the late 1800s exposed the secondary pyrite to oxygen and initiated a second cycle of acid sulfate weathering that led to some of the reports of unproductive black soils these soils developed extremely low ph upon drainage some of these highly acid conditions exist today arsenic in the original pyrite is moving through the landscape and is manifested in the unexpectedly high arsenic contents in streambed sediments of the kankakee river that drains the area this work shows that a whole landscape approach is necessary to understand how seemingly unrelated observations are all manifestations of a single natural phenomenon

ages of pristine noritic clasts from lunar breccias 15445 and 15455 abstract rb sr and sm nd isotopic studies were undertaken of two apollo 15 breccias 15445 and 15455 collected near spur crater on the apennine front seven pristine lithic clasts including four norites one anorthositic norite one troctolitic anorthosite and one spinel troctolite as well as a matrix sample of 15445 were analysed in addition a k ar age determination was also made for a plagioclase separate from a different anorthositic norite clast sm nd isotopic data of a pristine mg norite sample 15445 17 from the large white clast b of breccia 15445 yielded a precise internal isochron age of 4 46 0 07 ga for 147 sm 0 00654 ga 1 and an initial 143 nd 144 nd of 0 506058 0 000078 normalized to 148 nd 144 nd 0 24308 corresponding to an initial nd of 0 71 however sm nd isotopic results of another mg norite sample 15445 247 chipped from the same clast b about 1 cm away from 15445 17 yielded a significantly younger isochron age of 4 28 0 03 ga and a higher initial 143 nd 144 nd of 0 506246 0 000037 corresponding to an initial nd of 0 35 the sm nd data indicate that clast b is heterogeneous and contains at least two similar lithologies the rb sr isotopic systems were severely disturbed for both norites no useful isochron ages were observed the sm nd age and nd data for a 15 mg norites 15445 17 and 15445 247 a 17 mgnorite 78236 and two mg gabbronorites 73255 27 45 and 67667 are clearly resolved from each other four distinct parental magmas are required for derivation of these two major groups of mg suite noritic rocks the rb sr isotopic system of an anorthositic norite clast 15455 228 was slightly disturbed and isotopic data defined an isochron age of 4 59 0 13 ga for 87 rb 0 0139 ga 1 or 4 55 0 13 ga for 87 rb 0 01402 ga 1 the corresponding initial 87 sr 86 sr for the rock is 0 69899 0 00006 and is in satisfactory agreement with the luni value of nyquist et al 1974 the sm nd system is more disturbed than the rb sr system for this rock a tie line between whole rock samples and a pyroxene separate gives a sm nd age of 4 53 0 29 ga which is in nominal agreement with the rb sr isochron age the 39ar40ar age of a plagioclase separate of the rock has a weighted average value of 3 83 ga suggesting that the age was reset by the imbrium impact event probably the sm nd and rb sr systems of the clast were also partly reset by this event our age results indicate that some mg suite rocks are as old as ferroan anorthosite suite rocks furthermore age data of three major crustal rocks a mg suite a ferroan anorthosite suite and an evolved suite show that they all have variable ages these observations are difficult to explain by the magma ocean hypothesis alone petrogenetic processes such as production of mg suite rocks by serial magmatism walker 1983 of ferroan anorthosite suite rocks by multiple diapiric intrusions longhi and ashwal 1985 and evolved suite rocks by continuous magmatism meyer et al 1988 1989 probably all played a role these processes seem to be able to accommodate the wide ranges of ages and different origins observed for lunar crustal rocks

classification and environmental models of cool freshwater tufas abstract tufa deposits are common in the quaternary record facies developments are dependent upon localised carbonate precipitation generally these take the form of phytoherm build ups together with associated detrital deposits derived from disagragation of the former phytoherm cements differ from speleothems and floe calcite accumulations in being biologically mediated or modified this paper recognises the following five types perched spring line cascade fluviatile paludal and lacustrine facies each type is composed of distinctive constructional and detrital sediment associations these unique sediment combinations are the product of an interplay between angle of slope water discharge rate standing water bodies phytal and microbial colonization and ambient temperature the proposed models will be of value in the interpretation of ancient and partially exposed tufas

cosmogenic tungsten and the origin and earliest differentiation of the moon the decay of formerly live 182hf with a half life of 9 myr results in variations in the abundance of 182w in early solar system objects here we demonstrate that major excesses in 182w in some lunar samples are the results of cosmogenic additions apollo 17 high ti mare basalts yield high 182w 184w of up to w 11 1 even more extreme variations of up to w 22 1 are found for mineral separates although these lavas were erupted more than 500 myr after the start of the solar system the measured 182w excess in the separated minerals is correlated with their ta w confirming theoretical models that implicate the 181ta n 182ta 182w reaction from cosmic irradiation as the most likely cause in contrast olivine basalt 15555 which has a low cosmic ray exposure age displays no internal 182w variations and defines an w of 1 3 0 4 this is consistent with earlier conclusions that the moon formed about 50 myr after the start of the solar system the high ti mare basalt source with very high hf w has a w isotopic composition that is not grossly different from which a time limit of 70 myr after the start of the solar system can be inferred for the formation of ilmenite rich layers in the final stages of the lunar magma ocean

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

esr dating of spring deposited travertines abstract esr dating of spring deposited travertines is complicated by the presence of acid insoluble minerals which contain concentrations of radioactive elements that differ from those of the secondary calcite which is to be dated and the fact that most samples do not display esr signals which are suitable for dating however sampling of synsedimentarily formed crusts significantly increases the probability that the esr spectrum of the samples contains the signal at g 2 0007 which can be used for a dating attempt additionally the concentration of acid insoluble minerals in those crusts is normally negligible

the partitioning of trace elements between ilmenite ulvospinel armalcolite and silicate melts with implications for the early differentiation of the moon mineral melt trace element partition coefficients for a large number of trace elements zr hf ta nb v co cu zn sr ree sb sn mo cr w u th were determined experimentally for ilmenite fetio3 ulvospinel fe2tio4 minerals of the armalcolite solid solution fe mg ti2o5 the measured partition coefficients indicate that the high field strength elements zr hf nb and ta and some transition metals v cr co sn are moderately compatible in iron titanium oxides whereas other elements ree y sr u th mo sb and w are strongly incompatible the partition coefficients for u are always significantly higher than the th partition coefficients which makes fe ti oxides efficient in fractionating u from th our data also indicate that ilmenite and other iron titanium oxides are able to fractionate w from hf the latter of which is much more compatible this makes the iron titanium oxides very effective agents to influence hf w isotopic ratios during the evolution of the moon in addition we also present some trace element partition coefficients for iron and titanium bearing orthopyroxene

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

brunhes matuyama magnetic reversal dated at 790 000 yr b p by marine astronomical correlations abstract the presence of the brunhes matuyama magnetic reversal in deep sea core sediments makes possible an alternative to the usual k ar radioistope method of dating the reversal as found in rocks the alternative method uses correlations of northern hemisphere summer insolation with oxygen isotope ratios from tropical cores the latitude dependent insolation variations are calculated from planetary mechanics and thus provide a highly accurate astronomical time scale the insolation variations strongly influence glacial ice volume fluctuations that dominate the oxygenisotope ratio changes recorded in core sediments the summer half year insolation variations are identified with corresponding isotope ratio changes in cores from the present through glacial stage 20 misleading effects of discontinuities or major nonuniformities of sediment deposition are avoided by an analysis of the uniformity of v28 238 and v28 239 the principal cores studied and by comparisons with other cores the top section stages 1 to 10 of v28 238 is uniformly deposited and for this section an isotope ratio time scale is chosen that agrees with the thorium uranium date for the high sea stand of the last interglacial extreme over this interval major glacial extremes strong isotope ratio minima coincide consistently with major insolation minima at times of low orbital eccentricity in addition interstadials are directly associated with precessional insolation peaks and the envelope of isotope ratio peaks resembles the envelope of precessionally dominated insolation peaks the assumption that the glacial extremes depended similarly on insolation minima during stages 10 to 20 permits minor age shifts of strong isotope ratio minima in the two cores relative to ages based on uniform overal deposition to match the ages of low eccentricity insolation minima the age shifts reflect residual nonuniformities of deposition the validity of this matching procedure is supported by a resulting consistent identification of principal isotope ratio peaks with high and low latitude coincident insolation maxima the brunhes matuyama reversal is found intinterglacial stage 19 and is dated on the astronomical time scale at 790 000 5000 yr b p

lunar magma transport phenomena abstract an understanding of the most significant events during the first ga or so of lunar history global differentiation associated with a lunar magma ocean lmo and the later generation of about 107 km3 of mare basalts depends profoundly on magma transport dynamics lmo evolution is dominated by the characteristics of hard turbulent convection of a fluid undergoing phase change quench protocrust formed at the ocean surface in early times is repeatedly disrupted by bolide impact ocean body tides and associated crustal foundering during this epoch the ocean temperature is set by the balance between convective heat brought to the surface and brown body radiation from the surface at later times the convective flow is organized into a number of regimes from top to bottom these include conductive crustal lid a viscous sublayer an inertial core a lower viscous sublayer and a mushy cumulate region crystal settling and flotation is restricted to the viscous sublayer regions dilatancy pumping may prevent the efficient expulsion of intercumulus melt during cumulate formation typical velocities within the inertial region are of order 10 m s because late stage ti rich cumulates are dense relative to the earlier mg rich cumulates hyper to sub solidus convection tends to mix lmo crystallization products numerical simulations that account simultaneously for compositional and thermal buoyancy effects indicate a characteristic mixing time 200 ma statistical measures of mixing variance and spatial correlation length quantify the details of mixing the darcy percolative and vein drain models of melt extraction are briefly discussed because compaction lengths are small 102 m the rate of melt extraction is governed by the balance between melt buoyancy and darcy friction differential melt matrix velocities are of order 10 km ma for nominal values appropriate for mare basalt melt extraction from a heterogeneous mixed lmo source transport of magma through the lunar lithosphere via a connected crack network seems highly probable for the range of inferred discharge rates applicable for lunar mare volcanism lmv 103 to 107 m3 s typical fracture widths and ascent speeds are 10 1 to 50 m and 10 1 to 10 m s respectively a simple model is proposed to evaluate the extent of fractionation as magma traverses cold lunar lithosphere if apollo green glasses are primitive and have not undergone significant fractionation en route to the surface then mean ascent rates of 10 m s and cracks of widths 40 m are indicated lunar tephra and vesiculated basalts suggest that a volatile component plays a role in eruption dynamics the predominant vapor species appear to be co co2 and cos near the lunar surface the vapor fraction expands enormously and vapor internal energy is converted to mixture kinetic energy with the concomitant high speed ejection of vapor and pyroclasts to form lunar fire fountain deposits such as the apollo 17 orange and black glasses and apollo 15 green glass

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

quaternary continental stratigraphy and neocatastrophism abstract recent papers on pre quaternary stratigraphy have emphasized that the rock record represents only a small portion of geologic time with the gaps representing the majority of elapsed time quaternary continental stratigraphy also yields such evidence in abundance time between dated organic sites in glaciated areas is commonly depicted as filled by glacial ice yet there is much evidence of rapid sedimentation and most deposits could be laid down in short time spans non glaciated areas yield similar evidence because of gaps over which depositional rates are averaged calculated rates are often lower than they really are continental stratigraphy requires attention from many workers supported by much improved dating methods to establish time spans and gaps for the rock record

loess of the upper mississippi valley driftless area abstract loess of the driftless area includes four distinct late quaternary lithostratigraphic units the wyalusing new loveland roxana and peoria formations erosion has removed parts or all of the pre late wisconsian loess at many sites these formations consist largely of loess and retransported loess that typically occurs on uplands terraces and valley margins in the region the oldest widespread formation probably 125 000 yr b p is here formally named the wyalusing formation the three younger formations correlate with the loveland probably 125 000 yr b p roxana 55 000 25 000 yr b p and peoria 25 000 12 000 yr b p loesses recognized elsewhere in the midcontinental united states the soil stratigraphic morphology of the wyalusing loveland and roxana peoria couplets appears to represent two distinct loess sedimentation sequences related to major expansion and contraction of the laurentide ice sheet during oxygen isotope stages 6 and 3 2 respectively the occurrence frequency of loess units is inversely related to age illustrating the erosional nature of the driftless area landscape the occurrence of four loess units at some sites in driftless area stratigraphic sections corroborates loess stratigraphy along the length of the mississippi valley where typically not more than four or five loess units are found and they represent only the late and middle pleistocene

basaltic magmatism on the moon a perspective from volcanic picritic glass beads abstract it is widely accepted that basaltic magmas are products of partial fusion of periodotite within planetary mantles as such they provide valuable insights into the composition structure and processes of planetary interiors those compositions which approach primary melt compositions provide the most direct information about planetary interiors and serve as a starting point to understand basaltic evolution within the collection of lunar samples returned by the apollo and luna missions are homogeneous picritic glass beads of volcanic origin these picritic glasses are our closest approximations to primary magmas as such these glass beads provide a unique perspective concerning the origin of mare basalts the characteristics of the lunar interior and processes in the early differentiation of the moon we have obtained trace element data for these picritic glasses using sims techniques these data and literature isotopic and experimental data on the picritic glasses are placed within the framework of mare basaltic magmatism the volcanic glasses are very diverse in their trace element characteristics for example they have a wide range of ree pattern shapes and concentrations like the crystalline mare basalts all picritic glasses have a negative eu anomaly unlike the crystalline mare basalts there is little correlation between the size of the eu anomaly and overall ree concentrations trace element differences among the various glasses suggests that a kreep component was incorporated into their mantle source this implies large scale mixing of the lunar magma ocean derived cumulate pile subtle differences among glasses suggest that local mixing of sources may also have been an important process preservation of subtle chemical differences in the picritic glasses and crystalline basalts may be interpreted as indicating that they were produced by small to moderate degrees of partial melting and that the lunar mantle did not experience extensive melting during episodes of mare volcanism several lines of evidence are consistent with the view that the picritic glasses were derived from mantle sources that were compositionally distinct from the sources for crystalline mare basalts these are parallel but no common liquid lines of descent chemical differences between picritic glasses and the more primitive crystalline mare basalts experimental studies indicating that the picritic glasses are multiply saturated at depths greater than that of the mare basalts differences in lead isotopic data and the mode of eruption i e fire fountaining for glass beads these data also provide circumstantial evidence that suggests that the picritic glasses were derived from a source somewhat more volatile rich than that of the mare basalts several petrogenetic models are suggested by the trace element characteristics of the picritic glasses 1 1 partial melting of heterogeneous lunar mantle at depths greater than 300 km to produce the parental magmas picritic for both the mare basalts and picritic glasses picritic magmas represented by glass beads were erupted to the surface with small degrees of fractional crystallization while mare basalts were produced by larger degrees of fractional crystallization 15 30 of similar but not identical picritic magmas 2 2 picritic magmas represented by the glass beads were generated at depths greater than 400 km in a volatile enriched relative to the mare basalt source heterogeneous mantle while mare basalts are fractional crystallization products of picritic magmas generated at depths of less than 400 km 3 3 the picritic magmas represented by the glass beads represent polybaric melting that initiated at depths of at least 1000 km a primitive mantle component or less processed cumulate mantle components may have been involved in the generation of the picritic glasses in any of these models

thermal and magmatic evolution of the moon as with all science our continually developing concepts of lunar evolution are firmly tied to both new types of observations and the integration of these observations to the known pool of data this process invigorates the intellectual foundation on which old models are tested and new concepts are built just as the application of new observational tools to lunar science in 1610 galileo s telescope and 1840 photography yielded breakthroughs concerning the true nature of the lunar surface the computational and technological advances highlighted by the apollo and post apollo missions and associated scientific investigations provided a new view of the thermal and magmatic evolution of the moon 1 1 pre apollo view of the thermal and magmatic evolution of the moon many of the early views of the moon manifested in mythology and art throughout the world were primarily tied to lunar and terrestrial cycles and the relationships between the sun and the moon prophetically myths involving the lunar deities mwuetsi from zimbabwe and coyolxauhqui from mexico told of rather violent or catastrophic events in which the moon was expunged from the earth numerous ancient scientific observations were made about the nature of the moon ranging from those uncovered in early neolithic sites that correctly identified mare crisium and mare humorum to the insights made by greek philosophers such as anaxagoras ca 500 428 b c and democritus ca 460 370 b c who attached terrestrial analogues to its character stone mountains with the advent of the telescope 1610 and photography 1840 as scientific tools for lunar exploration semiquantitative data could be collected that would provide an intellectual foundation for scientific interpretation initially modern terrestrial geological analogs were extended to the moon lunar highlands volcanic craters seas combined with the rigors of computational modeling these observational data were extended to predict the original thermal state of the moon and its thermal and magmatic history its proximity to the earth

ice wedge casts and relict patterned ground in central illinois and their environmental significance abstract sediment features and soil patterns indicate that permafrost developed beyond the late wisconsinan woodfordian ice margin in illinois vertical wedge shaped bodies in woodfordian glacigenic deposits and buried by woodfordian loess are interpreted to be ice wedge casts large scale patterned ground common on the late wisconsinan drift plain and on the illinoian drift plain to the south and west also is interpreted to be the result of ice wedge formation permafrost extended to about 38 30 n latitude and formed during the interval from about 21 000 to 16 000 yr b p formation and degradation of permafrost was time transgressive directly related to the ice marginal climate and probably restricted temporally to less than 1000 years at a site the following environmental conditions are suggested near the ice margin mean annual ground temperature 3 c mean annual air temperature 6 2 c less precipitation than modern particularly in winter strong and likely dry wind systems and relatively open vegetation with few woody plants

lacustrine sediments in porter cave central indiana usa and possible relation to laurentide ice sheet marginal positions in the middle and late wisconsinan abstract proglacial lakes formed in the late quaternary with the advance of the laurentide ice sheet into mill creek valley of central indiana these lakes backfilled into the mouth of porter cave deposited organic matter and thinly bedded silty sediment that conforms to the underlying cave floor and shelves optical and radiocarbon ages indicate that deposition of fine grained sediments into porter cave occurred in two proglacial lake phases during marine oxygen isotope stage mis 3 ca 40 to 30 cal ka and mis 2 ca 27 to 18 cal ka the latter phase is consistent with other proxy evidence for ice sheet extent and timing we contend that the ice sheet lobe that dammed a proglacial lake during mis 3 in central indiana was 7 km behind the last glacial maximum limit based on current topography this conclusion is in opposition to previous assessments which infer ice free conditions in central illinois and central indiana ca 130 to 25 ka the paucity of mis 3 deposits may be due to erosion by the more extensive mis 2 ice sheet with glacial lacustrine sediments preserved in the protective confines of porter cave this outlet lobe in central indiana may be short lived and reflects a variable response of lobes of the laurentide ice sheet during mis 3 with expansion possibly associated with cooling during heinrich event 4

w hf isotope abundances and the early origin and evolution of the earth moon system abstract the decay of the short lived isotope 182hf to the isotope 182w early in solar system history provides clues to the origin and evolution of the earth and moon current time scales for the formation of proto planets in the solar system require early accretion of the proto earth accompanied with core formation which should lead to non chondritic radiogenic w isotope ratios 182w 184w in the earth s mantle surprisingly the observed ratio of 182w 184w in the earth s mantle is chondritic which requires special circumstances to explain halliday et al 1996 lee and halliday 1997 lee et al 1997 previous explanations include delayed core formation until 50 m yrs after the origin of the solar system or a very long time scale for accretion of the earth halliday et al 1996 lee and halliday 1997 lee et al 1997 in this paper we explore models consistent with the early formation of the proto earth a giant impact origin of the moon and substantial additional accretion to the earth following the impact the post impact processes responsible for the chondritic w isotopes may include late core mantle equilibration in the hot earth following the giant impact and later metal segregation and accretion in contrast to the earth various igneous rocks on the moon exhibit non chondritic positive anomalies in the ratio of 182w 184w the explanation for the lunar samples with chondritic w isotopes may also involve late metal segregation and accretion as in the earth the positive anomalies in lunar samples may be derived in part or whole through cosmogenic processes on the lunar surface hf w fractionation during core formation or hf w fractionation during lunar magma ocean crystallization if the latter the positive anomaly places constraints on the early differentiation of the lunar mantle and the duration of the crystallization of the lunar magma ocean the observed w hf systematics are best explained if the w anomalies are carried by late crystallizing ilmenite and high ca pyroxene which is later mixed into the source regions of the mare basalts in this model the crystallization of the magma ocean must occur in less than 40 million years this rapid crystallization implies that the very early lunar crust was not as stable and insulating as previously suggested and that the fundamental change from magmasphere to serial magmatism processes occurred very early in the evolution of the moon

re evaluating 142nd 144nd in lunar mare basalts with implications for the early evolution and bulk sm nd of the moon abstract the moon likely accreted from melt and vapor ejected during a cataclysmic collision between proto earth and a mars sized impactor very early in solar system history the identical w o k and cr isotope compositions between materials from the earth and moon require that the material from the two bodies were well homogenized during the collision process as such the ancient isotopic signatures preserved in lunar samples provide constraints on the bulk composition of the earth two recent studies to obtain high precision 142nd 144nd ratios of lunar mare basalts yielded contrasting results in one study after correction of neutron fluence effects imparted to the nd isotope compositions of the samples the coupled 142nd 143nd systematics were interpreted to be consistent with a bulk moon having a chondritic sm nd ratio rankenburg k brandon a d and neal c r 2006 neodymium isotope evidence for a chondritic composition of the moon science 312 1369 1372 the other study found that their data on the same and similar lunar mare basalts were consistent with a bulk moon having a superchondritic sm nd ratio boyet m and carlson r w 2007 a highly depleted moon or a non magma origin for the lunar crust earth planet sci lett 262 505 516 delineating between these two potential scenarios has key ramifications for a comprehensive understanding of the formation and early evolution of the moon and for constraining the types of materials available for accretion into large terrestrial planets such as earth to further examine this issue the same six lunar mare basalt samples measured in rankenburg et al rankenburg k brandon a d and neal c r 2006 neodymium isotope evidence for a chondritic composition of the moon science 312 1369 1372 were re measured for high precision nd isotopes using a multidynamic routine with reproducible internal and external precisions to better than 3 ppm 2 for 142nd 144nd ratios the measurements were repeated in a distinct second analytical campaign to further test their reproducibility evaluation of accuracy and neutron fluence corrections indicates that the multidynamic nd isotope measurements in this study and the 3 in boyet and carlson boyet m and carlson r w 2007 a highly depleted moon or a non magma origin for the lunar crust earth planet sci lett 262 505 516 are reproducible while static measurements in the previous two studies show analytical artifacts and cannot be used at the resolution of 10 ppm to determine a bulk moon with either chondritic or superchondritic sm nd ratios the multidynamic data are best explained by a bulk moon with a superchondritic sm nd ratio that is similar to the present day average for depleted morb hafnium isotope data were collected on the same aliquots measured for their 142nd 144nd isotope ratios in order to assess if the correlation line for 142nd 143nd systematics reflect mixing processes or times at which lunar mantle sources formed based on the combined 142nd 143nd 176hf obtained we conclude that the 142nd 143nd correlation line measured in this study is best interpreted as an isochron with an age of 229 24 20ma after the onset of nebular condensation the uncertainties in the data permit the sources of these samples to have formed over a 44 ma time interval these new results for lunar mare basalts are thus consistent with a later sm nd isotope closure time of their source regions than some recent studies have postulated and a superchondritic bulk sm nd ratio of the moon and earth the superchondritic sm nd signature was inherited from the materials that accreted to make up the earth moon system although collisional erosion of crust from planetesimals is favored here to remove subchondritic sm nd portions and drive the bulk of these bodies to superchondritic in composition removal of explosive basalt material via gravitational escape from such bodies or chondrule sorting in the inner solar system may also explain the compositional features that deviate from average chondrites that make up the earth moon system this inferred superchondritic nature for the earth similar to the modern convecting mantle means that there is no reason to invoke a missing subchondritic reservoir to mass balance the earth back to chondritic for sm nd ratios however to account for the subchondritic sm nd ratios of continental crust a second superchondritic sm nd mantle reservoir is required

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

age and origin of the moon the age and origin of the moon have been studied with the use of the recently developed short lived hafnium tungsten chronometer 182hf 182w half life of nine million years the tungsten isotopic compositions of 21 lunar samples range from chondritic to slightly radiogenic w 0 50 0 60 to 6 75 0 42 this heterogeneity may have been inherited from material excavated from earth and the putative impactor but it is more likely the result of late radioactive decay within the moon itself in this case the moon formed 4 52 to 4 50 billion years ago and its mantle has since remained poorly mixed

nb zr fractionation on the moon and the search for extinct 92nb a comprehensive zr isotopic study was conducted on eleven lunar basalts and highland rocks to search for evidence of the extinct nuclide 92nb which decays to 92zr with a half life of 36 ma internal isochrons were determined for two early highland rocks 77215 and 60025 no resolvable zr isotopic variations were detected in this wide range of lunar samples and thus there is no evidence for the former existence of live 92nb on the moon the nb zr ratios of lunar ilmenites and bulk rock samples vary by only a factor of two to three relative to the chondritic nb zr ratio no evidence for larger nb zr fractionation was found this limited fractionation and late isotopic closure of the source region prevents the formation of measurable 92zr anomalies in high ti mare basalts as a consequence it is not possible to draw conclusions from the 92nb 92zr chronometer about the timing of early lunar differentiation and to constrain the role of ilmenite in the source region of high ti mare basalts however the fractionation is still sufficient to deduce an upper limit for the initial 92nb 93nb ratio of the solar system of 5 10 4

volatile and siderophile element geochemistry of the moon a reappraisal abstract lunar volcanic glasses lvg contain high abundances of many volatile elements as compared to mare basalts whereas the latter were derived from devolatilized source regions in the outer few hundred kilometers of the moon lvg are believed to come from a globally extensive source region at greater depths which is relatively rich in volatile components abundances of volatile elements in lvg and their source regions are reviewed and in many cases found to resemble those in the earth s mantle likewise siderophile element abundances including the highly siderophile elements ir os au and re are similar in the earth s mantle and in the source regions of lvg the close geochemical similarity between the lvg source region i e the lunar lower mantle and the terrestrial mantle constitutes strong evidence that protolunar material was derived primarily from the earth s mantle since highly siderophile elements are believed to have been added to the earth as an oxidised veneer at the end of its accretion and then convectively mixed into the mantle the removal of protolunar material from the earth must have occurred after this late addition which may represent carbonaceous chondritic or cometary material from the outer solar system it is widely believed that the moon was formed by the impact of a giant planetesimal on the protoearth the planetesimal is presumed to have formed in the inner solar system and to have differentiated internally into a mantle and core numerical modelling of the giant impact shows that most of the material now in the moon would have been derived from the mantle of the impactor however this is contradicted by the geochemical evidence provided by lvg which implies that the moon is composed mainly of material derived from the terrestrial mantle a possible answer to this dilemma is provided by the observation that the lvg source region reflects the geochemistry of the late oxidised veneer which accreted on the earth this suggests that protolunar material may have been removed from the earth s mantle by impacts from one or more high velocity 30 km s planetesimals composed mainly of ices and derived from the outer solar system the volatiles from the impacting planetesimals were lost after these collisions the impacts probably ejected material from the earth s mantle as jets of molten matter which was rapidly quenched thereby retaining a large proportion of its terrestrial volatile inventory

timing of fluvial terrace formation and concomitant travertine deposition in the upper sutlej river tirthapuri southwestern tibet and paleoclimatic implications abstract travertines are carbonates precipitated from hydrothermal springs and are relatively common on the tibetan plateau and occur along tectonically active faults the karakoram fault system is an active strike slip fault that extends from the pamir into southwestern tibet where it controls the course of the upper sutlej river and the occurrence of several hydrothermal springs including the tirthapuri hot springs multiple fluvial terraces that are partly capped by travertine are preserved in the tirthapuri area four main fluvial terrace levels labelled as t1 to t4 with increasing height above river were identified and several meter thick travertine platforms occur on the current river level as well as the t2 and t3 terraces sedimentological and petrographic observations suggest that the travertine platforms were deposited on active floodplains of the paleo and modern sutlej river and preserved from fluvial erosion because travertine precipitation was immediately followed by vertical river bed incision and thus terrace abandonment results of 230th u in combination with luminescence dating show that the deposition of travertine platform and river incision that led to the formation of t3 terrace 93 m above the sutlej took place at ca 127 5 ka the development of terrace t2 and overlying travertine platform 28 m above the sutlej occurred between ca 10 0 and 8 8 ka fluvial incision has arrived at the modern level at least ca 0 2 ka ago both the travertine deposition and major river incision are likely triggered by the intensified indian summer monsoon and are linked to phases of maximum monsoon strength during strong monsoon phases a large quantity of moisture is transported into southwestern tibet activating hot springs and thus travertine precipitation facilitating fluvial incision and stripping off sediments from the regional hill slopes at least over the last glacial cycle we suggest that the tirthapuri travertine and associated fluvial incision are sensitive indicators of peak monsoonal activity and can thus provide valuable insights into past climate change and climate driven landscape evolution on the southwestern tibetan plateau comparison of our findings with published data further suggests that monsoon controlled fluvial aggradation and incision during the early holocene is synchronous in southwestern tibet and the adjacent sector of the himalayan orogen north western sub to high himalaya

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

geology of the moscoviense basin 1 the moscoviense basin on the northern portion of the lunar farside displays topography with a partial peak ring in addition to rings that are offset to the southeast these rings do not follow the typical concentric ring spacing that is recognized with other basins suggesting that they may have formed as a result of an oblique impact or perhaps multiple impacts in addition to the unusual ring spacing present the moscoviense basin contains diverse mare basalt units covering the basin floor and a few highland mafic exposures within its rings new analysis of previously mapped mare units suggests that the oldest mare unit is the remnant of the impact melt sheet the moscoviense basin provides a glimpse into the lunar highlands terrain and an opportunity to explore the geologic context of initial lunar crustal development and modification

osl ages on glaciofluvial sediment in northern lower michigan constrain expansion of the laurentide ice sheet abstract we report new ages on glaciofluvial outwash sediment from a large upland in northern lower michigan the grayling fingers the fingers are cored with 150 m of outwash which is often overlain by the informal blue lake till of marine isotope stage mis 2 they are part of an even larger interlobate upland comprised of sandy drift known locally as the high plains the ages determined using optically stimulated luminescence osl methods indicate that subaerial deposition of this outwash occurred between 25 7 and 29 0 ka probably associated with a stable mis 2 ice margin with mean ages of ca 27 ka these dates establish a maximum limiting age of ca 27 ka for the mis 2 late wisconsin advance into central northern lower michigan we suggest that widespread ice sheet stabilization at the margins of the northern lower peninsula during this advance and later during its episodic retreat partly explains the thick assemblages of coarse textured drift there our work also supports the general assumption of a highly lobate ice margin during the mis 2 advance in the great lakes region with the fingers an interlobate upland remaining ice free until ca 27 ka