floodplain aggradation and pedogenesis in a semiarid environment alluvial valley fills in the upper republican river basin southwestern nebraska provide evidence for processes of aggradation and pedogenesis on semiarid cut and fill floodplains sheetflow deposition on unchanneled valley floors represents an important mechanism of valley aggradation sheetflow deposits contain parallel to sub parallel laminae and discontinuous lobate sedimentary structures rates of sediment deposition on cut and fill floodplains strongly determine the degree to which pedogenic features develop within aggrading alluvium three pedofacies common to semiarid alluvial deposits correspond with increasing aggradation rates 1 cumulic soils 2 multiple buried soils and 3 no pedogenic features radiocarbon age determinations from alluvial fills indicate that floodplain aggradation greater than approximately 0 5 cm year 1 limits soil formation this represents a threshold rate of pedogenic assimilation floodplain soils formed under aggradation rates lower than this exhibit a strong positive relationship between aggradation rate and total caco3 percent and a negative relationship between aggradation rate and organic carbon percent recognizing the associations between pedogenic sedimentologic features and floodplain aggradation rates can help interpret past rates of sediment transport storage and deposition

middle pleistocene climate and hydrological environment at the boxgrove hominin site west sussex uk from ostracod records the sediments of the slindon formation at the junction of the chalk south downs and the west sussex coastal plain as revealed and studied at boxgrove contain evidence for early middle pleistocene environments in southern england around half a million years ago the archaeological importance of the deposits is attested to by the recovery of stone and organic tools butchered fauna and fossil hominin remains we combine palaeoecological and geochemical analyses of ostracods from the coastal plain deposits to reconstruct the climate and environment at one period of the hominin occupation the stratigraphy of our study area is indicative of a terrestrial environment surrounding a small lake or pond ostracod assemblages from the sediments indicate that the ponds were shallow but permanent and fed by groundwater and springwater however the species alone cannot confirm that these ponds were completely fresh application of mutual climatic range mcr techniques shows that summer temperatures were similar to present day values and winter temperatures were probably colder whereas mean annual air temperature was similar to present or perhaps slightly cooler trace element and strontium isotope analyses of ostracods from the sediments support the conclusion that the ponds were fed largely by fresh groundwater derived from the chalk although there may have been a minor seawater input the carbon isotope ratios of the ostracod shells are consistent with a groundwater source although they also indicate that the dissolved inorganic carbon most likely did not reach equilibrium with atmospheric carbon dioxide suggesting that the ponds had short residence time the combination of palaeotemperature estimates with oxygen isotope values from ostracod shells allowed us to reconstruct the oxygen isotope ratio of the pond water which was close to the value of early middle pleistocene precipitation at this site values were similar to present day suggesting that there may have been a change in seasonality or precipitation source since the mean air temperatures might have been lower

pb isotopic evidence for an early enriched crust on mars abstract martian meteorite nwa 7533 is a regolith breccia that compositionally resembles the martian surface measured by orbiters and landers nwa 7533 contains monzonitic clasts that have zircon with u pb ages of 4 428 ga the pb isotopic compositions of plagioclase and alkali feldspars as well as u pb isotopic compositions of chlorapatite in the monzonitic clasts of nwa 7533 have been measured by secondary ion mass spectrometry sims the u pb isotopic compositions measured from the chlorapatite in nwa 7533 yield an age of 1 357 81 ga 2 the least radiogenic pb isotopic compositions measured in plagioclase and k feldspar lie within error of the 4 428 ga geochron these data indicate that the monzonitic clasts in nwa 7533 are a product of a differentiation history that includes residence in a reservoir that formed prior to 4 428 ga with a value 238 u 204 pb of at least 13 4 1 7 2 and a value 232 th 238 u of 4 3 this value is more than three times higher than any other documented martian reservoir these results indicate either the martian mantle is significantly more heterogeneous than previously thought value of 1 14 vs 1 5 and or the monzonitic clasts formed by the melting of martian crust with a value of at least 13 4 therefore nwa 7533 may contain the first isotopic evidence for an enriched differentiated crust on mars

isotopic and ree studies of lunar basalt 12038 implications for petrogenesis of aluminous mare basalts we report sr nd and sm isotopic studies of lunar basalt 12038 one of the so called aluminous mare basalts a precise internal rb sr isochron yields a crystallization age of 3 35 0 09 ae and initial87sr 86sr 0 69922 2 2 error limits 1ae 109 years 87rb 0 0139ae 1 an internal sm nd isochron yields an age of 3 28 0 23ae and initial143nd 144nd 0 50764 28 present day143nd 144nd is less than the chondritic value i e nd 0 2 3 0 4 where nd is the deviation of143nd 144nd from chondritic evolution expressed as parts in 104 at the time of crystallization nd 3 2ae 1 5 0 6 we have successfully modeled the evolution of the sr and nd isotopic compositions and the ree abundances within the framework of our earlier model for apollo 12 olivine pigeonite and ilmenite basalts the isotopic and trace element features of 12038 can be modeled as produced by partial melting of a cumulate mantle source which crystallized from a lunar magma ocean with a chondrite normalized ree pattern of constant negative slope chondrite normalized la yb 2 2 for this hypothetical magma ocean pattern a plot of i sr versus nd for the apollo 12 basalts clearly shows the influence of varying proportions of olivine clinopyroxene orthopyroxene and plagioclase in the basalt source regions a small percentage of plagioclase 5 in the 12038 source apparently is responsible for low i sr and nd in this basalt aluminous mare basalts from mare crisium luna 24 and by inference mare fecunditatis luna 16 occupy locations on the i sr nd plot similar to that of 12038 implying that some basalts from three widely separated lunar regions came from plagioclase bearing source regions a summary of model calculations for mare basalts shows a record of lunar mantle solidification during the period when ree abundances in the lunar magma ocean increased from 20 chondritic to 100 chondritic although there is a general trend from olivine to clinopyroxene dominated source regions with progressive magma ocean evolution significant mineralogical heterogeneities in mantle composition apparently formed at any given stage of evolution as evidenced in particular by the three apollo 12 magma types

further evidence for a low u pb source in the moon uthpb smnd and arar isotopic systematics of lunar meteorite yamato 793169 abstract the coarse grained lunar meteorites yamato 793169 and asuka 881757 represent a new type of low ti mare basalt this paper reports the results of a u th pb sm nd and ar ar isotopic study of yamato 793169 performed as part of a consortium studies of lunar basaltic meteorites the isotopic study was carried out on a small sample 100 mg so that only three density fractions could be separated these fractions were leached with dilute acid in order to eliminate terrestrial pb contamination however the leaching procedure did not completely remove this contamination in some fractions and also apparently caused a fractionation of elements u th pb due to preferential leaching effects producing a secondary disturbance of the systematics furthermore the ar ar analyses indicate that the isotopic systematics in this meteorite might have been disturbed sometime later than 750 ma for these reasons the ages obtained using different isotopic systems disagree with each other and a precise formation age could not be obtained for this meteorite however using what results there are two reasonable interpretations can be made 1 the sm nd system yielded an age of 3 4 ga that could be interpreted as the formation age assuming that this system is possibly the least disturbed during the metamorphic event s that this meteorite experienced at least once and that all other isotopic systems and their corresponding ages were disturbed and 2 the u pb system yielded a nearly concordant age of 3 8 ga that could be interpreted as the formation age and the sm nd isotopic systematics were somehow disturbed we prefer the second interpretation for the reasons discussed below on a concordia diagram the cdt canon diablo troilite corrected u pb isotopic data yield a discordia line similar to the lunar catastrophic array indicating that the source of the meteorite formed during early lunar differentiation 4 4 ga and that the basalt was generated near 3 9 ga total ar ar age on plagioclase is 3 26 ga which seems to be too old if the formation age is 3 4 ga because low temperature fractions lost large amounts of radiogenic 40 ar during the late thermal event if we assume a formation age of 3 8 ga the estimated source 238 u 204 pb is 21 6 3 5 and nd is 3 9 0 3 these results indicate that the source of yamato 793169 is more depleted than apollo 12 and 15 lt basalts but less depleted than asuka 881757 therefore yamato 793169 may represent a new type of lt or vlt like mare basalt that is different from asuka 881757 the wide variety of lead and neodymium isotopic characteristics among lt and vlt mare basalts indicate that the lunar mantle was very heterogeneous with respect to trace element abundances

origin of lead from green glass of apollo 15426 a search for primitive lunar lead a major obstacle in lunar u pb chronology is the elusiveness of the primary pb isotopic composition and u pb ratio and therefore the pb evolution for the early history of the moon in an attempt to seek the primitive lunar pb isotopic composition green glass from lunar clod 15426 49 was studied for u th pb systematics because it is extremely mg rich and known to be the most primitive among sampled lunar volcanic rocks green glass and yellow impact glass were handpicked washed with water then washed in an acid mixture 0 3 n hbr 0 2 n hf and the washes and residues were analyzed in contrast to the pb from apollo 17 orange glass pb from the surface of the green glass spherules is totally different from that of the spherule interior but is similar to lunar surface lead data for the interior pb yield a 207pb 206pb age of 3 41 ga because of the low pb concentration and high u pb ratio observed for the interior the initial pb was poorly defined nevertheless the data indicate that lunar pb evolved in an environment with 238u 204pb 19 55 which is considerably lower than those for mare basalts around 300 but higher than values for the earth 6 8

timing of crystallization of the lunar magma ocean constrained by the oldest zircon the primitive moon was covered with a thick layer of melt known as the lunar magma ocean whose crystallization resulted in the moon s surface as it is observed today dating of the oldest zircon so far in lunar rocks indicates that much of the magma was probably crystallized within 100 million years of the moon s formation

origin and evolution of lunettes on the high plains of texas and new mexico lunettes isolated dunes on the lee side of playa basins are common landforms on the southern high plains of northwest texas and eastern new mexico the dunes contain calcareous 15 40 caco3 sandy loam or loamy sand with minor amounts of sepiolite deposited 25 000 800014c yr b p and derived by deflation of lacustrine carbonate in the basins the dunes also contain low carbonate 0 15 caco3 sand or loamy sand that was deposited 25 000 15 000 yr b p and 8000 5000 yr b p and was derived by deflation that created the basins or deflated from sand deposited in the basins buried soils are common in the lunettes a bk profiles characterize soils formed in the calcareous sandy loam the sandy low carbonate sediments contain a bt profiles in the oldest sand of some dunes and a bw a bt or a btk in the early and middle holocene sand the dune stratigraphy combined with carbon isotope data derived from dated a horizons in lunettes suggests the following scenario for the southern high plains the lunettes began forming as low carbonate sand dunes in the late pleistocene as playa basins were formed or deepened by wind erosion the erosion repeatedly alternated with stability the environment probably was cool and dry but one or more cool and wet intervals 25 000 15 000 yr b p resulted in a rise in the water table and deposition of lacustrine carbonate in the deepest basins there may have been short departures toward warmer and probably toward drier conditions throughout this time episodically dry conditions 15 000 8 000 yr b p resulted in deflation of the carbonate and further dune construction by repeated accretion of calcareous sandy loam or loamy sand the low carbonate sand was deposited during widespread drought and deflation 8000 5000 yr b p the dunes have been largely stable in the late holocene

comparison of radiocarbon dating of buried paleosols using arbuscular mycorrhizae spores and bulk soil samples ten paleosols from four separate soil pits located in karkevagge a glaciated trough in swedish lapland were dated using radiocarbon each soil was dated using both conventional bulk soil organic material som and a pure sample of arbuscular mycorrhizae am fungal spores the latter are produced by ubiquitous mycorrhizal fungi associated with the roots of many plant genera and may be viewed as a fossil material that has not interacted with any soil constituent subsequent to its emplacement in the soil at a time presumed to mark the cessation of a favorable soil forming environment regional deglaciation is presumed to have been about 10 000 bp while a cosmogenic exposure date obtained from the valley floor in karkevagge dated at 13 100 1638 bp the youngest paleosol buried at similar to 6 cm in soil pit m3 produced a spore date of 0 281 cal yr bp 1 sigma however bulk som dates of the same paleosol a horizon gave widely divergent dates and varied with the sample pretreatment ie the combustion temperature and the acid base treatment for example the bulk som dates for that paleosol ranged from a post bomb date of 0 314 cal yr bp 1 sigma to 2366 2710 cal yr bp 1 sigma when subjected to different pretreatments acid only acid base acid and the ignition temperatures 400 800 or 900 degrees c the oldest paleosol in the set buried at similar to 61 cm in soil pit m6 dated at 5479 5698 cal yr bp 1 sigma using spores but beyond calibration using bulk som the spore dates were all within the range to be expected of postglacial paleosols but the bulk som dates were frequently beyond the generally accepted time of deglaciation in addition all of the spore dates followed a conventional age depth pattern while the bulk som dates did not there are known possible sources of geogenic carbon contamination in karkevagge which may well account for the obviously invalid older bulk som dates an additional complication is that the spore dates vary somewhat with their density and diameter however where other types of fossil or charcoal are unavailable it appears that the enormously broad distribution of spores and their lack of interaction within the soil and persistence may well offer the prospect of an unusually useful radiocarbon dating medium within paleosols

on the elusive isotopic composition of lunar pb highly radiogenic pb isotope compositions determined for volcanic glass beads from the apollo 14 soil sample 14163 are similar to those commonly determined for mare basalts and are correlated with chemical variations observed in the beads this indicates that pb unsupported by in situ u decay has a similar origin in both glass beads and mare basalt samples and is likely to reflect variations of 238u 204pb in the lunar mantle an alternative explanation that this pb is a result of late equilibration with the radiogenic pb present in soil is less likely as it would imply that all other characteristics of glass beads such as their chemistry must also be a consequence of equilibration near the lunar surface regardless of the origin of unsupported pb observed variations of pb isotope compositions in the glass beads and mare basalts appear to be a result of two component mixing between a primitive reservoir with a value similar to the earth s mantle and kreep with a value in excess of several thousand this range cannot be explained by the fractionation of major rock forming minerals from the crystallising lunar magma ocean and instead requires substantial extraction of sulphide late in the crystallisation sequence the proportion of sulphide required to produce the inferred range places limits on the starting of the moon prior to differentiation demanding a relatively high value of about 100 200 low indicated by several basalt samples and previously analysed volcanic glass beads can be explained by the preservation of an early but post ferroan anorthosite sulphide rich reservoir in the lunar mantle while a complete range of pb isotope compositions observed in the glass beads and mare basalts can be interpreted as mixing between this sulphide rich reservoir and kreep

new evidence for complex climate change in mis 11 from hoxne suffolk uk the climatic signal of marine isotope stage mis 11 is well documented in marine and ice sheet isotopic records and is known to comprise at least two major warm episodes with an intervening cool phase terrestrial records of mis 11 though of high resolution are often fragmentary and their chronology is poorly constrained however some notable exceptions include sequences from the maar lakes in france and tenaghi philippon in greece in the uk the hoxnian interglacial has been considered to correlate with mis 11 new investigations at hoxne suffolk provide an opportunity to re evaluate the terrestrial record of mis 11 at hoxne the type hoxnian interglacial sediments are overlain by a post hoxnian cold temperate sequence the interglacial sediments and the later temperate phase are separated by the so called arctic bed from which cold climate macroscopic plant and beetle remains have been recovered the later temperate phase was deposited during an episode of boreal woodland and is associated with the artefacts a diverse vertebrate fauna and molluscs new amino acid geochronological data and biostratigraphical considerations suggest that the post hoxnian sequence correlates with late substages of mis 11 the paper further investigates the correlation of the sequence at hoxne with the palynological sequences found elsewhere in europe and adjacent offshore areas

radiocarbon dating of soil organic matter radiocarbon ages of soil organic matter are evaluated with a model which incorporates the dynamics of the14c content of soil organic matter measured14c ages of soil organic matter or its fractions are always younger than the true ages of soils due to continuous input of organic matter into soils differences in soil c dynamics due to climate or soil depth will result in significantly different14c signatures of soil organic matter for soils of the same age as a result the deviation of the measured14c age from the true age of soil formation could differ significantly among different soils or soil horizons our model calculations also suggest that14c ages of soil organic matter will eventually reach a steady state provided that no climatic or ecological perturbations occur once a soil or a soil horizon has reached a steady state 14c dating of soil organic matter will provide no useful information regarding the age of the soil however for soils in which steady state has not been reached it is possible to estimate the age of soil formation by modeling the measured14c contents of soil organic matter radiocarbon dating of buried soils could in general overestimate the true age of the burial by as much as the steady state age of the soil or soil horizon

a new method to constrain soil development time using both osl and radiocarbon dating abstract the time over which a soil has developed since the parent materials were deposited and subaerially exposed referred to here as soil development time is of considerable interest to pedologists geomorphologists geologists archeologist and paleoclimatologists soil development time has been estimated both indirectly based on the degree of soil development and directly by radiocarbon dating of soil organic matter optically stimulated luminescence osl dating of parent material deposition and through exposure dating using cosmogenic nuclides here we propose a new model for estimating the soil development time by subtracting the low molecular weight lmw or pyrolysis volatile 14c age of the uppermost a horizon of a soil from the osl age of the c horizon of the parent material soil time osl age parent c horizon 14c age lmw fraction of uppermost a horizon the lmw organic compound fraction represents the most mobile carbon compounds in the soil organic carbon pool and is least resistant to physical chemical and biodegradation in the soil environment potentially yielding the youngest 14c age osl dating of the c horizon provides an estimate of the time since deposition of unconsolidated parent material thus the difference in the two ages can be used to estimate the time that has elapsed for pedogenic alteration from deposition of the parent material to the most recent additions of soil organic carbon we applied this new approach in four scenarios 1 in a modern soil that developed downward in loess 2 in a buried soil developed in aggrading loess a cumulative soil which grows upward 3 in a buried soil formed in dune sand and 4 in a counterexample showing that simple subtraction is not always appropriate because of changes in soil s parent materials from loess to sand these case studies reveal that this approach constrains soil development time more reasonably than can be commonly done with either osl or radiocarbon dating alone the difference in 14c ages between the uppermost and lowermost sola of a soil profile almost certainly underestimates the time of soil development and the difference in osl ages taken from sediment units overlying and underlying a buried soil most likely overestimates it a combination of osl and radiocarbon dating better constrains soil development time broadening the applications of these two dating methods beyond their use for cross checking the accuracy of the other dating method

marine isotope stage 11 palaeoclimates palaeoenvironments and its role as an analogue for the current interglacial abstract interglacials of the quaternary period are currently the focus of a great deal of attention within the scientific community this is primarily because they play a vital role in distinguishing between natural and human climate change in the current interglacial and in understanding how the holocene would evolve in the absence of anthropogenic greenhouse warming in this respect marine isotope stage 11 mis 11 ca 410 000 yr bp is one of the key interglacial stages of the past 450 000 yr the pattern of insolation variability that occurs during mis 11 matches that which occurs in the holocene more closely than in any other warm stage of the past half a million years in addition there is now an extensive range of evidence for mis 11 palaeoclimates and palaeoenvironments from marine ice core lacustrine and terrestrial sequences the aim of this paper is to provide a comprehensive review of the current state of our understanding of mis 11 this is the first paper to provide a detailed review of mis 11 that incorporates the wide range of marine ice core long lacustrine and terrestrial records that have been generated over the last ten years since the last major overview crucially it is the first review of mis 11 that incorporates a detailed synthesis of the high resolution terrestrial sequences of western and central europe this paper therefore provides a holistic integration of a diverse range of proxies and archives to provide a detailed understanding of the expression of mis 11 in the earth system in particular the review focuses on 1 the climatic background of mis 11 2 the robustness of the identification of mis 11 in a diverse range of sequences 3 the climatic structure of mis 11 4 the magnitude of warmth that occurred in this warm stage 5 mis 11 sea level magnitude and variability 6 the duration of mis 11 7 evidence for abrupt climatic events within the interglacial of mis 11 and 8 precipitation patterns and trends during this interglacial the paper concludes by considering how useful mis 11 is as an analogue for holocene climates and compares it with other proposed analogues such as mis 19 with particular reference to the early anthropogenic hypothesis

lunar basalt chronology mantle differentiation and implications for determining the age of the moon despite more than 40 years of studying apollo samples the age and early evolution of the moon remain contentious following the formation of the moon in the aftermath of a giant impact the result

direct measurement of ar diffusion profiles in a gem quality madagascar k feldspar using the ultra violet laser ablation microprobe uvlamp abstract controversy surrounding the mechanisms and controls on argon diffusion in k feldspar has led us to undertake direct diffusion measurements on a crystal with simple microtextures over a range of temperatures measurements of argon diffusion profiles in a gem quality iron rich orthoclase heated in a cold seal apparatus have been undertaken in situ using an ultra violet laser ablation microprobe uvlamp technique the results agree very closely with the previously determined bulk values for benson mines orthoclase activation energy e 43 8 1 kcal mol 1 and vacuum furnace cycle heating studies of k feldspars e 46 6 kcal mol 1 however instead of defining a single activation energy e and diffusion coefficient do the data yield two sets of parameters a low temperature 550 720 c array with an e of 47 2 2 5 kcal mol 1 198 2 10 5 kj mol 1 and a do of 0 0374 0 1123 0 0281 cm2 s 1 and a high temperature 725 1019 c array with an e of 63 8 3 4 kcal mol 1 268 0 14 3 kj mol 1 and a do of 55 0 225 5 44 2 cm2 s 1 the new results closely reproduce two sets of apparent activation energies previously measured in cycle heating studies of madagascar k feldspar 40 3 and 57 3 kcal mol 1 previous interpretations of the two arrays have included multiple domains with variable activation energies and fast track diffusion however the uv depth profile analyses indicate simple diffusion to the grain surface and importantly diffusion radii calculated by combining the uvlamp and cycle heating data are the same as the physical grain sizes used in the experiments around 1 mm vacuum furnace stepped heating experiments on slowly cooled k feldspars have been interpreted as showing diffusion radii of around 6 m and indicate complex populations of sub grains this study indicates that madagascar k feldspar and thus probably all gem quality k feldspars act as single diffusion domains and that short circuit or pipe diffusion was not an important loss mechanism an apparent diffusion compensation relationship in the stepped heating data for madagascar k feldspar implies that similar relationships seen in other k feldspars are a result of a range of diffusion mechanisms

riparian landscapes and human habitat preferences during the hoxnian mis 11 interglacial the archaeological environmental and geological data from hoxnian interglacial marine isotope stage mis 11 sites from britain are examined to elucidate the type of habitats that humans preferred during this temperate episode the conclusion is that humans avoided lacustrine situations but did make use of the full range of resources that fluvial environments provide this model is strengthened by the examination of other non archaeological hoxnian sites the problem of archaeological visibility in lacustrine sediment sequences is also discussed and methods of identifying other evidence of human presence are suggested that may offset the deficiencies in the lithic record these include presence of cut marked bone micro debitage and possibly charcoal in fine grained sediments deposited in distal settings the reasons for human selection of fluvial situations are discussed it is concluded that these environments provide a greater diversity of animal plant and lithic resources but also are major route ways through the landscape patterns of human site use are identified which seem to be triggered by local changes in hydrology and drainage themselves possibly caused by regional changes in climate finally lower palaeolithic sites on the interfluves are discussed although they lack environmental or dating evidence it is tentatively suggested that they were used during cooler episodes when more open conditions prevailed copyright 2006 john wiley sons ltd

isotopic and rock magnetic expression of environmental change at the pleistocene holocene transition in the central great plains abstract in a region too dry for the effective use of the traditional palynological approach loess deposits of the central great plains offer a source of proxy information for the reconstruction of past climates the brady soil a ubiquitous feature developed within the uppermost late pleistocene peoria loess recorded the character of vegetation change associated with climate shifts during the pleistocene holocene transition stable carbon isotope ratio analysis and two room temperature magnetic parameters were used to examine the nature of the change during this period 13 c values derived from soil organic matter indicate that in the late pleistocene minor populations of drought tolerant c4 plants were interspersed among the dominant cool season grasses c3 in the west while c3 grasses were accompanied by trees in the east by the early holocene c4 grasses were the dominant vegetation in the west and contributed substantially to the 13 c signal in the east magnitude of the 13 c shift suggests an increase in july mean daily temperature of 8 10 c according to existing models magnetic susceptibility and frequency dependence signal the cessation of loess deposition and development of the brady soil and indicate a spatial pattern in the intensity of weathering across the region

origin of the lunar highlands mg suite an integrated petrology geochemistry chronology and remote sensing perspective the mg suite represents an enigmatic episode of lunar highlands magmatism that presumably represents the first stage of crustal building following primordial differentiation this review examines the mineralogy geochemistry petrology chronology and the planetary scale distribution of this suite of highlands plutonic rocks presents models for their origin examines petrogenetic relationships to other highlands rocks and explores the link between this style of magmatism and early stages of lunar differentiation of the models considered for the origin of the parent magmas for the mg suite the data best fit a process in which hot solidus temperature at 2 gpa 1600 to 1800 c and less dense 3100 kg m3 early lunar magma ocean cumulates rise to the base of the crust during cumulate pile overturn some decompressional melting would occur but placing a hot cumulate horizon adjacent to the plagioclase rich primordial crust and kreep rich lithologies at temperatures of 1300 c would result in the hybridization of these divergent primordial lithologies producing mg suite parent magmas as urkreep primeval kreep is not the petrologic driver of this style of magmatism outside of the procellarum kreep terrane pkt mg suite magmas are not required to have a kreep signature evaluation of the chronology of this episode of highlands evolution indicates that mg suite magmatism was initiated soon after primordial differentiation 10 m y alternatively the thermal event associated with the mantle overturn may have disrupted the chronometers utilized to date the primordial crust petrogenetic relationships between the mg suite and other highlands suites e g alkali suite and magnesian anorthositic granulites are consistent with both fractional crystallization processes and melting of distinctly different hybrid sources

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

pb pb ages of feldspathic clasts in two apollo 14 breccia samples pb pb isochron ages of ca 3 92 ga for three k feldspar rich clasts from apollo 14 breccias 14303 and 14083 were determinedusing secondary ion mass spectrometry sims these ages are interpreted t

the timing of basaltic volcanism at the apollo landing sites precise crystallisation ages have been determined for a range of apollo basalts from pb pb isochrons generated using secondary ion mass spectrometry sims analyses of multiple accessory phases including k feldspar k rich glass and phosphates the samples analysed in this study include five apollo 11 high ti basalts one apollo 14 high al basalt seven apollo 15 low ti basalts and five apollo 17 high ti basalts together with the samples analysed in two previous similar studies pb pb isochron ages have been determined for all of the major basaltic suites sampled during the apollo missions the accuracy of these ages has been assessed as part of a thorough review of existing age determinations for apollo basalts which reveals a good agreement with previous studies of the same samples as well as with average ages that have been calculated for the emplacement of the different basaltic suites at the apollo landing sites furthermore the precision of the new age determinations helps to resolve distinctions between the ages of different basaltic suites in more detail than was previously possible the proposed ages for the basaltic surface flows at the apollo landing sites have been reviewed in light of these new sample ages finally the data presented here have also been used to constrain the initial pb isotopic compositions of the mare basalts which indicate a significant degree of heterogeneity in the lunar mantle source regions even among the basalts collected at individual landing sites

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

stratigraphy and geochronology of upper quaternary eolian sand on the southern high plains of texas and new mexico united states eolian sand in dune fields and sand sheets cover 10 000 km 2 10 of the southern high plains of northwestern texas and eastern new mexico these deposits are concentrated in three west east trending belts of dunes the muleshoe lea yoakum and andrews dune fields from north to south that appear to be eastern extensions of the mescalero monahans dune system in the pecos river valley and in the seminole sand sheet a discontinuous accumulation of sheet sands between the lea yoakum and monahans andrews dunes the most common landforms are parabolic dunes associated with blowouts coppice dunes and sand sheets all typical of sandy vegetated semiarid landscapes barchan dunes in keeping with a relatively limited sand supply and an underlying surface that is relatively hard blackwater draw formation pleistocene and fence row dunes historic dunes formed along field boundaries these eolian deposits accumulated episodically in the late pleistocene and holocene and provide clues to the history of regional drought and aridity the earliest phase of sedimentation occurred when sheet sands were deposited between 11 000 and 8000 14 c yr b p probably in several phases based on archaeological data as a result of episodic drought beginning between 11 000 and 10 000 yr b p eolian deposits dating between 8000 and 3000 yr b p are rare although eolian sediment 8000 4500 14 c yr b p is ubiquitous in the draws that cross the region and paleoenvironmental indicators show that the region was subjected to aridity throughout middle holocene time the middle holocene deposits most likely were remobilized in late holocene time most of the deposits and landforms of the dune fields and sand sheets are late holocene dating before 4000 14 c yr b p and mostly before 1500 14 c yr b p the muleshoe and lea yoakum dunes and the seminole sand sheet underwent substantial eastward expansion in late holocene time buried soils and radiocarbon ages show that the eolian sand accumulated in several stages probably in response to cyclic drought the muleshoe dunes accumulated after ca 1300 cal yr b p ca 1400 14 c yr b p after ca 750 670 cal yr b p ca 850 750 14 c yr b p just after ca 500 cal yr b p ca 450 14 c yr b p and during the nineteenth and twentieth centuries the lea yoakum dunes were active after ca 3400 cal yr b p ca 3200 14 c yr b p and historically the seminole sand sheet was active ca 430 330 cal yr b p ca 360 14 c yr b p and in the twentieth century the andrews dunes were subjected to at least two phases of eolian sedimentation after ca 2320 cal yr b p ca 2320 14 c yr b p comparisons with eolian chronologies from other regions on the great plains suggest that dune mobilization was a regional phenomenon after ca 2300 cal yr b p ca 2300 14 c yr b p after ca 1500 1400 cal yr b p ca 1650 1550 14 c yr b p after ca 700 cal yr b p ca 800 14 c yr b p between 500 and 300 cal yr b p ca 450 300 14 c yr b p and in the nineteenth century the climatic fluctuations responsible for mobilizing the dunes probably were relatively minor yet the landscape impacts were substantial resulting in widespread wind erosion and dune construction

mineral chemistry and in situ upb geochronology of the mare basalt northwest africa 10597 implications for low ti mare volcanism around 3 0 ga abstract unbrecciated mare basalts are rare in the lunar meteorite collection found in 2015 northwest africa nwa 10597 is a medium grained low ti mare basalt with a subophitic texture the meteorite consists mostly of mm sized pyroxene and plagioclase with minor olivine spinel ilmenite phosphates silica and trace zr rich minerals such as baddeleyite zirconolite and tranquillityite a portion of plagioclase and silica has been transformed to their high pressure polymorphs due to shock metamorphism nwa 10597 has a low tio2 content 2 9 wt but is relatively enriched in rare earth elements ree laaverage 65 ci with an overall unfractionated pattern except for a negative eu anomaly calculated ree concentrations of parent melts in equilibrium with mg rich pyroxene and ca rich plagioclase suggest no significant assimilation of ree rich melts after the onset of pyroxene crystallization in situ u pb analyses of baddeleyite and apatite reveal a mutually consistent age of 3 0 ga which is also in excellent agreement with that of low ti mare basalts nwa 4734 and lapaz icefield lap 02205 dated with other independent techniques the concordance suggests no significant thermal disturbance in the u pb isotopic system of nwa 10597 although it was heavily shocked nwa 10597 closely resembles nwa 4734 in terms of petrographic texture mineral chemistry and geochronology indicating a pairing relationship

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

application of proton microprobe data to trace element partitioning in volcanic rocks abstract in situ proton microprobe analyses are used to calculate partition coefficients d for mn fe cu zr ga rb sr y zr ba and pb and more restricted data for ni ge nb and as in pyroxenes olivines biotites hornblendes feldspars and fe ti oxides from 32 volcanic rocks all with glassy matrices these range from leucitite and picritic basalt to high silica and peralkaline rhyolites data for pigeonite aenigmatite allanite and leucite are included where these occur as additional phases coefficients have also been rayleigh fractionation corrected this correction being significant for those elements with high coefficients in specific mineral phases and where pronounced crystallisation has occurred partition coefficients are presented as plots vs nbo t ratios of coexisting glasses melts negative correlations are observed based on log transformed data for mn zn fe and y pyroxenes mn zn and fe olivines mn and zn fe ti oxides nb y sr and zr hornblendes sr plagioclase and ba cu zn and fe feldspars these element partition coefficients are not correlated with bulk mineral compositions zr and ga are not correlated with either glass or mineral compositions except zr in hornblende the correlations support the role of melt polymerisation in controlling element partitioning at least for those elements listed although possible effects of temperature cannot be uniquely isolated in the present data set the coefficients presented here are generally consistent with published values for equivalent rock compositions one difference being that some of the higher published coefficients e g sr in plagioclase are not matched in the present data set from a practical viewpoint the relative regularity of the coefficient data presented does facilitate choice of relevant coefficient values that are required for petrogenetic modelling procedures

the rate of iron oxide enrichment in arid zone alluvial fan soils tunisian southern atlas measured by mineral magnetic techniques abstract rates of iron oxide enrichment of soils on a segmented alluvial fan in southern tunisia are examined mineral magnetic and chemical characteristics of soils developed on two dated relict segments and on contemporary alluvium suggest that the rate of fe oxide enrichment was more rapid in the holocene 2 6 10 8 g g 1 yr 1 over the last 5000 years than in the pleistocene 1 91 10 9 g g 1 yr 1 over the previous 45 000 years thus fe oxide concentration may be used to determine an ordinal chronology of some geomorphological surfaces in drylands but rates of enrichment cannot be assumed to be uniform over time

the origin of geochemical diversity of lunar mantle sources inferred from the combined u pb rb sr and sm nd isotope systematics of mare basalt 10017 the results of our combined u pb rb sr and sm nd isotope study of mare basalt 10017 contribute to the understanding of the petrogenetic processes involved in the origin of geochemical diversity in lunar mare basalt sources as well as the u pb isotope systematics of the moon the rb sr sm nd and 238 u 206 pb isotope systems yield concordant crystallization ages of 3 633 0 057 ga 3 678 0 069 ga and 3 616 0 098 ga respectively the 235 u 207 pb isochron yields an older though still concordant age of 3 80 0 12 ga neither the 206 pb 207 pb system nor u pb concordia system yields an age for 10017 that is concordant with the age determined from the sm nd rb sr and 238 u 206 pb systems the initial 87 sr 86 sr of 10017 is 0 69941 7 and the initial end is 3 2 0 4 initial pb isotopic compositions determined from the u pb isochrons are 206 pb 204 pbi 31 11 and 207 pb 204 pbi 34 15 together these initial pb compositions constrain the l value of the 10017 source to be 70 30 assuming a single stage pb growth model this is considerably lower than l values typically estimated for mare basalt sources 100 600 regardless the l values calculated for the sources of mare basalts as well as other lunar samples show a range that is larger than can be explained by fractionation of u from pb solely by crystallization of silicate phases and ilmenite during magma ocean solidification and formation of lunar mantle sources the u pb isotope systematics may reflect late stage formation of a sulfide phase which strongly fractionates pb from u but has minimal effect on rb sr or sm nd compositions during crystallization of the lunar magma ocean 2007 elsevier ltd all rights reserved

apollo 15 yellow brown volcanic glass chemistry and petrogenetic relations to green volcanic glass and olivine normative mare basalts abstract apollo 15 yellow brown glass is one of twenty five high mg primary magmas emplaced on the lunar surface in pyroclastic eruptions forty spherules of this glass were individually analyzed by electron microprobe and inaa for major and trace elements e g sc v cr co la ce nd sm eu ho tm yb lu hf ta and u the abundances demonstrate that this primary magma was produced by partial melting of differentiated cumulates in the lunar mantle models are developed to explain the possible source regions of several apollo 15 and apollo 12 low ti mare magmas as being products of hybridization involving three ancient differentiated components of a primordial lunar magma ocean a early olivine orthopyroxene cumulates b late stage clinopyroxene pigeonite ilmenite plagioclase cumulates and c late stage inter cumulus liquid isotopic constraints on sm nd fractionation and least squares tests of potential mixing models require models of apollo 15 yellow brown glass and apollo 12 and 15 olivine mare basalts involving low f 3 cumulate remelting of sources in which olivine and orthopyroxene are residual phases models of the apollo 15 green glass composition indicate higher 4 7 degrees of melting but with only a slight preference for orthopyroxene rich relative to orthopyroxene free sources the modeled dependence on residual orthopyroxene in mare source regions places source depths at 400 km or greater in order to maintain olivine and orthopyroxene on the liquidus hybridization at such depths would likely result from convective overturn of the primordial magma ocean and suggests that separate fractionating masses were positioned at various depths our models for developing hybridized source regions of primary low ti mare magmas do not require selective contamination of primary liquids the preferred model for apollo 15 yellow brown glass is presented as the commingling of 95 early cumulate olivine orthopyroxene 1 9 clinopyroxene 0 27 pigeonite 1 7 plagioclase 0 02 ilmenite and 0 56 trapped liquid respective proportions for the apollo 15 olivine mare basalt source model are 98 5 0 37 0 0 79 0 16 and 0 13 and the proportions used for the preferred apollo 12 olivine mare basalt model are 97 6 0 73 0 24 0 77 0 42 and 0 21 our preferred model for the green glass source composition f 0 07 requires the commingling of 97 4 early olivine orthopyroxene 0 18 clinopyroxene 1 32 pigeonite 0 85 plagioclase and 0 28 trapped liquid

pyrolysis combustion 14c dating of soil organic matter abstract radiocarbon 14c dating of total soil organic matter som often yields results inconsistent with the stratigraphic sequence the onerous chemical extractions for som fractions do not always produce satisfactory 14c dates in an effort to develop an alternative method the pyrolysis combustion technique was investigated to partition som into pyrolysis volatile py v and pyrolysis residue py r fractions the py v fractions obtained from a thick glacigenic loess succession in illinois yielded 14c dates much younger but more reasonable than the counterpart py r fractions for the soil residence time carbon isotopic composition 13c was heavier in the py v fractions suggesting a greater abundance of carbohydrate and protein related constituents and 13c was lighter in the py r fractions suggesting more lignin and lipid related constituents the combination of 14c dates and 13c values indicates that the py v fractions are less biodegradation resistant and the py r fractions are more biodegradation resistant the pyrolysis combustion method provides a less cumbersome approach for 14c dating of som fractions with further study this method may become a useful tool for analyzing unlithified terrestrial sediments when macrofossils are absent

chronology and geochemistry of late holocene eolian deposits in the brandon sand hills manitoba canada abstract accelerator mass spectrometry and conventional radiocarbon age determinations of organic matter from paleosols indicate that the brandon sand hills area of southern manitoba has been subjected to recurrent intervals of eolian activity in the past 5000 years although precise regional correlations are precluded by dating uncertainties periods of most notable paleosol development occurred around 2300 to 2000 1400 to 1000 and 600 to 500 cal yr bp with eolian activity occurring before and after each of these periods episodes of eolian activity may correspond to periods of regional drought whereas paleosols mark periods of increased moisture availability and stabilization by vegetation the geochemistry of the eolian sands paleosols and source sediments indicates that partial leaching of carbonates occurs from pedogenesis during humid climatic phases and that this is probably the primary mechanism of carbonate depletion of eolian sands in this area recent trends in sand dune activity from historic aerial photography and early explorers accounts indicate that the few active dunes that presently exist have stabilized at a rate of 10 20 per decade despite several severe droughts in the 20th century this may be attributed to pre settlement droughts that were more severe than those in historic times although regional dune stabilization may also be related in part to the spread of forest cover in the past few hundred years

trace element partitioning between high an plagioclase and basaltic to basaltic andesite melt at 1 atmosphere pressure we determined plagioclase melt partition coefficients for 18 elements by performing controlled cooling rate 1 atmosphere experiments using both natural and synthetic basaltic 51 wt sio2 and basaltic andesite 56 wt sio2 powders in a vertical quench furnace the experiments produced an69 to an87 composition plagioclase three starting powders were gorda ridge basalt synthetic diopside 40 albite 28 anorthite 32 mixture and arenal volcano costa rica basaltic andesite the gorda and synthetic powders were doped at both low concentrations 20 200 ppm and high concentration 200 5000 ppm whereas the arenal powder was doped only at high concentrations resulting in two doped gorda powders low np and high sdp two doped diopside albite anorthite powders low dad high sdd and one doped arenal powder high ar99 2 trace elements concentrations in both glass and plagioclase were measured by secondary ion mass spectrometry sims and or by laser ablation inductively coupled plasma mass spectrometry la icp ms results for the partitioning of trace elements between plagioclase and melt at different doping levels demonstrate both adherence to henry s law and good agreement between the different analytical techniques in general plagioclase melt partition coefficients determined in the an69 73 range are similar to other published values however some of those occurring for plagioclase compositions an75 are distinctly lower than those predicted by current regression formulations we applied a two lattice melt model to these data to account for differences in melt composition and temperature and found that there were no aberrations associated with partition coefficients a new set of regression formulations is determined involving the newly determined dataset for plagioclase with an contents between 75 and 87

pb isotopes in the impact melt breccia 66095 association with the imbrium basin and the isotopic composition of lithologies at the apollo 16 landing site recent in situ secondary ion mass spectrometry sims pb isotope analyses of lunar basalts have provided precise crystallisation ages and initial pb isotopic compositions for these samples in this

a revised chronology for aeolian activity in subarctic fennoscandia during the holocene detailed sedimentological studies and parallel sampling for 14c and infra red stimulated luminescence age assays were undertaken at six sites lying beyond and below the tree line with the objective of establishing the historical development of aeolian landforms in lapland the main issues were a the timing of dune activity and processes of stabilization b the specific processes responsible for the past and contemporary activity new data indicate that many of the primary dunes were active for several millennia after deglaciation diachronous stabilization at both local and regional scales appears likely initial stabilization occurred in local interdune areas and where regional dune fields were colonized by pine generally before 7 ka local large dunes and some regional dunefields only became stable around 4 3 ka when the regional groundwater table rose and late pine colonization was possible the latest episode of aeolian activity dates from ad 1100 1650 across the area a unique deflation trigg

ostracodological studies in archaeological settings a review during recent years geo archaeology has been revitalised and much effort has been made to combine geo archaeological sciences like geomorphology sedimentology micropalaeontology and geochemistry with the cultural archaeological approach the first definition of geo archaeology dates back to the late seventies and since then has evolved to include more and more multidisciplinary studies in this perspective ostracods play a crucial role since they are valuable palaeoenvironmental indicators in all aquatic habitats from freshwater to marine despite their potential the integration of ostracods in archaeological studies has not been immediate only in the nineties did ostracod geo archaeology seem to finally take its place including a systematic approach to ostracod studies in archaeological excavations since then many geo archaeological investigations have included ostracod analyses exploiting their potential as multitask tools the research papers composing this special issue demonstrate that ostracods can be used in the most diverse settings as tracers of archaeological material provenance proxies for palaeoenvironmental and palaeoclimate reconstructions as well as clues to human impact

humans in the hoxnian habitat context and fire use at beeches pit west stow suffolk uk a lower palaeolithic industry at beeches pit west stow suffolk occurs within an interglacial sequence that immediately overlies glacial deposits referable to the anglian lowestoft formation there is strong biostratigraphical evidence from both vertebrates and molluscs that the interglacial represented is the hoxnian mis 11 this conclusion is supported by uranium series dates from carbonate nodules 400 kyr tl dates from burnt flint 414 30 kyr and a range of amino acid racemisation data the archaeology consists of flint artefacts of acheulian character including many refitting examples charred material is abundant in three stratigraphical units and many bones and flints have been burnt indicating repeated occurrence of fire several discrete areas of burnt sediment appear to be hearths this interpretation is supported by 1 the intensity of burning 600 8008c implied by the charred and calcined bones 2 the intersection of two of the burnt areas implying separate burning events at slightly different overlapping locations 3 the discovery of two burnt flakes that refit onto an adjacent group that are unburnt indicating that the burning was highly localised and 4 the spatial distribution of artefacts respects the features interpreted as hearths suggesting fireside knapping fossils associated with the archaeology indicate occupation within closed deciduous forest in a fully temperate climate attractions to this unusual environment would have included the fresh water provided by springs a rich supply of potential food and a prolific source of good quality flint for tool manufacture the archaeological evidence therefore suggests that the site repeatedly served as an area of focused activities perhaps a home base during much of the interglacial the upper levels of the sequence provide clear faunal evidence of climatic deterioration during which human occupation and fire use persisted biostratigraphical correlations with other lower palaeolithic sites lend support to the suggestion that acheulian and clactonian industries occurred in britain during the same substage of the hoxnian although not necessarily at precisely the same time copyright 2006 john wiley sons ltd

dynamics and driving factors of late holocene gullying in the main ethiopian rift mer abstract the issue of determining the driving factors in gullying apart from land use is somewhat lagging in comparison with the study of their physical modelling and control technology available information focuses on the basic ideas of climatic control anthropic determinism and internal authigenic dynamics high resolution chronology of cyclic systems common in extensively gullied areas can provide a clue to the weight of each factor this paper reports a study of this kind focusing on two gully catchments in the main ethiopian rift mer but backed by an extensive regional survey by integrating tracing and correlation of unconformity bounded stratigraphic units and soils with radiocarbon dating a detailed chronology was obtained for the last 5000 years this could be compared with proxy climate reconstructions of similar detail clear evidence of climatic control emerged gully filling is triggered by decreased stream transport capacity and increased sediment supply during transitions towards drier climate phases while gully entrenchment appears to take place at the start of moist intervals for the reverse reasons a broader consideration of geological setting however puts forward a more general interpretation these gullies actually formed in the beginning as part of the land surface response to sudden very recent tectonic events which created accommodation space for temporary sediment stores they should then be seen in the frame of the discontinuous ephemeral stream des concept as such they are intrinsically non linear and complex phenomena whose response is linearized by a strong climatic vegetational forcing acting on both channel flow and sediment supply

use geopedological methods for the evaluation of sedimentation rates on river floodplains southern quebec canada abstract this article pertains to the fluvial dynamics of rivers in southern quebec in particular to the aggradation and pedogenetic processes observed in floodplains affected by periodic floods the frequency of flood events notably along the saint francois river and its main tributaries leads to fine materials being frequently deposited on floodplains and affected development of alluvial soils particle size and physical and chemical analyses have led to a better understanding of the dynamics involved in the formation of floodplains and the development of soils related to this fluvial environment also sedimentological analyses layer texture and thickness microstructure combined with radiocarbon dating 14c and isotopic methods 210pb 226rd enabled the determination of sedimentation rates along the floodplains the radiocarbon dating results obtained from the organic layers buried in alluvial soils show relatively variable ages i e between 2210 60 and 30 70 years bp the data gathered reveal an active overbank deposition which shows evidence of the high flood recurrence in many rivers of the basin it is estimated that the annual floodplain aggradation ranges from 1 0 to 7 6 mm yr 1 on average which causes increases in floodplain elevations vertical accretion the sedimentation rates obtained using the constant rate supply dating model 210pb show average values that range from 2 1 to 10 7 mm yr 1 also the presence of contaminated layers at the lower level 100 cm of the floodplains suggested an active sedimentation rates along the rivers affected by floods

ion microprobe studies of trace elements in apollo 14 volcanic glass beads comparisons to apollo 14 mare basalts and petrogenesis of picritic magmas abstract the major element geochemistry of picritic lunar glass beads indicates that they represent primary basaltic liquid compositions and as such provide unique information concerning the origin of mare basalts and characteristics of the lunar interior this study used ion microprobe techniques for trace element analysis of individual glass beads representing seven compositionally distinct types of picritic glass beads from the apollo 14 site high ti glasses 17 11 tio2 red black orange intermediate ti glasses 5 4 tio2 yellow low ti glasses 2 8 tio2 lap low alkali picritic papike et al 1989 very low ti glasses ba sr 1 of these glasses are different from low ti mare basalts at other sites but are similar to crystalline basalts at the apollo 14 site the intermediate to high ti picritic glasses exhibit a flat to slightly positive lree slope and a negative hree slope the orange glass has a higher total ree abundance and a slightly larger negative eu anomaly than the red black and yellow glasses relative to the apollo 17 high ti glasses apollo 14 high ti glasses are enriched in ree lree hree y v zr sr ba and ba sr and are similar in alkali elements li rb co and sc trace element modeling within the context of liquid lines of descent and major element characteristics indicates that the picritic glass beads at the a 14 site are not related by low pressure fractional crystallization to each other or to crystalline basalts at the apollo 14 or other landing sites a possible exception is the relationship between lap and basalts of the high al basalt suite the wide range of primary magma compositions and the lack of petrogenetic linkage via crystal fractionation to crystalline basalts indicates that either a wide compositional range of evolved mare basalts has not yet been sampled or a unique mechanism is selectively tapping these picritic magmas directly from their mantle source region the wide range of major and trace element characteristics of the volcanic glass beads is consistent with derivation from mineralogically distinct sources which consist of varying proportions of olivine orthopyroxene clinopyroxene ilmenite plagioclase kreep component the evolved kreep component may have been incorporated into these primary picritic magmas by either assimilation fractional crystallization type processes afc or by hybridization of the mantle source the former appears less likely due to the general systematic increase in incompatible elements relative to ti concentration and the apparent lack of crystallization that is required in afc type models the hybridization processes may be the result of sinker mechanisms as proposed by ringwood and kesson 1976 a manifestation of original mantle inhomogeneities or a magma ocean stirred by large impacts

dating modern deltas progress problems and prognostics 1 abstract radiocarbon dating is the method most frequently used to date holocene deltaic sequences but less than one quarter of 14c dates are within 500 years of predicted age such dates tend to be unreliable in other words often too old and commonly inverted upsection and core sample dates obtained near deltaic plain surfaces may be as old as mid to late holocene stratigraphic irregularities result primarily from downslope reworking of upland alluvial sediment with displacement of old carbon in the sediment that accumulates in lower valleys and deltaic plains use of dates that are too old results in inaccurately calculated rates most often too low of relative sea level rise and or land subsidence more reliable timing of deltaic sediment requires a multiple method dating approach including where possible identification of associated archaeological material developing an accurate dating strategy is a critical step for implementing reliable coastal protection measures needed for the rapi

a new multistage construction chronology for the great serpent mound usa abstract effigy mounds occur across the midcontinent of north america but their cultural purposes and construction chronologies are rarely known and often controversial determining the age and construction history of monuments is important to relate religious symbolism scientific knowledge and cultural continuity to groups within a region based mainly on circumstantial evidence researchers have long held that serpent mound in ohio usa was constructed 2000 3000 years ago during the early woodland adena or middle woodland hopewell periods excavations in 1991 recovered charcoal buried at shallow depths 35 45 cm in fill units of the mound and the 14 c ages from two of these units indicated that serpent mound was built 900 years ago during the late prehistoric fort ancient period much later than originally thought our recent multidisciplinary work provides a more complex robust construction history of serpent mound we used geophysics to map the mound and solid earth cores to provide accurate stratigraphy and organic samples for 14 c age estimates from the base of the mound bayesian statistical analyses of the seven 14 c ages from serpent mound suggest that it was first constructed 2300 years ago during the early woodland adena period but was renovated 1400 years later during the late prehistoric fort ancient period probably to repair eroded portions of the mound modification of the mound is also indicated by a possible abandoned coil that is located near the head of the serpent and visible only in the magnetometer survey

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

holocene eolian activity in the minot dune field north dakota stabilized eolian sand is common over much of the great plains region of the united states and canada including a subhumid area of 1500 km2 near minot north dakota eolian landforms consist of sand sheets and northwest trending parabolic dunes dunes and sand sheets in the minot field are presently stabilized by a cover of prairie grasses or oak woodland stratigraphic studies and accelerator mass spectrometry radiocarbon dating of paleosols indicate at least two periods of eolian sand movement in the late holocene pedologic data suggest that all of the dune field has experienced late holocene dune activity though not all parts of the dune field may have been active simultaneously similar immobile element ti zr la ce concentrations support the interpretation that eolian sands are derived from local glaciofluvial and glaciolacustrine sediments however glaciolacustrine and glaciofluvial source sediments have high ca concentrations from carbonate minerals whereas dune sands are depleted in ca

uranium lead systematics of low ti basaltic meteorite dhofar 287a affinity to apollo 15 green glasses article i nfo dhofar 287 is a lunar meteorite found in oman in 2001 which consists of a major portion 95 of low ti mare basalt dho 287a and a minor attached part 5 of regolith breccia dho 287b here we report the u pb systematics of dho 287a using data collected with a sensitive high resolution ion microprobe shrimp in situ analyses of five merrillite and three apatite grains which are resistant to secondary petrologic events resulted in a total pb u isochron age of 3 34 0 20 ga in 238 u 206 pb 207 pb 206 pb 204 pb 206 pb 3 d space 95 confidence level the observed pb pb isochron of these eight phosphates coupled with four plagioclase grains alsoyieldeda 207 pb 206 pbageof3 35 0 13ga thisformationage whenconsideredasthecrystallizationageof

terrestrial environments during mis 11 evidence from the palaeolithic site at west stow suffolk uk abstract multidisciplinary investigations of the sequence at beeches pit west stow suffolk uk have a direct bearing the age of the hoxnian interglacial and its correlation with the continental holsteinian and with the global marine record at this site glacial deposits till and outwash gravels referable to the anglian lowestoft formation fill a subglacial channel cut in chalk bedrock above these glacial deposits a series of interglacial sediments occurs consisting of limnic tufaceous and colluvial silts lacking pollen but rich in shells ostracods and vertebrates lower palaeolithic flint artefacts of acheulian character have also been recovered including refitting examples charred material is abundant at certain horizons and many of the bones have been burned several discrete areas of burnt sediment are interpreted as hearths the molluscan fauna comprises some 78 taxa and includes species of considerable zoogeographical and biostratigraphical importance the land snail assemblage from the tufa consists of woodland taxa with no modern analogue including species that are either extinct e g zonitoides sepultus or which no longer live in britain e g platyla polita p similis neniatlanta pauli this is also the type locality of retinella lyrodiscus skertchlyi which belongs to a subgenus of zonitid land snail now living only on the canary islands there are indications from this fauna the lyrodiscus biome that the climate was wetter and perhaps warmer than the present day the vertebrate fauna is also noteworthy with species of open habitats such as rabbit oryctolagus cf cuniculus and of closed forest such as squirrel sciurus sp and garden dormouse eliomys quercinus present at different times the occurrence of southern thermophiles such as aesculapian snake zamenis longissimus indicates temperatures warmer than those of eastern england today the upper levels include much material reworked from the interglacial sediments although there is clear faunal evidence for climatic deterioration both the molluscan and vertebrate faunas suggest correlation of the interglacial sediments with the hoxnian uranium series dates from the tufa 455 ka bp tl dates from burnt flints 414 30 ka bp and a range of amino acid racemization data all support correlation of this interglacial with mis 11 however four osl dates from sand beneath the interglacial sequence yield a mean age of 261 31 ka bp far younger than all other age determinations and far younger than implied by the biostratigraphy archaeologically the site is unusual in showing prolonged human occupation within closed deciduous forest and evidence for controlled use of fire in a lower palaeolithic context biostratigraphical correlations with other lower palaeolithic sites support the suggestion that acheulian and clactonian industries both occurred in southern britain during the same substage of the hoxnian although not necessarily at precisely the same time the characteristics of the mis 11 interglacial in britain are discussed in the light of evidence from beeches pit and elsewhere

timing and origin for sand dunes in the green river lowland of illinois upper mississippi river valley usa abstract the recent increase in dune studies in north america has been heavily focused in the great plains while less attention has historically been given to the dune fields east of the mississippi river here we report ages and suggest a potential sediment source for sand dunes in the green river lowland illinois which may provide a better understanding of the dynamic interactions between eolian glacial lacustrine and fluvial processes that shaped the landscapes of the upper midwest seven coherent optically stimulated luminescence ages osl or optical ages obtained from four sites suggest that major dune construction in the green river lowland occurred within a narrow time window around 17 500 ago this implies either an enhanced aridity or an episodic increase of sediment supply at 17 500 years ago or combination of the both contrary to previous assertions that dune sand was sourced from the deflation of the underlying outwash sand deposited when the lake michigan lobe retreated from the area we propose that green river lowland dunes sand originated from the green bay lobe through the rock river specifically sediment supply increased in the rock river valley during drainage of glacial lake scuppernong which formed between 18 000 and 17 000 years ago when the green bay lobe retreated from its terminal moraine the lake drained catastrophically through the rock river valley providing glacial sediment and water to erode the preexisting sandy sediments throughout the remainder of the late pleistocene the laurentide ice sheet drained into larger more northerly glacial lakes that in turn drained through other river valleys therefore the dunes in the green river lowland formed only during the catastrophic drainage of glacial lake scuppernong but were stabilized through the remainder of the pleistocene this scenario explains the abrupt dune construction around 17 500 years ago and explains the lack of later dune activity up to the pleistocene holocene transition osl and radiocarbon ages also indicate that dunes were reactivated during the early middle and late holocene some eolian activation occurred within well defined dry intervals in the upper midwest suggesting that increased aridity may have been the primary driver in mobilizing sand however many ages do not correspond to drier periods in contrast to the relative coherency of the pleistocene osl ages from multiple study sites the holocene osl ages do not overlap from one site to another suggesting that increased aridity alone cannot explain the multiple phases of dune reactivation in the holocene therefore we conclude that the combined effect of localized disturbances and greater aridity acted in concert to increase eolian sand activity in the holocene the multiple periods of eolian activity during the holocene suggest a high potential for future sand activation in the region and these results are informative for environmental prediction and potential future mitigation

variation in radiocarbon ages of soil organic matter fractions from late quaternary buried soils radiocarbon dating of three organic matter fractions total humic acid and residue isolated from late quaternary buried soils of the central great plains reveals that there often are considerable differences among but no consistent order to the ages of fractions for late holocene soils the residue fraction or the total fraction generally produces the oldest age for late pleistocene soils however no fraction was consistently the oldest the absence of a consistent sequence of fraction ages is attributed to postburial contamination of soils when bulk samples from the same soil were split and sent to two laboratories different radiocarbon ages were usually obtained the variability in radiocarbon ages of soil organic matter confirms that caution should be taken when using radiocarbon ages obtained from different laboratories to make regional stratigraphic correlations

early holocene alluvial stratigraphy chronology and paleoindian early archaic geoarchaeology in the loup river basin nebraska u s a abstract the preservation of alluvium dictates the discovery of archaeological sites in valleys we address two questions in our study of the loup river basin in the midcontinent of north america 1 what is the alluvial chronology of the loup river basin between about 10 300 and 7700 bp and 2 what is the potential for preservation and exposure of paleoindian and early archaic sites cleaned cut banks walls of backhoe trenches and archaeological test units cores collected with a trailer mounted giddings soil probe and bucket auger samples were described buried a horizons organic enriched alluvial strata peat and charcoal were sampled for radiocarbon dating dating was supplemented by temporally diagnostic cultural materials we recognize the absence of 14 000 10 300 bp alluvium in the loup river basin floodplain stability very slow aggradation occurred from 10 300 10 000 bp rapid floodplain aggradation is inferred between 10 000 and 9450 bp between 9450 and about 9250 bp erosion initially produced the kilgore creek terrace the valley floor landscape stabilized from about 9250 to 9100 bp before an episode of rapid aggradation overwhelmed floodplains and alluvial colluvial fans the fans stabilized about 8600 8500 bp while floodplains in larger valleys 5th order stabilized shortly after about 8400 8200 bp renewed valley bottom aggradation after 8200 was interrupted at about 7750 the absence of alluvium dated between 14 000 and 10 300 bp in the loup river basin precludes discovery of early paleoindian sites in valleys and contrasts with the presence of alluvium and buried soils containing clovis and folsom paleoindian sites in other drainage basins in the u s central great plains although the distribution of the kilgore creek terrace is an excellent proxy of preservation of 10 300 9450 bp alluvium in the loup river basin and thus late paleoindian sites very few remnants of this terrace have been preserved two early holocene erosional episodes have been documented in the loup river basin at 9450 9250 bp and again immediately before 8300 8200 bp alluvium deposited between 10 300 and 9450 contains one archaeological site and alluvium deposited 9250 8200 contains five other paleoindian sites five early archaic sites are documented in three alluvial colluvial fans and on a terrace remnant in the north loup river valley but have not been discovered in an alluvial stratigraphic context outside of fans although stable surfaces are much more likely to accumulate a greater density of artifacts than sedimentary units that are deposited rapidly we document three paleoindian components that are in alluvium between buried soils

soil and sedimentary charcoal evidence for holocene forest fires in an inland temperate rainforest east central british columbia canada accelerator radiocarbon dating of 147 charcoal samples recovered from colluvial and alluvial fan deposits at 29 sites was used to reconstruct the holocene fire history of an inland temperate rainforest watershed in east central british columbia bc canada radiocarbon dates ranged from 182 to 9558 cal yr bp with prominent peaks in the probability distribution of calibrated dates at c 7100 3900 2300 1600 and 250 1000 cal yr bp the inferred median fire return interval fri was 800 1200 cal yr depending on the extent of inbuilt age errors resulting from charring of wood pre dating actual fire ages this fri is likely an overestimate as less severe events may not have created sufficient erosion and slope instability to preserve a record of charcoal in buried soils and slope deposits median time since fire was 467 cal yr based on ages of the uppermost charcoal found at each site but the severity of heart rots in the dominant redcedars thuja plicata donn ex d don prevented independent confirmation of stand ages by dendrochronology sites with multiple charcoal containing layers having similar radiocarbon ages can be explained with reference to contemporary post fire mass wasting processes peaks in fire related sedimentation probability coincided broadly with periods of higher fire frequency c 600 1000 1300 2400 and 3500 4500 cal yr bp inferred from sedimentary charcoal records at subalpine sites in southwestern bc correspondence with fire records from more distant sites in northwestern north america was less clear

late quaternary loess in northeastern colorado part i age and paleoclimatic significance loess in eastern colorado covers an estimated 14 000 km 2 and is the westernmost part of the north american midcontinent loess province stratigraphic studies indicate there were two periods of loess deposition in eastern colorado during late quaternary time the first period spanned ca 20 000 to 12 000 14 c yr b p ca 20 14 ka and correlates reasonably well with the culmination and retreat of pinedale glaciers in the colorado front range during the last glacial maximum the second period of loess deposition occurred between ca 11000 and 9000 14 c yr b p this interval may be holocene or may correlate with a hypothesized younger dryas glacial advance in the colorado front range sedimentologic mineralogic and geochemical data indicate that as many as three sources could have supplied loess in eastern colorado these sources include glaciogenic silt derived from the colorado front range and two bedrock sources volcaniclastic silt from the white river group and clays from the pierre shale the sediment sources imply a generally westerly paleowind during the last glacial maximum new carbon isotope data combined with published faunal data indicate that the loess was probably deposited on a cool steppe implying a last glacial maximum july temperature depression relative to the present of at least 5 6 c overall loess deposition in eastern colorado occurred mostly toward the end of the last glacial maximum under cooler and drier conditions with generally westerly winds from more than one source

an extremely low source in the moon uthpb smnd rbsr and isotopic systematics and age of lunar meteorite asuka 881757 abstract we have undertaken u th pb sm nd rb sr and 40 ar 39 ar isotopic studies on asuka 881757 a coarse grained basaltic lunar meteorite whose chemical composition is close to low ti and very low ti vlt mare basalts the pb pb internal isochron obtained for acid leached residues of separated mineral fractions yields an age of 3940 28 ma which is similar to the u pb 3850 150 ma and th pb 3820 290 ma internal isochron ages the sm nd data for the mineral separates yield an internal isochron age of 3871 57 ma and an initial 143 nd 144 nd value of 0 50797 10 the rb sr data yield an internal isochron age of 3840 32 ma 87 rb 1 42 10 11 yr 1 and a low initial 87 sr 86 sr ratio of 0 69910 2 the 40 ar 39 ar age spectra for a glass fragment and a maskelynitized plagioclase are relatively flat and give a weighted mean plateau age of 3798 12 ma we interpret these ages to indicate that the basalt crystallized from a melt 3 87 ga ago the sm nd age and an impact event disturbed the rb sr system and completely reset the k ar system at 3 80 ga the slightly higher pb pb age compared to the sm nd age could be due to the secondary pb from terrestrial and or lunar surface pb contamination that remained in the residues after acid leaching alternatively the following interpretation is also possible the meteorite crystallized at 3 94 ga the pb pb age and the sm nd rb sr and k ar systems were disturbed by an impact event at 3 80 ga the crystallization age obtained here is older than those reported for low ti basalts 3 2 3 5 ga and for vlt basalts 3 4 ga but similar to ages of some mare basalts indicating that the basalt may have formed from a magma related to a basin forming event imbrium the age span for vlt basalts from different sampling sites suggest that they were erupted over a wide area during an interval of at least 500 million years the impact event that thermally reset the k ar system of asuka 881757 must have been post imbrium perhaps orientale in age the lead isotopic composition of asuka 881757 is nonradiogenic compared with typical apollo mare basalts and the estimated 238 u 204 pb value for the basalt source is 10 3 this source value is the lowest so far measured for lunar rocks a large positive nd value 7 4 0 5 and the time averaged 147 sm 144 nd ratio for the basalt source are similar to those for some apollo 12 15 and 17 basalts suggesting a lree depleted mantle which is consistent with the global magma ocean hypothesis the u th pb sm nd and rb sr data on asuka 881757 suggest that the basalt was derived from a low u pb low rb sr and high sm nd source region mainly composed of olivine and orthopyroxene with minor amounts of plagioclase or clinopyroxene and with sulfides enriched in volatile chalcophile elements the basalt source may be deep in origin and different in chemistry from those previously estimated from studies of apollo and luna mare basalts indicating heterogeneous sources for mare basalts

gravitational differentiation due to initial chemical stratification origin of lunar asymmetry by the creep of dense kreep abstract models for the evolution of the moon must explain a number of important characteristics of its magmatic history primary among them is the emplacement of mare basalts primarily on one side of the moon and in a region of the surface roughly correlating with that containing high subsurface concentrations of kreep it is thus important to explore mechanisms which will regionally concentrate a kreep layer early in lunar evolution and which 400 500 myr later give rise to mare basalt generation beneath the same region gravitational instability of a chemically dense ilmenite rich cumulate created during the fractionation of an anorthositic crust is one candidate model if so gravitational instability must occur at long wavelength to explain the hemispheric asymmetry we examine the rayleigh taylor instability of a dense layer near the surface of a sphere representing the lunar mantle in which the viscosity varies with depth our results show that spherical harmonic degree 1 is the fastest growing wavelength of instability if the viscosity of the dense layer is sufficiently low relative to that of the deeper mantle or if the viscosity of the mantle increases with depth however the viscosity increase cannot be distributed over a depth that is too large we explore whether a residual kreep like layer near the base of anorthositic crust might give rise to these needed conditions

u pb ages of angrites abstract precise u pb ages determined with double spike 202 pb 205 pb thermal ionization m1ass spectrometry are reported for angrites angra dos reis ador lewis cliff 86010 lew and d orbigny nineteen of 23 acid washed pyroxene fractions from these meteorites and whole rock fractions from d orbigny contain between 0 5 and 1 3 pg of total common pb indistinguishable from analytical blank measured 206 pb 204 pb ratios in these fractions are between 6300 and 14 100 for ador 1160 4500 for lew and 608 8500 for d orbigny blank corrected 206 pb 204 pb ratios for all three meteorites vary from 2160 to over 100 000 these fractions yielded precise and reproducible 207 pb 206 pb dates with the average values of 4557 65 0 13 ma for ador 4558 55 0 15 ma for lew and 4564 42 0 12 ma for d orbigny pb pb isochrons including data with slightly elevated common pb and u pb upper concordia intercepts yield similar dates the implications of these new pb isotopic ages of angrites are threefold first they demonstrate that ador and lew are not coeval and the group of slowly cooled angrites is therefore genetically diverse second the new age of lew suggests an upward revision of 53 mn 53 cr absolute ages by 0 7 ma third a precise age of d orbigny allows consistent linking of the 53 mn 53 cr and 26 al 26 mg extinct nuclide chronometers to the absolute lime scale

long term storage and age biased export of fluvial organic carbon field evidence from west iceland terrestrial organic carbon oc plays an important role in the carbon cycle but questions remain regarding the controls and timescale s over which atmospheric co remains sequestered as particulate oc poc motivated by observations that terrestrial poc is physically stored within soils and other shallow sedimentary deposits we examined the role that sediment storage plays in the terrestrial oc cycle specifically we tested the hypothesis that sediment storage impacts the age of terrestrial poc we focused on the efri haukadalsa river catchment in iceland as it lacks ancient sedimentary bedrock that would otherwise bias radiocarbon based determinations of poc storage duration by supplying pre aged petrogenic poc our radiocarbon measurements of riverine suspended sediments and deposits implicated millennial scale storage times comparison between the sample types suspended and deposits suggested an age offset between transported suspended sediments and stored deposits poc at the time of sampling which is predicted by theory for the sediment age distribution in floodplains we also observed that poc in suspended sediments is younger than the predicted mean storage duration generated from independent geomorphological data which suggested an additional role for oc cycling consistent with this we observed interparticle heterogeneity in the composition of poc by imaging our samples at the microscale using x ray absorption spectroscopy specifically we found that particles within individual samples differed in their sulfur oxidation state which is indicative of multiple origins and or diagenetic histories altogether our results support recent coupled sediment storage and oc cycling models and indicate that the physical drivers of sediment storage are important factors controlling the cadence of carbon cycling

ostracod based palaeotemperature reconstructions for mis 11 human occupation at beeches pit west stow suffolk uk abstract the mutual ostracod temperature range motr method is applied to ostracod assemblages from the well documented middle pleistocene mis 11 human occupation site of beeches pit west stow suffolk england the results provide palaeotemperature reconstructions which are compared against other proxy data from molluscs and ostracod indicator species ostracod assemblages from the lower part of the sequence beds 3 and 4 suggest a temperate climate with mean monthly temperatures january and july not dissimilar to those of today while those of the overlying bed 7 indicate a climatic shift to a more continental climate with winter temperatures at least 4 c colder than today these results corroborate previous suggestions that the evidence of human occupation at beeches pit occurs not only in the interglacial mis 11c but also in a succeeding cold phase possibly mis 11b and provide the first quantitative palaeotemperature reconstructions for this site and interval