coastal eolian sands paleosols and pleistocene geoarchaeology of the southwestern cape south africa abstract narratives of pleistocene prehistory for mis 4 to 9 are primarily constructed on the basis of what appear to be subcontinuous archaeological records in cave sites with subsidiary geo and bioarchaeological research attempting to determine the nature of external environments and biotic resources from the inside rather than the outside the present study seeks to establish a detailed chronostratigraphy for faunal and archaeological sites linked with coastal sediments in the southwestern cape province accelerated shore deflation during glacio eustatic oscillations of sea level deposited multiple eolianites and textural changes of such calcified sands identify both transgressive and regressive sea level trends these provide a proxy for local shore proximity sometimes directly linked to high sea level stands such sediments are subdivided into lithostratigraphic sequences by multiple paleosols that range from abc soils to calcretes or plinthite ferricrete horizons repeated intervals of solution or karstic activity created underground cavities that allowed fossil bone to collect in or below hyena lairs such fills further connect sedimentary units with pedogenic events to integrate local stratigraphies into a regional lithostratigraphy that can be readily correlated with global chronostratigraphies mis stages and dansgaard oeschger events derived from polar ice and deep sea cores as well as long stalagmite and pollen records the faunal assemblages see table 9 of mis 5 and early 4 were penecontemporaneous with pedogenic phases that record greater moisture during intervals when sea level oscillated a little below that of today dominated by larger grazers such assemblages argue for a more open environment than the modern fynbos sclerophyllous heath brush and specifically a land cover of higher productivity and nutritional status such conditions probably affected only a fraction of mis 5 time middle stone age msa assemblages are limited to late mis 4 cave overhang sites also linked to such pedogenic phases although an msa like site dates to mis 5d older littoral sands modified by plinthite development include the acheulian and faunal site of duinefontein 2 that may represent mis 9 visible evidence for human occupation including cave overhang sites during mis 4 to 9 see table 9 was strikingly discontinuous in the southwestern cape begging questions about the number of prehistoric groups demography spatial patterning and ecological context

late quaternary paleotemperatures derived from a speleothem from cango caves cape province south africa abstract an oxygen isotope temperature record over a large part of the past 30 000 yr has been obtained for the southern cape province of south africa by combining data on the isotopic composition of a stalagmite from a deep cave with that of a confined groundwater aquifer in the same region results show that temperatures during the last glacial maximum were on average about 6 c lower than those today with peaks up to 7 c lower a detailed analysis of the past 5000 yr suggests multiple fluctuations with generally lower temperatures 1 2 c around 4500 and 3000 yr b p the carbon isotopic composition of the stalagmite indicates significant vegetation changes between the late pleistocene and today and also during the second half of the holocene

turbulent heat flux in the upper ocean under sea ice turbulence data from three arctic drift station experiments demonstrate features of turbulent heat transfer in the oceanic boundary layer time series analysis of several w t records shows that heat and momentum flux occur at nearly the same scales typically by turbulent eddies of the order of 10 20 m in horizontal extent and a few meters in vertical extent probability distribution functions of w t have large skewness and kurtosis where the latter confirms that most of the flux occurs in intermittent events with positive and negative excursions an order of magnitude larger than the mean value an estimate of the eddy heat diffusivity in the outer ekman part of the boundary layer based on measured heat flux and temperature gradient during a diurnal tidal cycle over the yermak plateau slope north of fram strait agrees reasonably well with the eddy viscosity with values as high as 0 15 m2 s 1 an analysis of measurements made near the ice ocean interface at the three stations shows that heat flux increases with both temperature elevation above freezing and with friction velocity at the interface it also reveals a surprising uniformity in parameters describing the heat and mass transfer e g the thickness of the transition sublayer from a modified version of the yaglom kader theory is about 10 cm at all three sites despite nearly a fivefold difference in the under ice roughness z0 which ranges from approximately 2 to 9 cm a much simplified model for heat and mass transfer at the ice ocean interface suggested by the relative uniformity of the heat transfer coefficients at the three sites is outlined

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

high resolution record of climate stability in france during the last interglacial period the last interglacial period 127 110 kyr ago has been considered to be an analogue to the present interglacial period the holocene which may help us to understand present climate evolution but whereas holocene climate has been essentially stable in europe variability in climate during the last interglacial period has remained unresolved because climate reconstructions from ice cores1 2 continental records3 4 and marine sediment cores5 6 give conflicting results for this period7 here we present a high resolution multi proxy lacustrine record of climate change during the last interglacial period based on oxygen isotopes in diatom silica diatom assemblages and pollen climate transfer functions from the ribains maar in france contrary to a previous study8 our data do not show a cold event interrupting the warm interglacial climate instead we find an early temperature maximum with a transition to a colder climate about halfway through the sequence the end of the interglacial period is clearly marked by an abrupt change in all proxy records our study confirms that in southwestern europe the last interglacial period was a time of climatic stability and is therefore still likely to represent a useful analogue for the present climate

lagrangian analysis of a convective mixed layer 1 we characterize and quantify the transport of heat boussinesq density in a highly idealized entraining convective mixed layer based on simulations of lagrangian measurements in a two dimensional model the primary objectives are to assess and explore the merits and difficulties in estimating the heat budget from perfect and imperfect lagrangian floats a significant advantage of lagrangian measurements is that the time derivative of temperature along these trajectories gives a direct measure of the diffusive heat flux using simulated perfect lagrangian floats estimates of the surface buoyancy flux the depth of the mixed layer vertical profiles of advective and diffusive heat flux and the overall rate of cooling are shown to agree accurately with the known results extracted from the eulerian simulations the lagrangian nature of the data is exploited to reveal the structure of the flow within the convective layer and to quantify the heat fluxes associated with the different types of eddies phase plots of lagrangian trajectories in density depth space reveal three distinct classes of motions 1 plumes which develop in the cold heavy near surface thermal boundary layer and plunge into the mixed layer interior carrying heavy water downward 2 interior turbulence comprising random motions between the base of the thermal boundary layer and the base of the surface mixed layer and 3 entrainment of interior water into plumes below the thermal boundary layer i e a transition from class 2 to class 1 plumes dominate the heat transport simulations were also made using slightly buoyant floats these are not perfectly lagrangian buoyancy concentrates the floats near the surface resulting in an oversampling of the stronger plumes making the same heat budget calculations as with the perfect floats results in a nonzero estimated lagrangian heating rate in the interior and a curved profile of vertical heat flux that is up to 3 times too large the local time rate change of density is not significantly affected a correction of the heat transport for oversampling of the plumes removes most of the error this technique allows the correct heat budget to be measured for this flow using weakly buoyant floats

plumes in rotating convection part 1 ensemble statistics and dynamical balances atmospheric and oceanic convection often occurs over areas occupied by many localized circulation elements known as plumes the convective transports therefore may depend not only on the individual elements but also on the interactions between plumes and the turbulent environment created by other plumes however many attempts to understand these plumes focus on individual isolated elements and the behaviour of an ensemble is not understood geophysical convection may be influenced by rotation when the transit time of a convecting element is long compared to an inertial period for example in deep oceanic convection much recent attention has been given to the effect of rotation on individual plumes but the role of rotation in modifying the behaviour of an ensemble is not fully understood here we examine the behaviour of plumes within an ensemble both with and without rotation to identify the influence of rotation on ensemble plume dynamics we identify the coherent structures plumes present in numerical solutions of turbulent rayleigh benard convection a canonical example of a turbulent plume ensemble we use a conditional sampling compositing technique to extract the typical structure in both non rotating and rotating solutions the dynamical balances of these composite plumes are evaluated and compared with entraining plume models we find many differences between non rotating and rotating plumes in their transports of mass buoyancy and momentum as shown in previous studies the expansion of the turbulent plume by entrainment of exterior fluid is suppressed by strong rotation our most significant new result is quantification of the continuous mixing between the plume and ambient fluid which occurs at high rotation without any net changes in plume volume this mixing is generated by the plume plume interactions and acts to reduce the buoyancy anomaly of the plume by contrast in the non rotating case no such loss of buoyancy by mixing occurs as a result the total buoyancy transport by upwardly moving plumes diminishes across the layer in the rotating case while remaining approximately constant in the non rotating case at high values of rotation the net vertical acceleration is considerably reduced compared to the non rotating case due to loss of momentum through entrainment and mixing and a decelerating pressure gradient which partially balances the buoyancy driven acceleration of plumes as a result of the dilution of buoyancy the pressure gradient deceleration and the loss of momentum due to mixing with the environment in the rotating solutions the conversion of potential energy to kinetic energy is significantly less than that of non rotating plumes the combination of efficient lateral mixing and slow vertical movement by the plumes accounts for the unstable mean temperature gradient that occurs in rotating rayleigh benard convection while the less penetrative convection found at low rossby number is a consequence of the reduced kinetic energy transport within the ensemble of plumes identified by the conditional sampling algorithm distributions of vertical velocity buoyancy and vorticity mimic those of the volume as a whole plumes cover a small fraction of the total area yet account for most of the vertical heat flux

mid pleistocene hominin occupation at elandsfontein western cape south africa abstract the current understanding of landscape scale variation in mid pleistocene hominin behavior is limited most of our understanding derives from a few localities in eastern africa consequently we know very little about hominin landscape use outside this region despite the fact that mid pleistocene hominins occupied other climatic zones including temperate and mid latitude ecosystems the winter rainfall zone in south africa represents one of the world s most diverse ecosystems although mammal diversity is relatively low in these habitats this is compensated by the tremendous floral diversity buried pleistocene land surfaces in the region provide an opportunity to understand how humans adapted to this unique mid latitude environment prior to the last interglacial the dunefield locality of elandsfontein in the western cape of south africa is one of the richest known paleontological and archeological sites in southern africa it records details of landscape formation history enabling detailed reconstruction of the ancient environments in this winter rainfall dominated region this dunefield archive allows us to posit the taphonomic history of newly excavated archaeological material and previously collected specimens here we provide initial results from the excavation and geological analysis of the elandsfontein dunefield and provide new insights into the formation history of the archaeological and paleontological deposits this includes indications of multiple pedogenic intervals and groundwater table fluctuations the combination of geological paleontological and archaeological data provides a framework for evaluating how hominins interacted with the unique ecosystems of the cape floral region of south africa during the mid pleistocene

challenges for a cross disciplinary geoarchaeology the intersection between environmental history and geomorphology abstract geoarchaeology is a growing subfield of cross disciplinary research at the intersection between geomorphology environmental history and archaeology this prospective essay does not aim to analyze the nature or evolution of geoarachaeology or to review available techniques and methods instead it addresses challenges exciting challenges confront geoarchaeology in the form of persistent problems that demand satisfactory solutions despite improving skills and innovative technologies drawing from the full record of human history a number of practical issues can be highlighted to explicate these challenges 1 open air archaeological sites are the main object of study for the early to mid pleistocene even though they represent open systems that raise fundamental questions about archaeo taphonomic integrity how were sites buried and then modified by selective preservation horizontal or vertical disturbance and the role of carnivores is it possible to determine the degree to which such sites accurately record prehistoric human behavior prior to the late pleistocene when hearths and living structures lend better definition to occupation surfaces can non primary open air sites also shed light on human activities and environmental history 2 cave sites have long been favored by archaeologists because of the impression that they represent relatively complete and undisturbed archaeostratigraphic sequences but serious problems also exist here in regard to the nature of accumulation and the sources of mineral and biogenic sediments in what were open systems liable to disturbance despite comparatively low energy processes 3 less familiar are urban and other architectural sites where processes of formation and degradation mimic natural sedimentation and erosion such a geoarchaeology can be highly informative for urban processes demographic cycles or the intersection between sites and their surrounding landscapes 4 spatial components of geoarchaeological research need more systematic consideration for locational strategies and with an appreciation that site presence or absence allows a more dynamic modeling of settlement and procurement strategies 5 regional settlement expansion and contraction may also inform on mosaic evolution or pleistocene dispersals including the out of africa hypothesis 5 finally multiple themes connected with environmental degradation during holocene times may open new windows to examine specific problems by objective criteria so contributing to a wider academic discourse about long term trends the interfingering of climatic and land use factors in cause and effect dilemmas or the construction of future scenarios in an era of accelerating planetary change the focus of archaeology is shifting to later ranges of prehistory so that geoarchaeologists now have a mandate to engage more directly with urban spatial and degradation issues this should be met with a broader and more inclusive agenda one that optimizes on expertise with historical geomorphology and environmental history but in collaboration with archaeologists and other social scientists that would sustain a more prominent role for geoarchaeology in the university curriculum

late quaternary dietary shifts of the cape grysbok raphicerus melanotis in southern africa abstract the cape grysbok is endemic to southern africa s cape floral region where it selectively browses various species of dicotyledonous vegetation fossil evidence indicates that the grysbok persisted under glacial and interglacial conditions throughout the late quaternary and inhabited a range of environments this study employs mesowear analysis to reconstruct grysbok diets over time and in response to changing environments at nelson bay cave die kelders cave 1 klasies river mouth and swartklip 1 results indicate that the amount of grasses monocots versus leafy vegetation dicots included in the diet fluctuated over time and largely in agreement with changes in faunal community structure the case for dietary flexibility is particularly clear at nelson bay cave where there is a significant trend from mixed feeding towards increased browsing from the late pleistocene 18 500 14 c yr bp through the holocene dietary shifts at nelson bay cave are consistent with the hypothesis that declining grassland productivity is responsible for the terminal pleistocene extinction of several large ungulates in southern africa furthermore the short term dietary shifts demonstrated here 100s to 1000s of years provide an important caution against relying on taxonomic uniformitarianism when reconstructing the dietary preferences of fossil ungulates both extant and extinct

u series measurements in tyrrhenian deposits from mallorca further evidence for two last interglacial high sea levels in the balearic islands the campo de tiro type section for the tyrrhenian ecostratigraphic beds of the balearic islands shows four indurated littoral conglomerates and beach rocks unconformably superimposed the lower two units 1 and 2 are separated by a thin layer of reddish continental silts both contain a typical eutyrrhenian fauna whereas a neotyrrhenian fauna characterizes the overlying units 3 and 4 thu measurements by thermal ionisation mass spectrometry on mollusk shells from these deposits yielded ages of 135 ka unit 1 117 ka units 2 and 3 and a scatter of ages around 100 ka unit 4 the stratigraphic relationships and thu data indicate i that uranium was uptaken by mollusks shells but arca sp each time during a relatively short early diagenetic interval before cementation ensured a fair closure of the radioactive system ii two high sea stands characterized the last interglacial isotopic substage 5e of the balearic islands area iii the duration of this episode was 17 ka and iv the change in faunal assemblages and disconformity observed between units 2 and 3 are due to fluctuations in sea level and surface water conditions which occurred during the second high sea level episode of the last interglacial

first excavation of intact middle stone age layers at ysterfontein western cape province south africa implications for middle stone age ecology abstract excavations into a coastal cliff at ysterfontein yft 1 south africa have revealed 2 5 3 m of stratified sands containing classic middle stone age msa stone artifacts abundant mussel and limpet shells numerous fragments of ostrich eggshell and somewhat rarer bones from mammals birds tortoises and snakes the sands apparently filled a crevice like calcrete shelter where the artifacts and animal remains accumulated partly in place and perhaps partly through slippage down the face of a dune that once stood between the site and the sea accelerator radiocarbon dating of ostrich eggshell places the sequence before 33 400 years ago artifact typology provisionally suggests that it formed after 70 000 years ago the fauna resembles faunas from the handful of other known coastal msa sites and contrasts with faunas from regional later stone age lsa sites in its low diversity of coastal marine species and in the large size of its limpets and tortoises the difference suggests that msa people exploited local resources less intensively probably because their populations were less dense

rapid environmental changes in southern europe during the last glacial period oxygen isotope records from greenland ice cores1 2 indicate numerous rapid climate fluctuations during the last glacial period north atlantic marine sediment cores show comparable variability in sea surface temperature and the deposition of ice rafted debris3 4 5 in contrast very few continental records of this time period provide the temporal resolution and environmental sensitivity necessary to reveal the extent and effects of these environmental fluctuations on the continents here we present high resolution geochemical physical and pollen data from lake sediments in italy and from a mediterranean sediment core linked by a common tephrochronology our lacustrine sequence extends to the past 102 000 years many of its features correlate well with the greenland ice core records demonstrating that the closely coupled ocean atmosphere system of the northern hemisphere during the last glacial4 extended its influence at least as far as the central mediterranean region numerous vegetation changes were rapid frequently occurring in less than 200 years showing that the terrestrial biosphere participated fully in last glacial climate variability earlier than 65 000 years ago our record shows more climate fluctuations than are apparent in the greenland ice cores together the multi proxy data from the continental and marine records reveal differences in the seasonal character of climate during successive interstadials and provide a step towards determining the underlying mechanisms of the centennial millennial scale variability

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

turbulent vertical kinetic energy in the ocean mixed layer abstract vertical velocities in the ocean boundary layer were measured for two weeks at an open ocean wintertime site using neutrally buoyant floats simultaneous measurements of the surface meteorology and surface waves showed a large variability in both wind and wave properties and only weak correlations between them buoyancy forcing was weak the mean square vertical velocity in the boundary layer 2w measured from the vertical motion of the floats was proportional to the squared friction velocity u2 estimated from shipboard meteorological measurements using bulk formulas thus 2w au2 the rate of momentum transport from the atmosphere to the ocean is u2 where is the density of the water the deviations from this relation can be attributed entirely to statistical variation and measurement error the measured values of 2w were corrected for measurement biases and the nonturbulent contributions of internal waves the value of the turbulent part of a is 1 75 2 times that measured in laborato

on the relative and absolute ages of seven lunar front face basins i from viscosity arguments the seven basins orientale imbrium crisium nectaris humorum and an unnamed basin between werner and the altai ring show rims whose absolute and relative heights are correlated with the sharpness and crispness of the features on the assumption that the decline in average outer rim height not scarp height measures the age of the basin and also that the decline represents a hot creep of rocks of very high viscosity absolute ages were derived basins were found to increase in age in the sequence listed above with a range from about 3 82 to 4 30 109 years the average or effective viscosity of the surface layers down to whatever level was involved in the creep was calculated as increasing from 9 46 1024 poises at about 4 30 109 years to 1 86 1030 poises at present it should be clear at the outset what the assumptions and associated observations are and why they are necessary to a solution they will be listed in this abstract and expanded upon in the text 1 1 the original rim height of each basin was a function only of basin diameter 2 2 the original rim height was given by pike s 1983 relation for fresh craters extrapolated to basin diameters 3 3 the present rim height is that of the most prominent ring structure 4 4 the smaller rim height of all seven basins relative to the height predicted by 2 is due largely to creep in the lunar rocks down to some undetermined level other forces may contribute to the sinking of the rims but these are considered to be of lesser importance and are discussed in the text 5 5 the relative ages of the seven basins are as given in table i this sequence differs slightly from that of wilhelms 1984 for example but it is that found in baldwin 1974 1987 and is consistent with the results of this paper 6 6 the age of formation of the imbrium basin 3 85 109 years inferred from lunar sample studies particularly apollo 15 is correct 7 7 the age of formation of the serenitatis basin 3 87 04 109 years inferred from petrologic and geochemical studies of apollo 17 boulders is incorrect this is not an assumption but is a result of the analysis of this paper 8 8 the rheology of the moon may be described for the purposes of this paper by an effective viscosity valid throughout the layers involved in the creep 9 9 this effective viscosity is used as a tool to determine basin ages and is not important in itself it does appear to vary in the same range as terrestrial rocks but not the lithosphere 10 10 other factors such as isostasy shaking due to jar from later impacts modification due to rim relief by ejecta and erosion from small impacts are all close to exponential in nature declining toward the present and hence may be included in the determination of the effective viscosity 11 11 the rim height of the imbrium basin subsided by 25 m in the last 2 5 109 years this value was chosen arbitrarily it could have been 250 300 m and the basin ages would not have been affected except for orientale and that only minutely 12 12 the effective viscosity of the moon was observed to change continuously and monotonically with time 13 13 judging by table iii the probable error of an absolute age is in the range of 10 to 50 106 years it is difficult to determine exactly what this means it will be constrained by points 14 15 and 16 14 14 an error in the age determination should not be large enough to alter the relative ages of the basins judging by crater counts baldwin 1974 1987 15 15 if the viscosity of the moon declined in the post imbrium period of mare formation the only basin to be affected would be orientale and this by no great amount inasmuch as the basin is older than nearby maria 16 16 if the effective viscosity were less than about 1022 poises at the time of the oldest basin then presaturation surfaces would not show the numerous craters and portions of craters that are obvious in this time span 17 17 considerably prior to the time of saturation the outer layers of the moon had a low enough viscosity so that they could not retain the record of the then occuring cratering 18 18 the approximations of this paper were adopted because it does not appear possible to make an unambiguous selection from the more elegant mathematical treatments of creep and isostasy that would lead toward reasonable ages for the giant basins

the last interglacial sea level high stand on the southern cape coastline of south africa abstract the continental margin of southern south africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long term eustatic sea level changes we report a suite of optical luminescence ages and supplementary amino acid racemization data which provide paleosea level index points for three sites on this coastline deposits in the swartvlei and groot brak estuaries display tidal inlet facies overlain by shoreface or eolian facies contemporary facies relations suggest a probable high stand 6 0 8 5 m above modern sea level amsl at cape agulhas evidence of a past sea level high stand comprises a gravel beach ca 3 8 m amsl and an overlying sandy shoreface facies up to 7 5 m amsl osl ages between 138 7 ka and 118 7 ka confirm a last interglacial age for all marginal marine facies the high stand was followed by a sea level regression that was associated with the accumulation of eolian dunes dating to between 122 7 ka and 113 6 ka these data provide the first rigorous numerical age constraints for last interglacial sea level fluctuations in this region revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far field locations

pollen analytical biostratigraphy of the last five climatic cycles from a long continental sequence from the velay region massif central france in the volcanic region of velay massif central france lake sediment sequences derived from maar craters situated close to one another ribains praclaux and lac du bouchet have been correlated on the basis of tephrostratigraphical analyses this has enabled the construction of a sequence 2980 pollen spectra that begins during the glaciation preceding the holsteinian and ends in the present this sequence covers the period from 450 ka i e from the end of marine oxygen isotope stage 12 to the present time and includes five climatic cycles the study of a second core from the praclaux site completed the long velay sequence the biostratigraphy of the whole sequence is described in detail and illustrated by a synthetic and simplified pollen diagram thirteen temperate forest episodes interglacials or interstadials and as many cold periods glacials or stadials are defined each temperate episode is characterised by particular forest development and vegetation dynamics and all of them with the exception of the holocene begin and end with a pinus forest the vegetation dynamics observed during the holocene resemble more closely those recorded during the interstadials than during the interglacials copyright 2000 john wiley sons ltd

was the climate of the eemian stable a quantitative climate reconstruction from seven european pollen records the aim of the present study is to estimate the range of the climatic variability during the eemian interglacial which lasted about 10 000 years marine isotopic stage 5e the modem pollen analogue technique is applied to seven high resolution pollen records from france and poland to infer the annual precipitation and the mean temperature of the coldest month the succession of pollen taxa and the reconstructed climate can be interpreted coherently the warmest winter temperatures are centred in the first three millennia of the eemian interglacial during the mixed oak forest phase with quercus and corylus as dominant trees a rapid shift to cooler winter temperatures of about 6 degrees to 10 degrees c occurred between 4000 and 5000 years after the beginning of the eemian related to the spread of the carpinus forest this shift is more obvious for the reconstructed temperatures than for precipitation and is unique and irreversible for the whole eemian period following this climatic shift of the eemian variations of temperature and precipitation during the fast 5000 years were only slight with an amplitude of about 2 degrees to 4 degrees c and 200 to 400 mm yr the estimated temperature changes were certainly not as strong as those reconstructed for the stage 6 5e termination or the transition 5e 5d this is consistent with the constantly high ratio of tree pollen throughout the eemian indicative of a succession of temperate forest types this gradual transition between different forest landscapes can be related to intrinsic competition between the species rather than to a drastic climatic change c 1998 elsevier science b v all rights reserved

west coast dune plumes climate driven contrasts in dunefield morphogenesis along the western and southern south african coasts abstract this study examines two major late quaternary coastal dune systems situated in the southwestern most extremity of africa the false bay and duinefontyn dune plumes formed in close proximity but under contrasting oceanographic regimes warm agulhas and cold benguela oceanic current systems respectively the false bay and duinefontyn dune plumes have hitherto lacked the objective numerical chronology required to realize their full potential in unraveling the complex palaeo oceanographic and palaeoclimatic history of the region here we present a dual amino acid racemizationn aar and optically stimulated luminescence osl chronological framework from the extensive three dimensional exposures in sea cliffs at false bay three generations of dune deposition corresponding with orbitally forced climatic sea level cycles mis 7 mis 5 and holocene were resolved whereas the duinefontyn plume is dominated by mis 5 and holocene sedimentation at false bay and duinefontyn glacial periods are marked by the development of mature palaeosols confirming the link between glacio eustacy and dune deposition determined previously on the west and southern coasts of south africa along the west coast dune plumes typify dunefield morphology whereas shoreline parallel dune cordons are commonly developed on the southern coast these regional variations in dune system morphogenesis are largely controlled by contrasting wind and rainfall patterns the attenuated dimensions of the mis 5 plumes at false bay and duinefontyn may indicate a weakening of the south atlantic anticyclone during the last interglacial at false bay stone artifacts illustrate a human presence in the region during mis 7

climatic and sea level controls on late quaternary eolian activity on the agulhas plain south africa abstract located at the interface between the temperate westerly and sub tropical climate systems south africa s winter rainfall zone wrz is a key location in understanding late quaternary atmospheric circulation dynamics inactive eolian deposits in the wrz comprising pan fringing lunette and coastal dunes were investigated to establish their depositional ages and utility as paleoenvironmental indicators the resulting optical luminescence chronology reveals episodic lunette accretion at 60 000 45 000 yr 12 000 13 000 yr 2800 2600 yr 1200 yr and episodes of lunette and coastal dune accretion on the agulhas plain are temporally distinct reflecting differing fundamental controls on their activity comparisons to previously published data also reveal that the lunettes differ in age from more ancient coastal eolianites lunette deposition is asynchronous between locations reflecting the topographic and hydrological setting of the individual pans in near coastal settings with limited surface recharge lunette accretion appears to be at least partially controlled by sea level induced changes in groundwater levels those pans with more significant surface recharge particularly from fluvial systems may produce less ambiguous paleoenvironmental records with pan status more strongly reflecting regional hydrological conditions lunette orientation is indicative of strong westerly winds during both the pleistocene and holocene lunette accretion would have been promoted by reduced on shore moisture transport during the summer months enhancing rainfall seasonality such conditions would have been promoted by increased continentality as the agulhas bank was exposed during low sea level stands

carnivore size and quaternary climatic change in southern africa abstract the relationship between carnassial length and latitude south is analyzed for 17 african carnivore species to determine if individuals tend to be larger in cooler climates as predicted by bergmann s rule with modern data in support middle and late quaternary temperatures might then be inferred from mean carnassial length in fossil samples such as those from equus cave elandsfontein sea harvest duinefontein and swartklip in the cape province of south africa one problematic aspect of the study is the use of carnassial length and latitude as necessary but imperfect substitutes for body size and temperature respectively for some species another difficulty is the relatively small number of available modern specimens combined with their uneven latitudinal spread still in 14 of the species carnassial length does tend to increase with latitude south while mean carnassial length in the same species tends to be greater in those fossil samples which accumulated under relatively cool conditions as inferred from sedimentologic palynological or geochemical data given larger modern samples from a wide variety of latitudes refinement of the mathematical relationship between carnassial length and latitude in various species may even permit quantitative estimates of past temperatures in southern africa

multiple episodes of aridity in southern africa since the last interglacial period there is generally a dearth of evidence of the nature of quaternary climate change within desert systems which has limited previous interpretations of past environmental change at low latitudes the last glacial maximum has previously been identified as the peak of late quaternary aridity when desert systems expanded to five times their present extent1 2 3 and low latitude aridity has been described for previous glaciations4 but little evidence has been derived directly for large desert basins particularly southern africa here we report new chronological optical dating evidence of arid episodes recorded in aeolian sediments from the mega kalahari sand sea episodic aeolian activity is recorded at the northeastern desert margin whereas more sustained activity is evident from the southwestern desert core several significant arid events are apparent since the last interglacial period with dune building arid phases at 95 115 41 46 20 26 and 9 16 kyr before present existing atmospheric general circulation model simulations and independent palaeoclimate data indicate that the changes in aridity are related to changes in the northeast southwest summer rainfall gradient which are in turn related to sea surface temperatures in the southeastern atlantic ocean

the case for a younger imbrium basin new 40ar 39ar ages of apollo 14 rocks petrographically and chemically well characterized rocks of the apollo 14 landing site 12 impact melt breccias 3 clast free impact melt rocks 2 granulitic rocks 1 cataclastic noritic anorthosite 1 shocked gabbronorite 1 mare basalt and 1 plagioclase single crystal have been dated by the 40ar 39ar technique the samples represent two different formations at the apollo 14 site 1 small lithic clasts 10 specimens from fragmental breccia 14063 ejected from the 26 ma old cone crater and one clast mare basalt from cone crater soil 14140 and 2 large rock samples 10 specimens collected throughout the regolith of the landing site the first group of samples has exposure ages close to 26 ma and 40ar 39ar ages ranging from 3 86 to 4 09 ga which indicates that breccia 14063 was assembled 3 86 ga ago the second group of samples displays lower 40ar 39ar ages ranging from 3 73 to 3 85 ga we interpret breccia 14063 as part of a nectarian megabreccia unit which was incorporated into the fra mauro formation as a megablock by secondary mass wasting of the ejecta blanket of a local pre imbrian crater the remaining samples are thought to represent clasts of the apollo 14 subregolith basement megabreccia defined as the fra mauro formation consequently the reported ages of these clasts confirm previous suggestions that the fra mauro formation and therefore the imbrium basin is only 3 75 ga old and not 3 85 ga as commonly assumed

excavation of buried late acheulean mid quaternary land surfaces at duinefontein 2 western cape province south africa abstract duinefontein 2 dft2 preserves at least two buried land surfaces within a 10 m thick dune plume on the atlantic coast of south africa about 35 km north of cape town optically stimulated luminescence dating indicates that the sands enclosing the upper surface accumulated around 270 ky ago while the sands between the two surfaces were accumulating about 290 ky ago excavation so far has focused on the upper buried surface which is now exposed over 480 m 2 historically there was no body of fresh water nearby and the surrounding vegetation was a variant of the regional fine leafed shrub or fynbos pedogenic alteration of the sands and bones of water loving mammals and amphibians indicate however that the bones and associated acheulean artifacts accumulated near the edge of a large pond or marsh in addition the principal mammal species buffalo wildebeest and kudu imply a sharply different regional vegetation in which grass and broad leafed bush were much more common the artifacts are distributed across the upper buried surface in no apparent pattern but the large mammal bones tend to occur as clusters of skulls vertebrae ribs and other axial elements often in near anatomical order limb bones are mostly missing and the clusters appear to mark carcasses from which the limb bones were selectively removed the bones rarely show marks from stone tools but marks from carnivore teeth are common together with numerous hyena coprolites the abundant tooth marks suggest that hyenas and perhaps other carnivores were largely responsible for carcass disarticulation the human role appears to have been insignificant which suggests that local acheulean people obtained few large mammals whether by hunting or scavenging among the small number of other acheulean carcass sites for which bone damage observations are available the best documented sites suggest the same limited human ability to acquire large mammals but many additional sites will be necessary to determine if this was the acheulean norm greatly expanded excavation of the lower buried surface at dft2 can provide an additional high quality data point

fully lagrangian floats in labrador sea deep convection comparison of numerical and experimental results measurements of deep convection from fully lagrangian floats deployed in the labrador sea during february and march 1997 are compared with results from model drifters embedded in a large eddy simulation les of the rapidly deepening mixed layer the deep lagrangian floats dlfs have a large vertical drag and are designed to nearly match the density and compressibility of seawater the high resolution numerical simulation of deep convective turbulence uses initial conditions and surface forcing obtained from in situ oceanic and atmospheric observations made by the r v knorr the response of model floats to the resolved large eddy fields of buoyancy and velocity is simulated for floats that are 5 g too buoyant as well as for floats that are correctly ballasted mean profiles of potential temperature lagrangian rates of heating and acceleration vertical turbulent kinetic energy tke vertical heat flux potential temperature variance and float probability distribution functions pdfs are compared for actual and model floats horizontally homogeneous convection as represented by the les model accounts for most of the first and second order statistics from float observations except that observed temperature variance is several times larger than model variance there are no correspondingly large differences in vertical tke heat flux or mixed layer depth the augmented temperature variance may be due to mixing across large scale temperature and salinity gradients that are largely compensated in buoyancy the rest of the dlf statistics agree well with the response of correctly ballasted model floats in the lowest 75 of the mixed layer and are less consistent with results from buoyantly ballasted model floats other differences between observation and simulation in the mean profiles of heat flux vertical tke and lagrangian heating and vertical acceleration rates are confined to the upper quarter of the mixed layer these differences are small contributions to layer averaged quantities but represent statistically significant profile features larger observed values of heat flux and vertical tke in the upper quarter of the mixed layer are more consistent with model floats ballasted light float buoyancy however cannot fully account for the observed pdfs temperature profiles and lagrangian rates of heating and acceleration a test of lagrangian self consistency comparing vertical tke and lagrangian acceleration also shows that dlf measurements are not significantly affected by excess float buoyancy these upper mixed layer features may instead be due to the interaction of wind driven currents and baroclinicity

size variation in the cape dune molerat bathyergus suillus and late quaternary climatic change in the southwestern cape province south africa abstract within their historic range at the southwestern tip of africa cape dune molerats bathyergus suillus tend to be significantly larger in areas of higher rainfall they also tend to be large in late quaternary fossil samples associated with independent evidence for relatively moist climate and small in samples associated with evidence for relatively dry conditions together with sedimentologic geomorphic and other faunal observations fluctuations in fossil dune molerat size imply that the regional climate was very moist during an early late quaternary interval corresponding to marine isotope stage 4 74 000 to 59 000 yr b p or perhaps to substage 5b or 5d centered on 110 000 and 90 000 yr b p respectively it was comparably moist again from roughly 14 000 to 8 000 yr b p somewhat drier than at present from about 8000 until 4000 yr b p and mainly near the modern average after 4000 yr b p together the modern and fossil data suggest that dune molerat size is a reliable index of past precipitation but it may not be useful for revealing extremely arid conditions because these seem to be associated with depositional occupational gaps in most local paleontological archeological sites

the last climatic cycle at kopais central greece thick lacustrine sequences from southern europe provide an opportunity to derive continuous records where the chronostratigraphical position of pre holocene stages can be determined with increased confidence here high resolution sediment and pollen analytical results from a 60 m core recovered from the kopais basin central greece spanning the interval from the last interglacial to the early holocene are presented the record shows distinct shifts between open vegetation periods of increased erosion with sediment inwashing and forest periods associated with calcite precipitation in the lake the sequence of major events of the last climatic cycle contained at kopais bears strong similarities to other records in greece but also reveals the presence of high frequency oscillations with higher amplitudes than previously seen at other sites

measurements of turbulent vertical kinetic energy in the ocean mixed layer from lagrangian floats d asaro in previous work using nearly neutrally buoyant lagrangian floats in a wind forced mixed layer found w2 5 where w2 is the mean square vertical velocity and u is the friction velocity estimated 2 au from shipboard meteorological measurements using bulk formulas depth profiles of a z 5 w 2 z within 2 u the mixed layer showed a maximum value of a z of about 2 which is 1 75 2 times that measured in solidwall turbulent boundary layers driven by a wall stress alone this result implied that the ocean mixed layer was more energetic than shear driven turbulent boundary layers driven by the same stress here these results are verified using observations of vertical velocity in the mixed layer from 72 float days of data from two lagrangian floats in the north pacific ocean in the autumn of 2000 these floats were more neutrally buoyant than those used previously by d asaro thus reducing possible biases wind stress was estimated from quick scatterometer satellite measurements and is thus subject to errors and biases different from those in d asaro s previous work despite these instrumental differences the new results are very similar to those of the previous work except that no corrections for internal wave velocities are needed the values of w 2

geoarchaeological approaches to the environmental history of cyprus explication and critical evaluation geoarchaeology represents crossdisciplinary research focused on environmental issues and human activities and directed primarily to social scientists site micro studies are central to the enterprise emphasizing cultural sediments and the taphonomic record of site formation preservation or destruction but when expanded to include off site investigation and watershed studies geoarchaeology can go well beyond stratigraphy and context to address human impacts on the environment or long term sustainability this paper articulates a research agenda to evaluate the largely anecdotal premise that the island of cyprus has been degraded by millennia of improvident land use first it outlines holocene settlement land use and forest histories as a differentiated model against which to apply specific types of investigation and in conjunction with other archaeological sciences second it applies quaternary style watershed study to confront commonplace misunderstandings about possible degradation to show that most of the slope and stream deposits on cyprus are of pleistocene age third it switches to examples of site micro geoarchaeology to illustrate the possibilities of understanding detailed change the purpose is heuristic in the absence of many more site and off site studies that incorporate bioarchaeology provisional inferences suggest that environmental damage may be limited that even with heavy land use stress climatic triggers were critical to inaugurate change and that the system may be more resilient than anticipated such caveats may encourage greater attention to environmental research design in ongoing and future excavation projects

thermobaric cabbeling over maud rise theory and large eddy simulation abstract a large eddy simulation les of the wintertime upper ocean below seasonal antarctic ice cover over maud rise was carried out using observed time dependent surface forcing from 1994 antarctic zone flux experiment anzflux observations surface ice formation increases the density of the cold fresher surface mixed layer sml that overlies warmer saltier weddell deep water wdw this reduces the stability of the thermocline until it reaches a critical point for instabilities arising from the nonlinear equation of state nes for seawater density this simulation was intended to model the thermobaric detrainment of sml fluid a nes instability predicted to result from the dependence of seawater density on the product p of temperature and pressure instead model results demonstrate a different instability arising from the combination of thermobaricity with cabbeling the nes effect due primarily to the dependence of on 2 this combined thermobaric cabbeling instability drives turbulent convection in a deep interior mixed layer iml that may grow hundreds of meters thick below the thermocline largely decoupled from sml dynamics in the les thermobaric cabbeling and iml convection shoals the sml through entrainment from below until ice motion increases in the observationally based model forcing increased upper ocean model heat flux due to higher ice speed melts surface ice increasing thermocline stratification and eventually bringing the simulated instability to a halt in an auxiliary simulation the lull preceding strong ice motion in field observations is artificially extended by temporarily holding model surface forcing constant until the sml shoals entirely bringing the modified wdw of the iml 2 c above freezing directly to the surface subsequently reverting to the observed surface forcing and its attendant strong ice motion melts the ice cover entirely demonstrating a possible mechanism for open ocean antarctic polynya formation the same process as halted prematurely in the les using the forcing observed may also be responsible for thick deep internal layers and localized chimney structures observed in the weddell sea

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

pleistocene shoreline deposition and sea level history at swartklip south africa abstract a 50 m thick succession of poorly cemented sandstone is exposed along the northern shore of false bay south africa this late pleistocene succession is attributed to shorezone estuarine deposition in the last interglacial and dune activity during the highstand and early in the succeeding sea level withdrawal facies analyses allow us to establish that the last interglacial sea level high 120 ka locally reached an elevation between the upper and lower boundaries of a washover sequence that is 5 1 to 8 0 m above present mean sea level four depositional facies are recognized on the basis of distinct lithologies and assemblages of sedimentary structures beachrock is present intermittently in the present intertidal zone as a seaward dipping unit of flatbedded sandstone capped by calcrete we interpret this facies as a beach foreshore wedge which originated in warmer climates of the 135 ka sea level high and which developed its calcrete crust in the lowstand which immediately followed subsequent sea level rise at 120 ka and shoreline progradation is reflected in a two meter thick estuarine fill containing tomichia ventricosta a third facies comprises landward dipping sheetsands which overlie the estuarine fill on the basis of facies relationships and primary sedimentary structures this unit is attributed to washover fan deposition the last and dominant facies comprises calcite cemented sandstone arranged in sets of very large scale crossbeds pulmonate gastropods occur throughout poorly developed calcretes interrupt the succession deposition of this facies is believed to have occurred as parabolic dunes in a coastal foredune complex near the start of the wurm wisconsinan glacial climate when atmospheric circulation was more intense modern pedotubule and hardpan calcretes cap the succession

late quaternary palaeoenvironments of the southwestern cape south africa a regional synthesis the contemporary uniqueness of the southwestern cape environemnt suggests that its response to the environmental perturbations of the late quaternary may have been correspondingly distinctive despite the wide variety of palaeoenvironmental evidence which has accumulated from within the region a coherent picture of the evolution and development of its environments has remained elusive since the publication of several regional reviews over the last decade or so a considerable body of palynological and other palaeoecological evidence has emerged which prompts a fresh synthesis as to the nature of late quaternary environmental changes in the southwestern cape s fynbos biome although there are few sediments which date to the appropriate period the last glacial maximum in contrast to the situation evident in the summer rainfall region is suggested to be a period characterised by considerably cooler and wetter conditions in certain parts of the biome the first half of the holocene appears to have been somewhat drier than much of the second half and the warmer temperatures of the holocene hypsithermal are associated with reduced moisture availability intra regional contrasts are evident in the response to late quaternary environmental changes furthermore it transpires that for much of the later quaternary and for large areas of the region precipitation may have fluctuated out of phase with changes in the interior of the subcontinent a situation which has great relevance to the prediction of future environmental changes and their impacts in the southwestern cape

the ocean boundary layer below hurricane dennis abstract three neutrally buoyant floats were air deployed ahead of hurricane dennis on 28 august 1999 these floats were designed to accurately follow three dimensional water trajectories and measure pressure i e their own depth and temperature the hurricane eye passed between two of the floats both measured the properties of the ocean boundary layer beneath sustained 30 m s 1 winds the floats repeatedly moved through a mixed layer 30 70 m deep at average vertical speeds of 0 03 0 06 m s 1 the speed was roughly proportional to the friction velocity mixed layer temperature cooled about 2 8 and 0 75 c at the floats on the east and west sides of the northward going storm respectively much of the cooling occurred before the eye passage the remaining terms in the horizontally averaged mixed layer heat budget the vertical velocity temperature covariance and the lagrangian heating rate were computed from the float data surface heat fluxes accounted for only a small part of the cooling most of th

the wave driven ocean circulation oceanic surface gravity waves have a mean lagrangian motion the stokes drift the dynamics of winddriven basin scale oceanic currents in the presence of stokes drift are modified by the addition of so called vortex forces and wave induced material advection as well by wave averaged effects in the surface boundary conditions for the dynamic pressure sea level and vertical velocity some theoretical analyses previously have been made for the gravity wave influences on boundary layer motions including the ekman currents the present paper extends this theory to the basin scale depth integrated circulation in a bounded domain it is shown that the sverdrup circulation relation with the meridional transport proportional to the curl of the surface wind stress applies to lagrangian transport while the associated eulerian transport is shown to have a component opposite to the stokes drift transport a wave induced correction to the relation between sea level and surface dynamic pressure is also derived preliminary assessments are made of the relative importance of these influences using a global wind climatology and an empirical relationship between the wind and wave fields recommendations are made for further development and testing of this theory and for its inclusion in general circulation models

40ar 39ar age spectra of apollo 15 impact melt rocks by laser step heating and their bearing on the history of lunar basin formation we have obtained 26 high resolution 16 51 steps 40ar 39ar age spectra using a continuous laser system on submilligram fragments of recrystallized melt and single crystal plagioclase clasts from 12 apollo 15 impact melt rocks collected at the apennine front where the imbrium and serenitatis basins intersect these melt rocks represent a wide range of compositions and at least half a dozen different impacts six of the melt rocks have reproducible intermediate temperature plateaus over 40 or more of the 39ar released the plateaus are interpreted as crystallization impact ages and much of the non plateau behavior is attributable to recoil samples 15294 6 21 15304 7 69 15314 26 156 15357 15 and 15359 12 have mean 40ar 39ar plateau ages that are statistically indistinguishable and fall within the narrow range 3852 14 2 ma to 3870 12 ma with a weighted mean of 3865 5 ma sample 15356 9 has a mean plateau age of 3836 11 ma and may represent a distinctly younger impact a seventh sample 15314 30 158 has a peculiar but reproducible double plateau a low t one at 3873 9 ma which we think records the crystallization age and a high t one of 3831 10 ma which we interpret as an experimental 39ar recoil artifact four of the remaining melt rocks 15308 9 15414 2 37 15436 2 15445 253 have complex 40ar 39ar age spectra that indicate that they either formed in or were disturbed by impacts that occurred 3850 ma but did not completely reset the k ar isotopic system sample 15414 3 36 is different its spectrum may represent release mainly from clasts that were not well degassed in a melt event at 3870 ma the melt phase contains little potassium because most of the apennine front material must be coeval with or predate formation of the imbrium basin it seems likely that the imbrium impact is no older than 3870 ma and probably no older than 3836 ma so far there is no convincing evidence in the lunar record for melt producing impacts such as basin formation older than about 3 9 ga

luminescence dating in less than ideal conditions case studies from klasies river main site and duinefontein south africa abstract luminescence dating results are reported for two south african archaeological sites where changes in the dose rate through time are apparent a subtraction procedure involving analysis of both quartz and potassium feldspar extracts is applied to detect and correct for these changes at the middle stone age site of klasies river the dose rate changes inferred from geologic evidence for shell dissolution turn out not to be significant having occurred rapidly after deposition the dates here range from 50 115 ka in broad agreement with other evidence the important howiesons poort component here appears to date somewhat later about 55 60 ka than at several other sites in south africa at the acheulian site of duinefontein the dose rate changes also thought to be caused by shell dissolution are on the other hand very significant the subtraction ages here 125 300 ka agree with independent chronological assessments

the timing and environmental significance of late quaternary linear dune development in western zambia optical luminescence dates for 19 samples from the degraded linear dune field of western zambia indicate multiple periods of regional dune building for the late quaternary 32 000 27 000 16 000 13 000 10 000 8000 and 5000 4000 yr ago these dates show that the last glacial maximum was not the only time when dune construction commonly linked to marked aridity occurred in central southern africa during the late quaternary whereas rainfall significantly less than today s ca 1400 mm yr 1 is a prerequisite for dune construction in the area adequate sediment supply also determines dune construction and preservation so that dune building cannot be simply and singularly linked to marked aridity the zambezi river system is proposed as an important source of dune sediments with the nature of linear dune activity explaining why stacked sediments preserve several phases of dune formation chronologies of dune construction in western zimbabwe and the southwest kalahari are in broad agreement with our zambian chronology and support a model of rainfall shifts along a sw ne gradient with some notable disparities these are probably a function of interregional sediment supply differences the number of samples used to delimit constructional periods and the multicausal nature of forcing mechanisms

precise dating of dansgaard oeschger climate oscillations in western europe from stalagmite data the signature of dansgaard oeschger events millennial scale abrupt climate oscillations during the last glacial period is well established in ice cores and marine records but the effects of such events in continental settings are not as clear and their absolute chronology is uncertain beyond the limit of 14 c dating and annual layer counting for marine records and ice cores respectively here we present carbon and oxygen isotope records from a stalagmite collected in southwest france which have been precisely dated using 234u 230th ratios we find rapid climate oscillations coincident with the established dansgaard oeschger events between 83 000 and 32 000 years ago in both isotope records the oxygen isotope signature is similar to a record from soreq cave israel and deep sea records indicating the large spatial scale of the climate oscillations the signal in the carbon isotopes gives evidence of drastic and rapid vegetation changes in western europe an important site in human cultural evolution we also find evidence for a long phase of extremely cold climate in southwest france between 61 2 0 6 and 67 4 0 9 kyr ago

the still bay points of blombos cave south africa we present the results of a technological and morphometric analysis of all the still bay points n 371 recovered from the 1993 to 2004 excavations at blombos cave we have been able to reconstruct the manufacturing sequence of the bifacial points from initial shaping by direct internal percussion to finished morphology by direct marginal percussion identifications of impact fractures and manufacturing breaks are based on comparisons with experimental and archaeological bifacial points of verified function i e paleoindian points from bison kill sites replicates of solutrean points mounted as spear heads or arrowheads and shot into adult cattle and experimental replication on local raw materials our analysis shows that a only a minority of the points are finished forms and that a large number of pieces are production failures a situation known at bifacial point production sites of later ages b morphometric and impact scar analyses should take into account this process and distinguish finished points from preforms and unfinished points c there were at least three different kinds of raw material sources and that there is a marked increase in the frequencies of silcrete with respect to the m2 and m3 phases at blombos d three kinds of evidence prove that some of the points were hafted axially and used as spear tips e production of bifacial points was a primary activity at the site but the hypothesis of intergroup exchange of still bay points cannot be sustained on the basis of present evidence and f the still bay phase appears to initiate a trend to relatively rapid changes in specialized hunting weaponry and that this innovation is congruent with other innovations such as bone tools shell beads and engraved ochre of the m1 and m2 phases at blombos

primeval displacements of the lunar pole abstract the hypothesis that the magnetic field which magnetized the lunar crust was generated by the dynamo process in a small fluid iron core can now be tested because the coriolis force was a dominant term in the equations of motion in this core the mean lunar field was aligned along the ancient axis of rotation from hood s modelling of the magnetic anomalies in the lunar crust mapped by the apollo 15 and 16 subsatellites the palaeo directions of this field have been determined from them palaeopole positions have been determined and are found to be grouped with respect to age the palaeoequators corresponding to ages 4 ga and 3 85 ga show close relationships with the circular maria or mascons on the near side and multi ring basins of corresponding age on the far side the polar displacements indicated from lunar palaeomagnetism can be explained by the changes in the moment of inertia tensor consequent on the excavation and later flooding of these circular mare small moons in the primeval earth moon system are inferred to be the impacting bodies