middle to late holocene moisture changes in the desert of northwest namibia derived from fossil hyrax dung pollen new pollen results and radiocarbon dating from fossil hyrax middens derived from the edge of the northern namib desert address the shortage of continental palaeobotanical evidence in arid namibia by providing evidence for the environmental conditions during the mid to late holocene in the region the results obtained reflect long term stability in the area throughout most of the sequence higher than modern moisture availability is suggested between c 6 and 1 ka bp by the increased abundance of poaceae cyperaceae or chenopodiaceae which respond rapidly by flowering after modest quantities of rainfall around 1 ka and recently arid conditions seem to have prevailed with a decrease in poaceae and an increase in acanthaceae other palaeoecological evidence from the local and regional surroundings that focused on fluvial deposits marine palynology and mineralogy confirms this mid holocene increase in more effective rainfall

the use of multivariate statistics to elucidate patterns of floodplain sedimentation at different spatial scales floodplains are depositional features of riverine landscapes that display complex sedimentation patterns that are amenable to multi scale approaches we examined sedimentation in the lower balonne floodplain queensland australia at three different spatial scales the channel 103 km floodplain process zone 10 km and geomorphic unit 102 m scales and compared scale related patterns evident from stratigraphy with those evident from quantitative multivariate analysis three stratigraphic sequences were found in the lower balonne floodplain generally fining upward episodic fining upward and mud dominated stratigraphical analysis revealed the detailed character of sedimentary sequences embedded within the scale patterns derived from multivariate analysis multivariate statistical analyses of a range of textural and geochemical data revealed different patterns of floodplain sedimentation at each scale at the channel scale sediment texture and geochemistry were more heterogeneous in the culgoa river than in briarie creek at the floodplain process zone scale clear patterns of sediment texture and geochemistry were observed along the upper mid and lower floodplain process zones of briarie creek but not along the culgoa river at the geomorphic unit scale clear patterns of sediment texture and geochemistry were observed among the bank buried channel and flat floodplain units of the culgoa river but were not as clear in briarie creek recognition of rivers as hierarchically organized systems is an emerging paradigm in river science our study supports this paradigm by demonstrating that different sedimentation patterns occur at different scales to reveal a hierarchically organized floodplain environment copyright 2006 john wiley sons ltd

dating the quaternary progress in luminescence dating of sediments abstract luminescence dating comprises a collection of numerical age techniques that are among the most significant chronological tools currently used in quaternary research this paper briefly reviews the key historical developments in luminescence dating from its roots in thermoluminescence dating of heated minerals to the development of optical dating methods for sunlight exposed sediments we describe the principles and practicalities of the various techniques commonly used in luminescence dating including multiple aliquot single aliquot and single grain procedures and we discuss some of the latest approaches to recognising and minimising potential errors in age estimation e g by means of component analysis and dose distribution methods in optical dating the overview also introduces the other papers in this special issue of quaternary science reviews which address a selection of important issues in basic research technique development and application of luminescence dating to critical questions in the geological and archaeological sciences illustrated with examples from around the world and the last million years of earth history

pleistocene multiple growth lacustrine oncoids from the poacher s point formation etosha pan northern namibia the poacher s point formation is located within the etosha pan northern namibia it contains pleistocene stromatolites ooids and silica nodules the stromatolites were constructed by cyanobacteria in very lowenergy lacustrine conditions the internal structure of the oncoids is complex and subdivided into shells by unconformities each unconformity bounded shell probably represents stromatolite growth during a distinct lacustrine event shallower conditions are represented by colloform growth and deeper water by smooth oncoid mat morphology the unconformities represent hiatuses of unknown duration at least six stromatolite growth shells are recognized silica concretions which may have developed during shallowing lake stages are also present the lack of clastic material in the carbonate lithologies suggests that the lake waters may have accumulated from collecting rainwater or have been spring fed the lowest bed of the succession is a saline clay which represents a seasonally flooded salt pan deposited in an arid to semi arid climate similar to that of today the overlying carbonates represent sedimentation during a series of transient lacustrine events representing intermittent wetter periods finally due to progressive aridity the lacustrine succession was terminated by calcrete development

the amspoort silts northern namib desert namibia formation age and palaeoclimatic evidence of river end deposits abstract detailed geomorphological and chronological investigations of the nw namibian amspoort silt formation show that the sediments are typical river end deposits this type of endoreic sediment occuring only in desert margin areas provides valuable information about the palaeo environment in the hoanib valley the fine grained deposits have buried riverine trees radiocarbon dating of the wood and luminescence dating of the sediments allow a detailed reconstruction of the aggradation processes accumulation started 10 km downstream of amspoort around the beginning of the 15th century and ended in the 19th century some kilometres upstream of amspoort this upstream shift of sedimentation during the little ice age was caused by gradually decreasing runoff resulting from aridification of the upper part of the hoanib river catchment lying east of the namib desert margin 1 200 m a s l the amspoort silt terrace is evidence of palaeo hydrological fluctuations in nw namibia at present the hoanib river erodes deeply into the silty deposits indicating that nw namibia receives more monsoonal rainfall today than during the little ice age however this contradicts the hypothesis of a continual natural aridification of nw namibia damaraland kaokoveld since the mid 19th century in the course of global climatic change rather deposition and erosion of the amspoort silts indicate that landscape degradation in nw namibia is primarily anthropogenically induced and most probably not accelerated by a decrease in precipitation

determining the burial time of single grains of quartz using optically stimulated luminescence abstract in the optical dating of sediments it is usually assumed that the optically stimulated luminescence osl signal has been completely reset by light exposure prior to burial this assumption is often not valid one approach to testing and perhaps circumventing this assumption is to examine the apparent date of last exposure to daylight of individual sediment grains this paper reports on the application for the first time of 2 new measurement protocols to the estimation of the radiation dose received during burial for individual quartz grains from an aeolian deposit of known age 10 000 year old which is considered likely to have been completely reset by sunlight at deposition additive dose laboratory doses added to the burial dose before osl measurement and regenerative dose doses added after measurement of osl from burial dose single aliquot protocols are applied to 28 and 25 individual grains respectively each grain provides an independent estimate d e of the burial dose the average d e from the additive dose protocol 21 8 1 1 gy is in good agreement with the average from the regenerative dose protocol 23 8 1 0 gy both agree well with 1 13 multiple grain regenerative dose single aliquot measurements each on 1 mg sub samples of 23 9 0 3 gy 2 9 multiple grain additive dose single aliquot measurements also on 1 mg sub samples of 22 4 0 7 gy and 3 one previously published multiple aliquot additive dose estimate of 23 5 0 6 gy using 52 sub samples each of 5 mg the resulting optical ages are in good accord with 14 c and thermoluminescence age determinations the distribution of equivalent doses in the single grains is however unexpectedly large 23 of mean d e given the very likely complete resetting of the osl signal at deposition possible reasons are discussed and it is concluded that heterogeneity in beta dosimetry is the most likely explanation the single grain optical dating protocols reported here allow a detailed examination of the dose distribution in very small samples thus they should enable accurate dates to be obtained for sediments and soils that contain poorly bleached or mixed age components as well as deposits in which quartz grains are present in extremely low abundance

optically stimulated luminescence osl dating and palaeoenvironmental studies of pan playa sediment from witpan south africa abstract robust dateable sources of palaeoenvironmental proxy data are scarce in the southwestern kalahari desert and this study investigates the potential of pan playa floor sediments as an archive of late quaternary environmental change augering has revealed the presence of up to 3 m of clay and silt rich deposits in the base of witpan a small pan basin set amongst linear and lunette dunes the weakly stratified deposits include aeolian quartz sands and evaporites amongst a clay rich groundmass and are believed to have accumulated on a wetter than present pan surface the aeolian quartz fraction has been dated with optically stimulated luminescence osl and reveals accumulation of at least 50 cm of sediment at around 20 ka and previous accumulation at around 32 ka the northern and southern sections of the pan are shown to maintain some hydrological independence attributed to bedrock outcropping and also show distinct differences in their physical sedimentology biogenic proxies are poorly preserved with neither diatoms nor pollen found in adequate quantities although phytoliths found in both the pan floor sediments and the fringing lunette dune may offer a more resilient palaeoenvironmental indicator the possible value of pan floor sediments as dryland archives of physical and chemical and possibly selected biogenic palaeoenvironmental proxies combined with osl constrained chronologies should not be discounted

geomorphic development and middle stone age archaeology of the lower cunene river namibia angola border abstract during geomorphic reconnaissance of the lower cunene river near the reach of serra cafema a significant accumulation of middle stone age artifacts was discovered along the namibia angolan border the archaeological site is downstream of the marienfluss hartmann valley and lies along the eastern perimeter of the hyperarid cunene erg sandsea within the study area the cunene river is a bedrock anabranching mixed bedrock alluvial anabranching system with a morphology that is strongly controlled by lithology and structure and a hydrology dominated by tropical rainfall in the headwaters a 5 m high alluvial terrace along the left bank of the perennial river is mantled with a surface lag of cobbles and gravels that includes msa lithics more than 30 artifacts are preserved in this open air context finds include quartzite flakes cores and levallois mousterian points with varying degrees of edge abrasion and varnish these appear to be the first levallois mousterian points found in this region of africa since the archaeology of this region is poorly known these cultural assemblages enable initial correlations across southern africa a replicate osl sar date 220 kyr provides initial age constraints on a sand preserved within the cobble boulder terrace fill and constrains a maximum age for the overlying archaeological assemblage this is the first msa site in northern namibia in direct stratigraphic context with a securely dated unit the artifact assemblage underscores the importance of riparian corridors in reconstructing hominin behaviours during the middle pleistocene the time frame marked by the first appearance and the dispersal of the modern human species homo sapiens

kibaran a type granitoids and mafic rocks generated by two mantle sources in a late orogenic setting burundi in the mesoproterozoic northeastern kibaran belt of burundi central africa two distinct late kibaran magmatic suites coexist both including a type granitoids they are located along the boundary zone between the kibaran mobile belt western internal domain and the archaean tanzanian craton overlain by mesoproterozoic foreland deposits eastern external domain intense deformation high temperature metamorphism and intrusion of abundant peraluminous anatectic crustal granites occur only in the former domain whereas the mesoproterozoic sedimentary cover of the latter is much less or even nearly undeformed nor metamorphosed the first late kibaran magmatism 350 km long kabanga musongati with an emplacement age of 1275 ma u pb on zircon is mainly composed of mafic and ultramafic layered rocks with subordinate a type acidic differentiates moderately enriched in incompatible elements initial isotopic ratios srlr 0 708 nd 8 indicate an old continental lithospheric mantle origin the emplacement of these late kibaran magmatic rocks was controlled by late lateral shear possibly contemporaneous with the latest intrusions of the kibaran peraluminous synkinematic granites of the western internal domain 1330 1260 ma the second late kibaran magmatism 40 km long gitega makebuko and bukirasazi alignment with an emplacement age of 1249 s ma u pb on zircon is limited in volume it is mainly granitic in composition a type can be strongly enriched in incompatible elements and comprises both syenites and mafic rocks initial isotopic ratios srlr 0 702 na 4 5 to 1 4 point to an oib type asthenospheric lower continental lithospheric mantle origin with only slight contamination by the lower crust during differentiation this group was also intruded during the late lateral shear in both groups liquid lines of descent can be reconstructed although some of the rocks have been strongly albitized this indicates that the granites are produced by differentiation of less evolved magmas and not by crustal anatexis upwelling of the asthenosphere along the tanzanian craton can generate by adiabatic pressure release the oibtype basic melts and provide the heat necessary to melt the continental lithospheric mantle sources this mechanism assigns a major role to a lithosphere scale late kibaran shear event occurring at the end of the regional compressive deformation between two rheologically contrasted domains ascent of the asthenosphere continental lithospheric mantle delamination and late orogenic extensional collapse of the western internal domain are suggested as a possible geodynamic model for the entire northeastern kibaran belt additional work is however necessary to test this model finally our results indicate that in the northeastern kibaran belt the kibaran orogeny ended at 1250 ma despite various reactivation events occurring later e g at 1137 ma

hydroclimate in africa during the medieval climate anomaly the medieval climate anomaly mca is a recognized period of distinct pre industrial climate change with a core period of 1000 1200 ce the field of palaeoclimatology has made major progress over the past 15 years during which a great number of high and medium resolution case studies were published reconstructing climate change of the past millennia in many parts of the world regional data coverage has now reached a point which allows compiling palaeoclimate maps for well defined time intervals here we present hydroclimatic trend maps for the mca in africa based on 99 published study locations key hydroclimatic proxy curves are visualized and compared in a series of 16 correlation panels proxy types are described and possible issues discussed based on the combined mca dataset temporal and spatial trends are interpreted and mapped out three areas have been identified in africa in which rainfall seems to have increased during the mca namely tunisia western sahel and the majority of southern africa at the same time a reduction in precipitation occurred in the rest of africa comprising of nw and ne africa west africa eastern africa and the winter rainfall zone of south africa mca hydroclimate change in africa appears to have been associated with characteristic phases of ocean cycles as also supported by modern climate observations aridity in morocco typically coincides with the positive phase of the north atlantic oscillation nao whilst increased rainfall in the western sahel is often coupled to the positive phase of the atlantic multidecadal oscillation amo reduction in rainfall in the region gulf of aden southern red sea to eastern africa could be linked to a negative indian ocean dipole iod or a derived long term equivalent indian ocean cycle parameter the intertropical convergence zone itcz appears to have been shifted pole wards during the mca for both the january and july positions mca hydroclimate mapping revealed major data gaps in the sahara south sudan somalia central african republic democratic republic of congo angola northern mozambique zambia and zimbabwe special efforts are needed to fill these gaps e g through a dedicated structured research program in which new multiproxy datasets are created based on the learnings from previous african mca studies

interpreting geoproxies of late quaternary climate change in african drylands implications for understanding environmental change and early human behaviour abstract climate and environmental change in the late quaternary are widely regarded as key drivers of early human development and dispersal in africa robust records of change are required to assess the nature of potential impacts today s late quaternary palaeoenvironmental palaeoclimate reconstructions from the interior southern african basin kalahari are more spatially detailed have a stronger chronometric underpinning and span a longer time range than those of 10 20 years ago but are no less controversial reconstructions for the last 150 ka are usually interpreted in terms of changes in hydrological balance from conditions more humid or more arid than today and expressed in climatological terms as the changing latitudinal interplay between monsoon easterlies and tropical and mid latitude westerlies with more data than ever before why then is the record not yet delivering a more coherent picture of regional climate change this paper deliberately addresses current challenges and controversies including issues often ignored or neglected with the view that it is essential to do so if more robust interpretations of the past are to be generated in the future sources of palaeo data from the interior are predominantly geoproxies reconstructions not based on highly resolved organic or isotope records but on interpretation of spatially extensive geomorphological proxies of past environments despite being increasingly datable using osl their inclusion in syntheses has proved complex not least when interpretations appear to conflict with records from other sources consequently they are sometimes removed from regional syntheses of climate change these omissions are often replaced by spatially exaggerated interpretations of higher quality local records allowing more spatially coherent timeslice interpretations to be presented yet this is counter intuitive to the spatial complexity of conditions present in the palaeoenvironmental proxies or in climatic and environmental systems today in addition the quest to link regional records to master records from ice and ocean cores can force interpretation within a temporal scale that may be inappropriate for their analysis underplaying the reality of complexity within the environmental system there are not necessarily good or bad records of terrestrial palaeoenvironments in interior southern africa rather there are records that contain different suites of information about past land surface hydrological and climate conditions preserved at temporal scales which can sometimes be incomparable consideration of these factors may resolve apparent conflicts between datasets resulting in a better understanding of past environmental dynamics and revealing the nature of environmental variability which may be a key facet to which human development has responded

isotopic constraints on the genesis of the rogaland anorthositic suite southwest norway demaiffe d weis d michot j and duchesne j c 1986 isotopic constraints on the genesis of the rogaland anorthositic suite southwest norway in s deutsch and a w hofmann editors isotopes in geology picciotto volume chem geol 57 167 179 isotopic data were obtained on the sveconorwegian 1200 900 ma anorthosites and associated norites and charnockites of the rogaland igneous complex sw norway the isotopic data isr 0 703 0 7077 end 0 4 to 5 5 suf 4pb 1 8 1 8 2 so 5 2 to 6 6 c suggest an upper mantle origin for the parental magma of the anorthosites and related norites and jotunites or an origin in the lower crust by melting of mantle derived basic rocks shortly after their formation in two well documented cases the egersund ogna and the hidra bodies a progressive contamination by u depleted but not rb depleted lower crustal material is apparent during the differentiation process the late stage liquids have higher i up to 0 7086 lower but still slightly positive end less radiogenic pb isotopic composition the intrusive acidic rocks some of them of the charnockitic type display variable isotopic data is 0 7055 0 709 end 0 5 to 0 8 pb isotopic compositions comparable to that of some of the surrounding gneisses suggesting that there are in general no direct cogenetic relations between the anorthosites and the charnockites our data point to an origin of some of these acidic rocks by anatectic melting of the surrounding high grade metamorphic gneisses

chronology of sand ridges and the late quaternary evolution of the etosha pan namibia abstract etosha pan situated at the southern border of tropical africa is a vast endorheic plain in namibia s semi arid north the most recent studies agree that the pan was the floor of a former lake with varying water levels here we explored this idea further by investigating the link between lake level change and records of late pleistocene and holocene climate change the varying lake levels were inferred through sediment analysis and optical dating of sand deposits that form ridges parallel to the current shore along the northern and western margins of the pan our results support the view that the sand ridges are shoreline deposits of an evaporitic lake the ridges result from the interplay between intermittent river discharge and riverine sediment supply from the north prevailing north easterly wind and shore parallel waves therefore they are a proxy for former levels of a perennial lake we infer higher levels during the late pleistocene and a drastic drop shortly after 10 ka since around 8 ka etosha pan was covered by a shallow water body this lake water level reconstruction is not in line with the histories of itcz migration and strength of benguela current upwelling we confirm that the linkages between the evolution of the etosha pan and the climate mechanisms driving hydrological changes in subtropical southwest africa are poorly resolved and need further investigation

chronology during the bronze age in the archaeological site tell qubr abu al atiq syria abstract archaeosediments are deposits with a direct or indirect anthropogenic component they provide useful information about past human activities and interaction with the environment when other materials such as pottery are present in archaeosediment layers the combination of tl ages from pottery and osl ages from sediments can provide complete data about the occupation and evolution of an archaeological setting in mesopotamia tells are mounds formed by the debris of human occupation and the accumulation of muddy sediments mainly due to the decomposition of mud bricks in ancient towns many other materials such as pottery fragments bones and charcoal can be found in the sediment layers the combination of osl tl and radiocarbon ages can be very useful in the case of the bronze age period in syria allowing the occupation sequence of such archaeological sites to be reconstructed tell qubr abu al atiq is located on the left bank of the middle euphrates river syria the archaeological artefacts found in the sediment layers pottery collected during excavations in two areas of the site indicated the occupation of the tell during the early and late bronze age by typological pottery classification the radiocarbon ages of charcoal indicate that human occupation fits the archaeological hypothesis providing an older and maximum occupation period between 2800 and 2300 bc and a younger period between 1400 and 900 bc osl dating of sediments shows ages younger than charcoal while tl ages of pottery are generally older than sediment and charcoal ages this can be explained as the different materials correspond to different events the charcoal and pottery correspond to occupation periods while sediments correspond to the further destruction of the site

testing optically stimulated luminescence dating of sand sized quartz and feldspar from fluvial deposits abstract we apply single aliquot optically stimulated luminescence osl dating to quartz and feldspar rich extracts from fluvial channel deposits of the rhine meuse system in the netherlands the time of deposition of these deposits is tightly constrained by radiocarbon dating or historical sources this allows us to compare osl ages obtained on quartz and infrared osl ir osl ages obtained on potassium rich feldspar with independent ages over the range of 0 3 13 ka we show that the quartz osl ages are in good agreement with the expected age using ir osl dating of feldspar we find a slight age overestimate for the youngest sample whereas for older samples the age is significantly underestimated we also apply osl dating to older fluvial and estuarine channel deposits with limited independent chronological constraints comparison of feldspar ir osl ages with the quartz osl ages up to 200 ka shows a clear trend where the former severely underestimates the latter this trend is similar to that found for the samples with independent age control indicating that the feldspar ir osl ages are erroneously young for the entire age range in the youngest samples incomplete resetting of the ir osl signal prior to deposition probably masks the age underestimation we show that the ir osl age underestimation is partly caused by changes in trapping probability due to preheating correction for this phenomenon improves the ir osl ages slightly but does not provide a complete solution to the discrepancy we suggest that in the light of the problems encountered in the ir osl dating of feldspar quartz is the mineral of choice for osl dating of these deposits however feldspar dating should continue to be investigated because it has potential application to longer time scales

late quaternary landscape evolution in the keep river region northwestern australia abstract this paper evaluates the late quaternary chronostratigraphic context of archaeological sites in the keep river region northern territory australia cosmogenic dating luminescence dating and sediment characterisation reveal sedimentary processes commencing from erosion of the escarpment and plateaux source through temporary storage in sand sheets to final deposition in alluvial floodplains erosion of the sandstone plateaux 5 mm ka 1 and escarpment faces probably 50 100 mm ka 1 provide the main sediment source for the adjacent sand sheets which have evolved over the past 100 000 years as the product of ongoing cycles of accumulation and denudation the rate of sediment accumulation is lowest near the escarpments on the low energy sediment limited sand sheets 1 and greatest near the main streams 400 mm ka 1 that have more numerous sediment sources collectively luminescence ages indicate an apparent increase in sediment accumulation rate in the sand sheets from 100 mm ka 1 in the late pleistocene to over 200 mm ka 1 in the holocene this most likely reflects enhanced monsoonal activity following postglacial marine transgression palaeosol horizons in the creek profile distinguished by sediment mottling mark potentially significant palaeoenvironmental and palaeoclimatic changes during the quaternary

equivalent dose distributions from single grains of quartz at sibudu south africa context causes and consequences for optical dating of archaeological deposits abstract optical ages for 14 sediment samples collected from the post howiesons poort late middle stone age msa and final msa deposits at sibudu kwazulu natal south africa were reported in a companion paper jacobs z wintle a g duller g a t roberts r g wadley l new ages for the post howiesons poort late and final middle stone age at sibudu south africa journal of archaeological science 2008 these ages were based on equivalent dose d e distributions that were overdispersed in this paper we investigate factors both internal and external to the grains that may contribute to such higher than expected overdispersion in single grain d e values intrinsic factors accounted for some but not all of the observed scatter and application of a set of rejection criteria filtered grains for which erroneous d e values would otherwise be calculated we investigated sediment mixing and differences in the beta dose received by individual grains in their burial environment as two likely reasons for the observed overdispersion the scatter in d e distributions for all the samples is best explained by grains that were deposited at the same time and which were well bleached but that subsequently received a range of beta doses a procedure is presented for adjusting the measured beta dose rate and its associated error we show that using a combination of single grain osl measurements of d e the finite mixture model and adjustment of the beta dose rate result in stratigraphically consistent ages these ages are more consistent than the ages obtained from multiple grain aliquot d e values and the average dose rates for each sample the multiple grain ages are about 10 older partly because of the variable dose rate and partly because these aliquots contained grains with undesirable osl characteristics

mega lake in the kalahari a late pleistocene record of the palaeolake makgadikgadi system abstract a distinct series of beach ridges marking the former shorelines of large inter connected lacustrine basins in the kalahari can be clearly identified from landsat imagery and shuttle radar topography mission srtm data these basins which form the terminal sump of the okavango system in northern botswana are now almost completely dry during the quaternary they were intermittently occupied by large stable lake bodies and are thought to have periodically filled to a point of coalescence inundating an area that at its largest extent encompassed 66 000 km 2 poor chronological control has previously limited the utility of this important palaeo archive as part of a region wide lake palaeo shoreline research programme a systematic optically stimulated luminescence osl dating programme has utilised a lightweight hydraulic auger to take samples at depth from relict shoreline features twenty drill sites have generated 140 samples for dating establishing a firm chronology for multiple lake full phases in all three component basins ngami mababe and makgadikgadi of this mega lake this paper presents the final set of ages in the programme derived from four cores from the western and north eastern shorelines of makgadikgadi and uses these ages to establish a chronology of mega lake high stands during the last 300 ka providing a rare directly dated long terrestrial record of positive hydrological excursions within the southern hemisphere

evidence from the rio bayo valley on the extent of the north patagonian icefield during the late pleistocene holocene transition abstract this paper presents data on the extent of the north patagonian icefield during the late pleistocene holocene transition using cosmogenic nuclide exposure age and optically stimulated luminescence dating we describe geomorphological and geochronological evidence for glacier extent in one of the major valleys surrounding the north patagonian icefield the rio bayo valley geomorphological mapping provides evidence for the existence of two types of former ice masses in this area i a large outlet glacier of the north patagonian icefield which occupied the main rio bayo valley and ii a number of small glaciers that developed in cirques on the slopes of the mountains surrounding the valley cosmogenic nuclide exposure age dating of two erratic boulders on the floor of the rio bayo valley indicate that the outlet glacier of the icefield withdrew from the rio bayo valley after 10 900 1000 yr the mean of two boulders dated to 11 400 900 yr and 10 500 800 yr single grain optically stimulated luminescence osl dating of an ice contact landform constructed against this glacier indicates that this ice mass remained in the valley until at least 9700 700 yr the agreement between the two independent dating techniques osl and cosmogenic nuclide exposure age dating increases our confidence in these age estimates a date obtained from a boulder on a cirque moraine above the main valley indicates that glaciers advanced in cirques surrounding the icefield some time around 12 500 900 yr this evidence for an expanded north patagonian icefield between 10 900 1000 yr and 9700 700 yr implies cold climatic conditions dominated at this time

optical dating of tibetan human hand and footprints an implication for the palaeoenvironment of the last glaciation of the tibetan plateau 1 the tibetan plateau is a cold and arid environment with poor archaeological finds it is generally assumed to have been covered by ice sheet during the last ice age nineteen handprints and footprints of homo sapiens on hot spring travertine and the remnant of a fireplace have been found at an elevation of 4200 m on the tibetan plateau based on the optically stimulated luminescence of quartz extracted from samples of the baked and unheated travertine the age of the prints and the fireplace are around 20 000 these finds suggest that there were humans living in this area around the time of the last glacial maximum lgm and that the ice sheet did not cover the entire tibetan plateau at this time

the crustal tongue melting model and the origin of massive anorthosites recent detailed field studies in several anorthosite complexes have shown that anorthosites are frequently associated with weakness zones in the crust which may have favoured their emplacement at mid crust levels recent experimental data have shown that the parent magma compositions of various anorthosite massifs lie on thermal highs in the relevant phase diagrams at 10 13 kbar indicating that these magmas cannot be derived by fractionation of peridotitic mantle melts but by melting of gabbronoritic sources in the lower crust at 40 50 km depths in the sveconorwegian province terne boundaries have been traced in deep seismic profiles to moho offsets or to tongues of lower crustal material underthrust to depths higher than 40 km in southern norway we suggest that a lithospheric scale weakness zone the feda transition zone has channelled the rogaland anorthosites through linear delamination asthenospheric uprise and melting of a mafic lower crustal tongue

denisovan dna in late pleistocene sediments from baishiya karst cave on the tibetan plateau a late middle pleistocene mandible from baishiya karst cave bkc on the tibetan plateau has been inferred to be from a denisovan an asian hominin related to neanderthals on the basis of an amino acid substitution in its collagen here we describe the stratigraphy chronology and mitochondrial dna extracted from the sediments in bkc we recover denisovan mitochondrial dna from sediments deposited 100 thousand and 60 thousand years ago ka and possibly as recently as 45 ka the long term occupation of bkc by denisovans suggests that they may have adapted to life at high altitudes and may have contributed such adaptations to modern humans on the tibetan plateau

paleohydrology of extraordinary floods along the swakop river at the margin of the namib desert and their paleoclimate implications abstract the swakop river is a major ephemeral river drainage basin area about 30 000 km 2 crossing the western namib desert its hydrology and limited water resources depend on storms and floods therefore the hydrology and flow regime in the swakop river basin determines the availability of water for human use in this study we present a millennia long record of extreme floods using paleoflood hydrological methods and optically stimulated luminescence osl ages the record includes 44 large floods ranging in date from the late pleistocene to the present the oldest six to eight floods are dated from the late pleistocene to the mid holocene between 14 900 1700 and 5100 620 years ago with calculated peak discharges of 550 1280 m 3 s 1 eighteen floods eleven of which were between 1000 and 1600 m 3 s 1 occurred between 740 90 and 190 10 years ago additional 17 later floods occurred between about ad 1850 and 1963 with peak discharges between 100 and 1000 m 3 s 1 the historical record which partly parallels the latter period recorded 17 large floods during the period 1893 1963 flood frequency analysis ffa of the combined systematically gaged record 1963 2003 and the paleoflood record since ad 1270 740 90 years the most complete record was applied using the maximum likelihood method a two component extreme value distribution tcev estimates the 1 annual exceedance probability magnitude using only the systematic gaged record at 520 m 3 s 1 the combined paleoflood historical and gage records resulted in a much larger magnitudes for the 1 annual exceedance probability flood magnitude of 1320 1350 m 3 s 1 the 0 1 annual exceedance probability magnitude is estimated at 770 m 3 s 1 and 2100 2150 m 3 s 1 respectively the hydroclimatic interpretation of this paleoflood record is complex due to the discontinuity of the record during the late holocene our flood data show three intervals differing in their flood regime 1 1280 80 to 740 90 years bp with one extraordinary flood 200 m 3 s 1 about every 180 years 2 740 90 to 200 45 14 c years bp with one large flood per 80 years and 3 200 45 14 c years bp to ad1963 with one large flood per 7 years interval 2 represents large floods probably related to the transition from a drier climate to the colder and probably wetter climate of the little ice age lia the third period relates to the end of the lia and to a wetter period of the 19th and early 20th centuries in which more rainfall in the kalahari and namib deserts and many historical floods were documented the presence of three distinct calcretes rich in calcified rhizoliths at one of the sites two of which were dated by osl to 13 2 1 9 ka and 8 8 1 0 ka indicates at least locally higher moisture availability than in the current semiarid climate the presence of denser vegetation can be associated with increased groundwater seepage and wetter climatic conditions

reassessment of carbonate ages by dating both carbonate and organic material from an etosha pan namibia stromatolite evidence of humid phases during the last 20ka abstract previous research on lacustrine stromatolites from etosha pan in namibia obtained ages on carbonate close to or beyond the limits of radiocarbon dating these ages suggested that the basin was likely not subject to extensive flooding during the last ca 40 ka this study shows that ams radiocarbon ages for the carbonate of a stromatolite from poacher s point are 15 21 ka older than ages for organic material in the stromatolite structure calibrated ages range from 30 to 40 ka for carbonate and 3 19 ka for the organic residue the new ages together with petrographic and isotopic data for the stromatolite have provided important new information on past flooding of etosha pan including evidence of prolonged lacustrine conditions during the holocene climatic optimum

geomorphological contributions to palaeolimnology on the african continent abstract article history received 19 december 2007received in revised form 5 july 2008accepted 22 july 2008available online 3 august 2008keywords quaternarybeach ridgeshorelinelakemultiproxyosl lakes are highly informative repositories of information of the terrestrial response to regional and global climatedrivers in quaternary studies lake oor records are now frequently used to establish the magnitude timing andgeographicalextentofhumid aridtransitionsovertimescalesof10 2 10 4 years whiletheresolutionof thisrecordisunparalleled much of the geochemical and sedimentary da ta is challenging to interpret and highly basin speci c geomorphologicalproxies particularlyshorelines offeranadditionaloralternativerecordoflakehistory withrecenttechnological advances facilitating both access to and the utility of this proxy record recent advances in opticallystimulated luminescence osl dating allow the determination of the age of beach ridge emplacement in theabsence of organic material while the availabilityof shuttle radar topography mission srtm data in conjunctionwith digital elevation models dem aids in the identi cation of shoreline features and the topographicreconstruction of the former extent of palaeolakes here we highlight and illustrate the use of lacustrine shorelinefeatures for unravelling a quaternary climate signal wit hin africa from otherwise inaccessible and undatablepalaeolake records in the semi arid and arid subtropics an d identify their contribution towards high resolutionmultiproxy reconstructions of tropical low latitude quaternary environments and climates 2008 elsevier b v all rights reserved

an observational study of the southern stratospheric spring wave features during 1979 1982 utilizing toms data total ozone mapping spectrometer toms data during the southern hemisphere spring are analyzed to obtain time mean and transient wave amplitudes for zonal wave numbers 1 10 it is found that at latitudes south of 50 s the october total ozone is dominated by the wave number 1 time mean component with largest amplitudes occurring in 1979 and 1982 the november wave number 1 time mean amplitudes are reduced from their october values the largest reductions occur in 1979 and 1982 in contrast at 40 45 s the transient amplitudes are dominant phases angles for time mean wave number 1 are also presented and little year to year variation is noted south of 50 s also obtained with these data are traveling wave power and coherence squared spectra the spectra for eastward traveling features having zonal wave numbers 1 3 are presented all of these wave numbers exhibit eastward traveling features at high latitudes with no evidence of westward traveling features

igneous charnockites and related rocks from the bjerkreim sokndal layered intrusion southwest norway a jotunite hypersthene monzodiorite derived a type granitoid suite the upper part of the bjerkreim sokndal layered intrusion bksk introduction comprises a suite of charnockitic granitoids mangerite quartz charnockitic granitoids are a major component of mangerite and charnockite with some jotunites the petrology and anorthosite mangerite charnockite rapakivi granite geochemistry major and trace elements of eight main rock types amcg complexes and therefore play a crucial role in 88 samples are considered the rocks form a suite of k2o rich the formation and evolution of the proterozoic crust alkali calcic granitoids of a type deriving from jotunitic magma their origin has been long debated though intimately two trends of inferred liquids are distinguished the main liquid associated with massif anorthosites they are generally line of descent which passes from jotunites through two pyroxene considered to be derived from distinct parental magmas quartz mangerites to amphibole charnockites the second one which generated in different sources emslie 1978 1991 morse encompasses olivine bearing quartz mangerites and charnockites and 1982 duchesne 1984 wiebe 1992 ashwal 1993 it is rooted into mangeritic liquids comparison with the tellnes rock has however been recognized that some charnockitic series reveals that contamination by leucogranitic material has taken rocks could also be derived from an intermediate monplace simultaneously with fractional crystallization in both bksk zodioritic to ferrodioritic jotunitic magma duchesne trends zr rb cs and th are particularly sensitive to assimilation et al 1989 wilmart et al 1989 owens et al 1993 and the higher water content in bksk zircon and apatite have whose origin is also controversial the jotunitic magma saturated at the liquidus of quartz mangerite around 900 c close could either be derived from a crustal source by the to the fayalite magnetite quartz fmq buffer the two pyroxene partial melting of basic rocks duchesne et al 1989 quartz mangerites cannot have been equilibrated with the mangerite duchesne 1990 or be residual magmas after the forcumulates on which they rest a major influx of magma took place mation of massif anorthosites which have been conwhen mangeritic cumulates were being deposited it mingled and partly mixed with the resident contaminated magma taminated to various degrees by crustal material emslie et al 1994 the latter hypothesis seems to explain a large number of amcg complexes in the grenville and nain provinces and elsewhere accepting that some charnockites are derived from jotunites there is a logical

optical and radiocarbon dating at jinmium rock shelter in northern australia the jinmium rock shelter is located in the kimberley region of northern australia claims for ancient rock art and an early human presence at this site1 were based on thermoluminescence ages of 50 75 thousand years kyr for quartz sands associated with buried circular engravings pecked cupules and on thermoluminescence ages of 116 176 kyr for the underlying artefact bearing deposits here we report substantially younger optical ages for quartz sand and ages based on measurements of radioactive carbon in charcoal fragments from the occupation deposit using conventional multiple grain optical dating methods we estimate that the base of the deposit is 22 kyr however dating of individual grains shows that some have been buried more recently the single grain optical ages indicate that the jinmium deposit is younger than 10 kyr this result is in agreement with the late holocene ages obtained for the upper two thirds of the deposit from radiocarbon measurements we suggest that some grains have older optical ages because they receivedinsufficient exposure to sunlight before burial the presence of such grains in a sample will cause age overestimates using multiple grain methods whether using thermoluminescence or optical dating

late quaternary lake level fluctuations in the mababe depression middle kalahari palaeolakes and the role of zambezi inflows abstract a systematic drilling and optical dating programme on middle kalahari beach ridge relict shoreline sediments has enabled the identification of multiple episodes of lake high stands of an extensive palaeolake system at the terminus of the okavango delta northern botswana this paper presents 23 ages from the mababe depression and establishes four shoreline construction phases in the late quaternary coeval with other sub basin lake high stands lake ngami these synchronous lake phases result from a coalescence of the sub basins into a unified palaeolake lake thamalakane covering an area of 32 000 km2 six additional ages are also presented from the chobe enclave to the north of the basin where shoreline ridges were emplaced at the same time as lake thamalakane phases this suggests that increased flow in the chobe and zambezi system significantly contributed to the middle kalahari lake phases in both the post glacial and holocene periods the integration of these new data and their compatibility with other regional and tropical palaeo archives is discussed in the light of understanding quaternary climate drivers within the kalahari

the role of rare rainstorms in the formation of calcic soil horizons on alluvial surfaces in extreme deserts abstract soils in similar geomorphic settings in hyperarid deserts 1 should have similar characteristics because a negative moisture balance controls their development however reg soils in the hyperarid southern negev and namib deserts are distinctly different soils developed on stable alluvial surfaces with only direct input of rainfall and dust depend heavily on rainfall characteristics annual rainfall amount can be similar 15 30 mm but storm duration can drastically alter reg soil properties in deserts the cooler fall winter and dry hot summers of the southern negev desert with a predominance brief 1 day rainstorms result in gypsic saline soils without any calcic soil horizon although the namib desert receives only 50 60 of the southern negev annual rainfall its rainstorm duration is commonly 2 4 days this improves leaching of the top soil under even lower annual rainfall amount and results in weeks long grass cover the long term cumulative effect of these rare rain grass relationships produces a calcic gypsic saline soil the development of these different kinds of desert soils highlights the importance of daily to seasonal rainfall characteristics in influencing soil moisture regime in deserts and has important implications for the use of key desert soil properties as proxies in paleoclimatology

imaging downward granitic magma transport in the rogaland igneous complex sw norway combining geological mapping and petrological structural and geophysical gravity and seismic data already available for the late proterozoic rogaland igneous complex of norway allows the 3d shape of the bjerkreim sokndal layered intrusion to be modelled as a thick cumulate series capped by massive granitic rocks using the latter data along with the spectacular convergent linear flow pattern that covers both the cumulates and the felsic rocks of this chamber evidence is presented to show that the granitic material was downdragged through the sinking of its high density mafic floor into lower density anorthosites and granulitic gneisses this example illustrates that downward gravity driven flows of rocks were active in addition to upward flows in the building of the early crust up to late proterozoic times helping to explain the geochemical and structural complexities of the old crust

late quaternary environmental change in central southern africa new data synthesis issues and prospects much of the interior of central southern africa is a sand sea within which aeolian and lacustrine landforms and sediments of local and regional extent are preserved closed cave sites are restricted to very few locations while fluvial systems traverse the margins of the interior until the early 1990s chronologies of late quaternary environmental and climatic changes developed for this region were based on only a limited number of proxy data sets derived largely from lacustrine deposits and precipitates in particular directly determined ages from aeolian deposits the most extensive suite of features in the region were absent the application of luminescence dating techniques to dune sediments and the development of further detailed chronologies from cave precipitates is now providing a more comprehensive record for the last 50 ka with some chronologies extending back a further 100 ka we present and review these data assess their contribution to enhanced understanding of late quaternary environmental changes in the region and for the first time assess them against corrected radiocarbon ages from lacustrine sites it is concluded that there is now an enhanced understanding of the spatial and temporal complexity of climate changes affecting the region in the last glacial cycle including a complex record of punctuated aridity but that many issues including data set integration and forcing mechanism controls are imperfectly understood

optical dating of holocene sediments from a variety of geomorphic settings using single grains of quartz this paper presents an improved method for the optical dating of holocene sediments from a variety of geomorphic settings we have measured the equivalent dose de in individual grains of quartz using green laser light for optical stimulation and have simulated the de distributions for multiple grain synthetic aliquots using the single grain data for 12 samples of known independent age we show that application of a minimum age model to the single grain and small 10 grain aliquot de data provides the most accurate estimate of the burial dose for nine of the samples examined 3 aeolian 5 fluvial and 1 marine the weighted mean de as obtained using the central age model gives rise to burial age overestimates of up to a factor of 10 for these nine samples whether single grains small aliquots or large 100 grain aliquots are used for the other three samples two aeolian and one fluvial application of either the minimum age model or the central age model to the single grain small aliquot and large aliquot de data yields burial ages in accord with the independent age control we infer that these three samples were well bleached at the time of deposition these results show that heterogeneous bleaching of the optical dating signal is commonplace in nature and that aeolian transport offers no guarantee that the sample will be well bleached at the time of deposition we also show that grains sensitive to infrared ir stimulation can give rise to low de values which will result in significant underestimation of the burial dose and hence of the age of deposition we demonstrate that use of a modified single aliquot regenerative dose protocol incorporating ir stimulation prior to green light stimulation deals effectively with contamination by ir sensitive grains we conclude that application of the modified protocol to single grains or small aliquots of quartz using the lowest de population to estimate the burial dose is the best means of obtaining reliable ages for holocene sediments from a wide range of depositional environments d 2003 elsevier b v all rights reserved

evidence for a permanent lake in sua pan kalahari botswana during the early centuries of the last millennium indicated by distribution of baobab trees adansonia digitata on kubu island abstract the makgadikgadi basin in the middle kalahari desert of botswana exhibits a complex of salt pans which may partly be filled to shallow water depths during the rainy season there is good evidence that during the pleistocene and early holocene a large lake existed in the makgadikgadi basin which however became increasingly smaller during the holocene for the late holocene when the regional human population began to grow no data except for the last two centuries about lake levels and thus surface water availability have been published age estimates of selected baobab trees of two size classes growing on kubu island a granite outcrop which is located in a coastal position at the south western edge of sua pan are used to infer that at least during the early centuries of the last millennium a maximum lake level of 908 m a s l was reached during this lake phase sua pan and ntwetwe pan were interconnected and large wetlands were created large numbers of game and livestock could be sustained these data are in line with palaeoclimate data but cannot be used to differentiate the medieval warm period which was supposedly relatively wet from the subsequent little ice age which likely was comparatively dry

early human occupation at devil s lair southwestern australia 50 000 years ago abstract new dating confirms that people occupied the australian continent before the earliest time inferred from conventional radiocarbon analysis many of the new ages were obtained by accelerator mass spectrometry 14c dating after an acid base acid pretreatment with bulk combustion aba bc or after a newly developed acid base wet oxidation pretreatment with stepped combustion abox sc the samples charcoal came from the earliest occupation levels of the devil s lair site in southwestern western australia initial occupation of this site was previously dated 35 000 14c yr b p whereas the aba bc ages are indistinguishable from background beyond 42 000 14c yr b p the abox sc ages are in stratigraphic order to 55 000 14c yr b p the abox sc chronology suggests that people were in the area by 48 000 cal yr b p optically stimulated luminescence osl electron spin resonance esr ages u series dating of flowstones and 14c dating of emu eggshell carbonate are in agreement with the abox sc 14c chronology these results based on four independent techniques reinforce arguments for early colonization of the australian continent

optical dating of tsunami laid sands abstract the ages of some tsunami deposits can be determined by optical dating a key requirement being that the deposits are derived from sediment that was reworked and exposed to daylight by tidal currents waves wind or bioturbation during the last years before the tsunami measurements have been made using 1 4 ev infrared excitation of k feldspar grains separated from samples of prehistoric tsunami sand sheets and modern analogs of tsunami source sediments at four sites in washington state and british columbia source sands gave equivalent doses indicative of recent exposure to daylight tsunami sand at cultus bay washington yielded an optical age of 1285 95 yr calendric years before a d 1995 1 at 2 this age overlaps the range of from 1030 to 1100 yr determined through a combination of high precision radiocarbon dating and stratigraphic correlation tsunami sands at three sites near tofino and port alberni on vancouver island british columbia have optical ages of 260 20 325 25 and 335 45 yr historical records and radiocarbon dating show that the sand at each of the three sites is between 150 and 400 yr old these optical ages support the hypothesis that the vancouver island sands were deposited by a tsunami generated by a large earthquake on the cascadia subduction zone about 300 yr ago

shoshonitic liquid line of descent from diorite to granite the late precambrian post collisional tismana pluton south carpathians romania abstract the post collision late kinematic tismana pluton belongs to the shoshonitic series it is part of a late precambrian basement within the alpine danubian nappes of the south carpathians romania this pluton displays an exceptionally complete range of compositions from ultramafic to felsic rocks granites widespread mingling mixing relationships at all scales give rise to a variety of facies a liquid line of descent from the diorites to the granites is reconstructed by considering the variation in major and trace elements ree sr rb ba nb zr hf zn v co cr u th ga pb from 33 selected samples as well as mineral melt equilibrium relationships the first step of fractional crystallization is the separation from a monzodioritic parent magma of a peridotitic cumulate similar to the ultramafic rock found in the massif a possible contamination by lower crustal mafic component takes place at this stage the second step marks the appearance of apatite and fe ti oxide minerals as liquidus phases and the third step saturation of zircon mixing by hybridisation of magmas produced at different stages of the evolution along the liquid line of descent is also operating endo hybridisation as depicted by nd and sr isotopes fractional crystallization was combined to an important early contamination by a mafic lower crust in a deep seated magma chamber and to a later and mild contamination by a felsic medium crust in an intermediate chamber the mingling essentially occurred during the final emplacement in the high level magma chamber the monzodioritic parent magma identified by major and trace element modelling is shown by sr and nd isotopes to have its source in the lithospheric mantle or in a juvenile mafic lower crust derived from it the necessarily recent enrichment in k2o and associated elements of the lithospheric mantle is likely to be related to the preceding pan african subduction period the partial melting of this newly formed deep source has to be linked to a major change in the thermal state of the plate

the neoproterozoic pan african basement from the alpine lower danubian nappe system south carpathians romania abstract the south carpathians which were thrust to the moesian platform in the alpine orogeny late cretaceous to tertiary include the danubian nappe system the danubian pre alpine basement comprises two variscan nappes each one made up of partially retrogressed amphibolite facies rocks intruded by granitoids and capped by an ordovician devonian volcano sedimentary cover no lithological correlation can be established between the pre ordovician basements of these two units the metamorphic basement from the first variscan nappe the dr gsan group is composed of banded amphibolites with some augen and aluminous gneisses intruded by granodioritic to tonalitic plutons the banded structure of the amphibolites together with their geochemistry suggests a volcano sedimentary sequence zircon u pb data on an intercalated augen gneiss have given an age of 777 3 ma for the emplacement of the protolith of this gneiss nd model ages t dm for the amphibolites range from 717 ma to 817 ma at 777 ma nd values cluster is at 8 3 to 9 8 and sr initial ratios range between 0 7007 and 0 7023 indicating an oceanic origin without continental crust contamination major and trace elements from the dr gsan amphibolites consistently display an island arc signature with three differentiation trends evolving from an early tholeiitic trend to a more differentiated low k calc alkaline one the dr gsan terrane is similar to the early pan african juvenile terranes of the sahara the basement of the second variscan nappe the lainici p ius group is made up of metasedimentary rocks mainly quartzites marbles and graphitic mica gneisses cut by early leucogranitic dykes medium k calc alkaline and alkali calcic mainly granitic plutons and late medium k porphyry diorite dykes this magmatism can be bracketed between 588 ma and 567 ma u pb zircon ages the best preserved pluton tismana 567 ma old displays a composite alkali calcic very high k calc alkaline magmatic sequence ranging from gabbro diorite to monzogranite including an ultramafic pod ages and geochemical signatures resemble the saharan late pan african granitoids the existence of late precambrian partly juvenile terrains is thus confirmed within the basement of south carpathians which renders then a segment of the european alpine belt that can be successfully compared to the pan african trans saharan belt

some phase equilibrium constraints on the origin of proterozoic massif anorthosites and related rocks experimental data in the range of 1 bar to 13 kbar enable us to introduction map the liquidus equilibria relevant to proterozoic massif anorthere is hardly a consensus on the petrogenesis of thosites and related mafic rocks massif anorthosites are widely proterozoic massif anorthosites but many investigators believed to have formed by accumulation of plagioclase into highbelieve in a petrogenetic scheme that involves at least al basaltic liquids mantle derived basaltic liquids fractionating two major stages 1 extensive crystallization asat pressures sufficiently high 10 13 kbar to crystallize the highly similation of a mantle derived magma ponded at or aluminous orthopyroxene megacrysts typically observed in anorthosite near the base of the crust that produces suspensions of massifs reach plagioclase saturation at low normative silica contents plagioclase in fe rich high al gabbroic liquids followed peritectic like equilibria e g liq opx plag cpx sp by 2 intrusion of these suspensions into the mid upper and a thermal divide on the plagioclase pyroxene liquidus surface crust where they form complex magma chambers e g ensure that mantle derived liquids become nepheline normative with duchesne 1984 emslie 1985 ashwal 1993 wiebe further crystallization and crustal assimilation at depth such 1994 a key component of the scheme is the presence liquids cannot produce the full range of troctolitic noritic to trocin most massifs of high al orthopyroxene megacrysts tolitic gabbroic mineral assemblages observed in anorthosite massifs haom emslie 1975 that appear to preserve a record without extensive low pressure granite assimilation conversely the of the high pressure stage maquil duchesne 1984 array of plausible anorthosite parental liquids not only lies along longhi et al 1993 the structures of massifs vary from the trace of the plagioclase two pyroxene cotectic from 10 to 13 those that are composites of multiple diapiric intrusions kbar but also straddles the thermal divide on the plagioclase harp lake emslie 1980 rogaland duchesne 1984 pyroxene liquidus surface this condition requires mafic source to intrusive bodies with well developed layering of regions such as lower continental crust or foundered mafic plutons leucocratic troctolites and leuconorites or leucogabbros for liquids parental to massif anorthosites and associated mafic overlain by masses of anorthosite michikamau emslie intrusions 1970 laramie frost et al 1993 so there may be

stratospheric circulation in the southern summer northern winter 1980 81 behavior of zonal waves 1 10 abstract daily global grids of high quality satellite borne microwave measurements have been used to study the behavior of stratospheric waves during november 1980 march 1981 the primary motivation was to investigate by comparing with earlier analyses the interannual variation of recently reported medium scale wave domination of southern hemisphere sh summer circulation zonal means as well as time mean and transient zonal waves 1 10 are studied in addition space time spectra are determined from the 138 day record prominent medium scale features are found to occur in 1980 81 although wave 4 is strongest in contrast to the global weather experiment period 1978 79 when wave 5 dominated the sh summer circulation the same highly continuous regular eastward phase movement of sh medium scale waves is found in 1980 81 as in 1978 79 a second noteworthy observation is that of strong time mean waves 3 4 with symmetry about the equator with positive temperature perturbations over the western paci

luminescence dating of rock art and past environments using mud wasp nests in northern australia mud nesting wasps are found in all of the main biogeographical regions of the world1 2 3 and construct nests that become petrified after abandonment nests built by mud dauber and potter wasps in rock shelters in northern australia1 4 often overlie and occasionally underlie prehistoric rock paintings mud nests contain pollen spores and phytoliths from which information about local palaeovegetation can be gleaned here we report a new application of optical dating5 6 7 using optically stimulated luminescence osl and accelerator mass spectrometry ams 14c dating of pollen8 to determine the ages of mud wasp nests associated with rock paintings in the kimberley region of western australia9 10 optical dating of quartz sand including the analysis of individual grains embedded in the mud of fossilized nests shows that some anthropomorphic paintings are more than 17 000 years old reconstructions of past local environments are also possible from the range of pollen and phytolith types identified this approach should have widespread application to studies of rock art dating and late quaternary environmental change on continents where mud wasps once lived and other sources of palaeoecological information are absent

optical dating studies of quartz and feldspar sediment extracts abstract continuing developmental work into optical dating has led to some clarification of the optical behaviour of quartz and feldspar sediment extracts we have verified the key assumption intrinsic to the method that the optical signal is zeroed completely upon exposure to daylight we also show that the rate of zeroing in optical dating is much more rapid than it is in tl dating studies concerned with the extraction of the thermally stable signal from laboratory irradiated samples showed that problems may arise from medium to high temperature preheating of young samples optical alternatives to thermal stabilization were tested using dye and krypton lasers using a krypton laser we have succeeded in obtaining an equivalent dose of 0 0 0 7 gy for the quartz from a modern intertidal sand and an average dose of 120 22 gy for the feldspar extract of a 70 ka sand unit both were obtained using six wavelengths from the infrared to the violet and no dependence on wavelength was found we found that the photon energies of infrared and deep red light can stimulate luminescence in unirradiated quartz and feldspar extracts of sediments this was not expected and suggests that the process of trap emptying is more complex than we had envisioned but implies a far greater than expected degree of technical flexibility for the optical dating method

geochemical constraints on the genesis of the tellnes ilmenite deposit southwest norway the ilmenite norite of the tellnes fe ti deposit in the aana sira massif type anorthosite is connected to a main dike which varies in composition from monzonorite to quartz mangerite fine grained satellite dikes also occur in the vicinity of the main dike a number of rock samples have been analyzed for 36 major and trace elements an rb sr whole rock isochron 12 samples gives an age of 930 ma initial sr isotope compositions of the ilmenite noritc the main dike and the satellite dikes are 0 7050 0 7069 and 0 7100 respectively thus precluding a comagmatic origin without invoking contamination the evolution of the main dike can be accounted for by a closed system fractional crystallization of a monzonoritic magma that is without progressive contamination which gave rise to a series of liquids prior to intrusion mass balance calculation permits a two stage process in which noritic cumulates were subtracted trace element behavior is also consistent with such a model the satellite dikes represent undifferentiated monzonorites with trace elements and isotopic ratios implying a source material quite different from that of the main dike monzonorite the orebody is made up of ilmenite norite and small amounts of more plagioclase rich rocks which plot on linear trends in variation diagrams it is interpreted as a noritic cumulate which was enriched in dense oxide rich magma before being emplaced as a crystal mush the parental magma was noritic in composition unsaturated in apatite and probably derived from the crystallization of the enclosing massif anorthosite it is not precluded either that it could have given rise to the main dike monzonoritic liquid after being contaminated by lower crustal material nevertheless as an alternative it is not possible to reject two distinct parental magmas for the orebody and the main dike they would have evolved in two separated magma chambers before the tapping of these chambers and simultaneous injection of their contents in the dike the main dike illustrates the process by which a quartz mangerite can derive from a monzonoritic magma and gives support to a comagmatic origin of charnockitic and monzonoritic rocks

a record of rapid holocene climate change preserved in hyrax middens from southwestern africa the discovery of sensitive paleoenvironmental proxies contained within fossilized rock hyrax middens from the margin of the central namib desert africa is providing unprecedented insight into the region s environmental history high resolution stable carbon and nitrogen isotope records spanning 0 11 700 cal calibrated yr b p indicate phases of relatively humid conditions from 8700 7500 6900 6700 5600 4900 and 4200 3500 cal yr b p with a period of marked aridity occurring from 3500 until ca 300 cal yr b p transitions between these phases appear to have occurred very rapidly often within 200 years of particular importance are 1 the observed relationship between regional aridifi cation and the decline in northern hemisphere insolation across the holocene and 2 the signifi cance of suborbital scale variations in climate that covary strongly with fl uctuations in solar forcing together these elements call for a fundamental reexamination of the role of orbital forcing on tropical african systems and a reconsideration of what factors drive climate change in the region the quality and resolution of these data far surpass any other evidence available from the region and the continued development of this unique archive promises to revolutionize paleoenvironmental studies in southern africa

luminescence based dune chronologies in southern africa analysis and interpretation of dune database records across the subcontinent abstract over 600 luminescence ages have to date been published from southern africa s continental dunefields and isolated dunes providing a rich record of aeolian system dynamics during the late quaternary the majority of records come from sites within the five linear dune dominated dunefields of the kalahari with lesser representation of other major dune areas including the namib and west coast dunefields and of other dune types including lunettes and transverse forms dune database records are analysed not only in terms of the evidence they provide for late quaternary environmental changes over the last 190 ka the purpose for which most ages have been produced but in terms of the analytical techniques used data quality and data presentation as these all impact on how dune luminescence ages have been or should be interpreted as a tool for palaeoenvironmental and dune development studies it is concluded that even despite the number of dated dune records from southern africa there is a marked spatial unevenness within and between dunefields in the data available for assessing dune depositional ages and conditions however this is not a situation that can simply be improved upon by adding more and more ages to the full set of records it is both necessary to appreciate the spatial differences in dune sensitivities to activation and relationships to potential changes in hydrological and other activity controls and to establish better tools and approaches for analysing a rich but presently environmentally ambiguous record of dune accumulation

holocene environmental changes in namibia inferred from pollen analysis of swamp and lake deposits spring deposits exposed during building operations in downtown windhoek and lake sediments retrieved from underneath 50 m of water in a sinkhole lake otjikoto contain pollen profiles which reflect environmental changes in namibia during the holocene at windhoek moist local conditions are reflected by pollen in the spring deposits which were radiocarbon dated to between ca 7000 and 6000 bp they remained relatively favourable until 5630 bp despite signs of drying weedy compositae lactucoideae or liguliflorae increased until the end of this record ca 2410 bp indicating local disturbance deposits from lake otjikoto were dated to the late holocene although an accurate chronology could not be estabiished for the sequence due to unexpected results with radiocarbon measurements pollen accumulation values and composition indicate relatively dry conditions after 3500 bp which were followed temporarily by a wetter climate during more recent times

optical dating in archaeology thirty years in retrospect and grand challenges for the future in 1982 when richard klein first became one of the editors of this journal the luminescence dating community was embarking on a new phase of exploratory research attention was turning from the use of thermoluminescence tl dating to estimate the time of last heating of archaeological objects such as pottery and burnt flint to the tl dating of unheated sediments that had been transported by wind and then deposited on the landscape this revolutionary development enabled the extension of tl dating to sedimentary deposits in a variety of environmental settings and to the multitude of archaeological sites that lack suitably heated artefacts in sediment dating the age of most interest is usually the time elapsed since grains of quartz or feldspar were last exposed to sunlight as the energy of the sun s rays is sufficient to evict electrons from their light sensitive traps these traps are steadily refilled after sediment deposition and the longer the grains remain buried the more tl they will emit when measured in 1985 huntley and colleagues proposed optical dating as a simpler and superior means of stimulating the light sensitive traps in quaternary sediments and this is now the principal luminescence based method of dating geological and archaeological deposits optical dating is an umbrella term for an armada of acronyms the most common in archaeological contexts being osl optically stimulated luminescence tt osl thermally transferred osl irsl infrared stimulated luminescence and pirir post infrared irsl all of these variants are founded on the same basic tenet measurement of a light sensitive signal to determine typically the last time that sediment grains were sun bleached but each approach has its virtues and vices in this paper we review this family of luminescence dating techniques and look back on 30 years of optical dating in archaeology some of the more interesting and important achievements are highlighted including the critical insights gained in the last two decades from osl measurements of individual grains of quartz we also look to the future of optical dating in archaeological contexts efforts to extend the age limits of optical dating to older hominin and archaeological sites will remain a key goal and understanding how archaeological sites of all ages form and evolve over time could be improved greatly by combining micromorphology analysis with optical dating of undisturbed intact sediments the latter poses a series of particularly formidable technical challenges but if the past is any guide to the future then we can expect optical dating to illuminate much more of human history before celebrating its golden jubilee

testing of a single grain osl chronology across the middle to upper palaeolithic transition at les cottes france abstract the timing of the middle palaeolithic to upper palaeolithic transition in france is important to help understand when where and how neanderthals have been replaced by homo sapiens radiocarbon dating has been the dating workhorse in constructing the chronological framework pertinent to these questions in this study we are testing whether single grain osl dating has the accuracy and precision to be useful as a complementary dating method the site of les cottes provides an ideal testing ground because of its stratigraphic integrity and reliable radiocarbon chronology we applied single grain osl dating of quartz to 19 samples and multi aliquot met pirir dating of potassium rich feldspar grains to 5 samples to explicitly test assumptions of pre depositional resetting of the osl signal and post depositional exposure to variable beta dose rates the good agreement between the single grain osl and the multi aliquot met pirir ages suggest that the optical signals of both quartz and feldspar grains were reset prior to deposition and that much of the extra scatter observed in the equivalent dose distribution of quartz grains are likely due to the small scale differences in beta dose delivered to individual grains both the quartz osl and feldspar met pirir ages show great consistency with the 14 c ages on bone collected from the same units this gives confidence in the measurement and analytical approaches used to derive both the equivalent dose and dose rate the numerator and denominator respectively of the luminescence age equation these results suggest that a systematic and detailed single grain osl dating study can have the accuracy and precision that is necessary to play a powerful role in the dating of the middle and upper palaeolithic transition and other questions of importance in this time range and geographical area

depositional environment and osl chronology of the homeb silt deposits kuiseb river namibia previous studies suggest that the homeb silts of the kuiseb valley namibia i accumulated in a dune dammed lake ii are end point deposits iii represent an aggrading river bed and iv are slackwater deposits thus they have been used alternatively as evidence of past drier conditions or past wetter conditions lithostratigraphic analysis of two sediment sequences at homeb indicates sedimentation by aggradation of the kuiseb river triggered by a transition from an arid to humid climate osl ages for the sequences were obtained by the sar protocol on aliquots of 9 6 mm and 4 0 mm diameter and on single grains four millimeter aliquot minimum ages closely approximate the single grain minimum ages and are younger than 9 6 mm aliquot minimum and central ages based on these results the small aliquot 4 mm approach appears to provide ages comparable to those obtained by the more laborious and time consuming single grain method minimum ages indicate rapid deposition of the homeb silts in at least two episodes centered at 15 ka and 6 ka during climate transitions from arid to humid flash floods eroded the valley fills during slightly more arid conditions

optical dating of river terrace sediments from kanto plains japan abstract optical dating of river terrace sediments has been carried out in a test of the methodology for luminescence age determination of river terrace formation over the last 100 ka in this study samples were collected at river terraces whose ages were estimated by marker tephra geochronology and from a recent riverbed in the kanto plain japan samples from the recent riverbed show a weak osl signal only and gave young ages samples of river terrace sediments for optical dating were collected systematically from the section of about 8 m at the wall of a gravel quarry the optical ages found corresponded well with those estimated by the age of the marker tephras for samples deeper than 2 5 m however the samples from the ground surface to 2 5 m exhibited considerable scatter in the growth curves and gave a wide range of ages all significantly exceeding expectation this was attributed to the mixing of different age sediments by inundation and or human activities analyses of osl from single grains of quartz confirmed that these sediments were composed of grains having a wide range of palaeodoses consistent with such mixing

evidence of past climatic change in the namib desert abstract a preliminary survey of some areas of the central and northern namib desert was undertaken in order to identify geomorphic and sedimentary features that could potentially provide information on past climatic change in the region wherever possible samples were collected for radiocarbon dating the visits to the skeleton coast area were especially revealing practically every river valley in this tract shows a sequence of terraces and deposits that would warrant a detailed study in all about 120 new radiocarbon dates were obtained for the region these have supplied a wealth of individual results and collectively have enabled the construction of a tentative chronological sequence of the changes in climate for the past 40 000 yr three periods of increased aridity in the hinterland but with decreasing intensity are postulated during the last glacial maximum the early holocene and between a d 1200 and a d 1600 the inter pleniglacial up to 23 000 yr b p the late glacial and the period between about 4000 yr b p and 1200 yr b p on the other hand were more humid than today also with decreasing intensity other indicators of past climate were also identified but since they lie beyond the range of radiocarbon dating they cannot as yet be placed in a chronological context of significance is the fact that convincing evidence was obtained for climatic change within the last millennium and especially the rainfall is found to have been increasing since the 16th century

luminescence dating of hillslope deposits a review abstract luminescence dating determines the last exposure to light of quartz and feldspar mineral grains and thus the time a sediment was laid down prerequisite is that the sediment grains were sufficiently exposed to light prior to deposition for eolian deposits this seems a fair assumption although exceptions may well exist for other depositional environments light exposure prior to burial is often restricted in duration intensity and spectral composition and may result in an age overestimation recent developments now allow dating of sediments that were exposed to only little light prior to deposition the main developments are single aliquot techniques and statistical tests that allow extraction of valid age estimates even from deposits in which bleached and unbleached grains are mixed these developments in combination with the fact that the great majority of sediments near the earth s surface are not of eolian origin have resulted in the large interest in the luminescence dating of non eolian deposits here we review possibilities and challenges of luminescence dating of colluvial deposits we summarize techniques for the detection and handling of insufficiently bleached sediments a common condition in colluvial deposits we give an overview how luminescence dating has been applied on hillslope sediments for reconstructing landscape response to climate change to analyze past fault activity and unravel human induced soil erosion we discuss sampling strategies and give guidelines as to which techniques are best suited to establish luminescence chronologies for colluvium

the human colonisation of australia optical dates of 53 000 and 60 000 years bracket human arrival at deaf adder gorge northern territory the date at which people entered australia has important implications for the debate on modern human origins thermoluminescence dates of 50 60 ka reported for initial occupation of the malakunanja ii site in northern australia have been used as a means of calibrating the rate of mitochondrial and nuclear dna evolution in modern humans optical dating of unburnt quartzose sediments from a rock shelter site nauwalabila i lindner site in deaf adder gorge 70 km south of malakunanja ii provides new evidence for the timing of the colonisation of the continent optical dates were determined for several stratigraphic levels within a 3 m deep excavation in which flaked stone artefacts and ground pigments were found in primary depositional setting the lowest human occupation levels are bracketed by dates of 53 4 5 4 ka and 60 3 6 7 ka while the upper levels show good agreement between optical and calibrated 14c age estimates high quality haematite with ground facets and striations is associated directly with the 53 ka level and indicates the use of pigments by these early australians the optical dates independently confirm evidence for the colonisation of northern australia shortly after 60 ka and should be seen in the context of this region as having been a likely entry route for the first human movements into sahul

timing of lake level changes in etosha pan namibia since the middle holocene from osl ages of relict shorelines in the okondeka region abstract in 2003 examination of aerial photographs revealed a series of previously unknown relict shorelines on the arcuate ridge possibly a clay lunette dune that marks the western boundary of etosha pan in namibia the shorelines are 120 600 m wide and the most prominent extend for tens of km around the lunette dune the shorelines were examined on the ground in 2004 and an attempt was made to date the three lowest levels at ca 5 2 5 and 1 m above the present pan surface the osl ages obtained indicate higher and more prolonged lake conditions than today at ca 6 4 4 0 and 2 1 ka with the youngest shoreline sediments resting on an ancient pan surface dating to ca 13 ka the evidence indicates dry conditions in the pan at ca 13 ka wetter conditions and higher lake levels in the middle holocene followed by a decline in lake levels to the present periods of inundation were of sufficient duration to produce shorelines at the southwestern end of the pan due to the prevailing northeasterly winds that would have maximized wave action along this section of the pan margin the etosha findings together with other regional paleoclimate data suggest four periods of increased wetness in sw africa during the holocene at 7 5 4 5 3 5 2 5 1 7 and ca 1 0 ka there is widespread evidence for the oldest of these periods suggesting that it was a prominent and widespread interval of wetness prior to ca 8 0 ka the climate may have been drier than today

southern hemisphere medium scale waves and total ozone disturbances in a spectral general circulation model the ozone distribution and its variability is simulated with a general circulation model gcm which includes self consistent representation of the physical processes and an accurate parameterization of the ozone photochemical sources and sinks emphasis is placed on analysis of the action of atmospheric waves on the o3 distribution in particular the model generates the medium scale waves which are often observed in the southern hemisphere these waves tend to form quasi regular o3 patterns with zonal wave numbers 4 5 and 6 in fairly good agreement with the observations baroclinic instability generates the waves in the lower troposphere but it is their equivalent barotropic structure in the upper troposphere lower stratosphere which produces the signal on the total ozone column since o3 disturbances are nearly in phase in this altitude range episodes of large amplitude of the medium scale waves occur when the transient waves interact with a stationary wave this standing wave has a zonal wave number close to 4 and appears to result from the large convective activity within the south pacific convergence zone and its southward extension at mid latitudes this study gives a good illustration of the important role played by gcms in understanding the interactions between dynamical and physical processes in the troposphere and wave activity and o3 distribution in the lower stratosphere

new ages for the upper palaeolithic site of xibaimaying in the nihewan basin northern china implications for small tool and microblade industries in north east asia during marine isotope stages 2 and 3 it has been suggested that the small tool and microblade upper palaeolithic industries coexisted in the nihewan basin of northern china for about 8 14 000 years during marine isotope stage mis 2 this inference was based on uranium series ages of around 15 and 18 ka for bovid teeth recovered from the latest small tool site of xibaimaying the youngest occurrence of such tools in the region and optically stimulated luminescence osl dating of the earliest typical microblade site youfang 26 29 ka in this study we re dated the xibaimaying site using single grain osl methods and the resulting ages indicate that the cultural layer was deposited 46 3 ka ago during mis 3 more than 20 millennia earlier than previously thought and older also than the so called earliest primitive and typical microblade tools found at zhiyu 31 39 ka cal bp and youfang these new ages for human occupation of xibaimaying remove support for the parallel development of the small tool and microblade industries in the nihewan basin during the upper palaeolithic but reliable age estimates from additional sites are needed to confidently infer the nature of the chronological relationship between these two upper palaeolithic industries and the associated toolmakers

euhedral sparitic calcite in buried surface horizons in lake basins southwestern kalahari namibia rhombohedral sparitic calcite crystals are recognized in a subsurface interval in three pan basins of the southwestern kalahari eastern namibia they occur in the upper part of a correlatable unit separated from the overlying deposits by a discontinuity that represents an important hiatus the carbonates occur both in the groundmass and in pores crystals in the groundmass formed predominantly in the upper part of the buried interval by partially incorporative intrasediment growth crystals in pores formed by evaporation of solutions in the macropore system including pores created by animal activity and possible mouldic voids the crystals are locally reworked in the basal part of the deposits that overlie the palaeosurface with which they are associated

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples

holocene climatic optimum in southwest africa evidence from the marine clay mineral record abstract sediment composition grain size and clay mineral record of a high resolution sediment core from the continental slope off namibia was investigated to gain information on the deposition of terrigenous matter in this part of the southwest african continental margin during the last 18 k y the depositional processes involved are fluvial input by the kunene river and eolian input from the namib and kalahari deserts each supplying characteristic mineral suites during low sea level erosion of the exposed shelf yields additional material the amount of eolian or fluvial matter depends on the strength of the transport process which is a function of aridity or humidity of the source area thus allowing paleoclimatic interpretations arid conditions prevailed during a low sea level from 18 to 15 ka and unconsolidated shelf sediment was mobilized and supplied to the slope by short distance transport by southerly winds a dramatic increase in the accumulation of terrigenous sediment is recorded from 15 to 10 ka without major changes in sediment composition which is attributed to increased runoff of the kunene river and fluvial erosion of shelf sediments this period coincides with a strengthening of the monsoonal system during a precessional minimum which is observed in numerous sites in central africa and indicates an intensified influence of the monsoon at the kunene headwaters a distinct shift in clay mineralogy towards river derived material marks a second period of increased river runoff during high sea level from 9 to 5 ka indicating maximum humidity in the source area from 6 to 5 ka this corresponds to the holocene climatic optimum observed in the arid belts of northern africa the present balance between fluvial and eolian input was reached approximately at 4 ka

characteristics and osl minimum ages of relict fluvial deposits near sossus vlei tsauchab river namibia and a regional climate record for the last 30 ka the present end point of the tsauchab river is at sossus vlei 30 km into the namib sand sea interdune deposits in three depressions west and southwest of the vlei include channel and interdune lithofacies associations but no deposits typical of river end points or of groundwater seepage into interdune areas the two lithofacies associations show that the tsauchab river extended further into the sand sea in the past it had a well developed channel and a higher flow than today that caused flooding of adjacent interdune areas osl 4 mm aliquot minimum ages indicate that the tsauchab river reached 2 3 km beyond its present end point at ca 25 ka and ca 9 7 ka and that the river was more active from 0 9 0 3 ka the eastward migration of the river end point since ca 7 ka suggests a reduction in flood magnitude accompanied by the gradual invasion of the sossus vlei area by dunes the regional data indicate an additional wet interval at ca 15 ka that is so far not recorded in the sossus area copyright 2006 john wiley sons ltd