a record of holocene climate change from lake geochemical analyses in southeastern arabia lacustrine sediments from southeastern arabia reveal variations in lake level corresponding to changes in the strength and duration of indian ocean monsoon iom summer rainfall and winter cyclonic rainfall the late glacial holocene transition of the region was characterised by the development of mega linear dunes these dunes became stabilised and vegetated during the early holocene and interdunal lakes formed in response to the incursion of the iom at approximately 8500 cal yr bp with the development of c3 dominated savanna grasslands the iom weakened ca 6000 cal yr bp with the onset of regional aridity aeolian sedimentation and dune reactivation and accretion despite this reduction in precipitation the lake was maintained by winter dominated rainfall there was a shift to drier adapted c4 grasslands across the dune field lake sediment geochemical analyses record precipitation minima at 8200 5000 and 4200 cal yr bp that coincide with bond events in the north atlantic a number of these events correspond with changes in cultural periods suggesting that climate was a key mechanism affecting human occupation and exploitation of this region

phytoliths indicators of grassland dynamics during the late holocene in intertropical africa abstract the reconstruction of african tropical grassland history during the late holocene can be carried out using phytolith analysis fossil phytolith assemblages from lake guiers in the sahelian region of senegal and from lake sinnda in the guineo congolian region of congo were investigated the results are interpreted on the basis of modern phytolith assemblages from the same regions and compared to pollen data previously obtained tall or short grass associations are discriminated by their phytolith index iph saddle cross dumbel saddle while the density of shrubs and trees is indicated by relative proportions of the dicotyledon phytoliths the phytolith data emphasize that in the guineo congolian region around lake sinnda the driest phase of the late holocene occurred between 4000 and 1200 yr b p commencing with the opening of the dense forest and its replacement by a short grass savanna from ca 1000 yr b p wetter climatic conditions developed as represented by the setting up of a tall grass savanna woodland the modern shrub and tall grass savanna was developed ca 700 yr b p in the sahelian region around lake guiers the driest phase occurred after about 2000 yr b p and has not been followed by moister conditions a tall grass savanna woodland was gradually replaced by a shrub and short grass savanna which still occurs a short period of development of swampy vegetation which can be related to a lake level change interrupted the semi arid adaptation of the vegetation between about 2000 yr b p and the present

palaeoclimate in the saharan and arabian deserts during the middle palaeolithic and the potential for hominin dispersals to disperse out of sub saharan africa it was necessary for hominins to cross the deserts of either the sahara and or arabia thus understanding the palaeoclimate of the saharo arabian region is central to determining the role these deserts played in the peopling of the planet when did they act as barriers and when were they more humid opening dispersal routes across them to address these questions we have conducted a temporal and spatial evaluation of dated sites from 20 to 350 ka using combined probability density function pdf and geographical information system gis analyses of all sites dated using uranium thorium u th or optically stimulated luminescence osl methods radiocarbon dates were not considered because of contamination problems in this time range the results show that during mis 2 there is little evidence for humidity in arabia as would be expected during the height of the last glacial maximum however the sahara shows a sharp rise in probability at the beginning of mis 2 peaking near the boundary with mis 3 at 29 ka there appear to be brief periods of humidity in mis 3 and 6 though at different times in the sahara ca 37 44 138 154 and 180 ka and arabia ca 40 54 and 163 ka during mis 5 both regions show much evidence for humidity with pdf peaks corresponding to insolation maxima though not all maxima are represented in either the saharan or arabian record this situation can be explained by eccentricity modulated precession when eccentricity is strong insolation is enhanced but also more variable and the desert climate is generally more humid particularly at times of high insolation the opposite happens when eccentricity is low and deserts tend to be more arid but local factors exert more of an influence on climate affecting the timing and strength of the brief humid periods experienced so that they no longer coincide with insolation maxima the spatial distribution of humid sites is compatible with a number of different modern human dispersal theories southern arabia experienced humid periods centred on 54 ka and 125 ka and this could have facilitated dispersal from east africa to southern arabia and beyond via the bab el mandab the sahara shows considerable evidence for humidity during mis 5 and may have had dispersal across its expanse at this time

latest pleistocene and holocene dune construction at the north eastern edge of the rub al khali united arab emirates abstract optical dating of two dune pro les developed in linear dunes in ras alkhaimah united arab emirates has been used to establish the timing and rateof dune accretion one section at awa was over 17 m high while that at idhnwas over 40 m high the awa dune appears to have accumulated very rapidly 10 000 years ago with a vertical accumulation rate of about 3ae3mka 1 theidhn dune appears to have accumulated over the past 1000 years with 20 m ofsediment accumulating in a time period of about 270 years the awa dunemay have accumulated in response to the transgression of the persian gulf byrising sea levels in late pleistocene and holocene times the idhn dune mayhave accumulated rapidly because of intensi ed human activity a short livedclimatic event or because it may periodically be reactivated after erosion by uvial action at its base keywords linear dune optical dating rub al khali sand accumulation introductionthere remains some uncertainty surrounding thestyle and timing of deposition of large aeoliandunes with authors supporting both gradual andpunctuated models of dune development for adiscussion see thomas 1997 this divergence ofopinion results from both the general absence ofdating control within dunes in most studies anddif culties in gaining exposures within some ofthe larger dune bedforms the purpose of thispaper is to establish a chronology of dunedevelopment for two thick 10 m dune sectionsexcavated within large complex linear dunesfrom within the rub al khali near ras alkhaimah in the north of the united arabemirates fig 1 the sites were selected becauseof the availability of thick fresh sections inrecently excavated moist sand with an area of around 600 000 km

terminal pleistocene and early holocene archaeology and stratigraphy of the southern nejd oman abstract archaeological geoarchaeological and geochronological research at the terminal pleistocene early holocene sites of al hatab ghazal and khamseen rockshelters help to elucidate our understanding of the late palaeolithic occupation of the south arabian highlands the stone tools found at these sites are attributed to the nejd leptolithic tradition an autochthonous lithic culture found across dhofar oman the artifact bearing deposits excavated within these rockshelters have been chronologically constrained by optically stimulated luminescence dating while sedimentological analyses help to establish site formation processes together these methods provide a chronological anchor for some nejd leptolithic archaeological findspots across dhofar the archaeological evidence from surface and stratified sites indicates a technological continuum across the shifting climatic regimes of the terminal pleistocene early holocene this technological continuity points to possible population persistence within one of the posited south arabian refugia

remote sensing and gis techniques for reconstructing arabian palaeohydrology and identifying archaeological sites freshwater availability is critical for human survival and in the saharo arabian desert belt repeated fluctuations between aridity and humidity over the quaternary mean the distribution of freshwater was likely a primary control upon routes and opportunities for hominin dispersals however our knowledge of the spatio temporal distribution of palaeohydrological resources within arabia during mid late pleistocene episodes of climatic amelioration remains limited in this paper we outline a combined method for remotely mapping the location of palaeodrainage and palaeolakes in currently arid regions that were formerly subject to more humid conditions we demonstrate the potential of this approach by mapping palaeochannels across the whole arabian peninsula and palaeolakes and marshes for select regions covering c 10 of its surface our palaeodrainage mapping is based upon quantitative thresholding of hydrosheds data which applies flow routing to digital elevation model dem data while our palaeolake mapping uses an innovative method where spectral classification of landsat thematic mapper tm imagery is used to detect palaeolake deposits within endorheic closed basins before modelling maximum lake extents by flooding the basin to the level of the elevation of the highest detected deposit field survey in the nefud desert and the dawadmi and shuwaymis regions of saudi arabia indicates accuracies of 86 for palaeodrainage mapping and 96 for identifying former palaeolake basins 73 accuracy of classification of individual deposits the palaeolake mapping method has also demonstrated potential for identifying surface and stratified archaeological site locations with 76 of the surveyed palaeolake basins containing archaeological material including stratified palaeolithic archaeology initial examination of palaeodrainage in relation to archaeological sites indicates a relationship between mapped features and previously recorded palaeolithic sites an example of the application of these data for period specific regional palaeohydrological and archaeological reconstructions is presented for a region of northern saudi arabia covering the southern nefud desert and adjacent lava fields

geomorphological and palaeoenvironmental investigations in the southeastern arabian gulf region and the implication for the archaeology of the region abstract during the late quaternary the climate of arabia has fluctuated between periods of higher rainfall and fluvial activity dominated by the influence of the indian ocean monsoon iom and drier arid conditions under the influence of the westerlies this has left a rich legacy of landforms from which temporal and spatial patterns of environmental change are reconstructed the coastal desert region of the southeastern arabian gulf has been a focal point for human settlement since 8000 cal yr bp the region is strategically located on an important trade route between two cradles of civilization namely mesopotamia and the indus changes in the evolution and modification of this landscape under varying climatic conditions have influenced humans living in and exploiting this landscape for food and water raw materials and trade routes in this study geomorphological and palaeoenvironmental investigations are integrated to provide a framework of environmental change for the late glacial and early mid holocene periods against which the archaeology of the area can be set the late glacial and earliest holocene was characterised by intense aridity and accumulation of mega linear dunes driven by the shamal winds in the arabian gulf region this continued into the earliest part of the holocene whilst southern arabia was under the influence of the iom the monsoon rains migrated into the gulf region between 8500 6000 cal bp during this time semi nomadic herders occupied this region and grazing their animals in a landscape covered with c3 savanna grassland the neolithic peoples also practised hunting and fishing and the collection of shellfish was an important activity pottery shows links with mesopotamia at this time from 6000 cal bp the iom retreated south and rainfall was derived from winterly westerly sources under drier conditions a switch occurred to a sparser cover of c4 grasses from 4500 cal bp the climate became much drier with the development of stronger westerly summer shamal winds and the reactivation of dunes across the region an intense arid period occurred at 4100 bp which corresponds with major drought conditions in mesopotamia and the indus region which led to major changes in society this event occurs at a major transition in the arabian gulf bronze age archaeological record with a decline in population and trade the last 4000 yr has largely been characterised by arid conditions similar to those found in the region today

viscosity effects in vibratory mobilization of residual oil the last decade has seen clarifications of the underlying capillary physics behind stimulation of oil production by seismic waves and vibrations computational studies have prevailed however and no viscous hydrodynamic theory of the phenomenon has been proposed for a body of oil entrapped in a pore channel viscosity effects are naturally incorporated through a model of two phase core annular flow these effects are significant at the postmobilization stage when the resistance of capillary forces is overcome and viscosity becomes the only force resisting an oil ganglion s motion aviscousequationofmotionfollows andcomputational fluid dynamics cfd establishes the limits of its applicability the theory allows inexpensive calculation of important geophysical parameters of reservoir stimulation for given pore geometries such as the frequency and amplitude of vibrationsneededtomobilizetheresidualoil thetheoretical mobilizingaccelerationinseismicwavesforagivenfrequency is accurate to within approximately 30 or better when checked against cfd the advantages of the viscous theory over the inviscid one are twofold the former can calculate complete time histories of forced displacement of an oil blob in a pore channel including retardation by capillary forces mobilization by vibrations and an ensuing haines jump it also provides an approximately factor of two improvement in the calculation of the mobilizing acceleration needed to unplugastaticganglion

strong coherence between solar variability and the monsoon in oman between 9 and 6 kyr ago variations in the amount of solar radiation reaching the earth are thought to influence climate but the extent of this influence on timescales of millennia to decades is unclear a number of climate records show correlations between solar cycles and climate1 but the absolute changes in solar intensity over the range of decades to millennia are small2 and the influence of solar flux on climate is not well established the formation of stalagmites in northern oman has recorded past northward shifts of the intertropical convergence zone3 whose northward migration stops near the southern shoreline of arabia in the present climate4 here we present a high resolution record of oxygen isotope variations for the period from 9 6 to 6 1 kyr before present in a th u dated stalagmite from oman the 18o record from the stalagmite which serves as a proxy for variations in the tropical circulation and monsoon rainfall allows us to make a direct comparison of the 18o record with the 14c record from tree rings5 which largely reflects changes in solar activity6 7 the excellent correlation between the two records suggests that one of the primary controls on centennial to decadal scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation

late quaternary humidity and aridity dynamics in the northeast rub al khali united arab emirates implications for early human dispersal and occupation of eastern arabia the major driver of palaeoclimatic dynamics over the southeast arabian region is the varying latitudinal interface between the westerly driven shamaal winds and a northward branch of the southwesterly indian ocean summer monsoon iom at present this latter system is restricted in extent to the southern coastal regions of yemen and oman monsoonal winds are widely believed to have increased in strength and penetrated much further north across southeast arabia at various intervals during the quaternary resulting in a series of humid phases which early studies suggested focussed within mis 3 and mis 1 recent speleothem studies from oman and uae have indicated humidity within mis 5 which with current debates surrounding early human dispersal and occupation could be significant for affirming the regional potential for early occupation we investigate two new geoproxy suites from al ain and tawi asmar northern uae in the presently hyper arid rub al khali sand sea that preserve evidence of multiple episodes of aeolian deposition and humidity in the form of fluvial gravels sands and silts and dune sands 35 osl ages demonstrate humid episodes occurred in mis 5e 5a and the early holocene with a major dry dune building phase in late mis 3 and the onset of dry conditions again from 6 ka the fluvial sedimentary evidence from mis 5e and 5a suggest that the present hyper arid desert landscape of the northeastern rub al khali was at those times represented by an environment experiencing significant seasonal wadi flow this provides an environmental context that supports recent studies indicating archaeological visibility in arabia dating from mis 5 and the presence of anatomically modern humans in arabia at this time

timing and intensity of groundwater movement during egyptian sahara pluvial periods by u series analysis of secondary u in ores and carbonates abstract wet climatic episodes are known to have prevailed in the egyptian sahara several times during the late quaternary most recently during the holocene 8000 yr ago earlier wet episodes have been recognized as having occurred during the past 300 000 yr and have been dated by u series methods in speleothems and in lake travertines we show here that the times of enhanced groundwater movement can also be determined by 230 th 234 u dating of secondary u in ores of uranium iron and phosphate we also present evidence that such acceleration of groundwater movements is indicated by relatively low 234 u 238 u activity ratios in the secondary uranium our new data show that pluvial periods in egypt occurred during marine oxygen isotope stages 4 5 6 and 7 and therefore are consistent with the view that the wet episodes are the results of migration of the tropical monsoonal belt driven primarily by the 23 000 yr precession cycle of the milankovich curve modulated by the 100 000 yr eccentricity cycle

palaeoenvironmental and sea level changes during the holocene in eastern saudi arabia and their implications for neolithic populations abstract this paper presents the key findings of a multidisciplinary study investigating the nature and timing of coastal landscape evolution in eastern saudi arabia during the holocene to date most sea level reconstructions for the arabo persian gulf are based on uncalibrated 14c ages without correction for marine reservoir effects or lack precision with regard to the effects of neotectonic changes indicators of sea level used errors in elevation of sedimentary units used and the relationship with actual tides as a consequence the nature and timing of relative sea level rsl changes during the late pleistocene and holocene remain poorly understood to help address this we use sea level index points slips based on calibrated 14c ages to present a rsl curve for the central southern gulf of saudi arabia from coastal sabkha deposits near the archaeological site of dosariyah the sediments record rapid transgression during the early holocene with a mid holocene high stand immediately prior to 6880 6560 cal bp when the upper limit for the palaeo mean highest high tide water mhhw was 2 8 3 10 m above present day mean sea level transgression continued until shortly after 5575 5310 cal bp with an upper limit to the palaeo mhhw of 3 75 m above present sea levels thereafter a fall in rsl was recorded with the regression leading to the progradation of the coastal system and the development of coastal sabkhas nonetheless later transgressions are recorded in the region between 4848 4536 and 4335 3949 cal bp radiometric dating results from archaeological excavations at dosariyah one of the most important neolithic coastal sites in the gulf suggest that occupation of the site during the neolithic coincides with the mid holocene marine transgression ca 7200 6500 cal bp whilst the close proximity of the site to the sea may have facilitated maritime exchange activities occupation of the site was short lived and the phase of abandonment occurred during a period of rapid rsl rise which would have transformed the area around dosariyah into an island or certainly cut it off tidally from the mainland

stratigraphic placement and age of modern humans from kibish ethiopia in 1967 the kibish formation in southern ethiopia yielded hominid cranial remains identified as early anatomically modern humans assigned to homo sapiens however the provenance and age of the fossils have been much debated here we confirm that the omo i and omo ii hominid fossils are from similar stratigraphic levels in member i of the kibish formation despite the view that omo i is more modern in appearance than omo ii 40ar 39ar ages on feldspar crystals from pumice clasts within a tuff in member i below the hominid levels place an older limit of 198 14 kyr weighted mean age 196 2 kyr on the hominids a younger age limit of 104 7 kyr is provided by feldspars from pumice clasts in a member iii tuff geological evidence indicates rapid deposition of each member of the kibish formation isotopic ages on the kibish formation correspond to ages of mediterranean sapropels which reflect increased flow of the nile river and necessarily increased flow of the omo river thus the 40ar 39ar age measurements together with the sapropel correlations indicate that the hominid fossils have an age close to the older limit our preferred estimate of the age of the kibish hominids is 195 5 kyr making them the earliest well dated anatomically modern humans yet described

freshwater on the route of hominids out of africa revealed by u th in red sea corals a fundamental issue in the evolution of human culture concerns the route and conditions of anatomically modern hominids during the migration out of africa a particular question is how could anatomically modern hominids cross the hyperarid arabian deserts here we outline the evidence for significant presence of freshwater along the red sea shores during the last interglacial period freshwater caused an extensive recrystallization of coral reefs from aragonite to calcite indicating uplift of the reefs through well developed phreatic freshwater coastal aquifers applying novel open system u th dating methodology to the calcitic corals we dated the freshwater recrystallization to ca 140 ka consistent with other geological lines of evidence placing the migration of anatomically modern hominids out of africa at the onset of the last interglacial

a multi proxy record of holocene environmental change peatland development and carbon accumulation from staroselsky moch peatland russia despite their huge extent the peatlands of russia are an under exploited source of data on palaeoenvironmental change we investigated the holocene history of staroselsky moch an ombrotrophic peatland in the tver region of european russia by analysis of testate amoebae peat physical properties plant macrofossils and pollen the peatland developed through a classic hydroseral succession in the early holocene with a sharp decline in mineral input to 6200 cal bc followed by an abrupt transition from fen to bog vegetation around 5500 cal bc through the holocene the peatland has accumulated carbon at a mean apparent rate of 21 5 g c m 2 yr 1 suggesting that carbon accumulation rates in peatlands of european russia lie close to the global average and contrasting with a short sequence of eddy covariance data which implies a net loss of carbon the testate amoeba record shows considerable variability which may be driven by climate but changes are not well replicated in the macrofossil or pollen data we

epipalaeolithic occupation and palaeoenvironments of the southern nefud desert saudi arabia during the terminal pleistocene and early holocene the transition from the terminal pleistocene to the early holocene is poorly represented in the geological and archaeological records of northern arabia and the climatic conditions that prevailed in the region during that period are unclear here we present a new record from the site of al rabyah in the jubbah basin southern nefud desert saudi arabia where a sequence of fossiliferous lacustrine and palustrine deposits containing an archaeological assemblage is preserved sedimentological and palaeoenvironmental investigations both at al rabyah and elsewhere in the jubbah area indicate phases of humid conditions during which shallow lakes developed in the basin separated by drier periods at al rabyah the end of a terminal pleistocene phase of lake expansion has been dated to 12 2 ka using optically stimulated luminescence osl with a mid holocene humid phase dated to after 6 6 ka palaeoecological reconstructions based primarily on non marine molluscs and ostracods from the younger lacustrine deposits indicate a relatively shallow body of freshwater surrounded by moist well vegetated environments a lithic assemblage characterized by bladelets and geometric microliths was excavated from sediments attributed to a drier climatic phase dated to 10 1 ka the lithic artefact types exhibit similarities to epipalaeolithic industries of the levant and their occurrence well beyond the core region of such assemblages and at a significantly later date has important implications for understanding interactions between levantine and arabian populations during the terminal pleistocene early holocene we suggest that the presence of foraging populations in the southern nefud during periods of drier climate is due to the prolonged presence of a freshwater oasis in the jubbah basin during the terminal pleistocene early holocene which enabled them to subsist in the region when neighbouring areas of northern arabia and the levant were increasingly hostile

middle paleolithic occupation on a marine isotope stage 5 lakeshore in the nefud desert saudi arabia major hydrological variations associated with glacial and interglacial climates in north africa and the levant have been related to middle paleolithic occupations and dispersals but suitable archaeological sites to explore such relationships are rare on the arabian peninsula here we report the discovery of middle paleolithic assemblages in the nefud desert of northern arabia associated with stratified deposits dated to 75 000 years ago the site is located in close proximity to a substantial relict lake and indicates that middle paleolithic hominins penetrated deeply into the arabian peninsula to inhabit landscapes vegetated by grasses and some trees our discovery supports the hypothesis of range expansion by middle paleolithic populations into arabia during the final humid phase of marine isotope stage 5 when environmental conditions were still favorable

cultural and human dynamics in southern arabia at the end of the middle paleolithic abstract the arabian peninsula has long been considered as a region devoid of long term human settlement until the holocene period as a result of drastic climatic changes throughout the pleistocene it might be expected that the area was deserted during hyper arid and arid periods and populated by new migrant groups during humid events according to a push and pull phenomenon although this scenario may be perfectly valid for a large part of the peninsula a set of recent data points to the persistence of populations in several regions which may have served as refugia for human groups who developed their own technological traditions such a scenario is suggested by 1 the succession of dense human occupations under arid conditions between ca 60 and 50 ka in the wadi surdud basin a small sedimentary basin in the foothills of the yemeni western highlands this archaeological site complex encompasses several successive human settlements characterized by a middle paleolithic tradition which significantly differs from the middle paleolithic and middle stone age contemporaneous traditions from neighboring regions 2 the regional diversity of the middle paleolithic throughout the saharo arabian arid belt during mis 3 expressed by an array of local techno typological facies that likely relate to distant and disconnected source regions where populations contracted when climate worsened together with a set of high resolution archaeological contexts recently discovered in the arabian peninsula and dated to mis 5 these data suggest that the major human expansion waves which occurred in the region during the upper pleistocene are correlated with the wet phases of mis 5 while populations probably contracted into a few refugia areas at the beginning of mis 3

an early mis 3 pluvial phase in southeast arabia climatic and archaeological implications climatic changes in arabia are of critical importance to our understanding of both monsoon variability and the dispersal of anatomically modern humans amh out of africa the timing of dispersal is associated with the occurrence of pluvial periods during marine isotope stage mis 5 ca 130 74 ka after which arid conditions between ca 74 and 10 5 ka are thought to have restricted further migration and range expansion within the arabian interior whilst a number of records indicate that this phase of aridity was punctuated by an increase in monsoon strength during mis 3 uncertainties regarding the precision of terrestrial records and suitability of marine archives as records of precipitation mean that the occurrence of this pluvial remains debated here we present evidence from a series of relict lake deposits within southeastern arabia which formed at the onset of mis 3 ca 61 58 ka at this time the incursion of monsoon rainfall into the arabian interior activated a network of channels associated with an alluvial fan system along the western flanks of the hajar mountains leading to lake formation multiproxy evidence indicates that precipitation increases intermittently recharged fluvial systems within the region leading to lake expansion in distal fan zones conversely decreased precipitation led to reduced channel flow lake contraction and a shift to saline conditions these findings are in contrast to the many other palaeoclimatic records from arabia which suggest that during mis 3 the latitudinal position of the monsoon was substantially further south and did not penetrate the peninsula additionally the occurrence of increased rainfall at this time challenges the notion that the climate of arabia following mis 5 was too harsh to permit the further range expansion of indigenous communities

holocene vegetation dynamics in the northeastern rub al khali desert arabian peninsula a phytolith pollen and carbon isotope study the holocene vegetation history of the arabian peninsula is poorly understood with few palaeobotanical studies to date at awafi ras al khaimah uae a 3 3 m lake sediment sequence records the vegetation development for the period 8500 cal yr bp to 3000 cal yr bp 13 c isotope pollen and phytolith analyses indicate that c3 pooid grassland with a strong woody element existed during the early holocene between 8500 and 6000 cal yr bp and became replaced by mixed c3 and c4 grasses with a strong c4 panicoid tall grass element between 5900 and 5400 cal yr bp an intense arid event occurred at 4100 cal yr bp when the lake desiccated and was infilled by aeolian sand from 4100 cal yr bp the vegetation was dominated by c4 chloridoid types and cyperaceae suggesting an incomplete vegetation cover and aeolian dune reactivation owing to increased regio nal aridity these data outline the ecosystem dynamics and carbon cycling in response to palaeomon soon and north westerly variability during the holocene copyright 2004 john wiley sons ltd

humid periods in southern arabia windows of opportunity for modern human dispersal arabia is a key area for the dispersal of anatomically modern humans amh homo sapiens out of africa given its modern hostile environment the question of the timing of dispersal is also a question of climatic conditions fresh water and food were crucial factors facilitating amh expansions into arabia by dating relict lake deposits four periods of lake formation were identified one during the early holocene and three during the late pleistocene centered ca 80 ca 100 and ca 125 ka favorable environmental conditions during these periods allowed amh to migrate across southern arabia between ca 75 and 10 5 ka arid conditions prevailed and turned southern arabia into a natural barrier for human dispersal thus expansion of amh through the southern corridor into asia must have taken place before 75 ka possibly in multiple dispersals

desert speleothems reveal climatic window for african exodus of early modern humans one of the fi rst movements of early modern humans out of africa occurred 130 100 thousand years ago ka when they migrated northward to the levant region the climatic conditions that accompanied this migration are still under debate using high precision multicollector inductively coupled plasma mass spectrometry mc icp ms u th methods we dated carbonate cave deposits speleothems from the central and southern negev desert of israel located at the northeastern margin of the saharan arabian desert speleothems grow only when rainwater enters the unsaturated zone and this study reveals that a major cluster of wet episodes the last recorded in the area occurred between 140 and 110 ka this episodic wet period coincided with increased monsoonal precipitation in the southern parts of the saharanarabian desert the disappearance at this time of the desert barrier between central africa and the levant and particularly in the sinai negev land bridge between africa and asia would have created a climatic window for early modern human dispersion to the levant

first evidence for episodic flooding events in the arid interior of central saudi arabia over the last 60 ka although evidence for quaternary environmental changes in the arabian peninsula is now growing research has mostly been conducted in the united arab emirates uae and in the sultanate of oman there have been virtually no recent studies in saudi arabia especially in the central region such as around al quwaiayh in this area there are a series of outwash plains developed along the eastern edge of the arabian shield that formed in the late quaternary four sedimentary sections which are representative of the deposits that have accumulated have been studied and five luminescence ages obtained these are the first luminescence ages acquired from quaternary sediments in central saudi arabia the preserved fluvial deposits in the study area have formed during humid events at ca 54 ka ca 39 ka and ca 0 8 ka in more recent times aeolian sands have been encroaching on to the distal parts of the outwash plains copyright 2008 john wiley sons ltd

the greening of arabia multiple opportunities for human occupation of the arabian peninsula during the late pleistocene inferred from an ensemble of climate model simulations climate models are potentially useful tools for addressing human dispersals and demographic change the arabian peninsula is becoming increasingly significant in the story of human dispersals out of africa during the late pleistocene although characterised largely by arid environments today emerging climate records indicate that the peninsula was wetter many times in the past suggesting that the region may have been inhabited considerably more than hitherto thought explaining the origins and spatial distribution of increased rainfall is challenging because palaeoenvironmental research in the region is in an early developmental stage we address environmental oscillations by assembling and analysing an ensemble of five global climate models ccsm3 cosmos hadcm3 kcm and noresm we focus on precipitation as the variable is key for the development of lakes rivers and savannas the climate models generated here were compared with published palaeoenvironmental data such as palaeolakes speleothems and alluvial fan records as a means of validation all five models showed to varying degrees that the arabia peninsula was significantly wetter than today during the last interglacial 130 ka and 126 125 ka timeslices and that the main source of increased rainfall was from the north african summer monsoon rather than the indian ocean monsoon or from mediterranean climate patterns where available 104 ka mis 5c 56 ka early mis 3 and 21 ka lgm timeslices showed rainfall was present but not as extensive as during the last interglacial the results favour the hypothesis that humans potentially moved out of africa and into arabia on multiple occasions during pluvial phases of the late pleistocene

quantifying spatial and temporal holocene carbon accumulation in ombrotrophic peatlands of the eastmain region quebec canada 1 northern peatlands represent important stocks of organic carbon c peatland c dynamics have the potential to influence atmospheric greenhouse gas concentrations and are therefore of interest concerning future climate change quantification of holocene variations in peat c accumulation rates is often based on a single deep core however deep cores may overestimate accumulation rates when extrapolated to the ecosystem scale we propose a reconstruction of c sequestration patterns based on multiple cores from three ombrotrophic peatlands in boreal quebec canada both total c accumulation and temporal variations herein were quantified radiocarbon dated stratigraphies from different sections resulted in peatland specific age depth models peatland initiation started rapidly after deglaciation around 7500 cal bp vertical accumulation slowed down in the course of the holocene whereas lateral expansion was rapid in the early stages but slowed down near mid holocene total c accumulation showed maximum rates between 5250 and 3500 cal bp with a regional mean holocene apparent rate of 16 2 g m 2 yr 1 the eastmain peatlands have been modest sinks of organic c compared to those of alaska western canada and western siberia although differences in calculation methods hamper direct comparisons considering within peatland dynamics maximum total c sequestration coincided with a period of slowing down in both lateral expansion and vertical accumulation late holocene diminishing peatland c sink functions have been attributed to autogenic as well as allogenic factors height induced surface drying and or neoglacial cooling effects may have forced the slowing down of c sequestration in the studied bogs results further show that in order to obtain an accurate quantification of past c sequestration reconstructions of peatland expansion are essential

shoreline reconstructions for the persian gulf since the last glacial maximum abstract sea level change in the persian gulf since the time of the last maximum glaciation at about 18 000 yr bp is predicted to exhibit considerable spatial variability because of the response of the earth to glacial unloading of the distant ice sheets and to the meltwater loading of the gulf itself and the adjacent ocean models for these glacio hydro isostatic effects have been compared with observations of sea level change and palaeoshoreline reconstructions of the gulf have been made from the peak of the glaciation until about 14 000 yr bp the gulf is free of marine influence out to the edge of the biaban shelf by 14 000 yr bp the strait of hormuz had opened up as a narrow waterway and by about 12 500 years ago the marine incursion into the central basin had started the western basin flooded about 1000 years later momentary stillstands may have occurred during the gulf flooding phase at about 11 300 and 10 500 yr bp the present shorelines was reached shortly before 6000 yr ago and exceeded as relative sea level rose 1 2 m above its present level inundating the low lying areas of lower mesopotamia these reconstructions have implications for models of the evolution of the euphrates tigris karun delta as well as for the movements of people and the timing of the earliest settlements in lower mesopotamia for example the early gulf floor would have provided a natural route for people moving westwards from regions to the east of iran from the late palaeolithic to early neolithic

the great arc of dispersal of modern humans africa to australia abstract during the late pleistocene anatomically modern humans amh dispersed out of africa across the continents their routes obeyed the limitations placed on any large terrestrial mammal dependent on daily drinking water following certain climate permissive corridors amh first spread north with game across the sahara to the levant during the eemian interglacial c 125 ka but failed to continue to europe then occupied by neanderthals the savannah ecosystem in north africa and the middle east then dried up and amh vanished from the levantine fossil record being replaced there by neanderthals later amh successfully left africa as a single group by the southern route to india the added ability to make short but deliberate open water crossings allowed them first to cross the mouth of the red sea from eritrea and subsequently wallace s line to reach the isolated sahul continent at least by 48 000 years ago and possibly by 60 50 000 years ago they only finally arrived in europe from south asia around 45 50 000 years ago probably linked to climatic amelioration during ois 3

the environmental context of paleolithic settlement at jebel faya emirate sharjah uae abstract key to the understanding of pleistocene human dispersals and settlement dynamics is knowledge about the distribution of human habitats in space and time to add information about the characteristics of inhabited environments along the south arabian dispersal route this paper presents paleo environmental data from deposits excavated at jebel faya fay ne1 in the emirate of sharjah uae the sedimentary sequence at fay ne1 spans a period of about 125 000 years including the last interglacial and the holocene particle size and phytolith content of samples from two sediment columns were analyzed including both archaeology bearing layers and archaeologically sterile layers the results demonstrate that human occupation of the site is related to pluvial periods assemblage c dated to about 127 123 ka was deposited during a wet phase with an environment characterized by an increased proportion of c 3 grasses grassland with sedges but lacking tree cover characterize ecological conditions during the youngest of the paleolithic occupation periods assemblage a dated to about 45 40 ka environmental conditions during periods lacking archaeological remains are characterized by the absence of vegetation cover during phases of desiccation there is no evidence for human presence at the site between 38 and 11 ka