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

causal links between nile floods and eastern mediterranean sapropel formation during the past 125 kyr confirmed by osl and radiocarbon dating of blue and white nile sediments abstract it has long been hypothesised that beds of highly organic mud or sapropels seen in marine sediment cores retrieved from the floor of the eastern mediterranean accumulated during times of high nile fluvial discharge our recent fieldwork in the valleys of the blue nile the white nile and the main nile has for the first time revealed a sequence of extreme flood episodes synchronous with sapropel units s5 124 kyr s4 102 kyr s3 81 kyr s2 55 kyr and s1 13 5 6 5 kyr there are more weakly defined links with nile floods and sapropel units s9 240 kyr s8 217 kyr s7 195 kyr s6 172 kyr but the dating error terms are too large to allow us to be too definite during times of extreme floods over the past 125 kyr wide distributary channels of the blue nile flowed across the gezira alluvial fan in central sudan and transported a bed load of sand and gravel into the lower white nile valley the sands were reworked by wind to form source bordering dunes all of which contain heavy minerals of ethiopian provenance these source bordering dunes were active at 115 105 kyr 60 kyr and 12 7 kyr all times of extreme blue nile floods the flood and dune sediments were dated using a combination of optically stimulated luminescence osl and radiocarbon analyses the quaternary record of nile floods discussed here shows a precessional signal and reflects episodes of stronger summer monsoon and more northerly seasonal movement of the itcz linked to times of higher insolation in northern tropical latitudes progressive aggradation of holocene nile channels in northern sudan has had a profound influence upon human settlement in the last 8 kyr

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

late quaternary glacial interglacial cyclicity models of the red sea the benthic foraminiferal faunas from samples of two piston cores retrieved along a north south transect in the red sea were studied the northern core was collected during meteor cruise m 31 2 while the southern one was collected during the sonne cruise 121 benthic foraminiferal faunas from both sites exhibit large variability with respect to density diversity species composition and assemblages combined with stable oxygen and carbon isotope records of planktic and benthic foraminifera one hundered thirty benthic foraminiferal species were identified in the investigated cores the faunal data set of the northern core was reduced to five assemblages factors while the southern one was reduced to four assemblages all assemblages were ranked according to their ecological significance besides relative abundance of major benthic foraminiferal suborders textulariina agglutinating foraminifera miliolina and rotaliina in addition to infaunal epifaunal relative abundance were used as paleoenvironmental proxies allowing the reconstruction of past changes in deep water salinity ventilation and organic carbon fluxes at the sea floor four distinct glacial interglacial cycle during the past 380 kyr have been recognized in the red sea the identified four cycles reveal deviation in deep sea ecosystem between the northern and southern red sea in the northern red sea salinity fluctuations productivity and deep water ventilation and formation had the major impact on benthic foraminiferal pattern corresponding to glacial interglacial cycles and glacio eustatic sea level changes coupled with the impact of mediterranean climate regime on the otherhand in the southern red sea region the oscillation trend of benthic foraminiferal pattern within the glacials and interglacials stages indicates a high frequency environmental alternation this alternation is consistent with the extent of ne monsoonal wind that controls the intensity and extension of the productivity which in turn determine organic matter fluxes and oxygen level at the sea floor

palaeolimnological approaches to climate change with special regard to the biological record abstract lakes systems respond physically chemically and biologically to changes in climate and these responses are registered in many various ways in lake sediment records this paper focuses principally on the biological record and describes recent research that aims to reconstruct i past variability in effective moisture and ii past variability in temperature changes in effective moisture are manifested especially by changes in lake water level in closed lake basins water level change can cause significant changes in water salinity that is registered in sediments by changes in the composition of fossil assemblages especially diatoms in open freshwater lake basins changes in water level are best reconstructed from the aquatic macrofossil record and potentially from the ratio of open water to littoral species of cladocera ostracods and diatoms the most promising biological method for reconstructing past temperature is chironomid analysis and a range of new chironomid temperature transfer functions are being developed however biological responses to changing temperature are usually indirect as a result of temperature effects on water column stratification nutrient cycling and alkalinity generation and in most cases a correct interpretation of the climatic significance of changes in the fossil record requires an understanding of the processes that are operating in the water column a multi proxy whole lake approach is advocated as the best way forward not only as a means of reconstructing past climate but also as a means of assessing the impact of climate change on lake systems

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

100 000 years of african monsoon variability recorded in sediments of the nile margin abstract multiproxy analyses were performed on core ms27pt recovered in hemipelagic sediments deposited on the nile margin in order to reconstruct nile river palaeohydrological fluctuations during the last 100 000 years the strontium and neodymium isotope composition of the terrigenous fraction and the major element distribution reveal large and abrupt changes in source oscillating between a dominant aeolian saharan contribution during arid periods and a dominant nile river contribution during pluvial periods iron content shows a strong correlation with strontium and neodymium isotopes this allows the use of a high resolution continuous fe record as a proxy of blue nile sediment input over the last 100 000 years the detailed fe record with approximately 10 years resolution during pluvial periods is consistent with subtropical african records of well dated lake level fluctuations and thus constitutes a first continuous high resolution record of the east african monsoon regime intensity over ethiopia the detailed fe record shows the two main known pluvial periods attributed to strengthening of the african monsoon over ethiopia the nabtian period from 14 to 8 ka cal bp and the saharan period from 98 to 72 ka bp for the first time the last glacial period marine isotope stage mis 2 3 and 4 is documented with a continuous record showing large oscillations between high and low east african palaeo monsoon regimes the end of the nabtian period occurred at 8 ka in core ms27pt i e much earlier than on the east equatorial african region where it ended around 5 5 ka we interpret this as evidence that the southward shift of the rain belt occurred 3000 years earlier over the eastern ethiopian highland and propose that the gradual southward migration of the rain belt was associated with highly variable intensity and longer rainy seasons from 8 to 5 ka during the last glacial period two wet periods are present around 60 50 ka bp and 38 30 ka bp these two humid periods are in phase with the rise of atmospheric ch4 concentrations suggesting that wetland tropical african area was one of the sources of the atmospheric ch4 during the mis 3 during the last glacial maximum and mis 4 high saharan aeolian influxes in phase with records of aeolian dust deposited in east antarctica are documented this study highlights the importance of reconstructions of monsoon rainfall fluctuation at high temporal resolution to better understand the link between low and high latitude climate variability at millennial timescales

alluvial fan records from southeast arabia reveal multiple windows for human dispersal the dispersal of human populations out of africa into arabia was most likely linked to episodes of climatic amelioration when increased monsoon rainfall led to the activation of drainage systems improved freshwater availability and the development of regional vegetation here we present the first dated terrestrial record from southeast arabia that provides evidence for increased rainfall and the expansion of vegetation during both glacial and interglacial periods findings from extensive alluvial fan deposits indicate that drainage system activation occurred during marine isotope stage mis 6 ca 160 150 ka mis 5 ca 130 75 ka and during early mis 3 ca 55 ka the development of active freshwater systems during these periods corresponds with monsoon intensity increases during insolation maxima suggesting that humid periods in arabia were not confined to eccentricity paced deglaciations and providing paleoenvironmental support for multiple windows of opportunity for dispersal out of africa during the late pleistocene

palaeo environmental implications derived from lake and sabkha deposits of the southern rub al khali saudi arabia and oman abstract shallow lakes and sabkha deposits are evidence of past periods of higher groundwater table than today and hence reflect increased humidity in the rub al khali the large desert in the southern part of the arabian peninsula reported here are the observations made during four expeditions into this remote area in combination with luminescence dating constraining the age of the deposits the results presented extend the spatial coverage of evidence and show that most of the deposits correlate to mis 5 ca 130 70 ka and the early mid holocene ca 11 5 5 ka a single sample points towards potentially more humid conditions during the transition mis 4 3 ca 65 55 ka the presence of the mussel unio in some of the deposits attributed to mis 5 is indirect evidence for the presence of fish in the lakes which must have supported a rich and diverse fauna and probably also flora together with other evidence this demonstrates that a number of small persistent lakes were spread across the rub al khali for at least some of the time these lakes would not only have been a potential source of freshwater but could also have provided an additional and easy accessible food source via the fish for humans migrating through the area the presented palaeoenvironmental data underlines that parts of mis 5 represent a time window of opportunity for a potential expansion of modern humans across arabia

mediterranean climate and oceanography and the periodic development of anoxic events sapropels mediterranean sapropels are layers with elevated organic carbon concentrations that contrast with surrounding sediments which are organic poor sapropels occur quasi periodically in sedimentary sequences of the last 13 5 million years and exist both in the eastern and western mediterranean sub basins they have been the subject of extensive study based on records from both short conventional and long ocean drilling program sediment cores and from a wide variety of uplifted marine sediment sequences on the basin margins and islands previous syntheses in the 1990s and 2000s have discussed how the formation of sapropels is commonly ascribed to deep sea anoxia enhanced export productivity or a combination of these effects however a wealth of new evidence and insights has emerged during the past 1 2 decades based on traditional and novel proxy data as well as modelling which has revealed intriguing new aspects and nuances to the reconstructed conditions hence it is timely to present a new synthesis of current understanding of the processes behind the formation of sapropels which have over the past decade also become a matter of commercial interest in sub salt hydrocarbon exploration in this review we present a context of modern mediterranean climate and oceanography followed by an integrated assessment of the growing understanding of climatological and ocean circulation changes that were associated with sapropel deposition we find that sapropels predominantly formed during astronomically timed episodes when climatic and oceanographic conditions and ecological responses broadly preconditioned the basin for sapropel deposition there is strong correspondence with times of monsoon intensification fuelling runoff from north africa into the mediterranean sea while preconditioning due to sea level rise and regional precipitation and runoff may have contributed as well within these broad episodes of surface buoyancy gain and resultant decline in deep water ventilation specific deposition under dysoxic anoxic or even euxinic conditions occurred within a clearly dynamic system that was characterised by complex spatial and depth dependent patterns gradients with distinct temporal variability on at least decadal to centennial millennial timescales in the final section we evaluate the implications of different modes of deep water removal from silled basins to investigate why sapropels are more frequently and often more intensely developed in the eastern mediterranean than in the western mediterranean

middle late quaternary palaeoclimate variability from lake and wetland deposits in the nefud desert northern arabia abstract records of former lake and wetland development in present day arid hyper arid environments provide an important source of information for palaeoclimatic and palaeoenvironmental studies in arabia such records are typically confined to eccentricity modulated insolation maxima and are often spatially and temporally discontinuous here we present records from a single locality in northern arabia of wetter interludes during both global interglacial and glacial conditions providing a unique opportunity to examine the nature of these events in a common setting at jubbah in the southern nefud desert lake and wetland deposits reveal the repeated formation of a water body within a large endorheic basin over the past ca 360 kyr lake wetland formation occurred during mis 11 9 7 5 3 and the early holocene assisted by local topographic controls and spring recharge palaeoenvironmental and palaeoecological data reveal the existence of a large still water body formed during either mis 11 or 9 ca 363 ka and basin wide alluviation followed by lake formation during mis 7 ca 212 ka during mis 5e ca 130 ka a large freshwater lake occupied the basin while during mis 5a ca 80 ka the basin contained a shallow wetland and freshwater lake complex lake wetland formation also occurred during early mis 3 ca 60 ka at the terminal pleistocene holocene transition ca 12 5 ka and the early middle holocene ca 9 6 5 ka phases of lake and wetland development coincided with human occupation of the basin during the middle palaeolithic epipalaeolithic and neolithic periods highlighting the significance of the region for early demographic change

holocene and pleistocene pluvial periods in yemen southern arabia arabia is an important potential pathway for the dispersal of homo sapiens out of africa yet because of its arid to hyper arid climate humans could only migrate across southern arabia during pluvial periods when environmental conditions were favorable however knowledge on the timing of arabian pluvial periods prior to the holocene is mainly based on a single and possibly incomplete speleothem record from hoti cave in northern oman additional terrestrial records from the arabian peninsula are needed to confirm the hoti cave record here we present a new speleothem record from mukalla cave in southern yemen the mukalla cave and hoti cave records clearly reveal that speleothems growth occurred solely during peak interglacial periods corresponding to marine isotope stages mis 1 early to mid holocene 5 1 5 3 5 5 eemian 7 1 7 5 and 9 of these humid periods highest precipitation occurred during mis 5 5 and lowest during early to middle holocene

a 9000 year oxygen and carbon isotope record of hydrological change in a small ethiopian crater lake the stable isotope composition of authigenic calcites in a core from lake tilo a small crater lake in the ethiopian rift valley provides a subcentury scale record of lake response to climatic change over the last 8850 14c yrs 9850 cal yrs an unusually high range of 18o and 13c values 15 is attributed in part to major changes in hydrothermal groundwater flux although hydrothermal groundwater influx to the lake was high during the early holocene its flow rate was relatively stable and thus climatically induced changes to the water budget can be inferred from variations in 18o and 13c ratios a major decline in hydrothermal groundwater input from 5500 14c yrs bp increased lakewater residence time and led to substantial increases in 18o and 13c before the mid holocene transition to more arid conditions during the last 2700 14c years diagenetic processes have resulted in extremely varied 18o and 13c values the holocene isotope record from lake tilo challenges the widely held assumpti

uranium concentration and isotope ratio profiles within mercenaria shells geochronological implications shells of nineteen specimens of mercenaria from unconsolidated sediments of the southeastern usa coast ranging in age from alive to pliocene were each separated into three to six sections parallel to the shell surface the uranium concentration and isotope ratio of each subsample was determined the results confirm those of previous studies that whole fossil shells have about 8 times as much uranium 300 vs 40 ppb and considerably higher 234u 238u ratios than do whole live collected shells however it was also found that uranium concentrations fall very steeply by factors of 300 and 15 in live and fossil shells respectively from the exterior of the shell to about two thirds of the shell thickness between this depth and the interior surface the uranium concentrations of live shells increase by about a factor of 5 while fossils have gradients which vary from moderately positive to moderately negative the most surprising finding of the study is that the interior portions of the shells become closed chemical systems by no more than about 15 ka after their death this is known from the observation that these portions of late pleistocene shells still have oceanic uranium isotope ratios while the exterior portions of the same shells have ratios which reflect an uptake of uranium from continental groundwaters the water the shells have been in contact with for the vast majority of their existence thus the u series ages of the interior portions of mercenaria shells may be valid after a small correction though shells older than about 200 ka seem less promising firm conclusions cannot be drawn regarding them because of the great scatter in the data

a multi proxy analysis of the holocene humid phase from the united arab emirates and its implications for southeast arabia s neolithic populations an early to mid holocene humid phase has been identified in various arabian geo archives although significant regional heterogeneity has been reported in the onset duration and stability of this period a multi proxy lake and dune record from wahalah in the united arab emirates uae documents significant variations in hydrology biological productivity and landscape stability during the first half of the holocene these data reveal that post last glacial maximum dune emplacement continued into the earliest part of the holocene with the onset of permanent lacustrine sedimentation at the site commencing 8 5 ka cal bp a long term shift towards more arid conditions is inferred between 7 8 and 5 9 ka cal bp with intermittent flooding of the basin and distinct phases of instability throughout the catchment area this transition is linked to the southwards migration of the intertropical convergence zone itcz and associated weakening of monsoon rains a peak in landscape instability is recorded between 5 9 and 5 3 ka cal bp and is marked by a pronounced increase in regional dune emplacement these variations are considered alongside the record of human settlement raising important questions about the interactions between population demographics climate and environment in southeast arabia during the neolithic

monitoring the variations of the socotra upwelling system during the last 250 kyr a biogenic and geochemical approach abstract a combination of changes in the species composition of the radiolarian populations and in the sediment chemical composition content and mass accumulation rates of carbonate organic carbon and selected major and trace elements with special attention paid to ba is used to reconstruct the variations in upwelling activity over the last 250 kyr in the socotra gyre area somali socotra upwelling system nw indian ocean in the socotra gyre core md 962073 at 10 n the variations in upwelling intensity are reconstructed by the upwelling radiolarian index uri while the thermocline surface radiolarian index tsri testifies to productivity variations during non upwelling intervals despite an origin related both to marine and terrigenous inputs the geochemical records of organic carbon silica and trace elements ba p cu and zn normalized to al are controlled by the variations in surface paleoproductivity the data indicate a continuous increase in upwelling intensity during the last 250 kyr with a maximum activity within the mis 3 while high productivity periods in between the upwelling seasons occurred both during glacial and interglacial intervals a comparison of our data with published observations from another gyre of the somalian upwelling area located at 5 n in the somali gyre area shows differences regarding periods of upwelling activity and their geochemical imprint three hypotheses are proposed to explain these differences 1 changes in the planktonic community resulting in more silica rich deposits in the socotra gyre and more carbonate rich deposits in the somali gyre that are controlled by differences in the source water of the upwelling 2 a more important terrigenous input in the southern gyre and 3 a different location of the sites relative to the geographic distribution of the upwelling gyres and hydrologic fronts

luminescence dating of the stratzing loess profile austria testing the potential of an elevated temperature post ir irsl protocol abstract feldspar infrared stimulated luminescence irsl signals saturate at 2000 gy i e 500 700 ka assuming a dose rate of 3 4 gy ka typical for loess and it is therefore theoretically possible to date middle pleistocene loess however the accuracy of age estimates is hampered by anomalous fading which leads to significant age underestimation fading corrections have been proposed but these corrections are reliant on inherent assumptions and in any case are inapplicable at large doses as the growth curve approaches saturation recent studies have identified a post ir irsl signal that shows less fading and is thus less dependent on accurate fading corrections this study builds upon these investigations and applies a post ir irsl sar dating protocol to polymineral fine grain samples of the loess palaeosol sequence in stratzing lower austria after a preheat at 320 c 60 s and an ir bleach at 50 c 200 s irsl was measured at 290 c for 200 s the same set of conditions were used to measure the response to a test dose recycling ratios recuperation and dose recovery tests show that this protocol is suitable for the loess under investigation although finite residual doses of up to 20 gy are observed for the oldest samples the natural signal is in or close to saturation indicating that fading is negligible in nature this observation is inconsistent with the measured laboratory fading rates of 1 1 5 decade and needs further investigation

lunar orbital evolution a synthesis of recent results the present rate of tidal dissipation in the earth moon system is known to be anomalously high in the sense that the implied age of the lunar orbit is only 1 5 109 years though other evidence suggests an age closer to 4 109 years to assess how long the anomalous dissipation has persisted we use published estimates of lunar orbital configurations derived from a fine grained sediments containing tidal laminations and b numerical ocean models averaged over varying ocean geometries the implied histories of the lunar semimajor axis are surprisingly consistent over the past 109 years the ocean models imply on average reduced dissipation in the past because of a spatial mismatch between tidal forcing and oceanic normal modes of higher frequencies webb s ocean model suggests that the anomalous oceanic dissipation began about 109 years ago and has been increasing since then

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

human occupation of the arabian empty quarter during mis 5 evidence from mundafan al buhayrah saudi arabia the empty quarter or rub al khali of the arabian peninsula is the largest continuous sandy desert in the world it has been known for several decades that late pleistocene and holocene deposits representing phases of wetter climate are preserved there these sequences have yielded palaeontological evidence in the form of a variety of vertebrate and invertebrate fossils and have been dated using various radiometric techniques however evidence for human presence during these wetter phases has until now been ephemeral here we report on the first stratified and dated archaeology from the empty quarter recovered from the site of mundafan al buhayrah mdf 61 human occupation at the site represented by stone tools has been dated to the later part of marine isotope stage mis 5 using multiple luminescence dating techniques multigrain and single grain osl tt osl the sequence consists primarily of lacustrine and palustrine sediments from which evidence for changing local environmental conditions has been obtained through analysis of fossil assemblages phytoliths and non marine molluscs and ostracods the discovery of securely dated archaeological material at 100 to 80 ka in the empty quarter has important implications for hypotheses concerning the timing and routes of dispersal of homo sapiens out of africa which have been much debated consequently the data presented here fill a crucial gap in palaeoenvironmental and archaeological understanding of the southern arabian interior fossils of h sapiens in the levant also dated to mis 5 together with middle palaeolithic archaeological sites in arabia and india are thought to represent the earliest dispersal of our species out of africa we suggest that the widespread occurrence of similar lithic technologies across southern asia coupled with a growing body of evidence for environmental amelioration across the saharo arabian belt indicates that occupation of the levant by h sapiens during mis 5 may not have been a brief localized failed dispersal but part of a wider demographic expansion

changing moisture sources over the last 330 000 years in northern oman from fluid inclusion evidence in speleothems speleothems from hoti cave in northern oman provide a record of continental pluvial periods over the last 330 000 yr periods of rapid speleothem deposition occurred from 6000 to 10 500 78 000 to 82 000 120 000 to 135 000 180 000 to 200 000 and 300 000 to 330 000 yr ago with little or no growth during the intervening periods during each of these five pluvial periods d values of water extracted from speleothem fluid inclusions dfi are between 60 and 20 vsmow and 18o values of speleothem calcite 18oc are between 12 and 4 to vpdb these values are much more negative than modern rainfall for d or modern stalagmites for 18o previous work on the isotopic composition of rainfall in oman has shown that northern and southern moisture sources are isotopically distinct combined measurements of the d values of fluid inclusion water with calculated 18o values from peak interglacial speleothems indicate that groundwater was predominantly recharged by the southern indian ocean moisture source when the monsoon rainfall belt moved northward and reached northern oman during each of these periods

middle late quaternary paleoclimate of northern margins of the saharan arabian desert reconstruction from speleothems of negev desert israel abstract speleothems in arid and hyper arid areas of negev desert israel are used in paleoclimate reconstruction of northern margins of saharan arabian desert focused on the following objectives 1 precise u th dating of the timing of speleothem growth as an indicator of periods of humid climate i e positive effective precipitation 2 the origin of rainfall using the speleothem 18 o and changes in spatial pattern of speleothem deposition and speleothem thickness along a north south transect 3 changes of vegetation cover based on speleothem 13 c variations during the last 350 ka major humid periods referred to herein as negev humid periods nhp occurred in the central and southern negev desert at 350 310 ka nhp 4 310 290 ka nhp 3 220 190 ka nhp 2 and 142 109 ka nhp 1 nhp 4 nhp 2 and nhp 1 are interglacial events whereas nhp 3 is associated with a glacial period during nhp 1 2 and 3 the thickness and volume of the speleothems decrease from the north to the south and in the most southern part of the region only a very thin flowstone layer formed during nhp 1 with no speleothem deposition occurring during nhp 2 and 3 these data imply that the eastern mediterranean sea was the major source of the rainfall in northern and central negev more negative speleothem 18 o values relative to central parts of israel soreq cave are attributed to rayleigh distillation because of the increasing distance from the mediterranean sea speleothem deposition during the nhp 4 in the southern negev was more intensive than in most of the central negev suggesting the prominence of the tropical rain source decrease in speleothem 13 c during nhp events indicates growth of the vegetation cover nevertheless the ranges of 13 c values show that the vegetation remained semi desert c4 type throughout the nhps with an additional significant carbon fraction coming from the host rock and the atmosphere these observations together with small thickness of the speleothem layers favor that nhp events consisted of clusters of very short humid episodes interspersed with long droughts nhp events were contemporaneous with climate periods with monsoon index of 51 cal cm 2 day and with the formation of sapropel layers in the mediterranean sea such simultaneous intensification of the monsoon and atlantic mediterranean cyclones is probably related to the weakening of the high pressure cell above sub tropical atlantic ocean which enabled more rainfall to penetrate into the saharan arabian desert from the north and south the contemporaneous occurrence of the nhp events and the increased monsoon rainfall could have opened migration corridors creating climatic windows of opportunity for dispersals of hominids and animals out of the african continent

eemian tropical and subtropical african moisture transport an isotope modelling study during the last interglacial insolation maximum eemian mis 5e the tropical and subtropical african hydrological cycle was enhanced during boreal summer months the climate anomalies are examined with a general circulation model echam4 that is equipped with a module for the direct simulation of 18o and deuterium h218o and hdo respectively in all components of the hydrological cycle a mechanism is proposed to explain the physical processes that lead to the modelled anomalies differential surface heating due to anomalies in orbital insolation forcing induce a zonal flow which results in enhanced moisture advection and precipitation increased cloud cover reduces incoming short wave radiation and induces a cooling between 10 n and 20 n the isotopic composition of rainfall at these latitudes is therefore significantly altered increased amount of precipitation and stronger advection of moisture from the atlantic result in isotopically more depleted rainfall in the eemian east african subtropics compared to pre industrial climate the east west gradient of the isotopic rainfall composition reverses in the eemian simulation towards depleted values in the east compared to more depleted western african rainfall in the pre industrial simulation the modelled re distribution of 18o and d is the result of a change in the forcing of the zonal flow anomaly we conclude that the orbitally induced forcing for african monsoon maxima extends further eastward over the continent and leaves a distinct isotopic signal that can be tested against proxy archives such as lake sediment cores from the ethiopian region

the hydrogeology and groundwater resources development of the cambro ordovician sandstone aquifer in saudi arabia and jordan abstract the saq cambro ordovician sandstones form the major national aquifer in saudi arabia and jordan significant abstraction of groundwater has taken place since the early 1950s and monitoring of the aquifer responses indicates a moderate transmissivity but high specific yield the groundwater quality is excellent for irrigation which is the present major use and is also good for potable purposes although large drawdowns are being experienced locally in confined areas of the aquifer the unconfined area responses show the aquifer to have an excellent potential for development under groundwater mining principles that may be considered for use outside the areas of occurrence

lateral variation of the cutoff depth of shallow earthquakes beneath the japan islands and its implications for seismogenesis abstract we estimated the spatial distribution of the cut off depth of shallow seismicity beneath the japan islands based on data from a recently constructed nationwide dense seismic network in order to avoid the effect of heterogeneous seismic velocity structure we determined the 3d seismic velocity structure for the whole of japan which was then used to relocate the hypocenters the cut off depth was determined by calculating d90 the depth above which 90 of the earthquakes occur a spatial distribution of estimated d90 values shows a considerable lateral variation ranging from about 5 km to about 40 km the d90 s are deep along the pacific coast of eastern japan locally shallow d90 s extend along belt like stretches of volcanic areas heat flow is low along the pacific coast in eastern japan and high in the volcanic areas this indicates that the lateral variation of d90 s is formed mainly by lateral geotherm variation cooling by the subducting old very cold pacific plate may cause the deep d90 s along the pacific coast in eastern japan heating by magma supplied from the mantle wedge below is considered to be the main cause of the shallow d90 s in the volcanic areas magma and or aqueous fluids derived from solidified magma contribute not only to locally shallow d90 s but also to the weakening of ambient rocks in the lower crust resulting in stress concentrations in the upper crust just above them large shallow inland earthquakes tend to occur in such areas suggesting that a model of shallow earthquake generation applied to tohoku can be used in other areas in japan as well

increased seasonality in middle east temperatures during the last interglacial period the last interglacial period about 125 000 years ago is thought to have been at least as warm as the present climate owing to changes in the earth s orbit around the sun it is thought that insolation in the northern hemisphere varied more strongly than today on seasonal timescales which would have led to corresponding changes in the seasonal temperature cycle here we present seasonally resolved proxy records using corals from the northernmost red sea which record climate during the last interglacial period the late holocene epoch and the present we find an increased seasonality in the temperature recorded in the last interglacial coral today climate in the northern red sea is sensitive to the north atlantic oscillation a climate oscillation that strongly influences winter temperatures and precipitation in the north atlantic region from our coral records and simulations with a coupled atmosphere ocean circulation model we conclude that a tendency towards the high index state of the north atlantic oscillation during the last interglacial period which is consistent with european proxy records contributed to the larger amplitude of the seasonal cycle in the middle east

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

middle to late pleistocene human habitation in the western nefud desert saudi arabia abstract the nefud desert is crucial for resolving debates concerning hominin demography and behaviour in the saharo arabian belt situated at the interface between the mediterranean westerlies and african monsoonal climate systems the nefud lies at the centre of the arid zone crossed by homo sapiens dispersing into eurasia and the edges of the southernmost known extent of the neanderthal range in 2013 the palaeodeserts project conducted an intensive survey of the western nefud to 1 evaluate pleistocene population dynamics in this important region of the saharo arabian belt and 2 contribute towards understanding early modern human range expansions and interactions between different hominin species thirteen lower and middle palaeolithic sites were discovered in association with palaeolake basins one of the sites t is al ghadah may feature the earliest middle palaeolithic assemblage of arabia preliminary analyses show that the lower and middle palaeolithic sites discovered display diverse technological characteristics indicating that the nefud was important for population turnovers and exchanges throughout the pleistocene periodic environmental amelioration appears to have attracted hominin incursions into the region and subsequent ephemeral occupations structured around lakes and to a lesser extent raw material sources however differences between the lower and middle palaeolithic sites are indicative of greater mobility during the later pleistocene a rarity of formal tools but strong similarities in lithic production techniques are also suggestive of demographic affinities across the nefud during the pleistocene and perhaps beyond these preliminary results support the view that the arabian peninsula was a critically important region of southwest asia during the late pleistocene in which demographic responses to climatic amelioration may have structured connectivity across the saharo arabian belt the levant and as far as india

east african climate change and orbital forcing during the last 175 kyr bp abstract variations in the temporal and spatial distribution of solar radiation caused by orbital changes provide a partial explanation for the observed long term fluctuations in african lake levels the understanding of such relationships is essential for designing climate prediction models for the tropics our assessment of the nature and timing of east african climate change is based on lake level fluctuations of lake naivasha in the central kenya rift 0 55 s 36 20 e inferred from sediment characteristics diatoms authigenic mineral assemblages and 17 single crystal 40ar 39ar age determinations assuming that these fluctuations reflect climate changes the lake naivasha record demonstrates that periods of increased humidity in east africa mainly followed maximum equatorial solar radiation in march or september interestingly the most dramatic change in the naivasha basin occurred as early as 146 kyr bp and the highest lake level was recorded at about 139 133 kyr bp this is consistent with other well dated low latitude climate records but does not correspond to peaks in northern hemisphere summer insolation as the trigger for the ice age cycles the naivasha record therefore provides evidence for low latitude forcing of the ice age climate cycles

the early holocene humid period in nw saudi arabia sediments microfossils and palaeo hydrological modelling abstract an early to mid holocene humid period has been inferred from a variety of geo bio archives of the sahara and the arabian peninsula including sabkhas palaeo lakes sand dunes wadis speleothems or marine sediments on the arabian peninsula most of these records are located in the southern and southeastern part studies from the northern part are rare this paper presents the first results from palaeo environmental and hydrological investigations on the sabkha basin of the tayma oasis northwestern saudi arabia sedimentary characteristics micro and macrofauna a digital elevation model based on dgps measurements and 14 c ams data indicate the presence of a perennial lake with a minimum depth of 13 m a stored water volume of 1 16 10 7 m 3 and a surface of 18 45 km 2 between 10 000 9000 cal bp foraminiferal test malformations and the shape of sieve pores on ostracod valves were used to detect trends in palaeo salinity and ecological stress conditions the reconstructed gradual contraction of the lake at least after 8500 cal bp reflects the long term aridisation trend on the arabian peninsula after the early holocene based on the hydrological water balance equation quantitative data on minimum palaeo rainfall during the early holocene humid period were calculated input parameters for the equation are the minimum lake level lake surface and lake volume during the peak of the early holocene humid period as well as palaeo evapotranspiration groundwater infiltration and surface runoff accordingly a perennial lake in the endorheic basin of the modern sabkha with a lake level at the same elevation as the uppermost shoreline deposit would have required a minimum annual precipitation of 150 25 mm this value amounts to c 300 of recent precipitation rates

holocene palaeohydrology and climate variability in northeastern spain the sedimentary record of lake estanya pre pyrenean range abstract this multi proxy study of sediment cores from karstic lake estanya pre pyrenean range ne spain provides the first complete continuous record of the hydrological evolution in the northeastern iberian peninsula over the last 9500 yr six sedimentary facies and four main sedimentary units have been defined after integration of sedimentological mineralogical and geochemical analyses the use of total sulphur content and sedimentary facies as paleohydrological proxies allows reconstruction of relative changes in lake level the estanya record shows a large increase in water availability after 9 2 ka fluctuating lake levels and salinity during the period 9 2 4 2 ka and generally higher lake levels after 1 7 ka periods of increased run off and sediment delivery and less saline conditions occurred at 8 5 8 2 6 7 5 9 and 4 9 4 2 ka dominant lower lake levels and concentrated waters during the period 4 2 0 8 ka were punctuated by a higher lake level higher clastic input episode ca 1 7 1 ka fluctuating but higher lake levels occurred during the last 800 years the main hydrological phases in lake estanya are coherent with western mediterranean and north atlantic holocene reconstructions but they also show similarities with northern african records

amplitudes of orbitally induced climatic cycles and patterns of hominin speciation abstract palaeoanthropologists and archaeologists have long invoked climate change to explain aspects of human evolution collection of new climatic and environmental data combined with new fossil discoveries and methodological improvements continue to make exploration of this link a vital endeavour in studying human evolution the current study employs a global climatic dataset and a rigorously compiled catalogue of hominin first and last appearance dates to test the effects of changes in temperature on hominin speciation and extinction through the use of wavelet analysis and bandpass filters the eccentricity obliquity and precession components of the studied climatic record are extracted and tested independently for associations with patterns of speciation and extinction results suggest that all three components may play a role in speciation events but that only the obliquity cycle shows a statistically significant relationship with extinction events it is suggested that whilst climatic factors could contribute to the appearance of new hominin species subsequent competition between these species may lead to their extinction

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

playa lake basins on the southern high plains of texas and new mexico part ii a hydrologic model and mass balance arguments for their development hydrologic geologic geomorphic and mass balance data suggest that most of the 30 000 playa lake basins on the southern high plains have developed by a combination of dissolution of caliche and piping of surface material into the unsaturated zone rather than by eolian processes as has generally been stated a conceptual model suggests that particulate organic material much of which is sorbed on smectite clays is carried downward from the surface into the unsaturated zone by recharging water the organic material is oxidized to co 2 which dissolves in the water forms carbonic acid and dissolves lithologic carbonates because organic material is transported and oxidized deep in the unsaturated zone co 2 concentrations are much higher at depth than in the soil zone and recharging water remains thermodynamically subsaturated with respect to carbonates and thus able to dissolve them throughout the unsaturated zone dissolution promotes lithologic instability leading to piping and eluviation of material within the unsaturated zone playa basins expand laterally as recharge is concentrated at the edge of the playa floor because of lowered permeability in the center that results from accumulation of clays and other fine sediment mass balance calculations of gas liquid and solid fluxes beneath a playa basin suggest that sufficient mass is transported to account for the volume of the depression particulate flux is estimated by relating it to the co 2 flux out of the unsaturated zone solute flux is estimated from the difference between input values from the playa lake water and that observed in ground water gas flux is measured directly from gas samples at specific depths below the surface

monsoon triggered formation of quaternary alluvial megafans in the interior of oman a vast bajada consisting of coalescing low gradient 0 3 alluvial fans exceeding 100 km in length formed along the southwestern margin of the oman mountains it comprises an old fan sequence of inferred miocene to pliocene age termed barzaman formation diagenetically highly altered to dolomitic clays and a thin veneer of weakly cemented quaternary gravels a combination of remote sensing lithological analyses and luminescence dating is used to interpret the complex aggradation history of the quaternary alluvial fans from the interior of oman in the context of independent regional climate records from satellite imagery and clast analysis four fans can be discerned in the study area while two early periods of fan formation are tentatively correlated to the miocene pliocene and the early pleistocene luminescence dating allows the distinction of five phases of fan aggradation during the middle late pleistocene these phases are correlated with pluvial periods from marine isotope stage mis 11 through 3 when southern arabia was affected by monsoonal precipitation it is concluded that the aggradation of the alluvial fans was triggered by the interplay of increased sediment production during arid periods and high rainfall with enhanced erosion of hillslopes and transport rates during strong monsoon phases however the lack of fine grained sediments bioturbation and organic material implies that although the quaternary fans are sourced by monsoonal rains they formed in a semi arid environment thus it appears that in contrast to the oman mountains the interior was not directly affected by monsoonal precipitation