holocene climate variability in the levant from the dead sea pollen record abstract the dead sea located at the deepest place on continent and between the subtropical mediterranean zone and the desert reflects in its water composition and levels and sedimentary records the hydrological conditions in the southern levant region temporal variations in rainfall and temperatures of the holocene levant are reconstructed here from pollen data recovered from a sediment core drilled at the ein gedi shore applying a novel biome model based on bayesian statistics our results suggest that the region was arid and warm in the early holocene period 10 6 5 ka cal bp wetter and colder in the mid holocene 6 3 3 3 ka cal bp and drier and warmer in the late holocene 3 2 ka cal bp to present these periods comprise multi centennial climate cycles that are characterized by rapid changes in temperature and precipitation reflecting sea surface temperature sst and atmospheric conditions over the atlantic ocean the pollen record responds within a short time interval to the climate conditions and marks rapid shifts from mediterranean to desert environmental conditions and back in the southern levant region we also evaluate our results in the light of possible disturbances of the natural vegetation e g the possibility of forest decrease since the neolithic

changes in tourmaline composition during magmatic and hydrothermal processes leading to tin ore deposition the cornubian batholith sw england abstract to investigate the potential of tourmaline as a geochemical monitor a comprehensive dataset on major minor and trace element concentrations as well as fe3 fe ratios of tourmaline is presented the dataset includes samples from five plutonic complexes related to diverse magmatic to hydrothermal stages of the cornubian batholith sw england tourmaline composition found in barren and cassiterite bearing samples include all three primary tourmaline groups and tourmaline species with the general endmembers schorl dravite elbaite uvite feruvite foitite and mg foitite based on textures and compositions it is possible to distinguish not only between late magmatic and hydrothermal tourmaline but also between several formation stages hence tourmaline monitors late magmatic processes and the partitioning of elements during exsolution of an aqueous phase for example in hydrothermal tourmaline sn is strongly enriched while ti cr v and sc are depleted compared to late magmatic tourmaline of the same sample several tourmaline generations that precipitated from magmatic fluids can be distinguished with differing major and minor elements and ree patterns depending on the composition of the melt from which they were expelled from strongly zoned tourmaline allows for unraveling the hydrothermal history of a distinct location including ore precipitation the precipitation of sno2 in the study area was probably caused by mixing between acidic reduced sn bearing magmatic fluids and oxidized meteoric fluids which is in agreement with london and manning 1995 and williamson et al 2000 hence the ability of tourmaline composition to monitor changes in sn concentration and redox conditions in hydrothermal fluids has potential as an exploration tool

palynology sedimentology and palaeoecology of the late holocene dead sea abstract palynological and sedimentological studies were performed at two holocene profiles in erosion gullies ze elim and ein feshkha which dissect the retreating western shore of the dead sea the aim of the project was to analyse possible links between climate lithology and vegetation development the section in ze elim shows both lacustrine and fluvial sediments whereas sedimentation at ein feshkha is predominantly lacustrine the ze elim profile previously used for paleo lake reconstruction provides an opportunity to compare climate triggered lake levels as paleo hydrological indicators and vegetation history by use of palynology the vegetation development in ze elim and ein feshkha is influenced by both climate and human impact the pollen record of ze elim begins in the pottery neolithic the section of ein feshkha in the late bronze age both records end in the middle ages the ze elim section is characterized by sedimentary hiati between the beginning of the chalcolithic period until the middle bronze age and within the late bronze age settlement periods during the middle bronze age iron age and hellenistic roman byzantine period are indicated by high values of anthropogenic indicators and or mediterranean trees collapses of agriculture which can be related to climate effects are evident during the late bronze age during the iron age and at the end of the byzantine period when the lake level curve indicates arid conditions a comparison of the two pollen records from different environments illustrates a more prominent influence of mediterranean vegetation and cultivated plants in the pollen diagram of ein feshkha the southern dead sea region at the desert fringe is more vulnerable to regional climate change

incision of alluvial channels in response to a continuous base level fall field characterization modeling and validation along the dead sea abstract the dramatic lake level drop of the dead sea during the twentieth century 30 m provides a field scale experiment in transport limited incision of gravel bed channels in response to quasi continuous base level fall at approximately constant rate we apply a one dimensional numerical incision model based on a linear diffusion equation to seven ephemeral channels draining into the dead sea the model inputs include the measured twentieth century lake level curve annual shoreline location i e annual channel lengthening following the lake level drop reconstructed longitudinal profiles of each of the channels based on mapped and surveyed terraces and the current profiles of the active channels the model parameters included the diffusion coefficient and the upstream derived sediment flux both were first calibrated using a set of longitudinal profiles of known ages and then validated using additional sets of longitudinal profiles the maximum at station total incision observed at each of the studied channels was significantly less then the total lake level drop and varied in response to both drainage area and lake bathymetry the model applied predicted degradation rates and the pattern of degradation with high accuracy this suggests that sediment flux in the modeled channels is indeed linearly dependent on slope further support for this linear dependency is provided by a linear correlation between the diffusion coefficient and the mean annual rain volume over each basin a proxy for discharge the model presented could be a valuable tool for planning in rapid base level fall environments where incision may risk infrastructure

palaeoclimate interpretations of late pleistocene vegetated linear dune mobilization episodes evidence from the northwestern negev dunefield israel abstract the vegetated linear dune vld field of the northwestern nw negev desert situated at the downwind eastern end of the northern sinai nw negev erg constitutes an ideal setting for dating and interpreting its late quaternary dune encroachment episodes this study builds upon the results of roskin et al age origin and climatic controls on vegetated linear dunes in the northwestern negev desert israel quaternary science reviews 30 2011 1649 1674 that presented the stratigraphy of 35 sections and 97 optically stimulated luminescence osl ages from the nw negev dunefield here we refine our analysis of the negev late pleistocene dune mobilizations and stabilizations and interpret their palaeoclimatic controls in light of regional and global sediment records and proxies while initial dune encroachment into and stabilization in the nw negev took place during the last glacial maximum lgm at 23 18 ka spatial and statistical analyses of the osl dataset suggest that since the lgm negev dune activity was concentrated in two significant mobilization stabilization episodes a main episode at 16 13 7 ka and a minor one at 12 4 11 6 ka when the dunes reached their maximum spatial extent and stabilized these episodes include rapid dune encroachment and accretion events and coincide with the heinrich 1 and younger dryas cold events respectively the late pleistocene sand transporting winds were characterized by a westerly direction that resulted in west east vld elongation dune mobilizations may have occurred in response to wintertime east mediterranean cyclonic systems that brought storms of rainfall and strong winds the rapid dune mobilization events and their concurrence with the heinrich 1 and younger dryas cold events suggest a more global control despite the rainfall the elongating vlds were probably sparsely vegetated because of the high wind power their stabilization resulted from a decrease in storminess with the onset of a more arid holocene climate other global low latitude dune mobilizations and stabilizations are concentrated at the end of the late pleistocene leading us to suggest that these were also controlled mainly by global cold events and subsequent changes in windiness the recurring discontinuous aeolian sedimentation pattern found in osl dated vlds provides new and important chronological and sedimentological insight into prominent dune mobilization and stabilization processes the suggested link between global drops in cold event windiness and low latitude dune stabilization episodes emphasizes the prevalence of winds over aridity regarding major dune mobilizations for low latitude dunes even if vegetated

effect of rainfall intensity slope and antecedent moisture content on sediment concentration and sediment enrichment ratio abstract the transportability of sediment by runoff and its potential for subsequent deposition is dependent on the size and distribution of the transported material and the sediment concentration the size distribution of the eroded sediment is also expected to vary depending on which erosion process is predominant this study discusses the results of laboratory analysis to evaluate the effect of rainfall intensity slope steepness soil types and antecedent moisture content on sediment concentration runoff coefficients and sediment enrichment ratios to achieve the objectives laboratory experiments were conducted using fel 3 rainfall simulator and erosion pan rainfall intensity of 120 70 and 55 mm h was applied sequentially at 9 25 and 45 slope for three soil types found in alemaya watershed eastern ethiopia alemaya black soil soil a regosols soil b and cambisols soil c varied from clay to sandy clay loam in texture with wet and dry antecedent moisture contents the rate of sediment concentration significantly varied with moisture contents for soil a sediment concentrations 24 3 g l from an initially air dry surface and 18 7 g l from an initially wet surface were observed wetting decreased sediment concentration of soil a b and c by 23 45 7 and 1 3 respectively sediment concentration didn t show any trend with rainfall intensities for soil b the highest average silt enrichment ratio of 2 15 was observed followed by average clay enrichment ratio of 1 61 for soil a and soil c average clay enrichment ratios of 1 13 and 1 91 were observed respectively initial moisture contents had effect on the enrichment ratio however the actual effect varied with soil type and the size of the particle results of the study indicated that the actual effect of slope as well as rainfall intensity on sediment concentration and sediment yield vary with soil types and moisture contents

twentieth century floods recorded in the deep mediterranean sediments flood generated turbidity currents represent an important process of marine sedimentation however no deposit related to this process has yet been described at sea turbiditic sequences cored at 2000 m water depth in the mediterranean show tractive structures and superposition of reverse and normal grading they are related to floods triggered during the twentieth century deposits from flood generated turbidity currents have a great impact on the interpretation of deep ocean paleoclimate records obtained near continental margins by linking deep marine sedimentary records to continental climatic changes through flood frequency and magnitude implications of this study should help redefine the reservoir character of oil fields in fine grained turbidites

stratigraphy depositional environments and level reconstruction of the last interglacial lake samra in the dead sea basin in this paper we describe the stratigraphy and sediments deposited in lake samra that occupied the dead sea basin between 135 and 75 ka this information is combined with u th dating of primary aragonites in order to estimate a relative lake level curve that serves as a regional paleohydrological monitor the lake stood at an elevation of 340 m below mean sea level msl during most of the last interglacial this level is relatively higher than the average holocene dead sea 400 30 m below msl at 120 and 85 ka lake samra rose to 320 m below msl while it dropped to levels lower than 380 m below msl at 135 and 75 ka reflecting arid conditions in the drainage area lowstands are correlated with warm intervals in the northern hemisphere while minor lake rises are probably related to cold episodes during mis 5b and mis 5d similar climate relationships are documented for the last glacial highstand lake lisan and the lowstand holocene dead sea yet the dominance of detrital calcites and precipitation of travertines in the dead sea basin during the last interglacial interval suggest intense pluvial conditions and possible contribution of southern sources of wetness to the region

impacts of abrupt climate changes in the levant from last glacial dead sea levels abstract a new detailed lake level curve for lake lisan the last glacial dead sea reveals a high frequency of abrupt fluctuations during marine isotope stage 3 mis3 compared to the relatively high stand characterizing mis2 and the significantly lower holocene lake the lake level fluctuations reflect the hydrological conditions in the large watershed of the lake which in turn reflects the hydro climatic conditions in the central levant region the new curve shows that the fluctuations coincide on millennial timescales with temperature variations recorded in greenland four patterns of correlation are observed through the last ice age 1 maximum lake elevations were reached during mis2 the coldest interval 2 abrupt lake level drops to the lowest elevations coincided with the occurrence of heinrich h events 3 the lake returned to higher stand conditions along with warming in greenland that followed h events 4 significant lake level fluctuations coincided with virtually every greenland stadial interstadial cycle over glacial interglacial time scales northern hemisphere glacial cooling induces extreme wetness in the levant with high lake levels reaching 160 m below mean sea level mbmsl approximately 240 m above typical holocene levels of 400 mbmsl these orbital time scale shifts are driven by expansions of the european ice sheet which deflect westerly storm tracks southward to the eastern mediterranean resulting in increased sea air temperature gradients that invoke increased cyclogenesis and enhanced moisture delivery to the levant the millennial scale lake level drops associated with greenland stadials are most extreme during heinrich stadials and reflect abrupt cooling of the eastern mediterranean atmosphere and sea surface which weaken the cyclogenic rain engine and cause extreme levant droughts during the recovery from the effect of heinrich stadials the regional climate configuration resumed typical glacial conditions with enhanced levant precipitation and a rise in lake lisan levels similar cyclicity in the transfer of moisture to the levant affected lake levels during all of the non heinrich stadial interstadial cycles

late holocene lake levels of the dead sea this work presents a high resolution lake level record of the late holocene dead sea a hypersaline terminal lake whose drainage basin encompasses both mediterranean and hyperarid climatic zones the lake level curve reflects the regional hydrologic variations in the drainage basin which in turn represent the levant paleoclimates the curve is based on 46 radiocarbon ages of organic remains from well exposed sedimentary sequences along the dead sea shores these sequences record fluvial and lacustrine depositional environments the paleolakeshores are marked by shore ridges coarse sand units and aragonite crusts in the modern dead sea such features indicate the exact elevation of the shore the late holocene dead sea level fluctuated within the range of 390 to 415 m below sea level mbsl for most of the time the lake was below the topographic sill 402 mbsl separating the northern and southern basins of the dead sea and was confined to the deep northern basin nevertheless short term rises in the late holocene dead sea level caused the flooding of the shallow and flat southern basin highstands occurred in the second and first centuries b c and the fourth century a d during the roman and early byzan tine periods respectively in the eleventh and twelfth centuries a d during the crusader period and at the end of the nineteenth century a d the rises mark a significant change in the annual rainfall in the region which likely exceeded the instrumentally measured modern average the curve also indicates drastic drops that exposed the sedimentary sequences to erosion the oldest and probably deepest drop in the lake level culminated during the fifteenth and fourteenth centuries b c after a retreat from a higher lake stand the longest lowstand occurred after the byzantine period and continued at least until the ninth century a d this arid period coincided with the invasion of moslem arab tribes into the area during the seventh century a d the dramatic fall of the dead sea level during the twentieth century is primarily artificial and has been caused by the diversion of runoff water for the drainage basin but the magnitude is not considered exceptional for the late holocene although the past drops in the lake never exceeded the modern artificial drop rates they do represent extreme arid conditions that occurred frequently over the past several thousand years

response of alluvial fan systems to the late pleistocene to holocene climatic transition contrasts between the margins of pluvial lakes lahontan and mojave nevada and california usa abstract dated shorelines of late pleistocene pluvial lakes lahontan great basin desert northwest nevada and mojave mojave desert eastern california provide timelines for the assessment of alluvial fan sedimentation at the lake margins during the late pleistocene to early holocene two sets of alluvial fan systems have been mapped the stillwater fans feeding lake lahontan and the zzyzx fans feeding lake mojave their contrasting morphologies suggest different responses of the two fan systems to late pleistocene to early holocene climatic change at the time the stillwater fan systems underwent minimal sedimentation with the catchment hillslopes apparently stable the zzyzx fans experienced major changes in water and sediment supply from the catchment hillslopes there was a major phase of hillslope debris flow activity followed by fanhead trenching and distal fan progradation both areas were wetter and colder in the late pleistocene than they are today but during the transition to the holocene the zzyzx area was more likely to experience intense rains associated with the monsoonal penetration of warm moist tropical air into the southwest vegetation reconstructions for the late pleistocene to the early holocene suggest that catchment hillslopes in the mojave supported a desert shrub vegetation but those in the stillwaters supported juniper woodland and grasses at low elevations and pine at higher elevations contrasts in hillslope vegetation cover together with storm activity may account for the different responses of the alluvial fans to climatic change during the pleistocene to holocene climatic transition after the falls in lake levels of lakes lahontan and mojave in the early holocene both areas underwent aridification resulting in reductions in hillslope vegetation cover increased storm runoff led to fanhead trenching and distal progradation of the alluvial fans variations in fan style at that time may relate primarily to base level conditions resulting from different gradients on the exposed lake shores

digital topography and bathymetry of the area of the dead sea depression abstract the dead sea depression occupies the central part of that segment of the syrian african rift extending from the mountains of southern lebanon to the arava valley north of the gulf of aqaba on the red sea the lowest continental feature in the world it encloses the dead sea whose surface now lies at about 409 m this shrunken sea consists of a shallow southern basin occupied by evaporation pans and a northern basin 50 km in length by 13 17 km in width with a flat floor some 731 m below msl the depression is asymmetric with the mountains to the east being up to 500 m higher the closed depression has two outlets one at 60 5 m altitude into the mediterranean via the jezreel valley near afula and a second into the red sea at about 200 m altitude in the arava valley a digital terrain model dtm based upon the local 1 50 000 scale topographic maps and modern bathymetric surveys gives elevations to decimeter resolution on a grid with 25 m spacing when visualized as shaded relief or in coloured hypsometric format the dtm graphically shows the overall morphology and its many features these include the local tectonics from the major boundary faults to the associated subsidiary faults and lineaments and their possible relationships with the incised canyons offshore also clearly visible are the volcanic cones on the golan heights the coast paralleling kurkar ridges and the halokinetic disruptions to the deep offshore topography the dtm was used to compute a hypsometric curve for the closed depression from 731 m to 60 m the maximum area and volume of a lake extending to the afula spillway would be 5985 km 2 and 1602 km 3 respectively inflection points were observed at 715 m where the dead sea s flat bottom meets its steep flanks at 385 m where the northern basin meets the flat floor of the southern basin and surrounding plain at 228 with the step up to the basin of the sea of galilee and at mediterranean sea level

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

lithology of the long sediment record recovered by the icdp dead sea deep drilling project dsddp abstract the sedimentary sections that were deposited from the holocene dead sea and its pleistocene precursors are excellent archives of the climatic environmental and seismic history of the levant region yet most of the previous work has been carried out on sequences of lacustrine sediments exposed at the margins of the present day dead sea which were deposited only when the lake surface level rose above these terraces e g during the last glacial period and typically are discontinuous due to major lake level variations in the past continuous sedimentation can only be expected in the deepest part of the basin and therefore a deep drilling has been accomplished in the northern basin of the dead sea during winter of 2010 2011 within the dead sea deep drilling project dsddp in the framework of the icdp program approximately 720 m of sediment cores have been retrieved from two deep and several short boreholes the longest profile 5017 1 revealed at a water depth of 300 m reaches 455 m below the lake floor blf i e to 1175 m below global mean sea level and comprises approximately the last 220 240 ka the record covers the upper part of the amora penultimate glacial the last interglacial samra the last glacial lisan and the holocene ze elim formations and therewith two entire glacial interglacial cycles thereby for the first time consecutive sediments deposited during the mis 6 5 5 4 and 2 1 transitions were recovered from the dead sea basin which are not represented in sediments outcropping on the present day lake shores in this paper we present essential lithological data including continuous magnetic susceptibility and geochemical scanning data and the basic stratigraphy including first chronological data of the long profile 5017 1 from the deep basin the results presented here a focus on the correlation of the deep basin deposits with main on shore stratigraphic units thus providing a unique comprehensive stratigraphic framework for regional paleoenvironmental reconstruction and b highlight the outstanding potential of the dead sea deep sedimentary archive to record hydrological changes during interglacial glacial and transitional intervals

a 45 kyr laminae record from the dead sea implications for basin erosion and floods recurrence abstract recording and analyzing how climate change impacts flood recurrence basin erosion and sedimentation can improve our understanding of these systems the aragonite detritus laminae couplets comprising the lacustrine formations that were deposited in the dead sea are considered as faithful monitors of the freshwater supply to the lakes we count a total of 5600 laminae couplets deposited in the last 45 kyr mis3 mis1 at the dead sea center which encompass the upper 142 m of the icdp core 5017 1 the present study shows that aragonite and detritus laminae are thinner and occur at high frequency during mis 3 2 while they are much thicker and less frequent during mis 1 by analyzing multiple climate connected factors we propose that significant lake level drops enhanced dust input and low vegetative cover in the drainage basin during the last deglaciation 22 11 6 ka have considerably increased erodible materials in the dead sea watershed we find a decoupling existed between the significant lake level drop lake size reduction and lamina thickness change during the last deglaciation we argue that during the last glacial and the holocene the variation of lamina thickness at the multiple millennium scale was not controlled directly by the lake level size change we interpret this decoupling implying the transport capacity of flash floods is low and might be saturated by the oversupply of erodible materials and indicating a transport limited regime during the time period we suggest the observed thickness and frequency distribution of aragonite detritus laminae points to the high frequency of small magnitude floods during the last glacial in contrast to low frequency but large magnitude floods during the holocene

geomorphic changes leading to natural desertification versus anthropogenic land conservation in an arid environment the negev highlands israel the negev highlands in southern israel are currently under an erosive regime causing degradation of soil and vegetation a process which has often been attributed to land mismanagement and overgrazing caused by the local bedouin population to estimate the anthropogenic role in the erosional processes in the negev highlands two similar drainage basins were selected and studied one undisturbed with almost no human impact and the other with intensive human modification including the establishment of roman to early islamic agriculture field observations and luminescence dating indicate that during the late pleistocene glacial period ois 4 and 3 deposition of fluvio loess sediments with minor erosion cycles occurred in the negev highlands severe erosion started during ois 2 and continued into the holocene as the climate shifted during the termination of the pleistocene to the present interglacial phase higher rain intensity generated the incision of gullies and channels into the fine grained alluvial sediments of the previous phase causing extended soil erosion and reducing the natural biomass and the agricultural potential establishment of runoff harvesting farms in the 3rd century interrupted the holocene natural erosion and gully incision and led to the redeposition of up to 3 5 m of fine alluvial loess sediments originating from late pleistocene loess sections this accumulation is not related to any late holocene pluvial climatic phase and is solely the result of farming we conclude that since the end of the pleistocene a dynamic change in the soil rock ratio related to the long term process of adjustment of the geomorphologic system to the holocene climate has been taking place within the drainage basins in the negev highlands the fluvio loess sediments deposited in the region during ois 4 and 3 have been eroding since the latest pleistocene throughout the holocene this process causes degradation of the biomass and agricultural potential and leads onto natural desertification of the region the historical intervention by establishment of runoff harvesting agriculture which as a by product resulted in the accumulation of redeposited loess sediments counteracted the natural trend of soil erosion this was in fact a land conservation act applied by the ancient farmers in the semi arid regions of the middle east deserts this activity and its geomorphic consequences are in contrast to the well documented land degradation trend generated by recent anthropogenic impact on marginal lands elsewhere in any case the human impact either contributing to land degradation or to soil conservation is super imposed on the natural long term trend leading toward desertification

10 000 yr record of extreme hydrologic events well dated lacustrine sediments provide a hydrologic record indicating that the frequency and magnitude of runoff events and by inference storms have varied over the past 10 k y in northern new england we used five sediment cores and radiocarbon dating to develop a chronology of holocene hydrologic events for the ritterbush pond basin northern vermont chemical and physical analyses allow us to identify 52 distinct layers of predominately inorganic sediment that represent terrestrially derived material delivered to the pond by runoff events the thickness of some layers suggests hydrologic events at least equal in size to and probably much larger than any storm or flood recorded during nearly 300 yr of written regional history layer thickness and frequency and by analogy storm size and recurrence change through the holocene the largest events occurred 2620 6840 and 9440 calibrated 14c years before present cal 14c yr b p the most frequent hydrologic events occurred in three periods 1750 to 2620 6330 to 6840 and 8600 cal yr b p the recurrence interval of layer deposition during stormy periods averages 130 100 cal yr whereas the recurrence interval during less stormy periods is longer 270 170 cal yr the ritterbush pond event record illustrates the potential of inorganic lacustrine sediment to serve as a proxy record for estimating paleoflood frequency and deciphering climate change

aggradation incision transition in arid environments at the end of the pleistocene an example from the negev highlands southern israel abstract one of the most significant environmental processes that occurred at the transition from the last glacial phase into the present inter glacial phase in arid regions was the shift from aggradation to incision in the drainage systems this is evident by the sharp transition from a fluvial regime depositing fine grained sediment within the wadis to intensive incision which formed gullies and narrow channels that dissected the late pleistocene sediments in order to investigate this transition we studied three small scale basins in the arid region of the negev highlands southern israel although the selected basins drain toward different base levels their geomorphological parameters particle size distribution of alluvial units and their osl ages are similar sediments from the penultimate glacial cycle are found in patches in the bigger catchments fluvial loess was widely deposited since at least 67 ka until after 28 ka covering valleys and slopes between 28 and 24 ka loess was washed from the slopes into the channels exposing the underlying colluvium at 24 ka erosion began with the transport of slope colluvium as gravels into the valleys that eroded the underlying loess sediments incision became dominant at 12 ka and is still ongoing and intensifying dust and reworked loess continued to be deposited during the main incision stages it is proposed that the transition from aggradation to incision was controlled by rates of loess supply and removal until 24 ka dust choked the drainage system and only after reduction in dust supply was erosion and incision possible it began first on the slopes and then in the channels our results show that an increase in precipitation is not a prerequisite for initiation of incision as is often assumed similar processes are described in other arid zones around the world

characterization of land degradation along the receding dead sea coastal zone using airborne laser scanning abstract the dead sea the lowest place on the earth s continents was at its highest level in 1896 reaching an elevation of 388 4 m below mean sea level m b m s l and 390 m in the early 1920s since then it has almost constantly been dropping reaching the level of 426 m b m s l in 2013 since the late 1990s its level has been decreasing by approximately 1 my 1 the rapid lake retreat accelerates large scale environmental deterioration including soil erosion land degradation rapid headcut migration and widespread development of collapse sinkhole fields these geomorphic elements threaten the natural environment and anthropogenic infrastructure we provide an overview of the geomorphic processes in the form of soil erosion channel incision land degradation and the development of collapse sinkholes we take advantage of the high resolution airborne laser scanning technology for three dimensional detection of surficial changes quantification of their volumes and documentation of the present state of the terrain with utmost accuracy and precision this type of information and the identification of future trends are vital for proper planning of any rapidly changing environment

strontium isotopic chemical and sedimentological evidence for the evolution of lake lisan and the dead sea precise strontium isotope ratios combined with chemical analyses and sedimentological information are used to monitor the water sources and the evolution of the dead sea and its late pleistocene precursor lake lisan 70 18 kyr b p the materials analyzed include bulk aragonite water leached soluble salts and residual aragonite and gypsum from the lisan formation in the perazim valley near the sw shore of the dead sea the residual aragonite and the associated soluble salts display systematic fluctuations in 17sr86sr ratios between 0 70803 and 0 70806 and from 0 70805 to 0 70807 respectively in individual soluble salt residual aragonite pairs the soluble salt displays a higher 87sr86sr ratio gypsum samples yield 17sr86sr ratios similar to the soluble salts from adjacent layers in the section this shows that in individual samples the source of sr in aragonite was distinct from that in soluble salts and the gypsum the sterility of the lisan sediments their strictly nonbioturbated fine lamination and their high content of chloride salts indicate that lake lisan was a saline or even hypersaline water body in the absence of alternative sources of hco3 and s042 the abundance of primary aragonite and gypsum in the lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake resulting in a density stratification of this water body the history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples respectively whereas the bicarbonate and much of the ca2 required for aragonite crystallization were supplied by the freshwater the complementary ca2 and sr 2 were added by the lower brine the upper water layer of lake lisan acted as a so42 capacitor during the lake s rise periods it was removed therefrom as prominent gypsum beds upon climatic induced drier period mixing or even complete overturn of the lake the evolution of lake lisan took place between two distinct modes the first was characterized by an extensive supply of freshwater and resulted in a rise of the lake s level a density layered structure and precipitation of aragonite the second mode was marked by a diminishing freshwater input resulting in mixing or complete overturn of its water and precipitation of gypsum these two modes reflect the climatic evolution of the region in the late pleistocene which fluctuated between drier and wetter periods the transition to the holocene is accompanied by the dry up of lake lisan and its contraction to the present dead sea

rapid coupling between ice volume and polar temperature over the past 150 000 years a new approach to dating a continuous sea level record using speleothem u th ages shows that past variations in global ice volume occurred within centuries of polar climate change with rates of sea level rise reaching at least 1 metre per century

silicon isotope fractionation during magmatic differentiation abstract the si isotopic composition of earth s mantle is thought to be homogeneous 30 si 0 29 0 08 2 s d and not greatly affected by partial melting and recycling previous analyses of evolved igneous material indicate that such rocks are isotopically heavy relative to the mantle to understand this variation it is necessary to investigate the degree of si isotopic fractionation that takes place during magmatic differentiation here we report si isotopic compositions of lavas from hekla volcano iceland which has formed in a region devoid of old geochemically diverse crust we show that si isotopic composition varies linearly as a function of silica content with more differentiated rocks possessing heavier isotopic compositions data for samples from the afar rift zone as well as various igneous usgs standards are collinear with the hekla trend providing evidence of a fundamental relationship between magmatic differentiation and si isotopes the effect of fractionation has been tested by studying cumulates from the skaergaard complex which show that olivine and pyroxene are isotopically light and plagioclase heavy relative to the si isotopic composition of the earth s mantle therefore si isotopes can be utilised to model the competing effects of mafic and felsic mineral fractionation in evolving silicate liquids and cumulates at an average sio 2 content of 60 wt the predicted 30 si value of the continental crust that should result from magmatic fractionation alone is 0 23 0 05 2 s e barely heavier than the mantle this is at most a maximum estimate as this does not take into account weathered material whose formation drives the products toward lighter 30 si values mass balance calculations suggest that removal of continental crust of this composition from the upper mantle will not affect the si isotopic composition of the mantle

evidence from lake lisan of solar influence on decadal to centennial scale climate variability during marine oxygen isotope stage 2 documentation of short term climate variability during the glacial period has been limited by the availability of well dated high resolution archives here we present a paleoclimate reconstruction from varved lacustrine sediments of lake lisan dead sea rift for ca 26 2 17 7 calendar ka the age is based on a floating varve chronology anchored to radiometric dates our reconstruction indicates that small ice rafting events a b c and d as well as heinrich events in the north atlantic are associated with the eastern mediterranean arid intervals study of seasonal sublaminae yields evidence of several additional decadal to century scale arid events that correlate with cooler temperatures at higher latitudes analyses in the frequency domain indicate the presence of periodicities centered at 1500 yr 500 yr 192 yr 139 yr 90 yr and 50 60 yr suggesting a solar forcing on climate

10be in lake lisan sediments a proxy for production or climate abstract the geochemical behavior of 10 be in the modern dead sea hydrological limnological system was studied in order to evaluate the feasibility of using dead sea and lake lisan the late pleistocene precursor of the dead sea sediments as archives of the variations in the 10 be production rate 10 be concentrations in detrital and aragonite material from lake lisan laminated sediments were compared to those measured in modern dust terra rossa soil aeolian in origin loess from the negev desert flood suspended load and waters along a rain flood development pathway the transition from rain to incipient runoff and fully developed floods 10 be concentrations decreased throughout the flood development profile from 8 2 10 3 atoms g 1 in the runoff down to 1 10 3 atoms g 1 in dead sea brine due to fast removal of 10 be by the soil and dust particles thus most of the 10 be in the lake is contained within the detrital sediments that collect the 10 be transported by particles from the surrounding terrain e g desert dust with 1 6 0 8 10 8 atoms g 1 and terra rossa soil material with up to 12 5 0 5 10 8 atoms g 1 the high stand periods of lake lisan were characterized by annual deposition of silty detritus sediments reflecting rapid transfer of desert dust to the lake by floods indeed the bulk sediments of lake lisan in which 10 be is associated mainly with silty detritus display 10 be concentrations similar to those of desert dust this demonstrates that 10 be variations were modulated by climate i e particle transport significant positive 10 be peaks up to 1 6 10 8 atoms g 1 appear during intervals of geomagnetic anomalies in lake lisan stratigraphy and in the global record i e during the laschamp geomagnetic event at 41 ka bp this indicates that 10 be atmospheric production signal is superimposed on the climatic 10 be variations we conclude that after de trending of the climatic signal lake lisan sediments may be used as an archive for atmospheric 10 be production

recurrence pattern of holocene earthquakes along the dead sea transform revealed by varve counting and radiocarbon dating of lacustrine sediments abstract a high resolution holocene seismic history of the dead sea transform dst is established from laminated sedimentary cores recovered at the shores of the dead sea radiocarbon dating and annual laminae counting yield excellent agreement between disturbed sedimentary structures identified as seismites and the historical earthquake record all recent and historical strong events of the area were identified including the major earthquakes of a d 1927 1837 1212 1033 749 and 31 b c the total of 53 seismites recognized along the entire holocene profile indicate varying recurrence intervals of seismic activity between a few and 1000 years with a conspicuous minimum rate at 2100 31 b c and a noticeable maximum during the past six to eight centuries most of the epicenters of the correlated earthquakes are situated very close to the dead sea within 150 km or up to 400 km north of it along the dst between 1000 b c and a d 1063 and from a d 1600 to recent time the epicenters are all located on the northern segment of the dst whereas prior to 1000 b c and between a d 1000 and 1600 they appear to scatter along several segments of the dst we establish how the local intensity exerts a control on the formation of seismites at historically estimated intensities greater than vii all well documented earthquakes are correlated whereas at intensities smaller than vi none are matching the periods with enhanced earthquake rate along the dst correlate with those along the north anatolian fault as opposed to the intervening east anatolian fault this may indicate some elastic coupling on plate boundary scale that may also underlie escape and extrusion tectonics typical of continental collision

a high magnitude storm and flood in a hyperarid catchment nahal zin negev desert israel in october 1991 a high magnitude rainstorm flood estimated return period 40 years occurred in nahal zin a 1400 km2 catchment in the hyperarid negev desert the meso scale structure of the storm was a curved squall line that developed from a thunderstorm in accordance with the topography of the catchment divide by which it was strongly affected tropical moisture reached the area via the subtropical jet stream in conjunction with a lower level northward intrusion of the red sea trough rst n into the mediterranean sea rainfall as measured at the few and sparse gauging stations was much too small to account for the resulting large flood peak flow and other hydraulic characteristics of the flood were indirectly reconstructed the techniques of palaeoflood hydrology used were based on sedimentological evidence of fine grained flood sediments deposited in back flooded tributaries as well as on other stage indicators the hec 2 procedure was employed to determine water surface profiles the spatial and temporal characteristics of the event were studied through a combination of rainstorm analysis remote sensing hydrological and sedimentological data they jointly explain the magnitude and timing of tributary contributions producing the integrated flood in the main channel the flood as reconstructed reveals a three peak hydrograph two peaks were generated by the same storm but had different floodwave arrival times in the main channel the third resulted from a local rainstorm which occurred on the following day and covered only one tributary the curved structure of the storm and its dynamics in relation to catchment orientation resulted in storm move ment in tandem with the floodwave the synchronous contribution from all main tributaries preserved evidence of the floodwave both in stage and volume by replacing the transmission losses in the sections with thick alluvium other high magnitude floods on record for the large negev desert catchments are caused by a cold upper air incursion associated with the rst n most of them occur in the autumn and are caused by storms with high intensity rainfall this is in stark contrast with the flooding behaviour of the semi arid zone further north which is linked primarily to the core of the mediterranean winter the complexities involved in the generation of a large desert flood as revealed by this study illustrate the fallacy of applying routine hydrological modelling to such events and underline the need to study the processes involved in adequate detail 1998 john wiley sons ltd

late quaternary weathering erosion and deposition in nahal yael israel an impact of climatic change on an arid watershed in their seminal paper in 1979 bull and schick proposed a conceptual model for the geomorphic response to pleistocene to holocene climate change based on the hyperarid nahal yael watershed in the southern negev desert in this model the change from semiarid late pleistocene to hyperarid early holocene climates reduced vegetation cover increased the yield of sediment from slopes and accelerated aggradation of terraces and alluvial fans the model is now over 30 yr old and during this time chronologic paleoenvironmental and hydrogeomorphic research has advanced here we reevaluate the model using data acquired in nahal yael over the 30yr since the original model was proposed recent studies indicate that the late pleistocene climate was hyperarid and a transition from semiarid to hyperarid climates did not occur the revised chronology reveals a major 35 20 ka episode of accelerated late pleistocene sediment production on slopes with lower rates probably already at ca 50ka due to increased frequency of wetting drying cycles caused by frequent extreme storms and floods between 35 and 27 ka without lag time these sediments were transported and aggraded in depositional landscape components fluvial terraces and alluvial fans this intensified sediment production and delivery phase is unrelated to the pleistocene holocene transition the depositional landforms were rapidly incised between 20 and 18 ka since and or soon after this last glacial maximum lgm incision most material leaving the basin originated from sediments stored in depositional landforms and was not produced from bedrock using these new data we propose a revision to the bull and schick model in this hyperarid environment our revision suggests that the model should include the frequent storms and floods responsible for a late pleistocene pulse of intense weathering due to numerous cycles of wetting and drying on slopes and coeval sediment transport to fluvial terraces and alluvial fans we also discuss the common use and pitfalls of using the bull and schick conceptual model to explain observations in diverse arid environments usually without sufficient data on basin specific stratigraphic chronologic paleoenvironmental and paleoclimatic information

sources and transport routes of fine detritus material to the late quaternary dead sea basin abstract the sources and routes of transport of fine detritus material fdm to the lakes filling the late quaternary dead sea basin were studied by petrographic mineralogical grain size chemical and sr nd isotope analyses on sediments of the late quaternary lacustrine formations including river flood material dust and loess from the lake watershed the lacustrine formations comprise two sedimentary facies one that consists of alternating laminae of primary aragonite and silty detritus material aad facies and another that consists mainly of laminated detritus particles and generally lacks aragonite ld facies the aad facies characterizes the glacial intervals e g mis2 and 4 when lake levels were high while the ld facies characterizes interglacials e g mis1 5 and warmer glacial intervals e g mis3 when lake levels were low the detritus of both aad and ld facies show similar mineralogy mainly quartz and calcite grains with minor feldspars and clays but distinct grain sizes 8 10 m and 50 60 m respectively and distinct 87 sr 86 sr and end 0 711 0 712 and 7 to 8 versus 0 709 0 710 and 5 respectively the aad and ld fdm comprise desert dust of mixed granitic basaltic composition that was blown from the sahara desert and from the nile delta to the northern negev desert e g the loess deposits and the judean mountains bordering the dead sea basin mainly during glacial intervals along with enhanced mediterranean rain fronts the aad fdm reflects an enhanced transport of saharan granitic dust to the vicinity of the lake mainly during glacials the ld fdm was recycled from the loess surface cover of the negev desert mainly during interglacials and warm glacial intervals