biological remains geochemistry and stable isotopes for the reconstruction of environmental and hydrological changes in the holocene lakes from north sahara abstract a detailed reconstruction of the holocene palaeoenvironments and palaeohydrology is presented for wwamp and lacustrine calcareous sediments which lie in closed depressions along the northern margin of the great western erg algeria it is based on a multidisciplinary approach using numerous techniques the chronological framework is established on the basis of 23 14 c dates on inorganic calcite and mollusc shells ranging from ca 9300 to 3000 yr b p and on an isolated 14 c age of ca 10 900 yr b p the significance of various environmental markers is discussed biological remains are abundant and diversified about 150 taxa including diatoms chrysophytes charophytes ostracods molluscs and foraminifera they provide information on the water chemistry total salinity ionic ratio ph and partial pressure of carbon dioxide and on the habitats water depth development of aquatic plants ephemerality etc emphasis is given to the total salinity individual organisms and palaeobiological assemblages are ordered as a function of their salt requirements and tolerances calibration based on modern diatom samples allows a tentative estimate of the palaeosalinities which range from fresh to marine like and even hypersaline waters attention is drawn to the possible colonization of marine organisms in continental basins without any connection with the sea stable isotope analyses have been carried out on both inorganic and biogenic mollusc and ostracod shells charophyte gyronites carbonates the 18 o contents demonstrate wide changes in the hydrological balance fluctuations in 13 c contents inform on water mixing residence time and on the importance of biological effects on total dissolved inorganic carbon geochemical analyses were performed on inorganic calcite and on ostracod shells high contents in fe and mn indicate reducing environments during stages of high salinity sr ca and mg ca are used as salinity indicators zn mg ratios suggest that the major water supply was the aquifer of the great western erg today down to about 50 m rather than surface waters from the atlas mountains salinities resulted from the balance between inputs from the water table evaporation rate leaching of pre existing salt crusts and seepage through the lake bottom a reconstruction of the evolution of the palaeosystems through time and space has been attempted with special attention to the instability of the water and ionic balances for different time scales short term fluctuations occurring during a single hydrological cycle annual or seasonal are deduced from the apparent discrepancies between the various indicators found in a given sample long term 10 2 10 3 years changes confirm the existence of a climatic phase being wetter than today from at least ca 9300 and may be from ca 10 900 yr b p to 3000 yr b p for the first time the salinity deduced from diatoms and the 18 o content of the water deduced from that of the carbonate at 25 c are used simultaneously to model the hydrological history of the basins and to estimate the relative humidity of the atmosphere during the holocene major environmental trends recorded from ca 9300 to 3000 yr b p do not show a clear synchronims between the different profiles studied therefore they cannot be interpreted in terms of palaeoclimate but instead demonstrate the importance of local hydrology in the evolution of closed basins associated with groundwater a common situation in arid and semi arid zones

stable isotope composition of late pleistocene holocene eobania vermiculata muller 1774 pulmonata stylommatophora shells from the central mediterranean basin data from grotta d oriente favignana sicily abstract this paper presents stable isotopic results oxygen and carbon from both modern and late pleistocene holocene shells of the land snail eobania vermiculata muller 1774 from favignana island sicily it aims to contribute to the understanding of climate and vegetation history of this region during formation of upper palaeolithic mesolithic and meso neolithic deposits of grotta d oriente ort results from both an evaporative model fbm and an empirical regional isotopic model i e linear relation between oxygen isotopic composition of shells 18 os and those of local precipitation 18 op indicate that the 18 os values of modern specimens are mainly controlled by local temperature relative humidity and 18 op at the time of snail activity data also suggest that the modern snails are nocturnally active almost all year round in the study area the carbon isotopic compositions of shells 13 cs of the same specimens indicate a diet prevalently or exclusively composed of c3 vegetation the 18 os values of late pleistocene specimens suggest that climate conditions at 14 2 ka cal bp were similar to the present day in agreement with additional 18 os records from southern italy by contrast early middle holocene shells are notably 18 o depleted and suggest wetter conditions possibly combined with a decrease in isotopic composition of precipitation source compared to the present day when compared with regional palaeoclimatic records a large scale isotopic response to millennial scale changes in atmospheric and hydrological conditions e g enhanced rainfall in the central eastern mediterranean is observed during the early middle holocene the 13 cs of late pleistocene and holocene specimens are consistently higher than those of modern ones for the late pleistocene this could be reasonably explained in terms of water stressed vegetation on the other hand this seems to be less valid for holocene counterparts when the climate was wetter probably 13 cs values result from the combination of distinct competing factors involving atmospheric co 2 concentration seasonal water budget vegetation type cover and other carbon sources results reveal coherent relationships between regional 18 os and 13 cs demonstrating that late pleistocene holocene land snail shell remains from archaeological sites may provide useful snapshots of past seasonal climate conditions

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

active tectonics and drainage evolution in the tunisian atlas driven by interaction between crustal shortening and mantle dynamics abstract active tectonics in north africa are fundamentally driven by nw se directed slow convergence between the nubia and eurasia plates leading to a region of thrust and strike slip faulting in this paper we analyse the morphometric characteristics of the northern tunisia sector we aim to identify unknown active tectonic structures and to further understand the mechanisms driving the drainage evolution in this region the interpretation of morphometric data was ground truthed with field data our analysis indicates that recent fluvial captures have been the main factor driving fluvial network reorganization in ne tunisia the medjerda river has increased its drainage area during the quaternary by capturing adjacent axial valleys to the north and south of its drainage divide these captures are probably driven by the gradual uplift of adjacent axial valleys by reverse oblique faults or associated folds like el alia teboursouk and dkhila faults our fieldwork found that these faults cut holocene sediments thus showing recent fault activity the growth and stabilization of the axial medjerda river contrary to the natural transverse drainage development of mature orogens might be caused by a combination of crustal shortening structures and mantle dynamic processes the medjerda river flows sw ne from the south atlassic dextral transfer zone to the regional topographic low defined by the gulf of gabes and the straits of sicily which in turn may be influenced by the underlying tunisian slab in the region

a high resolution record of the last deglaciation in the southern tyrrhenian sea environmental and climatic evolution a multidisciplinary study was carried out on core c106 collected in the salerno gulf southern tyrrhenian sea two tephra layers recovered in the core n 18 o record of globigerinoides ruber and globigerina bulloides and seven 14 c calibrated ages provided the stratigraphic framework the core sediments cover the last 28 kyr bp seismostratigraphic analysis of a high resolution acoustic profile integrated by the dated core samples allowed us to reconstruct the architecture and age of sedimentary bodies on the continental shelf an integrated study based on different taxonomic groups nannofossils pteropods foraminifera and palynomorphs provided palaeoclimatic trends in agreement with changes in the isotopic composition of oxygen the upper part of the last glacial period the deglaciation phase and the holocene were identified correlation between marine and continental records of palaeoenvironmental changes confirms a similar reconstruction of the last deglaciation as in the central and southern mediterranean sea the late pleistocene holocene boundary was recognised at about 11 7 kyr bp between about 9 5 and 6 kyr bpand at 3 3 kyr bpsome warmer episodes were recorded the measured lower isotopic values together with some features of the fossil assemblages recorded from 9 5 to 6 kyr bp may be related to the oceanographic setting that led to the deposition of sapropel s1 in the mediterranean basin 2002 elsevier science b v all rights reserved

long term development of holocene and pleistocene gullies in the protva river basin central russia abstract the specific geomorphic structure a combination of flat or gentle watersheds with short steep valley sides and the high resistance of surface material in the case study area in the centre of the russian plain are responsible for the specific pattern of holocene erosion no or minor sheet erosion the occasional appearance of new gullies on the valley sides four out of 19 studied and a concentration of erosion activity in old gullies that had existed since pre holocene times 15 out of 19 studied the erosion activity is studied using radiocarbon dating of gully sediments summed probability density distribution spdd of 65 radiocarbon dates is applied to detect changes of erosion rates over the last five millennia three millennium scale phases of erosion activity are distinguished phase 1 1200 years bp to the present intensive erosion phase 2 2800 to 1200 years bp weak erosion and phase 3 4800 to 2800 years bp intensive erosion short episodes or single events of relatively strong erosion have been found at around 4700 3800 3000 2200 1800 and 900 years bp erosion during phase 3 coincided with the holocene lowest population density in the whole region and the start of phase 1 coincided with a population gap at the case study area which suggests other than anthropogenic causes for changing erosion regimes these may be climatic factors because changes between millennium scale phases of erosion activity coincide with pronounced climatic changes the subboreal subatlantic transition and the start of the medieval warm period however a direct correlation between erosion activity and climatic parameters warmer cooler wetter drier has not been found presumably because the available palaeoclimatic reconstructions do not contain enough information on changing frequencies and magnitudes of hydrological extremes according to population dynamics charcoal frequency in erosion derived sediments and pollen data a human impact on erosion is suggested to have occurred from the 11th century ad and more confidently from the 14th 16th centuries this contributed to erosion acceleration that began some two centuries earlier apparently for climatic reasons

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

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

western mediterranean environmental changes evidences from fluvial archives abstract when dealing with current and past landscape evolution a key issue addresses responses of geomorphic systems to the large number of influencing variables identifying morphodynamic phases and revealing interrelations with specific driving forces are demanding tasks for quaternary research in this paper we present late pleistocene and holocene fluvial sedimentation patterns of three western mediterranean river catchments namely jarama river guadalete river and guadalquivir river that extent along a climatic transect from semi humid sw spain to semi arid central spain these studies are based on extensive fieldwork conducted on 36 exposures and 13 drillings in floodplain positions field data is supported by geochemical analyses while the chronological framework was obtained from the analyses of 70 radiocarbon samples results show distinct patterns of fluvial sedimentation as well as soil formation linked to floodplain stability for each river catchment on regional or catchment scale pollen stratigraphical correlation and comparison with lacustrine records show that fluvial dynamics have a strong reaction to climatic shifts with phases of high fragility characterized by catchment erosion and floodplain sedimentation in response to climatic aridification events and phases of climate change in general the comparison of the examined river systems reveals that periods of supra regional floodplain sedimentation in several catchments occurred from 8 0 to 7 0 5 0 to 3 8 2 2 to 1 5 and around 1 0 as well as 0 4 ka cal bp while we found periods of supra regional soil formation from 13 3 to 12 7 7 0 to 5 1 with a short interruption around 6 0 to 5 5 ka 2 8 to 2 3 ka 1 4 to 1 2 ka and 0 8 to 0 5 ka cal bp beside these consistencies we found deviating dynamic patterns that are apparently expressed in terms of differing onset and offset differing durations or even the lack of fluvial system response the main reasons for this can be seen in different regional climate condition and impacts of further influencing factors or in different levels of sensitivity of the river catchments that may be controlled by initial hydrological conditions catchment size or the degree of anthropogenic influence a larger scale assessment shows that fluvial dynamic patterns are hardly comparable across entire spain due to strong spatial heterogeneity of physiographic and climatic conditions on the iberian peninsula in particular when areas are influenced by different circulation systems e g regions influenced by the atlantic ocean vs regions influenced by the mediterranean sea however the consideration of north atlantic marine records reveals a certain coupling between north atlantic coolings atmospheric processes leading to arid climate over large parts of spain as well as increased landscape instability including strong fluvial sedimentation activity attendant atmospheric conditions are discussed

high resolution fluvial records of holocene environmental changes in the sahel the yame river at ounjougou mali west africa abstract the yame river in the bandiagara plateau dogon country mali is characterised by extensive alluvial sedimentary records particularly in the 1 km long ounjougou reach where holocene floodplain pockets are inset in the pleistocene formations these alluvial records have been investigated via geomorphologic fieldwork and sedimentologic and micromorphologic analyses and are supported by 79 radiocarbon dates the alluvial deposits of the valley floor correspond to a vertical accretion of 3 10 m the reconstruction of fluvial style changes provides evidence of four main aggradation periods from 11 500 to 8760 cal bp the alluvial architecture and grain size parameters indicate a wandering river this period included phases of pulsed high energy floods and avulsion related to a northward shift of the summer monsoon to around 14 n after 11 500 cal bp from 7800 to 5300 cal bp a swampy floodplain environment with standing water pools within a sudanian savanna woodland mosaic corresponds to the culmination of the holocene humid period from 3800 cal bp onwards rhythmic sedimentation attests to an increase in the duration and or intensity of the dry season giving a precise date for the local termination of the holocene optimum period during the last two millennia and for the first time during the holocene the alluvial formations are progressively restricted whereas the colluvial deposits increase indicating strong soil erosion and redeposition within the watershed related to an increase in human impact four major periods are characterised by incision i1 ante 11 500 i2 8760 7800 i3 6790 6500 cal bp i4 2400 1700 cal bp pointing to dramatic changes in fluvial style they result from high energy flood flows during dry spells and confirm the capacity of the floodplain pocket in the upstream reach of the sahelian belt to record rapid holocene climatic change

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

durations of soil formation and soil development indices in a holocene mediterranean floodplain abstract holocene and late pleistocene alluvial sequences of the mid medjerda floodplain northern tunisia reveal three types of soils with gradual transitions fluvisols calcaric cambisols calcaric and calcic luvisols chromic stratigraphic cross correlations palaeomagnetic secular variation and 14 c and irsl dating enable detailed information about ages and durations of soil formation in the floodplain weakly developed fluvisols calcaric commonly reveal late holocene ages with soil formation durations lasting between 100 and 300 years hence holocene soil formation is detectable in the exposures from durations of around 100 years onwards cambisols show predominantly mid holocene ages the durations of soil formation are between 800 and 5000 years calcic luvisols chromic feature late pleistocene ages with durations of soil formation between 10 000 and 40 000 years profile development indices were computed from simple field parameters like soil structure soil colour horizon thickness and leaching features the derived development indices show good correlation r 2 0 804 with the calculated durations of soil formation field parameters are well suited for a quantitative development index of holocene soil formation even if very weak developed soils are predominant the study shows that maturity stages of holocene alluvial soils in a homogeneous mediterranean environment are predominantly driven by soil formation duration

the arid humid transition in the sahara and the sahel during the last deglaciation at the time of the last glacial maximum the sahara and sahel regions of north africa were extremely dry new records of rainfall show that during the subsequent deglaciation the transition from arid to humid conditions in these regions occurred synchronously in two main steps comparison with other records of palaeoclimate in europe and the north atlantic ocean shows that certain common factors controlled changes in ocean and atmosphere dynamics during the deglaciation

contrasting patterns of hydrological changes in europe in response to holocene climate cooling phases the quantitative reconstruction of climatic parameters from pollen and lake level data obtained at saint jorioz lake annecy eastern france gives evidence for cooler and wetter conditions during the 8 2 ka cold event a comparison of these regional data with other hydrological records reconstructed in europe for the same period suggests as a working hypothesis that mid latitudes between ca 50 and 43 underwent wetter conditions in response to the cooling whereas northern and southern europe were marked by drier climate in the latter case leading to an interruption of the sapropel 1 formation in the mediterranean a similar hydrological tri partition of europe can be observed during other holocene cooling phases associated with north atlantic ird events data indicate that the middle zone characterised by wetter climate conditions could have had a more extended latitudinal amplitude during phases of climate cooling weaker than the 8 2 ka event the differences in expansion of the wet mid european zone depending on holocene climate cooling phases could reflect variations in the strength of the atlantic westerly jet in relation with the thermal gradient between high and low latitudes

high resolution fluvial record of late holocene geomorphic change in northern tunisia climatic or human impact abstract in northern tunisia the late holocene alluvial record of medjerda floodplain sediments indicates geomorphic changes due to fluctuations of past climate superimposed by the effects of human activity geomorphic activity occurred several times interrupting stable conditions enhanced fluvial dynamics occurred around 4 7 3 0 1 7 1 0 and 0 7 ka cal bp a peak of activity took place about 0 4 ka cal bp some periods of fluvial activity show event like phenomena in particular when an anthropogenic impact intensifies climatic aridification this has been the case around 1 7 1 0 0 7 and 0 4 ka cal bp with severe floods in the medjerda valley during antiquity as well as around 1 3 0 8 and 0 5 ka cal bp immature alluvial soils have developed the first one being the most distinct late holocene medjerda alluvial history shows that fluvial dynamics in northern tunisia were predominantly climate driven anthropogenic impact only intensified or weakened these processes

palynological evidence for climatic change and human activity during the holocene on minorca balearic islands four pollen diagrams from minorca balearic islands have been correlated with other previously studied sequences from majorca and minorca to define a holocene landscape sequence for the region from 8000 yr b p to the present the lower part of the pollen diagrams reflects a climatic phase with more rain and less marked seasonality than today significant quantities ofcorylus buxus and mesophilous taxa are found in the middle part between 5000 and 4000 yr b p a strong change is recorded in composition and structure of the vegetational landscape with vegetation appearing that was adapted to mediterranean conditions this episode coincided with the first human colonization of the island and also with a widespread climatic change in the western mediterranean region the change in taxa was complex and some sclerophyllous taxa sucholeaplayed an important role in the transformation of the landscape physiognomy from the mid holocene until the present although human activities have removed much of the mediterranean vegetation on the balearic islands it seems clear that the changes have been brought about in part by increasing dryness

succession and stable isotope composition of gastropods in holocene semi arid alluvial sequences bardenas reales ebro basin ne spain palaeoenvironmental implications three alluvial units ranging from the middle to late holocene in age were distinguished in bardenas reales natural park ebro basin ne spain based on morphosedimentary analysis and radiocarbon data in this sensitive mediterranean alluvial system the succession and isotopic composition of gastropods greatly contribute to establishing the prevailing palaeoenvironmental conditions the oldest unit 4763 87 to 2848 55 cal yr bp represents fluvial channels and swamped areas includes the greatest proportion of aquatic gastropods ancylus fluviatilis and lymnaea truncatula and marsh species vallonia pulchella and presents the most negative values of 18o mean 2 21 pdb the intermediate unit 1403 60 to 836 65 cal yr bp shows a high rate of alluvial activity related to irregular torrential rainfall with sedimentary features of aridity and this unit includes only dry open ground gastropods xeroplexa sp chondrinidae indet and granopupa granum and presents the least negative values of 18o

the 8 2 ka event and early mid holocene forests fires and flooding in the central ebro desert ne spain abstract the impact of the 8 2 ka cooling event during the early mid holocene has not been widely observed in southern europe which in contrast to northern europe was already experiencing a cooler than present climate at this time multi proxy analysis of sediment cores from two closed basin saline lakes in the central ebro desert ne spain has allowed us to investigate the impact of climatic changes around the time of this event in more detail long term changes in climate between the early and mid holocene indicate a shift in winter to a more positive nao resulting in declining lake levels in one lake sensitive to winter groundwater recharge and cooler winter temperatures reconstructed from pollen climate analysis reconstructed summer temperatures also declined over this period while annual precipitation and forest cover increased interpreted as a result of enhanced convection driven summer precipitation association with a northward displacement of the sub tropical high pressure around 8 2 ka a marked increase in fire frequency is shown between ca 8 8 and 8 0 ka bp along with an expansion of fire tolerant evergreen oak and peak in water levels in a second storm run off fed lake a maximum in fire intensity occurred with the deposition of a charcoal layer at both lake sites dated to 8150 130 and 8285 135 cal bp respectively the increase in fire is largely attributed to a temporary return southward of the summer sub tropical high pressure over the mediterranean which not only increased summer aridity but also caused a contradictory regional warming before hemispheric cooling set in

first evidence of a lake at ancient phaistos messara plain south central crete greece reconstructing paleoenvironments and differentiating the roles of human land use and paleoclimate from minoan to roman times phaistos was one of the most important minoan palaces in crete and previous studies have addressed its relationship with the paleo seashore position during historical times here we reconstruct the environmental evolution of phaistos from early minoan to roman times study of two stratigraphic sections and nine boreholes drilled in the westernmost part of the messara plain has revealed the stratigraphy of the mid to late holocene sediments laboratory analyses comprise granulometry magnetic susceptibility measurements and identification of mollusks diatoms and pollen grains eighteen radiocarbon dates provide a robust chronostratigraphy in addition a geophysical survey electric resistivity tomography ert method was conducted to reveal the sub surface morphology in the coring area the results reveal that a freshwater lake existed from ca 2100 2000 bc to ca 1200 1100 bc which subsequently became swampland until ca 700 bc a lake retreat is identified at ca 1200 1000 bc and can be interpreted as resulting from the 3 2 cal kyr bp rapid climate change rcc dry event observed elsewhere in the eastern mediterranean subsequently from the 7th to the 5th century bc there was the input of detrital material and fluvial dynamics prevailed until at least roman times the origin of the lake and its disappearance are discussed in the context of regional climate change and local tectonic activity without excluding possible human influences we also reconstruct the vegetation history for the period from the late minoan to the early archaic period pollen analysis reveals a mediterranean maquis landscape dominated by olea together with hygrophilous vegetation and highlights a clear transition from limnic to swampy environmental conditions around 1100 bc the pollen sequence is also important for assessing the impact of the 3 2 cal kyr bp rcc event and for assessing the possibility of an abrupt discontinuity in human activity around phaistos after the demise of the minoan civilization

abrupt onset and termination of the african humid period rapid climate responses to gradual insolation forcing a detailed ca 100 yr resolution and well dated 18 ams 14 c dates to 23 cal ka bp record of latest pleistocene holocene variations in terrigenous eolian sediment deposition at odp site 658c off cap blanc mauritania documents very abrupt large scale changes in subtropical north african climate the terrigenous record exhibits a well defined period of low influx between 14 8 and 5 5 cal ka bp associated with the african humid period when the sahara was nearly completely vegetated and supported numerous perennial lakes an arid interval corresponding to the younger dryas chronozone punctuates this humid period the african humid period has been attributed to a strengthening of the african monsoon due to gradual orbital increases in summer season insolation however the onset and termination of this humid period were very abrupt occurring within decades to centuries both transitions occurred when summer season insolation crossed a nearly identical threshold value which was 4 2 greater than present these abrupt climate responses to gradual insolation forcing require strongly non linear feedback processes and current coupled climate model studies invoke vegetation and ocean temperature feedbacks as candidate mechanisms for the non linear climate sensitivity the african monsoon climate system is thus a low latitude corollary to the bi stable behavior of high latitude deep ocean thermohaline circulation which is similarly capable of rapid and large amplitude climate transitions

holocene valley incision in the southern bukk foreland climate human environment interferences in northern hungary abstract prehistoric human settlement activities in northern hungary have been well studied for several decades recent studies from the great hungarian plain provide evidence of human impact starting as early as in the neolithic c 8200 cal bp archaeological records suggest that with establishment of the baden culture c 5500 cal bp settlements were moved from tisza river towards the northern mountainous area although quaternary landscape development of the bukk mountains is well studied holocene human environment interactions in particular have not been focused on so far here we present holocene landscape history around bogacs in the southern bukk mountain foreland sediment records were sampled from fans of secondary tributaries in the middle course of the hor valley morphology of the tributary valleys suggests different incision phases with older forms and less human impact in the northern part of the studied valley section type 1 and younger forms and stronger human impact in the southern part type 2 however 14c dates from the fan of a type 2 valley in the southern part suggest initial incision between 9000 and 8000 cal bp whereas human activity is not reflected in the sediments in the fan sediments of a type 1 tributary in the northern part of the studied valley section daub was found in the context of deposits dated to 3000 cal bp here thickness of holocene sediments suggest significant soil erosion it can be summarised that post pleistocene valley incision was restricted to short periods of extreme climate conditions during the early to mid holocene human activities did not contribute to initial valley incision nevertheless human activities seem to have enhanced soil erosion in the catchments of type 1 tributaries

vegetation sedimentary deposits and climates during the late pleistocene and holocene in eastern morocco abstract geological investigations in the oujda region eastern morocco of the period corresponding to the last hundred thousand years have made it possible to discover several geological and archaeological sites which are rich in charcoal by including information from prehistory absolute chronology and palaeoenvironmental studies the data from charcoals analyses can be placed in their context this allows us to outline the bioclimatic evolution of a poorly known region from north to south there is a decrease in climatic fluctuations as the beni snassen mountains evolved from a humid to semi arid climate supraoromediterranean to thermomediterranean the angads plain and the oujda mountains remained under thermomediterranean conditions with slight fluctuations between sub humid and semi arid southwards the alfa and artemisia steppe dominated the northern part of the hauts plateaux with some variations from an arid climate in the oujda mountains the data are abundant and the climatic fluctuations which are indicated by the flora sediments from rock shelter sites and fluvial terraces indicate that the soltanian last glacial is principally a dry period within a semi arid climate this climate is temperate to cool and interrupted by three periods of warmer and more humid conditions the rharbian holocene begins ca 12 000 b p with a slightly more humid phase which is followed first by a short arid period and later by the climatic optimum which is warm and humid 6000 4500 b p the return of the arid climatic conditions occurs at ca 4000 b p but they are interrupted by a short more humid phase 3000 to 2000 b p

the holocene fluvial chronology of spain evidence from a newly compiled radiocarbon database abstract a critical analysis of 74 radiocarbon dates selected from a total of 102 published and unpublished dates from holocene fluvial environments in spain has identified a number of periods of increased fluvial activity in spain namely 11 170 10 230 9630 8785 7980 6860 5800 4800 3880 3085 2895 1820 1300 0 cal bp the latter period reflecting sustained fluvial response to increased human impact the radiocarbon samples were classified according to type of depositional environment a alluvial overbank b flood basin c alluvial channel gravels d fluvio torrential deposits and e slackwater flood deposits palaeofloods dates from slackwater flood deposits indicated at least five phases of increased frequency of large magnitude floods during the holocene 10 855 10 230 9530 8780 2880 2430 975 790 and 520 265 cal yr bp flood basin type deposition occurred from 7980 to 4830 cal yr bp the main clusters of dates from alluvial floodplain deposits occurred at 2750 2150 and 930 520 cal yr bp the record is discussed in relation to other palaeoenvironmental archives including pollen records of holocene vegetation change and palaeoclimatic proxies such as the north atlantic drift ice record comparison with the latter indicates that major holocene flooding coincided with cold climate phases during 9530 9280 2880 2430 and 520 265 cal yr bp a cooling phase at 10 855 10 230 and warming phases at 9030 8780 and 975 790 cal yr bp

late holocene fluvial chronology of spain the role of climatic variability and human impact abstract a database of published and unpublished radiocarbon dates from late holocene fluvial environments in spain was critically analysed in order to obtain a fluvial chronology for this period the principal types of depositional environment represented in the record were slackwater flood deposits 28 dates alluvial overbank facies 12 dates and alluvial channel facies 7 dates the sedimentary context of each date was classified in order to identify those samples that specifically dated change in the fluvial environment analysis of the different depositional environment data sets using summed probability plots identified phases of alluviation at 2800 2350 and 800 500 cal bp increased frequency of large magnitude floods occurred at 2850 2500 1000 800 and 520 250 cal bp the results indicate that in mediterranean regions slackwater flood deposits are valuable archives of climatic variability even during periods of increased human impact

sediments from lago di mezzano central italy a record of lateglacial holocene climatic variations and anthropogenic impact microscopic geochemical and pollen analysis of sediment samples of a lateglacial holocene profile from lago di mezzano a maar lake in central italy reveals evidence of significant climatic and human induced environmental changes time control is provided by a combination of varve chronology and radiocarbon dating the well known lateglacial climatic variations a warmer interstadial and the younger dryas cold phase are clearly represented in all the parameters during the interval between 9200 and 5600 cal bp of the holocene climatic optimum annually laminated organic rich diatom gyttja was deposited two periods of diminished total organic carbon are identified within this interval the first one p1 ranges from 8200 to 7800 cal bp while the second p2 is centred around 6500 cal bp during p1 a predominance of diatoms stephanodiscus parvus and s minutulus over other algae represented by the total organic carbon content is observed the timing of this period coincides with the early to mid holocene climatic transition reported from ice cores and lake sediments stager and mayewski 1997 p2 is characterized by a decrease in all biogenic parameters including biogenic opal organic carbon as well as arboreal pollen from 5000 cal bp to date the sediment pattern changes coincide with the mid holocene climatic deterioration in addition to these natural variations human impact has been recorded and recognized from sedimentological features such as turbidites and charcoal as well as from reduced arboreal pollen content two middle bronze age 3700 cal bp and 3300 cal bp etruscan early roman 2500 cal bp longobardic ad 900 and modern settlements since ad 1700 have been distinguished on the basis of these data

north atlantic influence on holocene flooding in the southern greater caucasus in the context of global climate change flooding becomes an increasingly serious threat to modern societies and future flooding can only be understood using long term geological flood records als

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

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

sea land oxygen isotopic relationships from planktonic foraminifera and speleothems in the eastern mediterranean region and their implication for paleorainfall during interglacial intervals the oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change here we examine the question of the regionality of this isotopic record and its linkage with the marine isotopic record in the eastern mediterranean em region the study presents a new accurately dated 250 kyr 18o and 13c record determined from speleothems of the peqiin cave northern israel its comparison with the continuous 185 kyr isotopic record of the soreq cave speleothems from central israel reveals striking similarities thus a strong regional climatic signal brought about by variations in temperature and rainfall amount is reflected in both cave records low 18o minima in the peqiin profile for the last 250 to 185 kyr period interglacial marine isotopic stage 7 match the timing of sapropels 9 to 7 and are indicative of high rainfall in the em region at these times the combined soreq and peqiin 18o record for the last 250 kyr excellently matches the published globigerinoides ruber g ruber marine 18o record for the em sea with the isotopic compositional difference g ruber speleothems remaining relatively constant at 5 6 0 7 thus establishing for the first time a robust exploitable link between the land and the marine isotopic records the correspondence of low 18o speleothem values and high cave water stands with low g ruber 18o values during interglacial sapropel events indicates that these periods were characterized by enhanced rainfall in the em land and sea regions by use of sea surface temperatures derived from alkenone data as a proxy for land temperatures at the soreq cave we calculate the paleorainfall 18o values and its amounts maximum rainfall and lowest temperature conditions occurred at the beginning of the sapropel events and were followed by decrease in rainfall and increase in temperatures leading to arid conditions the record for the last 7000 yr shows a trend toward increasing aridity and agrees well with climatic and archeological data from north africa and the middle east

the september 14 2015 phreatomagmatic eruption of nakadake first crater aso volcano japan eruption sequence inferred from ballistic pyroclastic density current and fallout deposits abstract an explosive eruption occurred at nakadake first crater aso volcano in central kyushu southwestern japan on september 14 2015 the sequence and causes of the eruption were reconstructed from the distribution textures grain size component and chemical characteristics of the related deposits and video record the eruptive deposits are divided into ballistics pyroclastic density current and ash fall deposits a large number of ballistic clasts mostly

vegetation response to rainfall variation and human impact in central kenya during the past 1100 years pollen data from a 625 cm sediment core from crescent island crater a subbasin of lake naivasha kenya provide an 1100 year record of vegetation change at a mean time resolution of 15 years earlier data from the same core show a record of lake depth and thus inferred rainfall variation in the form of changing sedimentary facies supported by salinity inferences based on diatom and chironomid assemblages stratigraphic variation in the abundances of aquatic and semi aquatic plants and chlorophyte algae generally supports the reconstructed lake depths woody afromontane and woodland plant taxa decreased relative to poaceae grasses during low rainfall periods and increased during high rainfall periods a decrease in the extent of lower montane forest coincident with favourable climatic conditions after about ad 1700 was probably caused by kikuyu immigration and population expansion around that time as indicated by simultaneous appearance of the food crop zea mays maize increases in ruderal herbaceous and exotic tree pollen during the twentieth century indicate increased local landscape disturbance during the colonial period there is little direct pollen evidence for accelerating clearance of the montane forest during recent decades

testing the reliability of detrital cave sediments as recorders of paleomagnetic secular variations seso cave system central pyrenees spain abstract a paleomagnetic study has been carried out on a waterlaid detrital sedimentary sequence of 240 cm thick within the seso cave system west central pyrenees in these sediments seven charcoal samples were dated using 14c ams ranging from 2080 to 650 cal yr bp 130 bc 1300 ad two levels of human occupation of the cave have been recognized by ceramics associated to the iberian period and to the roman period respectively the detrital sedimentary sequence is made of autochthonous piping detached material from the eocene marls host rock inside of the cavity and allochthonous stream transported sediments from the outside sediments the autochthonous material first 100 cm made of fine grain laminated sediments lutites and marls corresponds to pond facies the allochthonous material 190 240 cm is made of lutites and sands and corresponds to stream facies and both facies are mixed from 100 to 190 cm the increase in sedimentation rate towards the end of the sequence stream facies points to an intensification of the alluvial activity as a possible consequence of a more arid climate during the medieval climate anomaly for the paleomagnetic study 44 discrete cylindrical samples were taken along the detrital sequence the values of the natural remanent magnetization and magnetic susceptibility are significantly lower in the pond sediments than in the stream sediments the declination and inclination of the paleomagnetic characteristic component sister samples analyzed by both alternating field and temperature demagnetizing procedure of each depth point is compared to the spanish archeomagnetic catalog and available geomagnetic models arch3k 1 cals3k 4 cals10k 1b and scha dif 3k in order to determine the accuracy of these sediments recording the earth s magnetic field results suggest that these sediments poorly record the earth s magnetic field however paleomagnetic inclination shows similar results between both demagnetizing methods and the inclination is well recorded especially in the younger stream facies the lack of archeological remains with absolute dates from 925 to 1545 cal yr bp in the iberian paleomagnetic secular variation reference curve has prevented up to now the study of that time period therefore the inclination data from the seso cave deposit is the first record of the iberian paleomagnetic secular variation during most part of the medieval time and they are closer to the inclination values of one geomagnetic model cals10k 1b

seismic constraints on shallow crustal emplacement processes at the fast spreading east pacific rise we present the results of nine on bottom seismic refraction experiments carried out over young east pacific rise crust the experiments are unusual in that both the source and receiver are located within a few meters of the seafloor allowing high resolution determinations of shallow crustal structure three experiments were located within the axial summit caldera asc over zero age crust the seismic structure at these three locations is fundamentally the same with a thin 60 m surficial low velocity 2 5 km s layer a 100 to 150 m thick transition zone with velocities increasing by 2 5 km s and a layer with velocities of 5 km s at a depth beneath the seafloor of 130 190 m the surficial low velocity layer and transition zone are defined as seismic layer 2a and the 5 km s layer is defined as the top of layer 2b both the surficial low velocity layer and the transition zone double in thickness within 1 km of the rise axis we model layer 2a as the extrusive sequence and transition zone and the 2a 2b boundary as the top of the sheeted dikes the primary implication of this interpretation is that the depth to the top of the sheeted dikes deepens from 150 m to 300 m within 1 km of the asc the thickening of the extrusive layer is interpreted to be due to lava that either overflows the asc walls is emplaced through eruptions outside of the asc or travels laterally from the asc through conduits the most probable cause for the thickening of the transition zone is sill emplacement outside of the asc either from magma that does not reach the surface in an off axis eruption or magma that is transported laterally during the drainage process creating the asc we suggest that the mechanism controlling the magnitude and rate of the dike subsidence is the mechanism that determines the thickness of the extrusive section and the total thickness of layer 2a

holocene environmental variability in the central ebro basin ne spain from geoarchaeological and pedological records abstract environmental fluctuations during the holocene caused important landscape changes in the central ebro basin which is a very sensitive region due to its semiarid climate lithology and continuous human presence severe erosion processes hinder palaeoenvironmental and archaeological record preservation infills of ephemeral stream valleys in semiarid environments are some of the best contexts for geoarchaeological studies in this paper we analyse the geomorphological processes pedological features and charcoal and pollen content and composition of the sedimentary sequence of la poza valley catchment area with the support of additional information from la bajada valley 14 c dates for 13 charcoal fragments provide the necessary chronological control we describe 5 sedimentary units and a polycyclic sequence of six soils that covers most of the holocene beginning ca 9 5 ky cal bp buried soils help to identify stability periods in the sedimentary sequence while incision stages are detected through erosive contacts and terraced organisation of the sedimentary units charcoal and pollen content and composition as well as the soil development reveal an open forest of junipers and pines for the early holocene in the lower part of the sequence mainly in unit 1 very different from the current deforested landscape also represented in the sequence unit 4 thus la poza record shows the environment was favourable for hunter gatherers from the late mesolithic and for the first neolithic farmers from then on progressive degradation due to a combination of climate changes and increasing human pressure led to the current deforested landscape

resource pressure and environmental change on the north african littoral epipalaeolithic to roman gastropods from cyrenaica libya abstract this paper discusses the marine and terrestrial shell on epipalaeolithic to classical period sites in the cyrenaican coastlands northeast libya with particular reference to the haua fteah with parallel studies at a late roman farmstead and two small caves together they provide evidence for coastal and terrestrial environments and for the continued nutritional importance of gastropods to humans during the holocene land snail evidence is consistent with regional vegetation in coastal cyrenaica becoming increasingly open through the holocene as a result of some combination of climate change and human impact marine species suggest that the coastline near the haua had been rocky throughout the holocene at hagfet al gama changing faunas provide evidence for sand encroachment onto a previously rocky shoreline in hellenistic times a biometric study of osilinus turbinatus shows that in the archaeological sites these shells are systematically smaller than modern specimens providing evidence for long term dietary stress in the human populations around the haua fteah with particularly severe stress in parts of the epipalaeolithic a biometric study of patella spp provided evidence for size selection but also seems to show evidence for resource pressure it is unlikely that variations in resource pressure seen in the mollusc biometrics are the result of climatic stress or natural ecological factors and explanations must be sought in society environment dynamics

lacustrine clay mineral assemblages as a proxy for land use and climate changes over the last 4 kyr the amik lake case study southern turkey abstract lake sediments are sensitive to landscape changes and most of these changes seem to be modulated by land use anthropogenic factors coupled to palaeoenvironmental palaeoclimatic changes in its detrital fraction the lacustrine sediments record the history of soil erosion within its catchment via the inputs of clays and others detrital products within a mediterranean context the study investigates the upper sediments infilling the central part of the amik basin in southern turkey this tectonic basin was occupied and exploited by modern human at least since 6000 7000 bce we focus on the clay mineralogy x ray diffraction on oriented aggregates and magnetic susceptibility measurements bartington of the sedimentary record in the area over the last 4000 years to assess environmental changes in relation with the different land uses and or weathering during the successive bronze iron roman islamic ottoman and modern civilizations the clay fraction of amik lake sediments comprises smectite kaolinite illite chlorite and chlorite smectite mixed layers that are the inherited clay phases a relative change in abundance and crystallinity and chemistry of illite attests that environmental conditions evolved in the amik plain from the bronze to modern age in relation with climates and or land use changes the history of the amik lake reveals different soil erosion episode the most intense erosion phase occurred during the bronze iron ages as indicated by the clay and magnetic susceptibility proxies the roman period was an exceptional period with soil erosion products arriving from the watershed probably due the water channelization a reduction of soil erosion occurred during the post roman period until nowadays significant pedogenesis transformations are evidenced especially during the islamic ottoman periods suggesting intense chemical weathering conditions related to climate change

synchroneity between marine and terrestrial responses to millennial scale climatic variability during the last glacial period in the mediterranean region land sea climatic proxies have been obtained from the last glacial section of images core md95 2043 western mediterranean sea vegetation and alkenone derived sst curves indicate rapid 150 years and synchronous terrestrial and marine climatic changes paralleling the dansgaard oeschger d o climatic variability over greenland this frequency of climate change can be related to shifts between the two modes of operation of the north atlantic oscillation nao transfer functions applied to the pollen data indicate that there was an amplification of the climatic signal during heinrich events hes in comparison with other d o stadials the development and persistence of both scandinavian and atlantic mobile polar highs over southwestern europe may explain the extreme cooling 10 c and dryness 400 mm during heinrich events 5 and 4 in the mediterranean region comparison of the results of core md95 2043 with similar climatic data from images core md95 2042 located off portugal indicates that thermal and precipitation gradients occurred between the mediterranean and the atlantic sides of iberia within hes hes 4 and 5 are associated with more humid conditions in the atlantic by 200 mm than in the mediterranean site as is the case at the present time this comparison also illustrates the different behaviour of these areas during the d o stadials in contrast with the mediterranean site the atlantic site shows similar precipitation and temperature drops for all the d o stadials including those related to the hes here we propose the operation of different mobile polar highs mph as the driving mechanism for this difference in behaviour between the atlantic and mediterranean sides of iberia hes are related to a stronger influence of the scandinavian mph forcing a severe aridification and cooling of the full iberian peninsula the atlantic mph may have been dominant during the other stadials which would preferentially affect southwestern iberia

constraining the timing of alluvial fan response to late quaternary climatic changes southern tunisia the evolution of the oued es seffaia alluvial fan during the last 50 000 years is analyzed in the light of chronometric data derived from ams radiocarbon and optical dating techniques these ages have enabled the temporal constraint of the distalward progression of the intersection point the upper limit of the locus of deposition which has resulted in the telescopic segmentation of the fan comparison of these data with the late quaternary climatic history of the maghreb highlights several problems of interpretation due both to our limited knowledge of regional palaeoclimates and of the response of dryland fluvial systems to climate changes however our data provide some evidence to suggest that fan incision and formation of telescopic segments occurs in response to changes from arid to less arid conditions supporting the conclusions of some of the work from other areas

anthropogenic and climatic impact on holocene sediment dynamics in se spain a review the climatic and anthropogenic control on holocene sediment dynamics was not well constrained for the western mediterranean basin the paucity of high resolution palaeoenvironmental records long hampered a detailed understanding of the human impact on erosion rates this paper analyses holocene sediment dynamics in the context of regional climatic conditions land cover and human occupation based on an extended compilation of recently published high resolution paleoenvironmental proxy data from both terrestrial and marine environments the palaeoenvironmental reconstruction identified four main aridification episodes a at 5600 4700 a4 4100 3400 a3 2800 2500 a2 and 1900 1300 1200 a1 cal bp most of the severe aridification phases were climatically induced not human driven and well correlated with a large dataset of paleoenvironmental records from the western mediterranean basin and north atlantic ocean the phases of enhanced aridity are generally associated with enhanced sediment dynamics independent of the intensity and type of human occupation in contrast wet climatic conditions are found to be associated with both high and low sediment dynamics dependent on the human impact on the environment the mid late phoenician phoenician ii republican rome civilizations and the christian reconquest are all associated with high human impact on the environment and high erosion rates are reported for the vera basin and ne spain despite the improved hydrological conditions human occupation is not necessarily associated with geomorphic instability as shown by the post argaric omeya and nazarene periods that are characterized by low erosion rates and geomorphic stability

unraveling north african riverine and eolian contributions to central mediterranean sediments during holocene sapropel s1 formation hydroclimate variability has exerted a fundamental control on the alternating deposition of organic lean marl and organic rich sapropel sediments in the eastern mediterranean sea ems however the exact mechanisms regarding the freshwater sources and related changes are still debated here sr and nd isotopes and high resolution elemental data are used to constrain different riverine and eolian supplies to the central mediterranean over the past 9 8 ka the detrital sediments in core cp10bc taken at the margin of the libyan shelf in the southwestern ionian sea can be described by a three endmember mixing system based on sr and nd isotopic compositions the same systematics can also be deduced from ti and k compositional variability the endmembers comprise saharan dust aegean nile and libyan soil representing the eolian supply from north africa the riverine inputs from the aegean nile areas as well as the riverine and shelf derived fluxes from the libyan tunisian margin respectively for the sapropel s1 period in particular we find important detrital supplies from fossil river wadi systems along the libyan tunisian margin activated by intensified african monsoon precipitation combining the temporal profiles with the consistent variability observed in the 87sr 86sr 1000 sr diagram such libyan contribution has been most prominent during the uppermost period of sapropel s1 in core cp10bc this observation is in agreement with hydroclimate reconstructions of northwestern libya comparison of the sr nd isotope data between core cp10bc and four cores taken along a west east transect throughout the ems shows that this detrital supply originated mainly from western libya tunisia and was transported as far eastward as 25 e while being diluted by an increasing nile contribution

interpreting drivers of change in fluvial archives of the western mediterranean a critical view abstract fluvial archives in particular late glacial to holocene floodplain records may provide valuable information regarding past environmental conditions and stages of landscape evolution in view of the high significance of floodplain dynamics for the development of entire landscapes the number of studies that have been performed on floodplain sediments remains comparatively low especially regarding the western mediterranean region however one of the reasons could be seen in the high complexity and diversity of processes and factors that control and influence fluvial activity that often hampers a straightforward interpretation of floodplain dynamics therefore a basic demand on fluvial archive research is to address the complexity of the factors that control the characteristics of fluvial sequences in order to provide a robust basis for their interpretation as a starting point for discussion this paper aims to give an overview of fluvial dynamic patterns in the western mediterranean for the last 15 ka in order to examine their relevance for palaeoenvironmental reconstructions the basis for this is provided by previous investigations on four different river systems in spain and northern africa the results of which are herein synthesized in order to propose a regional late pleistocene and holocene fluvial history for the western mediterranean realm basic results are related to alluvial floodplain deposits and visible features within them such as alluvial soils incision marks and aggradation phenomena since fluvial systems are open systems we discuss our findings against the background of different influencing factors that could modify fluvial architecture and may restrict palaeoenvironmental reconstructions a more comprehensive interpretation focuses on signals that are common to each of the studied river systems in this respect we critically discuss the customary nature of cumulative probability functions for the identification of regional flooding episodes and point out the benefits of a stratigraphy supported approach for characterizing regional floodplain dynamics finally three alluvial soil formation periods were found in all settings a first phase after 15 ka ending with the younger dryas event a second one from 7 to 5 ka with a break between 6 5 and 5 5 ka and a third phase between 3 and 2 ka these soil formation periods were interrupted and framed by fluvial dynamic phases accompanied by channel aggradation floodplain deposition floodplain erosion and or river incision in particular after 5 ka around 1 6 and at 1 ka and during the little ice age lia floodplain aggradation affected river systems in iberia and northern africa as well a cautious assessment of these results and extensive comparisons with secondary archive information prompts us to relate the aggradation periods with climate forcing by means of a supra regional aridification that effected large areas of the western mediterranean in contrast the three mentioned soil formation periods can be linked with landscape stability most probably triggered by favorable climate conditions in the western mediterranean apart from these large scale patterns we discuss the reliability of information emerging from floodplain records against the background of individualistic river behavior and self organization regarding future work we want to emphasize the great potential of yet rarely applied system oriented approaches that also attach importance to sub catchment dynamics as a link between catchment slopes and the main river floodplain

successful combination of electron spin resonance luminescence and palaeomagnetic dating methods allows reconstruction of the pleistocene evolution of the lower moulouya river ne morocco abstract based on a combination of electron spin resonance esr dating of quartz luminescence dating of k feldspar and palaeomagnetism this study presents the first chronostratigraphic framework for the pleistocene fluvial deposits of the lower moulouya river in the triffa basin ne morocco k feldspar pirir225 and pirir290 signals of all samples are saturated suggesting fluvial deposition at least as early as the middle pleistocene 0 39 0 80 ma consequently further chronological information was obtained with esr dating of quartz grains from the ancient pleistocene fluvial deposits as for esr the multiple centres approach provides equivalent dose values derived from the al and ti centres that mostly agree within 1 error suggesting complete signal resetting from the former during fluvial transport esr dating results yield calabrian deposition ages for all river profiles from 1 1 to 1 5 ma these ages are remarkably consistent with the palaeomagnetic results the occurrence of mostly reversed polarity in the deposits indicates a matuyama age 0 78 ma while low incision rates in the triffa basin 0 025 0 003 mm a related to thrusting activity during the calabrian could be inferred the fluvial record points to an acyclic and discontinuous sedimentation pattern over the last 1 3 ma it thereby probably rules out climate as the main driver for fluvial aggradation in the lowermost sedimentary basin at a regional scale several indicators point to transient fluvial response resulting from major quaternary tectonic activity along the beni snassen gorge located directly upstream of the investigated basin we suggest that a capture event at the margin of the uplifting beni snassen massif occurred between 1 04 and 1 36 ma at the latest and subsequently led to the creation of the gorge

fluvial chronology in the east european plain over the last 20 ka and its palaeohydrological implications abstract a database containing 983 absolute ages of fluvial deposits was interpreted in palaeohydrological terms and 646 dates were found associated with 754 local palaeofluvial events geomorphic or sedimentological traces of changing fluvial activity combined probability density functions of high and low activity dates were used to detect time intervals of different palaeohydrological status after low fluvial activity during lgm two palaeohydrological epochs were designated extremely high activity in the end of mis 2 ca 18 11 7 ka before ce 2000 b2k and much lower activity in the holocene within the holocene two hierarchical levels of hydroclimatic variability were designated according to their duration and magnitude regional palaeohydrological phases centuries to few millennia and regional palaeofluvial episodes decades to few centuries tendency is rather clear of activity lowering in the first half and rise in the second half of the holocene extremes within the palaeohydrological phases were designated as 19 palaeofluvial episodes 7 high activity ha episodes 8 low activity stability la episodes and 4 contrast or complex ca episodes in most cases changes of fluvial activity were most likely induced by changing amounts of spring snowmelt runoff most distinct correlation of temperature and hydrological regimes was found in the late holocene high fluvial activity corresponded to cold climatic phases little ice age low activity to warm phases medieval climatic optimum current climate warming the suggested fluvial chronology was compared with independent hydroclimatic archives such as palaeosoils and lake levels correlation with soil formation alluviation epochs was found very close with some exceptions in the early holocene correspondence of fluvial activity to the caspian sea level changes is rather high in the second part of the holocene and is poor before 4 5 ka b2k which can be explained by insufficient data behind both types of reconstructions correlation of changes in fluvial activity within a west east transect over europe revealed relatively poor correlation in the early and mid holocene and much higher synchronism since 3 0 ka b2k which may indicate increasing role of westerlies in controlling european climates in the late holocene throughout the whole holocene changes of fluvial activity over eep were governed by natural climate forcing until the last few centuries when land use changes induced accelerated hillslope and gully erosion

application of geoarchaeological evolutionary models for the interpretation of complex archaeological structures in the central ebro basin spain in landscapes that are extremely sensitive to small environmental changes like some mediterranean areas archaeological contexts could present some problems to their interpretation and evolutionary reconstruction this is the case of los pedregales archaeological site located in the hoya de huesca ne of spain where several stone mounds of unknown age and function were found in an extensive badland the geomorphological edaphological and archaeological study together with radiocarbon and osl datings and contextualization into the geomorphological regional framework made it possible to interpret these structures and to establish an evolutionary model it was determined that they were silos excavated in pleistocene sands and silts unit 1 during the visigothic and early muslim epochs 6th 7th centuries and that they were later filled with limestone blocks successive aggradational and degradational stages units 2 3 and 4 during mca medieval climatic anomaly and lia little ice age periods covered and incised the area leaving the shape of positive structures included in the badland

centennial to millennial scale holocene climate deep water linkage in the north atlantic the stability of the earth s climate is strongly linked to the steadiness of the atmospheric and oceanic transport of heat from low to high latitudes high resolution holocene sedimentary records from the subpolar north atlantic demonstrate a persistent link between centennial to millennial scale fluctuations in the flow speed of iceland scotland overflow water inferred from granulometric proxy data and both the surface north atlantic current component of the meridional overturning circulation moc and published fennoscandian atmospheric temperature variability however these data also highlight the difficulties associated with the interpretation of geochemical and sedimentological deep water circulation proxies as they do not provide a wholly consistent picture the similarity between surface and deep ocean 13c records suggests a preformed component in the deep ocean 13c signal on the other hand the sedimentological results display a strong linkage to changing conditions in the overlying surface ocean waters suggesting this proxy better reflects the activity of the moc at least during the holocene of this region the most widespread oceanic perturbation coincides with an interval of possibly global climatic deterioration around 2700 years ago these results firmly establish deep water production in the nordic seas as a key component in the assortment of variables affecting climate during the holocene

late pleistocene and holocene alluvial archives in the southwestern mediterranean changes in fluvial dynamics and past human response abstract cohesive floodplains from the semiarid southwestern mediterranean morocco tunisia exhibit excellent preservation toward lateral erosion and present a continuous record of late pleistocene and holocene flood dynamics holocene mean sedimentation rates and 14 c cumulative probability plots from cohesive tunisian floodplain sequences reveal a coupling with north atlantic bond events short term periods of fluvial activity match well with north atlantic coolings the findings indicate a strong climatic link from 4 8 ka until today unlike fluvial archives from the humid mid latitudes semiarid southwest mediterranean alluvial archives exhibit phases of increased fluvial dynamics under generally drier conditions the 14 c cumulative probability plot of archeological sites in mediterranean north africa indicates correlations with alluvial records therefore prehistoric societies seemed to be very sensitive to past shifts in landscape dynamics

north african paleodrainage discharges to the central mediterranean during the last 18 000 years a multiproxy characterization using elemental geochemistry clay mineralogy grain size end member modeling and planktonic foraminiferal 18o we characterize the provenance of central mediterranean sediments over the past 18 ka the provenance is dust dominated before and after the african humid period ahp by contrast during the ahp 11 5 ka largely concurrent with organic rich sapropel s1 formation it is predominantly riverine from north african sources such fluvial supply is suggested to come from paleodrainage networks that were reactivated by intensified monsoon precipitation during the ahp the supply is characterized by high mg al and smectite contents and has been accompanied by considerable freshwater influx as indicated by the enhanced grain size and lighter foraminiferal 18o the clay mineral assemblages in our core and in nearby cores correspond with a provenance from the libyan tunisian margin mainly via the paleo river irharhar the inferred fluvial discharge is strongest during the late ahp 8 5 5 ka coinciding with reported enhanced fluvial dynamics and wettest conditions over western libya and tunisia algeria this period is not only synchronous with the largest extension of open water bodies in north africa and lowest saharan dust inputs but also consistent with precipitation records of the west african monsoon moreover our records show a remarkable correspondence with that of a paleodrainage system towards the atlantic west african margin inferring a common headwater region in the central saharan mountains and a similar climate mechanism taken together we suggest a dominant control of north african humid surfaces on the paleodrainage delivery modulated by groundwater level in response to the insolation driven west african monsoon precipitation

holocene climate and cultural evolution in late prehistoric early historic west asia abstract the precipitation climatology and the underlying climate mechanisms of the eastern mediterranean west asia and the indian subcontinent are reviewed with emphasis on upper and middle tropospheric flow in the subtropics and its steering of precipitation holocene climate change of the region is summarized from proxy records the indian monsoon weakened during the holocene over its northernmost region the ganges and indus catchments and the western arabian sea southern regions the indian peninsula do not show a reduction but an increase of summer monsoon rain across the holocene the long term trend towards drier conditions in the eastern mediterranean can be linked to a regionally complex monsoon evolution abrupt climate change events such as the widespread droughts around 8200 5200 and 4200 cal yr bp are suggested to be the result of altered subtropical upper level flow over the eastern mediterranean and asia the abrupt climate change events of the holocene radically altered precipitation fundamental for cereal agriculture across the expanse of late prehistoric early historic cultures known from the archaeological record in these regions social adaptations to reduced agro production in both dry farming and irrigation agriculture regions are visible in the archaeological record during each abrupt climate change event in west asia chronological refinement in both the paleoclimate and archaeological records and transfer functions for both precipitation and agro production are needed to understand precisely the evident causal linkages

sedimentation and soil formation phases in the ghardimaou basin northern tunisia during the holocene chronological and stratigraphical interpretations as well as 14c dates and geoarchaeological investigations of detailed profiles from the mid medjerda valley northern tunisia allow us to reconstruct one late pleistocene and four holocene sedimentation cycles within the floodplain area initial results from pedological examinations including thin sections indicate a latest pleistocene and three holocene soil formation periods our observations from the medjerda valley are discussed in relation to current research in the southwestern mediterranean region the crise romaine shown in the headwaters of the medjerda river system by thick cobble accumulations is exhibited in the basin region by a clear accentuation of the water level amplitude catastrophic flooding can be observed for the first time in the late roman period after soil formation during middle ages ending at about 450 bp flooding again increased

abrupt temperature changes in the western mediterranean over the past 250 000 years a continuous high resolution western mediterranean sea surface temperature sst alkenone record spanning the past 250 000 years shows that abrupt changes were more common at warming than at cooling during marine isotope stage mis 6 sst oscillated following a stadial interstadial pattern but at lower intensities and rates of change than in the dansgaard oeschger events of mis 3 some of the most prominent events occurred over miss 5 and 7 after prolonged warm periods of high stability climate during the whole period was predominantly maintained in interglacial interstadial conditions whereas the duration of stadials was much shorter

impacts of sediment connectivity on holocene alluvial records across a mediterranean basin guadalentin river se spain two contiguous alluvial valleys maria and guadalupe sectors of the upper guadalentin river se spain show distinct holocene alluvial architecture cut and fill nested and stepped fill terraces revealing a strong control of valley morphology and bedrock barriers on sediment delivery storage and preservation the headwater valley maria sector preserves four morphosedimentary alluvial units corresponding to two palaeogeographic stages morphosedimentary unit msu1 the most extensive is a major depositional valley infill dominated by sand and silt texture showing three stratigraphic sets dated 9000 8500 5300 4800 4000 3000 cal bp this vertically stacked alluvial accumulation occurs upstream of a narrow bedrock channel that limited sediment connectivity with the downstream guadalupe sector between 3000 and 2350 cal bp a 15 m deep incision on msu1 occurred and subsequent cut and fill cycles generated three alluvial terraces dated at 2350 1900 cal bp msu2 1800 700 cal bp msu3 and post 400 years msu4 in the downstream valley guadalupe sector six flights of alluvial terraces msug1 to msug6 were formed by episodic aggradation and quasi continuous incision in response to baselevel changes of the lower guadalentin river during the holocene alluvial chronologies in these two contiguous valleys show out of phase sedimentation periods under low connectivity conditions 9 3 ka and in phase cut and fill cycles after valley re connection post 3 0 ka the late holocene alluvial activity periods also coincide with morpho stratigraphic data from the lower guadalentin indicating that fluvial connectivity throughout the catchment was only completed in the late holocene

sub millennial climate shifts in the western mediterranean during the last glacial period recorded in a speleothem from mallorca spain very few high resolution and directly dated terrestrial archives of the last glacial period exist for the western mediterranean region yet this is a key locality for recording sub millennial north atlantic and mediterranean climate change here we present evidence of effective precipitation changes based on growth history and 13c of calcite in a mallorcan stalagmite that grew between 112 and 48 ka effective precipitation in mallorca appears to have been sensitive to proximal sea surface temperature variations and at certain times ca 76 ka for example changed rapidly from moist to arid conditions in only a few centuries a sea level highstand during marine isotope stage mis 5a interrupted growth regrowth started promptly after this but effective precipitation decreased markedly for much of the later part of mis 5a and also for shorter periods correlative with heinrich events h8 ca 90 ka and h6 ca 65 ka with growth ceasing during h5 ca 48 ka arid episodes in mallorca appear to be expressions of extremely cold periods recorded further north in europe and occur contemporaneously with rapid decreases in greenland temperature copyright 2008 john wiley sons ltd

unravelling fluvial deposition and pedogenesis in ephemeral stream deposits in the vicinity of the prehistoric rock shelter of ifri n ammar ne morocco during the last 100 ka abstract our study focuses on the ephemeral stream deposits of wadi selloum to identify phases of morphodynamic stability pedogenesis and activity flooding in the direct vicinity of the rock shelter of ifri n ammar ne morocco as one of the oldest settlement sites of anatomically modern humans amh in north africa ifri n ammar documents periodical occupations since 170 ka since the discontinuous settlement record may reflect climate forcing with subsequent landscape changes we aim at reconstructing the palaeoenvironmental variability recorded in the ephemeral stream deposits in addition to the use of micromorphological sedimentological geochemical and mineralogical methods the geochronological framework of ephemeral stream deposits was established by the application of different luminescence dating techniques the deposition ages between 102 8 ka and 1 3 0 2 ka span different morphodynamically stable and active phases periods of enhanced aggradation occurred around 100 ka 75 ka 55 ka after the lgm and during the holocene whilst sedimentation ended after 1 3 ka the wadi selloum might be characterised by enhanced flooding during humid phases pedogenesis may be used as environmental indicator for more humid climate conditions during mis 3 palaeo calcisol the early holocene calcisol and the late holocene fluvisol this study thus provides first insights into the palaeoenvironmental changes around the rock shelter of ifri n ammar during the last glacial interglacial cycle

centennial scale late pleistocene to mid holocene synthetic profile of the medjerda valley northern tunisia during the late pleistocene to mid holocene the medjerda river system in mediterranean tunisia shows events of increased flooding and aggradation of relatively coarse overbank deposits geomorphic activity in river systems within this region correlate with aridification of the climate but not with temperature the late pleistocene to mid holocene synthetic profile of the ghardimaou floodplain mid medjerda river indicates fluvial activity from 12 4 to 11 8 6 6 to 6 0 and after 4 8 ka cal bp external correlations imply global and regional causes of the late pleistocene to mid holocene climatic development such as north atlantic deep water formation fluctuations in saharan humidity and impacts of local mediterranean weather phenomena palaeomagnetic records offer additional opportunities to interpret fluvial activity in river systems especially for detecting chronological hiatuses in apparently homogeneous sediment sequences

past hydrological events reflected in the holocene fluvial record of europe abstract a comprehensive database of radiocarbon dated fluvial units in great britain poland and spain has been compiled to investigate the relationship between environmental change flooding and holocene river dynamics following the methodology recently developed by macklin and lewin macklin m g lewin j 2003 river sediments great floods and centennial scale holocene climate change journal of quaternary science 18 101 105 radiocarbon dates in fluvial sequences that coincide with a modification in sedimentation rate or style have been highlighted allowing geomorphologically significant changes in holocene river activity to be identified data analysis has been undertaken at both national and sub national scales and on catchments of different size type and land use history multiple phases of higher flood frequency characterized by accelerated erosion and sediment deposition on floodplains are recognized and compared with a range of climate proxies the relative and varying roles of climate and land use on river dynamics are considered and the value of the database for reconstructing past hydrological events as well as for predicting river response to future environmental change is assessed

fluvial response to climatic and anthropogenic forcing in the moselle drainage basin ne france during historical periods evidence from osl dating the aim of this paper is to study a low energy fluvial system response to natural and anthropogenic forcing during the last two millennia in contrast with longer timescales holocene to quaternary historical sedimentary archives are sparse in such systems which are typically characterized by the predominance of erosion compared with aggradation we studied three main sections in the moselle valley northeastern france by a multi proxy approach combining morphology sedimentology archaeological evidence historical archives and dating the geochronological framework was based on optically stimulated luminescence osl and validated by independent age control the exposed sediments were allocated to different historical periods from roman period to present the first results show that in contrast with many other fluvial systems the moselle and its tributaries did not experience major changes during historical periods climatic changes such as the little ice age had a minor influence on floodplain aggradation e g in grain size or sedimentation rates in the moselle valley and were only able to affect the fluvial style this provides evidence that the reworking of sediments is the main fluvial process at short timescales in the valley floors of the moselle catchment in contrast anthropogenic forcing seems important not only during recent centuries but also since roman times this is suggested by the case study of the metz mazelle section where significant headward erosion and sedimentation were recognized and may be related to human occupation the results therefore point to a need for increasing geoarchaeological and geochronological research in the moselle catchment and similar low energy fluvial systems such research is actually essential to improve the knowledge of the fluvial response to environmental changes during the historical periods and to recognize the respective influence of natural variability and human forcing copyright 2012 john wiley sons ltd

environmental changes during the upper pleistocene holocene in mediterranean ne spain as recorded by the mineralogy and geochemistry of alluvial records abstract landscape evolution and environmental conditions from last glacial maximum lgm to late holocene times were reconstructed from the mineralogical and geochemical characteristics of the alluvial morphochronostratigraphy recorded in bardenas reales natural park ebro basin ne spain alluvial architecture includes a lgm holocene gravelly unit 22 9 ka bp a lower holocene silty muddy unit 9 7 ka bp and an upper holocene sandy unit 5 0 1 ka bp increases in illite smectite mixed layers kaolinite chlorite and modified chemical index of alteration cia as well as the decrease in illite fwhm e are indicators of minor increases in the chemical weathering of the alluvial sediments the results suggest that this area although under broad semiarid conditions underwent the following environmental evolution i an increasing trend in moisture availability in the lower holocene and ii a variable pattern in water disposal at the onset of the upper holocene followed by a decrease in humidity during the last millennium this reconstruction proves the usefulness of mineralogical and geochemical proxies as indicators of rapid environmental changes under mediterranean conditions

fluvial sediments of the algeti river in southeastern georgia an archive of late quaternary landscape activity and stability in the transcaucasian region abstract in order to obtain information about landscape activity and stability during the late quaternary in the transcaucasian region fluvial sediments of the lower algeti river in se georgia were studied by means of geomorphologic sedimentologic and geochronologic methods these investigations show that sediments aggraded by the late pleistocene braided algeti river were strongly incised around the pleistocene holocene transition and subsequently a small scale pattern of diachronous fluvial terraces deposited by the now meandering river developed in the new valley during the holocene prior to ca 3 cal ka bp active phases of river channel aggradation and overbank sedimentation about 6 cal ka bp and 3 4 3 2 cal ka bp can be linked with climate driven vegetation changes i e stronger fluvial dynamics with sedimentation occurred during more arid and colder periods whereas the caucasian holocene climate optimum between 6 and 3 4 cal ka bp was characterized by stable geomorphologic conditions after 3 cal ka bp strongly increased human impact documented by former pollen studies is reflected by the fluvial dynamics as well i e an activity phase of strong overbank sedimentation 2 7 2 1 cal ka bp occurred during a period when forests in the lesser caucasus were burnt down two subsequent activity phases with fluvial sedimentation can be linked with historic events that probably both influenced vegetation distribution of the region i e a period of flourishing of georgia during the middle age and a time of large scale destruction of the country due to a persian invasion at the end of the 18th century ad respectively thus whereas no influence of tectonic events or fluctuations of the caspian sea level on the fluvial dynamics could be detected se georgia shows its fragile character with respect to climate and human driven vegetation changes similar to other semi arid landscapes of the mediterranean region

palaeogeographical and palaeoenvironmental reconstruction of the medjerda delta tunisia during the holocene abstract the progradation of the medjerda delta has been the subject of many studies since the 19th century the scale and the rapidity of this phenomenon interested researchers in various fields early on such as geomorphology geology palaeogeography history archaeology or geoarchaeology indeed the delta prograded by around 10 km over 3 millennia at the time of its foundation supposedly at the end of the 12th century bc the phoenician city of utica was located on a promontory bathed by the sea but the sediments carried by the medjerda progressively sealed the bay leaving the tip of the utica promontory now 10 km inland this area is therefore an exception to the general pattern along the tunisian coast since as over the same period everywhere else there is a regression of the coastline owing to a sea level rise of several decimeters based on multi proxy analyses of two coring transects this paper aims to reconstruct the palaeoenvironments and the palaeogeography of the medjerda delta s progradation since the mid holocene some aspects of which are described in ancient sources the results highlight in particular an episode of high intensity flooding around the 4th century ad which is consistent with episodes of high floods and an increase in sedimentation rates recorded in the watershed at the end of the roman period the gradual abandonment of the city of utica can certainly be related to the activity of the medjerda river but our results show that it is because of an increase of fluvial sediment contribution in connection with an erosive crisis in the headwaters and not because of the change of course of the river which had occurred long before

holocene climate variability and cultural evolution in the near east from the dead sea sedimentary record abstract a comprehensive record of lake level changes in the dead sea has been reconstructed using multiple well dated sediment cores recovered from the dead sea shore interpreting the lake level changes as monitors of precipitation in the dead sea drainage area and the regional eastern mediterranean palaeoclimate we document the presence of two major wet phases 10 8 6 and 5 6 3 5 cal kyr bp and multiple abrupt arid events during the holocene the arid events in the holocene dead sea appear to coincide with major breaks in the near east cultural evolution at 8 6 8 2 4 2 3 5 cal kyr bp wetter periods are marked by the enlargement of smaller settlements and growth of farming communities in desert regions suggesting a parallelism between climate and near east cultural development

climate forcing due to the 8200 cal yr bp event observed at early neolithic sites in the eastern mediterranean we explore the hypothesis that the abrupt drainage of laurentide lakes and associated rapid switch of the north atlantic thermohaline circulation 8200 yr ago had a catastrophic influence on neolithic civilisation in large parts of southeastern europe anatolia cyprus and the near east the event at 8200 cal yr bp is observed in a large number of high resolution climate proxies in the northern hemisphere and in many cases corresponds to markedly cold and arid conditions we identify the relevant archaeological levels of major neolithic settlements in central anatolia cyprus greece and bulgaria and examine published stratigraphic architectural cultural and geoarchaeological studies for these sites the specific archaeological events and processes we observe at a number of these sites during the study interval 8400 8000 cal yr bp lead us to refine some previously established neolithisation models the introduction of farming to south east europe occurs in all study regions thrace macedonia thessaly bulgaria near 8200 cal yr bp we observe major disruptions of neolithic cultures in the levant north syria south east anatolia central anatolia and cyprus at the same time we conclude that the 8200 cal yr bp aridity event triggered the spread of early farmers by different routes out of west asia and the near east into greece and bulgaria

enhanced aridity and atmospheric high pressure stability over the western mediterranean during the north atlantic cold events of the past 50 k y multiproxy paleoenvironmental records pollen and planktonic isotope from ocean drilling program site 976 alboran sea document rapid ocean and climate variations during the last glacial that follow the dansgaard oeschger climate oscillations seen in the greenland ice core records thus suggesting a close link of the mediterranean climate swings with north atlantic climates continental conditions rapidly oscillated through cold arid and warm wet conditions in the course of stadial interstadial climate jumps at the time of heinrich events i e maximum meltwater flux to the north atlantic western mediterranean marine microflora and microfauna show rapid cooling correlated with increasing continental dryness enhanced aridity conceivably points to prolonged wintertime stability of atmospheric high pressure systems over the southwestern mediterranean in conjunction with cooling of the north atlantic

palaeoclimate and palaeoenvironmental responses in the western mediterranean over the last 140 ka evidence from mallorca spain climatic change in the western mediterranean basin over the last 140 ka has been investigated from sediment and soil sequences along the coast of the northeastern part of mallorca spain palaeoclimate and palaeoenvironments are reconstructed from sediment and soil structures marine and terrestrial molluscan fauna grain size distributions mineral magnetics sediment and soil chemistry sem and oxygen isotope values dating is by osl and amino acid geochronometry along with marine molluscan faunal assemblages all oxygen isotope stages and substages from ois 6 to 1 are recorded mean annual temperatures m a t of c 19 2 c for the climatic optimum of the last interglacial compare with c 17 3 c for the present and are associated with high sea level extensive woodland and stable soils although wide temperature ranges are detected during this stage with values as low as c 10 3 c through ois 5d to 5a m a t fluctuated from 8 2 c to 17 9 c low sea level open vegetation effective river activity and aeolian sand and dust deposition characterize 5d and 5b while relatively high sea level and soil development on stable landscapes dominate ois 5c and 5a ois 4 is represented by m a t of c 4 9 c with aeolian sand and loess deposition limited river activity and weak soil development loess deposition persisted into ois 3 but at this time the m a t was c 13 c and with higher humidity and vegetation growth during the lgm ois 2 m a t was c 8 1 c and effective river slope and aeolian processes along with associated with limited vegetation cover were responsible for the most extensive changes in the landscape major rates of change occur during periods of climatic deterioration when the high levels of geomorphic energy were imposed on a landscape undergoing a breakdown of vegetation cover

rivers of the hadramawt watershed yemen during the holocene clues of late functioning recent geoarchaeological investigations have been carried out in the thick silty alluvial formations of the northern hadramawt basin yemen field data was combined with a compilation of palaeoenvironmental records published from arabia and its margins research performed on palaeolakes and other geoarchives indicates that the wet early mid holocene has little in common with the continuously arid period after 5 2 ka bp the data sets allowed the authors to propose new perspectives for the holocene palaeohydrological evolution of southern arabia which was more variable and contrasting than previously thought furthermore these data provide the opportunity to go deeper into the holocene and to present a new precise palaeohydrological framework for the late holocene 7 0e2 0 ka bp river functioning fluvial aquifer dynamics and types of sedimentation are closely related to the rainfall regime length and intensity monsoonal or mediterranean and to the landscape conditions in the upper watersheds the development of fluvial palaeosols in the hadramawt valleys often associated with high levels of the aquifers is clearly in phase with humid periods until the beginning of the first millennium bc 5 9e5 3 4 8e4 5 and 4 0e2 7 ka river behaviour also impacted neolithic and early bronze age settlement systems in this lowland area as phases of floodplain stability favour site location the hyperarid 4 2 ka event is associated with an unprecedented fluvial detrital phase with high energy discharges in the entire hadramawt basin

millennial scale oceanic climate variability off the western iberian margin during the last two glacial periods high resolution palaeoclimate records recovered from the iberian margin in core md95 2040 exhibit large fluctuations in oceanographic conditions over the last 190 ka large scale cooling of the surface ocean is indicated by the presence of the polar planktonic foraminifer neogloboquadrina pachyderma sinistral and in some instances the occurrence of ice rafted debris ird ice rafting episodes were prevalent in both of the last two glacials with greater intensity in stages 2 through 4 than in stage 6 the six youngest heinrich events are well defined during the last glacial but detrital carbonate is absent from heinrich layers hl6 hl5 and hl3 dansgaard oeschger stadial equivalent sub millennial ird deposition events have been detected in particular during stage 3 allowing a good match with the cooling displayed in the greenland ice core gisp2 sea surface temperature off portugal in stage 6 was in general warmer than during the last glacial pointing towards a weaker southward influence of polar water masses ice rafting occurred mainly in mid mis marine isotope stage 6 between 173 and 153 kyr as a group of poorly differentiated short duration quasi continuous events mainly marked by the high abundance of sinistral n pachyderma differences exist in ird composition relative to the last glacial with a reduced canadian derived detrital carbonate component combined with an important contribution of volcanic particles the lower magnitude and higher frequency of these events suggest that the higher temperatures would have induced iceberg waning closer to the source areas

unravelling late pleistocene and holocene landscape dynamics the upper guadalentin basin se spain abstract landscapes in se spain have developed in response to tectonics climate fluctuations and more recently human activity fluvial and colluvial sediments such as river terraces and slope deposits found in the valleys reflect a complex interplay between landscape forming processes investigating these sediment archives we reconstructed landscape evolution for the upper guadalentin basin se spain placing recent erosion processes in a landscape evolution context palaeo lake sediments dated between 17 and 13 8 ka evidence that a late glacial lake existed in the area probably formed by a sudden blockage of the guadalentin river differences in relative height above the floodplain and age between the river terraces of parts of the guadalentin river indicate that they have not been in equilibrium in the late quaternary deposition of river terraces along the upstream part of the river is recorded at 13 and 9 5 ka whereas no evidence of deposition is found for that period along the lower part of the river there episodes of sedimentation occur at 7 5 5 ka 3 4 1 6 0 7 and 0 4 ka this discrepancy is explained by the palaeo lake and its influence on erosion and sedimentation processes through base level changes combining these processes we propose a schematic model of late pleistocene and holocene landscape evolution from the model we can conclude that i the influence of the palaeo lake on deposition and erosion processes both upstream and downstream is evident and for the younger river terraces that ii episodes of deposition seem to coincide in time but iii episodes of erosion in between terrace level aggradation do not coincide and neither do terrace level heights and iv no evidence of deposition is found for the upstream part of the river correlation of erosion and sedimentation episodes with climate change and human impact is discussed although some correlations can be made there is strong evidence that climate was not the main driver of landscape processes we suggest that internal dynamics and local processes are more important drivers for landscape dynamics in the upper guadalentin basin than external and regional factors

links between marine and atmospheric processes oscillating on a millennial time scale a multi proxy study of the last 50 000 yr from the alboran sea western mediterranean sea abstract the large dataset obtained from the extensive study of images core md95 2043 recovered from the alboran sea western mediterranean shows the periodicities and phase relationships of oceanographic and atmospheric processes on a millennial time scale the 1470 yr cycle is the most significant with the exception of the records reflecting climatic or environmental changes on land which show statistically significant 3300 and 8000 frequency bands the investigation of these core records on a millennial scale resolution allows us to establish the evolution of oceanographic and atmospheric mechanisms that influenced the western mediterranean region in the course of the dansgaard oeschger cycles accordingly possible land sea interactions can be identified and situated in the context of the temporal succession of the different climatic processes for instance saharan dust supply from northern africa appears to lead high latitude climate changes suggesting that low latitude feedback processes were involved in forcing the millennial climatic variability in the westernmost mediterranean

flood frequencies reveal holocene rapid climate changes lower moulouya river northeastern morocco current high resolution palaeoenvironmental records reveal short term holocene cool ings one of these major holocene rapid climate changes occurred between 3 2 and 2 7 cal ka bp the sensitivity of river systems vis a vis slight and short term holocene climatic variations is a subject of controversy in the scientific community in this paper we present a 4 0 to 1 4 cal ka bp palaeoflood record from the lower moulouya river northeastern morocco to demonstrate the high sensitivity of semiarid rivers in the southwestern mediterranean towards holocene environmental changes the lower moulouya flood deposits are characterised by thick well stratified predominantly clayey to silty overbank fine sediments these cohesive sediments show evidence of excellent preservation conditions against fluvial erosion and contain a continuous record of mid to late holocene flood sequences the moulouya palaeoflood record can be interpreted in the context of regional and global high resolution proxy data revealing a strong coupling with holocene rapid climate changes the centennial scale moulouya palaeohydrological history will be discussed with palaeoenvironmental data from the same record palaeomagnetics sedimentary charcoal record anthracological analyses snail analyses to generate new ideas about the mid to late holocene hydrological cycle in the southwestern mediterranean the deduced features of pronounced lower moulouya flooding and the decreased fire recurrence during holocene cooling remain somewhat inconsistent with the interpret ation of other palaeohydrological and paleaoecological records from the southwestern mediterranean however enhanced lower moulouya flood frequencies between 3 2 and 2 7 cal ka bp agree with increased floodplain aggradation in other major river systems of mediterranean north africa copyright 2009 john wiley sons ltd

late quaternary fluvial dynamics of the jarama river in central spain the jarama river and its catchment provide a valuable natural archive to study and reconstruct past environmental conditions in central spain this region is highly prone to changes in the hydrological cycle under predicted climate warming in particular with respect to aridity periods rainfall variability and the occurrence of extreme flood events this paper presents 15 exposures covering a time span of the last 44 ka which were documented in the field and of which seven exposures were soil chemical analyzed regarding soil texture organic matter as well as carbonate and iron content ages are based on radiocarbon dating on 32 samples latest holocene sediments were found within the channel belt where permanent remobilization of sediments takes place due to the migration of the meandering river course in more distal floodplain positions sediment sequences show a complex fluvial architecture referring to periods of varying character and intensity of alluviation as well as periods of geomorphic stability indicated by soil formation furthermore sedimentation patterns vary along different river sections aggradations of coarse gravels took place between 40 and 18 ka cal bp over the entire valley floor alluviation of fine material was documented between 17 and 16 at 7 5 between 5 1 and 3 3 at 2 8 between 2 1 and 1 5 at 1 0 and around 0 4 ka cal bp until recent times astonishingly in late holocene times between 4 2 and 3 1 ka cal bp aggradations of coarse gravels even in distal floodplain areas overlap with sedimentation of fine material in adjacent river sections pointing to a complex constellation of parameters involved periods of soil formation were detected around 43 at 31 between 16 and 12 6 after 7 5 until 5 1 between 2 8 and 2 1 and at times after 1 5 ka cal bp phases of geomorphic stagnation were found at 38 ka cal bp and for a duration of 200 years at 3 0 ka cal bp and refer to absent geomorphic or pedogenic processes all these patterns are an expression of the interaction between climatic variations tectonic impulses and human influences a comparison with other terrestrial archives enabled us to reconstruct late pleistocene and holocene palaeoenvironmental conditions on a regional scale and furthermore to link specific stages of floodplain development to prevalent influencing variables thus with emphasis on the fluvial system response a model of a cause and effect relationship is presented that concentrates on rapid climate changes long lasting climatic deteriorations and the role of human interventions

geomorphological dynamic changes during the holocene through ephemeral stream analyses from northwest argentina abstract this paper studies the changes in the geomorphological dynamics recorded in 18 ephemeral streams located on the east side of loma pelada tafi valley a part of the sierras subandinas northwest argentina the applied methodology is based on photointerpretation field survey and descriptions of the holocene alluvial fillings dated by tephras archaeological artefacts and absolute datings the records show a coupled system of slope terrace alluvial fans resulting from the environmental changes of four alternating aggradation degradation stages the oldest stage 1 was generated by climatic causes and covers early to mid holocene ca 13 000 10 000 bp to ca 4200 bp after the incision of these accumulations a new aggradation stage 2 was triggered by anthropogenic activity occurring from right before 2500 bp to the 15th century during that time human occupations of the tafi valley were intense two wetter events occurred around 4200 and 2800 bp in the area related to global cooling phases lastly two more recent phases 3 and 4 are associated with the climatic variability of the lia and the present warm period the results highlight the sensitivity of headwater catchments of dry subtropical mountainous areas to climate changes anthropogenic impact and their relationship with global climatic data