a multi proxy record of holocene climatic change in southwestern spain the laguna de medina cadiz palaeolimnological data diatoms ostracods foraminifera molluscs aquatic pollen and lithology from a radiocarbon dated sediment core from a saline lake the laguna de medina provide the first complete record of holocene lake level change for southwest spain for the last c 9000 cal years the lake has always been relatively shallow but has exhibited marked fluctuations in salinity and water depth especially in the earlier record when oscillations culminate in maximum lake levels from c 6960 6680 cal bp c 6070 5830 bp indicating enhanced early to mid holocene humidity and a mid holocene humidity maximum prolonged shallowing thereafter reflects in part increased aridity in the later holocene lake desiccation followed by a c 800 yr phase zone 2 of major limnological change commencing at c 8000 cal bp c 7200 bp and a number of other abrupt desiccation events are also noteworthy the mid holocene maximum is consistent with widespread evidence for high lake levels around 6000 bp but t

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

naticid drilling predation on gastropod assemblages across the k t boundary in rajahmundry india new evidence for escalation hypothesis abstract one of the important and well documented prey predator interactions in the fossil record is drilling predation done by naticid gastropods which diversified during the cretaceous although drilling frequencies showed fluctuating patterns most of the previous studies argued that naticid drilling predation was less intense during the cretaceous and the modern values were achieved since the paleocene we here present a new dataset of naticid drilling predations involving 31 929 gastropod specimens from the latest maastrichtian infratrappean bed in rajahmundry southern india these specimens belonged to 40 species of 20 families thus representing a spectacular gastropod diversity that was not known until recently from this region we examined 5884 complete or near complete specimens to quantify naticid drilling predation on this assemblage it appeared that drilling frequency was significantly higher from all previous cretaceous values this was true for both assemblage level and lower taxon level results along with high successful drilling and low unsuccessful drilling frequencies site and size stereotypy of drillholes suggest that naticid predators were highly efficient even in the cretaceous predators were prey selective and there was poor correlation between relative abundance and drilling frequency of prey taxa the present maastrichtian assemblage underlies the k t mass extinction level drilling frequency was zero in the straddler prey community in the intertrappean bed found immediately above the k t boundary the absence of any drillhole in surviving prey taxa may be due to sudden reduction in abundance of escalated predators although some prey taxa e g cerithiids continued this emphasizes the role of mass extinction in disrupting predator prey interaction we conclude that naticid drilling induced escalation was already established during the cretaceous and the present find extends the paleobiogeography of naticid predation which was previously reported from the western world up to india

palaeoflood and floodplain records from spain evidence for long term climate variability and environmental changes abstract palaeoflood chronologies from seven spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed these fluvial records were divided in to two sub sets namely atlantic 10 ka record and mediterranean 3 ka record river basins which represent distinct modern hydroclimatic conditions in atlantic basins floods result from intense widespread rainfalls associated with atlantic frontal systems transported by westerly airflow mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems mcss during autumn months evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10 750 10 240 9550 9130 4820 4440 2865 2350 960 790 and 520 290 cal bp despite the different flood producing weather conditions in atlantic and mediterranean rivers the radiocarbon sample clusters overlap and indicate changes in large scale atmospheric circulation and climatic conditions in the iberian peninsula comparison with proxy records of mean temperature for the northern hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases e g the 2650 yr bp climatic event or ad 1590 1650 period of the little ice age radiocarbon dates from aggraded floodplain sediments were clustered at 2710 2320 2000 1830 and 910 500 cal bp the first cluster period is in phase with the timing of slackwater deposition whereas the third 910 500 cal bp occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records it is argued that the 910 500 cal bp floodplain aggradation period reflects the first post roman evidence of environmental change related to generalised land use changes at the catchment scale which produced high sediment load transported to overbank areas during high flows

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

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

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

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

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

middle pleistocene to holocene geochronology of the river aguas terrace sequence iberian peninsula fluvial response to mediterranean environmental change abstract our results from the river aguas basin suggest that fluvial archives travertine and slope deposits provide sensitive resolution records of environmental changes during the last 170 kyr from the chronostratigraphic data sets we have established a model of middle and late pleistocene river response for littoral basins on the southern iberian peninsula u th and osl dating indicate the major periods of travertine formation of the alfaix travertine platform which range from 169 to 26 kyr at least four incision events interrupted this aggradation period between 167 and 148 kyr between 148 and 110 kyr around 95 kyr and at 71 kyr aggradation ceased after 26 kyr and incision occurred during ois 2 subsequently the terraces t4a and t4b were deposited osl dating of the t4a channel deposit provides maximum ages of 28 20 and 18 kyr however short climatic events such as the younger dryas produced two more river incision episodes during ois 2 nonetheless for river systems influenced by tectonics climate and sea level changes it is difficult to assess the weight of each controlling factor regarding the three mechanisms of pleistocene river dynamics in middle size catchment areas of the littoral region of southeastern spain our results support the hypothesis that large scale tectonics triggered the general downcutting trend whereas the main aggradation and incision phases occurred during periods of major sea level changes over short time scales the influence of climate variability as documented by pollen records plays a decisive role thus the river responses to the three cyclic mechanisms operate at different time scales although synergetic processes should be considered with respect to the magnitude of abrupt incision aggradation events

mid and late holocene fluvial chronology of tunisia abstract regarding fluvial response to recent climate change it is important to identify and understand previous changes of fluvial dynamics related to past climatic shifts in this paper periods of increased flood activity in central tunisian river systems are presented changes in holocene flood dynamics are reconstructed through a comprehensive analysis of 195 radiocarbon dates from alluvial archives holocene floodplain deposits in central tunisia normally consists of cohesive overbank fines which exhibit excellent preservation conditions against lateral erosion and therefore permit chronostratigraphic records of the entire holocene at most based on published radiocarbon dates two 14 c cumulative probability density plots are created for central tunisia the former represents activity dates indicating phases of increased fluvial dynamics the latter documents stability dates showing periods of soil formation and enhanced landscape stability within the floodplain and the catchment due to geomorphological considerations activity dates and stability dates should be mutually exclusive there is a good match for the mid holocene with increased periods of flooding from 6 2 to 6 0 4 8 to 4 5 4 1 to 3 7 and 3 3 to 3 0 ka these flood periods coincide with low soil formation signals on the other hand periods of increased alluvial soil formation from 6 8 to 6 6 5 9 to 4 8 4 5 to 4 1 3 7 to 3 3 3 0 to 2 8 and 1 8 to 1 6 ka coincide with periods of low flood plain aggradation the data reveal a coupling with north atlantic cooling short term periods of enhanced fluvial dynamics in central tunisia match well with north atlantic cooling the findings indicate a strong climatic link from 4 7 ka until today compared to the holocene floodplain dynamics in tunisian drylands the temperate mid latitudes show mid holocene switches in fluvial dynamics with opposite signs especially after 5 ka north atlantic driven flooding in the temperate central european river systems contrast sharply to flood dynamics in arid to semiarid mediterranean tunisia while under temperate climate conditions floodplain sedimentation decreases it increases under more arid conditions this may indicate that fluvial archives of dissimilar climatic zones reveal different threshold values and sedimentation patterns and therefore different responses to climatic shifts

chronostratigraphy site formation processes and pollen record of ifri n etsedda ne morocco abstract the rock shelter of ifri n etsedda is located at the southern flank of the kebdana mountains north east morocco at an altitude of around 300 m a s l twenty one radiocarbon ages attest an occupation of the shelter between 10 0 and 6 0 ka cal bp comb decorated pottery also known from other late neolithic sites of the area suggest a later occupation the presence of both epipalaeolithic and neolithic deposits offers the opportunity to study the neolithic transition in the area although the ifri n etsedda deposits contain a short hiatus next to the ifri oudadane shelter west of the melilla peninsula it is one of the few sites in the area allowing this approach the paper combines stratigraphic sedimentological and micromorphological studies in order to reconstruct the complex site formation processes pollen analysis offers exciting insights into environmental change human land use and subsistence strategies a short overview about the artefact assemblage allows the reconstruction of occupation history and a first placement of the site within the archaeological context of the area the epipalaeolithic occupation seems to be clearly bipartite and the ongoing study of the lithic assemblage promises the possibility of further subdivision in the area for the first time discontinuities of the epipalaeolithic might be connected to early holocene rapid climate change events rcc the neolithic occurred at about 7 2 ka cal bp marked by the appearance of pottery perforated snails ovicaprides and cereals hunting gathering and the use of terrestrial molluscs still played an important role during the neolithic as the main occupation phase the late early neolithic between 6 7 to about 6 0 ka cal bp appears striking similarities to other contemporary sites such as el zafrin at the nearby coast and the mtlili open air sites within the lower reaches of the moulouya river suggest that ifri n etsedda is part of a larger settlement cluster providing particular adaptations to mountainous landscapes

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

paleoflood hydrology origin progress prospects from an origin in diverse studies of flood geomorphology and quaternary geology paleoflood hydrology emerged as a geophysical and an applied hydrological science during the 1970s and 1980s since acquiring its formal name in 1982 the most productive approach in paleoflood hydrology has become energy based inverse hydraulic modeling of discrete paleoflood events recorded in appropriate settings as slackwater deposits and other paleostage indicators swd psi or as various threshold indicators of non exceedence technological advances particularly in hydraulic modeling and geochronology were instrumental in moving the discipline to its present status the most recent advances include 1 new techniques for the accurate geochronology of flood sediments notably tams radiocarbon analyses and osl dating and 2 the phenomenal increase in computer power that allows complex hydraulic calculations to become feasible for routine studies from its initial demonstration in the southwestern united states swd psi paleoflood hydrology proved its widespread applicability to various landscape environments particularly important studies have been accomplished in australia china india israel south africa spain and thailand paleoflood hydrology has also generated its share of controversy in part because of the differing viewpoints and attitudes of the two scientific traditions from which it emerged quaternary geology geomorphology versus applied hydrologic hydraulic engineering nevertheless the future growth of the discipline is assured given the rapid pace of discoveries that it engenders indeed so many international studies exist that it is appropriate to pursue global syntheses to address interesting and timely questions of extreme flood phenomena in relation to global climatic change

palaeoflood record of the tagus river central spain during the late pleistocene and holocene abstract palaeoflood hydrology of the tagus river central spain was reconstructed from slackwater deposits and palaeostage indicators in two canyon reaches located at el puente del arzobispo in the central part of the catchment 35 000 km 2 in drainage area and in alcantara at the lower part of the catchment 52 000 km 2 in drainage area near the portuguese border the palaeoflood record with more than 80 flood events shows clusters of floods at specific periods from 9440 to 9210 14 c yr bp 8540 8110 bc 8500 to 8000 14 c yr bp 7500 7000 bc 6750 14 c yr bp 5000 bc 1200 to 950 14 c yr bp ad 785 1205 410 14 c yr bp ad 1450 1500 170 to 80 14 c yr bp ad 1670 1950 the largest flood s occurred during the periods 9440 to 9210 14 c yr bp 6750 14 c yr bp and 1200 to 950 14 c yr bp reaching minimum discharge estimates of between 4000 and 4100 m 3 s 1 in the el puente del arzobispo reach and 13 700 15 000 m 3 s 1 in the alcantara reach these periods with increased flood magnitude and or frequency in the tagus river are strongly related to increased moisture influx and winter precipitation in the iberian peninsula especially in the western zone proxy records sensitive to winter precipitation such as lake levels and vegetation changes indicated by pollen records are in good agreement with the clusters of floods found in the tagus river this flood variability seems to correspond to changes in the prevailing atmospheric circulation pattern affecting the iberian peninsula

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

river braiding caused by rapid floodplain deformation insights from holocene dynamics of the jarama river in central spain abstract in this paper we will use an illustrative example to show the significance of rapid vertical movements inside floodplains as well as varying discharge values for the alteration of channel and sedimentation patterns during the holocene concerning such relationships well documented and well dated references from sedimentary records are rather rare the developments within the lower jarama valley have been significantly supported by an interaction of tectonic activity evaporite dissolution and halokinetics that initiated rapid vertical movements over short distances and caused the formation of knick points and gradient changes along the longitudinal floodplain profile furthermore the specific mediterranean climate caused highly variable discharges including extreme runoff peaks the juxtaposition of different floodplain gradients gave rise to spatial and temporal changes of discharge patterns and channel geometry which is reflected by varying sedimentation as well as erosion patterns we have been able to confirm that alluvial thickening due to intense dissolution and subsidence has been a characteristic and frequently recurring feature during the pleistocene moreover we want to emphasize that also during the holocene gradient adjustments exercised controlling influence on fluvial dynamics in particular with regard to channel response in fact we found consistency between low and moderate gradients and meandering single channel patterns associated with overbank deposition in distal floodplain positions only a section with stronger inclination revealed evidences for multiple channel discharge patterns in form of gravelly braided river deposits in comparison with recent discharge patterns and information from historical sources it appears that braided river deposition took place just within a short time frame between 5 and 3 ka cal bp this matches exactly a period of strong climatic aridity including highly variable precipitation and discharge patterns from that we conclude that in the first instance gradient changes promoted the change of channel and discharge patterns but however specific overlap of the parameters gradient and runoff is considered to have been necessary to generate braided discharge pattern a subsequent formation of braided patterns during the late holocene was presumably prevented by river entrenchment as well as a strong increase of sediment availability during the time of roman colonization on the basis of this study we can establish a number of general relationships between floodplain gradient runoff pattern and channel response during the holocene period that may help us to better understand fluvial behavior in various different areas

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

a high resolution late holocene palaeo environmental record from the central adriatic sea a multi proxy study of a holocene sediment core rf 93 30 from the western flank of the central adriatic in 77 m of water reveals a sequence of changes in terrestrial vegetation terrigenous sediment input and benthic fauna as well as evidence for variations in sea surface temperature spanning most of the last 7000 yr the chronology of sedimentation is based on several lines of evidence including ams 14c dates of foraminifera extracted from the core palaeomagnetic secular variation pollen indicators and dated tephra the temporal resolution increases towards the surface and for some of the properties measured is sub decadal for the last few centuries the main changes recorded in vegetation sedimentation and benthic foraminiferal assemblages appear to be directly related to human activity in the sediment source area which includes the po valley and the eastern flanks of the central and northern appenines the most striking episodes of deforestation and expanding human impact begin around 3600 bp late bronze age and 700 bp medieval and each leads to an acceleration in mass sedimentation and an increase in the proportion of terrigenous material reflecting the response of surface processes to widespread forest clearance and cultivation although human impact appears to be the proximal cause of these changes climatic effects may also have been important during these periods signs of stress are detectable in the benthic foram morphotype assemblages between these two periods of increased terrigeneous sedimentation there is smaller peak in sedimentation rate around 2400bp which is not associated with evidence for deforestation shifts in the balance between terrigenous and authigenic sedimentation or changes in benthic foraminifera the mineral magnetic record provides a sensitive indicator of changing sediment sources during forested periods of reduced terrigenous input it is dominated by authigenic bacterial magnetite whereas during periods of increased erosion anti ferromagetic minerals haematite and or goethite become more important as well as both paramagnetic minerals and super paramagnetic magnetite analysis of the alkenone u37k record provides an indication of possible changes in sea surface temperature during the period but it is premature to place too much reliance on these inferred changes until the indirect effects of past changes in the depth of the halocline and in circulation have been more fully evaluated the combination of methods used and the results obtained illustrate the potential value of such high resolution near shore marine sedimentary sequences for recording wide scale human impact documenting the effects of this on marine sedimentation and fauna and potentially disentangling evidence for human activities from that for past changes in climate

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

holocene atmosphere ocean interactions records from greenland and the aegean sea we compare paleoclimate proxy records from central greenland and the aegean sea to offer new insights into the causes timing and mechanisms of holocene atmosphere ocean interactions a direct atmospheric link is revealed between aegean sea surface temperature sst and high latitude climate the major holocene events in our proxies of aegean sst and winter spring intensity of the siberian high gisp2 k record follow an 2300 year spacing recognised also in the 14c record and in worldwide holocene glacier advance phases suggesting a solar modulation of climate we argue that the primary atmospheric response involved decadal centennial fluctuations in the meridional pressure gradient driving aegean sst events via changes in the strength duration and or frequency of northerly polar continental air outbreaks over the basin the observed natural variability should be accounted for in predictions of future climate change and our timeframe for the aegean climate events in addition provides an independent chronostratigraphic argument to middle eastern archaeological studies

investigating extreme flood response to holocene palaeoclimate in the chinese monsoonal zone a palaeoflood case study from the hanjiang river abstract palaeoflood events recorded by slackwater deposits swds were investigated extensively by sedimentological criteria of palaeohydrology along the upper hanjiang river valley modern flood swds were collected for comparison with palaeoflood swd in the same reaches three typical palaeoflood swds were observed within holocene loess soil blanket on the first river terrace land the grain size distributions of palaeoflood swds are similar to modern flood swds whereas they are different from eolian loess and soil palaeoflood swd lies in three major pedo stratigraphic boundaries ts l 0 l 0 s 0 and s 0 l t in the holocene loess soil profiles the chronology of three palaeoflood episodes was established by osl dating and pedo stratigraphic correlation with the well dated holocene loess soil profiles in the upper hanjiang river basin holocene palaeoflood events were dated to 9500 8500 3200 2800 and 1800 1700 a b p respectively palaeoflood discharges were estimated by the palaeoflood model i e slope area method and step backwater method the highest discharges are 51 680 53 950 m 3 s 1 at the 11 500 time scale in the xunyang reach of the upper hanjiang river valley holocene extraordinary hydroclimatic events in the hanjiang river often result from abnormal atmospheric circulations from southwest monsoons in the chinese monsoonal zone these results provide a regional expression of extreme flood response to holocene palaeoclimate to understand the effects of global climatic variations on the river system dynamics

holocene molluscan succession from ne morocco palaeoenvironmental reconstruction and biogeographical implications abstract fluvio lacustrine holocene sequences from the semi arid region of eastern morocco are rich in shells and show similar sedimentary levels that could correspond to synchronous environmental variations the high diversity of moroccan continental malacofaunas makes them a very suitable fossil group for palaeoenvironmental reconstructions and palaeobiodiversity implications the malacological study of blirh is the first in morocco to be based on a systematic sampling providing a complete faunal record in order to reconstruct palaeoenvironmental successions three biozones have been recognized they illustrate occurrence of a marsh and a lake from shortly before 10 600 cal bp followed by an abrupt drying up around 5000 cal bp this dramatic environmental change is not synchronous with lithological variations as stated by previous studies based on geological and palynological records the blirh lacustrine phase fits into the humid period that follows full glacial hyperarid conditions during the latest pleistocene in north africa from 14 800 cal bp the abrupt shift to dry conditions around 5000 cal bp inferred from the malacological succession correlates with the contraction of saharan lakes during the last biozone despite disappearance of the main water body marshy species persist and demonstrate occurrence of very wet environments in the middle moulouya plateau until historical times several species currently absent from the region were found within the holocene assemblages at least two new species of aquatic molluscs hydrobiidae have been discovered sampling of modern malacofaunas from wells and springs in the area has demonstrated that one of them is still living in the water table the blirh malacological record provides an insight of the palaeo biogeographical changes affecting this group during the holocene and demonstrates the very recent increase of human impact on the regional biodiversity

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

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

millennial surface water dynamics in the ria de vigo during the last 3000 years as revealed by coccoliths and molecular biomarkers a combined study of coccolith assemblages and biomarkers in a gravity core collected from the ria de vigo nw spain allowed us to reconstruct the paleoenvironmental conditions for the last 3000 years the quantitative distribution of coccolithophore species points to three different intervals within the core dated by ams radiocarbon measurements the first interval ca 975 bc 252 ad characterized by high abundances of calcidiscus leptoporus and gephyrocapsa muellerae i s thought to represent moderate water temperatures suggesting a transition from a warmer to a cooler period the second interval ca 252 1368 ad characterized by the dominance of coccolithus pelagicus helicosphaera carteri and syracosphaera spp and a high concentration of hexacosanol linked to terrestrial input is interpreted as having been a humid period with fluvial input the third interval ca 1368 ad 1950 is characterized by a high abundance of gephyrocapsa oceanica high alkenone values and low values of hexacosanol and is thought to represent a period dominated by oceanic conditions within the ria taking into account the ocean atmospheric system affecting the region studied here we propose an alternation in the mean state of north atlantic oscillation nao at millennial time scales awell developed upwelling system and an active ria ocean connection during the warmer interval i suggest a nao phase influenced by a hypsithermal period the occurrence of the humid and relatively warm interval ii is consistent with a negative phase in the nao as well as a relative restriction in ocean ria exchange interval iii which was drier and more productive again suggests the dominance of a positive phase in the nao with a more intense oceanic connection and more energized upwelling d 2004 elsevier b v all rights reserved

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

determining the sun s influence on lateglacial and holocene climates a focus on climate response to centennial scale solar forcing at 2800 cal bp abstract the influence of solar variability on the climate of the lateglacial and holocene periods has been the subject of increasing discussion during the last decade in the mid holocene several studies have identified cold wet events that occur at ca 2800 cal bp and a link with a reduction in solar activity inferred from the 14c record has been postulated we present results from a multi proxy study of peat humification plant macrofossils and testate amoebae from a raised bog at glen west northwest ireland that indicate that dry bog surface conditions were experienced in the north of ireland at the time of the solar anomaly starting at 2800 cal bp with the aid of 14c wiggle matching and tephrochronology an abrupt shift to wetter conditions is dated to ca 2700 cal bp coinciding with a 14c maximum but clearly post dating the 2800 cal bp event identified elsewhere in europe we explore the significance of this apparent lag in the irish record considering the possible role of the ocean in generating spatial and temporal complexities in the climate patterns of the north atlantic region we conclude that these complexities are likely to give rise to time transgressive climate responses around the north atlantic that will only be recognised by more critical chronological approaches

holocene alluvial morphopedosedimentary record and environmental changes in the bardenas reales natural park ne spain abstract a holocene alluvial morphostratigraphy based on geomorphological mapping sedimentological analysis soil development and radiocarbon chronology is presented for the semiarid blanca basin in the bardenas reales natural park ne spain four morphopedosedimentary alluvial units mu1 mu2 mu3 and mu4 were differentiated which may correspond to two palaeogeographical stages the first one includes the morphopedosedimentary unit mu1 and is the most extensive in the area it is made up of a complex aggradation fill up sequence comprising a braided channel system a sand mud flat 9200 7900 cal bp and a playa lake environment related to a nearly closed depression an intensive fluvial entrenchment period is recognized leading the opening of the blanca basin before the second stage that includes the units mu2 mu3 and mu4 this set of units forms a sequence of cut and fill and nested fill terraces recording the alluvial activity in the blanca basin during the last 6 ka the mu2 unit 5900 3300 cal bp in age represents a period of high geomorphic instability with rapid alluvial sedimentation channel incision oscillating changes on the other hand the mu3 unit has an age of 1050 500 cal bp and appears as a thin extensive alluvial cover overlying previous units finally the mu4 unit comprises superposition of numerous flood depositional sequences centimetric in scale dated from 450 10 cal bp the established soil chronosequence supports the numerical chronology of the four units these accumulation periods mu1 mu2 mu3 mu4 are associated with dry phases and or high hydrological variability floods and droughts at a regional scale changes on the north atlantic atmospheric circulation mode over southern europe may provide the key to explain the nature of alluvial activity during holocene in bardenas reales

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

the geothermal gradient of io consequences for lithosphere structure and volcanic eruptive activity we solve numerically the equations describing the transfer of heat through the lithosphere of io by a mixture of conduction and volcanic advection as proposed by o reilly and davies o reilly t c davies g f 1981 geophys res lett 8 313 316 removing the requirement that average material properties must be used as expected the dominance of advective heat transfer by volcanic eruptions means that io s geothermal gradient well away from volcanic centres is very small of order 1 k km 1 this result is independent of any reasonable assumptions about the radiogenic heating rate in the lithosphere the lithosphere temperature does not increase greatly above the surface temperature until the base of the lithosphere is approached except in limited areas around shallow magma bodies as a consequence solid volatile sulphur compounds mobilized by volcanic processes and re deposited on the surface of io commonly remain solid until they reach great depths as they are progressively buried by ongoing activity for current estimates of the volcanic heat transfer rate melting of so2 does not begin until a depth of 20 km and sulphur remains solid to a depth of 26 km in a 30 km thick lithosphere rising magmas can incorporate fluids from these deep sulphur compound aquifers and we quantify the major influence that this can have on the bulk density of the magma and hence the resulting possible intrusion and eruption styles

variability in terrigenous sedimentation processes off northwest africa and its relation to climate changes inferences from grain size distributions of a holocene marine sediment record variations in deposition of terrigenous fine sediments and their grain size distributions from a high resolution marine sediment record offshore northwest africa 30 51 0 n 10 16 1 w document climate changes on the african continent during the holocene end member grain size distributions of the terrigenous silt fraction which are related to fluvial and aeolian dust transport indicate millennial scale variability in the dominant transport processes at the investigation site off northwest africa as well as recurring periods of dry conditions in northwest africa during the holocene the terrigenous record from the subtropical north atlantic reflects generally humid conditions before the younger dryas during the early to mid holocene as well as after 1 3 kyr bp by contrast continental runoff was reduced and arid conditions were prevalent at the beginning of the younger dryas and during the mid and late holocene a comparison with high and low latitude holocene climate records reveals a strong link between northwest african climate and northern hemisphere atmospheric circulation throughout the holocene due to its proximal position close to an ephemeral river system draining the atlas mountains as well as the adjacent saharan desert this detailed marine sediment record which has a temporal resolution between 15 and 120 years is ideally suited to enhance our understanding of ocean continent atmosphere interactions in african climates and the hydrological cycle of northern africa after the last deglaciation

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

evidence for enhanced mediterranean thermohaline circulation during rapid climatic coolings molecular biomarkers c37 alkenones n nonacosane and n hexacosanol and toc are used together with benthic 18o and 13c data to document the hydrographic response of the western mediterranean sea to rapid climatic variability these proxies are recorded in core md 95 2043 alboran sea affording the study of the dansgaard oeschger d o and heinrich he variability during the last glacial period the results suggest that rapid changes in the western mediterranean thermohaline circulation occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation occurred during cold intervals he and d o stadials probably driven by a strengthening of north westerly wind over the north western mediterranean sea in contrast decreased intensity of the thermohaline circulation is detected during warm intervals d o interstadials which led to low oxygenated deep water masses and better preservation of the organic matter in the sediment

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

a long term flood discharge record derived from slackwater flood deposits of the llobregat river ne spain abstract slackwater palaeoflood deposits were identified along two bedrock gorge study reaches of the llobregat river at pont de vilomara and monistrol de montserrat the compiled palaeoflood record consists of two principal flood series a a relatively complete record of low to high magnitude flood events from the last ca 100 years and b evidence of the largest palaeoflood events that have occurred over the last ca 2700 years the longer term extreme palaeoflood record indicates that the discharge of the 1971 flood the largest on record was exceeded on at least eight occasions with two periods of high magnitude flooding identified a the late bronze age 2500 2700 years ago and b the little ice age ad 1500 1700 at pont de vilomara palaeodischarge estimates of 3700 4300 m 3 s compare to a discharge of 2300 m 3 s for the 1971 event downstream at monistrol an estimate of 4680 m 3 s for flood deposits dated as ad 1516 1642 and believed to be those of the ad 1617 flood compared to 2500 m 3 s for the 1971 flood

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

a lower pleistocene to holocene terrestrial record from the eskisehir graben central anatolia paleoclimatic and morphotectonic implications abstract as one of the rare terrestrial archive with continuous sedimentation back to almost 1 ma in anatolia the eskisehir graben was investigated in outcrops and cores by multi proxy analysis regarding chronology and paleoclimatology the present study comprises significant implications for both the impact of climate changes on fluvial systems in the timescales of the milankovitch band and the controversial age and rate of the crustal extension in western anatolia our findings indicate that loi950 and 18ocarb which are indicators for the amount of soil carbonate and paleo temperature respectively are collectively capable of distinguishing between glacial and interglacial periods in the predominantly floodplain deposits of the graben infill secondarily loi550 and 13ccarb values further help this discrimination via primary production and composition of vegetation cover respectively pollen data albeit highly discontinuous due to poor preservation under subaerial conditions point out a steppe like vegetation cover where the forest components expand particularly in the wet interglacial periods in the other hand the chronological frame provided by astronomical calibration of certain proxy records strongly suggest that the eskisehir fault zone initiated as a boundary fault of a half graben some 900 ka the rate of vertical movement on its southern branch since the last 70 ka is unexpectedly high 2 3 mm a a phenomenon that requires urgent risk assessment analysis in the vicinity of the eskisehir city

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

holocene vegetation dynamics fire and grazing in the sierra de gador southern spain this paper examines the mid to late holocene c 6850 1160 cal yr bp environmental history of sierra de gador in southern spain the local vegetation dynamics are reconstructed through the palaeoecological record obtained from a lacustrine deposit situated at 1530 m various hypotheses are considered to explain the vegetation dynamics apparent in the palaeoecological evidence including climatic change fire occurrence and human activity although the vegetation in this region is sensitive to climatic change threshold events driven by ecological factors are also apparent climatic events include a thermo mesophytic optimum with abundance of deciduous trees and maximum lake water level found from c 6850 to 5500 cal yr bp in contrast changes in the frequency of major fire episodes appear to have shaped interspecific relationships and vegetation change especially from c 4200 cal yr bp onwards biotic properties of the ecosystem such as the inertia of established tree populations interconnected wit

response of extreme floods in the southwestern united states to climatic variations in the late holocene a regional synthesis of paleoflood chronologies on rivers in arizona and southern utah reveals that the largest floods over the last 5000 years cluster into distinct time periods that are related to regional and global climatic fluctuations the flood chronologies were constructed using fine grained slackwater deposits that accumulate in protected areas along the margins of bedrock canyons and selectively preserve evidence of the largest events high magnitude floods were frequent on rivers throughout the region from 5000 to 360014c yrs bp dendrocalibrated age 3800 2200 bc and increased again after 2200 bp 400 bc with particularly prominent peaks in magnitude and frequency around 1100 900 bp ad 900 1100 and after 500 yrs bp ad 1400 in contrast the periods 3600 2200 bp 2200 400 bc and 800 600 yrs bp 1200 1400 ad are marked by sharp decreases in the occurrence of large floods on these rivers in the modern record storms that generate large floods 10 year in the region fall into three categories 1 winter north pacific frontal storms 2 late summer and fall storms that draw in moisture from recurved pacific tropical cyclones and 3 summer storms mainly convective thunderstorms winter storms and tropical cyclones are associated with the most severe floods on the rivers in this study and are the most probable causes of the paleofloods over the last 5000 years floods from both winter storms and tropical cyclones occur when deep mid latitude troughs steer storm systems into the region composite anomaly maps of daily 700 mbar heights indicate that these floods are associated with a low pressure anomaly off the california coast and a high pressure anomaly over the aleutians or gulf of alaska a strong connection exists between the negative phase of the southern oscillation index often associated with el nin o conditions and the large floods associated with winter storms and tropical cyclones the paleoflood records confirm the existence of centennial scale variations in the conditions conducive to the occurrence of extreme floods and flood generating storms in this region the episodes with an increased frequency of high magnitude floods coincide with periods of cool wet climate in the western u s whereas warm intervals such as the medieval warm period are times of dramatic decreases in the number of large floods a positive relationship between the paleofloods and long term variations in the frequency of el nin o events is evident over the last 1000 years this relationship continues over at least the last 3000 years with warm coastal sea surface temperatures indicative of el nin o like conditions

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

vertical accretion sand proxies of gaged floods along the upper little tennessee river blue ridge mountains usa abstract understanding environmental hazards presented by river flooding has been enhanced by paleoflood analysis which uses sedimentary records to document floods beyond historical records bottomland overbank deposits e g natural levees floodbasins meander scars low terraces have the potential as continuous paleoflood archives of flood frequency and magnitude but they have been under utilized because of uncertainty about their ability to derive flood magnitude estimates the purpose of this paper is to provide a case study that illuminates tremendous potential of bottomland overbank sediments as reliable proxies of both flood frequency and magnitude methods involve correlation of particle size measurements of the coarse tail of overbank deposits 0 25 mm sand from three separate sites with historical flood discharge records for the upper little tennessee river in the blue ridge mountains of the southeastern united states results show that essentially all floods larger than a 20 probability event can be detected by the coarse tail of particle size distributions especially if the temporal resolution of sampling is annual or sub annual coarser temporal resolution 1 0 to 2 5 year sample intervals provides an adequate record of large floods but is unable to discriminate individual floods separated by only one to three years measurements of 0 25 mm sand that are normalized against a smoothed trend line through the down column data produce highly significant correlations r 2 values of 0 50 to 0 60 with p values of 0 004 to

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

palynological evidence for environmental and climatic change in the lower guadiana valley portugal during the last 13 000 years pollen analysis of a 48 m ams radiocarbon dated sediment sequence from the guadiana estu ary provides the first record of lateglacial and holocene vegetation history in the algarve province of portugal this paper focuses on the record of terrestrial pollen taxa which document a series of forest expansions and declines during the period 13 000 cal bp to 1600 cal bp and provide insights into climate evolution in southwestern iberia the main vegetation phases identified in the guadiana valley are 1 lateglacial interstadial allerod forest with quercus and pinus under a temperate moist continental cli mate 2 a younger dryas forest decline quercus and expansion of pinewoods xeric scrub and open ground habitats with juniperus artemisia ephedra distachya type centaurea scabiosa type under arid and cold conditions 3 an early holocene forest scrub open ground vegetation mosaic developing under a warm dry and continental climate 4 a maximum of quercus forest and thermomediterranean ever green taxa olea phillyrea pistacia reflecting a warm moist oceanic climate between c 9000 cal bp and c 5000 cal bp and 5 the expansion of shrublands with cistaceae and ericaceae under a drier climatic regime and increasing anthropogenic activity since c 5000 cal bp holocene episodes of maximum cli matic aridity are identified in the record of xerophytic taxa juniperus artemisia ephedra distachya type centred around 10 200 cal bp 7800 cal bp 4800 cal bp 3100 cal bp and 1700 cal bp regional com parisons suggest a correlation of arid phases across southern iberia and northwest africa which can be related to abrupt north atlantic coolings bond events

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