assessment of the impact of climate and anthropogenic factors on holocene mediterranean vegetation in europe on the basis of palaeohydrological records abstract correlations between lake level and river activity records from the western mediterranean and palaeohydrological records from northern africa and central europe suggest a distinction in the western mediterranean region between an early holocene period characterised by cooler and moister conditions than at present favourable to temperate deciduous trees and after 5000 yr bp a later holocene period with a warmer and drier climate the second phase was favourable to the extension of evergreen sclerophyllous trees possibly reinforced by human activities these two successive holocene periods reflect orbitally induced changes in summer insolation furthermore superimposed on this general climatic trend century scale climatic oscillations punctuated the whole holocene period decreases in river activity in the western mediterranean region occurred at ca 11 500 10 500 9000 7000 4000 3000 2000 and 800 cal yr bp these decreases coincided with lake level lowering in jura eastern france and glacier retreat in the northern alps and could be associated with a temporary expansion of sclerophyllous trees this general pattern could have resulted from an alternatingly southward northward displacement of the atlantic westerly jet

maximum flood area during mis 1 in the almenara marshland western mediterranean benthic foraminifera and sedimentary record the sedimentological and micropaleontological analysis of three mechanical cores in the marshland of almenara valencian community spain has allowed the reconstruction of the holocene evolution o

arid and humid phases in southern spain during the last 4000 years the zonar lake record cordoba a multiproxy study of sediment cores from zonar lake 37 29 00 n 4 41 22 w 300 m a s l supported by 11 14c ams dates provides the first high resolution centennial scale reconstruction of past h

climatic change on the iberian peninsula recorded in a 30 000 yr pollen record from lake banyoles the banyoles lacustrine sequence shows that the vegetational history of the northeastern iberian peninsula during the last 30 000 yr follows the north atlantic pattern of climatic oscillations the banyoles pollen diagram supported by two calibrated 14c dates and nine u th dates shows a clear interstadial event between 30 000 and 27 000 yr b p a pleniglacial period with minor oscillations that ended abruptly ca 14 420 410 yr b p and a late glacial sequence that records the classical stages described in northern europe the bolling allerod interstade the younger dryas event at 12 000 yr b p u series age and a short warming phase between the younger dryas and the last cold event dated at 11 000 yr b p u series age

the mesolithic neolithic transition in southern iberia new data and a review of historiographic information from neolithic sites of the malaga and algarve coasts southern iberian peninsula and from the maghreb north africa reveal the existence of a neolithic settlement at least from 7 5 cal ka bp the agricultural and pastoralist food producing economy of that population rapidly replaced the coastal economies of the mesolithic populations the timing of this population and economic turnover coincided with major changes in the continental and marine ecosystems including upwelling intensity sea level changes and increased aridity in the sahara and along the iberian coast these changes likely impacted the subsistence strategies of the mesolithic populations along the iberian seascapes and resulted in abandonments manifested as sedimentary hiatuses in some areas during the mesolithic neolithic transition the rapid expansion and area of dispersal of the early neolithic traits suggest the use of marine technology different evidences for a maghrebian origin for the first colonists have been summarized the recognition of an early north african neolithic influence in southern iberia and the maghreb is vital for understanding the appearance and development of the neolithic in western europe our review suggests links between climate change resource allocation and population turnover

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

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

fluvial changes of the guadalquivir river during the holocene in cordoba southern spain this research was funded by a grant from proyectos de cordoba siglo xxi coordinated by prof r jose roldan canas universidad de cordoba

morphological pedological and sedimentary evolution on the fringe of the southwestern european drylands during the late pleistocene and holocene evidence of climate and land use changes abstract late quaternary alluvial sedimentary units in the guadiana menor river valley a tributary of the guadalquivir river in southern spain are described based on geomorphological mapping sedimentological analysis palaeosol development and radiocarbon chronology four infill units in the valleys were differentiated with surfaces at 45 mu1 70 mu2 8 6 mu3 and 10 m mu4 above the riverbed each unit is capped by a palaeosol unit mu1 late pleistocene 43 5 34 cal kyr bp consists of gravel and sand in channels and bars in braided river systems distally evolving to silty clays in the floodplain with vertic and clayic calcisols it is capped by dark clays with gleysol development representing wetland environments in endorheic basins channelized gravels alternating with sandy silts make up unit mu2 34 24 cal kyr bp capped by a gypsisol and interpreted as a semi arid alluvial fan distally evolving to playa lake depositional systems unit mu3 5600 2700 cal yr bp extending along the valley bottom is represented by gravels and sand distally evolving to a red and white laminated rhythmite of silt and clay deposited in the playa unit mu4 600 700 cal yr bp is scattered and represented by centimetre thick gravels and sand sheet layers deposited by sheet flows in semi arid constrained alluvial fans alternating intervals of alluvial aggradation 43 5 24 kyr bp 5700 2700 cal yr bp late middle ages and fluvial incision 24 6 cal kyr bp 2700 cal yr bp to 1200 ad 1500 ad to present are interpreted as valley responses to climate variations and changes in land use two regional geomorphological changes are recorded in the sediments 1 climate induced aridification after 34 cal kyr bp with an arid climax after 24 cal kyr bp before the incision linked to the last glacial period and 2 two human forced aggradation stages 5600 2700 cal yr bp and 1200 1400 ad interrupting the late pleistocene to early holocene incisional trend

beginnings of olive cultivation in eastern spain in relation to holocene bioclimatic changes morphometric analyses show quantitative differences in anatomical characters of wood and charcoal between wild and cultivated olive samples from modern olive wood in eastern spain levante provide five distinctive anatomical criteria growth width ring vessel surface number of vessels per group vessel density and vulnerability ratio multivariate analysis shows that growth ring width and number of vessels per group are both significant criteria for discriminating between wild and cultivated olive moreover bioclimatic environments of wild olive thermomediterranean and mesomediterranean stages are distinguished by vessel density ancient olive charcoal from archaeological sites at valencia and alicante implies increasing aridification from the cardial neolithic to the roman period this pattern may reflect the onset of a mediterranean climate and human deforestation charcoal from cultivated specimens of early neolithic age shows that the olive tree is the earliest cultivated temperate fruit

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

stratigraphic architecture and alluvial geoarchaeology of an ephemeral fluvial infilling climatic versus anthropogenic factors controlling the holocene fluvial evolution in southeastern spain drylands abstract two stages of depositional high discharge fluvial environments are recorded in the infilling of a rock shelter in a canyon of the segura river namely 1 first stage aggradational alluvial gravels in the lower part interpreted as braided channel bars seventh millennium to 2030 cal bc and 2 second stage slackwater flood deposits in the upper part between 2030 cal bc and after 900 ad during a stage of main channel incision reconstructed flood discharges for the second stage were a minimum of 700 m 3 s extreme palaeofloods that inundated the cave from the canyon inlet were successively higher and are correlated to quick rising flash floods the characteristics of cultural remains preserved by flood deposits reveal long periods of human cave occupation and passage through the canyon without extreme floods occurring these long periods of low discharge fluvial flow punctuated by catastrophic flash floods are linked to a torrential fluvial regime the torrential regime is the current hydrologic and climatic scenario in the streams of semi arid southeastern spain it is discusses the climatic versus anthropogenic factors affecting the fluvial development we conclude that the archaeo fluvial record of the pozo rock shelter indicates that the present day semi arid conditions of the southeastern spain drylands extend back to circa 4000 yr bp methodologically the combination of fluvial palaeohydrology and geoarchaeology appears to be a robust tool to reconstruct long term holocene climate changes

teleconnections between the subtropical monsoons and high latitude climates during the last deglaciation the major deglacial intensification of the southwest monsoon occurred at 11 450 150 calendar years before present synchronous with a major climate transition as recorded in greenland ice an earlier event of monsoon intensification at 16 000 150 calendar years before present occurred at the end of heinrich layer 1 in the atlantic and parallels the initial rise in global atmospheric methane concentrations and the first abrupt climate changes in the antarctic thus the evolution of the monsoonal and high latitude climates show teleconnections but hemispheric asymmetries superimposed on abrupt events the monsoonal climate shows high frequency variability of 1785 1450 and 1150 year oscillations and abrupt climate change seems to occur when at least two of these oscillations are in phase

environmental response of a fragile semiarid landscape bardenas reales natural park ne spain to early holocene climate variability a paleo and environmental magnetic approach abstract the bardenas reales natural park western ebro basin ne spain constitutes a fragile landscape where the prevailing semiarid climate and erodability of the bedrock have resulted in high sensitivity to erosion sedimentation oscillations during the holocene in this paper we present new chronologic sedimentologic paleomagnetic and environmental magnetic results from the oldest unit qah1 of a system of nested cut and fill alluvial sequences which is 18 m thick and crops out extensively in the central part of the natural park at the bardena blanca depression radiocarbon dating indicates that early holocene unit qah1 is younger than 9 38 8 89 cal kyr bp and gives ages of 8 92 8 42 and 7 59 7 37 cal kyr bp in the middle and uppermost parts of the unit respectively sedimentologic data indicate that distal alluvial sediments of unit qah1 accumulated in sandy mud flats and ephemeral playa lakes under arid conditions the coincidence of enhanced magnetite content with moderate to intense root bioturbation in the lowermost and likely also uppermost sediments of unit qah1 suggests that magnetite formed authigenically in response to relatively wetter conditions at the beginning and end of this dry period these results indicate that onset and cessation of alluvial aggradation mark the passing of a geomorphologic threshold most likely plant cover in the watershed during a progressive drying wetting event the radiocarbon based age model of unit qah1 indicates that alluvial aggradation under arid conditions began at 9 13 cal kyr bp and ended at 7 16 cal kyr bp this period is strikingly centered at around the 8 2 kyr cold event but spans a longer time period supporting the notion of a global climatic deterioration as the underlying cause for this event paleomagnetic directions do not clearly display the characteristic patterns recognized in paleosecular variation curves derived from other european lacustrine sediments and cannot be used to refine the radiocarbon based age model for unit qah1 our results demonstrate a quick and strong response of alluvial systems to early holocene climate variability in fragile mediterranean landscapes such as those at the semiarid bardenas reales natural park

does climate control the morphological fabric of freshwater carbonates a comparative study of holocene barrage tufas from spain and britain abstract calcium carbonate production in most freshwater tufa systems is controlled by a combination of physico chemical precipitation and biomediation associated with procaryote microphyte biofilms inorganic precipitation is dominant under turbulent flow regimes whereas biomediation necessitates sluggish flow or static water we show here that temperature is also likely to affect tufa formation rates and architecture leading to the development of a clearly definable range of fabrics two contrasting models are proposed warm semi arid tufas well seen in the ruidera pools national park albacete province central spain where tufa barrages consist of vertical narrow rimmed arcuate structures frequently these are bounded both upstream and downstream by deep lakes laterally accreting mammilate stromatolites dominate the upper two thirds of lake margin subaqueous overhangs whereas conical growth forms dominate shady basal parts of subaqueous overhangs dense reed stands grow in thin peats on top of the vertical lake margin walls resistivity survey and percussion augering show up to 20 m of earlier lake fill which is banded into dark and pale beds the upper 10 m accumulated in 4600 years there is little or no preservation of organic material within these deposits cool temperate tufas typified by slowly accumulating barrage tufas at caerwys n wales and alport n derbyshire uk transverse barriers across valleys are dominated by arcuate buttress developments built up of downstream facing tabular carbonate sheets pools upstream of the barriers are shallow dominated by clotted lime mud and organic sapropels in their depocentres and stromatolite dominated laminar to low domes or oncoidal facies in broad marginal zones marginal stands of semi aquatic vegetation are rooted in thick peats but frequently are also encrusted around their exposed stems by oncoidal carbonate fabric preservation is good for the carbonate material however marginal peats rapidly oxidise and stem encrustations collapse to produce cylindrical oncoid beds depocentre sapropels are always preserved and contain important pollen records otherwise rare in carbonate regions carbonates in both models accumulate relatively rapidly they have a moderate preservation potential within late cenozoic terrestrial successions the distinctly different characteristics of their preserved fabrics should allow recognition of two contrasting climatic models for fluvial barrage tufas in ancient deposits

carbonate systems along nutrient and temperature gradients some sedimentological and geochemical constraints research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems changes in climate ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry including carbonate saturation state and nutrient availability and thereby have determined boundary conditions for the biota that form carbonate platforms in turn the biota determine accumulation rates and facies zonations thus controlling platform geometry and facies dynamics in the first section of this paper we examine how nutrient availability influences carbonate facies associations we first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations then we discuss how carbonate sedimentation can be characterized along nutrient gradients in the second section we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems we highlight the variety of existing proxies and their limitations and suggest that multiple lines of evidence are needed for valid interpretations our short review discusses sedimentological biogenic and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations however it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs nutrient supplies changes and facies in ancient carbonate sequences

a platform to basin transition for lower aptian carbonates shuaiba formation of the northeastern jebel akhdar sultanate of oman abstract the platform to basin transition of the lower aptian shuaiba carbonate platform throughout a large part of the arabian peninsula has hitherto mainly been documented from subsurface data and has widely been regarded as having been progradational in northeastern jebel akhdar however the shuaiba platform did not prograde and was scarp bounded early lithification accounts for the rigid nature of the scarp a biological framework being nearly absent early exposure surfaces neptunian dykes sills internal breccias and other sediment features as well as the geographic coincidence of the platform scarp with older and younger scarps suggest a tectonic control of margin morphology and dynamics a contemporaneous peak of allodapic sediments and reactivation of older basement structures in adjacent basins also tends to indicate the importance of structural influence on platform margin organization

facies and depositional sequence evolution controlled by high frequency sea level changes in a shallow water carbonate ramp late kimmeridgian ne spain the outcrops of the sierra de albarracin ne spain allow a precise reconstruction of the shallow sedimentary domains of a late kimmeridgian carbonate ramp developed in western marginal areas of the iberian basin the sedimentary record shows a hierarchical sequence stratigraphic organization which implies sea level changes of different frequencies the studied succession is arranged in a long term transgressive regressive sequence which is likely to reflect local variation in the subsidence rates this sequence includes four higher order sequences a to d which have variable thickness from 3 to 21 m the similar sedimentary evolution observed in distant localities suggests the existence of high frequency sea level fluctuations controlling the sequence development the average amplitude of these cycles would range from 5 to 10 m the precise estimation of their duration some few hundreds of kyr and their possible assignment to any of the long term orbital cycles the 100 or the 400 kyr eccentricity cycles is uncertain sequences a and b formed during the long term transgressive interval are relatively thin from 3 to 9 m give up sequences that were never subaerially exposed these sequences are locally formed by five shallowing upward elementary sequences sequences c and d are catch down sequences with evidence of emersion of subtidal facies sequence c formed during the stage of maximum gain of long term accommodation is the thickest sequence from 13 to 21 m and includes coral microbial reefs pinnacles up to 16 m in height the increased production rates were able to fill part of the accommodation created during the early stage of high frequency sea level rise and the shallow platform was eventually exposed to subaereal erosion and meteoric cementation

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

mid holocene erosive episodes in tufa deposits from trabaque canyon central spain as a result of abrupt arid climate transitions during the holocene a series of tufa sediments were deposited from a karstic spring along the trabaque canyon central spain a long term lowering of the water table caused the location of the spring to be displaced from the upper sector of the canyon during the early holocene to the lower sector in the late holocene this progressive shift was in response to decreased precipitation in the region the depositional environments and their geomorphologic relationships were characterized thus five morphosedimentary units msus were identified within the holocene tufa deposits erosive episodes were recognized between msus and as most of the msus partially overlap the older ones are perched in relation to the younger ones the chronology of the msus is based on 14c dates and stable isotopes and total organic carbon content provided environmental information during the period of tufa sedimentation the successive dissection episodes in the trabaque canyon tufa deposits took place during transitioning climate conditions from the relatively wet early holocene to the more arid late holocene during this transitional period in the mid holocene wet phases alternated with more arid conditions causing the largest hydrological regime gradients in the holocene thus the four erosive episodes causing tufa dissection in trabaque during the holocene are interpreted as the result of abrupt transitional periods towards arid conditions

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

phosphogenesis carbon isotope stratigraphy and carbonate platform evolution along the lower cretaceous northern tethyan margin we distinguish three different stages in the evolution of the tithonian late jurassic to aptian early cretaceous northern tethyan carbonate platform 1 carbonate production in the coral oolite mode late tithonian to early valanginian early barremian to early aptian 2 carbonate production in the crinoid bryozoan mode early valanginian haute rivian late aptian and 3 platform retrogradation and destruction condensation and phosphogenesis that is platform drowning early valanginian to early hauterivian middle hauterivian late hauterivian to early barremian early to early late aptian and latest aptian to earliest albian transitions from the coral oolite mode to the crinoid bryozoan mode and consequently to platform drowning may have been driven by increases in nutrient levels on the shelf phases of relative sea level rise in times of carbonate production in the coral oolite mode are named constructive because of the observed platform regeneration following phases of widespread emersion during late sea level highstands in contrast phases of relative sea level rise in times of platform drowning are termed destructive the 13 c stratigraphies obtained from valanginian hauterivian and aptian albian hemipelagic successions beyond the platform correlate well with the early cretaceous pelagic 13 c record positive excursions in the pelagic 13 c record correspond in time to episodes of platform drowning this suggests the existence of a coupling mechanism between changes in the global carbon cycle and platform drowning in our view the early cretaceous crises in carbonate platform growth were the consequence of reinforced greenhouse conditions which may have been triggered by episodes of extensive flood basalt volcanism strong greenhouse conditions may have induced the following chain of feedback mechanisms enabling the biosphere to return to normal conditions climate warming sea level rise accelerated water cycle intensified weathering nutrient mobilization platform destruction increased productivity increased phosphogenesis and carbon burial weakened greenhouse conditions

holocene palaeoecology and floodplain evolution of the muge tributary lower tagus basin portugal abstract the lower muge valley a tributary of the lower tagus river portugal features an important archaeological record of mesolithic shell midden sites archaeological research has long assumed that tidally influenced valley floor environments in the immediate locality of the sites provided a rich food resource attracting mesolithic settlement to date there has been little attempt to use palaeoenvironmental records to reconstruct holocene floodplain evolution in the lower tagus valley the cultivated freshwater lower muge floodplain is locally underlain by 11 m of homogeneous fine grained sediments and peat comprising buried floodplain environments contemporary with mesolithic occupation 6200 4800 cal bc pollen and foraminifera analyses demonstrate that fine grained deposition forced by sea level rise commenced 6200 cal bc in an estuarine setting the lower muge floodplain experienced maximum tidal influence 5800 5500 cal bc subsequently sediment supply rates overtook the decreasing rate of sea level rise and fluvial environments expanded the pollen record may suggest regional desiccation from 5000 cal bc estuarine environments disappeared suddenly 3800 cal bc when freshwater wetlands were established although the initiation of mesolithic settlement is shown to coincide with the beginning of tidal influence site abandonment does not match with any major environmental change sea level still stand 2600 cal bc has been linked to valley floor stabilisation and soil formation alder floodplain woodland developed prior to 230 cal bc and was cleared probably during roman times for agriculture renewed deposition after 230 cal bc may relate to internal mechanisms or to human impact upon the catchment vegetation

holocene climatic change in morocco a quantitative reconstruction from pollen data annual precipitation july and january temperatures were reconstructed from a continuous holocene pollen sequence from the middle atlas morocco using the best modern analogues method the reconstructions show a clear difference between the early and late holocene from 10 ka to 6 5 ka the climate was drier and warmer than during the period since 6 5 ka the average value of annual precipitation was 870 mm until 6 5 ka then rose to 940 mm between 10 ka and 6 5 ka january and july temperatures were about 4 c higher than the present both temperatures show a marked decrease between 7 ka and 6 ka after 6 5 ka july and january temperatures fluctuated between 21 and 23 c and 2 5 and 5 c respectively january temperatures show a period of intermediate values 3 5 c between 4 ka and 5 5 ka the reconstructed climate values generally match palaeolimnological data from the same core which show five intervals of low lake level during the holocene they are also consistent with regional scale cohmap simulated palaeoclimate that shows contrasting patterns of rainfall variation between the northwesternmost part of africa and the intertropical band

human trace on the landscape during the holocene at el mirador cave sierra de atapuerca spain the palynological evidence the archaeological research focusing on el mirador cave sierra de atapuerca spain has revealed a succession of occupation levels in a dung layers context that span from the early neolithic to th

a palaeoenvironmental study in semi arid southeastern spain the palynological and sedimentological sequence at perneras cave lorca murcia abstract results are presented of palynological and sedimentological research at the palaeolithic site of perneras cave coastal murcia southeastern spain sedimentological features point to a warm somewhat humid phase corresponding with the lowermost part of the mousterian sequence which was followed by a climatic deterioration which lasted throughout the later mousterian and upper palaeolithic the palynological study described here barely allows palaeoclimatological inferences to be drawn but it does highlight interesting paleobotanical data namely the presence of ibero maghrebian and mediterranean elements which suggest that the site was an important refuge for thermophilous taxa the reliability of the interpretation of the pollen assemblages is assessed in terms of the incorporation preservation and distribution of pollen grains into the profile

late holocene vegetation dynamics on an atlantic mediterranean mountain in nw iberia abstract detailed studies on the late holocene vegetation dynamics of the mountains of nw iberia are rare furthermore the impact of human activities and changes in fire activity on the natural vegetation are not well known over these areas in order to improve the knowledge on these topics pollen and charcoal analyses were conducted on two new sedimentary sequences from the teleno mountains between ca 4500 and 3200 cal yr bp pinus type sylvestris and betula dominated the forests that covered the uplands of the teleno mountains at this point this pine birch forest was replaced with heathlands and grasslands which persisted during all the iron age and the roman period until ca 1500 cal yr bp this abrupt deforestation process could be caused by fire grazing and or mining activities linked to the exploitation of the metal resources of these mountains around 1250 cal yr bp a betula forest established in the uplands of the teleno mountains probably following a decrease in human activities the gradual rise in regional population density since ca 300 200 cal yr may be linked to the increase in fire activity that triggered the replacement of birch forest with heathlands lastly the extent of the pinus pinaster dominated forests in the lowlands is an illustrative example of how the economic activities of the local human population have controlled the vegetation cover in this area as it is very clear in the pollen record the recovery of natural p pinaster forests since ca ad 1900 associated to the start of resin exploitation

new speleothem data from molinos and ejulve caves reveal holocene hydrological variability in northeast iberia new speleothem records from northeastern iberian caves provide data to explore the climatic patterns during the holocene we present 13c and mg ca from three speleothems from two different caves located in the iberian range allowing replication of the climatic signal for several millennia through the integration of those stalagmites covering since the holocene onset to 2 ka the early holocene 11 7 8 5 ka appears as the wettest interval a marked change towards aridity is observed during the middle holocene 8 5 4 8 ka and an increase of humidity afterwards 4 8 2 ka this three part pattern contrasting with other iberian sequences seems to be associated with the different role that seasonality has played in the response of different proxies or records to changes in water availability interpreting our speleothem records as changes in winter spring precipitation along the holocene allows reconciling previous data on hydrological variability from the western mediterranean borderlands

the deep peru 2015 doublet earthquakes abstract on 24 november 2015 two events of magnitude mw 7 5 and mw 7 6 occurred at 600 km depth under the peru brazil boundary these two events were separated in time by 300 s deep event doublets occur often under south america the characteristics that control these events and the dynamic interaction between them are an unresolved problem we used teleseismic and regional data situated above the doublet to perform source inversion in order to characterize their ruptures the overall resemblance between these two events suggests that they share similar rupture process they are not identical but occur on the same fault surface dipping westward using a p wave stripping and stretching method we determine rupture speed of 2 25 km s from regional body wave inversion we find that stress drop is similar for both events they differ by a factor of two the similarity in geometry rupture velocity stress drop and radiated energy suggests that these two events looked like simple elliptical ruptures that propagated like classical sub shear brittle cracks

climate and anthropogenic factors affecting alluvial fan development during the late holocene in the central ebro valley northeast spain the late holocene in the central ebro depression is characterized by a number of morphodynamic stages that affected hillslopes and channels climate fluctuations and human activities together caused severe erosion and floods resulting in alternating stages of accumulation and incision in the valley floors seven accumulation levels n6 n0 correlated with ebro river fluvial terraces have been identified in the secondary fluvial network of the central ebro depression the main accumulation level n3 corresponds to a long period of increased hillslope erosion and sedimentation in the valleys from the neolithic to the late roman periods the accumulation levels are evident throughout the valleys and extend to the valley mouths where many connect with alluvial fans the study of several sedimentological profiles 14c ams dating and many archaeological remnants have enabled detailed assessment of sedimentation characteristics in the alluvial fans and the relationship thereof to the presence of human sett

lateglacial to early holocene recursive aridity events in the se mediterranean iberian peninsula the salines playa lake case study abstract twelve pollen inferred aridity major and minor events s1 to s12 have been identified at salines playa lake se iberian peninsula 475 m asl 38 30 02 n 00 53 18 w from the lateglacial to the early holocene boreal these dry events consist of an increase in the aridity quotient calculated as a function of selected pollen taxa at 13 4 13 12 55 12 2 11 9 11 45 11 10 6 10 3 10 9 5 and 8 3 ka cal bp these dry events correspond to the previous identified cold spells such as the younger dryas as well as the 8 7 6 and 5 bond events and 11 4 and 9 3 events this climate record highlights the complex glacial interglacial transition in extra tropical latitudes with centennial scale abrupt climate fluctuations a signature scarcely recorded in other palaeoecological records of the se iberian peninsula this work has major implications for the study of human socio ecological systems and resilience in se iberia during the epipaleolithic and mesolithic periods

the late holocene tufa decline in europe over much of europe it has been postulated that in the late holocene since c 2500 bp there was a marked decline in the deposition of tufa there has been considerable debate about the causes of this phenomenon with some authors postulating the importance of natural climatic changes and others asserting that miscellaneous human influences have been crucial this article discusses the role that various changes both natural and anthropogenic may have played and suggests ways in which the large number of possible hypotheses can be tested

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

microscopic charcoal in sediments quaternary fire history of the grassland and savanna regions in south africa the microscopic charcoal content of several quaternary pollen sequences is used to investigate fire history in south africa both during the holocene and the late pleistocene although fluctuations in charcoal composition are recorded it is difficult to link them directly to either human made or natural fires strong long term variations in microscopic charcoal of middle and upper pleistocene layers are independent of pollen indications of past temperature and moisture conditions holocene charcoal sequences from different areas show no correlation so no phases of regional burning are found some fluctuations in charcoal probably are the result of local burning in the various regions the arrival of iron age people some 2000 yr ago apparently did not coincide with widespread wild fires as these events do not consistently appear in regional microscopic charcoal records the only exception appears to be the wonderkrater spring deposit relatively open savanna environments which are implied by pollen analysis at some sites during this period and the generally low microscopic charcoal contents were either caused by climate change or controlled burning by iron age people copyright 2002 john wiley sons ltd

unsteady two dimensional paleohydraulic reconstruction of extreme floods over the last 4000 yr in segura river southeast spain summary floods in the almadenes canyon segura river southeast spain have been reconstructed using unsteady two dimensional shallow water modelling slackwater deposits archaeological age dating and hydraulic modelling allowed us to reconstruct some of the oldest extreme floods reported in spain the paleoreconstruction was performed for the first time in three steps retrodicted flood discharges for the most recent flood ad 900 were quantified comparing the simulated shields and froude numbers with respect to characteristic values for the existence of ripples and upper stage plane bed at a cave that served as a shelter for humans ensuing velocity shields and froude maps were then used as a forward predictor allowing the finding of additional paleostage indicators far from the shelter finally new psis were employed to verify the reliability of the reconstruction in doing so better insight into the paleoflood landscape was derived from consideration of the association of bedforms and modelled hydraulic conditions the present study assuming a stable geometry of the bedrock canyon during the late holocene extends the estimation of flow discharge magnitudes to ca 4000 yr bp ranging from 500 m 3 s in the oldest floods 3700 yr bp up to 700 1000 m 3 s in the most recent ad 900

sequence stratigraphy and architecture of a late early middle aptian carbonate platform succession from the western maestrat basin iberian chain spain abstract the attributes of a four systems tract sequence are at times difficult to identify in outcrop scale carbonate successions poor exposure conditions variable rates of sediment production erosion and or superposition of surfaces that are intrinsic to the nature of carbonate systems frequently conceal or remove its physical features the late early middle aptian platform carbonates of the western maestrat basin iberian chain spain display facies heterogeneity enabling platform platform margin and slope geometries to be identified and provide a case study that shows all the characteristics of a quintessential four systems tract based sequence five differentiated systems tracts belonging to two distinct depositional sequences can be recognized the highstand systems tract hst and forced regressive wedge systems tract frwst of depositional sequence a and the lowstand prograding wedge systems tract lpwst transgressive systems tract tst and subsequent return to a highstand stage of sea level hst of depositional sequence b an extensive carbonate platform of rudists and corals stacked in a prograding pattern marks the first hst the frwst is constituted by a detached slightly cross bedded calcarenite situated at the toe of the slope in a basinal position the lpwst is characterized by a small carbonate platform of rudists and corals downlapping over the frwst and onlapping landwards the tst exhibits platform backstepping and marly sedimentation resumed carbonate production in shelf and slope settings characterizes the second hst a basal surface of forced regression a subaerial unconformity a correlative conformity a transgressive surface and a maximum flooding surface bound these systems tracts and are well documented and widely mappable across the platform to basin transition area analyzed moreover the sedimentary succession studied is made up of four types of parasequence that constitute stratigraphic units deposited within a higher frequency sea level cyclicity ten lithofacies associations form these basic accretional units each facies assemblage can be ascribed to an inferred depositional environment in terms of bathymetry hydrodynamic conditions and trophic level the architecture of the carbonate platform systems reflects a flat topped non rimmed depositional profile furthermore these carbonate shelves are interpreted as having been formed in low hydrodynamic conditions the long term relative fall in sea level occurred during the uppermost early aptian which subaerially exposed the carbonate platform established during the first hst and resulted in the deposition of the frwst is interpreted as one of global significance moreover a possible relationship between this widespread sea level drop and glacio eustasy seems plausible and could be linked to the cooling event proposed in the literature for the late early aptian because of the important implications in sequence stratigraphy of this study the sedimentary succession analyzed herein could serve as an analogue for the application of the four systems tract sequence stratigraphic methodology to carbonate systems

forced regressions in a sequence stratigraphic framework concepts examples and exploration significance sequence stratigraphic concepts suggest that stratal geometries develop and are largely controlled by changes in relative sea level on the shelf lowstand deposits which form during falls and subsequent stillstands of relative sea level can be recognized by the presence of an unconformity at the base the isolated and basinward position relative to the previous shoreline and the abrupt seaward translation of shallow water and shoreline facies into the basin across an unconformity surface this seaward translation of facies and shoreline regression in response to relative sea level lowering is termed a forced regression a forced regression is independent of variations of sediment flux and is in contrast with normal regressions that occur in response to excess sediment flux relative to space available on the shelf i e accommodation forced regressions commonly are associated with a zone of sedimentary bypass subaerial exposure and possible fluvial erosion between the newly formed and preceding shorelines certain shelf sands previously interpreted as offshore or mid shelf sand bodies thus can be reinterpreted as stranded lowstand shorelines associated with forced regressions this alternative interpretation has economic significance insofar as it suggests different subsurface correlations and reservoir geometries with the potential for development of new play types and enhanced recovery in o der fields examples of forced regression can be observed at a variety of scales and ages several such examples include the modern east coulee fan delta and the lower cretaceous viking formation in alberta canada the quaternary rhone delta and the quaternary hudson valley system

human induced changes on wetlands a study case from nw iberia abstract wetlands are exceptional ecosystems that contribute to biodiversity and play a key role in the hydrological and carbon cycles knowledge of their long term ecology is essential for a proper understanding of these valuable ecosystems we present the application of multi proxy analyses to a 115 cm thick core from la molina mire alto de la espina located in nw iberia with a chronology spanning since 500 bc the mire is located in an area intensively mined for gold during the roman period and close to a water canalization system used for mining operations at that time our aim was to get insights into the development of the wetland by combining palynological records of hydro hygrophytes non pollen palynomorphs and geochemical analyses supported by 14c datings and multivariate statistics the results indicate a complex pattern of ecological succession during the local iron age the wetland was minerotrophic since 20 ad it was subjected to dramatic hydrological changes due to a rise of the water table fluctuating between the presence of open water and phases of drawdown finally by 745 ad the wetland experienced a rapid evolution towards ombrotrophic conditions high grazing pressure was detected for the last decades the significant change occurred during early roman empire seems to have been the consequence of the direct use of the wetland as a water reservoir of the canalisation system used for gold mining thus the current nature of the mire may be the result of human impact although multiple human and climate induced causes were potentially linked to the detected shifts however the system seems to have been resilient successfully buffering the changes without substantial alterations of its functioning our investigation shows that palaeoecological research is necessary to understand modifications in the structure of wetland ecosystems their long term ecology and the role of human induced changes

facies architecture and high resolution sequence stratigraphy of an upper cretaceous platform margin succession southern central pyrenees spain abstract excellent exposures of upper cretaceous santonian carbonate platforms on the northern flank of sant corneli anticline southern central pyrenees provide detailed information of facies architecture in both depositional strike and dip directions basic accretional units are differentiated by facies contrast across mappable surfaces these surfaces do not show clear evidence of subaerial erosion and are correlated basinward with bedding planes across which there are subtle changes in skeletal composition two types of basic accretional units have been identified based on bedding patterns internal facies architecture and skeletal composition 1 rudist buildups consist of a rudist and coral belt at the platform margin passing landward into a slender hippuritid lithosome locally overlain by a bioclastic blanket that passes basinward into bioclastic apron like clinobeds and into fine grained packstone wackestone 2 calcarenite wedges consist of yellow brown benthic foraminifer rich grainstones to grain dominated packstones with scattered rudist shells and small coral colonies passing basinward into mud dominated packstones to wackestones with variable siliciclastic content quartz sand to silt and clay rudist buildups and calcarenite wedges alternate although not rhythmically these changes in platform skeletal composition reflect changes in the dominant type of carbonate producing biota independently of the changes in accommodation both types of basic accretional units rudist buildups and calcarenite wedges form simple sequences and parasequences according to internal lithofacies arrangement and inferred sea level cyclicity cycles or paracycles high frequency sea level cyclicity fits in the milankovitch frequency band long term changes in accommodation governing aggradation progradation and backstepping of basic sequences and parasequences reflect tectonic influence rather than long term changes in eustatic sea level

circum mediterranean fire activity and climate changes during the mid holocene environmental transition 8500 2500 cal bp a mid to late holocene synthesis of fire activity from the mediterranean basin explores the linkages among fire climate variability and seasonality through several climatic and ecological transitions regional fire histories were created from 36 radiocarbon dated sedimentary charcoal records available from the global charcoal database during the mid holocene thermal maximum around 7500 4500 cal bp charcoal records from the northern mediterranean suggest an increase in fire while records from the southern mediterranean indicate a decrease associated with wetter than present summers a north south partition between 40 and 43 n latitude is apparent in the central and western mediterranean relatively abrupt changes in fire activity are observed c 5500 5000 cal bp records of holocene fire activity appear sensitive to both orbitally forced climate changes and shorter lived excursions which may be related to north atlantic cold events possibly modulated by an nao like climate mechanism in cases wh

the biogeographical role of pinus forest on the northern spanish meseta a new holocene sequence abstract the aim of this paper is to reconstruct the variation in the vegetation during the holocene on the northern meseta through pollen analysis in order to determine the roles played by pinus and quercus in the vegetation dynamics a new pollen sequence camporredondo in the centre of the duero river basin northern meseta spain is presented it covers the period from ca 11 250 to 1630 cal yr bp the camporredondo sequence suggests that a forested landscape existed from the start of the holocene with values of approximately 90 of arboreal pollen mainly derived from pine forests in the surroundings shortly after 8600 cal yr bp pine forests continued to dominate but the landscape became more open while stands of deciduous and evergreen quercus developed around 4500 years ago coinciding with the start of a period of less rainfall the lacustrine areas in these territories began to silt up favouring hydrophytic taxa such as salix or cyperaceae a comparison with other holocene pollen sequences from the central eastern part of the northern meseta confirms the presence of pine forests in the whole region since the early holocene we discuss the variations of the general vegetation pattern in terms of the local or regional conditions at each site throughout the holocene pinus forests dominated at least in the eastern half of the duero river basin the typical holocene substitution of conifers by broadleaf species as recorded in other parts of the iberian peninsula and europe never takes place in the study area the results of the present study suggest that the current view of the potential vegetation in the spanish northern meseta should be reviewed

unravelling the holocene environmental history of south western iberia through a palynological study of lake medina sediments lake medina is a small shallow and endorheic salt lake sensitive to climate variation in south western spain close to cadiz in western andalusia it is located in an evaporitic and karstic enviro

mid holocene vegetation history and neolithic land use in the lake banyoles area girona spain abstract this paper focuses on high resolution analysis of pollen and sedimentology and botanical macro remains analysis in a core from lake banyoles girona spain the core sequence comprises a high resolution mid holocene ca 8 9 3 35 cal ka bp vegetation succession and sedimentological geochemical and geomorphological proxies are related to both climatic and anthropogenic causes deforestation processes affected natural vegetation development in the early neolithic 7 25 5 55 cal ka bp and late neolithic 5 17 3 71 cal ka bp in the context of broadleaf deciduous forest resilience against cooling and drying oscillations changes in sedimentation dynamics and in lake water level caused the emergence of dry land on the lake margin where riparian forest was established from 5 55 cal ka bp onwards the data show that in the context of an increasing aridification process neolithic land use played an important role in vegetation history and environmental evolution

early holocene environments in the wadi faynan jordan hunt c elrishi h gilbertson d grattan j mclaren s pyatt b rushworth g barker g early holocene environments in the wadi faynan jordan the holocene 2004 14 6 pp 921 930

visions of ice sheets in a greenhouse world abstract backstripped eustatic estimates from new jersey and the russian platform show large 25 m and rapid 18 o record highlights the enigma this was the warmest interval of the past 200 my yet it was bracketed by two inferred eustatic falls of 25 m that were associated with two large 0 75 deep sea 18 o increases 92 93 ma mid turonian and 96 ma mid cenomanian we reconcile records of warm high latitudes with glacioeustasy by proposing that late cretaceous early eocene ice sheets generally reached maximum volumes of 8 12 10 6 km 3 20 30 m glacioeustatic equivalent but did not reach the antarctic coast hence coastal antarctica hence deep water remained relatively warm even though there were significant changes in sea level as the result of glaciation unlike the oligocene and younger icehouse world these ice sheets only existed during short intervals of peak milankovitch insolation leaving antarctica ice free during much of the greenhouse late cretaceous to middle eocene these results highlight the need to re evaluate the paradigm that polar ice sheets did not exist during times of warm high latitude climates

pollen and mollusc records for environmental change in central spain during the mid and late holocene the central part of the iberian peninsula has few radiocarbon dated records of vegetation and climatic history for the holocene extinct and active tufa forming sites occur along the northwestern margin of the sierra de alcaraz tufas are often closely associated with the remains of plants and animals and two extinct systems near the settlements of el jardin and alcaraz have yielded a record of environmental history that spans much of the last 6000 years the record indicates that the present day sedimentological regime and vegetation are human induced and probably extend back to about 2700 yr bp before this date oak dominated scrub mattoral was widespread prior to around 5000 yr bp the climate appears to have been relatively humid and possibly cooler and the catchments for the two sites were more wooded than today

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

holocene fire activity and vegetation response in south eastern iberia since fire has been recognized as an essential disturbance in mediterranean landscapes the study of long term fire ecology has developed rapidly we have reconstructed a sequence of vegetation dynamics and fire changes across south eastern iberia by coupling records of climate fire vegetation and human activities we calculated fire activity anomalies faas in relation to 3 ka cal bp for 10 8 ka cal bp 6 ka cal bp 4 ka cal bp and the present for most of the early to the mid holocene uneven but low fire events were the main vegetation driver at high altitudes where broadleaved and coniferous trees presented a highly dynamic post fire response at mid altitudes in the mainland segura mountains fire activity remained relatively stable at similar levels to recent times we hypothesize that coastal areas both mountains and lowlands were more fire prone landscapes as biomass was more likely to have accumulated than in the inland regions triggering regular fire events the wet and warm phase towards the mid holocene between ca 8 and 6 ka cal bp affected the whole region and promoted the spread of mesophytic forest co existing with pinus as faas appear strongly negative at 6 ka cal bp with a less important role of fire mid and late holocene landscapes were shaped by an increasing aridity trend and the rise of human occupation especially in the coastal mountains where forest disappeared from ca 2 ka cal bp mediterranean type vegetation evergreen oaks and pinus pinaster halepensis types showed the fastest post fire vegetation dynamics over time

vegetation history climate and human impact in the spanish central system over the last 9000 years abstract in this paper we present a review of the available holocene pollen records from the spanish central system 113 sites and 150 14 c dates palynological data obtained from pollen analyses of peat bogs lakes and archaeological sites as well as radiocarbon dating were used to infer the human impact on vegetation and landscape during the last 9 millennia the neolithic contribution to the configuration of landscape is scarce limited to the valleys while chalcolithic settlements and their related activities agriculture and grazing represent the first evidence of significant human impact on the high mountains the pollen record has allowed us to relate two cultural periods of changing the copper age early bronze age and late bronze age early iron age transitions to abrupt climate disruptions the so called 4 2 and 2 8 ka cal bp events respectively from the iron age to the early middle ages anthropic activities were still sporadic mainly located in the lowlands but from the feudal period onwards when la mesta transhumance system takes place high mountain landscapes changed dramatically late modern period brings a further intensification of human pressure especially related to forestry with widespread pinewood afforestation

estuarine fluvial floodplain formation in the holocene lower tagus valley central portugal and implications for quaternary fluvial system evolution abstract we present a brief synthesis of the quaternary fluvial record in the lower tagus basin central portugal concentrating on factors controlling infill and incision the holocene part of the record forms the focus of this paper and guides the questioning of the basic assumptions of the established quaternary fluvial evolution model in particular the link between sea level change and fluvial incision deposition we suggest that several incision aggradation phases may have occurred during glacial periods major aggradation events may overlap with cold episodes while incision appears to concentrate on the warming limb of climate transitions the complex stratigraphy of the quaternary record in the lower tagus valley is influenced by repeated base level and climate changes this paper submits the first chronostratigraphic framework for valley fill deposits in the lower tagus area sea level rise forced aggradation and controlled deposition of the fine grained sedimentary wedge underlying the low gradient lower tagus floodplain investigations have focused on the lower muge tributary where rapidly aggrading estuarine and fluvial environments were abruptly established 8150 cal bp as sea level rose base level at the valley mouth controlled the upstream extent of the fine grained backfill tidal environments disappeared abruptly 5800 cal bp when the open estuary at the muge confluence was infilled by the tagus river the decrease and final still stand of sea level rise led to floodplain stabilisation with peat 6400 5200 cal bp and soil formation 5200 2200 cal bp localised renewed sedimentation 2200 200 cal bp is linked to human activity

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

depositional sequences in shallow carbonate dominated sedimentary systems concepts for a high resolution analysis abstract oxfordian and berriasian sections representing shallow water carbonate dominated sedimentary systems have been studied in the swiss and french jura in spain and in normandy they all display a hierarchical stacking of depositional sequences facies evolution and stacking pattern allow to define elementary small scale medium scale and large scale sequences some depositional sequences display well marked sequence boundaries others are limited by transgressive or maximum flooding surfaces the hierarchical organisation of such sequence stratigraphic elements implies that sea level fluctuations were an important factor in their formation and that these fluctuations had different frequencies the superposition of high frequency sea level changes on a long term sea level trend leads to repetition of diagnostic surfaces defining sequence boundary and maximum flooding zones wherein the corresponding high frequency surfaces are well developed chronostratigraphic tie points permit us to estimate the duration of large scale sequences this time control and the observed hierarchical stacking suggest that the high frequency sea level changes were controlled by climatic cycles in the milankovitch frequency band the variability of stacking pattern and facies evolution between sections illustrates the complexity of the studied environments furthermore because of the minimal accommodation space available in these shallow water settings much of the geologic time is not recorded nevertheless detailed analysis of the depositional sequences allows the interpretation of the evolution of the sedimentary system with a high time resolution thus there is a potential to monitor sedimentological ecological and diagenetic processes on a time scale of 20 to 100 ka

evaporite evidence of a mid holocene c 4550 4400 cal yr bp aridity crisis in southwestern europe and palaeoenvironmental consequences sedimentological evidence for an abrupt dry spell in south eastern spain during the middle holocene from c 4906 to 4384 cal yr bp is presented this phase was determined primarily from halite beds deposited between muddy slimes in a lagoon system of puerto de mazarron murcia province with a peak phase from c 4550 to 4400 cal yr bp a multi core multi proxy study of 20 geotechnical drills was made in the lagoon basin to identify the main sedimentary episodes and depositional environments the results suggest that this halite bed more than 80 cm thick was conditioned by climate change and was accompanied by a generalized drying out of the basin halite precipitation was linked with palaeoecological changes including forest and mesophyte depletions and increasing cover and diversity of xerophytic plant species archaeological evidence indicates a demise of the population at this period probably due to resource exhaustion an overall picture of the biostratigraphy and palaeoclimates of the region is given in a broader geographical context

centennial scale vegetation and north atlantic oscillation changes during the late holocene in the southern iberia high reso ce to lution pollen analysis charcoal non pollen palynomorphs and magnetic susceptibility have been analyzed in the sediment record of a peat bog in sierra nevada in southern iberia the study of these proxies provided the reconstruction of vegetation climate fire and human activity of the last 4500 cal yr bp a progressive trend towards aridification during the late holocene is observed in this record this trend is interrupted by millennial and centennial scale variability of relatively more humid and arid periods arid conditions are recorded between 4000 and 3100 cal yr bp being characterized by a decline in arboreal pollen and with a spike in magnetic susceptibility this is followed by a relatively humid period from 3100 to 1600 cal yr bp coinciding partially with the iberian roman humid period and is indicated by the increase of pinus and the decrease in xerophytic taxa the last 1500 cal yr bp are characterized by several centennial scale climatic oscillations generally arid conditions from 450 to 1300 ce depicted by a decrease in pinus and an increase in artemisia comprise the dark ages and the medieval climate anomaly since 1300 to 1850 ce pronounced oscillations occur between relatively humid and arid conditions four periods depicted by relatively higher pinus coinciding with the beginning and end of the little ice age are interrupted by three arid events characterized by an increase in artemisia these alternating arid and humid shifts could be explained by centennial scale changes in the north atlantic oscillation and solar activity

radiogenic isotopes for deciphering terrigenous input provenance in the western mediterranean abstract radiogenic isotopic signatures in marine sediments can be used to trace terrigenous source areas and transport mechanisms which are in turn related to climate variability to date most of the published studies using this approach have been focused on eastern mediterranean sediments in contrast we study here the terrigenous input provenance in the westernmost mediterranean alboran sea basin by using radiogenic isotope proxies and nd model ages in a marine record spanning the last 20 ka nd sr and pb isotopes obtained from carbonate free samples from the

the reconstruction of boreal forest fire history from lake sediments a comparison of charcoal pollen sedimentological and geochemical indices abstract fossil charcoal fossil pollen sedimentological and geochemical analyses of lake sediments have been used previously to reconstruct a history of local fires and resulting vegetation change the rationale behind these approaches is described and the usefulness of each technique for reconstructing fire history in the boreal forest is assessed empirically historical and dendrochronological records provide regional and local fire histories for a site in wood buffalo national park alberta canada the local and regional history of fires is compared with the microscopic charcoal content macroscopic charcoal content elemental carbon content fossil pollen content sedimentology and geochemistry of annually laminated sediments from a small lake there is no significant correlation between the abundance of microscopic charcoal macroscopic charcoal and total elemental carbon content of the sediments automated measures of microscopic charcoal abundance made with an image analysis system are correlated significantly with optical counts of microscopic charcoal none of the charcoal measures provide unequivocal records of local fire activity and the abundance of microscopic charcoal appears to be influenced by variations in regional fire activity however the highest depositional rate of macrofossil charcoal occurred during the time of a fire that burned within the drainage basin variations in sedimentological measures and geochemistry do not correlate with local fire activity fossil pollen percentages and accumulation rates display a pattern of variation that is consistent with observed vegetation responses to fire in the boreal forest what is likely apparent in the pollen record are the results of a series of burns of sufficient extent and intensity to kill most of the above ground biomass of the vegetation in an area at least as great as the drainage basin the inability of evidence from lake sediments to provide detailed histories of past fire activity is not surprising given the wide range of variation in the spatial extent proximity intensity and impact of individual fires

palynology of badger coprolites from central spain this paper presents pollen analysis of badger coprolites from cueva de los torrejones central spain eleven of fourteen coprolite specimens showed good pollen preservation acceptable pollen concentration and diversity of both arboreal and herbaceous taxa together with a number of non pollen palynomorph types especially fungal spores radiocarbon dating suggests that the coprolite collection derives from badger colonies that established setts and latrines inside the cavern over the last three centuries the coprolite pollen record depicts a mosaic anthropogenic landscape very similar to the present day comprising pine forests quercus dominated formations woodland patches with juniperus thurifera and a cistaceaedominated understorey with heliophytes and nitrophilous assemblages although influential dietary behavior of the badgers does not preclude palaeoenvironmental interpretation of the coprolite pollen spectra d 2005 elsevier b v all rights reserved

the palaeogeography of mesolithic settlement subsistence and shell midden formation in the muge valley lower tagus basin portugal this paper reports the first detailed palaeogeographical analysis of the environmental context of late mesolithic shell midden sites in the lower tagus area and focuses on the lower muge valley which contains an internationally significant mesolithic record the lower muge valley fill comprises buried estuarine and fluvial environments contemporary with mesolithic settlement holocene environmental and palaeogeographic changes influenced mesolithic settlement subsistence and midden accumulation the sudden appearance of large late mesolithic shell middens throughout portugal represents a process of increased visibility and preferential preservation of the archaeological record prior to 6100 cal bc aggrading valley floor environments did not occupy the entire width of the present lower tagus floodplain and any sites located in the early holocene valley are currently deeply buried shell midden occupation on terrace levels followed the establishment of aggrading estuarine environments containing produ

combining allostratigraphic and lithostratigraphic perspectives to compile subregional records of fluvial responsiveness the case of the sustainably entrenching palancia river watershed mediterranean coast ne spain abstract we use a combined allostratigraphic and morpholithostratigraphic approach to establish a relative stratigraphy of macroscale sediment landform units in the mediterranean palancia river watershed 986 km2 ne spain four alloformations signifying important changes in sub regional scale geomorphic valley floor evolution were identified based on data from 1120 field sites and age determinations and from analyzing high resolution geodata the formation of the widespread and thick pleistocene alloformation can be attributed to climatically induced excessive sediment supply and flood activities during pleistocene cold intervals rather than representing time lagging response to plio pleistocene neotectonic uplift triggered by the turn to holocene climatic conditions three successively inset alloformations illustrate how stream grading and floodplain narrowing continuously have progressed over the holocene the overall degradational valley floor evolution in the holocene is interpreted as a response to the antecedent overly valley floor aggradation allostratigraphic and morphostratigraphic data suggest that the abandonment of the two earlier holocene alloformations geomorphologically represents a pulsed turn toward intensified entrenchment rather than pulsed sedimentation the most important benefit of amalgamating allostratigraphic and morpho lithostratigraphic concepts is that allostratigraphic ordering provides a formally conclusive approach to scale up morpho lithostratigraphic information from the reach scale to much larger scales of geographical extent consequently applying allostratigraphic principles opens a perspective to moving forward toward analyzing the relationships between climate neotectonics sea level change human impact and fluvial response in coupled hinterland coastal systems that require to evaluate sedimentary information at larger spatial scales

holocene environmental change in southwest turkey a palaeoecological record of lake and catchment related changes percentage concentration and accumulation pollen data together with diatom and non siliceous microfossil data are presented for the site of go lhisar go l u 37i8 n 29i36 e elevation 930 m a small intramontane lake in burdur province southwest turkey microfossil assemblages from the longest sediment core gha 813 cm record changes in local and regional vegetation and lake productivity over the last 9500 years pollen spectra indicate that vegetation progressed from an open landscape with an increase in arboreal pollen occurring 8500 bp to mixed forest comprising oak pine and juniper until around 3000 bp cal 1240 bc when a human occupation phase becomes discernible from the pollen spectra this occurs shortly after the deposition of a volcanic tephra layer which originated from the minoan eruption of santorini thera and radiocarbon dated to 3330 70 yr bp cal 1600 bc this human occupation phase is comparable to the beys ehir occupation phase recorded at other sites in southwest turkey and involved forest clearance and the cultivation of fruit trees such as olea juglans castanea and itis together with arable cereal growing and pastoralism the presence of pollen types associated with the beys ehir occupation phase in deposits above the santorini tephra layer confirms a late bronze age early anatolian dark age date for its commencement since 3000 bp notable changes in aquatic ecology associated with tephra deposition and subsequent nutrient and sediment flux from the lake catchment are recorded the beys ehir occupation phase at go lhisar go l u came to an end around 1300 bp cla ad 700 when pine appears to have become the dominant forest tree 1999 elsevier science ltd all rights reserved

carbonates and relative changes in sea level abstract in the geologic record some of the most accurate gauges of changes in sea level are the sediment type geometry and diagenesis of carbonate shelves and platforms this is because carbonates frequently occur at or very near sea level and are usually less compacted than siliciclastics world wide changes in relative sea level the sum of eustatic sea level changes sedimentation and crustal movements have occurred repeatedly and cyclicly through geologic time producing characteristic responses in carbonates 1 1 relative rises in sea level usually caused by the cumulative effect of tectonic subsidence and eustatic rise may result in the following 1 1 a drowned carbonate reefs or platforms here carbonate growth potential is exceeded by relative sea level rise and is characterized by shallow water sediments overlain by hardgrounds and or deep water sediments some of which may be condensed sequences 1 2 b platforms where only the fast growing rim and patches of the interior are able to match sea level rise while the remainder of the platform is drowned temporarily 1 3 c platforms which keep up and maintain a flat top at sea level and contain shallow water sediments whose thickness at the least matches the height of the sea level rise if terrigenous supply is limited prograding sheets of shelf carbonate occur frequently capped by supratidal evaporites with prograding shelf margin carbonate clinoforms and turbidites if terrigenous supply is high the shelf carbonates encroach on deltaics 2 2 relative drops in sea level caused by crustal uplift or by subsidence being outpaced by a eustatic drop in sea level cause karst and soil development over shelves and platforms deposition of deep water evaporites in adjacent semi enclosed basins and in open marine basins the deposition of deltaic and aeolian clastics that bypassed the shelf falls are accompanied by platform wide fresh water diagenesis during relative sea level rises marine diagenesis is common in the subtidal portions of the shoaling upward carbonates and fresh water diagenesis and dolomitization and sulphate deposition is common in their intertidal and supratidal portions the stratigraphic significance of these reponses to relative sea level change is that many are tied to eustatic events and so are predictable within a basin of deposition

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

changes in sedimentary patterns of coastal and deep sea successions from the north atlantic portugal linked to early cretaceous environmental change coastal mixed carbonate siliciclastic and carbonate deposits of late barremian to early aptian age from the lusitanian basin portugal are compared with a deep sea succession odp 641 off the coast of portugal the coastal deposits show an abrupt cessation of rudist dominated carbonate deposition marked by an emersion horizon and followed by the deposition of orbitolinid rich marls during the early aptian the subsequent development of the carbonate platform during the late aptian is masked by a hiatus for this time interval shallow water debris deposits of the deep sea succession odp 641 indicate that carbonate production in shallow water areas resume in the early late aptian carbon isotope stratigraphy in combination with available biostratigraphic data is used for intrabasinal correlation and for the correlation of the portuguese with shallow water successions from switzerland france oman and the pacific the correlation reveals that during the early aptian similar changes in their sedimentary patterns occur at the beginning of a marked negative shift of carbon isotope values associated with the global deposition of organic rich black shales in the deep sea oae 1a in all compared sections rudist dominated carbonate deposition is stopped and followed either by orbitolinid rich deposits the deposition of microbial carbonates or by the drowning of the carbonate platform the comparison shows that the deterioration for carbonate platform growth conditions during the early aptian occurred essentially simultaneously at the various localities during this episode the ocean waters were in a preconditioned state of acidification stressing biocalcifying organisms sea level change combined with local effects like elevated nutrient levels and higher temperatures were probably determining the nature of sedimentary change in shallow water environments during the carbonate crisis in the sections studied in portugal the high abundance of orbitolinids overlying rudist limestones indicates that increased nutrient input may have played an important local role among the factors that caused an overall deterioration for carbonate producers during the late early aptian

holocene climate variability vegetation dynamics and fire regime in the central pyrenees the basa de la mora sequence ne spain abstract high resolution multiproxy data pollen sedimentology geochemistry chironomids and charcoal from the basa de la mora bsm lake sequence 42 32 n 0 19 e 1914 m a s l show marked climate variability in the central southern pyrenees throughout the holocene a robust age model based on 15 ams radiocarbon dates underpins the first precise reconstruction of rapid climate changes during the holocene from this area during the early holocene increased winter snowpack and high snowmelt during summer as a consequence of high seasonality led to higher lake levels a chironomid community dominated by non lacustrine taxa orthocladiinae related to higher inlet streams and a forested landscape with intense run off processes in the watershed from 9 8 to 8 1 cal ka bp climate instability is inferred from rapid and intense forest shifts and high fluctuation in surface run off shifts among conifers and mesophytes reveal at least four short lived dry events at 9 7 9 3 8 8 and 8 3 cal ka bp between 8 1 and 5 7 cal ka bp a stable climate with higher precipitation favoured highest lake levels and forest expansion with spread of mesophytes withdrawal of conifers and intensification of fires coinciding with the holocene climate optimum at 5 7 cal ka bp a major change leading to drier conditions contributed to a regional decline in mesophytes expansion of pines and junipers and a significant lake level drop despite drier conditions fire activity dropped as consequence of biomass reduction two arid intervals occurred between 2 9 and 2 4 cal ka bp and at 1 2 0 7 cal ka bp 800 1300 ad the latter coincides with the medieval climate anomaly and is one of the most arid phases of the holocene in bsm sequence anthropogenic disturbances were small until 700 ad when human pressure over landscape intensified with olea cultivation in the lowlands and significant deforestation in highlands colder and unfavourable weather conditions during the second part of the little ice age caused a temporary cease of high land management the most intense anthropogenic disturbances occurred during the second half of 19th century last decades are characterized by recovery of the vegetation cover as a result of land abandonment and lowered lake levels probably due to higher temperatures

holocene climatic and environmental evolution on the southwestern iberian peninsula a high resolution multi proxy study from lake medina cadiz sw spain abstract the climatic and environmental history of the sw iberian peninsula is explored to fill in the gap of continental palaeoclimate data by a high resolution study of lake medina sediments from core co1313 a multi proxy approach comprising sedimentary facies analysis elemental geochemistry mineralogy palynology and micropaleontology was employed to reconstruct the complex limnological response to climate change and catchment dynamics since the early holocene the further definition of abrupt climate change events was supported by a robust age model and rapid sediment accumulation rate at the study site proxies indicate arid and warm climate conditions during the early holocene from around 9 5 to 7 8 cal ka bp with a desiccation event at 8 8 cal ka bp as well as tentative evidence for the regional expression of a cold and abrupt arid climate event centering on ca 8 2 cal ka bp the holocene climate optimum from around 7 8 to 5 5 cal ka bp is characterized by a humid climate and maximum lake level anoxic bottom water conditions are indicated by the preservation of sediment laminae and the occurrences of sulfur mottles which were observed for the first time within holocene sediments of saline lakes mid to late holocene times are governed by the 4 2 cal ka bp dry event as well as progressive aridification accompanied by the development of typical mediterranean low land vegetation during recent times further progressive loss in precipitation as well as fluctuating but overall increasing anthropogenic influence on lake medina sediments is observed

crossing forest thresholds inertia and collapse in a holocene sequence from south central spain a holocene palaeoecological sequence from villaverde south central spain is presented the pollen stratigraphy is used to infer past vegetation changes within a catchment area that represents the boundary between semi arid plateau and mountain vegetation from c 9700 7530 cal yr bp pinus is dominant probably as a result of a combination of a relatively dry climate and natural fire disturbance from c 7530 5900 cal yr bp moderate invasion by quercus appears to be a migrational response following increased moisture and temperature but in part shaped by competitive adjustments from c 5900 5000 cal yr bp the pine forests are replaced by deciduous quercus forests with an important contribution from corylus betula fraxinus and alnus mediterranean type forests spread from c 5000 to 1920 cal yr bp coincident with expansions of artemisia juniperus and other xerophytes from c 1920 1160 cal yr bp pinus becomes dominant after a disturbance mediated invasion of the oak forests human impact u

human landscape interactions in the conquezuela ambrona valley soria continental iberia from the early neolithic land use to the origin of the current oak woodland abstract the sedimentological geochemical and palynological analyses performed in the conquezuela palaeolake 41 11 n 2 33 w 1124 m a s l provide a detailed multiproxy palaeoenvironmental reconstruction in one of the key areas of inner iberian neolithic colonization combined with archaeobotanical and archaeological data from well dated settlements along the conquezuela ambrona valley we investigate how environmental conditions may affect both socio economic adaptations and livelihood strategies of prehistoric communities the first evidences of early neolithic occupation in the valley ca 7250 6450 cal yr bp 5300 4500 bc coincided with the onset of a period 7540 6200 cal yr bp 5590 4250 bc with higher water availability and warmer climate as alluvial environments were substituted by carbonate wetland environments in the basin the conquezuela record supports an early neolithic colonization of the inner regions of iberia favored by warmer and humid climate features and with preferential settlement patterns associated to lakes the maximum human occupation of the valley occurred during the mid late neolithic and chalcolithic 6200 3200 cal yr bp 4250 1250 bc as evidenced by the high number of archaeological sites although a number of hydrological oscillations have been detected during this period the intense landscape transformation at basin scale leading to a deforested landscape was largely a consequence of widespread farming and pastoral practices socio economic activities during bronze iron and roman times modified this inherited landscape but the second largest ecosystem transformation only occurred during mediaeval times when a new agrarian landscape developed with the expansion of stockbreeding transhumance the current vegetation cover characterized by patches of holm and marcescent oaks and fields reflects an intense human management combining both extensive herding with agrarian activities in order to transform the previous forested landscape into a dehesa like system

younger dryas early holocene transition in the south eastern iberian peninsula insights from land snail shell middens the land snail sphincterochila candidissima from archeological records in villena se spain was studied isotopically to estimate the younger dryas yd early holocene transition in the western mediterranean live collected individuals exhibited body 21 8 1 6 and shell 5 8 1 4 d 13 c values typical of a c3 plant diet probably combined with carbonate ingestion calculations of a carbon flux balance mixing model suggest that living specimens experienced similar metabolic rates with comparable ratio of input and output fluxes of bicarbonate from the snail hemolymph all fossil shells showed comparable d 13 c values among each other but values were 2 higher than living specimens this may be explained by higher water stress at the yd holocene transition or by the suess effect shell d 18 o values averaged 1 3 0 8 for living individuals 0 5 0 8 for holocene 8 4 10 2 cal ka bp specimens and 0 4 0 6 for yd 12 0 12 4 cal ka bp snails an oxygen flux balance mixing model suggests that yd shells precipitated during relative humidity rh values of 79 82 after which rh increased gradually reaching maximum values of 87 88 at 8 4 8 6 cal ka bp and from there rh eventually declined to present values of 82 comparisons with other snail data suggest that the xerophilous sphincterochila records different environmental signatures fro other contemporaneous taxa copyright 2013 john wiley sons ltd

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

stable isotope composition of middle to late holocene land snail shells from the marroquies archeological site jaen southern spain paleoenvironmental implications abstract the marroquies archeological site located in the metropolitan area of jaen 37 46 southern spain contains land snail shells which have been preserved jointly with other human and zooarcheological remains new radiocarbon analyses carried out on pristine domestic animal and human bones confirmed that these remains belong to the copper age interval 4470 3880 cal bp n 8 land snail entire shells of two species one herbivorous and one omnivorous were analyzed for 13 c 12 c and 18 o 16 o ratios to estimate the paleoenvironmental conditions prevailing during the middle to late holocene in the southernmost part of europe the 13 c values of fossil shells ranged from 13 8 to 8 1 n 15 whereas modern specimens ranged from 10 8 to 8 6 n 20 the fact that ancient and modern shells generally exhibited similar 13 c values suggests that the 13 c values of the vegetation have remained relatively stable during 4470 3880 cal bp and the present snail species did not differ in 13 c values despite their differing dietary habits the 18 o values of fossil shells ranged from 4 9 to 1 2 n 15 whereas modern specimens ranged from 2 8 to 0 9 n 20 fossil shells were on average 2 lower in 18 o values than modern shells calculations from a snail evaporative steady state flux balance model suggest that shells at 4470 3880 cal bp precipitated under appreciably higher relative humidity conditions than today whereas rain 18 o values and air temperatures at the soil air interface during snail active period were possibly similar although samples from this study represent a time period in which the well documented late holocene aridification trend in southern spain already started snails suggest conditions at 4470 3880 cal bp were yet noticeably wetter than at present this study shows that land snail shells preserved in holocene archeological sites offer valuable paleoenvironmental information in their isotope codes

late holocene pinewoods persistence in the gredos mountains central spain inferred from extensive megafossil evidence macro and megafossil studies are of great value in palaeoecology because such evidence is spatially precise directly radiocarbon dated and usually taxon specific here we present new macro and megafossil data from ten sites from the gredos mountains central iberian peninsula that suggest persistent forest cover through the late holocene with a widespread belt of pinewoods in the highlands of the central iberian mountains well preserved pine cones found at several sites revealed that both pinus sylvestris and pinus nigra were present in the area during the middle and late holocene at locations of important biogeographical interest the p sylvestris forests represent one of the southernmost locations of its entire range p nigra was not known to have occurred in central spain during the holocene it was found at the westernmost edge of its range in siliceous soils a rare environment compared with the rest of its distribution finally we explored the potential for obtaining a long pine chronology from central iberia using tree ring measurements and radiocarbon dating of pine subfossil logs

interactions between environmental change and shallow water carbonate buildup along the northern tethyan margin and their impact on the early cretaceous carbon isotope record 1 the evolution of the early cretaceous northern tethyan carbonate platform was not only influenced by changes in sea level detrital influx and surface water temperature but also by changes in trophic levels we distinguish between phases of carbonate production dominated by oligotrophic photozoan communities and by mesotrophic and eventually colder water heterozoan communities superimposed on this bimodal trend in platform evolution were phases of platform demise for which we provide improved age control based on ammonite biostratigraphy the initial phase of these episodes of platform demise corresponds in time to episodes of oceanic anoxic events and environmental change in general on the basis of a comparison between the temporal changes in an early cretaceous ammonite calibrated d 13 c record from southeastern france and coeval changes in the platform record we suggest that the history of carbon fractionation along the northern tethyan margin was not only influenced by changes in the oceanic carbon cycle such as in the rate of production and preservation of organic and carbonate carbon and in the size of the oceanic dissolved inorganic carbon reservoir but it was also influenced by the above mentioned changes in the ecology and geometry of the adjacent carbonate platform phases of photozoan carbonate production induced positive trends in the hemipelagic carbonate d 13 c record phases of heterozoan carbonate production pushed the d 13 c system toward more negative values platform drowning episodes implied an initial increase in d 13 c values followed by a longerterm decrease in d 13 c values

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

abrupt climatic changes during the last glaciation based on pollen analysis of the abric romani catalonia spain the abric romani continental pollen record provides evidence of abrupt climate variations during the last glaciation the pollen record reveals a pattern of high frequency variations similar to that in ice cores as shown by oxygen isotopes or dust content analyses of 14 travertine samples yield coherent u series ages in correct stratigraphic order ranging from 40 000 to 70 000 yr according to changes in the composition and structure of the vegetation five paleoclimatic phases have been differentiated the oldest ranging from 70 200 to 65 500 yr ago records thermophilous taxa which correspond to the last warm events of isotopic stage 5 the next phase from 65 500 to 56 800 yr records a cold humid climate that correlates with isotope stage 4 during the third phase from 56 800 to 49 500 yr relatively warm and cold events alternate the fourth phase from 49 500 to 46 200 yr records a cold dry climate the fifth phase ranging from 46 200 to 40 800 yr records a milder phase that is similar in appearance to the beginning of the holocene