impact of late holocene aridification trend climate variability and geodynamic control on the environment from a coastal area in sw spain a detailed pollen analysis has been carried out on two sediment cores taken from a marsh area located in the donana national park southwestern spain the studied sedimentary sequences contain a si

did the last sea level lowstand always lead to cross shelf valley formation and source to sink sediment flux 1 it is commonly believed that the efficiency of sediment flux from continents to oceans is maximized during relative sea level rsl lowstands by means of cross shelf valleys that are directly connected to the continental slope and deep marine environment while such conditions have been documented for the last rsl lowstand along several continental margins there is increasing evidence that radically different conditions persisted during the last glacial maximum lgm elsewhere with lowstand shorelines that remained on the continental shelf here we analyze the relationship between the lgm 21 ka shoreline and the shelf edge for the gulf of mexico off the united states and the bay of biscay off france a geophysical model is used to compute shoreline positions corrected for isostatic movements and the shelf edge position is quantified by means of curvature the conditions in the two study areas differed markedly throughout the gulf of mexico study area lgm sea level dropped to a point commonly 40 m below the shelf edge consistent with conventional sequence stratigraphic models while in the bay of biscay the modeled lgm shoreline remained well landward of the shelf edge in places separated by hundreds of kilometers these observations hint at potentially significant implications for 1 the source to sink sediment flux from continents to oceans and its variation in time and space 2 sequence stratigraphic models that predict deep marine sedimentation as being particularly prominent during rsl lowstands and 3 the occurrence of paleovalleys and related features on the continental shelf in addition our findings raise fundamental questions about the mechanics of shelf edge formation

isotopic reconstruction of the african humid period and congo air boundary migration at lake tana ethiopia abstract the african humid period of the early to mid holocene 12 000 5000 years ago had dramatic ecological and societal consequences including the expansion of vegetation and civilization into the green sahara while the humid period itself is well documented throughout northern and equatorial africa mechanisms behind observed regional variability in the timing and magnitude of the humid period remain disputed this paper presents a new hydrogen isotope record from leaf waxes d wax in a 15 000 year sediment core from lake tana ethiopia 12 n 37 e to provide insight into the timing duration and intensity of the african humid period over northeastern africa d wax at lake tana ranges between 80 and 170 with an abrupt transition from d enriched to d depleted waxes between 13 000 11 500 years before present 13 11 5 ka a similarly abrupt transition from d depleted to d enriched waxes occurs ca 8 5 8 ka and is followed by generally d enriched waxes throughout the late holocene trends in d wax covary with changes in northern hemisphere summer insolation and reflect increased precipitation at lake tana during the ahp however the transition from d depleted to d enriched waxes occurs earlier at lake tana ca 8 ka vs 5 ka than in many other regional records and the amplitude of d depletion during the ahp is larger at lake tana as well we attribute this early enrichment to a reduction of moisture derived from westerly sources the congo basin and atlantic ocean which we suggest are d depleted relative to moisture sourced from the east indian ocean and the north red sea and mediterranean sea our new record highlights the importance of both the northward migration of the tropical rain belt as well as east west migration of the congo air boundary to precipitation source and amount during the african humid period

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

saharan aeolian input and effective humidity variations over western europe during the holocene from a high altitude record saharan dust inputs affect present day ecosystems and biogeochemical cycles at a global scale previous saharan dust input reconstructions have been mainly based on marine records from the african margin nevertheless dust reaching western central europe is mainly transported by high altitude atmospheric currents and requires high altitude records for its reconstruction the organic and inorganic geochemical study of sediments from a southern iberia alpine lacustrine record has provided an exceptional reconstruction of saharan dust impact and regional climatic variations during the holocene after the last deglaciation results indicate that saharan dust reached western europe in a stepwise fashion from 7 0 to 6 0 cal kyr bp and increased since then until present promoting major geochemical changes in the lacustrine system effective humidity reconstruction indicates wetter conditions during the early holocene and progressive aridification during middle late holocene time boosting abrupt changes in the lacustrine system cyclostratigraphic analyses and transport mechanisms both point to solar irradiance and aridity as major triggering factors for dust supply over western europe during the holocene

mid to late holocene mediterranean climate variability contribution of multi proxy and multi sequence comparison using wavelet analysis in the northwestern mediterranean basin abstract forcings and mechanisms underlying holocene climate variability still remain poorly this work review already published paleoclimatic time series and proposes an alternative way to compare them using spectral analysis such an approach may emphasize joint features between different signals and lead us closer to the causes of climate changes ten paleoclimatic proxy records from 5 sequences from the gulf of lions and surrounding areas were compiled these paleoclimate time series were supplemented with proxies of the north atlantic oscillations nao el nino southern oscillations enso and the intertropical convergence zone itcz variability a comparison of their frequency content is proposed using wavelet analysis for unevenly sampled time series a new algorithm is used in order to propagate the age model errors within wavelet power spectra three main groups of shared features specific to the mid and late holocene after 7000 yrs cal bp can be defined on the basis of the results of these analyses an atlantic cyclic period solar cyclic periods and tropical cyclic periods the atlantic cyclic period is probably related to fluctuations of the atlantic thermohaline circulation which would induce changes in the storm track extension and position thereby impacting upon precipitation and storminess over a millennial scale the centennial scale solar variability might induce a nao like variability of the atmospheric circulation thereby influencing storminess in western europe and mediterranean finally tropical cyclic periods are possibly registered in of the gulf of lions and atlantic climate proxies potentially highlighting the influence of enso variability over the western mediterranean

stable isotope records of late quaternary climate and hydrology from mediterranean lakes the isomed synthesis lake isotope records can be used to assess the spatial coherency of late quaternary climate change across the circum mediterranean region we place modern and palaeo data within a simple conceptual lake response model to show that the isotope hydrology of most mediterranean lakes has been influenced strongly by water balance even in those systems that are chemically dilute i e freshwater 18o data on biogenic and endogenic carbonates from 24 lake basins are used to reconstruct multi millennial scale trends since the lgm while it is difficult to make direct comparisons between lake records in terms of single climatic parameters coherent regional isotopic trends can be identified during glacial times mediterranean lakes deposited carbonates isotopically heavier in 18o compared to the holocene partly due to source area effects isotopic enrichment was most marked during intervals corresponding to the h1 and younger dryas events confirming that late pleistocene cold stages in the north atlantic region were marked by aridity around much of the mediterranean almost all mediterranean lake records shifted to more depleted isotopic values during the last glacial interglacial transition lgit this shift is the reverse of the trend which characterised the same transition in lakes from northern and central europe and suggests that temperature changes were not an important direct driver of mediterranean lake isotopic records over glacial interglacial timescales in the early holocene many lakes in the eastern part of the region were more depleted isotopically than in recent millennia this corresponds with marine sapropel formation both chronologically and geographically and implies that increases in local rainfall contributed significantly to the creation of a freshwater lid and anoxia in the east mediterranean sea in contrast no such pattern is currently apparent from lake isotope records from the west mediterranean suggesting a possible nw se contrast in climate history during the holocene

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

late quaternary vegetation and fire dynamics on mount kenya abstract pollen and charcoal data generated from a 1469 cm core radiocarbon dated to 26 430 14 c yr bp recovered from rumuiku swamp on the southeast of mount kenya are used to document changes in the distribution and composition of montane vegetation and fire regimes over the late quaternary throughout the transition from the last glacial maximum lgm high resolution sub centennial scale analysis documents a highly dynamic ecosystem and fire regime the pollen record shows that under a cool but rather moist lgm climate ericaceae and stoebe species shifted down slope more than 1000 m relative to the present day rather than simple altitudinal lowering of current vegetation zonation these taxa formed a vegetation assemblage that mixed high altitude components with relatively lowland taxa in particular juniperus that is presently found at altitudes lower than the study site but on the drier side of mount kenya there is noticeable addition and co dominance of hagenia to the ecosystem from 20 500 14 c yr bp until around 14 000 14 c yr bp when a mix of ericaceous belt and upper montane forest taxa such as artemisia polycias schefflera and stoebe dominated the initial development of montane forest reduced levels of hagenia juniperus olea and podocarpus are recorded about the time of the younger dryas with highly variable presence of more mesic taxa such as polyscias and schefflera this development of montane forest over the late pleistocene to holocene transition reflects a significant reorganization of the ecosystem composition that was heavily influenced by a variable fire regime shifts in vegetation composition reflect the onset of a warmer moist climate from the beginning of holocene as mixed montane forest became more established the latter part of the holocene registers human impact and forest clearance with increased anthropogenic impact marked by a transition to open vegetation and increased fire frequency

holocene climatic changes in the western mediterranean from south east france to south east spain abstract holocene climatic changes along coastal regions from south east france to south east spain were studied using pollen ratios comparing modern pollen rain vegetation and climate along selected transects from the atlantic ocean to the mediterranean we obtained threshold values of two different ratios corresponding to the different climatic conditions along the transects these pollen ratios and threshold values were employed to characterize the holocene climatic changes from nine mediterranean coastal sites the results were compared with data from marine and continental pollen sequences distributed in the western mediterranean basin and with additional regional data independent of human activity lake level fluctuations alpine glacier advance and retreat chronology 14 c anomaly and cooling phases in eastern france and central europe the role of anthropogenic activities and climate on the changes in vegetation is discussed six major changes in vegetation cover were identified they correspond to aridification phases that occurred around 9500 9000 yr bp 10 900 9700 cal bp 7500 7000 yr bp 8400 7600 cal bp 4500 4000 yr bp 5300 4200 cal bp 3700 3300 yr bp 4300 3400 cal bp 2600 1900 yr bp 2850 1730 cal bp and 1300 1000 yr bp 1300 750 cal bp these arid episodes were regional responses to more global climatic changes and determined the changes in the vegetation cover humans undoubtedly enhanced the vegetation changes but none the less had to adapt to these new climatic conditions

impact of relative sea level and rapid climate changes on the architecture and lithofacies of the holocene rhone subaqueous delta western mediterranean sea abstract the modern rhone delta in the gulf of lions nw mediterranean is a typical wave dominated delta that developed after the stabilization of relative sea level following the last deglacial sea level rise similar to most other deltas worldwide it displays several stacked parasequences and lobes that reflect the complex interaction between accommodation sediment supply and autogenic processes on the architecture of a wave dominated delta the interpretation of a large set of newly acquired very high resolution seismic and sedimentological data well constrained by 14c dates provides a refined three dimensional image of the detailed architecture seismic bounding surfaces sedimentary facies of the rhone subaqueous delta and allows us to propose a scenario for delta evolution during the last deglaciation and holocene the subaqueous delta consists of parasequence like depositional wedges a few metres to 20 30 m in thickness these wedges first back stepped inland toward the nw in response to combined global sea level rise and overall westward oceanic circulation at a time when sediment supply could not keep pace with rapid absolute eustatic sea level rise at the younger dryas preboreal transition more rapid sea level rise led to the formation of a major flooding surface equivalent to a wave ravinement surface after stabilization of global sea level in the mid holocene accommodation became the leading factor in controlling delta architecture an eastward shift of depocentres occurred probably favoured by higher subsidence rate within the thick messinian rhone valley fill the transition between transgressive backstepping geometry and regressive prograding geometry para sequences resulted in creation of a maximum flooding surface mfs that differs from a classical mfs described in the literature it consists of a coarse grained interval incorporating reworked shoreface material within a silty clay matrix this distinct lithofacies results from condensation erosion which appears as an important process even within supply dominated deltaic systems due to avulsion of distributaries the age of the mfs varies along strike between ca 7 8 and 5 6 kyr cal bp in relation to the position of depocentres and climatically controlled sediment supply the last rapid climate change of the holocene the little ice age 1250 1850 ad had a distinct stratigraphic influence on the architecture and lithofacies of the rhone subaqueous delta through the progradation of two deltaic lobes in response to changes in sediment supply linked to rapid climate changes and to anthropic factors the rhone delta evolved from wave dominated to fluvial dominated and then wave dominated again

cryptic sequence boundaries in braided fluvial successions in braided fluvial deposits consisting of monotonous successions of sandstone or conglomerate it may be difficult to distinguish regionally significant bounding surfaces sequence boundaries from autogenic channel scour surfaces major surfaces may be characterized by erosional relief and draped by lag deposits but not all sequence boundaries show these characteristics other clues to the presence of a major surface are sharp changes in detrital composition shifts in regional palaeocurrent trends and evidence of early diagenesis of the sandstones immediately below the sequence boundary examples of these attributes of cryptic sequence boundaries are illustrated from three mesozoic units in the colorado plateau area of the united states in the chinle formation triassic near moab utah angular intraformational unconformities overlie sandstones showing evidence of early diagenesis in the castlegate sandstone upper cretaceous of east central utah a cryptic sequence boundary can be discriminated from other erosion surfaces by the evidence of detrital petrography and early diagenesis palaeocurrent data indicate changes in regional palaeoslope at two sequence boundaries within this unit evidence of early diagenesis is also present at a sequence boundary in the kayenta formation jurassic of westernmost colorado

geologic factors controlling co2 storage capacity and permanence case studies based on experience with heterogeneity in oil and gas reservoirs applied to co2 storage a variety of structural and stratigraphic factors control geological heterogeneity inferred to influence both sequestration capacity and effectiveness as well as seal capacity structural heterogeneity factors include faults folds and fracture intensity stratigraphic heterogeneity is primarily controlled by the geometry of depositional facies and sandbody continuity which controls permeability structure the permeability structure in turn has implications for co2 injectivity and near term migration pathways whereas the long term sequestration capacity can be inferred from the production history examples of gulf coast oil and gas reservoirs with differing styles of stratigraphic heterogeneity demonstrate the impact of facies variability on fluid flow and co2 sequestration potential beach and barrier island deposits in west ranch field in southeast texas are homogeneous and continuous in contrast seeligson and stratton fields in south texas examples of major heterogeneity in fluvial systems are composed of discontinuous channel fill sandstones confined to narrow sinuous belts these heterogeneous deposits contain limited compartments for potential co2 storage although co2 sequestration effectiveness may be enhanced by the high number of intraformational shale beds these field examples demonstrate that areas for co2 storage can be optimized by assessing sites for enhanced oil and gas recovery in mature hydrocarbon provinces

palaeoecological evidence for holocene environmental change from the virunga volcanoes in the albertine rift central africa abstract this study presents two new well dated sedimentary pollen and charcoal records from high altitude crater sites in the virunga volcanoes located in the albertine rift central africa currently part of one of the world s most biodiverse areas here we argue that holocene vegetation changes in a ca 8000 year palaeoenvironmental record from a crater swamp at an altitude of 3474 m and a ca 2800 year record from a crater lake at an altitude of 4127 m are linked to variations in both climate and human activity climatic changes during the mid to late holocene are reflected in the high altitude sites and more widely in adjacent parts of the albertine rift vegetation changes comprising a decline in ericaceous vegetation at ca 5000 cal yrs bp and subsequent expansion of afroalpine vegetation together with a later increase in taxa associated with lower montane forest particularly podocarpus reflect increasing aridity during the mid to late holocene human induced environmental change in the virunga volcanoes is apparent only within the last millennium despite the long history of human occupation of the area both study sites record significant forest clearance at ca 900 cal yrs bp involving a reduction in lower montane forest taxa and increases in disturbance indicators changes in the composition of upper montane forest and particularly the expansion of hagenia are possibly linked to anthropogenic induced changes in the fire regime and are apparent from ca 900 cal yrs bp human induced environmental modification from the early part of the last millennium likely associated with onset of the late iron age appears to have extended to high altitudes the importance of natural long term climate change as a major cause of environmental change in the albertine rift has been eclipsed within the last millennium by human induced environmental effects

evidence for a widespread climatic anomaly at around 9 2 ka before present 1 the 8 2 ka event was triggered by a meltwater pulse mwp into the north atlantic and resultant reduction of the thermohaline circulation thc this event was preceded by a series of at least 14 mwps their impact on early holocene climate has remained almost unknown a set of high quality paleoclimate records from across the northern hemisphere shows evidence for a widespread and significant climatic anomaly at 9 2 ka b p this event has climatic anomaly patterns very similar to the 8 2 ka b p event cooling occurred at high latitudes and midlatitudes and drying took place in the northern tropics and is concurrent with an mwp of considerable volume 8100 km3 as the 9 2 ka mwp occurs at a time of enhanced baseline freshwater flow into the north atlantic this mwp may have been despite its relatively small volume sufficient to weaken thc and to induce the observed climate anomaly pattern

orbital imprint on holocene palaeohydrological variations in west central europe as reflected by lake level changes at cerin jura mountains eastern france this paper presents a lake level record for the holocene at lake cerin jura mountains eastern france it is based on a range of sedimentological techniques validated in previous studies with a combination of systematic lithostratigraphic investigations of the infillings accumulated in the lacustrine basin and sediment analyses of two selected cores the chronology is based on 10 radiocarbon dates and pollen stratigraphy on a millennial scale the cerin lake level record shows three distinct successive phases characterised by higher lake level conditions until ca 9000 cal a bp followed by a maximal lowering at ca 9000 8500 cal a bp and a progressive rise until the present this rise was punctuated by centennial scale fluctuations with major events around 4000 2800 and after 1500 cal a bp considered on a multimillennial scale the general pattern of palaeohydrological changes reconstructed at cerin reflects the impact of orbitally driven summer insolation this is in agreement with other regional and extra regional palaeoclimatic records although every record shows peculiarities in timing and shape depending on the proxy used for reconstruction in this general context centennial to multicentennial oscillations appear to have been second order events in comparison with the major influence of the orbital factor copyright 2011 john wiley sons ltd

synsedimentary faults and amalgamated unconformities insights from 3d seismic and core analysis of the lower triassic middle buntsandstein ems trough north western germany the late permian early triassic succession of the central european basin ceb was repeatedly affected by the tectonic pulses associated with the earliest phases of tethyan and arctic north atlantic rifting effects of the differential tectonic subsidence are particularly well recorded by unconformities which form widespread sequence boundaries such unconformities are most obvious in areas occupied by fault controlled intra basinal highs swells in that areas stratigraphic loss may comprise entire lower and middle buntsandstein formations and in places remnant middle buntsandstein successions directly rest on permian strata analysis of 3d seismic data and well logs combined with high resolution sedimentological logging of drillcores at the western margin of the ems trough nw germany reveals details of synsedimentary tectonic control on sequence development early triassic extensional faulting of basement blocks provided stepwise addition of accommodation space for continental sequences by growth faulting along north south oriented fault zones blocks on the flanks of the east netherlands high this process is most evident during the development of the hardegsen unconformity which is characterised by an amalgamation of succeeding unconformity surfaces in areas of structurally controlled intrabasinal highs

climatic changes along the northwestern african continental margin over the last 30 kyrs two sediment cores were investigated to study the regional climatic variability of the nw african upwelling over the late quaternary biomarker data and sea surface temperatures ssts predicted from alkenones at 25 n and 21 n exhibited distinct features the amplitude of the last deglaciation was estimated to 4 5 c at 25 n and 2 2 5 c at 21 n at 25 n terrestrial and marine glacial inputs were higher than holocene ones as a result of a strengthening of the trade winds and intensification of oceanic production in contrast at 21 n warmer ssts and lower organic carbon and alkenone productions during the last glacial suggest a regression of the upwelling and therefore a change of wind regime low glacial n alkanols are consistent with the migration of the vegetation belt during the maximum of african aridity while their decrease towards the core top may be indicative of anthropogenic disturbances

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

diagenetic signatures of stratal surfaces in the upper jurassic fulmar formation central north sea ukcs sedimentation rate and changes in relative sea level affect early diagenetic cementation along key stratal surfaces within the deeply buried upper jurassic fulmar formation south central graben ukcs as a result of the bioturbated nature of the shallow marine strata variations in ichnofabrics and cross cutting relationships between trace fossils are important in identifying and correlating stratal surfaces two transgressive and two regressive surfaces sequence boundaries were studied using petrographical mineralogical and geochemical techniques cements including early diagenetic pyrite framboids grain rimming apatite microcrystalline dolomite and ankerite occur at above and immediately below both transgressive and forced regressive surfaces sequence boundaries breaks or subdued rates of sedimentation associated with both types of surfaces meant that the sediment package resided within early diagenetic zones for prolonged periods of time enhancing diagenetic reactions at and below the surfaces the distribution of ankerite despite being a deep burial cement was primarily controlled by concentrations of bioclasts that are particularly abundant at transgressive surfaces the diagenetic character of the forced regressive surfaces sequence boundaries is more complex than that of the transgressive surfaces both in terms of mineralogy and paragenesis this is attributed to the superimposition of diagenetic assemblages as a result of erosion re sedimentation and sediment by passing although the diagenetic signature of the surfaces has been modified by dissolution replacement reactions during deep burial early diagenetic signatures can still be distinguished

holocene climate variability of the western mediterranean surface water dynamics inferred from calcareous plankton assemblages a high resolution study centennial scale has been performed on the calcareous plankton assemblage of the holocene portion of the ocean drilling program site 976 alboran sea with the aim to iden

north atlantic influence on 19th 20th century rainfall in the dead sea watershed teleconnections with the sahel and implication for holocene climate fluctuations abstract the importance of understanding processes that govern the hydroclimate of the mediterranean basin is highlighted by the projected significant drying of the region in response to the increase in greenhouse gas concentrations here we study the long term hydroclimatic variability of the central levant region situated in the eastern boundary of the basin as reveled by instrumental observations and the holocene record of dead sea level variations observations of 19th and 20th century precipitation in the dead sea watershed region display a multidecadal anti phase relationship to north atlantic natl sea surface temperature sst variability such that when the natl is relatively cold jerusalem experiences higher than normal precipitation and vice versa this association is underlined by a negative correlation to precipitation in the sub saharan sahel and a positive correlation to precipitation in western north america areas that are also affected by multidecadal natl sst variability these observations are consistent with a broad range of holocene hydroclimatic fluctuations from the epochal to the millennial and centennial time scales as displayed by the dead sea lake level by lake levels in the sahel and by direct and indirect proxy indicators of natl ssts on the epochal time scale the gradual cooling of natl ssts throughout the holocene in response to precession driven reduction of summer insolation is associated with previously well studied wet to dry transition in the sahel and with a general increase in dead sea lake levels from low stands after the younger dryas to higher stands in the mid to late holocene on the millennial and centennial time scales there is also evidence for an anti phase relationship between holocene variations in the dead sea and sahelian lake levels and with proxy indicators of natl ssts however the records are punctuated by abrupt lake level drops which appear to be in phase and which occur during previously documented abrupt major cooling events in the northern hemisphere we propose that the mechanisms by which natl ssts affect precipitation in the central levant is related to the tendency for high low pressure anomalies to persist over the eastern north atlantic western mediterranean region when the basin is cold warm this in turn affects the likelihood of cold air outbreaks and cyclogenesis in the eastern mediterranean and consequently rainfall in the central levant region depending on its phase this natural mechanism can alleviate or exacerbate the anthropogenic impact on the regions hydroclimatic future

freshwater chlorophycean algae in recent marine sediments of the beaufort laptev and kara seas arctic ocean as indicators of river runoff freshwater chlorophycean algae are characteristic organic walled microfossils in recent coastal and shelf sediments from the beaufort laptev and kara seas arctic ocean the persistent occurrence of the chlorophycean algae pediastrum spp and botryococcus cf braunii in marine palynomorph assemblages is related to the discharge of freshwater and suspended matter from the large siberian and north american rivers into the arctic shelf seas the distribution patterns of these algae in the marine environments reflect the predominant deposition of riverine sediments and organic matter along the salinity gradient from the outer estuaries and prodeltas to the shelf break sedimentary processes overprint the primary distribution of these algae resuspension of sediments by waves and bottom currents may transport sediments in the bottom nepheloid layer along the submarine channels to the shelf break bottom sediments and microfossils may be incorporated into sea ice during freeze up in autumn and winter leading to an export from the shelves into the deep sea the presence of these freshwater algae in sea ice and bottom sediments in the central arctic ocean confirm that transport in sea ice is an important process which leads to a redistribution of shallow water microfossils

high resolution holocene climate and hydrological variability from two major mediterranean deltas nile and rhone high resolution records of sea surface temperatures ssts and terrestrial n alkanes terr alkanes combined with pollen from the same sedimentary sequences were generated to assess variations in the nile river discharge over the holocene these independent proxy records indicate a period of wetter conditions in the nile watershed during the early holocene consistent with insolation driven enhanced monsoon precipitation known as the african humid period ahp the detection of a dry episode around 9200 yr bp in the terr alkane and pollen time series suggests a temporary weakening of the monsoon intensity most probably triggered by extratropical cooling in the north atlantic an interval of c4 grass expansion between 8800 and 8400 yr bp was also evidenced from the terr alkane distribution and confirmed by palynological data ssts of the coastal waters off the nile delta reveal strong fluctuations in the early holocene followed by a slight warming and two pronounced cold intervals around 3500 yr bp and 150

variability of the north atlantic oscillation over the past 5 200 years the north atlantic oscillation influences climate in the arctic region and northern europe reconstructions of circulation patterns associated with the north atlantic oscillation from a 5 200 year long lake sediment record suggest that the atmospheric circulation responded to significant transitions in northern hemisphere climate

after the deluge mediterranean stagnation and sapropel formation in an east mediterranean marine core the upper sapropel begins soon after the start of a global event a very heavy precipitation which occurred in the equatorial latitudes during the late glacial early holocene this heavy precipitation in africa channelled by the nile river across 35 of latitude produced a low salinity surface layer in the east mediterranean in this confined basin with high bottom salinity the steep salinity gradient stratified the water column the stagnant bottom waters triggered the sapropel formation cretaceous sapropels in the tropical oceans may result from the same chain of events in warm humid climates with contrasting wet and dry seasonal rhythm

7000 years of paleostorm activity in the nw mediterranean sea in response to holocene climate events abstract a high resolution record of paleostorm events along the french mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the gulf of lions integrating grain size faunal analysis clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating we recorded seven periods of increased storm activity at 6300 6100 5650 5400 4400 4050 3650 3200 2800 2600 1950 1400 and 400 50 cal yr bp in the little ice age in contrast our results show that the medieval climate anomaly 1150 650 cal yr bp was characterised by low storm activity the evidence for high storm activity in the nw mediterranean sea is in agreement with the changes in coastal hydrodynamics observed over the eastern north atlantic and seems to correspond to holocene cooling in the north atlantic periods of low ssts there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies we hypothesise that the increase in storm activity during holocene cold events over the north atlantic and mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large central atlantic european domain

high and low latitude forcing of the nile river regime during the holocene inferred from laminated sediments of the nile deep sea fan sediments deposited on deep sea fans are an excellent geological archive to reconstruct past changes in fluvial discharge here we present a reconstruction of changes in the regime of the nile river during the holocene obtained using bulk elemental composition grain size analyses and radiogenic strontium sr and neodymium nd isotopes from a sediment core collected on the nile deep sea fan this 6 m long core was retrieved at view the mathml source water depth and is characterized by the presence of a 5 m thick section of finely laminated sediments which were deposited between 9 5 and 7 3 ka bp and correspond to the african humid period ahp the data show distinct changes in eolian dust inputs as well as variations in discharge of the blue nile and white nile sedimentation was mainly controlled by changes in fluvial discharge during the holocene which was predominantly forced by low latitude summer insolation and by the location of the eastern african rain belt the changes in relative contribution from the blue nile and white nile followed changes in low latitude spring autumn insolation which highlights the role of changes in seasonality of the precipitation on the nile river regime the relative intensity of the blue nile discharge was enhanced during the early and late holocene at times of higher spring insolation with massive erosion and runoff during the ahp at times of high summer insolation while it was reduced between 8 and 4 ka at times of high autumn insolation the gradual insolation paced changes in fluvial regime were interrupted by a short term arid event at 8 5 7 3 ka bp also associated with rejuvenation of bottom water ventilation above the nile fan which was likely related to northern hemisphere cooling events another arid event at 4 5 3 7 ka bp occurred as the apex of a gradually drier phase in ne africa and marks the end of the ahp

holocene itcz and indian monsoon dynamics recorded in stalagmites from oman and yemen socotra abstract high resolution oxygen isotope 18o profiles of holocene stalagmites from four caves in northern and southern oman and yemen socotra provide detailed information on fluctuations in precipitation along a latitudinal transect from 12 n to 23 n 18o values reflect the amount of precipitation which is primarily controlled by the mean latitudinal position of the itcz and dynamics of the indian summer monsoon ism during the early holocene rapidly decreasing 18o values indicate a rapid northward displacement in the mean latitudinal position of the summer itcz and the associated ism rainfall belt with decadal to centennial scale changes in monsoon precipitation correlating well with high latitude temperature variations recorded in greenland ice cores during the middle to late holocene the summer itcz continuously migrated southward and monsoon precipitation decreased gradually in response to decreasing solar insolation a trend which is also recorded in other monsoon records from the indian and east asian monsoon domains importantly there is no evidence for an abrupt middle holocene weakening in monsoon precipitation although abrupt monsoon events are apparent in all monsoon records they are short lived and clearly superimposed on the long term trend of decreasing monsoon precipitation for the late holocene there is an anti correlation between ism precipitation in oman and inter monsoon spring autumn precipitation on socotra revealing a possible long term change in the duration of the summer monsoon season since at least 4 5 ka bp together with the progressive shortening of the ism season gradual southward retreat of the mean summer itcz and weakening of the ism the total amount of precipitation decreased in those areas located at the northern fringe of the indian and asian monsoon domains but increased in areas closer to the equator

review and new aspects concerning the formation of eastern mediterranean sapropels abstract in this paper it is proposed that the formation of eastern mediterranean sapropels occurred in an anti estuarine type of circulation which was to some degree weakened relative to the present in response to reduction of the eastern mediterranean excess of evaporation over freshwater input this reduction of excess evaporation would have been imposed by intensifications of 1 the indian ocean summer sw monsoon influencing the eastern mediterranean via increased nile discharge and 2 the system of mediterranean depressions an element of the westerly atlantic system causing increased precipitation and decreased evaporation both the indian ocean summer monsoon and the westerly atlantic system would be intensified in response to the occurrence of distinct minima in the cycle of precession it is demonstrated that reduced excess evaporation whether or not coinciding with global phases of deglaciation would lead to reduction of surface water salinities in the eastern mediterranean causing isolation of previously formed high salinity cooler deep water thus mixing was severely reduced possibly even restricted to eddy diffusion with only occasional convective events that because of the existing density gradient hardly ever would reach the deepest parts of the basin the consequently diminished oxygen advection down from a few hundred meters in the water column favoured preservation of the sinking organic matter this would however suffice only to enable the formation of sapropels with low organic carbon contents the high organic carbon contents observed in various sapropels are argued to reflect superimposed increases of export production the described scenario accounts for previously reported 1 increases of organic carbon content with increasing depth of deposition within individual sapropels and 2 asymmetrical sequences of sapropel deposition characterized by gradual build up and rather abrupt ending it is furthermore in agreement with 3 isotopic and faunal reconstructions of the history of exchange transports through both the strait of sicily and the strait of gibraltar and 4 faunal and floral reflections of the presence or absence of a distinct deep chlorophyll maximum with its associated increases in export production indicating the presence or absence of a shallow pycnocline within the euphotic layer moreover the described scenario 5 is in no way conflicting with the reports of sapropels in the western mediterranean and 6 seems to be endorsed by occasionally intercalated intervals suggestive of somewhat improved oxygenation amidst anoxic benthic desert levels a situation that has been observed in a few quaternary and pliocene sapropels

itcz and enso like pacing of nile delta hydro geomorphology during the holocene abstract the nile valley accommodates the world s longest river and shaped the development of numerous complex societies providing a reliable source of water for farming and linking populations to sub saharan africa and the mediterranean sea its fertile delta lay at the heart of ancient egyptian civilization however little is known of its morpho sedimentary response to basin wide changes in holocene hydrology here we present two well resolved records from the nile delta based on 320 radiocarbon dates to reconstruct the timing and rhythm of catchment scale modifications during the past 8000 years on the orbital timescale we demonstrate that nilotic hydrology and sedimentation have responded to low latitude insolation forcing while on sub millennial timescales many of the major phases of deltaic modification were mediated by climate events linked to el nino southern oscillation type enso variability

vegetation fire and climate history of the lesser caucasus a new holocene record from zarishat fen armenia vegetation fire and climate history are investigated in the 10 000 year record of zarishat fen located today in the steppe grasslands of armenia near east pollen based climate quantification provides a reconstruction of seasonal parameters the development of in situ water dependant plants and of forests at lower altitude at 8200 cal a bp echoes the shift from an arid and cold annual precipitation pann 452mm mean temperature of the coldest month mtco 11 1uc early holocene to a more humid and warmer pann 721mm mtco 6 8uc mid late holocene this marks the onset of lower seasonality in particular more effective precipitation brought during late spring by the westerlies paralleling the mediterranean precipitation pattern precipitation in the near east and central asia decreased during the mid late holocene in favour of higher seasonality controlled in winter spring by the siberian high fire history and sedge based fen development record drier phases at approximately 6400 5300 4900 3000 2200 1500 and 400 cal a bp which resemble the precipitation pattern of the south western mediterranean and contrast with the holocene pattern in the south central and south eastern mediterranean regions arid phases in armenia are believed to be related to multi centennial scale variation of westerly activity north atlantic oscillation like copyright 2013 john wiley sons ltd

mid holocene climate variations revealed by high resolution speleothem records from soreq cave israel and their correlation with cultural changes mid holocene 7000 4000 yr bp paleoclimate conditions were reconstructed for the eastern mediterranean region through a high resolution 3 20 yr oxygen and carbon isotopic record in a speleothem

temperature and salinity records of the tyrrhenian sea during the last 18 000 years abstract we have used the modern analogue technique to derive sea surface temperature sst records of the last 18 000 years from two well dated deep sea cores recovered in the tyrrhenian sea results show two major cooling events synchronous with the european and north atlantic oldest and younger dryas events a later cooling of lower amplitude is observed between about 8000 and 4500 yr bp tyrrhenian ssts were similar to those of the upper holocene only during the bolling allerod event and at the beginning of the holocene we compared the sst and the planktonic foraminiferal oxygen isotope records to estimate the surface salinity variations our reconstruction shows that salinity decreased in the tyrrhenian sea during the three cold events whereas high ssts correlate with high salinities during most of the last 18 000 years tyrrhenian sea salinity variations were similar to those of the north atlantic ocean near the entrance of the mediterranean sea the salinity gradient between the two basins was thus constant indicating that the western mediterranean circulation pattern and the freshwater budget were not significantly different from the modern one the case was however different during the middle holocene when the strong salinity decrease associated with the sapropel deposit in the eastern mediterranean basin had no equivalent in the north atlantic ocean this peculiar event can only be explained by a local climatic change and an increase of precipitation

the deltaic nature of amazon shelf sedimentation despite the annual discharge of more than a billion tons of sediment by the amazon river the sedimentary environment near the river mouth has little subaerial expression and thus does not meet the classic definition of a delta the river mouth however is not an estuary either these observations raise a major question as to what type of sedimentary environment the amazon river mouth represents seismic stratigraphy has been examined on the continental shelf at the mouth of the amazon river using high frequency 3 5 khz seismic records from about 6 000 km of ship track these records demonstrate three regions 1 the amazon river has built a subaqueous feature which stretches for hundreds of kilometres offshore and alongshore from its mouth the feature is prograding seaward and accreting upward and it contains fine scale stratification typical of classic deltas the feature forming at the mouth of the amazon is a subaqueous delta it differs from classic deltas primarily in its lack of subaerial expression subaqueous deltas such as the amazon represent the general case of a major river entering an energetic oceanic regime

the importance of atmospheric input of terrestrial organic material to deep sea sediments the concentrations of lipids were determined in atmospheric particle gas and rain samples collected from the tropical north pacific to assess lipid sources transport mechanisms and fluxes to the ocean surface four lipid compound classes aliphatic hydrocarbons fatty alcohols fatty acid esters and salts all unequivocally show a terrestrial vascular plant source these aerosol lipids originate from wind erosion of asian and american soils and direct emission from vegetation the major fluxes result from rain rather than dry deposition these fluxes are large enough to have a major potential impact on the inventory of terrestrially derived lipid material found in deep sea sediments this has been showm for n alkanes fatty alcohols fatty acids total lipids and for organic carbon by comparing atmospheric and sediment trap fluxes with sediment accumulation rates it is suggested that some biogenic terrestrial material is more protected from degradation than marine derived material

global temperature calibration of the alkenone unsaturation index uk 37 in surface waters and comparison with surface sediments in this paper we compile the current surface seawater c37 alkenone unsaturation uk 37 measurements n 629 1 to 30 c temperature range to derive a global field based calibration of uk 37 with alkenone production temperature a single nonlinear global surface water calibration of uk 37 accurately predicts alkenone production temperatures over the diversity of modern day oceanic environments and alkenone synthesizing populations t 0 957 54 293 uk 37 52 894 uk 37 2 28 321 uk 37 3 r2 0 97 n 567 the mean standard error of estimation is 1 2 c with insignificant bias in estimated production temperature among the different ocean regions sampled an exception to these trends is regions characterized by strong lateral advection and extreme productivity and temperature gradients e g the brazil malvinas confluence in contrast to the surface water data the calibration of uk 37 in surface sediments with overlying annual mean sea surface temperature anno is best fit by a linear model anno 29 876 uk 37 1 334 r2 0 97 n 592 the standard error of estimation 1 1 c is similar to that of the surface water production calibration but a higher degree of bias is observed among the regional data sets the sediment calibration differs significantly from the surface water calibration uk 37 in surface sediments is consistently higher than that predicted from anno and the surface water production temperature calibration and the magnitude of the offset increases as the surface water anno decreases we apply the global production temperature calibration to the coretop uk 37 data to estimate the coretop alkenone integrated production temperature coretop ipt and compare this with the overlying annual mean sea surface temperature anno we use simple models to explore the possible causes of the deviation observed between the coretop temperature signal as estimated by uk 37 and anno our results indicate that the deviation can best be explained if seasonality in production and or thermocline production as well as differential degradation of 37 3 and 37 2 alkenones both affect the sedimentary alkenone signal

mid holocene emergence of a low frequency millennial oscillation in western mediterranean climate implications for past dynamics of the north atlantic atmospheric westerlies the nature and tempo of holocene climate variability is examined in the record of forest vegetation from western mediterranean marine core md95 2043 episodes of forest decline occurred at 10 1 9 2 8 3 7 4 5 4 4 5 and 3 7 2 9 cal ka bp and between 1 9 cal ka bp and the top of the record 1 3 cal ka bp wavelet analysis confirms a 900 yr periodicity prior to and during the early holocene and the dominance of a 1750 yr periodicity after 6 cal ka bp the 900 yr periodicity has counterparts in numerous north atlantic and northern hemisphere palaeoclimate records and in solar irradiance proxies 14c and 10be and may relate to a sun climate connection during the early holocene comparisons between the md95 2043 forest record and strategically located records from morocco iceland norway and israel suggest that the 1750 yr mid to late holocene oscillation reflects shifts between a prevailing strong and weak state of the zonal flow with impacts similar to the positive and negative modes of th

abrupt climate change sea surface salinity and paleoproductivity in the western mediterranean sea gulf of lion during the last 28 kyr abstract the planktonic foraminiferal record of core md99 2346 gulf of lion shows a decrease of sea surface temperature sst at the time of heinrich event h2 24 23 5 cal kyr bp younger dryas and during the early to middle holocene these events were associated with a decrease of surface water salinity the salinity lowering events were similar and synchronous to those recorded in the north atlantic ocean during h1 h2 and the younger dryas they can be explained by a decrease in the salinity of the atlantic surface water entering the mediterranean through the strait of gibraltar this result indicates that the mediterranean sea remained a concentration basin and that its freshwater budget was not significantly different from the modern conditions at the time of these low salinity events higher abundances of the benthic foraminifer cibicidoides pachydermus at the time of heinrich events h2 and h1 may result from a seasonal and more pulsed supply of labile organic matter a high abundance of intermediate and deep infaunal taxa globobulimina spp during the warm bolling allerod period is interpreted as a result of an increased lateral advection of organic matter to the deeper environments of the gulf of lion surface water productivity as reflected by the organic flux to the benthic ecosystem reaches a maximum during the cold younger dryas period it is possible that cold conditions at the time of the younger dryas have allowed an enhanced vertical mixing and deep water cascading in the gulf of lion this may have resulted in an increase of primary and export production this putative intensification of deep water cascading would have occurred after the sustained rise of the global sea level from 16 to 12 5 cal kyr bp the deglacial sea level rise may also have played an important role in favouring the downslope movement of dense shelf water enriched in organic matter originating from the early rhone delta complex the conditions during the holocene were characterized by a low surface productivity and oligotrophic environment similar to the modern situation

a synchronized dating of three greenland ice cores throughout the holocene as part of the effort to create the new greenland ice core chronology 2005 gicc05 a synchronized stratigraphical timescale for the holocene parts of the dye 3 grip and ngrip ice cores is made by using volcanic reference horizons in electri cal conductivity measurements to match the cores the main annual layer counting is carried out on the most suited records only exploit ing that the three ice cores have been drilled at locations with different climatic con ditions and differences in ice flow however supplemental counting on data from all cores has been performed between each set of reference horizons in order to verify the valid ity of the match after the verification the main dating is transferred to all records us ing the volcanic reference horizons as tie points an assessment of the mean annual layer thickness in each core section confirms that the new synchronized dating is consistent for all three cores the data used for the main annual layer counting of the past 7900 years are the dye 3 grip and ngrip stable isotope records as the high accumulation rate at the dye 3 drill site makes the seasonal cycle in the dye 3 stable isotopes very resistant to firn diffusion an effort has been made to extend the dye 3 holocene record the new syn chronized dating relies heavily on this record of 75 000 stable isotope samples the dat ing of the early holocene consists of an already established part of gicc05 for grip and ngrip which has now been transferred to the dye 3 core gicc05 dates the younger dryas termination as defined from deuterium excess to 11 703 b2k 130 years earlier than the previous grip dating

20 000 years of nile river dynamics and environmental changes in the nile catchment area as inferred from nile upper continental slope sediments multi proxy analysis of two marine sediment cores ms27pt and md04 2726 from the nile continental slope provides evidence of changes in nile sediment discharge related to changes in ethiopian african monsoon eam precipitation and allows us to reconstruct changes in nile river runoff vegetation and erosion in the nile headwaters sediment element composition and neodymium isotopic composition reveal significant changes in clastic sediment provenance with sources oscillating between a saharan aeolian contribution during the last glacial maximum deglacial transition and during the late holocene and a blue atbara nile fluvial contribution during the african humid period ahp this study provides a new understanding of past environmental changes between 14 6 and 14 13 ka there was a major input of sediments from the ethiopian highlands consistent with a stronger eam at that time climate in the nile basin was wetter between 14 8 and 8 4 ka with a corresponding increase in blue nile water and sediment discharge via the main nile into the eastern mediterranean the gradual climatic transition from the ahp to the present day dry climate was reflected in a decrease in blue nile sediment deposition and flood discharge between 8 4 and 3 7 ka with aridity at a maximum between 3 7 and 2 6 ka the onset of drier conditions in the blue nile basin seems to have begun before the 8 2 ka cooling event in the north atlantic we speculate that the climatic change from the wet ahp to the dry late holocene may have been a result of a break in the low latitude dynamic equilibrium between climate vegetation and erosion which may in turn have affected the climate in higher latitudes reduced nile flow may also have had an impact on levantine intermediate water originating in the eastern mediterranean through an increase in intermediate water formation

210pb and 137cs in margin sediments of the arctic ocean controls on boundary scavenging 1 210pb and 137cs were measured in 25 sediment cores collected during the international polar year from a transect spanning the north american arctic margin from the north bering sea to baffin bay davis strait profiles and inventories of the radioisotopes were used to determine sediment mixing and accumulation at each site and to assess the intensity of scavenging and burial sediment accumulation rates derived from 210pb and validated using 137cs are between 0 04 and 0 23 g cm 2 yr 1 210pb cannot be used to derive sedimentation rates for vigorously biomixed sediments from the north bering chukchi shelf elevated 137cs activities and inventories in recently deposited sediments imply delayed inputs of particle associated 137cs to the sediments likely transported from the watershed to the coast and subsequently redistributed to shelf slope sediments inventories of 210pbex in all cores meet or exceed the estimated supply of 210pbex from atmospheric deposition and decay of 226ra in the water column this implies that in contrast to the deep arctic ocean basin there is a sufficient supply of suspended particulates along the north american arctic margin to scavenge the supply of 210pbex 210pbex inventories in sediments are up to 21 fold greater than the in situ supply at some sites large inventories of 210pbex in sediments along the north bering chukchi shelf result primarily from focusing while those along the north chukchi slope barrow canyon and in baffin bay davis strait reflect strong boundary scavenging likely supported by lateral exchanges with deep interior atlantic origin waters

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

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

reconstruction of postglacial to early holocene vegetation history in terrestrial central europe via cuticular lipid biomarkers and pollen records from lake sediments high resolution environmental reconstruction for central european terrestrial settings is commonly based on sediment records that provide the pollen spectra used for reconstruction of vegetation development alternatively complementary algal insect or zooplankton assemblages and or carbonate 18 o isotope profiles are investigated in this study vegetation development and inferred climate evolution were documented on a decadal to centennial scale by analysis of land plant cuticular lipids accumulated in lake sediments wax lipids derived from land plant leaves and blades are source diagnostic and highly resistant to degradation their aerodynamic properties favor short distance eolian transport but they are less affected by possible long distance transportation that complicates pollen analysis the late glacial to holocene sedimentary record of lake steisslingen southwestern germany was investigated by palynological and geochemical means tundra type pioneer vegetation consisting predominantly of grasses and herbs is dominated by nc31 alkanes whereas pioneer birch forest yields preferentially nc27 alkanes establishment of a pine assemblage is recognizable by elevated nc29 and nc31 leaf wax alkanes and the diversification of deciduous forests in the holocene is marked by nc29 dominance lipid geochemistry and palynology resolve decadal excursions such as the mid younger dryas event centennial climate trends with pronounced and rapid changes at the oldest dryas bolling allerod younger dryas and younger dryas preboreal transitions are consistently reflected by molecular and palynological proxy data the demonstrated suitability of an independent molecular proxy in paleoenvironmental studies provides new perspectives in high resolution climate reconstruction

impacts of the north atlantic gyre circulation on holocene climate off northwest africa we present well dated high resolution holocene records of sea surface temperature sst and upwelling intensity off northwest nw africa we identify long term cooling trends over the holocene in the subtropical north atlantic in response to boreal summer insolation a pronounced cooling event of similar to 1 degrees c ca 8 5 cal ka indicates a large scale reorganization of the ocean current system possibly induced by meltwater from the northern north atlantic our alkenone sst record off cape ghir provides strong evidence for the impact of ocean circulation changes on subtropical north atlantic ssts it is likely that cold waters were propagated to the subtropics via the canary current in a way similar to heinrich events and the younger dryas off cape blanc we find 2 3 k y periodic variations in sst and upwelling intensity off nw africa superimposed on the cooling trend such a cycle has been documented in various paleoclimate archives in phase with solar forcing we show that these variations on millennial time scales are linked to the north atlantic subtropical gyre circulation and the northern hemisphere atmospheric circulation and in particular to changes in the pressure gradient between the icelandic low and the azores high this suggests that oceanic circulation in response to solar forcing played a more important role in the generation of 2 3 k y cyclicity than has been previously considered

present day coccolith fluxes recorded in central eastern mediterranean sediment traps and surface sediments two sediment traps were deployed in time series collection from november 1991 to august 1994 at 3000 and 3500 m respectively above and below the oxygenated sea water anoxic brine interface in the bannock basin central eastern mediterranean here the coccolithophore flux and its contribution to the carbonate particulate flux are presented for the 3000 m trap and compared with the record in eastern mediterranean surface sediments a marked seasonal variation is observed in the fluxes of total mass total coccoliths and whole coccospheres with flux maxima in late winter and spring the annual coccolith flux of 1 1010 coccoliths m 2 year 1 measured in the deep waters of bannock basin is much lower than published data from most other oceanographic settings even when corrected for the trap efficiency of 23 calculated from the 230th flux the biogenic and lithogenic fluxes are primarily controlled by coccolithophore production and saharan dust input respectively the calculated coccolith and coccosphere settling rates estimated from the comparison of maximum pigment concentration in the surface ocean and arrival of maximum flux at 3000 m water depth ranged from 17 to 25 m day 1 for coccoliths and 100 m day 1 for coccospheres at the study site carbonate dissolution is a minor process at both the trap depth and at the sea floor in both oxic and anoxic conditions and there is a high preservation of coccolith caco3 coccolithophores are the main contributor to the biogenic carbonate flux followed by thoracosphaerids emiliania huxleyi and florisphaera profunda followed by syracosphaera helicosphaera carteri and calcidiscus leptoporus are the dominant species in the sediment trap and surface sediments

landscape evolution and geodynamic controls in the gulf of cadiz huelva coast sw spain during the late quaternary abstract the coastal evolution of the el abalario area huelva southern spain during the late pleistocene and holocene is reinterpreted after a refinement of the available geochronology by means of optically stimulated luminescence osl dating new data come from the analysis of soft sediment deformation palaeosols geomorphological mapping and published seismic surveys on the onshore and offshore gulf of cadiz the present structure of el abalario dome resulted from the complex interaction of littoral catchment processes and sea level changes upon an emergent coastal plain conditioned by the upwarping of the underlying pliocene pleistocene prograding deltaic sequence upwarping is probably related to escape of over pressurized fluids accompanied by dewatering prior to and during ois oxygen isotopic stage 5 continued upwarping produced the large nw se gravitational fault of torre del loro tlf in the southwestern flank of the dome roughly parallel to the present coastline during ois 5 ois 4 the resulting escarpment favoured the accumulation of aeolian sand dunes units u1 u2 and u3 from ois 5 to early ois 1 unit u1 ois 5 ends upwards in a supersurface with a thick weathering profile that suggests moist and temperate climatic conditions unit u2 accumulated mainly during ois 4 and ois 3 with prevailing w e winds the supersurface between u2 and u3 records a part of ois 2 with relative low sea level sedimentation of unit u3 took place during the last deglaciation radiocarbon and osl ages with prevailing w sw winds under a temperate moist climate that became more arid towards the top holocene a major supersurface with an iron crust like layer ssfe developed during the holocene climatic optimum ois 1 under wetter and more temperate conditions than before fossilizing the tlf the supersurface is covered by younger aeolian dunes u4 u5 u6 and u7 transported by w sw winds since the late neolithic chalcolithic cultural period 5 0 ky cal bp

millennial scale sea surface temperature changes in the eastern mediterranean nile river delta region over the last 27 000 years 1 in this study we utilize two organic geochemical proxies the u37k index and tex86 to examine past sea surface temperatures sst from a site located near the nile river delta in the eastern mediterranean em sea the u37k and tex86 records generally are in agreement and indicate sst ranges of 14 c 26 c and 14 c 28 c respectively during the last 27 cal ka during the holocene tex86 based sst estimates are usually higher than u37k based sst estimates which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the em and is related to the onset of the modern flow regime of the nile river both records show that sst varied on centennial to millennial timescales in response to global climate events i e cooling during the last glacial maximum lgm heinrich event 1 h1 and the younger dryas yd and warming during the bolling allerod and in the early holocene during deposition of sapropel s1 the h1 cooling was particularly severe and is marked by a drop in sst of 4 5 c in comparison to pre h1 sst with temperatures 1 c cooler than during the lgm in contrast to high latitude and western mediterranean records which indicate both an abrupt onset and termination of the yd event the transition from the yd to the holocene was much more gradual in the em

persistent organic pollutants in ocean sediments from the north pacific to the arctic ocean concentrations of polychlorinated biphenyls pcbs organochlorine pesticides oc pesticides and polybrominated diphenyl ethers pbdes are reported in surficial sediments sampled along cruise transects from the bering sea to the central arctic ocean ocs and pcbs all had significantly higher concentrations in the relatively shallow water 500 m of the bering sea and arctic ocean e g canada basin pcb 149 102 pg g 1 dw concentrations were similar to or slightly lower than studies from the 1990s indicating a lack of a declining trend pbdes excluding bde 209 displayed very low concentrations e g range of median values 3 5 6 6 pg g dw in the shelf areas the sediments comprised similar proportions of silt and clay whereas the deep basin sediments were dominated by clay with a lower total organic carbon toc content while significant positive correlations were observed between persistent organic pollutant pop concentrations and toc pearson correlation r 0 66 0 75 p 0 05 the lack of strong correlations combined with differing chemical profiles between the sediments and technical formulations and or marine surface waters indicate substantial chemical processing during transfer to the benthic environment marked differences in sedimentation rates between the shallow and deeper water regions are apparent the 5 cm depth grab samples collected here representing 100 years of accumulation for the shelf sediments and 1000 years for the deeper ocean regions which may bias any comparisons nonetheless the sediments of the shallower coastal arctic seas appear to serve as significant repositories for pops deposited from surface waters