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

the medieval climate anomaly in the iberian peninsula reconstructed from marine and lake records abstract selected multi proxy and accurately dated marine and terrestrial records covering the past 2000 years in the iberian peninsula ip facilitated a comprehensive regional paleoclimate reconstruction for the medieval climate anomaly mca 900 1300 ad the sequences enabled an integrated approach to land sea comparisons and despite local differences and some minor chronological inconsistencies presented clear evidence that the mca was a dry period in the mediterranean ip it was a period characterized by decreased lake levels more xerophytic and heliophytic vegetation a low frequency of floods major saharan eolian fluxes and less fluvial input to marine basins in contrast reconstruction based on sequences from the atlantic ocean side of the peninsula indicated increased humidity the data highlight the unique characteristics of the mca relative to earlier the dark ages da ca 500 900 years ad and subsequent the little ice age lia 1300 1850 years ad colder periods the reconstruction supports the hypothesis of trouet et al 2009 that a persistent positive mode of the north atlantic oscillation nao dominated the mca

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

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

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

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

climate change and cultural response around 4000 cal yr b p in the western part of chinese loess plateau new data suggest that dramatic environmental change in the western loess plateau of china corresponded with substantial changes in human demography ca 4000 cal yr b p these data demonstrate that a rapid climatic transition from wet to dry led to an ecologically devastated period between 4090 and 3600 cal yr b p the sudden reduction in the number of archaeological sites during this period namely a reduction in the total number of sites and a contraction of the areal distribution of sites points to declining agricultural productivity associated with widespread aridification beginning at 4000 cal yr b p 2005 published by university of washington

application of a bayesian model to infer the contribution of coalbed natural gas produced water to the powder river wyoming and montana the powder river basin prb of wyoming and montana contains significant coal and coal bed natural gas cbng resources cbng extraction requires the production of large volumes of water much of which is discharged into existing drainages compared to surface waters the cbng produced water is high in sodium relative to calcium and magnesium elevating the sodium adsorption ratio sar to mitigate the possible impact this produced water may have on the quality of surface water used for irrigation the state of montana passed water anti degradation legislation which could affect cbng production in wyoming in this study we sought to determine the proportion of cbng produced water discharged to tributaries that reaches the powder river by implementing a four end member mixing model within a bayesian statistical framework the model accounts for the 87sr 86sr 13cdic sr and dic of cbng produced water and surface water interacting with the three primary lithologies exposed in the prb the model estimates the relative contribution of the end members to the river water while incorporating uncertainty associated with measurement and process error model results confirm that both of the tributaries associated with high cbng activity are mostly composed of cbng produced water 70 100 the model indicates that up to 50 of the powder river is composed of cbng produced water downstream from the cbng tributaries decreasing with distance by dilution from non cbng impacted tributaries from the point sources to 10 20 at the montana border this amount of cbng produced water does not significantly affect the sar or electrical conductivity of the powder river in montana copyright 2013 john wiley sons ltd

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

formal ratification of the quaternary system period and the pleistocene series epoch with a base at 2 58 ma in june 2009 the executive committee of the international union of geological sciences iugs formally ratified a proposal by the international commission on stratigraphy to lower the base of the quaternary system period to the global stratotype section and point gssp of the gelasian stage age at monte san nicola sicily italy the gelasian until then had been the uppermost stage of the pliocene series epoch the base of the gelasian corresponds to marine isotope stage 103 and has an astronomically tuned age of 2 58 ma a proposal that the base of the pleistocene series epoch be lowered to coincide with that of the quaternary the gelasian gssp was also accepted by the iugs executive committee the gssp at vrica calabria italy which had hitherto defined the basal boundary of both the quaternary and the pleistocene remains available as the base of the calabrian stage age now the second stage of the revised pleistocene in ratifying these proposals the iugs has acknowledged the distinctive qualities of the quaternary by reaffirming it as a full system period correctly complied with the hierarchical requirements of the geological timescale by lowering the base of the pleistocene to that of the quaternary and fully respected the historical and widespread current usage of both the terms quaternary and pleistocene copyright 2009 john wiley sons ltd

the response of stratified frictional flow of shelf and slope waters to fluctuating large scale low frequency wind forcing abstract numerical and analytical models are developed to discuss large scale low frequency wind driven fluctuations over the continental shelf and slope in the presence of realistic density stratification and bottom friction the models employ the long wave assumption that frequencies are small relative to the inertial frequency and that alongshore scales are large relative to cross cross shelf scales an attempt is made to make the effect of bottom friction on the flow as realistic as possible by taking into account the influence of surface gravity waves on bottom stress the results were obtained for sinusoidal wind forcing having frequency and alongshore wavenumber l and are described below a general criterion for barotropic shelf water response for wind forcing frequencies in the weather band 2 few weeks to 2 few days can be derived for the purpose of rapid calculation this criterion reduces approximately tohere ns2 is a shelf averaged value of the buoyancy frequency squared is

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

holocene palaeohydrological changes in the northern mediterranean borderlands as reflected by the lake level record of lake ledro northeastern italy a lake level record of lake ledro northern italy spans the entire holocenewith a chronology derived from51 radiocarbon dates it is based on a specific sedimentological approach that combines data fromfive sediment profiles sampled in distinct locations in the littoral zone on a millennial scale the lake level record shows two successive periods from 11 700 to 4500 cal yr bp and from 4500 cal yr bp to the present characterized by lower and higher average lake levels respectively in addition to key seasonal and inter hemispherical changes in insolation the major hydrological change around 4500 cal yr bp may be related to a non linear response of the climate system to orbitally driven gradual decrease in insolation the ledro record questions the notion of an accentuated summer rain regime in the northern mediterranean borderlands during the boreal insolation maximum moreover the ledro record highlights that the holocenewas punctuated by successive centennial scale highstands correlations with the preboreal oscillation and the 8 2 ka event and comparisonwith the atmospheric 14c residual record suggest that short lived lake level fluctuations developed at ledro in response to 1 final steps of the deglaciation in the north atlantic area and 2 variations in solar activity

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

late holocene drought responsible for the collapse of old world civilizations is recorded in an italian cave flowstone a severe drought in parts of low latitude northeastern africa and southwestern asia 4200 yr ago caused major disruption to ancient civilizations stable isotope trace element and organic fluorescence data from a calcite flowstone collected from the well watered alpi apuane karst of central western italy indicate that the climatic event responsible for this drought was also recorded in mid latitude europe although the timing of this event coincides with an episode of increased ice rafted debris to the subpolar north atlantic the regional ocean atmosphere response seems atypical of similar holocene ice rafting events furthermore comparison of the flowstone data with other regional proxies suggests that the most extreme part of the dry spell occurred toward the end of a longer term climate anomaly

chronology and tectono sedimentary evolution of the upper pliocene to quaternary deposits of the lower guadalquivir foreland basin sw spain this paper presents new litho chrono and magnetostratigraphic data from cores of 23 exploratory boreholes drilled in the abalario and marshlands areas of the lower guadalquivir basin the western sector of the guadalquivir foreland basin sw of spain the lithologic logs of these boreholes identify four main sedimentary formations namely almonte sand and gravel lebrija clay and gravel marismas clay and abalario sand respectively interpreted as proximal alluvial distal alluvial alluvial estuarine and aeolian from radiocarbon and magnetostratigraphic data these formations were dated as upper pliocene to holocene in the marshlands area three main sedimentary sequences are present an upper pliocene to lower pleistocene sequence of the almonte and lebrija lower unit formations a pleistocene sequence of the lebrija upper unit and the lower marismas formations and a latest pleistocene to present day sequence of the upper marismas formation the three sequences began as a rapid alluvial progradation on a previously eroded surface and a subsequent alluvial retrogradation in the third sequence estuarine and marsh sediments accumulated on top of the alluvial sediments the aeolian sands of the abalario topographic high developed coeval to alluvial and estuarine sedimentation after the first alluvial progradation and continuously until the present correlation with the surrounding areas show that the sequences are the result of the forebulge uplift of the northern margin of the basin sierra morena and the adjacent neogene oldest sediments of their northern fringe both form the main source area of the study formations this uplift occurred simultaneous to the flexural subsidence sse tilting of the southern part of the basin where sedimentary aggradation dominated

the coastal archives of the last 15 ka in the atlantic mediterranean spanish linkage area sea level and climate changes sea level and climate changes archived in various coastal environments during the last part of the last glacial and present interglacial periods are investigated by interpolating available geomorphology sedimentology palaeontology and geochronology data the coastal response to these changes depended on the environment and geographic location changes of sea level during the rising transgressive phase are well recorded in the sedimentary filling of the estuaries whereas during the phase of highstand they are best recorded in beach barrier environments the postglacial rise of sea level took place in two phases a rapid rise until 6500 cal bp and a second phase of near stability with minor oscillations of metric magnitude regarding climate changes there is no record of changing temperatures in the coastal zones of southern spain although there is in precipitation and wind intensity velocity after 7 5 cal ka bp the general climatic trend towards aridity was punctuated by several short lived centennial episodes of increased aridity that occurred with a millennial cycle often coincident with bond cool events and in some cases with decreases of sea surface temperatures the absence of human intervention in vegetation composition until 2000 bp suggests that most environmental coastal shifts were climatically driven

stress and palaeostress in the betic rif cordilleras miocene to the present palaeostress orientation in the betic rif cordilleras can be determined for the miocene to the quaternary by analysis of brittle microstructures faults joints striated pebbles and stylolites in the central and northern south iberian domain 1 was subhorizontal and trended nw se from the early miocene to the present in the northern alboran domain from the burdigalian to the serravallian palaeostress ellipsoids were oblate with 3 subhorizontal and trending ene wsw in the southern part of the south iberian domain and in the northern part of the alboran domain betic cordillera from the tortonian to the quaternary palaeostress ellipsoids were variable in the granada region they were prolate with 1 subvertical but in the almeria region they were triaxial with 2 subvertical and 3 subhorizontal and trending ne sw to e w in the rif the alboran and african maghrebian domains were affected by palaeostresses with 1 subhorizontal varying from ne sw in tortonian times to n s in the plio quaternary a study of earthquake focal mechanisms by the right dihedra method indicates that the present day general stress field around the betic rif cordilleras is compressional with 1 subhorizontal and trending nw se in the betic rif cordilleras this general stress field is modified and the present day orientations of 1 2 and 3 are nearly the same as those of the palaeostresses in the pliocene and quaternary the distribution and evolution of stresses in the betic rif cordilleras from the miocene to the present can be correlated with the main neogene deformations extensional structures in the central and northern alboran domain and the southern part of the south iberian domain and compressional structures in the south iberian and african maghrebian domains and in the southern part of the alboran domain

late holocene evolution of the southwestern donana national park guadalquivir estuary sw spain a multivariate approach four phases are distinguished in the late holocene evolution of the southwestern donana national park sw spain based on a multidisciplinary analysis of the sediments present in drill cores in the oldest phase 2400 2500 cal yr bp a coastal lagoon the roman lacus ligustinus was recognized in the central part of this area partly closed by the donana spit and limited by fluvial levees the following phase 2400 2200 cal yr bp is characterized by high energy events which caused the breakthrough of the donana spit and the creation of new littoral strands in the inner areas in the third phase 2200 2050 cal yr bp this new outlet was closed coinciding with the progradation of the donana spit the last phase 2050 cal yr bp recent comprises three periods a an unstable period 2050 1950 cal yr bp with the deposit of cheniers over the previous levees b an infilling period with a diminution of the marine influence and c the appearance of temporary ponds between the emerged levees and cheniers

correlation between foraminifera and sedimentary environments in recent estuaries of southwestern spain applications to holocene reconstructions a multivariate analysis of the foraminifera collected in three estuaries of southwestern spain guadiana piedras tinto odiel permits recognition of three main assemblages with spatial distribution depending on sedimentary environments grain size classes and salinity variations assemblage 1 trochammina inflata jadammina macrescens is typical of salt marsh deposits with high salinity variations and percentages of important silt assemblage 2 ammonia beccarii ammonia tepida astrononion stelligerum elphidium williamsoni includes the most abundant estuarine species with increasing densities from the channel margin to the subtidal channel assemblage 3 quinqueloculina seminulum elphidium crispum is mainly found in the sandy sediments of the subtidal channels located near the mouth with normal marine conditions these results and the sedimentological interpretation of seven drill cores collected in the domingo rubio channel tinto river allow reconstruction of the palaeogeographic changes of this small estuary in the last ca 6500 14 c years bp seven phases were distinguished with an evolution from an open marine bay to

environmental evolution and mid late holocene climate events in the valencia lagoon mediterranean coast of spain integration of geomorphological stratigraphic malacological sedimentological and micropalaeontological techniques and 14c dating allows us to characterise the processes and evolution of the coastal barrier lagoon system of valencia spain from the middle holocene to the historical epoch as well as the responses to global climate events four stages are recognised phase 1 around 8240 80 cal yr bp a brackish lagoon of moderate energy and in restricted environment was formed with an energy peak that could correspond to the maximum holocene marine transgression dating 8240 80 cal yr bp carried out in peat corresponds to a cold cycle and low water levels in inland lakes of the western mediterranean phase 2 from 6450 cal yr bp to 3710 130 cal yr bp a lagoon remained in restricted environment and connected with the sea but with a notable energy decrease and recurrent saturation processes similar to those described in other mediterranean continental lakes this phase is contemporaneous

lacustrine interdeltaic coal in fort union formation paleocene powder river basin wyoming abstract the tongue river member of the fort union formation the major coal bearing unit in the powder river basin of wyoming and montana records a history of paludal fluvial deltaic and lacustrine sedimentation tongue river deltas filled the basin primarily from the eastern margin as they prograded into a lake lebo shale member that occupied the basin axis major streams entered the fort union coastal plain from point sources resulting in areas of broad interdeltaic coastal plain isolated from major clastic influx we mapped the clastic framework facies and the regional distribution of thick tongue river coal seams using approximately 1 400 induction electric logs a detailed study of a thick coal seam in the center of the basin shows that coal occurrence is facies dependent peat accumulation began in interdeltaic and interdistributary areas at the loci of regional ground water discharge upon delta abandonment peat swamps overspread the abandoned lobes the result is a thick strike parallel interdeltaic coal seam bounded by fluvial deltaic framework facies the depositional model and coal occurrence maps provide a guide for coal exploration and a framework for interpreting individual deposits in the powder river basin end of article last page 931

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

geomorphological record of extreme wave events during roman times in the guadalquivir estuary gulf of cadiz sw spain an archaeological and paleogeographical approach abstract analysis of the geological record has made it possible to delimit for the guadalquivir estuary the traces of extreme wave events ewes during the roman period in the iberian peninsula 218 bce to 476 ce the largest event occurred in the 2nd 3rd century ce it generated clearly visible erosive effects in the coastal barriers including washover fans and erosional scarps in the inner estuary however the effects were minor crevasse splays that broke levees and cheniers as well as a residual sedimentary lag the significant development of the spits protected the inner estuary from the marine incursion which only caused a water level rise with low regime waves correlation of the geomorphological and sedimentary marks left by this event with the archaeological and geological evidence of other events recognized elsewhere in the gulf of cadiz effectively argues for a tsunami as to the nature of the 2nd 3rd century ce event yet this and the other identified ewes in the guadalquivir estuary during the pre roman and the roman period all fit a model of paleogeographic evolution dominated by processes of coastal progradation and estuarine infilling radiocarbon dating geomorphological analysis and historical references fail to warrant the so called 218 209 bce atlantic tsunami as hypothesized in the received scientific literature in pre roman and roman times human occupation at the mouth of the guadalquivir river was strongly influenced by various geodynamic processes the location of the settlements being contingent upon dependable fast communication with the sea and above all upon adequate protection from ewes on the leeward side of spits progressive progradation of these coastal barriers combined with the gradual infilling of the estuary to make navigation to open sea increasingly difficult and eventually to result in the abandonment of settlements

continental shelf circulation induced by a moving localized wind stress abstract a linear two dimensional model of a rotating stratified fluid is constructed to investigate the circulation induced by a moving localized line of surface stress this model is used to analyze the effect of moving cold fronts on continental shelf circulation the nature of the induced circulation depends on the relative magnitude of the translation speed of the storm and the natural internal wave speed if the surface stress moves slower than the internal wave speed the disturbance is quasi geostrophic and moves with the storm if the storm moves faster than the internal wave speed two sets of internal inertial waves are produced one set of waves is forced by the surface forcing and travels at the speed of the storm another set of waves is produced by reflection of the directly forced waves from the coastal wall we conclude that free surface deflection slope is responsible for the low frequency quasi geostrophic currents due to passing cold fronts the internal response is composed of t

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

a comparison of mechanisms generating vertical transport in the brazilian coastal upwelling regions 1 several mechanisms can drive vertical velocities in the coastal ocean including wind forcing and through gradients in the vorticity field generated by flow topography interactions a two layer steady wind driven analytical model is applied to the major upwelling systems of brazil cabo frio cf and cabo de santa marta csm regions comparisons are made between the relative roles of wind and flow topography interaction in inducing upwelling over these regions ekman pumping is the weakest mechanism over the shelf but does influence the along shelf temperature in the cf area away from coastline irregularities wind driven upwelling ekman transport dominates over all mechanisms however in the vicinity of capes and coastal features topographically driven upwelling plays a significant role and its transports may vary from 43 to 94 of wind driven upwelling upstream of capes topographically driven vertical motions are downwelling favorable and act against the wind driven coastal upwelling while downstream of capes they are upwelling favorable where all mechanisms add up to create strong upwelling peaks in total upwelling in the cf region are about twice as large as those in the csm area because the cf region has stronger winds and larger coastline perturbations than in the csm region observed sea surface temperatures sst agree well with variability in the vertical transports where upwelling peaks are in phase with low temperature peaks along the coast results suggest that on larger scales the sst variability along the coast is mainly controlled by wind driven upwelling while upwelling due to flow topography interaction is responsible for the smaller scale sst variability

a high resolution record of climate vegetation and fire in the mixed conifer forest of northern colorado usa high resolution pollen charcoal 13c total organic carbon toc and magnetic susceptibility data from sediment cores from a montane lake in northern colorado record variations in vegetation fire history and sedimentation since 14 5 ka 1 ka 1000 cal yr b p this record shows warm conditions during the bolling allerod and the coldest conditions in this area during the younger dryas event warming occurred throughout the early and middle holocene lasting until ca 5 ka when the warmest and wettest summer conditions were recorded progressive climate cooling and enhanced winter precipitation are then observed until present day these long term climatic trends correlate to changes in summer insolation charcoal accumulation rates char increased along with the arboreal vegetation from minima in the late glacial period to maxima during the early and middle holocene suggesting that charcoal influx was also controlled by climate and vegetation toc and 13c show a progressive increase and a decrease trend during the late pleistocene and holocene respectively related to changes in vegetation and productivity in the lake major peaks in the char record correspond with peaks in magnetic susceptibility indicating enhanced fire induced erosion and sedimentation millennial and centennial scale changes are also observed throughout the different proxy records they exhibit strong correlations with climate records from distant regions including greenland and the north atlantic providing evidence for global teleconnections among regional climates a solar climate connection is suggested by prominent ca 225 and 390 yr cycles which may correlate with the 208 yr suess and 400 yr solar cycles

radiocarbon dating of marine samples from gulf of cadiz the reservoir effect abstract the 14 c content of marine shells can be used as a proxy for past coastal upwelling intensity the iberian coast of the gulf of cadiz can be divided in two regions with different oceanographic conditions the southern portuguese coast with an active upwelling influenced by the northeastern atlantic circulation and the southwestern andalusian coast where due to its configuration a wind driven coastal upwelling is absent because these oceanographic conditions r a parameter that quantifies the marine reservoir effect has positive values with a weighted mean of 65 20 14 c yr southern portuguese coast or negative values with a weighted mean of 135 20 14 c yr andalusian coast nevertheless between 4400 bp and 4000 bp r values are strongly positive suggesting a very strong upwelling existed in the entire region of the gulf of cadiz this does not reflect wind driven processes but probably an eastward extension of the azores front which is characterized by locally intense upwelling along the azores current that penetrated into the gulf of cadiz the study highlights the importance of using appropriate calibration methods when developing 14 c chronologies from the gulf of cadiz as well as the potential of r for reconstructing palaeoceanographic conditions

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

late holocene intensification of colds fronts in southern brazil as indicated by dune development and provenance changes in the sao francisco do sul coastal barrier abstract holocene coastal barriers from southern brazil present great geomorphological changes during their late stages of development in this study we investigate the holocene evolution of the sao francisco do sul sfs barrier through geomorphological heavy minerals and grain size analyses constrained by optically stimulated luminescence osl dating the sfs barrier stands out among the southern brazilian barriers due to its well preserved morphology with a parabolic dune belt in the seaward portion the progradation of the sfs barrier started at least 4914 478 years ago and had a pronounced morphodynamic shift around 1891 155 years ago this shift is characterized by episodic development of parabolic dunes migrating to nnw associated with sand coarsening and a marked variation in sediment provenance represented by the input of sands derived from local coastal watersheds southward from the sfs barrier this morphodynamic provenance shift resulted from the strengthening of sse winds and associated wave systems responsible for the northward alongshore drift implying intensification of cold fronts coupled with higher precipitation since 1891 155 years ago osl dating combined with grain size heavy minerals and geomorphological analyses allowed assessing the response of coastal barriers to the impacts of centennial to millenial climate events occurred during the late holocene reconstruction of the late holocene climate variability and associated impacts on coastal sedimentation is a key issue to evaluate the sensitivity of coastal barriers to future climate changes

carbon isotope characterization of powder river basin coal bed waters key to minimizing unnecessary water production and implications for exploration and production of biogenic gas abstract compared to other natural waters water associated with biogenic natural gas is enriched in 13 carbon shallow coal seams regularly contain abundant resources of biogenic gas as such water associated with biogenic gas in these coal beds is isotopically distinct from other waters the production of gas from coal beds requires the removal of large volumes of produced water thus a method of discerning coalbed reservoir water from other natural waters surface and groundwater is important to both the coalbed natural gas cbng industry and associated environmental and regulatory agencies although isotopic tracers have been employed to identify coalbed natural gas produced waters the isotopic variability within the reservoir has not been documented and explained in this study we present the isotopic compositions of dissolved inorganic carbon oxygen and hydrogen for water produced from 197 cbng wells in the powder river basin of wyoming and montana this extensive database allows us to distinguish variations in isotopic compositions that may occur by multiple processes these include variations that identify efficient dewatering of coal beds variations characterizing incomplete hydraulic isolation of coal beds from adjacent strata and the subsequent mixing of groundwaters variations related to well completion design and variations associated with geochemical and biogenic processes that occur along groundwater flow paths these data suggest that little change in 13 c dic occurs within the reservoir as a result of water and gas production thus the carbon isotopic composition informs other processes within the reservoir unrelated to coalbed natural gas recovery the 13 c dic and d of groundwater vary along flow path across the basin reflecting different methanogenic pathways that are associated with different isotopic fractionations and the pathways that dominate in different areas within the basin in areas where several producing coal seams are present the 13 c dic and d of produced waters from each seam are distinct therefore on a local scale the isotopic composition of produced water can identify the particular coal seam from which water and gas are withdrawn the methods and results presented in this case study provide examples that illustrate how water quality and isotopic data can be used to determine the hydraulic connectivity between coal and non coal strata identify and quantify water from individual coal horizons as well as predict and understand the isotopic variability of the reservoir

distinguishing tsunami and storm deposits an example from martinhal sw portugal abstract geological identification of past tsunamis is important for risk assessment studies especially in areas where the historical record is limited or absent the main problem when using the geological evidence is to distinguish between tsunami and storm deposits both are high energy events that may leave marine traces in coastal stratigraphic sequences at martinhal sw portugal both storm surge and tsunami deposits are present at the same site within a single stratigraphic sequence which makes it suitable to study the differences between them excluding variations caused by local factors the tsunami associated with the lisbon earthquake of november 1st 1755 ad had a major impact on the geomorphology and sedimentology of martinhal it breached the barrier and laid down an extensive sheet of sand as described in eyewitness reports besides the tsunami deposit the stratigraphy of martinhal also displays evidence for storm surges that have breached and overtopped the barrier flooding the lowland and leaving sand layers both marine derived flood deposits show similar grain size characteristics and distinctive marine foraminifera the most important differences are the rip up clasts and boulders exclusively found in the tsunami deposit and the landward extent of the tsunami deposit that everywhere exceeds that of the storm deposits identification of both depositional units was only possible using a collection of different data and extensive stratigraphical information from cores as well as trenches

apparent long term cooling of the sea surface in the northeast atlantic and mediterranean during the holocene reconstructions of upper ocean temperature t during the holocene 10 0 ka b p were established using the alkenone method from seven high accumulation sediment cores raised from the northeast atlantic and the mediterranean sea 361n 751n all these paleo t records document an apparent long term cooling during the last 10 kyr in records with indication of a constant trend the apparent cooling ranges from 0 27 to 0 151c kyr 1 records with indication of time variable trend show peak to peak amplitudes in apparent temperatures of 1 2 2 91c a principal component analysis shows that there is one factor which accounts for a very large fraction 67 of the total variance in the biomarker paleo t records and which dominates these records over other potential secondary influences two possible contributions are 1 a widespread surface cooling which may be associated with the transition fromthe hypsithermal interval b9 5 7 ka b p to the neoglaciation b5 7 0 ka b p and 2 a change in the seasonal timing and or duration of the growth period of alkenone producers prymnesiophyte algae the first contribution is consistent with many climate proxy records from the northeast atlantic area and with climate model simulations including milankovitch forcing the second contribution is consistent with the divergence between biomarker and summer faunal paleo t fromearly to late holocene observed in two cores further work is necessary and in particular the apparent discordance between biomarker and faunal t records for the relative stable holocene period must be understood to better constrain the climatic and ecological contributions to the apparent cooling observed in the former records r 2002 elsevier science ltd all rights reserved

modeling the evolution of the guadalquivir foreland basin southern spain 1 previous quantitative studies dealing with the origin of foreland basins have focused primarily either on the rheological basis of the lithosphere mechanical response or on the relationship between orogenic loading and sediment geometry to link the evolution of the guadalquivir foreland basin south iberia with the thermomechanical stratification of the iberian lithosphere we combine quantitative approaches to deep and shallow processes thrust loading lithospheric flexure thickness changes of the crust and the lithospheric mantle and surface mass transport a planform flexural analysis of the present day load distribution shows that basement subsidence is related not only to upper crustal thrusting but also to a deep seated additional load on the basis of the observed gravity and geoid fields we propose this additional load to be related to a lithospheric mantle thickening larger than the coeval crustal thickening further modeling of the evolution of a basin cross section reveals that the architecture of the sedimentary basin is additionally related to the lithosphere rheological response the quantitative study of the evolution of basement faulting and the forebulge uplift of sierra morena leads us to conclude that viscous stress relaxation and or plastic yielding within the lithosphere are key processes to explain the flexural evolution of the basin

magnetobiochronology of lower pliocene marine sediments from the lower guadalquivir basin insights into the tectonic evolution of the strait of gibraltar area the gibraltar arc is a complex tectonic region and several competing models have been proposed to explain its evolution we studied the sedimentary fill of the guadalquivir basin to identify tectonic processes that were occurring when the reopening of the strait of gibraltar led to the reestablishment of mediterranean outflow we present a chronostratigraphic framework for the lower pliocene sediments from the lower guadalquivir basin sw spain the updated chronology is based on magnetobiostratigraphic data from several boreholes our results show that the studied interval in the la matilla core is in the early pliocene section providing better constraints on the sedimentary evolution of the basin during that period migrating depositional facies led to a younger onset of sandy deposition basinward at the northwestern passive margin a 0 7 m y period of sedimentary bypass related to a sharp decrease in sedimentation rates and lower sea levels resulted from the tectonic uplift of the forebulge in contrast high sedimentation rates with continuous deep marine sedimentation are recorded at the basin center due to continuous tectonic subsidence and west southwestward progradation of axial depositional systems the marginal forebulge uplift continuous tectonic basinal subsidence and southward progradation of clinoforms in the early pliocene can be explained by the pull of a lithospheric slab beneath the gibraltar arc as the strait of gibraltar opened these findings are to our knowledge the first reported sedimentary expression of slab pull beneath the betics related to the opening of the strait of gibraltar after the messinian salinity crisis

benthic foraminiferal salinity index in marginal marine environments a case study from the holocene guadalquivir estuary sw spain abstract here we developed and validated a new benthic foraminiferal salinity bfs index from marginal marine environments by analysing benthic foraminifera from the holocene guadalquivir estuary sediments sw spain this index is formulated utilising only four species ammonia tepida and haynesina germanica with higher tolerance to brackish waters and indicating lower salinity and elphidium translucens and elphidium granosum indicative of greater marine influence and pointing to higher salinity thus the bfs index is calculated easily and rapidly and therefore it makes it possible to analyse a higher number of samples in less time the bfs index values from the studied cores enabled the detailed description of subtle changes in the guadalquivir estuary restriction during the holocene for this purpose three degrees of salinity depending on marine influence were defined higher bfs index 0 0 0 4 high marine influence moderate bfs index 0 4 0 7 moderate marine influence and lower bfs index 0 7 1 0 low marine influence before 2000 bce the estuary was moderately open and well connected to the atlantic ocean from 2000 bce the estuary experienced a greater marine influence increasing in extension as a consequence of a sea level rise and subsidence immediately afterwards it began to experience restriction processes due to southward shoreline progradation related to the growth of littoral spits and sediment supply from 1400 to 1000 bce gradual restriction transformed the open estuary into a semiclosed estuary a last phase of estuary restriction occurred from 1000 bce to the present day leading to the lowest salinity and the highest estuary restriction finally the bfs index was successfully applied in two other marginal marine environments a pleistocene lagoon in northern italy and a pliocene coastal bay in southeastern spain the index allowed assessment of the degree of restriction in these different environments supporting its utility in different regions environments and timescales

low ash peat deposits from a dendritic intermontane basin in the tropics a new model for good quality coals many good quality thick low ash carboniferous cretaceous and tertiary coal deposits have dulling upward sequences that have been interpreted to be of ombrotrophic lowland coastal origin previous studies of potential modern analogues for thick dulling upward coal sequences have focused on tropical ombrotrophic coastal peats however most modern coastal ombrotrophic deposits would yield all bright coal seams new evidence from peat deposits of the southern intermontane tasek bera basin western malaysia reveals that thick low ash low sulfur peat may originate in narrow tributary valleys with moderately steep flank gradients these deposits may be favorable precursors to dulling upward coals in that they contain high wood and low ash content at depth and medium wood and slightly increasing ash content in the upper parts peat accumulation in the tasek bera basin began in mid holocene time during the past 4500 years 500 cm of low ash 40 cm white fluvial silty clay with wood fragments was deposited the clay rich sediments are overlain by limnic black mud sandy clay and dark brown mud rich peat up to 70 cm thick the ash content of the mud rich peat is as high as 31 wt the high ash peat is overlain by low ash sapric to hemic peat up to 5 m thick the basal 3 m of the peat deposits contain abundant logs and large woody fragments whereas the top 2 m have less hard wood but more arborescent fragments of palmae such as roots from pandanus atrocarpus the acrotelm top 50 cm has a low to medium ash content 10 wt with burial the deposits of southern tasek bera basin would yield a dendritic sediment pattern of sandstone shale carbonaceous shale and a dulling upward vitrain rich coal overlain by carbonaceous shale because of the dendritic nature of the tasek bera basin coal seams would most likely have a similar pattern as the carboniferous humic coal deposits of the black warrior basin in alabama usa however the good quality coals with dulling upward characteristics would be concentrated in the southern tributaries of the basin

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

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

inertial oscillations on the continental shelf of the gulf of lions observations and theory abstract observations in the gulf of lions northwestern mediterranean sea in summer have shown that gusts of wind lasting a few days generate transient upwellings and inertial motions oscillations at the inertial frequency were observed in current meter data near the shore and at a frequency 10 greater in the temperature data vertical coherences in current meter data show a strong baroclinic mode at frequencies greater than inertial frequency a simple one dimensional two layer transient model suggests that these motions are associated with two different physical processes the first process describes the local response of the ocean to meteorological forcing the second is associated with the propagation of long internal waves generated in the transient phase of the geostrophic adjustment process as suggested by the model the direction of propagation of the internal waves is computed from current and temperature data measured at one point and it is found that the shore is the source zone

sea surface temperature and wind stress curl variability near a cape abstractthe coupling between sea surface temperature sst sst gradients and wind stress curl variability near a cape off brazil is investigated using satellite observations and several different sst high resolution analyses the cape is characterized by strong sst fronts year round associated with upwelling and advection of warm water offshore in a western boundary current observations reveal a strong coupling between crosswind sst gradients and wind stress curl variability with the predominantly negative crosswind gradients leading to negative upwelling favorable wind stress curl anomalies the spatial correlation between empirical orthogonal functions eof of those variables is 0 6 while the correlation between the eof amplitude time series of the wind stress curl and crosswind sst gradients is larger than 0 7 the coupling occurs during summer and winter and is strongly modulated by variations in the wind stress directional steadiness the intensity of the coupling is weaker than around capes

forced shelf circulation by an alongshore wind band abstract the forced circulation over a continental shelf generated by the alongshore wind stress is studied within the frictional regime the model alongshore wind stress has a finite extent in the alongshore direction and oscillates monochromatically resembling a series of anticyclones traveling across the coast line both the shelf wave response and the localized non wavelike response exist within the wind band the numerical results show that the interaction of shelf waves with locally wind forced response generates a large increase in the phase speed within the wind band given an alongshore variation in the alongshore wind stress a right bounded phase propagation is possible even in the absence of continental shelf waves given a reasonable friction currently accepted for the east coast of the united states the resonance mechanism at the cutoff frequency may not be important and lower frequency wind events generate larger amplitude continental shelf circulation by reducing the friction energy a

formal subdivision of the holocene series epoch a discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommission on quaternary stratigraphy international commission on stratigraphy this discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommision on quaternary stratigraphy sqs of the international commission on stratigraphy ics considers the prospects for a formal subdivision of the holocene series epoch although previous attempts to subdivide the holocene have proved inconclusive recent developments in quaternary stratigraphy notably the definition of the pleistocene holocene boundary and the emergence of formal subdivisions of the pleistocene series epoch mean that it may be timely to revisit this matter the quaternary literature reveals a widespread but variable informal usage of a tripartite division of the holocene early middle or mid and late and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology we propose an early middle holocene boundary at 8200 a bp and a middle late holocene boundary at 4200 a bp each of which is linked to a global stratotype section and point gssp should the proposal find a broad measure of support from the quaternary community a submission will be made to the international union of geological sciences iugs via the sqs and the ics for formal ratification of this subdivision of the holocene series epoch copyright 2012 john wiley sons ltd

holocene vegetation and climate change recorded in alpine bog sediments from the borreguiles de la virgen sierra nevada southern spain high resolution pollen and magnetic susceptibility ms analyses have been carried out on a sediment core taken from a high elevation alpine bog area located in sierra nevada southern spain the earliest part of the record from 8200 to about 7000 cal yr bp is characterized by the highest abundance of arboreal pollen and pediastrum indicating the warmest and wettest conditions in the area at that time the pollen record shows a progressive aridification since 7000 cal yr bp that occurred in two steps first shown by a decrease in pinus replaced by poaceae from 7000 to 4600 cal yr bp and then by cyperaceae artemisia and amaranthaceae from 4600 to 1200 cal yr bp pediastrum also decreased progressively and totally disappeared at ca 3000 yr ago the progressive aridification is punctuated by periodically enhanced drought at ca 6500 5200 and 4000 cal yr bp that coincide in timing and duration with well known dry events in the mediterranean and other areas since 1200 cal yr bp several changes are observed in the vegetation that probably indicate the high impact of humans in the sierra nevada with pasturing leading to nutrient enrichment and eutrophication of the bog pinus reforestation and olea cultivation at lower elevations

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 fire climate and human disturbance history in the southwestern mediterranean area during the late holocene detailed pollen charcoal isotope and magnetic susceptibility data from an alpine lake sediment core from sierra nevada southern spain record changes in vegetation fire history and lake sedimentation since ca 4100 cal yr bp the proxies studied record an arid period from ca 3800 to 3100 cal yr bp characterized by more xerophytic vegetation and lower lake levels a humid period is recorded between ca 3100 and 1850 cal yr bp which occurred in two steps 1 an increase in evergreen quercus between 3100 and 2500 cal yr bp indicating milder conditions than previously and 2 an increase in deciduous quercus and higher lake levels between ca 2500 and 1850 cal yr bp indicating a further increase in humidity and reduction in seasonal contrast humid maxima occurred during the roman humid period previously identified in other studies in the mediterranean region intensified fire activity at this time could be related to an increase in fuel load and or in human disturbance an arid period subsequently occurred between 1850 and 650 cal yr bp though a decrease in quercus and an increase in xerophytes the alternation of persistent north atlantic oscillation modes probably played an important role in controlling these humid arid cycles

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

formation of chenier plain of the donana marshland sw spain observations and geomorphic model abstract the guadalquivir estuary is one of the most important in europe it is isolated from the sea by two important littoral spits donana and la algaida its sedimentary filling occurred as a result of deltaic contributions of the guadalquivir river giving rise to marshes primarily composed of mud deposits among which a succession of sandy and shelly ridges can be found the aim of this paper is to explain the genesis and evolution of these sandy and shelly ridges clarifying what types of ridges are found and their spatial distribution identifying the processes responsible for their formation these ridges extend in the form of long strands along the estuary influencing its evolution during the late holocene the geomorphologic and lithostratigraphic features of these ridges allow them to be defined as transgressive cheniers regressive cheniers and laterally accreted ridges spits as components of the guadalquivir estuary chenier plain complex this chenier plain has the peculiarity of developing on a semi enclosed shoreline contrary to other chenier plains in the world which develop on open coasts in the guadalquivir estuary the chenier plain formation is related to two relatively higher sea level 4200 2800 yr bp and 1400 1000 yr bp during which high energy events occur storms and tsunamis that transgressed the large littoral spits the carrizosa 4000 yr bp and vetalengua 1400 1300 yr bp spits have been formed across the inlet and prograded landwards of the estuary from here several sequences of cheniers mainly transgressive cheniers associated with these events were formed these cheniers form two groups las nuevas 1100 1000 yr bp and marilopez 3000 yr bp composed mainly of shells and shell fragments these cheniers were constructed by waves which reworked the shells above estuarine levees and led to their intense landward migration thus explaining the peculiar high inland position of the cheniers

lagrangian drifter dispersion in the southwestern atlantic ocean abstractin the framework of monitoring by ocean drifters mondo project a set of lagrangian drifters were released in proximity of the brazil current the western branch of the subtropical gyre in the south atlantic ocean the experimental strategy of deploying part of the buoys in clusters offers the opportunity to examine relative dispersion on a wide range of scales adopting a dynamical systems approach the authors focus their attention on scale dependent indicators like the finite scale lyapunov exponent fsle and the finite scale mean square relative velocity fsrv between two drifters as a function of their separation and compare them with classic time dependent statistical quantities like the mean square relative displacement between two drifters and the effective diffusivity as functions of the time lag from the release the authors find that dependently on the given observable the quasigeostrophic turbulence scenario is overall compatible with their data analysis with discrepancies fr

active continental subduction beneath the betic cordillera and the alboran sea p and s wave seismic tomography detect a low velocity anomaly in the upper mantle beneath the betic cordillera and the alboran sea region the anomaly is associated with the intermediate depth seismicity h

holocene climate variability in the western mediterranean region from a deepwater sediment record 1 the detailed analysis of the international marine past global changes study core md99 2343 recovered from a sediment drift at 2391 m water depth north of the island of minorca illustrates the effects of climate variability on thermohaline circulation in the western mediterranean during the last 12 kyr geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the western mediterranean basin during the holocene superimposed on the general trend eight centennial to millennial scale abrupt events appear consistently in both grain size and geochemical records which supports the occurrence of episodes of deepwater overturning reinforcement in the western mediterranean basin the observed periodicity for these abrupt events is in agreement with the previously defined holocene cooling events of the north atlantic region thus supporting a strong atlanticmediterranean climatic link at high frequency time intervals during the last 12 kyr the rapid response of the mediterranean thermohaline circulation to climate change in the north atlantic stresses the importance of atmospheric teleconnections in transferring climate variability from high latitudes to midlatitudes

the role of neo tectonics in the sedimentary infilling and geomorphological evolution of the guadalquivir estuary gulf of cadiz sw spain during the holocene abstract a multidisciplinary analysis of cores and geomorphic patterns in the marshes of donana national park sw spain has yielded new evidence regarding the sedimentary infilling and geomorphological evolution of the guadalquivir estuary during the holocene the sedimentation and geomorphological disposition have been strongly conditioned by neotectonic activity along a set of sw ne alignments interrupted by other alignments that follow e w and nw se directions the most conspicuous of the sw ne alignments is the torre carbonero marilopez fault tcmf south of this fault the estuary experienced a marked subsidence from about 4000 to 2000 cal yr bp through a series of sedimentary sequences of retrogradation and aggradation within the context of relative sea level rise from c 2000 cal yr bp to the present the subsidence has remained relatively dormant with progradation of the littoral systems and infilling of the marshland progressing within a context of sea level stability our results reveal that neotectonic activity is a critical factor that must also be reckoned with in any attempt to understand the holocene geomorphological evolution in the guadalquivir estuary

tilting neotectonics of the guadiamar drainage basin sw spain the guadiamar river ows from the southern iberian massif to the guadalquivir foreland basin sw spain its drainage basin displays asymmetries in the stream network the arrangement of alluvial terraces and the con guration of the trunk river valley the stream network asymmetry was studied using morphometric measures of transverse topographic sym metry asymmetry factor and drainage basin shape the alluvial terraces were studied through the lithologic logs of more than a hundred boreholes and eld mapping the morphometric methods demonstrate a regional tectonic tilting toward the sse causing both the migration of the guadiamar river toward the east and the migration of the guadiamar tributaries toward the southwest as a consequence of the guadiamar river migration an asymmetric valley developed with a steep eastern margin caused by river dissection and a gentle western margin where the main alluvial deposits are found the ages obtained using the 14c analysis of samples from several alluvial deposits show that the river migration and thus tilting has occurred during the holocene as well as earlier in the quaternary this interpretation revises the guadiamar longitudinal fault assumed by previous studies copyright 2003 john wiley sons ltd

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

seven ambiguities in the mediterranean palaeoenvironmental narrative abstract a review of seven outstanding issues on mediterranean palaeoenvironments is presented these are related to the dominant orbital pacing of climate variability the length of the interglacial vegetation succession the influence of the african summer monsoon the seasonality of precipitation during boreal insolation maxima the moisture balance during glacial maxima and the appearance of the mediterranean type climate rhythm and evolution of mediterranean sclerophyllous plants what emerges is that 1 marine 18oplanktonic and sst records show that precession has been a fundamental tempo of mediterranean climate change representing both a low latitude signal runoff from north africa and the direct influence of insolation at mediterranean latitudes but high latitude glacial effects 41 kyr and 100 kyr cycles became superimposed after 2 8 ma sapropel and dust deposition patterns in marine cores reveal that obliquity also has an effect on mediterranean climate through dry wet oscillations which are independent of glacial interglacial variability 2 the temperate part of interglacial vegetation succession has a duration of approximately half a precession cycle this persisted during the interval of obliquity dominated glacial cycles 2 8 1 ma with distinct forest successions following the precessional cycles however these are not always separated by an open vegetation phase because of minimal ice growth producing an impression of a prolonged interglacial forest interval 3 the effect of an enhanced african monsoon during summer insolation maxima has been mainly indirect in terms of nile discharge and runoff along the north african coast leading to increased freshwater input into the mediterranean sea reduced deep water ventilation and sapropel deposition 4 the notion of an accentuated summer rain regime in the northern mediterranean borderlands also contributing to a freshening of the mediterranean sea during boreal insolation maxima is not supported by the available evidence which suggests increased summer aridity 5 recent improvements in chronological precision and data resolution point to an increase in aridity and decreased temperatures during the last glacial maximum 21 2 ka but suggest an increase in effective moisture during the immediately preceding interval of 24 27 ka 6 the mediterranean type climate is not exclusively a post 3 6 ma phenomenon but may have appeared intermittently during the course of the tertiary or before 7 if that is the case then the paradigm that the sclerophyllous evergreen habit represents a pre adaptation to summer drought may need re evaluation

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

orogeny and stratigraphy numerical models of the paleozoic in the eastern interior of north america a computer model is used to estimate patterns of lithospheric deformation caused by obduction and removal of loads within orogenic belts regions of lithospheric downwarp become sedimentary depocenters and regions of lithospheric upwarp suffer erosion by following the deposition and erosion of sedimentary packages through a number of model time steps it is possible to calculate a synthetic stratigraphy for a given study area this model is applied to the post early ordovician stratigraphy of the eastern interior region of north america the loading that drives lithospheric deformation is associated with the development of the appalachian and ouachita orogens and the independent development of the michigan and illinois intracratonic basins model results are shown to be consistent with presently observed stratigraphy lithology and cumulative erosion and are then used to estimate the configuration of given sediment packages at discrete intervals following their deposition these estimates are presented in the form of isopach maps stratigraphic cross sections and time stratigraphic diagrams as a function of time over the last 470 ma by tracking the burial and erosion history of sedimentary units we are able to establish a cause and effect relationship between particular tectonic events and the extent of preservation of sedimentary units in particular we suggest that the pennsylvanian permian alleghanian orogeny produced major sediment cover over much of the study area

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

the response of the south brazil bight to the passage of wintertime cold fronts on the southeastern continental shelf of brazil the wintertime subtidal variability of the circulation is highly dominated by the passage of cold fronts hydrographic data for the region reveal that during this july august september season only a weak vertical stratification is observed in this paper the response of the region to cold fronts is studied by using a barotropic finite element model forced by a conceptual cold front wind field derived from the analysis of coastal winds and satellite imagery

maastrichtian paleocene foreland basin stratigraphies western canada a reciprocal sequence architecture palynological and magnetostratigraphic chronostratigraphic correlations of lower maastrichtian to paleocene strata along an east west western canada basin transect allow for the recognition of a reciprocal sequence architecture in nonmarine strata reference sections include three canadian continental drilling program cretaceous tertiary boundary project core holes and outcrops in alberta southern saskatchewan and north central montana the spatial and temporal position of the third order sequences provides evidence for the correlation of proximal sector regional disconformities and sedimentary wedges with distal sector sedimentary wedges and regional disconformities respectively the boundary between the two sectors is represented by a hingeline which separates the foreland basin syncline from the peripheral bulge the stratigraphies defined by reciprocal third order sequences are complicated by fourth order boundaries developed within proximal sedimentary wedges and with no correlative distal strata these results support tectonic control on foreland basin sedimentation a model for interpreting the various types of sequences in terms of foreland basin evolution vertical tectonics and orogenic cycles is provided it is argued that nonmarine sequence boundaries times of maximum uplift in the foreland region may be expressed as disconformities incised valleys top of mature paleosol levels or base of fluvial channels whereas nonmarine equivalents of marine maximum flooding surfaces times of maximum basinal subsidence may be indicated by extensive coal seams and or lacustrine sediments resume les correlations palynologiques magnetostratigraphiques et chronostratigraphiques des strates echelonnees du maastrichtien inferieur au paleocene le long du transect est ouest du bassin de la cordillere occidentale au canada permettent la reconnaissance d une ordonnance architecturale de sequences reciproques dans les strates continentales les coupes de reference incluent trois trous de forage carottes du canadian continental drilling program cretaceous tertiary boundary project et des affleurements localises en alberta dans le sud de la saskatchewan et dans le centre nord du montana la position spatiale et temporelle des sequences de troisieme ordre plaide pour la mise en correlation des discordances regionales et des depots sedimentaires en coin dans le secteur proximal avec les depots sedimentaires en coin et les discordances regionales dans le secteur distal respectivement une ligne de jonction represente la limite entre les deux secteurs qui separe le bassin d avant pays en forme de cuvette du bombement peripherique les stratigraphies definies par les sequences de troisieme ordre reciproques sont embrouillees par les limites de quatrieme ordre developpees au sein des depots sedimentaires en coin proximaux sans la presence de strates distales correlatives ces resultats appuient la these d un controle tectonique sur le bassin sedimentaire d avant pays on presente ici un modele interpretant les divers types de sequences en termes d evolution d un bassin d avant pays de tectonique verticale et de cycles orogeniques nous tentons de demontrer que les discordances les vallees entaillees les horizons sommitaux de paleosols matures ou la base des chenaux fluviaux peuvent aider a definir les limites des sequences continentales periodes de soulevement maximum dans la region de l avant pays tandis que les couches de charbon etendues et ou les sediments lacustres representent plutot les equivalents continentaux des aires d inondation maximale periodes de subsidence maximum du bassin traduit par la redaction catuneanu and sweet 703

global and regional factors controlling changes of coastlines in southern iberia spain during the holocene the interaction between global glacio eustatic sea level rise and regional factors oceanographic and tectonic has controlled the evolution of coastline during the holocene in southem iberia at ca 10 000 14c years bp a deceleration of relative sea level rise took place both in the atlantic and mediterranean littorals with a maximum transgression at 6450 14c years bp in subsiding areas present tidal flats estuaries illustrate a clear marine influence recorded both in sediments and the fauna while in uplifting areas prograding spit bar systems developed two phases of major progradation are distinguished in these systems the first one between 6450 and 3000 14c years bp with a sedimentary gap at ca 4000 14c years bp and the second one from 2750 14c years bp up to present with an intervening gap between 1200 and 1050 14c years bp these progradation phases develop during stillstands followed by relative sea level fall while the sedimentary gaps represent relative high sea level in the mediterranean areas with a higher uplift rate marine terraces almost coeval to those gaps occur the most pronounced modifications in littoral dynamics occurred at between 3000 and 2750 14c years bp represented by changes in the direction of longshore drift and prevailing winds and in the predominance of progradation over aggradation processes at ca 1000 14c years bp the estuaries record a greater fluvial than marine influence and at 500 years ago an extraordinary increase in coastal progradation took place in all littoral zones the european medieval warm period is characterized at least during its initial phase by low pressure climate conditions while during the little ice age anticyclonic conditions gave rise to a strong coastal progradation

sedimentation and hydrodynamic processes associated with the tsunami generated by the 1755 lisbon earthquake abstract an unusual sedimentary horizon believed to have been deposited by the tsunami associated with the 1755 lisbon earthquake has been identified at boca do rio in southern portugal this horizon marks a distinct sedimentological and micropalaeontological break from the deposits enclosing it the sedimentary characteristics of the horizon which consists of several distinct sub units vary greatly in both vertical and horizontal section detailed textural analysis through vertical sections of these sub units shows abrupt changes in particle size characteristics the highly variable nature of the horizon appears to be due to rapid variation in the hydrodynamic characteristics of the depositional event the lowermost section of the deposit appears to have been deposited from a highly turbulent water mass which was able to transport gravel sized clasts as well as gravel sized mud balls eroded from underlying material the water mass rapidly lost energy leading to the deposition of predominantly sand silt and clay particles sharp breaks in textural characteristics are likely to be due to changes in current direction caused by wave reflection or swash backwash interference the main sources of sand sized material within the deposit are the seaward barrier beach foredune system the tsunami deposit at boca do rio shares many of the sedimentary characteristics of tsunami deposits from other sites around the world

evidence of high energy events in the geological record mid holocene evolution of the southwestern donana national park sw spain abstract four phases are distinguished in the mid holocene evolution of the southwestern donana national park sw spain based on the multidisciplinary study of sediments in drill cores in the oldest phase 5500 5400 cal years bp a coastal brackish lagoon occupied the central part of the study area partly enclosed by the donana spit and limited by fluvial levees an evolution from subtidal to intertidal conditions characterized the areas located close to the inner side of the donana spit during the same phase the following phase 5400 5200 cal years bp is characterized by a high energy event tsunami which caused the breakthrough of the donana spit and the creation of new littoral strands in the inner areas in the first period of the third phase 5200 4200 cal years bp estuarine infilling was probably the dominant process with the accumulation of phyllosilicate rich clays in the lagoon bed this was followed by a renewed phase of instability 4200 4100 cal years bp indicated by the presence of fine storm lain deposits and thicker probably tsunami induced shelly deposits the last phase 4100 3700 cal years bp comprises a an infilling period with a diminution of the marine influence and b two new high energy events which caused the erosion of the donana spit and the creation of new cheniers in the last 7000 years the comparison of these results with a revision of both geological and historical records has revealed the occurrence of twenty tsunamis at least during this period in portugal and southern spain evidences of these high energy events are washover fans bioclastic coarse sized layers within salt marsh deposits or the presence of giant boulders and pebbles the determination of the recurrence period is very difficult owing to the very scarce data although our data and other authors do not discard a possible periodicity of 2000 years for a cycle of two events separated by 300 400 years

mineralogical assemblages geochemistry and fossil associations of pleistocene holocene complex siliciclastic deposits from the southwestern donana national park sw spain a palaeoenvironmental approach abstract on the basis of mineralogy chemical and palaeontological data collected in a long core 93 m three associations of facies are distinguished in the late pleistocene late holocene evolution of the sedimentary infilling in nowadays donana national park from the lower middle and upper associations of facies three sedimentological phases have been established in the oldest phase 44 kyr bp this area was occupied by supratidal freshwater marshes located close to a brackish lagoon and inundated suddenly by brackish marine inputs the following phase 44 7 kyr bp is characterized by the transition from supratidal to intertidal conditions with the alternation of freshwater or brackish marshes situated very close or in the margin of the former lagoon and submitted to episodes of desiccation or tidal inundation the last phase 7 3 0 cal kyr bp comprised a a marine inundation during the maximum of the flandrian transgression 7 6 5 cal kyr bp and b the progressive infilling of a brackish lagoon with marine connection and permanent fresh water inputs 6 5 3 5 cal kyr bp partially enclosed by the donana spit the phyllosilicate rich clayey silty sequence of this latter infilling is interrupted by tsunami like deposits at 4 2 3 6 cal kyr bp and 3 6 3 0 cal kyr bp these high energy events are characterized by textural bimodal grain size distribution sorting decrease mineralogical crystallochemical changes in illites increasing dolomite content and geochemical changes ti anomaly besides a sudden introduction of marine bivalves and microfauna and a strong decrease or the almost disappearance of the brackish ostracode assemblage ages of these deposits coincide with those indicated for other tsunamigenic layers detected in the southwestern spanish coasts and some deep cores collected near the african european plate boundary

model studies of the wind driven transient circulation in the middle atlantic bight part 1 adiabatic boundary conditions abstract a numerical model of the wind driven transient ocean circulation in the middle atlantic bight is described the model incorporates realistic topography and covers the continental shelf between the coast and the 200 m isobath from cape hatteras to the southern tip of nova scotia the traditional shallow water dynamics are used i e the vertically integrated and linearized equations for the flow of a homogeneous fluid driven by atmospheric pressure and wind stress fluctuations and damped by a quadratic bottom stress the equations are integrated in time using a simple modification of platzman s 1972 finite difference scheme with a 12 7 km grid spacing at the coast normal flow is required to vanish at non coastal boundaries the equivalent surface elevation is held fixed several classes of initial value experiments are used to study the free and forced modes of this model and the damped flow driven by a spatially uniform and stationary wind stress and by an idealized travelling synoptic sc

a pronounced dry event recorded around 4 2 ka in brine sediments from the northern red sea partly laminated sediments were sampled from the brine filled anoxic shaban deep basin in the northern red sea at about 4200 cal yr bp more than two millennia of anoxic sedimentation is replaced by a sub oxic facies strongly suggesting the episodic absence of the brine at the same time stable oxygen isotopes from surface dwelling foraminifera show a sharp increase within less than 100 yr pointing to a strong positive salinity anomaly at the sea surface this major evaporation event significantly enhanced the renewal of deep water and the subsequent ventilation of the small shaban deep basin the timing and strength of the reconstructed environmental changes around 4200 cal yr bp suggest that this event is the regional expression of a major drought event which is widely observed in the neighboring regions and which strongly affected middle east agricultural civilizations

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

changes in sedimentation trends in sw iberia holocene estuaries spain abstract an analysis of sedimentation rates during the holocene in estuaries in the southwestern coast of the iberian peninsula using depth age diagrams reveals the existence of two distinct phases the first between ca 10 000 and 6500 cal bp still in the transgressive phase yields values of sedimentation rates of 5 mm yr the second phase extends after the maximum transgressive ca 6500 cal bp until the present with sedimentation rates of 1 5 2 mm yr these results support the idea that marine sedimentation began during the transgressive phase and continued during the highstand phase far beyond the time of the transgressive maximum as postulated in some previous papers

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

late quaternary vegetation and coastal environmental changes at ilha do cardoso mangrove southeastern brazil abstract a 190 cm mangrove sediment core from the ilha do cardoso state park state of sao paulo southeastern brazil was analyzed for pollen diatoms as well as carbon and nitrogen isotopes the goal was to determine the dynamics of the coastal terrestrial aquatic ecosystems vegetation history and climate change in this region of the brazilian atlantic rainforest during the late pleistocene and holocene the values for total organic carbon toc from 3 up to 40 c n ratios from 10 up to 130 and 15n 0 to 8 are associated with well preserved aquatic and terrestrial organic matter and possibly influenced by nitrogen cycling e g denitrification that caused 15n enrichment between 40 000 cal yr b p and 23 000 cal yr b p depleted 13c values 28 0 are also observed and indicate the predominance of c3 plants during this time interval the pollen analysis reveals the presence of the genera ilex alchornea weinmannia myrsine symplocos drimys and podocarpus on a site currently occupied by mangrove vegetation these data suggest that in the past prevailed a colder and more humid climate than today with a low relative sea level from 23 000 cal yr b p to 2200 cal yr b p a sedimentary hiatus likely occurred related to an erosive event associated to the post glacial sea level rise since at least 2200 cal yr b p sediments are marked by relatively low c n ratios from 2 to 27 exhibit more enriched 13c from 26 0 to 24 0 and 15n up to 7 values and are characterized by the presence of marine diatoms this indicates the return of the marine coastal line to its current position and consequently the development of mangrove

the spring transition from horizontal to vertical thermal stratification on a midlatitude continental shelf 1 the spring transition from wintertime horizontal thermal stratification to the summertime vertically stratified state on a wide sloping midlatitude continental shelf is investigated the sigma z level model szm a new three dimensional primitive equation numerical ocean model employing a hybrid sigma coordinate and z level coordinate in the vertical simulates the continental shelf region a simple analytical model to describe the heating rate of a well mixed water column is applied to the problem to illustrate the importance of bottom slope in determining the evolution of the horizontal thermal stratification the applicability of this simple model to continental shelf dynamics forced by realistic surface fluxes is studied with a pseudo two dimensional x z form of the szm forced with daily heat flux and wind stress records from the west florida shelf a term by term analysis of the depth averaged time integrated temperature equation quantifies the contribution of each physical process to the evolution of the horizontal temperature field the simple model used to describe the heating rate of a homogeneous water column appears as the dominant balance in the integrated temperature equation cross shelf temperature advection associated with upwelling and downwelling alters the horizontal depth integrated temperature over the shelf predicted by the simple model two processes describe the spring transition the erosion of the wintertime horizontal thermal gradient occurs on a timescale of a few months when the water column is being heated and mixed periodically the second process is the formation of the seasonal thermocline following the last strong mixing event this occurs on a timescale of less than a week under a stabilizing heat flux and light winds completing the spring transition from horizontal to vertical thermal stratification

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

circulation on the western south atlantic continental shelf 2 spring and autumn realistic simulations 1 buoyancy driven currents are here investigated in a complex scenario where two river plumes the la plata river and the patos lagoon plumes occur in the vicinity of two opposing western boundary currents the malvinas and the brazil currents the study addresses the contrasting scenarios found during the austral spring and fall seasons due to variations in river discharge in wind stress and in the boundary current transport the winds blow preferably from the northeast during the spring and from the southwest during the fall the brazil current transport is stronger during the spring when the brazil malvinas confluence is displaced southward and weaker during the fall when the confluence moves northward the study is conducted as a series of numerical simulations which consider the river discharges the tides variable wind stress and thermohaline fields which are realistic in terms of the brazil malvinas confluence our discussion focuses on the riverine water distribution in each season the austral fall scenario shows coastally trapped plumes and the spring scenario shows significant offshore removal but our fall plumes are not too elongated and narrow as other authors found in the presence of constant winds no tides and no boundary currents and our spring offshore removal is not as strong as found by others

recent coastal evolution of the donana national park sw spain abstract since the last holocene sea level rise about 6900 bp a series of depositional littoral landforms has been generated at the outlet of the guadalquivir river with progradation along the predominant longshore drift towards the east the first coastal progradation occurred between 6900 and 4500 bp the donana and perhaps la algaida spits both associated with the oldest and highest marshland in the donana national park are assumed to have been developed at an early stage originally the guadalquivir estuary was wider and deeper than now and its environment was mainly marine the oldest littoral formations have been dated as ca 4735 bp they show erosional events and indicate the breaking up of earlier spit barriers to form inlets the marine environment became increasingly dominant with heavy erosion of cliffs and a retreating coastline this period was followed by another sedimentary cycle 4200 2600 bp that surrounded the earlier eroded barriers the size of the estuary decreased due to the increasing marsh deposits and a fluvial environment was born about 2600 years ago progradation gave way to a new period of intense erosion the resulting morphology of littoral strands and erosional surfaces permitted the return to a marine environment the shoreline again retreated from 2300 bp coastal progradation has prevailed with an erosional interruption at 1000 bp the present day outlet of the guadalquivir is an estuarine delta of inactive marshland the donana national park the dominant environment is fluvial

depositional response to foreland deformation in the carboniferous of eastern kentucky the appalachian basin is a typical foreland basin that has subsided episodically under the loads of successive thrust sheets the dynamics of basin subsidence and upwarping of basin margin arch systems reflects the flexural properties of the lithosphere quantitative models of the lithosphere depend on assumed rheological properties this study attempts to test these geodynamic models in a part of the appalachian basin mississippian deposition is correlated with waning acadian tectonism orogenic quiescence coincided with basin overdeepening and uplift of the cincinnati arch or forebulge although the foreland basin was mudstone dominated shoaling along the crest of the basin margin arch system resulted in reworking and wedges of unconformities in contrast the onset of alleghenian orogenesis during the pennsylvanian is reflected in a thick wedge of terrigenous clastic sediments the pennsylvanian basin fluctuated between underfilled restricted marine and overfilled nonmarine conditions rapid response of the basin to thrust sheet loading is inferred these characteristics of mississippian and pennsylvanian deposition support a viscoelastic model of the lithosphere