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

climate controlled multidecadal variability in north african dust transport to the mediterranean high resolution laser ablation inductively coupled plasma mass spectroscopy scanning of resin embedded laminated sediments is used to detail variability in the composition and magnitude of recent eolian dust deposition in the eastern mediterranean the composition of dust accumulating in the anoxic atalante basin varies in response to the strength of the summer blocking mode of mediterranean climate dust sources located upwind on the westerly airflow are favored during phases of weaker blocking hence stronger summer westerlies this mode is in turn correlated to the pronounced multidecadal oscillation in mediterranean sea surface temperature related to the atlantic multidecadal oscillation suggesting that coupled ocean atmosphere dynamics control the large scale transport of dust in the region variable precipitation in dust source regions may also exert an influence on the relative flux of dust from each source and hence the net composition of dust deposited in the basin persistent oscillations in the composition of deeper sediments indicate that the basin offers a high potential archive for reconstruction of climate controlled variability in dust transport prior to the instrumental era

quaternary fluvial systems of tropics major issues and status of research abstract fluvial systems in tropical regions are not only the lifeline for modern civilizations there but also form an important continental archive for reconstructing quaternary palaeoclimates and palaeoenvironments tropical rivers drain through a variety of geological and geomorphological settings across the world and have been studied for their hydrology sediment transport characteristics facies models stratigraphic development and flood hazards this paper presents an overview of the research on tropical rivers globally and identifies major gaps and unanswered research questions as a part of the igcp 582 on tropical rivers the participants of this project are continuing to tackle many of these issues the collection of papers in this special issue is an outcome of this activity and presents new data on processes and alluvial stratigraphy of the tropical rivers from china india south america and northern australia

geochemistry and particle size of surface sediments of gulf of manfredonia southern adriatic sea abstract in this study we describe mechanisms influencing the spatial distribution of the surface sediments in the gulf of manfredonia seventy three samples were collected on a regional grid and analyzed for grain size major and trace elements and organic matter content sediments contain marine derived carbonate as well as terrigenous fractions indicating highly heterogeneous sediment composition dictated by different provenance and complex transport processes principal component analysis provides information about processes involved in the formation and dispersal of the sediments the regional sediment distribution is function of the gulf s morphology and sedimentary inputs from fluvial sources mainly from the ofanto river and from the north and central adriatic basin biogenic carbonate reefs identified in two restricted coastal areas add complexity to sediment shelf dispersal the north adriatic current flowing southward transports and deposits sediments from the northern basin in the offshore area of the gulf while an inner anticyclonic current distributes and mixes northern and fluvial sediment with a clockwise pattern in order to better assess the fluvial contribution also bedload samples from the main river debouching into the gulf were sampled enabling the identification of geochemical indexes to distinguish the role of both fluvial inputs and hydrodynamic processes affecting solid particles dispersion within the gulf this study provides a contribution to a qualitative estimate of the sediment supply entailed in the southwestern adriatic basin

late quaternary sedimentary dynamics in western amazonia implications for the origin of open vegetation forest contrasts abstract this work investigated the evolution of sedimentary environments during the latest quaternary and their influence on the paradoxical occurrence of open vegetation patches in sharp contact with the amazonian forest the approach integrated pre existing geological and floristic data from lowlands in the brazilian amazonia with remote sensing imagery including multispectral optical images tm etm and aster phased array l band synthetic aperture radar palsar insar c band srtm dems and high resolution images obtained from google earth the detection of an abundance of paleomorphologies provided evidence of a scenario in which constant environmental shifts were linked to the evolution of fluvial and megafan depositional systems in all studied areas the open vegetation patches are not random but associated with sedimentary deposits representative of environments either deactivated during the holocene or presently in the process of deactivation sedimentary evolution would have determined the distribution of wetlands and terra firme in many areas of the amazonian lowlands and would have a major impact on the development of open vegetated patches within the modern rainforest subsiding areas were filled up with megafan deposits and many fluvial tributaries were rearranged on the landscape the close relationship between vegetation and the physical environment suggests that sedimentary history related to the evolution of depositional settings during the latest quaternary played a major role in the distribution of flooded and non flooded areas of the amazonian lowlands with a direct impact on the distribution of modern floristic patterns as the depositional sites were abandoned and their sedimentary deposits were exposed to the surface they became sites suitable for vegetation growth first of herbaceous species and then of forest although climate fluctuations might have been involved fault reactivation appears to have been the main cause of changes in depositional dynamics through time a process that had an immediate effect on the development of large open vegetation patches intermingled with the amazonian rainforest

a climatic model for southwestern amazonia in last glacial times abstract multidisciplinary data indicate that southwestern amazonia was a savanna environment during last glacial times interpretation of biogeographical and geological records as compared with the present climatic conditions permit us to postulate a dry season more pronounced and prolonged than the present one dry northerly winds vinculated with southern bemisphere trade winds dominated during the dry season and the southerly cold air masses locally termed friagem or surazo would have been more frequent and intensive than today

flat subduction dynamics and deformation of the south american plate insights from analog modeling received 14 june 2007 revised 13 january 2008 accepted 12 march 2008 published 21 june 2008 1 we present lithospheric scale analog models investigating how the absolute plates motion and subduction of buoyant oceanic plateaus can affect both the kinematics and the geometry of subduction possibly resulting in the appearance of flat slab segments and how it changes the overriding plate tectonic regime experiments suggest that flat subductions only occur if a large amount of a buoyant slab segment is forced into subduction by kinematic boundary conditions part of the buoyant plateau being incorporated in the steep part of the slab to balance the negative buoyancy of the dense oceanic slab slab flattening is a long term process 10 ma which requires the subduction of hundreds of kilometers of buoyant plateau the overriding plate shortening rate increases if the oceanic plateau is large enough to decrease the slab pull effect slab flattening increases the interplate friction force and results in migration of the shortening zone within the interior of the overriding plate the increase of the overriding plate topography close to the trench results from 1 the buoyancy of the plate subducting at trench and 2 the overriding plate shortening experiments are compared to the south american active margin where two major horizontal slab segments had formed since the pliocene along the south american subduction zone flat slab segments below peru and central chile nw argentina appeared at 7 ma following the beginning of buoyant slab segments subduction in northern ecuador and northern chile the process of slab flattening resulting from the carnegie and iquique ridges subductions respectively seems to be active but not completed the formation of flat slab segments below south america from the pliocene may explain the deceleration of the nazca plate trenchward velocity citation espurt n f funiciello j martinod b guillaume v regard c faccenna and s brusset 2008 flat subduction dynamics and deformation of the south american plate insights

neotectonics and tree mortality in a forest ecosystem of the negro basin geomorphic evidence of contemporary seismicity in the intracratonic brazilian amazonia abstract neotectonic activity was increasingly recorded over the amazonian lowlands even during historical times of a few tens of centuries however detailed analyses linking structures and styles of deformation are still few considering the large dimension of the region such events in a relatively recent time are expected to have caused conspicuous impacts on amazonian ecosystems and forest disturbance changes in topography and hydrology by fracturing faulting and folding during either subsidence or uplifting are direct effects on landscape that leave marks on the structure of the current forest such as tree mortality and community succession two rectangular elbow like shaped wetlands from the left margin of the middle negro river valley in northwestern amazonia were attributed to neotectonics remote sensing imagery was applied to test this hypothesis and also provide a tectonic model that can explain deformation dynamics in this area the studied wetlands and adjacent river systems display various morphostructural anomalies compatible with a tectonic control as well as lineaments paralleling main nw and ne trending regional structures the geomorphic analysis led to suggest that the wetlands are depressions formed by nw and ne trending master boundary faults of horizontal displacements intercepted by various subsidiary faults transtensional strike slip regime is recorded by both left and right lateral faults with the wetlands corresponding to subsiding areas owned to conjugate strike slip faults habitat fragmentation and other ecological processes promoted by tectonic deformation would have impacted the overlying forest canopy by changing its structure due to tree mortality the complex compartmentalization imposed by active tectonics would have exposed the ground to contrasting hydrological conditions which controlled the rate of tree mortality within the wetlands we pose that the tectonic disturbance and associated tree mortality documented in the middle negro river evidence contemporary seismicity within the intracratonic brazilian amazonia

climate dynamics in the borderlands of the aegean sea during formation of sapropel s1 deduced from a marine pollen record abstract to unravel the climatic and environmental dynamics in the borderlands of the aegean sea during the early and middle holocene and notably for the interval of sapropel s1 s1 formation we have analysed terrestrial palynomorphs from a marine core in the northern aegean sea the qualitative results were complemented by quantitative pollen based climate reconstructions a land sea correlation was established based on pollen data and sediment lightness measurements from the same core and previously published benthic foraminifer data from a nearby core the borderlands of the aegean sea underwent a transition from an open vegetation to oak dominated woodlands between 10 4 and 9 5 ka cal bp a coeval increase in winter precipitation suggests that moisture availability was the main factor controlling holocene reforestation the 50 higher winter precipitation during s1 formation relative to pre sapropelic conditions suggests a strong contribution from the borderlands of the aegean sea to the freshwater surplus during s1 formation the humid and mild winter conditions during s1 formation were repeatedly punctuated by short term climatic events that caused a partial deforestation and a reorganisation within the broad leaved arboreal vegetation in the marine realm these events are documented by improved benthic oxygenation the strongest event represents the regional expression of the 8 2 ka cold event and led to an interruption in s1 formation except for the interval of s1 formation the pollen derived winter temperatures correlate with the smoothed gisp2 k series they support the previously published marine based concept that the intensity of the siberian high strongly controlled the winter climate in the aegean region during s1 formation in the aegean sea however climate conditions in the borderlands were more strongly affected by the monsoonally influenced climate system of the lower latitudes

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

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

influence of the water content on x ray fluorescence core scanning measurements in soft marine sediments the x ray fluorescence xrf core scanner provides bulk sediment chemistry data measured nondestructively at the split core sediment surface although this method is widely accepted there is little known about the effects of physical properties such as density and water content on xrf core scanner data comparison of xrf scanner measurements from the sediment surface and dry powder samples of sediment core geob7920 indicates strongly reduced element intensities for the lighter elements al and si we relate the lower element intensities of the measurements taken at the sediment surface to the amount of water in the sample volume analyzed by the xrf core scanner the heavier elements k ca ti and fe remain relatively unaffected by the variation of any physical property within sediment core geob7920 additionally we successfully use the elemental intensity of cl as a proxy for the seawater content in the sample volume analyzed by the xrf core scanner this enables the establishment of a correction function for the elements al and si that corrects for the radiation absorption of the water content in sediment core geob7920 off cape blanc nw africa

plio quaternary volcanism in ecuador extensive sampling major element chemistry on over 300 samples and k ar radiometric dating have been carried out on the ecuadorian upper tertiary quaternary volcanoes the results show important space time variations of the volcanic activity between late miocene time and the present in late miocene time a continuous volcanic belt located approximately along the present volcanic front vf affected the whole country from the cuenca basin to the south up to colombia to the north major changes occurred at about 5 ma volcanic activity stopped south of the guayaquil fault belt and never resumed to the north the active volcanic axis shifted eastward to the cordillera real cr area with a simultaneous relative decrease in intensity since early quaternary time the volcanic belt widened westward to the western cordillera where the volcanism resumed at about 1 5 1 0 ma giving rise to the very wide active volcanic zone of ecuador the plio quaternary products show significant longitudinal and latitudinal chemical and mineralogical changes volcanics of the vf and interandean depression contain amphibole and define a calc alkaline trend with a k 2 o content lower than that of the cr products which are characterized by a mostly anhydrous phenocryst assemblage in both areas andesites dominate but extreme compositions basaltic andesites and rhyolites are more diffuse in the cr than the vf no significant transverse zoning has been detected in the northern region north of the chota mira transverse tectonic line the observed temporal and spatial variations are interpreted as a result of the subduction of the carnegie ridge anomalous oceanic crust underthrusting of which began approximately 6 ma ago

paleoclimate of the southern adriatic sea region during the medieval climate anomaly reflected by organic walled dinoflagellate cysts to obtain insight into the character and forcing of southern italian climate change during the medieval climate anomaly c ad 900 1200 marine sediments deposited between ad 990 and 1200 from t

oxygen 18 16 variability in greenland snow and ice with 10 3 to 105 year time resolution the 3 km long greenland ice sheet project 2 gisp2 ice core presents a 100 000 year detailed oxygen isotope profile covering almost a full glacial interglacial cycle measuranents of isotopic fluctuations in snow frost and atmospheric water vapor samples collected during summer field seasons up to 20 0 are compatible with the large and abrupt 80 160 changes observed in accumulated tim snow pit 15 80 profiles from the gisp2 summit area however show rapid smoothing of the 180 160 signal near the surface beyond about 2 m depth the smoothedi5180 signal is fairly well preserved and can be interpreted in terms of average local weather conditions and climate the longer climate fluctuations also have regional and often global significance in the older part of the record corresponding to marine isotope stages mis 5a to 5d the effect of orbital climate forcing via the 19 and 23 kyr precession cycles and the 41 kyr obliquity cycle is obvious from the end ofmis 5a at about 75 000 years b p till the end of the glacial at the younger dryas preboreal transition at 11 650 years b p the o180 160 record shows frequent rapid switches between intermediate interstadial and low stadial values fourier spectra of the oscillations that are superimposed on the orbitally induced changes contain a strong periodicity at 1 5 kyr a broad peak at 4 0 kyr and additional shorter periods detailed comparison of the gisp2 180 160 record with the vostok antarctica 15d record pacific ocean foraminiferal 180 160 grande pile france tree pollen and insolation indicates that a counterpart to many of the rapid 180 160 fluctuations of gisp2 can be found in the other records and that the gisp2 isotopic changes clearly are the local expression of climate changes of worldwide extent correlation of events on the independent gisp2 and specmap time scales for the interval 10 000 50 000 years b p shows excellent chronometric agreement except possibly for the event labeled 3 1 the glacial to interglacial transition evidently started simultaneously in the arctic and the antarctic but its development and its expression in greenland isotopes was later suppressed by the influence of meltwater especially from the barents sea ice sheet on deep water formation and ocean circulation meltwaters from different ice sheets bordering the north atlantic also influenced ocean circulation during the bolling allerod interstadial complex and the younger dryas and led to a distinct development of european climate and greenland 180 160 values the holocene interval with long term stable mean isotopic values contains several fluauations with periods from years to millennia dominant is a 6 3 year oscillation with amplitude up to 3 to 4 0 periodicities of 11 and 210 years also found in the solar modulated records of the cosmogenic isotopes 1obe and 14c suggest solar processes as the cause of these cycles depression of180 160 values cooling by volcanic eruptions is observed in stacked gisp215 80 records but the effect is small and not likely to trigger major climate changes

the late quaternary evolution of the negro river amazon brazil implications for island and floodplain formation in large anabranching tropical systems abstract the rio negro has responded significantly in the late pleistocene and holocene to lagged environmental changes largely associated with activity during the last glacial in the amazon basin on the basis of geological structure the rio negro can be divided into six distinct reaches that each reflects very marked differential processes and geomorphological styles no deposits of the upper pleniglacial were recognized in the field the oldest recognizable late pleistocene alluvial unit is the upper terrace of middle pleniglacial age ca 65 25 ka reach i tentatively correlated with the oldest terrace identified on the left bank of reach iii at that time the river was mainly an aggradational bed load system carrying abundant quartz sand a product of more seasonal conditions in the upper catchment the late glacial 14 10 ka is represented by a lower finer grained terrace along the upper basin reach i which was recognized in the tiquie curicuriari and vaupes rivers at that time the river carried abundant suspended load as a response to climatic changes associated with deglaciation since about 14 ka the river has behaved as a progradational system infilling in downstream series a sequence of structurally controlled sedimentary basins or compartments creating alluvial floodplains and associated anabranching channel systems reach ii was the first to be filled then reach iii both accumulating mainly sand fine deposits increase downstream in reach iii and become predominant in some anabranch islands of the distal reach the lowermost reaches of the negro v and vi have been greatly affected by a rising base level and associated backwater effect from aggradation of the amazon during late glacial and recent times reach v has acted almost entirely as a fine sediment trap the remarkable anavilhanas archipelago is the product of holocene deposition in the upper part of this sedimentary basin however suspended sediment load declined about 1 5 ka prior to the lower part of this basin becoming infilled the progradational behavior of the rio negro filling tectonic basins as successive sediment traps with sand in the upper basins and fines in the downstream ones illustrates how a large river system responses to profound changes in late quaternary base level and sediment supply the most stable equilibrium conditions have been achieved in the holocene in reaches iib and iiia where an anabranching channel and erosional relictual island system relatively efficiently convey water and sediment downstream reaches iiib and v never achieved equilibrium conditions during the holocene characterised as they are today with incomplete floodplains and open water

climatically controlled river terrace staircases a worldwide quaternary phenomenon a comparison of fluvial terrace sequences from around the world based on data collected as part of international geoscience programme igcp project no 449 has revealed significant patterns river terraces provide important records of uplift which is essential for their formation and of landscape evolution their cyclic formation however almost invariably seems to have been a response to climatic fluctuation sequences in the european core area of igcp 449 which has the longest and most extensive research history have been used as templates for worldwide comparison there is evidence for a global acceleration of uplift at the time of and perhaps in response to the mid pleistocene revolution when climatic fluctuation switched to 100 kyr milankovitch cycles terraces formed prior to this generally consist of wide aggradational sheets that probably each represent formation over several 41 kyr cycles subsequently river valleys became more steeply entrenched and terraces formed in response to the stronger 100 kyr climatic forcing in many cases at approximately one per cycle this paper uses the new data resource to explore differences between records in different climate zones between sequences with variable numbers of middle late pleistocene terraces and between systems in which the all important incision event has occurred in different parts of climatic cycles key records discussed include european examples from the rhine thames somme dniester dnieper don volga and aguas from asia the gediz turkey and orontes syria from north america the south platte and colorado from south africa the vaal and sundays from australia the shoalhaven and from south america the amazon paraguay and tributaries of the colorado and negro

a high resolution record of the last deglaciation in the central mediterranean sea palaeovegetation and palaeohydrological evolution abstract a high resolution palynological and stratigraphical record of a marine deep sea core in the adriatic sea documents marine and continental palaeoenvironmental changes in the basin during the last deglaciation and early holocene a chronology is derived from the oxygen isotope stratigraphy three periods of aridity marked by the development of a semi desert rich in artemisia occurred between 18 5 and 16 kyr between 14 4 and 12 7 kyr and between 11 1 and 9 7 kyr consistent with the last glacial maximum the oldest dryas and the younger dryas they are correlated with increases in productivity and intensification of the levantine water formation in the eastern mediterranean basin during the warmer bolling allerod 12 7 11 1 kyr the presence of the cold temperate dinocyst bitectatodinium tepikiense is interpreted as indicating the establishment of a strong seasonal thermal gradient probably linked to seasonal cold freshwater runoff from the po river attested by the unique presence of pollen of freshwater plants the expansion of forest and the development of the warmer dinocysts start with termination ib during the holocene three tree phases are recognized and are contemporaneous with the preboreal boreal and atlantic chronozones of europe the two phases of sapropel deposition are marked by higher pollen and dinocyst concentrations and a high representation of brigantedinium spp which indicate higher preservation of organic material and or freshwater runoff of the po river

abundant sr rich aragonite in eastern mediterranean sapropel s1 diagenetic vs detrital biogenic origin caco3 contents in eastern mediterranean sapropels are generally lower than in the enclosing marl sediments in sediments of a transect from 650 to 2100 m water depth at the sirte continental slope the opposite feature was observed although the increased sr ca ratios observed in these sediments agree with such feature observed in other eastern mediterranean s1 sediments their absolute magnitude is much higher the enhanced sr ca ratio in these sediments is associated with their aragonite content which for the sirte transect reaches levels of up to 40 wt the aragonite content and sr ca ratios in the s1 sediments of this transect decrease with increasing water depth and decrease with distance to the african coast for all eastern mediterranean cores in view of the lack of a coherent relationship with sedimentary reduced sulphur contents and porosity and considering the major amount of aragonite found specifically in the sediments of the sirte transect authigenic precipitation can contribute only a limited fraction at most sem observation and electron microprobe analyses showed that the needles and needle clusters are morphologically aragonite contain the highest sr ca ratio and are similar to skeleton fragments of the green alga halimeda consequently a detrital biogenic source is the likely mechanism for the major part of the aragonite enrichments found in s1 sediments possibly offshore directed surface water flows related to wind stress and or enhanced run off consistent with enhanced precipitation during sapropel s1 may have assisted in the transport of near coastal aragonitic organisms to more coast remote areas

short term climate variability during roman classical period in the eastern mediterranean abstract to obtain insight into character and potential forcing of short term climatic and oceanographic variability in the southern italian region during the roman classical period 60 bc ad 200 climatic and environmental reconstructions based on a dinoflagelate cyst record from a well dated site in the gulf of taranto located at the distal end of the po river discharge plume have been established with high temporal resolution short term fluctuations in accumulation rates of the adriatic surface water species lingulodinium machaerophorum the freshwater algae concentricystes and species resistant to aerobic degradation indicate that fluctuations in the trophic state of the upper waters are related to river discharge of northern and eastern italian rivers which in turn are strongly related to precipitation in italy the dinoflagellate cyst association indicates that local sea surface temperatures which in this region are strongly linked to local air temperatures were slightly higher than today we reconstruct that sea surface temperatures have been relatively high and stable between 60 bc ad 90 and show a decreasing trend after ad 90 fluctuations in temperature and river discharge rates have a strong cyclic character with main cyclicities of 7 8 and 11 years we argue that these cycles are related to variations of the north atlantic oscillation climate mode a strong correlation is observed with global variation in 14c anomalies suggesting that solar variability might be one of the major forcings of the regional climate apart from cyclic climate variability we observed a good correlation between non cyclic temperature drops and global volcanic activity indicating that the latter forms an additional major forcing factor of the southern italian climate during the roman classical period

particle transport in the bari canyon southern adriatic sea to define the sediment transport pathways along the southern adriatic shelf and slope two oceanographic cruises were carried out in the southern adriatic in july 2004 and in march april 2005 to study the role of the bari canyon system on sediment dispersal three moorings including sediment traps and current meters have been deployed near the bottom at depths of 600 m for one year march 2004 march 2005 two moorings were deployed within the canyon station b in the northern branch and station c in the southern branch and one on the adjacent open slope north of the canyon system station a total mass fluxes tmfs measured by sediment traps were always higher in the canyon than on the adjacent slope the highest values were measured at station c average 8 07 g m 2 d 1 roughly double those of station b 3 07 g m 2 d 1 and the lowest outside the canyon at station a 1 69 g m 2 d 1 the highest tmf were recorded in spring 2004 a period characterized by the lowest water temperatures and the highest current speeds up to 72 cm 1 which were associated with the highest across slope current component along the canyon axes the simultaneous variations of fluxes occurring at the three stations imply that similar processes are active along the entire southern adriatic margin and that they are amplified inside the canyon in spring a vein of southward flowing north adriatic dense water naddw was observed along the adriatic shelf this was related to an enhanced across slope current component which was responsible for the higher particle fluxes both on the open slope and at the canyon stations these data suggest that the bari canyon is an efficient conduit for sediment from the adriatic continental shelf to the deep basin downcore profiles of 210 pb in sediments collected below the traps have been used to estimate sediment mass accumulation rates mars on a century scale on the open slope the annual trap flux recorded in 2004 2005 was lower than mar on the contrary in the bari canyon the annual trap flux was higher than mar indicating that the lateral advection of particles becomes predominant and that a fraction of the particles intercepted by sediment traps was only in transit through the canyon 2007 elsevier b v all rights reserved

climate of the past 2500 years in the gulf of taranto central mediterranean sea a high resolution climate reconstruction based on δ18o and δ13c of globigerinoides ruber white we present a high resolution isotope stratigraphy based on globigerinoides ruber white over the past 2500 years in the gulf of taranto central mediterranean g ruber white reflects summer conditions in the gulf of taranto but is influenced by two major surface water masses the western adriatic current wac and the ionian surface water isw and their variations on a decadal to multicentennial scale our analysis of the 13c and 18o of g ruber white allows the distinction of several climatic periods the roman warm period rwp 450 0 bc with relatively wet and warm conditions and a higher influence of the wac the roman classical period rcp ad 1 200 characterized by salinity increase resulting from circulation changes the dark ages cold period dcp ad 500 750 where wetter conditions in the gulf of taranto region are coherent with an increase dominance of the wac the medieval warm period mwp with wet and warm conditions in the first and a gradual drying in the second half and finally the transition from the mwp to the little ice age lia which is characterized by continuing dry conditions

extraction of reflected events from sonic log waveforms using the karhunen loeve transform abstractsonic reflection logging a recently developed borehole geophysical scheme is in principle capable of providing a clear view of outside the well bore in this type of acoustic well logging a key technical obstacle is that the reflected wave signal is almost entirely obscured by the directly arriving p s and stoneley wave modes effective extraction of these reflection signals from the full acoustic waveforms is therefore a critical data processing step we have examined the use of the karhunen loeve kl transform combined with a band limiting filter as a technique for the extraction of reflections of interest from a mixture with directly arriving wave modes of much higher amplitude under the assumption that large energy squared amplitude differences exist between each wave component the direct stoneley wave s wave and the p wave are eliminated sequentially by subtracting the most significant principal components after which the remaining signal is seen to be dominated by reflected

geochemical and paleomagnetic evidence for the occurrence of missing sapropels in eastern mediterranean sediments the cyclic occurrence of sapropels appears to be associated with maxima in the 65 n summer insolation target curve studies of the most recent sapropel have revealed extensive oxidation of organic matter or even the complete removal of this unit geochemical and magnetic signals allow for the detection of such a missing sapropel in older sediments these signals are altered by ongoing diagenetic processes an important parameter to reveal missing sapropels is ba elevated concentrations of ba are always found in visible sapropels and even after oxidation of part of the sapropel the initial ba profile remains visible we use this tool to trace down missing sapropels in kc01b a 37 m kullenberg core from the calabrian ridge eastern mediterranean at least 8 of 11 sampled intervals around insolation maxima contain evidence of a completely oxidized sapropel ba trace metal distributions and magnetic parameters are similar to those observed around visible sapropels

multicentennial scale hydrological changes in the black sea and northern red sea during the holocene and the arctic north atlantic oscillation 1 paleoenvironmental proxy data for ocean properties eolian sediment input and continental rainfall based on high resolution analyses of sediment cores from the southwestern black sea and the northernmost gulf of aqaba were used to infer hydroclimatic changes in northern anatolia and the northern red sea region during the last 7500 years pronounced and coherent multicentennial variations in these records reveal patterns that strongly resemble modern temperature and rainfall anomalies related to the arctic oscillation north atlantic oscillation ao nao these patterns suggest a prominent role of ao nao like atmospheric variability during the holocene beyond interannual to interdecadal timescales most likely originating from solar output changes

late holocene climate variability in the adriatic sea central mediterranean planktic and benthic foraminifera assemblages from a set of sediment cores collected on the adriatic shelf and the southern adriatic deep basin provide compelling evidence of submillennial scale environmental changes during the last 6000 years repeated peaks in globigerinoides sacculifer represent warm dry intervals including the mediaeval warm period the roman age the late bronze age and the copper age the last occurrence lo of g sacculifer 550 years bp approximates the base of the little ice age lia significant turnovers in the structure of the water column reflect changes in the rate of formation and depth of flow of the north adriatic dense water naddw and the levantine intermediate water liw about 7500 years bp the benthic oxygen isotope records mark the timing when the naddw formation intensified on the slope and shifted to its modern route about 5500 years bp when sea level reached its modern high stand oxygen isotope records of intermediate planktic dwellers indicate a northward intrusion of the liw on the slope the oscillating isotope trends during the last five millennia document a discontinuous invasion of liw into the central adriatic possibly reflecting short term climate changes with weakened liw production during colder and wetter intervals

persistent positive north atlantic oscillation mode dominated the medieval climate anomaly the medieval climate anomaly mca was the most recent pre industrial era warm interval of european climate yet its driving mechanisms remain uncertain we present here a 947 year long multidecadal north atlantic oscillation nao reconstruction and find a persistent positive nao during the mca supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker nao conditions into the little ice age lia globally distributed proxy data suggest that this nao shift is one aspect of a global mca lia climate transition that probably was coupled to prevailing la nina like conditions amplified by an intensified atlantic meridional overturning circulation during the mca

uplift of the central andean plateau and bending of the bolivian orocline the topography of the central andes can be considered the primary tectonic signal of late cenozoic mountain building in an arid region where the effects of uplift and magmatism are little obscured by denudation the spatial coverage of the topographic signal is more complete than that for sparsely sampled geological and geophysical data a color coded image of digitized topography between 12 s and 37 s highlights the altiplano puna one of the world s most remarkable plateaus and reveals important physiographic clues about the formation of that major feature the topographic data combined with information on structure magmatism seismicity and paleomagnetism support a simple kinematical model for the late cenozoic evolution of the central andes the model does not require collisional effects or enormous volumes of intrusive additions to the crust but instead calls upon plausible amounts of crustal shortening and lithospheric thinning the model interrelates andean uplift a changing geometry of the subducted nazca plate and a changing outline in map view of the leading edge of the south american plate crustal shortening has accommodated convergence between the chilean peruvian forearc and the south american foreland the altiplano puna plateau can be constructed by a combination of crustal shortening and thickening and lithospheric thinning above a shallow dipping 20 30 subducted plate the seawardly concave bend of western south america the bolivian orocline was enhanced but not completely produced by an along strike variation in the amount of late cenozoic shortening maximum shortening in bolivia both produced the widest part of the plateau and increased the seaward concavity of the bolivian orocline the along strike variations of shortening are hypothesized to result from corresponding along strike variations in the width of a weakened zone in the overriding plate weakening occurs above the wedge of asthenosphere located between the subducted and overriding plates hence the width of the zone of weakening depends upon the dip of the subducted plate two types of shortening are recognized 1 a widespread basin and range laramide like shortening that characterizes modem activity in the sierras pampeanas and late miocene deformation of the altiplano puna and 2 on the eastern side of the cordilleras and plateau an east verging foreland fold thrust belt in which the underthrust foreland compresses and thickens the ductile lower crust and produces a plateau uplift of the upper crust the second type of shortening can be applied to plio quaternary deformations throughout the central andes but with a substantial narrowing of the region of plateau uplift in peru and south of 28 s a proposed monoclinal flexure of the upper crust on the western side of the plateau uplift explains the remarkably simple and regular morphology of the main western slope of the central andes the monocline is located above the tip of the asthenospheric wedge between the converging plates it is postulated to occur above the western limit of lower crustal thickening in the regions of horizontal subduction the monocline can be associated with a late miocene asthenospheric wedge tip

late quaternary of the middle caqueta river area colombian amazonia the late quaternary history of the middle caqueta river area in colombia northwestern amazonia is described based on observations of river bank sections radiocarbon dates and palynological analyses of organic layers in floodplain and low terrace sediments of the caqueta river it is shown that the late pleistocene and holocene climatic changes that took place in the andean cordilleras were related to the depositional and erosional history of the caqueta river in the colombian amazonian lowlands the low terrace sediments consist of sandy and gravelly deposits covered by clays that sometimes contain lenses of peaty material from these organic low terrace sediments seven finite radiocarbon dates were obtained of middle pleniglacial age between 56 000 and 30 000 yr bp the coarse textured basal deposits of the low terrace apparently stem from the early part of the middle pleniglaciai period during which the effective rainfall in the andes was relatively high and the andean glaciers had a considerable extension palynological data from silty sediments with organic remains at one site show an interval when drier and more open types of vegetation on poor soils must have covered a larger area than today but amazonian forest was still the dominating type of vegetation this interval might correspond to one of the middle pleniglacial savanna intervals from eastern amazonia carajas no organic sediments from the upper pleniglacial period were found and hence radiocarbon dates were not obtained in the andes this period had a very cold climate with low effective rainfall and in the east amazonian carajas area it is characterised by the relative extension of open savanna vegetation the river run off and sediment transport must have been much lower than in the middle pleniglacial and the caqueta river cut itself down in its own sediments two late glacial radiocarbon datings obtained at one site ca 12 500 yr bp indicate the existence of a late glacial sedimentation phase separated from the holocene sequence by a minor erosional phase organic layers in the holocene floodplain sediments yielded 28 radiocarbon dates between 10 000 and 355 yr bp holocene sedimentation started with the rapid deposition of sandy clay possibly in a partly permanently inundated caqueta valley during the major part of the holocene silty clays were deposited with a dominant seasonal inundation cycle

bromine counts from xrf scanning as an estimate of the marine organic carbon content of sediment cores 1 xrf sediment core scanning technology is increasingly used to quantify sediment composition the overall good correlation between biophilic halogen bromine br and sedimentary total organic carbon toc potentially allows the fast estimation of down core toc profiles by xrf scanning in order to test this approach we present data from the arabian sea and a mediterranean brine basin comparing xrf core scanning br data with discrete sample toc analyses overall br counts and toc show a clear correlation except when stable carbon isotope and c n data indicate intervals characterized by enhanced input of terrestrial organic matter hence solid phase br is exclusively associated with marine organic matter moc and can be used as a direct estimate of this parameter after a calibration is established high pore water br in the brine core steepens the br toc correlation but after salt correction shows a nearly identical gradient to that of the arabian sea core

short time scale variability in ventilation and export productivity during the formation of mediterranean sapropel s1 1 high resolution laser ablation inductively coupled plasma mass spectrometry la icp ms scanning of laminated sediments from the urania basin is used to investigate short time scale variability in export productivity and redox conditions during the formation of eastern mediterranean sapropel s1 sedimentary enrichments of molybdenum mo vanadium v and uranium u reflect deep water redox conditions most likely those near to the seawater brine interface while enrichment of ba is related to biogenic barite and hence to export productivity the enrichments of all four elements show strong variability on multidecadal to multicentennial time scales throughout s1 a partial decoupling of export productivity from redox conditions at the height of sapropel formation suggests that hydrographic changes i e a variable ventilation rate of the eastern mediterranean played an important role in determining deep water redox conditions a pronounced switch is observed in the enrichments of redox sensitive trace metals from dominantly 300 600 year variability during early s1 to dominantly 100 300 year variability during late s1 indicating a change in the mean frequency of variability in the ventilation rate the presence of a similar shift in the frequency of tropical and extratropical climate records at this time suggests that ventilation of the eastern mediterranean was coupled to global climate variability

the avaatech xrf core scanner technical description and applications to ne atlantic sediments abstract x ray fluorescence xrf core scanning provides rapid high resolution down to 1 mm records of chemical composition on split sediment cores the measurements are non destructive and require very limited sample preparation the new avaatech xrf core scanner operational since 2002 covers the atomic mass range from al to u instrument parameters especially tube voltage can be adjusted to provide optimum settings for selected elements or sets thereof owing to the nature of the surface of split sediment cores particularly effects resulting from sample inhomogeneity and surface roughness results are semiquantitative yet provide reliable records of the relative variability in elemental composition downcore selected case studies from diverse sedimentary settings in the ne atlantic ocean illustrate a range of applications of xrf logging data these include preliminary stratigraphic interpretations glacial interglacial cycles provenance studies of the terrigenous sediment fraction lithological characterization early diagenetic processes and distinction between carbonate phases aragonite v calcite

the glacial interglacial transition and holocene environmental changes in sediments from the gulf of taranto central mediterranean abstract an extensive high resolution sedimentological geochemical survey was done using geo acoustics xrf core scans icp aes ams 14c dating and grain size analyses of sediments in 11 cores from the gulf of taranto the southern adriatic sea and the central ionian sea spanning the last 16 cal ka bp comparable results were obtained for cores from the gallipoli shelf eastern gulf of taranto and the southern adriatic sea suggesting that the dominant provenance of gallipoli shelf sediments is from the western adriatic mud belt the 210pb and 14c dated high accumulation rate sediments permit a detailed reconstruction of climate variability over the last 16 cal ka bp although the glacial interglacial transition is generally dry and stable these conditions are interrupted by two phases of increased detrital input during the bolling allerod and the late younger dryas the event during the younger dryas period is characterized by increased sediment inputs from southern italian sources this suggests that run off was higher in southern compared to northern italy at approximately 7 cal ka bp increased detrital input from the adriatic mud belt related to sea level rise and the onset of deep water formation in the adriatic sea is observed and is coincident with the end of sapropel s1 formation in the southern adriatic sea during the mid to late holocene we observed millennial scale events of increased detrital input e g during the roman humid period and of decreased detrital input e g medieval warm period these dry wet spells are consistent with variability in the north atlantic oscillation nao a negative state of the nao and thus a more advanced penetration of the westerlies into the central mediterranean that result in wet conditions in the research area concord with events of high detrital input e g during the roman humid period in contrast a positive state of the nao resulting in dry conditions in the mediterranean dominated during events of rapid climate change such as the medieval warm period and the bronze age

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

biogenic barium and the detrital ba al ratio a comparison of their direct and indirect determination biogenic barium concentrations obtained from direct determination by a three step sequential extraction procedure are compared to those obtained from the widely used indirect normative calculation based on total digestion a comparison of the biogenic barium from the direct sequential extraction and the indirect normative calculation clearly shows that the detrital ba al ratio is the critical factor in the normative approach and that erroneous assumptions based on this ratio may introduce significant errors to the calculated biogenic barium overall the crustal average ba al ratio of 0 005 0 01 is much higher than our directly determined global average of 0 0037 this would result in an underestimation of the biogenic barium and thus of the primary productivity calculated using the ba flux obtained from the normatively calculated ba record using our ba al det ratio of 0 0037 leads to normatively calculated biogenic barium results that are in reasonable agreement with the biogenic barium from sequential extraction for samples of the atlantic pacific and indian ocean our directly determined regional ba al det ratios deviate from those calculated or assumed from hinterland ratios and our global average ba al det is lower than the one commonly reported therefore in sediments with a significant terrigenous fraction the sequential extraction technique is always required

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

validation of accumulation rates in teluk banten indonesia from commonly applied 210pb models using the 1883 krakatau tephra as time marker abstract teluk banten is a tropical shallow marine embayment on the north coast of java close to the krakatau volcanic complex the tsunami generated by the 1883 krakatau eruption resulted in the deposition of a tsunamite tephra layer on the bottom of teluk banten the krakatau event layer has been used as a time marker to validate 210 pb geochronological dating models this validation was performed to answer the question why should we believe excess 210 pb derived mass accumulation rates the commonly used models have therefore been applied to 210 pb activity profiles from 25 gravity cores models that have been validated are the constant flux and constant sedimentation cf cs with and without a surface mixed layer the constant initial concentration cic the constant rate of supply crs and the flux balance model after comparison of the mass accumulation rates mars of the different models with the mars obtained from the krakatau layer the following could be concluded firstly activity profiles without a surface mixed layer gave cf cs mars which were on average a factor 1 4 0 3 n 8 too high including a mixing rate of 0 5 0 4 cm 2 yr 1 into the model could explain this overestimation secondly for 210 pb activity profiles with a surface mixed layer the mars were in good comparison 1 0 0 3 n 12 with the mars derived from the krakatau event layer thirdly increased accumulation instead of reworking had to be the main cause of the comparatively thick upper layer of five cores with very high inventories fourthly assuming a variable accumulation rate and applying the cic model and crs model for these five cores the weighted average cic mars were in general more accurate than the crs mar finally the flux balance model which is not often used gave mars that were a factor 1 3 0 2 n 25 too high the advantage of this model is that it is independent of the profile shape the disadvantage is that a reliable and accurate initial activity over longer time scales has to be obtained

high resolution bathymetry and acoustic geophysical data from santa maria di leuca cold water coral province northern ionian sea apulian continental slope abstract a total of 800 km 2 of multibeam echo sounder coverage roughly 800 km of chirp sonar data and 18 km of side scan sonar profiles 100 500 khz were acquired a few km offshore santa maria di leuca south eastern italy from 200 m to 1300 m water depth the explored area belongs to the upper slope of the gently south eastward dipping apulian continental margin northern ionian sea acoustic datasets were collected by three different oceanographic expeditions where evidence of living cold water coral cwc colonies were documented by previous surveys and samples high resolution multibeam bathymetry indicated an extensive rough seafloor with an irregular faulted upper surface to the west reflecting large scale tectonic control on the margin and a highly disrupted upper slope formed by prominent downslope mass movements to the north a broad area in the east was influenced by mass transport deposition which resulted in a very complex hummocky seafloor mainly shaped by detached block like features and failure related bedforms i e low scarps downslope lineations and compressional ridges from the shallow seismic stratigraphic data failure events appeared to be multiple and recurrent and chaotic reflectors both buried and exposed at the seafloor affected most of the investigated area drift sedimentation was also recognised along a central large ridge resulting in an interplay between contour currents and downslope turbidity currents the spatial distribution of the cwc reefs was inferred from the acoustic facies interpretation based on video images and ground truthed by sediment samples it appeared that 1 within the investigated area living coral frameworks were located along large topographic highs facing the main flow of the bottom currents where hard and firm substrata and or failure related sediment bedforms occurred 2 cwc mainly settled on clustered and isolated mound like features tens to a few hundreds of metres long and no more than 25 m high and were located between 600 and 900 m water depth within the broad area affected by downslope mass transport deposits such mound like morphologies could thus be interpreted as a result of sediment accreted by coral growth with the consequent sediment trapping on small scale positive seafloor irregularities formed by different types of pleistocene exposed mass transport deposits their burial prevented by bottom currents

a geochemical application of the itrax scanner to a sediment core containing eastern mediterranean sapropel units the itrax micro x ray fluoresence xrf core scanner has been applied in a sediment geochemistry investigation the core sections selected contain examples of the organic rich sedimentary units sapropels that form periodically in the eastern mediterranean basin sapropels are visually obvious from their dark coloration but the itrax x radiograph also reveals physical property changes that result mainly from the high pore water content of sapropels a consideration of wavelength dispersive xrf data from discrete samples of the most recent sapropel s1 was made along with the set of elements reported by the itrax instrument s energy dispersive xrf system over core sections containing s1 this allowed selection of a suite of eight inter element ratios or element integrals through which characteristic features of sapropel development and geochemistry were revealed while recognizing that the measured xrf element integrals from the itrax do not have an exact constant relationship with element concentration over changing sediment types this combination of ratios provides significant information for geochemical interpretation these include evidence for i the presence of high corg contents in the visual sapropel from ba ti and br cl ratios ii a thinning of the original sapropel thickness by post depositional oxidation from mn ti and cu ti ratios iii pyrite authigenesis in the residual visual sapropel from fe ti and s cl ratios and the as integral and iv aragonite formation in and around the sapropel from the sr ca ratio these same ratios were then used to interpret itrax data from a deeper section of the same core containing the older sapropel s3 where the same characteristics including the relict post depositional oxidative thinning of the original unit could be identified with only minor differences of detail directions of supply of fe as and cu into the sapropels could be inferred from profile shapes

fluvial terraces as quantitative markers of late quaternary detachment folding and creeping thrust faulting in the peruvian huallaga basin abstract in the western huallaga basin located in the peruvian subandes a series of nine fluvial terraces with elevations of up to 160 m above current floodplain level fp were formed against the biabo anticline the terraces are progressively more folded with age and terrace elevation and present growth strata suggesting ongoing folding of the anticline optically and infrared stimulated luminescence osl and irsl dating of fluvial terrace sediments yielded ages of 10 8 0 7 ka for the t2 24 2 2 ka for the t4 and 46 9 ka for the t7 terrace uniform uplift rates of 2 mm a 1 for the past 46 ka were calculated terrace profiles and two new seismic profiles that cross the biabo anticline longitudinally and transversally were used to calculate shortening rates of 2 6 mm a 1 for the anticline over the past 46 ka our calculations took into account potential contributions of detachment thrusting parallel to the biabo fold and reverse tear faulting perpendicular to the fold tip as visible on the seismic sections a maximum uplift rate of 0 62 mm a 1 due to reverse thrusting of the bellavista tear fault for the past 46 ka could have contributed to the overall uplift of the bellavista terraces based on trigonometric relationships a reverse fault slip rate of 0 86 mm a 1 and an age of 137 ka were calculated for this fault in the eastern part of the huallaga basin a series of two fluvial terraces were formed with elevations of 13 15 m and 30 m fp and with osl ages of 6 9 0 7 ka for t1 and 30 2 3 1 ka for t2 the interpretation of a third new seismic profile crossing the study area in combination with field observations and trigonometric relationships shows that the terraces were formed by a complex system of oblique ramp and strike slip faulting resulting in uplift and shortening rates of 1 mm a 1 and 1 96 mm a 1 between 30 2 ka and 6 9 ka respectively and uplift and shortening rates of 2 mm a 1 and 3 70 mm a 1 from 6 9 ka until the present reverse slip of the shapaja oblique ramp that was responsible for uplift of the terraces was calculated at 2 19 mm a 1 for the period 30 2 to 6 9 ka and 4 15 mm a 1 from 6 9 ka until the present measured total slip in combination with the calculated slip rates allowed an age calculation of 181 ka for the shapaja thrust ramp our inferences showed that the studied tectonic structures absorb most of the present day deformation in the huallaga basin the calculated uplift and shortening rates are compatible with published present day crustal movement velocities and miocene to present shortening rates for various studied sites of the tropical subandes and suggest that it is deforming at a relatively uniform rate the timing of sedimentation of the terrace sediments may have corresponded to periods of increased precipitation which occurred coeval with the heinrich events of the northern hemisphere terrace records similar as ours have been described for other tectonically highly active areas in the tropical subandes but not in the tectonically less active amazonian lowlands it is suggested that uplift rates of at least 1 mm a 1 are needed to preserve suborbital climate cycles as individual terraces the tropical subandes could therefore be a new key area to investigate the interactions between tectonics suborbital climate forcing and fluvial response during the late quaternary

synchronous basin wide formation and redox controlled preservation of a mediterranean sapropel organic rich sedimentary units called sapropels have formed repeatedly in the eastern mediterranean sea in response to variations of solar radiation sapropel formation is due to a change either in the flux of organic matter to the sea floor from productivity changes or in preservation by bottom water oxygen levels however the relative importance of surface ocean productivity versus deep water preservation for the formation of these organic rich shale beds is still being debated and conflicting interpretations are often invoked1 2 3 4 5 6 7 here we analyse at high resolution the differences in the composition of the most recent sapropel s1 in a suite of cores covering the entire eastern mediterranean basin we demonstrate that during the 4 000 years of sapropel formation surface water salinity was reduced and the deep eastern mediterranean sea below 1 800 m depth was devoid of oxygen this resulted in the preferential basin wide preservation of sapropel s1 with different characteristics above and below 1 800 m depth as a result of different redox conditions we conclude that climate induced stratification of the ocean may therefore contribute to enhanced preservation of organic matter in sapropels and potentially also in black shales

the younger dryas in the eastern mediterranean abstract the younger dryas period is traced in pollen diagrams of the eastern mediterranean by means of radiocarbon dates the biostratigraphy in terms of pollen assemblages is compared with the absolute time scale the younger dryas as a pollen assemblage zone is at best vaguely visible in those parts that at present carry steppe or other open vegetation the part that nowadays carries forest produces pollen zones including the younger dryas which resemble those of parts of europe palynological developments in parts of the eastern mediterranean differ appreciably which implies that the vegetation developed differently also this suggests that the climatic development in the various parts of the region was not the same

the late holocene gargano subaqueous delta adriatic shelf sediment pathways and supply fluctuations the gargano subaqueous delta formed on the eastern and southeastern sides of the gargano promontory in the western adriatic this subaqueous deposit represents the southernmost portion of the late holocene highstand systems tract hst growing along the western side of the adriatic as an extensive wedge of deltaic and shallow marine mud the late holocene hst rests above a regional downlap surface that marks the time of maximum landward shift of the shoreline attained around 5 5 cal kyr bp at the end of the late pleistocene holocene sea level rise high resolution seismic stratigraphic and tephra correlation indicate the presence of a thin basal unit recording condensed deposition between 5 5 and 3 7 cal kyr bp over much of the basin above this unit sediment accumulation rates increased to high values as much as 1 5 cm yr 1 reflecting the stabilisation of relative sea level and the forcing from high frequency climatic or anthropogenic changes affecting river dynamics the late holocene mud wedge of which the gargano subaqueous delta is a significant component reaches up to 35 m in thickness and has a volume of ca 180 km3 the shore parallel thickness distribution of the mud wedge reflects the dominant oceanographic regime of the basin and the asymmetric location of the mostly western sediment sources with a combined modern delivery of 51 7 106 t yr 1 of mean suspended load in sections perpendicular to the coast the late holocene mud wedge appears composed of forestepping clinoforms with gently dipping foresets typically 0 5 the gargano subaqueous delta is characterised by a submarine topset in water depths shallower than 25 28 m and accounts for about 1 7th of the total volume of the late holocene mud wedge despite the absence of direct river supply to the gargano area in the area of maximum interaction between shore parallel currents and basin morphology progradation occurs onto a flat and barren bedrock outcrop in about 50 80 m water depth the rapid transition from a thickness of 30 m of late holocene mud to nil is a good indication of the role of southward flowing bottom hugging shelf currents in causing the redistribution of sediment along the adriatic inner shelf additional evidence of this regime comes from 1 the most recent sigmoid defined at seismic stratigraphic scale deposited since the onset of the little ice age showing a shore parallel thickness distribution and a main depocentre to the southeast of the gargano promontory 2 the maximum values of sediment accumulation rates over the last century documented by 210pb measurements defining a narrow shore parallel belt immediately seaward of the depocentre of the most recent sigmoid the gargano subaqueous delta grows from the outbuilding of progressively younger progradational sigmoids that tend to parallel the previous ones the gargano subaqueous delta differs from other documented late holocene subaqueous deltas because its growth reflects 1 sediment transport dominated by bottom currents sub parallel to the strike of the composing clinoforms 2 a complex supply regime including the po delta 350 km to the north and several coalescing apennine rivers acting as line source 3 several alternating intervals of enhanced outbuilding and condensed deposition and 4 an in phase growth of the most recent sigmoid with the major progradation of the po delta during the little ice age

fluvial archive of peculiar avulsive fluvial patterns in the largest quaternary intracratonic basin of tropical south america the bananal basin central brazil abstract the bananal basin is the most important intracratonic quaternary sedimentary basin of south america and preserves a good record of the paleohydrological conditions of central brazil at the cerrado amazon ecotone this area is currently a large tropical plain seasonally flooded by rainfall and water table saturation that can be classified as a seasonal wetland this paper presents a geological and geomorphological analysis supported with geochronological dating aiming to reconstruct the pleistocene environmental history of the bananal basin the basin was filled by the sediments sourced by the araguaia mortes fluvial system the deposits belong to the araguaia formation which covers 106 000 km 2 of the bananal basin tl and osl chronologies of the araguaia formation show that sedimentation started at least in the middle pleistocene mis 7 but aggradation and avulsion processes were important in the lower middle pleniglacial between 70 5 ka and 34 0 4 6 ka mis 4 and 3 and in the upper pleniglacial between 24 5 3 1 and 17 2 2 3 ka mis 2 river avulsions were more intense in the lower bananal basin bananal island region remarkably we did not record ages between 17 ka and 10 ka although avulsion seems to have been more active in the past the abandonment by the araguaia of a channel belt now occupied by the underfit javaes river indicates that avulsion is still active the avulsion processes are mainly related to palaeohydrological changes although present day seismic activity is also recorded additional data is needed to generate a more detailed scenario for the older middle pleistocene deposits the data is remarkable however because it is the first middle pleistocene record described in a large alluvial tropical system in brazil the fluvial record is temporally in agreement with records from other large brazilian fluvial systems such as the amazon and parana basins the bananal plain however is unique because of its particular style of sedimentation and geomorphologic processes that generated a mega scale anabranching like complex pattern of paleochannels presently occupied by underfit streams

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

recent terrestrial and carbonate fluxes in the pelagic eastern mediterranean a comparison between sediment trap and surface sediment a sediment trap mooring was deployed in the central eastern mediterranean from november 1991 to august 1994 at 3000 m water depth total mass al ca mg sr and 230th fluxes recovered by the sediment trap are highly seasonal with highest fluxes during early spring in 1992 and 1993 and during late spring early summer in 1994 comparison of historic annual satellite derived chlorophyll records coastal zone colour scanner with the trap flux time series indicates a lag of 4 6 months between maximum primary production in the surface ocean and maximum flux recorded by the trap only the flux of coccospheres to the trap is at a maximum 1 month after maximum pigment concentrations in surface waters a value commonly found in other areas quantification of the inorganic lithogenic flux to the trap indicates that saharan dust is likely to be the major contributor to the trap mass flux the trapping efficiency of the sediment trap as calculated from the intercepted 230th flux is only 23 and the trap al flux is similarly 4 lower than al fluxes measured in nearby uppermost sediments compared with surface sediments the trap intercepted carbonate fluxes are even lower 9 than the corresponding lithogenic fluxes this is partly due to the very low abundance of large 32 m foraminifera and pteropods found in the trap material compared to the surface sediment we speculate that the period of our sediment trap deployment was insufficiently long to recover episodical large fluxes such as may be triggered by north atlantic oscillation variations

geomorphic evidence for recent uplift of the fitzcarrald arch peru a response to the nazca ridge subduction abstract the 400 000 km 2 wide fitzcarrald arch constitutes a wide topographic high of the amazon basin against the central andes in order to constrain its formation mechanisms and in particular to test its relationships to the nazca ridge subduction a quantitative geomorphology analysis of the arch is performed using hypsometric integrals elongation and azimuths of 7th and 5th order catchments they all express a trend from high maturity to low maturity from nw towards se this maturity gradient coupled with the local drainage direction demonstrate that the fitzcarrald arch is not a classical alluvial fan since its apex is located 100 km east to the subandean thrust front and the corresponding sedimentary pile is lacking nor is the arch the superficial expression of an inherited transfer zone because its geomorphic shape is radial and it does not diverge from a symmetry axis moreover such a reactivated structure is not found at depth on seismic profiles in addition our data show that underlying geomorphic control on catchment initiation and development has progressed from nw to se which in combination with the observation of crustal doming by espurt et al espurt n baby p brusset s roddaz m hermoza w regard v antoine p o salas gismondi r bolanos r 2007 how does the nazca ridge subduction influence the modern amazonian foreland basin geology 35 515 518 suggests that this relief is caused by the eastward sliding of the buoyant nazca ridge beneath the south american lithosphere

rapid coupling between ice volume and polar temperature over the past 150 000 years a new approach to dating a continuous sea level record using speleothem u th ages shows that past variations in global ice volume occurred within centuries of polar climate change with rates of sea level rise reaching at least 1 metre per century

calibration of xrf core scanners for quantitative geochemical logging of sediment cores theory and application abstract on line analysis of split sediment cores by xrf core scanners has become increasingly popular in the past decade because it allows nondestructive extraction of near continuous records of element intensities from sediment cores with a minimum of analytical effort a disadvantage of xrf core scanning relative to conventional geochemical analysis is the problematic conversion of core scanner output to element concentrations the main reason for this long standing problem is the poorly constrained measurement geometry attributable to inhomogeneity of the specimens e g variable water content and grain size distribution irregularities of the split core surface and in some setups spatial variations in thickness of an adhesive pore water film which forms directly below a protective foil covering the core surface we propose a log ratio calibration model for xrf core scanners derived from a combination of xrf spectrometry theory principles of compositional data analysis and empirical evidence the log ratio calibration model provides accurate and precise predictions of sediment composition element concentrations from xrf core scanner output with a limited number of parameters namely 2 d 1 where d equals the number of chemical elements whose concentrations are to be estimated the model can accommodate the inherent non linearity of the relation between relative intensities and concentrations which is apparent from the fact that it provides unbiased estimates an immediate corollary of our results is that log ratios of element intensities which are related to log ratios of element abundances by a simple linear transformation provide the most easily interpretable signals of relative changes in chemical composition consistent use of log ratios of element intensities or concentrations should minimise the risk of drawing erroneous conclusions from geochemical proxies the relative standard deviation precision of predicted element concentrations in core geob7920 is less than 2 stochastic simulations indicate that this level of precision can be attained with 40 randomly selected calibration specimens improved control over input errors and development of robust goodness of fit statistics allows xrf core scanning to be developed into a rigorous quantitative measurement technology the log ratio calibration equation derived in this study may be adapted to inter laboratory and inter instrument calibration as well

the impact of sediment provenance on barium based productivity estimates abstract biogenic barium in marine sediments has been suggested to be a reliable proxy of export productivity from the surface ocean and algorithms have been developed to link these properties however problems arise when the proposed algorithms are applied to predominantly terrigenous sediments a major source of error is incorrect estimates of the terrigenous ba al ratio in normative calculations of the amount of biogenic barium in the sediment compared to an often used global average ba al ratio much better results can be obtained by estimating the terrigenous ba al ratio from exponential regression of the ba al ratios of surface sediments obtained from continental slope transects this method has been applied to surface sediments from the chilean continental slope the calculated regional terrigenous ba al ratios could be verified with purely terrigenous samples from chilean rivers the resulting accumulation rates of biogenic barium on the chilean continental slope reliably reproduce the regional pattern of primary productivity in the southern peru chile current indicating the potential of biogenic barium as a useful paleo productivity proxy

climatically sensitive eolian and hemipelagic deposition in the cariaco basin venezuela over the past 578 000 years results from al ti and k al al ti and k al ratios in bulk sediment are used to interpret wind blown and hemipelagic sources of deposition to a 578 kyr record in the cariaco basin venezuela ocean drilling program site 1002 graphical and cross spectral analyses indicate that these ratios vary extremely closely with planktonic foraminiferal 18o with both ratios being significantly higher during interglacials and lower during glacials k al indicates that during glacials the lower sea level that results in relative basin isolation increases the relative proportion of kaolinite derived from local rivers draining the relatively humid venezuelan margin al ti decreases during glacials suggesting greater proportions of eolian rutile sourced from the northern sahara due to increased wind strength and or aridity this interpretation is consistent with previous studies of the chemistry and mineralogy of saharan derived eolian matter in the caribbean and with a mass balance determining the effect of changes in eolian rutile accumulation on the bulk sedimentary al ti ratio

neotectonic influence on tropical rivers of southwestern amazon during the late quaternary the moa and ipixuna river basins brazil abstract neotectonic influence has conditioned the development of the moa and ipixuna fluvial belts in the southwestern brazilian amazon region the area underwent a compressive tectonics with reverse n s fault dipping to the west that formed an en echelon system system from west to east from the serras do divisor ranges to the jurua river as a response to stress subsiding blocks with nw se trends were developed the e w to n55 w topographic trends could represent transcurrent dextral transtensional faults width of alluvial belts increases along the sequence of en echelon system blocks correlated with the increase of width the quantity of channels formed by avulsion increases as well the moa and ipixuna alluvial belts respectively reaching ca 9 and 7 km maximum width are abnormally wide because they developed in subsiding blocks stretched in a nw se trend fluvial dynamics was dominated by avulsion in the subsiding blocks during the late pleistocene and probably during part of the holocene

middle to late holocene paleochannels and migration of the palar river tamil nadu implications of neotectonic activity abstract geomorphic tectonic and sedimentary investigations have been carried out to understand the landscape evolution of the palar river basin southern peninsular india for this purpose satellite data interpretations coupled with field investigations fluvial architecture and optically stimulated luminescence osl dating methods were adopted to infer climatic variations and neotectonic deformation that took place during the mid to late holocene period several paleochannels have been identified in the northern part of the present day palar river the distribution pattern of the palar paleochannels and its present course indicate its migration towards the south leaving behind the old palar river streams as paleochannels significant changes in the morphological characteristics channel width and river pattern in the successive paleochannels reveal evidences of channel movement by avulsion largely controlled by reactivation of pre existing lineaments and intensified ne monsoon based on osl ages two major phases of migration have been identified that occurred between 4 83 ka to 1 88 ka first phase occurred between 3 59 ka to 3 26 ka due to intensified monsoon accompanied with small scale neotectonic activity the second phase took place between 2 42 ka to 1 88 ka which occurred probably due to the rapid upstream avulsion this rapid avulsion is due to the close proximity of mpa and the reactivation of the pre existing lineaments moreover the present palar river basin exhibits evidences of neotectonic activity such as soft sediment deformation structures anomalous drainage deflections and reactivation of lineaments and faults further indicating that the palar river is still draining a tectonically active region thus neotctonics and fluctuations in the intensity of monsoon are largely responsible for sculpting the present landscape

new techniques in sediment core analysis an introduction marine sediment cores are the fundamental data source for information on seabed character depositional history and environmental change they provide raw data for a wide range of research including studies of global climate change palaeoceanography slope stability oil exploration pollution assessment and control and sea floor surveys for laying cables pipelines and siting of sea floor structures during the last three decades a varied suite of new technologies have been developed to analyse cores often non destructively to produce high quality closely spaced co located downcore measurements characterizing sediment physical properties geochemistry and composition in unprecedented detail distributions of a variety of palaeoenvironmentally significant proxies can now be logged at decadal and in some cases even annual or subannual scales allowing detailed insights into the history of climate and associated environmental change these advances have had a profound effect on many aspects of the earth sciences particularly palaeoceanography in this paper we review recent advances in analytical and logging technology and their application to the analysis of sediment cores developments in providing access to core data and associated datasets and data mining technology in order to integrate and interpret new and legacy datasets within the wider context of sea floor studies are also discussed despite the great advances in this field however challenges remain particularly in the development of standard measurement and calibration methodologies and in the development of data analysis methods new data visualization tools and techniques need to be developed to optimize the interpretation process and maximize scientific value amplified collaboration environments and tools are needed in order to capitalize on our analysis and interpretation capability of large multi parameter datasets sophisticated yet simple to use searchable internet databases with universal access and secure long term funding and data products resulting in user defined data mining query and display so far pioneered in the usa and australia provide robust models for efficient and effective core data stewardship

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

andean tectonics related to geometry of subducted nazca plate seismological and geological data show that tectonic segmentation of the andes coincides with segmentation of the subducted nazca plate which has nearly horizontal segments and 30 east dipping segments andean tectonics above a flat subducting segment between 28 s to 33 s are characterized by from west to east 1 a steady topographic rise from the coast to the crest of the andes 2 no significant quaternary and possibly neogene magmatism 3 a narrow belt of eastward migrating apparently thin skinned neogene to quaternary shortening of the andes and 4 plio pleistocene uplift of the crystalline basement on reverse faults in the pampeanas ranges from about 15 to 24 s over a 30 dipping subducted plate a west to east andes cross section includes 1 a longitudinal valley east of coastal mountains 2 an active neogene and holocene andesitic volcanic axis 3 the altiplano puna high plateau 4 a high neogene but inactive thrust belt eastern cordillera and 5 an active eastward migrating subandean thin skinned thrust belt tectonics above a steeply subducting segment south of 33 s are similar west of the volcanic axis but quite different to the east early cenozoic tectonics of western north america were quite similar to the neogene andes however duration of segmentation was longer and the width of deformation was greater in the western united states patterns of crustal seismicity are systematically related to plio quaternary structural provinces implying that current deformational processes have persisted since at least the pliocene horizontal compression parallel to the plate convergence direction is indicated to a distance of 800 km from the trench above flat subducting segments crustal seismicity occurs over a broad region whereas over steep segments it is confined to the narrow thrust belt strain patterns in the forearc region are complex and perhaps extensional and a broad region of the altiplano puna and eastern cordillera appears to be aseismic

geochemical evidence for high resolution variations during deposition of the holocene s1 sapropel on the cretan ridge eastern mediterranean abstract major and minor element distributions and solid phase phosphorus contents were measured in a sediment core from the cretan ridge that contains the holocene s1 sapropel micro xrf ultra high resolution analysis reveals multiple mn peaks in the oxidized upper portion of the sapropel which implies either a non steady state upward remobilization of mn or not constant downward diffusion of bottom water oxygen sequential extraction allowed the identification of different phosphorus phases detrital phosphorus increases in the sapropel layer suggesting enhanced delivery from land during sapropel deposition higher organic carbon to organic phosphorus ratios in the sapropel indicate enhanced regeneration of phosphorus relative to carbon under low oxygen conditions fourier analysis on the ultra high resolution xrf data reveals frequencies that are provisionally assigned to millennial to decennial solar cycles although these cycles have been reported from several continental and marine archives they have never been documented from sapropel s1 in the eastern mediterranean

dust deposition in the central mediterranean tyrrhenian and adriatic seas relationships with marine sediments and riverine input major al ca fe mg mn si and minor cd pb zn elements of aeolian dust samples collected onboard ship around italy were analysed and the concentrations of metal in the dusts were in good agreement with previously published data from the mediterranean sea the elemental composition of dust samples collected in four subareas adriatic ionian tyrrhenian and sicily channel was compared with the composition of marine deep sediments obtained in the same regions mn al cd and zn contents differentiated between the four areas in both sets of samples suggesting a possible geochemical signature of the atmospheric crustal contribution in marine deep sediments an estimate of the relative contribution of atmospheric dry deposition of cd pb and zn and riverine discharge indicates that a the metals deposited from the atmosphere to the adriatic basin are a small fraction 2 5 of those discharged by the po and adige rivers b almost the same amounts of cd pb and zn are delivered to the tyrrhenian sea by the atmosphere and by the arno and tiber rivers

late glacial and holocene sedimentation and fluctuations of river water level in the caqueta river area colombian amazonia the sequence of late glacial and holocene alluvial sedimentation in the middle caqueta river basin of colombian amazonia is described based on the study of the sediments and palynology of several river bank sections and on 30 radiocarbon dates an early late glacial sedimentation cycle is recognised followed by a minor late late glacial erosion phase the holocene valley fill consists of grey clays often present in the lower part of the sections deposited in open water and silty clays often with faint yellow mottling deposited under a regime of seasonal flooding the base of the holocene sections is formed by sands where exposed in two places the transition of sand to open water grey clay was dated around 10 000 yr bp and there is a suggestion that open water may have been more common at the beginning of the holocene than later when sedimentation by seasonal flooding became important in many places much of the earlier holocene sediments may have been removed by erosion and replaced by younger sediments by a process of lateral aggradation a considerable part of the present valley fill is younger than ca 3500 yr however in several places older holocene sediments are found apparently only little affected by later erosion lying below younger varzea silty clays during the holocene more organic sediments were formed in periods with reduced river discharge related to drier climates in the andes and possibly in amazonia these dry periods deduced from data in the caqueta river area correspond well with dry phases in other parts of northwestern south america e g between approximately 2700 1900 yr bp and approximately 3200 3800 yr bp rates of average net sedimentation calculated from dated sections that apparently lack major hiatuses caused by erosion were high in the lower holocene low during the middle holocene and increase again in the upper holocene levee deposits became coarser and the high river level of the caqueta increased during the late holocene these phenomena may be explained by the increasing influence of man on the vegetation cover in the andean headwater areas and possibly also in the amazonian catchment area of the caqueta river

evolution of the western amazon lowland relief impact of andean foreland dynamics the congruency in the depositional origin and age of the uppermost sedimentary strata forming non flooded rainforest ground terra firme in the western and central amazon lowlands is a much debated subject here we conclude from the study of remote sensing imagery that active andean foreland dynamics have played a major role in the evolution of the plio pleistocene fluvial landscape in the western amazon foreland dynamics have resulted in a terra firme composed of late tertiary alluvium and younger alluvial terraces and plains in peru thermoluminescence and 14c dating show local aggradation of this younger alluvium between 180 and 30 ka the documented high age heterogeneity of the terra firme has implications for considerations of the biogeography of the amazon forest

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

holocene environmental variability the record from lago grande di monticchio italy abstract the holocene pollen record from lago grande di monticchio reveals environmental changes throughout the holocene comparison of this record with other records of holocene environmental variability indicates that there is a temporal correlation between these changes and north atlantic events however the nature of this relationship and the underlying mechanism s is yet to be determined it is evidently complex with the apparent coincidence of sea surface temperature cooling events with both species expansions and disappearances the picture is further complicated by the interaction between human activity and natural environmental changes

temperature and productivity influences on u37k and their possible relation to solar forcing of the mediterranean winter to assess the extent and nature of human induced climate change we need to understand natural climate variability this heavily relies on proxy based climate reconstructions calling for excellent understanding of the conditions represented by the proxies here we report on an alkenone based u37k sea surface temperature sst proxy record originating from south italian marine sediments and covering 1305 a d to 1979 a d with a 3 87 year resolution the shallow water cores extracted from the gallipoli terrace in the gulf of taranto were dated by the torino group with high accuracy over the last two millennia using radiometric and tephroanalysis methods on the basis of comparison with historical and satellite derived climate and productivity data we propose that u37k reflects mainly sst of the cooler part of the year and is modified by variation in magnitude and timing of peak alkenone production on the seasonal temperature cycle comparison of the u37k record with the record of atmospheric 14c a proxy for solar energy variability shows a high correlation r 0 73 for the period between 1420 a d and before human interference with the 14c record by combustion of fossil carbon and the release of radioactive isotopes by nuclear tests this suggests a centennial scale solar forcing we propose that wind induced mixing resulting from mediterranean climate dynamics plays a crucial role in translating solar activity to alkenone productivity and sst during the cooler part of the year

pollen inferred late glacial and holocene climate in southern balkans lake maliq abstract high temporal resolution analysis of pollen records from lake maliq albania provides quantitative estimates of monthly temperature and precipitation changes since the last deglaciation the climate parameters were estimated using the best modern analogue technique with an updated modern pollen climate database composed of 2748 surface samples the record shows two main cooling phases in the maliq area the oldest and younger dryas and a cooling event around 8200 years which suggests that the forcing factors driving climate variations in the north atlantic area since the last glacial period also extended their influence into the mediterranean area the oldest and younger dryas are also characterized by an arid climate and a change in the seasonality of precipitation the summer precipitation tends to be greater during the cooling phases than during the temperate periods the holocene climate is relatively stable and the values of each parameter reach their modern levels except for an arid event between 8300 and 8100 cal bp

stratigraphic framework of the apulian deep water coral province ionian sea abstract shallow sediment lithology and stratigraphy were investigated at selected areas off santa maria di leuca sml on the apulian margin between 350 and 1200 m water depth in order to define the sea bottom character on which coral mounds have developed according to existing geophysical data and in situ observations deep coral growth in the sml area creates patches of colonies typically settled on hard substrates on the upper flanks and or near the top of mound like structures and elongated ridges the sedimentary stratigraphy is strongly influenced by the local topography which is modeled by tectonic and geomorphological forcing large scale erosional features slope failure and sediment mass accumulation are evident from seismic investigations additionally sites of preferential sediment accumulation due to the action of bottom currents are identified as a result a complex sedimentary pattern characterizes this part of the apulian margin with strong lateral variability in sediment type and age although hemipelagic silty clay constitutes the main lithology there are sites characterized by periodic accumulation of silt and fine sand and local re deposition of coarse biogenic sand from the surrounding areas and from shallower depths excluding one site where mid pleistocene sediments are brought very close to the bottom surface due to wide scale erosion all collected sediments are late pleistocene to holocene in age and fall biostratigraphically within the emiliania huxleyi acme nannofossil zone reworking detected through nannofossil analysis is common in most cores excluding the ones taken from topographic highs and is variable in extent from site to site and within the sediment column it includes cretaceous to early pleistocene species suggesting provenance from extended successions or various stratigraphic levels outcropping on the submerged apulian margin or in adjacent land sections reworking is often associated with a high content of lithogenic particles and an increase in the coarser silt fraction coral debris was collected at many stations both at the sediment surface and within the stratigraphic sequence with varying abundance in relation to proximity to the coral colonies radiometric dating and micropaleontological analyses at some sites allow us to propose a sequence of coral colonization phases

geodynamic environment of quaternary morphostructures of the subandean foreland basins of peru and bolivia characteristics and study methods abstract the quaternary evolution of western amazon basins is considered using morphostructural analysis of fluvial belts and lakes meandering rivers from the basin surface are analyzed using three scales of elements the ridge and swale pattern the mosaic pattern and the fluvial belt lake patterns are differentiated according to their shape the hydrological environment and the structural context influences of basement structures and neotectonic deformations when known are considered the morphostructural patterns are discussed in the context of a balance of internal tectonic and external hydraulic and sedimentologic processes special attention is focussed on the effect of neotectonics which is generally neglected on the formation and the location of quaternary morphostructures the adaptation of study methods and sampling to the characteristics of the different morphostructures is considered

water depth and diagenetic constraints on the use of barium as a palaeoproductivity indicator sediments underneath the high productivity areas of the coastal upwclling and equatorial divergence zones in the pacific and indian oceans are enriched in barium and on this basis the barium content of the sediments has long been suggested as a potential palaeoproductivity indicator analyses of sediments from the peru margin corroborate the pattern of enhanced barium accumulation in areas of high primary productivity in the deep ocean but also show that this pattern cannot be extended to shallow water deposits sediments from the peru shelf lack any barium enrichment whereas this element is significantly enriched in slope and basinal deposits in water columns deeper than 2000 m this depth effect is further illustrated at site 682 located in the rapidly subsiding lima basin the quaternary sequence deposited at water depths 3000 m is enriched in organic carbon opal and biogenic barium the miocene sediments although deposited under highly productive waters associated with a coastal upwclling centre do not show an enrichment in the barium record corresponding to the very high organic carbon and opal levels a pattern that is consistent with deposition in shallow basins in addition to the effect of water depth on the barium distribution overprinting of primary signals can be observed in sediments from upwclling areas undergoing strong anoxic diagenesis microcrystalline barite is partly dissolved in intervals depleted in interstitial sulphate as shown for sediments from the peru margin dissolution of barite in sulphate depleted intervals of deep water sections leads to high barium concentrations near the termination of the sulphate reducing zone where downward sulphate and upward barium diffusion foster local barite precipitation in diagenetic fronts the barium distribution in sedimentary oxic and suboxic environments at deep water depositional sites has a high potential as a palaeoproductivity indicator however barium accumulation as a proxy for ocean fertility should be used with caution in areas of varying water depths and in anoxic diagenetic environments where sulphate depletion undcrsatur ates the interstitial waters with respect to barite

one dimensional modeling of a recent ganga avulsion assessing the potential effect of tectonic subsidence on a large river abstract river avulsion as studied in small sized and medium sized rivers is partly explained by the water surface gradient advantage of a new channel course over the old course caused by spatial differences in aggradation and compaction recently the effect of meandering upstream of the avulsion node or bifurcation was shown to have an equally large effect on avulsion duration as gradient advantage these effects remain poorly understood for the largest rivers on earth where gradients are very small subtle gradient advantages are affected by tectonics and often several anabranches remain active simultaneously our objective was to assess the relative importance of these factors in the river ganga in determining the pacing of an avulsion we used a combination of historical data remote sensing and one dimensional modeling the course of the ganga in historical times was through the present ganga bhagirathi system but then there was either a gradual or sudden shift to the present ganga padma system historical evidence and remnant paleochannels as observed in satellite sensor data corroborate the changing pattern of the ganga river system but the exact causes of the shifting and of the short avulsion duration remain unclear based on generalized data using a one dimensional model we ran idealized scenarios bracketing different tectonic subsidence estimates for long term morphodynamic evolution of the upstream channel and the two downstream bifurcates the model predicts flow and sediment partitioning at the bifurcation node and includes the effect of migrating meanders at the bifurcation and width adjustment of the bifurcates our modeling demonstrates that the old and the new branches can remain open and morphologically active for a long time because of the large backwater effect and the high mobility of the sediment the bifurcation stabilizes at an asymmetrical flow and sediment division which in smaller rivers such as the river rhine would be followed by residual channel filling but in the much larger ganges results in morphologically active anabranches the model results reveal that neither a gradient advantage nor a bend upstream of the bifurcation leads to an avulsion within centuries as has been observed in some large rivers in tectonically inactive regions on the other hand a realistic tectonic uplift of the old branch or subsidence of the new branch may force an avulsion to take place quickly and historical data show that the study area is seismically active the combination of these factors leads to a realistic modeled avulsion duration of less than three centuries historical data indicate that these general conclusions might also apply to other large rivers in this region e g the brahmaputra and the teesta we conclude that large rivers may avulse quickly in response to tectonics but attain an anabranching pattern because of the large dimension of the residual channel and backwater effects

a late pleistocene holocene wetland megafan in the brazilian amazonia abstract despite the growing interest in megafans definitions provided for this type of environmental setting have not yet been widely agreed upon a record of sedimentary facies distribution in both space and time including a larger number of analogs is particularly needed for improving megafan facies models this work focuses on a large fan like feature from an amazonian wetland in northern brazil morphological data based on remote sensing as well as sedimentary facies and radiocarbon analyses were integrated to propose that this feature is related to a megafan system active during the late pleistocene to holocene the megafan displays a divergent drainage network gently dipping slope and concave up and convex up longitudinal and transverse profiles respectively near surface deposits correspond to fining and coarsening upward sands related to active channels and overbank sand sheets terminal fan lobes sediments are interbedded with abandoned channel floodplain and lake pond muds morphostructural analyses and drainage anomalies revealed a geological setting affected by reactivation of pre existing faults contemporaneous with sediment accumulation establishment of a megafan system in this wetland most likely occurred within a slightly tectonically subsiding basin under favorable climatic conditions during wet seasons high water discharge would have favored sediment transport from highlands into this depositional site high summer temperatures and drought under a monsoonal regime kept the water levels low the described megafan could serve as an analog for contemporary tropical wetland megafans formed under a monsoonal climate regime

coherent high and low latitude climate variability during the holocene warm period a faunal record of sea surface temperature sst variations off west africa documents a series of abrupt millennial scale cooling events which punctuated the holocene warm period these events evidently resulted from increased southward advection of cooler temperate or subpolar waters to this subtropical location or from enhanced regional upwelling the most recent of these events was the little ice age which occurred between 1300 to 1850 a d when subtropical ssts were reduced by 3 to 4 c these events were synchronous with holocene changes in subpolar north atlantic ssts documenting a strong in phase link between millennial scale variations in high and low latitude climate during the holocene

the holocene climatic optimum and pollen records of sapropel 1 in the eastern mediterranean 9000 6000 bp abstract the most recent sapropel in the deep eastern mediterranean sea has been deposited between 9 and 6 ka bp climate conditions as revealed by the pollen records of this sapropel in marine cores were most favorable for temperate deciduous trees which is in agreement with the inferences from records of peripheral land pollen sites the abundance of deciduous oak pollen is much higher than that of artemisia sage brush indicating that annual precipitation in the mid elevation borderlands was at least 550 mm without summer drought but more probably in the range 800 1300 mm the pollen of pistacia which formed a savanna at low elevations is also at its highest abundance and signals the absence of frost in winter while being capable of withstanding summer drought the early holocene therefore appears as the post glacial climatic optimum with the highest moisture and mildest winters in southwest asia this is also the time of the neolithic population explosion with incipient domestication of cereals possibly following natural selection of the tough rachis mutation in wheat and barley by the extreme aridity of the preceding younger dryas

provenance of surface sediments along the southeastern adriatic coast off italy an overview multi proxy studies are necessary to understand sediment composition and related provenance on continental shelfs here it is shown that the spatial distribution of geochemical composition and grain size for surface sediments along the southeastern italian coast is related to provenance and mechanisms influencing sediment pathways a northern adriatic italian provenance can be distinguished from a southern apennine river source this is done independent of grain size using the element ratios ce ni and zr cr furthermore the origin of organic matter is determined using bulk carbon isotopes and the c n ratio integrating these results with those from complementary studies on 18o and 13c of globigerinoides ruber white the bit index stable isotopes of plant waxes and dinoflagellate cyst distribution from the same set of samples reveals that sediments from the northwestern adriatic are transported as far southward as the gallipoli shelf eastern gulf of taranto by the western adriatic current wac along the wac there is a consistent southward decrease in po river northern apennines provenance and a concomitant decrease in terrestrial soil organic matter om whereas the percentage of marine om increases the provenance for gallipoli shelf sediments is for 80 attributed to po river northern apennines sources and for 20 to southern italian sources om in the eastern gulf of taranto contains more marine om than other areas within the wac whereas om and sediments from the western part of the gulf of taranto have a more local riverine provenanc

the holocene climatic evolution of mediterranean italy a review of the continental geological data we present a synthesis of geological stratigraphic geomorphological and stable isotope data collected from continental archives to highlight the environmental and climatic differences between the first and second half of the holocene of central and southern italy the beginning of the holocene is marked by rapid environmental change in mediterranean italy between c 9500 cal bp and c 6000 5500 cal bp average temperatures were probably higher and environmental conditions were generally stable between c 9000 and 7000 cal bp meteoric precipitation was at its highest the end of the wetter period seems to occur later at c 6000 5000 cal bp since c 6000 5000 cal bp rapid climatic excursions are apparent in different palaeoclimate proxies with both variability in meteoric precipitation and temperature evident of particular relevance is the event occurring at c 4200 cal bp this event heralds a period of significant environmental change in the apennines and more generally in central italy

the regional intraplate stress field in south america a compilation of lithospheric stress directions for continental south america and the inferred major patterns of the regional intraplate stress field are presented stress orientations are based primarily on earthquake focal mechanisms and quaternary fault slip inversion published in the literature four new focal mechanisms based on short period p wave modeling and selected centroid moment tensor solutions published by u s geological survey consistent with p wave first motions at south american and other world wide standard seismograph network stations are also included in the data base the observed patterns of intraplate stresses may be useful in constraining numerical models of the plate driving forces in the south american plate in the andean plateau altitudes greater than 3000 m n s extensional stresses predominate e w compressional stresses are observed in the sub andean and platform regions extending up to about 1000 km east of the andes the maximum horizontal stress shmax is uniformly oriented in the e w direction throughout western south america averages of the shmax direction at grid points spaced 2 5 o were taken as representing the regional field the e w direction of this regional field is not affected by the change of strike of the andean chain nor by the contact of a flat subducted slab underneath the regional shmax direction is oriented 15 o more clockwise than the direction of the nazca plate convergence the difference between the regional shmax orientations and the absolute plate motion may be only about 6 o this may indicate that contact forces with the nazca plate may not be the only major contributor to the intraplate stresses in western south america the eastern limit of this andean stress province seems to coincide with aseismic regions in the upper amazon basin and in the paraml basin in the central amazonian region seismicity and stress data suggest a seismic province with n s compressional stresses the origin of these stresses is not yet clearly understood but could possibly be related to lower crustal loading along the middle amazon basin in northeastern brazil seismicity is characterized by upper crustal strike slip earthquakes bordering the potiguar marginal basin a model is proposed for this region in which the stress field is the result of a superposition of regional e w compressional stresses and local extensional stresses oriented perpendicular to the continental margin possibly related to density contrasts and sediment loading in the continental shelf

seismicity fault plane solutions depth of faulting and active tectonics of the andes of peru ecuador and southern colombia the intracontinental seismicity of the andes of peru ecuador and southern colombia is concentrated along the easternmost flank of the cordillera beneath the western margin of the sub andes the focal depths and fault plane solutions of the largest events were constrained by comparing the observed long period p waves with synthetic waveforms in general the fault plane solutions show reverse faulting on steeply dipping nodal planes striking northwest southeast and reflect crustal shortening perpendicular to the range probably in response to the subduction of the nazca plate to the west earthquakes in the sub andes occur at depths of between 8 and 38 km indicating that much of the crust deforms in a brittle manner the seismicity seems to reflect antithetic underthrusting of the brazilian shield beneath the eastern margin of the andes however the earthquakes are too deep and their nodal planes are too steep to be associated with the thin skinned decollement of the sedimentary cover instead they appear to reflect the tectonic deformation of the underthrust basement west of the zone of active deformation at the surface in the sub andes hence the earthquakes on the east side of the andes may reflect the style of deformation in the hinterland of fold and thrust belts such as in the canadian rockies while much of the decollement farther east occurs aseismically in contrast normal faulting occurs in the high andes on planes parallel to the strike of the mountain belt thus there is a delicate balance between the compressive stress applied to the andes in the direction of subduction which causes thrust faulting in the sub andes and the gravitational body forces acting on the topographically higher parts and the crustal root of the andes which may cause normal faulting at high elevation

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

the gulf of taranto southern italy seismic stratigraphy and shallow structure abstract interpretation of seismic profiles across the gulf of taranto southern italy allows us to discuss the seismic stratigraphy and to define the shallow geological structure of this complex area of the northern ionian sea the apulian slope is a down faulted passive margin covered by irregular unconsolidated plio quaternary sediments the sedimentary fill rests on presumed discontinuous upper miocene deposits and on mesozoic and cainozoic strata acoustic basement the taranto valley is a thickly sedimented trench like feature that is the submerged extension of the onshore bradanic fore deep the eastern calabrian margin intensively cut by normal faulting comprises a lower acoustic sequence representing the widespread allochtonous apenninic units these units overthrust towards the east the unconsolidated taranto submarine valley sedimentary fill creating a sinuous nw se trending thrust front