importance of ekman transport and gyre circulation change on seasonal variation of surface dissolved iron in the western subarctic north pacific iron fe is an essential nutrient for marine phytoplankton and it constitutes an important element in the marine carbon cycle in the ocean this study examined the mechanisms controlling seasonal variation of dissolved fe dfe in the western subarctic north pacific wsnp using an ocean general circulation model coupled with a simple biogeochemical model incorporating a dfe cycle fed by two major sources atmospheric dust and continental shelf sediment the model reproduced the seasonal cycle of observed concentrations of dfe and macro nutrients at the surface in the oyashio region with maxima in winter february march and minima in summer july september although the simulated seasonal amplitudes are a half of the observed values analysis of the mixed layer dfe budget indicated that both local vertical entrainment and lateral advection are primary contributors to the wintertime increase in dfe concentration in early winter strengthened northwesterly winds excite southward ekman transport and ekman upwelling over the western subarctic gyre transporting dfe rich water southward in mid to late winter the southward western boundary current of the subarctic gyre and the outflow from the sea of okhotsk also bring dfe rich water to the oyashio region the contribution of atmospheric dust to the dfe budget is several times smaller than these ocean transport processes in winter these results suggest that the westerly wind induced ekman transport and gyre circulation systematically influence the seasonal cycle of wsnp surface dfe concentration

evaluation of atmospheric dry deposition as a source of nutrients and trace metals to lake tahoe abstract atmospheric deposition can be an important source of nutrients and trace metals to oligotrophic alpine lakes affecting their biogeochemistry we measured trace metal concentrations and lead pb isotope ratios in lake water river water ground water and aerosol total suspended particles tsp as well as nutrient no3 nh4 po43 concentrations in tsp in the tahoe basin the contribution of tsp deposition to the lake trace metal budget was assessed our results show seasonality in tsp and associated trace metal concentrations with higher concentrations during oct april however trace metal solubilities are higher during may sept resulting in a higher contribution of soluble trace metals to the lake water the source of most of the trace metals in tsp in the lake tahoe basin is mineral dust however zn cu and cd also have an anthropogenic origin among major nutrients no3 concentrations are slightly higher during oct april while nh4 and soluble reactive phosphorus srp are higher during may sept the distributions of trace metal concentrations and pb isotopic ratios are homogenous throughout the lake water column suggesting that the residence time of the trace metals in the lake is longer than the lake water mixing time the contribution of atmospheric tsp deposition to the upper 20 m of lake water trace metal inventory is low ranging from 0 03 for v to 5 7 for mn a triple isotopes plot of pb indicates that riverine and groundwater inputs are the major pb sources but aerosols still contribute some pb to the lake this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

biogeochemistry of arsenic and antimony in the north pacific ocean the biogeochemical cycles of the metalloid elements arsenic and antimony were examined along a 15 000 km surface water transect and at 9 vertical profile stations in the western north pacific ocean as part of the 2002 ioc contaminant baseline survey results show that the speciation of dissolved arsenic as iii as v and methylated as was subtly controlled by the arsenate asv phosphate ratio an additional fraction of presumed organic arsenic previously reported in coastal waters was also present 15 of the total as in oceanic surface waters dissolved inorganic antimony displayed mildly scavenged behavior that was confirmed by correlations with aluminum but atmospheric inputs that may be anthropogenic in origin also affected its concentrations monomethyl antimony the predominant organic form of the element behaved almost conservatively throughout the water column radically changing the known biogeochemical cycle of antimony

estimates of atmospheric processed soluble iron from observations and a global mineral aerosol model biogeochemical implications 1 desert dust deposition to the ocean may be a significant source of biogeochemically important elements specifically iron the bioavailability of iron in the oceans requires it to be in a soluble form and because atmospheric iron in desert dust is typically insoluble understanding the atmospheric processes that convert insoluble iron to more soluble forms is essential understanding these relationships is especially important in remote ocean regions where iron may be the limiting nutrient observations of soluble iron from 2001 cruise based aerosol measurements over the atlantic and pacific oceans ranged from 0 to 45 mean of 4 9 in the fine mode 2 5 m in diameter and 0 to 87 mean of 2 10 in the coarse mode we test two simple hypotheses of soluble iron enhancement in the atmosphere using a global model of mineral aerosols the first method assumes that iron solubility increases as iron is exposed to solar radiation approximating photoreduction reactions that are important pathways for enhancement of soluble iron in the presence of acidic solutions the second process imitates cloud processing of iron by increasing the amount of soluble iron when the mineral aerosol comes into contact with a cloud both methods resulted in similar average magnitudes of percent soluble iron compared to observations but did not capture specific events or have sufficient variability perhaps because the model does not include aerosol interactions between species other than mineral dust or other processes that may be important

the biogeochemistry of aluminum in the pacific ocean abstract vertical distributions and horizontal surface transects of dissolved and particulate al at several locations in the pacific ocean are presented here concentrations of dissolved al in the pacific range from 0 3 to 5 nmol kg in the surface waters from 0 1 to 1 nmol kg in mid depths and from 0 5 to 2 nmol kg in the deep waters from these data and published data from other regions it is evident that al has a unique oceanic chemistry relative to that of other metals external sources and rapid particle scavenging throughout the water column are the major controls on dissolved al distributions in the oceans vertical profiles generally exhibit a surface maximum a mid depth minimum and increasing concentrations toward the sediment water interface this suggests two sources of dissolved al one to the surface waters and one to the deep waters concentrations of dissolved al in surface waters are lowest within the eutrophic low salinity california current 0 3 1 nmol kg and increase westwardly into the subtropical gyre of the north pacific 5 nmol kg values in the south pacific gyre are fivefold lower these horizontal trends indicate that the primary source of dissolved al to the surface waters of the central pacific is from eolian input dissolved al supplied by rivers to the eastern north pacific appears to be rapidly scavenged in estuaries and or the highly productive coastal region the source of dissolved al to the deep waters is not known but could be due to a flux out of the sediments or a remineralization process suspended particulate al concentrations increase with depth at all stations and decrease with distance from the ocean boundary surface values range from 1 5 nmol kg near shore to 0 3 nmol kg in the central gyres of the pacific deep water concentrations range from 22 nmol kg near shore to 4 nmol kg in the north pacific central gyre and decrease to 1 3 nmol kg in the south pacific central gyre observed distributions indicate that suspended particulate al varies with the intensity of bottom sediment resuspension and the horizontal mixing of the resulting nepheloid layer out from ocean boundary regions particle residence times estimated are consistent with other reported values

a high relative sea level stand in the middle holocene of southeastern tunisia abstract study of the marine holocene deposits in southeastern tunisia shows bioclastic beaches at elevations ranging between 0 and 100 cm above high tide level a h t l depending on the elevation of these fossilized shorelines the ages obtained are different the age of the older deposits ranges between 5900 and 4000 14cc yr b p 6400 4300 calendar yr b p there deposits consist of bioclastic beaches attaining an elevation of about 40 to 100 cm a h t l the younger deposit is dated at around 2100 14c years ago 1850 calendar yr b p and is found today at the same elevation as the present sea level this deposit also consists of bioclastic beach material and contains pottery fragments postglacial melting should not be responsible for this observed higher relative sea level stand because deglaciation ended about 7000 6000 14c years ago fairbanks 1989 furthermore the regularity of the paleobeach deposit elevation over a broad area in southeastern tunisia suggests that tectonics cannot explain the emergence the emergence of up to 1 m of marine deposits dating back to between 5900 and 4000 14c yr b p should rather be interpreted as the result in the region of a postglacial hydro isostatic rebound as predicted in the theological models of continental margins by for example clark et al 1978 and lambeck 1993 the present situation was reached 2100 14c years ago

changes of relative sea level during the past 5000 years in the ancient harbor of marseilles southern france in the ancient harbor of marseilles marine fauna fixed upon archaeological structures as well as bio sedimentary units document a 1 5 m steady rise in relative sea level during the past 5000 years followed by a near stable level at present datum from about 1500 years ad to the last century this trend is similar to the one previously documented along the rocky coasts of the same region field observations inside and outside the harbor confirm that no sea level stand higher than the present ever occurred during the studied period in contradiction with the numerical model of peltier but in agreement with the glacio hydro isostatic models of lambeck and johnston and lambeck and bard q 2001 elsevier science b v all rights reserved

trends in the solubility of iron in dust dominated aerosols in the equatorial atlantic trade winds importance of iron speciation and sources 1 we present measurements of the solubility of fe ii and fe iii extracted from bulk and size fractionated african dust collected in summer trade winds at barbados west indies iron solubilities typically ranged from 1 to 3 fe iii dominates the iron solubility over the entire range of particle sizes at mineral dust concentrations below about 5 ug m3 fe ii believed to be largely derived from anthropogenic and biomass burning sources becomes increasingly important samples containing large soluble iron fractions and high fe ii fe iii ratios are associated with south atlantic back trajectories the gray coloration of the filters suggests that the source may be biomass burning in southern africa in general much of the variability in fe solubility is linked to fe ii concentration changes vanadium is often used as a tracer of anthropogenic impacts although many of our samples yielded v ti ratios much greater than average crustal abundances we could find no relationship between the enrichment of v and fe solubility our fe solubility results are quite similar to those obtained by others despite the fact that the measurements were made in diverse ocean regions and the protocols used were quite different in all cases this uniformity implies that the factors controlling aerosol iron solubility are largely inherent in the properties of the aerosols themselves and not the procedures used to extract the iron our results suggest that dust transport models that focus on the role of iron in ocean biogeochemistry must take into account aerosol origin in order to better model the solubility of iron

iron solubility driven by speciation in dust sources to the ocean particulate aerosols are thought to be the primary source of iron to the oceans but the factors determining their solubility and thus bioavailability are unclear x ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron

long term cycles of triassic climate change a new δ18o record from conodont apatite jat and isw gratefully acknowledge financial support from the australian research council dp1096252 mr is grateful for financial support from progetto d ateneo 2009 cpda090175 09 and 2012 cpda 121100 and prin 2008 2008bef5z7 005

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

sea level and initiation of predynastic culture in the nile delta predynastic occupation of the nile valley and delta dating back to at least 5000 bc has been attributed by most archaeologists to environmental factors primarily regional climate change and fluctuating nile flood stages1 5 here we propose instead that initiation of farming settlements in the nile delta was closely related to eustatic sea level we present geological analyses of late quaternary subsurface sections throughout the delta which reveal that the deceleration in sea level rise that occurred at about 6500 5500 bc was a prime factor in the accumulation of nile silt and the creation of the widespread and fertile delta plain as rising sea level reduced the gradient of the river course a system of meandering nile distributaries evolved with increased overbank deposition burying the former early holocene partially vegetated sandy plain the broadening seasonally flooded fecund plain with its increasing plant cover provided a setting that was conducive to evolving agricultural activity and was therefore instrumental in the development of predynastic communities in the nile delta

magnetostratigraphy of the lower triassic beds from chaohu china and its implications for the induan olenekian stage boundary a magnetostratigraphic study was performed on the lower 44 m of the west pingdingshan section near chaohu city anhui province china in order to provide a magnetic polarity scale for the early triassic data from 295 paleomagnetic samples are integrated with a detailed biostratigraphy and lithostratigraphy the tilt corrected mean direction from the west pingdingshan section passes the reversal and fold tests the overall mean direction after tilt correction is d 299 9 i 18 3 305 2 95 1 9 n 19 the inferred paleolatitude of the sampling sites 31 6 n 117 8 e is about 9 4 consistent with the stable south china block scb though the declinations indicate some 101 counter clockwise rotations with respect to the stable scb since the lower triassic low field anisotropy of magnetic susceptibility indicates evidence of weak strain the lower part of the yinkeng formation is dominated by reversed polarity with four normal polarity magnetozones wp2n to wp5n with evidence of some thinner 0 5 m thick normal magnetozones the continuous magnetostratigraphy from the yinkeng formation provides additional high resolution details of the polarity pattern through the later parts of the induan into the lowest olenekian the magnetostratigraphic and biostratigraphic data show that the conodont marker for the base of the olenekian first presence of neospathodus waageni is shortly prior to the base of normal magnetozone wp5n this provides a secondary marker for mapping the base of the olenekian into successions without conodonts this section provides the only well integrated study from a tethyan section across this boundary but problems remain in definitively relating this boundary into boreal sections with magnetostratigraphy

iron manganese and lead at hawaii ocean time series station aloha temporal variability and an intermediate water hydrothermal plume trace metal clean techniques were used to sample hawaii ocean time series hot station aloha on seven occasions between november 1998 and october 2002 on three occasions full water column profile samples were obtained on the other four occasions surface and near surface euphotic zone profiles were obtained together with three other published samplings this site may have been monitored for dissolved 0 4 or 0 2 m fe more frequently than any other open ocean site in the world low fe concentrations 2500 m the concentrations we observe 0 4 0 5 nmol kg 1 are significantly lower than some other deep north pacific stations but are similar to values that have been reported for a station 350 miles to the northeast we attribute these low deepwater values to transport of low fe antarctic bottom water into the basin and a balance between fe regeneration and scavenging in the deep water near surface waters have higher fe levels than observed in the lower euphotic zone significant temporal variability is seen in near surface fe concentrations ranging from 0 2 0 7 nmol kg 1 we attribute these surface fe fluctuations to variable dust deposition biological uptake and changes in the mixed layer depth this variability could occur only if the surface layer fe residence time is less than a few years and based on that constraint it appears that a higher percentage of the total fe must be released from north pacific aerosols compared to north atlantic aerosols surprisingly significant temporal variability and high particulate fe concentrations are observed for intermediate waters 1000 1500 m these features are seen in the depth interval where high 3he from the nearby loihi seamount hydrothermal fields has been observed the total fe 3he ratio implies that the hydrothermal vents are the source of the high and variable fe the vertical profile of mn at aloha qualitatively resembles other north pacific mn profiles with surface and intermediate water maxima but there are some significant quantitative differences from other reported profiles the 0 4 m mn concentration is highest near the surface decreases sharply in the upper 500 m then shows an intermediate water maximum at 800 m and then decreases in the deepest waters these concentrations are higher than observed at a station 350 miles to the northeast that shows similar vertical variations it appears that there is a significant mn gradient throughout the water column from hot towards the northeast compared to the first valid oceanic pb data for samples collected in 1976 pb at aloha in 1997 1999 shows decreases in surface waters and waters shallower than 200 m pb concentrations in central north pacific surface waters have decreased by a factor of 2 during the past 25 yr from 65 to 30 pmol kg 1 surface water pb concentrations in the central north atlantic and central north pacific are now comparable we attribute the surface water pb decrease to the elimination of leaded gasoline in japan and to some extent by the u s and canada we attribute most of the remaining pb in pacific surface waters to asian emissions more likely due to high temperature industrial activities such as coal burning rather than to leaded gasoline consumption a 3 year mixed layer time series from the nearby hale aloha mooring site 1997 1999 shows that there is an annual cycle in pb with concentrations 20 higher in winter months this rise may be created by downward mixing of the winter mixed layer into the steep gradient of higher pb in the upper thermocline pb concentrations double between the surface and 200 m from 200 m to the bottom pb concentrations decrease to levels of 5 9 pmol kg 1 near the bottom for most of the water column thermocline and deepwater pb concentrations do not appear to have changed significantly during the 23 yr interval

high resolution fluvial record of late holocene geomorphic change in northern tunisia climatic or human impact abstract in northern tunisia the late holocene alluvial record of medjerda floodplain sediments indicates geomorphic changes due to fluctuations of past climate superimposed by the effects of human activity geomorphic activity occurred several times interrupting stable conditions enhanced fluvial dynamics occurred around 4 7 3 0 1 7 1 0 and 0 7 ka cal bp a peak of activity took place about 0 4 ka cal bp some periods of fluvial activity show event like phenomena in particular when an anthropogenic impact intensifies climatic aridification this has been the case around 1 7 1 0 0 7 and 0 4 ka cal bp with severe floods in the medjerda valley during antiquity as well as around 1 3 0 8 and 0 5 ka cal bp immature alluvial soils have developed the first one being the most distinct late holocene medjerda alluvial history shows that fluvial dynamics in northern tunisia were predominantly climate driven anthropogenic impact only intensified or weakened these processes

human influence and the changing geomorphology of mediterranean deltas and coasts over the last 6000 years from progradation to destruction phase the present geomorphology of the mediterranean s coasts is largely a product of an intricate long term relationship between nature and human societies a cradle of ancient civilisations the mediterranean has seen its shores occupied by humans since prehistory and is therefore a particularly pertinent unit of analysis the morphotectonic context and other forcing agents e g climate shaped out a highly diversified coastal morphology and generated a sediment supply regime potentially favourable to the formation of numerous open coast deltas and bay head deltas in infilled rias as sea level stabilised during the mid holocene this supply of riverine sediment has also been the key agent in mediating human occupation of the mediterranean s clastic coasts expressions of this relationship have been extensively archived in clastic coastal deposits including base level deltaic and estuarine sedimentary sinks which comprise records to explore the interactions between geosystems and the human environment the stratigraphic sequences in these coastal sedimentary archives comprise in many places a clearly identified anthropogenic signature notably in ancient harbours some of which underwent extremely rapid silting up due to massive sediment sourcing generated by new agricultural practices from the neolithic onwards increasing human influence especially over the last 3000 years has been in turn an important driver of changes in sediment supply strongly modulating deltaic development pulses of sediment supply from catchments rendered vulnerable by human perturbations during the roman period resulted in a new cycle of inception of many other deltas and in rapid delta growth e g the ebro the po the arno and the ombrone another progradation dynamic during the little ice age at a time of strong rural population growth river discharge increases technological developments and urbanisation further consolidated delta growth understanding the life cycle of these deltas since their initial formation is in turn key to unravelling the relative role of natural and anthropogenic forcing agents rapid climate changes are deemed to have contributed through both the stripping of landscapes rendered fragile by human activities and active fluvial sediment transport to the coast but disentangling climate change effects from human impacts in the mediterranean remains a challenge the patterns of subsequent deltaic growth and delta morphodynamics reflect adaptations to pulsed sediment supply river discharge variations the microtidal fetch limited context of the mediterranean and direct engineering interventions the progradation dynamic of the roman period and little ice age contrasts markedly with the situation of common coastal destabilisation over the last two centuries particularly well documented for the last 50 years this period has been characterised by reduced sediment flux to base level geosystems due to catchment reforestation retenion within reservoirs fluvial regulation and dredging resulting in the erosion of deltas and barrier lagoon and beach dune systems large stretches of shoreline and narrow coastal plains have been massively engineered for coastal defence and protection against erosion but also for the construction of marinas leisure harbours and artificial beaches resulting in the emergence of veritable artificial seafronts these interventions have collectively and progressively raised societies to a pervasive and overarching position in the geomorphic stability instability of the mediterranean s coasts a situation that will be exacerbated by pressures from sea level rise paving the way for rampant coastal erosion and delta destruction

concentrations provenance and flux of aerosol trace elements during us geotraces western arctic cruise gn01 abstract the arctic region is undergoing significant changes in climate with a notable decrease in summertime sea ice coverage over the past three decades this trend means an increasing proportion of arctic ocean surface waters can receive direct deposition of material from the atmosphere potentially influencing marine biogeochemical cycles and delivery of pollutants to the arctic ecosystem here we present aerosol concentrations of selected trace elements al ti v mn fe co ni cu zn cd and pb measured during the us geotraces western arctic cruise gn01 also known as hly1502 in august october 2015 concentrations of lithogenic elements al ti v mn fe and co were similar to those measured in remote and predominantly marine influenced air masses in previous studies reflecting the remoteness of the arctic ocean from major dust sources concentrations of ni cu zn pb and cd showed significant enrichments over crustal values and were often of similar magnitude to concentrations measured over the north atlantic in air masses of north american or european provenance we use 7be inventory and flux data from gn01 to estimate a bulk atmospheric deposition velocity during the study period and combine it with our aerosol concentrations to calculate atmospheric deposition fluxes of the trace elements in the arctic region during late summer the resulting estimates for mineral dust and fe deposition fall at the low end of global estimates and confirm the arctic ocean as a low dust environment during the summer months this article is part of a special issue entitled conway geotraces edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

influence of anthropogenic combustion emissions on the deposition of soluble aerosol iron to the ocean empirical estimates for island sites in the north atlantic the results of several recent studies challenge the reigning paradigm that continental soil dust provides the only significant atmospheric source of dissolved iron to the surface ocean this evidence includes correlations between the operational solubility of aerosol iron and atmospheric loadings of black carbon and aluminum normalized vanadium and nickel each of which are associated with emissions from the combustion of fossil fuel oil these observations suggest that the relative solubility of aerosol iron hence the eolian flux of soluble iron to the surface ocean may be significantly impacted by anthropogenic oil combustion products using recent field data from the bermuda region we have developed an empirical method to estimate the solubility of aerosol iron using bulk aerosol concentrations of fe v and al we apply this method to a large body of published data from the aeroce program for north atlantic island sites on tenerife barbados bermuda and ireland where the relative proportions of anthropogenic aerosols range from minor to major respectively our aerosol iron solubility estimates suggest that anthropogenic emissions contribute approximately 70 and 85 of the annual dry deposition of soluble iron to the surface ocean near bermuda and ireland respectively implying that human activities have profoundly affected the iron budget of the north atlantic region the annual mean dry deposition of soluble iron at barbados and izana is dominated by soil dust the anthropogenic contribution at these two sites ranges from 12 to 30 and is highly dependent on the soil dust solubility of fe employed in the model the low end 12 estimate appears to be more representative of these high dust sites

exceptional vertebrate biotas from the triassic of china and the expansion of marine ecosystems after the permo triassic mass extinction abstract the triassic was a time of turmoil as life recovered from the most devastating of all mass extinctions the permo triassic event 252 million years ago the triassic marine rock succession of southwest china provides unique documentation of the recovery of marine life through a series of well dated exceptionally preserved fossil assemblages in the daye guanling zhuganpo and xiaowa formations new work shows the richness of the faunas of fishes and reptiles and that recovery of vertebrate faunas was delayed by harsh environmental conditions and then occurred rapidly in the anisian the key faunas of fishes and reptiles come from a limited area in eastern yunnan and western guizhou provinces and these may be dated relative to shared stratigraphic units and their palaeoenvironments reconstructed the luoping and panxian biotas both from the guanling formation are dated as anisian pelsonian on the basis of conodonts and radiometric dates the former being slightly older than the latter the xingyi biota is from the zhuganpo formation and is ladinian or early carnian while the guanling biota is from the overlying xiaowa formation dated as carnian the first three biotas include extensive benthos and burrowing in the sediments and they were located in restricted basins close to shore further even though the luoping and panxian biotas are of similar age their faunas differ significantly reflecting perhaps palaeogeographically isolated basins between the time of the xingyi and guanling biotas there was a major transgression and the guanling biota is entirely different in character from the other three being dominated by pelagic forms such as large floating crinoids attached to logs very large ichthyosaurs and thalattosaurs and pseudoplanktonic bivalves with no benthos and no burrowing phylogenetic study of the fishes and marine reptiles shows apparently explosive diversification among 20 actinopterygian lineages very early in the early triassic but a later expansion of marine reptile groups in the late olenekian and early anisian this offset in diversification patterns is matched by comparisons of feeding guild categories and body size data new research tools will shed considerable light on the phylogenetic and ecological implications of recovery of mairne vertebrates in the triassic

atmospheric transport of mineral dust from the indo gangetic plain temporal variability acid processing and iron solubility atmospheric transport of chemical constituents from the indo gangetic plain igp to the bay of bengal is a conspicuous seasonal feature that occurs during the late ne monsoon december march with this perspective aerosol composition and abundance of mineral dust have been studied during november 2009 to march 2010 from a sampling site kharagpur 22 3 n 87 3 e in the igp representing the atmospheric outflow to the bay of bengal the chemical composition of pm2 5 suggests the dominance of nss so42 6 9 24 3 g m 3 whereas the abundance of mineral dust varied from 3 to 18 g m 3 the concentration of aerosol iron fetot and its fractional solubility fews fews fetot 100 where fews is the water soluble fraction of fetot varied from 60 to 1144 ng m 3 and from 6 7 to 26 5 respectively a striking similarity in the temporal variability of total inorganic acidity tia no3 nss so42 and fews provides evidence for acid processing of mineral dust alluvium during atmospheric transport from the igp the contribution of tia to water soluble inorganic species nss so42 no3 wsis mass ratios of ca al and fe al and abundance of dust and fews in the igp outflow are similar to the aerosol composition over the bay of bengal with the rapid increase in anthropogenic activities over south and south east asia the enhanced fractional solubility of aerosol iron attributed to acid processing of mineral dust has implications to further increase in the air sea deposition of fe to the ocean surface

factors governing abundance of hydrolyzable amino acids in the sediments from the n w european continental margin 47 50 n fifty six samples representing 6 sediment cores taken along the n w european continental margin from the shelf slope and abyssal plain of the goban spur and meriadzek terrace were quantitatively analysed for total hydrolyzable amino acids thaa and clay minerals in descending order the five most abundant amino acids making up more than 70 of the total were aspartic acid glycine serine alanine and glutamic acid clay mineral proportions were typical for the n e atlantic in order of descending abundance illite kaolinite chlorite smectite and mixed layers the meriadzek terrace area is characterised by fine grain suspension sedimentation with a low pelagic carbonate input and the lowest content of thaa in contrast the goban spur transect is characterised by much higher carbonate inputs and more vigorous hydrodynamics as judged from granulometry and the high abundance of minerals of shelf and continental origin and a generally higher thaa content the pelagic portion of thaa deposited at the sea floor is more readily mineralised during early diagenesis than the more refractory clay mineral associated continental portion along this margin the average mineralization of thaa down to 25 cm in the sediment is about 54 there is a significant affinity between chlorites and amino acids which we suggest may involve the formation of ionic bonds between the octahedral layers of the clay and the amino acids

new insights on the relative sea level change during holocene along the coasts of tunisia and western libya from archaeological and geomorphological markers new data of sea level changes for the mediterranean region along the coasts of northern africa are presented data are inferred from archaeological sites of punic roman age located along the coast of tunisia between tunis and jerba island and along the western coast of libya between sabratha and leptis magna data are based on precise measures of presently submerged archaeological markers that are good indicators of past sea level elevation nineteen selected archaeological sites were studied in tunisia and four in libya all aged between 2 0 and 1 5 ka bp the functional elevations of significant archaeological markers were measured with respect to the sea level at the time of measurements applying corrections for tide and atmospheric pressure values the functional elevations of specific architectural parts of the sites were interpreted related to sea level at the time of their construction providing data on the relative changes between land and sea observations were compared against sea level change predictions derived from the glacio hydro isostatic model associated with the last glacial cycle the results indicate that local relative sea level change along the coast of tunisia and libya has increased 0 2 0 5 m since the last 2 ka besides minor vertical tectonic movements of the land the observed changes are produced by eustatic and glacio hydro isostatic variations acting in the mediterranean basin since the end of the last glacial maximum

rate and synchronicity of environmental changes on a shallow carbonate platform late oxfordian swiss jura mountains recent global change occurs within decades and leaves a significant imprint on shallow carbonate platforms to what extent can rate and synchronicity of environmental changes in the past be evaluated in order to allow comparisons with the processes and products of today sections of a carbonate dominated platform of late oxfordian age have been logged in detail in the swiss jura mountains the time frame based on ammonite biostratigraphy and the hierarchical stacking of the sedimentary sequences suggests that these formed by low amplitude high frequency sea level changes in tune with the orbital cycles the smallest unit the elementary sequence can thus be attributed to the 20 kyr precession cycle by identifying sequence stratigraphic elements such as maximum flooding surfaces within an elementary sequence an even higher time resolution can be obtained and reconstructions of changes in water depth and sea level are attempted sedimentation rates were highly irregular and discontinuity surfaces are common correlation of such surfaces from one section to the other is tentative because they could also have formed locally and are not necessarily synchronous on the scale of elementary sequences the vertical facies evolution permits interpretation of changes in water depth which were produced by eustatic sea level changes allocyclic and or by autocyclic processes the distribution of clay minerals indicates changes of sea level as well as of rainfall in the hinterland biotic changes were controlled by water depth and water quality and also by nutrient and clay input carbon and oxygen isotopes do not show significant shifts within the elementary sequences the original ecological mineralogical and geochemical signals have partly been homogenized because of time averaging through bioturbation and through reworking by storms and because of diagenetic modifications consequently there is potential to interpret environmental changes on the studied carbonate platform but the time resolution is not better than a few thousand years the rates and the synchronicity of the processes leading to the observed environmental changes can thus be estimated only within this time frame

constraining oceanic dust deposition using surface ocean dissolved al we use measurements of ocean surface dissolved al a global biogeochemical elemental cycling bec ocean model and the global dust entrainment and deposition dead model to constrain dust deposition to the oceans our al database contains all available measurements with best coverage in the atlantic vertical profiles and seasonal data exist in limited regions observations show that surface dissolved al is distributed similarly to the dust deposition predicted by dead and other models there is an equatorial atlantic al maximum that decreases toward higher latitudes there are high al concentrations in the mediterranean sea and the arabian sea and low concentrations in the pacific and the southern ocean the ocean basins maintain more distinct al profiles than fe profiles in the upper ocean consistent with a weaker biological influence on al than fe the bec predicted surface dissolved al compares relatively well with observations the al distribution reflects the combined effects of al input from dust and al removal by particle scavenging and biological uptake by diatoms model observed biases suggest a southward shift of maximum dust deposition compared to current dust model predictions dead appears to overestimate deposition north of 30 n in the pacific and to underestimate deposition south of 30 n observed al concentrations and the ocean model predicted surface al lifetime provide a semi independent method to estimate oceanic dust deposition this technique indicates that dead may overestimate dust deposition to the north equatorial atlantic but underestimate in other atlantic regions the southern ocean and the arabian sea however spatial variations in aerosol al solubility may also contribute to the model observation mismatch our results have implications for all dust borne ocean nutrients including fe and demonstrate the potential of marine geochemical data to constrain atmospheric aerosol deposition fields

meridional distribution of dissolved manganese in the tropical and equatorial pacific abstract the distribution of dissolved mn dmn was studied in the tropical and equatorial pacific along a meridional transect beginning at station aloha 22 45 n 158 w extending southwards to 7 s along 158 w results show that in the surface ocean 6000 km from the continents which suggests that dmn in the deep open ocean is strongly affected by remineralization the dmn aou linear relationship n 37 r 0 87 that we found in this work is consistent with culture studies and can be applied to mn models to reproduce the observed open ocean mn concentrations in deep waters

dissolution of aerosol iron in the surface waters of the north pacific and north atlantic oceans as determined by a semicontinuous flow through reactor method aerosol iron dissolution in oceanic waters is determined with a semicontinuous batch leaching method in this procedure aerosol samples that were collected from the marine boundary layer were leached in an all teflon flow through reaction chamber by multiple aliquots of similar to 40 ml 0 4 mu m filtered oceanic surface water collected using ultraclean techniques each aliquot of seawater is permitted to leach the aerosol sample in the reaction chamber for a predetermined time before the seawater solution is separated from the aerosol sample by a 0 4 mu m nucleopore filter membrane a new aliquot of seawater is then added to the leaching chamber to continue leaching the same aerosol particles retained on the filter the procedure is repeated with progressive increases in leaching time the method allows the fe released from the aerosol particles to be continuously removed from the system before saturating the complexation capacity of the seawater leaching solution or adsorbing onto the leaching chamber wall this method results in accurate measurements of seawater dissolvable labile aerosol fe that is independent of the total aerosol fe concentrations in the sample the aerosol fe solubility determined using this method ranges from 3 5 1 5 for the north atlantic during september 2005 to 5 7 2 0 for the north pacific during april 2005 and april 2006

spatial and particle size distributions of atmospheric dissolvable iron in aerosols and its input to the southern ocean and coastal east antarctica 1 to characterize atmospheric dissolvable iron over the southern ocean so and coastal east antarctica cea bulk and size segregated 0 056 18 m in diameter aerosols were collected from 34 s 109 e to 69 s 76 e and between 69 s 76 e and 66 s 110 e during a cruise during november 2010 to march 2011 aerosols were analyzed for total dissolvable fe and fe ii by uv visible spectroscopy and total fe by inductively coupled plasma mass spectrometry the average concentrations of total fe were 19 ng m 3 range 10 38 ng m 3 over the so and 26 ng m 3 range 14 56 ng m 3 in cea the average fe ii concentrations were 0 22 ng m 3 range 0 13 0 33 ng m 3 over the so and 0 53 ng m 3 range 0 18 1 3 ng m 3 over cea the total dissolvable fe followed the same trend over the so a single peak size distribution of fe ii existed over cea a bimodal size distribution of fe ii appeared with the first peak at 0 32 0 56 m and the second peak at 5 6 10 m higher fe concentrations over cea than over the so and the existence of coarse mode fe ii over cea suggest potential dust sources in antarctica the fractional fe ii solubility ranged from 0 58 to 6 5 and decreased with total fe concentration increase the estimated atmospheric fluxes of fe ii were 0 007 0 092 mg m 2 yr 1 over the so and 0 022 0 21 mg m 2 yr 1 in cea total dissolvable fe fluxes were 0 007 0 52 mg m 2 yr 1 over the so the atmospheric dissolvable fe input contributes to the dissolved fe pool in the so surface waters

biogeochemistry of iron in australian dust from eolian uplift to marine uptake 1 dust is an important vector for iron supply to the ocean which subsequently impacts ocean productivity atmospheric co2 concentrations and hence global climate here we synthesize the processes influencing the biogeochemistry of australian dust and compare them with those from other southern hemisphere dust sources our observations range from soil and dust physical properties to abrasion and cloud chamber chemistry experiments to dust storms and their dispersion and deposition we then present satellite observations of the impact of episodic dust deposition events on the productivity of low iron oceanic waters north i e low nitrate low chlorophyll lnlc and south i e high nitrate low chlorophyll hnlc of australia dust deposition from the largest dust storm in over 40 years did not result in iron mediated algal blooms in either oceanic region a comparison of australia with other southern hemisphere source regions reveals that the relatively well sampled australian system is a poor generic model furthermore there are marked distinctions between southern and northern hemisphere iron dust biogeochemistry that must be recognized by modelers and included in future simulations better information is required on the relative role of the atmosphere and ocean on influencing iron biogeochemistry and how their relative influences might change in the future due to climate change

biogeochemical iron budgets of the southern ocean south of australia decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply 1 climate change is projected to significantly alter the delivery stratification boundary currents aridification of landmasses glacial melt of iron to the southern ocean we report the most comprehensive suite of biogeochemical iron budgets to date for three contrasting sites in subantarctic and polar frontal waters south of australia distinct regional environments were responsible for differences in the mode and strength of iron supply mechanisms with higher iron stocks and fluxes observed in surface northern subantarctic waters where atmospheric iron fluxes were greater subsurface waters southeast of tasmania were also enriched with particulate iron manganese and aluminum indicative of a strong advective source from shelf sediments subantarctic phytoplankton blooms are thus driven by both seasonal iron supply from southward advection of subtropical waters and by wind blown dust deposition resulting in a strong decoupling of iron and nutrient cycles we discuss the broader global significance our iron budgets for other ocean regions sensitive to climate driven changes in iron supply

aerosol iron and aluminum solubility in the northwest pacific ocean results from the 2002 ioc cruise dust aerosol samples were collected across the western north pacific ocean during may june 2002 samples were analyzed for soluble aerosol fe ii fe ii fe iii and al as well as major cations and anions the aerosol samples were leached using a 10 second exposure to either filtered surface seawater or ultrapure deionized water yielding a measure of the instantaneous soluble fraction a variety of analytical methods were employed including 57fe isotope dilution high resolution icp ms energy dispersive x ray fluorescence graphite furnace aas ion chromatography and the felume chemiluminescent technique fe was found to be more soluble in ultrapure deionized water leaches especially during periods of higher dust concentrations fe solubility averaged 9 8 in ultrapure water leaches and 6 5 in seawater leaches significant correlations were found between both soluble aerosol fet and soluble fe ii concentrations and aerosol acidity however the percentages of soluble aerosol fet and fe ii did not correlate with aerosol acidity we also did not observe significant correlations between total and soluble aerosol fe concentrations and the concentrations of either particulate fe or dissolved fe in surface waters

palaeoenvironmental reconstruction of the ancient harbors of rome claudius and trajan s marine harbors on the tiber delta during the first and second centuries ad emperor claudius and then emperor trajan successively ordered the construction of two large harbors on the tyrrhenian coast research resulted in advances in understanding the palaeoenvironments of the portus from a bathymetric point of view the drillings indicate a 7 8 m depth for the main basins different sedimentary behaviors were observed claudius basin shows sand accretion whereas the access channel to trajan s basin shows mud accumulation trajan built the second hexagonal basin because claudius harbor did not protect the ships from the wind and swell and not because it was prone to rapid silting in terms of chronology the channel between both basins worked between the end of the 2nd century and the beginning of the 5th century when it became completely clogged this means that after the beginning of the 5th century only the junction channel canale traverso remained to provide an access to the tiber and to the sea

impact of anthropogenic combustion emissions on the fractional solubility of aerosol iron evidence from the sargasso sea we report empirical estimates of the fractional solubility of aerosol iron over the sargasso sea during periods characterized by high concentrations of saharan dust summer 2003 and by low concentrations of aerosols in north american maritime north atlantic air masses spring 2004 and early summer 2004 we observed a strong inverse relationship between the operational solubility of aerosol iron defined using a flow through deionized water leaching protocol and the total concentration of aerosol iron whereby the operational solubility of aerosol iron was elevated when total aerosol iron loadings were low this relationship is consistent with source dependent differences in the solubility characteristics of our aerosol samples and can be described by a simple mixing model wherein bulk aerosols represent a conservative mixture of two air mass end members that carry different aerosol types saharan air which contains a relatively high loading of aerosol iron 27 8 nmol fe m 3 that has a low fractional solubility 0 44 and north american air which contains a relatively low concentration of aerosol iron 0 5 nmol fe m 3 that has a high fractional solubility 19 historical data for aerosols collected on bermuda indicate that the low iron loadings associated with north american air masses are typically accompanied by elevated v al fe al and v mn mass ratios in the bulk aerosol relative to saharan dust which are indicative of anthropogenic fuel combustion products the identification of similar compositional trends in our sargasso sea aerosol samples leads us to suggest that the elevated solubility of iron in the aerosols associated with north american air masses reflects the presence of anthropogenic combustion products which contain iron that is readily soluble relative to iron in saharan soil dust we thus propose that the source dependent composition of aerosol particles specifically the relative proportion of anthropogenic combustion products is a primary determinant for the fractional solubility of aerosol iron over the sargasso sea this hypothesis implies that anthropogenic combustion emissions could play a significant role in determining the atmospheric input of soluble iron to the surface ocean

a mediterranean holocene restricted coastal lagoon under arid climate case of the sedimentary record of sabkha boujmel se tunisia abstract the holocene sedimentary record of sabkha boujmel se tunisia is expressed by a shallowing upward carbonate lagoon tidal flat cycle 2 3 m thick unconformably overlying continental silt sandy sediment late wurmian in age the sedimentary package of this cycle starts with transgressive marginal shallow marine intertidal to subtidal bioclastic sands grading upwards to black mudstone rich in organic matter t o c up to 1 3 deposited within a lagoon protected from the sea by upper pleistocene lithified sand spits the uppermost part of the cycle is represented by oobioclastic carbonate sands covered with dead biodegraded microbial mats and or reddish sands of aeolian origin deposited in intertidal to supratidal environments the facies arrangement particularly the spatial distribution of the ancient and the more recent microbial mats records the progressive infilling of the lagoon as well as the progradation of the shoreline during the last 2000 years the organic rich facies which provide an age varying between 4130 and 6800 yr b p were deposited when the boujmel lagoon started to be progressively separated from the mediterranean sea the main factors controlling the facies and the thickness variation are the local topographic sea floor irregularities most likely controlled by the inheritance morphology resulting from an important fluviatile digging that occurred during the last glacial maximum the relative sea level fluctuations the hydro isostatic rebound and the climate

further research on the historical seismicity of tunisia a first report on the historical seismicity of tunisia was read at the joint egs esc cec symposium bologna 1988 subsequently further research has revealed new information and confirmed previous doubts careful discussion of sources definitely throws out the famous 408 utica earthquake and increasingly the effects of the 306 310 and 365 events seem dubious on the other hand several sequences 981 1735 1835 1872 1881 1887 are better known although the location of most epicentres still remains vague while catalogues underestimate the frequency of events in northern as well as in southern tunisia where there is a zelzel legend they continue to overestimate the intensities of modern earthquakes

temporal evolution of sediment supply in lago puyehue southern chile during the last 600 yr and its climatic significance short term climate changes in southern chile are investigated by a multi proxy analysis of a 53 cm long sedimentary sequence selected among eight short cores retrieved in lago puyehue chile 40 s this core contains a 600 yr long undisturbed record of paleo precipitation changes two measurement methods for sediment density organic matter and biogenic silica contents are compared and the most appropriate techniques are selected together with aluminium and titanium concentrations grain size and geochemical properties of the organic matter these proxies are used to demonstrate paleo precipitation changes around 40 s increase of terrigenous particle supply between a d 1490 and a d 1700 suggests a humid period contemporaneously y 13 c data show increasing lake productivity in response to the high nutrient supply the a d 1700 1900 interval is characterized by a decreasing terrigenous supply and increasing y 13 c values interpreted as a drying period the magnetic susceptibility signal reflecting the terrigenous biogenic ratio demonstrates that similar variations occur in all the undisturbed sedimentary environments of lago puyehue the a d 1490 1700 wet period is associated with the onset of the european little ice age lia andinterpreted asits local signature this worksupports the fact that the liawasaglobal event not only restricted to thenorthern hemisphere d 2005 university of washington all rights reserved

atmospheric transport of iron and its deposition in the ocean the atmospheric transport of continental weathering products is responsible for much of the mineral material and fe entering the open ocean and is probably the dominant source of nutrient fe in the photic zone in regions where other nutrients are present in high concentrations the flux of fe from the atmosphere may be a limiting factor in primary productivity due to the larger source regions for dust north of the equator 8 times more atmospheric fe is deposited in the northern hemisphere than in the southern hemisphere the mineral aerosol and fe transport and deposition are highly variable due to the episodic nature of dust generation and its transport and deposition processes between 10 and 50 of the total atmospheric fe entering the world ocean appears to dissolve i e it will pass through a 0 4 m pore size filter rapidly when the mineral matter enters the ocean much of the atmospheric fe is present as fe ii apparently produced as a result of photochemical reduction reactions taking place during atmospheric transport this readily soluble fe ii should be available immediately for use as a nutrient by phytoplankton atmospheric transport from the continents is estimated to supply 3 times as much dissolved fe to the oceans as that delivered via rivers

cycle calibrated magnetostratigraphy of middle carnian from south china implications for late triassic time scale and termination of the yangtze platform abstract thick successions from the margins of the triassic yangtze platform of the south china block record a transition from carbonate rich facies zhuganpo formation and equivalents to clastic rich facies xiaowa formation and equivalents during the carnian early late triassic that mark the final phase of termination of this long lived platform cyclostratigraphy derived from spectral gamma ray sgr intensity curves was combined with magnetostratigraphy of two sections in guizhou province wayao transect and its upward extension into the geopark wayao in guanling county and the laishike section in zhenfeng county and one location in sichuan province hanwang section the cyclostratigraphy from all the guizhou sections indicates a persistent suite of ca 34 m 9 m and 1 8 m cycles which are consistent with the ratios of orbital climate oscillations caused by long eccentricity 405 kyr short eccentricity 100 kyr and precession 20 kyr the magnetostratigraphy of all sections is consistent with the cyclicity and characteristic sgr features thereby enabling a cycle tuned magnetic polarity scale spanning 2 4 myr the main feature is a 1 3 myr interval of reversed polarity containing brief normal polarity subchrons and this reversed polarity chron appears to correspond to the significant reversed polarity dominated interval spanning the upper half of the trachyceras aonoides through the lower half of the austrotrachyceras austriacum ammonoid zones of the upper julian the lower substage of carnian this magnetostratigraphic correlation implies that the termination of the yangtze platform is coeval with the beginning of the mid carnian episode of climatic disruption in europe which is locally called the carnian pluvial event or wet intermezzo and with the temporary cessation of the platform carbonates in the dolomites the cycle scaled magnetic polarity time scale supports the short tuvalian long norian age model of the late triassic in which the base of the cycle tuned polarity pattern from the newark group of eastern north america is younger than the end of the julian substage

sea level change during the holocene in sardinia and in the northeastern adriatic central mediterranean sea from archaeological and geomorphological data abstract we provide new data on relative sea level change from the late holocene for two locations in the central mediterranean sardinia and ne adriatico they are based on precise measures of submerged archaeological and tide notch markers that are good indicators of past sea level elevation twelve submerged archaeological sites were studied six aged between 2 5 and 1 6 ka bp located along the sardinia coast and a further six dated 2 0 ka bp located along the ne adriatic coast italy slovenia and croatia for sardinia we also use beach rock and core data that can be related to holocene sea level the elevations of selected significant archaeological markers were measured with respect to the present sea level applying corrections for tide and atmospheric pressure values at the time of surveys the interpretation of the functional heights related to sea level at the time of their construction provides data on the relative changes between land and sea these data are compared with predictions derived from a new glacio hydro isostatic model associated with the last glacial cycle sardinia is tectonically relatively stable and we use the sea level data from this island to calibrate our models for eustatic and glacio hydro isostatic change the results are consistent with those from another tectonically stable site the versilia plain of italy the northeast adriatic italy slovenia and croatia is an area of subsidence and we use the calibrated model results to separate out the isostatic from the tectonic contributions this indicates that the adriatic coast from the gulf of trieste to the southern end of istria has tectonically subsided by 1 5 m since roman times

climatic and biotic upheavals following the end permian mass extinction the recovery from the end permian mass extinction was slow and prolonged a temperature reconstruction shows that further biotic crises during the recovery were associated with extreme warmth

astrochronology of the anisian stage middle triassic at the guandao reference section south china abstract a high precision global timescale for the early and middle triassic is the key to understanding the nature pattern and rates of biotic recovery following the end permian mass extinction the guandao section of guizhou province of south china is an important reference section for the magnetic polarity pattern conodont datums geochemical anomalies and interpreted temperature history through the anisian middle triassic we analyzed the high resolution gamma ray and magnetic susceptibility series from the complete anisian stage intensity variations are indicative of fluctuating terrestrial clay influxes showing strong signals that match predicted astronomical solutions for eccentricity and precession astronomical tuning of these series to interpreted 405 kyr long eccentricity cycles yields a 5 3 myr duration for the anisian at guandao when combined with the astrochronology of the early triassic then the projected age of the anisian ladinian boundary relative to the base triassic date of 251 9 ma is 241 5 0 1 ma this provides a 10 myr reference timescale for other key geological events including conodont zones geomagnetic polarity chrons rates of marine carbon and oxygen isotope excursions and global sea level changes that were associated with the repeated biotic crises and recovery episodes after the end permian mass extinction the middle anisian humid phase in ca 244 244 5 ma was probably a global event which may have been linked to the middle anisian warming event and sea level change sea level fluctuations at guandao generally correlate with those in western tethyan and boreal regions in time confirming sea level changes during the anisian were of eustatic origin

late pleistocene and holocene alluvial archives in the southwestern mediterranean changes in fluvial dynamics and past human response abstract cohesive floodplains from the semiarid southwestern mediterranean morocco tunisia exhibit excellent preservation toward lateral erosion and present a continuous record of late pleistocene and holocene flood dynamics holocene mean sedimentation rates and 14 c cumulative probability plots from cohesive tunisian floodplain sequences reveal a coupling with north atlantic bond events short term periods of fluvial activity match well with north atlantic coolings the findings indicate a strong climatic link from 4 8 ka until today unlike fluvial archives from the humid mid latitudes semiarid southwest mediterranean alluvial archives exhibit phases of increased fluvial dynamics under generally drier conditions the 14 c cumulative probability plot of archeological sites in mediterranean north africa indicates correlations with alluvial records therefore prehistoric societies seemed to be very sensitive to past shifts in landscape dynamics

the palaeosalinity and vegetational history of garaet el ichkeul northwest tunisia palaeoecological studies of a 14c dated 6 m livingstone core collected from lac ichkeul n tunisia have allowed a palaeosalinity and vegetational history record for the last 3000 years to be derived from pollen chemical and faunal evidence the lake has been the subject of at least three different salinity regimes saline c 3000 bp c 2000 bp then brackish fresh c 2000 bp c 1500 bp and finally saline c 1500 bp present these changes in lake salinity are evaluated in the light of the known causes and the implications for the long term future of the waterfowl populations discussed an already disturbed mediterranean woodland dominated by quercus cf q suber and pinus possibly p halepensis with a significant amount of phillyrea characterizes the catchment vegetation from c 3000 bp from c 1900 bp a degree of stabilization and regeneration occurs as woodland reinvades and ruderal indicators decline however from c 1400 bp disturbance recommences and quercus ilex pollen is seen for t

soil abrasion and eolian dust production implications for iron partitioning and solubility 1 eolian dust is a source of iron for phytoplankton in many ocean areas and there are complex pathways of atmospheric processing from soil to ocean overlooked parts of the pathways are the impact of large 10 m grains including a role as proxies for the behavior of smaller grains and the effect of multiple cycles of uplift and abrasion in the dust source region partitioning readily released acid leachable and refractory and dissolution rates of iron were determined for an artificial dust produced by abrading an australian soil untreated soil abraded soil after production of the artificial dust and a natural australian eolian dust sample taken during a dust storm readily released iron is not created during abrasion and therefore the amount of readily released iron in a dust or dust derived soil depends on processing events since the dust or soil last experienced an abrasion event our study develops a method for the partitioning of iron within airborne dusts and appears to be the first to consider the effect of multiple uplift events on iron partitioning

simulation of high concentration of iron in dense shelf water in the okhotsk sea abstract an ocean general circulation model coupled with a simple biogeochemical model was developed to simulate iron circulation in and around the sea of okhotsk the model has two external sources of iron dust iron at the sea surface and sedimentary iron at the seabed shallower than 300 m the model represented characteristic features reasonably well such as high iron concentration in the dense shelf water dsw and its mixing which extends southward in the intermediate layer from the northwestern shelf along sakhalin island and finally flows into the pacific sensitivity experiments for the solubility of dust iron in seawater suggest that a solubility of 1 is appropriate in our simulation higher solubilities 5 and 10 result in too low phosphate in the northwestern north pacific in summer as well as too high iron concentrations at the sea surface compared with observations besides these experiments show that dust iron hardly contributes to the high iron concentration in the intermediate layer to investigate locations from which the iron in the intermediate layer originates the fate of sedimentary iron input from four regions in the okhotsk sea was examined results suggest that the western and central parts of the northern shelf are important

natural iron fertilization by the eyjafjallajokull volcanic eruption aerosol deposition from the 2010 eruption of the icelandic volcano eyjafjallajokull resulted in significant dissolved iron dfe inputs to the iceland basin of the north atlantic unique ship board measurements indicated strongly enhanced dfe concentrations up to 10 nm immediately under the ash plume bioassay experiments performed with ash collected at sea under the plume also demonstrated the potential for associated fe release to stimulate phytoplankton growth and nutrient drawdown combining fe dissolution measurements with modeled ash deposition suggested that the eruption had the potential to increase dfe by 0 2 nm over an area of up to 570 000 km2 although satellite ocean color data only indicated minor increases in phytoplankton abundance over a relatively constrained area comparison of in situ nitrate concentrations with historical records suggested that ash deposition may have resulted in enhanced major nutrient drawdown our observations thus suggest that the 2010 eyjafjallajokull eruption resulted in a significant perturbation to the biogeochemistry of the iceland basin

headwater valley response to climate and land use changes during the little ice age in the massif central yzeron basin france the geomorphological response of valley bottoms in eastern france to climatic fluctuations of the little ice age lia was investigated using sedimentological analysis together with optically stimulated luminescence osl and radiocarbon dating diachronic mapping of land use since the beginning of the nineteenth century was also carried out since a d 1500 the valley bottoms experienced three cycles of aggradation and subsequent incision each characterized by paired periods of high and low detritic activity while the impact of human activity on the aggradation of the alluvial plain is observed the vertical dynamics of the valley bottom deposits seemingly were also linked to the hydroclimatic fluctuations during the lia the sensitivity to these fluctuations was increased by human activity at the scale of the basin variations of the winter north atlantic oscillation nao and solar activity from the last five centuries correlate with wet and cold phases during which valley bottoms accumulated and dry and warm phases during which the streams incised into the valley floors this fluvial sensitivity to the meteorological conditions induced temporal variations in sedimentary supply originating from either direct input from remnants of periglacial alluvial sheets or local rocky outcrops and or from indirect input from the erosion of alluvial and colluvial deposits these two components combined with the sheet runoff over the ploughlands express the complex coupling between hillslopes and valley bottoms in the headwater catchments this caused a cascade shaped transit of the sediments characterized by alternating phases of storage and removal keywords little ice age headwater valley bottom deposits aggradation incision cycle osl and radiocarbon dating landscape history massif central

the continental margin is a key source of iron to the hnlc north pacific ocean here we show that labile particulate iron and manganese concentrations in the upper 500m of the western subarctic pacific an iron limited high nutrient low chlorophyll hnlc region have prominent subsurface maxima between 100 200 m reaching 3 nm and 600 pm respectively the subsurface concentration maxima in particulate fe are characterized by a more reduced oxidation state suggesting a source from primary volcagenic minerals such as from the kuril kamchatka margin the systematics of these profiles suggest a consistently strong lateral advection of labile mn and fe from redox mobilized labile sources at the continental shelf supplemented by a more variable source of fe from the upper continental slope this subsurface supply of iron from the continental margin is shallow enough to be accessible to the surface through winter upwelling and vertical mixing and is likely a key source of bioavailable fe to the hnlc north pacific

holocene stratigraphy and geomorphological evolution of the aegean coastal plains of anatolia abstract three main stages can be distinguished in the sedimentary development and geomorphological formation of the present delta plains on the aegean coast of turkey the early holocene is characterized by post glacial transgression and dependent sedimentation the middle holocene was the period when sea level reached the present level and apart from small fluctuations stopped rising alluviation and deltaic progradation were prevalent during this transition period from marine to terrestrial environments as for the late holocene deltaic progradation slowed down and delta plains were covered by floodplain sediments these characteristics can be observed in the same sequence throughout the aegean coast of turkey

multiple sources of soluble atmospheric iron to antarctic waters the ross sea antarctica is a highly productive region of the southern ocean significant new sources of iron fe are required to sustain phytoplankton blooms in the austral summer atmospheric deposition is one potential source the fractional solubility of fe is an important variable determining fe availability for biological uptake to constrain aerosol fe inputs to the ross sea region fractional solubility of fe was analyzed in a snow pit from roosevelt island eastern ross sea in addition aluminum dust and refractory black carbon rbc concentrations were analyzed to determine the contribution of mineral dust and combustion sources to the supply of aerosol fe we estimate exceptionally high dissolved fe dfe flux of 1 2 10 6 g m 2 y 1 and total dissolvable fe flux of 140 10 6 g m 2 y 1 for 2011 2012 deposition of dust fe al and rbc occurs primarily during spring summer the observed background fractional fe solubility of 0 7 is consistent with a mineral dust source radiogenic isotopic ratios and particle size distribution of dust indicates that the site is influenced by local and remote sources in 2011 2012 summer relatively high dfe concentrations paralleled both mineral dust and rbc deposition around half of the annual aerosol fe deposition occurred in the austral summer phytoplankton growth season however the fractional fe solubility was low our results suggest that the seasonality of dfe deposition can vary and should be considered on longer glacial interglacial timescales

developing a strategy for accurate definition of a geological boundary through radio isotopic and biochronological dating the early middle triassic boundary south china abstract the ages of critical periods in the geological record of the earth have to be determined and attached uncertainties quantified as precisely and accurately as possible this study tries to find an optimal strategy for sampling for both biochronology and high precision u pb analysis of zircon from ash beds and for the selection and statistical treatment of geochronological data this strategy is applied to the case of the early middle triassic boundary emtb in the southern nanpanjiang basin in south china aiming to obtain the most accurate age information for this boundary with an associated uncertainty the emtb has been located in a sedimentary section near monggan guangxi south china which permitted tight correlation between conodont biozones the carbon isotopic record and high precision zircon u pb data from volcanic ashes two residual maximal horizons were defined using characteristic associations of conodont species accurately bracketing the emtb the lower and upper age limits of these horizons as well as the first occurrence fo of the base middle triassic index fossil chiosella timorensis were numerically calibrated by high precision chemical abrasion isotope dilution thermal ionization mass spectrometry ca id tims u pb dates volcanic zircon in the analyzed ash beds reveals complex system behavior in particular i unresolved lead loss after chemical abrasion and ii pre eruptive growth and or recycling of zircon crystals leading to excess scatter in 206 pb 238 u dates and to violations of the stratigraphic sequence a sufficiently high number of closely spaced ash samples n and of u pb analyses per sample n promotes recognition of such complications two different age models were constructed from weighted mean 206 pb 238 u dates comparing smoothing cubic spline and bayesian interpolation approaches the statistical treatment of the combined datasets allows quantification of the lower and upper limits and associated uncertainties of the two conodont biozones as well as of the fo of c timorensis the age for the emtb is calculated from combined interpolated data at 247 05 0 16 ma the age model derived from bayesian interpolation is considered to be more adapted to the present case where discontinuous changes in sedimentation rates are expected to be important the smoothing spline represents a more parsimonious model producing a simpler solution in terms of smoothness but the model assumptions are too strong for many geological problems the additional freedom in constructing the bayesian interpolating curve presumably leads to more realistic albeit larger confidence intervals

mid holocene emergence of southern tunisian coasts abstract we present new sea level data from the coasts of southern tunisia between the gulf of gabes and the libyan border the work tests previously published evidence on holocene shorelines and confirmed that a distinct emergence has occurred in this area during this time the emergence peak lies at least 186 11 cm above present and is inferred from 1 ams radiocarbon dates of subtidal vermetids and boring shells collected in growth position and 2 careful assessment of tidal heights maximum emergence took place between about 6000 and 5000 14c years bp it cannot be ascribed to tectonics and is probably related to post glacial hydro isostatic effects it challenges the inference of a 3 m global sea level rise since 6000 years bp due to residual antarctic melting

oceanic iron supply mechanisms which support the spring diatom bloom in the oyashio region western subarctic pacific 1 multiyear 2003 2008 time series observations along the a line provided information on the temporal variability of the dissolved iron diss fe concentration in the oyashio region of the western subarctic pacific and the data indicated that there was an annual cycle in the concentration of surface diss fe occurring every year diss fe was supplied into the surface water in this region every winter and supports the spring phytoplankton bloom after development of the thermocline the diss fe concentration was drawn down during the phytoplankton bloom period and was depleted in summer in some water masses then diss fe increased from autumn to winter with the increasing depth of the surface mixed layer the high diss fe concentrations in the surface layer in winter were controlled by mesoscale oceanic intrinsic processes such as vertical winter mixing and horizontal fe rich intermediate water transport difference in magnitude of the winter mixing processes among different water masses caused the heterogeneous distribution of diss fe concentration in the surface layer moreover the vertical section profiles along a cross oyashio transect showed the occurrence of fe rich intermediate water and upward transport of materials from the intermediate water to the surface layer via tidal and winter mixing processes are important mechanisms to explain the high winter surface diss fe concentrations additionally the substantially higher diss fe no3 ratio in the winter surface layer in this studied area other than the high nutrient low chlorophyll region indicates that the winter surface water in the oyashio and the oyashio kuroshio transition zone has a high potential to stimulate phytoplankton growth

a 70 million year astronomical time scale for the deep sea bedded chert sequence inuyama japan implications for triassic jurassic geochronology abstract the astronomical time scale ats has provided high resolution geochronology however the early mesozoic ats is still under construction partly due to the lack of continuous pelagic sequences of the early mesozoic here we present ca 70 myr long ats constructed from the early mesozoic deep sea bedded chert sequence exposed in the inuyama area central japan the sedimentary rhythms of bedded chert display a full range of climatic precession related cycles 20 kyr cycle as a chert shale couplet and 100 405 2000 to 4000 and 10 000 kyr cycles as chert bed thickness variation the newly established ats inuyama ats is tuned by 405 kyr eccentricity cycle and is anchored at the end triassic radiolarian extinction level as 201 4 0 2 ma this inuyama ats gives ages consistent with the radiometric ages projected to the inuyama deep sea sequence using biostratigraphy and carbon isotope stratigraphy the inuyama ats provides the age constraints for the triassic and jurassic stage boundaries which support the long norian option of muttoni et al 2004 because the deep sea bedded chert sequence covers a long time interval before the cretaceous the ats for the bedded chert will serve as a template for the astrochronology of mesozoic and older ages

palaeogeographical and palaeoenvironmental reconstruction of the medjerda delta tunisia during the holocene abstract the progradation of the medjerda delta has been the subject of many studies since the 19th century the scale and the rapidity of this phenomenon interested researchers in various fields early on such as geomorphology geology palaeogeography history archaeology or geoarchaeology indeed the delta prograded by around 10 km over 3 millennia at the time of its foundation supposedly at the end of the 12th century bc the phoenician city of utica was located on a promontory bathed by the sea but the sediments carried by the medjerda progressively sealed the bay leaving the tip of the utica promontory now 10 km inland this area is therefore an exception to the general pattern along the tunisian coast since as over the same period everywhere else there is a regression of the coastline owing to a sea level rise of several decimeters based on multi proxy analyses of two coring transects this paper aims to reconstruct the palaeoenvironments and the palaeogeography of the medjerda delta s progradation since the mid holocene some aspects of which are described in ancient sources the results highlight in particular an episode of high intensity flooding around the 4th century ad which is consistent with episodes of high floods and an increase in sedimentation rates recorded in the watershed at the end of the roman period the gradual abandonment of the city of utica can certainly be related to the activity of the medjerda river but our results show that it is because of an increase of fluvial sediment contribution in connection with an erosive crisis in the headwaters and not because of the change of course of the river which had occurred long before

the evolution of low tunisian coasts in historical times from progradation to erosion and salinization abstract the geoarchaeological approach permits the separation at least two phases of evolution of the tunisian coast during historical time the first is mainly contemporary with the punic and roman occupation but it is not clear exactly when it ended it was marked by an important progradation of the coast at a time characterized by a sea level at least some decimetres below the present level the second phase of development took place after the roman occupation and continues to the present day but again we do not know exactly when it began one of its main characteristics has been a sea level rise which has led to the salinization of low unconsolidated areas and the fragility of the coast expressed by the advance of the sea at the expense of the shoreline even in areas where developments have been built recently

size dependence of iron solubility of asian mineral dust particles 1 asian mineral dust was sampled at hokkaido northern japan in spring 2004 and 2006 iron solubility of the bulk aerosol the size segregated aerosol 0 45 4 7 m we suggest that an iron solubility of around 0 4 is typical for asian mineral dust of large particles transported to hokkaido in the high nutrient low chlorophyll region of the western subarctic north pacific near the asian continent where the mineral dust deposition is dominated by large particles the iron solubility of the mineral dust entering the ocean is around 0 4

iron mobilization in mineral dust can anthropogenic so2 emissions affect ocean productivity 1 for fe contained in long range transported aeolian dust to act as a micronutrient for oceanic phytoplankton it must be first dissolved or mobilized we propose that fe mobilization can occur in mineral dust from east asia by the incorporation of so2 into the advecting dust plumes and subsequent acidification of the dust through heterogeneous so2 oxidation to test this hypothesis we consider a dust plume that originated from the gobi deserts and advected over the pacific ocean data collected over the yellow sea confirm that this plume contained high concentrations of dust and so2 significant gaseous hno3 concentrations indicate that the dust particles were acidified i e ph 2 at these ph s 1 2 of the fe contained in a deliquescent mineral dust particle would be mobilized within 3 5 days these results suggest a possible link between the rate of c fixation in so called high nitrate low chlorophyll regions of the pacific ocean and so2 emissions from east asia

sinking fluxes of minor and trace elements in the north pacific ocean measured during the vertigo program as part of the vertical transport in the global ocean vertigo program we collected and analyzed sinking particles using sediment traps at three depths in the oceanic mesopelagic zone and at two biogeochemically contrasting sites n central pacific at aloha n pacific western subarctic gyre at k2 in this paper we present the results of minor and trace element determinations made on these samples minor and trace elements in the sinking material showed 2 trends in flux with depth increasing and constant the sinking particulate phase of some elements al fe mn was dominated by material of lithogenic origin and exhibited flux that was constant with depth and consistent with eolian dust inputs aloha or increasing in flux with depth as a result of lateral inputs from a shelf k2 this shelf derived material also appears to have been confined to very small particles whose inherent sinking rates are slow and residence time within the mesopelagic twilight zone would be consequently long furthermore the flux of this material did not change with substantial changes in the rain of biogenic material from the surface k2 suggesting mechanistic decoupling from the flux of organic carbon and macronutrients micronutrient fe co zn and cu fluxes examined in a 1 d mass balance suggest widely differing sources and sinks in the water column as well as impacts from biological uptake and regeneration for example total fe fluxes into and out of the euphotic zone appeared to be dominated by lithogenic material and far exceed biological requirements the export flux of fe however appeared to be balanced by the eolian input of soluble fe for zn and cu the situation is reversed with atmospheric inputs insufficient to support fluxes and the cycling therefore dominated by the draw down of an internal pool for co the situation lies in between with important but ultimately insufficient atmospheric inputs

the vertical distribution of iron stable isotopes in the north atlantic near bermuda seawater dissolved iron isotope ratios 56 fe have been measured in the north atlantic near bermuda in a full depth profile seawater dissolved 56 fe is isotopically heavy compared to crustal values throughout the water column 56 fe irmm 014 0 30 to 0 71 iron isotope ratios are relatively homogenous in the upper water column between 0 30 to 0 45 above 1500 m and 56 fe increases below this to a maximum of 0 71 at 2500 m decreasing again to 0 35 at 4200 m the 56 fe profile is very different from the iron concentration profile in the upper water column fe is variable while 56 fe is relatively constant and in the deeper water column 56 fe varies while fe remains relatively constant the 56 fe profile is also not well correlated with other hydrographic tracers in the north atlantic such as temperature salinity or the concentrations of oxygen phosphate silica and cfc 11 the dissimilarity between 56 fe profiles and profiles of fe and other hydrographic tracers shows that fe isotope ratios provide a unique sort of information about ocean chemistry and they suggest that fe isotopes may therefore be a valuable new tool for tracing the global sources sinks and biogeochemical cycling of fe

dissolved rare earth elements tracing lithogenic inputs over the kerguelen plateau southern ocean abstract dissolved rare earth elements rees were measured in the water masses upstream from and over the kerguelen plateau indian sector of the southern ocean upstream from the plateau the ree profiles were consistent with published data from the southern and indian oceans over the plateau a one box model yields a lithogenic nd flux from the dissolution of lithogenic material of 89 20 t nd y 1 and a corresponding dissolved iron input larger than 100 000 t fe y 1 however despite evidence of this significant lithogenic input dissolved fe is strongly depleted in the upper layers contrasting with the enriched ree concentrations this contrast stresses the different behaviours of ree and iron in the surface waters and the fact that strong fertilization does not imply dissolved fe replete waters

dissolved and particulate fe in the western and central north pacific results from the 2002 ioc cruise 1 the goals of the 2002 intergovernmental oceanographic commission ioc cruise were to examine the variability in dissolved and particulate fe over the cruise track relate this variability to atmospheric aerosol fe input and examine the relationships between fe nitrate and dust deposition with regards to fe limitation particularly in the subarctic north pacific dissolved fe in the surface waters was quite variable ranging from 0 10 nm to 0 30 nm dissolved fe in the vertical profiles showed significant variability the most prominent feature being an fe maximum 1 5 nm fe associated with a broad nitrate maximum at 400 1000 m in the western subarctic gyre deep water fe values in the subarctic region ranged from 0 8 nm to 1 1 nm subtropical gyre surface water dissolved fe values were also quite variable ranging from 0 15 nm to 0 4 nm intermediate and deep water fe values were on the order of 0 6 0 9 nm significant differences were observed between total dissolvable fe and dissolved fe tdfe dfe in surface waters over the course of the cruise track and these differences are discussed in terms of particulate fe and possible sources of fe to surface waters finally nitrate fe ratios in the western subarctic gyre atmospheric dust flux estimates based on surface water aluminum concentrations and aerosol fe fluxes from ship based aerosol collections are used to evaluate the relative importance of atmospheric and or continental fe input versus upwelling fluxes of fe to the surface waters of the subarctic gyre

heavy metals as indicators for holocene sediment provenance in a semi arid mediterranean catchment in northern tunisia abstract investigation of sediment provenance supports geoarchaeological and geomorphological studies of holocene palaeoenvironments and fluvial change in northern tunisia information on sediment provenance is derived from heavy metal contents that are preserved in overbank floodplain deposits of the medjerda river and its tributaries the results show that the sedimentary successions in the mid medjerda valley mainly consist of sediments originating from the subcatchments of the semi arid south although climate changes occurred during the holocene which could have an influence on sediment yield this relationship remains constant over time

in search of the harbours new evidence of late roman and byzantine harbours of ephesus abstract ephesus greek name ephesos in western turkey was an important harbour city during antiquity the progradation of the kucuk menderes delta has continuously shifted the coastline westwards thus along with the delta progradation new harbour sites had to be established in a western direction historical sources refer to different harbours while much is known about the roman and older ones the exact location of the ports and the coastline in late roman and byzantine times is still an open question this article presents the results of geoarchaeological research in the area located along the southern flank of the kucuk menderes graben near ephesus sediments from cores were examined with geochemical sedimentological and microfaunal analyses these data were combined with the study of ancient maps and satellite images the chronological framework was rendered by ams 14 c ages and diagnostic ceramics the farthermost inland shoreline dates from 5000 bc since then delta progradation has continuously shifted the shoreline westwards canakgol today a little lake to the west of the city of ephesus is identified as the harbour site in late roman and byzantine times this harbour persisted at least until the 16th century ad further a landing site with a pier was discovered west of canakgol presumably dating to the late byzantine ottoman times

hydrographic observations during the 2002 ioc contaminant baseline survey in the western pacific ocean the 2002 ioc contaminant baseline survey in the western pacific ocean was the fourth in a series of cruises intended to establish the contemporary concentrations of trace elements and other materials in the major water masses of the ocean and to illuminate the pathways by which materials delivered to the surface ocean are incorporated in the subsurface waters the expedition occupied 9 vertical profile stations encompassing the subtropical and subarctic gyre of the western north pacific in addition underway surface water samples were collected during transits between the stations this paper uses the temperature salinity nutrient oxygen and chlorophyll data to set the hydrographic and biological background for the other papers in this theme

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research