metallogenesis at paleo spreading centers lead isotopes in sulfides rocks and sediments from the troodos ophiolite cyprus abstract new pb isotopic data for metalliferous deposits and pelagic sediments from the troodos ophiolite complex cyprus are presented we use these data to re evaluate the genetic models for these deposits in the light of recent results obtained for different types of hydrothermal sites presently active on spreading ridges in contrast to previous conclusions of earlier studies we find that the troodos hydrothermal deposits sulfides as well as umbers and mn crusts have isotopic compositions very similar to that of most of the rocks from this ophiolite complex they display a 207 pb 204 pb ratio higher than present day typical ridges this result has been interpreted as evidence for a subduction related origin of the troodos ophiolite this different geodynamic setting of the ophiolite is also the reason for the isotopic difference between troodos and semail oman sulfides the latter being typical of a normal oceanic crust when examined in more detail the troodos sulfide results are very homogeneous within one site but show significant differences from one site to another at least three different isotopic end members are required to interpret these variations one of these end members is found in the pelagic sediments data analyzed here which have a 207 pb 204 pb typical of continental crust signature higher than that of the rocks and sulfides on present ridges the involvement of such a component has been similarly described for the guaymas basin and for the gorda rise deposits however some of the isotopic variations observed between sulfides cannot be interpreted only by this end member one possibility is that a second sedimentary component as yet unidentified has been involved in the hydrothermal circulation as recently demonstrated for red sea brines finally the determination of the exact proportion of pb leached out of the ophiolite basaltic crust itself would require a more complete knowledge of the initial isotopic heterogeneities within the massif indeed several rock results are significantly less radiogenic than those of the sulfides which however show themselves initial compositions this could result either from a sediment contribution to the sulfide pb or from a biased sampling of the massif heterogeneities this question remains open in the present state of the data

a synthesis of lead isotopes in two millennia of european air four airborne particulate records from ombrotrophic peat bogs in southern norway extending back 300 years have been measured for chronology lead concentration and lead isotope composition since southern norway receives an airborne lead signal that accumulates emissions from the european continent the trend in the four bog records can be used to correlate previously reported measurements from france switzerland england and greenland that cover different ranges of time when these are compiled the integrated european record that emerges spans the last 2300 years of human influence on lead in the air over europe and suggests human control of lead in airborne particulates over the entire period from 366 bc through the first half of the 20th century lead isotopic compositions in european air have fallen within the range of compositions in european ore bodies since 1950 isotopic compositions have been beyond the range in those ore body compositions and have fallen within the array of lead isotope compositions typical of gasoline from western industrial nations a mixing line between us and australian lead in gasoline the overlap between the european record and the range in modern european air suggests an average isotopic composition of 206 pb 207 pb ca 1 13 and of 208p b 207 pb ca 2 41 in air over europe during the last 20 years 1999 elsevier science b v all rights reserved

tracing dust sources and transport patterns using sr nd and pb isotopes continental dust transported through the atmosphere can be a tracer of atmospheric circulation and transport as well as being a source of information about climate in the dust s source area this information about the provenance of dust transported from desert areas and deposited elsewhere on the oceans and continents can be evaluated using several observational techniques satellite imagery has been used to this end in recent decades and air mass back trajectories have been calculated to trace dust deposits back to their source area another method consists of analysis of the concentration and composition of certain tracers in the dust itself and comparing them to soils and sediments from possible source areas this method has the advantage of being useable for paleo atmospheric circulation and paleo dust transport studies whereas satellite imagery and air mass back trajectories are restricted to relatively recent times we review here different kinds of isotopic tracers that have been used to trace dust provenance but special attention is focused on the use of sr nd and pb isotopes we evaluate their use in studies of both spatially as well as temporally varying continental dust source and transport

influence of inheritance and pedogenesis on heavy metal distribution in soils of sicily italy abstract the recognition of the potential health hazards associated with heavy metals has focused attention on the levels and behaviours of these elements both in natural and contaminated environments various soil types developed from different parent materials in sicily italy have been analysed in order to compare heavy metal distribution under different geopedological conditions total metal concentrations metal partitioning and distribution profiles are discussed in relation to the inheritance factor and pedogenic processes parent material composition largely influences the contents of heavy metals in most of the analysed soils mainly differentiating pedons for their metal concentration on the basis of sedimentary and volcanic parent materials however an exception is represented by the carbonate free alfisols and mollisols which are markedly enriched in heavy metals with respect to the underlying limestones and calcarenites on the basis of chemical and mineralogical results supported by data from sequential extraction sep heavy metal enrichment in these soils is associated with the formation of common to abundant fe mn oxides and clay accumulation for mollisols there is evidence for a major role of organic matter in heavy metal retention in surface horizons in the other pedons pedogenic processes appear to mainly influence the redistribution of heavy metals throughout the soil horizons rather than affecting the total content argillopedoturbation seems to be responsible for a uniform distribution of heavy metals in vertisol profiles on marly clays accumulation of heavy metals in the topsoil of inceptisols on clays with gypsum and entisols on gypsarenites and diatomites is caused partially by adsorption on organic matter and mainly by dissolution of primary gypsum and opal a a pedogenic influence is less evident in young andisols whose heavy metal composition greatly reflects that of hawaiitic pyroclastic deposits interbedded within the profiles however a certain redistribution of cu accumulated as metal organic matter complexes is evidenced in the surface horizon by sep

stable lead isotope studies of central taurus ore sources and related artifacts from eastern mediterranean chalcolithic and bronze age sites abstract this is the first paper in a series presenting stable lead isotope studies of geological and archaelogical specimens obtained in 7 years of archaeometallurgical surveys in turkey the geological specimens presented here are ore and slag samples taken from ancient mining sites in the central taurus mountain range the archaelogical specimens are metal objects dating to the chalcolithic and bronze ages from anatolia syria mesopotamia greece and the aegean the isotopic measurements on these specimens have been made and statistically analysed as part of a collaborative effort between the smithsonian institution conservation analytical laboratory and the united states national institute of standards and technology nist a comprehensive data base of approximately 1000 stable lead isotope measurements on such eastern mediterranean specimens has been formed by combining the accumulated measurements at nist with analyses published in the literature the overlap between specimens in the overall data bank and the central taurus source specimens provides a realistic evaluations of the effectiveness of the use of stable lead isotope measurements for metallic ore source characterization and for the recognition of exchange patterns of metal and metal artifacts in the formative periods of metallurgy

new insights into the palaeoenvironmental evolution of magdala ancient harbour sea of galilee israel from ostracod assemblages geochemistry and sedimentology abstract despite several studies have focused on the past bio sedimentary response of the mediterranean coastal areas to ancient seaport activities only few geoarchaeological and palaeoecological data are available on strictly lacustrine harbours to date at the archaeological site of magdala taricheae sea of galilee north israel an interdisciplinary study combining ostracod fauna composition and shell chemistry with sedimentology geochemistry of sediments and archaeological data was undertaken on the sedimentary succession buried beneath the roman harbour structures in correspondence of two key sections this approach provided detailed information about past environmental changes otherwise not visible into a high resolution pottery based chronological framework at the transition from a natural pre harbour to anthropogenically influenced harbour lacustrine depositional setting new bio sedimentary and archaeological pottery data document that remarkable hydrodynamic and hydrochemical changes took place during the hellenistic period from the 3 rd 2 nd century bc to the first half of the 1 st century ad in response to the construction of the oldest magdala harbour installations and possibly to the following hasmonean structures the high v cr concentrations observed in the harbour sediments and the substantial increase of ostracod species pseudocandona albicans preferring slow moving waters and fine grained substrates point to the establishment of a semi enclosed shallow and organic rich setting coupled ostracod geochemical analyses also testify to an alkali ions na and k enrichment within whole sediment samples reasonably driven by increasing evaporation in response to the partial isolation of the lake margin the increase in sodium and potassium concentrations is accompanied by the sudden appearance of heterocypris salina a brackish tolerant species and by the almost absolute dominance of noded valves of cyprideis torosa whose shells are enriched in na k and cl the positive covariance between na 2 o k 2 o values and the frequencies of noded c torosa seems to confirm the relation between node development and changes in ionic concentration within hypohaline settings

the characterisation of saharan dusts and nile particulate matter in surface sediments from the levantine basin using sr isotopes abstract the provenance of sediments within the levantine basin of the eastern mediterranean was studied using 87 sr 86 sr isotopic ratios together with major elements measurements were made on the detrital fraction of surface sediments and the two most important sources of detrital matter to the region saharan dust was characterised by an 87 sr 86 sr isotopic ratio in the range 0 7160 0 7192 there was a small systematic decrease in 87 sr 86 sr from west to east which is interpreted as due to a change in the balance of aeolian source material the nile particulate matter had a 87 sr 86 sr isotopic ratio in the range 0 7057 0 7071 87 sr 86 sr isotopic signatures together with sr concentration were used to calculate the contributions made by saharan dust and nile particulate matter to the surface sediments of the levantine basin it was shown that nile derived sediment was dispersed widely across the levantine basin enabling the area affected by retention of sediment behind the aswan dam to be determined

pollutant lead reveals the pre hellenistic occupation and ancient growth of alexandria egypt 1 it is generally accepted that alexandria ad aegyptum was founded ex nihilo in 331 bc by alexander the great rapidly growing into one of antiquity s most opulent economic and intellectual centers however ancient texts by strabo 17 1 6 and pliny nh 5 11 62 suggest the existence of a pre hellenistic settlement named rhakotis this literary evidence has fuelled contentious scholarly debate for decades here we present new geochemical data from alexandria s ancient bay sediments elucidating unequivocal proof for pollutant lead pb input into the harbor during the egyptian old kingdom 2686 2181 bc a second contamination peak is detected during the iron age 1000 800 bc at the end of the prosperous ramesses reigns these findings evidence thriving pre hellenistic settlements in alexandria during the greek and roman periods we expound the largest pb pollution ever encountered in ancient city sediments with pb levels twice as high as those measured in contemporary industrialized estuaries

pb isotopic composition of ophiolitic volcanogenic sulphide deposits troodos complex cyprus the volcanogenic sulphide ore deposits in the ophiolitic rocks of the troodos massif cyprus are thought to be 80 myr old1 analogues of the metal sulphide accumulations actively being deposited from 350 c water at a depth of 2 6 km on the east pacific rise 21 n 2 4 in both cases mineralization is thought to be a consequence of heat transfer by convective seawater circulation within the oceanic crust5 6 evidence includes fluid inclusions in quartz from ore deposits in cyprus with modal trapping temperatures of 298 370 c which have a bulk composition of 3 2 0 5 equiv wt nacl 1 n 273 this salinity is identical to seawater with 3 5 wt total dissolved solids4 7 we have examined the isotopic composition of pb as a geochemical tracer to clarify the origin of one of the metals contained in the sulphide concentrations in the troodos complex it was anticipated that the bulk of the lead would have been derived by leaching of the mafic ophiolitic rocks and indeed such a component is found to be present however the isotope ratios suggest that the lead is actually a mixture and also contains an important component derived from sea water

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

a 6000 year geochemical record of human activities from alexandria egypt abstract recent multidisciplinary investigations of sediment cores from the ancient marine bay of alexandria egypt have documented local human activities during the iron age circa 900 1000 b c prior to alexander the great s arrival in 331 b c goiran 2001 veron et al 2006 stanley et al 2007 2010 corroborating the existence of the so called rakhotis as evoked in previous archaeological literature jondet 1916 weill 1919 chauveau 1999 baines 2003 lead pb isotopic analyses lia from alexandria bay indicate a possible anthropogenic imprint as early as circa 2300 2650 200 b c and to a lesser extent 3500 3800 170 b c veron et al 2006 here we demonstrate that lia in sediments from the nearby maryut lagoon display isotopic anomalies resulting from the release of contaminant pb into the lagoon during the egyptian early dynastic at 2897 187 b c and predynastic at 3520 145 b c periods that corroborate geochemical data from alexandria bay pb concentrations in maryut sediments show enrichments that mirror isotopic findings the absence of contaminant pb imprints within the sediments from the nearby nile canopic branch confirms that isotopic anomalies found in alexandria bay and maryut lagoon sediments are local and do not originate from long distance transport of contaminant pb associated with nile suspended material and or wind derived aerosols lia in alexandria sediment cores correspond to commonly mined pb and cu copper ores from turkey black sea region cyprus crete and the oman gulf lia substantiate the use of copper based relics in the alexandria region during the pre and early dynastic periods and provide insights into metal trading within the eastern mediterranean during the chalcolithic early bronze age transition 6000 years ago

archaeological reconstruction of medieval lead production implications for ancient metal provenance studies and paleopollution tracing by pb isotopes abstract the identification of metal provenance is often based on chemical and pb isotope analyses of materials from the operating chain mainly ores and metallic artefacts such analyses however have their limits some studies are unable to trace metallic artefacts or ingots to their ore sources even in well constrained archaeological contexts possible reasons for this difficulty are to be found among a variety of limiting factors i problems of ore signatures ii mixing of different ores alloys iii the use of additives during the metallurgical process iv metal recycling and v possible pb isotopic fractionation during metal production this paper focuses on the issue of pb isotope fractionation during smelting to address the issue of metal provenance through an experimental reconstruction of argentiferous pb production in the medieval period an attempt was made to better understand and interpret the pb isotopic composition of ore smelting products it is shown that the measured differences outside the total external uncertainties of 0 005 2 sd for 206 pb 204 pb ratios in pb signatures measured between ores slag and smoke are not due to pb mass fractionation processes but to 1 ore heterogeneity 206 pb 204 pb slag ores 0 066 and 2 the use of additives during the metallurgical process 206 pb 204 pb slag ores 0 083 even if these differences are due to causes 1 and or 2 smoke from the ore reduction appears to reflect the ore mining area without a significant disturbance of its pb signature for all the isotopic ratios 206 pb 204 pb smokes ores 0 026 thus because the isotopic heterogeneity of the mining district and additives is averaged in slags slag appears as the most relevant product to identify ancient metal provenance whereas aiming at identifying a given mine seems beyond the possibilities provided by the method searching for the mining district through analysis of the smelting workshop materials should provide a more appropriate approach in cases where no archaeological evidence of ancient mining is available furthermore smoke pb isotopic composition does not seem to be significantly affected by the metallurgical process paleopollution recorded in peat deposits could help to detect ancient mining production and workshops integrated collaboration between mining archaeologists and geochemists appears crucial to achieve this goal

tectonic and climatic control of paleogene sedimentation in the rhenodanubian flysch basin eastern alps austria abstract the paleocene to lowermost eocene formations of the rhenodanubian flysch were deposited in an abyssal environment at the continental rise to the south of the european plate the pattern of paleocurrents indicates a number of small distributary systems for the turbiditic material that entered the basin from the north and was deflected to the east and to the west heavy mineral assemblages in the turbidites suggest the erosion of medium grade metasediments in the danian and the progressive erosion of underlying metamorphic magmatic rocks in the thanetian and ypresian the most obvious sedimentary event is the breakdown in turbidite sedimentation during the late danian to the early thanetian remarkably this starvation of turbidites is associated with high values of chlorite in the clay mineral assemblages of interturbidite shales indicating increased mechanical erosion of the adjoining land areas tectonic uplift of these areas and associated block faulting and tilting is assumed to be responsible for this increase in erosion as well as for the synchronous cutting off of the basin from the source area of the turbidites this tectonic activity is related to the onset of the collision of the european and the adriatic plates a second major event documented in the paleogene record is the change from a predominantly siliciclastic system to a carbonate system in the latest thanetian associated with the global negative carbon isotope excursion cie in the upper part of calcareous nannozone np9 calcareous mudturbidites become the prevailing rock type eutrophication of surface waters is indicated by acmes of diatoms radiolaria and dinoflagellates at the level of the cie together with slightly increased values of kaolinite in the clay mineral assemblages of interturbidite shales this can be interpreted as a result of increased continental run off due to high precipitation rates in a humid climate the top of the increased kaolinite input is poorly constrained because of a very high input of smectite due to volcanic activity in sub zone np10a this igneous activity is assigned to the opening of the northern atlantic ocean and has no geodynamic relevance for the rhenodanubian basin

long term shoreline changes and the concentration of heavy minerals in beach sands of the nile delta egypt abstract analyses have been undertaken of shoreline positions established from beach profile surveys at 65 positions along the coastline of the nile delta spanning the years 1971 to 1990 the analyses identify long term linear trends as well as any cycles in the horizontal movement of shoreline positions the results reveal longshore patterns wherein erosion along a stretch of coast gives way to accretion in an adjacent stretch defining a subcell within the overall littoral system of the delta the rate of shoreline retreat has been greatest along the rosetta promontory 106 m yr and damietta promontory 10 4 m yr significant erosion has also occurred along the central bulge of the delta coast but at a lesser rate 6 5 m yr areas of accretion exist within the saddles or embayments between the promontories with the maximum shoreline advance averaging about 13 m yr the identified patterns of erosion versus accretion along the delta reflect the natural processes of wave induced longshore currents and sediment transport associated with this longshore sediment movement is a selective transport of different minerals according to their densities and grain sizes with the light minerals quartz and feldspar having the highest advection rates and the dense opaque minerals the lowest rates tending to remain behind as a lag within the erosion areas as a result of this longshore grain sorting paralleling the patterns of shoreline erosion versus accretion there are correlations between the rates of shoreline change and the heavy mineral contents and mean grain sizes of the beach sediments these large scale delta wide patterns are affected somewhat by local shoreline changes and mineral variations induced by the construction of jetties or shoreline protection structures

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

late quaternary palaeoclimatic oscillations in east africa recorded by heavy minerals in the nile delta because the nile carries a load derived from markedly different geological terrains and climatic zones it is expected that minera logical study of deposits in its delta could help define changes in palaeoclimate affecting east africa here we report measurements on heavy minerals in the nile delta which can be used as distinct markers of climatic shifts over africa during the late pleistocene to recent variations of heavy minerals in radiocarbon dated cores collected in this delta1 the nile s major depocentre2 correlate closely with oscillations in african palaeoclimate determined by other independent methods such as studies of lake levels these variations are largely a function of the characteristics of the nile it flows across nearly 35 of latitude from south of the equator to the mediterranean fig la and conditions in its drainage basin which includes central africa the ethiopian plateau and eastern sahara range from a tropical humid to a warm arid climate east african climatic belts migrated considerably during the quaternary3 5 modifying nile discharge and sediment load climatic oscillations have been recorded by changes of sediment yield and grain size along its course6 7 and by well defined depositional cycles8 including sapropels9 in the eastern mediterranean

new light on the age of the white nile landsat 5 thematic mapper and 7 enhanced thematic mapper imagery reveal lake shorelines in the white nile valley as far south as lat 10 n the highest shoreline is at 386 m elevation and was eroded when the white nile formed a lake as wide as 70 km and 500 km long finely laminated green clays laid down on the floor of this lake are overlain by alluvial sands and clays dated by optically stimulated luminescence as 15 ka to older than 250 ka the alluvium was deposited during interglacial episodes of stronger summer monsoons and very high white nile floods the white nile paleolake is much older than marine oxygen isotope stage 7 and may have formed ca 400 ka during the exceptionally long stage 11 interglacial

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

refractory element mobility in volcanic soils refractory trace element concentrations in strongly weathered hawaiian soils ranging in age from 20 to 4100 ka are highly elevated over parent rock values due to extensive mass loss of more soluble major elements during pedogenesis nb and ta exhibit virtually no mobility soil nb ta ratios are within the range of fresh bedrock even when soil nb concentrations are residually enriched by a factor of 10 in contrast al zr and hf are depleted relative to nb in surface soil horizons but are enriched at depth clearly indicating mobility of these elements variations in th nb ratios in soil profiles indicate significant th mobility within the soil column however mass balance calculations require that accretion of th enriched asian dust has resulted in a net increase in th in some soils soils developed on a 150 ka rainfall gradient show that the mobility and loss of zr increase with mean annual precipitation

reworking and discontinuities in holocene sedimentation in the nile delta documentation from amino acid racemization and stable isotopes in mollusk shells abstract the late holocene sedimentary history of the northwestern edge of the nile delta is reconstructed from amino acid racemization radiocarbon and stable isotope analysis of a series of bivalve shells from a core taken at the edge of lake maryut near alexandria amino acid racemization confirmed by radiocarbon and stable isotope analysis indicates that in many parts of the core mixed age mollusk assemblages are present dating of the time of sediment accumulation at various levels in the core is therefore based on the age of the youngest shells which are identified by amino acid racemization analysis lowest d l values ams radiocarbon analysis is used to determine the ages of the shells except for the most recent sediments last 100 yr for which aspartic acid racemization provides more precise ages amino acid racemization analysis of 59 shells from 21 levels in the 4 8 m holocene sequence in the core enabled identification of a large hiatus holocene sedimentation started at ca 2400 bc apparently corresponding to a westward shift of the course of the canopic nile distributary which lies to the east deposition continued at a rate of 1 4 mm per year ceasing at ca 550 bc at which time the canopic nile shifted eastward again and subsequently became defunct a marine connection during this period is indicated by stable isotope values of shells sediment accumulation began again only at the end of the 19th century when a series of irrigation canals was connected to the lake maryut basin stable isotope values indicate a strong freshwater influence deposition has continued to the present at a very high rate 19 mm per year due to supply of sediments by agricultural activity the relative ease with which racemization analyses can be carried out permits detailed analysis of core chronostratigraphy leading to more accurate reconstruction of core chronology hiatuses can be pinpointed and documented and age mixtures can be identified with appropriate individual shells being selected for ams radiocarbon analysis aspartic acid racemization analysis permits dating of samples from the last several hundred years a period for which radiocarbon analyses provide poor precision

a 7500 year strontium isotope record from the northwestern nile delta maryut lagoon egypt abstract during the holocene delta evolution has been collectively mediated by relative sea level changes continental hydrology and human impacts in this paper we present a strontium isotope record from the maryut lagoon northwestern nile delta to quantify the interplay between relative sea level variations and nile flow changes during the past 7500 years 87sr 86sr stratigraphy allows five hydrological stages to be defined 1 the marine transgression of the area is dated to 7 5 ka cal bp with a clear marine 87sr 86sr signature 0 70905 0 7091 2 between 7 and 5 5 ka in the context of the so called african humid period ahp freshwater inputs became progressively predominant in the maryut s hydrology deceleration of sea level rise coupled with high nile discharge induced coastal progradation which led to the progressive closure of the maryut lagoon 3 between 5 5 and 3 8 ka the end of the ahp is translated by a progressive hydrological shift from a nile dominated to a marine dominated lagoon 87sr 86sr shifts from 0 70865 to 0 7088 to 0 70905 0 70915 4 from 2 8 to 1 7 ka 87sr 86sr ratios shift towards lower values 0 7084 although this change is not precisely resolved because of a hiatus in the maryut s sedimentary record the 87sr 86sr transition from sea like to nile dominated values is attributed to irrigation practices since the early ptolemaic period i e since 2 3 ka including the alexandria canal which played a key role in isolating the maryut from the mediterranean sea 5 the final phase of the record covers the period between 1 7 and 0 2 ka 87sr 86sr ratios indicate high freshwater inputs from 0 7080 to 0 7085 except between 1 2 and 1 1 to 0 7 ka when a maryut lowstand and seawater intrusion are attested in modern times the nile s coastal lagoons have been increasingly supplied by freshwater linked to the diversion of waters from the two nile branches into the irrigation system it is suggested that this process began in early antiquity and has engendered a reduction in the number of nile branches from seven in ancient times to just two at present

nile delta s sinking past quantifiable links with holocene compaction and climate driven changes in sediment supply the nile delta is a subsiding sedimentary basin that hosts 66 of egypt s population and 60 of the country s food production projected sea level rise scenarios for the coming decades have sharpened focus on the delta s potential resilience to rapid changes in accommodation space we use chronostratigraphic data from 194 organic rich peat and lagoon points to quantitatively reevaluate the drivers of nile delta surface dynamics during the holocene reconstructed subsidence rates range from 0 03 to 4 5 mm yr and are highest in the manzala burullus idku and maryut lagoons areas that correspond to deep late pleistocene topography infi lled with compressible holocene strata 88 of the subsidence values are 2 mm yr we suggest that during the holocene two signifi cant but previously underestimated contributors to changes in nile delta mass balance have been sediment compaction and orbitally forced changes in sediment supply between 8000 and 4000 calibrated cal 14 c yr b p spatially averaged sedimentation rates were greater than subsidence meaning that delta aggradation was the dominant geomorphological process at the regional scale since ca 4000 cal yr b p a sharp climate driven fall in nile sediment supply coupled with the human induced drainage of deltaic wetlands has rendered the depocenter more sensitive to degradation by sea level rise and extreme fl ood events

organic facies variations in the valanginian mid hauterivian interval of the agrio formation chos malal area neuquen argentina local significance and global context

climate forcing of the pb isotope record of terrigenous input into the equatorial atlantic abstract pb isotopic compositions of bulk sediment cores from the tropical atlantic are used here to infer variations in the provenance of terrigenous input to the tropical atlantic during pleistocene climate cycles the 200 ka high precision 2 100 ppm pb isotope records of the ceara rise western atlantic and sierra leone rise eastern atlantic cores show a clear glacial interglacial cyclicity reflected by alternating unradiogenic pb and radiogenic pb in both cores the glacial interglacial pb isotopic contrast is also observed in pb pb space and can be explained in terms of binary mixing variations along the mixing lines reflecting changes in the relative proportions of the glacial unradiogenic and interglacial radiogenic pb source s the pleistocene pb isotopic variability of the terrigenous input to the ceara rise can be linked to changes in the weathering styles in the amazon basin and as a result in the amazon river discharge these changes are reflected by a greater contribution from the highlands andes pb source during glacial times and strengthening of the lowlands shield pb source during interglacials on the other hand pb isotopic variations in the sierra leone rise core indicate increased pb inputs from the saharan dust plume during glacial times in agreement with the wind patterns over africa furthermore this result bears some implications on the cause of the enhanced glacial terrigenous fluxes to the tropical atlantic which we infer to be due to increase in winter wind transport rather than glacial hyperaridity the cyclicity of the ceara rise and sierra leone rise pb isotopic records together with changes in the proportions of mixing sources throughout the last 200 ka monitor changes in the hydrological cycle over south america and the wind systems over africa respectively both of which are linked to the seasonal latitudinal migration of the intertropical convergence zone the correlation found between pb isotope cycles and other paleoclimate proxies suggests that pb isotopes may be responding to variations in earth s orbital parameters

sediment and pollen evidence for an early to mid holocene humid period in the eastern sahara a major problem in the study of holocene palaeoenvironments of the arid and wind deflated sahara is the low preservation potential of sediments from which a record of past climatic change can be established several indirect and imprecisely dated pieces of evidence have suggested humid episodes in the holocene that may have supported more productive ecosystems and denser human populations than today searches for reliable proxy data on past climates however have failed to yield satisfactory results we report here the discovery of buried lake muds in north west sudan in the hyperarid core of the eastern sahara which yield sedimentological and palynological data clearly interpretable as recording an early to mid holocene humid episode that supported a relatively deep stratified lake surrounded by tropical savanna woodland vegetation

the lead and strontium isotope geochemistry of metalliferous sediments associated with upper cretaceous ophiolitic rocks in cyprus syria and the sultanate of oman metalliferous sediments consisting dominantly of fine grained iron and manganese oxides and hydroxyoxides have been widely recorded from the crests of sea floor spreading ridges and as a basal faci

nile river sediment fluctuations over the past 7000 yr and their key role in sapropel development the provenance pattern of nile river sediments can be used as a proxy for paleoclimatic changes in east africa the 87sr 86sr ratios are particularly appropriate for such provenance investigations because the white nile drains predominantly crystalline basement rocks whereas the blue nile and atbara flow off the ethiopian highlands which consist of tertiary volcanic rocks a high resolution profile of 87sr 86sr and ti al ratios from a well dated core in the nile delta shows a close correspondence with known changes in nile flow over the past 7000 yr at times of higher river flow there was markedly decreased input of blue nile derived and total sediment this change was caused by northward movement of the inter tropical convergence zone resulting in increased vegetative cover in the ethiopian highlands due to higher rainfall and a longer wet season this inverse relationship between nile river flow and sediment flux may have had important implications in the development of agricultural technology in ancient egypt the marked minimum in 87sr 86sr at 4200 4500 yr b p is coincident with the end of the old kingdom in egypt and provides independent evidence that demise of the old kingdom might have been associated with an extended period of catastrophic low floods during the quaternary and late neogene there was periodic deposition of organic rich sediments sapropels in the eastern mediterranean that represent important indicators of major environmental change evidence from the ti al ratio suggests that the pattern of erosion and sediment supply from the nile catchment observed in this study also occurred throughout much of the neogene and quaternary the reduced inputs of blue nile sediment during times of sapropel formation contributed to the increased primary productivity by reducing the amount of phosphate removed on particles and to the observed change to n limitation in the eastern mediterranean which are important characteristics of sapropel deposition

environmental imprints of landscape evolution and human activities during the holocene in a small catchment of the calanques massif cassis southern france this paper is based on a multidisciplinary study using both paleoenvironmental methods biological sedimentological magnetic and geochemical and archaeological data in order to characterize landscape and hydrological network changes as well as human impact on a littoral catchment in the western mediterranean area sedimentary records obtained around a coastal alluvial plain cassis southeastern france reveal local environmental changes and human activities since the neolithic ca 6000 cal bp anthropogenic impact is already noticeable in the earliest record and we follow its evolution through time according to biological markers the holocene landscape of the calanques is dominated by a mosaic of open herbaceous formations partly generated by human activity the prevalence of cernuella virgata in malacofauna successions and of coprophilous fungal spores in the pollen record testifies to the spread of agro pastoral activities two increases of anthropogenic impact are highlighted during the roman ca 2000 cal bp and modern from ca 1450 to today periods lead isotope analyses indicate an anthropogenic release of lead possibly originating from the greek cyclades ca 2000 cal bp hydrographic and agricultural work is also enhanced during the roman period magnetic parameters and lead isotopes indicate that the modern anthropogenic impact may be associated with high temperature activities e g lime kiln fossil fuel