sources of sediment to the ionian sea and western levantine basin of the eastern mediterranean during s 1 sapropel times abstract the provenance of sediments to the ionian sea and western levantine basin during s 1 sapropel times was studied using 87 sr 86 sr isotopic ratios together with major elements measurements were made on sediment profiles from 5 box cores in the eastern mediterranean on saharan dust and on a core from the nile delta which included sediment deposited during s 1 sapropel times in the sediment profiles there was a decrease in 87 sr 86 sr ratio 1 sr ti al mg al and si al ratio starting at the upper mn peak and finishing at the base of the organic rich layer this showed that there was a major change in the nature of the detrital input during s 1 sapropel times the timing of the change in detrital input was similar to the change in surface salinity as measured by 18 o there was linear relationship between 87 sr 86 sr and 1 sr and for 87 sr 86 sr and ti al for all the sediment samples the favoured interpretation of this pattern was that the detrital input was a mixture of saharan dust similar to that being deposited today on corsica and a local riverine sediment source the data were incompatible with the riverine source to the ionian sea and western levantine basin being from the river nile the minor variations in sr isotopes and metal al ratios in the nile delta core was interpreted as due to changes in the proportion of blue nile to white nile inputs brought about by climatic variations it was calculated that the change in detrital input during s 1 time was caused by a simultaneous increase in riverine input and decrease in saharan dust input

climate swings in the northern red sea over the last 150 000 years from end and mg ca of marine sediments abstract the end and mg ca compositions of terrigenous material from a meridional transect of seven marine sediment cores located between the northern red sea and the gulf of aqaba together with modern dust sample compositions reveal the temporal and spatial changes in precipitation and dust sources over the last 150 kyrs and are further used to discuss the late quaternary climate history of this region two recent glacial periods marine isotopes stages mis 6 and 2 are characterized by low end values associated with a saharan dust source 12 while mg ca ratios suggest increased transport of dust containing authigenic clays during the last deglacial which most likely originated from the arabian peninsula by contrast mis5e sediments are characterized by an abrupt basin wide shift of end values toward the local arabian nubian shield end member 2 that are exposed around the red sea this shift stems from intense fluvial events and is coeval with other regional paleo precipitation records that all point to an extensive northward shift of precipitation from the tropics during mis5e considering model simulations and regional precipitation dynamics we conclude that although the african summer monsoon probably intensified and extended somewhat northward during mis5e it was not the driver of significant precipitation and the main contribution of precipitation to the northern red sea was due to increased frequency and possible intensity of tropical plumes and red sea troughs that triggered massive fluvial floods within the red sea catchment considering mis5e as an analogue to a future warmer world this currently hyperarid region could be exposed over the coming decades to an increased impact of extreme rainfall events with critical implications for water availability and infrastructure sustainability

clay minerals in late glacial and holocene sediments of the northern and southern aegean sea different source areas oceanography and climate regimes influenced the clay mineral assemblages and grain size distribution of two sediment cores from the north and south aegean sea during the last glacial and the holocene in the north aegean sea clay mineral composition is mainly controlled by sea level evolution melting of southeastern european glaciers and establishment of the connection between the black sea and aegean sea the long term development of clay mineral assemblages in the south aegean sea reflects changes in the nile discharge and african dust input at this site the establishment of pluvial conditions in the nile catchment during the early to middle holocene resulted in a substantial rise in smectite illite ratios in the late holocene stepwise aridification of the southern borderlands caused an increase in windblown sediment material and a decrease in nile suspended material the clay mineral records exhibit periodic millennial scale fluctuations in the north aegean sea the changes are centred at a period of 1 3 1 8 ka and can be attributed to short term climate and weathering changes in the northern borderlands the changes in the south aegean sea are centred at periods of 3 2 4 3 1 9 2 4 and 1 3 1 7 ka reflecting short term changes in wind strength and northeast african hydrology 2007 elsevier b v all rights reserved

saharan wind regimes traced by the sr nd isotopic composition of subtropical atlantic sediments last glacial maximum vs today new nd sr isotopic data on the 30 m lithic particles of surface and last glacial maximum sediments recovered along the african margin between the equator and the gibraltar strait are presented in combination with grain size measurements this 30 m size fraction allows us to eliminate any hemipelagic contribution that could occur in the coarser fractions in the eolian fraction both sr and nd isotopic tracers reveal the same major northwestern origin mauritania mali southern algeria and morocco the archaean formations of the western saharan shield could be the source of the very unradiogenic ratios observed here the more southern regions senegal guinea act only as secondary sources a similar pattern is observed for the lgm lithic particles are mostly transported by both trade and saharan air layer sal winds along an approximate ne sw axis this main feature matches the southern plume characterizing the dust transport observed during winter no significant latitudinal shift of the belt winds is observed between the lgm and today at the lgm however dust fluxes were 2 4 times higher than today leading to a more archaean type imprint in the deposits we do not observe any clear relationship between the latitudinal variability of the upwelling systems identified in this region at the lgm and the location of the major wind systems both enhanced aridity on the continent and increased wind speed probably occurred together over western tropical africa during the last glacial period

central zagros fold thrust belt iran new insights from seismic data field observation and sandbox modeling 1 we present five generalized cross sections across the central zagros fold and thrust belt iran these sections show that the fold geometry varies significantly both horizontally and vertically the style is closely related to the changes in the mechanical behavior of the lithostratigraphic horizons and in particular to the presence of intermediate decollements within the sedimentary pile restoration of the sections shows amounts of shortening of the same order from one section to the other however it appears to be unequally distributed suggesting variations in basal decollement shear strength analogue modeling has been performed to systematically investigate the effect of an intermediate decollement level at different depths on the style of folding the models demonstrate that the position of intermediate decollements is an important factor controlling both structural style and fold wavelength models with shallow intermediate decollement show regularly and widely spaced anticlines in these models the fold wavelength depends directly on the thickness of the dominant competent layer and short wavelength superficial structures mask broad anticlines at depth models with deep intermediate decollement are characterized by the rapid propagation of deformation with small rate of shortening along this decollement influencing localization of forthcoming anticlines in the upper levels such propagation favors the development of duplexes and multiwavelength folds on this basis fold kinematics in central zagros is discussed using the variation of structural style along different folds as an indicator of the sequence of deformation detachment folding is the main folding style at least for the initial stages of deformation and thrust faults developed only at later stages some of these faults branched on decollement levels express the progression of folding whereas others are linked to late basement faults cutting through early structures in general the decollement levels are activated sequentially from deeper horizons to shallower ones however in one case gachsaran decollement a shallow decollement is activated during the early stages of folding and then abandoned during the subsequent evolution

diagenetic history and reservoir properties of the cenomanian turonian carbonates in southwestern iran and the persian gulf abstract shallow marine carbonates of the mid cretaceous sarvak formation are important reservoir rocks in southern iran and the persian gulf region these carbonates were deposited on the margin of the arabian plate and rest on the kazhdumi formation which is one of the major hydrocarbon source rocks in the region the top of the sarvak formation coincides with the regional turonian unconformity most of the observed diagenetic features are genetically related to meteoric waters entering the sarvak formation during cenomanian turonian and mid turonian uplift and the subsequent paleoexposure integration of field and petrographic studies and isotope geochemistry reveals the history of a variety of diagenetic processes which include dissolution and development of secondary porosity which enhance reservoir properties of the upper sarvak carbonates various types of calcite cements were identified as the main cause for porosity loss in these carbonates their diagenetic environment is discussed using the geochemical data acquired as part of the present study the 18 o and 13 c values 12 3 to 0 6 and 5 8 3 6 vpdb respectively of the cements indicate precipitation from marine meteoric and or mixed meteoric marine fluids some drusy calcite cements exhibit 18 o and 13 c values 5 1 and 0 8 vpdb respectively and higher 87 sr 86 sr ratios comparing to mid cretaceous carbonates i e 0 70747 which may indicate precipitation from meteoric waters lower 18 o and 13 c values e g 5 1 0 8 vpdb combined with higher 87 sr 86 sr ratios e g 0 70747 of some drusy calcite could confirm their precipitation from meteoric waters lower 18 o values of some blocky calcite cements e g 12 3 vpdb and matrix replacive compression related dolomites i e 7 3 to 3 4 vpdb suggest their precipitation at rising temperatures during burial the range of 13 c values 5 8 3 6 vpdb suggests that the main source of carbon in the calcite cements was primarily marine mixed with isotopically more negative carbon from atmospheric soil derived co 2

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

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

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

new constraints on climate forcing and variability in the circum mediterranean region from magnetic and geochemical observations of sapropels s1 s5 and s6 eastern mediterranean sapropels are organic rich layers whose formation was triggered during boreal summer insolation maxima precession minima sapropel formation is associated with increased precipitation and runoff from europe and north africa although the relative influence of high and low latitude climate mechanisms is not fully resolved likewise it remains uncertain how centennial scale interruptions in conditions that give rise to sapropels may reflect atmospheric circulation changes in low latitudes we present magnetic geochemical and diffuse reflectance spectroscopy data from three sapropels that are representative of glacial s6 and interglacial s1 s5 conditions in the eastern mediterranean sea to assess environmental changes associated with sapropel formation the extent of diagenetic magnetite dissolution and authigenic formation of fine grained greigite in these sapropels and their underlying dissolution intervals are linked to enhanced sulphidic conditions during sapropel formation aeolian hematite and goethite are largely unaffected by this reductive dissolution except within the interglacial sapropel s5 and its underlying dissolution interval which formed under relatively stronger sulphidic conditions nevertheless low hematite contents indicate that the three studied sapropels accumulated under reduced aeolian dust inputs in response to an intensified african monsoon which resulted in expansion of savannah landscapes into ne saharan dust source areas small variations in goethite contents across sapropels indicate additional aeolian entrainment of goethite that formed under previous wet phases in the ne sahara or in subtropical savannahs located further south we link short lived dust abundance peaks within sapropels s1 and s6 to centennial scale periods of enhanced bottom water circulation reported previously for these sapropels although these sapropel interruptions are driven by high latitude cooling events our results indicate that such centennial scale episodes of atmospheric reorganization affected not only the eastern mediterranean northern borderlands but also subtropical north africa overall our results point to a dominant low latitude forcing on sapropel formation via boreal summer insolation maxima and intensification of the african monsoon

global climate instability reflected by eastern mediterranean marine records during the late holocene abstract extremely high sediment accumulation rates in the southeastern se mediterranean off israel make this region ideal for high resolution paleoceanographic reconstructions two cores were examined and foraminiferal oxygen and carbon isotope composition as well as physical and geochemical properties of the sediments were used to reconstruct the climatic and environmental changes of the se mediterranean basin during the late holocene 3 6 ka the 18o values of globigerinoides ruber suggest that the freshwater balance changed several times during this time interval humid phases took place between 3 5 3 0 ka bp and 1 7 1 0 ka bp the later was accompanied by enhanced preservation of terrestrial organic matter within the sediment ors event relatively more arid conditions prevailed in this area between 3 0 and 1 7 ka bp during the last millennia at ca 0 8 and 0 27 ka two climatic events occurred which are probably correlative to both the medieval warm period and the cooling global event known as the little ice age respectively a long term slight increase in planktonic foraminiferal 18o values occurs together with a gradual decrease in the 13c values of both g ruber and the benthic foraminifera uvigerina mediterranea this trend is associated with an increase in sedimentation rates ti al ratio magnetic susceptibility and color index of the sediments we suggest that this trend shown by various independent proxies seems to be related to the aridification process that started ca 7 0 ka in the mid low latitude desert belt and the se mediterranean region and continuous until the present the long term 13c decrease shown by surface and bottom water foraminifera reflects a gradual change in the 13c of the dissolved co2 of the entire se mediterranean water column this follows the global co2 rise in the late holocene as a result of the terrestrial biomass destruction during the aridification process moreover the gradual reduction of the vegetation cover in east africa led to an increased erratic flood related sediment flux via the nile river up to the present this is reflected by the general change in the local sediment composition at 3 6 ka the saharan eolian input reached 65 whereas at about 0 3 ka 70 of the se mediterranean sediment was composed of nile particulate matter

new data on sequence stratigraphy of the sarvak formation in malekshahi city ilam province zagros basin iran abstract two surface sections of the sarvak formation late albian late turonian named tange e bawlek and shahnakhjir were studied these sections are about 24 km apart located in the flanks of the kabirkuh and shahnakhjir anticlines in ilam province in the western part of the zagros fold thrust belt zftb the sarvak formation is 845 m and 412 m thick in these sections respectively the lower contact with the garau formation is erosional with karst features and abundant glauconite at the first section whereas it isn t exposed at the last section field evidences and laboratory examinations on thin sections of collected samples revealed five 3rd order depositional sequences in the sarvak formation of which the four lower sequences were deposited in a carbonate platform whereas the last one was deposited in a foreland basin the lower contact of the first and last sequences are type whereas rest of the boundaries are type ii in compare with the arabian plate lower boundary of the topmost sequence is assumed to coincide with the boundary between ap8 and ap9 sequences 1 and 2 predominantly comprising neritic facies whereas sequences 3 and 4 are composed of pelagic facies although the topmost sequence basically varies in biota content lithology and depositional setting from the rest of the formation overwhelming shale lithofacies in contrast to the other part of the formation along with unconformity in lower contact of this sequence strongly support to consider this part as separate lithostratigraphic unit hence we suggest this part to be considered as a potential new formation after further complementary studies

100 000 years of african monsoon variability recorded in sediments of the nile margin abstract multiproxy analyses were performed on core ms27pt recovered in hemipelagic sediments deposited on the nile margin in order to reconstruct nile river palaeohydrological fluctuations during the last 100 000 years the strontium and neodymium isotope composition of the terrigenous fraction and the major element distribution reveal large and abrupt changes in source oscillating between a dominant aeolian saharan contribution during arid periods and a dominant nile river contribution during pluvial periods iron content shows a strong correlation with strontium and neodymium isotopes this allows the use of a high resolution continuous fe record as a proxy of blue nile sediment input over the last 100 000 years the detailed fe record with approximately 10 years resolution during pluvial periods is consistent with subtropical african records of well dated lake level fluctuations and thus constitutes a first continuous high resolution record of the east african monsoon regime intensity over ethiopia the detailed fe record shows the two main known pluvial periods attributed to strengthening of the african monsoon over ethiopia the nabtian period from 14 to 8 ka cal bp and the saharan period from 98 to 72 ka bp for the first time the last glacial period marine isotope stage mis 2 3 and 4 is documented with a continuous record showing large oscillations between high and low east african palaeo monsoon regimes the end of the nabtian period occurred at 8 ka in core ms27pt i e much earlier than on the east equatorial african region where it ended around 5 5 ka we interpret this as evidence that the southward shift of the rain belt occurred 3000 years earlier over the eastern ethiopian highland and propose that the gradual southward migration of the rain belt was associated with highly variable intensity and longer rainy seasons from 8 to 5 ka during the last glacial period two wet periods are present around 60 50 ka bp and 38 30 ka bp these two humid periods are in phase with the rise of atmospheric ch4 concentrations suggesting that wetland tropical african area was one of the sources of the atmospheric ch4 during the mis 3 during the last glacial maximum and mis 4 high saharan aeolian influxes in phase with records of aeolian dust deposited in east antarctica are documented this study highlights the importance of reconstructions of monsoon rainfall fluctuation at high temporal resolution to better understand the link between low and high latitude climate variability at millennial timescales

late pleistocene sedimentation in the western mediterranean sea implications for productivity changes and climatic conditions in the catchment areas abstract sediment cores from the western mediterranean sea wms have been analyzed for their bulk element composition 18o values of planktic foraminiferal tests and 87sr 86sr and 143nd 144nd ratios of their bulk lithogenic components the investigated time interval comprises the last 215 kyr si al and ti al ratios as well as radiogenic isotope compositions indicate changes in the provenance of the lithogenic components between glacial intervals and interglacial phases comparison with modern data indicates that detrital input from the northwestern and northeastern sahara may have dominated during interglacial phases in contrast during glacial periods the accumulation rate of terrigenous sediment is high and changes in the sediment source areas are evident that may be related to changes in the prevailing atmospheric circulation over the basin and its source areas a productivity reconstruction based on bio mediated barium accumulation rates reveals increased surface productivity during glacial phases intervals time equivalent to sapropel formation in the eastern mediterranean sea ems show no changes in surface productivity compared to the intervening intervals comparison of the productivity patterns between the wms and ems suggests a decoupling during late pleistocene sapropel formation and highlights the importance of more localized factors such as the freshwater drainage basin

neodymium isotopes as tracers in marine sediments and aerosols north atlantic nd and sm concentrations and nd isotopic compositions were measured on the detrital fraction of deep sea surface sediments and on aerosols sampled over the north atlantic and mediterranean sea the data expressed asend 0 and as model ages ranged from 14 5 end 0 4 9 and from 0 01 to 2 21 ga respectively two areas where the sediments contain relatively less radiogenic nd are to the west off north africa and eastward of the canadian shield this distribution is consistent with other tracers in suggesting that a significant fraction of the sediments are derived from aeolian material transported by major wind systems saharan dust transported in the equatorial trade winds belt and north american soil material transported in the latitudes of the westerlies between these aeolian dominated belts along an axis from the azores to gibraltar and the mediterranean lies a zone of more radiogenicend 0 values in sediments and aerosols influenced by the recent volcanism of this region previously reported distributions of nd isotopes in bottom formed iron manganese crusts and coatings are similar to distributions of nd isotope values in detrital sediments and aerosols this suggests that the detrital fraction has undergone partial dissolution and desorption in the water column and or in the pore waters of near surface sediments and that a significant proportion of nd in the authigenic ferromanganese phases is derived from this source and may therefore not represent strictly dissolved seawater nd isotope ratios useful as watermass tracers

bulk composition of northern african dust and its source sediments a compilation abstract this paper presents a review of bulk compositional data of northern african dust and its potential source sediments and includes elemental isotope and mineralogical data northern african dust represents about one half of the total global atmospheric mineral dust burden and its uplift transport and deposition have strong impacts on climate and various terrestrial and marine ecosystems the chemical data set shows that an average northern african dust exhibits comparable si fe and mn contents with respect to the average composition of the upper continental crust is slightly depleted in the alkali metals k and na and enriched in ti and p however the complete data set yields clear evidence that northern african dust and its source sediments are compositionally heterogeneous on a regional scale and that this heterogeneity can be used to differentiate between major potential source areas on the basis of so called source markers an evaluation of these compositional fingerprints shows that the following parameters and especially their combination are effective in the discrimination of the most active source areas in northern africa ratio of ca mg fe wt calcite or carbonate content palygorskite occurrence and abundance illite kaolinite ratio nd 0 value and 87sr 86sr ratio for example the data set corroborates previous ideas which assign carbonate illite and palygorskite rich mineral dusts to north west ern source regions because most of the above listed source markers do not change substantially during transport even far traveled dusts may be assigned to specific potential source areas in northern africa some limitations of the presented data set are also discussed our compilation reveals some substantial gaps in the knowledge of the composition of source sediments and mineral dusts from important potential source areas that should be filled in the future the here compiled data set can be used as a reference frame when incorporating the composition of source sediments e g mineralogy into global or regional dust transport models and can be compared with source analysis by remote sensing or back trajectory analysis however source apportionment studies supported by our data set will not only be useful for actual dust samples but will also be helpful for the understanding of paleo wind directions and hence paleo climatological conditions through the investigation of quaternary eolian sediments deposited in and around northern africa

mediterranean climate and oceanography and the periodic development of anoxic events sapropels mediterranean sapropels are layers with elevated organic carbon concentrations that contrast with surrounding sediments which are organic poor sapropels occur quasi periodically in sedimentary sequences of the last 13 5 million years and exist both in the eastern and western mediterranean sub basins they have been the subject of extensive study based on records from both short conventional and long ocean drilling program sediment cores and from a wide variety of uplifted marine sediment sequences on the basin margins and islands previous syntheses in the 1990s and 2000s have discussed how the formation of sapropels is commonly ascribed to deep sea anoxia enhanced export productivity or a combination of these effects however a wealth of new evidence and insights has emerged during the past 1 2 decades based on traditional and novel proxy data as well as modelling which has revealed intriguing new aspects and nuances to the reconstructed conditions hence it is timely to present a new synthesis of current understanding of the processes behind the formation of sapropels which have over the past decade also become a matter of commercial interest in sub salt hydrocarbon exploration in this review we present a context of modern mediterranean climate and oceanography followed by an integrated assessment of the growing understanding of climatological and ocean circulation changes that were associated with sapropel deposition we find that sapropels predominantly formed during astronomically timed episodes when climatic and oceanographic conditions and ecological responses broadly preconditioned the basin for sapropel deposition there is strong correspondence with times of monsoon intensification fuelling runoff from north africa into the mediterranean sea while preconditioning due to sea level rise and regional precipitation and runoff may have contributed as well within these broad episodes of surface buoyancy gain and resultant decline in deep water ventilation specific deposition under dysoxic anoxic or even euxinic conditions occurred within a clearly dynamic system that was characterised by complex spatial and depth dependent patterns gradients with distinct temporal variability on at least decadal to centennial millennial timescales in the final section we evaluate the implications of different modes of deep water removal from silled basins to investigate why sapropels are more frequently and often more intensely developed in the eastern mediterranean than in the western mediterranean

origin of basal dolomitic claystone in the marsili basin tyrrhenian sea abstract red brown dolomitic claystones overlay the marsili basin basaltic basement at odp site 650 sequential leaching experiments reveal that most of the elements considered to have a hydrothermal or hydrogenous origin in a marine environment such as fe cu zn pb co ni are present mainly in the aluminosilicate fraction of the dolomitic claystones their vertical distribution content and partitioning chemistry of trace elements and ree patterns suggest enhanced terrigenous input during dolomite formation but no significant hydrothermal influence from the underlying basaltic basement positive correlations in the c and o isotopes in the dolomites reflect complex conditions during the dolomitization the stable isotopes can be controlled in part by temperature variations during the dolomitization majority of the samples however form a trend that is steeper than expected for only temperature control on the c and o isotopes the latter indicates possible isotopic heterogeneity in the proto carbonate that can be related to arid climatic conditions during the formation of the basal dolomitic claystones in addition the dolostones stable isotopic characteristics can be influenced by diagenetic release of heavier 18o from clay dehydration and or alteration of siliciclastic material strontium and pb isotopic data reveal that the non carbonate fraction the dye of the dolomitic claystones is controlled by saharan dust 75 80 and by material with isotopic characteristics similar to the aeolian arc volcanoes 20 25 the non carbonate fraction of the calcareous ooze overlying the dolomitic claystones has a sr and pb isotopic composition identical to that of the dolomitic claystones indicating that no change in the input sources to the sedimentary basin occurred during and after the dolomitization event combination of climato tectonic factors most probably resulted in suitable conditions for dolomitization in the marsili and the nearby vavilov basins the basal dolomitic claystone sequence was formed at the initiation of the opening of the marsili basin 2 ma which coincided with the consecutive glacial stage the glaciation caused arid climate and enhanced evaporation that possibly contributed to the stable isotope variations in the proto carbonate the conductive cooling of the young lithosphere produced high heat flow in the region causing low temperature passive convection of pore waters in the basal calcareous sediment we suggest that this pumping process was the major dolomitization mechanism since it is capable of driving large volumes of seawater the source of mg2 through the sediment the red brown hue of the dolomitic claystones is terrigenous contribution of the glacially induced high eolian influx and was not hydrothermally derived from the underlying basaltic basement the detailed geochemical investigation of the basal dolomitic sequence indicates that the dolomitization was most probably related to complex tectono climatic conditions set by the initial opening stages of the marsili basin and glaciation

tidally driven groundwater flow and solute exchange in a marsh numerical simulations 1 tidal fluctuations drive groundwater flow in salt marsh sediments this flow could cause significant chemical exchange across the sediment water interface and could affect marsh ecology numerical models of a generalized tidal creek and marsh were constructed to calculate flow patterns and solute exchange between the marsh and creek the governing equation for saturated unsaturated flow was modified to account for tide related changes in total stress groundwater flow occurred primarily in the creek bank even when the marsh platform was inundated at high tide for marsh sediments with a hydraulic conductivity of 10 4 m s 1 groundwater ages in simulations lasting 60 days were on the order of days near the creek bank and increased to 50 60 days with distance into the marsh the volume of water that discharged between high and low tide was 0 22 0 31 m3 per meter length of channel which for a creek drainage density of 0 012 m 1 corresponds to 10 14 l m 2 d 1 sediment permeability and capillarity were important controls on flow and groundwater age in the marsh sediment compressibility affected groundwater age for compressible sediments representative of mud but not for sediments with lower compressibilities representative of sand simulations were relatively insensitive to dispersivity a comparison of simulation results with other estimates of groundwater exchange from the north inlet south carolina suggest that tides could drive observed exchange there only if the pleistocene sands underlying muddy marsh sediments outcrop within the tidal range

on the late pleistocene holocene sapropel record of climatic and oceanographic variability in the eastern mediterranean sapropels and intercalated marls in a piston core from the eastern mediterranean are chemically and mineralogical distinct kaolinite smectite and total s contents fe a1 ba a1 co a1 mo a1 and v a1 are higher whereas quartz mg calcite illite contents si a1 ti a1 k a1 rb a1 and zr a1 are lower in the sapropels missing and ghost sapropels are identified by mineralogical and chemical properties that are not prone to diagenesis primary production was higher ba a1 and bottom water and or interstitial oxygenation was lower co a1 mo a1 ni a1 and v a1 during sapropel formation wind speeds quartz clay si a1 and zr a1 and bottom water salinities mg calcite calcite were higher during periods of marl formation sapropels represent a fundamentally different sedimentary facies whose formation is linked to changes in the hydrological balance in the basin driven by precessionally modulated changes in monsoon strength and subtropical precipitation changes which altered circulation production and sediment source areas

sequence stratigraphy of cenomanian turonian carbonate platform margins sarvak formation in the high zagros sw iran an outcrop reference model for the arabian plate

structural framework of the zagros fold thrust belt iran abstract data gleaned from the literature on the zagros have been compiled and used in conjunction with new interpretations to provide a better picture of the structures sedimentation history and deformation of this hydrocarbon rich mountain belt the belt parallel mountain front the n s trending kazerun izeh and e w trending bala rud fault zones are defined as the master structural elements of the belt these fault zones divide the zagros basin into zones with different stratigraphic successions and different rheological profiles this resulted in different structural styles developing along the belt during the subsequent collision the kazerun and izeh fault zones acted as the depositional system transition zone between the lurestan and fars regions in jurassic cretaceous time and partly controlled the distribution of the kazhdumi formation one of the major source rocks by the end of the cretaceous the nw se trending mountain front fault divided the present folded belt of the zagros into a major foreland basin to the southwest and a piggyback basin to the northeast activity along other major transfer fault zones including the izeh kazerun and bala rud fault zones occurred at this time and controlled the sedimentation and subsidence of the dezful embayment the main target region for hydrocarbon exploration these fault zones controlled the thickness of the asmari formation one of the main reservoirs and also the considerable thickness and facies changes of the gachsaran formation the major seal to the asmari formation the present morphology of the mountain belt is interpreted as being mainly related to the pinning of the mountain front fault to the northwest of the dezful embayment and to the north of the strait of hormuz

variation of structural style and basin evolution in the central zagros izeh zone and dezful embayment iran abstract structural style and its relationship to sedimentary facies and the evolution of sedimentary depocenters since late cretaceous times have been studied on the basis of one regional balanced transect and several updated isopach maps in the izeh zone and the dezful embayment central zagros this study relies on fieldwork data existing geological maps seismic data and well information a new structural classification for part of the zagros sedimentary cover is presented to highlight the different mechanical behavior of the formations in the stratigraphic column it shows the existence of several local decollement levels activated during folding these decollement levels separate lithotectonic units which accommodate shortening in different ways the lower paleozoic is the basal decollement level throughout the studied area triassic evaporites albian shales eocene marls and miocene evaporites can act as intermediate decollement levels and present variable facies in the central zagros lateral facies and thickness variations the sedimentary overburden and the close relationship with inherited fault patterns influenced the wavelength amplitude and style of folding in the study area furthermore surface structures do not necessarily coincide with deeper objectives where these disharmonic levels are involved in folding the evolution of sedimentary depocenters from the late cretaceous obduction episode until early miocene collision is described based on updated isopach maps and tectonic subsidence curves this analysis shows continuous compression and movements along n s and nw se trending faults in the zagros basement which predate the neogene zagros folding and influence sedimentation history it also indicates a southwestward migration of the depocenters through time in addition to the basement involvement below some folds during the zagros orogeny

late holocene dust accumulation within the ancient town of marea coastal zone of the south mediterranean sea n egypt abstract the ruins of the marea ancient town are located on the southern shore of maryut lake ancient mareotis 45 km to the southwest of alexandria egypt marea was a very important trade religious and agricultural centre in the 5th 7th century a d the area occupied by a town in the past has diversified relief local hills are built of sandstones constituted by calcified dunes the hills are separated by flat depressions of irregular shape the uppermost layer in the depressions covering loam and sand sediments is made up of structureless aeolian dust of 0 6 1 2 m thickness the following analyses of the sediments were conducted granulometric composition the mineralogical composition of samples the loss on ignition the total organic carbon toc organic matter om and calcium carbonate caco3 clay minerals and geochemistry results of osl dating indicate that the filling of the depressions with silt deposits started probably about 2450 years ago and that it is correlated with dust deposition the rate of the dust accumulation was about 0 49 mm year however diversified humus content in the deposits suggests that it was not a permanent process the accumulation took place during intensive dust storms the sediments in the depressions are fine silt and clay with uni and bi modal particle size distribution likely caused by both the local and the regional origin of the material most dust accumulated within the ancient town of marea originated from the border between sahel and sahara local and even regional sources of material were of lower importance geochemical ratios mg ca fe mn and na k distinguished in the deposits of the depressions show that the beginning of the dust accumulation took place during environmental conditions more humid than the contemporary ones that indicates a slight increase in the humidity of climate dated to ca 10th 12th century a d followed by its significant drying initiated ca 15th 16th century a d in addition results of analysis of trace elements suggest that already in the 5th century bc the town of marea or its closest vicinity may have been the site of development of industrial activity much earlier than the age of the oldest artefacts found within the town

nd isotopic compositions of eastern mediterranean sediments tracers of the nile influence during sapropel s1 formation abstract nd isotopic composition of eastern mediterranean sediments are used to investigate the influence of nile flux variations during the formation of the youngest sapropel s1 four box cores located on an east west transect around 35 n at increasing distance from the nile source were studied nd 0 signatures were measured in the lithogenic alumino silicate residue fraction and the authigenic biogenic carbonates organic matter and fe mn oxyhydroxides fraction of the sediment after 1 m hcl leaching the nd 0 profiles of the residual fraction show more radiogenic values in the sapropel layers than in the adjacent sediments these profiles follow the gaussian shaped ba al profile shape which defines s1 the nd 0 variations can be related to changes in the proportions of two continental sources of particulate material nile particles and saharan aerosols a simple mixing model reveals that the contribution of nile particulates to the sediments increases relative to saharan aerosols during sapropel formation indicating a higher nile discharge and a decrease in eolian input at that time for the cores located closest to the nile fan the nd 0 signatures of the leachable fraction are always higher in the sapropel layer 5 to 4 than in the adjacent sediments 6 the sapropel layer nd 0 values increase with decreasing distance to the nile towards values close to the nile particulates all the results obtained on the leachable fraction point towards a massive input of nile freshwater during s1 deposition

submarine groundwater discharge and solute transport under a transgressive barrier island abstract many recent investigations of groundwater dynamics in beaches employed groundwater models that assumed isotropic numerically convenient hydrogeological conditions real beaches exhibit local variability with respect to stratigraphy sediment grain size and associated topographic profile so that groundwater flow may diverge significantly from idealized models we used a combination of hydrogeologic field methods and a variable density saturated unsaturated transient groundwater flow model to investigate sgd and solute transport under cabretta beach a small transgressive barrier island seaward of sapelo island georgia we found that the inclusion of real beach heterogeneity drove important deviations from predictions based on theoretical beaches cabretta beach sustained a stronger upper saline plume than predicted due to the presence of a buried silty mud layer beneath the surface infiltration of seawater was greater for neap tides than for spring tides due to variations in beach slope the strength of the upper saline plume was greatest during spring tides contrary to recent model predictions the position and width of the upper saline plume was highly dynamic through the lunar cycle our results suggest that field measurements of salinity gradients may be useful for estimating rates of tidally and density driven recirculation through the beach finally our results indicate that several important biogeochemical cycles recently studied at cabretta beach were heavily influenced by groundwater flow and associated solute transport

planktonic foraminiferal zonation in the cretaceous yezo group central hokkaido japan abstract the mudstone of the yezo group exposed in central hokkaido yields abundant microfossils of calcareous nannofossils foraminifers radiolarians and dinoflagellates benthic foraminifers consisting of both agglutinated and calcareous species occur abundantly and consistently throughout the sequence while specimens of planktonic foraminifers are generally fewer than benthics in all samples we recognized the following 13 planktonic foraminiferal zones assigned to the late aptian to early campanian in the oyubari and haboro kotanbetsu areas 1 globigerinelloides spp 2 ticinella primula 3 biticinella breggiensis 4 rotalipora subicinensis rotalipora ticinensis 5 rotalipora appenninica 6 rotalipora globotruncanoides 7 rotalipora cushmani 8 whiteinella archaeocretacea 9 helvetoglobotruncana helvetica 10 marginotruncana pseudolinneiana 11 marginotruncana sinuosa 12 contusotruncana fornicata 13 globotruncana arca the globigerinelloides spp to h helvetica zones late aptian to early turonian can be correlated with standard zones in the tethyan regions whereas the assemblages from the m pseudolinneiana to g arca zones lack tropical zonal markers of dicarinella concavata d asymetrica and globotruncanita elevata in many studied sections the scarcity or lack of tropical zonal species during the late turonian to early campanian suggests that the oyubari and haboro kotanbetsu regions in hokkaido were located in the transitional to boreal biogeographical provinces

anti atlas moroccan chain as the source of lithogenic derived micronutrient fluxes to the deep northeast atlantic ocean identifying the source of atmospheric dust is crucial to better understand the global marine biogeochemical cycle as phytoplankton growth relies on dissolved micronutrient elements available in the open ocean mineralogical geochemical and sr isotope analyses of a one year time series april 2003 april 2004 of deep ocean particle flux at the madeira abyssal plain in the subtropical northeast atlantic are presented the lithogenic fraction has a high occurrence of palygorskite and smectite and an absence of kaolinite together with sr isotopic compositions similar to the northeast atlantic aerosols this indicates the anti atlas moroccan chain of paleozoic age as the source region the lithogenic fraction supplies 4 times more fe during a dust event than during the spring summer aeolian input a continuous input of only 1 of the lithogenic iron made available over a year period could lead to an increase in primary productivity of 40 relative to today s value

integral view of holocene precipitation and vegetation changes in the nile catchment area as inferred from its delta sediments we compare geochemical and pollen data of several well dated high resolution cores to provide an integral holocene overview of nile outflow sedimentation and vegetation in and around the nile delta we show that the focus point of the nile plume varied considerably as indicated by planktonic foraminifer globigerinoides ruber oxygen isotopes tracing nile discharge differences in an east west delta transect at 13 11 5 cal kyr bp nile discharge was low and runoff was predominantly directed to the western part of the delta sediment arriving in the delta during that period was dominated by ethiopian highland similar to blue nile material shown by high ti al values of the bulk sediment indicating dry conditions in the source area of the blue nile nile discharge increased from similar to 11 5 cal kyr bp and was high across the whole delta from similar to 10 6 5 cal kyr bp during this time the ti al values decreased within most nile delta sediments suggesting that the relative contribution of blue nile sediment decreased this was likely due to an increased vegetation cover causing diminished erosion in the ethiopian highlands nile discharge gradually decreased from similar to 6 5 cal kyr bp to present this decrease was more abrupt in the western province of the delta and became more gradual towards the east as the shrinking nile runoff was directed there the gradual decrease in precipitation in the nile catchment area seems not to be matched by a gradual response in vegetation growing around the river plain in the lower nile catchment our findings suggest a nonlinear response of northeast african vegetation to precipitation from the middle to late holocene c 2015 elsevier ltd all rights reserved

comparison of four numerical models for simulating seepage from salt marsh sediments a boundary integral equation method biem model and three differently formulated finite element method fem models were implemented to explore the spatial and temporal patterns in marsh pore water seepage that each generated the biem model is based on the laplace equation coupled to a dynamic free surface condition that assumes that as the water table changes the aquifer instantaneously loses or gains an amount of water equal to the change in head times the specific yield the fem models all implement a simplified richards equation that allows gradual desaturation or resaturation and thus flow in both the saturated and unsaturated zones of the aquifer two of the fem models are based on the governing equation for the usgs model sutra and thus take into account fluid and aquifer compressibility one of these was modified to take into account the effect of tidal loading on the total stress which is assumed to be constant in the derivation of the original version of sutra the third fem model assumes that neither the fluid or aquifer matrix is compressible so that changes in storage are due solely to changes in saturation the unmodified sutra model generated instantaneous boundary fluxes that were up to two orders of magnitude greater and spatially more uniform than those of the other models the fem model without compressibility generated spatial and temporal patterns of the boundary fluxes very similar to those produced by the biem model the sutra model with the tidal stress modification gave fluxes similar in magnitude to the biem and no compressibility models but with distinctly different distributions in space and time these results indicate that accurate simulation of seepage from marsh soils is highly sensitive to aquifer compressibility and to proper formulation of the effect of tidal loading on the total stress in the aquifer they also suggest that accurate simulation may require total stress correction not only for tidal loading but for changes in the water table as well finally to aid the development of methods for the measurement of compressibility we present a schematic pore scale model to illustrate the factors that may govern the compressibility of marsh soils

mixed convection and density dependent seawater circulation in coastal aquifers 1 density dependent circulation of seawater in coastal aquifers results in submarine groundwater discharge sgd across the seabed that is a mixture of terrestrial groundwater and former marine water in this study the controls of the relative amount of seawater to freshwater in sgd were investigated numerically using the feflow and sutra codes it was found that the key controls could be expressed in the form of a single nondimensional recirculation number that incorporates the combined effects of free convection forced convection and hydrodynamic dispersion on convective overturn within the coastal salt wedge anisotropy effects were incorporated into the recirculation number with limited success based on the principle of equivalent isotropic hydraulic conductivity the type of boundary condition employed along the seabed was shown to be important convective overturn was substantially increased if backward dispersion of salt into the aquifer from along the outflowing portion of the seabed boundary was prevented overall the results demonstrated a strong dependence of convective overturn on the aquifer dispersivities suggesting that results from numerical simulations are problematic to apply to real aquifer systems that typically exhibit uncertain scale dependent dispersion properties

unraveling north african riverine and eolian contributions to central mediterranean sediments during holocene sapropel s1 formation hydroclimate variability has exerted a fundamental control on the alternating deposition of organic lean marl and organic rich sapropel sediments in the eastern mediterranean sea ems however the exact mechanisms regarding the freshwater sources and related changes are still debated here sr and nd isotopes and high resolution elemental data are used to constrain different riverine and eolian supplies to the central mediterranean over the past 9 8 ka the detrital sediments in core cp10bc taken at the margin of the libyan shelf in the southwestern ionian sea can be described by a three endmember mixing system based on sr and nd isotopic compositions the same systematics can also be deduced from ti and k compositional variability the endmembers comprise saharan dust aegean nile and libyan soil representing the eolian supply from north africa the riverine inputs from the aegean nile areas as well as the riverine and shelf derived fluxes from the libyan tunisian margin respectively for the sapropel s1 period in particular we find important detrital supplies from fossil river wadi systems along the libyan tunisian margin activated by intensified african monsoon precipitation combining the temporal profiles with the consistent variability observed in the 87sr 86sr 1000 sr diagram such libyan contribution has been most prominent during the uppermost period of sapropel s1 in core cp10bc this observation is in agreement with hydroclimate reconstructions of northwestern libya comparison of the sr nd isotope data between core cp10bc and four cores taken along a west east transect throughout the ems shows that this detrital supply originated mainly from western libya tunisia and was transported as far eastward as 25 e while being diluted by an increasing nile contribution

origins of peri saharan dust deposits traced by their nd and sr isotopic composition abstract isotopic ratios of sr and nd can be used as very precise tracers in conjunction with mineralogical geochemical tracers and climatic models to identify the origins of dust deposit and to quantify their fluxes both today and throughout the last climati cycles this technique is useful for constraining aeolian transport and atmospheric circulation trajectories from desert sources and over the oceans the present work concerns dust deposits surrounding the saharan desert on the canary islands the african fraction of the dust deposits displays isotopic values which are typical of moroccan origin on the other hand tunisian loesses have been derived from the northern part of the sahara in this case tracers are sensitive enough to distinguish between center saharan shield origin and peri saharan secondary sources allowing us to distinguish between transport due to the trade winds vs the harmattan or mediterranean wind regimes

storm driven groundwater flow in a salt marsh 1 storms can cause significant groundwater flow in coastal settings but prior studies of the effects of storms on groundwater flow and transport have largely focused on very large storms and used salinity as a tracer we have little information about the effects of smaller storms on coastal flow and how storm induced variability affects key tidal wetlands like salt marshes which may remain saline throughout a storm here we show that even the distant passage of a moderate storm can strongly increase groundwater flow and transport in salt marsh ecosystems and adjacent barrier islands groundwater monitoring and radium isotope tracer analyses revealed significant influx of saline creek water into the confined aquifer below the marsh platform driven by storm surge this pulse of fluids reached depths exceeding 5 m and surge enhanced tides propagated through the aquifer to affect flow in the upland 100 m from the creek bank groundwater discharge from the marsh varied significantly prior to the storm doubling during inundating tides compared to a period of noninundating neap tides storm surge then caused groundwater discharge to decline 50 compared to similar inundating tides ra and nutrient poor creek water that entered the confined aquifer below the marsh was quickly enriched in nutrients and carbon even on 12 h tidal cycles so that nutrient discharge was likely proportional to groundwater discharge storm related flow could also drive significant contaminant discharge from developed coastlines the enhanced transport and variability observed here likely affected hundreds of kilometers of the coastline impacted by the storm

deep oxygen penetration drives nitrification in intertidal beach sands we discovered a hotspot of elevated nitrate concentration median 431 m in shallow beach pore water that extended across the entire length of two barrier islands in the southeastern united states of america we investigated this feature by surveying groundwater geochemistry measuring fluctuations in in situ dissolved oxygen do concentrations modeling groundwater flow and quantifying nitrification rates nitrification of groundwater ammonium was the only possible nitrate source with a measured potential rate of 0 84 mol m 2 h 1 however the observed nitrate concentrations were far in excess of the predicted maximum achievable by aerobic nitrification assuming a 2 1 ratio of o n and around 200 m do in air saturated seawater groundwater do concentrations within the hotspot 65 cm depth were consistently 20 50 m the nitrate hotspot was located at the top of the water table beneath dry undersaturated sand that allowed the penetration of air and the dissolution of excess oxygen into the pore fluids the total dissolved nitrogen concentration of the hotspot was higher than anywhere else on the island indicating nitrogen accumulation within the hotspot most likely via ammonium adsorption vertical dispersion was the dominant pathway for nitrate loss from the hotspot this nitrate was consumed in underlying anoxic sand coupling microbial pathways of nitrogen oxidation and reduction and removing bioavailable nitrogen from the beach ecosystem

tectonics versus eustatic control on supersequences of the zagros mountains of iran abstract at least 12 km of strata ranging in age from the latest precambrian to the recent are exposed in the zagros mountains of iran this sedimentary cover is characterized by distinct stratal packages separated by major unconformities forming twelve supersequences they are informally named as 1 late precambrian cambrian hakhamanesh supersequence 2 ordovician kourosh supersequence 3 silurian camboojiyeh supersequence 4 devonian darioush supersequence 5 mississippian pennsylvanian khashayar supersequence 6 permian triassic ashk supersequence 7 jurassic farhad supersequence 8 early cretaceous mehrdad supersequence 9 late cretaceous ardavan supersequence 10 paleocene oligocene sassan supersequence 11 oligocene miocene ardeshir supersequence and 12 miocene pleistocene shapour supersequence these supersequences and their correlatives in neighboring areas have been used to infer tectonic events the dominant interpretation has been that local or regional epeirogenic movements were responsible for the formation of these supersequences unconformities are considered as indications that epeirogenic movements associated with tectonic events affected the area the present investigation provides an alternative to the established view of the phanerozoic supersequences of the zagros mountains a good correlation exists between the lithofacies of supersequences in the zagros mountains and the second order eustatic sea level changes deposition of deep water marine shales occurred during periods of eustatic sea level rise platform wide unconformities coincided with eustatic sea level lows in fact supersequences of the zagros mountains are nearly identical to those described from the north american craton and the russian platform suggesting that these stratal packages are global these observations suggest that supersequences of the zagros mountains formed by second order eustatic sea level changes and not by local or regional epeirogenic movements although tectonic events did not produce supersequences of the zagros mountains they influenced regional lithofacies patterns through the formation of intrashelf depressions such as the hormoz salt basin during the precambrian and the dezful embayment and the lorestan basin during the mesozoic tectonic events also affected sedimentation during the tertiary collision of arabia and the central iran microplate through uplift erosion and the formation of the zagros foreland basin the results of this investigation necessitate a re evaluation of the role and the significance of pre tertiary tectonic events commonly used to interpret the geological evolution of the zagros mountains

modeling the flexural evolution of the amiran and mesopotamian foreland basins of nw zagros iran iraq the evolution of the amiran and mesopotamian flexural basins of the zagros belt is approached by coupled 2 d forward modeling of orogenic wedge formation lithospheric flexural isostasy and stream power erosion transport sedimentation thrust geometries and sequence of emplacement derived from geometric and kinematic models presented here are the inputs to our evolutionary model constrained by basin geometry sediment volume and topography modeling results confirm that the zagros flexural basins evolution is consistent with two stages of deformation 1 the obduction stage involving the kermanshah accretionary complex and a basement unit and 2 the collision stage emplacing the gaveh rud and sanandaj sirjan domains in the hinterland and forming a basement duplex in the outer part results provide quantitative insights into processes involved in mountain and basin building the lithospheric equivalent elastic thickness te changed from 20 km during the amiran stage 90 50 ma to 55 km during the mesopotamian subsidence stage last 20 myr the amiran basin results from flexure of the arabian plate below the load of the kermanshah cover and basement thrust sheets during this stage material eroded in the inner parts was enough to fill the flexural trough the mesopotamian basin formed in front of the outermost basement units flexing the arabian plate during this latter stage material eroded from the orogenic wedge was not enough to fill the mesopotamian basin an additional longitudinal sediment supply of up to 200 m myr is required to fill the flexural basin

an improved method for extracting marine sediment fractions and its application to sr and nd isotopic analysis the radiogenic isotopic composition of both detrital and fe mn fractions in marine sediments can be used in paleoceanography to infer changes of bottom water circulation we have examined various chemical techniques for the analysis of sr and nd isotope ratios in these fractions and present a robust method that can be used to separate both the fe mn oxides and the detrital fraction from a marine sediment sample for isotopic analysis our sequential leaching procedure involves the use of 10 acetic acid followed by 1 m hydroxylamine hydrochloride in 25 acetic acid to remove the carbonate component and the fe mn oxide fraction respectively the applicability of our chemical procedure is illustrated with examples from a marine sediment core raised from the northern cape basin southeast atlantic ocean

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

composition of clays along the continental shelf off israel contribution of the nile versus local sources the eastern mediterranean sedimentary regime is dominated by sediment transport from the nile river and its delta but recent studies have also suggested a certain contribution of clay fraction from streams to the continental shelf and slope off israel in the present study we focused on clay fraction deposition along the inner 40 1000 m water depth shelf of israel in order to substantiate and quantify its different sources for this purpose detailed xrd mineralogical determinations as well as chemical compositions of the clay 2 m fraction of marine and continental sediments were used the clay mineral composition of israeli stream sediments is variable with no distinct spatial or temporal trend but within a limited assemblage this clay assemblage is made up of illite smectite is phases 70 90 kaolinite 5 25 and illite 10 and is similar to that of the nile however it is clearly distinguished by the type of the is phases which are derived mainly from mesozoic outcrops and recent sediments soils and are less expandable than those of the nile which are derived mainly from weathered basalt the nile derived component is depleted in the marine clay fraction along the israel coast evidenced by a decrease of is expandability and the fe2o3 al2o3 ratio and an increase in the k2o al2o3 mgo al2o3 and cao al2o3 ratios the depletion is well pronounced north of tel aviv where the largest coastal plain stream flows to the sea a northward increase of carbonates in the clay fraction and particularly of the bioskeletal component is indicated by the ratios of mgo and sr to cao the contribution of the local streams to the shallow shelf marine clay fraction is estimated to be about 50 a minor contribution of desert dust is identified by the relative increase in kaolinite in the marine sediments south of tel aviv

geochemical and micropaleontological characterisation of a mediterranean sapropel s5 a case study from core ban89gc09 south of crete several geochemical and micropaleontological proxies were studied in a well developed sapropel s5 from a core collected south of crete to investigate the causes and the mechanisms of its deposition to reconstruct the paleoenvironmental and paleoceanographical conditions at time of its formation and to detect the roles played by productivity and anoxia the geochemical proxies are also used to unravel the sediment provenance and therefore to help tracing water circulation patterns and freshwater sources the multiproxy approach reveals that the sapropel layer has high internal variability and five different depositional phases can be identified four within the visible sapropel layer an increase in temperature and the development of a deep chlorophyll maximum characterise the onset of the sapropel phase 1 with enhanced productivity being favoured by local riverine input not clearly ascribable to nile river freshwater discharge and by the shoaling of the pycnocline nutricline surface water stratification and productivity develop together with strong seafloor dysoxia anoxia phase 2 is characterised by lower stratification slightly lower temperature and or higher seasonal contrast and still high productivity phase 3 records high productivity high temperature and high stratification probably more sustained by the nile input a sudden partial re oxygenation takes place at the end of this phase changing the main features of the sapropel in the fourth phase productivity starts to decrease water stratification seems to be partially broken down and sediment oxygenation increases a transitional phase phase 5 occurs between the end of the visible sapropel and the normal pelagic post sapropel sedimentation where productivity is still high and oxygenation improves compared to the visible sapropel layer the massive occurrence of polysphaeridium zoharyi cyst of a red tide forming dinoflagellate also characterises this phase the geochemical proxies indicate that pre sapropel and post sapropel sediments are quite different from each other and the provenance shifts from a more mixed to a more markedly southern origin of sediments

variations in eastern mediterranean hydrology during the last climatic cycle as inferred from neodymium isotopes in foraminifera abstract the nd isotopic compositions end of mixed planktonic foraminifera have been analyzed in two sediment cores collected in the nile deep sea fan in order to reconstruct past end of the eastern mediterranean deep water emdw and to assess the relative contributions of nile discharge and modified atlantic water maw inflow to the eastern mediterranean sea hydrology as well as their potential control on anoxic events over the last climatic cycle the two foraminiferal end records are similar and display an increase in end values during the african humid periods superimposed on this precession forced variability insolation received by the earth at low latitudes the record of variations in foraminiferal end indicates a 2 unit decrease in end during the interglacial marine isotope stages mis 5 and 1 compared to glacial mis6 4 3 and 2 the end results suggest that the long term glacial to interglacial changes in nd isotopic composition of emdw were not entirely induced by variations in nile river discharge and saharan dust inputs decreases in end during mis5 and mis1 interglacials indicate an increase in the contribution of unradiogenic maw to the eastern mediterranean sea related to high sea level stands and greater seawater exchange between the north atlantic and mediterranean basins in addition radiogenic seawater end values observed during african humid periods and sapropel events are associated with an intensification of nile discharge and an increase in residence time of deep water masses in the eastern mediterranean sea which induces an increase in the interaction between deep water masses and radiogenic sediments along the margin of the eastern mediterranean sea results confirm that an intensification of the hydrological exchanges between the western and eastern mediterranean basins during high sea level stand and the subsequent higher proportion of atlantic water in the levantine basin may have preconditioned the eastern mediterranean sea to sapropel depositions during the last climatic cycle

erratum to sources of sediment to the ionian sea and western levantine basin of the eastern mediterranean during s 1 sapropel times marine geology 160 1999 45 61

response of the nile and its catchment to millennial scale climatic change since the lgm from sr isotopes and major elements of east mediterranean sediments abstract changes in 87 sr 86 sr and major element geochemistry from two sediment cores 9509 and 9501 in the eastern mediterranean em were used to resolve changes in sediment provenance and hence determine climate changes in the nile catchment and eastern sahara desert over the past 25 ka the sediment was described by a three end member system comprising blue nile bn 87 sr 86 sr 0 7506 sr 210 ppm white nile wn 87 sr 86 sr 0 7094 sr 72 5 ppm and saharan dust sd 87 sr 86 sr 0 7183 sr 99 ppm the sedimentary record of these cores represents the suspended load carried down the nile river and discharged into the s e levantine basin and thus records palaeoclimatically controlled changes in erosion and transport in the catchment during arid periods 0 5 ka bp and prior to 11 ka bp fluxes of bn sediment at 9509 6 g cm 2 yr 10 12 g cm 2 yr respectively were greater than during the peak of the african humid period ahp from 5 to 11 ka bp 2 yr this latter period witnessed the deposition of the youngest organic rich sediment termed sapropel s 1 in the em basin by contrast the flux of wn increased during the ahp from 5 g cm 2 yr at 13 ka bp to 15 g cm 2 yr in the ethiopian highlands bn catchment increases in the amount and duration of the monsoon during the ahp caused more vegetation to grow resulting in less soil erosion in the wn catchment increased rainfall caused more catchment erosion and higher sediment flux through the sudd marshes the sedimentation rate in core 9509 increased during the ahp because of the greater importance of the wn sediment flux relative to the bn sediment flux saharan dust flux also decreased during the ahp reaching a minimum at 6 ka bp core 9509 due to greening of the sahara desert at the onset of s 1 the changes in nile flow as determined by 87 sr 86 sr and climatic changes in the em basin determined by 18 o of planktonic foraminifera were simultaneous confirming that such isotopic tracers cannot be used directly to determine the cause of the circulation changes in the em at this time the increase in the proportion of bn sediment at 9509 with a somewhat higher grain size during the h 1 period 15 17 ka bp was caused by erosion and redistribution of sediment from the nile delta and or the israeli coast as sea level rose

what time scales are important for monitoring tidally influenced submarine groundwater discharge insights from a salt marsh submarine groundwater discharge sgd varies significantly across time scales ranging from hours to years but studies that allow quantitative comparisons between different time scales are few most of these studies have focused on beach settings where the combined variations in fresh and saline sgd can be difficult to interpret we calculated variations in saline sgd based on a 1 year record of hydraulic head in a salt marsh where we could isolate variations in saline tidally driven sgd observed sgd varied by an order of magnitude over the course of the year groundwater discharge was proportional to tidal amplitude and varied by at least a factor of 2 between spring and neap tides monthly average sgd was inversely proportional to average sea level it increased by nearly a factor of 2 as sea level declined by 50 cm from late summer to late winter this variation was far larger than that predicted by analytic models owing to the flat topography and inundation of the marsh platform the effect of short term days variations in sea level associated with wind events and storms was small in comparison sgd is probably proportional to tidal amplitude in nearly all coastal settings including beaches seasonal variations in sea level may not affect the volume of sgd as significantly in coastal settings where the slope of the intertidal zone is relatively constant but such variations have the potential to strongly affect the composition of sgd

bacterial production of methane and its influence on ground water chemistry in east central texas aquifers geochemical and isotopic data for methane and ground water indicate that gaseous hydrocarbons in eocene aquifers in east central texas form by bacterial processes the 13c values of methane from five wells in the clay rich yegua and cook mountain formations range from 71 to 62 methane from ten wells in the cleaner sands of the sparta and queen city formations have 13c values between 57 and 53 the carbon isotopic difference between methanes from the yegua and sparta aquifers is comparable to the isotopic difference in sedimentary organic matter from outcrops of the units suggesting substrate control on the 13c of bacterial methane hydrogen isotopic compositions of methane from the aquifers are similar averaging 181 this high value suggests methane production predominantly by co2 reduction the 13c of dissolved inorganic carbon dic in high bicarbonate waters increases from about 20 to 0 with increasing dic mass balance calculations indicate that the dic added to the ground water has 13c values as high as 10 this 13c enriched carbon is predominantly derived from co2 production by fermentation and anaerobic oxidation reactions combined with co2 consumption by co2 reduction this process is responsible for high bicarbonate contents in these and probably other gulf coast ground waters

north african paleodrainage discharges to the central mediterranean during the last 18 000 years a multiproxy characterization using elemental geochemistry clay mineralogy grain size end member modeling and planktonic foraminiferal 18o we characterize the provenance of central mediterranean sediments over the past 18 ka the provenance is dust dominated before and after the african humid period ahp by contrast during the ahp 11 5 ka largely concurrent with organic rich sapropel s1 formation it is predominantly riverine from north african sources such fluvial supply is suggested to come from paleodrainage networks that were reactivated by intensified monsoon precipitation during the ahp the supply is characterized by high mg al and smectite contents and has been accompanied by considerable freshwater influx as indicated by the enhanced grain size and lighter foraminiferal 18o the clay mineral assemblages in our core and in nearby cores correspond with a provenance from the libyan tunisian margin mainly via the paleo river irharhar the inferred fluvial discharge is strongest during the late ahp 8 5 5 ka coinciding with reported enhanced fluvial dynamics and wettest conditions over western libya and tunisia algeria this period is not only synchronous with the largest extension of open water bodies in north africa and lowest saharan dust inputs but also consistent with precipitation records of the west african monsoon moreover our records show a remarkable correspondence with that of a paleodrainage system towards the atlantic west african margin inferring a common headwater region in the central saharan mountains and a similar climate mechanism taken together we suggest a dominant control of north african humid surfaces on the paleodrainage delivery modulated by groundwater level in response to the insolation driven west african monsoon precipitation

three million years of monsoon variability over the northern sahara we present a 3 million year record of aeolian dust supply into the eastern mediterranean sea based on hematite contents derived from magnetic properties of sediments from ocean drilling program site 967 our record has an average temporal resolution of 400 years geochemical data validate this record of hematite content as a proxy for the supply of aeolian dust from the sahara we deduce that the aeolian hematite in eastern mediterranean sediments derives from the eastern algerian libyan and western egyptian lowlands located north of the central saharan watershed 21 n in corroboration of earlier work we relate dust flux minima to penetration of the african summer monsoon front to the north of the central saharan watershed this would have enhanced soil humidity and vegetation cover in the source regions in agreement with results from green sahara climate models our results indicate that this northward monsoon penetration recurred during insolation maxima throughout the last 3 million years as would be expected this orbital precession scale mechanism is modulated on both short 100 kyr and long 400 kyr eccentricity time scales we also observe a strong expression of the 41 kyr obliquity cycle which we discuss in terms of high and low latitude mechanisms that involve southern hemisphere meridional temperature contrasts and shifts in the latitudes of the tropics respectively we also observe a marked increase in sub milankovitch variability around the mid pleistocene transition 0 95 ma which suggests a link between millennial scale climate variability including monsoon dynamics and the size of northern hemisphere ice sheets

late quaternary eolian deposition in central italy abstract records of eolian quartz from two continuous sediment sequences drilled in lagaccione and lago di vico volcanic lakes in central italy contribute to the knowledge of eolian deposition in the central mediterranean during the last 100 000 years the chronology is based on 14 c and 40 ar 39 ar dating and tephra analysis pollen data provide the paleoenvironmental framework and enable correlation between the cores eolian inputs were high during the steppe phases corresponding to oxygen isotope stages 4 and 2 low inputs correspond to the forest phases of the last interglacial and the middle holocene eolian inputs have increased in the late holocene patterns of eolian deposition in central italy resemble the antarctic dust record from the vostok ice core the italian patterns may also correspond with hydrological changes registered in north africa the main source of dust loading over the mediterranean now north africa may have played an important role in dust supply throughout the last climatic cycle

paleoenvironmental changes during sapropel 19 i cycle 90 deposition evidences from geochemical mineralogical and micropaleontological proxies in the mid pleistocene montalbano jonico land section southern italy an integrated micropaleontological geochemical and mineralogical study has been performed across the mid pleistocene sapropel 19 i cycle 90 from the montalbano jonico land section southern italy to reconstruct the paleoenvironmental conditions at time of its formation the sapropel interval is characterized by two oxygen depletion phases phase a and c interrupted by a temporary re oxygenation interval phase b the beginning and the end of sapropel deposition are dated at 957 0 81 kyr and 950 0 86 kyr respectively the duration of the interruption is estimated to 0 350 0 32 kyr the multiproxy approach highlights that deposition of sapropel 19 reflects a period of enhanced freshwater runoff induced by a wetter climate as a consequence of a more efficient fluvial erosion a higher terrigenous input mostly ascribable to a southern apennines source and an increased turbidity of surface waters accompanied most of sapropel deposition biotic and abiotic proxies document that different paleoenvironmental conditions occur through phases a c the beginning of phase a is characterized by warm on land paleoclimate as well as warm and oligotrophic surface water conditions during the upper part of phase a temperature starts decreasing and surface waters appear more productive this change probably represents the prelude to cooler and drier conditions characterizing phase b which displays a river supply reduction and an eolian input increase sahara dust during phase c the restored depleted oxygen environment at the bottom sediments is clearly coupled with the re establishment of humid conditions and increased river supply at the same time enhanced mixing of water column a cooler paleoclimate and increased productivity of surface waters are recorded the latter likely favored by the enhanced mixing of water column and also increased delivery of land derived nutrients the end of phase c is marked by a restored normal run off enhanced productivity in surface waters and low oxygen conditions at the bottom sediments persist slightly above phase c the overall results suggest that the onset of sapropel deposition is related to water stratification that caused low oxygen exchanges with the sea bottom although enhanced productivity characterizes most of the sapropel deposition it was not the primary factor triggering sapropel deposition

sediment trap and deep sea coretop sediments as tracers of recent changes in planktonic foraminifera assemblages in the southeastern ultra oligotrophic levantine basin abstract sediment trap and core top sediments were used to study the seasonal and longer term variability in the distribution and assemblage composition of planktonic foraminifera pf in the ultra oligotrophic eastern mediterranean levantine basin lb a continuous time series of particulate flux sampled every 11 12 days were retrieved from a sediment trap deployed at 1300 m between may 2017 and may 2018 the core top sediments were collected close to the sediment trap mooring site at 1500 m water depth the average annual planktonic foraminiferal pf flux was 93 shells m 2 d 1 the lowest value yet recorded among traps located in tropical subtropical oligotrophic regions a bimodal increase in pf flux is observed with highest numbers of 452 shells m 2 d 1 occurring in winter february responding directly to maxima in particulate mass flux a lower flux occurs in late summer from mid august to mid september with up to 197 shells m 2 d 1 ten species were found in the trap the majority were symbiont bearing spinose species that contribute 96 of the total flux globigerinoides ruber white predominate the assemblage composition during the winter peak together with globoturborotalita rubsecens and globigerinella calida during the subordinate summer peak the dominating species were g ruber white orbulina universa and globigerinoides ruber pink the relative abundance of g bulloides and g ruber pink is much lower in the sediment trap samples compared to their abundance in nearby coretop sediments this trend seems to indicate a recent drop in their numbers at the same time g rubescens and globoturborotalita tenella occur in higher numbers in the sediment trap compared with the coretop samples these opposite trends may reflect the current adjustment of certain pf species to the ongoing sea surface warming and decrease in food availability in the lb

roman and late roman glass from north eastern italy the isotopic perspective to provenance its raw materials in this study the strontium neodymium and oxygen isotopic composition of roman 1st 3rd century ad and late roman glass 4th 6th century ad from adria and aquileia two of the most important archaeological sites of north eastern italy is discussed the majority of glass analysed independent from age shows values of strontium isotope ratios close to that of modern seawater indicating that the source of lime in the glass was marine shell and likely coastal sands were used in its production the nd signature of all late roman glasses from aquileia and of the majority of the roman ones from adria independent from their chemical composition is homogeneous and higher than 6 end supporting the hypothesis of an eastern mediterranean origin probably located on syro palestinian coast however the composition of late roman samples with himt signature with lower 87sr 86sr values correlated to higher contents in fe2o3 tio2 mgo and lower contents in cao suggests an area of origin for this glass on the egyptian coast in addition the different nd signatures of two adria roman glasses end 7 suggest their primary production in western mediterranean oxygen isotopes proved to be a further diagnostic method to discriminate natron and soda plant ash glass and different silica sources in the case of the soda plant ash glass the combination of isotopic and chemical data supports the hypothesis of an eastern mediterranean origin for late roman glass which may be produced in few primary workshops on the syro palestinian and egyptian coast although not necessarily in the same ateliers as have been identified so far in the case of the roman glass investigated although the majority of data suggests an eastern mediterranean origin on the basis of nd isotopes and chemical compositions the existence of other primary glass producers located in the western mediterranean can be suggested

late holocene productivity and hydrographic variability in the eastern mediterranean inferred from benthic foraminiferal stable isotopes 1 the paleoproductivity paleo oxygenation and paleohydrographic configuration of the southeastern mediterranean during the late holocene was reconstructed on the basis of the isotopic composition of the epibenthic heterolepa floridana shallow endobenthic uvigerina mediterranea and the deeper endobenthic bulimina inflata from two high resolution cores ga 112 470 m and ga 110 670 m the 13c between h floridana and u mediterranea reveals four intervals of enhanced productivity from 3 3 2 6 2 3 1 9 1 5 1 1 and 0 8 0 4 kyr bp coinciding with increased nutrient supply by the nile river the entire basin was well aerated with oxygen consumption varying between 1 0 and 3 5 ml o2 l oxygen consumption increases toward present day probably because of higher accumulation of total organic carbon at 1 7 kyr bp coinciding with the appearance of the mesotropic benthic species the hydrographic configuration of the basin has changed during the course of the last 3 75 kyr the levantine intermediate water liw deepens below 470 m between 3 3 and 2 0 kyr and especially between 2 5 and 2 0 kyr during the last 1 5 kyr the liw becomes shallower than 470 m similar to the present day the change in the hydrographic configuration reflects changes in evaporation precipitation ratio and in temperature

climatically driven changes in sediment supply on the sw iberian shelf since the last glacial maximum the assemblages of marine sediments on the sw iberian shelf have been controlled by contributions from distinct sources which have varied in response to environmental changes since the last glacial maximum lgm the rapid decadal scale mediterranean overturning circulation permits mixing of suspended particles from the entire mediterranean sea they are entrained into the suspended particulate matter spm carried by mediterranean outflow water mow which enters the eastern north atlantic through the strait of gibraltar and spreads at intermediate depths in the gulf of cadiz and along the portuguese continental margin other major sediment sources that have contributed to the characteristics and budget of spm along the flow path of mow on the sw iberian shelf are north african dust and river transported particles from the iberian peninsula to reconstruct climate and circulation driven changes in the supply of sediments over the past 23 000 cal yr b p radiogenic nd sr and pb isotope records of the clay size sediment fraction were obtained from one gravity core in the gulf of cadiz 577 m water depth and from two gravity cores on the portuguese shelf 1745 m 1974 m water depth these records are supplemented by time series analyses of clay mineral abundances from the same set of samples contrary to expectations the transition from the lgm to the holocene was not accompanied by strong changes in sediment provenance or transport whereas heinrich event 1 h1 and the african humid period ahp were marked by significantly different isotopic signatures reflecting changes in source contributions caused by supply of ice rafted material originating from the north american craton during h1 and diminished supply of saharan dust during the ahp the data also reveal that the timing of variations in the clay mineral abundances was decoupled from that of the radiogenic isotope signatures

contribution of saharan dust to mediterranean soils assessed by sequential extraction and pb and sr isotopes abstract measurements of the concentrations and isotopic composition of pb and sr in al silicates and fe oxides of two soil profiles developed in the guadalquivir river basin andalusia southwestern spain are used in order to estimate the significance of local versus foreign sources lead concentrations are 10 6 mg kg in deep more than 100 cm soil samples and reach 30 60 mg kg near the surface 206 pb 207 pb values range from 1 200 to 1 206 in deep samples and from 1 186 to 1 191 in the upper most samples sr concentrations range from 30 to 69 mg kg showing no systematic trend with depth 87 sr 86 sr ratios range from 0 71753 to 0 72526 also with no systematic changes with depth in the fe oxide fraction but with a systematic increase in values with depth in the al silicate fraction of one of the soil profiles in all the samples the isotopic composition of pb in the al si fraction is slightly more radiogenic than its value in the fe oxide fraction the isotopic composition of sr exhibits the opposite behavior and 87 sr 86 sr values in the fe oxide fraction are always higher than in the al silicate fraction based on our data we calculate that al silicates in the fine soil fraction less than 5 m in both sites contain 33 86 of saharan dust and that the fe oxides contain less saharan dust and more material released by the weathering of basement granitoid type rocks in the case of pb a third source is present in the upper part of the soil i e anthropogenic pb probably added to the soil over millennia the results of the present study suggest that saharan dust makes up a significant fraction in al silicates and fe oxides of mediterranean soils but that local sources both natural rock derived and anthropogenic are not trivial

distribution of clay minerals in surface sediments of the aegean sea a compilation extensive published data sets and some new data on the clay mineral composition of surface sediments in the aegean sea northeastern mediterranean sea have been compiled in order to map the distribution patterns of clay mineral assemblages and to decipher source areas and transport paths we distinguished six provinces a northwest aegean province a marmara dardanelles province a west turkey province a southeast aegean province a kithira province and a central aegean province the clay mineral assemblages in the coastal and shelf areas carry the signature of the riverine sediment discharge from southeast europe and turkey respectively the southern aegean sea is probably influenced by the river nile discharge and transport of clay minerals by surface currents the clay minerals in the central aegean sea form a mixed assemblage comprising components of the other assemblages a dispersion and dilution of clay minerals by surface currents is obvious

anoxic development of sapropel s1 in the nile fan inferred from redox sensitive proxies fe speciation fe and mo isotopes abstract redox conditions and the mechanisms of redox development are a critical aspect of eastern mediterranean sapropels whose formation in oxygen depleted waters is closely related to water column stratification at times of global sea level rise and insolation maxima sapropels in the nile fan formed at relatively shallow water depths under the influence of the monsoon driven freshwater output from the river nile this work evaluates the redox evolution of holocene sapropel s1 in valpamed cruise core md9509 recovered at 880 mbsl in the ne nile fan using a combination of geochemical element proxies fe speciation fe and mo isotopes studies the productivity and redox proxies ba al mo al u al v al sb al show well defined enrichments in the sapropel but with a marked minimum at ca 8 2 ka indicative of reventilation corresponding to a well known global cooling event peak productivity and reducing signals occur close to the initiation of sapropel formation the proxy signals in sapropel 9509 are stronger and of longer duration than those of a second sapropel s1 recovered at the same depth but 380 km to the north md9501 supporting the notion suggested in previous studies of more reduced conditions in the nile fan the moef vs uef enrichment factor variations in core 9509 infer a transition from open marine suboxic conditions in the enclosing non sapropel sediments to anoxic non sulphidic water column conditions in the sapropel correspondingly the highly reactive fe pool fehr measured in fe speciation studies is dominated by fe oxyhydr oxide minerals in the background sediments whereas pyrite fepy becomes the dominant component of the fehr pool in the sapropel maximum fepy values in the sapropel coincide with peak productivity and reducing conditions implying a clear link between trace element uptake diagenetic bacterial sulphate reduction in anoxic porewater and fe mobilization in the sapropel iron isotope compositions 56fe in the sapropel do not show any departure from primary marine and detrital source sediment values and the absence of an fe al vs 56fe trend strongly argues against an fe shuttle molybdenum isotopes however show marked non conservative fractionation patterns background sediment 98 95mo values 0 2 to 0 7 are compatible with fractionation upon absorptive uptake by fe oxyhydr oxides and pyrite in contrast minimum 98 95mo values exhibited at peak sapropel reducing and pyrite producing conditions are most closely modeled by mo isotope fractionation during kinetically controlled conversion of aqueous molybdate to thiomolybdate species the conservative fe isotope behavior mo isotope fractionation minima in the sapropel may be a characteristic of organic rich sediment diagenesis below an anoxic non sulphidic water body without the operation of a benthic fe shuttle

effect of spatial distribution of hormuz salt on deformation style in the zagros fold and thrust belt an analogue modelling approach scaled analogue models of thin skinned simultaneous shortening above adjacent viscous and frictional decollements simulate the effect of hormuz salt on the shortening in the zagros fold and thrust belt the models consisted of sand layers that partly overlay a viscous layer of silicone and were shortened from one end spatial distribution of the viscous decollement varied along strike and dip as occurs in part of the zagros fold and thrust belt in this belt phanerozoic sedimentary cover was shortened partly above the hormuz salt lying on the precambrian crystalline basement behaving as a basal viscous decollement model results display how the nature of the decollement affects the evolution of an orogenic belt using model results we explain the development of deflection zones and discuss strain partitioning formation of different topographic wedges and differential sedimentation along the zagros fold and thrust belt model results suggest the formation of a gentle taper consisting of both foreward and backward thrusts above a viscous decollement and a relatively steeper taper consisting only of forward vergent imbricates above a frictional decollement however in our models the steepest wedge with the highest topography formed where the viscous substrate had a limited extent with a transitional boundary pinch out perpendicular to the shortening direction shortening of this boundary led to development of frontal ramps associated with significant uplift of the area behind the deformation front

first coupled sr and pb isotopic measurements in volcanic gas condensates and groundwaters of vulcano island italy 1 for the first time coupled sr pb concentrations and isotopic compositions have been measured on four crater fumaroles and six groundwaters sampled between 1999 and 2001 at vulcano island southern italy sr concentrations and isotopic compositions of groundwaters show that the sr budget results mainly from the leaching of volcanic rock by groundwaters leaching intensity is controlled by the variable dissolution of volcanic gases into shallow aquifers the data do not reveal any influence of seawater except at one coastal site low pb concentrations together with calculated saturation indexes with respect to mineral phases indicate that pb content in groundwaters is strongly influenced by adsorption and or precipitation processes pb isotopic ratios of two steam heated waters display a clear anthropized meteoric water signature suggesting gas dissolution or wall rock alteration to be a negligible process for this element in this particular context low 0 5 and high 102 103 enrichment factors were calculated for sr and pb respectively indicating their refractory and volatile behavior in volcanic gases most of the gas samples display sr and pb isotopic ratios similar to parent rocks these data suggest that sr is mainly derived from wall rock or particle contamination during gas ascent whereas pb results mainly from magma degassing however two gas condensates collected from two different fumarolic vents and at different periods show a dramatic pb and sr isotopic shift with a clear atmospheric anthropogenic signature episodic permeability variations of the volcanic structure probably arising from microseismicity swarms changes of local stress field and migration of self sealing processes lead to changing interactions between freshly infiltrated meteoric water and volcanic gases that temporarily modify the trace metal signature of the fumarolic gas

the importance of groundwater discharge to the methane budgets of nearshore and continental shelf waters of the northeastern gulf of mexico methane concentrations in groundwater wells sinkholes and springs averaged 61 9 mu m while concentrations in nearshore and continental shelf waters within the study area averaged 62 7 nm and 27 5 nm respectively we tested the hypothesis that the three orders of magnitude difference between groundwater and seawater concentration would make ch sub 4 an indicator of submarine groundwater discharge to surficial waters methane budgets for nearshore and continental shelf water columns were consistent with the hypothesis that groundwater seepage or seawater recirculation through the seabed is the dominant source of ch sub 4 relative to benthic diffusive flux riverine flux and in situ water column production seepage recirculation appears to account for approximately 83 99 of the total ch sub 4 input into the water column within the study area utilizing measured porewater ch sub 4 concentrations the calculated amounts of seepage required to support the observed benthic fluxes were comparable to seepage rates measured in the field nearshore seepage meter transacts showed a strong and direct correlation between the integrated quantity of groundwater seepage along a shoreline and the inventory of ch sub 4 in those waters our study further showed a similar correlation between sup 222 rn another potential groundwater tracer andmore ch sub 4 in offshore waters supporting the hypothesis of a common benthic source for these constituents 67 refs 10 figs 2 tabs less

the initiation and evolution of the river nile abstract the nile is generally regarded as the longest river in the world knowledge of the timing of the nile s initiation as a major river is important to a number of research questions for example the timing of the river s establishment as a catchment of continental proportions can be used to document surface uplift of its ethiopian upland drainage with implications for constraining rift tectonics furthermore the time of major freshwater input to the mediterranean is considered to be an important factor in the development of sapropels yet the river s initiation as a major drainage is currently constrained no more precisely than eocene to pleistocene within the modern nile catchment voluminous cenozoic continental flood basalts cfbs are unique to the ethiopian highlands thus first detection of their presence in the nile delta record indicates establishment of the river s drainage at continental proportions at that time we present the first detailed multiproxy provenance study of oligocene recent nile delta cone sediments we demonstrate the presence of ethiopian cfb detritus in the nile delta from the start of our studied record c 31 ma by 1 documenting the presence of zircons with u pb ages unique within the nile catchment to the ethiopian cfbs and 2 using sr nd data to construct a mixing model which indicates a contribution from the cfbs we thereby show that the nile river was established as a river of continental proportions by oligocene times we use petrography and heavy mineral data to show that previous petrographic provenance studies which proposed a pleistocene age for first arrival of ethiopian cfbs in the nile delta did not take into account the strong diagenetic influence on the samples we use a range of techniques to show that sediments were derived from phanerozoic sedimentary rocks that blanket north africa arabian nubian shield basement terranes and ethiopian cfb s we see no significant input from archaean cratons supplied directly via the white nile in any of our samples whilst there are subtle differences between our nile delta samples from the oligocene and pliocene compared to those from the miocene and pleistocene the overall stability of our signal throughout the delta record and its similarity to the modern nile signature indicates no major change in the nile s drainage from oligocene to present day

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

recent subsidence of the northern suez canal in contrast to a recent interpretation of delta coast stability1 we now show that the northeastern nile delta in egypt has been actively sinking relative to the sea during the recent holocene epoch the northern nile delta is only about 1 m above sea level making the northern suez canal and coastal cities of port said and port fuad combined population nearly 500 000 highly vulnerable subsidence and world sea level rises contribute to coastal erosion incursion of salt in the groundwater underlying the delta plain and silting problems in the canal entrances2 these processes must be considered when implementing protection measures for this area

methanotrophy controls groundwater methane export from a barrier island abstract methane concentrations can be high in coastal groundwater resulting in methane export driven by submarine groundwater discharge however the magnitude of this methane flux depends significantly on the rate of methanotrophy the often overlooked process of microbial methane consumption that occurs within coastal aquifer sediments here we describe a zone of methanogenesis within the freshwater lens of a barrier island aquifer and investigate the methane source sink behavior of the barrier island system as a whole the median concentration of methane dissolved in fresh groundwater beneath the center of the island was 0 6 mm supported by high rates of potential methanogenesis 22 mmol m 2 day 1 however rates of microbial methane consumption were also elevated in surrounding sediments 18 mmol m 2 day 1 groundwater flowing from the zone of methanogenesis to the point of discharge into the ocean had a long residence time within methanotrophic sediments 195 days such that the majority of the methane produced within the barrier island aquifer was likely consumed there

modern and late quaternary clay mineral distribution in the area of the se mediterranean sea the present day clay mineral distribution in the southeastern levantine sea and its borderlands reveals a complex pattern of different sources and distribution paths smectite dominates the suspended load of the nile river and of rivers in the near east illite sources are dust bearing winds from the sahara and southwestern europe kaolinite is prevalent in rivers of the sinai in egyptian wadis and in saharan dust a high resolution sediment core from the southeastern levantine sea spanning the last 27 ka shows that all these sources contributed during the late quaternary and that the nile river played a very important role in the supply of clay nile influence was reduced during the glacial period but was higher during the african humid period in contrast to the sharp beginning and end of the african humid period recorded in west african records 15 and 5 5 ka our data show a more transitional pattern and slightly lower nile river discharge rates not starting until 4 ka the similarity of the smectite concentrations with fluctuations in sea surface temperatures of the tropical western indian ocean indicates a close relationship between the indian ocean climate system and the discharge of the nile river

late quaternary nile flows as recorded in the levantine basin the palynological evidence abstract this study aims to trace changes in the river nile flows over the late quaternary and is based on palynomorphs which were embedded in the sea floor of the levantine basin the palynomorphs were extracted from two marine sediment cores which cover the last 86 ka and are located at the two ends of the levantine basin md 9509 at the southern part of the levantine basin and md 9501 at its northern part core md 9509 was taken from the nile cone and is characterized by high sedimentation rates and a good state of palynomorph preservation the assemblages included palynomorphs which were transported via the nile headwaters and therefore enabled the reconstruction of the river nile flows the results demonstrate that the last glacial period 75 16 ka was characterized by a decrease in nile water discharge and an increase in sediment influx while opposite trends were observed prior to the last glacial period as well as during the deglaciation and the holocene based on the study of the spores it is suggested that during the last glacial the main contributors of freshwater and sediment load to the eastern mediterranean sea were the blue nile and the atbara and only during interglacials was there a more significant contribution of the white nile within the northern core md 9501 pollen was preserved only during the formation of sapropels s3 and s1 the comparison of the sapropelic palynological spectra in both core sites clearly indicates that during sapropel deposition climate conditions were more humid in the northern levant reflecting the north south regional mediterranean climatic moisture gradient sapropel formation was a result of the intensification of the monsoonal climate system which was most probably related to the maximum insolation values at 65 n while currently the atlantic is the main influencing climate system in the region one of the most interesting observations in this study is that during heinrich events h2 h6 which originated in the north atlantic and were identified in md 9509 based on minimum arboreal pollen percentages pollen originating from tropical regions was not embedded in the levantine basin these results lend support to the view that episodes of dryness in tropical sub tropical eastern africa were associated not only with low latitude climate controls but also with high latitude glacial stress

application of 222rn and ch4 for assessment of groundwater discharge to the coastal ocean groundwater discharge is a neglected source of freshwater and dissolved constituents to the ocean it can occur via diffuse seepage and point source spring discharge two naturally occurring trace gases 222 rn and ch 4 are present in groundwater at concentrations that are elevated by several orders of magnitude relative to seawater and they may be useful in tracing groundwater inputs to surface waters water samples collected near a submarine spring in the northeastern gulf of mexico displayed radon and methane concentrations inversely related to salinity and considerably greater than those found in surrounding waters coastal water 222 rn and ch 4 inventories varied directly with groundwater seepage rates the integrated quantities of 222 rn and ch 4 in the nearshore waters overlying a seepage meter transect showed a significant positive

riverine supply to the eastern mediterranean during last interglacial sapropel s5 formation a basin wide perspective abstract organic rich sapropel sediments were repeatedly deposited in the eastern mediterranean sea ems in response to insolation driven freshwater forcing however the exact freshwater sources and causal associated paleoclimate related processes remain unresolved sapropel s5 formed during the insolation maximum of the last interglacial is one of the most intensely developed sapropels of the late quaternary here detrital sediments of sapropel s5 obtained from 8 cores together with 13 ems surface samples are analyzed for major elements rare earth elements ree and sr and nd isotopes this permits a basin wide investigation of the source and distribution of river borne material to the ems for sapropel s5 and its comparison to the present day and the holocene sapropel s1 period during the sapropel s5 there was minor saharan dust input the marked east west geochemical gradient in s5 detrital sediments across the ems is therefore attributed to mixing between fluvial contributions being nile discharge aegean adriatic riverine inputs and libyan tunisian paleodrainage fluxes the offshore distribution of nile sediments during sapropel s5 was comparable to those during s1 and the present the nile sediment contribution appears to be only dominant for the levantine basin decreasing to negligible values south of crete this rather limited sediment delivery despite inferred increased runoff during s5 is related to denser vegetation cover on the ethiopian highlands by contrast small rivers around the aegean and adriatic sea brought large amounts of detrital material into the ems this is particularly noticeable around crete and the northern ionian sea the enhanced riverine input is probably due to strong precipitation seasonality over the northern ems borderlands particularly for the early phase of the last interglacial maximum furthermore there are substantial fluvial contributions from the libyan tunisian margin to the ionian sea sediments in particular during the last part of sapropel s5 the inferred river borne material was transported via paleodrainage systems reactivated by intensified monsoon precipitation and derived from central saharan mountains compared to sapropel s1 these s5 related paleodrainage fluxes were not only stronger but also had a more predominant provenance from eastern rather than western libya in addition a similar averaged endmember of saharan dust sources is revealed by ree signatures

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